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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian distribution</em>.
355 Packages in the other archive areas (<tt>contrib</tt>,
356 <tt>non-free</tt>) are not considered to be part of the Debian
357 distribution, although we support their use and provide
358 infrastructure for them (such as our bug-tracking system and
359 mailing lists). This Debian Policy Manual applies to these
364 <heading>The Debian Free Software Guidelines</heading>
366 The Debian Free Software Guidelines (DFSG) form our
367 definition of "free software". These are:
369 <tag>1. Free Redistribution
372 The license of a Debian component may not restrict any
373 party from selling or giving away the software as a
374 component of an aggregate software distribution
375 containing programs from several different
376 sources. The license may not require a royalty or
377 other fee for such sale.
382 The program must include source code, and must allow
383 distribution in source code as well as compiled form.
385 <tag>3. Derived Works
388 The license must allow modifications and derived
389 works, and must allow them to be distributed under the
390 same terms as the license of the original software.
392 <tag>4. Integrity of The Author's Source Code
395 The license may restrict source-code from being
396 distributed in modified form <em>only</em> if the
397 license allows the distribution of "patch files"
398 with the source code for the purpose of modifying the
399 program at build time. The license must explicitly
400 permit distribution of software built from modified
401 source code. The license may require derived works to
402 carry a different name or version number from the
403 original software. (This is a compromise. The Debian
404 Project encourages all authors to not restrict any
405 files, source or binary, from being modified.)
407 <tag>5. No Discrimination Against Persons or Groups
410 The license must not discriminate against any person
413 <tag>6. No Discrimination Against Fields of Endeavor
416 The license must not restrict anyone from making use
417 of the program in a specific field of endeavor. For
418 example, it may not restrict the program from being
419 used in a business, or from being used for genetic
422 <tag>7. Distribution of License
425 The rights attached to the program must apply to all
426 to whom the program is redistributed without the need
427 for execution of an additional license by those
430 <tag>8. License Must Not Be Specific to Debian
433 The rights attached to the program must not depend on
434 the program's being part of a Debian system. If the
435 program is extracted from Debian and used or
436 distributed without Debian but otherwise within the
437 terms of the program's license, all parties to whom
438 the program is redistributed must have the same
439 rights as those that are granted in conjunction with
442 <tag>9. License Must Not Contaminate Other Software
445 The license must not place restrictions on other
446 software that is distributed along with the licensed
447 software. For example, the license must not insist
448 that all other programs distributed on the same medium
449 must be free software.
451 <tag>10. Example Licenses
454 The "GPL," "BSD," and "Artistic" licenses are examples of
455 licenses that we consider <em>free</em>.
462 <heading>Archive areas</heading>
465 <heading>The main archive area</heading>
468 Every package in <em>main</em> must comply with the DFSG
469 (Debian Free Software Guidelines).
473 In addition, the packages in <em>main</em>
474 <list compact="compact">
476 must not require a package outside of <em>main</em>
477 for compilation or execution (thus, the package must
478 not declare a "Depends", "Recommends", or
479 "Build-Depends" relationship on a non-<em>main</em>
483 must not be so buggy that we refuse to support them,
487 must meet all policy requirements presented in this
496 <heading>The contrib archive area</heading>
499 Every package in <em>contrib</em> must comply with the DFSG.
503 In addition, the packages in <em>contrib</em>
504 <list compact="compact">
506 must not be so buggy that we refuse to support them,
510 must meet all policy requirements presented in this
518 Examples of packages which would be included in
519 <em>contrib</em> are:
520 <list compact="compact">
522 free packages which require <em>contrib</em>,
523 <em>non-free</em> packages or packages which are not
524 in our archive at all for compilation or execution,
528 wrapper packages or other sorts of free accessories for
535 <sect1 id="non-free">
536 <heading>The non-free archive area</heading>
539 Packages must be placed in <em>non-free</em> if they are
540 not compliant with the DFSG or are encumbered by patents
541 or other legal issues that make their distribution
546 In addition, the packages in <em>non-free</em>
547 <list compact="compact">
549 must not be so buggy that we refuse to support them,
553 must meet all policy requirements presented in this
554 manual that it is possible for them to meet.
556 It is possible that there are policy
557 requirements which the package is unable to
558 meet, for example, if the source is
559 unavailable. These situations will need to be
560 handled on a case-by-case basis.
569 <sect id="pkgcopyright">
570 <heading>Copyright considerations</heading>
573 Every package must be accompanied by a verbatim copy of its
574 copyright information and distribution license in the file
575 <file>/usr/share/doc/<var>package</var>/copyright</file>
576 (see <ref id="copyrightfile"> for further details).
580 We reserve the right to restrict files from being included
581 anywhere in our archives if
582 <list compact="compact">
584 their use or distribution would break a law,
587 there is an ethical conflict in their distribution or
591 we would have to sign a license for them, or
594 their distribution would conflict with other project
601 Programs whose authors encourage the user to make
602 donations are fine for the main distribution, provided
603 that the authors do not claim that not donating is
604 immoral, unethical, illegal or something similar; in such
605 a case they must go in <em>non-free</em>.
609 Packages whose copyright permission notices (or patent
610 problems) do not even allow redistribution of binaries
611 only, and where no special permission has been obtained,
612 must not be placed on the Debian FTP site and its mirrors
617 Note that under international copyright law (this applies
618 in the United States, too), <em>no</em> distribution or
619 modification of a work is allowed without an explicit
620 notice saying so. Therefore a program without a copyright
621 notice <em>is</em> copyrighted and you may not do anything
622 to it without risking being sued! Likewise if a program
623 has a copyright notice but no statement saying what is
624 permitted then nothing is permitted.
628 Many authors are unaware of the problems that restrictive
629 copyrights (or lack of copyright notices) can cause for
630 the users of their supposedly-free software. It is often
631 worthwhile contacting such authors diplomatically to ask
632 them to modify their license terms. However, this can be a
633 politically difficult thing to do and you should ask for
634 advice on the <tt>debian-legal</tt> mailing list first, as
639 When in doubt about a copyright, send mail to
640 <email>debian-legal@lists.debian.org</email>. Be prepared
641 to provide us with the copyright statement. Software
642 covered by the GPL, public domain software and BSD-like
643 copyrights are safe; be wary of the phrases "commercial
644 use prohibited" and "distribution restricted".
648 <sect id="subsections">
649 <heading>Sections</heading>
652 The packages in the archive areas <em>main</em>,
653 <em>contrib</em> and <em>non-free</em> are grouped further into
654 <em>sections</em> to simplify handling.
658 The archive area and section for each package should be
659 specified in the package's <tt>Section</tt> control record (see
660 <ref id="f-Section">). However, the maintainer of the Debian
661 archive may override this selection to ensure the consistency of
662 the Debian distribution. The <tt>Section</tt> field should be
664 <list compact="compact">
666 <em>section</em> if the package is in the
667 <em>main</em> archive area,
670 <em>area/section</em> if the package is in
671 the <em>contrib</em> or <em>non-free</em>
678 The Debian archive maintainers provide the authoritative
679 list of sections. At present, they are:
680 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
681 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
682 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
683 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
684 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
685 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
686 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
687 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
688 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
689 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
690 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
691 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
692 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
693 <em>zope</em>. The additional section <em>debian-installer</em>
694 contains special packages used by the installer and is not used
695 for normal Debian packages.
699 For more information about the sections and their definitions,
700 see the <url id="http://packages.debian.org/unstable/"
701 name="list of sections in unstable">.
705 <sect id="priorities">
706 <heading>Priorities</heading>
709 Each package should have a <em>priority</em> value, which is
710 included in the package's <em>control record</em>
711 (see <ref id="f-Priority">).
712 This information is used by the Debian package management tools to
713 separate high-priority packages from less-important packages.
717 The following <em>priority levels</em> are recognized by the
718 Debian package management tools.
720 <tag><tt>required</tt></tag>
722 Packages which are necessary for the proper
723 functioning of the system (usually, this means that
724 dpkg functionality depends on these packages).
725 Removing a <tt>required</tt> package may cause your
726 system to become totally broken and you may not even
727 be able to use <prgn>dpkg</prgn> to put things back,
728 so only do so if you know what you are doing. Systems
729 with only the <tt>required</tt> packages are probably
730 unusable, but they do have enough functionality to
731 allow the sysadmin to boot and install more software.
733 <tag><tt>important</tt></tag>
735 Important programs, including those which one would
736 expect to find on any Unix-like system. If the
737 expectation is that an experienced Unix person who
738 found it missing would say "What on earth is going on,
739 where is <prgn>foo</prgn>?", it must be an
740 <tt>important</tt> package.<footnote>
741 This is an important criterion because we are
742 trying to produce, amongst other things, a free
745 Other packages without which the system will not run
746 well or be usable must also have priority
747 <tt>important</tt>. This does
748 <em>not</em> include Emacs, the X Window System, TeX
749 or any other large applications. The
750 <tt>important</tt> packages are just a bare minimum of
751 commonly-expected and necessary tools.
753 <tag><tt>standard</tt></tag>
755 These packages provide a reasonably small but not too
756 limited character-mode system. This is what will be
757 installed by default if the user doesn't select anything
758 else. It doesn't include many large applications.
760 <tag><tt>optional</tt></tag>
762 (In a sense everything that isn't required is
763 optional, but that's not what is meant here.) This is
764 all the software that you might reasonably want to
765 install if you didn't know what it was and don't have
766 specialized requirements. This is a much larger system
767 and includes the X Window System, a full TeX
768 distribution, and many applications. Note that
769 optional packages should not conflict with each other.
771 <tag><tt>extra</tt></tag>
773 This contains all packages that conflict with others
774 with required, important, standard or optional
775 priorities, or are only likely to be useful if you
776 already know what they are or have specialized
777 requirements (such as packages containing only detached
784 Packages must not depend on packages with lower priority
785 values (excluding build-time dependencies). In order to
786 ensure this, the priorities of one or more packages may need
795 <heading>Binary packages</heading>
798 The Debian distribution is based on the Debian
799 package management system, called <prgn>dpkg</prgn>. Thus,
800 all packages in the Debian distribution must be provided
801 in the <tt>.deb</tt> file format.
805 A <tt>.deb</tt> package contains two sets of files: a set of files
806 to install on the system when the package is installed, and a set
807 of files that provide additional metadata about the package or
808 which are executed when the package is installed or removed. This
809 second set of files is called <em>control information files</em>.
810 Among those files are the package maintainer scripts
811 and <file>control</file>, the <qref id="binarycontrolfiles">binary
812 package control file</qref> that contains the control fields for
813 the package. Other control information files
814 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
815 file</qref> used to store shared library dependency information
816 and the <file>conffiles</file> file that lists the package's
817 configuration files (described in <ref id="config-files">).
821 There is unfortunately a collision of terminology here between
822 control information files and files in the Debian control file
823 format. Throughout this document, a <em>control file</em> refers
824 to a file in the Debian control file format. These files are
825 documented in <ref id="controlfields">. Only files referred to
826 specifically as <em>control information files</em> are the files
827 included in the control information file member of
828 the <file>.deb</file> file format used by binary packages. Most
829 control information files are not in the Debian control file
834 <heading>The package name</heading>
837 Every package must have a name that's unique within the Debian
842 The package name is included in the control field
843 <tt>Package</tt>, the format of which is described
844 in <ref id="f-Package">.
845 The package name is also included as a part of the file name
846 of the <tt>.deb</tt> file.
851 <heading>The version of a package</heading>
854 Every package has a version number recorded in its
855 <tt>Version</tt> control file field, described in
856 <ref id="f-Version">.
860 The package management system imposes an ordering on version
861 numbers, so that it can tell whether packages are being up- or
862 downgraded and so that package system front end applications
863 can tell whether a package it finds available is newer than
864 the one installed on the system. The version number format
865 has the most significant parts (as far as comparison is
866 concerned) at the beginning.
870 If an upstream package has problematic version numbers they
871 should be converted to a sane form for use in the
872 <tt>Version</tt> field.
876 <heading>Version numbers based on dates</heading>
879 In general, Debian packages should use the same version
880 numbers as the upstream sources. However, upstream version
881 numbers based on some date formats (sometimes used for
882 development or "snapshot" releases) will not be ordered
883 correctly by the package management software. For
884 example, <prgn>dpkg</prgn> will consider "96May01" to be
885 greater than "96Dec24".
889 To prevent having to use epochs for every new upstream
890 version, the date-based portion of any upstream version number
891 should be given in a way that sorts correctly: four-digit year
892 first, followed by a two-digit numeric month, followed by a
893 two-digit numeric date, possibly with punctuation between the
898 Native Debian packages (i.e., packages which have been written
899 especially for Debian) whose version numbers include dates
900 should also follow these rules. If punctuation is desired
901 between the date components, remember that hyphen (<tt>-</tt>)
902 cannot be used in native package versions. Period
903 (<tt>.</tt>) is normally a good choice.
909 <sect id="maintainer">
910 <heading>The maintainer of a package</heading>
913 Every package must have a maintainer, except for orphaned
914 packages as described below. The maintainer may be one person
915 or a group of people reachable from a common email address, such
916 as a mailing list. The maintainer is responsible for
917 maintaining the Debian packaging files, evaluating and
918 responding appropriately to reported bugs, uploading new
919 versions of the package (either directly or through a sponsor),
920 ensuring that the package is placed in the appropriate archive
921 area and included in Debian releases as appropriate for the
922 stability and utility of the package, and requesting removal of
923 the package from the Debian distribution if it is no longer
924 useful or maintainable.
928 The maintainer must be specified in the <tt>Maintainer</tt>
929 control field with their correct name and a working email
930 address. The email address given in the <tt>Maintainer</tt>
931 control field must accept mail from those role accounts in
932 Debian used to send automated mails regarding the package. This
933 includes non-spam mail from the bug-tracking system, all mail
934 from the Debian archive maintenance software, and other role
935 accounts or automated processes that are commonly agreed on by
936 the project.<footnote>
937 A sample implementation of such a whitelist written for the
938 Mailman mailing list management software is used for mailing
939 lists hosted by alioth.debian.org.
941 If one person or team maintains several packages, they should
942 use the same form of their name and email address in
943 the <tt>Maintainer</tt> fields of those packages.
947 The format of the <tt>Maintainer</tt> control field is
948 described in <ref id="f-Maintainer">.
952 If the maintainer of the package is a team of people with a
953 shared email address, the <tt>Uploaders</tt> control field must
954 be present and must contain at least one human with their
955 personal email address. See <ref id="f-Uploaders"> for the
956 syntax of that field.
960 An orphaned package is one with no current maintainer. Orphaned
961 packages should have their <tt>Maintainer</tt> control field set
962 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
963 These packages are considered maintained by the Debian project
964 as a whole until someone else volunteers to take over
965 maintenance.<footnote>
966 The detailed procedure for gracefully orphaning a package can
967 be found in the Debian Developer's Reference
968 (see <ref id="related">).
973 <sect id="descriptions">
974 <heading>The description of a package</heading>
977 Every Debian package must have a <tt>Description</tt> control
978 field which contains a synopsis and extended description of the
979 package. Technical information about the format of the
980 <tt>Description</tt> field is in <ref id="f-Description">.
984 The description should describe the package (the program) to a
985 user (system administrator) who has never met it before so that
986 they have enough information to decide whether they want to
987 install it. This description should not just be copied verbatim
988 from the program's documentation.
992 Put important information first, both in the synopsis and
993 extended description. Sometimes only the first part of the
994 synopsis or of the description will be displayed. You can
995 assume that there will usually be a way to see the whole
996 extended description.
1000 The description should also give information about the
1001 significant dependencies and conflicts between this package
1002 and others, so that the user knows why these dependencies and
1003 conflicts have been declared.
1007 Instructions for configuring or using the package should
1008 not be included (that is what installation scripts,
1009 manual pages, info files, etc., are for). Copyright
1010 statements and other administrivia should not be included
1011 either (that is what the copyright file is for).
1014 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1017 The single line synopsis should be kept brief - certainly
1018 under 80 characters.
1022 Do not include the package name in the synopsis line. The
1023 display software knows how to display this already, and you
1024 do not need to state it. Remember that in many situations
1025 the user may only see the synopsis line - make it as
1026 informative as you can.
1031 <sect1 id="extendeddesc"><heading>The extended description</heading>
1034 Do not try to continue the single line synopsis into the
1035 extended description. This will not work correctly when
1036 the full description is displayed, and makes no sense
1037 where only the summary (the single line synopsis) is
1042 The extended description should describe what the package
1043 does and how it relates to the rest of the system (in terms
1044 of, for example, which subsystem it is which part of).
1048 The description field needs to make sense to anyone, even
1049 people who have no idea about any of the things the
1050 package deals with.<footnote>
1051 The blurb that comes with a program in its
1052 announcements and/or <prgn>README</prgn> files is
1053 rarely suitable for use in a description. It is
1054 usually aimed at people who are already in the
1055 community where the package is used.
1064 <heading>Dependencies</heading>
1067 Every package must specify the dependency information
1068 about other packages that are required for the first to
1073 For example, a dependency entry must be provided for any
1074 shared libraries required by a dynamically-linked executable
1075 binary in a package.
1079 Packages are not required to declare any dependencies they
1080 have on other packages which are marked <tt>Essential</tt>
1081 (see below), and should not do so unless they depend on a
1082 particular version of that package.<footnote>
1084 Essential is needed in part to avoid unresolvable dependency
1085 loops on upgrade. If packages add unnecessary dependencies
1086 on packages in this set, the chances that there
1087 <strong>will</strong> be an unresolvable dependency loop
1088 caused by forcing these Essential packages to be configured
1089 first before they need to be is greatly increased. It also
1090 increases the chances that frontends will be unable to
1091 <strong>calculate</strong> an upgrade path, even if one
1095 Also, functionality is rarely ever removed from the
1096 Essential set, but <em>packages</em> have been removed from
1097 the Essential set when the functionality moved to a
1098 different package. So depending on these packages <em>just
1099 in case</em> they stop being essential does way more harm
1106 Sometimes, a package requires another package to be installed
1107 <em>and</em> configured before it can be installed. In this
1108 case, you must specify a <tt>Pre-Depends</tt> entry for
1113 You should not specify a <tt>Pre-Depends</tt> entry for a
1114 package before this has been discussed on the
1115 <tt>debian-devel</tt> mailing list and a consensus about
1116 doing that has been reached.
1120 The format of the package interrelationship control fields is
1121 described in <ref id="relationships">.
