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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 the "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 removed. (In this case, it may be appropriate to
1365 specify a conflict against earlier versions of something
1366 that previously did not use
1367 <prgn>update-alternatives</prgn>; this is an exception to
1368 the usual rule that versioned conflicts should be
1372 <sect1 id="maintscriptprompt">
1373 <heading>Prompting in maintainer scripts</heading>
1375 Package maintainer scripts may prompt the user if
1376 necessary. Prompting must be done by communicating
1377 through a program, such as <prgn>debconf</prgn>, which
1378 conforms to the Debian Configuration Management
1379 Specification, version 2 or higher.
1383 Packages which are essential, or which are dependencies of
1384 essential packages, may fall back on another prompting method
1385 if no such interface is available when they are executed.
1389 The Debian Configuration Management Specification is included
1390 in the <file>debconf_specification</file> files in the
1391 <package>debian-policy</package> package.
1392 It is also available from the Debian web mirrors at
1393 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1394 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1398 Packages which use the Debian Configuration Management
1399 Specification may contain the additional control information
1400 files <file>config</file>
1401 and <file>templates</file>. <file>config</file> is an
1402 additional maintainer script used for package configuration,
1403 and <file>templates</file> contains templates used for user
1404 prompting. The <prgn>config</prgn> script might be run before
1405 the <prgn>preinst</prgn> script and before the package is
1406 unpacked or any of its dependencies or pre-dependencies are
1407 satisfied. Therefore it must work using only the tools
1408 present in <em>essential</em> packages.<footnote>
1409 <package>Debconf</package> or another tool that
1410 implements the Debian Configuration Management
1411 Specification will also be installed, and any
1412 versioned dependencies on it will be satisfied
1413 before preconfiguration begins.
1418 Packages which use the Debian Configuration Management
1419 Specification must allow for translation of their user-visible
1420 messages by using a gettext-based system such as the one
1421 provided by the <package>po-debconf</package> package.
1425 Packages should try to minimize the amount of prompting
1426 they need to do, and they should ensure that the user
1427 will only ever be asked each question once. This means
1428 that packages should try to use appropriate shared
1429 configuration files (such as <file>/etc/papersize</file> and
1430 <file>/etc/news/server</file>), and shared
1431 <package>debconf</package> variables rather than each
1432 prompting for their own list of required pieces of
1437 It also means that an upgrade should not ask the same
1438 questions again, unless the user has used
1439 <tt>dpkg --purge</tt> to remove the package's configuration.
1440 The answers to configuration questions should be stored in an
1441 appropriate place in <file>/etc</file> so that the user can
1442 modify them, and how this has been done should be
1447 If a package has a vitally important piece of
1448 information to pass to the user (such as "don't run me
1449 as I am, you must edit the following configuration files
1450 first or you risk your system emitting badly-formatted
1451 messages"), it should display this in the
1452 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1453 prompt the user to hit return to acknowledge the
1454 message. Copyright messages do not count as vitally
1455 important (they belong in
1456 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1457 neither do instructions on how to use a program (these
1458 should be in on-line documentation, where all the users
1463 Any necessary prompting should almost always be confined
1464 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1465 script. If it is done in the <prgn>postinst</prgn>, it
1466 should be protected with a conditional so that
1467 unnecessary prompting doesn't happen if a package's
1468 installation fails and the <prgn>postinst</prgn> is
1469 called with <tt>abort-upgrade</tt>,
1470 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1480 <heading>Source packages</heading>
1482 <sect id="standardsversion">
1483 <heading>Standards conformance</heading>
1486 Source packages should specify the most recent version number
1487 of this policy document with which your package complied
1488 when it was last updated.
1492 This information may be used to file bug reports
1493 automatically if your package becomes too much out of date.
1497 The version is specified in the <tt>Standards-Version</tt>
1499 The format of the <tt>Standards-Version</tt> field is
1500 described in <ref id="f-Standards-Version">.
1504 You should regularly, and especially if your package has
1505 become out of date, check for the newest Policy Manual
1506 available and update your package, if necessary. When your
1507 package complies with the new standards you should update the
1508 <tt>Standards-Version</tt> source package field and
1509 release it.<footnote>
1510 See the file <file>upgrading-checklist</file> for
1511 information about policy which has changed between
1512 different versions of this document.
1518 <sect id="pkg-relations">
1519 <heading>Package relationships</heading>
1522 Source packages should specify which binary packages they
1523 require to be installed or not to be installed in order to
1524 build correctly. For example, if building a package
1525 requires a certain compiler, then the compiler should be
1526 specified as a build-time dependency.
1530 It is not necessary to explicitly specify build-time
1531 relationships on a minimal set of packages that are always
1532 needed to compile, link and put in a Debian package a
1533 standard "Hello World!" program written in C or C++. The
1534 required packages are called <em>build-essential</em>, and
1535 an informational list can be found in
1536 <file>/usr/share/doc/build-essential/list</file> (which is
1537 contained in the <tt>build-essential</tt>
1540 <list compact="compact">
1542 This allows maintaining the list separately
1543 from the policy documents (the list does not
1544 need the kind of control that the policy
1548 Having a separate package allows one to install
1549 the build-essential packages on a machine, as
1550 well as allowing other packages such as tasks to
1551 require installation of the build-essential
1552 packages using the depends relation.
1555 The separate package allows bug reports against
1556 the list to be categorized separately from
1557 the policy management process in the BTS.
1564 When specifying the set of build-time dependencies, one
1565 should list only those packages explicitly required by the
1566 build. It is not necessary to list packages which are
1567 required merely because some other package in the list of
1568 build-time dependencies depends on them.<footnote>
1569 The reason for this is that dependencies change, and
1570 you should list all those packages, and <em>only</em>
1571 those packages that <em>you</em> need directly. What
1572 others need is their business. For example, if you
1573 only link against <file>libimlib</file>, you will need to
1574 build-depend on <package>libimlib2-dev</package> but
1575 not against any <tt>libjpeg*</tt> packages, even
1576 though <tt>libimlib2-dev</tt> currently depends on
1577 them: installation of <package>libimlib2-dev</package>
1578 will automatically ensure that all of its run-time
1579 dependencies are satisfied.
1584 If build-time dependencies are specified, it must be
1585 possible to build the package and produce working binaries
1586 on a system with only essential and build-essential
1587 packages installed and also those required to satisfy the
1588 build-time relationships (including any implied
1589 relationships). In particular, this means that version
1590 clauses should be used rigorously in build-time
1591 relationships so that one cannot produce bad or
1592 inconsistently configured packages when the relationships
1593 are properly satisfied.
1597 <ref id="relationships"> explains the technical details.
1602 <heading>Changes to the upstream sources</heading>
1605 If changes to the source code are made that are not
1606 specific to the needs of the Debian system, they should be
1607 sent to the upstream authors in whatever form they prefer
1608 so as to be included in the upstream version of the
1613 If you need to configure the package differently for
1614 Debian or for Linux, and the upstream source doesn't
1615 provide a way to do so, you should add such configuration
1616 facilities (for example, a new <prgn>autoconf</prgn> test
1617 or <tt>#define</tt>) and send the patch to the upstream
1618 authors, with the default set to the way they originally
1619 had it. You can then easily override the default in your
1620 <file>debian/rules</file> or wherever is appropriate.
1624 You should make sure that the <prgn>configure</prgn> utility
1625 detects the correct architecture specification string
1626 (refer to <ref id="arch-spec"> for details).
1630 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1631 <prgn>configure</prgn> scripts are used, you should edit the
1632 <file>.in</file> files rather than editing the
1633 <prgn>Makefile</prgn> directly. This allows the user to
1634 reconfigure the package if necessary. You should
1635 <em>not</em> configure the package and edit the generated
1636 <prgn>Makefile</prgn>! This makes it impossible for someone
1637 else to later reconfigure the package without losing the
1643 <sect id="dpkgchangelog">
1644 <heading>Debian changelog: <file>debian/changelog</file></heading>
1647 Changes in the Debian version of the package should be
1648 briefly explained in the Debian changelog file
1649 <file>debian/changelog</file>.<footnote>
1651 Mistakes in changelogs are usually best rectified by
1652 making a new changelog entry rather than "rewriting
1653 history" by editing old changelog entries.
1656 This includes modifications
1657 made in the Debian package compared to the upstream one
1658 as well as other changes and updates to the package.
1660 Although there is nothing stopping an author who is also
1661 the Debian maintainer from using this changelog for all
1662 their changes, it will have to be renamed if the Debian
1663 and upstream maintainers become different people. In such
1664 a case, however, it might be better to maintain the package
1665 as a non-native package.
1670 The format of the <file>debian/changelog</file> allows the
1671 package building tools to discover which version of the package
1672 is being built and find out other release-specific information.
1676 That format is a series of entries like this:
1678 <example compact="compact">
1679 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1681 [optional blank line(s), stripped]
1683 * <var>change details</var>
1684 <var>more change details</var>
1686 [blank line(s), included in output of dpkg-parsechangelog]
1688 * <var>even more change details</var>
1690 [optional blank line(s), stripped]
1692 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1697 <var>package</var> and <var>version</var> are the source
1698 package name and version number.
1702 <var>distribution(s)</var> lists the distributions where
1703 this version should be installed when it is uploaded - it
1704 is copied to the <tt>Distribution</tt> field in the
1705 <file>.changes</file> file. See <ref id="f-Distribution">.
1709 <var>urgency</var> is the value for the <tt>Urgency</tt>
1710 field in the <file>.changes</file> file for the upload
1711 (see <ref id="f-Urgency">). It is not possible to specify
1712 an urgency containing commas; commas are used to separate
1713 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1714 <prgn>dpkg</prgn> changelog format (though there is
1715 currently only one useful <var>keyword</var>,
1720 The change details may in fact be any series of lines
1721 starting with at least two spaces, but conventionally each
1722 change starts with an asterisk and a separating space and
1723 continuation lines are indented so as to bring them in
1724 line with the start of the text above. Blank lines may be
1725 used here to separate groups of changes, if desired.
1729 If this upload resolves bugs recorded in the Bug Tracking
1730 System (BTS), they may be automatically closed on the
1731 inclusion of this package into the Debian archive by
1732 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1733 in the change details.<footnote>
1734 To be precise, the string should match the following
1735 Perl regular expression:
1737 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1739 Then all of the bug numbers listed will be closed by the
1740 archive maintenance software (<prgn>dak</prgn>) using the
1741 <var>version</var> of the changelog entry.
1743 This information is conveyed via the <tt>Closes</tt> field
1744 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1748 The maintainer name and email address used in the changelog
1749 should be the details of the person uploading <em>this</em>
1750 version. They are <em>not</em> necessarily those of the
1751 usual package maintainer.<footnote>
1752 If the developer uploading the package is not one of the usual
1753 maintainers of the package (as listed in
1754 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1755 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1756 fields of the package), the first line of the changelog is
1757 conventionally used to explain why a non-maintainer is
1758 uploading the package. The Debian Developer's Reference
1759 (see <ref id="related">) documents the conventions
1761 The information here will be copied to the <tt>Changed-By</tt>
1762 field in the <tt>.changes</tt> file
1763 (see <ref id="f-Changed-By">), and then later used to send an
1764 acknowledgement when the upload has been installed.
1768 The <var>date</var> has the following format<footnote>
1769 This is the same as the format generated by <tt>date
1771 </footnote> (compatible and with the same semantics of
1772 RFC 2822 and RFC 5322):
1773 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1775 <list compact="compact">
1777 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1780 dd is a one- or two-digit day of the month (01-31)
1783 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1786 <item>yyyy is the four-digit year (e.g. 2010)</item>
1787 <item>hh is the two-digit hour (00-23)</item>
1788 <item>mm is the two-digit minutes (00-59)</item>
1789 <item>ss is the two-digit seconds (00-60)</item>
1791 +zzzz or -zzzz is the the time zone offset from Coordinated
1792 Universal Time (UTC). "+" indicates that the time is ahead
1793 of (i.e., east of) UTC and "-" indicates that the time is
1794 behind (i.e., west of) UTC. The first two digits indicate
1795 the hour difference from UTC and the last two digits
1796 indicate the number of additional minutes difference from
1797 UTC. The last two digits must be in the range 00-59.
1803 The first "title" line with the package name must start
1804 at the left hand margin. The "trailer" line with the
1805 maintainer and date details must be preceded by exactly
1806 one space. The maintainer details and the date must be
1807 separated by exactly two spaces.
1811 The entire changelog must be encoded in UTF-8.
1815 For more information on placement of the changelog files
1816 within binary packages, please see <ref id="changelogs">.
1820 <sect id="dpkgcopyright">
1821 <heading>Copyright: <file>debian/copyright</file></heading>
1823 Every package must be accompanied by a verbatim copy of its
1824 copyright information and distribution license in the file
1825 <file>/usr/share/doc/<var>package</var>/copyright</file>
1826 (see <ref id="copyrightfile"> for further details). Also see
1827 <ref id="pkgcopyright"> for further considerations related
1828 to copyrights for packages.
1832 <heading>Error trapping in makefiles</heading>
1835 When <prgn>make</prgn> invokes a command in a makefile
1836 (including your package's upstream makefiles and
1837 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1838 means that <prgn>sh</prgn>'s usual bad error handling
1839 properties apply: if you include a miniature script as one
1840 of the commands in your makefile you'll find that if you
1841 don't do anything about it then errors are not detected
1842 and <prgn>make</prgn> will blithely continue after
1847 Every time you put more than one shell command (this
1848 includes using a loop) in a makefile command you
1849 must make sure that errors are trapped. For
1850 simple compound commands, such as changing directory and
1851 then running a program, using <tt>&&</tt> rather
1852 than semicolon as a command separator is sufficient. For
1853 more complex commands including most loops and
1854 conditionals you should include a separate <tt>set -e</tt>
1855 command at the start of every makefile command that's
1856 actually one of these miniature shell scripts.
1860 <sect id="timestamps">
1861 <heading>Time Stamps</heading>
1863 Maintainers should preserve the modification times of the
1864 upstream source files in a package, as far as is reasonably
1866 The rationale is that there is some information conveyed
1867 by knowing the age of the file, for example, you could
1868 recognize that some documentation is very old by looking
1869 at the modification time, so it would be nice if the
1870 modification time of the upstream source would be
1876 <sect id="restrictions">
1877 <heading>Restrictions on objects in source packages</heading>
1880 The source package may not contain any hard links<footnote>
1882 This is not currently detected when building source
1883 packages, but only when extracting
1887 Hard links may be permitted at some point in the
1888 future, but would require a fair amount of
1891 </footnote>, device special files, sockets or setuid or
1892 setgid files.<footnote>
1893 Setgid directories are allowed.
1898 <sect id="debianrules">
1899 <heading>Main building script: <file>debian/rules</file></heading>
1902 This file must be an executable makefile, and contains the
1903 package-specific recipes for compiling the package and
1904 building binary package(s) from the source.
1908 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1909 so that it can be invoked by saying its name rather than
1910 invoking <prgn>make</prgn> explicitly. That is, invoking
1911 either of <tt>make -f debian/rules <em>args...</em></tt>
1912 or <tt>./debian/rules <em>args...</em></tt> must result in
1917 The following targets are required and must be implemented
1918 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1919 <tt>binary-arch</tt>, <tt>binary-indep</tt>, <tt>build</tt>,
1920 <tt>build-arch</tt> and <tt>build-indep</tt>.
1921 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1925 Since an interactive <file>debian/rules</file> script makes it
1926 impossible to auto-compile that package and also makes it hard
1927 for other people to reproduce the same binary package, all
1928 required targets must be non-interactive. It also follows that
1929 any target that these targets depend on must also be
1934 The targets are as follows:
1936 <tag><tt>build</tt> (required)</tag>
1939 The <tt>build</tt> target should perform all the
1940 configuration and compilation of the package.
1941 If a package has an interactive pre-build
1942 configuration routine, the Debian source package
1943 must either be built after this has taken place (so
1944 that the binary package can be built without rerunning
1945 the configuration) or the configuration routine
1946 modified to become non-interactive. (The latter is
1947 preferable if there are architecture-specific features
1948 detected by the configuration routine.)
1952 For some packages, notably ones where the same
1953 source tree is compiled in different ways to produce
1954 two binary packages, the <tt>build</tt> target
1955 does not make much sense. For these packages it is
1956 good enough to provide two (or more) targets
1957 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1958 for each of the ways of building the package, and a
1959 <tt>build</tt> target that does nothing. The
1960 <tt>binary</tt> target will have to build the
1961 package in each of the possible ways and make the
1962 binary package out of each.
1966 The <tt>build</tt> target must not do anything
1967 that might require root privilege.
1971 The <tt>build</tt> target may need to run the
1972 <tt>clean</tt> target first - see below.
1976 When a package has a configuration and build routine
1977 which takes a long time, or when the makefiles are
1978 poorly designed, or when <tt>build</tt> needs to
1979 run <tt>clean</tt> first, it is a good idea to
1980 <tt>touch build</tt> when the build process is
1981 complete. This will ensure that if <tt>debian/rules
1982 build</tt> is run again it will not rebuild the whole
1984 Another common way to do this is for <tt>build</tt>
1985 to depend on <prgn>build-stamp</prgn> and to do
1986 nothing else, and for the <prgn>build-stamp</prgn>
1987 target to do the building and to <tt>touch
1988 build-stamp</tt> on completion. This is
1989 especially useful if the build routine creates a
1990 file or directory called <tt>build</tt>; in such a
1991 case, <tt>build</tt> will need to be listed as
1992 a phony target (i.e., as a dependency of the
1993 <tt>.PHONY</tt> target). See the documentation of
1994 <prgn>make</prgn> for more information on phony
2000 <tag><tt>build-arch</tt> (required),
2001 <tt>build-indep</tt> (required)
2005 The <tt>build-arch</tt> target must
2006 perform all the configuration and compilation required for
2007 producing all architecture-dependant binary packages
2008 (those packages for which the body of the
2009 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2010 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2011 target must perform all the configuration
2012 and compilation required for producing all
2013 architecture-independent binary packages (those packages
2014 for which the body of the <tt>Architecture</tt> field
2015 in <tt>debian/control</tt> is <tt>all</tt>).
2016 The <tt>build</tt> target
2017 should either depend on those targets or take the same
2018 actions as invoking those targets would perform.<footnote>
2019 This split allows binary-only builds to not install the
2020 dependencies required for the <tt>build-indep</tt>
2021 target and skip any resource-intensive build tasks that
2022 are only required when building architecture-independent
2028 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2029 must not do anything that might require root privilege.
2033 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2034 (required), <tt>binary-indep</tt> (required)
2038 The <tt>binary</tt> target must be all that is
2039 necessary for the user to build the binary package(s)
2040 produced from this source package. It is
2041 split into two parts: <prgn>binary-arch</prgn> builds
2042 the binary packages which are specific to a particular
2043 architecture, and <tt>binary-indep</tt> builds
2044 those which are not.
2047 <tt>binary</tt> may be (and commonly is) a target with
2048 no commands which simply depends on
2049 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2052 Both <tt>binary-*</tt> targets should depend on the
2053 <tt>build</tt> target, or on the appropriate
2054 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2055 provided, so that the package is built if it has not
2056 been already. It should then create the relevant
2057 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2058 make their control files and <prgn>dpkg-deb</prgn> to
2059 build them and place them in the parent of the top
2064 Both the <tt>binary-arch</tt> and
2065 <tt>binary-indep</tt> targets <em>must</em> exist.
2066 If one of them has nothing to do (which will always be
2067 the case if the source generates only a single binary
2068 package, whether architecture-dependent or not), it
2069 must still exist and must always succeed.
2073 The <tt>binary</tt> targets must be invoked as
2075 The <prgn>fakeroot</prgn> package often allows one
2076 to build a package correctly even without being
2082 <tag><tt>clean</tt> (required)</tag>
2085 This must undo any effects that the <tt>build</tt>
2086 and <tt>binary</tt> targets may have had, except
2087 that it should leave alone any output files created in
2088 the parent directory by a run of a <tt>binary</tt>
2093 If a <tt>build</tt> file is touched at the end of
2094 the <tt>build</tt> target, as suggested above, it
2095 should be removed as the first action that
2096 <tt>clean</tt> performs, so that running
2097 <tt>build</tt> again after an interrupted
2098 <tt>clean</tt> doesn't think that everything is
2103 The <tt>clean</tt> target may need to be
2104 invoked as root if <tt>binary</tt> has been
2105 invoked since the last <tt>clean</tt>, or if
2106 <tt>build</tt> has been invoked as root (since
2107 <tt>build</tt> may create directories, for
2112 <tag><tt>get-orig-source</tt> (optional)</tag>
2115 This target fetches the most recent version of the
2116 original source package from a canonical archive site
2117 (via FTP or WWW, for example), does any necessary
2118 rearrangement to turn it into the original source
2119 tar file format described below, and leaves it in the
2124 This target may be invoked in any directory, and
2125 should take care to clean up any temporary files it
2130 This target is optional, but providing it if
2131 possible is a good idea.
2135 <tag><tt>patch</tt> (optional)</tag>
2138 This target performs whatever additional actions are
2139 required to make the source ready for editing (unpacking
2140 additional upstream archives, applying patches, etc.).
2141 It is recommended to be implemented for any package where
2142 <tt>dpkg-source -x</tt> does not result in source ready
2143 for additional modification. See
2144 <ref id="readmesource">.
2150 The <tt>build</tt>, <tt>binary</tt> and
2151 <tt>clean</tt> targets must be invoked with the current
2152 directory being the package's top-level directory.
2157 Additional targets may exist in <file>debian/rules</file>,
2158 either as published or undocumented interfaces or for the
2159 package's internal use.
2163 The architectures we build on and build for are determined
2164 by <prgn>make</prgn> variables using the
2165 utility <prgn>dpkg-architecture</prgn>.
2166 You can determine the Debian architecture and the GNU style
2167 architecture specification string for the build architecture as
2168 well as for the host architecture. The build architecture is
2169 the architecture on which <file>debian/rules</file> is run and
2170 the package build is performed. The host architecture is the
2171 architecture on which the resulting package will be installed
2172 and run. These are normally the same, but may be different in
2173 the case of cross-compilation (building packages for one
2174 architecture on machines of a different architecture).
2178 Here is a list of supported <prgn>make</prgn> variables:
2179 <list compact="compact">
2181 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2184 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2187 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2190 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2191 specification string)
2194 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2195 <tt>DEB_*_GNU_TYPE</tt>)
2198 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2199 <tt>DEB_*_GNU_TYPE</tt>)
2201 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2202 the build architecture or <tt>HOST</tt> for specification of the
2207 Backward compatibility can be provided in the rules file
2208 by setting the needed variables to suitable default
2209 values; please refer to the documentation of
2210 <prgn>dpkg-architecture</prgn> for details.
2214 It is important to understand that the <tt>DEB_*_ARCH</tt>
2215 string only determines which Debian architecture we are
2216 building on or for. It should not be used to get the CPU
2217 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2218 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2219 GNU style variables should generally only be used with upstream
2223 <sect1 id="debianrules-options">
2224 <heading><file>debian/rules</file> and
2225 <tt>DEB_BUILD_OPTIONS</tt></heading>
2228 Supporting the standardized environment variable
2229 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2230 contain several flags to change how a package is compiled and
2231 built. Each flag must be in the form <var>flag</var> or
2232 <var>flag</var>=<var>options</var>. If multiple flags are
2233 given, they must be separated by whitespace.<footnote>
2234 Some packages support any delimiter, but whitespace is the
2235 easiest to parse inside a makefile and avoids ambiguity with
2236 flag values that contain commas.
2238 <var>flag</var> must start with a lowercase letter
2239 (<tt>a-z</tt>) and consist only of lowercase letters,
2240 numbers (<tt>0-9</tt>), and the characters
2241 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2242 <var>options</var> must not contain whitespace. The same
2243 tag should not be given multiple times with conflicting
2244 values. Package maintainers may assume that
2245 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2249 The meaning of the following tags has been standardized:
2253 This tag says to not run any build-time test suite
2254 provided by the package.
2258 The presence of this tag means that the package should
2259 be compiled with a minimum of optimization. For C
2260 programs, it is best to add <tt>-O0</tt> to
2261 <tt>CFLAGS</tt> (although this is usually the default).
2262 Some programs might fail to build or run at this level
2263 of optimization; it may be necessary to use
2264 <tt>-O1</tt>, for example.
2268 This tag means that the debugging symbols should not be
2269 stripped from the binary during installation, so that
2270 debugging information may be included in the package.
2272 <tag>parallel=n</tag>
2274 This tag means that the package should be built using up
2275 to <tt>n</tt> parallel processes if the package build
2276 system supports this.<footnote>
2277 Packages built with <tt>make</tt> can often implement
2278 this by passing the <tt>-j</tt><var>n</var> option to
2281 If the package build system does not support parallel
2282 builds, this string must be ignored. If the package
2283 build system only supports a lower level of concurrency
2284 than <var>n</var>, the package should be built using as
2285 many parallel processes as the package build system
2286 supports. It is up to the package maintainer to decide
2287 whether the package build times are long enough and the
2288 package build system is robust enough to make supporting
2289 parallel builds worthwhile.
2295 Unknown flags must be ignored by <file>debian/rules</file>.
2299 The following makefile snippet is an example of how one may
2300 implement the build options; you will probably have to
2301 massage this example in order to make it work for your
2303 <example compact="compact">
2306 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2307 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2308 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2309 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2311 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2316 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2317 INSTALL_PROGRAM += -s
2319 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2320 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2321 MAKEFLAGS += -j$(NUMJOBS)
2326 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2327 # Code to run the package test suite.
2334 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2335 <sect id="substvars">
2336 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2339 When <prgn>dpkg-gencontrol</prgn>
2340 generates <qref id="binarycontrolfiles">binary package control
2341 files</qref> (<file>DEBIAN/control</file>), it performs variable
2342 substitutions on its output just before writing it. Variable
2343 substitutions have the form <tt>${<var>variable</var>}</tt>.
2344 The optional file <file>debian/substvars</file> contains
2345 variable substitutions to be used; variables can also be set
2346 directly from <file>debian/rules</file> using the <tt>-V</tt>
2347 option to the source packaging commands, and certain predefined
2348 variables are also available.
2352 The <file>debian/substvars</file> file is usually generated and
2353 modified dynamically by <file>debian/rules</file> targets, in
2354 which case it must be removed by the <tt>clean</tt> target.
2358 See <manref name="deb-substvars" section="5"> for full
2359 details about source variable substitutions, including the
2360 format of <file>debian/substvars</file>.</p>
2363 <sect id="debianwatch">
2364 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2367 This is an optional, recommended configuration file for the
2368 <tt>uscan</tt> utility which defines how to automatically scan
2369 ftp or http sites for newly available updates of the
2370 package. This is used
2371 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2372 tools to help with quality control and maintenance of the
2373 distribution as a whole.
2378 <sect id="debianfiles">
2379 <heading>Generated files list: <file>debian/files</file></heading>
2382 This file is not a permanent part of the source tree; it
2383 is used while building packages to record which files are
2384 being generated. <prgn>dpkg-genchanges</prgn> uses it
2385 when it generates a <file>.changes</file> file.
2389 It should not exist in a shipped source package, and so it
2390 (and any backup files or temporary files such as
2391 <file>files.new</file><footnote>
2392 <file>files.new</file> is used as a temporary file by
2393 <prgn>dpkg-gencontrol</prgn> and
2394 <prgn>dpkg-distaddfile</prgn> - they write a new
2395 version of <tt>files</tt> here before renaming it,
2396 to avoid leaving a corrupted copy if an error
2398 </footnote>) should be removed by the
2399 <tt>clean</tt> target. It may also be wise to
2400 ensure a fresh start by emptying or removing it at the
2401 start of the <tt>binary</tt> target.
2405 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2406 package, it adds an entry to <file>debian/files</file> for the
2407 <file>.deb</file> file that will be created when <tt>dpkg-deb
2408 --build</tt> is run for that binary package. So for most
2409 packages all that needs to be done with this file is to
2410 delete it in the <tt>clean</tt> target.
2414 If a package upload includes files besides the source
2415 package and any binary packages whose control files were
2416 made with <prgn>dpkg-gencontrol</prgn> then they should be
2417 placed in the parent of the package's top-level directory
2418 and <prgn>dpkg-distaddfile</prgn> should be called to add
2419 the file to the list in <file>debian/files</file>.</p>
2422 <sect id="embeddedfiles">
2423 <heading>Convenience copies of code</heading>
2426 Some software packages include in their distribution convenience
2427 copies of code from other software packages, generally so that
2428 users compiling from source don't have to download multiple
2429 packages. Debian packages should not make use of these
2430 convenience copies unless the included package is explicitly
2431 intended to be used in this way.<footnote>
2432 For example, parts of the GNU build system work like this.
2434 If the included code is already in the Debian archive in the
2435 form of a library, the Debian packaging should ensure that
2436 binary packages reference the libraries already in Debian and
2437 the convenience copy is not used. If the included code is not
2438 already in Debian, it should be packaged separately as a
2439 prerequisite if possible.
2441 Having multiple copies of the same code in Debian is
2442 inefficient, often creates either static linking or shared
2443 library conflicts, and, most importantly, increases the
2444 difficulty of handling security vulnerabilities in the
2450 <sect id="readmesource">
2451 <heading>Source package handling:
2452 <file>debian/README.source</file></heading>
2455 If running <prgn>dpkg-source -x</prgn> on a source package
2456 doesn't produce the source of the package, ready for editing,
2457 and allow one to make changes and run
2458 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2459 without taking any additional steps, creating a
2460 <file>debian/README.source</file> documentation file is
2461 recommended. This file should explain how to do all of the
2464 <item>Generate the fully patched source, in a form ready for
2465 editing, that would be built to create Debian
2466 packages. Doing this with a <tt>patch</tt> target in
2467 <file>debian/rules</file> is recommended; see
2468 <ref id="debianrules">.</item>
2469 <item>Modify the source and save those modifications so that
2470 they will be applied when building the package.</item>
2471 <item>Remove source modifications that are currently being
2472 applied when building the package.</item>
2473 <item>Optionally, document what steps are necessary to
2474 upgrade the Debian source package to a new upstream version,
2475 if applicable.</item>
2477 This explanation should include specific commands and mention
2478 any additional required Debian packages. It should not assume
2479 familiarity with any specific Debian packaging system or patch
2484 This explanation may refer to a documentation file installed by
2485 one of the package's build dependencies provided that the
2486 referenced documentation clearly explains these tasks and is not
2487 a general reference manual.
2491 <file>debian/README.source</file> may also include any other
2492 information that would be helpful to someone modifying the
2493 source package. Even if the package doesn't fit the above
2494 description, maintainers are encouraged to document in a
2495 <file>debian/README.source</file> file any source package with a
2496 particularly complex or unintuitive source layout or build
2497 system (for example, a package that builds the same source
2498 multiple times to generate different binary packages).
2504 <chapt id="controlfields">
2505 <heading>Control files and their fields</heading>
2508 The package management system manipulates data represented in
2509 a common format, known as <em>control data</em>, stored in
2510 <em>control files</em>.
2511 Control files are used for source packages, binary packages and
2512 the <file>.changes</file> files which control the installation
2513 of uploaded files<footnote>
2514 <prgn>dpkg</prgn>'s internal databases are in a similar
2519 <sect id="controlsyntax">
2520 <heading>Syntax of control files</heading>
2523 A control file consists of one or more paragraphs of
2525 The paragraphs are also sometimes referred to as stanzas.
2527 The paragraphs are separated by empty lines. Parsers may accept
2528 lines consisting solely of spaces and tabs as paragraph
2529 separators, but control files should use empty lines. Some control
2530 files allow only one paragraph; others allow several, in
2531 which case each paragraph usually refers to a different
2532 package. (For example, in source packages, the first
2533 paragraph refers to the source package, and later paragraphs
2534 refer to binary packages generated from the source.) The
2535 ordering of the paragraphs in control files is significant.
2539 Each paragraph consists of a series of data fields. Each field
2540 consists of the field name followed by a colon and then the
2541 data/value associated with that field. The field name is
2542 composed of US-ASCII characters excluding control characters,
2543 space, and colon (i.e., characters in the ranges 33-57 and
2544 59-126, inclusive). Field names must not begin with the comment
2545 character, <tt>#</tt>.
2549 The field ends at the end of the line or at the end of the last
2550 continuation line (see below). Horizontal whitespace (spaces
2551 and tabs) may occur immediately before or after the value and is
2552 ignored there; it is conventional to put a single space after
2553 the colon. For example, a field might be:
2554 <example compact="compact">
2557 the field name is <tt>Package</tt> and the field value
2562 A paragraph must not contain more than one instance of a
2563 particular field name.
2567 There are three types of fields:
2571 The field, including its value, must be a single line. Folding
2572 of the field is not permitted. This is the default field type
2573 if the definition of the field does not specify a different
2578 The value of a folded field is a logical line that may span
2579 several lines. The lines after the first are called
2580 continuation lines and must start with a space or a tab.
2581 Whitespace, including any newlines, is not significant in the
2582 field values of folded fields.<footnote>
2583 This folding method is similar to RFC 5322, allowing control
2584 files that contain only one paragraph and no multiline fields
2585 to be read by parsers written for RFC 5322.
2588 <tag>multiline</tag>
2590 The value of a multiline field may comprise multiple continuation
2591 lines. The first line of the value, the part on the same line as
2592 the field name, often has special significance or may have to be
2593 empty. Other lines are added following the same syntax as the
2594 continuation lines of the folded fields. Whitespace, including newlines,
2595 is significant in the values of multiline fields.
2601 Whitespace must not appear
2602 inside names (of packages, architectures, files or anything
2603 else) or version numbers, or between the characters of
2604 multi-character version relationships.
2608 The presence and purpose of a field, and the syntax of its
2609 value may differ between types of control files.
2613 Field names are not case-sensitive, but it is usual to
2614 capitalize the field names using mixed case as shown below.
2615 Field values are case-sensitive unless the description of the
2616 field says otherwise.
2620 Paragraph separators (empty lines) and lines consisting only of
2621 spaces and tabs are not allowed within field values or between
2622 fields. Empty lines in field values are usually escaped by
2623 representing them by a space followed by a dot.
2627 Lines starting with # without any preceding whitespace are comments
2628 lines that are only permitted in source package control files
2629 (<file>debian/control</file>). These comment lines are ignored, even
2630 between two continuation lines. They do not end logical lines.
2634 All control files must be encoded in UTF-8.
2638 <sect id="sourcecontrolfiles">
2639 <heading>Source package control files -- <file>debian/control</file></heading>
2642 The <file>debian/control</file> file contains the most vital
2643 (and version-independent) information about the source package
2644 and about the binary packages it creates.
2648 The first paragraph of the control file contains information about
2649 the source package in general. The subsequent sets each describe a
2650 binary package that the source tree builds.
2654 The fields in the general paragraph (the first one, for the source
2657 <list compact="compact">
2658 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2660 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2661 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2662 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2663 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2664 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2665 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2666 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2671 The fields in the binary package paragraphs are:
2673 <list compact="compact">
2674 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2675 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2676 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2677 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2678 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2679 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2680 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2681 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2682 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2683 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2688 The syntax and semantics of the fields are described below.
2692 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2693 generate control files for binary packages (see below), by
2694 <prgn>dpkg-genchanges</prgn> to generate the
2695 <file>.changes</file> file to accompany the upload, and by
2696 <prgn>dpkg-source</prgn> when it creates the
2697 <file>.dsc</file> source control file as part of a source
2698 archive. Some fields are folded in <file>debian/control</file>,
2699 but not in any other control
2700 file. These tools are responsible for removing the line
2701 breaks from such fields when using fields from
2702 <file>debian/control</file> to generate other control files.
2706 The fields here may contain variable references - their
2707 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2708 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2709 when they generate output control files.
2710 See <ref id="substvars"> for details.
2714 <sect id="binarycontrolfiles">
2715 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2718 The <file>DEBIAN/control</file> file contains the most vital
2719 (and version-dependent) information about a binary package. It
2720 consists of a single paragraph.
2724 The fields in this file are:
2726 <list compact="compact">
2727 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2728 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2729 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2730 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2731 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2732 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2733 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2734 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2735 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2736 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2738 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2739 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2744 <sect id="debiansourcecontrolfiles">
2745 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2748 This file consists of a single paragraph, possibly surrounded by
2749 a PGP signature. The fields of that paragraph are listed below.
