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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 Debian QA
2371 tools to help with quality control and maintenance of the
2372 distribution as a whole.
2377 <sect id="debianfiles">
2378 <heading>Generated files list: <file>debian/files</file></heading>
2381 This file is not a permanent part of the source tree; it
2382 is used while building packages to record which files are
2383 being generated. <prgn>dpkg-genchanges</prgn> uses it
2384 when it generates a <file>.changes</file> file.
2388 It should not exist in a shipped source package, and so it
2389 (and any backup files or temporary files such as
2390 <file>files.new</file><footnote>
2391 <file>files.new</file> is used as a temporary file by
2392 <prgn>dpkg-gencontrol</prgn> and
2393 <prgn>dpkg-distaddfile</prgn> - they write a new
2394 version of <tt>files</tt> here before renaming it,
2395 to avoid leaving a corrupted copy if an error
2397 </footnote>) should be removed by the
2398 <tt>clean</tt> target. It may also be wise to
2399 ensure a fresh start by emptying or removing it at the
2400 start of the <tt>binary</tt> target.
2404 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2405 package, it adds an entry to <file>debian/files</file> for the
2406 <file>.deb</file> file that will be created when <tt>dpkg-deb
2407 --build</tt> is run for that binary package. So for most
2408 packages all that needs to be done with this file is to
2409 delete it in the <tt>clean</tt> target.
2413 If a package upload includes files besides the source
2414 package and any binary packages whose control files were
2415 made with <prgn>dpkg-gencontrol</prgn> then they should be
2416 placed in the parent of the package's top-level directory
2417 and <prgn>dpkg-distaddfile</prgn> should be called to add
2418 the file to the list in <file>debian/files</file>.</p>
2421 <sect id="embeddedfiles">
2422 <heading>Convenience copies of code</heading>
2425 Some software packages include in their distribution convenience
2426 copies of code from other software packages, generally so that
2427 users compiling from source don't have to download multiple
2428 packages. Debian packages should not make use of these
2429 convenience copies unless the included package is explicitly
2430 intended to be used in this way.<footnote>
2431 For example, parts of the GNU build system work like this.
2433 If the included code is already in the Debian archive in the
2434 form of a library, the Debian packaging should ensure that
2435 binary packages reference the libraries already in Debian and
2436 the convenience copy is not used. If the included code is not
2437 already in Debian, it should be packaged separately as a
2438 prerequisite if possible.
2440 Having multiple copies of the same code in Debian is
2441 inefficient, often creates either static linking or shared
2442 library conflicts, and, most importantly, increases the
2443 difficulty of handling security vulnerabilities in the
2449 <sect id="readmesource">
2450 <heading>Source package handling:
2451 <file>debian/README.source</file></heading>
2454 If running <prgn>dpkg-source -x</prgn> on a source package
2455 doesn't produce the source of the package, ready for editing,
2456 and allow one to make changes and run
2457 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2458 without taking any additional steps, creating a
2459 <file>debian/README.source</file> documentation file is
2460 recommended. This file should explain how to do all of the
2463 <item>Generate the fully patched source, in a form ready for
2464 editing, that would be built to create Debian
2465 packages. Doing this with a <tt>patch</tt> target in
2466 <file>debian/rules</file> is recommended; see
2467 <ref id="debianrules">.</item>
2468 <item>Modify the source and save those modifications so that
2469 they will be applied when building the package.</item>
2470 <item>Remove source modifications that are currently being
2471 applied when building the package.</item>
2472 <item>Optionally, document what steps are necessary to
2473 upgrade the Debian source package to a new upstream version,
2474 if applicable.</item>
2476 This explanation should include specific commands and mention
2477 any additional required Debian packages. It should not assume
2478 familiarity with any specific Debian packaging system or patch
2483 This explanation may refer to a documentation file installed by
2484 one of the package's build dependencies provided that the
2485 referenced documentation clearly explains these tasks and is not
2486 a general reference manual.
2490 <file>debian/README.source</file> may also include any other
2491 information that would be helpful to someone modifying the
2492 source package. Even if the package doesn't fit the above
2493 description, maintainers are encouraged to document in a
2494 <file>debian/README.source</file> file any source package with a
2495 particularly complex or unintuitive source layout or build
2496 system (for example, a package that builds the same source
2497 multiple times to generate different binary packages).
2503 <chapt id="controlfields">
2504 <heading>Control files and their fields</heading>
2507 The package management system manipulates data represented in
2508 a common format, known as <em>control data</em>, stored in
2509 <em>control files</em>.
2510 Control files are used for source packages, binary packages and
2511 the <file>.changes</file> files which control the installation
2512 of uploaded files<footnote>
2513 <prgn>dpkg</prgn>'s internal databases are in a similar
2518 <sect id="controlsyntax">
2519 <heading>Syntax of control files</heading>
2522 A control file consists of one or more paragraphs of
2524 The paragraphs are also sometimes referred to as stanzas.
2526 The paragraphs are separated by empty lines. Parsers may accept
2527 lines consisting solely of spaces and tabs as paragraph
2528 separators, but control files should use empty lines. Some control
2529 files allow only one paragraph; others allow several, in
2530 which case each paragraph usually refers to a different
2531 package. (For example, in source packages, the first
2532 paragraph refers to the source package, and later paragraphs
2533 refer to binary packages generated from the source.) The
2534 ordering of the paragraphs in control files is significant.
2538 Each paragraph consists of a series of data fields. Each field
2539 consists of the field name followed by a colon and then the
2540 data/value associated with that field. The field name is
2541 composed of US-ASCII characters excluding control characters,
2542 space, and colon (i.e., characters in the ranges 33-57 and
2543 59-126, inclusive). Field names must not begin with the comment
2544 character, <tt>#</tt>, nor with the hyphen character, <tt>-</tt>.
2548 The field ends at the end of the line or at the end of the last
2549 continuation line (see below). Horizontal whitespace (spaces
2550 and tabs) may occur immediately before or after the value and is
2551 ignored there; it is conventional to put a single space after
2552 the colon. For example, a field might be:
2553 <example compact="compact">
2556 the field name is <tt>Package</tt> and the field value
2561 A paragraph must not contain more than one instance of a
2562 particular field name.
2566 There are three types of fields:
2570 The field, including its value, must be a single line. Folding
2571 of the field is not permitted. This is the default field type
2572 if the definition of the field does not specify a different
2577 The value of a folded field is a logical line that may span
2578 several lines. The lines after the first are called
2579 continuation lines and must start with a space or a tab.
2580 Whitespace, including any newlines, is not significant in the
2581 field values of folded fields.<footnote>
2582 This folding method is similar to RFC 5322, allowing control
2583 files that contain only one paragraph and no multiline fields
2584 to be read by parsers written for RFC 5322.
2587 <tag>multiline</tag>
2589 The value of a multiline field may comprise multiple continuation
2590 lines. The first line of the value, the part on the same line as
2591 the field name, often has special significance or may have to be
2592 empty. Other lines are added following the same syntax as the
2593 continuation lines of the folded fields. Whitespace, including newlines,
2594 is significant in the values of multiline fields.
2600 Whitespace must not appear
2601 inside names (of packages, architectures, files or anything
2602 else) or version numbers, or between the characters of
2603 multi-character version relationships.
2607 The presence and purpose of a field, and the syntax of its
2608 value may differ between types of control files.
2612 Field names are not case-sensitive, but it is usual to
2613 capitalize the field names using mixed case as shown below.
2614 Field values are case-sensitive unless the description of the
2615 field says otherwise.
2619 Paragraph separators (empty lines) and lines consisting only of
2620 spaces and tabs are not allowed within field values or between
2621 fields. Empty lines in field values are usually escaped by
2622 representing them by a space followed by a dot.
2626 Lines starting with # without any preceding whitespace are comments
2627 lines that are only permitted in source package control files
2628 (<file>debian/control</file>). These comment lines are ignored, even
2629 between two continuation lines. They do not end logical lines.
2633 All control files must be encoded in UTF-8.
2637 <sect id="sourcecontrolfiles">
2638 <heading>Source package control files -- <file>debian/control</file></heading>
2641 The <file>debian/control</file> file contains the most vital
2642 (and version-independent) information about the source package
2643 and about the binary packages it creates.
2647 The first paragraph of the control file contains information about
2648 the source package in general. The subsequent sets each describe a
2649 binary package that the source tree builds.
2653 The fields in the general paragraph (the first one, for the source
2656 <list compact="compact">
2657 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2660 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2661 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2662 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2663 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2664 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2665 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2670 The fields in the binary package paragraphs are:
2672 <list compact="compact">
2673 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2674 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2675 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2676 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2677 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2678 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2679 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2680 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2681 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2682 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2687 The syntax and semantics of the fields are described below.
2691 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2692 generate control files for binary packages (see below), by
2693 <prgn>dpkg-genchanges</prgn> to generate the
2694 <file>.changes</file> file to accompany the upload, and by
2695 <prgn>dpkg-source</prgn> when it creates the
2696 <file>.dsc</file> source control file as part of a source
2697 archive. Some fields are folded in <file>debian/control</file>,
2698 but not in any other control
2699 file. These tools are responsible for removing the line
2700 breaks from such fields when using fields from
2701 <file>debian/control</file> to generate other control files.
2705 The fields here may contain variable references - their
2706 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2707 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2708 when they generate output control files.
2709 See <ref id="substvars"> for details.
2713 <sect id="binarycontrolfiles">
2714 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2717 The <file>DEBIAN/control</file> file contains the most vital
2718 (and version-dependent) information about a binary package. It
2719 consists of a single paragraph.
2723 The fields in this file are:
2725 <list compact="compact">
2726 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2728 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2730 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2731 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2732 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2733 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2734 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2735 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2736 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2738 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2743 <sect id="debiansourcecontrolfiles">
2744 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2747 This file consists of a single paragraph, possibly surrounded by
2748 a PGP signature. The fields of that paragraph are listed below.
2749 Their syntax is described above, in <ref id="controlsyntax">.
2751 <list compact="compact">
2752 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2753 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2754 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2755 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2756 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2757 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2759 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2760 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2761 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2762 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2763 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2764 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2765 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2766 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2772 The Debian source control file is generated by
2773 <prgn>dpkg-source</prgn> when it builds the source
2774 archive, from other files in the source package,
2775 described above. When unpacking, it is checked against
2776 the files and directories in the other parts of the
2782 <sect id="debianchangesfiles">
2783 <heading>Debian changes files -- <file>.changes</file></heading>
2786 The <file>.changes</file> files are used by the Debian archive
2787 maintenance software to process updates to packages. They
2788 consist of a single paragraph, possibly surrounded by a PGP
2789 signature. That paragraph contains information from the
2790 <file>debian/control</file> file and other data about the
2791 source package gathered via <file>debian/changelog</file>
2792 and <file>debian/rules</file>.
2796 <file>.changes</file> files have a format version that is
2797 incremented whenever the documented fields or their meaning
2798 change. This document describes format &changesversion;.
2802 The fields in this file are:
2804 <list compact="compact">
2805 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2806 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2807 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2813 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2815 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2817 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2819 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2825 <sect id="controlfieldslist">
2826 <heading>List of fields</heading>
2828 <sect1 id="f-Source">
2829 <heading><tt>Source</tt></heading>
2832 This field identifies the source package name.
2836 In <file>debian/control</file> or a <file>.dsc</file> file,
2837 this field must contain only the name of the source package.
2841 In a binary package control file or a <file>.changes</file>
2842 file, the source package name may be followed by a version
2843 number in parentheses<footnote>
2844 It is customary to leave a space after the package name
2845 if a version number is specified.
2847 This version number may be omitted (and is, by
2848 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2849 the <tt>Version</tt> field of the binary package in
2850 question. The field itself may be omitted from a binary
2851 package control file when the source package has the same
2852 name and version as the binary package.
2856 Package names (both source and binary,
2857 see <ref id="f-Package">) must consist only of lower case
2858 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2859 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2860 (<tt>.</tt>). They must be at least two characters long and
2861 must start with an alphanumeric character.
2865 <sect1 id="f-Maintainer">
2866 <heading><tt>Maintainer</tt></heading>
2869 The package maintainer's name and email address. The name
2870 must come first, then the email address inside angle
2871 brackets <tt><></tt> (in RFC822 format).
2875 If the maintainer's name contains a full stop then the
2876 whole field will not work directly as an email address due
2877 to a misfeature in the syntax specified in RFC822; a
2878 program using this field as an address must check for this
2879 and correct the problem if necessary (for example by
2880 putting the name in round brackets and moving it to the
2881 end, and bringing the email address forward).
2885 See <ref id="maintainer"> for additional requirements and
2886 information about package maintainers.
2890 <sect1 id="f-Uploaders">
2891 <heading><tt>Uploaders</tt></heading>
2894 List of the names and email addresses of co-maintainers of the
2895 package, if any. If the package has other maintainers besides
2896 the one named in the <qref id="f-Maintainer">Maintainer
2897 field</qref>, their names and email addresses should be listed
2898 here. The format of each entry is the same as that of the
2899 Maintainer field, and multiple entries must be comma
2904 This is normally an optional field, but if
2905 the <tt>Maintainer</tt> control field names a group of people
2906 and a shared email address, the <tt>Uploaders</tt> field must
2907 be present and must contain at least one human with their
2908 personal email address.
2912 The Uploaders field in <file>debian/control</file> can be folded.
2916 <sect1 id="f-Changed-By">
2917 <heading><tt>Changed-By</tt></heading>
2920 The name and email address of the person who prepared this
2921 version of the package, usually a maintainer. The syntax is
2922 the same as for the <qref id="f-Maintainer">Maintainer
2927 <sect1 id="f-Section">
2928 <heading><tt>Section</tt></heading>
2931 This field specifies an application area into which the package
2932 has been classified. See <ref id="subsections">.
2936 When it appears in the <file>debian/control</file> file,
2937 it gives the value for the subfield of the same name in
2938 the <tt>Files</tt> field of the <file>.changes</file> file.
2939 It also gives the default for the same field in the binary
2944 <sect1 id="f-Priority">
2945 <heading><tt>Priority</tt></heading>
2948 This field represents how important it is that the user
2949 have the package installed. See <ref id="priorities">.
2953 When it appears in the <file>debian/control</file> file,
2954 it gives the value for the subfield of the same name in
2955 the <tt>Files</tt> field of the <file>.changes</file> file.
2956 It also gives the default for the same field in the binary
2961 <sect1 id="f-Package">
2962 <heading><tt>Package</tt></heading>
2965 The name of the binary package.
2969 Binary package names must follow the same syntax and
2970 restrictions as source package names. See <ref id="f-Source">
2975 <sect1 id="f-Architecture">
2976 <heading><tt>Architecture</tt></heading>
2979 Depending on context and the control file used, the
2980 <tt>Architecture</tt> field can include the following sets of
2984 A unique single word identifying a Debian machine
2985 architecture as described in <ref id="arch-spec">.
2988 An architecture wildcard identifying a set of Debian
2989 machine architectures, see <ref id="arch-wildcard-spec">.
2990 <tt>any</tt> matches all Debian machine architectures
2991 and is the most frequently used.
2994 <tt>all</tt>, which indicates an
2995 architecture-independent package.
2998 <tt>source</tt>, which indicates a source package.
3004 In the main <file>debian/control</file> file in the source
3005 package, this field may contain the special
3006 value <tt>all</tt>, the special architecture
3007 wildcard <tt>any</tt>, or a list of specific and wildcard
3008 architectures separated by spaces. If <tt>all</tt>
3009 or <tt>any</tt> appears, that value must be the entire
3010 contents of the field. Most packages will use
3011 either <tt>all</tt> or <tt>any</tt>.
3015 Specifying a specific list of architectures indicates that the
3016 source will build an architecture-dependent package only on
3017 architectures included in the list. Specifying a list of
3018 architecture wildcards indicates that the source will build an
3019 architecture-dependent package on only those architectures
3020 that match any of the specified architecture wildcards.
3021 Specifying a list of architectures or architecture wildcards
3022 other than <tt>any</tt> is for the minority of cases where a
3023 program is not portable or is not useful on some
3024 architectures. Where possible, the program should be made
3029 In the Debian source control file <file>.dsc</file>, this
3030 field contains a list of architectures and architecture
3031 wildcards separated by spaces. When the list contains the
3032 architecture wildcard <tt>any</tt>, the only other value
3033 allowed in the list is <tt>all</tt>.
3037 The list may include (or consist solely of) the special
3038 value <tt>all</tt>. In other words, in <file>.dsc</file>
3039 files unlike the <file>debian/control</file>, <tt>all</tt> may
3040 occur in combination with specific architectures.
3041 The <tt>Architecture</tt> field in the Debian source control
3042 file <file>.dsc</file> is generally constructed from
3043 the <tt>Architecture</tt> fields in
3044 the <file>debian/control</file> in the source package.
3048 Specifying only <tt>any</tt> indicates that the source package
3049 isn't dependent on any particular architecture and should
3050 compile fine on any one. The produced binary package(s)
3051 will be specific to whatever the current build architecture is.
3055 Specifying only <tt>all</tt> indicates that the source package
3056 will only build architecture-independent packages.
3060 Specifying <tt>any all</tt> indicates that the source package
3061 isn't dependent on any particular architecture. The set of
3062 produced binary packages will include at least one
3063 architecture-dependant package and one architecture-independent
3068 Specifying a list of architectures or architecture wildcards
3069 indicates that the source will build an architecture-dependent
3070 package, and will only work correctly on the listed or
3071 matching architectures. If the source package also builds at
3072 least one architecture-independent package, <tt>all</tt> will
3073 also be included in the list.
3077 In a <file>.changes</file> file, the <tt>Architecture</tt>
3078 field lists the architecture(s) of the package(s) currently
3079 being uploaded. This will be a list; if the source for the
3080 package is also being uploaded, the special
3081 entry <tt>source</tt> is also present. <tt>all</tt> will be
3082 present if any architecture-independent packages are being
3083 uploaded. Architecture wildcards such as <tt>any</tt> must
3084 never occur in the <tt>Architecture</tt> field in
3085 the <file>.changes</file> file.
3089 See <ref id="debianrules"> for information on how to get
3090 the architecture for the build process.
3094 <sect1 id="f-Essential">
3095 <heading><tt>Essential</tt></heading>
3098 This is a boolean field which may occur only in the
3099 control file of a binary package or in a per-package fields
3100 paragraph of a source package control file.
3104 If set to <tt>yes</tt> then the package management system
3105 will refuse to remove the package (upgrading and replacing
3106 it is still possible). The other possible value is <tt>no</tt>,
3107 which is the same as not having the field at all.
3112 <heading>Package interrelationship fields:
3113 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3114 <tt>Recommends</tt>, <tt>Suggests</tt>,
3115 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3116 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3120 These fields describe the package's relationships with
3121 other packages. Their syntax and semantics are described
3122 in <ref id="relationships">.</p>
3125 <sect1 id="f-Standards-Version">
3126 <heading><tt>Standards-Version</tt></heading>
3129 The most recent version of the standards (the policy
3130 manual and associated texts) with which the package
3135 The version number has four components: major and minor
3136 version number and major and minor patch level. When the
3137 standards change in a way that requires every package to
3138 change the major number will be changed. Significant
3139 changes that will require work in many packages will be
3140 signaled by a change to the minor number. The major patch
3141 level will be changed for any change to the meaning of the
3142 standards, however small; the minor patch level will be
3143 changed when only cosmetic, typographical or other edits
3144 are made which neither change the meaning of the document
3145 nor affect the contents of packages.
3149 Thus only the first three components of the policy version
3150 are significant in the <em>Standards-Version</em> control
3151 field, and so either these three components or all four
3152 components may be specified.<footnote>
3153 In the past, people specified the full version number
3154 in the Standards-Version field, for example "2.3.0.0".
3155 Since minor patch-level changes don't introduce new
3156 policy, it was thought it would be better to relax
3157 policy and only require the first 3 components to be
3158 specified, in this example "2.3.0". All four
3159 components may still be used if someone wishes to do so.
3165 <sect1 id="f-Version">
3166 <heading><tt>Version</tt></heading>
3169 The version number of a package. The format is:
3170 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3174 The three components here are:
3176 <tag><var>epoch</var></tag>
3179 This is a single (generally small) unsigned integer. It
3180 may be omitted, in which case zero is assumed. If it is
3181 omitted then the <var>upstream_version</var> may not
3186 It is provided to allow mistakes in the version numbers
3187 of older versions of a package, and also a package's
3188 previous version numbering schemes, to be left behind.
3192 <tag><var>upstream_version</var></tag>
3195 This is the main part of the version number. It is
3196 usually the version number of the original ("upstream")
3197 package from which the <file>.deb</file> file has been made,
3198 if this is applicable. Usually this will be in the same
3199 format as that specified by the upstream author(s);
3200 however, it may need to be reformatted to fit into the
3201 package management system's format and comparison
3206 The comparison behavior of the package management system
3207 with respect to the <var>upstream_version</var> is
3208 described below. The <var>upstream_version</var>
3209 portion of the version number is mandatory.
3213 The <var>upstream_version</var> may contain only
3214 alphanumerics<footnote>
3215 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3217 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3218 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3219 tilde) and should start with a digit. If there is no
3220 <var>debian_revision</var> then hyphens are not allowed;
3221 if there is no <var>epoch</var> then colons are not
3226 <tag><var>debian_revision</var></tag>
3229 This part of the version number specifies the version of
3230 the Debian package based on the upstream version. It
3231 may contain only alphanumerics and the characters
3232 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3233 tilde) and is compared in the same way as the
3234 <var>upstream_version</var> is.
3238 It is optional; if it isn't present then the
3239 <var>upstream_version</var> may not contain a hyphen.
3240 This format represents the case where a piece of
3241 software was written specifically to be a Debian
3242 package, where the Debian package source must always
3243 be identical to the pristine source and therefore no
3244 revision indication is required.
3248 It is conventional to restart the
3249 <var>debian_revision</var> at <tt>1</tt> each time the
3250 <var>upstream_version</var> is increased.
3254 The package management system will break the version
3255 number apart at the last hyphen in the string (if there
3256 is one) to determine the <var>upstream_version</var> and
3257 <var>debian_revision</var>. The absence of a
3258 <var>debian_revision</var> is equivalent to a
3259 <var>debian_revision</var> of <tt>0</tt>.
3266 When comparing two version numbers, first the <var>epoch</var>
3267 of each are compared, then the <var>upstream_version</var> if
3268 <var>epoch</var> is equal, and then <var>debian_revision</var>
3269 if <var>upstream_version</var> is also equal.
3270 <var>epoch</var> is compared numerically. The
3271 <var>upstream_version</var> and <var>debian_revision</var>
3272 parts are compared by the package management system using the
3273 following algorithm:
3277 The strings are compared from left to right.
3281 First the initial part of each string consisting entirely of
3282 non-digit characters is determined. These two parts (one of
3283 which may be empty) are compared lexically. If a difference
3284 is found it is returned. The lexical comparison is a
3285 comparison of ASCII values modified so that all the letters
3286 sort earlier than all the non-letters and so that a tilde
3287 sorts before anything, even the end of a part. For example,
3288 the following parts are in sorted order from earliest to
3289 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3290 <tt>a</tt>.<footnote>
3291 One common use of <tt>~</tt> is for upstream pre-releases.
3292 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3293 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3298 Then the initial part of the remainder of each string which
3299 consists entirely of digit characters is determined. The
3300 numerical values of these two parts are compared, and any
3301 difference found is returned as the result of the comparison.
3302 For these purposes an empty string (which can only occur at
3303 the end of one or both version strings being compared) counts
3308 These two steps (comparing and removing initial non-digit
3309 strings and initial digit strings) are repeated until a
3310 difference is found or both strings are exhausted.
3314 Note that the purpose of epochs is to allow us to leave behind
3315 mistakes in version numbering, and to cope with situations
3316 where the version numbering scheme changes. It is
3317 <em>not</em> intended to cope with version numbers containing
3318 strings of letters which the package management system cannot
3319 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3320 silly orderings.<footnote>
3321 The author of this manual has heard of a package whose
3322 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3323 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3329 <sect1 id="f-Description">
3330 <heading><tt>Description</tt></heading>
3333 In a source or binary control file, the <tt>Description</tt>
3334 field contains a description of the binary package, consisting
3335 of two parts, the synopsis or the short description, and the
3336 long description. It is a multiline field with the following
3342 Description: <single line synopsis>
3343 <extended description over several lines>
3348 The lines in the extended description can have these formats:
3354 Those starting with a single space are part of a paragraph.
3355 Successive lines of this form will be word-wrapped when
3356 displayed. The leading space will usually be stripped off.
3357 The line must contain at least one non-whitespace character.
3361 Those starting with two or more spaces. These will be
3362 displayed verbatim. If the display cannot be panned
3363 horizontally, the displaying program will line wrap them "hard"
3364 (i.e., without taking account of word breaks). If it can they
3365 will be allowed to trail off to the right. None, one or two
3366 initial spaces may be deleted, but the number of spaces
3367 deleted from each line will be the same (so that you can have
3368 indenting work correctly, for example). The line must
3369 contain at least one non-whitespace character.
3373 Those containing a single space followed by a single full stop
3374 character. These are rendered as blank lines. This is the
3375 <em>only</em> way to get a blank line<footnote>
3376 Completely empty lines will not be rendered as blank lines.
3377 Instead, they will cause the parser to think you're starting
3378 a whole new record in the control file, and will therefore
3379 likely abort with an error.
3384 Those containing a space, a full stop and some more characters.
3385 These are for future expansion. Do not use them.
3391 Do not use tab characters. Their effect is not predictable.
3395 See <ref id="descriptions"> for further information on this.
3399 In a <file>.changes</file> file, the <tt>Description</tt>
3400 field contains a summary of the descriptions for the packages
3401 being uploaded. For this case, the first line of the field
3402 value (the part on the same line as <tt>Description:</tt>) is
3403 always empty. It is a multiline field, with one
3404 line per package. Each line is
3405 indented by one space and contains the name of a binary
3406 package, a space, a hyphen (<tt>-</tt>), a space, and the
3407 short description line from that package.
3411 <sect1 id="f-Distribution">
3412 <heading><tt>Distribution</tt></heading>
3415 In a <file>.changes</file> file or parsed changelog output
3416 this contains the (space-separated) name(s) of the
3417 distribution(s) where this version of the package should
3418 be installed. Valid distributions are determined by the
3419 archive maintainers.<footnote>
3420 Example distribution names in the Debian archive used in
3421 <file>.changes</file> files are:
3422 <taglist compact="compact">
3423 <tag><em>unstable</em></tag>
3425 This distribution value refers to the
3426 <em>developmental</em> part of the Debian distribution
3427 tree. Most new packages, new upstream versions of
3428 packages and bug fixes go into the <em>unstable</em>
3432 <tag><em>experimental</em></tag>
3434 The packages with this distribution value are deemed
3435 by their maintainers to be high risk. Oftentimes they
3436 represent early beta or developmental packages from
3437 various sources that the maintainers want people to
3438 try, but are not ready to be a part of the other parts
3439 of the Debian distribution tree.
3444 Others are used for updating stable releases or for
3445 security uploads. More information is available in the
3446 Debian Developer's Reference, section "The Debian
3450 The Debian archive software only supports listing a single
3451 distribution. Migration of packages to other distributions is
3452 handled outside of the upload process.
3457 <heading><tt>Date</tt></heading>
3460 This field includes the date the package was built or last
3461 edited. It must be in the same format as the <var>date</var>
3462 in a <file>debian/changelog</file> entry.
3466 The value of this field is usually extracted from the
3467 <file>debian/changelog</file> file - see
3468 <ref id="dpkgchangelog">).
3472 <sect1 id="f-Format">
3473 <heading><tt>Format</tt></heading>
3476 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3477 files, this field declares the format version of that file.
3478 The syntax of the field value is the same as that of
3479 a <qref id="f-Version">package version number</qref> except
3480 that no epoch or Debian revision is allowed. The format
3481 described in this document is <tt>&changesversion;</tt>.
3485 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3486 Debian source control</qref> files, this field declares the
3487 format of the source package. The field value is used by
3488 programs acting on a source package to interpret the list of
3489 files in the source package and determine how to unpack it.
3490 The syntax of the field value is a numeric major revision, a
3491 period, a numeric minor revision, and then an optional subtype
3492 after whitespace, which if specified is an alphanumeric word
3493 in parentheses. The subtype is optional in the syntax but may
3494 be mandatory for particular source format revisions.
3496 The source formats currently supported by the Debian archive
3497 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3498 and <tt>3.0 (quilt)</tt>.
3503 <sect1 id="f-Urgency">
3504 <heading><tt>Urgency</tt></heading>
3507 This is a description of how important it is to upgrade to
3508 this version from previous ones. It consists of a single
3509 keyword taking one of the values <tt>low</tt>,
3510 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3511 <tt>critical</tt><footnote>
3512 Other urgency values are supported with configuration
3513 changes in the archive software but are not used in Debian.
3514 The urgency affects how quickly a package will be considered
3515 for inclusion into the <tt>testing</tt> distribution and
3516 gives an indication of the importance of any fixes included
3517 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3518 treated as synonymous.
3519 </footnote> (not case-sensitive) followed by an optional
3520 commentary (separated by a space) which is usually in
3521 parentheses. For example:
3524 Urgency: low (HIGH for users of diversions)
3530 The value of this field is usually extracted from the
3531 <file>debian/changelog</file> file - see
3532 <ref id="dpkgchangelog">.
3536 <sect1 id="f-Changes">
3537 <heading><tt>Changes</tt></heading>
3540 This multiline field contains the human-readable changes data, describing
3541 the differences between the last version and the current one.
3545 The first line of the field value (the part on the same line
3546 as <tt>Changes:</tt>) is always empty. The content of the
3547 field is expressed as continuation lines, with each line
3548 indented by at least one space. Blank lines must be
3549 represented by a line consisting only of a space and a full
3554 The value of this field is usually extracted from the
3555 <file>debian/changelog</file> file - see
3556 <ref id="dpkgchangelog">).
3560 Each version's change information should be preceded by a
3561 "title" line giving at least the version, distribution(s)
3562 and urgency, in a human-readable way.
3566 If data from several versions is being returned the entry
3567 for the most recent version should be returned first, and
3568 entries should be separated by the representation of a
3569 blank line (the "title" line may also be followed by the
3570 representation of a blank line).
3574 <sect1 id="f-Binary">
3575 <heading><tt>Binary</tt></heading>
3578 This folded field is a list of binary packages. Its syntax and
3579 meaning varies depending on the control file in which it
3584 When it appears in the <file>.dsc</file> file, it lists binary
3585 packages which a source package can produce, separated by
3587 A space after each comma is conventional.
3588 </footnote>. The source package
3589 does not necessarily produce all of these binary packages for
3590 every architecture. The source control file doesn't contain
3591 details of which architectures are appropriate for which of
3592 the binary packages.
3596 When it appears in a <file>.changes</file> file, it lists the
3597 names of the binary packages being uploaded, separated by
3598 whitespace (not commas).
3602 <sect1 id="f-Installed-Size">
3603 <heading><tt>Installed-Size</tt></heading>
3606 This field appears in the control files of binary packages,
3607 and in the <file>Packages</file> files. It gives an estimate
3608 of the total amount of disk space required to install the
3609 named package. Actual installed size may vary based on block
3610 size, file system properties, or actions taken by package
3615 The disk space is given as the integer value of the estimated
3616 installed size in bytes, divided by 1024 and rounded up.
3620 <sect1 id="f-Files">
3621 <heading><tt>Files</tt></heading>
3624 This field contains a list of files with information about
3625 each one. The exact information and syntax varies with
3630 In all cases, Files is a multiline field. The first line of
3631 the field value (the part on the same line as <tt>Files:</tt>)
3632 is always empty. The content of the field is expressed as
3633 continuation lines, one line per file. Each line must be
3634 indented by one space and contain a number of sub-fields,
3635 separated by spaces, as described below.
3639 In the <file>.dsc</file> file, each line contains the MD5
3640 checksum, size and filename of the tar file and (if
3641 applicable) diff file which make up the remainder of the
3642 source package<footnote>
3643 That is, the parts which are not the <tt>.dsc</tt>.
3644 </footnote>. For example:
3647 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3648 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3650 The exact forms of the filenames are described
3651 in <ref id="pkg-sourcearchives">.
3655 In the <file>.changes</file> file this contains one line per
3656 file being uploaded. Each line contains the MD5 checksum,
3657 size, section and priority and the filename. For example:
3660 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3661 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3662 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3663 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3665 The <qref id="f-Section">section</qref>
3666 and <qref id="f-Priority">priority</qref> are the values of
3667 the corresponding fields in the main source control file. If
3668 no section or priority is specified then <tt>-</tt> should be
3669 used, though section and priority values must be specified for
3670 new packages to be installed properly.
3674 The special value <tt>byhand</tt> for the section in a
3675 <tt>.changes</tt> file indicates that the file in question
3676 is not an ordinary package file and must by installed by
3677 hand by the distribution maintainers. If the section is
3678 <tt>byhand</tt> the priority should be <tt>-</tt>.
