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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>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian distribution</em>.
355 Packages in the other archive areas (<tt>contrib</tt>,
356 <tt>non-free</tt>) are not considered to be part of the Debian
357 distribution, although we support their use and provide
358 infrastructure for them (such as our bug-tracking system and
359 mailing lists). This Debian Policy Manual applies to these
364 <heading>The Debian Free Software Guidelines</heading>
366 The Debian Free Software Guidelines (DFSG) form our
367 definition of "free software". These are:
369 <tag>1. Free Redistribution
372 The license of a Debian component may not restrict any
373 party from selling or giving away the software as a
374 component of an aggregate software distribution
375 containing programs from several different
376 sources. The license may not require a royalty or
377 other fee for such sale.
382 The program must include source code, and must allow
383 distribution in source code as well as compiled form.
385 <tag>3. Derived Works
388 The license must allow modifications and derived
389 works, and must allow them to be distributed under the
390 same terms as the license of the original software.
392 <tag>4. Integrity of The Author's Source Code
395 The license may restrict source-code from being
396 distributed in modified form <em>only</em> if the
397 license allows the distribution of "patch files"
398 with the source code for the purpose of modifying the
399 program at build time. The license must explicitly
400 permit distribution of software built from modified
401 source code. The license may require derived works to
402 carry a different name or version number from the
403 original software. (This is a compromise. The Debian
404 Project encourages all authors to not restrict any
405 files, source or binary, from being modified.)
407 <tag>5. No Discrimination Against Persons or Groups
410 The license must not discriminate against any person
413 <tag>6. No Discrimination Against Fields of Endeavor
416 The license must not restrict anyone from making use
417 of the program in a specific field of endeavor. For
418 example, it may not restrict the program from being
419 used in a business, or from being used for genetic
422 <tag>7. Distribution of License
425 The rights attached to the program must apply to all
426 to whom the program is redistributed without the need
427 for execution of an additional license by those
430 <tag>8. License Must Not Be Specific to Debian
433 The rights attached to the program must not depend on
434 the program's being part of a Debian system. If the
435 program is extracted from Debian and used or
436 distributed without Debian but otherwise within the
437 terms of the program's license, all parties to whom
438 the program is redistributed must have the same
439 rights as those that are granted in conjunction with
442 <tag>9. License Must Not Contaminate Other Software
445 The license must not place restrictions on other
446 software that is distributed along with the licensed
447 software. For example, the license must not insist
448 that all other programs distributed on the same medium
449 must be free software.
451 <tag>10. Example Licenses
454 The "GPL," "BSD," and "Artistic" licenses are examples of
455 licenses that we consider <em>free</em>.
462 <heading>Archive areas</heading>
465 <heading>The main archive area</heading>
468 Every package in <em>main</em> must comply with the DFSG
469 (Debian Free Software Guidelines).
473 In addition, the packages in <em>main</em>
474 <list compact="compact">
476 must not require a package outside of <em>main</em>
477 for compilation or execution (thus, the package must
478 not declare a "Depends", "Recommends", or
479 "Build-Depends" relationship on a non-<em>main</em>
483 must not be so buggy that we refuse to support them,
487 must meet all policy requirements presented in this
496 <heading>The contrib archive area</heading>
499 Every package in <em>contrib</em> must comply with the DFSG.
503 In addition, the packages in <em>contrib</em>
504 <list compact="compact">
506 must not be so buggy that we refuse to support them,
510 must meet all policy requirements presented in this
518 Examples of packages which would be included in
519 <em>contrib</em> are:
520 <list compact="compact">
522 free packages which require <em>contrib</em>,
523 <em>non-free</em> packages or packages which are not
524 in our archive at all for compilation or execution,
528 wrapper packages or other sorts of free accessories for
535 <sect1 id="non-free">
536 <heading>The non-free archive area</heading>
539 Packages must be placed in <em>non-free</em> if they are
540 not compliant with the DFSG or are encumbered by patents
541 or other legal issues that make their distribution
546 In addition, the packages in <em>non-free</em>
547 <list compact="compact">
549 must not be so buggy that we refuse to support them,
553 must meet all policy requirements presented in this
554 manual that it is possible for them to meet.
556 It is possible that there are policy
557 requirements which the package is unable to
558 meet, for example, if the source is
559 unavailable. These situations will need to be
560 handled on a case-by-case basis.
569 <sect id="pkgcopyright">
570 <heading>Copyright considerations</heading>
573 Every package must be accompanied by a verbatim copy of its
574 copyright information and distribution license in the file
575 <file>/usr/share/doc/<var>package</var>/copyright</file>
576 (see <ref id="copyrightfile"> for further details).
580 We reserve the right to restrict files from being included
581 anywhere in our archives if
582 <list compact="compact">
584 their use or distribution would break a law,
587 there is an ethical conflict in their distribution or
591 we would have to sign a license for them, or
594 their distribution would conflict with other project
601 Programs whose authors encourage the user to make
602 donations are fine for the main distribution, provided
603 that the authors do not claim that not donating is
604 immoral, unethical, illegal or something similar; in such
605 a case they must go in <em>non-free</em>.
609 Packages whose copyright permission notices (or patent
610 problems) do not even allow redistribution of binaries
611 only, and where no special permission has been obtained,
612 must not be placed on the Debian FTP site and its mirrors
617 Note that under international copyright law (this applies
618 in the United States, too), <em>no</em> distribution or
619 modification of a work is allowed without an explicit
620 notice saying so. Therefore a program without a copyright
621 notice <em>is</em> copyrighted and you may not do anything
622 to it without risking being sued! Likewise if a program
623 has a copyright notice but no statement saying what is
624 permitted then nothing is permitted.
628 Many authors are unaware of the problems that restrictive
629 copyrights (or lack of copyright notices) can cause for
630 the users of their supposedly-free software. It is often
631 worthwhile contacting such authors diplomatically to ask
632 them to modify their license terms. However, this can be a
633 politically difficult thing to do and you should ask for
634 advice on the <tt>debian-legal</tt> mailing list first, as
639 When in doubt about a copyright, send mail to
640 <email>debian-legal@lists.debian.org</email>. Be prepared
641 to provide us with the copyright statement. Software
642 covered by the GPL, public domain software and BSD-like
643 copyrights are safe; be wary of the phrases "commercial
644 use prohibited" and "distribution restricted".
648 <sect id="subsections">
649 <heading>Sections</heading>
652 The packages in the archive areas <em>main</em>,
653 <em>contrib</em> and <em>non-free</em> are grouped further into
654 <em>sections</em> to simplify handling.
658 The archive area and section for each package should be
659 specified in the package's <tt>Section</tt> control record (see
660 <ref id="f-Section">). However, the maintainer of the Debian
661 archive may override this selection to ensure the consistency of
662 the Debian distribution. The <tt>Section</tt> field should be
664 <list compact="compact">
666 <em>section</em> if the package is in the
667 <em>main</em> archive area,
670 <em>area/section</em> if the package is in
671 the <em>contrib</em> or <em>non-free</em>
678 The Debian archive maintainers provide the authoritative
679 list of sections. At present, they are:
680 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
681 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
682 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
683 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
684 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
685 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
686 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
687 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
688 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
689 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
690 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
691 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
692 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
693 <em>zope</em>. The additional section <em>debian-installer</em>
694 contains special packages used by the installer and is not used
695 for normal Debian packages.
699 For more information about the sections and their definitions,
700 see the <url id="http://packages.debian.org/unstable/"
701 name="list of sections in unstable">.
705 <sect id="priorities">
706 <heading>Priorities</heading>
709 Each package should have a <em>priority</em> value, which is
710 included in the package's <em>control record</em>
711 (see <ref id="f-Priority">).
712 This information is used by the Debian package management tools to
713 separate high-priority packages from less-important packages.
717 The following <em>priority levels</em> are recognized by the
718 Debian package management tools.
720 <tag><tt>required</tt></tag>
722 Packages which are necessary for the proper
723 functioning of the system (usually, this means that
724 dpkg functionality depends on these packages).
725 Removing a <tt>required</tt> package may cause your
726 system to become totally broken and you may not even
727 be able to use <prgn>dpkg</prgn> to put things back,
728 so only do so if you know what you are doing. Systems
729 with only the <tt>required</tt> packages are probably
730 unusable, but they do have enough functionality to
731 allow the sysadmin to boot and install more software.
733 <tag><tt>important</tt></tag>
735 Important programs, including those which one would
736 expect to find on any Unix-like system. If the
737 expectation is that an experienced Unix person who
738 found it missing would say "What on earth is going on,
739 where is <prgn>foo</prgn>?", it must be an
740 <tt>important</tt> package.<footnote>
741 This is an important criterion because we are
742 trying to produce, amongst other things, a free
745 Other packages without which the system will not run
746 well or be usable must also have priority
747 <tt>important</tt>. This does
748 <em>not</em> include Emacs, the X Window System, TeX
749 or any other large applications. The
750 <tt>important</tt> packages are just a bare minimum of
751 commonly-expected and necessary tools.
753 <tag><tt>standard</tt></tag>
755 These packages provide a reasonably small but not too
756 limited character-mode system. This is what will be
757 installed by default if the user doesn't select anything
758 else. It doesn't include many large applications.
760 <tag><tt>optional</tt></tag>
762 (In a sense everything that isn't required is
763 optional, but that's not what is meant here.) This is
764 all the software that you might reasonably want to
765 install if you didn't know what it was and don't have
766 specialized requirements. This is a much larger system
767 and includes the X Window System, a full TeX
768 distribution, and many applications. Note that
769 optional packages should not conflict with each other.
771 <tag><tt>extra</tt></tag>
773 This contains all packages that conflict with others
774 with required, important, standard or optional
775 priorities, or are only likely to be useful if you
776 already know what they are or have specialized
777 requirements (such as packages containing only detached
784 Packages must not depend on packages with lower priority
785 values (excluding build-time dependencies). In order to
786 ensure this, the priorities of one or more packages may need
795 <heading>Binary packages</heading>
798 The Debian distribution is based on the Debian
799 package management system, called <prgn>dpkg</prgn>. Thus,
800 all packages in the Debian distribution must be provided
801 in the <tt>.deb</tt> file format.
805 A <tt>.deb</tt> package contains two sets of files: a set of files
806 to install on the system when the package is installed, and a set
807 of files that provide additional metadata about the package or
808 which are executed when the package is installed or removed. This
809 second set of files is called <em>control information files</em>.
810 Among those files are the package maintainer scripts
811 and <file>control</file>, the <qref id="binarycontrolfiles">binary
812 package control file</qref> that contains the control fields for
813 the package. Other control information files
814 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
815 file</qref> used to store shared library dependency information
816 and the <file>conffiles</file> file that lists the package's
817 configuration files (described in <ref id="config-files">).
821 There is unfortunately a collision of terminology here between
822 control information files and files in the Debian control file
823 format. Throughout this document, a <em>control file</em> refers
824 to a file in the Debian control file format. These files are
825 documented in <ref id="controlfields">. Only files referred to
826 specifically as <em>control information files</em> are the files
827 included in the control information file member of
828 the <file>.deb</file> file format used by binary packages. Most
829 control information files are not in the Debian control file
834 <heading>The package name</heading>
837 Every package must have a name that's unique within the Debian
842 The package name is included in the control field
843 <tt>Package</tt>, the format of which is described
844 in <ref id="f-Package">.
845 The package name is also included as a part of the file name
846 of the <tt>.deb</tt> file.
851 <heading>The version of a package</heading>
854 Every package has a version number recorded in its
855 <tt>Version</tt> control file field, described in
856 <ref id="f-Version">.
860 The package management system imposes an ordering on version
861 numbers, so that it can tell whether packages are being up- or
862 downgraded and so that package system front end applications
863 can tell whether a package it finds available is newer than
864 the one installed on the system. The version number format
865 has the most significant parts (as far as comparison is
866 concerned) at the beginning.
870 If an upstream package has problematic version numbers they
871 should be converted to a sane form for use in the
872 <tt>Version</tt> field.
876 <heading>Version numbers based on dates</heading>
879 In general, Debian packages should use the same version
880 numbers as the upstream sources. However, upstream version
881 numbers based on some date formats (sometimes used for
882 development or "snapshot" releases) will not be ordered
883 correctly by the package management software. For
884 example, <prgn>dpkg</prgn> will consider "96May01" to be
885 greater than "96Dec24".
889 To prevent having to use epochs for every new upstream
890 version, the date-based portion of any upstream version number
891 should be given in a way that sorts correctly: four-digit year
892 first, followed by a two-digit numeric month, followed by a
893 two-digit numeric date, possibly with punctuation between the
898 Native Debian packages (i.e., packages which have been written
899 especially for Debian) whose version numbers include dates
900 should also follow these rules. If punctuation is desired
901 between the date components, remember that hyphen (<tt>-</tt>)
902 cannot be used in native package versions. Period
903 (<tt>.</tt>) is normally a good choice.
909 <sect id="maintainer">
910 <heading>The maintainer of a package</heading>
913 Every package must have a maintainer, except for orphaned
914 packages as described below. The maintainer may be one person
915 or a group of people reachable from a common email address, such
916 as a mailing list. The maintainer is responsible for
917 maintaining the Debian packaging files, evaluating and
918 responding appropriately to reported bugs, uploading new
919 versions of the package (either directly or through a sponsor),
920 ensuring that the package is placed in the appropriate archive
921 area and included in Debian releases as appropriate for the
922 stability and utility of the package, and requesting removal of
923 the package from the Debian distribution if it is no longer
924 useful or maintainable.
928 The maintainer must be specified in the <tt>Maintainer</tt>
929 control field with their correct name and a working email
930 address. The email address given in the <tt>Maintainer</tt>
931 control field must accept mail from those role accounts in
932 Debian used to send automated mails regarding the package. This
933 includes non-spam mail from the bug-tracking system, all mail
934 from the Debian archive maintenance software, and other role
935 accounts or automated processes that are commonly agreed on by
936 the project.<footnote>
937 A sample implementation of such a whitelist written for the
938 Mailman mailing list management software is used for mailing
939 lists hosted by alioth.debian.org.
941 If one person or team maintains several packages, they should
942 use the same form of their name and email address in
943 the <tt>Maintainer</tt> fields of those packages.
947 The format of the <tt>Maintainer</tt> control field is
948 described in <ref id="f-Maintainer">.
952 If the maintainer of the package is a team of people with a
953 shared email address, the <tt>Uploaders</tt> control field must
954 be present and must contain at least one human with their
955 personal email address. See <ref id="f-Uploaders"> for the
956 syntax of that field.
960 An orphaned package is one with no current maintainer. Orphaned
961 packages should have their <tt>Maintainer</tt> control field set
962 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
963 These packages are considered maintained by the Debian project
964 as a whole until someone else volunteers to take over
965 maintenance.<footnote>
966 The detailed procedure for gracefully orphaning a package can
967 be found in the Debian Developer's Reference
968 (see <ref id="related">).
973 <sect id="descriptions">
974 <heading>The description of a package</heading>
977 Every Debian package must have a <tt>Description</tt> control
978 field which contains a synopsis and extended description of the
979 package. Technical information about the format of the
980 <tt>Description</tt> field is in <ref id="f-Description">.
984 The description should describe the package (the program) to a
985 user (system administrator) who has never met it before so that
986 they have enough information to decide whether they want to
987 install it. This description should not just be copied verbatim
988 from the program's documentation.
992 Put important information first, both in the synopsis and
993 extended description. Sometimes only the first part of the
994 synopsis or of the description will be displayed. You can
995 assume that there will usually be a way to see the whole
996 extended description.
1000 The description should also give information about the
1001 significant dependencies and conflicts between this package
1002 and others, so that the user knows why these dependencies and
1003 conflicts have been declared.
1007 Instructions for configuring or using the package should
1008 not be included (that is what installation scripts,
1009 manual pages, info files, etc., are for). Copyright
1010 statements and other administrivia should not be included
1011 either (that is what the copyright file is for).
1014 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1017 The single line synopsis should be kept brief - certainly
1018 under 80 characters.
1022 Do not include the package name in the synopsis line. The
1023 display software knows how to display this already, and you
1024 do not need to state it. Remember that in many situations
1025 the user may only see the synopsis line - make it as
1026 informative as you can.
1031 <sect1 id="extendeddesc"><heading>The extended description</heading>
1034 Do not try to continue the single line synopsis into the
1035 extended description. This will not work correctly when
1036 the full description is displayed, and makes no sense
1037 where only the summary (the single line synopsis) is
1042 The extended description should describe what the package
1043 does and how it relates to the rest of the system (in terms
1044 of, for example, which subsystem it is which part of).
1048 The description field needs to make sense to anyone, even
1049 people who have no idea about any of the things the
1050 package deals with.<footnote>
1051 The blurb that comes with a program in its
1052 announcements and/or <prgn>README</prgn> files is
1053 rarely suitable for use in a description. It is
1054 usually aimed at people who are already in the
1055 community where the package is used.
1064 <heading>Dependencies</heading>
1067 Every package must specify the dependency information
1068 about other packages that are required for the first to
1073 For example, a dependency entry must be provided for any
1074 shared libraries required by a dynamically-linked executable
1075 binary in a package.
1079 Packages are not required to declare any dependencies they
1080 have on other packages which are marked <tt>Essential</tt>
1081 (see below), and should not do so unless they depend on a
1082 particular version of that package.<footnote>
1084 Essential is needed in part to avoid unresolvable dependency
1085 loops on upgrade. If packages add unnecessary dependencies
1086 on packages in this set, the chances that there
1087 <strong>will</strong> be an unresolvable dependency loop
1088 caused by forcing these Essential packages to be configured
1089 first before they need to be is greatly increased. It also
1090 increases the chances that frontends will be unable to
1091 <strong>calculate</strong> an upgrade path, even if one
1095 Also, functionality is rarely ever removed from the
1096 Essential set, but <em>packages</em> have been removed from
1097 the Essential set when the functionality moved to a
1098 different package. So depending on these packages <em>just
1099 in case</em> they stop being essential does way more harm
1106 Sometimes, a package requires another package to be installed
1107 <em>and</em> configured before it can be installed. In this
1108 case, you must specify a <tt>Pre-Depends</tt> entry for
1113 You should not specify a <tt>Pre-Depends</tt> entry for a
1114 package before this has been discussed on the
1115 <tt>debian-devel</tt> mailing list and a consensus about
1116 doing that has been reached.
1120 The format of the package interrelationship control fields is
1121 described in <ref id="relationships">.
1125 <sect id="virtual_pkg">
1126 <heading>Virtual packages</heading>
1129 Sometimes, there are several packages which offer
1130 more-or-less the same functionality. In this case, it's
1131 useful to define a <em>virtual package</em> whose name
1132 describes that common functionality. (The virtual
1133 packages only exist logically, not physically; that's why
1134 they are called <em>virtual</em>.) The packages with this
1135 particular function will then <em>provide</em> the virtual
1136 package. Thus, any other package requiring that function
1137 can simply depend on the virtual package without having to
1138 specify all possible packages individually.
1142 All packages should use virtual package names where
1143 appropriate, and arrange to create new ones if necessary.
1144 They should not use virtual package names (except privately,
1145 amongst a cooperating group of packages) unless they have
1146 been agreed upon and appear in the list of virtual package
1147 names. (See also <ref id="virtual">)
1151 The latest version of the authoritative list of virtual
1152 package names can be found in the <tt>debian-policy</tt> package.
1153 It is also available from the Debian web mirrors at
1154 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1155 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1159 The procedure for updating the list is described in the preface
1166 <heading>Base system</heading>
1169 The <tt>base system</tt> is a minimum subset of the Debian
1170 system that is installed before everything else
1171 on a new system. Only very few packages are allowed to form
1172 part of the base system, in order to keep the required disk
1177 The base system consists of all those packages with priority
1178 <tt>required</tt> or <tt>important</tt>. Many of them will
1179 be tagged <tt>essential</tt> (see below).
1184 <heading>Essential packages</heading>
1187 Essential is defined as the minimal set of functionality that
1188 must be available and usable on the system at all times, even
1189 when packages are in an unconfigured (but unpacked) state.
1190 Packages are tagged <tt>essential</tt> for a system using the
1191 <tt>Essential</tt> control field. The format of the
1192 <tt>Essential</tt> control field is described in <ref
1197 Since these packages cannot be easily removed (one has to
1198 specify an extra <em>force option</em> to
1199 <prgn>dpkg</prgn> to do so), this flag must not be used
1200 unless absolutely necessary. A shared library package
1201 must not be tagged <tt>essential</tt>; dependencies will
1202 prevent its premature removal, and we need to be able to
1203 remove it when it has been superseded.
1207 Since dpkg will not prevent upgrading of other packages
1208 while an <tt>essential</tt> package is in an unconfigured
1209 state, all <tt>essential</tt> packages must supply all of
1210 their core functionality even when unconfigured. If the
1211 package cannot satisfy this requirement it must not be
1212 tagged as essential, and any packages depending on this
1213 package must instead have explicit dependency fields as
1218 Maintainers should take great care in adding any programs,
1219 interfaces, or functionality to <tt>essential</tt> packages.
1220 Packages may assume that functionality provided by
1221 <tt>essential</tt> packages is always available without
1222 declaring explicit dependencies, which means that removing
1223 functionality from the Essential set is very difficult and is
1224 almost never done. Any capability added to an
1225 <tt>essential</tt> package therefore creates an obligation to
1226 support that capability as part of the Essential set in
1231 You must not tag any packages <tt>essential</tt> before
1232 this has been discussed on the <tt>debian-devel</tt>
1233 mailing list and a consensus about doing that has been
1238 <sect id="maintscripts">
1239 <heading>Maintainer Scripts</heading>
1242 The package installation scripts should avoid producing
1243 output which is unnecessary for the user to see and
1244 should rely on <prgn>dpkg</prgn> to stave off boredom on
1245 the part of a user installing many packages. This means,
1246 amongst other things, using the <tt>--quiet</tt> option on
1247 <prgn>install-info</prgn>.
1251 Errors which occur during the execution of an installation
1252 script must be checked and the installation must not
1253 continue after an error.
1257 Note that in general <ref id="scripts"> applies to package
1258 maintainer scripts, too.
1262 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1263 to another package without consulting the maintainer of that
1264 package first. When adding or removing diversions, package
1265 maintainer scripts must provide the <tt>--package</tt> flag
1266 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1270 All packages which supply an instance of a common command
1271 name (or, in general, filename) should generally use
1272 <prgn>update-alternatives</prgn>, so that they may be
1273 installed together. If <prgn>update-alternatives</prgn>
1274 is not used, then each package must use
1275 <tt>Conflicts</tt> to ensure that other packages are
1276 de-installed. (In this case, it may be appropriate to
1277 specify a conflict against earlier versions of something
1278 that previously did not use
1279 <prgn>update-alternatives</prgn>; this is an exception to
1280 the usual rule that versioned conflicts should be
1284 <sect1 id="maintscriptprompt">
1285 <heading>Prompting in maintainer scripts</heading>
1287 Package maintainer scripts may prompt the user if
1288 necessary. Prompting must be done by communicating
1289 through a program, such as <prgn>debconf</prgn>, which
1290 conforms to the Debian Configuration Management
1291 Specification, version 2 or higher.
1295 Packages which are essential, or which are dependencies of
1296 essential packages, may fall back on another prompting method
1297 if no such interface is available when they are executed.
1301 The Debian Configuration Management Specification is included
1302 in the <file>debconf_specification</file> files in the
1303 <package>debian-policy</package> package.
1304 It is also available from the Debian web mirrors at
1305 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1306 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1310 Packages which use the Debian Configuration Management
1311 Specification may contain the additional control information
1312 files <file>config</file>
1313 and <file>templates</file>. <file>config</file> is an
1314 additional maintainer script used for package configuration,
1315 and <file>templates</file> contains templates used for user
1316 prompting. The <prgn>config</prgn> script might be run before
1317 the <prgn>preinst</prgn> script and before the package is
1318 unpacked or any of its dependencies or pre-dependencies are
1319 satisfied. Therefore it must work using only the tools
1320 present in <em>essential</em> packages.<footnote>
1321 <package>Debconf</package> or another tool that
1322 implements the Debian Configuration Management
1323 Specification will also be installed, and any
1324 versioned dependencies on it will be satisfied
1325 before preconfiguration begins.
1330 Packages which use the Debian Configuration Management
1331 Specification must allow for translation of their user-visible
1332 messages by using a gettext-based system such as the one
1333 provided by the <package>po-debconf</package> package.
1337 Packages should try to minimize the amount of prompting
1338 they need to do, and they should ensure that the user
1339 will only ever be asked each question once. This means
1340 that packages should try to use appropriate shared
1341 configuration files (such as <file>/etc/papersize</file> and
1342 <file>/etc/news/server</file>), and shared
1343 <package>debconf</package> variables rather than each
1344 prompting for their own list of required pieces of
1349 It also means that an upgrade should not ask the same
1350 questions again, unless the user has used
1351 <tt>dpkg --purge</tt> to remove the package's configuration.
1352 The answers to configuration questions should be stored in an
1353 appropriate place in <file>/etc</file> so that the user can
1354 modify them, and how this has been done should be
1359 If a package has a vitally important piece of
1360 information to pass to the user (such as "don't run me
1361 as I am, you must edit the following configuration files
1362 first or you risk your system emitting badly-formatted
1363 messages"), it should display this in the
1364 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1365 prompt the user to hit return to acknowledge the
1366 message. Copyright messages do not count as vitally
1367 important (they belong in
1368 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1369 neither do instructions on how to use a program (these
1370 should be in on-line documentation, where all the users
1375 Any necessary prompting should almost always be confined
1376 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1377 script. If it is done in the <prgn>postinst</prgn>, it
1378 should be protected with a conditional so that
1379 unnecessary prompting doesn't happen if a package's
1380 installation fails and the <prgn>postinst</prgn> is
1381 called with <tt>abort-upgrade</tt>,
1382 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1392 <heading>Source packages</heading>
1394 <sect id="standardsversion">
1395 <heading>Standards conformance</heading>
1398 Source packages should specify the most recent version number
1399 of this policy document with which your package complied
1400 when it was last updated.
1404 This information may be used to file bug reports
1405 automatically if your package becomes too much out of date.
1409 The version is specified in the <tt>Standards-Version</tt>
1411 The format of the <tt>Standards-Version</tt> field is
1412 described in <ref id="f-Standards-Version">.
1416 You should regularly, and especially if your package has
1417 become out of date, check for the newest Policy Manual
1418 available and update your package, if necessary. When your
1419 package complies with the new standards you should update the
1420 <tt>Standards-Version</tt> source package field and
1421 release it.<footnote>
1422 See the file <file>upgrading-checklist</file> for
1423 information about policy which has changed between
1424 different versions of this document.
1430 <sect id="pkg-relations">
1431 <heading>Package relationships</heading>
1434 Source packages should specify which binary packages they
1435 require to be installed or not to be installed in order to
1436 build correctly. For example, if building a package
1437 requires a certain compiler, then the compiler should be
1438 specified as a build-time dependency.
1442 It is not necessary to explicitly specify build-time
1443 relationships on a minimal set of packages that are always
1444 needed to compile, link and put in a Debian package a
1445 standard "Hello World!" program written in C or C++. The
1446 required packages are called <em>build-essential</em>, and
1447 an informational list can be found in
1448 <file>/usr/share/doc/build-essential/list</file> (which is
1449 contained in the <tt>build-essential</tt>
1452 <list compact="compact">
1454 This allows maintaining the list separately
1455 from the policy documents (the list does not
1456 need the kind of control that the policy
1460 Having a separate package allows one to install
1461 the build-essential packages on a machine, as
1462 well as allowing other packages such as tasks to
1463 require installation of the build-essential
1464 packages using the depends relation.
1467 The separate package allows bug reports against
1468 the list to be categorized separately from
1469 the policy management process in the BTS.
1476 When specifying the set of build-time dependencies, one
1477 should list only those packages explicitly required by the
1478 build. It is not necessary to list packages which are
1479 required merely because some other package in the list of
1480 build-time dependencies depends on them.<footnote>
1481 The reason for this is that dependencies change, and
1482 you should list all those packages, and <em>only</em>
1483 those packages that <em>you</em> need directly. What
1484 others need is their business. For example, if you
1485 only link against <file>libimlib</file>, you will need to
1486 build-depend on <package>libimlib2-dev</package> but
1487 not against any <tt>libjpeg*</tt> packages, even
1488 though <tt>libimlib2-dev</tt> currently depends on
1489 them: installation of <package>libimlib2-dev</package>
1490 will automatically ensure that all of its run-time
1491 dependencies are satisfied.
1496 If build-time dependencies are specified, it must be
1497 possible to build the package and produce working binaries
1498 on a system with only essential and build-essential
1499 packages installed and also those required to satisfy the
1500 build-time relationships (including any implied
1501 relationships). In particular, this means that version
1502 clauses should be used rigorously in build-time
1503 relationships so that one cannot produce bad or
1504 inconsistently configured packages when the relationships
1505 are properly satisfied.
1509 <ref id="relationships"> explains the technical details.
1514 <heading>Changes to the upstream sources</heading>
1517 If changes to the source code are made that are not
1518 specific to the needs of the Debian system, they should be
1519 sent to the upstream authors in whatever form they prefer
1520 so as to be included in the upstream version of the
1525 If you need to configure the package differently for
1526 Debian or for Linux, and the upstream source doesn't
1527 provide a way to do so, you should add such configuration
1528 facilities (for example, a new <prgn>autoconf</prgn> test
1529 or <tt>#define</tt>) and send the patch to the upstream
1530 authors, with the default set to the way they originally
1531 had it. You can then easily override the default in your
1532 <file>debian/rules</file> or wherever is appropriate.
1536 You should make sure that the <prgn>configure</prgn> utility
1537 detects the correct architecture specification string
1538 (refer to <ref id="arch-spec"> for details).
1542 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1543 <prgn>configure</prgn> scripts are used, you should edit the
1544 <file>.in</file> files rather than editing the
1545 <prgn>Makefile</prgn> directly. This allows the user to
1546 reconfigure the package if necessary. You should
1547 <em>not</em> configure the package and edit the generated
1548 <prgn>Makefile</prgn>! This makes it impossible for someone
1549 else to later reconfigure the package without losing the
1555 <sect id="dpkgchangelog">
1556 <heading>Debian changelog: <file>debian/changelog</file></heading>
1559 Changes in the Debian version of the package should be
1560 briefly explained in the Debian changelog file
1561 <file>debian/changelog</file>.<footnote>
1563 Mistakes in changelogs are usually best rectified by
1564 making a new changelog entry rather than "rewriting
1565 history" by editing old changelog entries.
1568 This includes modifications
1569 made in the Debian package compared to the upstream one
1570 as well as other changes and updates to the package.
1572 Although there is nothing stopping an author who is also
1573 the Debian maintainer from using this changelog for all
1574 their changes, it will have to be renamed if the Debian
1575 and upstream maintainers become different people. In such
1576 a case, however, it might be better to maintain the package
1577 as a non-native package.
1582 The format of the <file>debian/changelog</file> allows the
1583 package building tools to discover which version of the package
1584 is being built and find out other release-specific information.
1588 That format is a series of entries like this:
1590 <example compact="compact">
1591 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1593 [optional blank line(s), stripped]
1595 * <var>change details</var>
1596 <var>more change details</var>
1598 [blank line(s), included in output of dpkg-parsechangelog]
1600 * <var>even more change details</var>
1602 [optional blank line(s), stripped]
1604 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1609 <var>package</var> and <var>version</var> are the source
1610 package name and version number.
1614 <var>distribution(s)</var> lists the distributions where
1615 this version should be installed when it is uploaded - it
1616 is copied to the <tt>Distribution</tt> field in the
1617 <file>.changes</file> file. See <ref id="f-Distribution">.
1621 <var>urgency</var> is the value for the <tt>Urgency</tt>
1622 field in the <file>.changes</file> file for the upload
1623 (see <ref id="f-Urgency">). It is not possible to specify
1624 an urgency containing commas; commas are used to separate
1625 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1626 <prgn>dpkg</prgn> changelog format (though there is
1627 currently only one useful <var>keyword</var>,
1632 The change details may in fact be any series of lines
1633 starting with at least two spaces, but conventionally each
1634 change starts with an asterisk and a separating space and
1635 continuation lines are indented so as to bring them in
1636 line with the start of the text above. Blank lines may be
1637 used here to separate groups of changes, if desired.
1641 If this upload resolves bugs recorded in the Bug Tracking
1642 System (BTS), they may be automatically closed on the
1643 inclusion of this package into the Debian archive by
1644 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1645 in the change details.<footnote>
1646 To be precise, the string should match the following
1647 Perl regular expression:
1649 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1651 Then all of the bug numbers listed will be closed by the
1652 archive maintenance script (<prgn>katie</prgn>) using the
1653 <var>version</var> of the changelog entry.
1655 This information is conveyed via the <tt>Closes</tt> field
1656 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1660 The maintainer name and email address used in the changelog
1661 should be the details of the person uploading <em>this</em>
1662 version. They are <em>not</em> necessarily those of the
1663 usual package maintainer.<footnote>
1664 If the developer uploading the package is not one of the usual
1665 maintainers of the package (as listed in
1666 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1667 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1668 fields of the package), the first line of the changelog is
1669 conventionally used to explain why a non-maintainer is
1670 uploading the package. The Debian Developer's Reference
1671 (see <ref id="related">) documents the conventions
1673 The information here will be copied to the <tt>Changed-By</tt>
1674 field in the <tt>.changes</tt> file
1675 (see <ref id="f-Changed-By">), and then later used to send an
1676 acknowledgement when the upload has been installed.
1680 The <var>date</var> has the following format<footnote>
1681 This is the same as the format generated by <tt>date
1683 </footnote> (compatible and with the same semantics of
1684 RFC 2822 and RFC 5322):
1685 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1687 <list compact="compact">
1689 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1692 dd is a one- or two-digit day of the month (01-31)
1695 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1698 <item>yyyy is the four-digit year (e.g. 2010)</item>
1699 <item>hh is the two-digit hour (00-23)</item>
1700 <item>mm is the two-digit minutes (00-59)</item>
1701 <item>ss is the two-digit seconds (00-60)</item>
1703 +zzzz or -zzzz is the the time zone offset from Coordinated
1704 Universal Time (UTC). "+" indicates that the time is ahead
1705 of (i.e., east of) UTC and "-" indicates that the time is
1706 behind (i.e., west of) UTC. The first two digits indicate
1707 the hour difference from UTC and the last two digits
1708 indicate the number of additional minutes difference from
1709 UTC. The last two digits must be in the range 00-59.
1715 The first "title" line with the package name must start
1716 at the left hand margin. The "trailer" line with the
1717 maintainer and date details must be preceded by exactly
1718 one space. The maintainer details and the date must be
1719 separated by exactly two spaces.
1723 The entire changelog must be encoded in UTF-8.
1727 For more information on placement of the changelog files
1728 within binary packages, please see <ref id="changelogs">.
1732 <sect id="dpkgcopyright">
1733 <heading>Copyright: <file>debian/copyright</file></heading>
1735 Every package must be accompanied by a verbatim copy of its
1736 copyright information and distribution license in the file
1737 <file>/usr/share/doc/<var>package</var>/copyright</file>
1738 (see <ref id="copyrightfile"> for further details). Also see
1739 <ref id="pkgcopyright"> for further considerations related
1740 to copyrights for packages.
