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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
163 udebs (stripped-down binary packages used by the Debian Installer) do
164 not comply with all of the requirements discussed here. See the
165 <url name="Debian Installer internals manual"
166 id="http://d-i.alioth.debian.org/doc/internals/ch03.html"> for more
167 information about them.
172 <heading>New versions of this document</heading>
175 This manual is distributed via the Debian package
176 <package><url name="debian-policy"
177 id="http://packages.debian.org/debian-policy"></package>
178 (<httpsite>packages.debian.org</httpsite>
179 <httppath>/debian-policy</httppath>).
183 The current version of this document is also available from
184 the Debian web mirrors at
185 <tt><url name="/doc/debian-policy/"
186 id="http://www.debian.org/doc/debian-policy/"></tt>.
188 <httpsite>www.debian.org</httpsite>
189 <httppath>/doc/debian-policy/</httppath>)
190 Also available from the same directory are several other
191 formats: <file>policy.html.tar.gz</file>
192 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
193 <file>policy.pdf.gz</file>
194 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
195 and <file>policy.ps.gz</file>
196 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
200 The <package>debian-policy</package> package also includes the file
201 <file>upgrading-checklist.txt.gz</file> which indicates policy
202 changes between versions of this document.
207 <heading>Authors and Maintainers</heading>
210 Originally called "Debian GNU/Linux Policy Manual", this
211 manual was initially written in 1996 by Ian Jackson.
212 It was revised on November 27th, 1996 by David A. Morris.
213 Christian Schwarz added new sections on March 15th, 1997,
214 and reworked/restructured it in April-July 1997.
215 Christoph Lameter contributed the "Web Standard".
216 Julian Gilbey largely restructured it in 2001.
220 Since September 1998, the responsibility for the contents of
221 this document lies on the <url name="debian-policy mailing list"
222 id="mailto:debian-policy@lists.debian.org">. Proposals
223 are discussed there and inserted into policy after a certain
224 consensus is established.
225 <!-- insert shameless policy-process plug here eventually -->
226 The actual editing is done by a group of maintainers that have
227 no editorial powers. These are the current maintainers:
230 <item>Russ Allbery</item>
231 <item>Bill Allombert</item>
232 <item>Andrew McMillan</item>
233 <item>Manoj Srivastava</item>
234 <item>Colin Watson</item>
239 While the authors of this document have tried hard to avoid
240 typos and other errors, these do still occur. If you discover
241 an error in this manual or if you want to give any
242 comments, suggestions, or criticisms please send an email to
243 the Debian Policy List,
244 <email>debian-policy@lists.debian.org</email>, or submit a
245 bug report against the <tt>debian-policy</tt> package.
249 Please do not try to reach the individual authors or maintainers
250 of the Policy Manual regarding changes to the Policy.
255 <heading>Related documents</heading>
258 There are several other documents other than this Policy Manual
259 that are necessary to fully understand some Debian policies and
264 The external "sub-policy" documents are referred to in:
265 <list compact="compact">
266 <item><ref id="fhs"></item>
267 <item><ref id="virtual_pkg"></item>
268 <item><ref id="menus"></item>
269 <item><ref id="perl"></item>
270 <item><ref id="maintscriptprompt"></item>
271 <item><ref id="emacs"></item>
276 In addition to those, which carry the weight of policy, there
277 is the Debian Developer's Reference. This document describes
278 procedures and resources for Debian developers, but it is
279 <em>not</em> normative; rather, it includes things that don't
280 belong in the Policy, such as best practices for developers.
284 The Developer's Reference is available in the
285 <package>developers-reference</package> package.
286 It's also available from the Debian web mirrors at
287 <tt><url name="/doc/developers-reference/"
288 id="http://www.debian.org/doc/developers-reference/"></tt>.
292 Finally, a <qref id="copyrightformat">specification for
293 machine-readable copyright files</qref> is maintained as part of
294 the <package>debian-policy</package> package using the same
295 procedure as the other policy documents. Use of this format is
300 <sect id="definitions">
301 <heading>Definitions</heading>
304 The following terms are used in this Policy Manual:
308 The character encoding specified by ANSI X3.4-1986 and its
309 predecessor standards, referred to in MIME as US-ASCII, and
310 corresponding to an encoding in eight bits per character of
311 the first 128 <url id="http://www.unicode.org/"
312 name="Unicode"> characters, with the eighth bit always zero.
316 The transformation format (sometimes called encoding) of
317 <url id="http://www.unicode.org/" name="Unicode"> defined by
318 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
319 name="RFC 3629">. UTF-8 has the useful property of having
320 ASCII as a subset, so any text encoded in ASCII is trivially
330 <heading>The Debian Archive</heading>
333 The Debian system is maintained and distributed as a
334 collection of <em>packages</em>. Since there are so many of
335 them (currently well over 15000), they are split into
336 <em>sections</em> and given <em>priorities</em> to simplify
337 the handling of them.
341 The effort of the Debian project is to build a free operating
342 system, but not every package we want to make accessible is
343 <em>free</em> in our sense (see the Debian Free Software
344 Guidelines, below), or may be imported/exported without
345 restrictions. Thus, the archive is split into areas<footnote>
346 The Debian archive software uses the term "component" internally
347 and in the Release file format to refer to the division of an
348 archive. The Debian Social Contract simply refers to "areas."
349 This document uses terminology similar to the Social Contract.
350 </footnote> based on their licenses and other restrictions.
354 The aims of this are:
356 <list compact="compact">
357 <item>to allow us to make as much software available as we can</item>
358 <item>to allow us to encourage everyone to write free software,
360 <item>to allow us to make it easy for people to produce
361 CD-ROMs of our system without violating any licenses,
362 import/export restrictions, or any other laws.</item>
367 The <em>main</em> archive area forms the <em>Debian distribution</em>.
371 Packages in the other archive areas (<tt>contrib</tt>,
372 <tt>non-free</tt>) are not considered to be part of the Debian
373 distribution, although we support their use and provide
374 infrastructure for them (such as our bug-tracking system and
375 mailing lists). This Debian Policy Manual applies to these
380 <heading>The Debian Free Software Guidelines</heading>
382 The Debian Free Software Guidelines (DFSG) form our
383 definition of "free software". These are:
385 <tag>1. Free Redistribution
388 The license of a Debian component may not restrict any
389 party from selling or giving away the software as a
390 component of an aggregate software distribution
391 containing programs from several different
392 sources. The license may not require a royalty or
393 other fee for such sale.
398 The program must include source code, and must allow
399 distribution in source code as well as compiled form.
401 <tag>3. Derived Works
404 The license must allow modifications and derived
405 works, and must allow them to be distributed under the
406 same terms as the license of the original software.
408 <tag>4. Integrity of The Author's Source Code
411 The license may restrict source-code from being
412 distributed in modified form <em>only</em> if the
413 license allows the distribution of "patch files"
414 with the source code for the purpose of modifying the
415 program at build time. The license must explicitly
416 permit distribution of software built from modified
417 source code. The license may require derived works to
418 carry a different name or version number from the
419 original software. (This is a compromise. The Debian
420 Project encourages all authors to not restrict any
421 files, source or binary, from being modified.)
423 <tag>5. No Discrimination Against Persons or Groups
426 The license must not discriminate against any person
429 <tag>6. No Discrimination Against Fields of Endeavor
432 The license must not restrict anyone from making use
433 of the program in a specific field of endeavor. For
434 example, it may not restrict the program from being
435 used in a business, or from being used for genetic
438 <tag>7. Distribution of License
441 The rights attached to the program must apply to all
442 to whom the program is redistributed without the need
443 for execution of an additional license by those
446 <tag>8. License Must Not Be Specific to Debian
449 The rights attached to the program must not depend on
450 the program's being part of a Debian system. If the
451 program is extracted from Debian and used or
452 distributed without Debian but otherwise within the
453 terms of the program's license, all parties to whom
454 the program is redistributed must have the same
455 rights as those that are granted in conjunction with
458 <tag>9. License Must Not Contaminate Other Software
461 The license must not place restrictions on other
462 software that is distributed along with the licensed
463 software. For example, the license must not insist
464 that all other programs distributed on the same medium
465 must be free software.
467 <tag>10. Example Licenses
470 The "GPL," "BSD," and "Artistic" licenses are examples of
471 licenses that we consider <em>free</em>.
478 <heading>Archive areas</heading>
481 <heading>The main archive area</heading>
484 The <em>main</em> archive area comprises the Debian
485 distribution. Only the packages in this area are considered
486 part of the distribution. None of the packages in
487 the <em>main</em> archive area require software outside of
488 that area to function. Anyone may use, share, modify and
489 redistribute the packages in this archive area
491 See <url id="http://www.debian.org/intro/free"
492 name="What Does Free Mean?"> for
493 more about what we mean by free software.
498 Every package in <em>main</em> must comply with the DFSG
499 (Debian Free Software Guidelines).
503 In addition, the packages in <em>main</em>
504 <list compact="compact">
506 must not require or recommend a package outside
507 of <em>main</em> for compilation or execution (thus, the
508 package must not declare a "Pre-Depends", "Depends",
509 "Recommends", "Build-Depends", or "Build-Depends-Indep"
510 relationship on a non-<em>main</em> package),
513 must not be so buggy that we refuse to support them,
517 must meet all policy requirements presented in this
526 <heading>The contrib archive area</heading>
529 The <em>contrib</em> archive area contains supplemental
530 packages intended to work with the Debian distribution, but
531 which require software outside of the distribution to either
536 Every package in <em>contrib</em> must comply with the DFSG.
540 In addition, the packages in <em>contrib</em>
541 <list compact="compact">
543 must not be so buggy that we refuse to support them,
547 must meet all policy requirements presented in this
554 Examples of packages which would be included in
555 <em>contrib</em> are:
556 <list compact="compact">
558 free packages which require <em>contrib</em>,
559 <em>non-free</em> packages or packages which are not
560 in our archive at all for compilation or execution,
564 wrapper packages or other sorts of free accessories for
571 <sect1 id="non-free">
572 <heading>The non-free archive area</heading>
575 The <em>non-free</em> archive area contains supplemental
576 packages intended to work with the Debian distribution that do
577 not comply with the DFSG or have other problems that make
578 their distribution problematic. They may not comply with all
579 of the policy requirements in this manual due to restrictions
580 on modifications or other limitations.
584 Packages must be placed in <em>non-free</em> if they are
585 not compliant with the DFSG or are encumbered by patents
586 or other legal issues that make their distribution
591 In addition, the packages in <em>non-free</em>
592 <list compact="compact">
594 must not be so buggy that we refuse to support them,
598 must meet all policy requirements presented in this
599 manual that it is possible for them to meet.
601 It is possible that there are policy
602 requirements which the package is unable to
603 meet, for example, if the source is
604 unavailable. These situations will need to be
605 handled on a case-by-case basis.
614 <sect id="pkgcopyright">
615 <heading>Copyright considerations</heading>
618 Every package must be accompanied by a verbatim copy of its
619 copyright information and distribution license in the file
620 <file>/usr/share/doc/<var>package</var>/copyright</file>
621 (see <ref id="copyrightfile"> for further details).
625 We reserve the right to restrict files from being included
626 anywhere in our archives if
627 <list compact="compact">
629 their use or distribution would break a law,
632 there is an ethical conflict in their distribution or
636 we would have to sign a license for them, or
639 their distribution would conflict with other project
646 Programs whose authors encourage the user to make
647 donations are fine for the main distribution, provided
648 that the authors do not claim that not donating is
649 immoral, unethical, illegal or something similar; in such
650 a case they must go in <em>non-free</em>.
654 Packages whose copyright permission notices (or patent
655 problems) do not even allow redistribution of binaries
656 only, and where no special permission has been obtained,
657 must not be placed on the Debian FTP site and its mirrors
662 Note that under international copyright law (this applies
663 in the United States, too), <em>no</em> distribution or
664 modification of a work is allowed without an explicit
665 notice saying so. Therefore a program without a copyright
666 notice <em>is</em> copyrighted and you may not do anything
667 to it without risking being sued! Likewise if a program
668 has a copyright notice but no statement saying what is
669 permitted then nothing is permitted.
673 Many authors are unaware of the problems that restrictive
674 copyrights (or lack of copyright notices) can cause for
675 the users of their supposedly-free software. It is often
676 worthwhile contacting such authors diplomatically to ask
677 them to modify their license terms. However, this can be a
678 politically difficult thing to do and you should ask for
679 advice on the <tt>debian-legal</tt> mailing list first, as
684 When in doubt about a copyright, send mail to
685 <email>debian-legal@lists.debian.org</email>. Be prepared
686 to provide us with the copyright statement. Software
687 covered by the GPL, public domain software and BSD-like
688 copyrights are safe; be wary of the phrases "commercial
689 use prohibited" and "distribution restricted".
693 <sect id="subsections">
694 <heading>Sections</heading>
697 The packages in the archive areas <em>main</em>,
698 <em>contrib</em> and <em>non-free</em> are grouped further into
699 <em>sections</em> to simplify handling.
703 The archive area and section for each package should be
704 specified in the package's <tt>Section</tt> control record (see
705 <ref id="f-Section">). However, the maintainer of the Debian
706 archive may override this selection to ensure the consistency of
707 the Debian distribution. The <tt>Section</tt> field should be
709 <list compact="compact">
711 <em>section</em> if the package is in the
712 <em>main</em> archive area,
715 <em>area/section</em> if the package is in
716 the <em>contrib</em> or <em>non-free</em>
723 The Debian archive maintainers provide the authoritative
724 list of sections. At present, they are:
780 The additional section <em>debian-installer</em>
781 contains special packages used by the installer and is not used
782 for normal Debian packages.
786 For more information about the sections and their definitions,
787 see the <url id="http://packages.debian.org/unstable/"
788 name="list of sections in unstable">.
792 <sect id="priorities">
793 <heading>Priorities</heading>
796 Each package should have a <em>priority</em> value, which is
797 included in the package's <em>control record</em>
798 (see <ref id="f-Priority">).
799 This information is used by the Debian package management tools to
800 separate high-priority packages from less-important packages.
804 The following <em>priority levels</em> are recognized by the
805 Debian package management tools.
807 <tag><tt>required</tt></tag>
809 Packages which are necessary for the proper
810 functioning of the system (usually, this means that
811 dpkg functionality depends on these packages).
812 Removing a <tt>required</tt> package may cause your
813 system to become totally broken and you may not even
814 be able to use <prgn>dpkg</prgn> to put things back,
815 so only do so if you know what you are doing. Systems
816 with only the <tt>required</tt> packages are probably
817 unusable, but they do have enough functionality to
818 allow the sysadmin to boot and install more software.
820 <tag><tt>important</tt></tag>
822 Important programs, including those which one would
823 expect to find on any Unix-like system. If the
824 expectation is that an experienced Unix person who
825 found it missing would say "What on earth is going on,
826 where is <prgn>foo</prgn>?", it must be an
827 <tt>important</tt> package.<footnote>
828 This is an important criterion because we are
829 trying to produce, amongst other things, a free
832 Other packages without which the system will not run
833 well or be usable must also have priority
834 <tt>important</tt>. This does
835 <em>not</em> include Emacs, the X Window System, TeX
836 or any other large applications. The
837 <tt>important</tt> packages are just a bare minimum of
838 commonly-expected and necessary tools.
840 <tag><tt>standard</tt></tag>
842 These packages provide a reasonably small but not too
843 limited character-mode system. This is what will be
844 installed by default if the user doesn't select anything
845 else. It doesn't include many large applications.
847 <tag><tt>optional</tt></tag>
849 (In a sense everything that isn't required is
850 optional, but that's not what is meant here.) This is
851 all the software that you might reasonably want to
852 install if you didn't know what it was and don't have
853 specialized requirements. This is a much larger system
854 and includes the X Window System, a full TeX
855 distribution, and many applications. Note that
856 optional packages should not conflict with each other.
858 <tag><tt>extra</tt></tag>
860 This contains all packages that conflict with others
861 with required, important, standard or optional
862 priorities, or are only likely to be useful if you
863 already know what they are or have specialized
864 requirements (such as packages containing only detached
871 Packages must not depend on packages with lower priority
872 values (excluding build-time dependencies). In order to
873 ensure this, the priorities of one or more packages may need
882 <heading>Binary packages</heading>
885 The Debian distribution is based on the Debian
886 package management system, called <prgn>dpkg</prgn>. Thus,
887 all packages in the Debian distribution must be provided
888 in the <tt>.deb</tt> file format.
892 A <tt>.deb</tt> package contains two sets of files: a set of files
893 to install on the system when the package is installed, and a set
894 of files that provide additional metadata about the package or
895 which are executed when the package is installed or removed. This
896 second set of files is called <em>control information files</em>.
897 Among those files are the package maintainer scripts
898 and <file>control</file>, the <qref id="binarycontrolfiles">binary
899 package control file</qref> that contains the control fields for
900 the package. Other control information files include
901 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
902 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
903 used to store shared library dependency information and
904 the <file>conffiles</file> file that lists the package's
905 configuration files (described in <ref id="config-files">).
909 There is unfortunately a collision of terminology here between
910 control information files and files in the Debian control file
911 format. Throughout this document, a <em>control file</em> refers
912 to a file in the Debian control file format. These files are
913 documented in <ref id="controlfields">. Only files referred to
914 specifically as <em>control information files</em> are the files
915 included in the control information file member of
916 the <file>.deb</file> file format used by binary packages. Most
917 control information files are not in the Debian control file
922 <heading>The package name</heading>
925 Every package must have a name that's unique within the Debian
930 The package name is included in the control field
931 <tt>Package</tt>, the format of which is described
932 in <ref id="f-Package">.
933 The package name is also included as a part of the file name
934 of the <tt>.deb</tt> file.
939 <heading>The version of a package</heading>
942 Every package has a version number recorded in its
943 <tt>Version</tt> control file field, described in
944 <ref id="f-Version">.
948 The package management system imposes an ordering on version
949 numbers, so that it can tell whether packages are being up- or
950 downgraded and so that package system front end applications
951 can tell whether a package it finds available is newer than
952 the one installed on the system. The version number format
953 has the most significant parts (as far as comparison is
954 concerned) at the beginning.
958 If an upstream package has problematic version numbers they
959 should be converted to a sane form for use in the
960 <tt>Version</tt> field.
964 <heading>Version numbers based on dates</heading>
967 In general, Debian packages should use the same version
968 numbers as the upstream sources. However, upstream version
969 numbers based on some date formats (sometimes used for
970 development or "snapshot" releases) will not be ordered
971 correctly by the package management software. For
972 example, <prgn>dpkg</prgn> will consider "96May01" to be
973 greater than "96Dec24".
977 To prevent having to use epochs for every new upstream
978 version, the date-based portion of any upstream version number
979 should be given in a way that sorts correctly: four-digit year
980 first, followed by a two-digit numeric month, followed by a
981 two-digit numeric date, possibly with punctuation between the
986 Native Debian packages (i.e., packages which have been written
987 especially for Debian) whose version numbers include dates
988 should also follow these rules. If punctuation is desired
989 between the date components, remember that hyphen (<tt>-</tt>)
990 cannot be used in native package versions. Period
991 (<tt>.</tt>) is normally a good choice.
997 <sect id="maintainer">
998 <heading>The maintainer of a package</heading>
1001 Every package must have a maintainer, except for orphaned
1002 packages as described below. The maintainer may be one person
1003 or a group of people reachable from a common email address, such
1004 as a mailing list. The maintainer is responsible for
1005 maintaining the Debian packaging files, evaluating and
1006 responding appropriately to reported bugs, uploading new
1007 versions of the package (either directly or through a sponsor),
1008 ensuring that the package is placed in the appropriate archive
1009 area and included in Debian releases as appropriate for the
1010 stability and utility of the package, and requesting removal of
1011 the package from the Debian distribution if it is no longer
1012 useful or maintainable.
1016 The maintainer must be specified in the <tt>Maintainer</tt>
1017 control field with their correct name and a working email
1018 address. The email address given in the <tt>Maintainer</tt>
1019 control field must accept mail from those role accounts in
1020 Debian used to send automated mails regarding the package. This
1021 includes non-spam mail from the bug-tracking system, all mail
1022 from the Debian archive maintenance software, and other role
1023 accounts or automated processes that are commonly agreed on by
1024 the project.<footnote>
1025 A sample implementation of such a whitelist written for the
1026 Mailman mailing list management software is used for mailing
1027 lists hosted by alioth.debian.org.
1029 If one person or team maintains several packages, they should
1030 use the same form of their name and email address in
1031 the <tt>Maintainer</tt> fields of those packages.
1035 The format of the <tt>Maintainer</tt> control field is
1036 described in <ref id="f-Maintainer">.
1040 If the maintainer of the package is a team of people with a
1041 shared email address, the <tt>Uploaders</tt> control field must
1042 be present and must contain at least one human with their
1043 personal email address. See <ref id="f-Uploaders"> for the
1044 syntax of that field.
1048 An orphaned package is one with no current maintainer. Orphaned
1049 packages should have their <tt>Maintainer</tt> control field set
1050 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1051 These packages are considered maintained by the Debian project
1052 as a whole until someone else volunteers to take over
1053 maintenance.<footnote>
1054 The detailed procedure for gracefully orphaning a package can
1055 be found in the Debian Developer's Reference
1056 (see <ref id="related">).
1061 <sect id="descriptions">
1062 <heading>The description of a package</heading>
1065 Every Debian package must have a <tt>Description</tt> control
1066 field which contains a synopsis and extended description of the
1067 package. Technical information about the format of the
1068 <tt>Description</tt> field is in <ref id="f-Description">.
1072 The description should describe the package (the program) to a
1073 user (system administrator) who has never met it before so that
1074 they have enough information to decide whether they want to
1075 install it. This description should not just be copied verbatim
1076 from the program's documentation.
1080 Put important information first, both in the synopsis and
1081 extended description. Sometimes only the first part of the
1082 synopsis or of the description will be displayed. You can
1083 assume that there will usually be a way to see the whole
1084 extended description.
1088 The description should also give information about the
1089 significant dependencies and conflicts between this package
1090 and others, so that the user knows why these dependencies and
1091 conflicts have been declared.
1095 Instructions for configuring or using the package should
1096 not be included (that is what installation scripts,
1097 manual pages, info files, etc., are for). Copyright
1098 statements and other administrivia should not be included
1099 either (that is what the copyright file is for).
1102 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1105 The single line synopsis should be kept brief - certainly
1106 under 80 characters.
1110 Do not include the package name in the synopsis line. The
1111 display software knows how to display this already, and you
1112 do not need to state it. Remember that in many situations
1113 the user may only see the synopsis line - make it as
1114 informative as you can.
1119 <sect1 id="extendeddesc"><heading>The extended description</heading>
1122 Do not try to continue the single line synopsis into the
1123 extended description. This will not work correctly when
1124 the full description is displayed, and makes no sense
1125 where only the summary (the single line synopsis) is
1130 The extended description should describe what the package
1131 does and how it relates to the rest of the system (in terms
1132 of, for example, which subsystem it is which part of).
1136 The description field needs to make sense to anyone, even
1137 people who have no idea about any of the things the
1138 package deals with.<footnote>
1139 The blurb that comes with a program in its
1140 announcements and/or <prgn>README</prgn> files is
1141 rarely suitable for use in a description. It is
1142 usually aimed at people who are already in the
1143 community where the package is used.
1151 <sect id="dependencies">
1152 <heading>Dependencies</heading>
1155 Every package must specify the dependency information
1156 about other packages that are required for the first to
1161 For example, a dependency entry must be provided for any
1162 shared libraries required by a dynamically-linked executable
1163 binary in a package.
1167 Packages are not required to declare any dependencies they
1168 have on other packages which are marked <tt>Essential</tt>
1169 (see below), and should not do so unless they depend on a
1170 particular version of that package.<footnote>
1172 Essential is needed in part to avoid unresolvable dependency
1173 loops on upgrade. If packages add unnecessary dependencies
1174 on packages in this set, the chances that there
1175 <strong>will</strong> be an unresolvable dependency loop
1176 caused by forcing these Essential packages to be configured
1177 first before they need to be is greatly increased. It also
1178 increases the chances that frontends will be unable to
1179 <strong>calculate</strong> an upgrade path, even if one
1183 Also, functionality is rarely ever removed from the
1184 Essential set, but <em>packages</em> have been removed from
1185 the Essential set when the functionality moved to a
1186 different package. So depending on these packages <em>just
1187 in case</em> they stop being essential does way more harm
1194 Sometimes, unpacking one package requires that another package
1195 be first unpacked <em>and</em> configured. In this case, the
1196 depending package must specify this dependency in
1197 the <tt>Pre-Depends</tt> control field.
1201 You should not specify a <tt>Pre-Depends</tt> entry for a
1202 package before this has been discussed on the
1203 <tt>debian-devel</tt> mailing list and a consensus about
1204 doing that has been reached.
1208 The format of the package interrelationship control fields is
1209 described in <ref id="relationships">.
1213 <sect id="virtual_pkg">
1214 <heading>Virtual packages</heading>
1217 Sometimes, there are several packages which offer
1218 more-or-less the same functionality. In this case, it's
1219 useful to define a <em>virtual package</em> whose name
1220 describes that common functionality. (The virtual
1221 packages only exist logically, not physically; that's why
1222 they are called <em>virtual</em>.) The packages with this
1223 particular function will then <em>provide</em> the virtual
1224 package. Thus, any other package requiring that function
1225 can simply depend on the virtual package without having to
1226 specify all possible packages individually.
1230 All packages should use virtual package names where
1231 appropriate, and arrange to create new ones if necessary.
1232 They should not use virtual package names (except privately,
1233 amongst a cooperating group of packages) unless they have
1234 been agreed upon and appear in the list of virtual package
1235 names. (See also <ref id="virtual">)
1239 The latest version of the authoritative list of virtual
1240 package names can be found in the <tt>debian-policy</tt> package.
1241 It is also available from the Debian web mirrors at
1242 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1243 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1247 The procedure for updating the list is described in the preface
1254 <heading>Base system</heading>
1257 The <tt>base system</tt> is a minimum subset of the Debian
1258 system that is installed before everything else
1259 on a new system. Only very few packages are allowed to form
1260 part of the base system, in order to keep the required disk
1265 The base system consists of all those packages with priority
1266 <tt>required</tt> or <tt>important</tt>. Many of them will
1267 be tagged <tt>essential</tt> (see below).
1272 <heading>Essential packages</heading>
1275 Essential is defined as the minimal set of functionality that
1276 must be available and usable on the system at all times, even
1277 when packages are in an unconfigured (but unpacked) state.
1278 Packages are tagged <tt>essential</tt> for a system using the
1279 <tt>Essential</tt> control field. The format of the
1280 <tt>Essential</tt> control field is described in <ref
1285 Since these packages cannot be easily removed (one has to
1286 specify an extra <em>force option</em> to
1287 <prgn>dpkg</prgn> to do so), this flag must not be used
1288 unless absolutely necessary. A shared library package
1289 must not be tagged <tt>essential</tt>; dependencies will
1290 prevent its premature removal, and we need to be able to
1291 remove it when it has been superseded.
1295 Since dpkg will not prevent upgrading of other packages
1296 while an <tt>essential</tt> package is in an unconfigured
1297 state, all <tt>essential</tt> packages must supply all of
1298 their core functionality even when unconfigured. If the
1299 package cannot satisfy this requirement it must not be
1300 tagged as essential, and any packages depending on this
1301 package must instead have explicit dependency fields as
1306 Maintainers should take great care in adding any programs,
1307 interfaces, or functionality to <tt>essential</tt> packages.
1308 Packages may assume that functionality provided by
1309 <tt>essential</tt> packages is always available without
1310 declaring explicit dependencies, which means that removing
1311 functionality from the Essential set is very difficult and is
1312 almost never done. Any capability added to an
1313 <tt>essential</tt> package therefore creates an obligation to
1314 support that capability as part of the Essential set in
1319 You must not tag any packages <tt>essential</tt> before
1320 this has been discussed on the <tt>debian-devel</tt>
1321 mailing list and a consensus about doing that has been
1326 <sect id="maintscripts">
1327 <heading>Maintainer Scripts</heading>
1330 The package installation scripts should avoid producing
1331 output which is unnecessary for the user to see and
1332 should rely on <prgn>dpkg</prgn> to stave off boredom on
1333 the part of a user installing many packages. This means,
1334 amongst other things, not passing the <tt>--verbose</tt>
1335 option to <prgn>update-alternatives</prgn>.
1339 Errors which occur during the execution of an installation
1340 script must be checked and the installation must not
1341 continue after an error.
1345 Note that in general <ref id="scripts"> applies to package
1346 maintainer scripts, too.
1350 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1351 to another package without consulting the maintainer of that
1352 package first. When adding or removing diversions, package
1353 maintainer scripts must provide the <tt>--package</tt> flag
1354 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1358 All packages which supply an instance of a common command
1359 name (or, in general, filename) should generally use
1360 <prgn>update-alternatives</prgn>, so that they may be
1361 installed together. If <prgn>update-alternatives</prgn>
1362 is not used, then each package must use
1363 <tt>Conflicts</tt> to ensure that other packages are
1364 de-installed. (In this case, it may be appropriate to
1365 specify a conflict against earlier versions of something
1366 that previously did not use
1367 <prgn>update-alternatives</prgn>; this is an exception to
1368 the usual rule that versioned conflicts should be
1372 <sect1 id="maintscriptprompt">
1373 <heading>Prompting in maintainer scripts</heading>
1375 Package maintainer scripts may prompt the user if
1376 necessary. Prompting must be done by communicating
1377 through a program, such as <prgn>debconf</prgn>, which
1378 conforms to the Debian Configuration Management
1379 Specification, version 2 or higher.
1383 Packages which are essential, or which are dependencies of
1384 essential packages, may fall back on another prompting method
1385 if no such interface is available when they are executed.
1389 The Debian Configuration Management Specification is included
1390 in the <file>debconf_specification</file> files in the
1391 <package>debian-policy</package> package.
1392 It is also available from the Debian web mirrors at
1393 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1394 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1398 Packages which use the Debian Configuration Management
1399 Specification may contain the additional control information
1400 files <file>config</file>
1401 and <file>templates</file>. <file>config</file> is an
1402 additional maintainer script used for package configuration,
1403 and <file>templates</file> contains templates used for user
1404 prompting. The <prgn>config</prgn> script might be run before
1405 the <prgn>preinst</prgn> script and before the package is
1406 unpacked or any of its dependencies or pre-dependencies are
1407 satisfied. Therefore it must work using only the tools
1408 present in <em>essential</em> packages.<footnote>
1409 <package>Debconf</package> or another tool that
1410 implements the Debian Configuration Management
1411 Specification will also be installed, and any
1412 versioned dependencies on it will be satisfied
1413 before preconfiguration begins.
1418 Packages which use the Debian Configuration Management
1419 Specification must allow for translation of their user-visible
1420 messages by using a gettext-based system such as the one
1421 provided by the <package>po-debconf</package> package.
1425 Packages should try to minimize the amount of prompting
1426 they need to do, and they should ensure that the user
1427 will only ever be asked each question once. This means
1428 that packages should try to use appropriate shared
1429 configuration files (such as <file>/etc/papersize</file> and
1430 <file>/etc/news/server</file>), and shared
1431 <package>debconf</package> variables rather than each
1432 prompting for their own list of required pieces of
1437 It also means that an upgrade should not ask the same
1438 questions again, unless the user has used
1439 <tt>dpkg --purge</tt> to remove the package's configuration.
1440 The answers to configuration questions should be stored in an
1441 appropriate place in <file>/etc</file> so that the user can
1442 modify them, and how this has been done should be
1447 If a package has a vitally important piece of
1448 information to pass to the user (such as "don't run me
1449 as I am, you must edit the following configuration files
1450 first or you risk your system emitting badly-formatted
1451 messages"), it should display this in the
1452 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1453 prompt the user to hit return to acknowledge the
1454 message. Copyright messages do not count as vitally
1455 important (they belong in
1456 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1457 neither do instructions on how to use a program (these
1458 should be in on-line documentation, where all the users
1463 Any necessary prompting should almost always be confined
1464 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1465 script. If it is done in the <prgn>postinst</prgn>, it
1466 should be protected with a conditional so that
1467 unnecessary prompting doesn't happen if a package's
1468 installation fails and the <prgn>postinst</prgn> is
1469 called with <tt>abort-upgrade</tt>,
1470 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1480 <heading>Source packages</heading>
1482 <sect id="standardsversion">
1483 <heading>Standards conformance</heading>
1486 Source packages should specify the most recent version number
1487 of this policy document with which your package complied
1488 when it was last updated.
1492 This information may be used to file bug reports
1493 automatically if your package becomes too much out of date.
1497 The version is specified in the <tt>Standards-Version</tt>
1499 The format of the <tt>Standards-Version</tt> field is
1500 described in <ref id="f-Standards-Version">.
1504 You should regularly, and especially if your package has
1505 become out of date, check for the newest Policy Manual
1506 available and update your package, if necessary. When your
1507 package complies with the new standards you should update the
1508 <tt>Standards-Version</tt> source package field and
1509 release it.<footnote>
1510 See the file <file>upgrading-checklist</file> for
1511 information about policy which has changed between
1512 different versions of this document.
1518 <sect id="pkg-relations">
1519 <heading>Package relationships</heading>
1522 Source packages should specify which binary packages they
1523 require to be installed or not to be installed in order to
1524 build correctly. For example, if building a package
1525 requires a certain compiler, then the compiler should be
1526 specified as a build-time dependency.
1530 It is not necessary to explicitly specify build-time
1531 relationships on a minimal set of packages that are always
1532 needed to compile, link and put in a Debian package a
1533 standard "Hello World!" program written in C or C++. The
1534 required packages are called <em>build-essential</em>, and
1535 an informational list can be found in
1536 <file>/usr/share/doc/build-essential/list</file> (which is
1537 contained in the <tt>build-essential</tt>
1540 <list compact="compact">
1542 This allows maintaining the list separately
1543 from the policy documents (the list does not
1544 need the kind of control that the policy
1548 Having a separate package allows one to install
1549 the build-essential packages on a machine, as
1550 well as allowing other packages such as tasks to
1551 require installation of the build-essential
1552 packages using the depends relation.
1555 The separate package allows bug reports against
1556 the list to be categorized separately from
1557 the policy management process in the BTS.
1564 When specifying the set of build-time dependencies, one
1565 should list only those packages explicitly required by the
1566 build. It is not necessary to list packages which are
1567 required merely because some other package in the list of
1568 build-time dependencies depends on them.<footnote>
1569 The reason for this is that dependencies change, and
1570 you should list all those packages, and <em>only</em>
1571 those packages that <em>you</em> need directly. What
1572 others need is their business. For example, if you
1573 only link against <file>libimlib</file>, you will need to
1574 build-depend on <package>libimlib2-dev</package> but
1575 not against any <tt>libjpeg*</tt> packages, even
1576 though <tt>libimlib2-dev</tt> currently depends on
1577 them: installation of <package>libimlib2-dev</package>
1578 will automatically ensure that all of its run-time
1579 dependencies are satisfied.
1584 If build-time dependencies are specified, it must be
1585 possible to build the package and produce working binaries
1586 on a system with only essential and build-essential
1587 packages installed and also those required to satisfy the
1588 build-time relationships (including any implied
1589 relationships). In particular, this means that version
1590 clauses should be used rigorously in build-time
1591 relationships so that one cannot produce bad or
1592 inconsistently configured packages when the relationships
1593 are properly satisfied.
1597 <ref id="relationships"> explains the technical details.
1602 <heading>Changes to the upstream sources</heading>
1605 If changes to the source code are made that are not
1606 specific to the needs of the Debian system, they should be
1607 sent to the upstream authors in whatever form they prefer
1608 so as to be included in the upstream version of the
1613 If you need to configure the package differently for
1614 Debian or for Linux, and the upstream source doesn't
1615 provide a way to do so, you should add such configuration
1616 facilities (for example, a new <prgn>autoconf</prgn> test
1617 or <tt>#define</tt>) and send the patch to the upstream
1618 authors, with the default set to the way they originally
1619 had it. You can then easily override the default in your
1620 <file>debian/rules</file> or wherever is appropriate.
1624 You should make sure that the <prgn>configure</prgn> utility
1625 detects the correct architecture specification string
1626 (refer to <ref id="arch-spec"> for details).
1630 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1631 <prgn>configure</prgn> scripts are used, you should edit the
1632 <file>.in</file> files rather than editing the
1633 <prgn>Makefile</prgn> directly. This allows the user to
1634 reconfigure the package if necessary. You should
1635 <em>not</em> configure the package and edit the generated
1636 <prgn>Makefile</prgn>! This makes it impossible for someone
1637 else to later reconfigure the package without losing the
1643 <sect id="dpkgchangelog">
1644 <heading>Debian changelog: <file>debian/changelog</file></heading>
1647 Changes in the Debian version of the package should be
1648 briefly explained in the Debian changelog file
1649 <file>debian/changelog</file>.<footnote>
1651 Mistakes in changelogs are usually best rectified by
1652 making a new changelog entry rather than "rewriting
1653 history" by editing old changelog entries.
1656 This includes modifications
1657 made in the Debian package compared to the upstream one
1658 as well as other changes and updates to the package.
1660 Although there is nothing stopping an author who is also
1661 the Debian maintainer from using this changelog for all
1662 their changes, it will have to be renamed if the Debian
1663 and upstream maintainers become different people. In such
1664 a case, however, it might be better to maintain the package
1665 as a non-native package.
1670 The format of the <file>debian/changelog</file> allows the
1671 package building tools to discover which version of the package
1672 is being built and find out other release-specific information.
1676 That format is a series of entries like this:
1678 <example compact="compact">
1679 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1681 [optional blank line(s), stripped]
1683 * <var>change details</var>
1684 <var>more change details</var>
1686 [blank line(s), included in output of dpkg-parsechangelog]
1688 * <var>even more change details</var>
1690 [optional blank line(s), stripped]
1692 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1697 <var>package</var> and <var>version</var> are the source
1698 package name and version number.
1702 <var>distribution(s)</var> lists the distributions where
1703 this version should be installed when it is uploaded - it
1704 is copied to the <tt>Distribution</tt> field in the
1705 <file>.changes</file> file. See <ref id="f-Distribution">.
1709 <var>urgency</var> is the value for the <tt>Urgency</tt>
1710 field in the <file>.changes</file> file for the upload
1711 (see <ref id="f-Urgency">). It is not possible to specify
1712 an urgency containing commas; commas are used to separate
1713 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1714 <prgn>dpkg</prgn> changelog format (though there is
1715 currently only one useful <var>keyword</var>,
1720 The change details may in fact be any series of lines
1721 starting with at least two spaces, but conventionally each
1722 change starts with an asterisk and a separating space and
1723 continuation lines are indented so as to bring them in
1724 line with the start of the text above. Blank lines may be
1725 used here to separate groups of changes, if desired.
1729 If this upload resolves bugs recorded in the Bug Tracking
1730 System (BTS), they may be automatically closed on the
1731 inclusion of this package into the Debian archive by
1732 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1733 in the change details.<footnote>
1734 To be precise, the string should match the following
1735 Perl regular expression:
1737 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1739 Then all of the bug numbers listed will be closed by the
1740 archive maintenance software (<prgn>dak</prgn>) using the
1741 <var>version</var> of the changelog entry.
1743 This information is conveyed via the <tt>Closes</tt> field
1744 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1748 The maintainer name and email address used in the changelog
1749 should be the details of the person uploading <em>this</em>
1750 version. They are <em>not</em> necessarily those of the
1751 usual package maintainer.<footnote>
1752 If the developer uploading the package is not one of the usual
1753 maintainers of the package (as listed in
1754 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1755 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1756 fields of the package), the first line of the changelog is
1757 conventionally used to explain why a non-maintainer is
1758 uploading the package. The Debian Developer's Reference
1759 (see <ref id="related">) documents the conventions
1761 The information here will be copied to the <tt>Changed-By</tt>
1762 field in the <tt>.changes</tt> file
1763 (see <ref id="f-Changed-By">), and then later used to send an
1764 acknowledgement when the upload has been installed.