3682 If a new Debian revision of a package is being shipped and
3683 no new original source archive is being distributed the
3684 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3685 entry for the original source archive
3686 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3687 but the <file>.changes</file> file should leave it out. In
3688 this case the original source archive on the distribution
3689 site must match exactly, byte-for-byte, the original
3690 source archive which was used to generate the
3691 <file>.dsc</file> file and diff which are being uploaded.</p>
3694 <sect1 id="f-Closes">
3695 <heading><tt>Closes</tt></heading>
3698 A space-separated list of bug report numbers that the upload
3699 governed by the .changes file closes.
3703 <sect1 id="f-Homepage">
3704 <heading><tt>Homepage</tt></heading>
3707 The URL of the web site for this package, preferably (when
3708 applicable) the site from which the original source can be
3709 obtained and any additional upstream documentation or
3710 information may be found. The content of this field is a
3711 simple URL without any surrounding characters such as
3716 <sect1 id="f-Checksums">
3717 <heading><tt>Checksums-Sha1</tt>
3718 and <tt>Checksums-Sha256</tt></heading>
3721 These multiline fields contain a list of files with a checksum and size
3722 for each one. Both <tt>Checksums-Sha1</tt>
3723 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3724 only in the checksum algorithm used: SHA-1
3725 for <tt>Checksums-Sha1</tt> and SHA-256
3726 for <tt>Checksums-Sha256</tt>.
3730 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3731 multiline fields. The first line of the field value (the part
3732 on the same line as <tt>Checksums-Sha1:</tt>
3733 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3734 of the field is expressed as continuation lines, one line per
3735 file. Each line consists of the checksum, a space, the file
3736 size, a space, and the file name. For example (from
3737 a <file>.changes</file> file):
3740 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3741 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3742 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3743 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3745 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3746 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3747 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3748 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3753 In the <file>.dsc</file> file, these fields list all
3754 files that make up the source package. In
3755 the <file>.changes</file> file, these fields list all
3756 files being uploaded. The list of files in these fields
3757 must match the list of files in the <tt>Files</tt> field.
3762 <heading><tt>DM-Upload-Allowed</tt></heading>
3765 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3769 <sect1 id="f-VCS-fields">
3770 <heading>Version Control System (VCS) fields</heading>
3773 Debian source packages are increasingly developed using VCSs. The
3774 purpose of the following fields is to indicate a publicly accessible
3775 repository where the Debian source package is developed.
3778 <tag><tt>Vcs-Browser</tt></tag>
3781 URL of a web interface for browsing the repository.
3786 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3787 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3788 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3793 The field name identifies the VCS. The field's value uses the
3794 version control system's conventional syntax for describing
3795 repository locations and should be sufficient to locate the
3796 repository used for packaging. Ideally, it also locates the
3797 branch used for development of new versions of the Debian
3801 In the case of Git, the value consists of a URL, optionally
3802 followed by the word <tt>-b</tt> and the name of a branch in
3803 the indicated repository, following the syntax of the
3804 <tt>git clone</tt> command. If no branch is specified, the
3805 packaging should be on the default branch.
3808 More than one different VCS may be specified for the same
3816 <sect1 id="f-Package-List">
3817 <heading><tt>Package-List</tt></heading>
3820 Multiline field listing all the packages that can be built from
3821 the source package, considering every architecture. The first line
3822 of the field value is empty. Each one of the next lines describes
3823 one binary package, by listing its name, type, section and priority
3824 separated by spaces. Fifth and subsequent space-separated items
3825 may be present and parsers must allow them. See the
3826 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3831 <sect1 id="f-Package-Type">
3832 <heading><tt>Package-Type</tt></heading>
3835 Simple field containing a word indicating the type of package:
3836 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3837 packages. Other types not defined here may be indicated. In
3838 source package control files, the <tt>Package-Type</tt> field
3839 should be omitted instead of giving it a value of <tt>deb</tt>, as
3840 this value is assumed for paragraphs lacking this field.
3845 <heading><tt>Dgit</tt></heading>
3848 Folded field containing a single git commit hash, presented in
3849 full, followed optionally by whitespace and other data to be
3850 defined in future extensions.
3854 Declares that the source package corresponds exactly to a
3855 referenced commit in a Git repository available at the canonical
3856 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3857 bidirectional gateway between the Debian archive and Git. The
3858 commit is reachable from at least one reference whose name matches
3859 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3866 <heading>User-defined fields</heading>
3869 Additional user-defined fields may be added to the
3870 source package control file. Such fields will be
3871 ignored, and not copied to (for example) binary or
3872 Debian source control files or upload control files.
3876 If you wish to add additional unsupported fields to
3877 these output files you should use the mechanism
3882 Fields in the main source control information file with
3883 names starting <tt>X</tt>, followed by one or more of
3884 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3885 be copied to the output files. Only the part of the
3886 field name after the hyphen will be used in the output
3887 file. Where the letter <tt>B</tt> is used the field
3888 will appear in binary package control files, where the
3889 letter <tt>S</tt> is used in Debian source control
3890 files and where <tt>C</tt> is used in upload control
3891 (<tt>.changes</tt>) files.
3895 For example, if the main source information control file
3898 XBS-Comment: I stand between the candle and the star.
3900 then the binary and Debian source control files will contain the
3903 Comment: I stand between the candle and the star.
3909 <sect id="obsolete-control-data-fields">
3910 <heading>Obsolete fields</heading>
3913 The following fields have been obsoleted and may be found in packages
3914 conforming with previous versions of the Policy.
3917 <sect1 id="f-DM-Upload-Allowed">
3918 <heading><tt>DM-Upload-Allowed</tt></heading>
3921 Indicates that Debian Maintainers may upload this package to
3922 the Debian archive. The only valid value is <tt>yes</tt>. This
3923 field was used to regulate uploads by Debian Maintainers, See the
3924 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3925 name="Endorse the concept of Debian Maintainers"> for more details.
3934 <chapt id="maintainerscripts">
3935 <heading>Package maintainer scripts and installation procedure</heading>
3938 <heading>Introduction to package maintainer scripts</heading>
3941 It is possible to supply scripts as part of a package which
3942 the package management system will run for you when your
3943 package is installed, upgraded or removed.
3947 These scripts are the control information
3948 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3949 and <prgn>postrm</prgn>. They must be proper executable files;
3950 if they are scripts (which is recommended), they must start with
3951 the usual <tt>#!</tt> convention. They should be readable and
3952 executable by anyone, and must not be world-writable.
3956 The package management system looks at the exit status from
3957 these scripts. It is important that they exit with a
3958 non-zero status if there is an error, so that the package
3959 management system can stop its processing. For shell
3960 scripts this means that you <em>almost always</em> need to
3961 use <tt>set -e</tt> (this is usually true when writing shell
3962 scripts, in fact). It is also important, of course, that
3963 they exit with a zero status if everything went well.
3967 Additionally, packages interacting with users
3968 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3969 should install a <prgn>config</prgn> script as a control
3970 information file. See <ref id="maintscriptprompt"> for details.
3974 When a package is upgraded a combination of the scripts from
3975 the old and new packages is called during the upgrade
3976 procedure. If your scripts are going to be at all
3977 complicated you need to be aware of this, and may need to
3978 check the arguments to your scripts.
3982 Broadly speaking the <prgn>preinst</prgn> is called before
3983 (a particular version of) a package is unpacked, and the
3984 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3985 before (a version of) a package is removed and the
3986 <prgn>postrm</prgn> afterwards.
3990 Programs called from maintainer scripts should not normally
3991 have a path prepended to them. Before installation is
3992 started, the package management system checks to see if the
3993 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3994 and <prgn>update-rc.d</prgn> can be found via the
3995 <tt>PATH</tt> environment variable. Those programs, and any
3996 other program that one would expect to be in the
3997 <tt>PATH</tt>, should thus be invoked without an absolute
3998 pathname. Maintainer scripts should also not reset the
3999 <tt>PATH</tt>, though they might choose to modify it by
4000 prepending or appending package-specific directories. These
4001 considerations really apply to all shell scripts.</p>
4004 <sect id="idempotency">
4005 <heading>Maintainer scripts idempotency</heading>
4008 It is necessary for the error recovery procedures that the
4009 scripts be idempotent. This means that if it is run
4010 successfully, and then it is called again, it doesn't bomb
4011 out or cause any harm, but just ensures that everything is
4012 the way it ought to be. If the first call failed, or
4013 aborted half way through for some reason, the second call
4014 should merely do the things that were left undone the first
4015 time, if any, and exit with a success status if everything
4017 This is so that if an error occurs, the user interrupts
4018 <prgn>dpkg</prgn> or some other unforeseen circumstance
4019 happens you don't leave the user with a badly-broken
4020 package when <prgn>dpkg</prgn> attempts to repeat the
4026 <sect id="controllingterminal">
4027 <heading>Controlling terminal for maintainer scripts</heading>
4030 Maintainer scripts are not guaranteed to run with a controlling
4031 terminal and may not be able to interact with the user. They
4032 must be able to fall back to noninteractive behavior if no
4033 controlling terminal is available. Maintainer scripts that
4034 prompt via a program conforming to the Debian Configuration
4035 Management Specification (see <ref id="maintscriptprompt">) may
4036 assume that program will handle falling back to noninteractive
4041 For high-priority prompts without a reasonable default answer,
4042 maintainer scripts may abort if there is no controlling
4043 terminal. However, this situation should be avoided if at all
4044 possible, since it prevents automated or unattended installs.
4045 In most cases, users will consider this to be a bug in the
4050 <sect id="exitstatus">
4051 <heading>Exit status</heading>
4054 Each script must return a zero exit status for
4055 success, or a nonzero one for failure, since the package
4056 management system looks for the exit status of these scripts
4057 and determines what action to take next based on that datum.
4061 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4066 What follows is a summary of all the ways in which maintainer
4067 scripts may be called along with what facilities those scripts
4068 may rely on being available at that time. Script names preceded
4069 by <var>new-</var> are the scripts from the new version of a
4070 package being installed, upgraded to, or downgraded to. Script
4071 names preceded by <var>old-</var> are the scripts from the old
4072 version of a package that is being upgraded from or downgraded
4077 The <prgn>preinst</prgn> script may be called in the following
4080 <tag><var>new-preinst</var> <tt>install</tt></tag>
4081 <tag><var>new-preinst</var> <tt>install</tt>
4082 <var>old-version</var></tag>
4083 <tag><var>new-preinst</var> <tt>upgrade</tt>
4084 <var>old-version</var></tag>
4086 The package will not yet be unpacked, so
4087 the <prgn>preinst</prgn> script cannot rely on any files
4088 included in its package. Only essential packages and
4089 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4090 available. Pre-dependencies will have been configured at
4091 least once, but at the time the <prgn>preinst</prgn> is
4092 called they may only be in an "Unpacked" or "Half-Configured"
4093 state if a previous version of the pre-dependency was
4094 completely configured and has not been removed since then.
4097 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4098 <var>new-version</var></tag>
4100 Called during error handling of an upgrade that failed after
4101 unpacking the new package because the <tt>postrm
4102 upgrade</tt> action failed. The unpacked files may be
4103 partly from the new version or partly missing, so the script
4104 cannot rely on files included in the package. Package
4105 dependencies may not be available. Pre-dependencies will be
4106 at least "Unpacked" following the same rules as above, except
4107 they may be only "Half-Installed" if an upgrade of the
4108 pre-dependency failed.<footnote>
4109 This can happen if the new version of the package no
4110 longer pre-depends on a package that had been partially
4118 The <prgn>postinst</prgn> script may be called in the following
4121 <tag><var>postinst</var> <tt>configure</tt>
4122 <var>most-recently-configured-version</var></tag>
4124 The files contained in the package will be unpacked. All
4125 package dependencies will at least be "Unpacked". If there
4126 are no circular dependencies involved, all package
4127 dependencies will be configured. For behavior in the case
4128 of circular dependencies, see the discussion
4129 in <ref id="binarydeps">.
4132 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4133 <var>new-version</var></tag>
4134 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4135 <tt>in-favour</tt> <var>package</var>
4136 <var>new-version</var></tag>
4137 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4138 <tag><var>deconfigured's-postinst</var>
4139 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4140 <var>failed-install-package</var> <var>version</var>
4141 [<tt>removing</tt> <var>conflicting-package</var>
4142 <var>version</var>]</tag>
4144 The files contained in the package will be unpacked. All
4145 package dependencies will at least be "Half-Installed" and
4146 will have previously been configured and not removed.
4147 However, dependencies may not be configured or even fully
4148 unpacked in some error situations.<footnote>
4149 For example, suppose packages foo and bar are "Installed"
4150 with foo depending on bar. If an upgrade of bar were
4151 started and then aborted, and then an attempt to remove
4152 foo failed because its <prgn>prerm</prgn> script failed,
4153 foo's <tt>postinst abort-remove</tt> would be called with
4154 bar only "Half-Installed".
4156 The <prgn>postinst</prgn> should still attempt any actions
4157 for which its dependencies are required, since they will
4158 normally be available, but consider the correct error
4159 handling approach if those actions fail. Aborting
4160 the <prgn>postinst</prgn> action if commands or facilities
4161 from the package dependencies are not available is often the
4168 The <prgn>prerm</prgn> script may be called in the following
4171 <tag><var>prerm</var> <tt>remove</tt></tag>
4172 <tag><var>old-prerm</var>
4173 <tt>upgrade</tt><var>new-version</var></tag>
4174 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4175 <tt>in-favour</tt> <var>package</var>
4176 <var>new-version</var></tag>
4177 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4178 <tt>in-favour</tt> <var>package-being-installed</var>
4179 <var>version</var> [<tt>removing</tt>
4180 <var>conflicting-package</var> <var>version</var>]</tag>
4182 The package whose <prgn>prerm</prgn> is being called will be
4183 at least "Half-Installed". All package dependencies will at
4184 least be "Half-Installed" and will have previously been
4185 configured and not removed. If there was no error, all
4186 dependencies will at least be "Unpacked", but these actions
4187 may be called in various error states where dependencies are
4188 only "Half-Installed" due to a partial upgrade.
4191 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4192 <var>old-version</var></tag>
4194 Called during error handling when <tt>prerm upgrade</tt>
4195 fails. The new package will not yet be unpacked, and all
4196 the same constraints as for <tt>preinst upgrade</tt> apply.
4202 The <prgn>postrm</prgn> script may be called in the following
4205 <tag><var>postrm</var> <tt>remove</tt></tag>
4206 <tag><var>postrm</var> <tt>purge</tt></tag>
4207 <tag><var>old-postrm</var> <tt>upgrade</tt>
4208 <var>new-version</var></tag>
4209 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4210 <var>overwriter</var> <var>overwriter-version</var></tag>
4212 The <prgn>postrm</prgn> script is called after the package's
4213 files have been removed or replaced. The package
4214 whose <prgn>postrm</prgn> is being called may have
4215 previously been deconfigured and only be "Unpacked", at which
4216 point subsequent package changes do not consider its
4217 dependencies. Therefore, all <prgn>postrm</prgn> actions
4218 may only rely on essential packages and must gracefully skip
4219 any actions that require the package's dependencies if those
4220 dependencies are unavailable.<footnote>
4221 This is often done by checking whether the command or
4222 facility the <prgn>postrm</prgn> intends to call is
4223 available before calling it. For example:
4225 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4226 . /usr/share/debconf/confmodule
4230 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4231 configuration for the package
4232 if <package>debconf</package> is installed.
4236 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4237 <var>old-version</var></tag>
4239 Called when the old <tt>postrm upgrade</tt> action fails.
4240 The new package will be unpacked, but only essential
4241 packages and pre-dependencies can be relied on.
4242 Pre-dependencies will either be configured or will be
4243 "Unpacked" or "Half-Configured" but previously had been
4244 configured and was never removed.
4247 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4248 <tag><var>new-postrm</var> <tt>abort-install</tt>
4249 <var>old-version</var></tag>
4250 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4251 <var>old-version</var></tag>
4253 Called before unpacking the new package as part of the
4254 error handling of <prgn>preinst</prgn> failures. May assume
4255 the same state as <prgn>preinst</prgn> can assume.
4261 <sect id="unpackphase">
4262 <heading>Details of unpack phase of installation or upgrade</heading>
4265 The procedure on installation/upgrade/overwrite/disappear
4266 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4267 stage of <tt>dpkg --install</tt>) is as follows. In each
4268 case, if a major error occurs (unless listed below) the
4269 actions are, in general, run backwards - this means that the
4270 maintainer scripts are run with different arguments in
4271 reverse order. These are the "error unwind" calls listed
4278 If a version of the package is already "Installed", call
4279 <example compact="compact">
4280 <var>old-prerm</var> upgrade <var>new-version</var>
4284 If the script runs but exits with a non-zero
4285 exit status, <prgn>dpkg</prgn> will attempt:
4286 <example compact="compact">
4287 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4289 If this works, the upgrade continues. If this
4290 does not work, the error unwind:
4291 <example compact="compact">
4292 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4294 If this works, then the old-version is
4295 "Installed", if not, the old version is in a
4296 "Half-Configured" state.
4302 If a "conflicting" package is being removed at the same time,
4303 or if any package will be broken (due to <tt>Breaks</tt>):
4306 If <tt>--auto-deconfigure</tt> is
4307 specified, call, for each package to be deconfigured
4308 due to <tt>Breaks</tt>:
4309 <example compact="compact">
4310 <var>deconfigured's-prerm</var> deconfigure \
4311 in-favour <var>package-being-installed</var> <var>version</var>
4314 <example compact="compact">
4315 <var>deconfigured's-postinst</var> abort-deconfigure \
4316 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4318 The deconfigured packages are marked as
4319 requiring configuration, so that if
4320 <tt>--install</tt> is used they will be
4321 configured again if possible.
4324 If any packages depended on a conflicting
4325 package being removed and <tt>--auto-deconfigure</tt> is
4326 specified, call, for each such package:
4327 <example compact="compact">
4328 <var>deconfigured's-prerm</var> deconfigure \
4329 in-favour <var>package-being-installed</var> <var>version</var> \
4330 removing <var>conflicting-package</var> <var>version</var>
4333 <example compact="compact">
4334 <var>deconfigured's-postinst</var> abort-deconfigure \
4335 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4336 removing <var>conflicting-package</var> <var>version</var>
4338 The deconfigured packages are marked as
4339 requiring configuration, so that if
4340 <tt>--install</tt> is used they will be
4341 configured again if possible.
4344 To prepare for removal of each conflicting package, call:
4345 <example compact="compact">
4346 <var>conflictor's-prerm</var> remove \
4347 in-favour <var>package</var> <var>new-version</var>
4350 <example compact="compact">
4351 <var>conflictor's-postinst</var> abort-remove \
4352 in-favour <var>package</var> <var>new-version</var>
4361 If the package is being upgraded, call:
4362 <example compact="compact">
4363 <var>new-preinst</var> upgrade <var>old-version</var>
4365 If this fails, we call:
4367 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4374 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4376 is called. If this works, then the old version
4377 is in an "Installed" state, or else it is left
4378 in an "Unpacked" state.
4383 If it fails, then the old version is left
4384 in an "Half-Installed" state.
4391 Otherwise, if the package had some configuration
4392 files from a previous version installed (i.e., it
4393 is in the "Config-Files" state):
4394 <example compact="compact">
4395 <var>new-preinst</var> install <var>old-version</var>
4399 <var>new-postrm</var> abort-install <var>old-version</var>
4401 If this fails, the package is left in a
4402 "Half-Installed" state, which requires a
4403 reinstall. If it works, the packages is left in
4404 a "Config-Files" state.
4407 Otherwise (i.e., the package was completely purged):
4408 <example compact="compact">
4409 <var>new-preinst</var> install
4412 <example compact="compact">
4413 <var>new-postrm</var> abort-install
4415 If the error-unwind fails, the package is in a
4416 "Half-Installed" phase, and requires a
4417 reinstall. If the error unwind works, the
4418 package is in the "Not-Installed" state.
4425 The new package's files are unpacked, overwriting any
4426 that may be on the system already, for example any
4427 from the old version of the same package or from
4428 another package. Backups of the old files are kept
4429 temporarily, and if anything goes wrong the package
4430 management system will attempt to put them back as
4431 part of the error unwind.
4435 It is an error for a package to contain files which
4436 are on the system in another package, unless
4437 <tt>Replaces</tt> is used (see <ref id="replaces">).
4439 The following paragraph is not currently the case:
4440 Currently the <tt>- - force-overwrite</tt> flag is
4441 enabled, downgrading it to a warning, but this may not
4447 It is a more serious error for a package to contain a
4448 plain file or other kind of non-directory where another
4449 package has a directory (again, unless
4450 <tt>Replaces</tt> is used). This error can be
4451 overridden if desired using
4452 <tt>--force-overwrite-dir</tt>, but this is not
4457 Packages which overwrite each other's files produce
4458 behavior which, though deterministic, is hard for the
4459 system administrator to understand. It can easily
4460 lead to "missing" programs if, for example, a package
4461 is unpacked which overwrites a file from another
4462 package, and is then removed again.<footnote>
4463 Part of the problem is due to what is arguably a
4464 bug in <prgn>dpkg</prgn>.
4469 A directory will never be replaced by a symbolic link
4470 to a directory or vice versa; instead, the existing
4471 state (symlink or not) will be left alone and
4472 <prgn>dpkg</prgn> will follow the symlink if there is
4481 If the package is being upgraded, call
4482 <example compact="compact">
4483 <var>old-postrm</var> upgrade <var>new-version</var>
4487 If this fails, <prgn>dpkg</prgn> will attempt:
4488 <example compact="compact">
4489 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4491 If this works, installation continues. If not,
4493 <example compact="compact">
4494 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4496 If this fails, the old version is left in a
4497 "Half-Installed" state. If it works, dpkg now
4499 <example compact="compact">
4500 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4502 If this fails, the old version is left in a
4503 "Half-Installed" state. If it works, dpkg now
4505 <example compact="compact">
4506 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4508 If this fails, the old version is in an
4515 This is the point of no return - if
4516 <prgn>dpkg</prgn> gets this far, it won't back off
4517 past this point if an error occurs. This will
4518 leave the package in a fairly bad state, which
4519 will require a successful re-installation to clear
4520 up, but it's when <prgn>dpkg</prgn> starts doing
4521 things that are irreversible.
4526 Any files which were in the old version of the package
4527 but not in the new are removed.
4531 The new file list replaces the old.
4535 The new maintainer scripts replace the old.
4539 Any packages all of whose files have been overwritten
4540 during the installation, and which aren't required for
4541 dependencies, are considered to have been removed.
4542 For each such package
4545 <prgn>dpkg</prgn> calls:
4546 <example compact="compact">
4547 <var>disappearer's-postrm</var> disappear \
4548 <var>overwriter</var> <var>overwriter-version</var>
4552 The package's maintainer scripts are removed.
4555 It is noted in the status database as being in a
4556 sane state, namely "Not-Installed" (any conffiles
4557 it may have are ignored, rather than being
4558 removed by <prgn>dpkg</prgn>). Note that
4559 disappearing packages do not have their prerm
4560 called, because <prgn>dpkg</prgn> doesn't know
4561 in advance that the package is going to
4568 Any files in the package we're unpacking that are also
4569 listed in the file lists of other packages are removed
4570 from those lists. (This will lobotomize the file list
4571 of the "conflicting" package if there is one.)
4575 The backup files made during installation, above, are
4581 The new package's status is now sane, and recorded as
4586 Here is another point of no return - if the
4587 conflicting package's removal fails we do not unwind
4588 the rest of the installation; the conflicting package
4589 is left in a half-removed limbo.
4594 If there was a conflicting package we go and do the
4595 removal actions (described below), starting with the
4596 removal of the conflicting package's files (any that
4597 are also in the package being unpacked have already
4598 been removed from the conflicting package's file list,
4599 and so do not get removed now).
4605 <sect id="configdetails"><heading>Details of configuration</heading>
4608 When we configure a package (this happens with <tt>dpkg
4609 --install</tt> and <tt>dpkg --configure</tt>), we first
4610 update any <tt>conffile</tt>s and then call:
4611 <example compact="compact">
4612 <var>postinst</var> configure <var>most-recently-configured-version</var>
4617 No attempt is made to unwind after errors during
4618 configuration. If the configuration fails, the package is in
4619 a "Half-Configured" state, and an error message is generated.
4623 If there is no most recently configured version
4624 <prgn>dpkg</prgn> will pass a null argument.
4627 Historical note: Truly ancient (pre-1997) versions of
4628 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4629 (including the angle brackets) in this case. Even older
4630 ones did not pass a second argument at all, under any
4631 circumstance. Note that upgrades using such an old dpkg
4632 version are unlikely to work for other reasons, even if
4633 this old argument behavior is handled by your postinst script.
4639 <sect id="removedetails"><heading>Details of removal and/or
4640 configuration purging</heading>
4646 <example compact="compact">
4647 <var>prerm</var> remove
4651 If prerm fails during replacement due to conflict
4653 <var>conflictor's-postinst</var> abort-remove \
4654 in-favour <var>package</var> <var>new-version</var>
4658 <var>postinst</var> abort-remove
4662 If this fails, the package is in a "Half-Configured"
4663 state, or else it remains "Installed".
4667 The package's files are removed (except <tt>conffile</tt>s).
4670 <example compact="compact">
4671 <var>postrm</var> remove
4675 If it fails, there's no error unwind, and the package is in
4676 an "Half-Installed" state.
4681 All the maintainer scripts except the <prgn>postrm</prgn>
4686 If we aren't purging the package we stop here. Note
4687 that packages which have no <prgn>postrm</prgn> and no
4688 <tt>conffile</tt>s are automatically purged when
4689 removed, as there is no difference except for the
4690 <prgn>dpkg</prgn> status.
4694 The <tt>conffile</tt>s and any backup files
4695 (<tt>~</tt>-files, <tt>#*#</tt> files,
4696 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4701 <example compact="compact">
4702 <var>postrm</var> purge
4706 If this fails, the package remains in a "Config-Files"
4711 The package's file list is removed.
4720 <chapt id="relationships">
4721 <heading>Declaring relationships between packages</heading>
4723 <sect id="depsyntax">
4724 <heading>Syntax of relationship fields</heading>
4727 These fields all have a uniform syntax. They are a list of
4728 package names separated by commas.
4732 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4733 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4734 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4735 control fields of the package, which declare
4736 dependencies on other packages, the package names listed may
4737 also include lists of alternative package names, separated
4738 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4739 that part of the dependency can be satisfied by any one of
4740 the alternative packages.
4744 All of the fields except for <tt>Provides</tt> may restrict
4745 their applicability to particular versions of each named
4746 package. This is done in parentheses after each individual
4747 package name; the parentheses should contain a relation from
4748 the list below followed by a version number, in the format
4749 described in <ref id="f-Version">.
4753 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4754 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4755 earlier, earlier or equal, exactly equal, later or equal and
4756 strictly later, respectively. The deprecated
4757 forms <tt><</tt> and <tt>></tt> were confusingly used to
4758 mean earlier/later or equal, rather than strictly earlier/later,
4759 and must not appear in new packages (though <prgn>dpkg</prgn>
4760 still supports them with a warning).
4764 Whitespace may appear at any point in the version
4765 specification subject to the rules in <ref
4766 id="controlsyntax">, and must appear where it's necessary to
4767 disambiguate; it is not otherwise significant. All of the
4768 relationship fields can only be folded in source package control files. For
4769 consistency and in case of future changes to
4770 <prgn>dpkg</prgn> it is recommended that a single space be
4771 used after a version relationship and before a version
4772 number; it is also conventional to put a single space after
4773 each comma, on either side of each vertical bar, and before
4774 each open parenthesis. When opening a continuation line in a relationship field, it
4775 is conventional to do so after a comma and before the space
4776 following that comma.
4780 For example, a list of dependencies might appear as:
4781 <example compact="compact">
4784 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4789 Relationships may be restricted to a certain set of
4790 architectures. This is indicated in brackets after each
4791 individual package name and the optional version specification.
4792 The brackets enclose a non-empty list of Debian architecture names
4793 in the format described in <ref id="arch-spec">,
4794 separated by whitespace. Exclamation marks may be prepended to
4795 each of the names. (It is not permitted for some names to be
4796 prepended with exclamation marks while others aren't.)
4800 For build relationship fields
4801 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4802 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4803 the current Debian host architecture is not in this list and
4804 there are no exclamation marks in the list, or it is in the list
4805 with a prepended exclamation mark, the package name and the
4806 associated version specification are ignored completely for the
4807 purposes of defining the relationships.
4812 <example compact="compact">
4814 Build-Depends-Indep: texinfo
4815 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4816 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4818 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4819 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4820 <tt>gnumach-dev</tt> only on hurd-i386.
4824 For binary relationship fields and the <tt>Built-Using</tt>
4825 field, the architecture restriction
4826 syntax is only supported in the source package control
4827 file <file>debian/control</file>. When the corresponding binary
4828 package control file is generated, the relationship will either
4829 be omitted or included without the architecture restriction
4830 based on the architecture of the binary package. This means
4831 that architecture restrictions must not be used in binary
4832 relationship fields for architecture-independent packages
4833 (<tt>Architecture: all</tt>).
4838 <example compact="compact">
4839 Depends: foo [i386], bar [amd64]
4841 becomes <tt>Depends: foo</tt> when the package is built on
4842 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4843 package is built on the <tt>amd64</tt> architecture, and omitted
4844 entirely in binary packages built on all other architectures.
4848 If the architecture-restricted dependency is part of a set of
4849 alternatives using <tt>|</tt>, that alternative is ignored
4850 completely on architectures that do not match the restriction.
4852 <example compact="compact">
4853 Build-Depends: foo [!i386] | bar [!amd64]
4855 is equivalent to <tt>bar</tt> on the i386 architecture, to
4856 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4857 bar</tt> on all other architectures.
4861 Relationships may also be restricted to a certain set of
4862 architectures using architecture wildcards in the format
4863 described in <ref id="arch-wildcard-spec">. The syntax for
4864 declaring such restrictions is the same as declaring
4865 restrictions using a certain set of architectures without
4866 architecture wildcards. For example:
4867 <example compact="compact">
4868 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4870 is equivalent to <tt>foo</tt> on architectures using the Linux
4871 kernel and any cpu, <tt>bar</tt> on architectures using any
4872 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4873 using a kernel other than Linux.
4877 Note that the binary package relationship fields such as
4878 <tt>Depends</tt> appear in one of the binary package
4879 sections of the control file, whereas the build-time
4880 relationships such as <tt>Build-Depends</tt> appear in the
4881 source package section of the control file (which is the
4886 <sect id="binarydeps">
4887 <heading>Binary Dependencies - <tt>Depends</tt>,
4888 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4889 <tt>Pre-Depends</tt>
4893 Packages can declare in their control file that they have
4894 certain relationships to other packages - for example, that
4895 they may not be installed at the same time as certain other
4896 packages, and/or that they depend on the presence of others.
4900 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4901 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4902 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4903 <tt>Breaks</tt> is described in <ref id="breaks">, and
4904 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4905 rest are described below.
4909 These seven fields are used to declare a dependency
4910 relationship by one package on another. Except for
4911 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4912 depending (binary) package's control file.
4913 (<tt>Enhances</tt> appears in the recommending package's
4914 control file, and <tt>Breaks</tt> appears in the version of
4915 depended-on package which causes the named package to
4920 A <tt>Depends</tt> field takes effect <em>only</em> when a
4921 package is to be configured. It does not prevent a package
4922 being on the system in an unconfigured state while its
4923 dependencies are unsatisfied, and it is possible to replace
4924 a package whose dependencies are satisfied and which is
4925 properly installed with a different version whose
4926 dependencies are not and cannot be satisfied; when this is
4927 done the depending package will be left unconfigured (since
4928 attempts to configure it will give errors) and will not
4929 function properly. If it is necessary, a
4930 <tt>Pre-Depends</tt> field can be used, which has a partial
4931 effect even when a package is being unpacked, as explained
4932 in detail below. (The other three dependency fields,
4933 <tt>Recommends</tt>, <tt>Suggests</tt> and
4934 <tt>Enhances</tt>, are only used by the various front-ends
4935 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4936 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4940 Since <tt>Depends</tt> only places requirements on the order in
4941 which packages are configured, packages in an installation run
4942 are usually all unpacked first and all configured later.
4944 This approach makes dependency resolution easier. If two
4945 packages A and B are being upgraded, the installed package A
4946 depends on exactly the installed package B, and the new
4947 package A depends on exactly the new package B (a common
4948 situation when upgrading shared libraries and their
4949 corresponding development packages), satisfying the
4950 dependencies at every stage of the upgrade would be
4951 impossible. This relaxed restriction means that both new
4952 packages can be unpacked together and then configured in their
4958 If there is a circular dependency among packages being installed
4959 or removed, installation or removal order honoring the
4960 dependency order is impossible, requiring the dependency loop be
4961 broken at some point and the dependency requirements violated
4962 for at least one package. Packages involved in circular
4963 dependencies may not be able to rely on their dependencies being
4964 configured before they themselves are configured, depending on
4965 which side of the break of the circular dependency loop they
4966 happen to be on. If one of the packages in the loop has
4967 no <prgn>postinst</prgn> script, then the cycle will be broken
4968 at that package; this ensures that all <prgn>postinst</prgn>
4969 scripts are run with their dependencies properly configured if
4970 this is possible. Otherwise the breaking point is arbitrary.