1744 <heading>Error trapping in makefiles</heading>
1747 When <prgn>make</prgn> invokes a command in a makefile
1748 (including your package's upstream makefiles and
1749 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1750 means that <prgn>sh</prgn>'s usual bad error handling
1751 properties apply: if you include a miniature script as one
1752 of the commands in your makefile you'll find that if you
1753 don't do anything about it then errors are not detected
1754 and <prgn>make</prgn> will blithely continue after
1759 Every time you put more than one shell command (this
1760 includes using a loop) in a makefile command you
1761 must make sure that errors are trapped. For
1762 simple compound commands, such as changing directory and
1763 then running a program, using <tt>&&</tt> rather
1764 than semicolon as a command separator is sufficient. For
1765 more complex commands including most loops and
1766 conditionals you should include a separate <tt>set -e</tt>
1767 command at the start of every makefile command that's
1768 actually one of these miniature shell scripts.
1772 <sect id="timestamps">
1773 <heading>Time Stamps</heading>
1775 Maintainers should preserve the modification times of the
1776 upstream source files in a package, as far as is reasonably
1778 The rationale is that there is some information conveyed
1779 by knowing the age of the file, for example, you could
1780 recognize that some documentation is very old by looking
1781 at the modification time, so it would be nice if the
1782 modification time of the upstream source would be
1788 <sect id="restrictions">
1789 <heading>Restrictions on objects in source packages</heading>
1792 The source package may not contain any hard links<footnote>
1794 This is not currently detected when building source
1795 packages, but only when extracting
1799 Hard links may be permitted at some point in the
1800 future, but would require a fair amount of
1803 </footnote>, device special files, sockets or setuid or
1804 setgid files.<footnote>
1805 Setgid directories are allowed.
1810 <sect id="debianrules">
1811 <heading>Main building script: <file>debian/rules</file></heading>
1814 This file must be an executable makefile, and contains the
1815 package-specific recipes for compiling the package and
1816 building binary package(s) from the source.
1820 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1821 so that it can be invoked by saying its name rather than
1822 invoking <prgn>make</prgn> explicitly. That is, invoking
1823 either of <tt>make -f debian/rules <em>args...</em></tt>
1824 or <tt>./debian/rules <em>args...</em></tt> must result in
1829 The following targets are required and must be implemented
1830 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1831 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1832 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1836 Since an interactive <file>debian/rules</file> script makes it
1837 impossible to auto-compile that package and also makes it hard
1838 for other people to reproduce the same binary package, all
1839 required targets must be non-interactive. It also follows that
1840 any target that these targets depend on must also be
1845 The targets are as follows:
1847 <tag><tt>build</tt> (required)</tag>
1850 The <tt>build</tt> target should perform all the
1851 configuration and compilation of the package.
1852 If a package has an interactive pre-build
1853 configuration routine, the Debian source package
1854 must either be built after this has taken place (so
1855 that the binary package can be built without rerunning
1856 the configuration) or the configuration routine
1857 modified to become non-interactive. (The latter is
1858 preferable if there are architecture-specific features
1859 detected by the configuration routine.)
1863 For some packages, notably ones where the same
1864 source tree is compiled in different ways to produce
1865 two binary packages, the <tt>build</tt> target
1866 does not make much sense. For these packages it is
1867 good enough to provide two (or more) targets
1868 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1869 for each of the ways of building the package, and a
1870 <tt>build</tt> target that does nothing. The
1871 <tt>binary</tt> target will have to build the
1872 package in each of the possible ways and make the
1873 binary package out of each.
1877 The <tt>build</tt> target must not do anything
1878 that might require root privilege.
1882 The <tt>build</tt> target may need to run the
1883 <tt>clean</tt> target first - see below.
1887 When a package has a configuration and build routine
1888 which takes a long time, or when the makefiles are
1889 poorly designed, or when <tt>build</tt> needs to
1890 run <tt>clean</tt> first, it is a good idea to
1891 <tt>touch build</tt> when the build process is
1892 complete. This will ensure that if <tt>debian/rules
1893 build</tt> is run again it will not rebuild the whole
1895 Another common way to do this is for <tt>build</tt>
1896 to depend on <prgn>build-stamp</prgn> and to do
1897 nothing else, and for the <prgn>build-stamp</prgn>
1898 target to do the building and to <tt>touch
1899 build-stamp</tt> on completion. This is
1900 especially useful if the build routine creates a
1901 file or directory called <tt>build</tt>; in such a
1902 case, <tt>build</tt> will need to be listed as
1903 a phony target (i.e., as a dependency of the
1904 <tt>.PHONY</tt> target). See the documentation of
1905 <prgn>make</prgn> for more information on phony
1911 <tag><tt>build-arch</tt> (optional),
1912 <tt>build-indep</tt> (optional)
1916 A package may also provide both of the targets
1917 <tt>build-arch</tt> and <tt>build-indep</tt>.
1918 The <tt>build-arch</tt> target, if provided, should
1919 perform all the configuration and compilation required for
1920 producing all architecture-dependant binary packages
1921 (those packages for which the body of the
1922 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1923 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1924 target, if provided, should perform all the configuration
1925 and compilation required for producing all
1926 architecture-independent binary packages (those packages
1927 for which the body of the <tt>Architecture</tt> field
1928 in <tt>debian/control</tt> is <tt>all</tt>).
1929 The <tt>build</tt> target should depend on those of the
1930 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1931 are provided in the rules file.<footnote>
1932 The intent of this split is so that binary-only builds
1933 need not install the dependencies required for
1934 the <tt>build-indep</tt> target. However, this is not
1935 yet used in practice since <tt>dpkg-buildpackage
1936 -B</tt>, and therefore the autobuilders,
1937 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1938 due to the difficulties in determining whether the
1939 optional <tt>build-arch</tt> target exists.
1944 If one or both of the targets <tt>build-arch</tt> and
1945 <tt>build-indep</tt> are not provided, then invoking
1946 <file>debian/rules</file> with one of the not-provided
1947 targets as arguments should produce a exit status code
1948 of 2. Usually this is provided automatically by make
1949 if the target is missing.
1953 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1954 must not do anything that might require root privilege.
1958 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1959 (required), <tt>binary-indep</tt> (required)
1963 The <tt>binary</tt> target must be all that is
1964 necessary for the user to build the binary package(s)
1965 produced from this source package. It is
1966 split into two parts: <prgn>binary-arch</prgn> builds
1967 the binary packages which are specific to a particular
1968 architecture, and <tt>binary-indep</tt> builds
1969 those which are not.
1972 <tt>binary</tt> may be (and commonly is) a target with
1973 no commands which simply depends on
1974 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1977 Both <tt>binary-*</tt> targets should depend on the
1978 <tt>build</tt> target, or on the appropriate
1979 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1980 provided, so that the package is built if it has not
1981 been already. It should then create the relevant
1982 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1983 make their control files and <prgn>dpkg-deb</prgn> to
1984 build them and place them in the parent of the top
1989 Both the <tt>binary-arch</tt> and
1990 <tt>binary-indep</tt> targets <em>must</em> exist.
1991 If one of them has nothing to do (which will always be
1992 the case if the source generates only a single binary
1993 package, whether architecture-dependent or not), it
1994 must still exist and must always succeed.
1998 The <tt>binary</tt> targets must be invoked as
2000 The <prgn>fakeroot</prgn> package often allows one
2001 to build a package correctly even without being
2007 <tag><tt>clean</tt> (required)</tag>
2010 This must undo any effects that the <tt>build</tt>
2011 and <tt>binary</tt> targets may have had, except
2012 that it should leave alone any output files created in
2013 the parent directory by a run of a <tt>binary</tt>
2018 If a <tt>build</tt> file is touched at the end of
2019 the <tt>build</tt> target, as suggested above, it
2020 should be removed as the first action that
2021 <tt>clean</tt> performs, so that running
2022 <tt>build</tt> again after an interrupted
2023 <tt>clean</tt> doesn't think that everything is
2028 The <tt>clean</tt> target may need to be
2029 invoked as root if <tt>binary</tt> has been
2030 invoked since the last <tt>clean</tt>, or if
2031 <tt>build</tt> has been invoked as root (since
2032 <tt>build</tt> may create directories, for
2037 <tag><tt>get-orig-source</tt> (optional)</tag>
2040 This target fetches the most recent version of the
2041 original source package from a canonical archive site
2042 (via FTP or WWW, for example), does any necessary
2043 rearrangement to turn it into the original source
2044 tar file format described below, and leaves it in the
2049 This target may be invoked in any directory, and
2050 should take care to clean up any temporary files it
2055 This target is optional, but providing it if
2056 possible is a good idea.
2060 <tag><tt>patch</tt> (optional)</tag>
2063 This target performs whatever additional actions are
2064 required to make the source ready for editing (unpacking
2065 additional upstream archives, applying patches, etc.).
2066 It is recommended to be implemented for any package where
2067 <tt>dpkg-source -x</tt> does not result in source ready
2068 for additional modification. See
2069 <ref id="readmesource">.
2075 The <tt>build</tt>, <tt>binary</tt> and
2076 <tt>clean</tt> targets must be invoked with the current
2077 directory being the package's top-level directory.
2082 Additional targets may exist in <file>debian/rules</file>,
2083 either as published or undocumented interfaces or for the
2084 package's internal use.
2088 The architectures we build on and build for are determined
2089 by <prgn>make</prgn> variables using the
2090 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2091 You can determine the Debian architecture and the GNU style
2092 architecture specification string for the build architecture as
2093 well as for the host architecture. The build architecture is
2094 the architecture on which <file>debian/rules</file> is run and
2095 the package build is performed. The host architecture is the
2096 architecture on which the resulting package will be installed
2097 and run. These are normally the same, but may be different in
2098 the case of cross-compilation (building packages for one
2099 architecture on machines of a different architecture).
2103 Here is a list of supported <prgn>make</prgn> variables:
2104 <list compact="compact">
2106 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2109 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2112 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2115 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2116 specification string)
2119 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2120 <tt>DEB_*_GNU_TYPE</tt>)
2123 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2124 <tt>DEB_*_GNU_TYPE</tt>)
2126 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2127 the build architecture or <tt>HOST</tt> for specification of the
2132 Backward compatibility can be provided in the rules file
2133 by setting the needed variables to suitable default
2134 values; please refer to the documentation of
2135 <prgn>dpkg-architecture</prgn> for details.
2139 It is important to understand that the <tt>DEB_*_ARCH</tt>
2140 string only determines which Debian architecture we are
2141 building on or for. It should not be used to get the CPU
2142 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2143 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2144 GNU style variables should generally only be used with upstream
2148 <sect1 id="debianrules-options">
2149 <heading><file>debian/rules</file> and
2150 <tt>DEB_BUILD_OPTIONS</tt></heading>
2153 Supporting the standardized environment variable
2154 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2155 contain several flags to change how a package is compiled and
2156 built. Each flag must be in the form <var>flag</var> or
2157 <var>flag</var>=<var>options</var>. If multiple flags are
2158 given, they must be separated by whitespace.<footnote>
2159 Some packages support any delimiter, but whitespace is the
2160 easiest to parse inside a makefile and avoids ambiguity with
2161 flag values that contain commas.
2163 <var>flag</var> must start with a lowercase letter
2164 (<tt>a-z</tt>) and consist only of lowercase letters,
2165 numbers (<tt>0-9</tt>), and the characters
2166 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2167 <var>options</var> must not contain whitespace. The same
2168 tag should not be given multiple times with conflicting
2169 values. Package maintainers may assume that
2170 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2174 The meaning of the following tags has been standardized:
2178 This tag says to not run any build-time test suite
2179 provided by the package.
2183 The presence of this tag means that the package should
2184 be compiled with a minimum of optimization. For C
2185 programs, it is best to add <tt>-O0</tt> to
2186 <tt>CFLAGS</tt> (although this is usually the default).
2187 Some programs might fail to build or run at this level
2188 of optimization; it may be necessary to use
2189 <tt>-O1</tt>, for example.
2193 This tag means that the debugging symbols should not be
2194 stripped from the binary during installation, so that
2195 debugging information may be included in the package.
2197 <tag>parallel=n</tag>
2199 This tag means that the package should be built using up
2200 to <tt>n</tt> parallel processes if the package build
2201 system supports this.<footnote>
2202 Packages built with <tt>make</tt> can often implement
2203 this by passing the <tt>-j</tt><var>n</var> option to
2206 If the package build system does not support parallel
2207 builds, this string must be ignored. If the package
2208 build system only supports a lower level of concurrency
2209 than <var>n</var>, the package should be built using as
2210 many parallel processes as the package build system
2211 supports. It is up to the package maintainer to decide
2212 whether the package build times are long enough and the
2213 package build system is robust enough to make supporting
2214 parallel builds worthwhile.
2220 Unknown flags must be ignored by <file>debian/rules</file>.
2224 The following makefile snippet is an example of how one may
2225 implement the build options; you will probably have to
2226 massage this example in order to make it work for your
2228 <example compact="compact">
2231 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2232 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2233 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2234 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2236 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2241 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2242 INSTALL_PROGRAM += -s
2244 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2245 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2246 MAKEFLAGS += -j$(NUMJOBS)
2251 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2252 # Code to run the package test suite.
2259 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2260 <sect id="substvars">
2261 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2264 When <prgn>dpkg-gencontrol</prgn>
2265 generates <qref id="binarycontrolfiles">binary package control
2266 files</qref> (<file>DEBIAN/control</file>), it performs variable
2267 substitutions on its output just before writing it. Variable
2268 substitutions have the form <tt>${<var>variable</var>}</tt>.
2269 The optional file <file>debian/substvars</file> contains
2270 variable substitutions to be used; variables can also be set
2271 directly from <file>debian/rules</file> using the <tt>-V</tt>
2272 option to the source packaging commands, and certain predefined
2273 variables are also available.
2277 The <file>debian/substvars</file> file is usually generated and
2278 modified dynamically by <file>debian/rules</file> targets, in
2279 which case it must be removed by the <tt>clean</tt> target.
2283 See <manref name="deb-substvars" section="5"> for full
2284 details about source variable substitutions, including the
2285 format of <file>debian/substvars</file>.</p>
2288 <sect id="debianwatch">
2289 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2292 This is an optional, recommended configuration file for the
2293 <tt>uscan</tt> utility which defines how to automatically scan
2294 ftp or http sites for newly available updates of the
2295 package. This is used
2296 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2297 tools to help with quality control and maintenance of the
2298 distribution as a whole.
2303 <sect id="debianfiles">
2304 <heading>Generated files list: <file>debian/files</file></heading>
2307 This file is not a permanent part of the source tree; it
2308 is used while building packages to record which files are
2309 being generated. <prgn>dpkg-genchanges</prgn> uses it
2310 when it generates a <file>.changes</file> file.
2314 It should not exist in a shipped source package, and so it
2315 (and any backup files or temporary files such as
2316 <file>files.new</file><footnote>
2317 <file>files.new</file> is used as a temporary file by
2318 <prgn>dpkg-gencontrol</prgn> and
2319 <prgn>dpkg-distaddfile</prgn> - they write a new
2320 version of <tt>files</tt> here before renaming it,
2321 to avoid leaving a corrupted copy if an error
2323 </footnote>) should be removed by the
2324 <tt>clean</tt> target. It may also be wise to
2325 ensure a fresh start by emptying or removing it at the
2326 start of the <tt>binary</tt> target.
2330 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2331 package, it adds an entry to <file>debian/files</file> for the
2332 <file>.deb</file> file that will be created when <tt>dpkg-deb
2333 --build</tt> is run for that binary package. So for most
2334 packages all that needs to be done with this file is to
2335 delete it in the <tt>clean</tt> target.
2339 If a package upload includes files besides the source
2340 package and any binary packages whose control files were
2341 made with <prgn>dpkg-gencontrol</prgn> then they should be
2342 placed in the parent of the package's top-level directory
2343 and <prgn>dpkg-distaddfile</prgn> should be called to add
2344 the file to the list in <file>debian/files</file>.</p>
2347 <sect id="embeddedfiles">
2348 <heading>Convenience copies of code</heading>
2351 Some software packages include in their distribution convenience
2352 copies of code from other software packages, generally so that
2353 users compiling from source don't have to download multiple
2354 packages. Debian packages should not make use of these
2355 convenience copies unless the included package is explicitly
2356 intended to be used in this way.<footnote>
2357 For example, parts of the GNU build system work like this.
2359 If the included code is already in the Debian archive in the
2360 form of a library, the Debian packaging should ensure that
2361 binary packages reference the libraries already in Debian and
2362 the convenience copy is not used. If the included code is not
2363 already in Debian, it should be packaged separately as a
2364 prerequisite if possible.
2366 Having multiple copies of the same code in Debian is
2367 inefficient, often creates either static linking or shared
2368 library conflicts, and, most importantly, increases the
2369 difficulty of handling security vulnerabilities in the
2375 <sect id="readmesource">
2376 <heading>Source package handling:
2377 <file>debian/README.source</file></heading>
2380 If running <prgn>dpkg-source -x</prgn> on a source package
2381 doesn't produce the source of the package, ready for editing,
2382 and allow one to make changes and run
2383 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2384 without taking any additional steps, creating a
2385 <file>debian/README.source</file> documentation file is
2386 recommended. This file should explain how to do all of the
2389 <item>Generate the fully patched source, in a form ready for
2390 editing, that would be built to create Debian
2391 packages. Doing this with a <tt>patch</tt> target in
2392 <file>debian/rules</file> is recommended; see
2393 <ref id="debianrules">.</item>
2394 <item>Modify the source and save those modifications so that
2395 they will be applied when building the package.</item>
2396 <item>Remove source modifications that are currently being
2397 applied when building the package.</item>
2398 <item>Optionally, document what steps are necessary to
2399 upgrade the Debian source package to a new upstream version,
2400 if applicable.</item>
2402 This explanation should include specific commands and mention
2403 any additional required Debian packages. It should not assume
2404 familiarity with any specific Debian packaging system or patch
2409 This explanation may refer to a documentation file installed by
2410 one of the package's build dependencies provided that the
2411 referenced documentation clearly explains these tasks and is not
2412 a general reference manual.
2416 <file>debian/README.source</file> may also include any other
2417 information that would be helpful to someone modifying the
2418 source package. Even if the package doesn't fit the above
2419 description, maintainers are encouraged to document in a
2420 <file>debian/README.source</file> file any source package with a
2421 particularly complex or unintuitive source layout or build
2422 system (for example, a package that builds the same source
2423 multiple times to generate different binary packages).
2429 <chapt id="controlfields">
2430 <heading>Control files and their fields</heading>
2433 The package management system manipulates data represented in
2434 a common format, known as <em>control data</em>, stored in
2435 <em>control files</em>.
2436 Control files are used for source packages, binary packages and
2437 the <file>.changes</file> files which control the installation
2438 of uploaded files<footnote>
2439 <prgn>dpkg</prgn>'s internal databases are in a similar
2444 <sect id="controlsyntax">
2445 <heading>Syntax of control files</heading>
2448 A control file consists of one or more paragraphs of
2450 The paragraphs are also sometimes referred to as stanzas.
2452 The paragraphs are separated by blank lines. Some control
2453 files allow only one paragraph; others allow several, in
2454 which case each paragraph usually refers to a different
2455 package. (For example, in source packages, the first
2456 paragraph refers to the source package, and later paragraphs
2457 refer to binary packages generated from the source.)
2461 Each paragraph consists of a series of data fields; each
2462 field consists of the field name, followed by a colon and
2463 then the data/value associated with that field. It ends at
2464 the end of the (logical) line. Horizontal whitespace
2465 (spaces and tabs) may occur immediately before or after the
2466 value and is ignored there; it is conventional to put a
2467 single space after the colon. For example, a field might
2469 <example compact="compact">
2472 the field name is <tt>Package</tt> and the field value
2477 A paragraph must not contain more than one instance of a
2478 particular field name.
2482 Many fields' values may span several lines; in this case
2483 each continuation line must start with a space or a tab.
2484 Any trailing spaces or tabs at the end of individual
2485 lines of a field value are ignored.
2489 In fields where it is specified that lines may not wrap,
2490 only a single line of data is allowed and whitespace is not
2491 significant in a field body. Whitespace must not appear
2492 inside names (of packages, architectures, files or anything
2493 else) or version numbers, or between the characters of
2494 multi-character version relationships.
2498 Field names are not case-sensitive, but it is usual to
2499 capitalize the field names using mixed case as shown below.
2500 Field values are case-sensitive unless the description of the
2501 field says otherwise.
2505 Blank lines, or lines consisting only of spaces and tabs,
2506 are not allowed within field values or between fields - that
2507 would mean a new paragraph.
2511 All control files must be encoded in UTF-8.
2515 <sect id="sourcecontrolfiles">
2516 <heading>Source package control files -- <file>debian/control</file></heading>
2519 The <file>debian/control</file> file contains the most vital
2520 (and version-independent) information about the source package
2521 and about the binary packages it creates.
2525 The first paragraph of the control file contains information about
2526 the source package in general. The subsequent sets each describe a
2527 binary package that the source tree builds.
2531 The fields in the general paragraph (the first one, for the source
2534 <list compact="compact">
2535 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2538 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2539 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2540 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2541 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2542 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2547 The fields in the binary package paragraphs are:
2549 <list compact="compact">
2550 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2553 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2554 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2555 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2556 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2562 The syntax and semantics of the fields are described below.
2566 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2567 generate control files for binary packages (see below), by
2568 <prgn>dpkg-genchanges</prgn> to generate the
2569 <file>.changes</file> file to accompany the upload, and by
2570 <prgn>dpkg-source</prgn> when it creates the
2571 <file>.dsc</file> source control file as part of a source
2572 archive. Many fields are permitted to span multiple lines in
2573 <file>debian/control</file> but not in any other control
2574 file. These tools are responsible for removing the line
2575 breaks from such fields when using fields from
2576 <file>debian/control</file> to generate other control files.
2580 The fields here may contain variable references - their
2581 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2582 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2583 when they generate output control files.
2584 See <ref id="substvars"> for details.
2588 In addition to the control file syntax described <qref
2589 id="controlsyntax">above</qref>, this file may also contain
2590 comment lines starting with <tt>#</tt> without any preceding
2591 whitespace. All such lines are ignored, even in the middle of
2592 continuation lines for a multiline field, and do not end a
2598 <sect id="binarycontrolfiles">
2599 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2602 The <file>DEBIAN/control</file> file contains the most vital
2603 (and version-dependent) information about a binary package. It
2604 consists of a single paragraph.
2608 The fields in this file are:
2610 <list compact="compact">
2611 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2613 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2614 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2615 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2616 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2618 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2619 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2620 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2627 <sect id="debiansourcecontrolfiles">
2628 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2631 This file consists of a single paragraph, possibly surrounded by
2632 a PGP signature. The fields of that paragraph are listed below.
2633 Their syntax is described above, in <ref id="pkg-controlfields">.
2635 <list compact="compact">
2636 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2637 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2639 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2640 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2641 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2643 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2644 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2645 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2646 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2647 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2648 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2653 The source package control file is generated by
2654 <prgn>dpkg-source</prgn> when it builds the source
2655 archive, from other files in the source package,
2656 described above. When unpacking, it is checked against
2657 the files and directories in the other parts of the
2663 <sect id="debianchangesfiles">
2664 <heading>Debian changes files -- <file>.changes</file></heading>
2667 The <file>.changes</file> files are used by the Debian archive
2668 maintenance software to process updates to packages. They
2669 consist of a single paragraph, possibly surrounded by a PGP
2670 signature. That paragraph contains information from the
2671 <file>debian/control</file> file and other data about the
2672 source package gathered via <file>debian/changelog</file>
2673 and <file>debian/rules</file>.
2677 <file>.changes</file> files have a format version that is
2678 incremented whenever the documented fields or their meaning
2679 change. This document describes format &changesversion;.
2683 The fields in this file are:
2685 <list compact="compact">
2686 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2692 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2694 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2696 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2698 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2700 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2701 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2706 <sect id="controlfieldslist">
2707 <heading>List of fields</heading>
2709 <sect1 id="f-Source">
2710 <heading><tt>Source</tt></heading>
2713 This field identifies the source package name.
2717 In <file>debian/control</file> or a <file>.dsc</file> file,
2718 this field must contain only the name of the source package.
2722 In a binary package control file or a <file>.changes</file>
2723 file, the source package name may be followed by a version
2724 number in parentheses<footnote>
2725 It is customary to leave a space after the package name
2726 if a version number is specified.
2728 This version number may be omitted (and is, by
2729 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2730 the <tt>Version</tt> field of the binary package in
2731 question. The field itself may be omitted from a binary
2732 package control file when the source package has the same
2733 name and version as the binary package.
2737 Package names (both source and binary,
2738 see <ref id="f-Package">) must consist only of lower case
2739 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2740 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2741 (<tt>.</tt>). They must be at least two characters long and
2742 must start with an alphanumeric character.
2746 <sect1 id="f-Maintainer">
2747 <heading><tt>Maintainer</tt></heading>
2750 The package maintainer's name and email address. The name
2751 must come first, then the email address inside angle
2752 brackets <tt><></tt> (in RFC822 format).
2756 If the maintainer's name contains a full stop then the
2757 whole field will not work directly as an email address due
2758 to a misfeature in the syntax specified in RFC822; a
2759 program using this field as an address must check for this
2760 and correct the problem if necessary (for example by
2761 putting the name in round brackets and moving it to the
2762 end, and bringing the email address forward).
2766 See <ref id="maintainer"> for additional requirements and
2767 information about package maintainers.
2771 <sect1 id="f-Uploaders">
2772 <heading><tt>Uploaders</tt></heading>
2775 List of the names and email addresses of co-maintainers of the
2776 package, if any. If the package has other maintainers besides
2777 the one named in the <qref id="f-Maintainer">Maintainer
2778 field</qref>, their names and email addresses should be listed
2779 here. The format of each entry is the same as that of the
2780 Maintainer field, and multiple entries must be comma
2785 This is normally an optional field, but if
2786 the <tt>Maintainer</tt> control field names a group of people
2787 and a shared email address, the <tt>Uploaders</tt> field must
2788 be present and must contain at least one human with their
2789 personal email address.
2793 Any parser that interprets the Uploaders field in
2794 <file>debian/control</file> must permit it to span multiple
2795 lines. Line breaks in an Uploaders field that spans multiple
2796 lines are not significant and the semantics of the field are
2797 the same as if the line breaks had not been present.
2801 <sect1 id="f-Changed-By">
2802 <heading><tt>Changed-By</tt></heading>
2805 The name and email address of the person who prepared this
2806 version of the package, usually a maintainer. The syntax is
2807 the same as for the <qref id="f-Maintainer">Maintainer
2812 <sect1 id="f-Section">
2813 <heading><tt>Section</tt></heading>
2816 This field specifies an application area into which the package
2817 has been classified. See <ref id="subsections">.
2821 When it appears in the <file>debian/control</file> file,
2822 it gives the value for the subfield of the same name in
2823 the <tt>Files</tt> field of the <file>.changes</file> file.
2824 It also gives the default for the same field in the binary
2829 <sect1 id="f-Priority">
2830 <heading><tt>Priority</tt></heading>
2833 This field represents how important it is that the user
2834 have the package installed. See <ref id="priorities">.
2838 When it appears in the <file>debian/control</file> file,
2839 it gives the value for the subfield of the same name in
2840 the <tt>Files</tt> field of the <file>.changes</file> file.
2841 It also gives the default for the same field in the binary
2846 <sect1 id="f-Package">
2847 <heading><tt>Package</tt></heading>
2850 The name of the binary package.
2854 Binary package names must follow the same syntax and
2855 restrictions as source package names. See <ref id="f-Source">
2860 <sect1 id="f-Architecture">
2861 <heading><tt>Architecture</tt></heading>
2864 Depending on context and the control file used, the
2865 <tt>Architecture</tt> field can include the following sets of
2869 A unique single word identifying a Debian machine
2870 architecture as described in <ref id="arch-spec">.
2873 An architecture wildcard identifying a set of Debian
2874 machine architectures, see <ref id="arch-wildcard-spec">.
2875 <tt>any</tt> matches all Debian machine architectures
2876 and is the most frequently used.
2879 <tt>all</tt>, which indicates an
2880 architecture-independent package.
2883 <tt>source</tt>, which indicates a source package.
2889 In the main <file>debian/control</file> file in the source
2890 package, this field may contain the special
2891 value <tt>all</tt>, the special architecture
2892 wildcard <tt>any</tt>, or a list of specific and wildcard
2893 architectures separated by spaces. If <tt>all</tt>
2894 or <tt>any</tt> appears, that value must be the entire
2895 contents of the field. Most packages will use
2896 either <tt>all</tt> or <tt>any</tt>.
2900 Specifying a specific list of architectures indicates that the
2901 source will build an architecture-dependent package only on
2902 architectures included in the list. Specifying a list of
2903 architecture wildcards indicates that the source will build an
2904 architecture-dependent package on only those architectures
2905 that match any of the specified architecture wildcards.
2906 Specifying a list of architectures or architecture wildcards
2907 other than <tt>any</tt> is for the minority of cases where a
2908 program is not portable or is not useful on some
2909 architectures. Where possible, the program should be made
2914 In the source package control file <file>.dsc</file>, this
2915 field may contain either the architecture
2916 wildcard <tt>any</tt> or a list of architectures and
2917 architecture wildcards separated by spaces. If a list is
2918 given, it may include (or consist solely of) the special
2919 value <tt>all</tt>. In other words, in <file>.dsc</file>
2920 files unlike the <file>debian/control</file>, <tt>all</tt> may
2921 occur in combination with specific architectures.
2922 The <tt>Architecture</tt> field in the source package control
2923 file <file>.dsc</file> is generally constructed from
2924 the <tt>Architecture</tt> fields in
2925 the <file>debian/control</file> in the source package.
2929 Specifying <tt>any</tt> indicates that the source package
2930 isn't dependent on any particular architecture and should
2931 compile fine on any one. The produced binary package(s)
2932 will either be specific to whatever the current build
2933 architecture is or will be architecture-independent.
2937 Specifying only <tt>all</tt> indicates that the source package
2938 will only build architecture-independent packages. If this is
2939 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2940 <tt>any</tt> implies that the source package will build at
2941 least one architecture-dependent package.
2945 Specifying a list of architectures or architecture wildcards
2946 indicates that the source will build an architecture-dependent
2947 package, and will only work correctly on the listed or
2948 matching architectures. If the source package also builds at
2949 least one architecture-independent package, <tt>all</tt> will
2950 also be included in the list.
2954 In a <file>.changes</file> file, the <tt>Architecture</tt>
2955 field lists the architecture(s) of the package(s) currently
2956 being uploaded. This will be a list; if the source for the
2957 package is also being uploaded, the special
2958 entry <tt>source</tt> is also present. <tt>all</tt> will be
2959 present if any architecture-independent packages are being
2960 uploaded. Architecture wildcards such as <tt>any</tt> must
2961 never occur in the <tt>Architecture</tt> field in
2962 the <file>.changes</file> file.
2966 See <ref id="debianrules"> for information on how to get
2967 the architecture for the build process.
2971 <sect1 id="f-Essential">
2972 <heading><tt>Essential</tt></heading>
2975 This is a boolean field which may occur only in the
2976 control file of a binary package or in a per-package fields
2977 paragraph of a main source control data file.
2981 If set to <tt>yes</tt> then the package management system
2982 will refuse to remove the package (upgrading and replacing
2983 it is still possible). The other possible value is <tt>no</tt>,
2984 which is the same as not having the field at all.
2989 <heading>Package interrelationship fields:
2990 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2991 <tt>Recommends</tt>, <tt>Suggests</tt>,
2992 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2993 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2997 These fields describe the package's relationships with
2998 other packages. Their syntax and semantics are described
2999 in <ref id="relationships">.</p>
3002 <sect1 id="f-Standards-Version">
3003 <heading><tt>Standards-Version</tt></heading>
3006 The most recent version of the standards (the policy
3007 manual and associated texts) with which the package
3012 The version number has four components: major and minor
3013 version number and major and minor patch level. When the
3014 standards change in a way that requires every package to
3015 change the major number will be changed. Significant
3016 changes that will require work in many packages will be
3017 signaled by a change to the minor number. The major patch
3018 level will be changed for any change to the meaning of the
3019 standards, however small; the minor patch level will be
3020 changed when only cosmetic, typographical or other edits
3021 are made which neither change the meaning of the document
3022 nor affect the contents of packages.
3026 Thus only the first three components of the policy version
3027 are significant in the <em>Standards-Version</em> control
3028 field, and so either these three components or all four
3029 components may be specified.<footnote>
3030 In the past, people specified the full version number
3031 in the Standards-Version field, for example "2.3.0.0".
3032 Since minor patch-level changes don't introduce new
3033 policy, it was thought it would be better to relax
3034 policy and only require the first 3 components to be
3035 specified, in this example "2.3.0". All four
3036 components may still be used if someone wishes to do so.
3042 <sect1 id="f-Version">
3043 <heading><tt>Version</tt></heading>
3046 The version number of a package. The format is:
3047 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3051 The three components here are:
3053 <tag><var>epoch</var></tag>
3056 This is a single (generally small) unsigned integer. It
3057 may be omitted, in which case zero is assumed. If it is
3058 omitted then the <var>upstream_version</var> may not
3063 It is provided to allow mistakes in the version numbers
3064 of older versions of a package, and also a package's
3065 previous version numbering schemes, to be left behind.
3069 <tag><var>upstream_version</var></tag>
3072 This is the main part of the version number. It is
3073 usually the version number of the original ("upstream")
3074 package from which the <file>.deb</file> file has been made,
3075 if this is applicable. Usually this will be in the same
3076 format as that specified by the upstream author(s);
3077 however, it may need to be reformatted to fit into the
3078 package management system's format and comparison
3083 The comparison behavior of the package management system
3084 with respect to the <var>upstream_version</var> is
3085 described below. The <var>upstream_version</var>
3086 portion of the version number is mandatory.
3090 The <var>upstream_version</var> may contain only
3091 alphanumerics<footnote>
3092 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3094 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3095 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3096 tilde) and should start with a digit. If there is no
3097 <var>debian_revision</var> then hyphens are not allowed;
3098 if there is no <var>epoch</var> then colons are not
3103 <tag><var>debian_revision</var></tag>
3106 This part of the version number specifies the version of
3107 the Debian package based on the upstream version. It
3108 may contain only alphanumerics and the characters
3109 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3110 tilde) and is compared in the same way as the
3111 <var>upstream_version</var> is.
3115 It is optional; if it isn't present then the
3116 <var>upstream_version</var> may not contain a hyphen.
3117 This format represents the case where a piece of
3118 software was written specifically to be a Debian
3119 package, where the Debian package source must always
3120 be identical to the pristine source and therefore no
3121 revision indication is required.
3125 It is conventional to restart the
3126 <var>debian_revision</var> at <tt>1</tt> each time the
3127 <var>upstream_version</var> is increased.
3131 The package management system will break the version
3132 number apart at the last hyphen in the string (if there
3133 is one) to determine the <var>upstream_version</var> and
3134 <var>debian_revision</var>. The absence of a
3135 <var>debian_revision</var> is equivalent to a
3136 <var>debian_revision</var> of <tt>0</tt>.
3143 When comparing two version numbers, first the <var>epoch</var>
3144 of each are compared, then the <var>upstream_version</var> if
3145 <var>epoch</var> is equal, and then <var>debian_revision</var>
3146 if <var>upstream_version</var> is also equal.
