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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>, and <tt>build</tt>.
1920 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1924 Since an interactive <file>debian/rules</file> script makes it
1925 impossible to auto-compile that package and also makes it hard
1926 for other people to reproduce the same binary package, all
1927 required targets must be non-interactive. It also follows that
1928 any target that these targets depend on must also be
1933 The targets are as follows:
1935 <tag><tt>build</tt> (required)</tag>
1938 The <tt>build</tt> target should perform all the
1939 configuration and compilation of the package.
1940 If a package has an interactive pre-build
1941 configuration routine, the Debian source package
1942 must either be built after this has taken place (so
1943 that the binary package can be built without rerunning
1944 the configuration) or the configuration routine
1945 modified to become non-interactive. (The latter is
1946 preferable if there are architecture-specific features
1947 detected by the configuration routine.)
1951 For some packages, notably ones where the same
1952 source tree is compiled in different ways to produce
1953 two binary packages, the <tt>build</tt> target
1954 does not make much sense. For these packages it is
1955 good enough to provide two (or more) targets
1956 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1957 for each of the ways of building the package, and a
1958 <tt>build</tt> target that does nothing. The
1959 <tt>binary</tt> target will have to build the
1960 package in each of the possible ways and make the
1961 binary package out of each.
1965 The <tt>build</tt> target must not do anything
1966 that might require root privilege.
1970 The <tt>build</tt> target may need to run the
1971 <tt>clean</tt> target first - see below.
1975 When a package has a configuration and build routine
1976 which takes a long time, or when the makefiles are
1977 poorly designed, or when <tt>build</tt> needs to
1978 run <tt>clean</tt> first, it is a good idea to
1979 <tt>touch build</tt> when the build process is
1980 complete. This will ensure that if <tt>debian/rules
1981 build</tt> is run again it will not rebuild the whole
1983 Another common way to do this is for <tt>build</tt>
1984 to depend on <prgn>build-stamp</prgn> and to do
1985 nothing else, and for the <prgn>build-stamp</prgn>
1986 target to do the building and to <tt>touch
1987 build-stamp</tt> on completion. This is
1988 especially useful if the build routine creates a
1989 file or directory called <tt>build</tt>; in such a
1990 case, <tt>build</tt> will need to be listed as
1991 a phony target (i.e., as a dependency of the
1992 <tt>.PHONY</tt> target). See the documentation of
1993 <prgn>make</prgn> for more information on phony
1999 <tag><tt>build-arch</tt> (required),
2000 <tt>build-indep</tt> (required)
2004 The <tt>build-arch</tt> target must
2005 perform all the configuration and compilation required for
2006 producing all architecture-dependant binary packages
2007 (those packages for which the body of the
2008 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2009 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2010 target must perform all the configuration
2011 and compilation required for producing all
2012 architecture-independent binary packages (those packages
2013 for which the body of the <tt>Architecture</tt> field
2014 in <tt>debian/control</tt> is <tt>all</tt>).
2015 The <tt>build</tt> target
2016 should either depend on those targets or take the same
2017 actions as invoking those targets would perform.<footnote>
2018 This split allows binary-only builds to not install the
2019 dependencies required for the <tt>build-indep</tt>
2020 target and skip any resource-intensive build tasks that
2021 are only required when building architecture-independent
2027 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2028 must not do anything that might require root privilege.
2032 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2033 (required), <tt>binary-indep</tt> (required)
2037 The <tt>binary</tt> target must be all that is
2038 necessary for the user to build the binary package(s)
2039 produced from this source package. It is
2040 split into two parts: <prgn>binary-arch</prgn> builds
2041 the binary packages which are specific to a particular
2042 architecture, and <tt>binary-indep</tt> builds
2043 those which are not.
2046 <tt>binary</tt> may be (and commonly is) a target with
2047 no commands which simply depends on
2048 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2051 Both <tt>binary-*</tt> targets should depend on the
2052 <tt>build</tt> target, or on the appropriate
2053 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2054 provided, so that the package is built if it has not
2055 been already. It should then create the relevant
2056 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2057 make their control files and <prgn>dpkg-deb</prgn> to
2058 build them and place them in the parent of the top
2063 Both the <tt>binary-arch</tt> and
2064 <tt>binary-indep</tt> targets <em>must</em> exist.
2065 If one of them has nothing to do (which will always be
2066 the case if the source generates only a single binary
2067 package, whether architecture-dependent or not), it
2068 must still exist and must always succeed.
2072 The <tt>binary</tt> targets must be invoked as
2074 The <prgn>fakeroot</prgn> package often allows one
2075 to build a package correctly even without being
2081 <tag><tt>clean</tt> (required)</tag>
2084 This must undo any effects that the <tt>build</tt>
2085 and <tt>binary</tt> targets may have had, except
2086 that it should leave alone any output files created in
2087 the parent directory by a run of a <tt>binary</tt>
2092 If a <tt>build</tt> file is touched at the end of
2093 the <tt>build</tt> target, as suggested above, it
2094 should be removed as the first action that
2095 <tt>clean</tt> performs, so that running
2096 <tt>build</tt> again after an interrupted
2097 <tt>clean</tt> doesn't think that everything is
2102 The <tt>clean</tt> target may need to be
2103 invoked as root if <tt>binary</tt> has been
2104 invoked since the last <tt>clean</tt>, or if
2105 <tt>build</tt> has been invoked as root (since
2106 <tt>build</tt> may create directories, for
2111 <tag><tt>get-orig-source</tt> (optional)</tag>
2114 This target fetches the most recent version of the
2115 original source package from a canonical archive site
2116 (via FTP or WWW, for example), does any necessary
2117 rearrangement to turn it into the original source
2118 tar file format described below, and leaves it in the
2123 This target may be invoked in any directory, and
2124 should take care to clean up any temporary files it
2129 This target is optional, but providing it if
2130 possible is a good idea.
2134 <tag><tt>patch</tt> (optional)</tag>
2137 This target performs whatever additional actions are
2138 required to make the source ready for editing (unpacking
2139 additional upstream archives, applying patches, etc.).
2140 It is recommended to be implemented for any package where
2141 <tt>dpkg-source -x</tt> does not result in source ready
2142 for additional modification. See
2143 <ref id="readmesource">.
2149 The <tt>build</tt>, <tt>binary</tt> and
2150 <tt>clean</tt> targets must be invoked with the current
2151 directory being the package's top-level directory.
2156 Additional targets may exist in <file>debian/rules</file>,
2157 either as published or undocumented interfaces or for the
2158 package's internal use.
2162 The architectures we build on and build for are determined
2163 by <prgn>make</prgn> variables using the
2164 utility <prgn>dpkg-architecture</prgn>.
2165 You can determine the Debian architecture and the GNU style
2166 architecture specification string for the build architecture as
2167 well as for the host architecture. The build architecture is
2168 the architecture on which <file>debian/rules</file> is run and
2169 the package build is performed. The host architecture is the
2170 architecture on which the resulting package will be installed
2171 and run. These are normally the same, but may be different in
2172 the case of cross-compilation (building packages for one
2173 architecture on machines of a different architecture).
2177 Here is a list of supported <prgn>make</prgn> variables:
2178 <list compact="compact">
2180 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2183 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2186 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2189 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2190 specification string)
2193 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2194 <tt>DEB_*_GNU_TYPE</tt>)
2197 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2198 <tt>DEB_*_GNU_TYPE</tt>)
2200 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2201 the build architecture or <tt>HOST</tt> for specification of the
2206 Backward compatibility can be provided in the rules file
2207 by setting the needed variables to suitable default
2208 values; please refer to the documentation of
2209 <prgn>dpkg-architecture</prgn> for details.
2213 It is important to understand that the <tt>DEB_*_ARCH</tt>
2214 string only determines which Debian architecture we are
2215 building on or for. It should not be used to get the CPU
2216 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2217 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2218 GNU style variables should generally only be used with upstream
2222 <sect1 id="debianrules-options">
2223 <heading><file>debian/rules</file> and
2224 <tt>DEB_BUILD_OPTIONS</tt></heading>
2227 Supporting the standardized environment variable
2228 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2229 contain several flags to change how a package is compiled and
2230 built. Each flag must be in the form <var>flag</var> or
2231 <var>flag</var>=<var>options</var>. If multiple flags are
2232 given, they must be separated by whitespace.<footnote>
2233 Some packages support any delimiter, but whitespace is the
2234 easiest to parse inside a makefile and avoids ambiguity with
2235 flag values that contain commas.
2237 <var>flag</var> must start with a lowercase letter
2238 (<tt>a-z</tt>) and consist only of lowercase letters,
2239 numbers (<tt>0-9</tt>), and the characters
2240 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2241 <var>options</var> must not contain whitespace. The same
2242 tag should not be given multiple times with conflicting
2243 values. Package maintainers may assume that
2244 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2248 The meaning of the following tags has been standardized:
2252 This tag says to not run any build-time test suite
2253 provided by the package.
2257 The presence of this tag means that the package should
2258 be compiled with a minimum of optimization. For C
2259 programs, it is best to add <tt>-O0</tt> to
2260 <tt>CFLAGS</tt> (although this is usually the default).
2261 Some programs might fail to build or run at this level
2262 of optimization; it may be necessary to use
2263 <tt>-O1</tt>, for example.
2267 This tag means that the debugging symbols should not be
2268 stripped from the binary during installation, so that
2269 debugging information may be included in the package.
2271 <tag>parallel=n</tag>
2273 This tag means that the package should be built using up
2274 to <tt>n</tt> parallel processes if the package build
2275 system supports this.<footnote>
2276 Packages built with <tt>make</tt> can often implement
2277 this by passing the <tt>-j</tt><var>n</var> option to
2280 If the package build system does not support parallel
2281 builds, this string must be ignored. If the package
2282 build system only supports a lower level of concurrency
2283 than <var>n</var>, the package should be built using as
2284 many parallel processes as the package build system
2285 supports. It is up to the package maintainer to decide
2286 whether the package build times are long enough and the
2287 package build system is robust enough to make supporting
2288 parallel builds worthwhile.
2294 Unknown flags must be ignored by <file>debian/rules</file>.
2298 The following makefile snippet is an example of how one may
2299 implement the build options; you will probably have to
2300 massage this example in order to make it work for your
2302 <example compact="compact">
2305 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2306 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2307 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2308 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2310 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2315 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2316 INSTALL_PROGRAM += -s
2318 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2319 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2320 MAKEFLAGS += -j$(NUMJOBS)
2325 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2326 # Code to run the package test suite.
2333 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2334 <sect id="substvars">
2335 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2338 When <prgn>dpkg-gencontrol</prgn>
2339 generates <qref id="binarycontrolfiles">binary package control
2340 files</qref> (<file>DEBIAN/control</file>), it performs variable
2341 substitutions on its output just before writing it. Variable
2342 substitutions have the form <tt>${<var>variable</var>}</tt>.
2343 The optional file <file>debian/substvars</file> contains
2344 variable substitutions to be used; variables can also be set
2345 directly from <file>debian/rules</file> using the <tt>-V</tt>
2346 option to the source packaging commands, and certain predefined
2347 variables are also available.
2351 The <file>debian/substvars</file> file is usually generated and
2352 modified dynamically by <file>debian/rules</file> targets, in
2353 which case it must be removed by the <tt>clean</tt> target.
2357 See <manref name="deb-substvars" section="5"> for full
2358 details about source variable substitutions, including the
2359 format of <file>debian/substvars</file>.</p>
2362 <sect id="debianwatch">
2363 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2366 This is an optional, recommended configuration file for the
2367 <tt>uscan</tt> utility which defines how to automatically scan
2368 ftp or http sites for newly available updates of the
2369 package. This is used
2370 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2371 tools to help with quality control and maintenance of the
2372 distribution as a whole.
2377 <sect id="debianfiles">
2378 <heading>Generated files list: <file>debian/files</file></heading>
2381 This file is not a permanent part of the source tree; it
2382 is used while building packages to record which files are
2383 being generated. <prgn>dpkg-genchanges</prgn> uses it
2384 when it generates a <file>.changes</file> file.
2388 It should not exist in a shipped source package, and so it
2389 (and any backup files or temporary files such as
2390 <file>files.new</file><footnote>
2391 <file>files.new</file> is used as a temporary file by
2392 <prgn>dpkg-gencontrol</prgn> and
2393 <prgn>dpkg-distaddfile</prgn> - they write a new
2394 version of <tt>files</tt> here before renaming it,
2395 to avoid leaving a corrupted copy if an error
2397 </footnote>) should be removed by the
2398 <tt>clean</tt> target. It may also be wise to
2399 ensure a fresh start by emptying or removing it at the
2400 start of the <tt>binary</tt> target.
2404 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2405 package, it adds an entry to <file>debian/files</file> for the
2406 <file>.deb</file> file that will be created when <tt>dpkg-deb
2407 --build</tt> is run for that binary package. So for most
2408 packages all that needs to be done with this file is to
2409 delete it in the <tt>clean</tt> target.
2413 If a package upload includes files besides the source
2414 package and any binary packages whose control files were
2415 made with <prgn>dpkg-gencontrol</prgn> then they should be
2416 placed in the parent of the package's top-level directory
2417 and <prgn>dpkg-distaddfile</prgn> should be called to add
2418 the file to the list in <file>debian/files</file>.</p>
2421 <sect id="embeddedfiles">
2422 <heading>Convenience copies of code</heading>
2425 Some software packages include in their distribution convenience
2426 copies of code from other software packages, generally so that
2427 users compiling from source don't have to download multiple
2428 packages. Debian packages should not make use of these
2429 convenience copies unless the included package is explicitly
2430 intended to be used in this way.<footnote>
2431 For example, parts of the GNU build system work like this.
2433 If the included code is already in the Debian archive in the
2434 form of a library, the Debian packaging should ensure that
2435 binary packages reference the libraries already in Debian and
2436 the convenience copy is not used. If the included code is not
2437 already in Debian, it should be packaged separately as a
2438 prerequisite if possible.
2440 Having multiple copies of the same code in Debian is
2441 inefficient, often creates either static linking or shared
2442 library conflicts, and, most importantly, increases the
2443 difficulty of handling security vulnerabilities in the
2449 <sect id="readmesource">
2450 <heading>Source package handling:
2451 <file>debian/README.source</file></heading>
2454 If running <prgn>dpkg-source -x</prgn> on a source package
2455 doesn't produce the source of the package, ready for editing,
2456 and allow one to make changes and run
2457 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2458 without taking any additional steps, creating a
2459 <file>debian/README.source</file> documentation file is
2460 recommended. This file should explain how to do all of the
2463 <item>Generate the fully patched source, in a form ready for
2464 editing, that would be built to create Debian
2465 packages. Doing this with a <tt>patch</tt> target in
2466 <file>debian/rules</file> is recommended; see
2467 <ref id="debianrules">.</item>
2468 <item>Modify the source and save those modifications so that
2469 they will be applied when building the package.</item>
2470 <item>Remove source modifications that are currently being
2471 applied when building the package.</item>
2472 <item>Optionally, document what steps are necessary to
2473 upgrade the Debian source package to a new upstream version,
2474 if applicable.</item>
2476 This explanation should include specific commands and mention
2477 any additional required Debian packages. It should not assume
2478 familiarity with any specific Debian packaging system or patch
2483 This explanation may refer to a documentation file installed by
2484 one of the package's build dependencies provided that the
2485 referenced documentation clearly explains these tasks and is not
2486 a general reference manual.
2490 <file>debian/README.source</file> may also include any other
2491 information that would be helpful to someone modifying the
2492 source package. Even if the package doesn't fit the above
2493 description, maintainers are encouraged to document in a
2494 <file>debian/README.source</file> file any source package with a
2495 particularly complex or unintuitive source layout or build
2496 system (for example, a package that builds the same source
2497 multiple times to generate different binary packages).
2503 <chapt id="controlfields">
2504 <heading>Control files and their fields</heading>
2507 The package management system manipulates data represented in
2508 a common format, known as <em>control data</em>, stored in
2509 <em>control files</em>.
2510 Control files are used for source packages, binary packages and
2511 the <file>.changes</file> files which control the installation
2512 of uploaded files<footnote>
2513 <prgn>dpkg</prgn>'s internal databases are in a similar
2518 <sect id="controlsyntax">
2519 <heading>Syntax of control files</heading>
2522 A control file consists of one or more paragraphs of
2524 The paragraphs are also sometimes referred to as stanzas.
2526 The paragraphs are separated by empty lines. Parsers may accept
2527 lines consisting solely of spaces and tabs as paragraph
2528 separators, but control files should use empty lines. Some control
2529 files allow only one paragraph; others allow several, in
2530 which case each paragraph usually refers to a different
2531 package. (For example, in source packages, the first
2532 paragraph refers to the source package, and later paragraphs
2533 refer to binary packages generated from the source.) The
2534 ordering of the paragraphs in control files is significant.
2538 Each paragraph consists of a series of data fields. Each field
2539 consists of the field name followed by a colon and then the
2540 data/value associated with that field. The field name is
2541 composed of US-ASCII characters excluding control characters,
2542 space, and colon (i.e., characters in the ranges 33-57 and
2543 59-126, inclusive). Field names must not begin with the comment
2544 character, <tt>#</tt>.
2548 The field ends at the end of the line or at the end of the last
2549 continuation line (see below). Horizontal whitespace (spaces
2550 and tabs) may occur immediately before or after the value and is
2551 ignored there; it is conventional to put a single space after
2552 the colon. For example, a field might be:
2553 <example compact="compact">
2556 the field name is <tt>Package</tt> and the field value
2561 A paragraph must not contain more than one instance of a
2562 particular field name.
2566 There are three types of fields:
2570 The field, including its value, must be a single line. Folding
2571 of the field is not permitted. This is the default field type
2572 if the definition of the field does not specify a different
2577 The value of a folded field is a logical line that may span
2578 several lines. The lines after the first are called
2579 continuation lines and must start with a space or a tab.
2580 Whitespace, including any newlines, is not significant in the
2581 field values of folded fields.<footnote>
2582 This folding method is similar to RFC 5322, allowing control
2583 files that contain only one paragraph and no multiline fields
2584 to be read by parsers written for RFC 5322.
2587 <tag>multiline</tag>
2589 The value of a multiline field may comprise multiple continuation
2590 lines. The first line of the value, the part on the same line as
2591 the field name, often has special significance or may have to be
2592 empty. Other lines are added following the same syntax as the
2593 continuation lines of the folded fields. Whitespace, including newlines,
2594 is significant in the values of multiline fields.
2600 Whitespace must not appear
2601 inside names (of packages, architectures, files or anything
2602 else) or version numbers, or between the characters of
2603 multi-character version relationships.
2607 The presence and purpose of a field, and the syntax of its
2608 value may differ between types of control files.
2612 Field names are not case-sensitive, but it is usual to
2613 capitalize the field names using mixed case as shown below.
2614 Field values are case-sensitive unless the description of the
2615 field says otherwise.
2619 Paragraph separators (empty lines) and lines consisting only of
2620 spaces and tabs are not allowed within field values or between
2621 fields. Empty lines in field values are usually escaped by
2622 representing them by a space followed by a dot.
2626 Lines starting with # without any preceding whitespace are comments
2627 lines that are only permitted in source package control files
2628 (<file>debian/control</file>). These comment lines are ignored, even
2629 between two continuation lines. They do not end logical lines.
2633 All control files must be encoded in UTF-8.
2637 <sect id="sourcecontrolfiles">
2638 <heading>Source package control files -- <file>debian/control</file></heading>
2641 The <file>debian/control</file> file contains the most vital
2642 (and version-independent) information about the source package
2643 and about the binary packages it creates.
2647 The first paragraph of the control file contains information about
2648 the source package in general. The subsequent sets each describe a
2649 binary package that the source tree builds.
2653 The fields in the general paragraph (the first one, for the source
2656 <list compact="compact">
2657 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2660 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2661 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2662 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2663 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2664 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2665 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2670 The fields in the binary package paragraphs are:
2672 <list compact="compact">
2673 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2674 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2675 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2676 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2677 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2678 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2679 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2680 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2681 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2682 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2687 The syntax and semantics of the fields are described below.
2691 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2692 generate control files for binary packages (see below), by
2693 <prgn>dpkg-genchanges</prgn> to generate the
2694 <file>.changes</file> file to accompany the upload, and by
2695 <prgn>dpkg-source</prgn> when it creates the
2696 <file>.dsc</file> source control file as part of a source
2697 archive. Some fields are folded in <file>debian/control</file>,
2698 but not in any other control
2699 file. These tools are responsible for removing the line
2700 breaks from such fields when using fields from
2701 <file>debian/control</file> to generate other control files.
2705 The fields here may contain variable references - their
2706 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2707 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2708 when they generate output control files.
2709 See <ref id="substvars"> for details.
2713 <sect id="binarycontrolfiles">
2714 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2717 The <file>DEBIAN/control</file> file contains the most vital
2718 (and version-dependent) information about a binary package. It
2719 consists of a single paragraph.
2723 The fields in this file are:
2725 <list compact="compact">
2726 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2728 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2730 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2731 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2732 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2733 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2734 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2735 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2736 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2738 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2743 <sect id="debiansourcecontrolfiles">
2744 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2747 This file consists of a single paragraph, possibly surrounded by
2748 a PGP signature. The fields of that paragraph are listed below.
2749 Their syntax is described above, in <ref id="controlsyntax">.
2751 <list compact="compact">
2752 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2753 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2754 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2755 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2756 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2757 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2759 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2760 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2761 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2762 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2763 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2764 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2765 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2771 The Debian source control file is generated by
2772 <prgn>dpkg-source</prgn> when it builds the source
2773 archive, from other files in the source package,
2774 described above. When unpacking, it is checked against
2775 the files and directories in the other parts of the
2781 <sect id="debianchangesfiles">
2782 <heading>Debian changes files -- <file>.changes</file></heading>
2785 The <file>.changes</file> files are used by the Debian archive
2786 maintenance software to process updates to packages. They
2787 consist of a single paragraph, possibly surrounded by a PGP
2788 signature. That paragraph contains information from the
2789 <file>debian/control</file> file and other data about the
2790 source package gathered via <file>debian/changelog</file>
2791 and <file>debian/rules</file>.
2795 <file>.changes</file> files have a format version that is
2796 incremented whenever the documented fields or their meaning
2797 change. This document describes format &changesversion;.
2801 The fields in this file are:
2803 <list compact="compact">
2804 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2805 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2806 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2812 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2813 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2814 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2816 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2818 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2824 <sect id="controlfieldslist">
2825 <heading>List of fields</heading>
2827 <sect1 id="f-Source">
2828 <heading><tt>Source</tt></heading>
2831 This field identifies the source package name.
2835 In <file>debian/control</file> or a <file>.dsc</file> file,
2836 this field must contain only the name of the source package.
2840 In a binary package control file or a <file>.changes</file>
2841 file, the source package name may be followed by a version
2842 number in parentheses<footnote>
2843 It is customary to leave a space after the package name
2844 if a version number is specified.
2846 This version number may be omitted (and is, by
2847 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2848 the <tt>Version</tt> field of the binary package in
2849 question. The field itself may be omitted from a binary
2850 package control file when the source package has the same
2851 name and version as the binary package.
2855 Package names (both source and binary,
2856 see <ref id="f-Package">) must consist only of lower case
2857 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2858 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2859 (<tt>.</tt>). They must be at least two characters long and
2860 must start with an alphanumeric character.
2864 <sect1 id="f-Maintainer">
2865 <heading><tt>Maintainer</tt></heading>
2868 The package maintainer's name and email address. The name
2869 must come first, then the email address inside angle
2870 brackets <tt><></tt> (in RFC822 format).
2874 If the maintainer's name contains a full stop then the
2875 whole field will not work directly as an email address due
2876 to a misfeature in the syntax specified in RFC822; a
2877 program using this field as an address must check for this
2878 and correct the problem if necessary (for example by
2879 putting the name in round brackets and moving it to the
2880 end, and bringing the email address forward).
2884 See <ref id="maintainer"> for additional requirements and
2885 information about package maintainers.
2889 <sect1 id="f-Uploaders">
2890 <heading><tt>Uploaders</tt></heading>
2893 List of the names and email addresses of co-maintainers of the
2894 package, if any. If the package has other maintainers besides
2895 the one named in the <qref id="f-Maintainer">Maintainer
2896 field</qref>, their names and email addresses should be listed
2897 here. The format of each entry is the same as that of the
2898 Maintainer field, and multiple entries must be comma
2903 This is normally an optional field, but if
2904 the <tt>Maintainer</tt> control field names a group of people
2905 and a shared email address, the <tt>Uploaders</tt> field must
2906 be present and must contain at least one human with their
2907 personal email address.
2911 The Uploaders field in <file>debian/control</file> can be folded.
2915 <sect1 id="f-Changed-By">
2916 <heading><tt>Changed-By</tt></heading>
2919 The name and email address of the person who prepared this
2920 version of the package, usually a maintainer. The syntax is
2921 the same as for the <qref id="f-Maintainer">Maintainer
2926 <sect1 id="f-Section">
2927 <heading><tt>Section</tt></heading>
2930 This field specifies an application area into which the package
2931 has been classified. See <ref id="subsections">.
2935 When it appears in the <file>debian/control</file> file,
2936 it gives the value for the subfield of the same name in
2937 the <tt>Files</tt> field of the <file>.changes</file> file.
2938 It also gives the default for the same field in the binary
2943 <sect1 id="f-Priority">
2944 <heading><tt>Priority</tt></heading>
2947 This field represents how important it is that the user
2948 have the package installed. See <ref id="priorities">.
2952 When it appears in the <file>debian/control</file> file,
2953 it gives the value for the subfield of the same name in
2954 the <tt>Files</tt> field of the <file>.changes</file> file.
2955 It also gives the default for the same field in the binary
2960 <sect1 id="f-Package">
2961 <heading><tt>Package</tt></heading>
2964 The name of the binary package.
2968 Binary package names must follow the same syntax and
2969 restrictions as source package names. See <ref id="f-Source">
2974 <sect1 id="f-Architecture">
2975 <heading><tt>Architecture</tt></heading>
2978 Depending on context and the control file used, the
2979 <tt>Architecture</tt> field can include the following sets of
2983 A unique single word identifying a Debian machine
2984 architecture as described in <ref id="arch-spec">.
2987 An architecture wildcard identifying a set of Debian
2988 machine architectures, see <ref id="arch-wildcard-spec">.
2989 <tt>any</tt> matches all Debian machine architectures
2990 and is the most frequently used.
2993 <tt>all</tt>, which indicates an
2994 architecture-independent package.
2997 <tt>source</tt>, which indicates a source package.
3003 In the main <file>debian/control</file> file in the source
3004 package, this field may contain the special
3005 value <tt>all</tt>, the special architecture
3006 wildcard <tt>any</tt>, or a list of specific and wildcard
3007 architectures separated by spaces. If <tt>all</tt>
3008 or <tt>any</tt> appears, that value must be the entire
3009 contents of the field. Most packages will use
3010 either <tt>all</tt> or <tt>any</tt>.
3014 Specifying a specific list of architectures indicates that the
3015 source will build an architecture-dependent package only on
3016 architectures included in the list. Specifying a list of
3017 architecture wildcards indicates that the source will build an
3018 architecture-dependent package on only those architectures
3019 that match any of the specified architecture wildcards.
3020 Specifying a list of architectures or architecture wildcards
3021 other than <tt>any</tt> is for the minority of cases where a
3022 program is not portable or is not useful on some
3023 architectures. Where possible, the program should be made
3028 In the Debian source control file <file>.dsc</file>, this
3029 field contains a list of architectures and architecture
3030 wildcards separated by spaces. When the list contains the
3031 architecture wildcard <tt>any</tt>, the only other value
3032 allowed in the list is <tt>all</tt>.
3036 The list may include (or consist solely of) the special
3037 value <tt>all</tt>. In other words, in <file>.dsc</file>
3038 files unlike the <file>debian/control</file>, <tt>all</tt> may
3039 occur in combination with specific architectures.
3040 The <tt>Architecture</tt> field in the Debian source control
3041 file <file>.dsc</file> is generally constructed from
3042 the <tt>Architecture</tt> fields in
3043 the <file>debian/control</file> in the source package.
3047 Specifying only <tt>any</tt> indicates that the source package
3048 isn't dependent on any particular architecture and should
3049 compile fine on any one. The produced binary package(s)
3050 will be specific to whatever the current build architecture is.
3054 Specifying only <tt>all</tt> indicates that the source package
3055 will only build architecture-independent packages.
3059 Specifying <tt>any all</tt> indicates that the source package
3060 isn't dependent on any particular architecture. The set of
3061 produced binary packages will include at least one
3062 architecture-dependant package and one architecture-independent
3067 Specifying a list of architectures or architecture wildcards
3068 indicates that the source will build an architecture-dependent
3069 package, and will only work correctly on the listed or
3070 matching architectures. If the source package also builds at
3071 least one architecture-independent package, <tt>all</tt> will
3072 also be included in the list.
3076 In a <file>.changes</file> file, the <tt>Architecture</tt>
3077 field lists the architecture(s) of the package(s) currently
3078 being uploaded. This will be a list; if the source for the
3079 package is also being uploaded, the special
3080 entry <tt>source</tt> is also present. <tt>all</tt> will be
3081 present if any architecture-independent packages are being
3082 uploaded. Architecture wildcards such as <tt>any</tt> must
3083 never occur in the <tt>Architecture</tt> field in
3084 the <file>.changes</file> file.
3088 See <ref id="debianrules"> for information on how to get
3089 the architecture for the build process.
3093 <sect1 id="f-Essential">
3094 <heading><tt>Essential</tt></heading>
3097 This is a boolean field which may occur only in the
3098 control file of a binary package or in a per-package fields
3099 paragraph of a source package control file.
3103 If set to <tt>yes</tt> then the package management system
3104 will refuse to remove the package (upgrading and replacing
3105 it is still possible). The other possible value is <tt>no</tt>,
3106 which is the same as not having the field at all.
3111 <heading>Package interrelationship fields:
3112 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3113 <tt>Recommends</tt>, <tt>Suggests</tt>,
3114 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3115 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3119 These fields describe the package's relationships with
3120 other packages. Their syntax and semantics are described
3121 in <ref id="relationships">.</p>
3124 <sect1 id="f-Standards-Version">
3125 <heading><tt>Standards-Version</tt></heading>
3128 The most recent version of the standards (the policy
3129 manual and associated texts) with which the package
3134 The version number has four components: major and minor
3135 version number and major and minor patch level. When the
3136 standards change in a way that requires every package to
3137 change the major number will be changed. Significant
3138 changes that will require work in many packages will be
3139 signaled by a change to the minor number. The major patch
3140 level will be changed for any change to the meaning of the
3141 standards, however small; the minor patch level will be
3142 changed when only cosmetic, typographical or other edits
3143 are made which neither change the meaning of the document
3144 nor affect the contents of packages.
3148 Thus only the first three components of the policy version
3149 are significant in the <em>Standards-Version</em> control
3150 field, and so either these three components or all four
3151 components may be specified.<footnote>
3152 In the past, people specified the full version number
3153 in the Standards-Version field, for example "2.3.0.0".
3154 Since minor patch-level changes don't introduce new
3155 policy, it was thought it would be better to relax
3156 policy and only require the first 3 components to be
3157 specified, in this example "2.3.0". All four
3158 components may still be used if someone wishes to do so.
3164 <sect1 id="f-Version">
3165 <heading><tt>Version</tt></heading>
3168 The version number of a package. The format is:
3169 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3173 The three components here are:
3175 <tag><var>epoch</var></tag>
3178 This is a single (generally small) unsigned integer. It
3179 may be omitted, in which case zero is assumed. If it is
3180 omitted then the <var>upstream_version</var> may not
3185 It is provided to allow mistakes in the version numbers
3186 of older versions of a package, and also a package's
3187 previous version numbering schemes, to be left behind.
3191 <tag><var>upstream_version</var></tag>
3194 This is the main part of the version number. It is
3195 usually the version number of the original ("upstream")
3196 package from which the <file>.deb</file> file has been made,
3197 if this is applicable. Usually this will be in the same
3198 format as that specified by the upstream author(s);
3199 however, it may need to be reformatted to fit into the
3200 package management system's format and comparison
3205 The comparison behavior of the package management system
3206 with respect to the <var>upstream_version</var> is
3207 described below. The <var>upstream_version</var>
3208 portion of the version number is mandatory.
3212 The <var>upstream_version</var> may contain only
3213 alphanumerics<footnote>
3214 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3216 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3217 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3218 tilde) and should start with a digit. If there is no
3219 <var>debian_revision</var> then hyphens are not allowed;
3220 if there is no <var>epoch</var> then colons are not
3225 <tag><var>debian_revision</var></tag>
3228 This part of the version number specifies the version of
3229 the Debian package based on the upstream version. It
3230 may contain only alphanumerics and the characters
3231 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3232 tilde) and is compared in the same way as the
3233 <var>upstream_version</var> is.
3237 It is optional; if it isn't present then the
3238 <var>upstream_version</var> may not contain a hyphen.
3239 This format represents the case where a piece of
3240 software was written specifically to be a Debian
3241 package, where the Debian package source must always
3242 be identical to the pristine source and therefore no
3243 revision indication is required.
3247 It is conventional to restart the
3248 <var>debian_revision</var> at <tt>1</tt> each time the
3249 <var>upstream_version</var> is increased.
3253 The package management system will break the version
3254 number apart at the last hyphen in the string (if there
3255 is one) to determine the <var>upstream_version</var> and
3256 <var>debian_revision</var>. The absence of a
3257 <var>debian_revision</var> is equivalent to a
3258 <var>debian_revision</var> of <tt>0</tt>.
3265 When comparing two version numbers, first the <var>epoch</var>
3266 of each are compared, then the <var>upstream_version</var> if
3267 <var>epoch</var> is equal, and then <var>debian_revision</var>
3268 if <var>upstream_version</var> is also equal.
3269 <var>epoch</var> is compared numerically. The
3270 <var>upstream_version</var> and <var>debian_revision</var>
3271 parts are compared by the package management system using the
3272 following algorithm:
3276 The strings are compared from left to right.
3280 First the initial part of each string consisting entirely of
3281 non-digit characters is determined. These two parts (one of
3282 which may be empty) are compared lexically. If a difference
3283 is found it is returned. The lexical comparison is a
3284 comparison of ASCII values modified so that all the letters
3285 sort earlier than all the non-letters and so that a tilde
3286 sorts before anything, even the end of a part. For example,
3287 the following parts are in sorted order from earliest to
3288 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3289 <tt>a</tt>.<footnote>
3290 One common use of <tt>~</tt> is for upstream pre-releases.
3291 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3292 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3297 Then the initial part of the remainder of each string which
3298 consists entirely of digit characters is determined. The
3299 numerical values of these two parts are compared, and any
3300 difference found is returned as the result of the comparison.