1768 The <var>date</var> has the following format<footnote>
1769 This is the same as the format generated by <tt>date
1771 </footnote> (compatible and with the same semantics of
1772 RFC 2822 and RFC 5322):
1773 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1775 <list compact="compact">
1777 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1780 dd is a one- or two-digit day of the month (01-31)
1783 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1786 <item>yyyy is the four-digit year (e.g. 2010)</item>
1787 <item>hh is the two-digit hour (00-23)</item>
1788 <item>mm is the two-digit minutes (00-59)</item>
1789 <item>ss is the two-digit seconds (00-60)</item>
1791 +zzzz or -zzzz is the the time zone offset from Coordinated
1792 Universal Time (UTC). "+" indicates that the time is ahead
1793 of (i.e., east of) UTC and "-" indicates that the time is
1794 behind (i.e., west of) UTC. The first two digits indicate
1795 the hour difference from UTC and the last two digits
1796 indicate the number of additional minutes difference from
1797 UTC. The last two digits must be in the range 00-59.
1803 The first "title" line with the package name must start
1804 at the left hand margin. The "trailer" line with the
1805 maintainer and date details must be preceded by exactly
1806 one space. The maintainer details and the date must be
1807 separated by exactly two spaces.
1811 The entire changelog must be encoded in UTF-8.
1815 For more information on placement of the changelog files
1816 within binary packages, please see <ref id="changelogs">.
1820 <sect id="dpkgcopyright">
1821 <heading>Copyright: <file>debian/copyright</file></heading>
1823 Every package must be accompanied by a verbatim copy of its
1824 copyright information and distribution license in the file
1825 <file>/usr/share/doc/<var>package</var>/copyright</file>
1826 (see <ref id="copyrightfile"> for further details). Also see
1827 <ref id="pkgcopyright"> for further considerations related
1828 to copyrights for packages.
1832 <heading>Error trapping in makefiles</heading>
1835 When <prgn>make</prgn> invokes a command in a makefile
1836 (including your package's upstream makefiles and
1837 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1838 means that <prgn>sh</prgn>'s usual bad error handling
1839 properties apply: if you include a miniature script as one
1840 of the commands in your makefile you'll find that if you
1841 don't do anything about it then errors are not detected
1842 and <prgn>make</prgn> will blithely continue after
1847 Every time you put more than one shell command (this
1848 includes using a loop) in a makefile command you
1849 must make sure that errors are trapped. For
1850 simple compound commands, such as changing directory and
1851 then running a program, using <tt>&&</tt> rather
1852 than semicolon as a command separator is sufficient. For
1853 more complex commands including most loops and
1854 conditionals you should include a separate <tt>set -e</tt>
1855 command at the start of every makefile command that's
1856 actually one of these miniature shell scripts.
1860 <sect id="timestamps">
1861 <heading>Time Stamps</heading>
1863 Maintainers should preserve the modification times of the
1864 upstream source files in a package, as far as is reasonably
1866 The rationale is that there is some information conveyed
1867 by knowing the age of the file, for example, you could
1868 recognize that some documentation is very old by looking
1869 at the modification time, so it would be nice if the
1870 modification time of the upstream source would be
1876 <sect id="restrictions">
1877 <heading>Restrictions on objects in source packages</heading>
1880 The source package may not contain any hard links<footnote>
1882 This is not currently detected when building source
1883 packages, but only when extracting
1887 Hard links may be permitted at some point in the
1888 future, but would require a fair amount of
1891 </footnote>, device special files, sockets or setuid or
1892 setgid files.<footnote>
1893 Setgid directories are allowed.
1898 <sect id="debianrules">
1899 <heading>Main building script: <file>debian/rules</file></heading>
1902 This file must be an executable makefile, and contains the
1903 package-specific recipes for compiling the package and
1904 building binary package(s) from the source.
1908 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1909 so that it can be invoked by saying its name rather than
1910 invoking <prgn>make</prgn> explicitly. That is, invoking
1911 either of <tt>make -f debian/rules <em>args...</em></tt>
1912 or <tt>./debian/rules <em>args...</em></tt> must result in
1917 The following targets are required and must be implemented
1918 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1919 <tt>binary-arch</tt>, <tt>binary-indep</tt>, <tt>build</tt>,
1920 <tt>build-arch</tt> and <tt>build-indep</tt>.
1921 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1925 Since an interactive <file>debian/rules</file> script makes it
1926 impossible to auto-compile that package and also makes it hard
1927 for other people to reproduce the same binary package, all
1928 required targets must be non-interactive. It also follows that
1929 any target that these targets depend on must also be
1934 The targets are as follows:
1936 <tag><tt>build</tt> (required)</tag>
1939 The <tt>build</tt> target should perform all the
1940 configuration and compilation of the package.
1941 If a package has an interactive pre-build
1942 configuration routine, the Debian source package
1943 must either be built after this has taken place (so
1944 that the binary package can be built without rerunning
1945 the configuration) or the configuration routine
1946 modified to become non-interactive. (The latter is
1947 preferable if there are architecture-specific features
1948 detected by the configuration routine.)
1952 For some packages, notably ones where the same
1953 source tree is compiled in different ways to produce
1954 two binary packages, the <tt>build</tt> target
1955 does not make much sense. For these packages it is
1956 good enough to provide two (or more) targets
1957 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1958 for each of the ways of building the package, and a
1959 <tt>build</tt> target that does nothing. The
1960 <tt>binary</tt> target will have to build the
1961 package in each of the possible ways and make the
1962 binary package out of each.
1966 The <tt>build</tt> target must not do anything
1967 that might require root privilege.
1971 The <tt>build</tt> target may need to run the
1972 <tt>clean</tt> target first - see below.
1976 When a package has a configuration and build routine
1977 which takes a long time, or when the makefiles are
1978 poorly designed, or when <tt>build</tt> needs to
1979 run <tt>clean</tt> first, it is a good idea to
1980 <tt>touch build</tt> when the build process is
1981 complete. This will ensure that if <tt>debian/rules
1982 build</tt> is run again it will not rebuild the whole
1984 Another common way to do this is for <tt>build</tt>
1985 to depend on <prgn>build-stamp</prgn> and to do
1986 nothing else, and for the <prgn>build-stamp</prgn>
1987 target to do the building and to <tt>touch
1988 build-stamp</tt> on completion. This is
1989 especially useful if the build routine creates a
1990 file or directory called <tt>build</tt>; in such a
1991 case, <tt>build</tt> will need to be listed as
1992 a phony target (i.e., as a dependency of the
1993 <tt>.PHONY</tt> target). See the documentation of
1994 <prgn>make</prgn> for more information on phony
2000 <tag><tt>build-arch</tt> (required),
2001 <tt>build-indep</tt> (required)
2005 The <tt>build-arch</tt> target must
2006 perform all the configuration and compilation required for
2007 producing all architecture-dependant binary packages
2008 (those packages for which the body of the
2009 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2010 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2011 target must perform all the configuration
2012 and compilation required for producing all
2013 architecture-independent binary packages (those packages
2014 for which the body of the <tt>Architecture</tt> field
2015 in <tt>debian/control</tt> is <tt>all</tt>).
2016 The <tt>build</tt> target
2017 should either depend on those targets or take the same
2018 actions as invoking those targets would perform.<footnote>
2019 This split allows binary-only builds to not install the
2020 dependencies required for the <tt>build-indep</tt>
2021 target and skip any resource-intensive build tasks that
2022 are only required when building architecture-independent
2028 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2029 must not do anything that might require root privilege.
2033 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2034 (required), <tt>binary-indep</tt> (required)
2038 The <tt>binary</tt> target must be all that is
2039 necessary for the user to build the binary package(s)
2040 produced from this source package. It is
2041 split into two parts: <prgn>binary-arch</prgn> builds
2042 the binary packages which are specific to a particular
2043 architecture, and <tt>binary-indep</tt> builds
2044 those which are not.
2047 <tt>binary</tt> may be (and commonly is) a target with
2048 no commands which simply depends on
2049 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2052 Both <tt>binary-*</tt> targets should depend on the
2053 <tt>build</tt> target, or on the appropriate
2054 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2055 provided, so that the package is built if it has not
2056 been already. It should then create the relevant
2057 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2058 make their control files and <prgn>dpkg-deb</prgn> to
2059 build them and place them in the parent of the top
2064 Both the <tt>binary-arch</tt> and
2065 <tt>binary-indep</tt> targets <em>must</em> exist.
2066 If one of them has nothing to do (which will always be
2067 the case if the source generates only a single binary
2068 package, whether architecture-dependent or not), it
2069 must still exist and must always succeed.
2073 The <tt>binary</tt> targets must be invoked as
2075 The <prgn>fakeroot</prgn> package often allows one
2076 to build a package correctly even without being
2082 <tag><tt>clean</tt> (required)</tag>
2085 This must undo any effects that the <tt>build</tt>
2086 and <tt>binary</tt> targets may have had, except
2087 that it should leave alone any output files created in
2088 the parent directory by a run of a <tt>binary</tt>
2093 If a <tt>build</tt> file is touched at the end of
2094 the <tt>build</tt> target, as suggested above, it
2095 should be removed as the first action that
2096 <tt>clean</tt> performs, so that running
2097 <tt>build</tt> again after an interrupted
2098 <tt>clean</tt> doesn't think that everything is
2103 The <tt>clean</tt> target may need to be
2104 invoked as root if <tt>binary</tt> has been
2105 invoked since the last <tt>clean</tt>, or if
2106 <tt>build</tt> has been invoked as root (since
2107 <tt>build</tt> may create directories, for
2112 <tag><tt>get-orig-source</tt> (optional)</tag>
2115 This target fetches the most recent version of the
2116 original source package from a canonical archive site
2117 (via FTP or WWW, for example), does any necessary
2118 rearrangement to turn it into the original source
2119 tar file format described below, and leaves it in the
2124 This target may be invoked in any directory, and
2125 should take care to clean up any temporary files it
2130 This target is optional, but providing it if
2131 possible is a good idea.
2135 <tag><tt>patch</tt> (optional)</tag>
2138 This target performs whatever additional actions are
2139 required to make the source ready for editing (unpacking
2140 additional upstream archives, applying patches, etc.).
2141 It is recommended to be implemented for any package where
2142 <tt>dpkg-source -x</tt> does not result in source ready
2143 for additional modification. See
2144 <ref id="readmesource">.
2150 The <tt>build</tt>, <tt>binary</tt> and
2151 <tt>clean</tt> targets must be invoked with the current
2152 directory being the package's top-level directory.
2157 Additional targets may exist in <file>debian/rules</file>,
2158 either as published or undocumented interfaces or for the
2159 package's internal use.
2163 The architectures we build on and build for are determined
2164 by <prgn>make</prgn> variables using the
2165 utility <prgn>dpkg-architecture</prgn>.
2166 You can determine the Debian architecture and the GNU style
2167 architecture specification string for the build architecture as
2168 well as for the host architecture. The build architecture is
2169 the architecture on which <file>debian/rules</file> is run and
2170 the package build is performed. The host architecture is the
2171 architecture on which the resulting package will be installed
2172 and run. These are normally the same, but may be different in
2173 the case of cross-compilation (building packages for one
2174 architecture on machines of a different architecture).
2178 Here is a list of supported <prgn>make</prgn> variables:
2179 <list compact="compact">
2181 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2184 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2187 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2190 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2191 specification string)
2194 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2195 <tt>DEB_*_GNU_TYPE</tt>)
2198 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2199 <tt>DEB_*_GNU_TYPE</tt>)
2201 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2202 the build architecture or <tt>HOST</tt> for specification of the
2207 Backward compatibility can be provided in the rules file
2208 by setting the needed variables to suitable default
2209 values; please refer to the documentation of
2210 <prgn>dpkg-architecture</prgn> for details.
2214 It is important to understand that the <tt>DEB_*_ARCH</tt>
2215 string only determines which Debian architecture we are
2216 building on or for. It should not be used to get the CPU
2217 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2218 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2219 GNU style variables should generally only be used with upstream
2223 <sect1 id="debianrules-options">
2224 <heading><file>debian/rules</file> and
2225 <tt>DEB_BUILD_OPTIONS</tt></heading>
2228 Supporting the standardized environment variable
2229 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2230 contain several flags to change how a package is compiled and
2231 built. Each flag must be in the form <var>flag</var> or
2232 <var>flag</var>=<var>options</var>. If multiple flags are
2233 given, they must be separated by whitespace.<footnote>
2234 Some packages support any delimiter, but whitespace is the
2235 easiest to parse inside a makefile and avoids ambiguity with
2236 flag values that contain commas.
2238 <var>flag</var> must start with a lowercase letter
2239 (<tt>a-z</tt>) and consist only of lowercase letters,
2240 numbers (<tt>0-9</tt>), and the characters
2241 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2242 <var>options</var> must not contain whitespace. The same
2243 tag should not be given multiple times with conflicting
2244 values. Package maintainers may assume that
2245 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2249 The meaning of the following tags has been standardized:
2253 This tag says to not run any build-time test suite
2254 provided by the package.
2258 The presence of this tag means that the package should
2259 be compiled with a minimum of optimization. For C
2260 programs, it is best to add <tt>-O0</tt> to
2261 <tt>CFLAGS</tt> (although this is usually the default).
2262 Some programs might fail to build or run at this level
2263 of optimization; it may be necessary to use
2264 <tt>-O1</tt>, for example.
2268 This tag means that the debugging symbols should not be
2269 stripped from the binary during installation, so that
2270 debugging information may be included in the package.
2272 <tag>parallel=n</tag>
2274 This tag means that the package should be built using up
2275 to <tt>n</tt> parallel processes if the package build
2276 system supports this.<footnote>
2277 Packages built with <tt>make</tt> can often implement
2278 this by passing the <tt>-j</tt><var>n</var> option to
2281 If the package build system does not support parallel
2282 builds, this string must be ignored. If the package
2283 build system only supports a lower level of concurrency
2284 than <var>n</var>, the package should be built using as
2285 many parallel processes as the package build system
2286 supports. It is up to the package maintainer to decide
2287 whether the package build times are long enough and the
2288 package build system is robust enough to make supporting
2289 parallel builds worthwhile.
2295 Unknown flags must be ignored by <file>debian/rules</file>.
2299 The following makefile snippet is an example of how one may
2300 implement the build options; you will probably have to
2301 massage this example in order to make it work for your
2303 <example compact="compact">
2306 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2307 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2308 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2309 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2311 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2316 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2317 INSTALL_PROGRAM += -s
2319 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2320 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2321 MAKEFLAGS += -j$(NUMJOBS)
2326 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2327 # Code to run the package test suite.
2334 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2335 <sect id="substvars">
2336 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2339 When <prgn>dpkg-gencontrol</prgn>
2340 generates <qref id="binarycontrolfiles">binary package control
2341 files</qref> (<file>DEBIAN/control</file>), it performs variable
2342 substitutions on its output just before writing it. Variable
2343 substitutions have the form <tt>${<var>variable</var>}</tt>.
2344 The optional file <file>debian/substvars</file> contains
2345 variable substitutions to be used; variables can also be set
2346 directly from <file>debian/rules</file> using the <tt>-V</tt>
2347 option to the source packaging commands, and certain predefined
2348 variables are also available.
2352 The <file>debian/substvars</file> file is usually generated and
2353 modified dynamically by <file>debian/rules</file> targets, in
2354 which case it must be removed by the <tt>clean</tt> target.
2358 See <manref name="deb-substvars" section="5"> for full
2359 details about source variable substitutions, including the
2360 format of <file>debian/substvars</file>.</p>
2363 <sect id="debianwatch">
2364 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2367 This is an optional, recommended configuration file for the
2368 <tt>uscan</tt> utility which defines how to automatically scan
2369 ftp or http sites for newly available updates of the
2370 package. This is used
2371 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2372 tools to help with quality control and maintenance of the
2373 distribution as a whole.
2378 <sect id="debianfiles">
2379 <heading>Generated files list: <file>debian/files</file></heading>
2382 This file is not a permanent part of the source tree; it
2383 is used while building packages to record which files are
2384 being generated. <prgn>dpkg-genchanges</prgn> uses it
2385 when it generates a <file>.changes</file> file.
2389 It should not exist in a shipped source package, and so it
2390 (and any backup files or temporary files such as
2391 <file>files.new</file><footnote>
2392 <file>files.new</file> is used as a temporary file by
2393 <prgn>dpkg-gencontrol</prgn> and
2394 <prgn>dpkg-distaddfile</prgn> - they write a new
2395 version of <tt>files</tt> here before renaming it,
2396 to avoid leaving a corrupted copy if an error
2398 </footnote>) should be removed by the
2399 <tt>clean</tt> target. It may also be wise to
2400 ensure a fresh start by emptying or removing it at the
2401 start of the <tt>binary</tt> target.
2405 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2406 package, it adds an entry to <file>debian/files</file> for the
2407 <file>.deb</file> file that will be created when <tt>dpkg-deb
2408 --build</tt> is run for that binary package. So for most
2409 packages all that needs to be done with this file is to
2410 delete it in the <tt>clean</tt> target.
2414 If a package upload includes files besides the source
2415 package and any binary packages whose control files were
2416 made with <prgn>dpkg-gencontrol</prgn> then they should be
2417 placed in the parent of the package's top-level directory
2418 and <prgn>dpkg-distaddfile</prgn> should be called to add
2419 the file to the list in <file>debian/files</file>.</p>
2422 <sect id="embeddedfiles">
2423 <heading>Convenience copies of code</heading>
2426 Some software packages include in their distribution convenience
2427 copies of code from other software packages, generally so that
2428 users compiling from source don't have to download multiple
2429 packages. Debian packages should not make use of these
2430 convenience copies unless the included package is explicitly
2431 intended to be used in this way.<footnote>
2432 For example, parts of the GNU build system work like this.
2434 If the included code is already in the Debian archive in the
2435 form of a library, the Debian packaging should ensure that
2436 binary packages reference the libraries already in Debian and
2437 the convenience copy is not used. If the included code is not
2438 already in Debian, it should be packaged separately as a
2439 prerequisite if possible.
2441 Having multiple copies of the same code in Debian is
2442 inefficient, often creates either static linking or shared
2443 library conflicts, and, most importantly, increases the
2444 difficulty of handling security vulnerabilities in the
2450 <sect id="readmesource">
2451 <heading>Source package handling:
2452 <file>debian/README.source</file></heading>
2455 If running <prgn>dpkg-source -x</prgn> on a source package
2456 doesn't produce the source of the package, ready for editing,
2457 and allow one to make changes and run
2458 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2459 without taking any additional steps, creating a
2460 <file>debian/README.source</file> documentation file is
2461 recommended. This file should explain how to do all of the
2464 <item>Generate the fully patched source, in a form ready for
2465 editing, that would be built to create Debian
2466 packages. Doing this with a <tt>patch</tt> target in
2467 <file>debian/rules</file> is recommended; see
2468 <ref id="debianrules">.</item>
2469 <item>Modify the source and save those modifications so that
2470 they will be applied when building the package.</item>
2471 <item>Remove source modifications that are currently being
2472 applied when building the package.</item>
2473 <item>Optionally, document what steps are necessary to
2474 upgrade the Debian source package to a new upstream version,
2475 if applicable.</item>
2477 This explanation should include specific commands and mention
2478 any additional required Debian packages. It should not assume
2479 familiarity with any specific Debian packaging system or patch
2484 This explanation may refer to a documentation file installed by
2485 one of the package's build dependencies provided that the
2486 referenced documentation clearly explains these tasks and is not
2487 a general reference manual.
2491 <file>debian/README.source</file> may also include any other
2492 information that would be helpful to someone modifying the
2493 source package. Even if the package doesn't fit the above
2494 description, maintainers are encouraged to document in a
2495 <file>debian/README.source</file> file any source package with a
2496 particularly complex or unintuitive source layout or build
2497 system (for example, a package that builds the same source
2498 multiple times to generate different binary packages).
2504 <chapt id="controlfields">
2505 <heading>Control files and their fields</heading>
2508 The package management system manipulates data represented in
2509 a common format, known as <em>control data</em>, stored in
2510 <em>control files</em>.
2511 Control files are used for source packages, binary packages and
2512 the <file>.changes</file> files which control the installation
2513 of uploaded files<footnote>
2514 <prgn>dpkg</prgn>'s internal databases are in a similar
2519 <sect id="controlsyntax">
2520 <heading>Syntax of control files</heading>
2523 A control file consists of one or more paragraphs of
2525 The paragraphs are also sometimes referred to as stanzas.
2527 The paragraphs are separated by empty lines. Parsers may accept
2528 lines consisting solely of spaces and tabs as paragraph
2529 separators, but control files should use empty lines. Some control
2530 files allow only one paragraph; others allow several, in
2531 which case each paragraph usually refers to a different
2532 package. (For example, in source packages, the first
2533 paragraph refers to the source package, and later paragraphs
2534 refer to binary packages generated from the source.) The
2535 ordering of the paragraphs in control files is significant.
2539 Each paragraph consists of a series of data fields. Each field
2540 consists of the field name followed by a colon and then the
2541 data/value associated with that field. The field name is
2542 composed of US-ASCII characters excluding control characters,
2543 space, and colon (i.e., characters in the ranges 33-57 and
2544 59-126, inclusive). Field names must not begin with the comment
2545 character, <tt>#</tt>.
2549 The field ends at the end of the line or at the end of the last
2550 continuation line (see below). Horizontal whitespace (spaces
2551 and tabs) may occur immediately before or after the value and is
2552 ignored there; it is conventional to put a single space after
2553 the colon. For example, a field might be:
2554 <example compact="compact">
2557 the field name is <tt>Package</tt> and the field value
2562 A paragraph must not contain more than one instance of a
2563 particular field name.
2567 There are three types of fields:
2571 The field, including its value, must be a single line. Folding
2572 of the field is not permitted. This is the default field type
2573 if the definition of the field does not specify a different
2578 The value of a folded field is a logical line that may span
2579 several lines. The lines after the first are called
2580 continuation lines and must start with a space or a tab.
2581 Whitespace, including any newlines, is not significant in the
2582 field values of folded fields.<footnote>
2583 This folding method is similar to RFC 5322, allowing control
2584 files that contain only one paragraph and no multiline fields
2585 to be read by parsers written for RFC 5322.
2588 <tag>multiline</tag>
2590 The value of a multiline field may comprise multiple continuation
2591 lines. The first line of the value, the part on the same line as
2592 the field name, often has special significance or may have to be
2593 empty. Other lines are added following the same syntax as the
2594 continuation lines of the folded fields. Whitespace, including newlines,
2595 is significant in the values of multiline fields.
2601 Whitespace must not appear
2602 inside names (of packages, architectures, files or anything
2603 else) or version numbers, or between the characters of
2604 multi-character version relationships.
2608 The presence and purpose of a field, and the syntax of its
2609 value may differ between types of control files.
2613 Field names are not case-sensitive, but it is usual to
2614 capitalize the field names using mixed case as shown below.
2615 Field values are case-sensitive unless the description of the
2616 field says otherwise.
2620 Paragraph separators (empty lines) and lines consisting only of
2621 spaces and tabs are not allowed within field values or between
2622 fields. Empty lines in field values are usually escaped by
2623 representing them by a space followed by a dot.
2627 Lines starting with # without any preceding whitespace are comments
2628 lines that are only permitted in source package control files
2629 (<file>debian/control</file>). These comment lines are ignored, even
2630 between two continuation lines. They do not end logical lines.
2634 All control files must be encoded in UTF-8.
2638 <sect id="sourcecontrolfiles">
2639 <heading>Source package control files -- <file>debian/control</file></heading>
2642 The <file>debian/control</file> file contains the most vital
2643 (and version-independent) information about the source package
2644 and about the binary packages it creates.
2648 The first paragraph of the control file contains information about
2649 the source package in general. The subsequent sets each describe a
2650 binary package that the source tree builds.
2654 The fields in the general paragraph (the first one, for the source
2657 <list compact="compact">
2658 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2660 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2661 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2662 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2663 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2664 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2665 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2666 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2671 The fields in the binary package paragraphs are:
2673 <list compact="compact">
2674 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2675 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2676 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2677 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2678 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2679 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2680 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2681 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2682 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2683 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2688 The syntax and semantics of the fields are described below.
2692 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2693 generate control files for binary packages (see below), by
2694 <prgn>dpkg-genchanges</prgn> to generate the
2695 <file>.changes</file> file to accompany the upload, and by
2696 <prgn>dpkg-source</prgn> when it creates the
2697 <file>.dsc</file> source control file as part of a source
2698 archive. Some fields are folded in <file>debian/control</file>,
2699 but not in any other control
2700 file. These tools are responsible for removing the line
2701 breaks from such fields when using fields from
2702 <file>debian/control</file> to generate other control files.
2706 The fields here may contain variable references - their
2707 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2708 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2709 when they generate output control files.
2710 See <ref id="substvars"> for details.
2714 <sect id="binarycontrolfiles">
2715 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2718 The <file>DEBIAN/control</file> file contains the most vital
2719 (and version-dependent) information about a binary package. It
2720 consists of a single paragraph.
2724 The fields in this file are:
2726 <list compact="compact">
2727 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2728 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2729 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2730 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2731 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2732 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2733 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2734 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2735 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2736 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2738 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2739 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2744 <sect id="debiansourcecontrolfiles">
2745 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2748 This file consists of a single paragraph, possibly surrounded by
2749 a PGP signature. The fields of that paragraph are listed below.
2750 Their syntax is described above, in <ref id="controlsyntax">.
2752 <list compact="compact">
2753 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2754 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2755 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2756 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2757 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2760 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2761 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2762 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2763 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2764 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2765 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2766 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2772 The Debian source control file is generated by
2773 <prgn>dpkg-source</prgn> when it builds the source
2774 archive, from other files in the source package,
2775 described above. When unpacking, it is checked against
2776 the files and directories in the other parts of the
2782 <sect id="debianchangesfiles">
2783 <heading>Debian changes files -- <file>.changes</file></heading>
2786 The <file>.changes</file> files are used by the Debian archive
2787 maintenance software to process updates to packages. They
2788 consist of a single paragraph, possibly surrounded by a PGP
2789 signature. That paragraph contains information from the
2790 <file>debian/control</file> file and other data about the
2791 source package gathered via <file>debian/changelog</file>
2792 and <file>debian/rules</file>.
2796 <file>.changes</file> files have a format version that is
2797 incremented whenever the documented fields or their meaning
2798 change. This document describes format &changesversion;.
2802 The fields in this file are:
2804 <list compact="compact">
2805 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2806 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2813 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2815 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2817 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2819 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2825 <sect id="controlfieldslist">
2826 <heading>List of fields</heading>
2828 <sect1 id="f-Source">
2829 <heading><tt>Source</tt></heading>
2832 This field identifies the source package name.
2836 In <file>debian/control</file> or a <file>.dsc</file> file,
2837 this field must contain only the name of the source package.
2841 In a binary package control file or a <file>.changes</file>
2842 file, the source package name may be followed by a version
2843 number in parentheses<footnote>
2844 It is customary to leave a space after the package name
2845 if a version number is specified.
2847 This version number may be omitted (and is, by
2848 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2849 the <tt>Version</tt> field of the binary package in
2850 question. The field itself may be omitted from a binary
2851 package control file when the source package has the same
2852 name and version as the binary package.
2856 Package names (both source and binary,
2857 see <ref id="f-Package">) must consist only of lower case
2858 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2859 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2860 (<tt>.</tt>). They must be at least two characters long and
2861 must start with an alphanumeric character.
2865 <sect1 id="f-Maintainer">
2866 <heading><tt>Maintainer</tt></heading>
2869 The package maintainer's name and email address. The name
2870 must come first, then the email address inside angle
2871 brackets <tt><></tt> (in RFC822 format).
2875 If the maintainer's name contains a full stop then the
2876 whole field will not work directly as an email address due
2877 to a misfeature in the syntax specified in RFC822; a
2878 program using this field as an address must check for this
2879 and correct the problem if necessary (for example by
2880 putting the name in round brackets and moving it to the
2881 end, and bringing the email address forward).
2885 See <ref id="maintainer"> for additional requirements and
2886 information about package maintainers.
2890 <sect1 id="f-Uploaders">
2891 <heading><tt>Uploaders</tt></heading>
2894 List of the names and email addresses of co-maintainers of the
2895 package, if any. If the package has other maintainers besides
2896 the one named in the <qref id="f-Maintainer">Maintainer
2897 field</qref>, their names and email addresses should be listed
2898 here. The format of each entry is the same as that of the
2899 Maintainer field, and multiple entries must be comma
2904 This is normally an optional field, but if
2905 the <tt>Maintainer</tt> control field names a group of people
2906 and a shared email address, the <tt>Uploaders</tt> field must
2907 be present and must contain at least one human with their
2908 personal email address.
2912 The Uploaders field in <file>debian/control</file> can be folded.
2916 <sect1 id="f-Changed-By">
2917 <heading><tt>Changed-By</tt></heading>
2920 The name and email address of the person who prepared this
2921 version of the package, usually a maintainer. The syntax is
2922 the same as for the <qref id="f-Maintainer">Maintainer
2927 <sect1 id="f-Section">
2928 <heading><tt>Section</tt></heading>
2931 This field specifies an application area into which the package
2932 has been classified. See <ref id="subsections">.
2936 When it appears in the <file>debian/control</file> file,
2937 it gives the value for the subfield of the same name in
2938 the <tt>Files</tt> field of the <file>.changes</file> file.
2939 It also gives the default for the same field in the binary
2944 <sect1 id="f-Priority">
2945 <heading><tt>Priority</tt></heading>
2948 This field represents how important it is that the user
2949 have the package installed. See <ref id="priorities">.
2953 When it appears in the <file>debian/control</file> file,
2954 it gives the value for the subfield of the same name in
2955 the <tt>Files</tt> field of the <file>.changes</file> file.
2956 It also gives the default for the same field in the binary
2961 <sect1 id="f-Package">
2962 <heading><tt>Package</tt></heading>
2965 The name of the binary package.
2969 Binary package names must follow the same syntax and
2970 restrictions as source package names. See <ref id="f-Source">
2975 <sect1 id="f-Architecture">
2976 <heading><tt>Architecture</tt></heading>
2979 Depending on context and the control file used, the
2980 <tt>Architecture</tt> field can include the following sets of
2984 A unique single word identifying a Debian machine
2985 architecture as described in <ref id="arch-spec">.
2988 An architecture wildcard identifying a set of Debian
2989 machine architectures, see <ref id="arch-wildcard-spec">.
2990 <tt>any</tt> matches all Debian machine architectures
2991 and is the most frequently used.
2994 <tt>all</tt>, which indicates an
2995 architecture-independent package.
2998 <tt>source</tt>, which indicates a source package.
3004 In the main <file>debian/control</file> file in the source
3005 package, this field may contain the special
3006 value <tt>all</tt>, the special architecture
3007 wildcard <tt>any</tt>, or a list of specific and wildcard
3008 architectures separated by spaces. If <tt>all</tt>
3009 or <tt>any</tt> appears, that value must be the entire
3010 contents of the field. Most packages will use
3011 either <tt>all</tt> or <tt>any</tt>.
3015 Specifying a specific list of architectures indicates that the
3016 source will build an architecture-dependent package only on
3017 architectures included in the list. Specifying a list of
3018 architecture wildcards indicates that the source will build an
3019 architecture-dependent package on only those architectures
3020 that match any of the specified architecture wildcards.
3021 Specifying a list of architectures or architecture wildcards
3022 other than <tt>any</tt> is for the minority of cases where a
3023 program is not portable or is not useful on some
3024 architectures. Where possible, the program should be made
3029 In the Debian source control file <file>.dsc</file>, this
3030 field contains a list of architectures and architecture
3031 wildcards separated by spaces. When the list contains the
3032 architecture wildcard <tt>any</tt>, the only other value
3033 allowed in the list is <tt>all</tt>.
3037 The list may include (or consist solely of) the special
3038 value <tt>all</tt>. In other words, in <file>.dsc</file>
3039 files unlike the <file>debian/control</file>, <tt>all</tt> may
3040 occur in combination with specific architectures.
3041 The <tt>Architecture</tt> field in the Debian source control
3042 file <file>.dsc</file> is generally constructed from
3043 the <tt>Architecture</tt> fields in
3044 the <file>debian/control</file> in the source package.
3048 Specifying only <tt>any</tt> indicates that the source package
3049 isn't dependent on any particular architecture and should
3050 compile fine on any one. The produced binary package(s)
3051 will be specific to whatever the current build architecture is.
3055 Specifying only <tt>all</tt> indicates that the source package
3056 will only build architecture-independent packages.
3060 Specifying <tt>any all</tt> indicates that the source package
3061 isn't dependent on any particular architecture. The set of
3062 produced binary packages will include at least one
3063 architecture-dependant package and one architecture-independent
3068 Specifying a list of architectures or architecture wildcards
3069 indicates that the source will build an architecture-dependent
3070 package, and will only work correctly on the listed or
3071 matching architectures. If the source package also builds at
3072 least one architecture-independent package, <tt>all</tt> will
3073 also be included in the list.
3077 In a <file>.changes</file> file, the <tt>Architecture</tt>
3078 field lists the architecture(s) of the package(s) currently
3079 being uploaded. This will be a list; if the source for the
3080 package is also being uploaded, the special
3081 entry <tt>source</tt> is also present. <tt>all</tt> will be
3082 present if any architecture-independent packages are being
3083 uploaded. Architecture wildcards such as <tt>any</tt> must
3084 never occur in the <tt>Architecture</tt> field in
3085 the <file>.changes</file> file.
3089 See <ref id="debianrules"> for information on how to get
3090 the architecture for the build process.
3094 <sect1 id="f-Essential">
3095 <heading><tt>Essential</tt></heading>
3098 This is a boolean field which may occur only in the
3099 control file of a binary package or in a per-package fields
3100 paragraph of a source package control file.
3104 If set to <tt>yes</tt> then the package management system
3105 will refuse to remove the package (upgrading and replacing
3106 it is still possible). The other possible value is <tt>no</tt>,
3107 which is the same as not having the field at all.
3112 <heading>Package interrelationship fields:
3113 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3114 <tt>Recommends</tt>, <tt>Suggests</tt>,
3115 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3116 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3120 These fields describe the package's relationships with
3121 other packages. Their syntax and semantics are described
3122 in <ref id="relationships">.</p>
3125 <sect1 id="f-Standards-Version">
3126 <heading><tt>Standards-Version</tt></heading>
3129 The most recent version of the standards (the policy
3130 manual and associated texts) with which the package
3135 The version number has four components: major and minor
3136 version number and major and minor patch level. When the
3137 standards change in a way that requires every package to
3138 change the major number will be changed. Significant
3139 changes that will require work in many packages will be
3140 signaled by a change to the minor number. The major patch
3141 level will be changed for any change to the meaning of the
3142 standards, however small; the minor patch level will be
3143 changed when only cosmetic, typographical or other edits
3144 are made which neither change the meaning of the document
3145 nor affect the contents of packages.
3149 Thus only the first three components of the policy version
3150 are significant in the <em>Standards-Version</em> control
3151 field, and so either these three components or all four
3152 components may be specified.<footnote>
3153 In the past, people specified the full version number
3154 in the Standards-Version field, for example "2.3.0.0".
3155 Since minor patch-level changes don't introduce new
3156 policy, it was thought it would be better to relax
3157 policy and only require the first 3 components to be
3158 specified, in this example "2.3.0". All four
3159 components may still be used if someone wishes to do so.
3165 <sect1 id="f-Version">
3166 <heading><tt>Version</tt></heading>
3169 The version number of a package. The format is:
3170 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3174 The three components here are:
3176 <tag><var>epoch</var></tag>
3179 This is a single (generally small) unsigned integer. It
3180 may be omitted, in which case zero is assumed. If it is
3181 omitted then the <var>upstream_version</var> may not
3186 It is provided to allow mistakes in the version numbers
3187 of older versions of a package, and also a package's
3188 previous version numbering schemes, to be left behind.
3192 <tag><var>upstream_version</var></tag>
3195 This is the main part of the version number. It is
3196 usually the version number of the original ("upstream")
3197 package from which the <file>.deb</file> file has been made,
3198 if this is applicable. Usually this will be in the same
3199 format as that specified by the upstream author(s);
3200 however, it may need to be reformatted to fit into the
3201 package management system's format and comparison
3206 The comparison behavior of the package management system
3207 with respect to the <var>upstream_version</var> is
3208 described below. The <var>upstream_version</var>
3209 portion of the version number is mandatory.
3213 The <var>upstream_version</var> may contain only
3214 alphanumerics<footnote>
3215 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3217 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3218 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3219 tilde) and should start with a digit. If there is no
3220 <var>debian_revision</var> then hyphens are not allowed;
3221 if there is no <var>epoch</var> then colons are not
3226 <tag><var>debian_revision</var></tag>
3229 This part of the version number specifies the version of
3230 the Debian package based on the upstream version. It
3231 may contain only alphanumerics and the characters
3232 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3233 tilde) and is compared in the same way as the
3234 <var>upstream_version</var> is.
3238 It is optional; if it isn't present then the
3239 <var>upstream_version</var> may not contain a hyphen.
3240 This format represents the case where a piece of
3241 software was written specifically to be a Debian
3242 package, where the Debian package source must always
3243 be identical to the pristine source and therefore no
3244 revision indication is required.
3248 It is conventional to restart the
3249 <var>debian_revision</var> at <tt>1</tt> each time the
3250 <var>upstream_version</var> is increased.
3254 The package management system will break the version
3255 number apart at the last hyphen in the string (if there
3256 is one) to determine the <var>upstream_version</var> and
3257 <var>debian_revision</var>. The absence of a
3258 <var>debian_revision</var> is equivalent to a
3259 <var>debian_revision</var> of <tt>0</tt>.
3266 When comparing two version numbers, first the <var>epoch</var>
3267 of each are compared, then the <var>upstream_version</var> if
3268 <var>epoch</var> is equal, and then <var>debian_revision</var>
3269 if <var>upstream_version</var> is also equal.
3270 <var>epoch</var> is compared numerically. The
3271 <var>upstream_version</var> and <var>debian_revision</var>
3272 parts are compared by the package management system using the
3273 following algorithm:
3277 The strings are compared from left to right.
3281 First the initial part of each string consisting entirely of
3282 non-digit characters is determined. These two parts (one of
3283 which may be empty) are compared lexically. If a difference
3284 is found it is returned. The lexical comparison is a
3285 comparison of ASCII values modified so that all the letters
3286 sort earlier than all the non-letters and so that a tilde
3287 sorts before anything, even the end of a part. For example,
3288 the following parts are in sorted order from earliest to
3289 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3290 <tt>a</tt>.<footnote>
3291 One common use of <tt>~</tt> is for upstream pre-releases.
3292 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3293 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3298 Then the initial part of the remainder of each string which
3299 consists entirely of digit characters is determined. The
3300 numerical values of these two parts are compared, and any
3301 difference found is returned as the result of the comparison.
3302 For these purposes an empty string (which can only occur at
3303 the end of one or both version strings being compared) counts
3308 These two steps (comparing and removing initial non-digit
3309 strings and initial digit strings) are repeated until a
3310 difference is found or both strings are exhausted.
3314 Note that the purpose of epochs is to allow us to leave behind
3315 mistakes in version numbering, and to cope with situations
3316 where the version numbering scheme changes. It is
3317 <em>not</em> intended to cope with version numbers containing
3318 strings of letters which the package management system cannot
3319 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3320 silly orderings.<footnote>
3321 The author of this manual has heard of a package whose
3322 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3323 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3329 <sect1 id="f-Description">
3330 <heading><tt>Description</tt></heading>
3333 In a source or binary control file, the <tt>Description</tt>
3334 field contains a description of the binary package, consisting
3335 of two parts, the synopsis or the short description, and the
3336 long description. It is a multiline field with the following
3342 Description: <single line synopsis>
3343 <extended description over several lines>
3348 The lines in the extended description can have these formats:
3354 Those starting with a single space are part of a paragraph.
3355 Successive lines of this form will be word-wrapped when
3356 displayed. The leading space will usually be stripped off.
