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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian distribution</em>.
355 Packages in the other archive areas (<tt>contrib</tt>,
356 <tt>non-free</tt>) are not considered to be part of the Debian
357 distribution, although we support their use and provide
358 infrastructure for them (such as our bug-tracking system and
359 mailing lists). This Debian Policy Manual applies to these
364 <heading>The Debian Free Software Guidelines</heading>
366 The Debian Free Software Guidelines (DFSG) form our
367 definition of "free software". These are:
369 <tag>1. Free Redistribution
372 The license of a Debian component may not restrict any
373 party from selling or giving away the software as a
374 component of an aggregate software distribution
375 containing programs from several different
376 sources. The license may not require a royalty or
377 other fee for such sale.
382 The program must include source code, and must allow
383 distribution in source code as well as compiled form.
385 <tag>3. Derived Works
388 The license must allow modifications and derived
389 works, and must allow them to be distributed under the
390 same terms as the license of the original software.
392 <tag>4. Integrity of The Author's Source Code
395 The license may restrict source-code from being
396 distributed in modified form <em>only</em> if the
397 license allows the distribution of "patch files"
398 with the source code for the purpose of modifying the
399 program at build time. The license must explicitly
400 permit distribution of software built from modified
401 source code. The license may require derived works to
402 carry a different name or version number from the
403 original software. (This is a compromise. The Debian
404 Project encourages all authors to not restrict any
405 files, source or binary, from being modified.)
407 <tag>5. No Discrimination Against Persons or Groups
410 The license must not discriminate against any person
413 <tag>6. No Discrimination Against Fields of Endeavor
416 The license must not restrict anyone from making use
417 of the program in a specific field of endeavor. For
418 example, it may not restrict the program from being
419 used in a business, or from being used for genetic
422 <tag>7. Distribution of License
425 The rights attached to the program must apply to all
426 to whom the program is redistributed without the need
427 for execution of an additional license by those
430 <tag>8. License Must Not Be Specific to Debian
433 The rights attached to the program must not depend on
434 the program's being part of a Debian system. If the
435 program is extracted from Debian and used or
436 distributed without Debian but otherwise within the
437 terms of the program's license, all parties to whom
438 the program is redistributed must have the same
439 rights as those that are granted in conjunction with
442 <tag>9. License Must Not Contaminate Other Software
445 The license must not place restrictions on other
446 software that is distributed along with the licensed
447 software. For example, the license must not insist
448 that all other programs distributed on the same medium
449 must be free software.
451 <tag>10. Example Licenses
454 The "GPL," "BSD," and "Artistic" licenses are examples of
455 licenses that we consider <em>free</em>.
462 <heading>Archive areas</heading>
465 <heading>The main archive area</heading>
468 Every package in <em>main</em> must comply with the DFSG
469 (Debian Free Software Guidelines).
473 In addition, the packages in <em>main</em>
474 <list compact="compact">
476 must not require a package outside of <em>main</em>
477 for compilation or execution (thus, the package must
478 not declare a "Depends", "Recommends", or
479 "Build-Depends" relationship on a non-<em>main</em>
483 must not be so buggy that we refuse to support them,
487 must meet all policy requirements presented in this
496 <heading>The contrib archive area</heading>
499 Every package in <em>contrib</em> must comply with the DFSG.
503 In addition, the packages in <em>contrib</em>
504 <list compact="compact">
506 must not be so buggy that we refuse to support them,
510 must meet all policy requirements presented in this
518 Examples of packages which would be included in
519 <em>contrib</em> are:
520 <list compact="compact">
522 free packages which require <em>contrib</em>,
523 <em>non-free</em> packages or packages which are not
524 in our archive at all for compilation or execution,
528 wrapper packages or other sorts of free accessories for
535 <sect1 id="non-free">
536 <heading>The non-free archive area</heading>
539 Packages must be placed in <em>non-free</em> if they are
540 not compliant with the DFSG or are encumbered by patents
541 or other legal issues that make their distribution
546 In addition, the packages in <em>non-free</em>
547 <list compact="compact">
549 must not be so buggy that we refuse to support them,
553 must meet all policy requirements presented in this
554 manual that it is possible for them to meet.
556 It is possible that there are policy
557 requirements which the package is unable to
558 meet, for example, if the source is
559 unavailable. These situations will need to be
560 handled on a case-by-case basis.
569 <sect id="pkgcopyright">
570 <heading>Copyright considerations</heading>
573 Every package must be accompanied by a verbatim copy of its
574 copyright information and distribution license in the file
575 <file>/usr/share/doc/<var>package</var>/copyright</file>
576 (see <ref id="copyrightfile"> for further details).
580 We reserve the right to restrict files from being included
581 anywhere in our archives if
582 <list compact="compact">
584 their use or distribution would break a law,
587 there is an ethical conflict in their distribution or
591 we would have to sign a license for them, or
594 their distribution would conflict with other project
601 Programs whose authors encourage the user to make
602 donations are fine for the main distribution, provided
603 that the authors do not claim that not donating is
604 immoral, unethical, illegal or something similar; in such
605 a case they must go in <em>non-free</em>.
609 Packages whose copyright permission notices (or patent
610 problems) do not even allow redistribution of binaries
611 only, and where no special permission has been obtained,
612 must not be placed on the Debian FTP site and its mirrors
617 Note that under international copyright law (this applies
618 in the United States, too), <em>no</em> distribution or
619 modification of a work is allowed without an explicit
620 notice saying so. Therefore a program without a copyright
621 notice <em>is</em> copyrighted and you may not do anything
622 to it without risking being sued! Likewise if a program
623 has a copyright notice but no statement saying what is
624 permitted then nothing is permitted.
628 Many authors are unaware of the problems that restrictive
629 copyrights (or lack of copyright notices) can cause for
630 the users of their supposedly-free software. It is often
631 worthwhile contacting such authors diplomatically to ask
632 them to modify their license terms. However, this can be a
633 politically difficult thing to do and you should ask for
634 advice on the <tt>debian-legal</tt> mailing list first, as
639 When in doubt about a copyright, send mail to
640 <email>debian-legal@lists.debian.org</email>. Be prepared
641 to provide us with the copyright statement. Software
642 covered by the GPL, public domain software and BSD-like
643 copyrights are safe; be wary of the phrases "commercial
644 use prohibited" and "distribution restricted".
648 <sect id="subsections">
649 <heading>Sections</heading>
652 The packages in the archive areas <em>main</em>,
653 <em>contrib</em> and <em>non-free</em> are grouped further into
654 <em>sections</em> to simplify handling.
658 The archive area and section for each package should be
659 specified in the package's <tt>Section</tt> control record (see
660 <ref id="f-Section">). However, the maintainer of the Debian
661 archive may override this selection to ensure the consistency of
662 the Debian distribution. The <tt>Section</tt> field should be
664 <list compact="compact">
666 <em>section</em> if the package is in the
667 <em>main</em> archive area,
670 <em>area/section</em> if the package is in
671 the <em>contrib</em> or <em>non-free</em>
678 The Debian archive maintainers provide the authoritative
679 list of sections. At present, they are:
680 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
681 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
682 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
683 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
684 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
685 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
686 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
687 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
688 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
689 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
690 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
691 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
692 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
693 <em>zope</em>. The additional section <em>debian-installer</em>
694 contains special packages used by the installer and is not used
695 for normal Debian packages.
699 For more information about the sections and their definitions,
700 see the <url id="http://packages.debian.org/unstable/"
701 name="list of sections in unstable">.
705 <sect id="priorities">
706 <heading>Priorities</heading>
709 Each package should have a <em>priority</em> value, which is
710 included in the package's <em>control record</em>
711 (see <ref id="f-Priority">).
712 This information is used by the Debian package management tools to
713 separate high-priority packages from less-important packages.
717 The following <em>priority levels</em> are recognized by the
718 Debian package management tools.
720 <tag><tt>required</tt></tag>
722 Packages which are necessary for the proper
723 functioning of the system (usually, this means that
724 dpkg functionality depends on these packages).
725 Removing a <tt>required</tt> package may cause your
726 system to become totally broken and you may not even
727 be able to use <prgn>dpkg</prgn> to put things back,
728 so only do so if you know what you are doing. Systems
729 with only the <tt>required</tt> packages are probably
730 unusable, but they do have enough functionality to
731 allow the sysadmin to boot and install more software.
733 <tag><tt>important</tt></tag>
735 Important programs, including those which one would
736 expect to find on any Unix-like system. If the
737 expectation is that an experienced Unix person who
738 found it missing would say "What on earth is going on,
739 where is <prgn>foo</prgn>?", it must be an
740 <tt>important</tt> package.<footnote>
741 This is an important criterion because we are
742 trying to produce, amongst other things, a free
745 Other packages without which the system will not run
746 well or be usable must also have priority
747 <tt>important</tt>. This does
748 <em>not</em> include Emacs, the X Window System, TeX
749 or any other large applications. The
750 <tt>important</tt> packages are just a bare minimum of
751 commonly-expected and necessary tools.
753 <tag><tt>standard</tt></tag>
755 These packages provide a reasonably small but not too
756 limited character-mode system. This is what will be
757 installed by default if the user doesn't select anything
758 else. It doesn't include many large applications.
760 <tag><tt>optional</tt></tag>
762 (In a sense everything that isn't required is
763 optional, but that's not what is meant here.) This is
764 all the software that you might reasonably want to
765 install if you didn't know what it was and don't have
766 specialized requirements. This is a much larger system
767 and includes the X Window System, a full TeX
768 distribution, and many applications. Note that
769 optional packages should not conflict with each other.
771 <tag><tt>extra</tt></tag>
773 This contains all packages that conflict with others
774 with required, important, standard or optional
775 priorities, or are only likely to be useful if you
776 already know what they are or have specialized
777 requirements (such as packages containing only detached
784 Packages must not depend on packages with lower priority
785 values (excluding build-time dependencies). In order to
786 ensure this, the priorities of one or more packages may need
795 <heading>Binary packages</heading>
798 The Debian distribution is based on the Debian
799 package management system, called <prgn>dpkg</prgn>. Thus,
800 all packages in the Debian distribution must be provided
801 in the <tt>.deb</tt> file format.
805 A <tt>.deb</tt> package contains two sets of files: a set of files
806 to install on the system when the package is installed, and a set
807 of files that provide additional metadata about the package or
808 which are executed when the package is installed or removed. This
809 second set of files is called <em>control information files</em>.
810 Among those files are the package maintainer scripts
811 and <file>control</file>, the <qref id="binarycontrolfiles">binary
812 package control file</qref> that contains the control fields for
813 the package. Other control information files
814 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
815 file</qref> used to store shared library dependency information
816 and the <file>conffiles</file> file that lists the package's
817 configuration files (described in <ref id="config-files">).
821 There is unfortunately a collision of terminology here between
822 control information files and files in the Debian control file
823 format. Throughout this document, a <em>control file</em> refers
824 to a file in the Debian control file format. These files are
825 documented in <ref id="controlfields">. Only files referred to
826 specifically as <em>control information files</em> are the files
827 included in the control information file member of
828 the <file>.deb</file> file format used by binary packages. Most
829 control information files are not in the Debian control file
834 <heading>The package name</heading>
837 Every package must have a name that's unique within the Debian
842 The package name is included in the control field
843 <tt>Package</tt>, the format of which is described
844 in <ref id="f-Package">.
845 The package name is also included as a part of the file name
846 of the <tt>.deb</tt> file.
851 <heading>The version of a package</heading>
854 Every package has a version number recorded in its
855 <tt>Version</tt> control file field, described in
856 <ref id="f-Version">.
860 The package management system imposes an ordering on version
861 numbers, so that it can tell whether packages are being up- or
862 downgraded and so that package system front end applications
863 can tell whether a package it finds available is newer than
864 the one installed on the system. The version number format
865 has the most significant parts (as far as comparison is
866 concerned) at the beginning.
870 If an upstream package has problematic version numbers they
871 should be converted to a sane form for use in the
872 <tt>Version</tt> field.
876 <heading>Version numbers based on dates</heading>
879 In general, Debian packages should use the same version
880 numbers as the upstream sources. However, upstream version
881 numbers based on some date formats (sometimes used for
882 development or "snapshot" releases) will not be ordered
883 correctly by the package management software. For
884 example, <prgn>dpkg</prgn> will consider "96May01" to be
885 greater than "96Dec24".
889 To prevent having to use epochs for every new upstream
890 version, the date-based portion of any upstream version number
891 should be given in a way that sorts correctly: four-digit year
892 first, followed by a two-digit numeric month, followed by a
893 two-digit numeric date, possibly with punctuation between the
898 Native Debian packages (i.e., packages which have been written
899 especially for Debian) whose version numbers include dates
900 should also follow these rules. If punctuation is desired
901 between the date components, remember that hyphen (<tt>-</tt>)
902 cannot be used in native package versions. Period
903 (<tt>.</tt>) is normally a good choice.
909 <sect id="maintainer">
910 <heading>The maintainer of a package</heading>
913 Every package must have a maintainer, except for orphaned
914 packages as described below. The maintainer may be one person
915 or a group of people reachable from a common email address, such
916 as a mailing list. The maintainer is responsible for
917 maintaining the Debian packaging files, evaluating and
918 responding appropriately to reported bugs, uploading new
919 versions of the package (either directly or through a sponsor),
920 ensuring that the package is placed in the appropriate archive
921 area and included in Debian releases as appropriate for the
922 stability and utility of the package, and requesting removal of
923 the package from the Debian distribution if it is no longer
924 useful or maintainable.
928 The maintainer must be specified in the <tt>Maintainer</tt>
929 control field with their correct name and a working email
930 address. The email address given in the <tt>Maintainer</tt>
931 control field must accept mail from those role accounts in
932 Debian used to send automated mails regarding the package. This
933 includes non-spam mail from the bug-tracking system, all mail
934 from the Debian archive maintenance software, and other role
935 accounts or automated processes that are commonly agreed on by
936 the project.<footnote>
937 A sample implementation of such a whitelist written for the
938 Mailman mailing list management software is used for mailing
939 lists hosted by alioth.debian.org.
941 If one person or team maintains several packages, they should
942 use the same form of their name and email address in
943 the <tt>Maintainer</tt> fields of those packages.
947 The format of the <tt>Maintainer</tt> control field is
948 described in <ref id="f-Maintainer">.
952 If the maintainer of the package is a team of people with a
953 shared email address, the <tt>Uploaders</tt> control field must
954 be present and must contain at least one human with their
955 personal email address. See <ref id="f-Uploaders"> for the
956 syntax of that field.
960 An orphaned package is one with no current maintainer. Orphaned
961 packages should have their <tt>Maintainer</tt> control field set
962 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
963 These packages are considered maintained by the Debian project
964 as a whole until someone else volunteers to take over
965 maintenance.<footnote>
966 The detailed procedure for gracefully orphaning a package can
967 be found in the Debian Developer's Reference
968 (see <ref id="related">).
973 <sect id="descriptions">
974 <heading>The description of a package</heading>
977 Every Debian package must have a <tt>Description</tt> control
978 field which contains a synopsis and extended description of the
979 package. Technical information about the format of the
980 <tt>Description</tt> field is in <ref id="f-Description">.
984 The description should describe the package (the program) to a
985 user (system administrator) who has never met it before so that
986 they have enough information to decide whether they want to
987 install it. This description should not just be copied verbatim
988 from the program's documentation.
992 Put important information first, both in the synopsis and
993 extended description. Sometimes only the first part of the
994 synopsis or of the description will be displayed. You can
995 assume that there will usually be a way to see the whole
996 extended description.
1000 The description should also give information about the
1001 significant dependencies and conflicts between this package
1002 and others, so that the user knows why these dependencies and
1003 conflicts have been declared.
1007 Instructions for configuring or using the package should
1008 not be included (that is what installation scripts,
1009 manual pages, info files, etc., are for). Copyright
1010 statements and other administrivia should not be included
1011 either (that is what the copyright file is for).
1014 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1017 The single line synopsis should be kept brief - certainly
1018 under 80 characters.
1022 Do not include the package name in the synopsis line. The
1023 display software knows how to display this already, and you
1024 do not need to state it. Remember that in many situations
1025 the user may only see the synopsis line - make it as
1026 informative as you can.
1031 <sect1 id="extendeddesc"><heading>The extended description</heading>
1034 Do not try to continue the single line synopsis into the
1035 extended description. This will not work correctly when
1036 the full description is displayed, and makes no sense
1037 where only the summary (the single line synopsis) is
1042 The extended description should describe what the package
1043 does and how it relates to the rest of the system (in terms
1044 of, for example, which subsystem it is which part of).
1048 The description field needs to make sense to anyone, even
1049 people who have no idea about any of the things the
1050 package deals with.<footnote>
1051 The blurb that comes with a program in its
1052 announcements and/or <prgn>README</prgn> files is
1053 rarely suitable for use in a description. It is
1054 usually aimed at people who are already in the
1055 community where the package is used.
1064 <heading>Dependencies</heading>
1067 Every package must specify the dependency information
1068 about other packages that are required for the first to
1073 For example, a dependency entry must be provided for any
1074 shared libraries required by a dynamically-linked executable
1075 binary in a package.
1079 Packages are not required to declare any dependencies they
1080 have on other packages which are marked <tt>Essential</tt>
1081 (see below), and should not do so unless they depend on a
1082 particular version of that package.<footnote>
1084 Essential is needed in part to avoid unresolvable dependency
1085 loops on upgrade. If packages add unnecessary dependencies
1086 on packages in this set, the chances that there
1087 <strong>will</strong> be an unresolvable dependency loop
1088 caused by forcing these Essential packages to be configured
1089 first before they need to be is greatly increased. It also
1090 increases the chances that frontends will be unable to
1091 <strong>calculate</strong> an upgrade path, even if one
1095 Also, functionality is rarely ever removed from the
1096 Essential set, but <em>packages</em> have been removed from
1097 the Essential set when the functionality moved to a
1098 different package. So depending on these packages <em>just
1099 in case</em> they stop being essential does way more harm
1106 Sometimes, a package requires another package to be installed
1107 <em>and</em> configured before it can be installed. In this
1108 case, you must specify a <tt>Pre-Depends</tt> entry for
1113 You should not specify a <tt>Pre-Depends</tt> entry for a
1114 package before this has been discussed on the
1115 <tt>debian-devel</tt> mailing list and a consensus about
1116 doing that has been reached.
1120 The format of the package interrelationship control fields is
1121 described in <ref id="relationships">.
1125 <sect id="virtual_pkg">
1126 <heading>Virtual packages</heading>
1129 Sometimes, there are several packages which offer
1130 more-or-less the same functionality. In this case, it's
1131 useful to define a <em>virtual package</em> whose name
1132 describes that common functionality. (The virtual
1133 packages only exist logically, not physically; that's why
1134 they are called <em>virtual</em>.) The packages with this
1135 particular function will then <em>provide</em> the virtual
1136 package. Thus, any other package requiring that function
1137 can simply depend on the virtual package without having to
1138 specify all possible packages individually.
1142 All packages should use virtual package names where
1143 appropriate, and arrange to create new ones if necessary.
1144 They should not use virtual package names (except privately,
1145 amongst a cooperating group of packages) unless they have
1146 been agreed upon and appear in the list of virtual package
1147 names. (See also <ref id="virtual">)
1151 The latest version of the authoritative list of virtual
1152 package names can be found in the <tt>debian-policy</tt> package.
1153 It is also available from the Debian web mirrors at
1154 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1155 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1159 The procedure for updating the list is described in the preface
1166 <heading>Base system</heading>
1169 The <tt>base system</tt> is a minimum subset of the Debian
1170 system that is installed before everything else
1171 on a new system. Only very few packages are allowed to form
1172 part of the base system, in order to keep the required disk
1177 The base system consists of all those packages with priority
1178 <tt>required</tt> or <tt>important</tt>. Many of them will
1179 be tagged <tt>essential</tt> (see below).
1184 <heading>Essential packages</heading>
1187 Essential is defined as the minimal set of functionality that
1188 must be available and usable on the system at all times, even
1189 when packages are in an unconfigured (but unpacked) state.
1190 Packages are tagged <tt>essential</tt> for a system using the
1191 <tt>Essential</tt> control field. The format of the
1192 <tt>Essential</tt> control field is described in <ref
1197 Since these packages cannot be easily removed (one has to
1198 specify an extra <em>force option</em> to
1199 <prgn>dpkg</prgn> to do so), this flag must not be used
1200 unless absolutely necessary. A shared library package
1201 must not be tagged <tt>essential</tt>; dependencies will
1202 prevent its premature removal, and we need to be able to
1203 remove it when it has been superseded.
1207 Since dpkg will not prevent upgrading of other packages
1208 while an <tt>essential</tt> package is in an unconfigured
1209 state, all <tt>essential</tt> packages must supply all of
1210 their core functionality even when unconfigured. If the
1211 package cannot satisfy this requirement it must not be
1212 tagged as essential, and any packages depending on this
1213 package must instead have explicit dependency fields as
1218 Maintainers should take great care in adding any programs,
1219 interfaces, or functionality to <tt>essential</tt> packages.
1220 Packages may assume that functionality provided by
1221 <tt>essential</tt> packages is always available without
1222 declaring explicit dependencies, which means that removing
1223 functionality from the Essential set is very difficult and is
1224 almost never done. Any capability added to an
1225 <tt>essential</tt> package therefore creates an obligation to
1226 support that capability as part of the Essential set in
1231 You must not tag any packages <tt>essential</tt> before
1232 this has been discussed on the <tt>debian-devel</tt>
1233 mailing list and a consensus about doing that has been
1238 <sect id="maintscripts">
1239 <heading>Maintainer Scripts</heading>
1242 The package installation scripts should avoid producing
1243 output which is unnecessary for the user to see and
1244 should rely on <prgn>dpkg</prgn> to stave off boredom on
1245 the part of a user installing many packages. This means,
1246 amongst other things, using the <tt>--quiet</tt> option on
1247 <prgn>install-info</prgn>.
1251 Errors which occur during the execution of an installation
1252 script must be checked and the installation must not
1253 continue after an error.
1257 Note that in general <ref id="scripts"> applies to package
1258 maintainer scripts, too.
1262 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1263 to another package without consulting the maintainer of that
1264 package first. When adding or removing diversions, package
1265 maintainer scripts must provide the <tt>--package</tt> flag
1266 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1270 All packages which supply an instance of a common command
1271 name (or, in general, filename) should generally use
1272 <prgn>update-alternatives</prgn>, so that they may be
1273 installed together. If <prgn>update-alternatives</prgn>
1274 is not used, then each package must use
1275 <tt>Conflicts</tt> to ensure that other packages are
1276 de-installed. (In this case, it may be appropriate to
1277 specify a conflict against earlier versions of something
1278 that previously did not use
1279 <prgn>update-alternatives</prgn>; this is an exception to
1280 the usual rule that versioned conflicts should be
1284 <sect1 id="maintscriptprompt">
1285 <heading>Prompting in maintainer scripts</heading>
1287 Package maintainer scripts may prompt the user if
1288 necessary. Prompting must be done by communicating
1289 through a program, such as <prgn>debconf</prgn>, which
1290 conforms to the Debian Configuration Management
1291 Specification, version 2 or higher.
1295 Packages which are essential, or which are dependencies of
1296 essential packages, may fall back on another prompting method
1297 if no such interface is available when they are executed.
1301 The Debian Configuration Management Specification is included
1302 in the <file>debconf_specification</file> files in the
1303 <package>debian-policy</package> package.
1304 It is also available from the Debian web mirrors at
1305 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1306 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1310 Packages which use the Debian Configuration Management
1311 Specification may contain the additional control information
1312 files <file>config</file>
1313 and <file>templates</file>. <file>config</file> is an
1314 additional maintainer script used for package configuration,
1315 and <file>templates</file> contains templates used for user
1316 prompting. The <prgn>config</prgn> script might be run before
1317 the <prgn>preinst</prgn> script and before the package is
1318 unpacked or any of its dependencies or pre-dependencies are
1319 satisfied. Therefore it must work using only the tools
1320 present in <em>essential</em> packages.<footnote>
1321 <package>Debconf</package> or another tool that
1322 implements the Debian Configuration Management
1323 Specification will also be installed, and any
1324 versioned dependencies on it will be satisfied
1325 before preconfiguration begins.
1330 Packages which use the Debian Configuration Management
1331 Specification must allow for translation of their user-visible
1332 messages by using a gettext-based system such as the one
1333 provided by the <package>po-debconf</package> package.
1337 Packages should try to minimize the amount of prompting
1338 they need to do, and they should ensure that the user
1339 will only ever be asked each question once. This means
1340 that packages should try to use appropriate shared
1341 configuration files (such as <file>/etc/papersize</file> and
1342 <file>/etc/news/server</file>), and shared
1343 <package>debconf</package> variables rather than each
1344 prompting for their own list of required pieces of
1349 It also means that an upgrade should not ask the same
1350 questions again, unless the user has used
1351 <tt>dpkg --purge</tt> to remove the package's configuration.
1352 The answers to configuration questions should be stored in an
1353 appropriate place in <file>/etc</file> so that the user can
1354 modify them, and how this has been done should be
1359 If a package has a vitally important piece of
1360 information to pass to the user (such as "don't run me
1361 as I am, you must edit the following configuration files
1362 first or you risk your system emitting badly-formatted
1363 messages"), it should display this in the
1364 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1365 prompt the user to hit return to acknowledge the
1366 message. Copyright messages do not count as vitally
1367 important (they belong in
1368 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1369 neither do instructions on how to use a program (these
1370 should be in on-line documentation, where all the users
1375 Any necessary prompting should almost always be confined
1376 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1377 script. If it is done in the <prgn>postinst</prgn>, it
1378 should be protected with a conditional so that
1379 unnecessary prompting doesn't happen if a package's
1380 installation fails and the <prgn>postinst</prgn> is
1381 called with <tt>abort-upgrade</tt>,
1382 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1392 <heading>Source packages</heading>
1394 <sect id="standardsversion">
1395 <heading>Standards conformance</heading>
1398 Source packages should specify the most recent version number
1399 of this policy document with which your package complied
1400 when it was last updated.
1404 This information may be used to file bug reports
1405 automatically if your package becomes too much out of date.
1409 The version is specified in the <tt>Standards-Version</tt>
1411 The format of the <tt>Standards-Version</tt> field is
1412 described in <ref id="f-Standards-Version">.
1416 You should regularly, and especially if your package has
1417 become out of date, check for the newest Policy Manual
1418 available and update your package, if necessary. When your
1419 package complies with the new standards you should update the
1420 <tt>Standards-Version</tt> source package field and
1421 release it.<footnote>
1422 See the file <file>upgrading-checklist</file> for
1423 information about policy which has changed between
1424 different versions of this document.
1430 <sect id="pkg-relations">
1431 <heading>Package relationships</heading>
1434 Source packages should specify which binary packages they
1435 require to be installed or not to be installed in order to
1436 build correctly. For example, if building a package
1437 requires a certain compiler, then the compiler should be
1438 specified as a build-time dependency.
1442 It is not necessary to explicitly specify build-time
1443 relationships on a minimal set of packages that are always
1444 needed to compile, link and put in a Debian package a
1445 standard "Hello World!" program written in C or C++. The
1446 required packages are called <em>build-essential</em>, and
1447 an informational list can be found in
1448 <file>/usr/share/doc/build-essential/list</file> (which is
1449 contained in the <tt>build-essential</tt>
1452 <list compact="compact">
1454 This allows maintaining the list separately
1455 from the policy documents (the list does not
1456 need the kind of control that the policy
1460 Having a separate package allows one to install
1461 the build-essential packages on a machine, as
1462 well as allowing other packages such as tasks to
1463 require installation of the build-essential
1464 packages using the depends relation.
1467 The separate package allows bug reports against
1468 the list to be categorized separately from
1469 the policy management process in the BTS.
1476 When specifying the set of build-time dependencies, one
1477 should list only those packages explicitly required by the
1478 build. It is not necessary to list packages which are
1479 required merely because some other package in the list of
1480 build-time dependencies depends on them.<footnote>
1481 The reason for this is that dependencies change, and
1482 you should list all those packages, and <em>only</em>
1483 those packages that <em>you</em> need directly. What
1484 others need is their business. For example, if you
1485 only link against <file>libimlib</file>, you will need to
1486 build-depend on <package>libimlib2-dev</package> but
1487 not against any <tt>libjpeg*</tt> packages, even
1488 though <tt>libimlib2-dev</tt> currently depends on
1489 them: installation of <package>libimlib2-dev</package>
1490 will automatically ensure that all of its run-time
1491 dependencies are satisfied.
1496 If build-time dependencies are specified, it must be
1497 possible to build the package and produce working binaries
1498 on a system with only essential and build-essential
1499 packages installed and also those required to satisfy the
1500 build-time relationships (including any implied
1501 relationships). In particular, this means that version
1502 clauses should be used rigorously in build-time
1503 relationships so that one cannot produce bad or
1504 inconsistently configured packages when the relationships
1505 are properly satisfied.
1509 <ref id="relationships"> explains the technical details.
1514 <heading>Changes to the upstream sources</heading>
1517 If changes to the source code are made that are not
1518 specific to the needs of the Debian system, they should be
1519 sent to the upstream authors in whatever form they prefer
1520 so as to be included in the upstream version of the
1525 If you need to configure the package differently for
1526 Debian or for Linux, and the upstream source doesn't
1527 provide a way to do so, you should add such configuration
1528 facilities (for example, a new <prgn>autoconf</prgn> test
1529 or <tt>#define</tt>) and send the patch to the upstream
1530 authors, with the default set to the way they originally
1531 had it. You can then easily override the default in your
1532 <file>debian/rules</file> or wherever is appropriate.
1536 You should make sure that the <prgn>configure</prgn> utility
1537 detects the correct architecture specification string
1538 (refer to <ref id="arch-spec"> for details).
1542 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1543 <prgn>configure</prgn> scripts are used, you should edit the
1544 <file>.in</file> files rather than editing the
1545 <prgn>Makefile</prgn> directly. This allows the user to
1546 reconfigure the package if necessary. You should
1547 <em>not</em> configure the package and edit the generated
1548 <prgn>Makefile</prgn>! This makes it impossible for someone
1549 else to later reconfigure the package without losing the
1555 <sect id="dpkgchangelog">
1556 <heading>Debian changelog: <file>debian/changelog</file></heading>
1559 Changes in the Debian version of the package should be
1560 briefly explained in the Debian changelog file
1561 <file>debian/changelog</file>.<footnote>
1563 Mistakes in changelogs are usually best rectified by
1564 making a new changelog entry rather than "rewriting
1565 history" by editing old changelog entries.
1568 This includes modifications
1569 made in the Debian package compared to the upstream one
1570 as well as other changes and updates to the package.
1572 Although there is nothing stopping an author who is also
1573 the Debian maintainer from using this changelog for all
1574 their changes, it will have to be renamed if the Debian
1575 and upstream maintainers become different people. In such
1576 a case, however, it might be better to maintain the package
1577 as a non-native package.
1582 The format of the <file>debian/changelog</file> allows the
1583 package building tools to discover which version of the package
1584 is being built and find out other release-specific information.
1588 That format is a series of entries like this:
1590 <example compact="compact">
1591 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1593 [optional blank line(s), stripped]
1595 * <var>change details</var>
1596 <var>more change details</var>
1598 [blank line(s), included in output of dpkg-parsechangelog]
1600 * <var>even more change details</var>
1602 [optional blank line(s), stripped]
1604 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1609 <var>package</var> and <var>version</var> are the source
1610 package name and version number.
1614 <var>distribution(s)</var> lists the distributions where
1615 this version should be installed when it is uploaded - it
1616 is copied to the <tt>Distribution</tt> field in the
1617 <file>.changes</file> file. See <ref id="f-Distribution">.
1621 <var>urgency</var> is the value for the <tt>Urgency</tt>
1622 field in the <file>.changes</file> file for the upload
1623 (see <ref id="f-Urgency">). It is not possible to specify
1624 an urgency containing commas; commas are used to separate
1625 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1626 <prgn>dpkg</prgn> changelog format (though there is
1627 currently only one useful <var>keyword</var>,
1632 The change details may in fact be any series of lines
1633 starting with at least two spaces, but conventionally each
1634 change starts with an asterisk and a separating space and
1635 continuation lines are indented so as to bring them in
1636 line with the start of the text above. Blank lines may be
1637 used here to separate groups of changes, if desired.
1641 If this upload resolves bugs recorded in the Bug Tracking
1642 System (BTS), they may be automatically closed on the
1643 inclusion of this package into the Debian archive by
1644 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1645 in the change details.<footnote>
1646 To be precise, the string should match the following
1647 Perl regular expression:
1649 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1651 Then all of the bug numbers listed will be closed by the
1652 archive maintenance script (<prgn>katie</prgn>) using the
1653 <var>version</var> of the changelog entry.
1655 This information is conveyed via the <tt>Closes</tt> field
1656 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1660 The maintainer name and email address used in the changelog
1661 should be the details of the person uploading <em>this</em>
1662 version. They are <em>not</em> necessarily those of the
1663 usual package maintainer.<footnote>
1664 If the developer uploading the package is not one of the usual
1665 maintainers of the package (as listed in
1666 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1667 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1668 fields of the package), the first line of the changelog is
1669 conventionally used to explain why a non-maintainer is
1670 uploading the package. The Debian Developer's Reference
1671 (see <ref id="related">) documents the conventions
1673 The information here will be copied to the <tt>Changed-By</tt>
1674 field in the <tt>.changes</tt> file
1675 (see <ref id="f-Changed-By">), and then later used to send an
1676 acknowledgement when the upload has been installed.
1680 The <var>date</var> has the following format<footnote>
1681 This is the same as the format generated by <tt>date
1683 </footnote> (compatible and with the same semantics of
1684 RFC 2822 and RFC 5322):
1685 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1687 <list compact="compact">
1689 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1692 dd is a one- or two-digit day of the month (01-31)
1695 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1698 <item>yyyy is the four-digit year (e.g. 2010)</item>
1699 <item>hh is the two-digit hour (00-23)</item>
1700 <item>mm is the two-digit minutes (00-59)</item>
1701 <item>ss is the two-digit seconds (00-60)</item>
1703 +zzzz or -zzzz is the the time zone offset from Coordinated
1704 Universal Time (UTC). "+" indicates that the time is ahead
1705 of (i.e., east of) UTC and "-" indicates that the time is
1706 behind (i.e., west of) UTC. The first two digits indicate
1707 the hour difference from UTC and the last two digits
1708 indicate the number of additional minutes difference from
1709 UTC. The last two digits must be in the range 00-59.
1715 The first "title" line with the package name must start
1716 at the left hand margin. The "trailer" line with the
1717 maintainer and date details must be preceded by exactly
1718 one space. The maintainer details and the date must be
1719 separated by exactly two spaces.
1723 The entire changelog must be encoded in UTF-8.
1727 For more information on placement of the changelog files
1728 within binary packages, please see <ref id="changelogs">.
1732 <sect id="dpkgcopyright">
1733 <heading>Copyright: <file>debian/copyright</file></heading>
1735 Every package must be accompanied by a verbatim copy of its
1736 copyright information and distribution license in the file
1737 <file>/usr/share/doc/<var>package</var>/copyright</file>
1738 (see <ref id="copyrightfile"> for further details). Also see
1739 <ref id="pkgcopyright"> for further considerations related
1740 to copyrights for packages.