3301 For these purposes an empty string (which can only occur at
3302 the end of one or both version strings being compared) counts
3307 These two steps (comparing and removing initial non-digit
3308 strings and initial digit strings) are repeated until a
3309 difference is found or both strings are exhausted.
3313 Note that the purpose of epochs is to allow us to leave behind
3314 mistakes in version numbering, and to cope with situations
3315 where the version numbering scheme changes. It is
3316 <em>not</em> intended to cope with version numbers containing
3317 strings of letters which the package management system cannot
3318 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3319 silly orderings.<footnote>
3320 The author of this manual has heard of a package whose
3321 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3322 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3328 <sect1 id="f-Description">
3329 <heading><tt>Description</tt></heading>
3332 In a source or binary control file, the <tt>Description</tt>
3333 field contains a description of the binary package, consisting
3334 of two parts, the synopsis or the short description, and the
3335 long description. It is a multiline field with the following
3341 Description: <single line synopsis>
3342 <extended description over several lines>
3347 The lines in the extended description can have these formats:
3353 Those starting with a single space are part of a paragraph.
3354 Successive lines of this form will be word-wrapped when
3355 displayed. The leading space will usually be stripped off.
3356 The line must contain at least one non-whitespace character.
3360 Those starting with two or more spaces. These will be
3361 displayed verbatim. If the display cannot be panned
3362 horizontally, the displaying program will line wrap them "hard"
3363 (i.e., without taking account of word breaks). If it can they
3364 will be allowed to trail off to the right. None, one or two
3365 initial spaces may be deleted, but the number of spaces
3366 deleted from each line will be the same (so that you can have
3367 indenting work correctly, for example). The line must
3368 contain at least one non-whitespace character.
3372 Those containing a single space followed by a single full stop
3373 character. These are rendered as blank lines. This is the
3374 <em>only</em> way to get a blank line<footnote>
3375 Completely empty lines will not be rendered as blank lines.
3376 Instead, they will cause the parser to think you're starting
3377 a whole new record in the control file, and will therefore
3378 likely abort with an error.
3383 Those containing a space, a full stop and some more characters.
3384 These are for future expansion. Do not use them.
3390 Do not use tab characters. Their effect is not predictable.
3394 See <ref id="descriptions"> for further information on this.
3398 In a <file>.changes</file> file, the <tt>Description</tt>
3399 field contains a summary of the descriptions for the packages
3400 being uploaded. For this case, the first line of the field
3401 value (the part on the same line as <tt>Description:</tt>) is
3402 always empty. It is a multiline field, with one
3403 line per package. Each line is
3404 indented by one space and contains the name of a binary
3405 package, a space, a hyphen (<tt>-</tt>), a space, and the
3406 short description line from that package.
3410 <sect1 id="f-Distribution">
3411 <heading><tt>Distribution</tt></heading>
3414 In a <file>.changes</file> file or parsed changelog output
3415 this contains the (space-separated) name(s) of the
3416 distribution(s) where this version of the package should
3417 be installed. Valid distributions are determined by the
3418 archive maintainers.<footnote>
3419 Example distribution names in the Debian archive used in
3420 <file>.changes</file> files are:
3421 <taglist compact="compact">
3422 <tag><em>unstable</em></tag>
3424 This distribution value refers to the
3425 <em>developmental</em> part of the Debian distribution
3426 tree. Most new packages, new upstream versions of
3427 packages and bug fixes go into the <em>unstable</em>
3431 <tag><em>experimental</em></tag>
3433 The packages with this distribution value are deemed
3434 by their maintainers to be high risk. Oftentimes they
3435 represent early beta or developmental packages from
3436 various sources that the maintainers want people to
3437 try, but are not ready to be a part of the other parts
3438 of the Debian distribution tree.
3443 Others are used for updating stable releases or for
3444 security uploads. More information is available in the
3445 Debian Developer's Reference, section "The Debian
3449 The Debian archive software only supports listing a single
3450 distribution. Migration of packages to other distributions is
3451 handled outside of the upload process.
3456 <heading><tt>Date</tt></heading>
3459 This field includes the date the package was built or last
3460 edited. It must be in the same format as the <var>date</var>
3461 in a <file>debian/changelog</file> entry.
3465 The value of this field is usually extracted from the
3466 <file>debian/changelog</file> file - see
3467 <ref id="dpkgchangelog">).
3471 <sect1 id="f-Format">
3472 <heading><tt>Format</tt></heading>
3475 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3476 files, this field declares the format version of that file.
3477 The syntax of the field value is the same as that of
3478 a <qref id="f-Version">package version number</qref> except
3479 that no epoch or Debian revision is allowed. The format
3480 described in this document is <tt>&changesversion;</tt>.
3484 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3485 Debian source control</qref> files, this field declares the
3486 format of the source package. The field value is used by
3487 programs acting on a source package to interpret the list of
3488 files in the source package and determine how to unpack it.
3489 The syntax of the field value is a numeric major revision, a
3490 period, a numeric minor revision, and then an optional subtype
3491 after whitespace, which if specified is an alphanumeric word
3492 in parentheses. The subtype is optional in the syntax but may
3493 be mandatory for particular source format revisions.
3495 The source formats currently supported by the Debian archive
3496 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3497 and <tt>3.0 (quilt)</tt>.
3502 <sect1 id="f-Urgency">
3503 <heading><tt>Urgency</tt></heading>
3506 This is a description of how important it is to upgrade to
3507 this version from previous ones. It consists of a single
3508 keyword taking one of the values <tt>low</tt>,
3509 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3510 <tt>critical</tt><footnote>
3511 Other urgency values are supported with configuration
3512 changes in the archive software but are not used in Debian.
3513 The urgency affects how quickly a package will be considered
3514 for inclusion into the <tt>testing</tt> distribution and
3515 gives an indication of the importance of any fixes included
3516 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3517 treated as synonymous.
3518 </footnote> (not case-sensitive) followed by an optional
3519 commentary (separated by a space) which is usually in
3520 parentheses. For example:
3523 Urgency: low (HIGH for users of diversions)
3529 The value of this field is usually extracted from the
3530 <file>debian/changelog</file> file - see
3531 <ref id="dpkgchangelog">.
3535 <sect1 id="f-Changes">
3536 <heading><tt>Changes</tt></heading>
3539 This multiline field contains the human-readable changes data, describing
3540 the differences between the last version and the current one.
3544 The first line of the field value (the part on the same line
3545 as <tt>Changes:</tt>) is always empty. The content of the
3546 field is expressed as continuation lines, with each line
3547 indented by at least one space. Blank lines must be
3548 represented by a line consisting only of a space and a full
3553 The value of this field is usually extracted from the
3554 <file>debian/changelog</file> file - see
3555 <ref id="dpkgchangelog">).
3559 Each version's change information should be preceded by a
3560 "title" line giving at least the version, distribution(s)
3561 and urgency, in a human-readable way.
3565 If data from several versions is being returned the entry
3566 for the most recent version should be returned first, and
3567 entries should be separated by the representation of a
3568 blank line (the "title" line may also be followed by the
3569 representation of a blank line).
3573 <sect1 id="f-Binary">
3574 <heading><tt>Binary</tt></heading>
3577 This folded field is a list of binary packages. Its syntax and
3578 meaning varies depending on the control file in which it
3583 When it appears in the <file>.dsc</file> file, it lists binary
3584 packages which a source package can produce, separated by
3586 A space after each comma is conventional.
3587 </footnote>. The source package
3588 does not necessarily produce all of these binary packages for
3589 every architecture. The source control file doesn't contain
3590 details of which architectures are appropriate for which of
3591 the binary packages.
3595 When it appears in a <file>.changes</file> file, it lists the
3596 names of the binary packages being uploaded, separated by
3597 whitespace (not commas).
3601 <sect1 id="f-Installed-Size">
3602 <heading><tt>Installed-Size</tt></heading>
3605 This field appears in the control files of binary packages,
3606 and in the <file>Packages</file> files. It gives an estimate
3607 of the total amount of disk space required to install the
3608 named package. Actual installed size may vary based on block
3609 size, file system properties, or actions taken by package
3614 The disk space is given as the integer value of the estimated
3615 installed size in bytes, divided by 1024 and rounded up.
3619 <sect1 id="f-Files">
3620 <heading><tt>Files</tt></heading>
3623 This field contains a list of files with information about
3624 each one. The exact information and syntax varies with
3629 In all cases, Files is a multiline field. The first line of
3630 the field value (the part on the same line as <tt>Files:</tt>)
3631 is always empty. The content of the field is expressed as
3632 continuation lines, one line per file. Each line must be
3633 indented by one space and contain a number of sub-fields,
3634 separated by spaces, as described below.
3638 In the <file>.dsc</file> file, each line contains the MD5
3639 checksum, size and filename of the tar file and (if
3640 applicable) diff file which make up the remainder of the
3641 source package<footnote>
3642 That is, the parts which are not the <tt>.dsc</tt>.
3643 </footnote>. For example:
3646 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3647 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3649 The exact forms of the filenames are described
3650 in <ref id="pkg-sourcearchives">.
3654 In the <file>.changes</file> file this contains one line per
3655 file being uploaded. Each line contains the MD5 checksum,
3656 size, section and priority and the filename. For example:
3659 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3660 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3661 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3662 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3664 The <qref id="f-Section">section</qref>
3665 and <qref id="f-Priority">priority</qref> are the values of
3666 the corresponding fields in the main source control file. If
3667 no section or priority is specified then <tt>-</tt> should be
3668 used, though section and priority values must be specified for
3669 new packages to be installed properly.
3673 The special value <tt>byhand</tt> for the section in a
3674 <tt>.changes</tt> file indicates that the file in question
3675 is not an ordinary package file and must by installed by
3676 hand by the distribution maintainers. If the section is
3677 <tt>byhand</tt> the priority should be <tt>-</tt>.
3681 If a new Debian revision of a package is being shipped and
3682 no new original source archive is being distributed the
3683 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3684 entry for the original source archive
3685 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3686 but the <file>.changes</file> file should leave it out. In
3687 this case the original source archive on the distribution
3688 site must match exactly, byte-for-byte, the original
3689 source archive which was used to generate the
3690 <file>.dsc</file> file and diff which are being uploaded.</p>
3693 <sect1 id="f-Closes">
3694 <heading><tt>Closes</tt></heading>
3697 A space-separated list of bug report numbers that the upload
3698 governed by the .changes file closes.
3702 <sect1 id="f-Homepage">
3703 <heading><tt>Homepage</tt></heading>
3706 The URL of the web site for this package, preferably (when
3707 applicable) the site from which the original source can be
3708 obtained and any additional upstream documentation or
3709 information may be found. The content of this field is a
3710 simple URL without any surrounding characters such as
3715 <sect1 id="f-Checksums">
3716 <heading><tt>Checksums-Sha1</tt>
3717 and <tt>Checksums-Sha256</tt></heading>
3720 These multiline fields contain a list of files with a checksum and size
3721 for each one. Both <tt>Checksums-Sha1</tt>
3722 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3723 only in the checksum algorithm used: SHA-1
3724 for <tt>Checksums-Sha1</tt> and SHA-256
3725 for <tt>Checksums-Sha256</tt>.
3729 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3730 multiline fields. The first line of the field value (the part
3731 on the same line as <tt>Checksums-Sha1:</tt>
3732 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3733 of the field is expressed as continuation lines, one line per
3734 file. Each line consists of the checksum, a space, the file
3735 size, a space, and the file name. For example (from
3736 a <file>.changes</file> file):
3739 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3740 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3741 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3742 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3744 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3745 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3746 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3747 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3752 In the <file>.dsc</file> file, these fields list all
3753 files that make up the source package. In
3754 the <file>.changes</file> file, these fields list all
3755 files being uploaded. The list of files in these fields
3756 must match the list of files in the <tt>Files</tt> field.
3761 <heading><tt>DM-Upload-Allowed</tt></heading>
3764 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3768 <sect1 id="f-VCS-fields">
3769 <heading>Version Control System (VCS) fields</heading>
3772 Debian source packages are increasingly developed using VCSs. The
3773 purpose of the following fields is to indicate a publicly accessible
3774 repository where the Debian source package is developed.
3777 <tag><tt>Vcs-Browser</tt></tag>
3780 URL of a web interface for browsing the repository.
3785 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3786 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3787 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3792 The field name identifies the VCS. The field's value uses the
3793 version control system's conventional syntax for describing
3794 repository locations and should be sufficient to locate the
3795 repository used for packaging. Ideally, it also locates the
3796 branch used for development of new versions of the Debian
3800 In the case of Git, the value consists of a URL, optionally
3801 followed by the word <tt>-b</tt> and the name of a branch in
3802 the indicated repository, following the syntax of the
3803 <tt>git clone</tt> command. If no branch is specified, the
3804 packaging should be on the default branch.
3807 More than one different VCS may be specified for the same
3815 <sect1 id="f-Package-List">
3816 <heading><tt>Package-List</tt></heading>
3819 Multiline field listing all the packages that can be built from
3820 the source package, considering every architecture. The first line
3821 of the field value is empty. Each one of the next lines describes
3822 one binary package, by listing its name, type, section and priority
3823 separated by spaces. Fifth and subsequent space-separated items
3824 may be present and parsers must allow them. See the
3825 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3830 <sect1 id="f-Package-Type">
3831 <heading><tt>Package-Type</tt></heading>
3834 Simple field containing a word indicating the type of package:
3835 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3836 packages. Other types not defined here may be indicated. In
3837 source package control files, the <tt>Package-Type</tt> field
3838 should be omitted instead of giving it a value of <tt>deb</tt>, as
3839 this value is assumed for paragraphs lacking this field.
3845 <heading>User-defined fields</heading>
3848 Additional user-defined fields may be added to the
3849 source package control file. Such fields will be
3850 ignored, and not copied to (for example) binary or
3851 Debian source control files or upload control files.
3855 If you wish to add additional unsupported fields to
3856 these output files you should use the mechanism
3861 Fields in the main source control information file with
3862 names starting <tt>X</tt>, followed by one or more of
3863 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3864 be copied to the output files. Only the part of the
3865 field name after the hyphen will be used in the output
3866 file. Where the letter <tt>B</tt> is used the field
3867 will appear in binary package control files, where the
3868 letter <tt>S</tt> is used in Debian source control
3869 files and where <tt>C</tt> is used in upload control
3870 (<tt>.changes</tt>) files.
3874 For example, if the main source information control file
3877 XBS-Comment: I stand between the candle and the star.
3879 then the binary and Debian source control files will contain the
3882 Comment: I stand between the candle and the star.
3888 <sect id="obsolete-control-data-fields">
3889 <heading>Obsolete fields</heading>
3892 The following fields have been obsoleted and may be found in packages
3893 conforming with previous versions of the Policy.
3896 <sect1 id="f-DM-Upload-Allowed">
3897 <heading><tt>DM-Upload-Allowed</tt></heading>
3900 Indicates that Debian Maintainers may upload this package to
3901 the Debian archive. The only valid value is <tt>yes</tt>. This
3902 field was used to regulate uploads by Debian Maintainers, See the
3903 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3904 name="Endorse the concept of Debian Maintainers"> for more details.
3913 <chapt id="maintainerscripts">
3914 <heading>Package maintainer scripts and installation procedure</heading>
3917 <heading>Introduction to package maintainer scripts</heading>
3920 It is possible to supply scripts as part of a package which
3921 the package management system will run for you when your
3922 package is installed, upgraded or removed.
3926 These scripts are the control information
3927 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3928 and <prgn>postrm</prgn>. They must be proper executable files;
3929 if they are scripts (which is recommended), they must start with
3930 the usual <tt>#!</tt> convention. They should be readable and
3931 executable by anyone, and must not be world-writable.
3935 The package management system looks at the exit status from
3936 these scripts. It is important that they exit with a
3937 non-zero status if there is an error, so that the package
3938 management system can stop its processing. For shell
3939 scripts this means that you <em>almost always</em> need to
3940 use <tt>set -e</tt> (this is usually true when writing shell
3941 scripts, in fact). It is also important, of course, that
3942 they exit with a zero status if everything went well.
3946 Additionally, packages interacting with users
3947 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3948 should install a <prgn>config</prgn> script as a control
3949 information file. See <ref id="maintscriptprompt"> for details.
3953 When a package is upgraded a combination of the scripts from
3954 the old and new packages is called during the upgrade
3955 procedure. If your scripts are going to be at all
3956 complicated you need to be aware of this, and may need to
3957 check the arguments to your scripts.
3961 Broadly speaking the <prgn>preinst</prgn> is called before
3962 (a particular version of) a package is unpacked, and the
3963 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3964 before (a version of) a package is removed and the
3965 <prgn>postrm</prgn> afterwards.
3969 Programs called from maintainer scripts should not normally
3970 have a path prepended to them. Before installation is
3971 started, the package management system checks to see if the
3972 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3973 and <prgn>update-rc.d</prgn> can be found via the
3974 <tt>PATH</tt> environment variable. Those programs, and any
3975 other program that one would expect to be in the
3976 <tt>PATH</tt>, should thus be invoked without an absolute
3977 pathname. Maintainer scripts should also not reset the
3978 <tt>PATH</tt>, though they might choose to modify it by
3979 prepending or appending package-specific directories. These
3980 considerations really apply to all shell scripts.</p>
3983 <sect id="idempotency">
3984 <heading>Maintainer scripts idempotency</heading>
3987 It is necessary for the error recovery procedures that the
3988 scripts be idempotent. This means that if it is run
3989 successfully, and then it is called again, it doesn't bomb
3990 out or cause any harm, but just ensures that everything is
3991 the way it ought to be. If the first call failed, or
3992 aborted half way through for some reason, the second call
3993 should merely do the things that were left undone the first
3994 time, if any, and exit with a success status if everything
3996 This is so that if an error occurs, the user interrupts
3997 <prgn>dpkg</prgn> or some other unforeseen circumstance
3998 happens you don't leave the user with a badly-broken
3999 package when <prgn>dpkg</prgn> attempts to repeat the
4005 <sect id="controllingterminal">
4006 <heading>Controlling terminal for maintainer scripts</heading>
4009 Maintainer scripts are not guaranteed to run with a controlling
4010 terminal and may not be able to interact with the user. They
4011 must be able to fall back to noninteractive behavior if no
4012 controlling terminal is available. Maintainer scripts that
4013 prompt via a program conforming to the Debian Configuration
4014 Management Specification (see <ref id="maintscriptprompt">) may
4015 assume that program will handle falling back to noninteractive
4020 For high-priority prompts without a reasonable default answer,
4021 maintainer scripts may abort if there is no controlling
4022 terminal. However, this situation should be avoided if at all
4023 possible, since it prevents automated or unattended installs.
4024 In most cases, users will consider this to be a bug in the
4029 <sect id="exitstatus">
4030 <heading>Exit status</heading>
4033 Each script must return a zero exit status for
4034 success, or a nonzero one for failure, since the package
4035 management system looks for the exit status of these scripts
4036 and determines what action to take next based on that datum.
4040 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4045 What follows is a summary of all the ways in which maintainer
4046 scripts may be called along with what facilities those scripts
4047 may rely on being available at that time. Script names preceded
4048 by <var>new-</var> are the scripts from the new version of a
4049 package being installed, upgraded to, or downgraded to. Script
4050 names preceded by <var>old-</var> are the scripts from the old
4051 version of a package that is being upgraded from or downgraded
4056 The <prgn>preinst</prgn> script may be called in the following
4059 <tag><var>new-preinst</var> <tt>install</tt></tag>
4060 <tag><var>new-preinst</var> <tt>install</tt>
4061 <var>old-version</var></tag>
4062 <tag><var>new-preinst</var> <tt>upgrade</tt>
4063 <var>old-version</var></tag>
4065 The package will not yet be unpacked, so
4066 the <prgn>preinst</prgn> script cannot rely on any files
4067 included in its package. Only essential packages and
4068 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4069 available. Pre-dependencies will have been configured at
4070 least once, but at the time the <prgn>preinst</prgn> is
4071 called they may only be in an unpacked or "Half-Configured"
4072 state if a previous version of the pre-dependency was
4073 completely configured and has not been removed since then.
4076 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4077 <var>new-version</var></tag>
4079 Called during error handling of an upgrade that failed after
4080 unpacking the new package because the <tt>postrm
4081 upgrade</tt> action failed. The unpacked files may be
4082 partly from the new version or partly missing, so the script
4083 cannot rely on files included in the package. Package
4084 dependencies may not be available. Pre-dependencies will be
4085 at least unpacked following the same rules as above, except
4086 they may be only "Half-Installed" if an upgrade of the
4087 pre-dependency failed.<footnote>
4088 This can happen if the new version of the package no
4089 longer pre-depends on a package that had been partially
4097 The <prgn>postinst</prgn> script may be called in the following
4100 <tag><var>postinst</var> <tt>configure</tt>
4101 <var>most-recently-configured-version</var></tag>
4103 The files contained in the package will be unpacked. All
4104 package dependencies will at least be unpacked. If there
4105 are no circular dependencies involved, all package
4106 dependencies will be configured. For behavior in the case
4107 of circular dependencies, see the discussion
4108 in <ref id="binarydeps">.
4111 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4112 <var>new-version</var></tag>
4113 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4114 <tt>in-favour</tt> <var>package</var>
4115 <var>new-version</var></tag>
4116 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4117 <tag><var>deconfigured's-postinst</var>
4118 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4119 <var>failed-install-package</var> <var>version</var>
4120 [<tt>removing</tt> <var>conflicting-package</var>
4121 <var>version</var>]</tag>
4123 The files contained in the package will be unpacked. All
4124 package dependencies will at least be "Half-Installed" and
4125 will have previously been configured and not removed.
4126 However, dependencies may not be configured or even fully
4127 unpacked in some error situations.<footnote>
4128 For example, suppose packages foo and bar are installed
4129 with foo depending on bar. If an upgrade of bar were
4130 started and then aborted, and then an attempt to remove
4131 foo failed because its <prgn>prerm</prgn> script failed,
4132 foo's <tt>postinst abort-remove</tt> would be called with
4133 bar only "Half-Installed".
4135 The <prgn>postinst</prgn> should still attempt any actions
4136 for which its dependencies are required, since they will
4137 normally be available, but consider the correct error
4138 handling approach if those actions fail. Aborting
4139 the <prgn>postinst</prgn> action if commands or facilities
4140 from the package dependencies are not available is often the
4147 The <prgn>prerm</prgn> script may be called in the following
4150 <tag><var>prerm</var> <tt>remove</tt></tag>
4151 <tag><var>old-prerm</var>
4152 <tt>upgrade</tt><var>new-version</var></tag>
4153 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4154 <tt>in-favour</tt> <var>package</var>
4155 <var>new-version</var></tag>
4156 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4157 <tt>in-favour</tt> <var>package-being-installed</var>
4158 <var>version</var> [<tt>removing</tt>
4159 <var>conflicting-package</var> <var>version</var>]</tag>
4161 The package whose <prgn>prerm</prgn> is being called will be
4162 at least "Half-Installed". All package dependencies will at
4163 least be "Half-Installed" and will have previously been
4164 configured and not removed. If there was no error, all
4165 dependencies will at least be unpacked, but these actions
4166 may be called in various error states where dependencies are
4167 only "Half-Installed" due to a partial upgrade.
4170 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4171 <var>old-version</var></tag>
4173 Called during error handling when <tt>prerm upgrade</tt>
4174 fails. The new package will not yet be unpacked, and all
4175 the same constraints as for <tt>preinst upgrade</tt> apply.
4181 The <prgn>postrm</prgn> script may be called in the following
4184 <tag><var>postrm</var> <tt>remove</tt></tag>
4185 <tag><var>postrm</var> <tt>purge</tt></tag>
4186 <tag><var>old-postrm</var> <tt>upgrade</tt>
4187 <var>new-version</var></tag>
4188 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4189 <var>overwriter</var> <var>overwriter-version</var></tag>
4191 The <prgn>postrm</prgn> script is called after the package's
4192 files have been removed or replaced. The package
4193 whose <prgn>postrm</prgn> is being called may have
4194 previously been deconfigured and only be unpacked, at which
4195 point subsequent package changes do not consider its
4196 dependencies. Therefore, all <prgn>postrm</prgn> actions
4197 may only rely on essential packages and must gracefully skip
4198 any actions that require the package's dependencies if those
4199 dependencies are unavailable.<footnote>
4200 This is often done by checking whether the command or
4201 facility the <prgn>postrm</prgn> intends to call is
4202 available before calling it. For example:
4204 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4205 . /usr/share/debconf/confmodule
4209 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4210 configuration for the package
4211 if <package>debconf</package> is installed.
4215 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4216 <var>old-version</var></tag>
4218 Called when the old <tt>postrm upgrade</tt> action fails.
4219 The new package will be unpacked, but only essential
4220 packages and pre-dependencies can be relied on.
4221 Pre-dependencies will either be configured or will be
4222 "Unpacked" or "Half-Configured" but previously had been
4223 configured and was never removed.
4226 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4227 <tag><var>new-postrm</var> <tt>abort-install</tt>
4228 <var>old-version</var></tag>
4229 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4230 <var>old-version</var></tag>
4232 Called before unpacking the new package as part of the
4233 error handling of <prgn>preinst</prgn> failures. May assume
4234 the same state as <prgn>preinst</prgn> can assume.
4240 <sect id="unpackphase">
4241 <heading>Details of unpack phase of installation or upgrade</heading>
4244 The procedure on installation/upgrade/overwrite/disappear
4245 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4246 stage of <tt>dpkg --install</tt>) is as follows. In each
4247 case, if a major error occurs (unless listed below) the
4248 actions are, in general, run backwards - this means that the
4249 maintainer scripts are run with different arguments in
4250 reverse order. These are the "error unwind" calls listed
4257 If a version of the package is already installed, call
4258 <example compact="compact">
4259 <var>old-prerm</var> upgrade <var>new-version</var>
4263 If the script runs but exits with a non-zero
4264 exit status, <prgn>dpkg</prgn> will attempt:
4265 <example compact="compact">
4266 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4268 If this works, the upgrade continues. If this
4269 does not work, the error unwind:
4270 <example compact="compact">
4271 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4273 If this works, then the old-version is
4274 "Installed", if not, the old version is in a
4275 "Half-Configured" state.
4281 If a "conflicting" package is being removed at the same time,
4282 or if any package will be broken (due to <tt>Breaks</tt>):
4285 If <tt>--auto-deconfigure</tt> is
4286 specified, call, for each package to be deconfigured
4287 due to <tt>Breaks</tt>:
4288 <example compact="compact">
4289 <var>deconfigured's-prerm</var> deconfigure \
4290 in-favour <var>package-being-installed</var> <var>version</var>
4293 <example compact="compact">
4294 <var>deconfigured's-postinst</var> abort-deconfigure \
4295 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4297 The deconfigured packages are marked as
4298 requiring configuration, so that if
4299 <tt>--install</tt> is used they will be
4300 configured again if possible.
4303 If any packages depended on a conflicting
4304 package being removed and <tt>--auto-deconfigure</tt> is
4305 specified, call, for each such package:
4306 <example compact="compact">
4307 <var>deconfigured's-prerm</var> deconfigure \
4308 in-favour <var>package-being-installed</var> <var>version</var> \
4309 removing <var>conflicting-package</var> <var>version</var>
4312 <example compact="compact">
4313 <var>deconfigured's-postinst</var> abort-deconfigure \
4314 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4315 removing <var>conflicting-package</var> <var>version</var>
4317 The deconfigured packages are marked as
4318 requiring configuration, so that if
4319 <tt>--install</tt> is used they will be
4320 configured again if possible.
4323 To prepare for removal of each conflicting package, call:
4324 <example compact="compact">
4325 <var>conflictor's-prerm</var> remove \
4326 in-favour <var>package</var> <var>new-version</var>
4329 <example compact="compact">
4330 <var>conflictor's-postinst</var> abort-remove \
4331 in-favour <var>package</var> <var>new-version</var>
4340 If the package is being upgraded, call:
4341 <example compact="compact">
4342 <var>new-preinst</var> upgrade <var>old-version</var>
4344 If this fails, we call:
4346 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4353 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4355 is called. If this works, then the old version
4356 is in an "Installed" state, or else it is left
4357 in an "Unpacked" state.
4362 If it fails, then the old version is left
4363 in an "Half-Installed" state.
4370 Otherwise, if the package had some configuration
4371 files from a previous version installed (i.e., it
4372 is in the "configuration files only" state):
4373 <example compact="compact">
4374 <var>new-preinst</var> install <var>old-version</var>
4378 <var>new-postrm</var> abort-install <var>old-version</var>
4380 If this fails, the package is left in a
4381 "Half-Installed" state, which requires a
4382 reinstall. If it works, the packages is left in
4383 a "Config-Files" state.
4386 Otherwise (i.e., the package was completely purged):
4387 <example compact="compact">
4388 <var>new-preinst</var> install
4391 <example compact="compact">
4392 <var>new-postrm</var> abort-install
4394 If the error-unwind fails, the package is in a
4395 "Half-Installed" phase, and requires a
4396 reinstall. If the error unwind works, the
4397 package is in a not installed state.
4404 The new package's files are unpacked, overwriting any
4405 that may be on the system already, for example any
4406 from the old version of the same package or from
4407 another package. Backups of the old files are kept
4408 temporarily, and if anything goes wrong the package
4409 management system will attempt to put them back as
4410 part of the error unwind.
4414 It is an error for a package to contain files which
4415 are on the system in another package, unless
4416 <tt>Replaces</tt> is used (see <ref id="replaces">).
4418 The following paragraph is not currently the case:
4419 Currently the <tt>- - force-overwrite</tt> flag is
4420 enabled, downgrading it to a warning, but this may not
4426 It is a more serious error for a package to contain a
4427 plain file or other kind of non-directory where another
4428 package has a directory (again, unless
4429 <tt>Replaces</tt> is used). This error can be
4430 overridden if desired using
4431 <tt>--force-overwrite-dir</tt>, but this is not
4436 Packages which overwrite each other's files produce
4437 behavior which, though deterministic, is hard for the
4438 system administrator to understand. It can easily
4439 lead to "missing" programs if, for example, a package
4440 is unpacked which overwrites a file from another
4441 package, and is then removed again.<footnote>
4442 Part of the problem is due to what is arguably a
4443 bug in <prgn>dpkg</prgn>.
4448 A directory will never be replaced by a symbolic link
4449 to a directory or vice versa; instead, the existing
4450 state (symlink or not) will be left alone and
4451 <prgn>dpkg</prgn> will follow the symlink if there is
4460 If the package is being upgraded, call
4461 <example compact="compact">
4462 <var>old-postrm</var> upgrade <var>new-version</var>
4466 If this fails, <prgn>dpkg</prgn> will attempt:
4467 <example compact="compact">
4468 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4470 If this works, installation continues. If not,
4472 <example compact="compact">
4473 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4475 If this fails, the old version is left in a
4476 "Half-Installed" state. If it works, dpkg now
4478 <example compact="compact">
4479 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4481 If this fails, the old version is left in a
4482 "Half-Installed" state. If it works, dpkg now
4484 <example compact="compact">
4485 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4487 If this fails, the old version is in an
4494 This is the point of no return - if
4495 <prgn>dpkg</prgn> gets this far, it won't back off
4496 past this point if an error occurs. This will
4497 leave the package in a fairly bad state, which
4498 will require a successful re-installation to clear
4499 up, but it's when <prgn>dpkg</prgn> starts doing
4500 things that are irreversible.
4505 Any files which were in the old version of the package
4506 but not in the new are removed.
4510 The new file list replaces the old.
4514 The new maintainer scripts replace the old.
4518 Any packages all of whose files have been overwritten
4519 during the installation, and which aren't required for
4520 dependencies, are considered to have been removed.
4521 For each such package
4524 <prgn>dpkg</prgn> calls:
4525 <example compact="compact">
4526 <var>disappearer's-postrm</var> disappear \
4527 <var>overwriter</var> <var>overwriter-version</var>
4531 The package's maintainer scripts are removed.
4534 It is noted in the status database as being in a
4535 sane state, namely not installed (any conffiles
4536 it may have are ignored, rather than being
4537 removed by <prgn>dpkg</prgn>). Note that
4538 disappearing packages do not have their prerm
4539 called, because <prgn>dpkg</prgn> doesn't know
4540 in advance that the package is going to
4547 Any files in the package we're unpacking that are also
4548 listed in the file lists of other packages are removed
4549 from those lists. (This will lobotomize the file list
4550 of the "conflicting" package if there is one.)
4554 The backup files made during installation, above, are
4560 The new package's status is now sane, and recorded as
4565 Here is another point of no return - if the
4566 conflicting package's removal fails we do not unwind
4567 the rest of the installation; the conflicting package
4568 is left in a half-removed limbo.
4573 If there was a conflicting package we go and do the
4574 removal actions (described below), starting with the
4575 removal of the conflicting package's files (any that
4576 are also in the package being unpacked have already
4577 been removed from the conflicting package's file list,
4578 and so do not get removed now).
4584 <sect id="configdetails"><heading>Details of configuration</heading>
4587 When we configure a package (this happens with <tt>dpkg
4588 --install</tt> and <tt>dpkg --configure</tt>), we first
4589 update any <tt>conffile</tt>s and then call:
4590 <example compact="compact">
4591 <var>postinst</var> configure <var>most-recently-configured-version</var>
4596 No attempt is made to unwind after errors during
4597 configuration. If the configuration fails, the package is in
4598 a "Failed Config" state, and an error message is generated.
4602 If there is no most recently configured version
4603 <prgn>dpkg</prgn> will pass a null argument.
4606 Historical note: Truly ancient (pre-1997) versions of
4607 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4608 (including the angle brackets) in this case. Even older
4609 ones did not pass a second argument at all, under any
4610 circumstance. Note that upgrades using such an old dpkg
4611 version are unlikely to work for other reasons, even if
4612 this old argument behavior is handled by your postinst script.