4971 Packages should therefore avoid circular dependencies where
4972 possible, particularly if they have <prgn>postinst</prgn>
4977 The meaning of the five dependency fields is as follows:
4979 <tag><tt>Depends</tt></tag>
4982 This declares an absolute dependency. A package will
4983 not be configured unless all of the packages listed in
4984 its <tt>Depends</tt> field have been correctly
4985 configured (unless there is a circular dependency as
4990 The <tt>Depends</tt> field should be used if the
4991 depended-on package is required for the depending
4992 package to provide a significant amount of
4997 The <tt>Depends</tt> field should also be used if the
4998 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4999 require the depended-on package to be unpacked or
5000 configured in order to run. In the case of <tt>postinst
5001 configure</tt>, the depended-on packages will be unpacked
5002 and configured first. (If both packages are involved in a
5003 dependency loop, this might not work as expected; see the
5004 explanation a few paragraphs back.) In the case
5005 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5006 actions, the package dependencies will normally be at
5007 least unpacked, but they may be only "Half-Installed" if a
5008 previous upgrade of the dependency failed.
5012 Finally, the <tt>Depends</tt> field should be used if the
5013 depended-on package is needed by the <prgn>postrm</prgn>
5014 script to fully clean up after the package removal. There
5015 is no guarantee that package dependencies will be
5016 available when <prgn>postrm</prgn> is run, but the
5017 depended-on package is more likely to be available if the
5018 package declares a dependency (particularly in the case
5019 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5020 script must gracefully skip actions that require a
5021 dependency if that dependency isn't available.
5025 <tag><tt>Recommends</tt></tag>
5028 This declares a strong, but not absolute, dependency.
5032 The <tt>Recommends</tt> field should list packages
5033 that would be found together with this one in all but
5034 unusual installations.
5038 <tag><tt>Suggests</tt></tag>
5040 This is used to declare that one package may be more
5041 useful with one or more others. Using this field
5042 tells the packaging system and the user that the
5043 listed packages are related to this one and can
5044 perhaps enhance its usefulness, but that installing
5045 this one without them is perfectly reasonable.
5048 <tag><tt>Enhances</tt></tag>
5050 This field is similar to Suggests but works in the
5051 opposite direction. It is used to declare that a
5052 package can enhance the functionality of another
5056 <tag><tt>Pre-Depends</tt></tag>
5059 This field is like <tt>Depends</tt>, except that it
5060 also forces <prgn>dpkg</prgn> to complete installation
5061 of the packages named before even starting the
5062 installation of the package which declares the
5063 pre-dependency, as follows:
5067 When a package declaring a pre-dependency is about to
5068 be <em>unpacked</em> the pre-dependency can be
5069 satisfied if the depended-on package is either fully
5070 configured, <em>or even if</em> the depended-on
5071 package(s) are only in the "Unpacked" or the "Half-Configured"
5072 state, provided that they have been configured
5073 correctly at some point in the past (and not removed
5074 or partially removed since). In this case, both the
5075 previously-configured and currently "Unpacked" or
5076 "Half-Configured" versions must satisfy any version
5077 clause in the <tt>Pre-Depends</tt> field.
5081 When the package declaring a pre-dependency is about to
5082 be <em>configured</em>, the pre-dependency will be treated
5083 as a normal <tt>Depends</tt>. It will be considered
5084 satisfied only if the depended-on package has been
5085 correctly configured. However, unlike
5086 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5087 permit circular dependencies to be broken. If a circular
5088 dependency is encountered while attempting to honor
5089 <tt>Pre-Depends</tt>, the installation will be aborted.
5093 <tt>Pre-Depends</tt> are also required if the
5094 <prgn>preinst</prgn> script depends on the named package.
5095 It is best to avoid this situation if possible.
5099 <tt>Pre-Depends</tt> should be used sparingly,
5100 preferably only by packages whose premature upgrade or
5101 installation would hamper the ability of the system to
5102 continue with any upgrade that might be in progress.
5106 You should not specify a <tt>Pre-Depends</tt> entry for a
5107 package before this has been discussed on the
5108 <tt>debian-devel</tt> mailing list and a consensus about
5109 doing that has been reached. See <ref id="dependencies">.
5116 When selecting which level of dependency to use you should
5117 consider how important the depended-on package is to the
5118 functionality of the one declaring the dependency. Some
5119 packages are composed of components of varying degrees of
5120 importance. Such a package should list using
5121 <tt>Depends</tt> the package(s) which are required by the
5122 more important components. The other components'
5123 requirements may be mentioned as Suggestions or
5124 Recommendations, as appropriate to the components' relative
5130 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5133 When one binary package declares that it breaks another,
5134 <prgn>dpkg</prgn> will refuse to allow the package which
5135 declares <tt>Breaks</tt> to be unpacked unless the broken
5136 package is deconfigured first, and it will refuse to
5137 allow the broken package to be reconfigured.
5141 A package will not be regarded as causing breakage merely
5142 because its configuration files are still installed; it must
5143 be at least "Half-Installed".
5147 A special exception is made for packages which declare that
5148 they break their own package name or a virtual package which
5149 they provide (see below): this does not count as a real
5154 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5155 version clause; such a <tt>Breaks</tt> is introduced in the
5156 version of an (implicit or explicit) dependency which violates
5157 an assumption or reveals a bug in earlier versions of the broken
5158 package, or which takes over a file from earlier versions of the
5159 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5160 will inform higher-level package management tools that the
5161 broken package must be upgraded before the new one.
5165 If the breaking package also overwrites some files from the
5166 older package, it should use <tt>Replaces</tt> to ensure this
5167 goes smoothly. See <ref id="replaces"> for a full discussion
5168 of taking over files from other packages, including how to
5169 use <tt>Breaks</tt> in those cases.
5173 Many of the cases where <tt>Breaks</tt> should be used were
5174 previously handled with <tt>Conflicts</tt>
5175 because <tt>Breaks</tt> did not yet exist.
5176 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5177 See <ref id="conflicts"> for more information about the
5182 <sect id="conflicts">
5183 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5186 When one binary package declares a conflict with another using
5187 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5188 allow them to be unpacked on the system at the same time. This
5189 is a stronger restriction than <tt>Breaks</tt>, which prevents
5190 the broken package from being configured while the breaking
5191 package is in the "Unpacked" state but allows both packages to
5192 be unpacked at the same time.
5196 If one package is to be unpacked, the other must be removed
5197 first. If the package being unpacked is marked as replacing
5198 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5199 normally be used in this case) the one on the system, or the one
5200 on the system is marked as deselected, or both packages are
5201 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5202 automatically remove the package which is causing the conflict.
5203 Otherwise, it will halt the installation of the new package with
5204 an error. This mechanism is specifically designed to produce an
5205 error when the installed package is <tt>Essential</tt>, but the
5210 A package will not cause a conflict merely because its
5211 configuration files are still installed; it must be at least
5216 A special exception is made for packages which declare a
5217 conflict with their own package name, or with a virtual
5218 package which they provide (see below): this does not
5219 prevent their installation, and allows a package to conflict
5220 with others providing a replacement for it. You use this
5221 feature when you want the package in question to be the only
5222 package providing some feature.
5226 Normally, <tt>Breaks</tt> should be used instead
5227 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5228 stronger restriction on the ordering of package installation or
5229 upgrade and can make it more difficult for the package manager
5230 to find a correct solution to an upgrade or installation
5231 problem. <tt>Breaks</tt> should be used
5233 <item>when moving a file from one package to another (see
5234 <ref id="replaces">),</item>
5235 <item>when splitting a package (a special case of the previous
5237 <item>when the breaking package exposes a bug in or interacts
5238 badly with particular versions of the broken
5241 <tt>Conflicts</tt> should be used
5243 <item>when two packages provide the same file and will
5244 continue to do so,</item>
5245 <item>in conjunction with <tt>Provides</tt> when only one
5246 package providing a given virtual facility may be unpacked
5247 at a time (see <ref id="virtual">),</item>
5248 <item>in other cases where one must prevent simultaneous
5249 installation of two packages for reasons that are ongoing
5250 (not fixed in a later version of one of the packages) or
5251 that must prevent both packages from being unpacked at the
5252 same time, not just configured.</item>
5254 Be aware that adding <tt>Conflicts</tt> is normally not the best
5255 solution when two packages provide the same files. Depending on
5256 the reason for that conflict, using alternatives or renaming the
5257 files is often a better approach. See, for
5258 example, <ref id="binaries">.
5262 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5263 unless two packages cannot be installed at the same time or
5264 installing them both causes one of them to be broken or
5265 unusable. Having similar functionality or performing the same
5266 tasks as another package is not sufficient reason to
5267 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5271 A <tt>Conflicts</tt> entry may have an "earlier than" version
5272 clause if the reason for the conflict is corrected in a later
5273 version of one of the packages. However, normally the presence
5274 of an "earlier than" version clause is a sign
5275 that <tt>Breaks</tt> should have been used instead. An "earlier
5276 than" version clause in <tt>Conflicts</tt>
5277 prevents <prgn>dpkg</prgn> from upgrading or installing the
5278 package which declares such a conflict until the upgrade or
5279 removal of the conflicted-with package has been completed, which
5280 is a strong restriction.
5284 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5288 As well as the names of actual ("concrete") packages, the
5289 package relationship fields <tt>Depends</tt>,
5290 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5291 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5292 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5293 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5294 may mention "virtual packages".
5298 A <em>virtual package</em> is one which appears in the
5299 <tt>Provides</tt> control field of another package. The effect
5300 is as if the package(s) which provide a particular virtual
5301 package name had been listed by name everywhere the virtual
5302 package name appears. (See also <ref id="virtual_pkg">)
5306 If there are both concrete and virtual packages of the same
5307 name, then the dependency may be satisfied (or the conflict
5308 caused) by either the concrete package with the name in
5309 question or any other concrete package which provides the
5310 virtual package with the name in question. This is so that,
5311 for example, supposing we have
5312 <example compact="compact">
5315 </example> and someone else releases an enhanced version of
5316 the <tt>bar</tt> package they can say:
5317 <example compact="compact">
5321 and the <tt>bar-plus</tt> package will now also satisfy the
5322 dependency for the <tt>foo</tt> package.
5326 If a relationship field has a version number attached, only real
5327 packages will be considered to see whether the relationship is
5328 satisfied (or the prohibition violated, for a conflict or
5329 breakage). In other words, if a version number is specified,
5330 this is a request to ignore all <tt>Provides</tt> for that
5331 package name and consider only real packages. The package
5332 manager will assume that a package providing that virtual
5333 package is not of the "right" version. A <tt>Provides</tt>
5334 field may not contain version numbers, and the version number of
5335 the concrete package which provides a particular virtual package
5336 will not be considered when considering a dependency on or
5337 conflict with the virtual package name.<footnote>
5338 It is possible that a future release of <prgn>dpkg</prgn> may
5339 add the ability to specify a version number for each virtual
5340 package it provides. This feature is not yet present,
5341 however, and is expected to be used only infrequently.
5346 To specify which of a set of real packages should be the default
5347 to satisfy a particular dependency on a virtual package, list
5348 the real package as an alternative before the virtual one.
5352 If the virtual package represents a facility that can only be
5353 provided by one real package at a time, such as
5354 the <package>mail-transport-agent</package> virtual package that
5355 requires installation of a binary that would conflict with all
5356 other providers of that virtual package (see
5357 <ref id="mail-transport-agents">), all packages providing that
5358 virtual package should also declare a conflict with it
5359 using <tt>Conflicts</tt>. This will ensure that at most one
5360 provider of that virtual package is unpacked or installed at a
5365 <sect id="replaces"><heading>Overwriting files and replacing
5366 packages - <tt>Replaces</tt></heading>
5369 Packages can declare in their control file that they should
5370 overwrite files in certain other packages, or completely replace
5371 other packages. The <tt>Replaces</tt> control field has these
5372 two distinct purposes.
5375 <sect1><heading>Overwriting files in other packages</heading>
5378 It is usually an error for a package to contain files which
5379 are on the system in another package. However, if the
5380 overwriting package declares that it <tt>Replaces</tt> the one
5381 containing the file being overwritten, then <prgn>dpkg</prgn>
5382 will replace the file from the old package with that from the
5383 new. The file will no longer be listed as "owned" by the old
5384 package and will be taken over by the new package.
5385 Normally, <tt>Breaks</tt> should be used in conjunction
5386 with <tt>Replaces</tt>.<footnote>
5387 To see why <tt>Breaks</tt> is normally needed in addition
5388 to <tt>Replaces</tt>, consider the case of a file in the
5389 package <package>foo</package> being taken over by the
5390 package <package>foo-data</package>.
5391 <tt>Replaces</tt> will allow <package>foo-data</package> to
5392 be installed and take over that file. However,
5393 without <tt>Breaks</tt>, nothing
5394 requires <package>foo</package> to be upgraded to a newer
5395 version that knows it does not include that file and instead
5396 depends on <package>foo-data</package>. Nothing would
5397 prevent the new <package>foo-data</package> package from
5398 being installed and then removed, removing the file that it
5399 took over from <package>foo</package>. After that
5400 operation, the package manager would think the system was in
5401 a consistent state, but the <package>foo</package> package
5402 would be missing one of its files.
5407 For example, if a package <package>foo</package> is split
5408 into <package>foo</package> and <package>foo-data</package>
5409 starting at version 1.2-3, <package>foo-data</package> would
5411 <example compact="compact">
5412 Replaces: foo (<< 1.2-3)
5413 Breaks: foo (<< 1.2-3)
5415 in its control file. The new version of the
5416 package <package>foo</package> would normally have the field
5417 <example compact="compact">
5418 Depends: foo-data (>= 1.2-3)
5420 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5421 the files moved into <package>foo-data</package> are not
5422 required for normal operation).
5426 If a package is completely replaced in this way, so that
5427 <prgn>dpkg</prgn> does not know of any files it still
5428 contains, it is considered to have "disappeared". It will
5429 be marked as not wanted on the system (selected for
5430 removal) and "Not-Installed". Any <tt>conffile</tt>s
5431 details noted for the package will be ignored, as they
5432 will have been taken over by the overwriting package. The
5433 package's <prgn>postrm</prgn> script will be run with a
5434 special argument to allow the package to do any final
5435 cleanup required. See <ref id="mscriptsinstact">.
5437 Replaces is a one way relationship. You have to install
5438 the replacing package after the replaced package.
5443 For this usage of <tt>Replaces</tt>, virtual packages (see
5444 <ref id="virtual">) are not considered when looking at a
5445 <tt>Replaces</tt> field. The packages declared as being
5446 replaced must be mentioned by their real names.
5450 This usage of <tt>Replaces</tt> only takes effect when both
5451 packages are at least partially on the system at once. It is
5452 not relevant if the packages conflict unless the conflict has
5457 <sect1><heading>Replacing whole packages, forcing their
5461 Second, <tt>Replaces</tt> allows the packaging system to
5462 resolve which package should be removed when there is a
5463 conflict (see <ref id="conflicts">). This usage only takes
5464 effect when the two packages <em>do</em> conflict, so that the
5465 two usages of this field do not interfere with each other.
5469 In this situation, the package declared as being replaced
5470 can be a virtual package, so for example, all mail
5471 transport agents (MTAs) would have the following fields in
5472 their control files:
5473 <example compact="compact">
5474 Provides: mail-transport-agent
5475 Conflicts: mail-transport-agent
5476 Replaces: mail-transport-agent
5478 ensuring that only one MTA can be unpacked at any one
5479 time. See <ref id="virtual"> for more information about this
5484 <sect id="sourcebinarydeps">
5485 <heading>Relationships between source and binary packages -
5486 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5487 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5491 Source packages that require certain binary packages to be
5492 installed or absent at the time of building the package
5493 can declare relationships to those binary packages.
5497 This is done using the <tt>Build-Depends</tt>,
5498 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5499 <tt>Build-Conflicts-Indep</tt> control fields.
5503 Build-dependencies on "build-essential" binary packages can be
5504 omitted. Please see <ref id="pkg-relations"> for more information.
5508 The dependencies and conflicts they define must be satisfied
5509 (as defined earlier for binary packages) in order to invoke
5510 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5512 There is no Build-Depends-Arch; this role is essentially
5513 met with Build-Depends. Anyone building the
5514 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5515 assumed to be building the whole package, and therefore
5516 installation of all build dependencies is required.
5519 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5520 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5521 not yet know how to check for its existence, and
5522 <tt>binary-arch</tt>. The purpose of the original split
5523 between <tt>Build-Depends</tt> and
5524 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5525 wouldn't need to install extra packages needed only for the
5526 binary-indep targets. But without a build-arch/build-indep
5527 split, this didn't work, since most of the work is done in
5528 the build target, not in the binary target.
5532 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5533 <tt>binary-arch</tt></tag>
5535 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5536 fields must be satisfied when these targets are invoked.
5538 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5539 and <tt>binary-indep</tt></tag>
5541 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5542 <tt>Build-Depends-Indep</tt>, and
5543 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5544 these targets are invoked.
5550 <sect id="built-using">
5551 <heading>Additional source packages used to build the binary
5552 - <tt>Built-Using</tt>
5556 Some binary packages incorporate parts of other packages when built
5557 but do not have to depend on those packages. Examples include
5558 linking with static libraries or incorporating source code from
5559 another package during the build. In this case, the source packages
5560 of those other packages are a required part of the complete source
5561 (the binary package is not reproducible without them).
5565 A <tt>Built-Using</tt> field must list the corresponding source
5566 package for any such binary package incorporated during the build
5568 <tt>Build-Depends</tt> in the source package is not adequate since
5569 it (rightfully) does not document the exact version used in the
5572 including an "exactly equal" ("=") version relation on the version
5573 that was used to build that binary package<footnote>
5574 The archive software might reject packages that refer to
5575 non-existent sources.
5580 A package using the source code from the gcc-4.6-source
5581 binary package built from the gcc-4.6 source package would
5582 have this field in its control file:
5583 <example compact="compact">
5584 Built-Using: gcc-4.6 (= 4.6.0-11)
5589 A package including binaries from grub2 and loadlin would
5590 have this field in its control file:
5591 <example compact="compact">
5592 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5599 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5602 Packages containing shared libraries must be constructed with
5603 a little care to make sure that the shared library is always
5604 available. This is especially important for packages whose
5605 shared libraries are vitally important, such as the C library
5606 (currently <tt>libc6</tt>).
5610 This section deals only with public shared libraries: shared
5611 libraries that are placed in directories searched by the dynamic
5612 linker by default or which are intended to be linked against
5613 normally and possibly used by other, independent packages. Shared
5614 libraries that are internal to a particular package or that are
5615 only loaded as dynamic modules are not covered by this section and
5616 are not subject to its requirements.
5620 A shared library is identified by the <tt>SONAME</tt> attribute
5621 stored in its dynamic section. When a binary is linked against a
5622 shared library, the <tt>SONAME</tt> of the shared library is
5623 recorded in the binary's <tt>NEEDED</tt> section so that the
5624 dynamic linker knows that library must be loaded at runtime. The
5625 shared library file's full name (which usually contains additional
5626 version information not needed in the <tt>SONAME</tt>) is
5627 therefore normally not referenced directly. Instead, the shared
5628 library is loaded by its <tt>SONAME</tt>, which exists on the file
5629 system as a symlink pointing to the full name of the shared
5630 library. This symlink must be provided by the
5631 package. <ref id="sharedlibs-runtime"> describes how to do this.
5633 This is a convention of shared library versioning, but not a
5634 requirement. Some libraries use the <tt>SONAME</tt> as the full
5635 library file name instead and therefore do not need a symlink.
5636 Most, however, encode additional information about
5637 backwards-compatible revisions as a minor version number in the
5638 file name. The <tt>SONAME</tt> itself only changes when
5639 binaries linked with the earlier version of the shared library
5640 may no longer work, but the filename may change with each
5641 release of the library. See <ref id="sharedlibs-runtime"> for
5647 When linking a binary or another shared library against a shared
5648 library, the <tt>SONAME</tt> for that shared library is not yet
5649 known. Instead, the shared library is found by looking for a file
5650 matching the library name with <tt>.so</tt> appended. This file
5651 exists on the file system as a symlink pointing to the shared
5656 Shared libraries are normally split into several binary packages.
5657 The <tt>SONAME</tt> symlink is installed by the runtime shared
5658 library package, and the bare <tt>.so</tt> symlink is installed in
5659 the development package since it's only used when linking binaries
5660 or shared libraries. However, there are some exceptions for
5661 unusual shared libraries or for shared libraries that are also
5662 loaded as dynamic modules by other programs.
5666 This section is primarily concerned with how the separation of
5667 shared libraries into multiple packages should be done and how
5668 dependencies on and between shared library binary packages are
5669 managed in Debian. <ref id="libraries"> should be read in
5670 conjunction with this section and contains additional rules for
5671 the files contained in the shared library packages.
5674 <sect id="sharedlibs-runtime">
5675 <heading>Run-time shared libraries</heading>
5678 The run-time shared library must be placed in a package
5679 whose name changes whenever the <tt>SONAME</tt> of the shared
5680 library changes. This allows several versions of the shared
5681 library to be installed at the same time, allowing installation
5682 of the new version of the shared library without immediately
5683 breaking binaries that depend on the old version. Normally, the
5684 run-time shared library and its <tt>SONAME</tt> symlink should
5685 be placed in a package named
5686 <package><var>libraryname</var><var>soversion</var></package>,
5687 where <var>soversion</var> is the version number in
5688 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5689 would be confusing to directly append <var>soversion</var>
5690 to <var>libraryname</var> (if, for
5691 example, <var>libraryname</var> itself ends in a number), you
5693 <package><var>libraryname</var>-<var>soversion</var></package>
5698 To determine the <var>soversion</var>, look at
5699 the <tt>SONAME</tt> of the library, stored in the
5700 ELF <tt>SONAME</tt> attribute. It is usually of the
5701 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5702 example, <tt>libz.so.1</tt>). The version part is the part
5703 which comes after <tt>.so.</tt>, so in that example it
5704 is <tt>1</tt>. The soname may instead be of the
5705 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5706 as <tt>libdb-5.1.so</tt>, in which case the name would
5707 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5711 If you have several shared libraries built from the same source
5712 tree, you may lump them all together into a single shared
5713 library package provided that all of their <tt>SONAME</tt>s will
5714 always change together. Be aware that this is not normally the
5715 case, and if the <tt>SONAME</tt>s do not change together,
5716 upgrading such a merged shared library package will be
5717 unnecessarily difficult because of file conflicts with the old
5718 version of the package. When in doubt, always split shared
5719 library packages so that each binary package installs a single
5724 Every time the shared library ABI changes in a way that may
5725 break binaries linked against older versions of the shared
5726 library, the <tt>SONAME</tt> of the library and the
5727 corresponding name for the binary package containing the runtime
5728 shared library should change. Normally, this means
5729 the <tt>SONAME</tt> should change any time an interface is
5730 removed from the shared library or the signature of an interface
5731 (the number of parameters or the types of parameters that it
5732 takes, for example) is changed. This practice is vital to
5733 allowing clean upgrades from older versions of the package and
5734 clean transitions between the old ABI and new ABI without having
5735 to upgrade every affected package simultaneously.
5739 The <tt>SONAME</tt> and binary package name need not, and indeed
5740 normally should not, change if new interfaces are added but none
5741 are removed or changed, since this will not break binaries
5742 linked against the old shared library. Correct versioning of
5743 dependencies on the newer shared library by binaries that use
5744 the new interfaces is handled via
5745 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5746 or <tt>shlibs</tt> system</qref>.
5750 The package should install the shared libraries under
5751 their normal names. For example, the <package>libgdbm3</package>
5752 package should install <file>libgdbm.so.3.0.0</file> as
5753 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5754 renamed or re-linked by any <prgn>prerm</prgn> or
5755 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5756 of renaming things safely without affecting running programs,
5757 and attempts to interfere with this are likely to lead to
5762 Shared libraries should not be installed executable, since
5763 the dynamic linker does not require this and trying to
5764 execute a shared library usually results in a core dump.
5768 The run-time library package should include the symbolic link for
5769 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5770 the shared libraries. For example,
5771 the <package>libgdbm3</package> package should include a symbolic
5772 link from <file>/usr/lib/libgdbm.so.3</file> to
5773 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5774 linker (for example <prgn>ld.so</prgn> or
5775 <prgn>ld-linux.so.*</prgn>) can find the library between the
5776 time that <prgn>dpkg</prgn> installs it and the time that
5777 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5779 The package management system requires the library to be
5780 placed before the symbolic link pointing to it in the
5781 <file>.deb</file> file. This is so that when
5782 <prgn>dpkg</prgn> comes to install the symlink
5783 (overwriting the previous symlink pointing at an older
5784 version of the library), the new shared library is already
5785 in place. In the past, this was achieved by creating the
5786 library in the temporary packaging directory before
5787 creating the symlink. Unfortunately, this was not always
5788 effective, since the building of the tar file in the
5789 <file>.deb</file> depended on the behavior of the underlying
5790 file system. Some file systems (such as reiserfs) reorder
5791 the files so that the order of creation is forgotten.
5792 Since version 1.7.0, <prgn>dpkg</prgn>
5793 reorders the files itself as necessary when building a
5794 package. Thus it is no longer important to concern
5795 oneself with the order of file creation.
5799 <sect1 id="ldconfig">
5800 <heading><tt>ldconfig</tt></heading>
5803 Any package installing shared libraries in one of the default
5804 library directories of the dynamic linker (which are currently
5805 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5806 listed in <file>/etc/ld.so.conf</file><footnote>
5807 These are currently <file>/usr/local/lib</file> plus
5808 directories under <file>/lib</file> and <file>/usr/lib</file>
5809 matching the multiarch triplet for the system architecture.
5811 must use <prgn>ldconfig</prgn> to update the shared library
5816 The package maintainer scripts must only call
5817 <prgn>ldconfig</prgn> under these circumstances:
5818 <list compact="compact">
5819 <item>When the <prgn>postinst</prgn> script is run with a
5820 first argument of <tt>configure</tt>, the script must call
5821 <prgn>ldconfig</prgn>, and may optionally invoke
5822 <prgn>ldconfig</prgn> at other times.
5824 <item>When the <prgn>postrm</prgn> script is run with a
5825 first argument of <tt>remove</tt>, the script should call
5826 <prgn>ldconfig</prgn>.
5831 During install or upgrade, the preinst is called before
5832 the new files are unpacked, so calling "ldconfig" is
5833 pointless. The preinst of an existing package can also be
5834 called if an upgrade fails. However, this happens during
5835 the critical time when a shared libs may exist on-disk
5836 under a temporary name. Thus, it is dangerous and
5837 forbidden by current policy to call "ldconfig" at this
5842 When a package is installed or upgraded, "postinst
5843 configure" runs after the new files are safely on-disk.
5844 Since it is perfectly safe to invoke ldconfig
5845 unconditionally in a postinst, it is OK for a package to
5846 simply put ldconfig in its postinst without checking the
5847 argument. The postinst can also be called to recover from
5848 a failed upgrade. This happens before any new files are
5849 unpacked, so there is no reason to call "ldconfig" at this
5854 For a package that is being removed, prerm is
5855 called with all the files intact, so calling ldconfig is
5856 useless. The other calls to "prerm" happen in the case of
5857 upgrade at a time when all the files of the old package
5858 are on-disk, so again calling "ldconfig" is pointless.
5862 postrm, on the other hand, is called with the "remove"
5863 argument just after the files are removed, so this is
5864 the proper time to call "ldconfig" to notify the system
5865 of the fact that the shared libraries from the package
5866 are removed. The postrm can be called at several other
5867 times. At the time of "postrm purge", "postrm
5868 abort-install", or "postrm abort-upgrade", calling
5869 "ldconfig" is useless because the shared lib files are
5870 not on-disk. However, when "postrm" is invoked with
5871 arguments "upgrade", "failed-upgrade", or "disappear", a
5872 shared lib may exist on-disk under a temporary filename.
5880 <sect id="sharedlibs-support-files">
5881 <heading>Shared library support files</heading>
5884 If your package contains files whose names do not change with
5885 each change in the library shared object version, you must not
5886 put them in the shared library package. Otherwise, several
5887 versions of the shared library cannot be installed at the same
5888 time without filename clashes, making upgrades and transitions
5889 unnecessarily difficult.
5893 It is recommended that supporting files and run-time support
5894 programs that do not need to be invoked manually by users, but
5895 are nevertheless required for the package to function, be placed
5896 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5897 preferably under <file>/usr/lib/</file><var>package-name</var>.
5898 If the program or file is architecture independent, the
5899 recommendation is for it to be placed in a subdirectory of
5900 <file>/usr/share</file> instead, preferably under
5901 <file>/usr/share/</file><var>package-name</var>. Following the
5902 <var>package-name</var> naming convention ensures that the file
5903 names change when the shared object version changes.
5907 Run-time support programs that use the shared library but are
5908 not required for the library to function or files used by the
5909 shared library that can be used by any version of the shared
5910 library package should instead be put in a separate package.
5911 This package might typically be named
5912 <package><var>libraryname</var>-tools</package>; note the
5913 absence of the <var>soversion</var> in the package name.
5917 Files and support programs only useful when compiling software
5918 against the library should be included in the development
5919 package for the library.<footnote>
5920 For example, a <file><var>package-name</var>-config</file>
5921 script or <package>pkg-config</package> configuration files.
5926 <sect id="sharedlibs-static">
5927 <heading>Static libraries</heading>
5930 The static library (<file><var>libraryname.a</var></file>)
5931 is usually provided in addition to the shared version.
5932 It is placed into the development package (see below).
5936 In some cases, it is acceptable for a library to be
5937 available in static form only; these cases include:
5939 <item>libraries for languages whose shared library support
5940 is immature or unstable</item>
5941 <item>libraries whose interfaces are in flux or under
5942 development (commonly the case when the library's
5943 major version number is zero, or where the ABI breaks
5944 across patchlevels)</item>
5945 <item>libraries which are explicitly intended to be
5946 available only in static form by their upstream
5951 <sect id="sharedlibs-dev">
5952 <heading>Development files</heading>
5955 If there are development files associated with a shared library,
5956 the source package needs to generate a binary development package
5957 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5958 or if you prefer only to support one development version at a
5959 time, <package><var>libraryname</var>-dev</package>. Installing
5960 the development package must result in installation of all the
5961 development files necessary for compiling programs against that
5962 shared library.<footnote>
5963 This wording allows the development files to be split into
5964 several packages, such as a separate architecture-independent
5965 <package><var>libraryname</var>-headers</package>, provided that
5966 the development package depends on all the required additional
5972 In case several development versions of a library exist, you may
5973 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5974 <ref id="conflicts">) to ensure that the user only installs one
5975 development version at a time (as different development versions are
5976 likely to have the same header files in them, which would cause a
5977 filename clash if both were unpacked).
5981 The development package should contain a symlink for the associated
5982 shared library without a version number. For example, the
5983 <package>libgdbm-dev</package> package should include a symlink
5984 from <file>/usr/lib/libgdbm.so</file> to
5985 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5986 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5987 <file>libgdbm.so</file> when compiling dynamically.
5991 If the package provides Ada Library Information
5992 (<file>*.ali</file>) files for use with GNAT, these files must be
5993 installed read-only (mode 0444) so that GNAT will not attempt to
5994 recompile them. This overrides the normal file mode requirements
5995 given in <ref id="permissions-owners">.
5999 <sect id="sharedlibs-intradeps">
6000 <heading>Dependencies between the packages of the same library</heading>
6003 Typically the development version should have an exact
6004 version dependency on the runtime library, to make sure that
6005 compilation and linking happens correctly. The
6006 <tt>${binary:Version}</tt> substitution variable can be
6007 useful for this purpose.
6009 Previously, <tt>${Source-Version}</tt> was used, but its name
6010 was confusing and it has been deprecated since dpkg 1.13.19.
6015 <sect id="sharedlibs-depends">
6016 <heading>Dependencies between the library and other
6020 If a package contains a binary or library which links to a
6021 shared library, we must ensure that, when the package is
6022 installed on the system, all of the libraries needed are also
6023 installed. These dependencies must be added to the binary
6024 package when it is built, since they may change based on which
6025 version of a shared library the binary or library was linked
6026 with even if there are no changes to the source of the binary
6027 (for example, symbol versions change, macros become functions or
6028 vice versa, or the binary package may determine at compile-time
6029 whether new library interfaces are available and can be called).
6030 To allow these dependencies to be constructed, shared libraries
6031 must provide either a <file>symbols</file> file or
6032 a <file>shlibs</file> file. These provide information on the
6033 package dependencies required to ensure the presence of
6034 interfaces provided by this library. Any package with binaries
6035 or libraries linking to a shared library must use these files to
6036 determine the required dependencies when it is built. Other
6037 packages which use a shared library (for example using
6038 <tt>dlopen()</tt>) should compute appropriate dependencies
6039 using these files at build time as well.