1744 <heading>Error trapping in makefiles</heading>
1747 When <prgn>make</prgn> invokes a command in a makefile
1748 (including your package's upstream makefiles and
1749 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1750 means that <prgn>sh</prgn>'s usual bad error handling
1751 properties apply: if you include a miniature script as one
1752 of the commands in your makefile you'll find that if you
1753 don't do anything about it then errors are not detected
1754 and <prgn>make</prgn> will blithely continue after
1759 Every time you put more than one shell command (this
1760 includes using a loop) in a makefile command you
1761 must make sure that errors are trapped. For
1762 simple compound commands, such as changing directory and
1763 then running a program, using <tt>&&</tt> rather
1764 than semicolon as a command separator is sufficient. For
1765 more complex commands including most loops and
1766 conditionals you should include a separate <tt>set -e</tt>
1767 command at the start of every makefile command that's
1768 actually one of these miniature shell scripts.
1772 <sect id="timestamps">
1773 <heading>Time Stamps</heading>
1775 Maintainers should preserve the modification times of the
1776 upstream source files in a package, as far as is reasonably
1778 The rationale is that there is some information conveyed
1779 by knowing the age of the file, for example, you could
1780 recognize that some documentation is very old by looking
1781 at the modification time, so it would be nice if the
1782 modification time of the upstream source would be
1788 <sect id="restrictions">
1789 <heading>Restrictions on objects in source packages</heading>
1792 The source package may not contain any hard links<footnote>
1794 This is not currently detected when building source
1795 packages, but only when extracting
1799 Hard links may be permitted at some point in the
1800 future, but would require a fair amount of
1803 </footnote>, device special files, sockets or setuid or
1804 setgid files.<footnote>
1805 Setgid directories are allowed.
1810 <sect id="debianrules">
1811 <heading>Main building script: <file>debian/rules</file></heading>
1814 This file must be an executable makefile, and contains the
1815 package-specific recipes for compiling the package and
1816 building binary package(s) from the source.
1820 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1821 so that it can be invoked by saying its name rather than
1822 invoking <prgn>make</prgn> explicitly. That is, invoking
1823 either of <tt>make -f debian/rules <em>args...</em></tt>
1824 or <tt>./debian/rules <em>args...</em></tt> must result in
1829 The following targets are required and must be implemented
1830 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1831 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1832 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1836 Since an interactive <file>debian/rules</file> script makes it
1837 impossible to auto-compile that package and also makes it hard
1838 for other people to reproduce the same binary package, all
1839 required targets must be non-interactive. It also follows that
1840 any target that these targets depend on must also be
1845 The targets are as follows:
1847 <tag><tt>build</tt> (required)</tag>
1850 The <tt>build</tt> target should perform all the
1851 configuration and compilation of the package.
1852 If a package has an interactive pre-build
1853 configuration routine, the Debian source package
1854 must either be built after this has taken place (so
1855 that the binary package can be built without rerunning
1856 the configuration) or the configuration routine
1857 modified to become non-interactive. (The latter is
1858 preferable if there are architecture-specific features
1859 detected by the configuration routine.)
1863 For some packages, notably ones where the same
1864 source tree is compiled in different ways to produce
1865 two binary packages, the <tt>build</tt> target
1866 does not make much sense. For these packages it is
1867 good enough to provide two (or more) targets
1868 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1869 for each of the ways of building the package, and a
1870 <tt>build</tt> target that does nothing. The
1871 <tt>binary</tt> target will have to build the
1872 package in each of the possible ways and make the
1873 binary package out of each.
1877 The <tt>build</tt> target must not do anything
1878 that might require root privilege.
1882 The <tt>build</tt> target may need to run the
1883 <tt>clean</tt> target first - see below.
1887 When a package has a configuration and build routine
1888 which takes a long time, or when the makefiles are
1889 poorly designed, or when <tt>build</tt> needs to
1890 run <tt>clean</tt> first, it is a good idea to
1891 <tt>touch build</tt> when the build process is
1892 complete. This will ensure that if <tt>debian/rules
1893 build</tt> is run again it will not rebuild the whole
1895 Another common way to do this is for <tt>build</tt>
1896 to depend on <prgn>build-stamp</prgn> and to do
1897 nothing else, and for the <prgn>build-stamp</prgn>
1898 target to do the building and to <tt>touch
1899 build-stamp</tt> on completion. This is
1900 especially useful if the build routine creates a
1901 file or directory called <tt>build</tt>; in such a
1902 case, <tt>build</tt> will need to be listed as
1903 a phony target (i.e., as a dependency of the
1904 <tt>.PHONY</tt> target). See the documentation of
1905 <prgn>make</prgn> for more information on phony
1911 <tag><tt>build-arch</tt> (optional),
1912 <tt>build-indep</tt> (optional)
1916 A package may also provide both of the targets
1917 <tt>build-arch</tt> and <tt>build-indep</tt>.
1918 The <tt>build-arch</tt> target, if provided, should
1919 perform all the configuration and compilation required for
1920 producing all architecture-dependant binary packages
1921 (those packages for which the body of the
1922 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1923 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1924 target, if provided, should perform all the configuration
1925 and compilation required for producing all
1926 architecture-independent binary packages (those packages
1927 for which the body of the <tt>Architecture</tt> field
1928 in <tt>debian/control</tt> is <tt>all</tt>).
1929 The <tt>build</tt> target should depend on those of the
1930 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1931 are provided in the rules file.<footnote>
1932 The intent of this split is so that binary-only builds
1933 need not install the dependencies required for
1934 the <tt>build-indep</tt> target. However, this is not
1935 yet used in practice since <tt>dpkg-buildpackage
1936 -B</tt>, and therefore the autobuilders,
1937 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1938 due to the difficulties in determining whether the
1939 optional <tt>build-arch</tt> target exists.
1944 If one or both of the targets <tt>build-arch</tt> and
1945 <tt>build-indep</tt> are not provided, then invoking
1946 <file>debian/rules</file> with one of the not-provided
1947 targets as arguments should produce a exit status code
1948 of 2. Usually this is provided automatically by make
1949 if the target is missing.
1953 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1954 must not do anything that might require root privilege.
1958 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1959 (required), <tt>binary-indep</tt> (required)
1963 The <tt>binary</tt> target must be all that is
1964 necessary for the user to build the binary package(s)
1965 produced from this source package. It is
1966 split into two parts: <prgn>binary-arch</prgn> builds
1967 the binary packages which are specific to a particular
1968 architecture, and <tt>binary-indep</tt> builds
1969 those which are not.
1972 <tt>binary</tt> may be (and commonly is) a target with
1973 no commands which simply depends on
1974 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1977 Both <tt>binary-*</tt> targets should depend on the
1978 <tt>build</tt> target, or on the appropriate
1979 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1980 provided, so that the package is built if it has not
1981 been already. It should then create the relevant
1982 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1983 make their control files and <prgn>dpkg-deb</prgn> to
1984 build them and place them in the parent of the top
1989 Both the <tt>binary-arch</tt> and
1990 <tt>binary-indep</tt> targets <em>must</em> exist.
1991 If one of them has nothing to do (which will always be
1992 the case if the source generates only a single binary
1993 package, whether architecture-dependent or not), it
1994 must still exist and must always succeed.
1998 The <tt>binary</tt> targets must be invoked as
2000 The <prgn>fakeroot</prgn> package often allows one
2001 to build a package correctly even without being
2007 <tag><tt>clean</tt> (required)</tag>
2010 This must undo any effects that the <tt>build</tt>
2011 and <tt>binary</tt> targets may have had, except
2012 that it should leave alone any output files created in
2013 the parent directory by a run of a <tt>binary</tt>
2018 If a <tt>build</tt> file is touched at the end of
2019 the <tt>build</tt> target, as suggested above, it
2020 should be removed as the first action that
2021 <tt>clean</tt> performs, so that running
2022 <tt>build</tt> again after an interrupted
2023 <tt>clean</tt> doesn't think that everything is
2028 The <tt>clean</tt> target may need to be
2029 invoked as root if <tt>binary</tt> has been
2030 invoked since the last <tt>clean</tt>, or if
2031 <tt>build</tt> has been invoked as root (since
2032 <tt>build</tt> may create directories, for
2037 <tag><tt>get-orig-source</tt> (optional)</tag>
2040 This target fetches the most recent version of the
2041 original source package from a canonical archive site
2042 (via FTP or WWW, for example), does any necessary
2043 rearrangement to turn it into the original source
2044 tar file format described below, and leaves it in the
2049 This target may be invoked in any directory, and
2050 should take care to clean up any temporary files it
2055 This target is optional, but providing it if
2056 possible is a good idea.
2060 <tag><tt>patch</tt> (optional)</tag>
2063 This target performs whatever additional actions are
2064 required to make the source ready for editing (unpacking
2065 additional upstream archives, applying patches, etc.).
2066 It is recommended to be implemented for any package where
2067 <tt>dpkg-source -x</tt> does not result in source ready
2068 for additional modification. See
2069 <ref id="readmesource">.
2075 The <tt>build</tt>, <tt>binary</tt> and
2076 <tt>clean</tt> targets must be invoked with the current
2077 directory being the package's top-level directory.
2082 Additional targets may exist in <file>debian/rules</file>,
2083 either as published or undocumented interfaces or for the
2084 package's internal use.
2088 The architectures we build on and build for are determined
2089 by <prgn>make</prgn> variables using the
2090 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2091 You can determine the Debian architecture and the GNU style
2092 architecture specification string for the build architecture as
2093 well as for the host architecture. The build architecture is
2094 the architecture on which <file>debian/rules</file> is run and
2095 the package build is performed. The host architecture is the
2096 architecture on which the resulting package will be installed
2097 and run. These are normally the same, but may be different in
2098 the case of cross-compilation (building packages for one
2099 architecture on machines of a different architecture).
2103 Here is a list of supported <prgn>make</prgn> variables:
2104 <list compact="compact">
2106 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2109 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2112 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2115 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2116 specification string)
2119 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2120 <tt>DEB_*_GNU_TYPE</tt>)
2123 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2124 <tt>DEB_*_GNU_TYPE</tt>)
2126 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2127 the build architecture or <tt>HOST</tt> for specification of the
2132 Backward compatibility can be provided in the rules file
2133 by setting the needed variables to suitable default
2134 values; please refer to the documentation of
2135 <prgn>dpkg-architecture</prgn> for details.
2139 It is important to understand that the <tt>DEB_*_ARCH</tt>
2140 string only determines which Debian architecture we are
2141 building on or for. It should not be used to get the CPU
2142 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2143 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2144 GNU style variables should generally only be used with upstream
2148 <sect1 id="debianrules-options">
2149 <heading><file>debian/rules</file> and
2150 <tt>DEB_BUILD_OPTIONS</tt></heading>
2153 Supporting the standardized environment variable
2154 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2155 contain several flags to change how a package is compiled and
2156 built. Each flag must be in the form <var>flag</var> or
2157 <var>flag</var>=<var>options</var>. If multiple flags are
2158 given, they must be separated by whitespace.<footnote>
2159 Some packages support any delimiter, but whitespace is the
2160 easiest to parse inside a makefile and avoids ambiguity with
2161 flag values that contain commas.
2163 <var>flag</var> must start with a lowercase letter
2164 (<tt>a-z</tt>) and consist only of lowercase letters,
2165 numbers (<tt>0-9</tt>), and the characters
2166 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2167 <var>options</var> must not contain whitespace. The same
2168 tag should not be given multiple times with conflicting
2169 values. Package maintainers may assume that
2170 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2174 The meaning of the following tags has been standardized:
2178 This tag says to not run any build-time test suite
2179 provided by the package.
2183 The presence of this tag means that the package should
2184 be compiled with a minimum of optimization. For C
2185 programs, it is best to add <tt>-O0</tt> to
2186 <tt>CFLAGS</tt> (although this is usually the default).
2187 Some programs might fail to build or run at this level
2188 of optimization; it may be necessary to use
2189 <tt>-O1</tt>, for example.
2193 This tag means that the debugging symbols should not be
2194 stripped from the binary during installation, so that
2195 debugging information may be included in the package.
2197 <tag>parallel=n</tag>
2199 This tag means that the package should be built using up
2200 to <tt>n</tt> parallel processes if the package build
2201 system supports this.<footnote>
2202 Packages built with <tt>make</tt> can often implement
2203 this by passing the <tt>-j</tt><var>n</var> option to
2206 If the package build system does not support parallel
2207 builds, this string must be ignored. If the package
2208 build system only supports a lower level of concurrency
2209 than <var>n</var>, the package should be built using as
2210 many parallel processes as the package build system
2211 supports. It is up to the package maintainer to decide
2212 whether the package build times are long enough and the
2213 package build system is robust enough to make supporting
2214 parallel builds worthwhile.
2220 Unknown flags must be ignored by <file>debian/rules</file>.
2224 The following makefile snippet is an example of how one may
2225 implement the build options; you will probably have to
2226 massage this example in order to make it work for your
2228 <example compact="compact">
2231 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2232 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2233 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2234 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2236 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2241 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2242 INSTALL_PROGRAM += -s
2244 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2245 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2246 MAKEFLAGS += -j$(NUMJOBS)
2251 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2252 # Code to run the package test suite.
2259 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2260 <sect id="substvars">
2261 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2264 When <prgn>dpkg-gencontrol</prgn>
2265 generates <qref id="binarycontrolfiles">binary package control
2266 files</qref> (<file>DEBIAN/control</file>), it performs variable
2267 substitutions on its output just before writing it. Variable
2268 substitutions have the form <tt>${<var>variable</var>}</tt>.
2269 The optional file <file>debian/substvars</file> contains
2270 variable substitutions to be used; variables can also be set
2271 directly from <file>debian/rules</file> using the <tt>-V</tt>
2272 option to the source packaging commands, and certain predefined
2273 variables are also available.
2277 The <file>debian/substvars</file> file is usually generated and
2278 modified dynamically by <file>debian/rules</file> targets, in
2279 which case it must be removed by the <tt>clean</tt> target.
2283 See <manref name="deb-substvars" section="5"> for full
2284 details about source variable substitutions, including the
2285 format of <file>debian/substvars</file>.</p>
2288 <sect id="debianwatch">
2289 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2292 This is an optional, recommended configuration file for the
2293 <tt>uscan</tt> utility which defines how to automatically scan
2294 ftp or http sites for newly available updates of the
2295 package. This is used
2296 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2297 tools to help with quality control and maintenance of the
2298 distribution as a whole.
2303 <sect id="debianfiles">
2304 <heading>Generated files list: <file>debian/files</file></heading>
2307 This file is not a permanent part of the source tree; it
2308 is used while building packages to record which files are
2309 being generated. <prgn>dpkg-genchanges</prgn> uses it
2310 when it generates a <file>.changes</file> file.
2314 It should not exist in a shipped source package, and so it
2315 (and any backup files or temporary files such as
2316 <file>files.new</file><footnote>
2317 <file>files.new</file> is used as a temporary file by
2318 <prgn>dpkg-gencontrol</prgn> and
2319 <prgn>dpkg-distaddfile</prgn> - they write a new
2320 version of <tt>files</tt> here before renaming it,
2321 to avoid leaving a corrupted copy if an error
2323 </footnote>) should be removed by the
2324 <tt>clean</tt> target. It may also be wise to
2325 ensure a fresh start by emptying or removing it at the
2326 start of the <tt>binary</tt> target.
2330 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2331 package, it adds an entry to <file>debian/files</file> for the
2332 <file>.deb</file> file that will be created when <tt>dpkg-deb
2333 --build</tt> is run for that binary package. So for most
2334 packages all that needs to be done with this file is to
2335 delete it in the <tt>clean</tt> target.
2339 If a package upload includes files besides the source
2340 package and any binary packages whose control files were
2341 made with <prgn>dpkg-gencontrol</prgn> then they should be
2342 placed in the parent of the package's top-level directory
2343 and <prgn>dpkg-distaddfile</prgn> should be called to add
2344 the file to the list in <file>debian/files</file>.</p>
2347 <sect id="embeddedfiles">
2348 <heading>Convenience copies of code</heading>
2351 Some software packages include in their distribution convenience
2352 copies of code from other software packages, generally so that
2353 users compiling from source don't have to download multiple
2354 packages. Debian packages should not make use of these
2355 convenience copies unless the included package is explicitly
2356 intended to be used in this way.<footnote>
2357 For example, parts of the GNU build system work like this.
2359 If the included code is already in the Debian archive in the
2360 form of a library, the Debian packaging should ensure that
2361 binary packages reference the libraries already in Debian and
2362 the convenience copy is not used. If the included code is not
2363 already in Debian, it should be packaged separately as a
2364 prerequisite if possible.
2366 Having multiple copies of the same code in Debian is
2367 inefficient, often creates either static linking or shared
2368 library conflicts, and, most importantly, increases the
2369 difficulty of handling security vulnerabilities in the
2375 <sect id="readmesource">
2376 <heading>Source package handling:
2377 <file>debian/README.source</file></heading>
2380 If running <prgn>dpkg-source -x</prgn> on a source package
2381 doesn't produce the source of the package, ready for editing,
2382 and allow one to make changes and run
2383 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2384 without taking any additional steps, creating a
2385 <file>debian/README.source</file> documentation file is
2386 recommended. This file should explain how to do all of the
2389 <item>Generate the fully patched source, in a form ready for
2390 editing, that would be built to create Debian
2391 packages. Doing this with a <tt>patch</tt> target in
2392 <file>debian/rules</file> is recommended; see
2393 <ref id="debianrules">.</item>
2394 <item>Modify the source and save those modifications so that
2395 they will be applied when building the package.</item>
2396 <item>Remove source modifications that are currently being
2397 applied when building the package.</item>
2398 <item>Optionally, document what steps are necessary to
2399 upgrade the Debian source package to a new upstream version,
2400 if applicable.</item>
2402 This explanation should include specific commands and mention
2403 any additional required Debian packages. It should not assume
2404 familiarity with any specific Debian packaging system or patch
2409 This explanation may refer to a documentation file installed by
2410 one of the package's build dependencies provided that the
2411 referenced documentation clearly explains these tasks and is not
2412 a general reference manual.
2416 <file>debian/README.source</file> may also include any other
2417 information that would be helpful to someone modifying the
2418 source package. Even if the package doesn't fit the above
2419 description, maintainers are encouraged to document in a
2420 <file>debian/README.source</file> file any source package with a
2421 particularly complex or unintuitive source layout or build
2422 system (for example, a package that builds the same source
2423 multiple times to generate different binary packages).
2429 <chapt id="controlfields">
2430 <heading>Control files and their fields</heading>
2433 The package management system manipulates data represented in
2434 a common format, known as <em>control data</em>, stored in
2435 <em>control files</em>.
2436 Control files are used for source packages, binary packages and
2437 the <file>.changes</file> files which control the installation
2438 of uploaded files<footnote>
2439 <prgn>dpkg</prgn>'s internal databases are in a similar
2444 <sect id="controlsyntax">
2445 <heading>Syntax of control files</heading>
2448 A control file consists of one or more paragraphs of
2450 The paragraphs are also sometimes referred to as stanzas.
2452 The paragraphs are separated by blank lines. Some control
2453 files allow only one paragraph; others allow several, in
2454 which case each paragraph usually refers to a different
2455 package. (For example, in source packages, the first
2456 paragraph refers to the source package, and later paragraphs
2457 refer to binary packages generated from the source.)
2461 Each paragraph consists of a series of data fields; each
2462 field consists of the field name, followed by a colon and
2463 then the data/value associated with that field. It ends at
2464 the end of the (logical) line. Horizontal whitespace
2465 (spaces and tabs) may occur immediately before or after the
2466 value and is ignored there; it is conventional to put a
2467 single space after the colon. For example, a field might
2469 <example compact="compact">
2472 the field name is <tt>Package</tt> and the field value
2477 A paragraph must not contain more than one instance of a
2478 particular field name.
2482 Many fields' values may span several lines; in this case
2483 each continuation line must start with a space or a tab.
2484 Any trailing spaces or tabs at the end of individual
2485 lines of a field value are ignored.
2489 In fields where it is specified that lines may not wrap,
2490 only a single line of data is allowed and whitespace is not
2491 significant in a field body. Whitespace must not appear
2492 inside names (of packages, architectures, files or anything
2493 else) or version numbers, or between the characters of
2494 multi-character version relationships.
2498 Field names are not case-sensitive, but it is usual to
2499 capitalize the field names using mixed case as shown below.
2500 Field values are case-sensitive unless the description of the
2501 field says otherwise.
2505 Blank lines, or lines consisting only of spaces and tabs,
2506 are not allowed within field values or between fields - that
2507 would mean a new paragraph.
2511 All control files must be encoded in UTF-8.
2515 <sect id="sourcecontrolfiles">
2516 <heading>Source package control files -- <file>debian/control</file></heading>
2519 The <file>debian/control</file> file contains the most vital
2520 (and version-independent) information about the source package
2521 and about the binary packages it creates.
2525 The first paragraph of the control file contains information about
2526 the source package in general. The subsequent sets each describe a
2527 binary package that the source tree builds.
2531 The fields in the general paragraph (the first one, for the source
2534 <list compact="compact">
2535 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2538 <item><qref id="f-DM-Upload-Allowed"<tt>DM-Upload-Allowed</tt></qref></item>
2539 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2540 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2541 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2542 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2543 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2548 The fields in the binary package paragraphs are:
2550 <list compact="compact">
2551 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2553 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2554 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2555 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2556 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2557 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2558 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2563 The syntax and semantics of the fields are described below.
2567 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2568 generate control files for binary packages (see below), by
2569 <prgn>dpkg-genchanges</prgn> to generate the
2570 <file>.changes</file> file to accompany the upload, and by
2571 <prgn>dpkg-source</prgn> when it creates the
2572 <file>.dsc</file> source control file as part of a source
2573 archive. Many fields are permitted to span multiple lines in
2574 <file>debian/control</file> but not in any other control
2575 file. These tools are responsible for removing the line
2576 breaks from such fields when using fields from
2577 <file>debian/control</file> to generate other control files.
2581 The fields here may contain variable references - their
2582 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2583 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2584 when they generate output control files.
2585 See <ref id="substvars"> for details.
2589 In addition to the control file syntax described <qref
2590 id="controlsyntax">above</qref>, this file may also contain
2591 comment lines starting with <tt>#</tt> without any preceding
2592 whitespace. All such lines are ignored, even in the middle of
2593 continuation lines for a multiline field, and do not end a
2599 <sect id="binarycontrolfiles">
2600 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2603 The <file>DEBIAN/control</file> file contains the most vital
2604 (and version-dependent) information about a binary package. It
2605 consists of a single paragraph.
2609 The fields in this file are:
2611 <list compact="compact">
2612 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2614 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2616 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2617 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2618 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2619 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2620 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2621 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2628 <sect id="debiansourcecontrolfiles">
2629 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2632 This file consists of a single paragraph, possibly surrounded by
2633 a PGP signature. The fields of that paragraph are listed below.
2634 Their syntax is described above, in <ref id="pkg-controlfields">.
2636 <list compact="compact">
2637 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2640 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2641 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2644 <item><qref id="f-DM-Upload-Allowed"<tt>DM-Upload-Allowed</tt></qref></item>
2645 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2646 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2647 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2648 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2649 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2650 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2655 The source package control file is generated by
2656 <prgn>dpkg-source</prgn> when it builds the source
2657 archive, from other files in the source package,
2658 described above. When unpacking, it is checked against
2659 the files and directories in the other parts of the
2665 <sect id="debianchangesfiles">
2666 <heading>Debian changes files -- <file>.changes</file></heading>
2669 The <file>.changes</file> files are used by the Debian archive
2670 maintenance software to process updates to packages. They
2671 consist of a single paragraph, possibly surrounded by a PGP
2672 signature. That paragraph contains information from the
2673 <file>debian/control</file> file and other data about the
2674 source package gathered via <file>debian/changelog</file>
2675 and <file>debian/rules</file>.
2679 <file>.changes</file> files have a format version that is
2680 incremented whenever the documented fields or their meaning
2681 change. This document describes format &changesversion;.
2685 The fields in this file are:
2687 <list compact="compact">
2688 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2692 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2694 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2696 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2698 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2700 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2701 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2702 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2703 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2708 <sect id="controlfieldslist">
2709 <heading>List of fields</heading>
2711 <sect1 id="f-Source">
2712 <heading><tt>Source</tt></heading>
2715 This field identifies the source package name.
2719 In <file>debian/control</file> or a <file>.dsc</file> file,
2720 this field must contain only the name of the source package.
2724 In a binary package control file or a <file>.changes</file>
2725 file, the source package name may be followed by a version
2726 number in parentheses<footnote>
2727 It is customary to leave a space after the package name
2728 if a version number is specified.
2730 This version number may be omitted (and is, by
2731 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2732 the <tt>Version</tt> field of the binary package in
2733 question. The field itself may be omitted from a binary
2734 package control file when the source package has the same
2735 name and version as the binary package.
2739 Package names (both source and binary,
2740 see <ref id="f-Package">) must consist only of lower case
2741 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2742 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2743 (<tt>.</tt>). They must be at least two characters long and
2744 must start with an alphanumeric character.
2748 <sect1 id="f-Maintainer">
2749 <heading><tt>Maintainer</tt></heading>
2752 The package maintainer's name and email address. The name
2753 must come first, then the email address inside angle
2754 brackets <tt><></tt> (in RFC822 format).
2758 If the maintainer's name contains a full stop then the
2759 whole field will not work directly as an email address due
2760 to a misfeature in the syntax specified in RFC822; a
2761 program using this field as an address must check for this
2762 and correct the problem if necessary (for example by
2763 putting the name in round brackets and moving it to the
2764 end, and bringing the email address forward).
2768 See <ref id="maintainer"> for additional requirements and
2769 information about package maintainers.
2773 <sect1 id="f-Uploaders">
2774 <heading><tt>Uploaders</tt></heading>
2777 List of the names and email addresses of co-maintainers of the
2778 package, if any. If the package has other maintainers besides
2779 the one named in the <qref id="f-Maintainer">Maintainer
2780 field</qref>, their names and email addresses should be listed
2781 here. The format of each entry is the same as that of the
2782 Maintainer field, and multiple entries must be comma
2787 This is normally an optional field, but if
2788 the <tt>Maintainer</tt> control field names a group of people
2789 and a shared email address, the <tt>Uploaders</tt> field must
2790 be present and must contain at least one human with their
2791 personal email address.
2795 Any parser that interprets the Uploaders field in
2796 <file>debian/control</file> must permit it to span multiple
2797 lines. Line breaks in an Uploaders field that spans multiple
2798 lines are not significant and the semantics of the field are
2799 the same as if the line breaks had not been present.
2803 <sect1 id="f-Changed-By">
2804 <heading><tt>Changed-By</tt></heading>
2807 The name and email address of the person who prepared this
2808 version of the package, usually a maintainer. The syntax is
2809 the same as for the <qref id="f-Maintainer">Maintainer
2814 <sect1 id="f-Section">
2815 <heading><tt>Section</tt></heading>
2818 This field specifies an application area into which the package
2819 has been classified. See <ref id="subsections">.
2823 When it appears in the <file>debian/control</file> file,
2824 it gives the value for the subfield of the same name in
2825 the <tt>Files</tt> field of the <file>.changes</file> file.
2826 It also gives the default for the same field in the binary
2831 <sect1 id="f-Priority">
2832 <heading><tt>Priority</tt></heading>
2835 This field represents how important it is that the user
2836 have the package installed. See <ref id="priorities">.
2840 When it appears in the <file>debian/control</file> file,
2841 it gives the value for the subfield of the same name in
2842 the <tt>Files</tt> field of the <file>.changes</file> file.
2843 It also gives the default for the same field in the binary
2848 <sect1 id="f-Package">
2849 <heading><tt>Package</tt></heading>
2852 The name of the binary package.
2856 Binary package names must follow the same syntax and
2857 restrictions as source package names. See <ref id="f-Source">
2862 <sect1 id="f-Architecture">
2863 <heading><tt>Architecture</tt></heading>
2866 Depending on context and the control file used, the
2867 <tt>Architecture</tt> field can include the following sets of
2871 A unique single word identifying a Debian machine
2872 architecture as described in <ref id="arch-spec">.
2875 An architecture wildcard identifying a set of Debian
2876 machine architectures, see <ref id="arch-wildcard-spec">.
2877 <tt>any</tt> matches all Debian machine architectures
2878 and is the most frequently used.
2881 <tt>all</tt>, which indicates an
2882 architecture-independent package.
2885 <tt>source</tt>, which indicates a source package.
2891 In the main <file>debian/control</file> file in the source
2892 package, this field may contain the special
2893 value <tt>all</tt>, the special architecture
2894 wildcard <tt>any</tt>, or a list of specific and wildcard
2895 architectures separated by spaces. If <tt>all</tt>
2896 or <tt>any</tt> appears, that value must be the entire
2897 contents of the field. Most packages will use
2898 either <tt>all</tt> or <tt>any</tt>.
2902 Specifying a specific list of architectures indicates that the
2903 source will build an architecture-dependent package only on
2904 architectures included in the list. Specifying a list of
2905 architecture wildcards indicates that the source will build an
2906 architecture-dependent package on only those architectures
2907 that match any of the specified architecture wildcards.
2908 Specifying a list of architectures or architecture wildcards
2909 other than <tt>any</tt> is for the minority of cases where a
2910 program is not portable or is not useful on some
2911 architectures. Where possible, the program should be made
2916 In the source package control file <file>.dsc</file>, this
2917 field may contain either the architecture
2918 wildcard <tt>any</tt> or a list of architectures and
2919 architecture wildcards separated by spaces. If a list is
2920 given, it may include (or consist solely of) the special
2921 value <tt>all</tt>. In other words, in <file>.dsc</file>
2922 files unlike the <file>debian/control</file>, <tt>all</tt> may
2923 occur in combination with specific architectures.
2924 The <tt>Architecture</tt> field in the source package control
2925 file <file>.dsc</file> is generally constructed from
2926 the <tt>Architecture</tt> fields in
2927 the <file>debian/control</file> in the source package.
2931 Specifying <tt>any</tt> indicates that the source package
2932 isn't dependent on any particular architecture and should
2933 compile fine on any one. The produced binary package(s)
2934 will either be specific to whatever the current build
2935 architecture is or will be architecture-independent.
2939 Specifying only <tt>all</tt> indicates that the source package
2940 will only build architecture-independent packages. If this is
2941 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2942 <tt>any</tt> implies that the source package will build at
2943 least one architecture-dependent package.
2947 Specifying a list of architectures or architecture wildcards
2948 indicates that the source will build an architecture-dependent
2949 package, and will only work correctly on the listed or
2950 matching architectures. If the source package also builds at
2951 least one architecture-independent package, <tt>all</tt> will
2952 also be included in the list.
2956 In a <file>.changes</file> file, the <tt>Architecture</tt>
2957 field lists the architecture(s) of the package(s) currently
2958 being uploaded. This will be a list; if the source for the
2959 package is also being uploaded, the special
2960 entry <tt>source</tt> is also present. <tt>all</tt> will be
2961 present if any architecture-independent packages are being
2962 uploaded. Architecture wildcards such as <tt>any</tt> must
2963 never occur in the <tt>Architecture</tt> field in
2964 the <file>.changes</file> file.
2968 See <ref id="debianrules"> for information on how to get
2969 the architecture for the build process.
2973 <sect1 id="f-Essential">
2974 <heading><tt>Essential</tt></heading>
2977 This is a boolean field which may occur only in the
2978 control file of a binary package or in a per-package fields
2979 paragraph of a main source control data file.
2983 If set to <tt>yes</tt> then the package management system
2984 will refuse to remove the package (upgrading and replacing
2985 it is still possible). The other possible value is <tt>no</tt>,
2986 which is the same as not having the field at all.
2991 <heading>Package interrelationship fields:
2992 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2993 <tt>Recommends</tt>, <tt>Suggests</tt>,
2994 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2995 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2999 These fields describe the package's relationships with
3000 other packages. Their syntax and semantics are described
3001 in <ref id="relationships">.</p>
3004 <sect1 id="f-Standards-Version">
3005 <heading><tt>Standards-Version</tt></heading>
3008 The most recent version of the standards (the policy
3009 manual and associated texts) with which the package
3014 The version number has four components: major and minor
3015 version number and major and minor patch level. When the
3016 standards change in a way that requires every package to
3017 change the major number will be changed. Significant
3018 changes that will require work in many packages will be
3019 signaled by a change to the minor number. The major patch
3020 level will be changed for any change to the meaning of the
3021 standards, however small; the minor patch level will be
3022 changed when only cosmetic, typographical or other edits
3023 are made which neither change the meaning of the document
3024 nor affect the contents of packages.
3028 Thus only the first three components of the policy version
3029 are significant in the <em>Standards-Version</em> control
3030 field, and so either these three components or all four
3031 components may be specified.<footnote>
3032 In the past, people specified the full version number
3033 in the Standards-Version field, for example "2.3.0.0".
3034 Since minor patch-level changes don't introduce new
3035 policy, it was thought it would be better to relax
3036 policy and only require the first 3 components to be
3037 specified, in this example "2.3.0". All four
3038 components may still be used if someone wishes to do so.
3044 <sect1 id="f-Version">
3045 <heading><tt>Version</tt></heading>
3048 The version number of a package. The format is:
3049 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3053 The three components here are:
3055 <tag><var>epoch</var></tag>
3058 This is a single (generally small) unsigned integer. It
3059 may be omitted, in which case zero is assumed. If it is
3060 omitted then the <var>upstream_version</var> may not
3065 It is provided to allow mistakes in the version numbers
3066 of older versions of a package, and also a package's
3067 previous version numbering schemes, to be left behind.
3071 <tag><var>upstream_version</var></tag>
3074 This is the main part of the version number. It is
3075 usually the version number of the original ("upstream")
3076 package from which the <file>.deb</file> file has been made,
3077 if this is applicable. Usually this will be in the same
3078 format as that specified by the upstream author(s);
3079 however, it may need to be reformatted to fit into the
3080 package management system's format and comparison
3085 The comparison behavior of the package management system
3086 with respect to the <var>upstream_version</var> is
3087 described below. The <var>upstream_version</var>
3088 portion of the version number is mandatory.
3092 The <var>upstream_version</var> may contain only
3093 alphanumerics<footnote>
3094 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3096 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3097 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3098 tilde) and should start with a digit. If there is no
3099 <var>debian_revision</var> then hyphens are not allowed;
3100 if there is no <var>epoch</var> then colons are not
3105 <tag><var>debian_revision</var></tag>
3108 This part of the version number specifies the version of
3109 the Debian package based on the upstream version. It
3110 may contain only alphanumerics and the characters
3111 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3112 tilde) and is compared in the same way as the
3113 <var>upstream_version</var> is.
3117 It is optional; if it isn't present then the
3118 <var>upstream_version</var> may not contain a hyphen.
3119 This format represents the case where a piece of
3120 software was written specifically to be a Debian
3121 package, where the Debian package source must always
3122 be identical to the pristine source and therefore no
3123 revision indication is required.
3127 It is conventional to restart the
3128 <var>debian_revision</var> at <tt>1</tt> each time the
3129 <var>upstream_version</var> is increased.
3133 The package management system will break the version
3134 number apart at the last hyphen in the string (if there
3135 is one) to determine the <var>upstream_version</var> and
3136 <var>debian_revision</var>. The absence of a
3137 <var>debian_revision</var> is equivalent to a
3138 <var>debian_revision</var> of <tt>0</tt>.
3145 When comparing two version numbers, first the <var>epoch</var>
3146 of each are compared, then the <var>upstream_version</var> if
3147 <var>epoch</var> is equal, and then <var>debian_revision</var>
3148 if <var>upstream_version</var> is also equal.
