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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 GNU/Linux 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 GNU/Linux
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 GNU/Linux 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 GNU/Linux 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 GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
910 <sect id="maintainer">
911 <heading>The maintainer of a package</heading>
914 Every package must have a maintainer. The maintainer may be one
915 person or a group of people reachable from a common email
916 address, such as a mailing list. The maintainer is responsible
917 for 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 If the maintainer of a package no longer has time or desire to
961 maintain a package, it should be orphaned according to the
962 procedure described in the Debian Developer's Reference
963 (see <ref id="related">). The maintainer then
964 becomes <tt>Debian QA Group <packages@qa.debian.org></tt>.
965 These packages are considered maintained by the Debian project
966 as a whole until someone else volunteers to take over
971 <sect id="descriptions">
972 <heading>The description of a package</heading>
975 Every Debian package must have a <tt>Description</tt> control
976 field which contains a synopsis and extended description of the
977 package. Technical information about the format of the
978 <tt>Description</tt> field is in <ref id="f-Description">.
982 The description should describe the package (the program) to a
983 user (system administrator) who has never met it before so that
984 they have enough information to decide whether they want to
985 install it. This description should not just be copied verbatim
986 from the program's documentation.
990 Put important information first, both in the synopsis and
991 extended description. Sometimes only the first part of the
992 synopsis or of the description will be displayed. You can
993 assume that there will usually be a way to see the whole
994 extended description.
998 The description should also give information about the
999 significant dependencies and conflicts between this package
1000 and others, so that the user knows why these dependencies and
1001 conflicts have been declared.
1005 Instructions for configuring or using the package should
1006 not be included (that is what installation scripts,
1007 manual pages, info files, etc., are for). Copyright
1008 statements and other administrivia should not be included
1009 either (that is what the copyright file is for).
1012 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1015 The single line synopsis should be kept brief - certainly
1016 under 80 characters.
1020 Do not include the package name in the synopsis line. The
1021 display software knows how to display this already, and you
1022 do not need to state it. Remember that in many situations
1023 the user may only see the synopsis line - make it as
1024 informative as you can.
1029 <sect1 id="extendeddesc"><heading>The extended description</heading>
1032 Do not try to continue the single line synopsis into the
1033 extended description. This will not work correctly when
1034 the full description is displayed, and makes no sense
1035 where only the summary (the single line synopsis) is
1040 The extended description should describe what the package
1041 does and how it relates to the rest of the system (in terms
1042 of, for example, which subsystem it is which part of).
1046 The description field needs to make sense to anyone, even
1047 people who have no idea about any of the things the
1048 package deals with.<footnote>
1049 The blurb that comes with a program in its
1050 announcements and/or <prgn>README</prgn> files is
1051 rarely suitable for use in a description. It is
1052 usually aimed at people who are already in the
1053 community where the package is used.
1062 <heading>Dependencies</heading>
1065 Every package must specify the dependency information
1066 about other packages that are required for the first to
1071 For example, a dependency entry must be provided for any
1072 shared libraries required by a dynamically-linked executable
1073 binary in a package.
1077 Packages are not required to declare any dependencies they
1078 have on other packages which are marked <tt>Essential</tt>
1079 (see below), and should not do so unless they depend on a
1080 particular version of that package.<footnote>
1082 Essential is needed in part to avoid unresolvable dependency
1083 loops on upgrade. If packages add unnecessary dependencies
1084 on packages in this set, the chances that there
1085 <strong>will</strong> be an unresolvable dependency loop
1086 caused by forcing these Essential packages to be configured
1087 first before they need to be is greatly increased. It also
1088 increases the chances that frontends will be unable to
1089 <strong>calculate</strong> an upgrade path, even if one
1093 Also, functionality is rarely ever removed from the
1094 Essential set, but <em>packages</em> have been removed from
1095 the Essential set when the functionality moved to a
1096 different package. So depending on these packages <em>just
1097 in case</em> they stop being essential does way more harm
1104 Sometimes, a package requires another package to be installed
1105 <em>and</em> configured before it can be installed. In this
1106 case, you must specify a <tt>Pre-Depends</tt> entry for
1111 You should not specify a <tt>Pre-Depends</tt> entry for a
1112 package before this has been discussed on the
1113 <tt>debian-devel</tt> mailing list and a consensus about
1114 doing that has been reached.
1118 The format of the package interrelationship control fields is
1119 described in <ref id="relationships">.
1123 <sect id="virtual_pkg">
1124 <heading>Virtual packages</heading>
1127 Sometimes, there are several packages which offer
1128 more-or-less the same functionality. In this case, it's
1129 useful to define a <em>virtual package</em> whose name
1130 describes that common functionality. (The virtual
1131 packages only exist logically, not physically; that's why
1132 they are called <em>virtual</em>.) The packages with this
1133 particular function will then <em>provide</em> the virtual
1134 package. Thus, any other package requiring that function
1135 can simply depend on the virtual package without having to
1136 specify all possible packages individually.
1140 All packages should use virtual package names where
1141 appropriate, and arrange to create new ones if necessary.
1142 They should not use virtual package names (except privately,
1143 amongst a cooperating group of packages) unless they have
1144 been agreed upon and appear in the list of virtual package
1145 names. (See also <ref id="virtual">)
1149 The latest version of the authoritative list of virtual
1150 package names can be found in the <tt>debian-policy</tt> package.
1151 It is also available from the Debian web mirrors at
1152 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1153 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1157 The procedure for updating the list is described in the preface
1164 <heading>Base system</heading>
1167 The <tt>base system</tt> is a minimum subset of the Debian
1168 GNU/Linux system that is installed before everything else
1169 on a new system. Only very few packages are allowed to form
1170 part of the base system, in order to keep the required disk
1175 The base system consists of all those packages with priority
1176 <tt>required</tt> or <tt>important</tt>. Many of them will
1177 be tagged <tt>essential</tt> (see below).
1182 <heading>Essential packages</heading>
1185 Essential is defined as the minimal set of functionality that
1186 must be available and usable on the system at all times, even
1187 when packages are in an unconfigured (but unpacked) state.
1188 Packages are tagged <tt>essential</tt> for a system using the
1189 <tt>Essential</tt> control field. The format of the
1190 <tt>Essential</tt> control field is described in <ref
1195 Since these packages cannot be easily removed (one has to
1196 specify an extra <em>force option</em> to
1197 <prgn>dpkg</prgn> to do so), this flag must not be used
1198 unless absolutely necessary. A shared library package
1199 must not be tagged <tt>essential</tt>; dependencies will
1200 prevent its premature removal, and we need to be able to
1201 remove it when it has been superseded.
1205 Since dpkg will not prevent upgrading of other packages
1206 while an <tt>essential</tt> package is in an unconfigured
1207 state, all <tt>essential</tt> packages must supply all of
1208 their core functionality even when unconfigured. If the
1209 package cannot satisfy this requirement it must not be
1210 tagged as essential, and any packages depending on this
1211 package must instead have explicit dependency fields as
1216 Maintainers should take great care in adding any programs,
1217 interfaces, or functionality to <tt>essential</tt> packages.
1218 Packages may assume that functionality provided by
1219 <tt>essential</tt> packages is always available without
1220 declaring explicit dependencies, which means that removing
1221 functionality from the Essential set is very difficult and is
1222 almost never done. Any capability added to an
1223 <tt>essential</tt> package therefore creates an obligation to
1224 support that capability as part of the Essential set in
1229 You must not tag any packages <tt>essential</tt> before
1230 this has been discussed on the <tt>debian-devel</tt>
1231 mailing list and a consensus about doing that has been
1236 <sect id="maintscripts">
1237 <heading>Maintainer Scripts</heading>
1240 The package installation scripts should avoid producing
1241 output which is unnecessary for the user to see and
1242 should rely on <prgn>dpkg</prgn> to stave off boredom on
1243 the part of a user installing many packages. This means,
1244 amongst other things, using the <tt>--quiet</tt> option on
1245 <prgn>install-info</prgn>.
1249 Errors which occur during the execution of an installation
1250 script must be checked and the installation must not
1251 continue after an error.
1255 Note that in general <ref id="scripts"> applies to package
1256 maintainer scripts, too.
1260 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1261 to another package without consulting the maintainer of that
1262 package first. When adding or removing diversions, package
1263 maintainer scripts must provide the <tt>--package</tt> flag
1264 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1268 All packages which supply an instance of a common command
1269 name (or, in general, filename) should generally use
1270 <prgn>update-alternatives</prgn>, so that they may be
1271 installed together. If <prgn>update-alternatives</prgn>
1272 is not used, then each package must use
1273 <tt>Conflicts</tt> to ensure that other packages are
1274 de-installed. (In this case, it may be appropriate to
1275 specify a conflict against earlier versions of something
1276 that previously did not use
1277 <prgn>update-alternatives</prgn>; this is an exception to
1278 the usual rule that versioned conflicts should be
1282 <sect1 id="maintscriptprompt">
1283 <heading>Prompting in maintainer scripts</heading>
1285 Package maintainer scripts may prompt the user if
1286 necessary. Prompting must be done by communicating
1287 through a program, such as <prgn>debconf</prgn>, which
1288 conforms to the Debian Configuration Management
1289 Specification, version 2 or higher.
1293 Packages which are essential, or which are dependencies of
1294 essential packages, may fall back on another prompting method
1295 if no such interface is available when they are executed.
1299 The Debian Configuration Management Specification is included
1300 in the <file>debconf_specification</file> files in the
1301 <package>debian-policy</package> package.
1302 It is also available from the Debian web mirrors at
1303 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1304 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1308 Packages which use the Debian Configuration Management
1309 Specification may contain the additional control information
1310 files <file>config</file>
1311 and <file>templates</file>. <file>config</file> is an
1312 additional maintainer script used for package configuration,
1313 and <file>templates</file> contains templates used for user
1314 prompting. The <prgn>config</prgn> script might be run before
1315 the <prgn>preinst</prgn> script and before the package is
1316 unpacked or any of its dependencies or pre-dependencies are
1317 satisfied. Therefore it must work using only the tools
1318 present in <em>essential</em> packages.<footnote>
1319 <package>Debconf</package> or another tool that
1320 implements the Debian Configuration Management
1321 Specification will also be installed, and any
1322 versioned dependencies on it will be satisfied
1323 before preconfiguration begins.
1328 Packages which use the Debian Configuration Management
1329 Specification must allow for translation of their user-visible
1330 messages by using a gettext-based system such as the one
1331 provided by the <package>po-debconf</package> package.
1335 Packages should try to minimize the amount of prompting
1336 they need to do, and they should ensure that the user
1337 will only ever be asked each question once. This means
1338 that packages should try to use appropriate shared
1339 configuration files (such as <file>/etc/papersize</file> and
1340 <file>/etc/news/server</file>), and shared
1341 <package>debconf</package> variables rather than each
1342 prompting for their own list of required pieces of
1347 It also means that an upgrade should not ask the same
1348 questions again, unless the user has used
1349 <tt>dpkg --purge</tt> to remove the package's configuration.
1350 The answers to configuration questions should be stored in an
1351 appropriate place in <file>/etc</file> so that the user can
1352 modify them, and how this has been done should be
1357 If a package has a vitally important piece of
1358 information to pass to the user (such as "don't run me
1359 as I am, you must edit the following configuration files
1360 first or you risk your system emitting badly-formatted
1361 messages"), it should display this in the
1362 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1363 prompt the user to hit return to acknowledge the
1364 message. Copyright messages do not count as vitally
1365 important (they belong in
1366 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1367 neither do instructions on how to use a program (these
1368 should be in on-line documentation, where all the users
1373 Any necessary prompting should almost always be confined
1374 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1375 script. If it is done in the <prgn>postinst</prgn>, it
1376 should be protected with a conditional so that
1377 unnecessary prompting doesn't happen if a package's
1378 installation fails and the <prgn>postinst</prgn> is
1379 called with <tt>abort-upgrade</tt>,
1380 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1390 <heading>Source packages</heading>
1392 <sect id="standardsversion">
1393 <heading>Standards conformance</heading>
1396 Source packages should specify the most recent version number
1397 of this policy document with which your package complied
1398 when it was last updated.
1402 This information may be used to file bug reports
1403 automatically if your package becomes too much out of date.
1407 The version is specified in the <tt>Standards-Version</tt>
1409 The format of the <tt>Standards-Version</tt> field is
1410 described in <ref id="f-Standards-Version">.
1414 You should regularly, and especially if your package has
1415 become out of date, check for the newest Policy Manual
1416 available and update your package, if necessary. When your
1417 package complies with the new standards you should update the
1418 <tt>Standards-Version</tt> source package field and
1419 release it.<footnote>
1420 See the file <file>upgrading-checklist</file> for
1421 information about policy which has changed between
1422 different versions of this document.
1428 <sect id="pkg-relations">
1429 <heading>Package relationships</heading>
1432 Source packages should specify which binary packages they
1433 require to be installed or not to be installed in order to
1434 build correctly. For example, if building a package
1435 requires a certain compiler, then the compiler should be
1436 specified as a build-time dependency.
1440 It is not necessary to explicitly specify build-time
1441 relationships on a minimal set of packages that are always
1442 needed to compile, link and put in a Debian package a
1443 standard "Hello World!" program written in C or C++. The
1444 required packages are called <em>build-essential</em>, and
1445 an informational list can be found in
1446 <file>/usr/share/doc/build-essential/list</file> (which is
1447 contained in the <tt>build-essential</tt>
1450 <list compact="compact">
1452 This allows maintaining the list separately
1453 from the policy documents (the list does not
1454 need the kind of control that the policy
1458 Having a separate package allows one to install
1459 the build-essential packages on a machine, as
1460 well as allowing other packages such as tasks to
1461 require installation of the build-essential
1462 packages using the depends relation.
1465 The separate package allows bug reports against
1466 the list to be categorized separately from
1467 the policy management process in the BTS.
1474 When specifying the set of build-time dependencies, one
1475 should list only those packages explicitly required by the
1476 build. It is not necessary to list packages which are
1477 required merely because some other package in the list of
1478 build-time dependencies depends on them.<footnote>
1479 The reason for this is that dependencies change, and
1480 you should list all those packages, and <em>only</em>
1481 those packages that <em>you</em> need directly. What
1482 others need is their business. For example, if you
1483 only link against <file>libimlib</file>, you will need to
1484 build-depend on <package>libimlib2-dev</package> but
1485 not against any <tt>libjpeg*</tt> packages, even
1486 though <tt>libimlib2-dev</tt> currently depends on
1487 them: installation of <package>libimlib2-dev</package>
1488 will automatically ensure that all of its run-time
1489 dependencies are satisfied.
1494 If build-time dependencies are specified, it must be
1495 possible to build the package and produce working binaries
1496 on a system with only essential and build-essential
1497 packages installed and also those required to satisfy the
1498 build-time relationships (including any implied
1499 relationships). In particular, this means that version
1500 clauses should be used rigorously in build-time
1501 relationships so that one cannot produce bad or
1502 inconsistently configured packages when the relationships
1503 are properly satisfied.
1507 <ref id="relationships"> explains the technical details.
1512 <heading>Changes to the upstream sources</heading>
1515 If changes to the source code are made that are not
1516 specific to the needs of the Debian system, they should be
1517 sent to the upstream authors in whatever form they prefer
1518 so as to be included in the upstream version of the
1523 If you need to configure the package differently for
1524 Debian or for Linux, and the upstream source doesn't
1525 provide a way to do so, you should add such configuration
1526 facilities (for example, a new <prgn>autoconf</prgn> test
1527 or <tt>#define</tt>) and send the patch to the upstream
1528 authors, with the default set to the way they originally
1529 had it. You can then easily override the default in your
1530 <file>debian/rules</file> or wherever is appropriate.
1534 You should make sure that the <prgn>configure</prgn> utility
1535 detects the correct architecture specification string
1536 (refer to <ref id="arch-spec"> for details).
1540 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1541 <prgn>configure</prgn> scripts are used, you should edit the
1542 <file>.in</file> files rather than editing the
1543 <prgn>Makefile</prgn> directly. This allows the user to
1544 reconfigure the package if necessary. You should
1545 <em>not</em> configure the package and edit the generated
1546 <prgn>Makefile</prgn>! This makes it impossible for someone
1547 else to later reconfigure the package without losing the
1553 <sect id="dpkgchangelog">
1554 <heading>Debian changelog: <file>debian/changelog</file></heading>
1557 Changes in the Debian version of the package should be
1558 briefly explained in the Debian changelog file
1559 <file>debian/changelog</file>.<footnote>
1561 Mistakes in changelogs are usually best rectified by
1562 making a new changelog entry rather than "rewriting
1563 history" by editing old changelog entries.
1566 This includes modifications
1567 made in the Debian package compared to the upstream one
1568 as well as other changes and updates to the package.
1570 Although there is nothing stopping an author who is also
1571 the Debian maintainer from using this changelog for all
1572 their changes, it will have to be renamed if the Debian
1573 and upstream maintainers become different people. In such
1574 a case, however, it might be better to maintain the package
1575 as a non-native package.
1580 The format of the <file>debian/changelog</file> allows the
1581 package building tools to discover which version of the package
1582 is being built and find out other release-specific information.
1586 That format is a series of entries like this:
1588 <example compact="compact">
1589 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1591 [optional blank line(s), stripped]
1593 * <var>change details</var>
1594 <var>more change details</var>
1596 [blank line(s), included in output of dpkg-parsechangelog]
1598 * <var>even more change details</var>
1600 [optional blank line(s), stripped]
1602 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1607 <var>package</var> and <var>version</var> are the source
1608 package name and version number.
1612 <var>distribution(s)</var> lists the distributions where
1613 this version should be installed when it is uploaded - it
1614 is copied to the <tt>Distribution</tt> field in the
1615 <file>.changes</file> file. See <ref id="f-Distribution">.
1619 <var>urgency</var> is the value for the <tt>Urgency</tt>
1620 field in the <file>.changes</file> file for the upload
1621 (see <ref id="f-Urgency">). It is not possible to specify
1622 an urgency containing commas; commas are used to separate
1623 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1624 <prgn>dpkg</prgn> changelog format (though there is
1625 currently only one useful <var>keyword</var>,
1630 The change details may in fact be any series of lines
1631 starting with at least two spaces, but conventionally each
1632 change starts with an asterisk and a separating space and
1633 continuation lines are indented so as to bring them in
1634 line with the start of the text above. Blank lines may be
1635 used here to separate groups of changes, if desired.
1639 If this upload resolves bugs recorded in the Bug Tracking
1640 System (BTS), they may be automatically closed on the
1641 inclusion of this package into the Debian archive by
1642 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1643 in the change details.<footnote>
1644 To be precise, the string should match the following
1645 Perl regular expression:
1647 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1649 Then all of the bug numbers listed will be closed by the
1650 archive maintenance script (<prgn>katie</prgn>) using the
1651 <var>version</var> of the changelog entry.
1653 This information is conveyed via the <tt>Closes</tt> field
1654 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1658 The maintainer name and email address used in the changelog
1659 should be the details of the person uploading <em>this</em>
1660 version. They are <em>not</em> necessarily those of the
1661 usual package maintainer.<footnote>
1662 If the developer uploading the package is not one of the usual
1663 maintainers of the package (as listed in
1664 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1665 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1666 fields of the package), the first line of the changelog is
1667 conventionally used to explain why a non-maintainer is
1668 uploading the package. The Debian Developer's Reference
1669 (see <ref id="related">) documents the conventions
1671 The information here will be copied to the <tt>Changed-By</tt>
1672 field in the <tt>.changes</tt> file
1673 (see <ref id="f-Changed-By">), and then later used to send an
1674 acknowledgement when the upload has been installed.
1678 The <var>date</var> has the following format<footnote>
1679 This is the same as the format generated by <tt>date
1681 </footnote> (compatible and with the same semantics of
1682 RFC 2822 and RFC 5322):
1683 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1685 <list compact="compact">
1687 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1690 dd is a one- or two-digit day of the month (01-31)
1693 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1696 <item>yyyy is the four-digit year (e.g. 2010)</item>
1697 <item>hh is the two-digit hour (00-23)</item>
1698 <item>mm is the two-digit minutes (00-59)</item>
1699 <item>ss is the two-digit seconds (00-60)</item>
1701 +zzzz or -zzzz is the the time zone offset from Coordinated
1702 Universal Time (UTC). "+" indicates that the time is ahead
1703 of (i.e., east of) UTC and "-" indicates that the time is
1704 behind (i.e., west of) UTC. The first two digits indicate
1705 the hour difference from UTC and the last two digits
1706 indicate the number of additional minutes difference from
1707 UTC. The last two digits must be in the range 00-59.
1713 The first "title" line with the package name must start
1714 at the left hand margin. The "trailer" line with the
1715 maintainer and date details must be preceded by exactly
1716 one space. The maintainer details and the date must be
1717 separated by exactly two spaces.
1721 The entire changelog must be encoded in UTF-8.
1725 For more information on placement of the changelog files
1726 within binary packages, please see <ref id="changelogs">.
1730 <sect id="dpkgcopyright">
1731 <heading>Copyright: <file>debian/copyright</file></heading>
1733 Every package must be accompanied by a verbatim copy of its
1734 copyright information and distribution license in the file
1735 <file>/usr/share/doc/<var>package</var>/copyright</file>
1736 (see <ref id="copyrightfile"> for further details). Also see
1737 <ref id="pkgcopyright"> for further considerations related
1738 to copyrights for packages.
1742 <heading>Error trapping in makefiles</heading>
1745 When <prgn>make</prgn> invokes a command in a makefile
1746 (including your package's upstream makefiles and
1747 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1748 means that <prgn>sh</prgn>'s usual bad error handling
1749 properties apply: if you include a miniature script as one
1750 of the commands in your makefile you'll find that if you
1751 don't do anything about it then errors are not detected
1752 and <prgn>make</prgn> will blithely continue after
1757 Every time you put more than one shell command (this
1758 includes using a loop) in a makefile command you
1759 must make sure that errors are trapped. For
1760 simple compound commands, such as changing directory and
1761 then running a program, using <tt>&&</tt> rather
1762 than semicolon as a command separator is sufficient. For
1763 more complex commands including most loops and
1764 conditionals you should include a separate <tt>set -e</tt>
1765 command at the start of every makefile command that's
1766 actually one of these miniature shell scripts.
1770 <sect id="timestamps">
1771 <heading>Time Stamps</heading>
1773 Maintainers should preserve the modification times of the
1774 upstream source files in a package, as far as is reasonably
1776 The rationale is that there is some information conveyed
1777 by knowing the age of the file, for example, you could
1778 recognize that some documentation is very old by looking
1779 at the modification time, so it would be nice if the
1780 modification time of the upstream source would be
1786 <sect id="restrictions">
1787 <heading>Restrictions on objects in source packages</heading>
1790 The source package may not contain any hard links<footnote>
1792 This is not currently detected when building source
1793 packages, but only when extracting
1797 Hard links may be permitted at some point in the
1798 future, but would require a fair amount of
1801 </footnote>, device special files, sockets or setuid or
1802 setgid files.<footnote>
1803 Setgid directories are allowed.
1808 <sect id="debianrules">
1809 <heading>Main building script: <file>debian/rules</file></heading>
1812 This file must be an executable makefile, and contains the
1813 package-specific recipes for compiling the package and
1814 building binary package(s) from the source.
1818 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1819 so that it can be invoked by saying its name rather than
1820 invoking <prgn>make</prgn> explicitly. That is, invoking
1821 either of <tt>make -f debian/rules <em>args...</em></tt>
1822 or <tt>./debian/rules <em>args...</em></tt> must result in
1827 Since an interactive <file>debian/rules</file> script makes it
1828 impossible to auto-compile that package and also makes it
1829 hard for other people to reproduce the same binary
1830 package, all <em>required targets</em> must be
1831 non-interactive. At a minimum, required targets are the
1832 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1833 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1834 <em>binary-indep</em>, and <em>build</em>. It also follows
1835 that any target that these targets depend on must also be
1840 The targets are as follows (required unless stated otherwise):
1842 <tag><tt>build</tt></tag>
1845 The <tt>build</tt> target should perform all the
1846 configuration and compilation of the package.
1847 If a package has an interactive pre-build
1848 configuration routine, the Debian source package
1849 must either be built after this has taken place (so
1850 that the binary package can be built without rerunning
1851 the configuration) or the configuration routine
1852 modified to become non-interactive. (The latter is
1853 preferable if there are architecture-specific features
1854 detected by the configuration routine.)
1858 For some packages, notably ones where the same
1859 source tree is compiled in different ways to produce
1860 two binary packages, the <tt>build</tt> target
1861 does not make much sense. For these packages it is
1862 good enough to provide two (or more) targets
1863 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1864 for each of the ways of building the package, and a
1865 <tt>build</tt> target that does nothing. The
1866 <tt>binary</tt> target will have to build the
1867 package in each of the possible ways and make the
1868 binary package out of each.
1872 The <tt>build</tt> target must not do anything
1873 that might require root privilege.
1877 The <tt>build</tt> target may need to run the
1878 <tt>clean</tt> target first - see below.
1882 When a package has a configuration and build routine
1883 which takes a long time, or when the makefiles are
1884 poorly designed, or when <tt>build</tt> needs to
1885 run <tt>clean</tt> first, it is a good idea to
1886 <tt>touch build</tt> when the build process is
1887 complete. This will ensure that if <tt>debian/rules
1888 build</tt> is run again it will not rebuild the whole
1890 Another common way to do this is for <tt>build</tt>
1891 to depend on <prgn>build-stamp</prgn> and to do
1892 nothing else, and for the <prgn>build-stamp</prgn>
1893 target to do the building and to <tt>touch
1894 build-stamp</tt> on completion. This is
1895 especially useful if the build routine creates a
1896 file or directory called <tt>build</tt>; in such a
1897 case, <tt>build</tt> will need to be listed as
1898 a phony target (i.e., as a dependency of the
1899 <tt>.PHONY</tt> target). See the documentation of
1900 <prgn>make</prgn> for more information on phony
1906 <tag><tt>build-arch</tt> (optional),
1907 <tt>build-indep</tt> (optional)
1911 A package may also provide both of the targets
1912 <tt>build-arch</tt> and <tt>build-indep</tt>.
1913 The <tt>build-arch</tt> target, if provided, should
1914 perform all the configuration and compilation required for
1915 producing all architecture-dependant binary packages
1916 (those packages for which the body of the
1917 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1918 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1919 target, if provided, should perform all the configuration
1920 and compilation required for producing all
1921 architecture-independent binary packages (those packages
1922 for which the body of the <tt>Architecture</tt> field
1923 in <tt>debian/control</tt> is <tt>all</tt>).
1924 The <tt>build</tt> target should depend on those of the
1925 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1926 are provided in the rules file.<footnote>
1927 The intent of this split is so that binary-only builds
1928 need not install the dependencies required for
1929 the <tt>build-indep</tt> target. However, this is not
1930 yet used in practice since <tt>dpkg-buildpackage
1931 -B</tt>, and therefore the autobuilders,
1932 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1933 due to the difficulties in determining whether the
1934 optional <tt>build-arch</tt> target exists.
1939 If one or both of the targets <tt>build-arch</tt> and
1940 <tt>build-indep</tt> are not provided, then invoking
1941 <file>debian/rules</file> with one of the not-provided
1942 targets as arguments should produce a exit status code
1943 of 2. Usually this is provided automatically by make
1944 if the target is missing.
1948 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1949 must not do anything that might require root privilege.
1953 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1954 <tt>binary-indep</tt>
1958 The <tt>binary</tt> target must be all that is
1959 necessary for the user to build the binary package(s)
1960 produced from this source package. It is
1961 split into two parts: <prgn>binary-arch</prgn> builds
1962 the binary packages which are specific to a particular
1963 architecture, and <tt>binary-indep</tt> builds
1964 those which are not.
1967 <tt>binary</tt> may be (and commonly is) a target with
1968 no commands which simply depends on
1969 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1972 Both <tt>binary-*</tt> targets should depend on the
1973 <tt>build</tt> target, or on the appropriate
1974 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1975 provided, so that the package is built if it has not
1976 been already. It should then create the relevant
1977 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1978 make their control files and <prgn>dpkg-deb</prgn> to
1979 build them and place them in the parent of the top
1984 Both the <tt>binary-arch</tt> and
1985 <tt>binary-indep</tt> targets <em>must</em> exist.
1986 If one of them has nothing to do (which will always be
1987 the case if the source generates only a single binary
1988 package, whether architecture-dependent or not), it
1989 must still exist and must always succeed.
1993 The <tt>binary</tt> targets must be invoked as
1995 The <prgn>fakeroot</prgn> package often allows one
1996 to build a package correctly even without being
2002 <tag><tt>clean</tt></tag>
2005 This must undo any effects that the <tt>build</tt>
2006 and <tt>binary</tt> targets may have had, except
2007 that it should leave alone any output files created in
2008 the parent directory by a run of a <tt>binary</tt>
2013 If a <tt>build</tt> file is touched at the end of
2014 the <tt>build</tt> target, as suggested above, it
2015 should be removed as the first action that
2016 <tt>clean</tt> performs, so that running
2017 <tt>build</tt> again after an interrupted
2018 <tt>clean</tt> doesn't think that everything is
2023 The <tt>clean</tt> target may need to be
2024 invoked as root if <tt>binary</tt> has been
2025 invoked since the last <tt>clean</tt>, or if
2026 <tt>build</tt> has been invoked as root (since
2027 <tt>build</tt> may create directories, for
2032 <tag><tt>get-orig-source</tt> (optional)</tag>
2035 This target fetches the most recent version of the
2036 original source package from a canonical archive site
2037 (via FTP or WWW, for example), does any necessary
2038 rearrangement to turn it into the original source
2039 tar file format described below, and leaves it in the
2044 This target may be invoked in any directory, and
2045 should take care to clean up any temporary files it
2050 This target is optional, but providing it if
2051 possible is a good idea.
2055 <tag><tt>patch</tt> (optional)</tag>
2058 This target performs whatever additional actions are
2059 required to make the source ready for editing (unpacking
2060 additional upstream archives, applying patches, etc.).
2061 It is recommended to be implemented for any package where
2062 <tt>dpkg-source -x</tt> does not result in source ready
2063 for additional modification. See
2064 <ref id="readmesource">.
2070 The <tt>build</tt>, <tt>binary</tt> and
2071 <tt>clean</tt> targets must be invoked with the current
2072 directory being the package's top-level directory.
2077 Additional targets may exist in <file>debian/rules</file>,
2078 either as published or undocumented interfaces or for the
2079 package's internal use.
2083 The architectures we build on and build for are determined
2084 by <prgn>make</prgn> variables using the utility
2085 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2086 You can determine the
2087 Debian architecture and the GNU style architecture
2088 specification string for the build machine (the machine type
2089 we are building on) as well as for the host machine (the
2090 machine type we are building for). Here is a list of
2091 supported <prgn>make</prgn> variables:
2092 <list compact="compact">
2094 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2097 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2100 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2103 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2104 specification string)
2107 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2108 <tt>DEB_*_GNU_TYPE</tt>)
2111 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2112 <tt>DEB_*_GNU_TYPE</tt>)
2114 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2115 the build machine or <tt>HOST</tt> for specification of the
2120 Backward compatibility can be provided in the rules file
2121 by setting the needed variables to suitable default
2122 values; please refer to the documentation of
2123 <prgn>dpkg-architecture</prgn> for details.
2127 It is important to understand that the <tt>DEB_*_ARCH</tt>
2128 string only determines which Debian architecture we are
2129 building on or for. It should not be used to get the CPU
2130 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2131 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2132 GNU style variables should generally only be used with upstream
2136 <sect1 id="debianrules-options">
2137 <heading><file>debian/rules</file> and
2138 <tt>DEB_BUILD_OPTIONS</tt></heading>
2141 Supporting the standardized environment variable
2142 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2143 contain several flags to change how a package is compiled and
2144 built. Each flag must be in the form <var>flag</var> or
2145 <var>flag</var>=<var>options</var>. If multiple flags are
2146 given, they must be separated by whitespace.<footnote>
2147 Some packages support any delimiter, but whitespace is the
2148 easiest to parse inside a makefile and avoids ambiguity with
2149 flag values that contain commas.
2151 <var>flag</var> must start with a lowercase letter
2152 (<tt>a-z</tt>) and consist only of lowercase letters,
2153 numbers (<tt>0-9</tt>), and the characters
2154 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2155 <var>options</var> must not contain whitespace. The same
2156 tag should not be given multiple times with conflicting
2157 values. Package maintainers may assume that
2158 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2162 The meaning of the following tags has been standardized:
2166 This tag says to not run any build-time test suite
2167 provided by the package.
2171 The presence of this tag means that the package should
2172 be compiled with a minimum of optimization. For C
2173 programs, it is best to add <tt>-O0</tt> to
2174 <tt>CFLAGS</tt> (although this is usually the default).
2175 Some programs might fail to build or run at this level
2176 of optimization; it may be necessary to use
2177 <tt>-O1</tt>, for example.
2181 This tag means that the debugging symbols should not be
2182 stripped from the binary during installation, so that
2183 debugging information may be included in the package.
2185 <tag>parallel=n</tag>
2187 This tag means that the package should be built using up
2188 to <tt>n</tt> parallel processes if the package build
2189 system supports this.<footnote>
2190 Packages built with <tt>make</tt> can often implement
2191 this by passing the <tt>-j</tt><var>n</var> option to
2194 If the package build system does not support parallel
2195 builds, this string must be ignored. If the package
2196 build system only supports a lower level of concurrency
2197 than <var>n</var>, the package should be built using as
2198 many parallel processes as the package build system
2199 supports. It is up to the package maintainer to decide
2200 whether the package build times are long enough and the
2201 package build system is robust enough to make supporting
2202 parallel builds worthwhile.