1125 <sect id="virtual_pkg">
1126 <heading>Virtual packages</heading>
1129 Sometimes, there are several packages which offer
1130 more-or-less the same functionality. In this case, it's
1131 useful to define a <em>virtual package</em> whose name
1132 describes that common functionality. (The virtual
1133 packages only exist logically, not physically; that's why
1134 they are called <em>virtual</em>.) The packages with this
1135 particular function will then <em>provide</em> the virtual
1136 package. Thus, any other package requiring that function
1137 can simply depend on the virtual package without having to
1138 specify all possible packages individually.
1142 All packages should use virtual package names where
1143 appropriate, and arrange to create new ones if necessary.
1144 They should not use virtual package names (except privately,
1145 amongst a cooperating group of packages) unless they have
1146 been agreed upon and appear in the list of virtual package
1147 names. (See also <ref id="virtual">)
1151 The latest version of the authoritative list of virtual
1152 package names can be found in the <tt>debian-policy</tt> package.
1153 It is also available from the Debian web mirrors at
1154 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1155 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1159 The procedure for updating the list is described in the preface
1166 <heading>Base system</heading>
1169 The <tt>base system</tt> is a minimum subset of the Debian
1170 system that is installed before everything else
1171 on a new system. Only very few packages are allowed to form
1172 part of the base system, in order to keep the required disk
1177 The base system consists of all those packages with priority
1178 <tt>required</tt> or <tt>important</tt>. Many of them will
1179 be tagged <tt>essential</tt> (see below).
1184 <heading>Essential packages</heading>
1187 Essential is defined as the minimal set of functionality that
1188 must be available and usable on the system at all times, even
1189 when packages are in an unconfigured (but unpacked) state.
1190 Packages are tagged <tt>essential</tt> for a system using the
1191 <tt>Essential</tt> control field. The format of the
1192 <tt>Essential</tt> control field is described in <ref
1197 Since these packages cannot be easily removed (one has to
1198 specify an extra <em>force option</em> to
1199 <prgn>dpkg</prgn> to do so), this flag must not be used
1200 unless absolutely necessary. A shared library package
1201 must not be tagged <tt>essential</tt>; dependencies will
1202 prevent its premature removal, and we need to be able to
1203 remove it when it has been superseded.
1207 Since dpkg will not prevent upgrading of other packages
1208 while an <tt>essential</tt> package is in an unconfigured
1209 state, all <tt>essential</tt> packages must supply all of
1210 their core functionality even when unconfigured. If the
1211 package cannot satisfy this requirement it must not be
1212 tagged as essential, and any packages depending on this
1213 package must instead have explicit dependency fields as
1218 Maintainers should take great care in adding any programs,
1219 interfaces, or functionality to <tt>essential</tt> packages.
1220 Packages may assume that functionality provided by
1221 <tt>essential</tt> packages is always available without
1222 declaring explicit dependencies, which means that removing
1223 functionality from the Essential set is very difficult and is
1224 almost never done. Any capability added to an
1225 <tt>essential</tt> package therefore creates an obligation to
1226 support that capability as part of the Essential set in
1231 You must not tag any packages <tt>essential</tt> before
1232 this has been discussed on the <tt>debian-devel</tt>
1233 mailing list and a consensus about doing that has been
1238 <sect id="maintscripts">
1239 <heading>Maintainer Scripts</heading>
1242 The package installation scripts should avoid producing
1243 output which is unnecessary for the user to see and
1244 should rely on <prgn>dpkg</prgn> to stave off boredom on
1245 the part of a user installing many packages. This means,
1246 amongst other things, using the <tt>--quiet</tt> option on
1247 <prgn>install-info</prgn>.
1251 Errors which occur during the execution of an installation
1252 script must be checked and the installation must not
1253 continue after an error.
1257 Note that in general <ref id="scripts"> applies to package
1258 maintainer scripts, too.
1262 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1263 to another package without consulting the maintainer of that
1264 package first. When adding or removing diversions, package
1265 maintainer scripts must provide the <tt>--package</tt> flag
1266 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1270 All packages which supply an instance of a common command
1271 name (or, in general, filename) should generally use
1272 <prgn>update-alternatives</prgn>, so that they may be
1273 installed together. If <prgn>update-alternatives</prgn>
1274 is not used, then each package must use
1275 <tt>Conflicts</tt> to ensure that other packages are
1276 de-installed. (In this case, it may be appropriate to
1277 specify a conflict against earlier versions of something
1278 that previously did not use
1279 <prgn>update-alternatives</prgn>; this is an exception to
1280 the usual rule that versioned conflicts should be
1284 <sect1 id="maintscriptprompt">
1285 <heading>Prompting in maintainer scripts</heading>
1287 Package maintainer scripts may prompt the user if
1288 necessary. Prompting must be done by communicating
1289 through a program, such as <prgn>debconf</prgn>, which
1290 conforms to the Debian Configuration Management
1291 Specification, version 2 or higher.
1295 Packages which are essential, or which are dependencies of
1296 essential packages, may fall back on another prompting method
1297 if no such interface is available when they are executed.
1301 The Debian Configuration Management Specification is included
1302 in the <file>debconf_specification</file> files in the
1303 <package>debian-policy</package> package.
1304 It is also available from the Debian web mirrors at
1305 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1306 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1310 Packages which use the Debian Configuration Management
1311 Specification may contain the additional control information
1312 files <file>config</file>
1313 and <file>templates</file>. <file>config</file> is an
1314 additional maintainer script used for package configuration,
1315 and <file>templates</file> contains templates used for user
1316 prompting. The <prgn>config</prgn> script might be run before
1317 the <prgn>preinst</prgn> script and before the package is
1318 unpacked or any of its dependencies or pre-dependencies are
1319 satisfied. Therefore it must work using only the tools
1320 present in <em>essential</em> packages.<footnote>
1321 <package>Debconf</package> or another tool that
1322 implements the Debian Configuration Management
1323 Specification will also be installed, and any
1324 versioned dependencies on it will be satisfied
1325 before preconfiguration begins.
1330 Packages which use the Debian Configuration Management
1331 Specification must allow for translation of their user-visible
1332 messages by using a gettext-based system such as the one
1333 provided by the <package>po-debconf</package> package.
1337 Packages should try to minimize the amount of prompting
1338 they need to do, and they should ensure that the user
1339 will only ever be asked each question once. This means
1340 that packages should try to use appropriate shared
1341 configuration files (such as <file>/etc/papersize</file> and
1342 <file>/etc/news/server</file>), and shared
1343 <package>debconf</package> variables rather than each
1344 prompting for their own list of required pieces of
1349 It also means that an upgrade should not ask the same
1350 questions again, unless the user has used
1351 <tt>dpkg --purge</tt> to remove the package's configuration.
1352 The answers to configuration questions should be stored in an
1353 appropriate place in <file>/etc</file> so that the user can
1354 modify them, and how this has been done should be
1359 If a package has a vitally important piece of
1360 information to pass to the user (such as "don't run me
1361 as I am, you must edit the following configuration files
1362 first or you risk your system emitting badly-formatted
1363 messages"), it should display this in the
1364 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1365 prompt the user to hit return to acknowledge the
1366 message. Copyright messages do not count as vitally
1367 important (they belong in
1368 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1369 neither do instructions on how to use a program (these
1370 should be in on-line documentation, where all the users
1375 Any necessary prompting should almost always be confined
1376 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1377 script. If it is done in the <prgn>postinst</prgn>, it
1378 should be protected with a conditional so that
1379 unnecessary prompting doesn't happen if a package's
1380 installation fails and the <prgn>postinst</prgn> is
1381 called with <tt>abort-upgrade</tt>,
1382 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1392 <heading>Source packages</heading>
1394 <sect id="standardsversion">
1395 <heading>Standards conformance</heading>
1398 Source packages should specify the most recent version number
1399 of this policy document with which your package complied
1400 when it was last updated.
1404 This information may be used to file bug reports
1405 automatically if your package becomes too much out of date.
1409 The version is specified in the <tt>Standards-Version</tt>
1411 The format of the <tt>Standards-Version</tt> field is
1412 described in <ref id="f-Standards-Version">.
1416 You should regularly, and especially if your package has
1417 become out of date, check for the newest Policy Manual
1418 available and update your package, if necessary. When your
1419 package complies with the new standards you should update the
1420 <tt>Standards-Version</tt> source package field and
1421 release it.<footnote>
1422 See the file <file>upgrading-checklist</file> for
1423 information about policy which has changed between
1424 different versions of this document.
1430 <sect id="pkg-relations">
1431 <heading>Package relationships</heading>
1434 Source packages should specify which binary packages they
1435 require to be installed or not to be installed in order to
1436 build correctly. For example, if building a package
1437 requires a certain compiler, then the compiler should be
1438 specified as a build-time dependency.
1442 It is not necessary to explicitly specify build-time
1443 relationships on a minimal set of packages that are always
1444 needed to compile, link and put in a Debian package a
1445 standard "Hello World!" program written in C or C++. The
1446 required packages are called <em>build-essential</em>, and
1447 an informational list can be found in
1448 <file>/usr/share/doc/build-essential/list</file> (which is
1449 contained in the <tt>build-essential</tt>
1452 <list compact="compact">
1454 This allows maintaining the list separately
1455 from the policy documents (the list does not
1456 need the kind of control that the policy
1460 Having a separate package allows one to install
1461 the build-essential packages on a machine, as
1462 well as allowing other packages such as tasks to
1463 require installation of the build-essential
1464 packages using the depends relation.
1467 The separate package allows bug reports against
1468 the list to be categorized separately from
1469 the policy management process in the BTS.
1476 When specifying the set of build-time dependencies, one
1477 should list only those packages explicitly required by the
1478 build. It is not necessary to list packages which are
1479 required merely because some other package in the list of
1480 build-time dependencies depends on them.<footnote>
1481 The reason for this is that dependencies change, and
1482 you should list all those packages, and <em>only</em>
1483 those packages that <em>you</em> need directly. What
1484 others need is their business. For example, if you
1485 only link against <file>libimlib</file>, you will need to
1486 build-depend on <package>libimlib2-dev</package> but
1487 not against any <tt>libjpeg*</tt> packages, even
1488 though <tt>libimlib2-dev</tt> currently depends on
1489 them: installation of <package>libimlib2-dev</package>
1490 will automatically ensure that all of its run-time
1491 dependencies are satisfied.
1496 If build-time dependencies are specified, it must be
1497 possible to build the package and produce working binaries
1498 on a system with only essential and build-essential
1499 packages installed and also those required to satisfy the
1500 build-time relationships (including any implied
1501 relationships). In particular, this means that version
1502 clauses should be used rigorously in build-time
1503 relationships so that one cannot produce bad or
1504 inconsistently configured packages when the relationships
1505 are properly satisfied.
1509 <ref id="relationships"> explains the technical details.
1514 <heading>Changes to the upstream sources</heading>
1517 If changes to the source code are made that are not
1518 specific to the needs of the Debian system, they should be
1519 sent to the upstream authors in whatever form they prefer
1520 so as to be included in the upstream version of the
1525 If you need to configure the package differently for
1526 Debian or for Linux, and the upstream source doesn't
1527 provide a way to do so, you should add such configuration
1528 facilities (for example, a new <prgn>autoconf</prgn> test
1529 or <tt>#define</tt>) and send the patch to the upstream
1530 authors, with the default set to the way they originally
1531 had it. You can then easily override the default in your
1532 <file>debian/rules</file> or wherever is appropriate.
1536 You should make sure that the <prgn>configure</prgn> utility
1537 detects the correct architecture specification string
1538 (refer to <ref id="arch-spec"> for details).
1542 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1543 <prgn>configure</prgn> scripts are used, you should edit the
1544 <file>.in</file> files rather than editing the
1545 <prgn>Makefile</prgn> directly. This allows the user to
1546 reconfigure the package if necessary. You should
1547 <em>not</em> configure the package and edit the generated
1548 <prgn>Makefile</prgn>! This makes it impossible for someone
1549 else to later reconfigure the package without losing the
1555 <sect id="dpkgchangelog">
1556 <heading>Debian changelog: <file>debian/changelog</file></heading>
1559 Changes in the Debian version of the package should be
1560 briefly explained in the Debian changelog file
1561 <file>debian/changelog</file>.<footnote>
1563 Mistakes in changelogs are usually best rectified by
1564 making a new changelog entry rather than "rewriting
1565 history" by editing old changelog entries.
1568 This includes modifications
1569 made in the Debian package compared to the upstream one
1570 as well as other changes and updates to the package.
1572 Although there is nothing stopping an author who is also
1573 the Debian maintainer from using this changelog for all
1574 their changes, it will have to be renamed if the Debian
1575 and upstream maintainers become different people. In such
1576 a case, however, it might be better to maintain the package
1577 as a non-native package.
1582 The format of the <file>debian/changelog</file> allows the
1583 package building tools to discover which version of the package
1584 is being built and find out other release-specific information.
1588 That format is a series of entries like this:
1590 <example compact="compact">
1591 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1593 [optional blank line(s), stripped]
1595 * <var>change details</var>
1596 <var>more change details</var>
1598 [blank line(s), included in output of dpkg-parsechangelog]
1600 * <var>even more change details</var>
1602 [optional blank line(s), stripped]
1604 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1609 <var>package</var> and <var>version</var> are the source
1610 package name and version number.
1614 <var>distribution(s)</var> lists the distributions where
1615 this version should be installed when it is uploaded - it
1616 is copied to the <tt>Distribution</tt> field in the
1617 <file>.changes</file> file. See <ref id="f-Distribution">.
1621 <var>urgency</var> is the value for the <tt>Urgency</tt>
1622 field in the <file>.changes</file> file for the upload
1623 (see <ref id="f-Urgency">). It is not possible to specify
1624 an urgency containing commas; commas are used to separate
1625 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1626 <prgn>dpkg</prgn> changelog format (though there is
1627 currently only one useful <var>keyword</var>,
1632 The change details may in fact be any series of lines
1633 starting with at least two spaces, but conventionally each
1634 change starts with an asterisk and a separating space and
1635 continuation lines are indented so as to bring them in
1636 line with the start of the text above. Blank lines may be
1637 used here to separate groups of changes, if desired.
1641 If this upload resolves bugs recorded in the Bug Tracking
1642 System (BTS), they may be automatically closed on the
1643 inclusion of this package into the Debian archive by
1644 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1645 in the change details.<footnote>
1646 To be precise, the string should match the following
1647 Perl regular expression:
1649 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1651 Then all of the bug numbers listed will be closed by the
1652 archive maintenance script (<prgn>katie</prgn>) using the
1653 <var>version</var> of the changelog entry.
1655 This information is conveyed via the <tt>Closes</tt> field
1656 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1660 The maintainer name and email address used in the changelog
1661 should be the details of the person uploading <em>this</em>
1662 version. They are <em>not</em> necessarily those of the
1663 usual package maintainer.<footnote>
1664 If the developer uploading the package is not one of the usual
1665 maintainers of the package (as listed in
1666 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1667 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1668 fields of the package), the first line of the changelog is
1669 conventionally used to explain why a non-maintainer is
1670 uploading the package. The Debian Developer's Reference
1671 (see <ref id="related">) documents the conventions
1673 The information here will be copied to the <tt>Changed-By</tt>
1674 field in the <tt>.changes</tt> file
1675 (see <ref id="f-Changed-By">), and then later used to send an
1676 acknowledgement when the upload has been installed.
1680 The <var>date</var> has the following format<footnote>
1681 This is the same as the format generated by <tt>date
1683 </footnote> (compatible and with the same semantics of
1684 RFC 2822 and RFC 5322):
1685 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1687 <list compact="compact">
1689 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1692 dd is a one- or two-digit day of the month (01-31)
1695 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1698 <item>yyyy is the four-digit year (e.g. 2010)</item>
1699 <item>hh is the two-digit hour (00-23)</item>
1700 <item>mm is the two-digit minutes (00-59)</item>
1701 <item>ss is the two-digit seconds (00-60)</item>
1703 +zzzz or -zzzz is the the time zone offset from Coordinated
1704 Universal Time (UTC). "+" indicates that the time is ahead
1705 of (i.e., east of) UTC and "-" indicates that the time is
1706 behind (i.e., west of) UTC. The first two digits indicate
1707 the hour difference from UTC and the last two digits
1708 indicate the number of additional minutes difference from
1709 UTC. The last two digits must be in the range 00-59.
1715 The first "title" line with the package name must start
1716 at the left hand margin. The "trailer" line with the
1717 maintainer and date details must be preceded by exactly
1718 one space. The maintainer details and the date must be
1719 separated by exactly two spaces.
1723 The entire changelog must be encoded in UTF-8.
1727 For more information on placement of the changelog files
1728 within binary packages, please see <ref id="changelogs">.
1732 <sect id="dpkgcopyright">
1733 <heading>Copyright: <file>debian/copyright</file></heading>
1735 Every package must be accompanied by a verbatim copy of its
1736 copyright information and distribution license in the file
1737 <file>/usr/share/doc/<var>package</var>/copyright</file>
1738 (see <ref id="copyrightfile"> for further details). Also see
1739 <ref id="pkgcopyright"> for further considerations related
1740 to copyrights for packages.
1744 <heading>Error trapping in makefiles</heading>
1747 When <prgn>make</prgn> invokes a command in a makefile
1748 (including your package's upstream makefiles and
1749 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1750 means that <prgn>sh</prgn>'s usual bad error handling
1751 properties apply: if you include a miniature script as one
1752 of the commands in your makefile you'll find that if you
1753 don't do anything about it then errors are not detected
1754 and <prgn>make</prgn> will blithely continue after
1759 Every time you put more than one shell command (this
1760 includes using a loop) in a makefile command you
1761 must make sure that errors are trapped. For
1762 simple compound commands, such as changing directory and
1763 then running a program, using <tt>&&</tt> rather
1764 than semicolon as a command separator is sufficient. For
1765 more complex commands including most loops and
1766 conditionals you should include a separate <tt>set -e</tt>
1767 command at the start of every makefile command that's
1768 actually one of these miniature shell scripts.
1772 <sect id="timestamps">
1773 <heading>Time Stamps</heading>
1775 Maintainers should preserve the modification times of the
1776 upstream source files in a package, as far as is reasonably
1778 The rationale is that there is some information conveyed
1779 by knowing the age of the file, for example, you could
1780 recognize that some documentation is very old by looking
1781 at the modification time, so it would be nice if the
1782 modification time of the upstream source would be
1788 <sect id="restrictions">
1789 <heading>Restrictions on objects in source packages</heading>
1792 The source package may not contain any hard links<footnote>
1794 This is not currently detected when building source
1795 packages, but only when extracting
1799 Hard links may be permitted at some point in the
1800 future, but would require a fair amount of
1803 </footnote>, device special files, sockets or setuid or
1804 setgid files.<footnote>
1805 Setgid directories are allowed.
1810 <sect id="debianrules">
1811 <heading>Main building script: <file>debian/rules</file></heading>
1814 This file must be an executable makefile, and contains the
1815 package-specific recipes for compiling the package and
1816 building binary package(s) from the source.