2750 Their syntax is described above, in <ref id="controlsyntax">.
2752 <list compact="compact">
2753 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2754 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2755 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2756 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2757 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2760 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2761 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2762 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2763 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2764 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2765 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2766 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2767 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2768 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2773 The Debian source control file is generated by
2774 <prgn>dpkg-source</prgn> when it builds the source
2775 archive, from other files in the source package,
2776 described above. When unpacking, it is checked against
2777 the files and directories in the other parts of the
2783 <sect id="debianchangesfiles">
2784 <heading>Debian changes files -- <file>.changes</file></heading>
2787 The <file>.changes</file> files are used by the Debian archive
2788 maintenance software to process updates to packages. They
2789 consist of a single paragraph, possibly surrounded by a PGP
2790 signature. That paragraph contains information from the
2791 <file>debian/control</file> file and other data about the
2792 source package gathered via <file>debian/changelog</file>
2793 and <file>debian/rules</file>.
2797 <file>.changes</file> files have a format version that is
2798 incremented whenever the documented fields or their meaning
2799 change. This document describes format &changesversion;.
2803 The fields in this file are:
2805 <list compact="compact">
2806 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2813 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2814 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2816 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2818 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2820 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2821 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2826 <sect id="controlfieldslist">
2827 <heading>List of fields</heading>
2829 <sect1 id="f-Source">
2830 <heading><tt>Source</tt></heading>
2833 This field identifies the source package name.
2837 In <file>debian/control</file> or a <file>.dsc</file> file,
2838 this field must contain only the name of the source package.
2842 In a binary package control file or a <file>.changes</file>
2843 file, the source package name may be followed by a version
2844 number in parentheses<footnote>
2845 It is customary to leave a space after the package name
2846 if a version number is specified.
2848 This version number may be omitted (and is, by
2849 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2850 the <tt>Version</tt> field of the binary package in
2851 question. The field itself may be omitted from a binary
2852 package control file when the source package has the same
2853 name and version as the binary package.
2857 Package names (both source and binary,
2858 see <ref id="f-Package">) must consist only of lower case
2859 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2860 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2861 (<tt>.</tt>). They must be at least two characters long and
2862 must start with an alphanumeric character.
2866 <sect1 id="f-Maintainer">
2867 <heading><tt>Maintainer</tt></heading>
2870 The package maintainer's name and email address. The name
2871 must come first, then the email address inside angle
2872 brackets <tt><></tt> (in RFC822 format).
2876 If the maintainer's name contains a full stop then the
2877 whole field will not work directly as an email address due
2878 to a misfeature in the syntax specified in RFC822; a
2879 program using this field as an address must check for this
2880 and correct the problem if necessary (for example by
2881 putting the name in round brackets and moving it to the
2882 end, and bringing the email address forward).
2886 See <ref id="maintainer"> for additional requirements and
2887 information about package maintainers.
2891 <sect1 id="f-Uploaders">
2892 <heading><tt>Uploaders</tt></heading>
2895 List of the names and email addresses of co-maintainers of the
2896 package, if any. If the package has other maintainers besides
2897 the one named in the <qref id="f-Maintainer">Maintainer
2898 field</qref>, their names and email addresses should be listed
2899 here. The format of each entry is the same as that of the
2900 Maintainer field, and multiple entries must be comma
2905 This is normally an optional field, but if
2906 the <tt>Maintainer</tt> control field names a group of people
2907 and a shared email address, the <tt>Uploaders</tt> field must
2908 be present and must contain at least one human with their
2909 personal email address.
2913 The Uploaders field in <file>debian/control</file> can be folded.
2917 <sect1 id="f-Changed-By">
2918 <heading><tt>Changed-By</tt></heading>
2921 The name and email address of the person who prepared this
2922 version of the package, usually a maintainer. The syntax is
2923 the same as for the <qref id="f-Maintainer">Maintainer
2928 <sect1 id="f-Section">
2929 <heading><tt>Section</tt></heading>
2932 This field specifies an application area into which the package
2933 has been classified. See <ref id="subsections">.
2937 When it appears in the <file>debian/control</file> file,
2938 it gives the value for the subfield of the same name in
2939 the <tt>Files</tt> field of the <file>.changes</file> file.
2940 It also gives the default for the same field in the binary
2945 <sect1 id="f-Priority">
2946 <heading><tt>Priority</tt></heading>
2949 This field represents how important it is that the user
2950 have the package installed. See <ref id="priorities">.
2954 When it appears in the <file>debian/control</file> file,
2955 it gives the value for the subfield of the same name in
2956 the <tt>Files</tt> field of the <file>.changes</file> file.
2957 It also gives the default for the same field in the binary
2962 <sect1 id="f-Package">
2963 <heading><tt>Package</tt></heading>
2966 The name of the binary package.
2970 Binary package names must follow the same syntax and
2971 restrictions as source package names. See <ref id="f-Source">
2976 <sect1 id="f-Architecture">
2977 <heading><tt>Architecture</tt></heading>
2980 Depending on context and the control file used, the
2981 <tt>Architecture</tt> field can include the following sets of
2985 A unique single word identifying a Debian machine
2986 architecture as described in <ref id="arch-spec">.
2989 An architecture wildcard identifying a set of Debian
2990 machine architectures, see <ref id="arch-wildcard-spec">.
2991 <tt>any</tt> matches all Debian machine architectures
2992 and is the most frequently used.
2995 <tt>all</tt>, which indicates an
2996 architecture-independent package.
2999 <tt>source</tt>, which indicates a source package.
3005 In the main <file>debian/control</file> file in the source
3006 package, this field may contain the special
3007 value <tt>all</tt>, the special architecture
3008 wildcard <tt>any</tt>, or a list of specific and wildcard
3009 architectures separated by spaces. If <tt>all</tt>
3010 or <tt>any</tt> appears, that value must be the entire
3011 contents of the field. Most packages will use
3012 either <tt>all</tt> or <tt>any</tt>.
3016 Specifying a specific list of architectures indicates that the
3017 source will build an architecture-dependent package only on
3018 architectures included in the list. Specifying a list of
3019 architecture wildcards indicates that the source will build an
3020 architecture-dependent package on only those architectures
3021 that match any of the specified architecture wildcards.
3022 Specifying a list of architectures or architecture wildcards
3023 other than <tt>any</tt> is for the minority of cases where a
3024 program is not portable or is not useful on some
3025 architectures. Where possible, the program should be made
3030 In the Debian source control file <file>.dsc</file>, this
3031 field contains a list of architectures and architecture
3032 wildcards separated by spaces. When the list contains the
3033 architecture wildcard <tt>any</tt>, the only other value
3034 allowed in the list is <tt>all</tt>.
3038 The list may include (or consist solely of) the special
3039 value <tt>all</tt>. In other words, in <file>.dsc</file>
3040 files unlike the <file>debian/control</file>, <tt>all</tt> may
3041 occur in combination with specific architectures.
3042 The <tt>Architecture</tt> field in the Debian source control
3043 file <file>.dsc</file> is generally constructed from
3044 the <tt>Architecture</tt> fields in
3045 the <file>debian/control</file> in the source package.
3049 Specifying only <tt>any</tt> indicates that the source package
3050 isn't dependent on any particular architecture and should
3051 compile fine on any one. The produced binary package(s)
3052 will be specific to whatever the current build architecture is.
3056 Specifying only <tt>all</tt> indicates that the source package
3057 will only build architecture-independent packages.
3061 Specifying <tt>any all</tt> indicates that the source package
3062 isn't dependent on any particular architecture. The set of
3063 produced binary packages will include at least one
3064 architecture-dependant package and one architecture-independent
3069 Specifying a list of architectures or architecture wildcards
3070 indicates that the source will build an architecture-dependent
3071 package, and will only work correctly on the listed or
3072 matching architectures. If the source package also builds at
3073 least one architecture-independent package, <tt>all</tt> will
3074 also be included in the list.
3078 In a <file>.changes</file> file, the <tt>Architecture</tt>
3079 field lists the architecture(s) of the package(s) currently
3080 being uploaded. This will be a list; if the source for the
3081 package is also being uploaded, the special
3082 entry <tt>source</tt> is also present. <tt>all</tt> will be
3083 present if any architecture-independent packages are being
3084 uploaded. Architecture wildcards such as <tt>any</tt> must
3085 never occur in the <tt>Architecture</tt> field in
3086 the <file>.changes</file> file.
3090 See <ref id="debianrules"> for information on how to get
3091 the architecture for the build process.
3095 <sect1 id="f-Essential">
3096 <heading><tt>Essential</tt></heading>
3099 This is a boolean field which may occur only in the
3100 control file of a binary package or in a per-package fields
3101 paragraph of a source package control file.
3105 If set to <tt>yes</tt> then the package management system
3106 will refuse to remove the package (upgrading and replacing
3107 it is still possible). The other possible value is <tt>no</tt>,
3108 which is the same as not having the field at all.
3113 <heading>Package interrelationship fields:
3114 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3115 <tt>Recommends</tt>, <tt>Suggests</tt>,
3116 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3117 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3121 These fields describe the package's relationships with
3122 other packages. Their syntax and semantics are described
3123 in <ref id="relationships">.</p>
3126 <sect1 id="f-Standards-Version">
3127 <heading><tt>Standards-Version</tt></heading>
3130 The most recent version of the standards (the policy
3131 manual and associated texts) with which the package
3136 The version number has four components: major and minor
3137 version number and major and minor patch level. When the
3138 standards change in a way that requires every package to
3139 change the major number will be changed. Significant
3140 changes that will require work in many packages will be
3141 signaled by a change to the minor number. The major patch
3142 level will be changed for any change to the meaning of the
3143 standards, however small; the minor patch level will be
3144 changed when only cosmetic, typographical or other edits
3145 are made which neither change the meaning of the document
3146 nor affect the contents of packages.
3150 Thus only the first three components of the policy version
3151 are significant in the <em>Standards-Version</em> control
3152 field, and so either these three components or all four
3153 components may be specified.<footnote>
3154 In the past, people specified the full version number
3155 in the Standards-Version field, for example "2.3.0.0".
3156 Since minor patch-level changes don't introduce new
3157 policy, it was thought it would be better to relax
3158 policy and only require the first 3 components to be
3159 specified, in this example "2.3.0". All four
3160 components may still be used if someone wishes to do so.
3166 <sect1 id="f-Version">
3167 <heading><tt>Version</tt></heading>
3170 The version number of a package. The format is:
3171 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3175 The three components here are:
3177 <tag><var>epoch</var></tag>
3180 This is a single (generally small) unsigned integer. It
3181 may be omitted, in which case zero is assumed. If it is
3182 omitted then the <var>upstream_version</var> may not
3187 It is provided to allow mistakes in the version numbers
3188 of older versions of a package, and also a package's
3189 previous version numbering schemes, to be left behind.
3193 <tag><var>upstream_version</var></tag>
3196 This is the main part of the version number. It is
3197 usually the version number of the original ("upstream")
3198 package from which the <file>.deb</file> file has been made,
3199 if this is applicable. Usually this will be in the same
3200 format as that specified by the upstream author(s);
3201 however, it may need to be reformatted to fit into the
3202 package management system's format and comparison
3207 The comparison behavior of the package management system
3208 with respect to the <var>upstream_version</var> is
3209 described below. The <var>upstream_version</var>
3210 portion of the version number is mandatory.
3214 The <var>upstream_version</var> may contain only
3215 alphanumerics<footnote>
3216 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3218 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3219 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3220 tilde) and should start with a digit. If there is no
3221 <var>debian_revision</var> then hyphens are not allowed;
3222 if there is no <var>epoch</var> then colons are not
3227 <tag><var>debian_revision</var></tag>
3230 This part of the version number specifies the version of
3231 the Debian package based on the upstream version. It
3232 may contain only alphanumerics and the characters
3233 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3234 tilde) and is compared in the same way as the
3235 <var>upstream_version</var> is.
3239 It is optional; if it isn't present then the
3240 <var>upstream_version</var> may not contain a hyphen.
3241 This format represents the case where a piece of
3242 software was written specifically to be a Debian
3243 package, where the Debian package source must always
3244 be identical to the pristine source and therefore no
3245 revision indication is required.
3249 It is conventional to restart the
3250 <var>debian_revision</var> at <tt>1</tt> each time the
3251 <var>upstream_version</var> is increased.
3255 The package management system will break the version
3256 number apart at the last hyphen in the string (if there
3257 is one) to determine the <var>upstream_version</var> and
3258 <var>debian_revision</var>. The absence of a
3259 <var>debian_revision</var> is equivalent to a
3260 <var>debian_revision</var> of <tt>0</tt>.
3267 When comparing two version numbers, first the <var>epoch</var>
3268 of each are compared, then the <var>upstream_version</var> if
3269 <var>epoch</var> is equal, and then <var>debian_revision</var>
3270 if <var>upstream_version</var> is also equal.
3271 <var>epoch</var> is compared numerically. The
3272 <var>upstream_version</var> and <var>debian_revision</var>
3273 parts are compared by the package management system using the
3274 following algorithm:
3278 The strings are compared from left to right.
3282 First the initial part of each string consisting entirely of
3283 non-digit characters is determined. These two parts (one of
3284 which may be empty) are compared lexically. If a difference
3285 is found it is returned. The lexical comparison is a
3286 comparison of ASCII values modified so that all the letters
3287 sort earlier than all the non-letters and so that a tilde
3288 sorts before anything, even the end of a part. For example,
3289 the following parts are in sorted order from earliest to
3290 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3291 <tt>a</tt>.<footnote>
3292 One common use of <tt>~</tt> is for upstream pre-releases.
3293 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3294 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3299 Then the initial part of the remainder of each string which
3300 consists entirely of digit characters is determined. The
3301 numerical values of these two parts are compared, and any
3302 difference found is returned as the result of the comparison.
3303 For these purposes an empty string (which can only occur at
3304 the end of one or both version strings being compared) counts
3309 These two steps (comparing and removing initial non-digit
3310 strings and initial digit strings) are repeated until a
3311 difference is found or both strings are exhausted.
3315 Note that the purpose of epochs is to allow us to leave behind
3316 mistakes in version numbering, and to cope with situations
3317 where the version numbering scheme changes. It is
3318 <em>not</em> intended to cope with version numbers containing
3319 strings of letters which the package management system cannot
3320 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3321 silly orderings.<footnote>
3322 The author of this manual has heard of a package whose
3323 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3324 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3330 <sect1 id="f-Description">
3331 <heading><tt>Description</tt></heading>
3334 In a source or binary control file, the <tt>Description</tt>
3335 field contains a description of the binary package, consisting
3336 of two parts, the synopsis or the short description, and the
3337 long description. It is a multiline field with the following
3343 Description: <single line synopsis>
3344 <extended description over several lines>
3349 The lines in the extended description can have these formats:
3355 Those starting with a single space are part of a paragraph.
3356 Successive lines of this form will be word-wrapped when
3357 displayed. The leading space will usually be stripped off.
3358 The line must contain at least one non-whitespace character.
3362 Those starting with two or more spaces. These will be
3363 displayed verbatim. If the display cannot be panned
3364 horizontally, the displaying program will line wrap them "hard"
3365 (i.e., without taking account of word breaks). If it can they
3366 will be allowed to trail off to the right. None, one or two
3367 initial spaces may be deleted, but the number of spaces
3368 deleted from each line will be the same (so that you can have
3369 indenting work correctly, for example). The line must
3370 contain at least one non-whitespace character.
3374 Those containing a single space followed by a single full stop
3375 character. These are rendered as blank lines. This is the
3376 <em>only</em> way to get a blank line<footnote>
3377 Completely empty lines will not be rendered as blank lines.
3378 Instead, they will cause the parser to think you're starting
3379 a whole new record in the control file, and will therefore
3380 likely abort with an error.
3385 Those containing a space, a full stop and some more characters.
3386 These are for future expansion. Do not use them.
3392 Do not use tab characters. Their effect is not predictable.
3396 See <ref id="descriptions"> for further information on this.
3400 In a <file>.changes</file> file, the <tt>Description</tt>
3401 field contains a summary of the descriptions for the packages
3402 being uploaded. For this case, the first line of the field
3403 value (the part on the same line as <tt>Description:</tt>) is
3404 always empty. It is a multiline field, with one
3405 line per package. Each line is
3406 indented by one space and contains the name of a binary
3407 package, a space, a hyphen (<tt>-</tt>), a space, and the
3408 short description line from that package.
3412 <sect1 id="f-Distribution">
3413 <heading><tt>Distribution</tt></heading>
3416 In a <file>.changes</file> file or parsed changelog output
3417 this contains the (space-separated) name(s) of the
3418 distribution(s) where this version of the package should
3419 be installed. Valid distributions are determined by the
3420 archive maintainers.<footnote>
3421 Example distribution names in the Debian archive used in
3422 <file>.changes</file> files are:
3423 <taglist compact="compact">
3424 <tag><em>unstable</em></tag>
3426 This distribution value refers to the
3427 <em>developmental</em> part of the Debian distribution
3428 tree. Most new packages, new upstream versions of
3429 packages and bug fixes go into the <em>unstable</em>
3433 <tag><em>experimental</em></tag>
3435 The packages with this distribution value are deemed
3436 by their maintainers to be high risk. Oftentimes they
3437 represent early beta or developmental packages from
3438 various sources that the maintainers want people to
3439 try, but are not ready to be a part of the other parts
3440 of the Debian distribution tree.
3445 Others are used for updating stable releases or for
3446 security uploads. More information is available in the
3447 Debian Developer's Reference, section "The Debian
3451 The Debian archive software only supports listing a single
3452 distribution. Migration of packages to other distributions is
3453 handled outside of the upload process.
3458 <heading><tt>Date</tt></heading>
3461 This field includes the date the package was built or last
3462 edited. It must be in the same format as the <var>date</var>
3463 in a <file>debian/changelog</file> entry.
3467 The value of this field is usually extracted from the
3468 <file>debian/changelog</file> file - see
3469 <ref id="dpkgchangelog">).
3473 <sect1 id="f-Format">
3474 <heading><tt>Format</tt></heading>
3477 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3478 files, this field declares the format version of that file.
3479 The syntax of the field value is the same as that of
3480 a <qref id="f-Version">package version number</qref> except
3481 that no epoch or Debian revision is allowed. The format
3482 described in this document is <tt>&changesversion;</tt>.
3486 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3487 Debian source control</qref> files, this field declares the
3488 format of the source package. The field value is used by
3489 programs acting on a source package to interpret the list of
3490 files in the source package and determine how to unpack it.
3491 The syntax of the field value is a numeric major revision, a
3492 period, a numeric minor revision, and then an optional subtype
3493 after whitespace, which if specified is an alphanumeric word
3494 in parentheses. The subtype is optional in the syntax but may
3495 be mandatory for particular source format revisions.
3497 The source formats currently supported by the Debian archive
3498 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3499 and <tt>3.0 (quilt)</tt>.
3504 <sect1 id="f-Urgency">
3505 <heading><tt>Urgency</tt></heading>
3508 This is a description of how important it is to upgrade to
3509 this version from previous ones. It consists of a single
3510 keyword taking one of the values <tt>low</tt>,
3511 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3512 <tt>critical</tt><footnote>
3513 Other urgency values are supported with configuration
3514 changes in the archive software but are not used in Debian.
3515 The urgency affects how quickly a package will be considered
3516 for inclusion into the <tt>testing</tt> distribution and
3517 gives an indication of the importance of any fixes included
3518 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3519 treated as synonymous.
3520 </footnote> (not case-sensitive) followed by an optional
3521 commentary (separated by a space) which is usually in
3522 parentheses. For example:
3525 Urgency: low (HIGH for users of diversions)
3531 The value of this field is usually extracted from the
3532 <file>debian/changelog</file> file - see
3533 <ref id="dpkgchangelog">.
3537 <sect1 id="f-Changes">
3538 <heading><tt>Changes</tt></heading>
3541 This multiline field contains the human-readable changes data, describing
3542 the differences between the last version and the current one.
3546 The first line of the field value (the part on the same line
3547 as <tt>Changes:</tt>) is always empty. The content of the
3548 field is expressed as continuation lines, with each line
3549 indented by at least one space. Blank lines must be
3550 represented by a line consisting only of a space and a full
3555 The value of this field is usually extracted from the
3556 <file>debian/changelog</file> file - see
3557 <ref id="dpkgchangelog">).
3561 Each version's change information should be preceded by a
3562 "title" line giving at least the version, distribution(s)
3563 and urgency, in a human-readable way.
3567 If data from several versions is being returned the entry
3568 for the most recent version should be returned first, and
3569 entries should be separated by the representation of a
3570 blank line (the "title" line may also be followed by the
3571 representation of a blank line).
3575 <sect1 id="f-Binary">
3576 <heading><tt>Binary</tt></heading>
3579 This folded field is a list of binary packages. Its syntax and
3580 meaning varies depending on the control file in which it
3585 When it appears in the <file>.dsc</file> file, it lists binary
3586 packages which a source package can produce, separated by
3588 A space after each comma is conventional.
3589 </footnote>. The source package
3590 does not necessarily produce all of these binary packages for
3591 every architecture. The source control file doesn't contain
3592 details of which architectures are appropriate for which of
3593 the binary packages.
3597 When it appears in a <file>.changes</file> file, it lists the
3598 names of the binary packages being uploaded, separated by
3599 whitespace (not commas).
3603 <sect1 id="f-Installed-Size">
3604 <heading><tt>Installed-Size</tt></heading>
3607 This field appears in the control files of binary packages,
3608 and in the <file>Packages</file> files. It gives an estimate
3609 of the total amount of disk space required to install the
3610 named package. Actual installed size may vary based on block
3611 size, file system properties, or actions taken by package
3616 The disk space is given as the integer value of the estimated
3617 installed size in bytes, divided by 1024 and rounded up.
3621 <sect1 id="f-Files">
3622 <heading><tt>Files</tt></heading>
3625 This field contains a list of files with information about
3626 each one. The exact information and syntax varies with
3631 In all cases, Files is a multiline field. The first line of
3632 the field value (the part on the same line as <tt>Files:</tt>)
3633 is always empty. The content of the field is expressed as
3634 continuation lines, one line per file. Each line must be
3635 indented by one space and contain a number of sub-fields,
3636 separated by spaces, as described below.
3640 In the <file>.dsc</file> file, each line contains the MD5
3641 checksum, size and filename of the tar file and (if
3642 applicable) diff file which make up the remainder of the
3643 source package<footnote>
3644 That is, the parts which are not the <tt>.dsc</tt>.
3645 </footnote>. For example:
3648 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3649 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3651 The exact forms of the filenames are described
3652 in <ref id="pkg-sourcearchives">.
3656 In the <file>.changes</file> file this contains one line per
3657 file being uploaded. Each line contains the MD5 checksum,
3658 size, section and priority and the filename. For example:
3661 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3662 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3663 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3664 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3666 The <qref id="f-Section">section</qref>
3667 and <qref id="f-Priority">priority</qref> are the values of
3668 the corresponding fields in the main source control file. If
3669 no section or priority is specified then <tt>-</tt> should be
3670 used, though section and priority values must be specified for
3671 new packages to be installed properly.
3675 The special value <tt>byhand</tt> for the section in a
3676 <tt>.changes</tt> file indicates that the file in question
3677 is not an ordinary package file and must by installed by
3678 hand by the distribution maintainers. If the section is
3679 <tt>byhand</tt> the priority should be <tt>-</tt>.
3683 If a new Debian revision of a package is being shipped and
3684 no new original source archive is being distributed the
3685 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3686 entry for the original source archive
3687 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3688 but the <file>.changes</file> file should leave it out. In
3689 this case the original source archive on the distribution
3690 site must match exactly, byte-for-byte, the original
3691 source archive which was used to generate the
3692 <file>.dsc</file> file and diff which are being uploaded.</p>
3695 <sect1 id="f-Closes">
3696 <heading><tt>Closes</tt></heading>
3699 A space-separated list of bug report numbers that the upload
3700 governed by the .changes file closes.
3704 <sect1 id="f-Homepage">
3705 <heading><tt>Homepage</tt></heading>
3708 The URL of the web site for this package, preferably (when
3709 applicable) the site from which the original source can be
3710 obtained and any additional upstream documentation or
3711 information may be found. The content of this field is a
3712 simple URL without any surrounding characters such as
3717 <sect1 id="f-Checksums">
3718 <heading><tt>Checksums-Sha1</tt>
3719 and <tt>Checksums-Sha256</tt></heading>
3722 These multiline fields contain a list of files with a checksum and size
3723 for each one. Both <tt>Checksums-Sha1</tt>
3724 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3725 only in the checksum algorithm used: SHA-1
3726 for <tt>Checksums-Sha1</tt> and SHA-256
3727 for <tt>Checksums-Sha256</tt>.
3731 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3732 multiline fields. The first line of the field value (the part
3733 on the same line as <tt>Checksums-Sha1:</tt>
3734 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3735 of the field is expressed as continuation lines, one line per
3736 file. Each line consists of the checksum, a space, the file
3737 size, a space, and the file name. For example (from
3738 a <file>.changes</file> file):
3741 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3742 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3743 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3744 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3746 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3747 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3748 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3749 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3754 In the <file>.dsc</file> file, these fields list all
3755 files that make up the source package. In
3756 the <file>.changes</file> file, these fields list all
3757 files being uploaded. The list of files in these fields
3758 must match the list of files in the <tt>Files</tt> field.
3763 <heading><tt>DM-Upload-Allowed</tt></heading>
3766 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3770 <sect1 id="f-VCS-fields">
3771 <heading>Version Control System (VCS) fields</heading>
3774 Debian source packages are increasingly developed using VCSs. The
3775 purpose of the following fields is to indicate a publicly accessible
3776 repository where the Debian source package is developed.
3779 <tag><tt>Vcs-Browser</tt></tag>
3782 URL of a web interface for browsing the repository.
3787 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3788 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3789 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3794 The field name identifies the VCS. The field's value uses the
3795 version control system's conventional syntax for describing
3796 repository locations and should be sufficient to locate the
3797 repository used for packaging. Ideally, it also locates the
3798 branch used for development of new versions of the Debian
3802 In the case of Git, the value consists of a URL, optionally
3803 followed by the word <tt>-b</tt> and the name of a branch in
3804 the indicated repository, following the syntax of the
3805 <tt>git clone</tt> command. If no branch is specified, the
3806 packaging should be on the default branch.
3809 More than one different VCS may be specified for the same
3817 <sect1 id="f-Package-List">
3818 <heading><tt>Package-List</tt></heading>
3821 Multiline field listing all the packages that can be built from
3822 the source package, considering every architecture. The first line
3823 of the field value is empty. Each one of the next lines describes
3824 one binary package, by listing its name, type, section and priority
3825 separated by spaces. Fifth and subsequent space-separated items
3826 may be present and parsers must allow them. See the
3827 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3832 <sect1 id="f-Package-Type">
3833 <heading><tt>Package-Type</tt></heading>
3836 Simple field containing a word indicating the type of package:
3837 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3838 packages. Other types not defined here may be indicated. In
3839 source package control files, the <tt>Package-Type</tt> field
3840 should be omitted instead of giving it a value of <tt>deb</tt>, as
3841 this value is assumed for paragraphs lacking this field.
3846 <heading><tt>Dgit</tt></heading>
3849 Folded field containing a single git commit hash, presented in
3850 full, followed optionally by whitespace and other data to be
3851 defined in future extensions.
3855 Declares that the source package corresponds exactly to a
3856 referenced commit in a Git repository available at the canonical
3857 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3858 bidirectional gateway between the Debian archive and Git. The
3859 commit is reachable from at least one reference whose name matches
3860 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3867 <heading>User-defined fields</heading>
3870 Additional user-defined fields may be added to the
3871 source package control file. Such fields will be
3872 ignored, and not copied to (for example) binary or
3873 Debian source control files or upload control files.
3877 If you wish to add additional unsupported fields to
3878 these output files you should use the mechanism
3883 Fields in the main source control information file with
3884 names starting <tt>X</tt>, followed by one or more of
3885 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3886 be copied to the output files. Only the part of the
3887 field name after the hyphen will be used in the output
3888 file. Where the letter <tt>B</tt> is used the field
3889 will appear in binary package control files, where the
3890 letter <tt>S</tt> is used in Debian source control
3891 files and where <tt>C</tt> is used in upload control
3892 (<tt>.changes</tt>) files.
3896 For example, if the main source information control file
3899 XBS-Comment: I stand between the candle and the star.
3901 then the binary and Debian source control files will contain the
3904 Comment: I stand between the candle and the star.
3910 <sect id="obsolete-control-data-fields">
3911 <heading>Obsolete fields</heading>
3914 The following fields have been obsoleted and may be found in packages
3915 conforming with previous versions of the Policy.
3918 <sect1 id="f-DM-Upload-Allowed">
3919 <heading><tt>DM-Upload-Allowed</tt></heading>
3922 Indicates that Debian Maintainers may upload this package to
3923 the Debian archive. The only valid value is <tt>yes</tt>. This
3924 field was used to regulate uploads by Debian Maintainers, See the
3925 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3926 name="Endorse the concept of Debian Maintainers"> for more details.
3935 <chapt id="maintainerscripts">
3936 <heading>Package maintainer scripts and installation procedure</heading>
3939 <heading>Introduction to package maintainer scripts</heading>
3942 It is possible to supply scripts as part of a package which
3943 the package management system will run for you when your
3944 package is installed, upgraded or removed.
3948 These scripts are the control information
3949 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3950 and <prgn>postrm</prgn>. They must be proper executable files;
3951 if they are scripts (which is recommended), they must start with
3952 the usual <tt>#!</tt> convention. They should be readable and
3953 executable by anyone, and must not be world-writable.
3957 The package management system looks at the exit status from
3958 these scripts. It is important that they exit with a
3959 non-zero status if there is an error, so that the package
3960 management system can stop its processing. For shell
3961 scripts this means that you <em>almost always</em> need to
3962 use <tt>set -e</tt> (this is usually true when writing shell
3963 scripts, in fact). It is also important, of course, that
3964 they exit with a zero status if everything went well.
3968 Additionally, packages interacting with users
3969 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3970 should install a <prgn>config</prgn> script as a control
3971 information file. See <ref id="maintscriptprompt"> for details.
3975 When a package is upgraded a combination of the scripts from
3976 the old and new packages is called during the upgrade
3977 procedure. If your scripts are going to be at all
3978 complicated you need to be aware of this, and may need to
3979 check the arguments to your scripts.
3983 Broadly speaking the <prgn>preinst</prgn> is called before
3984 (a particular version of) a package is unpacked, and the
3985 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3986 before (a version of) a package is removed and the
3987 <prgn>postrm</prgn> afterwards.
3991 Programs called from maintainer scripts should not normally
3992 have a path prepended to them. Before installation is
3993 started, the package management system checks to see if the
3994 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3995 and <prgn>update-rc.d</prgn> can be found via the
3996 <tt>PATH</tt> environment variable. Those programs, and any
3997 other program that one would expect to be in the
3998 <tt>PATH</tt>, should thus be invoked without an absolute
3999 pathname. Maintainer scripts should also not reset the
4000 <tt>PATH</tt>, though they might choose to modify it by
4001 prepending or appending package-specific directories. These
4002 considerations really apply to all shell scripts.</p>
4005 <sect id="idempotency">
4006 <heading>Maintainer scripts idempotency</heading>
4009 It is necessary for the error recovery procedures that the
4010 scripts be idempotent. This means that if it is run
4011 successfully, and then it is called again, it doesn't bomb
4012 out or cause any harm, but just ensures that everything is
4013 the way it ought to be. If the first call failed, or
4014 aborted half way through for some reason, the second call
4015 should merely do the things that were left undone the first
4016 time, if any, and exit with a success status if everything
4018 This is so that if an error occurs, the user interrupts
4019 <prgn>dpkg</prgn> or some other unforeseen circumstance
4020 happens you don't leave the user with a badly-broken
4021 package when <prgn>dpkg</prgn> attempts to repeat the
4027 <sect id="controllingterminal">
4028 <heading>Controlling terminal for maintainer scripts</heading>
4031 Maintainer scripts are not guaranteed to run with a controlling
4032 terminal and may not be able to interact with the user. They
4033 must be able to fall back to noninteractive behavior if no
4034 controlling terminal is available. Maintainer scripts that
4035 prompt via a program conforming to the Debian Configuration
4036 Management Specification (see <ref id="maintscriptprompt">) may
4037 assume that program will handle falling back to noninteractive
4042 For high-priority prompts without a reasonable default answer,
4043 maintainer scripts may abort if there is no controlling
4044 terminal. However, this situation should be avoided if at all
4045 possible, since it prevents automated or unattended installs.
4046 In most cases, users will consider this to be a bug in the
4051 <sect id="exitstatus">
4052 <heading>Exit status</heading>
4055 Each script must return a zero exit status for
4056 success, or a nonzero one for failure, since the package
4057 management system looks for the exit status of these scripts
4058 and determines what action to take next based on that datum.
4062 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4067 What follows is a summary of all the ways in which maintainer
4068 scripts may be called along with what facilities those scripts
4069 may rely on being available at that time. Script names preceded
4070 by <var>new-</var> are the scripts from the new version of a
4071 package being installed, upgraded to, or downgraded to. Script
4072 names preceded by <var>old-</var> are the scripts from the old
4073 version of a package that is being upgraded from or downgraded
4078 The <prgn>preinst</prgn> script may be called in the following
4081 <tag><var>new-preinst</var> <tt>install</tt></tag>
4082 <tag><var>new-preinst</var> <tt>install</tt>
4083 <var>old-version</var></tag>
4084 <tag><var>new-preinst</var> <tt>upgrade</tt>
4085 <var>old-version</var></tag>
4087 The package will not yet be unpacked, so
4088 the <prgn>preinst</prgn> script cannot rely on any files
4089 included in its package. Only essential packages and
4090 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4091 available. Pre-dependencies will have been configured at
4092 least once, but at the time the <prgn>preinst</prgn> is
4093 called they may only be in an "Unpacked" or "Half-Configured"
4094 state if a previous version of the pre-dependency was
4095 completely configured and has not been removed since then.
4098 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4099 <var>new-version</var></tag>
4101 Called during error handling of an upgrade that failed after
4102 unpacking the new package because the <tt>postrm
4103 upgrade</tt> action failed. The unpacked files may be
4104 partly from the new version or partly missing, so the script
4105 cannot rely on files included in the package. Package
4106 dependencies may not be available. Pre-dependencies will be
4107 at least "Unpacked" following the same rules as above, except
4108 they may be only "Half-Installed" if an upgrade of the
4109 pre-dependency failed.<footnote>
4110 This can happen if the new version of the package no
4111 longer pre-depends on a package that had been partially
4119 The <prgn>postinst</prgn> script may be called in the following
4122 <tag><var>postinst</var> <tt>configure</tt>
4123 <var>most-recently-configured-version</var></tag>
4125 The files contained in the package will be unpacked. All
4126 package dependencies will at least be "Unpacked". If there
4127 are no circular dependencies involved, all package
4128 dependencies will be configured. For behavior in the case
4129 of circular dependencies, see the discussion
4130 in <ref id="binarydeps">.
4133 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4134 <var>new-version</var></tag>
4135 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4136 <tt>in-favour</tt> <var>package</var>
4137 <var>new-version</var></tag>
4138 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4139 <tag><var>deconfigured's-postinst</var>
4140 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4141 <var>failed-install-package</var> <var>version</var>
4142 [<tt>removing</tt> <var>conflicting-package</var>
4143 <var>version</var>]</tag>
4145 The files contained in the package will be unpacked. All
4146 package dependencies will at least be "Half-Installed" and
4147 will have previously been configured and not removed.
4148 However, dependencies may not be configured or even fully
4149 unpacked in some error situations.<footnote>
4150 For example, suppose packages foo and bar are "Installed"
4151 with foo depending on bar. If an upgrade of bar were
4152 started and then aborted, and then an attempt to remove
4153 foo failed because its <prgn>prerm</prgn> script failed,
4154 foo's <tt>postinst abort-remove</tt> would be called with
4155 bar only "Half-Installed".