3147 <var>epoch</var> is compared numerically. The
3148 <var>upstream_version</var> and <var>debian_revision</var>
3149 parts are compared by the package management system using the
3150 following algorithm:
3154 The strings are compared from left to right.
3158 First the initial part of each string consisting entirely of
3159 non-digit characters is determined. These two parts (one of
3160 which may be empty) are compared lexically. If a difference
3161 is found it is returned. The lexical comparison is a
3162 comparison of ASCII values modified so that all the letters
3163 sort earlier than all the non-letters and so that a tilde
3164 sorts before anything, even the end of a part. For example,
3165 the following parts are in sorted order from earliest to
3166 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3167 <tt>a</tt>.<footnote>
3168 One common use of <tt>~</tt> is for upstream pre-releases.
3169 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3170 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3175 Then the initial part of the remainder of each string which
3176 consists entirely of digit characters is determined. The
3177 numerical values of these two parts are compared, and any
3178 difference found is returned as the result of the comparison.
3179 For these purposes an empty string (which can only occur at
3180 the end of one or both version strings being compared) counts
3185 These two steps (comparing and removing initial non-digit
3186 strings and initial digit strings) are repeated until a
3187 difference is found or both strings are exhausted.
3191 Note that the purpose of epochs is to allow us to leave behind
3192 mistakes in version numbering, and to cope with situations
3193 where the version numbering scheme changes. It is
3194 <em>not</em> intended to cope with version numbers containing
3195 strings of letters which the package management system cannot
3196 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3197 silly orderings.<footnote>
3198 The author of this manual has heard of a package whose
3199 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3200 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3206 <sect1 id="f-Description">
3207 <heading><tt>Description</tt></heading>
3210 In a source or binary control file, the <tt>Description</tt>
3211 field contains a description of the binary package, consisting
3212 of two parts, the synopsis or the short description, and the
3213 long description. The field's format is as follows:
3218 Description: <single line synopsis>
3219 <extended description over several lines>
3224 The lines in the extended description can have these formats:
3230 Those starting with a single space are part of a paragraph.
3231 Successive lines of this form will be word-wrapped when
3232 displayed. The leading space will usually be stripped off.
3236 Those starting with two or more spaces. These will be
3237 displayed verbatim. If the display cannot be panned
3238 horizontally, the displaying program will line wrap them "hard"
3239 (i.e., without taking account of word breaks). If it can they
3240 will be allowed to trail off to the right. None, one or two
3241 initial spaces may be deleted, but the number of spaces
3242 deleted from each line will be the same (so that you can have
3243 indenting work correctly, for example).
3247 Those containing a single space followed by a single full stop
3248 character. These are rendered as blank lines. This is the
3249 <em>only</em> way to get a blank line<footnote>
3250 Completely empty lines will not be rendered as blank lines.
3251 Instead, they will cause the parser to think you're starting
3252 a whole new record in the control file, and will therefore
3253 likely abort with an error.
3258 Those containing a space, a full stop and some more characters.
3259 These are for future expansion. Do not use them.
3265 Do not use tab characters. Their effect is not predictable.
3269 See <ref id="descriptions"> for further information on this.
3273 In a <file>.changes</file> file, the <tt>Description</tt>
3274 field contains a summary of the descriptions for the packages
3275 being uploaded. For this case, the first line of the field
3276 value (the part on the same line as <tt>Description:</tt>) is
3277 always empty. The content of the field is expressed as
3278 continuation lines, one line per package. Each line is
3279 indented by one space and contains the name of a binary
3280 package, a space, a hyphen (<tt>-</tt>), a space, and the
3281 short description line from that package.
3285 <sect1 id="f-Distribution">
3286 <heading><tt>Distribution</tt></heading>
3289 In a <file>.changes</file> file or parsed changelog output
3290 this contains the (space-separated) name(s) of the
3291 distribution(s) where this version of the package should
3292 be installed. Valid distributions are determined by the
3293 archive maintainers.<footnote>
3294 Example distribution names in the Debian archive used in
3295 <file>.changes</file> files are:
3296 <taglist compact="compact">
3297 <tag><em>unstable</em></tag>
3299 This distribution value refers to the
3300 <em>developmental</em> part of the Debian distribution
3301 tree. Most new packages, new upstream versions of
3302 packages and bug fixes go into the <em>unstable</em>
3306 <tag><em>experimental</em></tag>
3308 The packages with this distribution value are deemed
3309 by their maintainers to be high risk. Oftentimes they
3310 represent early beta or developmental packages from
3311 various sources that the maintainers want people to
3312 try, but are not ready to be a part of the other parts
3313 of the Debian distribution tree.
3318 Others are used for updating stable releases or for
3319 security uploads. More information is available in the
3320 Debian Developer's Reference, section "The Debian
3324 The Debian archive software only supports listing a single
3325 distribution. Migration of packages to other distributions is
3326 handled outside of the upload process.
3331 <heading><tt>Date</tt></heading>
3334 This field includes the date the package was built or last
3335 edited. It must be in the same format as the <var>date</var>
3336 in a <file>debian/changelog</file> entry.
3340 The value of this field is usually extracted from the
3341 <file>debian/changelog</file> file - see
3342 <ref id="dpkgchangelog">).
3346 <sect1 id="f-Format">
3347 <heading><tt>Format</tt></heading>
3350 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3351 files, this field declares the format version of that file.
3352 The syntax of the field value is the same as that of
3353 a <qref id="f-Version">package version number</qref> except
3354 that no epoch or Debian revision is allowed. The format
3355 described in this document is <tt>&changesversion;</tt>.
3359 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3360 Debian source control</qref> files, this field declares the
3361 format of the source package. The field value is used by
3362 programs acting on a source package to interpret the list of
3363 files in the source package and determine how to unpack it.
3364 The syntax of the field value is a numeric major revision, a
3365 period, a numeric minor revision, and then an optional subtype
3366 after whitespace, which if specified is an alphanumeric word
3367 in parentheses. The subtype is optional in the syntax but may
3368 be mandatory for particular source format revisions.
3370 The source formats currently supported by the Debian archive
3371 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3372 and <tt>3.0 (quilt)</tt>.
3377 <sect1 id="f-Urgency">
3378 <heading><tt>Urgency</tt></heading>
3381 This is a description of how important it is to upgrade to
3382 this version from previous ones. It consists of a single
3383 keyword taking one of the values <tt>low</tt>,
3384 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3385 <tt>critical</tt><footnote>
3386 Other urgency values are supported with configuration
3387 changes in the archive software but are not used in Debian.
3388 The urgency affects how quickly a package will be considered
3389 for inclusion into the <tt>testing</tt> distribution and
3390 gives an indication of the importance of any fixes included
3391 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3392 treated as synonymous.
3393 </footnote> (not case-sensitive) followed by an optional
3394 commentary (separated by a space) which is usually in
3395 parentheses. For example:
3398 Urgency: low (HIGH for users of diversions)
3404 The value of this field is usually extracted from the
3405 <file>debian/changelog</file> file - see
3406 <ref id="dpkgchangelog">.
3410 <sect1 id="f-Changes">
3411 <heading><tt>Changes</tt></heading>
3414 This field contains the human-readable changes data, describing
3415 the differences between the last version and the current one.
3419 The first line of the field value (the part on the same line
3420 as <tt>Changes:</tt>) is always empty. The content of the
3421 field is expressed as continuation lines, with each line
3422 indented by at least one space. Blank lines must be
3423 represented by a line consisting only of a space and a full
3428 The value of this field is usually extracted from the
3429 <file>debian/changelog</file> file - see
3430 <ref id="dpkgchangelog">).
3434 Each version's change information should be preceded by a
3435 "title" line giving at least the version, distribution(s)
3436 and urgency, in a human-readable way.
3440 If data from several versions is being returned the entry
3441 for the most recent version should be returned first, and
3442 entries should be separated by the representation of a
3443 blank line (the "title" line may also be followed by the
3444 representation of a blank line).
3448 <sect1 id="f-Binary">
3449 <heading><tt>Binary</tt></heading>
3452 This field is a list of binary packages. Its syntax and
3453 meaning varies depending on the control file in which it
3458 When it appears in the <file>.dsc</file> file, it lists binary
3459 packages which a source package can produce, separated by
3461 A space after each comma is conventional.
3462 </footnote>. It may span multiple lines. The source package
3463 does not necessarily produce all of these binary packages for
3464 every architecture. The source control file doesn't contain
3465 details of which architectures are appropriate for which of
3466 the binary packages.
3470 When it appears in a <file>.changes</file> file, it lists the
3471 names of the binary packages being uploaded, separated by
3472 whitespace (not commas). It may span multiple lines.
3476 <sect1 id="f-Installed-Size">
3477 <heading><tt>Installed-Size</tt></heading>
3480 This field appears in the control files of binary packages,
3481 and in the <file>Packages</file> files. It gives an estimate
3482 of the total amount of disk space required to install the
3483 named package. Actual installed size may vary based on block
3484 size, file system properties, or actions taken by package
3489 The disk space is given as the integer value of the estimated
3490 installed size in bytes, divided by 1024 and rounded up.
3494 <sect1 id="f-Files">
3495 <heading><tt>Files</tt></heading>
3498 This field contains a list of files with information about
3499 each one. The exact information and syntax varies with
3504 In all cases, Files is a multiline field. The first line of
3505 the field value (the part on the same line as <tt>Files:</tt>)
3506 is always empty. The content of the field is expressed as
3507 continuation lines, one line per file. Each line must be
3508 indented by one space and contain a number of sub-fields,
3509 separated by spaces, as described below.
3513 In the <file>.dsc</file> file, each line contains the MD5
3514 checksum, size and filename of the tar file and (if
3515 applicable) diff file which make up the remainder of the
3516 source package<footnote>
3517 That is, the parts which are not the <tt>.dsc</tt>.
3518 </footnote>. For example:
3521 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3522 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3524 The exact forms of the filenames are described
3525 in <ref id="pkg-sourcearchives">.
3529 In the <file>.changes</file> file this contains one line per
3530 file being uploaded. Each line contains the MD5 checksum,
3531 size, section and priority and the filename. For example:
3534 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3535 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3536 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3537 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3539 The <qref id="f-Section">section</qref>
3540 and <qref id="f-Priority">priority</qref> are the values of
3541 the corresponding fields in the main source control file. If
3542 no section or priority is specified then <tt>-</tt> should be
3543 used, though section and priority values must be specified for
3544 new packages to be installed properly.
3548 The special value <tt>byhand</tt> for the section in a
3549 <tt>.changes</tt> file indicates that the file in question
3550 is not an ordinary package file and must by installed by
3551 hand by the distribution maintainers. If the section is
3552 <tt>byhand</tt> the priority should be <tt>-</tt>.
3556 If a new Debian revision of a package is being shipped and
3557 no new original source archive is being distributed the
3558 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3559 entry for the original source archive
3560 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3561 but the <file>.changes</file> file should leave it out. In
3562 this case the original source archive on the distribution
3563 site must match exactly, byte-for-byte, the original
3564 source archive which was used to generate the
3565 <file>.dsc</file> file and diff which are being uploaded.</p>
3568 <sect1 id="f-Closes">
3569 <heading><tt>Closes</tt></heading>
3572 A space-separated list of bug report numbers that the upload
3573 governed by the .changes file closes.
3577 <sect1 id="f-Homepage">
3578 <heading><tt>Homepage</tt></heading>
3581 The URL of the web site for this package, preferably (when
3582 applicable) the site from which the original source can be
3583 obtained and any additional upstream documentation or
3584 information may be found. The content of this field is a
3585 simple URL without any surrounding characters such as
3590 <sect1 id="f-Checksums">
3591 <heading><tt>Checksums-Sha1</tt>
3592 and <tt>Checksums-Sha256</tt></heading>
3595 These fields contain a list of files with a checksum and size
3596 for each one. Both <tt>Checksums-Sha1</tt>
3597 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3598 only in the checksum algorithm used: SHA-1
3599 for <tt>Checksums-Sha1</tt> and SHA-256
3600 for <tt>Checksums-Sha256</tt>.
3604 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3605 multiline fields. The first line of the field value (the part
3606 on the same line as <tt>Checksums-Sha1:</tt>
3607 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3608 of the field is expressed as continuation lines, one line per
3609 file. Each line consists of the checksum, a space, the file
3610 size, a space, and the file name. For example (from
3611 a <file>.changes</file> file):
3614 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3615 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3616 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3617 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3619 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3620 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3621 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3622 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3627 In the <file>.dsc</file> file, these fields should list all
3628 files that make up the source package. In
3629 the <file>.changes</file> file, these fields should list all
3630 files being uploaded. The list of files in these fields
3631 must match the list of files in the <tt>Files</tt> field.
3637 <heading>User-defined fields</heading>
3640 Additional user-defined fields may be added to the
3641 source package control file. Such fields will be
3642 ignored, and not copied to (for example) binary or
3643 source package control files or upload control files.
3647 If you wish to add additional unsupported fields to
3648 these output files you should use the mechanism
3653 Fields in the main source control information file with
3654 names starting <tt>X</tt>, followed by one or more of
3655 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3656 be copied to the output files. Only the part of the
3657 field name after the hyphen will be used in the output
3658 file. Where the letter <tt>B</tt> is used the field
3659 will appear in binary package control files, where the
3660 letter <tt>S</tt> is used in source package control
3661 files and where <tt>C</tt> is used in upload control
3662 (<tt>.changes</tt>) files.
3666 For example, if the main source information control file
3669 XBS-Comment: I stand between the candle and the star.
3671 then the binary and source package control files will contain the
3674 Comment: I stand between the candle and the star.
3683 <chapt id="maintainerscripts">
3684 <heading>Package maintainer scripts and installation procedure</heading>
3687 <heading>Introduction to package maintainer scripts</heading>
3690 It is possible to supply scripts as part of a package which
3691 the package management system will run for you when your
3692 package is installed, upgraded or removed.
3696 These scripts are the control information
3697 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3698 and <prgn>postrm</prgn>. They must be proper executable files;
3699 if they are scripts (which is recommended), they must start with
3700 the usual <tt>#!</tt> convention. They should be readable and
3701 executable by anyone, and must not be world-writable.
3705 The package management system looks at the exit status from
3706 these scripts. It is important that they exit with a
3707 non-zero status if there is an error, so that the package
3708 management system can stop its processing. For shell
3709 scripts this means that you <em>almost always</em> need to
3710 use <tt>set -e</tt> (this is usually true when writing shell
3711 scripts, in fact). It is also important, of course, that
3712 they exit with a zero status if everything went well.
3716 Additionally, packages interacting with users
3717 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3718 should install a <prgn>config</prgn> script as a control
3719 information file. See <ref id="maintscriptprompt"> for details.
3723 When a package is upgraded a combination of the scripts from
3724 the old and new packages is called during the upgrade
3725 procedure. If your scripts are going to be at all
3726 complicated you need to be aware of this, and may need to
3727 check the arguments to your scripts.
3731 Broadly speaking the <prgn>preinst</prgn> is called before
3732 (a particular version of) a package is installed, and the
3733 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3734 before (a version of) a package is removed and the
3735 <prgn>postrm</prgn> afterwards.
3739 Programs called from maintainer scripts should not normally
3740 have a path prepended to them. Before installation is
3741 started, the package management system checks to see if the
3742 programs <prgn>ldconfig</prgn>,
3743 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3744 and <prgn>update-rc.d</prgn> can be found via the
3745 <tt>PATH</tt> environment variable. Those programs, and any
3746 other program that one would expect to be in the
3747 <tt>PATH</tt>, should thus be invoked without an absolute
3748 pathname. Maintainer scripts should also not reset the
3749 <tt>PATH</tt>, though they might choose to modify it by
3750 prepending or appending package-specific directories. These
3751 considerations really apply to all shell scripts.</p>
3754 <sect id="idempotency">
3755 <heading>Maintainer scripts idempotency</heading>
3758 It is necessary for the error recovery procedures that the
3759 scripts be idempotent. This means that if it is run
3760 successfully, and then it is called again, it doesn't bomb
3761 out or cause any harm, but just ensures that everything is
3762 the way it ought to be. If the first call failed, or
3763 aborted half way through for some reason, the second call
3764 should merely do the things that were left undone the first
3765 time, if any, and exit with a success status if everything
3767 This is so that if an error occurs, the user interrupts
3768 <prgn>dpkg</prgn> or some other unforeseen circumstance
3769 happens you don't leave the user with a badly-broken
3770 package when <prgn>dpkg</prgn> attempts to repeat the
3776 <sect id="controllingterminal">
3777 <heading>Controlling terminal for maintainer scripts</heading>
3780 Maintainer scripts are not guaranteed to run with a controlling
3781 terminal and may not be able to interact with the user. They
3782 must be able to fall back to noninteractive behavior if no
3783 controlling terminal is available. Maintainer scripts that
3784 prompt via a program conforming to the Debian Configuration
3785 Management Specification (see <ref id="maintscriptprompt">) may
3786 assume that program will handle falling back to noninteractive
3791 For high-priority prompts without a reasonable default answer,
3792 maintainer scripts may abort if there is no controlling
3793 terminal. However, this situation should be avoided if at all
3794 possible, since it prevents automated or unattended installs.
3795 In most cases, users will consider this to be a bug in the
3800 <sect id="exitstatus">
3801 <heading>Exit status</heading>
3804 Each script must return a zero exit status for
3805 success, or a nonzero one for failure, since the package
3806 management system looks for the exit status of these scripts
3807 and determines what action to take next based on that datum.
3811 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3816 <list compact="compact">
3818 <var>new-preinst</var> <tt>install</tt>
3821 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3824 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3827 <var>old-preinst</var> <tt>abort-upgrade</tt>
3828 <var>new-version</var>
3833 <list compact="compact">
3835 <var>postinst</var> <tt>configure</tt>
3836 <var>most-recently-configured-version</var>
3839 <var>old-postinst</var> <tt>abort-upgrade</tt>
3840 <var>new-version</var>
3843 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3844 <tt>in-favour</tt> <var>package</var>
3845 <var>new-version</var>
3848 <var>postinst</var> <tt>abort-remove</tt>
3851 <var>deconfigured's-postinst</var>
3852 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3853 <var>failed-install-package</var> <var>version</var>
3854 [<tt>removing</tt> <var>conflicting-package</var>
3860 <list compact="compact">
3862 <var>prerm</var> <tt>remove</tt>
3865 <var>old-prerm</var> <tt>upgrade</tt>
3866 <var>new-version</var>
3869 <var>new-prerm</var> <tt>failed-upgrade</tt>
3870 <var>old-version</var>
3873 <var>conflictor's-prerm</var> <tt>remove</tt>
3874 <tt>in-favour</tt> <var>package</var>
3875 <var>new-version</var>
3878 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3879 <tt>in-favour</tt> <var>package-being-installed</var>
3880 <var>version</var> [<tt>removing</tt>
3881 <var>conflicting-package</var>
3887 <list compact="compact">
3889 <var>postrm</var> <tt>remove</tt>
3892 <var>postrm</var> <tt>purge</tt>
3895 <var>old-postrm</var> <tt>upgrade</tt>
3896 <var>new-version</var>
3899 <var>new-postrm</var> <tt>failed-upgrade</tt>
3900 <var>old-version</var>
3903 <var>new-postrm</var> <tt>abort-install</tt>
3906 <var>new-postrm</var> <tt>abort-install</tt>
3907 <var>old-version</var>
3910 <var>new-postrm</var> <tt>abort-upgrade</tt>
3911 <var>old-version</var>
3914 <var>disappearer's-postrm</var> <tt>disappear</tt>
3915 <var>overwriter</var>
3916 <var>overwriter-version</var>
3922 <sect id="unpackphase">
3923 <heading>Details of unpack phase of installation or upgrade</heading>
3926 The procedure on installation/upgrade/overwrite/disappear
3927 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3928 stage of <tt>dpkg --install</tt>) is as follows. In each
3929 case, if a major error occurs (unless listed below) the
3930 actions are, in general, run backwards - this means that the
3931 maintainer scripts are run with different arguments in
3932 reverse order. These are the "error unwind" calls listed
3939 If a version of the package is already installed, call
3940 <example compact="compact">
3941 <var>old-prerm</var> upgrade <var>new-version</var>
3945 If the script runs but exits with a non-zero
3946 exit status, <prgn>dpkg</prgn> will attempt:
3947 <example compact="compact">
3948 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3950 If this works, the upgrade continues. If this
3951 does not work, the error unwind:
3952 <example compact="compact">
3953 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3955 If this works, then the old-version is
3956 "Installed", if not, the old version is in a
3957 "Half-Configured" state.
3963 If a "conflicting" package is being removed at the same time,
3964 or if any package will be broken (due to <tt>Breaks</tt>):
3967 If <tt>--auto-deconfigure</tt> is
3968 specified, call, for each package to be deconfigured
3969 due to <tt>Breaks</tt>:
3970 <example compact="compact">
3971 <var>deconfigured's-prerm</var> deconfigure \
3972 in-favour <var>package-being-installed</var> <var>version</var>
3975 <example compact="compact">
3976 <var>deconfigured's-postinst</var> abort-deconfigure \
3977 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3979 The deconfigured packages are marked as
3980 requiring configuration, so that if
3981 <tt>--install</tt> is used they will be
3982 configured again if possible.
3985 If any packages depended on a conflicting
3986 package being removed and <tt>--auto-deconfigure</tt> is
3987 specified, call, for each such package:
3988 <example compact="compact">
3989 <var>deconfigured's-prerm</var> deconfigure \
3990 in-favour <var>package-being-installed</var> <var>version</var> \
3991 removing <var>conflicting-package</var> <var>version</var>
3994 <example compact="compact">
3995 <var>deconfigured's-postinst</var> abort-deconfigure \
3996 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3997 removing <var>conflicting-package</var> <var>version</var>
3999 The deconfigured packages are marked as
4000 requiring configuration, so that if
4001 <tt>--install</tt> is used they will be
4002 configured again if possible.
4005 To prepare for removal of each conflicting package, call:
4006 <example compact="compact">
4007 <var>conflictor's-prerm</var> remove \
4008 in-favour <var>package</var> <var>new-version</var>
4011 <example compact="compact">
4012 <var>conflictor's-postinst</var> abort-remove \
4013 in-favour <var>package</var> <var>new-version</var>
4022 If the package is being upgraded, call:
4023 <example compact="compact">
4024 <var>new-preinst</var> upgrade <var>old-version</var>
4026 If this fails, we call:
4028 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4035 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4037 is called. If this works, then the old version
4038 is in an "Installed" state, or else it is left
4039 in an "Unpacked" state.
4044 If it fails, then the old version is left
4045 in an "Half-Installed" state.
4052 Otherwise, if the package had some configuration
4053 files from a previous version installed (i.e., it
4054 is in the "configuration files only" state):
4055 <example compact="compact">
4056 <var>new-preinst</var> install <var>old-version</var>
4060 <var>new-postrm</var> abort-install <var>old-version</var>
4062 If this fails, the package is left in a
4063 "Half-Installed" state, which requires a
4064 reinstall. If it works, the packages is left in
4065 a "Config-Files" state.
4068 Otherwise (i.e., the package was completely purged):
4069 <example compact="compact">
4070 <var>new-preinst</var> install
4073 <example compact="compact">
4074 <var>new-postrm</var> abort-install
4076 If the error-unwind fails, the package is in a
4077 "Half-Installed" phase, and requires a
4078 reinstall. If the error unwind works, the
4079 package is in a not installed state.
4086 The new package's files are unpacked, overwriting any
4087 that may be on the system already, for example any
4088 from the old version of the same package or from
4089 another package. Backups of the old files are kept
4090 temporarily, and if anything goes wrong the package
4091 management system will attempt to put them back as
4092 part of the error unwind.
4096 It is an error for a package to contain files which
4097 are on the system in another package, unless
4098 <tt>Replaces</tt> is used (see <ref id="replaces">).
4100 The following paragraph is not currently the case:
4101 Currently the <tt>- - force-overwrite</tt> flag is
4102 enabled, downgrading it to a warning, but this may not
4108 It is a more serious error for a package to contain a
4109 plain file or other kind of non-directory where another
4110 package has a directory (again, unless
4111 <tt>Replaces</tt> is used). This error can be
4112 overridden if desired using
4113 <tt>--force-overwrite-dir</tt>, but this is not
4118 Packages which overwrite each other's files produce
4119 behavior which, though deterministic, is hard for the
4120 system administrator to understand. It can easily
4121 lead to "missing" programs if, for example, a package
4122 is installed which overwrites a file from another
4123 package, and is then removed again.<footnote>
4124 Part of the problem is due to what is arguably a
4125 bug in <prgn>dpkg</prgn>.
4130 A directory will never be replaced by a symbolic link
4131 to a directory or vice versa; instead, the existing
4132 state (symlink or not) will be left alone and
4133 <prgn>dpkg</prgn> will follow the symlink if there is
4142 If the package is being upgraded, call
4143 <example compact="compact">
4144 <var>old-postrm</var> upgrade <var>new-version</var>
4148 If this fails, <prgn>dpkg</prgn> will attempt:
4149 <example compact="compact">
4150 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4152 If this works, installation continues. If not,
4154 <example compact="compact">
4155 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4157 If this fails, the old version is left in a
4158 "Half-Installed" state. If it works, dpkg now
4160 <example compact="compact">
4161 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4163 If this fails, the old version is left in a
4164 "Half-Installed" state. If it works, dpkg now
4166 <example compact="compact">
4167 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4169 If this fails, the old version is in an
4176 This is the point of no return - if
4177 <prgn>dpkg</prgn> gets this far, it won't back off
4178 past this point if an error occurs. This will
4179 leave the package in a fairly bad state, which
4180 will require a successful re-installation to clear
4181 up, but it's when <prgn>dpkg</prgn> starts doing
4182 things that are irreversible.
4187 Any files which were in the old version of the package
4188 but not in the new are removed.
4192 The new file list replaces the old.
4196 The new maintainer scripts replace the old.
4200 Any packages all of whose files have been overwritten
4201 during the installation, and which aren't required for
4202 dependencies, are considered to have been removed.
4203 For each such package
4206 <prgn>dpkg</prgn> calls:
4207 <example compact="compact">
4208 <var>disappearer's-postrm</var> disappear \
4209 <var>overwriter</var> <var>overwriter-version</var>
4213 The package's maintainer scripts are removed.
4216 It is noted in the status database as being in a
4217 sane state, namely not installed (any conffiles
4218 it may have are ignored, rather than being
4219 removed by <prgn>dpkg</prgn>). Note that
4220 disappearing packages do not have their prerm
4221 called, because <prgn>dpkg</prgn> doesn't know
4222 in advance that the package is going to
4229 Any files in the package we're unpacking that are also
4230 listed in the file lists of other packages are removed
4231 from those lists. (This will lobotomize the file list
4232 of the "conflicting" package if there is one.)
4236 The backup files made during installation, above, are
4242 The new package's status is now sane, and recorded as
4247 Here is another point of no return - if the
4248 conflicting package's removal fails we do not unwind
4249 the rest of the installation; the conflicting package
4250 is left in a half-removed limbo.
4255 If there was a conflicting package we go and do the
4256 removal actions (described below), starting with the
4257 removal of the conflicting package's files (any that
4258 are also in the package being installed have already
4259 been removed from the conflicting package's file list,
4260 and so do not get removed now).
4266 <sect id="configdetails"><heading>Details of configuration</heading>
4269 When we configure a package (this happens with <tt>dpkg
4270 --install</tt> and <tt>dpkg --configure</tt>), we first
4271 update any <tt>conffile</tt>s and then call:
4272 <example compact="compact">
4273 <var>postinst</var> configure <var>most-recently-configured-version</var>
4278 No attempt is made to unwind after errors during
4279 configuration. If the configuration fails, the package is in
4280 a "Failed Config" state, and an error message is generated.
4284 If there is no most recently configured version
4285 <prgn>dpkg</prgn> will pass a null argument.
4288 Historical note: Truly ancient (pre-1997) versions of
4289 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4290 (including the angle brackets) in this case. Even older
4291 ones did not pass a second argument at all, under any
4292 circumstance. Note that upgrades using such an old dpkg
4293 version are unlikely to work for other reasons, even if
4294 this old argument behavior is handled by your postinst script.
4300 <sect id="removedetails"><heading>Details of removal and/or
4301 configuration purging</heading>
4307 <example compact="compact">
4308 <var>prerm</var> remove
4312 If prerm fails during replacement due to conflict
4314 <var>conflictor's-postinst</var> abort-remove \
4315 in-favour <var>package</var> <var>new-version</var>
4319 <var>postinst</var> abort-remove
4323 If this fails, the package is in a "Half-Configured"
4324 state, or else it remains "Installed".
4328 The package's files are removed (except <tt>conffile</tt>s).
4331 <example compact="compact">
4332 <var>postrm</var> remove
4336 If it fails, there's no error unwind, and the package is in
4337 an "Half-Installed" state.
4342 All the maintainer scripts except the <prgn>postrm</prgn>
4347 If we aren't purging the package we stop here. Note
4348 that packages which have no <prgn>postrm</prgn> and no
4349 <tt>conffile</tt>s are automatically purged when
4350 removed, as there is no difference except for the
4351 <prgn>dpkg</prgn> status.
4355 The <tt>conffile</tt>s and any backup files
4356 (<tt>~</tt>-files, <tt>#*#</tt> files,
4357 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4362 <example compact="compact">
4363 <var>postrm</var> purge
4367 If this fails, the package remains in a "Config-Files"
4372 The package's file list is removed.
4381 <chapt id="relationships">
4382 <heading>Declaring relationships between packages</heading>
4384 <sect id="depsyntax">
4385 <heading>Syntax of relationship fields</heading>
4388 These fields all have a uniform syntax. They are a list of
4389 package names separated by commas.
4393 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4394 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4395 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4396 control fields of the package, which declare
4397 dependencies on other packages, the package names listed may
4398 also include lists of alternative package names, separated
4399 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4400 if any one of the alternative packages is installed, that
4401 part of the dependency is considered to be satisfied.
4405 All of the fields except for <tt>Provides</tt> may restrict
4406 their applicability to particular versions of each named
4407 package. This is done in parentheses after each individual
4408 package name; the parentheses should contain a relation from
4409 the list below followed by a version number, in the format
4410 described in <ref id="f-Version">.
4414 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4415 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4416 strictly earlier, earlier or equal, exactly equal, later or
4417 equal and strictly later, respectively. The deprecated
4418 forms <tt><</tt> and <tt>></tt> were used to mean
4419 earlier/later or equal, rather than strictly earlier/later,
4420 so they should not appear in new packages (though
4421 <prgn>dpkg</prgn> still supports them).
4425 Whitespace may appear at any point in the version
4426 specification subject to the rules in <ref
4427 id="controlsyntax">, and must appear where it's necessary to
4428 disambiguate; it is not otherwise significant. All of the
4429 relationship fields may span multiple lines. For
4430 consistency and in case of future changes to
4431 <prgn>dpkg</prgn> it is recommended that a single space be
4432 used after a version relationship and before a version
4433 number; it is also conventional to put a single space after
4434 each comma, on either side of each vertical bar, and before
4435 each open parenthesis. When wrapping a relationship field, it
4436 is conventional to do so after a comma and before the space
4437 following that comma.
4441 For example, a list of dependencies might appear as:
4442 <example compact="compact">
4445 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4450 Relationships may be restricted to a certain set of
4451 architectures. This is indicated in brackets after each
4452 individual package name and the optional version specification.
4453 The brackets enclose a list of Debian architecture names
4454 separated by whitespace. Exclamation marks may be prepended to
4455 each of the names. (It is not permitted for some names to be
4456 prepended with exclamation marks while others aren't.)
4460 For build relationship fields
4461 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4462 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4463 the current Debian host architecture is not in this list and
4464 there are no exclamation marks in the list, or it is in the list
4465 with a prepended exclamation mark, the package name and the
4466 associated version specification are ignored completely for the
4467 purposes of defining the relationships.
4472 <example compact="compact">
4474 Build-Depends-Indep: texinfo
4475 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4476 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4478 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4479 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4480 <tt>gnumach-dev</tt> only on hurd-i386.
4484 For binary relationship fields, the architecture restriction
4485 syntax is only supported in the source package control
4486 file <file>debian/control</file>. When the corresponding binary
4487 package control file is generated, the relationship will either
4488 be omitted or included without the architecture restriction
4489 based on the architecture of the binary package. This means
4490 that architecture restrictions must not be used in binary
4491 relationship fields for architecture-independent packages
4492 (<tt>Architecture: all</tt>).
4497 <example compact="compact">
4498 Depends: foo [i386], bar [amd64]
4500 becomes <tt>Depends: foo</tt> when the package is built on
4501 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4502 package is built on the <tt>amd64</tt> architecture, and omitted
4503 entirely in binary packages built on all other architectures.
4507 If the architecture-restricted dependency is part of a set of
4508 alternatives using <tt>|</tt>, that alternative is ignored
4509 completely on architectures that do not match the restriction.
4511 <example compact="compact">
4512 Build-Depends: foo [!i386] | bar [!amd64]
4514 is equivalent to <tt>bar</tt> on the i386 architecture, to
4515 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4516 bar</tt> on all other architectures.
4520 Relationships may also be restricted to a certain set of
4521 architectures using architecture wildcards. The syntax for
4522 declaring such restrictions is the same as declaring
4523 restrictions using a certain set of architectures without
4524 architecture wildcards. For example:
4525 <example compact="compact">
4526 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4528 is equivalent to <tt>foo</tt> on architectures using the Linux
4529 kernel and any cpu, <tt>bar</tt> on architectures using any
4530 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4531 using a kernel other than Linux.
4535 Note that the binary package relationship fields such as
4536 <tt>Depends</tt> appear in one of the binary package
4537 sections of the control file, whereas the build-time
4538 relationships such as <tt>Build-Depends</tt> appear in the
4539 source package section of the control file (which is the
4544 <sect id="binarydeps">
4545 <heading>Binary Dependencies - <tt>Depends</tt>,
4546 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4547 <tt>Pre-Depends</tt>
4551 Packages can declare in their control file that they have
4552 certain relationships to other packages - for example, that
4553 they may not be installed at the same time as certain other
4554 packages, and/or that they depend on the presence of others.
4558 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4559 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4560 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4561 <tt>Breaks</tt> is described in <ref id="breaks">, and
4562 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4563 rest are described below.
4567 These seven fields are used to declare a dependency
4568 relationship by one package on another. Except for
4569 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4570 depending (binary) package's control file.
4571 (<tt>Enhances</tt> appears in the recommending package's
4572 control file, and <tt>Breaks</tt> appears in the version of
4573 depended-on package which causes the named package to
4578 A <tt>Depends</tt> field takes effect <em>only</em> when a
4579 package is to be configured. It does not prevent a package
4580 being on the system in an unconfigured state while its
4581 dependencies are unsatisfied, and it is possible to replace
4582 a package whose dependencies are satisfied and which is
4583 properly installed with a different version whose
4584 dependencies are not and cannot be satisfied; when this is
4585 done the depending package will be left unconfigured (since
4586 attempts to configure it will give errors) and will not
4587 function properly. If it is necessary, a
4588 <tt>Pre-Depends</tt> field can be used, which has a partial
4589 effect even when a package is being unpacked, as explained
4590 in detail below. (The other three dependency fields,
4591 <tt>Recommends</tt>, <tt>Suggests</tt> and
4592 <tt>Enhances</tt>, are only used by the various front-ends
4593 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4594 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4598 For this reason packages in an installation run are usually
4599 all unpacked first and all configured later; this gives
4600 later versions of packages with dependencies on later
4601 versions of other packages the opportunity to have their
4602 dependencies satisfied.