6043 The two mechanisms differ in the degree of detail that they
6044 provide. A <file>symbols</file> file documents, for each symbol
6045 exported by a library, the minimal version of the package any
6046 binary using this symbol will need. This is typically the
6047 version of the package in which the symbol was introduced. This
6048 information permits detailed analysis of the symbols used by a
6049 particular package and construction of an accurate dependency,
6050 but it requires the package maintainer to track more information
6051 about the shared library.
6055 A <file>shlibs</file> file, in contrast, only documents the last
6056 time the library ABI changed in any way. It only provides
6057 information about the library as a whole, not individual
6058 symbols. When a package is built using a shared library with
6059 only a <file>shlibs</file> file, the generated dependency will
6060 require a version of the shared library equal to or newer than
6061 the version of the last ABI change. This generates
6062 unnecessarily restrictive dependencies compared
6063 to <file>symbols</file> files if none of the symbols used by the
6064 package have changed. This, in turn, may make upgrades
6065 needlessly complex and unnecessarily restrict use of the package
6066 on systems with older versions of the shared libraries.
6070 <file>shlibs</file> files also only support a limited range of
6071 library SONAMEs, making it difficult to use <file>shlibs</file>
6072 files in some unusual corner cases.<footnote>
6073 A <file>shlibs</file> file represents an SONAME as a library
6074 name and version number, such as <tt>libfoo VERSION</tt>,
6075 instead of recording the actual SONAME. If the SONAME doesn't
6076 match one of the two expected formats
6077 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6078 cannot be represented.
6083 <file>symbols</file> files are therefore recommended for most
6084 shared library packages since they provide more accurate
6085 dependencies. For most C libraries, the additional detail
6086 required by <file>symbols</file> files is not too difficult to
6087 maintain. However, maintaining exhaustive symbols information
6088 for a C++ library can be quite onerous, so <file>shlibs</file>
6089 files may be more appropriate for most C++ libraries. Libraries
6090 with a corresponding udeb must also provide
6091 a <file>shlibs</file> file, since the udeb infrastructure does
6092 not use <file>symbols</file> files.
6095 <sect1 id="dpkg-shlibdeps">
6096 <heading>Generating dependencies on shared libraries</heading>
6099 When a package that contains any shared libraries or compiled
6100 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6101 each shared library and compiled binary to determine the
6102 libraries used and hence the dependencies needed by the
6104 <prgn>dpkg-shlibdeps</prgn> will use a program
6105 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6106 the libraries and the symbols in those libraries directly
6107 needed by the binaries or shared libraries in the package.
6109 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6110 your <file>debian/rules</file> file in the source package.
6111 List all of the compiled binaries, libraries, or loadable
6112 modules in your package.<footnote>
6113 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6114 correctly is to use a package helper framework such
6115 as <package>debhelper</package>. If you are
6116 using <package>debhelper</package>,
6117 the <prgn>dh_shlibdeps</prgn> program will do this work for
6118 you. It will also correctly handle multi-binary packages.
6120 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6121 or <file>shlibs</file> files installed by the shared libraries
6122 to generate dependency information. The package must then
6123 provide a substitution variable into which the discovered
6124 dependency information can be placed.
6128 If you are creating a udeb for use in the Debian Installer,
6129 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6130 should use the dependency line of type <tt>udeb</tt> by adding
6131 the <tt>-tudeb</tt> option<footnote>
6132 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6133 will automatically add this option if it knows it is
6135 </footnote>. If there is no dependency line of
6136 type <tt>udeb</tt> in the <file>shlibs</file>
6137 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6138 regular dependency line.
6142 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6143 into the <file>debian/substvars</file> file by default, which
6144 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6145 to place a <tt>${shlibs:Depends}</tt> variable in
6146 the <tt>Depends</tt> field in the control file of every binary
6147 package built by this source package that contains compiled
6148 binaries, libraries, or loadable modules. If you have
6149 multiple binary packages, you will need to
6150 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6151 compiled libraries or binaries. For example, you could use
6152 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6153 specify a different <file>substvars</file> file for each
6154 binary package.<footnote>
6155 Again, <prgn>dh_shlibdeps</prgn>
6156 and <prgn>dh_gencontrol</prgn> will handle everything except
6157 the addition of the variable to the control file for you if
6158 you're using <package>debhelper</package>, including
6159 generating separate <file>substvars</file> files for each
6160 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6161 the appropriate flags.
6166 For more details on <prgn>dpkg-shlibdeps</prgn>,
6167 see <manref name="dpkg-shlibdeps" section="1">.
6171 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6172 library <tt>libbar</tt> if it is explicitly linked with that
6173 library (that is, the library is listed in the
6174 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6175 to the link line when the binary is created). Other libraries
6176 that are needed by <tt>libbar</tt> are
6177 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6178 linker will load them automatically when it
6179 loads <tt>libbar</tt>. A package should depend on the
6180 libraries it directly uses, but not the libraries it only uses
6181 indirectly. The dependencies for the libraries used
6182 directly will automatically pull in the indirectly-used
6183 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6184 automatically, but package maintainers need to be aware of
6185 this distinction between directly and indirectly using a
6186 library if they have to override its results for some reason.
6188 A good example of where this helps is the following. We
6189 could update <tt>libimlib</tt> with a new version that
6190 supports a new revision of a graphics format called dgf (but
6191 retaining the same major version number) and depends on a
6192 new library package <package>libdgf4</package> instead of
6193 the older <package>libdgf3</package>. If we
6194 used <prgn>ldd</prgn> to add dependencies for every library
6195 directly or indirectly linked with a binary, every package
6196 that uses <tt>libimlib</tt> would need to be recompiled so
6197 it would also depend on <package>libdgf4</package> in order
6198 to retire the older <package>libdgf3</package> package.
6199 Since dependencies are only added based on
6200 ELF <tt>NEEDED</tt> attribute, packages
6201 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6202 having the dependency on an appropriate version
6203 of <tt>libdgf</tt> and do not need rebuilding.
6208 <sect1 id="sharedlibs-updates">
6209 <heading>Shared library ABI changes</heading>
6212 Maintaining a shared library package using
6213 either <file>symbols</file> or <file>shlibs</file> files
6214 requires being aware of the exposed ABI of the shared library
6215 and any changes to it. Both <file>symbols</file>
6216 and <file>shlibs</file> files record every change to the ABI
6217 of the shared library; <file>symbols</file> files do so per
6218 public symbol, whereas <file>shlibs</file> files record only
6219 the last change for the entire library.
6223 There are two types of ABI changes: ones that are
6224 backward-compatible and ones that are not. An ABI change is
6225 backward-compatible if any reasonable program or library that
6226 was linked with the previous version of the shared library
6227 will still work correctly with the new version of the shared
6229 An example of an "unreasonable" program is one that uses
6230 library interfaces that are documented as internal and
6231 unsupported. If the only programs or libraries affected by
6232 a change are "unreasonable" ones, other techniques, such as
6233 declaring <tt>Breaks</tt> relationships with affected
6234 packages or treating their usage of the library as bugs in
6235 those packages, may be appropriate instead of changing the
6236 SONAME. However, the default approach is to change the
6237 SONAME for any change to the ABI that could break a program.
6239 Adding new symbols to the shared library is a
6240 backward-compatible change. Removing symbols from the shared
6241 library is not. Changing the behavior of a symbol may or may
6242 not be backward-compatible depending on the change; for
6243 example, changing a function to accept a new enum constant not
6244 previously used by the library is generally
6245 backward-compatible, but changing the members of a struct that
6246 is passed into library functions is generally not unless the
6247 library takes special precautions to accept old versions of
6252 ABI changes that are not backward-compatible normally require
6253 changing the <tt>SONAME</tt> of the library and therefore the
6254 shared library package name, which forces rebuilding all
6255 packages using that shared library to update their
6256 dependencies and allow them to use the new version of the
6257 shared library. For more information,
6258 see <ref id="sharedlibs-runtime">. The remainder of this
6259 section will deal with backward-compatible changes.
6263 Backward-compatible changes require either updating or
6264 recording the <var>minimal-version</var> for that symbol
6265 in <file>symbols</file> files or updating the version in
6266 the <var>dependencies</var> in <file>shlibs</file> files. For
6267 more information on how to do this in the two formats, see
6268 <ref id="symbols"> and <ref id="shlibs">. Below are general
6269 rules that apply to both files.
6273 The easy case is when a public symbol is added. Simply add
6274 the version at which the symbol was introduced
6275 (for <file>symbols</file> files) or update the dependency
6276 version (for <file>shlibs</file>) files. But special care
6277 should be taken to update dependency versions when the
6278 behavior of a public symbol changes. This is easy to neglect,
6279 since there is no automated method of determining such
6280 changes, but failing to update versions in this case may
6281 result in binary packages with too-weak dependencies that will
6282 fail at runtime, possibly in ways that can cause security
6283 vulnerabilities. If the package maintainer believes that a
6284 symbol behavior change may have occurred but isn't sure, it's
6285 safer to update the version rather than leave it unmodified.
6286 This may result in unnecessarily strict dependencies, but it
6287 ensures that packages whose dependencies are satisfied will
6292 A common example of when a change to the dependency version
6293 is required is a function that takes an enum or struct
6294 argument that controls what the function does. For example:
6296 enum library_op { OP_FOO, OP_BAR };
6297 int library_do_operation(enum library_op);
6299 If a new operation, <tt>OP_BAZ</tt>, is added,
6300 the <var>minimal-version</var>
6301 of <tt>library_do_operation</tt> (for <file>symbols</file>
6302 files) or the version in the dependency for the shared library
6303 (for <file>shlibs</file> files) must be increased to the
6304 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6305 binary built against the new version of the library (having
6306 detected at compile-time that the library
6307 supports <tt>OP_BAZ</tt>) may be installed with a shared
6308 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6309 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6314 Dependency versions in either <file>symbols</file>
6315 or <file>shlibs</file> files normally should not contain the
6316 Debian revision of the package, since the library behavior is
6317 normally fixed for a particular upstream version and any
6318 Debian packaging of that upstream version will have the same
6319 behavior. In the rare case that the library behavior was
6320 changed in a particular Debian revision, appending <tt>~</tt>
6321 to the end of the version that includes the Debian revision is
6322 recommended, since this allows backports of the shared library
6323 package using the normal backport versioning convention to
6324 satisfy the dependency.
6328 <sect1 id="sharedlibs-symbols">
6329 <heading>The <tt>symbols</tt> system</heading>
6332 In the following sections, we will first describe where the
6333 various <file>symbols</file> files are to be found, then
6334 the <file>symbols</file> file format, and finally how to
6335 create <file>symbols</file> files if your package contains a
6339 <sect2 id="symbols-paths">
6340 <heading>The <file>symbols</file> files present on the
6344 <file>symbols</file> files for a shared library are normally
6345 provided by the shared library package as a control file,
6346 but there are several override paths that are checked first
6347 in case that information is wrong or missing. The following
6348 list gives them in the order in which they are read
6349 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6350 the required information is used.
6353 <p><file>debian/*/DEBIAN/symbols</file></p>
6356 During the package build, if the package itself
6357 contains shared libraries with <file>symbols</file>
6358 files, they will be generated in these staging
6359 directories by <prgn>dpkg-gensymbols</prgn>
6360 (see <ref id="providing-symbols">). <file>symbols</file>
6361 files found in the build tree take precedence
6362 over <file>symbols</file> files from other binary
6367 These files must exist
6368 before <prgn>dpkg-shlibdeps</prgn> is run or the
6369 dependencies of binaries and libraries from a source
6370 package on other libraries from that same source
6371 package will not be correct. In practice, this means
6372 that <prgn>dpkg-gensymbols</prgn> must be run
6373 before <prgn>dpkg-shlibdeps</prgn> during the package
6375 An example may clarify. Suppose the source
6376 package <tt>foo</tt> generates two binary
6377 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6378 When building the binary packages, the contents of
6379 the packages are staged in the
6380 directories <file>debian/libfoo2</file>
6381 and <file>debian/foo-runtime</file> respectively.
6382 (<file>debian/tmp</file> could be used instead of
6383 one of these.) Since <tt>libfoo2</tt> provides
6384 the <tt>libfoo</tt> shared library, it will contain
6385 a <tt>symbols</tt> file, which will be installed
6386 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6387 eventually to be included as a control file in that
6388 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6390 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6392 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6393 to determine whether <tt>foo-prog</tt>'s library
6394 dependencies are satisfied by any of the libraries
6395 provided by <tt>libfoo2</tt>. Since those binaries
6396 were linked against the just-built shared library as
6397 part of the build process, the <file>symbols</file>
6398 file for the newly-built <tt>libfoo2</tt> must take
6399 precedence over a <file>symbols</file> file for any
6400 other <tt>libfoo2</tt> package already installed on
6408 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6409 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6413 Per-system overrides of shared library dependencies.
6414 These files normally do not exist. They are
6415 maintained by the local system administrator and must
6416 not be created by any Debian package.
6421 <p><file>symbols</file> control files for packages
6422 installed on the system</p>
6425 The <file>symbols</file> control files for all the
6426 packages currently installed on the system are
6427 searched last. This will be the most common source of
6428 shared library dependency information. These are
6430 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6431 packages should not rely on this and instead should
6432 use <tt>dpkg-query --control-path <var>package</var>
6433 symbols</tt> if for some reason these files need to be
6441 Be aware that if a <file>debian/shlibs.local</file> exists
6442 in the source package, it will override
6443 any <file>symbols</file> files. This is the only case where
6444 a <file>shlibs</file> is used despite <file>symbols</file>
6445 files being present. See <ref id="shlibs-paths">
6446 and <ref id="sharedlibs-shlibdeps"> for more information.
6450 <sect2 id="symbols">
6451 <heading>The <file>symbols</file> File Format</heading>
6454 The following documents the format of
6455 the <file>symbols</file> control file as included in binary
6456 packages. These files are built from
6457 template <file>symbols</file> files in the source package
6458 by <prgn>dpkg-gensymbols</prgn>. The template files support
6459 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6460 do some of the tedious work involved in
6461 maintaining <file>symbols</file> files, such as handling C++
6462 symbols or optional symbols that may not exist on particular
6463 architectures. When writing <file>symbols</file> files for
6464 a shared library package, refer
6465 to <manref name="dpkg-gensymbols" section="1"> for the
6470 A <file>symbols</file> may contain one or more entries, one
6471 for each shared library contained in the package
6472 corresponding to that <file>symbols</file>. Each entry has
6473 the following format:
6478 <var>library-soname</var> <var>main-dependency-template</var>
6479 [| <var>alternative-dependency-template</var>]
6481 [* <var>field-name</var>: <var>field-value</var>]
6483 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6488 To explain this format, we'll use the the <tt>zlib1g</tt>
6489 package as an example, which (at the time of writing)
6491 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6492 lines will be described first, followed by optional lines.
6496 <var>library-soname</var> must contain exactly the value of
6497 the ELF <tt>SONAME</tt> attribute of the shared library. In
6498 our example, this is <tt>libz.so.1</tt>.<footnote>
6499 This can be determined by using the command
6500 <example compact="compact">
6501 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6507 <var>main-dependency-template</var> has the same syntax as a
6508 dependency field in a binary package control file, except
6509 that the string <tt>#MINVER#</tt> is replaced by a version
6510 restriction like <tt>(>= <var>version</var>)</tt> or by
6511 nothing if an unversioned dependency is deemed sufficient.
6512 The version restriction will be based on which symbols from
6513 the shared library are referenced and the version at which
6514 they were introduced (see below). In nearly all
6515 cases, <var>main-dependency-template</var> will
6516 be <tt><var>package</var> #MINVER#</tt>,
6517 where <var>package</var> is the name of the binary package
6518 containing the shared library. This adds a simple,
6519 possibly-versioned dependency on the shared library package.
6520 In some rare cases, such as when multiple packages provide
6521 the same shared library ABI, the dependency template may
6522 need to be more complex.
6526 In our example, the first line of
6527 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6528 <example compact="compact">
6529 libz.so.1 zlib1g #MINVER#
6534 Each public symbol exported by the shared library must have
6535 a corresponding symbol line, indented by one
6536 space. <var>symbol</var> is the exported symbol (which, for
6537 C++, means the mangled symbol) followed by <tt>@</tt> and
6538 the symbol version, or the string <tt>Base</tt> if there is
6539 no symbol version. <var>minimal-version</var> is the most
6540 recent version of the shared library that changed the
6541 behavior of that symbol, whether by adding it, changing its
6542 function signature (the parameters, their types, or the
6543 return type), or changing its behavior in a way that is
6544 visible to a caller.
6545 <var>id-of-dependency-template</var> is an optional
6546 field that references
6547 an <var>alternative-dependency-template</var>; see below for
6552 For example, <tt>libz.so.1</tt> contains the
6553 symbols <tt>compress</tt>
6554 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6555 version and last changed its behavior in upstream
6556 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6557 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6558 upstream version <tt>1:1.2.0</tt>, and has not changed its
6559 behavior. Its <file>symbols</file> file therefore contains
6561 <example compact="compact">
6562 compress@Base 1:1.1.4
6563 compressBound@ZLIB_1.2.0 1:1.2.0
6565 Packages using only <tt>compress</tt> would then get a
6566 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6567 using <tt>compressBound</tt> would get a dependency
6568 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6572 One or more <var>alternative-dependency-template</var> lines
6573 may be provided. These are used in cases where some symbols
6574 in the shared library should use one dependency template
6575 while others should use a different template. The
6576 alternative dependency templates are used only if a symbol
6577 line contains the <var>id-of-dependency-template</var>
6578 field. The first alternative dependency template is
6579 numbered 1, the second 2, and so forth.<footnote>
6580 An example of where this may be needed is with a library
6581 that implements the libGL interface. All GL
6582 implementations provide the same set of base interfaces,
6583 and then may provide some additional interfaces only used
6584 by programs that require that specific GL implementation.
6585 So, for example, libgl1-mesa-glx may use the
6586 following <file>symbols</file> file:
6589 | libgl1-mesa-glx #MINVER#
6590 publicGlSymbol@Base 6.3-1
6592 implementationSpecificSymbol@Base 6.5.2-7 1
6595 Binaries or shared libraries using
6596 only <tt>publicGlSymbol</tt> would depend only
6597 on <tt>libgl1</tt> (which may be provided by multiple
6599 using <tt>implementationSpecificSymbol</tt> would get a
6600 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6605 Finally, the entry for the library may contain one or more
6606 metadata fields. Currently, the only
6607 supported <var>field-name</var>
6608 is <tt>Build-Depends-Package</tt>, whose value lists
6609 the <qref id="sharedlibs-dev">library development
6610 package</qref> on which packages using this shared library
6611 declare a build dependency. If this field is
6612 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6613 the resulting binary package dependency on the shared
6614 library is at least as strict as the source package
6615 dependency on the shared library development
6617 This field should normally not be necessary, since if the
6618 behavior of any symbol has changed, the corresponding
6619 symbol <var>minimal-version</var> should have been
6620 increased. But including it makes the <tt>symbols</tt>
6621 system more robust by tightening the dependency in cases
6622 where the package using the shared library specifically
6623 requires at least a particular version of the shared
6624 library development package for some reason.
6626 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6628 <example compact="compact">
6629 * Build-Depends-Package: zlib1g-dev
6634 Also see <manref name="deb-symbols" section="5">.
6638 <sect2 id="providing-symbols">
6639 <heading>Providing a <file>symbols</file> file</heading>
6642 If your package provides a shared library, you should
6643 arrange to include a <file>symbols</file> control file
6644 following the format described above in that package. You
6645 must include either a <file>symbols</file> control file or
6646 a <file>shlibs</file> control file.
6650 Normally, this is done by creating a <file>symbols</file> in
6652 named <file>debian/<var>package</var>.symbols</file>
6653 or <file>debian/symbols</file>, possibly
6654 with <file>.<var>arch</var></file> appended if the symbols
6655 information varies by architecture. This file may use the
6656 extended syntax documented in <manref name="dpkg-gensymbols"
6657 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6658 part of the package build process. It will
6659 create <file>symbols</file> files in the package staging
6660 area based on the binaries and libraries in the package
6661 staging area and the <file>symbols</file> files in the
6662 source package.<footnote>
6664 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6665 take care of calling either <prgn>dpkg-gensymbols</prgn>
6666 or generating a <file>shlibs</file> file as appropriate.
6671 Packages that provide <file>symbols</file> files must keep
6672 them up-to-date to ensure correct dependencies in packages
6673 that use the shared libraries. This means updating
6674 the <file>symbols</file> file whenever a new public symbol
6675 is added, changing the <var>minimal-version</var> field
6676 whenever a symbol changes behavior or signature in a
6677 backward-compatible way (see <ref id="sharedlibs-updates">),
6678 and changing the <var>library-soname</var>
6679 and <var>main-dependency-template</var>, and probably all of
6680 the <var>minimal-version</var> fields, when the library
6681 changes <tt>SONAME</tt>. Removing a public symbol from
6682 the <file>symbols</file> file because it's no longer
6683 provided by the library normally requires changing
6684 the <tt>SONAME</tt> of the library.
6685 See <ref id="sharedlibs-runtime"> for more information
6686 on <tt>SONAME</tt>s.
6691 <sect1 id="sharedlibs-shlibdeps">
6692 <heading>The <tt>shlibs</tt> system</heading>
6695 The <tt>shlibs</tt> system is a simpler alternative to
6696 the <tt>symbols</tt> system for declaring dependencies for
6697 shared libraries. It may be more appropriate for C++
6698 libraries and other cases where tracking individual symbols is
6699 too difficult. It predated the <tt>symbols</tt> system and is
6700 therefore frequently seen in older packages. It is also
6701 required for udebs, which do not support <tt>symbols</tt>.
6705 In the following sections, we will first describe where the
6706 various <file>shlibs</file> files are to be found, then how to
6707 use <prgn>dpkg-shlibdeps</prgn>, and finally
6708 the <file>shlibs</file> file format and how to create them.
6711 <sect2 id="shlibs-paths">
6712 <heading>The <file>shlibs</file> files present on the
6716 There are several places where <tt>shlibs</tt> files are
6717 found. The following list gives them in the order in which
6718 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6719 one which gives the required information is used.)
6722 <p><file>debian/shlibs.local</file></p>
6725 This lists overrides for this package. This file
6726 should normally not be used, but may be needed
6727 temporarily in unusual situations to work around bugs
6728 in other packages, or in unusual cases where the
6729 normally declared dependency information in the
6730 installed <file>shlibs</file> file for a library
6731 cannot be used. This file overrides information
6732 obtained from any other source.
6737 <p><file>/etc/dpkg/shlibs.override</file></p>
6740 This lists global overrides. This list is normally
6741 empty. It is maintained by the local system
6747 <p><file>DEBIAN/shlibs</file> files in the "build
6751 These files are generated as part of the package build
6752 process and staged for inclusion as control files in
6753 the binary packages being built. They provide details
6754 of any shared libraries included in the same package.
6759 <p><file>shlibs</file> control files for packages
6760 installed on the system</p>
6763 The <file>shlibs</file> control files for all the
6764 packages currently installed on the system. These are
6766 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6767 packages should not rely on this and instead should
6768 use <tt>dpkg-query --control-path <var>package</var>
6769 shlibs</tt> if for some reason these files need to be
6775 <p><file>/etc/dpkg/shlibs.default</file></p>
6778 This file lists any shared libraries whose packages
6779 have failed to provide correct <file>shlibs</file>
6780 files. It was used when the <file>shlibs</file> setup
6781 was first introduced, but it is now normally empty.
6782 It is maintained by the <tt>dpkg</tt> maintainer.
6789 If a <file>symbols</file> file for a shared library package
6790 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6791 in preference to a <file>shlibs</file>, with the exception
6792 of <file>debian/shlibs.local</file>. The latter overrides
6793 any other <file>shlibs</file> or <file>symbols</file> files.
6798 <heading>The <file>shlibs</file> File Format</heading>
6801 Each <file>shlibs</file> file has the same format. Lines
6802 beginning with <tt>#</tt> are considered to be comments and
6803 are ignored. Each line is of the form:
6804 <example compact="compact">
6805 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6810 We will explain this by reference to the example of the
6811 <tt>zlib1g</tt> package, which (at the time of writing)
6813 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6817 <var>type</var> is an optional element that indicates the
6818 type of package for which the line is valid. The only type
6819 currently in use is <tt>udeb</tt>. The colon and space
6820 after the type are required.
6824 <var>library-name</var> is the name of the shared library,
6825 in this case <tt>libz</tt>. (This must match the name part
6826 of the soname, see below.)
6830 <var>soname-version</var> is the version part of the
6831 ELF <tt>SONAME</tt> attribute of the library, determined the
6832 same way that the <var>soversion</var> component of the
6833 recommended shared library package name is determined.
6834 See <ref id="sharedlibs-runtime"> for the details.
6838 <var>dependencies</var> has the same syntax as a dependency
6839 field in a binary package control file. It should give
6840 details of which packages are required to satisfy a binary
6841 built against the version of the library contained in the
6842 package. See <ref id="depsyntax"> for details on the
6843 syntax, and <ref id="sharedlibs-updates"> for details on how
6844 to maintain the dependency version constraint.
6848 In our example, if the last change to the <tt>zlib1g</tt>
6849 package that could change behavior for a client of that
6850 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6851 the <tt>shlibs</tt> entry for this library could say:
6852 <example compact="compact">
6853 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6855 This version restriction must be new enough that any binary
6856 built against the current version of the library will work
6857 with any version of the shared library that satisfies that
6862 As zlib1g also provides a udeb containing the shared
6863 library, there would also be a second line:
6864 <example compact="compact">
6865 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6871 <heading>Providing a <file>shlibs</file> file</heading>
6874 To provide a <file>shlibs</file> file for a shared library
6875 binary package, create a <file>shlibs</file> file following
6876 the format described above and place it in
6877 the <file>DEBIAN</file> directory for that package during
6878 the build. It will then be included as a control file for
6879 that package<footnote>
6880 This is what <prgn>dh_makeshlibs</prgn> in
6881 the <package>debhelper</package> suite does. If your
6882 package also has a udeb that provides a shared
6883 library, <prgn>dh_makeshlibs</prgn> can automatically
6884 generate the <tt>udeb:</tt> lines if you specify the name
6885 of the udeb with the <tt>--add-udeb</tt> option.
6890 Since <prgn>dpkg-shlibdeps</prgn> reads
6891 the <file>DEBIAN/shlibs</file> files in all of the binary
6892 packages being built from this source package, all of
6893 the <file>DEBIAN/shlibs</file> files should be installed
6894 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6903 <chapt id="opersys"><heading>The Operating System</heading>
6906 <heading>File system hierarchy</heading>
6910 <heading>File System Structure</heading>
6913 The location of all files and directories must comply with the
6914 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6915 exceptions noted below, and except where doing so would
6916 violate other terms of Debian Policy. The following
6917 exceptions to the FHS apply:
6922 The FHS requirement that architecture-independent
6923 application-specific static files be located in
6924 <file>/usr/share</file> is relaxed to a suggestion.
6926 In particular, a subdirectory of <file>/usr/lib</file> may
6927 be used by a package (or a collection of packages) to hold a
6928 mixture of architecture-independent and
6929 architecture-dependent files. However, when a directory is
6930 entirely composed of architecture-independent files, it
6931 should be located in <file>/usr/share</file>.
6936 The optional rules related to user specific
6937 configuration files for applications are stored in
6938 the user's home directory are relaxed. It is
6939 recommended that such files start with the
6940 '<tt>.</tt>' character (a "dot file"), and if an
6941 application needs to create more than one dot file
6942 then the preferred placement is in a subdirectory
6943 with a name starting with a '.' character, (a "dot
6944 directory"). In this case it is recommended the
6945 configuration files not start with the '.'
6951 The requirement for amd64 to use <file>/lib64</file>
6952 for 64 bit binaries is removed.
6957 The requirement for object files, internal binaries, and
6958 libraries, including <file>libc.so.*</file>, to be located
6959 directly under <file>/lib{,32}</file> and
6960 <file>/usr/lib{,32}</file> is amended, permitting files
6961 to instead be installed to
6962 <file>/lib/<var>triplet</var></file> and
6963 <file>/usr/lib/<var>triplet</var></file>, where
6964 <tt><var>triplet</var></tt> is the value returned by
6965 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6966 architecture of the package. Packages may <em>not</em>
6967 install files to any <var>triplet</var> path other
6968 than the one matching the architecture of that package;
6969 for instance, an <tt>Architecture: amd64</tt> package
6970 containing 32-bit x86 libraries may not install these
6971 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6973 This is necessary in order to reserve the directories for
6974 use in cross-installation of library packages from other
6975 architectures, as part of the planned deployment of
6980 Applications may also use a single subdirectory under
6981 <file>/usr/lib/<var>triplet</var></file>.
6984 The execution time linker/loader, ld*, must still be made
6985 available in the existing location under /lib or /lib64
6986 since this is part of the ELF ABI for the architecture.
6991 The requirement that
6992 <file>/usr/local/share/man</file> be "synonymous"
6993 with <file>/usr/local/man</file> is relaxed to a
6998 The requirement that windowmanagers with a single
6999 configuration file call it <file>system.*wmrc</file>
7000 is removed, as is the restriction that the window
7001 manager subdirectory be named identically to the
7002 window manager name itself.
7007 The requirement that boot manager configuration
7008 files live in <file>/etc</file>, or at least are
7009 symlinked there, is relaxed to a recommendation.
7014 The additional directory <file>/run</file> in the root
7015 file system is allowed. <file>/run</file>
7016 replaces <file>/var/run</file>, and the
7017 subdirectory <file>/run/lock</file>
7018 replaces <file>/var/lock</file>, with
7019 the <file>/var</file> directories replaced by symlinks
7020 for backwards compatibility. <file>/run</file>
7021 and <file>/run/lock</file> must follow all of the
7022 requirements in the FHS for <file>/var/run</file>
7023 and <file>/var/lock</file>, respectively, such as file
7024 naming conventions, file format requirements, or the
7025 requirement that files be cleared during the boot
7026 process. Files and directories residing
7027 in <file>/run</file> should be stored on a temporary
7031 Packages must not assume the <file>/run</file>
7032 directory exists or is usable without a dependency
7033 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7034 stable release of Debian supports <file>/run</file>.
7039 The <file>/sys</file> directory in the root filesystem is
7040 additionally allowed. <footnote>This directory is used as
7041 mount point to mount virtual filesystems to get access to
7042 kernel information.</footnote>
7047 The requirement for <file>/usr/local/lib<qual></file>
7048 to exist if <file>/lib<qual></file> or
7049 <file>/usr/lib<qual></file> exists is removed.
7054 On GNU/Hurd systems, the following additional
7055 directories are allowed in the root
7056 filesystem: <file>/hurd</file>
7057 and <file>/servers</file>.<footnote>
7058 These directories are used to store translators and as
7059 a set of standard names for mount points,
7068 The version of this document referred here can be
7069 found in the <tt>debian-policy</tt> package or on <url
7070 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7071 name="FHS (Debian copy)"> alongside this manual (or, if
7072 you have the <package>debian-policy</package> installed,
7074 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7075 (local copy)">). The
7076 latest version, which may be a more recent version, may
7078 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7079 Specific questions about following the standard may be
7080 asked on the <tt>debian-devel</tt> mailing list, or
7081 referred to the FHS mailing list (see the
7082 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7088 <heading>Site-specific programs</heading>
7091 As mandated by the FHS, packages must not place any
7092 files in <file>/usr/local</file>, either by putting them in
7093 the file system archive to be unpacked by <prgn>dpkg</prgn>
7094 or by manipulating them in their maintainer scripts.
7098 However, the package may create empty directories below
7099 <file>/usr/local</file> so that the system administrator knows
7100 where to place site-specific files. These are not
7101 directories <em>in</em> <file>/usr/local</file>, but are
7102 children of directories in <file>/usr/local</file>. These
7103 directories (<file>/usr/local/*/dir/</file>)
7104 should be removed on package removal if they are
7109 Note that this applies only to
7110 directories <em>below</em> <file>/usr/local</file>,
7111 not <em>in</em> <file>/usr/local</file>. Packages must
7112 not create sub-directories in the
7113 directory <file>/usr/local</file> itself, except those
7114 listed in FHS, section 4.5. However, you may create
7115 directories below them as you wish. You must not remove
7116 any of the directories listed in 4.5, even if you created
7121 Since <file>/usr/local</file> can be mounted read-only from a
7122 remote server, these directories must be created and
7123 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7124 maintainer scripts and not be included in the
7125 <file>.deb</file> archive. These scripts must not fail if
7126 either of these operations fail.
7130 For example, the <tt>emacsen-common</tt> package could
7131 contain something like
7132 <example compact="compact">
7133 if [ ! -e /usr/local/share/emacs ]; then
7134 if mkdir /usr/local/share/emacs 2>/dev/null; then
7135 if chown root:staff /usr/local/share/emacs; then
7136 chmod 2775 /usr/local/share/emacs || true
7141 in its <prgn>postinst</prgn> script, and
7142 <example compact="compact">
7143 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7144 rmdir /usr/local/share/emacs 2>/dev/null || true
7146 in the <prgn>prerm</prgn> script. (Note that this form is
7147 used to ensure that if the script is interrupted, the
7148 directory <file>/usr/local/share/emacs</file> will still be
7153 If you do create a directory in <file>/usr/local</file> for
7154 local additions to a package, you should ensure that
7155 settings in <file>/usr/local</file> take precedence over the
7156 equivalents in <file>/usr</file>.