1820 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1821 so that it can be invoked by saying its name rather than
1822 invoking <prgn>make</prgn> explicitly. That is, invoking
1823 either of <tt>make -f debian/rules <em>args...</em></tt>
1824 or <tt>./debian/rules <em>args...</em></tt> must result in
1829 The following targets are required and must be implemented
1830 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1831 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1832 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1836 Since an interactive <file>debian/rules</file> script makes it
1837 impossible to auto-compile that package and also makes it hard
1838 for other people to reproduce the same binary package, all
1839 required targets must be non-interactive. It also follows that
1840 any target that these targets depend on must also be
1845 The targets are as follows:
1847 <tag><tt>build</tt> (required)</tag>
1850 The <tt>build</tt> target should perform all the
1851 configuration and compilation of the package.
1852 If a package has an interactive pre-build
1853 configuration routine, the Debian source package
1854 must either be built after this has taken place (so
1855 that the binary package can be built without rerunning
1856 the configuration) or the configuration routine
1857 modified to become non-interactive. (The latter is
1858 preferable if there are architecture-specific features
1859 detected by the configuration routine.)
1863 For some packages, notably ones where the same
1864 source tree is compiled in different ways to produce
1865 two binary packages, the <tt>build</tt> target
1866 does not make much sense. For these packages it is
1867 good enough to provide two (or more) targets
1868 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1869 for each of the ways of building the package, and a
1870 <tt>build</tt> target that does nothing. The
1871 <tt>binary</tt> target will have to build the
1872 package in each of the possible ways and make the
1873 binary package out of each.
1877 The <tt>build</tt> target must not do anything
1878 that might require root privilege.
1882 The <tt>build</tt> target may need to run the
1883 <tt>clean</tt> target first - see below.
1887 When a package has a configuration and build routine
1888 which takes a long time, or when the makefiles are
1889 poorly designed, or when <tt>build</tt> needs to
1890 run <tt>clean</tt> first, it is a good idea to
1891 <tt>touch build</tt> when the build process is
1892 complete. This will ensure that if <tt>debian/rules
1893 build</tt> is run again it will not rebuild the whole
1895 Another common way to do this is for <tt>build</tt>
1896 to depend on <prgn>build-stamp</prgn> and to do
1897 nothing else, and for the <prgn>build-stamp</prgn>
1898 target to do the building and to <tt>touch
1899 build-stamp</tt> on completion. This is
1900 especially useful if the build routine creates a
1901 file or directory called <tt>build</tt>; in such a
1902 case, <tt>build</tt> will need to be listed as
1903 a phony target (i.e., as a dependency of the
1904 <tt>.PHONY</tt> target). See the documentation of
1905 <prgn>make</prgn> for more information on phony
1911 <tag><tt>build-arch</tt> (optional),
1912 <tt>build-indep</tt> (optional)
1916 A package may also provide both of the targets
1917 <tt>build-arch</tt> and <tt>build-indep</tt>.
1918 The <tt>build-arch</tt> target, if provided, should
1919 perform all the configuration and compilation required for
1920 producing all architecture-dependant binary packages
1921 (those packages for which the body of the
1922 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1923 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1924 target, if provided, should perform all the configuration
1925 and compilation required for producing all
1926 architecture-independent binary packages (those packages
1927 for which the body of the <tt>Architecture</tt> field
1928 in <tt>debian/control</tt> is <tt>all</tt>).
1929 The <tt>build</tt> target should depend on those of the
1930 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1931 are provided in the rules file.<footnote>
1932 The intent of this split is so that binary-only builds
1933 need not install the dependencies required for
1934 the <tt>build-indep</tt> target. However, this is not
1935 yet used in practice since <tt>dpkg-buildpackage
1936 -B</tt>, and therefore the autobuilders,
1937 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1938 due to the difficulties in determining whether the
1939 optional <tt>build-arch</tt> target exists.
1944 If one or both of the targets <tt>build-arch</tt> and
1945 <tt>build-indep</tt> are not provided, then invoking
1946 <file>debian/rules</file> with one of the not-provided
1947 targets as arguments should produce a exit status code
1948 of 2. Usually this is provided automatically by make
1949 if the target is missing.
1953 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1954 must not do anything that might require root privilege.
1958 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1959 (required), <tt>binary-indep</tt> (required)
1963 The <tt>binary</tt> target must be all that is
1964 necessary for the user to build the binary package(s)
1965 produced from this source package. It is
1966 split into two parts: <prgn>binary-arch</prgn> builds
1967 the binary packages which are specific to a particular
1968 architecture, and <tt>binary-indep</tt> builds
1969 those which are not.
1972 <tt>binary</tt> may be (and commonly is) a target with
1973 no commands which simply depends on
1974 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1977 Both <tt>binary-*</tt> targets should depend on the
1978 <tt>build</tt> target, or on the appropriate
1979 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1980 provided, so that the package is built if it has not
1981 been already. It should then create the relevant
1982 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1983 make their control files and <prgn>dpkg-deb</prgn> to
1984 build them and place them in the parent of the top
1989 Both the <tt>binary-arch</tt> and
1990 <tt>binary-indep</tt> targets <em>must</em> exist.
1991 If one of them has nothing to do (which will always be
1992 the case if the source generates only a single binary
1993 package, whether architecture-dependent or not), it
1994 must still exist and must always succeed.
1998 The <tt>binary</tt> targets must be invoked as
2000 The <prgn>fakeroot</prgn> package often allows one
2001 to build a package correctly even without being
2007 <tag><tt>clean</tt> (required)</tag>
2010 This must undo any effects that the <tt>build</tt>
2011 and <tt>binary</tt> targets may have had, except
2012 that it should leave alone any output files created in
2013 the parent directory by a run of a <tt>binary</tt>
2018 If a <tt>build</tt> file is touched at the end of
2019 the <tt>build</tt> target, as suggested above, it
2020 should be removed as the first action that
2021 <tt>clean</tt> performs, so that running
2022 <tt>build</tt> again after an interrupted
2023 <tt>clean</tt> doesn't think that everything is
2028 The <tt>clean</tt> target may need to be
2029 invoked as root if <tt>binary</tt> has been
2030 invoked since the last <tt>clean</tt>, or if
2031 <tt>build</tt> has been invoked as root (since
2032 <tt>build</tt> may create directories, for
2037 <tag><tt>get-orig-source</tt> (optional)</tag>
2040 This target fetches the most recent version of the
2041 original source package from a canonical archive site
2042 (via FTP or WWW, for example), does any necessary
2043 rearrangement to turn it into the original source
2044 tar file format described below, and leaves it in the
2049 This target may be invoked in any directory, and
2050 should take care to clean up any temporary files it
2055 This target is optional, but providing it if
2056 possible is a good idea.
2060 <tag><tt>patch</tt> (optional)</tag>
2063 This target performs whatever additional actions are
2064 required to make the source ready for editing (unpacking
2065 additional upstream archives, applying patches, etc.).
2066 It is recommended to be implemented for any package where
2067 <tt>dpkg-source -x</tt> does not result in source ready
2068 for additional modification. See
2069 <ref id="readmesource">.
2075 The <tt>build</tt>, <tt>binary</tt> and
2076 <tt>clean</tt> targets must be invoked with the current
2077 directory being the package's top-level directory.
2082 Additional targets may exist in <file>debian/rules</file>,
2083 either as published or undocumented interfaces or for the
2084 package's internal use.
2088 The architectures we build on and build for are determined
2089 by <prgn>make</prgn> variables using the
2090 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2091 You can determine the Debian architecture and the GNU style
2092 architecture specification string for the build architecture as
2093 well as for the host architecture. The build architecture is
2094 the architecture on which <file>debian/rules</file> is run and
2095 the package build is performed. The host architecture is the
2096 architecture on which the resulting package will be installed
2097 and run. These are normally the same, but may be different in
2098 the case of cross-compilation (building packages for one
2099 architecture on machines of a different architecture).
2103 Here is a list of supported <prgn>make</prgn> variables:
2104 <list compact="compact">
2106 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2109 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2112 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2115 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2116 specification string)
2119 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2120 <tt>DEB_*_GNU_TYPE</tt>)
2123 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2124 <tt>DEB_*_GNU_TYPE</tt>)
2126 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2127 the build architecture or <tt>HOST</tt> for specification of the
2132 Backward compatibility can be provided in the rules file
2133 by setting the needed variables to suitable default
2134 values; please refer to the documentation of
2135 <prgn>dpkg-architecture</prgn> for details.
2139 It is important to understand that the <tt>DEB_*_ARCH</tt>
2140 string only determines which Debian architecture we are
2141 building on or for. It should not be used to get the CPU
2142 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2143 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2144 GNU style variables should generally only be used with upstream
2148 <sect1 id="debianrules-options">
2149 <heading><file>debian/rules</file> and
2150 <tt>DEB_BUILD_OPTIONS</tt></heading>
2153 Supporting the standardized environment variable
2154 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2155 contain several flags to change how a package is compiled and
2156 built. Each flag must be in the form <var>flag</var> or
2157 <var>flag</var>=<var>options</var>. If multiple flags are
2158 given, they must be separated by whitespace.<footnote>
2159 Some packages support any delimiter, but whitespace is the
2160 easiest to parse inside a makefile and avoids ambiguity with
2161 flag values that contain commas.
2163 <var>flag</var> must start with a lowercase letter
2164 (<tt>a-z</tt>) and consist only of lowercase letters,
2165 numbers (<tt>0-9</tt>), and the characters
2166 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2167 <var>options</var> must not contain whitespace. The same
2168 tag should not be given multiple times with conflicting
2169 values. Package maintainers may assume that
2170 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2174 The meaning of the following tags has been standardized:
2178 This tag says to not run any build-time test suite
2179 provided by the package.
2183 The presence of this tag means that the package should
2184 be compiled with a minimum of optimization. For C
2185 programs, it is best to add <tt>-O0</tt> to
2186 <tt>CFLAGS</tt> (although this is usually the default).
2187 Some programs might fail to build or run at this level
2188 of optimization; it may be necessary to use
2189 <tt>-O1</tt>, for example.
2193 This tag means that the debugging symbols should not be
2194 stripped from the binary during installation, so that
2195 debugging information may be included in the package.
2197 <tag>parallel=n</tag>
2199 This tag means that the package should be built using up
2200 to <tt>n</tt> parallel processes if the package build
2201 system supports this.<footnote>
2202 Packages built with <tt>make</tt> can often implement
2203 this by passing the <tt>-j</tt><var>n</var> option to
2206 If the package build system does not support parallel
2207 builds, this string must be ignored. If the package
2208 build system only supports a lower level of concurrency
2209 than <var>n</var>, the package should be built using as
2210 many parallel processes as the package build system
2211 supports. It is up to the package maintainer to decide
2212 whether the package build times are long enough and the
2213 package build system is robust enough to make supporting
2214 parallel builds worthwhile.
2220 Unknown flags must be ignored by <file>debian/rules</file>.
2224 The following makefile snippet is an example of how one may
2225 implement the build options; you will probably have to
2226 massage this example in order to make it work for your
2228 <example compact="compact">
2231 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2232 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2233 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2234 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2236 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2241 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2242 INSTALL_PROGRAM += -s
2244 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2245 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2246 MAKEFLAGS += -j$(NUMJOBS)
2251 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2252 # Code to run the package test suite.
2259 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2260 <sect id="substvars">
2261 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2264 When <prgn>dpkg-gencontrol</prgn>
2265 generates <qref id="binarycontrolfiles">binary package control
2266 files</qref> (<file>DEBIAN/control</file>), it performs variable
2267 substitutions on its output just before writing it. Variable
2268 substitutions have the form <tt>${<var>variable</var>}</tt>.
2269 The optional file <file>debian/substvars</file> contains
2270 variable substitutions to be used; variables can also be set
2271 directly from <file>debian/rules</file> using the <tt>-V</tt>
2272 option to the source packaging commands, and certain predefined
2273 variables are also available.
2277 The <file>debian/substvars</file> file is usually generated and
2278 modified dynamically by <file>debian/rules</file> targets, in
2279 which case it must be removed by the <tt>clean</tt> target.
2283 See <manref name="deb-substvars" section="5"> for full
2284 details about source variable substitutions, including the
2285 format of <file>debian/substvars</file>.</p>
2288 <sect id="debianwatch">
2289 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2292 This is an optional, recommended configuration file for the
2293 <tt>uscan</tt> utility which defines how to automatically scan
2294 ftp or http sites for newly available updates of the
2295 package. This is used
2296 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2297 tools to help with quality control and maintenance of the
2298 distribution as a whole.
2303 <sect id="debianfiles">
2304 <heading>Generated files list: <file>debian/files</file></heading>
2307 This file is not a permanent part of the source tree; it
2308 is used while building packages to record which files are
2309 being generated. <prgn>dpkg-genchanges</prgn> uses it
2310 when it generates a <file>.changes</file> file.
2314 It should not exist in a shipped source package, and so it
2315 (and any backup files or temporary files such as
2316 <file>files.new</file><footnote>
2317 <file>files.new</file> is used as a temporary file by
2318 <prgn>dpkg-gencontrol</prgn> and
2319 <prgn>dpkg-distaddfile</prgn> - they write a new
2320 version of <tt>files</tt> here before renaming it,
2321 to avoid leaving a corrupted copy if an error
2323 </footnote>) should be removed by the
2324 <tt>clean</tt> target. It may also be wise to
2325 ensure a fresh start by emptying or removing it at the
2326 start of the <tt>binary</tt> target.
2330 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2331 package, it adds an entry to <file>debian/files</file> for the
2332 <file>.deb</file> file that will be created when <tt>dpkg-deb
2333 --build</tt> is run for that binary package. So for most
2334 packages all that needs to be done with this file is to
2335 delete it in the <tt>clean</tt> target.
2339 If a package upload includes files besides the source
2340 package and any binary packages whose control files were
2341 made with <prgn>dpkg-gencontrol</prgn> then they should be
2342 placed in the parent of the package's top-level directory
2343 and <prgn>dpkg-distaddfile</prgn> should be called to add
2344 the file to the list in <file>debian/files</file>.</p>
2347 <sect id="embeddedfiles">
2348 <heading>Convenience copies of code</heading>
2351 Some software packages include in their distribution convenience
2352 copies of code from other software packages, generally so that
2353 users compiling from source don't have to download multiple
2354 packages. Debian packages should not make use of these
2355 convenience copies unless the included package is explicitly
2356 intended to be used in this way.<footnote>
2357 For example, parts of the GNU build system work like this.
2359 If the included code is already in the Debian archive in the
2360 form of a library, the Debian packaging should ensure that
2361 binary packages reference the libraries already in Debian and
2362 the convenience copy is not used. If the included code is not
2363 already in Debian, it should be packaged separately as a
2364 prerequisite if possible.
2366 Having multiple copies of the same code in Debian is
2367 inefficient, often creates either static linking or shared
2368 library conflicts, and, most importantly, increases the
2369 difficulty of handling security vulnerabilities in the
2375 <sect id="readmesource">
2376 <heading>Source package handling:
2377 <file>debian/README.source</file></heading>
2380 If running <prgn>dpkg-source -x</prgn> on a source package
2381 doesn't produce the source of the package, ready for editing,
2382 and allow one to make changes and run
2383 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2384 without taking any additional steps, creating a
2385 <file>debian/README.source</file> documentation file is
2386 recommended. This file should explain how to do all of the
2389 <item>Generate the fully patched source, in a form ready for
2390 editing, that would be built to create Debian
2391 packages. Doing this with a <tt>patch</tt> target in
2392 <file>debian/rules</file> is recommended; see
2393 <ref id="debianrules">.</item>
2394 <item>Modify the source and save those modifications so that
2395 they will be applied when building the package.</item>
2396 <item>Remove source modifications that are currently being
2397 applied when building the package.</item>
2398 <item>Optionally, document what steps are necessary to
2399 upgrade the Debian source package to a new upstream version,
2400 if applicable.</item>
2402 This explanation should include specific commands and mention
2403 any additional required Debian packages. It should not assume
2404 familiarity with any specific Debian packaging system or patch
2409 This explanation may refer to a documentation file installed by
2410 one of the package's build dependencies provided that the
2411 referenced documentation clearly explains these tasks and is not
2412 a general reference manual.
2416 <file>debian/README.source</file> may also include any other
2417 information that would be helpful to someone modifying the
2418 source package. Even if the package doesn't fit the above
2419 description, maintainers are encouraged to document in a
2420 <file>debian/README.source</file> file any source package with a
2421 particularly complex or unintuitive source layout or build
2422 system (for example, a package that builds the same source
2423 multiple times to generate different binary packages).
2429 <chapt id="controlfields">
2430 <heading>Control files and their fields</heading>
2433 The package management system manipulates data represented in
2434 a common format, known as <em>control data</em>, stored in
2435 <em>control files</em>.
2436 Control files are used for source packages, binary packages and
2437 the <file>.changes</file> files which control the installation
2438 of uploaded files<footnote>
2439 <prgn>dpkg</prgn>'s internal databases are in a similar
2444 <sect id="controlsyntax">
2445 <heading>Syntax of control files</heading>
2448 A control file consists of one or more paragraphs of
2450 The paragraphs are also sometimes referred to as stanzas.
2452 The paragraphs are separated by blank lines. Some control
2453 files allow only one paragraph; others allow several, in
2454 which case each paragraph usually refers to a different
2455 package. (For example, in source packages, the first
2456 paragraph refers to the source package, and later paragraphs
2457 refer to binary packages generated from the source.)
2461 Each paragraph consists of a series of data fields; each
2462 field consists of the field name, followed by a colon and
2463 then the data/value associated with that field. It ends at
2464 the end of the (logical) line. Horizontal whitespace
2465 (spaces and tabs) may occur immediately before or after the
2466 value and is ignored there; it is conventional to put a
2467 single space after the colon. For example, a field might
2469 <example compact="compact">
2472 the field name is <tt>Package</tt> and the field value
2477 A paragraph must not contain more than one instance of a
2478 particular field name.
2482 Many fields' values may span several lines; in this case
2483 each continuation line must start with a space or a tab.
2484 Any trailing spaces or tabs at the end of individual
2485 lines of a field value are ignored.
2489 In fields where it is specified that lines may not wrap,
2490 only a single line of data is allowed and whitespace is not
2491 significant in a field body. Whitespace must not appear
2492 inside names (of packages, architectures, files or anything
2493 else) or version numbers, or between the characters of
2494 multi-character version relationships.
2498 Field names are not case-sensitive, but it is usual to
2499 capitalize the field names using mixed case as shown below.
2500 Field values are case-sensitive unless the description of the
2501 field says otherwise.
