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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></item>
261 <item><ref id="mime"></item>
262 <item><ref id="perl"></item>
263 <item><ref id="maintscriptprompt"></item>
264 <item><ref id="emacs"></item>
269 In addition to those, which carry the weight of policy, there
270 is the Debian Developer's Reference. This document describes
271 procedures and resources for Debian developers, but it is
272 <em>not</em> normative; rather, it includes things that don't
273 belong in the Policy, such as best practices for developers.
277 The Developer's Reference is available in the
278 <package>developers-reference</package> package.
279 It's also available from the Debian web mirrors at
280 <tt><url name="/doc/developers-reference/"
281 id="http://www.debian.org/doc/developers-reference/"></tt>.
285 <sect id="definitions">
286 <heading>Definitions</heading>
289 The following terms are used in this Policy Manual:
293 The character encoding specified by ANSI X3.4-1986 and its
294 predecessor standards, referred to in MIME as US-ASCII, and
295 corresponding to an encoding in eight bits per character of
296 the first 128 <url id="http://www.unicode.org/"
297 name="Unicode"> characters, with the eighth bit always zero.
301 The transformation format (sometimes called encoding) of
302 <url id="http://www.unicode.org/" name="Unicode"> defined by
303 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
304 name="RFC 3629">. UTF-8 has the useful property of having
305 ASCII as a subset, so any text encoded in ASCII is trivially
315 <heading>The Debian Archive</heading>
318 The Debian system is maintained and distributed as a
319 collection of <em>packages</em>. Since there are so many of
320 them (currently well over 15000), they are split into
321 <em>sections</em> and given <em>priorities</em> to simplify
322 the handling of them.
326 The effort of the Debian project is to build a free operating
327 system, but not every package we want to make accessible is
328 <em>free</em> in our sense (see the Debian Free Software
329 Guidelines, below), or may be imported/exported without
330 restrictions. Thus, the archive is split into areas<footnote>
331 The Debian archive software uses the term "component" internally
332 and in the Release file format to refer to the division of an
333 archive. The Debian Social Contract simply refers to "areas."
334 This document uses terminology similar to the Social Contract.
335 </footnote> based on their licenses and other restrictions.
339 The aims of this are:
341 <list compact="compact">
342 <item>to allow us to make as much software available as we can</item>
343 <item>to allow us to encourage everyone to write free software,
345 <item>to allow us to make it easy for people to produce
346 CD-ROMs of our system without violating any licenses,
347 import/export restrictions, or any other laws.</item>
352 The <em>main</em> archive area forms the <em>Debian distribution</em>.
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 The <em>main</em> archive area comprises the Debian
470 distribution. Only the packages in this area are considered
471 part of the distribution. None of the packages in
472 the <em>main</em> archive area require software outside of
473 that area to function. Anyone may use, share, modify and
474 redistribute the packages in this archive area
476 See <url id="http://www.debian.org/intro/free"
477 name="What Does Free Mean?"> for
478 more about what we mean by free software.
483 Every package in <em>main</em> must comply with the DFSG
484 (Debian Free Software Guidelines).
488 In addition, the packages in <em>main</em>
489 <list compact="compact">
491 must not require a package outside of <em>main</em>
492 for compilation or execution (thus, the package must
493 not declare a "Depends", "Recommends", or
494 "Build-Depends" relationship on a non-<em>main</em>
498 must not be so buggy that we refuse to support them,
502 must meet all policy requirements presented in this
511 <heading>The contrib archive area</heading>
514 The <em>contrib</em> archive area contains supplemental
515 packages intended to work with the Debian distribution, but
516 which require software outside of the distribution to either
521 Every package in <em>contrib</em> must comply with the DFSG.
525 In addition, the packages in <em>contrib</em>
526 <list compact="compact">
528 must not be so buggy that we refuse to support them,
532 must meet all policy requirements presented in this
539 Examples of packages which would be included in
540 <em>contrib</em> are:
541 <list compact="compact">
543 free packages which require <em>contrib</em>,
544 <em>non-free</em> packages or packages which are not
545 in our archive at all for compilation or execution,
549 wrapper packages or other sorts of free accessories for
556 <sect1 id="non-free">
557 <heading>The non-free archive area</heading>
560 The <em>non-free</em> archive area contains supplemental
561 packages intended to work with the Debian distribution that do
562 not comply with the DFSG or have other problems that make
563 their distribution problematic. They may not comply with all
564 of the policy requirements in this manual due to restrictions
565 on modifications or other limitations.
569 Packages must be placed in <em>non-free</em> if they are
570 not compliant with the DFSG or are encumbered by patents
571 or other legal issues that make their distribution
576 In addition, the packages in <em>non-free</em>
577 <list compact="compact">
579 must not be so buggy that we refuse to support them,
583 must meet all policy requirements presented in this
584 manual that it is possible for them to meet.
586 It is possible that there are policy
587 requirements which the package is unable to
588 meet, for example, if the source is
589 unavailable. These situations will need to be
590 handled on a case-by-case basis.
599 <sect id="pkgcopyright">
600 <heading>Copyright considerations</heading>
603 Every package must be accompanied by a verbatim copy of its
604 copyright information and distribution license in the file
605 <file>/usr/share/doc/<var>package</var>/copyright</file>
606 (see <ref id="copyrightfile"> for further details).
610 We reserve the right to restrict files from being included
611 anywhere in our archives if
612 <list compact="compact">
614 their use or distribution would break a law,
617 there is an ethical conflict in their distribution or
621 we would have to sign a license for them, or
624 their distribution would conflict with other project
631 Programs whose authors encourage the user to make
632 donations are fine for the main distribution, provided
633 that the authors do not claim that not donating is
634 immoral, unethical, illegal or something similar; in such
635 a case they must go in <em>non-free</em>.
639 Packages whose copyright permission notices (or patent
640 problems) do not even allow redistribution of binaries
641 only, and where no special permission has been obtained,
642 must not be placed on the Debian FTP site and its mirrors
647 Note that under international copyright law (this applies
648 in the United States, too), <em>no</em> distribution or
649 modification of a work is allowed without an explicit
650 notice saying so. Therefore a program without a copyright
651 notice <em>is</em> copyrighted and you may not do anything
652 to it without risking being sued! Likewise if a program
653 has a copyright notice but no statement saying what is
654 permitted then nothing is permitted.
658 Many authors are unaware of the problems that restrictive
659 copyrights (or lack of copyright notices) can cause for
660 the users of their supposedly-free software. It is often
661 worthwhile contacting such authors diplomatically to ask
662 them to modify their license terms. However, this can be a
663 politically difficult thing to do and you should ask for
664 advice on the <tt>debian-legal</tt> mailing list first, as
669 When in doubt about a copyright, send mail to
670 <email>debian-legal@lists.debian.org</email>. Be prepared
671 to provide us with the copyright statement. Software
672 covered by the GPL, public domain software and BSD-like
673 copyrights are safe; be wary of the phrases "commercial
674 use prohibited" and "distribution restricted".
678 <sect id="subsections">
679 <heading>Sections</heading>
682 The packages in the archive areas <em>main</em>,
683 <em>contrib</em> and <em>non-free</em> are grouped further into
684 <em>sections</em> to simplify handling.
688 The archive area and section for each package should be
689 specified in the package's <tt>Section</tt> control record (see
690 <ref id="f-Section">). However, the maintainer of the Debian
691 archive may override this selection to ensure the consistency of
692 the Debian distribution. The <tt>Section</tt> field should be
694 <list compact="compact">
696 <em>section</em> if the package is in the
697 <em>main</em> archive area,
700 <em>area/section</em> if the package is in
701 the <em>contrib</em> or <em>non-free</em>
708 The Debian archive maintainers provide the authoritative
709 list of sections. At present, they are:
710 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
711 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
712 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
713 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
714 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
715 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
716 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
717 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
718 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
719 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
720 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
721 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
722 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
723 <em>zope</em>. The additional section <em>debian-installer</em>
724 contains special packages used by the installer and is not used
725 for normal Debian packages.
729 For more information about the sections and their definitions,
730 see the <url id="http://packages.debian.org/unstable/"
731 name="list of sections in unstable">.
735 <sect id="priorities">
736 <heading>Priorities</heading>
739 Each package should have a <em>priority</em> value, which is
740 included in the package's <em>control record</em>
741 (see <ref id="f-Priority">).
742 This information is used by the Debian package management tools to
743 separate high-priority packages from less-important packages.
747 The following <em>priority levels</em> are recognized by the
748 Debian package management tools.
750 <tag><tt>required</tt></tag>
752 Packages which are necessary for the proper
753 functioning of the system (usually, this means that
754 dpkg functionality depends on these packages).
755 Removing a <tt>required</tt> package may cause your
756 system to become totally broken and you may not even
757 be able to use <prgn>dpkg</prgn> to put things back,
758 so only do so if you know what you are doing. Systems
759 with only the <tt>required</tt> packages are probably
760 unusable, but they do have enough functionality to
761 allow the sysadmin to boot and install more software.
763 <tag><tt>important</tt></tag>
765 Important programs, including those which one would
766 expect to find on any Unix-like system. If the
767 expectation is that an experienced Unix person who
768 found it missing would say "What on earth is going on,
769 where is <prgn>foo</prgn>?", it must be an
770 <tt>important</tt> package.<footnote>
771 This is an important criterion because we are
772 trying to produce, amongst other things, a free
775 Other packages without which the system will not run
776 well or be usable must also have priority
777 <tt>important</tt>. This does
778 <em>not</em> include Emacs, the X Window System, TeX
779 or any other large applications. The
780 <tt>important</tt> packages are just a bare minimum of
781 commonly-expected and necessary tools.
783 <tag><tt>standard</tt></tag>
785 These packages provide a reasonably small but not too
786 limited character-mode system. This is what will be
787 installed by default if the user doesn't select anything
788 else. It doesn't include many large applications.
790 <tag><tt>optional</tt></tag>
792 (In a sense everything that isn't required is
793 optional, but that's not what is meant here.) This is
794 all the software that you might reasonably want to
795 install if you didn't know what it was and don't have
796 specialized requirements. This is a much larger system
797 and includes the X Window System, a full TeX
798 distribution, and many applications. Note that
799 optional packages should not conflict with each other.
801 <tag><tt>extra</tt></tag>
803 This contains all packages that conflict with others
804 with required, important, standard or optional
805 priorities, or are only likely to be useful if you
806 already know what they are or have specialized
807 requirements (such as packages containing only detached
814 Packages must not depend on packages with lower priority
815 values (excluding build-time dependencies). In order to
816 ensure this, the priorities of one or more packages may need
825 <heading>Binary packages</heading>
828 The Debian distribution is based on the Debian
829 package management system, called <prgn>dpkg</prgn>. Thus,
830 all packages in the Debian distribution must be provided
831 in the <tt>.deb</tt> file format.
835 A <tt>.deb</tt> package contains two sets of files: a set of files
836 to install on the system when the package is installed, and a set
837 of files that provide additional metadata about the package or
838 which are executed when the package is installed or removed. This
839 second set of files is called <em>control information files</em>.
840 Among those files are the package maintainer scripts
841 and <file>control</file>, the <qref id="binarycontrolfiles">binary
842 package control file</qref> that contains the control fields for
843 the package. Other control information files
844 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
845 file</qref> used to store shared library dependency information
846 and the <file>conffiles</file> file that lists the package's
847 configuration files (described in <ref id="config-files">).
851 There is unfortunately a collision of terminology here between
852 control information files and files in the Debian control file
853 format. Throughout this document, a <em>control file</em> refers
854 to a file in the Debian control file format. These files are
855 documented in <ref id="controlfields">. Only files referred to
856 specifically as <em>control information files</em> are the files
857 included in the control information file member of
858 the <file>.deb</file> file format used by binary packages. Most
859 control information files are not in the Debian control file
864 <heading>The package name</heading>
867 Every package must have a name that's unique within the Debian
872 The package name is included in the control field
873 <tt>Package</tt>, the format of which is described
874 in <ref id="f-Package">.
875 The package name is also included as a part of the file name
876 of the <tt>.deb</tt> file.
881 <heading>The version of a package</heading>
884 Every package has a version number recorded in its
885 <tt>Version</tt> control file field, described in
886 <ref id="f-Version">.
890 The package management system imposes an ordering on version
891 numbers, so that it can tell whether packages are being up- or
892 downgraded and so that package system front end applications
893 can tell whether a package it finds available is newer than
894 the one installed on the system. The version number format
895 has the most significant parts (as far as comparison is
896 concerned) at the beginning.
900 If an upstream package has problematic version numbers they
901 should be converted to a sane form for use in the
902 <tt>Version</tt> field.
906 <heading>Version numbers based on dates</heading>
909 In general, Debian packages should use the same version
910 numbers as the upstream sources. However, upstream version
911 numbers based on some date formats (sometimes used for
912 development or "snapshot" releases) will not be ordered
913 correctly by the package management software. For
914 example, <prgn>dpkg</prgn> will consider "96May01" to be
915 greater than "96Dec24".
919 To prevent having to use epochs for every new upstream
920 version, the date-based portion of any upstream version number
921 should be given in a way that sorts correctly: four-digit year
922 first, followed by a two-digit numeric month, followed by a
923 two-digit numeric date, possibly with punctuation between the
928 Native Debian packages (i.e., packages which have been written
929 especially for Debian) whose version numbers include dates
930 should also follow these rules. If punctuation is desired
931 between the date components, remember that hyphen (<tt>-</tt>)
932 cannot be used in native package versions. Period
933 (<tt>.</tt>) is normally a good choice.
939 <sect id="maintainer">
940 <heading>The maintainer of a package</heading>
943 Every package must have a maintainer, except for orphaned
944 packages as described below. The maintainer may be one person
945 or a group of people reachable from a common email address, such
946 as a mailing list. The maintainer is responsible for
947 maintaining the Debian packaging files, evaluating and
948 responding appropriately to reported bugs, uploading new
949 versions of the package (either directly or through a sponsor),
950 ensuring that the package is placed in the appropriate archive
951 area and included in Debian releases as appropriate for the
952 stability and utility of the package, and requesting removal of
953 the package from the Debian distribution if it is no longer
954 useful or maintainable.
958 The maintainer must be specified in the <tt>Maintainer</tt>
959 control field with their correct name and a working email
960 address. The email address given in the <tt>Maintainer</tt>
961 control field must accept mail from those role accounts in
962 Debian used to send automated mails regarding the package. This
963 includes non-spam mail from the bug-tracking system, all mail
964 from the Debian archive maintenance software, and other role
965 accounts or automated processes that are commonly agreed on by
966 the project.<footnote>
967 A sample implementation of such a whitelist written for the
968 Mailman mailing list management software is used for mailing
969 lists hosted by alioth.debian.org.
971 If one person or team maintains several packages, they should
972 use the same form of their name and email address in
973 the <tt>Maintainer</tt> fields of those packages.
977 The format of the <tt>Maintainer</tt> control field is
978 described in <ref id="f-Maintainer">.
982 If the maintainer of the package is a team of people with a
983 shared email address, the <tt>Uploaders</tt> control field must
984 be present and must contain at least one human with their
985 personal email address. See <ref id="f-Uploaders"> for the
986 syntax of that field.
990 An orphaned package is one with no current maintainer. Orphaned
991 packages should have their <tt>Maintainer</tt> control field set
992 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
993 These packages are considered maintained by the Debian project
994 as a whole until someone else volunteers to take over
995 maintenance.<footnote>
996 The detailed procedure for gracefully orphaning a package can
997 be found in the Debian Developer's Reference
998 (see <ref id="related">).
1003 <sect id="descriptions">
1004 <heading>The description of a package</heading>
1007 Every Debian package must have a <tt>Description</tt> control
1008 field which contains a synopsis and extended description of the
1009 package. Technical information about the format of the
1010 <tt>Description</tt> field is in <ref id="f-Description">.
1014 The description should describe the package (the program) to a
1015 user (system administrator) who has never met it before so that
1016 they have enough information to decide whether they want to
1017 install it. This description should not just be copied verbatim
1018 from the program's documentation.
1022 Put important information first, both in the synopsis and
1023 extended description. Sometimes only the first part of the
1024 synopsis or of the description will be displayed. You can
1025 assume that there will usually be a way to see the whole
1026 extended description.
1030 The description should also give information about the
1031 significant dependencies and conflicts between this package
1032 and others, so that the user knows why these dependencies and
1033 conflicts have been declared.
1037 Instructions for configuring or using the package should
1038 not be included (that is what installation scripts,
1039 manual pages, info files, etc., are for). Copyright
1040 statements and other administrivia should not be included
1041 either (that is what the copyright file is for).
1044 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1047 The single line synopsis should be kept brief - certainly
1048 under 80 characters.
1052 Do not include the package name in the synopsis line. The
1053 display software knows how to display this already, and you
1054 do not need to state it. Remember that in many situations
1055 the user may only see the synopsis line - make it as
1056 informative as you can.
1061 <sect1 id="extendeddesc"><heading>The extended description</heading>
1064 Do not try to continue the single line synopsis into the
1065 extended description. This will not work correctly when
1066 the full description is displayed, and makes no sense
1067 where only the summary (the single line synopsis) is
1072 The extended description should describe what the package
1073 does and how it relates to the rest of the system (in terms
1074 of, for example, which subsystem it is which part of).
1078 The description field needs to make sense to anyone, even
1079 people who have no idea about any of the things the
1080 package deals with.<footnote>
1081 The blurb that comes with a program in its
1082 announcements and/or <prgn>README</prgn> files is
1083 rarely suitable for use in a description. It is
1084 usually aimed at people who are already in the
1085 community where the package is used.
1093 <sect id="dependencies">
1094 <heading>Dependencies</heading>
1097 Every package must specify the dependency information
1098 about other packages that are required for the first to
1103 For example, a dependency entry must be provided for any
1104 shared libraries required by a dynamically-linked executable
1105 binary in a package.
1109 Packages are not required to declare any dependencies they
1110 have on other packages which are marked <tt>Essential</tt>
1111 (see below), and should not do so unless they depend on a
1112 particular version of that package.<footnote>
1114 Essential is needed in part to avoid unresolvable dependency
1115 loops on upgrade. If packages add unnecessary dependencies
1116 on packages in this set, the chances that there
1117 <strong>will</strong> be an unresolvable dependency loop
1118 caused by forcing these Essential packages to be configured
1119 first before they need to be is greatly increased. It also
1120 increases the chances that frontends will be unable to
1121 <strong>calculate</strong> an upgrade path, even if one
1125 Also, functionality is rarely ever removed from the
1126 Essential set, but <em>packages</em> have been removed from
1127 the Essential set when the functionality moved to a
1128 different package. So depending on these packages <em>just
1129 in case</em> they stop being essential does way more harm
1136 Sometimes, unpacking one package requires that another package
1137 be first unpacked <em>and</em> configured. In this case, the
1138 depending package must specify this dependency in
1139 the <tt>Pre-Depends</tt> control field.
1143 You should not specify a <tt>Pre-Depends</tt> entry for a
1144 package before this has been discussed on the
1145 <tt>debian-devel</tt> mailing list and a consensus about
1146 doing that has been reached.
1150 The format of the package interrelationship control fields is
1151 described in <ref id="relationships">.
1155 <sect id="virtual_pkg">
1156 <heading>Virtual packages</heading>
1159 Sometimes, there are several packages which offer
1160 more-or-less the same functionality. In this case, it's
1161 useful to define a <em>virtual package</em> whose name
1162 describes that common functionality. (The virtual
1163 packages only exist logically, not physically; that's why
1164 they are called <em>virtual</em>.) The packages with this
1165 particular function will then <em>provide</em> the virtual
1166 package. Thus, any other package requiring that function
1167 can simply depend on the virtual package without having to
1168 specify all possible packages individually.
1172 All packages should use virtual package names where
1173 appropriate, and arrange to create new ones if necessary.
1174 They should not use virtual package names (except privately,
1175 amongst a cooperating group of packages) unless they have
1176 been agreed upon and appear in the list of virtual package
1177 names. (See also <ref id="virtual">)
1181 The latest version of the authoritative list of virtual
1182 package names can be found in the <tt>debian-policy</tt> package.
1183 It is also available from the Debian web mirrors at
1184 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1185 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1189 The procedure for updating the list is described in the preface
1196 <heading>Base system</heading>
1199 The <tt>base system</tt> is a minimum subset of the Debian
1200 system that is installed before everything else
1201 on a new system. Only very few packages are allowed to form
1202 part of the base system, in order to keep the required disk
1207 The base system consists of all those packages with priority
1208 <tt>required</tt> or <tt>important</tt>. Many of them will
1209 be tagged <tt>essential</tt> (see below).
1214 <heading>Essential packages</heading>
1217 Essential is defined as the minimal set of functionality that
1218 must be available and usable on the system at all times, even
1219 when packages are in an unconfigured (but unpacked) state.
1220 Packages are tagged <tt>essential</tt> for a system using the
1221 <tt>Essential</tt> control field. The format of the
1222 <tt>Essential</tt> control field is described in <ref
1227 Since these packages cannot be easily removed (one has to
1228 specify an extra <em>force option</em> to
1229 <prgn>dpkg</prgn> to do so), this flag must not be used
1230 unless absolutely necessary. A shared library package
1231 must not be tagged <tt>essential</tt>; dependencies will
1232 prevent its premature removal, and we need to be able to
1233 remove it when it has been superseded.
1237 Since dpkg will not prevent upgrading of other packages
1238 while an <tt>essential</tt> package is in an unconfigured
1239 state, all <tt>essential</tt> packages must supply all of
1240 their core functionality even when unconfigured. If the
1241 package cannot satisfy this requirement it must not be
1242 tagged as essential, and any packages depending on this
1243 package must instead have explicit dependency fields as
1248 Maintainers should take great care in adding any programs,
1249 interfaces, or functionality to <tt>essential</tt> packages.
1250 Packages may assume that functionality provided by
1251 <tt>essential</tt> packages is always available without
1252 declaring explicit dependencies, which means that removing
1253 functionality from the Essential set is very difficult and is
1254 almost never done. Any capability added to an
1255 <tt>essential</tt> package therefore creates an obligation to
1256 support that capability as part of the Essential set in
1261 You must not tag any packages <tt>essential</tt> before
1262 this has been discussed on the <tt>debian-devel</tt>
1263 mailing list and a consensus about doing that has been
1268 <sect id="maintscripts">
1269 <heading>Maintainer Scripts</heading>
1272 The package installation scripts should avoid producing
1273 output which is unnecessary for the user to see and
1274 should rely on <prgn>dpkg</prgn> to stave off boredom on
1275 the part of a user installing many packages. This means,
1276 amongst other things, using the <tt>--quiet</tt> option on
1277 <prgn>install-info</prgn>.
1281 Errors which occur during the execution of an installation
1282 script must be checked and the installation must not
1283 continue after an error.
1287 Note that in general <ref id="scripts"> applies to package
1288 maintainer scripts, too.
1292 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1293 to another package without consulting the maintainer of that
1294 package first. When adding or removing diversions, package
1295 maintainer scripts must provide the <tt>--package</tt> flag
1296 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1300 All packages which supply an instance of a common command
1301 name (or, in general, filename) should generally use
1302 <prgn>update-alternatives</prgn>, so that they may be
1303 installed together. If <prgn>update-alternatives</prgn>
1304 is not used, then each package must use
1305 <tt>Conflicts</tt> to ensure that other packages are
1306 de-installed. (In this case, it may be appropriate to
1307 specify a conflict against earlier versions of something
1308 that previously did not use
1309 <prgn>update-alternatives</prgn>; this is an exception to
1310 the usual rule that versioned conflicts should be
1314 <sect1 id="maintscriptprompt">
1315 <heading>Prompting in maintainer scripts</heading>
1317 Package maintainer scripts may prompt the user if
1318 necessary. Prompting must be done by communicating
1319 through a program, such as <prgn>debconf</prgn>, which
1320 conforms to the Debian Configuration Management
1321 Specification, version 2 or higher.
1325 Packages which are essential, or which are dependencies of
1326 essential packages, may fall back on another prompting method
1327 if no such interface is available when they are executed.
1331 The Debian Configuration Management Specification is included
1332 in the <file>debconf_specification</file> files in the
1333 <package>debian-policy</package> package.
1334 It is also available from the Debian web mirrors at
1335 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1336 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1340 Packages which use the Debian Configuration Management
1341 Specification may contain the additional control information
1342 files <file>config</file>
1343 and <file>templates</file>. <file>config</file> is an
1344 additional maintainer script used for package configuration,
1345 and <file>templates</file> contains templates used for user
1346 prompting. The <prgn>config</prgn> script might be run before
1347 the <prgn>preinst</prgn> script and before the package is
1348 unpacked or any of its dependencies or pre-dependencies are
1349 satisfied. Therefore it must work using only the tools
1350 present in <em>essential</em> packages.<footnote>
1351 <package>Debconf</package> or another tool that
1352 implements the Debian Configuration Management
1353 Specification will also be installed, and any
1354 versioned dependencies on it will be satisfied
1355 before preconfiguration begins.
1360 Packages which use the Debian Configuration Management
1361 Specification must allow for translation of their user-visible
1362 messages by using a gettext-based system such as the one
1363 provided by the <package>po-debconf</package> package.
1367 Packages should try to minimize the amount of prompting
1368 they need to do, and they should ensure that the user
1369 will only ever be asked each question once. This means
1370 that packages should try to use appropriate shared
1371 configuration files (such as <file>/etc/papersize</file> and
1372 <file>/etc/news/server</file>), and shared
1373 <package>debconf</package> variables rather than each
1374 prompting for their own list of required pieces of
1379 It also means that an upgrade should not ask the same
1380 questions again, unless the user has used
1381 <tt>dpkg --purge</tt> to remove the package's configuration.
1382 The answers to configuration questions should be stored in an
1383 appropriate place in <file>/etc</file> so that the user can
1384 modify them, and how this has been done should be
1389 If a package has a vitally important piece of
1390 information to pass to the user (such as "don't run me
1391 as I am, you must edit the following configuration files
1392 first or you risk your system emitting badly-formatted
1393 messages"), it should display this in the
1394 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1395 prompt the user to hit return to acknowledge the
1396 message. Copyright messages do not count as vitally
1397 important (they belong in
1398 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1399 neither do instructions on how to use a program (these
1400 should be in on-line documentation, where all the users
1405 Any necessary prompting should almost always be confined
1406 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1407 script. If it is done in the <prgn>postinst</prgn>, it
1408 should be protected with a conditional so that
1409 unnecessary prompting doesn't happen if a package's
1410 installation fails and the <prgn>postinst</prgn> is
1411 called with <tt>abort-upgrade</tt>,
1412 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1422 <heading>Source packages</heading>
1424 <sect id="standardsversion">
1425 <heading>Standards conformance</heading>
1428 Source packages should specify the most recent version number
1429 of this policy document with which your package complied
1430 when it was last updated.
1434 This information may be used to file bug reports
1435 automatically if your package becomes too much out of date.
1439 The version is specified in the <tt>Standards-Version</tt>
1441 The format of the <tt>Standards-Version</tt> field is
1442 described in <ref id="f-Standards-Version">.
1446 You should regularly, and especially if your package has
1447 become out of date, check for the newest Policy Manual
1448 available and update your package, if necessary. When your
1449 package complies with the new standards you should update the
1450 <tt>Standards-Version</tt> source package field and
1451 release it.<footnote>
1452 See the file <file>upgrading-checklist</file> for
1453 information about policy which has changed between
1454 different versions of this document.
1460 <sect id="pkg-relations">
1461 <heading>Package relationships</heading>
1464 Source packages should specify which binary packages they
1465 require to be installed or not to be installed in order to
1466 build correctly. For example, if building a package
1467 requires a certain compiler, then the compiler should be
1468 specified as a build-time dependency.
1472 It is not necessary to explicitly specify build-time
1473 relationships on a minimal set of packages that are always
1474 needed to compile, link and put in a Debian package a
1475 standard "Hello World!" program written in C or C++. The
1476 required packages are called <em>build-essential</em>, and
1477 an informational list can be found in
1478 <file>/usr/share/doc/build-essential/list</file> (which is
1479 contained in the <tt>build-essential</tt>
1482 <list compact="compact">
1484 This allows maintaining the list separately
1485 from the policy documents (the list does not
1486 need the kind of control that the policy
1490 Having a separate package allows one to install
1491 the build-essential packages on a machine, as
1492 well as allowing other packages such as tasks to
1493 require installation of the build-essential
1494 packages using the depends relation.
1497 The separate package allows bug reports against
1498 the list to be categorized separately from
1499 the policy management process in the BTS.
1506 When specifying the set of build-time dependencies, one
1507 should list only those packages explicitly required by the
1508 build. It is not necessary to list packages which are
1509 required merely because some other package in the list of
1510 build-time dependencies depends on them.<footnote>
1511 The reason for this is that dependencies change, and
1512 you should list all those packages, and <em>only</em>
1513 those packages that <em>you</em> need directly. What
1514 others need is their business. For example, if you
1515 only link against <file>libimlib</file>, you will need to
1516 build-depend on <package>libimlib2-dev</package> but
1517 not against any <tt>libjpeg*</tt> packages, even
1518 though <tt>libimlib2-dev</tt> currently depends on
1519 them: installation of <package>libimlib2-dev</package>
1520 will automatically ensure that all of its run-time
1521 dependencies are satisfied.
1526 If build-time dependencies are specified, it must be
1527 possible to build the package and produce working binaries
1528 on a system with only essential and build-essential
1529 packages installed and also those required to satisfy the
1530 build-time relationships (including any implied
1531 relationships). In particular, this means that version
1532 clauses should be used rigorously in build-time
1533 relationships so that one cannot produce bad or
1534 inconsistently configured packages when the relationships
1535 are properly satisfied.
1539 <ref id="relationships"> explains the technical details.
1544 <heading>Changes to the upstream sources</heading>
1547 If changes to the source code are made that are not
1548 specific to the needs of the Debian system, they should be
1549 sent to the upstream authors in whatever form they prefer
1550 so as to be included in the upstream version of the
1555 If you need to configure the package differently for
1556 Debian or for Linux, and the upstream source doesn't
1557 provide a way to do so, you should add such configuration
1558 facilities (for example, a new <prgn>autoconf</prgn> test
1559 or <tt>#define</tt>) and send the patch to the upstream
1560 authors, with the default set to the way they originally
1561 had it. You can then easily override the default in your
1562 <file>debian/rules</file> or wherever is appropriate.
1566 You should make sure that the <prgn>configure</prgn> utility
1567 detects the correct architecture specification string
1568 (refer to <ref id="arch-spec"> for details).
1572 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1573 <prgn>configure</prgn> scripts are used, you should edit the
1574 <file>.in</file> files rather than editing the
1575 <prgn>Makefile</prgn> directly. This allows the user to
1576 reconfigure the package if necessary. You should
1577 <em>not</em> configure the package and edit the generated
1578 <prgn>Makefile</prgn>! This makes it impossible for someone
1579 else to later reconfigure the package without losing the
1585 <sect id="dpkgchangelog">
1586 <heading>Debian changelog: <file>debian/changelog</file></heading>
1589 Changes in the Debian version of the package should be
1590 briefly explained in the Debian changelog file
1591 <file>debian/changelog</file>.<footnote>
1593 Mistakes in changelogs are usually best rectified by
1594 making a new changelog entry rather than "rewriting
1595 history" by editing old changelog entries.
1598 This includes modifications
1599 made in the Debian package compared to the upstream one
1600 as well as other changes and updates to the package.
1602 Although there is nothing stopping an author who is also
1603 the Debian maintainer from using this changelog for all
1604 their changes, it will have to be renamed if the Debian
1605 and upstream maintainers become different people. In such
1606 a case, however, it might be better to maintain the package
1607 as a non-native package.
1612 The format of the <file>debian/changelog</file> allows the
1613 package building tools to discover which version of the package
1614 is being built and find out other release-specific information.
1618 That format is a series of entries like this:
1620 <example compact="compact">
1621 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1623 [optional blank line(s), stripped]
1625 * <var>change details</var>
1626 <var>more change details</var>
1628 [blank line(s), included in output of dpkg-parsechangelog]
1630 * <var>even more change details</var>
1632 [optional blank line(s), stripped]
1634 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1639 <var>package</var> and <var>version</var> are the source
1640 package name and version number.
1644 <var>distribution(s)</var> lists the distributions where
1645 this version should be installed when it is uploaded - it
1646 is copied to the <tt>Distribution</tt> field in the
1647 <file>.changes</file> file. See <ref id="f-Distribution">.
1651 <var>urgency</var> is the value for the <tt>Urgency</tt>
1652 field in the <file>.changes</file> file for the upload
1653 (see <ref id="f-Urgency">). It is not possible to specify
1654 an urgency containing commas; commas are used to separate
1655 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1656 <prgn>dpkg</prgn> changelog format (though there is
1657 currently only one useful <var>keyword</var>,
1662 The change details may in fact be any series of lines
1663 starting with at least two spaces, but conventionally each
1664 change starts with an asterisk and a separating space and
1665 continuation lines are indented so as to bring them in
1666 line with the start of the text above. Blank lines may be
1667 used here to separate groups of changes, if desired.
1671 If this upload resolves bugs recorded in the Bug Tracking
1672 System (BTS), they may be automatically closed on the
1673 inclusion of this package into the Debian archive by
1674 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1675 in the change details.<footnote>
1676 To be precise, the string should match the following
1677 Perl regular expression:
1679 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1681 Then all of the bug numbers listed will be closed by the
1682 archive maintenance script (<prgn>katie</prgn>) using the
1683 <var>version</var> of the changelog entry.
1685 This information is conveyed via the <tt>Closes</tt> field
1686 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1690 The maintainer name and email address used in the changelog
1691 should be the details of the person uploading <em>this</em>
1692 version. They are <em>not</em> necessarily those of the
1693 usual package maintainer.<footnote>
1694 If the developer uploading the package is not one of the usual
1695 maintainers of the package (as listed in
1696 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1697 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1698 fields of the package), the first line of the changelog is
1699 conventionally used to explain why a non-maintainer is
1700 uploading the package. The Debian Developer's Reference
1701 (see <ref id="related">) documents the conventions
1703 The information here will be copied to the <tt>Changed-By</tt>
1704 field in the <tt>.changes</tt> file
1705 (see <ref id="f-Changed-By">), and then later used to send an
1706 acknowledgement when the upload has been installed.
1710 The <var>date</var> has the following format<footnote>
1711 This is the same as the format generated by <tt>date
1713 </footnote> (compatible and with the same semantics of
1714 RFC 2822 and RFC 5322):
1715 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1717 <list compact="compact">
1719 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1722 dd is a one- or two-digit day of the month (01-31)
1725 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1728 <item>yyyy is the four-digit year (e.g. 2010)</item>
1729 <item>hh is the two-digit hour (00-23)</item>
1730 <item>mm is the two-digit minutes (00-59)</item>
1731 <item>ss is the two-digit seconds (00-60)</item>
1733 +zzzz or -zzzz is the the time zone offset from Coordinated
1734 Universal Time (UTC). "+" indicates that the time is ahead
1735 of (i.e., east of) UTC and "-" indicates that the time is
1736 behind (i.e., west of) UTC. The first two digits indicate
1737 the hour difference from UTC and the last two digits
1738 indicate the number of additional minutes difference from
1739 UTC. The last two digits must be in the range 00-59.
1745 The first "title" line with the package name must start
1746 at the left hand margin. The "trailer" line with the
1747 maintainer and date details must be preceded by exactly
1748 one space. The maintainer details and the date must be
1749 separated by exactly two spaces.
1753 The entire changelog must be encoded in UTF-8.
1757 For more information on placement of the changelog files
1758 within binary packages, please see <ref id="changelogs">.
1762 <sect id="dpkgcopyright">
1763 <heading>Copyright: <file>debian/copyright</file></heading>
1765 Every package must be accompanied by a verbatim copy of its
1766 copyright information and distribution license in the file
1767 <file>/usr/share/doc/<var>package</var>/copyright</file>
1768 (see <ref id="copyrightfile"> for further details). Also see
1769 <ref id="pkgcopyright"> for further considerations related
1770 to copyrights for packages.