4157 The <prgn>postinst</prgn> should still attempt any actions
4158 for which its dependencies are required, since they will
4159 normally be available, but consider the correct error
4160 handling approach if those actions fail. Aborting
4161 the <prgn>postinst</prgn> action if commands or facilities
4162 from the package dependencies are not available is often the
4169 The <prgn>prerm</prgn> script may be called in the following
4172 <tag><var>prerm</var> <tt>remove</tt></tag>
4173 <tag><var>old-prerm</var>
4174 <tt>upgrade</tt><var>new-version</var></tag>
4175 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4176 <tt>in-favour</tt> <var>package</var>
4177 <var>new-version</var></tag>
4178 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4179 <tt>in-favour</tt> <var>package-being-installed</var>
4180 <var>version</var> [<tt>removing</tt>
4181 <var>conflicting-package</var> <var>version</var>]</tag>
4183 The package whose <prgn>prerm</prgn> is being called will be
4184 at least "Half-Installed". All package dependencies will at
4185 least be "Half-Installed" and will have previously been
4186 configured and not removed. If there was no error, all
4187 dependencies will at least be "Unpacked", but these actions
4188 may be called in various error states where dependencies are
4189 only "Half-Installed" due to a partial upgrade.
4192 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4193 <var>old-version</var></tag>
4195 Called during error handling when <tt>prerm upgrade</tt>
4196 fails. The new package will not yet be unpacked, and all
4197 the same constraints as for <tt>preinst upgrade</tt> apply.
4203 The <prgn>postrm</prgn> script may be called in the following
4206 <tag><var>postrm</var> <tt>remove</tt></tag>
4207 <tag><var>postrm</var> <tt>purge</tt></tag>
4208 <tag><var>old-postrm</var> <tt>upgrade</tt>
4209 <var>new-version</var></tag>
4210 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4211 <var>overwriter</var> <var>overwriter-version</var></tag>
4213 The <prgn>postrm</prgn> script is called after the package's
4214 files have been removed or replaced. The package
4215 whose <prgn>postrm</prgn> is being called may have
4216 previously been deconfigured and only be "Unpacked", at which
4217 point subsequent package changes do not consider its
4218 dependencies. Therefore, all <prgn>postrm</prgn> actions
4219 may only rely on essential packages and must gracefully skip
4220 any actions that require the package's dependencies if those
4221 dependencies are unavailable.<footnote>
4222 This is often done by checking whether the command or
4223 facility the <prgn>postrm</prgn> intends to call is
4224 available before calling it. For example:
4226 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4227 . /usr/share/debconf/confmodule
4231 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4232 configuration for the package
4233 if <package>debconf</package> is installed.
4237 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4238 <var>old-version</var></tag>
4240 Called when the old <tt>postrm upgrade</tt> action fails.
4241 The new package will be unpacked, but only essential
4242 packages and pre-dependencies can be relied on.
4243 Pre-dependencies will either be configured or will be
4244 "Unpacked" or "Half-Configured" but previously had been
4245 configured and was never removed.
4248 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4249 <tag><var>new-postrm</var> <tt>abort-install</tt>
4250 <var>old-version</var></tag>
4251 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4252 <var>old-version</var></tag>
4254 Called before unpacking the new package as part of the
4255 error handling of <prgn>preinst</prgn> failures. May assume
4256 the same state as <prgn>preinst</prgn> can assume.
4262 <sect id="unpackphase">
4263 <heading>Details of unpack phase of installation or upgrade</heading>
4266 The procedure on installation/upgrade/overwrite/disappear
4267 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4268 stage of <tt>dpkg --install</tt>) is as follows. In each
4269 case, if a major error occurs (unless listed below) the
4270 actions are, in general, run backwards - this means that the
4271 maintainer scripts are run with different arguments in
4272 reverse order. These are the "error unwind" calls listed
4279 If a version of the package is already "Installed", call
4280 <example compact="compact">
4281 <var>old-prerm</var> upgrade <var>new-version</var>
4285 If the script runs but exits with a non-zero
4286 exit status, <prgn>dpkg</prgn> will attempt:
4287 <example compact="compact">
4288 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4290 If this works, the upgrade continues. If this
4291 does not work, the error unwind:
4292 <example compact="compact">
4293 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4295 If this works, then the old-version is
4296 "Installed", if not, the old version is in a
4297 "Half-Configured" state.
4303 If a "conflicting" package is being removed at the same time,
4304 or if any package will be broken (due to <tt>Breaks</tt>):
4307 If <tt>--auto-deconfigure</tt> is
4308 specified, call, for each package to be deconfigured
4309 due to <tt>Breaks</tt>:
4310 <example compact="compact">
4311 <var>deconfigured's-prerm</var> deconfigure \
4312 in-favour <var>package-being-installed</var> <var>version</var>
4315 <example compact="compact">
4316 <var>deconfigured's-postinst</var> abort-deconfigure \
4317 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4319 The deconfigured packages are marked as
4320 requiring configuration, so that if
4321 <tt>--install</tt> is used they will be
4322 configured again if possible.
4325 If any packages depended on a conflicting
4326 package being removed and <tt>--auto-deconfigure</tt> is
4327 specified, call, for each such package:
4328 <example compact="compact">
4329 <var>deconfigured's-prerm</var> deconfigure \
4330 in-favour <var>package-being-installed</var> <var>version</var> \
4331 removing <var>conflicting-package</var> <var>version</var>
4334 <example compact="compact">
4335 <var>deconfigured's-postinst</var> abort-deconfigure \
4336 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4337 removing <var>conflicting-package</var> <var>version</var>
4339 The deconfigured packages are marked as
4340 requiring configuration, so that if
4341 <tt>--install</tt> is used they will be
4342 configured again if possible.
4345 To prepare for removal of each conflicting package, call:
4346 <example compact="compact">
4347 <var>conflictor's-prerm</var> remove \
4348 in-favour <var>package</var> <var>new-version</var>
4351 <example compact="compact">
4352 <var>conflictor's-postinst</var> abort-remove \
4353 in-favour <var>package</var> <var>new-version</var>
4362 If the package is being upgraded, call:
4363 <example compact="compact">
4364 <var>new-preinst</var> upgrade <var>old-version</var>
4366 If this fails, we call:
4368 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4375 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4377 is called. If this works, then the old version
4378 is in an "Installed" state, or else it is left
4379 in an "Unpacked" state.
4384 If it fails, then the old version is left
4385 in an "Half-Installed" state.
4392 Otherwise, if the package had some configuration
4393 files from a previous version installed (i.e., it
4394 is in the "Config-Files" state):
4395 <example compact="compact">
4396 <var>new-preinst</var> install <var>old-version</var>
4400 <var>new-postrm</var> abort-install <var>old-version</var>
4402 If this fails, the package is left in a
4403 "Half-Installed" state, which requires a
4404 reinstall. If it works, the packages is left in
4405 a "Config-Files" state.
4408 Otherwise (i.e., the package was completely purged):
4409 <example compact="compact">
4410 <var>new-preinst</var> install
4413 <example compact="compact">
4414 <var>new-postrm</var> abort-install
4416 If the error-unwind fails, the package is in a
4417 "Half-Installed" phase, and requires a
4418 reinstall. If the error unwind works, the
4419 package is in the "Not-Installed" state.
4426 The new package's files are unpacked, overwriting any
4427 that may be on the system already, for example any
4428 from the old version of the same package or from
4429 another package. Backups of the old files are kept
4430 temporarily, and if anything goes wrong the package
4431 management system will attempt to put them back as
4432 part of the error unwind.
4436 It is an error for a package to contain files which
4437 are on the system in another package, unless
4438 <tt>Replaces</tt> is used (see <ref id="replaces">).
4440 The following paragraph is not currently the case:
4441 Currently the <tt>- - force-overwrite</tt> flag is
4442 enabled, downgrading it to a warning, but this may not
4448 It is a more serious error for a package to contain a
4449 plain file or other kind of non-directory where another
4450 package has a directory (again, unless
4451 <tt>Replaces</tt> is used). This error can be
4452 overridden if desired using
4453 <tt>--force-overwrite-dir</tt>, but this is not
4458 Packages which overwrite each other's files produce
4459 behavior which, though deterministic, is hard for the
4460 system administrator to understand. It can easily
4461 lead to "missing" programs if, for example, a package
4462 is unpacked which overwrites a file from another
4463 package, and is then removed again.<footnote>
4464 Part of the problem is due to what is arguably a
4465 bug in <prgn>dpkg</prgn>.
4470 A directory will never be replaced by a symbolic link
4471 to a directory or vice versa; instead, the existing
4472 state (symlink or not) will be left alone and
4473 <prgn>dpkg</prgn> will follow the symlink if there is
4482 If the package is being upgraded, call
4483 <example compact="compact">
4484 <var>old-postrm</var> upgrade <var>new-version</var>
4488 If this fails, <prgn>dpkg</prgn> will attempt:
4489 <example compact="compact">
4490 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4492 If this works, installation continues. If not,
4494 <example compact="compact">
4495 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4497 If this fails, the old version is left in a
4498 "Half-Installed" state. If it works, dpkg now
4500 <example compact="compact">
4501 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4503 If this fails, the old version is left in a
4504 "Half-Installed" state. If it works, dpkg now
4506 <example compact="compact">
4507 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4509 If this fails, the old version is in an
4516 This is the point of no return - if
4517 <prgn>dpkg</prgn> gets this far, it won't back off
4518 past this point if an error occurs. This will
4519 leave the package in a fairly bad state, which
4520 will require a successful re-installation to clear
4521 up, but it's when <prgn>dpkg</prgn> starts doing
4522 things that are irreversible.
4527 Any files which were in the old version of the package
4528 but not in the new are removed.
4532 The new file list replaces the old.
4536 The new maintainer scripts replace the old.
4540 Any packages all of whose files have been overwritten
4541 during the installation, and which aren't required for
4542 dependencies, are considered to have been removed.
4543 For each such package
4546 <prgn>dpkg</prgn> calls:
4547 <example compact="compact">
4548 <var>disappearer's-postrm</var> disappear \
4549 <var>overwriter</var> <var>overwriter-version</var>
4553 The package's maintainer scripts are removed.
4556 It is noted in the status database as being in a
4557 sane state, namely "Not-Installed" (any conffiles
4558 it may have are ignored, rather than being
4559 removed by <prgn>dpkg</prgn>). Note that
4560 disappearing packages do not have their prerm
4561 called, because <prgn>dpkg</prgn> doesn't know
4562 in advance that the package is going to
4569 Any files in the package we're unpacking that are also
4570 listed in the file lists of other packages are removed
4571 from those lists. (This will lobotomize the file list
4572 of the "conflicting" package if there is one.)
4576 The backup files made during installation, above, are
4582 The new package's status is now sane, and recorded as
4587 Here is another point of no return - if the
4588 conflicting package's removal fails we do not unwind
4589 the rest of the installation; the conflicting package
4590 is left in a half-removed limbo.
4595 If there was a conflicting package we go and do the
4596 removal actions (described below), starting with the
4597 removal of the conflicting package's files (any that
4598 are also in the package being unpacked have already
4599 been removed from the conflicting package's file list,
4600 and so do not get removed now).
4606 <sect id="configdetails"><heading>Details of configuration</heading>
4609 When we configure a package (this happens with <tt>dpkg
4610 --install</tt> and <tt>dpkg --configure</tt>), we first
4611 update any <tt>conffile</tt>s and then call:
4612 <example compact="compact">
4613 <var>postinst</var> configure <var>most-recently-configured-version</var>
4618 No attempt is made to unwind after errors during
4619 configuration. If the configuration fails, the package is in
4620 a "Half-Configured" state, and an error message is generated.
4624 If there is no most recently configured version
4625 <prgn>dpkg</prgn> will pass a null argument.
4628 Historical note: Truly ancient (pre-1997) versions of
4629 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4630 (including the angle brackets) in this case. Even older
4631 ones did not pass a second argument at all, under any
4632 circumstance. Note that upgrades using such an old dpkg
4633 version are unlikely to work for other reasons, even if
4634 this old argument behavior is handled by your postinst script.
4640 <sect id="removedetails"><heading>Details of removal and/or
4641 configuration purging</heading>
4647 <example compact="compact">
4648 <var>prerm</var> remove
4652 If prerm fails during replacement due to conflict
4654 <var>conflictor's-postinst</var> abort-remove \
4655 in-favour <var>package</var> <var>new-version</var>
4659 <var>postinst</var> abort-remove
4663 If this fails, the package is in a "Half-Configured"
4664 state, or else it remains "Installed".
4668 The package's files are removed (except <tt>conffile</tt>s).
4671 <example compact="compact">
4672 <var>postrm</var> remove
4676 If it fails, there's no error unwind, and the package is in
4677 an "Half-Installed" state.
4682 All the maintainer scripts except the <prgn>postrm</prgn>
4687 If we aren't purging the package we stop here. Note
4688 that packages which have no <prgn>postrm</prgn> and no
4689 <tt>conffile</tt>s are automatically purged when
4690 removed, as there is no difference except for the
4691 <prgn>dpkg</prgn> status.
4695 The <tt>conffile</tt>s and any backup files
4696 (<tt>~</tt>-files, <tt>#*#</tt> files,
4697 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4702 <example compact="compact">
4703 <var>postrm</var> purge
4707 If this fails, the package remains in a "Config-Files"
4712 The package's file list is removed.
4721 <chapt id="relationships">
4722 <heading>Declaring relationships between packages</heading>
4724 <sect id="depsyntax">
4725 <heading>Syntax of relationship fields</heading>
4728 These fields all have a uniform syntax. They are a list of
4729 package names separated by commas.
4733 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4734 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4735 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4736 control fields of the package, which declare
4737 dependencies on other packages, the package names listed may
4738 also include lists of alternative package names, separated
4739 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4740 that part of the dependency can be satisfied by any one of
4741 the alternative packages.
4745 All of the fields except for <tt>Provides</tt> may restrict
4746 their applicability to particular versions of each named
4747 package. This is done in parentheses after each individual
4748 package name; the parentheses should contain a relation from
4749 the list below followed by a version number, in the format
4750 described in <ref id="f-Version">.
4754 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4755 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4756 earlier, earlier or equal, exactly equal, later or equal and
4757 strictly later, respectively. The deprecated
4758 forms <tt><</tt> and <tt>></tt> were confusingly used to
4759 mean earlier/later or equal, rather than strictly earlier/later,
4760 and must not appear in new packages (though <prgn>dpkg</prgn>
4761 still supports them with a warning).
4765 Whitespace may appear at any point in the version
4766 specification subject to the rules in <ref
4767 id="controlsyntax">, and must appear where it's necessary to
4768 disambiguate; it is not otherwise significant. All of the
4769 relationship fields can only be folded in source package control files. For
4770 consistency and in case of future changes to
4771 <prgn>dpkg</prgn> it is recommended that a single space be
4772 used after a version relationship and before a version
4773 number; it is also conventional to put a single space after
4774 each comma, on either side of each vertical bar, and before
4775 each open parenthesis. When opening a continuation line in a relationship field, it
4776 is conventional to do so after a comma and before the space
4777 following that comma.
4781 For example, a list of dependencies might appear as:
4782 <example compact="compact">
4785 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4790 Relationships may be restricted to a certain set of
4791 architectures. This is indicated in brackets after each
4792 individual package name and the optional version specification.
4793 The brackets enclose a non-empty list of Debian architecture names
4794 in the format described in <ref id="arch-spec">,
4795 separated by whitespace. Exclamation marks may be prepended to
4796 each of the names. (It is not permitted for some names to be
4797 prepended with exclamation marks while others aren't.)
4801 For build relationship fields
4802 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4803 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4804 the current Debian host architecture is not in this list and
4805 there are no exclamation marks in the list, or it is in the list
4806 with a prepended exclamation mark, the package name and the
4807 associated version specification are ignored completely for the
4808 purposes of defining the relationships.
4813 <example compact="compact">
4815 Build-Depends-Indep: texinfo
4816 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4817 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4819 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4820 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4821 <tt>gnumach-dev</tt> only on hurd-i386.
4825 For binary relationship fields and the <tt>Built-Using</tt>
4826 field, the architecture restriction
4827 syntax is only supported in the source package control
4828 file <file>debian/control</file>. When the corresponding binary
4829 package control file is generated, the relationship will either
4830 be omitted or included without the architecture restriction
4831 based on the architecture of the binary package. This means
4832 that architecture restrictions must not be used in binary
4833 relationship fields for architecture-independent packages
4834 (<tt>Architecture: all</tt>).
4839 <example compact="compact">
4840 Depends: foo [i386], bar [amd64]
4842 becomes <tt>Depends: foo</tt> when the package is built on
4843 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4844 package is built on the <tt>amd64</tt> architecture, and omitted
4845 entirely in binary packages built on all other architectures.
4849 If the architecture-restricted dependency is part of a set of
4850 alternatives using <tt>|</tt>, that alternative is ignored
4851 completely on architectures that do not match the restriction.
4853 <example compact="compact">
4854 Build-Depends: foo [!i386] | bar [!amd64]
4856 is equivalent to <tt>bar</tt> on the i386 architecture, to
4857 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4858 bar</tt> on all other architectures.
4862 Relationships may also be restricted to a certain set of
4863 architectures using architecture wildcards in the format
4864 described in <ref id="arch-wildcard-spec">. The syntax for
4865 declaring such restrictions is the same as declaring
4866 restrictions using a certain set of architectures without
4867 architecture wildcards. For example:
4868 <example compact="compact">
4869 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4871 is equivalent to <tt>foo</tt> on architectures using the Linux
4872 kernel and any cpu, <tt>bar</tt> on architectures using any
4873 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4874 using a kernel other than Linux.
4878 Note that the binary package relationship fields such as
4879 <tt>Depends</tt> appear in one of the binary package
4880 sections of the control file, whereas the build-time
4881 relationships such as <tt>Build-Depends</tt> appear in the
4882 source package section of the control file (which is the
4887 <sect id="binarydeps">
4888 <heading>Binary Dependencies - <tt>Depends</tt>,
4889 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4890 <tt>Pre-Depends</tt>
4894 Packages can declare in their control file that they have
4895 certain relationships to other packages - for example, that
4896 they may not be installed at the same time as certain other
4897 packages, and/or that they depend on the presence of others.
4901 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4902 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4903 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4904 <tt>Breaks</tt> is described in <ref id="breaks">, and
4905 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4906 rest are described below.
4910 These seven fields are used to declare a dependency
4911 relationship by one package on another. Except for
4912 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4913 depending (binary) package's control file.
4914 (<tt>Enhances</tt> appears in the recommending package's
4915 control file, and <tt>Breaks</tt> appears in the version of
4916 depended-on package which causes the named package to
4921 A <tt>Depends</tt> field takes effect <em>only</em> when a
4922 package is to be configured. It does not prevent a package
4923 being on the system in an unconfigured state while its
4924 dependencies are unsatisfied, and it is possible to replace
4925 a package whose dependencies are satisfied and which is
4926 properly installed with a different version whose
4927 dependencies are not and cannot be satisfied; when this is
4928 done the depending package will be left unconfigured (since
4929 attempts to configure it will give errors) and will not
4930 function properly. If it is necessary, a
4931 <tt>Pre-Depends</tt> field can be used, which has a partial
4932 effect even when a package is being unpacked, as explained
4933 in detail below. (The other three dependency fields,
4934 <tt>Recommends</tt>, <tt>Suggests</tt> and
4935 <tt>Enhances</tt>, are only used by the various front-ends
4936 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4937 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4941 Since <tt>Depends</tt> only places requirements on the order in
4942 which packages are configured, packages in an installation run
4943 are usually all unpacked first and all configured later.
4945 This approach makes dependency resolution easier. If two
4946 packages A and B are being upgraded, the installed package A
4947 depends on exactly the installed package B, and the new
4948 package A depends on exactly the new package B (a common
4949 situation when upgrading shared libraries and their
4950 corresponding development packages), satisfying the
4951 dependencies at every stage of the upgrade would be
4952 impossible. This relaxed restriction means that both new
4953 packages can be unpacked together and then configured in their
4959 If there is a circular dependency among packages being installed
4960 or removed, installation or removal order honoring the
4961 dependency order is impossible, requiring the dependency loop be
4962 broken at some point and the dependency requirements violated
4963 for at least one package. Packages involved in circular
4964 dependencies may not be able to rely on their dependencies being
4965 configured before they themselves are configured, depending on
4966 which side of the break of the circular dependency loop they
4967 happen to be on. If one of the packages in the loop has
4968 no <prgn>postinst</prgn> script, then the cycle will be broken
4969 at that package; this ensures that all <prgn>postinst</prgn>
4970 scripts are run with their dependencies properly configured if
4971 this is possible. Otherwise the breaking point is arbitrary.
4972 Packages should therefore avoid circular dependencies where
4973 possible, particularly if they have <prgn>postinst</prgn>
4978 The meaning of the five dependency fields is as follows:
4980 <tag><tt>Depends</tt></tag>
4983 This declares an absolute dependency. A package will
4984 not be configured unless all of the packages listed in
4985 its <tt>Depends</tt> field have been correctly
4986 configured (unless there is a circular dependency as
4991 The <tt>Depends</tt> field should be used if the
4992 depended-on package is required for the depending
4993 package to provide a significant amount of
4998 The <tt>Depends</tt> field should also be used if the
4999 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
5000 require the depended-on package to be unpacked or
5001 configured in order to run. In the case of <tt>postinst
5002 configure</tt>, the depended-on packages will be unpacked
5003 and configured first. (If both packages are involved in a
5004 dependency loop, this might not work as expected; see the
5005 explanation a few paragraphs back.) In the case
5006 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5007 actions, the package dependencies will normally be at
5008 least unpacked, but they may be only "Half-Installed" if a
5009 previous upgrade of the dependency failed.
5013 Finally, the <tt>Depends</tt> field should be used if the
5014 depended-on package is needed by the <prgn>postrm</prgn>
5015 script to fully clean up after the package removal. There
5016 is no guarantee that package dependencies will be
5017 available when <prgn>postrm</prgn> is run, but the
5018 depended-on package is more likely to be available if the
5019 package declares a dependency (particularly in the case
5020 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5021 script must gracefully skip actions that require a
5022 dependency if that dependency isn't available.
5026 <tag><tt>Recommends</tt></tag>
5029 This declares a strong, but not absolute, dependency.
5033 The <tt>Recommends</tt> field should list packages
5034 that would be found together with this one in all but
5035 unusual installations.
5039 <tag><tt>Suggests</tt></tag>
5041 This is used to declare that one package may be more
5042 useful with one or more others. Using this field
5043 tells the packaging system and the user that the
5044 listed packages are related to this one and can
5045 perhaps enhance its usefulness, but that installing
5046 this one without them is perfectly reasonable.
5049 <tag><tt>Enhances</tt></tag>
5051 This field is similar to Suggests but works in the
5052 opposite direction. It is used to declare that a
5053 package can enhance the functionality of another
5057 <tag><tt>Pre-Depends</tt></tag>
5060 This field is like <tt>Depends</tt>, except that it
5061 also forces <prgn>dpkg</prgn> to complete installation
5062 of the packages named before even starting the
5063 installation of the package which declares the
5064 pre-dependency, as follows:
5068 When a package declaring a pre-dependency is about to
5069 be <em>unpacked</em> the pre-dependency can be
5070 satisfied if the depended-on package is either fully
5071 configured, <em>or even if</em> the depended-on
5072 package(s) are only in the "Unpacked" or the "Half-Configured"
5073 state, provided that they have been configured
5074 correctly at some point in the past (and not removed
5075 or partially removed since). In this case, both the
5076 previously-configured and currently "Unpacked" or
5077 "Half-Configured" versions must satisfy any version
5078 clause in the <tt>Pre-Depends</tt> field.
5082 When the package declaring a pre-dependency is about to
5083 be <em>configured</em>, the pre-dependency will be treated
5084 as a normal <tt>Depends</tt>. It will be considered
5085 satisfied only if the depended-on package has been
5086 correctly configured. However, unlike
5087 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5088 permit circular dependencies to be broken. If a circular
5089 dependency is encountered while attempting to honor
5090 <tt>Pre-Depends</tt>, the installation will be aborted.
5094 <tt>Pre-Depends</tt> are also required if the
5095 <prgn>preinst</prgn> script depends on the named package.
5096 It is best to avoid this situation if possible.
5100 <tt>Pre-Depends</tt> should be used sparingly,
5101 preferably only by packages whose premature upgrade or
5102 installation would hamper the ability of the system to
5103 continue with any upgrade that might be in progress.
5107 You should not specify a <tt>Pre-Depends</tt> entry for a
5108 package before this has been discussed on the
5109 <tt>debian-devel</tt> mailing list and a consensus about
5110 doing that has been reached. See <ref id="dependencies">.
5117 When selecting which level of dependency to use you should
5118 consider how important the depended-on package is to the
5119 functionality of the one declaring the dependency. Some
5120 packages are composed of components of varying degrees of
5121 importance. Such a package should list using
5122 <tt>Depends</tt> the package(s) which are required by the
5123 more important components. The other components'
5124 requirements may be mentioned as Suggestions or
5125 Recommendations, as appropriate to the components' relative
5131 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5134 When one binary package declares that it breaks another,
5135 <prgn>dpkg</prgn> will refuse to allow the package which
5136 declares <tt>Breaks</tt> to be unpacked unless the broken
5137 package is deconfigured first, and it will refuse to
5138 allow the broken package to be reconfigured.
5142 A package will not be regarded as causing breakage merely
5143 because its configuration files are still installed; it must
5144 be at least "Half-Installed".
5148 A special exception is made for packages which declare that
5149 they break their own package name or a virtual package which
5150 they provide (see below): this does not count as a real
5155 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5156 version clause; such a <tt>Breaks</tt> is introduced in the
5157 version of an (implicit or explicit) dependency which violates
5158 an assumption or reveals a bug in earlier versions of the broken
5159 package, or which takes over a file from earlier versions of the
5160 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5161 will inform higher-level package management tools that the
5162 broken package must be upgraded before the new one.
5166 If the breaking package also overwrites some files from the
5167 older package, it should use <tt>Replaces</tt> to ensure this
5168 goes smoothly. See <ref id="replaces"> for a full discussion
5169 of taking over files from other packages, including how to
5170 use <tt>Breaks</tt> in those cases.
5174 Many of the cases where <tt>Breaks</tt> should be used were
5175 previously handled with <tt>Conflicts</tt>
5176 because <tt>Breaks</tt> did not yet exist.
5177 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5178 See <ref id="conflicts"> for more information about the
5183 <sect id="conflicts">
5184 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5187 When one binary package declares a conflict with another using
5188 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5189 allow them to be unpacked on the system at the same time. This
5190 is a stronger restriction than <tt>Breaks</tt>, which prevents
5191 the broken package from being configured while the breaking
5192 package is in the "Unpacked" state but allows both packages to
5193 be unpacked at the same time.
5197 If one package is to be unpacked, the other must be removed
5198 first. If the package being unpacked is marked as replacing
5199 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5200 normally be used in this case) the one on the system, or the one
5201 on the system is marked as deselected, or both packages are
5202 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5203 automatically remove the package which is causing the conflict.
5204 Otherwise, it will halt the installation of the new package with
5205 an error. This mechanism is specifically designed to produce an
5206 error when the installed package is <tt>Essential</tt>, but the
5211 A package will not cause a conflict merely because its
5212 configuration files are still installed; it must be at least
5217 A special exception is made for packages which declare a
5218 conflict with their own package name, or with a virtual
5219 package which they provide (see below): this does not
5220 prevent their installation, and allows a package to conflict
5221 with others providing a replacement for it. You use this
5222 feature when you want the package in question to be the only
5223 package providing some feature.
5227 Normally, <tt>Breaks</tt> should be used instead
5228 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5229 stronger restriction on the ordering of package installation or
5230 upgrade and can make it more difficult for the package manager
5231 to find a correct solution to an upgrade or installation
5232 problem. <tt>Breaks</tt> should be used
5234 <item>when moving a file from one package to another (see
5235 <ref id="replaces">),</item>
5236 <item>when splitting a package (a special case of the previous
5238 <item>when the breaking package exposes a bug in or interacts
5239 badly with particular versions of the broken
5242 <tt>Conflicts</tt> should be used
5244 <item>when two packages provide the same file and will
5245 continue to do so,</item>
5246 <item>in conjunction with <tt>Provides</tt> when only one
5247 package providing a given virtual facility may be unpacked
5248 at a time (see <ref id="virtual">),</item>
5249 <item>in other cases where one must prevent simultaneous
5250 installation of two packages for reasons that are ongoing
5251 (not fixed in a later version of one of the packages) or
5252 that must prevent both packages from being unpacked at the
5253 same time, not just configured.</item>
5255 Be aware that adding <tt>Conflicts</tt> is normally not the best
5256 solution when two packages provide the same files. Depending on
5257 the reason for that conflict, using alternatives or renaming the
5258 files is often a better approach. See, for
5259 example, <ref id="binaries">.
5263 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5264 unless two packages cannot be installed at the same time or
5265 installing them both causes one of them to be broken or
5266 unusable. Having similar functionality or performing the same
5267 tasks as another package is not sufficient reason to
5268 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5272 A <tt>Conflicts</tt> entry may have an "earlier than" version
5273 clause if the reason for the conflict is corrected in a later
5274 version of one of the packages. However, normally the presence
5275 of an "earlier than" version clause is a sign
5276 that <tt>Breaks</tt> should have been used instead. An "earlier
5277 than" version clause in <tt>Conflicts</tt>
5278 prevents <prgn>dpkg</prgn> from upgrading or installing the
5279 package which declares such a conflict until the upgrade or
5280 removal of the conflicted-with package has been completed, which
5281 is a strong restriction.
5285 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5289 As well as the names of actual ("concrete") packages, the
5290 package relationship fields <tt>Depends</tt>,
5291 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5292 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5293 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5294 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5295 may mention "virtual packages".
5299 A <em>virtual package</em> is one which appears in the
5300 <tt>Provides</tt> control field of another package. The effect
5301 is as if the package(s) which provide a particular virtual
5302 package name had been listed by name everywhere the virtual
5303 package name appears. (See also <ref id="virtual_pkg">)
5307 If there are both concrete and virtual packages of the same
5308 name, then the dependency may be satisfied (or the conflict
5309 caused) by either the concrete package with the name in
5310 question or any other concrete package which provides the
5311 virtual package with the name in question. This is so that,
5312 for example, supposing we have
5313 <example compact="compact">
5316 </example> and someone else releases an enhanced version of
5317 the <tt>bar</tt> package they can say:
5318 <example compact="compact">
5322 and the <tt>bar-plus</tt> package will now also satisfy the
5323 dependency for the <tt>foo</tt> package.
5327 If a relationship field has a version number attached, only real
5328 packages will be considered to see whether the relationship is
5329 satisfied (or the prohibition violated, for a conflict or
5330 breakage). In other words, if a version number is specified,
5331 this is a request to ignore all <tt>Provides</tt> for that
5332 package name and consider only real packages. The package
5333 manager will assume that a package providing that virtual
5334 package is not of the "right" version. A <tt>Provides</tt>
5335 field may not contain version numbers, and the version number of
5336 the concrete package which provides a particular virtual package
5337 will not be considered when considering a dependency on or
5338 conflict with the virtual package name.<footnote>
5339 It is possible that a future release of <prgn>dpkg</prgn> may
5340 add the ability to specify a version number for each virtual
5341 package it provides. This feature is not yet present,
5342 however, and is expected to be used only infrequently.
5347 To specify which of a set of real packages should be the default
5348 to satisfy a particular dependency on a virtual package, list
5349 the real package as an alternative before the virtual one.
5353 If the virtual package represents a facility that can only be
5354 provided by one real package at a time, such as
5355 the <package>mail-transport-agent</package> virtual package that
5356 requires installation of a binary that would conflict with all
5357 other providers of that virtual package (see
5358 <ref id="mail-transport-agents">), all packages providing that
5359 virtual package should also declare a conflict with it
5360 using <tt>Conflicts</tt>. This will ensure that at most one
5361 provider of that virtual package is unpacked or installed at a
5366 <sect id="replaces"><heading>Overwriting files and replacing
5367 packages - <tt>Replaces</tt></heading>
5370 Packages can declare in their control file that they should
5371 overwrite files in certain other packages, or completely replace
5372 other packages. The <tt>Replaces</tt> control field has these
5373 two distinct purposes.
5376 <sect1><heading>Overwriting files in other packages</heading>
5379 It is usually an error for a package to contain files which
5380 are on the system in another package. However, if the
5381 overwriting package declares that it <tt>Replaces</tt> the one
5382 containing the file being overwritten, then <prgn>dpkg</prgn>
5383 will replace the file from the old package with that from the
5384 new. The file will no longer be listed as "owned" by the old
5385 package and will be taken over by the new package.
5386 Normally, <tt>Breaks</tt> should be used in conjunction
5387 with <tt>Replaces</tt>.<footnote>
5388 To see why <tt>Breaks</tt> is normally needed in addition
5389 to <tt>Replaces</tt>, consider the case of a file in the
5390 package <package>foo</package> being taken over by the
5391 package <package>foo-data</package>.
5392 <tt>Replaces</tt> will allow <package>foo-data</package> to
5393 be installed and take over that file. However,
5394 without <tt>Breaks</tt>, nothing
5395 requires <package>foo</package> to be upgraded to a newer
5396 version that knows it does not include that file and instead
5397 depends on <package>foo-data</package>. Nothing would
5398 prevent the new <package>foo-data</package> package from
5399 being installed and then removed, removing the file that it
5400 took over from <package>foo</package>. After that
5401 operation, the package manager would think the system was in
5402 a consistent state, but the <package>foo</package> package
5403 would be missing one of its files.
5408 For example, if a package <package>foo</package> is split
5409 into <package>foo</package> and <package>foo-data</package>
5410 starting at version 1.2-3, <package>foo-data</package> would
5412 <example compact="compact">
5413 Replaces: foo (<< 1.2-3)
5414 Breaks: foo (<< 1.2-3)
5416 in its control file. The new version of the
5417 package <package>foo</package> would normally have the field
5418 <example compact="compact">
5419 Depends: foo-data (>= 1.2-3)
5421 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5422 the files moved into <package>foo-data</package> are not
5423 required for normal operation).
5427 If a package is completely replaced in this way, so that
5428 <prgn>dpkg</prgn> does not know of any files it still
5429 contains, it is considered to have "disappeared". It will
5430 be marked as not wanted on the system (selected for
5431 removal) and "Not-Installed". Any <tt>conffile</tt>s
5432 details noted for the package will be ignored, as they
5433 will have been taken over by the overwriting package. The
5434 package's <prgn>postrm</prgn> script will be run with a
5435 special argument to allow the package to do any final
5436 cleanup required. See <ref id="mscriptsinstact">.
5438 Replaces is a one way relationship. You have to install
5439 the replacing package after the replaced package.
5444 For this usage of <tt>Replaces</tt>, virtual packages (see
5445 <ref id="virtual">) are not considered when looking at a
5446 <tt>Replaces</tt> field. The packages declared as being
5447 replaced must be mentioned by their real names.
5451 This usage of <tt>Replaces</tt> only takes effect when both
5452 packages are at least partially on the system at once. It is
5453 not relevant if the packages conflict unless the conflict has
5458 <sect1><heading>Replacing whole packages, forcing their
5462 Second, <tt>Replaces</tt> allows the packaging system to
5463 resolve which package should be removed when there is a
5464 conflict (see <ref id="conflicts">). This usage only takes
5465 effect when the two packages <em>do</em> conflict, so that the
5466 two usages of this field do not interfere with each other.
5470 In this situation, the package declared as being replaced
5471 can be a virtual package, so for example, all mail
5472 transport agents (MTAs) would have the following fields in
5473 their control files:
5474 <example compact="compact">
5475 Provides: mail-transport-agent
5476 Conflicts: mail-transport-agent
5477 Replaces: mail-transport-agent
5479 ensuring that only one MTA can be unpacked at any one
5480 time. See <ref id="virtual"> for more information about this
5485 <sect id="sourcebinarydeps">
5486 <heading>Relationships between source and binary packages -
5487 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5488 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5492 Source packages that require certain binary packages to be
5493 installed or absent at the time of building the package
5494 can declare relationships to those binary packages.
5498 This is done using the <tt>Build-Depends</tt>,
5499 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5500 <tt>Build-Conflicts-Indep</tt> control fields.
5504 Build-dependencies on "build-essential" binary packages can be
5505 omitted. Please see <ref id="pkg-relations"> for more information.