2505 Blank lines, or lines consisting only of spaces and tabs,
2506 are not allowed within field values or between fields - that
2507 would mean a new paragraph.
2511 All control files must be encoded in UTF-8.
2515 <sect id="sourcecontrolfiles">
2516 <heading>Source package control files -- <file>debian/control</file></heading>
2519 The <file>debian/control</file> file contains the most vital
2520 (and version-independent) information about the source package
2521 and about the binary packages it creates.
2525 The first paragraph of the control file contains information about
2526 the source package in general. The subsequent sets each describe a
2527 binary package that the source tree builds.
2531 The fields in the general paragraph (the first one, for the source
2534 <list compact="compact">
2535 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2538 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2539 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2540 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2541 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2542 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2547 The fields in the binary package paragraphs are:
2549 <list compact="compact">
2550 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2553 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2554 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2555 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2556 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2562 The syntax and semantics of the fields are described below.
2566 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2567 generate control files for binary packages (see below), by
2568 <prgn>dpkg-genchanges</prgn> to generate the
2569 <file>.changes</file> file to accompany the upload, and by
2570 <prgn>dpkg-source</prgn> when it creates the
2571 <file>.dsc</file> source control file as part of a source
2572 archive. Many fields are permitted to span multiple lines in
2573 <file>debian/control</file> but not in any other control
2574 file. These tools are responsible for removing the line
2575 breaks from such fields when using fields from
2576 <file>debian/control</file> to generate other control files.
2580 The fields here may contain variable references - their
2581 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2582 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2583 when they generate output control files.
2584 See <ref id="substvars"> for details.
2588 In addition to the control file syntax described <qref
2589 id="controlsyntax">above</qref>, this file may also contain
2590 comment lines starting with <tt>#</tt> without any preceding
2591 whitespace. All such lines are ignored, even in the middle of
2592 continuation lines for a multiline field, and do not end a
2598 <sect id="binarycontrolfiles">
2599 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2602 The <file>DEBIAN/control</file> file contains the most vital
2603 (and version-dependent) information about a binary package. It
2604 consists of a single paragraph.
2608 The fields in this file are:
2610 <list compact="compact">
2611 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2613 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2614 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2615 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2616 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2618 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2619 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2620 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2627 <sect id="debiansourcecontrolfiles">
2628 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2631 This file consists of a single paragraph, possibly surrounded by
2632 a PGP signature. The fields of that paragraph are listed below.
2633 Their syntax is described above, in <ref id="pkg-controlfields">.
2635 <list compact="compact">
2636 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2637 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2639 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2640 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2641 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2643 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2644 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2645 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2646 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2647 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2648 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2653 The source package control file is generated by
2654 <prgn>dpkg-source</prgn> when it builds the source
2655 archive, from other files in the source package,
2656 described above. When unpacking, it is checked against
2657 the files and directories in the other parts of the
2663 <sect id="debianchangesfiles">
2664 <heading>Debian changes files -- <file>.changes</file></heading>
2667 The <file>.changes</file> files are used by the Debian archive
2668 maintenance software to process updates to packages. They
2669 consist of a single paragraph, possibly surrounded by a PGP
2670 signature. That paragraph contains information from the
2671 <file>debian/control</file> file and other data about the
2672 source package gathered via <file>debian/changelog</file>
2673 and <file>debian/rules</file>.
2677 <file>.changes</file> files have a format version that is
2678 incremented whenever the documented fields or their meaning
2679 change. This document describes format &changesversion;.
2683 The fields in this file are:
2685 <list compact="compact">
2686 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2692 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2694 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2696 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2698 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2700 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2701 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2706 <sect id="controlfieldslist">
2707 <heading>List of fields</heading>
2709 <sect1 id="f-Source">
2710 <heading><tt>Source</tt></heading>
2713 This field identifies the source package name.
2717 In <file>debian/control</file> or a <file>.dsc</file> file,
2718 this field must contain only the name of the source package.
2722 In a binary package control file or a <file>.changes</file>
2723 file, the source package name may be followed by a version
2724 number in parentheses<footnote>
2725 It is customary to leave a space after the package name
2726 if a version number is specified.
2728 This version number may be omitted (and is, by
2729 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2730 the <tt>Version</tt> field of the binary package in
2731 question. The field itself may be omitted from a binary
2732 package control file when the source package has the same
2733 name and version as the binary package.
2737 Package names (both source and binary,
2738 see <ref id="f-Package">) must consist only of lower case
2739 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2740 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2741 (<tt>.</tt>). They must be at least two characters long and
2742 must start with an alphanumeric character.
2746 <sect1 id="f-Maintainer">
2747 <heading><tt>Maintainer</tt></heading>
2750 The package maintainer's name and email address. The name
2751 must come first, then the email address inside angle
2752 brackets <tt><></tt> (in RFC822 format).
2756 If the maintainer's name contains a full stop then the
2757 whole field will not work directly as an email address due
2758 to a misfeature in the syntax specified in RFC822; a
2759 program using this field as an address must check for this
2760 and correct the problem if necessary (for example by
2761 putting the name in round brackets and moving it to the
2762 end, and bringing the email address forward).
2766 See <ref id="maintainer"> for additional requirements and
2767 information about package maintainers.
2771 <sect1 id="f-Uploaders">
2772 <heading><tt>Uploaders</tt></heading>
2775 List of the names and email addresses of co-maintainers of the
2776 package, if any. If the package has other maintainers besides
2777 the one named in the <qref id="f-Maintainer">Maintainer
2778 field</qref>, their names and email addresses should be listed
2779 here. The format of each entry is the same as that of the
2780 Maintainer field, and multiple entries must be comma
2785 This is normally an optional field, but if
2786 the <tt>Maintainer</tt> control field names a group of people
2787 and a shared email address, the <tt>Uploaders</tt> field must
2788 be present and must contain at least one human with their
2789 personal email address.
2793 Any parser that interprets the Uploaders field in
2794 <file>debian/control</file> must permit it to span multiple
2795 lines. Line breaks in an Uploaders field that spans multiple
2796 lines are not significant and the semantics of the field are
2797 the same as if the line breaks had not been present.
2801 <sect1 id="f-Changed-By">
2802 <heading><tt>Changed-By</tt></heading>
2805 The name and email address of the person who prepared this
2806 version of the package, usually a maintainer. The syntax is
2807 the same as for the <qref id="f-Maintainer">Maintainer
2812 <sect1 id="f-Section">
2813 <heading><tt>Section</tt></heading>
2816 This field specifies an application area into which the package
2817 has been classified. See <ref id="subsections">.
2821 When it appears in the <file>debian/control</file> file,
2822 it gives the value for the subfield of the same name in
2823 the <tt>Files</tt> field of the <file>.changes</file> file.
2824 It also gives the default for the same field in the binary
2829 <sect1 id="f-Priority">
2830 <heading><tt>Priority</tt></heading>
2833 This field represents how important it is that the user
2834 have the package installed. See <ref id="priorities">.
2838 When it appears in the <file>debian/control</file> file,
2839 it gives the value for the subfield of the same name in
2840 the <tt>Files</tt> field of the <file>.changes</file> file.
2841 It also gives the default for the same field in the binary
2846 <sect1 id="f-Package">
2847 <heading><tt>Package</tt></heading>
2850 The name of the binary package.
2854 Binary package names must follow the same syntax and
2855 restrictions as source package names. See <ref id="f-Source">
2860 <sect1 id="f-Architecture">
2861 <heading><tt>Architecture</tt></heading>
2864 Depending on context and the control file used, the
2865 <tt>Architecture</tt> field can include the following sets of
2869 A unique single word identifying a Debian machine
2870 architecture as described in <ref id="arch-spec">.
2873 An architecture wildcard identifying a set of Debian
2874 machine architectures, see <ref id="arch-wildcard-spec">.
2875 <tt>any</tt> matches all Debian machine architectures
2876 and is the most frequently used.
2879 <tt>all</tt>, which indicates an
2880 architecture-independent package.
2883 <tt>source</tt>, which indicates a source package.
2889 In the main <file>debian/control</file> file in the source
2890 package, this field may contain the special
2891 value <tt>all</tt>, the special architecture
2892 wildcard <tt>any</tt>, or a list of specific and wildcard
2893 architectures separated by spaces. If <tt>all</tt>
2894 or <tt>any</tt> appears, that value must be the entire
2895 contents of the field. Most packages will use
2896 either <tt>all</tt> or <tt>any</tt>.
2900 Specifying a specific list of architectures indicates that the
2901 source will build an architecture-dependent package only on
2902 architectures included in the list. Specifying a list of
2903 architecture wildcards indicates that the source will build an
2904 architecture-dependent package on only those architectures
2905 that match any of the specified architecture wildcards.
2906 Specifying a list of architectures or architecture wildcards
2907 other than <tt>any</tt> is for the minority of cases where a
2908 program is not portable or is not useful on some
2909 architectures. Where possible, the program should be made
2914 In the source package control file <file>.dsc</file>, this
2915 field may contain either the architecture
2916 wildcard <tt>any</tt> or a list of architectures and
2917 architecture wildcards separated by spaces. If a list is
2918 given, it may include (or consist solely of) the special
2919 value <tt>all</tt>. In other words, in <file>.dsc</file>
2920 files unlike the <file>debian/control</file>, <tt>all</tt> may
2921 occur in combination with specific architectures.
2922 The <tt>Architecture</tt> field in the source package control
2923 file <file>.dsc</file> is generally constructed from
2924 the <tt>Architecture</tt> fields in
2925 the <file>debian/control</file> in the source package.
2929 Specifying <tt>any</tt> indicates that the source package
2930 isn't dependent on any particular architecture and should
2931 compile fine on any one. The produced binary package(s)
2932 will either be specific to whatever the current build
2933 architecture is or will be architecture-independent.
2937 Specifying only <tt>all</tt> indicates that the source package
2938 will only build architecture-independent packages. If this is
2939 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2940 <tt>any</tt> implies that the source package will build at
2941 least one architecture-dependent package.
2945 Specifying a list of architectures or architecture wildcards
2946 indicates that the source will build an architecture-dependent
2947 package, and will only work correctly on the listed or
2948 matching architectures. If the source package also builds at
2949 least one architecture-independent package, <tt>all</tt> will
2950 also be included in the list.
2954 In a <file>.changes</file> file, the <tt>Architecture</tt>
2955 field lists the architecture(s) of the package(s) currently
2956 being uploaded. This will be a list; if the source for the
2957 package is also being uploaded, the special
2958 entry <tt>source</tt> is also present. <tt>all</tt> will be
2959 present if any architecture-independent packages are being
2960 uploaded. Architecture wildcards such as <tt>any</tt> must
2961 never occur in the <tt>Architecture</tt> field in
2962 the <file>.changes</file> file.
2966 See <ref id="debianrules"> for information on how to get
2967 the architecture for the build process.
2971 <sect1 id="f-Essential">
2972 <heading><tt>Essential</tt></heading>
2975 This is a boolean field which may occur only in the
2976 control file of a binary package or in a per-package fields
2977 paragraph of a main source control data file.
2981 If set to <tt>yes</tt> then the package management system
2982 will refuse to remove the package (upgrading and replacing
2983 it is still possible). The other possible value is <tt>no</tt>,
2984 which is the same as not having the field at all.
2989 <heading>Package interrelationship fields:
2990 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2991 <tt>Recommends</tt>, <tt>Suggests</tt>,
2992 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2993 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2997 These fields describe the package's relationships with
2998 other packages. Their syntax and semantics are described
2999 in <ref id="relationships">.</p>
3002 <sect1 id="f-Standards-Version">
3003 <heading><tt>Standards-Version</tt></heading>
3006 The most recent version of the standards (the policy
3007 manual and associated texts) with which the package
3012 The version number has four components: major and minor
3013 version number and major and minor patch level. When the
3014 standards change in a way that requires every package to
3015 change the major number will be changed. Significant
3016 changes that will require work in many packages will be
3017 signaled by a change to the minor number. The major patch
3018 level will be changed for any change to the meaning of the
3019 standards, however small; the minor patch level will be
3020 changed when only cosmetic, typographical or other edits
3021 are made which neither change the meaning of the document
3022 nor affect the contents of packages.
3026 Thus only the first three components of the policy version
3027 are significant in the <em>Standards-Version</em> control
3028 field, and so either these three components or all four
3029 components may be specified.<footnote>
3030 In the past, people specified the full version number
3031 in the Standards-Version field, for example "2.3.0.0".
3032 Since minor patch-level changes don't introduce new
3033 policy, it was thought it would be better to relax
3034 policy and only require the first 3 components to be
3035 specified, in this example "2.3.0". All four
3036 components may still be used if someone wishes to do so.
3042 <sect1 id="f-Version">
3043 <heading><tt>Version</tt></heading>
3046 The version number of a package. The format is:
3047 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3051 The three components here are:
3053 <tag><var>epoch</var></tag>
3056 This is a single (generally small) unsigned integer. It
3057 may be omitted, in which case zero is assumed. If it is
3058 omitted then the <var>upstream_version</var> may not
3063 It is provided to allow mistakes in the version numbers
3064 of older versions of a package, and also a package's
3065 previous version numbering schemes, to be left behind.
3069 <tag><var>upstream_version</var></tag>
3072 This is the main part of the version number. It is
3073 usually the version number of the original ("upstream")
3074 package from which the <file>.deb</file> file has been made,
3075 if this is applicable. Usually this will be in the same
3076 format as that specified by the upstream author(s);
3077 however, it may need to be reformatted to fit into the
3078 package management system's format and comparison
3083 The comparison behavior of the package management system
3084 with respect to the <var>upstream_version</var> is
3085 described below. The <var>upstream_version</var>
3086 portion of the version number is mandatory.
3090 The <var>upstream_version</var> may contain only
3091 alphanumerics<footnote>
3092 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3094 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3095 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3096 tilde) and should start with a digit. If there is no
3097 <var>debian_revision</var> then hyphens are not allowed;
3098 if there is no <var>epoch</var> then colons are not
3103 <tag><var>debian_revision</var></tag>
3106 This part of the version number specifies the version of
3107 the Debian package based on the upstream version. It
3108 may contain only alphanumerics and the characters
3109 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3110 tilde) and is compared in the same way as the
3111 <var>upstream_version</var> is.
3115 It is optional; if it isn't present then the
3116 <var>upstream_version</var> may not contain a hyphen.
3117 This format represents the case where a piece of
3118 software was written specifically to be a Debian
3119 package, where the Debian package source must always
3120 be identical to the pristine source and therefore no
3121 revision indication is required.
3125 It is conventional to restart the
3126 <var>debian_revision</var> at <tt>1</tt> each time the
3127 <var>upstream_version</var> is increased.
3131 The package management system will break the version
3132 number apart at the last hyphen in the string (if there
3133 is one) to determine the <var>upstream_version</var> and
3134 <var>debian_revision</var>. The absence of a
3135 <var>debian_revision</var> is equivalent to a
3136 <var>debian_revision</var> of <tt>0</tt>.
3143 When comparing two version numbers, first the <var>epoch</var>
3144 of each are compared, then the <var>upstream_version</var> if
3145 <var>epoch</var> is equal, and then <var>debian_revision</var>
3146 if <var>upstream_version</var> is also equal.
3147 <var>epoch</var> is compared numerically. The
3148 <var>upstream_version</var> and <var>debian_revision</var>
3149 parts are compared by the package management system using the
3150 following algorithm:
3154 The strings are compared from left to right.
3158 First the initial part of each string consisting entirely of
3159 non-digit characters is determined. These two parts (one of
3160 which may be empty) are compared lexically. If a difference
3161 is found it is returned. The lexical comparison is a
3162 comparison of ASCII values modified so that all the letters
3163 sort earlier than all the non-letters and so that a tilde
3164 sorts before anything, even the end of a part. For example,
3165 the following parts are in sorted order from earliest to
3166 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3167 <tt>a</tt>.<footnote>
3168 One common use of <tt>~</tt> is for upstream pre-releases.
3169 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3170 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3175 Then the initial part of the remainder of each string which
3176 consists entirely of digit characters is determined. The
3177 numerical values of these two parts are compared, and any
3178 difference found is returned as the result of the comparison.
3179 For these purposes an empty string (which can only occur at
3180 the end of one or both version strings being compared) counts
3185 These two steps (comparing and removing initial non-digit
3186 strings and initial digit strings) are repeated until a
3187 difference is found or both strings are exhausted.
3191 Note that the purpose of epochs is to allow us to leave behind
3192 mistakes in version numbering, and to cope with situations
3193 where the version numbering scheme changes. It is
3194 <em>not</em> intended to cope with version numbers containing
3195 strings of letters which the package management system cannot
3196 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3197 silly orderings.<footnote>
3198 The author of this manual has heard of a package whose
3199 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3200 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3206 <sect1 id="f-Description">
3207 <heading><tt>Description</tt></heading>
3210 In a source or binary control file, the <tt>Description</tt>
3211 field contains a description of the binary package, consisting
3212 of two parts, the synopsis or the short description, and the
3213 long description. The field's format is as follows:
3218 Description: <single line synopsis>
3219 <extended description over several lines>
3224 The lines in the extended description can have these formats:
3230 Those starting with a single space are part of a paragraph.
3231 Successive lines of this form will be word-wrapped when
3232 displayed. The leading space will usually be stripped off.
3236 Those starting with two or more spaces. These will be
3237 displayed verbatim. If the display cannot be panned
3238 horizontally, the displaying program will line wrap them "hard"
3239 (i.e., without taking account of word breaks). If it can they
3240 will be allowed to trail off to the right. None, one or two
3241 initial spaces may be deleted, but the number of spaces
3242 deleted from each line will be the same (so that you can have
3243 indenting work correctly, for example).
3247 Those containing a single space followed by a single full stop
3248 character. These are rendered as blank lines. This is the
3249 <em>only</em> way to get a blank line<footnote>
3250 Completely empty lines will not be rendered as blank lines.
3251 Instead, they will cause the parser to think you're starting
3252 a whole new record in the control file, and will therefore
3253 likely abort with an error.
3258 Those containing a space, a full stop and some more characters.
3259 These are for future expansion. Do not use them.
3265 Do not use tab characters. Their effect is not predictable.
3269 See <ref id="descriptions"> for further information on this.
3273 In a <file>.changes</file> file, the <tt>Description</tt>
3274 field contains a summary of the descriptions for the packages
3275 being uploaded. For this case, the first line of the field
3276 value (the part on the same line as <tt>Description:</tt>) is
3277 always empty. The content of the field is expressed as
3278 continuation lines, one line per package. Each line is
3279 indented by one space and contains the name of a binary
3280 package, a space, a hyphen (<tt>-</tt>), a space, and the
3281 short description line from that package.