3357 The line must contain at least one non-whitespace character.
3361 Those starting with two or more spaces. These will be
3362 displayed verbatim. If the display cannot be panned
3363 horizontally, the displaying program will line wrap them "hard"
3364 (i.e., without taking account of word breaks). If it can they
3365 will be allowed to trail off to the right. None, one or two
3366 initial spaces may be deleted, but the number of spaces
3367 deleted from each line will be the same (so that you can have
3368 indenting work correctly, for example). The line must
3369 contain at least one non-whitespace character.
3373 Those containing a single space followed by a single full stop
3374 character. These are rendered as blank lines. This is the
3375 <em>only</em> way to get a blank line<footnote>
3376 Completely empty lines will not be rendered as blank lines.
3377 Instead, they will cause the parser to think you're starting
3378 a whole new record in the control file, and will therefore
3379 likely abort with an error.
3384 Those containing a space, a full stop and some more characters.
3385 These are for future expansion. Do not use them.
3391 Do not use tab characters. Their effect is not predictable.
3395 See <ref id="descriptions"> for further information on this.
3399 In a <file>.changes</file> file, the <tt>Description</tt>
3400 field contains a summary of the descriptions for the packages
3401 being uploaded. For this case, the first line of the field
3402 value (the part on the same line as <tt>Description:</tt>) is
3403 always empty. It is a multiline field, with one
3404 line per package. Each line is
3405 indented by one space and contains the name of a binary
3406 package, a space, a hyphen (<tt>-</tt>), a space, and the
3407 short description line from that package.
3411 <sect1 id="f-Distribution">
3412 <heading><tt>Distribution</tt></heading>
3415 In a <file>.changes</file> file or parsed changelog output
3416 this contains the (space-separated) name(s) of the
3417 distribution(s) where this version of the package should
3418 be installed. Valid distributions are determined by the
3419 archive maintainers.<footnote>
3420 Example distribution names in the Debian archive used in
3421 <file>.changes</file> files are:
3422 <taglist compact="compact">
3423 <tag><em>unstable</em></tag>
3425 This distribution value refers to the
3426 <em>developmental</em> part of the Debian distribution
3427 tree. Most new packages, new upstream versions of
3428 packages and bug fixes go into the <em>unstable</em>
3432 <tag><em>experimental</em></tag>
3434 The packages with this distribution value are deemed
3435 by their maintainers to be high risk. Oftentimes they
3436 represent early beta or developmental packages from
3437 various sources that the maintainers want people to
3438 try, but are not ready to be a part of the other parts
3439 of the Debian distribution tree.
3444 Others are used for updating stable releases or for
3445 security uploads. More information is available in the
3446 Debian Developer's Reference, section "The Debian
3450 The Debian archive software only supports listing a single
3451 distribution. Migration of packages to other distributions is
3452 handled outside of the upload process.
3457 <heading><tt>Date</tt></heading>
3460 This field includes the date the package was built or last
3461 edited. It must be in the same format as the <var>date</var>
3462 in a <file>debian/changelog</file> entry.
3466 The value of this field is usually extracted from the
3467 <file>debian/changelog</file> file - see
3468 <ref id="dpkgchangelog">).
3472 <sect1 id="f-Format">
3473 <heading><tt>Format</tt></heading>
3476 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3477 files, this field declares the format version of that file.
3478 The syntax of the field value is the same as that of
3479 a <qref id="f-Version">package version number</qref> except
3480 that no epoch or Debian revision is allowed. The format
3481 described in this document is <tt>&changesversion;</tt>.
3485 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3486 Debian source control</qref> files, this field declares the
3487 format of the source package. The field value is used by
3488 programs acting on a source package to interpret the list of
3489 files in the source package and determine how to unpack it.
3490 The syntax of the field value is a numeric major revision, a
3491 period, a numeric minor revision, and then an optional subtype
3492 after whitespace, which if specified is an alphanumeric word
3493 in parentheses. The subtype is optional in the syntax but may
3494 be mandatory for particular source format revisions.
3496 The source formats currently supported by the Debian archive
3497 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3498 and <tt>3.0 (quilt)</tt>.
3503 <sect1 id="f-Urgency">
3504 <heading><tt>Urgency</tt></heading>
3507 This is a description of how important it is to upgrade to
3508 this version from previous ones. It consists of a single
3509 keyword taking one of the values <tt>low</tt>,
3510 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3511 <tt>critical</tt><footnote>
3512 Other urgency values are supported with configuration
3513 changes in the archive software but are not used in Debian.
3514 The urgency affects how quickly a package will be considered
3515 for inclusion into the <tt>testing</tt> distribution and
3516 gives an indication of the importance of any fixes included
3517 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3518 treated as synonymous.
3519 </footnote> (not case-sensitive) followed by an optional
3520 commentary (separated by a space) which is usually in
3521 parentheses. For example:
3524 Urgency: low (HIGH for users of diversions)
3530 The value of this field is usually extracted from the
3531 <file>debian/changelog</file> file - see
3532 <ref id="dpkgchangelog">.
3536 <sect1 id="f-Changes">
3537 <heading><tt>Changes</tt></heading>
3540 This multiline field contains the human-readable changes data, describing
3541 the differences between the last version and the current one.
3545 The first line of the field value (the part on the same line
3546 as <tt>Changes:</tt>) is always empty. The content of the
3547 field is expressed as continuation lines, with each line
3548 indented by at least one space. Blank lines must be
3549 represented by a line consisting only of a space and a full
3554 The value of this field is usually extracted from the
3555 <file>debian/changelog</file> file - see
3556 <ref id="dpkgchangelog">).
3560 Each version's change information should be preceded by a
3561 "title" line giving at least the version, distribution(s)
3562 and urgency, in a human-readable way.
3566 If data from several versions is being returned the entry
3567 for the most recent version should be returned first, and
3568 entries should be separated by the representation of a
3569 blank line (the "title" line may also be followed by the
3570 representation of a blank line).
3574 <sect1 id="f-Binary">
3575 <heading><tt>Binary</tt></heading>
3578 This folded field is a list of binary packages. Its syntax and
3579 meaning varies depending on the control file in which it
3584 When it appears in the <file>.dsc</file> file, it lists binary
3585 packages which a source package can produce, separated by
3587 A space after each comma is conventional.
3588 </footnote>. The source package
3589 does not necessarily produce all of these binary packages for
3590 every architecture. The source control file doesn't contain
3591 details of which architectures are appropriate for which of
3592 the binary packages.
3596 When it appears in a <file>.changes</file> file, it lists the
3597 names of the binary packages being uploaded, separated by
3598 whitespace (not commas).
3602 <sect1 id="f-Installed-Size">
3603 <heading><tt>Installed-Size</tt></heading>
3606 This field appears in the control files of binary packages,
3607 and in the <file>Packages</file> files. It gives an estimate
3608 of the total amount of disk space required to install the
3609 named package. Actual installed size may vary based on block
3610 size, file system properties, or actions taken by package
3615 The disk space is given as the integer value of the estimated
3616 installed size in bytes, divided by 1024 and rounded up.
3620 <sect1 id="f-Files">
3621 <heading><tt>Files</tt></heading>
3624 This field contains a list of files with information about
3625 each one. The exact information and syntax varies with
3630 In all cases, Files is a multiline field. The first line of
3631 the field value (the part on the same line as <tt>Files:</tt>)
3632 is always empty. The content of the field is expressed as
3633 continuation lines, one line per file. Each line must be
3634 indented by one space and contain a number of sub-fields,
3635 separated by spaces, as described below.
3639 In the <file>.dsc</file> file, each line contains the MD5
3640 checksum, size and filename of the tar file and (if
3641 applicable) diff file which make up the remainder of the
3642 source package<footnote>
3643 That is, the parts which are not the <tt>.dsc</tt>.
3644 </footnote>. For example:
3647 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3648 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3650 The exact forms of the filenames are described
3651 in <ref id="pkg-sourcearchives">.
3655 In the <file>.changes</file> file this contains one line per
3656 file being uploaded. Each line contains the MD5 checksum,
3657 size, section and priority and the filename. For example:
3660 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3661 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3662 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3663 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3665 The <qref id="f-Section">section</qref>
3666 and <qref id="f-Priority">priority</qref> are the values of
3667 the corresponding fields in the main source control file. If
3668 no section or priority is specified then <tt>-</tt> should be
3669 used, though section and priority values must be specified for
3670 new packages to be installed properly.
3674 The special value <tt>byhand</tt> for the section in a
3675 <tt>.changes</tt> file indicates that the file in question
3676 is not an ordinary package file and must by installed by
3677 hand by the distribution maintainers. If the section is
3678 <tt>byhand</tt> the priority should be <tt>-</tt>.
3682 If a new Debian revision of a package is being shipped and
3683 no new original source archive is being distributed the
3684 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3685 entry for the original source archive
3686 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3687 but the <file>.changes</file> file should leave it out. In
3688 this case the original source archive on the distribution
3689 site must match exactly, byte-for-byte, the original
3690 source archive which was used to generate the
3691 <file>.dsc</file> file and diff which are being uploaded.</p>
3694 <sect1 id="f-Closes">
3695 <heading><tt>Closes</tt></heading>
3698 A space-separated list of bug report numbers that the upload
3699 governed by the .changes file closes.
3703 <sect1 id="f-Homepage">
3704 <heading><tt>Homepage</tt></heading>
3707 The URL of the web site for this package, preferably (when
3708 applicable) the site from which the original source can be
3709 obtained and any additional upstream documentation or
3710 information may be found. The content of this field is a
3711 simple URL without any surrounding characters such as
3716 <sect1 id="f-Checksums">
3717 <heading><tt>Checksums-Sha1</tt>
3718 and <tt>Checksums-Sha256</tt></heading>
3721 These multiline fields contain a list of files with a checksum and size
3722 for each one. Both <tt>Checksums-Sha1</tt>
3723 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3724 only in the checksum algorithm used: SHA-1
3725 for <tt>Checksums-Sha1</tt> and SHA-256
3726 for <tt>Checksums-Sha256</tt>.
3730 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3731 multiline fields. The first line of the field value (the part
3732 on the same line as <tt>Checksums-Sha1:</tt>
3733 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3734 of the field is expressed as continuation lines, one line per
3735 file. Each line consists of the checksum, a space, the file
3736 size, a space, and the file name. For example (from
3737 a <file>.changes</file> file):
3740 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3741 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3742 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3743 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3745 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3746 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3747 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3748 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3753 In the <file>.dsc</file> file, these fields list all
3754 files that make up the source package. In
3755 the <file>.changes</file> file, these fields list all
3756 files being uploaded. The list of files in these fields
3757 must match the list of files in the <tt>Files</tt> field.
3762 <heading><tt>DM-Upload-Allowed</tt></heading>
3765 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3769 <sect1 id="f-VCS-fields">
3770 <heading>Version Control System (VCS) fields</heading>
3773 Debian source packages are increasingly developed using VCSs. The
3774 purpose of the following fields is to indicate a publicly accessible
3775 repository where the Debian source package is developed.
3778 <tag><tt>Vcs-Browser</tt></tag>
3781 URL of a web interface for browsing the repository.
3786 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3787 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3788 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3793 The field name identifies the VCS. The field's value uses the
3794 version control system's conventional syntax for describing
3795 repository locations and should be sufficient to locate the
3796 repository used for packaging. Ideally, it also locates the
3797 branch used for development of new versions of the Debian
3801 In the case of Git, the value consists of a URL, optionally
3802 followed by the word <tt>-b</tt> and the name of a branch in
3803 the indicated repository, following the syntax of the
3804 <tt>git clone</tt> command. If no branch is specified, the
3805 packaging should be on the default branch.
3808 More than one different VCS may be specified for the same
3816 <sect1 id="f-Package-List">
3817 <heading><tt>Package-List</tt></heading>
3820 Multiline field listing all the packages that can be built from
3821 the source package, considering every architecture. The first line
3822 of the field value is empty. Each one of the next lines describes
3823 one binary package, by listing its name, type, section and priority
3824 separated by spaces. Fifth and subsequent space-separated items
3825 may be present and parsers must allow them. See the
3826 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3831 <sect1 id="f-Package-Type">
3832 <heading><tt>Package-Type</tt></heading>
3835 Simple field containing a word indicating the type of package:
3836 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3837 packages. Other types not defined here may be indicated. In
3838 source package control files, the <tt>Package-Type</tt> field
3839 should be omitted instead of giving it a value of <tt>deb</tt>, as
3840 this value is assumed for paragraphs lacking this field.
3846 <heading>User-defined fields</heading>
3849 Additional user-defined fields may be added to the
3850 source package control file. Such fields will be
3851 ignored, and not copied to (for example) binary or
3852 Debian source control files or upload control files.
3856 If you wish to add additional unsupported fields to
3857 these output files you should use the mechanism
3862 Fields in the main source control information file with
3863 names starting <tt>X</tt>, followed by one or more of
3864 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3865 be copied to the output files. Only the part of the
3866 field name after the hyphen will be used in the output
3867 file. Where the letter <tt>B</tt> is used the field
3868 will appear in binary package control files, where the
3869 letter <tt>S</tt> is used in Debian source control
3870 files and where <tt>C</tt> is used in upload control
3871 (<tt>.changes</tt>) files.
3875 For example, if the main source information control file
3878 XBS-Comment: I stand between the candle and the star.
3880 then the binary and Debian source control files will contain the
3883 Comment: I stand between the candle and the star.
3889 <sect id="obsolete-control-data-fields">
3890 <heading>Obsolete fields</heading>
3893 The following fields have been obsoleted and may be found in packages
3894 conforming with previous versions of the Policy.
3897 <sect1 id="f-DM-Upload-Allowed">
3898 <heading><tt>DM-Upload-Allowed</tt></heading>
3901 Indicates that Debian Maintainers may upload this package to
3902 the Debian archive. The only valid value is <tt>yes</tt>. This
3903 field was used to regulate uploads by Debian Maintainers, See the
3904 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3905 name="Endorse the concept of Debian Maintainers"> for more details.
3914 <chapt id="maintainerscripts">
3915 <heading>Package maintainer scripts and installation procedure</heading>
3918 <heading>Introduction to package maintainer scripts</heading>
3921 It is possible to supply scripts as part of a package which
3922 the package management system will run for you when your
3923 package is installed, upgraded or removed.
3927 These scripts are the control information
3928 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3929 and <prgn>postrm</prgn>. They must be proper executable files;
3930 if they are scripts (which is recommended), they must start with
3931 the usual <tt>#!</tt> convention. They should be readable and
3932 executable by anyone, and must not be world-writable.
3936 The package management system looks at the exit status from
3937 these scripts. It is important that they exit with a
3938 non-zero status if there is an error, so that the package
3939 management system can stop its processing. For shell
3940 scripts this means that you <em>almost always</em> need to
3941 use <tt>set -e</tt> (this is usually true when writing shell
3942 scripts, in fact). It is also important, of course, that
3943 they exit with a zero status if everything went well.
3947 Additionally, packages interacting with users
3948 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3949 should install a <prgn>config</prgn> script as a control
3950 information file. See <ref id="maintscriptprompt"> for details.
3954 When a package is upgraded a combination of the scripts from
3955 the old and new packages is called during the upgrade
3956 procedure. If your scripts are going to be at all
3957 complicated you need to be aware of this, and may need to
3958 check the arguments to your scripts.
3962 Broadly speaking the <prgn>preinst</prgn> is called before
3963 (a particular version of) a package is unpacked, and the
3964 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3965 before (a version of) a package is removed and the
3966 <prgn>postrm</prgn> afterwards.
3970 Programs called from maintainer scripts should not normally
3971 have a path prepended to them. Before installation is
3972 started, the package management system checks to see if the
3973 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3974 and <prgn>update-rc.d</prgn> can be found via the
3975 <tt>PATH</tt> environment variable. Those programs, and any
3976 other program that one would expect to be in the
3977 <tt>PATH</tt>, should thus be invoked without an absolute
3978 pathname. Maintainer scripts should also not reset the
3979 <tt>PATH</tt>, though they might choose to modify it by
3980 prepending or appending package-specific directories. These
3981 considerations really apply to all shell scripts.</p>
3984 <sect id="idempotency">
3985 <heading>Maintainer scripts idempotency</heading>
3988 It is necessary for the error recovery procedures that the
3989 scripts be idempotent. This means that if it is run
3990 successfully, and then it is called again, it doesn't bomb
3991 out or cause any harm, but just ensures that everything is
3992 the way it ought to be. If the first call failed, or
3993 aborted half way through for some reason, the second call
3994 should merely do the things that were left undone the first
3995 time, if any, and exit with a success status if everything
3997 This is so that if an error occurs, the user interrupts
3998 <prgn>dpkg</prgn> or some other unforeseen circumstance
3999 happens you don't leave the user with a badly-broken
4000 package when <prgn>dpkg</prgn> attempts to repeat the
4006 <sect id="controllingterminal">
4007 <heading>Controlling terminal for maintainer scripts</heading>
4010 Maintainer scripts are not guaranteed to run with a controlling
4011 terminal and may not be able to interact with the user. They
4012 must be able to fall back to noninteractive behavior if no
4013 controlling terminal is available. Maintainer scripts that
4014 prompt via a program conforming to the Debian Configuration
4015 Management Specification (see <ref id="maintscriptprompt">) may
4016 assume that program will handle falling back to noninteractive
4021 For high-priority prompts without a reasonable default answer,
4022 maintainer scripts may abort if there is no controlling
4023 terminal. However, this situation should be avoided if at all
4024 possible, since it prevents automated or unattended installs.
4025 In most cases, users will consider this to be a bug in the
4030 <sect id="exitstatus">
4031 <heading>Exit status</heading>
4034 Each script must return a zero exit status for
4035 success, or a nonzero one for failure, since the package
4036 management system looks for the exit status of these scripts
4037 and determines what action to take next based on that datum.
4041 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4046 What follows is a summary of all the ways in which maintainer
4047 scripts may be called along with what facilities those scripts
4048 may rely on being available at that time. Script names preceded
4049 by <var>new-</var> are the scripts from the new version of a
4050 package being installed, upgraded to, or downgraded to. Script
4051 names preceded by <var>old-</var> are the scripts from the old
4052 version of a package that is being upgraded from or downgraded
4057 The <prgn>preinst</prgn> script may be called in the following
4060 <tag><var>new-preinst</var> <tt>install</tt></tag>
4061 <tag><var>new-preinst</var> <tt>install</tt>
4062 <var>old-version</var></tag>
4063 <tag><var>new-preinst</var> <tt>upgrade</tt>
4064 <var>old-version</var></tag>
4066 The package will not yet be unpacked, so
4067 the <prgn>preinst</prgn> script cannot rely on any files
4068 included in its package. Only essential packages and
4069 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4070 available. Pre-dependencies will have been configured at
4071 least once, but at the time the <prgn>preinst</prgn> is
4072 called they may only be in an unpacked or "Half-Configured"
4073 state if a previous version of the pre-dependency was
4074 completely configured and has not been removed since then.
4077 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4078 <var>new-version</var></tag>
4080 Called during error handling of an upgrade that failed after
4081 unpacking the new package because the <tt>postrm
4082 upgrade</tt> action failed. The unpacked files may be
4083 partly from the new version or partly missing, so the script
4084 cannot rely on files included in the package. Package
4085 dependencies may not be available. Pre-dependencies will be
4086 at least unpacked following the same rules as above, except
4087 they may be only "Half-Installed" if an upgrade of the
4088 pre-dependency failed.<footnote>
4089 This can happen if the new version of the package no
4090 longer pre-depends on a package that had been partially
4098 The <prgn>postinst</prgn> script may be called in the following
4101 <tag><var>postinst</var> <tt>configure</tt>
4102 <var>most-recently-configured-version</var></tag>
4104 The files contained in the package will be unpacked. All
4105 package dependencies will at least be unpacked. If there
4106 are no circular dependencies involved, all package
4107 dependencies will be configured. For behavior in the case
4108 of circular dependencies, see the discussion
4109 in <ref id="binarydeps">.
4112 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4113 <var>new-version</var></tag>
4114 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4115 <tt>in-favour</tt> <var>package</var>
4116 <var>new-version</var></tag>
4117 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4118 <tag><var>deconfigured's-postinst</var>
4119 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4120 <var>failed-install-package</var> <var>version</var>
4121 [<tt>removing</tt> <var>conflicting-package</var>
4122 <var>version</var>]</tag>
4124 The files contained in the package will be unpacked. All
4125 package dependencies will at least be "Half-Installed" and
4126 will have previously been configured and not removed.
4127 However, dependencies may not be configured or even fully
4128 unpacked in some error situations.<footnote>
4129 For example, suppose packages foo and bar are installed
4130 with foo depending on bar. If an upgrade of bar were
4131 started and then aborted, and then an attempt to remove
4132 foo failed because its <prgn>prerm</prgn> script failed,
4133 foo's <tt>postinst abort-remove</tt> would be called with
4134 bar only "Half-Installed".
4136 The <prgn>postinst</prgn> should still attempt any actions
4137 for which its dependencies are required, since they will
4138 normally be available, but consider the correct error
4139 handling approach if those actions fail. Aborting
4140 the <prgn>postinst</prgn> action if commands or facilities
4141 from the package dependencies are not available is often the
4148 The <prgn>prerm</prgn> script may be called in the following
4151 <tag><var>prerm</var> <tt>remove</tt></tag>
4152 <tag><var>old-prerm</var>
4153 <tt>upgrade</tt><var>new-version</var></tag>
4154 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4155 <tt>in-favour</tt> <var>package</var>
4156 <var>new-version</var></tag>
4157 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4158 <tt>in-favour</tt> <var>package-being-installed</var>
4159 <var>version</var> [<tt>removing</tt>
4160 <var>conflicting-package</var> <var>version</var>]</tag>
4162 The package whose <prgn>prerm</prgn> is being called will be
4163 at least "Half-Installed". All package dependencies will at
4164 least be "Half-Installed" and will have previously been
4165 configured and not removed. If there was no error, all
4166 dependencies will at least be unpacked, but these actions
4167 may be called in various error states where dependencies are
4168 only "Half-Installed" due to a partial upgrade.
4171 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4172 <var>old-version</var></tag>
4174 Called during error handling when <tt>prerm upgrade</tt>
4175 fails. The new package will not yet be unpacked, and all
4176 the same constraints as for <tt>preinst upgrade</tt> apply.
4182 The <prgn>postrm</prgn> script may be called in the following
4185 <tag><var>postrm</var> <tt>remove</tt></tag>
4186 <tag><var>postrm</var> <tt>purge</tt></tag>
4187 <tag><var>old-postrm</var> <tt>upgrade</tt>
4188 <var>new-version</var></tag>
4189 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4190 <var>overwriter</var> <var>overwriter-version</var></tag>
4192 The <prgn>postrm</prgn> script is called after the package's
4193 files have been removed or replaced. The package
4194 whose <prgn>postrm</prgn> is being called may have
4195 previously been deconfigured and only be unpacked, at which
4196 point subsequent package changes do not consider its
4197 dependencies. Therefore, all <prgn>postrm</prgn> actions
4198 may only rely on essential packages and must gracefully skip
4199 any actions that require the package's dependencies if those
4200 dependencies are unavailable.<footnote>
4201 This is often done by checking whether the command or
4202 facility the <prgn>postrm</prgn> intends to call is
4203 available before calling it. For example:
4205 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4206 . /usr/share/debconf/confmodule
4210 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4211 configuration for the package
4212 if <package>debconf</package> is installed.
4216 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4217 <var>old-version</var></tag>
4219 Called when the old <tt>postrm upgrade</tt> action fails.
4220 The new package will be unpacked, but only essential
4221 packages and pre-dependencies can be relied on.
4222 Pre-dependencies will either be configured or will be
4223 "Unpacked" or "Half-Configured" but previously had been
4224 configured and was never removed.
4227 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4228 <tag><var>new-postrm</var> <tt>abort-install</tt>
4229 <var>old-version</var></tag>
4230 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4231 <var>old-version</var></tag>
4233 Called before unpacking the new package as part of the
4234 error handling of <prgn>preinst</prgn> failures. May assume
4235 the same state as <prgn>preinst</prgn> can assume.
4241 <sect id="unpackphase">
4242 <heading>Details of unpack phase of installation or upgrade</heading>
4245 The procedure on installation/upgrade/overwrite/disappear
4246 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4247 stage of <tt>dpkg --install</tt>) is as follows. In each
4248 case, if a major error occurs (unless listed below) the
4249 actions are, in general, run backwards - this means that the
4250 maintainer scripts are run with different arguments in
4251 reverse order. These are the "error unwind" calls listed
4258 If a version of the package is already installed, call
4259 <example compact="compact">
4260 <var>old-prerm</var> upgrade <var>new-version</var>
4264 If the script runs but exits with a non-zero
4265 exit status, <prgn>dpkg</prgn> will attempt:
4266 <example compact="compact">
4267 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4269 If this works, the upgrade continues. If this
4270 does not work, the error unwind:
4271 <example compact="compact">
4272 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4274 If this works, then the old-version is
4275 "Installed", if not, the old version is in a
4276 "Half-Configured" state.
4282 If a "conflicting" package is being removed at the same time,
4283 or if any package will be broken (due to <tt>Breaks</tt>):
4286 If <tt>--auto-deconfigure</tt> is
4287 specified, call, for each package to be deconfigured
4288 due to <tt>Breaks</tt>:
4289 <example compact="compact">
4290 <var>deconfigured's-prerm</var> deconfigure \
4291 in-favour <var>package-being-installed</var> <var>version</var>
4294 <example compact="compact">
4295 <var>deconfigured's-postinst</var> abort-deconfigure \
4296 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4298 The deconfigured packages are marked as
4299 requiring configuration, so that if
4300 <tt>--install</tt> is used they will be
4301 configured again if possible.
4304 If any packages depended on a conflicting
4305 package being removed and <tt>--auto-deconfigure</tt> is
4306 specified, call, for each such package:
4307 <example compact="compact">
4308 <var>deconfigured's-prerm</var> deconfigure \
4309 in-favour <var>package-being-installed</var> <var>version</var> \
4310 removing <var>conflicting-package</var> <var>version</var>
4313 <example compact="compact">
4314 <var>deconfigured's-postinst</var> abort-deconfigure \
4315 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4316 removing <var>conflicting-package</var> <var>version</var>
4318 The deconfigured packages are marked as
4319 requiring configuration, so that if
4320 <tt>--install</tt> is used they will be
4321 configured again if possible.
4324 To prepare for removal of each conflicting package, call:
4325 <example compact="compact">
4326 <var>conflictor's-prerm</var> remove \
4327 in-favour <var>package</var> <var>new-version</var>
4330 <example compact="compact">
4331 <var>conflictor's-postinst</var> abort-remove \
4332 in-favour <var>package</var> <var>new-version</var>
4341 If the package is being upgraded, call:
4342 <example compact="compact">
4343 <var>new-preinst</var> upgrade <var>old-version</var>
4345 If this fails, we call:
4347 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4354 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4356 is called. If this works, then the old version
4357 is in an "Installed" state, or else it is left
4358 in an "Unpacked" state.
4363 If it fails, then the old version is left
4364 in an "Half-Installed" state.
4371 Otherwise, if the package had some configuration
4372 files from a previous version installed (i.e., it
4373 is in the "Config-Files" state):
4374 <example compact="compact">
4375 <var>new-preinst</var> install <var>old-version</var>
4379 <var>new-postrm</var> abort-install <var>old-version</var>
4381 If this fails, the package is left in a
4382 "Half-Installed" state, which requires a
4383 reinstall. If it works, the packages is left in
4384 a "Config-Files" state.
4387 Otherwise (i.e., the package was completely purged):
4388 <example compact="compact">
4389 <var>new-preinst</var> install
4392 <example compact="compact">
4393 <var>new-postrm</var> abort-install
4395 If the error-unwind fails, the package is in a
4396 "Half-Installed" phase, and requires a
4397 reinstall. If the error unwind works, the
4398 package is in the "Not-Installed" state.
4405 The new package's files are unpacked, overwriting any
4406 that may be on the system already, for example any
4407 from the old version of the same package or from
4408 another package. Backups of the old files are kept
4409 temporarily, and if anything goes wrong the package
4410 management system will attempt to put them back as
4411 part of the error unwind.
4415 It is an error for a package to contain files which
4416 are on the system in another package, unless
4417 <tt>Replaces</tt> is used (see <ref id="replaces">).
4419 The following paragraph is not currently the case:
4420 Currently the <tt>- - force-overwrite</tt> flag is
4421 enabled, downgrading it to a warning, but this may not
4427 It is a more serious error for a package to contain a
4428 plain file or other kind of non-directory where another
4429 package has a directory (again, unless
4430 <tt>Replaces</tt> is used). This error can be
4431 overridden if desired using
4432 <tt>--force-overwrite-dir</tt>, but this is not
4437 Packages which overwrite each other's files produce
4438 behavior which, though deterministic, is hard for the
4439 system administrator to understand. It can easily
4440 lead to "missing" programs if, for example, a package
4441 is unpacked which overwrites a file from another
4442 package, and is then removed again.<footnote>
4443 Part of the problem is due to what is arguably a
4444 bug in <prgn>dpkg</prgn>.
4449 A directory will never be replaced by a symbolic link
4450 to a directory or vice versa; instead, the existing
4451 state (symlink or not) will be left alone and
4452 <prgn>dpkg</prgn> will follow the symlink if there is
4461 If the package is being upgraded, call
4462 <example compact="compact">
4463 <var>old-postrm</var> upgrade <var>new-version</var>
4467 If this fails, <prgn>dpkg</prgn> will attempt:
4468 <example compact="compact">
4469 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4471 If this works, installation continues. If not,
4473 <example compact="compact">
4474 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4476 If this fails, the old version is left in a
4477 "Half-Installed" state. If it works, dpkg now
4479 <example compact="compact">
4480 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4482 If this fails, the old version is left in a
4483 "Half-Installed" state. If it works, dpkg now
4485 <example compact="compact">
4486 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4488 If this fails, the old version is in an
4495 This is the point of no return - if
4496 <prgn>dpkg</prgn> gets this far, it won't back off
4497 past this point if an error occurs. This will
4498 leave the package in a fairly bad state, which
4499 will require a successful re-installation to clear
4500 up, but it's when <prgn>dpkg</prgn> starts doing
4501 things that are irreversible.
4506 Any files which were in the old version of the package
4507 but not in the new are removed.
4511 The new file list replaces the old.
4515 The new maintainer scripts replace the old.
4519 Any packages all of whose files have been overwritten
4520 during the installation, and which aren't required for
4521 dependencies, are considered to have been removed.
4522 For each such package
4525 <prgn>dpkg</prgn> calls:
4526 <example compact="compact">
4527 <var>disappearer's-postrm</var> disappear \
4528 <var>overwriter</var> <var>overwriter-version</var>
4532 The package's maintainer scripts are removed.
4535 It is noted in the status database as being in a
4536 sane state, namely "Not-Installed" (any conffiles
4537 it may have are ignored, rather than being
4538 removed by <prgn>dpkg</prgn>). Note that
4539 disappearing packages do not have their prerm
4540 called, because <prgn>dpkg</prgn> doesn't know
4541 in advance that the package is going to
4548 Any files in the package we're unpacking that are also
4549 listed in the file lists of other packages are removed
4550 from those lists. (This will lobotomize the file list
4551 of the "conflicting" package if there is one.)
4555 The backup files made during installation, above, are
4561 The new package's status is now sane, and recorded as
4566 Here is another point of no return - if the
4567 conflicting package's removal fails we do not unwind
4568 the rest of the installation; the conflicting package
4569 is left in a half-removed limbo.
4574 If there was a conflicting package we go and do the
4575 removal actions (described below), starting with the
4576 removal of the conflicting package's files (any that
4577 are also in the package being unpacked have already
4578 been removed from the conflicting package's file list,
4579 and so do not get removed now).
4585 <sect id="configdetails"><heading>Details of configuration</heading>
4588 When we configure a package (this happens with <tt>dpkg
4589 --install</tt> and <tt>dpkg --configure</tt>), we first
4590 update any <tt>conffile</tt>s and then call:
4591 <example compact="compact">
4592 <var>postinst</var> configure <var>most-recently-configured-version</var>
4597 No attempt is made to unwind after errors during
4598 configuration. If the configuration fails, the package is in
4599 a "Half-Configured" state, and an error message is generated.
4603 If there is no most recently configured version
4604 <prgn>dpkg</prgn> will pass a null argument.
4607 Historical note: Truly ancient (pre-1997) versions of
4608 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4609 (including the angle brackets) in this case. Even older
4610 ones did not pass a second argument at all, under any
4611 circumstance. Note that upgrades using such an old dpkg
4612 version are unlikely to work for other reasons, even if
4613 this old argument behavior is handled by your postinst script.
4619 <sect id="removedetails"><heading>Details of removal and/or
4620 configuration purging</heading>
4626 <example compact="compact">
4627 <var>prerm</var> remove
4631 If prerm fails during replacement due to conflict
4633 <var>conflictor's-postinst</var> abort-remove \
4634 in-favour <var>package</var> <var>new-version</var>
4638 <var>postinst</var> abort-remove
4642 If this fails, the package is in a "Half-Configured"
4643 state, or else it remains "Installed".
4647 The package's files are removed (except <tt>conffile</tt>s).
4650 <example compact="compact">
4651 <var>postrm</var> remove
4655 If it fails, there's no error unwind, and the package is in
4656 an "Half-Installed" state.
4661 All the maintainer scripts except the <prgn>postrm</prgn>
4666 If we aren't purging the package we stop here. Note
4667 that packages which have no <prgn>postrm</prgn> and no
4668 <tt>conffile</tt>s are automatically purged when
4669 removed, as there is no difference except for the
4670 <prgn>dpkg</prgn> status.
4674 The <tt>conffile</tt>s and any backup files
4675 (<tt>~</tt>-files, <tt>#*#</tt> files,
4676 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4681 <example compact="compact">
4682 <var>postrm</var> purge
4686 If this fails, the package remains in a "Config-Files"
4691 The package's file list is removed.
4700 <chapt id="relationships">
4701 <heading>Declaring relationships between packages</heading>
4703 <sect id="depsyntax">
4704 <heading>Syntax of relationship fields</heading>
4707 These fields all have a uniform syntax. They are a list of
4708 package names separated by commas.
4712 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4713 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4714 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4715 control fields of the package, which declare
4716 dependencies on other packages, the package names listed may
4717 also include lists of alternative package names, separated
4718 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4719 if any one of the alternative packages is installed, that
4720 part of the dependency is considered to be satisfied.
4724 All of the fields except for <tt>Provides</tt> may restrict
4725 their applicability to particular versions of each named
4726 package. This is done in parentheses after each individual
4727 package name; the parentheses should contain a relation from
4728 the list below followed by a version number, in the format
4729 described in <ref id="f-Version">.
4733 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4734 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4735 earlier, earlier or equal, exactly equal, later or equal and
4736 strictly later, respectively. The deprecated
4737 forms <tt><</tt> and <tt>></tt> were confusingly used to
4738 mean earlier/later or equal, rather than strictly earlier/later,
4739 and must not appear in new packages (though <prgn>dpkg</prgn>
4740 still supports them with a warning).
4744 Whitespace may appear at any point in the version
4745 specification subject to the rules in <ref
4746 id="controlsyntax">, and must appear where it's necessary to
4747 disambiguate; it is not otherwise significant. All of the
4748 relationship fields can only be folded in source package control files. For
4749 consistency and in case of future changes to
4750 <prgn>dpkg</prgn> it is recommended that a single space be
4751 used after a version relationship and before a version
4752 number; it is also conventional to put a single space after
4753 each comma, on either side of each vertical bar, and before
4754 each open parenthesis. When opening a continuation line in a relationship field, it
4755 is conventional to do so after a comma and before the space
4756 following that comma.
4760 For example, a list of dependencies might appear as:
4761 <example compact="compact">
4764 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4769 Relationships may be restricted to a certain set of
4770 architectures. This is indicated in brackets after each
4771 individual package name and the optional version specification.
4772 The brackets enclose a non-empty list of Debian architecture names
4773 in the format described in <ref id="arch-spec">,
4774 separated by whitespace. Exclamation marks may be prepended to
4775 each of the names. (It is not permitted for some names to be
4776 prepended with exclamation marks while others aren't.)
4780 For build relationship fields
4781 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4782 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4783 the current Debian host architecture is not in this list and
4784 there are no exclamation marks in the list, or it is in the list
4785 with a prepended exclamation mark, the package name and the
4786 associated version specification are ignored completely for the
4787 purposes of defining the relationships.
4792 <example compact="compact">
4794 Build-Depends-Indep: texinfo
4795 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4796 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4798 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4799 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4800 <tt>gnumach-dev</tt> only on hurd-i386.
4804 For binary relationship fields and the <tt>Built-Using</tt>
4805 field, the architecture restriction
4806 syntax is only supported in the source package control
4807 file <file>debian/control</file>. When the corresponding binary
4808 package control file is generated, the relationship will either
4809 be omitted or included without the architecture restriction
4810 based on the architecture of the binary package. This means
4811 that architecture restrictions must not be used in binary
4812 relationship fields for architecture-independent packages
4813 (<tt>Architecture: all</tt>).
4818 <example compact="compact">
4819 Depends: foo [i386], bar [amd64]
4821 becomes <tt>Depends: foo</tt> when the package is built on
4822 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4823 package is built on the <tt>amd64</tt> architecture, and omitted
4824 entirely in binary packages built on all other architectures.
4828 If the architecture-restricted dependency is part of a set of
4829 alternatives using <tt>|</tt>, that alternative is ignored
4830 completely on architectures that do not match the restriction.
4832 <example compact="compact">
4833 Build-Depends: foo [!i386] | bar [!amd64]
4835 is equivalent to <tt>bar</tt> on the i386 architecture, to
4836 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4837 bar</tt> on all other architectures.
4841 Relationships may also be restricted to a certain set of
4842 architectures using architecture wildcards in the format
4843 described in <ref id="arch-wildcard-spec">. The syntax for
4844 declaring such restrictions is the same as declaring
4845 restrictions using a certain set of architectures without
4846 architecture wildcards. For example:
4847 <example compact="compact">
4848 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4850 is equivalent to <tt>foo</tt> on architectures using the Linux
4851 kernel and any cpu, <tt>bar</tt> on architectures using any
4852 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4853 using a kernel other than Linux.
4857 Note that the binary package relationship fields such as
4858 <tt>Depends</tt> appear in one of the binary package
4859 sections of the control file, whereas the build-time
4860 relationships such as <tt>Build-Depends</tt> appear in the
4861 source package section of the control file (which is the
4866 <sect id="binarydeps">
4867 <heading>Binary Dependencies - <tt>Depends</tt>,
4868 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4869 <tt>Pre-Depends</tt>
4873 Packages can declare in their control file that they have
4874 certain relationships to other packages - for example, that
4875 they may not be installed at the same time as certain other
4876 packages, and/or that they depend on the presence of others.
4880 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4881 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4882 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4883 <tt>Breaks</tt> is described in <ref id="breaks">, and
4884 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4885 rest are described below.
4889 These seven fields are used to declare a dependency
4890 relationship by one package on another. Except for
4891 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4892 depending (binary) package's control file.