4606 In case of circular dependencies, since installation or
4607 removal order honoring the dependency order can't be
4608 established, dependency loops are broken at some point
4609 (based on rules below), and some packages may not be able to
4610 rely on their dependencies being present when being
4611 installed or removed, depending on which side of the break
4612 of the circular dependency loop they happen to be on. If one
4613 of the packages in the loop has no postinst script, then the
4614 cycle will be broken at that package, so as to ensure that
4615 all postinst scripts run with the dependencies properly
4616 configured if this is possible. Otherwise the breaking point
4621 The <tt>Depends</tt> field thus allows package maintainers
4622 to impose an order in which packages should be configured.
4626 The meaning of the five dependency fields is as follows:
4628 <tag><tt>Depends</tt></tag>
4631 This declares an absolute dependency. A package will
4632 not be configured unless all of the packages listed in
4633 its <tt>Depends</tt> field have been correctly
4638 The <tt>Depends</tt> field should be used if the
4639 depended-on package is required for the depending
4640 package to provide a significant amount of
4645 The <tt>Depends</tt> field should also be used if the
4646 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4647 <prgn>postrm</prgn> scripts require the package to be
4648 present in order to run. Note, however, that the
4649 <prgn>postrm</prgn> cannot rely on any non-essential
4650 packages to be present during the <tt>purge</tt>
4654 <tag><tt>Recommends</tt></tag>
4657 This declares a strong, but not absolute, dependency.
4661 The <tt>Recommends</tt> field should list packages
4662 that would be found together with this one in all but
4663 unusual installations.
4667 <tag><tt>Suggests</tt></tag>
4669 This is used to declare that one package may be more
4670 useful with one or more others. Using this field
4671 tells the packaging system and the user that the
4672 listed packages are related to this one and can
4673 perhaps enhance its usefulness, but that installing
4674 this one without them is perfectly reasonable.
4677 <tag><tt>Enhances</tt></tag>
4679 This field is similar to Suggests but works in the
4680 opposite direction. It is used to declare that a
4681 package can enhance the functionality of another
4685 <tag><tt>Pre-Depends</tt></tag>
4688 This field is like <tt>Depends</tt>, except that it
4689 also forces <prgn>dpkg</prgn> to complete installation
4690 of the packages named before even starting the
4691 installation of the package which declares the
4692 pre-dependency, as follows:
4696 When a package declaring a pre-dependency is about to
4697 be <em>unpacked</em> the pre-dependency can be
4698 satisfied if the depended-on package is either fully
4699 configured, <em>or even if</em> the depended-on
4700 package(s) are only unpacked or in the "Half-Configured"
4701 state, provided that they have been configured
4702 correctly at some point in the past (and not removed
4703 or partially removed since). In this case, both the
4704 previously-configured and currently unpacked or
4705 "Half-Configured" versions must satisfy any version
4706 clause in the <tt>Pre-Depends</tt> field.
4710 When the package declaring a pre-dependency is about
4711 to be <em>configured</em>, the pre-dependency will be
4712 treated as a normal <tt>Depends</tt>, that is, it will
4713 be considered satisfied only if the depended-on
4714 package has been correctly configured.
4718 <tt>Pre-Depends</tt> should be used sparingly,
4719 preferably only by packages whose premature upgrade or
4720 installation would hamper the ability of the system to
4721 continue with any upgrade that might be in progress.
4725 <tt>Pre-Depends</tt> are also required if the
4726 <prgn>preinst</prgn> script depends on the named
4727 package. It is best to avoid this situation if
4735 When selecting which level of dependency to use you should
4736 consider how important the depended-on package is to the
4737 functionality of the one declaring the dependency. Some
4738 packages are composed of components of varying degrees of
4739 importance. Such a package should list using
4740 <tt>Depends</tt> the package(s) which are required by the
4741 more important components. The other components'
4742 requirements may be mentioned as Suggestions or
4743 Recommendations, as appropriate to the components' relative
4749 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4752 When one binary package declares that it breaks another,
4753 <prgn>dpkg</prgn> will refuse to allow the package which
4754 declares <tt>Breaks</tt> be installed unless the broken
4755 package is deconfigured first, and it will refuse to
4756 allow the broken package to be reconfigured.
4760 A package will not be regarded as causing breakage merely
4761 because its configuration files are still installed; it must
4762 be at least "Half-Installed".
4766 A special exception is made for packages which declare that
4767 they break their own package name or a virtual package which
4768 they provide (see below): this does not count as a real
4773 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4774 version clause; such a <tt>Breaks</tt> is introduced in the
4775 version of an (implicit or explicit) dependency which violates
4776 an assumption or reveals a bug in earlier versions of the broken
4777 package, or which takes over a file from earlier versions of the
4778 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4779 will inform higher-level package management tools that the
4780 broken package must be upgraded before the new one.
4784 If the breaking package also overwrites some files from the
4785 older package, it should use <tt>Replaces</tt> to ensure this
4786 goes smoothly. See <ref id="replaces"> for a full discussion
4787 of taking over files from other packages, including how to
4788 use <tt>Breaks</tt> in those cases.
4792 Many of the cases where <tt>Breaks</tt> should be used were
4793 previously handled with <tt>Conflicts</tt>
4794 because <tt>Breaks</tt> did not yet exist.
4795 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4796 See <ref id="conflicts"> for more information about the
4801 <sect id="conflicts">
4802 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4805 When one binary package declares a conflict with another
4806 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4807 refuse to allow them to be installed on the system at the
4808 same time. This is a stronger restriction than <tt>Breaks</tt>,
4809 which just prevents both packages from being configured at the
4810 same time. Conflicting packages cannot be unpacked on the
4811 system at the same time.
4815 If one package is to be installed, the other must be removed
4816 first. If the package being installed is marked as replacing
4817 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4818 normally be used in this case) the one on the system, or the one
4819 on the system is marked as deselected, or both packages are
4820 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4821 automatically remove the package which is causing the conflict.
4822 Otherwise, it will halt the installation of the new package with
4823 an error. This mechanism is specifically designed to produce an
4824 error when the installed package is <tt>Essential</tt>, but the
4829 A package will not cause a conflict merely because its
4830 configuration files are still installed; it must be at least
4835 A special exception is made for packages which declare a
4836 conflict with their own package name, or with a virtual
4837 package which they provide (see below): this does not
4838 prevent their installation, and allows a package to conflict
4839 with others providing a replacement for it. You use this
4840 feature when you want the package in question to be the only
4841 package providing some feature.
4845 Normally, <tt>Breaks</tt> should be used instead
4846 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4847 stronger restriction on the ordering of package installation or
4848 upgrade and can make it more difficult for the package manager
4849 to find a correct solution to an upgrade or installation
4850 problem. <tt>Breaks</tt> should be used
4852 <item>when moving a file from one package to another (see
4853 <ref id="replaces">),</item>
4854 <item>when splitting a package (a special case of the previous
4856 <item>when the breaking package exposes a bug in or interacts
4857 badly with particular versions of the broken
4860 <tt>Conflicts</tt> should be used
4862 <item>when two packages provide the same file and will
4863 continue to do so,</item>
4864 <item>in conjunction with <tt>Provides</tt> when only one
4865 package providing a given virtual facility may be installed
4866 at a time (see <ref id="virtual">),</item>
4867 <item>in other cases where one must prevent simultaneous
4868 installation of two packages for reasons that are ongoing
4869 (not fixed in a later version of one of the packages) or
4870 that must prevent both packages from being unpacked at the
4871 same time, not just configured.</item>
4873 Be aware that adding <tt>Conflicts</tt> is normally not the best
4874 solution when two packages provide the same files. Depending on
4875 the reason for that conflict, using alternatives or renaming the
4876 files is often a better approach. See, for
4877 example, <ref id="binaries">.
4881 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4882 unless two packages cannot be installed at the same time or
4883 installing them both causes one of them to be broken or
4884 unusable. Having similar functionality or performing the same
4885 tasks as another package is not sufficient reason to
4886 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4890 A <tt>Conflicts</tt> entry may have an "earlier than" version
4891 clause if the reason for the conflict is corrected in a later
4892 version of one of the packages. However, normally the presence
4893 of an "earlier than" version clause is a sign
4894 that <tt>Breaks</tt> should have been used instead. An "earlier
4895 than" version clause in <tt>Conflicts</tt>
4896 prevents <prgn>dpkg</prgn> from upgrading or installing the
4897 package which declares such a conflict until the upgrade or
4898 removal of the conflicted-with package has been completed, which
4899 is a strong restriction.
4903 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4907 As well as the names of actual ("concrete") packages, the
4908 package relationship fields <tt>Depends</tt>,
4909 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4910 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4911 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4912 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4913 may mention "virtual packages".
4917 A <em>virtual package</em> is one which appears in the
4918 <tt>Provides</tt> control field of another package. The effect
4919 is as if the package(s) which provide a particular virtual
4920 package name had been listed by name everywhere the virtual
4921 package name appears. (See also <ref id="virtual_pkg">)
4925 If there are both concrete and virtual packages of the same
4926 name, then the dependency may be satisfied (or the conflict
4927 caused) by either the concrete package with the name in
4928 question or any other concrete package which provides the
4929 virtual package with the name in question. This is so that,
4930 for example, supposing we have
4931 <example compact="compact">
4934 </example> and someone else releases an enhanced version of
4935 the <tt>bar</tt> package they can say:
4936 <example compact="compact">
4940 and the <tt>bar-plus</tt> package will now also satisfy the
4941 dependency for the <tt>foo</tt> package.
4945 If a relationship field has a version number attached, only real
4946 packages will be considered to see whether the relationship is
4947 satisfied (or the prohibition violated, for a conflict or
4948 breakage). In other words, if a version number is specified,
4949 this is a request to ignore all <tt>Provides</tt> for that
4950 package name and consider only real packages. The package
4951 manager will assume that a package providing that virtual
4952 package is not of the "right" version. A <tt>Provides</tt>
4953 field may not contain version numbers, and the version number of
4954 the concrete package which provides a particular virtual package
4955 will not be considered when considering a dependency on or
4956 conflict with the virtual package name.<footnote>
4957 It is possible that a future release of <prgn>dpkg</prgn> may
4958 add the ability to specify a version number for each virtual
4959 package it provides. This feature is not yet present,
4960 however, and is expected to be used only infrequently.
4965 To specify which of a set of real packages should be the default
4966 to satisfy a particular dependency on a virtual package, list
4967 the real package as an alternative before the virtual one.
4971 If the virtual package represents a facility that can only be
4972 provided by one real package at a time, such as
4973 the <package>mail-transport-agent</package> virtual package that
4974 requires installation of a binary that would conflict with all
4975 other providers of that virtual package (see
4976 <ref id="mail-transport-agents">), all packages providing that
4977 virtual package should also declare a conflict with it
4978 using <tt>Conflicts</tt>. This will ensure that at most one
4979 provider of that virtual package is unpacked or installed at a
4984 <sect id="replaces"><heading>Overwriting files and replacing
4985 packages - <tt>Replaces</tt></heading>
4988 Packages can declare in their control file that they should
4989 overwrite files in certain other packages, or completely replace
4990 other packages. The <tt>Replaces</tt> control field has these
4991 two distinct purposes.
4994 <sect1><heading>Overwriting files in other packages</heading>
4997 It is usually an error for a package to contain files which
4998 are on the system in another package. However, if the
4999 overwriting package declares that it <tt>Replaces</tt> the one
5000 containing the file being overwritten, then <prgn>dpkg</prgn>
5001 will replace the file from the old package with that from the
5002 new. The file will no longer be listed as "owned" by the old
5003 package and will be taken over by the new package.
5004 Normally, <tt>Breaks</tt> should be used in conjunction
5005 with <tt>Replaces</tt>.<footnote>
5006 To see why <tt>Breaks</tt> is normally needed in addition
5007 to <tt>Replaces</tt>, consider the case of a file in the
5008 package <package>foo</package> being taken over by the
5009 package <package>foo-data</package>.
5010 <tt>Replaces</tt> will allow <package>foo-data</package> to
5011 be installed and take over that file. However,
5012 without <tt>Breaks</tt>, nothing
5013 requires <package>foo</package> to be upgraded to a newer
5014 version that knows it does not include that file and instead
5015 depends on <package>foo-data</package>. Nothing would
5016 prevent the new <package>foo-data</package> package from
5017 being installed and then removed, removing the file that it
5018 took over from <package>foo</package>. After that
5019 operation, the package manager would think the system was in
5020 a consistent state, but the <package>foo</package> package
5021 would be missing one of its files.
5026 For example, if a package <package>foo</package> is split
5027 into <package>foo</package> and <package>foo-data</package>
5028 starting at version 1.2-3, <package>foo-data</package> would
5030 <example compact="compact">
5031 Replaces: foo (<< 1.2-3)
5032 Breaks: foo (<< 1.2-3)
5034 in its control file. The new version of the
5035 package <package>foo</package> would normally have the field
5036 <example compact="compact">
5037 Depends: foo-data (>= 1.2-3)
5039 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5040 the files moved into <package>foo-data</package> are not
5041 required for normal operation).
5045 If a package is completely replaced in this way, so that
5046 <prgn>dpkg</prgn> does not know of any files it still
5047 contains, it is considered to have "disappeared". It will
5048 be marked as not wanted on the system (selected for
5049 removal) and not installed. Any <tt>conffile</tt>s
5050 details noted for the package will be ignored, as they
5051 will have been taken over by the overwriting package. The
5052 package's <prgn>postrm</prgn> script will be run with a
5053 special argument to allow the package to do any final
5054 cleanup required. See <ref id="mscriptsinstact">.
5056 Replaces is a one way relationship. You have to install
5057 the replacing package after the replaced package.
5062 For this usage of <tt>Replaces</tt>, virtual packages (see
5063 <ref id="virtual">) are not considered when looking at a
5064 <tt>Replaces</tt> field. The packages declared as being
5065 replaced must be mentioned by their real names.
5069 This usage of <tt>Replaces</tt> only takes effect when both
5070 packages are at least partially on the system at once. It is
5071 not relevant if the packages conflict unless the conflict has
5076 <sect1><heading>Replacing whole packages, forcing their
5080 Second, <tt>Replaces</tt> allows the packaging system to
5081 resolve which package should be removed when there is a
5082 conflict (see <ref id="conflicts">). This usage only takes
5083 effect when the two packages <em>do</em> conflict, so that the
5084 two usages of this field do not interfere with each other.
5088 In this situation, the package declared as being replaced
5089 can be a virtual package, so for example, all mail
5090 transport agents (MTAs) would have the following fields in
5091 their control files:
5092 <example compact="compact">
5093 Provides: mail-transport-agent
5094 Conflicts: mail-transport-agent
5095 Replaces: mail-transport-agent
5097 ensuring that only one MTA can be installed at any one
5098 time. See <ref id="virtual"> for more information about this
5103 <sect id="sourcebinarydeps">
5104 <heading>Relationships between source and binary packages -
5105 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5106 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5110 Source packages that require certain binary packages to be
5111 installed or absent at the time of building the package
5112 can declare relationships to those binary packages.
5116 This is done using the <tt>Build-Depends</tt>,
5117 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5118 <tt>Build-Conflicts-Indep</tt> control fields.
5122 Build-dependencies on "build-essential" binary packages can be
5123 omitted. Please see <ref id="pkg-relations"> for more information.
5127 The dependencies and conflicts they define must be satisfied
5128 (as defined earlier for binary packages) in order to invoke
5129 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5131 There is no Build-Depends-Arch; this role is essentially
5132 met with Build-Depends. Anyone building the
5133 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5134 assumed to be building the whole package, and therefore
5135 installation of all build dependencies is required.
5138 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5139 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5140 not yet know how to check for its existence, and
5141 <tt>binary-arch</tt>. The purpose of the original split
5142 between <tt>Build-Depends</tt> and
5143 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5144 wouldn't need to install extra packages needed only for the
5145 binary-indep targets. But without a build-arch/build-indep
5146 split, this didn't work, since most of the work is done in
5147 the build target, not in the binary target.
5151 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5152 <tt>binary-arch</tt></tag>
5154 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5155 fields must be satisfied when these targets are invoked.
5157 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5158 and <tt>binary-indep</tt></tag>
5160 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5161 <tt>Build-Depends-Indep</tt>, and
5162 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5163 these targets are invoked.
5171 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5174 Packages containing shared libraries must be constructed with
5175 a little care to make sure that the shared library is always
5176 available. This is especially important for packages whose
5177 shared libraries are vitally important, such as the C library
5178 (currently <tt>libc6</tt>).
5182 This section deals only with public shared libraries: shared
5183 libraries that are placed in directories searched by the dynamic
5184 linker by default or which are intended to be linked against
5185 normally and possibly used by other, independent packages. Shared
5186 libraries that are internal to a particular package or that are
5187 only loaded as dynamic modules are not covered by this section and
5188 are not subject to its requirements.
5192 A shared library is identified by the <tt>SONAME</tt> attribute
5193 stored in its dynamic section. When a binary is linked against a
5194 shared library, the <tt>SONAME</tt> of the shared library is
5195 recorded in the binary's <tt>NEEDED</tt> section so that the
5196 dynamic linker knows that library must be loaded at runtime. The
5197 shared library file's full name (which usually contains additional
5198 version information not needed in the <tt>SONAME</tt>) is
5199 therefore normally not referenced directly. Instead, the shared
5200 library is loaded by its <tt>SONAME</tt>, which exists on the file
5201 system as a symlink pointing to the full name of the shared
5202 library. This symlink must be provided by the
5203 package. <ref id="sharedlibs-runtime"> describes how to do this.
5205 This is a convention of shared library versioning, but not a
5206 requirement. Some libraries use the <tt>SONAME</tt> as the full
5207 library file name instead and therefore do not need a symlink.
5208 Most, however, encode additional information about
5209 backwards-compatible revisions as a minor version number in the
5210 file name. The <tt>SONAME</tt> itself only changes when
5211 binaries linked with the earlier version of the shared library
5212 may no longer work, but the filename may change with each
5213 release of the library. See <ref id="sharedlibs-runtime"> for
5219 When linking a binary or another shared library against a shared
5220 library, the <tt>SONAME</tt> for that shared library is not yet
5221 known. Instead, the shared library is found by looking for a file
5222 matching the library name with <tt>.so</tt> appended. This file
5223 exists on the file system as a symlink pointing to the shared
5228 Shared libraries are normally split into several binary packages.
5229 The <tt>SONAME</tt> symlink is installed by the runtime shared
5230 library package, and the bare <tt>.so</tt> symlink is installed in
5231 the development package since it's only used when linking binaries
5232 or shared libraries. However, there are some exceptions for
5233 unusual shared libraries or for shared libraries that are also
5234 loaded as dynamic modules by other programs.
5238 This section is primarily concerned with how the separation of
5239 shared libraries into multiple packages should be done and how
5240 dependencies on and between shared library binary packages are
5241 managed in Debian. <ref id="libraries"> should be read in
5242 conjunction with this section and contains additional rules for
5243 the files contained in the shared library packages.
5246 <sect id="sharedlibs-runtime">
5247 <heading>Run-time shared libraries</heading>
5250 The run-time shared library must be placed in a package
5251 whose name changes whenever the <tt>SONAME</tt> of the shared
5252 library changes. This allows several versions of the shared
5253 library to be installed at the same time, allowing installation
5254 of the new version of the shared library without immediately
5255 breaking binaries that depend on the old version. Normally, the
5256 run-time shared library and its <tt>SONAME</tt> symlink should
5257 be placed in a package named
5258 <package><var>libraryname</var><var>soversion</var></package>,
5259 where <var>soversion</var> is the version number in
5260 the <tt>SONAME</tt> of the shared library.
5261 See <ref id="shlibs"> for detailed information on how to
5262 determine this version. Alternatively, if it would be confusing
5263 to directly append <var>soversion</var>
5264 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5265 itself ends in a number), you should use
5266 <package><var>libraryname</var>-<var>soversion</var></package>
5271 If you have several shared libraries built from the same source
5272 tree, you may lump them all together into a single shared
5273 library package provided that all of their <tt>SONAME</tt>s will
5274 always change together. Be aware that this is not normally the
5275 case, and if the <tt>SONAME</tt>s do not change together,
5276 upgrading such a merged shared library package will be
5277 unnecessarily difficult because of file conflicts with the old
5278 version of the package. When in doubt, always split shared
5279 library packages so that each binary package installs a single
5284 Every time the shared library ABI changes in a way that may
5285 break binaries linked against older versions of the shared
5286 library, the <tt>SONAME</tt> of the library and the
5287 corresponding name for the binary package containing the runtime
5288 shared library should change. Normally, this means
5289 the <tt>SONAME</tt> should change any time an interface is
5290 removed from the shared library or the signature of an interface
5291 (the number of parameters or the types of parameters that it
5292 takes, for example) is changed. This practice is vital to
5293 allowing clean upgrades from older versions of the package and
5294 clean transitions between the old ABI and new ABI without having
5295 to upgrade every affected package simultaneously.
5299 The <tt>SONAME</tt> and binary package name need not, and indeed
5300 normally should not, change if new interfaces are added but none
5301 are removed or changed, since this will not break binaries
5302 linked against the old shared library. Correct versioning of
5303 dependencies on the newer shared library by binaries that use
5304 the new interfaces is handled via
5305 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5306 system</qref> or via symbols files (see
5307 <manref name="deb-symbols" section="5">).
5311 The package should install the shared libraries under
5312 their normal names. For example, the <package>libgdbm3</package>
5313 package should install <file>libgdbm.so.3.0.0</file> as
5314 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5315 renamed or re-linked by any <prgn>prerm</prgn> or
5316 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5317 of renaming things safely without affecting running programs,
5318 and attempts to interfere with this are likely to lead to
5323 Shared libraries should not be installed executable, since
5324 the dynamic linker does not require this and trying to
5325 execute a shared library usually results in a core dump.
5329 The run-time library package should include the symbolic link for
5330 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5331 the shared libraries. For example,
5332 the <package>libgdbm3</package> package should include a symbolic
5333 link from <file>/usr/lib/libgdbm.so.3</file> to
5334 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5335 linker (for example <prgn>ld.so</prgn> or
5336 <prgn>ld-linux.so.*</prgn>) can find the library between the
5337 time that <prgn>dpkg</prgn> installs it and the time that
5338 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5340 The package management system requires the library to be
5341 placed before the symbolic link pointing to it in the
5342 <file>.deb</file> file. This is so that when
5343 <prgn>dpkg</prgn> comes to install the symlink
5344 (overwriting the previous symlink pointing at an older
5345 version of the library), the new shared library is already
5346 in place. In the past, this was achieved by creating the
5347 library in the temporary packaging directory before
5348 creating the symlink. Unfortunately, this was not always
5349 effective, since the building of the tar file in the
5350 <file>.deb</file> depended on the behavior of the underlying
5351 file system. Some file systems (such as reiserfs) reorder
5352 the files so that the order of creation is forgotten.
5353 Since version 1.7.0, <prgn>dpkg</prgn>
5354 reorders the files itself as necessary when building a
5355 package. Thus it is no longer important to concern
5356 oneself with the order of file creation.
5360 <sect1 id="ldconfig">
5361 <heading><tt>ldconfig</tt></heading>
5364 Any package installing shared libraries in one of the default
5365 library directories of the dynamic linker (which are currently
5366 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5367 listed in <file>/etc/ld.so.conf</file><footnote>
5369 <list compact="compact">
5370 <item>/usr/local/lib</item>
5371 <item>/usr/lib/libc5-compat</item>
5372 <item>/lib/libc5-compat</item>
5375 must use <prgn>ldconfig</prgn> to update the shared library
5380 The package maintainer scripts must only call
5381 <prgn>ldconfig</prgn> under these circumstances:
5382 <list compact="compact">
5383 <item>When the <prgn>postinst</prgn> script is run with a
5384 first argument of <tt>configure</tt>, the script must call
5385 <prgn>ldconfig</prgn>, and may optionally invoke
5386 <prgn>ldconfig</prgn> at other times.
5388 <item>When the <prgn>postrm</prgn> script is run with a
5389 first argument of <tt>remove</tt>, the script should call
5390 <prgn>ldconfig</prgn>.
5395 During install or upgrade, the preinst is called before
5396 the new files are installed, so calling "ldconfig" is
5397 pointless. The preinst of an existing package can also be
5398 called if an upgrade fails. However, this happens during
5399 the critical time when a shared libs may exist on-disk
5400 under a temporary name. Thus, it is dangerous and
5401 forbidden by current policy to call "ldconfig" at this
5406 When a package is installed or upgraded, "postinst
5407 configure" runs after the new files are safely on-disk.
5408 Since it is perfectly safe to invoke ldconfig
5409 unconditionally in a postinst, it is OK for a package to
5410 simply put ldconfig in its postinst without checking the
5411 argument. The postinst can also be called to recover from
5412 a failed upgrade. This happens before any new files are
5413 unpacked, so there is no reason to call "ldconfig" at this
5418 For a package that is being removed, prerm is
5419 called with all the files intact, so calling ldconfig is
5420 useless. The other calls to "prerm" happen in the case of
5421 upgrade at a time when all the files of the old package
5422 are on-disk, so again calling "ldconfig" is pointless.
5426 postrm, on the other hand, is called with the "remove"
5427 argument just after the files are removed, so this is
5428 the proper time to call "ldconfig" to notify the system
5429 of the fact that the shared libraries from the package
5430 are removed. The postrm can be called at several other
5431 times. At the time of "postrm purge", "postrm
5432 abort-install", or "postrm abort-upgrade", calling
5433 "ldconfig" is useless because the shared lib files are
5434 not on-disk. However, when "postrm" is invoked with
5435 arguments "upgrade", "failed-upgrade", or "disappear", a
5436 shared lib may exist on-disk under a temporary filename.
5444 <sect id="sharedlibs-support-files">
5445 <heading>Shared library support files</heading>
5448 If your package contains files whose names do not change with
5449 each change in the library shared object version, you must not
5450 put them in the shared library package. Otherwise, several
5451 versions of the shared library cannot be installed at the same
5452 time without filename clashes, making upgrades and transitions
5453 unnecessarily difficult.
5457 It is recommended that supporting files and run-time support
5458 programs that do not need to be invoked manually by users, but
5459 are nevertheless required for the package to function, be placed
5460 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5461 preferably under <file>/usr/lib/</file><var>package-name</var>.
5462 If the program or file is architecture independent, the
5463 recommendation is for it to be placed in a subdirectory of
5464 <file>/usr/share</file> instead, preferably under
5465 <file>/usr/share/</file><var>package-name</var>. Following the
5466 <var>package-name</var> naming convention ensures that the file
5467 names change when the shared object version changes.
5471 Run-time support programs that use the shared library but are
5472 not required for the library to function or files used by the
5473 shared library that can be used by any version of the shared
5474 library package should instead be put in a separate package.
5475 This package might typically be named
5476 <package><var>libraryname</var>-tools</package>; note the
5477 absence of the <var>soversion</var> in the package name.
5481 Files and support programs only useful when compiling software
5482 against the library should be included in the development
5483 package for the library.<footnote>
5484 For example, a <file><var>package-name</var>-config</file>
5485 script or <package>pkg-config</package> configuration files.
5490 <sect id="sharedlibs-static">
5491 <heading>Static libraries</heading>
5494 The static library (<file><var>libraryname.a</var></file>)
5495 is usually provided in addition to the shared version.
5496 It is placed into the development package (see below).
5500 In some cases, it is acceptable for a library to be
5501 available in static form only; these cases include:
5503 <item>libraries for languages whose shared library support
5504 is immature or unstable</item>
5505 <item>libraries whose interfaces are in flux or under
5506 development (commonly the case when the library's
5507 major version number is zero, or where the ABI breaks
5508 across patchlevels)</item>
5509 <item>libraries which are explicitly intended to be
5510 available only in static form by their upstream
5515 <sect id="sharedlibs-dev">
5516 <heading>Development files</heading>
5519 If there are development files associated with a shared library,
5520 the source package needs to generate a binary development package
5521 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5522 or if you prefer only to support one development version at a
5523 time, <package><var>libraryname</var>-dev</package>. Installing
5524 the development package must result in installation of all the
5525 development files necessary for compiling programs against that
5526 shared library.<footnote>
5527 This wording allows the development files to be split into
5528 several packages, such as a separate architecture-independent
5529 <package><var>libraryname</var>-headers</package>, provided that
5530 the development package depends on all the required additional
5536 In case several development versions of a library exist, you may
5537 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5538 <ref id="conflicts">) to ensure that the user only installs one
5539 development version at a time (as different development versions are
5540 likely to have the same header files in them, which would cause a
5541 filename clash if both were installed).
5545 The development package should contain a symlink for the associated
5546 shared library without a version number. For example, the
5547 <package>libgdbm-dev</package> package should include a symlink
5548 from <file>/usr/lib/libgdbm.so</file> to
5549 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5550 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5551 <file>libgdbm.so</file> when compiling dynamically.
5555 If the package provides Ada Library Information
5556 (<file>*.ali</file>) files for use with GNAT, these files must be
5557 installed read-only (mode 0444) so that GNAT will not attempt to
5558 recompile them. This overrides the normal file mode requirements
5559 given in <ref id="permissions-owners">.
5563 <sect id="sharedlibs-intradeps">
5564 <heading>Dependencies between the packages of the same library</heading>
5567 Typically the development version should have an exact
5568 version dependency on the runtime library, to make sure that
5569 compilation and linking happens correctly. The
5570 <tt>${binary:Version}</tt> substitution variable can be
5571 useful for this purpose.
5573 Previously, <tt>${Source-Version}</tt> was used, but its name
5574 was confusing and it has been deprecated since dpkg 1.13.19.
5579 <sect id="sharedlibs-shlibdeps">
5580 <heading>Dependencies between the library and other packages -
5581 the <tt>shlibs</tt> system</heading>
5584 If a package contains a binary or library which links to a
5585 shared library, we must ensure that when the package is
5586 installed on the system, all of the libraries needed are
5587 also installed. This requirement led to the creation of the
5588 <tt>shlibs</tt> system, which is very simple in its design:
5589 any package which <em>provides</em> a shared library also
5590 provides information on the package dependencies required to
5591 ensure the presence of this library, and any package which
5592 <em>uses</em> a shared library uses this information to
5593 determine the dependencies it requires. The files which
5594 contain the mapping from shared libraries to the necessary
5595 dependency information are called <file>shlibs</file> files.
5599 When a package is built which contains any shared libraries, it
5600 must provide a <file>shlibs</file> file for other packages to
5601 use. When a package is built which contains any shared
5602 libraries or compiled binaries, it must run
5603 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5604 on these to determine the libraries used and hence the
5605 dependencies needed by this package.<footnote>
5607 <prgn>dpkg-shlibdeps</prgn> will use a program
5608 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5609 the libraries directly needed by the binaries or shared
5610 libraries in the package.
5614 We say that a binary <tt>foo</tt> <em>directly</em> uses
5615 a library <tt>libbar</tt> if it is explicitly linked
5616 with that library (that is, the library is listed in the ELF
5617 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5618 to the link line when the binary is created). Other
5619 libraries that are needed by <tt>libbar</tt> are linked
5620 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5621 linker will load them automatically when it loads
5622 <tt>libbar</tt>. A package should depend on the libraries
5623 it directly uses, but not the libraries it indirectly uses.
5624 The dependencies for those libraries will automatically pull
5625 in the other libraries.
5629 A good example of where this helps is the following. We
5630 could update <tt>libimlib</tt> with a new version that
5631 supports a new graphics format called dgf (but retaining the
5632 same major version number) and depends on <tt>libdgf</tt>.
5633 If we used <prgn>ldd</prgn> to add dependencies for every
5634 library directly or indirectly linked with a binary, every
5635 package that uses <tt>libimlib</tt> would need to be
5636 recompiled so it would also depend on <tt>libdgf</tt> or it
5637 wouldn't run due to missing symbols. Since dependencies are
5638 only added based on ELF <tt>NEEDED</tt> attribute, packages
5639 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5640 having the dependency on <tt>libdgf</tt> and so they would
5641 not need rebuilding.
5647 In the following sections, we will first describe where the
5648 various <tt>shlibs</tt> files are to be found, then how to
5649 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5650 file format and how to create them if your package contains a
5655 <heading>The <tt>shlibs</tt> files present on the system</heading>
5658 There are several places where <tt>shlibs</tt> files are
5659 found. The following list gives them in the order in which
5661 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5662 (The first one which gives the required information is used.)
5668 <p><file>debian/shlibs.local</file></p>
5671 This lists overrides for this package. This file should
5672 normally not be used, but may be needed temporarily in
5673 unusual situations to work around bugs in other packages,
5674 or in unusual cases where the normally declared dependency
5675 information in the installed <file>shlibs</file> file for
5676 a library cannot be used. This file overrides information
5677 obtained from any other source.
5682 <p><file>/etc/dpkg/shlibs.override</file></p>
5685 This lists global overrides. This list is normally
5686 empty. It is maintained by the local system
5692 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5695 When packages are being built,
5696 any <file>debian/shlibs</file> files are copied into the
5697 control information file area of the temporary build
5698 directory and given the name <file>shlibs</file>. These
5699 files give details of any shared libraries included in the
5700 same package.<footnote>
5701 An example may help here. Let us say that the source
5702 package <tt>foo</tt> generates two binary
5703 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5704 When building the binary packages, the two packages are
5705 created in the directories <file>debian/libfoo2</file>
5706 and <file>debian/foo-runtime</file> respectively.
5707 (<file>debian/tmp</file> could be used instead of one of
5708 these.) Since <tt>libfoo2</tt> provides the
5709 <tt>libfoo</tt> shared library, it will require a
5710 <tt>shlibs</tt> file, which will be installed in
5711 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5712 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5713 When <prgn>dpkg-shlibdeps</prgn> is run on the
5714 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5716 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5717 determine whether <tt>foo-prog</tt>'s library
5718 dependencies are satisfied by any of the libraries
5719 provided by <tt>libfoo2</tt>. For this reason,
5720 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5721 the individual binary packages' <tt>shlibs</tt> files
5722 have been installed into the build directory.
5728 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5731 These are the <file>shlibs</file> files corresponding to
5732 all of the packages installed on the system, and are
5733 maintained by the relevant package maintainers.
5738 <p><file>/etc/dpkg/shlibs.default</file></p>
5741 This file lists any shared libraries whose packages
5742 have failed to provide correct <file>shlibs</file> files.
5743 It was used when the <file>shlibs</file> setup was first
5744 introduced, but it is now normally empty. It is
5745 maintained by the <tt>dpkg</tt> maintainer.
5753 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5754 <file>shlibs</file> files</heading>
5758 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5759 into your <file>debian/rules</file> file. If your package
5760 contains only compiled binaries and libraries (but no scripts),
5761 you can use a command such as:
5762 <example compact="compact">
5763 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5764 debian/tmp/usr/lib/*
5766 Otherwise, you will need to explicitly list the compiled
5767 binaries and libraries.<footnote>
5768 If you are using <tt>debhelper</tt>, the
5769 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5770 It will also correctly handle multi-binary packages.
5775 This command puts the dependency information into the
5776 <file>debian/substvars</file> file, which is then used by
5777 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5778 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5779 field in the control file for this to work.