4618 <sect id="removedetails"><heading>Details of removal and/or
4619 configuration purging</heading>
4625 <example compact="compact">
4626 <var>prerm</var> remove
4630 If prerm fails during replacement due to conflict
4632 <var>conflictor's-postinst</var> abort-remove \
4633 in-favour <var>package</var> <var>new-version</var>
4637 <var>postinst</var> abort-remove
4641 If this fails, the package is in a "Half-Configured"
4642 state, or else it remains "Installed".
4646 The package's files are removed (except <tt>conffile</tt>s).
4649 <example compact="compact">
4650 <var>postrm</var> remove
4654 If it fails, there's no error unwind, and the package is in
4655 an "Half-Installed" state.
4660 All the maintainer scripts except the <prgn>postrm</prgn>
4665 If we aren't purging the package we stop here. Note
4666 that packages which have no <prgn>postrm</prgn> and no
4667 <tt>conffile</tt>s are automatically purged when
4668 removed, as there is no difference except for the
4669 <prgn>dpkg</prgn> status.
4673 The <tt>conffile</tt>s and any backup files
4674 (<tt>~</tt>-files, <tt>#*#</tt> files,
4675 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4680 <example compact="compact">
4681 <var>postrm</var> purge
4685 If this fails, the package remains in a "Config-Files"
4690 The package's file list is removed.
4699 <chapt id="relationships">
4700 <heading>Declaring relationships between packages</heading>
4702 <sect id="depsyntax">
4703 <heading>Syntax of relationship fields</heading>
4706 These fields all have a uniform syntax. They are a list of
4707 package names separated by commas.
4711 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4712 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4713 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4714 control fields of the package, which declare
4715 dependencies on other packages, the package names listed may
4716 also include lists of alternative package names, separated
4717 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4718 if any one of the alternative packages is installed, that
4719 part of the dependency is considered to be satisfied.
4723 All of the fields except for <tt>Provides</tt> may restrict
4724 their applicability to particular versions of each named
4725 package. This is done in parentheses after each individual
4726 package name; the parentheses should contain a relation from
4727 the list below followed by a version number, in the format
4728 described in <ref id="f-Version">.
4732 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4733 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4734 earlier, earlier or equal, exactly equal, later or equal and
4735 strictly later, respectively. The deprecated
4736 forms <tt><</tt> and <tt>></tt> were confusingly used to
4737 mean earlier/later or equal, rather than strictly earlier/later,
4738 and must not appear in new packages (though <prgn>dpkg</prgn>
4739 still supports them with a warning).
4743 Whitespace may appear at any point in the version
4744 specification subject to the rules in <ref
4745 id="controlsyntax">, and must appear where it's necessary to
4746 disambiguate; it is not otherwise significant. All of the
4747 relationship fields can only be folded in source package control files. For
4748 consistency and in case of future changes to
4749 <prgn>dpkg</prgn> it is recommended that a single space be
4750 used after a version relationship and before a version
4751 number; it is also conventional to put a single space after
4752 each comma, on either side of each vertical bar, and before
4753 each open parenthesis. When opening a continuation line in a relationship field, it
4754 is conventional to do so after a comma and before the space
4755 following that comma.
4759 For example, a list of dependencies might appear as:
4760 <example compact="compact">
4763 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4768 Relationships may be restricted to a certain set of
4769 architectures. This is indicated in brackets after each
4770 individual package name and the optional version specification.
4771 The brackets enclose a non-empty list of Debian architecture names
4772 in the format described in <ref id="arch-spec">,
4773 separated by whitespace. Exclamation marks may be prepended to
4774 each of the names. (It is not permitted for some names to be
4775 prepended with exclamation marks while others aren't.)
4779 For build relationship fields
4780 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4781 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4782 the current Debian host architecture is not in this list and
4783 there are no exclamation marks in the list, or it is in the list
4784 with a prepended exclamation mark, the package name and the
4785 associated version specification are ignored completely for the
4786 purposes of defining the relationships.
4791 <example compact="compact">
4793 Build-Depends-Indep: texinfo
4794 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4795 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4797 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4798 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4799 <tt>gnumach-dev</tt> only on hurd-i386.
4803 For binary relationship fields and the <tt>Built-Using</tt>
4804 field, the architecture restriction
4805 syntax is only supported in the source package control
4806 file <file>debian/control</file>. When the corresponding binary
4807 package control file is generated, the relationship will either
4808 be omitted or included without the architecture restriction
4809 based on the architecture of the binary package. This means
4810 that architecture restrictions must not be used in binary
4811 relationship fields for architecture-independent packages
4812 (<tt>Architecture: all</tt>).
4817 <example compact="compact">
4818 Depends: foo [i386], bar [amd64]
4820 becomes <tt>Depends: foo</tt> when the package is built on
4821 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4822 package is built on the <tt>amd64</tt> architecture, and omitted
4823 entirely in binary packages built on all other architectures.
4827 If the architecture-restricted dependency is part of a set of
4828 alternatives using <tt>|</tt>, that alternative is ignored
4829 completely on architectures that do not match the restriction.
4831 <example compact="compact">
4832 Build-Depends: foo [!i386] | bar [!amd64]
4834 is equivalent to <tt>bar</tt> on the i386 architecture, to
4835 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4836 bar</tt> on all other architectures.
4840 Relationships may also be restricted to a certain set of
4841 architectures using architecture wildcards in the format
4842 described in <ref id="arch-wildcard-spec">. The syntax for
4843 declaring such restrictions is the same as declaring
4844 restrictions using a certain set of architectures without
4845 architecture wildcards. For example:
4846 <example compact="compact">
4847 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4849 is equivalent to <tt>foo</tt> on architectures using the Linux
4850 kernel and any cpu, <tt>bar</tt> on architectures using any
4851 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4852 using a kernel other than Linux.
4856 Note that the binary package relationship fields such as
4857 <tt>Depends</tt> appear in one of the binary package
4858 sections of the control file, whereas the build-time
4859 relationships such as <tt>Build-Depends</tt> appear in the
4860 source package section of the control file (which is the
4865 <sect id="binarydeps">
4866 <heading>Binary Dependencies - <tt>Depends</tt>,
4867 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4868 <tt>Pre-Depends</tt>
4872 Packages can declare in their control file that they have
4873 certain relationships to other packages - for example, that
4874 they may not be installed at the same time as certain other
4875 packages, and/or that they depend on the presence of others.
4879 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4880 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4881 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4882 <tt>Breaks</tt> is described in <ref id="breaks">, and
4883 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4884 rest are described below.
4888 These seven fields are used to declare a dependency
4889 relationship by one package on another. Except for
4890 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4891 depending (binary) package's control file.
4892 (<tt>Enhances</tt> appears in the recommending package's
4893 control file, and <tt>Breaks</tt> appears in the version of
4894 depended-on package which causes the named package to
4899 A <tt>Depends</tt> field takes effect <em>only</em> when a
4900 package is to be configured. It does not prevent a package
4901 being on the system in an unconfigured state while its
4902 dependencies are unsatisfied, and it is possible to replace
4903 a package whose dependencies are satisfied and which is
4904 properly installed with a different version whose
4905 dependencies are not and cannot be satisfied; when this is
4906 done the depending package will be left unconfigured (since
4907 attempts to configure it will give errors) and will not
4908 function properly. If it is necessary, a
4909 <tt>Pre-Depends</tt> field can be used, which has a partial
4910 effect even when a package is being unpacked, as explained
4911 in detail below. (The other three dependency fields,
4912 <tt>Recommends</tt>, <tt>Suggests</tt> and
4913 <tt>Enhances</tt>, are only used by the various front-ends
4914 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4915 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4919 Since <tt>Depends</tt> only places requirements on the order in
4920 which packages are configured, packages in an installation run
4921 are usually all unpacked first and all configured later.
4923 This approach makes dependency resolution easier. If two
4924 packages A and B are being upgraded, the installed package A
4925 depends on exactly the installed package B, and the new
4926 package A depends on exactly the new package B (a common
4927 situation when upgrading shared libraries and their
4928 corresponding development packages), satisfying the
4929 dependencies at every stage of the upgrade would be
4930 impossible. This relaxed restriction means that both new
4931 packages can be unpacked together and then configured in their
4937 If there is a circular dependency among packages being installed
4938 or removed, installation or removal order honoring the
4939 dependency order is impossible, requiring the dependency loop be
4940 broken at some point and the dependency requirements violated
4941 for at least one package. Packages involved in circular
4942 dependencies may not be able to rely on their dependencies being
4943 configured before they themselves are configured, depending on
4944 which side of the break of the circular dependency loop they
4945 happen to be on. If one of the packages in the loop has
4946 no <prgn>postinst</prgn> script, then the cycle will be broken
4947 at that package; this ensures that all <prgn>postinst</prgn>
4948 scripts are run with their dependencies properly configured if
4949 this is possible. Otherwise the breaking point is arbitrary.
4950 Packages should therefore avoid circular dependencies where
4951 possible, particularly if they have <prgn>postinst</prgn>
4956 The meaning of the five dependency fields is as follows:
4958 <tag><tt>Depends</tt></tag>
4961 This declares an absolute dependency. A package will
4962 not be configured unless all of the packages listed in
4963 its <tt>Depends</tt> field have been correctly
4964 configured (unless there is a circular dependency as
4969 The <tt>Depends</tt> field should be used if the
4970 depended-on package is required for the depending
4971 package to provide a significant amount of
4976 The <tt>Depends</tt> field should also be used if the
4977 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4978 require the depended-on package to be unpacked or
4979 configured in order to run. In the case of <tt>postinst
4980 configure</tt>, the depended-on packages will be unpacked
4981 and configured first. (If both packages are involved in a
4982 dependency loop, this might not work as expected; see the
4983 explanation a few paragraphs back.) In the case
4984 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4985 actions, the package dependencies will normally be at
4986 least unpacked, but they may be only "Half-Installed" if a
4987 previous upgrade of the dependency failed.
4991 Finally, the <tt>Depends</tt> field should be used if the
4992 depended-on package is needed by the <prgn>postrm</prgn>
4993 script to fully clean up after the package removal. There
4994 is no guarantee that package dependencies will be
4995 available when <prgn>postrm</prgn> is run, but the
4996 depended-on package is more likely to be available if the
4997 package declares a dependency (particularly in the case
4998 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4999 script must gracefully skip actions that require a
5000 dependency if that dependency isn't available.
5004 <tag><tt>Recommends</tt></tag>
5007 This declares a strong, but not absolute, dependency.
5011 The <tt>Recommends</tt> field should list packages
5012 that would be found together with this one in all but
5013 unusual installations.
5017 <tag><tt>Suggests</tt></tag>
5019 This is used to declare that one package may be more
5020 useful with one or more others. Using this field
5021 tells the packaging system and the user that the
5022 listed packages are related to this one and can
5023 perhaps enhance its usefulness, but that installing
5024 this one without them is perfectly reasonable.
5027 <tag><tt>Enhances</tt></tag>
5029 This field is similar to Suggests but works in the
5030 opposite direction. It is used to declare that a
5031 package can enhance the functionality of another
5035 <tag><tt>Pre-Depends</tt></tag>
5038 This field is like <tt>Depends</tt>, except that it
5039 also forces <prgn>dpkg</prgn> to complete installation
5040 of the packages named before even starting the
5041 installation of the package which declares the
5042 pre-dependency, as follows:
5046 When a package declaring a pre-dependency is about to
5047 be <em>unpacked</em> the pre-dependency can be
5048 satisfied if the depended-on package is either fully
5049 configured, <em>or even if</em> the depended-on
5050 package(s) are only unpacked or in the "Half-Configured"
5051 state, provided that they have been configured
5052 correctly at some point in the past (and not removed
5053 or partially removed since). In this case, both the
5054 previously-configured and currently unpacked or
5055 "Half-Configured" versions must satisfy any version
5056 clause in the <tt>Pre-Depends</tt> field.
5060 When the package declaring a pre-dependency is about to
5061 be <em>configured</em>, the pre-dependency will be treated
5062 as a normal <tt>Depends</tt>. It will be considered
5063 satisfied only if the depended-on package has been
5064 correctly configured. However, unlike
5065 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5066 permit circular dependencies to be broken. If a circular
5067 dependency is encountered while attempting to honor
5068 <tt>Pre-Depends</tt>, the installation will be aborted.
5072 <tt>Pre-Depends</tt> are also required if the
5073 <prgn>preinst</prgn> script depends on the named package.
5074 It is best to avoid this situation if possible.
5078 <tt>Pre-Depends</tt> should be used sparingly,
5079 preferably only by packages whose premature upgrade or
5080 installation would hamper the ability of the system to
5081 continue with any upgrade that might be in progress.
5085 You should not specify a <tt>Pre-Depends</tt> entry for a
5086 package before this has been discussed on the
5087 <tt>debian-devel</tt> mailing list and a consensus about
5088 doing that has been reached. See <ref id="dependencies">.
5095 When selecting which level of dependency to use you should
5096 consider how important the depended-on package is to the
5097 functionality of the one declaring the dependency. Some
5098 packages are composed of components of varying degrees of
5099 importance. Such a package should list using
5100 <tt>Depends</tt> the package(s) which are required by the
5101 more important components. The other components'
5102 requirements may be mentioned as Suggestions or
5103 Recommendations, as appropriate to the components' relative
5109 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5112 When one binary package declares that it breaks another,
5113 <prgn>dpkg</prgn> will refuse to allow the package which
5114 declares <tt>Breaks</tt> to be unpacked unless the broken
5115 package is deconfigured first, and it will refuse to
5116 allow the broken package to be reconfigured.
5120 A package will not be regarded as causing breakage merely
5121 because its configuration files are still installed; it must
5122 be at least "Half-Installed".
5126 A special exception is made for packages which declare that
5127 they break their own package name or a virtual package which
5128 they provide (see below): this does not count as a real
5133 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5134 version clause; such a <tt>Breaks</tt> is introduced in the
5135 version of an (implicit or explicit) dependency which violates
5136 an assumption or reveals a bug in earlier versions of the broken
5137 package, or which takes over a file from earlier versions of the
5138 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5139 will inform higher-level package management tools that the
5140 broken package must be upgraded before the new one.
5144 If the breaking package also overwrites some files from the
5145 older package, it should use <tt>Replaces</tt> to ensure this
5146 goes smoothly. See <ref id="replaces"> for a full discussion
5147 of taking over files from other packages, including how to
5148 use <tt>Breaks</tt> in those cases.
5152 Many of the cases where <tt>Breaks</tt> should be used were
5153 previously handled with <tt>Conflicts</tt>
5154 because <tt>Breaks</tt> did not yet exist.
5155 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5156 See <ref id="conflicts"> for more information about the
5161 <sect id="conflicts">
5162 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5165 When one binary package declares a conflict with another using
5166 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5167 allow them to be unpacked on the system at the same time. This
5168 is a stronger restriction than <tt>Breaks</tt>, which prevents
5169 the broken package from being configured while the breaking
5170 package is in the "Unpacked" state but allows both packages to
5171 be unpacked at the same time.
5175 If one package is to be unpacked, the other must be removed
5176 first. If the package being unpacked is marked as replacing
5177 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5178 normally be used in this case) the one on the system, or the one
5179 on the system is marked as deselected, or both packages are
5180 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5181 automatically remove the package which is causing the conflict.
5182 Otherwise, it will halt the installation of the new package with
5183 an error. This mechanism is specifically designed to produce an
5184 error when the installed package is <tt>Essential</tt>, but the
5189 A package will not cause a conflict merely because its
5190 configuration files are still installed; it must be at least
5195 A special exception is made for packages which declare a
5196 conflict with their own package name, or with a virtual
5197 package which they provide (see below): this does not
5198 prevent their installation, and allows a package to conflict
5199 with others providing a replacement for it. You use this
5200 feature when you want the package in question to be the only
5201 package providing some feature.
5205 Normally, <tt>Breaks</tt> should be used instead
5206 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5207 stronger restriction on the ordering of package installation or
5208 upgrade and can make it more difficult for the package manager
5209 to find a correct solution to an upgrade or installation
5210 problem. <tt>Breaks</tt> should be used
5212 <item>when moving a file from one package to another (see
5213 <ref id="replaces">),</item>
5214 <item>when splitting a package (a special case of the previous
5216 <item>when the breaking package exposes a bug in or interacts
5217 badly with particular versions of the broken
5220 <tt>Conflicts</tt> should be used
5222 <item>when two packages provide the same file and will
5223 continue to do so,</item>
5224 <item>in conjunction with <tt>Provides</tt> when only one
5225 package providing a given virtual facility may be unpacked
5226 at a time (see <ref id="virtual">),</item>
5227 <item>in other cases where one must prevent simultaneous
5228 installation of two packages for reasons that are ongoing
5229 (not fixed in a later version of one of the packages) or
5230 that must prevent both packages from being unpacked at the
5231 same time, not just configured.</item>
5233 Be aware that adding <tt>Conflicts</tt> is normally not the best
5234 solution when two packages provide the same files. Depending on
5235 the reason for that conflict, using alternatives or renaming the
5236 files is often a better approach. See, for
5237 example, <ref id="binaries">.
5241 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5242 unless two packages cannot be installed at the same time or
5243 installing them both causes one of them to be broken or
5244 unusable. Having similar functionality or performing the same
5245 tasks as another package is not sufficient reason to
5246 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5250 A <tt>Conflicts</tt> entry may have an "earlier than" version
5251 clause if the reason for the conflict is corrected in a later
5252 version of one of the packages. However, normally the presence
5253 of an "earlier than" version clause is a sign
5254 that <tt>Breaks</tt> should have been used instead. An "earlier
5255 than" version clause in <tt>Conflicts</tt>
5256 prevents <prgn>dpkg</prgn> from upgrading or installing the
5257 package which declares such a conflict until the upgrade or
5258 removal of the conflicted-with package has been completed, which
5259 is a strong restriction.
5263 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5267 As well as the names of actual ("concrete") packages, the
5268 package relationship fields <tt>Depends</tt>,
5269 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5270 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5271 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5272 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5273 may mention "virtual packages".
5277 A <em>virtual package</em> is one which appears in the
5278 <tt>Provides</tt> control field of another package. The effect
5279 is as if the package(s) which provide a particular virtual
5280 package name had been listed by name everywhere the virtual
5281 package name appears. (See also <ref id="virtual_pkg">)
5285 If there are both concrete and virtual packages of the same
5286 name, then the dependency may be satisfied (or the conflict
5287 caused) by either the concrete package with the name in
5288 question or any other concrete package which provides the
5289 virtual package with the name in question. This is so that,
5290 for example, supposing we have
5291 <example compact="compact">
5294 </example> and someone else releases an enhanced version of
5295 the <tt>bar</tt> package they can say:
5296 <example compact="compact">
5300 and the <tt>bar-plus</tt> package will now also satisfy the
5301 dependency for the <tt>foo</tt> package.
5305 If a relationship field has a version number attached, only real
5306 packages will be considered to see whether the relationship is
5307 satisfied (or the prohibition violated, for a conflict or
5308 breakage). In other words, if a version number is specified,
5309 this is a request to ignore all <tt>Provides</tt> for that
5310 package name and consider only real packages. The package
5311 manager will assume that a package providing that virtual
5312 package is not of the "right" version. A <tt>Provides</tt>
5313 field may not contain version numbers, and the version number of
5314 the concrete package which provides a particular virtual package
5315 will not be considered when considering a dependency on or
5316 conflict with the virtual package name.<footnote>
5317 It is possible that a future release of <prgn>dpkg</prgn> may
5318 add the ability to specify a version number for each virtual
5319 package it provides. This feature is not yet present,
5320 however, and is expected to be used only infrequently.
5325 To specify which of a set of real packages should be the default
5326 to satisfy a particular dependency on a virtual package, list
5327 the real package as an alternative before the virtual one.
5331 If the virtual package represents a facility that can only be
5332 provided by one real package at a time, such as
5333 the <package>mail-transport-agent</package> virtual package that
5334 requires installation of a binary that would conflict with all
5335 other providers of that virtual package (see
5336 <ref id="mail-transport-agents">), all packages providing that
5337 virtual package should also declare a conflict with it
5338 using <tt>Conflicts</tt>. This will ensure that at most one
5339 provider of that virtual package is unpacked or installed at a
5344 <sect id="replaces"><heading>Overwriting files and replacing
5345 packages - <tt>Replaces</tt></heading>
5348 Packages can declare in their control file that they should
5349 overwrite files in certain other packages, or completely replace
5350 other packages. The <tt>Replaces</tt> control field has these
5351 two distinct purposes.
5354 <sect1><heading>Overwriting files in other packages</heading>
5357 It is usually an error for a package to contain files which
5358 are on the system in another package. However, if the
5359 overwriting package declares that it <tt>Replaces</tt> the one
5360 containing the file being overwritten, then <prgn>dpkg</prgn>
5361 will replace the file from the old package with that from the
5362 new. The file will no longer be listed as "owned" by the old
5363 package and will be taken over by the new package.
5364 Normally, <tt>Breaks</tt> should be used in conjunction
5365 with <tt>Replaces</tt>.<footnote>
5366 To see why <tt>Breaks</tt> is normally needed in addition
5367 to <tt>Replaces</tt>, consider the case of a file in the
5368 package <package>foo</package> being taken over by the
5369 package <package>foo-data</package>.
5370 <tt>Replaces</tt> will allow <package>foo-data</package> to
5371 be installed and take over that file. However,
5372 without <tt>Breaks</tt>, nothing
5373 requires <package>foo</package> to be upgraded to a newer
5374 version that knows it does not include that file and instead
5375 depends on <package>foo-data</package>. Nothing would
5376 prevent the new <package>foo-data</package> package from
5377 being installed and then removed, removing the file that it
5378 took over from <package>foo</package>. After that
5379 operation, the package manager would think the system was in
5380 a consistent state, but the <package>foo</package> package
5381 would be missing one of its files.
5386 For example, if a package <package>foo</package> is split
5387 into <package>foo</package> and <package>foo-data</package>
5388 starting at version 1.2-3, <package>foo-data</package> would
5390 <example compact="compact">
5391 Replaces: foo (<< 1.2-3)
5392 Breaks: foo (<< 1.2-3)
5394 in its control file. The new version of the
5395 package <package>foo</package> would normally have the field
5396 <example compact="compact">
5397 Depends: foo-data (>= 1.2-3)
5399 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5400 the files moved into <package>foo-data</package> are not
5401 required for normal operation).
5405 If a package is completely replaced in this way, so that
5406 <prgn>dpkg</prgn> does not know of any files it still
5407 contains, it is considered to have "disappeared". It will
5408 be marked as not wanted on the system (selected for
5409 removal) and not installed. Any <tt>conffile</tt>s
5410 details noted for the package will be ignored, as they
5411 will have been taken over by the overwriting package. The
5412 package's <prgn>postrm</prgn> script will be run with a
5413 special argument to allow the package to do any final
5414 cleanup required. See <ref id="mscriptsinstact">.
5416 Replaces is a one way relationship. You have to install
5417 the replacing package after the replaced package.
5422 For this usage of <tt>Replaces</tt>, virtual packages (see
5423 <ref id="virtual">) are not considered when looking at a
5424 <tt>Replaces</tt> field. The packages declared as being
5425 replaced must be mentioned by their real names.
5429 This usage of <tt>Replaces</tt> only takes effect when both
5430 packages are at least partially on the system at once. It is
5431 not relevant if the packages conflict unless the conflict has
5436 <sect1><heading>Replacing whole packages, forcing their
5440 Second, <tt>Replaces</tt> allows the packaging system to
5441 resolve which package should be removed when there is a
5442 conflict (see <ref id="conflicts">). This usage only takes
5443 effect when the two packages <em>do</em> conflict, so that the
5444 two usages of this field do not interfere with each other.
5448 In this situation, the package declared as being replaced
5449 can be a virtual package, so for example, all mail
5450 transport agents (MTAs) would have the following fields in
5451 their control files:
5452 <example compact="compact">
5453 Provides: mail-transport-agent
5454 Conflicts: mail-transport-agent
5455 Replaces: mail-transport-agent
5457 ensuring that only one MTA can be unpacked at any one
5458 time. See <ref id="virtual"> for more information about this
5463 <sect id="sourcebinarydeps">
5464 <heading>Relationships between source and binary packages -
5465 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5466 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5470 Source packages that require certain binary packages to be
5471 installed or absent at the time of building the package
5472 can declare relationships to those binary packages.
5476 This is done using the <tt>Build-Depends</tt>,
5477 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5478 <tt>Build-Conflicts-Indep</tt> control fields.
5482 Build-dependencies on "build-essential" binary packages can be
5483 omitted. Please see <ref id="pkg-relations"> for more information.
5487 The dependencies and conflicts they define must be satisfied
5488 (as defined earlier for binary packages) in order to invoke
5489 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5491 There is no Build-Depends-Arch; this role is essentially
5492 met with Build-Depends. Anyone building the
5493 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5494 assumed to be building the whole package, and therefore
5495 installation of all build dependencies is required.
5498 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5499 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5500 not yet know how to check for its existence, and
5501 <tt>binary-arch</tt>. The purpose of the original split
5502 between <tt>Build-Depends</tt> and
5503 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5504 wouldn't need to install extra packages needed only for the
5505 binary-indep targets. But without a build-arch/build-indep
5506 split, this didn't work, since most of the work is done in
5507 the build target, not in the binary target.
5511 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5512 <tt>binary-arch</tt></tag>
5514 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5515 fields must be satisfied when these targets are invoked.
5517 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5518 and <tt>binary-indep</tt></tag>
5520 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5521 <tt>Build-Depends-Indep</tt>, and
5522 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5523 these targets are invoked.
5529 <sect id="built-using">
5530 <heading>Additional source packages used to build the binary
5531 - <tt>Built-Using</tt>
5535 Some binary packages incorporate parts of other packages when built
5536 but do not have to depend on those packages. Examples include
5537 linking with static libraries or incorporating source code from
5538 another package during the build. In this case, the source packages
5539 of those other packages are a required part of the complete source
5540 (the binary package is not reproducible without them).
5544 A <tt>Built-Using</tt> field must list the corresponding source
5545 package for any such binary package incorporated during the build
5547 <tt>Build-Depends</tt> in the source package is not adequate since
5548 it (rightfully) does not document the exact version used in the
5551 including an "exactly equal" ("=") version relation on the version
5552 that was used to build that binary package<footnote>
5553 The archive software might reject packages that refer to
5554 non-existent sources.
5559 A package using the source code from the gcc-4.6-source
5560 binary package built from the gcc-4.6 source package would
5561 have this field in its control file:
5562 <example compact="compact">
5563 Built-Using: gcc-4.6 (= 4.6.0-11)
5568 A package including binaries from grub2 and loadlin would
5569 have this field in its control file:
5570 <example compact="compact">
5571 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5578 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5581 Packages containing shared libraries must be constructed with
5582 a little care to make sure that the shared library is always
5583 available. This is especially important for packages whose
5584 shared libraries are vitally important, such as the C library
5585 (currently <tt>libc6</tt>).
5589 This section deals only with public shared libraries: shared
5590 libraries that are placed in directories searched by the dynamic
5591 linker by default or which are intended to be linked against
5592 normally and possibly used by other, independent packages. Shared
5593 libraries that are internal to a particular package or that are
5594 only loaded as dynamic modules are not covered by this section and
5595 are not subject to its requirements.
5599 A shared library is identified by the <tt>SONAME</tt> attribute
5600 stored in its dynamic section. When a binary is linked against a
5601 shared library, the <tt>SONAME</tt> of the shared library is
5602 recorded in the binary's <tt>NEEDED</tt> section so that the
5603 dynamic linker knows that library must be loaded at runtime. The
5604 shared library file's full name (which usually contains additional
5605 version information not needed in the <tt>SONAME</tt>) is
5606 therefore normally not referenced directly. Instead, the shared
5607 library is loaded by its <tt>SONAME</tt>, which exists on the file
5608 system as a symlink pointing to the full name of the shared
5609 library. This symlink must be provided by the
5610 package. <ref id="sharedlibs-runtime"> describes how to do this.
5612 This is a convention of shared library versioning, but not a
5613 requirement. Some libraries use the <tt>SONAME</tt> as the full
5614 library file name instead and therefore do not need a symlink.
5615 Most, however, encode additional information about
5616 backwards-compatible revisions as a minor version number in the
5617 file name. The <tt>SONAME</tt> itself only changes when
5618 binaries linked with the earlier version of the shared library
5619 may no longer work, but the filename may change with each
5620 release of the library. See <ref id="sharedlibs-runtime"> for
5626 When linking a binary or another shared library against a shared
5627 library, the <tt>SONAME</tt> for that shared library is not yet
5628 known. Instead, the shared library is found by looking for a file
5629 matching the library name with <tt>.so</tt> appended. This file
5630 exists on the file system as a symlink pointing to the shared
5635 Shared libraries are normally split into several binary packages.
5636 The <tt>SONAME</tt> symlink is installed by the runtime shared
5637 library package, and the bare <tt>.so</tt> symlink is installed in
5638 the development package since it's only used when linking binaries
5639 or shared libraries. However, there are some exceptions for
5640 unusual shared libraries or for shared libraries that are also
5641 loaded as dynamic modules by other programs.
5645 This section is primarily concerned with how the separation of
5646 shared libraries into multiple packages should be done and how
5647 dependencies on and between shared library binary packages are
5648 managed in Debian. <ref id="libraries"> should be read in
5649 conjunction with this section and contains additional rules for
5650 the files contained in the shared library packages.
5653 <sect id="sharedlibs-runtime">
5654 <heading>Run-time shared libraries</heading>
5657 The run-time shared library must be placed in a package
5658 whose name changes whenever the <tt>SONAME</tt> of the shared
5659 library changes. This allows several versions of the shared
5660 library to be installed at the same time, allowing installation
5661 of the new version of the shared library without immediately
5662 breaking binaries that depend on the old version. Normally, the
5663 run-time shared library and its <tt>SONAME</tt> symlink should
5664 be placed in a package named
5665 <package><var>libraryname</var><var>soversion</var></package>,
5666 where <var>soversion</var> is the version number in
5667 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5668 would be confusing to directly append <var>soversion</var>
5669 to <var>libraryname</var> (if, for
5670 example, <var>libraryname</var> itself ends in a number), you
5672 <package><var>libraryname</var>-<var>soversion</var></package>
5677 To determine the <var>soversion</var>, look at
5678 the <tt>SONAME</tt> of the library, stored in the
5679 ELF <tt>SONAME</tt> attribute. It is usually of the
5680 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5681 example, <tt>libz.so.1</tt>). The version part is the part
5682 which comes after <tt>.so.</tt>, so in that example it
5683 is <tt>1</tt>. The soname may instead be of the
5684 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5685 as <tt>libdb-5.1.so</tt>, in which case the name would
5686 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5690 If you have several shared libraries built from the same source
5691 tree, you may lump them all together into a single shared
5692 library package provided that all of their <tt>SONAME</tt>s will
5693 always change together. Be aware that this is not normally the
5694 case, and if the <tt>SONAME</tt>s do not change together,
5695 upgrading such a merged shared library package will be
5696 unnecessarily difficult because of file conflicts with the old
5697 version of the package. When in doubt, always split shared
5698 library packages so that each binary package installs a single
5703 Every time the shared library ABI changes in a way that may
5704 break binaries linked against older versions of the shared
5705 library, the <tt>SONAME</tt> of the library and the
5706 corresponding name for the binary package containing the runtime
5707 shared library should change. Normally, this means
5708 the <tt>SONAME</tt> should change any time an interface is
5709 removed from the shared library or the signature of an interface
5710 (the number of parameters or the types of parameters that it
5711 takes, for example) is changed. This practice is vital to
5712 allowing clean upgrades from older versions of the package and
5713 clean transitions between the old ABI and new ABI without having
5714 to upgrade every affected package simultaneously.
5718 The <tt>SONAME</tt> and binary package name need not, and indeed
5719 normally should not, change if new interfaces are added but none
5720 are removed or changed, since this will not break binaries
5721 linked against the old shared library. Correct versioning of
5722 dependencies on the newer shared library by binaries that use
5723 the new interfaces is handled via
5724 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5725 or <tt>shlibs</tt> system</qref>.
5729 The package should install the shared libraries under
5730 their normal names. For example, the <package>libgdbm3</package>
5731 package should install <file>libgdbm.so.3.0.0</file> as
5732 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5733 renamed or re-linked by any <prgn>prerm</prgn> or
5734 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5735 of renaming things safely without affecting running programs,
5736 and attempts to interfere with this are likely to lead to
5741 Shared libraries should not be installed executable, since
5742 the dynamic linker does not require this and trying to
5743 execute a shared library usually results in a core dump.
5747 The run-time library package should include the symbolic link for
5748 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5749 the shared libraries. For example,
5750 the <package>libgdbm3</package> package should include a symbolic
5751 link from <file>/usr/lib/libgdbm.so.3</file> to
5752 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5753 linker (for example <prgn>ld.so</prgn> or
5754 <prgn>ld-linux.so.*</prgn>) can find the library between the
5755 time that <prgn>dpkg</prgn> installs it and the time that
5756 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5758 The package management system requires the library to be
5759 placed before the symbolic link pointing to it in the
5760 <file>.deb</file> file. This is so that when
5761 <prgn>dpkg</prgn> comes to install the symlink
5762 (overwriting the previous symlink pointing at an older
5763 version of the library), the new shared library is already
5764 in place. In the past, this was achieved by creating the
5765 library in the temporary packaging directory before
5766 creating the symlink. Unfortunately, this was not always
5767 effective, since the building of the tar file in the
5768 <file>.deb</file> depended on the behavior of the underlying
5769 file system. Some file systems (such as reiserfs) reorder
5770 the files so that the order of creation is forgotten.
5771 Since version 1.7.0, <prgn>dpkg</prgn>
5772 reorders the files itself as necessary when building a
5773 package. Thus it is no longer important to concern
5774 oneself with the order of file creation.
5778 <sect1 id="ldconfig">
5779 <heading><tt>ldconfig</tt></heading>
5782 Any package installing shared libraries in one of the default
5783 library directories of the dynamic linker (which are currently
5784 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5785 listed in <file>/etc/ld.so.conf</file><footnote>
5786 These are currently <file>/usr/local/lib</file> plus
5787 directories under <file>/lib</file> and <file>/usr/lib</file>
5788 matching the multiarch triplet for the system architecture.
5790 must use <prgn>ldconfig</prgn> to update the shared library
5795 The package maintainer scripts must only call
5796 <prgn>ldconfig</prgn> under these circumstances:
5797 <list compact="compact">
5798 <item>When the <prgn>postinst</prgn> script is run with a
5799 first argument of <tt>configure</tt>, the script must call
5800 <prgn>ldconfig</prgn>, and may optionally invoke
5801 <prgn>ldconfig</prgn> at other times.