4893 (<tt>Enhances</tt> appears in the recommending package's
4894 control file, and <tt>Breaks</tt> appears in the version of
4895 depended-on package which causes the named package to
4900 A <tt>Depends</tt> field takes effect <em>only</em> when a
4901 package is to be configured. It does not prevent a package
4902 being on the system in an unconfigured state while its
4903 dependencies are unsatisfied, and it is possible to replace
4904 a package whose dependencies are satisfied and which is
4905 properly installed with a different version whose
4906 dependencies are not and cannot be satisfied; when this is
4907 done the depending package will be left unconfigured (since
4908 attempts to configure it will give errors) and will not
4909 function properly. If it is necessary, a
4910 <tt>Pre-Depends</tt> field can be used, which has a partial
4911 effect even when a package is being unpacked, as explained
4912 in detail below. (The other three dependency fields,
4913 <tt>Recommends</tt>, <tt>Suggests</tt> and
4914 <tt>Enhances</tt>, are only used by the various front-ends
4915 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4916 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4920 Since <tt>Depends</tt> only places requirements on the order in
4921 which packages are configured, packages in an installation run
4922 are usually all unpacked first and all configured later.
4924 This approach makes dependency resolution easier. If two
4925 packages A and B are being upgraded, the installed package A
4926 depends on exactly the installed package B, and the new
4927 package A depends on exactly the new package B (a common
4928 situation when upgrading shared libraries and their
4929 corresponding development packages), satisfying the
4930 dependencies at every stage of the upgrade would be
4931 impossible. This relaxed restriction means that both new
4932 packages can be unpacked together and then configured in their
4938 If there is a circular dependency among packages being installed
4939 or removed, installation or removal order honoring the
4940 dependency order is impossible, requiring the dependency loop be
4941 broken at some point and the dependency requirements violated
4942 for at least one package. Packages involved in circular
4943 dependencies may not be able to rely on their dependencies being
4944 configured before they themselves are configured, depending on
4945 which side of the break of the circular dependency loop they
4946 happen to be on. If one of the packages in the loop has
4947 no <prgn>postinst</prgn> script, then the cycle will be broken
4948 at that package; this ensures that all <prgn>postinst</prgn>
4949 scripts are run with their dependencies properly configured if
4950 this is possible. Otherwise the breaking point is arbitrary.
4951 Packages should therefore avoid circular dependencies where
4952 possible, particularly if they have <prgn>postinst</prgn>
4957 The meaning of the five dependency fields is as follows:
4959 <tag><tt>Depends</tt></tag>
4962 This declares an absolute dependency. A package will
4963 not be configured unless all of the packages listed in
4964 its <tt>Depends</tt> field have been correctly
4965 configured (unless there is a circular dependency as
4970 The <tt>Depends</tt> field should be used if the
4971 depended-on package is required for the depending
4972 package to provide a significant amount of
4977 The <tt>Depends</tt> field should also be used if the
4978 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4979 require the depended-on package to be unpacked or
4980 configured in order to run. In the case of <tt>postinst
4981 configure</tt>, the depended-on packages will be unpacked
4982 and configured first. (If both packages are involved in a
4983 dependency loop, this might not work as expected; see the
4984 explanation a few paragraphs back.) In the case
4985 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4986 actions, the package dependencies will normally be at
4987 least unpacked, but they may be only "Half-Installed" if a
4988 previous upgrade of the dependency failed.
4992 Finally, the <tt>Depends</tt> field should be used if the
4993 depended-on package is needed by the <prgn>postrm</prgn>
4994 script to fully clean up after the package removal. There
4995 is no guarantee that package dependencies will be
4996 available when <prgn>postrm</prgn> is run, but the
4997 depended-on package is more likely to be available if the
4998 package declares a dependency (particularly in the case
4999 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5000 script must gracefully skip actions that require a
5001 dependency if that dependency isn't available.
5005 <tag><tt>Recommends</tt></tag>
5008 This declares a strong, but not absolute, dependency.
5012 The <tt>Recommends</tt> field should list packages
5013 that would be found together with this one in all but
5014 unusual installations.
5018 <tag><tt>Suggests</tt></tag>
5020 This is used to declare that one package may be more
5021 useful with one or more others. Using this field
5022 tells the packaging system and the user that the
5023 listed packages are related to this one and can
5024 perhaps enhance its usefulness, but that installing
5025 this one without them is perfectly reasonable.
5028 <tag><tt>Enhances</tt></tag>
5030 This field is similar to Suggests but works in the
5031 opposite direction. It is used to declare that a
5032 package can enhance the functionality of another
5036 <tag><tt>Pre-Depends</tt></tag>
5039 This field is like <tt>Depends</tt>, except that it
5040 also forces <prgn>dpkg</prgn> to complete installation
5041 of the packages named before even starting the
5042 installation of the package which declares the
5043 pre-dependency, as follows:
5047 When a package declaring a pre-dependency is about to
5048 be <em>unpacked</em> the pre-dependency can be
5049 satisfied if the depended-on package is either fully
5050 configured, <em>or even if</em> the depended-on
5051 package(s) are only unpacked or in the "Half-Configured"
5052 state, provided that they have been configured
5053 correctly at some point in the past (and not removed
5054 or partially removed since). In this case, both the
5055 previously-configured and currently unpacked or
5056 "Half-Configured" versions must satisfy any version
5057 clause in the <tt>Pre-Depends</tt> field.
5061 When the package declaring a pre-dependency is about to
5062 be <em>configured</em>, the pre-dependency will be treated
5063 as a normal <tt>Depends</tt>. It will be considered
5064 satisfied only if the depended-on package has been
5065 correctly configured. However, unlike
5066 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5067 permit circular dependencies to be broken. If a circular
5068 dependency is encountered while attempting to honor
5069 <tt>Pre-Depends</tt>, the installation will be aborted.
5073 <tt>Pre-Depends</tt> are also required if the
5074 <prgn>preinst</prgn> script depends on the named package.
5075 It is best to avoid this situation if possible.
5079 <tt>Pre-Depends</tt> should be used sparingly,
5080 preferably only by packages whose premature upgrade or
5081 installation would hamper the ability of the system to
5082 continue with any upgrade that might be in progress.
5086 You should not specify a <tt>Pre-Depends</tt> entry for a
5087 package before this has been discussed on the
5088 <tt>debian-devel</tt> mailing list and a consensus about
5089 doing that has been reached. See <ref id="dependencies">.
5096 When selecting which level of dependency to use you should
5097 consider how important the depended-on package is to the
5098 functionality of the one declaring the dependency. Some
5099 packages are composed of components of varying degrees of
5100 importance. Such a package should list using
5101 <tt>Depends</tt> the package(s) which are required by the
5102 more important components. The other components'
5103 requirements may be mentioned as Suggestions or
5104 Recommendations, as appropriate to the components' relative
5110 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5113 When one binary package declares that it breaks another,
5114 <prgn>dpkg</prgn> will refuse to allow the package which
5115 declares <tt>Breaks</tt> to be unpacked unless the broken
5116 package is deconfigured first, and it will refuse to
5117 allow the broken package to be reconfigured.
5121 A package will not be regarded as causing breakage merely
5122 because its configuration files are still installed; it must
5123 be at least "Half-Installed".
5127 A special exception is made for packages which declare that
5128 they break their own package name or a virtual package which
5129 they provide (see below): this does not count as a real
5134 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5135 version clause; such a <tt>Breaks</tt> is introduced in the
5136 version of an (implicit or explicit) dependency which violates
5137 an assumption or reveals a bug in earlier versions of the broken
5138 package, or which takes over a file from earlier versions of the
5139 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5140 will inform higher-level package management tools that the
5141 broken package must be upgraded before the new one.
5145 If the breaking package also overwrites some files from the
5146 older package, it should use <tt>Replaces</tt> to ensure this
5147 goes smoothly. See <ref id="replaces"> for a full discussion
5148 of taking over files from other packages, including how to
5149 use <tt>Breaks</tt> in those cases.
5153 Many of the cases where <tt>Breaks</tt> should be used were
5154 previously handled with <tt>Conflicts</tt>
5155 because <tt>Breaks</tt> did not yet exist.
5156 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5157 See <ref id="conflicts"> for more information about the
5162 <sect id="conflicts">
5163 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5166 When one binary package declares a conflict with another using
5167 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5168 allow them to be unpacked on the system at the same time. This
5169 is a stronger restriction than <tt>Breaks</tt>, which prevents
5170 the broken package from being configured while the breaking
5171 package is in the "Unpacked" state but allows both packages to
5172 be unpacked at the same time.
5176 If one package is to be unpacked, the other must be removed
5177 first. If the package being unpacked is marked as replacing
5178 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5179 normally be used in this case) the one on the system, or the one
5180 on the system is marked as deselected, or both packages are
5181 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5182 automatically remove the package which is causing the conflict.
5183 Otherwise, it will halt the installation of the new package with
5184 an error. This mechanism is specifically designed to produce an
5185 error when the installed package is <tt>Essential</tt>, but the
5190 A package will not cause a conflict merely because its
5191 configuration files are still installed; it must be at least
5196 A special exception is made for packages which declare a
5197 conflict with their own package name, or with a virtual
5198 package which they provide (see below): this does not
5199 prevent their installation, and allows a package to conflict
5200 with others providing a replacement for it. You use this
5201 feature when you want the package in question to be the only
5202 package providing some feature.
5206 Normally, <tt>Breaks</tt> should be used instead
5207 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5208 stronger restriction on the ordering of package installation or
5209 upgrade and can make it more difficult for the package manager
5210 to find a correct solution to an upgrade or installation
5211 problem. <tt>Breaks</tt> should be used
5213 <item>when moving a file from one package to another (see
5214 <ref id="replaces">),</item>
5215 <item>when splitting a package (a special case of the previous
5217 <item>when the breaking package exposes a bug in or interacts
5218 badly with particular versions of the broken
5221 <tt>Conflicts</tt> should be used
5223 <item>when two packages provide the same file and will
5224 continue to do so,</item>
5225 <item>in conjunction with <tt>Provides</tt> when only one
5226 package providing a given virtual facility may be unpacked
5227 at a time (see <ref id="virtual">),</item>
5228 <item>in other cases where one must prevent simultaneous
5229 installation of two packages for reasons that are ongoing
5230 (not fixed in a later version of one of the packages) or
5231 that must prevent both packages from being unpacked at the
5232 same time, not just configured.</item>
5234 Be aware that adding <tt>Conflicts</tt> is normally not the best
5235 solution when two packages provide the same files. Depending on
5236 the reason for that conflict, using alternatives or renaming the
5237 files is often a better approach. See, for
5238 example, <ref id="binaries">.
5242 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5243 unless two packages cannot be installed at the same time or
5244 installing them both causes one of them to be broken or
5245 unusable. Having similar functionality or performing the same
5246 tasks as another package is not sufficient reason to
5247 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5251 A <tt>Conflicts</tt> entry may have an "earlier than" version
5252 clause if the reason for the conflict is corrected in a later
5253 version of one of the packages. However, normally the presence
5254 of an "earlier than" version clause is a sign
5255 that <tt>Breaks</tt> should have been used instead. An "earlier
5256 than" version clause in <tt>Conflicts</tt>
5257 prevents <prgn>dpkg</prgn> from upgrading or installing the
5258 package which declares such a conflict until the upgrade or
5259 removal of the conflicted-with package has been completed, which
5260 is a strong restriction.
5264 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5268 As well as the names of actual ("concrete") packages, the
5269 package relationship fields <tt>Depends</tt>,
5270 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5271 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5272 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5273 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5274 may mention "virtual packages".
5278 A <em>virtual package</em> is one which appears in the
5279 <tt>Provides</tt> control field of another package. The effect
5280 is as if the package(s) which provide a particular virtual
5281 package name had been listed by name everywhere the virtual
5282 package name appears. (See also <ref id="virtual_pkg">)
5286 If there are both concrete and virtual packages of the same
5287 name, then the dependency may be satisfied (or the conflict
5288 caused) by either the concrete package with the name in
5289 question or any other concrete package which provides the
5290 virtual package with the name in question. This is so that,
5291 for example, supposing we have
5292 <example compact="compact">
5295 </example> and someone else releases an enhanced version of
5296 the <tt>bar</tt> package they can say:
5297 <example compact="compact">
5301 and the <tt>bar-plus</tt> package will now also satisfy the
5302 dependency for the <tt>foo</tt> package.
5306 If a relationship field has a version number attached, only real
5307 packages will be considered to see whether the relationship is
5308 satisfied (or the prohibition violated, for a conflict or
5309 breakage). In other words, if a version number is specified,
5310 this is a request to ignore all <tt>Provides</tt> for that
5311 package name and consider only real packages. The package
5312 manager will assume that a package providing that virtual
5313 package is not of the "right" version. A <tt>Provides</tt>
5314 field may not contain version numbers, and the version number of
5315 the concrete package which provides a particular virtual package
5316 will not be considered when considering a dependency on or
5317 conflict with the virtual package name.<footnote>
5318 It is possible that a future release of <prgn>dpkg</prgn> may
5319 add the ability to specify a version number for each virtual
5320 package it provides. This feature is not yet present,
5321 however, and is expected to be used only infrequently.
5326 To specify which of a set of real packages should be the default
5327 to satisfy a particular dependency on a virtual package, list
5328 the real package as an alternative before the virtual one.
5332 If the virtual package represents a facility that can only be
5333 provided by one real package at a time, such as
5334 the <package>mail-transport-agent</package> virtual package that
5335 requires installation of a binary that would conflict with all
5336 other providers of that virtual package (see
5337 <ref id="mail-transport-agents">), all packages providing that
5338 virtual package should also declare a conflict with it
5339 using <tt>Conflicts</tt>. This will ensure that at most one
5340 provider of that virtual package is unpacked or installed at a
5345 <sect id="replaces"><heading>Overwriting files and replacing
5346 packages - <tt>Replaces</tt></heading>
5349 Packages can declare in their control file that they should
5350 overwrite files in certain other packages, or completely replace
5351 other packages. The <tt>Replaces</tt> control field has these
5352 two distinct purposes.
5355 <sect1><heading>Overwriting files in other packages</heading>
5358 It is usually an error for a package to contain files which
5359 are on the system in another package. However, if the
5360 overwriting package declares that it <tt>Replaces</tt> the one
5361 containing the file being overwritten, then <prgn>dpkg</prgn>
5362 will replace the file from the old package with that from the
5363 new. The file will no longer be listed as "owned" by the old
5364 package and will be taken over by the new package.
5365 Normally, <tt>Breaks</tt> should be used in conjunction
5366 with <tt>Replaces</tt>.<footnote>
5367 To see why <tt>Breaks</tt> is normally needed in addition
5368 to <tt>Replaces</tt>, consider the case of a file in the
5369 package <package>foo</package> being taken over by the
5370 package <package>foo-data</package>.
5371 <tt>Replaces</tt> will allow <package>foo-data</package> to
5372 be installed and take over that file. However,
5373 without <tt>Breaks</tt>, nothing
5374 requires <package>foo</package> to be upgraded to a newer
5375 version that knows it does not include that file and instead
5376 depends on <package>foo-data</package>. Nothing would
5377 prevent the new <package>foo-data</package> package from
5378 being installed and then removed, removing the file that it
5379 took over from <package>foo</package>. After that
5380 operation, the package manager would think the system was in
5381 a consistent state, but the <package>foo</package> package
5382 would be missing one of its files.
5387 For example, if a package <package>foo</package> is split
5388 into <package>foo</package> and <package>foo-data</package>
5389 starting at version 1.2-3, <package>foo-data</package> would
5391 <example compact="compact">
5392 Replaces: foo (<< 1.2-3)
5393 Breaks: foo (<< 1.2-3)
5395 in its control file. The new version of the
5396 package <package>foo</package> would normally have the field
5397 <example compact="compact">
5398 Depends: foo-data (>= 1.2-3)
5400 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5401 the files moved into <package>foo-data</package> are not
5402 required for normal operation).
5406 If a package is completely replaced in this way, so that
5407 <prgn>dpkg</prgn> does not know of any files it still
5408 contains, it is considered to have "disappeared". It will
5409 be marked as not wanted on the system (selected for
5410 removal) and "Not-Installed". Any <tt>conffile</tt>s
5411 details noted for the package will be ignored, as they
5412 will have been taken over by the overwriting package. The
5413 package's <prgn>postrm</prgn> script will be run with a
5414 special argument to allow the package to do any final
5415 cleanup required. See <ref id="mscriptsinstact">.
5417 Replaces is a one way relationship. You have to install
5418 the replacing package after the replaced package.
5423 For this usage of <tt>Replaces</tt>, virtual packages (see
5424 <ref id="virtual">) are not considered when looking at a
5425 <tt>Replaces</tt> field. The packages declared as being
5426 replaced must be mentioned by their real names.
5430 This usage of <tt>Replaces</tt> only takes effect when both
5431 packages are at least partially on the system at once. It is
5432 not relevant if the packages conflict unless the conflict has
5437 <sect1><heading>Replacing whole packages, forcing their
5441 Second, <tt>Replaces</tt> allows the packaging system to
5442 resolve which package should be removed when there is a
5443 conflict (see <ref id="conflicts">). This usage only takes
5444 effect when the two packages <em>do</em> conflict, so that the
5445 two usages of this field do not interfere with each other.
5449 In this situation, the package declared as being replaced
5450 can be a virtual package, so for example, all mail
5451 transport agents (MTAs) would have the following fields in
5452 their control files:
5453 <example compact="compact">
5454 Provides: mail-transport-agent
5455 Conflicts: mail-transport-agent
5456 Replaces: mail-transport-agent
5458 ensuring that only one MTA can be unpacked at any one
5459 time. See <ref id="virtual"> for more information about this
5464 <sect id="sourcebinarydeps">
5465 <heading>Relationships between source and binary packages -
5466 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5467 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5471 Source packages that require certain binary packages to be
5472 installed or absent at the time of building the package
5473 can declare relationships to those binary packages.
5477 This is done using the <tt>Build-Depends</tt>,
5478 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5479 <tt>Build-Conflicts-Indep</tt> control fields.
5483 Build-dependencies on "build-essential" binary packages can be
5484 omitted. Please see <ref id="pkg-relations"> for more information.
5488 The dependencies and conflicts they define must be satisfied
5489 (as defined earlier for binary packages) in order to invoke
5490 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5492 There is no Build-Depends-Arch; this role is essentially
5493 met with Build-Depends. Anyone building the
5494 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5495 assumed to be building the whole package, and therefore
5496 installation of all build dependencies is required.
5499 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5500 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5501 not yet know how to check for its existence, and
5502 <tt>binary-arch</tt>. The purpose of the original split
5503 between <tt>Build-Depends</tt> and
5504 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5505 wouldn't need to install extra packages needed only for the
5506 binary-indep targets. But without a build-arch/build-indep
5507 split, this didn't work, since most of the work is done in
5508 the build target, not in the binary target.
5512 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5513 <tt>binary-arch</tt></tag>
5515 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5516 fields must be satisfied when these targets are invoked.
5518 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5519 and <tt>binary-indep</tt></tag>
5521 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5522 <tt>Build-Depends-Indep</tt>, and
5523 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5524 these targets are invoked.
5530 <sect id="built-using">
5531 <heading>Additional source packages used to build the binary
5532 - <tt>Built-Using</tt>
5536 Some binary packages incorporate parts of other packages when built
5537 but do not have to depend on those packages. Examples include
5538 linking with static libraries or incorporating source code from
5539 another package during the build. In this case, the source packages
5540 of those other packages are a required part of the complete source
5541 (the binary package is not reproducible without them).
5545 A <tt>Built-Using</tt> field must list the corresponding source
5546 package for any such binary package incorporated during the build
5548 <tt>Build-Depends</tt> in the source package is not adequate since
5549 it (rightfully) does not document the exact version used in the
5552 including an "exactly equal" ("=") version relation on the version
5553 that was used to build that binary package<footnote>
5554 The archive software might reject packages that refer to
5555 non-existent sources.
5560 A package using the source code from the gcc-4.6-source
5561 binary package built from the gcc-4.6 source package would
5562 have this field in its control file:
5563 <example compact="compact">
5564 Built-Using: gcc-4.6 (= 4.6.0-11)
5569 A package including binaries from grub2 and loadlin would
5570 have this field in its control file:
5571 <example compact="compact">
5572 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5579 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5582 Packages containing shared libraries must be constructed with
5583 a little care to make sure that the shared library is always
5584 available. This is especially important for packages whose
5585 shared libraries are vitally important, such as the C library
5586 (currently <tt>libc6</tt>).
5590 This section deals only with public shared libraries: shared
5591 libraries that are placed in directories searched by the dynamic
5592 linker by default or which are intended to be linked against
5593 normally and possibly used by other, independent packages. Shared
5594 libraries that are internal to a particular package or that are
5595 only loaded as dynamic modules are not covered by this section and
5596 are not subject to its requirements.
5600 A shared library is identified by the <tt>SONAME</tt> attribute
5601 stored in its dynamic section. When a binary is linked against a
5602 shared library, the <tt>SONAME</tt> of the shared library is
5603 recorded in the binary's <tt>NEEDED</tt> section so that the
5604 dynamic linker knows that library must be loaded at runtime. The
5605 shared library file's full name (which usually contains additional
5606 version information not needed in the <tt>SONAME</tt>) is
5607 therefore normally not referenced directly. Instead, the shared
5608 library is loaded by its <tt>SONAME</tt>, which exists on the file
5609 system as a symlink pointing to the full name of the shared
5610 library. This symlink must be provided by the
5611 package. <ref id="sharedlibs-runtime"> describes how to do this.
5613 This is a convention of shared library versioning, but not a
5614 requirement. Some libraries use the <tt>SONAME</tt> as the full
5615 library file name instead and therefore do not need a symlink.
5616 Most, however, encode additional information about
5617 backwards-compatible revisions as a minor version number in the
5618 file name. The <tt>SONAME</tt> itself only changes when
5619 binaries linked with the earlier version of the shared library
5620 may no longer work, but the filename may change with each
5621 release of the library. See <ref id="sharedlibs-runtime"> for
5627 When linking a binary or another shared library against a shared
5628 library, the <tt>SONAME</tt> for that shared library is not yet
5629 known. Instead, the shared library is found by looking for a file
5630 matching the library name with <tt>.so</tt> appended. This file
5631 exists on the file system as a symlink pointing to the shared
5636 Shared libraries are normally split into several binary packages.
5637 The <tt>SONAME</tt> symlink is installed by the runtime shared
5638 library package, and the bare <tt>.so</tt> symlink is installed in
5639 the development package since it's only used when linking binaries
5640 or shared libraries. However, there are some exceptions for
5641 unusual shared libraries or for shared libraries that are also
5642 loaded as dynamic modules by other programs.
5646 This section is primarily concerned with how the separation of
5647 shared libraries into multiple packages should be done and how
5648 dependencies on and between shared library binary packages are
5649 managed in Debian. <ref id="libraries"> should be read in
5650 conjunction with this section and contains additional rules for
5651 the files contained in the shared library packages.
5654 <sect id="sharedlibs-runtime">
5655 <heading>Run-time shared libraries</heading>
5658 The run-time shared library must be placed in a package
5659 whose name changes whenever the <tt>SONAME</tt> of the shared
5660 library changes. This allows several versions of the shared
5661 library to be installed at the same time, allowing installation
5662 of the new version of the shared library without immediately
5663 breaking binaries that depend on the old version. Normally, the
5664 run-time shared library and its <tt>SONAME</tt> symlink should
5665 be placed in a package named
5666 <package><var>libraryname</var><var>soversion</var></package>,
5667 where <var>soversion</var> is the version number in
5668 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5669 would be confusing to directly append <var>soversion</var>
5670 to <var>libraryname</var> (if, for
5671 example, <var>libraryname</var> itself ends in a number), you
5673 <package><var>libraryname</var>-<var>soversion</var></package>
5678 To determine the <var>soversion</var>, look at
5679 the <tt>SONAME</tt> of the library, stored in the
5680 ELF <tt>SONAME</tt> attribute. It is usually of the
5681 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5682 example, <tt>libz.so.1</tt>). The version part is the part
5683 which comes after <tt>.so.</tt>, so in that example it
5684 is <tt>1</tt>. The soname may instead be of the
5685 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5686 as <tt>libdb-5.1.so</tt>, in which case the name would
5687 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5691 If you have several shared libraries built from the same source
5692 tree, you may lump them all together into a single shared
5693 library package provided that all of their <tt>SONAME</tt>s will
5694 always change together. Be aware that this is not normally the
5695 case, and if the <tt>SONAME</tt>s do not change together,
5696 upgrading such a merged shared library package will be
5697 unnecessarily difficult because of file conflicts with the old
5698 version of the package. When in doubt, always split shared
5699 library packages so that each binary package installs a single
5704 Every time the shared library ABI changes in a way that may
5705 break binaries linked against older versions of the shared
5706 library, the <tt>SONAME</tt> of the library and the
5707 corresponding name for the binary package containing the runtime
5708 shared library should change. Normally, this means
5709 the <tt>SONAME</tt> should change any time an interface is
5710 removed from the shared library or the signature of an interface
5711 (the number of parameters or the types of parameters that it
5712 takes, for example) is changed. This practice is vital to
5713 allowing clean upgrades from older versions of the package and
5714 clean transitions between the old ABI and new ABI without having
5715 to upgrade every affected package simultaneously.
5719 The <tt>SONAME</tt> and binary package name need not, and indeed
5720 normally should not, change if new interfaces are added but none
5721 are removed or changed, since this will not break binaries
5722 linked against the old shared library. Correct versioning of
5723 dependencies on the newer shared library by binaries that use
5724 the new interfaces is handled via
5725 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5726 or <tt>shlibs</tt> system</qref>.
5730 The package should install the shared libraries under
5731 their normal names. For example, the <package>libgdbm3</package>
5732 package should install <file>libgdbm.so.3.0.0</file> as
5733 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5734 renamed or re-linked by any <prgn>prerm</prgn> or
5735 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5736 of renaming things safely without affecting running programs,
5737 and attempts to interfere with this are likely to lead to
5742 Shared libraries should not be installed executable, since
5743 the dynamic linker does not require this and trying to
5744 execute a shared library usually results in a core dump.
5748 The run-time library package should include the symbolic link for
5749 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5750 the shared libraries. For example,
5751 the <package>libgdbm3</package> package should include a symbolic
5752 link from <file>/usr/lib/libgdbm.so.3</file> to
5753 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5754 linker (for example <prgn>ld.so</prgn> or
5755 <prgn>ld-linux.so.*</prgn>) can find the library between the
5756 time that <prgn>dpkg</prgn> installs it and the time that
5757 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5759 The package management system requires the library to be
5760 placed before the symbolic link pointing to it in the
5761 <file>.deb</file> file. This is so that when
5762 <prgn>dpkg</prgn> comes to install the symlink
5763 (overwriting the previous symlink pointing at an older
5764 version of the library), the new shared library is already
5765 in place. In the past, this was achieved by creating the
5766 library in the temporary packaging directory before
5767 creating the symlink. Unfortunately, this was not always
5768 effective, since the building of the tar file in the
5769 <file>.deb</file> depended on the behavior of the underlying
5770 file system. Some file systems (such as reiserfs) reorder
5771 the files so that the order of creation is forgotten.
5772 Since version 1.7.0, <prgn>dpkg</prgn>
5773 reorders the files itself as necessary when building a
5774 package. Thus it is no longer important to concern
5775 oneself with the order of file creation.
5779 <sect1 id="ldconfig">
5780 <heading><tt>ldconfig</tt></heading>
5783 Any package installing shared libraries in one of the default
5784 library directories of the dynamic linker (which are currently
5785 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5786 listed in <file>/etc/ld.so.conf</file><footnote>
5787 These are currently <file>/usr/local/lib</file> plus
5788 directories under <file>/lib</file> and <file>/usr/lib</file>
5789 matching the multiarch triplet for the system architecture.
5791 must use <prgn>ldconfig</prgn> to update the shared library
5796 The package maintainer scripts must only call
5797 <prgn>ldconfig</prgn> under these circumstances:
5798 <list compact="compact">
5799 <item>When the <prgn>postinst</prgn> script is run with a
5800 first argument of <tt>configure</tt>, the script must call
5801 <prgn>ldconfig</prgn>, and may optionally invoke
5802 <prgn>ldconfig</prgn> at other times.
5804 <item>When the <prgn>postrm</prgn> script is run with a
5805 first argument of <tt>remove</tt>, the script should call
5806 <prgn>ldconfig</prgn>.
5811 During install or upgrade, the preinst is called before
5812 the new files are unpacked, so calling "ldconfig" is
5813 pointless. The preinst of an existing package can also be
5814 called if an upgrade fails. However, this happens during
5815 the critical time when a shared libs may exist on-disk
5816 under a temporary name. Thus, it is dangerous and
5817 forbidden by current policy to call "ldconfig" at this
5822 When a package is installed or upgraded, "postinst
5823 configure" runs after the new files are safely on-disk.
5824 Since it is perfectly safe to invoke ldconfig
5825 unconditionally in a postinst, it is OK for a package to
5826 simply put ldconfig in its postinst without checking the
5827 argument. The postinst can also be called to recover from
5828 a failed upgrade. This happens before any new files are
5829 unpacked, so there is no reason to call "ldconfig" at this
5834 For a package that is being removed, prerm is
5835 called with all the files intact, so calling ldconfig is
5836 useless. The other calls to "prerm" happen in the case of
5837 upgrade at a time when all the files of the old package
5838 are on-disk, so again calling "ldconfig" is pointless.
5842 postrm, on the other hand, is called with the "remove"
5843 argument just after the files are removed, so this is
5844 the proper time to call "ldconfig" to notify the system
5845 of the fact that the shared libraries from the package
5846 are removed. The postrm can be called at several other
5847 times. At the time of "postrm purge", "postrm
5848 abort-install", or "postrm abort-upgrade", calling
5849 "ldconfig" is useless because the shared lib files are
5850 not on-disk. However, when "postrm" is invoked with
5851 arguments "upgrade", "failed-upgrade", or "disappear", a
5852 shared lib may exist on-disk under a temporary filename.
5860 <sect id="sharedlibs-support-files">
5861 <heading>Shared library support files</heading>
5864 If your package contains files whose names do not change with
5865 each change in the library shared object version, you must not
5866 put them in the shared library package. Otherwise, several
5867 versions of the shared library cannot be installed at the same
5868 time without filename clashes, making upgrades and transitions
5869 unnecessarily difficult.
5873 It is recommended that supporting files and run-time support
5874 programs that do not need to be invoked manually by users, but
5875 are nevertheless required for the package to function, be placed
5876 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5877 preferably under <file>/usr/lib/</file><var>package-name</var>.
5878 If the program or file is architecture independent, the
5879 recommendation is for it to be placed in a subdirectory of
5880 <file>/usr/share</file> instead, preferably under
5881 <file>/usr/share/</file><var>package-name</var>. Following the
5882 <var>package-name</var> naming convention ensures that the file
5883 names change when the shared object version changes.
5887 Run-time support programs that use the shared library but are
5888 not required for the library to function or files used by the
5889 shared library that can be used by any version of the shared
5890 library package should instead be put in a separate package.
5891 This package might typically be named
5892 <package><var>libraryname</var>-tools</package>; note the
5893 absence of the <var>soversion</var> in the package name.
5897 Files and support programs only useful when compiling software
5898 against the library should be included in the development
5899 package for the library.<footnote>
5900 For example, a <file><var>package-name</var>-config</file>
5901 script or <package>pkg-config</package> configuration files.
5906 <sect id="sharedlibs-static">
5907 <heading>Static libraries</heading>
5910 The static library (<file><var>libraryname.a</var></file>)
5911 is usually provided in addition to the shared version.
5912 It is placed into the development package (see below).
5916 In some cases, it is acceptable for a library to be
5917 available in static form only; these cases include:
5919 <item>libraries for languages whose shared library support
5920 is immature or unstable</item>
5921 <item>libraries whose interfaces are in flux or under
5922 development (commonly the case when the library's
5923 major version number is zero, or where the ABI breaks
5924 across patchlevels)</item>
5925 <item>libraries which are explicitly intended to be
5926 available only in static form by their upstream
5931 <sect id="sharedlibs-dev">
5932 <heading>Development files</heading>
5935 If there are development files associated with a shared library,
5936 the source package needs to generate a binary development package
5937 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5938 or if you prefer only to support one development version at a
5939 time, <package><var>libraryname</var>-dev</package>. Installing
5940 the development package must result in installation of all the
5941 development files necessary for compiling programs against that
5942 shared library.<footnote>
5943 This wording allows the development files to be split into
5944 several packages, such as a separate architecture-independent
5945 <package><var>libraryname</var>-headers</package>, provided that
5946 the development package depends on all the required additional
5952 In case several development versions of a library exist, you may
5953 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5954 <ref id="conflicts">) to ensure that the user only installs one
5955 development version at a time (as different development versions are
5956 likely to have the same header files in them, which would cause a
5957 filename clash if both were unpacked).
5961 The development package should contain a symlink for the associated
5962 shared library without a version number. For example, the
5963 <package>libgdbm-dev</package> package should include a symlink
5964 from <file>/usr/lib/libgdbm.so</file> to
5965 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5966 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5967 <file>libgdbm.so</file> when compiling dynamically.
5971 If the package provides Ada Library Information
5972 (<file>*.ali</file>) files for use with GNAT, these files must be
5973 installed read-only (mode 0444) so that GNAT will not attempt to
5974 recompile them. This overrides the normal file mode requirements
5975 given in <ref id="permissions-owners">.
5979 <sect id="sharedlibs-intradeps">
5980 <heading>Dependencies between the packages of the same library</heading>
5983 Typically the development version should have an exact
5984 version dependency on the runtime library, to make sure that
5985 compilation and linking happens correctly. The
5986 <tt>${binary:Version}</tt> substitution variable can be
5987 useful for this purpose.
5989 Previously, <tt>${Source-Version}</tt> was used, but its name
5990 was confusing and it has been deprecated since dpkg 1.13.19.
5995 <sect id="sharedlibs-depends">
5996 <heading>Dependencies between the library and other
6000 If a package contains a binary or library which links to a
6001 shared library, we must ensure that, when the package is
6002 installed on the system, all of the libraries needed are also
6003 installed. These dependencies must be added to the binary
6004 package when it is built, since they may change based on which
6005 version of a shared library the binary or library was linked
6006 with even if there are no changes to the source of the binary
6007 (for example, symbol versions change, macros become functions or
6008 vice versa, or the binary package may determine at compile-time
6009 whether new library interfaces are available and can be called).
6010 To allow these dependencies to be constructed, shared libraries
6011 must provide either a <file>symbols</file> file or
6012 a <file>shlibs</file> file. These provide information on the
6013 package dependencies required to ensure the presence of
6014 interfaces provided by this library. Any package with binaries
6015 or libraries linking to a shared library must use these files to
6016 determine the required dependencies when it is built. Other
6017 packages which use a shared library (for example using
6018 <tt>dlopen()</tt>) should compute appropriate dependencies
6019 using these files at build time as well.
6023 The two mechanisms differ in the degree of detail that they
6024 provide. A <file>symbols</file> file documents, for each symbol
6025 exported by a library, the minimal version of the package any
6026 binary using this symbol will need. This is typically the
6027 version of the package in which the symbol was introduced. This
6028 information permits detailed analysis of the symbols used by a
6029 particular package and construction of an accurate dependency,
6030 but it requires the package maintainer to track more information
6031 about the shared library.
6035 A <file>shlibs</file> file, in contrast, only documents the last
6036 time the library ABI changed in any way. It only provides
6037 information about the library as a whole, not individual
6038 symbols. When a package is built using a shared library with
6039 only a <file>shlibs</file> file, the generated dependency will
6040 require a version of the shared library equal to or newer than
6041 the version of the last ABI change. This generates
6042 unnecessarily restrictive dependencies compared
6043 to <file>symbols</file> files if none of the symbols used by the
6044 package have changed. This, in turn, may make upgrades
6045 needlessly complex and unnecessarily restrict use of the package
6046 on systems with older versions of the shared libraries.
6050 <file>shlibs</file> files also only support a limited range of
6051 library SONAMEs, making it difficult to use <file>shlibs</file>
6052 files in some unusual corner cases.<footnote>
6053 A <file>shlibs</file> file represents an SONAME as a library
6054 name and version number, such as <tt>libfoo VERSION</tt>,
6055 instead of recording the actual SONAME. If the SONAME doesn't
6056 match one of the two expected formats
6057 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6058 cannot be represented.
6063 <file>symbols</file> files are therefore recommended for most
6064 shared library packages since they provide more accurate
6065 dependencies. For most C libraries, the additional detail
6066 required by <file>symbols</file> files is not too difficult to
6067 maintain. However, maintaining exhaustive symbols information
6068 for a C++ library can be quite onerous, so <file>shlibs</file>
6069 files may be more appropriate for most C++ libraries. Libraries
6070 with a corresponding udeb must also provide
6071 a <file>shlibs</file> file, since the udeb infrastructure does
6072 not use <file>symbols</file> files.
6075 <sect1 id="dpkg-shlibdeps">
6076 <heading>Generating dependencies on shared libraries</heading>
6079 When a package that contains any shared libraries or compiled
6080 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6081 each shared library and compiled binary to determine the
6082 libraries used and hence the dependencies needed by the
6084 <prgn>dpkg-shlibdeps</prgn> will use a program
6085 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6086 the libraries and the symbols in those libraries directly
6087 needed by the binaries or shared libraries in the package.
6089 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6090 your <file>debian/rules</file> file in the source package.
6091 List all of the compiled binaries, libraries, or loadable
6092 modules in your package.<footnote>
6093 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6094 correctly is to use a package helper framework such
6095 as <package>debhelper</package>. If you are
6096 using <package>debhelper</package>,
6097 the <prgn>dh_shlibdeps</prgn> program will do this work for
6098 you. It will also correctly handle multi-binary packages.
6100 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6101 or <file>shlibs</file> files installed by the shared libraries
6102 to generate dependency information. The package must then
6103 provide a substitution variable into which the discovered
6104 dependency information can be placed.
6108 If you are creating a udeb for use in the Debian Installer,
6109 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6110 should use the dependency line of type <tt>udeb</tt> by adding
6111 the <tt>-tudeb</tt> option<footnote>
6112 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6113 will automatically add this option if it knows it is
6115 </footnote>. If there is no dependency line of
6116 type <tt>udeb</tt> in the <file>shlibs</file>
6117 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6118 regular dependency line.
6122 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6123 into the <file>debian/substvars</file> file by default, which
6124 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6125 to place a <tt>${shlibs:Depends}</tt> variable in
6126 the <tt>Depends</tt> field in the control file of every binary
6127 package built by this source package that contains compiled
6128 binaries, libraries, or loadable modules. If you have
6129 multiple binary packages, you will need to
6130 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6131 compiled libraries or binaries. For example, you could use
6132 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6133 specify a different <file>substvars</file> file for each
6134 binary package.<footnote>
6135 Again, <prgn>dh_shlibdeps</prgn>
6136 and <prgn>dh_gencontrol</prgn> will handle everything except
6137 the addition of the variable to the control file for you if
6138 you're using <package>debhelper</package>, including
6139 generating separate <file>substvars</file> files for each
6140 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6141 the appropriate flags.
6146 For more details on <prgn>dpkg-shlibdeps</prgn>,
6147 see <manref name="dpkg-shlibdeps" section="1">.
6151 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6152 library <tt>libbar</tt> if it is explicitly linked with that
6153 library (that is, the library is listed in the
6154 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6155 to the link line when the binary is created). Other libraries
6156 that are needed by <tt>libbar</tt> are
6157 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6158 linker will load them automatically when it
6159 loads <tt>libbar</tt>. A package should depend on the
6160 libraries it directly uses, but not the libraries it only uses
6161 indirectly. The dependencies for the libraries used
6162 directly will automatically pull in the indirectly-used
6163 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6164 automatically, but package maintainers need to be aware of
6165 this distinction between directly and indirectly using a
6166 library if they have to override its results for some reason.
6168 A good example of where this helps is the following. We
6169 could update <tt>libimlib</tt> with a new version that
6170 supports a new revision of a graphics format called dgf (but
6171 retaining the same major version number) and depends on a
6172 new library package <package>libdgf4</package> instead of
6173 the older <package>libdgf3</package>. If we
6174 used <prgn>ldd</prgn> to add dependencies for every library
6175 directly or indirectly linked with a binary, every package
6176 that uses <tt>libimlib</tt> would need to be recompiled so
6177 it would also depend on <package>libdgf4</package> in order
6178 to retire the older <package>libdgf3</package> package.