1774 <heading>Error trapping in makefiles</heading>
1777 When <prgn>make</prgn> invokes a command in a makefile
1778 (including your package's upstream makefiles and
1779 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1780 means that <prgn>sh</prgn>'s usual bad error handling
1781 properties apply: if you include a miniature script as one
1782 of the commands in your makefile you'll find that if you
1783 don't do anything about it then errors are not detected
1784 and <prgn>make</prgn> will blithely continue after
1789 Every time you put more than one shell command (this
1790 includes using a loop) in a makefile command you
1791 must make sure that errors are trapped. For
1792 simple compound commands, such as changing directory and
1793 then running a program, using <tt>&&</tt> rather
1794 than semicolon as a command separator is sufficient. For
1795 more complex commands including most loops and
1796 conditionals you should include a separate <tt>set -e</tt>
1797 command at the start of every makefile command that's
1798 actually one of these miniature shell scripts.
1802 <sect id="timestamps">
1803 <heading>Time Stamps</heading>
1805 Maintainers should preserve the modification times of the
1806 upstream source files in a package, as far as is reasonably
1808 The rationale is that there is some information conveyed
1809 by knowing the age of the file, for example, you could
1810 recognize that some documentation is very old by looking
1811 at the modification time, so it would be nice if the
1812 modification time of the upstream source would be
1818 <sect id="restrictions">
1819 <heading>Restrictions on objects in source packages</heading>
1822 The source package may not contain any hard links<footnote>
1824 This is not currently detected when building source
1825 packages, but only when extracting
1829 Hard links may be permitted at some point in the
1830 future, but would require a fair amount of
1833 </footnote>, device special files, sockets or setuid or
1834 setgid files.<footnote>
1835 Setgid directories are allowed.
1840 <sect id="debianrules">
1841 <heading>Main building script: <file>debian/rules</file></heading>
1844 This file must be an executable makefile, and contains the
1845 package-specific recipes for compiling the package and
1846 building binary package(s) from the source.
1850 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1851 so that it can be invoked by saying its name rather than
1852 invoking <prgn>make</prgn> explicitly. That is, invoking
1853 either of <tt>make -f debian/rules <em>args...</em></tt>
1854 or <tt>./debian/rules <em>args...</em></tt> must result in
1859 The following targets are required and must be implemented
1860 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1861 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1862 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1866 Since an interactive <file>debian/rules</file> script makes it
1867 impossible to auto-compile that package and also makes it hard
1868 for other people to reproduce the same binary package, all
1869 required targets must be non-interactive. It also follows that
1870 any target that these targets depend on must also be
1875 The targets are as follows:
1877 <tag><tt>build</tt> (required)</tag>
1880 The <tt>build</tt> target should perform all the
1881 configuration and compilation of the package.
1882 If a package has an interactive pre-build
1883 configuration routine, the Debian source package
1884 must either be built after this has taken place (so
1885 that the binary package can be built without rerunning
1886 the configuration) or the configuration routine
1887 modified to become non-interactive. (The latter is
1888 preferable if there are architecture-specific features
1889 detected by the configuration routine.)
1893 For some packages, notably ones where the same
1894 source tree is compiled in different ways to produce
1895 two binary packages, the <tt>build</tt> target
1896 does not make much sense. For these packages it is
1897 good enough to provide two (or more) targets
1898 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1899 for each of the ways of building the package, and a
1900 <tt>build</tt> target that does nothing. The
1901 <tt>binary</tt> target will have to build the
1902 package in each of the possible ways and make the
1903 binary package out of each.
1907 The <tt>build</tt> target must not do anything
1908 that might require root privilege.
1912 The <tt>build</tt> target may need to run the
1913 <tt>clean</tt> target first - see below.
1917 When a package has a configuration and build routine
1918 which takes a long time, or when the makefiles are
1919 poorly designed, or when <tt>build</tt> needs to
1920 run <tt>clean</tt> first, it is a good idea to
1921 <tt>touch build</tt> when the build process is
1922 complete. This will ensure that if <tt>debian/rules
1923 build</tt> is run again it will not rebuild the whole
1925 Another common way to do this is for <tt>build</tt>
1926 to depend on <prgn>build-stamp</prgn> and to do
1927 nothing else, and for the <prgn>build-stamp</prgn>
1928 target to do the building and to <tt>touch
1929 build-stamp</tt> on completion. This is
1930 especially useful if the build routine creates a
1931 file or directory called <tt>build</tt>; in such a
1932 case, <tt>build</tt> will need to be listed as
1933 a phony target (i.e., as a dependency of the
1934 <tt>.PHONY</tt> target). See the documentation of
1935 <prgn>make</prgn> for more information on phony
1941 <tag><tt>build-arch</tt> (optional),
1942 <tt>build-indep</tt> (optional)
1946 A package may also provide both of the targets
1947 <tt>build-arch</tt> and <tt>build-indep</tt>.
1948 The <tt>build-arch</tt> target, if provided, should
1949 perform all the configuration and compilation required for
1950 producing all architecture-dependant binary packages
1951 (those packages for which the body of the
1952 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1953 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1954 target, if provided, should perform all the configuration
1955 and compilation required for producing all
1956 architecture-independent binary packages (those packages
1957 for which the body of the <tt>Architecture</tt> field
1958 in <tt>debian/control</tt> is <tt>all</tt>).
1959 The <tt>build</tt> target should depend on those of the
1960 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1961 are provided in the rules file.<footnote>
1962 The intent of this split is so that binary-only builds
1963 need not install the dependencies required for
1964 the <tt>build-indep</tt> target. However, this is not
1965 yet used in practice since <tt>dpkg-buildpackage
1966 -B</tt>, and therefore the autobuilders,
1967 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1968 due to the difficulties in determining whether the
1969 optional <tt>build-arch</tt> target exists.
1974 If one or both of the targets <tt>build-arch</tt> and
1975 <tt>build-indep</tt> are not provided, then invoking
1976 <file>debian/rules</file> with one of the not-provided
1977 targets as arguments should produce a exit status code
1978 of 2. Usually this is provided automatically by make
1979 if the target is missing.
1983 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1984 must not do anything that might require root privilege.
1988 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1989 (required), <tt>binary-indep</tt> (required)
1993 The <tt>binary</tt> target must be all that is
1994 necessary for the user to build the binary package(s)
1995 produced from this source package. It is
1996 split into two parts: <prgn>binary-arch</prgn> builds
1997 the binary packages which are specific to a particular
1998 architecture, and <tt>binary-indep</tt> builds
1999 those which are not.
2002 <tt>binary</tt> may be (and commonly is) a target with
2003 no commands which simply depends on
2004 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2007 Both <tt>binary-*</tt> targets should depend on the
2008 <tt>build</tt> target, or on the appropriate
2009 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2010 provided, so that the package is built if it has not
2011 been already. It should then create the relevant
2012 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2013 make their control files and <prgn>dpkg-deb</prgn> to
2014 build them and place them in the parent of the top
2019 Both the <tt>binary-arch</tt> and
2020 <tt>binary-indep</tt> targets <em>must</em> exist.
2021 If one of them has nothing to do (which will always be
2022 the case if the source generates only a single binary
2023 package, whether architecture-dependent or not), it
2024 must still exist and must always succeed.
2028 The <tt>binary</tt> targets must be invoked as
2030 The <prgn>fakeroot</prgn> package often allows one
2031 to build a package correctly even without being
2037 <tag><tt>clean</tt> (required)</tag>
2040 This must undo any effects that the <tt>build</tt>
2041 and <tt>binary</tt> targets may have had, except
2042 that it should leave alone any output files created in
2043 the parent directory by a run of a <tt>binary</tt>
2048 If a <tt>build</tt> file is touched at the end of
2049 the <tt>build</tt> target, as suggested above, it
2050 should be removed as the first action that
2051 <tt>clean</tt> performs, so that running
2052 <tt>build</tt> again after an interrupted
2053 <tt>clean</tt> doesn't think that everything is
2058 The <tt>clean</tt> target may need to be
2059 invoked as root if <tt>binary</tt> has been
2060 invoked since the last <tt>clean</tt>, or if
2061 <tt>build</tt> has been invoked as root (since
2062 <tt>build</tt> may create directories, for
2067 <tag><tt>get-orig-source</tt> (optional)</tag>
2070 This target fetches the most recent version of the
2071 original source package from a canonical archive site
2072 (via FTP or WWW, for example), does any necessary
2073 rearrangement to turn it into the original source
2074 tar file format described below, and leaves it in the
2079 This target may be invoked in any directory, and
2080 should take care to clean up any temporary files it
2085 This target is optional, but providing it if
2086 possible is a good idea.
2090 <tag><tt>patch</tt> (optional)</tag>
2093 This target performs whatever additional actions are
2094 required to make the source ready for editing (unpacking
2095 additional upstream archives, applying patches, etc.).
2096 It is recommended to be implemented for any package where
2097 <tt>dpkg-source -x</tt> does not result in source ready
2098 for additional modification. See
2099 <ref id="readmesource">.
2105 The <tt>build</tt>, <tt>binary</tt> and
2106 <tt>clean</tt> targets must be invoked with the current
2107 directory being the package's top-level directory.
2112 Additional targets may exist in <file>debian/rules</file>,
2113 either as published or undocumented interfaces or for the
2114 package's internal use.
2118 The architectures we build on and build for are determined
2119 by <prgn>make</prgn> variables using the
2120 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2121 You can determine the Debian architecture and the GNU style
2122 architecture specification string for the build architecture as
2123 well as for the host architecture. The build architecture is
2124 the architecture on which <file>debian/rules</file> is run and
2125 the package build is performed. The host architecture is the
2126 architecture on which the resulting package will be installed
2127 and run. These are normally the same, but may be different in
2128 the case of cross-compilation (building packages for one
2129 architecture on machines of a different architecture).
2133 Here is a list of supported <prgn>make</prgn> variables:
2134 <list compact="compact">
2136 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2139 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2142 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2145 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2146 specification string)
2149 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2150 <tt>DEB_*_GNU_TYPE</tt>)
2153 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2154 <tt>DEB_*_GNU_TYPE</tt>)
2156 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2157 the build architecture or <tt>HOST</tt> for specification of the
2162 Backward compatibility can be provided in the rules file
2163 by setting the needed variables to suitable default
2164 values; please refer to the documentation of
2165 <prgn>dpkg-architecture</prgn> for details.
2169 It is important to understand that the <tt>DEB_*_ARCH</tt>
2170 string only determines which Debian architecture we are
2171 building on or for. It should not be used to get the CPU
2172 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2173 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2174 GNU style variables should generally only be used with upstream
2178 <sect1 id="debianrules-options">
2179 <heading><file>debian/rules</file> and
2180 <tt>DEB_BUILD_OPTIONS</tt></heading>
2183 Supporting the standardized environment variable
2184 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2185 contain several flags to change how a package is compiled and
2186 built. Each flag must be in the form <var>flag</var> or
2187 <var>flag</var>=<var>options</var>. If multiple flags are
2188 given, they must be separated by whitespace.<footnote>
2189 Some packages support any delimiter, but whitespace is the
2190 easiest to parse inside a makefile and avoids ambiguity with
2191 flag values that contain commas.
2193 <var>flag</var> must start with a lowercase letter
2194 (<tt>a-z</tt>) and consist only of lowercase letters,
2195 numbers (<tt>0-9</tt>), and the characters
2196 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2197 <var>options</var> must not contain whitespace. The same
2198 tag should not be given multiple times with conflicting
2199 values. Package maintainers may assume that
2200 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2204 The meaning of the following tags has been standardized:
2208 This tag says to not run any build-time test suite
2209 provided by the package.
2213 The presence of this tag means that the package should
2214 be compiled with a minimum of optimization. For C
2215 programs, it is best to add <tt>-O0</tt> to
2216 <tt>CFLAGS</tt> (although this is usually the default).
2217 Some programs might fail to build or run at this level
2218 of optimization; it may be necessary to use
2219 <tt>-O1</tt>, for example.
2223 This tag means that the debugging symbols should not be
2224 stripped from the binary during installation, so that
2225 debugging information may be included in the package.
2227 <tag>parallel=n</tag>
2229 This tag means that the package should be built using up
2230 to <tt>n</tt> parallel processes if the package build
2231 system supports this.<footnote>
2232 Packages built with <tt>make</tt> can often implement
2233 this by passing the <tt>-j</tt><var>n</var> option to
2236 If the package build system does not support parallel
2237 builds, this string must be ignored. If the package
2238 build system only supports a lower level of concurrency
2239 than <var>n</var>, the package should be built using as
2240 many parallel processes as the package build system
2241 supports. It is up to the package maintainer to decide
2242 whether the package build times are long enough and the
2243 package build system is robust enough to make supporting
2244 parallel builds worthwhile.
2250 Unknown flags must be ignored by <file>debian/rules</file>.
2254 The following makefile snippet is an example of how one may
2255 implement the build options; you will probably have to
2256 massage this example in order to make it work for your
2258 <example compact="compact">
2261 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2262 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2263 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2264 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2266 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2271 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2272 INSTALL_PROGRAM += -s
2274 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2275 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2276 MAKEFLAGS += -j$(NUMJOBS)
2281 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2282 # Code to run the package test suite.
2289 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2290 <sect id="substvars">
2291 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2294 When <prgn>dpkg-gencontrol</prgn>
2295 generates <qref id="binarycontrolfiles">binary package control
2296 files</qref> (<file>DEBIAN/control</file>), it performs variable
2297 substitutions on its output just before writing it. Variable
2298 substitutions have the form <tt>${<var>variable</var>}</tt>.
2299 The optional file <file>debian/substvars</file> contains
2300 variable substitutions to be used; variables can also be set
2301 directly from <file>debian/rules</file> using the <tt>-V</tt>
2302 option to the source packaging commands, and certain predefined
2303 variables are also available.
2307 The <file>debian/substvars</file> file is usually generated and
2308 modified dynamically by <file>debian/rules</file> targets, in
2309 which case it must be removed by the <tt>clean</tt> target.
2313 See <manref name="deb-substvars" section="5"> for full
2314 details about source variable substitutions, including the
2315 format of <file>debian/substvars</file>.</p>
2318 <sect id="debianwatch">
2319 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2322 This is an optional, recommended configuration file for the
2323 <tt>uscan</tt> utility which defines how to automatically scan
2324 ftp or http sites for newly available updates of the
2325 package. This is used
2326 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2327 tools to help with quality control and maintenance of the
2328 distribution as a whole.
2333 <sect id="debianfiles">
2334 <heading>Generated files list: <file>debian/files</file></heading>
2337 This file is not a permanent part of the source tree; it
2338 is used while building packages to record which files are
2339 being generated. <prgn>dpkg-genchanges</prgn> uses it
2340 when it generates a <file>.changes</file> file.
2344 It should not exist in a shipped source package, and so it
2345 (and any backup files or temporary files such as
2346 <file>files.new</file><footnote>
2347 <file>files.new</file> is used as a temporary file by
2348 <prgn>dpkg-gencontrol</prgn> and
2349 <prgn>dpkg-distaddfile</prgn> - they write a new
2350 version of <tt>files</tt> here before renaming it,
2351 to avoid leaving a corrupted copy if an error
2353 </footnote>) should be removed by the
2354 <tt>clean</tt> target. It may also be wise to
2355 ensure a fresh start by emptying or removing it at the
2356 start of the <tt>binary</tt> target.
2360 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2361 package, it adds an entry to <file>debian/files</file> for the
2362 <file>.deb</file> file that will be created when <tt>dpkg-deb
2363 --build</tt> is run for that binary package. So for most
2364 packages all that needs to be done with this file is to
2365 delete it in the <tt>clean</tt> target.
2369 If a package upload includes files besides the source
2370 package and any binary packages whose control files were
2371 made with <prgn>dpkg-gencontrol</prgn> then they should be
2372 placed in the parent of the package's top-level directory
2373 and <prgn>dpkg-distaddfile</prgn> should be called to add
2374 the file to the list in <file>debian/files</file>.</p>
2377 <sect id="embeddedfiles">
2378 <heading>Convenience copies of code</heading>
2381 Some software packages include in their distribution convenience
2382 copies of code from other software packages, generally so that
2383 users compiling from source don't have to download multiple
2384 packages. Debian packages should not make use of these
2385 convenience copies unless the included package is explicitly
2386 intended to be used in this way.<footnote>
2387 For example, parts of the GNU build system work like this.
2389 If the included code is already in the Debian archive in the
2390 form of a library, the Debian packaging should ensure that
2391 binary packages reference the libraries already in Debian and
2392 the convenience copy is not used. If the included code is not
2393 already in Debian, it should be packaged separately as a
2394 prerequisite if possible.
2396 Having multiple copies of the same code in Debian is
2397 inefficient, often creates either static linking or shared
2398 library conflicts, and, most importantly, increases the
2399 difficulty of handling security vulnerabilities in the
2405 <sect id="readmesource">
2406 <heading>Source package handling:
2407 <file>debian/README.source</file></heading>
2410 If running <prgn>dpkg-source -x</prgn> on a source package
2411 doesn't produce the source of the package, ready for editing,
2412 and allow one to make changes and run
2413 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2414 without taking any additional steps, creating a
2415 <file>debian/README.source</file> documentation file is
2416 recommended. This file should explain how to do all of the
2419 <item>Generate the fully patched source, in a form ready for
2420 editing, that would be built to create Debian
2421 packages. Doing this with a <tt>patch</tt> target in
2422 <file>debian/rules</file> is recommended; see
2423 <ref id="debianrules">.</item>
2424 <item>Modify the source and save those modifications so that
2425 they will be applied when building the package.</item>
2426 <item>Remove source modifications that are currently being
2427 applied when building the package.</item>
2428 <item>Optionally, document what steps are necessary to
2429 upgrade the Debian source package to a new upstream version,
2430 if applicable.</item>
2432 This explanation should include specific commands and mention
2433 any additional required Debian packages. It should not assume
2434 familiarity with any specific Debian packaging system or patch
2439 This explanation may refer to a documentation file installed by
2440 one of the package's build dependencies provided that the
2441 referenced documentation clearly explains these tasks and is not
2442 a general reference manual.
2446 <file>debian/README.source</file> may also include any other
2447 information that would be helpful to someone modifying the
2448 source package. Even if the package doesn't fit the above
2449 description, maintainers are encouraged to document in a
2450 <file>debian/README.source</file> file any source package with a
2451 particularly complex or unintuitive source layout or build
2452 system (for example, a package that builds the same source
2453 multiple times to generate different binary packages).
2459 <chapt id="controlfields">
2460 <heading>Control files and their fields</heading>
2463 The package management system manipulates data represented in
2464 a common format, known as <em>control data</em>, stored in
2465 <em>control files</em>.
2466 Control files are used for source packages, binary packages and
2467 the <file>.changes</file> files which control the installation
2468 of uploaded files<footnote>
2469 <prgn>dpkg</prgn>'s internal databases are in a similar
2474 <sect id="controlsyntax">
2475 <heading>Syntax of control files</heading>
2478 A control file consists of one or more paragraphs of
2480 The paragraphs are also sometimes referred to as stanzas.
2482 The paragraphs are separated by blank lines. Some control
2483 files allow only one paragraph; others allow several, in
2484 which case each paragraph usually refers to a different
2485 package. (For example, in source packages, the first
2486 paragraph refers to the source package, and later paragraphs
2487 refer to binary packages generated from the source.)
2491 Each paragraph consists of a series of data fields; each
2492 field consists of the field name, followed by a colon and
2493 then the data/value associated with that field. It ends at
2494 the end of the (logical) line. Horizontal whitespace
2495 (spaces and tabs) may occur immediately before or after the
2496 value and is ignored there; it is conventional to put a
2497 single space after the colon. For example, a field might
2499 <example compact="compact">
2502 the field name is <tt>Package</tt> and the field value
2507 A paragraph must not contain more than one instance of a
2508 particular field name.
2512 Many fields' values may span several lines; in this case
2513 each continuation line must start with a space or a tab.
2514 Any trailing spaces or tabs at the end of individual
2515 lines of a field value are ignored.
2519 In fields where it is specified that lines may not wrap,
2520 only a single line of data is allowed and whitespace is not
2521 significant in a field body. Whitespace must not appear
2522 inside names (of packages, architectures, files or anything
2523 else) or version numbers, or between the characters of
2524 multi-character version relationships.
2528 Field names are not case-sensitive, but it is usual to
2529 capitalize the field names using mixed case as shown below.
2530 Field values are case-sensitive unless the description of the
2531 field says otherwise.
2535 Blank lines, or lines consisting only of spaces and tabs,
2536 are not allowed within field values or between fields - that
2537 would mean a new paragraph.
2541 All control files must be encoded in UTF-8.
2545 <sect id="sourcecontrolfiles">
2546 <heading>Source package control files -- <file>debian/control</file></heading>
2549 The <file>debian/control</file> file contains the most vital
2550 (and version-independent) information about the source package
2551 and about the binary packages it creates.
2555 The first paragraph of the control file contains information about
2556 the source package in general. The subsequent sets each describe a
2557 binary package that the source tree builds.
2561 The fields in the general paragraph (the first one, for the source
2564 <list compact="compact">
2565 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2566 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2567 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2568 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2569 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2570 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2571 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2572 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2573 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2578 The fields in the binary package paragraphs are:
2580 <list compact="compact">
2581 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2582 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2583 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2584 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2585 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2586 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2587 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2588 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2593 The syntax and semantics of the fields are described below.
2597 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2598 generate control files for binary packages (see below), by
2599 <prgn>dpkg-genchanges</prgn> to generate the
2600 <file>.changes</file> file to accompany the upload, and by
2601 <prgn>dpkg-source</prgn> when it creates the
2602 <file>.dsc</file> source control file as part of a source
2603 archive. Many fields are permitted to span multiple lines in
2604 <file>debian/control</file> but not in any other control
2605 file. These tools are responsible for removing the line
2606 breaks from such fields when using fields from
2607 <file>debian/control</file> to generate other control files.
2611 The fields here may contain variable references - their
2612 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2613 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2614 when they generate output control files.
2615 See <ref id="substvars"> for details.
2619 In addition to the control file syntax described <qref
2620 id="controlsyntax">above</qref>, this file may also contain
2621 comment lines starting with <tt>#</tt> without any preceding
2622 whitespace. All such lines are ignored, even in the middle of
2623 continuation lines for a multiline field, and do not end a
2629 <sect id="binarycontrolfiles">
2630 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2633 The <file>DEBIAN/control</file> file contains the most vital
2634 (and version-dependent) information about a binary package. It
2635 consists of a single paragraph.
2639 The fields in this file are:
2641 <list compact="compact">
2642 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2644 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2646 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2649 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2650 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2658 <sect id="debiansourcecontrolfiles">
2659 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2662 This file consists of a single paragraph, possibly surrounded by
2663 a PGP signature. The fields of that paragraph are listed below.
2664 Their syntax is described above, in <ref id="pkg-controlfields">.
2666 <list compact="compact">
2667 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2668 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2669 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2670 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2671 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2672 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2673 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2674 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2675 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2676 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2677 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2678 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2679 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2680 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2685 The source package control file is generated by
2686 <prgn>dpkg-source</prgn> when it builds the source
2687 archive, from other files in the source package,
2688 described above. When unpacking, it is checked against
2689 the files and directories in the other parts of the
2695 <sect id="debianchangesfiles">
2696 <heading>Debian changes files -- <file>.changes</file></heading>
2699 The <file>.changes</file> files are used by the Debian archive
2700 maintenance software to process updates to packages. They
2701 consist of a single paragraph, possibly surrounded by a PGP
2702 signature. That paragraph contains information from the
2703 <file>debian/control</file> file and other data about the
2704 source package gathered via <file>debian/changelog</file>
2705 and <file>debian/rules</file>.
2709 <file>.changes</file> files have a format version that is
2710 incremented whenever the documented fields or their meaning
2711 change. This document describes format &changesversion;.
2715 The fields in this file are:
2717 <list compact="compact">
2718 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2721 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2722 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2724 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2725 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2726 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2728 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2730 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2731 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2732 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2733 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2738 <sect id="controlfieldslist">
2739 <heading>List of fields</heading>
2741 <sect1 id="f-Source">
2742 <heading><tt>Source</tt></heading>
2745 This field identifies the source package name.
2749 In <file>debian/control</file> or a <file>.dsc</file> file,
2750 this field must contain only the name of the source package.
2754 In a binary package control file or a <file>.changes</file>
2755 file, the source package name may be followed by a version
2756 number in parentheses<footnote>
2757 It is customary to leave a space after the package name
2758 if a version number is specified.
2760 This version number may be omitted (and is, by
2761 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2762 the <tt>Version</tt> field of the binary package in
2763 question. The field itself may be omitted from a binary
2764 package control file when the source package has the same
2765 name and version as the binary package.
2769 Package names (both source and binary,
2770 see <ref id="f-Package">) must consist only of lower case
2771 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2772 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2773 (<tt>.</tt>). They must be at least two characters long and
2774 must start with an alphanumeric character.
2778 <sect1 id="f-Maintainer">
2779 <heading><tt>Maintainer</tt></heading>
2782 The package maintainer's name and email address. The name
2783 must come first, then the email address inside angle
2784 brackets <tt><></tt> (in RFC822 format).
2788 If the maintainer's name contains a full stop then the
2789 whole field will not work directly as an email address due
2790 to a misfeature in the syntax specified in RFC822; a
2791 program using this field as an address must check for this
2792 and correct the problem if necessary (for example by
2793 putting the name in round brackets and moving it to the
2794 end, and bringing the email address forward).
2798 See <ref id="maintainer"> for additional requirements and
2799 information about package maintainers.
2803 <sect1 id="f-Uploaders">
2804 <heading><tt>Uploaders</tt></heading>
2807 List of the names and email addresses of co-maintainers of the
2808 package, if any. If the package has other maintainers besides
2809 the one named in the <qref id="f-Maintainer">Maintainer
2810 field</qref>, their names and email addresses should be listed
2811 here. The format of each entry is the same as that of the
2812 Maintainer field, and multiple entries must be comma
2817 This is normally an optional field, but if
2818 the <tt>Maintainer</tt> control field names a group of people
2819 and a shared email address, the <tt>Uploaders</tt> field must
2820 be present and must contain at least one human with their
2821 personal email address.
2825 Any parser that interprets the Uploaders field in
2826 <file>debian/control</file> must permit it to span multiple
2827 lines. Line breaks in an Uploaders field that spans multiple
2828 lines are not significant and the semantics of the field are
2829 the same as if the line breaks had not been present.
2833 <sect1 id="f-Changed-By">
2834 <heading><tt>Changed-By</tt></heading>
2837 The name and email address of the person who prepared this
2838 version of the package, usually a maintainer. The syntax is
2839 the same as for the <qref id="f-Maintainer">Maintainer
2844 <sect1 id="f-Section">
2845 <heading><tt>Section</tt></heading>
2848 This field specifies an application area into which the package
2849 has been classified. See <ref id="subsections">.
2853 When it appears in the <file>debian/control</file> file,
2854 it gives the value for the subfield of the same name in
2855 the <tt>Files</tt> field of the <file>.changes</file> file.
2856 It also gives the default for the same field in the binary
2861 <sect1 id="f-Priority">
2862 <heading><tt>Priority</tt></heading>
2865 This field represents how important it is that the user
2866 have the package installed. See <ref id="priorities">.
2870 When it appears in the <file>debian/control</file> file,
2871 it gives the value for the subfield of the same name in
2872 the <tt>Files</tt> field of the <file>.changes</file> file.
2873 It also gives the default for the same field in the binary
2878 <sect1 id="f-Package">
2879 <heading><tt>Package</tt></heading>
2882 The name of the binary package.
2886 Binary package names must follow the same syntax and
2887 restrictions as source package names. See <ref id="f-Source">
2892 <sect1 id="f-Architecture">
2893 <heading><tt>Architecture</tt></heading>
2896 Depending on context and the control file used, the
2897 <tt>Architecture</tt> field can include the following sets of
2901 A unique single word identifying a Debian machine
2902 architecture as described in <ref id="arch-spec">.
2905 An architecture wildcard identifying a set of Debian
2906 machine architectures, see <ref id="arch-wildcard-spec">.
2907 <tt>any</tt> matches all Debian machine architectures
2908 and is the most frequently used.
2911 <tt>all</tt>, which indicates an
2912 architecture-independent package.
2915 <tt>source</tt>, which indicates a source package.
2921 In the main <file>debian/control</file> file in the source
2922 package, this field may contain the special
2923 value <tt>all</tt>, the special architecture
2924 wildcard <tt>any</tt>, or a list of specific and wildcard
2925 architectures separated by spaces. If <tt>all</tt>
2926 or <tt>any</tt> appears, that value must be the entire
2927 contents of the field. Most packages will use
2928 either <tt>all</tt> or <tt>any</tt>.
2932 Specifying a specific list of architectures indicates that the
2933 source will build an architecture-dependent package only on
2934 architectures included in the list. Specifying a list of
2935 architecture wildcards indicates that the source will build an
2936 architecture-dependent package on only those architectures
2937 that match any of the specified architecture wildcards.
2938 Specifying a list of architectures or architecture wildcards
2939 other than <tt>any</tt> is for the minority of cases where a
2940 program is not portable or is not useful on some
2941 architectures. Where possible, the program should be made
2946 In the source package control file <file>.dsc</file>, this
2947 field may contain either the architecture
2948 wildcard <tt>any</tt> or a list of architectures and
2949 architecture wildcards separated by spaces. If a list is
2950 given, it may include (or consist solely of) the special
2951 value <tt>all</tt>. In other words, in <file>.dsc</file>
2952 files unlike the <file>debian/control</file>, <tt>all</tt> may
2953 occur in combination with specific architectures.
2954 The <tt>Architecture</tt> field in the source package control
2955 file <file>.dsc</file> is generally constructed from
2956 the <tt>Architecture</tt> fields in
2957 the <file>debian/control</file> in the source package.
2961 Specifying <tt>any</tt> indicates that the source package
2962 isn't dependent on any particular architecture and should
2963 compile fine on any one. The produced binary package(s)
2964 will either be specific to whatever the current build
2965 architecture is or will be architecture-independent.
2969 Specifying only <tt>all</tt> indicates that the source package
2970 will only build architecture-independent packages. If this is
2971 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2972 <tt>any</tt> implies that the source package will build at
2973 least one architecture-dependent package.
2977 Specifying a list of architectures or architecture wildcards
2978 indicates that the source will build an architecture-dependent
2979 package, and will only work correctly on the listed or
2980 matching architectures. If the source package also builds at
2981 least one architecture-independent package, <tt>all</tt> will
2982 also be included in the list.
2986 In a <file>.changes</file> file, the <tt>Architecture</tt>
2987 field lists the architecture(s) of the package(s) currently
2988 being uploaded. This will be a list; if the source for the
2989 package is also being uploaded, the special
2990 entry <tt>source</tt> is also present. <tt>all</tt> will be
2991 present if any architecture-independent packages are being
2992 uploaded. Architecture wildcards such as <tt>any</tt> must
2993 never occur in the <tt>Architecture</tt> field in
2994 the <file>.changes</file> file.
2998 See <ref id="debianrules"> for information on how to get
2999 the architecture for the build process.
3003 <sect1 id="f-Essential">
3004 <heading><tt>Essential</tt></heading>
3007 This is a boolean field which may occur only in the
3008 control file of a binary package or in a per-package fields
3009 paragraph of a main source control data file.
3013 If set to <tt>yes</tt> then the package management system
3014 will refuse to remove the package (upgrading and replacing
3015 it is still possible). The other possible value is <tt>no</tt>,
3016 which is the same as not having the field at all.
3021 <heading>Package interrelationship fields:
3022 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3023 <tt>Recommends</tt>, <tt>Suggests</tt>,
3024 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3025 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3029 These fields describe the package's relationships with
3030 other packages. Their syntax and semantics are described
3031 in <ref id="relationships">.</p>
3034 <sect1 id="f-Standards-Version">
3035 <heading><tt>Standards-Version</tt></heading>
3038 The most recent version of the standards (the policy
3039 manual and associated texts) with which the package
3044 The version number has four components: major and minor
3045 version number and major and minor patch level. When the
3046 standards change in a way that requires every package to
3047 change the major number will be changed. Significant
3048 changes that will require work in many packages will be
3049 signaled by a change to the minor number. The major patch
3050 level will be changed for any change to the meaning of the
3051 standards, however small; the minor patch level will be
3052 changed when only cosmetic, typographical or other edits
3053 are made which neither change the meaning of the document
3054 nor affect the contents of packages.
3058 Thus only the first three components of the policy version
3059 are significant in the <em>Standards-Version</em> control
3060 field, and so either these three components or all four
3061 components may be specified.<footnote>
3062 In the past, people specified the full version number
3063 in the Standards-Version field, for example "2.3.0.0".
3064 Since minor patch-level changes don't introduce new
3065 policy, it was thought it would be better to relax
3066 policy and only require the first 3 components to be
3067 specified, in this example "2.3.0". All four
3068 components may still be used if someone wishes to do so.
3074 <sect1 id="f-Version">
3075 <heading><tt>Version</tt></heading>
3078 The version number of a package. The format is:
3079 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3083 The three components here are:
3085 <tag><var>epoch</var></tag>
3088 This is a single (generally small) unsigned integer. It
3089 may be omitted, in which case zero is assumed. If it is
3090 omitted then the <var>upstream_version</var> may not
3095 It is provided to allow mistakes in the version numbers
3096 of older versions of a package, and also a package's
3097 previous version numbering schemes, to be left behind.
3101 <tag><var>upstream_version</var></tag>
3104 This is the main part of the version number. It is
3105 usually the version number of the original ("upstream")
3106 package from which the <file>.deb</file> file has been made,
3107 if this is applicable. Usually this will be in the same
3108 format as that specified by the upstream author(s);
3109 however, it may need to be reformatted to fit into the
3110 package management system's format and comparison
3115 The comparison behavior of the package management system
3116 with respect to the <var>upstream_version</var> is
3117 described below. The <var>upstream_version</var>
3118 portion of the version number is mandatory.
3122 The <var>upstream_version</var> may contain only
3123 alphanumerics<footnote>
3124 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3126 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3127 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3128 tilde) and should start with a digit. If there is no
3129 <var>debian_revision</var> then hyphens are not allowed;
3130 if there is no <var>epoch</var> then colons are not
3135 <tag><var>debian_revision</var></tag>
3138 This part of the version number specifies the version of
3139 the Debian package based on the upstream version. It
3140 may contain only alphanumerics and the characters
3141 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3142 tilde) and is compared in the same way as the
3143 <var>upstream_version</var> is.
3147 It is optional; if it isn't present then the
3148 <var>upstream_version</var> may not contain a hyphen.
3149 This format represents the case where a piece of
3150 software was written specifically to be a Debian
3151 package, where the Debian package source must always
3152 be identical to the pristine source and therefore no
3153 revision indication is required.
3157 It is conventional to restart the
3158 <var>debian_revision</var> at <tt>1</tt> each time the
3159 <var>upstream_version</var> is increased.
3163 The package management system will break the version
3164 number apart at the last hyphen in the string (if there
3165 is one) to determine the <var>upstream_version</var> and
3166 <var>debian_revision</var>. The absence of a
3167 <var>debian_revision</var> is equivalent to a
3168 <var>debian_revision</var> of <tt>0</tt>.
3175 When comparing two version numbers, first the <var>epoch</var>
3176 of each are compared, then the <var>upstream_version</var> if
3177 <var>epoch</var> is equal, and then <var>debian_revision</var>
3178 if <var>upstream_version</var> is also equal.
3179 <var>epoch</var> is compared numerically. The
3180 <var>upstream_version</var> and <var>debian_revision</var>
3181 parts are compared by the package management system using the
3182 following algorithm:
3186 The strings are compared from left to right.
3190 First the initial part of each string consisting entirely of
3191 non-digit characters is determined. These two parts (one of
3192 which may be empty) are compared lexically. If a difference
3193 is found it is returned. The lexical comparison is a
3194 comparison of ASCII values modified so that all the letters
3195 sort earlier than all the non-letters and so that a tilde
3196 sorts before anything, even the end of a part. For example,
3197 the following parts are in sorted order from earliest to
3198 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3199 <tt>a</tt>.<footnote>
3200 One common use of <tt>~</tt> is for upstream pre-releases.
3201 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3202 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3207 Then the initial part of the remainder of each string which
3208 consists entirely of digit characters is determined. The
3209 numerical values of these two parts are compared, and any
3210 difference found is returned as the result of the comparison.