5803 <item>When the <prgn>postrm</prgn> script is run with a
5804 first argument of <tt>remove</tt>, the script should call
5805 <prgn>ldconfig</prgn>.
5810 During install or upgrade, the preinst is called before
5811 the new files are unpacked, so calling "ldconfig" is
5812 pointless. The preinst of an existing package can also be
5813 called if an upgrade fails. However, this happens during
5814 the critical time when a shared libs may exist on-disk
5815 under a temporary name. Thus, it is dangerous and
5816 forbidden by current policy to call "ldconfig" at this
5821 When a package is installed or upgraded, "postinst
5822 configure" runs after the new files are safely on-disk.
5823 Since it is perfectly safe to invoke ldconfig
5824 unconditionally in a postinst, it is OK for a package to
5825 simply put ldconfig in its postinst without checking the
5826 argument. The postinst can also be called to recover from
5827 a failed upgrade. This happens before any new files are
5828 unpacked, so there is no reason to call "ldconfig" at this
5833 For a package that is being removed, prerm is
5834 called with all the files intact, so calling ldconfig is
5835 useless. The other calls to "prerm" happen in the case of
5836 upgrade at a time when all the files of the old package
5837 are on-disk, so again calling "ldconfig" is pointless.
5841 postrm, on the other hand, is called with the "remove"
5842 argument just after the files are removed, so this is
5843 the proper time to call "ldconfig" to notify the system
5844 of the fact that the shared libraries from the package
5845 are removed. The postrm can be called at several other
5846 times. At the time of "postrm purge", "postrm
5847 abort-install", or "postrm abort-upgrade", calling
5848 "ldconfig" is useless because the shared lib files are
5849 not on-disk. However, when "postrm" is invoked with
5850 arguments "upgrade", "failed-upgrade", or "disappear", a
5851 shared lib may exist on-disk under a temporary filename.
5859 <sect id="sharedlibs-support-files">
5860 <heading>Shared library support files</heading>
5863 If your package contains files whose names do not change with
5864 each change in the library shared object version, you must not
5865 put them in the shared library package. Otherwise, several
5866 versions of the shared library cannot be installed at the same
5867 time without filename clashes, making upgrades and transitions
5868 unnecessarily difficult.
5872 It is recommended that supporting files and run-time support
5873 programs that do not need to be invoked manually by users, but
5874 are nevertheless required for the package to function, be placed
5875 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5876 preferably under <file>/usr/lib/</file><var>package-name</var>.
5877 If the program or file is architecture independent, the
5878 recommendation is for it to be placed in a subdirectory of
5879 <file>/usr/share</file> instead, preferably under
5880 <file>/usr/share/</file><var>package-name</var>. Following the
5881 <var>package-name</var> naming convention ensures that the file
5882 names change when the shared object version changes.
5886 Run-time support programs that use the shared library but are
5887 not required for the library to function or files used by the
5888 shared library that can be used by any version of the shared
5889 library package should instead be put in a separate package.
5890 This package might typically be named
5891 <package><var>libraryname</var>-tools</package>; note the
5892 absence of the <var>soversion</var> in the package name.
5896 Files and support programs only useful when compiling software
5897 against the library should be included in the development
5898 package for the library.<footnote>
5899 For example, a <file><var>package-name</var>-config</file>
5900 script or <package>pkg-config</package> configuration files.
5905 <sect id="sharedlibs-static">
5906 <heading>Static libraries</heading>
5909 The static library (<file><var>libraryname.a</var></file>)
5910 is usually provided in addition to the shared version.
5911 It is placed into the development package (see below).
5915 In some cases, it is acceptable for a library to be
5916 available in static form only; these cases include:
5918 <item>libraries for languages whose shared library support
5919 is immature or unstable</item>
5920 <item>libraries whose interfaces are in flux or under
5921 development (commonly the case when the library's
5922 major version number is zero, or where the ABI breaks
5923 across patchlevels)</item>
5924 <item>libraries which are explicitly intended to be
5925 available only in static form by their upstream
5930 <sect id="sharedlibs-dev">
5931 <heading>Development files</heading>
5934 If there are development files associated with a shared library,
5935 the source package needs to generate a binary development package
5936 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5937 or if you prefer only to support one development version at a
5938 time, <package><var>libraryname</var>-dev</package>. Installing
5939 the development package must result in installation of all the
5940 development files necessary for compiling programs against that
5941 shared library.<footnote>
5942 This wording allows the development files to be split into
5943 several packages, such as a separate architecture-independent
5944 <package><var>libraryname</var>-headers</package>, provided that
5945 the development package depends on all the required additional
5951 In case several development versions of a library exist, you may
5952 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5953 <ref id="conflicts">) to ensure that the user only installs one
5954 development version at a time (as different development versions are
5955 likely to have the same header files in them, which would cause a
5956 filename clash if both were unpacked).
5960 The development package should contain a symlink for the associated
5961 shared library without a version number. For example, the
5962 <package>libgdbm-dev</package> package should include a symlink
5963 from <file>/usr/lib/libgdbm.so</file> to
5964 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5965 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5966 <file>libgdbm.so</file> when compiling dynamically.
5970 If the package provides Ada Library Information
5971 (<file>*.ali</file>) files for use with GNAT, these files must be
5972 installed read-only (mode 0444) so that GNAT will not attempt to
5973 recompile them. This overrides the normal file mode requirements
5974 given in <ref id="permissions-owners">.
5978 <sect id="sharedlibs-intradeps">
5979 <heading>Dependencies between the packages of the same library</heading>
5982 Typically the development version should have an exact
5983 version dependency on the runtime library, to make sure that
5984 compilation and linking happens correctly. The
5985 <tt>${binary:Version}</tt> substitution variable can be
5986 useful for this purpose.
5988 Previously, <tt>${Source-Version}</tt> was used, but its name
5989 was confusing and it has been deprecated since dpkg 1.13.19.
5994 <sect id="sharedlibs-depends">
5995 <heading>Dependencies between the library and other
5999 If a package contains a binary or library which links to a
6000 shared library, we must ensure that, when the package is
6001 installed on the system, all of the libraries needed are also
6002 installed. These dependencies must be added to the binary
6003 package when it is built, since they may change based on which
6004 version of a shared library the binary or library was linked
6005 with even if there are no changes to the source of the binary
6006 (for example, symbol versions change, macros become functions or
6007 vice versa, or the binary package may determine at compile-time
6008 whether new library interfaces are available and can be called).
6009 To allow these dependencies to be constructed, shared libraries
6010 must provide either a <file>symbols</file> file or
6011 a <file>shlibs</file> file. These provide information on the
6012 package dependencies required to ensure the presence of
6013 interfaces provided by this library. Any package with binaries
6014 or libraries linking to a shared library must use these files to
6015 determine the required dependencies when it is built. Other
6016 packages which use a shared library (for example using
6017 <tt>dlopen()</tt>) should compute appropriate dependencies
6018 using these files at build time as well.
6022 The two mechanisms differ in the degree of detail that they
6023 provide. A <file>symbols</file> file documents, for each symbol
6024 exported by a library, the minimal version of the package any
6025 binary using this symbol will need. This is typically the
6026 version of the package in which the symbol was introduced. This
6027 information permits detailed analysis of the symbols used by a
6028 particular package and construction of an accurate dependency,
6029 but it requires the package maintainer to track more information
6030 about the shared library.
6034 A <file>shlibs</file> file, in contrast, only documents the last
6035 time the library ABI changed in any way. It only provides
6036 information about the library as a whole, not individual
6037 symbols. When a package is built using a shared library with
6038 only a <file>shlibs</file> file, the generated dependency will
6039 require a version of the shared library equal to or newer than
6040 the version of the last ABI change. This generates
6041 unnecessarily restrictive dependencies compared
6042 to <file>symbols</file> files if none of the symbols used by the
6043 package have changed. This, in turn, may make upgrades
6044 needlessly complex and unnecessarily restrict use of the package
6045 on systems with older versions of the shared libraries.
6049 <file>shlibs</file> files also only support a limited range of
6050 library SONAMEs, making it difficult to use <file>shlibs</file>
6051 files in some unusual corner cases.<footnote>
6052 A <file>shlibs</file> file represents an SONAME as a library
6053 name and version number, such as <tt>libfoo VERSION</tt>,
6054 instead of recording the actual SONAME. If the SONAME doesn't
6055 match one of the two expected formats
6056 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6057 cannot be represented.
6062 <file>symbols</file> files are therefore recommended for most
6063 shared library packages since they provide more accurate
6064 dependencies. For most C libraries, the additional detail
6065 required by <file>symbols</file> files is not too difficult to
6066 maintain. However, maintaining exhaustive symbols information
6067 for a C++ library can be quite onerous, so <file>shlibs</file>
6068 files may be more appropriate for most C++ libraries. Libraries
6069 with a corresponding udeb must also provide
6070 a <file>shlibs</file> file, since the udeb infrastructure does
6071 not use <file>symbols</file> files.
6074 <sect1 id="dpkg-shlibdeps">
6075 <heading>Generating dependencies on shared libraries</heading>
6078 When a package that contains any shared libraries or compiled
6079 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6080 each shared library and compiled binary to determine the
6081 libraries used and hence the dependencies needed by the
6083 <prgn>dpkg-shlibdeps</prgn> will use a program
6084 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6085 the libraries and the symbols in those libraries directly
6086 needed by the binaries or shared libraries in the package.
6088 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6089 your <file>debian/rules</file> file in the source package.
6090 List all of the compiled binaries, libraries, or loadable
6091 modules in your package.<footnote>
6092 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6093 correctly is to use a package helper framework such
6094 as <package>debhelper</package>. If you are
6095 using <package>debhelper</package>,
6096 the <prgn>dh_shlibdeps</prgn> program will do this work for
6097 you. It will also correctly handle multi-binary packages.
6099 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6100 or <file>shlibs</file> files installed by the shared libraries
6101 to generate dependency information. The package must then
6102 provide a substitution variable into which the discovered
6103 dependency information can be placed.
6107 If you are creating a udeb for use in the Debian Installer,
6108 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6109 should use the dependency line of type <tt>udeb</tt> by adding
6110 the <tt>-tudeb</tt> option<footnote>
6111 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6112 will automatically add this option if it knows it is
6114 </footnote>. If there is no dependency line of
6115 type <tt>udeb</tt> in the <file>shlibs</file>
6116 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6117 regular dependency line.
6121 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6122 into the <file>debian/substvars</file> file by default, which
6123 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6124 to place a <tt>${shlibs:Depends}</tt> variable in
6125 the <tt>Depends</tt> field in the control file of every binary
6126 package built by this source package that contains compiled
6127 binaries, libraries, or loadable modules. If you have
6128 multiple binary packages, you will need to
6129 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6130 compiled libraries or binaries. For example, you could use
6131 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6132 specify a different <file>substvars</file> file for each
6133 binary package.<footnote>
6134 Again, <prgn>dh_shlibdeps</prgn>
6135 and <prgn>dh_gencontrol</prgn> will handle everything except
6136 the addition of the variable to the control file for you if
6137 you're using <package>debhelper</package>, including
6138 generating separate <file>substvars</file> files for each
6139 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6140 the appropriate flags.
6145 For more details on <prgn>dpkg-shlibdeps</prgn>,
6146 see <manref name="dpkg-shlibdeps" section="1">.
6150 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6151 library <tt>libbar</tt> if it is explicitly linked with that
6152 library (that is, the library is listed in the
6153 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6154 to the link line when the binary is created). Other libraries
6155 that are needed by <tt>libbar</tt> are
6156 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6157 linker will load them automatically when it
6158 loads <tt>libbar</tt>. A package should depend on the
6159 libraries it directly uses, but not the libraries it only uses
6160 indirectly. The dependencies for the libraries used
6161 directly will automatically pull in the indirectly-used
6162 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6163 automatically, but package maintainers need to be aware of
6164 this distinction between directly and indirectly using a
6165 library if they have to override its results for some reason.
6167 A good example of where this helps is the following. We
6168 could update <tt>libimlib</tt> with a new version that
6169 supports a new revision of a graphics format called dgf (but
6170 retaining the same major version number) and depends on a
6171 new library package <package>libdgf4</package> instead of
6172 the older <package>libdgf3</package>. If we
6173 used <prgn>ldd</prgn> to add dependencies for every library
6174 directly or indirectly linked with a binary, every package
6175 that uses <tt>libimlib</tt> would need to be recompiled so
6176 it would also depend on <package>libdgf4</package> in order
6177 to retire the older <package>libdgf3</package> package.
6178 Since dependencies are only added based on
6179 ELF <tt>NEEDED</tt> attribute, packages
6180 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6181 having the dependency on an appropriate version
6182 of <tt>libdgf</tt> and do not need rebuilding.
6187 <sect1 id="sharedlibs-updates">
6188 <heading>Shared library ABI changes</heading>
6191 Maintaining a shared library package using
6192 either <file>symbols</file> or <file>shlibs</file> files
6193 requires being aware of the exposed ABI of the shared library
6194 and any changes to it. Both <file>symbols</file>
6195 and <file>shlibs</file> files record every change to the ABI
6196 of the shared library; <file>symbols</file> files do so per
6197 public symbol, whereas <file>shlibs</file> files record only
6198 the last change for the entire library.
6202 There are two types of ABI changes: ones that are
6203 backward-compatible and ones that are not. An ABI change is
6204 backward-compatible if any reasonable program or library that
6205 was linked with the previous version of the shared library
6206 will still work correctly with the new version of the shared
6208 An example of an "unreasonable" program is one that uses
6209 library interfaces that are documented as internal and
6210 unsupported. If the only programs or libraries affected by
6211 a change are "unreasonable" ones, other techniques, such as
6212 declaring <tt>Breaks</tt> relationships with affected
6213 packages or treating their usage of the library as bugs in
6214 those packages, may be appropriate instead of changing the
6215 SONAME. However, the default approach is to change the
6216 SONAME for any change to the ABI that could break a program.
6218 Adding new symbols to the shared library is a
6219 backward-compatible change. Removing symbols from the shared
6220 library is not. Changing the behavior of a symbol may or may
6221 not be backward-compatible depending on the change; for
6222 example, changing a function to accept a new enum constant not
6223 previously used by the library is generally
6224 backward-compatible, but changing the members of a struct that
6225 is passed into library functions is generally not unless the
6226 library takes special precautions to accept old versions of
6231 ABI changes that are not backward-compatible normally require
6232 changing the <tt>SONAME</tt> of the library and therefore the
6233 shared library package name, which forces rebuilding all
6234 packages using that shared library to update their
6235 dependencies and allow them to use the new version of the
6236 shared library. For more information,
6237 see <ref id="sharedlibs-runtime">. The remainder of this
6238 section will deal with backward-compatible changes.
6242 Backward-compatible changes require either updating or
6243 recording the <var>minimal-version</var> for that symbol
6244 in <file>symbols</file> files or updating the version in
6245 the <var>dependencies</var> in <file>shlibs</file> files. For
6246 more information on how to do this in the two formats, see
6247 <ref id="symbols"> and <ref id="shlibs">. Below are general
6248 rules that apply to both files.
6252 The easy case is when a public symbol is added. Simply add
6253 the version at which the symbol was introduced
6254 (for <file>symbols</file> files) or update the dependency
6255 version (for <file>shlibs</file>) files. But special care
6256 should be taken to update dependency versions when the
6257 behavior of a public symbol changes. This is easy to neglect,
6258 since there is no automated method of determining such
6259 changes, but failing to update versions in this case may
6260 result in binary packages with too-weak dependencies that will
6261 fail at runtime, possibly in ways that can cause security
6262 vulnerabilities. If the package maintainer believes that a
6263 symbol behavior change may have occurred but isn't sure, it's
6264 safer to update the version rather than leave it unmodified.
6265 This may result in unnecessarily strict dependencies, but it
6266 ensures that packages whose dependencies are satisfied will
6271 A common example of when a change to the dependency version
6272 is required is a function that takes an enum or struct
6273 argument that controls what the function does. For example:
6275 enum library_op { OP_FOO, OP_BAR };
6276 int library_do_operation(enum library_op);
6278 If a new operation, <tt>OP_BAZ</tt>, is added,
6279 the <var>minimal-version</var>
6280 of <tt>library_do_operation</tt> (for <file>symbols</file>
6281 files) or the version in the dependency for the shared library
6282 (for <file>shlibs</file> files) must be increased to the
6283 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6284 binary built against the new version of the library (having
6285 detected at compile-time that the library
6286 supports <tt>OP_BAZ</tt>) may be installed with a shared
6287 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6288 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6293 Dependency versions in either <file>symbols</file>
6294 or <file>shlibs</file> files normally should not contain the
6295 Debian revision of the package, since the library behavior is
6296 normally fixed for a particular upstream version and any
6297 Debian packaging of that upstream version will have the same
6298 behavior. In the rare case that the library behavior was
6299 changed in a particular Debian revision, appending <tt>~</tt>
6300 to the end of the version that includes the Debian revision is
6301 recommended, since this allows backports of the shared library
6302 package using the normal backport versioning convention to
6303 satisfy the dependency.
6307 <sect1 id="sharedlibs-symbols">
6308 <heading>The <tt>symbols</tt> system</heading>
6311 In the following sections, we will first describe where the
6312 various <file>symbols</file> files are to be found, then
6313 the <file>symbols</file> file format, and finally how to
6314 create <file>symbols</file> files if your package contains a
6318 <sect2 id="symbols-paths">
6319 <heading>The <file>symbols</file> files present on the
6323 <file>symbols</file> files for a shared library are normally
6324 provided by the shared library package as a control file,
6325 but there are several override paths that are checked first
6326 in case that information is wrong or missing. The following
6327 list gives them in the order in which they are read
6328 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6329 the required information is used.
6332 <p><file>debian/*/DEBIAN/symbols</file></p>
6335 During the package build, if the package itself
6336 contains shared libraries with <file>symbols</file>
6337 files, they will be generated in these staging
6338 directories by <prgn>dpkg-gensymbols</prgn>
6339 (see <ref id="providing-symbols">). <file>symbols</file>
6340 files found in the build tree take precedence
6341 over <file>symbols</file> files from other binary
6346 These files must exist
6347 before <prgn>dpkg-shlibdeps</prgn> is run or the
6348 dependencies of binaries and libraries from a source
6349 package on other libraries from that same source
6350 package will not be correct. In practice, this means
6351 that <prgn>dpkg-gensymbols</prgn> must be run
6352 before <prgn>dpkg-shlibdeps</prgn> during the package
6354 An example may clarify. Suppose the source
6355 package <tt>foo</tt> generates two binary
6356 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6357 When building the binary packages, the contents of
6358 the packages are staged in the
6359 directories <file>debian/libfoo2</file>
6360 and <file>debian/foo-runtime</file> respectively.
6361 (<file>debian/tmp</file> could be used instead of
6362 one of these.) Since <tt>libfoo2</tt> provides
6363 the <tt>libfoo</tt> shared library, it will contain
6364 a <tt>symbols</tt> file, which will be installed
6365 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6366 eventually to be included as a control file in that
6367 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6369 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6371 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6372 to determine whether <tt>foo-prog</tt>'s library
6373 dependencies are satisfied by any of the libraries
6374 provided by <tt>libfoo2</tt>. Since those binaries
6375 were linked against the just-built shared library as
6376 part of the build process, the <file>symbols</file>
6377 file for the newly-built <tt>libfoo2</tt> must take
6378 precedence over a <file>symbols</file> file for any
6379 other <tt>libfoo2</tt> package already installed on
6387 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6388 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6392 Per-system overrides of shared library dependencies.
6393 These files normally do not exist. They are
6394 maintained by the local system administrator and must
6395 not be created by any Debian package.
6400 <p><file>symbols</file> control files for packages
6401 installed on the system</p>
6404 The <file>symbols</file> control files for all the
6405 packages currently installed on the system are
6406 searched last. This will be the most common source of
6407 shared library dependency information. These are
6409 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6410 packages should not rely on this and instead should
6411 use <tt>dpkg-query --control-path <var>package</var>
6412 symbols</tt> if for some reason these files need to be
6420 Be aware that if a <file>debian/shlibs.local</file> exists
6421 in the source package, it will override
6422 any <file>symbols</file> files. This is the only case where
6423 a <file>shlibs</file> is used despite <file>symbols</file>
6424 files being present. See <ref id="shlibs-paths">
6425 and <ref id="sharedlibs-shlibdeps"> for more information.
6429 <sect2 id="symbols">
6430 <heading>The <file>symbols</file> File Format</heading>
6433 The following documents the format of
6434 the <file>symbols</file> control file as included in binary
6435 packages. These files are built from
6436 template <file>symbols</file> files in the source package
6437 by <prgn>dpkg-gensymbols</prgn>. The template files support
6438 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6439 do some of the tedious work involved in
6440 maintaining <file>symbols</file> files, such as handling C++
6441 symbols or optional symbols that may not exist on particular
6442 architectures. When writing <file>symbols</file> files for
6443 a shared library package, refer
6444 to <manref name="dpkg-gensymbols" section="1"> for the
6449 A <file>symbols</file> may contain one or more entries, one
6450 for each shared library contained in the package
6451 corresponding to that <file>symbols</file>. Each entry has
6452 the following format:
6457 <var>library-soname</var> <var>main-dependency-template</var>
6458 [| <var>alternative-dependency-template</var>]
6460 [* <var>field-name</var>: <var>field-value</var>]
6462 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6467 To explain this format, we'll use the the <tt>zlib1g</tt>
6468 package as an example, which (at the time of writing)
6470 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6471 lines will be described first, followed by optional lines.
6475 <var>library-soname</var> must contain exactly the value of
6476 the ELF <tt>SONAME</tt> attribute of the shared library. In
6477 our example, this is <tt>libz.so.1</tt>.<footnote>
6478 This can be determined by using the command
6479 <example compact="compact">
6480 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6486 <var>main-dependency-template</var> has the same syntax as a
6487 dependency field in a binary package control file, except
6488 that the string <tt>#MINVER#</tt> is replaced by a version
6489 restriction like <tt>(>= <var>version</var>)</tt> or by
6490 nothing if an unversioned dependency is deemed sufficient.
6491 The version restriction will be based on which symbols from
6492 the shared library are referenced and the version at which
6493 they were introduced (see below). In nearly all
6494 cases, <var>main-dependency-template</var> will
6495 be <tt><var>package</var> #MINVER#</tt>,
6496 where <var>package</var> is the name of the binary package
6497 containing the shared library. This adds a simple,
6498 possibly-versioned dependency on the shared library package.
6499 In some rare cases, such as when multiple packages provide
6500 the same shared library ABI, the dependency template may
6501 need to be more complex.
6505 In our example, the first line of
6506 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6507 <example compact="compact">
6508 libz.so.1 zlib1g #MINVER#
6513 Each public symbol exported by the shared library must have
6514 a corresponding symbol line, indented by one
6515 space. <var>symbol</var> is the exported symbol (which, for
6516 C++, means the mangled symbol) followed by <tt>@</tt> and
6517 the symbol version, or the string <tt>Base</tt> if there is
6518 no symbol version. <var>minimal-version</var> is the most
6519 recent version of the shared library that changed the
6520 behavior of that symbol, whether by adding it, changing its
6521 function signature (the parameters, their types, or the
6522 return type), or changing its behavior in a way that is
6523 visible to a caller.
6524 <var>id-of-dependency-template</var> is an optional
6525 field that references
6526 an <var>alternative-dependency-template</var>; see below for
6531 For example, <tt>libz.so.1</tt> contains the
6532 symbols <tt>compress</tt>
6533 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6534 version and last changed its behavior in upstream
6535 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6536 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6537 upstream version <tt>1:1.2.0</tt>, and has not changed its
6538 behavior. Its <file>symbols</file> file therefore contains
6540 <example compact="compact">
6541 compress@Base 1:1.1.4
6542 compressBound@ZLIB_1.2.0 1:1.2.0
6544 Packages using only <tt>compress</tt> would then get a
6545 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6546 using <tt>compressBound</tt> would get a dependency
6547 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6551 One or more <var>alternative-dependency-template</var> lines
6552 may be provided. These are used in cases where some symbols
6553 in the shared library should use one dependency template
6554 while others should use a different template. The
6555 alternative dependency templates are used only if a symbol
6556 line contains the <var>id-of-dependency-template</var>
6557 field. The first alternative dependency template is
6558 numbered 1, the second 2, and so forth.<footnote>
6559 An example of where this may be needed is with a library
6560 that implements the libGL interface. All GL
6561 implementations provide the same set of base interfaces,
6562 and then may provide some additional interfaces only used
6563 by programs that require that specific GL implementation.
6564 So, for example, libgl1-mesa-glx may use the
6565 following <file>symbols</file> file:
6568 | libgl1-mesa-glx #MINVER#
6569 publicGlSymbol@Base 6.3-1
6571 implementationSpecificSymbol@Base 6.5.2-7 1
6574 Binaries or shared libraries using
6575 only <tt>publicGlSymbol</tt> would depend only
6576 on <tt>libgl1</tt> (which may be provided by multiple
6578 using <tt>implementationSpecificSymbol</tt> would get a
6579 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6584 Finally, the entry for the library may contain one or more
6585 metadata fields. Currently, the only
6586 supported <var>field-name</var>
6587 is <tt>Build-Depends-Package</tt>, whose value lists
6588 the <qref id="sharedlibs-dev">library development
6589 package</qref> on which packages using this shared library
6590 declare a build dependency. If this field is
6591 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6592 the resulting binary package dependency on the shared
6593 library is at least as strict as the source package
6594 dependency on the shared library development
6596 This field should normally not be necessary, since if the
6597 behavior of any symbol has changed, the corresponding
6598 symbol <var>minimal-version</var> should have been
6599 increased. But including it makes the <tt>symbols</tt>
6600 system more robust by tightening the dependency in cases
6601 where the package using the shared library specifically
6602 requires at least a particular version of the shared
6603 library development package for some reason.
6605 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6607 <example compact="compact">
6608 * Build-Depends-Package: zlib1g-dev
6613 Also see <manref name="deb-symbols" section="5">.
6617 <sect2 id="providing-symbols">
6618 <heading>Providing a <file>symbols</file> file</heading>
6621 If your package provides a shared library, you should
6622 arrange to include a <file>symbols</file> control file
6623 following the format described above in that package. You
6624 must include either a <file>symbols</file> control file or
6625 a <file>shlibs</file> control file.
6629 Normally, this is done by creating a <file>symbols</file> in
6631 named <file>debian/<var>package</var>.symbols</file>
6632 or <file>debian/symbols</file>, possibly
6633 with <file>.<var>arch</var></file> appended if the symbols
6634 information varies by architecture. This file may use the
6635 extended syntax documented in <manref name="dpkg-gensymbols"
6636 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6637 part of the package build process. It will
6638 create <file>symbols</file> files in the package staging
6639 area based on the binaries and libraries in the package
6640 staging area and the <file>symbols</file> files in the
6641 source package.<footnote>
6643 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6644 take care of calling either <prgn>dpkg-gensymbols</prgn>
6645 or generating a <file>shlibs</file> file as appropriate.
6650 Packages that provide <file>symbols</file> files must keep
6651 them up-to-date to ensure correct dependencies in packages
6652 that use the shared libraries. This means updating
6653 the <file>symbols</file> file whenever a new public symbol
6654 is added, changing the <var>minimal-version</var> field
6655 whenever a symbol changes behavior or signature in a
6656 backward-compatible way (see <ref id="sharedlibs-updates">),
6657 and changing the <var>library-soname</var>
6658 and <var>main-dependency-template</var>, and probably all of
6659 the <var>minimal-version</var> fields, when the library
6660 changes <tt>SONAME</tt>. Removing a public symbol from
6661 the <file>symbols</file> file because it's no longer
6662 provided by the library normally requires changing
6663 the <tt>SONAME</tt> of the library.
6664 See <ref id="sharedlibs-runtime"> for more information
6665 on <tt>SONAME</tt>s.
6670 <sect1 id="sharedlibs-shlibdeps">
6671 <heading>The <tt>shlibs</tt> system</heading>
6674 The <tt>shlibs</tt> system is a simpler alternative to
6675 the <tt>symbols</tt> system for declaring dependencies for
6676 shared libraries. It may be more appropriate for C++
6677 libraries and other cases where tracking individual symbols is
6678 too difficult. It predated the <tt>symbols</tt> system and is
6679 therefore frequently seen in older packages. It is also
6680 required for udebs, which do not support <tt>symbols</tt>.
6684 In the following sections, we will first describe where the
6685 various <file>shlibs</file> files are to be found, then how to
6686 use <prgn>dpkg-shlibdeps</prgn>, and finally
6687 the <file>shlibs</file> file format and how to create them.
6690 <sect2 id="shlibs-paths">
6691 <heading>The <file>shlibs</file> files present on the
6695 There are several places where <tt>shlibs</tt> files are
6696 found. The following list gives them in the order in which
6697 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6698 one which gives the required information is used.)
6701 <p><file>debian/shlibs.local</file></p>
6704 This lists overrides for this package. This file
6705 should normally not be used, but may be needed
6706 temporarily in unusual situations to work around bugs
6707 in other packages, or in unusual cases where the
6708 normally declared dependency information in the
6709 installed <file>shlibs</file> file for a library
6710 cannot be used. This file overrides information
6711 obtained from any other source.
6716 <p><file>/etc/dpkg/shlibs.override</file></p>
6719 This lists global overrides. This list is normally
6720 empty. It is maintained by the local system
6726 <p><file>DEBIAN/shlibs</file> files in the "build
6730 These files are generated as part of the package build
6731 process and staged for inclusion as control files in
6732 the binary packages being built. They provide details
6733 of any shared libraries included in the same package.
6738 <p><file>shlibs</file> control files for packages
6739 installed on the system</p>
6742 The <file>shlibs</file> control files for all the
6743 packages currently installed on the system. These are
6745 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6746 packages should not rely on this and instead should
6747 use <tt>dpkg-query --control-path <var>package</var>
6748 shlibs</tt> if for some reason these files need to be
6754 <p><file>/etc/dpkg/shlibs.default</file></p>
6757 This file lists any shared libraries whose packages
6758 have failed to provide correct <file>shlibs</file>
6759 files. It was used when the <file>shlibs</file> setup
6760 was first introduced, but it is now normally empty.
6761 It is maintained by the <tt>dpkg</tt> maintainer.
6768 If a <file>symbols</file> file for a shared library package
6769 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6770 in preference to a <file>shlibs</file>, with the exception
6771 of <file>debian/shlibs.local</file>. The latter overrides
6772 any other <file>shlibs</file> or <file>symbols</file> files.
6777 <heading>The <file>shlibs</file> File Format</heading>
6780 Each <file>shlibs</file> file has the same format. Lines
6781 beginning with <tt>#</tt> are considered to be comments and
6782 are ignored. Each line is of the form:
6783 <example compact="compact">
6784 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6789 We will explain this by reference to the example of the
6790 <tt>zlib1g</tt> package, which (at the time of writing)
6792 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6796 <var>type</var> is an optional element that indicates the
6797 type of package for which the line is valid. The only type
6798 currently in use is <tt>udeb</tt>. The colon and space
6799 after the type are required.
6803 <var>library-name</var> is the name of the shared library,
6804 in this case <tt>libz</tt>. (This must match the name part
6805 of the soname, see below.)
6809 <var>soname-version</var> is the version part of the
6810 ELF <tt>SONAME</tt> attribute of the library, determined the
6811 same way that the <var>soversion</var> component of the
6812 recommended shared library package name is determined.
6813 See <ref id="sharedlibs-runtime"> for the details.
6817 <var>dependencies</var> has the same syntax as a dependency
6818 field in a binary package control file. It should give
6819 details of which packages are required to satisfy a binary
6820 built against the version of the library contained in the
6821 package. See <ref id="depsyntax"> for details on the
6822 syntax, and <ref id="sharedlibs-updates"> for details on how
6823 to maintain the dependency version constraint.
6827 In our example, if the last change to the <tt>zlib1g</tt>
6828 package that could change behavior for a client of that
6829 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6830 the <tt>shlibs</tt> entry for this library could say:
6831 <example compact="compact">
6832 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6834 This version restriction must be new enough that any binary
6835 built against the current version of the library will work
6836 with any version of the shared library that satisfies that
6841 As zlib1g also provides a udeb containing the shared
6842 library, there would also be a second line:
6843 <example compact="compact">
6844 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6850 <heading>Providing a <file>shlibs</file> file</heading>
6853 To provide a <file>shlibs</file> file for a shared library
6854 binary package, create a <file>shlibs</file> file following
6855 the format described above and place it in
6856 the <file>DEBIAN</file> directory for that package during
6857 the build. It will then be included as a control file for
6858 that package<footnote>
6859 This is what <prgn>dh_makeshlibs</prgn> in
6860 the <package>debhelper</package> suite does. If your
6861 package also has a udeb that provides a shared
6862 library, <prgn>dh_makeshlibs</prgn> can automatically
6863 generate the <tt>udeb:</tt> lines if you specify the name
6864 of the udeb with the <tt>--add-udeb</tt> option.
6869 Since <prgn>dpkg-shlibdeps</prgn> reads
6870 the <file>DEBIAN/shlibs</file> files in all of the binary
6871 packages being built from this source package, all of
6872 the <file>DEBIAN/shlibs</file> files should be installed
6873 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6882 <chapt id="opersys"><heading>The Operating System</heading>
6885 <heading>File system hierarchy</heading>
6889 <heading>File System Structure</heading>
6892 The location of all files and directories must comply with the
6893 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6894 exceptions noted below, and except where doing so would
6895 violate other terms of Debian Policy. The following
6896 exceptions to the FHS apply:
6901 The optional rules related to user specific
6902 configuration files for applications are stored in
6903 the user's home directory are relaxed. It is
6904 recommended that such files start with the
6905 '<tt>.</tt>' character (a "dot file"), and if an
6906 application needs to create more than one dot file
6907 then the preferred placement is in a subdirectory
6908 with a name starting with a '.' character, (a "dot
6909 directory"). In this case it is recommended the
6910 configuration files not start with the '.'
6916 The requirement for amd64 to use <file>/lib64</file>
6917 for 64 bit binaries is removed.