3149 <var>epoch</var> is compared numerically. The
3150 <var>upstream_version</var> and <var>debian_revision</var>
3151 parts are compared by the package management system using the
3152 following algorithm:
3156 The strings are compared from left to right.
3160 First the initial part of each string consisting entirely of
3161 non-digit characters is determined. These two parts (one of
3162 which may be empty) are compared lexically. If a difference
3163 is found it is returned. The lexical comparison is a
3164 comparison of ASCII values modified so that all the letters
3165 sort earlier than all the non-letters and so that a tilde
3166 sorts before anything, even the end of a part. For example,
3167 the following parts are in sorted order from earliest to
3168 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3169 <tt>a</tt>.<footnote>
3170 One common use of <tt>~</tt> is for upstream pre-releases.
3171 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3172 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3177 Then the initial part of the remainder of each string which
3178 consists entirely of digit characters is determined. The
3179 numerical values of these two parts are compared, and any
3180 difference found is returned as the result of the comparison.
3181 For these purposes an empty string (which can only occur at
3182 the end of one or both version strings being compared) counts
3187 These two steps (comparing and removing initial non-digit
3188 strings and initial digit strings) are repeated until a
3189 difference is found or both strings are exhausted.
3193 Note that the purpose of epochs is to allow us to leave behind
3194 mistakes in version numbering, and to cope with situations
3195 where the version numbering scheme changes. It is
3196 <em>not</em> intended to cope with version numbers containing
3197 strings of letters which the package management system cannot
3198 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3199 silly orderings.<footnote>
3200 The author of this manual has heard of a package whose
3201 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3202 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3208 <sect1 id="f-Description">
3209 <heading><tt>Description</tt></heading>
3212 In a source or binary control file, the <tt>Description</tt>
3213 field contains a description of the binary package, consisting
3214 of two parts, the synopsis or the short description, and the
3215 long description. The field's format is as follows:
3220 Description: <single line synopsis>
3221 <extended description over several lines>
3226 The lines in the extended description can have these formats:
3232 Those starting with a single space are part of a paragraph.
3233 Successive lines of this form will be word-wrapped when
3234 displayed. The leading space will usually be stripped off.
3238 Those starting with two or more spaces. These will be
3239 displayed verbatim. If the display cannot be panned
3240 horizontally, the displaying program will line wrap them "hard"
3241 (i.e., without taking account of word breaks). If it can they
3242 will be allowed to trail off to the right. None, one or two
3243 initial spaces may be deleted, but the number of spaces
3244 deleted from each line will be the same (so that you can have
3245 indenting work correctly, for example).
3249 Those containing a single space followed by a single full stop
3250 character. These are rendered as blank lines. This is the
3251 <em>only</em> way to get a blank line<footnote>
3252 Completely empty lines will not be rendered as blank lines.
3253 Instead, they will cause the parser to think you're starting
3254 a whole new record in the control file, and will therefore
3255 likely abort with an error.
3260 Those containing a space, a full stop and some more characters.
3261 These are for future expansion. Do not use them.
3267 Do not use tab characters. Their effect is not predictable.
3271 See <ref id="descriptions"> for further information on this.
3275 In a <file>.changes</file> file, the <tt>Description</tt>
3276 field contains a summary of the descriptions for the packages
3277 being uploaded. For this case, the first line of the field
3278 value (the part on the same line as <tt>Description:</tt>) is
3279 always empty. The content of the field is expressed as
3280 continuation lines, one line per package. Each line is
3281 indented by one space and contains the name of a binary
3282 package, a space, a hyphen (<tt>-</tt>), a space, and the
3283 short description line from that package.
3287 <sect1 id="f-Distribution">
3288 <heading><tt>Distribution</tt></heading>
3291 In a <file>.changes</file> file or parsed changelog output
3292 this contains the (space-separated) name(s) of the
3293 distribution(s) where this version of the package should
3294 be installed. Valid distributions are determined by the
3295 archive maintainers.<footnote>
3296 Example distribution names in the Debian archive used in
3297 <file>.changes</file> files are:
3298 <taglist compact="compact">
3299 <tag><em>unstable</em></tag>
3301 This distribution value refers to the
3302 <em>developmental</em> part of the Debian distribution
3303 tree. Most new packages, new upstream versions of
3304 packages and bug fixes go into the <em>unstable</em>
3308 <tag><em>experimental</em></tag>
3310 The packages with this distribution value are deemed
3311 by their maintainers to be high risk. Oftentimes they
3312 represent early beta or developmental packages from
3313 various sources that the maintainers want people to
3314 try, but are not ready to be a part of the other parts
3315 of the Debian distribution tree.
3320 Others are used for updating stable releases or for
3321 security uploads. More information is available in the
3322 Debian Developer's Reference, section "The Debian
3326 The Debian archive software only supports listing a single
3327 distribution. Migration of packages to other distributions is
3328 handled outside of the upload process.
3333 <heading><tt>Date</tt></heading>
3336 This field includes the date the package was built or last
3337 edited. It must be in the same format as the <var>date</var>
3338 in a <file>debian/changelog</file> entry.
3342 The value of this field is usually extracted from the
3343 <file>debian/changelog</file> file - see
3344 <ref id="dpkgchangelog">).
3348 <sect1 id="f-Format">
3349 <heading><tt>Format</tt></heading>
3352 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3353 files, this field declares the format version of that file.
3354 The syntax of the field value is the same as that of
3355 a <qref id="f-Version">package version number</qref> except
3356 that no epoch or Debian revision is allowed. The format
3357 described in this document is <tt>&changesversion;</tt>.
3361 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3362 Debian source control</qref> files, this field declares the
3363 format of the source package. The field value is used by
3364 programs acting on a source package to interpret the list of
3365 files in the source package and determine how to unpack it.
3366 The syntax of the field value is a numeric major revision, a
3367 period, a numeric minor revision, and then an optional subtype
3368 after whitespace, which if specified is an alphanumeric word
3369 in parentheses. The subtype is optional in the syntax but may
3370 be mandatory for particular source format revisions.
3372 The source formats currently supported by the Debian archive
3373 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3374 and <tt>3.0 (quilt)</tt>.
3379 <sect1 id="f-Urgency">
3380 <heading><tt>Urgency</tt></heading>
3383 This is a description of how important it is to upgrade to
3384 this version from previous ones. It consists of a single
3385 keyword taking one of the values <tt>low</tt>,
3386 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3387 <tt>critical</tt><footnote>
3388 Other urgency values are supported with configuration
3389 changes in the archive software but are not used in Debian.
3390 The urgency affects how quickly a package will be considered
3391 for inclusion into the <tt>testing</tt> distribution and
3392 gives an indication of the importance of any fixes included
3393 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3394 treated as synonymous.
3395 </footnote> (not case-sensitive) followed by an optional
3396 commentary (separated by a space) which is usually in
3397 parentheses. For example:
3400 Urgency: low (HIGH for users of diversions)
3406 The value of this field is usually extracted from the
3407 <file>debian/changelog</file> file - see
3408 <ref id="dpkgchangelog">.
3412 <sect1 id="f-Changes">
3413 <heading><tt>Changes</tt></heading>
3416 This field contains the human-readable changes data, describing
3417 the differences between the last version and the current one.
3421 The first line of the field value (the part on the same line
3422 as <tt>Changes:</tt>) is always empty. The content of the
3423 field is expressed as continuation lines, with each line
3424 indented by at least one space. Blank lines must be
3425 represented by a line consisting only of a space and a full
3430 The value of this field is usually extracted from the
3431 <file>debian/changelog</file> file - see
3432 <ref id="dpkgchangelog">).
3436 Each version's change information should be preceded by a
3437 "title" line giving at least the version, distribution(s)
3438 and urgency, in a human-readable way.
3442 If data from several versions is being returned the entry
3443 for the most recent version should be returned first, and
3444 entries should be separated by the representation of a
3445 blank line (the "title" line may also be followed by the
3446 representation of a blank line).
3450 <sect1 id="f-Binary">
3451 <heading><tt>Binary</tt></heading>
3454 This field is a list of binary packages. Its syntax and
3455 meaning varies depending on the control file in which it
3460 When it appears in the <file>.dsc</file> file, it lists binary
3461 packages which a source package can produce, separated by
3463 A space after each comma is conventional.
3464 </footnote>. It may span multiple lines. The source package
3465 does not necessarily produce all of these binary packages for
3466 every architecture. The source control file doesn't contain
3467 details of which architectures are appropriate for which of
3468 the binary packages.
3472 When it appears in a <file>.changes</file> file, it lists the
3473 names of the binary packages being uploaded, separated by
3474 whitespace (not commas). It may span multiple lines.
3478 <sect1 id="f-Installed-Size">
3479 <heading><tt>Installed-Size</tt></heading>
3482 This field appears in the control files of binary packages,
3483 and in the <file>Packages</file> files. It gives an estimate
3484 of the total amount of disk space required to install the
3485 named package. Actual installed size may vary based on block
3486 size, file system properties, or actions taken by package
3491 The disk space is given as the integer value of the estimated
3492 installed size in bytes, divided by 1024 and rounded up.
3496 <sect1 id="f-Files">
3497 <heading><tt>Files</tt></heading>
3500 This field contains a list of files with information about
3501 each one. The exact information and syntax varies with
3506 In all cases, Files is a multiline field. The first line of
3507 the field value (the part on the same line as <tt>Files:</tt>)
3508 is always empty. The content of the field is expressed as
3509 continuation lines, one line per file. Each line must be
3510 indented by one space and contain a number of sub-fields,
3511 separated by spaces, as described below.
3515 In the <file>.dsc</file> file, each line contains the MD5
3516 checksum, size and filename of the tar file and (if
3517 applicable) diff file which make up the remainder of the
3518 source package<footnote>
3519 That is, the parts which are not the <tt>.dsc</tt>.
3520 </footnote>. For example:
3523 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3524 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3526 The exact forms of the filenames are described
3527 in <ref id="pkg-sourcearchives">.
3531 In the <file>.changes</file> file this contains one line per
3532 file being uploaded. Each line contains the MD5 checksum,
3533 size, section and priority and the filename. For example:
3536 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3537 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3538 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3539 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3541 The <qref id="f-Section">section</qref>
3542 and <qref id="f-Priority">priority</qref> are the values of
3543 the corresponding fields in the main source control file. If
3544 no section or priority is specified then <tt>-</tt> should be
3545 used, though section and priority values must be specified for
3546 new packages to be installed properly.
3550 The special value <tt>byhand</tt> for the section in a
3551 <tt>.changes</tt> file indicates that the file in question
3552 is not an ordinary package file and must by installed by
3553 hand by the distribution maintainers. If the section is
3554 <tt>byhand</tt> the priority should be <tt>-</tt>.
3558 If a new Debian revision of a package is being shipped and
3559 no new original source archive is being distributed the
3560 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3561 entry for the original source archive
3562 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3563 but the <file>.changes</file> file should leave it out. In
3564 this case the original source archive on the distribution
3565 site must match exactly, byte-for-byte, the original
3566 source archive which was used to generate the
3567 <file>.dsc</file> file and diff which are being uploaded.</p>
3570 <sect1 id="f-Closes">
3571 <heading><tt>Closes</tt></heading>
3574 A space-separated list of bug report numbers that the upload
3575 governed by the .changes file closes.
3579 <sect1 id="f-Homepage">
3580 <heading><tt>Homepage</tt></heading>
3583 The URL of the web site for this package, preferably (when
3584 applicable) the site from which the original source can be
3585 obtained and any additional upstream documentation or
3586 information may be found. The content of this field is a
3587 simple URL without any surrounding characters such as
3592 <sect1 id="f-Checksums">
3593 <heading><tt>Checksums-Sha1</tt>
3594 and <tt>Checksums-Sha256</tt></heading>
3597 These fields contain a list of files with a checksum and size
3598 for each one. Both <tt>Checksums-Sha1</tt>
3599 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3600 only in the checksum algorithm used: SHA-1
3601 for <tt>Checksums-Sha1</tt> and SHA-256
3602 for <tt>Checksums-Sha256</tt>.
3606 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3607 multiline fields. The first line of the field value (the part
3608 on the same line as <tt>Checksums-Sha1:</tt>
3609 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3610 of the field is expressed as continuation lines, one line per
3611 file. Each line consists of the checksum, a space, the file
3612 size, a space, and the file name. For example (from
3613 a <file>.changes</file> file):
3616 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3617 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3618 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3619 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3621 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3622 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3623 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3624 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3629 In the <file>.dsc</file> file, these fields should list all
3630 files that make up the source package. In
3631 the <file>.changes</file> file, these fields should list all
3632 files being uploaded. The list of files in these fields
3633 must match the list of files in the <tt>Files</tt> field.
3637 <sect1 id="f-DM-Upload-Allowed">
3638 <heading><tt>DM-Upload-Allowed</tt></heading>
3641 The most recent version of a package uploaded to unstable or
3642 experimental must include the field <tt>DM-Upload-Allowed:
3643 yes</tt> in the source section of its source control file for
3644 the Debian archive to accept uploads signed with a key in the
3645 Debian Maintainer keyring. See the General
3646 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3647 name="Endorse the concept of Debian Maintainers"> for more
3654 <heading>User-defined fields</heading>
3657 Additional user-defined fields may be added to the
3658 source package control file. Such fields will be
3659 ignored, and not copied to (for example) binary or
3660 source package control files or upload control files.
3664 If you wish to add additional unsupported fields to
3665 these output files you should use the mechanism
3670 Fields in the main source control information file with
3671 names starting <tt>X</tt>, followed by one or more of
3672 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3673 be copied to the output files. Only the part of the
3674 field name after the hyphen will be used in the output
3675 file. Where the letter <tt>B</tt> is used the field
3676 will appear in binary package control files, where the
3677 letter <tt>S</tt> is used in source package control
3678 files and where <tt>C</tt> is used in upload control
3679 (<tt>.changes</tt>) files.
3683 For example, if the main source information control file
3686 XBS-Comment: I stand between the candle and the star.
3688 then the binary and source package control files will contain the
3691 Comment: I stand between the candle and the star.
3700 <chapt id="maintainerscripts">
3701 <heading>Package maintainer scripts and installation procedure</heading>
3704 <heading>Introduction to package maintainer scripts</heading>
3707 It is possible to supply scripts as part of a package which
3708 the package management system will run for you when your
3709 package is installed, upgraded or removed.
3713 These scripts are the control information
3714 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3715 and <prgn>postrm</prgn>. They must be proper executable files;
3716 if they are scripts (which is recommended), they must start with
3717 the usual <tt>#!</tt> convention. They should be readable and
3718 executable by anyone, and must not be world-writable.
3722 The package management system looks at the exit status from
3723 these scripts. It is important that they exit with a
3724 non-zero status if there is an error, so that the package
3725 management system can stop its processing. For shell
3726 scripts this means that you <em>almost always</em> need to
3727 use <tt>set -e</tt> (this is usually true when writing shell
3728 scripts, in fact). It is also important, of course, that
3729 they exit with a zero status if everything went well.
3733 Additionally, packages interacting with users
3734 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3735 should install a <prgn>config</prgn> script as a control
3736 information file. See <ref id="maintscriptprompt"> for details.
3740 When a package is upgraded a combination of the scripts from
3741 the old and new packages is called during the upgrade
3742 procedure. If your scripts are going to be at all
3743 complicated you need to be aware of this, and may need to
3744 check the arguments to your scripts.
3748 Broadly speaking the <prgn>preinst</prgn> is called before
3749 (a particular version of) a package is installed, and the
3750 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3751 before (a version of) a package is removed and the
3752 <prgn>postrm</prgn> afterwards.
3756 Programs called from maintainer scripts should not normally
3757 have a path prepended to them. Before installation is
3758 started, the package management system checks to see if the
3759 programs <prgn>ldconfig</prgn>,
3760 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3761 and <prgn>update-rc.d</prgn> can be found via the
3762 <tt>PATH</tt> environment variable. Those programs, and any
3763 other program that one would expect to be in the
3764 <tt>PATH</tt>, should thus be invoked without an absolute
3765 pathname. Maintainer scripts should also not reset the
3766 <tt>PATH</tt>, though they might choose to modify it by
3767 prepending or appending package-specific directories. These
3768 considerations really apply to all shell scripts.</p>
3771 <sect id="idempotency">
3772 <heading>Maintainer scripts idempotency</heading>
3775 It is necessary for the error recovery procedures that the
3776 scripts be idempotent. This means that if it is run
3777 successfully, and then it is called again, it doesn't bomb
3778 out or cause any harm, but just ensures that everything is
3779 the way it ought to be. If the first call failed, or
3780 aborted half way through for some reason, the second call
3781 should merely do the things that were left undone the first
3782 time, if any, and exit with a success status if everything
3784 This is so that if an error occurs, the user interrupts
3785 <prgn>dpkg</prgn> or some other unforeseen circumstance
3786 happens you don't leave the user with a badly-broken
3787 package when <prgn>dpkg</prgn> attempts to repeat the
3793 <sect id="controllingterminal">
3794 <heading>Controlling terminal for maintainer scripts</heading>
3797 Maintainer scripts are not guaranteed to run with a controlling
3798 terminal and may not be able to interact with the user. They
3799 must be able to fall back to noninteractive behavior if no
3800 controlling terminal is available. Maintainer scripts that
3801 prompt via a program conforming to the Debian Configuration
3802 Management Specification (see <ref id="maintscriptprompt">) may
3803 assume that program will handle falling back to noninteractive
3808 For high-priority prompts without a reasonable default answer,
3809 maintainer scripts may abort if there is no controlling
3810 terminal. However, this situation should be avoided if at all
3811 possible, since it prevents automated or unattended installs.
3812 In most cases, users will consider this to be a bug in the
3817 <sect id="exitstatus">
3818 <heading>Exit status</heading>
3821 Each script must return a zero exit status for
3822 success, or a nonzero one for failure, since the package
3823 management system looks for the exit status of these scripts
3824 and determines what action to take next based on that datum.
3828 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3833 <list compact="compact">
3835 <var>new-preinst</var> <tt>install</tt>
3838 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3841 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3844 <var>old-preinst</var> <tt>abort-upgrade</tt>
3845 <var>new-version</var>
3850 <list compact="compact">
3852 <var>postinst</var> <tt>configure</tt>
3853 <var>most-recently-configured-version</var>
3856 <var>old-postinst</var> <tt>abort-upgrade</tt>
3857 <var>new-version</var>
3860 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3861 <tt>in-favour</tt> <var>package</var>
3862 <var>new-version</var>
3865 <var>postinst</var> <tt>abort-remove</tt>
3868 <var>deconfigured's-postinst</var>
3869 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3870 <var>failed-install-package</var> <var>version</var>
3871 [<tt>removing</tt> <var>conflicting-package</var>
3877 <list compact="compact">
3879 <var>prerm</var> <tt>remove</tt>
3882 <var>old-prerm</var> <tt>upgrade</tt>
3883 <var>new-version</var>
3886 <var>new-prerm</var> <tt>failed-upgrade</tt>
3887 <var>old-version</var>
3890 <var>conflictor's-prerm</var> <tt>remove</tt>
3891 <tt>in-favour</tt> <var>package</var>
3892 <var>new-version</var>
3895 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3896 <tt>in-favour</tt> <var>package-being-installed</var>
3897 <var>version</var> [<tt>removing</tt>
3898 <var>conflicting-package</var>
3904 <list compact="compact">
3906 <var>postrm</var> <tt>remove</tt>
3909 <var>postrm</var> <tt>purge</tt>
3912 <var>old-postrm</var> <tt>upgrade</tt>
3913 <var>new-version</var>
3916 <var>new-postrm</var> <tt>failed-upgrade</tt>
3917 <var>old-version</var>
3920 <var>new-postrm</var> <tt>abort-install</tt>
3923 <var>new-postrm</var> <tt>abort-install</tt>
3924 <var>old-version</var>
3927 <var>new-postrm</var> <tt>abort-upgrade</tt>
3928 <var>old-version</var>
3931 <var>disappearer's-postrm</var> <tt>disappear</tt>
3932 <var>overwriter</var>
3933 <var>overwriter-version</var>
3939 <sect id="unpackphase">
3940 <heading>Details of unpack phase of installation or upgrade</heading>
3943 The procedure on installation/upgrade/overwrite/disappear
3944 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3945 stage of <tt>dpkg --install</tt>) is as follows. In each
3946 case, if a major error occurs (unless listed below) the
3947 actions are, in general, run backwards - this means that the
3948 maintainer scripts are run with different arguments in
3949 reverse order. These are the "error unwind" calls listed
3956 If a version of the package is already installed, call
3957 <example compact="compact">
3958 <var>old-prerm</var> upgrade <var>new-version</var>
3962 If the script runs but exits with a non-zero
3963 exit status, <prgn>dpkg</prgn> will attempt:
3964 <example compact="compact">
3965 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3967 If this works, the upgrade continues. If this
3968 does not work, the error unwind:
3969 <example compact="compact">
3970 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3972 If this works, then the old-version is
3973 "Installed", if not, the old version is in a
3974 "Half-Configured" state.
3980 If a "conflicting" package is being removed at the same time,
3981 or if any package will be broken (due to <tt>Breaks</tt>):
3984 If <tt>--auto-deconfigure</tt> is
3985 specified, call, for each package to be deconfigured
3986 due to <tt>Breaks</tt>:
3987 <example compact="compact">
3988 <var>deconfigured's-prerm</var> deconfigure \
3989 in-favour <var>package-being-installed</var> <var>version</var>
3992 <example compact="compact">
3993 <var>deconfigured's-postinst</var> abort-deconfigure \
3994 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3996 The deconfigured packages are marked as
3997 requiring configuration, so that if
3998 <tt>--install</tt> is used they will be
3999 configured again if possible.
4002 If any packages depended on a conflicting
4003 package being removed and <tt>--auto-deconfigure</tt> is
4004 specified, call, for each such package:
4005 <example compact="compact">
4006 <var>deconfigured's-prerm</var> deconfigure \
4007 in-favour <var>package-being-installed</var> <var>version</var> \
4008 removing <var>conflicting-package</var> <var>version</var>
4011 <example compact="compact">
4012 <var>deconfigured's-postinst</var> abort-deconfigure \
4013 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4014 removing <var>conflicting-package</var> <var>version</var>
4016 The deconfigured packages are marked as
4017 requiring configuration, so that if
4018 <tt>--install</tt> is used they will be
4019 configured again if possible.
4022 To prepare for removal of each conflicting package, call:
4023 <example compact="compact">
4024 <var>conflictor's-prerm</var> remove \
4025 in-favour <var>package</var> <var>new-version</var>
4028 <example compact="compact">
4029 <var>conflictor's-postinst</var> abort-remove \
4030 in-favour <var>package</var> <var>new-version</var>
4039 If the package is being upgraded, call:
4040 <example compact="compact">
4041 <var>new-preinst</var> upgrade <var>old-version</var>
4043 If this fails, we call:
4045 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4052 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4054 is called. If this works, then the old version
4055 is in an "Installed" state, or else it is left
4056 in an "Unpacked" state.
4061 If it fails, then the old version is left
4062 in an "Half-Installed" state.
4069 Otherwise, if the package had some configuration
4070 files from a previous version installed (i.e., it
4071 is in the "configuration files only" state):
4072 <example compact="compact">
4073 <var>new-preinst</var> install <var>old-version</var>
4077 <var>new-postrm</var> abort-install <var>old-version</var>
4079 If this fails, the package is left in a
4080 "Half-Installed" state, which requires a
4081 reinstall. If it works, the packages is left in
4082 a "Config-Files" state.
4085 Otherwise (i.e., the package was completely purged):
4086 <example compact="compact">
4087 <var>new-preinst</var> install
4090 <example compact="compact">
4091 <var>new-postrm</var> abort-install
4093 If the error-unwind fails, the package is in a
4094 "Half-Installed" phase, and requires a
4095 reinstall. If the error unwind works, the
4096 package is in a not installed state.
4103 The new package's files are unpacked, overwriting any
4104 that may be on the system already, for example any
4105 from the old version of the same package or from
4106 another package. Backups of the old files are kept
4107 temporarily, and if anything goes wrong the package
4108 management system will attempt to put them back as
4109 part of the error unwind.
4113 It is an error for a package to contain files which
4114 are on the system in another package, unless
4115 <tt>Replaces</tt> is used (see <ref id="replaces">).
4117 The following paragraph is not currently the case:
4118 Currently the <tt>- - force-overwrite</tt> flag is
4119 enabled, downgrading it to a warning, but this may not
4125 It is a more serious error for a package to contain a
4126 plain file or other kind of non-directory where another
4127 package has a directory (again, unless
4128 <tt>Replaces</tt> is used). This error can be
4129 overridden if desired using
4130 <tt>--force-overwrite-dir</tt>, but this is not
4135 Packages which overwrite each other's files produce
4136 behavior which, though deterministic, is hard for the
4137 system administrator to understand. It can easily
4138 lead to "missing" programs if, for example, a package
4139 is installed which overwrites a file from another
4140 package, and is then removed again.<footnote>
4141 Part of the problem is due to what is arguably a
4142 bug in <prgn>dpkg</prgn>.
4147 A directory will never be replaced by a symbolic link
4148 to a directory or vice versa; instead, the existing
4149 state (symlink or not) will be left alone and
4150 <prgn>dpkg</prgn> will follow the symlink if there is
4159 If the package is being upgraded, call
4160 <example compact="compact">
4161 <var>old-postrm</var> upgrade <var>new-version</var>
4165 If this fails, <prgn>dpkg</prgn> will attempt:
4166 <example compact="compact">
4167 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4169 If this works, installation continues. If not,
4171 <example compact="compact">
4172 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4174 If this fails, the old version is left in a
4175 "Half-Installed" state. If it works, dpkg now
4177 <example compact="compact">
4178 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4180 If this fails, the old version is left in a
4181 "Half-Installed" state. If it works, dpkg now
4183 <example compact="compact">
4184 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4186 If this fails, the old version is in an
4193 This is the point of no return - if
4194 <prgn>dpkg</prgn> gets this far, it won't back off
4195 past this point if an error occurs. This will
4196 leave the package in a fairly bad state, which
4197 will require a successful re-installation to clear
4198 up, but it's when <prgn>dpkg</prgn> starts doing
4199 things that are irreversible.
4204 Any files which were in the old version of the package
4205 but not in the new are removed.
4209 The new file list replaces the old.
4213 The new maintainer scripts replace the old.
4217 Any packages all of whose files have been overwritten
4218 during the installation, and which aren't required for
4219 dependencies, are considered to have been removed.
4220 For each such package
4223 <prgn>dpkg</prgn> calls:
4224 <example compact="compact">
4225 <var>disappearer's-postrm</var> disappear \
4226 <var>overwriter</var> <var>overwriter-version</var>
4230 The package's maintainer scripts are removed.
4233 It is noted in the status database as being in a
4234 sane state, namely not installed (any conffiles
4235 it may have are ignored, rather than being
4236 removed by <prgn>dpkg</prgn>). Note that
4237 disappearing packages do not have their prerm
4238 called, because <prgn>dpkg</prgn> doesn't know
4239 in advance that the package is going to
4246 Any files in the package we're unpacking that are also
4247 listed in the file lists of other packages are removed
4248 from those lists. (This will lobotomize the file list
4249 of the "conflicting" package if there is one.)
4253 The backup files made during installation, above, are
4259 The new package's status is now sane, and recorded as
4264 Here is another point of no return - if the
4265 conflicting package's removal fails we do not unwind
4266 the rest of the installation; the conflicting package
4267 is left in a half-removed limbo.
4272 If there was a conflicting package we go and do the
4273 removal actions (described below), starting with the
4274 removal of the conflicting package's files (any that
4275 are also in the package being installed have already
4276 been removed from the conflicting package's file list,
4277 and so do not get removed now).
4283 <sect id="configdetails"><heading>Details of configuration</heading>
4286 When we configure a package (this happens with <tt>dpkg
4287 --install</tt> and <tt>dpkg --configure</tt>), we first
4288 update any <tt>conffile</tt>s and then call:
4289 <example compact="compact">
4290 <var>postinst</var> configure <var>most-recently-configured-version</var>
4295 No attempt is made to unwind after errors during
4296 configuration. If the configuration fails, the package is in
4297 a "Failed Config" state, and an error message is generated.
4301 If there is no most recently configured version
4302 <prgn>dpkg</prgn> will pass a null argument.
4305 Historical note: Truly ancient (pre-1997) versions of
4306 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4307 (including the angle brackets) in this case. Even older
4308 ones did not pass a second argument at all, under any
4309 circumstance. Note that upgrades using such an old dpkg
4310 version are unlikely to work for other reasons, even if
4311 this old argument behavior is handled by your postinst script.
4317 <sect id="removedetails"><heading>Details of removal and/or
4318 configuration purging</heading>
4324 <example compact="compact">
4325 <var>prerm</var> remove
4329 If prerm fails during replacement due to conflict
4331 <var>conflictor's-postinst</var> abort-remove \
4332 in-favour <var>package</var> <var>new-version</var>
4336 <var>postinst</var> abort-remove
4340 If this fails, the package is in a "Half-Configured"
4341 state, or else it remains "Installed".
4345 The package's files are removed (except <tt>conffile</tt>s).
4348 <example compact="compact">
4349 <var>postrm</var> remove
4353 If it fails, there's no error unwind, and the package is in
4354 an "Half-Installed" state.
4359 All the maintainer scripts except the <prgn>postrm</prgn>
4364 If we aren't purging the package we stop here. Note
4365 that packages which have no <prgn>postrm</prgn> and no
4366 <tt>conffile</tt>s are automatically purged when
4367 removed, as there is no difference except for the
4368 <prgn>dpkg</prgn> status.
4372 The <tt>conffile</tt>s and any backup files
4373 (<tt>~</tt>-files, <tt>#*#</tt> files,
4374 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4379 <example compact="compact">
4380 <var>postrm</var> purge
4384 If this fails, the package remains in a "Config-Files"
4389 The package's file list is removed.
4398 <chapt id="relationships">
4399 <heading>Declaring relationships between packages</heading>
4401 <sect id="depsyntax">
4402 <heading>Syntax of relationship fields</heading>
4405 These fields all have a uniform syntax. They are a list of
4406 package names separated by commas.
4410 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4411 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4412 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4413 control fields of the package, which declare
4414 dependencies on other packages, the package names listed may
4415 also include lists of alternative package names, separated
4416 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4417 if any one of the alternative packages is installed, that
4418 part of the dependency is considered to be satisfied.
4422 All of the fields except for <tt>Provides</tt> may restrict
4423 their applicability to particular versions of each named
4424 package. This is done in parentheses after each individual
4425 package name; the parentheses should contain a relation from
4426 the list below followed by a version number, in the format
4427 described in <ref id="f-Version">.
4431 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4432 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4433 strictly earlier, earlier or equal, exactly equal, later or
4434 equal and strictly later, respectively. The deprecated
4435 forms <tt><</tt> and <tt>></tt> were used to mean
4436 earlier/later or equal, rather than strictly earlier/later,
4437 so they should not appear in new packages (though
4438 <prgn>dpkg</prgn> still supports them).
4442 Whitespace may appear at any point in the version
4443 specification subject to the rules in <ref
4444 id="controlsyntax">, and must appear where it's necessary to
4445 disambiguate; it is not otherwise significant. All of the
4446 relationship fields may span multiple lines. For
4447 consistency and in case of future changes to
4448 <prgn>dpkg</prgn> it is recommended that a single space be
4449 used after a version relationship and before a version
4450 number; it is also conventional to put a single space after
4451 each comma, on either side of each vertical bar, and before
4452 each open parenthesis. When wrapping a relationship field, it
4453 is conventional to do so after a comma and before the space
4454 following that comma.
4458 For example, a list of dependencies might appear as:
4459 <example compact="compact">
4462 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4467 Relationships may be restricted to a certain set of
4468 architectures. This is indicated in brackets after each
4469 individual package name and the optional version specification.
4470 The brackets enclose a list of Debian architecture names
4471 separated by whitespace. Exclamation marks may be prepended to
4472 each of the names. (It is not permitted for some names to be
4473 prepended with exclamation marks while others aren't.)
4477 For build relationship fields
4478 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4479 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4480 the current Debian host architecture is not in this list and
4481 there are no exclamation marks in the list, or it is in the list
4482 with a prepended exclamation mark, the package name and the
4483 associated version specification are ignored completely for the
4484 purposes of defining the relationships.
4489 <example compact="compact">
4491 Build-Depends-Indep: texinfo
4492 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4493 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4495 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4496 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4497 <tt>gnumach-dev</tt> only on hurd-i386.
4501 For binary relationship fields, the architecture restriction
4502 syntax is only supported in the source package control
4503 file <file>debian/control</file>. When the corresponding binary
4504 package control file is generated, the relationship will either
4505 be omitted or included without the architecture restriction
4506 based on the architecture of the binary package. This means
4507 that architecture restrictions must not be used in binary
4508 relationship fields for architecture-independent packages
4509 (<tt>Architecture: all</tt>).
4514 <example compact="compact">
4515 Depends: foo [i386], bar [amd64]
4517 becomes <tt>Depends: foo</tt> when the package is built on
4518 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4519 package is built on the <tt>amd64</tt> architecture, and omitted
4520 entirely in binary packages built on all other architectures.
4524 If the architecture-restricted dependency is part of a set of
4525 alternatives using <tt>|</tt>, that alternative is ignored
4526 completely on architectures that do not match the restriction.
4528 <example compact="compact">
4529 Build-Depends: foo [!i386] | bar [!amd64]
4531 is equivalent to <tt>bar</tt> on the i386 architecture, to
4532 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4533 bar</tt> on all other architectures.
4537 Relationships may also be restricted to a certain set of
4538 architectures using architecture wildcards. The syntax for
4539 declaring such restrictions is the same as declaring
4540 restrictions using a certain set of architectures without
4541 architecture wildcards. For example:
4542 <example compact="compact">
4543 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4545 is equivalent to <tt>foo</tt> on architectures using the Linux
4546 kernel and any cpu, <tt>bar</tt> on architectures using any
4547 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4548 using a kernel other than Linux.
4552 Note that the binary package relationship fields such as
4553 <tt>Depends</tt> appear in one of the binary package
4554 sections of the control file, whereas the build-time
4555 relationships such as <tt>Build-Depends</tt> appear in the
4556 source package section of the control file (which is the
4561 <sect id="binarydeps">
4562 <heading>Binary Dependencies - <tt>Depends</tt>,
4563 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4564 <tt>Pre-Depends</tt>
4568 Packages can declare in their control file that they have
4569 certain relationships to other packages - for example, that
4570 they may not be installed at the same time as certain other
4571 packages, and/or that they depend on the presence of others.
4575 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4576 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4577 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4578 <tt>Breaks</tt> is described in <ref id="breaks">, and
4579 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4580 rest are described below.
4584 These seven fields are used to declare a dependency
4585 relationship by one package on another. Except for
4586 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4587 depending (binary) package's control file.