3211 For these purposes an empty string (which can only occur at
3212 the end of one or both version strings being compared) counts
3217 These two steps (comparing and removing initial non-digit
3218 strings and initial digit strings) are repeated until a
3219 difference is found or both strings are exhausted.
3223 Note that the purpose of epochs is to allow us to leave behind
3224 mistakes in version numbering, and to cope with situations
3225 where the version numbering scheme changes. It is
3226 <em>not</em> intended to cope with version numbers containing
3227 strings of letters which the package management system cannot
3228 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3229 silly orderings.<footnote>
3230 The author of this manual has heard of a package whose
3231 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3232 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3238 <sect1 id="f-Description">
3239 <heading><tt>Description</tt></heading>
3242 In a source or binary control file, the <tt>Description</tt>
3243 field contains a description of the binary package, consisting
3244 of two parts, the synopsis or the short description, and the
3245 long description. The field's format is as follows:
3250 Description: <single line synopsis>
3251 <extended description over several lines>
3256 The lines in the extended description can have these formats:
3262 Those starting with a single space are part of a paragraph.
3263 Successive lines of this form will be word-wrapped when
3264 displayed. The leading space will usually be stripped off.
3268 Those starting with two or more spaces. These will be
3269 displayed verbatim. If the display cannot be panned
3270 horizontally, the displaying program will line wrap them "hard"
3271 (i.e., without taking account of word breaks). If it can they
3272 will be allowed to trail off to the right. None, one or two
3273 initial spaces may be deleted, but the number of spaces
3274 deleted from each line will be the same (so that you can have
3275 indenting work correctly, for example).
3279 Those containing a single space followed by a single full stop
3280 character. These are rendered as blank lines. This is the
3281 <em>only</em> way to get a blank line<footnote>
3282 Completely empty lines will not be rendered as blank lines.
3283 Instead, they will cause the parser to think you're starting
3284 a whole new record in the control file, and will therefore
3285 likely abort with an error.
3290 Those containing a space, a full stop and some more characters.
3291 These are for future expansion. Do not use them.
3297 Do not use tab characters. Their effect is not predictable.
3301 See <ref id="descriptions"> for further information on this.
3305 In a <file>.changes</file> file, the <tt>Description</tt>
3306 field contains a summary of the descriptions for the packages
3307 being uploaded. For this case, the first line of the field
3308 value (the part on the same line as <tt>Description:</tt>) is
3309 always empty. The content of the field is expressed as
3310 continuation lines, one line per package. Each line is
3311 indented by one space and contains the name of a binary
3312 package, a space, a hyphen (<tt>-</tt>), a space, and the
3313 short description line from that package.
3317 <sect1 id="f-Distribution">
3318 <heading><tt>Distribution</tt></heading>
3321 In a <file>.changes</file> file or parsed changelog output
3322 this contains the (space-separated) name(s) of the
3323 distribution(s) where this version of the package should
3324 be installed. Valid distributions are determined by the
3325 archive maintainers.<footnote>
3326 Example distribution names in the Debian archive used in
3327 <file>.changes</file> files are:
3328 <taglist compact="compact">
3329 <tag><em>unstable</em></tag>
3331 This distribution value refers to the
3332 <em>developmental</em> part of the Debian distribution
3333 tree. Most new packages, new upstream versions of
3334 packages and bug fixes go into the <em>unstable</em>
3338 <tag><em>experimental</em></tag>
3340 The packages with this distribution value are deemed
3341 by their maintainers to be high risk. Oftentimes they
3342 represent early beta or developmental packages from
3343 various sources that the maintainers want people to
3344 try, but are not ready to be a part of the other parts
3345 of the Debian distribution tree.
3350 Others are used for updating stable releases or for
3351 security uploads. More information is available in the
3352 Debian Developer's Reference, section "The Debian
3356 The Debian archive software only supports listing a single
3357 distribution. Migration of packages to other distributions is
3358 handled outside of the upload process.
3363 <heading><tt>Date</tt></heading>
3366 This field includes the date the package was built or last
3367 edited. It must be in the same format as the <var>date</var>
3368 in a <file>debian/changelog</file> entry.
3372 The value of this field is usually extracted from the
3373 <file>debian/changelog</file> file - see
3374 <ref id="dpkgchangelog">).
3378 <sect1 id="f-Format">
3379 <heading><tt>Format</tt></heading>
3382 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3383 files, this field declares the format version of that file.
3384 The syntax of the field value is the same as that of
3385 a <qref id="f-Version">package version number</qref> except
3386 that no epoch or Debian revision is allowed. The format
3387 described in this document is <tt>&changesversion;</tt>.
3391 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3392 Debian source control</qref> files, this field declares the
3393 format of the source package. The field value is used by
3394 programs acting on a source package to interpret the list of
3395 files in the source package and determine how to unpack it.
3396 The syntax of the field value is a numeric major revision, a
3397 period, a numeric minor revision, and then an optional subtype
3398 after whitespace, which if specified is an alphanumeric word
3399 in parentheses. The subtype is optional in the syntax but may
3400 be mandatory for particular source format revisions.
3402 The source formats currently supported by the Debian archive
3403 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3404 and <tt>3.0 (quilt)</tt>.
3409 <sect1 id="f-Urgency">
3410 <heading><tt>Urgency</tt></heading>
3413 This is a description of how important it is to upgrade to
3414 this version from previous ones. It consists of a single
3415 keyword taking one of the values <tt>low</tt>,
3416 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3417 <tt>critical</tt><footnote>
3418 Other urgency values are supported with configuration
3419 changes in the archive software but are not used in Debian.
3420 The urgency affects how quickly a package will be considered
3421 for inclusion into the <tt>testing</tt> distribution and
3422 gives an indication of the importance of any fixes included
3423 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3424 treated as synonymous.
3425 </footnote> (not case-sensitive) followed by an optional
3426 commentary (separated by a space) which is usually in
3427 parentheses. For example:
3430 Urgency: low (HIGH for users of diversions)
3436 The value of this field is usually extracted from the
3437 <file>debian/changelog</file> file - see
3438 <ref id="dpkgchangelog">.
3442 <sect1 id="f-Changes">
3443 <heading><tt>Changes</tt></heading>
3446 This field contains the human-readable changes data, describing
3447 the differences between the last version and the current one.
3451 The first line of the field value (the part on the same line
3452 as <tt>Changes:</tt>) is always empty. The content of the
3453 field is expressed as continuation lines, with each line
3454 indented by at least one space. Blank lines must be
3455 represented by a line consisting only of a space and a full
3460 The value of this field is usually extracted from the
3461 <file>debian/changelog</file> file - see
3462 <ref id="dpkgchangelog">).
3466 Each version's change information should be preceded by a
3467 "title" line giving at least the version, distribution(s)
3468 and urgency, in a human-readable way.
3472 If data from several versions is being returned the entry
3473 for the most recent version should be returned first, and
3474 entries should be separated by the representation of a
3475 blank line (the "title" line may also be followed by the
3476 representation of a blank line).
3480 <sect1 id="f-Binary">
3481 <heading><tt>Binary</tt></heading>
3484 This field is a list of binary packages. Its syntax and
3485 meaning varies depending on the control file in which it
3490 When it appears in the <file>.dsc</file> file, it lists binary
3491 packages which a source package can produce, separated by
3493 A space after each comma is conventional.
3494 </footnote>. It may span multiple lines. The source package
3495 does not necessarily produce all of these binary packages for
3496 every architecture. The source control file doesn't contain
3497 details of which architectures are appropriate for which of
3498 the binary packages.
3502 When it appears in a <file>.changes</file> file, it lists the
3503 names of the binary packages being uploaded, separated by
3504 whitespace (not commas). It may span multiple lines.
3508 <sect1 id="f-Installed-Size">
3509 <heading><tt>Installed-Size</tt></heading>
3512 This field appears in the control files of binary packages,
3513 and in the <file>Packages</file> files. It gives an estimate
3514 of the total amount of disk space required to install the
3515 named package. Actual installed size may vary based on block
3516 size, file system properties, or actions taken by package
3521 The disk space is given as the integer value of the estimated
3522 installed size in bytes, divided by 1024 and rounded up.
3526 <sect1 id="f-Files">
3527 <heading><tt>Files</tt></heading>
3530 This field contains a list of files with information about
3531 each one. The exact information and syntax varies with
3536 In all cases, Files is a multiline field. The first line of
3537 the field value (the part on the same line as <tt>Files:</tt>)
3538 is always empty. The content of the field is expressed as
3539 continuation lines, one line per file. Each line must be
3540 indented by one space and contain a number of sub-fields,
3541 separated by spaces, as described below.
3545 In the <file>.dsc</file> file, each line contains the MD5
3546 checksum, size and filename of the tar file and (if
3547 applicable) diff file which make up the remainder of the
3548 source package<footnote>
3549 That is, the parts which are not the <tt>.dsc</tt>.
3550 </footnote>. For example:
3553 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3554 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3556 The exact forms of the filenames are described
3557 in <ref id="pkg-sourcearchives">.
3561 In the <file>.changes</file> file this contains one line per
3562 file being uploaded. Each line contains the MD5 checksum,
3563 size, section and priority and the filename. For example:
3566 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3567 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3568 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3569 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3571 The <qref id="f-Section">section</qref>
3572 and <qref id="f-Priority">priority</qref> are the values of
3573 the corresponding fields in the main source control file. If
3574 no section or priority is specified then <tt>-</tt> should be
3575 used, though section and priority values must be specified for
3576 new packages to be installed properly.
3580 The special value <tt>byhand</tt> for the section in a
3581 <tt>.changes</tt> file indicates that the file in question
3582 is not an ordinary package file and must by installed by
3583 hand by the distribution maintainers. If the section is
3584 <tt>byhand</tt> the priority should be <tt>-</tt>.
3588 If a new Debian revision of a package is being shipped and
3589 no new original source archive is being distributed the
3590 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3591 entry for the original source archive
3592 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3593 but the <file>.changes</file> file should leave it out. In
3594 this case the original source archive on the distribution
3595 site must match exactly, byte-for-byte, the original
3596 source archive which was used to generate the
3597 <file>.dsc</file> file and diff which are being uploaded.</p>
3600 <sect1 id="f-Closes">
3601 <heading><tt>Closes</tt></heading>
3604 A space-separated list of bug report numbers that the upload
3605 governed by the .changes file closes.
3609 <sect1 id="f-Homepage">
3610 <heading><tt>Homepage</tt></heading>
3613 The URL of the web site for this package, preferably (when
3614 applicable) the site from which the original source can be
3615 obtained and any additional upstream documentation or
3616 information may be found. The content of this field is a
3617 simple URL without any surrounding characters such as
3622 <sect1 id="f-Checksums">
3623 <heading><tt>Checksums-Sha1</tt>
3624 and <tt>Checksums-Sha256</tt></heading>
3627 These fields contain a list of files with a checksum and size
3628 for each one. Both <tt>Checksums-Sha1</tt>
3629 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3630 only in the checksum algorithm used: SHA-1
3631 for <tt>Checksums-Sha1</tt> and SHA-256
3632 for <tt>Checksums-Sha256</tt>.
3636 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3637 multiline fields. The first line of the field value (the part
3638 on the same line as <tt>Checksums-Sha1:</tt>
3639 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3640 of the field is expressed as continuation lines, one line per
3641 file. Each line consists of the checksum, a space, the file
3642 size, a space, and the file name. For example (from
3643 a <file>.changes</file> file):
3646 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3647 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3648 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3649 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3651 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3652 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3653 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3654 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3659 In the <file>.dsc</file> file, these fields should list all
3660 files that make up the source package. In
3661 the <file>.changes</file> file, these fields should list all
3662 files being uploaded. The list of files in these fields
3663 must match the list of files in the <tt>Files</tt> field.
3667 <sect1 id="f-DM-Upload-Allowed">
3668 <heading><tt>DM-Upload-Allowed</tt></heading>
3671 The most recent version of a package uploaded to unstable or
3672 experimental must include the field <tt>DM-Upload-Allowed:
3673 yes</tt> in the source section of its source control file for
3674 the Debian archive to accept uploads signed with a key in the
3675 Debian Maintainer keyring. See the General
3676 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3677 name="Endorse the concept of Debian Maintainers"> for more
3684 <heading>User-defined fields</heading>
3687 Additional user-defined fields may be added to the
3688 source package control file. Such fields will be
3689 ignored, and not copied to (for example) binary or
3690 source package control files or upload control files.
3694 If you wish to add additional unsupported fields to
3695 these output files you should use the mechanism
3700 Fields in the main source control information file with
3701 names starting <tt>X</tt>, followed by one or more of
3702 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3703 be copied to the output files. Only the part of the
3704 field name after the hyphen will be used in the output
3705 file. Where the letter <tt>B</tt> is used the field
3706 will appear in binary package control files, where the
3707 letter <tt>S</tt> is used in source package control
3708 files and where <tt>C</tt> is used in upload control
3709 (<tt>.changes</tt>) files.
3713 For example, if the main source information control file
3716 XBS-Comment: I stand between the candle and the star.
3718 then the binary and source package control files will contain the
3721 Comment: I stand between the candle and the star.
3730 <chapt id="maintainerscripts">
3731 <heading>Package maintainer scripts and installation procedure</heading>
3734 <heading>Introduction to package maintainer scripts</heading>
3737 It is possible to supply scripts as part of a package which
3738 the package management system will run for you when your
3739 package is installed, upgraded or removed.
3743 These scripts are the control information
3744 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3745 and <prgn>postrm</prgn>. They must be proper executable files;
3746 if they are scripts (which is recommended), they must start with
3747 the usual <tt>#!</tt> convention. They should be readable and
3748 executable by anyone, and must not be world-writable.
3752 The package management system looks at the exit status from
3753 these scripts. It is important that they exit with a
3754 non-zero status if there is an error, so that the package
3755 management system can stop its processing. For shell
3756 scripts this means that you <em>almost always</em> need to
3757 use <tt>set -e</tt> (this is usually true when writing shell
3758 scripts, in fact). It is also important, of course, that
3759 they exit with a zero status if everything went well.
3763 Additionally, packages interacting with users
3764 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3765 should install a <prgn>config</prgn> script as a control
3766 information file. See <ref id="maintscriptprompt"> for details.
3770 When a package is upgraded a combination of the scripts from
3771 the old and new packages is called during the upgrade
3772 procedure. If your scripts are going to be at all
3773 complicated you need to be aware of this, and may need to
3774 check the arguments to your scripts.
3778 Broadly speaking the <prgn>preinst</prgn> is called before
3779 (a particular version of) a package is unpacked, and the
3780 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3781 before (a version of) a package is removed and the
3782 <prgn>postrm</prgn> afterwards.
3786 Programs called from maintainer scripts should not normally
3787 have a path prepended to them. Before installation is
3788 started, the package management system checks to see if the
3789 programs <prgn>ldconfig</prgn>,
3790 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3791 and <prgn>update-rc.d</prgn> can be found via the
3792 <tt>PATH</tt> environment variable. Those programs, and any
3793 other program that one would expect to be in the
3794 <tt>PATH</tt>, should thus be invoked without an absolute
3795 pathname. Maintainer scripts should also not reset the
3796 <tt>PATH</tt>, though they might choose to modify it by
3797 prepending or appending package-specific directories. These
3798 considerations really apply to all shell scripts.</p>
3801 <sect id="idempotency">
3802 <heading>Maintainer scripts idempotency</heading>
3805 It is necessary for the error recovery procedures that the
3806 scripts be idempotent. This means that if it is run
3807 successfully, and then it is called again, it doesn't bomb
3808 out or cause any harm, but just ensures that everything is
3809 the way it ought to be. If the first call failed, or
3810 aborted half way through for some reason, the second call
3811 should merely do the things that were left undone the first
3812 time, if any, and exit with a success status if everything
3814 This is so that if an error occurs, the user interrupts
3815 <prgn>dpkg</prgn> or some other unforeseen circumstance
3816 happens you don't leave the user with a badly-broken
3817 package when <prgn>dpkg</prgn> attempts to repeat the
3823 <sect id="controllingterminal">
3824 <heading>Controlling terminal for maintainer scripts</heading>
3827 Maintainer scripts are not guaranteed to run with a controlling
3828 terminal and may not be able to interact with the user. They
3829 must be able to fall back to noninteractive behavior if no
3830 controlling terminal is available. Maintainer scripts that
3831 prompt via a program conforming to the Debian Configuration
3832 Management Specification (see <ref id="maintscriptprompt">) may
3833 assume that program will handle falling back to noninteractive
3838 For high-priority prompts without a reasonable default answer,
3839 maintainer scripts may abort if there is no controlling
3840 terminal. However, this situation should be avoided if at all
3841 possible, since it prevents automated or unattended installs.
3842 In most cases, users will consider this to be a bug in the
3847 <sect id="exitstatus">
3848 <heading>Exit status</heading>
3851 Each script must return a zero exit status for
3852 success, or a nonzero one for failure, since the package
3853 management system looks for the exit status of these scripts
3854 and determines what action to take next based on that datum.
3858 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3863 What follows is a summary of all the ways in which maintainer
3864 scripts may be called along with what facilities those scripts
3865 may rely on being available at that time. Script names preceded
3866 by <var>new-</var> are the scripts from the new version of a
3867 package being installed, upgraded to, or downgraded to. Script
3868 names preceded by <var>old-</var> are the scripts from the old
3869 version of a package that is being upgraded from or downgraded
3874 The <prgn>preinst</prgn> script may be called in the following
3877 <tag><var>new-preinst</var> <tt>install</tt></tag>
3878 <tag><var>new-preinst</var> <tt>install</tt>
3879 <var>old-version</var></tag>
3880 <tag><var>new-preinst</var> <tt>upgrade</tt>
3881 <var>old-version</var></tag>
3883 The package will not yet be unpacked, so
3884 the <prgn>preinst</prgn> script cannot rely on any files
3885 included in its package. Only essential packages and
3886 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3887 available. Pre-dependencies will have been configured at
3888 least once, but at the time the <prgn>preinst</prgn> is
3889 called they may only be in an unpacked or "Half-Configured"
3890 state if a previous version of the pre-dependency was
3891 completely configured and has not been removed since then.
3894 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3895 <var>new-version</var></tag>
3897 Called during error handling of an upgrade that failed after
3898 unpacking the new package because the <tt>postrm
3899 upgrade</tt> action failed. The unpacked files may be
3900 partly from the new version or partly missing, so the script
3901 cannot rely on files included in the package. Package
3902 dependencies may not be available. Pre-dependencies will be
3903 at least unpacked following the same rules as above, except
3904 they may be only "Half-Installed" if an upgrade of the
3905 pre-dependency failed.<footnote>
3906 This can happen if the new version of the package no
3907 longer pre-depends on a package that had been partially
3915 The <prgn>postinst</prgn> script may be called in the following
3918 <tag><var>postinst</var> <tt>configure</tt>
3919 <var>most-recently-configured-version</var></tag>
3921 The files contained in the package will be unpacked. All
3922 package dependencies will at least be unpacked. If there
3923 are no circular dependencies involved, all package
3924 dependencies will be configured. For behavior in the case
3925 of circular dependencies, see the discussion
3926 in <ref id="binarydeps">.
3929 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3930 <var>new-version</var></tag>
3931 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3932 <tt>in-favour</tt> <var>package</var>
3933 <var>new-version</var></tag>
3934 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3935 <tag><var>deconfigured's-postinst</var>
3936 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3937 <var>failed-install-package</var> <var>version</var>
3938 [<tt>removing</tt> <var>conflicting-package</var>
3939 <var>version</var>]</tag>
3941 The files contained in the package will be unpacked. All
3942 package dependencies will at least be "Half-Installed" and
3943 will have previously been configured and not removed.
3944 However, dependencies may not be configured or even fully
3945 unpacked in some error situations.<footnote>
3946 For example, suppose packages foo and bar are installed
3947 with foo depending on bar. If an upgrade of bar were
3948 started and then aborted, and then an attempt to remove
3949 foo failed because its <prgn>prerm</prgn> script failed,
3950 foo's <tt>postinst abort-remove</tt> would be called with
3951 bar only "Half-Installed".
3953 The <prgn>postinst</prgn> should still attempt any actions
3954 for which its dependencies are required, since they will
3955 normally be available, but consider the correct error
3956 handling approach if those actions fail. Aborting
3957 the <prgn>postinst</prgn> action if commands or facilities
3958 from the package dependencies are not available is often the
3965 The <prgn>prerm</prgn> script may be called in the following
3968 <tag><var>prerm</var> <tt>remove</tt></tag>
3969 <tag><var>old-prerm</var>
3970 <tt>upgrade</tt><var>new-version</var></tag>
3971 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
3972 <tt>in-favour</tt> <var>package</var>
3973 <var>new-version</var></tag>
3974 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3975 <tt>in-favour</tt> <var>package-being-installed</var>
3976 <var>version</var> [<tt>removing</tt>
3977 <var>conflicting-package</var> <var>version</var>]</tag>
3979 The package whose <prgn>prerm</prgn> is being called will be
3980 at least "Half-Installed". All package dependencies will at
3981 least be "Half-Installed" and will have previously been
3982 configured and not removed. If there was no error, all
3983 dependencies will at least be unpacked, but these actions
3984 may be called in various error states where dependencies are
3985 only "Half-Installed" due to a partial upgrade.
3988 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
3989 <var>old-version</var></tag>
3991 Called during error handling when <tt>prerm upgrade</tt>
3992 fails. The new package will not yet be unpacked, and all
3993 the same constraints as for <tt>preinst upgrade</tt> apply.
3999 The <prgn>postrm</prgn> script may be called in the following
4002 <tag><var>postrm</var> <tt>remove</tt></tag>
4003 <tag><var>postrm</var> <tt>purge</tt></tag>
4004 <tag><var>old-postrm</var> <tt>upgrade</tt>
4005 <var>new-version</var></tag>
4006 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4007 <var>overwriter</var> <var>overwriter-version</var></tag>
4009 The <prgn>postrm</prgn> script is called after the package's
4010 files have been removed or replaced. The package
4011 whose <prgn>postrm</prgn> is being called may have
4012 previously been deconfigured and only be unpacked, at which
4013 point subsequent package changes do not consider its
4014 dependencies. Therefore, all <prgn>postrm</prgn> actions
4015 may only rely on essential packages and must gracefully skip
4016 any actions that require the package's dependencies if those
4017 dependencies are unavailable.<footnote>
4018 This is often done by checking whether the command or
4019 facility the <prgn>postrm</prgn> intends to call is
4020 available before calling it. For example:
4022 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4023 . /usr/share/debconf/confmodule
4027 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4028 configuration for the package
4029 if <package>debconf</package> is installed.
4033 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4034 <var>old-version</var></tag>
4036 Called when the old <tt>postrm upgrade</tt> action fails.
4037 The new package will be unpacked, but only essential
4038 packages and pre-dependencies can be relied on.
4039 Pre-dependencies will either be configured or will be
4040 "Unpacked" or "Half-Configured" but previously had been
4041 configured and was never removed.
4044 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4045 <tag><var>new-postrm</var> <tt>abort-install</tt>
4046 <var>old-version</var></tag>
4047 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4048 <var>old-version</var></tag>
4050 Called before unpacking the new package as part of the
4051 error handling of <prgn>preinst</prgn> failures. May assume
4052 the same state as <prgn>preinst</prgn> can assume.
4058 <sect id="unpackphase">
4059 <heading>Details of unpack phase of installation or upgrade</heading>
4062 The procedure on installation/upgrade/overwrite/disappear
4063 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4064 stage of <tt>dpkg --install</tt>) is as follows. In each
4065 case, if a major error occurs (unless listed below) the
4066 actions are, in general, run backwards - this means that the
4067 maintainer scripts are run with different arguments in
4068 reverse order. These are the "error unwind" calls listed
4075 If a version of the package is already installed, call
4076 <example compact="compact">
4077 <var>old-prerm</var> upgrade <var>new-version</var>
4081 If the script runs but exits with a non-zero
4082 exit status, <prgn>dpkg</prgn> will attempt:
4083 <example compact="compact">
4084 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4086 If this works, the upgrade continues. If this
4087 does not work, the error unwind:
4088 <example compact="compact">
4089 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4091 If this works, then the old-version is
4092 "Installed", if not, the old version is in a
4093 "Half-Configured" state.
4099 If a "conflicting" package is being removed at the same time,
4100 or if any package will be broken (due to <tt>Breaks</tt>):
4103 If <tt>--auto-deconfigure</tt> is
4104 specified, call, for each package to be deconfigured
4105 due to <tt>Breaks</tt>:
4106 <example compact="compact">
4107 <var>deconfigured's-prerm</var> deconfigure \
4108 in-favour <var>package-being-installed</var> <var>version</var>
4111 <example compact="compact">
4112 <var>deconfigured's-postinst</var> abort-deconfigure \
4113 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4115 The deconfigured packages are marked as
4116 requiring configuration, so that if
4117 <tt>--install</tt> is used they will be
4118 configured again if possible.
4121 If any packages depended on a conflicting
4122 package being removed and <tt>--auto-deconfigure</tt> is
4123 specified, call, for each such package:
4124 <example compact="compact">
4125 <var>deconfigured's-prerm</var> deconfigure \
4126 in-favour <var>package-being-installed</var> <var>version</var> \
4127 removing <var>conflicting-package</var> <var>version</var>
4130 <example compact="compact">
4131 <var>deconfigured's-postinst</var> abort-deconfigure \
4132 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4133 removing <var>conflicting-package</var> <var>version</var>
4135 The deconfigured packages are marked as
4136 requiring configuration, so that if
4137 <tt>--install</tt> is used they will be
4138 configured again if possible.
4141 To prepare for removal of each conflicting package, call:
4142 <example compact="compact">
4143 <var>conflictor's-prerm</var> remove \
4144 in-favour <var>package</var> <var>new-version</var>
4147 <example compact="compact">
4148 <var>conflictor's-postinst</var> abort-remove \
4149 in-favour <var>package</var> <var>new-version</var>
4158 If the package is being upgraded, call:
4159 <example compact="compact">
4160 <var>new-preinst</var> upgrade <var>old-version</var>
4162 If this fails, we call:
4164 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4171 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4173 is called. If this works, then the old version
4174 is in an "Installed" state, or else it is left
4175 in an "Unpacked" state.
4180 If it fails, then the old version is left
4181 in an "Half-Installed" state.
4188 Otherwise, if the package had some configuration
4189 files from a previous version installed (i.e., it
4190 is in the "configuration files only" state):
4191 <example compact="compact">
4192 <var>new-preinst</var> install <var>old-version</var>
4196 <var>new-postrm</var> abort-install <var>old-version</var>
4198 If this fails, the package is left in a
4199 "Half-Installed" state, which requires a
4200 reinstall. If it works, the packages is left in
4201 a "Config-Files" state.
4204 Otherwise (i.e., the package was completely purged):
4205 <example compact="compact">
4206 <var>new-preinst</var> install
4209 <example compact="compact">
4210 <var>new-postrm</var> abort-install
4212 If the error-unwind fails, the package is in a
4213 "Half-Installed" phase, and requires a
4214 reinstall. If the error unwind works, the
4215 package is in a not installed state.
4222 The new package's files are unpacked, overwriting any
4223 that may be on the system already, for example any
4224 from the old version of the same package or from
4225 another package. Backups of the old files are kept
4226 temporarily, and if anything goes wrong the package
4227 management system will attempt to put them back as
4228 part of the error unwind.
4232 It is an error for a package to contain files which
4233 are on the system in another package, unless
4234 <tt>Replaces</tt> is used (see <ref id="replaces">).
4236 The following paragraph is not currently the case:
4237 Currently the <tt>- - force-overwrite</tt> flag is
4238 enabled, downgrading it to a warning, but this may not
4244 It is a more serious error for a package to contain a
4245 plain file or other kind of non-directory where another
4246 package has a directory (again, unless
4247 <tt>Replaces</tt> is used). This error can be
4248 overridden if desired using
4249 <tt>--force-overwrite-dir</tt>, but this is not
4254 Packages which overwrite each other's files produce
4255 behavior which, though deterministic, is hard for the
4256 system administrator to understand. It can easily
4257 lead to "missing" programs if, for example, a package
4258 is unpacked which overwrites a file from another
4259 package, and is then removed again.<footnote>
4260 Part of the problem is due to what is arguably a
4261 bug in <prgn>dpkg</prgn>.
4266 A directory will never be replaced by a symbolic link
4267 to a directory or vice versa; instead, the existing
4268 state (symlink or not) will be left alone and
4269 <prgn>dpkg</prgn> will follow the symlink if there is
4278 If the package is being upgraded, call
4279 <example compact="compact">
4280 <var>old-postrm</var> upgrade <var>new-version</var>
4284 If this fails, <prgn>dpkg</prgn> will attempt:
4285 <example compact="compact">
4286 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4288 If this works, installation continues. If not,
4290 <example compact="compact">
4291 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4293 If this fails, the old version is left in a
4294 "Half-Installed" state. If it works, dpkg now
4296 <example compact="compact">
4297 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4299 If this fails, the old version is left in a
4300 "Half-Installed" state. If it works, dpkg now
4302 <example compact="compact">
4303 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4305 If this fails, the old version is in an
4312 This is the point of no return - if
4313 <prgn>dpkg</prgn> gets this far, it won't back off
4314 past this point if an error occurs. This will
4315 leave the package in a fairly bad state, which
4316 will require a successful re-installation to clear
4317 up, but it's when <prgn>dpkg</prgn> starts doing
4318 things that are irreversible.
4323 Any files which were in the old version of the package
4324 but not in the new are removed.
4328 The new file list replaces the old.
4332 The new maintainer scripts replace the old.
4336 Any packages all of whose files have been overwritten
4337 during the installation, and which aren't required for
4338 dependencies, are considered to have been removed.
4339 For each such package
4342 <prgn>dpkg</prgn> calls:
4343 <example compact="compact">
4344 <var>disappearer's-postrm</var> disappear \
4345 <var>overwriter</var> <var>overwriter-version</var>
4349 The package's maintainer scripts are removed.
4352 It is noted in the status database as being in a
4353 sane state, namely not installed (any conffiles
4354 it may have are ignored, rather than being
4355 removed by <prgn>dpkg</prgn>). Note that
4356 disappearing packages do not have their prerm
4357 called, because <prgn>dpkg</prgn> doesn't know
4358 in advance that the package is going to
4365 Any files in the package we're unpacking that are also
4366 listed in the file lists of other packages are removed
4367 from those lists. (This will lobotomize the file list
4368 of the "conflicting" package if there is one.)
4372 The backup files made during installation, above, are
4378 The new package's status is now sane, and recorded as
4383 Here is another point of no return - if the
4384 conflicting package's removal fails we do not unwind
4385 the rest of the installation; the conflicting package
4386 is left in a half-removed limbo.
4391 If there was a conflicting package we go and do the
4392 removal actions (described below), starting with the
4393 removal of the conflicting package's files (any that
4394 are also in the package being unpacked have already
4395 been removed from the conflicting package's file list,
4396 and so do not get removed now).
4402 <sect id="configdetails"><heading>Details of configuration</heading>
4405 When we configure a package (this happens with <tt>dpkg
4406 --install</tt> and <tt>dpkg --configure</tt>), we first
4407 update any <tt>conffile</tt>s and then call:
4408 <example compact="compact">
4409 <var>postinst</var> configure <var>most-recently-configured-version</var>
4414 No attempt is made to unwind after errors during
4415 configuration. If the configuration fails, the package is in
4416 a "Failed Config" state, and an error message is generated.
4420 If there is no most recently configured version
4421 <prgn>dpkg</prgn> will pass a null argument.
4424 Historical note: Truly ancient (pre-1997) versions of
4425 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4426 (including the angle brackets) in this case. Even older
4427 ones did not pass a second argument at all, under any
4428 circumstance. Note that upgrades using such an old dpkg
4429 version are unlikely to work for other reasons, even if
4430 this old argument behavior is handled by your postinst script.
4436 <sect id="removedetails"><heading>Details of removal and/or
4437 configuration purging</heading>
4443 <example compact="compact">
4444 <var>prerm</var> remove
4448 If prerm fails during replacement due to conflict
4450 <var>conflictor's-postinst</var> abort-remove \
4451 in-favour <var>package</var> <var>new-version</var>
4455 <var>postinst</var> abort-remove
4459 If this fails, the package is in a "Half-Configured"
4460 state, or else it remains "Installed".
4464 The package's files are removed (except <tt>conffile</tt>s).
4467 <example compact="compact">
4468 <var>postrm</var> remove
4472 If it fails, there's no error unwind, and the package is in
4473 an "Half-Installed" state.
4478 All the maintainer scripts except the <prgn>postrm</prgn>
4483 If we aren't purging the package we stop here. Note
4484 that packages which have no <prgn>postrm</prgn> and no
4485 <tt>conffile</tt>s are automatically purged when
4486 removed, as there is no difference except for the
4487 <prgn>dpkg</prgn> status.
4491 The <tt>conffile</tt>s and any backup files
4492 (<tt>~</tt>-files, <tt>#*#</tt> files,
4493 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4498 <example compact="compact">
4499 <var>postrm</var> purge
4503 If this fails, the package remains in a "Config-Files"
4508 The package's file list is removed.
4517 <chapt id="relationships">
4518 <heading>Declaring relationships between packages</heading>
4520 <sect id="depsyntax">
4521 <heading>Syntax of relationship fields</heading>
4524 These fields all have a uniform syntax. They are a list of
4525 package names separated by commas.
4529 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4530 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4531 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4532 control fields of the package, which declare
4533 dependencies on other packages, the package names listed may
4534 also include lists of alternative package names, separated
4535 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4536 if any one of the alternative packages is installed, that
4537 part of the dependency is considered to be satisfied.
4541 All of the fields except for <tt>Provides</tt> may restrict
4542 their applicability to particular versions of each named
4543 package. This is done in parentheses after each individual
4544 package name; the parentheses should contain a relation from
4545 the list below followed by a version number, in the format
4546 described in <ref id="f-Version">.
4550 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4551 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4552 strictly earlier, earlier or equal, exactly equal, later or
4553 equal and strictly later, respectively. The deprecated
4554 forms <tt><</tt> and <tt>></tt> were used to mean
4555 earlier/later or equal, rather than strictly earlier/later,
4556 so they should not appear in new packages (though
4557 <prgn>dpkg</prgn> still supports them).
4561 Whitespace may appear at any point in the version
4562 specification subject to the rules in <ref
4563 id="controlsyntax">, and must appear where it's necessary to
4564 disambiguate; it is not otherwise significant. All of the
4565 relationship fields may span multiple lines. For
4566 consistency and in case of future changes to
4567 <prgn>dpkg</prgn> it is recommended that a single space be
4568 used after a version relationship and before a version
4569 number; it is also conventional to put a single space after
4570 each comma, on either side of each vertical bar, and before
4571 each open parenthesis. When wrapping a relationship field, it
4572 is conventional to do so after a comma and before the space
4573 following that comma.
4577 For example, a list of dependencies might appear as:
4578 <example compact="compact">
4581 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4586 Relationships may be restricted to a certain set of
4587 architectures. This is indicated in brackets after each
4588 individual package name and the optional version specification.
4589 The brackets enclose a list of Debian architecture names
4590 separated by whitespace. Exclamation marks may be prepended to
4591 each of the names. (It is not permitted for some names to be
4592 prepended with exclamation marks while others aren't.)
4596 For build relationship fields
4597 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4598 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4599 the current Debian host architecture is not in this list and
4600 there are no exclamation marks in the list, or it is in the list
4601 with a prepended exclamation mark, the package name and the
4602 associated version specification are ignored completely for the
4603 purposes of defining the relationships.
4608 <example compact="compact">
4610 Build-Depends-Indep: texinfo
4611 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4612 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4614 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4615 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4616 <tt>gnumach-dev</tt> only on hurd-i386.
4620 For binary relationship fields, the architecture restriction
4621 syntax is only supported in the source package control
4622 file <file>debian/control</file>. When the corresponding binary
4623 package control file is generated, the relationship will either
4624 be omitted or included without the architecture restriction
4625 based on the architecture of the binary package. This means
4626 that architecture restrictions must not be used in binary
4627 relationship fields for architecture-independent packages
4628 (<tt>Architecture: all</tt>).
4633 <example compact="compact">
4634 Depends: foo [i386], bar [amd64]
4636 becomes <tt>Depends: foo</tt> when the package is built on
4637 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4638 package is built on the <tt>amd64</tt> architecture, and omitted
4639 entirely in binary packages built on all other architectures.