7160 However, because <file>/usr/local</file> and its contents are
7161 for exclusive use of the local administrator, a package
7162 must not rely on the presence or absence of files or
7163 directories in <file>/usr/local</file> for normal operation.
7167 The <file>/usr/local</file> directory itself and all the
7168 subdirectories created by the package should (by default) have
7169 permissions 2775 (group-writable and set-group-id) and be
7170 owned by <tt>root:staff</tt>.
7175 <heading>The system-wide mail directory</heading>
7177 The system-wide mail directory
7178 is <file>/var/mail</file>. This directory is part of the
7179 base system and should not be owned by any particular mail
7180 agents. The use of the old
7181 location <file>/var/spool/mail</file> is deprecated, even
7182 though the spool may still be physically located there.
7186 <sect1 id="fhs-run">
7187 <heading><file>/run</file> and <file>/run/lock</file></heading>
7190 The directory <file>/run</file> is cleared at boot, normally
7191 by being a mount point for a temporary file system. Packages
7192 therefore must not assume that any files or directories
7193 under <file>/run</file> other than <file>/run/lock</file>
7194 exist unless the package has arranged to create those files or
7195 directories since the last reboot. Normally, this is done by
7196 the package via an init script. See <ref id="writing-init">
7197 for more information.
7201 Packages must not include files or directories
7202 under <file>/run</file>, or under the
7203 older <file>/var/run</file> and <file>/var/lock</file> paths.
7204 The latter paths will normally be symlinks or other
7205 redirections to <file>/run</file> for backwards compatibility.
7211 <heading>Users and groups</heading>
7214 <heading>Introduction</heading>
7216 The Debian system can be configured to use either plain or
7221 Some user ids (UIDs) and group ids (GIDs) are reserved
7222 globally for use by certain packages. Because some
7223 packages need to include files which are owned by these
7224 users or groups, or need the ids compiled into binaries,
7225 these ids must be used on any Debian system only for the
7226 purpose for which they are allocated. This is a serious
7227 restriction, and we should avoid getting in the way of
7228 local administration policies. In particular, many sites
7229 allocate users and/or local system groups starting at 100.
7233 Apart from this we should have dynamically allocated ids,
7234 which should by default be arranged in some sensible
7235 order, but the behavior should be configurable.
7239 Packages other than <tt>base-passwd</tt> must not modify
7240 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7241 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7246 <heading>UID and GID classes</heading>
7248 The UID and GID numbers are divided into classes as
7254 Globally allocated by the Debian project, the same
7255 on every Debian system. These ids will appear in
7256 the <file>passwd</file> and <file>group</file> files of all
7257 Debian systems, new ids in this range being added
7258 automatically as the <tt>base-passwd</tt> package is
7263 Packages which need a single statically allocated
7264 uid or gid should use one of these; their
7265 maintainers should ask the <tt>base-passwd</tt>
7273 Dynamically allocated system users and groups.
7274 Packages which need a user or group, but can have
7275 this user or group allocated dynamically and
7276 differently on each system, should use <tt>adduser
7277 --system</tt> to create the group and/or user.
7278 <prgn>adduser</prgn> will check for the existence of
7279 the user or group, and if necessary choose an unused
7280 id based on the ranges specified in
7281 <file>adduser.conf</file>.
7285 <tag>1000-59999:</tag>
7288 Dynamically allocated user accounts. By default
7289 <prgn>adduser</prgn> will choose UIDs and GIDs for
7290 user accounts in this range, though
7291 <file>adduser.conf</file> may be used to modify this
7296 <tag>60000-64999:</tag>
7299 Globally allocated by the Debian project, but only
7300 created on demand. The ids are allocated centrally
7301 and statically, but the actual accounts are only
7302 created on users' systems on demand.
7306 These ids are for packages which are obscure or
7307 which require many statically-allocated ids. These
7308 packages should check for and create the accounts in
7309 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7310 <prgn>adduser</prgn> if it has this facility) if
7311 necessary. Packages which are likely to require
7312 further allocations should have a "hole" left after
7313 them in the allocation, to give them room to
7318 <tag>65000-65533:</tag>
7326 User <tt>nobody</tt>. The corresponding gid refers
7327 to the group <tt>nogroup</tt>.
7334 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7335 not</em> be used, because it is the error return
7344 <sect id="sysvinit">
7345 <heading>System run levels and <file>init.d</file> scripts</heading>
7347 <sect1 id="/etc/init.d">
7348 <heading>Introduction</heading>
7351 The <file>/etc/init.d</file> directory contains the scripts
7352 executed by <prgn>init</prgn> at boot time and when the
7353 init state (or "runlevel") is changed (see <manref
7354 name="init" section="8">).
7358 There are at least two different, yet functionally
7359 equivalent, ways of handling these scripts. For the sake
7360 of simplicity, this document describes only the symbolic
7361 link method. However, it must not be assumed by maintainer
7362 scripts that this method is being used, and any automated
7363 manipulation of the various runlevel behaviors by
7364 maintainer scripts must be performed using
7365 <prgn>update-rc.d</prgn> as described below and not by
7366 manually installing or removing symlinks. For information
7367 on the implementation details of the other method,
7368 implemented in the <tt>file-rc</tt> package, please refer
7369 to the documentation of that package.
7373 These scripts are referenced by symbolic links in the
7374 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7375 runlevels, <prgn>init</prgn> looks in the directory
7376 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7377 execute, where <tt><var>n</var></tt> is the runlevel that
7378 is being changed to, or <tt>S</tt> for the boot-up
7383 The names of the links all have the form
7384 <file>S<var>mm</var><var>script</var></file> or
7385 <file>K<var>mm</var><var>script</var></file> where
7386 <var>mm</var> is a two-digit number and <var>script</var>
7387 is the name of the script (this should be the same as the
7388 name of the actual script in <file>/etc/init.d</file>).
7392 When <prgn>init</prgn> changes runlevel first the targets
7393 of the links whose names start with a <tt>K</tt> are
7394 executed, each with the single argument <tt>stop</tt>,
7395 followed by the scripts prefixed with an <tt>S</tt>, each
7396 with the single argument <tt>start</tt>. (The links are
7397 those in the <file>/etc/rc<var>n</var>.d</file> directory
7398 corresponding to the new runlevel.) The <tt>K</tt> links
7399 are responsible for killing services and the <tt>S</tt>
7400 link for starting services upon entering the runlevel.
7404 For example, if we are changing from runlevel 2 to
7405 runlevel 3, init will first execute all of the <tt>K</tt>
7406 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7407 all of the <tt>S</tt> prefixed scripts in that directory.
7408 The links starting with <tt>K</tt> will cause the
7409 referred-to file to be executed with an argument of
7410 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7415 The two-digit number <var>mm</var> is used to determine
7416 the order in which to run the scripts: low-numbered links
7417 have their scripts run first. For example, the
7418 <tt>K20</tt> scripts will be executed before the
7419 <tt>K30</tt> scripts. This is used when a certain service
7420 must be started before another. For example, the name
7421 server <prgn>bind</prgn> might need to be started before
7422 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7423 can set up its access lists. In this case, the script
7424 that starts <prgn>bind</prgn> would have a lower number
7425 than the script that starts <prgn>inn</prgn> so that it
7427 <example compact="compact">
7434 The two runlevels 0 (halt) and 6 (reboot) are slightly
7435 different. In these runlevels, the links with an
7436 <tt>S</tt> prefix are still called after those with a
7437 <tt>K</tt> prefix, but they too are called with the single
7438 argument <tt>stop</tt>.
7442 <sect1 id="writing-init">
7443 <heading>Writing the scripts</heading>
7446 Packages that include daemons for system services should
7447 place scripts in <file>/etc/init.d</file> to start or stop
7448 services at boot time or during a change of runlevel.
7449 These scripts should be named
7450 <file>/etc/init.d/<var>package</var></file>, and they should
7451 accept one argument, saying what to do:
7454 <tag><tt>start</tt></tag>
7455 <item>start the service,</item>
7457 <tag><tt>stop</tt></tag>
7458 <item>stop the service,</item>
7460 <tag><tt>restart</tt></tag>
7461 <item>stop and restart the service if it's already running,
7462 otherwise start the service</item>
7464 <tag><tt>reload</tt></tag>
7465 <item><p>cause the configuration of the service to be
7466 reloaded without actually stopping and restarting
7469 <tag><tt>force-reload</tt></tag>
7470 <item>cause the configuration to be reloaded if the
7471 service supports this, otherwise restart the
7475 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7476 <tt>force-reload</tt> options should be supported by all
7477 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7482 The <file>init.d</file> scripts must ensure that they will
7483 behave sensibly (i.e., returning success and not starting
7484 multiple copies of a service) if invoked with <tt>start</tt>
7485 when the service is already running, or with <tt>stop</tt>
7486 when it isn't, and that they don't kill unfortunately-named
7487 user processes. The best way to achieve this is usually to
7488 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7493 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7494 scripts. Writing correct <file>init.d</file> scripts requires
7495 accepting various error exit statuses when daemons are already
7496 running or already stopped without aborting
7497 the <file>init.d</file> script, and common <file>init.d</file>
7498 function libraries are not safe to call with <tt>set -e</tt>
7500 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7501 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7502 in effect and echoing status messages to the console fails,
7504 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7505 to not use <tt>set -e</tt> and instead check the result of
7506 each command separately.
7510 If a service reloads its configuration automatically (as
7511 in the case of <prgn>cron</prgn>, for example), the
7512 <tt>reload</tt> option of the <file>init.d</file> script
7513 should behave as if the configuration has been reloaded
7518 The <file>/etc/init.d</file> scripts must be treated as
7519 configuration files, either (if they are present in the
7520 package, that is, in the .deb file) by marking them as
7521 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7522 by managing them correctly in the maintainer scripts (see
7523 <ref id="config-files">). This is important since we want
7524 to give the local system administrator the chance to adapt
7525 the scripts to the local system, e.g., to disable a
7526 service without de-installing the package, or to specify
7527 some special command line options when starting a service,
7528 while making sure their changes aren't lost during the next
7533 These scripts should not fail obscurely when the
7534 configuration files remain but the package has been
7535 removed, as configuration files remain on the system after
7536 the package has been removed. Only when <prgn>dpkg</prgn>
7537 is executed with the <tt>--purge</tt> option will
7538 configuration files be removed. In particular, as the
7539 <file>/etc/init.d/<var>package</var></file> script itself is
7540 usually a <tt>conffile</tt>, it will remain on the system
7541 if the package is removed but not purged. Therefore, you
7542 should include a <tt>test</tt> statement at the top of the
7544 <example compact="compact">
7545 test -f <var>program-executed-later-in-script</var> || exit 0
7550 Often there are some variables in the <file>init.d</file>
7551 scripts whose values control the behavior of the scripts,
7552 and which a system administrator is likely to want to
7553 change. As the scripts themselves are frequently
7554 <tt>conffile</tt>s, modifying them requires that the
7555 administrator merge in their changes each time the package
7556 is upgraded and the <tt>conffile</tt> changes. To ease
7557 the burden on the system administrator, such configurable
7558 values should not be placed directly in the script.
7559 Instead, they should be placed in a file in
7560 <file>/etc/default</file>, which typically will have the same
7561 base name as the <file>init.d</file> script. This extra file
7562 should be sourced by the script when the script runs. It
7563 must contain only variable settings and comments in SUSv3
7564 <prgn>sh</prgn> format. It may either be a
7565 <tt>conffile</tt> or a configuration file maintained by
7566 the package maintainer scripts. See <ref id="config-files">
7571 To ensure that vital configurable values are always
7572 available, the <file>init.d</file> script should set default
7573 values for each of the shell variables it uses, either
7574 before sourcing the <file>/etc/default/</file> file or
7575 afterwards using something like the <tt>:
7576 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7577 script must behave sensibly and not fail if the
7578 <file>/etc/default</file> file is deleted.
7582 Files and directories under <file>/run</file>, including ones
7583 referred to via the compatibility paths <file>/var/run</file>
7584 and <file>/var/lock</file>, are normally stored on a temporary
7585 filesystem and are normally not persistent across a reboot.
7586 The <file>init.d</file> scripts must handle this correctly.
7587 This will typically mean creating any required subdirectories
7588 dynamically when the <file>init.d</file> script is run.
7589 See <ref id="fhs-run"> for more information.
7594 <heading>Interfacing with the initscript system</heading>
7597 Maintainers should use the abstraction layer provided by
7598 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7599 programs to deal with initscripts in their packages'
7600 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7601 and <prgn>postrm</prgn>.
7605 Directly managing the /etc/rc?.d links and directly
7606 invoking the <file>/etc/init.d/</file> initscripts should
7607 be done only by packages providing the initscript
7608 subsystem (such as <prgn>sysv-rc</prgn> and
7609 <prgn>file-rc</prgn>).
7613 <heading>Managing the links</heading>
7616 The program <prgn>update-rc.d</prgn> is provided for
7617 package maintainers to arrange for the proper creation and
7618 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7619 or their functional equivalent if another method is being
7620 used. This may be used by maintainers in their packages'
7621 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7625 You must not include any <file>/etc/rc<var>n</var>.d</file>
7626 symbolic links in the actual archive or manually create or
7627 remove the symbolic links in maintainer scripts; you must
7628 use the <prgn>update-rc.d</prgn> program instead. (The
7629 former will fail if an alternative method of maintaining
7630 runlevel information is being used.) You must not include
7631 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7632 in the archive either. (Only the <tt>sysvinit</tt>
7637 By default <prgn>update-rc.d</prgn> will start services in
7638 each of the multi-user state runlevels (2, 3, 4, and 5)
7639 and stop them in the halt runlevel (0), the single-user
7640 runlevel (1) and the reboot runlevel (6). The system
7641 administrator will have the opportunity to customize
7642 runlevels by simply adding, moving, or removing the
7643 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7644 symbolic links are being used, or by modifying
7645 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7650 To get the default behavior for your package, put in your
7651 <prgn>postinst</prgn> script
7652 <example compact="compact">
7653 update-rc.d <var>package</var> defaults
7655 and in your <prgn>postrm</prgn>
7656 <example compact="compact">
7657 if [ "$1" = purge ]; then
7658 update-rc.d <var>package</var> remove
7660 </example>. Note that if your package changes runlevels
7661 or priority, you may have to remove and recreate the links,
7662 since otherwise the old links may persist. Refer to the
7663 documentation of <prgn>update-rc.d</prgn>.
7667 This will use a default sequence number of 20. If it does
7668 not matter when or in which order the <file>init.d</file>
7669 script is run, use this default. If it does, then you
7670 should talk to the maintainer of the <prgn>sysvinit</prgn>
7671 package or post to <tt>debian-devel</tt>, and they will
7672 help you choose a number.
7676 For more information about using <tt>update-rc.d</tt>,
7677 please consult its man page <manref name="update-rc.d"
7683 <heading>Running initscripts</heading>
7685 The program <prgn>invoke-rc.d</prgn> is provided to make
7686 it easier for package maintainers to properly invoke an
7687 initscript, obeying runlevel and other locally-defined
7688 constraints that might limit a package's right to start,
7689 stop and otherwise manage services. This program may be
7690 used by maintainers in their packages' scripts.
7694 The package maintainer scripts must use
7695 <prgn>invoke-rc.d</prgn> to invoke the
7696 <file>/etc/init.d/*</file> initscripts, instead of
7697 calling them directly.
7701 By default, <prgn>invoke-rc.d</prgn> will pass any
7702 action requests (start, stop, reload, restart...) to the
7703 <file>/etc/init.d</file> script, filtering out requests
7704 to start or restart a service out of its intended
7709 Most packages will simply need to change:
7710 <example compact="compact">/etc/init.d/<package>
7711 <action></example> in their <prgn>postinst</prgn>
7712 and <prgn>prerm</prgn> scripts to:
7713 <example compact="compact">
7714 if which invoke-rc.d >/dev/null 2>&1; then
7715 invoke-rc.d <var>package</var> <action>
7717 /etc/init.d/<var>package</var> <action>
7723 A package should register its initscript services using
7724 <prgn>update-rc.d</prgn> before it tries to invoke them
7725 using <prgn>invoke-rc.d</prgn>. Invocation of
7726 unregistered services may fail.
7730 For more information about using
7731 <prgn>invoke-rc.d</prgn>, please consult its man page
7732 <manref name="invoke-rc.d" section="8">.
7738 <heading>Boot-time initialization</heading>
7741 There used to be another directory, <file>/etc/rc.boot</file>,
7742 which contained scripts which were run once per machine
7743 boot. This has been deprecated in favour of links from
7744 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7745 described in <ref id="/etc/init.d">. Packages must not
7746 place files in <file>/etc/rc.boot</file>.
7751 <heading>Example</heading>
7754 An example on which you can base your
7755 <file>/etc/init.d</file> scripts is found in
7756 <file>/etc/init.d/skeleton</file>.
7763 <heading>Console messages from <file>init.d</file> scripts</heading>
7766 This section describes the formats to be used for messages
7767 written to standard output by the <file>/etc/init.d</file>
7768 scripts. The intent is to improve the consistency of
7769 Debian's startup and shutdown look and feel. For this
7770 reason, please look very carefully at the details. We want
7771 the messages to have the same format in terms of wording,
7772 spaces, punctuation and case of letters.
7776 Here is a list of overall rules that should be used for
7777 messages generated by <file>/etc/init.d</file> scripts.
7783 The message should fit in one line (fewer than 80
7784 characters), start with a capital letter and end with
7785 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7789 If the script is performing some time consuming task in
7790 the background (not merely starting or stopping a
7791 program, for instance), an ellipsis (three dots:
7792 <tt>...</tt>) should be output to the screen, with no
7793 leading or tailing whitespace or line feeds.
7797 The messages should appear as if the computer is telling
7798 the user what it is doing (politely :-), but should not
7799 mention "it" directly. For example, instead of:
7800 <example compact="compact">
7801 I'm starting network daemons: nfsd mountd.
7803 the message should say
7804 <example compact="compact">
7805 Starting network daemons: nfsd mountd.
7812 <tt>init.d</tt> script should use the following standard
7813 message formats for the situations enumerated below.
7819 <p>When daemons are started</p>
7822 If the script starts one or more daemons, the output
7823 should look like this (a single line, no leading
7825 <example compact="compact">
7826 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7828 The <var>description</var> should describe the
7829 subsystem the daemon or set of daemons are part of,
7830 while <var>daemon-1</var> up to <var>daemon-n</var>
7831 denote each daemon's name (typically the file name of
7836 For example, the output of <file>/etc/init.d/lpd</file>
7838 <example compact="compact">
7839 Starting printer spooler: lpd.
7844 This can be achieved by saying
7845 <example compact="compact">
7846 echo -n "Starting printer spooler: lpd"
7847 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7850 in the script. If there are more than one daemon to
7851 start, the output should look like this:
7852 <example compact="compact">
7853 echo -n "Starting remote file system services:"
7854 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7855 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7856 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7859 This makes it possible for the user to see what is
7860 happening and when the final daemon has been started.
7861 Care should be taken in the placement of white spaces:
7862 in the example above the system administrators can
7863 easily comment out a line if they don't want to start
7864 a specific daemon, while the displayed message still
7870 <p>When a system parameter is being set</p>
7873 If you have to set up different system parameters
7874 during the system boot, you should use this format:
7875 <example compact="compact">
7876 Setting <var>parameter</var> to "<var>value</var>".
7881 You can use a statement such as the following to get
7883 <example compact="compact">
7884 echo "Setting DNS domainname to \"$domainname\"."
7889 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7890 for the left and right quotation marks. A grave accent
7891 (<tt>`</tt>) is not a quote character; neither is an
7892 apostrophe (<tt>'</tt>).
7897 <p>When a daemon is stopped or restarted</p>
7900 When you stop or restart a daemon, you should issue a
7901 message identical to the startup message, except that
7902 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7903 or <tt>Restarting</tt> respectively.
7907 For example, stopping the printer daemon will look like
7909 <example compact="compact">
7910 Stopping printer spooler: lpd.
7916 <p>When something is executed</p>
7919 There are several examples where you have to run a
7920 program at system startup or shutdown to perform a
7921 specific task, for example, setting the system's clock
7922 using <prgn>netdate</prgn> or killing all processes
7923 when the system shuts down. Your message should look
7925 <example compact="compact">
7926 Doing something very useful...done.
7928 You should print the <tt>done.</tt> immediately after
7929 the job has been completed, so that the user is
7930 informed why they have to wait. You can get this
7932 <example compact="compact">
7933 echo -n "Doing something very useful..."
7942 <p>When the configuration is reloaded</p>
7945 When a daemon is forced to reload its configuration
7946 files you should use the following format:
7947 <example compact="compact">
7948 Reloading <var>description</var> configuration...done.
7950 where <var>description</var> is the same as in the
7951 daemon starting message.
7958 <sect id="cron-jobs">
7959 <heading>Cron jobs</heading>
7962 Packages must not modify the configuration file
7963 <file>/etc/crontab</file>, and they must not modify the files in
7964 <file>/var/spool/cron/crontabs</file>.
7968 If a package wants to install a job that has to be executed via
7969 cron, it should place a file named as specified
7970 in <ref id="cron-files"> into one or more of the following
7972 <example compact="compact">
7978 As these directory names imply, the files within them are
7979 executed on an hourly, daily, weekly, or monthly basis,
7980 respectively. The exact times are listed in
7981 <file>/etc/crontab</file>.
7985 All files installed in any of these directories must be
7986 scripts (e.g., shell scripts or Perl scripts) so that they
7987 can easily be modified by the local system administrator.
7988 In addition, they must be treated as configuration files.
7992 If a certain job has to be executed at some other frequency or
7993 at a specific time, the package should install a file in
7994 <file>/etc/cron.d</file> with a name as specified
7995 in <ref id="cron-files">. This file uses the same syntax
7996 as <file>/etc/crontab</file> and is processed
7997 by <prgn>cron</prgn> automatically. The file must also be
7998 treated as a configuration file. (Note that entries in the
7999 <file>/etc/cron.d</file> directory are not handled by
8000 <prgn>anacron</prgn>. Thus, you should only use this
8001 directory for jobs which may be skipped if the system is not
8006 Unlike <file>crontab</file> files described in the IEEE Std
8007 1003.1-2008 (POSIX.1) available from
8008 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
8009 name="The Open Group">, the files in
8010 <file>/etc/cron.d</file> and the file
8011 <file>/etc/crontab</file> have seven fields; namely:
8013 <item>Minute [0,59]</item>
8014 <item>Hour [0,23]</item>
8015 <item>Day of the month [1,31]</item>
8016 <item>Month of the year [1,12]</item>
8017 <item>Day of the week ([0,6] with 0=Sunday)</item>
8018 <item>Username</item>
8019 <item>Command to be run</item>
8021 Ranges of numbers are allowed. Ranges are two numbers
8022 separated with a hyphen. The specified range is inclusive.
8023 Lists are allowed. A list is a set of numbers (or ranges)
8024 separated by commas. Step values can be used in conjunction
8029 The scripts or <tt>crontab</tt> entries in these directories should
8030 check if all necessary programs are installed before they
8031 try to execute them. Otherwise, problems will arise when a
8032 package was removed but not purged since configuration files
8033 are kept on the system in this situation.
8037 Any <tt>cron</tt> daemon must provide
8038 <file>/usr/bin/crontab</file> and support normal
8039 <tt>crontab</tt> entries as specified in POSIX. The daemon
8040 must also support names for days and months, ranges, and
8041 step values. It has to support <file>/etc/crontab</file>,
8042 and correctly execute the scripts in
8043 <file>/etc/cron.d</file>. The daemon must also correctly
8045 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8048 <sect1 id="cron-files">
8049 <heading>Cron job file names</heading>
8052 The file name of a cron job file should normally match the
8053 name of the package from which it comes.
8057 If a package supplies multiple cron job files files in the
8058 same directory, the file names should all start with the name
8059 of the package (possibly modified as described below) followed
8060 by a hyphen (<tt>-</tt>) and a suitable suffix.
8064 A cron job file name must not include any period or plus
8065 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8066 cause cron to ignore the file. Underscores (<tt>_</tt>)
8067 should be used instead of <tt>.</tt> and <tt>+</tt>
8074 <heading>Menus</heading>
8077 The Debian <tt>menu</tt> package provides a standard
8078 interface between packages providing applications and
8079 <em>menu programs</em> (either X window managers or
8080 text-based menu programs such as <prgn>pdmenu</prgn>).
8084 All packages that provide applications that need not be
8085 passed any special command line arguments for normal
8086 operation should register a menu entry for those
8087 applications, so that users of the <tt>menu</tt> package
8088 will automatically get menu entries in their window
8089 managers, as well in shells like <tt>pdmenu</tt>.
8093 Menu entries should follow the current menu policy.
8097 The menu policy can be found in the <tt>menu-policy</tt>
8098 files in the <tt>debian-policy</tt> package.
8099 It is also available from the Debian web mirrors at
8100 <tt><url name="/doc/packaging-manuals/menu-policy/"
8101 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8105 Please also refer to the <em>Debian Menu System</em>
8106 documentation that comes with the <package>menu</package>
8107 package for information about how to register your
8113 <heading>Multimedia handlers</heading>
8116 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8117 is a mechanism for encoding files and data streams and
8118 providing meta-information about them, in particular their
8119 type (e.g. audio or video) and format (e.g. PNG, HTML,
8124 Registration of MIME type handlers allows programs like mail
8125 user agents and web browsers to invoke these handlers to
8126 view, edit or display MIME types they don't support directly.
8130 Packages which provide programs to view/show/play, compose, edit or
8131 print MIME types should register them as such by placing a file in
8132 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8133 <file>/usr/lib/mime/packages/</file>. The file name should be the
8134 binary package's name.
8138 The <package>mime-support</package> package provides the
8139 <prgn>update-mime</prgn> program, which integrates these
8140 registrations in the <file>/etc/mailcap</file> file, using dpkg
8142 Creating, modifying or removing a file in
8143 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8144 not activate the trigger. In that case, it can be done by calling
8145 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8146 the maintainer script after creating, modifying, or removing
8149 Packages using this facility <em>should not</em> depend on,
8150 recommend, or suggest <prgn>mime-support</prgn>.
8155 <heading>Keyboard configuration</heading>
8158 To achieve a consistent keyboard configuration so that all
8159 applications interpret a keyboard event the same way, all
8160 programs in the Debian distribution must be configured to
8161 comply with the following guidelines.
8165 The following keys must have the specified interpretations:
8168 <tag><tt><--</tt></tag>
8169 <item>delete the character to the left of the cursor</item>
8171 <tag><tt>Delete</tt></tag>
8172 <item>delete the character to the right of the cursor</item>
8174 <tag><tt>Control+H</tt></tag>
8175 <item>emacs: the help prefix</item>
8178 The interpretation of any keyboard events should be
8179 independent of the terminal that is used, be it a virtual
8180 console, an X terminal emulator, an rlogin/telnet session,
8185 The following list explains how the different programs
8186 should be set up to achieve this:
8192 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8196 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8200 X translations are set up to make
8201 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8202 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8203 is the vt220 escape code for the "delete character"
8204 key). This must be done by loading the X resources
8205 using <prgn>xrdb</prgn> on all local X displays, not
8206 using the application defaults, so that the
8207 translation resources used correspond to the
8208 <prgn>xmodmap</prgn> settings.
8212 The Linux console is configured to make
8213 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8214 generate <tt>ESC [ 3 ~</tt>.
8218 X applications are configured so that <tt><</tt>
8219 deletes left, and <tt>Delete</tt> deletes right. Motif
8220 applications already work like this.
8224 Terminals should have <tt>stty erase ^?</tt> .
8228 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8229 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8230 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8234 Emacs is programmed to map <tt>KB_Backspace</tt> or
8235 the <tt>stty erase</tt> character to
8236 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8237 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8238 <tt>^H</tt> to <tt>help</tt> as always.
8242 Other applications use the <tt>stty erase</tt>
8243 character and <tt>kdch1</tt> for the two delete keys,
8244 with ASCII DEL being "delete previous character" and
8245 <tt>kdch1</tt> being "delete character under
8253 This will solve the problem except for the following
8260 Some terminals have a <tt><--</tt> key that cannot
8261 be made to produce anything except <tt>^H</tt>. On
8262 these terminals Emacs help will be unavailable on
8263 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8264 character takes precedence in Emacs, and has been set
8265 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8266 available) can be used instead.
8270 Some operating systems use <tt>^H</tt> for <tt>stty
8271 erase</tt>. However, modern telnet versions and all
8272 rlogin versions propagate <tt>stty</tt> settings, and
8273 almost all UNIX versions honour <tt>stty erase</tt>.
8274 Where the <tt>stty</tt> settings are not propagated
8275 correctly, things can be made to work by using
8276 <tt>stty</tt> manually.
8280 Some systems (including previous Debian versions) use
8281 <prgn>xmodmap</prgn> to arrange for both
8282 <tt><--</tt> and <tt>Delete</tt> to generate
8283 <tt>KB_Delete</tt>. We can change the behavior of
8284 their X clients using the same X resources that we use
8285 to do it for our own clients, or configure our clients
8286 using their resources when things are the other way
8287 around. On displays configured like this
8288 <tt>Delete</tt> will not work, but <tt><--</tt>
8293 Some operating systems have different <tt>kdch1</tt>
8294 settings in their <tt>terminfo</tt> database for
8295 <tt>xterm</tt> and others. On these systems the
8296 <tt>Delete</tt> key will not work correctly when you
8297 log in from a system conforming to our policy, but
8298 <tt><--</tt> will.
8305 <heading>Environment variables</heading>
8308 A program must not depend on environment variables to get
8309 reasonable defaults. (That's because these environment
8310 variables would have to be set in a system-wide
8311 configuration file like <file>/etc/profile</file>, which is not
8312 supported by all shells.)
8316 If a program usually depends on environment variables for its
8317 configuration, the program should be changed to fall back to
8318 a reasonable default configuration if these environment
8319 variables are not present. If this cannot be done easily
8320 (e.g., if the source code of a non-free program is not
8321 available), the program must be replaced by a small
8322 "wrapper" shell script which sets the environment variables
8323 if they are not already defined, and calls the original program.
8327 Here is an example of a wrapper script for this purpose:
8329 <example compact="compact">
8331 BAR=${BAR:-/var/lib/fubar}
8333 exec /usr/lib/foo/foo "$@"
8338 Furthermore, as <file>/etc/profile</file> is a configuration
8339 file of the <prgn>base-files</prgn> package, other packages must
8340 not put any environment variables or other commands into that
8345 <sect id="doc-base">
8346 <heading>Registering Documents using doc-base</heading>
8349 The <package>doc-base</package> package implements a
8350 flexible mechanism for handling and presenting
8351 documentation. The recommended practice is for every Debian
8352 package that provides online documentation (other than just
8353 manual pages) to register these documents with
8354 <package>doc-base</package> by installing a
8355 <package>doc-base</package> control file in
8356 <file>/usr/share/doc-base/</file>.
8359 Please refer to the documentation that comes with the
8360 <package>doc-base</package> package for information and
8365 <sect id="alternateinit">
8366 <heading>Alternate init systems</heading>
8368 A number of other init systems are available now in Debian that
8369 can be used in place of <package>sysvinit</package>. Alternative
8370 init implementations must support running SysV init scripts as
8371 described at <ref id="sysvinit"> for compatibility.
8374 Packages may integrate with these replacement init systems by
8375 providing implementation-specific configuration information about
8376 how and when to start a service or in what order to run certain
8377 tasks at boot time. However, any package integrating with other
8378 init systems must also be backwards-compatible with
8379 <package>sysvinit</package> by providing a SysV-style init script
8380 with the same name as and equivalent functionality to any
8381 init-specific job, as this is the only start-up configuration
8382 method guaranteed to be supported by all init implementations. An
8383 exception to this rule is scripts or jobs provided by the init
8384 implementation itself; such jobs may be required for an
8385 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8386 scripts and may not have a one-to-one correspondence with the init
8389 <sect1 id="upstart">
8390 <heading>Event-based boot with upstart</heading>
8393 Packages may integrate with the <prgn>upstart</prgn> event-based
8394 boot system by installing job files in the
8395 <file>/etc/init</file> directory. SysV init scripts for which
8396 an equivalent upstart job is available must query the output of
8397 the command <prgn>initctl version</prgn> for the string
8398 <tt>upstart</tt> and avoid running in favor of the native
8399 upstart job, using a test such as this:
8400 <example compact="compact">
8401 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8408 Because packages shipping upstart jobs may be installed on
8409 systems that are not using upstart, maintainer scripts must
8410 still use the common <prgn>update-rc.d</prgn> and
8411 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8412 and for starting and stopping services. These maintainer
8413 scripts must not call the upstart <prgn>start</prgn>,
8414 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8415 interfaces directly. Instead, implementations of
8416 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8417 when an upstart job with the same name as an init script is
8418 present, and perform the requested action using the upstart job
8419 instead of the init script.