6922 The requirement for object files, internal binaries, and
6923 libraries, including <file>libc.so.*</file>, to be located
6924 directly under <file>/lib{,32}</file> and
6925 <file>/usr/lib{,32}</file> is amended, permitting files
6926 to instead be installed to
6927 <file>/lib/<var>triplet</var></file> and
6928 <file>/usr/lib/<var>triplet</var></file>, where
6929 <tt><var>triplet</var></tt> is the value returned by
6930 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6931 architecture of the package. Packages may <em>not</em>
6932 install files to any <var>triplet</var> path other
6933 than the one matching the architecture of that package;
6934 for instance, an <tt>Architecture: amd64</tt> package
6935 containing 32-bit x86 libraries may not install these
6936 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6938 This is necessary in order to reserve the directories for
6939 use in cross-installation of library packages from other
6940 architectures, as part of the planned deployment of
6945 Applications may also use a single subdirectory under
6946 <file>/usr/lib/<var>triplet</var></file>.
6949 The execution time linker/loader, ld*, must still be made
6950 available in the existing location under /lib or /lib64
6951 since this is part of the ELF ABI for the architecture.
6956 The requirement that
6957 <file>/usr/local/share/man</file> be "synonymous"
6958 with <file>/usr/local/man</file> is relaxed to a
6963 The requirement that windowmanagers with a single
6964 configuration file call it <file>system.*wmrc</file>
6965 is removed, as is the restriction that the window
6966 manager subdirectory be named identically to the
6967 window manager name itself.
6972 The requirement that boot manager configuration
6973 files live in <file>/etc</file>, or at least are
6974 symlinked there, is relaxed to a recommendation.
6979 The additional directory <file>/run</file> in the root
6980 file system is allowed. <file>/run</file>
6981 replaces <file>/var/run</file>, and the
6982 subdirectory <file>/run/lock</file>
6983 replaces <file>/var/lock</file>, with
6984 the <file>/var</file> directories replaced by symlinks
6985 for backwards compatibility. <file>/run</file>
6986 and <file>/run/lock</file> must follow all of the
6987 requirements in the FHS for <file>/var/run</file>
6988 and <file>/var/lock</file>, respectively, such as file
6989 naming conventions, file format requirements, or the
6990 requirement that files be cleared during the boot
6991 process. Files and directories residing
6992 in <file>/run</file> should be stored on a temporary
6996 Packages must not assume the <file>/run</file>
6997 directory exists or is usable without a dependency
6998 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
6999 stable release of Debian supports <file>/run</file>.
7004 The following directories in the root filesystem are
7005 additionally allowed: <file>/sys</file> and
7006 <file>/selinux</file>. <footnote>These directories
7007 are used as mount points to mount virtual filesystems
7008 to get access to kernel information.</footnote>
7013 On GNU/Hurd systems, the following additional
7014 directories are allowed in the root
7015 filesystem: <file>/hurd</file>
7016 and <file>/servers</file>.<footnote>
7017 These directories are used to store translators and as
7018 a set of standard names for mount points,
7027 The version of this document referred here can be
7028 found in the <tt>debian-policy</tt> package or on <url
7029 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7030 name="FHS (Debian copy)"> alongside this manual (or, if
7031 you have the <package>debian-policy</package> installed,
7033 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7034 (local copy)">). The
7035 latest version, which may be a more recent version, may
7037 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7038 Specific questions about following the standard may be
7039 asked on the <tt>debian-devel</tt> mailing list, or
7040 referred to the FHS mailing list (see the
7041 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7047 <heading>Site-specific programs</heading>
7050 As mandated by the FHS, packages must not place any
7051 files in <file>/usr/local</file>, either by putting them in
7052 the file system archive to be unpacked by <prgn>dpkg</prgn>
7053 or by manipulating them in their maintainer scripts.
7057 However, the package may create empty directories below
7058 <file>/usr/local</file> so that the system administrator knows
7059 where to place site-specific files. These are not
7060 directories <em>in</em> <file>/usr/local</file>, but are
7061 children of directories in <file>/usr/local</file>. These
7062 directories (<file>/usr/local/*/dir/</file>)
7063 should be removed on package removal if they are
7068 Note that this applies only to
7069 directories <em>below</em> <file>/usr/local</file>,
7070 not <em>in</em> <file>/usr/local</file>. Packages must
7071 not create sub-directories in the
7072 directory <file>/usr/local</file> itself, except those
7073 listed in FHS, section 4.5. However, you may create
7074 directories below them as you wish. You must not remove
7075 any of the directories listed in 4.5, even if you created
7080 Since <file>/usr/local</file> can be mounted read-only from a
7081 remote server, these directories must be created and
7082 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7083 maintainer scripts and not be included in the
7084 <file>.deb</file> archive. These scripts must not fail if
7085 either of these operations fail.
7089 For example, the <tt>emacsen-common</tt> package could
7090 contain something like
7091 <example compact="compact">
7092 if [ ! -e /usr/local/share/emacs ]; then
7093 if mkdir /usr/local/share/emacs 2>/dev/null; then
7094 if chown root:staff /usr/local/share/emacs; then
7095 chmod 2775 /usr/local/share/emacs || true
7100 in its <prgn>postinst</prgn> script, and
7101 <example compact="compact">
7102 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7103 rmdir /usr/local/share/emacs 2>/dev/null || true
7105 in the <prgn>prerm</prgn> script. (Note that this form is
7106 used to ensure that if the script is interrupted, the
7107 directory <file>/usr/local/share/emacs</file> will still be
7112 If you do create a directory in <file>/usr/local</file> for
7113 local additions to a package, you should ensure that
7114 settings in <file>/usr/local</file> take precedence over the
7115 equivalents in <file>/usr</file>.
7119 However, because <file>/usr/local</file> and its contents are
7120 for exclusive use of the local administrator, a package
7121 must not rely on the presence or absence of files or
7122 directories in <file>/usr/local</file> for normal operation.
7126 The <file>/usr/local</file> directory itself and all the
7127 subdirectories created by the package should (by default) have
7128 permissions 2775 (group-writable and set-group-id) and be
7129 owned by <tt>root:staff</tt>.
7134 <heading>The system-wide mail directory</heading>
7136 The system-wide mail directory
7137 is <file>/var/mail</file>. This directory is part of the
7138 base system and should not be owned by any particular mail
7139 agents. The use of the old
7140 location <file>/var/spool/mail</file> is deprecated, even
7141 though the spool may still be physically located there.
7145 <sect1 id="fhs-run">
7146 <heading><file>/run</file> and <file>/run/lock</file></heading>
7149 The directory <file>/run</file> is cleared at boot, normally
7150 by being a mount point for a temporary file system. Packages
7151 therefore must not assume that any files or directories
7152 under <file>/run</file> other than <file>/run/lock</file>
7153 exist unless the package has arranged to create those files or
7154 directories since the last reboot. Normally, this is done by
7155 the package via an init script. See <ref id="writing-init">
7156 for more information.
7160 Packages must not include files or directories
7161 under <file>/run</file>, or under the
7162 older <file>/var/run</file> and <file>/var/lock</file> paths.
7163 The latter paths will normally be symlinks or other
7164 redirections to <file>/run</file> for backwards compatibility.
7170 <heading>Users and groups</heading>
7173 <heading>Introduction</heading>
7175 The Debian system can be configured to use either plain or
7180 Some user ids (UIDs) and group ids (GIDs) are reserved
7181 globally for use by certain packages. Because some
7182 packages need to include files which are owned by these
7183 users or groups, or need the ids compiled into binaries,
7184 these ids must be used on any Debian system only for the
7185 purpose for which they are allocated. This is a serious
7186 restriction, and we should avoid getting in the way of
7187 local administration policies. In particular, many sites
7188 allocate users and/or local system groups starting at 100.
7192 Apart from this we should have dynamically allocated ids,
7193 which should by default be arranged in some sensible
7194 order, but the behavior should be configurable.
7198 Packages other than <tt>base-passwd</tt> must not modify
7199 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7200 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7205 <heading>UID and GID classes</heading>
7207 The UID and GID numbers are divided into classes as
7213 Globally allocated by the Debian project, the same
7214 on every Debian system. These ids will appear in
7215 the <file>passwd</file> and <file>group</file> files of all
7216 Debian systems, new ids in this range being added
7217 automatically as the <tt>base-passwd</tt> package is
7222 Packages which need a single statically allocated
7223 uid or gid should use one of these; their
7224 maintainers should ask the <tt>base-passwd</tt>
7232 Dynamically allocated system users and groups.
7233 Packages which need a user or group, but can have
7234 this user or group allocated dynamically and
7235 differently on each system, should use <tt>adduser
7236 --system</tt> to create the group and/or user.
7237 <prgn>adduser</prgn> will check for the existence of
7238 the user or group, and if necessary choose an unused
7239 id based on the ranges specified in
7240 <file>adduser.conf</file>.
7244 <tag>1000-59999:</tag>
7247 Dynamically allocated user accounts. By default
7248 <prgn>adduser</prgn> will choose UIDs and GIDs for
7249 user accounts in this range, though
7250 <file>adduser.conf</file> may be used to modify this
7255 <tag>60000-64999:</tag>
7258 Globally allocated by the Debian project, but only
7259 created on demand. The ids are allocated centrally
7260 and statically, but the actual accounts are only
7261 created on users' systems on demand.
7265 These ids are for packages which are obscure or
7266 which require many statically-allocated ids. These
7267 packages should check for and create the accounts in
7268 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7269 <prgn>adduser</prgn> if it has this facility) if
7270 necessary. Packages which are likely to require
7271 further allocations should have a "hole" left after
7272 them in the allocation, to give them room to
7277 <tag>65000-65533:</tag>
7285 User <tt>nobody</tt>. The corresponding gid refers
7286 to the group <tt>nogroup</tt>.
7293 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7294 not</em> be used, because it is the error return
7303 <sect id="sysvinit">
7304 <heading>System run levels and <file>init.d</file> scripts</heading>
7306 <sect1 id="/etc/init.d">
7307 <heading>Introduction</heading>
7310 The <file>/etc/init.d</file> directory contains the scripts
7311 executed by <prgn>init</prgn> at boot time and when the
7312 init state (or "runlevel") is changed (see <manref
7313 name="init" section="8">).
7317 There are at least two different, yet functionally
7318 equivalent, ways of handling these scripts. For the sake
7319 of simplicity, this document describes only the symbolic
7320 link method. However, it must not be assumed by maintainer
7321 scripts that this method is being used, and any automated
7322 manipulation of the various runlevel behaviors by
7323 maintainer scripts must be performed using
7324 <prgn>update-rc.d</prgn> as described below and not by
7325 manually installing or removing symlinks. For information
7326 on the implementation details of the other method,
7327 implemented in the <tt>file-rc</tt> package, please refer
7328 to the documentation of that package.
7332 These scripts are referenced by symbolic links in the
7333 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7334 runlevels, <prgn>init</prgn> looks in the directory
7335 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7336 execute, where <tt><var>n</var></tt> is the runlevel that
7337 is being changed to, or <tt>S</tt> for the boot-up
7342 The names of the links all have the form
7343 <file>S<var>mm</var><var>script</var></file> or
7344 <file>K<var>mm</var><var>script</var></file> where
7345 <var>mm</var> is a two-digit number and <var>script</var>
7346 is the name of the script (this should be the same as the
7347 name of the actual script in <file>/etc/init.d</file>).
7351 When <prgn>init</prgn> changes runlevel first the targets
7352 of the links whose names start with a <tt>K</tt> are
7353 executed, each with the single argument <tt>stop</tt>,
7354 followed by the scripts prefixed with an <tt>S</tt>, each
7355 with the single argument <tt>start</tt>. (The links are
7356 those in the <file>/etc/rc<var>n</var>.d</file> directory
7357 corresponding to the new runlevel.) The <tt>K</tt> links
7358 are responsible for killing services and the <tt>S</tt>
7359 link for starting services upon entering the runlevel.
7363 For example, if we are changing from runlevel 2 to
7364 runlevel 3, init will first execute all of the <tt>K</tt>
7365 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7366 all of the <tt>S</tt> prefixed scripts in that directory.
7367 The links starting with <tt>K</tt> will cause the
7368 referred-to file to be executed with an argument of
7369 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7374 The two-digit number <var>mm</var> is used to determine
7375 the order in which to run the scripts: low-numbered links
7376 have their scripts run first. For example, the
7377 <tt>K20</tt> scripts will be executed before the
7378 <tt>K30</tt> scripts. This is used when a certain service
7379 must be started before another. For example, the name
7380 server <prgn>bind</prgn> might need to be started before
7381 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7382 can set up its access lists. In this case, the script
7383 that starts <prgn>bind</prgn> would have a lower number
7384 than the script that starts <prgn>inn</prgn> so that it
7386 <example compact="compact">
7393 The two runlevels 0 (halt) and 6 (reboot) are slightly
7394 different. In these runlevels, the links with an
7395 <tt>S</tt> prefix are still called after those with a
7396 <tt>K</tt> prefix, but they too are called with the single
7397 argument <tt>stop</tt>.
7401 <sect1 id="writing-init">
7402 <heading>Writing the scripts</heading>
7405 Packages that include daemons for system services should
7406 place scripts in <file>/etc/init.d</file> to start or stop
7407 services at boot time or during a change of runlevel.
7408 These scripts should be named
7409 <file>/etc/init.d/<var>package</var></file>, and they should
7410 accept one argument, saying what to do:
7413 <tag><tt>start</tt></tag>
7414 <item>start the service,</item>
7416 <tag><tt>stop</tt></tag>
7417 <item>stop the service,</item>
7419 <tag><tt>restart</tt></tag>
7420 <item>stop and restart the service if it's already running,
7421 otherwise start the service</item>
7423 <tag><tt>reload</tt></tag>
7424 <item><p>cause the configuration of the service to be
7425 reloaded without actually stopping and restarting
7428 <tag><tt>force-reload</tt></tag>
7429 <item>cause the configuration to be reloaded if the
7430 service supports this, otherwise restart the
7434 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7435 <tt>force-reload</tt> options should be supported by all
7436 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7441 The <file>init.d</file> scripts must ensure that they will
7442 behave sensibly (i.e., returning success and not starting
7443 multiple copies of a service) if invoked with <tt>start</tt>
7444 when the service is already running, or with <tt>stop</tt>
7445 when it isn't, and that they don't kill unfortunately-named
7446 user processes. The best way to achieve this is usually to
7447 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7452 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7453 scripts. Writing correct <file>init.d</file> scripts requires
7454 accepting various error exit statuses when daemons are already
7455 running or already stopped without aborting
7456 the <file>init.d</file> script, and common <file>init.d</file>
7457 function libraries are not safe to call with <tt>set -e</tt>
7459 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7460 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7461 in effect and echoing status messages to the console fails,
7463 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7464 to not use <tt>set -e</tt> and instead check the result of
7465 each command separately.
7469 If a service reloads its configuration automatically (as
7470 in the case of <prgn>cron</prgn>, for example), the
7471 <tt>reload</tt> option of the <file>init.d</file> script
7472 should behave as if the configuration has been reloaded
7477 The <file>/etc/init.d</file> scripts must be treated as
7478 configuration files, either (if they are present in the
7479 package, that is, in the .deb file) by marking them as
7480 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7481 by managing them correctly in the maintainer scripts (see
7482 <ref id="config-files">). This is important since we want
7483 to give the local system administrator the chance to adapt
7484 the scripts to the local system, e.g., to disable a
7485 service without de-installing the package, or to specify
7486 some special command line options when starting a service,
7487 while making sure their changes aren't lost during the next
7492 These scripts should not fail obscurely when the
7493 configuration files remain but the package has been
7494 removed, as configuration files remain on the system after
7495 the package has been removed. Only when <prgn>dpkg</prgn>
7496 is executed with the <tt>--purge</tt> option will
7497 configuration files be removed. In particular, as the
7498 <file>/etc/init.d/<var>package</var></file> script itself is
7499 usually a <tt>conffile</tt>, it will remain on the system
7500 if the package is removed but not purged. Therefore, you
7501 should include a <tt>test</tt> statement at the top of the
7503 <example compact="compact">
7504 test -f <var>program-executed-later-in-script</var> || exit 0
7509 Often there are some variables in the <file>init.d</file>
7510 scripts whose values control the behavior of the scripts,
7511 and which a system administrator is likely to want to
7512 change. As the scripts themselves are frequently
7513 <tt>conffile</tt>s, modifying them requires that the
7514 administrator merge in their changes each time the package
7515 is upgraded and the <tt>conffile</tt> changes. To ease
7516 the burden on the system administrator, such configurable
7517 values should not be placed directly in the script.
7518 Instead, they should be placed in a file in
7519 <file>/etc/default</file>, which typically will have the same
7520 base name as the <file>init.d</file> script. This extra file
7521 should be sourced by the script when the script runs. It
7522 must contain only variable settings and comments in SUSv3
7523 <prgn>sh</prgn> format. It may either be a
7524 <tt>conffile</tt> or a configuration file maintained by
7525 the package maintainer scripts. See <ref id="config-files">
7530 To ensure that vital configurable values are always
7531 available, the <file>init.d</file> script should set default
7532 values for each of the shell variables it uses, either
7533 before sourcing the <file>/etc/default/</file> file or
7534 afterwards using something like the <tt>:
7535 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7536 script must behave sensibly and not fail if the
7537 <file>/etc/default</file> file is deleted.
7541 Files and directories under <file>/run</file>, including ones
7542 referred to via the compatibility paths <file>/var/run</file>
7543 and <file>/var/lock</file>, are normally stored on a temporary
7544 filesystem and are normally not persistent across a reboot.
7545 The <file>init.d</file> scripts must handle this correctly.
7546 This will typically mean creating any required subdirectories
7547 dynamically when the <file>init.d</file> script is run.
7548 See <ref id="fhs-run"> for more information.
7553 <heading>Interfacing with the initscript system</heading>
7556 Maintainers should use the abstraction layer provided by
7557 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7558 programs to deal with initscripts in their packages'
7559 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7560 and <prgn>postrm</prgn>.
7564 Directly managing the /etc/rc?.d links and directly
7565 invoking the <file>/etc/init.d/</file> initscripts should
7566 be done only by packages providing the initscript
7567 subsystem (such as <prgn>sysv-rc</prgn> and
7568 <prgn>file-rc</prgn>).
7572 <heading>Managing the links</heading>
7575 The program <prgn>update-rc.d</prgn> is provided for
7576 package maintainers to arrange for the proper creation and
7577 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7578 or their functional equivalent if another method is being
7579 used. This may be used by maintainers in their packages'
7580 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7584 You must not include any <file>/etc/rc<var>n</var>.d</file>
7585 symbolic links in the actual archive or manually create or
7586 remove the symbolic links in maintainer scripts; you must
7587 use the <prgn>update-rc.d</prgn> program instead. (The
7588 former will fail if an alternative method of maintaining
7589 runlevel information is being used.) You must not include
7590 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7591 in the archive either. (Only the <tt>sysvinit</tt>
7596 By default <prgn>update-rc.d</prgn> will start services in
7597 each of the multi-user state runlevels (2, 3, 4, and 5)
7598 and stop them in the halt runlevel (0), the single-user
7599 runlevel (1) and the reboot runlevel (6). The system
7600 administrator will have the opportunity to customize
7601 runlevels by simply adding, moving, or removing the
7602 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7603 symbolic links are being used, or by modifying
7604 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7609 To get the default behavior for your package, put in your
7610 <prgn>postinst</prgn> script
7611 <example compact="compact">
7612 update-rc.d <var>package</var> defaults
7614 and in your <prgn>postrm</prgn>
7615 <example compact="compact">
7616 if [ "$1" = purge ]; then
7617 update-rc.d <var>package</var> remove
7619 </example>. Note that if your package changes runlevels
7620 or priority, you may have to remove and recreate the links,
7621 since otherwise the old links may persist. Refer to the
7622 documentation of <prgn>update-rc.d</prgn>.
7626 This will use a default sequence number of 20. If it does
7627 not matter when or in which order the <file>init.d</file>
7628 script is run, use this default. If it does, then you
7629 should talk to the maintainer of the <prgn>sysvinit</prgn>
7630 package or post to <tt>debian-devel</tt>, and they will
7631 help you choose a number.
7635 For more information about using <tt>update-rc.d</tt>,
7636 please consult its man page <manref name="update-rc.d"
7642 <heading>Running initscripts</heading>
7644 The program <prgn>invoke-rc.d</prgn> is provided to make
7645 it easier for package maintainers to properly invoke an
7646 initscript, obeying runlevel and other locally-defined
7647 constraints that might limit a package's right to start,
7648 stop and otherwise manage services. This program may be
7649 used by maintainers in their packages' scripts.
7653 The package maintainer scripts must use
7654 <prgn>invoke-rc.d</prgn> to invoke the
7655 <file>/etc/init.d/*</file> initscripts, instead of
7656 calling them directly.
7660 By default, <prgn>invoke-rc.d</prgn> will pass any
7661 action requests (start, stop, reload, restart...) to the
7662 <file>/etc/init.d</file> script, filtering out requests
7663 to start or restart a service out of its intended
7668 Most packages will simply need to change:
7669 <example compact="compact">/etc/init.d/<package>
7670 <action></example> in their <prgn>postinst</prgn>
7671 and <prgn>prerm</prgn> scripts to:
7672 <example compact="compact">
7673 if which invoke-rc.d >/dev/null 2>&1; then
7674 invoke-rc.d <var>package</var> <action>
7676 /etc/init.d/<var>package</var> <action>
7682 A package should register its initscript services using
7683 <prgn>update-rc.d</prgn> before it tries to invoke them
7684 using <prgn>invoke-rc.d</prgn>. Invocation of
7685 unregistered services may fail.
7689 For more information about using
7690 <prgn>invoke-rc.d</prgn>, please consult its man page
7691 <manref name="invoke-rc.d" section="8">.
7697 <heading>Boot-time initialization</heading>
7700 There used to be another directory, <file>/etc/rc.boot</file>,
7701 which contained scripts which were run once per machine
7702 boot. This has been deprecated in favour of links from
7703 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7704 described in <ref id="/etc/init.d">. Packages must not
7705 place files in <file>/etc/rc.boot</file>.
7710 <heading>Example</heading>
7713 An example on which you can base your
7714 <file>/etc/init.d</file> scripts is found in
7715 <file>/etc/init.d/skeleton</file>.
7722 <heading>Console messages from <file>init.d</file> scripts</heading>
7725 This section describes the formats to be used for messages
7726 written to standard output by the <file>/etc/init.d</file>
7727 scripts. The intent is to improve the consistency of
7728 Debian's startup and shutdown look and feel. For this
7729 reason, please look very carefully at the details. We want
7730 the messages to have the same format in terms of wording,
7731 spaces, punctuation and case of letters.
7735 Here is a list of overall rules that should be used for
7736 messages generated by <file>/etc/init.d</file> scripts.
7742 The message should fit in one line (fewer than 80
7743 characters), start with a capital letter and end with
7744 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7748 If the script is performing some time consuming task in
7749 the background (not merely starting or stopping a
7750 program, for instance), an ellipsis (three dots:
7751 <tt>...</tt>) should be output to the screen, with no
7752 leading or tailing whitespace or line feeds.
7756 The messages should appear as if the computer is telling
7757 the user what it is doing (politely :-), but should not
7758 mention "it" directly. For example, instead of:
7759 <example compact="compact">
7760 I'm starting network daemons: nfsd mountd.
7762 the message should say
7763 <example compact="compact">
7764 Starting network daemons: nfsd mountd.
7771 <tt>init.d</tt> script should use the following standard
7772 message formats for the situations enumerated below.
7778 <p>When daemons are started</p>
7781 If the script starts one or more daemons, the output
7782 should look like this (a single line, no leading
7784 <example compact="compact">
7785 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7787 The <var>description</var> should describe the
7788 subsystem the daemon or set of daemons are part of,
7789 while <var>daemon-1</var> up to <var>daemon-n</var>
7790 denote each daemon's name (typically the file name of
7795 For example, the output of <file>/etc/init.d/lpd</file>
7797 <example compact="compact">
7798 Starting printer spooler: lpd.
7803 This can be achieved by saying
7804 <example compact="compact">
7805 echo -n "Starting printer spooler: lpd"
7806 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7809 in the script. If there are more than one daemon to
7810 start, the output should look like this:
7811 <example compact="compact">
7812 echo -n "Starting remote file system services:"
7813 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7814 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7815 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7818 This makes it possible for the user to see what is
7819 happening and when the final daemon has been started.
7820 Care should be taken in the placement of white spaces:
7821 in the example above the system administrators can
7822 easily comment out a line if they don't want to start
7823 a specific daemon, while the displayed message still
7829 <p>When a system parameter is being set</p>
7832 If you have to set up different system parameters
7833 during the system boot, you should use this format:
7834 <example compact="compact">
7835 Setting <var>parameter</var> to "<var>value</var>".
7840 You can use a statement such as the following to get
7842 <example compact="compact">
7843 echo "Setting DNS domainname to \"$domainname\"."
7848 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7849 for the left and right quotation marks. A grave accent
7850 (<tt>`</tt>) is not a quote character; neither is an
7851 apostrophe (<tt>'</tt>).
7856 <p>When a daemon is stopped or restarted</p>
7859 When you stop or restart a daemon, you should issue a
7860 message identical to the startup message, except that
7861 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7862 or <tt>Restarting</tt> respectively.
7866 For example, stopping the printer daemon will look like
7868 <example compact="compact">
7869 Stopping printer spooler: lpd.
7875 <p>When something is executed</p>
7878 There are several examples where you have to run a
7879 program at system startup or shutdown to perform a
7880 specific task, for example, setting the system's clock
7881 using <prgn>netdate</prgn> or killing all processes
7882 when the system shuts down. Your message should look
7884 <example compact="compact">
7885 Doing something very useful...done.
7887 You should print the <tt>done.</tt> immediately after
7888 the job has been completed, so that the user is
7889 informed why they have to wait. You can get this
7891 <example compact="compact">
7892 echo -n "Doing something very useful..."
7901 <p>When the configuration is reloaded</p>
7904 When a daemon is forced to reload its configuration
7905 files you should use the following format:
7906 <example compact="compact">
7907 Reloading <var>description</var> configuration...done.
7909 where <var>description</var> is the same as in the
7910 daemon starting message.
7917 <sect id="cron-jobs">
7918 <heading>Cron jobs</heading>
7921 Packages must not modify the configuration file
7922 <file>/etc/crontab</file>, and they must not modify the files in
7923 <file>/var/spool/cron/crontabs</file>.
7927 If a package wants to install a job that has to be executed via
7928 cron, it should place a file named as specified
7929 in <ref id="cron-files"> into one or more of the following
7931 <example compact="compact">
7937 As these directory names imply, the files within them are
7938 executed on an hourly, daily, weekly, or monthly basis,
7939 respectively. The exact times are listed in
7940 <file>/etc/crontab</file>.
7944 All files installed in any of these directories must be
7945 scripts (e.g., shell scripts or Perl scripts) so that they
7946 can easily be modified by the local system administrator.
7947 In addition, they must be treated as configuration files.
7951 If a certain job has to be executed at some other frequency or
7952 at a specific time, the package should install a file in
7953 <file>/etc/cron.d</file> with a name as specified
7954 in <ref id="cron-files">. This file uses the same syntax
7955 as <file>/etc/crontab</file> and is processed
7956 by <prgn>cron</prgn> automatically. The file must also be
7957 treated as a configuration file. (Note that entries in the
7958 <file>/etc/cron.d</file> directory are not handled by
7959 <prgn>anacron</prgn>. Thus, you should only use this
7960 directory for jobs which may be skipped if the system is not
7965 Unlike <file>crontab</file> files described in the IEEE Std
7966 1003.1-2008 (POSIX.1) available from
7967 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7968 name="The Open Group">, the files in
7969 <file>/etc/cron.d</file> and the file
7970 <file>/etc/crontab</file> have seven fields; namely:
7972 <item>Minute [0,59]</item>
7973 <item>Hour [0,23]</item>
7974 <item>Day of the month [1,31]</item>
7975 <item>Month of the year [1,12]</item>
7976 <item>Day of the week ([0,6] with 0=Sunday)</item>
7977 <item>Username</item>
7978 <item>Command to be run</item>
7980 Ranges of numbers are allowed. Ranges are two numbers
7981 separated with a hyphen. The specified range is inclusive.
7982 Lists are allowed. A list is a set of numbers (or ranges)
7983 separated by commas. Step values can be used in conjunction
7988 The scripts or <tt>crontab</tt> entries in these directories should
7989 check if all necessary programs are installed before they
7990 try to execute them. Otherwise, problems will arise when a
7991 package was removed but not purged since configuration files
7992 are kept on the system in this situation.
7996 Any <tt>cron</tt> daemon must provide
7997 <file>/usr/bin/crontab</file> and support normal
7998 <tt>crontab</tt> entries as specified in POSIX. The daemon
7999 must also support names for days and months, ranges, and
8000 step values. It has to support <file>/etc/crontab</file>,
8001 and correctly execute the scripts in
8002 <file>/etc/cron.d</file>. The daemon must also correctly
8004 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8007 <sect1 id="cron-files">
8008 <heading>Cron job file names</heading>
8011 The file name of a cron job file should normally match the
8012 name of the package from which it comes.
8016 If a package supplies multiple cron job files files in the
8017 same directory, the file names should all start with the name
8018 of the package (possibly modified as described below) followed
8019 by a hyphen (<tt>-</tt>) and a suitable suffix.
8023 A cron job file name must not include any period or plus
8024 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8025 cause cron to ignore the file. Underscores (<tt>_</tt>)
8026 should be used instead of <tt>.</tt> and <tt>+</tt>
8033 <heading>Menus</heading>
8036 The Debian <tt>menu</tt> package provides a standard
8037 interface between packages providing applications and
8038 <em>menu programs</em> (either X window managers or
8039 text-based menu programs such as <prgn>pdmenu</prgn>).
8043 All packages that provide applications that need not be
8044 passed any special command line arguments for normal
8045 operation should register a menu entry for those
8046 applications, so that users of the <tt>menu</tt> package
8047 will automatically get menu entries in their window
8048 managers, as well in shells like <tt>pdmenu</tt>.
8052 Menu entries should follow the current menu policy.
8056 The menu policy can be found in the <tt>menu-policy</tt>
8057 files in the <tt>debian-policy</tt> package.
8058 It is also available from the Debian web mirrors at
8059 <tt><url name="/doc/packaging-manuals/menu-policy/"
8060 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8064 Please also refer to the <em>Debian Menu System</em>
8065 documentation that comes with the <package>menu</package>
8066 package for information about how to register your
8072 <heading>Multimedia handlers</heading>
8075 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8076 is a mechanism for encoding files and data streams and
8077 providing meta-information about them, in particular their
8078 type (e.g. audio or video) and format (e.g. PNG, HTML,
8083 Registration of MIME type handlers allows programs like mail
8084 user agents and web browsers to invoke these handlers to
8085 view, edit or display MIME types they don't support directly.
8089 Packages which provide programs to view/show/play, compose, edit or
8090 print MIME types should register them as such by placing a file in
8091 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8092 <file>/usr/lib/mime/packages/</file>. The file name should be the
8093 binary package's name.
8097 The <package>mime-support</package> package provides the
8098 <prgn>update-mime</prgn> program, which integrates these
8099 registrations in the <file>/etc/mailcap</file> file, using dpkg
8101 Creating, modifying or removing a file in
8102 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8103 not activate the trigger. In that case, it can be done by calling
8104 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8105 the maintainer script after creating, modifying, or removing
8108 Packages using this facility <em>should not</em> depend on,
8109 recommend, or suggest <prgn>mime-support</prgn>.
8114 <heading>Keyboard configuration</heading>
8117 To achieve a consistent keyboard configuration so that all
8118 applications interpret a keyboard event the same way, all
8119 programs in the Debian distribution must be configured to
8120 comply with the following guidelines.
8124 The following keys must have the specified interpretations:
8127 <tag><tt><--</tt></tag>
8128 <item>delete the character to the left of the cursor</item>
8130 <tag><tt>Delete</tt></tag>
8131 <item>delete the character to the right of the cursor</item>
8133 <tag><tt>Control+H</tt></tag>
8134 <item>emacs: the help prefix</item>
8137 The interpretation of any keyboard events should be
8138 independent of the terminal that is used, be it a virtual
8139 console, an X terminal emulator, an rlogin/telnet session,
8144 The following list explains how the different programs
8145 should be set up to achieve this:
8151 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8155 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8159 X translations are set up to make
8160 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8161 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8162 is the vt220 escape code for the "delete character"
8163 key). This must be done by loading the X resources
8164 using <prgn>xrdb</prgn> on all local X displays, not
8165 using the application defaults, so that the
8166 translation resources used correspond to the
8167 <prgn>xmodmap</prgn> settings.
8171 The Linux console is configured to make
8172 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8173 generate <tt>ESC [ 3 ~</tt>.
8177 X applications are configured so that <tt><</tt>
8178 deletes left, and <tt>Delete</tt> deletes right. Motif
8179 applications already work like this.
8183 Terminals should have <tt>stty erase ^?</tt> .
8187 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8188 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8189 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8193 Emacs is programmed to map <tt>KB_Backspace</tt> or
8194 the <tt>stty erase</tt> character to
8195 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8196 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8197 <tt>^H</tt> to <tt>help</tt> as always.
8201 Other applications use the <tt>stty erase</tt>
8202 character and <tt>kdch1</tt> for the two delete keys,
8203 with ASCII DEL being "delete previous character" and
8204 <tt>kdch1</tt> being "delete character under
8212 This will solve the problem except for the following
8219 Some terminals have a <tt><--</tt> key that cannot
8220 be made to produce anything except <tt>^H</tt>. On
8221 these terminals Emacs help will be unavailable on
8222 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8223 character takes precedence in Emacs, and has been set
8224 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8225 available) can be used instead.
8229 Some operating systems use <tt>^H</tt> for <tt>stty
8230 erase</tt>. However, modern telnet versions and all
8231 rlogin versions propagate <tt>stty</tt> settings, and
8232 almost all UNIX versions honour <tt>stty erase</tt>.
8233 Where the <tt>stty</tt> settings are not propagated
8234 correctly, things can be made to work by using
8235 <tt>stty</tt> manually.