4643 If the architecture-restricted dependency is part of a set of
4644 alternatives using <tt>|</tt>, that alternative is ignored
4645 completely on architectures that do not match the restriction.
4647 <example compact="compact">
4648 Build-Depends: foo [!i386] | bar [!amd64]
4650 is equivalent to <tt>bar</tt> on the i386 architecture, to
4651 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4652 bar</tt> on all other architectures.
4656 Relationships may also be restricted to a certain set of
4657 architectures using architecture wildcards. The syntax for
4658 declaring such restrictions is the same as declaring
4659 restrictions using a certain set of architectures without
4660 architecture wildcards. For example:
4661 <example compact="compact">
4662 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4664 is equivalent to <tt>foo</tt> on architectures using the Linux
4665 kernel and any cpu, <tt>bar</tt> on architectures using any
4666 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4667 using a kernel other than Linux.
4671 Note that the binary package relationship fields such as
4672 <tt>Depends</tt> appear in one of the binary package
4673 sections of the control file, whereas the build-time
4674 relationships such as <tt>Build-Depends</tt> appear in the
4675 source package section of the control file (which is the
4680 <sect id="binarydeps">
4681 <heading>Binary Dependencies - <tt>Depends</tt>,
4682 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4683 <tt>Pre-Depends</tt>
4687 Packages can declare in their control file that they have
4688 certain relationships to other packages - for example, that
4689 they may not be installed at the same time as certain other
4690 packages, and/or that they depend on the presence of others.
4694 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4695 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4696 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4697 <tt>Breaks</tt> is described in <ref id="breaks">, and
4698 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4699 rest are described below.
4703 These seven fields are used to declare a dependency
4704 relationship by one package on another. Except for
4705 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4706 depending (binary) package's control file.
4707 (<tt>Enhances</tt> appears in the recommending package's
4708 control file, and <tt>Breaks</tt> appears in the version of
4709 depended-on package which causes the named package to
4714 A <tt>Depends</tt> field takes effect <em>only</em> when a
4715 package is to be configured. It does not prevent a package
4716 being on the system in an unconfigured state while its
4717 dependencies are unsatisfied, and it is possible to replace
4718 a package whose dependencies are satisfied and which is
4719 properly installed with a different version whose
4720 dependencies are not and cannot be satisfied; when this is
4721 done the depending package will be left unconfigured (since
4722 attempts to configure it will give errors) and will not
4723 function properly. If it is necessary, a
4724 <tt>Pre-Depends</tt> field can be used, which has a partial
4725 effect even when a package is being unpacked, as explained
4726 in detail below. (The other three dependency fields,
4727 <tt>Recommends</tt>, <tt>Suggests</tt> and
4728 <tt>Enhances</tt>, are only used by the various front-ends
4729 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4730 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4734 Since <tt>Depends</tt> only places requirements on the order in
4735 which packages are configured, packages in an installation run
4736 are usually all unpacked first and all configured later.
4738 This approach makes dependency resolution easier. If two
4739 packages A and B are being upgraded, the installed package A
4740 depends on exactly the installed package B, and the new
4741 package A depends on exactly the new package B (a common
4742 situation when upgrading shared libraries and their
4743 corresponding development packages), satisfying the
4744 dependencies at every stage of the upgrade would be
4745 impossible. This relaxed restriction means that both new
4746 packages can be unpacked together and then configured in their
4752 If there is a circular dependency among packages being installed
4753 or removed, installation or removal order honoring the
4754 dependency order is impossible, requiring the dependency loop be
4755 broken at some point and the dependency requirements violated
4756 for at least one package. Packages involved in circular
4757 dependencies may not be able to rely on their dependencies being
4758 configured before they themselves are configured, depending on
4759 which side of the break of the circular dependency loop they
4760 happen to be on. If one of the packages in the loop has
4761 no <prgn>postinst</prgn> script, then the cycle will be broken
4762 at that package; this ensures that all <prgn>postinst</prgn>
4763 scripts are run with their dependencies properly configured if
4764 this is possible. Otherwise the breaking point is arbitrary.
4765 Packages should therefore avoid circular dependencies where
4766 possible, particularly if they have <prgn>postinst</prgn>
4771 The meaning of the five dependency fields is as follows:
4773 <tag><tt>Depends</tt></tag>
4776 This declares an absolute dependency. A package will
4777 not be configured unless all of the packages listed in
4778 its <tt>Depends</tt> field have been correctly
4779 configured (unless there is a circular dependency as
4784 The <tt>Depends</tt> field should be used if the
4785 depended-on package is required for the depending
4786 package to provide a significant amount of
4791 The <tt>Depends</tt> field should also be used if the
4792 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4793 require the depended-on package to be unpacked or
4794 configured in order to run. In the case of <tt>postinst
4795 configure</tt>, the depended-on packages will be unpacked
4796 and configured first. (If both packages are involved in a
4797 dependency loop, this might not work as expected; see the
4798 explanation a few paragraphs back.) In the case
4799 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4800 actions, the package dependencies will normally be at
4801 least unpacked, but they may be only "Half-Installed" if a
4802 previous upgrade of the dependency failed.
4806 Finally, the <tt>Depends</tt> field should be used if the
4807 depended-on package is needed by the <prgn>postrm</prgn>
4808 script to fully clean up after the package removal. There
4809 is no guarantee that package dependencies will be
4810 available when <prgn>postrm</prgn> is run, but the
4811 depended-on package is more likely to be available if the
4812 package declares a dependency (particularly in the case
4813 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4814 script must gracefully skip actions that require a
4815 dependency if that dependency isn't available.
4819 <tag><tt>Recommends</tt></tag>
4822 This declares a strong, but not absolute, dependency.
4826 The <tt>Recommends</tt> field should list packages
4827 that would be found together with this one in all but
4828 unusual installations.
4832 <tag><tt>Suggests</tt></tag>
4834 This is used to declare that one package may be more
4835 useful with one or more others. Using this field
4836 tells the packaging system and the user that the
4837 listed packages are related to this one and can
4838 perhaps enhance its usefulness, but that installing
4839 this one without them is perfectly reasonable.
4842 <tag><tt>Enhances</tt></tag>
4844 This field is similar to Suggests but works in the
4845 opposite direction. It is used to declare that a
4846 package can enhance the functionality of another
4850 <tag><tt>Pre-Depends</tt></tag>
4853 This field is like <tt>Depends</tt>, except that it
4854 also forces <prgn>dpkg</prgn> to complete installation
4855 of the packages named before even starting the
4856 installation of the package which declares the
4857 pre-dependency, as follows:
4861 When a package declaring a pre-dependency is about to
4862 be <em>unpacked</em> the pre-dependency can be
4863 satisfied if the depended-on package is either fully
4864 configured, <em>or even if</em> the depended-on
4865 package(s) are only unpacked or in the "Half-Configured"
4866 state, provided that they have been configured
4867 correctly at some point in the past (and not removed
4868 or partially removed since). In this case, both the
4869 previously-configured and currently unpacked or
4870 "Half-Configured" versions must satisfy any version
4871 clause in the <tt>Pre-Depends</tt> field.
4875 When the package declaring a pre-dependency is about to
4876 be <em>configured</em>, the pre-dependency will be treated
4877 as a normal <tt>Depends</tt>. It will be considered
4878 satisfied only if the depended-on package has been
4879 correctly configured. However, unlike
4880 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4881 permit circular dependencies to be broken. If a circular
4882 dependency is encountered while attempting to honor
4883 <tt>Pre-Depends</tt>, the installation will be aborted.
4887 <tt>Pre-Depends</tt> are also required if the
4888 <prgn>preinst</prgn> script depends on the named package.
4889 It is best to avoid this situation if possible.
4893 <tt>Pre-Depends</tt> should be used sparingly,
4894 preferably only by packages whose premature upgrade or
4895 installation would hamper the ability of the system to
4896 continue with any upgrade that might be in progress.
4900 You should not specify a <tt>Pre-Depends</tt> entry for a
4901 package before this has been discussed on the
4902 <tt>debian-devel</tt> mailing list and a consensus about
4903 doing that has been reached. See <ref id="dependencies">.
4910 When selecting which level of dependency to use you should
4911 consider how important the depended-on package is to the
4912 functionality of the one declaring the dependency. Some
4913 packages are composed of components of varying degrees of
4914 importance. Such a package should list using
4915 <tt>Depends</tt> the package(s) which are required by the
4916 more important components. The other components'
4917 requirements may be mentioned as Suggestions or
4918 Recommendations, as appropriate to the components' relative
4924 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4927 When one binary package declares that it breaks another,
4928 <prgn>dpkg</prgn> will refuse to allow the package which
4929 declares <tt>Breaks</tt> to be unpacked unless the broken
4930 package is deconfigured first, and it will refuse to
4931 allow the broken package to be reconfigured.
4935 A package will not be regarded as causing breakage merely
4936 because its configuration files are still installed; it must
4937 be at least "Half-Installed".
4941 A special exception is made for packages which declare that
4942 they break their own package name or a virtual package which
4943 they provide (see below): this does not count as a real
4948 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4949 version clause; such a <tt>Breaks</tt> is introduced in the
4950 version of an (implicit or explicit) dependency which violates
4951 an assumption or reveals a bug in earlier versions of the broken
4952 package, or which takes over a file from earlier versions of the
4953 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4954 will inform higher-level package management tools that the
4955 broken package must be upgraded before the new one.
4959 If the breaking package also overwrites some files from the
4960 older package, it should use <tt>Replaces</tt> to ensure this
4961 goes smoothly. See <ref id="replaces"> for a full discussion
4962 of taking over files from other packages, including how to
4963 use <tt>Breaks</tt> in those cases.
4967 Many of the cases where <tt>Breaks</tt> should be used were
4968 previously handled with <tt>Conflicts</tt>
4969 because <tt>Breaks</tt> did not yet exist.
4970 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4971 See <ref id="conflicts"> for more information about the
4976 <sect id="conflicts">
4977 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4980 When one binary package declares a conflict with another using
4981 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
4982 allow them to be unpacked on the system at the same time. This
4983 is a stronger restriction than <tt>Breaks</tt>, which prevents
4984 the broken package from being configured while the breaking
4985 package is in the "Unpacked" state but allows both packages to
4986 be unpacked at the same time.
4990 If one package is to be unpacked, the other must be removed
4991 first. If the package being unpacked is marked as replacing
4992 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4993 normally be used in this case) the one on the system, or the one
4994 on the system is marked as deselected, or both packages are
4995 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4996 automatically remove the package which is causing the conflict.
4997 Otherwise, it will halt the installation of the new package with
4998 an error. This mechanism is specifically designed to produce an
4999 error when the installed package is <tt>Essential</tt>, but the
5004 A package will not cause a conflict merely because its
5005 configuration files are still installed; it must be at least
5010 A special exception is made for packages which declare a
5011 conflict with their own package name, or with a virtual
5012 package which they provide (see below): this does not
5013 prevent their installation, and allows a package to conflict
5014 with others providing a replacement for it. You use this
5015 feature when you want the package in question to be the only
5016 package providing some feature.
5020 Normally, <tt>Breaks</tt> should be used instead
5021 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5022 stronger restriction on the ordering of package installation or
5023 upgrade and can make it more difficult for the package manager
5024 to find a correct solution to an upgrade or installation
5025 problem. <tt>Breaks</tt> should be used
5027 <item>when moving a file from one package to another (see
5028 <ref id="replaces">),</item>
5029 <item>when splitting a package (a special case of the previous
5031 <item>when the breaking package exposes a bug in or interacts
5032 badly with particular versions of the broken
5035 <tt>Conflicts</tt> should be used
5037 <item>when two packages provide the same file and will
5038 continue to do so,</item>
5039 <item>in conjunction with <tt>Provides</tt> when only one
5040 package providing a given virtual facility may be unpacked
5041 at a time (see <ref id="virtual">),</item>
5042 <item>in other cases where one must prevent simultaneous
5043 installation of two packages for reasons that are ongoing
5044 (not fixed in a later version of one of the packages) or
5045 that must prevent both packages from being unpacked at the
5046 same time, not just configured.</item>
5048 Be aware that adding <tt>Conflicts</tt> is normally not the best
5049 solution when two packages provide the same files. Depending on
5050 the reason for that conflict, using alternatives or renaming the
5051 files is often a better approach. See, for
5052 example, <ref id="binaries">.
5056 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5057 unless two packages cannot be installed at the same time or
5058 installing them both causes one of them to be broken or
5059 unusable. Having similar functionality or performing the same
5060 tasks as another package is not sufficient reason to
5061 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5065 A <tt>Conflicts</tt> entry may have an "earlier than" version
5066 clause if the reason for the conflict is corrected in a later
5067 version of one of the packages. However, normally the presence
5068 of an "earlier than" version clause is a sign
5069 that <tt>Breaks</tt> should have been used instead. An "earlier
5070 than" version clause in <tt>Conflicts</tt>
5071 prevents <prgn>dpkg</prgn> from upgrading or installing the
5072 package which declares such a conflict until the upgrade or
5073 removal of the conflicted-with package has been completed, which
5074 is a strong restriction.
5078 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5082 As well as the names of actual ("concrete") packages, the
5083 package relationship fields <tt>Depends</tt>,
5084 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5085 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5086 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5087 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5088 may mention "virtual packages".
5092 A <em>virtual package</em> is one which appears in the
5093 <tt>Provides</tt> control field of another package. The effect
5094 is as if the package(s) which provide a particular virtual
5095 package name had been listed by name everywhere the virtual
5096 package name appears. (See also <ref id="virtual_pkg">)
5100 If there are both concrete and virtual packages of the same
5101 name, then the dependency may be satisfied (or the conflict
5102 caused) by either the concrete package with the name in
5103 question or any other concrete package which provides the
5104 virtual package with the name in question. This is so that,
5105 for example, supposing we have
5106 <example compact="compact">
5109 </example> and someone else releases an enhanced version of
5110 the <tt>bar</tt> package they can say:
5111 <example compact="compact">
5115 and the <tt>bar-plus</tt> package will now also satisfy the
5116 dependency for the <tt>foo</tt> package.
5120 If a relationship field has a version number attached, only real
5121 packages will be considered to see whether the relationship is
5122 satisfied (or the prohibition violated, for a conflict or
5123 breakage). In other words, if a version number is specified,
5124 this is a request to ignore all <tt>Provides</tt> for that
5125 package name and consider only real packages. The package
5126 manager will assume that a package providing that virtual
5127 package is not of the "right" version. A <tt>Provides</tt>
5128 field may not contain version numbers, and the version number of
5129 the concrete package which provides a particular virtual package
5130 will not be considered when considering a dependency on or
5131 conflict with the virtual package name.<footnote>
5132 It is possible that a future release of <prgn>dpkg</prgn> may
5133 add the ability to specify a version number for each virtual
5134 package it provides. This feature is not yet present,
5135 however, and is expected to be used only infrequently.
5140 To specify which of a set of real packages should be the default
5141 to satisfy a particular dependency on a virtual package, list
5142 the real package as an alternative before the virtual one.
5146 If the virtual package represents a facility that can only be
5147 provided by one real package at a time, such as
5148 the <package>mail-transport-agent</package> virtual package that
5149 requires installation of a binary that would conflict with all
5150 other providers of that virtual package (see
5151 <ref id="mail-transport-agents">), all packages providing that
5152 virtual package should also declare a conflict with it
5153 using <tt>Conflicts</tt>. This will ensure that at most one
5154 provider of that virtual package is unpacked or installed at a
5159 <sect id="replaces"><heading>Overwriting files and replacing
5160 packages - <tt>Replaces</tt></heading>
5163 Packages can declare in their control file that they should
5164 overwrite files in certain other packages, or completely replace
5165 other packages. The <tt>Replaces</tt> control field has these
5166 two distinct purposes.
5169 <sect1><heading>Overwriting files in other packages</heading>
5172 It is usually an error for a package to contain files which
5173 are on the system in another package. However, if the
5174 overwriting package declares that it <tt>Replaces</tt> the one
5175 containing the file being overwritten, then <prgn>dpkg</prgn>
5176 will replace the file from the old package with that from the
5177 new. The file will no longer be listed as "owned" by the old
5178 package and will be taken over by the new package.
5179 Normally, <tt>Breaks</tt> should be used in conjunction
5180 with <tt>Replaces</tt>.<footnote>
5181 To see why <tt>Breaks</tt> is normally needed in addition
5182 to <tt>Replaces</tt>, consider the case of a file in the
5183 package <package>foo</package> being taken over by the
5184 package <package>foo-data</package>.
5185 <tt>Replaces</tt> will allow <package>foo-data</package> to
5186 be installed and take over that file. However,
5187 without <tt>Breaks</tt>, nothing
5188 requires <package>foo</package> to be upgraded to a newer
5189 version that knows it does not include that file and instead
5190 depends on <package>foo-data</package>. Nothing would
5191 prevent the new <package>foo-data</package> package from
5192 being installed and then removed, removing the file that it
5193 took over from <package>foo</package>. After that
5194 operation, the package manager would think the system was in
5195 a consistent state, but the <package>foo</package> package
5196 would be missing one of its files.
5201 For example, if a package <package>foo</package> is split
5202 into <package>foo</package> and <package>foo-data</package>
5203 starting at version 1.2-3, <package>foo-data</package> would
5205 <example compact="compact">
5206 Replaces: foo (<< 1.2-3)
5207 Breaks: foo (<< 1.2-3)
5209 in its control file. The new version of the
5210 package <package>foo</package> would normally have the field
5211 <example compact="compact">
5212 Depends: foo-data (>= 1.2-3)
5214 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5215 the files moved into <package>foo-data</package> are not
5216 required for normal operation).
5220 If a package is completely replaced in this way, so that
5221 <prgn>dpkg</prgn> does not know of any files it still
5222 contains, it is considered to have "disappeared". It will
5223 be marked as not wanted on the system (selected for
5224 removal) and not installed. Any <tt>conffile</tt>s
5225 details noted for the package will be ignored, as they
5226 will have been taken over by the overwriting package. The
5227 package's <prgn>postrm</prgn> script will be run with a
5228 special argument to allow the package to do any final
5229 cleanup required. See <ref id="mscriptsinstact">.
5231 Replaces is a one way relationship. You have to install
5232 the replacing package after the replaced package.
5237 For this usage of <tt>Replaces</tt>, virtual packages (see
5238 <ref id="virtual">) are not considered when looking at a
5239 <tt>Replaces</tt> field. The packages declared as being
5240 replaced must be mentioned by their real names.
5244 This usage of <tt>Replaces</tt> only takes effect when both
5245 packages are at least partially on the system at once. It is
5246 not relevant if the packages conflict unless the conflict has
5251 <sect1><heading>Replacing whole packages, forcing their
5255 Second, <tt>Replaces</tt> allows the packaging system to
5256 resolve which package should be removed when there is a
5257 conflict (see <ref id="conflicts">). This usage only takes
5258 effect when the two packages <em>do</em> conflict, so that the
5259 two usages of this field do not interfere with each other.
5263 In this situation, the package declared as being replaced
5264 can be a virtual package, so for example, all mail
5265 transport agents (MTAs) would have the following fields in
5266 their control files:
5267 <example compact="compact">
5268 Provides: mail-transport-agent
5269 Conflicts: mail-transport-agent
5270 Replaces: mail-transport-agent
5272 ensuring that only one MTA can be unpacked at any one
5273 time. See <ref id="virtual"> for more information about this
5278 <sect id="sourcebinarydeps">
5279 <heading>Relationships between source and binary packages -
5280 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5281 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5285 Source packages that require certain binary packages to be
5286 installed or absent at the time of building the package
5287 can declare relationships to those binary packages.
5291 This is done using the <tt>Build-Depends</tt>,
5292 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5293 <tt>Build-Conflicts-Indep</tt> control fields.
5297 Build-dependencies on "build-essential" binary packages can be
5298 omitted. Please see <ref id="pkg-relations"> for more information.
5302 The dependencies and conflicts they define must be satisfied
5303 (as defined earlier for binary packages) in order to invoke
5304 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5306 There is no Build-Depends-Arch; this role is essentially
5307 met with Build-Depends. Anyone building the
5308 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5309 assumed to be building the whole package, and therefore
5310 installation of all build dependencies is required.
5313 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5314 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5315 not yet know how to check for its existence, and
5316 <tt>binary-arch</tt>. The purpose of the original split
5317 between <tt>Build-Depends</tt> and
5318 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5319 wouldn't need to install extra packages needed only for the
5320 binary-indep targets. But without a build-arch/build-indep
5321 split, this didn't work, since most of the work is done in
5322 the build target, not in the binary target.
5326 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5327 <tt>binary-arch</tt></tag>
5329 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5330 fields must be satisfied when these targets are invoked.
5332 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5333 and <tt>binary-indep</tt></tag>
5335 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5336 <tt>Build-Depends-Indep</tt>, and
5337 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5338 these targets are invoked.
5346 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5349 Packages containing shared libraries must be constructed with
5350 a little care to make sure that the shared library is always
5351 available. This is especially important for packages whose
5352 shared libraries are vitally important, such as the C library
5353 (currently <tt>libc6</tt>).
5357 This section deals only with public shared libraries: shared
5358 libraries that are placed in directories searched by the dynamic
5359 linker by default or which are intended to be linked against
5360 normally and possibly used by other, independent packages. Shared
5361 libraries that are internal to a particular package or that are
5362 only loaded as dynamic modules are not covered by this section and
5363 are not subject to its requirements.
5367 A shared library is identified by the <tt>SONAME</tt> attribute
5368 stored in its dynamic section. When a binary is linked against a
5369 shared library, the <tt>SONAME</tt> of the shared library is
5370 recorded in the binary's <tt>NEEDED</tt> section so that the
5371 dynamic linker knows that library must be loaded at runtime. The
5372 shared library file's full name (which usually contains additional
5373 version information not needed in the <tt>SONAME</tt>) is
5374 therefore normally not referenced directly. Instead, the shared
5375 library is loaded by its <tt>SONAME</tt>, which exists on the file
5376 system as a symlink pointing to the full name of the shared
5377 library. This symlink must be provided by the
5378 package. <ref id="sharedlibs-runtime"> describes how to do this.
5380 This is a convention of shared library versioning, but not a
5381 requirement. Some libraries use the <tt>SONAME</tt> as the full
5382 library file name instead and therefore do not need a symlink.
5383 Most, however, encode additional information about
5384 backwards-compatible revisions as a minor version number in the
5385 file name. The <tt>SONAME</tt> itself only changes when
5386 binaries linked with the earlier version of the shared library
5387 may no longer work, but the filename may change with each
5388 release of the library. See <ref id="sharedlibs-runtime"> for
5394 When linking a binary or another shared library against a shared
5395 library, the <tt>SONAME</tt> for that shared library is not yet
5396 known. Instead, the shared library is found by looking for a file
5397 matching the library name with <tt>.so</tt> appended. This file
5398 exists on the file system as a symlink pointing to the shared
5403 Shared libraries are normally split into several binary packages.
5404 The <tt>SONAME</tt> symlink is installed by the runtime shared
5405 library package, and the bare <tt>.so</tt> symlink is installed in
5406 the development package since it's only used when linking binaries
5407 or shared libraries. However, there are some exceptions for
5408 unusual shared libraries or for shared libraries that are also
5409 loaded as dynamic modules by other programs.
5413 This section is primarily concerned with how the separation of
5414 shared libraries into multiple packages should be done and how
5415 dependencies on and between shared library binary packages are
5416 managed in Debian. <ref id="libraries"> should be read in
5417 conjunction with this section and contains additional rules for
5418 the files contained in the shared library packages.
5421 <sect id="sharedlibs-runtime">
5422 <heading>Run-time shared libraries</heading>
5425 The run-time shared library must be placed in a package
5426 whose name changes whenever the <tt>SONAME</tt> of the shared
5427 library changes. This allows several versions of the shared
5428 library to be installed at the same time, allowing installation
5429 of the new version of the shared library without immediately
5430 breaking binaries that depend on the old version. Normally, the
5431 run-time shared library and its <tt>SONAME</tt> symlink should
5432 be placed in a package named
5433 <package><var>libraryname</var><var>soversion</var></package>,
5434 where <var>soversion</var> is the version number in
5435 the <tt>SONAME</tt> of the shared library.
5436 See <ref id="shlibs"> for detailed information on how to
5437 determine this version. Alternatively, if it would be confusing
5438 to directly append <var>soversion</var>
5439 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5440 itself ends in a number), you should use
5441 <package><var>libraryname</var>-<var>soversion</var></package>
5446 If you have several shared libraries built from the same source
5447 tree, you may lump them all together into a single shared
5448 library package provided that all of their <tt>SONAME</tt>s will
5449 always change together. Be aware that this is not normally the
5450 case, and if the <tt>SONAME</tt>s do not change together,
5451 upgrading such a merged shared library package will be
5452 unnecessarily difficult because of file conflicts with the old
5453 version of the package. When in doubt, always split shared
5454 library packages so that each binary package installs a single
5459 Every time the shared library ABI changes in a way that may
5460 break binaries linked against older versions of the shared
5461 library, the <tt>SONAME</tt> of the library and the
5462 corresponding name for the binary package containing the runtime
5463 shared library should change. Normally, this means
5464 the <tt>SONAME</tt> should change any time an interface is
5465 removed from the shared library or the signature of an interface
5466 (the number of parameters or the types of parameters that it
5467 takes, for example) is changed. This practice is vital to
5468 allowing clean upgrades from older versions of the package and
5469 clean transitions between the old ABI and new ABI without having
5470 to upgrade every affected package simultaneously.
5474 The <tt>SONAME</tt> and binary package name need not, and indeed
5475 normally should not, change if new interfaces are added but none
5476 are removed or changed, since this will not break binaries
5477 linked against the old shared library. Correct versioning of
5478 dependencies on the newer shared library by binaries that use
5479 the new interfaces is handled via
5480 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5481 system</qref> or via symbols files (see
5482 <manref name="deb-symbols" section="5">).
5486 The package should install the shared libraries under
5487 their normal names. For example, the <package>libgdbm3</package>
5488 package should install <file>libgdbm.so.3.0.0</file> as
5489 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5490 renamed or re-linked by any <prgn>prerm</prgn> or
5491 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5492 of renaming things safely without affecting running programs,
5493 and attempts to interfere with this are likely to lead to
5498 Shared libraries should not be installed executable, since
5499 the dynamic linker does not require this and trying to
5500 execute a shared library usually results in a core dump.
5504 The run-time library package should include the symbolic link for
5505 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5506 the shared libraries. For example,
5507 the <package>libgdbm3</package> package should include a symbolic
5508 link from <file>/usr/lib/libgdbm.so.3</file> to
5509 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5510 linker (for example <prgn>ld.so</prgn> or
5511 <prgn>ld-linux.so.*</prgn>) can find the library between the
5512 time that <prgn>dpkg</prgn> installs it and the time that
5513 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5515 The package management system requires the library to be
5516 placed before the symbolic link pointing to it in the
5517 <file>.deb</file> file. This is so that when
5518 <prgn>dpkg</prgn> comes to install the symlink
5519 (overwriting the previous symlink pointing at an older
5520 version of the library), the new shared library is already
5521 in place. In the past, this was achieved by creating the
5522 library in the temporary packaging directory before
5523 creating the symlink. Unfortunately, this was not always
5524 effective, since the building of the tar file in the
5525 <file>.deb</file> depended on the behavior of the underlying
5526 file system. Some file systems (such as reiserfs) reorder
5527 the files so that the order of creation is forgotten.
5528 Since version 1.7.0, <prgn>dpkg</prgn>
5529 reorders the files itself as necessary when building a
5530 package. Thus it is no longer important to concern
5531 oneself with the order of file creation.
5535 <sect1 id="ldconfig">
5536 <heading><tt>ldconfig</tt></heading>
5539 Any package installing shared libraries in one of the default
5540 library directories of the dynamic linker (which are currently
5541 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5542 listed in <file>/etc/ld.so.conf</file><footnote>
5543 These are currently <file>/usr/local/lib</file> plus
5544 directories under <file>/lib</file> and <file>/usr/lib</file>
5545 matching the multiarch triplet for the system architecture.
5547 must use <prgn>ldconfig</prgn> to update the shared library
5552 The package maintainer scripts must only call
5553 <prgn>ldconfig</prgn> under these circumstances:
5554 <list compact="compact">
5555 <item>When the <prgn>postinst</prgn> script is run with a
5556 first argument of <tt>configure</tt>, the script must call
5557 <prgn>ldconfig</prgn>, and may optionally invoke
5558 <prgn>ldconfig</prgn> at other times.
5560 <item>When the <prgn>postrm</prgn> script is run with a
5561 first argument of <tt>remove</tt>, the script should call
5562 <prgn>ldconfig</prgn>.
5567 During install or upgrade, the preinst is called before
5568 the new files are unpacked, so calling "ldconfig" is
5569 pointless. The preinst of an existing package can also be
5570 called if an upgrade fails. However, this happens during
5571 the critical time when a shared libs may exist on-disk
5572 under a temporary name. Thus, it is dangerous and
5573 forbidden by current policy to call "ldconfig" at this
5578 When a package is installed or upgraded, "postinst
5579 configure" runs after the new files are safely on-disk.
5580 Since it is perfectly safe to invoke ldconfig
5581 unconditionally in a postinst, it is OK for a package to
5582 simply put ldconfig in its postinst without checking the
5583 argument. The postinst can also be called to recover from
5584 a failed upgrade. This happens before any new files are
5585 unpacked, so there is no reason to call "ldconfig" at this
5590 For a package that is being removed, prerm is
5591 called with all the files intact, so calling ldconfig is
5592 useless. The other calls to "prerm" happen in the case of
5593 upgrade at a time when all the files of the old package
5594 are on-disk, so again calling "ldconfig" is pointless.
5598 postrm, on the other hand, is called with the "remove"
5599 argument just after the files are removed, so this is
5600 the proper time to call "ldconfig" to notify the system
5601 of the fact that the shared libraries from the package
5602 are removed. The postrm can be called at several other
5603 times. At the time of "postrm purge", "postrm
5604 abort-install", or "postrm abort-upgrade", calling
5605 "ldconfig" is useless because the shared lib files are
5606 not on-disk. However, when "postrm" is invoked with
5607 arguments "upgrade", "failed-upgrade", or "disappear", a
5608 shared lib may exist on-disk under a temporary filename.
5616 <sect id="sharedlibs-support-files">
5617 <heading>Shared library support files</heading>
5620 If your package contains files whose names do not change with
5621 each change in the library shared object version, you must not
5622 put them in the shared library package. Otherwise, several
5623 versions of the shared library cannot be installed at the same
5624 time without filename clashes, making upgrades and transitions
5625 unnecessarily difficult.
5629 It is recommended that supporting files and run-time support
5630 programs that do not need to be invoked manually by users, but
5631 are nevertheless required for the package to function, be placed
5632 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5633 preferably under <file>/usr/lib/</file><var>package-name</var>.
5634 If the program or file is architecture independent, the
5635 recommendation is for it to be placed in a subdirectory of
5636 <file>/usr/share</file> instead, preferably under
5637 <file>/usr/share/</file><var>package-name</var>. Following the
5638 <var>package-name</var> naming convention ensures that the file
5639 names change when the shared object version changes.
5643 Run-time support programs that use the shared library but are
5644 not required for the library to function or files used by the
5645 shared library that can be used by any version of the shared
5646 library package should instead be put in a separate package.
5647 This package might typically be named
5648 <package><var>libraryname</var>-tools</package>; note the
5649 absence of the <var>soversion</var> in the package name.
5653 Files and support programs only useful when compiling software
5654 against the library should be included in the development
5655 package for the library.<footnote>
5656 For example, a <file><var>package-name</var>-config</file>
5657 script or <package>pkg-config</package> configuration files.
5662 <sect id="sharedlibs-static">
5663 <heading>Static libraries</heading>
5666 The static library (<file><var>libraryname.a</var></file>)
5667 is usually provided in addition to the shared version.
5668 It is placed into the development package (see below).
5672 In some cases, it is acceptable for a library to be
5673 available in static form only; these cases include:
5675 <item>libraries for languages whose shared library support
5676 is immature or unstable</item>
5677 <item>libraries whose interfaces are in flux or under
5678 development (commonly the case when the library's
5679 major version number is zero, or where the ABI breaks
5680 across patchlevels)</item>
5681 <item>libraries which are explicitly intended to be
5682 available only in static form by their upstream
5687 <sect id="sharedlibs-dev">
5688 <heading>Development files</heading>
5691 If there are development files associated with a shared library,
5692 the source package needs to generate a binary development package
5693 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5694 or if you prefer only to support one development version at a
5695 time, <package><var>libraryname</var>-dev</package>. Installing
5696 the development package must result in installation of all the
5697 development files necessary for compiling programs against that
5698 shared library.<footnote>
5699 This wording allows the development files to be split into
5700 several packages, such as a separate architecture-independent
5701 <package><var>libraryname</var>-headers</package>, provided that
5702 the development package depends on all the required additional
5708 In case several development versions of a library exist, you may
5709 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5710 <ref id="conflicts">) to ensure that the user only installs one
5711 development version at a time (as different development versions are
5712 likely to have the same header files in them, which would cause a
5713 filename clash if both were unpacked).
5717 The development package should contain a symlink for the associated
5718 shared library without a version number. For example, the
5719 <package>libgdbm-dev</package> package should include a symlink
5720 from <file>/usr/lib/libgdbm.so</file> to
5721 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5722 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5723 <file>libgdbm.so</file> when compiling dynamically.
5727 If the package provides Ada Library Information
5728 (<file>*.ali</file>) files for use with GNAT, these files must be
5729 installed read-only (mode 0444) so that GNAT will not attempt to
5730 recompile them. This overrides the normal file mode requirements
5731 given in <ref id="permissions-owners">.
5735 <sect id="sharedlibs-intradeps">
5736 <heading>Dependencies between the packages of the same library</heading>
5739 Typically the development version should have an exact
5740 version dependency on the runtime library, to make sure that
5741 compilation and linking happens correctly. The
5742 <tt>${binary:Version}</tt> substitution variable can be
5743 useful for this purpose.
5745 Previously, <tt>${Source-Version}</tt> was used, but its name
5746 was confusing and it has been deprecated since dpkg 1.13.19.
5751 <sect id="sharedlibs-shlibdeps">
5752 <heading>Dependencies between the library and other packages -
5753 the <tt>shlibs</tt> system</heading>
5756 If a package contains a binary or library which links to a
5757 shared library, we must ensure that when the package is
5758 installed on the system, all of the libraries needed are
5759 also installed. This requirement led to the creation of the
5760 <tt>shlibs</tt> system, which is very simple in its design:
5761 any package which <em>provides</em> a shared library also
5762 provides information on the package dependencies required to
5763 ensure the presence of this library, and any package which
5764 <em>uses</em> a shared library uses this information to
5765 determine the dependencies it requires. The files which
5766 contain the mapping from shared libraries to the necessary
5767 dependency information are called <file>shlibs</file> files.
5771 When a package is built which contains any shared libraries, it
5772 must provide a <file>shlibs</file> file for other packages to
5773 use. When a package is built which contains any shared
5774 libraries or compiled binaries, it must run
5775 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5776 on these to determine the libraries used and hence the
5777 dependencies needed by this package.<footnote>
5779 <prgn>dpkg-shlibdeps</prgn> will use a program
5780 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5781 the libraries directly needed by the binaries or shared
5782 libraries in the package.
5786 We say that a binary <tt>foo</tt> <em>directly</em> uses
5787 a library <tt>libbar</tt> if it is explicitly linked
5788 with that library (that is, the library is listed in the ELF
5789 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5790 to the link line when the binary is created). Other
5791 libraries that are needed by <tt>libbar</tt> are linked
5792 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5793 linker will load them automatically when it loads
5794 <tt>libbar</tt>. A package should depend on the libraries
5795 it directly uses, but not the libraries it indirectly uses.
5796 The dependencies for those libraries will automatically pull
5797 in the other libraries.
5801 A good example of where this helps is the following. We
5802 could update <tt>libimlib</tt> with a new version that
5803 supports a new graphics format called dgf (but retaining the
5804 same major version number) and depends on <tt>libdgf</tt>.