2208 Unknown flags must be ignored by <file>debian/rules</file>.
2212 The following makefile snippet is an example of how one may
2213 implement the build options; you will probably have to
2214 massage this example in order to make it work for your
2216 <example compact="compact">
2219 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2220 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2221 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2222 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2224 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2229 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2230 INSTALL_PROGRAM += -s
2232 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2233 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2234 MAKEFLAGS += -j$(NUMJOBS)
2239 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2240 # Code to run the package test suite.
2247 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2248 <sect id="substvars">
2249 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2252 When <prgn>dpkg-gencontrol</prgn>
2253 generates <qref id="binarycontrolfiles">binary package control
2254 files</qref> (<file>DEBIAN/control</file>), it performs variable
2255 substitutions on its output just before writing it. Variable
2256 substitutions have the form <tt>${<var>variable</var>}</tt>.
2257 The optional file <file>debian/substvars</file> contains
2258 variable substitutions to be used; variables can also be set
2259 directly from <file>debian/rules</file> using the <tt>-V</tt>
2260 option to the source packaging commands, and certain predefined
2261 variables are also available.
2265 The <file>debian/substvars</file> file is usually generated and
2266 modified dynamically by <file>debian/rules</file> targets, in
2267 which case it must be removed by the <tt>clean</tt> target.
2271 See <manref name="deb-substvars" section="5"> for full
2272 details about source variable substitutions, including the
2273 format of <file>debian/substvars</file>.</p>
2276 <sect id="debianwatch">
2277 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2280 This is an optional, recommended configuration file for the
2281 <tt>uscan</tt> utility which defines how to automatically scan
2282 ftp or http sites for newly available updates of the
2283 package. This is used
2284 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2285 tools to help with quality control and maintenance of the
2286 distribution as a whole.
2291 <sect id="debianfiles">
2292 <heading>Generated files list: <file>debian/files</file></heading>
2295 This file is not a permanent part of the source tree; it
2296 is used while building packages to record which files are
2297 being generated. <prgn>dpkg-genchanges</prgn> uses it
2298 when it generates a <file>.changes</file> file.
2302 It should not exist in a shipped source package, and so it
2303 (and any backup files or temporary files such as
2304 <file>files.new</file><footnote>
2305 <file>files.new</file> is used as a temporary file by
2306 <prgn>dpkg-gencontrol</prgn> and
2307 <prgn>dpkg-distaddfile</prgn> - they write a new
2308 version of <tt>files</tt> here before renaming it,
2309 to avoid leaving a corrupted copy if an error
2311 </footnote>) should be removed by the
2312 <tt>clean</tt> target. It may also be wise to
2313 ensure a fresh start by emptying or removing it at the
2314 start of the <tt>binary</tt> target.
2318 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2319 package, it adds an entry to <file>debian/files</file> for the
2320 <file>.deb</file> file that will be created when <tt>dpkg-deb
2321 --build</tt> is run for that binary package. So for most
2322 packages all that needs to be done with this file is to
2323 delete it in the <tt>clean</tt> target.
2327 If a package upload includes files besides the source
2328 package and any binary packages whose control files were
2329 made with <prgn>dpkg-gencontrol</prgn> then they should be
2330 placed in the parent of the package's top-level directory
2331 and <prgn>dpkg-distaddfile</prgn> should be called to add
2332 the file to the list in <file>debian/files</file>.</p>
2335 <sect id="embeddedfiles">
2336 <heading>Convenience copies of code</heading>
2339 Some software packages include in their distribution convenience
2340 copies of code from other software packages, generally so that
2341 users compiling from source don't have to download multiple
2342 packages. Debian packages should not make use of these
2343 convenience copies unless the included package is explicitly
2344 intended to be used in this way.<footnote>
2345 For example, parts of the GNU build system work like this.
2347 If the included code is already in the Debian archive in the
2348 form of a library, the Debian packaging should ensure that
2349 binary packages reference the libraries already in Debian and
2350 the convenience copy is not used. If the included code is not
2351 already in Debian, it should be packaged separately as a
2352 prerequisite if possible.
2354 Having multiple copies of the same code in Debian is
2355 inefficient, often creates either static linking or shared
2356 library conflicts, and, most importantly, increases the
2357 difficulty of handling security vulnerabilities in the
2363 <sect id="readmesource">
2364 <heading>Source package handling:
2365 <file>debian/README.source</file></heading>
2368 If running <prgn>dpkg-source -x</prgn> on a source package
2369 doesn't produce the source of the package, ready for editing,
2370 and allow one to make changes and run
2371 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2372 without taking any additional steps, creating a
2373 <file>debian/README.source</file> documentation file is
2374 recommended. This file should explain how to do all of the
2377 <item>Generate the fully patched source, in a form ready for
2378 editing, that would be built to create Debian
2379 packages. Doing this with a <tt>patch</tt> target in
2380 <file>debian/rules</file> is recommended; see
2381 <ref id="debianrules">.</item>
2382 <item>Modify the source and save those modifications so that
2383 they will be applied when building the package.</item>
2384 <item>Remove source modifications that are currently being
2385 applied when building the package.</item>
2386 <item>Optionally, document what steps are necessary to
2387 upgrade the Debian source package to a new upstream version,
2388 if applicable.</item>
2390 This explanation should include specific commands and mention
2391 any additional required Debian packages. It should not assume
2392 familiarity with any specific Debian packaging system or patch
2397 This explanation may refer to a documentation file installed by
2398 one of the package's build dependencies provided that the
2399 referenced documentation clearly explains these tasks and is not
2400 a general reference manual.
2404 <file>debian/README.source</file> may also include any other
2405 information that would be helpful to someone modifying the
2406 source package. Even if the package doesn't fit the above
2407 description, maintainers are encouraged to document in a
2408 <file>debian/README.source</file> file any source package with a
2409 particularly complex or unintuitive source layout or build
2410 system (for example, a package that builds the same source
2411 multiple times to generate different binary packages).
2417 <chapt id="controlfields">
2418 <heading>Control files and their fields</heading>
2421 The package management system manipulates data represented in
2422 a common format, known as <em>control data</em>, stored in
2423 <em>control files</em>.
2424 Control files are used for source packages, binary packages and
2425 the <file>.changes</file> files which control the installation
2426 of uploaded files<footnote>
2427 <prgn>dpkg</prgn>'s internal databases are in a similar
2432 <sect id="controlsyntax">
2433 <heading>Syntax of control files</heading>
2436 A control file consists of one or more paragraphs of
2438 The paragraphs are also sometimes referred to as stanzas.
2440 The paragraphs are separated by blank lines. Some control
2441 files allow only one paragraph; others allow several, in
2442 which case each paragraph usually refers to a different
2443 package. (For example, in source packages, the first
2444 paragraph refers to the source package, and later paragraphs
2445 refer to binary packages generated from the source.)
2449 Each paragraph consists of a series of data fields; each
2450 field consists of the field name, followed by a colon and
2451 then the data/value associated with that field. It ends at
2452 the end of the (logical) line. Horizontal whitespace
2453 (spaces and tabs) may occur immediately before or after the
2454 value and is ignored there; it is conventional to put a
2455 single space after the colon. For example, a field might
2457 <example compact="compact">
2460 the field name is <tt>Package</tt> and the field value
2465 A paragraph must not contain more than one instance of a
2466 particular field name.
2470 Many fields' values may span several lines; in this case
2471 each continuation line must start with a space or a tab.
2472 Any trailing spaces or tabs at the end of individual
2473 lines of a field value are ignored.
2477 In fields where it is specified that lines may not wrap,
2478 only a single line of data is allowed and whitespace is not
2479 significant in a field body. Whitespace must not appear
2480 inside names (of packages, architectures, files or anything
2481 else) or version numbers, or between the characters of
2482 multi-character version relationships.
2486 Field names are not case-sensitive, but it is usual to
2487 capitalize the field names using mixed case as shown below.
2488 Field values are case-sensitive unless the description of the
2489 field says otherwise.
2493 Blank lines, or lines consisting only of spaces and tabs,
2494 are not allowed within field values or between fields - that
2495 would mean a new paragraph.
2499 All control files must be encoded in UTF-8.
2503 <sect id="sourcecontrolfiles">
2504 <heading>Source package control files -- <file>debian/control</file></heading>
2507 The <file>debian/control</file> file contains the most vital
2508 (and version-independent) information about the source package
2509 and about the binary packages it creates.
2513 The first paragraph of the control file contains information about
2514 the source package in general. The subsequent sets each describe a
2515 binary package that the source tree builds.
2519 The fields in the general paragraph (the first one, for the source
2522 <list compact="compact">
2523 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2524 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2525 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2526 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2527 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2528 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2529 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2530 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2535 The fields in the binary package paragraphs are:
2537 <list compact="compact">
2538 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2539 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2540 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2541 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2542 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2543 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2544 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2550 The syntax and semantics of the fields are described below.
2554 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2555 generate control files for binary packages (see below), by
2556 <prgn>dpkg-genchanges</prgn> to generate the
2557 <file>.changes</file> file to accompany the upload, and by
2558 <prgn>dpkg-source</prgn> when it creates the
2559 <file>.dsc</file> source control file as part of a source
2560 archive. Many fields are permitted to span multiple lines in
2561 <file>debian/control</file> but not in any other control
2562 file. These tools are responsible for removing the line
2563 breaks from such fields when using fields from
2564 <file>debian/control</file> to generate other control files.
2568 The fields here may contain variable references - their
2569 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2570 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2571 when they generate output control files.
2572 See <ref id="substvars"> for details.
2576 In addition to the control file syntax described <qref
2577 id="controlsyntax">above</qref>, this file may also contain
2578 comment lines starting with <tt>#</tt> without any preceding
2579 whitespace. All such lines are ignored, even in the middle of
2580 continuation lines for a multiline field, and do not end a
2586 <sect id="binarycontrolfiles">
2587 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2590 The <file>DEBIAN/control</file> file contains the most vital
2591 (and version-dependent) information about a binary package. It
2592 consists of a single paragraph.
2596 The fields in this file are:
2598 <list compact="compact">
2599 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2600 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2601 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2602 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2603 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2604 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2605 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2606 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2607 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2608 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2609 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2610 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2615 <sect id="debiansourcecontrolfiles">
2616 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2619 This file consists of a single paragraph, possibly surrounded by
2620 a PGP signature. The fields of that paragraph are listed below.
2621 Their syntax is described above, in <ref id="pkg-controlfields">.
2623 <list compact="compact">
2624 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2627 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2628 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2631 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2632 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2633 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2634 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2635 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2636 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2641 The source package control file is generated by
2642 <prgn>dpkg-source</prgn> when it builds the source
2643 archive, from other files in the source package,
2644 described above. When unpacking, it is checked against
2645 the files and directories in the other parts of the
2651 <sect id="debianchangesfiles">
2652 <heading>Debian changes files -- <file>.changes</file></heading>
2655 The <file>.changes</file> files are used by the Debian archive
2656 maintenance software to process updates to packages. They
2657 consist of a single paragraph, possibly surrounded by a PGP
2658 signature. That paragraph contains information from the
2659 <file>debian/control</file> file and other data about the
2660 source package gathered via <file>debian/changelog</file>
2661 and <file>debian/rules</file>.
2665 <file>.changes</file> files have a format version that is
2666 incremented whenever the documented fields or their meaning
2667 change. This document describes format &changesversion;.
2671 The fields in this file are:
2673 <list compact="compact">
2674 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2675 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2676 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2677 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2679 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2680 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2681 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2682 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2683 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2684 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2685 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2686 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2688 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2689 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2694 <sect id="controlfieldslist">
2695 <heading>List of fields</heading>
2697 <sect1 id="f-Source">
2698 <heading><tt>Source</tt></heading>
2701 This field identifies the source package name.
2705 In <file>debian/control</file> or a <file>.dsc</file> file,
2706 this field must contain only the name of the source package.
2710 In a binary package control file or a <file>.changes</file>
2711 file, the source package name may be followed by a version
2712 number in parentheses<footnote>
2713 It is customary to leave a space after the package name
2714 if a version number is specified.
2716 This version number may be omitted (and is, by
2717 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2718 the <tt>Version</tt> field of the binary package in
2719 question. The field itself may be omitted from a binary
2720 package control file when the source package has the same
2721 name and version as the binary package.
2725 Package names (both source and binary,
2726 see <ref id="f-Package">) must consist only of lower case
2727 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2728 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2729 (<tt>.</tt>). They must be at least two characters long and
2730 must start with an alphanumeric character.
2734 <sect1 id="f-Maintainer">
2735 <heading><tt>Maintainer</tt></heading>
2738 The package maintainer's name and email address. The name
2739 must come first, then the email address inside angle
2740 brackets <tt><></tt> (in RFC822 format).
2744 If the maintainer's name contains a full stop then the
2745 whole field will not work directly as an email address due
2746 to a misfeature in the syntax specified in RFC822; a
2747 program using this field as an address must check for this
2748 and correct the problem if necessary (for example by
2749 putting the name in round brackets and moving it to the
2750 end, and bringing the email address forward).
2754 See <ref id="maintainer"> for additional requirements and
2755 information about package maintainers.
2759 <sect1 id="f-Uploaders">
2760 <heading><tt>Uploaders</tt></heading>
2763 List of the names and email addresses of co-maintainers of the
2764 package, if any. If the package has other maintainers besides
2765 the one named in the <qref id="f-Maintainer">Maintainer
2766 field</qref>, their names and email addresses should be listed
2767 here. The format of each entry is the same as that of the
2768 Maintainer field, and multiple entries must be comma
2773 This is normally an optional field, but if
2774 the <tt>Maintainer</tt> control field names a group of people
2775 and a shared email address, the <tt>Uploaders</tt> field must
2776 be present and must contain at least one human with their
2777 personal email address.
2781 Any parser that interprets the Uploaders field in
2782 <file>debian/control</file> must permit it to span multiple
2783 lines. Line breaks in an Uploaders field that spans multiple
2784 lines are not significant and the semantics of the field are
2785 the same as if the line breaks had not been present.
2789 <sect1 id="f-Changed-By">
2790 <heading><tt>Changed-By</tt></heading>
2793 The name and email address of the person who prepared this
2794 version of the package, usually a maintainer. The syntax is
2795 the same as for the <qref id="f-Maintainer">Maintainer
2800 <sect1 id="f-Section">
2801 <heading><tt>Section</tt></heading>
2804 This field specifies an application area into which the package
2805 has been classified. See <ref id="subsections">.
2809 When it appears in the <file>debian/control</file> file,
2810 it gives the value for the subfield of the same name in
2811 the <tt>Files</tt> field of the <file>.changes</file> file.
2812 It also gives the default for the same field in the binary
2817 <sect1 id="f-Priority">
2818 <heading><tt>Priority</tt></heading>
2821 This field represents how important it is that the user
2822 have the package installed. See <ref id="priorities">.
2826 When it appears in the <file>debian/control</file> file,
2827 it gives the value for the subfield of the same name in
2828 the <tt>Files</tt> field of the <file>.changes</file> file.
2829 It also gives the default for the same field in the binary
2834 <sect1 id="f-Package">
2835 <heading><tt>Package</tt></heading>
2838 The name of the binary package.
2842 Binary package names must follow the same syntax and
2843 restrictions as source package names. See <ref id="f-Source">
2848 <sect1 id="f-Architecture">
2849 <heading><tt>Architecture</tt></heading>
2852 Depending on context and the control file used, the
2853 <tt>Architecture</tt> field can include the following sets of
2857 A unique single word identifying a Debian machine
2858 architecture as described in <ref id="arch-spec">.
2861 An architecture wildcard identifying a set of Debian
2862 machine architectures, see <ref id="arch-wildcard-spec">.
2863 <tt>any</tt> matches all Debian machine architectures
2864 and is the most frequently used.
2867 <tt>all</tt>, which indicates an
2868 architecture-independent package.
2871 <tt>source</tt>, which indicates a source package.
2877 In the main <file>debian/control</file> file in the source
2878 package, this field may contain the special
2879 value <tt>all</tt>, the special architecture
2880 wildcard <tt>any</tt>, or a list of specific and wildcard
2881 architectures separated by spaces. If <tt>all</tt>
2882 or <tt>any</tt> appears, that value must be the entire
2883 contents of the field. Most packages will use
2884 either <tt>all</tt> or <tt>any</tt>.
2888 Specifying a specific list of architectures indicates that the
2889 source will build an architecture-dependent package only on
2890 architectures included in the list. Specifying a list of
2891 architecture wildcards indicates that the source will build an
2892 architecture-dependent package on only those architectures
2893 that match any of the specified architecture wildcards.
2894 Specifying a list of architectures or architecture wildcards
2895 other than <tt>any</tt> is for the minority of cases where a
2896 program is not portable or is not useful on some
2897 architectures. Where possible, the program should be made
2902 In the source package control file <file>.dsc</file>, this
2903 field may contain either the architecture
2904 wildcard <tt>any</tt> or a list of architectures and
2905 architecture wildcards separated by spaces. If a list is
2906 given, it may include (or consist solely of) the special
2907 value <tt>all</tt>. In other words, in <file>.dsc</file>
2908 files unlike the <file>debian/control</file>, <tt>all</tt> may
2909 occur in combination with specific architectures.
2910 The <tt>Architecture</tt> field in the source package control
2911 file <file>.dsc</file> is generally constructed from
2912 the <tt>Architecture</tt> fields in
2913 the <file>debian/control</file> in the source package.
2917 Specifying <tt>any</tt> indicates that the source package
2918 isn't dependent on any particular architecture and should
2919 compile fine on any one. The produced binary package(s)
2920 will either be specific to whatever the current build
2921 architecture is or will be architecture-independent.
2925 Specifying only <tt>all</tt> indicates that the source package
2926 will only build architecture-independent packages. If this is
2927 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2928 <tt>any</tt> implies that the source package will build at
2929 least one architecture-dependent package.
2933 Specifying a list of architectures or architecture wildcards
2934 indicates that the source will build an architecture-dependent
2935 package, and will only work correctly on the listed or
2936 matching architectures. If the source package also builds at
2937 least one architecture-independent package, <tt>all</tt> will
2938 also be included in the list.
2942 In a <file>.changes</file> file, the <tt>Architecture</tt>
2943 field lists the architecture(s) of the package(s) currently
2944 being uploaded. This will be a list; if the source for the
2945 package is also being uploaded, the special
2946 entry <tt>source</tt> is also present. <tt>all</tt> will be
2947 present if any architecture-independent packages are being
2948 uploaded. Architecture wildcards such as <tt>any</tt> must
2949 never occur in the <tt>Architecture</tt> field in
2950 the <file>.changes</file> file.
2954 See <ref id="debianrules"> for information on how to get
2955 the architecture for the build process.
2959 <sect1 id="f-Essential">
2960 <heading><tt>Essential</tt></heading>
2963 This is a boolean field which may occur only in the
2964 control file of a binary package or in a per-package fields
2965 paragraph of a main source control data file.
2969 If set to <tt>yes</tt> then the package management system
2970 will refuse to remove the package (upgrading and replacing
2971 it is still possible). The other possible value is <tt>no</tt>,
2972 which is the same as not having the field at all.
2977 <heading>Package interrelationship fields:
2978 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2979 <tt>Recommends</tt>, <tt>Suggests</tt>,
2980 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2981 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2985 These fields describe the package's relationships with
2986 other packages. Their syntax and semantics are described
2987 in <ref id="relationships">.</p>
2990 <sect1 id="f-Standards-Version">
2991 <heading><tt>Standards-Version</tt></heading>
2994 The most recent version of the standards (the policy
2995 manual and associated texts) with which the package
3000 The version number has four components: major and minor
3001 version number and major and minor patch level. When the
3002 standards change in a way that requires every package to
3003 change the major number will be changed. Significant
3004 changes that will require work in many packages will be
3005 signaled by a change to the minor number. The major patch
3006 level will be changed for any change to the meaning of the
3007 standards, however small; the minor patch level will be
3008 changed when only cosmetic, typographical or other edits
3009 are made which neither change the meaning of the document
3010 nor affect the contents of packages.
3014 Thus only the first three components of the policy version
3015 are significant in the <em>Standards-Version</em> control
3016 field, and so either these three components or all four
3017 components may be specified.<footnote>
3018 In the past, people specified the full version number
3019 in the Standards-Version field, for example "2.3.0.0".
3020 Since minor patch-level changes don't introduce new
3021 policy, it was thought it would be better to relax
3022 policy and only require the first 3 components to be
3023 specified, in this example "2.3.0". All four
3024 components may still be used if someone wishes to do so.
3030 <sect1 id="f-Version">
3031 <heading><tt>Version</tt></heading>
3034 The version number of a package. The format is:
3035 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3039 The three components here are:
3041 <tag><var>epoch</var></tag>
3044 This is a single (generally small) unsigned integer. It
3045 may be omitted, in which case zero is assumed. If it is
3046 omitted then the <var>upstream_version</var> may not
3051 It is provided to allow mistakes in the version numbers
3052 of older versions of a package, and also a package's
3053 previous version numbering schemes, to be left behind.
3057 <tag><var>upstream_version</var></tag>
3060 This is the main part of the version number. It is
3061 usually the version number of the original ("upstream")
3062 package from which the <file>.deb</file> file has been made,
3063 if this is applicable. Usually this will be in the same
3064 format as that specified by the upstream author(s);
3065 however, it may need to be reformatted to fit into the
3066 package management system's format and comparison
3071 The comparison behavior of the package management system
3072 with respect to the <var>upstream_version</var> is
3073 described below. The <var>upstream_version</var>
3074 portion of the version number is mandatory.
3078 The <var>upstream_version</var> may contain only
3079 alphanumerics<footnote>
3080 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3082 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3083 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3084 tilde) and should start with a digit. If there is no
3085 <var>debian_revision</var> then hyphens are not allowed;
3086 if there is no <var>epoch</var> then colons are not
3091 <tag><var>debian_revision</var></tag>
3094 This part of the version number specifies the version of
3095 the Debian package based on the upstream version. It
3096 may contain only alphanumerics and the characters
3097 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3098 tilde) and is compared in the same way as the
3099 <var>upstream_version</var> is.
3103 It is optional; if it isn't present then the
3104 <var>upstream_version</var> may not contain a hyphen.
3105 This format represents the case where a piece of
3106 software was written specifically to be a Debian
3107 package, where the Debian package source must always
3108 be identical to the pristine source and therefore no
3109 revision indication is required.
3113 It is conventional to restart the
3114 <var>debian_revision</var> at <tt>1</tt> each time the
3115 <var>upstream_version</var> is increased.
3119 The package management system will break the version
3120 number apart at the last hyphen in the string (if there
3121 is one) to determine the <var>upstream_version</var> and
3122 <var>debian_revision</var>. The absence of a
3123 <var>debian_revision</var> is equivalent to a
3124 <var>debian_revision</var> of <tt>0</tt>.
3131 When comparing two version numbers, first the <var>epoch</var>
3132 of each are compared, then the <var>upstream_version</var> if
3133 <var>epoch</var> is equal, and then <var>debian_revision</var>
3134 if <var>upstream_version</var> is also equal.
3135 <var>epoch</var> is compared numerically. The
3136 <var>upstream_version</var> and <var>debian_revision</var>
3137 parts are compared by the package management system using the
3138 following algorithm:
3142 The strings are compared from left to right.
3146 First the initial part of each string consisting entirely of
3147 non-digit characters is determined. These two parts (one of
3148 which may be empty) are compared lexically. If a difference
3149 is found it is returned. The lexical comparison is a
3150 comparison of ASCII values modified so that all the letters
3151 sort earlier than all the non-letters and so that a tilde
3152 sorts before anything, even the end of a part. For example,
3153 the following parts are in sorted order from earliest to
3154 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3155 <tt>a</tt>.<footnote>
3156 One common use of <tt>~</tt> is for upstream pre-releases.
3157 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3158 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3163 Then the initial part of the remainder of each string which
3164 consists entirely of digit characters is determined. The
3165 numerical values of these two parts are compared, and any
3166 difference found is returned as the result of the comparison.
3167 For these purposes an empty string (which can only occur at
3168 the end of one or both version strings being compared) counts
3173 These two steps (comparing and removing initial non-digit
3174 strings and initial digit strings) are repeated until a
3175 difference is found or both strings are exhausted.
3179 Note that the purpose of epochs is to allow us to leave behind
3180 mistakes in version numbering, and to cope with situations
3181 where the version numbering scheme changes. It is
3182 <em>not</em> intended to cope with version numbers containing
3183 strings of letters which the package management system cannot
3184 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3185 silly orderings.<footnote>
3186 The author of this manual has heard of a package whose
3187 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3188 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3194 <sect1 id="f-Description">
3195 <heading><tt>Description</tt></heading>
3198 In a source or binary control file, the <tt>Description</tt>
3199 field contains a description of the binary package, consisting
3200 of two parts, the synopsis or the short description, and the
3201 long description. The field's format is as follows:
3206 Description: <single line synopsis>
3207 <extended description over several lines>
3212 The lines in the extended description can have these formats:
3218 Those starting with a single space are part of a paragraph.
3219 Successive lines of this form will be word-wrapped when
3220 displayed. The leading space will usually be stripped off.
3224 Those starting with two or more spaces. These will be
3225 displayed verbatim. If the display cannot be panned
3226 horizontally, the displaying program will line wrap them "hard"
3227 (i.e., without taking account of word breaks). If it can they
3228 will be allowed to trail off to the right. None, one or two
3229 initial spaces may be deleted, but the number of spaces
3230 deleted from each line will be the same (so that you can have
3231 indenting work correctly, for example).
3235 Those containing a single space followed by a single full stop
3236 character. These are rendered as blank lines. This is the
3237 <em>only</em> way to get a blank line<footnote>
3238 Completely empty lines will not be rendered as blank lines.
3239 Instead, they will cause the parser to think you're starting
3240 a whole new record in the control file, and will therefore
3241 likely abort with an error.
3246 Those containing a space, a full stop and some more characters.
3247 These are for future expansion. Do not use them.
3253 Do not use tab characters. Their effect is not predictable.
3257 See <ref id="descriptions"> for further information on this.
3261 In a <file>.changes</file> file, the <tt>Description</tt>
3262 field contains a summary of the descriptions for the packages
3263 being uploaded. For this case, the first line of the field
3264 value (the part on the same line as <tt>Description:</tt>) is
3265 always empty. The content of the field is expressed as
3266 continuation lines, one line per package. Each line is
3267 indented by one space and contains the name of a binary
3268 package, a space, a hyphen (<tt>-</tt>), a space, and the
3269 short description line from that package.
3273 <sect1 id="f-Distribution">
3274 <heading><tt>Distribution</tt></heading>
3277 In a <file>.changes</file> file or parsed changelog output
3278 this contains the (space-separated) name(s) of the
3279 distribution(s) where this version of the package should
3280 be installed. Valid distributions are determined by the
3281 archive maintainers.<footnote>
3282 Example distribution names in the Debian archive used in
3283 <file>.changes</file> files are:
3284 <taglist compact="compact">
3285 <tag><em>unstable</em></tag>
3287 This distribution value refers to the
3288 <em>developmental</em> part of the Debian distribution
3289 tree. Most new packages, new upstream versions of
3290 packages and bug fixes go into the <em>unstable</em>
3294 <tag><em>experimental</em></tag>
3296 The packages with this distribution value are deemed
3297 by their maintainers to be high risk. Oftentimes they
3298 represent early beta or developmental packages from
3299 various sources that the maintainers want people to
3300 try, but are not ready to be a part of the other parts
3301 of the Debian distribution tree.
3306 Others are used for updating stable releases or for
3307 security uploads. More information is available in the
3308 Debian Developer's Reference, section "The Debian
3312 The Debian archive software only supports listing a single
3313 distribution. Migration of packages to other distributions is
3314 handled outside of the upload process.
3319 <heading><tt>Date</tt></heading>
3322 This field includes the date the package was built or last
3323 edited. It must be in the same format as the <var>date</var>
3324 in a <file>debian/changelog</file> entry.
3328 The value of this field is usually extracted from the
3329 <file>debian/changelog</file> file - see
3330 <ref id="dpkgchangelog">).
3334 <sect1 id="f-Format">
3335 <heading><tt>Format</tt></heading>
3338 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3339 files, this field declares the format version of that file.
3340 The syntax of the field value is the same as that of
3341 a <qref id="f-Version">package version number</qref> except
3342 that no epoch or Debian revision is allowed. The format
3343 described in this document is <tt>&changesversion;</tt>.
3347 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3348 Debian source control</qref> files, this field declares the
3349 format of the source package. The field value is used by
3350 programs acting on a source package to interpret the list of
3351 files in the source package and determine how to unpack it.
3352 The syntax of the field value is a numeric major revision, a
3353 period, a numeric minor revision, and then an optional subtype
3354 after whitespace, which if specified is an alphanumeric word
3355 in parentheses. The subtype is optional in the syntax but may
3356 be mandatory for particular source format revisions.
3358 The source formats currently supported by the Debian archive
3359 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3360 and <tt>3.0 (quilt)</tt>.
3365 <sect1 id="f-Urgency">
3366 <heading><tt>Urgency</tt></heading>
3369 This is a description of how important it is to upgrade to
3370 this version from previous ones. It consists of a single
3371 keyword taking one of the values <tt>low</tt>,
3372 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3373 <tt>critical</tt><footnote>
3374 Other urgency values are supported with configuration
3375 changes in the archive software but are not used in Debian.
3376 The urgency affects how quickly a package will be considered
3377 for inclusion into the <tt>testing</tt> distribution and
3378 gives an indication of the importance of any fixes included
3379 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3380 treated as synonymous.
3381 </footnote> (not case-sensitive) followed by an optional
3382 commentary (separated by a space) which is usually in
3383 parentheses. For example:
3386 Urgency: low (HIGH for users of diversions)
3392 The value of this field is usually extracted from the
3393 <file>debian/changelog</file> file - see
3394 <ref id="dpkgchangelog">.
3398 <sect1 id="f-Changes">
3399 <heading><tt>Changes</tt></heading>
3402 This field contains the human-readable changes data, describing
3403 the differences between the last version and the current one.
3407 The first line of the field value (the part on the same line
3408 as <tt>Changes:</tt>) is always empty. The content of the
3409 field is expressed as continuation lines, with each line
3410 indented by at least one space. Blank lines must be
3411 represented by a line consisting only of a space and a full
3416 The value of this field is usually extracted from the
3417 <file>debian/changelog</file> file - see
3418 <ref id="dpkgchangelog">).
3422 Each version's change information should be preceded by a
3423 "title" line giving at least the version, distribution(s)
3424 and urgency, in a human-readable way.
3428 If data from several versions is being returned the entry
3429 for the most recent version should be returned first, and
3430 entries should be separated by the representation of a
3431 blank line (the "title" line may also be followed by the
3432 representation of a blank line).
3436 <sect1 id="f-Binary">
3437 <heading><tt>Binary</tt></heading>
3440 This field is a list of binary packages. Its syntax and
3441 meaning varies depending on the control file in which it
3446 When it appears in the <file>.dsc</file> file, it lists binary
3447 packages which a source package can produce, separated by
3449 A space after each comma is conventional.
3450 </footnote>. It may span multiple lines. The source package
3451 does not necessarily produce all of these binary packages for
3452 every architecture. The source control file doesn't contain
3453 details of which architectures are appropriate for which of
3454 the binary packages.
3458 When it appears in a <file>.changes</file> file, it lists the
3459 names of the binary packages being uploaded, separated by
3460 whitespace (not commas). It may span multiple lines.
3464 <sect1 id="f-Installed-Size">
3465 <heading><tt>Installed-Size</tt></heading>
3468 This field appears in the control files of binary packages,
3469 and in the <file>Packages</file> files. It gives an estimate
3470 of the total amount of disk space required to install the
3471 named package. Actual installed size may vary based on block
3472 size, file system properties, or actions taken by package
3477 The disk space is given as the integer value of the estimated
3478 installed size in bytes, divided by 1024 and rounded up.
3482 <sect1 id="f-Files">
3483 <heading><tt>Files</tt></heading>
3486 This field contains a list of files with information about
3487 each one. The exact information and syntax varies with
3492 In all cases, Files is a multiline field. The first line of
3493 the field value (the part on the same line as <tt>Files:</tt>)
3494 is always empty. The content of the field is expressed as
3495 continuation lines, one line per file. Each line must be
3496 indented by one space and contain a number of sub-fields,
3497 separated by spaces, as described below.
3501 In the <file>.dsc</file> file, each line contains the MD5
3502 checksum, size and filename of the tar file and (if
3503 applicable) diff file which make up the remainder of the
3504 source package<footnote>
3505 That is, the parts which are not the <tt>.dsc</tt>.
3506 </footnote>. For example:
3509 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3510 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3512 The exact forms of the filenames are described
3513 in <ref id="pkg-sourcearchives">.
3517 In the <file>.changes</file> file this contains one line per
3518 file being uploaded. Each line contains the MD5 checksum,
3519 size, section and priority and the filename. For example:
3522 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3523 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3524 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3525 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3527 The <qref id="f-Section">section</qref>
3528 and <qref id="f-Priority">priority</qref> are the values of
3529 the corresponding fields in the main source control file. If
3530 no section or priority is specified then <tt>-</tt> should be
3531 used, though section and priority values must be specified for
3532 new packages to be installed properly.
3536 The special value <tt>byhand</tt> for the section in a
3537 <tt>.changes</tt> file indicates that the file in question
3538 is not an ordinary package file and must by installed by
3539 hand by the distribution maintainers. If the section is
3540 <tt>byhand</tt> the priority should be <tt>-</tt>.