8239 Some systems (including previous Debian versions) use
8240 <prgn>xmodmap</prgn> to arrange for both
8241 <tt><--</tt> and <tt>Delete</tt> to generate
8242 <tt>KB_Delete</tt>. We can change the behavior of
8243 their X clients using the same X resources that we use
8244 to do it for our own clients, or configure our clients
8245 using their resources when things are the other way
8246 around. On displays configured like this
8247 <tt>Delete</tt> will not work, but <tt><--</tt>
8252 Some operating systems have different <tt>kdch1</tt>
8253 settings in their <tt>terminfo</tt> database for
8254 <tt>xterm</tt> and others. On these systems the
8255 <tt>Delete</tt> key will not work correctly when you
8256 log in from a system conforming to our policy, but
8257 <tt><--</tt> will.
8264 <heading>Environment variables</heading>
8267 A program must not depend on environment variables to get
8268 reasonable defaults. (That's because these environment
8269 variables would have to be set in a system-wide
8270 configuration file like <file>/etc/profile</file>, which is not
8271 supported by all shells.)
8275 If a program usually depends on environment variables for its
8276 configuration, the program should be changed to fall back to
8277 a reasonable default configuration if these environment
8278 variables are not present. If this cannot be done easily
8279 (e.g., if the source code of a non-free program is not
8280 available), the program must be replaced by a small
8281 "wrapper" shell script which sets the environment variables
8282 if they are not already defined, and calls the original program.
8286 Here is an example of a wrapper script for this purpose:
8288 <example compact="compact">
8290 BAR=${BAR:-/var/lib/fubar}
8292 exec /usr/lib/foo/foo "$@"
8297 Furthermore, as <file>/etc/profile</file> is a configuration
8298 file of the <prgn>base-files</prgn> package, other packages must
8299 not put any environment variables or other commands into that
8304 <sect id="doc-base">
8305 <heading>Registering Documents using doc-base</heading>
8308 The <package>doc-base</package> package implements a
8309 flexible mechanism for handling and presenting
8310 documentation. The recommended practice is for every Debian
8311 package that provides online documentation (other than just
8312 manual pages) to register these documents with
8313 <package>doc-base</package> by installing a
8314 <package>doc-base</package> control file in
8315 <file>/usr/share/doc-base/</file>.
8318 Please refer to the documentation that comes with the
8319 <package>doc-base</package> package for information and
8324 <sect id="alternateinit">
8325 <heading>Alternate init systems</heading>
8327 A number of other init systems are available now in Debian that
8328 can be used in place of <package>sysvinit</package>. Alternative
8329 init implementations must support running SysV init scripts as
8330 described at <ref id="sysvinit"> for compatibility.
8333 Packages may integrate with these replacement init systems by
8334 providing implementation-specific configuration information about
8335 how and when to start a service or in what order to run certain
8336 tasks at boot time. However, any package integrating with other
8337 init systems must also be backwards-compatible with
8338 <package>sysvinit</package> by providing a SysV-style init script
8339 with the same name as and equivalent functionality to any
8340 init-specific job, as this is the only start-up configuration
8341 method guaranteed to be supported by all init implementations. An
8342 exception to this rule is scripts or jobs provided by the init
8343 implementation itself; such jobs may be required for an
8344 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8345 scripts and may not have a one-to-one correspondence with the init
8348 <sect1 id="upstart">
8349 <heading>Event-based boot with upstart</heading>
8352 Packages may integrate with the <prgn>upstart</prgn> event-based
8353 boot system by installing job files in the
8354 <file>/etc/init</file> directory. SysV init scripts for which
8355 an equivalent upstart job is available must query the output of
8356 the command <prgn>initctl version</prgn> for the string
8357 <tt>upstart</tt> and avoid running in favor of the native
8358 upstart job, using a test such as this:
8359 <example compact="compact">
8360 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8367 Because packages shipping upstart jobs may be installed on
8368 systems that are not using upstart, maintainer scripts must
8369 still use the common <prgn>update-rc.d</prgn> and
8370 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8371 and for starting and stopping services. These maintainer
8372 scripts must not call the upstart <prgn>start</prgn>,
8373 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8374 interfaces directly. Instead, implementations of
8375 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8376 when an upstart job with the same name as an init script is
8377 present, and perform the requested action using the upstart job
8378 instead of the init script.
8381 Dependency-based boot managers for SysV init scripts, such as
8382 <prgn>startpar</prgn>, may avoid running a given init script
8383 entirely when an equivalent upstart job is present, to avoid
8384 unnecessary forking of no-op init scripts. In this case, the
8385 boot manager should integrate with upstart to detect when the
8386 upstart job in question is started or stopped to know when the
8387 dependency has been satisfied.
8396 <heading>Files</heading>
8398 <sect id="binaries">
8399 <heading>Binaries</heading>
8402 Two different packages must not install programs with
8403 different functionality but with the same filenames. (The
8404 case of two programs having the same functionality but
8405 different implementations is handled via "alternatives" or
8406 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8407 <ref id="conflicts"> respectively.) If this case happens,
8408 one of the programs must be renamed. The maintainers should
8409 report this to the <tt>debian-devel</tt> mailing list and
8410 try to find a consensus about which program will have to be
8411 renamed. If a consensus cannot be reached, <em>both</em>
8412 programs must be renamed.
8416 By default, when a package is being built, any binaries
8417 created should include debugging information, as well as
8418 being compiled with optimization. You should also turn on
8419 as many reasonable compilation warnings as possible; this
8420 makes life easier for porters, who can then look at build
8421 logs for possible problems. For the C programming language,
8422 this means the following compilation parameters should be
8424 <example compact="compact">
8426 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8428 INSTALL = install -s # (or use strip on the files in debian/tmp)
8433 Note that by default all installed binaries should be stripped,
8434 either by using the <tt>-s</tt> flag to
8435 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8436 the binaries after they have been copied into
8437 <file>debian/tmp</file> but before the tree is made into a
8442 Although binaries in the build tree should be compiled with
8443 debugging information by default, it can often be difficult to
8444 debug programs if they are also subjected to compiler
8445 optimization. For this reason, it is recommended to support the
8446 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8447 (see <ref id="debianrules-options">). This variable can contain
8448 several flags to change how a package is compiled and built.
8452 It is up to the package maintainer to decide what
8453 compilation options are best for the package. Certain
8454 binaries (such as computationally-intensive programs) will
8455 function better with certain flags (<tt>-O3</tt>, for
8456 example); feel free to use them. Please use good judgment
8457 here. Don't use flags for the sake of it; only use them
8458 if there is good reason to do so. Feel free to override
8459 the upstream author's ideas about which compilation
8460 options are best: they are often inappropriate for our
8466 <sect id="libraries">
8467 <heading>Libraries</heading>
8470 If the package is <strong>architecture: any</strong>, then
8471 the shared library compilation and linking flags must have
8472 <tt>-fPIC</tt>, or the package shall not build on some of
8473 the supported architectures<footnote>
8475 If you are using GCC, <tt>-fPIC</tt> produces code with
8476 relocatable position independent code, which is required for
8477 most architectures to create a shared library, with i386 and
8478 perhaps some others where non position independent code is
8479 permitted in a shared library.
8482 Position independent code may have a performance penalty,
8483 especially on <tt>i386</tt>. However, in most cases the
8484 speed penalty must be measured against the memory wasted on
8485 the few architectures where non position independent code is
8488 </footnote>. Any exception to this rule must be discussed on
8489 the mailing list <em>debian-devel@lists.debian.org</em>, and
8490 a rough consensus obtained. The reasons for not compiling
8491 with <tt>-fPIC</tt> flag must be recorded in the file
8492 <tt>README.Debian</tt>, and care must be taken to either
8493 restrict the architecture or arrange for <tt>-fPIC</tt> to
8494 be used on architectures where it is required.<footnote>
8496 Some of the reasons why this might be required is if the
8497 library contains hand crafted assembly code that is not
8498 relocatable, the speed penalty is excessive for compute
8499 intensive libs, and similar reasons.
8504 As to the static libraries, the common case is not to have
8505 relocatable code, since there is no benefit, unless in specific
8506 cases; therefore the static version must not be compiled
8507 with the <tt>-fPIC</tt> flag. Any exception to this rule
8508 should be discussed on the mailing list
8509 <em>debian-devel@lists.debian.org</em>, and the reasons for
8510 compiling with the <tt>-fPIC</tt> flag must be recorded in
8511 the file <tt>README.Debian</tt>. <footnote>
8513 Some of the reasons for linking static libraries with
8514 the <tt>-fPIC</tt> flag are if, for example, one needs a
8515 Perl API for a library that is under rapid development,
8516 and has an unstable API, so shared libraries are
8517 pointless at this phase of the library's development. In
8518 that case, since Perl needs a library with relocatable
8519 code, it may make sense to create a static library with
8520 relocatable code. Another reason cited is if you are
8521 distilling various libraries into a common shared
8522 library, like <tt>mklibs</tt> does in the Debian
8528 In other words, if both a shared and a static library is
8529 being built, each source unit (<tt>*.c</tt>, for example,
8530 for C files) will need to be compiled twice, for the normal
8535 Libraries should be built with threading support and to be
8536 thread-safe if the library supports this.
8540 Although not enforced by the build tools, shared libraries
8541 must be linked against all libraries that they use symbols from
8542 in the same way that binaries are. This ensures the correct
8543 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8544 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8545 systems and guarantees that all libraries can be safely opened
8546 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8547 option <tt>-Wl,-z,defs</tt> when building a shared library.
8548 Since this option enforces symbol resolution at build time,
8549 a missing library reference will be caught early as a fatal
8554 All installed shared libraries should be stripped with
8555 <example compact="compact">
8556 strip --strip-unneeded <var>your-lib</var>
8558 (The option <tt>--strip-unneeded</tt> makes
8559 <prgn>strip</prgn> remove only the symbols which aren't
8560 needed for relocation processing.) Shared libraries can
8561 function perfectly well when stripped, since the symbols for
8562 dynamic linking are in a separate part of the ELF object
8564 You might also want to use the options
8565 <tt>--remove-section=.comment</tt> and
8566 <tt>--remove-section=.note</tt> on both shared libraries
8567 and executables, and <tt>--strip-debug</tt> on static
8573 Note that under some circumstances it may be useful to
8574 install a shared library unstripped, for example when
8575 building a separate package to support debugging.
8579 Shared object files (often <file>.so</file> files) that are not
8580 public libraries, that is, they are not meant to be linked
8581 to by third party executables (binaries of other packages),
8582 should be installed in subdirectories of the
8583 <file>/usr/lib</file> directory. Such files are exempt from the
8584 rules that govern ordinary shared libraries, except that
8585 they must not be installed executable and should be
8587 A common example are the so-called "plug-ins",
8588 internal shared objects that are dynamically loaded by
8589 programs using <manref name="dlopen" section="3">.
8594 Packages that use <prgn>libtool</prgn> to create and install
8595 their shared libraries install a file containing additional
8596 metadata (ending in <file>.la</file>) alongside the library.
8597 For public libraries intended for use by other packages, these
8598 files normally should not be included in the Debian package,
8599 since the information they include is not necessary to link with
8600 the shared library on Debian and can add unnecessary additional
8601 dependencies to other programs or libraries.<footnote>
8602 These files store, among other things, all libraries on which
8603 that shared library depends. Unfortunately, if
8604 the <file>.la</file> file is present and contains that
8605 dependency information, using <prgn>libtool</prgn> when
8606 linking against that library will cause the resulting program
8607 or library to be linked against those dependencies as well,
8608 even if this is unnecessary. This can create unneeded
8609 dependencies on shared library packages that would otherwise
8610 be hidden behind the library ABI, and can make library
8611 transitions to new SONAMEs unnecessarily complicated and
8612 difficult to manage.
8614 If the <file>.la</file> file is required for that library (if,
8615 for instance, it's loaded via <tt>libltdl</tt> in a way that
8616 requires that meta-information), the <tt>dependency_libs</tt>
8617 setting in the <file>.la</file> file should normally be set to
8618 the empty string. If the shared library development package has
8619 historically included the <file>.la</file>, it must be retained
8620 in the development package (with <tt>dependency_libs</tt>
8621 emptied) until all libraries that depend on it have removed or
8622 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8623 files to prevent linking with those other libraries
8624 using <prgn>libtool</prgn> from failing.
8628 If the <file>.la</file> must be included, it should be included
8629 in the development (<tt>-dev</tt>) package, unless the library
8630 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8631 library. If it is intended for use with <tt>libltdl</tt>,
8632 the <file>.la</file> files must go in the run-time library
8637 These requirements for handling of <file>.la</file> files do not
8638 apply to loadable modules or libraries not installed in
8639 directories searched by default by the dynamic linker. Packages
8640 installing loadable modules will frequently need to install
8641 the <file>.la</file> files alongside the modules so that they
8642 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8643 does not need to be modified for libraries or modules that are
8644 not installed in directories searched by the dynamic linker by
8645 default and not intended for use by other packages.
8649 You must make sure that you use only released versions of
8650 shared libraries to build your packages; otherwise other
8651 users will not be able to run your binaries
8652 properly. Producing source packages that depend on
8653 unreleased compilers is also usually a bad
8660 <heading>Shared libraries</heading>
8662 This section has moved to <ref id="sharedlibs">.
8668 <heading>Scripts</heading>
8671 All command scripts, including the package maintainer
8672 scripts inside the package and used by <prgn>dpkg</prgn>,
8673 should have a <tt>#!</tt> line naming the shell to be used
8678 In the case of Perl scripts this should be
8679 <tt>#!/usr/bin/perl</tt>.
8683 When scripts are installed into a directory in the system
8684 PATH, the script name should not include an extension such
8685 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8686 language currently used to implement it.
8689 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8690 <file>init.d</file> scripts should almost certainly start
8691 with <tt>set -e</tt> so that errors are detected.
8692 <file>init.d</file> scripts are something of a special case, due
8693 to how frequently they need to call commands that are allowed to
8694 fail, and it may instead be easier to check the exit status of
8695 commands directly. See <ref id="writing-init"> for more
8696 information about writing <file>init.d</file> scripts.
8699 Every script should use <tt>set -e</tt> or check the exit status
8700 of <em>every</em> command.
8703 Scripts may assume that <file>/bin/sh</file> implements the
8704 SUSv3 Shell Command Language<footnote>
8705 Single UNIX Specification, version 3, which is also IEEE
8706 1003.1-2004 (POSIX), and is available on the World Wide Web
8707 from <url id="http://www.unix.org/version3/online.html"
8708 name="The Open Group"> after free
8709 registration.</footnote>
8710 plus the following additional features not mandated by
8712 These features are in widespread use in the Linux community
8713 and are implemented in all of bash, dash, and ksh, the most
8714 common shells users may wish to use as <file>/bin/sh</file>.
8717 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8718 must not generate a newline.</item>
8719 <item><tt>test</tt>, if implemented as a shell built-in, must
8720 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8722 <item><tt>local</tt> to create a scoped variable must be
8723 supported, including listing multiple variables in a single
8724 local command and assigning a value to a variable at the
8725 same time as localizing it. <tt>local</tt> may or
8726 may not preserve the variable value from an outer scope if
8727 no assignment is present. Uses such as:
8731 # ... use a, b, c, d ...
8734 must be supported and must set the value of <tt>c</tt> to
8737 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8738 -<var>signal</var></tt>, where <var>signal</var> is either
8739 the name of a signal or one of the numeric signals listed in
8740 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8741 supported if <prgn>kill</prgn> is implemented as a shell
8744 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8745 signals must be supported. In addition to the signal
8746 numbers listed in the extension, which are the same as for
8747 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8750 If a shell script requires non-SUSv3 features from the shell
8751 interpreter other than those listed above, the appropriate shell
8752 must be specified in the first line of the script (e.g.,
8753 <tt>#!/bin/bash</tt>) and the package must depend on the package
8754 providing the shell (unless the shell package is marked
8755 "Essential", as in the case of <prgn>bash</prgn>).
8759 You may wish to restrict your script to SUSv3 features plus the
8760 above set when possible so that it may use <file>/bin/sh</file>
8761 as its interpreter. Checking your script
8762 with <prgn>checkbashisms</prgn> from
8763 the <package>devscripts</package> package or running your script
8764 with an alternate shell such as <prgn>posh</prgn> may help
8765 uncover violations of the above requirements. If in doubt
8766 whether a script complies with these requirements,
8767 use <file>/bin/bash</file>.
8771 Perl scripts should check for errors when making any
8772 system calls, including <tt>open</tt>, <tt>print</tt>,
8773 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8777 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8778 scripting languages. See <em>Csh Programming Considered
8779 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8780 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8781 If an upstream package comes with <prgn>csh</prgn> scripts
8782 then you must make sure that they start with
8783 <tt>#!/bin/csh</tt> and make your package depend on the
8784 <prgn>c-shell</prgn> virtual package.
8788 Any scripts which create files in world-writeable
8789 directories (e.g., in <file>/tmp</file>) must use a
8790 mechanism which will fail atomically if a file with the same
8791 name already exists.
8795 The Debian base system provides the <prgn>tempfile</prgn>
8796 and <prgn>mktemp</prgn> utilities for use by scripts for
8803 <heading>Symbolic links</heading>
8806 In general, symbolic links within a top-level directory should
8807 be relative, and symbolic links pointing from one top-level
8808 directory to or into another should be absolute. (A top-level
8809 directory is a sub-directory of the root
8810 directory <file>/</file>.) For example, a symbolic link
8811 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8812 should be relative (<file>../share/bar</file>), but a symbolic
8813 link from <file>/var/run</file> to <file>/run</file> should be
8815 This is necessary to allow top-level directories to be
8816 symlinks. If linking <file>/var/run</file>
8817 to <file>/run</file> were done with the relative symbolic
8818 link <file>../run</file>, but <file>/var</file> were a
8819 symbolic link to <file>/srv/disk1</file>, the symbolic link
8820 would point to <file>/srv/run</file> rather than the intended
8826 In addition, symbolic links should be specified as short as
8827 possible, i.e., link targets like <file>foo/../bar</file> are
8832 Note that when creating a relative link using
8833 <prgn>ln</prgn> it is not necessary for the target of the
8834 link to exist relative to the working directory you're
8835 running <prgn>ln</prgn> from, nor is it necessary to change
8836 directory to the directory where the link is to be made.
8837 Simply include the string that should appear as the target
8838 of the link (this will be a pathname relative to the
8839 directory in which the link resides) as the first argument
8844 For example, in your <prgn>Makefile</prgn> or
8845 <file>debian/rules</file>, you can do things like:
8846 <example compact="compact">
8847 ln -fs gcc $(prefix)/bin/cc
8848 ln -fs gcc debian/tmp/usr/bin/cc
8849 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8850 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8855 A symbolic link pointing to a compressed file should always
8856 have the same file extension as the referenced file. (For
8857 example, if a file <file>foo.gz</file> is referenced by a
8858 symbolic link, the filename of the link has to end with
8859 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8864 <heading>Device files</heading>
8867 Packages must not include device files or named pipes in the
8872 If a package needs any special device files that are not
8873 included in the base system, it must call
8874 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8875 after notifying the user<footnote>
8876 This notification could be done via a (low-priority)
8877 debconf message, or an echo (printf) statement.
8882 Packages must not remove any device files in the
8883 <prgn>postrm</prgn> or any other script. This is left to the
8884 system administrator.
8888 Debian uses the serial devices
8889 <file>/dev/ttyS*</file>. Programs using the old
8890 <file>/dev/cu*</file> devices should be changed to use
8891 <file>/dev/ttyS*</file>.
8895 Named pipes needed by the package must be created in
8896 the <prgn>postinst</prgn> script<footnote>
8897 It's better to use <prgn>mkfifo</prgn> rather
8898 than <prgn>mknod</prgn> to create named pipes so that
8899 automated checks for packages incorrectly creating device
8900 files with <prgn>mknod</prgn> won't have false positives.
8901 </footnote> and removed in
8902 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8907 <sect id="config-files">
8908 <heading>Configuration files</heading>
8911 <heading>Definitions</heading>
8915 <tag>configuration file</tag>
8917 A file that affects the operation of a program, or
8918 provides site- or host-specific information, or
8919 otherwise customizes the behavior of a program.
8920 Typically, configuration files are intended to be
8921 modified by the system administrator (if needed or
8922 desired) to conform to local policy or to provide
8923 more useful site-specific behavior.
8926 <tag><tt>conffile</tt></tag>
8928 A file listed in a package's <tt>conffiles</tt>
8929 file, and is treated specially by <prgn>dpkg</prgn>
8930 (see <ref id="configdetails">).
8936 The distinction between these two is important; they are
8937 not interchangeable concepts. Almost all
8938 <tt>conffile</tt>s are configuration files, but many
8939 configuration files are not <tt>conffiles</tt>.
8943 As noted elsewhere, <file>/etc/init.d</file> scripts,
8944 <file>/etc/default</file> files, scripts installed in
8945 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8946 configuration installed in <file>/etc/cron.d</file> must be
8947 treated as configuration files. In general, any script that
8948 embeds configuration information is de-facto a configuration
8949 file and should be treated as such.
8954 <heading>Location</heading>
8957 Any configuration files created or used by your package
8958 must reside in <file>/etc</file>. If there are several,
8959 consider creating a subdirectory of <file>/etc</file>
8960 named after your package.
8964 If your package creates or uses configuration files
8965 outside of <file>/etc</file>, and it is not feasible to modify
8966 the package to use <file>/etc</file> directly, put the files
8967 in <file>/etc</file> and create symbolic links to those files
8968 from the location that the package requires.
8973 <heading>Behavior</heading>
8976 Configuration file handling must conform to the following
8978 <list compact="compact">
8980 local changes must be preserved during a package
8984 configuration files must be preserved when the
8985 package is removed, and only deleted when the
8989 Obsolete configuration files without local changes may be
8990 removed by the package during upgrade.
8994 The easy way to achieve this behavior is to make the
8995 configuration file a <tt>conffile</tt>. This is
8996 appropriate only if it is possible to distribute a default
8997 version that will work for most installations, although
8998 some system administrators may choose to modify it. This
8999 implies that the default version will be part of the
9000 package distribution, and must not be modified by the
9001 maintainer scripts during installation (or at any other
9006 In order to ensure that local changes are preserved
9007 correctly, no package may contain or make hard links to
9008 conffiles.<footnote>
9009 Rationale: There are two problems with hard links.
9010 The first is that some editors break the link while
9011 editing one of the files, so that the two files may
9012 unwittingly become unlinked and different. The second
9013 is that <prgn>dpkg</prgn> might break the hard link
9014 while upgrading <tt>conffile</tt>s.
9019 The other way to do it is via the maintainer scripts. In
9020 this case, the configuration file must not be listed as a
9021 <tt>conffile</tt> and must not be part of the package
9022 distribution. If the existence of a file is required for
9023 the package to be sensibly configured it is the
9024 responsibility of the package maintainer to provide
9025 maintainer scripts which correctly create, update and
9026 maintain the file and remove it on purge. (See <ref
9027 id="maintainerscripts"> for more information.) These
9028 scripts must be idempotent (i.e., must work correctly if
9029 <prgn>dpkg</prgn> needs to re-run them due to errors
9030 during installation or removal), must cope with all the
9031 variety of ways <prgn>dpkg</prgn> can call maintainer
9032 scripts, must not overwrite or otherwise mangle the user's
9033 configuration without asking, must not ask unnecessary
9034 questions (particularly during upgrades), and must
9035 otherwise be good citizens.
9039 The scripts are not required to configure every possible
9040 option for the package, but only those necessary to get
9041 the package running on a given system. Ideally the
9042 sysadmin should not have to do any configuration other
9043 than that done (semi-)automatically by the
9044 <prgn>postinst</prgn> script.
9048 A common practice is to create a script called
9049 <file><var>package</var>-configure</file> and have the
9050 package's <prgn>postinst</prgn> call it if and only if the
9051 configuration file does not already exist. In certain
9052 cases it is useful for there to be an example or template
9053 file which the maintainer scripts use. Such files should
9054 be in <file>/usr/share/<var>package</var></file> or
9055 <file>/usr/lib/<var>package</var></file> (depending on whether
9056 they are architecture-independent or not). There should
9057 be symbolic links to them from
9058 <file>/usr/share/doc/<var>package</var>/examples</file> if
9059 they are examples, and should be perfectly ordinary
9060 <prgn>dpkg</prgn>-handled files (<em>not</em>
9061 configuration files).
9065 These two styles of configuration file handling must
9066 not be mixed, for that way lies madness:
9067 <prgn>dpkg</prgn> will ask about overwriting the file
9068 every time the package is upgraded.
9073 <heading>Sharing configuration files</heading>
9076 If two or more packages use the same configuration file
9077 and it is reasonable for both to be installed at the same
9078 time, one of these packages must be defined as
9079 <em>owner</em> of the configuration file, i.e., it will be
9080 the package which handles that file as a configuration
9081 file. Other packages that use the configuration file must
9082 depend on the owning package if they require the
9083 configuration file to operate. If the other package will
9084 use the configuration file if present, but is capable of
9085 operating without it, no dependency need be declared.
9089 If it is desirable for two or more related packages to
9090 share a configuration file <em>and</em> for all of the
9091 related packages to be able to modify that configuration
9092 file, then the following should be done:
9093 <enumlist compact="compact">
9095 One of the related packages (the "owning" package)
9096 will manage the configuration file with maintainer
9097 scripts as described in the previous section.
9100 The owning package should also provide a program
9101 that the other packages may use to modify the
9105 The related packages must use the provided program
9106 to make any desired modifications to the
9107 configuration file. They should either depend on
9108 the core package to guarantee that the configuration
9109 modifier program is available or accept gracefully
9110 that they cannot modify the configuration file if it
9111 is not. (This is in addition to the fact that the
9112 configuration file may not even be present in the
9119 Sometimes it's appropriate to create a new package which
9120 provides the basic infrastructure for the other packages
9121 and which manages the shared configuration files. (The
9122 <tt>sgml-base</tt> package is a good example.)
9126 If the configuration file cannot be shared as described above,
9127 the packages must be marked as conflicting with each other.
9128 Two packages that specify the same file as
9129 a <tt>conffile</tt> must conflict. This is an instance of the
9130 general rule about not sharing files. Neither alternatives
9131 nor diversions are likely to be appropriate in this case; in
9132 particular, <prgn>dpkg</prgn> does not handle diverted
9133 <tt>conffile</tt>s well.
9137 When two packages both declare the same <tt>conffile</tt>, they
9138 may see left-over configuration files from each other even
9139 though they conflict with each other. If a user removes
9140 (without purging) one of the packages and installs the other,
9141 the new package will take over the <tt>conffile</tt> from the
9142 old package. If the file was modified by the user, it will be
9143 treated the same as any other locally
9144 modified <tt>conffile</tt> during an upgrade.
9148 The maintainer scripts must not alter a <tt>conffile</tt>
9149 of <em>any</em> package, including the one the scripts
9155 <heading>User configuration files ("dotfiles")</heading>
9158 The files in <file>/etc/skel</file> will automatically be
9159 copied into new user accounts by <prgn>adduser</prgn>.
9160 No other program should reference the files in
9161 <file>/etc/skel</file>.
9165 Therefore, if a program needs a dotfile to exist in
9166 advance in <file>$HOME</file> to work sensibly, that dotfile
9167 should be installed in <file>/etc/skel</file> and treated as a
9172 However, programs that require dotfiles in order to
9173 operate sensibly are a bad thing, unless they do create
9174 the dotfiles themselves automatically.
9178 Furthermore, programs should be configured by the Debian
9179 default installation to behave as closely to the upstream
9180 default behavior as possible.
9184 Therefore, if a program in a Debian package needs to be
9185 configured in some way in order to operate sensibly, that
9186 should be done using a site-wide configuration file placed
9187 in <file>/etc</file>. Only if the program doesn't support a
9188 site-wide default configuration and the package maintainer
9189 doesn't have time to add it may a default per-user file be
9190 placed in <file>/etc/skel</file>.
9194 <file>/etc/skel</file> should be as empty as we can make it.
9195 This is particularly true because there is no easy (or
9196 necessarily desirable) mechanism for ensuring that the
9197 appropriate dotfiles are copied into the accounts of
9198 existing users when a package is installed.
9204 <heading>Log files</heading>
9206 Log files should usually be named
9207 <file>/var/log/<var>package</var>.log</file>. If you have many
9208 log files, or need a separate directory for permission
9209 reasons (<file>/var/log</file> is writable only by
9210 <file>root</file>), you should usually create a directory named
9211 <file>/var/log/<var>package</var></file> and place your log
9216 Log files must be rotated occasionally so that they don't grow
9217 indefinitely. The best way to do this is to install a log
9218 rotation configuration file in the
9219 directory <file>/etc/logrotate.d</file>, normally
9220 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9221 the facilities provided by <prgn>logrotate</prgn>.
9224 The traditional approach to log files has been to set up
9225 <em>ad hoc</em> log rotation schemes using simple shell
9226 scripts and cron. While this approach is highly
9227 customizable, it requires quite a lot of sysadmin work.
9228 Even though the original Debian system helped a little
9229 by automatically installing a system which can be used
9230 as a template, this was deemed not enough.
9234 The use of <prgn>logrotate</prgn>, a program developed
9235 by Red Hat, is better, as it centralizes log management.
9236 It has both a configuration file
9237 (<file>/etc/logrotate.conf</file>) and a directory where
9238 packages can drop their individual log rotation
9239 configurations (<file>/etc/logrotate.d</file>).
9242 Here is a good example for a logrotate config
9243 file (for more information see <manref name="logrotate"
9245 <example compact="compact">
9246 /var/log/foo/*.log {
9252 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9256 This rotates all files under <file>/var/log/foo</file>, saves 12
9257 compressed generations, and tells the daemon to reopen its log
9258 files after the log rotation. It skips this log rotation
9259 (via <tt>missingok</tt>) if no such log file is present, which
9260 avoids errors if the package is removed but not purged.
9264 Log files should be removed when the package is
9265 purged (but not when it is only removed). This should be
9266 done by the <prgn>postrm</prgn> script when it is called
9267 with the argument <tt>purge</tt> (see <ref
9268 id="removedetails">).
9272 <sect id="permissions-owners">
9273 <heading>Permissions and owners</heading>
9276 The rules in this section are guidelines for general use.
9277 If necessary you may deviate from the details below.
9278 However, if you do so you must make sure that what is done
9279 is secure and you should try to be as consistent as possible
9280 with the rest of the system. You should probably also
9281 discuss it on <prgn>debian-devel</prgn> first.
9285 Files should be owned by <tt>root:root</tt>, and made
9286 writable only by the owner and universally readable (and
9287 executable, if appropriate), that is mode 644 or 755.
9291 Directories should be mode 755 or (for group-writability)
9292 mode 2775. The ownership of the directory should be
9293 consistent with its mode: if a directory is mode 2775, it
9294 should be owned by the group that needs write access to
9297 When a package is upgraded, and the owner or permissions
9298 of a file included in the package has changed, dpkg
9299 arranges for the ownership and permissions to be
9300 correctly set upon installation. However, this does not
9301 extend to directories; the permissions and ownership of
9302 directories already on the system does not change on
9303 install or upgrade of packages. This makes sense, since
9304 otherwise common directories like <tt>/usr</tt> would
9305 always be in flux. To correctly change permissions of a
9306 directory the package owns, explicit action is required,
9307 usually in the <tt>postinst</tt> script. Care must be
9308 taken to handle downgrades as well, in that case.
9314 Control information files should be owned by <tt>root:root</tt>
9315 and either mode 644 (for most files) or mode 755 (for
9316 executables such as <qref id="maintscripts">maintainer
9321 Setuid and setgid executables should be mode 4755 or 2755
9322 respectively, and owned by the appropriate user or group.
9323 They should not be made unreadable (modes like 4711 or
9324 2711 or even 4111); doing so achieves no extra security,
9325 because anyone can find the binary in the freely available
9326 Debian package; it is merely inconvenient. For the same
9327 reason you should not restrict read or execute permissions
9328 on non-set-id executables.
9332 Some setuid programs need to be restricted to particular
9333 sets of users, using file permissions. In this case they
9334 should be owned by the uid to which they are set-id, and by
9335 the group which should be allowed to execute them. They
9336 should have mode 4754; again there is no point in making
9337 them unreadable to those users who must not be allowed to
9342 It is possible to arrange that the system administrator can
9343 reconfigure the package to correspond to their local
9344 security policy by changing the permissions on a binary:
9345 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9346 described below.<footnote>
9347 Ordinary files installed by <prgn>dpkg</prgn> (as
9348 opposed to <tt>conffile</tt>s and other similar objects)
9349 normally have their permissions reset to the distributed
9350 permissions when the package is reinstalled. However,
9351 the use of <prgn>dpkg-statoverride</prgn> overrides this
9354 Another method you should consider is to create a group for
9355 people allowed to use the program(s) and make any setuid
9356 executables executable only by that group.
9360 If you need to create a new user or group for your package
9361 there are two possibilities. Firstly, you may need to
9362 make some files in the binary package be owned by this
9363 user or group, or you may need to compile the user or
9364 group id (rather than just the name) into the binary
9365 (though this latter should be avoided if possible, as in
9366 this case you need a statically allocated id).</p>
9369 If you need a statically allocated id, you must ask for a
9370 user or group id from the <tt>base-passwd</tt> maintainer,
9371 and must not release the package until you have been
9372 allocated one. Once you have been allocated one you must
9373 either make the package depend on a version of the
9374 <tt>base-passwd</tt> package with the id present in
9375 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9376 your package to create the user or group itself with the
9377 correct id (using <tt>adduser</tt>) in its
9378 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9379 the <prgn>postinst</prgn> is to be preferred if it is
9380 possible, otherwise a pre-dependency will be needed on the
9381 <tt>adduser</tt> package.)
9385 On the other hand, the program might be able to determine
9386 the uid or gid from the user or group name at runtime, so
9387 that a dynamically allocated id can be used. In this case
9388 you should choose an appropriate user or group name,
9389 discussing this on <prgn>debian-devel</prgn> and checking
9390 with the <package/base-passwd/ maintainer that it is unique and that
9391 they do not wish you to use a statically allocated id
9392 instead. When this has been checked you must arrange for
9393 your package to create the user or group if necessary using
9394 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9395 <prgn>postinst</prgn> script (again, the latter is to be
9396 preferred if it is possible).
9400 Note that changing the numeric value of an id associated
9401 with a name is very difficult, and involves searching the
9402 file system for all appropriate files. You need to think
9403 carefully whether a static or dynamic id is required, since
9404 changing your mind later will cause problems.
9407 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9409 This section is not intended as policy, but as a
9410 description of the use of <prgn>dpkg-statoverride</prgn>.