5509 The dependencies and conflicts they define must be satisfied
5510 (as defined earlier for binary packages) in order to invoke
5511 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5513 There is no Build-Depends-Arch; this role is essentially
5514 met with Build-Depends. Anyone building the
5515 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5516 assumed to be building the whole package, and therefore
5517 installation of all build dependencies is required.
5520 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5521 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5522 not yet know how to check for its existence, and
5523 <tt>binary-arch</tt>. The purpose of the original split
5524 between <tt>Build-Depends</tt> and
5525 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5526 wouldn't need to install extra packages needed only for the
5527 binary-indep targets. But without a build-arch/build-indep
5528 split, this didn't work, since most of the work is done in
5529 the build target, not in the binary target.
5533 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5534 <tt>binary-arch</tt></tag>
5536 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5537 fields must be satisfied when these targets are invoked.
5539 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5540 and <tt>binary-indep</tt></tag>
5542 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5543 <tt>Build-Depends-Indep</tt>, and
5544 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5545 these targets are invoked.
5551 <sect id="built-using">
5552 <heading>Additional source packages used to build the binary
5553 - <tt>Built-Using</tt>
5557 Some binary packages incorporate parts of other packages when built
5558 but do not have to depend on those packages. Examples include
5559 linking with static libraries or incorporating source code from
5560 another package during the build. In this case, the source packages
5561 of those other packages are a required part of the complete source
5562 (the binary package is not reproducible without them).
5566 A <tt>Built-Using</tt> field must list the corresponding source
5567 package for any such binary package incorporated during the build
5569 <tt>Build-Depends</tt> in the source package is not adequate since
5570 it (rightfully) does not document the exact version used in the
5573 including an "exactly equal" ("=") version relation on the version
5574 that was used to build that binary package<footnote>
5575 The archive software might reject packages that refer to
5576 non-existent sources.
5581 A package using the source code from the gcc-4.6-source
5582 binary package built from the gcc-4.6 source package would
5583 have this field in its control file:
5584 <example compact="compact">
5585 Built-Using: gcc-4.6 (= 4.6.0-11)
5590 A package including binaries from grub2 and loadlin would
5591 have this field in its control file:
5592 <example compact="compact">
5593 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5600 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5603 Packages containing shared libraries must be constructed with
5604 a little care to make sure that the shared library is always
5605 available. This is especially important for packages whose
5606 shared libraries are vitally important, such as the C library
5607 (currently <tt>libc6</tt>).
5611 This section deals only with public shared libraries: shared
5612 libraries that are placed in directories searched by the dynamic
5613 linker by default or which are intended to be linked against
5614 normally and possibly used by other, independent packages. Shared
5615 libraries that are internal to a particular package or that are
5616 only loaded as dynamic modules are not covered by this section and
5617 are not subject to its requirements.
5621 A shared library is identified by the <tt>SONAME</tt> attribute
5622 stored in its dynamic section. When a binary is linked against a
5623 shared library, the <tt>SONAME</tt> of the shared library is
5624 recorded in the binary's <tt>NEEDED</tt> section so that the
5625 dynamic linker knows that library must be loaded at runtime. The
5626 shared library file's full name (which usually contains additional
5627 version information not needed in the <tt>SONAME</tt>) is
5628 therefore normally not referenced directly. Instead, the shared
5629 library is loaded by its <tt>SONAME</tt>, which exists on the file
5630 system as a symlink pointing to the full name of the shared
5631 library. This symlink must be provided by the
5632 package. <ref id="sharedlibs-runtime"> describes how to do this.
5634 This is a convention of shared library versioning, but not a
5635 requirement. Some libraries use the <tt>SONAME</tt> as the full
5636 library file name instead and therefore do not need a symlink.
5637 Most, however, encode additional information about
5638 backwards-compatible revisions as a minor version number in the
5639 file name. The <tt>SONAME</tt> itself only changes when
5640 binaries linked with the earlier version of the shared library
5641 may no longer work, but the filename may change with each
5642 release of the library. See <ref id="sharedlibs-runtime"> for
5648 When linking a binary or another shared library against a shared
5649 library, the <tt>SONAME</tt> for that shared library is not yet
5650 known. Instead, the shared library is found by looking for a file
5651 matching the library name with <tt>.so</tt> appended. This file
5652 exists on the file system as a symlink pointing to the shared
5657 Shared libraries are normally split into several binary packages.
5658 The <tt>SONAME</tt> symlink is installed by the runtime shared
5659 library package, and the bare <tt>.so</tt> symlink is installed in
5660 the development package since it's only used when linking binaries
5661 or shared libraries. However, there are some exceptions for
5662 unusual shared libraries or for shared libraries that are also
5663 loaded as dynamic modules by other programs.
5667 This section is primarily concerned with how the separation of
5668 shared libraries into multiple packages should be done and how
5669 dependencies on and between shared library binary packages are
5670 managed in Debian. <ref id="libraries"> should be read in
5671 conjunction with this section and contains additional rules for
5672 the files contained in the shared library packages.
5675 <sect id="sharedlibs-runtime">
5676 <heading>Run-time shared libraries</heading>
5679 The run-time shared library must be placed in a package
5680 whose name changes whenever the <tt>SONAME</tt> of the shared
5681 library changes. This allows several versions of the shared
5682 library to be installed at the same time, allowing installation
5683 of the new version of the shared library without immediately
5684 breaking binaries that depend on the old version. Normally, the
5685 run-time shared library and its <tt>SONAME</tt> symlink should
5686 be placed in a package named
5687 <package><var>libraryname</var><var>soversion</var></package>,
5688 where <var>soversion</var> is the version number in
5689 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5690 would be confusing to directly append <var>soversion</var>
5691 to <var>libraryname</var> (if, for
5692 example, <var>libraryname</var> itself ends in a number), you
5694 <package><var>libraryname</var>-<var>soversion</var></package>
5699 To determine the <var>soversion</var>, look at
5700 the <tt>SONAME</tt> of the library, stored in the
5701 ELF <tt>SONAME</tt> attribute. It is usually of the
5702 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5703 example, <tt>libz.so.1</tt>). The version part is the part
5704 which comes after <tt>.so.</tt>, so in that example it
5705 is <tt>1</tt>. The soname may instead be of the
5706 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5707 as <tt>libdb-5.1.so</tt>, in which case the name would
5708 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5712 If you have several shared libraries built from the same source
5713 tree, you may lump them all together into a single shared
5714 library package provided that all of their <tt>SONAME</tt>s will
5715 always change together. Be aware that this is not normally the
5716 case, and if the <tt>SONAME</tt>s do not change together,
5717 upgrading such a merged shared library package will be
5718 unnecessarily difficult because of file conflicts with the old
5719 version of the package. When in doubt, always split shared
5720 library packages so that each binary package installs a single
5725 Every time the shared library ABI changes in a way that may
5726 break binaries linked against older versions of the shared
5727 library, the <tt>SONAME</tt> of the library and the
5728 corresponding name for the binary package containing the runtime
5729 shared library should change. Normally, this means
5730 the <tt>SONAME</tt> should change any time an interface is
5731 removed from the shared library or the signature of an interface
5732 (the number of parameters or the types of parameters that it
5733 takes, for example) is changed. This practice is vital to
5734 allowing clean upgrades from older versions of the package and
5735 clean transitions between the old ABI and new ABI without having
5736 to upgrade every affected package simultaneously.
5740 The <tt>SONAME</tt> and binary package name need not, and indeed
5741 normally should not, change if new interfaces are added but none
5742 are removed or changed, since this will not break binaries
5743 linked against the old shared library. Correct versioning of
5744 dependencies on the newer shared library by binaries that use
5745 the new interfaces is handled via
5746 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5747 or <tt>shlibs</tt> system</qref>.
5751 The package should install the shared libraries under
5752 their normal names. For example, the <package>libgdbm3</package>
5753 package should install <file>libgdbm.so.3.0.0</file> as
5754 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5755 renamed or re-linked by any <prgn>prerm</prgn> or
5756 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5757 of renaming things safely without affecting running programs,
5758 and attempts to interfere with this are likely to lead to
5763 Shared libraries should not be installed executable, since
5764 the dynamic linker does not require this and trying to
5765 execute a shared library usually results in a core dump.
5769 The run-time library package should include the symbolic link for
5770 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5771 the shared libraries. For example,
5772 the <package>libgdbm3</package> package should include a symbolic
5773 link from <file>/usr/lib/libgdbm.so.3</file> to
5774 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5775 linker (for example <prgn>ld.so</prgn> or
5776 <prgn>ld-linux.so.*</prgn>) can find the library between the
5777 time that <prgn>dpkg</prgn> installs it and the time that
5778 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5780 The package management system requires the library to be
5781 placed before the symbolic link pointing to it in the
5782 <file>.deb</file> file. This is so that when
5783 <prgn>dpkg</prgn> comes to install the symlink
5784 (overwriting the previous symlink pointing at an older
5785 version of the library), the new shared library is already
5786 in place. In the past, this was achieved by creating the
5787 library in the temporary packaging directory before
5788 creating the symlink. Unfortunately, this was not always
5789 effective, since the building of the tar file in the
5790 <file>.deb</file> depended on the behavior of the underlying
5791 file system. Some file systems (such as reiserfs) reorder
5792 the files so that the order of creation is forgotten.
5793 Since version 1.7.0, <prgn>dpkg</prgn>
5794 reorders the files itself as necessary when building a
5795 package. Thus it is no longer important to concern
5796 oneself with the order of file creation.
5800 <sect1 id="ldconfig">
5801 <heading><tt>ldconfig</tt></heading>
5804 Any package installing shared libraries in one of the default
5805 library directories of the dynamic linker (which are currently
5806 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5807 listed in <file>/etc/ld.so.conf</file><footnote>
5808 These are currently <file>/usr/local/lib</file> plus
5809 directories under <file>/lib</file> and <file>/usr/lib</file>
5810 matching the multiarch triplet for the system architecture.
5812 must use <prgn>ldconfig</prgn> to update the shared library
5817 The package maintainer scripts must only call
5818 <prgn>ldconfig</prgn> under these circumstances:
5819 <list compact="compact">
5820 <item>When the <prgn>postinst</prgn> script is run with a
5821 first argument of <tt>configure</tt>, the script must call
5822 <prgn>ldconfig</prgn>, and may optionally invoke
5823 <prgn>ldconfig</prgn> at other times.
5825 <item>When the <prgn>postrm</prgn> script is run with a
5826 first argument of <tt>remove</tt>, the script should call
5827 <prgn>ldconfig</prgn>.
5832 During install or upgrade, the preinst is called before
5833 the new files are unpacked, so calling "ldconfig" is
5834 pointless. The preinst of an existing package can also be
5835 called if an upgrade fails. However, this happens during
5836 the critical time when a shared libs may exist on-disk
5837 under a temporary name. Thus, it is dangerous and
5838 forbidden by current policy to call "ldconfig" at this
5843 When a package is installed or upgraded, "postinst
5844 configure" runs after the new files are safely on-disk.
5845 Since it is perfectly safe to invoke ldconfig
5846 unconditionally in a postinst, it is OK for a package to
5847 simply put ldconfig in its postinst without checking the
5848 argument. The postinst can also be called to recover from
5849 a failed upgrade. This happens before any new files are
5850 unpacked, so there is no reason to call "ldconfig" at this
5855 For a package that is being removed, prerm is
5856 called with all the files intact, so calling ldconfig is
5857 useless. The other calls to "prerm" happen in the case of
5858 upgrade at a time when all the files of the old package
5859 are on-disk, so again calling "ldconfig" is pointless.
5863 postrm, on the other hand, is called with the "remove"
5864 argument just after the files are removed, so this is
5865 the proper time to call "ldconfig" to notify the system
5866 of the fact that the shared libraries from the package
5867 are removed. The postrm can be called at several other
5868 times. At the time of "postrm purge", "postrm
5869 abort-install", or "postrm abort-upgrade", calling
5870 "ldconfig" is useless because the shared lib files are
5871 not on-disk. However, when "postrm" is invoked with
5872 arguments "upgrade", "failed-upgrade", or "disappear", a
5873 shared lib may exist on-disk under a temporary filename.
5881 <sect id="sharedlibs-support-files">
5882 <heading>Shared library support files</heading>
5885 If your package contains files whose names do not change with
5886 each change in the library shared object version, you must not
5887 put them in the shared library package. Otherwise, several
5888 versions of the shared library cannot be installed at the same
5889 time without filename clashes, making upgrades and transitions
5890 unnecessarily difficult.
5894 It is recommended that supporting files and run-time support
5895 programs that do not need to be invoked manually by users, but
5896 are nevertheless required for the package to function, be placed
5897 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5898 preferably under <file>/usr/lib/</file><var>package-name</var>.
5899 If the program or file is architecture independent, the
5900 recommendation is for it to be placed in a subdirectory of
5901 <file>/usr/share</file> instead, preferably under
5902 <file>/usr/share/</file><var>package-name</var>. Following the
5903 <var>package-name</var> naming convention ensures that the file
5904 names change when the shared object version changes.
5908 Run-time support programs that use the shared library but are
5909 not required for the library to function or files used by the
5910 shared library that can be used by any version of the shared
5911 library package should instead be put in a separate package.
5912 This package might typically be named
5913 <package><var>libraryname</var>-tools</package>; note the
5914 absence of the <var>soversion</var> in the package name.
5918 Files and support programs only useful when compiling software
5919 against the library should be included in the development
5920 package for the library.<footnote>
5921 For example, a <file><var>package-name</var>-config</file>
5922 script or <package>pkg-config</package> configuration files.
5927 <sect id="sharedlibs-static">
5928 <heading>Static libraries</heading>
5931 The static library (<file><var>libraryname.a</var></file>)
5932 is usually provided in addition to the shared version.
5933 It is placed into the development package (see below).
5937 In some cases, it is acceptable for a library to be
5938 available in static form only; these cases include:
5940 <item>libraries for languages whose shared library support
5941 is immature or unstable</item>
5942 <item>libraries whose interfaces are in flux or under
5943 development (commonly the case when the library's
5944 major version number is zero, or where the ABI breaks
5945 across patchlevels)</item>
5946 <item>libraries which are explicitly intended to be
5947 available only in static form by their upstream
5952 <sect id="sharedlibs-dev">
5953 <heading>Development files</heading>
5956 If there are development files associated with a shared library,
5957 the source package needs to generate a binary development package
5958 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5959 or if you prefer only to support one development version at a
5960 time, <package><var>libraryname</var>-dev</package>. Installing
5961 the development package must result in installation of all the
5962 development files necessary for compiling programs against that
5963 shared library.<footnote>
5964 This wording allows the development files to be split into
5965 several packages, such as a separate architecture-independent
5966 <package><var>libraryname</var>-headers</package>, provided that
5967 the development package depends on all the required additional
5973 In case several development versions of a library exist, you may
5974 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5975 <ref id="conflicts">) to ensure that the user only installs one
5976 development version at a time (as different development versions are
5977 likely to have the same header files in them, which would cause a
5978 filename clash if both were unpacked).
5982 The development package should contain a symlink for the associated
5983 shared library without a version number. For example, the
5984 <package>libgdbm-dev</package> package should include a symlink
5985 from <file>/usr/lib/libgdbm.so</file> to
5986 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5987 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5988 <file>libgdbm.so</file> when compiling dynamically.
5992 If the package provides Ada Library Information
5993 (<file>*.ali</file>) files for use with GNAT, these files must be
5994 installed read-only (mode 0444) so that GNAT will not attempt to
5995 recompile them. This overrides the normal file mode requirements
5996 given in <ref id="permissions-owners">.
6000 <sect id="sharedlibs-intradeps">
6001 <heading>Dependencies between the packages of the same library</heading>
6004 Typically the development version should have an exact
6005 version dependency on the runtime library, to make sure that
6006 compilation and linking happens correctly. The
6007 <tt>${binary:Version}</tt> substitution variable can be
6008 useful for this purpose.
6010 Previously, <tt>${Source-Version}</tt> was used, but its name
6011 was confusing and it has been deprecated since dpkg 1.13.19.
6016 <sect id="sharedlibs-depends">
6017 <heading>Dependencies between the library and other
6021 If a package contains a binary or library which links to a
6022 shared library, we must ensure that, when the package is
6023 installed on the system, all of the libraries needed are also
6024 installed. These dependencies must be added to the binary
6025 package when it is built, since they may change based on which
6026 version of a shared library the binary or library was linked
6027 with even if there are no changes to the source of the binary
6028 (for example, symbol versions change, macros become functions or
6029 vice versa, or the binary package may determine at compile-time
6030 whether new library interfaces are available and can be called).
6031 To allow these dependencies to be constructed, shared libraries
6032 must provide either a <file>symbols</file> file or
6033 a <file>shlibs</file> file. These provide information on the
6034 package dependencies required to ensure the presence of
6035 interfaces provided by this library. Any package with binaries
6036 or libraries linking to a shared library must use these files to
6037 determine the required dependencies when it is built. Other
6038 packages which use a shared library (for example using
6039 <tt>dlopen()</tt>) should compute appropriate dependencies
6040 using these files at build time as well.
6044 The two mechanisms differ in the degree of detail that they
6045 provide. A <file>symbols</file> file documents, for each symbol
6046 exported by a library, the minimal version of the package any
6047 binary using this symbol will need. This is typically the
6048 version of the package in which the symbol was introduced. This
6049 information permits detailed analysis of the symbols used by a
6050 particular package and construction of an accurate dependency,
6051 but it requires the package maintainer to track more information
6052 about the shared library.
6056 A <file>shlibs</file> file, in contrast, only documents the last
6057 time the library ABI changed in any way. It only provides
6058 information about the library as a whole, not individual
6059 symbols. When a package is built using a shared library with
6060 only a <file>shlibs</file> file, the generated dependency will
6061 require a version of the shared library equal to or newer than
6062 the version of the last ABI change. This generates
6063 unnecessarily restrictive dependencies compared
6064 to <file>symbols</file> files if none of the symbols used by the
6065 package have changed. This, in turn, may make upgrades
6066 needlessly complex and unnecessarily restrict use of the package
6067 on systems with older versions of the shared libraries.
6071 <file>shlibs</file> files also only support a limited range of
6072 library SONAMEs, making it difficult to use <file>shlibs</file>
6073 files in some unusual corner cases.<footnote>
6074 A <file>shlibs</file> file represents an SONAME as a library
6075 name and version number, such as <tt>libfoo VERSION</tt>,
6076 instead of recording the actual SONAME. If the SONAME doesn't
6077 match one of the two expected formats
6078 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6079 cannot be represented.
6084 <file>symbols</file> files are therefore recommended for most
6085 shared library packages since they provide more accurate
6086 dependencies. For most C libraries, the additional detail
6087 required by <file>symbols</file> files is not too difficult to
6088 maintain. However, maintaining exhaustive symbols information
6089 for a C++ library can be quite onerous, so <file>shlibs</file>
6090 files may be more appropriate for most C++ libraries. Libraries
6091 with a corresponding udeb must also provide
6092 a <file>shlibs</file> file, since the udeb infrastructure does
6093 not use <file>symbols</file> files.
6096 <sect1 id="dpkg-shlibdeps">
6097 <heading>Generating dependencies on shared libraries</heading>
6100 When a package that contains any shared libraries or compiled
6101 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6102 each shared library and compiled binary to determine the
6103 libraries used and hence the dependencies needed by the
6105 <prgn>dpkg-shlibdeps</prgn> will use a program
6106 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6107 the libraries and the symbols in those libraries directly
6108 needed by the binaries or shared libraries in the package.
6110 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6111 your <file>debian/rules</file> file in the source package.
6112 List all of the compiled binaries, libraries, or loadable
6113 modules in your package.<footnote>
6114 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6115 correctly is to use a package helper framework such
6116 as <package>debhelper</package>. If you are
6117 using <package>debhelper</package>,
6118 the <prgn>dh_shlibdeps</prgn> program will do this work for
6119 you. It will also correctly handle multi-binary packages.
6121 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6122 or <file>shlibs</file> files installed by the shared libraries
6123 to generate dependency information. The package must then
6124 provide a substitution variable into which the discovered
6125 dependency information can be placed.
6129 If you are creating a udeb for use in the Debian Installer,
6130 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6131 should use the dependency line of type <tt>udeb</tt> by adding
6132 the <tt>-tudeb</tt> option<footnote>
6133 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6134 will automatically add this option if it knows it is
6136 </footnote>. If there is no dependency line of
6137 type <tt>udeb</tt> in the <file>shlibs</file>
6138 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6139 regular dependency line.
6143 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6144 into the <file>debian/substvars</file> file by default, which
6145 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6146 to place a <tt>${shlibs:Depends}</tt> variable in
6147 the <tt>Depends</tt> field in the control file of every binary
6148 package built by this source package that contains compiled
6149 binaries, libraries, or loadable modules. If you have
6150 multiple binary packages, you will need to
6151 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6152 compiled libraries or binaries. For example, you could use
6153 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6154 specify a different <file>substvars</file> file for each
6155 binary package.<footnote>
6156 Again, <prgn>dh_shlibdeps</prgn>
6157 and <prgn>dh_gencontrol</prgn> will handle everything except
6158 the addition of the variable to the control file for you if
6159 you're using <package>debhelper</package>, including
6160 generating separate <file>substvars</file> files for each
6161 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6162 the appropriate flags.
6167 For more details on <prgn>dpkg-shlibdeps</prgn>,
6168 see <manref name="dpkg-shlibdeps" section="1">.
6172 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6173 library <tt>libbar</tt> if it is explicitly linked with that
6174 library (that is, the library is listed in the
6175 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6176 to the link line when the binary is created). Other libraries
6177 that are needed by <tt>libbar</tt> are
6178 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6179 linker will load them automatically when it
6180 loads <tt>libbar</tt>. A package should depend on the
6181 libraries it directly uses, but not the libraries it only uses
6182 indirectly. The dependencies for the libraries used
6183 directly will automatically pull in the indirectly-used
6184 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6185 automatically, but package maintainers need to be aware of
6186 this distinction between directly and indirectly using a
6187 library if they have to override its results for some reason.
6189 A good example of where this helps is the following. We
6190 could update <tt>libimlib</tt> with a new version that
6191 supports a new revision of a graphics format called dgf (but
6192 retaining the same major version number) and depends on a
6193 new library package <package>libdgf4</package> instead of
6194 the older <package>libdgf3</package>. If we
6195 used <prgn>ldd</prgn> to add dependencies for every library
6196 directly or indirectly linked with a binary, every package
6197 that uses <tt>libimlib</tt> would need to be recompiled so
6198 it would also depend on <package>libdgf4</package> in order
6199 to retire the older <package>libdgf3</package> package.
6200 Since dependencies are only added based on
6201 ELF <tt>NEEDED</tt> attribute, packages
6202 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6203 having the dependency on an appropriate version
6204 of <tt>libdgf</tt> and do not need rebuilding.
6209 <sect1 id="sharedlibs-updates">
6210 <heading>Shared library ABI changes</heading>
6213 Maintaining a shared library package using
6214 either <file>symbols</file> or <file>shlibs</file> files
6215 requires being aware of the exposed ABI of the shared library
6216 and any changes to it. Both <file>symbols</file>
6217 and <file>shlibs</file> files record every change to the ABI
6218 of the shared library; <file>symbols</file> files do so per
6219 public symbol, whereas <file>shlibs</file> files record only
6220 the last change for the entire library.
6224 There are two types of ABI changes: ones that are
6225 backward-compatible and ones that are not. An ABI change is
6226 backward-compatible if any reasonable program or library that
6227 was linked with the previous version of the shared library
6228 will still work correctly with the new version of the shared
6230 An example of an "unreasonable" program is one that uses
6231 library interfaces that are documented as internal and
6232 unsupported. If the only programs or libraries affected by
6233 a change are "unreasonable" ones, other techniques, such as
6234 declaring <tt>Breaks</tt> relationships with affected
6235 packages or treating their usage of the library as bugs in
6236 those packages, may be appropriate instead of changing the
6237 SONAME. However, the default approach is to change the
6238 SONAME for any change to the ABI that could break a program.
6240 Adding new symbols to the shared library is a
6241 backward-compatible change. Removing symbols from the shared
6242 library is not. Changing the behavior of a symbol may or may
6243 not be backward-compatible depending on the change; for
6244 example, changing a function to accept a new enum constant not
6245 previously used by the library is generally
6246 backward-compatible, but changing the members of a struct that
6247 is passed into library functions is generally not unless the
6248 library takes special precautions to accept old versions of
6253 ABI changes that are not backward-compatible normally require
6254 changing the <tt>SONAME</tt> of the library and therefore the
6255 shared library package name, which forces rebuilding all
6256 packages using that shared library to update their
6257 dependencies and allow them to use the new version of the
6258 shared library. For more information,
6259 see <ref id="sharedlibs-runtime">. The remainder of this
6260 section will deal with backward-compatible changes.
6264 Backward-compatible changes require either updating or
6265 recording the <var>minimal-version</var> for that symbol
6266 in <file>symbols</file> files or updating the version in
6267 the <var>dependencies</var> in <file>shlibs</file> files. For
6268 more information on how to do this in the two formats, see
6269 <ref id="symbols"> and <ref id="shlibs">. Below are general
6270 rules that apply to both files.
6274 The easy case is when a public symbol is added. Simply add
6275 the version at which the symbol was introduced
6276 (for <file>symbols</file> files) or update the dependency
6277 version (for <file>shlibs</file>) files. But special care
6278 should be taken to update dependency versions when the
6279 behavior of a public symbol changes. This is easy to neglect,
6280 since there is no automated method of determining such
6281 changes, but failing to update versions in this case may
6282 result in binary packages with too-weak dependencies that will
6283 fail at runtime, possibly in ways that can cause security
6284 vulnerabilities. If the package maintainer believes that a
6285 symbol behavior change may have occurred but isn't sure, it's
6286 safer to update the version rather than leave it unmodified.
6287 This may result in unnecessarily strict dependencies, but it
6288 ensures that packages whose dependencies are satisfied will
6293 A common example of when a change to the dependency version
6294 is required is a function that takes an enum or struct
6295 argument that controls what the function does. For example:
6297 enum library_op { OP_FOO, OP_BAR };
6298 int library_do_operation(enum library_op);
6300 If a new operation, <tt>OP_BAZ</tt>, is added,
6301 the <var>minimal-version</var>
6302 of <tt>library_do_operation</tt> (for <file>symbols</file>
6303 files) or the version in the dependency for the shared library
6304 (for <file>shlibs</file> files) must be increased to the
6305 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6306 binary built against the new version of the library (having
6307 detected at compile-time that the library
6308 supports <tt>OP_BAZ</tt>) may be installed with a shared
6309 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6310 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6315 Dependency versions in either <file>symbols</file>
6316 or <file>shlibs</file> files normally should not contain the
6317 Debian revision of the package, since the library behavior is
6318 normally fixed for a particular upstream version and any
6319 Debian packaging of that upstream version will have the same
6320 behavior. In the rare case that the library behavior was
6321 changed in a particular Debian revision, appending <tt>~</tt>
6322 to the end of the version that includes the Debian revision is
6323 recommended, since this allows backports of the shared library
6324 package using the normal backport versioning convention to
6325 satisfy the dependency.
6329 <sect1 id="sharedlibs-symbols">
6330 <heading>The <tt>symbols</tt> system</heading>
6333 In the following sections, we will first describe where the
6334 various <file>symbols</file> files are to be found, then
6335 the <file>symbols</file> file format, and finally how to
6336 create <file>symbols</file> files if your package contains a
6340 <sect2 id="symbols-paths">
6341 <heading>The <file>symbols</file> files present on the
6345 <file>symbols</file> files for a shared library are normally
6346 provided by the shared library package as a control file,
6347 but there are several override paths that are checked first
6348 in case that information is wrong or missing. The following
6349 list gives them in the order in which they are read
6350 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6351 the required information is used.
6354 <p><file>debian/*/DEBIAN/symbols</file></p>
6357 During the package build, if the package itself
6358 contains shared libraries with <file>symbols</file>
6359 files, they will be generated in these staging
6360 directories by <prgn>dpkg-gensymbols</prgn>
6361 (see <ref id="providing-symbols">). <file>symbols</file>
6362 files found in the build tree take precedence
6363 over <file>symbols</file> files from other binary
6368 These files must exist
6369 before <prgn>dpkg-shlibdeps</prgn> is run or the
6370 dependencies of binaries and libraries from a source
6371 package on other libraries from that same source
6372 package will not be correct. In practice, this means
6373 that <prgn>dpkg-gensymbols</prgn> must be run
6374 before <prgn>dpkg-shlibdeps</prgn> during the package
6376 An example may clarify. Suppose the source
6377 package <tt>foo</tt> generates two binary
6378 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6379 When building the binary packages, the contents of
6380 the packages are staged in the
6381 directories <file>debian/libfoo2</file>
6382 and <file>debian/foo-runtime</file> respectively.
6383 (<file>debian/tmp</file> could be used instead of
6384 one of these.) Since <tt>libfoo2</tt> provides
6385 the <tt>libfoo</tt> shared library, it will contain
6386 a <tt>symbols</tt> file, which will be installed
6387 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6388 eventually to be included as a control file in that
6389 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6391 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6393 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6394 to determine whether <tt>foo-prog</tt>'s library
6395 dependencies are satisfied by any of the libraries
6396 provided by <tt>libfoo2</tt>. Since those binaries
6397 were linked against the just-built shared library as
6398 part of the build process, the <file>symbols</file>
6399 file for the newly-built <tt>libfoo2</tt> must take
6400 precedence over a <file>symbols</file> file for any
6401 other <tt>libfoo2</tt> package already installed on
6409 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6410 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6414 Per-system overrides of shared library dependencies.
6415 These files normally do not exist. They are
6416 maintained by the local system administrator and must
6417 not be created by any Debian package.
6422 <p><file>symbols</file> control files for packages
6423 installed on the system</p>
6426 The <file>symbols</file> control files for all the
6427 packages currently installed on the system are
6428 searched last. This will be the most common source of
6429 shared library dependency information. These are
6431 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6432 packages should not rely on this and instead should
6433 use <tt>dpkg-query --control-path <var>package</var>
6434 symbols</tt> if for some reason these files need to be
6442 Be aware that if a <file>debian/shlibs.local</file> exists
6443 in the source package, it will override
6444 any <file>symbols</file> files. This is the only case where
6445 a <file>shlibs</file> is used despite <file>symbols</file>
6446 files being present. See <ref id="shlibs-paths">
6447 and <ref id="sharedlibs-shlibdeps"> for more information.
6451 <sect2 id="symbols">
6452 <heading>The <file>symbols</file> File Format</heading>
6455 The following documents the format of
6456 the <file>symbols</file> control file as included in binary
6457 packages. These files are built from
6458 template <file>symbols</file> files in the source package
6459 by <prgn>dpkg-gensymbols</prgn>. The template files support
6460 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6461 do some of the tedious work involved in
6462 maintaining <file>symbols</file> files, such as handling C++
6463 symbols or optional symbols that may not exist on particular
6464 architectures. When writing <file>symbols</file> files for
6465 a shared library package, refer
6466 to <manref name="dpkg-gensymbols" section="1"> for the
6471 A <file>symbols</file> may contain one or more entries, one
6472 for each shared library contained in the package
6473 corresponding to that <file>symbols</file>. Each entry has
6474 the following format:
6479 <var>library-soname</var> <var>main-dependency-template</var>
6480 [| <var>alternative-dependency-template</var>]
6482 [* <var>field-name</var>: <var>field-value</var>]
6484 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6489 To explain this format, we'll use the the <tt>zlib1g</tt>
6490 package as an example, which (at the time of writing)
6492 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6493 lines will be described first, followed by optional lines.
6497 <var>library-soname</var> must contain exactly the value of
6498 the ELF <tt>SONAME</tt> attribute of the shared library. In
6499 our example, this is <tt>libz.so.1</tt>.<footnote>
6500 This can be determined by using the command
6501 <example compact="compact">
6502 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6508 <var>main-dependency-template</var> has the same syntax as a
6509 dependency field in a binary package control file, except
6510 that the string <tt>#MINVER#</tt> is replaced by a version
6511 restriction like <tt>(>= <var>version</var>)</tt> or by
6512 nothing if an unversioned dependency is deemed sufficient.
6513 The version restriction will be based on which symbols from
6514 the shared library are referenced and the version at which
6515 they were introduced (see below). In nearly all
6516 cases, <var>main-dependency-template</var> will
6517 be <tt><var>package</var> #MINVER#</tt>,
6518 where <var>package</var> is the name of the binary package
6519 containing the shared library. This adds a simple,
6520 possibly-versioned dependency on the shared library package.
6521 In some rare cases, such as when multiple packages provide
6522 the same shared library ABI, the dependency template may
6523 need to be more complex.
6527 In our example, the first line of
6528 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6529 <example compact="compact">
6530 libz.so.1 zlib1g #MINVER#
6535 Each public symbol exported by the shared library must have
6536 a corresponding symbol line, indented by one
6537 space. <var>symbol</var> is the exported symbol (which, for
6538 C++, means the mangled symbol) followed by <tt>@</tt> and
6539 the symbol version, or the string <tt>Base</tt> if there is
6540 no symbol version. <var>minimal-version</var> is the most
6541 recent version of the shared library that changed the
6542 behavior of that symbol, whether by adding it, changing its
6543 function signature (the parameters, their types, or the
6544 return type), or changing its behavior in a way that is
6545 visible to a caller.
6546 <var>id-of-dependency-template</var> is an optional
6547 field that references
6548 an <var>alternative-dependency-template</var>; see below for
6553 For example, <tt>libz.so.1</tt> contains the
6554 symbols <tt>compress</tt>
6555 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6556 version and last changed its behavior in upstream
6557 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6558 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6559 upstream version <tt>1:1.2.0</tt>, and has not changed its
6560 behavior. Its <file>symbols</file> file therefore contains
6562 <example compact="compact">
6563 compress@Base 1:1.1.4
6564 compressBound@ZLIB_1.2.0 1:1.2.0
6566 Packages using only <tt>compress</tt> would then get a
6567 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6568 using <tt>compressBound</tt> would get a dependency
6569 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6573 One or more <var>alternative-dependency-template</var> lines
6574 may be provided. These are used in cases where some symbols
6575 in the shared library should use one dependency template
6576 while others should use a different template. The
6577 alternative dependency templates are used only if a symbol
6578 line contains the <var>id-of-dependency-template</var>
6579 field. The first alternative dependency template is
6580 numbered 1, the second 2, and so forth.<footnote>
6581 An example of where this may be needed is with a library
6582 that implements the libGL interface. All GL
6583 implementations provide the same set of base interfaces,
6584 and then may provide some additional interfaces only used
6585 by programs that require that specific GL implementation.
6586 So, for example, libgl1-mesa-glx may use the
6587 following <file>symbols</file> file:
6590 | libgl1-mesa-glx #MINVER#
6591 publicGlSymbol@Base 6.3-1
6593 implementationSpecificSymbol@Base 6.5.2-7 1
6596 Binaries or shared libraries using
6597 only <tt>publicGlSymbol</tt> would depend only
6598 on <tt>libgl1</tt> (which may be provided by multiple
6600 using <tt>implementationSpecificSymbol</tt> would get a
6601 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6606 Finally, the entry for the library may contain one or more
6607 metadata fields. Currently, the only
6608 supported <var>field-name</var>
6609 is <tt>Build-Depends-Package</tt>, whose value lists
6610 the <qref id="sharedlibs-dev">library development
6611 package</qref> on which packages using this shared library
6612 declare a build dependency. If this field is
6613 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6614 the resulting binary package dependency on the shared
6615 library is at least as strict as the source package
6616 dependency on the shared library development
6618 This field should normally not be necessary, since if the
6619 behavior of any symbol has changed, the corresponding
6620 symbol <var>minimal-version</var> should have been
6621 increased. But including it makes the <tt>symbols</tt>
6622 system more robust by tightening the dependency in cases
6623 where the package using the shared library specifically
6624 requires at least a particular version of the shared
6625 library development package for some reason.
6627 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6629 <example compact="compact">
6630 * Build-Depends-Package: zlib1g-dev
6635 Also see <manref name="deb-symbols" section="5">.
6639 <sect2 id="providing-symbols">
6640 <heading>Providing a <file>symbols</file> file</heading>
6643 If your package provides a shared library, you should
6644 arrange to include a <file>symbols</file> control file
6645 following the format described above in that package. You
6646 must include either a <file>symbols</file> control file or
6647 a <file>shlibs</file> control file.