5783 If you have multiple binary packages, you will need to call
5784 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5785 compiled libraries or binaries. In such a case, you will
5786 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5787 utilities to specify a different <file>substvars</file> file.
5791 If you are creating a udeb for use in the Debian Installer,
5792 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5793 should use the dependency line of type <tt>udeb</tt> by
5794 adding the <tt>-tudeb</tt> option<footnote>
5795 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5796 will automatically add this option if it knows it is
5798 </footnote>. If there is no dependency line of
5799 type <tt>udeb</tt> in the <file>shlibs</file>
5800 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5805 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5806 <ref id="pkg-dpkg-shlibdeps"> and
5807 <manref name="dpkg-shlibdeps" section="1">.
5812 <heading>The <file>shlibs</file> File Format</heading>
5815 Each <file>shlibs</file> file has the same format. Lines
5816 beginning with <tt>#</tt> are considered to be comments and
5817 are ignored. Each line is of the form:
5818 <example compact="compact">
5819 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5824 We will explain this by reference to the example of the
5825 <tt>zlib1g</tt> package, which (at the time of writing)
5826 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5830 <var>type</var> is an optional element that indicates the type
5831 of package for which the line is valid. The only type currently
5832 in use is <tt>udeb</tt>. The colon and space after the type are
5837 <var>library-name</var> is the name of the shared library,
5838 in this case <tt>libz</tt>. (This must match the name part
5839 of the soname, see below.)
5843 <var>soname-version</var> is the version part of the soname of
5844 the library. The soname is the thing that must exactly match
5845 for the library to be recognized by the dynamic linker, and is
5847 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5848 example, <tt>libz.so.1</tt>.<footnote>
5849 This can be determined using the command
5850 <example compact="compact">
5851 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5854 The version part is the part which comes after
5855 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5856 instead be of the form
5857 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5858 as <tt>libdb-4.8.so</tt>, in which case the name would
5859 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5863 <var>dependencies</var> has the same syntax as a dependency
5864 field in a binary package control file. It should give
5865 details of which packages are required to satisfy a binary
5866 built against the version of the library contained in the
5867 package. See <ref id="depsyntax"> for details.
5871 In our example, if the first version of the <tt>zlib1g</tt>
5872 package which contained a minor number of at least
5873 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5874 <tt>shlibs</tt> entry for this library could say:
5875 <example compact="compact">
5876 libz 1 zlib1g (>= 1:1.1.3)
5878 The version-specific dependency is to avoid warnings from
5879 the dynamic linker about using older shared libraries with
5884 As zlib1g also provides a udeb containing the shared library,
5885 there would also be a second line:
5886 <example compact="compact">
5887 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5893 <heading>Providing a <file>shlibs</file> file</heading>
5896 If your package provides a shared library, you need to create
5897 a <file>shlibs</file> file following the format described above.
5898 It is usual to call this file <file>debian/shlibs</file> (but if
5899 you have multiple binary packages, you might want to call it
5900 <file>debian/shlibs.<var>package</var></file> instead). Then
5901 let <file>debian/rules</file> install it in the control
5902 information file area:
5903 <example compact="compact">
5904 install -m644 debian/shlibs debian/tmp/DEBIAN
5906 or, in the case of a multi-binary package:
5907 <example compact="compact">
5908 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5910 An alternative way of doing this is to create the
5911 <file>shlibs</file> file in the control information file area
5912 directly from <file>debian/rules</file> without using
5913 a <file>debian/shlibs</file> file at all,<footnote>
5914 This is what <prgn>dh_makeshlibs</prgn> in
5915 the <package>debhelper</package> suite does. If your package
5916 also has a udeb that provides a shared
5917 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5918 the <tt>udeb:</tt> lines if you specify the name of the udeb
5919 with the <tt>--add-udeb</tt> option.
5921 since the <file>debian/shlibs</file> file itself is ignored by
5922 <prgn>dpkg-shlibdeps</prgn>.
5926 As <prgn>dpkg-shlibdeps</prgn> reads the
5927 <file>DEBIAN/shlibs</file> files in all of the binary packages
5928 being built from this source package, all of the
5929 <file>DEBIAN/shlibs</file> files should be installed before
5930 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5938 <chapt id="opersys"><heading>The Operating System</heading>
5941 <heading>File system hierarchy</heading>
5945 <heading>File System Structure</heading>
5948 The location of all installed files and directories must
5949 comply with the Filesystem Hierarchy Standard (FHS),
5950 version 2.3, with the exceptions noted below, and except
5951 where doing so would violate other terms of Debian
5952 Policy. The following exceptions to the FHS apply:
5957 The optional rules related to user specific
5958 configuration files for applications are stored in
5959 the user's home directory are relaxed. It is
5960 recommended that such files start with the
5961 '<tt>.</tt>' character (a "dot file"), and if an
5962 application needs to create more than one dot file
5963 then the preferred placement is in a subdirectory
5964 with a name starting with a '.' character, (a "dot
5965 directory"). In this case it is recommended the
5966 configuration files not start with the '.'
5972 The requirement for amd64 to use <file>/lib64</file>
5973 for 64 bit binaries is removed.
5978 The requirement for object files, internal binaries, and
5979 libraries, including <file>libc.so.*</file>, to be located
5980 directly under <file>/lib{,32}</file> and
5981 <file>/usr/lib{,32}</file> is amended, permitting files
5982 to instead be installed to
5983 <file>/lib/<var>triplet</var></file> and
5984 <file>/usr/lib/<var>triplet</var></file>, where
5985 <tt><var>triplet</var></tt> is the value returned by
5986 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5987 architecture of the package. Packages may <em>not</em>
5988 install files to any <var>triplet</var> path other
5989 than the one matching the architecture of that package;
5990 for instance, an <tt>Architecture: amd64</tt> package
5991 containing 32-bit x86 libraries may not install these
5992 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5994 This is necessary in order to reserve the directories for
5995 use in cross-installation of library packages from other
5996 architectures, as part of the planned deployment of
6001 Applications may also use a single subdirectory under
6002 <file>/usr/lib/<var>triplet</var></file>.
6005 The execution time linker/loader, ld*, must still be made
6006 available in the existing location under /lib or /lib64
6007 since this is part of the ELF ABI for the architecture.
6012 The requirement that
6013 <file>/usr/local/share/man</file> be "synonymous"
6014 with <file>/usr/local/man</file> is relaxed to a
6019 The requirement that windowmanagers with a single
6020 configuration file call it <file>system.*wmrc</file>
6021 is removed, as is the restriction that the window
6022 manager subdirectory be named identically to the
6023 window manager name itself.
6028 The requirement that boot manager configuration
6029 files live in <file>/etc</file>, or at least are
6030 symlinked there, is relaxed to a recommendation.
6035 The following directories in the root filesystem are
6036 additionally allowed: <file>/sys</file> and
6037 <file>/selinux</file>. <footnote>These directories
6038 are used as mount points to mount virtual filesystems
6039 to get access to kernel information.</footnote>
6046 The version of this document referred here can be
6047 found in the <tt>debian-policy</tt> package or on <url
6048 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6049 name="FHS (Debian copy)"> alongside this manual (or, if
6050 you have the <package>debian-policy</package> installed,
6052 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6053 (local copy)">). The
6054 latest version, which may be a more recent version, may
6056 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6057 Specific questions about following the standard may be
6058 asked on the <tt>debian-devel</tt> mailing list, or
6059 referred to the FHS mailing list (see the
6060 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6066 <heading>Site-specific programs</heading>
6069 As mandated by the FHS, packages must not place any
6070 files in <file>/usr/local</file>, either by putting them in
6071 the file system archive to be unpacked by <prgn>dpkg</prgn>
6072 or by manipulating them in their maintainer scripts.
6076 However, the package may create empty directories below
6077 <file>/usr/local</file> so that the system administrator knows
6078 where to place site-specific files. These are not
6079 directories <em>in</em> <file>/usr/local</file>, but are
6080 children of directories in <file>/usr/local</file>. These
6081 directories (<file>/usr/local/*/dir/</file>)
6082 should be removed on package removal if they are
6087 Note that this applies only to
6088 directories <em>below</em> <file>/usr/local</file>,
6089 not <em>in</em> <file>/usr/local</file>. Packages must
6090 not create sub-directories in the
6091 directory <file>/usr/local</file> itself, except those
6092 listed in FHS, section 4.5. However, you may create
6093 directories below them as you wish. You must not remove
6094 any of the directories listed in 4.5, even if you created
6099 Since <file>/usr/local</file> can be mounted read-only from a
6100 remote server, these directories must be created and
6101 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6102 maintainer scripts and not be included in the
6103 <file>.deb</file> archive. These scripts must not fail if
6104 either of these operations fail.
6108 For example, the <tt>emacsen-common</tt> package could
6109 contain something like
6110 <example compact="compact">
6111 if [ ! -e /usr/local/share/emacs ]
6113 if mkdir /usr/local/share/emacs 2>/dev/null
6115 chown root:staff /usr/local/share/emacs
6116 chmod 2775 /usr/local/share/emacs
6120 in its <prgn>postinst</prgn> script, and
6121 <example compact="compact">
6122 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6123 rmdir /usr/local/share/emacs 2>/dev/null || true
6125 in the <prgn>prerm</prgn> script. (Note that this form is
6126 used to ensure that if the script is interrupted, the
6127 directory <file>/usr/local/share/emacs</file> will still be
6132 If you do create a directory in <file>/usr/local</file> for
6133 local additions to a package, you should ensure that
6134 settings in <file>/usr/local</file> take precedence over the
6135 equivalents in <file>/usr</file>.
6139 However, because <file>/usr/local</file> and its contents are
6140 for exclusive use of the local administrator, a package
6141 must not rely on the presence or absence of files or
6142 directories in <file>/usr/local</file> for normal operation.
6146 The <file>/usr/local</file> directory itself and all the
6147 subdirectories created by the package should (by default) have
6148 permissions 2775 (group-writable and set-group-id) and be
6149 owned by <tt>root:staff</tt>.
6154 <heading>The system-wide mail directory</heading>
6156 The system-wide mail directory
6157 is <file>/var/mail</file>. This directory is part of the
6158 base system and should not be owned by any particular mail
6159 agents. The use of the old
6160 location <file>/var/spool/mail</file> is deprecated, even
6161 though the spool may still be physically located there.
6167 <heading>Users and groups</heading>
6170 <heading>Introduction</heading>
6172 The Debian system can be configured to use either plain or
6177 Some user ids (UIDs) and group ids (GIDs) are reserved
6178 globally for use by certain packages. Because some
6179 packages need to include files which are owned by these
6180 users or groups, or need the ids compiled into binaries,
6181 these ids must be used on any Debian system only for the
6182 purpose for which they are allocated. This is a serious
6183 restriction, and we should avoid getting in the way of
6184 local administration policies. In particular, many sites
6185 allocate users and/or local system groups starting at 100.
6189 Apart from this we should have dynamically allocated ids,
6190 which should by default be arranged in some sensible
6191 order, but the behavior should be configurable.
6195 Packages other than <tt>base-passwd</tt> must not modify
6196 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6197 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6202 <heading>UID and GID classes</heading>
6204 The UID and GID numbers are divided into classes as
6210 Globally allocated by the Debian project, the same
6211 on every Debian system. These ids will appear in
6212 the <file>passwd</file> and <file>group</file> files of all
6213 Debian systems, new ids in this range being added
6214 automatically as the <tt>base-passwd</tt> package is
6219 Packages which need a single statically allocated
6220 uid or gid should use one of these; their
6221 maintainers should ask the <tt>base-passwd</tt>
6229 Dynamically allocated system users and groups.
6230 Packages which need a user or group, but can have
6231 this user or group allocated dynamically and
6232 differently on each system, should use <tt>adduser
6233 --system</tt> to create the group and/or user.
6234 <prgn>adduser</prgn> will check for the existence of
6235 the user or group, and if necessary choose an unused
6236 id based on the ranges specified in
6237 <file>adduser.conf</file>.
6241 <tag>1000-59999:</tag>
6244 Dynamically allocated user accounts. By default
6245 <prgn>adduser</prgn> will choose UIDs and GIDs for
6246 user accounts in this range, though
6247 <file>adduser.conf</file> may be used to modify this
6252 <tag>60000-64999:</tag>
6255 Globally allocated by the Debian project, but only
6256 created on demand. The ids are allocated centrally
6257 and statically, but the actual accounts are only
6258 created on users' systems on demand.
6262 These ids are for packages which are obscure or
6263 which require many statically-allocated ids. These
6264 packages should check for and create the accounts in
6265 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6266 <prgn>adduser</prgn> if it has this facility) if
6267 necessary. Packages which are likely to require
6268 further allocations should have a "hole" left after
6269 them in the allocation, to give them room to
6274 <tag>65000-65533:</tag>
6282 User <tt>nobody</tt>. The corresponding gid refers
6283 to the group <tt>nogroup</tt>.
6290 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6291 not</em> be used, because it is the error return
6300 <sect id="sysvinit">
6301 <heading>System run levels and <file>init.d</file> scripts</heading>
6303 <sect1 id="/etc/init.d">
6304 <heading>Introduction</heading>
6307 The <file>/etc/init.d</file> directory contains the scripts
6308 executed by <prgn>init</prgn> at boot time and when the
6309 init state (or "runlevel") is changed (see <manref
6310 name="init" section="8">).
6314 There are at least two different, yet functionally
6315 equivalent, ways of handling these scripts. For the sake
6316 of simplicity, this document describes only the symbolic
6317 link method. However, it must not be assumed by maintainer
6318 scripts that this method is being used, and any automated
6319 manipulation of the various runlevel behaviors by
6320 maintainer scripts must be performed using
6321 <prgn>update-rc.d</prgn> as described below and not by
6322 manually installing or removing symlinks. For information
6323 on the implementation details of the other method,
6324 implemented in the <tt>file-rc</tt> package, please refer
6325 to the documentation of that package.
6329 These scripts are referenced by symbolic links in the
6330 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6331 runlevels, <prgn>init</prgn> looks in the directory
6332 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6333 execute, where <tt><var>n</var></tt> is the runlevel that
6334 is being changed to, or <tt>S</tt> for the boot-up
6339 The names of the links all have the form
6340 <file>S<var>mm</var><var>script</var></file> or
6341 <file>K<var>mm</var><var>script</var></file> where
6342 <var>mm</var> is a two-digit number and <var>script</var>
6343 is the name of the script (this should be the same as the
6344 name of the actual script in <file>/etc/init.d</file>).
6348 When <prgn>init</prgn> changes runlevel first the targets
6349 of the links whose names start with a <tt>K</tt> are
6350 executed, each with the single argument <tt>stop</tt>,
6351 followed by the scripts prefixed with an <tt>S</tt>, each
6352 with the single argument <tt>start</tt>. (The links are
6353 those in the <file>/etc/rc<var>n</var>.d</file> directory
6354 corresponding to the new runlevel.) The <tt>K</tt> links
6355 are responsible for killing services and the <tt>S</tt>
6356 link for starting services upon entering the runlevel.
6360 For example, if we are changing from runlevel 2 to
6361 runlevel 3, init will first execute all of the <tt>K</tt>
6362 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6363 all of the <tt>S</tt> prefixed scripts in that directory.
6364 The links starting with <tt>K</tt> will cause the
6365 referred-to file to be executed with an argument of
6366 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6371 The two-digit number <var>mm</var> is used to determine
6372 the order in which to run the scripts: low-numbered links
6373 have their scripts run first. For example, the
6374 <tt>K20</tt> scripts will be executed before the
6375 <tt>K30</tt> scripts. This is used when a certain service
6376 must be started before another. For example, the name
6377 server <prgn>bind</prgn> might need to be started before
6378 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6379 can set up its access lists. In this case, the script
6380 that starts <prgn>bind</prgn> would have a lower number
6381 than the script that starts <prgn>inn</prgn> so that it
6383 <example compact="compact">
6390 The two runlevels 0 (halt) and 6 (reboot) are slightly
6391 different. In these runlevels, the links with an
6392 <tt>S</tt> prefix are still called after those with a
6393 <tt>K</tt> prefix, but they too are called with the single
6394 argument <tt>stop</tt>.
6398 <sect1 id="writing-init">
6399 <heading>Writing the scripts</heading>
6402 Packages that include daemons for system services should
6403 place scripts in <file>/etc/init.d</file> to start or stop
6404 services at boot time or during a change of runlevel.
6405 These scripts should be named
6406 <file>/etc/init.d/<var>package</var></file>, and they should
6407 accept one argument, saying what to do:
6410 <tag><tt>start</tt></tag>
6411 <item>start the service,</item>
6413 <tag><tt>stop</tt></tag>
6414 <item>stop the service,</item>
6416 <tag><tt>restart</tt></tag>
6417 <item>stop and restart the service if it's already running,
6418 otherwise start the service</item>
6420 <tag><tt>reload</tt></tag>
6421 <item><p>cause the configuration of the service to be
6422 reloaded without actually stopping and restarting
6425 <tag><tt>force-reload</tt></tag>
6426 <item>cause the configuration to be reloaded if the
6427 service supports this, otherwise restart the
6431 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6432 <tt>force-reload</tt> options should be supported by all
6433 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6438 The <file>init.d</file> scripts must ensure that they will
6439 behave sensibly (i.e., returning success and not starting
6440 multiple copies of a service) if invoked with <tt>start</tt>
6441 when the service is already running, or with <tt>stop</tt>
6442 when it isn't, and that they don't kill unfortunately-named
6443 user processes. The best way to achieve this is usually to
6444 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6449 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6450 scripts. Writing correct <file>init.d</file> scripts requires
6451 accepting various error exit statuses when daemons are already
6452 running or already stopped without aborting
6453 the <file>init.d</file> script, and common <file>init.d</file>
6454 function libraries are not safe to call with <tt>set -e</tt>
6456 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6457 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6458 in effect and echoing status messages to the console fails,
6460 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6461 to not use <tt>set -e</tt> and instead check the result of
6462 each command separately.
6466 If a service reloads its configuration automatically (as
6467 in the case of <prgn>cron</prgn>, for example), the
6468 <tt>reload</tt> option of the <file>init.d</file> script
6469 should behave as if the configuration has been reloaded
6474 The <file>/etc/init.d</file> scripts must be treated as
6475 configuration files, either (if they are present in the
6476 package, that is, in the .deb file) by marking them as
6477 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6478 by managing them correctly in the maintainer scripts (see
6479 <ref id="config-files">). This is important since we want
6480 to give the local system administrator the chance to adapt
6481 the scripts to the local system, e.g., to disable a
6482 service without de-installing the package, or to specify
6483 some special command line options when starting a service,
6484 while making sure their changes aren't lost during the next
6489 These scripts should not fail obscurely when the
6490 configuration files remain but the package has been
6491 removed, as configuration files remain on the system after
6492 the package has been removed. Only when <prgn>dpkg</prgn>
6493 is executed with the <tt>--purge</tt> option will
6494 configuration files be removed. In particular, as the
6495 <file>/etc/init.d/<var>package</var></file> script itself is
6496 usually a <tt>conffile</tt>, it will remain on the system
6497 if the package is removed but not purged. Therefore, you
6498 should include a <tt>test</tt> statement at the top of the
6500 <example compact="compact">
6501 test -f <var>program-executed-later-in-script</var> || exit 0
6506 Often there are some variables in the <file>init.d</file>
6507 scripts whose values control the behavior of the scripts,
6508 and which a system administrator is likely to want to
6509 change. As the scripts themselves are frequently
6510 <tt>conffile</tt>s, modifying them requires that the
6511 administrator merge in their changes each time the package
6512 is upgraded and the <tt>conffile</tt> changes. To ease
6513 the burden on the system administrator, such configurable
6514 values should not be placed directly in the script.
6515 Instead, they should be placed in a file in
6516 <file>/etc/default</file>, which typically will have the same
6517 base name as the <file>init.d</file> script. This extra file
6518 should be sourced by the script when the script runs. It
6519 must contain only variable settings and comments in SUSv3
6520 <prgn>sh</prgn> format. It may either be a
6521 <tt>conffile</tt> or a configuration file maintained by
6522 the package maintainer scripts. See <ref id="config-files">
6527 To ensure that vital configurable values are always
6528 available, the <file>init.d</file> script should set default
6529 values for each of the shell variables it uses, either
6530 before sourcing the <file>/etc/default/</file> file or
6531 afterwards using something like the <tt>:
6532 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6533 script must behave sensibly and not fail if the
6534 <file>/etc/default</file> file is deleted.
6538 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6539 as temporary filesystems<footnote>
6540 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6541 options in <file>/etc/default/rcS</file>.
6542 </footnote>, so the <file>init.d</file> scripts must handle this
6543 correctly. This will typically amount to creating any required
6544 subdirectories dynamically when the <file>init.d</file> script
6545 is run, rather than including them in the package and relying on
6546 <prgn>dpkg</prgn> to create them.
6551 <heading>Interfacing with the initscript system</heading>
6554 Maintainers should use the abstraction layer provided by
6555 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6556 programs to deal with initscripts in their packages'
6557 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6558 and <prgn>postrm</prgn>.
6562 Directly managing the /etc/rc?.d links and directly
6563 invoking the <file>/etc/init.d/</file> initscripts should
6564 be done only by packages providing the initscript
6565 subsystem (such as <prgn>sysv-rc</prgn> and
6566 <prgn>file-rc</prgn>).
6570 <heading>Managing the links</heading>
6573 The program <prgn>update-rc.d</prgn> is provided for
6574 package maintainers to arrange for the proper creation and
6575 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6576 or their functional equivalent if another method is being
6577 used. This may be used by maintainers in their packages'
6578 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6582 You must not include any <file>/etc/rc<var>n</var>.d</file>
6583 symbolic links in the actual archive or manually create or
6584 remove the symbolic links in maintainer scripts; you must
6585 use the <prgn>update-rc.d</prgn> program instead. (The
6586 former will fail if an alternative method of maintaining
6587 runlevel information is being used.) You must not include
6588 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6589 in the archive either. (Only the <tt>sysvinit</tt>
6594 By default <prgn>update-rc.d</prgn> will start services in
6595 each of the multi-user state runlevels (2, 3, 4, and 5)
6596 and stop them in the halt runlevel (0), the single-user
6597 runlevel (1) and the reboot runlevel (6). The system
6598 administrator will have the opportunity to customize
6599 runlevels by simply adding, moving, or removing the
6600 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6601 symbolic links are being used, or by modifying
6602 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6607 To get the default behavior for your package, put in your
6608 <prgn>postinst</prgn> script
6609 <example compact="compact">
6610 update-rc.d <var>package</var> defaults
6612 and in your <prgn>postrm</prgn>
6613 <example compact="compact">
6614 if [ "$1" = purge ]; then
6615 update-rc.d <var>package</var> remove
6617 </example>. Note that if your package changes runlevels
6618 or priority, you may have to remove and recreate the links,
6619 since otherwise the old links may persist. Refer to the
6620 documentation of <prgn>update-rc.d</prgn>.
6624 This will use a default sequence number of 20. If it does
6625 not matter when or in which order the <file>init.d</file>
6626 script is run, use this default. If it does, then you
6627 should talk to the maintainer of the <prgn>sysvinit</prgn>
6628 package or post to <tt>debian-devel</tt>, and they will
6629 help you choose a number.
6633 For more information about using <tt>update-rc.d</tt>,
6634 please consult its man page <manref name="update-rc.d"
6640 <heading>Running initscripts</heading>
6642 The program <prgn>invoke-rc.d</prgn> is provided to make
6643 it easier for package maintainers to properly invoke an
6644 initscript, obeying runlevel and other locally-defined
6645 constraints that might limit a package's right to start,
6646 stop and otherwise manage services. This program may be
6647 used by maintainers in their packages' scripts.
6651 The package maintainer scripts must use
6652 <prgn>invoke-rc.d</prgn> to invoke the
6653 <file>/etc/init.d/*</file> initscripts, instead of
6654 calling them directly.
6658 By default, <prgn>invoke-rc.d</prgn> will pass any
6659 action requests (start, stop, reload, restart...) to the
6660 <file>/etc/init.d</file> script, filtering out requests
6661 to start or restart a service out of its intended
6666 Most packages will simply need to change:
6667 <example compact="compact">/etc/init.d/<package>
6668 <action></example> in their <prgn>postinst</prgn>
6669 and <prgn>prerm</prgn> scripts to:
6670 <example compact="compact">
6671 if which invoke-rc.d >/dev/null 2>&1; then
6672 invoke-rc.d <var>package</var> <action>
6674 /etc/init.d/<var>package</var> <action>
6680 A package should register its initscript services using
6681 <prgn>update-rc.d</prgn> before it tries to invoke them
6682 using <prgn>invoke-rc.d</prgn>. Invocation of
6683 unregistered services may fail.
6687 For more information about using
6688 <prgn>invoke-rc.d</prgn>, please consult its man page
6689 <manref name="invoke-rc.d" section="8">.
6695 <heading>Boot-time initialization</heading>
6698 There used to be another directory, <file>/etc/rc.boot</file>,
6699 which contained scripts which were run once per machine
6700 boot. This has been deprecated in favour of links from
6701 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6702 described in <ref id="/etc/init.d">. Packages must not
6703 place files in <file>/etc/rc.boot</file>.
6708 <heading>Example</heading>
6711 An example on which you can base your
6712 <file>/etc/init.d</file> scripts is found in
6713 <file>/etc/init.d/skeleton</file>.
6720 <heading>Console messages from <file>init.d</file> scripts</heading>
6723 This section describes the formats to be used for messages
6724 written to standard output by the <file>/etc/init.d</file>
6725 scripts. The intent is to improve the consistency of
6726 Debian's startup and shutdown look and feel. For this
6727 reason, please look very carefully at the details. We want
6728 the messages to have the same format in terms of wording,
6729 spaces, punctuation and case of letters.
6733 Here is a list of overall rules that should be used for
6734 messages generated by <file>/etc/init.d</file> scripts.
6740 The message should fit in one line (fewer than 80
6741 characters), start with a capital letter and end with
6742 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6746 If the script is performing some time consuming task in
6747 the background (not merely starting or stopping a
6748 program, for instance), an ellipsis (three dots:
6749 <tt>...</tt>) should be output to the screen, with no
6750 leading or tailing whitespace or line feeds.
6754 The messages should appear as if the computer is telling
6755 the user what it is doing (politely :-), but should not
6756 mention "it" directly. For example, instead of:
6757 <example compact="compact">
6758 I'm starting network daemons: nfsd mountd.
6760 the message should say
6761 <example compact="compact">
6762 Starting network daemons: nfsd mountd.
6769 <tt>init.d</tt> script should use the following standard
6770 message formats for the situations enumerated below.
6776 <p>When daemons are started</p>
6779 If the script starts one or more daemons, the output
6780 should look like this (a single line, no leading
6782 <example compact="compact">
6783 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6785 The <var>description</var> should describe the
6786 subsystem the daemon or set of daemons are part of,
6787 while <var>daemon-1</var> up to <var>daemon-n</var>
6788 denote each daemon's name (typically the file name of
6793 For example, the output of <file>/etc/init.d/lpd</file>
6795 <example compact="compact">
6796 Starting printer spooler: lpd.
6801 This can be achieved by saying
6802 <example compact="compact">
6803 echo -n "Starting printer spooler: lpd"
6804 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6807 in the script. If there are more than one daemon to
6808 start, the output should look like this:
6809 <example compact="compact">
6810 echo -n "Starting remote file system services:"
6811 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6812 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6813 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6816 This makes it possible for the user to see what is
6817 happening and when the final daemon has been started.
6818 Care should be taken in the placement of white spaces:
6819 in the example above the system administrators can
6820 easily comment out a line if they don't want to start
6821 a specific daemon, while the displayed message still
6827 <p>When a system parameter is being set</p>
6830 If you have to set up different system parameters
6831 during the system boot, you should use this format:
6832 <example compact="compact">
6833 Setting <var>parameter</var> to "<var>value</var>".
6838 You can use a statement such as the following to get
6840 <example compact="compact">
6841 echo "Setting DNS domainname to \"$domainname\"."
6846 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6847 for the left and right quotation marks. A grave accent
6848 (<tt>`</tt>) is not a quote character; neither is an
6849 apostrophe (<tt>'</tt>).
6854 <p>When a daemon is stopped or restarted</p>
6857 When you stop or restart a daemon, you should issue a
6858 message identical to the startup message, except that
6859 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6860 or <tt>Restarting</tt> respectively.
6864 For example, stopping the printer daemon will look like
6866 <example compact="compact">
6867 Stopping printer spooler: lpd.
6873 <p>When something is executed</p>
6876 There are several examples where you have to run a
6877 program at system startup or shutdown to perform a
6878 specific task, for example, setting the system's clock
6879 using <prgn>netdate</prgn> or killing all processes
6880 when the system shuts down. Your message should look
6882 <example compact="compact">
6883 Doing something very useful...done.
6885 You should print the <tt>done.</tt> immediately after
6886 the job has been completed, so that the user is
6887 informed why they have to wait. You can get this
6889 <example compact="compact">
6890 echo -n "Doing something very useful..."
6899 <p>When the configuration is reloaded</p>
6902 When a daemon is forced to reload its configuration
6903 files you should use the following format:
6904 <example compact="compact">
6905 Reloading <var>description</var> configuration...done.
6907 where <var>description</var> is the same as in the
6908 daemon starting message.
6916 <heading>Cron jobs</heading>
6919 Packages must not modify the configuration file
6920 <file>/etc/crontab</file>, and they must not modify the files in
6921 <file>/var/spool/cron/crontabs</file>.</p>
6924 If a package wants to install a job that has to be executed
6925 via cron, it should place a file with the name of the
6926 package in one or more of the following directories:
6927 <example compact="compact">
6933 As these directory names imply, the files within them are
6934 executed on an hourly, daily, weekly, or monthly basis,
6935 respectively. The exact times are listed in
6936 <file>/etc/crontab</file>.</p>
6939 All files installed in any of these directories must be
6940 scripts (e.g., shell scripts or Perl scripts) so that they
6941 can easily be modified by the local system administrator.
6942 In addition, they must be treated as configuration files.
6946 If a certain job has to be executed at some other frequency or
6947 at a specific time, the package should install a file
6948 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6949 same syntax as <file>/etc/crontab</file> and is processed by
6950 <prgn>cron</prgn> automatically. The file must also be
6951 treated as a configuration file. (Note that entries in the
6952 <file>/etc/cron.d</file> directory are not handled by
6953 <prgn>anacron</prgn>. Thus, you should only use this
6954 directory for jobs which may be skipped if the system is not
6957 Unlike <file>crontab</file> files described in the IEEE Std
6958 1003.1-2008 (POSIX.1) available from
6959 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6960 name="The Open Group">, the files in
6961 <file>/etc/cron.d</file> and the file
6962 <file>/etc/crontab</file> have seven fields; namely:
6964 <item>Minute [0,59]</item>
6965 <item>Hour [0,23]</item>
6966 <item>Day of the month [1,31]</item>
6967 <item>Month of the year [1,12]</item>
6968 <item>Day of the week ([0,6] with 0=Sunday)</item>
6969 <item>Username</item>
6970 <item>Command to be run</item>
6972 Ranges of numbers are allowed. Ranges are two numbers
6973 separated with a hyphen. The specified range is inclusive.
6974 Lists are allowed. A list is a set of numbers (or ranges)
6975 separated by commas. Step values can be used in conjunction
6980 The scripts or <tt>crontab</tt> entries in these directories should
6981 check if all necessary programs are installed before they
6982 try to execute them. Otherwise, problems will arise when a
6983 package was removed but not purged since configuration files
6984 are kept on the system in this situation.
6988 Any <tt>cron</tt> daemon must provide
6989 <file>/usr/bin/crontab</file> and support normal
6990 <tt>crontab</tt> entries as specified in POSIX. The daemon
6991 must also support names for days and months, ranges, and
6992 step values. It has to support <file>/etc/crontab</file>,
6993 and correctly execute the scripts in
6994 <file>/etc/cron.d</file>. The daemon must also correctly
6996 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7001 <heading>Menus</heading>
7004 The Debian <tt>menu</tt> package provides a standard
7005 interface between packages providing applications and
7006 <em>menu programs</em> (either X window managers or
7007 text-based menu programs such as <prgn>pdmenu</prgn>).
7011 All packages that provide applications that need not be
7012 passed any special command line arguments for normal
7013 operation should register a menu entry for those
7014 applications, so that users of the <tt>menu</tt> package
7015 will automatically get menu entries in their window
7016 managers, as well in shells like <tt>pdmenu</tt>.
7020 Menu entries should follow the current menu policy.
7024 The menu policy can be found in the <tt>menu-policy</tt>
7025 files in the <tt>debian-policy</tt> package.
7026 It is also available from the Debian web mirrors at
7027 <tt><url name="/doc/packaging-manuals/menu-policy/"
7028 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7032 Please also refer to the <em>Debian Menu System</em>
7033 documentation that comes with the <package>menu</package>
7034 package for information about how to register your
7040 <heading>Multimedia handlers</heading>
7043 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7044 is a mechanism for encoding files and data streams and
7045 providing meta-information about them, in particular their
7046 type (e.g. audio or video) and format (e.g. PNG, HTML,
7051 Registration of MIME type handlers allows programs like mail
7052 user agents and web browsers to invoke these handlers to
7053 view, edit or display MIME types they don't support directly.
7057 Packages which provide the ability to view/show/play,
7058 compose, edit or print MIME types should register themselves
7059 as such following the current MIME support policy.
7063 The MIME support policy can be found in the <tt>mime-policy</tt>
7064 files in the <tt>debian-policy</tt> package.
7065 It is also available from the Debian web mirrors at
7066 <tt><url name="/doc/packaging-manuals/mime-policy/"
7067 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7073 <heading>Keyboard configuration</heading>
7076 To achieve a consistent keyboard configuration so that all
7077 applications interpret a keyboard event the same way, all
7078 programs in the Debian distribution must be configured to
7079 comply with the following guidelines.
7083 The following keys must have the specified interpretations:
7086 <tag><tt><--</tt></tag>
7087 <item>delete the character to the left of the cursor</item>
7089 <tag><tt>Delete</tt></tag>
7090 <item>delete the character to the right of the cursor</item>
7092 <tag><tt>Control+H</tt></tag>
7093 <item>emacs: the help prefix</item>
7096 The interpretation of any keyboard events should be
7097 independent of the terminal that is used, be it a virtual
7098 console, an X terminal emulator, an rlogin/telnet session,
7103 The following list explains how the different programs
7104 should be set up to achieve this:
7110 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7114 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7118 X translations are set up to make
7119 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7120 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7121 is the vt220 escape code for the "delete character"
7122 key). This must be done by loading the X resources
7123 using <prgn>xrdb</prgn> on all local X displays, not
7124 using the application defaults, so that the
7125 translation resources used correspond to the
7126 <prgn>xmodmap</prgn> settings.
7130 The Linux console is configured to make
7131 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7132 generate <tt>ESC [ 3 ~</tt>.
7136 X applications are configured so that <tt><</tt>
7137 deletes left, and <tt>Delete</tt> deletes right. Motif
7138 applications already work like this.
7142 Terminals should have <tt>stty erase ^?</tt> .
7146 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7147 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7148 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7152 Emacs is programmed to map <tt>KB_Backspace</tt> or
7153 the <tt>stty erase</tt> character to
7154 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7155 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7156 <tt>^H</tt> to <tt>help</tt> as always.