6179 Since dependencies are only added based on
6180 ELF <tt>NEEDED</tt> attribute, packages
6181 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6182 having the dependency on an appropriate version
6183 of <tt>libdgf</tt> and do not need rebuilding.
6188 <sect1 id="sharedlibs-updates">
6189 <heading>Shared library ABI changes</heading>
6192 Maintaining a shared library package using
6193 either <file>symbols</file> or <file>shlibs</file> files
6194 requires being aware of the exposed ABI of the shared library
6195 and any changes to it. Both <file>symbols</file>
6196 and <file>shlibs</file> files record every change to the ABI
6197 of the shared library; <file>symbols</file> files do so per
6198 public symbol, whereas <file>shlibs</file> files record only
6199 the last change for the entire library.
6203 There are two types of ABI changes: ones that are
6204 backward-compatible and ones that are not. An ABI change is
6205 backward-compatible if any reasonable program or library that
6206 was linked with the previous version of the shared library
6207 will still work correctly with the new version of the shared
6209 An example of an "unreasonable" program is one that uses
6210 library interfaces that are documented as internal and
6211 unsupported. If the only programs or libraries affected by
6212 a change are "unreasonable" ones, other techniques, such as
6213 declaring <tt>Breaks</tt> relationships with affected
6214 packages or treating their usage of the library as bugs in
6215 those packages, may be appropriate instead of changing the
6216 SONAME. However, the default approach is to change the
6217 SONAME for any change to the ABI that could break a program.
6219 Adding new symbols to the shared library is a
6220 backward-compatible change. Removing symbols from the shared
6221 library is not. Changing the behavior of a symbol may or may
6222 not be backward-compatible depending on the change; for
6223 example, changing a function to accept a new enum constant not
6224 previously used by the library is generally
6225 backward-compatible, but changing the members of a struct that
6226 is passed into library functions is generally not unless the
6227 library takes special precautions to accept old versions of
6232 ABI changes that are not backward-compatible normally require
6233 changing the <tt>SONAME</tt> of the library and therefore the
6234 shared library package name, which forces rebuilding all
6235 packages using that shared library to update their
6236 dependencies and allow them to use the new version of the
6237 shared library. For more information,
6238 see <ref id="sharedlibs-runtime">. The remainder of this
6239 section will deal with backward-compatible changes.
6243 Backward-compatible changes require either updating or
6244 recording the <var>minimal-version</var> for that symbol
6245 in <file>symbols</file> files or updating the version in
6246 the <var>dependencies</var> in <file>shlibs</file> files. For
6247 more information on how to do this in the two formats, see
6248 <ref id="symbols"> and <ref id="shlibs">. Below are general
6249 rules that apply to both files.
6253 The easy case is when a public symbol is added. Simply add
6254 the version at which the symbol was introduced
6255 (for <file>symbols</file> files) or update the dependency
6256 version (for <file>shlibs</file>) files. But special care
6257 should be taken to update dependency versions when the
6258 behavior of a public symbol changes. This is easy to neglect,
6259 since there is no automated method of determining such
6260 changes, but failing to update versions in this case may
6261 result in binary packages with too-weak dependencies that will
6262 fail at runtime, possibly in ways that can cause security
6263 vulnerabilities. If the package maintainer believes that a
6264 symbol behavior change may have occurred but isn't sure, it's
6265 safer to update the version rather than leave it unmodified.
6266 This may result in unnecessarily strict dependencies, but it
6267 ensures that packages whose dependencies are satisfied will
6272 A common example of when a change to the dependency version
6273 is required is a function that takes an enum or struct
6274 argument that controls what the function does. For example:
6276 enum library_op { OP_FOO, OP_BAR };
6277 int library_do_operation(enum library_op);
6279 If a new operation, <tt>OP_BAZ</tt>, is added,
6280 the <var>minimal-version</var>
6281 of <tt>library_do_operation</tt> (for <file>symbols</file>
6282 files) or the version in the dependency for the shared library
6283 (for <file>shlibs</file> files) must be increased to the
6284 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6285 binary built against the new version of the library (having
6286 detected at compile-time that the library
6287 supports <tt>OP_BAZ</tt>) may be installed with a shared
6288 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6289 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6294 Dependency versions in either <file>symbols</file>
6295 or <file>shlibs</file> files normally should not contain the
6296 Debian revision of the package, since the library behavior is
6297 normally fixed for a particular upstream version and any
6298 Debian packaging of that upstream version will have the same
6299 behavior. In the rare case that the library behavior was
6300 changed in a particular Debian revision, appending <tt>~</tt>
6301 to the end of the version that includes the Debian revision is
6302 recommended, since this allows backports of the shared library
6303 package using the normal backport versioning convention to
6304 satisfy the dependency.
6308 <sect1 id="sharedlibs-symbols">
6309 <heading>The <tt>symbols</tt> system</heading>
6312 In the following sections, we will first describe where the
6313 various <file>symbols</file> files are to be found, then
6314 the <file>symbols</file> file format, and finally how to
6315 create <file>symbols</file> files if your package contains a
6319 <sect2 id="symbols-paths">
6320 <heading>The <file>symbols</file> files present on the
6324 <file>symbols</file> files for a shared library are normally
6325 provided by the shared library package as a control file,
6326 but there are several override paths that are checked first
6327 in case that information is wrong or missing. The following
6328 list gives them in the order in which they are read
6329 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6330 the required information is used.
6333 <p><file>debian/*/DEBIAN/symbols</file></p>
6336 During the package build, if the package itself
6337 contains shared libraries with <file>symbols</file>
6338 files, they will be generated in these staging
6339 directories by <prgn>dpkg-gensymbols</prgn>
6340 (see <ref id="providing-symbols">). <file>symbols</file>
6341 files found in the build tree take precedence
6342 over <file>symbols</file> files from other binary
6347 These files must exist
6348 before <prgn>dpkg-shlibdeps</prgn> is run or the
6349 dependencies of binaries and libraries from a source
6350 package on other libraries from that same source
6351 package will not be correct. In practice, this means
6352 that <prgn>dpkg-gensymbols</prgn> must be run
6353 before <prgn>dpkg-shlibdeps</prgn> during the package
6355 An example may clarify. Suppose the source
6356 package <tt>foo</tt> generates two binary
6357 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6358 When building the binary packages, the contents of
6359 the packages are staged in the
6360 directories <file>debian/libfoo2</file>
6361 and <file>debian/foo-runtime</file> respectively.
6362 (<file>debian/tmp</file> could be used instead of
6363 one of these.) Since <tt>libfoo2</tt> provides
6364 the <tt>libfoo</tt> shared library, it will contain
6365 a <tt>symbols</tt> file, which will be installed
6366 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6367 eventually to be included as a control file in that
6368 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6370 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6372 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6373 to determine whether <tt>foo-prog</tt>'s library
6374 dependencies are satisfied by any of the libraries
6375 provided by <tt>libfoo2</tt>. Since those binaries
6376 were linked against the just-built shared library as
6377 part of the build process, the <file>symbols</file>
6378 file for the newly-built <tt>libfoo2</tt> must take
6379 precedence over a <file>symbols</file> file for any
6380 other <tt>libfoo2</tt> package already installed on
6388 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6389 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6393 Per-system overrides of shared library dependencies.
6394 These files normally do not exist. They are
6395 maintained by the local system administrator and must
6396 not be created by any Debian package.
6401 <p><file>symbols</file> control files for packages
6402 installed on the system</p>
6405 The <file>symbols</file> control files for all the
6406 packages currently installed on the system are
6407 searched last. This will be the most common source of
6408 shared library dependency information. These are
6410 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6411 packages should not rely on this and instead should
6412 use <tt>dpkg-query --control-path <var>package</var>
6413 symbols</tt> if for some reason these files need to be
6421 Be aware that if a <file>debian/shlibs.local</file> exists
6422 in the source package, it will override
6423 any <file>symbols</file> files. This is the only case where
6424 a <file>shlibs</file> is used despite <file>symbols</file>
6425 files being present. See <ref id="shlibs-paths">
6426 and <ref id="sharedlibs-shlibdeps"> for more information.
6430 <sect2 id="symbols">
6431 <heading>The <file>symbols</file> File Format</heading>
6434 The following documents the format of
6435 the <file>symbols</file> control file as included in binary
6436 packages. These files are built from
6437 template <file>symbols</file> files in the source package
6438 by <prgn>dpkg-gensymbols</prgn>. The template files support
6439 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6440 do some of the tedious work involved in
6441 maintaining <file>symbols</file> files, such as handling C++
6442 symbols or optional symbols that may not exist on particular
6443 architectures. When writing <file>symbols</file> files for
6444 a shared library package, refer
6445 to <manref name="dpkg-gensymbols" section="1"> for the
6450 A <file>symbols</file> may contain one or more entries, one
6451 for each shared library contained in the package
6452 corresponding to that <file>symbols</file>. Each entry has
6453 the following format:
6458 <var>library-soname</var> <var>main-dependency-template</var>
6459 [| <var>alternative-dependency-template</var>]
6461 [* <var>field-name</var>: <var>field-value</var>]
6463 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6468 To explain this format, we'll use the the <tt>zlib1g</tt>
6469 package as an example, which (at the time of writing)
6471 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6472 lines will be described first, followed by optional lines.
6476 <var>library-soname</var> must contain exactly the value of
6477 the ELF <tt>SONAME</tt> attribute of the shared library. In
6478 our example, this is <tt>libz.so.1</tt>.<footnote>
6479 This can be determined by using the command
6480 <example compact="compact">
6481 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6487 <var>main-dependency-template</var> has the same syntax as a
6488 dependency field in a binary package control file, except
6489 that the string <tt>#MINVER#</tt> is replaced by a version
6490 restriction like <tt>(>= <var>version</var>)</tt> or by
6491 nothing if an unversioned dependency is deemed sufficient.
6492 The version restriction will be based on which symbols from
6493 the shared library are referenced and the version at which
6494 they were introduced (see below). In nearly all
6495 cases, <var>main-dependency-template</var> will
6496 be <tt><var>package</var> #MINVER#</tt>,
6497 where <var>package</var> is the name of the binary package
6498 containing the shared library. This adds a simple,
6499 possibly-versioned dependency on the shared library package.
6500 In some rare cases, such as when multiple packages provide
6501 the same shared library ABI, the dependency template may
6502 need to be more complex.
6506 In our example, the first line of
6507 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6508 <example compact="compact">
6509 libz.so.1 zlib1g #MINVER#
6514 Each public symbol exported by the shared library must have
6515 a corresponding symbol line, indented by one
6516 space. <var>symbol</var> is the exported symbol (which, for
6517 C++, means the mangled symbol) followed by <tt>@</tt> and
6518 the symbol version, or the string <tt>Base</tt> if there is
6519 no symbol version. <var>minimal-version</var> is the most
6520 recent version of the shared library that changed the
6521 behavior of that symbol, whether by adding it, changing its
6522 function signature (the parameters, their types, or the
6523 return type), or changing its behavior in a way that is
6524 visible to a caller.
6525 <var>id-of-dependency-template</var> is an optional
6526 field that references
6527 an <var>alternative-dependency-template</var>; see below for
6532 For example, <tt>libz.so.1</tt> contains the
6533 symbols <tt>compress</tt>
6534 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6535 version and last changed its behavior in upstream
6536 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6537 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6538 upstream version <tt>1:1.2.0</tt>, and has not changed its
6539 behavior. Its <file>symbols</file> file therefore contains
6541 <example compact="compact">
6542 compress@Base 1:1.1.4
6543 compressBound@ZLIB_1.2.0 1:1.2.0
6545 Packages using only <tt>compress</tt> would then get a
6546 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6547 using <tt>compressBound</tt> would get a dependency
6548 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6552 One or more <var>alternative-dependency-template</var> lines
6553 may be provided. These are used in cases where some symbols
6554 in the shared library should use one dependency template
6555 while others should use a different template. The
6556 alternative dependency templates are used only if a symbol
6557 line contains the <var>id-of-dependency-template</var>
6558 field. The first alternative dependency template is
6559 numbered 1, the second 2, and so forth.<footnote>
6560 An example of where this may be needed is with a library
6561 that implements the libGL interface. All GL
6562 implementations provide the same set of base interfaces,
6563 and then may provide some additional interfaces only used
6564 by programs that require that specific GL implementation.
6565 So, for example, libgl1-mesa-glx may use the
6566 following <file>symbols</file> file:
6569 | libgl1-mesa-glx #MINVER#
6570 publicGlSymbol@Base 6.3-1
6572 implementationSpecificSymbol@Base 6.5.2-7 1
6575 Binaries or shared libraries using
6576 only <tt>publicGlSymbol</tt> would depend only
6577 on <tt>libgl1</tt> (which may be provided by multiple
6579 using <tt>implementationSpecificSymbol</tt> would get a
6580 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6585 Finally, the entry for the library may contain one or more
6586 metadata fields. Currently, the only
6587 supported <var>field-name</var>
6588 is <tt>Build-Depends-Package</tt>, whose value lists
6589 the <qref id="sharedlibs-dev">library development
6590 package</qref> on which packages using this shared library
6591 declare a build dependency. If this field is
6592 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6593 the resulting binary package dependency on the shared
6594 library is at least as strict as the source package
6595 dependency on the shared library development
6597 This field should normally not be necessary, since if the
6598 behavior of any symbol has changed, the corresponding
6599 symbol <var>minimal-version</var> should have been
6600 increased. But including it makes the <tt>symbols</tt>
6601 system more robust by tightening the dependency in cases
6602 where the package using the shared library specifically
6603 requires at least a particular version of the shared
6604 library development package for some reason.
6606 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6608 <example compact="compact">
6609 * Build-Depends-Package: zlib1g-dev
6614 Also see <manref name="deb-symbols" section="5">.
6618 <sect2 id="providing-symbols">
6619 <heading>Providing a <file>symbols</file> file</heading>
6622 If your package provides a shared library, you should
6623 arrange to include a <file>symbols</file> control file
6624 following the format described above in that package. You
6625 must include either a <file>symbols</file> control file or
6626 a <file>shlibs</file> control file.
6630 Normally, this is done by creating a <file>symbols</file> in
6632 named <file>debian/<var>package</var>.symbols</file>
6633 or <file>debian/symbols</file>, possibly
6634 with <file>.<var>arch</var></file> appended if the symbols
6635 information varies by architecture. This file may use the
6636 extended syntax documented in <manref name="dpkg-gensymbols"
6637 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6638 part of the package build process. It will
6639 create <file>symbols</file> files in the package staging
6640 area based on the binaries and libraries in the package
6641 staging area and the <file>symbols</file> files in the
6642 source package.<footnote>
6644 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6645 take care of calling either <prgn>dpkg-gensymbols</prgn>
6646 or generating a <file>shlibs</file> file as appropriate.
6651 Packages that provide <file>symbols</file> files must keep
6652 them up-to-date to ensure correct dependencies in packages
6653 that use the shared libraries. This means updating
6654 the <file>symbols</file> file whenever a new public symbol
6655 is added, changing the <var>minimal-version</var> field
6656 whenever a symbol changes behavior or signature in a
6657 backward-compatible way (see <ref id="sharedlibs-updates">),
6658 and changing the <var>library-soname</var>
6659 and <var>main-dependency-template</var>, and probably all of
6660 the <var>minimal-version</var> fields, when the library
6661 changes <tt>SONAME</tt>. Removing a public symbol from
6662 the <file>symbols</file> file because it's no longer
6663 provided by the library normally requires changing
6664 the <tt>SONAME</tt> of the library.
6665 See <ref id="sharedlibs-runtime"> for more information
6666 on <tt>SONAME</tt>s.
6671 <sect1 id="sharedlibs-shlibdeps">
6672 <heading>The <tt>shlibs</tt> system</heading>
6675 The <tt>shlibs</tt> system is a simpler alternative to
6676 the <tt>symbols</tt> system for declaring dependencies for
6677 shared libraries. It may be more appropriate for C++
6678 libraries and other cases where tracking individual symbols is
6679 too difficult. It predated the <tt>symbols</tt> system and is
6680 therefore frequently seen in older packages. It is also
6681 required for udebs, which do not support <tt>symbols</tt>.
6685 In the following sections, we will first describe where the
6686 various <file>shlibs</file> files are to be found, then how to
6687 use <prgn>dpkg-shlibdeps</prgn>, and finally
6688 the <file>shlibs</file> file format and how to create them.
6691 <sect2 id="shlibs-paths">
6692 <heading>The <file>shlibs</file> files present on the
6696 There are several places where <tt>shlibs</tt> files are
6697 found. The following list gives them in the order in which
6698 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6699 one which gives the required information is used.)
6702 <p><file>debian/shlibs.local</file></p>
6705 This lists overrides for this package. This file
6706 should normally not be used, but may be needed
6707 temporarily in unusual situations to work around bugs
6708 in other packages, or in unusual cases where the
6709 normally declared dependency information in the
6710 installed <file>shlibs</file> file for a library
6711 cannot be used. This file overrides information
6712 obtained from any other source.
6717 <p><file>/etc/dpkg/shlibs.override</file></p>
6720 This lists global overrides. This list is normally
6721 empty. It is maintained by the local system
6727 <p><file>DEBIAN/shlibs</file> files in the "build
6731 These files are generated as part of the package build
6732 process and staged for inclusion as control files in
6733 the binary packages being built. They provide details
6734 of any shared libraries included in the same package.
6739 <p><file>shlibs</file> control files for packages
6740 installed on the system</p>
6743 The <file>shlibs</file> control files for all the
6744 packages currently installed on the system. These are
6746 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6747 packages should not rely on this and instead should
6748 use <tt>dpkg-query --control-path <var>package</var>
6749 shlibs</tt> if for some reason these files need to be
6755 <p><file>/etc/dpkg/shlibs.default</file></p>
6758 This file lists any shared libraries whose packages
6759 have failed to provide correct <file>shlibs</file>
6760 files. It was used when the <file>shlibs</file> setup
6761 was first introduced, but it is now normally empty.
6762 It is maintained by the <tt>dpkg</tt> maintainer.
6769 If a <file>symbols</file> file for a shared library package
6770 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6771 in preference to a <file>shlibs</file>, with the exception
6772 of <file>debian/shlibs.local</file>. The latter overrides
6773 any other <file>shlibs</file> or <file>symbols</file> files.
6778 <heading>The <file>shlibs</file> File Format</heading>
6781 Each <file>shlibs</file> file has the same format. Lines
6782 beginning with <tt>#</tt> are considered to be comments and
6783 are ignored. Each line is of the form:
6784 <example compact="compact">
6785 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6790 We will explain this by reference to the example of the
6791 <tt>zlib1g</tt> package, which (at the time of writing)
6793 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6797 <var>type</var> is an optional element that indicates the
6798 type of package for which the line is valid. The only type
6799 currently in use is <tt>udeb</tt>. The colon and space
6800 after the type are required.
6804 <var>library-name</var> is the name of the shared library,
6805 in this case <tt>libz</tt>. (This must match the name part
6806 of the soname, see below.)
6810 <var>soname-version</var> is the version part of the
6811 ELF <tt>SONAME</tt> attribute of the library, determined the
6812 same way that the <var>soversion</var> component of the
6813 recommended shared library package name is determined.
6814 See <ref id="sharedlibs-runtime"> for the details.
6818 <var>dependencies</var> has the same syntax as a dependency
6819 field in a binary package control file. It should give
6820 details of which packages are required to satisfy a binary
6821 built against the version of the library contained in the
6822 package. See <ref id="depsyntax"> for details on the
6823 syntax, and <ref id="sharedlibs-updates"> for details on how
6824 to maintain the dependency version constraint.
6828 In our example, if the last change to the <tt>zlib1g</tt>
6829 package that could change behavior for a client of that
6830 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6831 the <tt>shlibs</tt> entry for this library could say:
6832 <example compact="compact">
6833 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6835 This version restriction must be new enough that any binary
6836 built against the current version of the library will work
6837 with any version of the shared library that satisfies that
6842 As zlib1g also provides a udeb containing the shared
6843 library, there would also be a second line:
6844 <example compact="compact">
6845 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6851 <heading>Providing a <file>shlibs</file> file</heading>
6854 To provide a <file>shlibs</file> file for a shared library
6855 binary package, create a <file>shlibs</file> file following
6856 the format described above and place it in
6857 the <file>DEBIAN</file> directory for that package during
6858 the build. It will then be included as a control file for
6859 that package<footnote>
6860 This is what <prgn>dh_makeshlibs</prgn> in
6861 the <package>debhelper</package> suite does. If your
6862 package also has a udeb that provides a shared
6863 library, <prgn>dh_makeshlibs</prgn> can automatically
6864 generate the <tt>udeb:</tt> lines if you specify the name
6865 of the udeb with the <tt>--add-udeb</tt> option.
6870 Since <prgn>dpkg-shlibdeps</prgn> reads
6871 the <file>DEBIAN/shlibs</file> files in all of the binary
6872 packages being built from this source package, all of
6873 the <file>DEBIAN/shlibs</file> files should be installed
6874 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6883 <chapt id="opersys"><heading>The Operating System</heading>
6886 <heading>File system hierarchy</heading>
6890 <heading>File System Structure</heading>
6893 The location of all files and directories must comply with the
6894 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6895 exceptions noted below, and except where doing so would
6896 violate other terms of Debian Policy. The following
6897 exceptions to the FHS apply:
6902 The optional rules related to user specific
6903 configuration files for applications are stored in
6904 the user's home directory are relaxed. It is
6905 recommended that such files start with the
6906 '<tt>.</tt>' character (a "dot file"), and if an
6907 application needs to create more than one dot file
6908 then the preferred placement is in a subdirectory
6909 with a name starting with a '.' character, (a "dot
6910 directory"). In this case it is recommended the
6911 configuration files not start with the '.'
6917 The requirement for amd64 to use <file>/lib64</file>
6918 for 64 bit binaries is removed.
6923 The requirement for object files, internal binaries, and
6924 libraries, including <file>libc.so.*</file>, to be located
6925 directly under <file>/lib{,32}</file> and
6926 <file>/usr/lib{,32}</file> is amended, permitting files
6927 to instead be installed to
6928 <file>/lib/<var>triplet</var></file> and
6929 <file>/usr/lib/<var>triplet</var></file>, where
6930 <tt><var>triplet</var></tt> is the value returned by
6931 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6932 architecture of the package. Packages may <em>not</em>
6933 install files to any <var>triplet</var> path other
6934 than the one matching the architecture of that package;
6935 for instance, an <tt>Architecture: amd64</tt> package
6936 containing 32-bit x86 libraries may not install these
6937 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6939 This is necessary in order to reserve the directories for
6940 use in cross-installation of library packages from other
6941 architectures, as part of the planned deployment of
6946 Applications may also use a single subdirectory under
6947 <file>/usr/lib/<var>triplet</var></file>.
6950 The execution time linker/loader, ld*, must still be made
6951 available in the existing location under /lib or /lib64
6952 since this is part of the ELF ABI for the architecture.
6957 The requirement that
6958 <file>/usr/local/share/man</file> be "synonymous"
6959 with <file>/usr/local/man</file> is relaxed to a
6964 The requirement that windowmanagers with a single
6965 configuration file call it <file>system.*wmrc</file>
6966 is removed, as is the restriction that the window
6967 manager subdirectory be named identically to the
6968 window manager name itself.
6973 The requirement that boot manager configuration
6974 files live in <file>/etc</file>, or at least are
6975 symlinked there, is relaxed to a recommendation.
6980 The additional directory <file>/run</file> in the root
6981 file system is allowed. <file>/run</file>
6982 replaces <file>/var/run</file>, and the
6983 subdirectory <file>/run/lock</file>
6984 replaces <file>/var/lock</file>, with
6985 the <file>/var</file> directories replaced by symlinks
6986 for backwards compatibility. <file>/run</file>
6987 and <file>/run/lock</file> must follow all of the
6988 requirements in the FHS for <file>/var/run</file>
6989 and <file>/var/lock</file>, respectively, such as file
6990 naming conventions, file format requirements, or the
6991 requirement that files be cleared during the boot
6992 process. Files and directories residing
6993 in <file>/run</file> should be stored on a temporary
6997 Packages must not assume the <file>/run</file>
6998 directory exists or is usable without a dependency
6999 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7000 stable release of Debian supports <file>/run</file>.
7005 The following directories in the root filesystem are
7006 additionally allowed: <file>/sys</file> and
7007 <file>/selinux</file>. <footnote>These directories
7008 are used as mount points to mount virtual filesystems
7009 to get access to kernel information.</footnote>
7014 On GNU/Hurd systems, the following additional
7015 directories are allowed in the root
7016 filesystem: <file>/hurd</file>
7017 and <file>/servers</file>.<footnote>
7018 These directories are used to store translators and as
7019 a set of standard names for mount points,
7028 The version of this document referred here can be
7029 found in the <tt>debian-policy</tt> package or on <url
7030 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7031 name="FHS (Debian copy)"> alongside this manual (or, if
7032 you have the <package>debian-policy</package> installed,
7034 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7035 (local copy)">). The
7036 latest version, which may be a more recent version, may
7038 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7039 Specific questions about following the standard may be
7040 asked on the <tt>debian-devel</tt> mailing list, or
7041 referred to the FHS mailing list (see the
7042 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7048 <heading>Site-specific programs</heading>
7051 As mandated by the FHS, packages must not place any
7052 files in <file>/usr/local</file>, either by putting them in
7053 the file system archive to be unpacked by <prgn>dpkg</prgn>
7054 or by manipulating them in their maintainer scripts.
7058 However, the package may create empty directories below
7059 <file>/usr/local</file> so that the system administrator knows
7060 where to place site-specific files. These are not
7061 directories <em>in</em> <file>/usr/local</file>, but are
7062 children of directories in <file>/usr/local</file>. These
7063 directories (<file>/usr/local/*/dir/</file>)
7064 should be removed on package removal if they are
7069 Note that this applies only to
7070 directories <em>below</em> <file>/usr/local</file>,
7071 not <em>in</em> <file>/usr/local</file>. Packages must
7072 not create sub-directories in the
7073 directory <file>/usr/local</file> itself, except those
7074 listed in FHS, section 4.5. However, you may create
7075 directories below them as you wish. You must not remove
7076 any of the directories listed in 4.5, even if you created
7081 Since <file>/usr/local</file> can be mounted read-only from a
7082 remote server, these directories must be created and
7083 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7084 maintainer scripts and not be included in the
7085 <file>.deb</file> archive. These scripts must not fail if
7086 either of these operations fail.
7090 For example, the <tt>emacsen-common</tt> package could
7091 contain something like
7092 <example compact="compact">
7093 if [ ! -e /usr/local/share/emacs ]; then
7094 if mkdir /usr/local/share/emacs 2>/dev/null; then
7095 if chown root:staff /usr/local/share/emacs; then
7096 chmod 2775 /usr/local/share/emacs || true
7101 in its <prgn>postinst</prgn> script, and
7102 <example compact="compact">
7103 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7104 rmdir /usr/local/share/emacs 2>/dev/null || true
7106 in the <prgn>prerm</prgn> script. (Note that this form is
7107 used to ensure that if the script is interrupted, the
7108 directory <file>/usr/local/share/emacs</file> will still be
7113 If you do create a directory in <file>/usr/local</file> for
7114 local additions to a package, you should ensure that
7115 settings in <file>/usr/local</file> take precedence over the
7116 equivalents in <file>/usr</file>.
7120 However, because <file>/usr/local</file> and its contents are
7121 for exclusive use of the local administrator, a package
7122 must not rely on the presence or absence of files or
7123 directories in <file>/usr/local</file> for normal operation.
7127 The <file>/usr/local</file> directory itself and all the
7128 subdirectories created by the package should (by default) have
7129 permissions 2775 (group-writable and set-group-id) and be
7130 owned by <tt>root:staff</tt>.
7135 <heading>The system-wide mail directory</heading>
7137 The system-wide mail directory
7138 is <file>/var/mail</file>. This directory is part of the
7139 base system and should not be owned by any particular mail
7140 agents. The use of the old
7141 location <file>/var/spool/mail</file> is deprecated, even
7142 though the spool may still be physically located there.
7146 <sect1 id="fhs-run">
7147 <heading><file>/run</file> and <file>/run/lock</file></heading>
7150 The directory <file>/run</file> is cleared at boot, normally
7151 by being a mount point for a temporary file system. Packages
7152 therefore must not assume that any files or directories
7153 under <file>/run</file> other than <file>/run/lock</file>
7154 exist unless the package has arranged to create those files or
7155 directories since the last reboot. Normally, this is done by
7156 the package via an init script. See <ref id="writing-init">
7157 for more information.
7161 Packages must not include files or directories
7162 under <file>/run</file>, or under the
7163 older <file>/var/run</file> and <file>/var/lock</file> paths.
7164 The latter paths will normally be symlinks or other
7165 redirections to <file>/run</file> for backwards compatibility.
7171 <heading>Users and groups</heading>
7174 <heading>Introduction</heading>
7176 The Debian system can be configured to use either plain or
7181 Some user ids (UIDs) and group ids (GIDs) are reserved
7182 globally for use by certain packages. Because some
7183 packages need to include files which are owned by these
7184 users or groups, or need the ids compiled into binaries,
7185 these ids must be used on any Debian system only for the
7186 purpose for which they are allocated. This is a serious
7187 restriction, and we should avoid getting in the way of
7188 local administration policies. In particular, many sites
7189 allocate users and/or local system groups starting at 100.
7193 Apart from this we should have dynamically allocated ids,
7194 which should by default be arranged in some sensible
7195 order, but the behavior should be configurable.
7199 Packages other than <tt>base-passwd</tt> must not modify
7200 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7201 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7206 <heading>UID and GID classes</heading>
7208 The UID and GID numbers are divided into classes as
7214 Globally allocated by the Debian project, the same
7215 on every Debian system. These ids will appear in
7216 the <file>passwd</file> and <file>group</file> files of all
7217 Debian systems, new ids in this range being added
7218 automatically as the <tt>base-passwd</tt> package is
7223 Packages which need a single statically allocated
7224 uid or gid should use one of these; their
7225 maintainers should ask the <tt>base-passwd</tt>
7233 Dynamically allocated system users and groups.
7234 Packages which need a user or group, but can have
7235 this user or group allocated dynamically and
7236 differently on each system, should use <tt>adduser
7237 --system</tt> to create the group and/or user.
7238 <prgn>adduser</prgn> will check for the existence of
7239 the user or group, and if necessary choose an unused
7240 id based on the ranges specified in
7241 <file>adduser.conf</file>.
7245 <tag>1000-59999:</tag>
7248 Dynamically allocated user accounts. By default
7249 <prgn>adduser</prgn> will choose UIDs and GIDs for
7250 user accounts in this range, though
7251 <file>adduser.conf</file> may be used to modify this
7256 <tag>60000-64999:</tag>
7259 Globally allocated by the Debian project, but only
7260 created on demand. The ids are allocated centrally
7261 and statically, but the actual accounts are only
7262 created on users' systems on demand.
7266 These ids are for packages which are obscure or
7267 which require many statically-allocated ids. These
7268 packages should check for and create the accounts in
7269 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7270 <prgn>adduser</prgn> if it has this facility) if
7271 necessary. Packages which are likely to require
7272 further allocations should have a "hole" left after
7273 them in the allocation, to give them room to
7278 <tag>65000-65533:</tag>
7286 User <tt>nobody</tt>. The corresponding gid refers
7287 to the group <tt>nogroup</tt>.
7294 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7295 not</em> be used, because it is the error return
7304 <sect id="sysvinit">
7305 <heading>System run levels and <file>init.d</file> scripts</heading>
7307 <sect1 id="/etc/init.d">
7308 <heading>Introduction</heading>
7311 The <file>/etc/init.d</file> directory contains the scripts
7312 executed by <prgn>init</prgn> at boot time and when the
7313 init state (or "runlevel") is changed (see <manref
7314 name="init" section="8">).
7318 There are at least two different, yet functionally
7319 equivalent, ways of handling these scripts. For the sake
7320 of simplicity, this document describes only the symbolic
7321 link method. However, it must not be assumed by maintainer
7322 scripts that this method is being used, and any automated
7323 manipulation of the various runlevel behaviors by
7324 maintainer scripts must be performed using
7325 <prgn>update-rc.d</prgn> as described below and not by
7326 manually installing or removing symlinks. For information
7327 on the implementation details of the other method,
7328 implemented in the <tt>file-rc</tt> package, please refer
7329 to the documentation of that package.
7333 These scripts are referenced by symbolic links in the
7334 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7335 runlevels, <prgn>init</prgn> looks in the directory
7336 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7337 execute, where <tt><var>n</var></tt> is the runlevel that
7338 is being changed to, or <tt>S</tt> for the boot-up
7343 The names of the links all have the form
7344 <file>S<var>mm</var><var>script</var></file> or
7345 <file>K<var>mm</var><var>script</var></file> where
7346 <var>mm</var> is a two-digit number and <var>script</var>
7347 is the name of the script (this should be the same as the
7348 name of the actual script in <file>/etc/init.d</file>).
7352 When <prgn>init</prgn> changes runlevel first the targets
7353 of the links whose names start with a <tt>K</tt> are
7354 executed, each with the single argument <tt>stop</tt>,
7355 followed by the scripts prefixed with an <tt>S</tt>, each
7356 with the single argument <tt>start</tt>. (The links are
7357 those in the <file>/etc/rc<var>n</var>.d</file> directory
7358 corresponding to the new runlevel.) The <tt>K</tt> links
7359 are responsible for killing services and the <tt>S</tt>
7360 link for starting services upon entering the runlevel.
7364 For example, if we are changing from runlevel 2 to
7365 runlevel 3, init will first execute all of the <tt>K</tt>
7366 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7367 all of the <tt>S</tt> prefixed scripts in that directory.
7368 The links starting with <tt>K</tt> will cause the
7369 referred-to file to be executed with an argument of
7370 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7375 The two-digit number <var>mm</var> is used to determine
7376 the order in which to run the scripts: low-numbered links
7377 have their scripts run first. For example, the
7378 <tt>K20</tt> scripts will be executed before the
7379 <tt>K30</tt> scripts. This is used when a certain service
7380 must be started before another. For example, the name
7381 server <prgn>bind</prgn> might need to be started before
7382 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7383 can set up its access lists. In this case, the script
7384 that starts <prgn>bind</prgn> would have a lower number
7385 than the script that starts <prgn>inn</prgn> so that it
7387 <example compact="compact">
7394 The two runlevels 0 (halt) and 6 (reboot) are slightly
7395 different. In these runlevels, the links with an
7396 <tt>S</tt> prefix are still called after those with a
7397 <tt>K</tt> prefix, but they too are called with the single
7398 argument <tt>stop</tt>.
7402 <sect1 id="writing-init">
7403 <heading>Writing the scripts</heading>
7406 Packages that include daemons for system services should
7407 place scripts in <file>/etc/init.d</file> to start or stop
7408 services at boot time or during a change of runlevel.
7409 These scripts should be named
7410 <file>/etc/init.d/<var>package</var></file>, and they should
7411 accept one argument, saying what to do:
7414 <tag><tt>start</tt></tag>
7415 <item>start the service,</item>
7417 <tag><tt>stop</tt></tag>
7418 <item>stop the service,</item>
7420 <tag><tt>restart</tt></tag>
7421 <item>stop and restart the service if it's already running,
7422 otherwise start the service</item>
7424 <tag><tt>reload</tt></tag>
7425 <item><p>cause the configuration of the service to be
7426 reloaded without actually stopping and restarting
7429 <tag><tt>force-reload</tt></tag>
7430 <item>cause the configuration to be reloaded if the
7431 service supports this, otherwise restart the
7435 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7436 <tt>force-reload</tt> options should be supported by all
7437 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7442 The <file>init.d</file> scripts must ensure that they will
7443 behave sensibly (i.e., returning success and not starting
7444 multiple copies of a service) if invoked with <tt>start</tt>
7445 when the service is already running, or with <tt>stop</tt>
7446 when it isn't, and that they don't kill unfortunately-named
7447 user processes. The best way to achieve this is usually to
7448 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7453 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7454 scripts. Writing correct <file>init.d</file> scripts requires
7455 accepting various error exit statuses when daemons are already
7456 running or already stopped without aborting
7457 the <file>init.d</file> script, and common <file>init.d</file>
7458 function libraries are not safe to call with <tt>set -e</tt>
7460 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7461 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7462 in effect and echoing status messages to the console fails,
7464 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7465 to not use <tt>set -e</tt> and instead check the result of
7466 each command separately.
7470 If a service reloads its configuration automatically (as
7471 in the case of <prgn>cron</prgn>, for example), the
7472 <tt>reload</tt> option of the <file>init.d</file> script
7473 should behave as if the configuration has been reloaded
7478 The <file>/etc/init.d</file> scripts must be treated as
7479 configuration files, either (if they are present in the
7480 package, that is, in the .deb file) by marking them as
7481 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7482 by managing them correctly in the maintainer scripts (see
7483 <ref id="config-files">). This is important since we want
7484 to give the local system administrator the chance to adapt
7485 the scripts to the local system, e.g., to disable a
7486 service without de-installing the package, or to specify
7487 some special command line options when starting a service,
7488 while making sure their changes aren't lost during the next
7493 These scripts should not fail obscurely when the
7494 configuration files remain but the package has been
7495 removed, as configuration files remain on the system after
7496 the package has been removed. Only when <prgn>dpkg</prgn>
7497 is executed with the <tt>--purge</tt> option will
7498 configuration files be removed. In particular, as the
7499 <file>/etc/init.d/<var>package</var></file> script itself is
7500 usually a <tt>conffile</tt>, it will remain on the system
7501 if the package is removed but not purged. Therefore, you
7502 should include a <tt>test</tt> statement at the top of the
7504 <example compact="compact">
7505 test -f <var>program-executed-later-in-script</var> || exit 0
7510 Often there are some variables in the <file>init.d</file>
7511 scripts whose values control the behavior of the scripts,
7512 and which a system administrator is likely to want to
7513 change. As the scripts themselves are frequently
7514 <tt>conffile</tt>s, modifying them requires that the
7515 administrator merge in their changes each time the package
7516 is upgraded and the <tt>conffile</tt> changes. To ease
7517 the burden on the system administrator, such configurable
7518 values should not be placed directly in the script.
7519 Instead, they should be placed in a file in
7520 <file>/etc/default</file>, which typically will have the same
7521 base name as the <file>init.d</file> script. This extra file
7522 should be sourced by the script when the script runs. It
7523 must contain only variable settings and comments in SUSv3
7524 <prgn>sh</prgn> format. It may either be a
7525 <tt>conffile</tt> or a configuration file maintained by
7526 the package maintainer scripts. See <ref id="config-files">
7531 To ensure that vital configurable values are always
7532 available, the <file>init.d</file> script should set default
7533 values for each of the shell variables it uses, either
7534 before sourcing the <file>/etc/default/</file> file or
7535 afterwards using something like the <tt>:
7536 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7537 script must behave sensibly and not fail if the
7538 <file>/etc/default</file> file is deleted.
7542 Files and directories under <file>/run</file>, including ones
7543 referred to via the compatibility paths <file>/var/run</file>
7544 and <file>/var/lock</file>, are normally stored on a temporary
7545 filesystem and are normally not persistent across a reboot.
7546 The <file>init.d</file> scripts must handle this correctly.
7547 This will typically mean creating any required subdirectories
7548 dynamically when the <file>init.d</file> script is run.
7549 See <ref id="fhs-run"> for more information.
7554 <heading>Interfacing with the initscript system</heading>
7557 Maintainers should use the abstraction layer provided by
7558 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7559 programs to deal with initscripts in their packages'
7560 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7561 and <prgn>postrm</prgn>.