3544 If a new Debian revision of a package is being shipped and
3545 no new original source archive is being distributed the
3546 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3547 entry for the original source archive
3548 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3549 but the <file>.changes</file> file should leave it out. In
3550 this case the original source archive on the distribution
3551 site must match exactly, byte-for-byte, the original
3552 source archive which was used to generate the
3553 <file>.dsc</file> file and diff which are being uploaded.</p>
3556 <sect1 id="f-Closes">
3557 <heading><tt>Closes</tt></heading>
3560 A space-separated list of bug report numbers that the upload
3561 governed by the .changes file closes.
3565 <sect1 id="f-Homepage">
3566 <heading><tt>Homepage</tt></heading>
3569 The URL of the web site for this package, preferably (when
3570 applicable) the site from which the original source can be
3571 obtained and any additional upstream documentation or
3572 information may be found. The content of this field is a
3573 simple URL without any surrounding characters such as
3578 <sect1 id="f-Checksums">
3579 <heading><tt>Checksums-Sha1</tt>
3580 and <tt>Checksums-Sha256</tt></heading>
3583 These fields contain a list of files with a checksum and size
3584 for each one. Both <tt>Checksums-Sha1</tt>
3585 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3586 only in the checksum algorithm used: SHA-1
3587 for <tt>Checksums-Sha1</tt> and SHA-256
3588 for <tt>Checksums-Sha256</tt>.
3592 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3593 multiline fields. The first line of the field value (the part
3594 on the same line as <tt>Checksums-Sha1:</tt>
3595 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3596 of the field is expressed as continuation lines, one line per
3597 file. Each line consists of the checksum, a space, the file
3598 size, a space, and the file name. For example (from
3599 a <file>.changes</file> file):
3602 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3603 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3604 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3605 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3607 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3608 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3609 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3610 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3615 In the <file>.dsc</file> file, these fields should list all
3616 files that make up the source package. In
3617 the <file>.changes</file> file, these fields should list all
3618 files being uploaded. The list of files in these fields
3619 must match the list of files in the <tt>Files</tt> field.
3625 <heading>User-defined fields</heading>
3628 Additional user-defined fields may be added to the
3629 source package control file. Such fields will be
3630 ignored, and not copied to (for example) binary or
3631 source package control files or upload control files.
3635 If you wish to add additional unsupported fields to
3636 these output files you should use the mechanism
3641 Fields in the main source control information file with
3642 names starting <tt>X</tt>, followed by one or more of
3643 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3644 be copied to the output files. Only the part of the
3645 field name after the hyphen will be used in the output
3646 file. Where the letter <tt>B</tt> is used the field
3647 will appear in binary package control files, where the
3648 letter <tt>S</tt> is used in source package control
3649 files and where <tt>C</tt> is used in upload control
3650 (<tt>.changes</tt>) files.
3654 For example, if the main source information control file
3657 XBS-Comment: I stand between the candle and the star.
3659 then the binary and source package control files will contain the
3662 Comment: I stand between the candle and the star.
3671 <chapt id="maintainerscripts">
3672 <heading>Package maintainer scripts and installation procedure</heading>
3675 <heading>Introduction to package maintainer scripts</heading>
3678 It is possible to supply scripts as part of a package which
3679 the package management system will run for you when your
3680 package is installed, upgraded or removed.
3684 These scripts are the control information
3685 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3686 and <prgn>postrm</prgn>. They must be proper executable files;
3687 if they are scripts (which is recommended), they must start with
3688 the usual <tt>#!</tt> convention. They should be readable and
3689 executable by anyone, and must not be world-writable.
3693 The package management system looks at the exit status from
3694 these scripts. It is important that they exit with a
3695 non-zero status if there is an error, so that the package
3696 management system can stop its processing. For shell
3697 scripts this means that you <em>almost always</em> need to
3698 use <tt>set -e</tt> (this is usually true when writing shell
3699 scripts, in fact). It is also important, of course, that
3700 they exit with a zero status if everything went well.
3704 Additionally, packages interacting with users
3705 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3706 should install a <prgn>config</prgn> script as a control
3707 information file. See <ref id="maintscriptprompt"> for details.
3711 When a package is upgraded a combination of the scripts from
3712 the old and new packages is called during the upgrade
3713 procedure. If your scripts are going to be at all
3714 complicated you need to be aware of this, and may need to
3715 check the arguments to your scripts.
3719 Broadly speaking the <prgn>preinst</prgn> is called before
3720 (a particular version of) a package is installed, and the
3721 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3722 before (a version of) a package is removed and the
3723 <prgn>postrm</prgn> afterwards.
3727 Programs called from maintainer scripts should not normally
3728 have a path prepended to them. Before installation is
3729 started, the package management system checks to see if the
3730 programs <prgn>ldconfig</prgn>,
3731 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3732 and <prgn>update-rc.d</prgn> can be found via the
3733 <tt>PATH</tt> environment variable. Those programs, and any
3734 other program that one would expect to be in the
3735 <tt>PATH</tt>, should thus be invoked without an absolute
3736 pathname. Maintainer scripts should also not reset the
3737 <tt>PATH</tt>, though they might choose to modify it by
3738 prepending or appending package-specific directories. These
3739 considerations really apply to all shell scripts.</p>
3742 <sect id="idempotency">
3743 <heading>Maintainer scripts idempotency</heading>
3746 It is necessary for the error recovery procedures that the
3747 scripts be idempotent. This means that if it is run
3748 successfully, and then it is called again, it doesn't bomb
3749 out or cause any harm, but just ensures that everything is
3750 the way it ought to be. If the first call failed, or
3751 aborted half way through for some reason, the second call
3752 should merely do the things that were left undone the first
3753 time, if any, and exit with a success status if everything
3755 This is so that if an error occurs, the user interrupts
3756 <prgn>dpkg</prgn> or some other unforeseen circumstance
3757 happens you don't leave the user with a badly-broken
3758 package when <prgn>dpkg</prgn> attempts to repeat the
3764 <sect id="controllingterminal">
3765 <heading>Controlling terminal for maintainer scripts</heading>
3768 Maintainer scripts are not guaranteed to run with a controlling
3769 terminal and may not be able to interact with the user. They
3770 must be able to fall back to noninteractive behavior if no
3771 controlling terminal is available. Maintainer scripts that
3772 prompt via a program conforming to the Debian Configuration
3773 Management Specification (see <ref id="maintscriptprompt">) may
3774 assume that program will handle falling back to noninteractive
3779 For high-priority prompts without a reasonable default answer,
3780 maintainer scripts may abort if there is no controlling
3781 terminal. However, this situation should be avoided if at all
3782 possible, since it prevents automated or unattended installs.
3783 In most cases, users will consider this to be a bug in the
3788 <sect id="exitstatus">
3789 <heading>Exit status</heading>
3792 Each script must return a zero exit status for
3793 success, or a nonzero one for failure, since the package
3794 management system looks for the exit status of these scripts
3795 and determines what action to take next based on that datum.
3799 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3804 <list compact="compact">
3806 <var>new-preinst</var> <tt>install</tt>
3809 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3812 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3815 <var>old-preinst</var> <tt>abort-upgrade</tt>
3816 <var>new-version</var>
3821 <list compact="compact">
3823 <var>postinst</var> <tt>configure</tt>
3824 <var>most-recently-configured-version</var>
3827 <var>old-postinst</var> <tt>abort-upgrade</tt>
3828 <var>new-version</var>
3831 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3832 <tt>in-favour</tt> <var>package</var>
3833 <var>new-version</var>
3836 <var>postinst</var> <tt>abort-remove</tt>
3839 <var>deconfigured's-postinst</var>
3840 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3841 <var>failed-install-package</var> <var>version</var>
3842 [<tt>removing</tt> <var>conflicting-package</var>
3848 <list compact="compact">
3850 <var>prerm</var> <tt>remove</tt>
3853 <var>old-prerm</var> <tt>upgrade</tt>
3854 <var>new-version</var>
3857 <var>new-prerm</var> <tt>failed-upgrade</tt>
3858 <var>old-version</var>
3861 <var>conflictor's-prerm</var> <tt>remove</tt>
3862 <tt>in-favour</tt> <var>package</var>
3863 <var>new-version</var>
3866 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3867 <tt>in-favour</tt> <var>package-being-installed</var>
3868 <var>version</var> [<tt>removing</tt>
3869 <var>conflicting-package</var>
3875 <list compact="compact">
3877 <var>postrm</var> <tt>remove</tt>
3880 <var>postrm</var> <tt>purge</tt>
3883 <var>old-postrm</var> <tt>upgrade</tt>
3884 <var>new-version</var>
3887 <var>new-postrm</var> <tt>failed-upgrade</tt>
3888 <var>old-version</var>
3891 <var>new-postrm</var> <tt>abort-install</tt>
3894 <var>new-postrm</var> <tt>abort-install</tt>
3895 <var>old-version</var>
3898 <var>new-postrm</var> <tt>abort-upgrade</tt>
3899 <var>old-version</var>
3902 <var>disappearer's-postrm</var> <tt>disappear</tt>
3903 <var>overwriter</var>
3904 <var>overwriter-version</var>
3910 <sect id="unpackphase">
3911 <heading>Details of unpack phase of installation or upgrade</heading>
3914 The procedure on installation/upgrade/overwrite/disappear
3915 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3916 stage of <tt>dpkg --install</tt>) is as follows. In each
3917 case, if a major error occurs (unless listed below) the
3918 actions are, in general, run backwards - this means that the
3919 maintainer scripts are run with different arguments in
3920 reverse order. These are the "error unwind" calls listed
3927 If a version of the package is already installed, call
3928 <example compact="compact">
3929 <var>old-prerm</var> upgrade <var>new-version</var>
3933 If the script runs but exits with a non-zero
3934 exit status, <prgn>dpkg</prgn> will attempt:
3935 <example compact="compact">
3936 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3938 If this works, the upgrade continues. If this
3939 does not work, the error unwind:
3940 <example compact="compact">
3941 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3943 If this works, then the old-version is
3944 "Installed", if not, the old version is in a
3945 "Half-Configured" state.
3951 If a "conflicting" package is being removed at the same time,
3952 or if any package will be broken (due to <tt>Breaks</tt>):
3955 If <tt>--auto-deconfigure</tt> is
3956 specified, call, for each package to be deconfigured
3957 due to <tt>Breaks</tt>:
3958 <example compact="compact">
3959 <var>deconfigured's-prerm</var> deconfigure \
3960 in-favour <var>package-being-installed</var> <var>version</var>
3963 <example compact="compact">
3964 <var>deconfigured's-postinst</var> abort-deconfigure \
3965 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3967 The deconfigured packages are marked as
3968 requiring configuration, so that if
3969 <tt>--install</tt> is used they will be
3970 configured again if possible.
3973 If any packages depended on a conflicting
3974 package being removed and <tt>--auto-deconfigure</tt> is
3975 specified, call, for each such package:
3976 <example compact="compact">
3977 <var>deconfigured's-prerm</var> deconfigure \
3978 in-favour <var>package-being-installed</var> <var>version</var> \
3979 removing <var>conflicting-package</var> <var>version</var>
3982 <example compact="compact">
3983 <var>deconfigured's-postinst</var> abort-deconfigure \
3984 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3985 removing <var>conflicting-package</var> <var>version</var>
3987 The deconfigured packages are marked as
3988 requiring configuration, so that if
3989 <tt>--install</tt> is used they will be
3990 configured again if possible.
3993 To prepare for removal of each conflicting package, call:
3994 <example compact="compact">
3995 <var>conflictor's-prerm</var> remove \
3996 in-favour <var>package</var> <var>new-version</var>
3999 <example compact="compact">
4000 <var>conflictor's-postinst</var> abort-remove \
4001 in-favour <var>package</var> <var>new-version</var>
4010 If the package is being upgraded, call:
4011 <example compact="compact">
4012 <var>new-preinst</var> upgrade <var>old-version</var>
4014 If this fails, we call:
4016 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4023 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4025 is called. If this works, then the old version
4026 is in an "Installed" state, or else it is left
4027 in an "Unpacked" state.
4032 If it fails, then the old version is left
4033 in an "Half-Installed" state.
4040 Otherwise, if the package had some configuration
4041 files from a previous version installed (i.e., it
4042 is in the "configuration files only" state):
4043 <example compact="compact">
4044 <var>new-preinst</var> install <var>old-version</var>
4048 <var>new-postrm</var> abort-install <var>old-version</var>
4050 If this fails, the package is left in a
4051 "Half-Installed" state, which requires a
4052 reinstall. If it works, the packages is left in
4053 a "Config-Files" state.
4056 Otherwise (i.e., the package was completely purged):
4057 <example compact="compact">
4058 <var>new-preinst</var> install
4061 <example compact="compact">
4062 <var>new-postrm</var> abort-install
4064 If the error-unwind fails, the package is in a
4065 "Half-Installed" phase, and requires a
4066 reinstall. If the error unwind works, the
4067 package is in a not installed state.
4074 The new package's files are unpacked, overwriting any
4075 that may be on the system already, for example any
4076 from the old version of the same package or from
4077 another package. Backups of the old files are kept
4078 temporarily, and if anything goes wrong the package
4079 management system will attempt to put them back as
4080 part of the error unwind.
4084 It is an error for a package to contain files which
4085 are on the system in another package, unless
4086 <tt>Replaces</tt> is used (see <ref id="replaces">).
4088 The following paragraph is not currently the case:
4089 Currently the <tt>- - force-overwrite</tt> flag is
4090 enabled, downgrading it to a warning, but this may not
4096 It is a more serious error for a package to contain a
4097 plain file or other kind of non-directory where another
4098 package has a directory (again, unless
4099 <tt>Replaces</tt> is used). This error can be
4100 overridden if desired using
4101 <tt>--force-overwrite-dir</tt>, but this is not
4106 Packages which overwrite each other's files produce
4107 behavior which, though deterministic, is hard for the
4108 system administrator to understand. It can easily
4109 lead to "missing" programs if, for example, a package
4110 is installed which overwrites a file from another
4111 package, and is then removed again.<footnote>
4112 Part of the problem is due to what is arguably a
4113 bug in <prgn>dpkg</prgn>.
4118 A directory will never be replaced by a symbolic link
4119 to a directory or vice versa; instead, the existing
4120 state (symlink or not) will be left alone and
4121 <prgn>dpkg</prgn> will follow the symlink if there is
4130 If the package is being upgraded, call
4131 <example compact="compact">
4132 <var>old-postrm</var> upgrade <var>new-version</var>
4136 If this fails, <prgn>dpkg</prgn> will attempt:
4137 <example compact="compact">
4138 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4140 If this works, installation continues. If not,
4142 <example compact="compact">
4143 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4145 If this fails, the old version is left in a
4146 "Half-Installed" state. If it works, dpkg now
4148 <example compact="compact">
4149 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4151 If this fails, the old version is left in a
4152 "Half-Installed" state. If it works, dpkg now
4154 <example compact="compact">
4155 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4157 If this fails, the old version is in an
4164 This is the point of no return - if
4165 <prgn>dpkg</prgn> gets this far, it won't back off
4166 past this point if an error occurs. This will
4167 leave the package in a fairly bad state, which
4168 will require a successful re-installation to clear
4169 up, but it's when <prgn>dpkg</prgn> starts doing
4170 things that are irreversible.
4175 Any files which were in the old version of the package
4176 but not in the new are removed.
4180 The new file list replaces the old.
4184 The new maintainer scripts replace the old.
4188 Any packages all of whose files have been overwritten
4189 during the installation, and which aren't required for
4190 dependencies, are considered to have been removed.
4191 For each such package
4194 <prgn>dpkg</prgn> calls:
4195 <example compact="compact">
4196 <var>disappearer's-postrm</var> disappear \
4197 <var>overwriter</var> <var>overwriter-version</var>
4201 The package's maintainer scripts are removed.
4204 It is noted in the status database as being in a
4205 sane state, namely not installed (any conffiles
4206 it may have are ignored, rather than being
4207 removed by <prgn>dpkg</prgn>). Note that
4208 disappearing packages do not have their prerm
4209 called, because <prgn>dpkg</prgn> doesn't know
4210 in advance that the package is going to
4217 Any files in the package we're unpacking that are also
4218 listed in the file lists of other packages are removed
4219 from those lists. (This will lobotomize the file list
4220 of the "conflicting" package if there is one.)
4224 The backup files made during installation, above, are
4230 The new package's status is now sane, and recorded as
4235 Here is another point of no return - if the
4236 conflicting package's removal fails we do not unwind
4237 the rest of the installation; the conflicting package
4238 is left in a half-removed limbo.
4243 If there was a conflicting package we go and do the
4244 removal actions (described below), starting with the
4245 removal of the conflicting package's files (any that
4246 are also in the package being installed have already
4247 been removed from the conflicting package's file list,
4248 and so do not get removed now).
4254 <sect id="configdetails"><heading>Details of configuration</heading>
4257 When we configure a package (this happens with <tt>dpkg
4258 --install</tt> and <tt>dpkg --configure</tt>), we first
4259 update any <tt>conffile</tt>s and then call:
4260 <example compact="compact">
4261 <var>postinst</var> configure <var>most-recently-configured-version</var>
4266 No attempt is made to unwind after errors during
4267 configuration. If the configuration fails, the package is in
4268 a "Failed Config" state, and an error message is generated.
4272 If there is no most recently configured version
4273 <prgn>dpkg</prgn> will pass a null argument.
4276 Historical note: Truly ancient (pre-1997) versions of
4277 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4278 (including the angle brackets) in this case. Even older
4279 ones did not pass a second argument at all, under any
4280 circumstance. Note that upgrades using such an old dpkg
4281 version are unlikely to work for other reasons, even if
4282 this old argument behavior is handled by your postinst script.
4288 <sect id="removedetails"><heading>Details of removal and/or
4289 configuration purging</heading>
4295 <example compact="compact">
4296 <var>prerm</var> remove
4300 If prerm fails during replacement due to conflict
4302 <var>conflictor's-postinst</var> abort-remove \
4303 in-favour <var>package</var> <var>new-version</var>
4307 <var>postinst</var> abort-remove
4311 If this fails, the package is in a "Half-Configured"
4312 state, or else it remains "Installed".
4316 The package's files are removed (except <tt>conffile</tt>s).
4319 <example compact="compact">
4320 <var>postrm</var> remove
4324 If it fails, there's no error unwind, and the package is in
4325 an "Half-Installed" state.
4330 All the maintainer scripts except the <prgn>postrm</prgn>
4335 If we aren't purging the package we stop here. Note
4336 that packages which have no <prgn>postrm</prgn> and no
4337 <tt>conffile</tt>s are automatically purged when
4338 removed, as there is no difference except for the
4339 <prgn>dpkg</prgn> status.
4343 The <tt>conffile</tt>s and any backup files
4344 (<tt>~</tt>-files, <tt>#*#</tt> files,
4345 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4350 <example compact="compact">
4351 <var>postrm</var> purge
4355 If this fails, the package remains in a "Config-Files"
4360 The package's file list is removed.
4369 <chapt id="relationships">
4370 <heading>Declaring relationships between packages</heading>
4372 <sect id="depsyntax">
4373 <heading>Syntax of relationship fields</heading>
4376 These fields all have a uniform syntax. They are a list of
4377 package names separated by commas.
4381 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4382 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4383 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4384 control fields of the package, which declare
4385 dependencies on other packages, the package names listed may
4386 also include lists of alternative package names, separated
4387 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4388 if any one of the alternative packages is installed, that
4389 part of the dependency is considered to be satisfied.
4393 All of the fields except for <tt>Provides</tt> may restrict
4394 their applicability to particular versions of each named
4395 package. This is done in parentheses after each individual
4396 package name; the parentheses should contain a relation from
4397 the list below followed by a version number, in the format
4398 described in <ref id="f-Version">.
4402 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4403 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4404 strictly earlier, earlier or equal, exactly equal, later or
4405 equal and strictly later, respectively. The deprecated
4406 forms <tt><</tt> and <tt>></tt> were used to mean
4407 earlier/later or equal, rather than strictly earlier/later,
4408 so they should not appear in new packages (though
4409 <prgn>dpkg</prgn> still supports them).
4413 Whitespace may appear at any point in the version
4414 specification subject to the rules in <ref
4415 id="controlsyntax">, and must appear where it's necessary to
4416 disambiguate; it is not otherwise significant. All of the
4417 relationship fields may span multiple lines. For
4418 consistency and in case of future changes to
4419 <prgn>dpkg</prgn> it is recommended that a single space be
4420 used after a version relationship and before a version
4421 number; it is also conventional to put a single space after
4422 each comma, on either side of each vertical bar, and before
4423 each open parenthesis. When wrapping a relationship field, it
4424 is conventional to do so after a comma and before the space
4425 following that comma.
4429 For example, a list of dependencies might appear as:
4430 <example compact="compact">
4433 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4438 Relationships may be restricted to a certain set of
4439 architectures. This is indicated in brackets after each
4440 individual package name and the optional version specification.
4441 The brackets enclose a list of Debian architecture names
4442 separated by whitespace. Exclamation marks may be prepended to
4443 each of the names. (It is not permitted for some names to be
4444 prepended with exclamation marks while others aren't.)
4448 For build relationship fields
4449 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4450 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4451 the current Debian host architecture is not in this list and
4452 there are no exclamation marks in the list, or it is in the list
4453 with a prepended exclamation mark, the package name and the
4454 associated version specification are ignored completely for the
4455 purposes of defining the relationships.
4460 <example compact="compact">
4462 Build-Depends-Indep: texinfo
4463 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4464 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4466 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4467 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4468 <tt>gnumach-dev</tt> only on hurd-i386.
4472 For binary relationship fields, the architecture restriction
4473 syntax is only supported in the source package control
4474 file <file>debian/control</file>. When the corresponding binary
4475 package control file is generated, the relationship will either
4476 be omitted or included without the architecture restriction
4477 based on the architecture of the binary package. This means
4478 that architecture restrictions must not be used in binary
4479 relationship fields for architecture-independent packages
4480 (<tt>Architecture: all</tt>).
4485 <example compact="compact">
4486 Depends: foo [i386], bar [amd64]
4488 becomes <tt>Depends: foo</tt> when the package is built on
4489 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4490 package is built on the <tt>amd64</tt> architecture, and omitted
4491 entirely in binary packages built on all other architectures.
4495 If the architecture-restricted dependency is part of a set of
4496 alternatives using <tt>|</tt>, that alternative is ignored
4497 completely on architectures that do not match the restriction.
4499 <example compact="compact">
4500 Build-Depends: foo [!i386] | bar [!amd64]
4502 is equivalent to <tt>bar</tt> on the i386 architecture, to
4503 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4504 bar</tt> on all other architectures.
4508 Relationships may also be restricted to a certain set of
4509 architectures using architecture wildcards. The syntax for
4510 declaring such restrictions is the same as declaring
4511 restrictions using a certain set of architectures without
4512 architecture wildcards. For example:
4513 <example compact="compact">
4514 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4516 is equivalent to <tt>foo</tt> on architectures using the Linux
4517 kernel and any cpu, <tt>bar</tt> on architectures using any
4518 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4519 using a kernel other than Linux.
4523 Note that the binary package relationship fields such as
4524 <tt>Depends</tt> appear in one of the binary package
4525 sections of the control file, whereas the build-time
4526 relationships such as <tt>Build-Depends</tt> appear in the
4527 source package section of the control file (which is the
4532 <sect id="binarydeps">
4533 <heading>Binary Dependencies - <tt>Depends</tt>,
4534 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4535 <tt>Pre-Depends</tt>
4539 Packages can declare in their control file that they have
4540 certain relationships to other packages - for example, that
4541 they may not be installed at the same time as certain other
4542 packages, and/or that they depend on the presence of others.
4546 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4547 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4548 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4549 <tt>Breaks</tt> is described in <ref id="breaks">, and
4550 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4551 rest are described below.
4555 These seven fields are used to declare a dependency
4556 relationship by one package on another. Except for
4557 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4558 depending (binary) package's control file.
4559 (<tt>Enhances</tt> appears in the recommending package's
4560 control file, and <tt>Breaks</tt> appears in the version of
4561 depended-on package which causes the named package to
4566 A <tt>Depends</tt> field takes effect <em>only</em> when a
4567 package is to be configured. It does not prevent a package
4568 being on the system in an unconfigured state while its
4569 dependencies are unsatisfied, and it is possible to replace
4570 a package whose dependencies are satisfied and which is
4571 properly installed with a different version whose
4572 dependencies are not and cannot be satisfied; when this is
4573 done the depending package will be left unconfigured (since
4574 attempts to configure it will give errors) and will not
4575 function properly. If it is necessary, a
4576 <tt>Pre-Depends</tt> field can be used, which has a partial
4577 effect even when a package is being unpacked, as explained
4578 in detail below. (The other three dependency fields,
4579 <tt>Recommends</tt>, <tt>Suggests</tt> and
4580 <tt>Enhances</tt>, are only used by the various front-ends
4581 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4582 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4586 For this reason packages in an installation run are usually
4587 all unpacked first and all configured later; this gives
4588 later versions of packages with dependencies on later
4589 versions of other packages the opportunity to have their
4590 dependencies satisfied.
4594 In case of circular dependencies, since installation or
4595 removal order honoring the dependency order can't be
4596 established, dependency loops are broken at some point
4597 (based on rules below), and some packages may not be able to
4598 rely on their dependencies being present when being
4599 installed or removed, depending on which side of the break
4600 of the circular dependency loop they happen to be on. If one
4601 of the packages in the loop has no postinst script, then the
4602 cycle will be broken at that package, so as to ensure that
4603 all postinst scripts run with the dependencies properly
4604 configured if this is possible. Otherwise the breaking point
4609 The <tt>Depends</tt> field thus allows package maintainers
4610 to impose an order in which packages should be configured.
4614 The meaning of the five dependency fields is as follows:
4616 <tag><tt>Depends</tt></tag>
4619 This declares an absolute dependency. A package will
4620 not be configured unless all of the packages listed in
4621 its <tt>Depends</tt> field have been correctly
4626 The <tt>Depends</tt> field should be used if the
4627 depended-on package is required for the depending
4628 package to provide a significant amount of
4633 The <tt>Depends</tt> field should also be used if the
4634 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4635 <prgn>postrm</prgn> scripts require the package to be
4636 present in order to run. Note, however, that the
4637 <prgn>postrm</prgn> cannot rely on any non-essential
4638 packages to be present during the <tt>purge</tt>
4642 <tag><tt>Recommends</tt></tag>
4645 This declares a strong, but not absolute, dependency.
4649 The <tt>Recommends</tt> field should list packages
4650 that would be found together with this one in all but
4651 unusual installations.
4655 <tag><tt>Suggests</tt></tag>
4657 This is used to declare that one package may be more
4658 useful with one or more others. Using this field
4659 tells the packaging system and the user that the
4660 listed packages are related to this one and can
4661 perhaps enhance its usefulness, but that installing
4662 this one without them is perfectly reasonable.
4665 <tag><tt>Enhances</tt></tag>
4667 This field is similar to Suggests but works in the
4668 opposite direction. It is used to declare that a
4669 package can enhance the functionality of another
4673 <tag><tt>Pre-Depends</tt></tag>
4676 This field is like <tt>Depends</tt>, except that it
4677 also forces <prgn>dpkg</prgn> to complete installation
4678 of the packages named before even starting the
4679 installation of the package which declares the
4680 pre-dependency, as follows:
4684 When a package declaring a pre-dependency is about to
4685 be <em>unpacked</em> the pre-dependency can be
4686 satisfied if the depended-on package is either fully
4687 configured, <em>or even if</em> the depended-on
4688 package(s) are only unpacked or in the "Half-Configured"
4689 state, provided that they have been configured
4690 correctly at some point in the past (and not removed
4691 or partially removed since). In this case, both the
4692 previously-configured and currently unpacked or
4693 "Half-Configured" versions must satisfy any version
4694 clause in the <tt>Pre-Depends</tt> field.
4698 When the package declaring a pre-dependency is about
4699 to be <em>configured</em>, the pre-dependency will be
4700 treated as a normal <tt>Depends</tt>, that is, it will
4701 be considered satisfied only if the depended-on
4702 package has been correctly configured.
4706 <tt>Pre-Depends</tt> should be used sparingly,
4707 preferably only by packages whose premature upgrade or
4708 installation would hamper the ability of the system to
4709 continue with any upgrade that might be in progress.
4713 <tt>Pre-Depends</tt> are also required if the
4714 <prgn>preinst</prgn> script depends on the named
4715 package. It is best to avoid this situation if
4723 When selecting which level of dependency to use you should
4724 consider how important the depended-on package is to the
4725 functionality of the one declaring the dependency. Some
4726 packages are composed of components of varying degrees of
4727 importance. Such a package should list using
4728 <tt>Depends</tt> the package(s) which are required by the
4729 more important components. The other components'
4730 requirements may be mentioned as Suggestions or
4731 Recommendations, as appropriate to the components' relative
4737 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4740 When one binary package declares that it breaks another,
4741 <prgn>dpkg</prgn> will refuse to allow the package which
4742 declares <tt>Breaks</tt> be installed unless the broken
4743 package is deconfigured first, and it will refuse to
4744 allow the broken package to be reconfigured.
4748 A package will not be regarded as causing breakage merely
4749 because its configuration files are still installed; it must
4750 be at least "Half-Installed".
4754 A special exception is made for packages which declare that
4755 they break their own package name or a virtual package which
4756 they provide (see below): this does not count as a real
4761 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4762 version clause; such a <tt>Breaks</tt> is introduced in the
4763 version of an (implicit or explicit) dependency which violates
4764 an assumption or reveals a bug in earlier versions of the broken
4765 package, or which takes over a file from earlier versions of the
4766 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4767 will inform higher-level package management tools that the
4768 broken package must be upgraded before the new one.
4772 If the breaking package also overwrites some files from the
4773 older package, it should use <tt>Replaces</tt> to ensure this
4774 goes smoothly. See <ref id="replaces"> for a full discussion
4775 of taking over files from other packages, including how to
4776 use <tt>Breaks</tt> in those cases.
4780 Many of the cases where <tt>Breaks</tt> should be used were
4781 previously handled with <tt>Conflicts</tt>
4782 because <tt>Breaks</tt> did not yet exist.
4783 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4784 See <ref id="conflicts"> for more information about the
4789 <sect id="conflicts">
4790 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4793 When one binary package declares a conflict with another
4794 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4795 refuse to allow them to be installed on the system at the
4796 same time. This is a stronger restriction than <tt>Breaks</tt>,
4797 which just prevents both packages from being configured at the
4798 same time. Conflicting packages cannot be unpacked on the
4799 system at the same time.
4803 If one package is to be installed, the other must be removed
4804 first. If the package being installed is marked as replacing
4805 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4806 normally be used in this case) the one on the system, or the one
4807 on the system is marked as deselected, or both packages are
4808 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4809 automatically remove the package which is causing the conflict.
4810 Otherwise, it will halt the installation of the new package with
4811 an error. This mechanism is specifically designed to produce an
4812 error when the installed package is <tt>Essential</tt>, but the
4817 A package will not cause a conflict merely because its
4818 configuration files are still installed; it must be at least
4823 A special exception is made for packages which declare a
4824 conflict with their own package name, or with a virtual
4825 package which they provide (see below): this does not
4826 prevent their installation, and allows a package to conflict
4827 with others providing a replacement for it. You use this
4828 feature when you want the package in question to be the only
4829 package providing some feature.
4833 Normally, <tt>Breaks</tt> should be used instead
4834 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4835 stronger restriction on the ordering of package installation or
4836 upgrade and can make it more difficult for the package manager
4837 to find a correct solution to an upgrade or installation
4838 problem. <tt>Breaks</tt> should be used
4840 <item>when moving a file from one package to another (see
4841 <ref id="replaces">),</item>
4842 <item>when splitting a package (a special case of the previous
4844 <item>when the breaking package exposes a bug in or interacts
4845 badly with particular versions of the broken
4848 <tt>Conflicts</tt> should be used
4850 <item>when two packages provide the same file and will
4851 continue to do so,</item>
4852 <item>in conjunction with <tt>Provides</tt> when only one
4853 package providing a given virtual facility may be installed
4854 at a time (see <ref id="virtual">),</item>
4855 <item>in other cases where one must prevent simultaneous
4856 installation of two packages for reasons that are ongoing
4857 (not fixed in a later version of one of the packages) or
4858 that must prevent both packages from being unpacked at the
4859 same time, not just configured.</item>
4861 Be aware that adding <tt>Conflicts</tt> is normally not the best
4862 solution when two packages provide the same files. Depending on
4863 the reason for that conflict, using alternatives or renaming the
4864 files is often a better approach. See, for
4865 example, <ref id="binaries">.
4869 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4870 unless two packages cannot be installed at the same time or
4871 installing them both causes one of them to be broken or
4872 unusable. Having similar functionality or performing the same
4873 tasks as another package is not sufficient reason to
4874 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4878 A <tt>Conflicts</tt> entry may have an "earlier than" version
4879 clause if the reason for the conflict is corrected in a later
4880 version of one of the packages. However, normally the presence
4881 of an "earlier than" version clause is a sign
4882 that <tt>Breaks</tt> should have been used instead. An "earlier
4883 than" version clause in <tt>Conflicts</tt>
4884 prevents <prgn>dpkg</prgn> from upgrading or installing the
4885 package which declares such a conflict until the upgrade or
4886 removal of the conflicted-with package has been completed, which
4887 is a strong restriction.
4891 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4895 As well as the names of actual ("concrete") packages, the
4896 package relationship fields <tt>Depends</tt>,
4897 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4898 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4899 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4900 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4901 may mention "virtual packages".