7160 Other applications use the <tt>stty erase</tt>
7161 character and <tt>kdch1</tt> for the two delete keys,
7162 with ASCII DEL being "delete previous character" and
7163 <tt>kdch1</tt> being "delete character under
7171 This will solve the problem except for the following
7178 Some terminals have a <tt><--</tt> key that cannot
7179 be made to produce anything except <tt>^H</tt>. On
7180 these terminals Emacs help will be unavailable on
7181 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7182 character takes precedence in Emacs, and has been set
7183 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7184 available) can be used instead.
7188 Some operating systems use <tt>^H</tt> for <tt>stty
7189 erase</tt>. However, modern telnet versions and all
7190 rlogin versions propagate <tt>stty</tt> settings, and
7191 almost all UNIX versions honour <tt>stty erase</tt>.
7192 Where the <tt>stty</tt> settings are not propagated
7193 correctly, things can be made to work by using
7194 <tt>stty</tt> manually.
7198 Some systems (including previous Debian versions) use
7199 <prgn>xmodmap</prgn> to arrange for both
7200 <tt><--</tt> and <tt>Delete</tt> to generate
7201 <tt>KB_Delete</tt>. We can change the behavior of
7202 their X clients using the same X resources that we use
7203 to do it for our own clients, or configure our clients
7204 using their resources when things are the other way
7205 around. On displays configured like this
7206 <tt>Delete</tt> will not work, but <tt><--</tt>
7211 Some operating systems have different <tt>kdch1</tt>
7212 settings in their <tt>terminfo</tt> database for
7213 <tt>xterm</tt> and others. On these systems the
7214 <tt>Delete</tt> key will not work correctly when you
7215 log in from a system conforming to our policy, but
7216 <tt><--</tt> will.
7223 <heading>Environment variables</heading>
7226 A program must not depend on environment variables to get
7227 reasonable defaults. (That's because these environment
7228 variables would have to be set in a system-wide
7229 configuration file like <file>/etc/profile</file>, which is not
7230 supported by all shells.)
7234 If a program usually depends on environment variables for its
7235 configuration, the program should be changed to fall back to
7236 a reasonable default configuration if these environment
7237 variables are not present. If this cannot be done easily
7238 (e.g., if the source code of a non-free program is not
7239 available), the program must be replaced by a small
7240 "wrapper" shell script which sets the environment variables
7241 if they are not already defined, and calls the original program.
7245 Here is an example of a wrapper script for this purpose:
7247 <example compact="compact">
7249 BAR=${BAR:-/var/lib/fubar}
7251 exec /usr/lib/foo/foo "$@"
7256 Furthermore, as <file>/etc/profile</file> is a configuration
7257 file of the <prgn>base-files</prgn> package, other packages must
7258 not put any environment variables or other commands into that
7263 <sect id="doc-base">
7264 <heading>Registering Documents using doc-base</heading>
7267 The <package>doc-base</package> package implements a
7268 flexible mechanism for handling and presenting
7269 documentation. The recommended practice is for every Debian
7270 package that provides online documentation (other than just
7271 manual pages) to register these documents with
7272 <package>doc-base</package> by installing a
7273 <package>doc-base</package> control file via the
7274 <prgn/install-docs/ script at installation time and
7275 de-register the manuals again when the package is removed.
7278 Please refer to the documentation that comes with the
7279 <package>doc-base</package> package for information and
7288 <heading>Files</heading>
7290 <sect id="binaries">
7291 <heading>Binaries</heading>
7294 Two different packages must not install programs with
7295 different functionality but with the same filenames. (The
7296 case of two programs having the same functionality but
7297 different implementations is handled via "alternatives" or
7298 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7299 <ref id="conflicts"> respectively.) If this case happens,
7300 one of the programs must be renamed. The maintainers should
7301 report this to the <tt>debian-devel</tt> mailing list and
7302 try to find a consensus about which program will have to be
7303 renamed. If a consensus cannot be reached, <em>both</em>
7304 programs must be renamed.
7308 By default, when a package is being built, any binaries
7309 created should include debugging information, as well as
7310 being compiled with optimization. You should also turn on
7311 as many reasonable compilation warnings as possible; this
7312 makes life easier for porters, who can then look at build
7313 logs for possible problems. For the C programming language,
7314 this means the following compilation parameters should be
7316 <example compact="compact">
7318 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7320 INSTALL = install -s # (or use strip on the files in debian/tmp)
7325 Note that by default all installed binaries should be stripped,
7326 either by using the <tt>-s</tt> flag to
7327 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7328 the binaries after they have been copied into
7329 <file>debian/tmp</file> but before the tree is made into a
7334 Although binaries in the build tree should be compiled with
7335 debugging information by default, it can often be difficult to
7336 debug programs if they are also subjected to compiler
7337 optimization. For this reason, it is recommended to support the
7338 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7339 (see <ref id="debianrules-options">). This variable can contain
7340 several flags to change how a package is compiled and built.
7344 It is up to the package maintainer to decide what
7345 compilation options are best for the package. Certain
7346 binaries (such as computationally-intensive programs) will
7347 function better with certain flags (<tt>-O3</tt>, for
7348 example); feel free to use them. Please use good judgment
7349 here. Don't use flags for the sake of it; only use them
7350 if there is good reason to do so. Feel free to override
7351 the upstream author's ideas about which compilation
7352 options are best: they are often inappropriate for our
7358 <sect id="libraries">
7359 <heading>Libraries</heading>
7362 If the package is <strong>architecture: any</strong>, then
7363 the shared library compilation and linking flags must have
7364 <tt>-fPIC</tt>, or the package shall not build on some of
7365 the supported architectures<footnote>
7367 If you are using GCC, <tt>-fPIC</tt> produces code with
7368 relocatable position independent code, which is required for
7369 most architectures to create a shared library, with i386 and
7370 perhaps some others where non position independent code is
7371 permitted in a shared library.
7374 Position independent code may have a performance penalty,
7375 especially on <tt>i386</tt>. However, in most cases the
7376 speed penalty must be measured against the memory wasted on
7377 the few architectures where non position independent code is
7380 </footnote>. Any exception to this rule must be discussed on
7381 the mailing list <em>debian-devel@lists.debian.org</em>, and
7382 a rough consensus obtained. The reasons for not compiling
7383 with <tt>-fPIC</tt> flag must be recorded in the file
7384 <tt>README.Debian</tt>, and care must be taken to either
7385 restrict the architecture or arrange for <tt>-fPIC</tt> to
7386 be used on architectures where it is required.<footnote>
7388 Some of the reasons why this might be required is if the
7389 library contains hand crafted assembly code that is not
7390 relocatable, the speed penalty is excessive for compute
7391 intensive libs, and similar reasons.
7396 As to the static libraries, the common case is not to have
7397 relocatable code, since there is no benefit, unless in specific
7398 cases; therefore the static version must not be compiled
7399 with the <tt>-fPIC</tt> flag. Any exception to this rule
7400 should be discussed on the mailing list
7401 <em>debian-devel@lists.debian.org</em>, and the reasons for
7402 compiling with the <tt>-fPIC</tt> flag must be recorded in
7403 the file <tt>README.Debian</tt>. <footnote>
7405 Some of the reasons for linking static libraries with
7406 the <tt>-fPIC</tt> flag are if, for example, one needs a
7407 Perl API for a library that is under rapid development,
7408 and has an unstable API, so shared libraries are
7409 pointless at this phase of the library's development. In
7410 that case, since Perl needs a library with relocatable
7411 code, it may make sense to create a static library with
7412 relocatable code. Another reason cited is if you are
7413 distilling various libraries into a common shared
7414 library, like <tt>mklibs</tt> does in the Debian
7420 In other words, if both a shared and a static library is
7421 being built, each source unit (<tt>*.c</tt>, for example,
7422 for C files) will need to be compiled twice, for the normal
7427 Libraries should be built with threading support and to be
7428 thread-safe if the library supports this.
7432 Although not enforced by the build tools, shared libraries
7433 must be linked against all libraries that they use symbols from
7434 in the same way that binaries are. This ensures the correct
7435 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7436 system and guarantees that all libraries can be safely opened
7437 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7438 option <tt>-Wl,-z,defs</tt> when building a shared library.
7439 Since this option enforces symbol resolution at build time,
7440 a missing library reference will be caught early as a fatal
7445 All installed shared libraries should be stripped with
7446 <example compact="compact">
7447 strip --strip-unneeded <var>your-lib</var>
7449 (The option <tt>--strip-unneeded</tt> makes
7450 <prgn>strip</prgn> remove only the symbols which aren't
7451 needed for relocation processing.) Shared libraries can
7452 function perfectly well when stripped, since the symbols for
7453 dynamic linking are in a separate part of the ELF object
7455 You might also want to use the options
7456 <tt>--remove-section=.comment</tt> and
7457 <tt>--remove-section=.note</tt> on both shared libraries
7458 and executables, and <tt>--strip-debug</tt> on static
7464 Note that under some circumstances it may be useful to
7465 install a shared library unstripped, for example when
7466 building a separate package to support debugging.
7470 Shared object files (often <file>.so</file> files) that are not
7471 public libraries, that is, they are not meant to be linked
7472 to by third party executables (binaries of other packages),
7473 should be installed in subdirectories of the
7474 <file>/usr/lib</file> directory. Such files are exempt from the
7475 rules that govern ordinary shared libraries, except that
7476 they must not be installed executable and should be
7478 A common example are the so-called "plug-ins",
7479 internal shared objects that are dynamically loaded by
7480 programs using <manref name="dlopen" section="3">.
7485 Packages that use <prgn>libtool</prgn> to create and install
7486 their shared libraries install a file containing additional
7487 metadata (ending in <file>.la</file>) alongside the library.
7488 For public libraries intended for use by other packages, these
7489 files normally should not be included in the Debian package,
7490 since the information they include is not necessary to link with
7491 the shared library on Debian and can add unnecessary additional
7492 dependencies to other programs or libraries.<footnote>
7493 These files store, among other things, all libraries on which
7494 that shared library depends. Unfortunately, if
7495 the <file>.la</file> file is present and contains that
7496 dependency information, using <prgn>libtool</prgn> when
7497 linking against that library will cause the resulting program
7498 or library to be linked against those dependencies as well,
7499 even if this is unnecessary. This can create unneeded
7500 dependencies on shared library packages that would otherwise
7501 be hidden behind the library ABI, and can make library
7502 transitions to new SONAMEs unnecessarily complicated and
7503 difficult to manage.
7505 If the <file>.la</file> file is required for that library (if,
7506 for instance, it's loaded via <tt>libltdl</tt> in a way that
7507 requires that meta-information), the <tt>dependency_libs</tt>
7508 setting in the <file>.la</file> file should normally be set to
7509 the empty string. If the shared library development package has
7510 historically included the <file>.la</file>, it must be retained
7511 in the development package (with <tt>dependency_libs</tt>
7512 emptied) until all libraries that depend on it have removed or
7513 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7514 files to prevent linking with those other libraries
7515 using <prgn>libtool</prgn> from failing.
7519 If the <file>.la</file> must be included, it should be included
7520 in the development (<tt>-dev</tt>) package, unless the library
7521 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7522 library. If it is intended for use with <tt>libltdl</tt>,
7523 the <file>.la</file> files must go in the run-time library
7528 These requirements for handling of <file>.la</file> files do not
7529 apply to loadable modules or libraries not installed in
7530 directories searched by default by the dynamic linker. Packages
7531 installing loadable modules will frequently need to install
7532 the <file>.la</file> files alongside the modules so that they
7533 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7534 does not need to be modified for libraries or modules that are
7535 not installed in directories searched by the dynamic linker by
7536 default and not intended for use by other packages.
7540 You must make sure that you use only released versions of
7541 shared libraries to build your packages; otherwise other
7542 users will not be able to run your binaries
7543 properly. Producing source packages that depend on
7544 unreleased compilers is also usually a bad
7551 <heading>Shared libraries</heading>
7553 This section has moved to <ref id="sharedlibs">.
7559 <heading>Scripts</heading>
7562 All command scripts, including the package maintainer
7563 scripts inside the package and used by <prgn>dpkg</prgn>,
7564 should have a <tt>#!</tt> line naming the shell to be used
7569 In the case of Perl scripts this should be
7570 <tt>#!/usr/bin/perl</tt>.
7574 When scripts are installed into a directory in the system
7575 PATH, the script name should not include an extension such
7576 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7577 language currently used to implement it.
7580 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7581 <file>init.d</file> scripts should almost certainly start
7582 with <tt>set -e</tt> so that errors are detected.
7583 <file>init.d</file> scripts are something of a special case, due
7584 to how frequently they need to call commands that are allowed to
7585 fail, and it may instead be easier to check the exit status of
7586 commands directly. See <ref id="writing-init"> for more
7587 information about writing <file>init.d</file> scripts.
7590 Every script should use <tt>set -e</tt> or check the exit status
7591 of <em>every</em> command.
7594 Scripts may assume that <file>/bin/sh</file> implements the
7595 SUSv3 Shell Command Language<footnote>
7596 Single UNIX Specification, version 3, which is also IEEE
7597 1003.1-2004 (POSIX), and is available on the World Wide Web
7598 from <url id="http://www.unix.org/version3/online.html"
7599 name="The Open Group"> after free
7600 registration.</footnote>
7601 plus the following additional features not mandated by
7603 These features are in widespread use in the Linux community
7604 and are implemented in all of bash, dash, and ksh, the most
7605 common shells users may wish to use as <file>/bin/sh</file>.
7608 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7609 must not generate a newline.</item>
7610 <item><tt>test</tt>, if implemented as a shell built-in, must
7611 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7613 <item><tt>local</tt> to create a scoped variable must be
7614 supported, including listing multiple variables in a single
7615 local command and assigning a value to a variable at the
7616 same time as localizing it. <tt>local</tt> may or
7617 may not preserve the variable value from an outer scope if
7618 no assignment is present. Uses such as:
7622 # ... use a, b, c, d ...
7625 must be supported and must set the value of <tt>c</tt> to
7628 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7629 -<var>signal</var></tt>, where <var>signal</var> is either
7630 the name of a signal or one of the numeric signals listed in
7631 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7632 supported if <prgn>kill</prgn> is implemented as a shell
7635 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7636 signals must be supported. In addition to the signal
7637 numbers listed in the extension, which are the same as for
7638 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7641 If a shell script requires non-SUSv3 features from the shell
7642 interpreter other than those listed above, the appropriate shell
7643 must be specified in the first line of the script (e.g.,
7644 <tt>#!/bin/bash</tt>) and the package must depend on the package
7645 providing the shell (unless the shell package is marked
7646 "Essential", as in the case of <prgn>bash</prgn>).
7650 You may wish to restrict your script to SUSv3 features plus the
7651 above set when possible so that it may use <file>/bin/sh</file>
7652 as its interpreter. If your script works with <prgn>dash</prgn>
7653 (originally called <prgn>ash</prgn>), it probably complies with
7654 the above requirements, but if you are in doubt, use
7655 <file>/bin/bash</file>.
7659 Perl scripts should check for errors when making any
7660 system calls, including <tt>open</tt>, <tt>print</tt>,
7661 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7665 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7666 scripting languages. See <em>Csh Programming Considered
7667 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7668 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7669 If an upstream package comes with <prgn>csh</prgn> scripts
7670 then you must make sure that they start with
7671 <tt>#!/bin/csh</tt> and make your package depend on the
7672 <prgn>c-shell</prgn> virtual package.
7676 Any scripts which create files in world-writeable
7677 directories (e.g., in <file>/tmp</file>) must use a
7678 mechanism which will fail atomically if a file with the same
7679 name already exists.
7683 The Debian base system provides the <prgn>tempfile</prgn>
7684 and <prgn>mktemp</prgn> utilities for use by scripts for
7691 <heading>Symbolic links</heading>
7694 In general, symbolic links within a top-level directory
7695 should be relative, and symbolic links pointing from one
7696 top-level directory into another should be absolute. (A
7697 top-level directory is a sub-directory of the root
7698 directory <file>/</file>.)
7702 In addition, symbolic links should be specified as short as
7703 possible, i.e., link targets like <file>foo/../bar</file> are
7708 Note that when creating a relative link using
7709 <prgn>ln</prgn> it is not necessary for the target of the
7710 link to exist relative to the working directory you're
7711 running <prgn>ln</prgn> from, nor is it necessary to change
7712 directory to the directory where the link is to be made.
7713 Simply include the string that should appear as the target
7714 of the link (this will be a pathname relative to the
7715 directory in which the link resides) as the first argument
7720 For example, in your <prgn>Makefile</prgn> or
7721 <file>debian/rules</file>, you can do things like:
7722 <example compact="compact">
7723 ln -fs gcc $(prefix)/bin/cc
7724 ln -fs gcc debian/tmp/usr/bin/cc
7725 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7726 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7731 A symbolic link pointing to a compressed file should always
7732 have the same file extension as the referenced file. (For
7733 example, if a file <file>foo.gz</file> is referenced by a
7734 symbolic link, the filename of the link has to end with
7735 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7740 <heading>Device files</heading>
7743 Packages must not include device files or named pipes in the
7748 If a package needs any special device files that are not
7749 included in the base system, it must call
7750 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7751 after notifying the user<footnote>
7752 This notification could be done via a (low-priority)
7753 debconf message, or an echo (printf) statement.
7758 Packages must not remove any device files in the
7759 <prgn>postrm</prgn> or any other script. This is left to the
7760 system administrator.
7764 Debian uses the serial devices
7765 <file>/dev/ttyS*</file>. Programs using the old
7766 <file>/dev/cu*</file> devices should be changed to use
7767 <file>/dev/ttyS*</file>.
7771 Named pipes needed by the package must be created in
7772 the <prgn>postinst</prgn> script<footnote>
7773 It's better to use <prgn>mkfifo</prgn> rather
7774 than <prgn>mknod</prgn> to create named pipes so that
7775 automated checks for packages incorrectly creating device
7776 files with <prgn>mknod</prgn> won't have false positives.
7777 </footnote> and removed in
7778 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7783 <sect id="config-files">
7784 <heading>Configuration files</heading>
7787 <heading>Definitions</heading>
7791 <tag>configuration file</tag>
7793 A file that affects the operation of a program, or
7794 provides site- or host-specific information, or
7795 otherwise customizes the behavior of a program.
7796 Typically, configuration files are intended to be
7797 modified by the system administrator (if needed or
7798 desired) to conform to local policy or to provide
7799 more useful site-specific behavior.
7802 <tag><tt>conffile</tt></tag>
7804 A file listed in a package's <tt>conffiles</tt>
7805 file, and is treated specially by <prgn>dpkg</prgn>
7806 (see <ref id="configdetails">).
7812 The distinction between these two is important; they are
7813 not interchangeable concepts. Almost all
7814 <tt>conffile</tt>s are configuration files, but many
7815 configuration files are not <tt>conffiles</tt>.
7819 As noted elsewhere, <file>/etc/init.d</file> scripts,
7820 <file>/etc/default</file> files, scripts installed in
7821 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7822 configuration installed in <file>/etc/cron.d</file> must be
7823 treated as configuration files. In general, any script that
7824 embeds configuration information is de-facto a configuration
7825 file and should be treated as such.
7830 <heading>Location</heading>
7833 Any configuration files created or used by your package
7834 must reside in <file>/etc</file>. If there are several,
7835 consider creating a subdirectory of <file>/etc</file>
7836 named after your package.
7840 If your package creates or uses configuration files
7841 outside of <file>/etc</file>, and it is not feasible to modify
7842 the package to use <file>/etc</file> directly, put the files
7843 in <file>/etc</file> and create symbolic links to those files
7844 from the location that the package requires.
7849 <heading>Behavior</heading>
7852 Configuration file handling must conform to the following
7854 <list compact="compact">
7856 local changes must be preserved during a package
7860 configuration files must be preserved when the
7861 package is removed, and only deleted when the
7865 Obsolete configuration files without local changes may be
7866 removed by the package during upgrade.
7870 The easy way to achieve this behavior is to make the
7871 configuration file a <tt>conffile</tt>. This is
7872 appropriate only if it is possible to distribute a default
7873 version that will work for most installations, although
7874 some system administrators may choose to modify it. This
7875 implies that the default version will be part of the
7876 package distribution, and must not be modified by the
7877 maintainer scripts during installation (or at any other
7882 In order to ensure that local changes are preserved
7883 correctly, no package may contain or make hard links to
7884 conffiles.<footnote>
7885 Rationale: There are two problems with hard links.
7886 The first is that some editors break the link while
7887 editing one of the files, so that the two files may
7888 unwittingly become unlinked and different. The second
7889 is that <prgn>dpkg</prgn> might break the hard link
7890 while upgrading <tt>conffile</tt>s.
7895 The other way to do it is via the maintainer scripts. In
7896 this case, the configuration file must not be listed as a
7897 <tt>conffile</tt> and must not be part of the package
7898 distribution. If the existence of a file is required for
7899 the package to be sensibly configured it is the
7900 responsibility of the package maintainer to provide
7901 maintainer scripts which correctly create, update and
7902 maintain the file and remove it on purge. (See <ref
7903 id="maintainerscripts"> for more information.) These
7904 scripts must be idempotent (i.e., must work correctly if
7905 <prgn>dpkg</prgn> needs to re-run them due to errors
7906 during installation or removal), must cope with all the
7907 variety of ways <prgn>dpkg</prgn> can call maintainer
7908 scripts, must not overwrite or otherwise mangle the user's
7909 configuration without asking, must not ask unnecessary
7910 questions (particularly during upgrades), and must
7911 otherwise be good citizens.
7915 The scripts are not required to configure every possible
7916 option for the package, but only those necessary to get
7917 the package running on a given system. Ideally the
7918 sysadmin should not have to do any configuration other
7919 than that done (semi-)automatically by the
7920 <prgn>postinst</prgn> script.
7924 A common practice is to create a script called
7925 <file><var>package</var>-configure</file> and have the
7926 package's <prgn>postinst</prgn> call it if and only if the
7927 configuration file does not already exist. In certain
7928 cases it is useful for there to be an example or template
7929 file which the maintainer scripts use. Such files should
7930 be in <file>/usr/share/<var>package</var></file> or
7931 <file>/usr/lib/<var>package</var></file> (depending on whether
7932 they are architecture-independent or not). There should
7933 be symbolic links to them from
7934 <file>/usr/share/doc/<var>package</var>/examples</file> if
7935 they are examples, and should be perfectly ordinary
7936 <prgn>dpkg</prgn>-handled files (<em>not</em>
7937 configuration files).
7941 These two styles of configuration file handling must
7942 not be mixed, for that way lies madness:
7943 <prgn>dpkg</prgn> will ask about overwriting the file
7944 every time the package is upgraded.
7949 <heading>Sharing configuration files</heading>
7952 Packages which specify the same file as a
7953 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7954 with each other. (This is an instance of the general rule
7955 about not sharing files. Note that neither alternatives
7956 nor diversions are likely to be appropriate in this case;
7957 in particular, <prgn>dpkg</prgn> does not handle diverted
7958 <tt>conffile</tt>s well.)
7962 The maintainer scripts must not alter a <tt>conffile</tt>
7963 of <em>any</em> package, including the one the scripts
7968 If two or more packages use the same configuration file
7969 and it is reasonable for both to be installed at the same
7970 time, one of these packages must be defined as
7971 <em>owner</em> of the configuration file, i.e., it will be
7972 the package which handles that file as a configuration
7973 file. Other packages that use the configuration file must
7974 depend on the owning package if they require the
7975 configuration file to operate. If the other package will
7976 use the configuration file if present, but is capable of
7977 operating without it, no dependency need be declared.
7981 If it is desirable for two or more related packages to
7982 share a configuration file <em>and</em> for all of the
7983 related packages to be able to modify that configuration
7984 file, then the following should be done:
7985 <enumlist compact="compact">
7987 One of the related packages (the "owning" package)
7988 will manage the configuration file with maintainer
7989 scripts as described in the previous section.
7992 The owning package should also provide a program
7993 that the other packages may use to modify the
7997 The related packages must use the provided program
7998 to make any desired modifications to the
7999 configuration file. They should either depend on
8000 the core package to guarantee that the configuration
8001 modifier program is available or accept gracefully
8002 that they cannot modify the configuration file if it
8003 is not. (This is in addition to the fact that the
8004 configuration file may not even be present in the
8011 Sometimes it's appropriate to create a new package which
8012 provides the basic infrastructure for the other packages
8013 and which manages the shared configuration files. (The
8014 <tt>sgml-base</tt> package is a good example.)
8019 <heading>User configuration files ("dotfiles")</heading>
8022 The files in <file>/etc/skel</file> will automatically be
8023 copied into new user accounts by <prgn>adduser</prgn>.
8024 No other program should reference the files in
8025 <file>/etc/skel</file>.
8029 Therefore, if a program needs a dotfile to exist in
8030 advance in <file>$HOME</file> to work sensibly, that dotfile
8031 should be installed in <file>/etc/skel</file> and treated as a
8036 However, programs that require dotfiles in order to
8037 operate sensibly are a bad thing, unless they do create
8038 the dotfiles themselves automatically.
8042 Furthermore, programs should be configured by the Debian
8043 default installation to behave as closely to the upstream
8044 default behavior as possible.
8048 Therefore, if a program in a Debian package needs to be
8049 configured in some way in order to operate sensibly, that
8050 should be done using a site-wide configuration file placed
8051 in <file>/etc</file>. Only if the program doesn't support a
8052 site-wide default configuration and the package maintainer
8053 doesn't have time to add it may a default per-user file be
8054 placed in <file>/etc/skel</file>.
8058 <file>/etc/skel</file> should be as empty as we can make it.
8059 This is particularly true because there is no easy (or
8060 necessarily desirable) mechanism for ensuring that the
8061 appropriate dotfiles are copied into the accounts of
8062 existing users when a package is installed.
8068 <heading>Log files</heading>
8070 Log files should usually be named
8071 <file>/var/log/<var>package</var>.log</file>. If you have many
8072 log files, or need a separate directory for permission
8073 reasons (<file>/var/log</file> is writable only by
8074 <file>root</file>), you should usually create a directory named
8075 <file>/var/log/<var>package</var></file> and place your log
8080 Log files must be rotated occasionally so that they don't grow
8081 indefinitely. The best way to do this is to install a log
8082 rotation configuration file in the
8083 directory <file>/etc/logrotate.d</file>, normally
8084 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8085 the facilities provided by <prgn>logrotate</prgn>.
8088 The traditional approach to log files has been to set up
8089 <em>ad hoc</em> log rotation schemes using simple shell
8090 scripts and cron. While this approach is highly
8091 customizable, it requires quite a lot of sysadmin work.
8092 Even though the original Debian system helped a little
8093 by automatically installing a system which can be used
8094 as a template, this was deemed not enough.
8098 The use of <prgn>logrotate</prgn>, a program developed
8099 by Red Hat, is better, as it centralizes log management.
8100 It has both a configuration file
8101 (<file>/etc/logrotate.conf</file>) and a directory where
8102 packages can drop their individual log rotation
8103 configurations (<file>/etc/logrotate.d</file>).
8106 Here is a good example for a logrotate config
8107 file (for more information see <manref name="logrotate"
8109 <example compact="compact">
8110 /var/log/foo/*.log {
8116 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8120 This rotates all files under <file>/var/log/foo</file>, saves 12
8121 compressed generations, and tells the daemon to reopen its log
8122 files after the log rotation. It skips this log rotation
8123 (via <tt>missingok</tt>) if no such log file is present, which
8124 avoids errors if the package is removed but not purged.
8128 Log files should be removed when the package is
8129 purged (but not when it is only removed). This should be
8130 done by the <prgn>postrm</prgn> script when it is called
8131 with the argument <tt>purge</tt> (see <ref
8132 id="removedetails">).
8136 <sect id="permissions-owners">
8137 <heading>Permissions and owners</heading>
8140 The rules in this section are guidelines for general use.
8141 If necessary you may deviate from the details below.
8142 However, if you do so you must make sure that what is done
8143 is secure and you should try to be as consistent as possible
8144 with the rest of the system. You should probably also
8145 discuss it on <prgn>debian-devel</prgn> first.
8149 Files should be owned by <tt>root:root</tt>, and made
8150 writable only by the owner and universally readable (and
8151 executable, if appropriate), that is mode 644 or 755.
8155 Directories should be mode 755 or (for group-writability)
8156 mode 2775. The ownership of the directory should be
8157 consistent with its mode: if a directory is mode 2775, it
8158 should be owned by the group that needs write access to
8161 When a package is upgraded, and the owner or permissions
8162 of a file included in the package has changed, dpkg
8163 arranges for the ownership and permissions to be
8164 correctly set upon installation. However, this does not
8165 extend to directories; the permissions and ownership of
8166 directories already on the system does not change on
8167 install or upgrade of packages. This makes sense, since
8168 otherwise common directories like <tt>/usr</tt> would
8169 always be in flux. To correctly change permissions of a
8170 directory the package owns, explicit action is required,
8171 usually in the <tt>postinst</tt> script. Care must be
8172 taken to handle downgrades as well, in that case.
8178 Control information files should be owned by <tt>root:root</tt>
8179 and either mode 644 (for most files) or mode 755 (for
8180 executables such as <qref id="maintscripts">maintainer
8185 Setuid and setgid executables should be mode 4755 or 2755
8186 respectively, and owned by the appropriate user or group.
8187 They should not be made unreadable (modes like 4711 or
8188 2711 or even 4111); doing so achieves no extra security,
8189 because anyone can find the binary in the freely available
8190 Debian package; it is merely inconvenient. For the same
8191 reason you should not restrict read or execute permissions
8192 on non-set-id executables.
8196 Some setuid programs need to be restricted to particular
8197 sets of users, using file permissions. In this case they
8198 should be owned by the uid to which they are set-id, and by
8199 the group which should be allowed to execute them. They
8200 should have mode 4754; again there is no point in making
8201 them unreadable to those users who must not be allowed to
8206 It is possible to arrange that the system administrator can
8207 reconfigure the package to correspond to their local
8208 security policy by changing the permissions on a binary:
8209 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8210 described below.<footnote>
8211 Ordinary files installed by <prgn>dpkg</prgn> (as
8212 opposed to <tt>conffile</tt>s and other similar objects)
8213 normally have their permissions reset to the distributed
8214 permissions when the package is reinstalled. However,
8215 the use of <prgn>dpkg-statoverride</prgn> overrides this
8218 Another method you should consider is to create a group for
8219 people allowed to use the program(s) and make any setuid
8220 executables executable only by that group.
8224 If you need to create a new user or group for your package
8225 there are two possibilities. Firstly, you may need to
8226 make some files in the binary package be owned by this
8227 user or group, or you may need to compile the user or
8228 group id (rather than just the name) into the binary
8229 (though this latter should be avoided if possible, as in
8230 this case you need a statically allocated id).</p>
8233 If you need a statically allocated id, you must ask for a
8234 user or group id from the <tt>base-passwd</tt> maintainer,
8235 and must not release the package until you have been
8236 allocated one. Once you have been allocated one you must
8237 either make the package depend on a version of the
8238 <tt>base-passwd</tt> package with the id present in
8239 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8240 your package to create the user or group itself with the
8241 correct id (using <tt>adduser</tt>) in its
8242 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8243 the <prgn>postinst</prgn> is to be preferred if it is
8244 possible, otherwise a pre-dependency will be needed on the
8245 <tt>adduser</tt> package.)
8249 On the other hand, the program might be able to determine
8250 the uid or gid from the user or group name at runtime, so
8251 that a dynamically allocated id can be used. In this case
8252 you should choose an appropriate user or group name,
8253 discussing this on <prgn>debian-devel</prgn> and checking
8254 with the <package/base-passwd/ maintainer that it is unique and that
8255 they do not wish you to use a statically allocated id
8256 instead. When this has been checked you must arrange for
8257 your package to create the user or group if necessary using
8258 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8259 <prgn>postinst</prgn> script (again, the latter is to be
8260 preferred if it is possible).
8264 Note that changing the numeric value of an id associated
8265 with a name is very difficult, and involves searching the
8266 file system for all appropriate files. You need to think
8267 carefully whether a static or dynamic id is required, since
8268 changing your mind later will cause problems.
8271 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8273 This section is not intended as policy, but as a
8274 description of the use of <prgn>dpkg-statoverride</prgn>.
8278 If a system administrator wishes to have a file (or
8279 directory or other such thing) installed with owner and
8280 permissions different from those in the distributed Debian
8281 package, they can use the <prgn>dpkg-statoverride</prgn>
8282 program to instruct <prgn>dpkg</prgn> to use the different
8283 settings every time the file is installed. Thus the
8284 package maintainer should distribute the files with their
8285 normal permissions, and leave it for the system
8286 administrator to make any desired changes. For example, a
8287 daemon which is normally required to be setuid root, but
8288 in certain situations could be used without being setuid,
8289 should be installed setuid in the <tt>.deb</tt>. Then the
8290 local system administrator can change this if they wish.
8291 If there are two standard ways of doing it, the package
8292 maintainer can use <tt>debconf</tt> to find out the
8293 preference, and call <prgn>dpkg-statoverride</prgn> in the
8294 maintainer script if necessary to accommodate the system
8295 administrator's choice. Care must be taken during
8296 upgrades to not override an existing setting.
8300 Given the above, <prgn>dpkg-statoverride</prgn> is
8301 essentially a tool for system administrators and would not
8302 normally be needed in the maintainer scripts. There is
8303 one type of situation, though, where calls to
8304 <prgn>dpkg-statoverride</prgn> would be needed in the
8305 maintainer scripts, and that involves packages which use
8306 dynamically allocated user or group ids. In such a
8307 situation, something like the following idiom can be very
8308 helpful in the package's <prgn>postinst</prgn>, where
8309 <tt>sysuser</tt> is a dynamically allocated id:
8311 for i in /usr/bin/foo /usr/sbin/bar
8313 # only do something when no setting exists
8314 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8316 #include: debconf processing, question about foo and bar
8317 if [ "$RET" = "true" ] ; then
8318 dpkg-statoverride --update --add sysuser root 4755 $i
8323 The corresponding code to remove the override when the package
8326 for i in /usr/bin/foo /usr/sbin/bar
8328 if dpkg-statoverride --list $i >/dev/null 2>&1
8330 dpkg-statoverride --remove $i
8340 <chapt id="customized-programs">
8341 <heading>Customized programs</heading>
8343 <sect id="arch-spec">
8344 <heading>Architecture specification strings</heading>
8347 If a program needs to specify an <em>architecture specification
8348 string</em> in some place, it should select one of the strings
8349 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8350 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8351 part is sometimes elided, as when the OS is Linux.
8355 Note that we don't want to use
8356 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8357 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8358 since this would make our programs incompatible with other
8359 Linux distributions. We also don't use something like
8360 <tt><var>arch</var>-unknown-linux</tt>, since the
8361 <tt>unknown</tt> does not look very good.
8364 <sect1 id="arch-wildcard-spec">
8365 <heading>Architecture wildcards</heading>
8368 A package may specify an architecture wildcard. Architecture
8369 wildcards are in the format <tt>any</tt> (which matches every
8370 architecture), <tt><var>os</var></tt>-any, or
8371 any-<tt><var>cpu</var></tt>. <footnote>
8372 Internally, the package system normalizes the GNU triplets
8373 and the Debian arches into Debian arch triplets (which are
8374 kind of inverted GNU triplets), with the first component of
8375 the triplet representing the libc and ABI in use, and then
8376 does matching against those triplets. However, such
8377 triplets are an internal implementation detail that should
8378 not be used by packages directly. The libc and ABI portion
8379 is handled internally by the package system based on
8380 the <var>os</var> and <var>cpu</var>.