5805 If we used <prgn>ldd</prgn> to add dependencies for every
5806 library directly or indirectly linked with a binary, every
5807 package that uses <tt>libimlib</tt> would need to be
5808 recompiled so it would also depend on <tt>libdgf</tt> or it
5809 wouldn't run due to missing symbols. Since dependencies are
5810 only added based on ELF <tt>NEEDED</tt> attribute, packages
5811 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5812 having the dependency on <tt>libdgf</tt> and so they would
5813 not need rebuilding.
5819 In the following sections, we will first describe where the
5820 various <tt>shlibs</tt> files are to be found, then how to
5821 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5822 file format and how to create them if your package contains a
5827 <heading>The <tt>shlibs</tt> files present on the system</heading>
5830 There are several places where <tt>shlibs</tt> files are
5831 found. The following list gives them in the order in which
5833 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5834 (The first one which gives the required information is used.)
5840 <p><file>debian/shlibs.local</file></p>
5843 This lists overrides for this package. This file should
5844 normally not be used, but may be needed temporarily in
5845 unusual situations to work around bugs in other packages,
5846 or in unusual cases where the normally declared dependency
5847 information in the installed <file>shlibs</file> file for
5848 a library cannot be used. This file overrides information
5849 obtained from any other source.
5854 <p><file>/etc/dpkg/shlibs.override</file></p>
5857 This lists global overrides. This list is normally
5858 empty. It is maintained by the local system
5864 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5867 When packages are being built,
5868 any <file>debian/shlibs</file> files are copied into the
5869 control information file area of the temporary build
5870 directory and given the name <file>shlibs</file>. These
5871 files give details of any shared libraries included in the
5872 same package.<footnote>
5873 An example may help here. Let us say that the source
5874 package <tt>foo</tt> generates two binary
5875 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5876 When building the binary packages, the two packages are
5877 created in the directories <file>debian/libfoo2</file>
5878 and <file>debian/foo-runtime</file> respectively.
5879 (<file>debian/tmp</file> could be used instead of one of
5880 these.) Since <tt>libfoo2</tt> provides the
5881 <tt>libfoo</tt> shared library, it will require a
5882 <tt>shlibs</tt> file, which will be installed in
5883 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5884 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5885 When <prgn>dpkg-shlibdeps</prgn> is run on the
5886 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5888 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5889 determine whether <tt>foo-prog</tt>'s library
5890 dependencies are satisfied by any of the libraries
5891 provided by <tt>libfoo2</tt>. For this reason,
5892 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5893 the individual binary packages' <tt>shlibs</tt> files
5894 have been installed into the build directory.
5900 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5903 These are the <file>shlibs</file> files corresponding to
5904 all of the packages installed on the system, and are
5905 maintained by the relevant package maintainers.
5910 <p><file>/etc/dpkg/shlibs.default</file></p>
5913 This file lists any shared libraries whose packages
5914 have failed to provide correct <file>shlibs</file> files.
5915 It was used when the <file>shlibs</file> setup was first
5916 introduced, but it is now normally empty. It is
5917 maintained by the <tt>dpkg</tt> maintainer.
5925 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5926 <file>shlibs</file> files</heading>
5930 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5931 into your <file>debian/rules</file> file. If your package
5932 contains only compiled binaries and libraries (but no scripts),
5933 you can use a command such as:
5934 <example compact="compact">
5935 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5936 debian/tmp/usr/lib/*
5938 Otherwise, you will need to explicitly list the compiled
5939 binaries and libraries.<footnote>
5940 If you are using <tt>debhelper</tt>, the
5941 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5942 It will also correctly handle multi-binary packages.
5947 This command puts the dependency information into the
5948 <file>debian/substvars</file> file, which is then used by
5949 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5950 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5951 field in the control file for this to work.
5955 If you have multiple binary packages, you will need to call
5956 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5957 compiled libraries or binaries. In such a case, you will
5958 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5959 utilities to specify a different <file>substvars</file> file.
5963 If you are creating a udeb for use in the Debian Installer,
5964 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5965 should use the dependency line of type <tt>udeb</tt> by
5966 adding the <tt>-tudeb</tt> option<footnote>
5967 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5968 will automatically add this option if it knows it is
5970 </footnote>. If there is no dependency line of
5971 type <tt>udeb</tt> in the <file>shlibs</file>
5972 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5977 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5978 <ref id="pkg-dpkg-shlibdeps"> and
5979 <manref name="dpkg-shlibdeps" section="1">.
5984 <heading>The <file>shlibs</file> File Format</heading>
5987 Each <file>shlibs</file> file has the same format. Lines
5988 beginning with <tt>#</tt> are considered to be comments and
5989 are ignored. Each line is of the form:
5990 <example compact="compact">
5991 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5996 We will explain this by reference to the example of the
5997 <tt>zlib1g</tt> package, which (at the time of writing)
5998 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6002 <var>type</var> is an optional element that indicates the type
6003 of package for which the line is valid. The only type currently
6004 in use is <tt>udeb</tt>. The colon and space after the type are
6009 <var>library-name</var> is the name of the shared library,
6010 in this case <tt>libz</tt>. (This must match the name part
6011 of the soname, see below.)
6015 <var>soname-version</var> is the version part of the soname of
6016 the library. The soname is the thing that must exactly match
6017 for the library to be recognized by the dynamic linker, and is
6019 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6020 example, <tt>libz.so.1</tt>.<footnote>
6021 This can be determined using the command
6022 <example compact="compact">
6023 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6026 The version part is the part which comes after
6027 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6028 instead be of the form
6029 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6030 as <tt>libdb-4.8.so</tt>, in which case the name would
6031 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6035 <var>dependencies</var> has the same syntax as a dependency
6036 field in a binary package control file. It should give
6037 details of which packages are required to satisfy a binary
6038 built against the version of the library contained in the
6039 package. See <ref id="depsyntax"> for details.
6043 In our example, if the first version of the <tt>zlib1g</tt>
6044 package which contained a minor number of at least
6045 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6046 <tt>shlibs</tt> entry for this library could say:
6047 <example compact="compact">
6048 libz 1 zlib1g (>= 1:1.1.3)
6050 The version-specific dependency is to avoid warnings from
6051 the dynamic linker about using older shared libraries with
6056 As zlib1g also provides a udeb containing the shared library,
6057 there would also be a second line:
6058 <example compact="compact">
6059 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6065 <heading>Providing a <file>shlibs</file> file</heading>
6068 If your package provides a shared library, you need to create
6069 a <file>shlibs</file> file following the format described above.
6070 It is usual to call this file <file>debian/shlibs</file> (but if
6071 you have multiple binary packages, you might want to call it
6072 <file>debian/shlibs.<var>package</var></file> instead). Then
6073 let <file>debian/rules</file> install it in the control
6074 information file area:
6075 <example compact="compact">
6076 install -m644 debian/shlibs debian/tmp/DEBIAN
6078 or, in the case of a multi-binary package:
6079 <example compact="compact">
6080 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6082 An alternative way of doing this is to create the
6083 <file>shlibs</file> file in the control information file area
6084 directly from <file>debian/rules</file> without using
6085 a <file>debian/shlibs</file> file at all,<footnote>
6086 This is what <prgn>dh_makeshlibs</prgn> in
6087 the <package>debhelper</package> suite does. If your package
6088 also has a udeb that provides a shared
6089 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6090 the <tt>udeb:</tt> lines if you specify the name of the udeb
6091 with the <tt>--add-udeb</tt> option.
6093 since the <file>debian/shlibs</file> file itself is ignored by
6094 <prgn>dpkg-shlibdeps</prgn>.
6098 As <prgn>dpkg-shlibdeps</prgn> reads the
6099 <file>DEBIAN/shlibs</file> files in all of the binary packages
6100 being built from this source package, all of the
6101 <file>DEBIAN/shlibs</file> files should be installed before
6102 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6110 <chapt id="opersys"><heading>The Operating System</heading>
6113 <heading>File system hierarchy</heading>
6117 <heading>File System Structure</heading>
6120 The location of all installed files and directories must
6121 comply with the Filesystem Hierarchy Standard (FHS),
6122 version 2.3, with the exceptions noted below, and except
6123 where doing so would violate other terms of Debian
6124 Policy. The following exceptions to the FHS apply:
6129 The optional rules related to user specific
6130 configuration files for applications are stored in
6131 the user's home directory are relaxed. It is
6132 recommended that such files start with the
6133 '<tt>.</tt>' character (a "dot file"), and if an
6134 application needs to create more than one dot file
6135 then the preferred placement is in a subdirectory
6136 with a name starting with a '.' character, (a "dot
6137 directory"). In this case it is recommended the
6138 configuration files not start with the '.'
6144 The requirement for amd64 to use <file>/lib64</file>
6145 for 64 bit binaries is removed.
6150 The requirement for object files, internal binaries, and
6151 libraries, including <file>libc.so.*</file>, to be located
6152 directly under <file>/lib{,32}</file> and
6153 <file>/usr/lib{,32}</file> is amended, permitting files
6154 to instead be installed to
6155 <file>/lib/<var>triplet</var></file> and
6156 <file>/usr/lib/<var>triplet</var></file>, where
6157 <tt><var>triplet</var></tt> is the value returned by
6158 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6159 architecture of the package. Packages may <em>not</em>
6160 install files to any <var>triplet</var> path other
6161 than the one matching the architecture of that package;
6162 for instance, an <tt>Architecture: amd64</tt> package
6163 containing 32-bit x86 libraries may not install these
6164 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6166 This is necessary in order to reserve the directories for
6167 use in cross-installation of library packages from other
6168 architectures, as part of the planned deployment of
6173 Applications may also use a single subdirectory under
6174 <file>/usr/lib/<var>triplet</var></file>.
6177 The execution time linker/loader, ld*, must still be made
6178 available in the existing location under /lib or /lib64
6179 since this is part of the ELF ABI for the architecture.
6184 The requirement that
6185 <file>/usr/local/share/man</file> be "synonymous"
6186 with <file>/usr/local/man</file> is relaxed to a
6191 The requirement that windowmanagers with a single
6192 configuration file call it <file>system.*wmrc</file>
6193 is removed, as is the restriction that the window
6194 manager subdirectory be named identically to the
6195 window manager name itself.
6200 The requirement that boot manager configuration
6201 files live in <file>/etc</file>, or at least are
6202 symlinked there, is relaxed to a recommendation.
6207 The following directories in the root filesystem are
6208 additionally allowed: <file>/sys</file> and
6209 <file>/selinux</file>. <footnote>These directories
6210 are used as mount points to mount virtual filesystems
6211 to get access to kernel information.</footnote>
6216 On GNU/Hurd systems, the following additional
6217 directories are allowed in the root
6218 filesystem: <file>/hurd</file>
6219 and <file>/servers</file>.<footnote>
6220 These directories are used to store translators and as
6221 a set of standard names for mount points,
6230 The version of this document referred here can be
6231 found in the <tt>debian-policy</tt> package or on <url
6232 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6233 name="FHS (Debian copy)"> alongside this manual (or, if
6234 you have the <package>debian-policy</package> installed,
6236 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6237 (local copy)">). The
6238 latest version, which may be a more recent version, may
6240 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6241 Specific questions about following the standard may be
6242 asked on the <tt>debian-devel</tt> mailing list, or
6243 referred to the FHS mailing list (see the
6244 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6250 <heading>Site-specific programs</heading>
6253 As mandated by the FHS, packages must not place any
6254 files in <file>/usr/local</file>, either by putting them in
6255 the file system archive to be unpacked by <prgn>dpkg</prgn>
6256 or by manipulating them in their maintainer scripts.
6260 However, the package may create empty directories below
6261 <file>/usr/local</file> so that the system administrator knows
6262 where to place site-specific files. These are not
6263 directories <em>in</em> <file>/usr/local</file>, but are
6264 children of directories in <file>/usr/local</file>. These
6265 directories (<file>/usr/local/*/dir/</file>)
6266 should be removed on package removal if they are
6271 Note that this applies only to
6272 directories <em>below</em> <file>/usr/local</file>,
6273 not <em>in</em> <file>/usr/local</file>. Packages must
6274 not create sub-directories in the
6275 directory <file>/usr/local</file> itself, except those
6276 listed in FHS, section 4.5. However, you may create
6277 directories below them as you wish. You must not remove
6278 any of the directories listed in 4.5, even if you created
6283 Since <file>/usr/local</file> can be mounted read-only from a
6284 remote server, these directories must be created and
6285 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6286 maintainer scripts and not be included in the
6287 <file>.deb</file> archive. These scripts must not fail if
6288 either of these operations fail.
6292 For example, the <tt>emacsen-common</tt> package could
6293 contain something like
6294 <example compact="compact">
6295 if [ ! -e /usr/local/share/emacs ]
6297 if mkdir /usr/local/share/emacs 2>/dev/null
6299 chown root:staff /usr/local/share/emacs
6300 chmod 2775 /usr/local/share/emacs
6304 in its <prgn>postinst</prgn> script, and
6305 <example compact="compact">
6306 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6307 rmdir /usr/local/share/emacs 2>/dev/null || true
6309 in the <prgn>prerm</prgn> script. (Note that this form is
6310 used to ensure that if the script is interrupted, the
6311 directory <file>/usr/local/share/emacs</file> will still be
6316 If you do create a directory in <file>/usr/local</file> for
6317 local additions to a package, you should ensure that
6318 settings in <file>/usr/local</file> take precedence over the
6319 equivalents in <file>/usr</file>.
6323 However, because <file>/usr/local</file> and its contents are
6324 for exclusive use of the local administrator, a package
6325 must not rely on the presence or absence of files or
6326 directories in <file>/usr/local</file> for normal operation.
6330 The <file>/usr/local</file> directory itself and all the
6331 subdirectories created by the package should (by default) have
6332 permissions 2775 (group-writable and set-group-id) and be
6333 owned by <tt>root:staff</tt>.
6338 <heading>The system-wide mail directory</heading>
6340 The system-wide mail directory
6341 is <file>/var/mail</file>. This directory is part of the
6342 base system and should not be owned by any particular mail
6343 agents. The use of the old
6344 location <file>/var/spool/mail</file> is deprecated, even
6345 though the spool may still be physically located there.
6351 <heading>Users and groups</heading>
6354 <heading>Introduction</heading>
6356 The Debian system can be configured to use either plain or
6361 Some user ids (UIDs) and group ids (GIDs) are reserved
6362 globally for use by certain packages. Because some
6363 packages need to include files which are owned by these
6364 users or groups, or need the ids compiled into binaries,
6365 these ids must be used on any Debian system only for the
6366 purpose for which they are allocated. This is a serious
6367 restriction, and we should avoid getting in the way of
6368 local administration policies. In particular, many sites
6369 allocate users and/or local system groups starting at 100.
6373 Apart from this we should have dynamically allocated ids,
6374 which should by default be arranged in some sensible
6375 order, but the behavior should be configurable.
6379 Packages other than <tt>base-passwd</tt> must not modify
6380 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6381 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6386 <heading>UID and GID classes</heading>
6388 The UID and GID numbers are divided into classes as
6394 Globally allocated by the Debian project, the same
6395 on every Debian system. These ids will appear in
6396 the <file>passwd</file> and <file>group</file> files of all
6397 Debian systems, new ids in this range being added
6398 automatically as the <tt>base-passwd</tt> package is
6403 Packages which need a single statically allocated
6404 uid or gid should use one of these; their
6405 maintainers should ask the <tt>base-passwd</tt>
6413 Dynamically allocated system users and groups.
6414 Packages which need a user or group, but can have
6415 this user or group allocated dynamically and
6416 differently on each system, should use <tt>adduser
6417 --system</tt> to create the group and/or user.
6418 <prgn>adduser</prgn> will check for the existence of
6419 the user or group, and if necessary choose an unused
6420 id based on the ranges specified in
6421 <file>adduser.conf</file>.
6425 <tag>1000-59999:</tag>
6428 Dynamically allocated user accounts. By default
6429 <prgn>adduser</prgn> will choose UIDs and GIDs for
6430 user accounts in this range, though
6431 <file>adduser.conf</file> may be used to modify this
6436 <tag>60000-64999:</tag>
6439 Globally allocated by the Debian project, but only
6440 created on demand. The ids are allocated centrally
6441 and statically, but the actual accounts are only
6442 created on users' systems on demand.
6446 These ids are for packages which are obscure or
6447 which require many statically-allocated ids. These
6448 packages should check for and create the accounts in
6449 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6450 <prgn>adduser</prgn> if it has this facility) if
6451 necessary. Packages which are likely to require
6452 further allocations should have a "hole" left after
6453 them in the allocation, to give them room to
6458 <tag>65000-65533:</tag>
6466 User <tt>nobody</tt>. The corresponding gid refers
6467 to the group <tt>nogroup</tt>.
6474 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6475 not</em> be used, because it is the error return
6484 <sect id="sysvinit">
6485 <heading>System run levels and <file>init.d</file> scripts</heading>
6487 <sect1 id="/etc/init.d">
6488 <heading>Introduction</heading>
6491 The <file>/etc/init.d</file> directory contains the scripts
6492 executed by <prgn>init</prgn> at boot time and when the
6493 init state (or "runlevel") is changed (see <manref
6494 name="init" section="8">).
6498 There are at least two different, yet functionally
6499 equivalent, ways of handling these scripts. For the sake
6500 of simplicity, this document describes only the symbolic
6501 link method. However, it must not be assumed by maintainer
6502 scripts that this method is being used, and any automated
6503 manipulation of the various runlevel behaviors by
6504 maintainer scripts must be performed using
6505 <prgn>update-rc.d</prgn> as described below and not by
6506 manually installing or removing symlinks. For information
6507 on the implementation details of the other method,
6508 implemented in the <tt>file-rc</tt> package, please refer
6509 to the documentation of that package.
6513 These scripts are referenced by symbolic links in the
6514 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6515 runlevels, <prgn>init</prgn> looks in the directory
6516 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6517 execute, where <tt><var>n</var></tt> is the runlevel that
6518 is being changed to, or <tt>S</tt> for the boot-up
6523 The names of the links all have the form
6524 <file>S<var>mm</var><var>script</var></file> or
6525 <file>K<var>mm</var><var>script</var></file> where
6526 <var>mm</var> is a two-digit number and <var>script</var>
6527 is the name of the script (this should be the same as the
6528 name of the actual script in <file>/etc/init.d</file>).
6532 When <prgn>init</prgn> changes runlevel first the targets
6533 of the links whose names start with a <tt>K</tt> are
6534 executed, each with the single argument <tt>stop</tt>,
6535 followed by the scripts prefixed with an <tt>S</tt>, each
6536 with the single argument <tt>start</tt>. (The links are
6537 those in the <file>/etc/rc<var>n</var>.d</file> directory
6538 corresponding to the new runlevel.) The <tt>K</tt> links
6539 are responsible for killing services and the <tt>S</tt>
6540 link for starting services upon entering the runlevel.
6544 For example, if we are changing from runlevel 2 to
6545 runlevel 3, init will first execute all of the <tt>K</tt>
6546 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6547 all of the <tt>S</tt> prefixed scripts in that directory.
6548 The links starting with <tt>K</tt> will cause the
6549 referred-to file to be executed with an argument of
6550 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6555 The two-digit number <var>mm</var> is used to determine
6556 the order in which to run the scripts: low-numbered links
6557 have their scripts run first. For example, the
6558 <tt>K20</tt> scripts will be executed before the
6559 <tt>K30</tt> scripts. This is used when a certain service
6560 must be started before another. For example, the name
6561 server <prgn>bind</prgn> might need to be started before
6562 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6563 can set up its access lists. In this case, the script
6564 that starts <prgn>bind</prgn> would have a lower number
6565 than the script that starts <prgn>inn</prgn> so that it
6567 <example compact="compact">
6574 The two runlevels 0 (halt) and 6 (reboot) are slightly
6575 different. In these runlevels, the links with an
6576 <tt>S</tt> prefix are still called after those with a
6577 <tt>K</tt> prefix, but they too are called with the single
6578 argument <tt>stop</tt>.
6582 <sect1 id="writing-init">
6583 <heading>Writing the scripts</heading>
6586 Packages that include daemons for system services should
6587 place scripts in <file>/etc/init.d</file> to start or stop
6588 services at boot time or during a change of runlevel.
6589 These scripts should be named
6590 <file>/etc/init.d/<var>package</var></file>, and they should
6591 accept one argument, saying what to do:
6594 <tag><tt>start</tt></tag>
6595 <item>start the service,</item>
6597 <tag><tt>stop</tt></tag>
6598 <item>stop the service,</item>
6600 <tag><tt>restart</tt></tag>
6601 <item>stop and restart the service if it's already running,
6602 otherwise start the service</item>
6604 <tag><tt>reload</tt></tag>
6605 <item><p>cause the configuration of the service to be
6606 reloaded without actually stopping and restarting
6609 <tag><tt>force-reload</tt></tag>
6610 <item>cause the configuration to be reloaded if the
6611 service supports this, otherwise restart the
6615 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6616 <tt>force-reload</tt> options should be supported by all
6617 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6622 The <file>init.d</file> scripts must ensure that they will
6623 behave sensibly (i.e., returning success and not starting
6624 multiple copies of a service) if invoked with <tt>start</tt>
6625 when the service is already running, or with <tt>stop</tt>
6626 when it isn't, and that they don't kill unfortunately-named
6627 user processes. The best way to achieve this is usually to
6628 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6633 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6634 scripts. Writing correct <file>init.d</file> scripts requires
6635 accepting various error exit statuses when daemons are already
6636 running or already stopped without aborting
6637 the <file>init.d</file> script, and common <file>init.d</file>
6638 function libraries are not safe to call with <tt>set -e</tt>
6640 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6641 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6642 in effect and echoing status messages to the console fails,
6644 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6645 to not use <tt>set -e</tt> and instead check the result of
6646 each command separately.
6650 If a service reloads its configuration automatically (as
6651 in the case of <prgn>cron</prgn>, for example), the
6652 <tt>reload</tt> option of the <file>init.d</file> script
6653 should behave as if the configuration has been reloaded
6658 The <file>/etc/init.d</file> scripts must be treated as
6659 configuration files, either (if they are present in the
6660 package, that is, in the .deb file) by marking them as
6661 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6662 by managing them correctly in the maintainer scripts (see
6663 <ref id="config-files">). This is important since we want
6664 to give the local system administrator the chance to adapt
6665 the scripts to the local system, e.g., to disable a
6666 service without de-installing the package, or to specify
6667 some special command line options when starting a service,
6668 while making sure their changes aren't lost during the next
6673 These scripts should not fail obscurely when the
6674 configuration files remain but the package has been
6675 removed, as configuration files remain on the system after
6676 the package has been removed. Only when <prgn>dpkg</prgn>
6677 is executed with the <tt>--purge</tt> option will
6678 configuration files be removed. In particular, as the
6679 <file>/etc/init.d/<var>package</var></file> script itself is
6680 usually a <tt>conffile</tt>, it will remain on the system
6681 if the package is removed but not purged. Therefore, you
6682 should include a <tt>test</tt> statement at the top of the
6684 <example compact="compact">
6685 test -f <var>program-executed-later-in-script</var> || exit 0
6690 Often there are some variables in the <file>init.d</file>
6691 scripts whose values control the behavior of the scripts,
6692 and which a system administrator is likely to want to
6693 change. As the scripts themselves are frequently
6694 <tt>conffile</tt>s, modifying them requires that the
6695 administrator merge in their changes each time the package
6696 is upgraded and the <tt>conffile</tt> changes. To ease
6697 the burden on the system administrator, such configurable
6698 values should not be placed directly in the script.
6699 Instead, they should be placed in a file in
6700 <file>/etc/default</file>, which typically will have the same
6701 base name as the <file>init.d</file> script. This extra file
6702 should be sourced by the script when the script runs. It
6703 must contain only variable settings and comments in SUSv3
6704 <prgn>sh</prgn> format. It may either be a
6705 <tt>conffile</tt> or a configuration file maintained by
6706 the package maintainer scripts. See <ref id="config-files">
6711 To ensure that vital configurable values are always
6712 available, the <file>init.d</file> script should set default
6713 values for each of the shell variables it uses, either
6714 before sourcing the <file>/etc/default/</file> file or
6715 afterwards using something like the <tt>:
6716 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6717 script must behave sensibly and not fail if the
6718 <file>/etc/default</file> file is deleted.
6722 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6723 as temporary filesystems<footnote>
6724 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6725 options in <file>/etc/default/rcS</file>.
6726 </footnote>, so the <file>init.d</file> scripts must handle this
6727 correctly. This will typically amount to creating any required
6728 subdirectories dynamically when the <file>init.d</file> script
6729 is run, rather than including them in the package and relying on
6730 <prgn>dpkg</prgn> to create them.
6735 <heading>Interfacing with the initscript system</heading>
6738 Maintainers should use the abstraction layer provided by
6739 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6740 programs to deal with initscripts in their packages'
6741 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6742 and <prgn>postrm</prgn>.
6746 Directly managing the /etc/rc?.d links and directly
6747 invoking the <file>/etc/init.d/</file> initscripts should
6748 be done only by packages providing the initscript
6749 subsystem (such as <prgn>sysv-rc</prgn> and
6750 <prgn>file-rc</prgn>).
6754 <heading>Managing the links</heading>
6757 The program <prgn>update-rc.d</prgn> is provided for
6758 package maintainers to arrange for the proper creation and
6759 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6760 or their functional equivalent if another method is being
6761 used. This may be used by maintainers in their packages'
6762 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6766 You must not include any <file>/etc/rc<var>n</var>.d</file>
6767 symbolic links in the actual archive or manually create or
6768 remove the symbolic links in maintainer scripts; you must
6769 use the <prgn>update-rc.d</prgn> program instead. (The
6770 former will fail if an alternative method of maintaining
6771 runlevel information is being used.) You must not include
6772 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6773 in the archive either. (Only the <tt>sysvinit</tt>
6778 By default <prgn>update-rc.d</prgn> will start services in
6779 each of the multi-user state runlevels (2, 3, 4, and 5)
6780 and stop them in the halt runlevel (0), the single-user
6781 runlevel (1) and the reboot runlevel (6). The system
6782 administrator will have the opportunity to customize
6783 runlevels by simply adding, moving, or removing the
6784 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6785 symbolic links are being used, or by modifying
6786 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6791 To get the default behavior for your package, put in your
6792 <prgn>postinst</prgn> script
6793 <example compact="compact">
6794 update-rc.d <var>package</var> defaults
6796 and in your <prgn>postrm</prgn>
6797 <example compact="compact">
6798 if [ "$1" = purge ]; then
6799 update-rc.d <var>package</var> remove
6801 </example>. Note that if your package changes runlevels
6802 or priority, you may have to remove and recreate the links,
6803 since otherwise the old links may persist. Refer to the
6804 documentation of <prgn>update-rc.d</prgn>.
6808 This will use a default sequence number of 20. If it does
6809 not matter when or in which order the <file>init.d</file>
6810 script is run, use this default. If it does, then you
6811 should talk to the maintainer of the <prgn>sysvinit</prgn>
6812 package or post to <tt>debian-devel</tt>, and they will
6813 help you choose a number.
6817 For more information about using <tt>update-rc.d</tt>,
6818 please consult its man page <manref name="update-rc.d"
6824 <heading>Running initscripts</heading>
6826 The program <prgn>invoke-rc.d</prgn> is provided to make
6827 it easier for package maintainers to properly invoke an
6828 initscript, obeying runlevel and other locally-defined
6829 constraints that might limit a package's right to start,
6830 stop and otherwise manage services. This program may be
6831 used by maintainers in their packages' scripts.
6835 The package maintainer scripts must use
6836 <prgn>invoke-rc.d</prgn> to invoke the
6837 <file>/etc/init.d/*</file> initscripts, instead of
6838 calling them directly.
6842 By default, <prgn>invoke-rc.d</prgn> will pass any
6843 action requests (start, stop, reload, restart...) to the
6844 <file>/etc/init.d</file> script, filtering out requests
6845 to start or restart a service out of its intended
6850 Most packages will simply need to change:
6851 <example compact="compact">/etc/init.d/<package>
6852 <action></example> in their <prgn>postinst</prgn>
6853 and <prgn>prerm</prgn> scripts to:
6854 <example compact="compact">
6855 if which invoke-rc.d >/dev/null 2>&1; then
6856 invoke-rc.d <var>package</var> <action>
6858 /etc/init.d/<var>package</var> <action>
6864 A package should register its initscript services using
6865 <prgn>update-rc.d</prgn> before it tries to invoke them
6866 using <prgn>invoke-rc.d</prgn>. Invocation of
6867 unregistered services may fail.
6871 For more information about using
6872 <prgn>invoke-rc.d</prgn>, please consult its man page
6873 <manref name="invoke-rc.d" section="8">.
6879 <heading>Boot-time initialization</heading>
6882 There used to be another directory, <file>/etc/rc.boot</file>,
6883 which contained scripts which were run once per machine
6884 boot. This has been deprecated in favour of links from
6885 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6886 described in <ref id="/etc/init.d">. Packages must not
6887 place files in <file>/etc/rc.boot</file>.
6892 <heading>Example</heading>
6895 An example on which you can base your
6896 <file>/etc/init.d</file> scripts is found in
6897 <file>/etc/init.d/skeleton</file>.
6904 <heading>Console messages from <file>init.d</file> scripts</heading>
6907 This section describes the formats to be used for messages
6908 written to standard output by the <file>/etc/init.d</file>
6909 scripts. The intent is to improve the consistency of
6910 Debian's startup and shutdown look and feel. For this
6911 reason, please look very carefully at the details. We want
6912 the messages to have the same format in terms of wording,
6913 spaces, punctuation and case of letters.
6917 Here is a list of overall rules that should be used for
6918 messages generated by <file>/etc/init.d</file> scripts.
6924 The message should fit in one line (fewer than 80
6925 characters), start with a capital letter and end with
6926 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6930 If the script is performing some time consuming task in
6931 the background (not merely starting or stopping a
6932 program, for instance), an ellipsis (three dots:
6933 <tt>...</tt>) should be output to the screen, with no
6934 leading or tailing whitespace or line feeds.
6938 The messages should appear as if the computer is telling
6939 the user what it is doing (politely :-), but should not
6940 mention "it" directly. For example, instead of:
6941 <example compact="compact">
6942 I'm starting network daemons: nfsd mountd.
6944 the message should say
6945 <example compact="compact">
6946 Starting network daemons: nfsd mountd.
6953 <tt>init.d</tt> script should use the following standard
6954 message formats for the situations enumerated below.
6960 <p>When daemons are started</p>
6963 If the script starts one or more daemons, the output
6964 should look like this (a single line, no leading
6966 <example compact="compact">
6967 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6969 The <var>description</var> should describe the
6970 subsystem the daemon or set of daemons are part of,
6971 while <var>daemon-1</var> up to <var>daemon-n</var>
6972 denote each daemon's name (typically the file name of
6977 For example, the output of <file>/etc/init.d/lpd</file>
6979 <example compact="compact">
6980 Starting printer spooler: lpd.
6985 This can be achieved by saying
6986 <example compact="compact">
6987 echo -n "Starting printer spooler: lpd"
6988 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6991 in the script. If there are more than one daemon to
6992 start, the output should look like this:
6993 <example compact="compact">
6994 echo -n "Starting remote file system services:"
6995 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6996 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6997 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7000 This makes it possible for the user to see what is
7001 happening and when the final daemon has been started.
7002 Care should be taken in the placement of white spaces:
7003 in the example above the system administrators can
7004 easily comment out a line if they don't want to start
7005 a specific daemon, while the displayed message still
7011 <p>When a system parameter is being set</p>
7014 If you have to set up different system parameters
7015 during the system boot, you should use this format:
7016 <example compact="compact">
7017 Setting <var>parameter</var> to "<var>value</var>".
7022 You can use a statement such as the following to get
7024 <example compact="compact">
7025 echo "Setting DNS domainname to \"$domainname\"."
7030 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7031 for the left and right quotation marks. A grave accent
7032 (<tt>`</tt>) is not a quote character; neither is an
7033 apostrophe (<tt>'</tt>).
7038 <p>When a daemon is stopped or restarted</p>
7041 When you stop or restart a daemon, you should issue a
7042 message identical to the startup message, except that
7043 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7044 or <tt>Restarting</tt> respectively.
7048 For example, stopping the printer daemon will look like
7050 <example compact="compact">
7051 Stopping printer spooler: lpd.
7057 <p>When something is executed</p>
7060 There are several examples where you have to run a
7061 program at system startup or shutdown to perform a
7062 specific task, for example, setting the system's clock
7063 using <prgn>netdate</prgn> or killing all processes
7064 when the system shuts down. Your message should look
7066 <example compact="compact">
7067 Doing something very useful...done.
7069 You should print the <tt>done.</tt> immediately after
7070 the job has been completed, so that the user is
7071 informed why they have to wait. You can get this
7073 <example compact="compact">
7074 echo -n "Doing something very useful..."
7083 <p>When the configuration is reloaded</p>
7086 When a daemon is forced to reload its configuration
7087 files you should use the following format:
7088 <example compact="compact">
7089 Reloading <var>description</var> configuration...done.
7091 where <var>description</var> is the same as in the
7092 daemon starting message.
7100 <heading>Cron jobs</heading>
7103 Packages must not modify the configuration file
7104 <file>/etc/crontab</file>, and they must not modify the files in
7105 <file>/var/spool/cron/crontabs</file>.</p>
7108 If a package wants to install a job that has to be executed
7109 via cron, it should place a file with the name of the
7110 package in one or more of the following directories:
7111 <example compact="compact">
7117 As these directory names imply, the files within them are
7118 executed on an hourly, daily, weekly, or monthly basis,
7119 respectively. The exact times are listed in
7120 <file>/etc/crontab</file>.</p>
7123 All files installed in any of these directories must be
7124 scripts (e.g., shell scripts or Perl scripts) so that they
7125 can easily be modified by the local system administrator.
7126 In addition, they must be treated as configuration files.
7130 If a certain job has to be executed at some other frequency or
7131 at a specific time, the package should install a file
7132 <file>/etc/cron.d/<var>package</var></file>. This file uses the
7133 same syntax as <file>/etc/crontab</file> and is processed by
7134 <prgn>cron</prgn> automatically. The file must also be
7135 treated as a configuration file. (Note that entries in the
7136 <file>/etc/cron.d</file> directory are not handled by
7137 <prgn>anacron</prgn>. Thus, you should only use this
7138 directory for jobs which may be skipped if the system is not
7141 Unlike <file>crontab</file> files described in the IEEE Std
7142 1003.1-2008 (POSIX.1) available from
7143 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7144 name="The Open Group">, the files in
7145 <file>/etc/cron.d</file> and the file
7146 <file>/etc/crontab</file> have seven fields; namely:
7148 <item>Minute [0,59]</item>
7149 <item>Hour [0,23]</item>
7150 <item>Day of the month [1,31]</item>
7151 <item>Month of the year [1,12]</item>
7152 <item>Day of the week ([0,6] with 0=Sunday)</item>
7153 <item>Username</item>
7154 <item>Command to be run</item>
7156 Ranges of numbers are allowed. Ranges are two numbers
7157 separated with a hyphen. The specified range is inclusive.
7158 Lists are allowed. A list is a set of numbers (or ranges)
7159 separated by commas. Step values can be used in conjunction
7164 The scripts or <tt>crontab</tt> entries in these directories should
7165 check if all necessary programs are installed before they
7166 try to execute them. Otherwise, problems will arise when a
7167 package was removed but not purged since configuration files
7168 are kept on the system in this situation.
7172 Any <tt>cron</tt> daemon must provide
7173 <file>/usr/bin/crontab</file> and support normal
7174 <tt>crontab</tt> entries as specified in POSIX. The daemon
7175 must also support names for days and months, ranges, and
7176 step values. It has to support <file>/etc/crontab</file>,
7177 and correctly execute the scripts in
7178 <file>/etc/cron.d</file>. The daemon must also correctly
7180 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7185 <heading>Menus</heading>
7188 The Debian <tt>menu</tt> package provides a standard
7189 interface between packages providing applications and
7190 <em>menu programs</em> (either X window managers or
7191 text-based menu programs such as <prgn>pdmenu</prgn>).
7195 All packages that provide applications that need not be
7196 passed any special command line arguments for normal
7197 operation should register a menu entry for those
7198 applications, so that users of the <tt>menu</tt> package
7199 will automatically get menu entries in their window
7200 managers, as well in shells like <tt>pdmenu</tt>.