3285 <sect1 id="f-Distribution">
3286 <heading><tt>Distribution</tt></heading>
3289 In a <file>.changes</file> file or parsed changelog output
3290 this contains the (space-separated) name(s) of the
3291 distribution(s) where this version of the package should
3292 be installed. Valid distributions are determined by the
3293 archive maintainers.<footnote>
3294 Example distribution names in the Debian archive used in
3295 <file>.changes</file> files are:
3296 <taglist compact="compact">
3297 <tag><em>unstable</em></tag>
3299 This distribution value refers to the
3300 <em>developmental</em> part of the Debian distribution
3301 tree. Most new packages, new upstream versions of
3302 packages and bug fixes go into the <em>unstable</em>
3306 <tag><em>experimental</em></tag>
3308 The packages with this distribution value are deemed
3309 by their maintainers to be high risk. Oftentimes they
3310 represent early beta or developmental packages from
3311 various sources that the maintainers want people to
3312 try, but are not ready to be a part of the other parts
3313 of the Debian distribution tree.
3318 Others are used for updating stable releases or for
3319 security uploads. More information is available in the
3320 Debian Developer's Reference, section "The Debian
3324 The Debian archive software only supports listing a single
3325 distribution. Migration of packages to other distributions is
3326 handled outside of the upload process.
3331 <heading><tt>Date</tt></heading>
3334 This field includes the date the package was built or last
3335 edited. It must be in the same format as the <var>date</var>
3336 in a <file>debian/changelog</file> entry.
3340 The value of this field is usually extracted from the
3341 <file>debian/changelog</file> file - see
3342 <ref id="dpkgchangelog">).
3346 <sect1 id="f-Format">
3347 <heading><tt>Format</tt></heading>
3350 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3351 files, this field declares the format version of that file.
3352 The syntax of the field value is the same as that of
3353 a <qref id="f-Version">package version number</qref> except
3354 that no epoch or Debian revision is allowed. The format
3355 described in this document is <tt>&changesversion;</tt>.
3359 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3360 Debian source control</qref> files, this field declares the
3361 format of the source package. The field value is used by
3362 programs acting on a source package to interpret the list of
3363 files in the source package and determine how to unpack it.
3364 The syntax of the field value is a numeric major revision, a
3365 period, a numeric minor revision, and then an optional subtype
3366 after whitespace, which if specified is an alphanumeric word
3367 in parentheses. The subtype is optional in the syntax but may
3368 be mandatory for particular source format revisions.
3370 The source formats currently supported by the Debian archive
3371 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3372 and <tt>3.0 (quilt)</tt>.
3377 <sect1 id="f-Urgency">
3378 <heading><tt>Urgency</tt></heading>
3381 This is a description of how important it is to upgrade to
3382 this version from previous ones. It consists of a single
3383 keyword taking one of the values <tt>low</tt>,
3384 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3385 <tt>critical</tt><footnote>
3386 Other urgency values are supported with configuration
3387 changes in the archive software but are not used in Debian.
3388 The urgency affects how quickly a package will be considered
3389 for inclusion into the <tt>testing</tt> distribution and
3390 gives an indication of the importance of any fixes included
3391 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3392 treated as synonymous.
3393 </footnote> (not case-sensitive) followed by an optional
3394 commentary (separated by a space) which is usually in
3395 parentheses. For example:
3398 Urgency: low (HIGH for users of diversions)
3404 The value of this field is usually extracted from the
3405 <file>debian/changelog</file> file - see
3406 <ref id="dpkgchangelog">.
3410 <sect1 id="f-Changes">
3411 <heading><tt>Changes</tt></heading>
3414 This field contains the human-readable changes data, describing
3415 the differences between the last version and the current one.
3419 The first line of the field value (the part on the same line
3420 as <tt>Changes:</tt>) is always empty. The content of the
3421 field is expressed as continuation lines, with each line
3422 indented by at least one space. Blank lines must be
3423 represented by a line consisting only of a space and a full
3428 The value of this field is usually extracted from the
3429 <file>debian/changelog</file> file - see
3430 <ref id="dpkgchangelog">).
3434 Each version's change information should be preceded by a
3435 "title" line giving at least the version, distribution(s)
3436 and urgency, in a human-readable way.
3440 If data from several versions is being returned the entry
3441 for the most recent version should be returned first, and
3442 entries should be separated by the representation of a
3443 blank line (the "title" line may also be followed by the
3444 representation of a blank line).
3448 <sect1 id="f-Binary">
3449 <heading><tt>Binary</tt></heading>
3452 This field is a list of binary packages. Its syntax and
3453 meaning varies depending on the control file in which it
3458 When it appears in the <file>.dsc</file> file, it lists binary
3459 packages which a source package can produce, separated by
3461 A space after each comma is conventional.
3462 </footnote>. It may span multiple lines. The source package
3463 does not necessarily produce all of these binary packages for
3464 every architecture. The source control file doesn't contain
3465 details of which architectures are appropriate for which of
3466 the binary packages.
3470 When it appears in a <file>.changes</file> file, it lists the
3471 names of the binary packages being uploaded, separated by
3472 whitespace (not commas). It may span multiple lines.
3476 <sect1 id="f-Installed-Size">
3477 <heading><tt>Installed-Size</tt></heading>
3480 This field appears in the control files of binary packages,
3481 and in the <file>Packages</file> files. It gives an estimate
3482 of the total amount of disk space required to install the
3483 named package. Actual installed size may vary based on block
3484 size, file system properties, or actions taken by package
3489 The disk space is given as the integer value of the estimated
3490 installed size in bytes, divided by 1024 and rounded up.
3494 <sect1 id="f-Files">
3495 <heading><tt>Files</tt></heading>
3498 This field contains a list of files with information about
3499 each one. The exact information and syntax varies with
3504 In all cases, Files is a multiline field. The first line of
3505 the field value (the part on the same line as <tt>Files:</tt>)
3506 is always empty. The content of the field is expressed as
3507 continuation lines, one line per file. Each line must be
3508 indented by one space and contain a number of sub-fields,
3509 separated by spaces, as described below.
3513 In the <file>.dsc</file> file, each line contains the MD5
3514 checksum, size and filename of the tar file and (if
3515 applicable) diff file which make up the remainder of the
3516 source package<footnote>
3517 That is, the parts which are not the <tt>.dsc</tt>.
3518 </footnote>. For example:
3521 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3522 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3524 The exact forms of the filenames are described
3525 in <ref id="pkg-sourcearchives">.
3529 In the <file>.changes</file> file this contains one line per
3530 file being uploaded. Each line contains the MD5 checksum,
3531 size, section and priority and the filename. For example:
3534 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3535 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3536 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3537 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3539 The <qref id="f-Section">section</qref>
3540 and <qref id="f-Priority">priority</qref> are the values of
3541 the corresponding fields in the main source control file. If
3542 no section or priority is specified then <tt>-</tt> should be
3543 used, though section and priority values must be specified for
3544 new packages to be installed properly.
3548 The special value <tt>byhand</tt> for the section in a
3549 <tt>.changes</tt> file indicates that the file in question
3550 is not an ordinary package file and must by installed by
3551 hand by the distribution maintainers. If the section is
3552 <tt>byhand</tt> the priority should be <tt>-</tt>.
3556 If a new Debian revision of a package is being shipped and
3557 no new original source archive is being distributed the
3558 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3559 entry for the original source archive
3560 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3561 but the <file>.changes</file> file should leave it out. In
3562 this case the original source archive on the distribution
3563 site must match exactly, byte-for-byte, the original
3564 source archive which was used to generate the
3565 <file>.dsc</file> file and diff which are being uploaded.</p>
3568 <sect1 id="f-Closes">
3569 <heading><tt>Closes</tt></heading>
3572 A space-separated list of bug report numbers that the upload
3573 governed by the .changes file closes.
3577 <sect1 id="f-Homepage">
3578 <heading><tt>Homepage</tt></heading>
3581 The URL of the web site for this package, preferably (when
3582 applicable) the site from which the original source can be
3583 obtained and any additional upstream documentation or
3584 information may be found. The content of this field is a
3585 simple URL without any surrounding characters such as
3590 <sect1 id="f-Checksums">
3591 <heading><tt>Checksums-Sha1</tt>
3592 and <tt>Checksums-Sha256</tt></heading>
3595 These fields contain a list of files with a checksum and size
3596 for each one. Both <tt>Checksums-Sha1</tt>
3597 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3598 only in the checksum algorithm used: SHA-1
3599 for <tt>Checksums-Sha1</tt> and SHA-256
3600 for <tt>Checksums-Sha256</tt>.
3604 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3605 multiline fields. The first line of the field value (the part
3606 on the same line as <tt>Checksums-Sha1:</tt>
3607 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3608 of the field is expressed as continuation lines, one line per
3609 file. Each line consists of the checksum, a space, the file
3610 size, a space, and the file name. For example (from
3611 a <file>.changes</file> file):
3614 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3615 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3616 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3617 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3619 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3620 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3621 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3622 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3627 In the <file>.dsc</file> file, these fields should list all
3628 files that make up the source package. In
3629 the <file>.changes</file> file, these fields should list all
3630 files being uploaded. The list of files in these fields
3631 must match the list of files in the <tt>Files</tt> field.
3637 <heading>User-defined fields</heading>
3640 Additional user-defined fields may be added to the
3641 source package control file. Such fields will be
3642 ignored, and not copied to (for example) binary or
3643 source package control files or upload control files.
3647 If you wish to add additional unsupported fields to
3648 these output files you should use the mechanism
3653 Fields in the main source control information file with
3654 names starting <tt>X</tt>, followed by one or more of
3655 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3656 be copied to the output files. Only the part of the
3657 field name after the hyphen will be used in the output
3658 file. Where the letter <tt>B</tt> is used the field
3659 will appear in binary package control files, where the
3660 letter <tt>S</tt> is used in source package control
3661 files and where <tt>C</tt> is used in upload control
3662 (<tt>.changes</tt>) files.
3666 For example, if the main source information control file
3669 XBS-Comment: I stand between the candle and the star.
3671 then the binary and source package control files will contain the
3674 Comment: I stand between the candle and the star.
3683 <chapt id="maintainerscripts">
3684 <heading>Package maintainer scripts and installation procedure</heading>
3687 <heading>Introduction to package maintainer scripts</heading>
3690 It is possible to supply scripts as part of a package which
3691 the package management system will run for you when your
3692 package is installed, upgraded or removed.
3696 These scripts are the control information
3697 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3698 and <prgn>postrm</prgn>. They must be proper executable files;
3699 if they are scripts (which is recommended), they must start with
3700 the usual <tt>#!</tt> convention. They should be readable and
3701 executable by anyone, and must not be world-writable.
3705 The package management system looks at the exit status from
3706 these scripts. It is important that they exit with a
3707 non-zero status if there is an error, so that the package
3708 management system can stop its processing. For shell
3709 scripts this means that you <em>almost always</em> need to
3710 use <tt>set -e</tt> (this is usually true when writing shell
3711 scripts, in fact). It is also important, of course, that
3712 they exit with a zero status if everything went well.
3716 Additionally, packages interacting with users
3717 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3718 should install a <prgn>config</prgn> script as a control
3719 information file. See <ref id="maintscriptprompt"> for details.
3723 When a package is upgraded a combination of the scripts from
3724 the old and new packages is called during the upgrade
3725 procedure. If your scripts are going to be at all
3726 complicated you need to be aware of this, and may need to
3727 check the arguments to your scripts.
3731 Broadly speaking the <prgn>preinst</prgn> is called before
3732 (a particular version of) a package is installed, and the
3733 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3734 before (a version of) a package is removed and the
3735 <prgn>postrm</prgn> afterwards.
3739 Programs called from maintainer scripts should not normally
3740 have a path prepended to them. Before installation is
3741 started, the package management system checks to see if the
3742 programs <prgn>ldconfig</prgn>,
3743 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3744 and <prgn>update-rc.d</prgn> can be found via the
3745 <tt>PATH</tt> environment variable. Those programs, and any
3746 other program that one would expect to be in the
3747 <tt>PATH</tt>, should thus be invoked without an absolute
3748 pathname. Maintainer scripts should also not reset the
3749 <tt>PATH</tt>, though they might choose to modify it by
3750 prepending or appending package-specific directories. These
3751 considerations really apply to all shell scripts.</p>
3754 <sect id="idempotency">
3755 <heading>Maintainer scripts idempotency</heading>
3758 It is necessary for the error recovery procedures that the
3759 scripts be idempotent. This means that if it is run
3760 successfully, and then it is called again, it doesn't bomb
3761 out or cause any harm, but just ensures that everything is
3762 the way it ought to be. If the first call failed, or
3763 aborted half way through for some reason, the second call
3764 should merely do the things that were left undone the first
3765 time, if any, and exit with a success status if everything
3767 This is so that if an error occurs, the user interrupts
3768 <prgn>dpkg</prgn> or some other unforeseen circumstance
3769 happens you don't leave the user with a badly-broken
3770 package when <prgn>dpkg</prgn> attempts to repeat the
3776 <sect id="controllingterminal">
3777 <heading>Controlling terminal for maintainer scripts</heading>
3780 Maintainer scripts are not guaranteed to run with a controlling
3781 terminal and may not be able to interact with the user. They
3782 must be able to fall back to noninteractive behavior if no
3783 controlling terminal is available. Maintainer scripts that
3784 prompt via a program conforming to the Debian Configuration
3785 Management Specification (see <ref id="maintscriptprompt">) may
3786 assume that program will handle falling back to noninteractive
3791 For high-priority prompts without a reasonable default answer,
3792 maintainer scripts may abort if there is no controlling
3793 terminal. However, this situation should be avoided if at all
3794 possible, since it prevents automated or unattended installs.
3795 In most cases, users will consider this to be a bug in the
3800 <sect id="exitstatus">
3801 <heading>Exit status</heading>
3804 Each script must return a zero exit status for
3805 success, or a nonzero one for failure, since the package
3806 management system looks for the exit status of these scripts
3807 and determines what action to take next based on that datum.
3811 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3816 <list compact="compact">
3818 <var>new-preinst</var> <tt>install</tt>
3821 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3824 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3827 <var>old-preinst</var> <tt>abort-upgrade</tt>
3828 <var>new-version</var>
3833 <list compact="compact">
3835 <var>postinst</var> <tt>configure</tt>
3836 <var>most-recently-configured-version</var>
3839 <var>old-postinst</var> <tt>abort-upgrade</tt>
3840 <var>new-version</var>
3843 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3844 <tt>in-favour</tt> <var>package</var>
3845 <var>new-version</var>
3848 <var>postinst</var> <tt>abort-remove</tt>
3851 <var>deconfigured's-postinst</var>
3852 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3853 <var>failed-install-package</var> <var>version</var>
3854 [<tt>removing</tt> <var>conflicting-package</var>
3860 <list compact="compact">
3862 <var>prerm</var> <tt>remove</tt>
3865 <var>old-prerm</var> <tt>upgrade</tt>
3866 <var>new-version</var>
3869 <var>new-prerm</var> <tt>failed-upgrade</tt>
3870 <var>old-version</var>
3873 <var>conflictor's-prerm</var> <tt>remove</tt>
3874 <tt>in-favour</tt> <var>package</var>
3875 <var>new-version</var>
3878 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3879 <tt>in-favour</tt> <var>package-being-installed</var>
3880 <var>version</var> [<tt>removing</tt>
3881 <var>conflicting-package</var>
3887 <list compact="compact">
3889 <var>postrm</var> <tt>remove</tt>
3892 <var>postrm</var> <tt>purge</tt>
3895 <var>old-postrm</var> <tt>upgrade</tt>
3896 <var>new-version</var>
3899 <var>new-postrm</var> <tt>failed-upgrade</tt>
3900 <var>old-version</var>
3903 <var>new-postrm</var> <tt>abort-install</tt>
3906 <var>new-postrm</var> <tt>abort-install</tt>
3907 <var>old-version</var>
3910 <var>new-postrm</var> <tt>abort-upgrade</tt>
3911 <var>old-version</var>
3914 <var>disappearer's-postrm</var> <tt>disappear</tt>
3915 <var>overwriter</var>
3916 <var>overwriter-version</var>
3922 <sect id="unpackphase">
3923 <heading>Details of unpack phase of installation or upgrade</heading>
3926 The procedure on installation/upgrade/overwrite/disappear
3927 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3928 stage of <tt>dpkg --install</tt>) is as follows. In each
3929 case, if a major error occurs (unless listed below) the
3930 actions are, in general, run backwards - this means that the
3931 maintainer scripts are run with different arguments in
3932 reverse order. These are the "error unwind" calls listed
3939 If a version of the package is already installed, call
3940 <example compact="compact">
3941 <var>old-prerm</var> upgrade <var>new-version</var>
3945 If the script runs but exits with a non-zero
3946 exit status, <prgn>dpkg</prgn> will attempt:
3947 <example compact="compact">
3948 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3950 If this works, the upgrade continues. If this
3951 does not work, the error unwind:
3952 <example compact="compact">
3953 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3955 If this works, then the old-version is
3956 "Installed", if not, the old version is in a
3957 "Half-Configured" state.
3963 If a "conflicting" package is being removed at the same time,
3964 or if any package will be broken (due to <tt>Breaks</tt>):
3967 If <tt>--auto-deconfigure</tt> is
3968 specified, call, for each package to be deconfigured
3969 due to <tt>Breaks</tt>:
3970 <example compact="compact">
3971 <var>deconfigured's-prerm</var> deconfigure \
3972 in-favour <var>package-being-installed</var> <var>version</var>
3975 <example compact="compact">
3976 <var>deconfigured's-postinst</var> abort-deconfigure \
3977 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3979 The deconfigured packages are marked as
3980 requiring configuration, so that if
3981 <tt>--install</tt> is used they will be
3982 configured again if possible.
3985 If any packages depended on a conflicting
3986 package being removed and <tt>--auto-deconfigure</tt> is
3987 specified, call, for each such package:
3988 <example compact="compact">
3989 <var>deconfigured's-prerm</var> deconfigure \
3990 in-favour <var>package-being-installed</var> <var>version</var> \
3991 removing <var>conflicting-package</var> <var>version</var>
3994 <example compact="compact">
3995 <var>deconfigured's-postinst</var> abort-deconfigure \
3996 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3997 removing <var>conflicting-package</var> <var>version</var>
3999 The deconfigured packages are marked as
4000 requiring configuration, so that if
4001 <tt>--install</tt> is used they will be
4002 configured again if possible.