9414 If a system administrator wishes to have a file (or
9415 directory or other such thing) installed with owner and
9416 permissions different from those in the distributed Debian
9417 package, they can use the <prgn>dpkg-statoverride</prgn>
9418 program to instruct <prgn>dpkg</prgn> to use the different
9419 settings every time the file is installed. Thus the
9420 package maintainer should distribute the files with their
9421 normal permissions, and leave it for the system
9422 administrator to make any desired changes. For example, a
9423 daemon which is normally required to be setuid root, but
9424 in certain situations could be used without being setuid,
9425 should be installed setuid in the <tt>.deb</tt>. Then the
9426 local system administrator can change this if they wish.
9427 If there are two standard ways of doing it, the package
9428 maintainer can use <tt>debconf</tt> to find out the
9429 preference, and call <prgn>dpkg-statoverride</prgn> in the
9430 maintainer script if necessary to accommodate the system
9431 administrator's choice. Care must be taken during
9432 upgrades to not override an existing setting.
9436 Given the above, <prgn>dpkg-statoverride</prgn> is
9437 essentially a tool for system administrators and would not
9438 normally be needed in the maintainer scripts. There is
9439 one type of situation, though, where calls to
9440 <prgn>dpkg-statoverride</prgn> would be needed in the
9441 maintainer scripts, and that involves packages which use
9442 dynamically allocated user or group ids. In such a
9443 situation, something like the following idiom can be very
9444 helpful in the package's <prgn>postinst</prgn>, where
9445 <tt>sysuser</tt> is a dynamically allocated id:
9447 for i in /usr/bin/foo /usr/sbin/bar
9449 # only do something when no setting exists
9450 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9452 #include: debconf processing, question about foo and bar
9453 if [ "$RET" = "true" ] ; then
9454 dpkg-statoverride --update --add sysuser root 4755 $i
9459 The corresponding code to remove the override when the package
9462 for i in /usr/bin/foo /usr/sbin/bar
9464 if dpkg-statoverride --list $i >/dev/null 2>&1
9466 dpkg-statoverride --remove $i
9476 <chapt id="customized-programs">
9477 <heading>Customized programs</heading>
9479 <sect id="arch-spec">
9480 <heading>Architecture specification strings</heading>
9483 If a program needs to specify an <em>architecture specification
9484 string</em> in some place, it should select one of the strings
9485 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9486 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9487 part is sometimes elided, as when the OS is Linux.
9491 Note that we don't want to use
9492 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9493 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9494 since this would make our programs incompatible with other
9495 Linux distributions. We also don't use something like
9496 <tt><var>arch</var>-unknown-linux</tt>, since the
9497 <tt>unknown</tt> does not look very good.
9500 <sect1 id="arch-wildcard-spec">
9501 <heading>Architecture wildcards</heading>
9504 A package may specify an architecture wildcard. Architecture
9505 wildcards are in the format <tt>any</tt> (which matches every
9506 architecture), <tt><var>os</var></tt>-any, or
9507 any-<tt><var>cpu</var></tt>. <footnote>
9508 Internally, the package system normalizes the GNU triplets
9509 and the Debian arches into Debian arch triplets (which are
9510 kind of inverted GNU triplets), with the first component of
9511 the triplet representing the libc and ABI in use, and then
9512 does matching against those triplets. However, such
9513 triplets are an internal implementation detail that should
9514 not be used by packages directly. The libc and ABI portion
9515 is handled internally by the package system based on
9516 the <var>os</var> and <var>cpu</var>.
9523 <heading>Daemons</heading>
9526 The configuration files <file>/etc/services</file>,
9527 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9528 by the <prgn>netbase</prgn> package and must not be modified
9533 If a package requires a new entry in one of these files, the
9534 maintainer should get in contact with the
9535 <prgn>netbase</prgn> maintainer, who will add the entries
9536 and release a new version of the <prgn>netbase</prgn>
9541 The configuration file <file>/etc/inetd.conf</file> must not be
9542 modified by the package's scripts except via the
9543 <prgn>update-inetd</prgn> script or the
9544 <file>DebianNet.pm</file> Perl module. See their documentation
9545 for details on how to add entries.
9549 If a package wants to install an example entry into
9550 <file>/etc/inetd.conf</file>, the entry must be preceded with
9551 exactly one hash character (<tt>#</tt>). Such lines are
9552 treated as "commented out by user" by the
9553 <prgn>update-inetd</prgn> script and are not changed or
9554 activated during package updates.
9559 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9563 Some programs need to create pseudo-ttys. This should be done
9564 using Unix98 ptys if the C library supports it. The resulting
9565 program must not be installed setuid root, unless that
9566 is required for other functionality.
9570 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9571 <file>/var/log/lastlog</file> must be installed writable by
9572 group <tt>utmp</tt>. Programs which need to modify those
9573 files must be installed setgid <tt>utmp</tt>.
9578 <heading>Editors and pagers</heading>
9581 Some programs have the ability to launch an editor or pager
9582 program to edit or display a text document. Since there are
9583 lots of different editors and pagers available in the Debian
9584 distribution, the system administrator and each user should
9585 have the possibility to choose their preferred editor and
9590 In addition, every program should choose a good default
9591 editor/pager if none is selected by the user or system
9596 Thus, every program that launches an editor or pager must
9597 use the EDITOR or PAGER environment variable to determine
9598 the editor or pager the user wishes to use. If these
9599 variables are not set, the programs <file>/usr/bin/editor</file>
9600 and <file>/usr/bin/pager</file> should be used, respectively.
9604 These two files are managed through the <prgn>dpkg</prgn>
9605 "alternatives" mechanism. Every package providing an editor or
9606 pager must call the <prgn>update-alternatives</prgn> script to
9607 register as an alternative for <file>/usr/bin/editor</file>
9608 or <file>/usr/bin/pager</file> as appropriate. The alternative
9609 should have a slave alternative
9610 for <file>/usr/share/man/man1/editor.1.gz</file>
9611 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9612 corresponding manual page.
9616 If it is very hard to adapt a program to make use of the
9617 EDITOR or PAGER variables, that program may be configured to
9618 use <file>/usr/bin/sensible-editor</file> and
9619 <file>/usr/bin/sensible-pager</file> as the editor or pager
9620 program respectively. These are two scripts provided in the
9621 <package>sensible-utils</package> package that check the EDITOR
9622 and PAGER variables and launch the appropriate program, and fall
9623 back to <file>/usr/bin/editor</file>
9624 and <file>/usr/bin/pager</file> if the variable is not set.
9628 A program may also use the VISUAL environment variable to
9629 determine the user's choice of editor. If it exists, it
9630 should take precedence over EDITOR. This is in fact what
9631 <file>/usr/bin/sensible-editor</file> does.
9635 It is not required for a package to depend on
9636 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9637 package to provide such virtual packages.<footnote>
9638 The Debian base system already provides an editor and a
9644 <sect id="web-appl">
9645 <heading>Web servers and applications</heading>
9648 This section describes the locations and URLs that should
9649 be used by all web servers and web applications in the
9656 Cgi-bin executable files are installed in the
9658 <example compact="compact">
9659 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9661 or a subdirectory of that directory, and should be
9663 <example compact="compact">
9664 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9666 (possibly with a subdirectory name
9667 before <var>cgi-bin-name</var>).
9671 <p>Access to HTML documents</p>
9674 HTML documents for a package are stored in
9675 <file>/usr/share/doc/<var>package</var></file>
9676 and can be referred to as
9677 <example compact="compact">
9678 http://localhost/doc/<var>package</var>/<var>filename</var>
9683 The web server should restrict access to the document
9684 tree so that only clients on the same host can read
9685 the documents. If the web server does not support such
9686 access controls, then it should not provide access at
9687 all, or ask about providing access during installation.
9692 <p>Access to images</p>
9694 It is recommended that images for a package be stored
9695 in <tt>/usr/share/images/<var>package</var></tt> and
9696 may be referred to through an alias <tt>/images/</tt>
9699 http://localhost/images/<package>/<filename>
9706 <p>Web Document Root</p>
9709 Web Applications should try to avoid storing files in
9710 the Web Document Root. Instead they should use the
9711 /usr/share/doc/<var>package</var> directory for
9712 documents and register the Web Application via the
9713 <package>doc-base</package> package. If access to the
9714 web document root is unavoidable then use
9715 <example compact="compact">
9718 as the Document Root. This might be just a symbolic
9719 link to the location where the system administrator
9720 has put the real document root.
9723 <item><p>Providing httpd and/or httpd-cgi</p>
9725 All web servers should provide the virtual package
9726 <tt>httpd</tt>. If a web server has CGI support it should
9727 provide <tt>httpd-cgi</tt> additionally.
9730 All web applications which do not contain CGI scripts should
9731 depend on <tt>httpd</tt>, all those web applications which
9732 <tt>do</tt> contain CGI scripts, should depend on
9740 <sect id="mail-transport-agents">
9741 <heading>Mail transport, delivery and user agents</heading>
9744 Debian packages which process electronic mail, whether mail
9745 user agents (MUAs) or mail transport agents (MTAs), must
9746 ensure that they are compatible with the configuration
9747 decisions below. Failure to do this may result in lost
9748 mail, broken <tt>From:</tt> lines, and other serious brain
9753 The mail spool is <file>/var/mail</file> and the interface to
9754 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9755 the FHS). On older systems, the mail spool may be
9756 physically located in <file>/var/spool/mail</file>, but all
9757 access to the mail spool should be via the
9758 <file>/var/mail</file> symlink. The mail spool is part of the
9759 base system and not part of the MTA package.
9763 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9764 programs (such as IMAP daemons) must lock the mailbox in an
9765 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9766 be combined with dot locking. To avoid deadlocks, a program
9767 should use <tt>fcntl()</tt> first and dot locking after
9768 this, or alternatively implement the two locking methods in
9769 a non blocking way<footnote>
9770 If it is not possible to establish both locks, the
9771 system shouldn't wait for the second lock to be
9772 established, but remove the first lock, wait a (random)
9773 time, and start over locking again.
9774 </footnote>. Using the functions <tt>maillock</tt> and
9775 <tt>mailunlock</tt> provided by the
9776 <tt>liblockfile*</tt><footnote>
9777 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9778 to use these functions.
9779 </footnote> packages is the recommended way to realize this.
9783 Mailboxes are generally either mode 600 and owned by
9784 <var>user</var> or mode 660 and owned by
9785 <tt><var>user</var>:mail</tt><footnote>
9786 There are two traditional permission schemes for mail spools:
9787 mode 600 with all mail delivery done by processes running as
9788 the destination user, or mode 660 and owned by group mail with
9789 mail delivery done by a process running as a system user in
9790 group mail. Historically, Debian required mode 660 mail
9791 spools to enable the latter model, but that model has become
9792 increasingly uncommon and the principle of least privilege
9793 indicates that mail systems that use the first model should
9794 use permissions of 600. If delivery to programs is permitted,
9795 it's easier to keep the mail system secure if the delivery
9796 agent runs as the destination user. Debian Policy therefore
9797 permits either scheme.
9798 </footnote>. The local system administrator may choose a
9799 different permission scheme; packages should not make
9800 assumptions about the permission and ownership of mailboxes
9801 unless required (such as when creating a new mailbox). A MUA
9802 may remove a mailbox (unless it has nonstandard permissions) in
9803 which case the MTA or another MUA must recreate it if needed.
9807 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9808 be setgid mail to do the locking mentioned above (and
9809 must obviously avoid accessing other users' mailboxes
9810 using this privilege).</p>
9813 <file>/etc/aliases</file> is the source file for the system mail
9814 aliases (e.g., postmaster, usenet, etc.), it is the one
9815 which the sysadmin and <prgn>postinst</prgn> scripts may
9816 edit. After <file>/etc/aliases</file> is edited the program or
9817 human editing it must call <prgn>newaliases</prgn>. All MTA
9818 packages must come with a <prgn>newaliases</prgn> program,
9819 even if it does nothing, but older MTA packages did not do
9820 this so programs should not fail if <prgn>newaliases</prgn>
9821 cannot be found. Note that because of this, all MTA
9822 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9823 <tt>Replaces: mail-transport-agent</tt> control fields.
9827 The convention of writing <tt>forward to
9828 <var>address</var></tt> in the mailbox itself is not
9829 supported. Use a <tt>.forward</tt> file instead.</p>
9832 The <prgn>rmail</prgn> program used by UUCP
9833 for incoming mail should be <file>/usr/sbin/rmail</file>.
9834 Likewise, <prgn>rsmtp</prgn>, for receiving
9835 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9839 If your package needs to know what hostname to use on (for
9840 example) outgoing news and mail messages which are generated
9841 locally, you should use the file <file>/etc/mailname</file>. It
9842 will contain the portion after the username and <tt>@</tt>
9843 (at) sign for email addresses of users on the machine
9844 (followed by a newline).
9848 Such a package should check for the existence of this file
9849 when it is being configured. If it exists, it should be
9850 used without comment, although an MTA's configuration script
9851 may wish to prompt the user even if it finds that this file
9852 exists. If the file does not exist, the package should
9853 prompt the user for the value (preferably using
9854 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9855 as well as using it in the package's configuration. The
9856 prompt should make it clear that the name will not just be
9857 used by that package. For example, in this situation the
9858 <tt>inn</tt> package could say something like:
9859 <example compact="compact">
9860 Please enter the "mail name" of your system. This is the
9861 hostname portion of the address to be shown on outgoing
9862 news and mail messages. The default is
9863 <var>syshostname</var>, your system's host name. Mail
9864 name ["<var>syshostname</var>"]:
9866 where <var>syshostname</var> is the output of <tt>hostname
9872 <heading>News system configuration</heading>
9875 All the configuration files related to the NNTP (news)
9876 servers and clients should be located under
9877 <file>/etc/news</file>.</p>
9880 There are some configuration issues that apply to a number
9881 of news clients and server packages on the machine. These
9885 <tag><file>/etc/news/organization</file></tag>
9887 A string which should appear as the
9888 organization header for all messages posted
9889 by NNTP clients on the machine
9892 <tag><file>/etc/news/server</file></tag>
9894 Contains the FQDN of the upstream NNTP
9895 server, or localhost if the local machine is
9900 Other global files may be added as required for cross-package news
9907 <heading>Programs for the X Window System</heading>
9910 <heading>Providing X support and package priorities</heading>
9913 Programs that can be configured with support for the X
9914 Window System must be configured to do so and must declare
9915 any package dependencies necessary to satisfy their
9916 runtime requirements when using the X Window System. If
9917 such a package is of higher priority than the X packages
9918 on which it depends, it is required that either the
9919 X-specific components be split into a separate package, or
9920 that an alternative version of the package, which includes
9921 X support, be provided, or that the package's priority be
9927 <heading>Packages providing an X server</heading>
9930 Packages that provide an X server that, directly or
9931 indirectly, communicates with real input and display
9932 hardware should declare in their <tt>Provides</tt> control
9933 field that they provide the virtual
9934 package <tt>xserver</tt>.<footnote>
9935 This implements current practice, and provides an
9936 actual policy for usage of the <tt>xserver</tt>
9937 virtual package which appears in the virtual packages
9938 list. In a nutshell, X servers that interface
9939 directly with the display and input hardware or via
9940 another subsystem (e.g., GGI) should provide
9941 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9942 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9948 <heading>Packages providing a terminal emulator</heading>
9951 Packages that provide a terminal emulator for the X Window
9952 System which meet the criteria listed below should declare in
9953 their <tt>Provides</tt> control field that they provide the
9954 virtual package <tt>x-terminal-emulator</tt>. They should
9955 also register themselves as an alternative for
9956 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9957 20. That alternative should have a slave alternative
9958 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9959 pointing to the corresponding manual page.
9963 To be an <tt>x-terminal-emulator</tt>, a program must:
9964 <list compact="compact">
9966 Be able to emulate a DEC VT100 terminal, or a
9967 compatible terminal.
9971 Support the command-line option <tt>-e
9972 <var>command</var></tt>, which creates a new
9973 terminal window<footnote>
9974 "New terminal window" does not necessarily mean
9975 a new top-level X window directly parented by
9976 the window manager; it could, if the terminal
9977 emulator application were so coded, be a new
9978 "view" in a multiple-document interface (MDI).
9980 and runs the specified <var>command</var>,
9981 interpreting the entirety of the rest of the command
9982 line as a command to pass straight to exec, in the
9983 manner that <tt>xterm</tt> does.
9987 Support the command-line option <tt>-T
9988 <var>title</var></tt>, which creates a new terminal
9989 window with the window title <var>title</var>.
9996 <heading>Packages providing a window manager</heading>
9999 Packages that provide a window manager should declare in
10000 their <tt>Provides</tt> control field that they provide the
10001 virtual package <tt>x-window-manager</tt>. They should also
10002 register themselves as an alternative for
10003 <file>/usr/bin/x-window-manager</file>, with a priority
10004 calculated as follows:
10005 <list compact="compact">
10007 Start with a priority of 20.
10011 If the window manager supports the Debian menu
10012 system, add 20 points if this support is available
10013 in the package's default configuration (i.e., no
10014 configuration files belonging to the system or user
10015 have to be edited to activate the feature); if
10016 configuration files must be modified, add only 10
10022 If the window manager complies with <url
10023 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10024 name="The Window Manager Specification Project">,
10025 written by the <url id="http://www.freedesktop.org/wiki/"
10026 name="Free Desktop Group">, add 40 points.
10030 If the window manager permits the X session to be
10031 restarted using a <em>different</em> window manager
10032 (without killing the X server) in its default
10033 configuration, add 10 points; otherwise add none.
10036 That alternative should have a slave alternative
10037 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10038 pointing to the corresponding manual page.
10043 <heading>Packages providing fonts</heading>
10046 Packages that provide fonts for the X Window
10048 For the purposes of Debian Policy, a "font for the X
10049 Window System" is one which is accessed via X protocol
10050 requests. Fonts for the Linux console, for PostScript
10051 renderer, or any other purpose, do not fit this
10052 definition. Any tool which makes such fonts available
10053 to the X Window System, however, must abide by this
10056 must do a number of things to ensure that they are both
10057 available without modification of the X or font server
10058 configuration, and that they do not corrupt files used by
10059 other font packages to register information about
10063 Fonts of any type supported by the X Window System
10064 must be in a separate binary package from any
10065 executables, libraries, or documentation (except
10066 that specific to the fonts shipped, such as their
10067 license information). If one or more of the fonts
10068 so packaged are necessary for proper operation of
10069 the package with which they are associated the font
10070 package may be Recommended; if the fonts merely
10071 provide an enhancement, a Suggests relationship may
10072 be used. Packages must not Depend on font
10073 packages.<footnote>
10074 This is because the X server may retrieve fonts
10075 from the local file system or over the network
10076 from an X font server; the Debian package system
10077 is empowered to deal only with the local
10083 BDF fonts must be converted to PCF fonts with the
10084 <prgn>bdftopcf</prgn> utility (available in the
10085 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10086 placed in a directory that corresponds to their
10088 <list compact="compact">
10090 100 dpi fonts must be placed in
10091 <file>/usr/share/fonts/X11/100dpi/</file>.
10095 75 dpi fonts must be placed in
10096 <file>/usr/share/fonts/X11/75dpi/</file>.
10100 Character-cell fonts, cursor fonts, and other
10101 low-resolution fonts must be placed in
10102 <file>/usr/share/fonts/X11/misc/</file>.
10108 Type 1 fonts must be placed in
10109 <file>/usr/share/fonts/X11/Type1/</file>. If font
10110 metric files are available, they must be placed here
10115 Subdirectories of <file>/usr/share/fonts/X11/</file>
10116 other than those listed above must be neither
10117 created nor used. (The <file>PEX</file>, <file>CID</file>,
10118 <file>Speedo</file>, and <file>cyrillic</file> directories
10119 are excepted for historical reasons, but installation of
10120 files into these directories remains discouraged.)
10124 Font packages may, instead of placing files directly
10125 in the X font directories listed above, provide
10126 symbolic links in that font directory pointing to
10127 the files' actual location in the filesystem. Such
10128 a location must comply with the FHS.
10132 Font packages should not contain both 75dpi and
10133 100dpi versions of a font. If both are available,
10134 they should be provided in separate binary packages
10135 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10136 the names of the packages containing the
10137 corresponding fonts.
10141 Fonts destined for the <file>misc</file> subdirectory
10142 should not be included in the same package as 75dpi
10143 or 100dpi fonts; instead, they should be provided in
10144 a separate package with <tt>-misc</tt> appended to
10149 Font packages must not provide the files
10150 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10151 <file>fonts.scale</file> in a font directory:
10154 <file>fonts.dir</file> files must not be provided at all.
10158 <file>fonts.alias</file> and <file>fonts.scale</file>
10159 files, if needed, should be provided in the
10161 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10162 where <var>fontdir</var> is the name of the
10164 <file>/usr/share/fonts/X11/</file> where the
10165 package's corresponding fonts are stored
10166 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10167 <var>package</var> is the name of the package
10168 that provides these fonts, and
10169 <var>extension</var> is either <tt>scale</tt>
10170 or <tt>alias</tt>, whichever corresponds to
10177 Font packages must declare a dependency on
10178 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10179 or <tt>Pre-Depends</tt> control field.
10183 Font packages that provide one or more
10184 <file>fonts.scale</file> files as described above must
10185 invoke <prgn>update-fonts-scale</prgn> on each
10186 directory into which they installed fonts
10187 <em>before</em> invoking
10188 <prgn>update-fonts-dir</prgn> on that directory.
10189 This invocation must occur in both the
10190 <prgn>postinst</prgn> (for all arguments) and
10191 <prgn>postrm</prgn> (for all arguments except
10192 <tt>upgrade</tt>) scripts.
10196 Font packages that provide one or more
10197 <file>fonts.alias</file> files as described above must
10198 invoke <prgn>update-fonts-alias</prgn> on each
10199 directory into which they installed fonts. This
10200 invocation must occur in both the
10201 <prgn>postinst</prgn> (for all arguments) and
10202 <prgn>postrm</prgn> (for all arguments except
10203 <tt>upgrade</tt>) scripts.
10207 Font packages must invoke
10208 <prgn>update-fonts-dir</prgn> on each directory into
10209 which they installed fonts. This invocation must
10210 occur in both the <prgn>postinst</prgn> (for all
10211 arguments) and <prgn>postrm</prgn> (for all
10212 arguments except <tt>upgrade</tt>) scripts.
10216 Font packages must not provide alias names for the
10217 fonts they include which collide with alias names
10218 already in use by fonts already packaged.
10222 Font packages must not provide fonts with the same
10223 XLFD registry name as another font already packaged.
10229 <sect1 id="appdefaults">
10230 <heading>Application defaults files</heading>
10233 Application defaults files must be installed in the
10234 directory <file>/etc/X11/app-defaults/</file> (use of a
10235 localized subdirectory of <file>/etc/X11/</file> as described
10236 in the <em>X Toolkit Intrinsics - C Language
10237 Interface</em> manual is also permitted). They must be
10238 registered as <tt>conffile</tt>s or handled as
10239 configuration files.
10243 Customization of programs' X resources may also be
10244 supported with the provision of a file with the same name
10245 as that of the package placed in
10246 the <file>/etc/X11/Xresources/</file> directory, which
10247 must be registered as a <tt>conffile</tt> or handled as a
10248 configuration file.<footnote>
10249 Note that this mechanism is not the same as using
10250 app-defaults; app-defaults are tied to the client
10251 binary on the local file system, whereas X resources
10252 are stored in the X server and affect all connecting
10259 <heading>Installation directory issues</heading>
10262 Historically, packages using the X Window System used a
10263 separate set of installation directories from other packages.
10264 This practice has been discontinued and packages using the X
10265 Window System should now generally be installed in the same
10266 directories as any other package. Specifically, packages must
10267 not install files under the <file>/usr/X11R6/</file> directory
10268 and the <file>/usr/X11R6/</file> directory hierarchy should be
10269 regarded as obsolete.
10273 Include files previously installed under
10274 <file>/usr/X11R6/include/X11/</file> should be installed into
10275 <file>/usr/include/X11/</file>. For files previously
10276 installed into subdirectories of
10277 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10278 determine if subdirectories of <file>/usr/lib/</file> and
10279 <file>/usr/share/</file> can be used. If not, a subdirectory
10280 of <file>/usr/lib/X11/</file> should be used.
10284 Configuration files for window, display, or session managers
10285 or other applications that are tightly integrated with the X
10286 Window System may be placed in a subdirectory
10287 of <file>/etc/X11/</file> corresponding to the package name.
10288 Other X Window System applications should use
10289 the <file>/etc/</file> directory unless otherwise mandated by
10290 policy (such as for <ref id="appdefaults">).
10296 <heading>Perl programs and modules</heading>
10299 Perl programs and modules should follow the current Perl policy.
10303 The Perl policy can be found in the <tt>perl-policy</tt>
10304 files in the <tt>debian-policy</tt> package.
10305 It is also available from the Debian web mirrors at
10306 <tt><url name="/doc/packaging-manuals/perl-policy/"
10307 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10312 <heading>Emacs lisp programs</heading>
10315 Please refer to the "Debian Emacs Policy" for details of how to
10316 package emacs lisp programs.
10320 The Emacs policy is available in
10321 <file>debian-emacs-policy.gz</file> of the
10322 <package>emacsen-common</package> package.
10323 It is also available from the Debian web mirrors at
10324 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10325 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10330 <heading>Games</heading>
10333 The permissions on <file>/var/games</file> are mode 755, owner
10334 <tt>root</tt> and group <tt>root</tt>.
10338 Each game decides on its own security policy.</p>
10341 Games which require protected, privileged access to
10342 high-score files, saved games, etc., may be made
10343 set-<em>group</em>-id (mode 2755) and owned by
10344 <tt>root:games</tt>, and use files and directories with
10345 appropriate permissions (770 <tt>root:games</tt>, for
10346 example). They must not be made
10347 set-<em>user</em>-id, as this causes security problems. (If
10348 an attacker can subvert any set-user-id game they can
10349 overwrite the executable of any other, causing other players
10350 of these games to run a Trojan horse program. With a
10351 set-group-id game the attacker only gets access to less
10352 important game data, and if they can get at the other
10353 players' accounts at all it will take considerably more
10357 Some packages, for example some fortune cookie programs, are
10358 configured by the upstream authors to install with their
10359 data files or other static information made unreadable so
10360 that they can only be accessed through set-id programs
10361 provided. You should not do this in a Debian package: anyone can
10362 download the <file>.deb</file> file and read the data from it,
10363 so there is no point making the files unreadable. Not
10364 making the files unreadable also means that you don't have
10365 to make so many programs set-id, which reduces the risk of a
10369 As described in the FHS, binaries of games should be
10370 installed in the directory <file>/usr/games</file>. This also
10371 applies to games that use the X Window System. Manual pages
10372 for games (X and non-X games) should be installed in
10373 <file>/usr/share/man/man6</file>.</p>
10379 <heading>Documentation</heading>
10382 <heading>Manual pages</heading>
10385 You should install manual pages in <prgn>nroff</prgn> source
10386 form, in appropriate places under <file>/usr/share/man</file>.
10387 You should only use sections 1 to 9 (see the FHS for more
10388 details). You must not install a pre-formatted "cat page".
10392 Each program, utility, and function should have an
10393 associated manual page included in the same package. It is
10394 suggested that all configuration files also have a manual
10395 page included as well. Manual pages for protocols and other
10396 auxiliary things are optional.
10400 If no manual page is available, this is considered as a bug
10401 and should be reported to the Debian Bug Tracking System (the
10402 maintainer of the package is allowed to write this bug report
10403 themselves, if they so desire). Do not close the bug report
10404 until a proper man page is available.<footnote>
10405 It is not very hard to write a man page. See the
10406 <url id="http://www.schweikhardt.net/man_page_howto.html"
10407 name="Man-Page-HOWTO">,
10408 <manref name="man" section="7">, the examples created
10409 by <prgn>dh_make</prgn>, the helper
10410 program <prgn>help2man</prgn>, or the
10411 directory <file>/usr/share/doc/man-db/examples</file>.
10416 You may forward a complaint about a missing man page to the
10417 upstream authors, and mark the bug as forwarded in the
10418 Debian bug tracking system. Even though the GNU Project do
10419 not in general consider the lack of a man page to be a bug,
10420 we do; if they tell you that they don't consider it a bug
10421 you should leave the bug in our bug tracking system open
10426 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10430 If one man page needs to be accessible via several names it
10431 is better to use a symbolic link than the <file>.so</file>
10432 feature, but there is no need to fiddle with the relevant
10433 parts of the upstream source to change from <file>.so</file> to
10434 symlinks: don't do it unless it's easy. You should not
10435 create hard links in the manual page directories, nor put
10436 absolute filenames in <file>.so</file> directives. The filename
10437 in a <file>.so</file> in a man page should be relative to the
10438 base of the man page tree (usually
10439 <file>/usr/share/man</file>). If you do not create any links
10440 (whether symlinks, hard links, or <tt>.so</tt> directives)
10441 in the file system to the alternate names of the man page,
10442 then you should not rely on <prgn>man</prgn> finding your
10443 man page under those names based solely on the information in
10444 the man page's header.<footnote>
10445 Supporting this in <prgn>man</prgn> often requires
10446 unreasonable processing time to find a manual page or to
10447 report that none exists, and moves knowledge into man's
10448 database that would be better left in the file system.
10449 This support is therefore deprecated and will cease to
10450 be present in the future.
10455 Manual pages in locale-specific subdirectories of
10456 <file>/usr/share/man</file> should use either UTF-8 or the usual
10457 legacy encoding for that language (normally the one corresponding
10458 to the shortest relevant locale name in
10459 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10460 <file>/usr/share/man/fr</file> should use either UTF-8 or
10461 ISO-8859-1.<footnote>
10462 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10463 use. In future, all manual pages will be required to use
10469 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10470 included in the subdirectory name unless it indicates a
10471 significant difference in the language, as this excludes
10472 speakers of the language in other countries.<footnote>
10473 At the time of writing, Chinese and Portuguese are the main
10474 languages with such differences, so <file>pt_BR</file>,
10475 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10480 If a localized version of a manual page is provided, it should
10481 either be up-to-date or it should be obvious to the reader that
10482 it is outdated and the original manual page should be used
10483 instead. This can be done either by a note at the beginning of
10484 the manual page or by showing the missing or changed portions in
10485 the original language instead of the target language.
10490 <heading>Info documents</heading>
10493 Info documents should be installed in <file>/usr/share/info</file>.
10494 They should be compressed with <tt>gzip -9</tt>.
10498 The <prgn>install-info</prgn> program maintains a directory of
10499 installed info documents in <file>/usr/share/info/dir</file> for the
10500 use of info readers. This file must not be included in packages
10501 other than <package>install-info</package>.
10505 <prgn>install-info</prgn> is automatically invoked when
10506 appropriate using dpkg triggers. Packages other than
10507 <package>install-info</package> <em>should not</em> invoke
10508 <prgn>install-info</prgn> directly and <em>should not</em>
10509 depend on, recommend, or suggest <package>install-info</package>
10514 Info readers requiring the <file>/usr/share/info/dir</file> file
10515 should depend on <package>install-info</package>.
10519 Info documents should contain section and directory entry
10520 information in the document for the use
10521 of <prgn>install-info</prgn>. The section should be specified
10522 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10523 space and the section of this info page. The directory entry or
10524 entries should be included between
10525 a <tt>START-INFO-DIR-ENTRY</tt> line and
10526 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10528 INFO-DIR-SECTION Individual utilities
10529 START-INFO-DIR-ENTRY
10530 * example: (example). An example info directory entry.
10533 To determine which section to use, you should look
10534 at <file>/usr/share/info/dir</file> on your system and choose
10535 the most relevant (or create a new section if none of the
10536 current sections are relevant).<footnote>
10537 Normally, info documents are generated from Texinfo source.
10538 To include this information in the generated info document, if
10539 it is absent, add commands like:
10541 @dircategory Individual utilities
10543 * example: (example). An example info directory entry.
10546 to the Texinfo source of the document and ensure that the info
10547 documents are rebuilt from source during the package build.
10553 <heading>Additional documentation</heading>
10556 Any additional documentation that comes with the package may
10557 be installed at the discretion of the package maintainer.
10558 Plain text documentation should be installed in the directory
10559 <file>/usr/share/doc/<var>package</var></file>, where
10560 <var>package</var> is the name of the package, and
10561 compressed with <tt>gzip -9</tt> unless it is small.
10565 If a package comes with large amounts of documentation which
10566 many users of the package will not require you should create
10567 a separate binary package to contain it, so that it does not
10568 take up disk space on the machines of users who do not need
10569 or want it installed.</p>
10572 It is often a good idea to put text information files
10573 (<file>README</file>s, changelogs, and so forth) that come with
10574 the source package in <file>/usr/share/doc/<var>package</var></file>
10575 in the binary package. However, you don't need to install
10576 the instructions for building and installing the package, of
10580 Packages must not require the existence of any files in
10581 <file>/usr/share/doc/</file> in order to function
10583 The system administrator should be able to
10584 delete files in <file>/usr/share/doc/</file> without causing
10585 any programs to break.
10587 Any files that are referenced by programs but are also
10588 useful as stand alone documentation should be installed under
10589 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10590 <file>/usr/share/doc/<var>package</var></file>.
10594 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10595 link to another directory in <file>/usr/share/doc</file> only if
10596 the two packages both come from the same source and the
10597 first package Depends on the second.<footnote>
10599 Please note that this does not override the section on
10600 changelog files below, so the file
10601 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10602 must refer to the changelog for the current version of
10603 <var>package</var> in question. In practice, this means
10604 that the sources of the target and the destination of the
10605 symlink must be the same (same source package and
10612 Former Debian releases placed all additional documentation
10613 in <file>/usr/doc/<var>package</var></file>. This has been
10614 changed to <file>/usr/share/doc/<var>package</var></file>,
10615 and packages must not put documentation in the directory
10616 <file>/usr/doc/<var>package</var></file>. <footnote>
10617 At this phase of the transition, we no longer require a
10618 symbolic link in <file>/usr/doc/</file>. At a later point,
10619 policy shall change to make the symbolic links a bug.
10625 <heading>Preferred documentation formats</heading>
10628 The unification of Debian documentation is being carried out
10632 If your package comes with extensive documentation in a
10633 markup format that can be converted to various other formats
10634 you should if possible ship HTML versions in a binary
10635 package, in the directory
10636 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10637 its subdirectories.<footnote>
10638 The rationale: The important thing here is that HTML
10639 docs should be available in <em>some</em> package, not
10640 necessarily in the main binary package.