4588 (<tt>Enhances</tt> appears in the recommending package's
4589 control file, and <tt>Breaks</tt> appears in the version of
4590 depended-on package which causes the named package to
4595 A <tt>Depends</tt> field takes effect <em>only</em> when a
4596 package is to be configured. It does not prevent a package
4597 being on the system in an unconfigured state while its
4598 dependencies are unsatisfied, and it is possible to replace
4599 a package whose dependencies are satisfied and which is
4600 properly installed with a different version whose
4601 dependencies are not and cannot be satisfied; when this is
4602 done the depending package will be left unconfigured (since
4603 attempts to configure it will give errors) and will not
4604 function properly. If it is necessary, a
4605 <tt>Pre-Depends</tt> field can be used, which has a partial
4606 effect even when a package is being unpacked, as explained
4607 in detail below. (The other three dependency fields,
4608 <tt>Recommends</tt>, <tt>Suggests</tt> and
4609 <tt>Enhances</tt>, are only used by the various front-ends
4610 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4611 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4615 For this reason packages in an installation run are usually
4616 all unpacked first and all configured later; this gives
4617 later versions of packages with dependencies on later
4618 versions of other packages the opportunity to have their
4619 dependencies satisfied.
4623 In case of circular dependencies, since installation or
4624 removal order honoring the dependency order can't be
4625 established, dependency loops are broken at some point
4626 (based on rules below), and some packages may not be able to
4627 rely on their dependencies being present when being
4628 installed or removed, depending on which side of the break
4629 of the circular dependency loop they happen to be on. If one
4630 of the packages in the loop has no postinst script, then the
4631 cycle will be broken at that package, so as to ensure that
4632 all postinst scripts run with the dependencies properly
4633 configured if this is possible. Otherwise the breaking point
4638 The <tt>Depends</tt> field thus allows package maintainers
4639 to impose an order in which packages should be configured.
4643 The meaning of the five dependency fields is as follows:
4645 <tag><tt>Depends</tt></tag>
4648 This declares an absolute dependency. A package will
4649 not be configured unless all of the packages listed in
4650 its <tt>Depends</tt> field have been correctly
4655 The <tt>Depends</tt> field should be used if the
4656 depended-on package is required for the depending
4657 package to provide a significant amount of
4662 The <tt>Depends</tt> field should also be used if the
4663 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4664 <prgn>postrm</prgn> scripts require the package to be
4665 present in order to run. Note, however, that the
4666 <prgn>postrm</prgn> cannot rely on any non-essential
4667 packages to be present during the <tt>purge</tt>
4671 <tag><tt>Recommends</tt></tag>
4674 This declares a strong, but not absolute, dependency.
4678 The <tt>Recommends</tt> field should list packages
4679 that would be found together with this one in all but
4680 unusual installations.
4684 <tag><tt>Suggests</tt></tag>
4686 This is used to declare that one package may be more
4687 useful with one or more others. Using this field
4688 tells the packaging system and the user that the
4689 listed packages are related to this one and can
4690 perhaps enhance its usefulness, but that installing
4691 this one without them is perfectly reasonable.
4694 <tag><tt>Enhances</tt></tag>
4696 This field is similar to Suggests but works in the
4697 opposite direction. It is used to declare that a
4698 package can enhance the functionality of another
4702 <tag><tt>Pre-Depends</tt></tag>
4705 This field is like <tt>Depends</tt>, except that it
4706 also forces <prgn>dpkg</prgn> to complete installation
4707 of the packages named before even starting the
4708 installation of the package which declares the
4709 pre-dependency, as follows:
4713 When a package declaring a pre-dependency is about to
4714 be <em>unpacked</em> the pre-dependency can be
4715 satisfied if the depended-on package is either fully
4716 configured, <em>or even if</em> the depended-on
4717 package(s) are only unpacked or in the "Half-Configured"
4718 state, provided that they have been configured
4719 correctly at some point in the past (and not removed
4720 or partially removed since). In this case, both the
4721 previously-configured and currently unpacked or
4722 "Half-Configured" versions must satisfy any version
4723 clause in the <tt>Pre-Depends</tt> field.
4727 When the package declaring a pre-dependency is about
4728 to be <em>configured</em>, the pre-dependency will be
4729 treated as a normal <tt>Depends</tt>, that is, it will
4730 be considered satisfied only if the depended-on
4731 package has been correctly configured.
4735 <tt>Pre-Depends</tt> should be used sparingly,
4736 preferably only by packages whose premature upgrade or
4737 installation would hamper the ability of the system to
4738 continue with any upgrade that might be in progress.
4742 <tt>Pre-Depends</tt> are also required if the
4743 <prgn>preinst</prgn> script depends on the named
4744 package. It is best to avoid this situation if
4752 When selecting which level of dependency to use you should
4753 consider how important the depended-on package is to the
4754 functionality of the one declaring the dependency. Some
4755 packages are composed of components of varying degrees of
4756 importance. Such a package should list using
4757 <tt>Depends</tt> the package(s) which are required by the
4758 more important components. The other components'
4759 requirements may be mentioned as Suggestions or
4760 Recommendations, as appropriate to the components' relative
4766 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4769 When one binary package declares that it breaks another,
4770 <prgn>dpkg</prgn> will refuse to allow the package which
4771 declares <tt>Breaks</tt> be installed unless the broken
4772 package is deconfigured first, and it will refuse to
4773 allow the broken package to be reconfigured.
4777 A package will not be regarded as causing breakage merely
4778 because its configuration files are still installed; it must
4779 be at least "Half-Installed".
4783 A special exception is made for packages which declare that
4784 they break their own package name or a virtual package which
4785 they provide (see below): this does not count as a real
4790 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4791 version clause; such a <tt>Breaks</tt> is introduced in the
4792 version of an (implicit or explicit) dependency which violates
4793 an assumption or reveals a bug in earlier versions of the broken
4794 package, or which takes over a file from earlier versions of the
4795 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4796 will inform higher-level package management tools that the
4797 broken package must be upgraded before the new one.
4801 If the breaking package also overwrites some files from the
4802 older package, it should use <tt>Replaces</tt> to ensure this
4803 goes smoothly. See <ref id="replaces"> for a full discussion
4804 of taking over files from other packages, including how to
4805 use <tt>Breaks</tt> in those cases.
4809 Many of the cases where <tt>Breaks</tt> should be used were
4810 previously handled with <tt>Conflicts</tt>
4811 because <tt>Breaks</tt> did not yet exist.
4812 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4813 See <ref id="conflicts"> for more information about the
4818 <sect id="conflicts">
4819 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4822 When one binary package declares a conflict with another
4823 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4824 refuse to allow them to be installed on the system at the
4825 same time. This is a stronger restriction than <tt>Breaks</tt>,
4826 which just prevents both packages from being configured at the
4827 same time. Conflicting packages cannot be unpacked on the
4828 system at the same time.
4832 If one package is to be installed, the other must be removed
4833 first. If the package being installed is marked as replacing
4834 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4835 normally be used in this case) the one on the system, or the one
4836 on the system is marked as deselected, or both packages are
4837 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4838 automatically remove the package which is causing the conflict.
4839 Otherwise, it will halt the installation of the new package with
4840 an error. This mechanism is specifically designed to produce an
4841 error when the installed package is <tt>Essential</tt>, but the
4846 A package will not cause a conflict merely because its
4847 configuration files are still installed; it must be at least
4852 A special exception is made for packages which declare a
4853 conflict with their own package name, or with a virtual
4854 package which they provide (see below): this does not
4855 prevent their installation, and allows a package to conflict
4856 with others providing a replacement for it. You use this
4857 feature when you want the package in question to be the only
4858 package providing some feature.
4862 Normally, <tt>Breaks</tt> should be used instead
4863 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4864 stronger restriction on the ordering of package installation or
4865 upgrade and can make it more difficult for the package manager
4866 to find a correct solution to an upgrade or installation
4867 problem. <tt>Breaks</tt> should be used
4869 <item>when moving a file from one package to another (see
4870 <ref id="replaces">),</item>
4871 <item>when splitting a package (a special case of the previous
4873 <item>when the breaking package exposes a bug in or interacts
4874 badly with particular versions of the broken
4877 <tt>Conflicts</tt> should be used
4879 <item>when two packages provide the same file and will
4880 continue to do so,</item>
4881 <item>in conjunction with <tt>Provides</tt> when only one
4882 package providing a given virtual facility may be installed
4883 at a time (see <ref id="virtual">),</item>
4884 <item>in other cases where one must prevent simultaneous
4885 installation of two packages for reasons that are ongoing
4886 (not fixed in a later version of one of the packages) or
4887 that must prevent both packages from being unpacked at the
4888 same time, not just configured.</item>
4890 Be aware that adding <tt>Conflicts</tt> is normally not the best
4891 solution when two packages provide the same files. Depending on
4892 the reason for that conflict, using alternatives or renaming the
4893 files is often a better approach. See, for
4894 example, <ref id="binaries">.
4898 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4899 unless two packages cannot be installed at the same time or
4900 installing them both causes one of them to be broken or
4901 unusable. Having similar functionality or performing the same
4902 tasks as another package is not sufficient reason to
4903 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4907 A <tt>Conflicts</tt> entry may have an "earlier than" version
4908 clause if the reason for the conflict is corrected in a later
4909 version of one of the packages. However, normally the presence
4910 of an "earlier than" version clause is a sign
4911 that <tt>Breaks</tt> should have been used instead. An "earlier
4912 than" version clause in <tt>Conflicts</tt>
4913 prevents <prgn>dpkg</prgn> from upgrading or installing the
4914 package which declares such a conflict until the upgrade or
4915 removal of the conflicted-with package has been completed, which
4916 is a strong restriction.
4920 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4924 As well as the names of actual ("concrete") packages, the
4925 package relationship fields <tt>Depends</tt>,
4926 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4927 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4928 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4929 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4930 may mention "virtual packages".
4934 A <em>virtual package</em> is one which appears in the
4935 <tt>Provides</tt> control field of another package. The effect
4936 is as if the package(s) which provide a particular virtual
4937 package name had been listed by name everywhere the virtual
4938 package name appears. (See also <ref id="virtual_pkg">)
4942 If there are both concrete and virtual packages of the same
4943 name, then the dependency may be satisfied (or the conflict
4944 caused) by either the concrete package with the name in
4945 question or any other concrete package which provides the
4946 virtual package with the name in question. This is so that,
4947 for example, supposing we have
4948 <example compact="compact">
4951 </example> and someone else releases an enhanced version of
4952 the <tt>bar</tt> package they can say:
4953 <example compact="compact">
4957 and the <tt>bar-plus</tt> package will now also satisfy the
4958 dependency for the <tt>foo</tt> package.
4962 If a relationship field has a version number attached, only real
4963 packages will be considered to see whether the relationship is
4964 satisfied (or the prohibition violated, for a conflict or
4965 breakage). In other words, if a version number is specified,
4966 this is a request to ignore all <tt>Provides</tt> for that
4967 package name and consider only real packages. The package
4968 manager will assume that a package providing that virtual
4969 package is not of the "right" version. A <tt>Provides</tt>
4970 field may not contain version numbers, and the version number of
4971 the concrete package which provides a particular virtual package
4972 will not be considered when considering a dependency on or
4973 conflict with the virtual package name.<footnote>
4974 It is possible that a future release of <prgn>dpkg</prgn> may
4975 add the ability to specify a version number for each virtual
4976 package it provides. This feature is not yet present,
4977 however, and is expected to be used only infrequently.
4982 To specify which of a set of real packages should be the default
4983 to satisfy a particular dependency on a virtual package, list
4984 the real package as an alternative before the virtual one.
4988 If the virtual package represents a facility that can only be
4989 provided by one real package at a time, such as
4990 the <package>mail-transport-agent</package> virtual package that
4991 requires installation of a binary that would conflict with all
4992 other providers of that virtual package (see
4993 <ref id="mail-transport-agents">), all packages providing that
4994 virtual package should also declare a conflict with it
4995 using <tt>Conflicts</tt>. This will ensure that at most one
4996 provider of that virtual package is unpacked or installed at a
5001 <sect id="replaces"><heading>Overwriting files and replacing
5002 packages - <tt>Replaces</tt></heading>
5005 Packages can declare in their control file that they should
5006 overwrite files in certain other packages, or completely replace
5007 other packages. The <tt>Replaces</tt> control field has these
5008 two distinct purposes.
5011 <sect1><heading>Overwriting files in other packages</heading>
5014 It is usually an error for a package to contain files which
5015 are on the system in another package. However, if the
5016 overwriting package declares that it <tt>Replaces</tt> the one
5017 containing the file being overwritten, then <prgn>dpkg</prgn>
5018 will replace the file from the old package with that from the
5019 new. The file will no longer be listed as "owned" by the old
5020 package and will be taken over by the new package.
5021 Normally, <tt>Breaks</tt> should be used in conjunction
5022 with <tt>Replaces</tt>.<footnote>
5023 To see why <tt>Breaks</tt> is normally needed in addition
5024 to <tt>Replaces</tt>, consider the case of a file in the
5025 package <package>foo</package> being taken over by the
5026 package <package>foo-data</package>.
5027 <tt>Replaces</tt> will allow <package>foo-data</package> to
5028 be installed and take over that file. However,
5029 without <tt>Breaks</tt>, nothing
5030 requires <package>foo</package> to be upgraded to a newer
5031 version that knows it does not include that file and instead
5032 depends on <package>foo-data</package>. Nothing would
5033 prevent the new <package>foo-data</package> package from
5034 being installed and then removed, removing the file that it
5035 took over from <package>foo</package>. After that
5036 operation, the package manager would think the system was in
5037 a consistent state, but the <package>foo</package> package
5038 would be missing one of its files.
5043 For example, if a package <package>foo</package> is split
5044 into <package>foo</package> and <package>foo-data</package>
5045 starting at version 1.2-3, <package>foo-data</package> would
5047 <example compact="compact">
5048 Replaces: foo (<< 1.2-3)
5049 Breaks: foo (<< 1.2-3)
5051 in its control file. The new version of the
5052 package <package>foo</package> would normally have the field
5053 <example compact="compact">
5054 Depends: foo-data (>= 1.2-3)
5056 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5057 the files moved into <package>foo-data</package> are not
5058 required for normal operation).
5062 If a package is completely replaced in this way, so that
5063 <prgn>dpkg</prgn> does not know of any files it still
5064 contains, it is considered to have "disappeared". It will
5065 be marked as not wanted on the system (selected for
5066 removal) and not installed. Any <tt>conffile</tt>s
5067 details noted for the package will be ignored, as they
5068 will have been taken over by the overwriting package. The
5069 package's <prgn>postrm</prgn> script will be run with a
5070 special argument to allow the package to do any final
5071 cleanup required. See <ref id="mscriptsinstact">.
5073 Replaces is a one way relationship. You have to install
5074 the replacing package after the replaced package.
5079 For this usage of <tt>Replaces</tt>, virtual packages (see
5080 <ref id="virtual">) are not considered when looking at a
5081 <tt>Replaces</tt> field. The packages declared as being
5082 replaced must be mentioned by their real names.
5086 This usage of <tt>Replaces</tt> only takes effect when both
5087 packages are at least partially on the system at once. It is
5088 not relevant if the packages conflict unless the conflict has
5093 <sect1><heading>Replacing whole packages, forcing their
5097 Second, <tt>Replaces</tt> allows the packaging system to
5098 resolve which package should be removed when there is a
5099 conflict (see <ref id="conflicts">). This usage only takes
5100 effect when the two packages <em>do</em> conflict, so that the
5101 two usages of this field do not interfere with each other.
5105 In this situation, the package declared as being replaced
5106 can be a virtual package, so for example, all mail
5107 transport agents (MTAs) would have the following fields in
5108 their control files:
5109 <example compact="compact">
5110 Provides: mail-transport-agent
5111 Conflicts: mail-transport-agent
5112 Replaces: mail-transport-agent
5114 ensuring that only one MTA can be installed at any one
5115 time. See <ref id="virtual"> for more information about this
5120 <sect id="sourcebinarydeps">
5121 <heading>Relationships between source and binary packages -
5122 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5123 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5127 Source packages that require certain binary packages to be
5128 installed or absent at the time of building the package
5129 can declare relationships to those binary packages.
5133 This is done using the <tt>Build-Depends</tt>,
5134 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5135 <tt>Build-Conflicts-Indep</tt> control fields.
5139 Build-dependencies on "build-essential" binary packages can be
5140 omitted. Please see <ref id="pkg-relations"> for more information.
5144 The dependencies and conflicts they define must be satisfied
5145 (as defined earlier for binary packages) in order to invoke
5146 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5148 There is no Build-Depends-Arch; this role is essentially
5149 met with Build-Depends. Anyone building the
5150 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5151 assumed to be building the whole package, and therefore
5152 installation of all build dependencies is required.
5155 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5156 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5157 not yet know how to check for its existence, and
5158 <tt>binary-arch</tt>. The purpose of the original split
5159 between <tt>Build-Depends</tt> and
5160 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5161 wouldn't need to install extra packages needed only for the
5162 binary-indep targets. But without a build-arch/build-indep
5163 split, this didn't work, since most of the work is done in
5164 the build target, not in the binary target.
5168 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5169 <tt>binary-arch</tt></tag>
5171 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5172 fields must be satisfied when these targets are invoked.
5174 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5175 and <tt>binary-indep</tt></tag>
5177 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5178 <tt>Build-Depends-Indep</tt>, and
5179 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5180 these targets are invoked.
5188 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5191 Packages containing shared libraries must be constructed with
5192 a little care to make sure that the shared library is always
5193 available. This is especially important for packages whose
5194 shared libraries are vitally important, such as the C library
5195 (currently <tt>libc6</tt>).
5199 This section deals only with public shared libraries: shared
5200 libraries that are placed in directories searched by the dynamic
5201 linker by default or which are intended to be linked against
5202 normally and possibly used by other, independent packages. Shared
5203 libraries that are internal to a particular package or that are
5204 only loaded as dynamic modules are not covered by this section and
5205 are not subject to its requirements.
5209 A shared library is identified by the <tt>SONAME</tt> attribute
5210 stored in its dynamic section. When a binary is linked against a
5211 shared library, the <tt>SONAME</tt> of the shared library is
5212 recorded in the binary's <tt>NEEDED</tt> section so that the
5213 dynamic linker knows that library must be loaded at runtime. The
5214 shared library file's full name (which usually contains additional
5215 version information not needed in the <tt>SONAME</tt>) is
5216 therefore normally not referenced directly. Instead, the shared
5217 library is loaded by its <tt>SONAME</tt>, which exists on the file
5218 system as a symlink pointing to the full name of the shared
5219 library. This symlink must be provided by the
5220 package. <ref id="sharedlibs-runtime"> describes how to do this.
5222 This is a convention of shared library versioning, but not a
5223 requirement. Some libraries use the <tt>SONAME</tt> as the full
5224 library file name instead and therefore do not need a symlink.
5225 Most, however, encode additional information about
5226 backwards-compatible revisions as a minor version number in the
5227 file name. The <tt>SONAME</tt> itself only changes when
5228 binaries linked with the earlier version of the shared library
5229 may no longer work, but the filename may change with each
5230 release of the library. See <ref id="sharedlibs-runtime"> for
5236 When linking a binary or another shared library against a shared
5237 library, the <tt>SONAME</tt> for that shared library is not yet
5238 known. Instead, the shared library is found by looking for a file
5239 matching the library name with <tt>.so</tt> appended. This file
5240 exists on the file system as a symlink pointing to the shared
5245 Shared libraries are normally split into several binary packages.
5246 The <tt>SONAME</tt> symlink is installed by the runtime shared
5247 library package, and the bare <tt>.so</tt> symlink is installed in
5248 the development package since it's only used when linking binaries
5249 or shared libraries. However, there are some exceptions for
5250 unusual shared libraries or for shared libraries that are also
5251 loaded as dynamic modules by other programs.
5255 This section is primarily concerned with how the separation of
5256 shared libraries into multiple packages should be done and how
5257 dependencies on and between shared library binary packages are
5258 managed in Debian. <ref id="libraries"> should be read in
5259 conjunction with this section and contains additional rules for
5260 the files contained in the shared library packages.
5263 <sect id="sharedlibs-runtime">
5264 <heading>Run-time shared libraries</heading>
5267 The run-time shared library must be placed in a package
5268 whose name changes whenever the <tt>SONAME</tt> of the shared
5269 library changes. This allows several versions of the shared
5270 library to be installed at the same time, allowing installation
5271 of the new version of the shared library without immediately
5272 breaking binaries that depend on the old version. Normally, the
5273 run-time shared library and its <tt>SONAME</tt> symlink should
5274 be placed in a package named
5275 <package><var>libraryname</var><var>soversion</var></package>,
5276 where <var>soversion</var> is the version number in
5277 the <tt>SONAME</tt> of the shared library.
5278 See <ref id="shlibs"> for detailed information on how to
5279 determine this version. Alternatively, if it would be confusing
5280 to directly append <var>soversion</var>
5281 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5282 itself ends in a number), you should use
5283 <package><var>libraryname</var>-<var>soversion</var></package>
5288 If you have several shared libraries built from the same source
5289 tree, you may lump them all together into a single shared
5290 library package provided that all of their <tt>SONAME</tt>s will
5291 always change together. Be aware that this is not normally the
5292 case, and if the <tt>SONAME</tt>s do not change together,
5293 upgrading such a merged shared library package will be
5294 unnecessarily difficult because of file conflicts with the old
5295 version of the package. When in doubt, always split shared
5296 library packages so that each binary package installs a single
5301 Every time the shared library ABI changes in a way that may
5302 break binaries linked against older versions of the shared
5303 library, the <tt>SONAME</tt> of the library and the
5304 corresponding name for the binary package containing the runtime
5305 shared library should change. Normally, this means
5306 the <tt>SONAME</tt> should change any time an interface is
5307 removed from the shared library or the signature of an interface
5308 (the number of parameters or the types of parameters that it
5309 takes, for example) is changed. This practice is vital to
5310 allowing clean upgrades from older versions of the package and
5311 clean transitions between the old ABI and new ABI without having
5312 to upgrade every affected package simultaneously.
5316 The <tt>SONAME</tt> and binary package name need not, and indeed
5317 normally should not, change if new interfaces are added but none
5318 are removed or changed, since this will not break binaries
5319 linked against the old shared library. Correct versioning of
5320 dependencies on the newer shared library by binaries that use
5321 the new interfaces is handled via
5322 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5323 system</qref> or via symbols files (see
5324 <manref name="deb-symbols" section="5">).
5328 The package should install the shared libraries under
5329 their normal names. For example, the <package>libgdbm3</package>
5330 package should install <file>libgdbm.so.3.0.0</file> as
5331 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5332 renamed or re-linked by any <prgn>prerm</prgn> or
5333 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5334 of renaming things safely without affecting running programs,
5335 and attempts to interfere with this are likely to lead to
5340 Shared libraries should not be installed executable, since
5341 the dynamic linker does not require this and trying to
5342 execute a shared library usually results in a core dump.
5346 The run-time library package should include the symbolic link for
5347 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5348 the shared libraries. For example,
5349 the <package>libgdbm3</package> package should include a symbolic
5350 link from <file>/usr/lib/libgdbm.so.3</file> to
5351 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5352 linker (for example <prgn>ld.so</prgn> or
5353 <prgn>ld-linux.so.*</prgn>) can find the library between the
5354 time that <prgn>dpkg</prgn> installs it and the time that
5355 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5357 The package management system requires the library to be
5358 placed before the symbolic link pointing to it in the
5359 <file>.deb</file> file. This is so that when
5360 <prgn>dpkg</prgn> comes to install the symlink
5361 (overwriting the previous symlink pointing at an older
5362 version of the library), the new shared library is already
5363 in place. In the past, this was achieved by creating the
5364 library in the temporary packaging directory before
5365 creating the symlink. Unfortunately, this was not always
5366 effective, since the building of the tar file in the
5367 <file>.deb</file> depended on the behavior of the underlying
5368 file system. Some file systems (such as reiserfs) reorder
5369 the files so that the order of creation is forgotten.
5370 Since version 1.7.0, <prgn>dpkg</prgn>
5371 reorders the files itself as necessary when building a
5372 package. Thus it is no longer important to concern
5373 oneself with the order of file creation.
5377 <sect1 id="ldconfig">
5378 <heading><tt>ldconfig</tt></heading>
5381 Any package installing shared libraries in one of the default
5382 library directories of the dynamic linker (which are currently
5383 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5384 listed in <file>/etc/ld.so.conf</file><footnote>
5385 These are currently <file>/usr/local/lib</file> plus
5386 directories under <file>/lib</file> and <file>/usr/lib</file>
5387 matching the multiarch triplet for the system architecture.
5389 must use <prgn>ldconfig</prgn> to update the shared library
5394 The package maintainer scripts must only call
5395 <prgn>ldconfig</prgn> under these circumstances:
5396 <list compact="compact">
5397 <item>When the <prgn>postinst</prgn> script is run with a
5398 first argument of <tt>configure</tt>, the script must call
5399 <prgn>ldconfig</prgn>, and may optionally invoke
5400 <prgn>ldconfig</prgn> at other times.
5402 <item>When the <prgn>postrm</prgn> script is run with a
5403 first argument of <tt>remove</tt>, the script should call
5404 <prgn>ldconfig</prgn>.
5409 During install or upgrade, the preinst is called before
5410 the new files are installed, so calling "ldconfig" is
5411 pointless. The preinst of an existing package can also be
5412 called if an upgrade fails. However, this happens during
5413 the critical time when a shared libs may exist on-disk
5414 under a temporary name. Thus, it is dangerous and
5415 forbidden by current policy to call "ldconfig" at this
5420 When a package is installed or upgraded, "postinst
5421 configure" runs after the new files are safely on-disk.
5422 Since it is perfectly safe to invoke ldconfig
5423 unconditionally in a postinst, it is OK for a package to
5424 simply put ldconfig in its postinst without checking the
5425 argument. The postinst can also be called to recover from
5426 a failed upgrade. This happens before any new files are
5427 unpacked, so there is no reason to call "ldconfig" at this
5432 For a package that is being removed, prerm is
5433 called with all the files intact, so calling ldconfig is
5434 useless. The other calls to "prerm" happen in the case of
5435 upgrade at a time when all the files of the old package
5436 are on-disk, so again calling "ldconfig" is pointless.
5440 postrm, on the other hand, is called with the "remove"
5441 argument just after the files are removed, so this is
5442 the proper time to call "ldconfig" to notify the system
5443 of the fact that the shared libraries from the package
5444 are removed. The postrm can be called at several other
5445 times. At the time of "postrm purge", "postrm
5446 abort-install", or "postrm abort-upgrade", calling
5447 "ldconfig" is useless because the shared lib files are
5448 not on-disk. However, when "postrm" is invoked with
5449 arguments "upgrade", "failed-upgrade", or "disappear", a
5450 shared lib may exist on-disk under a temporary filename.
5458 <sect id="sharedlibs-support-files">
5459 <heading>Shared library support files</heading>
5462 If your package contains files whose names do not change with
5463 each change in the library shared object version, you must not
5464 put them in the shared library package. Otherwise, several
5465 versions of the shared library cannot be installed at the same
5466 time without filename clashes, making upgrades and transitions
5467 unnecessarily difficult.
5471 It is recommended that supporting files and run-time support
5472 programs that do not need to be invoked manually by users, but
5473 are nevertheless required for the package to function, be placed
5474 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5475 preferably under <file>/usr/lib/</file><var>package-name</var>.
5476 If the program or file is architecture independent, the
5477 recommendation is for it to be placed in a subdirectory of
5478 <file>/usr/share</file> instead, preferably under
5479 <file>/usr/share/</file><var>package-name</var>. Following the
5480 <var>package-name</var> naming convention ensures that the file
5481 names change when the shared object version changes.
5485 Run-time support programs that use the shared library but are
5486 not required for the library to function or files used by the
5487 shared library that can be used by any version of the shared
5488 library package should instead be put in a separate package.
5489 This package might typically be named
5490 <package><var>libraryname</var>-tools</package>; note the
5491 absence of the <var>soversion</var> in the package name.
5495 Files and support programs only useful when compiling software
5496 against the library should be included in the development
5497 package for the library.<footnote>
5498 For example, a <file><var>package-name</var>-config</file>
5499 script or <package>pkg-config</package> configuration files.
5504 <sect id="sharedlibs-static">
5505 <heading>Static libraries</heading>
5508 The static library (<file><var>libraryname.a</var></file>)
5509 is usually provided in addition to the shared version.
5510 It is placed into the development package (see below).
5514 In some cases, it is acceptable for a library to be
5515 available in static form only; these cases include:
5517 <item>libraries for languages whose shared library support
5518 is immature or unstable</item>
5519 <item>libraries whose interfaces are in flux or under
5520 development (commonly the case when the library's
5521 major version number is zero, or where the ABI breaks
5522 across patchlevels)</item>
5523 <item>libraries which are explicitly intended to be
5524 available only in static form by their upstream
5529 <sect id="sharedlibs-dev">
5530 <heading>Development files</heading>
5533 If there are development files associated with a shared library,
5534 the source package needs to generate a binary development package
5535 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5536 or if you prefer only to support one development version at a
5537 time, <package><var>libraryname</var>-dev</package>. Installing
5538 the development package must result in installation of all the
5539 development files necessary for compiling programs against that
5540 shared library.<footnote>
5541 This wording allows the development files to be split into
5542 several packages, such as a separate architecture-independent
5543 <package><var>libraryname</var>-headers</package>, provided that
5544 the development package depends on all the required additional
5550 In case several development versions of a library exist, you may
5551 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5552 <ref id="conflicts">) to ensure that the user only installs one
5553 development version at a time (as different development versions are
5554 likely to have the same header files in them, which would cause a
5555 filename clash if both were installed).
5559 The development package should contain a symlink for the associated
5560 shared library without a version number. For example, the
5561 <package>libgdbm-dev</package> package should include a symlink
5562 from <file>/usr/lib/libgdbm.so</file> to
5563 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5564 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5565 <file>libgdbm.so</file> when compiling dynamically.
5569 If the package provides Ada Library Information
5570 (<file>*.ali</file>) files for use with GNAT, these files must be
5571 installed read-only (mode 0444) so that GNAT will not attempt to
5572 recompile them. This overrides the normal file mode requirements
5573 given in <ref id="permissions-owners">.
5577 <sect id="sharedlibs-intradeps">
5578 <heading>Dependencies between the packages of the same library</heading>
5581 Typically the development version should have an exact
5582 version dependency on the runtime library, to make sure that
5583 compilation and linking happens correctly. The
5584 <tt>${binary:Version}</tt> substitution variable can be
5585 useful for this purpose.
5587 Previously, <tt>${Source-Version}</tt> was used, but its name
5588 was confusing and it has been deprecated since dpkg 1.13.19.
5593 <sect id="sharedlibs-shlibdeps">
5594 <heading>Dependencies between the library and other packages -
5595 the <tt>shlibs</tt> system</heading>
5598 If a package contains a binary or library which links to a
5599 shared library, we must ensure that when the package is
5600 installed on the system, all of the libraries needed are
5601 also installed. This requirement led to the creation of the
5602 <tt>shlibs</tt> system, which is very simple in its design:
5603 any package which <em>provides</em> a shared library also
5604 provides information on the package dependencies required to
5605 ensure the presence of this library, and any package which
5606 <em>uses</em> a shared library uses this information to
5607 determine the dependencies it requires. The files which
5608 contain the mapping from shared libraries to the necessary
5609 dependency information are called <file>shlibs</file> files.
5613 When a package is built which contains any shared libraries, it
5614 must provide a <file>shlibs</file> file for other packages to
5615 use. When a package is built which contains any shared
5616 libraries or compiled binaries, it must run
5617 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5618 on these to determine the libraries used and hence the
5619 dependencies needed by this package.<footnote>
5621 <prgn>dpkg-shlibdeps</prgn> will use a program
5622 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5623 the libraries directly needed by the binaries or shared
5624 libraries in the package.
5628 We say that a binary <tt>foo</tt> <em>directly</em> uses
5629 a library <tt>libbar</tt> if it is explicitly linked
5630 with that library (that is, the library is listed in the ELF
5631 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5632 to the link line when the binary is created). Other
5633 libraries that are needed by <tt>libbar</tt> are linked
5634 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5635 linker will load them automatically when it loads
5636 <tt>libbar</tt>. A package should depend on the libraries
5637 it directly uses, but not the libraries it indirectly uses.
5638 The dependencies for those libraries will automatically pull
5639 in the other libraries.
5643 A good example of where this helps is the following. We
5644 could update <tt>libimlib</tt> with a new version that
5645 supports a new graphics format called dgf (but retaining the
5646 same major version number) and depends on <tt>libdgf</tt>.
5647 If we used <prgn>ldd</prgn> to add dependencies for every
5648 library directly or indirectly linked with a binary, every
5649 package that uses <tt>libimlib</tt> would need to be
5650 recompiled so it would also depend on <tt>libdgf</tt> or it
5651 wouldn't run due to missing symbols. Since dependencies are
5652 only added based on ELF <tt>NEEDED</tt> attribute, packages
5653 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5654 having the dependency on <tt>libdgf</tt> and so they would
5655 not need rebuilding.
5661 In the following sections, we will first describe where the
5662 various <tt>shlibs</tt> files are to be found, then how to
5663 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5664 file format and how to create them if your package contains a
5669 <heading>The <tt>shlibs</tt> files present on the system</heading>
5672 There are several places where <tt>shlibs</tt> files are
5673 found. The following list gives them in the order in which
5675 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5676 (The first one which gives the required information is used.)
5682 <p><file>debian/shlibs.local</file></p>
5685 This lists overrides for this package. This file should
5686 normally not be used, but may be needed temporarily in
5687 unusual situations to work around bugs in other packages,
5688 or in unusual cases where the normally declared dependency
5689 information in the installed <file>shlibs</file> file for
5690 a library cannot be used. This file overrides information
5691 obtained from any other source.
5696 <p><file>/etc/dpkg/shlibs.override</file></p>
5699 This lists global overrides. This list is normally
5700 empty. It is maintained by the local system
5706 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5709 When packages are being built,
5710 any <file>debian/shlibs</file> files are copied into the
5711 control information file area of the temporary build
5712 directory and given the name <file>shlibs</file>. These
5713 files give details of any shared libraries included in the
5714 same package.<footnote>
5715 An example may help here. Let us say that the source
5716 package <tt>foo</tt> generates two binary
5717 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5718 When building the binary packages, the two packages are
5719 created in the directories <file>debian/libfoo2</file>
5720 and <file>debian/foo-runtime</file> respectively.
5721 (<file>debian/tmp</file> could be used instead of one of
5722 these.) Since <tt>libfoo2</tt> provides the
5723 <tt>libfoo</tt> shared library, it will require a
5724 <tt>shlibs</tt> file, which will be installed in
5725 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5726 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5727 When <prgn>dpkg-shlibdeps</prgn> is run on the
5728 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5730 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5731 determine whether <tt>foo-prog</tt>'s library
5732 dependencies are satisfied by any of the libraries
5733 provided by <tt>libfoo2</tt>. For this reason,
5734 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5735 the individual binary packages' <tt>shlibs</tt> files
5736 have been installed into the build directory.
5742 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5745 These are the <file>shlibs</file> files corresponding to
5746 all of the packages installed on the system, and are
5747 maintained by the relevant package maintainers.
5752 <p><file>/etc/dpkg/shlibs.default</file></p>
5755 This file lists any shared libraries whose packages
5756 have failed to provide correct <file>shlibs</file> files.
5757 It was used when the <file>shlibs</file> setup was first
5758 introduced, but it is now normally empty. It is
5759 maintained by the <tt>dpkg</tt> maintainer.
5767 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5768 <file>shlibs</file> files</heading>
5772 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5773 into your <file>debian/rules</file> file. If your package
5774 contains only compiled binaries and libraries (but no scripts),
5775 you can use a command such as:
5776 <example compact="compact">
5777 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5778 debian/tmp/usr/lib/*
5780 Otherwise, you will need to explicitly list the compiled
5781 binaries and libraries.<footnote>
5782 If you are using <tt>debhelper</tt>, the
5783 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5784 It will also correctly handle multi-binary packages.