6651 Normally, this is done by creating a <file>symbols</file> in
6653 named <file>debian/<var>package</var>.symbols</file>
6654 or <file>debian/symbols</file>, possibly
6655 with <file>.<var>arch</var></file> appended if the symbols
6656 information varies by architecture. This file may use the
6657 extended syntax documented in <manref name="dpkg-gensymbols"
6658 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6659 part of the package build process. It will
6660 create <file>symbols</file> files in the package staging
6661 area based on the binaries and libraries in the package
6662 staging area and the <file>symbols</file> files in the
6663 source package.<footnote>
6665 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6666 take care of calling either <prgn>dpkg-gensymbols</prgn>
6667 or generating a <file>shlibs</file> file as appropriate.
6672 Packages that provide <file>symbols</file> files must keep
6673 them up-to-date to ensure correct dependencies in packages
6674 that use the shared libraries. This means updating
6675 the <file>symbols</file> file whenever a new public symbol
6676 is added, changing the <var>minimal-version</var> field
6677 whenever a symbol changes behavior or signature in a
6678 backward-compatible way (see <ref id="sharedlibs-updates">),
6679 and changing the <var>library-soname</var>
6680 and <var>main-dependency-template</var>, and probably all of
6681 the <var>minimal-version</var> fields, when the library
6682 changes <tt>SONAME</tt>. Removing a public symbol from
6683 the <file>symbols</file> file because it's no longer
6684 provided by the library normally requires changing
6685 the <tt>SONAME</tt> of the library.
6686 See <ref id="sharedlibs-runtime"> for more information
6687 on <tt>SONAME</tt>s.
6692 <sect1 id="sharedlibs-shlibdeps">
6693 <heading>The <tt>shlibs</tt> system</heading>
6696 The <tt>shlibs</tt> system is a simpler alternative to
6697 the <tt>symbols</tt> system for declaring dependencies for
6698 shared libraries. It may be more appropriate for C++
6699 libraries and other cases where tracking individual symbols is
6700 too difficult. It predated the <tt>symbols</tt> system and is
6701 therefore frequently seen in older packages. It is also
6702 required for udebs, which do not support <tt>symbols</tt>.
6706 In the following sections, we will first describe where the
6707 various <file>shlibs</file> files are to be found, then how to
6708 use <prgn>dpkg-shlibdeps</prgn>, and finally
6709 the <file>shlibs</file> file format and how to create them.
6712 <sect2 id="shlibs-paths">
6713 <heading>The <file>shlibs</file> files present on the
6717 There are several places where <tt>shlibs</tt> files are
6718 found. The following list gives them in the order in which
6719 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6720 one which gives the required information is used.)
6723 <p><file>debian/shlibs.local</file></p>
6726 This lists overrides for this package. This file
6727 should normally not be used, but may be needed
6728 temporarily in unusual situations to work around bugs
6729 in other packages, or in unusual cases where the
6730 normally declared dependency information in the
6731 installed <file>shlibs</file> file for a library
6732 cannot be used. This file overrides information
6733 obtained from any other source.
6738 <p><file>/etc/dpkg/shlibs.override</file></p>
6741 This lists global overrides. This list is normally
6742 empty. It is maintained by the local system
6748 <p><file>DEBIAN/shlibs</file> files in the "build
6752 These files are generated as part of the package build
6753 process and staged for inclusion as control files in
6754 the binary packages being built. They provide details
6755 of any shared libraries included in the same package.
6760 <p><file>shlibs</file> control files for packages
6761 installed on the system</p>
6764 The <file>shlibs</file> control files for all the
6765 packages currently installed on the system. These are
6767 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6768 packages should not rely on this and instead should
6769 use <tt>dpkg-query --control-path <var>package</var>
6770 shlibs</tt> if for some reason these files need to be
6776 <p><file>/etc/dpkg/shlibs.default</file></p>
6779 This file lists any shared libraries whose packages
6780 have failed to provide correct <file>shlibs</file>
6781 files. It was used when the <file>shlibs</file> setup
6782 was first introduced, but it is now normally empty.
6783 It is maintained by the <tt>dpkg</tt> maintainer.
6790 If a <file>symbols</file> file for a shared library package
6791 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6792 in preference to a <file>shlibs</file>, with the exception
6793 of <file>debian/shlibs.local</file>. The latter overrides
6794 any other <file>shlibs</file> or <file>symbols</file> files.
6799 <heading>The <file>shlibs</file> File Format</heading>
6802 Each <file>shlibs</file> file has the same format. Lines
6803 beginning with <tt>#</tt> are considered to be comments and
6804 are ignored. Each line is of the form:
6805 <example compact="compact">
6806 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6811 We will explain this by reference to the example of the
6812 <tt>zlib1g</tt> package, which (at the time of writing)
6814 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6818 <var>type</var> is an optional element that indicates the
6819 type of package for which the line is valid. The only type
6820 currently in use is <tt>udeb</tt>. The colon and space
6821 after the type are required.
6825 <var>library-name</var> is the name of the shared library,
6826 in this case <tt>libz</tt>. (This must match the name part
6827 of the soname, see below.)
6831 <var>soname-version</var> is the version part of the
6832 ELF <tt>SONAME</tt> attribute of the library, determined the
6833 same way that the <var>soversion</var> component of the
6834 recommended shared library package name is determined.
6835 See <ref id="sharedlibs-runtime"> for the details.
6839 <var>dependencies</var> has the same syntax as a dependency
6840 field in a binary package control file. It should give
6841 details of which packages are required to satisfy a binary
6842 built against the version of the library contained in the
6843 package. See <ref id="depsyntax"> for details on the
6844 syntax, and <ref id="sharedlibs-updates"> for details on how
6845 to maintain the dependency version constraint.
6849 In our example, if the last change to the <tt>zlib1g</tt>
6850 package that could change behavior for a client of that
6851 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6852 the <tt>shlibs</tt> entry for this library could say:
6853 <example compact="compact">
6854 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6856 This version restriction must be new enough that any binary
6857 built against the current version of the library will work
6858 with any version of the shared library that satisfies that
6863 As zlib1g also provides a udeb containing the shared
6864 library, there would also be a second line:
6865 <example compact="compact">
6866 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6872 <heading>Providing a <file>shlibs</file> file</heading>
6875 To provide a <file>shlibs</file> file for a shared library
6876 binary package, create a <file>shlibs</file> file following
6877 the format described above and place it in
6878 the <file>DEBIAN</file> directory for that package during
6879 the build. It will then be included as a control file for
6880 that package<footnote>
6881 This is what <prgn>dh_makeshlibs</prgn> in
6882 the <package>debhelper</package> suite does. If your
6883 package also has a udeb that provides a shared
6884 library, <prgn>dh_makeshlibs</prgn> can automatically
6885 generate the <tt>udeb:</tt> lines if you specify the name
6886 of the udeb with the <tt>--add-udeb</tt> option.
6891 Since <prgn>dpkg-shlibdeps</prgn> reads
6892 the <file>DEBIAN/shlibs</file> files in all of the binary
6893 packages being built from this source package, all of
6894 the <file>DEBIAN/shlibs</file> files should be installed
6895 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6904 <chapt id="opersys"><heading>The Operating System</heading>
6907 <heading>File system hierarchy</heading>
6911 <heading>File System Structure</heading>
6914 The location of all files and directories must comply with the
6915 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6916 exceptions noted below, and except where doing so would
6917 violate other terms of Debian Policy. The following
6918 exceptions to the FHS apply:
6923 The optional rules related to user specific
6924 configuration files for applications are stored in
6925 the user's home directory are relaxed. It is
6926 recommended that such files start with the
6927 '<tt>.</tt>' character (a "dot file"), and if an
6928 application needs to create more than one dot file
6929 then the preferred placement is in a subdirectory
6930 with a name starting with a '.' character, (a "dot
6931 directory"). In this case it is recommended the
6932 configuration files not start with the '.'
6938 The requirement for amd64 to use <file>/lib64</file>
6939 for 64 bit binaries is removed.
6944 The requirement for object files, internal binaries, and
6945 libraries, including <file>libc.so.*</file>, to be located
6946 directly under <file>/lib{,32}</file> and
6947 <file>/usr/lib{,32}</file> is amended, permitting files
6948 to instead be installed to
6949 <file>/lib/<var>triplet</var></file> and
6950 <file>/usr/lib/<var>triplet</var></file>, where
6951 <tt><var>triplet</var></tt> is the value returned by
6952 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6953 architecture of the package. Packages may <em>not</em>
6954 install files to any <var>triplet</var> path other
6955 than the one matching the architecture of that package;
6956 for instance, an <tt>Architecture: amd64</tt> package
6957 containing 32-bit x86 libraries may not install these
6958 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6960 This is necessary in order to reserve the directories for
6961 use in cross-installation of library packages from other
6962 architectures, as part of the planned deployment of
6967 Applications may also use a single subdirectory under
6968 <file>/usr/lib/<var>triplet</var></file>.
6971 The execution time linker/loader, ld*, must still be made
6972 available in the existing location under /lib or /lib64
6973 since this is part of the ELF ABI for the architecture.
6978 The requirement that
6979 <file>/usr/local/share/man</file> be "synonymous"
6980 with <file>/usr/local/man</file> is relaxed to a
6985 The requirement that windowmanagers with a single
6986 configuration file call it <file>system.*wmrc</file>
6987 is removed, as is the restriction that the window
6988 manager subdirectory be named identically to the
6989 window manager name itself.
6994 The requirement that boot manager configuration
6995 files live in <file>/etc</file>, or at least are
6996 symlinked there, is relaxed to a recommendation.
7001 The additional directory <file>/run</file> in the root
7002 file system is allowed. <file>/run</file>
7003 replaces <file>/var/run</file>, and the
7004 subdirectory <file>/run/lock</file>
7005 replaces <file>/var/lock</file>, with
7006 the <file>/var</file> directories replaced by symlinks
7007 for backwards compatibility. <file>/run</file>
7008 and <file>/run/lock</file> must follow all of the
7009 requirements in the FHS for <file>/var/run</file>
7010 and <file>/var/lock</file>, respectively, such as file
7011 naming conventions, file format requirements, or the
7012 requirement that files be cleared during the boot
7013 process. Files and directories residing
7014 in <file>/run</file> should be stored on a temporary
7018 Packages must not assume the <file>/run</file>
7019 directory exists or is usable without a dependency
7020 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7021 stable release of Debian supports <file>/run</file>.
7026 The <file>/sys</file> directory in the root filesystem is
7027 additionally allowed. <footnote>This directory is used as
7028 mount point to mount virtual filesystems to get access to
7029 kernel information.</footnote>
7034 On GNU/Hurd systems, the following additional
7035 directories are allowed in the root
7036 filesystem: <file>/hurd</file>
7037 and <file>/servers</file>.<footnote>
7038 These directories are used to store translators and as
7039 a set of standard names for mount points,
7048 The version of this document referred here can be
7049 found in the <tt>debian-policy</tt> package or on <url
7050 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7051 name="FHS (Debian copy)"> alongside this manual (or, if
7052 you have the <package>debian-policy</package> installed,
7054 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7055 (local copy)">). The
7056 latest version, which may be a more recent version, may
7058 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7059 Specific questions about following the standard may be
7060 asked on the <tt>debian-devel</tt> mailing list, or
7061 referred to the FHS mailing list (see the
7062 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7068 <heading>Site-specific programs</heading>
7071 As mandated by the FHS, packages must not place any
7072 files in <file>/usr/local</file>, either by putting them in
7073 the file system archive to be unpacked by <prgn>dpkg</prgn>
7074 or by manipulating them in their maintainer scripts.
7078 However, the package may create empty directories below
7079 <file>/usr/local</file> so that the system administrator knows
7080 where to place site-specific files. These are not
7081 directories <em>in</em> <file>/usr/local</file>, but are
7082 children of directories in <file>/usr/local</file>. These
7083 directories (<file>/usr/local/*/dir/</file>)
7084 should be removed on package removal if they are
7089 Note that this applies only to
7090 directories <em>below</em> <file>/usr/local</file>,
7091 not <em>in</em> <file>/usr/local</file>. Packages must
7092 not create sub-directories in the
7093 directory <file>/usr/local</file> itself, except those
7094 listed in FHS, section 4.5. However, you may create
7095 directories below them as you wish. You must not remove
7096 any of the directories listed in 4.5, even if you created
7101 Since <file>/usr/local</file> can be mounted read-only from a
7102 remote server, these directories must be created and
7103 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7104 maintainer scripts and not be included in the
7105 <file>.deb</file> archive. These scripts must not fail if
7106 either of these operations fail.
7110 For example, the <tt>emacsen-common</tt> package could
7111 contain something like
7112 <example compact="compact">
7113 if [ ! -e /usr/local/share/emacs ]; then
7114 if mkdir /usr/local/share/emacs 2>/dev/null; then
7115 if chown root:staff /usr/local/share/emacs; then
7116 chmod 2775 /usr/local/share/emacs || true
7121 in its <prgn>postinst</prgn> script, and
7122 <example compact="compact">
7123 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7124 rmdir /usr/local/share/emacs 2>/dev/null || true
7126 in the <prgn>prerm</prgn> script. (Note that this form is
7127 used to ensure that if the script is interrupted, the
7128 directory <file>/usr/local/share/emacs</file> will still be
7133 If you do create a directory in <file>/usr/local</file> for
7134 local additions to a package, you should ensure that
7135 settings in <file>/usr/local</file> take precedence over the
7136 equivalents in <file>/usr</file>.
7140 However, because <file>/usr/local</file> and its contents are
7141 for exclusive use of the local administrator, a package
7142 must not rely on the presence or absence of files or
7143 directories in <file>/usr/local</file> for normal operation.
7147 The <file>/usr/local</file> directory itself and all the
7148 subdirectories created by the package should (by default) have
7149 permissions 2775 (group-writable and set-group-id) and be
7150 owned by <tt>root:staff</tt>.
7155 <heading>The system-wide mail directory</heading>
7157 The system-wide mail directory
7158 is <file>/var/mail</file>. This directory is part of the
7159 base system and should not be owned by any particular mail
7160 agents. The use of the old
7161 location <file>/var/spool/mail</file> is deprecated, even
7162 though the spool may still be physically located there.
7166 <sect1 id="fhs-run">
7167 <heading><file>/run</file> and <file>/run/lock</file></heading>
7170 The directory <file>/run</file> is cleared at boot, normally
7171 by being a mount point for a temporary file system. Packages
7172 therefore must not assume that any files or directories
7173 under <file>/run</file> other than <file>/run/lock</file>
7174 exist unless the package has arranged to create those files or
7175 directories since the last reboot. Normally, this is done by
7176 the package via an init script. See <ref id="writing-init">
7177 for more information.
7181 Packages must not include files or directories
7182 under <file>/run</file>, or under the
7183 older <file>/var/run</file> and <file>/var/lock</file> paths.
7184 The latter paths will normally be symlinks or other
7185 redirections to <file>/run</file> for backwards compatibility.
7191 <heading>Users and groups</heading>
7194 <heading>Introduction</heading>
7196 The Debian system can be configured to use either plain or
7201 Some user ids (UIDs) and group ids (GIDs) are reserved
7202 globally for use by certain packages. Because some
7203 packages need to include files which are owned by these
7204 users or groups, or need the ids compiled into binaries,
7205 these ids must be used on any Debian system only for the
7206 purpose for which they are allocated. This is a serious
7207 restriction, and we should avoid getting in the way of
7208 local administration policies. In particular, many sites
7209 allocate users and/or local system groups starting at 100.
7213 Apart from this we should have dynamically allocated ids,
7214 which should by default be arranged in some sensible
7215 order, but the behavior should be configurable.
7219 Packages other than <tt>base-passwd</tt> must not modify
7220 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7221 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7226 <heading>UID and GID classes</heading>
7228 The UID and GID numbers are divided into classes as
7234 Globally allocated by the Debian project, the same
7235 on every Debian system. These ids will appear in
7236 the <file>passwd</file> and <file>group</file> files of all
7237 Debian systems, new ids in this range being added
7238 automatically as the <tt>base-passwd</tt> package is
7243 Packages which need a single statically allocated
7244 uid or gid should use one of these; their
7245 maintainers should ask the <tt>base-passwd</tt>
7253 Dynamically allocated system users and groups.
7254 Packages which need a user or group, but can have
7255 this user or group allocated dynamically and
7256 differently on each system, should use <tt>adduser
7257 --system</tt> to create the group and/or user.
7258 <prgn>adduser</prgn> will check for the existence of
7259 the user or group, and if necessary choose an unused
7260 id based on the ranges specified in
7261 <file>adduser.conf</file>.
7265 <tag>1000-59999:</tag>
7268 Dynamically allocated user accounts. By default
7269 <prgn>adduser</prgn> will choose UIDs and GIDs for
7270 user accounts in this range, though
7271 <file>adduser.conf</file> may be used to modify this
7276 <tag>60000-64999:</tag>
7279 Globally allocated by the Debian project, but only
7280 created on demand. The ids are allocated centrally
7281 and statically, but the actual accounts are only
7282 created on users' systems on demand.
7286 These ids are for packages which are obscure or
7287 which require many statically-allocated ids. These
7288 packages should check for and create the accounts in
7289 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7290 <prgn>adduser</prgn> if it has this facility) if
7291 necessary. Packages which are likely to require
7292 further allocations should have a "hole" left after
7293 them in the allocation, to give them room to
7298 <tag>65000-65533:</tag>
7306 User <tt>nobody</tt>. The corresponding gid refers
7307 to the group <tt>nogroup</tt>.
7314 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7315 not</em> be used, because it is the error return
7324 <sect id="sysvinit">
7325 <heading>System run levels and <file>init.d</file> scripts</heading>
7327 <sect1 id="/etc/init.d">
7328 <heading>Introduction</heading>
7331 The <file>/etc/init.d</file> directory contains the scripts
7332 executed by <prgn>init</prgn> at boot time and when the
7333 init state (or "runlevel") is changed (see <manref
7334 name="init" section="8">).
7338 There are at least two different, yet functionally
7339 equivalent, ways of handling these scripts. For the sake
7340 of simplicity, this document describes only the symbolic
7341 link method. However, it must not be assumed by maintainer
7342 scripts that this method is being used, and any automated
7343 manipulation of the various runlevel behaviors by
7344 maintainer scripts must be performed using
7345 <prgn>update-rc.d</prgn> as described below and not by
7346 manually installing or removing symlinks. For information
7347 on the implementation details of the other method,
7348 implemented in the <tt>file-rc</tt> package, please refer
7349 to the documentation of that package.
7353 These scripts are referenced by symbolic links in the
7354 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7355 runlevels, <prgn>init</prgn> looks in the directory
7356 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7357 execute, where <tt><var>n</var></tt> is the runlevel that
7358 is being changed to, or <tt>S</tt> for the boot-up
7363 The names of the links all have the form
7364 <file>S<var>mm</var><var>script</var></file> or
7365 <file>K<var>mm</var><var>script</var></file> where
7366 <var>mm</var> is a two-digit number and <var>script</var>
7367 is the name of the script (this should be the same as the
7368 name of the actual script in <file>/etc/init.d</file>).
7372 When <prgn>init</prgn> changes runlevel first the targets
7373 of the links whose names start with a <tt>K</tt> are
7374 executed, each with the single argument <tt>stop</tt>,
7375 followed by the scripts prefixed with an <tt>S</tt>, each
7376 with the single argument <tt>start</tt>. (The links are
7377 those in the <file>/etc/rc<var>n</var>.d</file> directory
7378 corresponding to the new runlevel.) The <tt>K</tt> links
7379 are responsible for killing services and the <tt>S</tt>
7380 link for starting services upon entering the runlevel.
7384 For example, if we are changing from runlevel 2 to
7385 runlevel 3, init will first execute all of the <tt>K</tt>
7386 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7387 all of the <tt>S</tt> prefixed scripts in that directory.
7388 The links starting with <tt>K</tt> will cause the
7389 referred-to file to be executed with an argument of
7390 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7395 The two-digit number <var>mm</var> is used to determine
7396 the order in which to run the scripts: low-numbered links
7397 have their scripts run first. For example, the
7398 <tt>K20</tt> scripts will be executed before the
7399 <tt>K30</tt> scripts. This is used when a certain service
7400 must be started before another. For example, the name
7401 server <prgn>bind</prgn> might need to be started before
7402 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7403 can set up its access lists. In this case, the script
7404 that starts <prgn>bind</prgn> would have a lower number
7405 than the script that starts <prgn>inn</prgn> so that it
7407 <example compact="compact">
7414 The two runlevels 0 (halt) and 6 (reboot) are slightly
7415 different. In these runlevels, the links with an
7416 <tt>S</tt> prefix are still called after those with a
7417 <tt>K</tt> prefix, but they too are called with the single
7418 argument <tt>stop</tt>.
7422 <sect1 id="writing-init">
7423 <heading>Writing the scripts</heading>
7426 Packages that include daemons for system services should
7427 place scripts in <file>/etc/init.d</file> to start or stop
7428 services at boot time or during a change of runlevel.
7429 These scripts should be named
7430 <file>/etc/init.d/<var>package</var></file>, and they should
7431 accept one argument, saying what to do:
7434 <tag><tt>start</tt></tag>
7435 <item>start the service,</item>
7437 <tag><tt>stop</tt></tag>
7438 <item>stop the service,</item>
7440 <tag><tt>restart</tt></tag>
7441 <item>stop and restart the service if it's already running,
7442 otherwise start the service</item>
7444 <tag><tt>reload</tt></tag>
7445 <item><p>cause the configuration of the service to be
7446 reloaded without actually stopping and restarting
7449 <tag><tt>force-reload</tt></tag>
7450 <item>cause the configuration to be reloaded if the
7451 service supports this, otherwise restart the
7455 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7456 <tt>force-reload</tt> options should be supported by all
7457 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7462 The <file>init.d</file> scripts must ensure that they will
7463 behave sensibly (i.e., returning success and not starting
7464 multiple copies of a service) if invoked with <tt>start</tt>
7465 when the service is already running, or with <tt>stop</tt>
7466 when it isn't, and that they don't kill unfortunately-named
7467 user processes. The best way to achieve this is usually to
7468 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7473 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7474 scripts. Writing correct <file>init.d</file> scripts requires
7475 accepting various error exit statuses when daemons are already
7476 running or already stopped without aborting
7477 the <file>init.d</file> script, and common <file>init.d</file>
7478 function libraries are not safe to call with <tt>set -e</tt>
7480 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7481 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7482 in effect and echoing status messages to the console fails,
7484 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7485 to not use <tt>set -e</tt> and instead check the result of
7486 each command separately.
7490 If a service reloads its configuration automatically (as
7491 in the case of <prgn>cron</prgn>, for example), the
7492 <tt>reload</tt> option of the <file>init.d</file> script
7493 should behave as if the configuration has been reloaded
7498 The <file>/etc/init.d</file> scripts must be treated as
7499 configuration files, either (if they are present in the
7500 package, that is, in the .deb file) by marking them as
7501 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7502 by managing them correctly in the maintainer scripts (see
7503 <ref id="config-files">). This is important since we want
7504 to give the local system administrator the chance to adapt
7505 the scripts to the local system, e.g., to disable a
7506 service without de-installing the package, or to specify
7507 some special command line options when starting a service,
7508 while making sure their changes aren't lost during the next
7513 These scripts should not fail obscurely when the
7514 configuration files remain but the package has been
7515 removed, as configuration files remain on the system after
7516 the package has been removed. Only when <prgn>dpkg</prgn>
7517 is executed with the <tt>--purge</tt> option will
7518 configuration files be removed. In particular, as the
7519 <file>/etc/init.d/<var>package</var></file> script itself is
7520 usually a <tt>conffile</tt>, it will remain on the system
7521 if the package is removed but not purged. Therefore, you
7522 should include a <tt>test</tt> statement at the top of the
7524 <example compact="compact">
7525 test -f <var>program-executed-later-in-script</var> || exit 0
7530 Often there are some variables in the <file>init.d</file>
7531 scripts whose values control the behavior of the scripts,
7532 and which a system administrator is likely to want to
7533 change. As the scripts themselves are frequently
7534 <tt>conffile</tt>s, modifying them requires that the
7535 administrator merge in their changes each time the package
7536 is upgraded and the <tt>conffile</tt> changes. To ease
7537 the burden on the system administrator, such configurable
7538 values should not be placed directly in the script.
7539 Instead, they should be placed in a file in
7540 <file>/etc/default</file>, which typically will have the same
7541 base name as the <file>init.d</file> script. This extra file
7542 should be sourced by the script when the script runs. It
7543 must contain only variable settings and comments in SUSv3
7544 <prgn>sh</prgn> format. It may either be a
7545 <tt>conffile</tt> or a configuration file maintained by
7546 the package maintainer scripts. See <ref id="config-files">
7551 To ensure that vital configurable values are always
7552 available, the <file>init.d</file> script should set default
7553 values for each of the shell variables it uses, either
7554 before sourcing the <file>/etc/default/</file> file or
7555 afterwards using something like the <tt>:
7556 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7557 script must behave sensibly and not fail if the
7558 <file>/etc/default</file> file is deleted.
7562 Files and directories under <file>/run</file>, including ones
7563 referred to via the compatibility paths <file>/var/run</file>
7564 and <file>/var/lock</file>, are normally stored on a temporary
7565 filesystem and are normally not persistent across a reboot.
7566 The <file>init.d</file> scripts must handle this correctly.
7567 This will typically mean creating any required subdirectories
7568 dynamically when the <file>init.d</file> script is run.
7569 See <ref id="fhs-run"> for more information.
7574 <heading>Interfacing with the initscript system</heading>
7577 Maintainers should use the abstraction layer provided by
7578 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7579 programs to deal with initscripts in their packages'
7580 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7581 and <prgn>postrm</prgn>.
7585 Directly managing the /etc/rc?.d links and directly
7586 invoking the <file>/etc/init.d/</file> initscripts should
7587 be done only by packages providing the initscript
7588 subsystem (such as <prgn>sysv-rc</prgn> and
7589 <prgn>file-rc</prgn>).
7593 <heading>Managing the links</heading>
7596 The program <prgn>update-rc.d</prgn> is provided for
7597 package maintainers to arrange for the proper creation and
7598 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7599 or their functional equivalent if another method is being
7600 used. This may be used by maintainers in their packages'
7601 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7605 You must not include any <file>/etc/rc<var>n</var>.d</file>
7606 symbolic links in the actual archive or manually create or
7607 remove the symbolic links in maintainer scripts; you must
7608 use the <prgn>update-rc.d</prgn> program instead. (The
7609 former will fail if an alternative method of maintaining
7610 runlevel information is being used.) You must not include
7611 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7612 in the archive either. (Only the <tt>sysvinit</tt>
7617 By default <prgn>update-rc.d</prgn> will start services in
7618 each of the multi-user state runlevels (2, 3, 4, and 5)
7619 and stop them in the halt runlevel (0), the single-user
7620 runlevel (1) and the reboot runlevel (6). The system
7621 administrator will have the opportunity to customize
7622 runlevels by simply adding, moving, or removing the
7623 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7624 symbolic links are being used, or by modifying
7625 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7630 To get the default behavior for your package, put in your
7631 <prgn>postinst</prgn> script
7632 <example compact="compact">
7633 update-rc.d <var>package</var> defaults
7635 and in your <prgn>postrm</prgn>
7636 <example compact="compact">
7637 if [ "$1" = purge ]; then
7638 update-rc.d <var>package</var> remove
7640 </example>. Note that if your package changes runlevels
7641 or priority, you may have to remove and recreate the links,
7642 since otherwise the old links may persist. Refer to the
7643 documentation of <prgn>update-rc.d</prgn>.
7647 This will use a default sequence number of 20. If it does
7648 not matter when or in which order the <file>init.d</file>
7649 script is run, use this default. If it does, then you
7650 should talk to the maintainer of the <prgn>sysvinit</prgn>
7651 package or post to <tt>debian-devel</tt>, and they will
7652 help you choose a number.
7656 For more information about using <tt>update-rc.d</tt>,
7657 please consult its man page <manref name="update-rc.d"
7663 <heading>Running initscripts</heading>
7665 The program <prgn>invoke-rc.d</prgn> is provided to make
7666 it easier for package maintainers to properly invoke an
7667 initscript, obeying runlevel and other locally-defined
7668 constraints that might limit a package's right to start,
7669 stop and otherwise manage services. This program may be
7670 used by maintainers in their packages' scripts.
7674 The package maintainer scripts must use
7675 <prgn>invoke-rc.d</prgn> to invoke the
7676 <file>/etc/init.d/*</file> initscripts, instead of
7677 calling them directly.
7681 By default, <prgn>invoke-rc.d</prgn> will pass any
7682 action requests (start, stop, reload, restart...) to the
7683 <file>/etc/init.d</file> script, filtering out requests
7684 to start or restart a service out of its intended
7689 Most packages will simply need to change:
7690 <example compact="compact">/etc/init.d/<package>
7691 <action></example> in their <prgn>postinst</prgn>
7692 and <prgn>prerm</prgn> scripts to:
7693 <example compact="compact">
7694 if which invoke-rc.d >/dev/null 2>&1; then
7695 invoke-rc.d <var>package</var> <action>
7697 /etc/init.d/<var>package</var> <action>
7703 A package should register its initscript services using
7704 <prgn>update-rc.d</prgn> before it tries to invoke them
7705 using <prgn>invoke-rc.d</prgn>. Invocation of
7706 unregistered services may fail.
7710 For more information about using
7711 <prgn>invoke-rc.d</prgn>, please consult its man page
7712 <manref name="invoke-rc.d" section="8">.
7718 <heading>Boot-time initialization</heading>
7721 There used to be another directory, <file>/etc/rc.boot</file>,
7722 which contained scripts which were run once per machine
7723 boot. This has been deprecated in favour of links from
7724 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7725 described in <ref id="/etc/init.d">. Packages must not
7726 place files in <file>/etc/rc.boot</file>.
7731 <heading>Example</heading>
7734 An example on which you can base your
7735 <file>/etc/init.d</file> scripts is found in
7736 <file>/etc/init.d/skeleton</file>.
7743 <heading>Console messages from <file>init.d</file> scripts</heading>
7746 This section describes the formats to be used for messages
7747 written to standard output by the <file>/etc/init.d</file>
7748 scripts. The intent is to improve the consistency of
7749 Debian's startup and shutdown look and feel. For this
7750 reason, please look very carefully at the details. We want
7751 the messages to have the same format in terms of wording,
7752 spaces, punctuation and case of letters.
7756 Here is a list of overall rules that should be used for
7757 messages generated by <file>/etc/init.d</file> scripts.
7763 The message should fit in one line (fewer than 80
7764 characters), start with a capital letter and end with
7765 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7769 If the script is performing some time consuming task in
7770 the background (not merely starting or stopping a
7771 program, for instance), an ellipsis (three dots:
7772 <tt>...</tt>) should be output to the screen, with no
7773 leading or tailing whitespace or line feeds.
7777 The messages should appear as if the computer is telling
7778 the user what it is doing (politely :-), but should not
7779 mention "it" directly. For example, instead of:
7780 <example compact="compact">
7781 I'm starting network daemons: nfsd mountd.
7783 the message should say
7784 <example compact="compact">
7785 Starting network daemons: nfsd mountd.
7792 <tt>init.d</tt> script should use the following standard
7793 message formats for the situations enumerated below.
7799 <p>When daemons are started</p>
7802 If the script starts one or more daemons, the output
7803 should look like this (a single line, no leading
7805 <example compact="compact">
7806 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7808 The <var>description</var> should describe the
7809 subsystem the daemon or set of daemons are part of,
7810 while <var>daemon-1</var> up to <var>daemon-n</var>
7811 denote each daemon's name (typically the file name of
7816 For example, the output of <file>/etc/init.d/lpd</file>
7818 <example compact="compact">
7819 Starting printer spooler: lpd.
7824 This can be achieved by saying
7825 <example compact="compact">
7826 echo -n "Starting printer spooler: lpd"
7827 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7830 in the script. If there are more than one daemon to
7831 start, the output should look like this:
7832 <example compact="compact">
7833 echo -n "Starting remote file system services:"
7834 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7835 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7836 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7839 This makes it possible for the user to see what is
7840 happening and when the final daemon has been started.
7841 Care should be taken in the placement of white spaces:
7842 in the example above the system administrators can
7843 easily comment out a line if they don't want to start
7844 a specific daemon, while the displayed message still
7850 <p>When a system parameter is being set</p>
7853 If you have to set up different system parameters
7854 during the system boot, you should use this format:
7855 <example compact="compact">
7856 Setting <var>parameter</var> to "<var>value</var>".
7861 You can use a statement such as the following to get
7863 <example compact="compact">
7864 echo "Setting DNS domainname to \"$domainname\"."
7869 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7870 for the left and right quotation marks. A grave accent
7871 (<tt>`</tt>) is not a quote character; neither is an
7872 apostrophe (<tt>'</tt>).
7877 <p>When a daemon is stopped or restarted</p>
7880 When you stop or restart a daemon, you should issue a
7881 message identical to the startup message, except that
7882 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7883 or <tt>Restarting</tt> respectively.
7887 For example, stopping the printer daemon will look like
7889 <example compact="compact">
7890 Stopping printer spooler: lpd.
7896 <p>When something is executed</p>
7899 There are several examples where you have to run a
7900 program at system startup or shutdown to perform a
7901 specific task, for example, setting the system's clock
7902 using <prgn>netdate</prgn> or killing all processes
7903 when the system shuts down. Your message should look
7905 <example compact="compact">
7906 Doing something very useful...done.
7908 You should print the <tt>done.</tt> immediately after
7909 the job has been completed, so that the user is
7910 informed why they have to wait. You can get this
7912 <example compact="compact">
7913 echo -n "Doing something very useful..."
7922 <p>When the configuration is reloaded</p>
7925 When a daemon is forced to reload its configuration
7926 files you should use the following format:
7927 <example compact="compact">
7928 Reloading <var>description</var> configuration...done.
7930 where <var>description</var> is the same as in the
7931 daemon starting message.
7938 <sect id="cron-jobs">
7939 <heading>Cron jobs</heading>
7942 Packages must not modify the configuration file
7943 <file>/etc/crontab</file>, and they must not modify the files in
7944 <file>/var/spool/cron/crontabs</file>.
7948 If a package wants to install a job that has to be executed via
7949 cron, it should place a file named as specified
7950 in <ref id="cron-files"> into one or more of the following
7952 <example compact="compact">
7958 As these directory names imply, the files within them are
7959 executed on an hourly, daily, weekly, or monthly basis,
7960 respectively. The exact times are listed in
7961 <file>/etc/crontab</file>.
7965 All files installed in any of these directories must be
7966 scripts (e.g., shell scripts or Perl scripts) so that they
7967 can easily be modified by the local system administrator.
7968 In addition, they must be treated as configuration files.
7972 If a certain job has to be executed at some other frequency or
7973 at a specific time, the package should install a file in
7974 <file>/etc/cron.d</file> with a name as specified
7975 in <ref id="cron-files">. This file uses the same syntax
7976 as <file>/etc/crontab</file> and is processed
7977 by <prgn>cron</prgn> automatically. The file must also be
7978 treated as a configuration file. (Note that entries in the
7979 <file>/etc/cron.d</file> directory are not handled by
7980 <prgn>anacron</prgn>. Thus, you should only use this
7981 directory for jobs which may be skipped if the system is not
7986 Unlike <file>crontab</file> files described in the IEEE Std
7987 1003.1-2008 (POSIX.1) available from
7988 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7989 name="The Open Group">, the files in
7990 <file>/etc/cron.d</file> and the file
7991 <file>/etc/crontab</file> have seven fields; namely:
7993 <item>Minute [0,59]</item>
7994 <item>Hour [0,23]</item>
7995 <item>Day of the month [1,31]</item>
7996 <item>Month of the year [1,12]</item>
7997 <item>Day of the week ([0,6] with 0=Sunday)</item>
7998 <item>Username</item>
7999 <item>Command to be run</item>
8001 Ranges of numbers are allowed. Ranges are two numbers
8002 separated with a hyphen. The specified range is inclusive.
8003 Lists are allowed. A list is a set of numbers (or ranges)
8004 separated by commas. Step values can be used in conjunction
8009 The scripts or <tt>crontab</tt> entries in these directories should
8010 check if all necessary programs are installed before they
8011 try to execute them. Otherwise, problems will arise when a
8012 package was removed but not purged since configuration files
8013 are kept on the system in this situation.