4905 A <em>virtual package</em> is one which appears in the
4906 <tt>Provides</tt> control field of another package. The effect
4907 is as if the package(s) which provide a particular virtual
4908 package name had been listed by name everywhere the virtual
4909 package name appears. (See also <ref id="virtual_pkg">)
4913 If there are both concrete and virtual packages of the same
4914 name, then the dependency may be satisfied (or the conflict
4915 caused) by either the concrete package with the name in
4916 question or any other concrete package which provides the
4917 virtual package with the name in question. This is so that,
4918 for example, supposing we have
4919 <example compact="compact">
4922 </example> and someone else releases an enhanced version of
4923 the <tt>bar</tt> package they can say:
4924 <example compact="compact">
4928 and the <tt>bar-plus</tt> package will now also satisfy the
4929 dependency for the <tt>foo</tt> package.
4933 If a relationship field has a version number attached, only real
4934 packages will be considered to see whether the relationship is
4935 satisfied (or the prohibition violated, for a conflict or
4936 breakage). In other words, if a version number is specified,
4937 this is a request to ignore all <tt>Provides</tt> for that
4938 package name and consider only real packages. The package
4939 manager will assume that a package providing that virtual
4940 package is not of the "right" version. A <tt>Provides</tt>
4941 field may not contain version numbers, and the version number of
4942 the concrete package which provides a particular virtual package
4943 will not be considered when considering a dependency on or
4944 conflict with the virtual package name.<footnote>
4945 It is possible that a future release of <prgn>dpkg</prgn> may
4946 add the ability to specify a version number for each virtual
4947 package it provides. This feature is not yet present,
4948 however, and is expected to be used only infrequently.
4953 To specify which of a set of real packages should be the default
4954 to satisfy a particular dependency on a virtual package, list
4955 the real package as an alternative before the virtual one.
4959 If the virtual package represents a facility that can only be
4960 provided by one real package at a time, such as
4961 the <package>mail-transport-agent</package> virtual package that
4962 requires installation of a binary that would conflict with all
4963 other providers of that virtual package (see
4964 <ref id="mail-transport-agents">), all packages providing that
4965 virtual package should also declare a conflict with it
4966 using <tt>Conflicts</tt>. This will ensure that at most one
4967 provider of that virtual package is unpacked or installed at a
4972 <sect id="replaces"><heading>Overwriting files and replacing
4973 packages - <tt>Replaces</tt></heading>
4976 Packages can declare in their control file that they should
4977 overwrite files in certain other packages, or completely replace
4978 other packages. The <tt>Replaces</tt> control field has these
4979 two distinct purposes.
4982 <sect1><heading>Overwriting files in other packages</heading>
4985 It is usually an error for a package to contain files which
4986 are on the system in another package. However, if the
4987 overwriting package declares that it <tt>Replaces</tt> the one
4988 containing the file being overwritten, then <prgn>dpkg</prgn>
4989 will replace the file from the old package with that from the
4990 new. The file will no longer be listed as "owned" by the old
4991 package and will be taken over by the new package.
4992 Normally, <tt>Breaks</tt> should be used in conjunction
4993 with <tt>Replaces</tt>.<footnote>
4994 To see why <tt>Breaks</tt> is normally needed in addition
4995 to <tt>Replaces</tt>, consider the case of a file in the
4996 package <package>foo</package> being taken over by the
4997 package <package>foo-data</package>.
4998 <tt>Replaces</tt> will allow <package>foo-data</package> to
4999 be installed and take over that file. However,
5000 without <tt>Breaks</tt>, nothing
5001 requires <package>foo</package> to be upgraded to a newer
5002 version that knows it does not include that file and instead
5003 depends on <package>foo-data</package>. Nothing would
5004 prevent the new <package>foo-data</package> package from
5005 being installed and then removed, removing the file that it
5006 took over from <package>foo</package>. After that
5007 operation, the package manager would think the system was in
5008 a consistent state, but the <package>foo</package> package
5009 would be missing one of its files.
5014 For example, if a package <package>foo</package> is split
5015 into <package>foo</package> and <package>foo-data</package>
5016 starting at version 1.2-3, <package>foo-data</package> would
5018 <example compact="compact">
5019 Replaces: foo (<< 1.2-3)
5020 Breaks: foo (<< 1.2-3)
5022 in its control file. The new version of the
5023 package <package>foo</package> would normally have the field
5024 <example compact="compact">
5025 Depends: foo-data (>= 1.2-3)
5027 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5028 the files moved into <package>foo-data</package> are not
5029 required for normal operation).
5033 If a package is completely replaced in this way, so that
5034 <prgn>dpkg</prgn> does not know of any files it still
5035 contains, it is considered to have "disappeared". It will
5036 be marked as not wanted on the system (selected for
5037 removal) and not installed. Any <tt>conffile</tt>s
5038 details noted for the package will be ignored, as they
5039 will have been taken over by the overwriting package. The
5040 package's <prgn>postrm</prgn> script will be run with a
5041 special argument to allow the package to do any final
5042 cleanup required. See <ref id="mscriptsinstact">.
5044 Replaces is a one way relationship. You have to install
5045 the replacing package after the replaced package.
5050 For this usage of <tt>Replaces</tt>, virtual packages (see
5051 <ref id="virtual">) are not considered when looking at a
5052 <tt>Replaces</tt> field. The packages declared as being
5053 replaced must be mentioned by their real names.
5057 This usage of <tt>Replaces</tt> only takes effect when both
5058 packages are at least partially on the system at once. It is
5059 not relevant if the packages conflict unless the conflict has
5064 <sect1><heading>Replacing whole packages, forcing their
5068 Second, <tt>Replaces</tt> allows the packaging system to
5069 resolve which package should be removed when there is a
5070 conflict (see <ref id="conflicts">). This usage only takes
5071 effect when the two packages <em>do</em> conflict, so that the
5072 two usages of this field do not interfere with each other.
5076 In this situation, the package declared as being replaced
5077 can be a virtual package, so for example, all mail
5078 transport agents (MTAs) would have the following fields in
5079 their control files:
5080 <example compact="compact">
5081 Provides: mail-transport-agent
5082 Conflicts: mail-transport-agent
5083 Replaces: mail-transport-agent
5085 ensuring that only one MTA can be installed at any one
5086 time. See <ref id="virtual"> for more information about this
5091 <sect id="sourcebinarydeps">
5092 <heading>Relationships between source and binary packages -
5093 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5094 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5098 Source packages that require certain binary packages to be
5099 installed or absent at the time of building the package
5100 can declare relationships to those binary packages.
5104 This is done using the <tt>Build-Depends</tt>,
5105 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5106 <tt>Build-Conflicts-Indep</tt> control fields.
5110 Build-dependencies on "build-essential" binary packages can be
5111 omitted. Please see <ref id="pkg-relations"> for more information.
5115 The dependencies and conflicts they define must be satisfied
5116 (as defined earlier for binary packages) in order to invoke
5117 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5119 There is no Build-Depends-Arch; this role is essentially
5120 met with Build-Depends. Anyone building the
5121 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5122 assumed to be building the whole package, and therefore
5123 installation of all build dependencies is required.
5126 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5127 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5128 not yet know how to check for its existence, and
5129 <tt>binary-arch</tt>. The purpose of the original split
5130 between <tt>Build-Depends</tt> and
5131 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5132 wouldn't need to install extra packages needed only for the
5133 binary-indep targets. But without a build-arch/build-indep
5134 split, this didn't work, since most of the work is done in
5135 the build target, not in the binary target.
5139 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5140 <tt>binary-arch</tt></tag>
5142 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5143 fields must be satisfied when these targets are invoked.
5145 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5146 and <tt>binary-indep</tt></tag>
5148 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5149 <tt>Build-Depends-Indep</tt>, and
5150 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5151 these targets are invoked.
5159 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5162 Packages containing shared libraries must be constructed with
5163 a little care to make sure that the shared library is always
5164 available. This is especially important for packages whose
5165 shared libraries are vitally important, such as the C library
5166 (currently <tt>libc6</tt>).
5170 This section deals only with public shared libraries: shared
5171 libraries that are placed in directories searched by the dynamic
5172 linker by default or which are intended to be linked against
5173 normally and possibly used by other, independent packages. Shared
5174 libraries that are internal to a particular package or that are
5175 only loaded as dynamic modules are not covered by this section and
5176 are not subject to its requirements.
5180 A shared library is identified by the <tt>SONAME</tt> attribute
5181 stored in its dynamic section. When a binary is linked against a
5182 shared library, the <tt>SONAME</tt> of the shared library is
5183 recorded in the binary's <tt>NEEDED</tt> section so that the
5184 dynamic linker knows that library must be loaded at runtime. The
5185 shared library file's full name (which usually contains additional
5186 version information not needed in the <tt>SONAME</tt>) is
5187 therefore normally not referenced directly. Instead, the shared
5188 library is loaded by its <tt>SONAME</tt>, which exists on the file
5189 system as a symlink pointing to the full name of the shared
5190 library. This symlink must be provided by the
5191 package. <ref id="sharedlibs-runtime"> describes how to do this.
5193 This is a convention of shared library versioning, but not a
5194 requirement. Some libraries use the <tt>SONAME</tt> as the full
5195 library file name instead and therefore do not need a symlink.
5196 Most, however, encode additional information about
5197 backwards-compatible revisions as a minor version number in the
5198 file name. The <tt>SONAME</tt> itself only changes when
5199 binaries linked with the earlier version of the shared library
5200 may no longer work, but the filename may change with each
5201 release of the library. See <ref id="sharedlibs-runtime"> for
5207 When linking a binary or another shared library against a shared
5208 library, the <tt>SONAME</tt> for that shared library is not yet
5209 known. Instead, the shared library is found by looking for a file
5210 matching the library name with <tt>.so</tt> appended. This file
5211 exists on the file system as a symlink pointing to the shared
5216 Shared libraries are normally split into several binary packages.
5217 The <tt>SONAME</tt> symlink is installed by the runtime shared
5218 library package, and the bare <tt>.so</tt> symlink is installed in
5219 the development package since it's only used when linking binaries
5220 or shared libraries. However, there are some exceptions for
5221 unusual shared libraries or for shared libraries that are also
5222 loaded as dynamic modules by other programs.
5226 This section is primarily concerned with how the separation of
5227 shared libraries into multiple packages should be done and how
5228 dependencies on and between shared library binary packages are
5229 managed in Debian. <ref id="libraries"> should be read in
5230 conjunction with this section and contains additional rules for
5231 the files contained in the shared library packages.
5234 <sect id="sharedlibs-runtime">
5235 <heading>Run-time shared libraries</heading>
5238 The run-time shared library must be placed in a package
5239 whose name changes whenever the <tt>SONAME</tt> of the shared
5240 library changes. This allows several versions of the shared
5241 library to be installed at the same time, allowing installation
5242 of the new version of the shared library without immediately
5243 breaking binaries that depend on the old version. Normally, the
5244 run-time shared library and its <tt>SONAME</tt> symlink should
5245 be placed in a package named
5246 <package><var>libraryname</var><var>soversion</var></package>,
5247 where <var>soversion</var> is the version number in
5248 the <tt>SONAME</tt> of the shared library.
5249 See <ref id="shlibs"> for detailed information on how to
5250 determine this version. Alternatively, if it would be confusing
5251 to directly append <var>soversion</var>
5252 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5253 itself ends in a number), you should use
5254 <package><var>libraryname</var>-<var>soversion</var></package>
5259 If you have several shared libraries built from the same source
5260 tree, you may lump them all together into a single shared
5261 library package provided that all of their <tt>SONAME</tt>s will
5262 always change together. Be aware that this is not normally the
5263 case, and if the <tt>SONAME</tt>s do not change together,
5264 upgrading such a merged shared library package will be
5265 unnecessarily difficult because of file conflicts with the old
5266 version of the package. When in doubt, always split shared
5267 library packages so that each binary package installs a single
5272 Every time the shared library ABI changes in a way that may
5273 break binaries linked against older versions of the shared
5274 library, the <tt>SONAME</tt> of the library and the
5275 corresponding name for the binary package containing the runtime
5276 shared library should change. Normally, this means
5277 the <tt>SONAME</tt> should change any time an interface is
5278 removed from the shared library or the signature of an interface
5279 (the number of parameters or the types of parameters that it
5280 takes, for example) is changed. This practice is vital to
5281 allowing clean upgrades from older versions of the package and
5282 clean transitions between the old ABI and new ABI without having
5283 to upgrade every affected package simultaneously.
5287 The <tt>SONAME</tt> and binary package name need not, and indeed
5288 normally should not, change if new interfaces are added but none
5289 are removed or changed, since this will not break binaries
5290 linked against the old shared library. Correct versioning of
5291 dependencies on the newer shared library by binaries that use
5292 the new interfaces is handled via
5293 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5294 system</qref> or via symbols files (see
5295 <manref name="deb-symbols" section="5">).
5299 The package should install the shared libraries under
5300 their normal names. For example, the <package>libgdbm3</package>
5301 package should install <file>libgdbm.so.3.0.0</file> as
5302 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5303 renamed or re-linked by any <prgn>prerm</prgn> or
5304 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5305 of renaming things safely without affecting running programs,
5306 and attempts to interfere with this are likely to lead to
5311 Shared libraries should not be installed executable, since
5312 the dynamic linker does not require this and trying to
5313 execute a shared library usually results in a core dump.
5317 The run-time library package should include the symbolic link for
5318 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5319 the shared libraries. For example,
5320 the <package>libgdbm3</package> package should include a symbolic
5321 link from <file>/usr/lib/libgdbm.so.3</file> to
5322 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5323 linker (for example <prgn>ld.so</prgn> or
5324 <prgn>ld-linux.so.*</prgn>) can find the library between the
5325 time that <prgn>dpkg</prgn> installs it and the time that
5326 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5328 The package management system requires the library to be
5329 placed before the symbolic link pointing to it in the
5330 <file>.deb</file> file. This is so that when
5331 <prgn>dpkg</prgn> comes to install the symlink
5332 (overwriting the previous symlink pointing at an older
5333 version of the library), the new shared library is already
5334 in place. In the past, this was achieved by creating the
5335 library in the temporary packaging directory before
5336 creating the symlink. Unfortunately, this was not always
5337 effective, since the building of the tar file in the
5338 <file>.deb</file> depended on the behavior of the underlying
5339 file system. Some file systems (such as reiserfs) reorder
5340 the files so that the order of creation is forgotten.
5341 Since version 1.7.0, <prgn>dpkg</prgn>
5342 reorders the files itself as necessary when building a
5343 package. Thus it is no longer important to concern
5344 oneself with the order of file creation.
5348 <sect1 id="ldconfig">
5349 <heading><tt>ldconfig</tt></heading>
5352 Any package installing shared libraries in one of the default
5353 library directories of the dynamic linker (which are currently
5354 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5355 listed in <file>/etc/ld.so.conf</file><footnote>
5357 <list compact="compact">
5358 <item>/usr/local/lib</item>
5359 <item>/usr/lib/libc5-compat</item>
5360 <item>/lib/libc5-compat</item>
5363 must use <prgn>ldconfig</prgn> to update the shared library
5368 The package maintainer scripts must only call
5369 <prgn>ldconfig</prgn> under these circumstances:
5370 <list compact="compact">
5371 <item>When the <prgn>postinst</prgn> script is run with a
5372 first argument of <tt>configure</tt>, the script must call
5373 <prgn>ldconfig</prgn>, and may optionally invoke
5374 <prgn>ldconfig</prgn> at other times.
5376 <item>When the <prgn>postrm</prgn> script is run with a
5377 first argument of <tt>remove</tt>, the script should call
5378 <prgn>ldconfig</prgn>.
5383 During install or upgrade, the preinst is called before
5384 the new files are installed, so calling "ldconfig" is
5385 pointless. The preinst of an existing package can also be
5386 called if an upgrade fails. However, this happens during
5387 the critical time when a shared libs may exist on-disk
5388 under a temporary name. Thus, it is dangerous and
5389 forbidden by current policy to call "ldconfig" at this
5394 When a package is installed or upgraded, "postinst
5395 configure" runs after the new files are safely on-disk.
5396 Since it is perfectly safe to invoke ldconfig
5397 unconditionally in a postinst, it is OK for a package to
5398 simply put ldconfig in its postinst without checking the
5399 argument. The postinst can also be called to recover from
5400 a failed upgrade. This happens before any new files are
5401 unpacked, so there is no reason to call "ldconfig" at this
5406 For a package that is being removed, prerm is
5407 called with all the files intact, so calling ldconfig is
5408 useless. The other calls to "prerm" happen in the case of
5409 upgrade at a time when all the files of the old package
5410 are on-disk, so again calling "ldconfig" is pointless.
5414 postrm, on the other hand, is called with the "remove"
5415 argument just after the files are removed, so this is
5416 the proper time to call "ldconfig" to notify the system
5417 of the fact that the shared libraries from the package
5418 are removed. The postrm can be called at several other
5419 times. At the time of "postrm purge", "postrm
5420 abort-install", or "postrm abort-upgrade", calling
5421 "ldconfig" is useless because the shared lib files are
5422 not on-disk. However, when "postrm" is invoked with
5423 arguments "upgrade", "failed-upgrade", or "disappear", a
5424 shared lib may exist on-disk under a temporary filename.
5432 <sect id="sharedlibs-support-files">
5433 <heading>Shared library support files</heading>
5436 If your package contains files whose names do not change with
5437 each change in the library shared object version, you must not
5438 put them in the shared library package. Otherwise, several
5439 versions of the shared library cannot be installed at the same
5440 time without filename clashes, making upgrades and transitions
5441 unnecessarily difficult.
5445 It is recommended that supporting files and run-time support
5446 programs that do not need to be invoked manually by users, but
5447 are nevertheless required for the package to function, be placed
5448 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5449 preferably under <file>/usr/lib/</file><var>package-name</var>.
5450 If the program or file is architecture independent, the
5451 recommendation is for it to be placed in a subdirectory of
5452 <file>/usr/share</file> instead, preferably under
5453 <file>/usr/share/</file><var>package-name</var>. Following the
5454 <var>package-name</var> naming convention ensures that the file
5455 names change when the shared object version changes.
5459 Run-time support programs that use the shared library but are
5460 not required for the library to function or files used by the
5461 shared library that can be used by any version of the shared
5462 library package should instead be put in a separate package.
5463 This package might typically be named
5464 <package><var>libraryname</var>-tools</package>; note the
5465 absence of the <var>soversion</var> in the package name.
5469 Files and support programs only useful when compiling software
5470 against the library should be included in the development
5471 package for the library.<footnote>
5472 For example, a <file><var>package-name</var>-config</file>
5473 script or <package>pkg-config</package> configuration files.
5478 <sect id="sharedlibs-static">
5479 <heading>Static libraries</heading>
5482 The static library (<file><var>libraryname.a</var></file>)
5483 is usually provided in addition to the shared version.
5484 It is placed into the development package (see below).
5488 In some cases, it is acceptable for a library to be
5489 available in static form only; these cases include:
5491 <item>libraries for languages whose shared library support
5492 is immature or unstable</item>
5493 <item>libraries whose interfaces are in flux or under
5494 development (commonly the case when the library's
5495 major version number is zero, or where the ABI breaks
5496 across patchlevels)</item>
5497 <item>libraries which are explicitly intended to be
5498 available only in static form by their upstream
5503 <sect id="sharedlibs-dev">
5504 <heading>Development files</heading>
5507 If there are development files associated with a shared library,
5508 the source package needs to generate a binary development package
5509 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5510 or if you prefer only to support one development version at a
5511 time, <package><var>libraryname</var>-dev</package>. Installing
5512 the development package must result in installation of all the
5513 development files necessary for compiling programs against that
5514 shared library.<footnote>
5515 This wording allows the development files to be split into
5516 several packages, such as a separate architecture-independent
5517 <package><var>libraryname</var>-headers</package>, provided that
5518 the development package depends on all the required additional
5524 In case several development versions of a library exist, you may
5525 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5526 <ref id="conflicts">) to ensure that the user only installs one
5527 development version at a time (as different development versions are
5528 likely to have the same header files in them, which would cause a
5529 filename clash if both were installed).
5533 The development package should contain a symlink for the associated
5534 shared library without a version number. For example, the
5535 <package>libgdbm-dev</package> package should include a symlink
5536 from <file>/usr/lib/libgdbm.so</file> to
5537 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5538 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5539 <file>libgdbm.so</file> when compiling dynamically.
5543 If the package provides Ada Library Information
5544 (<file>*.ali</file>) files for use with GNAT, these files must be
5545 installed read-only (mode 0444) so that GNAT will not attempt to
5546 recompile them. This overrides the normal file mode requirements
5547 given in <ref id="permissions-owners">.
5551 <sect id="sharedlibs-intradeps">
5552 <heading>Dependencies between the packages of the same library</heading>
5555 Typically the development version should have an exact
5556 version dependency on the runtime library, to make sure that
5557 compilation and linking happens correctly. The
5558 <tt>${binary:Version}</tt> substitution variable can be
5559 useful for this purpose.
5561 Previously, <tt>${Source-Version}</tt> was used, but its name
5562 was confusing and it has been deprecated since dpkg 1.13.19.
5567 <sect id="sharedlibs-shlibdeps">
5568 <heading>Dependencies between the library and other packages -
5569 the <tt>shlibs</tt> system</heading>
5572 If a package contains a binary or library which links to a
5573 shared library, we must ensure that when the package is
5574 installed on the system, all of the libraries needed are
5575 also installed. This requirement led to the creation of the
5576 <tt>shlibs</tt> system, which is very simple in its design:
5577 any package which <em>provides</em> a shared library also
5578 provides information on the package dependencies required to
5579 ensure the presence of this library, and any package which
5580 <em>uses</em> a shared library uses this information to
5581 determine the dependencies it requires. The files which
5582 contain the mapping from shared libraries to the necessary
5583 dependency information are called <file>shlibs</file> files.
5587 When a package is built which contains any shared libraries, it
5588 must provide a <file>shlibs</file> file for other packages to
5589 use. When a package is built which contains any shared
5590 libraries or compiled binaries, it must run
5591 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5592 on these to determine the libraries used and hence the
5593 dependencies needed by this package.<footnote>
5595 <prgn>dpkg-shlibdeps</prgn> will use a program
5596 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5597 the libraries directly needed by the binaries or shared
5598 libraries in the package.
5602 We say that a binary <tt>foo</tt> <em>directly</em> uses
5603 a library <tt>libbar</tt> if it is explicitly linked
5604 with that library (that is, the library is listed in the ELF
5605 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5606 to the link line when the binary is created). Other
5607 libraries that are needed by <tt>libbar</tt> are linked
5608 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5609 linker will load them automatically when it loads
5610 <tt>libbar</tt>. A package should depend on the libraries
5611 it directly uses, but not the libraries it indirectly uses.
5612 The dependencies for those libraries will automatically pull
5613 in the other libraries.
5617 A good example of where this helps is the following. We
5618 could update <tt>libimlib</tt> with a new version that
5619 supports a new graphics format called dgf (but retaining the
5620 same major version number) and depends on <tt>libdgf</tt>.
5621 If we used <prgn>ldd</prgn> to add dependencies for every
5622 library directly or indirectly linked with a binary, every
5623 package that uses <tt>libimlib</tt> would need to be
5624 recompiled so it would also depend on <tt>libdgf</tt> or it
5625 wouldn't run due to missing symbols. Since dependencies are
5626 only added based on ELF <tt>NEEDED</tt> attribute, packages
5627 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5628 having the dependency on <tt>libdgf</tt> and so they would
5629 not need rebuilding.
5635 In the following sections, we will first describe where the
5636 various <tt>shlibs</tt> files are to be found, then how to
5637 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5638 file format and how to create them if your package contains a
5643 <heading>The <tt>shlibs</tt> files present on the system</heading>
5646 There are several places where <tt>shlibs</tt> files are
5647 found. The following list gives them in the order in which
5649 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5650 (The first one which gives the required information is used.)
5656 <p><file>debian/shlibs.local</file></p>
5659 This lists overrides for this package. This file should
5660 normally not be used, but may be needed temporarily in
5661 unusual situations to work around bugs in other packages,
5662 or in unusual cases where the normally declared dependency
5663 information in the installed <file>shlibs</file> file for
5664 a library cannot be used. This file overrides information
5665 obtained from any other source.
5670 <p><file>/etc/dpkg/shlibs.override</file></p>
5673 This lists global overrides. This list is normally
5674 empty. It is maintained by the local system
5680 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5683 When packages are being built,
5684 any <file>debian/shlibs</file> files are copied into the
5685 control information file area of the temporary build
5686 directory and given the name <file>shlibs</file>. These
5687 files give details of any shared libraries included in the
5688 same package.<footnote>
5689 An example may help here. Let us say that the source
5690 package <tt>foo</tt> generates two binary
5691 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5692 When building the binary packages, the two packages are
5693 created in the directories <file>debian/libfoo2</file>
5694 and <file>debian/foo-runtime</file> respectively.
5695 (<file>debian/tmp</file> could be used instead of one of
5696 these.) Since <tt>libfoo2</tt> provides the
5697 <tt>libfoo</tt> shared library, it will require a
5698 <tt>shlibs</tt> file, which will be installed in
5699 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5700 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5701 When <prgn>dpkg-shlibdeps</prgn> is run on the
5702 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5704 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5705 determine whether <tt>foo-prog</tt>'s library
5706 dependencies are satisfied by any of the libraries
5707 provided by <tt>libfoo2</tt>. For this reason,
5708 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5709 the individual binary packages' <tt>shlibs</tt> files
5710 have been installed into the build directory.
5716 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5719 These are the <file>shlibs</file> files corresponding to
5720 all of the packages installed on the system, and are
5721 maintained by the relevant package maintainers.
5726 <p><file>/etc/dpkg/shlibs.default</file></p>
5729 This file lists any shared libraries whose packages
5730 have failed to provide correct <file>shlibs</file> files.
5731 It was used when the <file>shlibs</file> setup was first
5732 introduced, but it is now normally empty. It is
5733 maintained by the <tt>dpkg</tt> maintainer.
5741 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5742 <file>shlibs</file> files</heading>
5746 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5747 into your <file>debian/rules</file> file. If your package
5748 contains only compiled binaries and libraries (but no scripts),
5749 you can use a command such as:
5750 <example compact="compact">
5751 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5752 debian/tmp/usr/lib/*
5754 Otherwise, you will need to explicitly list the compiled
5755 binaries and libraries.<footnote>
5756 If you are using <tt>debhelper</tt>, the
5757 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5758 It will also correctly handle multi-binary packages.
5763 This command puts the dependency information into the
5764 <file>debian/substvars</file> file, which is then used by
5765 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5766 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5767 field in the control file for this to work.
5771 If you have multiple binary packages, you will need to call
5772 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5773 compiled libraries or binaries. In such a case, you will
5774 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5775 utilities to specify a different <file>substvars</file> file.
5779 If you are creating a udeb for use in the Debian Installer,
5780 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5781 should use the dependency line of type <tt>udeb</tt> by
5782 adding the <tt>-tudeb</tt> option<footnote>
5783 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5784 will automatically add this option if it knows it is
5786 </footnote>. If there is no dependency line of
5787 type <tt>udeb</tt> in the <file>shlibs</file>
5788 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5793 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5794 <ref id="pkg-dpkg-shlibdeps"> and
5795 <manref name="dpkg-shlibdeps" section="1">.
5800 <heading>The <file>shlibs</file> File Format</heading>
5803 Each <file>shlibs</file> file has the same format. Lines
5804 beginning with <tt>#</tt> are considered to be comments and
5805 are ignored. Each line is of the form:
5806 <example compact="compact">
5807 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5812 We will explain this by reference to the example of the
5813 <tt>zlib1g</tt> package, which (at the time of writing)
5814 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5818 <var>type</var> is an optional element that indicates the type
5819 of package for which the line is valid. The only type currently
5820 in use is <tt>udeb</tt>. The colon and space after the type are
5825 <var>library-name</var> is the name of the shared library,
5826 in this case <tt>libz</tt>. (This must match the name part
5827 of the soname, see below.)
5831 <var>soname-version</var> is the version part of the soname of
5832 the library. The soname is the thing that must exactly match
5833 for the library to be recognized by the dynamic linker, and is
5835 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5836 example, <tt>libz.so.1</tt>.<footnote>
5837 This can be determined using the command
5838 <example compact="compact">
5839 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5842 The version part is the part which comes after
5843 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5844 instead be of the form
5845 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5846 as <tt>libdb-4.8.so</tt>, in which case the name would
5847 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5851 <var>dependencies</var> has the same syntax as a dependency
5852 field in a binary package control file. It should give
5853 details of which packages are required to satisfy a binary
5854 built against the version of the library contained in the
5855 package. See <ref id="depsyntax"> for details.
5859 In our example, if the first version of the <tt>zlib1g</tt>
5860 package which contained a minor number of at least
5861 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5862 <tt>shlibs</tt> entry for this library could say:
5863 <example compact="compact">
5864 libz 1 zlib1g (>= 1:1.1.3)
5866 The version-specific dependency is to avoid warnings from
5867 the dynamic linker about using older shared libraries with
5872 As zlib1g also provides a udeb containing the shared library,
5873 there would also be a second line:
5874 <example compact="compact">
5875 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5881 <heading>Providing a <file>shlibs</file> file</heading>
5884 If your package provides a shared library, you need to create
5885 a <file>shlibs</file> file following the format described above.
5886 It is usual to call this file <file>debian/shlibs</file> (but if
5887 you have multiple binary packages, you might want to call it
5888 <file>debian/shlibs.<var>package</var></file> instead). Then
5889 let <file>debian/rules</file> install it in the control
5890 information file area:
5891 <example compact="compact">
5892 install -m644 debian/shlibs debian/tmp/DEBIAN
5894 or, in the case of a multi-binary package:
5895 <example compact="compact">
5896 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5898 An alternative way of doing this is to create the
5899 <file>shlibs</file> file in the control information file area
5900 directly from <file>debian/rules</file> without using
5901 a <file>debian/shlibs</file> file at all,<footnote>
5902 This is what <prgn>dh_makeshlibs</prgn> in
5903 the <package>debhelper</package> suite does. If your package
5904 also has a udeb that provides a shared
5905 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5906 the <tt>udeb:</tt> lines if you specify the name of the udeb
5907 with the <tt>--add-udeb</tt> option.
5909 since the <file>debian/shlibs</file> file itself is ignored by
5910 <prgn>dpkg-shlibdeps</prgn>.
5914 As <prgn>dpkg-shlibdeps</prgn> reads the
5915 <file>DEBIAN/shlibs</file> files in all of the binary packages
5916 being built from this source package, all of the
5917 <file>DEBIAN/shlibs</file> files should be installed before
5918 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5926 <chapt id="opersys"><heading>The Operating System</heading>
5929 <heading>File system hierarchy</heading>
5933 <heading>File System Structure</heading>
5936 The location of all installed files and directories must
5937 comply with the Filesystem Hierarchy Standard (FHS),
5938 version 2.3, with the exceptions noted below, and except
5939 where doing so would violate other terms of Debian
5940 Policy. The following exceptions to the FHS apply:
5945 The optional rules related to user specific
5946 configuration files for applications are stored in
5947 the user's home directory are relaxed. It is
5948 recommended that such files start with the
5949 '<tt>.</tt>' character (a "dot file"), and if an
5950 application needs to create more than one dot file
5951 then the preferred placement is in a subdirectory
5952 with a name starting with a '.' character, (a "dot
5953 directory"). In this case it is recommended the
5954 configuration files not start with the '.'
5960 The requirement for amd64 to use <file>/lib64</file>
5961 for 64 bit binaries is removed.
5966 The requirement for object files, internal binaries, and
5967 libraries, including <file>libc.so.*</file>, to be located
5968 directly under <file>/lib{,32}</file> and
5969 <file>/usr/lib{,32}</file> is amended, permitting files
5970 to instead be installed to
5971 <file>/lib/<var>triplet</var></file> and
5972 <file>/usr/lib/<var>triplet</var></file>, where
5973 <tt><var>triplet</var></tt> is the value returned by
5974 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5975 architecture of the package. Packages may <em>not</em>
5976 install files to any <var>triplet</var> path other
5977 than the one matching the architecture of that package;
5978 for instance, an <tt>Architecture: amd64</tt> package
5979 containing 32-bit x86 libraries may not install these
5980 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5982 This is necessary in order to reserve the directories for
5983 use in cross-installation of library packages from other
5984 architectures, as part of the planned deployment of
5989 Applications may also use a single subdirectory under
5990 <file>/usr/lib/<var>triplet</var></file>.
5993 The execution time linker/loader, ld*, must still be made
5994 available in the existing location under /lib or /lib64
5995 since this is part of the ELF ABI for the architecture.
6000 The requirement that
6001 <file>/usr/local/share/man</file> be "synonymous"
6002 with <file>/usr/local/man</file> is relaxed to a
6007 The requirement that windowmanagers with a single
6008 configuration file call it <file>system.*wmrc</file>
6009 is removed, as is the restriction that the window
6010 manager subdirectory be named identically to the
6011 window manager name itself.
6016 The requirement that boot manager configuration
6017 files live in <file>/etc</file>, or at least are
6018 symlinked there, is relaxed to a recommendation.