5789 This command puts the dependency information into the
5790 <file>debian/substvars</file> file, which is then used by
5791 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5792 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5793 field in the control file for this to work.
5797 If you have multiple binary packages, you will need to call
5798 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5799 compiled libraries or binaries. In such a case, you will
5800 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5801 utilities to specify a different <file>substvars</file> file.
5805 If you are creating a udeb for use in the Debian Installer,
5806 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5807 should use the dependency line of type <tt>udeb</tt> by
5808 adding the <tt>-tudeb</tt> option<footnote>
5809 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5810 will automatically add this option if it knows it is
5812 </footnote>. If there is no dependency line of
5813 type <tt>udeb</tt> in the <file>shlibs</file>
5814 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5819 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5820 <ref id="pkg-dpkg-shlibdeps"> and
5821 <manref name="dpkg-shlibdeps" section="1">.
5826 <heading>The <file>shlibs</file> File Format</heading>
5829 Each <file>shlibs</file> file has the same format. Lines
5830 beginning with <tt>#</tt> are considered to be comments and
5831 are ignored. Each line is of the form:
5832 <example compact="compact">
5833 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5838 We will explain this by reference to the example of the
5839 <tt>zlib1g</tt> package, which (at the time of writing)
5840 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5844 <var>type</var> is an optional element that indicates the type
5845 of package for which the line is valid. The only type currently
5846 in use is <tt>udeb</tt>. The colon and space after the type are
5851 <var>library-name</var> is the name of the shared library,
5852 in this case <tt>libz</tt>. (This must match the name part
5853 of the soname, see below.)
5857 <var>soname-version</var> is the version part of the soname of
5858 the library. The soname is the thing that must exactly match
5859 for the library to be recognized by the dynamic linker, and is
5861 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5862 example, <tt>libz.so.1</tt>.<footnote>
5863 This can be determined using the command
5864 <example compact="compact">
5865 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5868 The version part is the part which comes after
5869 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5870 instead be of the form
5871 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5872 as <tt>libdb-4.8.so</tt>, in which case the name would
5873 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5877 <var>dependencies</var> has the same syntax as a dependency
5878 field in a binary package control file. It should give
5879 details of which packages are required to satisfy a binary
5880 built against the version of the library contained in the
5881 package. See <ref id="depsyntax"> for details.
5885 In our example, if the first version of the <tt>zlib1g</tt>
5886 package which contained a minor number of at least
5887 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5888 <tt>shlibs</tt> entry for this library could say:
5889 <example compact="compact">
5890 libz 1 zlib1g (>= 1:1.1.3)
5892 The version-specific dependency is to avoid warnings from
5893 the dynamic linker about using older shared libraries with
5898 As zlib1g also provides a udeb containing the shared library,
5899 there would also be a second line:
5900 <example compact="compact">
5901 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5907 <heading>Providing a <file>shlibs</file> file</heading>
5910 If your package provides a shared library, you need to create
5911 a <file>shlibs</file> file following the format described above.
5912 It is usual to call this file <file>debian/shlibs</file> (but if
5913 you have multiple binary packages, you might want to call it
5914 <file>debian/shlibs.<var>package</var></file> instead). Then
5915 let <file>debian/rules</file> install it in the control
5916 information file area:
5917 <example compact="compact">
5918 install -m644 debian/shlibs debian/tmp/DEBIAN
5920 or, in the case of a multi-binary package:
5921 <example compact="compact">
5922 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5924 An alternative way of doing this is to create the
5925 <file>shlibs</file> file in the control information file area
5926 directly from <file>debian/rules</file> without using
5927 a <file>debian/shlibs</file> file at all,<footnote>
5928 This is what <prgn>dh_makeshlibs</prgn> in
5929 the <package>debhelper</package> suite does. If your package
5930 also has a udeb that provides a shared
5931 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5932 the <tt>udeb:</tt> lines if you specify the name of the udeb
5933 with the <tt>--add-udeb</tt> option.
5935 since the <file>debian/shlibs</file> file itself is ignored by
5936 <prgn>dpkg-shlibdeps</prgn>.
5940 As <prgn>dpkg-shlibdeps</prgn> reads the
5941 <file>DEBIAN/shlibs</file> files in all of the binary packages
5942 being built from this source package, all of the
5943 <file>DEBIAN/shlibs</file> files should be installed before
5944 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5952 <chapt id="opersys"><heading>The Operating System</heading>
5955 <heading>File system hierarchy</heading>
5959 <heading>File System Structure</heading>
5962 The location of all installed files and directories must
5963 comply with the Filesystem Hierarchy Standard (FHS),
5964 version 2.3, with the exceptions noted below, and except
5965 where doing so would violate other terms of Debian
5966 Policy. The following exceptions to the FHS apply:
5971 The optional rules related to user specific
5972 configuration files for applications are stored in
5973 the user's home directory are relaxed. It is
5974 recommended that such files start with the
5975 '<tt>.</tt>' character (a "dot file"), and if an
5976 application needs to create more than one dot file
5977 then the preferred placement is in a subdirectory
5978 with a name starting with a '.' character, (a "dot
5979 directory"). In this case it is recommended the
5980 configuration files not start with the '.'
5986 The requirement for amd64 to use <file>/lib64</file>
5987 for 64 bit binaries is removed.
5992 The requirement for object files, internal binaries, and
5993 libraries, including <file>libc.so.*</file>, to be located
5994 directly under <file>/lib{,32}</file> and
5995 <file>/usr/lib{,32}</file> is amended, permitting files
5996 to instead be installed to
5997 <file>/lib/<var>triplet</var></file> and
5998 <file>/usr/lib/<var>triplet</var></file>, where
5999 <tt><var>triplet</var></tt> is the value returned by
6000 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
6001 architecture of the package. Packages may <em>not</em>
6002 install files to any <var>triplet</var> path other
6003 than the one matching the architecture of that package;
6004 for instance, an <tt>Architecture: amd64</tt> package
6005 containing 32-bit x86 libraries may not install these
6006 libraries to <file>/usr/lib/i486-linux-gnu</file>.
6008 This is necessary in order to reserve the directories for
6009 use in cross-installation of library packages from other
6010 architectures, as part of the planned deployment of
6015 Applications may also use a single subdirectory under
6016 <file>/usr/lib/<var>triplet</var></file>.
6019 The execution time linker/loader, ld*, must still be made
6020 available in the existing location under /lib or /lib64
6021 since this is part of the ELF ABI for the architecture.
6026 The requirement that
6027 <file>/usr/local/share/man</file> be "synonymous"
6028 with <file>/usr/local/man</file> is relaxed to a
6033 The requirement that windowmanagers with a single
6034 configuration file call it <file>system.*wmrc</file>
6035 is removed, as is the restriction that the window
6036 manager subdirectory be named identically to the
6037 window manager name itself.
6042 The requirement that boot manager configuration
6043 files live in <file>/etc</file>, or at least are
6044 symlinked there, is relaxed to a recommendation.
6049 The following directories in the root filesystem are
6050 additionally allowed: <file>/sys</file> and
6051 <file>/selinux</file>. <footnote>These directories
6052 are used as mount points to mount virtual filesystems
6053 to get access to kernel information.</footnote>
6058 On GNU/Hurd systems, the following additional
6059 directories are allowed in the root
6060 filesystem: <file>/hurd</file>
6061 and <file>/servers</file>.<footnote>
6062 These directories are used to store translators and as
6063 a set of standard names for mount points,
6072 The version of this document referred here can be
6073 found in the <tt>debian-policy</tt> package or on <url
6074 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6075 name="FHS (Debian copy)"> alongside this manual (or, if
6076 you have the <package>debian-policy</package> installed,
6078 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6079 (local copy)">). The
6080 latest version, which may be a more recent version, may
6082 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6083 Specific questions about following the standard may be
6084 asked on the <tt>debian-devel</tt> mailing list, or
6085 referred to the FHS mailing list (see the
6086 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6092 <heading>Site-specific programs</heading>
6095 As mandated by the FHS, packages must not place any
6096 files in <file>/usr/local</file>, either by putting them in
6097 the file system archive to be unpacked by <prgn>dpkg</prgn>
6098 or by manipulating them in their maintainer scripts.
6102 However, the package may create empty directories below
6103 <file>/usr/local</file> so that the system administrator knows
6104 where to place site-specific files. These are not
6105 directories <em>in</em> <file>/usr/local</file>, but are
6106 children of directories in <file>/usr/local</file>. These
6107 directories (<file>/usr/local/*/dir/</file>)
6108 should be removed on package removal if they are
6113 Note that this applies only to
6114 directories <em>below</em> <file>/usr/local</file>,
6115 not <em>in</em> <file>/usr/local</file>. Packages must
6116 not create sub-directories in the
6117 directory <file>/usr/local</file> itself, except those
6118 listed in FHS, section 4.5. However, you may create
6119 directories below them as you wish. You must not remove
6120 any of the directories listed in 4.5, even if you created
6125 Since <file>/usr/local</file> can be mounted read-only from a
6126 remote server, these directories must be created and
6127 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6128 maintainer scripts and not be included in the
6129 <file>.deb</file> archive. These scripts must not fail if
6130 either of these operations fail.
6134 For example, the <tt>emacsen-common</tt> package could
6135 contain something like
6136 <example compact="compact">
6137 if [ ! -e /usr/local/share/emacs ]
6139 if mkdir /usr/local/share/emacs 2>/dev/null
6141 chown root:staff /usr/local/share/emacs
6142 chmod 2775 /usr/local/share/emacs
6146 in its <prgn>postinst</prgn> script, and
6147 <example compact="compact">
6148 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6149 rmdir /usr/local/share/emacs 2>/dev/null || true
6151 in the <prgn>prerm</prgn> script. (Note that this form is
6152 used to ensure that if the script is interrupted, the
6153 directory <file>/usr/local/share/emacs</file> will still be
6158 If you do create a directory in <file>/usr/local</file> for
6159 local additions to a package, you should ensure that
6160 settings in <file>/usr/local</file> take precedence over the
6161 equivalents in <file>/usr</file>.
6165 However, because <file>/usr/local</file> and its contents are
6166 for exclusive use of the local administrator, a package
6167 must not rely on the presence or absence of files or
6168 directories in <file>/usr/local</file> for normal operation.
6172 The <file>/usr/local</file> directory itself and all the
6173 subdirectories created by the package should (by default) have
6174 permissions 2775 (group-writable and set-group-id) and be
6175 owned by <tt>root:staff</tt>.
6180 <heading>The system-wide mail directory</heading>
6182 The system-wide mail directory
6183 is <file>/var/mail</file>. This directory is part of the
6184 base system and should not be owned by any particular mail
6185 agents. The use of the old
6186 location <file>/var/spool/mail</file> is deprecated, even
6187 though the spool may still be physically located there.
6193 <heading>Users and groups</heading>
6196 <heading>Introduction</heading>
6198 The Debian system can be configured to use either plain or
6203 Some user ids (UIDs) and group ids (GIDs) are reserved
6204 globally for use by certain packages. Because some
6205 packages need to include files which are owned by these
6206 users or groups, or need the ids compiled into binaries,
6207 these ids must be used on any Debian system only for the
6208 purpose for which they are allocated. This is a serious
6209 restriction, and we should avoid getting in the way of
6210 local administration policies. In particular, many sites
6211 allocate users and/or local system groups starting at 100.
6215 Apart from this we should have dynamically allocated ids,
6216 which should by default be arranged in some sensible
6217 order, but the behavior should be configurable.
6221 Packages other than <tt>base-passwd</tt> must not modify
6222 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6223 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6228 <heading>UID and GID classes</heading>
6230 The UID and GID numbers are divided into classes as
6236 Globally allocated by the Debian project, the same
6237 on every Debian system. These ids will appear in
6238 the <file>passwd</file> and <file>group</file> files of all
6239 Debian systems, new ids in this range being added
6240 automatically as the <tt>base-passwd</tt> package is
6245 Packages which need a single statically allocated
6246 uid or gid should use one of these; their
6247 maintainers should ask the <tt>base-passwd</tt>
6255 Dynamically allocated system users and groups.
6256 Packages which need a user or group, but can have
6257 this user or group allocated dynamically and
6258 differently on each system, should use <tt>adduser
6259 --system</tt> to create the group and/or user.
6260 <prgn>adduser</prgn> will check for the existence of
6261 the user or group, and if necessary choose an unused
6262 id based on the ranges specified in
6263 <file>adduser.conf</file>.
6267 <tag>1000-59999:</tag>
6270 Dynamically allocated user accounts. By default
6271 <prgn>adduser</prgn> will choose UIDs and GIDs for
6272 user accounts in this range, though
6273 <file>adduser.conf</file> may be used to modify this
6278 <tag>60000-64999:</tag>
6281 Globally allocated by the Debian project, but only
6282 created on demand. The ids are allocated centrally
6283 and statically, but the actual accounts are only
6284 created on users' systems on demand.
6288 These ids are for packages which are obscure or
6289 which require many statically-allocated ids. These
6290 packages should check for and create the accounts in
6291 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6292 <prgn>adduser</prgn> if it has this facility) if
6293 necessary. Packages which are likely to require
6294 further allocations should have a "hole" left after
6295 them in the allocation, to give them room to
6300 <tag>65000-65533:</tag>
6308 User <tt>nobody</tt>. The corresponding gid refers
6309 to the group <tt>nogroup</tt>.
6316 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6317 not</em> be used, because it is the error return
6326 <sect id="sysvinit">
6327 <heading>System run levels and <file>init.d</file> scripts</heading>
6329 <sect1 id="/etc/init.d">
6330 <heading>Introduction</heading>
6333 The <file>/etc/init.d</file> directory contains the scripts
6334 executed by <prgn>init</prgn> at boot time and when the
6335 init state (or "runlevel") is changed (see <manref
6336 name="init" section="8">).
6340 There are at least two different, yet functionally
6341 equivalent, ways of handling these scripts. For the sake
6342 of simplicity, this document describes only the symbolic
6343 link method. However, it must not be assumed by maintainer
6344 scripts that this method is being used, and any automated
6345 manipulation of the various runlevel behaviors by
6346 maintainer scripts must be performed using
6347 <prgn>update-rc.d</prgn> as described below and not by
6348 manually installing or removing symlinks. For information
6349 on the implementation details of the other method,
6350 implemented in the <tt>file-rc</tt> package, please refer
6351 to the documentation of that package.
6355 These scripts are referenced by symbolic links in the
6356 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6357 runlevels, <prgn>init</prgn> looks in the directory
6358 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6359 execute, where <tt><var>n</var></tt> is the runlevel that
6360 is being changed to, or <tt>S</tt> for the boot-up
6365 The names of the links all have the form
6366 <file>S<var>mm</var><var>script</var></file> or
6367 <file>K<var>mm</var><var>script</var></file> where
6368 <var>mm</var> is a two-digit number and <var>script</var>
6369 is the name of the script (this should be the same as the
6370 name of the actual script in <file>/etc/init.d</file>).
6374 When <prgn>init</prgn> changes runlevel first the targets
6375 of the links whose names start with a <tt>K</tt> are
6376 executed, each with the single argument <tt>stop</tt>,
6377 followed by the scripts prefixed with an <tt>S</tt>, each
6378 with the single argument <tt>start</tt>. (The links are
6379 those in the <file>/etc/rc<var>n</var>.d</file> directory
6380 corresponding to the new runlevel.) The <tt>K</tt> links
6381 are responsible for killing services and the <tt>S</tt>
6382 link for starting services upon entering the runlevel.
6386 For example, if we are changing from runlevel 2 to
6387 runlevel 3, init will first execute all of the <tt>K</tt>
6388 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6389 all of the <tt>S</tt> prefixed scripts in that directory.
6390 The links starting with <tt>K</tt> will cause the
6391 referred-to file to be executed with an argument of
6392 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6397 The two-digit number <var>mm</var> is used to determine
6398 the order in which to run the scripts: low-numbered links
6399 have their scripts run first. For example, the
6400 <tt>K20</tt> scripts will be executed before the
6401 <tt>K30</tt> scripts. This is used when a certain service
6402 must be started before another. For example, the name
6403 server <prgn>bind</prgn> might need to be started before
6404 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6405 can set up its access lists. In this case, the script
6406 that starts <prgn>bind</prgn> would have a lower number
6407 than the script that starts <prgn>inn</prgn> so that it
6409 <example compact="compact">
6416 The two runlevels 0 (halt) and 6 (reboot) are slightly
6417 different. In these runlevels, the links with an
6418 <tt>S</tt> prefix are still called after those with a
6419 <tt>K</tt> prefix, but they too are called with the single
6420 argument <tt>stop</tt>.
6424 <sect1 id="writing-init">
6425 <heading>Writing the scripts</heading>
6428 Packages that include daemons for system services should
6429 place scripts in <file>/etc/init.d</file> to start or stop
6430 services at boot time or during a change of runlevel.
6431 These scripts should be named
6432 <file>/etc/init.d/<var>package</var></file>, and they should
6433 accept one argument, saying what to do:
6436 <tag><tt>start</tt></tag>
6437 <item>start the service,</item>
6439 <tag><tt>stop</tt></tag>
6440 <item>stop the service,</item>
6442 <tag><tt>restart</tt></tag>
6443 <item>stop and restart the service if it's already running,
6444 otherwise start the service</item>
6446 <tag><tt>reload</tt></tag>
6447 <item><p>cause the configuration of the service to be
6448 reloaded without actually stopping and restarting
6451 <tag><tt>force-reload</tt></tag>
6452 <item>cause the configuration to be reloaded if the
6453 service supports this, otherwise restart the
6457 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6458 <tt>force-reload</tt> options should be supported by all
6459 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6464 The <file>init.d</file> scripts must ensure that they will
6465 behave sensibly (i.e., returning success and not starting
6466 multiple copies of a service) if invoked with <tt>start</tt>
6467 when the service is already running, or with <tt>stop</tt>
6468 when it isn't, and that they don't kill unfortunately-named
6469 user processes. The best way to achieve this is usually to
6470 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6475 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6476 scripts. Writing correct <file>init.d</file> scripts requires
6477 accepting various error exit statuses when daemons are already
6478 running or already stopped without aborting
6479 the <file>init.d</file> script, and common <file>init.d</file>
6480 function libraries are not safe to call with <tt>set -e</tt>
6482 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6483 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6484 in effect and echoing status messages to the console fails,
6486 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6487 to not use <tt>set -e</tt> and instead check the result of
6488 each command separately.
6492 If a service reloads its configuration automatically (as
6493 in the case of <prgn>cron</prgn>, for example), the
6494 <tt>reload</tt> option of the <file>init.d</file> script
6495 should behave as if the configuration has been reloaded
6500 The <file>/etc/init.d</file> scripts must be treated as
6501 configuration files, either (if they are present in the
6502 package, that is, in the .deb file) by marking them as
6503 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6504 by managing them correctly in the maintainer scripts (see
6505 <ref id="config-files">). This is important since we want
6506 to give the local system administrator the chance to adapt
6507 the scripts to the local system, e.g., to disable a
6508 service without de-installing the package, or to specify
6509 some special command line options when starting a service,
6510 while making sure their changes aren't lost during the next
6515 These scripts should not fail obscurely when the
6516 configuration files remain but the package has been
6517 removed, as configuration files remain on the system after
6518 the package has been removed. Only when <prgn>dpkg</prgn>
6519 is executed with the <tt>--purge</tt> option will
6520 configuration files be removed. In particular, as the
6521 <file>/etc/init.d/<var>package</var></file> script itself is
6522 usually a <tt>conffile</tt>, it will remain on the system
6523 if the package is removed but not purged. Therefore, you
6524 should include a <tt>test</tt> statement at the top of the
6526 <example compact="compact">
6527 test -f <var>program-executed-later-in-script</var> || exit 0
6532 Often there are some variables in the <file>init.d</file>
6533 scripts whose values control the behavior of the scripts,
6534 and which a system administrator is likely to want to
6535 change. As the scripts themselves are frequently
6536 <tt>conffile</tt>s, modifying them requires that the
6537 administrator merge in their changes each time the package
6538 is upgraded and the <tt>conffile</tt> changes. To ease
6539 the burden on the system administrator, such configurable
6540 values should not be placed directly in the script.
6541 Instead, they should be placed in a file in
6542 <file>/etc/default</file>, which typically will have the same
6543 base name as the <file>init.d</file> script. This extra file
6544 should be sourced by the script when the script runs. It
6545 must contain only variable settings and comments in SUSv3
6546 <prgn>sh</prgn> format. It may either be a
6547 <tt>conffile</tt> or a configuration file maintained by
6548 the package maintainer scripts. See <ref id="config-files">
6553 To ensure that vital configurable values are always
6554 available, the <file>init.d</file> script should set default
6555 values for each of the shell variables it uses, either
6556 before sourcing the <file>/etc/default/</file> file or
6557 afterwards using something like the <tt>:
6558 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6559 script must behave sensibly and not fail if the
6560 <file>/etc/default</file> file is deleted.
6564 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6565 as temporary filesystems<footnote>
6566 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6567 options in <file>/etc/default/rcS</file>.
6568 </footnote>, so the <file>init.d</file> scripts must handle this
6569 correctly. This will typically amount to creating any required
6570 subdirectories dynamically when the <file>init.d</file> script
6571 is run, rather than including them in the package and relying on
6572 <prgn>dpkg</prgn> to create them.
6577 <heading>Interfacing with the initscript system</heading>
6580 Maintainers should use the abstraction layer provided by
6581 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6582 programs to deal with initscripts in their packages'
6583 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6584 and <prgn>postrm</prgn>.
6588 Directly managing the /etc/rc?.d links and directly
6589 invoking the <file>/etc/init.d/</file> initscripts should
6590 be done only by packages providing the initscript
6591 subsystem (such as <prgn>sysv-rc</prgn> and
6592 <prgn>file-rc</prgn>).
6596 <heading>Managing the links</heading>
6599 The program <prgn>update-rc.d</prgn> is provided for
6600 package maintainers to arrange for the proper creation and
6601 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6602 or their functional equivalent if another method is being
6603 used. This may be used by maintainers in their packages'
6604 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6608 You must not include any <file>/etc/rc<var>n</var>.d</file>
6609 symbolic links in the actual archive or manually create or
6610 remove the symbolic links in maintainer scripts; you must
6611 use the <prgn>update-rc.d</prgn> program instead. (The
6612 former will fail if an alternative method of maintaining
6613 runlevel information is being used.) You must not include
6614 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6615 in the archive either. (Only the <tt>sysvinit</tt>
6620 By default <prgn>update-rc.d</prgn> will start services in
6621 each of the multi-user state runlevels (2, 3, 4, and 5)
6622 and stop them in the halt runlevel (0), the single-user
6623 runlevel (1) and the reboot runlevel (6). The system
6624 administrator will have the opportunity to customize
6625 runlevels by simply adding, moving, or removing the
6626 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6627 symbolic links are being used, or by modifying
6628 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6633 To get the default behavior for your package, put in your
6634 <prgn>postinst</prgn> script
6635 <example compact="compact">
6636 update-rc.d <var>package</var> defaults
6638 and in your <prgn>postrm</prgn>
6639 <example compact="compact">
6640 if [ "$1" = purge ]; then
6641 update-rc.d <var>package</var> remove
6643 </example>. Note that if your package changes runlevels
6644 or priority, you may have to remove and recreate the links,
6645 since otherwise the old links may persist. Refer to the
6646 documentation of <prgn>update-rc.d</prgn>.
6650 This will use a default sequence number of 20. If it does
6651 not matter when or in which order the <file>init.d</file>
6652 script is run, use this default. If it does, then you
6653 should talk to the maintainer of the <prgn>sysvinit</prgn>
6654 package or post to <tt>debian-devel</tt>, and they will
6655 help you choose a number.
6659 For more information about using <tt>update-rc.d</tt>,
6660 please consult its man page <manref name="update-rc.d"
6666 <heading>Running initscripts</heading>
6668 The program <prgn>invoke-rc.d</prgn> is provided to make
6669 it easier for package maintainers to properly invoke an
6670 initscript, obeying runlevel and other locally-defined
6671 constraints that might limit a package's right to start,
6672 stop and otherwise manage services. This program may be
6673 used by maintainers in their packages' scripts.
6677 The package maintainer scripts must use
6678 <prgn>invoke-rc.d</prgn> to invoke the
6679 <file>/etc/init.d/*</file> initscripts, instead of
6680 calling them directly.
6684 By default, <prgn>invoke-rc.d</prgn> will pass any
6685 action requests (start, stop, reload, restart...) to the
6686 <file>/etc/init.d</file> script, filtering out requests
6687 to start or restart a service out of its intended
6692 Most packages will simply need to change:
6693 <example compact="compact">/etc/init.d/<package>
6694 <action></example> in their <prgn>postinst</prgn>
6695 and <prgn>prerm</prgn> scripts to:
6696 <example compact="compact">
6697 if which invoke-rc.d >/dev/null 2>&1; then
6698 invoke-rc.d <var>package</var> <action>
6700 /etc/init.d/<var>package</var> <action>
6706 A package should register its initscript services using
6707 <prgn>update-rc.d</prgn> before it tries to invoke them
6708 using <prgn>invoke-rc.d</prgn>. Invocation of
6709 unregistered services may fail.
6713 For more information about using
6714 <prgn>invoke-rc.d</prgn>, please consult its man page
6715 <manref name="invoke-rc.d" section="8">.
6721 <heading>Boot-time initialization</heading>
6724 There used to be another directory, <file>/etc/rc.boot</file>,
6725 which contained scripts which were run once per machine
6726 boot. This has been deprecated in favour of links from
6727 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6728 described in <ref id="/etc/init.d">. Packages must not
6729 place files in <file>/etc/rc.boot</file>.
6734 <heading>Example</heading>
6737 An example on which you can base your
6738 <file>/etc/init.d</file> scripts is found in
6739 <file>/etc/init.d/skeleton</file>.
6746 <heading>Console messages from <file>init.d</file> scripts</heading>
6749 This section describes the formats to be used for messages
6750 written to standard output by the <file>/etc/init.d</file>
6751 scripts. The intent is to improve the consistency of
6752 Debian's startup and shutdown look and feel. For this
6753 reason, please look very carefully at the details. We want
6754 the messages to have the same format in terms of wording,
6755 spaces, punctuation and case of letters.
6759 Here is a list of overall rules that should be used for
6760 messages generated by <file>/etc/init.d</file> scripts.
6766 The message should fit in one line (fewer than 80
6767 characters), start with a capital letter and end with
6768 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6772 If the script is performing some time consuming task in
6773 the background (not merely starting or stopping a
6774 program, for instance), an ellipsis (three dots:
6775 <tt>...</tt>) should be output to the screen, with no
6776 leading or tailing whitespace or line feeds.
6780 The messages should appear as if the computer is telling
6781 the user what it is doing (politely :-), but should not
6782 mention "it" directly. For example, instead of:
6783 <example compact="compact">
6784 I'm starting network daemons: nfsd mountd.
6786 the message should say
6787 <example compact="compact">
6788 Starting network daemons: nfsd mountd.
6795 <tt>init.d</tt> script should use the following standard
6796 message formats for the situations enumerated below.
6802 <p>When daemons are started</p>
6805 If the script starts one or more daemons, the output
6806 should look like this (a single line, no leading
6808 <example compact="compact">
6809 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6811 The <var>description</var> should describe the
6812 subsystem the daemon or set of daemons are part of,
6813 while <var>daemon-1</var> up to <var>daemon-n</var>
6814 denote each daemon's name (typically the file name of
6819 For example, the output of <file>/etc/init.d/lpd</file>
6821 <example compact="compact">
6822 Starting printer spooler: lpd.
6827 This can be achieved by saying
6828 <example compact="compact">
6829 echo -n "Starting printer spooler: lpd"
6830 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6833 in the script. If there are more than one daemon to
6834 start, the output should look like this:
6835 <example compact="compact">
6836 echo -n "Starting remote file system services:"
6837 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6838 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6839 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6842 This makes it possible for the user to see what is
6843 happening and when the final daemon has been started.
6844 Care should be taken in the placement of white spaces:
6845 in the example above the system administrators can
6846 easily comment out a line if they don't want to start
6847 a specific daemon, while the displayed message still
6853 <p>When a system parameter is being set</p>
6856 If you have to set up different system parameters
6857 during the system boot, you should use this format:
6858 <example compact="compact">
6859 Setting <var>parameter</var> to "<var>value</var>".
6864 You can use a statement such as the following to get
6866 <example compact="compact">
6867 echo "Setting DNS domainname to \"$domainname\"."
6872 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6873 for the left and right quotation marks. A grave accent
6874 (<tt>`</tt>) is not a quote character; neither is an
6875 apostrophe (<tt>'</tt>).
6880 <p>When a daemon is stopped or restarted</p>
6883 When you stop or restart a daemon, you should issue a
6884 message identical to the startup message, except that
6885 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6886 or <tt>Restarting</tt> respectively.
6890 For example, stopping the printer daemon will look like
6892 <example compact="compact">
6893 Stopping printer spooler: lpd.
6899 <p>When something is executed</p>
6902 There are several examples where you have to run a
6903 program at system startup or shutdown to perform a
6904 specific task, for example, setting the system's clock
6905 using <prgn>netdate</prgn> or killing all processes
6906 when the system shuts down. Your message should look
6908 <example compact="compact">
6909 Doing something very useful...done.
6911 You should print the <tt>done.</tt> immediately after
6912 the job has been completed, so that the user is
6913 informed why they have to wait. You can get this
6915 <example compact="compact">
6916 echo -n "Doing something very useful..."
6925 <p>When the configuration is reloaded</p>
6928 When a daemon is forced to reload its configuration
6929 files you should use the following format:
6930 <example compact="compact">
6931 Reloading <var>description</var> configuration...done.
6933 where <var>description</var> is the same as in the
6934 daemon starting message.
6942 <heading>Cron jobs</heading>
6945 Packages must not modify the configuration file
6946 <file>/etc/crontab</file>, and they must not modify the files in
6947 <file>/var/spool/cron/crontabs</file>.</p>
6950 If a package wants to install a job that has to be executed
6951 via cron, it should place a file with the name of the
6952 package in one or more of the following directories:
6953 <example compact="compact">
6959 As these directory names imply, the files within them are
6960 executed on an hourly, daily, weekly, or monthly basis,
6961 respectively. The exact times are listed in
6962 <file>/etc/crontab</file>.</p>
6965 All files installed in any of these directories must be
6966 scripts (e.g., shell scripts or Perl scripts) so that they
6967 can easily be modified by the local system administrator.
6968 In addition, they must be treated as configuration files.
6972 If a certain job has to be executed at some other frequency or
6973 at a specific time, the package should install a file
6974 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6975 same syntax as <file>/etc/crontab</file> and is processed by
6976 <prgn>cron</prgn> automatically. The file must also be
6977 treated as a configuration file. (Note that entries in the
6978 <file>/etc/cron.d</file> directory are not handled by
6979 <prgn>anacron</prgn>. Thus, you should only use this
6980 directory for jobs which may be skipped if the system is not
6983 Unlike <file>crontab</file> files described in the IEEE Std
6984 1003.1-2008 (POSIX.1) available from
6985 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6986 name="The Open Group">, the files in
6987 <file>/etc/cron.d</file> and the file
6988 <file>/etc/crontab</file> have seven fields; namely:
6990 <item>Minute [0,59]</item>
6991 <item>Hour [0,23]</item>
6992 <item>Day of the month [1,31]</item>
6993 <item>Month of the year [1,12]</item>
6994 <item>Day of the week ([0,6] with 0=Sunday)</item>
6995 <item>Username</item>
6996 <item>Command to be run</item>
6998 Ranges of numbers are allowed. Ranges are two numbers
6999 separated with a hyphen. The specified range is inclusive.
7000 Lists are allowed. A list is a set of numbers (or ranges)
7001 separated by commas. Step values can be used in conjunction
7006 The scripts or <tt>crontab</tt> entries in these directories should
7007 check if all necessary programs are installed before they
7008 try to execute them. Otherwise, problems will arise when a
7009 package was removed but not purged since configuration files
7010 are kept on the system in this situation.
7014 Any <tt>cron</tt> daemon must provide
7015 <file>/usr/bin/crontab</file> and support normal
7016 <tt>crontab</tt> entries as specified in POSIX. The daemon
7017 must also support names for days and months, ranges, and
7018 step values. It has to support <file>/etc/crontab</file>,
7019 and correctly execute the scripts in
7020 <file>/etc/cron.d</file>. The daemon must also correctly
7022 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7027 <heading>Menus</heading>
7030 The Debian <tt>menu</tt> package provides a standard
7031 interface between packages providing applications and
7032 <em>menu programs</em> (either X window managers or
7033 text-based menu programs such as <prgn>pdmenu</prgn>).
7037 All packages that provide applications that need not be
7038 passed any special command line arguments for normal
7039 operation should register a menu entry for those
7040 applications, so that users of the <tt>menu</tt> package
7041 will automatically get menu entries in their window
7042 managers, as well in shells like <tt>pdmenu</tt>.
7046 Menu entries should follow the current menu policy.
7050 The menu policy can be found in the <tt>menu-policy</tt>
7051 files in the <tt>debian-policy</tt> package.
7052 It is also available from the Debian web mirrors at
7053 <tt><url name="/doc/packaging-manuals/menu-policy/"
7054 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7058 Please also refer to the <em>Debian Menu System</em>
7059 documentation that comes with the <package>menu</package>
7060 package for information about how to register your
7066 <heading>Multimedia handlers</heading>
7069 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7070 is a mechanism for encoding files and data streams and
7071 providing meta-information about them, in particular their
7072 type (e.g. audio or video) and format (e.g. PNG, HTML,
7077 Registration of MIME type handlers allows programs like mail
7078 user agents and web browsers to invoke these handlers to
7079 view, edit or display MIME types they don't support directly.
7083 Packages which provide the ability to view/show/play,
7084 compose, edit or print MIME types should register themselves
7085 as such following the current MIME support policy.
7089 The MIME support policy can be found in the <tt>mime-policy</tt>
7090 files in the <tt>debian-policy</tt> package.
7091 It is also available from the Debian web mirrors at
7092 <tt><url name="/doc/packaging-manuals/mime-policy/"
7093 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7099 <heading>Keyboard configuration</heading>
7102 To achieve a consistent keyboard configuration so that all
7103 applications interpret a keyboard event the same way, all
7104 programs in the Debian distribution must be configured to
7105 comply with the following guidelines.
7109 The following keys must have the specified interpretations:
7112 <tag><tt><--</tt></tag>
7113 <item>delete the character to the left of the cursor</item>
7115 <tag><tt>Delete</tt></tag>
7116 <item>delete the character to the right of the cursor</item>
7118 <tag><tt>Control+H</tt></tag>
7119 <item>emacs: the help prefix</item>
7122 The interpretation of any keyboard events should be
7123 independent of the terminal that is used, be it a virtual
7124 console, an X terminal emulator, an rlogin/telnet session,
7129 The following list explains how the different programs
7130 should be set up to achieve this:
7136 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7140 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7144 X translations are set up to make
7145 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7146 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7147 is the vt220 escape code for the "delete character"
7148 key). This must be done by loading the X resources
7149 using <prgn>xrdb</prgn> on all local X displays, not
7150 using the application defaults, so that the
7151 translation resources used correspond to the
7152 <prgn>xmodmap</prgn> settings.
7156 The Linux console is configured to make
7157 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7158 generate <tt>ESC [ 3 ~</tt>.