7204 Menu entries should follow the current menu policy.
7208 The menu policy can be found in the <tt>menu-policy</tt>
7209 files in the <tt>debian-policy</tt> package.
7210 It is also available from the Debian web mirrors at
7211 <tt><url name="/doc/packaging-manuals/menu-policy/"
7212 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7216 Please also refer to the <em>Debian Menu System</em>
7217 documentation that comes with the <package>menu</package>
7218 package for information about how to register your
7224 <heading>Multimedia handlers</heading>
7227 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7228 is a mechanism for encoding files and data streams and
7229 providing meta-information about them, in particular their
7230 type (e.g. audio or video) and format (e.g. PNG, HTML,
7235 Registration of MIME type handlers allows programs like mail
7236 user agents and web browsers to invoke these handlers to
7237 view, edit or display MIME types they don't support directly.
7241 Packages which provide the ability to view/show/play,
7242 compose, edit or print MIME types should register themselves
7243 as such following the current MIME support policy.
7247 The MIME support policy can be found in the <tt>mime-policy</tt>
7248 files in the <tt>debian-policy</tt> package.
7249 It is also available from the Debian web mirrors at
7250 <tt><url name="/doc/packaging-manuals/mime-policy/"
7251 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7257 <heading>Keyboard configuration</heading>
7260 To achieve a consistent keyboard configuration so that all
7261 applications interpret a keyboard event the same way, all
7262 programs in the Debian distribution must be configured to
7263 comply with the following guidelines.
7267 The following keys must have the specified interpretations:
7270 <tag><tt><--</tt></tag>
7271 <item>delete the character to the left of the cursor</item>
7273 <tag><tt>Delete</tt></tag>
7274 <item>delete the character to the right of the cursor</item>
7276 <tag><tt>Control+H</tt></tag>
7277 <item>emacs: the help prefix</item>
7280 The interpretation of any keyboard events should be
7281 independent of the terminal that is used, be it a virtual
7282 console, an X terminal emulator, an rlogin/telnet session,
7287 The following list explains how the different programs
7288 should be set up to achieve this:
7294 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7298 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7302 X translations are set up to make
7303 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7304 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7305 is the vt220 escape code for the "delete character"
7306 key). This must be done by loading the X resources
7307 using <prgn>xrdb</prgn> on all local X displays, not
7308 using the application defaults, so that the
7309 translation resources used correspond to the
7310 <prgn>xmodmap</prgn> settings.
7314 The Linux console is configured to make
7315 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7316 generate <tt>ESC [ 3 ~</tt>.
7320 X applications are configured so that <tt><</tt>
7321 deletes left, and <tt>Delete</tt> deletes right. Motif
7322 applications already work like this.
7326 Terminals should have <tt>stty erase ^?</tt> .
7330 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7331 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7332 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7336 Emacs is programmed to map <tt>KB_Backspace</tt> or
7337 the <tt>stty erase</tt> character to
7338 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7339 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7340 <tt>^H</tt> to <tt>help</tt> as always.
7344 Other applications use the <tt>stty erase</tt>
7345 character and <tt>kdch1</tt> for the two delete keys,
7346 with ASCII DEL being "delete previous character" and
7347 <tt>kdch1</tt> being "delete character under
7355 This will solve the problem except for the following
7362 Some terminals have a <tt><--</tt> key that cannot
7363 be made to produce anything except <tt>^H</tt>. On
7364 these terminals Emacs help will be unavailable on
7365 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7366 character takes precedence in Emacs, and has been set
7367 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7368 available) can be used instead.
7372 Some operating systems use <tt>^H</tt> for <tt>stty
7373 erase</tt>. However, modern telnet versions and all
7374 rlogin versions propagate <tt>stty</tt> settings, and
7375 almost all UNIX versions honour <tt>stty erase</tt>.
7376 Where the <tt>stty</tt> settings are not propagated
7377 correctly, things can be made to work by using
7378 <tt>stty</tt> manually.
7382 Some systems (including previous Debian versions) use
7383 <prgn>xmodmap</prgn> to arrange for both
7384 <tt><--</tt> and <tt>Delete</tt> to generate
7385 <tt>KB_Delete</tt>. We can change the behavior of
7386 their X clients using the same X resources that we use
7387 to do it for our own clients, or configure our clients
7388 using their resources when things are the other way
7389 around. On displays configured like this
7390 <tt>Delete</tt> will not work, but <tt><--</tt>
7395 Some operating systems have different <tt>kdch1</tt>
7396 settings in their <tt>terminfo</tt> database for
7397 <tt>xterm</tt> and others. On these systems the
7398 <tt>Delete</tt> key will not work correctly when you
7399 log in from a system conforming to our policy, but
7400 <tt><--</tt> will.
7407 <heading>Environment variables</heading>
7410 A program must not depend on environment variables to get
7411 reasonable defaults. (That's because these environment
7412 variables would have to be set in a system-wide
7413 configuration file like <file>/etc/profile</file>, which is not
7414 supported by all shells.)
7418 If a program usually depends on environment variables for its
7419 configuration, the program should be changed to fall back to
7420 a reasonable default configuration if these environment
7421 variables are not present. If this cannot be done easily
7422 (e.g., if the source code of a non-free program is not
7423 available), the program must be replaced by a small
7424 "wrapper" shell script which sets the environment variables
7425 if they are not already defined, and calls the original program.
7429 Here is an example of a wrapper script for this purpose:
7431 <example compact="compact">
7433 BAR=${BAR:-/var/lib/fubar}
7435 exec /usr/lib/foo/foo "$@"
7440 Furthermore, as <file>/etc/profile</file> is a configuration
7441 file of the <prgn>base-files</prgn> package, other packages must
7442 not put any environment variables or other commands into that
7447 <sect id="doc-base">
7448 <heading>Registering Documents using doc-base</heading>
7451 The <package>doc-base</package> package implements a
7452 flexible mechanism for handling and presenting
7453 documentation. The recommended practice is for every Debian
7454 package that provides online documentation (other than just
7455 manual pages) to register these documents with
7456 <package>doc-base</package> by installing a
7457 <package>doc-base</package> control file via the
7458 <prgn/install-docs/ script at installation time and
7459 de-register the manuals again when the package is removed.
7462 Please refer to the documentation that comes with the
7463 <package>doc-base</package> package for information and
7472 <heading>Files</heading>
7474 <sect id="binaries">
7475 <heading>Binaries</heading>
7478 Two different packages must not install programs with
7479 different functionality but with the same filenames. (The
7480 case of two programs having the same functionality but
7481 different implementations is handled via "alternatives" or
7482 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7483 <ref id="conflicts"> respectively.) If this case happens,
7484 one of the programs must be renamed. The maintainers should
7485 report this to the <tt>debian-devel</tt> mailing list and
7486 try to find a consensus about which program will have to be
7487 renamed. If a consensus cannot be reached, <em>both</em>
7488 programs must be renamed.
7492 By default, when a package is being built, any binaries
7493 created should include debugging information, as well as
7494 being compiled with optimization. You should also turn on
7495 as many reasonable compilation warnings as possible; this
7496 makes life easier for porters, who can then look at build
7497 logs for possible problems. For the C programming language,
7498 this means the following compilation parameters should be
7500 <example compact="compact">
7502 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7504 INSTALL = install -s # (or use strip on the files in debian/tmp)
7509 Note that by default all installed binaries should be stripped,
7510 either by using the <tt>-s</tt> flag to
7511 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7512 the binaries after they have been copied into
7513 <file>debian/tmp</file> but before the tree is made into a
7518 Although binaries in the build tree should be compiled with
7519 debugging information by default, it can often be difficult to
7520 debug programs if they are also subjected to compiler
7521 optimization. For this reason, it is recommended to support the
7522 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7523 (see <ref id="debianrules-options">). This variable can contain
7524 several flags to change how a package is compiled and built.
7528 It is up to the package maintainer to decide what
7529 compilation options are best for the package. Certain
7530 binaries (such as computationally-intensive programs) will
7531 function better with certain flags (<tt>-O3</tt>, for
7532 example); feel free to use them. Please use good judgment
7533 here. Don't use flags for the sake of it; only use them
7534 if there is good reason to do so. Feel free to override
7535 the upstream author's ideas about which compilation
7536 options are best: they are often inappropriate for our
7542 <sect id="libraries">
7543 <heading>Libraries</heading>
7546 If the package is <strong>architecture: any</strong>, then
7547 the shared library compilation and linking flags must have
7548 <tt>-fPIC</tt>, or the package shall not build on some of
7549 the supported architectures<footnote>
7551 If you are using GCC, <tt>-fPIC</tt> produces code with
7552 relocatable position independent code, which is required for
7553 most architectures to create a shared library, with i386 and
7554 perhaps some others where non position independent code is
7555 permitted in a shared library.
7558 Position independent code may have a performance penalty,
7559 especially on <tt>i386</tt>. However, in most cases the
7560 speed penalty must be measured against the memory wasted on
7561 the few architectures where non position independent code is
7564 </footnote>. Any exception to this rule must be discussed on
7565 the mailing list <em>debian-devel@lists.debian.org</em>, and
7566 a rough consensus obtained. The reasons for not compiling
7567 with <tt>-fPIC</tt> flag must be recorded in the file
7568 <tt>README.Debian</tt>, and care must be taken to either
7569 restrict the architecture or arrange for <tt>-fPIC</tt> to
7570 be used on architectures where it is required.<footnote>
7572 Some of the reasons why this might be required is if the
7573 library contains hand crafted assembly code that is not
7574 relocatable, the speed penalty is excessive for compute
7575 intensive libs, and similar reasons.
7580 As to the static libraries, the common case is not to have
7581 relocatable code, since there is no benefit, unless in specific
7582 cases; therefore the static version must not be compiled
7583 with the <tt>-fPIC</tt> flag. Any exception to this rule
7584 should be discussed on the mailing list
7585 <em>debian-devel@lists.debian.org</em>, and the reasons for
7586 compiling with the <tt>-fPIC</tt> flag must be recorded in
7587 the file <tt>README.Debian</tt>. <footnote>
7589 Some of the reasons for linking static libraries with
7590 the <tt>-fPIC</tt> flag are if, for example, one needs a
7591 Perl API for a library that is under rapid development,
7592 and has an unstable API, so shared libraries are
7593 pointless at this phase of the library's development. In
7594 that case, since Perl needs a library with relocatable
7595 code, it may make sense to create a static library with
7596 relocatable code. Another reason cited is if you are
7597 distilling various libraries into a common shared
7598 library, like <tt>mklibs</tt> does in the Debian
7604 In other words, if both a shared and a static library is
7605 being built, each source unit (<tt>*.c</tt>, for example,
7606 for C files) will need to be compiled twice, for the normal
7611 Libraries should be built with threading support and to be
7612 thread-safe if the library supports this.
7616 Although not enforced by the build tools, shared libraries
7617 must be linked against all libraries that they use symbols from
7618 in the same way that binaries are. This ensures the correct
7619 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7620 system and guarantees that all libraries can be safely opened
7621 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7622 option <tt>-Wl,-z,defs</tt> when building a shared library.
7623 Since this option enforces symbol resolution at build time,
7624 a missing library reference will be caught early as a fatal
7629 All installed shared libraries should be stripped with
7630 <example compact="compact">
7631 strip --strip-unneeded <var>your-lib</var>
7633 (The option <tt>--strip-unneeded</tt> makes
7634 <prgn>strip</prgn> remove only the symbols which aren't
7635 needed for relocation processing.) Shared libraries can
7636 function perfectly well when stripped, since the symbols for
7637 dynamic linking are in a separate part of the ELF object
7639 You might also want to use the options
7640 <tt>--remove-section=.comment</tt> and
7641 <tt>--remove-section=.note</tt> on both shared libraries
7642 and executables, and <tt>--strip-debug</tt> on static
7648 Note that under some circumstances it may be useful to
7649 install a shared library unstripped, for example when
7650 building a separate package to support debugging.
7654 Shared object files (often <file>.so</file> files) that are not
7655 public libraries, that is, they are not meant to be linked
7656 to by third party executables (binaries of other packages),
7657 should be installed in subdirectories of the
7658 <file>/usr/lib</file> directory. Such files are exempt from the
7659 rules that govern ordinary shared libraries, except that
7660 they must not be installed executable and should be
7662 A common example are the so-called "plug-ins",
7663 internal shared objects that are dynamically loaded by
7664 programs using <manref name="dlopen" section="3">.
7669 Packages that use <prgn>libtool</prgn> to create and install
7670 their shared libraries install a file containing additional
7671 metadata (ending in <file>.la</file>) alongside the library.
7672 For public libraries intended for use by other packages, these
7673 files normally should not be included in the Debian package,
7674 since the information they include is not necessary to link with
7675 the shared library on Debian and can add unnecessary additional
7676 dependencies to other programs or libraries.<footnote>
7677 These files store, among other things, all libraries on which
7678 that shared library depends. Unfortunately, if
7679 the <file>.la</file> file is present and contains that
7680 dependency information, using <prgn>libtool</prgn> when
7681 linking against that library will cause the resulting program
7682 or library to be linked against those dependencies as well,
7683 even if this is unnecessary. This can create unneeded
7684 dependencies on shared library packages that would otherwise
7685 be hidden behind the library ABI, and can make library
7686 transitions to new SONAMEs unnecessarily complicated and
7687 difficult to manage.
7689 If the <file>.la</file> file is required for that library (if,
7690 for instance, it's loaded via <tt>libltdl</tt> in a way that
7691 requires that meta-information), the <tt>dependency_libs</tt>
7692 setting in the <file>.la</file> file should normally be set to
7693 the empty string. If the shared library development package has
7694 historically included the <file>.la</file>, it must be retained
7695 in the development package (with <tt>dependency_libs</tt>
7696 emptied) until all libraries that depend on it have removed or
7697 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7698 files to prevent linking with those other libraries
7699 using <prgn>libtool</prgn> from failing.
7703 If the <file>.la</file> must be included, it should be included
7704 in the development (<tt>-dev</tt>) package, unless the library
7705 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7706 library. If it is intended for use with <tt>libltdl</tt>,
7707 the <file>.la</file> files must go in the run-time library
7712 These requirements for handling of <file>.la</file> files do not
7713 apply to loadable modules or libraries not installed in
7714 directories searched by default by the dynamic linker. Packages
7715 installing loadable modules will frequently need to install
7716 the <file>.la</file> files alongside the modules so that they
7717 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7718 does not need to be modified for libraries or modules that are
7719 not installed in directories searched by the dynamic linker by
7720 default and not intended for use by other packages.
7724 You must make sure that you use only released versions of
7725 shared libraries to build your packages; otherwise other
7726 users will not be able to run your binaries
7727 properly. Producing source packages that depend on
7728 unreleased compilers is also usually a bad
7735 <heading>Shared libraries</heading>
7737 This section has moved to <ref id="sharedlibs">.
7743 <heading>Scripts</heading>
7746 All command scripts, including the package maintainer
7747 scripts inside the package and used by <prgn>dpkg</prgn>,
7748 should have a <tt>#!</tt> line naming the shell to be used
7753 In the case of Perl scripts this should be
7754 <tt>#!/usr/bin/perl</tt>.
7758 When scripts are installed into a directory in the system
7759 PATH, the script name should not include an extension such
7760 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7761 language currently used to implement it.
7764 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7765 <file>init.d</file> scripts should almost certainly start
7766 with <tt>set -e</tt> so that errors are detected.
7767 <file>init.d</file> scripts are something of a special case, due
7768 to how frequently they need to call commands that are allowed to
7769 fail, and it may instead be easier to check the exit status of
7770 commands directly. See <ref id="writing-init"> for more
7771 information about writing <file>init.d</file> scripts.
7774 Every script should use <tt>set -e</tt> or check the exit status
7775 of <em>every</em> command.
7778 Scripts may assume that <file>/bin/sh</file> implements the
7779 SUSv3 Shell Command Language<footnote>
7780 Single UNIX Specification, version 3, which is also IEEE
7781 1003.1-2004 (POSIX), and is available on the World Wide Web
7782 from <url id="http://www.unix.org/version3/online.html"
7783 name="The Open Group"> after free
7784 registration.</footnote>
7785 plus the following additional features not mandated by
7787 These features are in widespread use in the Linux community
7788 and are implemented in all of bash, dash, and ksh, the most
7789 common shells users may wish to use as <file>/bin/sh</file>.
7792 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7793 must not generate a newline.</item>
7794 <item><tt>test</tt>, if implemented as a shell built-in, must
7795 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7797 <item><tt>local</tt> to create a scoped variable must be
7798 supported, including listing multiple variables in a single
7799 local command and assigning a value to a variable at the
7800 same time as localizing it. <tt>local</tt> may or
7801 may not preserve the variable value from an outer scope if
7802 no assignment is present. Uses such as:
7806 # ... use a, b, c, d ...
7809 must be supported and must set the value of <tt>c</tt> to
7812 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7813 -<var>signal</var></tt>, where <var>signal</var> is either
7814 the name of a signal or one of the numeric signals listed in
7815 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7816 supported if <prgn>kill</prgn> is implemented as a shell
7819 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7820 signals must be supported. In addition to the signal
7821 numbers listed in the extension, which are the same as for
7822 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7825 If a shell script requires non-SUSv3 features from the shell
7826 interpreter other than those listed above, the appropriate shell
7827 must be specified in the first line of the script (e.g.,
7828 <tt>#!/bin/bash</tt>) and the package must depend on the package
7829 providing the shell (unless the shell package is marked
7830 "Essential", as in the case of <prgn>bash</prgn>).
7834 You may wish to restrict your script to SUSv3 features plus the
7835 above set when possible so that it may use <file>/bin/sh</file>
7836 as its interpreter. If your script works with <prgn>dash</prgn>
7837 (originally called <prgn>ash</prgn>), it probably complies with
7838 the above requirements, but if you are in doubt, use
7839 <file>/bin/bash</file>.
7843 Perl scripts should check for errors when making any
7844 system calls, including <tt>open</tt>, <tt>print</tt>,
7845 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7849 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7850 scripting languages. See <em>Csh Programming Considered
7851 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7852 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7853 If an upstream package comes with <prgn>csh</prgn> scripts
7854 then you must make sure that they start with
7855 <tt>#!/bin/csh</tt> and make your package depend on the
7856 <prgn>c-shell</prgn> virtual package.
7860 Any scripts which create files in world-writeable
7861 directories (e.g., in <file>/tmp</file>) must use a
7862 mechanism which will fail atomically if a file with the same
7863 name already exists.
7867 The Debian base system provides the <prgn>tempfile</prgn>
7868 and <prgn>mktemp</prgn> utilities for use by scripts for
7875 <heading>Symbolic links</heading>
7878 In general, symbolic links within a top-level directory
7879 should be relative, and symbolic links pointing from one
7880 top-level directory into another should be absolute. (A
7881 top-level directory is a sub-directory of the root
7882 directory <file>/</file>.)
7886 In addition, symbolic links should be specified as short as
7887 possible, i.e., link targets like <file>foo/../bar</file> are
7892 Note that when creating a relative link using
7893 <prgn>ln</prgn> it is not necessary for the target of the
7894 link to exist relative to the working directory you're
7895 running <prgn>ln</prgn> from, nor is it necessary to change
7896 directory to the directory where the link is to be made.
7897 Simply include the string that should appear as the target
7898 of the link (this will be a pathname relative to the
7899 directory in which the link resides) as the first argument
7904 For example, in your <prgn>Makefile</prgn> or
7905 <file>debian/rules</file>, you can do things like:
7906 <example compact="compact">
7907 ln -fs gcc $(prefix)/bin/cc
7908 ln -fs gcc debian/tmp/usr/bin/cc
7909 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7910 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7915 A symbolic link pointing to a compressed file should always
7916 have the same file extension as the referenced file. (For
7917 example, if a file <file>foo.gz</file> is referenced by a
7918 symbolic link, the filename of the link has to end with
7919 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7924 <heading>Device files</heading>
7927 Packages must not include device files or named pipes in the
7932 If a package needs any special device files that are not
7933 included in the base system, it must call
7934 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7935 after notifying the user<footnote>
7936 This notification could be done via a (low-priority)
7937 debconf message, or an echo (printf) statement.
7942 Packages must not remove any device files in the
7943 <prgn>postrm</prgn> or any other script. This is left to the
7944 system administrator.
7948 Debian uses the serial devices
7949 <file>/dev/ttyS*</file>. Programs using the old
7950 <file>/dev/cu*</file> devices should be changed to use
7951 <file>/dev/ttyS*</file>.
7955 Named pipes needed by the package must be created in
7956 the <prgn>postinst</prgn> script<footnote>
7957 It's better to use <prgn>mkfifo</prgn> rather
7958 than <prgn>mknod</prgn> to create named pipes so that
7959 automated checks for packages incorrectly creating device
7960 files with <prgn>mknod</prgn> won't have false positives.
7961 </footnote> and removed in
7962 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7967 <sect id="config-files">
7968 <heading>Configuration files</heading>
7971 <heading>Definitions</heading>
7975 <tag>configuration file</tag>
7977 A file that affects the operation of a program, or
7978 provides site- or host-specific information, or
7979 otherwise customizes the behavior of a program.
7980 Typically, configuration files are intended to be
7981 modified by the system administrator (if needed or
7982 desired) to conform to local policy or to provide
7983 more useful site-specific behavior.
7986 <tag><tt>conffile</tt></tag>
7988 A file listed in a package's <tt>conffiles</tt>
7989 file, and is treated specially by <prgn>dpkg</prgn>
7990 (see <ref id="configdetails">).
7996 The distinction between these two is important; they are
7997 not interchangeable concepts. Almost all
7998 <tt>conffile</tt>s are configuration files, but many
7999 configuration files are not <tt>conffiles</tt>.
8003 As noted elsewhere, <file>/etc/init.d</file> scripts,
8004 <file>/etc/default</file> files, scripts installed in
8005 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8006 configuration installed in <file>/etc/cron.d</file> must be
8007 treated as configuration files. In general, any script that
8008 embeds configuration information is de-facto a configuration
8009 file and should be treated as such.
8014 <heading>Location</heading>
8017 Any configuration files created or used by your package
8018 must reside in <file>/etc</file>. If there are several,
8019 consider creating a subdirectory of <file>/etc</file>
8020 named after your package.
8024 If your package creates or uses configuration files
8025 outside of <file>/etc</file>, and it is not feasible to modify
8026 the package to use <file>/etc</file> directly, put the files
8027 in <file>/etc</file> and create symbolic links to those files
8028 from the location that the package requires.
8033 <heading>Behavior</heading>
8036 Configuration file handling must conform to the following
8038 <list compact="compact">
8040 local changes must be preserved during a package
8044 configuration files must be preserved when the
8045 package is removed, and only deleted when the
8049 Obsolete configuration files without local changes may be
8050 removed by the package during upgrade.
8054 The easy way to achieve this behavior is to make the
8055 configuration file a <tt>conffile</tt>. This is
8056 appropriate only if it is possible to distribute a default
8057 version that will work for most installations, although
8058 some system administrators may choose to modify it. This
8059 implies that the default version will be part of the
8060 package distribution, and must not be modified by the
8061 maintainer scripts during installation (or at any other
8066 In order to ensure that local changes are preserved
8067 correctly, no package may contain or make hard links to
8068 conffiles.<footnote>
8069 Rationale: There are two problems with hard links.
8070 The first is that some editors break the link while
8071 editing one of the files, so that the two files may
8072 unwittingly become unlinked and different. The second
8073 is that <prgn>dpkg</prgn> might break the hard link
8074 while upgrading <tt>conffile</tt>s.
8079 The other way to do it is via the maintainer scripts. In
8080 this case, the configuration file must not be listed as a
8081 <tt>conffile</tt> and must not be part of the package
8082 distribution. If the existence of a file is required for
8083 the package to be sensibly configured it is the
8084 responsibility of the package maintainer to provide
8085 maintainer scripts which correctly create, update and
8086 maintain the file and remove it on purge. (See <ref
8087 id="maintainerscripts"> for more information.) These
8088 scripts must be idempotent (i.e., must work correctly if
8089 <prgn>dpkg</prgn> needs to re-run them due to errors
8090 during installation or removal), must cope with all the
8091 variety of ways <prgn>dpkg</prgn> can call maintainer
8092 scripts, must not overwrite or otherwise mangle the user's
8093 configuration without asking, must not ask unnecessary
8094 questions (particularly during upgrades), and must
8095 otherwise be good citizens.
8099 The scripts are not required to configure every possible
8100 option for the package, but only those necessary to get
8101 the package running on a given system. Ideally the
8102 sysadmin should not have to do any configuration other
8103 than that done (semi-)automatically by the
8104 <prgn>postinst</prgn> script.
8108 A common practice is to create a script called
8109 <file><var>package</var>-configure</file> and have the
8110 package's <prgn>postinst</prgn> call it if and only if the
8111 configuration file does not already exist. In certain
8112 cases it is useful for there to be an example or template
8113 file which the maintainer scripts use. Such files should
8114 be in <file>/usr/share/<var>package</var></file> or
8115 <file>/usr/lib/<var>package</var></file> (depending on whether
8116 they are architecture-independent or not). There should
8117 be symbolic links to them from
8118 <file>/usr/share/doc/<var>package</var>/examples</file> if
8119 they are examples, and should be perfectly ordinary
8120 <prgn>dpkg</prgn>-handled files (<em>not</em>
8121 configuration files).
8125 These two styles of configuration file handling must
8126 not be mixed, for that way lies madness:
8127 <prgn>dpkg</prgn> will ask about overwriting the file
8128 every time the package is upgraded.
8133 <heading>Sharing configuration files</heading>
8136 Packages which specify the same file as a
8137 <tt>conffile</tt> must be tagged as <em>conflicting</em>
8138 with each other. (This is an instance of the general rule
8139 about not sharing files. Note that neither alternatives
8140 nor diversions are likely to be appropriate in this case;
8141 in particular, <prgn>dpkg</prgn> does not handle diverted
8142 <tt>conffile</tt>s well.)
8146 The maintainer scripts must not alter a <tt>conffile</tt>
8147 of <em>any</em> package, including the one the scripts
8152 If two or more packages use the same configuration file
8153 and it is reasonable for both to be installed at the same
8154 time, one of these packages must be defined as
8155 <em>owner</em> of the configuration file, i.e., it will be
8156 the package which handles that file as a configuration
8157 file. Other packages that use the configuration file must
8158 depend on the owning package if they require the
8159 configuration file to operate. If the other package will
8160 use the configuration file if present, but is capable of
8161 operating without it, no dependency need be declared.
8165 If it is desirable for two or more related packages to
8166 share a configuration file <em>and</em> for all of the
8167 related packages to be able to modify that configuration
8168 file, then the following should be done:
8169 <enumlist compact="compact">
8171 One of the related packages (the "owning" package)
8172 will manage the configuration file with maintainer
8173 scripts as described in the previous section.
8176 The owning package should also provide a program
8177 that the other packages may use to modify the
8181 The related packages must use the provided program
8182 to make any desired modifications to the
8183 configuration file. They should either depend on
8184 the core package to guarantee that the configuration
8185 modifier program is available or accept gracefully
8186 that they cannot modify the configuration file if it
8187 is not. (This is in addition to the fact that the
8188 configuration file may not even be present in the
8195 Sometimes it's appropriate to create a new package which
8196 provides the basic infrastructure for the other packages
8197 and which manages the shared configuration files. (The
8198 <tt>sgml-base</tt> package is a good example.)
8203 <heading>User configuration files ("dotfiles")</heading>
8206 The files in <file>/etc/skel</file> will automatically be
8207 copied into new user accounts by <prgn>adduser</prgn>.
8208 No other program should reference the files in
8209 <file>/etc/skel</file>.
8213 Therefore, if a program needs a dotfile to exist in
8214 advance in <file>$HOME</file> to work sensibly, that dotfile
8215 should be installed in <file>/etc/skel</file> and treated as a
8220 However, programs that require dotfiles in order to
8221 operate sensibly are a bad thing, unless they do create
8222 the dotfiles themselves automatically.
8226 Furthermore, programs should be configured by the Debian
8227 default installation to behave as closely to the upstream
8228 default behavior as possible.
8232 Therefore, if a program in a Debian package needs to be
8233 configured in some way in order to operate sensibly, that
8234 should be done using a site-wide configuration file placed
8235 in <file>/etc</file>. Only if the program doesn't support a
8236 site-wide default configuration and the package maintainer
8237 doesn't have time to add it may a default per-user file be
8238 placed in <file>/etc/skel</file>.
8242 <file>/etc/skel</file> should be as empty as we can make it.
8243 This is particularly true because there is no easy (or
8244 necessarily desirable) mechanism for ensuring that the
8245 appropriate dotfiles are copied into the accounts of
8246 existing users when a package is installed.
8252 <heading>Log files</heading>
8254 Log files should usually be named
8255 <file>/var/log/<var>package</var>.log</file>. If you have many
8256 log files, or need a separate directory for permission
8257 reasons (<file>/var/log</file> is writable only by
8258 <file>root</file>), you should usually create a directory named
8259 <file>/var/log/<var>package</var></file> and place your log
8264 Log files must be rotated occasionally so that they don't grow
8265 indefinitely. The best way to do this is to install a log
8266 rotation configuration file in the
8267 directory <file>/etc/logrotate.d</file>, normally
8268 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8269 the facilities provided by <prgn>logrotate</prgn>.
8272 The traditional approach to log files has been to set up
8273 <em>ad hoc</em> log rotation schemes using simple shell
8274 scripts and cron. While this approach is highly
8275 customizable, it requires quite a lot of sysadmin work.
8276 Even though the original Debian system helped a little
8277 by automatically installing a system which can be used
8278 as a template, this was deemed not enough.
8282 The use of <prgn>logrotate</prgn>, a program developed
8283 by Red Hat, is better, as it centralizes log management.
8284 It has both a configuration file
8285 (<file>/etc/logrotate.conf</file>) and a directory where
8286 packages can drop their individual log rotation
8287 configurations (<file>/etc/logrotate.d</file>).
8290 Here is a good example for a logrotate config
8291 file (for more information see <manref name="logrotate"
8293 <example compact="compact">
8294 /var/log/foo/*.log {
8300 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8304 This rotates all files under <file>/var/log/foo</file>, saves 12
8305 compressed generations, and tells the daemon to reopen its log
8306 files after the log rotation. It skips this log rotation
8307 (via <tt>missingok</tt>) if no such log file is present, which
8308 avoids errors if the package is removed but not purged.
8312 Log files should be removed when the package is
8313 purged (but not when it is only removed). This should be
8314 done by the <prgn>postrm</prgn> script when it is called
8315 with the argument <tt>purge</tt> (see <ref
8316 id="removedetails">).
8320 <sect id="permissions-owners">
8321 <heading>Permissions and owners</heading>
8324 The rules in this section are guidelines for general use.
8325 If necessary you may deviate from the details below.
8326 However, if you do so you must make sure that what is done
8327 is secure and you should try to be as consistent as possible
8328 with the rest of the system. You should probably also
8329 discuss it on <prgn>debian-devel</prgn> first.
8333 Files should be owned by <tt>root:root</tt>, and made
8334 writable only by the owner and universally readable (and
8335 executable, if appropriate), that is mode 644 or 755.
8339 Directories should be mode 755 or (for group-writability)
8340 mode 2775. The ownership of the directory should be
8341 consistent with its mode: if a directory is mode 2775, it
8342 should be owned by the group that needs write access to
8345 When a package is upgraded, and the owner or permissions
8346 of a file included in the package has changed, dpkg
8347 arranges for the ownership and permissions to be
8348 correctly set upon installation. However, this does not
8349 extend to directories; the permissions and ownership of
8350 directories already on the system does not change on
8351 install or upgrade of packages. This makes sense, since
8352 otherwise common directories like <tt>/usr</tt> would
8353 always be in flux. To correctly change permissions of a
8354 directory the package owns, explicit action is required,
8355 usually in the <tt>postinst</tt> script. Care must be
8356 taken to handle downgrades as well, in that case.
8362 Control information files should be owned by <tt>root:root</tt>
8363 and either mode 644 (for most files) or mode 755 (for
8364 executables such as <qref id="maintscripts">maintainer
8369 Setuid and setgid executables should be mode 4755 or 2755
8370 respectively, and owned by the appropriate user or group.
8371 They should not be made unreadable (modes like 4711 or
8372 2711 or even 4111); doing so achieves no extra security,
8373 because anyone can find the binary in the freely available
8374 Debian package; it is merely inconvenient. For the same
8375 reason you should not restrict read or execute permissions
8376 on non-set-id executables.
8380 Some setuid programs need to be restricted to particular
8381 sets of users, using file permissions. In this case they
8382 should be owned by the uid to which they are set-id, and by
8383 the group which should be allowed to execute them. They
8384 should have mode 4754; again there is no point in making
8385 them unreadable to those users who must not be allowed to
8390 It is possible to arrange that the system administrator can
8391 reconfigure the package to correspond to their local
8392 security policy by changing the permissions on a binary:
8393 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8394 described below.<footnote>
8395 Ordinary files installed by <prgn>dpkg</prgn> (as
8396 opposed to <tt>conffile</tt>s and other similar objects)
8397 normally have their permissions reset to the distributed
8398 permissions when the package is reinstalled. However,
8399 the use of <prgn>dpkg-statoverride</prgn> overrides this
8402 Another method you should consider is to create a group for
8403 people allowed to use the program(s) and make any setuid
8404 executables executable only by that group.
8408 If you need to create a new user or group for your package
8409 there are two possibilities. Firstly, you may need to
8410 make some files in the binary package be owned by this
8411 user or group, or you may need to compile the user or
8412 group id (rather than just the name) into the binary
8413 (though this latter should be avoided if possible, as in
8414 this case you need a statically allocated id).</p>
8417 If you need a statically allocated id, you must ask for a
8418 user or group id from the <tt>base-passwd</tt> maintainer,
8419 and must not release the package until you have been
8420 allocated one. Once you have been allocated one you must
8421 either make the package depend on a version of the
8422 <tt>base-passwd</tt> package with the id present in
8423 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8424 your package to create the user or group itself with the
8425 correct id (using <tt>adduser</tt>) in its
8426 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8427 the <prgn>postinst</prgn> is to be preferred if it is
8428 possible, otherwise a pre-dependency will be needed on the
8429 <tt>adduser</tt> package.)
8433 On the other hand, the program might be able to determine
8434 the uid or gid from the user or group name at runtime, so
8435 that a dynamically allocated id can be used. In this case
8436 you should choose an appropriate user or group name,
8437 discussing this on <prgn>debian-devel</prgn> and checking
8438 with the <package/base-passwd/ maintainer that it is unique and that
8439 they do not wish you to use a statically allocated id
8440 instead. When this has been checked you must arrange for
8441 your package to create the user or group if necessary using
8442 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8443 <prgn>postinst</prgn> script (again, the latter is to be
8444 preferred if it is possible).
8448 Note that changing the numeric value of an id associated
8449 with a name is very difficult, and involves searching the
8450 file system for all appropriate files. You need to think
8451 carefully whether a static or dynamic id is required, since
8452 changing your mind later will cause problems.
8455 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8457 This section is not intended as policy, but as a
8458 description of the use of <prgn>dpkg-statoverride</prgn>.
8462 If a system administrator wishes to have a file (or
8463 directory or other such thing) installed with owner and
8464 permissions different from those in the distributed Debian
8465 package, they can use the <prgn>dpkg-statoverride</prgn>
8466 program to instruct <prgn>dpkg</prgn> to use the different
8467 settings every time the file is installed. Thus the
8468 package maintainer should distribute the files with their
8469 normal permissions, and leave it for the system
8470 administrator to make any desired changes. For example, a
8471 daemon which is normally required to be setuid root, but
8472 in certain situations could be used without being setuid,
8473 should be installed setuid in the <tt>.deb</tt>. Then the
8474 local system administrator can change this if they wish.
8475 If there are two standard ways of doing it, the package
8476 maintainer can use <tt>debconf</tt> to find out the
8477 preference, and call <prgn>dpkg-statoverride</prgn> in the
8478 maintainer script if necessary to accommodate the system
8479 administrator's choice. Care must be taken during
8480 upgrades to not override an existing setting.