6023 The following directories in the root filesystem are
6024 additionally allowed: <file>/sys</file> and
6025 <file>/selinux</file>. <footnote>These directories
6026 are used as mount points to mount virtual filesystems
6027 to get access to kernel information.</footnote>
6034 The version of this document referred here can be
6035 found in the <tt>debian-policy</tt> package or on <url
6036 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6037 name="FHS (Debian copy)"> alongside this manual (or, if
6038 you have the <package>debian-policy</package> installed,
6040 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6041 (local copy)">). The
6042 latest version, which may be a more recent version, may
6044 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6045 Specific questions about following the standard may be
6046 asked on the <tt>debian-devel</tt> mailing list, or
6047 referred to the FHS mailing list (see the
6048 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6054 <heading>Site-specific programs</heading>
6057 As mandated by the FHS, packages must not place any
6058 files in <file>/usr/local</file>, either by putting them in
6059 the file system archive to be unpacked by <prgn>dpkg</prgn>
6060 or by manipulating them in their maintainer scripts.
6064 However, the package may create empty directories below
6065 <file>/usr/local</file> so that the system administrator knows
6066 where to place site-specific files. These are not
6067 directories <em>in</em> <file>/usr/local</file>, but are
6068 children of directories in <file>/usr/local</file>. These
6069 directories (<file>/usr/local/*/dir/</file>)
6070 should be removed on package removal if they are
6075 Note that this applies only to
6076 directories <em>below</em> <file>/usr/local</file>,
6077 not <em>in</em> <file>/usr/local</file>. Packages must
6078 not create sub-directories in the
6079 directory <file>/usr/local</file> itself, except those
6080 listed in FHS, section 4.5. However, you may create
6081 directories below them as you wish. You must not remove
6082 any of the directories listed in 4.5, even if you created
6087 Since <file>/usr/local</file> can be mounted read-only from a
6088 remote server, these directories must be created and
6089 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6090 maintainer scripts and not be included in the
6091 <file>.deb</file> archive. These scripts must not fail if
6092 either of these operations fail.
6096 For example, the <tt>emacsen-common</tt> package could
6097 contain something like
6098 <example compact="compact">
6099 if [ ! -e /usr/local/share/emacs ]
6101 if mkdir /usr/local/share/emacs 2>/dev/null
6103 chown root:staff /usr/local/share/emacs
6104 chmod 2775 /usr/local/share/emacs
6108 in its <prgn>postinst</prgn> script, and
6109 <example compact="compact">
6110 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6111 rmdir /usr/local/share/emacs 2>/dev/null || true
6113 in the <prgn>prerm</prgn> script. (Note that this form is
6114 used to ensure that if the script is interrupted, the
6115 directory <file>/usr/local/share/emacs</file> will still be
6120 If you do create a directory in <file>/usr/local</file> for
6121 local additions to a package, you should ensure that
6122 settings in <file>/usr/local</file> take precedence over the
6123 equivalents in <file>/usr</file>.
6127 However, because <file>/usr/local</file> and its contents are
6128 for exclusive use of the local administrator, a package
6129 must not rely on the presence or absence of files or
6130 directories in <file>/usr/local</file> for normal operation.
6134 The <file>/usr/local</file> directory itself and all the
6135 subdirectories created by the package should (by default) have
6136 permissions 2775 (group-writable and set-group-id) and be
6137 owned by <tt>root:staff</tt>.
6142 <heading>The system-wide mail directory</heading>
6144 The system-wide mail directory
6145 is <file>/var/mail</file>. This directory is part of the
6146 base system and should not be owned by any particular mail
6147 agents. The use of the old
6148 location <file>/var/spool/mail</file> is deprecated, even
6149 though the spool may still be physically located there.
6155 <heading>Users and groups</heading>
6158 <heading>Introduction</heading>
6160 The Debian system can be configured to use either plain or
6165 Some user ids (UIDs) and group ids (GIDs) are reserved
6166 globally for use by certain packages. Because some
6167 packages need to include files which are owned by these
6168 users or groups, or need the ids compiled into binaries,
6169 these ids must be used on any Debian system only for the
6170 purpose for which they are allocated. This is a serious
6171 restriction, and we should avoid getting in the way of
6172 local administration policies. In particular, many sites
6173 allocate users and/or local system groups starting at 100.
6177 Apart from this we should have dynamically allocated ids,
6178 which should by default be arranged in some sensible
6179 order, but the behavior should be configurable.
6183 Packages other than <tt>base-passwd</tt> must not modify
6184 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6185 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6190 <heading>UID and GID classes</heading>
6192 The UID and GID numbers are divided into classes as
6198 Globally allocated by the Debian project, the same
6199 on every Debian system. These ids will appear in
6200 the <file>passwd</file> and <file>group</file> files of all
6201 Debian systems, new ids in this range being added
6202 automatically as the <tt>base-passwd</tt> package is
6207 Packages which need a single statically allocated
6208 uid or gid should use one of these; their
6209 maintainers should ask the <tt>base-passwd</tt>
6217 Dynamically allocated system users and groups.
6218 Packages which need a user or group, but can have
6219 this user or group allocated dynamically and
6220 differently on each system, should use <tt>adduser
6221 --system</tt> to create the group and/or user.
6222 <prgn>adduser</prgn> will check for the existence of
6223 the user or group, and if necessary choose an unused
6224 id based on the ranges specified in
6225 <file>adduser.conf</file>.
6229 <tag>1000-59999:</tag>
6232 Dynamically allocated user accounts. By default
6233 <prgn>adduser</prgn> will choose UIDs and GIDs for
6234 user accounts in this range, though
6235 <file>adduser.conf</file> may be used to modify this
6240 <tag>60000-64999:</tag>
6243 Globally allocated by the Debian project, but only
6244 created on demand. The ids are allocated centrally
6245 and statically, but the actual accounts are only
6246 created on users' systems on demand.
6250 These ids are for packages which are obscure or
6251 which require many statically-allocated ids. These
6252 packages should check for and create the accounts in
6253 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6254 <prgn>adduser</prgn> if it has this facility) if
6255 necessary. Packages which are likely to require
6256 further allocations should have a "hole" left after
6257 them in the allocation, to give them room to
6262 <tag>65000-65533:</tag>
6270 User <tt>nobody</tt>. The corresponding gid refers
6271 to the group <tt>nogroup</tt>.
6278 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6279 not</em> be used, because it is the error return
6288 <sect id="sysvinit">
6289 <heading>System run levels and <file>init.d</file> scripts</heading>
6291 <sect1 id="/etc/init.d">
6292 <heading>Introduction</heading>
6295 The <file>/etc/init.d</file> directory contains the scripts
6296 executed by <prgn>init</prgn> at boot time and when the
6297 init state (or "runlevel") is changed (see <manref
6298 name="init" section="8">).
6302 There are at least two different, yet functionally
6303 equivalent, ways of handling these scripts. For the sake
6304 of simplicity, this document describes only the symbolic
6305 link method. However, it must not be assumed by maintainer
6306 scripts that this method is being used, and any automated
6307 manipulation of the various runlevel behaviors by
6308 maintainer scripts must be performed using
6309 <prgn>update-rc.d</prgn> as described below and not by
6310 manually installing or removing symlinks. For information
6311 on the implementation details of the other method,
6312 implemented in the <tt>file-rc</tt> package, please refer
6313 to the documentation of that package.
6317 These scripts are referenced by symbolic links in the
6318 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6319 runlevels, <prgn>init</prgn> looks in the directory
6320 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6321 execute, where <tt><var>n</var></tt> is the runlevel that
6322 is being changed to, or <tt>S</tt> for the boot-up
6327 The names of the links all have the form
6328 <file>S<var>mm</var><var>script</var></file> or
6329 <file>K<var>mm</var><var>script</var></file> where
6330 <var>mm</var> is a two-digit number and <var>script</var>
6331 is the name of the script (this should be the same as the
6332 name of the actual script in <file>/etc/init.d</file>).
6336 When <prgn>init</prgn> changes runlevel first the targets
6337 of the links whose names start with a <tt>K</tt> are
6338 executed, each with the single argument <tt>stop</tt>,
6339 followed by the scripts prefixed with an <tt>S</tt>, each
6340 with the single argument <tt>start</tt>. (The links are
6341 those in the <file>/etc/rc<var>n</var>.d</file> directory
6342 corresponding to the new runlevel.) The <tt>K</tt> links
6343 are responsible for killing services and the <tt>S</tt>
6344 link for starting services upon entering the runlevel.
6348 For example, if we are changing from runlevel 2 to
6349 runlevel 3, init will first execute all of the <tt>K</tt>
6350 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6351 all of the <tt>S</tt> prefixed scripts in that directory.
6352 The links starting with <tt>K</tt> will cause the
6353 referred-to file to be executed with an argument of
6354 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6359 The two-digit number <var>mm</var> is used to determine
6360 the order in which to run the scripts: low-numbered links
6361 have their scripts run first. For example, the
6362 <tt>K20</tt> scripts will be executed before the
6363 <tt>K30</tt> scripts. This is used when a certain service
6364 must be started before another. For example, the name
6365 server <prgn>bind</prgn> might need to be started before
6366 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6367 can set up its access lists. In this case, the script
6368 that starts <prgn>bind</prgn> would have a lower number
6369 than the script that starts <prgn>inn</prgn> so that it
6371 <example compact="compact">
6378 The two runlevels 0 (halt) and 6 (reboot) are slightly
6379 different. In these runlevels, the links with an
6380 <tt>S</tt> prefix are still called after those with a
6381 <tt>K</tt> prefix, but they too are called with the single
6382 argument <tt>stop</tt>.
6386 <sect1 id="writing-init">
6387 <heading>Writing the scripts</heading>
6390 Packages that include daemons for system services should
6391 place scripts in <file>/etc/init.d</file> to start or stop
6392 services at boot time or during a change of runlevel.
6393 These scripts should be named
6394 <file>/etc/init.d/<var>package</var></file>, and they should
6395 accept one argument, saying what to do:
6398 <tag><tt>start</tt></tag>
6399 <item>start the service,</item>
6401 <tag><tt>stop</tt></tag>
6402 <item>stop the service,</item>
6404 <tag><tt>restart</tt></tag>
6405 <item>stop and restart the service if it's already running,
6406 otherwise start the service</item>
6408 <tag><tt>reload</tt></tag>
6409 <item><p>cause the configuration of the service to be
6410 reloaded without actually stopping and restarting
6413 <tag><tt>force-reload</tt></tag>
6414 <item>cause the configuration to be reloaded if the
6415 service supports this, otherwise restart the
6419 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6420 <tt>force-reload</tt> options should be supported by all
6421 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6426 The <file>init.d</file> scripts must ensure that they will
6427 behave sensibly (i.e., returning success and not starting
6428 multiple copies of a service) if invoked with <tt>start</tt>
6429 when the service is already running, or with <tt>stop</tt>
6430 when it isn't, and that they don't kill unfortunately-named
6431 user processes. The best way to achieve this is usually to
6432 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6437 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6438 scripts. Writing correct <file>init.d</file> scripts requires
6439 accepting various error exit statuses when daemons are already
6440 running or already stopped without aborting
6441 the <file>init.d</file> script, and common <file>init.d</file>
6442 function libraries are not safe to call with <tt>set -e</tt>
6444 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6445 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6446 in effect and echoing status messages to the console fails,
6448 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6449 to not use <tt>set -e</tt> and instead check the result of
6450 each command separately.
6454 If a service reloads its configuration automatically (as
6455 in the case of <prgn>cron</prgn>, for example), the
6456 <tt>reload</tt> option of the <file>init.d</file> script
6457 should behave as if the configuration has been reloaded
6462 The <file>/etc/init.d</file> scripts must be treated as
6463 configuration files, either (if they are present in the
6464 package, that is, in the .deb file) by marking them as
6465 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6466 by managing them correctly in the maintainer scripts (see
6467 <ref id="config-files">). This is important since we want
6468 to give the local system administrator the chance to adapt
6469 the scripts to the local system, e.g., to disable a
6470 service without de-installing the package, or to specify
6471 some special command line options when starting a service,
6472 while making sure their changes aren't lost during the next
6477 These scripts should not fail obscurely when the
6478 configuration files remain but the package has been
6479 removed, as configuration files remain on the system after
6480 the package has been removed. Only when <prgn>dpkg</prgn>
6481 is executed with the <tt>--purge</tt> option will
6482 configuration files be removed. In particular, as the
6483 <file>/etc/init.d/<var>package</var></file> script itself is
6484 usually a <tt>conffile</tt>, it will remain on the system
6485 if the package is removed but not purged. Therefore, you
6486 should include a <tt>test</tt> statement at the top of the
6488 <example compact="compact">
6489 test -f <var>program-executed-later-in-script</var> || exit 0
6494 Often there are some variables in the <file>init.d</file>
6495 scripts whose values control the behavior of the scripts,
6496 and which a system administrator is likely to want to
6497 change. As the scripts themselves are frequently
6498 <tt>conffile</tt>s, modifying them requires that the
6499 administrator merge in their changes each time the package
6500 is upgraded and the <tt>conffile</tt> changes. To ease
6501 the burden on the system administrator, such configurable
6502 values should not be placed directly in the script.
6503 Instead, they should be placed in a file in
6504 <file>/etc/default</file>, which typically will have the same
6505 base name as the <file>init.d</file> script. This extra file
6506 should be sourced by the script when the script runs. It
6507 must contain only variable settings and comments in SUSv3
6508 <prgn>sh</prgn> format. It may either be a
6509 <tt>conffile</tt> or a configuration file maintained by
6510 the package maintainer scripts. See <ref id="config-files">
6515 To ensure that vital configurable values are always
6516 available, the <file>init.d</file> script should set default
6517 values for each of the shell variables it uses, either
6518 before sourcing the <file>/etc/default/</file> file or
6519 afterwards using something like the <tt>:
6520 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6521 script must behave sensibly and not fail if the
6522 <file>/etc/default</file> file is deleted.
6526 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6527 as temporary filesystems<footnote>
6528 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6529 options in <file>/etc/default/rcS</file>.
6530 </footnote>, so the <file>init.d</file> scripts must handle this
6531 correctly. This will typically amount to creating any required
6532 subdirectories dynamically when the <file>init.d</file> script
6533 is run, rather than including them in the package and relying on
6534 <prgn>dpkg</prgn> to create them.
6539 <heading>Interfacing with the initscript system</heading>
6542 Maintainers should use the abstraction layer provided by
6543 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6544 programs to deal with initscripts in their packages'
6545 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6546 and <prgn>postrm</prgn>.
6550 Directly managing the /etc/rc?.d links and directly
6551 invoking the <file>/etc/init.d/</file> initscripts should
6552 be done only by packages providing the initscript
6553 subsystem (such as <prgn>sysv-rc</prgn> and
6554 <prgn>file-rc</prgn>).
6558 <heading>Managing the links</heading>
6561 The program <prgn>update-rc.d</prgn> is provided for
6562 package maintainers to arrange for the proper creation and
6563 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6564 or their functional equivalent if another method is being
6565 used. This may be used by maintainers in their packages'
6566 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6570 You must not include any <file>/etc/rc<var>n</var>.d</file>
6571 symbolic links in the actual archive or manually create or
6572 remove the symbolic links in maintainer scripts; you must
6573 use the <prgn>update-rc.d</prgn> program instead. (The
6574 former will fail if an alternative method of maintaining
6575 runlevel information is being used.) You must not include
6576 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6577 in the archive either. (Only the <tt>sysvinit</tt>
6582 By default <prgn>update-rc.d</prgn> will start services in
6583 each of the multi-user state runlevels (2, 3, 4, and 5)
6584 and stop them in the halt runlevel (0), the single-user
6585 runlevel (1) and the reboot runlevel (6). The system
6586 administrator will have the opportunity to customize
6587 runlevels by simply adding, moving, or removing the
6588 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6589 symbolic links are being used, or by modifying
6590 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6595 To get the default behavior for your package, put in your
6596 <prgn>postinst</prgn> script
6597 <example compact="compact">
6598 update-rc.d <var>package</var> defaults
6600 and in your <prgn>postrm</prgn>
6601 <example compact="compact">
6602 if [ "$1" = purge ]; then
6603 update-rc.d <var>package</var> remove
6605 </example>. Note that if your package changes runlevels
6606 or priority, you may have to remove and recreate the links,
6607 since otherwise the old links may persist. Refer to the
6608 documentation of <prgn>update-rc.d</prgn>.
6612 This will use a default sequence number of 20. If it does
6613 not matter when or in which order the <file>init.d</file>
6614 script is run, use this default. If it does, then you
6615 should talk to the maintainer of the <prgn>sysvinit</prgn>
6616 package or post to <tt>debian-devel</tt>, and they will
6617 help you choose a number.
6621 For more information about using <tt>update-rc.d</tt>,
6622 please consult its man page <manref name="update-rc.d"
6628 <heading>Running initscripts</heading>
6630 The program <prgn>invoke-rc.d</prgn> is provided to make
6631 it easier for package maintainers to properly invoke an
6632 initscript, obeying runlevel and other locally-defined
6633 constraints that might limit a package's right to start,
6634 stop and otherwise manage services. This program may be
6635 used by maintainers in their packages' scripts.
6639 The package maintainer scripts must use
6640 <prgn>invoke-rc.d</prgn> to invoke the
6641 <file>/etc/init.d/*</file> initscripts, instead of
6642 calling them directly.
6646 By default, <prgn>invoke-rc.d</prgn> will pass any
6647 action requests (start, stop, reload, restart...) to the
6648 <file>/etc/init.d</file> script, filtering out requests
6649 to start or restart a service out of its intended
6654 Most packages will simply need to change:
6655 <example compact="compact">/etc/init.d/<package>
6656 <action></example> in their <prgn>postinst</prgn>
6657 and <prgn>prerm</prgn> scripts to:
6658 <example compact="compact">
6659 if which invoke-rc.d >/dev/null 2>&1; then
6660 invoke-rc.d <var>package</var> <action>
6662 /etc/init.d/<var>package</var> <action>
6668 A package should register its initscript services using
6669 <prgn>update-rc.d</prgn> before it tries to invoke them
6670 using <prgn>invoke-rc.d</prgn>. Invocation of
6671 unregistered services may fail.
6675 For more information about using
6676 <prgn>invoke-rc.d</prgn>, please consult its man page
6677 <manref name="invoke-rc.d" section="8">.
6683 <heading>Boot-time initialization</heading>
6686 There used to be another directory, <file>/etc/rc.boot</file>,
6687 which contained scripts which were run once per machine
6688 boot. This has been deprecated in favour of links from
6689 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6690 described in <ref id="/etc/init.d">. Packages must not
6691 place files in <file>/etc/rc.boot</file>.
6696 <heading>Example</heading>
6699 An example on which you can base your
6700 <file>/etc/init.d</file> scripts is found in
6701 <file>/etc/init.d/skeleton</file>.
6708 <heading>Console messages from <file>init.d</file> scripts</heading>
6711 This section describes the formats to be used for messages
6712 written to standard output by the <file>/etc/init.d</file>
6713 scripts. The intent is to improve the consistency of
6714 Debian's startup and shutdown look and feel. For this
6715 reason, please look very carefully at the details. We want
6716 the messages to have the same format in terms of wording,
6717 spaces, punctuation and case of letters.
6721 Here is a list of overall rules that should be used for
6722 messages generated by <file>/etc/init.d</file> scripts.
6728 The message should fit in one line (fewer than 80
6729 characters), start with a capital letter and end with
6730 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6734 If the script is performing some time consuming task in
6735 the background (not merely starting or stopping a
6736 program, for instance), an ellipsis (three dots:
6737 <tt>...</tt>) should be output to the screen, with no
6738 leading or tailing whitespace or line feeds.
6742 The messages should appear as if the computer is telling
6743 the user what it is doing (politely :-), but should not
6744 mention "it" directly. For example, instead of:
6745 <example compact="compact">
6746 I'm starting network daemons: nfsd mountd.
6748 the message should say
6749 <example compact="compact">
6750 Starting network daemons: nfsd mountd.
6757 <tt>init.d</tt> script should use the following standard
6758 message formats for the situations enumerated below.
6764 <p>When daemons are started</p>
6767 If the script starts one or more daemons, the output
6768 should look like this (a single line, no leading
6770 <example compact="compact">
6771 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6773 The <var>description</var> should describe the
6774 subsystem the daemon or set of daemons are part of,
6775 while <var>daemon-1</var> up to <var>daemon-n</var>
6776 denote each daemon's name (typically the file name of
6781 For example, the output of <file>/etc/init.d/lpd</file>
6783 <example compact="compact">
6784 Starting printer spooler: lpd.
6789 This can be achieved by saying
6790 <example compact="compact">
6791 echo -n "Starting printer spooler: lpd"
6792 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6795 in the script. If there are more than one daemon to
6796 start, the output should look like this:
6797 <example compact="compact">
6798 echo -n "Starting remote file system services:"
6799 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6800 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6801 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6804 This makes it possible for the user to see what is
6805 happening and when the final daemon has been started.
6806 Care should be taken in the placement of white spaces:
6807 in the example above the system administrators can
6808 easily comment out a line if they don't want to start
6809 a specific daemon, while the displayed message still
6815 <p>When a system parameter is being set</p>
6818 If you have to set up different system parameters
6819 during the system boot, you should use this format:
6820 <example compact="compact">
6821 Setting <var>parameter</var> to "<var>value</var>".
6826 You can use a statement such as the following to get
6828 <example compact="compact">
6829 echo "Setting DNS domainname to \"$domainname\"."
6834 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6835 for the left and right quotation marks. A grave accent
6836 (<tt>`</tt>) is not a quote character; neither is an
6837 apostrophe (<tt>'</tt>).
6842 <p>When a daemon is stopped or restarted</p>
6845 When you stop or restart a daemon, you should issue a
6846 message identical to the startup message, except that
6847 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6848 or <tt>Restarting</tt> respectively.
6852 For example, stopping the printer daemon will look like
6854 <example compact="compact">
6855 Stopping printer spooler: lpd.
6861 <p>When something is executed</p>
6864 There are several examples where you have to run a
6865 program at system startup or shutdown to perform a
6866 specific task, for example, setting the system's clock
6867 using <prgn>netdate</prgn> or killing all processes
6868 when the system shuts down. Your message should look
6870 <example compact="compact">
6871 Doing something very useful...done.
6873 You should print the <tt>done.</tt> immediately after
6874 the job has been completed, so that the user is
6875 informed why they have to wait. You can get this
6877 <example compact="compact">
6878 echo -n "Doing something very useful..."
6887 <p>When the configuration is reloaded</p>
6890 When a daemon is forced to reload its configuration
6891 files you should use the following format:
6892 <example compact="compact">
6893 Reloading <var>description</var> configuration...done.
6895 where <var>description</var> is the same as in the
6896 daemon starting message.
6904 <heading>Cron jobs</heading>
6907 Packages must not modify the configuration file
6908 <file>/etc/crontab</file>, and they must not modify the files in
6909 <file>/var/spool/cron/crontabs</file>.</p>
6912 If a package wants to install a job that has to be executed
6913 via cron, it should place a file with the name of the
6914 package in one or more of the following directories:
6915 <example compact="compact">
6921 As these directory names imply, the files within them are
6922 executed on an hourly, daily, weekly, or monthly basis,
6923 respectively. The exact times are listed in
6924 <file>/etc/crontab</file>.</p>
6927 All files installed in any of these directories must be
6928 scripts (e.g., shell scripts or Perl scripts) so that they
6929 can easily be modified by the local system administrator.
6930 In addition, they must be treated as configuration files.
6934 If a certain job has to be executed at some other frequency or
6935 at a specific time, the package should install a file
6936 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6937 same syntax as <file>/etc/crontab</file> and is processed by
6938 <prgn>cron</prgn> automatically. The file must also be
6939 treated as a configuration file. (Note that entries in the
6940 <file>/etc/cron.d</file> directory are not handled by
6941 <prgn>anacron</prgn>. Thus, you should only use this
6942 directory for jobs which may be skipped if the system is not
6945 Unlike <file>crontab</file> files described in the IEEE Std
6946 1003.1-2008 (POSIX.1) available from
6947 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6948 name="The Open Group">, the files in
6949 <file>/etc/cron.d</file> and the file
6950 <file>/etc/crontab</file> have seven fields; namely:
6952 <item>Minute [0,59]</item>
6953 <item>Hour [0,23]</item>
6954 <item>Day of the month [1,31]</item>
6955 <item>Month of the year [1,12]</item>
6956 <item>Day of the week ([0,6] with 0=Sunday)</item>
6957 <item>Username</item>
6958 <item>Command to be run</item>
6960 Ranges of numbers are allowed. Ranges are two numbers
6961 separated with a hyphen. The specified range is inclusive.
6962 Lists are allowed. A list is a set of numbers (or ranges)
6963 separated by commas. Step values can be used in conjunction
6968 The scripts or <tt>crontab</tt> entries in these directories should
6969 check if all necessary programs are installed before they
6970 try to execute them. Otherwise, problems will arise when a
6971 package was removed but not purged since configuration files
6972 are kept on the system in this situation.
6976 Any <tt>cron</tt> daemon must provide
6977 <file>/usr/bin/crontab</file> and support normal
6978 <tt>crontab</tt> entries as specified in POSIX. The daemon
6979 must also support names for days and months, ranges, and
6980 step values. It has to support <file>/etc/crontab</file>,
6981 and correctly execute the scripts in
6982 <file>/etc/cron.d</file>. The daemon must also correctly
6984 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6989 <heading>Menus</heading>
6992 The Debian <tt>menu</tt> package provides a standard
6993 interface between packages providing applications and
6994 <em>menu programs</em> (either X window managers or
6995 text-based menu programs such as <prgn>pdmenu</prgn>).
6999 All packages that provide applications that need not be
7000 passed any special command line arguments for normal
7001 operation should register a menu entry for those
7002 applications, so that users of the <tt>menu</tt> package
7003 will automatically get menu entries in their window
7004 managers, as well in shells like <tt>pdmenu</tt>.
7008 Menu entries should follow the current menu policy.
7012 The menu policy can be found in the <tt>menu-policy</tt>
7013 files in the <tt>debian-policy</tt> package.
7014 It is also available from the Debian web mirrors at
7015 <tt><url name="/doc/packaging-manuals/menu-policy/"
7016 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7020 Please also refer to the <em>Debian Menu System</em>
7021 documentation that comes with the <package>menu</package>
7022 package for information about how to register your
7028 <heading>Multimedia handlers</heading>
7031 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7032 is a mechanism for encoding files and data streams and
7033 providing meta-information about them, in particular their
7034 type (e.g. audio or video) and format (e.g. PNG, HTML,
7039 Registration of MIME type handlers allows programs like mail
7040 user agents and web browsers to invoke these handlers to
7041 view, edit or display MIME types they don't support directly.
7045 Packages which provide the ability to view/show/play,
7046 compose, edit or print MIME types should register themselves
7047 as such following the current MIME support policy.
7051 The MIME support policy can be found in the <tt>mime-policy</tt>
7052 files in the <tt>debian-policy</tt> package.
7053 It is also available from the Debian web mirrors at
7054 <tt><url name="/doc/packaging-manuals/mime-policy/"
7055 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7061 <heading>Keyboard configuration</heading>
7064 To achieve a consistent keyboard configuration so that all
7065 applications interpret a keyboard event the same way, all
7066 programs in the Debian distribution must be configured to
7067 comply with the following guidelines.
7071 The following keys must have the specified interpretations:
7074 <tag><tt><--</tt></tag>
7075 <item>delete the character to the left of the cursor</item>
7077 <tag><tt>Delete</tt></tag>
7078 <item>delete the character to the right of the cursor</item>
7080 <tag><tt>Control+H</tt></tag>
7081 <item>emacs: the help prefix</item>
7084 The interpretation of any keyboard events should be
7085 independent of the terminal that is used, be it a virtual
7086 console, an X terminal emulator, an rlogin/telnet session,
7091 The following list explains how the different programs
7092 should be set up to achieve this:
7098 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7102 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7106 X translations are set up to make
7107 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7108 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7109 is the vt220 escape code for the "delete character"
7110 key). This must be done by loading the X resources
7111 using <prgn>xrdb</prgn> on all local X displays, not
7112 using the application defaults, so that the
7113 translation resources used correspond to the
7114 <prgn>xmodmap</prgn> settings.
7118 The Linux console is configured to make
7119 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7120 generate <tt>ESC [ 3 ~</tt>.
7124 X applications are configured so that <tt><</tt>
7125 deletes left, and <tt>Delete</tt> deletes right. Motif
7126 applications already work like this.
7130 Terminals should have <tt>stty erase ^?</tt> .
7134 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7135 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7136 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7140 Emacs is programmed to map <tt>KB_Backspace</tt> or
7141 the <tt>stty erase</tt> character to
7142 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7143 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7144 <tt>^H</tt> to <tt>help</tt> as always.
7148 Other applications use the <tt>stty erase</tt>
7149 character and <tt>kdch1</tt> for the two delete keys,
7150 with ASCII DEL being "delete previous character" and
7151 <tt>kdch1</tt> being "delete character under
7159 This will solve the problem except for the following
7166 Some terminals have a <tt><--</tt> key that cannot
7167 be made to produce anything except <tt>^H</tt>. On
7168 these terminals Emacs help will be unavailable on
7169 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7170 character takes precedence in Emacs, and has been set
7171 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7172 available) can be used instead.
7176 Some operating systems use <tt>^H</tt> for <tt>stty
7177 erase</tt>. However, modern telnet versions and all
7178 rlogin versions propagate <tt>stty</tt> settings, and
7179 almost all UNIX versions honour <tt>stty erase</tt>.
7180 Where the <tt>stty</tt> settings are not propagated
7181 correctly, things can be made to work by using
7182 <tt>stty</tt> manually.
7186 Some systems (including previous Debian versions) use
7187 <prgn>xmodmap</prgn> to arrange for both
7188 <tt><--</tt> and <tt>Delete</tt> to generate
7189 <tt>KB_Delete</tt>. We can change the behavior of
7190 their X clients using the same X resources that we use
7191 to do it for our own clients, or configure our clients
7192 using their resources when things are the other way
7193 around. On displays configured like this
7194 <tt>Delete</tt> will not work, but <tt><--</tt>
7199 Some operating systems have different <tt>kdch1</tt>
7200 settings in their <tt>terminfo</tt> database for
7201 <tt>xterm</tt> and others. On these systems the
7202 <tt>Delete</tt> key will not work correctly when you
7203 log in from a system conforming to our policy, but
7204 <tt><--</tt> will.
7211 <heading>Environment variables</heading>
7214 A program must not depend on environment variables to get
7215 reasonable defaults. (That's because these environment
7216 variables would have to be set in a system-wide
7217 configuration file like <file>/etc/profile</file>, which is not
7218 supported by all shells.)
7222 If a program usually depends on environment variables for its
7223 configuration, the program should be changed to fall back to
7224 a reasonable default configuration if these environment
7225 variables are not present. If this cannot be done easily
7226 (e.g., if the source code of a non-free program is not
7227 available), the program must be replaced by a small
7228 "wrapper" shell script which sets the environment variables
7229 if they are not already defined, and calls the original program.
7233 Here is an example of a wrapper script for this purpose:
7235 <example compact="compact">
7237 BAR=${BAR:-/var/lib/fubar}
7239 exec /usr/lib/foo/foo "$@"
7244 Furthermore, as <file>/etc/profile</file> is a configuration
7245 file of the <prgn>base-files</prgn> package, other packages must
7246 not put any environment variables or other commands into that
7251 <sect id="doc-base">
7252 <heading>Registering Documents using doc-base</heading>
7255 The <package>doc-base</package> package implements a
7256 flexible mechanism for handling and presenting
7257 documentation. The recommended practice is for every Debian
7258 package that provides online documentation (other than just
7259 manual pages) to register these documents with
7260 <package>doc-base</package> by installing a
7261 <package>doc-base</package> control file via the
7262 <prgn/install-docs/ script at installation time and
7263 de-register the manuals again when the package is removed.
7266 Please refer to the documentation that comes with the
7267 <package>doc-base</package> package for information and
7276 <heading>Files</heading>
7278 <sect id="binaries">
7279 <heading>Binaries</heading>
7282 Two different packages must not install programs with
7283 different functionality but with the same filenames. (The
7284 case of two programs having the same functionality but
7285 different implementations is handled via "alternatives" or
7286 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7287 <ref id="conflicts"> respectively.) If this case happens,
7288 one of the programs must be renamed. The maintainers should
7289 report this to the <tt>debian-devel</tt> mailing list and
7290 try to find a consensus about which program will have to be
7291 renamed. If a consensus cannot be reached, <em>both</em>
7292 programs must be renamed.
7296 By default, when a package is being built, any binaries
7297 created should include debugging information, as well as
7298 being compiled with optimization. You should also turn on
7299 as many reasonable compilation warnings as possible; this
7300 makes life easier for porters, who can then look at build
7301 logs for possible problems. For the C programming language,
7302 this means the following compilation parameters should be
7304 <example compact="compact">
7306 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7308 INSTALL = install -s # (or use strip on the files in debian/tmp)
7313 Note that by default all installed binaries should be stripped,
7314 either by using the <tt>-s</tt> flag to
7315 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7316 the binaries after they have been copied into
7317 <file>debian/tmp</file> but before the tree is made into a
7322 Although binaries in the build tree should be compiled with
7323 debugging information by default, it can often be difficult to
7324 debug programs if they are also subjected to compiler
7325 optimization. For this reason, it is recommended to support the
7326 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7327 (see <ref id="debianrules-options">). This variable can contain
7328 several flags to change how a package is compiled and built.
7332 It is up to the package maintainer to decide what
7333 compilation options are best for the package. Certain
7334 binaries (such as computationally-intensive programs) will
7335 function better with certain flags (<tt>-O3</tt>, for
7336 example); feel free to use them. Please use good judgment
7337 here. Don't use flags for the sake of it; only use them
7338 if there is good reason to do so. Feel free to override
7339 the upstream author's ideas about which compilation
7340 options are best: they are often inappropriate for our
7346 <sect id="libraries">
7347 <heading>Libraries</heading>
7350 If the package is <strong>architecture: any</strong>, then
7351 the shared library compilation and linking flags must have
7352 <tt>-fPIC</tt>, or the package shall not build on some of
7353 the supported architectures<footnote>
7355 If you are using GCC, <tt>-fPIC</tt> produces code with
7356 relocatable position independent code, which is required for
7357 most architectures to create a shared library, with i386 and
7358 perhaps some others where non position independent code is
7359 permitted in a shared library.