8387 <heading>Daemons</heading>
8390 The configuration files <file>/etc/services</file>,
8391 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8392 by the <prgn>netbase</prgn> package and must not be modified
8397 If a package requires a new entry in one of these files, the
8398 maintainer should get in contact with the
8399 <prgn>netbase</prgn> maintainer, who will add the entries
8400 and release a new version of the <prgn>netbase</prgn>
8405 The configuration file <file>/etc/inetd.conf</file> must not be
8406 modified by the package's scripts except via the
8407 <prgn>update-inetd</prgn> script or the
8408 <file>DebianNet.pm</file> Perl module. See their documentation
8409 for details on how to add entries.
8413 If a package wants to install an example entry into
8414 <file>/etc/inetd.conf</file>, the entry must be preceded with
8415 exactly one hash character (<tt>#</tt>). Such lines are
8416 treated as "commented out by user" by the
8417 <prgn>update-inetd</prgn> script and are not changed or
8418 activated during package updates.
8423 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8427 Some programs need to create pseudo-ttys. This should be done
8428 using Unix98 ptys if the C library supports it. The resulting
8429 program must not be installed setuid root, unless that
8430 is required for other functionality.
8434 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8435 <file>/var/log/lastlog</file> must be installed writable by
8436 group <tt>utmp</tt>. Programs which need to modify those
8437 files must be installed setgid <tt>utmp</tt>.
8442 <heading>Editors and pagers</heading>
8445 Some programs have the ability to launch an editor or pager
8446 program to edit or display a text document. Since there are
8447 lots of different editors and pagers available in the Debian
8448 distribution, the system administrator and each user should
8449 have the possibility to choose their preferred editor and
8454 In addition, every program should choose a good default
8455 editor/pager if none is selected by the user or system
8460 Thus, every program that launches an editor or pager must
8461 use the EDITOR or PAGER environment variable to determine
8462 the editor or pager the user wishes to use. If these
8463 variables are not set, the programs <file>/usr/bin/editor</file>
8464 and <file>/usr/bin/pager</file> should be used, respectively.
8468 These two files are managed through the <prgn>dpkg</prgn>
8469 "alternatives" mechanism. Every package providing an editor or
8470 pager must call the <prgn>update-alternatives</prgn> script to
8471 register as an alternative for <file>/usr/bin/editor</file>
8472 or <file>/usr/bin/pager</file> as appropriate. The alternative
8473 should have a slave alternative
8474 for <file>/usr/share/man/man1/editor.1.gz</file>
8475 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8476 corresponding manual page.
8480 If it is very hard to adapt a program to make use of the
8481 EDITOR or PAGER variables, that program may be configured to
8482 use <file>/usr/bin/sensible-editor</file> and
8483 <file>/usr/bin/sensible-pager</file> as the editor or pager
8484 program respectively. These are two scripts provided in the
8485 <package>sensible-utils</package> package that check the EDITOR
8486 and PAGER variables and launch the appropriate program, and fall
8487 back to <file>/usr/bin/editor</file>
8488 and <file>/usr/bin/pager</file> if the variable is not set.
8492 A program may also use the VISUAL environment variable to
8493 determine the user's choice of editor. If it exists, it
8494 should take precedence over EDITOR. This is in fact what
8495 <file>/usr/bin/sensible-editor</file> does.
8499 It is not required for a package to depend on
8500 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8501 package to provide such virtual packages.<footnote>
8502 The Debian base system already provides an editor and a
8508 <sect id="web-appl">
8509 <heading>Web servers and applications</heading>
8512 This section describes the locations and URLs that should
8513 be used by all web servers and web applications in the
8520 Cgi-bin executable files are installed in the
8522 <example compact="compact">
8523 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8525 or a subdirectory of that directory, and should be
8527 <example compact="compact">
8528 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8530 (possibly with a subdirectory name
8531 before <var>cgi-bin-name</var>).
8535 <p>Access to HTML documents</p>
8538 HTML documents for a package are stored in
8539 <file>/usr/share/doc/<var>package</var></file>
8540 and can be referred to as
8541 <example compact="compact">
8542 http://localhost/doc/<var>package</var>/<var>filename</var>
8547 The web server should restrict access to the document
8548 tree so that only clients on the same host can read
8549 the documents. If the web server does not support such
8550 access controls, then it should not provide access at
8551 all, or ask about providing access during installation.
8556 <p>Access to images</p>
8558 It is recommended that images for a package be stored
8559 in <tt>/usr/share/images/<var>package</var></tt> and
8560 may be referred to through an alias <tt>/images/</tt>
8563 http://localhost/images/<package>/<filename>
8570 <p>Web Document Root</p>
8573 Web Applications should try to avoid storing files in
8574 the Web Document Root. Instead they should use the
8575 /usr/share/doc/<var>package</var> directory for
8576 documents and register the Web Application via the
8577 <package>doc-base</package> package. If access to the
8578 web document root is unavoidable then use
8579 <example compact="compact">
8582 as the Document Root. This might be just a symbolic
8583 link to the location where the system administrator
8584 has put the real document root.
8587 <item><p>Providing httpd and/or httpd-cgi</p>
8589 All web servers should provide the virtual package
8590 <tt>httpd</tt>. If a web server has CGI support it should
8591 provide <tt>httpd-cgi</tt> additionally.
8594 All web applications which do not contain CGI scripts should
8595 depend on <tt>httpd</tt>, all those web applications which
8596 <tt>do</tt> contain CGI scripts, should depend on
8604 <sect id="mail-transport-agents">
8605 <heading>Mail transport, delivery and user agents</heading>
8608 Debian packages which process electronic mail, whether mail
8609 user agents (MUAs) or mail transport agents (MTAs), must
8610 ensure that they are compatible with the configuration
8611 decisions below. Failure to do this may result in lost
8612 mail, broken <tt>From:</tt> lines, and other serious brain
8617 The mail spool is <file>/var/mail</file> and the interface to
8618 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8619 the FHS). On older systems, the mail spool may be
8620 physically located in <file>/var/spool/mail</file>, but all
8621 access to the mail spool should be via the
8622 <file>/var/mail</file> symlink. The mail spool is part of the
8623 base system and not part of the MTA package.
8627 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8628 programs (such as IMAP daemons) must lock the mailbox in an
8629 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8630 be combined with dot locking. To avoid deadlocks, a program
8631 should use <tt>fcntl()</tt> first and dot locking after
8632 this, or alternatively implement the two locking methods in
8633 a non blocking way<footnote>
8634 If it is not possible to establish both locks, the
8635 system shouldn't wait for the second lock to be
8636 established, but remove the first lock, wait a (random)
8637 time, and start over locking again.
8638 </footnote>. Using the functions <tt>maillock</tt> and
8639 <tt>mailunlock</tt> provided by the
8640 <tt>liblockfile*</tt><footnote>
8641 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8642 to use these functions.
8643 </footnote> packages is the recommended way to realize this.
8647 Mailboxes are generally either mode 600 and owned by
8648 <var>user</var> or mode 660 and owned by
8649 <tt><var>user</var>:mail</tt><footnote>
8650 There are two traditional permission schemes for mail spools:
8651 mode 600 with all mail delivery done by processes running as
8652 the destination user, or mode 660 and owned by group mail with
8653 mail delivery done by a process running as a system user in
8654 group mail. Historically, Debian required mode 660 mail
8655 spools to enable the latter model, but that model has become
8656 increasingly uncommon and the principle of least privilege
8657 indicates that mail systems that use the first model should
8658 use permissions of 600. If delivery to programs is permitted,
8659 it's easier to keep the mail system secure if the delivery
8660 agent runs as the destination user. Debian Policy therefore
8661 permits either scheme.
8662 </footnote>. The local system administrator may choose a
8663 different permission scheme; packages should not make
8664 assumptions about the permission and ownership of mailboxes
8665 unless required (such as when creating a new mailbox). A MUA
8666 may remove a mailbox (unless it has nonstandard permissions) in
8667 which case the MTA or another MUA must recreate it if needed.
8671 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8672 be setgid mail to do the locking mentioned above (and
8673 must obviously avoid accessing other users' mailboxes
8674 using this privilege).</p>
8677 <file>/etc/aliases</file> is the source file for the system mail
8678 aliases (e.g., postmaster, usenet, etc.), it is the one
8679 which the sysadmin and <prgn>postinst</prgn> scripts may
8680 edit. After <file>/etc/aliases</file> is edited the program or
8681 human editing it must call <prgn>newaliases</prgn>. All MTA
8682 packages must come with a <prgn>newaliases</prgn> program,
8683 even if it does nothing, but older MTA packages did not do
8684 this so programs should not fail if <prgn>newaliases</prgn>
8685 cannot be found. Note that because of this, all MTA
8686 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8687 <tt>Replaces: mail-transport-agent</tt> control fields.
8691 The convention of writing <tt>forward to
8692 <var>address</var></tt> in the mailbox itself is not
8693 supported. Use a <tt>.forward</tt> file instead.</p>
8696 The <prgn>rmail</prgn> program used by UUCP
8697 for incoming mail should be <file>/usr/sbin/rmail</file>.
8698 Likewise, <prgn>rsmtp</prgn>, for receiving
8699 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8703 If your package needs to know what hostname to use on (for
8704 example) outgoing news and mail messages which are generated
8705 locally, you should use the file <file>/etc/mailname</file>. It
8706 will contain the portion after the username and <tt>@</tt>
8707 (at) sign for email addresses of users on the machine
8708 (followed by a newline).
8712 Such a package should check for the existence of this file
8713 when it is being configured. If it exists, it should be
8714 used without comment, although an MTA's configuration script
8715 may wish to prompt the user even if it finds that this file
8716 exists. If the file does not exist, the package should
8717 prompt the user for the value (preferably using
8718 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8719 as well as using it in the package's configuration. The
8720 prompt should make it clear that the name will not just be
8721 used by that package. For example, in this situation the
8722 <tt>inn</tt> package could say something like:
8723 <example compact="compact">
8724 Please enter the "mail name" of your system. This is the
8725 hostname portion of the address to be shown on outgoing
8726 news and mail messages. The default is
8727 <var>syshostname</var>, your system's host name. Mail
8728 name ["<var>syshostname</var>"]:
8730 where <var>syshostname</var> is the output of <tt>hostname
8736 <heading>News system configuration</heading>
8739 All the configuration files related to the NNTP (news)
8740 servers and clients should be located under
8741 <file>/etc/news</file>.</p>
8744 There are some configuration issues that apply to a number
8745 of news clients and server packages on the machine. These
8749 <tag><file>/etc/news/organization</file></tag>
8751 A string which should appear as the
8752 organization header for all messages posted
8753 by NNTP clients on the machine
8756 <tag><file>/etc/news/server</file></tag>
8758 Contains the FQDN of the upstream NNTP
8759 server, or localhost if the local machine is
8764 Other global files may be added as required for cross-package news
8771 <heading>Programs for the X Window System</heading>
8774 <heading>Providing X support and package priorities</heading>
8777 Programs that can be configured with support for the X
8778 Window System must be configured to do so and must declare
8779 any package dependencies necessary to satisfy their
8780 runtime requirements when using the X Window System. If
8781 such a package is of higher priority than the X packages
8782 on which it depends, it is required that either the
8783 X-specific components be split into a separate package, or
8784 that an alternative version of the package, which includes
8785 X support, be provided, or that the package's priority be
8791 <heading>Packages providing an X server</heading>
8794 Packages that provide an X server that, directly or
8795 indirectly, communicates with real input and display
8796 hardware should declare in their <tt>Provides</tt> control
8797 field that they provide the virtual
8798 package <tt>xserver</tt>.<footnote>
8799 This implements current practice, and provides an
8800 actual policy for usage of the <tt>xserver</tt>
8801 virtual package which appears in the virtual packages
8802 list. In a nutshell, X servers that interface
8803 directly with the display and input hardware or via
8804 another subsystem (e.g., GGI) should provide
8805 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8806 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8812 <heading>Packages providing a terminal emulator</heading>
8815 Packages that provide a terminal emulator for the X Window
8816 System which meet the criteria listed below should declare in
8817 their <tt>Provides</tt> control field that they provide the
8818 virtual package <tt>x-terminal-emulator</tt>. They should
8819 also register themselves as an alternative for
8820 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8821 20. That alternative should have a slave alternative
8822 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8823 pointing to the corresponding manual page.
8827 To be an <tt>x-terminal-emulator</tt>, a program must:
8828 <list compact="compact">
8830 Be able to emulate a DEC VT100 terminal, or a
8831 compatible terminal.
8835 Support the command-line option <tt>-e
8836 <var>command</var></tt>, which creates a new
8837 terminal window<footnote>
8838 "New terminal window" does not necessarily mean
8839 a new top-level X window directly parented by
8840 the window manager; it could, if the terminal
8841 emulator application were so coded, be a new
8842 "view" in a multiple-document interface (MDI).
8844 and runs the specified <var>command</var>,
8845 interpreting the entirety of the rest of the command
8846 line as a command to pass straight to exec, in the
8847 manner that <tt>xterm</tt> does.
8851 Support the command-line option <tt>-T
8852 <var>title</var></tt>, which creates a new terminal
8853 window with the window title <var>title</var>.
8860 <heading>Packages providing a window manager</heading>
8863 Packages that provide a window manager should declare in
8864 their <tt>Provides</tt> control field that they provide the
8865 virtual package <tt>x-window-manager</tt>. They should also
8866 register themselves as an alternative for
8867 <file>/usr/bin/x-window-manager</file>, with a priority
8868 calculated as follows:
8869 <list compact="compact">
8871 Start with a priority of 20.
8875 If the window manager supports the Debian menu
8876 system, add 20 points if this support is available
8877 in the package's default configuration (i.e., no
8878 configuration files belonging to the system or user
8879 have to be edited to activate the feature); if
8880 configuration files must be modified, add only 10
8886 If the window manager complies with <url
8887 id="http://www.freedesktop.org/Standards/wm-spec"
8888 name="The Window Manager Specification Project">,
8889 written by the <url id="http://www.freedesktop.org/"
8890 name="Free Desktop Group">, add 40 points.
8894 If the window manager permits the X session to be
8895 restarted using a <em>different</em> window manager
8896 (without killing the X server) in its default
8897 configuration, add 10 points; otherwise add none.
8900 That alternative should have a slave alternative
8901 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8902 pointing to the corresponding manual page.
8907 <heading>Packages providing fonts</heading>
8910 Packages that provide fonts for the X Window
8912 For the purposes of Debian Policy, a "font for the X
8913 Window System" is one which is accessed via X protocol
8914 requests. Fonts for the Linux console, for PostScript
8915 renderer, or any other purpose, do not fit this
8916 definition. Any tool which makes such fonts available
8917 to the X Window System, however, must abide by this
8920 must do a number of things to ensure that they are both
8921 available without modification of the X or font server
8922 configuration, and that they do not corrupt files used by
8923 other font packages to register information about
8927 Fonts of any type supported by the X Window System
8928 must be in a separate binary package from any
8929 executables, libraries, or documentation (except
8930 that specific to the fonts shipped, such as their
8931 license information). If one or more of the fonts
8932 so packaged are necessary for proper operation of
8933 the package with which they are associated the font
8934 package may be Recommended; if the fonts merely
8935 provide an enhancement, a Suggests relationship may
8936 be used. Packages must not Depend on font
8938 This is because the X server may retrieve fonts
8939 from the local file system or over the network
8940 from an X font server; the Debian package system
8941 is empowered to deal only with the local
8947 BDF fonts must be converted to PCF fonts with the
8948 <prgn>bdftopcf</prgn> utility (available in the
8949 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8950 placed in a directory that corresponds to their
8952 <list compact="compact">
8954 100 dpi fonts must be placed in
8955 <file>/usr/share/fonts/X11/100dpi/</file>.
8959 75 dpi fonts must be placed in
8960 <file>/usr/share/fonts/X11/75dpi/</file>.
8964 Character-cell fonts, cursor fonts, and other
8965 low-resolution fonts must be placed in
8966 <file>/usr/share/fonts/X11/misc/</file>.
8972 Type 1 fonts must be placed in
8973 <file>/usr/share/fonts/X11/Type1/</file>. If font
8974 metric files are available, they must be placed here
8979 Subdirectories of <file>/usr/share/fonts/X11/</file>
8980 other than those listed above must be neither
8981 created nor used. (The <file>PEX</file>, <file>CID</file>,
8982 <file>Speedo</file>, and <file>cyrillic</file> directories
8983 are excepted for historical reasons, but installation of
8984 files into these directories remains discouraged.)
8988 Font packages may, instead of placing files directly
8989 in the X font directories listed above, provide
8990 symbolic links in that font directory pointing to
8991 the files' actual location in the filesystem. Such
8992 a location must comply with the FHS.
8996 Font packages should not contain both 75dpi and
8997 100dpi versions of a font. If both are available,
8998 they should be provided in separate binary packages
8999 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9000 the names of the packages containing the
9001 corresponding fonts.
9005 Fonts destined for the <file>misc</file> subdirectory
9006 should not be included in the same package as 75dpi
9007 or 100dpi fonts; instead, they should be provided in
9008 a separate package with <tt>-misc</tt> appended to
9013 Font packages must not provide the files
9014 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9015 <file>fonts.scale</file> in a font directory:
9018 <file>fonts.dir</file> files must not be provided at all.
9022 <file>fonts.alias</file> and <file>fonts.scale</file>
9023 files, if needed, should be provided in the
9025 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9026 where <var>fontdir</var> is the name of the
9028 <file>/usr/share/fonts/X11/</file> where the
9029 package's corresponding fonts are stored
9030 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9031 <var>package</var> is the name of the package
9032 that provides these fonts, and
9033 <var>extension</var> is either <tt>scale</tt>
9034 or <tt>alias</tt>, whichever corresponds to
9041 Font packages must declare a dependency on
9042 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9043 or <tt>Pre-Depends</tt> control field.
9047 Font packages that provide one or more
9048 <file>fonts.scale</file> files as described above must
9049 invoke <prgn>update-fonts-scale</prgn> on each
9050 directory into which they installed fonts
9051 <em>before</em> invoking
9052 <prgn>update-fonts-dir</prgn> on that directory.
9053 This invocation must occur in both the
9054 <prgn>postinst</prgn> (for all arguments) and
9055 <prgn>postrm</prgn> (for all arguments except
9056 <tt>upgrade</tt>) scripts.
9060 Font packages that provide one or more
9061 <file>fonts.alias</file> files as described above must
9062 invoke <prgn>update-fonts-alias</prgn> on each
9063 directory into which they installed fonts. This
9064 invocation must occur in both the
9065 <prgn>postinst</prgn> (for all arguments) and
9066 <prgn>postrm</prgn> (for all arguments except
9067 <tt>upgrade</tt>) scripts.
9071 Font packages must invoke
9072 <prgn>update-fonts-dir</prgn> on each directory into
9073 which they installed fonts. This invocation must
9074 occur in both the <prgn>postinst</prgn> (for all
9075 arguments) and <prgn>postrm</prgn> (for all
9076 arguments except <tt>upgrade</tt>) scripts.
9080 Font packages must not provide alias names for the
9081 fonts they include which collide with alias names
9082 already in use by fonts already packaged.
9086 Font packages must not provide fonts with the same
9087 XLFD registry name as another font already packaged.
9093 <sect1 id="appdefaults">
9094 <heading>Application defaults files</heading>
9097 Application defaults files must be installed in the
9098 directory <file>/etc/X11/app-defaults/</file> (use of a
9099 localized subdirectory of <file>/etc/X11/</file> as described
9100 in the <em>X Toolkit Intrinsics - C Language
9101 Interface</em> manual is also permitted). They must be
9102 registered as <tt>conffile</tt>s or handled as
9103 configuration files.
9107 Customization of programs' X resources may also be
9108 supported with the provision of a file with the same name
9109 as that of the package placed in
9110 the <file>/etc/X11/Xresources/</file> directory, which
9111 must be registered as a <tt>conffile</tt> or handled as a
9112 configuration file.<footnote>
9113 Note that this mechanism is not the same as using
9114 app-defaults; app-defaults are tied to the client
9115 binary on the local file system, whereas X resources
9116 are stored in the X server and affect all connecting
9123 <heading>Installation directory issues</heading>
9126 Historically, packages using the X Window System used a
9127 separate set of installation directories from other packages.
9128 This practice has been discontinued and packages using the X
9129 Window System should now generally be installed in the same
9130 directories as any other package. Specifically, packages must
9131 not install files under the <file>/usr/X11R6/</file> directory
9132 and the <file>/usr/X11R6/</file> directory hierarchy should be
9133 regarded as obsolete.
9137 Include files previously installed under
9138 <file>/usr/X11R6/include/X11/</file> should be installed into
9139 <file>/usr/include/X11/</file>. For files previously
9140 installed into subdirectories of
9141 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9142 determine if subdirectories of <file>/usr/lib/</file> and
9143 <file>/usr/share/</file> can be used. If not, a subdirectory
9144 of <file>/usr/lib/X11/</file> should be used.
9148 Configuration files for window, display, or session managers
9149 or other applications that are tightly integrated with the X
9150 Window System may be placed in a subdirectory
9151 of <file>/etc/X11/</file> corresponding to the package name.
9152 Other X Window System applications should use
9153 the <file>/etc/</file> directory unless otherwise mandated by
9154 policy (such as for <ref id="appdefaults">).
9159 <heading>The OSF/Motif and OpenMotif libraries</heading>
9162 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9163 OpenMotif libraries</em><footnote>
9164 OSF/Motif and OpenMotif are collectively referred to as
9165 "Motif" in this policy document.
9167 should be compiled against and tested with LessTif (a free
9168 re-implementation of Motif) instead. If the maintainer
9169 judges that the program or programs do not work
9170 sufficiently well with LessTif to be distributed and
9171 supported, but do so when compiled against Motif, then two
9172 versions of the package should be created; one linked
9173 statically against Motif and with <tt>-smotif</tt>
9174 appended to the package name, and one linked dynamically
9175 against Motif and with <tt>-dmotif</tt> appended to the
9180 Both Motif-linked versions are dependent
9181 upon non-DFSG-compliant software and thus cannot be
9182 uploaded to the <em>main</em> distribution; if the
9183 software is itself DFSG-compliant it may be uploaded to
9184 the <em>contrib</em> distribution. While known existing
9185 versions of Motif permit unlimited redistribution of
9186 binaries linked against the library (whether statically or
9187 dynamically), it is the package maintainer's
9188 responsibility to determine whether this is permitted by
9189 the license of the copy of Motif in their possession.
9195 <heading>Perl programs and modules</heading>
9198 Perl programs and modules should follow the current Perl policy.
9202 The Perl policy can be found in the <tt>perl-policy</tt>
9203 files in the <tt>debian-policy</tt> package.
9204 It is also available from the Debian web mirrors at
9205 <tt><url name="/doc/packaging-manuals/perl-policy/"
9206 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9211 <heading>Emacs lisp programs</heading>
9214 Please refer to the "Debian Emacs Policy" for details of how to
9215 package emacs lisp programs.
9219 The Emacs policy is available in
9220 <file>debian-emacs-policy.gz</file> of the
9221 <package>emacsen-common</package> package.
9222 It is also available from the Debian web mirrors at
9223 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9224 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9229 <heading>Games</heading>
9232 The permissions on <file>/var/games</file> are mode 755, owner
9233 <tt>root</tt> and group <tt>root</tt>.
9237 Each game decides on its own security policy.</p>
9240 Games which require protected, privileged access to
9241 high-score files, saved games, etc., may be made
9242 set-<em>group</em>-id (mode 2755) and owned by
9243 <tt>root:games</tt>, and use files and directories with
9244 appropriate permissions (770 <tt>root:games</tt>, for
9245 example). They must not be made
9246 set-<em>user</em>-id, as this causes security problems. (If
9247 an attacker can subvert any set-user-id game they can
9248 overwrite the executable of any other, causing other players
9249 of these games to run a Trojan horse program. With a
9250 set-group-id game the attacker only gets access to less
9251 important game data, and if they can get at the other
9252 players' accounts at all it will take considerably more
9256 Some packages, for example some fortune cookie programs, are
9257 configured by the upstream authors to install with their
9258 data files or other static information made unreadable so
9259 that they can only be accessed through set-id programs
9260 provided. You should not do this in a Debian package: anyone can
9261 download the <file>.deb</file> file and read the data from it,
9262 so there is no point making the files unreadable. Not
9263 making the files unreadable also means that you don't have
9264 to make so many programs set-id, which reduces the risk of a
9268 As described in the FHS, binaries of games should be
9269 installed in the directory <file>/usr/games</file>. This also
9270 applies to games that use the X Window System. Manual pages
9271 for games (X and non-X games) should be installed in
9272 <file>/usr/share/man/man6</file>.</p>
9278 <heading>Documentation</heading>
9281 <heading>Manual pages</heading>
9284 You should install manual pages in <prgn>nroff</prgn> source
9285 form, in appropriate places under <file>/usr/share/man</file>.
9286 You should only use sections 1 to 9 (see the FHS for more
9287 details). You must not install a pre-formatted "cat page".
9291 Each program, utility, and function should have an
9292 associated manual page included in the same package. It is
9293 suggested that all configuration files also have a manual
9294 page included as well. Manual pages for protocols and other
9295 auxiliary things are optional.
9299 If no manual page is available, this is considered as a bug
9300 and should be reported to the Debian Bug Tracking System (the
9301 maintainer of the package is allowed to write this bug report
9302 themselves, if they so desire). Do not close the bug report
9303 until a proper man page is available.<footnote>
9304 It is not very hard to write a man page. See the
9305 <url id="http://www.schweikhardt.net/man_page_howto.html"
9306 name="Man-Page-HOWTO">,
9307 <manref name="man" section="7">, the examples
9308 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9309 the helper program <prgn>help2man</prgn>, or the
9310 directory <file>/usr/share/doc/man-db/examples</file>.
9315 You may forward a complaint about a missing man page to the
9316 upstream authors, and mark the bug as forwarded in the
9317 Debian bug tracking system. Even though the GNU Project do
9318 not in general consider the lack of a man page to be a bug,
9319 we do; if they tell you that they don't consider it a bug
9320 you should leave the bug in our bug tracking system open
9325 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9329 If one man page needs to be accessible via several names it
9330 is better to use a symbolic link than the <file>.so</file>
9331 feature, but there is no need to fiddle with the relevant
9332 parts of the upstream source to change from <file>.so</file> to
9333 symlinks: don't do it unless it's easy. You should not
9334 create hard links in the manual page directories, nor put
9335 absolute filenames in <file>.so</file> directives. The filename
9336 in a <file>.so</file> in a man page should be relative to the
9337 base of the man page tree (usually
9338 <file>/usr/share/man</file>). If you do not create any links
9339 (whether symlinks, hard links, or <tt>.so</tt> directives)
9340 in the file system to the alternate names of the man page,
9341 then you should not rely on <prgn>man</prgn> finding your
9342 man page under those names based solely on the information in
9343 the man page's header.<footnote>
9344 Supporting this in <prgn>man</prgn> often requires
9345 unreasonable processing time to find a manual page or to
9346 report that none exists, and moves knowledge into man's
9347 database that would be better left in the file system.
9348 This support is therefore deprecated and will cease to
9349 be present in the future.
9354 Manual pages in locale-specific subdirectories of
9355 <file>/usr/share/man</file> should use either UTF-8 or the usual
9356 legacy encoding for that language (normally the one corresponding
9357 to the shortest relevant locale name in
9358 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9359 <file>/usr/share/man/fr</file> should use either UTF-8 or
9360 ISO-8859-1.<footnote>
9361 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9362 use. In future, all manual pages will be required to use
9368 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9369 included in the subdirectory name unless it indicates a
9370 significant difference in the language, as this excludes
9371 speakers of the language in other countries.<footnote>
9372 At the time of writing, Chinese and Portuguese are the main
9373 languages with such differences, so <file>pt_BR</file>,
9374 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9379 If a localized version of a manual page is provided, it should
9380 either be up-to-date or it should be obvious to the reader that
9381 it is outdated and the original manual page should be used
9382 instead. This can be done either by a note at the beginning of
9383 the manual page or by showing the missing or changed portions in
9384 the original language instead of the target language.
9389 <heading>Info documents</heading>
9392 Info documents should be installed in <file>/usr/share/info</file>.
9393 They should be compressed with <tt>gzip -9</tt>.
9397 The <prgn>install-info</prgn> program maintains a directory of
9398 installed info documents in <file>/usr/share/info/dir</file> for
9399 the use of info readers.<footnote>
9400 It was previously necessary for packages installing info
9401 documents to run <prgn>install-info</prgn> from maintainer
9402 scripts. This is no longer necessary. The installation
9403 system now uses dpkg triggers.
9405 This file must not be included in packages. Packages containing
9406 info documents should depend on <tt>dpkg (>= 1.15.4) |
9407 install-info</tt> to ensure that the directory file is properly
9408 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9413 Info documents should contain section and directory entry
9414 information in the document for the use
9415 of <prgn>install-info</prgn>. The section should be specified
9416 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9417 space and the section of this info page. The directory entry or
9418 entries should be included between
9419 a <tt>START-INFO-DIR-ENTRY</tt> line and
9420 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9422 INFO-DIR-SECTION Individual utilities
9423 START-INFO-DIR-ENTRY
9424 * example: (example). An example info directory entry.
9427 To determine which section to use, you should look
9428 at <file>/usr/share/info/dir</file> on your system and choose
9429 the most relevant (or create a new section if none of the
9430 current sections are relevant).<footnote>
9431 Normally, info documents are generated from Texinfo source.
9432 To include this information in the generated info document, if
9433 it is absent, add commands like:
9435 @dircategory Individual utilities
9437 * example: (example). An example info directory entry.
9440 to the Texinfo source of the document and ensure that the info
9441 documents are rebuilt from source during the package build.
9447 <heading>Additional documentation</heading>
9450 Any additional documentation that comes with the package may
9451 be installed at the discretion of the package maintainer.
9452 Plain text documentation should be installed in the directory
9453 <file>/usr/share/doc/<var>package</var></file>, where
9454 <var>package</var> is the name of the package, and
9455 compressed with <tt>gzip -9</tt> unless it is small.
9459 If a package comes with large amounts of documentation which
9460 many users of the package will not require you should create
9461 a separate binary package to contain it, so that it does not
9462 take up disk space on the machines of users who do not need
9463 or want it installed.</p>
9466 It is often a good idea to put text information files
9467 (<file>README</file>s, changelogs, and so forth) that come with
9468 the source package in <file>/usr/share/doc/<var>package</var></file>
9469 in the binary package. However, you don't need to install
9470 the instructions for building and installing the package, of
9474 Packages must not require the existence of any files in
9475 <file>/usr/share/doc/</file> in order to function
9477 The system administrator should be able to
9478 delete files in <file>/usr/share/doc/</file> without causing
9479 any programs to break.
9481 Any files that are referenced by programs but are also
9482 useful as stand alone documentation should be installed under
9483 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9484 <file>/usr/share/doc/<var>package</var></file>.
9488 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9489 link to another directory in <file>/usr/share/doc</file> only if
9490 the two packages both come from the same source and the
9491 first package Depends on the second.<footnote>
9493 Please note that this does not override the section on
9494 changelog files below, so the file
9495 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9496 must refer to the changelog for the current version of
9497 <var>package</var> in question. In practice, this means
9498 that the sources of the target and the destination of the
9499 symlink must be the same (same source package and
9506 Former Debian releases placed all additional documentation
9507 in <file>/usr/doc/<var>package</var></file>. This has been
9508 changed to <file>/usr/share/doc/<var>package</var></file>,
9509 and packages must not put documentation in the directory
9510 <file>/usr/doc/<var>package</var></file>. <footnote>
9511 At this phase of the transition, we no longer require a
9512 symbolic link in <file>/usr/doc/</file>. At a later point,
9513 policy shall change to make the symbolic links a bug.
9519 <heading>Preferred documentation formats</heading>
9522 The unification of Debian documentation is being carried out
9526 If your package comes with extensive documentation in a
9527 markup format that can be converted to various other formats
9528 you should if possible ship HTML versions in a binary
9529 package, in the directory
9530 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9531 its subdirectories.<footnote>
9532 The rationale: The important thing here is that HTML
9533 docs should be available in <em>some</em> package, not
9534 necessarily in the main binary package.
9539 Other formats such as PostScript may be provided at the
9540 package maintainer's discretion.
9544 <sect id="copyrightfile">
9545 <heading>Copyright information</heading>
9548 Every package must be accompanied by a verbatim copy of its
9549 copyright information and distribution license in the file
9550 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9551 file must neither be compressed nor be a symbolic link.
9555 In addition, the copyright file must say where the upstream
9556 sources (if any) were obtained. It should name the original
9557 authors of the package and the Debian maintainer(s) who were
9558 involved with its creation.
9562 Packages in the <em>contrib</em> or <em>non-free</em> archive
9563 areas should state in the copyright file that the package is not
9564 part of the Debian distribution and briefly explain why.
9568 A copy of the file which will be installed in
9569 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9570 be in <file>debian/copyright</file> in the source package.
9574 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9575 link to another directory in <file>/usr/share/doc</file> only if
9576 the two packages both come from the same source and the
9577 first package Depends on the second. These rules are
9578 important because copyrights must be extractable by
9583 Packages distributed under the Apache license (version 2.0), the
9584 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9585 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9586 1.3) should refer to the corresponding files
9587 under <file>/usr/share/common-licenses</file>,<footnote>
9590 <file>/usr/share/common-licenses/Apache-2.0</file>,
9591 <file>/usr/share/common-licenses/Artistic</file>,
9592 <file>/usr/share/common-licenses/GPL-1</file>,
9593 <file>/usr/share/common-licenses/GPL-2</file>,
9594 <file>/usr/share/common-licenses/GPL-3</file>,
9595 <file>/usr/share/common-licenses/LGPL-2</file>,
9596 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9597 <file>/usr/share/common-licenses/LGPL-3</file>,
9598 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9599 <file>/usr/share/common-licenses/GFDL-1.3</file>
9600 respectively. The University of California BSD license is
9601 also included in <package>base-files</package> as
9602 <file>/usr/share/common-licenses/BSD</file>, but given the
9603 brevity of this license, its specificity to code whose
9604 copyright is held by the Regents of the University of
9605 California, and the frequency of minor wording changes, its
9606 text should be included in the copyright file rather than
9607 referencing this file.
9609 </footnote> rather than quoting them in the copyright
9614 You should not use the copyright file as a general <file>README</file>
9615 file. If your package has such a file it should be
9616 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9617 <file>README.Debian</file> or some other appropriate place.</p>
9621 <heading>Examples</heading>
9624 Any examples (configurations, source files, whatever),
9625 should be installed in a directory
9626 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9627 files should not be referenced by any program: they're there
9628 for the benefit of the system administrator and users as
9629 documentation only. Architecture-specific example files
9630 should be installed in a directory
9631 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9633 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9634 latter directory itself may be a symbolic link to the
9639 If the purpose of a package is to provide examples, then the
9640 example files may be installed into
9641 <file>/usr/share/doc/<var>package</var></file>.