8484 Given the above, <prgn>dpkg-statoverride</prgn> is
8485 essentially a tool for system administrators and would not
8486 normally be needed in the maintainer scripts. There is
8487 one type of situation, though, where calls to
8488 <prgn>dpkg-statoverride</prgn> would be needed in the
8489 maintainer scripts, and that involves packages which use
8490 dynamically allocated user or group ids. In such a
8491 situation, something like the following idiom can be very
8492 helpful in the package's <prgn>postinst</prgn>, where
8493 <tt>sysuser</tt> is a dynamically allocated id:
8495 for i in /usr/bin/foo /usr/sbin/bar
8497 # only do something when no setting exists
8498 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8500 #include: debconf processing, question about foo and bar
8501 if [ "$RET" = "true" ] ; then
8502 dpkg-statoverride --update --add sysuser root 4755 $i
8507 The corresponding code to remove the override when the package
8510 for i in /usr/bin/foo /usr/sbin/bar
8512 if dpkg-statoverride --list $i >/dev/null 2>&1
8514 dpkg-statoverride --remove $i
8524 <chapt id="customized-programs">
8525 <heading>Customized programs</heading>
8527 <sect id="arch-spec">
8528 <heading>Architecture specification strings</heading>
8531 If a program needs to specify an <em>architecture specification
8532 string</em> in some place, it should select one of the strings
8533 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8534 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8535 part is sometimes elided, as when the OS is Linux.
8539 Note that we don't want to use
8540 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8541 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8542 since this would make our programs incompatible with other
8543 Linux distributions. We also don't use something like
8544 <tt><var>arch</var>-unknown-linux</tt>, since the
8545 <tt>unknown</tt> does not look very good.
8548 <sect1 id="arch-wildcard-spec">
8549 <heading>Architecture wildcards</heading>
8552 A package may specify an architecture wildcard. Architecture
8553 wildcards are in the format <tt>any</tt> (which matches every
8554 architecture), <tt><var>os</var></tt>-any, or
8555 any-<tt><var>cpu</var></tt>. <footnote>
8556 Internally, the package system normalizes the GNU triplets
8557 and the Debian arches into Debian arch triplets (which are
8558 kind of inverted GNU triplets), with the first component of
8559 the triplet representing the libc and ABI in use, and then
8560 does matching against those triplets. However, such
8561 triplets are an internal implementation detail that should
8562 not be used by packages directly. The libc and ABI portion
8563 is handled internally by the package system based on
8564 the <var>os</var> and <var>cpu</var>.
8571 <heading>Daemons</heading>
8574 The configuration files <file>/etc/services</file>,
8575 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8576 by the <prgn>netbase</prgn> package and must not be modified
8581 If a package requires a new entry in one of these files, the
8582 maintainer should get in contact with the
8583 <prgn>netbase</prgn> maintainer, who will add the entries
8584 and release a new version of the <prgn>netbase</prgn>
8589 The configuration file <file>/etc/inetd.conf</file> must not be
8590 modified by the package's scripts except via the
8591 <prgn>update-inetd</prgn> script or the
8592 <file>DebianNet.pm</file> Perl module. See their documentation
8593 for details on how to add entries.
8597 If a package wants to install an example entry into
8598 <file>/etc/inetd.conf</file>, the entry must be preceded with
8599 exactly one hash character (<tt>#</tt>). Such lines are
8600 treated as "commented out by user" by the
8601 <prgn>update-inetd</prgn> script and are not changed or
8602 activated during package updates.
8607 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8611 Some programs need to create pseudo-ttys. This should be done
8612 using Unix98 ptys if the C library supports it. The resulting
8613 program must not be installed setuid root, unless that
8614 is required for other functionality.
8618 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8619 <file>/var/log/lastlog</file> must be installed writable by
8620 group <tt>utmp</tt>. Programs which need to modify those
8621 files must be installed setgid <tt>utmp</tt>.
8626 <heading>Editors and pagers</heading>
8629 Some programs have the ability to launch an editor or pager
8630 program to edit or display a text document. Since there are
8631 lots of different editors and pagers available in the Debian
8632 distribution, the system administrator and each user should
8633 have the possibility to choose their preferred editor and
8638 In addition, every program should choose a good default
8639 editor/pager if none is selected by the user or system
8644 Thus, every program that launches an editor or pager must
8645 use the EDITOR or PAGER environment variable to determine
8646 the editor or pager the user wishes to use. If these
8647 variables are not set, the programs <file>/usr/bin/editor</file>
8648 and <file>/usr/bin/pager</file> should be used, respectively.
8652 These two files are managed through the <prgn>dpkg</prgn>
8653 "alternatives" mechanism. Every package providing an editor or
8654 pager must call the <prgn>update-alternatives</prgn> script to
8655 register as an alternative for <file>/usr/bin/editor</file>
8656 or <file>/usr/bin/pager</file> as appropriate. The alternative
8657 should have a slave alternative
8658 for <file>/usr/share/man/man1/editor.1.gz</file>
8659 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8660 corresponding manual page.
8664 If it is very hard to adapt a program to make use of the
8665 EDITOR or PAGER variables, that program may be configured to
8666 use <file>/usr/bin/sensible-editor</file> and
8667 <file>/usr/bin/sensible-pager</file> as the editor or pager
8668 program respectively. These are two scripts provided in the
8669 <package>sensible-utils</package> package that check the EDITOR
8670 and PAGER variables and launch the appropriate program, and fall
8671 back to <file>/usr/bin/editor</file>
8672 and <file>/usr/bin/pager</file> if the variable is not set.
8676 A program may also use the VISUAL environment variable to
8677 determine the user's choice of editor. If it exists, it
8678 should take precedence over EDITOR. This is in fact what
8679 <file>/usr/bin/sensible-editor</file> does.
8683 It is not required for a package to depend on
8684 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8685 package to provide such virtual packages.<footnote>
8686 The Debian base system already provides an editor and a
8692 <sect id="web-appl">
8693 <heading>Web servers and applications</heading>
8696 This section describes the locations and URLs that should
8697 be used by all web servers and web applications in the
8704 Cgi-bin executable files are installed in the
8706 <example compact="compact">
8707 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8709 or a subdirectory of that directory, and should be
8711 <example compact="compact">
8712 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8714 (possibly with a subdirectory name
8715 before <var>cgi-bin-name</var>).
8719 <p>Access to HTML documents</p>
8722 HTML documents for a package are stored in
8723 <file>/usr/share/doc/<var>package</var></file>
8724 and can be referred to as
8725 <example compact="compact">
8726 http://localhost/doc/<var>package</var>/<var>filename</var>
8731 The web server should restrict access to the document
8732 tree so that only clients on the same host can read
8733 the documents. If the web server does not support such
8734 access controls, then it should not provide access at
8735 all, or ask about providing access during installation.
8740 <p>Access to images</p>
8742 It is recommended that images for a package be stored
8743 in <tt>/usr/share/images/<var>package</var></tt> and
8744 may be referred to through an alias <tt>/images/</tt>
8747 http://localhost/images/<package>/<filename>
8754 <p>Web Document Root</p>
8757 Web Applications should try to avoid storing files in
8758 the Web Document Root. Instead they should use the
8759 /usr/share/doc/<var>package</var> directory for
8760 documents and register the Web Application via the
8761 <package>doc-base</package> package. If access to the
8762 web document root is unavoidable then use
8763 <example compact="compact">
8766 as the Document Root. This might be just a symbolic
8767 link to the location where the system administrator
8768 has put the real document root.
8771 <item><p>Providing httpd and/or httpd-cgi</p>
8773 All web servers should provide the virtual package
8774 <tt>httpd</tt>. If a web server has CGI support it should
8775 provide <tt>httpd-cgi</tt> additionally.
8778 All web applications which do not contain CGI scripts should
8779 depend on <tt>httpd</tt>, all those web applications which
8780 <tt>do</tt> contain CGI scripts, should depend on
8788 <sect id="mail-transport-agents">
8789 <heading>Mail transport, delivery and user agents</heading>
8792 Debian packages which process electronic mail, whether mail
8793 user agents (MUAs) or mail transport agents (MTAs), must
8794 ensure that they are compatible with the configuration
8795 decisions below. Failure to do this may result in lost
8796 mail, broken <tt>From:</tt> lines, and other serious brain
8801 The mail spool is <file>/var/mail</file> and the interface to
8802 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8803 the FHS). On older systems, the mail spool may be
8804 physically located in <file>/var/spool/mail</file>, but all
8805 access to the mail spool should be via the
8806 <file>/var/mail</file> symlink. The mail spool is part of the
8807 base system and not part of the MTA package.
8811 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8812 programs (such as IMAP daemons) must lock the mailbox in an
8813 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8814 be combined with dot locking. To avoid deadlocks, a program
8815 should use <tt>fcntl()</tt> first and dot locking after
8816 this, or alternatively implement the two locking methods in
8817 a non blocking way<footnote>
8818 If it is not possible to establish both locks, the
8819 system shouldn't wait for the second lock to be
8820 established, but remove the first lock, wait a (random)
8821 time, and start over locking again.
8822 </footnote>. Using the functions <tt>maillock</tt> and
8823 <tt>mailunlock</tt> provided by the
8824 <tt>liblockfile*</tt><footnote>
8825 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8826 to use these functions.
8827 </footnote> packages is the recommended way to realize this.
8831 Mailboxes are generally either mode 600 and owned by
8832 <var>user</var> or mode 660 and owned by
8833 <tt><var>user</var>:mail</tt><footnote>
8834 There are two traditional permission schemes for mail spools:
8835 mode 600 with all mail delivery done by processes running as
8836 the destination user, or mode 660 and owned by group mail with
8837 mail delivery done by a process running as a system user in
8838 group mail. Historically, Debian required mode 660 mail
8839 spools to enable the latter model, but that model has become
8840 increasingly uncommon and the principle of least privilege
8841 indicates that mail systems that use the first model should
8842 use permissions of 600. If delivery to programs is permitted,
8843 it's easier to keep the mail system secure if the delivery
8844 agent runs as the destination user. Debian Policy therefore
8845 permits either scheme.
8846 </footnote>. The local system administrator may choose a
8847 different permission scheme; packages should not make
8848 assumptions about the permission and ownership of mailboxes
8849 unless required (such as when creating a new mailbox). A MUA
8850 may remove a mailbox (unless it has nonstandard permissions) in
8851 which case the MTA or another MUA must recreate it if needed.
8855 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8856 be setgid mail to do the locking mentioned above (and
8857 must obviously avoid accessing other users' mailboxes
8858 using this privilege).</p>
8861 <file>/etc/aliases</file> is the source file for the system mail
8862 aliases (e.g., postmaster, usenet, etc.), it is the one
8863 which the sysadmin and <prgn>postinst</prgn> scripts may
8864 edit. After <file>/etc/aliases</file> is edited the program or
8865 human editing it must call <prgn>newaliases</prgn>. All MTA
8866 packages must come with a <prgn>newaliases</prgn> program,
8867 even if it does nothing, but older MTA packages did not do
8868 this so programs should not fail if <prgn>newaliases</prgn>
8869 cannot be found. Note that because of this, all MTA
8870 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8871 <tt>Replaces: mail-transport-agent</tt> control fields.
8875 The convention of writing <tt>forward to
8876 <var>address</var></tt> in the mailbox itself is not
8877 supported. Use a <tt>.forward</tt> file instead.</p>
8880 The <prgn>rmail</prgn> program used by UUCP
8881 for incoming mail should be <file>/usr/sbin/rmail</file>.
8882 Likewise, <prgn>rsmtp</prgn>, for receiving
8883 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8887 If your package needs to know what hostname to use on (for
8888 example) outgoing news and mail messages which are generated
8889 locally, you should use the file <file>/etc/mailname</file>. It
8890 will contain the portion after the username and <tt>@</tt>
8891 (at) sign for email addresses of users on the machine
8892 (followed by a newline).
8896 Such a package should check for the existence of this file
8897 when it is being configured. If it exists, it should be
8898 used without comment, although an MTA's configuration script
8899 may wish to prompt the user even if it finds that this file
8900 exists. If the file does not exist, the package should
8901 prompt the user for the value (preferably using
8902 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8903 as well as using it in the package's configuration. The
8904 prompt should make it clear that the name will not just be
8905 used by that package. For example, in this situation the
8906 <tt>inn</tt> package could say something like:
8907 <example compact="compact">
8908 Please enter the "mail name" of your system. This is the
8909 hostname portion of the address to be shown on outgoing
8910 news and mail messages. The default is
8911 <var>syshostname</var>, your system's host name. Mail
8912 name ["<var>syshostname</var>"]:
8914 where <var>syshostname</var> is the output of <tt>hostname
8920 <heading>News system configuration</heading>
8923 All the configuration files related to the NNTP (news)
8924 servers and clients should be located under
8925 <file>/etc/news</file>.</p>
8928 There are some configuration issues that apply to a number
8929 of news clients and server packages on the machine. These
8933 <tag><file>/etc/news/organization</file></tag>
8935 A string which should appear as the
8936 organization header for all messages posted
8937 by NNTP clients on the machine
8940 <tag><file>/etc/news/server</file></tag>
8942 Contains the FQDN of the upstream NNTP
8943 server, or localhost if the local machine is
8948 Other global files may be added as required for cross-package news
8955 <heading>Programs for the X Window System</heading>
8958 <heading>Providing X support and package priorities</heading>
8961 Programs that can be configured with support for the X
8962 Window System must be configured to do so and must declare
8963 any package dependencies necessary to satisfy their
8964 runtime requirements when using the X Window System. If
8965 such a package is of higher priority than the X packages
8966 on which it depends, it is required that either the
8967 X-specific components be split into a separate package, or
8968 that an alternative version of the package, which includes
8969 X support, be provided, or that the package's priority be
8975 <heading>Packages providing an X server</heading>
8978 Packages that provide an X server that, directly or
8979 indirectly, communicates with real input and display
8980 hardware should declare in their <tt>Provides</tt> control
8981 field that they provide the virtual
8982 package <tt>xserver</tt>.<footnote>
8983 This implements current practice, and provides an
8984 actual policy for usage of the <tt>xserver</tt>
8985 virtual package which appears in the virtual packages
8986 list. In a nutshell, X servers that interface
8987 directly with the display and input hardware or via
8988 another subsystem (e.g., GGI) should provide
8989 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8990 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8996 <heading>Packages providing a terminal emulator</heading>
8999 Packages that provide a terminal emulator for the X Window
9000 System which meet the criteria listed below should declare in
9001 their <tt>Provides</tt> control field that they provide the
9002 virtual package <tt>x-terminal-emulator</tt>. They should
9003 also register themselves as an alternative for
9004 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9005 20. That alternative should have a slave alternative
9006 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9007 pointing to the corresponding manual page.
9011 To be an <tt>x-terminal-emulator</tt>, a program must:
9012 <list compact="compact">
9014 Be able to emulate a DEC VT100 terminal, or a
9015 compatible terminal.
9019 Support the command-line option <tt>-e
9020 <var>command</var></tt>, which creates a new
9021 terminal window<footnote>
9022 "New terminal window" does not necessarily mean
9023 a new top-level X window directly parented by
9024 the window manager; it could, if the terminal
9025 emulator application were so coded, be a new
9026 "view" in a multiple-document interface (MDI).
9028 and runs the specified <var>command</var>,
9029 interpreting the entirety of the rest of the command
9030 line as a command to pass straight to exec, in the
9031 manner that <tt>xterm</tt> does.
9035 Support the command-line option <tt>-T
9036 <var>title</var></tt>, which creates a new terminal
9037 window with the window title <var>title</var>.
9044 <heading>Packages providing a window manager</heading>
9047 Packages that provide a window manager should declare in
9048 their <tt>Provides</tt> control field that they provide the
9049 virtual package <tt>x-window-manager</tt>. They should also
9050 register themselves as an alternative for
9051 <file>/usr/bin/x-window-manager</file>, with a priority
9052 calculated as follows:
9053 <list compact="compact">
9055 Start with a priority of 20.
9059 If the window manager supports the Debian menu
9060 system, add 20 points if this support is available
9061 in the package's default configuration (i.e., no
9062 configuration files belonging to the system or user
9063 have to be edited to activate the feature); if
9064 configuration files must be modified, add only 10
9070 If the window manager complies with <url
9071 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9072 name="The Window Manager Specification Project">,
9073 written by the <url id="http://www.freedesktop.org/wiki/"
9074 name="Free Desktop Group">, add 40 points.
9078 If the window manager permits the X session to be
9079 restarted using a <em>different</em> window manager
9080 (without killing the X server) in its default
9081 configuration, add 10 points; otherwise add none.
9084 That alternative should have a slave alternative
9085 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9086 pointing to the corresponding manual page.
9091 <heading>Packages providing fonts</heading>
9094 Packages that provide fonts for the X Window
9096 For the purposes of Debian Policy, a "font for the X
9097 Window System" is one which is accessed via X protocol
9098 requests. Fonts for the Linux console, for PostScript
9099 renderer, or any other purpose, do not fit this
9100 definition. Any tool which makes such fonts available
9101 to the X Window System, however, must abide by this
9104 must do a number of things to ensure that they are both
9105 available without modification of the X or font server
9106 configuration, and that they do not corrupt files used by
9107 other font packages to register information about
9111 Fonts of any type supported by the X Window System
9112 must be in a separate binary package from any
9113 executables, libraries, or documentation (except
9114 that specific to the fonts shipped, such as their
9115 license information). If one or more of the fonts
9116 so packaged are necessary for proper operation of
9117 the package with which they are associated the font
9118 package may be Recommended; if the fonts merely
9119 provide an enhancement, a Suggests relationship may
9120 be used. Packages must not Depend on font
9122 This is because the X server may retrieve fonts
9123 from the local file system or over the network
9124 from an X font server; the Debian package system
9125 is empowered to deal only with the local
9131 BDF fonts must be converted to PCF fonts with the
9132 <prgn>bdftopcf</prgn> utility (available in the
9133 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9134 placed in a directory that corresponds to their
9136 <list compact="compact">
9138 100 dpi fonts must be placed in
9139 <file>/usr/share/fonts/X11/100dpi/</file>.
9143 75 dpi fonts must be placed in
9144 <file>/usr/share/fonts/X11/75dpi/</file>.
9148 Character-cell fonts, cursor fonts, and other
9149 low-resolution fonts must be placed in
9150 <file>/usr/share/fonts/X11/misc/</file>.
9156 Type 1 fonts must be placed in
9157 <file>/usr/share/fonts/X11/Type1/</file>. If font
9158 metric files are available, they must be placed here
9163 Subdirectories of <file>/usr/share/fonts/X11/</file>
9164 other than those listed above must be neither
9165 created nor used. (The <file>PEX</file>, <file>CID</file>,
9166 <file>Speedo</file>, and <file>cyrillic</file> directories
9167 are excepted for historical reasons, but installation of
9168 files into these directories remains discouraged.)
9172 Font packages may, instead of placing files directly
9173 in the X font directories listed above, provide
9174 symbolic links in that font directory pointing to
9175 the files' actual location in the filesystem. Such
9176 a location must comply with the FHS.
9180 Font packages should not contain both 75dpi and
9181 100dpi versions of a font. If both are available,
9182 they should be provided in separate binary packages
9183 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9184 the names of the packages containing the
9185 corresponding fonts.
9189 Fonts destined for the <file>misc</file> subdirectory
9190 should not be included in the same package as 75dpi
9191 or 100dpi fonts; instead, they should be provided in
9192 a separate package with <tt>-misc</tt> appended to
9197 Font packages must not provide the files
9198 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9199 <file>fonts.scale</file> in a font directory:
9202 <file>fonts.dir</file> files must not be provided at all.
9206 <file>fonts.alias</file> and <file>fonts.scale</file>
9207 files, if needed, should be provided in the
9209 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9210 where <var>fontdir</var> is the name of the
9212 <file>/usr/share/fonts/X11/</file> where the
9213 package's corresponding fonts are stored
9214 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9215 <var>package</var> is the name of the package
9216 that provides these fonts, and
9217 <var>extension</var> is either <tt>scale</tt>
9218 or <tt>alias</tt>, whichever corresponds to
9225 Font packages must declare a dependency on
9226 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9227 or <tt>Pre-Depends</tt> control field.
9231 Font packages that provide one or more
9232 <file>fonts.scale</file> files as described above must
9233 invoke <prgn>update-fonts-scale</prgn> on each
9234 directory into which they installed fonts
9235 <em>before</em> invoking
9236 <prgn>update-fonts-dir</prgn> on that directory.
9237 This invocation must occur in both the
9238 <prgn>postinst</prgn> (for all arguments) and
9239 <prgn>postrm</prgn> (for all arguments except
9240 <tt>upgrade</tt>) scripts.
9244 Font packages that provide one or more
9245 <file>fonts.alias</file> files as described above must
9246 invoke <prgn>update-fonts-alias</prgn> on each
9247 directory into which they installed fonts. This
9248 invocation must occur in both the
9249 <prgn>postinst</prgn> (for all arguments) and
9250 <prgn>postrm</prgn> (for all arguments except
9251 <tt>upgrade</tt>) scripts.
9255 Font packages must invoke
9256 <prgn>update-fonts-dir</prgn> on each directory into
9257 which they installed fonts. This invocation must
9258 occur in both the <prgn>postinst</prgn> (for all
9259 arguments) and <prgn>postrm</prgn> (for all
9260 arguments except <tt>upgrade</tt>) scripts.
9264 Font packages must not provide alias names for the
9265 fonts they include which collide with alias names
9266 already in use by fonts already packaged.
9270 Font packages must not provide fonts with the same
9271 XLFD registry name as another font already packaged.
9277 <sect1 id="appdefaults">
9278 <heading>Application defaults files</heading>
9281 Application defaults files must be installed in the
9282 directory <file>/etc/X11/app-defaults/</file> (use of a
9283 localized subdirectory of <file>/etc/X11/</file> as described
9284 in the <em>X Toolkit Intrinsics - C Language
9285 Interface</em> manual is also permitted). They must be
9286 registered as <tt>conffile</tt>s or handled as
9287 configuration files.
9291 Customization of programs' X resources may also be
9292 supported with the provision of a file with the same name
9293 as that of the package placed in
9294 the <file>/etc/X11/Xresources/</file> directory, which
9295 must be registered as a <tt>conffile</tt> or handled as a
9296 configuration file.<footnote>
9297 Note that this mechanism is not the same as using
9298 app-defaults; app-defaults are tied to the client
9299 binary on the local file system, whereas X resources
9300 are stored in the X server and affect all connecting
9307 <heading>Installation directory issues</heading>
9310 Historically, packages using the X Window System used a
9311 separate set of installation directories from other packages.
9312 This practice has been discontinued and packages using the X
9313 Window System should now generally be installed in the same
9314 directories as any other package. Specifically, packages must
9315 not install files under the <file>/usr/X11R6/</file> directory
9316 and the <file>/usr/X11R6/</file> directory hierarchy should be
9317 regarded as obsolete.
9321 Include files previously installed under
9322 <file>/usr/X11R6/include/X11/</file> should be installed into
9323 <file>/usr/include/X11/</file>. For files previously
9324 installed into subdirectories of
9325 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9326 determine if subdirectories of <file>/usr/lib/</file> and
9327 <file>/usr/share/</file> can be used. If not, a subdirectory
9328 of <file>/usr/lib/X11/</file> should be used.
9332 Configuration files for window, display, or session managers
9333 or other applications that are tightly integrated with the X
9334 Window System may be placed in a subdirectory
9335 of <file>/etc/X11/</file> corresponding to the package name.
9336 Other X Window System applications should use
9337 the <file>/etc/</file> directory unless otherwise mandated by
9338 policy (such as for <ref id="appdefaults">).
9343 <heading>The OSF/Motif and OpenMotif libraries</heading>
9346 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9347 OpenMotif libraries</em><footnote>
9348 OSF/Motif and OpenMotif are collectively referred to as
9349 "Motif" in this policy document.
9351 should be compiled against and tested with LessTif (a free
9352 re-implementation of Motif) instead. If the maintainer
9353 judges that the program or programs do not work
9354 sufficiently well with LessTif to be distributed and
9355 supported, but do so when compiled against Motif, then two
9356 versions of the package should be created; one linked
9357 statically against Motif and with <tt>-smotif</tt>
9358 appended to the package name, and one linked dynamically
9359 against Motif and with <tt>-dmotif</tt> appended to the
9364 Both Motif-linked versions are dependent
9365 upon non-DFSG-compliant software and thus cannot be
9366 uploaded to the <em>main</em> distribution; if the
9367 software is itself DFSG-compliant it may be uploaded to
9368 the <em>contrib</em> distribution. While known existing
9369 versions of Motif permit unlimited redistribution of
9370 binaries linked against the library (whether statically or
9371 dynamically), it is the package maintainer's
9372 responsibility to determine whether this is permitted by
9373 the license of the copy of Motif in their possession.
9379 <heading>Perl programs and modules</heading>
9382 Perl programs and modules should follow the current Perl policy.
9386 The Perl policy can be found in the <tt>perl-policy</tt>
9387 files in the <tt>debian-policy</tt> package.
9388 It is also available from the Debian web mirrors at
9389 <tt><url name="/doc/packaging-manuals/perl-policy/"
9390 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9395 <heading>Emacs lisp programs</heading>
9398 Please refer to the "Debian Emacs Policy" for details of how to
9399 package emacs lisp programs.
9403 The Emacs policy is available in
9404 <file>debian-emacs-policy.gz</file> of the
9405 <package>emacsen-common</package> package.
9406 It is also available from the Debian web mirrors at
9407 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9408 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9413 <heading>Games</heading>
9416 The permissions on <file>/var/games</file> are mode 755, owner
9417 <tt>root</tt> and group <tt>root</tt>.
9421 Each game decides on its own security policy.</p>
9424 Games which require protected, privileged access to
9425 high-score files, saved games, etc., may be made
9426 set-<em>group</em>-id (mode 2755) and owned by
9427 <tt>root:games</tt>, and use files and directories with
9428 appropriate permissions (770 <tt>root:games</tt>, for
9429 example). They must not be made
9430 set-<em>user</em>-id, as this causes security problems. (If
9431 an attacker can subvert any set-user-id game they can
9432 overwrite the executable of any other, causing other players
9433 of these games to run a Trojan horse program. With a
9434 set-group-id game the attacker only gets access to less
9435 important game data, and if they can get at the other
9436 players' accounts at all it will take considerably more
9440 Some packages, for example some fortune cookie programs, are
9441 configured by the upstream authors to install with their
9442 data files or other static information made unreadable so
9443 that they can only be accessed through set-id programs
9444 provided. You should not do this in a Debian package: anyone can
9445 download the <file>.deb</file> file and read the data from it,
9446 so there is no point making the files unreadable. Not
9447 making the files unreadable also means that you don't have
9448 to make so many programs set-id, which reduces the risk of a
9452 As described in the FHS, binaries of games should be
9453 installed in the directory <file>/usr/games</file>. This also
9454 applies to games that use the X Window System. Manual pages
9455 for games (X and non-X games) should be installed in
9456 <file>/usr/share/man/man6</file>.</p>
9462 <heading>Documentation</heading>
9465 <heading>Manual pages</heading>
9468 You should install manual pages in <prgn>nroff</prgn> source
9469 form, in appropriate places under <file>/usr/share/man</file>.
9470 You should only use sections 1 to 9 (see the FHS for more
9471 details). You must not install a pre-formatted "cat page".
9475 Each program, utility, and function should have an
9476 associated manual page included in the same package. It is
9477 suggested that all configuration files also have a manual
9478 page included as well. Manual pages for protocols and other
9479 auxiliary things are optional.
9483 If no manual page is available, this is considered as a bug
9484 and should be reported to the Debian Bug Tracking System (the
9485 maintainer of the package is allowed to write this bug report
9486 themselves, if they so desire). Do not close the bug report
9487 until a proper man page is available.<footnote>
9488 It is not very hard to write a man page. See the
9489 <url id="http://www.schweikhardt.net/man_page_howto.html"
9490 name="Man-Page-HOWTO">,
9491 <manref name="man" section="7">, the examples created
9492 by <prgn>dh_make</prgn>, the helper
9493 program <prgn>help2man</prgn>, or the
9494 directory <file>/usr/share/doc/man-db/examples</file>.
9499 You may forward a complaint about a missing man page to the
9500 upstream authors, and mark the bug as forwarded in the
9501 Debian bug tracking system. Even though the GNU Project do
9502 not in general consider the lack of a man page to be a bug,
9503 we do; if they tell you that they don't consider it a bug
9504 you should leave the bug in our bug tracking system open
9509 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9513 If one man page needs to be accessible via several names it
9514 is better to use a symbolic link than the <file>.so</file>
9515 feature, but there is no need to fiddle with the relevant
9516 parts of the upstream source to change from <file>.so</file> to
9517 symlinks: don't do it unless it's easy. You should not
9518 create hard links in the manual page directories, nor put
9519 absolute filenames in <file>.so</file> directives. The filename
9520 in a <file>.so</file> in a man page should be relative to the
9521 base of the man page tree (usually
9522 <file>/usr/share/man</file>). If you do not create any links
9523 (whether symlinks, hard links, or <tt>.so</tt> directives)
9524 in the file system to the alternate names of the man page,
9525 then you should not rely on <prgn>man</prgn> finding your
9526 man page under those names based solely on the information in
9527 the man page's header.<footnote>
9528 Supporting this in <prgn>man</prgn> often requires
9529 unreasonable processing time to find a manual page or to
9530 report that none exists, and moves knowledge into man's
9531 database that would be better left in the file system.
9532 This support is therefore deprecated and will cease to
9533 be present in the future.
9538 Manual pages in locale-specific subdirectories of
9539 <file>/usr/share/man</file> should use either UTF-8 or the usual
9540 legacy encoding for that language (normally the one corresponding
9541 to the shortest relevant locale name in
9542 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9543 <file>/usr/share/man/fr</file> should use either UTF-8 or
9544 ISO-8859-1.<footnote>
9545 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9546 use. In future, all manual pages will be required to use
9552 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9553 included in the subdirectory name unless it indicates a
9554 significant difference in the language, as this excludes
9555 speakers of the language in other countries.<footnote>
9556 At the time of writing, Chinese and Portuguese are the main
9557 languages with such differences, so <file>pt_BR</file>,
9558 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9563 If a localized version of a manual page is provided, it should
9564 either be up-to-date or it should be obvious to the reader that
9565 it is outdated and the original manual page should be used
9566 instead. This can be done either by a note at the beginning of
9567 the manual page or by showing the missing or changed portions in
9568 the original language instead of the target language.
9573 <heading>Info documents</heading>
9576 Info documents should be installed in <file>/usr/share/info</file>.
9577 They should be compressed with <tt>gzip -9</tt>.
9581 The <prgn>install-info</prgn> program maintains a directory of
9582 installed info documents in <file>/usr/share/info/dir</file> for
9583 the use of info readers.<footnote>
9584 It was previously necessary for packages installing info
9585 documents to run <prgn>install-info</prgn> from maintainer
9586 scripts. This is no longer necessary. The installation
9587 system now uses dpkg triggers.
9589 This file must not be included in packages. Packages containing
9590 info documents should depend on <tt>dpkg (>= 1.15.4) |
9591 install-info</tt> to ensure that the directory file is properly
9592 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9597 Info documents should contain section and directory entry
9598 information in the document for the use
9599 of <prgn>install-info</prgn>. The section should be specified
9600 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9601 space and the section of this info page. The directory entry or
9602 entries should be included between
9603 a <tt>START-INFO-DIR-ENTRY</tt> line and
9604 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9606 INFO-DIR-SECTION Individual utilities
9607 START-INFO-DIR-ENTRY
9608 * example: (example). An example info directory entry.
9611 To determine which section to use, you should look
9612 at <file>/usr/share/info/dir</file> on your system and choose
9613 the most relevant (or create a new section if none of the
9614 current sections are relevant).<footnote>
9615 Normally, info documents are generated from Texinfo source.
9616 To include this information in the generated info document, if
9617 it is absent, add commands like:
9619 @dircategory Individual utilities
9621 * example: (example). An example info directory entry.
9624 to the Texinfo source of the document and ensure that the info
9625 documents are rebuilt from source during the package build.
9631 <heading>Additional documentation</heading>
9634 Any additional documentation that comes with the package may
9635 be installed at the discretion of the package maintainer.
9636 Plain text documentation should be installed in the directory
9637 <file>/usr/share/doc/<var>package</var></file>, where
9638 <var>package</var> is the name of the package, and
9639 compressed with <tt>gzip -9</tt> unless it is small.
9643 If a package comes with large amounts of documentation which
9644 many users of the package will not require you should create
9645 a separate binary package to contain it, so that it does not
9646 take up disk space on the machines of users who do not need
9647 or want it installed.</p>
9650 It is often a good idea to put text information files
9651 (<file>README</file>s, changelogs, and so forth) that come with
9652 the source package in <file>/usr/share/doc/<var>package</var></file>
9653 in the binary package. However, you don't need to install
9654 the instructions for building and installing the package, of
9658 Packages must not require the existence of any files in
9659 <file>/usr/share/doc/</file> in order to function
9661 The system administrator should be able to
9662 delete files in <file>/usr/share/doc/</file> without causing
9663 any programs to break.
9665 Any files that are referenced by programs but are also
9666 useful as stand alone documentation should be installed under
9667 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9668 <file>/usr/share/doc/<var>package</var></file>.
9672 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9673 link to another directory in <file>/usr/share/doc</file> only if
9674 the two packages both come from the same source and the
9675 first package Depends on the second.<footnote>
9677 Please note that this does not override the section on
9678 changelog files below, so the file
9679 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9680 must refer to the changelog for the current version of
9681 <var>package</var> in question. In practice, this means
9682 that the sources of the target and the destination of the
9683 symlink must be the same (same source package and
9690 Former Debian releases placed all additional documentation
9691 in <file>/usr/doc/<var>package</var></file>. This has been
9692 changed to <file>/usr/share/doc/<var>package</var></file>,
9693 and packages must not put documentation in the directory
9694 <file>/usr/doc/<var>package</var></file>. <footnote>
9695 At this phase of the transition, we no longer require a
9696 symbolic link in <file>/usr/doc/</file>. At a later point,
9697 policy shall change to make the symbolic links a bug.
9703 <heading>Preferred documentation formats</heading>
9706 The unification of Debian documentation is being carried out
9710 If your package comes with extensive documentation in a
9711 markup format that can be converted to various other formats
9712 you should if possible ship HTML versions in a binary
9713 package, in the directory
9714 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9715 its subdirectories.<footnote>
9716 The rationale: The important thing here is that HTML
9717 docs should be available in <em>some</em> package, not
9718 necessarily in the main binary package.
9723 Other formats such as PostScript may be provided at the
9724 package maintainer's discretion.
9728 <sect id="copyrightfile">
9729 <heading>Copyright information</heading>
9732 Every package must be accompanied by a verbatim copy of its
9733 copyright information and distribution license in the file
9734 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9735 file must neither be compressed nor be a symbolic link.
9739 In addition, the copyright file must say where the upstream
9740 sources (if any) were obtained. It should name the original
9741 authors of the package and the Debian maintainer(s) who were
9742 involved with its creation.
9746 Packages in the <em>contrib</em> or <em>non-free</em> archive
9747 areas should state in the copyright file that the package is not
9748 part of the Debian distribution and briefly explain why.
9752 A copy of the file which will be installed in
9753 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9754 be in <file>debian/copyright</file> in the source package.
9758 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9759 link to another directory in <file>/usr/share/doc</file> only if
9760 the two packages both come from the same source and the
9761 first package Depends on the second. These rules are
9762 important because copyrights must be extractable by
9767 Packages distributed under the Apache license (version 2.0), the
9768 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9769 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9770 1.3) should refer to the corresponding files
9771 under <file>/usr/share/common-licenses</file>,<footnote>
9774 <file>/usr/share/common-licenses/Apache-2.0</file>,
9775 <file>/usr/share/common-licenses/Artistic</file>,
9776 <file>/usr/share/common-licenses/GPL-1</file>,
9777 <file>/usr/share/common-licenses/GPL-2</file>,
9778 <file>/usr/share/common-licenses/GPL-3</file>,
9779 <file>/usr/share/common-licenses/LGPL-2</file>,
9780 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9781 <file>/usr/share/common-licenses/LGPL-3</file>,
9782 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9783 <file>/usr/share/common-licenses/GFDL-1.3</file>
9784 respectively. The University of California BSD license is
9785 also included in <package>base-files</package> as
9786 <file>/usr/share/common-licenses/BSD</file>, but given the
9787 brevity of this license, its specificity to code whose
9788 copyright is held by the Regents of the University of
9789 California, and the frequency of minor wording changes, its
9790 text should be included in the copyright file rather than
9791 referencing this file.