7362 Position independent code may have a performance penalty,
7363 especially on <tt>i386</tt>. However, in most cases the
7364 speed penalty must be measured against the memory wasted on
7365 the few architectures where non position independent code is
7368 </footnote>. Any exception to this rule must be discussed on
7369 the mailing list <em>debian-devel@lists.debian.org</em>, and
7370 a rough consensus obtained. The reasons for not compiling
7371 with <tt>-fPIC</tt> flag must be recorded in the file
7372 <tt>README.Debian</tt>, and care must be taken to either
7373 restrict the architecture or arrange for <tt>-fPIC</tt> to
7374 be used on architectures where it is required.<footnote>
7376 Some of the reasons why this might be required is if the
7377 library contains hand crafted assembly code that is not
7378 relocatable, the speed penalty is excessive for compute
7379 intensive libs, and similar reasons.
7384 As to the static libraries, the common case is not to have
7385 relocatable code, since there is no benefit, unless in specific
7386 cases; therefore the static version must not be compiled
7387 with the <tt>-fPIC</tt> flag. Any exception to this rule
7388 should be discussed on the mailing list
7389 <em>debian-devel@lists.debian.org</em>, and the reasons for
7390 compiling with the <tt>-fPIC</tt> flag must be recorded in
7391 the file <tt>README.Debian</tt>. <footnote>
7393 Some of the reasons for linking static libraries with
7394 the <tt>-fPIC</tt> flag are if, for example, one needs a
7395 Perl API for a library that is under rapid development,
7396 and has an unstable API, so shared libraries are
7397 pointless at this phase of the library's development. In
7398 that case, since Perl needs a library with relocatable
7399 code, it may make sense to create a static library with
7400 relocatable code. Another reason cited is if you are
7401 distilling various libraries into a common shared
7402 library, like <tt>mklibs</tt> does in the Debian
7408 In other words, if both a shared and a static library is
7409 being built, each source unit (<tt>*.c</tt>, for example,
7410 for C files) will need to be compiled twice, for the normal
7415 Libraries should be built with threading support and to be
7416 thread-safe if the library supports this.
7420 Although not enforced by the build tools, shared libraries
7421 must be linked against all libraries that they use symbols from
7422 in the same way that binaries are. This ensures the correct
7423 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7424 system and guarantees that all libraries can be safely opened
7425 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7426 option <tt>-Wl,-z,defs</tt> when building a shared library.
7427 Since this option enforces symbol resolution at build time,
7428 a missing library reference will be caught early as a fatal
7433 All installed shared libraries should be stripped with
7434 <example compact="compact">
7435 strip --strip-unneeded <var>your-lib</var>
7437 (The option <tt>--strip-unneeded</tt> makes
7438 <prgn>strip</prgn> remove only the symbols which aren't
7439 needed for relocation processing.) Shared libraries can
7440 function perfectly well when stripped, since the symbols for
7441 dynamic linking are in a separate part of the ELF object
7443 You might also want to use the options
7444 <tt>--remove-section=.comment</tt> and
7445 <tt>--remove-section=.note</tt> on both shared libraries
7446 and executables, and <tt>--strip-debug</tt> on static
7452 Note that under some circumstances it may be useful to
7453 install a shared library unstripped, for example when
7454 building a separate package to support debugging.
7458 Shared object files (often <file>.so</file> files) that are not
7459 public libraries, that is, they are not meant to be linked
7460 to by third party executables (binaries of other packages),
7461 should be installed in subdirectories of the
7462 <file>/usr/lib</file> directory. Such files are exempt from the
7463 rules that govern ordinary shared libraries, except that
7464 they must not be installed executable and should be
7466 A common example are the so-called "plug-ins",
7467 internal shared objects that are dynamically loaded by
7468 programs using <manref name="dlopen" section="3">.
7473 Packages that use <prgn>libtool</prgn> to create and install
7474 their shared libraries install a file containing additional
7475 metadata (ending in <file>.la</file>) alongside the library.
7476 For public libraries intended for use by other packages, these
7477 files normally should not be included in the Debian package,
7478 since the information they include is not necessary to link with
7479 the shared library on Debian and can add unnecessary additional
7480 dependencies to other programs or libraries.<footnote>
7481 These files store, among other things, all libraries on which
7482 that shared library depends. Unfortunately, if
7483 the <file>.la</file> file is present and contains that
7484 dependency information, using <prgn>libtool</prgn> when
7485 linking against that library will cause the resulting program
7486 or library to be linked against those dependencies as well,
7487 even if this is unnecessary. This can create unneeded
7488 dependencies on shared library packages that would otherwise
7489 be hidden behind the library ABI, and can make library
7490 transitions to new SONAMEs unnecessarily complicated and
7491 difficult to manage.
7493 If the <file>.la</file> file is required for that library (if,
7494 for instance, it's loaded via <tt>libltdl</tt> in a way that
7495 requires that meta-information), the <tt>dependency_libs</tt>
7496 setting in the <file>.la</file> file should normally be set to
7497 the empty string. If the shared library development package has
7498 historically included the <file>.la</file>, it must be retained
7499 in the development package (with <tt>dependency_libs</tt>
7500 emptied) until all libraries that depend on it have removed or
7501 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7502 files to prevent linking with those other libraries
7503 using <prgn>libtool</prgn> from failing.
7507 If the <file>.la</file> must be included, it should be included
7508 in the development (<tt>-dev</tt>) package, unless the library
7509 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7510 library. If it is intended for use with <tt>libltdl</tt>,
7511 the <file>.la</file> files must go in the run-time library
7516 These requirements for handling of <file>.la</file> files do not
7517 apply to loadable modules or libraries not installed in
7518 directories searched by default by the dynamic linker. Packages
7519 installing loadable modules will frequently need to install
7520 the <file>.la</file> files alongside the modules so that they
7521 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7522 does not need to be modified for libraries or modules that are
7523 not installed in directories searched by the dynamic linker by
7524 default and not intended for use by other packages.
7528 You must make sure that you use only released versions of
7529 shared libraries to build your packages; otherwise other
7530 users will not be able to run your binaries
7531 properly. Producing source packages that depend on
7532 unreleased compilers is also usually a bad
7539 <heading>Shared libraries</heading>
7541 This section has moved to <ref id="sharedlibs">.
7547 <heading>Scripts</heading>
7550 All command scripts, including the package maintainer
7551 scripts inside the package and used by <prgn>dpkg</prgn>,
7552 should have a <tt>#!</tt> line naming the shell to be used
7557 In the case of Perl scripts this should be
7558 <tt>#!/usr/bin/perl</tt>.
7562 When scripts are installed into a directory in the system
7563 PATH, the script name should not include an extension such
7564 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7565 language currently used to implement it.
7568 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7569 <file>init.d</file> scripts should almost certainly start
7570 with <tt>set -e</tt> so that errors are detected.
7571 <file>init.d</file> scripts are something of a special case, due
7572 to how frequently they need to call commands that are allowed to
7573 fail, and it may instead be easier to check the exit status of
7574 commands directly. See <ref id="writing-init"> for more
7575 information about writing <file>init.d</file> scripts.
7578 Every script should use <tt>set -e</tt> or check the exit status
7579 of <em>every</em> command.
7582 Scripts may assume that <file>/bin/sh</file> implements the
7583 SUSv3 Shell Command Language<footnote>
7584 Single UNIX Specification, version 3, which is also IEEE
7585 1003.1-2004 (POSIX), and is available on the World Wide Web
7586 from <url id="http://www.unix.org/version3/online.html"
7587 name="The Open Group"> after free
7588 registration.</footnote>
7589 plus the following additional features not mandated by
7591 These features are in widespread use in the Linux community
7592 and are implemented in all of bash, dash, and ksh, the most
7593 common shells users may wish to use as <file>/bin/sh</file>.
7596 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7597 must not generate a newline.</item>
7598 <item><tt>test</tt>, if implemented as a shell built-in, must
7599 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7601 <item><tt>local</tt> to create a scoped variable must be
7602 supported, including listing multiple variables in a single
7603 local command and assigning a value to a variable at the
7604 same time as localizing it. <tt>local</tt> may or
7605 may not preserve the variable value from an outer scope if
7606 no assignment is present. Uses such as:
7610 # ... use a, b, c, d ...
7613 must be supported and must set the value of <tt>c</tt> to
7616 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7617 -<var>signal</var></tt>, where <var>signal</var> is either
7618 the name of a signal or one of the numeric signals listed in
7619 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7620 supported if <prgn>kill</prgn> is implemented as a shell
7623 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7624 signals must be supported. In addition to the signal
7625 numbers listed in the extension, which are the same as for
7626 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7629 If a shell script requires non-SUSv3 features from the shell
7630 interpreter other than those listed above, the appropriate shell
7631 must be specified in the first line of the script (e.g.,
7632 <tt>#!/bin/bash</tt>) and the package must depend on the package
7633 providing the shell (unless the shell package is marked
7634 "Essential", as in the case of <prgn>bash</prgn>).
7638 You may wish to restrict your script to SUSv3 features plus the
7639 above set when possible so that it may use <file>/bin/sh</file>
7640 as its interpreter. If your script works with <prgn>dash</prgn>
7641 (originally called <prgn>ash</prgn>), it probably complies with
7642 the above requirements, but if you are in doubt, use
7643 <file>/bin/bash</file>.
7647 Perl scripts should check for errors when making any
7648 system calls, including <tt>open</tt>, <tt>print</tt>,
7649 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7653 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7654 scripting languages. See <em>Csh Programming Considered
7655 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7656 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7657 If an upstream package comes with <prgn>csh</prgn> scripts
7658 then you must make sure that they start with
7659 <tt>#!/bin/csh</tt> and make your package depend on the
7660 <prgn>c-shell</prgn> virtual package.
7664 Any scripts which create files in world-writeable
7665 directories (e.g., in <file>/tmp</file>) must use a
7666 mechanism which will fail atomically if a file with the same
7667 name already exists.
7671 The Debian base system provides the <prgn>tempfile</prgn>
7672 and <prgn>mktemp</prgn> utilities for use by scripts for
7679 <heading>Symbolic links</heading>
7682 In general, symbolic links within a top-level directory
7683 should be relative, and symbolic links pointing from one
7684 top-level directory into another should be absolute. (A
7685 top-level directory is a sub-directory of the root
7686 directory <file>/</file>.)
7690 In addition, symbolic links should be specified as short as
7691 possible, i.e., link targets like <file>foo/../bar</file> are
7696 Note that when creating a relative link using
7697 <prgn>ln</prgn> it is not necessary for the target of the
7698 link to exist relative to the working directory you're
7699 running <prgn>ln</prgn> from, nor is it necessary to change
7700 directory to the directory where the link is to be made.
7701 Simply include the string that should appear as the target
7702 of the link (this will be a pathname relative to the
7703 directory in which the link resides) as the first argument
7708 For example, in your <prgn>Makefile</prgn> or
7709 <file>debian/rules</file>, you can do things like:
7710 <example compact="compact">
7711 ln -fs gcc $(prefix)/bin/cc
7712 ln -fs gcc debian/tmp/usr/bin/cc
7713 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7714 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7719 A symbolic link pointing to a compressed file should always
7720 have the same file extension as the referenced file. (For
7721 example, if a file <file>foo.gz</file> is referenced by a
7722 symbolic link, the filename of the link has to end with
7723 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7728 <heading>Device files</heading>
7731 Packages must not include device files or named pipes in the
7736 If a package needs any special device files that are not
7737 included in the base system, it must call
7738 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7739 after notifying the user<footnote>
7740 This notification could be done via a (low-priority)
7741 debconf message, or an echo (printf) statement.
7746 Packages must not remove any device files in the
7747 <prgn>postrm</prgn> or any other script. This is left to the
7748 system administrator.
7752 Debian uses the serial devices
7753 <file>/dev/ttyS*</file>. Programs using the old
7754 <file>/dev/cu*</file> devices should be changed to use
7755 <file>/dev/ttyS*</file>.
7759 Named pipes needed by the package must be created in
7760 the <prgn>postinst</prgn> script<footnote>
7761 It's better to use <prgn>mkfifo</prgn> rather
7762 than <prgn>mknod</prgn> to create named pipes so that
7763 automated checks for packages incorrectly creating device
7764 files with <prgn>mknod</prgn> won't have false positives.
7765 </footnote> and removed in
7766 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7771 <sect id="config-files">
7772 <heading>Configuration files</heading>
7775 <heading>Definitions</heading>
7779 <tag>configuration file</tag>
7781 A file that affects the operation of a program, or
7782 provides site- or host-specific information, or
7783 otherwise customizes the behavior of a program.
7784 Typically, configuration files are intended to be
7785 modified by the system administrator (if needed or
7786 desired) to conform to local policy or to provide
7787 more useful site-specific behavior.
7790 <tag><tt>conffile</tt></tag>
7792 A file listed in a package's <tt>conffiles</tt>
7793 file, and is treated specially by <prgn>dpkg</prgn>
7794 (see <ref id="configdetails">).
7800 The distinction between these two is important; they are
7801 not interchangeable concepts. Almost all
7802 <tt>conffile</tt>s are configuration files, but many
7803 configuration files are not <tt>conffiles</tt>.
7807 As noted elsewhere, <file>/etc/init.d</file> scripts,
7808 <file>/etc/default</file> files, scripts installed in
7809 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7810 configuration installed in <file>/etc/cron.d</file> must be
7811 treated as configuration files. In general, any script that
7812 embeds configuration information is de-facto a configuration
7813 file and should be treated as such.
7818 <heading>Location</heading>
7821 Any configuration files created or used by your package
7822 must reside in <file>/etc</file>. If there are several,
7823 consider creating a subdirectory of <file>/etc</file>
7824 named after your package.
7828 If your package creates or uses configuration files
7829 outside of <file>/etc</file>, and it is not feasible to modify
7830 the package to use <file>/etc</file> directly, put the files
7831 in <file>/etc</file> and create symbolic links to those files
7832 from the location that the package requires.
7837 <heading>Behavior</heading>
7840 Configuration file handling must conform to the following
7842 <list compact="compact">
7844 local changes must be preserved during a package
7848 configuration files must be preserved when the
7849 package is removed, and only deleted when the
7853 Obsolete configuration files without local changes may be
7854 removed by the package during upgrade.
7858 The easy way to achieve this behavior is to make the
7859 configuration file a <tt>conffile</tt>. This is
7860 appropriate only if it is possible to distribute a default
7861 version that will work for most installations, although
7862 some system administrators may choose to modify it. This
7863 implies that the default version will be part of the
7864 package distribution, and must not be modified by the
7865 maintainer scripts during installation (or at any other
7870 In order to ensure that local changes are preserved
7871 correctly, no package may contain or make hard links to
7872 conffiles.<footnote>
7873 Rationale: There are two problems with hard links.
7874 The first is that some editors break the link while
7875 editing one of the files, so that the two files may
7876 unwittingly become unlinked and different. The second
7877 is that <prgn>dpkg</prgn> might break the hard link
7878 while upgrading <tt>conffile</tt>s.
7883 The other way to do it is via the maintainer scripts. In
7884 this case, the configuration file must not be listed as a
7885 <tt>conffile</tt> and must not be part of the package
7886 distribution. If the existence of a file is required for
7887 the package to be sensibly configured it is the
7888 responsibility of the package maintainer to provide
7889 maintainer scripts which correctly create, update and
7890 maintain the file and remove it on purge. (See <ref
7891 id="maintainerscripts"> for more information.) These
7892 scripts must be idempotent (i.e., must work correctly if
7893 <prgn>dpkg</prgn> needs to re-run them due to errors
7894 during installation or removal), must cope with all the
7895 variety of ways <prgn>dpkg</prgn> can call maintainer
7896 scripts, must not overwrite or otherwise mangle the user's
7897 configuration without asking, must not ask unnecessary
7898 questions (particularly during upgrades), and must
7899 otherwise be good citizens.
7903 The scripts are not required to configure every possible
7904 option for the package, but only those necessary to get
7905 the package running on a given system. Ideally the
7906 sysadmin should not have to do any configuration other
7907 than that done (semi-)automatically by the
7908 <prgn>postinst</prgn> script.
7912 A common practice is to create a script called
7913 <file><var>package</var>-configure</file> and have the
7914 package's <prgn>postinst</prgn> call it if and only if the
7915 configuration file does not already exist. In certain
7916 cases it is useful for there to be an example or template
7917 file which the maintainer scripts use. Such files should
7918 be in <file>/usr/share/<var>package</var></file> or
7919 <file>/usr/lib/<var>package</var></file> (depending on whether
7920 they are architecture-independent or not). There should
7921 be symbolic links to them from
7922 <file>/usr/share/doc/<var>package</var>/examples</file> if
7923 they are examples, and should be perfectly ordinary
7924 <prgn>dpkg</prgn>-handled files (<em>not</em>
7925 configuration files).
7929 These two styles of configuration file handling must
7930 not be mixed, for that way lies madness:
7931 <prgn>dpkg</prgn> will ask about overwriting the file
7932 every time the package is upgraded.
7937 <heading>Sharing configuration files</heading>
7940 Packages which specify the same file as a
7941 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7942 with each other. (This is an instance of the general rule
7943 about not sharing files. Note that neither alternatives
7944 nor diversions are likely to be appropriate in this case;
7945 in particular, <prgn>dpkg</prgn> does not handle diverted
7946 <tt>conffile</tt>s well.)
7950 The maintainer scripts must not alter a <tt>conffile</tt>
7951 of <em>any</em> package, including the one the scripts
7956 If two or more packages use the same configuration file
7957 and it is reasonable for both to be installed at the same
7958 time, one of these packages must be defined as
7959 <em>owner</em> of the configuration file, i.e., it will be
7960 the package which handles that file as a configuration
7961 file. Other packages that use the configuration file must
7962 depend on the owning package if they require the
7963 configuration file to operate. If the other package will
7964 use the configuration file if present, but is capable of
7965 operating without it, no dependency need be declared.
7969 If it is desirable for two or more related packages to
7970 share a configuration file <em>and</em> for all of the
7971 related packages to be able to modify that configuration
7972 file, then the following should be done:
7973 <enumlist compact="compact">
7975 One of the related packages (the "owning" package)
7976 will manage the configuration file with maintainer
7977 scripts as described in the previous section.
7980 The owning package should also provide a program
7981 that the other packages may use to modify the
7985 The related packages must use the provided program
7986 to make any desired modifications to the
7987 configuration file. They should either depend on
7988 the core package to guarantee that the configuration
7989 modifier program is available or accept gracefully
7990 that they cannot modify the configuration file if it
7991 is not. (This is in addition to the fact that the
7992 configuration file may not even be present in the
7999 Sometimes it's appropriate to create a new package which
8000 provides the basic infrastructure for the other packages
8001 and which manages the shared configuration files. (The
8002 <tt>sgml-base</tt> package is a good example.)
8007 <heading>User configuration files ("dotfiles")</heading>
8010 The files in <file>/etc/skel</file> will automatically be
8011 copied into new user accounts by <prgn>adduser</prgn>.
8012 No other program should reference the files in
8013 <file>/etc/skel</file>.
8017 Therefore, if a program needs a dotfile to exist in
8018 advance in <file>$HOME</file> to work sensibly, that dotfile
8019 should be installed in <file>/etc/skel</file> and treated as a
8024 However, programs that require dotfiles in order to
8025 operate sensibly are a bad thing, unless they do create
8026 the dotfiles themselves automatically.
8030 Furthermore, programs should be configured by the Debian
8031 default installation to behave as closely to the upstream
8032 default behavior as possible.
8036 Therefore, if a program in a Debian package needs to be
8037 configured in some way in order to operate sensibly, that
8038 should be done using a site-wide configuration file placed
8039 in <file>/etc</file>. Only if the program doesn't support a
8040 site-wide default configuration and the package maintainer
8041 doesn't have time to add it may a default per-user file be
8042 placed in <file>/etc/skel</file>.
8046 <file>/etc/skel</file> should be as empty as we can make it.
8047 This is particularly true because there is no easy (or
8048 necessarily desirable) mechanism for ensuring that the
8049 appropriate dotfiles are copied into the accounts of
8050 existing users when a package is installed.
8056 <heading>Log files</heading>
8058 Log files should usually be named
8059 <file>/var/log/<var>package</var>.log</file>. If you have many
8060 log files, or need a separate directory for permission
8061 reasons (<file>/var/log</file> is writable only by
8062 <file>root</file>), you should usually create a directory named
8063 <file>/var/log/<var>package</var></file> and place your log
8068 Log files must be rotated occasionally so that they don't grow
8069 indefinitely. The best way to do this is to install a log
8070 rotation configuration file in the
8071 directory <file>/etc/logrotate.d</file>, normally
8072 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8073 the facilities provided by <prgn>logrotate</prgn>.
8076 The traditional approach to log files has been to set up
8077 <em>ad hoc</em> log rotation schemes using simple shell
8078 scripts and cron. While this approach is highly
8079 customizable, it requires quite a lot of sysadmin work.
8080 Even though the original Debian system helped a little
8081 by automatically installing a system which can be used
8082 as a template, this was deemed not enough.
8086 The use of <prgn>logrotate</prgn>, a program developed
8087 by Red Hat, is better, as it centralizes log management.
8088 It has both a configuration file
8089 (<file>/etc/logrotate.conf</file>) and a directory where
8090 packages can drop their individual log rotation
8091 configurations (<file>/etc/logrotate.d</file>).
8094 Here is a good example for a logrotate config
8095 file (for more information see <manref name="logrotate"
8097 <example compact="compact">
8098 /var/log/foo/*.log {
8104 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8108 This rotates all files under <file>/var/log/foo</file>, saves 12
8109 compressed generations, and tells the daemon to reopen its log
8110 files after the log rotation. It skips this log rotation
8111 (via <tt>missingok</tt>) if no such log file is present, which
8112 avoids errors if the package is removed but not purged.
8116 Log files should be removed when the package is
8117 purged (but not when it is only removed). This should be
8118 done by the <prgn>postrm</prgn> script when it is called
8119 with the argument <tt>purge</tt> (see <ref
8120 id="removedetails">).
8124 <sect id="permissions-owners">
8125 <heading>Permissions and owners</heading>
8128 The rules in this section are guidelines for general use.
8129 If necessary you may deviate from the details below.
8130 However, if you do so you must make sure that what is done
8131 is secure and you should try to be as consistent as possible
8132 with the rest of the system. You should probably also
8133 discuss it on <prgn>debian-devel</prgn> first.
8137 Files should be owned by <tt>root:root</tt>, and made
8138 writable only by the owner and universally readable (and
8139 executable, if appropriate), that is mode 644 or 755.
8143 Directories should be mode 755 or (for group-writability)
8144 mode 2775. The ownership of the directory should be
8145 consistent with its mode: if a directory is mode 2775, it
8146 should be owned by the group that needs write access to
8149 When a package is upgraded, and the owner or permissions
8150 of a file included in the package has changed, dpkg
8151 arranges for the ownership and permissions to be
8152 correctly set upon installation. However, this does not
8153 extend to directories; the permissions and ownership of
8154 directories already on the system does not change on
8155 install or upgrade of packages. This makes sense, since
8156 otherwise common directories like <tt>/usr</tt> would
8157 always be in flux. To correctly change permissions of a
8158 directory the package owns, explicit action is required,
8159 usually in the <tt>postinst</tt> script. Care must be
8160 taken to handle downgrades as well, in that case.
8166 Control information files should be owned by <tt>root:root</tt>
8167 and either mode 644 (for most files) or mode 755 (for
8168 executables such as <qref id="maintscripts">maintainer
8173 Setuid and setgid executables should be mode 4755 or 2755
8174 respectively, and owned by the appropriate user or group.
8175 They should not be made unreadable (modes like 4711 or
8176 2711 or even 4111); doing so achieves no extra security,
8177 because anyone can find the binary in the freely available
8178 Debian package; it is merely inconvenient. For the same
8179 reason you should not restrict read or execute permissions
8180 on non-set-id executables.
8184 Some setuid programs need to be restricted to particular
8185 sets of users, using file permissions. In this case they
8186 should be owned by the uid to which they are set-id, and by
8187 the group which should be allowed to execute them. They
8188 should have mode 4754; again there is no point in making
8189 them unreadable to those users who must not be allowed to
8194 It is possible to arrange that the system administrator can
8195 reconfigure the package to correspond to their local
8196 security policy by changing the permissions on a binary:
8197 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8198 described below.<footnote>
8199 Ordinary files installed by <prgn>dpkg</prgn> (as
8200 opposed to <tt>conffile</tt>s and other similar objects)
8201 normally have their permissions reset to the distributed
8202 permissions when the package is reinstalled. However,
8203 the use of <prgn>dpkg-statoverride</prgn> overrides this
8206 Another method you should consider is to create a group for
8207 people allowed to use the program(s) and make any setuid
8208 executables executable only by that group.
8212 If you need to create a new user or group for your package
8213 there are two possibilities. Firstly, you may need to
8214 make some files in the binary package be owned by this
8215 user or group, or you may need to compile the user or
8216 group id (rather than just the name) into the binary
8217 (though this latter should be avoided if possible, as in
8218 this case you need a statically allocated id).</p>
8221 If you need a statically allocated id, you must ask for a
8222 user or group id from the <tt>base-passwd</tt> maintainer,
8223 and must not release the package until you have been
8224 allocated one. Once you have been allocated one you must
8225 either make the package depend on a version of the
8226 <tt>base-passwd</tt> package with the id present in
8227 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8228 your package to create the user or group itself with the
8229 correct id (using <tt>adduser</tt>) in its
8230 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8231 the <prgn>postinst</prgn> is to be preferred if it is
8232 possible, otherwise a pre-dependency will be needed on the
8233 <tt>adduser</tt> package.)
8237 On the other hand, the program might be able to determine
8238 the uid or gid from the user or group name at runtime, so
8239 that a dynamically allocated id can be used. In this case
8240 you should choose an appropriate user or group name,
8241 discussing this on <prgn>debian-devel</prgn> and checking
8242 with the <package/base-passwd/ maintainer that it is unique and that
8243 they do not wish you to use a statically allocated id
8244 instead. When this has been checked you must arrange for
8245 your package to create the user or group if necessary using
8246 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8247 <prgn>postinst</prgn> script (again, the latter is to be
8248 preferred if it is possible).
8252 Note that changing the numeric value of an id associated
8253 with a name is very difficult, and involves searching the
8254 file system for all appropriate files. You need to think
8255 carefully whether a static or dynamic id is required, since
8256 changing your mind later will cause problems.
8259 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8261 This section is not intended as policy, but as a
8262 description of the use of <prgn>dpkg-statoverride</prgn>.
8266 If a system administrator wishes to have a file (or
8267 directory or other such thing) installed with owner and
8268 permissions different from those in the distributed Debian
8269 package, they can use the <prgn>dpkg-statoverride</prgn>
8270 program to instruct <prgn>dpkg</prgn> to use the different
8271 settings every time the file is installed. Thus the
8272 package maintainer should distribute the files with their
8273 normal permissions, and leave it for the system
8274 administrator to make any desired changes. For example, a
8275 daemon which is normally required to be setuid root, but
8276 in certain situations could be used without being setuid,
8277 should be installed setuid in the <tt>.deb</tt>. Then the
8278 local system administrator can change this if they wish.
8279 If there are two standard ways of doing it, the package
8280 maintainer can use <tt>debconf</tt> to find out the
8281 preference, and call <prgn>dpkg-statoverride</prgn> in the
8282 maintainer script if necessary to accommodate the system
8283 administrator's choice. Care must be taken during
8284 upgrades to not override an existing setting.
8288 Given the above, <prgn>dpkg-statoverride</prgn> is
8289 essentially a tool for system administrators and would not
8290 normally be needed in the maintainer scripts. There is
8291 one type of situation, though, where calls to
8292 <prgn>dpkg-statoverride</prgn> would be needed in the
8293 maintainer scripts, and that involves packages which use
8294 dynamically allocated user or group ids. In such a
8295 situation, something like the following idiom can be very
8296 helpful in the package's <prgn>postinst</prgn>, where
8297 <tt>sysuser</tt> is a dynamically allocated id:
8299 for i in /usr/bin/foo /usr/sbin/bar
8301 # only do something when no setting exists
8302 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8304 #include: debconf processing, question about foo and bar
8305 if [ "$RET" = "true" ] ; then
8306 dpkg-statoverride --update --add sysuser root 4755 $i
8311 The corresponding code to remove the override when the package
8314 for i in /usr/bin/foo /usr/sbin/bar
8316 if dpkg-statoverride --list $i >/dev/null 2>&1
8318 dpkg-statoverride --remove $i
8328 <chapt id="customized-programs">
8329 <heading>Customized programs</heading>
8331 <sect id="arch-spec">
8332 <heading>Architecture specification strings</heading>
8335 If a program needs to specify an <em>architecture specification
8336 string</em> in some place, it should select one of the strings
8337 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8338 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8339 part is sometimes elided, as when the OS is Linux.
8343 Note that we don't want to use
8344 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8345 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8346 since this would make our programs incompatible with other
8347 Linux distributions. We also don't use something like
8348 <tt><var>arch</var>-unknown-linux</tt>, since the
8349 <tt>unknown</tt> does not look very good.
8352 <sect1 id="arch-wildcard-spec">
8353 <heading>Architecture wildcards</heading>
8356 A package may specify an architecture wildcard. Architecture
8357 wildcards are in the format <tt>any</tt> (which matches every
8358 architecture), <tt><var>os</var></tt>-any, or
8359 any-<tt><var>cpu</var></tt>. <footnote>
8360 Internally, the package system normalizes the GNU triplets
8361 and the Debian arches into Debian arch triplets (which are
8362 kind of inverted GNU triplets), with the first component of
8363 the triplet representing the libc and ABI in use, and then
8364 does matching against those triplets. However, such
8365 triplets are an internal implementation detail that should
8366 not be used by packages directly. The libc and ABI portion
8367 is handled internally by the package system based on
8368 the <var>os</var> and <var>cpu</var>.
8375 <heading>Daemons</heading>
8378 The configuration files <file>/etc/services</file>,
8379 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8380 by the <prgn>netbase</prgn> package and must not be modified
8385 If a package requires a new entry in one of these files, the
8386 maintainer should get in contact with the
8387 <prgn>netbase</prgn> maintainer, who will add the entries
8388 and release a new version of the <prgn>netbase</prgn>
8393 The configuration file <file>/etc/inetd.conf</file> must not be
8394 modified by the package's scripts except via the
8395 <prgn>update-inetd</prgn> script or the
8396 <file>DebianNet.pm</file> Perl module. See their documentation
8397 for details on how to add entries.
8401 If a package wants to install an example entry into
8402 <file>/etc/inetd.conf</file>, the entry must be preceded with
8403 exactly one hash character (<tt>#</tt>). Such lines are
8404 treated as "commented out by user" by the
8405 <prgn>update-inetd</prgn> script and are not changed or
8406 activated during package updates.
8411 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8415 Some programs need to create pseudo-ttys. This should be done
8416 using Unix98 ptys if the C library supports it. The resulting
8417 program must not be installed setuid root, unless that
8418 is required for other functionality.
8422 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8423 <file>/var/log/lastlog</file> must be installed writable by
8424 group <tt>utmp</tt>. Programs which need to modify those
8425 files must be installed setgid <tt>utmp</tt>.
8430 <heading>Editors and pagers</heading>
8433 Some programs have the ability to launch an editor or pager
8434 program to edit or display a text document. Since there are
8435 lots of different editors and pagers available in the Debian
8436 distribution, the system administrator and each user should
8437 have the possibility to choose their preferred editor and
8442 In addition, every program should choose a good default
8443 editor/pager if none is selected by the user or system
8448 Thus, every program that launches an editor or pager must
8449 use the EDITOR or PAGER environment variable to determine
8450 the editor or pager the user wishes to use. If these
8451 variables are not set, the programs <file>/usr/bin/editor</file>
8452 and <file>/usr/bin/pager</file> should be used, respectively.
8456 These two files are managed through the <prgn>dpkg</prgn>
8457 "alternatives" mechanism. Every package providing an editor or
8458 pager must call the <prgn>update-alternatives</prgn> script to
8459 register as an alternative for <file>/usr/bin/editor</file>
8460 or <file>/usr/bin/pager</file> as appropriate. The alternative
8461 should have a slave alternative
8462 for <file>/usr/share/man/man1/editor.1.gz</file>
8463 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8464 corresponding manual page.
8468 If it is very hard to adapt a program to make use of the
8469 EDITOR or PAGER variables, that program may be configured to
8470 use <file>/usr/bin/sensible-editor</file> and
8471 <file>/usr/bin/sensible-pager</file> as the editor or pager
8472 program respectively. These are two scripts provided in the
8473 <package>sensible-utils</package> package that check the EDITOR
8474 and PAGER variables and launch the appropriate program, and fall
8475 back to <file>/usr/bin/editor</file>
8476 and <file>/usr/bin/pager</file> if the variable is not set.
8480 A program may also use the VISUAL environment variable to
8481 determine the user's choice of editor. If it exists, it
8482 should take precedence over EDITOR. This is in fact what
8483 <file>/usr/bin/sensible-editor</file> does.