8017 Any <tt>cron</tt> daemon must provide
8018 <file>/usr/bin/crontab</file> and support normal
8019 <tt>crontab</tt> entries as specified in POSIX. The daemon
8020 must also support names for days and months, ranges, and
8021 step values. It has to support <file>/etc/crontab</file>,
8022 and correctly execute the scripts in
8023 <file>/etc/cron.d</file>. The daemon must also correctly
8025 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8028 <sect1 id="cron-files">
8029 <heading>Cron job file names</heading>
8032 The file name of a cron job file should normally match the
8033 name of the package from which it comes.
8037 If a package supplies multiple cron job files files in the
8038 same directory, the file names should all start with the name
8039 of the package (possibly modified as described below) followed
8040 by a hyphen (<tt>-</tt>) and a suitable suffix.
8044 A cron job file name must not include any period or plus
8045 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8046 cause cron to ignore the file. Underscores (<tt>_</tt>)
8047 should be used instead of <tt>.</tt> and <tt>+</tt>
8054 <heading>Menus</heading>
8057 The Debian <tt>menu</tt> package provides a standard
8058 interface between packages providing applications and
8059 <em>menu programs</em> (either X window managers or
8060 text-based menu programs such as <prgn>pdmenu</prgn>).
8064 All packages that provide applications that need not be
8065 passed any special command line arguments for normal
8066 operation should register a menu entry for those
8067 applications, so that users of the <tt>menu</tt> package
8068 will automatically get menu entries in their window
8069 managers, as well in shells like <tt>pdmenu</tt>.
8073 Menu entries should follow the current menu policy.
8077 The menu policy can be found in the <tt>menu-policy</tt>
8078 files in the <tt>debian-policy</tt> package.
8079 It is also available from the Debian web mirrors at
8080 <tt><url name="/doc/packaging-manuals/menu-policy/"
8081 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8085 Please also refer to the <em>Debian Menu System</em>
8086 documentation that comes with the <package>menu</package>
8087 package for information about how to register your
8093 <heading>Multimedia handlers</heading>
8096 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8097 is a mechanism for encoding files and data streams and
8098 providing meta-information about them, in particular their
8099 type (e.g. audio or video) and format (e.g. PNG, HTML,
8104 Registration of MIME type handlers allows programs like mail
8105 user agents and web browsers to invoke these handlers to
8106 view, edit or display MIME types they don't support directly.
8110 Packages which provide programs to view/show/play, compose, edit or
8111 print MIME types should register them as such by placing a file in
8112 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8113 <file>/usr/lib/mime/packages/</file>. The file name should be the
8114 binary package's name.
8118 The <package>mime-support</package> package provides the
8119 <prgn>update-mime</prgn> program, which integrates these
8120 registrations in the <file>/etc/mailcap</file> file, using dpkg
8122 Creating, modifying or removing a file in
8123 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8124 not activate the trigger. In that case, it can be done by calling
8125 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8126 the maintainer script after creating, modifying, or removing
8129 Packages using this facility <em>should not</em> depend on,
8130 recommend, or suggest <prgn>mime-support</prgn>.
8135 <heading>Keyboard configuration</heading>
8138 To achieve a consistent keyboard configuration so that all
8139 applications interpret a keyboard event the same way, all
8140 programs in the Debian distribution must be configured to
8141 comply with the following guidelines.
8145 The following keys must have the specified interpretations:
8148 <tag><tt><--</tt></tag>
8149 <item>delete the character to the left of the cursor</item>
8151 <tag><tt>Delete</tt></tag>
8152 <item>delete the character to the right of the cursor</item>
8154 <tag><tt>Control+H</tt></tag>
8155 <item>emacs: the help prefix</item>
8158 The interpretation of any keyboard events should be
8159 independent of the terminal that is used, be it a virtual
8160 console, an X terminal emulator, an rlogin/telnet session,
8165 The following list explains how the different programs
8166 should be set up to achieve this:
8172 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8176 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8180 X translations are set up to make
8181 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8182 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8183 is the vt220 escape code for the "delete character"
8184 key). This must be done by loading the X resources
8185 using <prgn>xrdb</prgn> on all local X displays, not
8186 using the application defaults, so that the
8187 translation resources used correspond to the
8188 <prgn>xmodmap</prgn> settings.
8192 The Linux console is configured to make
8193 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8194 generate <tt>ESC [ 3 ~</tt>.
8198 X applications are configured so that <tt><</tt>
8199 deletes left, and <tt>Delete</tt> deletes right. Motif
8200 applications already work like this.
8204 Terminals should have <tt>stty erase ^?</tt> .
8208 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8209 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8210 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8214 Emacs is programmed to map <tt>KB_Backspace</tt> or
8215 the <tt>stty erase</tt> character to
8216 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8217 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8218 <tt>^H</tt> to <tt>help</tt> as always.
8222 Other applications use the <tt>stty erase</tt>
8223 character and <tt>kdch1</tt> for the two delete keys,
8224 with ASCII DEL being "delete previous character" and
8225 <tt>kdch1</tt> being "delete character under
8233 This will solve the problem except for the following
8240 Some terminals have a <tt><--</tt> key that cannot
8241 be made to produce anything except <tt>^H</tt>. On
8242 these terminals Emacs help will be unavailable on
8243 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8244 character takes precedence in Emacs, and has been set
8245 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8246 available) can be used instead.
8250 Some operating systems use <tt>^H</tt> for <tt>stty
8251 erase</tt>. However, modern telnet versions and all
8252 rlogin versions propagate <tt>stty</tt> settings, and
8253 almost all UNIX versions honour <tt>stty erase</tt>.
8254 Where the <tt>stty</tt> settings are not propagated
8255 correctly, things can be made to work by using
8256 <tt>stty</tt> manually.
8260 Some systems (including previous Debian versions) use
8261 <prgn>xmodmap</prgn> to arrange for both
8262 <tt><--</tt> and <tt>Delete</tt> to generate
8263 <tt>KB_Delete</tt>. We can change the behavior of
8264 their X clients using the same X resources that we use
8265 to do it for our own clients, or configure our clients
8266 using their resources when things are the other way
8267 around. On displays configured like this
8268 <tt>Delete</tt> will not work, but <tt><--</tt>
8273 Some operating systems have different <tt>kdch1</tt>
8274 settings in their <tt>terminfo</tt> database for
8275 <tt>xterm</tt> and others. On these systems the
8276 <tt>Delete</tt> key will not work correctly when you
8277 log in from a system conforming to our policy, but
8278 <tt><--</tt> will.
8285 <heading>Environment variables</heading>
8288 A program must not depend on environment variables to get
8289 reasonable defaults. (That's because these environment
8290 variables would have to be set in a system-wide
8291 configuration file like <file>/etc/profile</file>, which is not
8292 supported by all shells.)
8296 If a program usually depends on environment variables for its
8297 configuration, the program should be changed to fall back to
8298 a reasonable default configuration if these environment
8299 variables are not present. If this cannot be done easily
8300 (e.g., if the source code of a non-free program is not
8301 available), the program must be replaced by a small
8302 "wrapper" shell script which sets the environment variables
8303 if they are not already defined, and calls the original program.
8307 Here is an example of a wrapper script for this purpose:
8309 <example compact="compact">
8311 BAR=${BAR:-/var/lib/fubar}
8313 exec /usr/lib/foo/foo "$@"
8318 Furthermore, as <file>/etc/profile</file> is a configuration
8319 file of the <prgn>base-files</prgn> package, other packages must
8320 not put any environment variables or other commands into that
8325 <sect id="doc-base">
8326 <heading>Registering Documents using doc-base</heading>
8329 The <package>doc-base</package> package implements a
8330 flexible mechanism for handling and presenting
8331 documentation. The recommended practice is for every Debian
8332 package that provides online documentation (other than just
8333 manual pages) to register these documents with
8334 <package>doc-base</package> by installing a
8335 <package>doc-base</package> control file in
8336 <file>/usr/share/doc-base/</file>.
8339 Please refer to the documentation that comes with the
8340 <package>doc-base</package> package for information and
8345 <sect id="alternateinit">
8346 <heading>Alternate init systems</heading>
8348 A number of other init systems are available now in Debian that
8349 can be used in place of <package>sysvinit</package>. Alternative
8350 init implementations must support running SysV init scripts as
8351 described at <ref id="sysvinit"> for compatibility.
8354 Packages may integrate with these replacement init systems by
8355 providing implementation-specific configuration information about
8356 how and when to start a service or in what order to run certain
8357 tasks at boot time. However, any package integrating with other
8358 init systems must also be backwards-compatible with
8359 <package>sysvinit</package> by providing a SysV-style init script
8360 with the same name as and equivalent functionality to any
8361 init-specific job, as this is the only start-up configuration
8362 method guaranteed to be supported by all init implementations. An
8363 exception to this rule is scripts or jobs provided by the init
8364 implementation itself; such jobs may be required for an
8365 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8366 scripts and may not have a one-to-one correspondence with the init
8369 <sect1 id="upstart">
8370 <heading>Event-based boot with upstart</heading>
8373 Packages may integrate with the <prgn>upstart</prgn> event-based
8374 boot system by installing job files in the
8375 <file>/etc/init</file> directory. SysV init scripts for which
8376 an equivalent upstart job is available must query the output of
8377 the command <prgn>initctl version</prgn> for the string
8378 <tt>upstart</tt> and avoid running in favor of the native
8379 upstart job, using a test such as this:
8380 <example compact="compact">
8381 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8388 Because packages shipping upstart jobs may be installed on
8389 systems that are not using upstart, maintainer scripts must
8390 still use the common <prgn>update-rc.d</prgn> and
8391 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8392 and for starting and stopping services. These maintainer
8393 scripts must not call the upstart <prgn>start</prgn>,
8394 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8395 interfaces directly. Instead, implementations of
8396 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8397 when an upstart job with the same name as an init script is
8398 present, and perform the requested action using the upstart job
8399 instead of the init script.
8402 Dependency-based boot managers for SysV init scripts, such as
8403 <prgn>startpar</prgn>, may avoid running a given init script
8404 entirely when an equivalent upstart job is present, to avoid
8405 unnecessary forking of no-op init scripts. In this case, the
8406 boot manager should integrate with upstart to detect when the
8407 upstart job in question is started or stopped to know when the
8408 dependency has been satisfied.
8417 <heading>Files</heading>
8419 <sect id="binaries">
8420 <heading>Binaries</heading>
8423 Two different packages must not install programs with
8424 different functionality but with the same filenames. (The
8425 case of two programs having the same functionality but
8426 different implementations is handled via "alternatives" or
8427 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8428 <ref id="conflicts"> respectively.) If this case happens,
8429 one of the programs must be renamed. The maintainers should
8430 report this to the <tt>debian-devel</tt> mailing list and
8431 try to find a consensus about which program will have to be
8432 renamed. If a consensus cannot be reached, <em>both</em>
8433 programs must be renamed.
8437 By default, when a package is being built, any binaries
8438 created should include debugging information, as well as
8439 being compiled with optimization. You should also turn on
8440 as many reasonable compilation warnings as possible; this
8441 makes life easier for porters, who can then look at build
8442 logs for possible problems. For the C programming language,
8443 this means the following compilation parameters should be
8445 <example compact="compact">
8447 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8449 INSTALL = install -s # (or use strip on the files in debian/tmp)
8454 Note that by default all installed binaries should be stripped,
8455 either by using the <tt>-s</tt> flag to
8456 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8457 the binaries after they have been copied into
8458 <file>debian/tmp</file> but before the tree is made into a
8463 Although binaries in the build tree should be compiled with
8464 debugging information by default, it can often be difficult to
8465 debug programs if they are also subjected to compiler
8466 optimization. For this reason, it is recommended to support the
8467 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8468 (see <ref id="debianrules-options">). This variable can contain
8469 several flags to change how a package is compiled and built.
8473 It is up to the package maintainer to decide what
8474 compilation options are best for the package. Certain
8475 binaries (such as computationally-intensive programs) will
8476 function better with certain flags (<tt>-O3</tt>, for
8477 example); feel free to use them. Please use good judgment
8478 here. Don't use flags for the sake of it; only use them
8479 if there is good reason to do so. Feel free to override
8480 the upstream author's ideas about which compilation
8481 options are best: they are often inappropriate for our
8487 <sect id="libraries">
8488 <heading>Libraries</heading>
8491 If the package is <strong>architecture: any</strong>, then
8492 the shared library compilation and linking flags must have
8493 <tt>-fPIC</tt>, or the package shall not build on some of
8494 the supported architectures<footnote>
8496 If you are using GCC, <tt>-fPIC</tt> produces code with
8497 relocatable position independent code, which is required for
8498 most architectures to create a shared library, with i386 and
8499 perhaps some others where non position independent code is
8500 permitted in a shared library.
8503 Position independent code may have a performance penalty,
8504 especially on <tt>i386</tt>. However, in most cases the
8505 speed penalty must be measured against the memory wasted on
8506 the few architectures where non position independent code is
8509 </footnote>. Any exception to this rule must be discussed on
8510 the mailing list <em>debian-devel@lists.debian.org</em>, and
8511 a rough consensus obtained. The reasons for not compiling
8512 with <tt>-fPIC</tt> flag must be recorded in the file
8513 <tt>README.Debian</tt>, and care must be taken to either
8514 restrict the architecture or arrange for <tt>-fPIC</tt> to
8515 be used on architectures where it is required.<footnote>
8517 Some of the reasons why this might be required is if the
8518 library contains hand crafted assembly code that is not
8519 relocatable, the speed penalty is excessive for compute
8520 intensive libs, and similar reasons.
8525 As to the static libraries, the common case is not to have
8526 relocatable code, since there is no benefit, unless in specific
8527 cases; therefore the static version must not be compiled
8528 with the <tt>-fPIC</tt> flag. Any exception to this rule
8529 should be discussed on the mailing list
8530 <em>debian-devel@lists.debian.org</em>, and the reasons for
8531 compiling with the <tt>-fPIC</tt> flag must be recorded in
8532 the file <tt>README.Debian</tt>. <footnote>
8534 Some of the reasons for linking static libraries with
8535 the <tt>-fPIC</tt> flag are if, for example, one needs a
8536 Perl API for a library that is under rapid development,
8537 and has an unstable API, so shared libraries are
8538 pointless at this phase of the library's development. In
8539 that case, since Perl needs a library with relocatable
8540 code, it may make sense to create a static library with
8541 relocatable code. Another reason cited is if you are
8542 distilling various libraries into a common shared
8543 library, like <tt>mklibs</tt> does in the Debian
8549 In other words, if both a shared and a static library is
8550 being built, each source unit (<tt>*.c</tt>, for example,
8551 for C files) will need to be compiled twice, for the normal
8556 Libraries should be built with threading support and to be
8557 thread-safe if the library supports this.
8561 Although not enforced by the build tools, shared libraries
8562 must be linked against all libraries that they use symbols from
8563 in the same way that binaries are. This ensures the correct
8564 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8565 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8566 systems and guarantees that all libraries can be safely opened
8567 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8568 option <tt>-Wl,-z,defs</tt> when building a shared library.
8569 Since this option enforces symbol resolution at build time,
8570 a missing library reference will be caught early as a fatal
8575 All installed shared libraries should be stripped with
8576 <example compact="compact">
8577 strip --strip-unneeded <var>your-lib</var>
8579 (The option <tt>--strip-unneeded</tt> makes
8580 <prgn>strip</prgn> remove only the symbols which aren't
8581 needed for relocation processing.) Shared libraries can
8582 function perfectly well when stripped, since the symbols for
8583 dynamic linking are in a separate part of the ELF object
8585 You might also want to use the options
8586 <tt>--remove-section=.comment</tt> and
8587 <tt>--remove-section=.note</tt> on both shared libraries
8588 and executables, and <tt>--strip-debug</tt> on static
8594 Note that under some circumstances it may be useful to
8595 install a shared library unstripped, for example when
8596 building a separate package to support debugging.
8600 Shared object files (often <file>.so</file> files) that are not
8601 public libraries, that is, they are not meant to be linked
8602 to by third party executables (binaries of other packages),
8603 should be installed in subdirectories of the
8604 <file>/usr/lib</file> directory. Such files are exempt from the
8605 rules that govern ordinary shared libraries, except that
8606 they must not be installed executable and should be
8608 A common example are the so-called "plug-ins",
8609 internal shared objects that are dynamically loaded by
8610 programs using <manref name="dlopen" section="3">.
8615 Packages that use <prgn>libtool</prgn> to create and install
8616 their shared libraries install a file containing additional
8617 metadata (ending in <file>.la</file>) alongside the library.
8618 For public libraries intended for use by other packages, these
8619 files normally should not be included in the Debian package,
8620 since the information they include is not necessary to link with
8621 the shared library on Debian and can add unnecessary additional
8622 dependencies to other programs or libraries.<footnote>
8623 These files store, among other things, all libraries on which
8624 that shared library depends. Unfortunately, if
8625 the <file>.la</file> file is present and contains that
8626 dependency information, using <prgn>libtool</prgn> when
8627 linking against that library will cause the resulting program
8628 or library to be linked against those dependencies as well,
8629 even if this is unnecessary. This can create unneeded
8630 dependencies on shared library packages that would otherwise
8631 be hidden behind the library ABI, and can make library
8632 transitions to new SONAMEs unnecessarily complicated and
8633 difficult to manage.
8635 If the <file>.la</file> file is required for that library (if,
8636 for instance, it's loaded via <tt>libltdl</tt> in a way that
8637 requires that meta-information), the <tt>dependency_libs</tt>
8638 setting in the <file>.la</file> file should normally be set to
8639 the empty string. If the shared library development package has
8640 historically included the <file>.la</file>, it must be retained
8641 in the development package (with <tt>dependency_libs</tt>
8642 emptied) until all libraries that depend on it have removed or
8643 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8644 files to prevent linking with those other libraries
8645 using <prgn>libtool</prgn> from failing.
8649 If the <file>.la</file> must be included, it should be included
8650 in the development (<tt>-dev</tt>) package, unless the library
8651 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8652 library. If it is intended for use with <tt>libltdl</tt>,
8653 the <file>.la</file> files must go in the run-time library
8658 These requirements for handling of <file>.la</file> files do not
8659 apply to loadable modules or libraries not installed in
8660 directories searched by default by the dynamic linker. Packages
8661 installing loadable modules will frequently need to install
8662 the <file>.la</file> files alongside the modules so that they
8663 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8664 does not need to be modified for libraries or modules that are
8665 not installed in directories searched by the dynamic linker by
8666 default and not intended for use by other packages.
8670 You must make sure that you use only released versions of
8671 shared libraries to build your packages; otherwise other
8672 users will not be able to run your binaries
8673 properly. Producing source packages that depend on
8674 unreleased compilers is also usually a bad
8681 <heading>Shared libraries</heading>
8683 This section has moved to <ref id="sharedlibs">.
8689 <heading>Scripts</heading>
8692 All command scripts, including the package maintainer
8693 scripts inside the package and used by <prgn>dpkg</prgn>,
8694 should have a <tt>#!</tt> line naming the shell to be used
8699 In the case of Perl scripts this should be
8700 <tt>#!/usr/bin/perl</tt>.
8704 When scripts are installed into a directory in the system
8705 PATH, the script name should not include an extension such
8706 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8707 language currently used to implement it.
8710 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8711 <file>init.d</file> scripts should almost certainly start
8712 with <tt>set -e</tt> so that errors are detected.
8713 <file>init.d</file> scripts are something of a special case, due
8714 to how frequently they need to call commands that are allowed to
8715 fail, and it may instead be easier to check the exit status of
8716 commands directly. See <ref id="writing-init"> for more
8717 information about writing <file>init.d</file> scripts.
8720 Every script should use <tt>set -e</tt> or check the exit status
8721 of <em>every</em> command.
8724 Scripts may assume that <file>/bin/sh</file> implements the
8725 SUSv3 Shell Command Language<footnote>
8726 Single UNIX Specification, version 3, which is also IEEE
8727 1003.1-2004 (POSIX), and is available on the World Wide Web
8728 from <url id="http://www.unix.org/version3/online.html"
8729 name="The Open Group"> after free
8730 registration.</footnote>
8731 plus the following additional features not mandated by
8733 These features are in widespread use in the Linux community
8734 and are implemented in all of bash, dash, and ksh, the most
8735 common shells users may wish to use as <file>/bin/sh</file>.
8738 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8739 must not generate a newline.</item>
8740 <item><tt>test</tt>, if implemented as a shell built-in, must
8741 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8743 <item><tt>local</tt> to create a scoped variable must be
8744 supported, including listing multiple variables in a single
8745 local command and assigning a value to a variable at the
8746 same time as localizing it. <tt>local</tt> may or
8747 may not preserve the variable value from an outer scope if
8748 no assignment is present. Uses such as:
8752 # ... use a, b, c, d ...
8755 must be supported and must set the value of <tt>c</tt> to
8758 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8759 -<var>signal</var></tt>, where <var>signal</var> is either
8760 the name of a signal or one of the numeric signals listed in
8761 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8762 supported if <prgn>kill</prgn> is implemented as a shell
8765 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8766 signals must be supported. In addition to the signal
8767 numbers listed in the extension, which are the same as for
8768 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8771 If a shell script requires non-SUSv3 features from the shell
8772 interpreter other than those listed above, the appropriate shell
8773 must be specified in the first line of the script (e.g.,
8774 <tt>#!/bin/bash</tt>) and the package must depend on the package
8775 providing the shell (unless the shell package is marked
8776 "Essential", as in the case of <prgn>bash</prgn>).
8780 You may wish to restrict your script to SUSv3 features plus the
8781 above set when possible so that it may use <file>/bin/sh</file>
8782 as its interpreter. Checking your script
8783 with <prgn>checkbashisms</prgn> from
8784 the <package>devscripts</package> package or running your script
8785 with an alternate shell such as <prgn>posh</prgn> may help
8786 uncover violations of the above requirements. If in doubt
8787 whether a script complies with these requirements,
8788 use <file>/bin/bash</file>.
8792 Perl scripts should check for errors when making any
8793 system calls, including <tt>open</tt>, <tt>print</tt>,
8794 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8798 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8799 scripting languages. See <em>Csh Programming Considered
8800 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8801 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8802 If an upstream package comes with <prgn>csh</prgn> scripts
8803 then you must make sure that they start with
8804 <tt>#!/bin/csh</tt> and make your package depend on the
8805 <prgn>c-shell</prgn> virtual package.
8809 Any scripts which create files in world-writeable
8810 directories (e.g., in <file>/tmp</file>) must use a
8811 mechanism which will fail atomically if a file with the same
8812 name already exists.
8816 The Debian base system provides the <prgn>tempfile</prgn>
8817 and <prgn>mktemp</prgn> utilities for use by scripts for
8824 <heading>Symbolic links</heading>
8827 In general, symbolic links within a top-level directory should
8828 be relative, and symbolic links pointing from one top-level
8829 directory to or into another should be absolute. (A top-level
8830 directory is a sub-directory of the root
8831 directory <file>/</file>.) For example, a symbolic link
8832 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8833 should be relative (<file>../share/bar</file>), but a symbolic
8834 link from <file>/var/run</file> to <file>/run</file> should be
8836 This is necessary to allow top-level directories to be
8837 symlinks. If linking <file>/var/run</file>
8838 to <file>/run</file> were done with the relative symbolic
8839 link <file>../run</file>, but <file>/var</file> were a
8840 symbolic link to <file>/srv/disk1</file>, the symbolic link
8841 would point to <file>/srv/run</file> rather than the intended
8847 In addition, symbolic links should be specified as short as
8848 possible, i.e., link targets like <file>foo/../bar</file> are
8853 Note that when creating a relative link using
8854 <prgn>ln</prgn> it is not necessary for the target of the
8855 link to exist relative to the working directory you're
8856 running <prgn>ln</prgn> from, nor is it necessary to change
8857 directory to the directory where the link is to be made.
8858 Simply include the string that should appear as the target
8859 of the link (this will be a pathname relative to the
8860 directory in which the link resides) as the first argument
8865 For example, in your <prgn>Makefile</prgn> or
8866 <file>debian/rules</file>, you can do things like:
8867 <example compact="compact">
8868 ln -fs gcc $(prefix)/bin/cc
8869 ln -fs gcc debian/tmp/usr/bin/cc
8870 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8871 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8876 A symbolic link pointing to a compressed file (in the sense
8877 that it is meant to be uncompressed with <prgn>unzip</prgn>
8878 or <prgn>zless</prgn> etc.) should always
8879 have the same file extension as the referenced file. (For
8880 example, if a file <file>foo.gz</file> is referenced by a
8881 symbolic link, the filename of the link has to end with
8882 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8887 <heading>Device files</heading>
8890 Packages must not include device files or named pipes in the
8895 If a package needs any special device files that are not
8896 included in the base system, it must call
8897 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8898 after notifying the user<footnote>
8899 This notification could be done via a (low-priority)
8900 debconf message, or an echo (printf) statement.
8905 Packages must not remove any device files in the
8906 <prgn>postrm</prgn> or any other script. This is left to the
8907 system administrator.
8911 Debian uses the serial devices
8912 <file>/dev/ttyS*</file>. Programs using the old
8913 <file>/dev/cu*</file> devices should be changed to use
8914 <file>/dev/ttyS*</file>.
8918 Named pipes needed by the package must be created in
8919 the <prgn>postinst</prgn> script<footnote>
8920 It's better to use <prgn>mkfifo</prgn> rather
8921 than <prgn>mknod</prgn> to create named pipes so that
8922 automated checks for packages incorrectly creating device
8923 files with <prgn>mknod</prgn> won't have false positives.
8924 </footnote> and removed in
8925 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8930 <sect id="config-files">
8931 <heading>Configuration files</heading>
8934 <heading>Definitions</heading>
8938 <tag>configuration file</tag>
8940 A file that affects the operation of a program, or
8941 provides site- or host-specific information, or
8942 otherwise customizes the behavior of a program.
8943 Typically, configuration files are intended to be
8944 modified by the system administrator (if needed or
8945 desired) to conform to local policy or to provide
8946 more useful site-specific behavior.
8949 <tag><tt>conffile</tt></tag>
8951 A file listed in a package's <tt>conffiles</tt>
8952 file, and is treated specially by <prgn>dpkg</prgn>
8953 (see <ref id="configdetails">).
8959 The distinction between these two is important; they are
8960 not interchangeable concepts. Almost all
8961 <tt>conffile</tt>s are configuration files, but many
8962 configuration files are not <tt>conffiles</tt>.
8966 As noted elsewhere, <file>/etc/init.d</file> scripts,
8967 <file>/etc/default</file> files, scripts installed in
8968 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8969 configuration installed in <file>/etc/cron.d</file> must be
8970 treated as configuration files. In general, any script that
8971 embeds configuration information is de-facto a configuration
8972 file and should be treated as such.
8977 <heading>Location</heading>
8980 Any configuration files created or used by your package
8981 must reside in <file>/etc</file>. If there are several,
8982 consider creating a subdirectory of <file>/etc</file>
8983 named after your package.
8987 If your package creates or uses configuration files
8988 outside of <file>/etc</file>, and it is not feasible to modify
8989 the package to use <file>/etc</file> directly, put the files
8990 in <file>/etc</file> and create symbolic links to those files
8991 from the location that the package requires.
8996 <heading>Behavior</heading>
8999 Configuration file handling must conform to the following
9001 <list compact="compact">
9003 local changes must be preserved during a package
9007 configuration files must be preserved when the
9008 package is removed, and only deleted when the
9012 Obsolete configuration files without local changes may be
9013 removed by the package during upgrade.
9017 The easy way to achieve this behavior is to make the
9018 configuration file a <tt>conffile</tt>. This is
9019 appropriate only if it is possible to distribute a default
9020 version that will work for most installations, although
9021 some system administrators may choose to modify it. This
9022 implies that the default version will be part of the
9023 package distribution, and must not be modified by the
9024 maintainer scripts during installation (or at any other
9029 In order to ensure that local changes are preserved
9030 correctly, no package may contain or make hard links to
9031 conffiles.<footnote>
9032 Rationale: There are two problems with hard links.
9033 The first is that some editors break the link while
9034 editing one of the files, so that the two files may
9035 unwittingly become unlinked and different. The second
9036 is that <prgn>dpkg</prgn> might break the hard link
9037 while upgrading <tt>conffile</tt>s.
9042 The other way to do it is via the maintainer scripts. In
9043 this case, the configuration file must not be listed as a
9044 <tt>conffile</tt> and must not be part of the package
9045 distribution. If the existence of a file is required for
9046 the package to be sensibly configured it is the
9047 responsibility of the package maintainer to provide
9048 maintainer scripts which correctly create, update and
9049 maintain the file and remove it on purge. (See <ref
9050 id="maintainerscripts"> for more information.) These
9051 scripts must be idempotent (i.e., must work correctly if
9052 <prgn>dpkg</prgn> needs to re-run them due to errors
9053 during installation or removal), must cope with all the
9054 variety of ways <prgn>dpkg</prgn> can call maintainer
9055 scripts, must not overwrite or otherwise mangle the user's
9056 configuration without asking, must not ask unnecessary
9057 questions (particularly during upgrades), and must
9058 otherwise be good citizens.
9062 The scripts are not required to configure every possible
9063 option for the package, but only those necessary to get
9064 the package running on a given system. Ideally the
9065 sysadmin should not have to do any configuration other
9066 than that done (semi-)automatically by the
9067 <prgn>postinst</prgn> script.
9071 A common practice is to create a script called
9072 <file><var>package</var>-configure</file> and have the
9073 package's <prgn>postinst</prgn> call it if and only if the
9074 configuration file does not already exist. In certain
9075 cases it is useful for there to be an example or template
9076 file which the maintainer scripts use. Such files should
9077 be in <file>/usr/share/<var>package</var></file> or
9078 <file>/usr/lib/<var>package</var></file> (depending on whether
9079 they are architecture-independent or not). There should
9080 be symbolic links to them from
9081 <file>/usr/share/doc/<var>package</var>/examples</file> if
9082 they are examples, and should be perfectly ordinary
9083 <prgn>dpkg</prgn>-handled files (<em>not</em>
9084 configuration files).
9088 These two styles of configuration file handling must
9089 not be mixed, for that way lies madness:
9090 <prgn>dpkg</prgn> will ask about overwriting the file
9091 every time the package is upgraded.
9096 <heading>Sharing configuration files</heading>
9099 If two or more packages use the same configuration file
9100 and it is reasonable for both to be installed at the same
9101 time, one of these packages must be defined as
9102 <em>owner</em> of the configuration file, i.e., it will be
9103 the package which handles that file as a configuration
9104 file. Other packages that use the configuration file must
9105 depend on the owning package if they require the
9106 configuration file to operate. If the other package will
9107 use the configuration file if present, but is capable of
9108 operating without it, no dependency need be declared.
9112 If it is desirable for two or more related packages to
9113 share a configuration file <em>and</em> for all of the
9114 related packages to be able to modify that configuration
9115 file, then the following should be done:
9116 <enumlist compact="compact">
9118 One of the related packages (the "owning" package)
9119 will manage the configuration file with maintainer
9120 scripts as described in the previous section.
9123 The owning package should also provide a program
9124 that the other packages may use to modify the
9128 The related packages must use the provided program
9129 to make any desired modifications to the
9130 configuration file. They should either depend on
9131 the core package to guarantee that the configuration
9132 modifier program is available or accept gracefully
9133 that they cannot modify the configuration file if it
9134 is not. (This is in addition to the fact that the
9135 configuration file may not even be present in the
9142 Sometimes it's appropriate to create a new package which
9143 provides the basic infrastructure for the other packages
9144 and which manages the shared configuration files. (The
9145 <tt>sgml-base</tt> package is a good example.)
9149 If the configuration file cannot be shared as described above,
9150 the packages must be marked as conflicting with each other.
9151 Two packages that specify the same file as
9152 a <tt>conffile</tt> must conflict. This is an instance of the
9153 general rule about not sharing files. Neither alternatives
9154 nor diversions are likely to be appropriate in this case; in
9155 particular, <prgn>dpkg</prgn> does not handle diverted
9156 <tt>conffile</tt>s well.
9160 When two packages both declare the same <tt>conffile</tt>, they
9161 may see left-over configuration files from each other even
9162 though they conflict with each other. If a user removes
9163 (without purging) one of the packages and installs the other,
9164 the new package will take over the <tt>conffile</tt> from the
9165 old package. If the file was modified by the user, it will be
9166 treated the same as any other locally
9167 modified <tt>conffile</tt> during an upgrade.
9171 The maintainer scripts must not alter a <tt>conffile</tt>
9172 of <em>any</em> package, including the one the scripts
9178 <heading>User configuration files ("dotfiles")</heading>
9181 The files in <file>/etc/skel</file> will automatically be
9182 copied into new user accounts by <prgn>adduser</prgn>.
9183 No other program should reference the files in
9184 <file>/etc/skel</file>.
9188 Therefore, if a program needs a dotfile to exist in
9189 advance in <file>$HOME</file> to work sensibly, that dotfile
9190 should be installed in <file>/etc/skel</file> and treated as a
9195 However, programs that require dotfiles in order to
9196 operate sensibly are a bad thing, unless they do create
9197 the dotfiles themselves automatically.
9201 Furthermore, programs should be configured by the Debian
9202 default installation to behave as closely to the upstream
9203 default behavior as possible.
9207 Therefore, if a program in a Debian package needs to be
9208 configured in some way in order to operate sensibly, that
9209 should be done using a site-wide configuration file placed
9210 in <file>/etc</file>. Only if the program doesn't support a
9211 site-wide default configuration and the package maintainer
9212 doesn't have time to add it may a default per-user file be
9213 placed in <file>/etc/skel</file>.
9217 <file>/etc/skel</file> should be as empty as we can make it.
9218 This is particularly true because there is no easy (or
9219 necessarily desirable) mechanism for ensuring that the
9220 appropriate dotfiles are copied into the accounts of
9221 existing users when a package is installed.
9227 <heading>Log files</heading>
9229 Log files should usually be named
9230 <file>/var/log/<var>package</var>.log</file>. If you have many
9231 log files, or need a separate directory for permission
9232 reasons (<file>/var/log</file> is writable only by
9233 <file>root</file>), you should usually create a directory named
9234 <file>/var/log/<var>package</var></file> and place your log
9239 Log files must be rotated occasionally so that they don't grow
9240 indefinitely. The best way to do this is to install a log
9241 rotation configuration file in the
9242 directory <file>/etc/logrotate.d</file>, normally
9243 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9244 the facilities provided by <prgn>logrotate</prgn>.
9247 The traditional approach to log files has been to set up
9248 <em>ad hoc</em> log rotation schemes using simple shell
9249 scripts and cron. While this approach is highly
9250 customizable, it requires quite a lot of sysadmin work.
9251 Even though the original Debian system helped a little
9252 by automatically installing a system which can be used
9253 as a template, this was deemed not enough.
9257 The use of <prgn>logrotate</prgn>, a program developed
9258 by Red Hat, is better, as it centralizes log management.
9259 It has both a configuration file
9260 (<file>/etc/logrotate.conf</file>) and a directory where
9261 packages can drop their individual log rotation
9262 configurations (<file>/etc/logrotate.d</file>).
9265 Here is a good example for a logrotate config
9266 file (for more information see <manref name="logrotate"
9268 <example compact="compact">
9269 /var/log/foo/*.log {
9275 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9279 This rotates all files under <file>/var/log/foo</file>, saves 12
9280 compressed generations, and tells the daemon to reopen its log
9281 files after the log rotation. It skips this log rotation
9282 (via <tt>missingok</tt>) if no such log file is present, which
9283 avoids errors if the package is removed but not purged.
9287 Log files should be removed when the package is
9288 purged (but not when it is only removed). This should be
9289 done by the <prgn>postrm</prgn> script when it is called
9290 with the argument <tt>purge</tt> (see <ref
9291 id="removedetails">).
9295 <sect id="permissions-owners">
9296 <heading>Permissions and owners</heading>
9299 The rules in this section are guidelines for general use.
9300 If necessary you may deviate from the details below.
9301 However, if you do so you must make sure that what is done
9302 is secure and you should try to be as consistent as possible
9303 with the rest of the system. You should probably also
9304 discuss it on <prgn>debian-devel</prgn> first.
9308 Files should be owned by <tt>root:root</tt>, and made
9309 writable only by the owner and universally readable (and
9310 executable, if appropriate), that is mode 644 or 755.