7162 X applications are configured so that <tt><</tt>
7163 deletes left, and <tt>Delete</tt> deletes right. Motif
7164 applications already work like this.
7168 Terminals should have <tt>stty erase ^?</tt> .
7172 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7173 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7174 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7178 Emacs is programmed to map <tt>KB_Backspace</tt> or
7179 the <tt>stty erase</tt> character to
7180 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7181 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7182 <tt>^H</tt> to <tt>help</tt> as always.
7186 Other applications use the <tt>stty erase</tt>
7187 character and <tt>kdch1</tt> for the two delete keys,
7188 with ASCII DEL being "delete previous character" and
7189 <tt>kdch1</tt> being "delete character under
7197 This will solve the problem except for the following
7204 Some terminals have a <tt><--</tt> key that cannot
7205 be made to produce anything except <tt>^H</tt>. On
7206 these terminals Emacs help will be unavailable on
7207 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7208 character takes precedence in Emacs, and has been set
7209 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7210 available) can be used instead.
7214 Some operating systems use <tt>^H</tt> for <tt>stty
7215 erase</tt>. However, modern telnet versions and all
7216 rlogin versions propagate <tt>stty</tt> settings, and
7217 almost all UNIX versions honour <tt>stty erase</tt>.
7218 Where the <tt>stty</tt> settings are not propagated
7219 correctly, things can be made to work by using
7220 <tt>stty</tt> manually.
7224 Some systems (including previous Debian versions) use
7225 <prgn>xmodmap</prgn> to arrange for both
7226 <tt><--</tt> and <tt>Delete</tt> to generate
7227 <tt>KB_Delete</tt>. We can change the behavior of
7228 their X clients using the same X resources that we use
7229 to do it for our own clients, or configure our clients
7230 using their resources when things are the other way
7231 around. On displays configured like this
7232 <tt>Delete</tt> will not work, but <tt><--</tt>
7237 Some operating systems have different <tt>kdch1</tt>
7238 settings in their <tt>terminfo</tt> database for
7239 <tt>xterm</tt> and others. On these systems the
7240 <tt>Delete</tt> key will not work correctly when you
7241 log in from a system conforming to our policy, but
7242 <tt><--</tt> will.
7249 <heading>Environment variables</heading>
7252 A program must not depend on environment variables to get
7253 reasonable defaults. (That's because these environment
7254 variables would have to be set in a system-wide
7255 configuration file like <file>/etc/profile</file>, which is not
7256 supported by all shells.)
7260 If a program usually depends on environment variables for its
7261 configuration, the program should be changed to fall back to
7262 a reasonable default configuration if these environment
7263 variables are not present. If this cannot be done easily
7264 (e.g., if the source code of a non-free program is not
7265 available), the program must be replaced by a small
7266 "wrapper" shell script which sets the environment variables
7267 if they are not already defined, and calls the original program.
7271 Here is an example of a wrapper script for this purpose:
7273 <example compact="compact">
7275 BAR=${BAR:-/var/lib/fubar}
7277 exec /usr/lib/foo/foo "$@"
7282 Furthermore, as <file>/etc/profile</file> is a configuration
7283 file of the <prgn>base-files</prgn> package, other packages must
7284 not put any environment variables or other commands into that
7289 <sect id="doc-base">
7290 <heading>Registering Documents using doc-base</heading>
7293 The <package>doc-base</package> package implements a
7294 flexible mechanism for handling and presenting
7295 documentation. The recommended practice is for every Debian
7296 package that provides online documentation (other than just
7297 manual pages) to register these documents with
7298 <package>doc-base</package> by installing a
7299 <package>doc-base</package> control file via the
7300 <prgn/install-docs/ script at installation time and
7301 de-register the manuals again when the package is removed.
7304 Please refer to the documentation that comes with the
7305 <package>doc-base</package> package for information and
7314 <heading>Files</heading>
7316 <sect id="binaries">
7317 <heading>Binaries</heading>
7320 Two different packages must not install programs with
7321 different functionality but with the same filenames. (The
7322 case of two programs having the same functionality but
7323 different implementations is handled via "alternatives" or
7324 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7325 <ref id="conflicts"> respectively.) If this case happens,
7326 one of the programs must be renamed. The maintainers should
7327 report this to the <tt>debian-devel</tt> mailing list and
7328 try to find a consensus about which program will have to be
7329 renamed. If a consensus cannot be reached, <em>both</em>
7330 programs must be renamed.
7334 By default, when a package is being built, any binaries
7335 created should include debugging information, as well as
7336 being compiled with optimization. You should also turn on
7337 as many reasonable compilation warnings as possible; this
7338 makes life easier for porters, who can then look at build
7339 logs for possible problems. For the C programming language,
7340 this means the following compilation parameters should be
7342 <example compact="compact">
7344 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7346 INSTALL = install -s # (or use strip on the files in debian/tmp)
7351 Note that by default all installed binaries should be stripped,
7352 either by using the <tt>-s</tt> flag to
7353 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7354 the binaries after they have been copied into
7355 <file>debian/tmp</file> but before the tree is made into a
7360 Although binaries in the build tree should be compiled with
7361 debugging information by default, it can often be difficult to
7362 debug programs if they are also subjected to compiler
7363 optimization. For this reason, it is recommended to support the
7364 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7365 (see <ref id="debianrules-options">). This variable can contain
7366 several flags to change how a package is compiled and built.
7370 It is up to the package maintainer to decide what
7371 compilation options are best for the package. Certain
7372 binaries (such as computationally-intensive programs) will
7373 function better with certain flags (<tt>-O3</tt>, for
7374 example); feel free to use them. Please use good judgment
7375 here. Don't use flags for the sake of it; only use them
7376 if there is good reason to do so. Feel free to override
7377 the upstream author's ideas about which compilation
7378 options are best: they are often inappropriate for our
7384 <sect id="libraries">
7385 <heading>Libraries</heading>
7388 If the package is <strong>architecture: any</strong>, then
7389 the shared library compilation and linking flags must have
7390 <tt>-fPIC</tt>, or the package shall not build on some of
7391 the supported architectures<footnote>
7393 If you are using GCC, <tt>-fPIC</tt> produces code with
7394 relocatable position independent code, which is required for
7395 most architectures to create a shared library, with i386 and
7396 perhaps some others where non position independent code is
7397 permitted in a shared library.
7400 Position independent code may have a performance penalty,
7401 especially on <tt>i386</tt>. However, in most cases the
7402 speed penalty must be measured against the memory wasted on
7403 the few architectures where non position independent code is
7406 </footnote>. Any exception to this rule must be discussed on
7407 the mailing list <em>debian-devel@lists.debian.org</em>, and
7408 a rough consensus obtained. The reasons for not compiling
7409 with <tt>-fPIC</tt> flag must be recorded in the file
7410 <tt>README.Debian</tt>, and care must be taken to either
7411 restrict the architecture or arrange for <tt>-fPIC</tt> to
7412 be used on architectures where it is required.<footnote>
7414 Some of the reasons why this might be required is if the
7415 library contains hand crafted assembly code that is not
7416 relocatable, the speed penalty is excessive for compute
7417 intensive libs, and similar reasons.
7422 As to the static libraries, the common case is not to have
7423 relocatable code, since there is no benefit, unless in specific
7424 cases; therefore the static version must not be compiled
7425 with the <tt>-fPIC</tt> flag. Any exception to this rule
7426 should be discussed on the mailing list
7427 <em>debian-devel@lists.debian.org</em>, and the reasons for
7428 compiling with the <tt>-fPIC</tt> flag must be recorded in
7429 the file <tt>README.Debian</tt>. <footnote>
7431 Some of the reasons for linking static libraries with
7432 the <tt>-fPIC</tt> flag are if, for example, one needs a
7433 Perl API for a library that is under rapid development,
7434 and has an unstable API, so shared libraries are
7435 pointless at this phase of the library's development. In
7436 that case, since Perl needs a library with relocatable
7437 code, it may make sense to create a static library with
7438 relocatable code. Another reason cited is if you are
7439 distilling various libraries into a common shared
7440 library, like <tt>mklibs</tt> does in the Debian
7446 In other words, if both a shared and a static library is
7447 being built, each source unit (<tt>*.c</tt>, for example,
7448 for C files) will need to be compiled twice, for the normal
7453 Libraries should be built with threading support and to be
7454 thread-safe if the library supports this.
7458 Although not enforced by the build tools, shared libraries
7459 must be linked against all libraries that they use symbols from
7460 in the same way that binaries are. This ensures the correct
7461 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7462 system and guarantees that all libraries can be safely opened
7463 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7464 option <tt>-Wl,-z,defs</tt> when building a shared library.
7465 Since this option enforces symbol resolution at build time,
7466 a missing library reference will be caught early as a fatal
7471 All installed shared libraries should be stripped with
7472 <example compact="compact">
7473 strip --strip-unneeded <var>your-lib</var>
7475 (The option <tt>--strip-unneeded</tt> makes
7476 <prgn>strip</prgn> remove only the symbols which aren't
7477 needed for relocation processing.) Shared libraries can
7478 function perfectly well when stripped, since the symbols for
7479 dynamic linking are in a separate part of the ELF object
7481 You might also want to use the options
7482 <tt>--remove-section=.comment</tt> and
7483 <tt>--remove-section=.note</tt> on both shared libraries
7484 and executables, and <tt>--strip-debug</tt> on static
7490 Note that under some circumstances it may be useful to
7491 install a shared library unstripped, for example when
7492 building a separate package to support debugging.
7496 Shared object files (often <file>.so</file> files) that are not
7497 public libraries, that is, they are not meant to be linked
7498 to by third party executables (binaries of other packages),
7499 should be installed in subdirectories of the
7500 <file>/usr/lib</file> directory. Such files are exempt from the
7501 rules that govern ordinary shared libraries, except that
7502 they must not be installed executable and should be
7504 A common example are the so-called "plug-ins",
7505 internal shared objects that are dynamically loaded by
7506 programs using <manref name="dlopen" section="3">.
7511 Packages that use <prgn>libtool</prgn> to create and install
7512 their shared libraries install a file containing additional
7513 metadata (ending in <file>.la</file>) alongside the library.
7514 For public libraries intended for use by other packages, these
7515 files normally should not be included in the Debian package,
7516 since the information they include is not necessary to link with
7517 the shared library on Debian and can add unnecessary additional
7518 dependencies to other programs or libraries.<footnote>
7519 These files store, among other things, all libraries on which
7520 that shared library depends. Unfortunately, if
7521 the <file>.la</file> file is present and contains that
7522 dependency information, using <prgn>libtool</prgn> when
7523 linking against that library will cause the resulting program
7524 or library to be linked against those dependencies as well,
7525 even if this is unnecessary. This can create unneeded
7526 dependencies on shared library packages that would otherwise
7527 be hidden behind the library ABI, and can make library
7528 transitions to new SONAMEs unnecessarily complicated and
7529 difficult to manage.
7531 If the <file>.la</file> file is required for that library (if,
7532 for instance, it's loaded via <tt>libltdl</tt> in a way that
7533 requires that meta-information), the <tt>dependency_libs</tt>
7534 setting in the <file>.la</file> file should normally be set to
7535 the empty string. If the shared library development package has
7536 historically included the <file>.la</file>, it must be retained
7537 in the development package (with <tt>dependency_libs</tt>
7538 emptied) until all libraries that depend on it have removed or
7539 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7540 files to prevent linking with those other libraries
7541 using <prgn>libtool</prgn> from failing.
7545 If the <file>.la</file> must be included, it should be included
7546 in the development (<tt>-dev</tt>) package, unless the library
7547 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7548 library. If it is intended for use with <tt>libltdl</tt>,
7549 the <file>.la</file> files must go in the run-time library
7554 These requirements for handling of <file>.la</file> files do not
7555 apply to loadable modules or libraries not installed in
7556 directories searched by default by the dynamic linker. Packages
7557 installing loadable modules will frequently need to install
7558 the <file>.la</file> files alongside the modules so that they
7559 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7560 does not need to be modified for libraries or modules that are
7561 not installed in directories searched by the dynamic linker by
7562 default and not intended for use by other packages.
7566 You must make sure that you use only released versions of
7567 shared libraries to build your packages; otherwise other
7568 users will not be able to run your binaries
7569 properly. Producing source packages that depend on
7570 unreleased compilers is also usually a bad
7577 <heading>Shared libraries</heading>
7579 This section has moved to <ref id="sharedlibs">.
7585 <heading>Scripts</heading>
7588 All command scripts, including the package maintainer
7589 scripts inside the package and used by <prgn>dpkg</prgn>,
7590 should have a <tt>#!</tt> line naming the shell to be used
7595 In the case of Perl scripts this should be
7596 <tt>#!/usr/bin/perl</tt>.
7600 When scripts are installed into a directory in the system
7601 PATH, the script name should not include an extension such
7602 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7603 language currently used to implement it.
7606 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7607 <file>init.d</file> scripts should almost certainly start
7608 with <tt>set -e</tt> so that errors are detected.
7609 <file>init.d</file> scripts are something of a special case, due
7610 to how frequently they need to call commands that are allowed to
7611 fail, and it may instead be easier to check the exit status of
7612 commands directly. See <ref id="writing-init"> for more
7613 information about writing <file>init.d</file> scripts.
7616 Every script should use <tt>set -e</tt> or check the exit status
7617 of <em>every</em> command.
7620 Scripts may assume that <file>/bin/sh</file> implements the
7621 SUSv3 Shell Command Language<footnote>
7622 Single UNIX Specification, version 3, which is also IEEE
7623 1003.1-2004 (POSIX), and is available on the World Wide Web
7624 from <url id="http://www.unix.org/version3/online.html"
7625 name="The Open Group"> after free
7626 registration.</footnote>
7627 plus the following additional features not mandated by
7629 These features are in widespread use in the Linux community
7630 and are implemented in all of bash, dash, and ksh, the most
7631 common shells users may wish to use as <file>/bin/sh</file>.
7634 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7635 must not generate a newline.</item>
7636 <item><tt>test</tt>, if implemented as a shell built-in, must
7637 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7639 <item><tt>local</tt> to create a scoped variable must be
7640 supported, including listing multiple variables in a single
7641 local command and assigning a value to a variable at the
7642 same time as localizing it. <tt>local</tt> may or
7643 may not preserve the variable value from an outer scope if
7644 no assignment is present. Uses such as:
7648 # ... use a, b, c, d ...
7651 must be supported and must set the value of <tt>c</tt> to
7654 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7655 -<var>signal</var></tt>, where <var>signal</var> is either
7656 the name of a signal or one of the numeric signals listed in
7657 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7658 supported if <prgn>kill</prgn> is implemented as a shell
7661 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7662 signals must be supported. In addition to the signal
7663 numbers listed in the extension, which are the same as for
7664 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7667 If a shell script requires non-SUSv3 features from the shell
7668 interpreter other than those listed above, the appropriate shell
7669 must be specified in the first line of the script (e.g.,
7670 <tt>#!/bin/bash</tt>) and the package must depend on the package
7671 providing the shell (unless the shell package is marked
7672 "Essential", as in the case of <prgn>bash</prgn>).
7676 You may wish to restrict your script to SUSv3 features plus the
7677 above set when possible so that it may use <file>/bin/sh</file>
7678 as its interpreter. If your script works with <prgn>dash</prgn>
7679 (originally called <prgn>ash</prgn>), it probably complies with
7680 the above requirements, but if you are in doubt, use
7681 <file>/bin/bash</file>.
7685 Perl scripts should check for errors when making any
7686 system calls, including <tt>open</tt>, <tt>print</tt>,
7687 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7691 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7692 scripting languages. See <em>Csh Programming Considered
7693 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7694 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7695 If an upstream package comes with <prgn>csh</prgn> scripts
7696 then you must make sure that they start with
7697 <tt>#!/bin/csh</tt> and make your package depend on the
7698 <prgn>c-shell</prgn> virtual package.
7702 Any scripts which create files in world-writeable
7703 directories (e.g., in <file>/tmp</file>) must use a
7704 mechanism which will fail atomically if a file with the same
7705 name already exists.
7709 The Debian base system provides the <prgn>tempfile</prgn>
7710 and <prgn>mktemp</prgn> utilities for use by scripts for
7717 <heading>Symbolic links</heading>
7720 In general, symbolic links within a top-level directory
7721 should be relative, and symbolic links pointing from one
7722 top-level directory into another should be absolute. (A
7723 top-level directory is a sub-directory of the root
7724 directory <file>/</file>.)
7728 In addition, symbolic links should be specified as short as
7729 possible, i.e., link targets like <file>foo/../bar</file> are
7734 Note that when creating a relative link using
7735 <prgn>ln</prgn> it is not necessary for the target of the
7736 link to exist relative to the working directory you're
7737 running <prgn>ln</prgn> from, nor is it necessary to change
7738 directory to the directory where the link is to be made.
7739 Simply include the string that should appear as the target
7740 of the link (this will be a pathname relative to the
7741 directory in which the link resides) as the first argument
7746 For example, in your <prgn>Makefile</prgn> or
7747 <file>debian/rules</file>, you can do things like:
7748 <example compact="compact">
7749 ln -fs gcc $(prefix)/bin/cc
7750 ln -fs gcc debian/tmp/usr/bin/cc
7751 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7752 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7757 A symbolic link pointing to a compressed file should always
7758 have the same file extension as the referenced file. (For
7759 example, if a file <file>foo.gz</file> is referenced by a
7760 symbolic link, the filename of the link has to end with
7761 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7766 <heading>Device files</heading>
7769 Packages must not include device files or named pipes in the
7774 If a package needs any special device files that are not
7775 included in the base system, it must call
7776 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7777 after notifying the user<footnote>
7778 This notification could be done via a (low-priority)
7779 debconf message, or an echo (printf) statement.
7784 Packages must not remove any device files in the
7785 <prgn>postrm</prgn> or any other script. This is left to the
7786 system administrator.
7790 Debian uses the serial devices
7791 <file>/dev/ttyS*</file>. Programs using the old
7792 <file>/dev/cu*</file> devices should be changed to use
7793 <file>/dev/ttyS*</file>.
7797 Named pipes needed by the package must be created in
7798 the <prgn>postinst</prgn> script<footnote>
7799 It's better to use <prgn>mkfifo</prgn> rather
7800 than <prgn>mknod</prgn> to create named pipes so that
7801 automated checks for packages incorrectly creating device
7802 files with <prgn>mknod</prgn> won't have false positives.
7803 </footnote> and removed in
7804 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7809 <sect id="config-files">
7810 <heading>Configuration files</heading>
7813 <heading>Definitions</heading>
7817 <tag>configuration file</tag>
7819 A file that affects the operation of a program, or
7820 provides site- or host-specific information, or
7821 otherwise customizes the behavior of a program.
7822 Typically, configuration files are intended to be
7823 modified by the system administrator (if needed or
7824 desired) to conform to local policy or to provide
7825 more useful site-specific behavior.
7828 <tag><tt>conffile</tt></tag>
7830 A file listed in a package's <tt>conffiles</tt>
7831 file, and is treated specially by <prgn>dpkg</prgn>
7832 (see <ref id="configdetails">).
7838 The distinction between these two is important; they are
7839 not interchangeable concepts. Almost all
7840 <tt>conffile</tt>s are configuration files, but many
7841 configuration files are not <tt>conffiles</tt>.
7845 As noted elsewhere, <file>/etc/init.d</file> scripts,
7846 <file>/etc/default</file> files, scripts installed in
7847 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7848 configuration installed in <file>/etc/cron.d</file> must be
7849 treated as configuration files. In general, any script that
7850 embeds configuration information is de-facto a configuration
7851 file and should be treated as such.
7856 <heading>Location</heading>
7859 Any configuration files created or used by your package
7860 must reside in <file>/etc</file>. If there are several,
7861 consider creating a subdirectory of <file>/etc</file>
7862 named after your package.
7866 If your package creates or uses configuration files
7867 outside of <file>/etc</file>, and it is not feasible to modify
7868 the package to use <file>/etc</file> directly, put the files
7869 in <file>/etc</file> and create symbolic links to those files
7870 from the location that the package requires.
7875 <heading>Behavior</heading>
7878 Configuration file handling must conform to the following
7880 <list compact="compact">
7882 local changes must be preserved during a package
7886 configuration files must be preserved when the
7887 package is removed, and only deleted when the
7891 Obsolete configuration files without local changes may be
7892 removed by the package during upgrade.
7896 The easy way to achieve this behavior is to make the
7897 configuration file a <tt>conffile</tt>. This is
7898 appropriate only if it is possible to distribute a default
7899 version that will work for most installations, although
7900 some system administrators may choose to modify it. This
7901 implies that the default version will be part of the
7902 package distribution, and must not be modified by the
7903 maintainer scripts during installation (or at any other
7908 In order to ensure that local changes are preserved
7909 correctly, no package may contain or make hard links to
7910 conffiles.<footnote>
7911 Rationale: There are two problems with hard links.
7912 The first is that some editors break the link while
7913 editing one of the files, so that the two files may
7914 unwittingly become unlinked and different. The second
7915 is that <prgn>dpkg</prgn> might break the hard link
7916 while upgrading <tt>conffile</tt>s.
7921 The other way to do it is via the maintainer scripts. In
7922 this case, the configuration file must not be listed as a
7923 <tt>conffile</tt> and must not be part of the package
7924 distribution. If the existence of a file is required for
7925 the package to be sensibly configured it is the
7926 responsibility of the package maintainer to provide
7927 maintainer scripts which correctly create, update and
7928 maintain the file and remove it on purge. (See <ref
7929 id="maintainerscripts"> for more information.) These
7930 scripts must be idempotent (i.e., must work correctly if
7931 <prgn>dpkg</prgn> needs to re-run them due to errors
7932 during installation or removal), must cope with all the
7933 variety of ways <prgn>dpkg</prgn> can call maintainer
7934 scripts, must not overwrite or otherwise mangle the user's
7935 configuration without asking, must not ask unnecessary
7936 questions (particularly during upgrades), and must
7937 otherwise be good citizens.
7941 The scripts are not required to configure every possible
7942 option for the package, but only those necessary to get
7943 the package running on a given system. Ideally the
7944 sysadmin should not have to do any configuration other
7945 than that done (semi-)automatically by the
7946 <prgn>postinst</prgn> script.
7950 A common practice is to create a script called
7951 <file><var>package</var>-configure</file> and have the
7952 package's <prgn>postinst</prgn> call it if and only if the
7953 configuration file does not already exist. In certain
7954 cases it is useful for there to be an example or template
7955 file which the maintainer scripts use. Such files should
7956 be in <file>/usr/share/<var>package</var></file> or
7957 <file>/usr/lib/<var>package</var></file> (depending on whether
7958 they are architecture-independent or not). There should
7959 be symbolic links to them from
7960 <file>/usr/share/doc/<var>package</var>/examples</file> if
7961 they are examples, and should be perfectly ordinary
7962 <prgn>dpkg</prgn>-handled files (<em>not</em>
7963 configuration files).
7967 These two styles of configuration file handling must
7968 not be mixed, for that way lies madness:
7969 <prgn>dpkg</prgn> will ask about overwriting the file
7970 every time the package is upgraded.
7975 <heading>Sharing configuration files</heading>
7978 Packages which specify the same file as a
7979 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7980 with each other. (This is an instance of the general rule
7981 about not sharing files. Note that neither alternatives
7982 nor diversions are likely to be appropriate in this case;
7983 in particular, <prgn>dpkg</prgn> does not handle diverted
7984 <tt>conffile</tt>s well.)
7988 The maintainer scripts must not alter a <tt>conffile</tt>
7989 of <em>any</em> package, including the one the scripts
7994 If two or more packages use the same configuration file
7995 and it is reasonable for both to be installed at the same
7996 time, one of these packages must be defined as
7997 <em>owner</em> of the configuration file, i.e., it will be
7998 the package which handles that file as a configuration
7999 file. Other packages that use the configuration file must
8000 depend on the owning package if they require the
8001 configuration file to operate. If the other package will
8002 use the configuration file if present, but is capable of
8003 operating without it, no dependency need be declared.
8007 If it is desirable for two or more related packages to
8008 share a configuration file <em>and</em> for all of the
8009 related packages to be able to modify that configuration
8010 file, then the following should be done:
8011 <enumlist compact="compact">
8013 One of the related packages (the "owning" package)
8014 will manage the configuration file with maintainer
8015 scripts as described in the previous section.
8018 The owning package should also provide a program
8019 that the other packages may use to modify the
8023 The related packages must use the provided program
8024 to make any desired modifications to the
8025 configuration file. They should either depend on
8026 the core package to guarantee that the configuration
8027 modifier program is available or accept gracefully
8028 that they cannot modify the configuration file if it
8029 is not. (This is in addition to the fact that the
8030 configuration file may not even be present in the
8037 Sometimes it's appropriate to create a new package which
8038 provides the basic infrastructure for the other packages
8039 and which manages the shared configuration files. (The
8040 <tt>sgml-base</tt> package is a good example.)
8045 <heading>User configuration files ("dotfiles")</heading>
8048 The files in <file>/etc/skel</file> will automatically be
8049 copied into new user accounts by <prgn>adduser</prgn>.
8050 No other program should reference the files in
8051 <file>/etc/skel</file>.
8055 Therefore, if a program needs a dotfile to exist in
8056 advance in <file>$HOME</file> to work sensibly, that dotfile
8057 should be installed in <file>/etc/skel</file> and treated as a
8062 However, programs that require dotfiles in order to
8063 operate sensibly are a bad thing, unless they do create
8064 the dotfiles themselves automatically.
8068 Furthermore, programs should be configured by the Debian
8069 default installation to behave as closely to the upstream
8070 default behavior as possible.
8074 Therefore, if a program in a Debian package needs to be
8075 configured in some way in order to operate sensibly, that
8076 should be done using a site-wide configuration file placed
8077 in <file>/etc</file>. Only if the program doesn't support a
8078 site-wide default configuration and the package maintainer
8079 doesn't have time to add it may a default per-user file be
8080 placed in <file>/etc/skel</file>.
8084 <file>/etc/skel</file> should be as empty as we can make it.
8085 This is particularly true because there is no easy (or
8086 necessarily desirable) mechanism for ensuring that the
8087 appropriate dotfiles are copied into the accounts of
8088 existing users when a package is installed.
8094 <heading>Log files</heading>
8096 Log files should usually be named
8097 <file>/var/log/<var>package</var>.log</file>. If you have many
8098 log files, or need a separate directory for permission
8099 reasons (<file>/var/log</file> is writable only by
8100 <file>root</file>), you should usually create a directory named
8101 <file>/var/log/<var>package</var></file> and place your log
8106 Log files must be rotated occasionally so that they don't grow
8107 indefinitely. The best way to do this is to install a log
8108 rotation configuration file in the
8109 directory <file>/etc/logrotate.d</file>, normally
8110 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8111 the facilities provided by <prgn>logrotate</prgn>.
8114 The traditional approach to log files has been to set up
8115 <em>ad hoc</em> log rotation schemes using simple shell
8116 scripts and cron. While this approach is highly
8117 customizable, it requires quite a lot of sysadmin work.
8118 Even though the original Debian system helped a little
8119 by automatically installing a system which can be used
8120 as a template, this was deemed not enough.
8124 The use of <prgn>logrotate</prgn>, a program developed
8125 by Red Hat, is better, as it centralizes log management.
8126 It has both a configuration file
8127 (<file>/etc/logrotate.conf</file>) and a directory where
8128 packages can drop their individual log rotation
8129 configurations (<file>/etc/logrotate.d</file>).
8132 Here is a good example for a logrotate config
8133 file (for more information see <manref name="logrotate"
8135 <example compact="compact">
8136 /var/log/foo/*.log {
8142 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8146 This rotates all files under <file>/var/log/foo</file>, saves 12
8147 compressed generations, and tells the daemon to reopen its log
8148 files after the log rotation. It skips this log rotation
8149 (via <tt>missingok</tt>) if no such log file is present, which
8150 avoids errors if the package is removed but not purged.
8154 Log files should be removed when the package is
8155 purged (but not when it is only removed). This should be
8156 done by the <prgn>postrm</prgn> script when it is called
8157 with the argument <tt>purge</tt> (see <ref
8158 id="removedetails">).
8162 <sect id="permissions-owners">
8163 <heading>Permissions and owners</heading>
8166 The rules in this section are guidelines for general use.
8167 If necessary you may deviate from the details below.
8168 However, if you do so you must make sure that what is done
8169 is secure and you should try to be as consistent as possible
8170 with the rest of the system. You should probably also
8171 discuss it on <prgn>debian-devel</prgn> first.
8175 Files should be owned by <tt>root:root</tt>, and made
8176 writable only by the owner and universally readable (and
8177 executable, if appropriate), that is mode 644 or 755.
8181 Directories should be mode 755 or (for group-writability)
8182 mode 2775. The ownership of the directory should be
8183 consistent with its mode: if a directory is mode 2775, it
8184 should be owned by the group that needs write access to
8187 When a package is upgraded, and the owner or permissions
8188 of a file included in the package has changed, dpkg
8189 arranges for the ownership and permissions to be
8190 correctly set upon installation. However, this does not
8191 extend to directories; the permissions and ownership of
8192 directories already on the system does not change on
8193 install or upgrade of packages. This makes sense, since
8194 otherwise common directories like <tt>/usr</tt> would
8195 always be in flux. To correctly change permissions of a
8196 directory the package owns, explicit action is required,
8197 usually in the <tt>postinst</tt> script. Care must be
8198 taken to handle downgrades as well, in that case.
8204 Control information files should be owned by <tt>root:root</tt>
8205 and either mode 644 (for most files) or mode 755 (for
8206 executables such as <qref id="maintscripts">maintainer
8211 Setuid and setgid executables should be mode 4755 or 2755
8212 respectively, and owned by the appropriate user or group.
8213 They should not be made unreadable (modes like 4711 or
8214 2711 or even 4111); doing so achieves no extra security,
8215 because anyone can find the binary in the freely available
8216 Debian package; it is merely inconvenient. For the same
8217 reason you should not restrict read or execute permissions
8218 on non-set-id executables.
8222 Some setuid programs need to be restricted to particular
8223 sets of users, using file permissions. In this case they
8224 should be owned by the uid to which they are set-id, and by
8225 the group which should be allowed to execute them. They
8226 should have mode 4754; again there is no point in making
8227 them unreadable to those users who must not be allowed to
8232 It is possible to arrange that the system administrator can
8233 reconfigure the package to correspond to their local
8234 security policy by changing the permissions on a binary:
8235 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8236 described below.<footnote>
8237 Ordinary files installed by <prgn>dpkg</prgn> (as
8238 opposed to <tt>conffile</tt>s and other similar objects)
8239 normally have their permissions reset to the distributed
8240 permissions when the package is reinstalled. However,
8241 the use of <prgn>dpkg-statoverride</prgn> overrides this
8244 Another method you should consider is to create a group for
8245 people allowed to use the program(s) and make any setuid
8246 executables executable only by that group.
8250 If you need to create a new user or group for your package
8251 there are two possibilities. Firstly, you may need to
8252 make some files in the binary package be owned by this
8253 user or group, or you may need to compile the user or
8254 group id (rather than just the name) into the binary
8255 (though this latter should be avoided if possible, as in
8256 this case you need a statically allocated id).</p>
8259 If you need a statically allocated id, you must ask for a
8260 user or group id from the <tt>base-passwd</tt> maintainer,
8261 and must not release the package until you have been
8262 allocated one. Once you have been allocated one you must
8263 either make the package depend on a version of the
8264 <tt>base-passwd</tt> package with the id present in
8265 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8266 your package to create the user or group itself with the
8267 correct id (using <tt>adduser</tt>) in its
8268 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8269 the <prgn>postinst</prgn> is to be preferred if it is
8270 possible, otherwise a pre-dependency will be needed on the
8271 <tt>adduser</tt> package.)
8275 On the other hand, the program might be able to determine
8276 the uid or gid from the user or group name at runtime, so
8277 that a dynamically allocated id can be used. In this case
8278 you should choose an appropriate user or group name,
8279 discussing this on <prgn>debian-devel</prgn> and checking
8280 with the <package/base-passwd/ maintainer that it is unique and that
8281 they do not wish you to use a statically allocated id
8282 instead. When this has been checked you must arrange for
8283 your package to create the user or group if necessary using
8284 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8285 <prgn>postinst</prgn> script (again, the latter is to be
8286 preferred if it is possible).
8290 Note that changing the numeric value of an id associated
8291 with a name is very difficult, and involves searching the
8292 file system for all appropriate files. You need to think
8293 carefully whether a static or dynamic id is required, since
8294 changing your mind later will cause problems.
8297 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8299 This section is not intended as policy, but as a
8300 description of the use of <prgn>dpkg-statoverride</prgn>.
8304 If a system administrator wishes to have a file (or
8305 directory or other such thing) installed with owner and
8306 permissions different from those in the distributed Debian
8307 package, they can use the <prgn>dpkg-statoverride</prgn>
8308 program to instruct <prgn>dpkg</prgn> to use the different
8309 settings every time the file is installed. Thus the
8310 package maintainer should distribute the files with their
8311 normal permissions, and leave it for the system
8312 administrator to make any desired changes. For example, a
8313 daemon which is normally required to be setuid root, but
8314 in certain situations could be used without being setuid,
8315 should be installed setuid in the <tt>.deb</tt>. Then the
8316 local system administrator can change this if they wish.
8317 If there are two standard ways of doing it, the package
8318 maintainer can use <tt>debconf</tt> to find out the
8319 preference, and call <prgn>dpkg-statoverride</prgn> in the
8320 maintainer script if necessary to accommodate the system
8321 administrator's choice. Care must be taken during
8322 upgrades to not override an existing setting.
8326 Given the above, <prgn>dpkg-statoverride</prgn> is
8327 essentially a tool for system administrators and would not
8328 normally be needed in the maintainer scripts. There is
8329 one type of situation, though, where calls to
8330 <prgn>dpkg-statoverride</prgn> would be needed in the
8331 maintainer scripts, and that involves packages which use
8332 dynamically allocated user or group ids. In such a
8333 situation, something like the following idiom can be very
8334 helpful in the package's <prgn>postinst</prgn>, where
8335 <tt>sysuser</tt> is a dynamically allocated id:
8337 for i in /usr/bin/foo /usr/sbin/bar
8339 # only do something when no setting exists
8340 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8342 #include: debconf processing, question about foo and bar
8343 if [ "$RET" = "true" ] ; then
8344 dpkg-statoverride --update --add sysuser root 4755 $i
8349 The corresponding code to remove the override when the package
8352 for i in /usr/bin/foo /usr/sbin/bar
8354 if dpkg-statoverride --list $i >/dev/null 2>&1
8356 dpkg-statoverride --remove $i
8366 <chapt id="customized-programs">
8367 <heading>Customized programs</heading>
8369 <sect id="arch-spec">
8370 <heading>Architecture specification strings</heading>
8373 If a program needs to specify an <em>architecture specification
8374 string</em> in some place, it should select one of the strings
8375 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8376 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8377 part is sometimes elided, as when the OS is Linux.
8381 Note that we don't want to use
8382 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8383 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8384 since this would make our programs incompatible with other
8385 Linux distributions. We also don't use something like
8386 <tt><var>arch</var>-unknown-linux</tt>, since the
8387 <tt>unknown</tt> does not look very good.