4005 To prepare for removal of each conflicting package, call:
4006 <example compact="compact">
4007 <var>conflictor's-prerm</var> remove \
4008 in-favour <var>package</var> <var>new-version</var>
4011 <example compact="compact">
4012 <var>conflictor's-postinst</var> abort-remove \
4013 in-favour <var>package</var> <var>new-version</var>
4022 If the package is being upgraded, call:
4023 <example compact="compact">
4024 <var>new-preinst</var> upgrade <var>old-version</var>
4026 If this fails, we call:
4028 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4035 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4037 is called. If this works, then the old version
4038 is in an "Installed" state, or else it is left
4039 in an "Unpacked" state.
4044 If it fails, then the old version is left
4045 in an "Half-Installed" state.
4052 Otherwise, if the package had some configuration
4053 files from a previous version installed (i.e., it
4054 is in the "configuration files only" state):
4055 <example compact="compact">
4056 <var>new-preinst</var> install <var>old-version</var>
4060 <var>new-postrm</var> abort-install <var>old-version</var>
4062 If this fails, the package is left in a
4063 "Half-Installed" state, which requires a
4064 reinstall. If it works, the packages is left in
4065 a "Config-Files" state.
4068 Otherwise (i.e., the package was completely purged):
4069 <example compact="compact">
4070 <var>new-preinst</var> install
4073 <example compact="compact">
4074 <var>new-postrm</var> abort-install
4076 If the error-unwind fails, the package is in a
4077 "Half-Installed" phase, and requires a
4078 reinstall. If the error unwind works, the
4079 package is in a not installed state.
4086 The new package's files are unpacked, overwriting any
4087 that may be on the system already, for example any
4088 from the old version of the same package or from
4089 another package. Backups of the old files are kept
4090 temporarily, and if anything goes wrong the package
4091 management system will attempt to put them back as
4092 part of the error unwind.
4096 It is an error for a package to contain files which
4097 are on the system in another package, unless
4098 <tt>Replaces</tt> is used (see <ref id="replaces">).
4100 The following paragraph is not currently the case:
4101 Currently the <tt>- - force-overwrite</tt> flag is
4102 enabled, downgrading it to a warning, but this may not
4108 It is a more serious error for a package to contain a
4109 plain file or other kind of non-directory where another
4110 package has a directory (again, unless
4111 <tt>Replaces</tt> is used). This error can be
4112 overridden if desired using
4113 <tt>--force-overwrite-dir</tt>, but this is not
4118 Packages which overwrite each other's files produce
4119 behavior which, though deterministic, is hard for the
4120 system administrator to understand. It can easily
4121 lead to "missing" programs if, for example, a package
4122 is installed which overwrites a file from another
4123 package, and is then removed again.<footnote>
4124 Part of the problem is due to what is arguably a
4125 bug in <prgn>dpkg</prgn>.
4130 A directory will never be replaced by a symbolic link
4131 to a directory or vice versa; instead, the existing
4132 state (symlink or not) will be left alone and
4133 <prgn>dpkg</prgn> will follow the symlink if there is
4142 If the package is being upgraded, call
4143 <example compact="compact">
4144 <var>old-postrm</var> upgrade <var>new-version</var>
4148 If this fails, <prgn>dpkg</prgn> will attempt:
4149 <example compact="compact">
4150 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4152 If this works, installation continues. If not,
4154 <example compact="compact">
4155 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4157 If this fails, the old version is left in a
4158 "Half-Installed" state. If it works, dpkg now
4160 <example compact="compact">
4161 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4163 If this fails, the old version is left in a
4164 "Half-Installed" state. If it works, dpkg now
4166 <example compact="compact">
4167 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4169 If this fails, the old version is in an
4176 This is the point of no return - if
4177 <prgn>dpkg</prgn> gets this far, it won't back off
4178 past this point if an error occurs. This will
4179 leave the package in a fairly bad state, which
4180 will require a successful re-installation to clear
4181 up, but it's when <prgn>dpkg</prgn> starts doing
4182 things that are irreversible.
4187 Any files which were in the old version of the package
4188 but not in the new are removed.
4192 The new file list replaces the old.
4196 The new maintainer scripts replace the old.
4200 Any packages all of whose files have been overwritten
4201 during the installation, and which aren't required for
4202 dependencies, are considered to have been removed.
4203 For each such package
4206 <prgn>dpkg</prgn> calls:
4207 <example compact="compact">
4208 <var>disappearer's-postrm</var> disappear \
4209 <var>overwriter</var> <var>overwriter-version</var>
4213 The package's maintainer scripts are removed.
4216 It is noted in the status database as being in a
4217 sane state, namely not installed (any conffiles
4218 it may have are ignored, rather than being
4219 removed by <prgn>dpkg</prgn>). Note that
4220 disappearing packages do not have their prerm
4221 called, because <prgn>dpkg</prgn> doesn't know
4222 in advance that the package is going to
4229 Any files in the package we're unpacking that are also
4230 listed in the file lists of other packages are removed
4231 from those lists. (This will lobotomize the file list
4232 of the "conflicting" package if there is one.)
4236 The backup files made during installation, above, are
4242 The new package's status is now sane, and recorded as
4247 Here is another point of no return - if the
4248 conflicting package's removal fails we do not unwind
4249 the rest of the installation; the conflicting package
4250 is left in a half-removed limbo.
4255 If there was a conflicting package we go and do the
4256 removal actions (described below), starting with the
4257 removal of the conflicting package's files (any that
4258 are also in the package being installed have already
4259 been removed from the conflicting package's file list,
4260 and so do not get removed now).
4266 <sect id="configdetails"><heading>Details of configuration</heading>
4269 When we configure a package (this happens with <tt>dpkg
4270 --install</tt> and <tt>dpkg --configure</tt>), we first
4271 update any <tt>conffile</tt>s and then call:
4272 <example compact="compact">
4273 <var>postinst</var> configure <var>most-recently-configured-version</var>
4278 No attempt is made to unwind after errors during
4279 configuration. If the configuration fails, the package is in
4280 a "Failed Config" state, and an error message is generated.
4284 If there is no most recently configured version
4285 <prgn>dpkg</prgn> will pass a null argument.
4288 Historical note: Truly ancient (pre-1997) versions of
4289 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4290 (including the angle brackets) in this case. Even older
4291 ones did not pass a second argument at all, under any
4292 circumstance. Note that upgrades using such an old dpkg
4293 version are unlikely to work for other reasons, even if
4294 this old argument behavior is handled by your postinst script.
4300 <sect id="removedetails"><heading>Details of removal and/or
4301 configuration purging</heading>
4307 <example compact="compact">
4308 <var>prerm</var> remove
4312 If prerm fails during replacement due to conflict
4314 <var>conflictor's-postinst</var> abort-remove \
4315 in-favour <var>package</var> <var>new-version</var>
4319 <var>postinst</var> abort-remove
4323 If this fails, the package is in a "Half-Configured"
4324 state, or else it remains "Installed".
4328 The package's files are removed (except <tt>conffile</tt>s).
4331 <example compact="compact">
4332 <var>postrm</var> remove
4336 If it fails, there's no error unwind, and the package is in
4337 an "Half-Installed" state.
4342 All the maintainer scripts except the <prgn>postrm</prgn>
4347 If we aren't purging the package we stop here. Note
4348 that packages which have no <prgn>postrm</prgn> and no
4349 <tt>conffile</tt>s are automatically purged when
4350 removed, as there is no difference except for the
4351 <prgn>dpkg</prgn> status.
4355 The <tt>conffile</tt>s and any backup files
4356 (<tt>~</tt>-files, <tt>#*#</tt> files,
4357 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4362 <example compact="compact">
4363 <var>postrm</var> purge
4367 If this fails, the package remains in a "Config-Files"
4372 The package's file list is removed.
4381 <chapt id="relationships">
4382 <heading>Declaring relationships between packages</heading>
4384 <sect id="depsyntax">
4385 <heading>Syntax of relationship fields</heading>
4388 These fields all have a uniform syntax. They are a list of
4389 package names separated by commas.
4393 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4394 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4395 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4396 control fields of the package, which declare
4397 dependencies on other packages, the package names listed may
4398 also include lists of alternative package names, separated
4399 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4400 if any one of the alternative packages is installed, that
4401 part of the dependency is considered to be satisfied.
4405 All of the fields except for <tt>Provides</tt> may restrict
4406 their applicability to particular versions of each named
4407 package. This is done in parentheses after each individual
4408 package name; the parentheses should contain a relation from
4409 the list below followed by a version number, in the format
4410 described in <ref id="f-Version">.
4414 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4415 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4416 strictly earlier, earlier or equal, exactly equal, later or
4417 equal and strictly later, respectively. The deprecated
4418 forms <tt><</tt> and <tt>></tt> were used to mean
4419 earlier/later or equal, rather than strictly earlier/later,
4420 so they should not appear in new packages (though
4421 <prgn>dpkg</prgn> still supports them).
4425 Whitespace may appear at any point in the version
4426 specification subject to the rules in <ref
4427 id="controlsyntax">, and must appear where it's necessary to
4428 disambiguate; it is not otherwise significant. All of the
4429 relationship fields may span multiple lines. For
4430 consistency and in case of future changes to
4431 <prgn>dpkg</prgn> it is recommended that a single space be
4432 used after a version relationship and before a version
4433 number; it is also conventional to put a single space after
4434 each comma, on either side of each vertical bar, and before
4435 each open parenthesis. When wrapping a relationship field, it
4436 is conventional to do so after a comma and before the space
4437 following that comma.
4441 For example, a list of dependencies might appear as:
4442 <example compact="compact">
4445 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4450 Relationships may be restricted to a certain set of
4451 architectures. This is indicated in brackets after each
4452 individual package name and the optional version specification.
4453 The brackets enclose a list of Debian architecture names
4454 separated by whitespace. Exclamation marks may be prepended to
4455 each of the names. (It is not permitted for some names to be
4456 prepended with exclamation marks while others aren't.)
4460 For build relationship fields
4461 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4462 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4463 the current Debian host architecture is not in this list and
4464 there are no exclamation marks in the list, or it is in the list
4465 with a prepended exclamation mark, the package name and the
4466 associated version specification are ignored completely for the
4467 purposes of defining the relationships.
4472 <example compact="compact">
4474 Build-Depends-Indep: texinfo
4475 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4476 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4478 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4479 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4480 <tt>gnumach-dev</tt> only on hurd-i386.
4484 For binary relationship fields, the architecture restriction
4485 syntax is only supported in the source package control
4486 file <file>debian/control</file>. When the corresponding binary
4487 package control file is generated, the relationship will either
4488 be omitted or included without the architecture restriction
4489 based on the architecture of the binary package. This means
4490 that architecture restrictions must not be used in binary
4491 relationship fields for architecture-independent packages
4492 (<tt>Architecture: all</tt>).
4497 <example compact="compact">
4498 Depends: foo [i386], bar [amd64]
4500 becomes <tt>Depends: foo</tt> when the package is built on
4501 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4502 package is built on the <tt>amd64</tt> architecture, and omitted
4503 entirely in binary packages built on all other architectures.
4507 If the architecture-restricted dependency is part of a set of
4508 alternatives using <tt>|</tt>, that alternative is ignored
4509 completely on architectures that do not match the restriction.
4511 <example compact="compact">
4512 Build-Depends: foo [!i386] | bar [!amd64]
4514 is equivalent to <tt>bar</tt> on the i386 architecture, to
4515 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4516 bar</tt> on all other architectures.
4520 Relationships may also be restricted to a certain set of
4521 architectures using architecture wildcards. The syntax for
4522 declaring such restrictions is the same as declaring
4523 restrictions using a certain set of architectures without
4524 architecture wildcards. For example:
4525 <example compact="compact">
4526 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4528 is equivalent to <tt>foo</tt> on architectures using the Linux
4529 kernel and any cpu, <tt>bar</tt> on architectures using any
4530 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4531 using a kernel other than Linux.
4535 Note that the binary package relationship fields such as
4536 <tt>Depends</tt> appear in one of the binary package
4537 sections of the control file, whereas the build-time
4538 relationships such as <tt>Build-Depends</tt> appear in the
4539 source package section of the control file (which is the
4544 <sect id="binarydeps">
4545 <heading>Binary Dependencies - <tt>Depends</tt>,
4546 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4547 <tt>Pre-Depends</tt>
4551 Packages can declare in their control file that they have
4552 certain relationships to other packages - for example, that
4553 they may not be installed at the same time as certain other
4554 packages, and/or that they depend on the presence of others.
4558 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4559 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4560 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4561 <tt>Breaks</tt> is described in <ref id="breaks">, and
4562 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4563 rest are described below.
4567 These seven fields are used to declare a dependency
4568 relationship by one package on another. Except for
4569 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4570 depending (binary) package's control file.
4571 (<tt>Enhances</tt> appears in the recommending package's
4572 control file, and <tt>Breaks</tt> appears in the version of
4573 depended-on package which causes the named package to
4578 A <tt>Depends</tt> field takes effect <em>only</em> when a
4579 package is to be configured. It does not prevent a package
4580 being on the system in an unconfigured state while its
4581 dependencies are unsatisfied, and it is possible to replace
4582 a package whose dependencies are satisfied and which is
4583 properly installed with a different version whose
4584 dependencies are not and cannot be satisfied; when this is
4585 done the depending package will be left unconfigured (since
4586 attempts to configure it will give errors) and will not
4587 function properly. If it is necessary, a
4588 <tt>Pre-Depends</tt> field can be used, which has a partial
4589 effect even when a package is being unpacked, as explained
4590 in detail below. (The other three dependency fields,
4591 <tt>Recommends</tt>, <tt>Suggests</tt> and
4592 <tt>Enhances</tt>, are only used by the various front-ends
4593 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4594 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4598 For this reason packages in an installation run are usually
4599 all unpacked first and all configured later; this gives
4600 later versions of packages with dependencies on later
4601 versions of other packages the opportunity to have their
4602 dependencies satisfied.
4606 In case of circular dependencies, since installation or
4607 removal order honoring the dependency order can't be
4608 established, dependency loops are broken at some point
4609 (based on rules below), and some packages may not be able to
4610 rely on their dependencies being present when being
4611 installed or removed, depending on which side of the break
4612 of the circular dependency loop they happen to be on. If one
4613 of the packages in the loop has no postinst script, then the
4614 cycle will be broken at that package, so as to ensure that
4615 all postinst scripts run with the dependencies properly
4616 configured if this is possible. Otherwise the breaking point
4621 The <tt>Depends</tt> field thus allows package maintainers
4622 to impose an order in which packages should be configured.
4626 The meaning of the five dependency fields is as follows:
4628 <tag><tt>Depends</tt></tag>
4631 This declares an absolute dependency. A package will
4632 not be configured unless all of the packages listed in
4633 its <tt>Depends</tt> field have been correctly
4638 The <tt>Depends</tt> field should be used if the
4639 depended-on package is required for the depending
4640 package to provide a significant amount of
4645 The <tt>Depends</tt> field should also be used if the
4646 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4647 <prgn>postrm</prgn> scripts require the package to be
4648 present in order to run. Note, however, that the
4649 <prgn>postrm</prgn> cannot rely on any non-essential
4650 packages to be present during the <tt>purge</tt>
4654 <tag><tt>Recommends</tt></tag>
4657 This declares a strong, but not absolute, dependency.
4661 The <tt>Recommends</tt> field should list packages
4662 that would be found together with this one in all but
4663 unusual installations.
4667 <tag><tt>Suggests</tt></tag>
4669 This is used to declare that one package may be more
4670 useful with one or more others. Using this field
4671 tells the packaging system and the user that the
4672 listed packages are related to this one and can
4673 perhaps enhance its usefulness, but that installing
4674 this one without them is perfectly reasonable.
4677 <tag><tt>Enhances</tt></tag>
4679 This field is similar to Suggests but works in the
4680 opposite direction. It is used to declare that a
4681 package can enhance the functionality of another
4685 <tag><tt>Pre-Depends</tt></tag>
4688 This field is like <tt>Depends</tt>, except that it
4689 also forces <prgn>dpkg</prgn> to complete installation
4690 of the packages named before even starting the
4691 installation of the package which declares the
4692 pre-dependency, as follows:
4696 When a package declaring a pre-dependency is about to
4697 be <em>unpacked</em> the pre-dependency can be
4698 satisfied if the depended-on package is either fully
4699 configured, <em>or even if</em> the depended-on
4700 package(s) are only unpacked or in the "Half-Configured"
4701 state, provided that they have been configured
4702 correctly at some point in the past (and not removed
4703 or partially removed since). In this case, both the
4704 previously-configured and currently unpacked or
4705 "Half-Configured" versions must satisfy any version
4706 clause in the <tt>Pre-Depends</tt> field.
4710 When the package declaring a pre-dependency is about
4711 to be <em>configured</em>, the pre-dependency will be
4712 treated as a normal <tt>Depends</tt>, that is, it will
4713 be considered satisfied only if the depended-on
4714 package has been correctly configured.
4718 <tt>Pre-Depends</tt> should be used sparingly,
4719 preferably only by packages whose premature upgrade or
4720 installation would hamper the ability of the system to
4721 continue with any upgrade that might be in progress.
4725 <tt>Pre-Depends</tt> are also required if the
4726 <prgn>preinst</prgn> script depends on the named
4727 package. It is best to avoid this situation if
4735 When selecting which level of dependency to use you should
4736 consider how important the depended-on package is to the
4737 functionality of the one declaring the dependency. Some
4738 packages are composed of components of varying degrees of
4739 importance. Such a package should list using
4740 <tt>Depends</tt> the package(s) which are required by the
4741 more important components. The other components'
4742 requirements may be mentioned as Suggestions or
4743 Recommendations, as appropriate to the components' relative
4749 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4752 When one binary package declares that it breaks another,
4753 <prgn>dpkg</prgn> will refuse to allow the package which
4754 declares <tt>Breaks</tt> be installed unless the broken
4755 package is deconfigured first, and it will refuse to
4756 allow the broken package to be reconfigured.
4760 A package will not be regarded as causing breakage merely
4761 because its configuration files are still installed; it must
4762 be at least "Half-Installed".
4766 A special exception is made for packages which declare that
4767 they break their own package name or a virtual package which
4768 they provide (see below): this does not count as a real
4773 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4774 version clause; such a <tt>Breaks</tt> is introduced in the
4775 version of an (implicit or explicit) dependency which violates
4776 an assumption or reveals a bug in earlier versions of the broken
4777 package, or which takes over a file from earlier versions of the
4778 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4779 will inform higher-level package management tools that the
4780 broken package must be upgraded before the new one.
4784 If the breaking package also overwrites some files from the
4785 older package, it should use <tt>Replaces</tt> to ensure this
4786 goes smoothly. See <ref id="replaces"> for a full discussion
4787 of taking over files from other packages, including how to
4788 use <tt>Breaks</tt> in those cases.
4792 Many of the cases where <tt>Breaks</tt> should be used were
4793 previously handled with <tt>Conflicts</tt>
4794 because <tt>Breaks</tt> did not yet exist.