8487 It is not required for a package to depend on
8488 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8489 package to provide such virtual packages.<footnote>
8490 The Debian base system already provides an editor and a
8496 <sect id="web-appl">
8497 <heading>Web servers and applications</heading>
8500 This section describes the locations and URLs that should
8501 be used by all web servers and web applications in the
8508 Cgi-bin executable files are installed in the
8510 <example compact="compact">
8511 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8513 or a subdirectory of that directory, and should be
8515 <example compact="compact">
8516 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8518 (possibly with a subdirectory name
8519 before <var>cgi-bin-name</var>).
8523 <p>Access to HTML documents</p>
8526 HTML documents for a package are stored in
8527 <file>/usr/share/doc/<var>package</var></file>
8528 and can be referred to as
8529 <example compact="compact">
8530 http://localhost/doc/<var>package</var>/<var>filename</var>
8535 The web server should restrict access to the document
8536 tree so that only clients on the same host can read
8537 the documents. If the web server does not support such
8538 access controls, then it should not provide access at
8539 all, or ask about providing access during installation.
8544 <p>Access to images</p>
8546 It is recommended that images for a package be stored
8547 in <tt>/usr/share/images/<var>package</var></tt> and
8548 may be referred to through an alias <tt>/images/</tt>
8551 http://localhost/images/<package>/<filename>
8558 <p>Web Document Root</p>
8561 Web Applications should try to avoid storing files in
8562 the Web Document Root. Instead they should use the
8563 /usr/share/doc/<var>package</var> directory for
8564 documents and register the Web Application via the
8565 <package>doc-base</package> package. If access to the
8566 web document root is unavoidable then use
8567 <example compact="compact">
8570 as the Document Root. This might be just a symbolic
8571 link to the location where the system administrator
8572 has put the real document root.
8575 <item><p>Providing httpd and/or httpd-cgi</p>
8577 All web servers should provide the virtual package
8578 <tt>httpd</tt>. If a web server has CGI support it should
8579 provide <tt>httpd-cgi</tt> additionally.
8582 All web applications which do not contain CGI scripts should
8583 depend on <tt>httpd</tt>, all those web applications which
8584 <tt>do</tt> contain CGI scripts, should depend on
8592 <sect id="mail-transport-agents">
8593 <heading>Mail transport, delivery and user agents</heading>
8596 Debian packages which process electronic mail, whether mail
8597 user agents (MUAs) or mail transport agents (MTAs), must
8598 ensure that they are compatible with the configuration
8599 decisions below. Failure to do this may result in lost
8600 mail, broken <tt>From:</tt> lines, and other serious brain
8605 The mail spool is <file>/var/mail</file> and the interface to
8606 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8607 the FHS). On older systems, the mail spool may be
8608 physically located in <file>/var/spool/mail</file>, but all
8609 access to the mail spool should be via the
8610 <file>/var/mail</file> symlink. The mail spool is part of the
8611 base system and not part of the MTA package.
8615 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8616 programs (such as IMAP daemons) must lock the mailbox in an
8617 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8618 be combined with dot locking. To avoid deadlocks, a program
8619 should use <tt>fcntl()</tt> first and dot locking after
8620 this, or alternatively implement the two locking methods in
8621 a non blocking way<footnote>
8622 If it is not possible to establish both locks, the
8623 system shouldn't wait for the second lock to be
8624 established, but remove the first lock, wait a (random)
8625 time, and start over locking again.
8626 </footnote>. Using the functions <tt>maillock</tt> and
8627 <tt>mailunlock</tt> provided by the
8628 <tt>liblockfile*</tt><footnote>
8629 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8630 to use these functions.
8631 </footnote> packages is the recommended way to realize this.
8635 Mailboxes are generally either mode 600 and owned by
8636 <var>user</var> or mode 660 and owned by
8637 <tt><var>user</var>:mail</tt><footnote>
8638 There are two traditional permission schemes for mail spools:
8639 mode 600 with all mail delivery done by processes running as
8640 the destination user, or mode 660 and owned by group mail with
8641 mail delivery done by a process running as a system user in
8642 group mail. Historically, Debian required mode 660 mail
8643 spools to enable the latter model, but that model has become
8644 increasingly uncommon and the principle of least privilege
8645 indicates that mail systems that use the first model should
8646 use permissions of 600. If delivery to programs is permitted,
8647 it's easier to keep the mail system secure if the delivery
8648 agent runs as the destination user. Debian Policy therefore
8649 permits either scheme.
8650 </footnote>. The local system administrator may choose a
8651 different permission scheme; packages should not make
8652 assumptions about the permission and ownership of mailboxes
8653 unless required (such as when creating a new mailbox). A MUA
8654 may remove a mailbox (unless it has nonstandard permissions) in
8655 which case the MTA or another MUA must recreate it if needed.
8659 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8660 be setgid mail to do the locking mentioned above (and
8661 must obviously avoid accessing other users' mailboxes
8662 using this privilege).</p>
8665 <file>/etc/aliases</file> is the source file for the system mail
8666 aliases (e.g., postmaster, usenet, etc.), it is the one
8667 which the sysadmin and <prgn>postinst</prgn> scripts may
8668 edit. After <file>/etc/aliases</file> is edited the program or
8669 human editing it must call <prgn>newaliases</prgn>. All MTA
8670 packages must come with a <prgn>newaliases</prgn> program,
8671 even if it does nothing, but older MTA packages did not do
8672 this so programs should not fail if <prgn>newaliases</prgn>
8673 cannot be found. Note that because of this, all MTA
8674 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8675 <tt>Replaces: mail-transport-agent</tt> control fields.
8679 The convention of writing <tt>forward to
8680 <var>address</var></tt> in the mailbox itself is not
8681 supported. Use a <tt>.forward</tt> file instead.</p>
8684 The <prgn>rmail</prgn> program used by UUCP
8685 for incoming mail should be <file>/usr/sbin/rmail</file>.
8686 Likewise, <prgn>rsmtp</prgn>, for receiving
8687 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8691 If your package needs to know what hostname to use on (for
8692 example) outgoing news and mail messages which are generated
8693 locally, you should use the file <file>/etc/mailname</file>. It
8694 will contain the portion after the username and <tt>@</tt>
8695 (at) sign for email addresses of users on the machine
8696 (followed by a newline).
8700 Such a package should check for the existence of this file
8701 when it is being configured. If it exists, it should be
8702 used without comment, although an MTA's configuration script
8703 may wish to prompt the user even if it finds that this file
8704 exists. If the file does not exist, the package should
8705 prompt the user for the value (preferably using
8706 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8707 as well as using it in the package's configuration. The
8708 prompt should make it clear that the name will not just be
8709 used by that package. For example, in this situation the
8710 <tt>inn</tt> package could say something like:
8711 <example compact="compact">
8712 Please enter the "mail name" of your system. This is the
8713 hostname portion of the address to be shown on outgoing
8714 news and mail messages. The default is
8715 <var>syshostname</var>, your system's host name. Mail
8716 name ["<var>syshostname</var>"]:
8718 where <var>syshostname</var> is the output of <tt>hostname
8724 <heading>News system configuration</heading>
8727 All the configuration files related to the NNTP (news)
8728 servers and clients should be located under
8729 <file>/etc/news</file>.</p>
8732 There are some configuration issues that apply to a number
8733 of news clients and server packages on the machine. These
8737 <tag><file>/etc/news/organization</file></tag>
8739 A string which should appear as the
8740 organization header for all messages posted
8741 by NNTP clients on the machine
8744 <tag><file>/etc/news/server</file></tag>
8746 Contains the FQDN of the upstream NNTP
8747 server, or localhost if the local machine is
8752 Other global files may be added as required for cross-package news
8759 <heading>Programs for the X Window System</heading>
8762 <heading>Providing X support and package priorities</heading>
8765 Programs that can be configured with support for the X
8766 Window System must be configured to do so and must declare
8767 any package dependencies necessary to satisfy their
8768 runtime requirements when using the X Window System. If
8769 such a package is of higher priority than the X packages
8770 on which it depends, it is required that either the
8771 X-specific components be split into a separate package, or
8772 that an alternative version of the package, which includes
8773 X support, be provided, or that the package's priority be
8779 <heading>Packages providing an X server</heading>
8782 Packages that provide an X server that, directly or
8783 indirectly, communicates with real input and display
8784 hardware should declare in their <tt>Provides</tt> control
8785 field that they provide the virtual
8786 package <tt>xserver</tt>.<footnote>
8787 This implements current practice, and provides an
8788 actual policy for usage of the <tt>xserver</tt>
8789 virtual package which appears in the virtual packages
8790 list. In a nutshell, X servers that interface
8791 directly with the display and input hardware or via
8792 another subsystem (e.g., GGI) should provide
8793 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8794 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8800 <heading>Packages providing a terminal emulator</heading>
8803 Packages that provide a terminal emulator for the X Window
8804 System which meet the criteria listed below should declare in
8805 their <tt>Provides</tt> control field that they provide the
8806 virtual package <tt>x-terminal-emulator</tt>. They should
8807 also register themselves as an alternative for
8808 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8809 20. That alternative should have a slave alternative
8810 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8811 pointing to the corresponding manual page.
8815 To be an <tt>x-terminal-emulator</tt>, a program must:
8816 <list compact="compact">
8818 Be able to emulate a DEC VT100 terminal, or a
8819 compatible terminal.
8823 Support the command-line option <tt>-e
8824 <var>command</var></tt>, which creates a new
8825 terminal window<footnote>
8826 "New terminal window" does not necessarily mean
8827 a new top-level X window directly parented by
8828 the window manager; it could, if the terminal
8829 emulator application were so coded, be a new
8830 "view" in a multiple-document interface (MDI).
8832 and runs the specified <var>command</var>,
8833 interpreting the entirety of the rest of the command
8834 line as a command to pass straight to exec, in the
8835 manner that <tt>xterm</tt> does.
8839 Support the command-line option <tt>-T
8840 <var>title</var></tt>, which creates a new terminal
8841 window with the window title <var>title</var>.
8848 <heading>Packages providing a window manager</heading>
8851 Packages that provide a window manager should declare in
8852 their <tt>Provides</tt> control field that they provide the
8853 virtual package <tt>x-window-manager</tt>. They should also
8854 register themselves as an alternative for
8855 <file>/usr/bin/x-window-manager</file>, with a priority
8856 calculated as follows:
8857 <list compact="compact">
8859 Start with a priority of 20.
8863 If the window manager supports the Debian menu
8864 system, add 20 points if this support is available
8865 in the package's default configuration (i.e., no
8866 configuration files belonging to the system or user
8867 have to be edited to activate the feature); if
8868 configuration files must be modified, add only 10
8874 If the window manager complies with <url
8875 id="http://www.freedesktop.org/Standards/wm-spec"
8876 name="The Window Manager Specification Project">,
8877 written by the <url id="http://www.freedesktop.org/"
8878 name="Free Desktop Group">, add 40 points.
8882 If the window manager permits the X session to be
8883 restarted using a <em>different</em> window manager
8884 (without killing the X server) in its default
8885 configuration, add 10 points; otherwise add none.
8888 That alternative should have a slave alternative
8889 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8890 pointing to the corresponding manual page.
8895 <heading>Packages providing fonts</heading>
8898 Packages that provide fonts for the X Window
8900 For the purposes of Debian Policy, a "font for the X
8901 Window System" is one which is accessed via X protocol
8902 requests. Fonts for the Linux console, for PostScript
8903 renderer, or any other purpose, do not fit this
8904 definition. Any tool which makes such fonts available
8905 to the X Window System, however, must abide by this
8908 must do a number of things to ensure that they are both
8909 available without modification of the X or font server
8910 configuration, and that they do not corrupt files used by
8911 other font packages to register information about
8915 Fonts of any type supported by the X Window System
8916 must be in a separate binary package from any
8917 executables, libraries, or documentation (except
8918 that specific to the fonts shipped, such as their
8919 license information). If one or more of the fonts
8920 so packaged are necessary for proper operation of
8921 the package with which they are associated the font
8922 package may be Recommended; if the fonts merely
8923 provide an enhancement, a Suggests relationship may
8924 be used. Packages must not Depend on font
8926 This is because the X server may retrieve fonts
8927 from the local file system or over the network
8928 from an X font server; the Debian package system
8929 is empowered to deal only with the local
8935 BDF fonts must be converted to PCF fonts with the
8936 <prgn>bdftopcf</prgn> utility (available in the
8937 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8938 placed in a directory that corresponds to their
8940 <list compact="compact">
8942 100 dpi fonts must be placed in
8943 <file>/usr/share/fonts/X11/100dpi/</file>.
8947 75 dpi fonts must be placed in
8948 <file>/usr/share/fonts/X11/75dpi/</file>.
8952 Character-cell fonts, cursor fonts, and other
8953 low-resolution fonts must be placed in
8954 <file>/usr/share/fonts/X11/misc/</file>.
8960 Type 1 fonts must be placed in
8961 <file>/usr/share/fonts/X11/Type1/</file>. If font
8962 metric files are available, they must be placed here
8967 Subdirectories of <file>/usr/share/fonts/X11/</file>
8968 other than those listed above must be neither
8969 created nor used. (The <file>PEX</file>, <file>CID</file>,
8970 <file>Speedo</file>, and <file>cyrillic</file> directories
8971 are excepted for historical reasons, but installation of
8972 files into these directories remains discouraged.)
8976 Font packages may, instead of placing files directly
8977 in the X font directories listed above, provide
8978 symbolic links in that font directory pointing to
8979 the files' actual location in the filesystem. Such
8980 a location must comply with the FHS.
8984 Font packages should not contain both 75dpi and
8985 100dpi versions of a font. If both are available,
8986 they should be provided in separate binary packages
8987 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8988 the names of the packages containing the
8989 corresponding fonts.
8993 Fonts destined for the <file>misc</file> subdirectory
8994 should not be included in the same package as 75dpi
8995 or 100dpi fonts; instead, they should be provided in
8996 a separate package with <tt>-misc</tt> appended to
9001 Font packages must not provide the files
9002 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9003 <file>fonts.scale</file> in a font directory:
9006 <file>fonts.dir</file> files must not be provided at all.
9010 <file>fonts.alias</file> and <file>fonts.scale</file>
9011 files, if needed, should be provided in the
9013 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9014 where <var>fontdir</var> is the name of the
9016 <file>/usr/share/fonts/X11/</file> where the
9017 package's corresponding fonts are stored
9018 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9019 <var>package</var> is the name of the package
9020 that provides these fonts, and
9021 <var>extension</var> is either <tt>scale</tt>
9022 or <tt>alias</tt>, whichever corresponds to
9029 Font packages must declare a dependency on
9030 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9031 or <tt>Pre-Depends</tt> control field.
9035 Font packages that provide one or more
9036 <file>fonts.scale</file> files as described above must
9037 invoke <prgn>update-fonts-scale</prgn> on each
9038 directory into which they installed fonts
9039 <em>before</em> invoking
9040 <prgn>update-fonts-dir</prgn> on that directory.
9041 This invocation must occur in both the
9042 <prgn>postinst</prgn> (for all arguments) and
9043 <prgn>postrm</prgn> (for all arguments except
9044 <tt>upgrade</tt>) scripts.
9048 Font packages that provide one or more
9049 <file>fonts.alias</file> files as described above must
9050 invoke <prgn>update-fonts-alias</prgn> on each
9051 directory into which they installed fonts. This
9052 invocation must occur in both the
9053 <prgn>postinst</prgn> (for all arguments) and
9054 <prgn>postrm</prgn> (for all arguments except
9055 <tt>upgrade</tt>) scripts.
9059 Font packages must invoke
9060 <prgn>update-fonts-dir</prgn> on each directory into
9061 which they installed fonts. This invocation must
9062 occur in both the <prgn>postinst</prgn> (for all
9063 arguments) and <prgn>postrm</prgn> (for all
9064 arguments except <tt>upgrade</tt>) scripts.
9068 Font packages must not provide alias names for the
9069 fonts they include which collide with alias names
9070 already in use by fonts already packaged.
9074 Font packages must not provide fonts with the same
9075 XLFD registry name as another font already packaged.
9081 <sect1 id="appdefaults">
9082 <heading>Application defaults files</heading>
9085 Application defaults files must be installed in the
9086 directory <file>/etc/X11/app-defaults/</file> (use of a
9087 localized subdirectory of <file>/etc/X11/</file> as described
9088 in the <em>X Toolkit Intrinsics - C Language
9089 Interface</em> manual is also permitted). They must be
9090 registered as <tt>conffile</tt>s or handled as
9091 configuration files.
9095 Customization of programs' X resources may also be
9096 supported with the provision of a file with the same name
9097 as that of the package placed in
9098 the <file>/etc/X11/Xresources/</file> directory, which
9099 must be registered as a <tt>conffile</tt> or handled as a
9100 configuration file.<footnote>
9101 Note that this mechanism is not the same as using
9102 app-defaults; app-defaults are tied to the client
9103 binary on the local file system, whereas X resources
9104 are stored in the X server and affect all connecting
9111 <heading>Installation directory issues</heading>
9114 Historically, packages using the X Window System used a
9115 separate set of installation directories from other packages.
9116 This practice has been discontinued and packages using the X
9117 Window System should now generally be installed in the same
9118 directories as any other package. Specifically, packages must
9119 not install files under the <file>/usr/X11R6/</file> directory
9120 and the <file>/usr/X11R6/</file> directory hierarchy should be
9121 regarded as obsolete.
9125 Include files previously installed under
9126 <file>/usr/X11R6/include/X11/</file> should be installed into
9127 <file>/usr/include/X11/</file>. For files previously
9128 installed into subdirectories of
9129 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9130 determine if subdirectories of <file>/usr/lib/</file> and
9131 <file>/usr/share/</file> can be used. If not, a subdirectory
9132 of <file>/usr/lib/X11/</file> should be used.
9136 Configuration files for window, display, or session managers
9137 or other applications that are tightly integrated with the X
9138 Window System may be placed in a subdirectory
9139 of <file>/etc/X11/</file> corresponding to the package name.
9140 Other X Window System applications should use
9141 the <file>/etc/</file> directory unless otherwise mandated by
9142 policy (such as for <ref id="appdefaults">).
9147 <heading>The OSF/Motif and OpenMotif libraries</heading>
9150 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9151 OpenMotif libraries</em><footnote>
9152 OSF/Motif and OpenMotif are collectively referred to as
9153 "Motif" in this policy document.
9155 should be compiled against and tested with LessTif (a free
9156 re-implementation of Motif) instead. If the maintainer
9157 judges that the program or programs do not work
9158 sufficiently well with LessTif to be distributed and
9159 supported, but do so when compiled against Motif, then two
9160 versions of the package should be created; one linked
9161 statically against Motif and with <tt>-smotif</tt>
9162 appended to the package name, and one linked dynamically
9163 against Motif and with <tt>-dmotif</tt> appended to the
9168 Both Motif-linked versions are dependent
9169 upon non-DFSG-compliant software and thus cannot be
9170 uploaded to the <em>main</em> distribution; if the
9171 software is itself DFSG-compliant it may be uploaded to
9172 the <em>contrib</em> distribution. While known existing
9173 versions of Motif permit unlimited redistribution of
9174 binaries linked against the library (whether statically or
9175 dynamically), it is the package maintainer's
9176 responsibility to determine whether this is permitted by
9177 the license of the copy of Motif in their possession.
9183 <heading>Perl programs and modules</heading>
9186 Perl programs and modules should follow the current Perl policy.
9190 The Perl policy can be found in the <tt>perl-policy</tt>
9191 files in the <tt>debian-policy</tt> package.
9192 It is also available from the Debian web mirrors at
9193 <tt><url name="/doc/packaging-manuals/perl-policy/"
9194 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9199 <heading>Emacs lisp programs</heading>
9202 Please refer to the "Debian Emacs Policy" for details of how to
9203 package emacs lisp programs.
9207 The Emacs policy is available in
9208 <file>debian-emacs-policy.gz</file> of the
9209 <package>emacsen-common</package> package.
9210 It is also available from the Debian web mirrors at
9211 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9212 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9217 <heading>Games</heading>
9220 The permissions on <file>/var/games</file> are mode 755, owner
9221 <tt>root</tt> and group <tt>root</tt>.
9225 Each game decides on its own security policy.</p>
9228 Games which require protected, privileged access to
9229 high-score files, saved games, etc., may be made
9230 set-<em>group</em>-id (mode 2755) and owned by
9231 <tt>root:games</tt>, and use files and directories with
9232 appropriate permissions (770 <tt>root:games</tt>, for
9233 example). They must not be made
9234 set-<em>user</em>-id, as this causes security problems. (If
9235 an attacker can subvert any set-user-id game they can
9236 overwrite the executable of any other, causing other players
9237 of these games to run a Trojan horse program. With a
9238 set-group-id game the attacker only gets access to less
9239 important game data, and if they can get at the other
9240 players' accounts at all it will take considerably more
9244 Some packages, for example some fortune cookie programs, are
9245 configured by the upstream authors to install with their
9246 data files or other static information made unreadable so
9247 that they can only be accessed through set-id programs
9248 provided. You should not do this in a Debian package: anyone can
9249 download the <file>.deb</file> file and read the data from it,
9250 so there is no point making the files unreadable. Not
9251 making the files unreadable also means that you don't have
9252 to make so many programs set-id, which reduces the risk of a
9256 As described in the FHS, binaries of games should be
9257 installed in the directory <file>/usr/games</file>. This also
9258 applies to games that use the X Window System. Manual pages
9259 for games (X and non-X games) should be installed in
9260 <file>/usr/share/man/man6</file>.</p>
9266 <heading>Documentation</heading>
9269 <heading>Manual pages</heading>
9272 You should install manual pages in <prgn>nroff</prgn> source
9273 form, in appropriate places under <file>/usr/share/man</file>.
9274 You should only use sections 1 to 9 (see the FHS for more
9275 details). You must not install a pre-formatted "cat page".
9279 Each program, utility, and function should have an
9280 associated manual page included in the same package. It is
9281 suggested that all configuration files also have a manual
9282 page included as well. Manual pages for protocols and other
9283 auxiliary things are optional.
9287 If no manual page is available, this is considered as a bug
9288 and should be reported to the Debian Bug Tracking System (the
9289 maintainer of the package is allowed to write this bug report
9290 themselves, if they so desire). Do not close the bug report
9291 until a proper man page is available.<footnote>
9292 It is not very hard to write a man page. See the
9293 <url id="http://www.schweikhardt.net/man_page_howto.html"
9294 name="Man-Page-HOWTO">,
9295 <manref name="man" section="7">, the examples
9296 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9297 the helper program <prgn>help2man</prgn>, or the
9298 directory <file>/usr/share/doc/man-db/examples</file>.
9303 You may forward a complaint about a missing man page to the
9304 upstream authors, and mark the bug as forwarded in the
9305 Debian bug tracking system. Even though the GNU Project do
9306 not in general consider the lack of a man page to be a bug,
9307 we do; if they tell you that they don't consider it a bug
9308 you should leave the bug in our bug tracking system open
9313 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9317 If one man page needs to be accessible via several names it
9318 is better to use a symbolic link than the <file>.so</file>
9319 feature, but there is no need to fiddle with the relevant
9320 parts of the upstream source to change from <file>.so</file> to
9321 symlinks: don't do it unless it's easy. You should not
9322 create hard links in the manual page directories, nor put
9323 absolute filenames in <file>.so</file> directives. The filename
9324 in a <file>.so</file> in a man page should be relative to the
9325 base of the man page tree (usually
9326 <file>/usr/share/man</file>). If you do not create any links
9327 (whether symlinks, hard links, or <tt>.so</tt> directives)
9328 in the file system to the alternate names of the man page,
9329 then you should not rely on <prgn>man</prgn> finding your
9330 man page under those names based solely on the information in
9331 the man page's header.<footnote>
9332 Supporting this in <prgn>man</prgn> often requires
9333 unreasonable processing time to find a manual page or to
9334 report that none exists, and moves knowledge into man's
9335 database that would be better left in the file system.
9336 This support is therefore deprecated and will cease to
9337 be present in the future.
9342 Manual pages in locale-specific subdirectories of
9343 <file>/usr/share/man</file> should use either UTF-8 or the usual
9344 legacy encoding for that language (normally the one corresponding
9345 to the shortest relevant locale name in
9346 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9347 <file>/usr/share/man/fr</file> should use either UTF-8 or
9348 ISO-8859-1.<footnote>
9349 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9350 use. In future, all manual pages will be required to use
9356 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9357 included in the subdirectory name unless it indicates a
9358 significant difference in the language, as this excludes
9359 speakers of the language in other countries.<footnote>
9360 At the time of writing, Chinese and Portuguese are the main
9361 languages with such differences, so <file>pt_BR</file>,
9362 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9367 If a localized version of a manual page is provided, it should
9368 either be up-to-date or it should be obvious to the reader that
9369 it is outdated and the original manual page should be used
9370 instead. This can be done either by a note at the beginning of
9371 the manual page or by showing the missing or changed portions in
9372 the original language instead of the target language.
9377 <heading>Info documents</heading>
9380 Info documents should be installed in <file>/usr/share/info</file>.
9381 They should be compressed with <tt>gzip -9</tt>.
9385 The <prgn>install-info</prgn> program maintains a directory of
9386 installed info documents in <file>/usr/share/info/dir</file> for
9387 the use of info readers.<footnote>
9388 It was previously necessary for packages installing info
9389 documents to run <prgn>install-info</prgn> from maintainer
9390 scripts. This is no longer necessary. The installation
9391 system now uses dpkg triggers.
9393 This file must not be included in packages. Packages containing
9394 info documents should depend on <tt>dpkg (>= 1.15.4) |
9395 install-info</tt> to ensure that the directory file is properly
9396 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9401 Info documents should contain section and directory entry
9402 information in the document for the use
9403 of <prgn>install-info</prgn>. The section should be specified
9404 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9405 space and the section of this info page. The directory entry or
9406 entries should be included between
9407 a <tt>START-INFO-DIR-ENTRY</tt> line and
9408 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9410 INFO-DIR-SECTION Individual utilities
9411 START-INFO-DIR-ENTRY
9412 * example: (example). An example info directory entry.
9415 To determine which section to use, you should look
9416 at <file>/usr/share/info/dir</file> on your system and choose
9417 the most relevant (or create a new section if none of the
9418 current sections are relevant).<footnote>
9419 Normally, info documents are generated from Texinfo source.
9420 To include this information in the generated info document, if
9421 it is absent, add commands like:
9423 @dircategory Individual utilities
9425 * example: (example). An example info directory entry.
9428 to the Texinfo source of the document and ensure that the info
9429 documents are rebuilt from source during the package build.
9435 <heading>Additional documentation</heading>
9438 Any additional documentation that comes with the package may
9439 be installed at the discretion of the package maintainer.
9440 Plain text documentation should be installed in the directory
9441 <file>/usr/share/doc/<var>package</var></file>, where
9442 <var>package</var> is the name of the package, and
9443 compressed with <tt>gzip -9</tt> unless it is small.
9447 If a package comes with large amounts of documentation which
9448 many users of the package will not require you should create
9449 a separate binary package to contain it, so that it does not
9450 take up disk space on the machines of users who do not need
9451 or want it installed.</p>
9454 It is often a good idea to put text information files
9455 (<file>README</file>s, changelogs, and so forth) that come with
9456 the source package in <file>/usr/share/doc/<var>package</var></file>
9457 in the binary package. However, you don't need to install
9458 the instructions for building and installing the package, of
9462 Packages must not require the existence of any files in
9463 <file>/usr/share/doc/</file> in order to function
9465 The system administrator should be able to
9466 delete files in <file>/usr/share/doc/</file> without causing
9467 any programs to break.
9469 Any files that are referenced by programs but are also
9470 useful as stand alone documentation should be installed under
9471 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9472 <file>/usr/share/doc/<var>package</var></file>.
9476 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9477 link to another directory in <file>/usr/share/doc</file> only if
9478 the two packages both come from the same source and the
9479 first package Depends on the second.<footnote>
9481 Please note that this does not override the section on
9482 changelog files below, so the file
9483 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9484 must refer to the changelog for the current version of
9485 <var>package</var> in question. In practice, this means
9486 that the sources of the target and the destination of the
9487 symlink must be the same (same source package and
9494 Former Debian releases placed all additional documentation
9495 in <file>/usr/doc/<var>package</var></file>. This has been
9496 changed to <file>/usr/share/doc/<var>package</var></file>,
9497 and packages must not put documentation in the directory
9498 <file>/usr/doc/<var>package</var></file>. <footnote>
9499 At this phase of the transition, we no longer require a
9500 symbolic link in <file>/usr/doc/</file>. At a later point,
9501 policy shall change to make the symbolic links a bug.
9507 <heading>Preferred documentation formats</heading>
9510 The unification of Debian documentation is being carried out
9514 If your package comes with extensive documentation in a
9515 markup format that can be converted to various other formats
9516 you should if possible ship HTML versions in a binary
9517 package, in the directory
9518 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9519 its subdirectories.<footnote>
9520 The rationale: The important thing here is that HTML
9521 docs should be available in <em>some</em> package, not
9522 necessarily in the main binary package.
9527 Other formats such as PostScript may be provided at the
9528 package maintainer's discretion.
9532 <sect id="copyrightfile">
9533 <heading>Copyright information</heading>
9536 Every package must be accompanied by a verbatim copy of its
9537 copyright information and distribution license in the file
9538 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9539 file must neither be compressed nor be a symbolic link.
9543 In addition, the copyright file must say where the upstream
9544 sources (if any) were obtained. It should name the original
9545 authors of the package and the Debian maintainer(s) who were
9546 involved with its creation.
9550 Packages in the <em>contrib</em> or <em>non-free</em> archive
9551 areas should state in the copyright file that the package is not
9552 part of the Debian GNU/Linux distribution and briefly explain
9557 A copy of the file which will be installed in
9558 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9559 be in <file>debian/copyright</file> in the source package.
9563 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9564 link to another directory in <file>/usr/share/doc</file> only if
9565 the two packages both come from the same source and the
9566 first package Depends on the second. These rules are
9567 important because copyrights must be extractable by
9572 Packages distributed under the Apache license (version 2.0), the
9573 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9574 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9575 1.3) should refer to the corresponding files
9576 under <file>/usr/share/common-licenses</file>,<footnote>
9579 <file>/usr/share/common-licenses/Apache-2.0</file>,
9580 <file>/usr/share/common-licenses/Artistic</file>,
9581 <file>/usr/share/common-licenses/GPL-1</file>,
9582 <file>/usr/share/common-licenses/GPL-2</file>,
9583 <file>/usr/share/common-licenses/GPL-3</file>,
9584 <file>/usr/share/common-licenses/LGPL-2</file>,
9585 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9586 <file>/usr/share/common-licenses/LGPL-3</file>,
9587 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9588 <file>/usr/share/common-licenses/GFDL-1.3</file>
9589 respectively. The University of California BSD license is
9590 also included in <package>base-files</package> as
9591 <file>/usr/share/common-licenses/BSD</file>, but given the
9592 brevity of this license, its specificity to code whose
9593 copyright is held by the Regents of the University of
9594 California, and the frequency of minor wording changes, its
9595 text should be included in the copyright file rather than
9596 referencing this file.
9598 </footnote> rather than quoting them in the copyright
9603 You should not use the copyright file as a general <file>README</file>
9604 file. If your package has such a file it should be
9605 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9606 <file>README.Debian</file> or some other appropriate place.</p>
9610 <heading>Examples</heading>
9613 Any examples (configurations, source files, whatever),
9614 should be installed in a directory
9615 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9616 files should not be referenced by any program: they're there
9617 for the benefit of the system administrator and users as
9618 documentation only. Architecture-specific example files
9619 should be installed in a directory
9620 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9622 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9623 latter directory itself may be a symbolic link to the
9628 If the purpose of a package is to provide examples, then the
9629 example files may be installed into
9630 <file>/usr/share/doc/<var>package</var></file>.
9634 <sect id="changelogs">
9635 <heading>Changelog files</heading>
9638 Packages that are not Debian-native must contain a
9639 compressed copy of the <file>debian/changelog</file> file from
9640 the Debian source tree in
9641 <file>/usr/share/doc/<var>package</var></file> with the name
9642 <file>changelog.Debian.gz</file>.
9646 If an upstream changelog is available, it should be accessible as
9647 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9648 plain text. If the upstream changelog is distributed in
9649 HTML, it should be made available in that form as
9650 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9651 and a plain text <file>changelog.gz</file> should be generated
9652 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9653 the upstream changelog files do not already conform to this
9654 naming convention, then this may be achieved either by
9655 renaming the files, or by adding a symbolic link, at the
9656 maintainer's discretion.<footnote>
9657 Rationale: People should not have to look in places for
9658 upstream changelogs merely because they are given
9659 different names or are distributed in HTML format.
9664 All of these files should be installed compressed using
9665 <tt>gzip -9</tt>, as they will become large with time even
9666 if they start out small.
9670 If the package has only one changelog which is used both as
9671 the Debian changelog and the upstream one because there is
9672 no separate upstream maintainer then that changelog should
9673 usually be installed as
9674 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9675 there is a separate upstream maintainer, but no upstream
9676 changelog, then the Debian changelog should still be called
9677 <file>changelog.Debian.gz</file>.
9681 For details about the format and contents of the Debian
9682 changelog file, please see <ref id="dpkgchangelog">.
9687 <appendix id="pkg-scope">
9688 <heading>Introduction and scope of these appendices</heading>
9691 These appendices are taken essentially verbatim from the
9692 now-deprecated Packaging Manual, version 3.2.1.0. They are
9693 the chapters which are likely to be of use to package
9694 maintainers and which have not already been included in the
9695 policy document itself. Most of these sections are very likely
9696 not relevant to policy; they should be treated as
9697 documentation for the packaging system. Please note that these
9698 appendices are included for convenience, and for historical
9699 reasons: they used to be part of policy package, and they have
9700 not yet been incorporated into dpkg documentation. However,
9701 they still have value, and hence they are presented here.