8390 <sect1 id="arch-wildcard-spec">
8391 <heading>Architecture wildcards</heading>
8394 A package may specify an architecture wildcard. Architecture
8395 wildcards are in the format <tt>any</tt> (which matches every
8396 architecture), <tt><var>os</var></tt>-any, or
8397 any-<tt><var>cpu</var></tt>. <footnote>
8398 Internally, the package system normalizes the GNU triplets
8399 and the Debian arches into Debian arch triplets (which are
8400 kind of inverted GNU triplets), with the first component of
8401 the triplet representing the libc and ABI in use, and then
8402 does matching against those triplets. However, such
8403 triplets are an internal implementation detail that should
8404 not be used by packages directly. The libc and ABI portion
8405 is handled internally by the package system based on
8406 the <var>os</var> and <var>cpu</var>.
8413 <heading>Daemons</heading>
8416 The configuration files <file>/etc/services</file>,
8417 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8418 by the <prgn>netbase</prgn> package and must not be modified
8423 If a package requires a new entry in one of these files, the
8424 maintainer should get in contact with the
8425 <prgn>netbase</prgn> maintainer, who will add the entries
8426 and release a new version of the <prgn>netbase</prgn>
8431 The configuration file <file>/etc/inetd.conf</file> must not be
8432 modified by the package's scripts except via the
8433 <prgn>update-inetd</prgn> script or the
8434 <file>DebianNet.pm</file> Perl module. See their documentation
8435 for details on how to add entries.
8439 If a package wants to install an example entry into
8440 <file>/etc/inetd.conf</file>, the entry must be preceded with
8441 exactly one hash character (<tt>#</tt>). Such lines are
8442 treated as "commented out by user" by the
8443 <prgn>update-inetd</prgn> script and are not changed or
8444 activated during package updates.
8449 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8453 Some programs need to create pseudo-ttys. This should be done
8454 using Unix98 ptys if the C library supports it. The resulting
8455 program must not be installed setuid root, unless that
8456 is required for other functionality.
8460 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8461 <file>/var/log/lastlog</file> must be installed writable by
8462 group <tt>utmp</tt>. Programs which need to modify those
8463 files must be installed setgid <tt>utmp</tt>.
8468 <heading>Editors and pagers</heading>
8471 Some programs have the ability to launch an editor or pager
8472 program to edit or display a text document. Since there are
8473 lots of different editors and pagers available in the Debian
8474 distribution, the system administrator and each user should
8475 have the possibility to choose their preferred editor and
8480 In addition, every program should choose a good default
8481 editor/pager if none is selected by the user or system
8486 Thus, every program that launches an editor or pager must
8487 use the EDITOR or PAGER environment variable to determine
8488 the editor or pager the user wishes to use. If these
8489 variables are not set, the programs <file>/usr/bin/editor</file>
8490 and <file>/usr/bin/pager</file> should be used, respectively.
8494 These two files are managed through the <prgn>dpkg</prgn>
8495 "alternatives" mechanism. Every package providing an editor or
8496 pager must call the <prgn>update-alternatives</prgn> script to
8497 register as an alternative for <file>/usr/bin/editor</file>
8498 or <file>/usr/bin/pager</file> as appropriate. The alternative
8499 should have a slave alternative
8500 for <file>/usr/share/man/man1/editor.1.gz</file>
8501 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8502 corresponding manual page.
8506 If it is very hard to adapt a program to make use of the
8507 EDITOR or PAGER variables, that program may be configured to
8508 use <file>/usr/bin/sensible-editor</file> and
8509 <file>/usr/bin/sensible-pager</file> as the editor or pager
8510 program respectively. These are two scripts provided in the
8511 <package>sensible-utils</package> package that check the EDITOR
8512 and PAGER variables and launch the appropriate program, and fall
8513 back to <file>/usr/bin/editor</file>
8514 and <file>/usr/bin/pager</file> if the variable is not set.
8518 A program may also use the VISUAL environment variable to
8519 determine the user's choice of editor. If it exists, it
8520 should take precedence over EDITOR. This is in fact what
8521 <file>/usr/bin/sensible-editor</file> does.
8525 It is not required for a package to depend on
8526 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8527 package to provide such virtual packages.<footnote>
8528 The Debian base system already provides an editor and a
8534 <sect id="web-appl">
8535 <heading>Web servers and applications</heading>
8538 This section describes the locations and URLs that should
8539 be used by all web servers and web applications in the
8546 Cgi-bin executable files are installed in the
8548 <example compact="compact">
8549 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8551 or a subdirectory of that directory, and should be
8553 <example compact="compact">
8554 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8556 (possibly with a subdirectory name
8557 before <var>cgi-bin-name</var>).
8561 <p>Access to HTML documents</p>
8564 HTML documents for a package are stored in
8565 <file>/usr/share/doc/<var>package</var></file>
8566 and can be referred to as
8567 <example compact="compact">
8568 http://localhost/doc/<var>package</var>/<var>filename</var>
8573 The web server should restrict access to the document
8574 tree so that only clients on the same host can read
8575 the documents. If the web server does not support such
8576 access controls, then it should not provide access at
8577 all, or ask about providing access during installation.
8582 <p>Access to images</p>
8584 It is recommended that images for a package be stored
8585 in <tt>/usr/share/images/<var>package</var></tt> and
8586 may be referred to through an alias <tt>/images/</tt>
8589 http://localhost/images/<package>/<filename>
8596 <p>Web Document Root</p>
8599 Web Applications should try to avoid storing files in
8600 the Web Document Root. Instead they should use the
8601 /usr/share/doc/<var>package</var> directory for
8602 documents and register the Web Application via the
8603 <package>doc-base</package> package. If access to the
8604 web document root is unavoidable then use
8605 <example compact="compact">
8608 as the Document Root. This might be just a symbolic
8609 link to the location where the system administrator
8610 has put the real document root.
8613 <item><p>Providing httpd and/or httpd-cgi</p>
8615 All web servers should provide the virtual package
8616 <tt>httpd</tt>. If a web server has CGI support it should
8617 provide <tt>httpd-cgi</tt> additionally.
8620 All web applications which do not contain CGI scripts should
8621 depend on <tt>httpd</tt>, all those web applications which
8622 <tt>do</tt> contain CGI scripts, should depend on
8630 <sect id="mail-transport-agents">
8631 <heading>Mail transport, delivery and user agents</heading>
8634 Debian packages which process electronic mail, whether mail
8635 user agents (MUAs) or mail transport agents (MTAs), must
8636 ensure that they are compatible with the configuration
8637 decisions below. Failure to do this may result in lost
8638 mail, broken <tt>From:</tt> lines, and other serious brain
8643 The mail spool is <file>/var/mail</file> and the interface to
8644 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8645 the FHS). On older systems, the mail spool may be
8646 physically located in <file>/var/spool/mail</file>, but all
8647 access to the mail spool should be via the
8648 <file>/var/mail</file> symlink. The mail spool is part of the
8649 base system and not part of the MTA package.
8653 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8654 programs (such as IMAP daemons) must lock the mailbox in an
8655 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8656 be combined with dot locking. To avoid deadlocks, a program
8657 should use <tt>fcntl()</tt> first and dot locking after
8658 this, or alternatively implement the two locking methods in
8659 a non blocking way<footnote>
8660 If it is not possible to establish both locks, the
8661 system shouldn't wait for the second lock to be
8662 established, but remove the first lock, wait a (random)
8663 time, and start over locking again.
8664 </footnote>. Using the functions <tt>maillock</tt> and
8665 <tt>mailunlock</tt> provided by the
8666 <tt>liblockfile*</tt><footnote>
8667 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8668 to use these functions.
8669 </footnote> packages is the recommended way to realize this.
8673 Mailboxes are generally either mode 600 and owned by
8674 <var>user</var> or mode 660 and owned by
8675 <tt><var>user</var>:mail</tt><footnote>
8676 There are two traditional permission schemes for mail spools:
8677 mode 600 with all mail delivery done by processes running as
8678 the destination user, or mode 660 and owned by group mail with
8679 mail delivery done by a process running as a system user in
8680 group mail. Historically, Debian required mode 660 mail
8681 spools to enable the latter model, but that model has become
8682 increasingly uncommon and the principle of least privilege
8683 indicates that mail systems that use the first model should
8684 use permissions of 600. If delivery to programs is permitted,
8685 it's easier to keep the mail system secure if the delivery
8686 agent runs as the destination user. Debian Policy therefore
8687 permits either scheme.
8688 </footnote>. The local system administrator may choose a
8689 different permission scheme; packages should not make
8690 assumptions about the permission and ownership of mailboxes
8691 unless required (such as when creating a new mailbox). A MUA
8692 may remove a mailbox (unless it has nonstandard permissions) in
8693 which case the MTA or another MUA must recreate it if needed.
8697 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8698 be setgid mail to do the locking mentioned above (and
8699 must obviously avoid accessing other users' mailboxes
8700 using this privilege).</p>
8703 <file>/etc/aliases</file> is the source file for the system mail
8704 aliases (e.g., postmaster, usenet, etc.), it is the one
8705 which the sysadmin and <prgn>postinst</prgn> scripts may
8706 edit. After <file>/etc/aliases</file> is edited the program or
8707 human editing it must call <prgn>newaliases</prgn>. All MTA
8708 packages must come with a <prgn>newaliases</prgn> program,
8709 even if it does nothing, but older MTA packages did not do
8710 this so programs should not fail if <prgn>newaliases</prgn>
8711 cannot be found. Note that because of this, all MTA
8712 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8713 <tt>Replaces: mail-transport-agent</tt> control fields.
8717 The convention of writing <tt>forward to
8718 <var>address</var></tt> in the mailbox itself is not
8719 supported. Use a <tt>.forward</tt> file instead.</p>
8722 The <prgn>rmail</prgn> program used by UUCP
8723 for incoming mail should be <file>/usr/sbin/rmail</file>.
8724 Likewise, <prgn>rsmtp</prgn>, for receiving
8725 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8729 If your package needs to know what hostname to use on (for
8730 example) outgoing news and mail messages which are generated
8731 locally, you should use the file <file>/etc/mailname</file>. It
8732 will contain the portion after the username and <tt>@</tt>
8733 (at) sign for email addresses of users on the machine
8734 (followed by a newline).
8738 Such a package should check for the existence of this file
8739 when it is being configured. If it exists, it should be
8740 used without comment, although an MTA's configuration script
8741 may wish to prompt the user even if it finds that this file
8742 exists. If the file does not exist, the package should
8743 prompt the user for the value (preferably using
8744 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8745 as well as using it in the package's configuration. The
8746 prompt should make it clear that the name will not just be
8747 used by that package. For example, in this situation the
8748 <tt>inn</tt> package could say something like:
8749 <example compact="compact">
8750 Please enter the "mail name" of your system. This is the
8751 hostname portion of the address to be shown on outgoing
8752 news and mail messages. The default is
8753 <var>syshostname</var>, your system's host name. Mail
8754 name ["<var>syshostname</var>"]:
8756 where <var>syshostname</var> is the output of <tt>hostname
8762 <heading>News system configuration</heading>
8765 All the configuration files related to the NNTP (news)
8766 servers and clients should be located under
8767 <file>/etc/news</file>.</p>
8770 There are some configuration issues that apply to a number
8771 of news clients and server packages on the machine. These
8775 <tag><file>/etc/news/organization</file></tag>
8777 A string which should appear as the
8778 organization header for all messages posted
8779 by NNTP clients on the machine
8782 <tag><file>/etc/news/server</file></tag>
8784 Contains the FQDN of the upstream NNTP
8785 server, or localhost if the local machine is
8790 Other global files may be added as required for cross-package news
8797 <heading>Programs for the X Window System</heading>
8800 <heading>Providing X support and package priorities</heading>
8803 Programs that can be configured with support for the X
8804 Window System must be configured to do so and must declare
8805 any package dependencies necessary to satisfy their
8806 runtime requirements when using the X Window System. If
8807 such a package is of higher priority than the X packages
8808 on which it depends, it is required that either the
8809 X-specific components be split into a separate package, or
8810 that an alternative version of the package, which includes
8811 X support, be provided, or that the package's priority be
8817 <heading>Packages providing an X server</heading>
8820 Packages that provide an X server that, directly or
8821 indirectly, communicates with real input and display
8822 hardware should declare in their <tt>Provides</tt> control
8823 field that they provide the virtual
8824 package <tt>xserver</tt>.<footnote>
8825 This implements current practice, and provides an
8826 actual policy for usage of the <tt>xserver</tt>
8827 virtual package which appears in the virtual packages
8828 list. In a nutshell, X servers that interface
8829 directly with the display and input hardware or via
8830 another subsystem (e.g., GGI) should provide
8831 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8832 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8838 <heading>Packages providing a terminal emulator</heading>
8841 Packages that provide a terminal emulator for the X Window
8842 System which meet the criteria listed below should declare in
8843 their <tt>Provides</tt> control field that they provide the
8844 virtual package <tt>x-terminal-emulator</tt>. They should
8845 also register themselves as an alternative for
8846 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8847 20. That alternative should have a slave alternative
8848 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8849 pointing to the corresponding manual page.
8853 To be an <tt>x-terminal-emulator</tt>, a program must:
8854 <list compact="compact">
8856 Be able to emulate a DEC VT100 terminal, or a
8857 compatible terminal.
8861 Support the command-line option <tt>-e
8862 <var>command</var></tt>, which creates a new
8863 terminal window<footnote>
8864 "New terminal window" does not necessarily mean
8865 a new top-level X window directly parented by
8866 the window manager; it could, if the terminal
8867 emulator application were so coded, be a new
8868 "view" in a multiple-document interface (MDI).
8870 and runs the specified <var>command</var>,
8871 interpreting the entirety of the rest of the command
8872 line as a command to pass straight to exec, in the
8873 manner that <tt>xterm</tt> does.
8877 Support the command-line option <tt>-T
8878 <var>title</var></tt>, which creates a new terminal
8879 window with the window title <var>title</var>.
8886 <heading>Packages providing a window manager</heading>
8889 Packages that provide a window manager should declare in
8890 their <tt>Provides</tt> control field that they provide the
8891 virtual package <tt>x-window-manager</tt>. They should also
8892 register themselves as an alternative for
8893 <file>/usr/bin/x-window-manager</file>, with a priority
8894 calculated as follows:
8895 <list compact="compact">
8897 Start with a priority of 20.
8901 If the window manager supports the Debian menu
8902 system, add 20 points if this support is available
8903 in the package's default configuration (i.e., no
8904 configuration files belonging to the system or user
8905 have to be edited to activate the feature); if
8906 configuration files must be modified, add only 10
8912 If the window manager complies with <url
8913 id="http://www.freedesktop.org/Standards/wm-spec"
8914 name="The Window Manager Specification Project">,
8915 written by the <url id="http://www.freedesktop.org/"
8916 name="Free Desktop Group">, add 40 points.
8920 If the window manager permits the X session to be
8921 restarted using a <em>different</em> window manager
8922 (without killing the X server) in its default
8923 configuration, add 10 points; otherwise add none.
8926 That alternative should have a slave alternative
8927 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8928 pointing to the corresponding manual page.
8933 <heading>Packages providing fonts</heading>
8936 Packages that provide fonts for the X Window
8938 For the purposes of Debian Policy, a "font for the X
8939 Window System" is one which is accessed via X protocol
8940 requests. Fonts for the Linux console, for PostScript
8941 renderer, or any other purpose, do not fit this
8942 definition. Any tool which makes such fonts available
8943 to the X Window System, however, must abide by this
8946 must do a number of things to ensure that they are both
8947 available without modification of the X or font server
8948 configuration, and that they do not corrupt files used by
8949 other font packages to register information about
8953 Fonts of any type supported by the X Window System
8954 must be in a separate binary package from any
8955 executables, libraries, or documentation (except
8956 that specific to the fonts shipped, such as their
8957 license information). If one or more of the fonts
8958 so packaged are necessary for proper operation of
8959 the package with which they are associated the font
8960 package may be Recommended; if the fonts merely
8961 provide an enhancement, a Suggests relationship may
8962 be used. Packages must not Depend on font
8964 This is because the X server may retrieve fonts
8965 from the local file system or over the network
8966 from an X font server; the Debian package system
8967 is empowered to deal only with the local
8973 BDF fonts must be converted to PCF fonts with the
8974 <prgn>bdftopcf</prgn> utility (available in the
8975 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8976 placed in a directory that corresponds to their
8978 <list compact="compact">
8980 100 dpi fonts must be placed in
8981 <file>/usr/share/fonts/X11/100dpi/</file>.
8985 75 dpi fonts must be placed in
8986 <file>/usr/share/fonts/X11/75dpi/</file>.
8990 Character-cell fonts, cursor fonts, and other
8991 low-resolution fonts must be placed in
8992 <file>/usr/share/fonts/X11/misc/</file>.
8998 Type 1 fonts must be placed in
8999 <file>/usr/share/fonts/X11/Type1/</file>. If font
9000 metric files are available, they must be placed here
9005 Subdirectories of <file>/usr/share/fonts/X11/</file>
9006 other than those listed above must be neither
9007 created nor used. (The <file>PEX</file>, <file>CID</file>,
9008 <file>Speedo</file>, and <file>cyrillic</file> directories
9009 are excepted for historical reasons, but installation of
9010 files into these directories remains discouraged.)
9014 Font packages may, instead of placing files directly
9015 in the X font directories listed above, provide
9016 symbolic links in that font directory pointing to
9017 the files' actual location in the filesystem. Such
9018 a location must comply with the FHS.
9022 Font packages should not contain both 75dpi and
9023 100dpi versions of a font. If both are available,
9024 they should be provided in separate binary packages
9025 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9026 the names of the packages containing the
9027 corresponding fonts.
9031 Fonts destined for the <file>misc</file> subdirectory
9032 should not be included in the same package as 75dpi
9033 or 100dpi fonts; instead, they should be provided in
9034 a separate package with <tt>-misc</tt> appended to
9039 Font packages must not provide the files
9040 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9041 <file>fonts.scale</file> in a font directory:
9044 <file>fonts.dir</file> files must not be provided at all.
9048 <file>fonts.alias</file> and <file>fonts.scale</file>
9049 files, if needed, should be provided in the
9051 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9052 where <var>fontdir</var> is the name of the
9054 <file>/usr/share/fonts/X11/</file> where the
9055 package's corresponding fonts are stored
9056 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9057 <var>package</var> is the name of the package
9058 that provides these fonts, and
9059 <var>extension</var> is either <tt>scale</tt>
9060 or <tt>alias</tt>, whichever corresponds to
9067 Font packages must declare a dependency on
9068 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9069 or <tt>Pre-Depends</tt> control field.
9073 Font packages that provide one or more
9074 <file>fonts.scale</file> files as described above must
9075 invoke <prgn>update-fonts-scale</prgn> on each
9076 directory into which they installed fonts
9077 <em>before</em> invoking
9078 <prgn>update-fonts-dir</prgn> on that directory.
9079 This invocation must occur in both the
9080 <prgn>postinst</prgn> (for all arguments) and
9081 <prgn>postrm</prgn> (for all arguments except
9082 <tt>upgrade</tt>) scripts.
9086 Font packages that provide one or more
9087 <file>fonts.alias</file> files as described above must
9088 invoke <prgn>update-fonts-alias</prgn> on each
9089 directory into which they installed fonts. This
9090 invocation must occur in both the
9091 <prgn>postinst</prgn> (for all arguments) and
9092 <prgn>postrm</prgn> (for all arguments except
9093 <tt>upgrade</tt>) scripts.
9097 Font packages must invoke
9098 <prgn>update-fonts-dir</prgn> on each directory into
9099 which they installed fonts. This invocation must
9100 occur in both the <prgn>postinst</prgn> (for all
9101 arguments) and <prgn>postrm</prgn> (for all
9102 arguments except <tt>upgrade</tt>) scripts.
9106 Font packages must not provide alias names for the
9107 fonts they include which collide with alias names
9108 already in use by fonts already packaged.
9112 Font packages must not provide fonts with the same
9113 XLFD registry name as another font already packaged.
9119 <sect1 id="appdefaults">
9120 <heading>Application defaults files</heading>
9123 Application defaults files must be installed in the
9124 directory <file>/etc/X11/app-defaults/</file> (use of a
9125 localized subdirectory of <file>/etc/X11/</file> as described
9126 in the <em>X Toolkit Intrinsics - C Language
9127 Interface</em> manual is also permitted). They must be
9128 registered as <tt>conffile</tt>s or handled as
9129 configuration files.
9133 Customization of programs' X resources may also be
9134 supported with the provision of a file with the same name
9135 as that of the package placed in
9136 the <file>/etc/X11/Xresources/</file> directory, which
9137 must be registered as a <tt>conffile</tt> or handled as a
9138 configuration file.<footnote>
9139 Note that this mechanism is not the same as using
9140 app-defaults; app-defaults are tied to the client
9141 binary on the local file system, whereas X resources
9142 are stored in the X server and affect all connecting
9149 <heading>Installation directory issues</heading>
9152 Historically, packages using the X Window System used a
9153 separate set of installation directories from other packages.
9154 This practice has been discontinued and packages using the X
9155 Window System should now generally be installed in the same
9156 directories as any other package. Specifically, packages must
9157 not install files under the <file>/usr/X11R6/</file> directory
9158 and the <file>/usr/X11R6/</file> directory hierarchy should be
9159 regarded as obsolete.
9163 Include files previously installed under
9164 <file>/usr/X11R6/include/X11/</file> should be installed into
9165 <file>/usr/include/X11/</file>. For files previously
9166 installed into subdirectories of
9167 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9168 determine if subdirectories of <file>/usr/lib/</file> and
9169 <file>/usr/share/</file> can be used. If not, a subdirectory
9170 of <file>/usr/lib/X11/</file> should be used.
9174 Configuration files for window, display, or session managers
9175 or other applications that are tightly integrated with the X
9176 Window System may be placed in a subdirectory
9177 of <file>/etc/X11/</file> corresponding to the package name.
9178 Other X Window System applications should use
9179 the <file>/etc/</file> directory unless otherwise mandated by
9180 policy (such as for <ref id="appdefaults">).
9185 <heading>The OSF/Motif and OpenMotif libraries</heading>
9188 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9189 OpenMotif libraries</em><footnote>
9190 OSF/Motif and OpenMotif are collectively referred to as
9191 "Motif" in this policy document.
9193 should be compiled against and tested with LessTif (a free
9194 re-implementation of Motif) instead. If the maintainer
9195 judges that the program or programs do not work
9196 sufficiently well with LessTif to be distributed and
9197 supported, but do so when compiled against Motif, then two
9198 versions of the package should be created; one linked
9199 statically against Motif and with <tt>-smotif</tt>
9200 appended to the package name, and one linked dynamically
9201 against Motif and with <tt>-dmotif</tt> appended to the
9206 Both Motif-linked versions are dependent
9207 upon non-DFSG-compliant software and thus cannot be
9208 uploaded to the <em>main</em> distribution; if the
9209 software is itself DFSG-compliant it may be uploaded to
9210 the <em>contrib</em> distribution. While known existing
9211 versions of Motif permit unlimited redistribution of
9212 binaries linked against the library (whether statically or
9213 dynamically), it is the package maintainer's
9214 responsibility to determine whether this is permitted by
9215 the license of the copy of Motif in their possession.
9221 <heading>Perl programs and modules</heading>
9224 Perl programs and modules should follow the current Perl policy.
9228 The Perl policy can be found in the <tt>perl-policy</tt>
9229 files in the <tt>debian-policy</tt> package.
9230 It is also available from the Debian web mirrors at
9231 <tt><url name="/doc/packaging-manuals/perl-policy/"
9232 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9237 <heading>Emacs lisp programs</heading>
9240 Please refer to the "Debian Emacs Policy" for details of how to
9241 package emacs lisp programs.
9245 The Emacs policy is available in
9246 <file>debian-emacs-policy.gz</file> of the
9247 <package>emacsen-common</package> package.
9248 It is also available from the Debian web mirrors at
9249 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9250 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9255 <heading>Games</heading>
9258 The permissions on <file>/var/games</file> are mode 755, owner
9259 <tt>root</tt> and group <tt>root</tt>.
9263 Each game decides on its own security policy.</p>
9266 Games which require protected, privileged access to
9267 high-score files, saved games, etc., may be made
9268 set-<em>group</em>-id (mode 2755) and owned by
9269 <tt>root:games</tt>, and use files and directories with
9270 appropriate permissions (770 <tt>root:games</tt>, for
9271 example). They must not be made
9272 set-<em>user</em>-id, as this causes security problems. (If
9273 an attacker can subvert any set-user-id game they can
9274 overwrite the executable of any other, causing other players
9275 of these games to run a Trojan horse program. With a
9276 set-group-id game the attacker only gets access to less
9277 important game data, and if they can get at the other
9278 players' accounts at all it will take considerably more
9282 Some packages, for example some fortune cookie programs, are
9283 configured by the upstream authors to install with their
9284 data files or other static information made unreadable so
9285 that they can only be accessed through set-id programs
9286 provided. You should not do this in a Debian package: anyone can
9287 download the <file>.deb</file> file and read the data from it,
9288 so there is no point making the files unreadable. Not
9289 making the files unreadable also means that you don't have
9290 to make so many programs set-id, which reduces the risk of a
9294 As described in the FHS, binaries of games should be
9295 installed in the directory <file>/usr/games</file>. This also
9296 applies to games that use the X Window System. Manual pages
9297 for games (X and non-X games) should be installed in
9298 <file>/usr/share/man/man6</file>.</p>
9304 <heading>Documentation</heading>
9307 <heading>Manual pages</heading>
9310 You should install manual pages in <prgn>nroff</prgn> source
9311 form, in appropriate places under <file>/usr/share/man</file>.
9312 You should only use sections 1 to 9 (see the FHS for more
9313 details). You must not install a pre-formatted "cat page".
9317 Each program, utility, and function should have an
9318 associated manual page included in the same package. It is
9319 suggested that all configuration files also have a manual
9320 page included as well. Manual pages for protocols and other
9321 auxiliary things are optional.
9325 If no manual page is available, this is considered as a bug
9326 and should be reported to the Debian Bug Tracking System (the
9327 maintainer of the package is allowed to write this bug report
9328 themselves, if they so desire). Do not close the bug report
9329 until a proper man page is available.<footnote>
9330 It is not very hard to write a man page. See the
9331 <url id="http://www.schweikhardt.net/man_page_howto.html"
9332 name="Man-Page-HOWTO">,
9333 <manref name="man" section="7">, the examples
9334 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9335 the helper program <prgn>help2man</prgn>, or the
9336 directory <file>/usr/share/doc/man-db/examples</file>.
9341 You may forward a complaint about a missing man page to the
9342 upstream authors, and mark the bug as forwarded in the
9343 Debian bug tracking system. Even though the GNU Project do
9344 not in general consider the lack of a man page to be a bug,
9345 we do; if they tell you that they don't consider it a bug
9346 you should leave the bug in our bug tracking system open
9351 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9355 If one man page needs to be accessible via several names it
9356 is better to use a symbolic link than the <file>.so</file>
9357 feature, but there is no need to fiddle with the relevant
9358 parts of the upstream source to change from <file>.so</file> to
9359 symlinks: don't do it unless it's easy. You should not
9360 create hard links in the manual page directories, nor put
9361 absolute filenames in <file>.so</file> directives. The filename
9362 in a <file>.so</file> in a man page should be relative to the
9363 base of the man page tree (usually
9364 <file>/usr/share/man</file>). If you do not create any links
9365 (whether symlinks, hard links, or <tt>.so</tt> directives)
9366 in the file system to the alternate names of the man page,
9367 then you should not rely on <prgn>man</prgn> finding your
9368 man page under those names based solely on the information in
9369 the man page's header.<footnote>
9370 Supporting this in <prgn>man</prgn> often requires
9371 unreasonable processing time to find a manual page or to
9372 report that none exists, and moves knowledge into man's
9373 database that would be better left in the file system.
9374 This support is therefore deprecated and will cease to
9375 be present in the future.
9380 Manual pages in locale-specific subdirectories of
9381 <file>/usr/share/man</file> should use either UTF-8 or the usual
9382 legacy encoding for that language (normally the one corresponding
9383 to the shortest relevant locale name in
9384 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9385 <file>/usr/share/man/fr</file> should use either UTF-8 or
9386 ISO-8859-1.<footnote>
9387 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9388 use. In future, all manual pages will be required to use
9394 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9395 included in the subdirectory name unless it indicates a
9396 significant difference in the language, as this excludes
9397 speakers of the language in other countries.<footnote>
9398 At the time of writing, Chinese and Portuguese are the main
9399 languages with such differences, so <file>pt_BR</file>,
9400 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9405 If a localized version of a manual page is provided, it should
9406 either be up-to-date or it should be obvious to the reader that
9407 it is outdated and the original manual page should be used
9408 instead. This can be done either by a note at the beginning of
9409 the manual page or by showing the missing or changed portions in
9410 the original language instead of the target language.
9415 <heading>Info documents</heading>
9418 Info documents should be installed in <file>/usr/share/info</file>.
9419 They should be compressed with <tt>gzip -9</tt>.
9423 The <prgn>install-info</prgn> program maintains a directory of
9424 installed info documents in <file>/usr/share/info/dir</file> for
9425 the use of info readers.<footnote>
9426 It was previously necessary for packages installing info
9427 documents to run <prgn>install-info</prgn> from maintainer
9428 scripts. This is no longer necessary. The installation
9429 system now uses dpkg triggers.
9431 This file must not be included in packages. Packages containing
9432 info documents should depend on <tt>dpkg (>= 1.15.4) |
9433 install-info</tt> to ensure that the directory file is properly
9434 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9439 Info documents should contain section and directory entry
9440 information in the document for the use
9441 of <prgn>install-info</prgn>. The section should be specified
9442 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9443 space and the section of this info page. The directory entry or
9444 entries should be included between
9445 a <tt>START-INFO-DIR-ENTRY</tt> line and
9446 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9448 INFO-DIR-SECTION Individual utilities
9449 START-INFO-DIR-ENTRY
9450 * example: (example). An example info directory entry.
9453 To determine which section to use, you should look
9454 at <file>/usr/share/info/dir</file> on your system and choose
9455 the most relevant (or create a new section if none of the
9456 current sections are relevant).<footnote>
9457 Normally, info documents are generated from Texinfo source.
9458 To include this information in the generated info document, if
9459 it is absent, add commands like:
9461 @dircategory Individual utilities
9463 * example: (example). An example info directory entry.
9466 to the Texinfo source of the document and ensure that the info
9467 documents are rebuilt from source during the package build.
9473 <heading>Additional documentation</heading>
9476 Any additional documentation that comes with the package may
9477 be installed at the discretion of the package maintainer.
9478 Plain text documentation should be installed in the directory
9479 <file>/usr/share/doc/<var>package</var></file>, where
9480 <var>package</var> is the name of the package, and
9481 compressed with <tt>gzip -9</tt> unless it is small.
9485 If a package comes with large amounts of documentation which
9486 many users of the package will not require you should create
9487 a separate binary package to contain it, so that it does not
9488 take up disk space on the machines of users who do not need
9489 or want it installed.</p>
9492 It is often a good idea to put text information files
9493 (<file>README</file>s, changelogs, and so forth) that come with
9494 the source package in <file>/usr/share/doc/<var>package</var></file>
9495 in the binary package. However, you don't need to install
9496 the instructions for building and installing the package, of
9500 Packages must not require the existence of any files in
9501 <file>/usr/share/doc/</file> in order to function
9503 The system administrator should be able to
9504 delete files in <file>/usr/share/doc/</file> without causing
9505 any programs to break.
9507 Any files that are referenced by programs but are also
9508 useful as stand alone documentation should be installed under
9509 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9510 <file>/usr/share/doc/<var>package</var></file>.
9514 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9515 link to another directory in <file>/usr/share/doc</file> only if
9516 the two packages both come from the same source and the
9517 first package Depends on the second.<footnote>
9519 Please note that this does not override the section on
9520 changelog files below, so the file
9521 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9522 must refer to the changelog for the current version of
9523 <var>package</var> in question. In practice, this means
9524 that the sources of the target and the destination of the
9525 symlink must be the same (same source package and
9532 Former Debian releases placed all additional documentation
9533 in <file>/usr/doc/<var>package</var></file>. This has been
9534 changed to <file>/usr/share/doc/<var>package</var></file>,
9535 and packages must not put documentation in the directory
9536 <file>/usr/doc/<var>package</var></file>. <footnote>
9537 At this phase of the transition, we no longer require a
9538 symbolic link in <file>/usr/doc/</file>. At a later point,
9539 policy shall change to make the symbolic links a bug.
9545 <heading>Preferred documentation formats</heading>
9548 The unification of Debian documentation is being carried out
9552 If your package comes with extensive documentation in a
9553 markup format that can be converted to various other formats
9554 you should if possible ship HTML versions in a binary
9555 package, in the directory
9556 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9557 its subdirectories.<footnote>
9558 The rationale: The important thing here is that HTML
9559 docs should be available in <em>some</em> package, not
9560 necessarily in the main binary package.
9565 Other formats such as PostScript may be provided at the
9566 package maintainer's discretion.
9570 <sect id="copyrightfile">
9571 <heading>Copyright information</heading>
9574 Every package must be accompanied by a verbatim copy of its
9575 copyright information and distribution license in the file
9576 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9577 file must neither be compressed nor be a symbolic link.
9581 In addition, the copyright file must say where the upstream
9582 sources (if any) were obtained. It should name the original
9583 authors of the package and the Debian maintainer(s) who were
9584 involved with its creation.
9588 Packages in the <em>contrib</em> or <em>non-free</em> archive
9589 areas should state in the copyright file that the package is not
9590 part of the Debian distribution and briefly explain why.
9594 A copy of the file which will be installed in
9595 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9596 be in <file>debian/copyright</file> in the source package.
9600 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9601 link to another directory in <file>/usr/share/doc</file> only if
9602 the two packages both come from the same source and the
9603 first package Depends on the second. These rules are
9604 important because copyrights must be extractable by
9609 Packages distributed under the Apache license (version 2.0), the
9610 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9611 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9612 1.3) should refer to the corresponding files
9613 under <file>/usr/share/common-licenses</file>,<footnote>
9616 <file>/usr/share/common-licenses/Apache-2.0</file>,
9617 <file>/usr/share/common-licenses/Artistic</file>,
9618 <file>/usr/share/common-licenses/GPL-1</file>,
9619 <file>/usr/share/common-licenses/GPL-2</file>,
9620 <file>/usr/share/common-licenses/GPL-3</file>,
9621 <file>/usr/share/common-licenses/LGPL-2</file>,
9622 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9623 <file>/usr/share/common-licenses/LGPL-3</file>,
9624 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9625 <file>/usr/share/common-licenses/GFDL-1.3</file>
9626 respectively. The University of California BSD license is
9627 also included in <package>base-files</package> as
9628 <file>/usr/share/common-licenses/BSD</file>, but given the
9629 brevity of this license, its specificity to code whose
9630 copyright is held by the Regents of the University of
9631 California, and the frequency of minor wording changes, its
9632 text should be included in the copyright file rather than
9633 referencing this file.
9635 </footnote> rather than quoting them in the copyright
9640 You should not use the copyright file as a general <file>README</file>
9641 file. If your package has such a file it should be
9642 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9643 <file>README.Debian</file> or some other appropriate place.</p>
9647 <heading>Examples</heading>
9650 Any examples (configurations, source files, whatever),
9651 should be installed in a directory
9652 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9653 files should not be referenced by any program: they're there
9654 for the benefit of the system administrator and users as
9655 documentation only. Architecture-specific example files
9656 should be installed in a directory
9657 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9659 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9660 latter directory itself may be a symbolic link to the
9665 If the purpose of a package is to provide examples, then the
9666 example files may be installed into
9667 <file>/usr/share/doc/<var>package</var></file>.