4795 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4796 See <ref id="conflicts"> for more information about the
4801 <sect id="conflicts">
4802 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4805 When one binary package declares a conflict with another
4806 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4807 refuse to allow them to be installed on the system at the
4808 same time. This is a stronger restriction than <tt>Breaks</tt>,
4809 which just prevents both packages from being configured at the
4810 same time. Conflicting packages cannot be unpacked on the
4811 system at the same time.
4815 If one package is to be installed, the other must be removed
4816 first. If the package being installed is marked as replacing
4817 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4818 normally be used in this case) the one on the system, or the one
4819 on the system is marked as deselected, or both packages are
4820 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4821 automatically remove the package which is causing the conflict.
4822 Otherwise, it will halt the installation of the new package with
4823 an error. This mechanism is specifically designed to produce an
4824 error when the installed package is <tt>Essential</tt>, but the
4829 A package will not cause a conflict merely because its
4830 configuration files are still installed; it must be at least
4835 A special exception is made for packages which declare a
4836 conflict with their own package name, or with a virtual
4837 package which they provide (see below): this does not
4838 prevent their installation, and allows a package to conflict
4839 with others providing a replacement for it. You use this
4840 feature when you want the package in question to be the only
4841 package providing some feature.
4845 Normally, <tt>Breaks</tt> should be used instead
4846 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4847 stronger restriction on the ordering of package installation or
4848 upgrade and can make it more difficult for the package manager
4849 to find a correct solution to an upgrade or installation
4850 problem. <tt>Breaks</tt> should be used
4852 <item>when moving a file from one package to another (see
4853 <ref id="replaces">),</item>
4854 <item>when splitting a package (a special case of the previous
4856 <item>when the breaking package exposes a bug in or interacts
4857 badly with particular versions of the broken
4860 <tt>Conflicts</tt> should be used
4862 <item>when two packages provide the same file and will
4863 continue to do so,</item>
4864 <item>in conjunction with <tt>Provides</tt> when only one
4865 package providing a given virtual facility may be installed
4866 at a time (see <ref id="virtual">),</item>
4867 <item>in other cases where one must prevent simultaneous
4868 installation of two packages for reasons that are ongoing
4869 (not fixed in a later version of one of the packages) or
4870 that must prevent both packages from being unpacked at the
4871 same time, not just configured.</item>
4873 Be aware that adding <tt>Conflicts</tt> is normally not the best
4874 solution when two packages provide the same files. Depending on
4875 the reason for that conflict, using alternatives or renaming the
4876 files is often a better approach. See, for
4877 example, <ref id="binaries">.
4881 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4882 unless two packages cannot be installed at the same time or
4883 installing them both causes one of them to be broken or
4884 unusable. Having similar functionality or performing the same
4885 tasks as another package is not sufficient reason to
4886 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4890 A <tt>Conflicts</tt> entry may have an "earlier than" version
4891 clause if the reason for the conflict is corrected in a later
4892 version of one of the packages. However, normally the presence
4893 of an "earlier than" version clause is a sign
4894 that <tt>Breaks</tt> should have been used instead. An "earlier
4895 than" version clause in <tt>Conflicts</tt>
4896 prevents <prgn>dpkg</prgn> from upgrading or installing the
4897 package which declares such a conflict until the upgrade or
4898 removal of the conflicted-with package has been completed, which
4899 is a strong restriction.
4903 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4907 As well as the names of actual ("concrete") packages, the
4908 package relationship fields <tt>Depends</tt>,
4909 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4910 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4911 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4912 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4913 may mention "virtual packages".
4917 A <em>virtual package</em> is one which appears in the
4918 <tt>Provides</tt> control field of another package. The effect
4919 is as if the package(s) which provide a particular virtual
4920 package name had been listed by name everywhere the virtual
4921 package name appears. (See also <ref id="virtual_pkg">)
4925 If there are both concrete and virtual packages of the same
4926 name, then the dependency may be satisfied (or the conflict
4927 caused) by either the concrete package with the name in
4928 question or any other concrete package which provides the
4929 virtual package with the name in question. This is so that,
4930 for example, supposing we have
4931 <example compact="compact">
4934 </example> and someone else releases an enhanced version of
4935 the <tt>bar</tt> package they can say:
4936 <example compact="compact">
4940 and the <tt>bar-plus</tt> package will now also satisfy the
4941 dependency for the <tt>foo</tt> package.
4945 If a relationship field has a version number attached, only real
4946 packages will be considered to see whether the relationship is
4947 satisfied (or the prohibition violated, for a conflict or
4948 breakage). In other words, if a version number is specified,
4949 this is a request to ignore all <tt>Provides</tt> for that
4950 package name and consider only real packages. The package
4951 manager will assume that a package providing that virtual
4952 package is not of the "right" version. A <tt>Provides</tt>
4953 field may not contain version numbers, and the version number of
4954 the concrete package which provides a particular virtual package
4955 will not be considered when considering a dependency on or
4956 conflict with the virtual package name.<footnote>
4957 It is possible that a future release of <prgn>dpkg</prgn> may
4958 add the ability to specify a version number for each virtual
4959 package it provides. This feature is not yet present,
4960 however, and is expected to be used only infrequently.
4965 To specify which of a set of real packages should be the default
4966 to satisfy a particular dependency on a virtual package, list
4967 the real package as an alternative before the virtual one.
4971 If the virtual package represents a facility that can only be
4972 provided by one real package at a time, such as
4973 the <package>mail-transport-agent</package> virtual package that
4974 requires installation of a binary that would conflict with all
4975 other providers of that virtual package (see
4976 <ref id="mail-transport-agents">), all packages providing that
4977 virtual package should also declare a conflict with it
4978 using <tt>Conflicts</tt>. This will ensure that at most one
4979 provider of that virtual package is unpacked or installed at a
4984 <sect id="replaces"><heading>Overwriting files and replacing
4985 packages - <tt>Replaces</tt></heading>
4988 Packages can declare in their control file that they should
4989 overwrite files in certain other packages, or completely replace
4990 other packages. The <tt>Replaces</tt> control field has these
4991 two distinct purposes.
4994 <sect1><heading>Overwriting files in other packages</heading>
4997 It is usually an error for a package to contain files which
4998 are on the system in another package. However, if the
4999 overwriting package declares that it <tt>Replaces</tt> the one
5000 containing the file being overwritten, then <prgn>dpkg</prgn>
5001 will replace the file from the old package with that from the
5002 new. The file will no longer be listed as "owned" by the old
5003 package and will be taken over by the new package.
5004 Normally, <tt>Breaks</tt> should be used in conjunction
5005 with <tt>Replaces</tt>.<footnote>
5006 To see why <tt>Breaks</tt> is normally needed in addition
5007 to <tt>Replaces</tt>, consider the case of a file in the
5008 package <package>foo</package> being taken over by the
5009 package <package>foo-data</package>.
5010 <tt>Replaces</tt> will allow <package>foo-data</package> to
5011 be installed and take over that file. However,
5012 without <tt>Breaks</tt>, nothing
5013 requires <package>foo</package> to be upgraded to a newer
5014 version that knows it does not include that file and instead
5015 depends on <package>foo-data</package>. Nothing would
5016 prevent the new <package>foo-data</package> package from
5017 being installed and then removed, removing the file that it
5018 took over from <package>foo</package>. After that
5019 operation, the package manager would think the system was in
5020 a consistent state, but the <package>foo</package> package
5021 would be missing one of its files.
5026 For example, if a package <package>foo</package> is split
5027 into <package>foo</package> and <package>foo-data</package>
5028 starting at version 1.2-3, <package>foo-data</package> would
5030 <example compact="compact">
5031 Replaces: foo (<< 1.2-3)
5032 Breaks: foo (<< 1.2-3)
5034 in its control file. The new version of the
5035 package <package>foo</package> would normally have the field
5036 <example compact="compact">
5037 Depends: foo-data (>= 1.2-3)
5039 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5040 the files moved into <package>foo-data</package> are not
5041 required for normal operation).
5045 If a package is completely replaced in this way, so that
5046 <prgn>dpkg</prgn> does not know of any files it still
5047 contains, it is considered to have "disappeared". It will
5048 be marked as not wanted on the system (selected for
5049 removal) and not installed. Any <tt>conffile</tt>s
5050 details noted for the package will be ignored, as they
5051 will have been taken over by the overwriting package. The
5052 package's <prgn>postrm</prgn> script will be run with a
5053 special argument to allow the package to do any final
5054 cleanup required. See <ref id="mscriptsinstact">.
5056 Replaces is a one way relationship. You have to install
5057 the replacing package after the replaced package.
5062 For this usage of <tt>Replaces</tt>, virtual packages (see
5063 <ref id="virtual">) are not considered when looking at a
5064 <tt>Replaces</tt> field. The packages declared as being
5065 replaced must be mentioned by their real names.
5069 This usage of <tt>Replaces</tt> only takes effect when both
5070 packages are at least partially on the system at once. It is
5071 not relevant if the packages conflict unless the conflict has
5076 <sect1><heading>Replacing whole packages, forcing their
5080 Second, <tt>Replaces</tt> allows the packaging system to
5081 resolve which package should be removed when there is a
5082 conflict (see <ref id="conflicts">). This usage only takes
5083 effect when the two packages <em>do</em> conflict, so that the
5084 two usages of this field do not interfere with each other.
5088 In this situation, the package declared as being replaced
5089 can be a virtual package, so for example, all mail
5090 transport agents (MTAs) would have the following fields in
5091 their control files:
5092 <example compact="compact">
5093 Provides: mail-transport-agent
5094 Conflicts: mail-transport-agent
5095 Replaces: mail-transport-agent
5097 ensuring that only one MTA can be installed at any one
5098 time. See <ref id="virtual"> for more information about this
5103 <sect id="sourcebinarydeps">
5104 <heading>Relationships between source and binary packages -
5105 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5106 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5110 Source packages that require certain binary packages to be
5111 installed or absent at the time of building the package
5112 can declare relationships to those binary packages.
5116 This is done using the <tt>Build-Depends</tt>,
5117 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5118 <tt>Build-Conflicts-Indep</tt> control fields.
5122 Build-dependencies on "build-essential" binary packages can be
5123 omitted. Please see <ref id="pkg-relations"> for more information.
5127 The dependencies and conflicts they define must be satisfied
5128 (as defined earlier for binary packages) in order to invoke
5129 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5131 There is no Build-Depends-Arch; this role is essentially
5132 met with Build-Depends. Anyone building the
5133 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5134 assumed to be building the whole package, and therefore
5135 installation of all build dependencies is required.
5138 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5139 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5140 not yet know how to check for its existence, and
5141 <tt>binary-arch</tt>. The purpose of the original split
5142 between <tt>Build-Depends</tt> and
5143 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5144 wouldn't need to install extra packages needed only for the
5145 binary-indep targets. But without a build-arch/build-indep
5146 split, this didn't work, since most of the work is done in
5147 the build target, not in the binary target.
5151 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5152 <tt>binary-arch</tt></tag>
5154 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5155 fields must be satisfied when these targets are invoked.
5157 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5158 and <tt>binary-indep</tt></tag>
5160 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5161 <tt>Build-Depends-Indep</tt>, and
5162 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5163 these targets are invoked.
5171 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5174 Packages containing shared libraries must be constructed with
5175 a little care to make sure that the shared library is always
5176 available. This is especially important for packages whose
5177 shared libraries are vitally important, such as the C library
5178 (currently <tt>libc6</tt>).
5182 This section deals only with public shared libraries: shared
5183 libraries that are placed in directories searched by the dynamic
5184 linker by default or which are intended to be linked against
5185 normally and possibly used by other, independent packages. Shared
5186 libraries that are internal to a particular package or that are
5187 only loaded as dynamic modules are not covered by this section and
5188 are not subject to its requirements.
5192 A shared library is identified by the <tt>SONAME</tt> attribute
5193 stored in its dynamic section. When a binary is linked against a
5194 shared library, the <tt>SONAME</tt> of the shared library is
5195 recorded in the binary's <tt>NEEDED</tt> section so that the
5196 dynamic linker knows that library must be loaded at runtime. The
5197 shared library file's full name (which usually contains additional
5198 version information not needed in the <tt>SONAME</tt>) is
5199 therefore normally not referenced directly. Instead, the shared
5200 library is loaded by its <tt>SONAME</tt>, which exists on the file
5201 system as a symlink pointing to the full name of the shared
5202 library. This symlink must be provided by the
5203 package. <ref id="sharedlibs-runtime"> describes how to do this.
5205 This is a convention of shared library versioning, but not a
5206 requirement. Some libraries use the <tt>SONAME</tt> as the full
5207 library file name instead and therefore do not need a symlink.
5208 Most, however, encode additional information about
5209 backwards-compatible revisions as a minor version number in the
5210 file name. The <tt>SONAME</tt> itself only changes when
5211 binaries linked with the earlier version of the shared library
5212 may no longer work, but the filename may change with each
5213 release of the library. See <ref id="sharedlibs-runtime"> for
5219 When linking a binary or another shared library against a shared
5220 library, the <tt>SONAME</tt> for that shared library is not yet
5221 known. Instead, the shared library is found by looking for a file
5222 matching the library name with <tt>.so</tt> appended. This file
5223 exists on the file system as a symlink pointing to the shared
5228 Shared libraries are normally split into several binary packages.
5229 The <tt>SONAME</tt> symlink is installed by the runtime shared
5230 library package, and the bare <tt>.so</tt> symlink is installed in
5231 the development package since it's only used when linking binaries
5232 or shared libraries. However, there are some exceptions for
5233 unusual shared libraries or for shared libraries that are also
5234 loaded as dynamic modules by other programs.
5238 This section is primarily concerned with how the separation of
5239 shared libraries into multiple packages should be done and how
5240 dependencies on and between shared library binary packages are
5241 managed in Debian. <ref id="libraries"> should be read in
5242 conjunction with this section and contains additional rules for
5243 the files contained in the shared library packages.
5246 <sect id="sharedlibs-runtime">
5247 <heading>Run-time shared libraries</heading>
5250 The run-time shared library must be placed in a package
5251 whose name changes whenever the <tt>SONAME</tt> of the shared
5252 library changes. This allows several versions of the shared
5253 library to be installed at the same time, allowing installation
5254 of the new version of the shared library without immediately
5255 breaking binaries that depend on the old version. Normally, the
5256 run-time shared library and its <tt>SONAME</tt> symlink should
5257 be placed in a package named
5258 <package><var>libraryname</var><var>soversion</var></package>,
5259 where <var>soversion</var> is the version number in
5260 the <tt>SONAME</tt> of the shared library.
5261 See <ref id="shlibs"> for detailed information on how to
5262 determine this version. Alternatively, if it would be confusing
5263 to directly append <var>soversion</var>
5264 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5265 itself ends in a number), you should use
5266 <package><var>libraryname</var>-<var>soversion</var></package>
5271 If you have several shared libraries built from the same source
5272 tree, you may lump them all together into a single shared
5273 library package provided that all of their <tt>SONAME</tt>s will
5274 always change together. Be aware that this is not normally the
5275 case, and if the <tt>SONAME</tt>s do not change together,
5276 upgrading such a merged shared library package will be
5277 unnecessarily difficult because of file conflicts with the old
5278 version of the package. When in doubt, always split shared
5279 library packages so that each binary package installs a single
5284 Every time the shared library ABI changes in a way that may
5285 break binaries linked against older versions of the shared
5286 library, the <tt>SONAME</tt> of the library and the
5287 corresponding name for the binary package containing the runtime
5288 shared library should change. Normally, this means
5289 the <tt>SONAME</tt> should change any time an interface is
5290 removed from the shared library or the signature of an interface
5291 (the number of parameters or the types of parameters that it
5292 takes, for example) is changed. This practice is vital to
5293 allowing clean upgrades from older versions of the package and
5294 clean transitions between the old ABI and new ABI without having
5295 to upgrade every affected package simultaneously.
5299 The <tt>SONAME</tt> and binary package name need not, and indeed
5300 normally should not, change if new interfaces are added but none
5301 are removed or changed, since this will not break binaries
5302 linked against the old shared library. Correct versioning of
5303 dependencies on the newer shared library by binaries that use
5304 the new interfaces is handled via
5305 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5306 system</qref> or via symbols files (see
5307 <manref name="deb-symbols" section="5">).
5311 The package should install the shared libraries under
5312 their normal names. For example, the <package>libgdbm3</package>
5313 package should install <file>libgdbm.so.3.0.0</file> as
5314 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5315 renamed or re-linked by any <prgn>prerm</prgn> or
5316 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5317 of renaming things safely without affecting running programs,
5318 and attempts to interfere with this are likely to lead to
5323 Shared libraries should not be installed executable, since
5324 the dynamic linker does not require this and trying to
5325 execute a shared library usually results in a core dump.
5329 The run-time library package should include the symbolic link for
5330 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5331 the shared libraries. For example,
5332 the <package>libgdbm3</package> package should include a symbolic
5333 link from <file>/usr/lib/libgdbm.so.3</file> to
5334 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5335 linker (for example <prgn>ld.so</prgn> or
5336 <prgn>ld-linux.so.*</prgn>) can find the library between the
5337 time that <prgn>dpkg</prgn> installs it and the time that
5338 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5340 The package management system requires the library to be
5341 placed before the symbolic link pointing to it in the
5342 <file>.deb</file> file. This is so that when
5343 <prgn>dpkg</prgn> comes to install the symlink
5344 (overwriting the previous symlink pointing at an older
5345 version of the library), the new shared library is already
5346 in place. In the past, this was achieved by creating the
5347 library in the temporary packaging directory before
5348 creating the symlink. Unfortunately, this was not always
5349 effective, since the building of the tar file in the
5350 <file>.deb</file> depended on the behavior of the underlying
5351 file system. Some file systems (such as reiserfs) reorder
5352 the files so that the order of creation is forgotten.
5353 Since version 1.7.0, <prgn>dpkg</prgn>
5354 reorders the files itself as necessary when building a
5355 package. Thus it is no longer important to concern
5356 oneself with the order of file creation.
5360 <sect1 id="ldconfig">
5361 <heading><tt>ldconfig</tt></heading>
5364 Any package installing shared libraries in one of the default
5365 library directories of the dynamic linker (which are currently
5366 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5367 listed in <file>/etc/ld.so.conf</file><footnote>
5368 These are currently <file>/usr/local/lib</file> plus
5369 directories under <file>/lib</file> and <file>/usr/lib</file>
5370 matching the multiarch triplet for the system architecture.