9705 They have not yet been checked to ensure that they are
9706 compatible with the contents of policy, and if there are any
9707 contradictions, the version in the main policy document takes
9708 precedence. The remaining chapters of the old Packaging
9709 Manual have also not been read in detail to ensure that there
9710 are not parts which have been left out. Both of these will be
9715 Certain parts of the Packaging manual were integrated into the
9716 Policy Manual proper, and removed from the appendices. Links
9717 have been placed from the old locations to the new ones.
9721 <prgn>dpkg</prgn> is a suite of programs for creating binary
9722 package files and installing and removing them on Unix
9724 <prgn>dpkg</prgn> is targeted primarily at Debian
9725 GNU/Linux, but may work on or be ported to other
9731 The binary packages are designed for the management of
9732 installed executable programs (usually compiled binaries) and
9733 their associated data, though source code examples and
9734 documentation are provided as part of some packages.</p>
9737 This manual describes the technical aspects of creating Debian
9738 binary packages (<file>.deb</file> files). It documents the
9739 behavior of the package management programs
9740 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9741 they interact with packages.</p>
9744 It also documents the interaction between
9745 <prgn>dselect</prgn>'s core and the access method scripts it
9746 uses to actually install the selected packages, and describes
9747 how to create a new access method.</p>
9750 This manual does not go into detail about the options and
9751 usage of the package building and installation tools. It
9752 should therefore be read in conjunction with those programs'
9757 The utility programs which are provided with <prgn>dpkg</prgn>
9758 for managing various system configuration and similar issues,
9759 such as <prgn>update-rc.d</prgn> and
9760 <prgn>install-info</prgn>, are not described in detail here -
9761 please see their man pages.
9765 It is assumed that the reader is reasonably familiar with the
9766 <prgn>dpkg</prgn> System Administrators' manual.
9767 Unfortunately this manual does not yet exist.
9771 The Debian version of the FSF's GNU hello program is provided
9772 as an example for people wishing to create Debian
9773 packages. The Debian <prgn>debmake</prgn> package is
9774 recommended as a very helpful tool in creating and maintaining
9775 Debian packages. However, while the tools and examples are
9776 helpful, they do not replace the need to read and follow the
9777 Policy and Programmer's Manual.</p>
9780 <appendix id="pkg-binarypkg">
9781 <heading>Binary packages (from old Packaging Manual)</heading>
9784 The binary package has two main sections. The first part
9785 consists of various control information files and scripts used
9786 by <prgn>dpkg</prgn> when installing and removing. See <ref
9787 id="pkg-controlarea">.
9791 The second part is an archive containing the files and
9792 directories to be installed.
9796 In the future binary packages may also contain other
9797 components, such as checksums and digital signatures. The
9798 format for the archive is described in full in the
9799 <file>deb(5)</file> man page.
9803 <sect id="pkg-bincreating"><heading>Creating package files -
9804 <prgn>dpkg-deb</prgn>
9808 All manipulation of binary package files is done by
9809 <prgn>dpkg-deb</prgn>; it's the only program that has
9810 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9811 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9812 will spot that the options requested are appropriate to
9813 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9818 In order to create a binary package you must make a
9819 directory tree which contains all the files and directories
9820 you want to have in the file system data part of the package.
9821 In Debian-format source packages this directory is usually
9822 <file>debian/tmp</file>, relative to the top of the package's
9827 They should have the locations (relative to the root of the
9828 directory tree you're constructing) ownerships and
9829 permissions which you want them to have on the system when
9834 With current versions of <prgn>dpkg</prgn> the uid/username
9835 and gid/groupname mappings for the users and groups being
9836 used should be the same on the system where the package is
9837 built and the one where it is installed.
9841 You need to add one special directory to the root of the
9842 miniature file system tree you're creating:
9843 <prgn>DEBIAN</prgn>. It should contain the control
9844 information files, notably the binary package control file
9845 (see <ref id="pkg-controlfile">).
9849 The <prgn>DEBIAN</prgn> directory will not appear in the
9850 file system archive of the package, and so won't be installed
9851 by <prgn>dpkg</prgn> when the package is installed.
9855 When you've prepared the package, you should invoke:
9857 dpkg --build <var>directory</var>
9862 This will build the package in
9863 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9864 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9865 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9870 See the man page <manref name="dpkg-deb" section="8"> for details of how
9871 to examine the contents of this newly-created file. You may find the
9872 output of following commands enlightening:
9874 dpkg-deb --info <var>filename</var>.deb
9875 dpkg-deb --contents <var>filename</var>.deb
9876 dpkg --contents <var>filename</var>.deb
9878 To view the copyright file for a package you could use this command:
9880 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9885 <sect id="pkg-controlarea">
9886 <heading>Package control information files</heading>
9889 The control information portion of a binary package is a
9890 collection of files with names known to <prgn>dpkg</prgn>.
9891 It will treat the contents of these files specially - some
9892 of them contain information used by <prgn>dpkg</prgn> when
9893 installing or removing the package; others are scripts which
9894 the package maintainer wants <prgn>dpkg</prgn> to run.
9898 It is possible to put other files in the package control
9899 information file area, but this is not generally a good idea
9900 (though they will largely be ignored).
9904 Here is a brief list of the control information files supported
9905 by <prgn>dpkg</prgn> and a summary of what they're used for.
9910 <tag><tt>control</tt>
9913 This is the key description file used by
9914 <prgn>dpkg</prgn>. It specifies the package's name
9915 and version, gives its description for the user,
9916 states its relationships with other packages, and so
9917 forth. See <ref id="sourcecontrolfiles"> and
9918 <ref id="binarycontrolfiles">.
9922 It is usually generated automatically from information
9923 in the source package by the
9924 <prgn>dpkg-gencontrol</prgn> program, and with
9925 assistance from <prgn>dpkg-shlibdeps</prgn>.
9926 See <ref id="pkg-sourcetools">.
9930 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9935 These are executable files (usually scripts) which
9936 <prgn>dpkg</prgn> runs during installation, upgrade
9937 and removal of packages. They allow the package to
9938 deal with matters which are particular to that package
9939 or require more complicated processing than that
9940 provided by <prgn>dpkg</prgn>. Details of when and
9941 how they are called are in <ref id="maintainerscripts">.
9945 It is very important to make these scripts idempotent.
9946 See <ref id="idempotency">.
9950 The maintainer scripts are not guaranteed to run with a
9951 controlling terminal and may not be able to interact with
9952 the user. See <ref id="controllingterminal">.
9956 <tag><tt>conffiles</tt>
9959 This file contains a list of configuration files which
9960 are to be handled automatically by <prgn>dpkg</prgn>
9961 (see <ref id="pkg-conffiles">). Note that not necessarily
9962 every configuration file should be listed here.
9965 <tag><tt>shlibs</tt>
9968 This file contains a list of the shared libraries
9969 supplied by the package, with dependency details for
9970 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9971 when it determines what dependencies are required in a
9972 package control file. The <tt>shlibs</tt> file format
9973 is described on <ref id="shlibs">.
9978 <sect id="pkg-controlfile">
9979 <heading>The main control information file: <tt>control</tt></heading>
9982 The most important control information file used by
9983 <prgn>dpkg</prgn> when it installs a package is
9984 <tt>control</tt>. It contains all the package's "vital
9989 The binary package control files of packages built from
9990 Debian sources are made by a special tool,
9991 <prgn>dpkg-gencontrol</prgn>, which reads
9992 <file>debian/control</file> and <file>debian/changelog</file> to
9993 find the information it needs. See <ref id="pkg-sourcepkg"> for
9998 The fields in binary package control files are listed in
9999 <ref id="binarycontrolfiles">.
10003 A description of the syntax of control files and the purpose
10004 of the fields is available in <ref id="controlfields">.
10009 <heading>Time Stamps</heading>
10012 See <ref id="timestamps">.
10017 <appendix id="pkg-sourcepkg">
10018 <heading>Source packages (from old Packaging Manual) </heading>
10021 The Debian binary packages in the distribution are generated
10022 from Debian sources, which are in a special format to assist
10023 the easy and automatic building of binaries.
10026 <sect id="pkg-sourcetools">
10027 <heading>Tools for processing source packages</heading>
10030 Various tools are provided for manipulating source packages;
10031 they pack and unpack sources and help build of binary
10032 packages and help manage the distribution of new versions.
10036 They are introduced and typical uses described here; see
10037 <manref name="dpkg-source" section="1"> for full
10038 documentation about their arguments and operation.
10042 For examples of how to construct a Debian source package,
10043 and how to use those utilities that are used by Debian
10044 source packages, please see the <prgn>hello</prgn> example
10048 <sect1 id="pkg-dpkg-source">
10050 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10055 This program is frequently used by hand, and is also
10056 called from package-independent automated building scripts
10057 such as <prgn>dpkg-buildpackage</prgn>.
10061 To unpack a package it is typically invoked with
10063 dpkg-source -x <var>.../path/to/filename</var>.dsc
10068 with the <file><var>filename</var>.tar.gz</file> and
10069 <file><var>filename</var>.diff.gz</file> (if applicable) in
10070 the same directory. It unpacks into
10071 <file><var>package</var>-<var>version</var></file>, and if
10073 <file><var>package</var>-<var>version</var>.orig</file>, in
10074 the current directory.
10078 To create a packed source archive it is typically invoked:
10080 dpkg-source -b <var>package</var>-<var>version</var>
10085 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10086 <file>.diff.gz</file> (if appropriate) in the current
10087 directory. <prgn>dpkg-source</prgn> does not clean the
10088 source tree first - this must be done separately if it is
10093 See also <ref id="pkg-sourcearchives">.</p>
10097 <sect1 id="pkg-dpkg-buildpackage">
10099 <prgn>dpkg-buildpackage</prgn> - overall package-building
10104 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10105 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10106 targets <tt>clean</tt>, <tt>build</tt> and
10107 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10108 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10109 source and binary package upload.
10113 It is usually invoked by hand from the top level of the
10114 built or unbuilt source directory. It may be invoked with
10115 no arguments; useful arguments include:
10116 <taglist compact="compact">
10117 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10120 Do not sign the <tt>.changes</tt> file or the
10121 source package <tt>.dsc</tt> file, respectively.</p>
10123 <tag><tt>-p<var>sign-command</var></tt></tag>
10126 Invoke <var>sign-command</var> instead of finding
10127 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10128 <var>sign-command</var> must behave just like
10129 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10131 <tag><tt>-r<var>root-command</var></tt></tag>
10134 When root privilege is required, invoke the command
10135 <var>root-command</var>. <var>root-command</var>
10136 should invoke its first argument as a command, from
10137 the <prgn>PATH</prgn> if necessary, and pass its
10138 second and subsequent arguments to the command it
10139 calls. If no <var>root-command</var> is supplied
10140 then <var>dpkg-buildpackage</var> will take no
10141 special action to gain root privilege, so that for
10142 most packages it will have to be invoked as root to
10145 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10148 Two types of binary-only build and upload - see
10149 <manref name="dpkg-source" section="1">.
10156 <sect1 id="pkg-dpkg-gencontrol">
10158 <prgn>dpkg-gencontrol</prgn> - generates binary package
10163 This program is usually called from <file>debian/rules</file>
10164 (see <ref id="pkg-sourcetree">) in the top level of the source
10169 This is usually done just before the files and directories in the
10170 temporary directory tree where the package is being built have their
10171 permissions and ownerships set and the package is constructed using
10172 <prgn>dpkg-deb/</prgn>
10174 This is so that the control file which is produced has
10175 the right permissions
10180 <prgn>dpkg-gencontrol</prgn> must be called after all the
10181 files which are to go into the package have been placed in
10182 the temporary build directory, so that its calculation of
10183 the installed size of a package is correct.
10187 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10188 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10189 variable substitutions created by
10190 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10195 For a package which generates only one binary package, and
10196 which builds it in <file>debian/tmp</file> relative to the top
10197 of the source package, it is usually sufficient to call
10198 <prgn>dpkg-gencontrol</prgn>.
10202 Sources which build several binaries will typically need
10205 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10206 </example> The <tt>-P</tt> tells
10207 <prgn>dpkg-gencontrol</prgn> that the package is being
10208 built in a non-default directory, and the <tt>-p</tt>
10209 tells it which package's control file should be generated.
10213 <prgn>dpkg-gencontrol</prgn> also adds information to the
10214 list of files in <file>debian/files</file>, for the benefit of
10215 (for example) a future invocation of
10216 <prgn>dpkg-genchanges</prgn>.</p>
10219 <sect1 id="pkg-dpkg-shlibdeps">
10221 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10226 This program is usually called from <file>debian/rules</file>
10227 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10228 id="pkg-sourcetree">), in the top level of the source tree.
10232 Its arguments are executables and shared libraries
10235 They may be specified either in the locations in the
10236 source tree where they are created or in the locations
10237 in the temporary build tree where they are installed
10238 prior to binary package creation.
10240 </footnote> for which shared library dependencies should
10241 be included in the binary package's control file.
10245 If some of the found shared libraries should only
10246 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10247 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10248 by using the <tt>-d<var>dependency-field</var></tt> option
10249 before those executable(s). (Each <tt>-d</tt> option
10250 takes effect until the next <tt>-d</tt>.)
10254 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10255 output control file to be modified. Instead by default it
10256 adds to the <file>debian/substvars</file> file variable
10257 settings like <tt>shlibs:Depends</tt>. These variable
10258 settings must be referenced in dependency fields in the
10259 appropriate per-binary-package sections of the source
10264 For example, a package that generates an essential part
10265 which requires dependencies, and optional parts that
10266 which only require a recommendation, would separate those
10267 two sets of dependencies into two different fields.<footnote>
10268 At the time of writing, an example for this was the
10269 <package/xmms/ package, with Depends used for the xmms
10270 executable, Recommends for the plug-ins and Suggests for
10271 even more optional features provided by unzip.
10273 It can say in its <file>debian/rules</file>:
10275 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10276 -dRecommends <var>optionalpart anotheroptionalpart</var>
10278 and then in its main control file <file>debian/control</file>:
10281 Depends: ${shlibs:Depends}
10282 Recommends: ${shlibs:Recommends}
10288 Sources which produce several binary packages with
10289 different shared library dependency requirements can use
10290 the <tt>-p<var>varnameprefix</var></tt> option to override
10291 the default <tt>shlibs:</tt> prefix (one invocation of
10292 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10293 They can thus produce several sets of dependency
10294 variables, each of the form
10295 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10296 which can be referred to in the appropriate parts of the
10297 binary package control files.
10302 <sect1 id="pkg-dpkg-distaddfile">
10304 <prgn>dpkg-distaddfile</prgn> - adds a file to
10305 <file>debian/files</file>
10309 Some packages' uploads need to include files other than
10310 the source and binary package files.
10314 <prgn>dpkg-distaddfile</prgn> adds a file to the
10315 <file>debian/files</file> file so that it will be included in
10316 the <file>.changes</file> file when
10317 <prgn>dpkg-genchanges</prgn> is run.
10321 It is usually invoked from the <tt>binary</tt> target of
10322 <file>debian/rules</file>:
10324 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10326 The <var>filename</var> is relative to the directory where
10327 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10328 is usually the directory above the top level of the source
10329 tree. The <file>debian/rules</file> target should put the
10330 file there just before or just after calling
10331 <prgn>dpkg-distaddfile</prgn>.
10335 The <var>section</var> and <var>priority</var> are passed
10336 unchanged into the resulting <file>.changes</file> file.
10341 <sect1 id="pkg-dpkg-genchanges">
10343 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10344 upload control file
10348 This program is usually called by package-independent
10349 automatic building scripts such as
10350 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10355 It is usually called in the top level of a built source
10356 tree, and when invoked with no arguments will print out a
10357 straightforward <file>.changes</file> file based on the
10358 information in the source package's changelog and control
10359 file and the binary and source packages which should have
10365 <sect1 id="pkg-dpkg-parsechangelog">
10367 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10368 representation of a changelog
10372 This program is used internally by
10373 <prgn>dpkg-source</prgn> et al. It may also occasionally
10374 be useful in <file>debian/rules</file> and elsewhere. It
10375 parses a changelog, <file>debian/changelog</file> by default,
10376 and prints a control-file format representation of the
10377 information in it to standard output.
10381 <sect1 id="pkg-dpkg-architecture">
10383 <prgn>dpkg-architecture</prgn> - information about the build and
10388 This program can be used manually, but is also invoked by
10389 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10390 environment or make variables which specify the build and host
10391 architecture for the package building process.
10396 <sect id="pkg-sourcetree">
10397 <heading>The Debian package source tree</heading>
10400 The source archive scheme described later is intended to
10401 allow a Debian package source tree with some associated
10402 control information to be reproduced and transported easily.
10403 The Debian package source tree is a version of the original
10404 program with certain files added for the benefit of the
10405 packaging process, and with any other changes required
10406 made to the rest of the source code and installation
10411 The extra files created for Debian are in the subdirectory
10412 <file>debian</file> of the top level of the Debian package
10413 source tree. They are described below.
10416 <sect1 id="pkg-debianrules">
10417 <heading><file>debian/rules</file> - the main building script</heading>
10420 See <ref id="debianrules">.
10424 <sect1 id="pkg-srcsubstvars">
10425 <heading><file>debian/substvars</file> and variable substitutions</heading>
10428 See <ref id="substvars">.
10434 <heading><file>debian/files</file></heading>
10437 See <ref id="debianfiles">.
10441 <sect1><heading><file>debian/tmp</file>
10445 This is the canonical temporary location for the
10446 construction of binary packages by the <tt>binary</tt>
10447 target. The directory <file>tmp</file> serves as the root of
10448 the file system tree as it is being constructed (for
10449 example, by using the package's upstream makefiles install
10450 targets and redirecting the output there), and it also
10451 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10452 id="pkg-bincreating">.
10456 If several binary packages are generated from the same
10457 source tree it is usual to use several
10458 <file>debian/tmp<var>something</var></file> directories, for
10459 example <file>tmp-a</file> or <file>tmp-doc</file>.
10463 Whatever <file>tmp</file> directories are created and used by
10464 <tt>binary</tt> must of course be removed by the
10465 <tt>clean</tt> target.</p></sect1>
10469 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10473 As it exists on the FTP site, a Debian source package
10474 consists of three related files. You must have the right
10475 versions of all three to be able to use them.
10480 <tag>Debian source control file - <tt>.dsc</tt></tag>
10482 This file is a control file used by <prgn>dpkg-source</prgn>
10483 to extract a source package.
10484 See <ref id="debiansourcecontrolfiles">.
10488 Original source archive -
10490 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10496 This is a compressed (with <tt>gzip -9</tt>)
10497 <prgn>tar</prgn> file containing the source code from
10498 the upstream authors of the program.
10503 Debian package diff -
10505 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10511 This is a unified context diff (<tt>diff -u</tt>)
10512 giving the changes which are required to turn the
10513 original source into the Debian source. These changes
10514 may only include editing and creating plain files.
10515 The permissions of files, the targets of symbolic
10516 links and the characteristics of special files or
10517 pipes may not be changed and no files may be removed
10522 All the directories in the diff must exist, except the
10523 <file>debian</file> subdirectory of the top of the source
10524 tree, which will be created by
10525 <prgn>dpkg-source</prgn> if necessary when unpacking.
10529 The <prgn>dpkg-source</prgn> program will
10530 automatically make the <file>debian/rules</file> file
10531 executable (see below).</p></item>
10536 If there is no original source code - for example, if the
10537 package is specially prepared for Debian or the Debian
10538 maintainer is the same as the upstream maintainer - the
10539 format is slightly different: then there is no diff, and the
10541 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10542 and preferably contains a directory named
10543 <file><var>package</var>-<var>version</var></file>.
10548 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10551 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10552 Debian source package. However, if it is not available it
10553 is possible to unpack a Debian source archive as follows:
10554 <enumlist compact="compact">
10557 Untar the tarfile, which will create a <file>.orig</file>
10561 <p>Rename the <file>.orig</file> directory to
10562 <file><var>package</var>-<var>version</var></file>.</p>
10566 Create the subdirectory <file>debian</file> at the top of
10567 the source tree.</p>
10569 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10571 <item><p>Untar the tarfile again if you want a copy of the original
10572 source code alongside the Debian version.</p>
10577 It is not possible to generate a valid Debian source archive
10578 without using <prgn>dpkg-source</prgn>. In particular,
10579 attempting to use <prgn>diff</prgn> directly to generate the
10580 <file>.diff.gz</file> file will not work.
10584 <heading>Restrictions on objects in source packages</heading>
10587 The source package may not contain any hard links
10589 This is not currently detected when building source
10590 packages, but only when extracting
10594 Hard links may be permitted at some point in the
10595 future, but would require a fair amount of
10597 </footnote>, device special files, sockets or setuid or
10600 Setgid directories are allowed.
10605 The source packaging tools manage the changes between the
10606 original and Debian source using <prgn>diff</prgn> and
10607 <prgn>patch</prgn>. Turning the original source tree as
10608 included in the <file>.orig.tar.gz</file> into the Debian
10609 package source must not involve any changes which cannot be
10610 handled by these tools. Problematic changes which cause
10611 <prgn>dpkg-source</prgn> to halt with an error when
10612 building the source package are:
10613 <list compact="compact">
10614 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10616 <item><p>Changing the targets of symbolic links.</p>
10618 <item><p>Creating directories, other than <file>debian</file>.</p>
10620 <item><p>Changes to the contents of binary files.</p></item>
10621 </list> Changes which cause <prgn>dpkg-source</prgn> to
10622 print a warning but continue anyway are:
10623 <list compact="compact">
10626 Removing files, directories or symlinks.
10628 Renaming a file is not treated specially - it is
10629 seen as the removal of the old file (which
10630 generates a warning, but is otherwise ignored),
10631 and the creation of the new one.
10637 Changed text files which are missing the usual final
10638 newline (either in the original or the modified
10643 Changes which are not represented, but which are not detected by
10644 <prgn>dpkg-source</prgn>, are:
10645 <list compact="compact">
10646 <item><p>Changing the permissions of files (other than
10647 <file>debian/rules</file>) and directories.</p></item>
10652 The <file>debian</file> directory and <file>debian/rules</file>
10653 are handled specially by <prgn>dpkg-source</prgn> - before
10654 applying the changes it will create the <file>debian</file>
10655 directory, and afterwards it will make
10656 <file>debian/rules</file> world-executable.
10662 <appendix id="pkg-controlfields">
10663 <heading>Control files and their fields (from old Packaging Manual)</heading>
10666 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10667 data in a common format, known as control files. Binary and
10668 source packages have control data as do the <file>.changes</file>
10669 files which control the installation of uploaded files, and
10670 <prgn>dpkg</prgn>'s internal databases are in a similar
10675 <heading>Syntax of control files</heading>
10678 See <ref id="controlsyntax">.
10682 It is important to note that there are several fields which
10683 are optional as far as <prgn>dpkg</prgn> and the related
10684 tools are concerned, but which must appear in every Debian
10685 package, or whose omission may cause problems.
10690 <heading>List of fields</heading>
10693 See <ref id="controlfieldslist">.
10697 This section now contains only the fields that didn't belong
10698 to the Policy manual.
10701 <sect1 id="pkg-f-Filename">
10702 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10705 These fields in <tt>Packages</tt> files give the
10706 filename(s) of (the parts of) a package in the
10707 distribution directories, relative to the root of the
10708 Debian hierarchy. If the package has been split into
10709 several parts the parts are all listed in order, separated
10714 <sect1 id="pkg-f-Size">
10715 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10718 These fields in <file>Packages</file> files give the size (in
10719 bytes, expressed in decimal) and MD5 checksum of the
10720 file(s) which make(s) up a binary package in the
10721 distribution. If the package is split into several parts
10722 the values for the parts are listed in order, separated by
10727 <sect1 id="pkg-f-Status">
10728 <heading><tt>Status</tt></heading>
10731 This field in <prgn>dpkg</prgn>'s status file records
10732 whether the user wants a package installed, removed or
10733 left alone, whether it is broken (requiring
10734 re-installation) or not and what its current state on the
10735 system is. Each of these pieces of information is a
10740 <sect1 id="pkg-f-Config-Version">
10741 <heading><tt>Config-Version</tt></heading>
10744 If a package is not installed or not configured, this
10745 field in <prgn>dpkg</prgn>'s status file records the last
10746 version of the package which was successfully
10751 <sect1 id="pkg-f-Conffiles">
10752 <heading><tt>Conffiles</tt></heading>
10755 This field in <prgn>dpkg</prgn>'s status file contains
10756 information about the automatically-managed configuration
10757 files held by a package. This field should <em>not</em>
10758 appear anywhere in a package!
10763 <heading>Obsolete fields</heading>
10766 These are still recognized by <prgn>dpkg</prgn> but should
10767 not appear anywhere any more.
10769 <taglist compact="compact">
10771 <tag><tt>Revision</tt></tag>
10772 <tag><tt>Package-Revision</tt></tag>
10773 <tag><tt>Package_Revision</tt></tag>
10775 The Debian revision part of the package version was
10776 at one point in a separate control field. This
10777 field went through several names.
10780 <tag><tt>Recommended</tt></tag>
10781 <item>Old name for <tt>Recommends</tt>.</item>
10783 <tag><tt>Optional</tt></tag>
10784 <item>Old name for <tt>Suggests</tt>.</item>
10786 <tag><tt>Class</tt></tag>
10787 <item>Old name for <tt>Priority</tt>.</item>
10796 <appendix id="pkg-conffiles">
10797 <heading>Configuration file handling (from old Packaging Manual)</heading>
10800 <prgn>dpkg</prgn> can do a certain amount of automatic
10801 handling of package configuration files.
10805 Whether this mechanism is appropriate depends on a number of
10806 factors, but basically there are two approaches to any
10807 particular configuration file.
10811 The easy method is to ship a best-effort configuration in the
10812 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10813 handle updates. If the user is unlikely to want to edit the
10814 file, but you need them to be able to without losing their
10815 changes, and a new package with a changed version of the file
10816 is only released infrequently, this is a good approach.
10820 The hard method is to build the configuration file from
10821 scratch in the <prgn>postinst</prgn> script, and to take the
10822 responsibility for fixing any mistakes made in earlier
10823 versions of the package automatically. This will be
10824 appropriate if the file is likely to need to be different on
10828 <sect><heading>Automatic handling of configuration files by
10833 A package may contain a control information file called
10834 <tt>conffiles</tt>. This file should be a list of filenames
10835 of configuration files needing automatic handling, separated
10836 by newlines. The filenames should be absolute pathnames,
10837 and the files referred to should actually exist in the
10842 When a package is upgraded <prgn>dpkg</prgn> will process
10843 the configuration files during the configuration stage,
10844 shortly before it runs the package's <prgn>postinst</prgn>
10849 For each file it checks to see whether the version of the
10850 file included in the package is the same as the one that was
10851 included in the last version of the package (the one that is
10852 being upgraded from); it also compares the version currently
10853 installed on the system with the one shipped with the last
10858 If neither the user nor the package maintainer has changed
10859 the file, it is left alone. If one or the other has changed
10860 their version, then the changed version is preferred - i.e.,
10861 if the user edits their file, but the package maintainer
10862 doesn't ship a different version, the user's changes will
10863 stay, silently, but if the maintainer ships a new version
10864 and the user hasn't edited it the new version will be
10865 installed (with an informative message). If both have
10866 changed their version the user is prompted about the problem
10867 and must resolve the differences themselves.
10871 The comparisons are done by calculating the MD5 message
10872 digests of the files, and storing the MD5 of the file as it
10873 was included in the most recent version of the package.
10877 When a package is installed for the first time
10878 <prgn>dpkg</prgn> will install the file that comes with it,
10879 unless that would mean overwriting a file already on the
10884 However, note that <prgn>dpkg</prgn> will <em>not</em>
10885 replace a conffile that was removed by the user (or by a
10886 script). This is necessary because with some programs a
10887 missing file produces an effect hard or impossible to
10888 achieve in another way, so that a missing file needs to be
10889 kept that way if the user did it.
10893 Note that a package should <em>not</em> modify a
10894 <prgn>dpkg</prgn>-handled conffile in its maintainer
10895 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10896 the user confusing and possibly dangerous options for
10897 conffile update when the package is upgraded.</p>
10900 <sect><heading>Fully-featured maintainer script configuration
10905 For files which contain site-specific information such as
10906 the hostname and networking details and so forth, it is
10907 better to create the file in the package's
10908 <prgn>postinst</prgn> script.
10912 This will typically involve examining the state of the rest
10913 of the system to determine values and other information, and
10914 may involve prompting the user for some information which
10915 can't be obtained some other way.
10919 When using this method there are a couple of important
10920 issues which should be considered:
10924 If you discover a bug in the program which generates the
10925 configuration file, or if the format of the file changes
10926 from one version to the next, you will have to arrange for
10927 the postinst script to do something sensible - usually this
10928 will mean editing the installed configuration file to remove
10929 the problem or change the syntax. You will have to do this
10930 very carefully, since the user may have changed the file,
10931 perhaps to fix the very problem that your script is trying
10932 to deal with - you will have to detect these situations and
10933 deal with them correctly.
10937 If you do go down this route it's probably a good idea to
10938 make the program that generates the configuration file(s) a
10939 separate program in <file>/usr/sbin</file>, by convention called
10940 <file><var>package</var>config</file> and then run that if
10941 appropriate from the post-installation script. The
10942 <tt><var>package</var>config</tt> program should not
10943 unquestioningly overwrite an existing configuration - if its
10944 mode of operation is geared towards setting up a package for
10945 the first time (rather than any arbitrary reconfiguration
10946 later) you should have it check whether the configuration
10947 already exists, and require a <tt>--force</tt> flag to
10948 overwrite it.</p></sect>
10951 <appendix id="pkg-alternatives"><heading>Alternative versions of
10952 an interface - <prgn>update-alternatives</prgn> (from old
10957 When several packages all provide different versions of the
10958 same program or file it is useful to have the system select a
10959 default, but to allow the system administrator to change it
10960 and have their decisions respected.
10964 For example, there are several versions of the <prgn>vi</prgn>
10965 editor, and there is no reason to prevent all of them from
10966 being installed at once, each under their own name
10967 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10968 Nevertheless it is desirable to have the name <tt>vi</tt>
10969 refer to something, at least by default.
10973 If all the packages involved cooperate, this can be done with
10974 <prgn>update-alternatives</prgn>.
10978 Each package provides its own version under its own name, and
10979 calls <prgn>update-alternatives</prgn> in its postinst to
10980 register its version (and again in its prerm to deregister
10985 See the man page <manref name="update-alternatives"
10986 section="8"> for details.
10990 If <prgn>update-alternatives</prgn> does not seem appropriate
10991 you may wish to consider using diversions instead.</p>
10994 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10995 package's version of a file (from old Packaging Manual)
10999 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11000 when it reinstalls the package it belongs to, and to have it
11001 put the file from the package somewhere else instead.
11005 This can be used locally to override a package's version of a
11006 file, or by one package to override another's version (or
11007 provide a wrapper for it).
11011 Before deciding to use a diversion, read <ref
11012 id="pkg-alternatives"> to see if you really want a diversion
11013 rather than several alternative versions of a program.
11017 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11018 and updated by a special program <prgn>dpkg-divert</prgn>.
11019 Please see <manref name="dpkg-divert" section="8"> for full
11020 details of its operation.
11024 When a package wishes to divert a file from another, it should
11025 call <prgn>dpkg-divert</prgn> in its preinst to add the
11026 diversion and rename the existing file. For example,
11027 supposing that a <prgn>smailwrapper</prgn> package wishes to
11028 install a wrapper around <file>/usr/sbin/smail</file>:
11030 dpkg-divert --package smailwrapper --add --rename \
11031 --divert /usr/sbin/smail.real /usr/sbin/smail
11032 </example> The <tt>--package smailwrapper</tt> ensures that
11033 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11034 can bypass the diversion and get installed as the true version.
11035 It's safe to add the diversion unconditionally on upgrades since
11036 it will be left unchanged if it already exists, but
11037 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11038 message, make the command conditional on the version from which
11039 the package is being upgraded:
11041 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11042 dpkg-divert --package smailwrapper --add --rename \
11043 --divert /usr/sbin/smail.real /usr/sbin/smail
11045 </example> where <tt>1.0-2</tt> is the version at which the
11046 diversion was first added to the package. Running the command
11047 during abort-upgrade is pointless but harmless.
11051 The postrm has to do the reverse:
11053 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11054 dpkg-divert --package smailwrapper --remove --rename \
11055 --divert /usr/sbin/smail.real /usr/sbin/smail
11057 </example> If the diversion was added at a particular version, the
11058 postrm should also handle the failure case of upgrading from an
11059 older version (unless the older version is so old that direct
11060 upgrades are no longer supported):
11062 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11063 dpkg-divert --package smailwrapper --remove --rename \
11064 --divert /usr/sbin/smail.real /usr/sbin/smail
11066 </example> where <tt>1.02-2</tt> is the version at which the
11067 diversion was first added to the package. The postrm should not
11068 remove the diversion on upgrades both because there's no reason to
11069 remove the diversion only to immediately re-add it and since the
11070 postrm of the old package is run after unpacking so the removal of
11071 the diversion will fail.
11075 Do not attempt to divert a file which is vitally important for
11076 the system's operation - when using <prgn>dpkg-divert</prgn>
11077 there is a time, after it has been diverted but before
11078 <prgn>dpkg</prgn> has installed the new version, when the file
11079 does not exist.</p>
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