7565 Directly managing the /etc/rc?.d links and directly
7566 invoking the <file>/etc/init.d/</file> initscripts should
7567 be done only by packages providing the initscript
7568 subsystem (such as <prgn>sysv-rc</prgn> and
7569 <prgn>file-rc</prgn>).
7573 <heading>Managing the links</heading>
7576 The program <prgn>update-rc.d</prgn> is provided for
7577 package maintainers to arrange for the proper creation and
7578 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7579 or their functional equivalent if another method is being
7580 used. This may be used by maintainers in their packages'
7581 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7585 You must not include any <file>/etc/rc<var>n</var>.d</file>
7586 symbolic links in the actual archive or manually create or
7587 remove the symbolic links in maintainer scripts; you must
7588 use the <prgn>update-rc.d</prgn> program instead. (The
7589 former will fail if an alternative method of maintaining
7590 runlevel information is being used.) You must not include
7591 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7592 in the archive either. (Only the <tt>sysvinit</tt>
7597 By default <prgn>update-rc.d</prgn> will start services in
7598 each of the multi-user state runlevels (2, 3, 4, and 5)
7599 and stop them in the halt runlevel (0), the single-user
7600 runlevel (1) and the reboot runlevel (6). The system
7601 administrator will have the opportunity to customize
7602 runlevels by simply adding, moving, or removing the
7603 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7604 symbolic links are being used, or by modifying
7605 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7610 To get the default behavior for your package, put in your
7611 <prgn>postinst</prgn> script
7612 <example compact="compact">
7613 update-rc.d <var>package</var> defaults
7615 and in your <prgn>postrm</prgn>
7616 <example compact="compact">
7617 if [ "$1" = purge ]; then
7618 update-rc.d <var>package</var> remove
7620 </example>. Note that if your package changes runlevels
7621 or priority, you may have to remove and recreate the links,
7622 since otherwise the old links may persist. Refer to the
7623 documentation of <prgn>update-rc.d</prgn>.
7627 This will use a default sequence number of 20. If it does
7628 not matter when or in which order the <file>init.d</file>
7629 script is run, use this default. If it does, then you
7630 should talk to the maintainer of the <prgn>sysvinit</prgn>
7631 package or post to <tt>debian-devel</tt>, and they will
7632 help you choose a number.
7636 For more information about using <tt>update-rc.d</tt>,
7637 please consult its man page <manref name="update-rc.d"
7643 <heading>Running initscripts</heading>
7645 The program <prgn>invoke-rc.d</prgn> is provided to make
7646 it easier for package maintainers to properly invoke an
7647 initscript, obeying runlevel and other locally-defined
7648 constraints that might limit a package's right to start,
7649 stop and otherwise manage services. This program may be
7650 used by maintainers in their packages' scripts.
7654 The package maintainer scripts must use
7655 <prgn>invoke-rc.d</prgn> to invoke the
7656 <file>/etc/init.d/*</file> initscripts, instead of
7657 calling them directly.
7661 By default, <prgn>invoke-rc.d</prgn> will pass any
7662 action requests (start, stop, reload, restart...) to the
7663 <file>/etc/init.d</file> script, filtering out requests
7664 to start or restart a service out of its intended
7669 Most packages will simply need to change:
7670 <example compact="compact">/etc/init.d/<package>
7671 <action></example> in their <prgn>postinst</prgn>
7672 and <prgn>prerm</prgn> scripts to:
7673 <example compact="compact">
7674 if which invoke-rc.d >/dev/null 2>&1; then
7675 invoke-rc.d <var>package</var> <action>
7677 /etc/init.d/<var>package</var> <action>
7683 A package should register its initscript services using
7684 <prgn>update-rc.d</prgn> before it tries to invoke them
7685 using <prgn>invoke-rc.d</prgn>. Invocation of
7686 unregistered services may fail.
7690 For more information about using
7691 <prgn>invoke-rc.d</prgn>, please consult its man page
7692 <manref name="invoke-rc.d" section="8">.
7698 <heading>Boot-time initialization</heading>
7701 There used to be another directory, <file>/etc/rc.boot</file>,
7702 which contained scripts which were run once per machine
7703 boot. This has been deprecated in favour of links from
7704 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7705 described in <ref id="/etc/init.d">. Packages must not
7706 place files in <file>/etc/rc.boot</file>.
7711 <heading>Example</heading>
7714 An example on which you can base your
7715 <file>/etc/init.d</file> scripts is found in
7716 <file>/etc/init.d/skeleton</file>.
7723 <heading>Console messages from <file>init.d</file> scripts</heading>
7726 This section describes the formats to be used for messages
7727 written to standard output by the <file>/etc/init.d</file>
7728 scripts. The intent is to improve the consistency of
7729 Debian's startup and shutdown look and feel. For this
7730 reason, please look very carefully at the details. We want
7731 the messages to have the same format in terms of wording,
7732 spaces, punctuation and case of letters.
7736 Here is a list of overall rules that should be used for
7737 messages generated by <file>/etc/init.d</file> scripts.
7743 The message should fit in one line (fewer than 80
7744 characters), start with a capital letter and end with
7745 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7749 If the script is performing some time consuming task in
7750 the background (not merely starting or stopping a
7751 program, for instance), an ellipsis (three dots:
7752 <tt>...</tt>) should be output to the screen, with no
7753 leading or tailing whitespace or line feeds.
7757 The messages should appear as if the computer is telling
7758 the user what it is doing (politely :-), but should not
7759 mention "it" directly. For example, instead of:
7760 <example compact="compact">
7761 I'm starting network daemons: nfsd mountd.
7763 the message should say
7764 <example compact="compact">
7765 Starting network daemons: nfsd mountd.
7772 <tt>init.d</tt> script should use the following standard
7773 message formats for the situations enumerated below.
7779 <p>When daemons are started</p>
7782 If the script starts one or more daemons, the output
7783 should look like this (a single line, no leading
7785 <example compact="compact">
7786 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7788 The <var>description</var> should describe the
7789 subsystem the daemon or set of daemons are part of,
7790 while <var>daemon-1</var> up to <var>daemon-n</var>
7791 denote each daemon's name (typically the file name of
7796 For example, the output of <file>/etc/init.d/lpd</file>
7798 <example compact="compact">
7799 Starting printer spooler: lpd.
7804 This can be achieved by saying
7805 <example compact="compact">
7806 echo -n "Starting printer spooler: lpd"
7807 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7810 in the script. If there are more than one daemon to
7811 start, the output should look like this:
7812 <example compact="compact">
7813 echo -n "Starting remote file system services:"
7814 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7815 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7816 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7819 This makes it possible for the user to see what is
7820 happening and when the final daemon has been started.
7821 Care should be taken in the placement of white spaces:
7822 in the example above the system administrators can
7823 easily comment out a line if they don't want to start
7824 a specific daemon, while the displayed message still
7830 <p>When a system parameter is being set</p>
7833 If you have to set up different system parameters
7834 during the system boot, you should use this format:
7835 <example compact="compact">
7836 Setting <var>parameter</var> to "<var>value</var>".
7841 You can use a statement such as the following to get
7843 <example compact="compact">
7844 echo "Setting DNS domainname to \"$domainname\"."
7849 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7850 for the left and right quotation marks. A grave accent
7851 (<tt>`</tt>) is not a quote character; neither is an
7852 apostrophe (<tt>'</tt>).
7857 <p>When a daemon is stopped or restarted</p>
7860 When you stop or restart a daemon, you should issue a
7861 message identical to the startup message, except that
7862 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7863 or <tt>Restarting</tt> respectively.
7867 For example, stopping the printer daemon will look like
7869 <example compact="compact">
7870 Stopping printer spooler: lpd.
7876 <p>When something is executed</p>
7879 There are several examples where you have to run a
7880 program at system startup or shutdown to perform a
7881 specific task, for example, setting the system's clock
7882 using <prgn>netdate</prgn> or killing all processes
7883 when the system shuts down. Your message should look
7885 <example compact="compact">
7886 Doing something very useful...done.
7888 You should print the <tt>done.</tt> immediately after
7889 the job has been completed, so that the user is
7890 informed why they have to wait. You can get this
7892 <example compact="compact">
7893 echo -n "Doing something very useful..."
7902 <p>When the configuration is reloaded</p>
7905 When a daemon is forced to reload its configuration
7906 files you should use the following format:
7907 <example compact="compact">
7908 Reloading <var>description</var> configuration...done.
7910 where <var>description</var> is the same as in the
7911 daemon starting message.
7918 <sect id="cron-jobs">
7919 <heading>Cron jobs</heading>
7922 Packages must not modify the configuration file
7923 <file>/etc/crontab</file>, and they must not modify the files in
7924 <file>/var/spool/cron/crontabs</file>.
7928 If a package wants to install a job that has to be executed via
7929 cron, it should place a file named as specified
7930 in <ref id="cron-files"> into one or more of the following
7932 <example compact="compact">
7938 As these directory names imply, the files within them are
7939 executed on an hourly, daily, weekly, or monthly basis,
7940 respectively. The exact times are listed in
7941 <file>/etc/crontab</file>.
7945 All files installed in any of these directories must be
7946 scripts (e.g., shell scripts or Perl scripts) so that they
7947 can easily be modified by the local system administrator.
7948 In addition, they must be treated as configuration files.
7952 If a certain job has to be executed at some other frequency or
7953 at a specific time, the package should install a file in
7954 <file>/etc/cron.d</file> with a name as specified
7955 in <ref id="cron-files">. This file uses the same syntax
7956 as <file>/etc/crontab</file> and is processed
7957 by <prgn>cron</prgn> automatically. The file must also be
7958 treated as a configuration file. (Note that entries in the
7959 <file>/etc/cron.d</file> directory are not handled by
7960 <prgn>anacron</prgn>. Thus, you should only use this
7961 directory for jobs which may be skipped if the system is not
7966 Unlike <file>crontab</file> files described in the IEEE Std
7967 1003.1-2008 (POSIX.1) available from
7968 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7969 name="The Open Group">, the files in
7970 <file>/etc/cron.d</file> and the file
7971 <file>/etc/crontab</file> have seven fields; namely:
7973 <item>Minute [0,59]</item>
7974 <item>Hour [0,23]</item>
7975 <item>Day of the month [1,31]</item>
7976 <item>Month of the year [1,12]</item>
7977 <item>Day of the week ([0,6] with 0=Sunday)</item>
7978 <item>Username</item>
7979 <item>Command to be run</item>
7981 Ranges of numbers are allowed. Ranges are two numbers
7982 separated with a hyphen. The specified range is inclusive.
7983 Lists are allowed. A list is a set of numbers (or ranges)
7984 separated by commas. Step values can be used in conjunction
7989 The scripts or <tt>crontab</tt> entries in these directories should
7990 check if all necessary programs are installed before they
7991 try to execute them. Otherwise, problems will arise when a
7992 package was removed but not purged since configuration files
7993 are kept on the system in this situation.
7997 Any <tt>cron</tt> daemon must provide
7998 <file>/usr/bin/crontab</file> and support normal
7999 <tt>crontab</tt> entries as specified in POSIX. The daemon
8000 must also support names for days and months, ranges, and
8001 step values. It has to support <file>/etc/crontab</file>,
8002 and correctly execute the scripts in
8003 <file>/etc/cron.d</file>. The daemon must also correctly
8005 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8008 <sect1 id="cron-files">
8009 <heading>Cron job file names</heading>
8012 The file name of a cron job file should normally match the
8013 name of the package from which it comes.
8017 If a package supplies multiple cron job files files in the
8018 same directory, the file names should all start with the name
8019 of the package (possibly modified as described below) followed
8020 by a hyphen (<tt>-</tt>) and a suitable suffix.
8024 A cron job file name must not include any period or plus
8025 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8026 cause cron to ignore the file. Underscores (<tt>_</tt>)
8027 should be used instead of <tt>.</tt> and <tt>+</tt>
8034 <heading>Menus</heading>
8037 The Debian <tt>menu</tt> package provides a standard
8038 interface between packages providing applications and
8039 <em>menu programs</em> (either X window managers or
8040 text-based menu programs such as <prgn>pdmenu</prgn>).
8044 All packages that provide applications that need not be
8045 passed any special command line arguments for normal
8046 operation should register a menu entry for those
8047 applications, so that users of the <tt>menu</tt> package
8048 will automatically get menu entries in their window
8049 managers, as well in shells like <tt>pdmenu</tt>.
8053 Menu entries should follow the current menu policy.
8057 The menu policy can be found in the <tt>menu-policy</tt>
8058 files in the <tt>debian-policy</tt> package.
8059 It is also available from the Debian web mirrors at
8060 <tt><url name="/doc/packaging-manuals/menu-policy/"
8061 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8065 Please also refer to the <em>Debian Menu System</em>
8066 documentation that comes with the <package>menu</package>
8067 package for information about how to register your
8073 <heading>Multimedia handlers</heading>
8076 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8077 is a mechanism for encoding files and data streams and
8078 providing meta-information about them, in particular their
8079 type (e.g. audio or video) and format (e.g. PNG, HTML,
8084 Registration of MIME type handlers allows programs like mail
8085 user agents and web browsers to invoke these handlers to
8086 view, edit or display MIME types they don't support directly.
8090 Packages which provide programs to view/show/play, compose, edit or
8091 print MIME types should register them as such by placing a file in
8092 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8093 <file>/usr/lib/mime/packages/</file>. The file name should be the
8094 binary package's name.
8098 The <package>mime-support</package> package provides the
8099 <prgn>update-mime</prgn> program, which integrates these
8100 registrations in the <file>/etc/mailcap</file> file, using dpkg
8102 Creating, modifying or removing a file in
8103 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8104 not activate the trigger. In that case, it can be done by calling
8105 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8106 the maintainer script after creating, modifying, or removing
8109 Packages using this facility <em>should not</em> depend on,
8110 recommend, or suggest <prgn>mime-support</prgn>.
8115 <heading>Keyboard configuration</heading>
8118 To achieve a consistent keyboard configuration so that all
8119 applications interpret a keyboard event the same way, all
8120 programs in the Debian distribution must be configured to
8121 comply with the following guidelines.
8125 The following keys must have the specified interpretations:
8128 <tag><tt><--</tt></tag>
8129 <item>delete the character to the left of the cursor</item>
8131 <tag><tt>Delete</tt></tag>
8132 <item>delete the character to the right of the cursor</item>
8134 <tag><tt>Control+H</tt></tag>
8135 <item>emacs: the help prefix</item>
8138 The interpretation of any keyboard events should be
8139 independent of the terminal that is used, be it a virtual
8140 console, an X terminal emulator, an rlogin/telnet session,
8145 The following list explains how the different programs
8146 should be set up to achieve this:
8152 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8156 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8160 X translations are set up to make
8161 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8162 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8163 is the vt220 escape code for the "delete character"
8164 key). This must be done by loading the X resources
8165 using <prgn>xrdb</prgn> on all local X displays, not
8166 using the application defaults, so that the
8167 translation resources used correspond to the
8168 <prgn>xmodmap</prgn> settings.
8172 The Linux console is configured to make
8173 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8174 generate <tt>ESC [ 3 ~</tt>.
8178 X applications are configured so that <tt><</tt>
8179 deletes left, and <tt>Delete</tt> deletes right. Motif
8180 applications already work like this.
8184 Terminals should have <tt>stty erase ^?</tt> .
8188 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8189 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8190 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8194 Emacs is programmed to map <tt>KB_Backspace</tt> or
8195 the <tt>stty erase</tt> character to
8196 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8197 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8198 <tt>^H</tt> to <tt>help</tt> as always.
8202 Other applications use the <tt>stty erase</tt>
8203 character and <tt>kdch1</tt> for the two delete keys,
8204 with ASCII DEL being "delete previous character" and
8205 <tt>kdch1</tt> being "delete character under
8213 This will solve the problem except for the following
8220 Some terminals have a <tt><--</tt> key that cannot
8221 be made to produce anything except <tt>^H</tt>. On
8222 these terminals Emacs help will be unavailable on
8223 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8224 character takes precedence in Emacs, and has been set
8225 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8226 available) can be used instead.
8230 Some operating systems use <tt>^H</tt> for <tt>stty
8231 erase</tt>. However, modern telnet versions and all
8232 rlogin versions propagate <tt>stty</tt> settings, and
8233 almost all UNIX versions honour <tt>stty erase</tt>.
8234 Where the <tt>stty</tt> settings are not propagated
8235 correctly, things can be made to work by using
8236 <tt>stty</tt> manually.
8240 Some systems (including previous Debian versions) use
8241 <prgn>xmodmap</prgn> to arrange for both
8242 <tt><--</tt> and <tt>Delete</tt> to generate
8243 <tt>KB_Delete</tt>. We can change the behavior of
8244 their X clients using the same X resources that we use
8245 to do it for our own clients, or configure our clients
8246 using their resources when things are the other way
8247 around. On displays configured like this
8248 <tt>Delete</tt> will not work, but <tt><--</tt>
8253 Some operating systems have different <tt>kdch1</tt>
8254 settings in their <tt>terminfo</tt> database for
8255 <tt>xterm</tt> and others. On these systems the
8256 <tt>Delete</tt> key will not work correctly when you
8257 log in from a system conforming to our policy, but
8258 <tt><--</tt> will.
8265 <heading>Environment variables</heading>
8268 A program must not depend on environment variables to get
8269 reasonable defaults. (That's because these environment
8270 variables would have to be set in a system-wide
8271 configuration file like <file>/etc/profile</file>, which is not
8272 supported by all shells.)
8276 If a program usually depends on environment variables for its
8277 configuration, the program should be changed to fall back to
8278 a reasonable default configuration if these environment
8279 variables are not present. If this cannot be done easily
8280 (e.g., if the source code of a non-free program is not
8281 available), the program must be replaced by a small
8282 "wrapper" shell script which sets the environment variables
8283 if they are not already defined, and calls the original program.
8287 Here is an example of a wrapper script for this purpose:
8289 <example compact="compact">
8291 BAR=${BAR:-/var/lib/fubar}
8293 exec /usr/lib/foo/foo "$@"
8298 Furthermore, as <file>/etc/profile</file> is a configuration
8299 file of the <prgn>base-files</prgn> package, other packages must
8300 not put any environment variables or other commands into that
8305 <sect id="doc-base">
8306 <heading>Registering Documents using doc-base</heading>
8309 The <package>doc-base</package> package implements a
8310 flexible mechanism for handling and presenting
8311 documentation. The recommended practice is for every Debian
8312 package that provides online documentation (other than just
8313 manual pages) to register these documents with
8314 <package>doc-base</package> by installing a
8315 <package>doc-base</package> control file in
8316 <file>/usr/share/doc-base/</file>.
8319 Please refer to the documentation that comes with the
8320 <package>doc-base</package> package for information and
8325 <sect id="alternateinit">
8326 <heading>Alternate init systems</heading>
8328 A number of other init systems are available now in Debian that
8329 can be used in place of <package>sysvinit</package>. Alternative
8330 init implementations must support running SysV init scripts as
8331 described at <ref id="sysvinit"> for compatibility.
8334 Packages may integrate with these replacement init systems by
8335 providing implementation-specific configuration information about
8336 how and when to start a service or in what order to run certain
8337 tasks at boot time. However, any package integrating with other
8338 init systems must also be backwards-compatible with
8339 <package>sysvinit</package> by providing a SysV-style init script
8340 with the same name as and equivalent functionality to any
8341 init-specific job, as this is the only start-up configuration
8342 method guaranteed to be supported by all init implementations. An
8343 exception to this rule is scripts or jobs provided by the init
8344 implementation itself; such jobs may be required for an
8345 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8346 scripts and may not have a one-to-one correspondence with the init
8349 <sect1 id="upstart">
8350 <heading>Event-based boot with upstart</heading>
8353 Packages may integrate with the <prgn>upstart</prgn> event-based
8354 boot system by installing job files in the
8355 <file>/etc/init</file> directory. SysV init scripts for which
8356 an equivalent upstart job is available must query the output of
8357 the command <prgn>initctl version</prgn> for the string
8358 <tt>upstart</tt> and avoid running in favor of the native
8359 upstart job, using a test such as this:
8360 <example compact="compact">
8361 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8368 Because packages shipping upstart jobs may be installed on
8369 systems that are not using upstart, maintainer scripts must
8370 still use the common <prgn>update-rc.d</prgn> and
8371 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8372 and for starting and stopping services. These maintainer
8373 scripts must not call the upstart <prgn>start</prgn>,
8374 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8375 interfaces directly. Instead, implementations of
8376 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8377 when an upstart job with the same name as an init script is
8378 present, and perform the requested action using the upstart job
8379 instead of the init script.
8382 Dependency-based boot managers for SysV init scripts, such as
8383 <prgn>startpar</prgn>, may avoid running a given init script
8384 entirely when an equivalent upstart job is present, to avoid
8385 unnecessary forking of no-op init scripts. In this case, the
8386 boot manager should integrate with upstart to detect when the
8387 upstart job in question is started or stopped to know when the
8388 dependency has been satisfied.
8397 <heading>Files</heading>
8399 <sect id="binaries">
8400 <heading>Binaries</heading>
8403 Two different packages must not install programs with
8404 different functionality but with the same filenames. (The
8405 case of two programs having the same functionality but
8406 different implementations is handled via "alternatives" or
8407 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8408 <ref id="conflicts"> respectively.) If this case happens,
8409 one of the programs must be renamed. The maintainers should
8410 report this to the <tt>debian-devel</tt> mailing list and
8411 try to find a consensus about which program will have to be
8412 renamed. If a consensus cannot be reached, <em>both</em>
8413 programs must be renamed.
8417 By default, when a package is being built, any binaries
8418 created should include debugging information, as well as
8419 being compiled with optimization. You should also turn on
8420 as many reasonable compilation warnings as possible; this
8421 makes life easier for porters, who can then look at build
8422 logs for possible problems. For the C programming language,
8423 this means the following compilation parameters should be
8425 <example compact="compact">
8427 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8429 INSTALL = install -s # (or use strip on the files in debian/tmp)
8434 Note that by default all installed binaries should be stripped,
8435 either by using the <tt>-s</tt> flag to
8436 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8437 the binaries after they have been copied into
8438 <file>debian/tmp</file> but before the tree is made into a
8443 Although binaries in the build tree should be compiled with
8444 debugging information by default, it can often be difficult to
8445 debug programs if they are also subjected to compiler
8446 optimization. For this reason, it is recommended to support the
8447 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8448 (see <ref id="debianrules-options">). This variable can contain
8449 several flags to change how a package is compiled and built.
8453 It is up to the package maintainer to decide what
8454 compilation options are best for the package. Certain
8455 binaries (such as computationally-intensive programs) will
8456 function better with certain flags (<tt>-O3</tt>, for
8457 example); feel free to use them. Please use good judgment
8458 here. Don't use flags for the sake of it; only use them
8459 if there is good reason to do so. Feel free to override
8460 the upstream author's ideas about which compilation
8461 options are best: they are often inappropriate for our
8467 <sect id="libraries">
8468 <heading>Libraries</heading>
8471 If the package is <strong>architecture: any</strong>, then
8472 the shared library compilation and linking flags must have
8473 <tt>-fPIC</tt>, or the package shall not build on some of
8474 the supported architectures<footnote>
8476 If you are using GCC, <tt>-fPIC</tt> produces code with
8477 relocatable position independent code, which is required for
8478 most architectures to create a shared library, with i386 and
8479 perhaps some others where non position independent code is
8480 permitted in a shared library.
8483 Position independent code may have a performance penalty,
8484 especially on <tt>i386</tt>. However, in most cases the
8485 speed penalty must be measured against the memory wasted on
8486 the few architectures where non position independent code is
8489 </footnote>. Any exception to this rule must be discussed on
8490 the mailing list <em>debian-devel@lists.debian.org</em>, and
8491 a rough consensus obtained. The reasons for not compiling
8492 with <tt>-fPIC</tt> flag must be recorded in the file
8493 <tt>README.Debian</tt>, and care must be taken to either
8494 restrict the architecture or arrange for <tt>-fPIC</tt> to
8495 be used on architectures where it is required.<footnote>
8497 Some of the reasons why this might be required is if the
8498 library contains hand crafted assembly code that is not
8499 relocatable, the speed penalty is excessive for compute
8500 intensive libs, and similar reasons.
8505 As to the static libraries, the common case is not to have
8506 relocatable code, since there is no benefit, unless in specific
8507 cases; therefore the static version must not be compiled
8508 with the <tt>-fPIC</tt> flag. Any exception to this rule
8509 should be discussed on the mailing list
8510 <em>debian-devel@lists.debian.org</em>, and the reasons for
8511 compiling with the <tt>-fPIC</tt> flag must be recorded in
8512 the file <tt>README.Debian</tt>. <footnote>
8514 Some of the reasons for linking static libraries with
8515 the <tt>-fPIC</tt> flag are if, for example, one needs a
8516 Perl API for a library that is under rapid development,
8517 and has an unstable API, so shared libraries are
8518 pointless at this phase of the library's development. In
8519 that case, since Perl needs a library with relocatable
8520 code, it may make sense to create a static library with
8521 relocatable code. Another reason cited is if you are
8522 distilling various libraries into a common shared
8523 library, like <tt>mklibs</tt> does in the Debian
8529 In other words, if both a shared and a static library is
8530 being built, each source unit (<tt>*.c</tt>, for example,
8531 for C files) will need to be compiled twice, for the normal
8536 Libraries should be built with threading support and to be
8537 thread-safe if the library supports this.
8541 Although not enforced by the build tools, shared libraries
8542 must be linked against all libraries that they use symbols from
8543 in the same way that binaries are. This ensures the correct
8544 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8545 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8546 systems and guarantees that all libraries can be safely opened
8547 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8548 option <tt>-Wl,-z,defs</tt> when building a shared library.
8549 Since this option enforces symbol resolution at build time,
8550 a missing library reference will be caught early as a fatal
8555 All installed shared libraries should be stripped with
8556 <example compact="compact">
8557 strip --strip-unneeded <var>your-lib</var>
8559 (The option <tt>--strip-unneeded</tt> makes
8560 <prgn>strip</prgn> remove only the symbols which aren't
8561 needed for relocation processing.) Shared libraries can
8562 function perfectly well when stripped, since the symbols for
8563 dynamic linking are in a separate part of the ELF object
8565 You might also want to use the options
8566 <tt>--remove-section=.comment</tt> and
8567 <tt>--remove-section=.note</tt> on both shared libraries
8568 and executables, and <tt>--strip-debug</tt> on static
8574 Note that under some circumstances it may be useful to
8575 install a shared library unstripped, for example when
8576 building a separate package to support debugging.
8580 Shared object files (often <file>.so</file> files) that are not
8581 public libraries, that is, they are not meant to be linked
8582 to by third party executables (binaries of other packages),
8583 should be installed in subdirectories of the
8584 <file>/usr/lib</file> directory. Such files are exempt from the
8585 rules that govern ordinary shared libraries, except that
8586 they must not be installed executable and should be
8588 A common example are the so-called "plug-ins",
8589 internal shared objects that are dynamically loaded by
8590 programs using <manref name="dlopen" section="3">.
8595 Packages that use <prgn>libtool</prgn> to create and install
8596 their shared libraries install a file containing additional
8597 metadata (ending in <file>.la</file>) alongside the library.
8598 For public libraries intended for use by other packages, these
8599 files normally should not be included in the Debian package,
8600 since the information they include is not necessary to link with
8601 the shared library on Debian and can add unnecessary additional
8602 dependencies to other programs or libraries.<footnote>
8603 These files store, among other things, all libraries on which
8604 that shared library depends. Unfortunately, if
8605 the <file>.la</file> file is present and contains that
8606 dependency information, using <prgn>libtool</prgn> when
8607 linking against that library will cause the resulting program
8608 or library to be linked against those dependencies as well,
8609 even if this is unnecessary. This can create unneeded
8610 dependencies on shared library packages that would otherwise
8611 be hidden behind the library ABI, and can make library
8612 transitions to new SONAMEs unnecessarily complicated and
8613 difficult to manage.
8615 If the <file>.la</file> file is required for that library (if,
8616 for instance, it's loaded via <tt>libltdl</tt> in a way that
8617 requires that meta-information), the <tt>dependency_libs</tt>
8618 setting in the <file>.la</file> file should normally be set to
8619 the empty string. If the shared library development package has
8620 historically included the <file>.la</file>, it must be retained
8621 in the development package (with <tt>dependency_libs</tt>
8622 emptied) until all libraries that depend on it have removed or
8623 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8624 files to prevent linking with those other libraries
8625 using <prgn>libtool</prgn> from failing.
8629 If the <file>.la</file> must be included, it should be included
8630 in the development (<tt>-dev</tt>) package, unless the library
8631 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8632 library. If it is intended for use with <tt>libltdl</tt>,
8633 the <file>.la</file> files must go in the run-time library
8638 These requirements for handling of <file>.la</file> files do not
8639 apply to loadable modules or libraries not installed in
8640 directories searched by default by the dynamic linker. Packages
8641 installing loadable modules will frequently need to install
8642 the <file>.la</file> files alongside the modules so that they
8643 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8644 does not need to be modified for libraries or modules that are
8645 not installed in directories searched by the dynamic linker by
8646 default and not intended for use by other packages.
8650 You must make sure that you use only released versions of
8651 shared libraries to build your packages; otherwise other
8652 users will not be able to run your binaries
8653 properly. Producing source packages that depend on
8654 unreleased compilers is also usually a bad
8661 <heading>Shared libraries</heading>
8663 This section has moved to <ref id="sharedlibs">.
8669 <heading>Scripts</heading>
8672 All command scripts, including the package maintainer
8673 scripts inside the package and used by <prgn>dpkg</prgn>,
8674 should have a <tt>#!</tt> line naming the shell to be used
8679 In the case of Perl scripts this should be
8680 <tt>#!/usr/bin/perl</tt>.
8684 When scripts are installed into a directory in the system
8685 PATH, the script name should not include an extension such
8686 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8687 language currently used to implement it.
8690 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8691 <file>init.d</file> scripts should almost certainly start
8692 with <tt>set -e</tt> so that errors are detected.
8693 <file>init.d</file> scripts are something of a special case, due
8694 to how frequently they need to call commands that are allowed to
8695 fail, and it may instead be easier to check the exit status of
8696 commands directly. See <ref id="writing-init"> for more
8697 information about writing <file>init.d</file> scripts.
8700 Every script should use <tt>set -e</tt> or check the exit status
8701 of <em>every</em> command.
8704 Scripts may assume that <file>/bin/sh</file> implements the
8705 SUSv3 Shell Command Language<footnote>
8706 Single UNIX Specification, version 3, which is also IEEE
8707 1003.1-2004 (POSIX), and is available on the World Wide Web
8708 from <url id="http://www.unix.org/version3/online.html"
8709 name="The Open Group"> after free
8710 registration.</footnote>
8711 plus the following additional features not mandated by
8713 These features are in widespread use in the Linux community
8714 and are implemented in all of bash, dash, and ksh, the most
8715 common shells users may wish to use as <file>/bin/sh</file>.
8718 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8719 must not generate a newline.</item>
8720 <item><tt>test</tt>, if implemented as a shell built-in, must
8721 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8723 <item><tt>local</tt> to create a scoped variable must be
8724 supported, including listing multiple variables in a single
8725 local command and assigning a value to a variable at the
8726 same time as localizing it. <tt>local</tt> may or
8727 may not preserve the variable value from an outer scope if
8728 no assignment is present. Uses such as:
8732 # ... use a, b, c, d ...
8735 must be supported and must set the value of <tt>c</tt> to
8738 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8739 -<var>signal</var></tt>, where <var>signal</var> is either
8740 the name of a signal or one of the numeric signals listed in
8741 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8742 supported if <prgn>kill</prgn> is implemented as a shell
8745 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8746 signals must be supported. In addition to the signal
8747 numbers listed in the extension, which are the same as for
8748 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8751 If a shell script requires non-SUSv3 features from the shell
8752 interpreter other than those listed above, the appropriate shell
8753 must be specified in the first line of the script (e.g.,
8754 <tt>#!/bin/bash</tt>) and the package must depend on the package
8755 providing the shell (unless the shell package is marked
8756 "Essential", as in the case of <prgn>bash</prgn>).
8760 You may wish to restrict your script to SUSv3 features plus the
8761 above set when possible so that it may use <file>/bin/sh</file>
8762 as its interpreter. Checking your script
8763 with <prgn>checkbashisms</prgn> from
8764 the <package>devscripts</package> package or running your script
8765 with an alternate shell such as <prgn>posh</prgn> may help
8766 uncover violations of the above requirements. If in doubt
8767 whether a script complies with these requirements,
8768 use <file>/bin/bash</file>.
8772 Perl scripts should check for errors when making any
8773 system calls, including <tt>open</tt>, <tt>print</tt>,
8774 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8778 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8779 scripting languages. See <em>Csh Programming Considered
8780 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8781 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8782 If an upstream package comes with <prgn>csh</prgn> scripts
8783 then you must make sure that they start with
8784 <tt>#!/bin/csh</tt> and make your package depend on the
8785 <prgn>c-shell</prgn> virtual package.
8789 Any scripts which create files in world-writeable
8790 directories (e.g., in <file>/tmp</file>) must use a
8791 mechanism which will fail atomically if a file with the same
8792 name already exists.
8796 The Debian base system provides the <prgn>tempfile</prgn>
8797 and <prgn>mktemp</prgn> utilities for use by scripts for
8804 <heading>Symbolic links</heading>
8807 In general, symbolic links within a top-level directory should
8808 be relative, and symbolic links pointing from one top-level
8809 directory to or into another should be absolute. (A top-level
8810 directory is a sub-directory of the root
8811 directory <file>/</file>.) For example, a symbolic link
8812 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8813 should be relative (<file>../share/bar</file>), but a symbolic
8814 link from <file>/var/run</file> to <file>/run</file> should be
8816 This is necessary to allow top-level directories to be
8817 symlinks. If linking <file>/var/run</file>
8818 to <file>/run</file> were done with the relative symbolic
8819 link <file>../run</file>, but <file>/var</file> were a
8820 symbolic link to <file>/srv/disk1</file>, the symbolic link
8821 would point to <file>/srv/run</file> rather than the intended
8827 In addition, symbolic links should be specified as short as
8828 possible, i.e., link targets like <file>foo/../bar</file> are
8833 Note that when creating a relative link using
8834 <prgn>ln</prgn> it is not necessary for the target of the
8835 link to exist relative to the working directory you're
8836 running <prgn>ln</prgn> from, nor is it necessary to change
8837 directory to the directory where the link is to be made.
8838 Simply include the string that should appear as the target
8839 of the link (this will be a pathname relative to the
8840 directory in which the link resides) as the first argument
8845 For example, in your <prgn>Makefile</prgn> or
8846 <file>debian/rules</file>, you can do things like:
8847 <example compact="compact">
8848 ln -fs gcc $(prefix)/bin/cc
8849 ln -fs gcc debian/tmp/usr/bin/cc
8850 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8851 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8856 A symbolic link pointing to a compressed file should always
8857 have the same file extension as the referenced file. (For
8858 example, if a file <file>foo.gz</file> is referenced by a
8859 symbolic link, the filename of the link has to end with
8860 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8865 <heading>Device files</heading>
8868 Packages must not include device files or named pipes in the
8873 If a package needs any special device files that are not
8874 included in the base system, it must call
8875 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8876 after notifying the user<footnote>
8877 This notification could be done via a (low-priority)
8878 debconf message, or an echo (printf) statement.
8883 Packages must not remove any device files in the
8884 <prgn>postrm</prgn> or any other script. This is left to the
8885 system administrator.
8889 Debian uses the serial devices
8890 <file>/dev/ttyS*</file>. Programs using the old
8891 <file>/dev/cu*</file> devices should be changed to use
8892 <file>/dev/ttyS*</file>.
8896 Named pipes needed by the package must be created in
8897 the <prgn>postinst</prgn> script<footnote>
8898 It's better to use <prgn>mkfifo</prgn> rather
8899 than <prgn>mknod</prgn> to create named pipes so that
8900 automated checks for packages incorrectly creating device
8901 files with <prgn>mknod</prgn> won't have false positives.
8902 </footnote> and removed in
8903 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8908 <sect id="config-files">
8909 <heading>Configuration files</heading>
8912 <heading>Definitions</heading>
8916 <tag>configuration file</tag>
8918 A file that affects the operation of a program, or
8919 provides site- or host-specific information, or
8920 otherwise customizes the behavior of a program.
8921 Typically, configuration files are intended to be
8922 modified by the system administrator (if needed or
8923 desired) to conform to local policy or to provide
8924 more useful site-specific behavior.
8927 <tag><tt>conffile</tt></tag>
8929 A file listed in a package's <tt>conffiles</tt>
8930 file, and is treated specially by <prgn>dpkg</prgn>
8931 (see <ref id="configdetails">).
8937 The distinction between these two is important; they are
8938 not interchangeable concepts. Almost all
8939 <tt>conffile</tt>s are configuration files, but many
8940 configuration files are not <tt>conffiles</tt>.
8944 As noted elsewhere, <file>/etc/init.d</file> scripts,
8945 <file>/etc/default</file> files, scripts installed in
8946 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8947 configuration installed in <file>/etc/cron.d</file> must be
8948 treated as configuration files. In general, any script that
8949 embeds configuration information is de-facto a configuration
8950 file and should be treated as such.
8955 <heading>Location</heading>
8958 Any configuration files created or used by your package
8959 must reside in <file>/etc</file>. If there are several,
8960 consider creating a subdirectory of <file>/etc</file>
8961 named after your package.
8965 If your package creates or uses configuration files
8966 outside of <file>/etc</file>, and it is not feasible to modify
8967 the package to use <file>/etc</file> directly, put the files
8968 in <file>/etc</file> and create symbolic links to those files
8969 from the location that the package requires.
8974 <heading>Behavior</heading>
8977 Configuration file handling must conform to the following
8979 <list compact="compact">
8981 local changes must be preserved during a package
8985 configuration files must be preserved when the
8986 package is removed, and only deleted when the
8990 Obsolete configuration files without local changes may be
8991 removed by the package during upgrade.
8995 The easy way to achieve this behavior is to make the
8996 configuration file a <tt>conffile</tt>. This is
8997 appropriate only if it is possible to distribute a default
8998 version that will work for most installations, although
8999 some system administrators may choose to modify it. This
9000 implies that the default version will be part of the
9001 package distribution, and must not be modified by the
9002 maintainer scripts during installation (or at any other
9007 In order to ensure that local changes are preserved
9008 correctly, no package may contain or make hard links to
9009 conffiles.<footnote>
9010 Rationale: There are two problems with hard links.
9011 The first is that some editors break the link while
9012 editing one of the files, so that the two files may
9013 unwittingly become unlinked and different. The second
9014 is that <prgn>dpkg</prgn> might break the hard link
9015 while upgrading <tt>conffile</tt>s.
9020 The other way to do it is via the maintainer scripts. In
9021 this case, the configuration file must not be listed as a
9022 <tt>conffile</tt> and must not be part of the package
9023 distribution. If the existence of a file is required for
9024 the package to be sensibly configured it is the
9025 responsibility of the package maintainer to provide
9026 maintainer scripts which correctly create, update and
9027 maintain the file and remove it on purge. (See <ref
9028 id="maintainerscripts"> for more information.) These
9029 scripts must be idempotent (i.e., must work correctly if
9030 <prgn>dpkg</prgn> needs to re-run them due to errors
9031 during installation or removal), must cope with all the
9032 variety of ways <prgn>dpkg</prgn> can call maintainer
9033 scripts, must not overwrite or otherwise mangle the user's
9034 configuration without asking, must not ask unnecessary
9035 questions (particularly during upgrades), and must
9036 otherwise be good citizens.
9040 The scripts are not required to configure every possible
9041 option for the package, but only those necessary to get
9042 the package running on a given system. Ideally the
9043 sysadmin should not have to do any configuration other
9044 than that done (semi-)automatically by the
9045 <prgn>postinst</prgn> script.