10645 Other formats such as PostScript may be provided at the
10646 package maintainer's discretion.
10650 <sect id="copyrightfile">
10651 <heading>Copyright information</heading>
10654 Every package must be accompanied by a verbatim copy of its
10655 copyright information and distribution license in the file
10656 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10657 file must neither be compressed nor be a symbolic link.
10661 In addition, the copyright file must say where the upstream
10662 sources (if any) were obtained, and should name the original
10667 Packages in the <em>contrib</em> or <em>non-free</em> archive
10668 areas should state in the copyright file that the package is not
10669 part of the Debian distribution and briefly explain why.
10673 A copy of the file which will be installed in
10674 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10675 be in <file>debian/copyright</file> in the source package.
10679 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10680 link to another directory in <file>/usr/share/doc</file> only if
10681 the two packages both come from the same source and the
10682 first package Depends on the second. These rules are important
10683 because <file>copyright</file> files must be extractable by
10688 Packages distributed under the Apache license (version 2.0), the
10689 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10690 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10691 1.3) should refer to the corresponding files
10692 under <file>/usr/share/common-licenses</file>,<footnote>
10695 <file>/usr/share/common-licenses/Apache-2.0</file>,
10696 <file>/usr/share/common-licenses/Artistic</file>,
10697 <file>/usr/share/common-licenses/GPL-1</file>,
10698 <file>/usr/share/common-licenses/GPL-2</file>,
10699 <file>/usr/share/common-licenses/GPL-3</file>,
10700 <file>/usr/share/common-licenses/LGPL-2</file>,
10701 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10702 <file>/usr/share/common-licenses/LGPL-3</file>,
10703 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10704 <file>/usr/share/common-licenses/GFDL-1.3</file>
10705 respectively. The University of California BSD license is
10706 also included in <package>base-files</package> as
10707 <file>/usr/share/common-licenses/BSD</file>, but given the
10708 brevity of this license, its specificity to code whose
10709 copyright is held by the Regents of the University of
10710 California, and the frequency of minor wording changes, its
10711 text should be included in the copyright file rather than
10712 referencing this file.
10714 </footnote> rather than quoting them in the copyright
10719 You should not use the copyright file as a general <file>README</file>
10720 file. If your package has such a file it should be
10721 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10722 <file>README.Debian</file> or some other appropriate place.
10726 All copyright files must be encoded in UTF-8.
10729 <sect1 id="copyrightformat">
10730 <heading>Machine-readable copyright information</heading>
10733 A specification for a standard, machine-readable format
10734 for <file>debian/copyright</file> files is maintained as part
10735 of the <package>debian-policy</package> package. This
10736 document may be found in the <file>copyright-format</file>
10737 files in the <package>debian-policy</package> package. It is
10738 also available from the Debian web mirrors at
10739 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10740 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10744 Use of this format is optional.
10750 <heading>Examples</heading>
10753 Any examples (configurations, source files, whatever),
10754 should be installed in a directory
10755 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10756 files should not be referenced by any program: they're there
10757 for the benefit of the system administrator and users as
10758 documentation only. Architecture-specific example files
10759 should be installed in a directory
10760 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10762 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10763 latter directory itself may be a symbolic link to the
10768 If the purpose of a package is to provide examples, then the
10769 example files may be installed into
10770 <file>/usr/share/doc/<var>package</var></file>.
10774 <sect id="changelogs">
10775 <heading>Changelog files</heading>
10778 Packages that are not Debian-native must contain a
10779 compressed copy of the <file>debian/changelog</file> file from
10780 the Debian source tree in
10781 <file>/usr/share/doc/<var>package</var></file> with the name
10782 <file>changelog.Debian.gz</file>.
10786 If an upstream changelog is available, it should be accessible as
10787 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10788 plain text. If the upstream changelog is distributed in
10789 HTML, it should be made available in that form as
10790 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10791 and a plain text <file>changelog.gz</file> should be generated
10792 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10793 the upstream changelog files do not already conform to this
10794 naming convention, then this may be achieved either by
10795 renaming the files, or by adding a symbolic link, at the
10796 maintainer's discretion.<footnote>
10797 Rationale: People should not have to look in places for
10798 upstream changelogs merely because they are given
10799 different names or are distributed in HTML format.
10804 All of these files should be installed compressed using
10805 <tt>gzip -9</tt>, as they will become large with time even
10806 if they start out small.
10810 If the package has only one changelog which is used both as
10811 the Debian changelog and the upstream one because there is
10812 no separate upstream maintainer then that changelog should
10813 usually be installed as
10814 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10815 there is a separate upstream maintainer, but no upstream
10816 changelog, then the Debian changelog should still be called
10817 <file>changelog.Debian.gz</file>.
10821 For details about the format and contents of the Debian
10822 changelog file, please see <ref id="dpkgchangelog">.
10827 <appendix id="pkg-scope">
10828 <heading>Introduction and scope of these appendices</heading>
10831 These appendices are taken essentially verbatim from the
10832 now-deprecated Packaging Manual, version 3.2.1.0. They are
10833 the chapters which are likely to be of use to package
10834 maintainers and which have not already been included in the
10835 policy document itself. Most of these sections are very likely
10836 not relevant to policy; they should be treated as
10837 documentation for the packaging system. Please note that these
10838 appendices are included for convenience, and for historical
10839 reasons: they used to be part of policy package, and they have
10840 not yet been incorporated into dpkg documentation. However,
10841 they still have value, and hence they are presented here.
10845 They have not yet been checked to ensure that they are
10846 compatible with the contents of policy, and if there are any
10847 contradictions, the version in the main policy document takes
10848 precedence. The remaining chapters of the old Packaging
10849 Manual have also not been read in detail to ensure that there
10850 are not parts which have been left out. Both of these will be
10851 done in due course.
10855 Certain parts of the Packaging manual were integrated into the
10856 Policy Manual proper, and removed from the appendices. Links
10857 have been placed from the old locations to the new ones.
10861 <prgn>dpkg</prgn> is a suite of programs for creating binary
10862 package files and installing and removing them on Unix
10864 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10865 work on or be ported to other systems.
10870 The binary packages are designed for the management of
10871 installed executable programs (usually compiled binaries) and
10872 their associated data, though source code examples and
10873 documentation are provided as part of some packages.</p>
10876 This manual describes the technical aspects of creating Debian
10877 binary packages (<file>.deb</file> files). It documents the
10878 behavior of the package management programs
10879 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10880 they interact with packages.</p>
10883 This manual does not go into detail about the options and
10884 usage of the package building and installation tools. It
10885 should therefore be read in conjunction with those programs'
10890 The utility programs which are provided with <prgn>dpkg</prgn>
10891 not described in detail here, are documented in their man pages.
10895 It is assumed that the reader is reasonably familiar with the
10896 <prgn>dpkg</prgn> System Administrators' manual.
10897 Unfortunately this manual does not yet exist.
10901 The Debian version of the FSF's GNU hello program is provided as
10902 an example for people wishing to create Debian packages. However,
10903 while the examples are helpful, they do not replace the need to
10904 read and follow the Policy and Programmer's Manual.</p>
10907 <appendix id="pkg-binarypkg">
10908 <heading>Binary packages (from old Packaging Manual)</heading>
10911 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10914 <sect id="pkg-bincreating"><heading>Creating package files -
10915 <prgn>dpkg-deb</prgn>
10919 All manipulation of binary package files is done by
10920 <prgn>dpkg-deb</prgn>; it's the only program that has
10921 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10922 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10923 will spot that the options requested are appropriate to
10924 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10929 In order to create a binary package you must make a
10930 directory tree which contains all the files and directories
10931 you want to have in the file system data part of the package.
10932 In Debian-format source packages this directory is usually
10933 <file>debian/tmp</file>, relative to the top of the package's
10938 They should have the locations (relative to the root of the
10939 directory tree you're constructing) ownerships and
10940 permissions which you want them to have on the system when
10941 they are installed.
10945 With current versions of <prgn>dpkg</prgn> the uid/username
10946 and gid/groupname mappings for the users and groups being
10947 used should be the same on the system where the package is
10948 built and the one where it is installed.
10952 You need to add one special directory to the root of the
10953 miniature file system tree you're creating:
10954 <prgn>DEBIAN</prgn>. It should contain the control
10955 information files, notably the binary package control file
10956 (see <ref id="pkg-controlfile">).
10960 The <prgn>DEBIAN</prgn> directory will not appear in the
10961 file system archive of the package, and so won't be installed
10962 by <prgn>dpkg</prgn> when the package is unpacked.
10966 When you've prepared the package, you should invoke:
10968 dpkg --build <var>directory</var>
10973 This will build the package in
10974 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10975 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10976 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10977 build the package.)
10981 See the man page <manref name="dpkg-deb" section="8"> for details of how
10982 to examine the contents of this newly-created file. You may find the
10983 output of following commands enlightening:
10985 dpkg-deb --info <var>filename</var>.deb
10986 dpkg-deb --contents <var>filename</var>.deb
10987 dpkg --contents <var>filename</var>.deb
10989 To view the copyright file for a package you could use this command:
10991 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10996 <sect id="pkg-controlarea">
10997 <heading>Package control information files</heading>
11000 The control information portion of a binary package is a
11001 collection of files with names known to <prgn>dpkg</prgn>.
11002 It will treat the contents of these files specially - some
11003 of them contain information used by <prgn>dpkg</prgn> when
11004 installing or removing the package; others are scripts which
11005 the package maintainer wants <prgn>dpkg</prgn> to run.
11009 It is possible to put other files in the package control
11010 information file area, but this is not generally a good idea
11011 (though they will largely be ignored).
11015 Here is a brief list of the control information files supported
11016 by <prgn>dpkg</prgn> and a summary of what they're used for.
11021 <tag><tt>control</tt>
11024 This is the key description file used by
11025 <prgn>dpkg</prgn>. It specifies the package's name
11026 and version, gives its description for the user,
11027 states its relationships with other packages, and so
11028 forth. See <ref id="sourcecontrolfiles"> and
11029 <ref id="binarycontrolfiles">.
11033 It is usually generated automatically from information
11034 in the source package by the
11035 <prgn>dpkg-gencontrol</prgn> program, and with
11036 assistance from <prgn>dpkg-shlibdeps</prgn>.
11037 See <ref id="pkg-sourcetools">.
11041 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11046 These are executable files (usually scripts) which
11047 <prgn>dpkg</prgn> runs during installation, upgrade
11048 and removal of packages. They allow the package to
11049 deal with matters which are particular to that package
11050 or require more complicated processing than that
11051 provided by <prgn>dpkg</prgn>. Details of when and
11052 how they are called are in <ref id="maintainerscripts">.
11056 It is very important to make these scripts idempotent.
11057 See <ref id="idempotency">.
11061 The maintainer scripts are not guaranteed to run with a
11062 controlling terminal and may not be able to interact with
11063 the user. See <ref id="controllingterminal">.
11067 <tag><tt>conffiles</tt>
11070 This file contains a list of configuration files which
11071 are to be handled automatically by <prgn>dpkg</prgn>
11072 (see <ref id="pkg-conffiles">). Note that not necessarily
11073 every configuration file should be listed here.
11076 <tag><tt>shlibs</tt>
11079 This file contains a list of the shared libraries
11080 supplied by the package, with dependency details for
11081 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11082 when it determines what dependencies are required in a
11083 package control file. The <tt>shlibs</tt> file format
11084 is described on <ref id="shlibs">.
11089 <sect id="pkg-controlfile">
11090 <heading>The main control information file: <tt>control</tt></heading>
11093 The most important control information file used by
11094 <prgn>dpkg</prgn> when it installs a package is
11095 <tt>control</tt>. It contains all the package's "vital
11100 The binary package control files of packages built from
11101 Debian sources are made by a special tool,
11102 <prgn>dpkg-gencontrol</prgn>, which reads
11103 <file>debian/control</file> and <file>debian/changelog</file> to
11104 find the information it needs. See <ref id="pkg-sourcepkg"> for
11109 The fields in binary package control files are listed in
11110 <ref id="binarycontrolfiles">.
11114 A description of the syntax of control files and the purpose
11115 of the fields is available in <ref id="controlfields">.
11120 <heading>Time Stamps</heading>
11123 See <ref id="timestamps">.
11128 <appendix id="pkg-sourcepkg">
11129 <heading>Source packages (from old Packaging Manual) </heading>
11132 The Debian binary packages in the distribution are generated
11133 from Debian sources, which are in a special format to assist
11134 the easy and automatic building of binaries.
11137 <sect id="pkg-sourcetools">
11138 <heading>Tools for processing source packages</heading>
11141 Various tools are provided for manipulating source packages;
11142 they pack and unpack sources and help build of binary
11143 packages and help manage the distribution of new versions.
11147 They are introduced and typical uses described here; see
11148 <manref name="dpkg-source" section="1"> for full
11149 documentation about their arguments and operation.
11153 For examples of how to construct a Debian source package,
11154 and how to use those utilities that are used by Debian
11155 source packages, please see the <prgn>hello</prgn> example
11159 <sect1 id="pkg-dpkg-source">
11161 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11166 This program is frequently used by hand, and is also
11167 called from package-independent automated building scripts
11168 such as <prgn>dpkg-buildpackage</prgn>.
11172 To unpack a package it is typically invoked with
11174 dpkg-source -x <var>.../path/to/filename</var>.dsc
11179 with the <file><var>filename</var>.tar.gz</file> and
11180 <file><var>filename</var>.diff.gz</file> (if applicable) in
11181 the same directory. It unpacks into
11182 <file><var>package</var>-<var>version</var></file>, and if
11184 <file><var>package</var>-<var>version</var>.orig</file>, in
11185 the current directory.
11189 To create a packed source archive it is typically invoked:
11191 dpkg-source -b <var>package</var>-<var>version</var>
11196 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11197 <file>.diff.gz</file> (if appropriate) in the current
11198 directory. <prgn>dpkg-source</prgn> does not clean the
11199 source tree first - this must be done separately if it is
11204 See also <ref id="pkg-sourcearchives">.</p>
11208 <sect1 id="pkg-dpkg-buildpackage">
11210 <prgn>dpkg-buildpackage</prgn> - overall package-building
11215 See <manref name="dpkg-buildpackage" section="1">.
11219 <sect1 id="pkg-dpkg-gencontrol">
11221 <prgn>dpkg-gencontrol</prgn> - generates binary package
11226 This program is usually called from <file>debian/rules</file>
11227 (see <ref id="pkg-sourcetree">) in the top level of the source
11232 This is usually done just before the files and directories in the
11233 temporary directory tree where the package is being built have their
11234 permissions and ownerships set and the package is constructed using
11235 <prgn>dpkg-deb/</prgn>
11237 This is so that the control file which is produced has
11238 the right permissions
11243 <prgn>dpkg-gencontrol</prgn> must be called after all the
11244 files which are to go into the package have been placed in
11245 the temporary build directory, so that its calculation of
11246 the installed size of a package is correct.
11250 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11251 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11252 variable substitutions created by
11253 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11258 For a package which generates only one binary package, and
11259 which builds it in <file>debian/tmp</file> relative to the top
11260 of the source package, it is usually sufficient to call
11261 <prgn>dpkg-gencontrol</prgn>.
11265 Sources which build several binaries will typically need
11268 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11269 </example> The <tt>-P</tt> tells
11270 <prgn>dpkg-gencontrol</prgn> that the package is being
11271 built in a non-default directory, and the <tt>-p</tt>
11272 tells it which package's control file should be generated.
11276 <prgn>dpkg-gencontrol</prgn> also adds information to the
11277 list of files in <file>debian/files</file>, for the benefit of
11278 (for example) a future invocation of
11279 <prgn>dpkg-genchanges</prgn>.</p>
11282 <sect1 id="pkg-dpkg-shlibdeps">
11284 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11289 See <manref name="dpkg-shlibdeps" section="1">.
11293 <sect1 id="pkg-dpkg-distaddfile">
11295 <prgn>dpkg-distaddfile</prgn> - adds a file to
11296 <file>debian/files</file>
11300 Some packages' uploads need to include files other than
11301 the source and binary package files.
11305 <prgn>dpkg-distaddfile</prgn> adds a file to the
11306 <file>debian/files</file> file so that it will be included in
11307 the <file>.changes</file> file when
11308 <prgn>dpkg-genchanges</prgn> is run.
11312 It is usually invoked from the <tt>binary</tt> target of
11313 <file>debian/rules</file>:
11315 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11317 The <var>filename</var> is relative to the directory where
11318 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11319 is usually the directory above the top level of the source
11320 tree. The <file>debian/rules</file> target should put the
11321 file there just before or just after calling
11322 <prgn>dpkg-distaddfile</prgn>.
11326 The <var>section</var> and <var>priority</var> are passed
11327 unchanged into the resulting <file>.changes</file> file.
11332 <sect1 id="pkg-dpkg-genchanges">
11334 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11335 upload control file
11339 See <manref name="dpkg-genchanges" section="1">.
11343 <sect1 id="pkg-dpkg-parsechangelog">
11345 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11346 representation of a changelog
11350 See <manref name="dpkg-parsechangelog" section="1">.
11354 <sect1 id="pkg-dpkg-architecture">
11356 <prgn>dpkg-architecture</prgn> - information about the build and
11361 See <manref name="dpkg-architecture" section="1">.
11366 <sect id="pkg-sourcetree">
11367 <heading>The Debian package source tree</heading>
11370 The source archive scheme described later is intended to
11371 allow a Debian package source tree with some associated
11372 control information to be reproduced and transported easily.
11373 The Debian package source tree is a version of the original
11374 program with certain files added for the benefit of the
11375 packaging process, and with any other changes required
11376 made to the rest of the source code and installation
11381 The extra files created for Debian are in the subdirectory
11382 <file>debian</file> of the top level of the Debian package
11383 source tree. They are described below.
11386 <sect1 id="pkg-debianrules">
11387 <heading><file>debian/rules</file> - the main building script</heading>
11390 See <ref id="debianrules">.
11394 <sect1 id="pkg-srcsubstvars">
11395 <heading><file>debian/substvars</file> and variable substitutions</heading>
11398 See <ref id="substvars">.
11404 <heading><file>debian/files</file></heading>
11407 See <ref id="debianfiles">.
11411 <sect1><heading><file>debian/tmp</file>
11415 This is the canonical temporary location for the
11416 construction of binary packages by the <tt>binary</tt>
11417 target. The directory <file>tmp</file> serves as the root of
11418 the file system tree as it is being constructed (for
11419 example, by using the package's upstream makefiles install
11420 targets and redirecting the output there), and it also
11421 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11422 id="pkg-bincreating">.
11426 If several binary packages are generated from the same
11427 source tree it is usual to use several
11428 <file>debian/tmp<var>something</var></file> directories, for
11429 example <file>tmp-a</file> or <file>tmp-doc</file>.
11433 Whatever <file>tmp</file> directories are created and used by
11434 <tt>binary</tt> must of course be removed by the
11435 <tt>clean</tt> target.</p></sect1>
11439 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11443 As it exists on the FTP site, a Debian source package
11444 consists of three related files. You must have the right
11445 versions of all three to be able to use them.
11450 <tag>Debian source control file - <tt>.dsc</tt></tag>
11452 This file is a control file used by <prgn>dpkg-source</prgn>
11453 to extract a source package.
11454 See <ref id="debiansourcecontrolfiles">.
11458 Original source archive -
11460 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11466 This is a compressed (with <tt>gzip -9</tt>)
11467 <prgn>tar</prgn> file containing the source code from
11468 the upstream authors of the program.
11473 Debian package diff -
11475 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11481 This is a unified context diff (<tt>diff -u</tt>)
11482 giving the changes which are required to turn the
11483 original source into the Debian source. These changes
11484 may only include editing and creating plain files.
11485 The permissions of files, the targets of symbolic
11486 links and the characteristics of special files or
11487 pipes may not be changed and no files may be removed
11492 All the directories in the diff must exist, except the
11493 <file>debian</file> subdirectory of the top of the source
11494 tree, which will be created by
11495 <prgn>dpkg-source</prgn> if necessary when unpacking.
11499 The <prgn>dpkg-source</prgn> program will
11500 automatically make the <file>debian/rules</file> file
11501 executable (see below).</p></item>
11506 If there is no original source code - for example, if the
11507 package is specially prepared for Debian or the Debian
11508 maintainer is the same as the upstream maintainer - the
11509 format is slightly different: then there is no diff, and the
11511 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11512 and preferably contains a directory named
11513 <file><var>package</var>-<var>version</var></file>.
11518 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11521 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11522 Debian source package. However, if it is not available it
11523 is possible to unpack a Debian source archive as follows:
11524 <enumlist compact="compact">
11527 Untar the tarfile, which will create a <file>.orig</file>
11531 <p>Rename the <file>.orig</file> directory to
11532 <file><var>package</var>-<var>version</var></file>.</p>
11536 Create the subdirectory <file>debian</file> at the top of
11537 the source tree.</p>
11539 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11541 <item><p>Untar the tarfile again if you want a copy of the original
11542 source code alongside the Debian version.</p>
11547 It is not possible to generate a valid Debian source archive
11548 without using <prgn>dpkg-source</prgn>. In particular,
11549 attempting to use <prgn>diff</prgn> directly to generate the
11550 <file>.diff.gz</file> file will not work.
11554 <heading>Restrictions on objects in source packages</heading>
11557 The source package may not contain any hard links
11559 This is not currently detected when building source
11560 packages, but only when extracting
11564 Hard links may be permitted at some point in the
11565 future, but would require a fair amount of
11567 </footnote>, device special files, sockets or setuid or
11570 Setgid directories are allowed.
11575 The source packaging tools manage the changes between the
11576 original and Debian source using <prgn>diff</prgn> and
11577 <prgn>patch</prgn>. Turning the original source tree as
11578 included in the <file>.orig.tar.gz</file> into the Debian
11579 package source must not involve any changes which cannot be
11580 handled by these tools. Problematic changes which cause
11581 <prgn>dpkg-source</prgn> to halt with an error when
11582 building the source package are:
11583 <list compact="compact">
11584 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11586 <item><p>Changing the targets of symbolic links.</p>
11588 <item><p>Creating directories, other than <file>debian</file>.</p>
11590 <item><p>Changes to the contents of binary files.</p></item>
11591 </list> Changes which cause <prgn>dpkg-source</prgn> to
11592 print a warning but continue anyway are:
11593 <list compact="compact">
11596 Removing files, directories or symlinks.
11598 Renaming a file is not treated specially - it is
11599 seen as the removal of the old file (which
11600 generates a warning, but is otherwise ignored),
11601 and the creation of the new one.
11607 Changed text files which are missing the usual final
11608 newline (either in the original or the modified
11613 Changes which are not represented, but which are not detected by
11614 <prgn>dpkg-source</prgn>, are:
11615 <list compact="compact">
11616 <item><p>Changing the permissions of files (other than
11617 <file>debian/rules</file>) and directories.</p></item>
11622 The <file>debian</file> directory and <file>debian/rules</file>
11623 are handled specially by <prgn>dpkg-source</prgn> - before
11624 applying the changes it will create the <file>debian</file>
11625 directory, and afterwards it will make
11626 <file>debian/rules</file> world-executable.
11632 <appendix id="pkg-controlfields">
11633 <heading>Control files and their fields (from old Packaging Manual)</heading>
11636 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11637 data in a common format, known as control files. Binary and
11638 source packages have control data as do the <file>.changes</file>
11639 files which control the installation of uploaded files, and
11640 <prgn>dpkg</prgn>'s internal databases are in a similar
11645 <heading>Syntax of control files</heading>
11648 See <ref id="controlsyntax">.
11652 It is important to note that there are several fields which
11653 are optional as far as <prgn>dpkg</prgn> and the related
11654 tools are concerned, but which must appear in every Debian
11655 package, or whose omission may cause problems.
11660 <heading>List of fields</heading>
11663 See <ref id="controlfieldslist">.
11667 This section now contains only the fields that didn't belong
11668 to the Policy manual.
11671 <sect1 id="pkg-f-Filename">
11672 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11675 These fields in <tt>Packages</tt> files give the
11676 filename(s) of (the parts of) a package in the
11677 distribution directories, relative to the root of the
11678 Debian hierarchy. If the package has been split into
11679 several parts the parts are all listed in order, separated
11684 <sect1 id="pkg-f-Size">
11685 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11688 These fields in <file>Packages</file> files give the size (in
11689 bytes, expressed in decimal) and MD5 checksum of the
11690 file(s) which make(s) up a binary package in the
11691 distribution. If the package is split into several parts
11692 the values for the parts are listed in order, separated by
11697 <sect1 id="pkg-f-Status">
11698 <heading><tt>Status</tt></heading>
11701 This field in <prgn>dpkg</prgn>'s status file records
11702 whether the user wants a package installed, removed or
11703 left alone, whether it is broken (requiring
11704 re-installation) or not and what its current state on the
11705 system is. Each of these pieces of information is a
11710 <sect1 id="pkg-f-Config-Version">
11711 <heading><tt>Config-Version</tt></heading>
11714 If a package is not installed or not configured, this
11715 field in <prgn>dpkg</prgn>'s status file records the last
11716 version of the package which was successfully
11721 <sect1 id="pkg-f-Conffiles">
11722 <heading><tt>Conffiles</tt></heading>
11725 This field in <prgn>dpkg</prgn>'s status file contains
11726 information about the automatically-managed configuration
11727 files held by a package. This field should <em>not</em>
11728 appear anywhere in a package!
11733 <heading>Obsolete fields</heading>
11736 These are still recognized by <prgn>dpkg</prgn> but should
11737 not appear anywhere any more.
11739 <taglist compact="compact">
11741 <tag><tt>Revision</tt></tag>
11742 <tag><tt>Package-Revision</tt></tag>
11743 <tag><tt>Package_Revision</tt></tag>
11745 The Debian revision part of the package version was
11746 at one point in a separate control field. This
11747 field went through several names.
11750 <tag><tt>Recommended</tt></tag>
11751 <item>Old name for <tt>Recommends</tt>.</item>
11753 <tag><tt>Optional</tt></tag>
11754 <item>Old name for <tt>Suggests</tt>.</item>
11756 <tag><tt>Class</tt></tag>
11757 <item>Old name for <tt>Priority</tt>.</item>
11766 <appendix id="pkg-conffiles">
11767 <heading>Configuration file handling (from old Packaging Manual)</heading>
11770 <prgn>dpkg</prgn> can do a certain amount of automatic
11771 handling of package configuration files.
11775 Whether this mechanism is appropriate depends on a number of
11776 factors, but basically there are two approaches to any
11777 particular configuration file.
11781 The easy method is to ship a best-effort configuration in the
11782 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11783 handle updates. If the user is unlikely to want to edit the
11784 file, but you need them to be able to without losing their
11785 changes, and a new package with a changed version of the file
11786 is only released infrequently, this is a good approach.
11790 The hard method is to build the configuration file from
11791 scratch in the <prgn>postinst</prgn> script, and to take the
11792 responsibility for fixing any mistakes made in earlier
11793 versions of the package automatically. This will be
11794 appropriate if the file is likely to need to be different on
11798 <sect><heading>Automatic handling of configuration files by
11803 A package may contain a control information file called
11804 <tt>conffiles</tt>. This file should be a list of filenames
11805 of configuration files needing automatic handling, separated
11806 by newlines. The filenames should be absolute pathnames,
11807 and the files referred to should actually exist in the
11812 When a package is upgraded <prgn>dpkg</prgn> will process
11813 the configuration files during the configuration stage,
11814 shortly before it runs the package's <prgn>postinst</prgn>
11819 For each file it checks to see whether the version of the
11820 file included in the package is the same as the one that was
11821 included in the last version of the package (the one that is
11822 being upgraded from); it also compares the version currently
11823 installed on the system with the one shipped with the last
11828 If neither the user nor the package maintainer has changed
11829 the file, it is left alone. If one or the other has changed
11830 their version, then the changed version is preferred - i.e.,
11831 if the user edits their file, but the package maintainer
11832 doesn't ship a different version, the user's changes will
11833 stay, silently, but if the maintainer ships a new version
11834 and the user hasn't edited it the new version will be
11835 installed (with an informative message). If both have
11836 changed their version the user is prompted about the problem
11837 and must resolve the differences themselves.
11841 The comparisons are done by calculating the MD5 message
11842 digests of the files, and storing the MD5 of the file as it
11843 was included in the most recent version of the package.
11847 When a package is installed for the first time
11848 <prgn>dpkg</prgn> will install the file that comes with it,
11849 unless that would mean overwriting a file already on the
11854 However, note that <prgn>dpkg</prgn> will <em>not</em>
11855 replace a conffile that was removed by the user (or by a
11856 script). This is necessary because with some programs a
11857 missing file produces an effect hard or impossible to
11858 achieve in another way, so that a missing file needs to be
11859 kept that way if the user did it.
11863 Note that a package should <em>not</em> modify a
11864 <prgn>dpkg</prgn>-handled conffile in its maintainer
11865 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11866 the user confusing and possibly dangerous options for
11867 conffile update when the package is upgraded.</p>
11870 <sect><heading>Fully-featured maintainer script configuration
11875 For files which contain site-specific information such as
11876 the hostname and networking details and so forth, it is
11877 better to create the file in the package's
11878 <prgn>postinst</prgn> script.
11882 This will typically involve examining the state of the rest
11883 of the system to determine values and other information, and
11884 may involve prompting the user for some information which
11885 can't be obtained some other way.
11889 When using this method there are a couple of important
11890 issues which should be considered:
11894 If you discover a bug in the program which generates the
11895 configuration file, or if the format of the file changes
11896 from one version to the next, you will have to arrange for
11897 the postinst script to do something sensible - usually this
11898 will mean editing the installed configuration file to remove
11899 the problem or change the syntax. You will have to do this
11900 very carefully, since the user may have changed the file,
11901 perhaps to fix the very problem that your script is trying
11902 to deal with - you will have to detect these situations and
11903 deal with them correctly.
11907 If you do go down this route it's probably a good idea to
11908 make the program that generates the configuration file(s) a
11909 separate program in <file>/usr/sbin</file>, by convention called
11910 <file><var>package</var>config</file> and then run that if
11911 appropriate from the post-installation script. The
11912 <tt><var>package</var>config</tt> program should not
11913 unquestioningly overwrite an existing configuration - if its
11914 mode of operation is geared towards setting up a package for
11915 the first time (rather than any arbitrary reconfiguration
11916 later) you should have it check whether the configuration
11917 already exists, and require a <tt>--force</tt> flag to
11918 overwrite it.</p></sect>
11921 <appendix id="pkg-alternatives"><heading>Alternative versions of
11922 an interface - <prgn>update-alternatives</prgn> (from old
11927 When several packages all provide different versions of the
11928 same program or file it is useful to have the system select a
11929 default, but to allow the system administrator to change it
11930 and have their decisions respected.
11934 For example, there are several versions of the <prgn>vi</prgn>
11935 editor, and there is no reason to prevent all of them from
11936 being installed at once, each under their own name
11937 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11938 Nevertheless it is desirable to have the name <tt>vi</tt>
11939 refer to something, at least by default.
11943 If all the packages involved cooperate, this can be done with
11944 <prgn>update-alternatives</prgn>.
11948 Each package provides its own version under its own name, and
11949 calls <prgn>update-alternatives</prgn> in its postinst to
11950 register its version (and again in its prerm to deregister
11955 See the man page <manref name="update-alternatives"
11956 section="8"> for details.
11960 If <prgn>update-alternatives</prgn> does not seem appropriate
11961 you may wish to consider using diversions instead.</p>
11964 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11965 package's version of a file (from old Packaging Manual)
11969 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11970 when it reinstalls the package it belongs to, and to have it
11971 put the file from the package somewhere else instead.
11975 This can be used locally to override a package's version of a
11976 file, or by one package to override another's version (or
11977 provide a wrapper for it).
11981 Before deciding to use a diversion, read <ref
11982 id="pkg-alternatives"> to see if you really want a diversion
11983 rather than several alternative versions of a program.
11987 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11988 and updated by a special program <prgn>dpkg-divert</prgn>.
11989 Please see <manref name="dpkg-divert" section="8"> for full
11990 details of its operation.
11994 When a package wishes to divert a file from another, it should
11995 call <prgn>dpkg-divert</prgn> in its preinst to add the
11996 diversion and rename the existing file. For example,
11997 supposing that a <prgn>smailwrapper</prgn> package wishes to
11998 install a wrapper around <file>/usr/sbin/smail</file>:
12000 dpkg-divert --package smailwrapper --add --rename \
12001 --divert /usr/sbin/smail.real /usr/sbin/smail
12002 </example> The <tt>--package smailwrapper</tt> ensures that
12003 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12004 can bypass the diversion and get installed as the true version.
12005 It's safe to add the diversion unconditionally on upgrades since
12006 it will be left unchanged if it already exists, but
12007 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12008 message, make the command conditional on the version from which
12009 the package is being upgraded:
12011 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12012 dpkg-divert --package smailwrapper --add --rename \
12013 --divert /usr/sbin/smail.real /usr/sbin/smail
12015 </example> where <tt>1.0-2</tt> is the version at which the
12016 diversion was first added to the package. Running the command
12017 during abort-upgrade is pointless but harmless.
12021 The postrm has to do the reverse:
12023 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12024 dpkg-divert --package smailwrapper --remove --rename \
12025 --divert /usr/sbin/smail.real /usr/sbin/smail
12027 </example> If the diversion was added at a particular version, the
12028 postrm should also handle the failure case of upgrading from an
12029 older version (unless the older version is so old that direct
12030 upgrades are no longer supported):
12032 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12033 dpkg-divert --package smailwrapper --remove --rename \
12034 --divert /usr/sbin/smail.real /usr/sbin/smail
12036 </example> where <tt>1.0-2</tt> is the version at which the
12037 diversion was first added to the package. The postrm should not
12038 remove the diversion on upgrades both because there's no reason to
12039 remove the diversion only to immediately re-add it and since the
12040 postrm of the old package is run after unpacking so the removal of
12041 the diversion will fail.
12045 Do not attempt to divert a file which is vitally important for
12046 the system's operation - when using <prgn>dpkg-divert</prgn>
12047 there is a time, after it has been diverted but before
12048 <prgn>dpkg</prgn> has installed the new version, when the file
12049 does not exist.</p>
12052 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12059 <!-- Local variables: -->
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