8422 Dependency-based boot managers for SysV init scripts, such as
8423 <prgn>startpar</prgn>, may avoid running a given init script
8424 entirely when an equivalent upstart job is present, to avoid
8425 unnecessary forking of no-op init scripts. In this case, the
8426 boot manager should integrate with upstart to detect when the
8427 upstart job in question is started or stopped to know when the
8428 dependency has been satisfied.
8437 <heading>Files</heading>
8439 <sect id="binaries">
8440 <heading>Binaries</heading>
8443 Two different packages must not install programs with
8444 different functionality but with the same filenames. (The
8445 case of two programs having the same functionality but
8446 different implementations is handled via "alternatives" or
8447 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8448 <ref id="conflicts"> respectively.) If this case happens,
8449 one of the programs must be renamed. The maintainers should
8450 report this to the <tt>debian-devel</tt> mailing list and
8451 try to find a consensus about which program will have to be
8452 renamed. If a consensus cannot be reached, <em>both</em>
8453 programs must be renamed.
8457 By default, when a package is being built, any binaries
8458 created should include debugging information, as well as
8459 being compiled with optimization. You should also turn on
8460 as many reasonable compilation warnings as possible; this
8461 makes life easier for porters, who can then look at build
8462 logs for possible problems. For the C programming language,
8463 this means the following compilation parameters should be
8465 <example compact="compact">
8467 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8469 INSTALL = install -s # (or use strip on the files in debian/tmp)
8474 Note that by default all installed binaries should be stripped,
8475 either by using the <tt>-s</tt> flag to
8476 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8477 the binaries after they have been copied into
8478 <file>debian/tmp</file> but before the tree is made into a
8483 Although binaries in the build tree should be compiled with
8484 debugging information by default, it can often be difficult to
8485 debug programs if they are also subjected to compiler
8486 optimization. For this reason, it is recommended to support the
8487 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8488 (see <ref id="debianrules-options">). This variable can contain
8489 several flags to change how a package is compiled and built.
8493 It is up to the package maintainer to decide what
8494 compilation options are best for the package. Certain
8495 binaries (such as computationally-intensive programs) will
8496 function better with certain flags (<tt>-O3</tt>, for
8497 example); feel free to use them. Please use good judgment
8498 here. Don't use flags for the sake of it; only use them
8499 if there is good reason to do so. Feel free to override
8500 the upstream author's ideas about which compilation
8501 options are best: they are often inappropriate for our
8507 <sect id="libraries">
8508 <heading>Libraries</heading>
8511 If the package is <strong>architecture: any</strong>, then
8512 the shared library compilation and linking flags must have
8513 <tt>-fPIC</tt>, or the package shall not build on some of
8514 the supported architectures<footnote>
8516 If you are using GCC, <tt>-fPIC</tt> produces code with
8517 relocatable position independent code, which is required for
8518 most architectures to create a shared library, with i386 and
8519 perhaps some others where non position independent code is
8520 permitted in a shared library.
8523 Position independent code may have a performance penalty,
8524 especially on <tt>i386</tt>. However, in most cases the
8525 speed penalty must be measured against the memory wasted on
8526 the few architectures where non position independent code is
8529 </footnote>. Any exception to this rule must be discussed on
8530 the mailing list <em>debian-devel@lists.debian.org</em>, and
8531 a rough consensus obtained. The reasons for not compiling
8532 with <tt>-fPIC</tt> flag must be recorded in the file
8533 <tt>README.Debian</tt>, and care must be taken to either
8534 restrict the architecture or arrange for <tt>-fPIC</tt> to
8535 be used on architectures where it is required.<footnote>
8537 Some of the reasons why this might be required is if the
8538 library contains hand crafted assembly code that is not
8539 relocatable, the speed penalty is excessive for compute
8540 intensive libs, and similar reasons.
8545 As to the static libraries, the common case is not to have
8546 relocatable code, since there is no benefit, unless in specific
8547 cases; therefore the static version must not be compiled
8548 with the <tt>-fPIC</tt> flag. Any exception to this rule
8549 should be discussed on the mailing list
8550 <em>debian-devel@lists.debian.org</em>, and the reasons for
8551 compiling with the <tt>-fPIC</tt> flag must be recorded in
8552 the file <tt>README.Debian</tt>. <footnote>
8554 Some of the reasons for linking static libraries with
8555 the <tt>-fPIC</tt> flag are if, for example, one needs a
8556 Perl API for a library that is under rapid development,
8557 and has an unstable API, so shared libraries are
8558 pointless at this phase of the library's development. In
8559 that case, since Perl needs a library with relocatable
8560 code, it may make sense to create a static library with
8561 relocatable code. Another reason cited is if you are
8562 distilling various libraries into a common shared
8563 library, like <tt>mklibs</tt> does in the Debian
8569 In other words, if both a shared and a static library is
8570 being built, each source unit (<tt>*.c</tt>, for example,
8571 for C files) will need to be compiled twice, for the normal
8576 Libraries should be built with threading support and to be
8577 thread-safe if the library supports this.
8581 Although not enforced by the build tools, shared libraries
8582 must be linked against all libraries that they use symbols from
8583 in the same way that binaries are. This ensures the correct
8584 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8585 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8586 systems and guarantees that all libraries can be safely opened
8587 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8588 option <tt>-Wl,-z,defs</tt> when building a shared library.
8589 Since this option enforces symbol resolution at build time,
8590 a missing library reference will be caught early as a fatal
8595 All installed shared libraries should be stripped with
8596 <example compact="compact">
8597 strip --strip-unneeded <var>your-lib</var>
8599 (The option <tt>--strip-unneeded</tt> makes
8600 <prgn>strip</prgn> remove only the symbols which aren't
8601 needed for relocation processing.) Shared libraries can
8602 function perfectly well when stripped, since the symbols for
8603 dynamic linking are in a separate part of the ELF object
8605 You might also want to use the options
8606 <tt>--remove-section=.comment</tt> and
8607 <tt>--remove-section=.note</tt> on both shared libraries
8608 and executables, and <tt>--strip-debug</tt> on static
8614 Note that under some circumstances it may be useful to
8615 install a shared library unstripped, for example when
8616 building a separate package to support debugging.
8620 Shared object files (often <file>.so</file> files) that are not
8621 public libraries, that is, they are not meant to be linked
8622 to by third party executables (binaries of other packages),
8623 should be installed in subdirectories of the
8624 <file>/usr/lib</file> directory. Such files are exempt from the
8625 rules that govern ordinary shared libraries, except that
8626 they must not be installed executable and should be
8628 A common example are the so-called "plug-ins",
8629 internal shared objects that are dynamically loaded by
8630 programs using <manref name="dlopen" section="3">.
8635 Packages that use <prgn>libtool</prgn> to create and install
8636 their shared libraries install a file containing additional
8637 metadata (ending in <file>.la</file>) alongside the library.
8638 For public libraries intended for use by other packages, these
8639 files normally should not be included in the Debian package,
8640 since the information they include is not necessary to link with
8641 the shared library on Debian and can add unnecessary additional
8642 dependencies to other programs or libraries.<footnote>
8643 These files store, among other things, all libraries on which
8644 that shared library depends. Unfortunately, if
8645 the <file>.la</file> file is present and contains that
8646 dependency information, using <prgn>libtool</prgn> when
8647 linking against that library will cause the resulting program
8648 or library to be linked against those dependencies as well,
8649 even if this is unnecessary. This can create unneeded
8650 dependencies on shared library packages that would otherwise
8651 be hidden behind the library ABI, and can make library
8652 transitions to new SONAMEs unnecessarily complicated and
8653 difficult to manage.
8655 If the <file>.la</file> file is required for that library (if,
8656 for instance, it's loaded via <tt>libltdl</tt> in a way that
8657 requires that meta-information), the <tt>dependency_libs</tt>
8658 setting in the <file>.la</file> file should normally be set to
8659 the empty string. If the shared library development package has
8660 historically included the <file>.la</file>, it must be retained
8661 in the development package (with <tt>dependency_libs</tt>
8662 emptied) until all libraries that depend on it have removed or
8663 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8664 files to prevent linking with those other libraries
8665 using <prgn>libtool</prgn> from failing.
8669 If the <file>.la</file> must be included, it should be included
8670 in the development (<tt>-dev</tt>) package, unless the library
8671 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8672 library. If it is intended for use with <tt>libltdl</tt>,
8673 the <file>.la</file> files must go in the run-time library
8678 These requirements for handling of <file>.la</file> files do not
8679 apply to loadable modules or libraries not installed in
8680 directories searched by default by the dynamic linker. Packages
8681 installing loadable modules will frequently need to install
8682 the <file>.la</file> files alongside the modules so that they
8683 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8684 does not need to be modified for libraries or modules that are
8685 not installed in directories searched by the dynamic linker by
8686 default and not intended for use by other packages.
8690 You must make sure that you use only released versions of
8691 shared libraries to build your packages; otherwise other
8692 users will not be able to run your binaries
8693 properly. Producing source packages that depend on
8694 unreleased compilers is also usually a bad
8701 <heading>Shared libraries</heading>
8703 This section has moved to <ref id="sharedlibs">.
8709 <heading>Scripts</heading>
8712 All command scripts, including the package maintainer
8713 scripts inside the package and used by <prgn>dpkg</prgn>,
8714 should have a <tt>#!</tt> line naming the shell to be used
8719 In the case of Perl scripts this should be
8720 <tt>#!/usr/bin/perl</tt>.
8724 When scripts are installed into a directory in the system
8725 PATH, the script name should not include an extension such
8726 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8727 language currently used to implement it.
8730 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8731 <file>init.d</file> scripts should almost certainly start
8732 with <tt>set -e</tt> so that errors are detected.
8733 <file>init.d</file> scripts are something of a special case, due
8734 to how frequently they need to call commands that are allowed to
8735 fail, and it may instead be easier to check the exit status of
8736 commands directly. See <ref id="writing-init"> for more
8737 information about writing <file>init.d</file> scripts.
8740 Every script should use <tt>set -e</tt> or check the exit status
8741 of <em>every</em> command.
8744 Scripts may assume that <file>/bin/sh</file> implements the
8745 SUSv3 Shell Command Language<footnote>
8746 Single UNIX Specification, version 3, which is also IEEE
8747 1003.1-2004 (POSIX), and is available on the World Wide Web
8748 from <url id="http://www.unix.org/version3/online.html"
8749 name="The Open Group"> after free
8750 registration.</footnote>
8751 plus the following additional features not mandated by
8753 These features are in widespread use in the Linux community
8754 and are implemented in all of bash, dash, and ksh, the most
8755 common shells users may wish to use as <file>/bin/sh</file>.
8758 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8759 must not generate a newline.</item>
8760 <item><tt>test</tt>, if implemented as a shell built-in, must
8761 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8763 <item><tt>local</tt> to create a scoped variable must be
8764 supported, including listing multiple variables in a single
8765 local command and assigning a value to a variable at the
8766 same time as localizing it. <tt>local</tt> may or
8767 may not preserve the variable value from an outer scope if
8768 no assignment is present. Uses such as:
8772 # ... use a, b, c, d ...
8775 must be supported and must set the value of <tt>c</tt> to
8778 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8779 -<var>signal</var></tt>, where <var>signal</var> is either
8780 the name of a signal or one of the numeric signals listed in
8781 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8782 supported if <prgn>kill</prgn> is implemented as a shell
8785 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8786 signals must be supported. In addition to the signal
8787 numbers listed in the extension, which are the same as for
8788 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8791 If a shell script requires non-SUSv3 features from the shell
8792 interpreter other than those listed above, the appropriate shell
8793 must be specified in the first line of the script (e.g.,
8794 <tt>#!/bin/bash</tt>) and the package must depend on the package
8795 providing the shell (unless the shell package is marked
8796 "Essential", as in the case of <prgn>bash</prgn>).
8800 You may wish to restrict your script to SUSv3 features plus the
8801 above set when possible so that it may use <file>/bin/sh</file>
8802 as its interpreter. Checking your script
8803 with <prgn>checkbashisms</prgn> from
8804 the <package>devscripts</package> package or running your script
8805 with an alternate shell such as <prgn>posh</prgn> may help
8806 uncover violations of the above requirements. If in doubt
8807 whether a script complies with these requirements,
8808 use <file>/bin/bash</file>.
8812 Perl scripts should check for errors when making any
8813 system calls, including <tt>open</tt>, <tt>print</tt>,
8814 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8818 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8819 scripting languages. See <em>Csh Programming Considered
8820 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8821 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8822 If an upstream package comes with <prgn>csh</prgn> scripts
8823 then you must make sure that they start with
8824 <tt>#!/bin/csh</tt> and make your package depend on the
8825 <prgn>c-shell</prgn> virtual package.
8829 Any scripts which create files in world-writeable
8830 directories (e.g., in <file>/tmp</file>) must use a
8831 mechanism which will fail atomically if a file with the same
8832 name already exists.
8836 The Debian base system provides the <prgn>tempfile</prgn>
8837 and <prgn>mktemp</prgn> utilities for use by scripts for
8844 <heading>Symbolic links</heading>
8847 In general, symbolic links within a top-level directory should
8848 be relative, and symbolic links pointing from one top-level
8849 directory to or into another should be absolute. (A top-level
8850 directory is a sub-directory of the root
8851 directory <file>/</file>.) For example, a symbolic link
8852 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8853 should be relative (<file>../share/bar</file>), but a symbolic
8854 link from <file>/var/run</file> to <file>/run</file> should be
8856 This is necessary to allow top-level directories to be
8857 symlinks. If linking <file>/var/run</file>
8858 to <file>/run</file> were done with the relative symbolic
8859 link <file>../run</file>, but <file>/var</file> were a
8860 symbolic link to <file>/srv/disk1</file>, the symbolic link
8861 would point to <file>/srv/run</file> rather than the intended
8867 In addition, symbolic links should be specified as short as
8868 possible, i.e., link targets like <file>foo/../bar</file> are
8873 Note that when creating a relative link using
8874 <prgn>ln</prgn> it is not necessary for the target of the
8875 link to exist relative to the working directory you're
8876 running <prgn>ln</prgn> from, nor is it necessary to change
8877 directory to the directory where the link is to be made.
8878 Simply include the string that should appear as the target
8879 of the link (this will be a pathname relative to the
8880 directory in which the link resides) as the first argument
8885 For example, in your <prgn>Makefile</prgn> or
8886 <file>debian/rules</file>, you can do things like:
8887 <example compact="compact">
8888 ln -fs gcc $(prefix)/bin/cc
8889 ln -fs gcc debian/tmp/usr/bin/cc
8890 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8891 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8896 A symbolic link pointing to a compressed file (in the sense
8897 that it is meant to be uncompressed with <prgn>unzip</prgn>
8898 or <prgn>zless</prgn> etc.) should always
8899 have the same file extension as the referenced file. (For
8900 example, if a file <file>foo.gz</file> is referenced by a
8901 symbolic link, the filename of the link has to end with
8902 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8907 <heading>Device files</heading>
8910 Packages must not include device files or named pipes in the
8915 If a package needs any special device files that are not
8916 included in the base system, it must call
8917 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8918 after notifying the user<footnote>
8919 This notification could be done via a (low-priority)
8920 debconf message, or an echo (printf) statement.
8925 Packages must not remove any device files in the
8926 <prgn>postrm</prgn> or any other script. This is left to the
8927 system administrator.
8931 Debian uses the serial devices
8932 <file>/dev/ttyS*</file>. Programs using the old
8933 <file>/dev/cu*</file> devices should be changed to use
8934 <file>/dev/ttyS*</file>.
8938 Named pipes needed by the package must be created in
8939 the <prgn>postinst</prgn> script<footnote>
8940 It's better to use <prgn>mkfifo</prgn> rather
8941 than <prgn>mknod</prgn> to create named pipes so that
8942 automated checks for packages incorrectly creating device
8943 files with <prgn>mknod</prgn> won't have false positives.
8944 </footnote> and removed in
8945 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8950 <sect id="config-files">
8951 <heading>Configuration files</heading>
8954 <heading>Definitions</heading>
8958 <tag>configuration file</tag>
8960 A file that affects the operation of a program, or
8961 provides site- or host-specific information, or
8962 otherwise customizes the behavior of a program.
8963 Typically, configuration files are intended to be
8964 modified by the system administrator (if needed or
8965 desired) to conform to local policy or to provide
8966 more useful site-specific behavior.
8969 <tag><tt>conffile</tt></tag>
8971 A file listed in a package's <tt>conffiles</tt>
8972 file, and is treated specially by <prgn>dpkg</prgn>
8973 (see <ref id="configdetails">).
8979 The distinction between these two is important; they are
8980 not interchangeable concepts. Almost all
8981 <tt>conffile</tt>s are configuration files, but many
8982 configuration files are not <tt>conffiles</tt>.
8986 As noted elsewhere, <file>/etc/init.d</file> scripts,
8987 <file>/etc/default</file> files, scripts installed in
8988 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8989 configuration installed in <file>/etc/cron.d</file> must be
8990 treated as configuration files. In general, any script that
8991 embeds configuration information is de-facto a configuration
8992 file and should be treated as such.
8997 <heading>Location</heading>
9000 Any configuration files created or used by your package
9001 must reside in <file>/etc</file>. If there are several,
9002 consider creating a subdirectory of <file>/etc</file>
9003 named after your package.
9007 If your package creates or uses configuration files
9008 outside of <file>/etc</file>, and it is not feasible to modify
9009 the package to use <file>/etc</file> directly, put the files
9010 in <file>/etc</file> and create symbolic links to those files
9011 from the location that the package requires.
9016 <heading>Behavior</heading>
9019 Configuration file handling must conform to the following
9021 <list compact="compact">
9023 local changes must be preserved during a package
9027 configuration files must be preserved when the
9028 package is removed, and only deleted when the
9032 Obsolete configuration files without local changes should be
9033 removed by the package during upgrade.<footnote>
9034 The <prgn>dpkg-maintscript-helper</prgn> tool, available from the
9035 <package>dpkg</package> package, can help for this task.</footnote>
9039 The easy way to achieve this behavior is to make the
9040 configuration file a <tt>conffile</tt>. This is
9041 appropriate only if it is possible to distribute a default
9042 version that will work for most installations, although
9043 some system administrators may choose to modify it. This
9044 implies that the default version will be part of the
9045 package distribution, and must not be modified by the
9046 maintainer scripts during installation (or at any other
9051 In order to ensure that local changes are preserved
9052 correctly, no package may contain or make hard links to
9053 conffiles.<footnote>
9054 Rationale: There are two problems with hard links.
9055 The first is that some editors break the link while
9056 editing one of the files, so that the two files may
9057 unwittingly become unlinked and different. The second
9058 is that <prgn>dpkg</prgn> might break the hard link
9059 while upgrading <tt>conffile</tt>s.
9064 The other way to do it is via the maintainer scripts. In
9065 this case, the configuration file must not be listed as a
9066 <tt>conffile</tt> and must not be part of the package
9067 distribution. If the existence of a file is required for
9068 the package to be sensibly configured it is the
9069 responsibility of the package maintainer to provide
9070 maintainer scripts which correctly create, update and
9071 maintain the file and remove it on purge. (See <ref
9072 id="maintainerscripts"> for more information.) These
9073 scripts must be idempotent (i.e., must work correctly if
9074 <prgn>dpkg</prgn> needs to re-run them due to errors
9075 during installation or removal), must cope with all the
9076 variety of ways <prgn>dpkg</prgn> can call maintainer
9077 scripts, must not overwrite or otherwise mangle the user's
9078 configuration without asking, must not ask unnecessary
9079 questions (particularly during upgrades), and must
9080 otherwise be good citizens.
9084 The scripts are not required to configure every possible
9085 option for the package, but only those necessary to get
9086 the package running on a given system. Ideally the
9087 sysadmin should not have to do any configuration other
9088 than that done (semi-)automatically by the
9089 <prgn>postinst</prgn> script.
9093 A common practice is to create a script called
9094 <file><var>package</var>-configure</file> and have the
9095 package's <prgn>postinst</prgn> call it if and only if the
9096 configuration file does not already exist. In certain
9097 cases it is useful for there to be an example or template
9098 file which the maintainer scripts use. Such files should
9099 be in <file>/usr/share/<var>package</var></file> or
9100 <file>/usr/lib/<var>package</var></file> (depending on whether
9101 they are architecture-independent or not). There should
9102 be symbolic links to them from
9103 <file>/usr/share/doc/<var>package</var>/examples</file> if
9104 they are examples, and should be perfectly ordinary
9105 <prgn>dpkg</prgn>-handled files (<em>not</em>
9106 configuration files).
9110 These two styles of configuration file handling must
9111 not be mixed, for that way lies madness:
9112 <prgn>dpkg</prgn> will ask about overwriting the file
9113 every time the package is upgraded.
9118 <heading>Sharing configuration files</heading>
9121 If two or more packages use the same configuration file
9122 and it is reasonable for both to be installed at the same
9123 time, one of these packages must be defined as
9124 <em>owner</em> of the configuration file, i.e., it will be
9125 the package which handles that file as a configuration
9126 file. Other packages that use the configuration file must
9127 depend on the owning package if they require the
9128 configuration file to operate. If the other package will
9129 use the configuration file if present, but is capable of
9130 operating without it, no dependency need be declared.
9134 If it is desirable for two or more related packages to
9135 share a configuration file <em>and</em> for all of the
9136 related packages to be able to modify that configuration
9137 file, then the following should be done:
9138 <enumlist compact="compact">
9140 One of the related packages (the "owning" package)
9141 will manage the configuration file with maintainer
9142 scripts as described in the previous section.
9145 The owning package should also provide a program
9146 that the other packages may use to modify the
9150 The related packages must use the provided program
9151 to make any desired modifications to the
9152 configuration file. They should either depend on
9153 the core package to guarantee that the configuration
9154 modifier program is available or accept gracefully
9155 that they cannot modify the configuration file if it
9156 is not. (This is in addition to the fact that the
9157 configuration file may not even be present in the
9164 Sometimes it's appropriate to create a new package which
9165 provides the basic infrastructure for the other packages
9166 and which manages the shared configuration files. (The
9167 <tt>sgml-base</tt> package is a good example.)
9171 If the configuration file cannot be shared as described above,
9172 the packages must be marked as conflicting with each other.
9173 Two packages that specify the same file as
9174 a <tt>conffile</tt> must conflict. This is an instance of the
9175 general rule about not sharing files. Neither alternatives
9176 nor diversions are likely to be appropriate in this case; in
9177 particular, <prgn>dpkg</prgn> does not handle diverted
9178 <tt>conffile</tt>s well.
9182 When two packages both declare the same <tt>conffile</tt>, they
9183 may see left-over configuration files from each other even
9184 though they conflict with each other. If a user removes
9185 (without purging) one of the packages and installs the other,
9186 the new package will take over the <tt>conffile</tt> from the
9187 old package. If the file was modified by the user, it will be
9188 treated the same as any other locally
9189 modified <tt>conffile</tt> during an upgrade.
9193 The maintainer scripts must not alter a <tt>conffile</tt>
9194 of <em>any</em> package, including the one the scripts
9200 <heading>User configuration files ("dotfiles")</heading>
9203 The files in <file>/etc/skel</file> will automatically be
9204 copied into new user accounts by <prgn>adduser</prgn>.
9205 No other program should reference the files in
9206 <file>/etc/skel</file>.
9210 Therefore, if a program needs a dotfile to exist in
9211 advance in <file>$HOME</file> to work sensibly, that dotfile
9212 should be installed in <file>/etc/skel</file> and treated as a
9217 However, programs that require dotfiles in order to
9218 operate sensibly are a bad thing, unless they do create
9219 the dotfiles themselves automatically.
9223 Furthermore, programs should be configured by the Debian
9224 default installation to behave as closely to the upstream
9225 default behavior as possible.
9229 Therefore, if a program in a Debian package needs to be
9230 configured in some way in order to operate sensibly, that
9231 should be done using a site-wide configuration file placed
9232 in <file>/etc</file>. Only if the program doesn't support a
9233 site-wide default configuration and the package maintainer
9234 doesn't have time to add it may a default per-user file be
9235 placed in <file>/etc/skel</file>.
9239 <file>/etc/skel</file> should be as empty as we can make it.
9240 This is particularly true because there is no easy (or
9241 necessarily desirable) mechanism for ensuring that the
9242 appropriate dotfiles are copied into the accounts of
9243 existing users when a package is installed.
9249 <heading>Log files</heading>
9251 Log files should usually be named
9252 <file>/var/log/<var>package</var>.log</file>. If you have many
9253 log files, or need a separate directory for permission
9254 reasons (<file>/var/log</file> is writable only by
9255 <file>root</file>), you should usually create a directory named
9256 <file>/var/log/<var>package</var></file> and place your log
9261 Log files must be rotated occasionally so that they don't grow
9262 indefinitely. The best way to do this is to install a log
9263 rotation configuration file in the
9264 directory <file>/etc/logrotate.d</file>, normally
9265 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9266 the facilities provided by <prgn>logrotate</prgn>.
9269 The traditional approach to log files has been to set up
9270 <em>ad hoc</em> log rotation schemes using simple shell
9271 scripts and cron. While this approach is highly
9272 customizable, it requires quite a lot of sysadmin work.
9273 Even though the original Debian system helped a little
9274 by automatically installing a system which can be used
9275 as a template, this was deemed not enough.
9279 The use of <prgn>logrotate</prgn>, a program developed
9280 by Red Hat, is better, as it centralizes log management.
9281 It has both a configuration file
9282 (<file>/etc/logrotate.conf</file>) and a directory where
9283 packages can drop their individual log rotation
9284 configurations (<file>/etc/logrotate.d</file>).
9287 Here is a good example for a logrotate config
9288 file (for more information see <manref name="logrotate"
9290 <example compact="compact">
9291 /var/log/foo/*.log {
9297 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9301 This rotates all files under <file>/var/log/foo</file>, saves 12
9302 compressed generations, and tells the daemon to reopen its log
9303 files after the log rotation. It skips this log rotation
9304 (via <tt>missingok</tt>) if no such log file is present, which
9305 avoids errors if the package is removed but not purged.
9309 Log files should be removed when the package is
9310 purged (but not when it is only removed). This should be
9311 done by the <prgn>postrm</prgn> script when it is called
9312 with the argument <tt>purge</tt> (see <ref
9313 id="removedetails">).
9317 <sect id="permissions-owners">
9318 <heading>Permissions and owners</heading>
9321 The rules in this section are guidelines for general use.
9322 If necessary you may deviate from the details below.
9323 However, if you do so you must make sure that what is done
9324 is secure and you should try to be as consistent as possible
9325 with the rest of the system. You should probably also
9326 discuss it on <prgn>debian-devel</prgn> first.
9330 Files should be owned by <tt>root:root</tt>, and made
9331 writable only by the owner and universally readable (and
9332 executable, if appropriate), that is mode 644 or 755.
9336 Directories should be mode 755 or (for group-writability)
9337 mode 2775. The ownership of the directory should be
9338 consistent with its mode: if a directory is mode 2775, it
9339 should be owned by the group that needs write access to
9342 When a package is upgraded, and the owner or permissions
9343 of a file included in the package has changed, dpkg
9344 arranges for the ownership and permissions to be
9345 correctly set upon installation. However, this does not
9346 extend to directories; the permissions and ownership of
9347 directories already on the system does not change on
9348 install or upgrade of packages. This makes sense, since
9349 otherwise common directories like <tt>/usr</tt> would
9350 always be in flux. To correctly change permissions of a
9351 directory the package owns, explicit action is required,
9352 usually in the <tt>postinst</tt> script. Care must be
9353 taken to handle downgrades as well, in that case.
9359 Control information files should be owned by <tt>root:root</tt>
9360 and either mode 644 (for most files) or mode 755 (for
9361 executables such as <qref id="maintscripts">maintainer
9366 Setuid and setgid executables should be mode 4755 or 2755
9367 respectively, and owned by the appropriate user or group.
9368 They should not be made unreadable (modes like 4711 or
9369 2711 or even 4111); doing so achieves no extra security,
9370 because anyone can find the binary in the freely available
9371 Debian package; it is merely inconvenient. For the same
9372 reason you should not restrict read or execute permissions
9373 on non-set-id executables.
9377 Some setuid programs need to be restricted to particular
9378 sets of users, using file permissions. In this case they
9379 should be owned by the uid to which they are set-id, and by
9380 the group which should be allowed to execute them. They
9381 should have mode 4754; again there is no point in making
9382 them unreadable to those users who must not be allowed to
9387 It is possible to arrange that the system administrator can
9388 reconfigure the package to correspond to their local
9389 security policy by changing the permissions on a binary:
9390 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9391 described below.<footnote>
9392 Ordinary files installed by <prgn>dpkg</prgn> (as
9393 opposed to <tt>conffile</tt>s and other similar objects)
9394 normally have their permissions reset to the distributed
9395 permissions when the package is reinstalled. However,
9396 the use of <prgn>dpkg-statoverride</prgn> overrides this
9399 Another method you should consider is to create a group for
9400 people allowed to use the program(s) and make any setuid
9401 executables executable only by that group.
9405 If you need to create a new user or group for your package
9406 there are two possibilities. Firstly, you may need to
9407 make some files in the binary package be owned by this
9408 user or group, or you may need to compile the user or
9409 group id (rather than just the name) into the binary
9410 (though this latter should be avoided if possible, as in
9411 this case you need a statically allocated id).</p>
9414 If you need a statically allocated id, you must ask for a
9415 user or group id from the <tt>base-passwd</tt> maintainer,
9416 and must not release the package until you have been
9417 allocated one. Once you have been allocated one you must
9418 either make the package depend on a version of the
9419 <tt>base-passwd</tt> package with the id present in
9420 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9421 your package to create the user or group itself with the
9422 correct id (using <tt>adduser</tt>) in its
9423 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9424 the <prgn>postinst</prgn> is to be preferred if it is
9425 possible, otherwise a pre-dependency will be needed on the
9426 <tt>adduser</tt> package.)
9430 On the other hand, the program might be able to determine
9431 the uid or gid from the user or group name at runtime, so
9432 that a dynamically allocated id can be used. In this case
9433 you should choose an appropriate user or group name,
9434 discussing this on <prgn>debian-devel</prgn> and checking
9435 with the <package/base-passwd/ maintainer that it is unique and that
9436 they do not wish you to use a statically allocated id
9437 instead. When this has been checked you must arrange for
9438 your package to create the user or group if necessary using
9439 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9440 <prgn>postinst</prgn> script (again, the latter is to be
9441 preferred if it is possible).
9445 Note that changing the numeric value of an id associated
9446 with a name is very difficult, and involves searching the
9447 file system for all appropriate files. You need to think
9448 carefully whether a static or dynamic id is required, since
9449 changing your mind later will cause problems.
9452 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9454 This section is not intended as policy, but as a
9455 description of the use of <prgn>dpkg-statoverride</prgn>.
9459 If a system administrator wishes to have a file (or
9460 directory or other such thing) installed with owner and
9461 permissions different from those in the distributed Debian
9462 package, they can use the <prgn>dpkg-statoverride</prgn>
9463 program to instruct <prgn>dpkg</prgn> to use the different
9464 settings every time the file is installed. Thus the
9465 package maintainer should distribute the files with their
9466 normal permissions, and leave it for the system
9467 administrator to make any desired changes. For example, a
9468 daemon which is normally required to be setuid root, but
9469 in certain situations could be used without being setuid,
9470 should be installed setuid in the <tt>.deb</tt>. Then the
9471 local system administrator can change this if they wish.
9472 If there are two standard ways of doing it, the package
9473 maintainer can use <tt>debconf</tt> to find out the
9474 preference, and call <prgn>dpkg-statoverride</prgn> in the
9475 maintainer script if necessary to accommodate the system
9476 administrator's choice. Care must be taken during
9477 upgrades to not override an existing setting.
9481 Given the above, <prgn>dpkg-statoverride</prgn> is
9482 essentially a tool for system administrators and would not
9483 normally be needed in the maintainer scripts. There is
9484 one type of situation, though, where calls to
9485 <prgn>dpkg-statoverride</prgn> would be needed in the
9486 maintainer scripts, and that involves packages which use
9487 dynamically allocated user or group ids. In such a
9488 situation, something like the following idiom can be very
9489 helpful in the package's <prgn>postinst</prgn>, where
9490 <tt>sysuser</tt> is a dynamically allocated id:
9492 for i in /usr/bin/foo /usr/sbin/bar
9494 # only do something when no setting exists
9495 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9497 #include: debconf processing, question about foo and bar
9498 if [ "$RET" = "true" ] ; then
9499 dpkg-statoverride --update --add sysuser root 4755 $i
9504 The corresponding code to remove the override when the package
9507 for i in /usr/bin/foo /usr/sbin/bar
9509 if dpkg-statoverride --list $i >/dev/null 2>&1
9511 dpkg-statoverride --remove $i
9519 <sect id="filenames">
9520 <heading>File names</heading>
9523 The name of the files installed by binary packages in the system PATH
9524 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9525 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9530 The name of the files and directories installed by binary packages
9531 outside the system PATH must be encoded in UTF-8 and should be
9532 restricted to ASCII when it is possible to do so.
9538 <chapt id="customized-programs">
9539 <heading>Customized programs</heading>
9541 <sect id="arch-spec">
9542 <heading>Architecture specification strings</heading>
9545 If a program needs to specify an <em>architecture specification
9546 string</em> in some place, it should select one of the strings
9547 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9548 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9549 part is sometimes elided, as when the OS is Linux.