9049 A common practice is to create a script called
9050 <file><var>package</var>-configure</file> and have the
9051 package's <prgn>postinst</prgn> call it if and only if the
9052 configuration file does not already exist. In certain
9053 cases it is useful for there to be an example or template
9054 file which the maintainer scripts use. Such files should
9055 be in <file>/usr/share/<var>package</var></file> or
9056 <file>/usr/lib/<var>package</var></file> (depending on whether
9057 they are architecture-independent or not). There should
9058 be symbolic links to them from
9059 <file>/usr/share/doc/<var>package</var>/examples</file> if
9060 they are examples, and should be perfectly ordinary
9061 <prgn>dpkg</prgn>-handled files (<em>not</em>
9062 configuration files).
9066 These two styles of configuration file handling must
9067 not be mixed, for that way lies madness:
9068 <prgn>dpkg</prgn> will ask about overwriting the file
9069 every time the package is upgraded.
9074 <heading>Sharing configuration files</heading>
9077 If two or more packages use the same configuration file
9078 and it is reasonable for both to be installed at the same
9079 time, one of these packages must be defined as
9080 <em>owner</em> of the configuration file, i.e., it will be
9081 the package which handles that file as a configuration
9082 file. Other packages that use the configuration file must
9083 depend on the owning package if they require the
9084 configuration file to operate. If the other package will
9085 use the configuration file if present, but is capable of
9086 operating without it, no dependency need be declared.
9090 If it is desirable for two or more related packages to
9091 share a configuration file <em>and</em> for all of the
9092 related packages to be able to modify that configuration
9093 file, then the following should be done:
9094 <enumlist compact="compact">
9096 One of the related packages (the "owning" package)
9097 will manage the configuration file with maintainer
9098 scripts as described in the previous section.
9101 The owning package should also provide a program
9102 that the other packages may use to modify the
9106 The related packages must use the provided program
9107 to make any desired modifications to the
9108 configuration file. They should either depend on
9109 the core package to guarantee that the configuration
9110 modifier program is available or accept gracefully
9111 that they cannot modify the configuration file if it
9112 is not. (This is in addition to the fact that the
9113 configuration file may not even be present in the
9120 Sometimes it's appropriate to create a new package which
9121 provides the basic infrastructure for the other packages
9122 and which manages the shared configuration files. (The
9123 <tt>sgml-base</tt> package is a good example.)
9127 If the configuration file cannot be shared as described above,
9128 the packages must be marked as conflicting with each other.
9129 Two packages that specify the same file as
9130 a <tt>conffile</tt> must conflict. This is an instance of the
9131 general rule about not sharing files. Neither alternatives
9132 nor diversions are likely to be appropriate in this case; in
9133 particular, <prgn>dpkg</prgn> does not handle diverted
9134 <tt>conffile</tt>s well.
9138 When two packages both declare the same <tt>conffile</tt>, they
9139 may see left-over configuration files from each other even
9140 though they conflict with each other. If a user removes
9141 (without purging) one of the packages and installs the other,
9142 the new package will take over the <tt>conffile</tt> from the
9143 old package. If the file was modified by the user, it will be
9144 treated the same as any other locally
9145 modified <tt>conffile</tt> during an upgrade.
9149 The maintainer scripts must not alter a <tt>conffile</tt>
9150 of <em>any</em> package, including the one the scripts
9156 <heading>User configuration files ("dotfiles")</heading>
9159 The files in <file>/etc/skel</file> will automatically be
9160 copied into new user accounts by <prgn>adduser</prgn>.
9161 No other program should reference the files in
9162 <file>/etc/skel</file>.
9166 Therefore, if a program needs a dotfile to exist in
9167 advance in <file>$HOME</file> to work sensibly, that dotfile
9168 should be installed in <file>/etc/skel</file> and treated as a
9173 However, programs that require dotfiles in order to
9174 operate sensibly are a bad thing, unless they do create
9175 the dotfiles themselves automatically.
9179 Furthermore, programs should be configured by the Debian
9180 default installation to behave as closely to the upstream
9181 default behavior as possible.
9185 Therefore, if a program in a Debian package needs to be
9186 configured in some way in order to operate sensibly, that
9187 should be done using a site-wide configuration file placed
9188 in <file>/etc</file>. Only if the program doesn't support a
9189 site-wide default configuration and the package maintainer
9190 doesn't have time to add it may a default per-user file be
9191 placed in <file>/etc/skel</file>.
9195 <file>/etc/skel</file> should be as empty as we can make it.
9196 This is particularly true because there is no easy (or
9197 necessarily desirable) mechanism for ensuring that the
9198 appropriate dotfiles are copied into the accounts of
9199 existing users when a package is installed.
9205 <heading>Log files</heading>
9207 Log files should usually be named
9208 <file>/var/log/<var>package</var>.log</file>. If you have many
9209 log files, or need a separate directory for permission
9210 reasons (<file>/var/log</file> is writable only by
9211 <file>root</file>), you should usually create a directory named
9212 <file>/var/log/<var>package</var></file> and place your log
9217 Log files must be rotated occasionally so that they don't grow
9218 indefinitely. The best way to do this is to install a log
9219 rotation configuration file in the
9220 directory <file>/etc/logrotate.d</file>, normally
9221 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9222 the facilities provided by <prgn>logrotate</prgn>.
9225 The traditional approach to log files has been to set up
9226 <em>ad hoc</em> log rotation schemes using simple shell
9227 scripts and cron. While this approach is highly
9228 customizable, it requires quite a lot of sysadmin work.
9229 Even though the original Debian system helped a little
9230 by automatically installing a system which can be used
9231 as a template, this was deemed not enough.
9235 The use of <prgn>logrotate</prgn>, a program developed
9236 by Red Hat, is better, as it centralizes log management.
9237 It has both a configuration file
9238 (<file>/etc/logrotate.conf</file>) and a directory where
9239 packages can drop their individual log rotation
9240 configurations (<file>/etc/logrotate.d</file>).
9243 Here is a good example for a logrotate config
9244 file (for more information see <manref name="logrotate"
9246 <example compact="compact">
9247 /var/log/foo/*.log {
9253 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9257 This rotates all files under <file>/var/log/foo</file>, saves 12
9258 compressed generations, and tells the daemon to reopen its log
9259 files after the log rotation. It skips this log rotation
9260 (via <tt>missingok</tt>) if no such log file is present, which
9261 avoids errors if the package is removed but not purged.
9265 Log files should be removed when the package is
9266 purged (but not when it is only removed). This should be
9267 done by the <prgn>postrm</prgn> script when it is called
9268 with the argument <tt>purge</tt> (see <ref
9269 id="removedetails">).
9273 <sect id="permissions-owners">
9274 <heading>Permissions and owners</heading>
9277 The rules in this section are guidelines for general use.
9278 If necessary you may deviate from the details below.
9279 However, if you do so you must make sure that what is done
9280 is secure and you should try to be as consistent as possible
9281 with the rest of the system. You should probably also
9282 discuss it on <prgn>debian-devel</prgn> first.
9286 Files should be owned by <tt>root:root</tt>, and made
9287 writable only by the owner and universally readable (and
9288 executable, if appropriate), that is mode 644 or 755.
9292 Directories should be mode 755 or (for group-writability)
9293 mode 2775. The ownership of the directory should be
9294 consistent with its mode: if a directory is mode 2775, it
9295 should be owned by the group that needs write access to
9298 When a package is upgraded, and the owner or permissions
9299 of a file included in the package has changed, dpkg
9300 arranges for the ownership and permissions to be
9301 correctly set upon installation. However, this does not
9302 extend to directories; the permissions and ownership of
9303 directories already on the system does not change on
9304 install or upgrade of packages. This makes sense, since
9305 otherwise common directories like <tt>/usr</tt> would
9306 always be in flux. To correctly change permissions of a
9307 directory the package owns, explicit action is required,
9308 usually in the <tt>postinst</tt> script. Care must be
9309 taken to handle downgrades as well, in that case.
9315 Control information files should be owned by <tt>root:root</tt>
9316 and either mode 644 (for most files) or mode 755 (for
9317 executables such as <qref id="maintscripts">maintainer
9322 Setuid and setgid executables should be mode 4755 or 2755
9323 respectively, and owned by the appropriate user or group.
9324 They should not be made unreadable (modes like 4711 or
9325 2711 or even 4111); doing so achieves no extra security,
9326 because anyone can find the binary in the freely available
9327 Debian package; it is merely inconvenient. For the same
9328 reason you should not restrict read or execute permissions
9329 on non-set-id executables.
9333 Some setuid programs need to be restricted to particular
9334 sets of users, using file permissions. In this case they
9335 should be owned by the uid to which they are set-id, and by
9336 the group which should be allowed to execute them. They
9337 should have mode 4754; again there is no point in making
9338 them unreadable to those users who must not be allowed to
9343 It is possible to arrange that the system administrator can
9344 reconfigure the package to correspond to their local
9345 security policy by changing the permissions on a binary:
9346 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9347 described below.<footnote>
9348 Ordinary files installed by <prgn>dpkg</prgn> (as
9349 opposed to <tt>conffile</tt>s and other similar objects)
9350 normally have their permissions reset to the distributed
9351 permissions when the package is reinstalled. However,
9352 the use of <prgn>dpkg-statoverride</prgn> overrides this
9355 Another method you should consider is to create a group for
9356 people allowed to use the program(s) and make any setuid
9357 executables executable only by that group.
9361 If you need to create a new user or group for your package
9362 there are two possibilities. Firstly, you may need to
9363 make some files in the binary package be owned by this
9364 user or group, or you may need to compile the user or
9365 group id (rather than just the name) into the binary
9366 (though this latter should be avoided if possible, as in
9367 this case you need a statically allocated id).</p>
9370 If you need a statically allocated id, you must ask for a
9371 user or group id from the <tt>base-passwd</tt> maintainer,
9372 and must not release the package until you have been
9373 allocated one. Once you have been allocated one you must
9374 either make the package depend on a version of the
9375 <tt>base-passwd</tt> package with the id present in
9376 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9377 your package to create the user or group itself with the
9378 correct id (using <tt>adduser</tt>) in its
9379 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9380 the <prgn>postinst</prgn> is to be preferred if it is
9381 possible, otherwise a pre-dependency will be needed on the
9382 <tt>adduser</tt> package.)
9386 On the other hand, the program might be able to determine
9387 the uid or gid from the user or group name at runtime, so
9388 that a dynamically allocated id can be used. In this case
9389 you should choose an appropriate user or group name,
9390 discussing this on <prgn>debian-devel</prgn> and checking
9391 with the <package/base-passwd/ maintainer that it is unique and that
9392 they do not wish you to use a statically allocated id
9393 instead. When this has been checked you must arrange for
9394 your package to create the user or group if necessary using
9395 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9396 <prgn>postinst</prgn> script (again, the latter is to be
9397 preferred if it is possible).
9401 Note that changing the numeric value of an id associated
9402 with a name is very difficult, and involves searching the
9403 file system for all appropriate files. You need to think
9404 carefully whether a static or dynamic id is required, since
9405 changing your mind later will cause problems.
9408 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9410 This section is not intended as policy, but as a
9411 description of the use of <prgn>dpkg-statoverride</prgn>.
9415 If a system administrator wishes to have a file (or
9416 directory or other such thing) installed with owner and
9417 permissions different from those in the distributed Debian
9418 package, they can use the <prgn>dpkg-statoverride</prgn>
9419 program to instruct <prgn>dpkg</prgn> to use the different
9420 settings every time the file is installed. Thus the
9421 package maintainer should distribute the files with their
9422 normal permissions, and leave it for the system
9423 administrator to make any desired changes. For example, a
9424 daemon which is normally required to be setuid root, but
9425 in certain situations could be used without being setuid,
9426 should be installed setuid in the <tt>.deb</tt>. Then the
9427 local system administrator can change this if they wish.
9428 If there are two standard ways of doing it, the package
9429 maintainer can use <tt>debconf</tt> to find out the
9430 preference, and call <prgn>dpkg-statoverride</prgn> in the
9431 maintainer script if necessary to accommodate the system
9432 administrator's choice. Care must be taken during
9433 upgrades to not override an existing setting.
9437 Given the above, <prgn>dpkg-statoverride</prgn> is
9438 essentially a tool for system administrators and would not
9439 normally be needed in the maintainer scripts. There is
9440 one type of situation, though, where calls to
9441 <prgn>dpkg-statoverride</prgn> would be needed in the
9442 maintainer scripts, and that involves packages which use
9443 dynamically allocated user or group ids. In such a
9444 situation, something like the following idiom can be very
9445 helpful in the package's <prgn>postinst</prgn>, where
9446 <tt>sysuser</tt> is a dynamically allocated id:
9448 for i in /usr/bin/foo /usr/sbin/bar
9450 # only do something when no setting exists
9451 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9453 #include: debconf processing, question about foo and bar
9454 if [ "$RET" = "true" ] ; then
9455 dpkg-statoverride --update --add sysuser root 4755 $i
9460 The corresponding code to remove the override when the package
9463 for i in /usr/bin/foo /usr/sbin/bar
9465 if dpkg-statoverride --list $i >/dev/null 2>&1
9467 dpkg-statoverride --remove $i
9477 <chapt id="customized-programs">
9478 <heading>Customized programs</heading>
9480 <sect id="arch-spec">
9481 <heading>Architecture specification strings</heading>
9484 If a program needs to specify an <em>architecture specification
9485 string</em> in some place, it should select one of the strings
9486 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9487 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9488 part is sometimes elided, as when the OS is Linux.
9492 Note that we don't want to use
9493 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9494 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9495 since this would make our programs incompatible with other
9496 Linux distributions. We also don't use something like
9497 <tt><var>arch</var>-unknown-linux</tt>, since the
9498 <tt>unknown</tt> does not look very good.
9501 <sect1 id="arch-wildcard-spec">
9502 <heading>Architecture wildcards</heading>
9505 A package may specify an architecture wildcard. Architecture
9506 wildcards are in the format <tt>any</tt> (which matches every
9507 architecture), <tt><var>os</var></tt>-any, or
9508 any-<tt><var>cpu</var></tt>. <footnote>
9509 Internally, the package system normalizes the GNU triplets
9510 and the Debian arches into Debian arch triplets (which are
9511 kind of inverted GNU triplets), with the first component of
9512 the triplet representing the libc and ABI in use, and then
9513 does matching against those triplets. However, such
9514 triplets are an internal implementation detail that should
9515 not be used by packages directly. The libc and ABI portion
9516 is handled internally by the package system based on
9517 the <var>os</var> and <var>cpu</var>.
9524 <heading>Daemons</heading>
9527 The configuration files <file>/etc/services</file>,
9528 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9529 by the <prgn>netbase</prgn> package and must not be modified
9534 If a package requires a new entry in one of these files, the
9535 maintainer should get in contact with the
9536 <prgn>netbase</prgn> maintainer, who will add the entries
9537 and release a new version of the <prgn>netbase</prgn>
9542 The configuration file <file>/etc/inetd.conf</file> must not be
9543 modified by the package's scripts except via the
9544 <prgn>update-inetd</prgn> script or the
9545 <file>DebianNet.pm</file> Perl module. See their documentation
9546 for details on how to add entries.
9550 If a package wants to install an example entry into
9551 <file>/etc/inetd.conf</file>, the entry must be preceded with
9552 exactly one hash character (<tt>#</tt>). Such lines are
9553 treated as "commented out by user" by the
9554 <prgn>update-inetd</prgn> script and are not changed or
9555 activated during package updates.
9560 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9564 Some programs need to create pseudo-ttys. This should be done
9565 using Unix98 ptys if the C library supports it. The resulting
9566 program must not be installed setuid root, unless that
9567 is required for other functionality.
9571 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9572 <file>/var/log/lastlog</file> must be installed writable by
9573 group <tt>utmp</tt>. Programs which need to modify those
9574 files must be installed setgid <tt>utmp</tt>.
9579 <heading>Editors and pagers</heading>
9582 Some programs have the ability to launch an editor or pager
9583 program to edit or display a text document. Since there are
9584 lots of different editors and pagers available in the Debian
9585 distribution, the system administrator and each user should
9586 have the possibility to choose their preferred editor and
9591 In addition, every program should choose a good default
9592 editor/pager if none is selected by the user or system
9597 Thus, every program that launches an editor or pager must
9598 use the EDITOR or PAGER environment variable to determine
9599 the editor or pager the user wishes to use. If these
9600 variables are not set, the programs <file>/usr/bin/editor</file>
9601 and <file>/usr/bin/pager</file> should be used, respectively.
9605 These two files are managed through the <prgn>dpkg</prgn>
9606 "alternatives" mechanism. Every package providing an editor or
9607 pager must call the <prgn>update-alternatives</prgn> script to
9608 register as an alternative for <file>/usr/bin/editor</file>
9609 or <file>/usr/bin/pager</file> as appropriate. The alternative
9610 should have a slave alternative
9611 for <file>/usr/share/man/man1/editor.1.gz</file>
9612 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9613 corresponding manual page.
9617 If it is very hard to adapt a program to make use of the
9618 EDITOR or PAGER variables, that program may be configured to
9619 use <file>/usr/bin/sensible-editor</file> and
9620 <file>/usr/bin/sensible-pager</file> as the editor or pager
9621 program respectively. These are two scripts provided in the
9622 <package>sensible-utils</package> package that check the EDITOR
9623 and PAGER variables and launch the appropriate program, and fall
9624 back to <file>/usr/bin/editor</file>
9625 and <file>/usr/bin/pager</file> if the variable is not set.
9629 A program may also use the VISUAL environment variable to
9630 determine the user's choice of editor. If it exists, it
9631 should take precedence over EDITOR. This is in fact what
9632 <file>/usr/bin/sensible-editor</file> does.
9636 It is not required for a package to depend on
9637 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9638 package to provide such virtual packages.<footnote>
9639 The Debian base system already provides an editor and a
9645 <sect id="web-appl">
9646 <heading>Web servers and applications</heading>
9649 This section describes the locations and URLs that should
9650 be used by all web servers and web applications in the
9657 Cgi-bin executable files are installed in the
9659 <example compact="compact">
9660 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9662 or a subdirectory of that directory, and should be
9664 <example compact="compact">
9665 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9667 (possibly with a subdirectory name
9668 before <var>cgi-bin-name</var>).
9672 <p>Access to HTML documents</p>
9675 HTML documents for a package are stored in
9676 <file>/usr/share/doc/<var>package</var></file>
9677 and can be referred to as
9678 <example compact="compact">
9679 http://localhost/doc/<var>package</var>/<var>filename</var>
9684 The web server should restrict access to the document
9685 tree so that only clients on the same host can read
9686 the documents. If the web server does not support such
9687 access controls, then it should not provide access at
9688 all, or ask about providing access during installation.
9693 <p>Access to images</p>
9695 It is recommended that images for a package be stored
9696 in <tt>/usr/share/images/<var>package</var></tt> and
9697 may be referred to through an alias <tt>/images/</tt>
9700 http://localhost/images/<package>/<filename>
9707 <p>Web Document Root</p>
9710 Web Applications should try to avoid storing files in
9711 the Web Document Root. Instead they should use the
9712 /usr/share/doc/<var>package</var> directory for
9713 documents and register the Web Application via the
9714 <package>doc-base</package> package. If access to the
9715 web document root is unavoidable then use
9716 <example compact="compact">
9719 as the Document Root. This might be just a symbolic
9720 link to the location where the system administrator
9721 has put the real document root.
9724 <item><p>Providing httpd and/or httpd-cgi</p>
9726 All web servers should provide the virtual package
9727 <tt>httpd</tt>. If a web server has CGI support it should
9728 provide <tt>httpd-cgi</tt> additionally.
9731 All web applications which do not contain CGI scripts should
9732 depend on <tt>httpd</tt>, all those web applications which
9733 <tt>do</tt> contain CGI scripts, should depend on
9741 <sect id="mail-transport-agents">
9742 <heading>Mail transport, delivery and user agents</heading>
9745 Debian packages which process electronic mail, whether mail
9746 user agents (MUAs) or mail transport agents (MTAs), must
9747 ensure that they are compatible with the configuration
9748 decisions below. Failure to do this may result in lost
9749 mail, broken <tt>From:</tt> lines, and other serious brain
9754 The mail spool is <file>/var/mail</file> and the interface to
9755 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9756 the FHS). On older systems, the mail spool may be
9757 physically located in <file>/var/spool/mail</file>, but all
9758 access to the mail spool should be via the
9759 <file>/var/mail</file> symlink. The mail spool is part of the
9760 base system and not part of the MTA package.
9764 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9765 programs (such as IMAP daemons) must lock the mailbox in an
9766 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9767 be combined with dot locking. To avoid deadlocks, a program
9768 should use <tt>fcntl()</tt> first and dot locking after
9769 this, or alternatively implement the two locking methods in
9770 a non blocking way<footnote>
9771 If it is not possible to establish both locks, the
9772 system shouldn't wait for the second lock to be
9773 established, but remove the first lock, wait a (random)
9774 time, and start over locking again.
9775 </footnote>. Using the functions <tt>maillock</tt> and
9776 <tt>mailunlock</tt> provided by the
9777 <tt>liblockfile*</tt><footnote>
9778 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9779 to use these functions.
9780 </footnote> packages is the recommended way to realize this.
9784 Mailboxes are generally either mode 600 and owned by
9785 <var>user</var> or mode 660 and owned by
9786 <tt><var>user</var>:mail</tt><footnote>
9787 There are two traditional permission schemes for mail spools:
9788 mode 600 with all mail delivery done by processes running as
9789 the destination user, or mode 660 and owned by group mail with
9790 mail delivery done by a process running as a system user in
9791 group mail. Historically, Debian required mode 660 mail
9792 spools to enable the latter model, but that model has become
9793 increasingly uncommon and the principle of least privilege
9794 indicates that mail systems that use the first model should
9795 use permissions of 600. If delivery to programs is permitted,
9796 it's easier to keep the mail system secure if the delivery
9797 agent runs as the destination user. Debian Policy therefore
9798 permits either scheme.
9799 </footnote>. The local system administrator may choose a
9800 different permission scheme; packages should not make
9801 assumptions about the permission and ownership of mailboxes
9802 unless required (such as when creating a new mailbox). A MUA
9803 may remove a mailbox (unless it has nonstandard permissions) in
9804 which case the MTA or another MUA must recreate it if needed.
9808 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9809 be setgid mail to do the locking mentioned above (and
9810 must obviously avoid accessing other users' mailboxes
9811 using this privilege).</p>
9814 <file>/etc/aliases</file> is the source file for the system mail
9815 aliases (e.g., postmaster, usenet, etc.), it is the one
9816 which the sysadmin and <prgn>postinst</prgn> scripts may
9817 edit. After <file>/etc/aliases</file> is edited the program or
9818 human editing it must call <prgn>newaliases</prgn>. All MTA
9819 packages must come with a <prgn>newaliases</prgn> program,
9820 even if it does nothing, but older MTA packages did not do
9821 this so programs should not fail if <prgn>newaliases</prgn>
9822 cannot be found. Note that because of this, all MTA
9823 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9824 <tt>Replaces: mail-transport-agent</tt> control fields.
9828 The convention of writing <tt>forward to
9829 <var>address</var></tt> in the mailbox itself is not
9830 supported. Use a <tt>.forward</tt> file instead.</p>
9833 The <prgn>rmail</prgn> program used by UUCP
9834 for incoming mail should be <file>/usr/sbin/rmail</file>.
9835 Likewise, <prgn>rsmtp</prgn>, for receiving
9836 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9840 If your package needs to know what hostname to use on (for
9841 example) outgoing news and mail messages which are generated
9842 locally, you should use the file <file>/etc/mailname</file>. It
9843 will contain the portion after the username and <tt>@</tt>
9844 (at) sign for email addresses of users on the machine
9845 (followed by a newline).
9849 Such a package should check for the existence of this file
9850 when it is being configured. If it exists, it should be
9851 used without comment, although an MTA's configuration script
9852 may wish to prompt the user even if it finds that this file
9853 exists. If the file does not exist, the package should
9854 prompt the user for the value (preferably using
9855 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9856 as well as using it in the package's configuration. The
9857 prompt should make it clear that the name will not just be
9858 used by that package. For example, in this situation the
9859 <tt>inn</tt> package could say something like:
9860 <example compact="compact">
9861 Please enter the "mail name" of your system. This is the
9862 hostname portion of the address to be shown on outgoing
9863 news and mail messages. The default is
9864 <var>syshostname</var>, your system's host name. Mail
9865 name ["<var>syshostname</var>"]:
9867 where <var>syshostname</var> is the output of <tt>hostname
9873 <heading>News system configuration</heading>
9876 All the configuration files related to the NNTP (news)
9877 servers and clients should be located under
9878 <file>/etc/news</file>.</p>
9881 There are some configuration issues that apply to a number
9882 of news clients and server packages on the machine. These
9886 <tag><file>/etc/news/organization</file></tag>
9888 A string which should appear as the
9889 organization header for all messages posted
9890 by NNTP clients on the machine
9893 <tag><file>/etc/news/server</file></tag>
9895 Contains the FQDN of the upstream NNTP
9896 server, or localhost if the local machine is
9901 Other global files may be added as required for cross-package news
9908 <heading>Programs for the X Window System</heading>
9911 <heading>Providing X support and package priorities</heading>
9914 Programs that can be configured with support for the X
9915 Window System must be configured to do so and must declare
9916 any package dependencies necessary to satisfy their
9917 runtime requirements when using the X Window System. If
9918 such a package is of higher priority than the X packages
9919 on which it depends, it is required that either the
9920 X-specific components be split into a separate package, or
9921 that an alternative version of the package, which includes
9922 X support, be provided, or that the package's priority be
9928 <heading>Packages providing an X server</heading>
9931 Packages that provide an X server that, directly or
9932 indirectly, communicates with real input and display
9933 hardware should declare in their <tt>Provides</tt> control
9934 field that they provide the virtual
9935 package <tt>xserver</tt>.<footnote>
9936 This implements current practice, and provides an
9937 actual policy for usage of the <tt>xserver</tt>
9938 virtual package which appears in the virtual packages
9939 list. In a nutshell, X servers that interface
9940 directly with the display and input hardware or via
9941 another subsystem (e.g., GGI) should provide
9942 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9943 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9949 <heading>Packages providing a terminal emulator</heading>
9952 Packages that provide a terminal emulator for the X Window
9953 System which meet the criteria listed below should declare in
9954 their <tt>Provides</tt> control field that they provide the
9955 virtual package <tt>x-terminal-emulator</tt>. They should
9956 also register themselves as an alternative for
9957 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9958 20. That alternative should have a slave alternative
9959 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9960 pointing to the corresponding manual page.
9964 To be an <tt>x-terminal-emulator</tt>, a program must:
9965 <list compact="compact">
9967 Be able to emulate a DEC VT100 terminal, or a
9968 compatible terminal.
9972 Support the command-line option <tt>-e
9973 <var>command</var></tt>, which creates a new
9974 terminal window<footnote>
9975 "New terminal window" does not necessarily mean
9976 a new top-level X window directly parented by
9977 the window manager; it could, if the terminal
9978 emulator application were so coded, be a new
9979 "view" in a multiple-document interface (MDI).
9981 and runs the specified <var>command</var>,
9982 interpreting the entirety of the rest of the command
9983 line as a command to pass straight to exec, in the
9984 manner that <tt>xterm</tt> does.
9988 Support the command-line option <tt>-T
9989 <var>title</var></tt>, which creates a new terminal
9990 window with the window title <var>title</var>.
9997 <heading>Packages providing a window manager</heading>
10000 Packages that provide a window manager should declare in
10001 their <tt>Provides</tt> control field that they provide the
10002 virtual package <tt>x-window-manager</tt>. They should also
10003 register themselves as an alternative for
10004 <file>/usr/bin/x-window-manager</file>, with a priority
10005 calculated as follows:
10006 <list compact="compact">
10008 Start with a priority of 20.
10012 If the window manager supports the Debian menu
10013 system, add 20 points if this support is available
10014 in the package's default configuration (i.e., no
10015 configuration files belonging to the system or user
10016 have to be edited to activate the feature); if
10017 configuration files must be modified, add only 10
10023 If the window manager complies with <url
10024 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10025 name="The Window Manager Specification Project">,
10026 written by the <url id="http://www.freedesktop.org/wiki/"
10027 name="Free Desktop Group">, add 40 points.
10031 If the window manager permits the X session to be
10032 restarted using a <em>different</em> window manager
10033 (without killing the X server) in its default
10034 configuration, add 10 points; otherwise add none.
10037 That alternative should have a slave alternative
10038 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10039 pointing to the corresponding manual page.
10044 <heading>Packages providing fonts</heading>
10047 Packages that provide fonts for the X Window
10049 For the purposes of Debian Policy, a "font for the X
10050 Window System" is one which is accessed via X protocol
10051 requests. Fonts for the Linux console, for PostScript
10052 renderer, or any other purpose, do not fit this
10053 definition. Any tool which makes such fonts available
10054 to the X Window System, however, must abide by this
10057 must do a number of things to ensure that they are both
10058 available without modification of the X or font server
10059 configuration, and that they do not corrupt files used by
10060 other font packages to register information about
10064 Fonts of any type supported by the X Window System
10065 must be in a separate binary package from any
10066 executables, libraries, or documentation (except
10067 that specific to the fonts shipped, such as their
10068 license information). If one or more of the fonts
10069 so packaged are necessary for proper operation of
10070 the package with which they are associated the font
10071 package may be Recommended; if the fonts merely
10072 provide an enhancement, a Suggests relationship may
10073 be used. Packages must not Depend on font
10074 packages.<footnote>
10075 This is because the X server may retrieve fonts
10076 from the local file system or over the network
10077 from an X font server; the Debian package system
10078 is empowered to deal only with the local
10084 BDF fonts must be converted to PCF fonts with the
10085 <prgn>bdftopcf</prgn> utility (available in the
10086 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10087 placed in a directory that corresponds to their
10089 <list compact="compact">
10091 100 dpi fonts must be placed in
10092 <file>/usr/share/fonts/X11/100dpi/</file>.
10096 75 dpi fonts must be placed in
10097 <file>/usr/share/fonts/X11/75dpi/</file>.
10101 Character-cell fonts, cursor fonts, and other
10102 low-resolution fonts must be placed in
10103 <file>/usr/share/fonts/X11/misc/</file>.
10109 Type 1 fonts must be placed in
10110 <file>/usr/share/fonts/X11/Type1/</file>. If font
10111 metric files are available, they must be placed here
10116 Subdirectories of <file>/usr/share/fonts/X11/</file>
10117 other than those listed above must be neither
10118 created nor used. (The <file>PEX</file>, <file>CID</file>,
10119 <file>Speedo</file>, and <file>cyrillic</file> directories
10120 are excepted for historical reasons, but installation of
10121 files into these directories remains discouraged.)
10125 Font packages may, instead of placing files directly
10126 in the X font directories listed above, provide
10127 symbolic links in that font directory pointing to
10128 the files' actual location in the filesystem. Such
10129 a location must comply with the FHS.
10133 Font packages should not contain both 75dpi and
10134 100dpi versions of a font. If both are available,
10135 they should be provided in separate binary packages
10136 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10137 the names of the packages containing the
10138 corresponding fonts.
10142 Fonts destined for the <file>misc</file> subdirectory
10143 should not be included in the same package as 75dpi
10144 or 100dpi fonts; instead, they should be provided in
10145 a separate package with <tt>-misc</tt> appended to
10150 Font packages must not provide the files
10151 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10152 <file>fonts.scale</file> in a font directory:
10155 <file>fonts.dir</file> files must not be provided at all.
10159 <file>fonts.alias</file> and <file>fonts.scale</file>
10160 files, if needed, should be provided in the
10162 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10163 where <var>fontdir</var> is the name of the
10165 <file>/usr/share/fonts/X11/</file> where the
10166 package's corresponding fonts are stored
10167 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10168 <var>package</var> is the name of the package
10169 that provides these fonts, and
10170 <var>extension</var> is either <tt>scale</tt>
10171 or <tt>alias</tt>, whichever corresponds to
10178 Font packages must declare a dependency on
10179 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10180 or <tt>Pre-Depends</tt> control field.
10184 Font packages that provide one or more
10185 <file>fonts.scale</file> files as described above must
10186 invoke <prgn>update-fonts-scale</prgn> on each
10187 directory into which they installed fonts
10188 <em>before</em> invoking
10189 <prgn>update-fonts-dir</prgn> on that directory.
10190 This invocation must occur in both the
10191 <prgn>postinst</prgn> (for all arguments) and
10192 <prgn>postrm</prgn> (for all arguments except
10193 <tt>upgrade</tt>) scripts.
10197 Font packages that provide one or more
10198 <file>fonts.alias</file> files as described above must
10199 invoke <prgn>update-fonts-alias</prgn> on each
10200 directory into which they installed fonts. This
10201 invocation must occur in both the
10202 <prgn>postinst</prgn> (for all arguments) and
10203 <prgn>postrm</prgn> (for all arguments except
10204 <tt>upgrade</tt>) scripts.
10208 Font packages must invoke
10209 <prgn>update-fonts-dir</prgn> on each directory into
10210 which they installed fonts. This invocation must
10211 occur in both the <prgn>postinst</prgn> (for all
10212 arguments) and <prgn>postrm</prgn> (for all
10213 arguments except <tt>upgrade</tt>) scripts.
10217 Font packages must not provide alias names for the
10218 fonts they include which collide with alias names
10219 already in use by fonts already packaged.
10223 Font packages must not provide fonts with the same
10224 XLFD registry name as another font already packaged.
10230 <sect1 id="appdefaults">
10231 <heading>Application defaults files</heading>
10234 Application defaults files must be installed in the
10235 directory <file>/etc/X11/app-defaults/</file> (use of a
10236 localized subdirectory of <file>/etc/X11/</file> as described
10237 in the <em>X Toolkit Intrinsics - C Language
10238 Interface</em> manual is also permitted). They must be
10239 registered as <tt>conffile</tt>s or handled as
10240 configuration files.
10244 Customization of programs' X resources may also be
10245 supported with the provision of a file with the same name
10246 as that of the package placed in
10247 the <file>/etc/X11/Xresources/</file> directory, which
10248 must be registered as a <tt>conffile</tt> or handled as a
10249 configuration file.<footnote>
10250 Note that this mechanism is not the same as using
10251 app-defaults; app-defaults are tied to the client
10252 binary on the local file system, whereas X resources
10253 are stored in the X server and affect all connecting
10260 <heading>Installation directory issues</heading>
10263 Historically, packages using the X Window System used a
10264 separate set of installation directories from other packages.
10265 This practice has been discontinued and packages using the X
10266 Window System should now generally be installed in the same
10267 directories as any other package. Specifically, packages must
10268 not install files under the <file>/usr/X11R6/</file> directory
10269 and the <file>/usr/X11R6/</file> directory hierarchy should be
10270 regarded as obsolete.
10274 Include files previously installed under
10275 <file>/usr/X11R6/include/X11/</file> should be installed into
10276 <file>/usr/include/X11/</file>. For files previously
10277 installed into subdirectories of
10278 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10279 determine if subdirectories of <file>/usr/lib/</file> and
10280 <file>/usr/share/</file> can be used. If not, a subdirectory
10281 of <file>/usr/lib/X11/</file> should be used.
10285 Configuration files for window, display, or session managers
10286 or other applications that are tightly integrated with the X
10287 Window System may be placed in a subdirectory
10288 of <file>/etc/X11/</file> corresponding to the package name.
10289 Other X Window System applications should use
10290 the <file>/etc/</file> directory unless otherwise mandated by
10291 policy (such as for <ref id="appdefaults">).
10297 <heading>Perl programs and modules</heading>
10300 Perl programs and modules should follow the current Perl policy.
10304 The Perl policy can be found in the <tt>perl-policy</tt>
10305 files in the <tt>debian-policy</tt> package.
10306 It is also available from the Debian web mirrors at
10307 <tt><url name="/doc/packaging-manuals/perl-policy/"
10308 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10313 <heading>Emacs lisp programs</heading>
10316 Please refer to the "Debian Emacs Policy" for details of how to
10317 package emacs lisp programs.
10321 The Emacs policy is available in
10322 <file>debian-emacs-policy.gz</file> of the
10323 <package>emacsen-common</package> package.
10324 It is also available from the Debian web mirrors at
10325 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10326 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10331 <heading>Games</heading>
10334 The permissions on <file>/var/games</file> are mode 755, owner
10335 <tt>root</tt> and group <tt>root</tt>.
10339 Each game decides on its own security policy.</p>
10342 Games which require protected, privileged access to
10343 high-score files, saved games, etc., may be made
10344 set-<em>group</em>-id (mode 2755) and owned by
10345 <tt>root:games</tt>, and use files and directories with
10346 appropriate permissions (770 <tt>root:games</tt>, for
10347 example). They must not be made
10348 set-<em>user</em>-id, as this causes security problems. (If
10349 an attacker can subvert any set-user-id game they can
10350 overwrite the executable of any other, causing other players
10351 of these games to run a Trojan horse program. With a
10352 set-group-id game the attacker only gets access to less
10353 important game data, and if they can get at the other
10354 players' accounts at all it will take considerably more
10358 Some packages, for example some fortune cookie programs, are
10359 configured by the upstream authors to install with their
10360 data files or other static information made unreadable so
10361 that they can only be accessed through set-id programs
10362 provided. You should not do this in a Debian package: anyone can
10363 download the <file>.deb</file> file and read the data from it,
10364 so there is no point making the files unreadable. Not
10365 making the files unreadable also means that you don't have
10366 to make so many programs set-id, which reduces the risk of a
10370 As described in the FHS, binaries of games should be
10371 installed in the directory <file>/usr/games</file>. This also
10372 applies to games that use the X Window System. Manual pages
10373 for games (X and non-X games) should be installed in
10374 <file>/usr/share/man/man6</file>.</p>
10380 <heading>Documentation</heading>
10383 <heading>Manual pages</heading>
10386 You should install manual pages in <prgn>nroff</prgn> source
10387 form, in appropriate places under <file>/usr/share/man</file>.
10388 You should only use sections 1 to 9 (see the FHS for more
10389 details). You must not install a pre-formatted "cat page".
10393 Each program, utility, and function should have an
10394 associated manual page included in the same package. It is
10395 suggested that all configuration files also have a manual
10396 page included as well. Manual pages for protocols and other
10397 auxiliary things are optional.
10401 If no manual page is available, this is considered as a bug
10402 and should be reported to the Debian Bug Tracking System (the
10403 maintainer of the package is allowed to write this bug report
10404 themselves, if they so desire). Do not close the bug report
10405 until a proper man page is available.<footnote>
10406 It is not very hard to write a man page. See the
10407 <url id="http://www.schweikhardt.net/man_page_howto.html"
10408 name="Man-Page-HOWTO">,
10409 <manref name="man" section="7">, the examples created
10410 by <prgn>dh_make</prgn>, the helper
10411 program <prgn>help2man</prgn>, or the
10412 directory <file>/usr/share/doc/man-db/examples</file>.
10417 You may forward a complaint about a missing man page to the
10418 upstream authors, and mark the bug as forwarded in the
10419 Debian bug tracking system. Even though the GNU Project do
10420 not in general consider the lack of a man page to be a bug,
10421 we do; if they tell you that they don't consider it a bug
10422 you should leave the bug in our bug tracking system open
10427 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10431 If one man page needs to be accessible via several names it
10432 is better to use a symbolic link than the <file>.so</file>
10433 feature, but there is no need to fiddle with the relevant
10434 parts of the upstream source to change from <file>.so</file> to
10435 symlinks: don't do it unless it's easy. You should not
10436 create hard links in the manual page directories, nor put
10437 absolute filenames in <file>.so</file> directives. The filename
10438 in a <file>.so</file> in a man page should be relative to the
10439 base of the man page tree (usually
10440 <file>/usr/share/man</file>). If you do not create any links
10441 (whether symlinks, hard links, or <tt>.so</tt> directives)
10442 in the file system to the alternate names of the man page,
10443 then you should not rely on <prgn>man</prgn> finding your
10444 man page under those names based solely on the information in
10445 the man page's header.<footnote>
10446 Supporting this in <prgn>man</prgn> often requires
10447 unreasonable processing time to find a manual page or to
10448 report that none exists, and moves knowledge into man's
10449 database that would be better left in the file system.