9671 <sect id="changelogs">
9672 <heading>Changelog files</heading>
9675 Packages that are not Debian-native must contain a
9676 compressed copy of the <file>debian/changelog</file> file from
9677 the Debian source tree in
9678 <file>/usr/share/doc/<var>package</var></file> with the name
9679 <file>changelog.Debian.gz</file>.
9683 If an upstream changelog is available, it should be accessible as
9684 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9685 plain text. If the upstream changelog is distributed in
9686 HTML, it should be made available in that form as
9687 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9688 and a plain text <file>changelog.gz</file> should be generated
9689 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9690 the upstream changelog files do not already conform to this
9691 naming convention, then this may be achieved either by
9692 renaming the files, or by adding a symbolic link, at the
9693 maintainer's discretion.<footnote>
9694 Rationale: People should not have to look in places for
9695 upstream changelogs merely because they are given
9696 different names or are distributed in HTML format.
9701 All of these files should be installed compressed using
9702 <tt>gzip -9</tt>, as they will become large with time even
9703 if they start out small.
9707 If the package has only one changelog which is used both as
9708 the Debian changelog and the upstream one because there is
9709 no separate upstream maintainer then that changelog should
9710 usually be installed as
9711 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9712 there is a separate upstream maintainer, but no upstream
9713 changelog, then the Debian changelog should still be called
9714 <file>changelog.Debian.gz</file>.
9718 For details about the format and contents of the Debian
9719 changelog file, please see <ref id="dpkgchangelog">.
9724 <appendix id="pkg-scope">
9725 <heading>Introduction and scope of these appendices</heading>
9728 These appendices are taken essentially verbatim from the
9729 now-deprecated Packaging Manual, version 3.2.1.0. They are
9730 the chapters which are likely to be of use to package
9731 maintainers and which have not already been included in the
9732 policy document itself. Most of these sections are very likely
9733 not relevant to policy; they should be treated as
9734 documentation for the packaging system. Please note that these
9735 appendices are included for convenience, and for historical
9736 reasons: they used to be part of policy package, and they have
9737 not yet been incorporated into dpkg documentation. However,
9738 they still have value, and hence they are presented here.
9742 They have not yet been checked to ensure that they are
9743 compatible with the contents of policy, and if there are any
9744 contradictions, the version in the main policy document takes
9745 precedence. The remaining chapters of the old Packaging
9746 Manual have also not been read in detail to ensure that there
9747 are not parts which have been left out. Both of these will be
9752 Certain parts of the Packaging manual were integrated into the
9753 Policy Manual proper, and removed from the appendices. Links
9754 have been placed from the old locations to the new ones.
9758 <prgn>dpkg</prgn> is a suite of programs for creating binary
9759 package files and installing and removing them on Unix
9761 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
9762 work on or be ported to other systems.
9767 The binary packages are designed for the management of
9768 installed executable programs (usually compiled binaries) and
9769 their associated data, though source code examples and
9770 documentation are provided as part of some packages.</p>
9773 This manual describes the technical aspects of creating Debian
9774 binary packages (<file>.deb</file> files). It documents the
9775 behavior of the package management programs
9776 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9777 they interact with packages.</p>
9780 It also documents the interaction between
9781 <prgn>dselect</prgn>'s core and the access method scripts it
9782 uses to actually install the selected packages, and describes
9783 how to create a new access method.</p>
9786 This manual does not go into detail about the options and
9787 usage of the package building and installation tools. It
9788 should therefore be read in conjunction with those programs'
9793 The utility programs which are provided with <prgn>dpkg</prgn>
9794 for managing various system configuration and similar issues,
9795 such as <prgn>update-rc.d</prgn> and
9796 <prgn>install-info</prgn>, are not described in detail here -
9797 please see their man pages.
9801 It is assumed that the reader is reasonably familiar with the
9802 <prgn>dpkg</prgn> System Administrators' manual.
9803 Unfortunately this manual does not yet exist.
9807 The Debian version of the FSF's GNU hello program is provided
9808 as an example for people wishing to create Debian
9809 packages. The Debian <prgn>debmake</prgn> package is
9810 recommended as a very helpful tool in creating and maintaining
9811 Debian packages. However, while the tools and examples are
9812 helpful, they do not replace the need to read and follow the
9813 Policy and Programmer's Manual.</p>
9816 <appendix id="pkg-binarypkg">
9817 <heading>Binary packages (from old Packaging Manual)</heading>
9820 The binary package has two main sections. The first part
9821 consists of various control information files and scripts used
9822 by <prgn>dpkg</prgn> when installing and removing. See <ref
9823 id="pkg-controlarea">.
9827 The second part is an archive containing the files and
9828 directories to be installed.
9832 In the future binary packages may also contain other
9833 components, such as checksums and digital signatures. The
9834 format for the archive is described in full in the
9835 <file>deb(5)</file> man page.
9839 <sect id="pkg-bincreating"><heading>Creating package files -
9840 <prgn>dpkg-deb</prgn>
9844 All manipulation of binary package files is done by
9845 <prgn>dpkg-deb</prgn>; it's the only program that has
9846 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9847 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9848 will spot that the options requested are appropriate to
9849 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9854 In order to create a binary package you must make a
9855 directory tree which contains all the files and directories
9856 you want to have in the file system data part of the package.
9857 In Debian-format source packages this directory is usually
9858 <file>debian/tmp</file>, relative to the top of the package's
9863 They should have the locations (relative to the root of the
9864 directory tree you're constructing) ownerships and
9865 permissions which you want them to have on the system when
9870 With current versions of <prgn>dpkg</prgn> the uid/username
9871 and gid/groupname mappings for the users and groups being
9872 used should be the same on the system where the package is
9873 built and the one where it is installed.
9877 You need to add one special directory to the root of the
9878 miniature file system tree you're creating:
9879 <prgn>DEBIAN</prgn>. It should contain the control
9880 information files, notably the binary package control file
9881 (see <ref id="pkg-controlfile">).
9885 The <prgn>DEBIAN</prgn> directory will not appear in the
9886 file system archive of the package, and so won't be installed
9887 by <prgn>dpkg</prgn> when the package is installed.
9891 When you've prepared the package, you should invoke:
9893 dpkg --build <var>directory</var>
9898 This will build the package in
9899 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9900 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9901 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9906 See the man page <manref name="dpkg-deb" section="8"> for details of how
9907 to examine the contents of this newly-created file. You may find the
9908 output of following commands enlightening:
9910 dpkg-deb --info <var>filename</var>.deb
9911 dpkg-deb --contents <var>filename</var>.deb
9912 dpkg --contents <var>filename</var>.deb
9914 To view the copyright file for a package you could use this command:
9916 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9921 <sect id="pkg-controlarea">
9922 <heading>Package control information files</heading>
9925 The control information portion of a binary package is a
9926 collection of files with names known to <prgn>dpkg</prgn>.
9927 It will treat the contents of these files specially - some
9928 of them contain information used by <prgn>dpkg</prgn> when
9929 installing or removing the package; others are scripts which
9930 the package maintainer wants <prgn>dpkg</prgn> to run.
9934 It is possible to put other files in the package control
9935 information file area, but this is not generally a good idea
9936 (though they will largely be ignored).
9940 Here is a brief list of the control information files supported
9941 by <prgn>dpkg</prgn> and a summary of what they're used for.
9946 <tag><tt>control</tt>
9949 This is the key description file used by
9950 <prgn>dpkg</prgn>. It specifies the package's name
9951 and version, gives its description for the user,
9952 states its relationships with other packages, and so
9953 forth. See <ref id="sourcecontrolfiles"> and
9954 <ref id="binarycontrolfiles">.
9958 It is usually generated automatically from information
9959 in the source package by the
9960 <prgn>dpkg-gencontrol</prgn> program, and with
9961 assistance from <prgn>dpkg-shlibdeps</prgn>.
9962 See <ref id="pkg-sourcetools">.
9966 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9971 These are executable files (usually scripts) which
9972 <prgn>dpkg</prgn> runs during installation, upgrade
9973 and removal of packages. They allow the package to
9974 deal with matters which are particular to that package
9975 or require more complicated processing than that
9976 provided by <prgn>dpkg</prgn>. Details of when and
9977 how they are called are in <ref id="maintainerscripts">.
9981 It is very important to make these scripts idempotent.
9982 See <ref id="idempotency">.
9986 The maintainer scripts are not guaranteed to run with a
9987 controlling terminal and may not be able to interact with
9988 the user. See <ref id="controllingterminal">.
9992 <tag><tt>conffiles</tt>
9995 This file contains a list of configuration files which
9996 are to be handled automatically by <prgn>dpkg</prgn>
9997 (see <ref id="pkg-conffiles">). Note that not necessarily
9998 every configuration file should be listed here.
10001 <tag><tt>shlibs</tt>
10004 This file contains a list of the shared libraries
10005 supplied by the package, with dependency details for
10006 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10007 when it determines what dependencies are required in a
10008 package control file. The <tt>shlibs</tt> file format
10009 is described on <ref id="shlibs">.
10014 <sect id="pkg-controlfile">
10015 <heading>The main control information file: <tt>control</tt></heading>
10018 The most important control information file used by
10019 <prgn>dpkg</prgn> when it installs a package is
10020 <tt>control</tt>. It contains all the package's "vital
10025 The binary package control files of packages built from
10026 Debian sources are made by a special tool,
10027 <prgn>dpkg-gencontrol</prgn>, which reads
10028 <file>debian/control</file> and <file>debian/changelog</file> to
10029 find the information it needs. See <ref id="pkg-sourcepkg"> for
10034 The fields in binary package control files are listed in
10035 <ref id="binarycontrolfiles">.
10039 A description of the syntax of control files and the purpose
10040 of the fields is available in <ref id="controlfields">.
10045 <heading>Time Stamps</heading>
10048 See <ref id="timestamps">.
10053 <appendix id="pkg-sourcepkg">
10054 <heading>Source packages (from old Packaging Manual) </heading>
10057 The Debian binary packages in the distribution are generated
10058 from Debian sources, which are in a special format to assist
10059 the easy and automatic building of binaries.
10062 <sect id="pkg-sourcetools">
10063 <heading>Tools for processing source packages</heading>
10066 Various tools are provided for manipulating source packages;
10067 they pack and unpack sources and help build of binary
10068 packages and help manage the distribution of new versions.
10072 They are introduced and typical uses described here; see
10073 <manref name="dpkg-source" section="1"> for full
10074 documentation about their arguments and operation.
10078 For examples of how to construct a Debian source package,
10079 and how to use those utilities that are used by Debian
10080 source packages, please see the <prgn>hello</prgn> example
10084 <sect1 id="pkg-dpkg-source">
10086 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10091 This program is frequently used by hand, and is also
10092 called from package-independent automated building scripts
10093 such as <prgn>dpkg-buildpackage</prgn>.
10097 To unpack a package it is typically invoked with
10099 dpkg-source -x <var>.../path/to/filename</var>.dsc
10104 with the <file><var>filename</var>.tar.gz</file> and
10105 <file><var>filename</var>.diff.gz</file> (if applicable) in
10106 the same directory. It unpacks into
10107 <file><var>package</var>-<var>version</var></file>, and if
10109 <file><var>package</var>-<var>version</var>.orig</file>, in
10110 the current directory.
10114 To create a packed source archive it is typically invoked:
10116 dpkg-source -b <var>package</var>-<var>version</var>
10121 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10122 <file>.diff.gz</file> (if appropriate) in the current
10123 directory. <prgn>dpkg-source</prgn> does not clean the
10124 source tree first - this must be done separately if it is
10129 See also <ref id="pkg-sourcearchives">.</p>
10133 <sect1 id="pkg-dpkg-buildpackage">
10135 <prgn>dpkg-buildpackage</prgn> - overall package-building
10140 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10141 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10142 targets <tt>clean</tt>, <tt>build</tt> and
10143 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10144 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10145 source and binary package upload.
10149 It is usually invoked by hand from the top level of the
10150 built or unbuilt source directory. It may be invoked with
10151 no arguments; useful arguments include:
10152 <taglist compact="compact">
10153 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10156 Do not sign the <tt>.changes</tt> file or the
10157 source package <tt>.dsc</tt> file, respectively.</p>
10159 <tag><tt>-p<var>sign-command</var></tt></tag>
10162 Invoke <var>sign-command</var> instead of finding
10163 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10164 <var>sign-command</var> must behave just like
10165 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10167 <tag><tt>-r<var>root-command</var></tt></tag>
10170 When root privilege is required, invoke the command
10171 <var>root-command</var>. <var>root-command</var>
10172 should invoke its first argument as a command, from
10173 the <prgn>PATH</prgn> if necessary, and pass its
10174 second and subsequent arguments to the command it
10175 calls. If no <var>root-command</var> is supplied
10176 then <var>dpkg-buildpackage</var> will take no
10177 special action to gain root privilege, so that for
10178 most packages it will have to be invoked as root to
10181 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10184 Two types of binary-only build and upload - see
10185 <manref name="dpkg-source" section="1">.
10192 <sect1 id="pkg-dpkg-gencontrol">
10194 <prgn>dpkg-gencontrol</prgn> - generates binary package
10199 This program is usually called from <file>debian/rules</file>
10200 (see <ref id="pkg-sourcetree">) in the top level of the source
10205 This is usually done just before the files and directories in the
10206 temporary directory tree where the package is being built have their
10207 permissions and ownerships set and the package is constructed using
10208 <prgn>dpkg-deb/</prgn>
10210 This is so that the control file which is produced has
10211 the right permissions
10216 <prgn>dpkg-gencontrol</prgn> must be called after all the
10217 files which are to go into the package have been placed in
10218 the temporary build directory, so that its calculation of
10219 the installed size of a package is correct.
10223 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10224 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10225 variable substitutions created by
10226 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10231 For a package which generates only one binary package, and
10232 which builds it in <file>debian/tmp</file> relative to the top
10233 of the source package, it is usually sufficient to call
10234 <prgn>dpkg-gencontrol</prgn>.
10238 Sources which build several binaries will typically need
10241 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10242 </example> The <tt>-P</tt> tells
10243 <prgn>dpkg-gencontrol</prgn> that the package is being
10244 built in a non-default directory, and the <tt>-p</tt>
10245 tells it which package's control file should be generated.
10249 <prgn>dpkg-gencontrol</prgn> also adds information to the
10250 list of files in <file>debian/files</file>, for the benefit of
10251 (for example) a future invocation of
10252 <prgn>dpkg-genchanges</prgn>.</p>
10255 <sect1 id="pkg-dpkg-shlibdeps">
10257 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10262 This program is usually called from <file>debian/rules</file>
10263 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10264 id="pkg-sourcetree">), in the top level of the source tree.
10268 Its arguments are executables and shared libraries
10271 They may be specified either in the locations in the
10272 source tree where they are created or in the locations
10273 in the temporary build tree where they are installed
10274 prior to binary package creation.
10276 </footnote> for which shared library dependencies should
10277 be included in the binary package's control file.
10281 If some of the found shared libraries should only
10282 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10283 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10284 by using the <tt>-d<var>dependency-field</var></tt> option
10285 before those executable(s). (Each <tt>-d</tt> option
10286 takes effect until the next <tt>-d</tt>.)
10290 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10291 output control file to be modified. Instead by default it
10292 adds to the <file>debian/substvars</file> file variable
10293 settings like <tt>shlibs:Depends</tt>. These variable
10294 settings must be referenced in dependency fields in the
10295 appropriate per-binary-package sections of the source
10300 For example, a package that generates an essential part
10301 which requires dependencies, and optional parts that
10302 which only require a recommendation, would separate those
10303 two sets of dependencies into two different fields.<footnote>
10304 At the time of writing, an example for this was the
10305 <package/xmms/ package, with Depends used for the xmms
10306 executable, Recommends for the plug-ins and Suggests for
10307 even more optional features provided by unzip.
10309 It can say in its <file>debian/rules</file>:
10311 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10312 -dRecommends <var>optionalpart anotheroptionalpart</var>
10314 and then in its main control file <file>debian/control</file>:
10317 Depends: ${shlibs:Depends}
10318 Recommends: ${shlibs:Recommends}
10324 Sources which produce several binary packages with
10325 different shared library dependency requirements can use
10326 the <tt>-p<var>varnameprefix</var></tt> option to override
10327 the default <tt>shlibs:</tt> prefix (one invocation of
10328 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10329 They can thus produce several sets of dependency
10330 variables, each of the form
10331 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10332 which can be referred to in the appropriate parts of the
10333 binary package control files.
10338 <sect1 id="pkg-dpkg-distaddfile">
10340 <prgn>dpkg-distaddfile</prgn> - adds a file to
10341 <file>debian/files</file>
10345 Some packages' uploads need to include files other than
10346 the source and binary package files.
10350 <prgn>dpkg-distaddfile</prgn> adds a file to the
10351 <file>debian/files</file> file so that it will be included in
10352 the <file>.changes</file> file when
10353 <prgn>dpkg-genchanges</prgn> is run.
10357 It is usually invoked from the <tt>binary</tt> target of
10358 <file>debian/rules</file>:
10360 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10362 The <var>filename</var> is relative to the directory where
10363 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10364 is usually the directory above the top level of the source
10365 tree. The <file>debian/rules</file> target should put the
10366 file there just before or just after calling
10367 <prgn>dpkg-distaddfile</prgn>.
10371 The <var>section</var> and <var>priority</var> are passed
10372 unchanged into the resulting <file>.changes</file> file.
10377 <sect1 id="pkg-dpkg-genchanges">
10379 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10380 upload control file
10384 This program is usually called by package-independent
10385 automatic building scripts such as
10386 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10391 It is usually called in the top level of a built source
10392 tree, and when invoked with no arguments will print out a
10393 straightforward <file>.changes</file> file based on the
10394 information in the source package's changelog and control
10395 file and the binary and source packages which should have
10401 <sect1 id="pkg-dpkg-parsechangelog">
10403 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10404 representation of a changelog
10408 This program is used internally by
10409 <prgn>dpkg-source</prgn> et al. It may also occasionally
10410 be useful in <file>debian/rules</file> and elsewhere. It
10411 parses a changelog, <file>debian/changelog</file> by default,
10412 and prints a control-file format representation of the
10413 information in it to standard output.
10417 <sect1 id="pkg-dpkg-architecture">
10419 <prgn>dpkg-architecture</prgn> - information about the build and
10424 This program can be used manually, but is also invoked by
10425 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10426 environment or make variables which specify the build and host
10427 architecture for the package building process.
10432 <sect id="pkg-sourcetree">
10433 <heading>The Debian package source tree</heading>
10436 The source archive scheme described later is intended to
10437 allow a Debian package source tree with some associated
10438 control information to be reproduced and transported easily.
10439 The Debian package source tree is a version of the original
10440 program with certain files added for the benefit of the
10441 packaging process, and with any other changes required
10442 made to the rest of the source code and installation
10447 The extra files created for Debian are in the subdirectory
10448 <file>debian</file> of the top level of the Debian package
10449 source tree. They are described below.
10452 <sect1 id="pkg-debianrules">
10453 <heading><file>debian/rules</file> - the main building script</heading>
10456 See <ref id="debianrules">.
10460 <sect1 id="pkg-srcsubstvars">
10461 <heading><file>debian/substvars</file> and variable substitutions</heading>
10464 See <ref id="substvars">.
10470 <heading><file>debian/files</file></heading>
10473 See <ref id="debianfiles">.
10477 <sect1><heading><file>debian/tmp</file>
10481 This is the canonical temporary location for the
10482 construction of binary packages by the <tt>binary</tt>
10483 target. The directory <file>tmp</file> serves as the root of
10484 the file system tree as it is being constructed (for
10485 example, by using the package's upstream makefiles install
10486 targets and redirecting the output there), and it also
10487 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10488 id="pkg-bincreating">.
10492 If several binary packages are generated from the same
10493 source tree it is usual to use several
10494 <file>debian/tmp<var>something</var></file> directories, for
10495 example <file>tmp-a</file> or <file>tmp-doc</file>.
10499 Whatever <file>tmp</file> directories are created and used by
10500 <tt>binary</tt> must of course be removed by the
10501 <tt>clean</tt> target.</p></sect1>
10505 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10509 As it exists on the FTP site, a Debian source package
10510 consists of three related files. You must have the right
10511 versions of all three to be able to use them.
10516 <tag>Debian source control file - <tt>.dsc</tt></tag>
10518 This file is a control file used by <prgn>dpkg-source</prgn>
10519 to extract a source package.
10520 See <ref id="debiansourcecontrolfiles">.
10524 Original source archive -
10526 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10532 This is a compressed (with <tt>gzip -9</tt>)
10533 <prgn>tar</prgn> file containing the source code from
10534 the upstream authors of the program.
10539 Debian package diff -
10541 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10547 This is a unified context diff (<tt>diff -u</tt>)
10548 giving the changes which are required to turn the
10549 original source into the Debian source. These changes
10550 may only include editing and creating plain files.
10551 The permissions of files, the targets of symbolic
10552 links and the characteristics of special files or
10553 pipes may not be changed and no files may be removed
10558 All the directories in the diff must exist, except the
10559 <file>debian</file> subdirectory of the top of the source
10560 tree, which will be created by
10561 <prgn>dpkg-source</prgn> if necessary when unpacking.
10565 The <prgn>dpkg-source</prgn> program will
10566 automatically make the <file>debian/rules</file> file
10567 executable (see below).</p></item>
10572 If there is no original source code - for example, if the
10573 package is specially prepared for Debian or the Debian
10574 maintainer is the same as the upstream maintainer - the
10575 format is slightly different: then there is no diff, and the
10577 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10578 and preferably contains a directory named
10579 <file><var>package</var>-<var>version</var></file>.
10584 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10587 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10588 Debian source package. However, if it is not available it
10589 is possible to unpack a Debian source archive as follows:
10590 <enumlist compact="compact">
10593 Untar the tarfile, which will create a <file>.orig</file>
10597 <p>Rename the <file>.orig</file> directory to
10598 <file><var>package</var>-<var>version</var></file>.</p>
10602 Create the subdirectory <file>debian</file> at the top of
10603 the source tree.</p>
10605 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10607 <item><p>Untar the tarfile again if you want a copy of the original
10608 source code alongside the Debian version.</p>
10613 It is not possible to generate a valid Debian source archive
10614 without using <prgn>dpkg-source</prgn>. In particular,
10615 attempting to use <prgn>diff</prgn> directly to generate the
10616 <file>.diff.gz</file> file will not work.
10620 <heading>Restrictions on objects in source packages</heading>
10623 The source package may not contain any hard links
10625 This is not currently detected when building source
10626 packages, but only when extracting
10630 Hard links may be permitted at some point in the
10631 future, but would require a fair amount of
10633 </footnote>, device special files, sockets or setuid or
10636 Setgid directories are allowed.
10641 The source packaging tools manage the changes between the
10642 original and Debian source using <prgn>diff</prgn> and
10643 <prgn>patch</prgn>. Turning the original source tree as
10644 included in the <file>.orig.tar.gz</file> into the Debian
10645 package source must not involve any changes which cannot be
10646 handled by these tools. Problematic changes which cause
10647 <prgn>dpkg-source</prgn> to halt with an error when
10648 building the source package are:
10649 <list compact="compact">
10650 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10652 <item><p>Changing the targets of symbolic links.</p>
10654 <item><p>Creating directories, other than <file>debian</file>.</p>
10656 <item><p>Changes to the contents of binary files.</p></item>
10657 </list> Changes which cause <prgn>dpkg-source</prgn> to
10658 print a warning but continue anyway are:
10659 <list compact="compact">
10662 Removing files, directories or symlinks.
10664 Renaming a file is not treated specially - it is
10665 seen as the removal of the old file (which
10666 generates a warning, but is otherwise ignored),
10667 and the creation of the new one.
10673 Changed text files which are missing the usual final
10674 newline (either in the original or the modified
10679 Changes which are not represented, but which are not detected by
10680 <prgn>dpkg-source</prgn>, are:
10681 <list compact="compact">
10682 <item><p>Changing the permissions of files (other than
10683 <file>debian/rules</file>) and directories.</p></item>
10688 The <file>debian</file> directory and <file>debian/rules</file>
10689 are handled specially by <prgn>dpkg-source</prgn> - before
10690 applying the changes it will create the <file>debian</file>
10691 directory, and afterwards it will make
10692 <file>debian/rules</file> world-executable.
10698 <appendix id="pkg-controlfields">
10699 <heading>Control files and their fields (from old Packaging Manual)</heading>
10702 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10703 data in a common format, known as control files. Binary and
10704 source packages have control data as do the <file>.changes</file>
10705 files which control the installation of uploaded files, and
10706 <prgn>dpkg</prgn>'s internal databases are in a similar
10711 <heading>Syntax of control files</heading>
10714 See <ref id="controlsyntax">.
10718 It is important to note that there are several fields which
10719 are optional as far as <prgn>dpkg</prgn> and the related
10720 tools are concerned, but which must appear in every Debian
10721 package, or whose omission may cause problems.
10726 <heading>List of fields</heading>
10729 See <ref id="controlfieldslist">.
10733 This section now contains only the fields that didn't belong
10734 to the Policy manual.
10737 <sect1 id="pkg-f-Filename">
10738 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10741 These fields in <tt>Packages</tt> files give the
10742 filename(s) of (the parts of) a package in the
10743 distribution directories, relative to the root of the
10744 Debian hierarchy. If the package has been split into
10745 several parts the parts are all listed in order, separated
10750 <sect1 id="pkg-f-Size">
10751 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10754 These fields in <file>Packages</file> files give the size (in
10755 bytes, expressed in decimal) and MD5 checksum of the
10756 file(s) which make(s) up a binary package in the
10757 distribution. If the package is split into several parts
10758 the values for the parts are listed in order, separated by
10763 <sect1 id="pkg-f-Status">
10764 <heading><tt>Status</tt></heading>
10767 This field in <prgn>dpkg</prgn>'s status file records
10768 whether the user wants a package installed, removed or
10769 left alone, whether it is broken (requiring
10770 re-installation) or not and what its current state on the
10771 system is. Each of these pieces of information is a
10776 <sect1 id="pkg-f-Config-Version">
10777 <heading><tt>Config-Version</tt></heading>
10780 If a package is not installed or not configured, this
10781 field in <prgn>dpkg</prgn>'s status file records the last
10782 version of the package which was successfully
10787 <sect1 id="pkg-f-Conffiles">
10788 <heading><tt>Conffiles</tt></heading>
10791 This field in <prgn>dpkg</prgn>'s status file contains
10792 information about the automatically-managed configuration
10793 files held by a package. This field should <em>not</em>
10794 appear anywhere in a package!
10799 <heading>Obsolete fields</heading>
10802 These are still recognized by <prgn>dpkg</prgn> but should
10803 not appear anywhere any more.
10805 <taglist compact="compact">
10807 <tag><tt>Revision</tt></tag>
10808 <tag><tt>Package-Revision</tt></tag>
10809 <tag><tt>Package_Revision</tt></tag>
10811 The Debian revision part of the package version was
10812 at one point in a separate control field. This
10813 field went through several names.
10816 <tag><tt>Recommended</tt></tag>
10817 <item>Old name for <tt>Recommends</tt>.</item>
10819 <tag><tt>Optional</tt></tag>
10820 <item>Old name for <tt>Suggests</tt>.</item>
10822 <tag><tt>Class</tt></tag>
10823 <item>Old name for <tt>Priority</tt>.</item>
10832 <appendix id="pkg-conffiles">
10833 <heading>Configuration file handling (from old Packaging Manual)</heading>
10836 <prgn>dpkg</prgn> can do a certain amount of automatic
10837 handling of package configuration files.
10841 Whether this mechanism is appropriate depends on a number of
10842 factors, but basically there are two approaches to any
10843 particular configuration file.
10847 The easy method is to ship a best-effort configuration in the
10848 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10849 handle updates. If the user is unlikely to want to edit the
10850 file, but you need them to be able to without losing their
10851 changes, and a new package with a changed version of the file
10852 is only released infrequently, this is a good approach.
10856 The hard method is to build the configuration file from
10857 scratch in the <prgn>postinst</prgn> script, and to take the
10858 responsibility for fixing any mistakes made in earlier
10859 versions of the package automatically. This will be
10860 appropriate if the file is likely to need to be different on
10864 <sect><heading>Automatic handling of configuration files by
10869 A package may contain a control information file called
10870 <tt>conffiles</tt>. This file should be a list of filenames
10871 of configuration files needing automatic handling, separated
10872 by newlines. The filenames should be absolute pathnames,
10873 and the files referred to should actually exist in the
10878 When a package is upgraded <prgn>dpkg</prgn> will process
10879 the configuration files during the configuration stage,
10880 shortly before it runs the package's <prgn>postinst</prgn>
10885 For each file it checks to see whether the version of the
10886 file included in the package is the same as the one that was
10887 included in the last version of the package (the one that is
10888 being upgraded from); it also compares the version currently
10889 installed on the system with the one shipped with the last
10894 If neither the user nor the package maintainer has changed
10895 the file, it is left alone. If one or the other has changed
10896 their version, then the changed version is preferred - i.e.,
10897 if the user edits their file, but the package maintainer
10898 doesn't ship a different version, the user's changes will
10899 stay, silently, but if the maintainer ships a new version
10900 and the user hasn't edited it the new version will be
10901 installed (with an informative message). If both have
10902 changed their version the user is prompted about the problem
10903 and must resolve the differences themselves.
10907 The comparisons are done by calculating the MD5 message
10908 digests of the files, and storing the MD5 of the file as it
10909 was included in the most recent version of the package.
10913 When a package is installed for the first time
10914 <prgn>dpkg</prgn> will install the file that comes with it,
10915 unless that would mean overwriting a file already on the
10920 However, note that <prgn>dpkg</prgn> will <em>not</em>
10921 replace a conffile that was removed by the user (or by a
10922 script). This is necessary because with some programs a
10923 missing file produces an effect hard or impossible to
10924 achieve in another way, so that a missing file needs to be
10925 kept that way if the user did it.
10929 Note that a package should <em>not</em> modify a
10930 <prgn>dpkg</prgn>-handled conffile in its maintainer
10931 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10932 the user confusing and possibly dangerous options for
10933 conffile update when the package is upgraded.</p>
10936 <sect><heading>Fully-featured maintainer script configuration
10941 For files which contain site-specific information such as
10942 the hostname and networking details and so forth, it is
10943 better to create the file in the package's
10944 <prgn>postinst</prgn> script.
10948 This will typically involve examining the state of the rest
10949 of the system to determine values and other information, and
10950 may involve prompting the user for some information which
10951 can't be obtained some other way.
10955 When using this method there are a couple of important
10956 issues which should be considered:
10960 If you discover a bug in the program which generates the
10961 configuration file, or if the format of the file changes
10962 from one version to the next, you will have to arrange for
10963 the postinst script to do something sensible - usually this
10964 will mean editing the installed configuration file to remove
10965 the problem or change the syntax. You will have to do this
10966 very carefully, since the user may have changed the file,
10967 perhaps to fix the very problem that your script is trying
10968 to deal with - you will have to detect these situations and
10969 deal with them correctly.
10973 If you do go down this route it's probably a good idea to
10974 make the program that generates the configuration file(s) a
10975 separate program in <file>/usr/sbin</file>, by convention called
10976 <file><var>package</var>config</file> and then run that if
10977 appropriate from the post-installation script. The
10978 <tt><var>package</var>config</tt> program should not
10979 unquestioningly overwrite an existing configuration - if its
10980 mode of operation is geared towards setting up a package for
10981 the first time (rather than any arbitrary reconfiguration
10982 later) you should have it check whether the configuration
10983 already exists, and require a <tt>--force</tt> flag to
10984 overwrite it.</p></sect>
10987 <appendix id="pkg-alternatives"><heading>Alternative versions of
10988 an interface - <prgn>update-alternatives</prgn> (from old
10993 When several packages all provide different versions of the
10994 same program or file it is useful to have the system select a
10995 default, but to allow the system administrator to change it
10996 and have their decisions respected.
11000 For example, there are several versions of the <prgn>vi</prgn>
11001 editor, and there is no reason to prevent all of them from
11002 being installed at once, each under their own name
11003 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11004 Nevertheless it is desirable to have the name <tt>vi</tt>
11005 refer to something, at least by default.
11009 If all the packages involved cooperate, this can be done with
11010 <prgn>update-alternatives</prgn>.
11014 Each package provides its own version under its own name, and
11015 calls <prgn>update-alternatives</prgn> in its postinst to
11016 register its version (and again in its prerm to deregister
11021 See the man page <manref name="update-alternatives"
11022 section="8"> for details.
11026 If <prgn>update-alternatives</prgn> does not seem appropriate
11027 you may wish to consider using diversions instead.</p>
11030 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11031 package's version of a file (from old Packaging Manual)
11035 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11036 when it reinstalls the package it belongs to, and to have it
11037 put the file from the package somewhere else instead.
11041 This can be used locally to override a package's version of a
11042 file, or by one package to override another's version (or
11043 provide a wrapper for it).
11047 Before deciding to use a diversion, read <ref
11048 id="pkg-alternatives"> to see if you really want a diversion
11049 rather than several alternative versions of a program.
11053 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11054 and updated by a special program <prgn>dpkg-divert</prgn>.
11055 Please see <manref name="dpkg-divert" section="8"> for full
11056 details of its operation.
11060 When a package wishes to divert a file from another, it should
11061 call <prgn>dpkg-divert</prgn> in its preinst to add the
11062 diversion and rename the existing file. For example,
11063 supposing that a <prgn>smailwrapper</prgn> package wishes to
11064 install a wrapper around <file>/usr/sbin/smail</file>:
11066 dpkg-divert --package smailwrapper --add --rename \
11067 --divert /usr/sbin/smail.real /usr/sbin/smail
11068 </example> The <tt>--package smailwrapper</tt> ensures that
11069 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11070 can bypass the diversion and get installed as the true version.
11071 It's safe to add the diversion unconditionally on upgrades since
11072 it will be left unchanged if it already exists, but
11073 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11074 message, make the command conditional on the version from which
11075 the package is being upgraded:
11077 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11078 dpkg-divert --package smailwrapper --add --rename \
11079 --divert /usr/sbin/smail.real /usr/sbin/smail
11081 </example> where <tt>1.0-2</tt> is the version at which the
11082 diversion was first added to the package. Running the command
11083 during abort-upgrade is pointless but harmless.
11087 The postrm has to do the reverse:
11089 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11090 dpkg-divert --package smailwrapper --remove --rename \
11091 --divert /usr/sbin/smail.real /usr/sbin/smail
11093 </example> If the diversion was added at a particular version, the
11094 postrm should also handle the failure case of upgrading from an
11095 older version (unless the older version is so old that direct
11096 upgrades are no longer supported):
11098 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11099 dpkg-divert --package smailwrapper --remove --rename \
11100 --divert /usr/sbin/smail.real /usr/sbin/smail
11102 </example> where <tt>1.02-2</tt> is the version at which the
11103 diversion was first added to the package. The postrm should not
11104 remove the diversion on upgrades both because there's no reason to
11105 remove the diversion only to immediately re-add it and since the
11106 postrm of the old package is run after unpacking so the removal of
11107 the diversion will fail.
11111 Do not attempt to divert a file which is vitally important for
11112 the system's operation - when using <prgn>dpkg-divert</prgn>
11113 there is a time, after it has been diverted but before
11114 <prgn>dpkg</prgn> has installed the new version, when the file
11115 does not exist.</p>
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