9314 Directories should be mode 755 or (for group-writability)
9315 mode 2775. The ownership of the directory should be
9316 consistent with its mode: if a directory is mode 2775, it
9317 should be owned by the group that needs write access to
9320 When a package is upgraded, and the owner or permissions
9321 of a file included in the package has changed, dpkg
9322 arranges for the ownership and permissions to be
9323 correctly set upon installation. However, this does not
9324 extend to directories; the permissions and ownership of
9325 directories already on the system does not change on
9326 install or upgrade of packages. This makes sense, since
9327 otherwise common directories like <tt>/usr</tt> would
9328 always be in flux. To correctly change permissions of a
9329 directory the package owns, explicit action is required,
9330 usually in the <tt>postinst</tt> script. Care must be
9331 taken to handle downgrades as well, in that case.
9337 Control information files should be owned by <tt>root:root</tt>
9338 and either mode 644 (for most files) or mode 755 (for
9339 executables such as <qref id="maintscripts">maintainer
9344 Setuid and setgid executables should be mode 4755 or 2755
9345 respectively, and owned by the appropriate user or group.
9346 They should not be made unreadable (modes like 4711 or
9347 2711 or even 4111); doing so achieves no extra security,
9348 because anyone can find the binary in the freely available
9349 Debian package; it is merely inconvenient. For the same
9350 reason you should not restrict read or execute permissions
9351 on non-set-id executables.
9355 Some setuid programs need to be restricted to particular
9356 sets of users, using file permissions. In this case they
9357 should be owned by the uid to which they are set-id, and by
9358 the group which should be allowed to execute them. They
9359 should have mode 4754; again there is no point in making
9360 them unreadable to those users who must not be allowed to
9365 It is possible to arrange that the system administrator can
9366 reconfigure the package to correspond to their local
9367 security policy by changing the permissions on a binary:
9368 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9369 described below.<footnote>
9370 Ordinary files installed by <prgn>dpkg</prgn> (as
9371 opposed to <tt>conffile</tt>s and other similar objects)
9372 normally have their permissions reset to the distributed
9373 permissions when the package is reinstalled. However,
9374 the use of <prgn>dpkg-statoverride</prgn> overrides this
9377 Another method you should consider is to create a group for
9378 people allowed to use the program(s) and make any setuid
9379 executables executable only by that group.
9383 If you need to create a new user or group for your package
9384 there are two possibilities. Firstly, you may need to
9385 make some files in the binary package be owned by this
9386 user or group, or you may need to compile the user or
9387 group id (rather than just the name) into the binary
9388 (though this latter should be avoided if possible, as in
9389 this case you need a statically allocated id).</p>
9392 If you need a statically allocated id, you must ask for a
9393 user or group id from the <tt>base-passwd</tt> maintainer,
9394 and must not release the package until you have been
9395 allocated one. Once you have been allocated one you must
9396 either make the package depend on a version of the
9397 <tt>base-passwd</tt> package with the id present in
9398 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9399 your package to create the user or group itself with the
9400 correct id (using <tt>adduser</tt>) in its
9401 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9402 the <prgn>postinst</prgn> is to be preferred if it is
9403 possible, otherwise a pre-dependency will be needed on the
9404 <tt>adduser</tt> package.)
9408 On the other hand, the program might be able to determine
9409 the uid or gid from the user or group name at runtime, so
9410 that a dynamically allocated id can be used. In this case
9411 you should choose an appropriate user or group name,
9412 discussing this on <prgn>debian-devel</prgn> and checking
9413 with the <package/base-passwd/ maintainer that it is unique and that
9414 they do not wish you to use a statically allocated id
9415 instead. When this has been checked you must arrange for
9416 your package to create the user or group if necessary using
9417 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9418 <prgn>postinst</prgn> script (again, the latter is to be
9419 preferred if it is possible).
9423 Note that changing the numeric value of an id associated
9424 with a name is very difficult, and involves searching the
9425 file system for all appropriate files. You need to think
9426 carefully whether a static or dynamic id is required, since
9427 changing your mind later will cause problems.
9430 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9432 This section is not intended as policy, but as a
9433 description of the use of <prgn>dpkg-statoverride</prgn>.
9437 If a system administrator wishes to have a file (or
9438 directory or other such thing) installed with owner and
9439 permissions different from those in the distributed Debian
9440 package, they can use the <prgn>dpkg-statoverride</prgn>
9441 program to instruct <prgn>dpkg</prgn> to use the different
9442 settings every time the file is installed. Thus the
9443 package maintainer should distribute the files with their
9444 normal permissions, and leave it for the system
9445 administrator to make any desired changes. For example, a
9446 daemon which is normally required to be setuid root, but
9447 in certain situations could be used without being setuid,
9448 should be installed setuid in the <tt>.deb</tt>. Then the
9449 local system administrator can change this if they wish.
9450 If there are two standard ways of doing it, the package
9451 maintainer can use <tt>debconf</tt> to find out the
9452 preference, and call <prgn>dpkg-statoverride</prgn> in the
9453 maintainer script if necessary to accommodate the system
9454 administrator's choice. Care must be taken during
9455 upgrades to not override an existing setting.
9459 Given the above, <prgn>dpkg-statoverride</prgn> is
9460 essentially a tool for system administrators and would not
9461 normally be needed in the maintainer scripts. There is
9462 one type of situation, though, where calls to
9463 <prgn>dpkg-statoverride</prgn> would be needed in the
9464 maintainer scripts, and that involves packages which use
9465 dynamically allocated user or group ids. In such a
9466 situation, something like the following idiom can be very
9467 helpful in the package's <prgn>postinst</prgn>, where
9468 <tt>sysuser</tt> is a dynamically allocated id:
9470 for i in /usr/bin/foo /usr/sbin/bar
9472 # only do something when no setting exists
9473 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9475 #include: debconf processing, question about foo and bar
9476 if [ "$RET" = "true" ] ; then
9477 dpkg-statoverride --update --add sysuser root 4755 $i
9482 The corresponding code to remove the override when the package
9485 for i in /usr/bin/foo /usr/sbin/bar
9487 if dpkg-statoverride --list $i >/dev/null 2>&1
9489 dpkg-statoverride --remove $i
9497 <sect id="filenames">
9498 <heading>File names</heading>
9501 The name of the files installed by binary packages in the system PATH
9502 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9503 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9508 The name of the files and directories installed by binary packages
9509 outside the system PATH must be encoded in UTF-8 and should be
9510 restricted to ASCII when it is possible to do so.
9516 <chapt id="customized-programs">
9517 <heading>Customized programs</heading>
9519 <sect id="arch-spec">
9520 <heading>Architecture specification strings</heading>
9523 If a program needs to specify an <em>architecture specification
9524 string</em> in some place, it should select one of the strings
9525 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9526 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9527 part is sometimes elided, as when the OS is Linux.
9531 Note that we don't want to use
9532 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9533 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9534 since this would make our programs incompatible with other
9535 Linux distributions. We also don't use something like
9536 <tt><var>arch</var>-unknown-linux</tt>, since the
9537 <tt>unknown</tt> does not look very good.
9540 <sect1 id="arch-wildcard-spec">
9541 <heading>Architecture wildcards</heading>
9544 A package may specify an architecture wildcard. Architecture
9545 wildcards are in the format <tt>any</tt> (which matches every
9546 architecture), <tt><var>os</var></tt>-any, or
9547 any-<tt><var>cpu</var></tt>. <footnote>
9548 Internally, the package system normalizes the GNU triplets
9549 and the Debian arches into Debian arch triplets (which are
9550 kind of inverted GNU triplets), with the first component of
9551 the triplet representing the libc and ABI in use, and then
9552 does matching against those triplets. However, such
9553 triplets are an internal implementation detail that should
9554 not be used by packages directly. The libc and ABI portion
9555 is handled internally by the package system based on
9556 the <var>os</var> and <var>cpu</var>.
9563 <heading>Daemons</heading>
9566 The configuration files <file>/etc/services</file>,
9567 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9568 by the <prgn>netbase</prgn> package and must not be modified
9573 If a package requires a new entry in one of these files, the
9574 maintainer should get in contact with the
9575 <prgn>netbase</prgn> maintainer, who will add the entries
9576 and release a new version of the <prgn>netbase</prgn>
9581 The configuration file <file>/etc/inetd.conf</file> must not be
9582 modified by the package's scripts except via the
9583 <prgn>update-inetd</prgn> script or the
9584 <file>DebianNet.pm</file> Perl module. See their documentation
9585 for details on how to add entries.
9589 If a package wants to install an example entry into
9590 <file>/etc/inetd.conf</file>, the entry must be preceded with
9591 exactly one hash character (<tt>#</tt>). Such lines are
9592 treated as "commented out by user" by the
9593 <prgn>update-inetd</prgn> script and are not changed or
9594 activated during package updates.
9599 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9603 Some programs need to create pseudo-ttys. This should be done
9604 using Unix98 ptys if the C library supports it. The resulting
9605 program must not be installed setuid root, unless that
9606 is required for other functionality.
9610 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9611 <file>/var/log/lastlog</file> must be installed writable by
9612 group <tt>utmp</tt>. Programs which need to modify those
9613 files must be installed setgid <tt>utmp</tt>.
9618 <heading>Editors and pagers</heading>
9621 Some programs have the ability to launch an editor or pager
9622 program to edit or display a text document. Since there are
9623 lots of different editors and pagers available in the Debian
9624 distribution, the system administrator and each user should
9625 have the possibility to choose their preferred editor and
9630 In addition, every program should choose a good default
9631 editor/pager if none is selected by the user or system
9636 Thus, every program that launches an editor or pager must
9637 use the EDITOR or PAGER environment variable to determine
9638 the editor or pager the user wishes to use. If these
9639 variables are not set, the programs <file>/usr/bin/editor</file>
9640 and <file>/usr/bin/pager</file> should be used, respectively.
9644 These two files are managed through the <prgn>dpkg</prgn>
9645 "alternatives" mechanism. Every package providing an editor or
9646 pager must call the <prgn>update-alternatives</prgn> script to
9647 register as an alternative for <file>/usr/bin/editor</file>
9648 or <file>/usr/bin/pager</file> as appropriate. The alternative
9649 should have a slave alternative
9650 for <file>/usr/share/man/man1/editor.1.gz</file>
9651 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9652 corresponding manual page.
9656 If it is very hard to adapt a program to make use of the
9657 EDITOR or PAGER variables, that program may be configured to
9658 use <file>/usr/bin/sensible-editor</file> and
9659 <file>/usr/bin/sensible-pager</file> as the editor or pager
9660 program respectively. These are two scripts provided in the
9661 <package>sensible-utils</package> package that check the EDITOR
9662 and PAGER variables and launch the appropriate program, and fall
9663 back to <file>/usr/bin/editor</file>
9664 and <file>/usr/bin/pager</file> if the variable is not set.
9668 A program may also use the VISUAL environment variable to
9669 determine the user's choice of editor. If it exists, it
9670 should take precedence over EDITOR. This is in fact what
9671 <file>/usr/bin/sensible-editor</file> does.
9675 It is not required for a package to depend on
9676 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9677 package to provide such virtual packages.<footnote>
9678 The Debian base system already provides an editor and a
9684 <sect id="web-appl">
9685 <heading>Web servers and applications</heading>
9688 This section describes the locations and URLs that should
9689 be used by all web servers and web applications in the
9696 Cgi-bin executable files are installed in the
9698 <example compact="compact">
9699 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9701 or a subdirectory of that directory, and should be
9703 <example compact="compact">
9704 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9706 (possibly with a subdirectory name
9707 before <var>cgi-bin-name</var>).
9715 <p>Access to images</p>
9717 It is recommended that images for a package be stored
9718 in <tt>/usr/share/images/<var>package</var></tt> and
9719 may be referred to through an alias <tt>/images/</tt>
9722 http://localhost/images/<package>/<filename>
9729 <p>Web Document Root</p>
9732 Web Applications should try to avoid storing files in
9733 the Web Document Root. Instead they should use the
9734 /usr/share/doc/<var>package</var> directory for
9735 documents and register the Web Application via the
9736 <package>doc-base</package> package. If access to the
9737 web document root is unavoidable then use
9738 <example compact="compact">
9741 as the Document Root. This might be just a symbolic
9742 link to the location where the system administrator
9743 has put the real document root.
9746 <item><p>Providing httpd and/or httpd-cgi</p>
9748 All web servers should provide the virtual package
9749 <tt>httpd</tt>. If a web server has CGI support it should
9750 provide <tt>httpd-cgi</tt> additionally.
9753 All web applications which do not contain CGI scripts should
9754 depend on <tt>httpd</tt>, all those web applications which
9755 <tt>do</tt> contain CGI scripts, should depend on
9763 <sect id="mail-transport-agents">
9764 <heading>Mail transport, delivery and user agents</heading>
9767 Debian packages which process electronic mail, whether mail
9768 user agents (MUAs) or mail transport agents (MTAs), must
9769 ensure that they are compatible with the configuration
9770 decisions below. Failure to do this may result in lost
9771 mail, broken <tt>From:</tt> lines, and other serious brain
9776 The mail spool is <file>/var/mail</file> and the interface to
9777 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9778 the FHS). On older systems, the mail spool may be
9779 physically located in <file>/var/spool/mail</file>, but all
9780 access to the mail spool should be via the
9781 <file>/var/mail</file> symlink. The mail spool is part of the
9782 base system and not part of the MTA package.
9786 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9787 programs (such as IMAP daemons) must lock the mailbox in an
9788 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9789 be combined with dot locking. To avoid deadlocks, a program
9790 should use <tt>fcntl()</tt> first and dot locking after
9791 this, or alternatively implement the two locking methods in
9792 a non blocking way<footnote>
9793 If it is not possible to establish both locks, the
9794 system shouldn't wait for the second lock to be
9795 established, but remove the first lock, wait a (random)
9796 time, and start over locking again.
9797 </footnote>. Using the functions <tt>maillock</tt> and
9798 <tt>mailunlock</tt> provided by the
9799 <tt>liblockfile*</tt><footnote>
9800 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9801 to use these functions.
9802 </footnote> packages is the recommended way to realize this.
9806 Mailboxes are generally either mode 600 and owned by
9807 <var>user</var> or mode 660 and owned by
9808 <tt><var>user</var>:mail</tt><footnote>
9809 There are two traditional permission schemes for mail spools:
9810 mode 600 with all mail delivery done by processes running as
9811 the destination user, or mode 660 and owned by group mail with
9812 mail delivery done by a process running as a system user in
9813 group mail. Historically, Debian required mode 660 mail
9814 spools to enable the latter model, but that model has become
9815 increasingly uncommon and the principle of least privilege
9816 indicates that mail systems that use the first model should
9817 use permissions of 600. If delivery to programs is permitted,
9818 it's easier to keep the mail system secure if the delivery
9819 agent runs as the destination user. Debian Policy therefore
9820 permits either scheme.
9821 </footnote>. The local system administrator may choose a
9822 different permission scheme; packages should not make
9823 assumptions about the permission and ownership of mailboxes
9824 unless required (such as when creating a new mailbox). A MUA
9825 may remove a mailbox (unless it has nonstandard permissions) in
9826 which case the MTA or another MUA must recreate it if needed.
9830 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9831 be setgid mail to do the locking mentioned above (and
9832 must obviously avoid accessing other users' mailboxes
9833 using this privilege).</p>
9836 <file>/etc/aliases</file> is the source file for the system mail
9837 aliases (e.g., postmaster, usenet, etc.), it is the one
9838 which the sysadmin and <prgn>postinst</prgn> scripts may
9839 edit. After <file>/etc/aliases</file> is edited the program or
9840 human editing it must call <prgn>newaliases</prgn>. All MTA
9841 packages must come with a <prgn>newaliases</prgn> program,
9842 even if it does nothing, but older MTA packages did not do
9843 this so programs should not fail if <prgn>newaliases</prgn>
9844 cannot be found. Note that because of this, all MTA
9845 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9846 <tt>Replaces: mail-transport-agent</tt> control fields.
9850 The convention of writing <tt>forward to
9851 <var>address</var></tt> in the mailbox itself is not
9852 supported. Use a <tt>.forward</tt> file instead.</p>
9855 The <prgn>rmail</prgn> program used by UUCP
9856 for incoming mail should be <file>/usr/sbin/rmail</file>.
9857 Likewise, <prgn>rsmtp</prgn>, for receiving
9858 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9862 If your package needs to know what hostname to use on (for
9863 example) outgoing news and mail messages which are generated
9864 locally, you should use the file <file>/etc/mailname</file>. It
9865 will contain the portion after the username and <tt>@</tt>
9866 (at) sign for email addresses of users on the machine
9867 (followed by a newline).
9871 Such a package should check for the existence of this file
9872 when it is being configured. If it exists, it should be
9873 used without comment, although an MTA's configuration script
9874 may wish to prompt the user even if it finds that this file
9875 exists. If the file does not exist, the package should
9876 prompt the user for the value (preferably using
9877 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9878 as well as using it in the package's configuration. The
9879 prompt should make it clear that the name will not just be
9880 used by that package. For example, in this situation the
9881 <tt>inn</tt> package could say something like:
9882 <example compact="compact">
9883 Please enter the "mail name" of your system. This is the
9884 hostname portion of the address to be shown on outgoing
9885 news and mail messages. The default is
9886 <var>syshostname</var>, your system's host name. Mail
9887 name ["<var>syshostname</var>"]:
9889 where <var>syshostname</var> is the output of <tt>hostname
9895 <heading>News system configuration</heading>
9898 All the configuration files related to the NNTP (news)
9899 servers and clients should be located under
9900 <file>/etc/news</file>.</p>
9903 There are some configuration issues that apply to a number
9904 of news clients and server packages on the machine. These
9908 <tag><file>/etc/news/organization</file></tag>
9910 A string which should appear as the
9911 organization header for all messages posted
9912 by NNTP clients on the machine
9915 <tag><file>/etc/news/server</file></tag>
9917 Contains the FQDN of the upstream NNTP
9918 server, or localhost if the local machine is
9923 Other global files may be added as required for cross-package news
9930 <heading>Programs for the X Window System</heading>
9933 <heading>Providing X support and package priorities</heading>
9936 Programs that can be configured with support for the X
9937 Window System must be configured to do so and must declare
9938 any package dependencies necessary to satisfy their
9939 runtime requirements when using the X Window System. If
9940 such a package is of higher priority than the X packages
9941 on which it depends, it is required that either the
9942 X-specific components be split into a separate package, or
9943 that an alternative version of the package, which includes
9944 X support, be provided, or that the package's priority be
9950 <heading>Packages providing an X server</heading>
9953 Packages that provide an X server that, directly or
9954 indirectly, communicates with real input and display
9955 hardware should declare in their <tt>Provides</tt> control
9956 field that they provide the virtual
9957 package <tt>xserver</tt>.<footnote>
9958 This implements current practice, and provides an
9959 actual policy for usage of the <tt>xserver</tt>
9960 virtual package which appears in the virtual packages
9961 list. In a nutshell, X servers that interface
9962 directly with the display and input hardware or via
9963 another subsystem (e.g., GGI) should provide
9964 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9965 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9971 <heading>Packages providing a terminal emulator</heading>
9974 Packages that provide a terminal emulator for the X Window
9975 System which meet the criteria listed below should declare in
9976 their <tt>Provides</tt> control field that they provide the
9977 virtual package <tt>x-terminal-emulator</tt>. They should
9978 also register themselves as an alternative for
9979 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9980 20. That alternative should have a slave alternative
9981 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9982 pointing to the corresponding manual page.
9986 To be an <tt>x-terminal-emulator</tt>, a program must:
9987 <list compact="compact">
9989 Be able to emulate a DEC VT100 terminal, or a
9990 compatible terminal.
9994 Support the command-line option <tt>-e
9995 <var>command</var></tt>, which creates a new
9996 terminal window<footnote>
9997 "New terminal window" does not necessarily mean
9998 a new top-level X window directly parented by
9999 the window manager; it could, if the terminal
10000 emulator application were so coded, be a new
10001 "view" in a multiple-document interface (MDI).
10003 and runs the specified <var>command</var>,
10004 interpreting the entirety of the rest of the command
10005 line as a command to pass straight to exec, in the
10006 manner that <tt>xterm</tt> does.
10010 Support the command-line option <tt>-T
10011 <var>title</var></tt>, which creates a new terminal
10012 window with the window title <var>title</var>.
10019 <heading>Packages providing a window manager</heading>
10022 Packages that provide a window manager should declare in
10023 their <tt>Provides</tt> control field that they provide the
10024 virtual package <tt>x-window-manager</tt>. They should also
10025 register themselves as an alternative for
10026 <file>/usr/bin/x-window-manager</file>, with a priority
10027 calculated as follows:
10028 <list compact="compact">
10030 Start with a priority of 20.
10034 If the window manager supports the Debian menu
10035 system, add 20 points if this support is available
10036 in the package's default configuration (i.e., no
10037 configuration files belonging to the system or user
10038 have to be edited to activate the feature); if
10039 configuration files must be modified, add only 10
10045 If the window manager complies with <url
10046 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10047 name="The Window Manager Specification Project">,
10048 written by the <url id="http://www.freedesktop.org/wiki/"
10049 name="Free Desktop Group">, add 40 points.
10053 If the window manager permits the X session to be
10054 restarted using a <em>different</em> window manager
10055 (without killing the X server) in its default
10056 configuration, add 10 points; otherwise add none.
10059 That alternative should have a slave alternative
10060 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10061 pointing to the corresponding manual page.
10066 <heading>Packages providing fonts</heading>
10069 Packages that provide fonts for the X Window
10071 For the purposes of Debian Policy, a "font for the X
10072 Window System" is one which is accessed via X protocol
10073 requests. Fonts for the Linux console, for PostScript
10074 renderer, or any other purpose, do not fit this
10075 definition. Any tool which makes such fonts available
10076 to the X Window System, however, must abide by this
10079 must do a number of things to ensure that they are both
10080 available without modification of the X or font server
10081 configuration, and that they do not corrupt files used by
10082 other font packages to register information about
10086 Fonts of any type supported by the X Window System
10087 must be in a separate binary package from any
10088 executables, libraries, or documentation (except
10089 that specific to the fonts shipped, such as their
10090 license information). If one or more of the fonts
10091 so packaged are necessary for proper operation of
10092 the package with which they are associated the font
10093 package may be Recommended; if the fonts merely
10094 provide an enhancement, a Suggests relationship may
10095 be used. Packages must not Depend on font
10096 packages.<footnote>
10097 This is because the X server may retrieve fonts
10098 from the local file system or over the network
10099 from an X font server; the Debian package system
10100 is empowered to deal only with the local
10106 BDF fonts must be converted to PCF fonts with the
10107 <prgn>bdftopcf</prgn> utility (available in the
10108 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10109 placed in a directory that corresponds to their
10111 <list compact="compact">
10113 100 dpi fonts must be placed in
10114 <file>/usr/share/fonts/X11/100dpi/</file>.
10118 75 dpi fonts must be placed in
10119 <file>/usr/share/fonts/X11/75dpi/</file>.
10123 Character-cell fonts, cursor fonts, and other
10124 low-resolution fonts must be placed in
10125 <file>/usr/share/fonts/X11/misc/</file>.
10131 Type 1 fonts must be placed in
10132 <file>/usr/share/fonts/X11/Type1/</file>. If font
10133 metric files are available, they must be placed here
10138 Subdirectories of <file>/usr/share/fonts/X11/</file>
10139 other than those listed above must be neither
10140 created nor used. (The <file>PEX</file>, <file>CID</file>,
10141 <file>Speedo</file>, and <file>cyrillic</file> directories
10142 are excepted for historical reasons, but installation of
10143 files into these directories remains discouraged.)
10147 Font packages may, instead of placing files directly
10148 in the X font directories listed above, provide
10149 symbolic links in that font directory pointing to
10150 the files' actual location in the filesystem. Such
10151 a location must comply with the FHS.
10155 Font packages should not contain both 75dpi and
10156 100dpi versions of a font. If both are available,
10157 they should be provided in separate binary packages
10158 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10159 the names of the packages containing the
10160 corresponding fonts.
10164 Fonts destined for the <file>misc</file> subdirectory
10165 should not be included in the same package as 75dpi
10166 or 100dpi fonts; instead, they should be provided in
10167 a separate package with <tt>-misc</tt> appended to
10172 Font packages must not provide the files
10173 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10174 <file>fonts.scale</file> in a font directory:
10177 <file>fonts.dir</file> files must not be provided at all.
10181 <file>fonts.alias</file> and <file>fonts.scale</file>
10182 files, if needed, should be provided in the
10184 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10185 where <var>fontdir</var> is the name of the
10187 <file>/usr/share/fonts/X11/</file> where the
10188 package's corresponding fonts are stored
10189 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10190 <var>package</var> is the name of the package
10191 that provides these fonts, and
10192 <var>extension</var> is either <tt>scale</tt>
10193 or <tt>alias</tt>, whichever corresponds to
10200 Font packages must declare a dependency on
10201 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10202 or <tt>Pre-Depends</tt> control field.
10206 Font packages that provide one or more
10207 <file>fonts.scale</file> files as described above must
10208 invoke <prgn>update-fonts-scale</prgn> on each
10209 directory into which they installed fonts
10210 <em>before</em> invoking
10211 <prgn>update-fonts-dir</prgn> on that directory.
10212 This invocation must occur in both the
10213 <prgn>postinst</prgn> (for all arguments) and
10214 <prgn>postrm</prgn> (for all arguments except
10215 <tt>upgrade</tt>) scripts.
10219 Font packages that provide one or more
10220 <file>fonts.alias</file> files as described above must
10221 invoke <prgn>update-fonts-alias</prgn> on each
10222 directory into which they installed fonts. This
10223 invocation must occur in both the
10224 <prgn>postinst</prgn> (for all arguments) and
10225 <prgn>postrm</prgn> (for all arguments except
10226 <tt>upgrade</tt>) scripts.
10230 Font packages must invoke
10231 <prgn>update-fonts-dir</prgn> on each directory into
10232 which they installed fonts. This invocation must
10233 occur in both the <prgn>postinst</prgn> (for all
10234 arguments) and <prgn>postrm</prgn> (for all
10235 arguments except <tt>upgrade</tt>) scripts.
10239 Font packages must not provide alias names for the
10240 fonts they include which collide with alias names
10241 already in use by fonts already packaged.
10245 Font packages must not provide fonts with the same
10246 XLFD registry name as another font already packaged.
10252 <sect1 id="appdefaults">
10253 <heading>Application defaults files</heading>
10256 Application defaults files must be installed in the
10257 directory <file>/etc/X11/app-defaults/</file> (use of a
10258 localized subdirectory of <file>/etc/X11/</file> as described
10259 in the <em>X Toolkit Intrinsics - C Language
10260 Interface</em> manual is also permitted). They must be
10261 registered as <tt>conffile</tt>s or handled as
10262 configuration files.
10266 Customization of programs' X resources may also be
10267 supported with the provision of a file with the same name
10268 as that of the package placed in
10269 the <file>/etc/X11/Xresources/</file> directory, which
10270 must be registered as a <tt>conffile</tt> or handled as a
10271 configuration file.<footnote>
10272 Note that this mechanism is not the same as using
10273 app-defaults; app-defaults are tied to the client
10274 binary on the local file system, whereas X resources
10275 are stored in the X server and affect all connecting
10282 <heading>Installation directory issues</heading>
10285 Historically, packages using the X Window System used a
10286 separate set of installation directories from other packages.
10287 This practice has been discontinued and packages using the X
10288 Window System should now generally be installed in the same
10289 directories as any other package. Specifically, packages must
10290 not install files under the <file>/usr/X11R6/</file> directory
10291 and the <file>/usr/X11R6/</file> directory hierarchy should be
10292 regarded as obsolete.
10296 Include files previously installed under
10297 <file>/usr/X11R6/include/X11/</file> should be installed into
10298 <file>/usr/include/X11/</file>. For files previously
10299 installed into subdirectories of
10300 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10301 determine if subdirectories of <file>/usr/lib/</file> and
10302 <file>/usr/share/</file> can be used. If not, a subdirectory
10303 of <file>/usr/lib/X11/</file> should be used.
10307 Configuration files for window, display, or session managers
10308 or other applications that are tightly integrated with the X
10309 Window System may be placed in a subdirectory
10310 of <file>/etc/X11/</file> corresponding to the package name.
10311 Other X Window System applications should use
10312 the <file>/etc/</file> directory unless otherwise mandated by
10313 policy (such as for <ref id="appdefaults">).
10319 <heading>Perl programs and modules</heading>
10322 Perl programs and modules should follow the current Perl policy.
10326 The Perl policy can be found in the <tt>perl-policy</tt>
10327 files in the <tt>debian-policy</tt> package.
10328 It is also available from the Debian web mirrors at
10329 <tt><url name="/doc/packaging-manuals/perl-policy/"
10330 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10335 <heading>Emacs lisp programs</heading>
10338 Please refer to the "Debian Emacs Policy" for details of how to
10339 package emacs lisp programs.
10343 The Emacs policy is available in
10344 <file>debian-emacs-policy.gz</file> of the
10345 <package>emacsen-common</package> package.
10346 It is also available from the Debian web mirrors at
10347 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10348 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10353 <heading>Games</heading>
10356 The permissions on <file>/var/games</file> are mode 755, owner
10357 <tt>root</tt> and group <tt>root</tt>.
10361 Each game decides on its own security policy.</p>
10364 Games which require protected, privileged access to
10365 high-score files, saved games, etc., may be made
10366 set-<em>group</em>-id (mode 2755) and owned by
10367 <tt>root:games</tt>, and use files and directories with
10368 appropriate permissions (770 <tt>root:games</tt>, for
10369 example). They must not be made
10370 set-<em>user</em>-id, as this causes security problems. (If
10371 an attacker can subvert any set-user-id game they can
10372 overwrite the executable of any other, causing other players
10373 of these games to run a Trojan horse program. With a
10374 set-group-id game the attacker only gets access to less
10375 important game data, and if they can get at the other
10376 players' accounts at all it will take considerably more
10380 Some packages, for example some fortune cookie programs, are
10381 configured by the upstream authors to install with their
10382 data files or other static information made unreadable so
10383 that they can only be accessed through set-id programs
10384 provided. You should not do this in a Debian package: anyone can
10385 download the <file>.deb</file> file and read the data from it,
10386 so there is no point making the files unreadable. Not
10387 making the files unreadable also means that you don't have
10388 to make so many programs set-id, which reduces the risk of a
10392 As described in the FHS, binaries of games should be
10393 installed in the directory <file>/usr/games</file>. This also
10394 applies to games that use the X Window System. Manual pages
10395 for games (X and non-X games) should be installed in
10396 <file>/usr/share/man/man6</file>.</p>
10402 <heading>Documentation</heading>
10405 <heading>Manual pages</heading>
10408 You should install manual pages in <prgn>nroff</prgn> source
10409 form, in appropriate places under <file>/usr/share/man</file>.
10410 You should only use sections 1 to 9 (see the FHS for more
10411 details). You must not install a pre-formatted "cat page".
10415 Each program, utility, and function should have an
10416 associated manual page included in the same package. It is
10417 suggested that all configuration files also have a manual
10418 page included as well. Manual pages for protocols and other
10419 auxiliary things are optional.
10423 If no manual page is available, this is considered as a bug
10424 and should be reported to the Debian Bug Tracking System (the
10425 maintainer of the package is allowed to write this bug report
10426 themselves, if they so desire). Do not close the bug report
10427 until a proper man page is available.<footnote>
10428 It is not very hard to write a man page. See the
10429 <url id="http://www.schweikhardt.net/man_page_howto.html"
10430 name="Man-Page-HOWTO">,
10431 <manref name="man" section="7">, the examples created
10432 by <prgn>dh_make</prgn>, the helper
10433 program <prgn>help2man</prgn>, or the
10434 directory <file>/usr/share/doc/man-db/examples</file>.
10439 You may forward a complaint about a missing man page to the
10440 upstream authors, and mark the bug as forwarded in the
10441 Debian bug tracking system. Even though the GNU Project do
10442 not in general consider the lack of a man page to be a bug,
10443 we do; if they tell you that they don't consider it a bug
10444 you should leave the bug in our bug tracking system open
10449 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10453 If one man page needs to be accessible via several names it
10454 is better to use a symbolic link than the <file>.so</file>
10455 feature, but there is no need to fiddle with the relevant
10456 parts of the upstream source to change from <file>.so</file> to
10457 symlinks: don't do it unless it's easy. You should not
10458 create hard links in the manual page directories, nor put
10459 absolute filenames in <file>.so</file> directives. The filename
10460 in a <file>.so</file> in a man page should be relative to the
10461 base of the man page tree (usually
10462 <file>/usr/share/man</file>). If you do not create any links
10463 (whether symlinks, hard links, or <tt>.so</tt> directives)
10464 in the file system to the alternate names of the man page,
10465 then you should not rely on <prgn>man</prgn> finding your
10466 man page under those names based solely on the information in
10467 the man page's header.<footnote>
10468 Supporting this in <prgn>man</prgn> often requires
10469 unreasonable processing time to find a manual page or to
10470 report that none exists, and moves knowledge into man's
10471 database that would be better left in the file system.
10472 This support is therefore deprecated and will cease to
10473 be present in the future.
10478 Manual pages in locale-specific subdirectories of
10479 <file>/usr/share/man</file> should use either UTF-8 or the usual
10480 legacy encoding for that language (normally the one corresponding
10481 to the shortest relevant locale name in
10482 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10483 <file>/usr/share/man/fr</file> should use either UTF-8 or
10484 ISO-8859-1.<footnote>
10485 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10486 use. In future, all manual pages will be required to use
10492 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10493 included in the subdirectory name unless it indicates a
10494 significant difference in the language, as this excludes
10495 speakers of the language in other countries.<footnote>
10496 At the time of writing, Chinese and Portuguese are the main
10497 languages with such differences, so <file>pt_BR</file>,
10498 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10503 If a localized version of a manual page is provided, it should
10504 either be up-to-date or it should be obvious to the reader that
10505 it is outdated and the original manual page should be used
10506 instead. This can be done either by a note at the beginning of
10507 the manual page or by showing the missing or changed portions in
10508 the original language instead of the target language.
10513 <heading>Info documents</heading>
10516 Info documents should be installed in <file>/usr/share/info</file>.
10517 They should be compressed with <tt>gzip -9</tt>.
10521 The <prgn>install-info</prgn> program maintains a directory of
10522 installed info documents in <file>/usr/share/info/dir</file> for the
10523 use of info readers. This file must not be included in packages
10524 other than <package>install-info</package>.
10528 <prgn>install-info</prgn> is automatically invoked when
10529 appropriate using dpkg triggers. Packages other than
10530 <package>install-info</package> <em>should not</em> invoke
10531 <prgn>install-info</prgn> directly and <em>should not</em>
10532 depend on, recommend, or suggest <package>install-info</package>
10537 Info readers requiring the <file>/usr/share/info/dir</file> file
10538 should depend on <package>install-info</package>.
10542 Info documents should contain section and directory entry
10543 information in the document for the use
10544 of <prgn>install-info</prgn>. The section should be specified
10545 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10546 space and the section of this info page. The directory entry or
10547 entries should be included between
10548 a <tt>START-INFO-DIR-ENTRY</tt> line and
10549 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10551 INFO-DIR-SECTION Individual utilities
10552 START-INFO-DIR-ENTRY
10553 * example: (example). An example info directory entry.
10556 To determine which section to use, you should look
10557 at <file>/usr/share/info/dir</file> on your system and choose
10558 the most relevant (or create a new section if none of the
10559 current sections are relevant).<footnote>
10560 Normally, info documents are generated from Texinfo source.
10561 To include this information in the generated info document, if
10562 it is absent, add commands like:
10564 @dircategory Individual utilities
10566 * example: (example). An example info directory entry.
10569 to the Texinfo source of the document and ensure that the info
10570 documents are rebuilt from source during the package build.
10576 <heading>Additional documentation</heading>
10579 Any additional documentation that comes with the package may
10580 be installed at the discretion of the package maintainer.
10581 Plain text documentation should be installed in the directory
10582 <file>/usr/share/doc/<var>package</var></file>, where
10583 <var>package</var> is the name of the package, and
10584 compressed with <tt>gzip -9</tt> unless it is small.