10450 This support is therefore deprecated and will cease to
10451 be present in the future.
10456 Manual pages in locale-specific subdirectories of
10457 <file>/usr/share/man</file> should use either UTF-8 or the usual
10458 legacy encoding for that language (normally the one corresponding
10459 to the shortest relevant locale name in
10460 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10461 <file>/usr/share/man/fr</file> should use either UTF-8 or
10462 ISO-8859-1.<footnote>
10463 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10464 use. In future, all manual pages will be required to use
10470 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10471 included in the subdirectory name unless it indicates a
10472 significant difference in the language, as this excludes
10473 speakers of the language in other countries.<footnote>
10474 At the time of writing, Chinese and Portuguese are the main
10475 languages with such differences, so <file>pt_BR</file>,
10476 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10481 If a localized version of a manual page is provided, it should
10482 either be up-to-date or it should be obvious to the reader that
10483 it is outdated and the original manual page should be used
10484 instead. This can be done either by a note at the beginning of
10485 the manual page or by showing the missing or changed portions in
10486 the original language instead of the target language.
10491 <heading>Info documents</heading>
10494 Info documents should be installed in <file>/usr/share/info</file>.
10495 They should be compressed with <tt>gzip -9</tt>.
10499 The <prgn>install-info</prgn> program maintains a directory of
10500 installed info documents in <file>/usr/share/info/dir</file> for the
10501 use of info readers. This file must not be included in packages
10502 other than <package>install-info</package>.
10506 <prgn>install-info</prgn> is automatically invoked when
10507 appropriate using dpkg triggers. Packages other than
10508 <package>install-info</package> <em>should not</em> invoke
10509 <prgn>install-info</prgn> directly and <em>should not</em>
10510 depend on, recommend, or suggest <package>install-info</package>
10515 Info readers requiring the <file>/usr/share/info/dir</file> file
10516 should depend on <package>install-info</package>.
10520 Info documents should contain section and directory entry
10521 information in the document for the use
10522 of <prgn>install-info</prgn>. The section should be specified
10523 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10524 space and the section of this info page. The directory entry or
10525 entries should be included between
10526 a <tt>START-INFO-DIR-ENTRY</tt> line and
10527 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10529 INFO-DIR-SECTION Individual utilities
10530 START-INFO-DIR-ENTRY
10531 * example: (example). An example info directory entry.
10534 To determine which section to use, you should look
10535 at <file>/usr/share/info/dir</file> on your system and choose
10536 the most relevant (or create a new section if none of the
10537 current sections are relevant).<footnote>
10538 Normally, info documents are generated from Texinfo source.
10539 To include this information in the generated info document, if
10540 it is absent, add commands like:
10542 @dircategory Individual utilities
10544 * example: (example). An example info directory entry.
10547 to the Texinfo source of the document and ensure that the info
10548 documents are rebuilt from source during the package build.
10554 <heading>Additional documentation</heading>
10557 Any additional documentation that comes with the package may
10558 be installed at the discretion of the package maintainer.
10559 Plain text documentation should be installed in the directory
10560 <file>/usr/share/doc/<var>package</var></file>, where
10561 <var>package</var> is the name of the package, and
10562 compressed with <tt>gzip -9</tt> unless it is small.
10566 If a package comes with large amounts of documentation which
10567 many users of the package will not require you should create
10568 a separate binary package to contain it, so that it does not
10569 take up disk space on the machines of users who do not need
10570 or want it installed.</p>
10573 It is often a good idea to put text information files
10574 (<file>README</file>s, changelogs, and so forth) that come with
10575 the source package in <file>/usr/share/doc/<var>package</var></file>
10576 in the binary package. However, you don't need to install
10577 the instructions for building and installing the package, of
10581 Packages must not require the existence of any files in
10582 <file>/usr/share/doc/</file> in order to function
10584 The system administrator should be able to
10585 delete files in <file>/usr/share/doc/</file> without causing
10586 any programs to break.
10588 Any files that are referenced by programs but are also
10589 useful as stand alone documentation should be installed under
10590 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10591 <file>/usr/share/doc/<var>package</var></file>.
10595 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10596 link to another directory in <file>/usr/share/doc</file> only if
10597 the two packages both come from the same source and the
10598 first package Depends on the second.<footnote>
10600 Please note that this does not override the section on
10601 changelog files below, so the file
10602 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10603 must refer to the changelog for the current version of
10604 <var>package</var> in question. In practice, this means
10605 that the sources of the target and the destination of the
10606 symlink must be the same (same source package and
10613 Former Debian releases placed all additional documentation
10614 in <file>/usr/doc/<var>package</var></file>. This has been
10615 changed to <file>/usr/share/doc/<var>package</var></file>,
10616 and packages must not put documentation in the directory
10617 <file>/usr/doc/<var>package</var></file>. <footnote>
10618 At this phase of the transition, we no longer require a
10619 symbolic link in <file>/usr/doc/</file>. At a later point,
10620 policy shall change to make the symbolic links a bug.
10626 <heading>Preferred documentation formats</heading>
10629 The unification of Debian documentation is being carried out
10633 If your package comes with extensive documentation in a
10634 markup format that can be converted to various other formats
10635 you should if possible ship HTML versions in a binary
10636 package, in the directory
10637 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10638 its subdirectories.<footnote>
10639 The rationale: The important thing here is that HTML
10640 docs should be available in <em>some</em> package, not
10641 necessarily in the main binary package.
10646 Other formats such as PostScript may be provided at the
10647 package maintainer's discretion.
10651 <sect id="copyrightfile">
10652 <heading>Copyright information</heading>
10655 Every package must be accompanied by a verbatim copy of its
10656 copyright information and distribution license in the file
10657 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10658 file must neither be compressed nor be a symbolic link.
10662 In addition, the copyright file must say where the upstream
10663 sources (if any) were obtained, and should name the original
10668 Packages in the <em>contrib</em> or <em>non-free</em> archive
10669 areas should state in the copyright file that the package is not
10670 part of the Debian distribution and briefly explain why.
10674 A copy of the file which will be installed in
10675 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10676 be in <file>debian/copyright</file> in the source package.
10680 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10681 link to another directory in <file>/usr/share/doc</file> only if
10682 the two packages both come from the same source and the
10683 first package Depends on the second. These rules are important
10684 because <file>copyright</file> files must be extractable by
10689 Packages distributed under the Apache license (version 2.0), the
10690 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10691 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10692 1.3) should refer to the corresponding files
10693 under <file>/usr/share/common-licenses</file>,<footnote>
10696 <file>/usr/share/common-licenses/Apache-2.0</file>,
10697 <file>/usr/share/common-licenses/Artistic</file>,
10698 <file>/usr/share/common-licenses/GPL-1</file>,
10699 <file>/usr/share/common-licenses/GPL-2</file>,
10700 <file>/usr/share/common-licenses/GPL-3</file>,
10701 <file>/usr/share/common-licenses/LGPL-2</file>,
10702 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10703 <file>/usr/share/common-licenses/LGPL-3</file>,
10704 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10705 <file>/usr/share/common-licenses/GFDL-1.3</file>
10706 respectively. The University of California BSD license is
10707 also included in <package>base-files</package> as
10708 <file>/usr/share/common-licenses/BSD</file>, but given the
10709 brevity of this license, its specificity to code whose
10710 copyright is held by the Regents of the University of
10711 California, and the frequency of minor wording changes, its
10712 text should be included in the copyright file rather than
10713 referencing this file.
10715 </footnote> rather than quoting them in the copyright
10720 You should not use the copyright file as a general <file>README</file>
10721 file. If your package has such a file it should be
10722 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10723 <file>README.Debian</file> or some other appropriate place.
10727 All copyright files must be encoded in UTF-8.
10730 <sect1 id="copyrightformat">
10731 <heading>Machine-readable copyright information</heading>
10734 A specification for a standard, machine-readable format
10735 for <file>debian/copyright</file> files is maintained as part
10736 of the <package>debian-policy</package> package. This
10737 document may be found in the <file>copyright-format</file>
10738 files in the <package>debian-policy</package> package. It is
10739 also available from the Debian web mirrors at
10740 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10741 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10745 Use of this format is optional.
10751 <heading>Examples</heading>
10754 Any examples (configurations, source files, whatever),
10755 should be installed in a directory
10756 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10757 files should not be referenced by any program: they're there
10758 for the benefit of the system administrator and users as
10759 documentation only. Architecture-specific example files
10760 should be installed in a directory
10761 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10763 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10764 latter directory itself may be a symbolic link to the
10769 If the purpose of a package is to provide examples, then the
10770 example files may be installed into
10771 <file>/usr/share/doc/<var>package</var></file>.
10775 <sect id="changelogs">
10776 <heading>Changelog files</heading>
10779 Packages that are not Debian-native must contain a
10780 compressed copy of the <file>debian/changelog</file> file from
10781 the Debian source tree in
10782 <file>/usr/share/doc/<var>package</var></file> with the name
10783 <file>changelog.Debian.gz</file>.
10787 If an upstream changelog is available, it should be accessible as
10788 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10789 plain text. If the upstream changelog is distributed in
10790 HTML, it should be made available in that form as
10791 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10792 and a plain text <file>changelog.gz</file> should be generated
10793 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10794 the upstream changelog files do not already conform to this
10795 naming convention, then this may be achieved either by
10796 renaming the files, or by adding a symbolic link, at the
10797 maintainer's discretion.<footnote>
10798 Rationale: People should not have to look in places for
10799 upstream changelogs merely because they are given
10800 different names or are distributed in HTML format.
10805 All of these files should be installed compressed using
10806 <tt>gzip -9</tt>, as they will become large with time even
10807 if they start out small.
10811 If the package has only one changelog which is used both as
10812 the Debian changelog and the upstream one because there is
10813 no separate upstream maintainer then that changelog should
10814 usually be installed as
10815 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10816 there is a separate upstream maintainer, but no upstream
10817 changelog, then the Debian changelog should still be called
10818 <file>changelog.Debian.gz</file>.
10822 For details about the format and contents of the Debian
10823 changelog file, please see <ref id="dpkgchangelog">.
10828 <appendix id="pkg-scope">
10829 <heading>Introduction and scope of these appendices</heading>
10832 These appendices are taken essentially verbatim from the
10833 now-deprecated Packaging Manual, version 3.2.1.0. They are
10834 the chapters which are likely to be of use to package
10835 maintainers and which have not already been included in the
10836 policy document itself. Most of these sections are very likely
10837 not relevant to policy; they should be treated as
10838 documentation for the packaging system. Please note that these
10839 appendices are included for convenience, and for historical
10840 reasons: they used to be part of policy package, and they have
10841 not yet been incorporated into dpkg documentation. However,
10842 they still have value, and hence they are presented here.
10846 They have not yet been checked to ensure that they are
10847 compatible with the contents of policy, and if there are any
10848 contradictions, the version in the main policy document takes
10849 precedence. The remaining chapters of the old Packaging
10850 Manual have also not been read in detail to ensure that there
10851 are not parts which have been left out. Both of these will be
10852 done in due course.
10856 Certain parts of the Packaging manual were integrated into the
10857 Policy Manual proper, and removed from the appendices. Links
10858 have been placed from the old locations to the new ones.
10862 <prgn>dpkg</prgn> is a suite of programs for creating binary
10863 package files and installing and removing them on Unix
10865 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10866 work on or be ported to other systems.
10871 The binary packages are designed for the management of
10872 installed executable programs (usually compiled binaries) and
10873 their associated data, though source code examples and
10874 documentation are provided as part of some packages.</p>
10877 This manual describes the technical aspects of creating Debian
10878 binary packages (<file>.deb</file> files). It documents the
10879 behavior of the package management programs
10880 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10881 they interact with packages.</p>
10884 This manual does not go into detail about the options and
10885 usage of the package building and installation tools. It
10886 should therefore be read in conjunction with those programs'
10891 The utility programs which are provided with <prgn>dpkg</prgn>
10892 not described in detail here, are documented in their man pages.
10896 It is assumed that the reader is reasonably familiar with the
10897 <prgn>dpkg</prgn> System Administrators' manual.
10898 Unfortunately this manual does not yet exist.
10902 The Debian version of the FSF's GNU hello program is provided as
10903 an example for people wishing to create Debian packages. However,
10904 while the examples are helpful, they do not replace the need to
10905 read and follow the Policy and Programmer's Manual.</p>
10908 <appendix id="pkg-binarypkg">
10909 <heading>Binary packages (from old Packaging Manual)</heading>
10912 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10915 <sect id="pkg-bincreating"><heading>Creating package files -
10916 <prgn>dpkg-deb</prgn>
10920 All manipulation of binary package files is done by
10921 <prgn>dpkg-deb</prgn>; it's the only program that has
10922 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10923 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10924 will spot that the options requested are appropriate to
10925 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10930 In order to create a binary package you must make a
10931 directory tree which contains all the files and directories
10932 you want to have in the file system data part of the package.
10933 In Debian-format source packages this directory is usually
10934 <file>debian/tmp</file>, relative to the top of the package's
10939 They should have the locations (relative to the root of the
10940 directory tree you're constructing) ownerships and
10941 permissions which you want them to have on the system when
10942 they are installed.
10946 With current versions of <prgn>dpkg</prgn> the uid/username
10947 and gid/groupname mappings for the users and groups being
10948 used should be the same on the system where the package is
10949 built and the one where it is installed.
10953 You need to add one special directory to the root of the
10954 miniature file system tree you're creating:
10955 <prgn>DEBIAN</prgn>. It should contain the control
10956 information files, notably the binary package control file
10957 (see <ref id="pkg-controlfile">).
10961 The <prgn>DEBIAN</prgn> directory will not appear in the
10962 file system archive of the package, and so won't be installed
10963 by <prgn>dpkg</prgn> when the package is unpacked.
10967 When you've prepared the package, you should invoke:
10969 dpkg --build <var>directory</var>
10974 This will build the package in
10975 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10976 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10977 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10978 build the package.)
10982 See the man page <manref name="dpkg-deb" section="8"> for details of how
10983 to examine the contents of this newly-created file. You may find the
10984 output of following commands enlightening:
10986 dpkg-deb --info <var>filename</var>.deb
10987 dpkg-deb --contents <var>filename</var>.deb
10988 dpkg --contents <var>filename</var>.deb
10990 To view the copyright file for a package you could use this command:
10992 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10997 <sect id="pkg-controlarea">
10998 <heading>Package control information files</heading>
11001 The control information portion of a binary package is a
11002 collection of files with names known to <prgn>dpkg</prgn>.
11003 It will treat the contents of these files specially - some
11004 of them contain information used by <prgn>dpkg</prgn> when
11005 installing or removing the package; others are scripts which
11006 the package maintainer wants <prgn>dpkg</prgn> to run.
11010 It is possible to put other files in the package control
11011 information file area, but this is not generally a good idea
11012 (though they will largely be ignored).
11016 Here is a brief list of the control information files supported
11017 by <prgn>dpkg</prgn> and a summary of what they're used for.
11022 <tag><tt>control</tt>
11025 This is the key description file used by
11026 <prgn>dpkg</prgn>. It specifies the package's name
11027 and version, gives its description for the user,
11028 states its relationships with other packages, and so
11029 forth. See <ref id="sourcecontrolfiles"> and
11030 <ref id="binarycontrolfiles">.
11034 It is usually generated automatically from information
11035 in the source package by the
11036 <prgn>dpkg-gencontrol</prgn> program, and with
11037 assistance from <prgn>dpkg-shlibdeps</prgn>.
11038 See <ref id="pkg-sourcetools">.
11042 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11047 These are executable files (usually scripts) which
11048 <prgn>dpkg</prgn> runs during installation, upgrade
11049 and removal of packages. They allow the package to
11050 deal with matters which are particular to that package
11051 or require more complicated processing than that
11052 provided by <prgn>dpkg</prgn>. Details of when and
11053 how they are called are in <ref id="maintainerscripts">.
11057 It is very important to make these scripts idempotent.
11058 See <ref id="idempotency">.
11062 The maintainer scripts are not guaranteed to run with a
11063 controlling terminal and may not be able to interact with
11064 the user. See <ref id="controllingterminal">.
11068 <tag><tt>conffiles</tt>
11071 This file contains a list of configuration files which
11072 are to be handled automatically by <prgn>dpkg</prgn>
11073 (see <ref id="pkg-conffiles">). Note that not necessarily
11074 every configuration file should be listed here.
11077 <tag><tt>shlibs</tt>
11080 This file contains a list of the shared libraries
11081 supplied by the package, with dependency details for
11082 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11083 when it determines what dependencies are required in a
11084 package control file. The <tt>shlibs</tt> file format
11085 is described on <ref id="shlibs">.
11090 <sect id="pkg-controlfile">
11091 <heading>The main control information file: <tt>control</tt></heading>
11094 The most important control information file used by
11095 <prgn>dpkg</prgn> when it installs a package is
11096 <tt>control</tt>. It contains all the package's "vital
11101 The binary package control files of packages built from
11102 Debian sources are made by a special tool,
11103 <prgn>dpkg-gencontrol</prgn>, which reads
11104 <file>debian/control</file> and <file>debian/changelog</file> to
11105 find the information it needs. See <ref id="pkg-sourcepkg"> for
11110 The fields in binary package control files are listed in
11111 <ref id="binarycontrolfiles">.
11115 A description of the syntax of control files and the purpose
11116 of the fields is available in <ref id="controlfields">.
11121 <heading>Time Stamps</heading>
11124 See <ref id="timestamps">.
11129 <appendix id="pkg-sourcepkg">
11130 <heading>Source packages (from old Packaging Manual) </heading>
11133 The Debian binary packages in the distribution are generated
11134 from Debian sources, which are in a special format to assist
11135 the easy and automatic building of binaries.
11138 <sect id="pkg-sourcetools">
11139 <heading>Tools for processing source packages</heading>
11142 Various tools are provided for manipulating source packages;
11143 they pack and unpack sources and help build of binary
11144 packages and help manage the distribution of new versions.
11148 They are introduced and typical uses described here; see
11149 <manref name="dpkg-source" section="1"> for full
11150 documentation about their arguments and operation.
11154 For examples of how to construct a Debian source package,
11155 and how to use those utilities that are used by Debian
11156 source packages, please see the <prgn>hello</prgn> example
11160 <sect1 id="pkg-dpkg-source">
11162 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11167 This program is frequently used by hand, and is also
11168 called from package-independent automated building scripts
11169 such as <prgn>dpkg-buildpackage</prgn>.
11173 To unpack a package it is typically invoked with
11175 dpkg-source -x <var>.../path/to/filename</var>.dsc
11180 with the <file><var>filename</var>.tar.gz</file> and
11181 <file><var>filename</var>.diff.gz</file> (if applicable) in
11182 the same directory. It unpacks into
11183 <file><var>package</var>-<var>version</var></file>, and if
11185 <file><var>package</var>-<var>version</var>.orig</file>, in
11186 the current directory.
11190 To create a packed source archive it is typically invoked:
11192 dpkg-source -b <var>package</var>-<var>version</var>
11197 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11198 <file>.diff.gz</file> (if appropriate) in the current
11199 directory. <prgn>dpkg-source</prgn> does not clean the
11200 source tree first - this must be done separately if it is
11205 See also <ref id="pkg-sourcearchives">.</p>
11209 <sect1 id="pkg-dpkg-buildpackage">
11211 <prgn>dpkg-buildpackage</prgn> - overall package-building
11216 See <manref name="dpkg-buildpackage" section="1">.
11220 <sect1 id="pkg-dpkg-gencontrol">
11222 <prgn>dpkg-gencontrol</prgn> - generates binary package
11227 This program is usually called from <file>debian/rules</file>
11228 (see <ref id="pkg-sourcetree">) in the top level of the source
11233 This is usually done just before the files and directories in the
11234 temporary directory tree where the package is being built have their
11235 permissions and ownerships set and the package is constructed using
11236 <prgn>dpkg-deb/</prgn>
11238 This is so that the control file which is produced has
11239 the right permissions
11244 <prgn>dpkg-gencontrol</prgn> must be called after all the
11245 files which are to go into the package have been placed in
11246 the temporary build directory, so that its calculation of
11247 the installed size of a package is correct.
11251 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11252 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11253 variable substitutions created by
11254 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11259 For a package which generates only one binary package, and
11260 which builds it in <file>debian/tmp</file> relative to the top
11261 of the source package, it is usually sufficient to call
11262 <prgn>dpkg-gencontrol</prgn>.
11266 Sources which build several binaries will typically need
11269 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11270 </example> The <tt>-P</tt> tells
11271 <prgn>dpkg-gencontrol</prgn> that the package is being
11272 built in a non-default directory, and the <tt>-p</tt>
11273 tells it which package's control file should be generated.
11277 <prgn>dpkg-gencontrol</prgn> also adds information to the
11278 list of files in <file>debian/files</file>, for the benefit of
11279 (for example) a future invocation of
11280 <prgn>dpkg-genchanges</prgn>.</p>
11283 <sect1 id="pkg-dpkg-shlibdeps">
11285 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11290 See <manref name="dpkg-shlibdeps" section="1">.
11294 <sect1 id="pkg-dpkg-distaddfile">
11296 <prgn>dpkg-distaddfile</prgn> - adds a file to
11297 <file>debian/files</file>
11301 Some packages' uploads need to include files other than
11302 the source and binary package files.
11306 <prgn>dpkg-distaddfile</prgn> adds a file to the
11307 <file>debian/files</file> file so that it will be included in
11308 the <file>.changes</file> file when
11309 <prgn>dpkg-genchanges</prgn> is run.
11313 It is usually invoked from the <tt>binary</tt> target of
11314 <file>debian/rules</file>:
11316 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11318 The <var>filename</var> is relative to the directory where
11319 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11320 is usually the directory above the top level of the source
11321 tree. The <file>debian/rules</file> target should put the
11322 file there just before or just after calling
11323 <prgn>dpkg-distaddfile</prgn>.
11327 The <var>section</var> and <var>priority</var> are passed
11328 unchanged into the resulting <file>.changes</file> file.
11333 <sect1 id="pkg-dpkg-genchanges">
11335 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11336 upload control file
11340 See <manref name="dpkg-genchanges" section="1">.
11344 <sect1 id="pkg-dpkg-parsechangelog">
11346 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11347 representation of a changelog
11351 See <manref name="dpkg-parsechangelog" section="1">.
11355 <sect1 id="pkg-dpkg-architecture">
11357 <prgn>dpkg-architecture</prgn> - information about the build and
11362 See <manref name="dpkg-architecture" section="1">.
11367 <sect id="pkg-sourcetree">
11368 <heading>The Debian package source tree</heading>
11371 The source archive scheme described later is intended to
11372 allow a Debian package source tree with some associated
11373 control information to be reproduced and transported easily.
11374 The Debian package source tree is a version of the original
11375 program with certain files added for the benefit of the
11376 packaging process, and with any other changes required
11377 made to the rest of the source code and installation
11382 The extra files created for Debian are in the subdirectory
11383 <file>debian</file> of the top level of the Debian package
11384 source tree. They are described below.
11387 <sect1 id="pkg-debianrules">
11388 <heading><file>debian/rules</file> - the main building script</heading>
11391 See <ref id="debianrules">.
11395 <sect1 id="pkg-srcsubstvars">
11396 <heading><file>debian/substvars</file> and variable substitutions</heading>
11399 See <ref id="substvars">.
11405 <heading><file>debian/files</file></heading>
11408 See <ref id="debianfiles">.
11412 <sect1><heading><file>debian/tmp</file>
11416 This is the canonical temporary location for the
11417 construction of binary packages by the <tt>binary</tt>
11418 target. The directory <file>tmp</file> serves as the root of
11419 the file system tree as it is being constructed (for
11420 example, by using the package's upstream makefiles install
11421 targets and redirecting the output there), and it also
11422 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11423 id="pkg-bincreating">.
11427 If several binary packages are generated from the same
11428 source tree it is usual to use several
11429 <file>debian/tmp<var>something</var></file> directories, for
11430 example <file>tmp-a</file> or <file>tmp-doc</file>.
11434 Whatever <file>tmp</file> directories are created and used by
11435 <tt>binary</tt> must of course be removed by the
11436 <tt>clean</tt> target.</p></sect1>
11440 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11444 As it exists on the FTP site, a Debian source package
11445 consists of three related files. You must have the right
11446 versions of all three to be able to use them.
11451 <tag>Debian source control file - <tt>.dsc</tt></tag>
11453 This file is a control file used by <prgn>dpkg-source</prgn>
11454 to extract a source package.
11455 See <ref id="debiansourcecontrolfiles">.
11459 Original source archive -
11461 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11467 This is a compressed (with <tt>gzip -9</tt>)
11468 <prgn>tar</prgn> file containing the source code from
11469 the upstream authors of the program.
11474 Debian package diff -
11476 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11482 This is a unified context diff (<tt>diff -u</tt>)
11483 giving the changes which are required to turn the
11484 original source into the Debian source. These changes
11485 may only include editing and creating plain files.
11486 The permissions of files, the targets of symbolic
11487 links and the characteristics of special files or
11488 pipes may not be changed and no files may be removed
11493 All the directories in the diff must exist, except the
11494 <file>debian</file> subdirectory of the top of the source
11495 tree, which will be created by
11496 <prgn>dpkg-source</prgn> if necessary when unpacking.
11500 The <prgn>dpkg-source</prgn> program will
11501 automatically make the <file>debian/rules</file> file
11502 executable (see below).</p></item>
11507 If there is no original source code - for example, if the
11508 package is specially prepared for Debian or the Debian
11509 maintainer is the same as the upstream maintainer - the
11510 format is slightly different: then there is no diff, and the
11512 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11513 and preferably contains a directory named
11514 <file><var>package</var>-<var>version</var></file>.
11519 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11522 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11523 Debian source package. However, if it is not available it
11524 is possible to unpack a Debian source archive as follows:
11525 <enumlist compact="compact">
11528 Untar the tarfile, which will create a <file>.orig</file>
11532 <p>Rename the <file>.orig</file> directory to
11533 <file><var>package</var>-<var>version</var></file>.</p>
11537 Create the subdirectory <file>debian</file> at the top of
11538 the source tree.</p>
11540 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11542 <item><p>Untar the tarfile again if you want a copy of the original
11543 source code alongside the Debian version.</p>
11548 It is not possible to generate a valid Debian source archive
11549 without using <prgn>dpkg-source</prgn>. In particular,
11550 attempting to use <prgn>diff</prgn> directly to generate the
11551 <file>.diff.gz</file> file will not work.
11555 <heading>Restrictions on objects in source packages</heading>
11558 The source package may not contain any hard links
11560 This is not currently detected when building source
11561 packages, but only when extracting
11565 Hard links may be permitted at some point in the
11566 future, but would require a fair amount of
11568 </footnote>, device special files, sockets or setuid or
11571 Setgid directories are allowed.
11576 The source packaging tools manage the changes between the
11577 original and Debian source using <prgn>diff</prgn> and
11578 <prgn>patch</prgn>. Turning the original source tree as
11579 included in the <file>.orig.tar.gz</file> into the Debian
11580 package source must not involve any changes which cannot be
11581 handled by these tools. Problematic changes which cause
11582 <prgn>dpkg-source</prgn> to halt with an error when
11583 building the source package are:
11584 <list compact="compact">
11585 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11587 <item><p>Changing the targets of symbolic links.</p>
11589 <item><p>Creating directories, other than <file>debian</file>.</p>
11591 <item><p>Changes to the contents of binary files.</p></item>
11592 </list> Changes which cause <prgn>dpkg-source</prgn> to
11593 print a warning but continue anyway are:
11594 <list compact="compact">
11597 Removing files, directories or symlinks.
11599 Renaming a file is not treated specially - it is
11600 seen as the removal of the old file (which
11601 generates a warning, but is otherwise ignored),
11602 and the creation of the new one.
11608 Changed text files which are missing the usual final
11609 newline (either in the original or the modified
11614 Changes which are not represented, but which are not detected by
11615 <prgn>dpkg-source</prgn>, are:
11616 <list compact="compact">
11617 <item><p>Changing the permissions of files (other than
11618 <file>debian/rules</file>) and directories.</p></item>
11623 The <file>debian</file> directory and <file>debian/rules</file>
11624 are handled specially by <prgn>dpkg-source</prgn> - before
11625 applying the changes it will create the <file>debian</file>
11626 directory, and afterwards it will make
11627 <file>debian/rules</file> world-executable.
11633 <appendix id="pkg-controlfields">
11634 <heading>Control files and their fields (from old Packaging Manual)</heading>
11637 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11638 data in a common format, known as control files. Binary and
11639 source packages have control data as do the <file>.changes</file>
11640 files which control the installation of uploaded files, and
11641 <prgn>dpkg</prgn>'s internal databases are in a similar
11646 <heading>Syntax of control files</heading>
11649 See <ref id="controlsyntax">.
11653 It is important to note that there are several fields which
11654 are optional as far as <prgn>dpkg</prgn> and the related
11655 tools are concerned, but which must appear in every Debian
11656 package, or whose omission may cause problems.
11661 <heading>List of fields</heading>
11664 See <ref id="controlfieldslist">.
11668 This section now contains only the fields that didn't belong
11669 to the Policy manual.
11672 <sect1 id="pkg-f-Filename">
11673 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11676 These fields in <tt>Packages</tt> files give the
11677 filename(s) of (the parts of) a package in the
11678 distribution directories, relative to the root of the
11679 Debian hierarchy. If the package has been split into
11680 several parts the parts are all listed in order, separated
11685 <sect1 id="pkg-f-Size">
11686 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11689 These fields in <file>Packages</file> files give the size (in
11690 bytes, expressed in decimal) and MD5 checksum of the
11691 file(s) which make(s) up a binary package in the
11692 distribution. If the package is split into several parts
11693 the values for the parts are listed in order, separated by
11698 <sect1 id="pkg-f-Status">
11699 <heading><tt>Status</tt></heading>
11702 This field in <prgn>dpkg</prgn>'s status file records
11703 whether the user wants a package installed, removed or
11704 left alone, whether it is broken (requiring
11705 re-installation) or not and what its current state on the
11706 system is. Each of these pieces of information is a
11711 <sect1 id="pkg-f-Config-Version">
11712 <heading><tt>Config-Version</tt></heading>
11715 If a package is not installed or not configured, this
11716 field in <prgn>dpkg</prgn>'s status file records the last
11717 version of the package which was successfully
11722 <sect1 id="pkg-f-Conffiles">
11723 <heading><tt>Conffiles</tt></heading>
11726 This field in <prgn>dpkg</prgn>'s status file contains
11727 information about the automatically-managed configuration
11728 files held by a package. This field should <em>not</em>
11729 appear anywhere in a package!
11734 <heading>Obsolete fields</heading>
11737 These are still recognized by <prgn>dpkg</prgn> but should
11738 not appear anywhere any more.
11740 <taglist compact="compact">
11742 <tag><tt>Revision</tt></tag>
11743 <tag><tt>Package-Revision</tt></tag>
11744 <tag><tt>Package_Revision</tt></tag>
11746 The Debian revision part of the package version was
11747 at one point in a separate control field. This
11748 field went through several names.
11751 <tag><tt>Recommended</tt></tag>
11752 <item>Old name for <tt>Recommends</tt>.</item>
11754 <tag><tt>Optional</tt></tag>
11755 <item>Old name for <tt>Suggests</tt>.</item>
11757 <tag><tt>Class</tt></tag>
11758 <item>Old name for <tt>Priority</tt>.</item>
11767 <appendix id="pkg-conffiles">
11768 <heading>Configuration file handling (from old Packaging Manual)</heading>
11771 <prgn>dpkg</prgn> can do a certain amount of automatic
11772 handling of package configuration files.
11776 Whether this mechanism is appropriate depends on a number of
11777 factors, but basically there are two approaches to any
11778 particular configuration file.
11782 The easy method is to ship a best-effort configuration in the
11783 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11784 handle updates. If the user is unlikely to want to edit the
11785 file, but you need them to be able to without losing their
11786 changes, and a new package with a changed version of the file
11787 is only released infrequently, this is a good approach.
11791 The hard method is to build the configuration file from
11792 scratch in the <prgn>postinst</prgn> script, and to take the
11793 responsibility for fixing any mistakes made in earlier
11794 versions of the package automatically. This will be
11795 appropriate if the file is likely to need to be different on
11799 <sect><heading>Automatic handling of configuration files by
11804 A package may contain a control information file called
11805 <tt>conffiles</tt>. This file should be a list of filenames
11806 of configuration files needing automatic handling, separated
11807 by newlines. The filenames should be absolute pathnames,
11808 and the files referred to should actually exist in the
11813 When a package is upgraded <prgn>dpkg</prgn> will process
11814 the configuration files during the configuration stage,
11815 shortly before it runs the package's <prgn>postinst</prgn>
11820 For each file it checks to see whether the version of the
11821 file included in the package is the same as the one that was
11822 included in the last version of the package (the one that is
11823 being upgraded from); it also compares the version currently
11824 installed on the system with the one shipped with the last
11829 If neither the user nor the package maintainer has changed
11830 the file, it is left alone. If one or the other has changed
11831 their version, then the changed version is preferred - i.e.,
11832 if the user edits their file, but the package maintainer
11833 doesn't ship a different version, the user's changes will
11834 stay, silently, but if the maintainer ships a new version
11835 and the user hasn't edited it the new version will be
11836 installed (with an informative message). If both have
11837 changed their version the user is prompted about the problem
11838 and must resolve the differences themselves.
11842 The comparisons are done by calculating the MD5 message
11843 digests of the files, and storing the MD5 of the file as it
11844 was included in the most recent version of the package.
11848 When a package is installed for the first time
11849 <prgn>dpkg</prgn> will install the file that comes with it,
11850 unless that would mean overwriting a file already on the
11855 However, note that <prgn>dpkg</prgn> will <em>not</em>
11856 replace a conffile that was removed by the user (or by a
11857 script). This is necessary because with some programs a
11858 missing file produces an effect hard or impossible to
11859 achieve in another way, so that a missing file needs to be
11860 kept that way if the user did it.
11864 Note that a package should <em>not</em> modify a
11865 <prgn>dpkg</prgn>-handled conffile in its maintainer
11866 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11867 the user confusing and possibly dangerous options for
11868 conffile update when the package is upgraded.</p>
11871 <sect><heading>Fully-featured maintainer script configuration
11876 For files which contain site-specific information such as
11877 the hostname and networking details and so forth, it is
11878 better to create the file in the package's
11879 <prgn>postinst</prgn> script.
11883 This will typically involve examining the state of the rest
11884 of the system to determine values and other information, and
11885 may involve prompting the user for some information which
11886 can't be obtained some other way.
11890 When using this method there are a couple of important
11891 issues which should be considered:
11895 If you discover a bug in the program which generates the
11896 configuration file, or if the format of the file changes
11897 from one version to the next, you will have to arrange for
11898 the postinst script to do something sensible - usually this
11899 will mean editing the installed configuration file to remove
11900 the problem or change the syntax. You will have to do this
11901 very carefully, since the user may have changed the file,
11902 perhaps to fix the very problem that your script is trying
11903 to deal with - you will have to detect these situations and
11904 deal with them correctly.
11908 If you do go down this route it's probably a good idea to
11909 make the program that generates the configuration file(s) a
11910 separate program in <file>/usr/sbin</file>, by convention called
11911 <file><var>package</var>config</file> and then run that if
11912 appropriate from the post-installation script. The
11913 <tt><var>package</var>config</tt> program should not
11914 unquestioningly overwrite an existing configuration - if its
11915 mode of operation is geared towards setting up a package for
11916 the first time (rather than any arbitrary reconfiguration
11917 later) you should have it check whether the configuration
11918 already exists, and require a <tt>--force</tt> flag to
11919 overwrite it.</p></sect>
11922 <appendix id="pkg-alternatives"><heading>Alternative versions of
11923 an interface - <prgn>update-alternatives</prgn> (from old
11928 When several packages all provide different versions of the
11929 same program or file it is useful to have the system select a
11930 default, but to allow the system administrator to change it
11931 and have their decisions respected.
11935 For example, there are several versions of the <prgn>vi</prgn>
11936 editor, and there is no reason to prevent all of them from
11937 being installed at once, each under their own name
11938 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11939 Nevertheless it is desirable to have the name <tt>vi</tt>
11940 refer to something, at least by default.
11944 If all the packages involved cooperate, this can be done with
11945 <prgn>update-alternatives</prgn>.
11949 Each package provides its own version under its own name, and
11950 calls <prgn>update-alternatives</prgn> in its postinst to
11951 register its version (and again in its prerm to deregister
11956 See the man page <manref name="update-alternatives"
11957 section="8"> for details.
11961 If <prgn>update-alternatives</prgn> does not seem appropriate
11962 you may wish to consider using diversions instead.</p>
11965 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11966 package's version of a file (from old Packaging Manual)
11970 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11971 when it reinstalls the package it belongs to, and to have it
11972 put the file from the package somewhere else instead.
11976 This can be used locally to override a package's version of a
11977 file, or by one package to override another's version (or
11978 provide a wrapper for it).
11982 Before deciding to use a diversion, read <ref
11983 id="pkg-alternatives"> to see if you really want a diversion
11984 rather than several alternative versions of a program.
11988 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11989 and updated by a special program <prgn>dpkg-divert</prgn>.
11990 Please see <manref name="dpkg-divert" section="8"> for full
11991 details of its operation.
11995 When a package wishes to divert a file from another, it should
11996 call <prgn>dpkg-divert</prgn> in its preinst to add the
11997 diversion and rename the existing file. For example,
11998 supposing that a <prgn>smailwrapper</prgn> package wishes to
11999 install a wrapper around <file>/usr/sbin/smail</file>:
12001 dpkg-divert --package smailwrapper --add --rename \
12002 --divert /usr/sbin/smail.real /usr/sbin/smail
12003 </example> The <tt>--package smailwrapper</tt> ensures that
12004 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12005 can bypass the diversion and get installed as the true version.
12006 It's safe to add the diversion unconditionally on upgrades since
12007 it will be left unchanged if it already exists, but
12008 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12009 message, make the command conditional on the version from which
12010 the package is being upgraded:
12012 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12013 dpkg-divert --package smailwrapper --add --rename \
12014 --divert /usr/sbin/smail.real /usr/sbin/smail
12016 </example> where <tt>1.0-2</tt> is the version at which the
12017 diversion was first added to the package. Running the command
12018 during abort-upgrade is pointless but harmless.
12022 The postrm has to do the reverse:
12024 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12025 dpkg-divert --package smailwrapper --remove --rename \
12026 --divert /usr/sbin/smail.real /usr/sbin/smail
12028 </example> If the diversion was added at a particular version, the
12029 postrm should also handle the failure case of upgrading from an
12030 older version (unless the older version is so old that direct
12031 upgrades are no longer supported):
12033 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12034 dpkg-divert --package smailwrapper --remove --rename \
12035 --divert /usr/sbin/smail.real /usr/sbin/smail
12037 </example> where <tt>1.0-2</tt> is the version at which the
12038 diversion was first added to the package. The postrm should not
12039 remove the diversion on upgrades both because there's no reason to
12040 remove the diversion only to immediately re-add it and since the
12041 postrm of the old package is run after unpacking so the removal of
12042 the diversion will fail.
12046 Do not attempt to divert a file which is vitally important for
12047 the system's operation - when using <prgn>dpkg-divert</prgn>
12048 there is a time, after it has been diverted but before
12049 <prgn>dpkg</prgn> has installed the new version, when the file
12050 does not exist.</p>
12053 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12060 <!-- Local variables: -->
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