9645 <sect id="changelogs">
9646 <heading>Changelog files</heading>
9649 Packages that are not Debian-native must contain a
9650 compressed copy of the <file>debian/changelog</file> file from
9651 the Debian source tree in
9652 <file>/usr/share/doc/<var>package</var></file> with the name
9653 <file>changelog.Debian.gz</file>.
9657 If an upstream changelog is available, it should be accessible as
9658 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9659 plain text. If the upstream changelog is distributed in
9660 HTML, it should be made available in that form as
9661 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9662 and a plain text <file>changelog.gz</file> should be generated
9663 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9664 the upstream changelog files do not already conform to this
9665 naming convention, then this may be achieved either by
9666 renaming the files, or by adding a symbolic link, at the
9667 maintainer's discretion.<footnote>
9668 Rationale: People should not have to look in places for
9669 upstream changelogs merely because they are given
9670 different names or are distributed in HTML format.
9675 All of these files should be installed compressed using
9676 <tt>gzip -9</tt>, as they will become large with time even
9677 if they start out small.
9681 If the package has only one changelog which is used both as
9682 the Debian changelog and the upstream one because there is
9683 no separate upstream maintainer then that changelog should
9684 usually be installed as
9685 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9686 there is a separate upstream maintainer, but no upstream
9687 changelog, then the Debian changelog should still be called
9688 <file>changelog.Debian.gz</file>.
9692 For details about the format and contents of the Debian
9693 changelog file, please see <ref id="dpkgchangelog">.
9698 <appendix id="pkg-scope">
9699 <heading>Introduction and scope of these appendices</heading>
9702 These appendices are taken essentially verbatim from the
9703 now-deprecated Packaging Manual, version 3.2.1.0. They are
9704 the chapters which are likely to be of use to package
9705 maintainers and which have not already been included in the
9706 policy document itself. Most of these sections are very likely
9707 not relevant to policy; they should be treated as
9708 documentation for the packaging system. Please note that these
9709 appendices are included for convenience, and for historical
9710 reasons: they used to be part of policy package, and they have
9711 not yet been incorporated into dpkg documentation. However,
9712 they still have value, and hence they are presented here.
9716 They have not yet been checked to ensure that they are
9717 compatible with the contents of policy, and if there are any
9718 contradictions, the version in the main policy document takes
9719 precedence. The remaining chapters of the old Packaging
9720 Manual have also not been read in detail to ensure that there
9721 are not parts which have been left out. Both of these will be
9726 Certain parts of the Packaging manual were integrated into the
9727 Policy Manual proper, and removed from the appendices. Links
9728 have been placed from the old locations to the new ones.
9732 <prgn>dpkg</prgn> is a suite of programs for creating binary
9733 package files and installing and removing them on Unix
9735 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
9736 work on or be ported to other systems.
9741 The binary packages are designed for the management of
9742 installed executable programs (usually compiled binaries) and
9743 their associated data, though source code examples and
9744 documentation are provided as part of some packages.</p>
9747 This manual describes the technical aspects of creating Debian
9748 binary packages (<file>.deb</file> files). It documents the
9749 behavior of the package management programs
9750 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9751 they interact with packages.</p>
9754 It also documents the interaction between
9755 <prgn>dselect</prgn>'s core and the access method scripts it
9756 uses to actually install the selected packages, and describes
9757 how to create a new access method.</p>
9760 This manual does not go into detail about the options and
9761 usage of the package building and installation tools. It
9762 should therefore be read in conjunction with those programs'
9767 The utility programs which are provided with <prgn>dpkg</prgn>
9768 for managing various system configuration and similar issues,
9769 such as <prgn>update-rc.d</prgn> and
9770 <prgn>install-info</prgn>, are not described in detail here -
9771 please see their man pages.
9775 It is assumed that the reader is reasonably familiar with the
9776 <prgn>dpkg</prgn> System Administrators' manual.
9777 Unfortunately this manual does not yet exist.
9781 The Debian version of the FSF's GNU hello program is provided
9782 as an example for people wishing to create Debian
9783 packages. The Debian <prgn>debmake</prgn> package is
9784 recommended as a very helpful tool in creating and maintaining
9785 Debian packages. However, while the tools and examples are
9786 helpful, they do not replace the need to read and follow the
9787 Policy and Programmer's Manual.</p>
9790 <appendix id="pkg-binarypkg">
9791 <heading>Binary packages (from old Packaging Manual)</heading>
9794 The binary package has two main sections. The first part
9795 consists of various control information files and scripts used
9796 by <prgn>dpkg</prgn> when installing and removing. See <ref
9797 id="pkg-controlarea">.
9801 The second part is an archive containing the files and
9802 directories to be installed.
9806 In the future binary packages may also contain other
9807 components, such as checksums and digital signatures. The
9808 format for the archive is described in full in the
9809 <file>deb(5)</file> man page.
9813 <sect id="pkg-bincreating"><heading>Creating package files -
9814 <prgn>dpkg-deb</prgn>
9818 All manipulation of binary package files is done by
9819 <prgn>dpkg-deb</prgn>; it's the only program that has
9820 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9821 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9822 will spot that the options requested are appropriate to
9823 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9828 In order to create a binary package you must make a
9829 directory tree which contains all the files and directories
9830 you want to have in the file system data part of the package.
9831 In Debian-format source packages this directory is usually
9832 <file>debian/tmp</file>, relative to the top of the package's
9837 They should have the locations (relative to the root of the
9838 directory tree you're constructing) ownerships and
9839 permissions which you want them to have on the system when
9844 With current versions of <prgn>dpkg</prgn> the uid/username
9845 and gid/groupname mappings for the users and groups being
9846 used should be the same on the system where the package is
9847 built and the one where it is installed.
9851 You need to add one special directory to the root of the
9852 miniature file system tree you're creating:
9853 <prgn>DEBIAN</prgn>. It should contain the control
9854 information files, notably the binary package control file
9855 (see <ref id="pkg-controlfile">).
9859 The <prgn>DEBIAN</prgn> directory will not appear in the
9860 file system archive of the package, and so won't be installed
9861 by <prgn>dpkg</prgn> when the package is installed.
9865 When you've prepared the package, you should invoke:
9867 dpkg --build <var>directory</var>
9872 This will build the package in
9873 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9874 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9875 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9880 See the man page <manref name="dpkg-deb" section="8"> for details of how
9881 to examine the contents of this newly-created file. You may find the
9882 output of following commands enlightening:
9884 dpkg-deb --info <var>filename</var>.deb
9885 dpkg-deb --contents <var>filename</var>.deb
9886 dpkg --contents <var>filename</var>.deb
9888 To view the copyright file for a package you could use this command:
9890 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9895 <sect id="pkg-controlarea">
9896 <heading>Package control information files</heading>
9899 The control information portion of a binary package is a
9900 collection of files with names known to <prgn>dpkg</prgn>.
9901 It will treat the contents of these files specially - some
9902 of them contain information used by <prgn>dpkg</prgn> when
9903 installing or removing the package; others are scripts which
9904 the package maintainer wants <prgn>dpkg</prgn> to run.
9908 It is possible to put other files in the package control
9909 information file area, but this is not generally a good idea
9910 (though they will largely be ignored).
9914 Here is a brief list of the control information files supported
9915 by <prgn>dpkg</prgn> and a summary of what they're used for.
9920 <tag><tt>control</tt>
9923 This is the key description file used by
9924 <prgn>dpkg</prgn>. It specifies the package's name
9925 and version, gives its description for the user,
9926 states its relationships with other packages, and so
9927 forth. See <ref id="sourcecontrolfiles"> and
9928 <ref id="binarycontrolfiles">.
9932 It is usually generated automatically from information
9933 in the source package by the
9934 <prgn>dpkg-gencontrol</prgn> program, and with
9935 assistance from <prgn>dpkg-shlibdeps</prgn>.
9936 See <ref id="pkg-sourcetools">.
9940 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9945 These are executable files (usually scripts) which
9946 <prgn>dpkg</prgn> runs during installation, upgrade
9947 and removal of packages. They allow the package to
9948 deal with matters which are particular to that package
9949 or require more complicated processing than that
9950 provided by <prgn>dpkg</prgn>. Details of when and
9951 how they are called are in <ref id="maintainerscripts">.
9955 It is very important to make these scripts idempotent.
9956 See <ref id="idempotency">.
9960 The maintainer scripts are not guaranteed to run with a
9961 controlling terminal and may not be able to interact with
9962 the user. See <ref id="controllingterminal">.
9966 <tag><tt>conffiles</tt>
9969 This file contains a list of configuration files which
9970 are to be handled automatically by <prgn>dpkg</prgn>
9971 (see <ref id="pkg-conffiles">). Note that not necessarily
9972 every configuration file should be listed here.
9975 <tag><tt>shlibs</tt>
9978 This file contains a list of the shared libraries
9979 supplied by the package, with dependency details for
9980 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9981 when it determines what dependencies are required in a
9982 package control file. The <tt>shlibs</tt> file format
9983 is described on <ref id="shlibs">.
9988 <sect id="pkg-controlfile">
9989 <heading>The main control information file: <tt>control</tt></heading>
9992 The most important control information file used by
9993 <prgn>dpkg</prgn> when it installs a package is
9994 <tt>control</tt>. It contains all the package's "vital
9999 The binary package control files of packages built from
10000 Debian sources are made by a special tool,
10001 <prgn>dpkg-gencontrol</prgn>, which reads
10002 <file>debian/control</file> and <file>debian/changelog</file> to
10003 find the information it needs. See <ref id="pkg-sourcepkg"> for
10008 The fields in binary package control files are listed in
10009 <ref id="binarycontrolfiles">.
10013 A description of the syntax of control files and the purpose
10014 of the fields is available in <ref id="controlfields">.
10019 <heading>Time Stamps</heading>
10022 See <ref id="timestamps">.
10027 <appendix id="pkg-sourcepkg">
10028 <heading>Source packages (from old Packaging Manual) </heading>
10031 The Debian binary packages in the distribution are generated
10032 from Debian sources, which are in a special format to assist
10033 the easy and automatic building of binaries.
10036 <sect id="pkg-sourcetools">
10037 <heading>Tools for processing source packages</heading>
10040 Various tools are provided for manipulating source packages;
10041 they pack and unpack sources and help build of binary
10042 packages and help manage the distribution of new versions.
10046 They are introduced and typical uses described here; see
10047 <manref name="dpkg-source" section="1"> for full
10048 documentation about their arguments and operation.
10052 For examples of how to construct a Debian source package,
10053 and how to use those utilities that are used by Debian
10054 source packages, please see the <prgn>hello</prgn> example
10058 <sect1 id="pkg-dpkg-source">
10060 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10065 This program is frequently used by hand, and is also
10066 called from package-independent automated building scripts
10067 such as <prgn>dpkg-buildpackage</prgn>.
10071 To unpack a package it is typically invoked with
10073 dpkg-source -x <var>.../path/to/filename</var>.dsc
10078 with the <file><var>filename</var>.tar.gz</file> and
10079 <file><var>filename</var>.diff.gz</file> (if applicable) in
10080 the same directory. It unpacks into
10081 <file><var>package</var>-<var>version</var></file>, and if
10083 <file><var>package</var>-<var>version</var>.orig</file>, in
10084 the current directory.
10088 To create a packed source archive it is typically invoked:
10090 dpkg-source -b <var>package</var>-<var>version</var>
10095 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10096 <file>.diff.gz</file> (if appropriate) in the current
10097 directory. <prgn>dpkg-source</prgn> does not clean the
10098 source tree first - this must be done separately if it is
10103 See also <ref id="pkg-sourcearchives">.</p>
10107 <sect1 id="pkg-dpkg-buildpackage">
10109 <prgn>dpkg-buildpackage</prgn> - overall package-building
10114 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10115 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10116 targets <tt>clean</tt>, <tt>build</tt> and
10117 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10118 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10119 source and binary package upload.
10123 It is usually invoked by hand from the top level of the
10124 built or unbuilt source directory. It may be invoked with
10125 no arguments; useful arguments include:
10126 <taglist compact="compact">
10127 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10130 Do not sign the <tt>.changes</tt> file or the
10131 source package <tt>.dsc</tt> file, respectively.</p>
10133 <tag><tt>-p<var>sign-command</var></tt></tag>
10136 Invoke <var>sign-command</var> instead of finding
10137 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10138 <var>sign-command</var> must behave just like
10139 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10141 <tag><tt>-r<var>root-command</var></tt></tag>
10144 When root privilege is required, invoke the command
10145 <var>root-command</var>. <var>root-command</var>
10146 should invoke its first argument as a command, from
10147 the <prgn>PATH</prgn> if necessary, and pass its
10148 second and subsequent arguments to the command it
10149 calls. If no <var>root-command</var> is supplied
10150 then <var>dpkg-buildpackage</var> will take no
10151 special action to gain root privilege, so that for
10152 most packages it will have to be invoked as root to
10155 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10158 Two types of binary-only build and upload - see
10159 <manref name="dpkg-source" section="1">.
10166 <sect1 id="pkg-dpkg-gencontrol">
10168 <prgn>dpkg-gencontrol</prgn> - generates binary package
10173 This program is usually called from <file>debian/rules</file>
10174 (see <ref id="pkg-sourcetree">) in the top level of the source
10179 This is usually done just before the files and directories in the
10180 temporary directory tree where the package is being built have their
10181 permissions and ownerships set and the package is constructed using
10182 <prgn>dpkg-deb/</prgn>
10184 This is so that the control file which is produced has
10185 the right permissions
10190 <prgn>dpkg-gencontrol</prgn> must be called after all the
10191 files which are to go into the package have been placed in
10192 the temporary build directory, so that its calculation of
10193 the installed size of a package is correct.
10197 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10198 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10199 variable substitutions created by
10200 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10205 For a package which generates only one binary package, and
10206 which builds it in <file>debian/tmp</file> relative to the top
10207 of the source package, it is usually sufficient to call
10208 <prgn>dpkg-gencontrol</prgn>.
10212 Sources which build several binaries will typically need
10215 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10216 </example> The <tt>-P</tt> tells
10217 <prgn>dpkg-gencontrol</prgn> that the package is being
10218 built in a non-default directory, and the <tt>-p</tt>
10219 tells it which package's control file should be generated.
10223 <prgn>dpkg-gencontrol</prgn> also adds information to the
10224 list of files in <file>debian/files</file>, for the benefit of
10225 (for example) a future invocation of
10226 <prgn>dpkg-genchanges</prgn>.</p>
10229 <sect1 id="pkg-dpkg-shlibdeps">
10231 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10236 This program is usually called from <file>debian/rules</file>
10237 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10238 id="pkg-sourcetree">), in the top level of the source tree.
10242 Its arguments are executables and shared libraries
10245 They may be specified either in the locations in the
10246 source tree where they are created or in the locations
10247 in the temporary build tree where they are installed
10248 prior to binary package creation.
10250 </footnote> for which shared library dependencies should
10251 be included in the binary package's control file.
10255 If some of the found shared libraries should only
10256 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10257 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10258 by using the <tt>-d<var>dependency-field</var></tt> option
10259 before those executable(s). (Each <tt>-d</tt> option
10260 takes effect until the next <tt>-d</tt>.)
10264 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10265 output control file to be modified. Instead by default it
10266 adds to the <file>debian/substvars</file> file variable
10267 settings like <tt>shlibs:Depends</tt>. These variable
10268 settings must be referenced in dependency fields in the
10269 appropriate per-binary-package sections of the source
10274 For example, a package that generates an essential part
10275 which requires dependencies, and optional parts that
10276 which only require a recommendation, would separate those
10277 two sets of dependencies into two different fields.<footnote>
10278 At the time of writing, an example for this was the
10279 <package/xmms/ package, with Depends used for the xmms
10280 executable, Recommends for the plug-ins and Suggests for
10281 even more optional features provided by unzip.
10283 It can say in its <file>debian/rules</file>:
10285 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10286 -dRecommends <var>optionalpart anotheroptionalpart</var>
10288 and then in its main control file <file>debian/control</file>:
10291 Depends: ${shlibs:Depends}
10292 Recommends: ${shlibs:Recommends}
10298 Sources which produce several binary packages with
10299 different shared library dependency requirements can use
10300 the <tt>-p<var>varnameprefix</var></tt> option to override
10301 the default <tt>shlibs:</tt> prefix (one invocation of
10302 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10303 They can thus produce several sets of dependency
10304 variables, each of the form
10305 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10306 which can be referred to in the appropriate parts of the
10307 binary package control files.
10312 <sect1 id="pkg-dpkg-distaddfile">
10314 <prgn>dpkg-distaddfile</prgn> - adds a file to
10315 <file>debian/files</file>
10319 Some packages' uploads need to include files other than
10320 the source and binary package files.
10324 <prgn>dpkg-distaddfile</prgn> adds a file to the
10325 <file>debian/files</file> file so that it will be included in
10326 the <file>.changes</file> file when
10327 <prgn>dpkg-genchanges</prgn> is run.
10331 It is usually invoked from the <tt>binary</tt> target of
10332 <file>debian/rules</file>:
10334 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10336 The <var>filename</var> is relative to the directory where
10337 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10338 is usually the directory above the top level of the source
10339 tree. The <file>debian/rules</file> target should put the
10340 file there just before or just after calling
10341 <prgn>dpkg-distaddfile</prgn>.
10345 The <var>section</var> and <var>priority</var> are passed
10346 unchanged into the resulting <file>.changes</file> file.
10351 <sect1 id="pkg-dpkg-genchanges">
10353 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10354 upload control file
10358 This program is usually called by package-independent
10359 automatic building scripts such as
10360 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10365 It is usually called in the top level of a built source
10366 tree, and when invoked with no arguments will print out a
10367 straightforward <file>.changes</file> file based on the
10368 information in the source package's changelog and control
10369 file and the binary and source packages which should have
10375 <sect1 id="pkg-dpkg-parsechangelog">
10377 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10378 representation of a changelog
10382 This program is used internally by
10383 <prgn>dpkg-source</prgn> et al. It may also occasionally
10384 be useful in <file>debian/rules</file> and elsewhere. It
10385 parses a changelog, <file>debian/changelog</file> by default,
10386 and prints a control-file format representation of the
10387 information in it to standard output.
10391 <sect1 id="pkg-dpkg-architecture">
10393 <prgn>dpkg-architecture</prgn> - information about the build and
10398 This program can be used manually, but is also invoked by
10399 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10400 environment or make variables which specify the build and host
10401 architecture for the package building process.
10406 <sect id="pkg-sourcetree">
10407 <heading>The Debian package source tree</heading>
10410 The source archive scheme described later is intended to
10411 allow a Debian package source tree with some associated
10412 control information to be reproduced and transported easily.
10413 The Debian package source tree is a version of the original
10414 program with certain files added for the benefit of the
10415 packaging process, and with any other changes required
10416 made to the rest of the source code and installation
10421 The extra files created for Debian are in the subdirectory
10422 <file>debian</file> of the top level of the Debian package
10423 source tree. They are described below.
10426 <sect1 id="pkg-debianrules">
10427 <heading><file>debian/rules</file> - the main building script</heading>
10430 See <ref id="debianrules">.
10434 <sect1 id="pkg-srcsubstvars">
10435 <heading><file>debian/substvars</file> and variable substitutions</heading>
10438 See <ref id="substvars">.
10444 <heading><file>debian/files</file></heading>
10447 See <ref id="debianfiles">.
10451 <sect1><heading><file>debian/tmp</file>
10455 This is the canonical temporary location for the
10456 construction of binary packages by the <tt>binary</tt>
10457 target. The directory <file>tmp</file> serves as the root of
10458 the file system tree as it is being constructed (for
10459 example, by using the package's upstream makefiles install
10460 targets and redirecting the output there), and it also
10461 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10462 id="pkg-bincreating">.
10466 If several binary packages are generated from the same
10467 source tree it is usual to use several
10468 <file>debian/tmp<var>something</var></file> directories, for
10469 example <file>tmp-a</file> or <file>tmp-doc</file>.
10473 Whatever <file>tmp</file> directories are created and used by
10474 <tt>binary</tt> must of course be removed by the
10475 <tt>clean</tt> target.</p></sect1>
10479 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10483 As it exists on the FTP site, a Debian source package
10484 consists of three related files. You must have the right
10485 versions of all three to be able to use them.
10490 <tag>Debian source control file - <tt>.dsc</tt></tag>
10492 This file is a control file used by <prgn>dpkg-source</prgn>
10493 to extract a source package.
10494 See <ref id="debiansourcecontrolfiles">.
10498 Original source archive -
10500 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10506 This is a compressed (with <tt>gzip -9</tt>)
10507 <prgn>tar</prgn> file containing the source code from
10508 the upstream authors of the program.
10513 Debian package diff -
10515 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10521 This is a unified context diff (<tt>diff -u</tt>)
10522 giving the changes which are required to turn the
10523 original source into the Debian source. These changes
10524 may only include editing and creating plain files.
10525 The permissions of files, the targets of symbolic
10526 links and the characteristics of special files or
10527 pipes may not be changed and no files may be removed
10532 All the directories in the diff must exist, except the
10533 <file>debian</file> subdirectory of the top of the source
10534 tree, which will be created by
10535 <prgn>dpkg-source</prgn> if necessary when unpacking.
10539 The <prgn>dpkg-source</prgn> program will
10540 automatically make the <file>debian/rules</file> file
10541 executable (see below).</p></item>
10546 If there is no original source code - for example, if the
10547 package is specially prepared for Debian or the Debian
10548 maintainer is the same as the upstream maintainer - the
10549 format is slightly different: then there is no diff, and the
10551 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10552 and preferably contains a directory named
10553 <file><var>package</var>-<var>version</var></file>.
10558 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10561 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10562 Debian source package. However, if it is not available it
10563 is possible to unpack a Debian source archive as follows:
10564 <enumlist compact="compact">
10567 Untar the tarfile, which will create a <file>.orig</file>
10571 <p>Rename the <file>.orig</file> directory to
10572 <file><var>package</var>-<var>version</var></file>.</p>
10576 Create the subdirectory <file>debian</file> at the top of
10577 the source tree.</p>
10579 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10581 <item><p>Untar the tarfile again if you want a copy of the original
10582 source code alongside the Debian version.</p>
10587 It is not possible to generate a valid Debian source archive
10588 without using <prgn>dpkg-source</prgn>. In particular,
10589 attempting to use <prgn>diff</prgn> directly to generate the
10590 <file>.diff.gz</file> file will not work.
10594 <heading>Restrictions on objects in source packages</heading>
10597 The source package may not contain any hard links
10599 This is not currently detected when building source
10600 packages, but only when extracting
10604 Hard links may be permitted at some point in the
10605 future, but would require a fair amount of
10607 </footnote>, device special files, sockets or setuid or
10610 Setgid directories are allowed.
10615 The source packaging tools manage the changes between the
10616 original and Debian source using <prgn>diff</prgn> and
10617 <prgn>patch</prgn>. Turning the original source tree as
10618 included in the <file>.orig.tar.gz</file> into the Debian
10619 package source must not involve any changes which cannot be
10620 handled by these tools. Problematic changes which cause
10621 <prgn>dpkg-source</prgn> to halt with an error when
10622 building the source package are:
10623 <list compact="compact">
10624 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10626 <item><p>Changing the targets of symbolic links.</p>
10628 <item><p>Creating directories, other than <file>debian</file>.</p>
10630 <item><p>Changes to the contents of binary files.</p></item>
10631 </list> Changes which cause <prgn>dpkg-source</prgn> to
10632 print a warning but continue anyway are:
10633 <list compact="compact">
10636 Removing files, directories or symlinks.
10638 Renaming a file is not treated specially - it is
10639 seen as the removal of the old file (which
10640 generates a warning, but is otherwise ignored),
10641 and the creation of the new one.
10647 Changed text files which are missing the usual final
10648 newline (either in the original or the modified
10653 Changes which are not represented, but which are not detected by
10654 <prgn>dpkg-source</prgn>, are:
10655 <list compact="compact">
10656 <item><p>Changing the permissions of files (other than
10657 <file>debian/rules</file>) and directories.</p></item>
10662 The <file>debian</file> directory and <file>debian/rules</file>
10663 are handled specially by <prgn>dpkg-source</prgn> - before
10664 applying the changes it will create the <file>debian</file>
10665 directory, and afterwards it will make
10666 <file>debian/rules</file> world-executable.
10672 <appendix id="pkg-controlfields">
10673 <heading>Control files and their fields (from old Packaging Manual)</heading>
10676 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10677 data in a common format, known as control files. Binary and
10678 source packages have control data as do the <file>.changes</file>
10679 files which control the installation of uploaded files, and
10680 <prgn>dpkg</prgn>'s internal databases are in a similar
10685 <heading>Syntax of control files</heading>
10688 See <ref id="controlsyntax">.
10692 It is important to note that there are several fields which
10693 are optional as far as <prgn>dpkg</prgn> and the related
10694 tools are concerned, but which must appear in every Debian
10695 package, or whose omission may cause problems.
10700 <heading>List of fields</heading>
10703 See <ref id="controlfieldslist">.
10707 This section now contains only the fields that didn't belong
10708 to the Policy manual.
10711 <sect1 id="pkg-f-Filename">
10712 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10715 These fields in <tt>Packages</tt> files give the
10716 filename(s) of (the parts of) a package in the
10717 distribution directories, relative to the root of the
10718 Debian hierarchy. If the package has been split into
10719 several parts the parts are all listed in order, separated
10724 <sect1 id="pkg-f-Size">
10725 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10728 These fields in <file>Packages</file> files give the size (in
10729 bytes, expressed in decimal) and MD5 checksum of the
10730 file(s) which make(s) up a binary package in the
10731 distribution. If the package is split into several parts
10732 the values for the parts are listed in order, separated by
10737 <sect1 id="pkg-f-Status">
10738 <heading><tt>Status</tt></heading>
10741 This field in <prgn>dpkg</prgn>'s status file records
10742 whether the user wants a package installed, removed or
10743 left alone, whether it is broken (requiring
10744 re-installation) or not and what its current state on the
10745 system is. Each of these pieces of information is a
10750 <sect1 id="pkg-f-Config-Version">
10751 <heading><tt>Config-Version</tt></heading>
10754 If a package is not installed or not configured, this
10755 field in <prgn>dpkg</prgn>'s status file records the last
10756 version of the package which was successfully
10761 <sect1 id="pkg-f-Conffiles">
10762 <heading><tt>Conffiles</tt></heading>
10765 This field in <prgn>dpkg</prgn>'s status file contains
10766 information about the automatically-managed configuration
10767 files held by a package. This field should <em>not</em>
10768 appear anywhere in a package!
10773 <heading>Obsolete fields</heading>
10776 These are still recognized by <prgn>dpkg</prgn> but should
10777 not appear anywhere any more.
10779 <taglist compact="compact">
10781 <tag><tt>Revision</tt></tag>
10782 <tag><tt>Package-Revision</tt></tag>
10783 <tag><tt>Package_Revision</tt></tag>
10785 The Debian revision part of the package version was
10786 at one point in a separate control field. This
10787 field went through several names.
10790 <tag><tt>Recommended</tt></tag>
10791 <item>Old name for <tt>Recommends</tt>.</item>
10793 <tag><tt>Optional</tt></tag>
10794 <item>Old name for <tt>Suggests</tt>.</item>
10796 <tag><tt>Class</tt></tag>
10797 <item>Old name for <tt>Priority</tt>.</item>
10806 <appendix id="pkg-conffiles">
10807 <heading>Configuration file handling (from old Packaging Manual)</heading>
10810 <prgn>dpkg</prgn> can do a certain amount of automatic
10811 handling of package configuration files.
10815 Whether this mechanism is appropriate depends on a number of
10816 factors, but basically there are two approaches to any
10817 particular configuration file.
10821 The easy method is to ship a best-effort configuration in the
10822 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10823 handle updates. If the user is unlikely to want to edit the
10824 file, but you need them to be able to without losing their
10825 changes, and a new package with a changed version of the file
10826 is only released infrequently, this is a good approach.
10830 The hard method is to build the configuration file from
10831 scratch in the <prgn>postinst</prgn> script, and to take the
10832 responsibility for fixing any mistakes made in earlier
10833 versions of the package automatically. This will be
10834 appropriate if the file is likely to need to be different on
10838 <sect><heading>Automatic handling of configuration files by
10843 A package may contain a control information file called
10844 <tt>conffiles</tt>. This file should be a list of filenames
10845 of configuration files needing automatic handling, separated
10846 by newlines. The filenames should be absolute pathnames,
10847 and the files referred to should actually exist in the
10852 When a package is upgraded <prgn>dpkg</prgn> will process
10853 the configuration files during the configuration stage,
10854 shortly before it runs the package's <prgn>postinst</prgn>
10859 For each file it checks to see whether the version of the
10860 file included in the package is the same as the one that was
10861 included in the last version of the package (the one that is
10862 being upgraded from); it also compares the version currently
10863 installed on the system with the one shipped with the last
10868 If neither the user nor the package maintainer has changed
10869 the file, it is left alone. If one or the other has changed
10870 their version, then the changed version is preferred - i.e.,
10871 if the user edits their file, but the package maintainer
10872 doesn't ship a different version, the user's changes will
10873 stay, silently, but if the maintainer ships a new version
10874 and the user hasn't edited it the new version will be
10875 installed (with an informative message). If both have
10876 changed their version the user is prompted about the problem
10877 and must resolve the differences themselves.
10881 The comparisons are done by calculating the MD5 message
10882 digests of the files, and storing the MD5 of the file as it
10883 was included in the most recent version of the package.
10887 When a package is installed for the first time
10888 <prgn>dpkg</prgn> will install the file that comes with it,
10889 unless that would mean overwriting a file already on the
10894 However, note that <prgn>dpkg</prgn> will <em>not</em>
10895 replace a conffile that was removed by the user (or by a
10896 script). This is necessary because with some programs a
10897 missing file produces an effect hard or impossible to
10898 achieve in another way, so that a missing file needs to be
10899 kept that way if the user did it.
10903 Note that a package should <em>not</em> modify a
10904 <prgn>dpkg</prgn>-handled conffile in its maintainer
10905 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10906 the user confusing and possibly dangerous options for
10907 conffile update when the package is upgraded.</p>
10910 <sect><heading>Fully-featured maintainer script configuration
10915 For files which contain site-specific information such as
10916 the hostname and networking details and so forth, it is
10917 better to create the file in the package's
10918 <prgn>postinst</prgn> script.
10922 This will typically involve examining the state of the rest
10923 of the system to determine values and other information, and
10924 may involve prompting the user for some information which
10925 can't be obtained some other way.
10929 When using this method there are a couple of important
10930 issues which should be considered:
10934 If you discover a bug in the program which generates the
10935 configuration file, or if the format of the file changes
10936 from one version to the next, you will have to arrange for
10937 the postinst script to do something sensible - usually this
10938 will mean editing the installed configuration file to remove
10939 the problem or change the syntax. You will have to do this
10940 very carefully, since the user may have changed the file,
10941 perhaps to fix the very problem that your script is trying
10942 to deal with - you will have to detect these situations and
10943 deal with them correctly.
10947 If you do go down this route it's probably a good idea to
10948 make the program that generates the configuration file(s) a
10949 separate program in <file>/usr/sbin</file>, by convention called
10950 <file><var>package</var>config</file> and then run that if
10951 appropriate from the post-installation script. The
10952 <tt><var>package</var>config</tt> program should not
10953 unquestioningly overwrite an existing configuration - if its
10954 mode of operation is geared towards setting up a package for
10955 the first time (rather than any arbitrary reconfiguration
10956 later) you should have it check whether the configuration
10957 already exists, and require a <tt>--force</tt> flag to
10958 overwrite it.</p></sect>
10961 <appendix id="pkg-alternatives"><heading>Alternative versions of
10962 an interface - <prgn>update-alternatives</prgn> (from old
10967 When several packages all provide different versions of the
10968 same program or file it is useful to have the system select a
10969 default, but to allow the system administrator to change it
10970 and have their decisions respected.
10974 For example, there are several versions of the <prgn>vi</prgn>
10975 editor, and there is no reason to prevent all of them from
10976 being installed at once, each under their own name
10977 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10978 Nevertheless it is desirable to have the name <tt>vi</tt>
10979 refer to something, at least by default.
10983 If all the packages involved cooperate, this can be done with
10984 <prgn>update-alternatives</prgn>.
10988 Each package provides its own version under its own name, and
10989 calls <prgn>update-alternatives</prgn> in its postinst to
10990 register its version (and again in its prerm to deregister
10995 See the man page <manref name="update-alternatives"
10996 section="8"> for details.
11000 If <prgn>update-alternatives</prgn> does not seem appropriate
11001 you may wish to consider using diversions instead.</p>
11004 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11005 package's version of a file (from old Packaging Manual)
11009 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11010 when it reinstalls the package it belongs to, and to have it
11011 put the file from the package somewhere else instead.
11015 This can be used locally to override a package's version of a
11016 file, or by one package to override another's version (or
11017 provide a wrapper for it).
11021 Before deciding to use a diversion, read <ref
11022 id="pkg-alternatives"> to see if you really want a diversion
11023 rather than several alternative versions of a program.
11027 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11028 and updated by a special program <prgn>dpkg-divert</prgn>.
11029 Please see <manref name="dpkg-divert" section="8"> for full
11030 details of its operation.
11034 When a package wishes to divert a file from another, it should
11035 call <prgn>dpkg-divert</prgn> in its preinst to add the
11036 diversion and rename the existing file. For example,
11037 supposing that a <prgn>smailwrapper</prgn> package wishes to
11038 install a wrapper around <file>/usr/sbin/smail</file>:
11040 dpkg-divert --package smailwrapper --add --rename \
11041 --divert /usr/sbin/smail.real /usr/sbin/smail
11042 </example> The <tt>--package smailwrapper</tt> ensures that
11043 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11044 can bypass the diversion and get installed as the true version.
11045 It's safe to add the diversion unconditionally on upgrades since
11046 it will be left unchanged if it already exists, but
11047 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11048 message, make the command conditional on the version from which
11049 the package is being upgraded:
11051 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11052 dpkg-divert --package smailwrapper --add --rename \
11053 --divert /usr/sbin/smail.real /usr/sbin/smail
11055 </example> where <tt>1.0-2</tt> is the version at which the
11056 diversion was first added to the package. Running the command
11057 during abort-upgrade is pointless but harmless.
11061 The postrm has to do the reverse:
11063 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11064 dpkg-divert --package smailwrapper --remove --rename \
11065 --divert /usr/sbin/smail.real /usr/sbin/smail
11067 </example> If the diversion was added at a particular version, the
11068 postrm should also handle the failure case of upgrading from an
11069 older version (unless the older version is so old that direct
11070 upgrades are no longer supported):
11072 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11073 dpkg-divert --package smailwrapper --remove --rename \
11074 --divert /usr/sbin/smail.real /usr/sbin/smail
11076 </example> where <tt>1.02-2</tt> is the version at which the
11077 diversion was first added to the package. The postrm should not
11078 remove the diversion on upgrades both because there's no reason to
11079 remove the diversion only to immediately re-add it and since the
11080 postrm of the old package is run after unpacking so the removal of
11081 the diversion will fail.
11085 Do not attempt to divert a file which is vitally important for
11086 the system's operation - when using <prgn>dpkg-divert</prgn>
11087 there is a time, after it has been diverted but before
11088 <prgn>dpkg</prgn> has installed the new version, when the file
11089 does not exist.</p>
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