10588 If a package comes with large amounts of documentation which
10589 many users of the package will not require you should create
10590 a separate binary package to contain it, so that it does not
10591 take up disk space on the machines of users who do not need
10592 or want it installed.</p>
10595 It is often a good idea to put text information files
10596 (<file>README</file>s, changelogs, and so forth) that come with
10597 the source package in <file>/usr/share/doc/<var>package</var></file>
10598 in the binary package. However, you don't need to install
10599 the instructions for building and installing the package, of
10603 Packages must not require the existence of any files in
10604 <file>/usr/share/doc/</file> in order to function
10606 The system administrator should be able to
10607 delete files in <file>/usr/share/doc/</file> without causing
10608 any programs to break.
10610 Any files that are referenced by programs but are also
10611 useful as stand alone documentation should be installed under
10612 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10613 <file>/usr/share/doc/<var>package</var></file>.
10617 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10618 link to another directory in <file>/usr/share/doc</file> only if
10619 the two packages both come from the same source and the
10620 first package Depends on the second.<footnote>
10622 Please note that this does not override the section on
10623 changelog files below, so the file
10624 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10625 must refer to the changelog for the current version of
10626 <var>package</var> in question. In practice, this means
10627 that the sources of the target and the destination of the
10628 symlink must be the same (same source package and
10635 Former Debian releases placed all additional documentation
10636 in <file>/usr/doc/<var>package</var></file>. This has been
10637 changed to <file>/usr/share/doc/<var>package</var></file>,
10638 and packages must not put documentation in the directory
10639 <file>/usr/doc/<var>package</var></file>. <footnote>
10640 At this phase of the transition, we no longer require a
10641 symbolic link in <file>/usr/doc/</file>. At a later point,
10642 policy shall change to make the symbolic links a bug.
10648 <heading>Preferred documentation formats</heading>
10651 The unification of Debian documentation is being carried out
10655 If your package comes with extensive documentation in a
10656 markup format that can be converted to various other formats
10657 you should if possible ship HTML versions in a binary
10658 package, in the directory
10659 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10660 its subdirectories.<footnote>
10661 The rationale: The important thing here is that HTML
10662 docs should be available in <em>some</em> package, not
10663 necessarily in the main binary package.
10668 Other formats such as PostScript may be provided at the
10669 package maintainer's discretion.
10673 <sect id="copyrightfile">
10674 <heading>Copyright information</heading>
10677 Every package must be accompanied by a verbatim copy of its
10678 copyright information and distribution license in the file
10679 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10680 file must neither be compressed nor be a symbolic link.
10684 In addition, the copyright file must say where the upstream
10685 sources (if any) were obtained, and should name the original
10690 Packages in the <em>contrib</em> or <em>non-free</em> archive
10691 areas should state in the copyright file that the package is not
10692 part of the Debian distribution and briefly explain why.
10696 A copy of the file which will be installed in
10697 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10698 be in <file>debian/copyright</file> in the source package.
10702 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10703 link to another directory in <file>/usr/share/doc</file> only if
10704 the two packages both come from the same source and the
10705 first package Depends on the second. These rules are important
10706 because <file>copyright</file> files must be extractable by
10711 Packages distributed under the Apache license (version 2.0), the
10712 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10713 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10714 1.3) should refer to the corresponding files
10715 under <file>/usr/share/common-licenses</file>,<footnote>
10718 <file>/usr/share/common-licenses/Apache-2.0</file>,
10719 <file>/usr/share/common-licenses/Artistic</file>,
10720 <file>/usr/share/common-licenses/GPL-1</file>,
10721 <file>/usr/share/common-licenses/GPL-2</file>,
10722 <file>/usr/share/common-licenses/GPL-3</file>,
10723 <file>/usr/share/common-licenses/LGPL-2</file>,
10724 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10725 <file>/usr/share/common-licenses/LGPL-3</file>,
10726 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10727 <file>/usr/share/common-licenses/GFDL-1.3</file>
10728 respectively. The University of California BSD license is
10729 also included in <package>base-files</package> as
10730 <file>/usr/share/common-licenses/BSD</file>, but given the
10731 brevity of this license, its specificity to code whose
10732 copyright is held by the Regents of the University of
10733 California, and the frequency of minor wording changes, its
10734 text should be included in the copyright file rather than
10735 referencing this file.
10737 </footnote> rather than quoting them in the copyright
10742 You should not use the copyright file as a general <file>README</file>
10743 file. If your package has such a file it should be
10744 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10745 <file>README.Debian</file> or some other appropriate place.
10749 All copyright files must be encoded in UTF-8.
10752 <sect1 id="copyrightformat">
10753 <heading>Machine-readable copyright information</heading>
10756 A specification for a standard, machine-readable format
10757 for <file>debian/copyright</file> files is maintained as part
10758 of the <package>debian-policy</package> package. This
10759 document may be found in the <file>copyright-format</file>
10760 files in the <package>debian-policy</package> package. It is
10761 also available from the Debian web mirrors at
10762 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10763 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10767 Use of this format is optional.
10773 <heading>Examples</heading>
10776 Any examples (configurations, source files, whatever),
10777 should be installed in a directory
10778 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10779 files should not be referenced by any program: they're there
10780 for the benefit of the system administrator and users as
10781 documentation only. Architecture-specific example files
10782 should be installed in a directory
10783 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10785 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10786 latter directory itself may be a symbolic link to the
10791 If the purpose of a package is to provide examples, then the
10792 example files may be installed into
10793 <file>/usr/share/doc/<var>package</var></file>.
10797 <sect id="changelogs">
10798 <heading>Changelog files</heading>
10801 Packages that are not Debian-native must contain a
10802 compressed copy of the <file>debian/changelog</file> file from
10803 the Debian source tree in
10804 <file>/usr/share/doc/<var>package</var></file> with the name
10805 <file>changelog.Debian.gz</file>.
10809 If an upstream changelog is available, it should be accessible as
10810 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10811 plain text. If the upstream changelog is distributed in
10812 HTML, it should be made available in that form as
10813 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10814 and a plain text <file>changelog.gz</file> should be generated
10815 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10816 the upstream changelog files do not already conform to this
10817 naming convention, then this may be achieved either by
10818 renaming the files, or by adding a symbolic link, at the
10819 maintainer's discretion.<footnote>
10820 Rationale: People should not have to look in places for
10821 upstream changelogs merely because they are given
10822 different names or are distributed in HTML format.
10827 All of these files should be installed compressed using
10828 <tt>gzip -9</tt>, as they will become large with time even
10829 if they start out small.
10833 If the package has only one changelog which is used both as
10834 the Debian changelog and the upstream one because there is
10835 no separate upstream maintainer then that changelog should
10836 usually be installed as
10837 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10838 there is a separate upstream maintainer, but no upstream
10839 changelog, then the Debian changelog should still be called
10840 <file>changelog.Debian.gz</file>.
10844 For details about the format and contents of the Debian
10845 changelog file, please see <ref id="dpkgchangelog">.
10850 <appendix id="pkg-scope">
10851 <heading>Introduction and scope of these appendices</heading>
10854 These appendices are taken essentially verbatim from the
10855 now-deprecated Packaging Manual, version 3.2.1.0. They are
10856 the chapters which are likely to be of use to package
10857 maintainers and which have not already been included in the
10858 policy document itself. Most of these sections are very likely
10859 not relevant to policy; they should be treated as
10860 documentation for the packaging system. Please note that these
10861 appendices are included for convenience, and for historical
10862 reasons: they used to be part of policy package, and they have
10863 not yet been incorporated into dpkg documentation. However,
10864 they still have value, and hence they are presented here.
10868 They have not yet been checked to ensure that they are
10869 compatible with the contents of policy, and if there are any
10870 contradictions, the version in the main policy document takes
10871 precedence. The remaining chapters of the old Packaging
10872 Manual have also not been read in detail to ensure that there
10873 are not parts which have been left out. Both of these will be
10874 done in due course.
10878 Certain parts of the Packaging manual were integrated into the
10879 Policy Manual proper, and removed from the appendices. Links
10880 have been placed from the old locations to the new ones.
10884 <prgn>dpkg</prgn> is a suite of programs for creating binary
10885 package files and installing and removing them on Unix
10887 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10888 work on or be ported to other systems.
10893 The binary packages are designed for the management of
10894 installed executable programs (usually compiled binaries) and
10895 their associated data, though source code examples and
10896 documentation are provided as part of some packages.</p>
10899 This manual describes the technical aspects of creating Debian
10900 binary packages (<file>.deb</file> files). It documents the
10901 behavior of the package management programs
10902 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10903 they interact with packages.</p>
10906 This manual does not go into detail about the options and
10907 usage of the package building and installation tools. It
10908 should therefore be read in conjunction with those programs'
10913 The utility programs which are provided with <prgn>dpkg</prgn>
10914 not described in detail here, are documented in their man pages.
10918 It is assumed that the reader is reasonably familiar with the
10919 <prgn>dpkg</prgn> System Administrators' manual.
10920 Unfortunately this manual does not yet exist.
10924 The Debian version of the FSF's GNU hello program is provided as
10925 an example for people wishing to create Debian packages. However,
10926 while the examples are helpful, they do not replace the need to
10927 read and follow the Policy and Programmer's Manual.</p>
10930 <appendix id="pkg-binarypkg">
10931 <heading>Binary packages (from old Packaging Manual)</heading>
10934 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10937 <sect id="pkg-bincreating"><heading>Creating package files -
10938 <prgn>dpkg-deb</prgn>
10942 All manipulation of binary package files is done by
10943 <prgn>dpkg-deb</prgn>; it's the only program that has
10944 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10945 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10946 will spot that the options requested are appropriate to
10947 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10952 In order to create a binary package you must make a
10953 directory tree which contains all the files and directories
10954 you want to have in the file system data part of the package.
10955 In Debian-format source packages this directory is usually
10956 <file>debian/tmp</file>, relative to the top of the package's
10961 They should have the locations (relative to the root of the
10962 directory tree you're constructing) ownerships and
10963 permissions which you want them to have on the system when
10964 they are installed.
10968 With current versions of <prgn>dpkg</prgn> the uid/username
10969 and gid/groupname mappings for the users and groups being
10970 used should be the same on the system where the package is
10971 built and the one where it is installed.
10975 You need to add one special directory to the root of the
10976 miniature file system tree you're creating:
10977 <prgn>DEBIAN</prgn>. It should contain the control
10978 information files, notably the binary package control file
10979 (see <ref id="pkg-controlfile">).
10983 The <prgn>DEBIAN</prgn> directory will not appear in the
10984 file system archive of the package, and so won't be installed
10985 by <prgn>dpkg</prgn> when the package is unpacked.
10989 When you've prepared the package, you should invoke:
10991 dpkg --build <var>directory</var>
10996 This will build the package in
10997 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10998 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10999 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11000 build the package.)
11004 See the man page <manref name="dpkg-deb" section="8"> for details of how
11005 to examine the contents of this newly-created file. You may find the
11006 output of following commands enlightening:
11008 dpkg-deb --info <var>filename</var>.deb
11009 dpkg-deb --contents <var>filename</var>.deb
11010 dpkg --contents <var>filename</var>.deb
11012 To view the copyright file for a package you could use this command:
11014 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11019 <sect id="pkg-controlarea">
11020 <heading>Package control information files</heading>
11023 The control information portion of a binary package is a
11024 collection of files with names known to <prgn>dpkg</prgn>.
11025 It will treat the contents of these files specially - some
11026 of them contain information used by <prgn>dpkg</prgn> when
11027 installing or removing the package; others are scripts which
11028 the package maintainer wants <prgn>dpkg</prgn> to run.
11032 It is possible to put other files in the package control
11033 information file area, but this is not generally a good idea
11034 (though they will largely be ignored).
11038 Here is a brief list of the control information files supported
11039 by <prgn>dpkg</prgn> and a summary of what they're used for.
11044 <tag><tt>control</tt>
11047 This is the key description file used by
11048 <prgn>dpkg</prgn>. It specifies the package's name
11049 and version, gives its description for the user,
11050 states its relationships with other packages, and so
11051 forth. See <ref id="sourcecontrolfiles"> and
11052 <ref id="binarycontrolfiles">.
11056 It is usually generated automatically from information
11057 in the source package by the
11058 <prgn>dpkg-gencontrol</prgn> program, and with
11059 assistance from <prgn>dpkg-shlibdeps</prgn>.
11060 See <ref id="pkg-sourcetools">.
11064 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11069 These are executable files (usually scripts) which
11070 <prgn>dpkg</prgn> runs during installation, upgrade
11071 and removal of packages. They allow the package to
11072 deal with matters which are particular to that package
11073 or require more complicated processing than that
11074 provided by <prgn>dpkg</prgn>. Details of when and
11075 how they are called are in <ref id="maintainerscripts">.
11079 It is very important to make these scripts idempotent.
11080 See <ref id="idempotency">.
11084 The maintainer scripts are not guaranteed to run with a
11085 controlling terminal and may not be able to interact with
11086 the user. See <ref id="controllingterminal">.
11090 <tag><tt>conffiles</tt>
11093 This file contains a list of configuration files which
11094 are to be handled automatically by <prgn>dpkg</prgn>
11095 (see <ref id="pkg-conffiles">). Note that not necessarily
11096 every configuration file should be listed here.
11099 <tag><tt>shlibs</tt>
11102 This file contains a list of the shared libraries
11103 supplied by the package, with dependency details for
11104 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11105 when it determines what dependencies are required in a
11106 package control file. The <tt>shlibs</tt> file format
11107 is described on <ref id="shlibs">.
11112 <sect id="pkg-controlfile">
11113 <heading>The main control information file: <tt>control</tt></heading>
11116 The most important control information file used by
11117 <prgn>dpkg</prgn> when it installs a package is
11118 <tt>control</tt>. It contains all the package's "vital
11123 The binary package control files of packages built from
11124 Debian sources are made by a special tool,
11125 <prgn>dpkg-gencontrol</prgn>, which reads
11126 <file>debian/control</file> and <file>debian/changelog</file> to
11127 find the information it needs. See <ref id="pkg-sourcepkg"> for
11132 The fields in binary package control files are listed in
11133 <ref id="binarycontrolfiles">.
11137 A description of the syntax of control files and the purpose
11138 of the fields is available in <ref id="controlfields">.
11143 <heading>Time Stamps</heading>
11146 See <ref id="timestamps">.
11151 <appendix id="pkg-sourcepkg">
11152 <heading>Source packages (from old Packaging Manual) </heading>
11155 The Debian binary packages in the distribution are generated
11156 from Debian sources, which are in a special format to assist
11157 the easy and automatic building of binaries.
11160 <sect id="pkg-sourcetools">
11161 <heading>Tools for processing source packages</heading>
11164 Various tools are provided for manipulating source packages;
11165 they pack and unpack sources and help build of binary
11166 packages and help manage the distribution of new versions.
11170 They are introduced and typical uses described here; see
11171 <manref name="dpkg-source" section="1"> for full
11172 documentation about their arguments and operation.
11176 For examples of how to construct a Debian source package,
11177 and how to use those utilities that are used by Debian
11178 source packages, please see the <prgn>hello</prgn> example
11182 <sect1 id="pkg-dpkg-source">
11184 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11189 This program is frequently used by hand, and is also
11190 called from package-independent automated building scripts
11191 such as <prgn>dpkg-buildpackage</prgn>.
11195 To unpack a package it is typically invoked with
11197 dpkg-source -x <var>.../path/to/filename</var>.dsc
11202 with the <file><var>filename</var>.tar.gz</file> and
11203 <file><var>filename</var>.diff.gz</file> (if applicable) in
11204 the same directory. It unpacks into
11205 <file><var>package</var>-<var>version</var></file>, and if
11207 <file><var>package</var>-<var>version</var>.orig</file>, in
11208 the current directory.
11212 To create a packed source archive it is typically invoked:
11214 dpkg-source -b <var>package</var>-<var>version</var>
11219 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11220 <file>.diff.gz</file> (if appropriate) in the current
11221 directory. <prgn>dpkg-source</prgn> does not clean the
11222 source tree first - this must be done separately if it is
11227 See also <ref id="pkg-sourcearchives">.</p>
11231 <sect1 id="pkg-dpkg-buildpackage">
11233 <prgn>dpkg-buildpackage</prgn> - overall package-building
11238 See <manref name="dpkg-buildpackage" section="1">.
11242 <sect1 id="pkg-dpkg-gencontrol">
11244 <prgn>dpkg-gencontrol</prgn> - generates binary package
11249 This program is usually called from <file>debian/rules</file>
11250 (see <ref id="pkg-sourcetree">) in the top level of the source
11255 This is usually done just before the files and directories in the
11256 temporary directory tree where the package is being built have their
11257 permissions and ownerships set and the package is constructed using
11258 <prgn>dpkg-deb/</prgn>
11260 This is so that the control file which is produced has
11261 the right permissions
11266 <prgn>dpkg-gencontrol</prgn> must be called after all the
11267 files which are to go into the package have been placed in
11268 the temporary build directory, so that its calculation of
11269 the installed size of a package is correct.
11273 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11274 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11275 variable substitutions created by
11276 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11281 For a package which generates only one binary package, and
11282 which builds it in <file>debian/tmp</file> relative to the top
11283 of the source package, it is usually sufficient to call
11284 <prgn>dpkg-gencontrol</prgn>.
11288 Sources which build several binaries will typically need
11291 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11292 </example> The <tt>-P</tt> tells
11293 <prgn>dpkg-gencontrol</prgn> that the package is being
11294 built in a non-default directory, and the <tt>-p</tt>
11295 tells it which package's control file should be generated.
11299 <prgn>dpkg-gencontrol</prgn> also adds information to the
11300 list of files in <file>debian/files</file>, for the benefit of
11301 (for example) a future invocation of
11302 <prgn>dpkg-genchanges</prgn>.</p>
11305 <sect1 id="pkg-dpkg-shlibdeps">
11307 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11312 See <manref name="dpkg-shlibdeps" section="1">.
11316 <sect1 id="pkg-dpkg-distaddfile">
11318 <prgn>dpkg-distaddfile</prgn> - adds a file to
11319 <file>debian/files</file>
11323 Some packages' uploads need to include files other than
11324 the source and binary package files.
11328 <prgn>dpkg-distaddfile</prgn> adds a file to the
11329 <file>debian/files</file> file so that it will be included in
11330 the <file>.changes</file> file when
11331 <prgn>dpkg-genchanges</prgn> is run.
11335 It is usually invoked from the <tt>binary</tt> target of
11336 <file>debian/rules</file>:
11338 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11340 The <var>filename</var> is relative to the directory where
11341 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11342 is usually the directory above the top level of the source
11343 tree. The <file>debian/rules</file> target should put the
11344 file there just before or just after calling
11345 <prgn>dpkg-distaddfile</prgn>.
11349 The <var>section</var> and <var>priority</var> are passed
11350 unchanged into the resulting <file>.changes</file> file.
11355 <sect1 id="pkg-dpkg-genchanges">
11357 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11358 upload control file
11362 See <manref name="dpkg-genchanges" section="1">.
11366 <sect1 id="pkg-dpkg-parsechangelog">
11368 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11369 representation of a changelog
11373 See <manref name="dpkg-parsechangelog" section="1">.
11377 <sect1 id="pkg-dpkg-architecture">
11379 <prgn>dpkg-architecture</prgn> - information about the build and
11384 See <manref name="dpkg-architecture" section="1">.
11389 <sect id="pkg-sourcetree">
11390 <heading>The Debian package source tree</heading>
11393 The source archive scheme described later is intended to
11394 allow a Debian package source tree with some associated
11395 control information to be reproduced and transported easily.
11396 The Debian package source tree is a version of the original
11397 program with certain files added for the benefit of the
11398 packaging process, and with any other changes required
11399 made to the rest of the source code and installation
11404 The extra files created for Debian are in the subdirectory
11405 <file>debian</file> of the top level of the Debian package
11406 source tree. They are described below.
11409 <sect1 id="pkg-debianrules">
11410 <heading><file>debian/rules</file> - the main building script</heading>
11413 See <ref id="debianrules">.
11417 <sect1 id="pkg-srcsubstvars">
11418 <heading><file>debian/substvars</file> and variable substitutions</heading>
11421 See <ref id="substvars">.
11427 <heading><file>debian/files</file></heading>
11430 See <ref id="debianfiles">.
11434 <sect1><heading><file>debian/tmp</file>
11438 This is the canonical temporary location for the
11439 construction of binary packages by the <tt>binary</tt>
11440 target. The directory <file>tmp</file> serves as the root of
11441 the file system tree as it is being constructed (for
11442 example, by using the package's upstream makefiles install
11443 targets and redirecting the output there), and it also
11444 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11445 id="pkg-bincreating">.
11449 If several binary packages are generated from the same
11450 source tree it is usual to use several
11451 <file>debian/tmp<var>something</var></file> directories, for
11452 example <file>tmp-a</file> or <file>tmp-doc</file>.
11456 Whatever <file>tmp</file> directories are created and used by
11457 <tt>binary</tt> must of course be removed by the
11458 <tt>clean</tt> target.</p></sect1>
11462 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11466 As it exists on the FTP site, a Debian source package
11467 consists of three related files. You must have the right
11468 versions of all three to be able to use them.
11473 <tag>Debian source control file - <tt>.dsc</tt></tag>
11475 This file is a control file used by <prgn>dpkg-source</prgn>
11476 to extract a source package.
11477 See <ref id="debiansourcecontrolfiles">.
11481 Original source archive -
11483 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11489 This is a compressed (with <tt>gzip -9</tt>)
11490 <prgn>tar</prgn> file containing the source code from
11491 the upstream authors of the program.
11496 Debian package diff -
11498 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11504 This is a unified context diff (<tt>diff -u</tt>)
11505 giving the changes which are required to turn the
11506 original source into the Debian source. These changes
11507 may only include editing and creating plain files.
11508 The permissions of files, the targets of symbolic
11509 links and the characteristics of special files or
11510 pipes may not be changed and no files may be removed
11515 All the directories in the diff must exist, except the
11516 <file>debian</file> subdirectory of the top of the source
11517 tree, which will be created by
11518 <prgn>dpkg-source</prgn> if necessary when unpacking.
11522 The <prgn>dpkg-source</prgn> program will
11523 automatically make the <file>debian/rules</file> file
11524 executable (see below).</p></item>
11529 If there is no original source code - for example, if the
11530 package is specially prepared for Debian or the Debian
11531 maintainer is the same as the upstream maintainer - the
11532 format is slightly different: then there is no diff, and the
11534 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11535 and preferably contains a directory named
11536 <file><var>package</var>-<var>version</var></file>.
11541 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11544 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11545 Debian source package. However, if it is not available it
11546 is possible to unpack a Debian source archive as follows:
11547 <enumlist compact="compact">
11550 Untar the tarfile, which will create a <file>.orig</file>
11554 <p>Rename the <file>.orig</file> directory to
11555 <file><var>package</var>-<var>version</var></file>.</p>
11559 Create the subdirectory <file>debian</file> at the top of
11560 the source tree.</p>
11562 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11564 <item><p>Untar the tarfile again if you want a copy of the original
11565 source code alongside the Debian version.</p>
11570 It is not possible to generate a valid Debian source archive
11571 without using <prgn>dpkg-source</prgn>. In particular,
11572 attempting to use <prgn>diff</prgn> directly to generate the
11573 <file>.diff.gz</file> file will not work.
11577 <heading>Restrictions on objects in source packages</heading>
11580 The source package may not contain any hard links
11582 This is not currently detected when building source
11583 packages, but only when extracting
11587 Hard links may be permitted at some point in the
11588 future, but would require a fair amount of
11590 </footnote>, device special files, sockets or setuid or
11593 Setgid directories are allowed.
11598 The source packaging tools manage the changes between the
11599 original and Debian source using <prgn>diff</prgn> and
11600 <prgn>patch</prgn>. Turning the original source tree as
11601 included in the <file>.orig.tar.gz</file> into the Debian
11602 package source must not involve any changes which cannot be
11603 handled by these tools. Problematic changes which cause
11604 <prgn>dpkg-source</prgn> to halt with an error when
11605 building the source package are:
11606 <list compact="compact">
11607 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11609 <item><p>Changing the targets of symbolic links.</p>
11611 <item><p>Creating directories, other than <file>debian</file>.</p>
11613 <item><p>Changes to the contents of binary files.</p></item>
11614 </list> Changes which cause <prgn>dpkg-source</prgn> to
11615 print a warning but continue anyway are:
11616 <list compact="compact">
11619 Removing files, directories or symlinks.
11621 Renaming a file is not treated specially - it is
11622 seen as the removal of the old file (which
11623 generates a warning, but is otherwise ignored),
11624 and the creation of the new one.
11630 Changed text files which are missing the usual final
11631 newline (either in the original or the modified
11636 Changes which are not represented, but which are not detected by
11637 <prgn>dpkg-source</prgn>, are:
11638 <list compact="compact">
11639 <item><p>Changing the permissions of files (other than
11640 <file>debian/rules</file>) and directories.</p></item>
11645 The <file>debian</file> directory and <file>debian/rules</file>
11646 are handled specially by <prgn>dpkg-source</prgn> - before
11647 applying the changes it will create the <file>debian</file>
11648 directory, and afterwards it will make
11649 <file>debian/rules</file> world-executable.
11655 <appendix id="pkg-controlfields">
11656 <heading>Control files and their fields (from old Packaging Manual)</heading>
11659 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11660 data in a common format, known as control files. Binary and
11661 source packages have control data as do the <file>.changes</file>
11662 files which control the installation of uploaded files, and
11663 <prgn>dpkg</prgn>'s internal databases are in a similar
11668 <heading>Syntax of control files</heading>
11671 See <ref id="controlsyntax">.
11675 It is important to note that there are several fields which
11676 are optional as far as <prgn>dpkg</prgn> and the related
11677 tools are concerned, but which must appear in every Debian
11678 package, or whose omission may cause problems.
11683 <heading>List of fields</heading>
11686 See <ref id="controlfieldslist">.
11690 This section now contains only the fields that didn't belong
11691 to the Policy manual.
11694 <sect1 id="pkg-f-Filename">
11695 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11698 These fields in <tt>Packages</tt> files give the
11699 filename(s) of (the parts of) a package in the
11700 distribution directories, relative to the root of the
11701 Debian hierarchy. If the package has been split into
11702 several parts the parts are all listed in order, separated
11707 <sect1 id="pkg-f-Size">
11708 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11711 These fields in <file>Packages</file> files give the size (in
11712 bytes, expressed in decimal) and MD5 checksum of the
11713 file(s) which make(s) up a binary package in the
11714 distribution. If the package is split into several parts
11715 the values for the parts are listed in order, separated by
11720 <sect1 id="pkg-f-Status">
11721 <heading><tt>Status</tt></heading>
11724 This field in <prgn>dpkg</prgn>'s status file records
11725 whether the user wants a package installed, removed or
11726 left alone, whether it is broken (requiring
11727 re-installation) or not and what its current state on the
11728 system is. Each of these pieces of information is a
11733 <sect1 id="pkg-f-Config-Version">
11734 <heading><tt>Config-Version</tt></heading>
11737 If a package is not installed or not configured, this
11738 field in <prgn>dpkg</prgn>'s status file records the last
11739 version of the package which was successfully
11744 <sect1 id="pkg-f-Conffiles">
11745 <heading><tt>Conffiles</tt></heading>
11748 This field in <prgn>dpkg</prgn>'s status file contains
11749 information about the automatically-managed configuration
11750 files held by a package. This field should <em>not</em>
11751 appear anywhere in a package!
11756 <heading>Obsolete fields</heading>
11759 These are still recognized by <prgn>dpkg</prgn> but should
11760 not appear anywhere any more.
11762 <taglist compact="compact">
11764 <tag><tt>Revision</tt></tag>
11765 <tag><tt>Package-Revision</tt></tag>
11766 <tag><tt>Package_Revision</tt></tag>
11768 The Debian revision part of the package version was
11769 at one point in a separate control field. This
11770 field went through several names.
11773 <tag><tt>Recommended</tt></tag>
11774 <item>Old name for <tt>Recommends</tt>.</item>
11776 <tag><tt>Optional</tt></tag>
11777 <item>Old name for <tt>Suggests</tt>.</item>
11779 <tag><tt>Class</tt></tag>
11780 <item>Old name for <tt>Priority</tt>.</item>
11789 <appendix id="pkg-conffiles">
11790 <heading>Configuration file handling (from old Packaging Manual)</heading>
11793 <prgn>dpkg</prgn> can do a certain amount of automatic
11794 handling of package configuration files.
11798 Whether this mechanism is appropriate depends on a number of
11799 factors, but basically there are two approaches to any
11800 particular configuration file.
11804 The easy method is to ship a best-effort configuration in the
11805 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11806 handle updates. If the user is unlikely to want to edit the
11807 file, but you need them to be able to without losing their
11808 changes, and a new package with a changed version of the file
11809 is only released infrequently, this is a good approach.
11813 The hard method is to build the configuration file from
11814 scratch in the <prgn>postinst</prgn> script, and to take the
11815 responsibility for fixing any mistakes made in earlier
11816 versions of the package automatically. This will be
11817 appropriate if the file is likely to need to be different on
11821 <sect><heading>Automatic handling of configuration files by
11826 A package may contain a control information file called
11827 <tt>conffiles</tt>. This file should be a list of filenames
11828 of configuration files needing automatic handling, separated
11829 by newlines. The filenames should be absolute pathnames,
11830 and the files referred to should actually exist in the
11835 When a package is upgraded <prgn>dpkg</prgn> will process
11836 the configuration files during the configuration stage,
11837 shortly before it runs the package's <prgn>postinst</prgn>
11842 For each file it checks to see whether the version of the
11843 file included in the package is the same as the one that was
11844 included in the last version of the package (the one that is
11845 being upgraded from); it also compares the version currently
11846 installed on the system with the one shipped with the last
11851 If neither the user nor the package maintainer has changed
11852 the file, it is left alone. If one or the other has changed
11853 their version, then the changed version is preferred - i.e.,
11854 if the user edits their file, but the package maintainer
11855 doesn't ship a different version, the user's changes will
11856 stay, silently, but if the maintainer ships a new version
11857 and the user hasn't edited it the new version will be
11858 installed (with an informative message). If both have
11859 changed their version the user is prompted about the problem
11860 and must resolve the differences themselves.
11864 The comparisons are done by calculating the MD5 message
11865 digests of the files, and storing the MD5 of the file as it
11866 was included in the most recent version of the package.
11870 When a package is installed for the first time
11871 <prgn>dpkg</prgn> will install the file that comes with it,
11872 unless that would mean overwriting a file already on the
11877 However, note that <prgn>dpkg</prgn> will <em>not</em>
11878 replace a conffile that was removed by the user (or by a
11879 script). This is necessary because with some programs a
11880 missing file produces an effect hard or impossible to
11881 achieve in another way, so that a missing file needs to be
11882 kept that way if the user did it.
11886 Note that a package should <em>not</em> modify a
11887 <prgn>dpkg</prgn>-handled conffile in its maintainer
11888 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11889 the user confusing and possibly dangerous options for
11890 conffile update when the package is upgraded.</p>
11893 <sect><heading>Fully-featured maintainer script configuration
11898 For files which contain site-specific information such as
11899 the hostname and networking details and so forth, it is
11900 better to create the file in the package's
11901 <prgn>postinst</prgn> script.
11905 This will typically involve examining the state of the rest
11906 of the system to determine values and other information, and
11907 may involve prompting the user for some information which
11908 can't be obtained some other way.
11912 When using this method there are a couple of important
11913 issues which should be considered:
11917 If you discover a bug in the program which generates the
11918 configuration file, or if the format of the file changes
11919 from one version to the next, you will have to arrange for
11920 the postinst script to do something sensible - usually this
11921 will mean editing the installed configuration file to remove
11922 the problem or change the syntax. You will have to do this
11923 very carefully, since the user may have changed the file,
11924 perhaps to fix the very problem that your script is trying
11925 to deal with - you will have to detect these situations and
11926 deal with them correctly.
11930 If you do go down this route it's probably a good idea to
11931 make the program that generates the configuration file(s) a
11932 separate program in <file>/usr/sbin</file>, by convention called
11933 <file><var>package</var>config</file> and then run that if
11934 appropriate from the post-installation script. The
11935 <tt><var>package</var>config</tt> program should not
11936 unquestioningly overwrite an existing configuration - if its
11937 mode of operation is geared towards setting up a package for
11938 the first time (rather than any arbitrary reconfiguration
11939 later) you should have it check whether the configuration
11940 already exists, and require a <tt>--force</tt> flag to
11941 overwrite it.</p></sect>
11944 <appendix id="pkg-alternatives"><heading>Alternative versions of
11945 an interface - <prgn>update-alternatives</prgn> (from old
11950 When several packages all provide different versions of the
11951 same program or file it is useful to have the system select a
11952 default, but to allow the system administrator to change it
11953 and have their decisions respected.
11957 For example, there are several versions of the <prgn>vi</prgn>
11958 editor, and there is no reason to prevent all of them from
11959 being installed at once, each under their own name
11960 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11961 Nevertheless it is desirable to have the name <tt>vi</tt>
11962 refer to something, at least by default.
11966 If all the packages involved cooperate, this can be done with
11967 <prgn>update-alternatives</prgn>.
11971 Each package provides its own version under its own name, and
11972 calls <prgn>update-alternatives</prgn> in its postinst to
11973 register its version (and again in its prerm to deregister
11978 See the man page <manref name="update-alternatives"
11979 section="8"> for details.
11983 If <prgn>update-alternatives</prgn> does not seem appropriate
11984 you may wish to consider using diversions instead.</p>
11987 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11988 package's version of a file (from old Packaging Manual)
11992 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11993 when it reinstalls the package it belongs to, and to have it
11994 put the file from the package somewhere else instead.
11998 This can be used locally to override a package's version of a
11999 file, or by one package to override another's version (or
12000 provide a wrapper for it).
12004 Before deciding to use a diversion, read <ref
12005 id="pkg-alternatives"> to see if you really want a diversion
12006 rather than several alternative versions of a program.
12010 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12011 and updated by a special program <prgn>dpkg-divert</prgn>.
12012 Please see <manref name="dpkg-divert" section="8"> for full
12013 details of its operation.
12017 When a package wishes to divert a file from another, it should
12018 call <prgn>dpkg-divert</prgn> in its preinst to add the
12019 diversion and rename the existing file. For example,
12020 supposing that a <prgn>smailwrapper</prgn> package wishes to
12021 install a wrapper around <file>/usr/sbin/smail</file>:
12023 dpkg-divert --package smailwrapper --add --rename \
12024 --divert /usr/sbin/smail.real /usr/sbin/smail
12025 </example> The <tt>--package smailwrapper</tt> ensures that
12026 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12027 can bypass the diversion and get installed as the true version.
12028 It's safe to add the diversion unconditionally on upgrades since
12029 it will be left unchanged if it already exists, but
12030 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12031 message, make the command conditional on the version from which
12032 the package is being upgraded:
12034 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12035 dpkg-divert --package smailwrapper --add --rename \
12036 --divert /usr/sbin/smail.real /usr/sbin/smail
12038 </example> where <tt>1.0-2</tt> is the version at which the
12039 diversion was first added to the package. Running the command
12040 during abort-upgrade is pointless but harmless.
12044 The postrm has to do the reverse:
12046 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12047 dpkg-divert --package smailwrapper --remove --rename \
12048 --divert /usr/sbin/smail.real /usr/sbin/smail
12050 </example> If the diversion was added at a particular version, the
12051 postrm should also handle the failure case of upgrading from an
12052 older version (unless the older version is so old that direct
12053 upgrades are no longer supported):
12055 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12056 dpkg-divert --package smailwrapper --remove --rename \
12057 --divert /usr/sbin/smail.real /usr/sbin/smail
12059 </example> where <tt>1.0-2</tt> is the version at which the
12060 diversion was first added to the package. The postrm should not
12061 remove the diversion on upgrades both because there's no reason to
12062 remove the diversion only to immediately re-add it and since the
12063 postrm of the old package is run after unpacking so the removal of
12064 the diversion will fail.
12068 Do not attempt to divert a file which is vitally important for
12069 the system's operation - when using <prgn>dpkg-divert</prgn>
12070 there is a time, after it has been diverted but before
12071 <prgn>dpkg</prgn> has installed the new version, when the file
12072 does not exist.</p>
12075 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12082 <!-- Local variables: -->
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