9553 Note that we don't want to use
9554 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9555 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9556 since this would make our programs incompatible with other
9557 Linux distributions. We also don't use something like
9558 <tt><var>arch</var>-unknown-linux</tt>, since the
9559 <tt>unknown</tt> does not look very good.
9562 <sect1 id="arch-wildcard-spec">
9563 <heading>Architecture wildcards</heading>
9566 A package may specify an architecture wildcard. Architecture
9567 wildcards are in the format <tt>any</tt> (which matches every
9568 architecture), <tt><var>os</var></tt>-any, or
9569 any-<tt><var>cpu</var></tt>. <footnote>
9570 Internally, the package system normalizes the GNU triplets
9571 and the Debian arches into Debian arch triplets (which are
9572 kind of inverted GNU triplets), with the first component of
9573 the triplet representing the libc and ABI in use, and then
9574 does matching against those triplets. However, such
9575 triplets are an internal implementation detail that should
9576 not be used by packages directly. The libc and ABI portion
9577 is handled internally by the package system based on
9578 the <var>os</var> and <var>cpu</var>.
9585 <heading>Daemons</heading>
9588 The configuration files <file>/etc/services</file>,
9589 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9590 by the <prgn>netbase</prgn> package and must not be modified
9595 If a package requires a new entry in one of these files, the
9596 maintainer should get in contact with the
9597 <prgn>netbase</prgn> maintainer, who will add the entries
9598 and release a new version of the <prgn>netbase</prgn>
9603 The configuration file <file>/etc/inetd.conf</file> must not be
9604 modified by the package's scripts except via the
9605 <prgn>update-inetd</prgn> script or the
9606 <file>DebianNet.pm</file> Perl module. See their documentation
9607 for details on how to add entries.
9611 If a package wants to install an example entry into
9612 <file>/etc/inetd.conf</file>, the entry must be preceded with
9613 exactly one hash character (<tt>#</tt>). Such lines are
9614 treated as "commented out by user" by the
9615 <prgn>update-inetd</prgn> script and are not changed or
9616 activated during package updates.
9621 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9625 Some programs need to create pseudo-ttys. This should be done
9626 using Unix98 ptys if the C library supports it. The resulting
9627 program must not be installed setuid root, unless that
9628 is required for other functionality.
9632 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9633 <file>/var/log/lastlog</file> must be installed writable by
9634 group <tt>utmp</tt>. Programs which need to modify those
9635 files must be installed setgid <tt>utmp</tt>.
9640 <heading>Editors and pagers</heading>
9643 Some programs have the ability to launch an editor or pager
9644 program to edit or display a text document. Since there are
9645 lots of different editors and pagers available in the Debian
9646 distribution, the system administrator and each user should
9647 have the possibility to choose their preferred editor and
9652 In addition, every program should choose a good default
9653 editor/pager if none is selected by the user or system
9658 Thus, every program that launches an editor or pager must
9659 use the EDITOR or PAGER environment variable to determine
9660 the editor or pager the user wishes to use. If these
9661 variables are not set, the programs <file>/usr/bin/editor</file>
9662 and <file>/usr/bin/pager</file> should be used, respectively.
9666 These two files are managed through the <prgn>dpkg</prgn>
9667 "alternatives" mechanism. Every package providing an editor or
9668 pager must call the <prgn>update-alternatives</prgn> script to
9669 register as an alternative for <file>/usr/bin/editor</file>
9670 or <file>/usr/bin/pager</file> as appropriate. The alternative
9671 should have a slave alternative
9672 for <file>/usr/share/man/man1/editor.1.gz</file>
9673 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9674 corresponding manual page.
9678 If it is very hard to adapt a program to make use of the
9679 EDITOR or PAGER variables, that program may be configured to
9680 use <file>/usr/bin/sensible-editor</file> and
9681 <file>/usr/bin/sensible-pager</file> as the editor or pager
9682 program respectively. These are two scripts provided in the
9683 <package>sensible-utils</package> package that check the EDITOR
9684 and PAGER variables and launch the appropriate program, and fall
9685 back to <file>/usr/bin/editor</file>
9686 and <file>/usr/bin/pager</file> if the variable is not set.
9690 A program may also use the VISUAL environment variable to
9691 determine the user's choice of editor. If it exists, it
9692 should take precedence over EDITOR. This is in fact what
9693 <file>/usr/bin/sensible-editor</file> does.
9697 It is not required for a package to depend on
9698 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9699 package to provide such virtual packages.<footnote>
9700 The Debian base system already provides an editor and a
9706 <sect id="web-appl">
9707 <heading>Web servers and applications</heading>
9710 This section describes the locations and URLs that should
9711 be used by all web servers and web applications in the
9718 Cgi-bin executable files are installed in the
9720 <example compact="compact">
9723 or a subdirectory of that directory, and the script
9724 <example compact="compact">
9725 /usr/lib/cgi-bin/.../<var>cgi-bin-name</var>
9727 should be referred to as
9728 <example compact="compact">
9729 http://localhost/cgi-bin/.../<var>cgi-bin-name</var>
9738 <p>Access to images</p>
9740 It is recommended that images for a package be stored
9741 in <tt>/usr/share/images/<var>package</var></tt> and
9742 may be referred to through an alias <tt>/images/</tt>
9745 http://localhost/images/<package>/<filename>
9752 <p>Web Document Root</p>
9755 Web Applications should try to avoid storing files in
9756 the Web Document Root. Instead they should use the
9757 /usr/share/doc/<var>package</var> directory for
9758 documents and register the Web Application via the
9759 <package>doc-base</package> package. If access to the
9760 web document root is unavoidable then use
9761 <example compact="compact">
9764 as the Document Root. This might be just a symbolic
9765 link to the location where the system administrator
9766 has put the real document root.
9769 <item><p>Providing httpd and/or httpd-cgi</p>
9771 All web servers should provide the virtual package
9772 <tt>httpd</tt>. If a web server has CGI support it should
9773 provide <tt>httpd-cgi</tt> additionally.
9776 All web applications which do not contain CGI scripts should
9777 depend on <tt>httpd</tt>, all those web applications which
9778 <tt>do</tt> contain CGI scripts, should depend on
9786 <sect id="mail-transport-agents">
9787 <heading>Mail transport, delivery and user agents</heading>
9790 Debian packages which process electronic mail, whether mail
9791 user agents (MUAs) or mail transport agents (MTAs), must
9792 ensure that they are compatible with the configuration
9793 decisions below. Failure to do this may result in lost
9794 mail, broken <tt>From:</tt> lines, and other serious brain
9799 The mail spool is <file>/var/mail</file> and the interface to
9800 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9801 the FHS). On older systems, the mail spool may be
9802 physically located in <file>/var/spool/mail</file>, but all
9803 access to the mail spool should be via the
9804 <file>/var/mail</file> symlink. The mail spool is part of the
9805 base system and not part of the MTA package.
9809 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9810 programs (such as IMAP daemons) must lock the mailbox in an
9811 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9812 be combined with dot locking. To avoid deadlocks, a program
9813 should use <tt>fcntl()</tt> first and dot locking after
9814 this, or alternatively implement the two locking methods in
9815 a non blocking way<footnote>
9816 If it is not possible to establish both locks, the
9817 system shouldn't wait for the second lock to be
9818 established, but remove the first lock, wait a (random)
9819 time, and start over locking again.
9820 </footnote>. Using the functions <tt>maillock</tt> and
9821 <tt>mailunlock</tt> provided by the
9822 <tt>liblockfile*</tt><footnote>
9823 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9824 to use these functions.
9825 </footnote> packages is the recommended way to realize this.
9829 Mailboxes are generally either mode 600 and owned by
9830 <var>user</var> or mode 660 and owned by
9831 <tt><var>user</var>:mail</tt><footnote>
9832 There are two traditional permission schemes for mail spools:
9833 mode 600 with all mail delivery done by processes running as
9834 the destination user, or mode 660 and owned by group mail with
9835 mail delivery done by a process running as a system user in
9836 group mail. Historically, Debian required mode 660 mail
9837 spools to enable the latter model, but that model has become
9838 increasingly uncommon and the principle of least privilege
9839 indicates that mail systems that use the first model should
9840 use permissions of 600. If delivery to programs is permitted,
9841 it's easier to keep the mail system secure if the delivery
9842 agent runs as the destination user. Debian Policy therefore
9843 permits either scheme.
9844 </footnote>. The local system administrator may choose a
9845 different permission scheme; packages should not make
9846 assumptions about the permission and ownership of mailboxes
9847 unless required (such as when creating a new mailbox). A MUA
9848 may remove a mailbox (unless it has nonstandard permissions) in
9849 which case the MTA or another MUA must recreate it if needed.
9853 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9854 be setgid mail to do the locking mentioned above (and
9855 must obviously avoid accessing other users' mailboxes
9856 using this privilege).</p>
9859 <file>/etc/aliases</file> is the source file for the system mail
9860 aliases (e.g., postmaster, usenet, etc.), it is the one
9861 which the sysadmin and <prgn>postinst</prgn> scripts may
9862 edit. After <file>/etc/aliases</file> is edited the program or
9863 human editing it must call <prgn>newaliases</prgn>. All MTA
9864 packages must come with a <prgn>newaliases</prgn> program,
9865 even if it does nothing, but older MTA packages did not do
9866 this so programs should not fail if <prgn>newaliases</prgn>
9867 cannot be found. Note that because of this, all MTA
9868 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9869 <tt>Replaces: mail-transport-agent</tt> control fields.
9873 The convention of writing <tt>forward to
9874 <var>address</var></tt> in the mailbox itself is not
9875 supported. Use a <tt>.forward</tt> file instead.</p>
9878 The <prgn>rmail</prgn> program used by UUCP
9879 for incoming mail should be <file>/usr/sbin/rmail</file>.
9880 Likewise, <prgn>rsmtp</prgn>, for receiving
9881 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9885 If your package needs to know what hostname to use on (for
9886 example) outgoing news and mail messages which are generated
9887 locally, you should use the file <file>/etc/mailname</file>. It
9888 will contain the portion after the username and <tt>@</tt>
9889 (at) sign for email addresses of users on the machine
9890 (followed by a newline).
9894 Such a package should check for the existence of this file
9895 when it is being configured. If it exists, it should be
9896 used without comment, although an MTA's configuration script
9897 may wish to prompt the user even if it finds that this file
9898 exists. If the file does not exist, the package should
9899 prompt the user for the value (preferably using
9900 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9901 as well as using it in the package's configuration. The
9902 prompt should make it clear that the name will not just be
9903 used by that package. For example, in this situation the
9904 <tt>inn</tt> package could say something like:
9905 <example compact="compact">
9906 Please enter the "mail name" of your system. This is the
9907 hostname portion of the address to be shown on outgoing
9908 news and mail messages. The default is
9909 <var>syshostname</var>, your system's host name. Mail
9910 name ["<var>syshostname</var>"]:
9912 where <var>syshostname</var> is the output of <tt>hostname
9918 <heading>News system configuration</heading>
9921 All the configuration files related to the NNTP (news)
9922 servers and clients should be located under
9923 <file>/etc/news</file>.</p>
9926 There are some configuration issues that apply to a number
9927 of news clients and server packages on the machine. These
9931 <tag><file>/etc/news/organization</file></tag>
9933 A string which should appear as the
9934 organization header for all messages posted
9935 by NNTP clients on the machine
9938 <tag><file>/etc/news/server</file></tag>
9940 Contains the FQDN of the upstream NNTP
9941 server, or localhost if the local machine is
9946 Other global files may be added as required for cross-package news
9953 <heading>Programs for the X Window System</heading>
9956 <heading>Providing X support and package priorities</heading>
9959 Programs that can be configured with support for the X
9960 Window System must be configured to do so and must declare
9961 any package dependencies necessary to satisfy their
9962 runtime requirements when using the X Window System. If
9963 such a package is of higher priority than the X packages
9964 on which it depends, it is required that either the
9965 X-specific components be split into a separate package, or
9966 that an alternative version of the package, which includes
9967 X support, be provided, or that the package's priority be
9973 <heading>Packages providing an X server</heading>
9976 Packages that provide an X server that, directly or
9977 indirectly, communicates with real input and display
9978 hardware should declare in their <tt>Provides</tt> control
9979 field that they provide the virtual
9980 package <tt>xserver</tt>.<footnote>
9981 This implements current practice, and provides an
9982 actual policy for usage of the <tt>xserver</tt>
9983 virtual package which appears in the virtual packages
9984 list. In a nutshell, X servers that interface
9985 directly with the display and input hardware or via
9986 another subsystem (e.g., GGI) should provide
9987 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9988 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9994 <heading>Packages providing a terminal emulator</heading>
9997 Packages that provide a terminal emulator for the X Window
9998 System which meet the criteria listed below should declare in
9999 their <tt>Provides</tt> control field that they provide the
10000 virtual package <tt>x-terminal-emulator</tt>. They should
10001 also register themselves as an alternative for
10002 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
10003 20. That alternative should have a slave alternative
10004 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
10005 pointing to the corresponding manual page.
10009 To be an <tt>x-terminal-emulator</tt>, a program must:
10010 <list compact="compact">
10012 Be able to emulate a DEC VT100 terminal, or a
10013 compatible terminal.
10017 Support the command-line option <tt>-e
10018 <var>command</var></tt>, which creates a new
10019 terminal window<footnote>
10020 "New terminal window" does not necessarily mean
10021 a new top-level X window directly parented by
10022 the window manager; it could, if the terminal
10023 emulator application were so coded, be a new
10024 "view" in a multiple-document interface (MDI).
10026 and runs the specified <var>command</var>,
10027 interpreting the entirety of the rest of the command
10028 line as a command to pass straight to exec, in the
10029 manner that <tt>xterm</tt> does.
10033 Support the command-line option <tt>-T
10034 <var>title</var></tt>, which creates a new terminal
10035 window with the window title <var>title</var>.
10042 <heading>Packages providing a window manager</heading>
10045 Packages that provide a window manager should declare in
10046 their <tt>Provides</tt> control field that they provide the
10047 virtual package <tt>x-window-manager</tt>. They should also
10048 register themselves as an alternative for
10049 <file>/usr/bin/x-window-manager</file>, with a priority
10050 calculated as follows:
10051 <list compact="compact">
10053 Start with a priority of 20.
10057 If the window manager supports the Debian menu
10058 system, add 20 points if this support is available
10059 in the package's default configuration (i.e., no
10060 configuration files belonging to the system or user
10061 have to be edited to activate the feature); if
10062 configuration files must be modified, add only 10
10068 If the window manager complies with <url
10069 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10070 name="The Window Manager Specification Project">,
10071 written by the <url id="http://www.freedesktop.org/wiki/"
10072 name="Free Desktop Group">, add 40 points.
10076 If the window manager permits the X session to be
10077 restarted using a <em>different</em> window manager
10078 (without killing the X server) in its default
10079 configuration, add 10 points; otherwise add none.
10082 That alternative should have a slave alternative
10083 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10084 pointing to the corresponding manual page.
10089 <heading>Packages providing fonts</heading>
10092 Packages that provide fonts for the X Window
10094 For the purposes of Debian Policy, a "font for the X
10095 Window System" is one which is accessed via X protocol
10096 requests. Fonts for the Linux console, for PostScript
10097 renderer, or any other purpose, do not fit this
10098 definition. Any tool which makes such fonts available
10099 to the X Window System, however, must abide by this
10102 must do a number of things to ensure that they are both
10103 available without modification of the X or font server
10104 configuration, and that they do not corrupt files used by
10105 other font packages to register information about
10109 Fonts of any type supported by the X Window System
10110 must be in a separate binary package from any
10111 executables, libraries, or documentation (except
10112 that specific to the fonts shipped, such as their
10113 license information). If one or more of the fonts
10114 so packaged are necessary for proper operation of
10115 the package with which they are associated the font
10116 package may be Recommended; if the fonts merely
10117 provide an enhancement, a Suggests relationship may
10118 be used. Packages must not Depend on font
10119 packages.<footnote>
10120 This is because the X server may retrieve fonts
10121 from the local file system or over the network
10122 from an X font server; the Debian package system
10123 is empowered to deal only with the local
10129 BDF fonts must be converted to PCF fonts with the
10130 <prgn>bdftopcf</prgn> utility (available in the
10131 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10132 placed in a directory that corresponds to their
10134 <list compact="compact">
10136 100 dpi fonts must be placed in
10137 <file>/usr/share/fonts/X11/100dpi/</file>.
10141 75 dpi fonts must be placed in
10142 <file>/usr/share/fonts/X11/75dpi/</file>.
10146 Character-cell fonts, cursor fonts, and other
10147 low-resolution fonts must be placed in
10148 <file>/usr/share/fonts/X11/misc/</file>.
10154 Type 1 fonts must be placed in
10155 <file>/usr/share/fonts/X11/Type1/</file>. If font
10156 metric files are available, they must be placed here
10161 Subdirectories of <file>/usr/share/fonts/X11/</file>
10162 other than those listed above must be neither
10163 created nor used. (The <file>PEX</file>, <file>CID</file>,
10164 <file>Speedo</file>, and <file>cyrillic</file> directories
10165 are excepted for historical reasons, but installation of
10166 files into these directories remains discouraged.)
10170 Font packages may, instead of placing files directly
10171 in the X font directories listed above, provide
10172 symbolic links in that font directory pointing to
10173 the files' actual location in the filesystem. Such
10174 a location must comply with the FHS.
10178 Font packages should not contain both 75dpi and
10179 100dpi versions of a font. If both are available,
10180 they should be provided in separate binary packages
10181 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10182 the names of the packages containing the
10183 corresponding fonts.
10187 Fonts destined for the <file>misc</file> subdirectory
10188 should not be included in the same package as 75dpi
10189 or 100dpi fonts; instead, they should be provided in
10190 a separate package with <tt>-misc</tt> appended to
10195 Font packages must not provide the files
10196 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10197 <file>fonts.scale</file> in a font directory:
10200 <file>fonts.dir</file> files must not be provided at all.
10204 <file>fonts.alias</file> and <file>fonts.scale</file>
10205 files, if needed, should be provided in the
10207 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10208 where <var>fontdir</var> is the name of the
10210 <file>/usr/share/fonts/X11/</file> where the
10211 package's corresponding fonts are stored
10212 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10213 <var>package</var> is the name of the package
10214 that provides these fonts, and
10215 <var>extension</var> is either <tt>scale</tt>
10216 or <tt>alias</tt>, whichever corresponds to
10223 Font packages must declare a dependency on
10224 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10225 or <tt>Pre-Depends</tt> control field.
10229 Font packages that provide one or more
10230 <file>fonts.scale</file> files as described above must
10231 invoke <prgn>update-fonts-scale</prgn> on each
10232 directory into which they installed fonts
10233 <em>before</em> invoking
10234 <prgn>update-fonts-dir</prgn> on that directory.
10235 This invocation must occur in both the
10236 <prgn>postinst</prgn> (for all arguments) and
10237 <prgn>postrm</prgn> (for all arguments except
10238 <tt>upgrade</tt>) scripts.
10242 Font packages that provide one or more
10243 <file>fonts.alias</file> files as described above must
10244 invoke <prgn>update-fonts-alias</prgn> on each
10245 directory into which they installed fonts. This
10246 invocation must occur in both the
10247 <prgn>postinst</prgn> (for all arguments) and
10248 <prgn>postrm</prgn> (for all arguments except
10249 <tt>upgrade</tt>) scripts.
10253 Font packages must invoke
10254 <prgn>update-fonts-dir</prgn> on each directory into
10255 which they installed fonts. This invocation must
10256 occur in both the <prgn>postinst</prgn> (for all
10257 arguments) and <prgn>postrm</prgn> (for all
10258 arguments except <tt>upgrade</tt>) scripts.
10262 Font packages must not provide alias names for the
10263 fonts they include which collide with alias names
10264 already in use by fonts already packaged.
10268 Font packages must not provide fonts with the same
10269 XLFD registry name as another font already packaged.
10275 <sect1 id="appdefaults">
10276 <heading>Application defaults files</heading>
10279 Application defaults files must be installed in the
10280 directory <file>/etc/X11/app-defaults/</file> (use of a
10281 localized subdirectory of <file>/etc/X11/</file> as described
10282 in the <em>X Toolkit Intrinsics - C Language
10283 Interface</em> manual is also permitted). They must be
10284 registered as <tt>conffile</tt>s or handled as
10285 configuration files.
10289 Customization of programs' X resources may also be
10290 supported with the provision of a file with the same name
10291 as that of the package placed in
10292 the <file>/etc/X11/Xresources/</file> directory, which
10293 must be registered as a <tt>conffile</tt> or handled as a
10294 configuration file.<footnote>
10295 Note that this mechanism is not the same as using
10296 app-defaults; app-defaults are tied to the client
10297 binary on the local file system, whereas X resources
10298 are stored in the X server and affect all connecting
10305 <heading>Installation directory issues</heading>
10308 Historically, packages using the X Window System used a
10309 separate set of installation directories from other packages.
10310 This practice has been discontinued and packages using the X
10311 Window System should now generally be installed in the same
10312 directories as any other package. Specifically, packages must
10313 not install files under the <file>/usr/X11R6/</file> directory
10314 and the <file>/usr/X11R6/</file> directory hierarchy should be
10315 regarded as obsolete.
10319 Include files previously installed under
10320 <file>/usr/X11R6/include/X11/</file> should be installed into
10321 <file>/usr/include/X11/</file>. For files previously
10322 installed into subdirectories of
10323 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10324 determine if subdirectories of <file>/usr/lib/</file> and
10325 <file>/usr/share/</file> can be used. If not, a subdirectory
10326 of <file>/usr/lib/X11/</file> should be used.
10330 Configuration files for window, display, or session managers
10331 or other applications that are tightly integrated with the X
10332 Window System may be placed in a subdirectory
10333 of <file>/etc/X11/</file> corresponding to the package name.
10334 Other X Window System applications should use
10335 the <file>/etc/</file> directory unless otherwise mandated by
10336 policy (such as for <ref id="appdefaults">).
10342 <heading>Perl programs and modules</heading>
10345 Perl programs and modules should follow the current Perl policy.
10349 The Perl policy can be found in the <tt>perl-policy</tt>
10350 files in the <tt>debian-policy</tt> package.
10351 It is also available from the Debian web mirrors at
10352 <tt><url name="/doc/packaging-manuals/perl-policy/"
10353 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10358 <heading>Emacs lisp programs</heading>
10361 Please refer to the "Debian Emacs Policy" for details of how to
10362 package emacs lisp programs.
10366 The Emacs policy is available in
10367 <file>debian-emacs-policy.gz</file> of the
10368 <package>emacsen-common</package> package.
10369 It is also available from the Debian web mirrors at
10370 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10371 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10376 <heading>Games</heading>
10379 The permissions on <file>/var/games</file> are mode 755, owner
10380 <tt>root</tt> and group <tt>root</tt>.
10384 Each game decides on its own security policy.</p>
10387 Games which require protected, privileged access to
10388 high-score files, saved games, etc., may be made
10389 set-<em>group</em>-id (mode 2755) and owned by
10390 <tt>root:games</tt>, and use files and directories with
10391 appropriate permissions (770 <tt>root:games</tt>, for
10392 example). They must not be made
10393 set-<em>user</em>-id, as this causes security problems. (If
10394 an attacker can subvert any set-user-id game they can
10395 overwrite the executable of any other, causing other players
10396 of these games to run a Trojan horse program. With a
10397 set-group-id game the attacker only gets access to less
10398 important game data, and if they can get at the other
10399 players' accounts at all it will take considerably more
10403 Some packages, for example some fortune cookie programs, are
10404 configured by the upstream authors to install with their
10405 data files or other static information made unreadable so
10406 that they can only be accessed through set-id programs
10407 provided. You should not do this in a Debian package: anyone can
10408 download the <file>.deb</file> file and read the data from it,
10409 so there is no point making the files unreadable. Not
10410 making the files unreadable also means that you don't have
10411 to make so many programs set-id, which reduces the risk of a
10415 As described in the FHS, binaries of games should be
10416 installed in the directory <file>/usr/games</file>. This also
10417 applies to games that use the X Window System. Manual pages
10418 for games (X and non-X games) should be installed in
10419 <file>/usr/share/man/man6</file>.</p>
10425 <heading>Documentation</heading>
10428 <heading>Manual pages</heading>
10431 You should install manual pages in <prgn>nroff</prgn> source
10432 form, in appropriate places under <file>/usr/share/man</file>.
10433 You should only use sections 1 to 9 (see the FHS for more
10434 details). You must not install a pre-formatted "cat page".
10438 Each program, utility, and function should have an
10439 associated manual page included in the same package. It is
10440 suggested that all configuration files also have a manual
10441 page included as well. Manual pages for protocols and other
10442 auxiliary things are optional.
10446 If no manual page is available, this is considered as a bug
10447 and should be reported to the Debian Bug Tracking System (the
10448 maintainer of the package is allowed to write this bug report
10449 themselves, if they so desire). Do not close the bug report
10450 until a proper man page is available.<footnote>
10451 It is not very hard to write a man page. See the
10452 <url id="http://www.schweikhardt.net/man_page_howto.html"
10453 name="Man-Page-HOWTO">,
10454 <manref name="man" section="7">, the examples created
10455 by <prgn>dh_make</prgn>, the helper
10456 program <prgn>help2man</prgn>, or the
10457 directory <file>/usr/share/doc/man-db/examples</file>.
10462 You may forward a complaint about a missing man page to the
10463 upstream authors, and mark the bug as forwarded in the
10464 Debian bug tracking system. Even though the GNU Project do
10465 not in general consider the lack of a man page to be a bug,
10466 we do; if they tell you that they don't consider it a bug
10467 you should leave the bug in our bug tracking system open
10472 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10476 If one man page needs to be accessible via several names it
10477 is better to use a symbolic link than the <file>.so</file>
10478 feature, but there is no need to fiddle with the relevant
10479 parts of the upstream source to change from <file>.so</file> to
10480 symlinks: don't do it unless it's easy. You should not
10481 create hard links in the manual page directories, nor put
10482 absolute filenames in <file>.so</file> directives. The filename
10483 in a <file>.so</file> in a man page should be relative to the
10484 base of the man page tree (usually
10485 <file>/usr/share/man</file>). If you do not create any links
10486 (whether symlinks, hard links, or <tt>.so</tt> directives)
10487 in the file system to the alternate names of the man page,
10488 then you should not rely on <prgn>man</prgn> finding your
10489 man page under those names based solely on the information in
10490 the man page's header.<footnote>
10491 Supporting this in <prgn>man</prgn> often requires
10492 unreasonable processing time to find a manual page or to
10493 report that none exists, and moves knowledge into man's
10494 database that would be better left in the file system.
10495 This support is therefore deprecated and will cease to
10496 be present in the future.
10501 Manual pages in locale-specific subdirectories of
10502 <file>/usr/share/man</file> should use either UTF-8 or the usual
10503 legacy encoding for that language (normally the one corresponding
10504 to the shortest relevant locale name in
10505 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10506 <file>/usr/share/man/fr</file> should use either UTF-8 or
10507 ISO-8859-1.<footnote>
10508 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10509 use. In future, all manual pages will be required to use
10515 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10516 included in the subdirectory name unless it indicates a
10517 significant difference in the language, as this excludes
10518 speakers of the language in other countries.<footnote>
10519 At the time of writing, Chinese and Portuguese are the main
10520 languages with such differences, so <file>pt_BR</file>,
10521 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10526 If a localized version of a manual page is provided, it should
10527 either be up-to-date or it should be obvious to the reader that
10528 it is outdated and the original manual page should be used
10529 instead. This can be done either by a note at the beginning of
10530 the manual page or by showing the missing or changed portions in
10531 the original language instead of the target language.
10536 <heading>Info documents</heading>
10539 Info documents should be installed in <file>/usr/share/info</file>.
10540 They should be compressed with <tt>gzip -9</tt>.
10544 The <prgn>install-info</prgn> program maintains a directory of
10545 installed info documents in <file>/usr/share/info/dir</file> for the
10546 use of info readers. This file must not be included in packages
10547 other than <package>install-info</package>.
10551 <prgn>install-info</prgn> is automatically invoked when
10552 appropriate using dpkg triggers. Packages other than
10553 <package>install-info</package> <em>should not</em> invoke
10554 <prgn>install-info</prgn> directly and <em>should not</em>
10555 depend on, recommend, or suggest <package>install-info</package>
10560 Info readers requiring the <file>/usr/share/info/dir</file> file
10561 should depend on <package>install-info</package>.
10565 Info documents should contain section and directory entry
10566 information in the document for the use
10567 of <prgn>install-info</prgn>. The section should be specified
10568 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10569 space and the section of this info page. The directory entry or
10570 entries should be included between
10571 a <tt>START-INFO-DIR-ENTRY</tt> line and
10572 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10574 INFO-DIR-SECTION Individual utilities
10575 START-INFO-DIR-ENTRY
10576 * example: (example). An example info directory entry.
10579 To determine which section to use, you should look
10580 at <file>/usr/share/info/dir</file> on your system and choose
10581 the most relevant (or create a new section if none of the
10582 current sections are relevant).<footnote>
10583 Normally, info documents are generated from Texinfo source.
10584 To include this information in the generated info document, if
10585 it is absent, add commands like:
10587 @dircategory Individual utilities
10589 * example: (example). An example info directory entry.
10592 to the Texinfo source of the document and ensure that the info
10593 documents are rebuilt from source during the package build.
10599 <heading>Additional documentation</heading>
10602 Any additional documentation that comes with the package may
10603 be installed at the discretion of the package maintainer.
10604 Plain text documentation should be installed in the directory
10605 <file>/usr/share/doc/<var>package</var></file>, where
10606 <var>package</var> is the name of the package, and
10607 compressed with <tt>gzip -9</tt> unless it is small.
10611 If a package comes with large amounts of documentation which
10612 many users of the package will not require you should create
10613 a separate binary package to contain it, so that it does not
10614 take up disk space on the machines of users who do not need
10615 or want it installed.</p>
10618 It is often a good idea to put text information files
10619 (<file>README</file>s, changelogs, and so forth) that come with
10620 the source package in <file>/usr/share/doc/<var>package</var></file>
10621 in the binary package. However, you don't need to install
10622 the instructions for building and installing the package, of
10626 Packages must not require the existence of any files in
10627 <file>/usr/share/doc/</file> in order to function
10629 The system administrator should be able to
10630 delete files in <file>/usr/share/doc/</file> without causing
10631 any programs to break.
10633 Any files that are referenced by programs but are also
10634 useful as stand alone documentation should be installed under
10635 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10636 <file>/usr/share/doc/<var>package</var></file>.
10640 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10641 link to another directory in <file>/usr/share/doc</file> only if
10642 the two packages both come from the same source and the
10643 first package Depends on the second.<footnote>
10645 Please note that this does not override the section on
10646 changelog files below, so the file
10647 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10648 must refer to the changelog for the current version of
10649 <var>package</var> in question. In practice, this means
10650 that the sources of the target and the destination of the
10651 symlink must be the same (same source package and
10658 Former Debian releases placed all additional documentation
10659 in <file>/usr/doc/<var>package</var></file>. This has been
10660 changed to <file>/usr/share/doc/<var>package</var></file>,
10661 and packages must not put documentation in the directory
10662 <file>/usr/doc/<var>package</var></file>. <footnote>
10663 At this phase of the transition, we no longer require a
10664 symbolic link in <file>/usr/doc/</file>. At a later point,
10665 policy shall change to make the symbolic links a bug.
10671 <heading>Preferred documentation formats</heading>
10674 The unification of Debian documentation is being carried out
10678 If your package comes with extensive documentation in a
10679 markup format that can be converted to various other formats
10680 you should if possible ship HTML versions in a binary
10681 package, in the directory
10682 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10683 its subdirectories.<footnote>
10684 The rationale: The important thing here is that HTML
10685 docs should be available in <em>some</em> package, not
10686 necessarily in the main binary package.
10691 Other formats such as PostScript may be provided at the
10692 package maintainer's discretion.
10696 <sect id="copyrightfile">
10697 <heading>Copyright information</heading>
10700 Every package must be accompanied by a verbatim copy of its
10701 copyright information and distribution license in the file
10702 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10703 file must neither be compressed nor be a symbolic link.
10707 In addition, the copyright file must say where the upstream
10708 sources (if any) were obtained, and should name the original
10713 Packages in the <em>contrib</em> or <em>non-free</em> archive
10714 areas should state in the copyright file that the package is not
10715 part of the Debian distribution and briefly explain why.
10719 A copy of the file which will be installed in
10720 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10721 be in <file>debian/copyright</file> in the source package.