9793 </footnote> rather than quoting them in the copyright
9798 You should not use the copyright file as a general <file>README</file>
9799 file. If your package has such a file it should be
9800 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9801 <file>README.Debian</file> or some other appropriate place.</p>
9805 <heading>Examples</heading>
9808 Any examples (configurations, source files, whatever),
9809 should be installed in a directory
9810 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9811 files should not be referenced by any program: they're there
9812 for the benefit of the system administrator and users as
9813 documentation only. Architecture-specific example files
9814 should be installed in a directory
9815 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9817 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9818 latter directory itself may be a symbolic link to the
9823 If the purpose of a package is to provide examples, then the
9824 example files may be installed into
9825 <file>/usr/share/doc/<var>package</var></file>.
9829 <sect id="changelogs">
9830 <heading>Changelog files</heading>
9833 Packages that are not Debian-native must contain a
9834 compressed copy of the <file>debian/changelog</file> file from
9835 the Debian source tree in
9836 <file>/usr/share/doc/<var>package</var></file> with the name
9837 <file>changelog.Debian.gz</file>.
9841 If an upstream changelog is available, it should be accessible as
9842 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9843 plain text. If the upstream changelog is distributed in
9844 HTML, it should be made available in that form as
9845 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9846 and a plain text <file>changelog.gz</file> should be generated
9847 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9848 the upstream changelog files do not already conform to this
9849 naming convention, then this may be achieved either by
9850 renaming the files, or by adding a symbolic link, at the
9851 maintainer's discretion.<footnote>
9852 Rationale: People should not have to look in places for
9853 upstream changelogs merely because they are given
9854 different names or are distributed in HTML format.
9859 All of these files should be installed compressed using
9860 <tt>gzip -9</tt>, as they will become large with time even
9861 if they start out small.
9865 If the package has only one changelog which is used both as
9866 the Debian changelog and the upstream one because there is
9867 no separate upstream maintainer then that changelog should
9868 usually be installed as
9869 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9870 there is a separate upstream maintainer, but no upstream
9871 changelog, then the Debian changelog should still be called
9872 <file>changelog.Debian.gz</file>.
9876 For details about the format and contents of the Debian
9877 changelog file, please see <ref id="dpkgchangelog">.
9882 <appendix id="pkg-scope">
9883 <heading>Introduction and scope of these appendices</heading>
9886 These appendices are taken essentially verbatim from the
9887 now-deprecated Packaging Manual, version 3.2.1.0. They are
9888 the chapters which are likely to be of use to package
9889 maintainers and which have not already been included in the
9890 policy document itself. Most of these sections are very likely
9891 not relevant to policy; they should be treated as
9892 documentation for the packaging system. Please note that these
9893 appendices are included for convenience, and for historical
9894 reasons: they used to be part of policy package, and they have
9895 not yet been incorporated into dpkg documentation. However,
9896 they still have value, and hence they are presented here.
9900 They have not yet been checked to ensure that they are
9901 compatible with the contents of policy, and if there are any
9902 contradictions, the version in the main policy document takes
9903 precedence. The remaining chapters of the old Packaging
9904 Manual have also not been read in detail to ensure that there
9905 are not parts which have been left out. Both of these will be
9910 Certain parts of the Packaging manual were integrated into the
9911 Policy Manual proper, and removed from the appendices. Links
9912 have been placed from the old locations to the new ones.
9916 <prgn>dpkg</prgn> is a suite of programs for creating binary
9917 package files and installing and removing them on Unix
9919 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
9920 work on or be ported to other systems.
9925 The binary packages are designed for the management of
9926 installed executable programs (usually compiled binaries) and
9927 their associated data, though source code examples and
9928 documentation are provided as part of some packages.</p>
9931 This manual describes the technical aspects of creating Debian
9932 binary packages (<file>.deb</file> files). It documents the
9933 behavior of the package management programs
9934 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9935 they interact with packages.</p>
9938 It also documents the interaction between
9939 <prgn>dselect</prgn>'s core and the access method scripts it
9940 uses to actually install the selected packages, and describes
9941 how to create a new access method.</p>
9944 This manual does not go into detail about the options and
9945 usage of the package building and installation tools. It
9946 should therefore be read in conjunction with those programs'
9951 The utility programs which are provided with <prgn>dpkg</prgn>
9952 for managing various system configuration and similar issues,
9953 such as <prgn>update-rc.d</prgn> and
9954 <prgn>install-info</prgn>, are not described in detail here -
9955 please see their man pages.
9959 It is assumed that the reader is reasonably familiar with the
9960 <prgn>dpkg</prgn> System Administrators' manual.
9961 Unfortunately this manual does not yet exist.
9965 The Debian version of the FSF's GNU hello program is provided as
9966 an example for people wishing to create Debian packages. However,
9967 while the examples are helpful, they do not replace the need to
9968 read and follow the Policy and Programmer's Manual.</p>
9971 <appendix id="pkg-binarypkg">
9972 <heading>Binary packages (from old Packaging Manual)</heading>
9975 The binary package has two main sections. The first part
9976 consists of various control information files and scripts used
9977 by <prgn>dpkg</prgn> when installing and removing. See <ref
9978 id="pkg-controlarea">.
9982 The second part is an archive containing the files and
9983 directories to be installed.
9987 In the future binary packages may also contain other
9988 components, such as checksums and digital signatures. The
9989 format for the archive is described in full in the
9990 <file>deb(5)</file> man page.
9994 <sect id="pkg-bincreating"><heading>Creating package files -
9995 <prgn>dpkg-deb</prgn>
9999 All manipulation of binary package files is done by
10000 <prgn>dpkg-deb</prgn>; it's the only program that has
10001 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10002 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10003 will spot that the options requested are appropriate to
10004 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10009 In order to create a binary package you must make a
10010 directory tree which contains all the files and directories
10011 you want to have in the file system data part of the package.
10012 In Debian-format source packages this directory is usually
10013 <file>debian/tmp</file>, relative to the top of the package's
10018 They should have the locations (relative to the root of the
10019 directory tree you're constructing) ownerships and
10020 permissions which you want them to have on the system when
10021 they are installed.
10025 With current versions of <prgn>dpkg</prgn> the uid/username
10026 and gid/groupname mappings for the users and groups being
10027 used should be the same on the system where the package is
10028 built and the one where it is installed.
10032 You need to add one special directory to the root of the
10033 miniature file system tree you're creating:
10034 <prgn>DEBIAN</prgn>. It should contain the control
10035 information files, notably the binary package control file
10036 (see <ref id="pkg-controlfile">).
10040 The <prgn>DEBIAN</prgn> directory will not appear in the
10041 file system archive of the package, and so won't be installed
10042 by <prgn>dpkg</prgn> when the package is unpacked.
10046 When you've prepared the package, you should invoke:
10048 dpkg --build <var>directory</var>
10053 This will build the package in
10054 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10055 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10056 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10057 build the package.)
10061 See the man page <manref name="dpkg-deb" section="8"> for details of how
10062 to examine the contents of this newly-created file. You may find the
10063 output of following commands enlightening:
10065 dpkg-deb --info <var>filename</var>.deb
10066 dpkg-deb --contents <var>filename</var>.deb
10067 dpkg --contents <var>filename</var>.deb
10069 To view the copyright file for a package you could use this command:
10071 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10076 <sect id="pkg-controlarea">
10077 <heading>Package control information files</heading>
10080 The control information portion of a binary package is a
10081 collection of files with names known to <prgn>dpkg</prgn>.
10082 It will treat the contents of these files specially - some
10083 of them contain information used by <prgn>dpkg</prgn> when
10084 installing or removing the package; others are scripts which
10085 the package maintainer wants <prgn>dpkg</prgn> to run.
10089 It is possible to put other files in the package control
10090 information file area, but this is not generally a good idea
10091 (though they will largely be ignored).
10095 Here is a brief list of the control information files supported
10096 by <prgn>dpkg</prgn> and a summary of what they're used for.
10101 <tag><tt>control</tt>
10104 This is the key description file used by
10105 <prgn>dpkg</prgn>. It specifies the package's name
10106 and version, gives its description for the user,
10107 states its relationships with other packages, and so
10108 forth. See <ref id="sourcecontrolfiles"> and
10109 <ref id="binarycontrolfiles">.
10113 It is usually generated automatically from information
10114 in the source package by the
10115 <prgn>dpkg-gencontrol</prgn> program, and with
10116 assistance from <prgn>dpkg-shlibdeps</prgn>.
10117 See <ref id="pkg-sourcetools">.
10121 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10126 These are executable files (usually scripts) which
10127 <prgn>dpkg</prgn> runs during installation, upgrade
10128 and removal of packages. They allow the package to
10129 deal with matters which are particular to that package
10130 or require more complicated processing than that
10131 provided by <prgn>dpkg</prgn>. Details of when and
10132 how they are called are in <ref id="maintainerscripts">.
10136 It is very important to make these scripts idempotent.
10137 See <ref id="idempotency">.
10141 The maintainer scripts are not guaranteed to run with a
10142 controlling terminal and may not be able to interact with
10143 the user. See <ref id="controllingterminal">.
10147 <tag><tt>conffiles</tt>
10150 This file contains a list of configuration files which
10151 are to be handled automatically by <prgn>dpkg</prgn>
10152 (see <ref id="pkg-conffiles">). Note that not necessarily
10153 every configuration file should be listed here.
10156 <tag><tt>shlibs</tt>
10159 This file contains a list of the shared libraries
10160 supplied by the package, with dependency details for
10161 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10162 when it determines what dependencies are required in a
10163 package control file. The <tt>shlibs</tt> file format
10164 is described on <ref id="shlibs">.
10169 <sect id="pkg-controlfile">
10170 <heading>The main control information file: <tt>control</tt></heading>
10173 The most important control information file used by
10174 <prgn>dpkg</prgn> when it installs a package is
10175 <tt>control</tt>. It contains all the package's "vital
10180 The binary package control files of packages built from
10181 Debian sources are made by a special tool,
10182 <prgn>dpkg-gencontrol</prgn>, which reads
10183 <file>debian/control</file> and <file>debian/changelog</file> to
10184 find the information it needs. See <ref id="pkg-sourcepkg"> for
10189 The fields in binary package control files are listed in
10190 <ref id="binarycontrolfiles">.
10194 A description of the syntax of control files and the purpose
10195 of the fields is available in <ref id="controlfields">.
10200 <heading>Time Stamps</heading>
10203 See <ref id="timestamps">.
10208 <appendix id="pkg-sourcepkg">
10209 <heading>Source packages (from old Packaging Manual) </heading>
10212 The Debian binary packages in the distribution are generated
10213 from Debian sources, which are in a special format to assist
10214 the easy and automatic building of binaries.
10217 <sect id="pkg-sourcetools">
10218 <heading>Tools for processing source packages</heading>
10221 Various tools are provided for manipulating source packages;
10222 they pack and unpack sources and help build of binary
10223 packages and help manage the distribution of new versions.
10227 They are introduced and typical uses described here; see
10228 <manref name="dpkg-source" section="1"> for full
10229 documentation about their arguments and operation.
10233 For examples of how to construct a Debian source package,
10234 and how to use those utilities that are used by Debian
10235 source packages, please see the <prgn>hello</prgn> example
10239 <sect1 id="pkg-dpkg-source">
10241 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10246 This program is frequently used by hand, and is also
10247 called from package-independent automated building scripts
10248 such as <prgn>dpkg-buildpackage</prgn>.
10252 To unpack a package it is typically invoked with
10254 dpkg-source -x <var>.../path/to/filename</var>.dsc
10259 with the <file><var>filename</var>.tar.gz</file> and
10260 <file><var>filename</var>.diff.gz</file> (if applicable) in
10261 the same directory. It unpacks into
10262 <file><var>package</var>-<var>version</var></file>, and if
10264 <file><var>package</var>-<var>version</var>.orig</file>, in
10265 the current directory.
10269 To create a packed source archive it is typically invoked:
10271 dpkg-source -b <var>package</var>-<var>version</var>
10276 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10277 <file>.diff.gz</file> (if appropriate) in the current
10278 directory. <prgn>dpkg-source</prgn> does not clean the
10279 source tree first - this must be done separately if it is
10284 See also <ref id="pkg-sourcearchives">.</p>
10288 <sect1 id="pkg-dpkg-buildpackage">
10290 <prgn>dpkg-buildpackage</prgn> - overall package-building
10295 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10296 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10297 targets <tt>clean</tt>, <tt>build</tt> and
10298 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10299 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10300 source and binary package upload.
10304 It is usually invoked by hand from the top level of the
10305 built or unbuilt source directory. It may be invoked with
10306 no arguments; useful arguments include:
10307 <taglist compact="compact">
10308 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10311 Do not sign the <tt>.changes</tt> file or the
10312 source package <tt>.dsc</tt> file, respectively.</p>
10314 <tag><tt>-p<var>sign-command</var></tt></tag>
10317 Invoke <var>sign-command</var> instead of finding
10318 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10319 <var>sign-command</var> must behave just like
10320 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10322 <tag><tt>-r<var>root-command</var></tt></tag>
10325 When root privilege is required, invoke the command
10326 <var>root-command</var>. <var>root-command</var>
10327 should invoke its first argument as a command, from
10328 the <prgn>PATH</prgn> if necessary, and pass its
10329 second and subsequent arguments to the command it
10330 calls. If no <var>root-command</var> is supplied
10331 then <var>dpkg-buildpackage</var> will take no
10332 special action to gain root privilege, so that for
10333 most packages it will have to be invoked as root to
10336 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10339 Two types of binary-only build and upload - see
10340 <manref name="dpkg-source" section="1">.
10347 <sect1 id="pkg-dpkg-gencontrol">
10349 <prgn>dpkg-gencontrol</prgn> - generates binary package
10354 This program is usually called from <file>debian/rules</file>
10355 (see <ref id="pkg-sourcetree">) in the top level of the source
10360 This is usually done just before the files and directories in the
10361 temporary directory tree where the package is being built have their
10362 permissions and ownerships set and the package is constructed using
10363 <prgn>dpkg-deb/</prgn>
10365 This is so that the control file which is produced has
10366 the right permissions
10371 <prgn>dpkg-gencontrol</prgn> must be called after all the
10372 files which are to go into the package have been placed in
10373 the temporary build directory, so that its calculation of
10374 the installed size of a package is correct.
10378 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10379 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10380 variable substitutions created by
10381 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10386 For a package which generates only one binary package, and
10387 which builds it in <file>debian/tmp</file> relative to the top
10388 of the source package, it is usually sufficient to call
10389 <prgn>dpkg-gencontrol</prgn>.
10393 Sources which build several binaries will typically need
10396 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10397 </example> The <tt>-P</tt> tells
10398 <prgn>dpkg-gencontrol</prgn> that the package is being
10399 built in a non-default directory, and the <tt>-p</tt>
10400 tells it which package's control file should be generated.
10404 <prgn>dpkg-gencontrol</prgn> also adds information to the
10405 list of files in <file>debian/files</file>, for the benefit of
10406 (for example) a future invocation of
10407 <prgn>dpkg-genchanges</prgn>.</p>
10410 <sect1 id="pkg-dpkg-shlibdeps">
10412 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10417 This program is usually called from <file>debian/rules</file>
10418 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10419 id="pkg-sourcetree">), in the top level of the source tree.
10423 Its arguments are executables and shared libraries
10426 They may be specified either in the locations in the
10427 source tree where they are created or in the locations
10428 in the temporary build tree where they are installed
10429 prior to binary package creation.
10431 </footnote> for which shared library dependencies should
10432 be included in the binary package's control file.
10436 If some of the found shared libraries should only
10437 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10438 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10439 by using the <tt>-d<var>dependency-field</var></tt> option
10440 before those executable(s). (Each <tt>-d</tt> option
10441 takes effect until the next <tt>-d</tt>.)
10445 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10446 output control file to be modified. Instead by default it
10447 adds to the <file>debian/substvars</file> file variable
10448 settings like <tt>shlibs:Depends</tt>. These variable
10449 settings must be referenced in dependency fields in the
10450 appropriate per-binary-package sections of the source
10455 For example, a package that generates an essential part
10456 which requires dependencies, and optional parts that
10457 which only require a recommendation, would separate those
10458 two sets of dependencies into two different fields.<footnote>
10459 At the time of writing, an example for this was the
10460 <package/xmms/ package, with Depends used for the xmms
10461 executable, Recommends for the plug-ins and Suggests for
10462 even more optional features provided by unzip.
10464 It can say in its <file>debian/rules</file>:
10466 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10467 -dRecommends <var>optionalpart anotheroptionalpart</var>
10469 and then in its main control file <file>debian/control</file>:
10472 Depends: ${shlibs:Depends}
10473 Recommends: ${shlibs:Recommends}
10479 Sources which produce several binary packages with
10480 different shared library dependency requirements can use
10481 the <tt>-p<var>varnameprefix</var></tt> option to override
10482 the default <tt>shlibs:</tt> prefix (one invocation of
10483 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10484 They can thus produce several sets of dependency
10485 variables, each of the form
10486 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10487 which can be referred to in the appropriate parts of the
10488 binary package control files.
10493 <sect1 id="pkg-dpkg-distaddfile">
10495 <prgn>dpkg-distaddfile</prgn> - adds a file to
10496 <file>debian/files</file>
10500 Some packages' uploads need to include files other than
10501 the source and binary package files.
10505 <prgn>dpkg-distaddfile</prgn> adds a file to the
10506 <file>debian/files</file> file so that it will be included in
10507 the <file>.changes</file> file when
10508 <prgn>dpkg-genchanges</prgn> is run.
10512 It is usually invoked from the <tt>binary</tt> target of
10513 <file>debian/rules</file>:
10515 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10517 The <var>filename</var> is relative to the directory where
10518 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10519 is usually the directory above the top level of the source
10520 tree. The <file>debian/rules</file> target should put the
10521 file there just before or just after calling
10522 <prgn>dpkg-distaddfile</prgn>.
10526 The <var>section</var> and <var>priority</var> are passed
10527 unchanged into the resulting <file>.changes</file> file.
10532 <sect1 id="pkg-dpkg-genchanges">
10534 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10535 upload control file
10539 This program is usually called by package-independent
10540 automatic building scripts such as
10541 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10546 It is usually called in the top level of a built source
10547 tree, and when invoked with no arguments will print out a
10548 straightforward <file>.changes</file> file based on the
10549 information in the source package's changelog and control
10550 file and the binary and source packages which should have
10556 <sect1 id="pkg-dpkg-parsechangelog">
10558 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10559 representation of a changelog
10563 This program is used internally by
10564 <prgn>dpkg-source</prgn> et al. It may also occasionally
10565 be useful in <file>debian/rules</file> and elsewhere. It
10566 parses a changelog, <file>debian/changelog</file> by default,
10567 and prints a control-file format representation of the
10568 information in it to standard output.
10572 <sect1 id="pkg-dpkg-architecture">
10574 <prgn>dpkg-architecture</prgn> - information about the build and
10579 This program can be used manually, but is also invoked by
10580 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10581 environment or make variables which specify the build and host
10582 architecture for the package building process.
10587 <sect id="pkg-sourcetree">
10588 <heading>The Debian package source tree</heading>
10591 The source archive scheme described later is intended to
10592 allow a Debian package source tree with some associated
10593 control information to be reproduced and transported easily.
10594 The Debian package source tree is a version of the original
10595 program with certain files added for the benefit of the
10596 packaging process, and with any other changes required
10597 made to the rest of the source code and installation
10602 The extra files created for Debian are in the subdirectory
10603 <file>debian</file> of the top level of the Debian package
10604 source tree. They are described below.
10607 <sect1 id="pkg-debianrules">
10608 <heading><file>debian/rules</file> - the main building script</heading>
10611 See <ref id="debianrules">.
10615 <sect1 id="pkg-srcsubstvars">
10616 <heading><file>debian/substvars</file> and variable substitutions</heading>
10619 See <ref id="substvars">.
10625 <heading><file>debian/files</file></heading>
10628 See <ref id="debianfiles">.
10632 <sect1><heading><file>debian/tmp</file>
10636 This is the canonical temporary location for the
10637 construction of binary packages by the <tt>binary</tt>
10638 target. The directory <file>tmp</file> serves as the root of
10639 the file system tree as it is being constructed (for
10640 example, by using the package's upstream makefiles install
10641 targets and redirecting the output there), and it also
10642 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10643 id="pkg-bincreating">.
10647 If several binary packages are generated from the same
10648 source tree it is usual to use several
10649 <file>debian/tmp<var>something</var></file> directories, for
10650 example <file>tmp-a</file> or <file>tmp-doc</file>.
10654 Whatever <file>tmp</file> directories are created and used by
10655 <tt>binary</tt> must of course be removed by the
10656 <tt>clean</tt> target.</p></sect1>
10660 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10664 As it exists on the FTP site, a Debian source package
10665 consists of three related files. You must have the right
10666 versions of all three to be able to use them.
10671 <tag>Debian source control file - <tt>.dsc</tt></tag>
10673 This file is a control file used by <prgn>dpkg-source</prgn>
10674 to extract a source package.
10675 See <ref id="debiansourcecontrolfiles">.
10679 Original source archive -
10681 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10687 This is a compressed (with <tt>gzip -9</tt>)
10688 <prgn>tar</prgn> file containing the source code from
10689 the upstream authors of the program.
10694 Debian package diff -
10696 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10702 This is a unified context diff (<tt>diff -u</tt>)
10703 giving the changes which are required to turn the
10704 original source into the Debian source. These changes
10705 may only include editing and creating plain files.
10706 The permissions of files, the targets of symbolic
10707 links and the characteristics of special files or
10708 pipes may not be changed and no files may be removed
10713 All the directories in the diff must exist, except the
10714 <file>debian</file> subdirectory of the top of the source
10715 tree, which will be created by
10716 <prgn>dpkg-source</prgn> if necessary when unpacking.
10720 The <prgn>dpkg-source</prgn> program will
10721 automatically make the <file>debian/rules</file> file
10722 executable (see below).</p></item>
10727 If there is no original source code - for example, if the
10728 package is specially prepared for Debian or the Debian
10729 maintainer is the same as the upstream maintainer - the
10730 format is slightly different: then there is no diff, and the
10732 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10733 and preferably contains a directory named
10734 <file><var>package</var>-<var>version</var></file>.
10739 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10742 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10743 Debian source package. However, if it is not available it
10744 is possible to unpack a Debian source archive as follows:
10745 <enumlist compact="compact">
10748 Untar the tarfile, which will create a <file>.orig</file>
10752 <p>Rename the <file>.orig</file> directory to
10753 <file><var>package</var>-<var>version</var></file>.</p>
10757 Create the subdirectory <file>debian</file> at the top of
10758 the source tree.</p>
10760 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10762 <item><p>Untar the tarfile again if you want a copy of the original
10763 source code alongside the Debian version.</p>
10768 It is not possible to generate a valid Debian source archive
10769 without using <prgn>dpkg-source</prgn>. In particular,
10770 attempting to use <prgn>diff</prgn> directly to generate the
10771 <file>.diff.gz</file> file will not work.
10775 <heading>Restrictions on objects in source packages</heading>
10778 The source package may not contain any hard links
10780 This is not currently detected when building source
10781 packages, but only when extracting
10785 Hard links may be permitted at some point in the
10786 future, but would require a fair amount of
10788 </footnote>, device special files, sockets or setuid or
10791 Setgid directories are allowed.
10796 The source packaging tools manage the changes between the
10797 original and Debian source using <prgn>diff</prgn> and
10798 <prgn>patch</prgn>. Turning the original source tree as
10799 included in the <file>.orig.tar.gz</file> into the Debian
10800 package source must not involve any changes which cannot be
10801 handled by these tools. Problematic changes which cause
10802 <prgn>dpkg-source</prgn> to halt with an error when
10803 building the source package are:
10804 <list compact="compact">
10805 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10807 <item><p>Changing the targets of symbolic links.</p>
10809 <item><p>Creating directories, other than <file>debian</file>.</p>
10811 <item><p>Changes to the contents of binary files.</p></item>
10812 </list> Changes which cause <prgn>dpkg-source</prgn> to
10813 print a warning but continue anyway are:
10814 <list compact="compact">
10817 Removing files, directories or symlinks.
10819 Renaming a file is not treated specially - it is
10820 seen as the removal of the old file (which
10821 generates a warning, but is otherwise ignored),
10822 and the creation of the new one.
10828 Changed text files which are missing the usual final
10829 newline (either in the original or the modified
10834 Changes which are not represented, but which are not detected by
10835 <prgn>dpkg-source</prgn>, are:
10836 <list compact="compact">
10837 <item><p>Changing the permissions of files (other than
10838 <file>debian/rules</file>) and directories.</p></item>
10843 The <file>debian</file> directory and <file>debian/rules</file>
10844 are handled specially by <prgn>dpkg-source</prgn> - before
10845 applying the changes it will create the <file>debian</file>
10846 directory, and afterwards it will make
10847 <file>debian/rules</file> world-executable.
10853 <appendix id="pkg-controlfields">
10854 <heading>Control files and their fields (from old Packaging Manual)</heading>
10857 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10858 data in a common format, known as control files. Binary and
10859 source packages have control data as do the <file>.changes</file>
10860 files which control the installation of uploaded files, and
10861 <prgn>dpkg</prgn>'s internal databases are in a similar
10866 <heading>Syntax of control files</heading>
10869 See <ref id="controlsyntax">.
10873 It is important to note that there are several fields which
10874 are optional as far as <prgn>dpkg</prgn> and the related
10875 tools are concerned, but which must appear in every Debian
10876 package, or whose omission may cause problems.
10881 <heading>List of fields</heading>
10884 See <ref id="controlfieldslist">.
10888 This section now contains only the fields that didn't belong
10889 to the Policy manual.
10892 <sect1 id="pkg-f-Filename">
10893 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10896 These fields in <tt>Packages</tt> files give the
10897 filename(s) of (the parts of) a package in the
10898 distribution directories, relative to the root of the
10899 Debian hierarchy. If the package has been split into
10900 several parts the parts are all listed in order, separated
10905 <sect1 id="pkg-f-Size">
10906 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10909 These fields in <file>Packages</file> files give the size (in
10910 bytes, expressed in decimal) and MD5 checksum of the
10911 file(s) which make(s) up a binary package in the
10912 distribution. If the package is split into several parts
10913 the values for the parts are listed in order, separated by
10918 <sect1 id="pkg-f-Status">
10919 <heading><tt>Status</tt></heading>
10922 This field in <prgn>dpkg</prgn>'s status file records
10923 whether the user wants a package installed, removed or
10924 left alone, whether it is broken (requiring
10925 re-installation) or not and what its current state on the
10926 system is. Each of these pieces of information is a
10931 <sect1 id="pkg-f-Config-Version">
10932 <heading><tt>Config-Version</tt></heading>
10935 If a package is not installed or not configured, this
10936 field in <prgn>dpkg</prgn>'s status file records the last
10937 version of the package which was successfully
10942 <sect1 id="pkg-f-Conffiles">
10943 <heading><tt>Conffiles</tt></heading>
10946 This field in <prgn>dpkg</prgn>'s status file contains
10947 information about the automatically-managed configuration
10948 files held by a package. This field should <em>not</em>
10949 appear anywhere in a package!
10954 <heading>Obsolete fields</heading>
10957 These are still recognized by <prgn>dpkg</prgn> but should
10958 not appear anywhere any more.
10960 <taglist compact="compact">
10962 <tag><tt>Revision</tt></tag>
10963 <tag><tt>Package-Revision</tt></tag>
10964 <tag><tt>Package_Revision</tt></tag>
10966 The Debian revision part of the package version was
10967 at one point in a separate control field. This
10968 field went through several names.
10971 <tag><tt>Recommended</tt></tag>
10972 <item>Old name for <tt>Recommends</tt>.</item>
10974 <tag><tt>Optional</tt></tag>
10975 <item>Old name for <tt>Suggests</tt>.</item>
10977 <tag><tt>Class</tt></tag>
10978 <item>Old name for <tt>Priority</tt>.</item>
10987 <appendix id="pkg-conffiles">
10988 <heading>Configuration file handling (from old Packaging Manual)</heading>
10991 <prgn>dpkg</prgn> can do a certain amount of automatic
10992 handling of package configuration files.
10996 Whether this mechanism is appropriate depends on a number of
10997 factors, but basically there are two approaches to any
10998 particular configuration file.
11002 The easy method is to ship a best-effort configuration in the
11003 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11004 handle updates. If the user is unlikely to want to edit the
11005 file, but you need them to be able to without losing their
11006 changes, and a new package with a changed version of the file
11007 is only released infrequently, this is a good approach.
11011 The hard method is to build the configuration file from
11012 scratch in the <prgn>postinst</prgn> script, and to take the
11013 responsibility for fixing any mistakes made in earlier
11014 versions of the package automatically. This will be
11015 appropriate if the file is likely to need to be different on
11019 <sect><heading>Automatic handling of configuration files by
11024 A package may contain a control information file called
11025 <tt>conffiles</tt>. This file should be a list of filenames
11026 of configuration files needing automatic handling, separated
11027 by newlines. The filenames should be absolute pathnames,
11028 and the files referred to should actually exist in the
11033 When a package is upgraded <prgn>dpkg</prgn> will process
11034 the configuration files during the configuration stage,
11035 shortly before it runs the package's <prgn>postinst</prgn>
11040 For each file it checks to see whether the version of the
11041 file included in the package is the same as the one that was
11042 included in the last version of the package (the one that is
11043 being upgraded from); it also compares the version currently
11044 installed on the system with the one shipped with the last
11049 If neither the user nor the package maintainer has changed
11050 the file, it is left alone. If one or the other has changed
11051 their version, then the changed version is preferred - i.e.,
11052 if the user edits their file, but the package maintainer
11053 doesn't ship a different version, the user's changes will
11054 stay, silently, but if the maintainer ships a new version
11055 and the user hasn't edited it the new version will be
11056 installed (with an informative message). If both have
11057 changed their version the user is prompted about the problem
11058 and must resolve the differences themselves.
11062 The comparisons are done by calculating the MD5 message
11063 digests of the files, and storing the MD5 of the file as it
11064 was included in the most recent version of the package.
11068 When a package is installed for the first time
11069 <prgn>dpkg</prgn> will install the file that comes with it,
11070 unless that would mean overwriting a file already on the
11075 However, note that <prgn>dpkg</prgn> will <em>not</em>
11076 replace a conffile that was removed by the user (or by a
11077 script). This is necessary because with some programs a
11078 missing file produces an effect hard or impossible to
11079 achieve in another way, so that a missing file needs to be
11080 kept that way if the user did it.
11084 Note that a package should <em>not</em> modify a
11085 <prgn>dpkg</prgn>-handled conffile in its maintainer
11086 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11087 the user confusing and possibly dangerous options for
11088 conffile update when the package is upgraded.</p>
11091 <sect><heading>Fully-featured maintainer script configuration
11096 For files which contain site-specific information such as
11097 the hostname and networking details and so forth, it is
11098 better to create the file in the package's
11099 <prgn>postinst</prgn> script.
11103 This will typically involve examining the state of the rest
11104 of the system to determine values and other information, and
11105 may involve prompting the user for some information which
11106 can't be obtained some other way.
11110 When using this method there are a couple of important
11111 issues which should be considered:
11115 If you discover a bug in the program which generates the
11116 configuration file, or if the format of the file changes
11117 from one version to the next, you will have to arrange for
11118 the postinst script to do something sensible - usually this
11119 will mean editing the installed configuration file to remove
11120 the problem or change the syntax. You will have to do this
11121 very carefully, since the user may have changed the file,
11122 perhaps to fix the very problem that your script is trying
11123 to deal with - you will have to detect these situations and
11124 deal with them correctly.
11128 If you do go down this route it's probably a good idea to
11129 make the program that generates the configuration file(s) a
11130 separate program in <file>/usr/sbin</file>, by convention called
11131 <file><var>package</var>config</file> and then run that if
11132 appropriate from the post-installation script. The
11133 <tt><var>package</var>config</tt> program should not
11134 unquestioningly overwrite an existing configuration - if its
11135 mode of operation is geared towards setting up a package for
11136 the first time (rather than any arbitrary reconfiguration
11137 later) you should have it check whether the configuration
11138 already exists, and require a <tt>--force</tt> flag to
11139 overwrite it.</p></sect>
11142 <appendix id="pkg-alternatives"><heading>Alternative versions of
11143 an interface - <prgn>update-alternatives</prgn> (from old
11148 When several packages all provide different versions of the
11149 same program or file it is useful to have the system select a
11150 default, but to allow the system administrator to change it
11151 and have their decisions respected.
11155 For example, there are several versions of the <prgn>vi</prgn>
11156 editor, and there is no reason to prevent all of them from
11157 being installed at once, each under their own name
11158 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11159 Nevertheless it is desirable to have the name <tt>vi</tt>
11160 refer to something, at least by default.
11164 If all the packages involved cooperate, this can be done with
11165 <prgn>update-alternatives</prgn>.
11169 Each package provides its own version under its own name, and
11170 calls <prgn>update-alternatives</prgn> in its postinst to
11171 register its version (and again in its prerm to deregister
11176 See the man page <manref name="update-alternatives"
11177 section="8"> for details.
11181 If <prgn>update-alternatives</prgn> does not seem appropriate
11182 you may wish to consider using diversions instead.</p>
11185 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11186 package's version of a file (from old Packaging Manual)
11190 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11191 when it reinstalls the package it belongs to, and to have it
11192 put the file from the package somewhere else instead.
11196 This can be used locally to override a package's version of a
11197 file, or by one package to override another's version (or
11198 provide a wrapper for it).
11202 Before deciding to use a diversion, read <ref
11203 id="pkg-alternatives"> to see if you really want a diversion
11204 rather than several alternative versions of a program.
11208 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11209 and updated by a special program <prgn>dpkg-divert</prgn>.
11210 Please see <manref name="dpkg-divert" section="8"> for full
11211 details of its operation.
11215 When a package wishes to divert a file from another, it should
11216 call <prgn>dpkg-divert</prgn> in its preinst to add the
11217 diversion and rename the existing file. For example,
11218 supposing that a <prgn>smailwrapper</prgn> package wishes to
11219 install a wrapper around <file>/usr/sbin/smail</file>:
11221 dpkg-divert --package smailwrapper --add --rename \
11222 --divert /usr/sbin/smail.real /usr/sbin/smail
11223 </example> The <tt>--package smailwrapper</tt> ensures that
11224 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11225 can bypass the diversion and get installed as the true version.
11226 It's safe to add the diversion unconditionally on upgrades since
11227 it will be left unchanged if it already exists, but
11228 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11229 message, make the command conditional on the version from which
11230 the package is being upgraded:
11232 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11233 dpkg-divert --package smailwrapper --add --rename \
11234 --divert /usr/sbin/smail.real /usr/sbin/smail
11236 </example> where <tt>1.0-2</tt> is the version at which the
11237 diversion was first added to the package. Running the command
11238 during abort-upgrade is pointless but harmless.
11242 The postrm has to do the reverse:
11244 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11245 dpkg-divert --package smailwrapper --remove --rename \
11246 --divert /usr/sbin/smail.real /usr/sbin/smail
11248 </example> If the diversion was added at a particular version, the
11249 postrm should also handle the failure case of upgrading from an
11250 older version (unless the older version is so old that direct
11251 upgrades are no longer supported):
11253 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11254 dpkg-divert --package smailwrapper --remove --rename \
11255 --divert /usr/sbin/smail.real /usr/sbin/smail
11257 </example> where <tt>1.02-2</tt> is the version at which the
11258 diversion was first added to the package. The postrm should not
11259 remove the diversion on upgrades both because there's no reason to
11260 remove the diversion only to immediately re-add it and since the
11261 postrm of the old package is run after unpacking so the removal of
11262 the diversion will fail.
11266 Do not attempt to divert a file which is vitally important for
11267 the system's operation - when using <prgn>dpkg-divert</prgn>
11268 there is a time, after it has been diverted but before
11269 <prgn>dpkg</prgn> has installed the new version, when the file
11270 does not exist.</p>
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