10725 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10726 link to another directory in <file>/usr/share/doc</file> only if
10727 the two packages both come from the same source and the
10728 first package Depends on the second. These rules are important
10729 because <file>copyright</file> files must be extractable by
10734 Packages distributed under the Apache license (version 2.0), the
10735 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10736 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10737 1.3) should refer to the corresponding files
10738 under <file>/usr/share/common-licenses</file>,<footnote>
10741 <file>/usr/share/common-licenses/Apache-2.0</file>,
10742 <file>/usr/share/common-licenses/Artistic</file>,
10743 <file>/usr/share/common-licenses/GPL-1</file>,
10744 <file>/usr/share/common-licenses/GPL-2</file>,
10745 <file>/usr/share/common-licenses/GPL-3</file>,
10746 <file>/usr/share/common-licenses/LGPL-2</file>,
10747 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10748 <file>/usr/share/common-licenses/LGPL-3</file>,
10749 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10750 <file>/usr/share/common-licenses/GFDL-1.3</file>
10751 respectively. The University of California BSD license is
10752 also included in <package>base-files</package> as
10753 <file>/usr/share/common-licenses/BSD</file>, but given the
10754 brevity of this license, its specificity to code whose
10755 copyright is held by the Regents of the University of
10756 California, and the frequency of minor wording changes, its
10757 text should be included in the copyright file rather than
10758 referencing this file.
10760 </footnote> rather than quoting them in the copyright
10765 You should not use the copyright file as a general <file>README</file>
10766 file. If your package has such a file it should be
10767 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10768 <file>README.Debian</file> or some other appropriate place.
10772 All copyright files must be encoded in UTF-8.
10775 <sect1 id="copyrightformat">
10776 <heading>Machine-readable copyright information</heading>
10779 A specification for a standard, machine-readable format
10780 for <file>debian/copyright</file> files is maintained as part
10781 of the <package>debian-policy</package> package. This
10782 document may be found in the <file>copyright-format</file>
10783 files in the <package>debian-policy</package> package. It is
10784 also available from the Debian web mirrors at
10785 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10786 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10790 Use of this format is optional.
10796 <heading>Examples</heading>
10799 Any examples (configurations, source files, whatever),
10800 should be installed in a directory
10801 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10802 files should not be referenced by any program: they're there
10803 for the benefit of the system administrator and users as
10804 documentation only. Architecture-specific example files
10805 should be installed in a directory
10806 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10808 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10809 latter directory itself may be a symbolic link to the
10814 If the purpose of a package is to provide examples, then the
10815 example files may be installed into
10816 <file>/usr/share/doc/<var>package</var></file>.
10820 <sect id="changelogs">
10821 <heading>Changelog files</heading>
10824 Packages that are not Debian-native must contain a
10825 compressed copy of the <file>debian/changelog</file> file from
10826 the Debian source tree in
10827 <file>/usr/share/doc/<var>package</var></file> with the name
10828 <file>changelog.Debian.gz</file>.
10832 If an upstream changelog is available, it should be accessible as
10833 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10834 plain text. If the upstream changelog is distributed in
10835 HTML, it should be made available in that form as
10836 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10837 and a plain text <file>changelog.gz</file> should be generated
10838 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10839 the upstream changelog files do not already conform to this
10840 naming convention, then this may be achieved either by
10841 renaming the files, or by adding a symbolic link, at the
10842 maintainer's discretion.<footnote>
10843 Rationale: People should not have to look in places for
10844 upstream changelogs merely because they are given
10845 different names or are distributed in HTML format.
10850 All of these files should be installed compressed using
10851 <tt>gzip -9</tt>, as they will become large with time even
10852 if they start out small.
10856 If the package has only one changelog which is used both as
10857 the Debian changelog and the upstream one because there is
10858 no separate upstream maintainer then that changelog should
10859 usually be installed as
10860 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10861 there is a separate upstream maintainer, but no upstream
10862 changelog, then the Debian changelog should still be called
10863 <file>changelog.Debian.gz</file>.
10867 For details about the format and contents of the Debian
10868 changelog file, please see <ref id="dpkgchangelog">.
10873 <appendix id="pkg-scope">
10874 <heading>Introduction and scope of these appendices</heading>
10877 These appendices are taken essentially verbatim from the
10878 now-deprecated Packaging Manual, version 3.2.1.0. They are
10879 the chapters which are likely to be of use to package
10880 maintainers and which have not already been included in the
10881 policy document itself. Most of these sections are very likely
10882 not relevant to policy; they should be treated as
10883 documentation for the packaging system. Please note that these
10884 appendices are included for convenience, and for historical
10885 reasons: they used to be part of policy package, and they have
10886 not yet been incorporated into dpkg documentation. However,
10887 they still have value, and hence they are presented here.
10891 They have not yet been checked to ensure that they are
10892 compatible with the contents of policy, and if there are any
10893 contradictions, the version in the main policy document takes
10894 precedence. The remaining chapters of the old Packaging
10895 Manual have also not been read in detail to ensure that there
10896 are not parts which have been left out. Both of these will be
10897 done in due course.
10901 Certain parts of the Packaging manual were integrated into the
10902 Policy Manual proper, and removed from the appendices. Links
10903 have been placed from the old locations to the new ones.
10907 <prgn>dpkg</prgn> is a suite of programs for creating binary
10908 package files and installing and removing them on Unix
10910 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10911 work on or be ported to other systems.
10916 The binary packages are designed for the management of
10917 installed executable programs (usually compiled binaries) and
10918 their associated data, though source code examples and
10919 documentation are provided as part of some packages.</p>
10922 This manual describes the technical aspects of creating Debian
10923 binary packages (<file>.deb</file> files). It documents the
10924 behavior of the package management programs
10925 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10926 they interact with packages.</p>
10929 This manual does not go into detail about the options and
10930 usage of the package building and installation tools. It
10931 should therefore be read in conjunction with those programs'
10936 The utility programs which are provided with <prgn>dpkg</prgn>
10937 not described in detail here, are documented in their man pages.
10941 It is assumed that the reader is reasonably familiar with the
10942 <prgn>dpkg</prgn> System Administrators' manual.
10943 Unfortunately this manual does not yet exist.
10947 The Debian version of the FSF's GNU hello program is provided as
10948 an example for people wishing to create Debian packages. However,
10949 while the examples are helpful, they do not replace the need to
10950 read and follow the Policy and Programmer's Manual.</p>
10953 <appendix id="pkg-binarypkg">
10954 <heading>Binary packages (from old Packaging Manual)</heading>
10957 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10960 <sect id="pkg-bincreating"><heading>Creating package files -
10961 <prgn>dpkg-deb</prgn>
10965 All manipulation of binary package files is done by
10966 <prgn>dpkg-deb</prgn>; it's the only program that has
10967 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10968 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10969 will spot that the options requested are appropriate to
10970 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10975 In order to create a binary package you must make a
10976 directory tree which contains all the files and directories
10977 you want to have in the file system data part of the package.
10978 In Debian-format source packages this directory is usually
10979 <file>debian/tmp</file>, relative to the top of the package's
10984 They should have the locations (relative to the root of the
10985 directory tree you're constructing) ownerships and
10986 permissions which you want them to have on the system when
10987 they are installed.
10991 With current versions of <prgn>dpkg</prgn> the uid/username
10992 and gid/groupname mappings for the users and groups being
10993 used should be the same on the system where the package is
10994 built and the one where it is installed.
10998 You need to add one special directory to the root of the
10999 miniature file system tree you're creating:
11000 <prgn>DEBIAN</prgn>. It should contain the control
11001 information files, notably the binary package control file
11002 (see <ref id="pkg-controlfile">).
11006 The <prgn>DEBIAN</prgn> directory will not appear in the
11007 file system archive of the package, and so won't be installed
11008 by <prgn>dpkg</prgn> when the package is unpacked.
11012 When you've prepared the package, you should invoke:
11014 dpkg --build <var>directory</var>
11019 This will build the package in
11020 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
11021 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
11022 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11023 build the package.)
11027 See the man page <manref name="dpkg-deb" section="8"> for details of how
11028 to examine the contents of this newly-created file. You may find the
11029 output of following commands enlightening:
11031 dpkg-deb --info <var>filename</var>.deb
11032 dpkg-deb --contents <var>filename</var>.deb
11033 dpkg --contents <var>filename</var>.deb
11035 To view the copyright file for a package you could use this command:
11037 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11042 <sect id="pkg-controlarea">
11043 <heading>Package control information files</heading>
11046 The control information portion of a binary package is a
11047 collection of files with names known to <prgn>dpkg</prgn>.
11048 It will treat the contents of these files specially - some
11049 of them contain information used by <prgn>dpkg</prgn> when
11050 installing or removing the package; others are scripts which
11051 the package maintainer wants <prgn>dpkg</prgn> to run.
11055 It is possible to put other files in the package control
11056 information file area, but this is not generally a good idea
11057 (though they will largely be ignored).
11061 Here is a brief list of the control information files supported
11062 by <prgn>dpkg</prgn> and a summary of what they're used for.
11067 <tag><tt>control</tt>
11070 This is the key description file used by
11071 <prgn>dpkg</prgn>. It specifies the package's name
11072 and version, gives its description for the user,
11073 states its relationships with other packages, and so
11074 forth. See <ref id="sourcecontrolfiles"> and
11075 <ref id="binarycontrolfiles">.
11079 It is usually generated automatically from information
11080 in the source package by the
11081 <prgn>dpkg-gencontrol</prgn> program, and with
11082 assistance from <prgn>dpkg-shlibdeps</prgn>.
11083 See <ref id="pkg-sourcetools">.
11087 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11092 These are executable files (usually scripts) which
11093 <prgn>dpkg</prgn> runs during installation, upgrade
11094 and removal of packages. They allow the package to
11095 deal with matters which are particular to that package
11096 or require more complicated processing than that
11097 provided by <prgn>dpkg</prgn>. Details of when and
11098 how they are called are in <ref id="maintainerscripts">.
11102 It is very important to make these scripts idempotent.
11103 See <ref id="idempotency">.
11107 The maintainer scripts are not guaranteed to run with a
11108 controlling terminal and may not be able to interact with
11109 the user. See <ref id="controllingterminal">.
11113 <tag><tt>conffiles</tt>
11116 This file contains a list of configuration files which
11117 are to be handled automatically by <prgn>dpkg</prgn>
11118 (see <ref id="pkg-conffiles">). Note that not necessarily
11119 every configuration file should be listed here.
11122 <tag><tt>shlibs</tt>
11125 This file contains a list of the shared libraries
11126 supplied by the package, with dependency details for
11127 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11128 when it determines what dependencies are required in a
11129 package control file. The <tt>shlibs</tt> file format
11130 is described on <ref id="shlibs">.
11135 <sect id="pkg-controlfile">
11136 <heading>The main control information file: <tt>control</tt></heading>
11139 The most important control information file used by
11140 <prgn>dpkg</prgn> when it installs a package is
11141 <tt>control</tt>. It contains all the package's "vital
11146 The binary package control files of packages built from
11147 Debian sources are made by a special tool,
11148 <prgn>dpkg-gencontrol</prgn>, which reads
11149 <file>debian/control</file> and <file>debian/changelog</file> to
11150 find the information it needs. See <ref id="pkg-sourcepkg"> for
11155 The fields in binary package control files are listed in
11156 <ref id="binarycontrolfiles">.
11160 A description of the syntax of control files and the purpose
11161 of the fields is available in <ref id="controlfields">.
11166 <heading>Time Stamps</heading>
11169 See <ref id="timestamps">.
11174 <appendix id="pkg-sourcepkg">
11175 <heading>Source packages (from old Packaging Manual) </heading>
11178 The Debian binary packages in the distribution are generated
11179 from Debian sources, which are in a special format to assist
11180 the easy and automatic building of binaries.
11183 <sect id="pkg-sourcetools">
11184 <heading>Tools for processing source packages</heading>
11187 Various tools are provided for manipulating source packages;
11188 they pack and unpack sources and help build of binary
11189 packages and help manage the distribution of new versions.
11193 They are introduced and typical uses described here; see
11194 <manref name="dpkg-source" section="1"> for full
11195 documentation about their arguments and operation.
11199 For examples of how to construct a Debian source package,
11200 and how to use those utilities that are used by Debian
11201 source packages, please see the <prgn>hello</prgn> example
11205 <sect1 id="pkg-dpkg-source">
11207 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11212 This program is frequently used by hand, and is also
11213 called from package-independent automated building scripts
11214 such as <prgn>dpkg-buildpackage</prgn>.
11218 To unpack a package it is typically invoked with
11220 dpkg-source -x <var>.../path/to/filename</var>.dsc
11225 with the <file><var>filename</var>.tar.gz</file> and
11226 <file><var>filename</var>.diff.gz</file> (if applicable) in
11227 the same directory. It unpacks into
11228 <file><var>package</var>-<var>version</var></file>, and if
11230 <file><var>package</var>-<var>version</var>.orig</file>, in
11231 the current directory.
11235 To create a packed source archive it is typically invoked:
11237 dpkg-source -b <var>package</var>-<var>version</var>
11242 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11243 <file>.diff.gz</file> (if appropriate) in the current
11244 directory. <prgn>dpkg-source</prgn> does not clean the
11245 source tree first - this must be done separately if it is
11250 See also <ref id="pkg-sourcearchives">.</p>
11254 <sect1 id="pkg-dpkg-buildpackage">
11256 <prgn>dpkg-buildpackage</prgn> - overall package-building
11261 See <manref name="dpkg-buildpackage" section="1">.
11265 <sect1 id="pkg-dpkg-gencontrol">
11267 <prgn>dpkg-gencontrol</prgn> - generates binary package
11272 This program is usually called from <file>debian/rules</file>
11273 (see <ref id="pkg-sourcetree">) in the top level of the source
11278 This is usually done just before the files and directories in the
11279 temporary directory tree where the package is being built have their
11280 permissions and ownerships set and the package is constructed using
11281 <prgn>dpkg-deb/</prgn>
11283 This is so that the control file which is produced has
11284 the right permissions
11289 <prgn>dpkg-gencontrol</prgn> must be called after all the
11290 files which are to go into the package have been placed in
11291 the temporary build directory, so that its calculation of
11292 the installed size of a package is correct.
11296 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11297 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11298 variable substitutions created by
11299 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11304 For a package which generates only one binary package, and
11305 which builds it in <file>debian/tmp</file> relative to the top
11306 of the source package, it is usually sufficient to call
11307 <prgn>dpkg-gencontrol</prgn>.
11311 Sources which build several binaries will typically need
11314 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11315 </example> The <tt>-P</tt> tells
11316 <prgn>dpkg-gencontrol</prgn> that the package is being
11317 built in a non-default directory, and the <tt>-p</tt>
11318 tells it which package's control file should be generated.
11322 <prgn>dpkg-gencontrol</prgn> also adds information to the
11323 list of files in <file>debian/files</file>, for the benefit of
11324 (for example) a future invocation of
11325 <prgn>dpkg-genchanges</prgn>.</p>
11328 <sect1 id="pkg-dpkg-shlibdeps">
11330 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11335 See <manref name="dpkg-shlibdeps" section="1">.
11339 <sect1 id="pkg-dpkg-distaddfile">
11341 <prgn>dpkg-distaddfile</prgn> - adds a file to
11342 <file>debian/files</file>
11346 Some packages' uploads need to include files other than
11347 the source and binary package files.
11351 <prgn>dpkg-distaddfile</prgn> adds a file to the
11352 <file>debian/files</file> file so that it will be included in
11353 the <file>.changes</file> file when
11354 <prgn>dpkg-genchanges</prgn> is run.
11358 It is usually invoked from the <tt>binary</tt> target of
11359 <file>debian/rules</file>:
11361 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11363 The <var>filename</var> is relative to the directory where
11364 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11365 is usually the directory above the top level of the source
11366 tree. The <file>debian/rules</file> target should put the
11367 file there just before or just after calling
11368 <prgn>dpkg-distaddfile</prgn>.
11372 The <var>section</var> and <var>priority</var> are passed
11373 unchanged into the resulting <file>.changes</file> file.
11378 <sect1 id="pkg-dpkg-genchanges">
11380 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11381 upload control file
11385 See <manref name="dpkg-genchanges" section="1">.
11389 <sect1 id="pkg-dpkg-parsechangelog">
11391 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11392 representation of a changelog
11396 See <manref name="dpkg-parsechangelog" section="1">.
11400 <sect1 id="pkg-dpkg-architecture">
11402 <prgn>dpkg-architecture</prgn> - information about the build and
11407 See <manref name="dpkg-architecture" section="1">.
11412 <sect id="pkg-sourcetree">
11413 <heading>The Debian package source tree</heading>
11416 The source archive scheme described later is intended to
11417 allow a Debian package source tree with some associated
11418 control information to be reproduced and transported easily.
11419 The Debian package source tree is a version of the original
11420 program with certain files added for the benefit of the
11421 packaging process, and with any other changes required
11422 made to the rest of the source code and installation
11427 The extra files created for Debian are in the subdirectory
11428 <file>debian</file> of the top level of the Debian package
11429 source tree. They are described below.
11432 <sect1 id="pkg-debianrules">
11433 <heading><file>debian/rules</file> - the main building script</heading>
11436 See <ref id="debianrules">.
11440 <sect1 id="pkg-srcsubstvars">
11441 <heading><file>debian/substvars</file> and variable substitutions</heading>
11444 See <ref id="substvars">.
11450 <heading><file>debian/files</file></heading>
11453 See <ref id="debianfiles">.
11457 <sect1><heading><file>debian/tmp</file>
11461 This is the canonical temporary location for the
11462 construction of binary packages by the <tt>binary</tt>
11463 target. The directory <file>tmp</file> serves as the root of
11464 the file system tree as it is being constructed (for
11465 example, by using the package's upstream makefiles install
11466 targets and redirecting the output there), and it also
11467 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11468 id="pkg-bincreating">.
11472 If several binary packages are generated from the same
11473 source tree it is usual to use several
11474 <file>debian/tmp<var>something</var></file> directories, for
11475 example <file>tmp-a</file> or <file>tmp-doc</file>.
11479 Whatever <file>tmp</file> directories are created and used by
11480 <tt>binary</tt> must of course be removed by the
11481 <tt>clean</tt> target.</p></sect1>
11485 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11489 As it exists on the FTP site, a Debian source package
11490 consists of three related files. You must have the right
11491 versions of all three to be able to use them.
11496 <tag>Debian source control file - <tt>.dsc</tt></tag>
11498 This file is a control file used by <prgn>dpkg-source</prgn>
11499 to extract a source package.
11500 See <ref id="debiansourcecontrolfiles">.
11504 Original source archive -
11506 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11512 This is a compressed (with <tt>gzip -9</tt>)
11513 <prgn>tar</prgn> file containing the source code from
11514 the upstream authors of the program.
11519 Debian package diff -
11521 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11527 This is a unified context diff (<tt>diff -u</tt>)
11528 giving the changes which are required to turn the
11529 original source into the Debian source. These changes
11530 may only include editing and creating plain files.
11531 The permissions of files, the targets of symbolic
11532 links and the characteristics of special files or
11533 pipes may not be changed and no files may be removed
11538 All the directories in the diff must exist, except the
11539 <file>debian</file> subdirectory of the top of the source
11540 tree, which will be created by
11541 <prgn>dpkg-source</prgn> if necessary when unpacking.
11545 The <prgn>dpkg-source</prgn> program will
11546 automatically make the <file>debian/rules</file> file
11547 executable (see below).</p></item>
11552 If there is no original source code - for example, if the
11553 package is specially prepared for Debian or the Debian
11554 maintainer is the same as the upstream maintainer - the
11555 format is slightly different: then there is no diff, and the
11557 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11558 and preferably contains a directory named
11559 <file><var>package</var>-<var>version</var></file>.
11564 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11567 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11568 Debian source package. However, if it is not available it
11569 is possible to unpack a Debian source archive as follows:
11570 <enumlist compact="compact">
11573 Untar the tarfile, which will create a <file>.orig</file>
11577 <p>Rename the <file>.orig</file> directory to
11578 <file><var>package</var>-<var>version</var></file>.</p>
11582 Create the subdirectory <file>debian</file> at the top of
11583 the source tree.</p>
11585 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11587 <item><p>Untar the tarfile again if you want a copy of the original
11588 source code alongside the Debian version.</p>
11593 It is not possible to generate a valid Debian source archive
11594 without using <prgn>dpkg-source</prgn>. In particular,
11595 attempting to use <prgn>diff</prgn> directly to generate the
11596 <file>.diff.gz</file> file will not work.
11600 <heading>Restrictions on objects in source packages</heading>
11603 The source package may not contain any hard links
11605 This is not currently detected when building source
11606 packages, but only when extracting
11610 Hard links may be permitted at some point in the
11611 future, but would require a fair amount of
11613 </footnote>, device special files, sockets or setuid or
11616 Setgid directories are allowed.
11621 The source packaging tools manage the changes between the
11622 original and Debian source using <prgn>diff</prgn> and
11623 <prgn>patch</prgn>. Turning the original source tree as
11624 included in the <file>.orig.tar.gz</file> into the Debian
11625 package source must not involve any changes which cannot be
11626 handled by these tools. Problematic changes which cause
11627 <prgn>dpkg-source</prgn> to halt with an error when
11628 building the source package are:
11629 <list compact="compact">
11630 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11632 <item><p>Changing the targets of symbolic links.</p>
11634 <item><p>Creating directories, other than <file>debian</file>.</p>
11636 <item><p>Changes to the contents of binary files.</p></item>
11637 </list> Changes which cause <prgn>dpkg-source</prgn> to
11638 print a warning but continue anyway are:
11639 <list compact="compact">
11642 Removing files, directories or symlinks.
11644 Renaming a file is not treated specially - it is
11645 seen as the removal of the old file (which
11646 generates a warning, but is otherwise ignored),
11647 and the creation of the new one.
11653 Changed text files which are missing the usual final
11654 newline (either in the original or the modified
11659 Changes which are not represented, but which are not detected by
11660 <prgn>dpkg-source</prgn>, are:
11661 <list compact="compact">
11662 <item><p>Changing the permissions of files (other than
11663 <file>debian/rules</file>) and directories.</p></item>
11668 The <file>debian</file> directory and <file>debian/rules</file>
11669 are handled specially by <prgn>dpkg-source</prgn> - before
11670 applying the changes it will create the <file>debian</file>
11671 directory, and afterwards it will make
11672 <file>debian/rules</file> world-executable.
11678 <appendix id="pkg-controlfields">
11679 <heading>Control files and their fields (from old Packaging Manual)</heading>
11682 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11683 data in a common format, known as control files. Binary and
11684 source packages have control data as do the <file>.changes</file>
11685 files which control the installation of uploaded files, and
11686 <prgn>dpkg</prgn>'s internal databases are in a similar
11691 <heading>Syntax of control files</heading>
11694 See <ref id="controlsyntax">.
11698 It is important to note that there are several fields which
11699 are optional as far as <prgn>dpkg</prgn> and the related
11700 tools are concerned, but which must appear in every Debian
11701 package, or whose omission may cause problems.
11706 <heading>List of fields</heading>
11709 See <ref id="controlfieldslist">.
11713 This section now contains only the fields that didn't belong
11714 to the Policy manual.
11717 <sect1 id="pkg-f-Filename">
11718 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11721 These fields in <tt>Packages</tt> files give the
11722 filename(s) of (the parts of) a package in the
11723 distribution directories, relative to the root of the
11724 Debian hierarchy. If the package has been split into
11725 several parts the parts are all listed in order, separated
11730 <sect1 id="pkg-f-Size">
11731 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11734 These fields in <file>Packages</file> files give the size (in
11735 bytes, expressed in decimal) and MD5 checksum of the
11736 file(s) which make(s) up a binary package in the
11737 distribution. If the package is split into several parts
11738 the values for the parts are listed in order, separated by
11743 <sect1 id="pkg-f-Status">
11744 <heading><tt>Status</tt></heading>
11747 This field in <prgn>dpkg</prgn>'s status file records
11748 whether the user wants a package installed, removed or
11749 left alone, whether it is broken (requiring
11750 re-installation) or not and what its current state on the
11751 system is. Each of these pieces of information is a
11756 <sect1 id="pkg-f-Config-Version">
11757 <heading><tt>Config-Version</tt></heading>
11760 If a package is not installed or not configured, this
11761 field in <prgn>dpkg</prgn>'s status file records the last
11762 version of the package which was successfully
11767 <sect1 id="pkg-f-Conffiles">
11768 <heading><tt>Conffiles</tt></heading>
11771 This field in <prgn>dpkg</prgn>'s status file contains
11772 information about the automatically-managed configuration
11773 files held by a package. This field should <em>not</em>
11774 appear anywhere in a package!
11779 <heading>Obsolete fields</heading>
11782 These are still recognized by <prgn>dpkg</prgn> but should
11783 not appear anywhere any more.
11785 <taglist compact="compact">
11787 <tag><tt>Revision</tt></tag>
11788 <tag><tt>Package-Revision</tt></tag>
11789 <tag><tt>Package_Revision</tt></tag>
11791 The Debian revision part of the package version was
11792 at one point in a separate control field. This
11793 field went through several names.
11796 <tag><tt>Recommended</tt></tag>
11797 <item>Old name for <tt>Recommends</tt>.</item>
11799 <tag><tt>Optional</tt></tag>
11800 <item>Old name for <tt>Suggests</tt>.</item>
11802 <tag><tt>Class</tt></tag>
11803 <item>Old name for <tt>Priority</tt>.</item>
11812 <appendix id="pkg-conffiles">
11813 <heading>Configuration file handling (from old Packaging Manual)</heading>
11816 <prgn>dpkg</prgn> can do a certain amount of automatic
11817 handling of package configuration files.
11821 Whether this mechanism is appropriate depends on a number of
11822 factors, but basically there are two approaches to any
11823 particular configuration file.
11827 The easy method is to ship a best-effort configuration in the
11828 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11829 handle updates. If the user is unlikely to want to edit the
11830 file, but you need them to be able to without losing their
11831 changes, and a new package with a changed version of the file
11832 is only released infrequently, this is a good approach.
11836 The hard method is to build the configuration file from
11837 scratch in the <prgn>postinst</prgn> script, and to take the
11838 responsibility for fixing any mistakes made in earlier
11839 versions of the package automatically. This will be
11840 appropriate if the file is likely to need to be different on
11844 <sect><heading>Automatic handling of configuration files by
11849 A package may contain a control information file called
11850 <tt>conffiles</tt>. This file should be a list of filenames
11851 of configuration files needing automatic handling, separated
11852 by newlines. The filenames should be absolute pathnames,
11853 and the files referred to should actually exist in the
11858 When a package is upgraded <prgn>dpkg</prgn> will process
11859 the configuration files during the configuration stage,
11860 shortly before it runs the package's <prgn>postinst</prgn>
11865 For each file it checks to see whether the version of the
11866 file included in the package is the same as the one that was
11867 included in the last version of the package (the one that is
11868 being upgraded from); it also compares the version currently
11869 installed on the system with the one shipped with the last
11874 If neither the user nor the package maintainer has changed
11875 the file, it is left alone. If one or the other has changed
11876 their version, then the changed version is preferred - i.e.,
11877 if the user edits their file, but the package maintainer
11878 doesn't ship a different version, the user's changes will
11879 stay, silently, but if the maintainer ships a new version
11880 and the user hasn't edited it the new version will be
11881 installed (with an informative message). If both have
11882 changed their version the user is prompted about the problem
11883 and must resolve the differences themselves.
11887 The comparisons are done by calculating the MD5 message
11888 digests of the files, and storing the MD5 of the file as it
11889 was included in the most recent version of the package.
11893 When a package is installed for the first time
11894 <prgn>dpkg</prgn> will install the file that comes with it,
11895 unless that would mean overwriting a file already on the
11900 However, note that <prgn>dpkg</prgn> will <em>not</em>
11901 replace a conffile that was removed by the user (or by a
11902 script). This is necessary because with some programs a
11903 missing file produces an effect hard or impossible to
11904 achieve in another way, so that a missing file needs to be
11905 kept that way if the user did it.
11909 Note that a package should <em>not</em> modify a
11910 <prgn>dpkg</prgn>-handled conffile in its maintainer
11911 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11912 the user confusing and possibly dangerous options for
11913 conffile update when the package is upgraded.</p>
11916 <sect><heading>Fully-featured maintainer script configuration
11921 For files which contain site-specific information such as
11922 the hostname and networking details and so forth, it is
11923 better to create the file in the package's
11924 <prgn>postinst</prgn> script.
11928 This will typically involve examining the state of the rest
11929 of the system to determine values and other information, and
11930 may involve prompting the user for some information which
11931 can't be obtained some other way.
11935 When using this method there are a couple of important
11936 issues which should be considered:
11940 If you discover a bug in the program which generates the
11941 configuration file, or if the format of the file changes
11942 from one version to the next, you will have to arrange for
11943 the postinst script to do something sensible - usually this
11944 will mean editing the installed configuration file to remove
11945 the problem or change the syntax. You will have to do this
11946 very carefully, since the user may have changed the file,
11947 perhaps to fix the very problem that your script is trying
11948 to deal with - you will have to detect these situations and
11949 deal with them correctly.
11953 If you do go down this route it's probably a good idea to
11954 make the program that generates the configuration file(s) a
11955 separate program in <file>/usr/sbin</file>, by convention called
11956 <file><var>package</var>config</file> and then run that if
11957 appropriate from the post-installation script. The
11958 <tt><var>package</var>config</tt> program should not
11959 unquestioningly overwrite an existing configuration - if its
11960 mode of operation is geared towards setting up a package for
11961 the first time (rather than any arbitrary reconfiguration
11962 later) you should have it check whether the configuration
11963 already exists, and require a <tt>--force</tt> flag to
11964 overwrite it.</p></sect>
11967 <appendix id="pkg-alternatives"><heading>Alternative versions of
11968 an interface - <prgn>update-alternatives</prgn> (from old
11973 When several packages all provide different versions of the
11974 same program or file it is useful to have the system select a
11975 default, but to allow the system administrator to change it
11976 and have their decisions respected.
11980 For example, there are several versions of the <prgn>vi</prgn>
11981 editor, and there is no reason to prevent all of them from
11982 being installed at once, each under their own name
11983 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11984 Nevertheless it is desirable to have the name <tt>vi</tt>
11985 refer to something, at least by default.
11989 If all the packages involved cooperate, this can be done with
11990 <prgn>update-alternatives</prgn>.
11994 Each package provides its own version under its own name, and
11995 calls <prgn>update-alternatives</prgn> in its postinst to
11996 register its version (and again in its prerm to deregister
12001 See the man page <manref name="update-alternatives"
12002 section="8"> for details.
12006 If <prgn>update-alternatives</prgn> does not seem appropriate
12007 you may wish to consider using diversions instead.</p>
12010 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12011 package's version of a file (from old Packaging Manual)
12015 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12016 when it reinstalls the package it belongs to, and to have it
12017 put the file from the package somewhere else instead.
12021 This can be used locally to override a package's version of a
12022 file, or by one package to override another's version (or
12023 provide a wrapper for it).
12027 Before deciding to use a diversion, read <ref
12028 id="pkg-alternatives"> to see if you really want a diversion
12029 rather than several alternative versions of a program.
12033 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12034 and updated by a special program <prgn>dpkg-divert</prgn>.
12035 Please see <manref name="dpkg-divert" section="8"> for full
12036 details of its operation.
12040 When a package wishes to divert a file from another, it should
12041 call <prgn>dpkg-divert</prgn> in its preinst to add the
12042 diversion and rename the existing file. For example,
12043 supposing that a <prgn>smailwrapper</prgn> package wishes to
12044 install a wrapper around <file>/usr/sbin/smail</file>:
12046 dpkg-divert --package smailwrapper --add --rename \
12047 --divert /usr/sbin/smail.real /usr/sbin/smail
12048 </example> The <tt>--package smailwrapper</tt> ensures that
12049 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12050 can bypass the diversion and get installed as the true version.
12051 It's safe to add the diversion unconditionally on upgrades since
12052 it will be left unchanged if it already exists, but
12053 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12054 message, make the command conditional on the version from which
12055 the package is being upgraded:
12057 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12058 dpkg-divert --package smailwrapper --add --rename \
12059 --divert /usr/sbin/smail.real /usr/sbin/smail
12061 </example> where <tt>1.0-2</tt> is the version at which the
12062 diversion was first added to the package. Running the command
12063 during abort-upgrade is pointless but harmless.
12067 The postrm has to do the reverse:
12069 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12070 dpkg-divert --package smailwrapper --remove --rename \
12071 --divert /usr/sbin/smail.real /usr/sbin/smail
12073 </example> If the diversion was added at a particular version, the
12074 postrm should also handle the failure case of upgrading from an
12075 older version (unless the older version is so old that direct
12076 upgrades are no longer supported):
12078 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12079 dpkg-divert --package smailwrapper --remove --rename \
12080 --divert /usr/sbin/smail.real /usr/sbin/smail
12082 </example> where <tt>1.0-2</tt> is the version at which the
12083 diversion was first added to the package. The postrm should not
12084 remove the diversion on upgrades both because there's no reason to
12085 remove the diversion only to immediately re-add it and since the
12086 postrm of the old package is run after unpacking so the removal of
12087 the diversion will fail.
12091 Do not attempt to divert a file which is vitally important for
12092 the system's operation - when using <prgn>dpkg-divert</prgn>
12093 there is a time, after it has been diverted but before
12094 <prgn>dpkg</prgn> has installed the new version, when the file
12095 does not exist.</p>
12098 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12105 <!-- Local variables: -->
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