5372 must use <prgn>ldconfig</prgn> to update the shared library
5377 The package maintainer scripts must only call
5378 <prgn>ldconfig</prgn> under these circumstances:
5379 <list compact="compact">
5380 <item>When the <prgn>postinst</prgn> script is run with a
5381 first argument of <tt>configure</tt>, the script must call
5382 <prgn>ldconfig</prgn>, and may optionally invoke
5383 <prgn>ldconfig</prgn> at other times.
5385 <item>When the <prgn>postrm</prgn> script is run with a
5386 first argument of <tt>remove</tt>, the script should call
5387 <prgn>ldconfig</prgn>.
5392 During install or upgrade, the preinst is called before
5393 the new files are installed, so calling "ldconfig" is
5394 pointless. The preinst of an existing package can also be
5395 called if an upgrade fails. However, this happens during
5396 the critical time when a shared libs may exist on-disk
5397 under a temporary name. Thus, it is dangerous and
5398 forbidden by current policy to call "ldconfig" at this
5403 When a package is installed or upgraded, "postinst
5404 configure" runs after the new files are safely on-disk.
5405 Since it is perfectly safe to invoke ldconfig
5406 unconditionally in a postinst, it is OK for a package to
5407 simply put ldconfig in its postinst without checking the
5408 argument. The postinst can also be called to recover from
5409 a failed upgrade. This happens before any new files are
5410 unpacked, so there is no reason to call "ldconfig" at this
5415 For a package that is being removed, prerm is
5416 called with all the files intact, so calling ldconfig is
5417 useless. The other calls to "prerm" happen in the case of
5418 upgrade at a time when all the files of the old package
5419 are on-disk, so again calling "ldconfig" is pointless.
5423 postrm, on the other hand, is called with the "remove"
5424 argument just after the files are removed, so this is
5425 the proper time to call "ldconfig" to notify the system
5426 of the fact that the shared libraries from the package
5427 are removed. The postrm can be called at several other
5428 times. At the time of "postrm purge", "postrm
5429 abort-install", or "postrm abort-upgrade", calling
5430 "ldconfig" is useless because the shared lib files are
5431 not on-disk. However, when "postrm" is invoked with
5432 arguments "upgrade", "failed-upgrade", or "disappear", a
5433 shared lib may exist on-disk under a temporary filename.
5441 <sect id="sharedlibs-support-files">
5442 <heading>Shared library support files</heading>
5445 If your package contains files whose names do not change with
5446 each change in the library shared object version, you must not
5447 put them in the shared library package. Otherwise, several
5448 versions of the shared library cannot be installed at the same
5449 time without filename clashes, making upgrades and transitions
5450 unnecessarily difficult.
5454 It is recommended that supporting files and run-time support
5455 programs that do not need to be invoked manually by users, but
5456 are nevertheless required for the package to function, be placed
5457 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5458 preferably under <file>/usr/lib/</file><var>package-name</var>.
5459 If the program or file is architecture independent, the
5460 recommendation is for it to be placed in a subdirectory of
5461 <file>/usr/share</file> instead, preferably under
5462 <file>/usr/share/</file><var>package-name</var>. Following the
5463 <var>package-name</var> naming convention ensures that the file
5464 names change when the shared object version changes.
5468 Run-time support programs that use the shared library but are
5469 not required for the library to function or files used by the
5470 shared library that can be used by any version of the shared
5471 library package should instead be put in a separate package.
5472 This package might typically be named
5473 <package><var>libraryname</var>-tools</package>; note the
5474 absence of the <var>soversion</var> in the package name.
5478 Files and support programs only useful when compiling software
5479 against the library should be included in the development
5480 package for the library.<footnote>
5481 For example, a <file><var>package-name</var>-config</file>
5482 script or <package>pkg-config</package> configuration files.
5487 <sect id="sharedlibs-static">
5488 <heading>Static libraries</heading>
5491 The static library (<file><var>libraryname.a</var></file>)
5492 is usually provided in addition to the shared version.
5493 It is placed into the development package (see below).
5497 In some cases, it is acceptable for a library to be
5498 available in static form only; these cases include:
5500 <item>libraries for languages whose shared library support
5501 is immature or unstable</item>
5502 <item>libraries whose interfaces are in flux or under
5503 development (commonly the case when the library's
5504 major version number is zero, or where the ABI breaks
5505 across patchlevels)</item>
5506 <item>libraries which are explicitly intended to be
5507 available only in static form by their upstream
5512 <sect id="sharedlibs-dev">
5513 <heading>Development files</heading>
5516 If there are development files associated with a shared library,
5517 the source package needs to generate a binary development package
5518 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5519 or if you prefer only to support one development version at a
5520 time, <package><var>libraryname</var>-dev</package>. Installing
5521 the development package must result in installation of all the
5522 development files necessary for compiling programs against that
5523 shared library.<footnote>
5524 This wording allows the development files to be split into
5525 several packages, such as a separate architecture-independent
5526 <package><var>libraryname</var>-headers</package>, provided that
5527 the development package depends on all the required additional
5533 In case several development versions of a library exist, you may
5534 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5535 <ref id="conflicts">) to ensure that the user only installs one
5536 development version at a time (as different development versions are
5537 likely to have the same header files in them, which would cause a
5538 filename clash if both were installed).
5542 The development package should contain a symlink for the associated
5543 shared library without a version number. For example, the
5544 <package>libgdbm-dev</package> package should include a symlink
5545 from <file>/usr/lib/libgdbm.so</file> to
5546 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5547 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5548 <file>libgdbm.so</file> when compiling dynamically.
5552 If the package provides Ada Library Information
5553 (<file>*.ali</file>) files for use with GNAT, these files must be
5554 installed read-only (mode 0444) so that GNAT will not attempt to
5555 recompile them. This overrides the normal file mode requirements
5556 given in <ref id="permissions-owners">.
5560 <sect id="sharedlibs-intradeps">
5561 <heading>Dependencies between the packages of the same library</heading>
5564 Typically the development version should have an exact
5565 version dependency on the runtime library, to make sure that
5566 compilation and linking happens correctly. The
5567 <tt>${binary:Version}</tt> substitution variable can be
5568 useful for this purpose.
5570 Previously, <tt>${Source-Version}</tt> was used, but its name
5571 was confusing and it has been deprecated since dpkg 1.13.19.
5576 <sect id="sharedlibs-shlibdeps">
5577 <heading>Dependencies between the library and other packages -
5578 the <tt>shlibs</tt> system</heading>
5581 If a package contains a binary or library which links to a
5582 shared library, we must ensure that when the package is
5583 installed on the system, all of the libraries needed are
5584 also installed. This requirement led to the creation of the
5585 <tt>shlibs</tt> system, which is very simple in its design:
5586 any package which <em>provides</em> a shared library also
5587 provides information on the package dependencies required to
5588 ensure the presence of this library, and any package which
5589 <em>uses</em> a shared library uses this information to
5590 determine the dependencies it requires. The files which
5591 contain the mapping from shared libraries to the necessary
5592 dependency information are called <file>shlibs</file> files.
5596 When a package is built which contains any shared libraries, it
5597 must provide a <file>shlibs</file> file for other packages to
5598 use. When a package is built which contains any shared
5599 libraries or compiled binaries, it must run
5600 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5601 on these to determine the libraries used and hence the
5602 dependencies needed by this package.<footnote>
5604 <prgn>dpkg-shlibdeps</prgn> will use a program
5605 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5606 the libraries directly needed by the binaries or shared
5607 libraries in the package.
5611 We say that a binary <tt>foo</tt> <em>directly</em> uses
5612 a library <tt>libbar</tt> if it is explicitly linked
5613 with that library (that is, the library is listed in the ELF
5614 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5615 to the link line when the binary is created). Other
5616 libraries that are needed by <tt>libbar</tt> are linked
5617 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5618 linker will load them automatically when it loads
5619 <tt>libbar</tt>. A package should depend on the libraries
5620 it directly uses, but not the libraries it indirectly uses.
5621 The dependencies for those libraries will automatically pull
5622 in the other libraries.
5626 A good example of where this helps is the following. We
5627 could update <tt>libimlib</tt> with a new version that
5628 supports a new graphics format called dgf (but retaining the
5629 same major version number) and depends on <tt>libdgf</tt>.
5630 If we used <prgn>ldd</prgn> to add dependencies for every
5631 library directly or indirectly linked with a binary, every
5632 package that uses <tt>libimlib</tt> would need to be
5633 recompiled so it would also depend on <tt>libdgf</tt> or it
5634 wouldn't run due to missing symbols. Since dependencies are
5635 only added based on ELF <tt>NEEDED</tt> attribute, packages
5636 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5637 having the dependency on <tt>libdgf</tt> and so they would
5638 not need rebuilding.
5644 In the following sections, we will first describe where the
5645 various <tt>shlibs</tt> files are to be found, then how to
5646 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5647 file format and how to create them if your package contains a
5652 <heading>The <tt>shlibs</tt> files present on the system</heading>
5655 There are several places where <tt>shlibs</tt> files are
5656 found. The following list gives them in the order in which
5658 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5659 (The first one which gives the required information is used.)
5665 <p><file>debian/shlibs.local</file></p>
5668 This lists overrides for this package. This file should
5669 normally not be used, but may be needed temporarily in
5670 unusual situations to work around bugs in other packages,
5671 or in unusual cases where the normally declared dependency
5672 information in the installed <file>shlibs</file> file for
5673 a library cannot be used. This file overrides information
5674 obtained from any other source.
5679 <p><file>/etc/dpkg/shlibs.override</file></p>
5682 This lists global overrides. This list is normally
5683 empty. It is maintained by the local system
5689 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5692 When packages are being built,
5693 any <file>debian/shlibs</file> files are copied into the
5694 control information file area of the temporary build
5695 directory and given the name <file>shlibs</file>. These
5696 files give details of any shared libraries included in the
5697 same package.<footnote>
5698 An example may help here. Let us say that the source
5699 package <tt>foo</tt> generates two binary
5700 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5701 When building the binary packages, the two packages are
5702 created in the directories <file>debian/libfoo2</file>
5703 and <file>debian/foo-runtime</file> respectively.
5704 (<file>debian/tmp</file> could be used instead of one of
5705 these.) Since <tt>libfoo2</tt> provides the
5706 <tt>libfoo</tt> shared library, it will require a
5707 <tt>shlibs</tt> file, which will be installed in
5708 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5709 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5710 When <prgn>dpkg-shlibdeps</prgn> is run on the
5711 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5713 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5714 determine whether <tt>foo-prog</tt>'s library
5715 dependencies are satisfied by any of the libraries
5716 provided by <tt>libfoo2</tt>. For this reason,
5717 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5718 the individual binary packages' <tt>shlibs</tt> files
5719 have been installed into the build directory.
5725 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5728 These are the <file>shlibs</file> files corresponding to
5729 all of the packages installed on the system, and are
5730 maintained by the relevant package maintainers.
5735 <p><file>/etc/dpkg/shlibs.default</file></p>
5738 This file lists any shared libraries whose packages
5739 have failed to provide correct <file>shlibs</file> files.
5740 It was used when the <file>shlibs</file> setup was first
5741 introduced, but it is now normally empty. It is
5742 maintained by the <tt>dpkg</tt> maintainer.
5750 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5751 <file>shlibs</file> files</heading>
5755 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5756 into your <file>debian/rules</file> file. If your package
5757 contains only compiled binaries and libraries (but no scripts),
5758 you can use a command such as:
5759 <example compact="compact">
5760 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5761 debian/tmp/usr/lib/*
5763 Otherwise, you will need to explicitly list the compiled
5764 binaries and libraries.<footnote>
5765 If you are using <tt>debhelper</tt>, the
5766 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5767 It will also correctly handle multi-binary packages.
5772 This command puts the dependency information into the
5773 <file>debian/substvars</file> file, which is then used by
5774 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5775 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5776 field in the control file for this to work.
5780 If you have multiple binary packages, you will need to call
5781 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5782 compiled libraries or binaries. In such a case, you will
5783 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5784 utilities to specify a different <file>substvars</file> file.
5788 If you are creating a udeb for use in the Debian Installer,
5789 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5790 should use the dependency line of type <tt>udeb</tt> by
5791 adding the <tt>-tudeb</tt> option<footnote>
5792 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5793 will automatically add this option if it knows it is
5795 </footnote>. If there is no dependency line of
5796 type <tt>udeb</tt> in the <file>shlibs</file>
5797 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5802 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5803 <ref id="pkg-dpkg-shlibdeps"> and
5804 <manref name="dpkg-shlibdeps" section="1">.
5809 <heading>The <file>shlibs</file> File Format</heading>
5812 Each <file>shlibs</file> file has the same format. Lines
5813 beginning with <tt>#</tt> are considered to be comments and
5814 are ignored. Each line is of the form:
5815 <example compact="compact">
5816 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5821 We will explain this by reference to the example of the
5822 <tt>zlib1g</tt> package, which (at the time of writing)
5823 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5827 <var>type</var> is an optional element that indicates the type
5828 of package for which the line is valid. The only type currently
5829 in use is <tt>udeb</tt>. The colon and space after the type are
5834 <var>library-name</var> is the name of the shared library,
5835 in this case <tt>libz</tt>. (This must match the name part
5836 of the soname, see below.)
5840 <var>soname-version</var> is the version part of the soname of
5841 the library. The soname is the thing that must exactly match
5842 for the library to be recognized by the dynamic linker, and is
5844 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5845 example, <tt>libz.so.1</tt>.<footnote>
5846 This can be determined using the command
5847 <example compact="compact">
5848 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5851 The version part is the part which comes after
5852 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5853 instead be of the form
5854 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5855 as <tt>libdb-4.8.so</tt>, in which case the name would
5856 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5860 <var>dependencies</var> has the same syntax as a dependency
5861 field in a binary package control file. It should give
5862 details of which packages are required to satisfy a binary
5863 built against the version of the library contained in the
5864 package. See <ref id="depsyntax"> for details.
5868 In our example, if the first version of the <tt>zlib1g</tt>
5869 package which contained a minor number of at least
5870 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5871 <tt>shlibs</tt> entry for this library could say:
5872 <example compact="compact">
5873 libz 1 zlib1g (>= 1:1.1.3)
5875 The version-specific dependency is to avoid warnings from
5876 the dynamic linker about using older shared libraries with
5881 As zlib1g also provides a udeb containing the shared library,
5882 there would also be a second line:
5883 <example compact="compact">
5884 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5890 <heading>Providing a <file>shlibs</file> file</heading>
5893 If your package provides a shared library, you need to create
5894 a <file>shlibs</file> file following the format described above.
5895 It is usual to call this file <file>debian/shlibs</file> (but if
5896 you have multiple binary packages, you might want to call it
5897 <file>debian/shlibs.<var>package</var></file> instead). Then
5898 let <file>debian/rules</file> install it in the control
5899 information file area:
5900 <example compact="compact">
5901 install -m644 debian/shlibs debian/tmp/DEBIAN
5903 or, in the case of a multi-binary package:
5904 <example compact="compact">
5905 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5907 An alternative way of doing this is to create the
5908 <file>shlibs</file> file in the control information file area
5909 directly from <file>debian/rules</file> without using
5910 a <file>debian/shlibs</file> file at all,<footnote>
5911 This is what <prgn>dh_makeshlibs</prgn> in
5912 the <package>debhelper</package> suite does. If your package
5913 also has a udeb that provides a shared
5914 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5915 the <tt>udeb:</tt> lines if you specify the name of the udeb
5916 with the <tt>--add-udeb</tt> option.
5918 since the <file>debian/shlibs</file> file itself is ignored by
5919 <prgn>dpkg-shlibdeps</prgn>.
5923 As <prgn>dpkg-shlibdeps</prgn> reads the
5924 <file>DEBIAN/shlibs</file> files in all of the binary packages
5925 being built from this source package, all of the
5926 <file>DEBIAN/shlibs</file> files should be installed before
5927 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5935 <chapt id="opersys"><heading>The Operating System</heading>
5938 <heading>File system hierarchy</heading>
5942 <heading>File System Structure</heading>
5945 The location of all installed files and directories must
5946 comply with the Filesystem Hierarchy Standard (FHS),
5947 version 2.3, with the exceptions noted below, and except
5948 where doing so would violate other terms of Debian
5949 Policy. The following exceptions to the FHS apply:
5954 The optional rules related to user specific
5955 configuration files for applications are stored in
5956 the user's home directory are relaxed. It is
5957 recommended that such files start with the
5958 '<tt>.</tt>' character (a "dot file"), and if an
5959 application needs to create more than one dot file
5960 then the preferred placement is in a subdirectory
5961 with a name starting with a '.' character, (a "dot
5962 directory"). In this case it is recommended the
5963 configuration files not start with the '.'
5969 The requirement for amd64 to use <file>/lib64</file>
5970 for 64 bit binaries is removed.
5975 The requirement for object files, internal binaries, and
5976 libraries, including <file>libc.so.*</file>, to be located
5977 directly under <file>/lib{,32}</file> and
5978 <file>/usr/lib{,32}</file> is amended, permitting files
5979 to instead be installed to
5980 <file>/lib/<var>triplet</var></file> and
5981 <file>/usr/lib/<var>triplet</var></file>, where
5982 <tt><var>triplet</var></tt> is the value returned by
5983 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5984 architecture of the package. Packages may <em>not</em>
5985 install files to any <var>triplet</var> path other
5986 than the one matching the architecture of that package;
5987 for instance, an <tt>Architecture: amd64</tt> package
5988 containing 32-bit x86 libraries may not install these
5989 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5991 This is necessary in order to reserve the directories for
5992 use in cross-installation of library packages from other
5993 architectures, as part of the planned deployment of
5998 Applications may also use a single subdirectory under
5999 <file>/usr/lib/<var>triplet</var></file>.
6002 The execution time linker/loader, ld*, must still be made
6003 available in the existing location under /lib or /lib64
6004 since this is part of the ELF ABI for the architecture.
6009 The requirement that
6010 <file>/usr/local/share/man</file> be "synonymous"
6011 with <file>/usr/local/man</file> is relaxed to a
6016 The requirement that windowmanagers with a single
6017 configuration file call it <file>system.*wmrc</file>
6018 is removed, as is the restriction that the window
6019 manager subdirectory be named identically to the
6020 window manager name itself.
6025 The requirement that boot manager configuration
6026 files live in <file>/etc</file>, or at least are
6027 symlinked there, is relaxed to a recommendation.
6032 The following directories in the root filesystem are
6033 additionally allowed: <file>/sys</file> and
6034 <file>/selinux</file>. <footnote>These directories
6035 are used as mount points to mount virtual filesystems
6036 to get access to kernel information.</footnote>
6041 On GNU/Hurd systems, the following additional
6042 directories are allowed in the root
6043 filesystem: <file>/hurd</file>
6044 and <file>/servers</file>.<footnote>
6045 These directories are used to store translators and as
6046 a set of standard names for mount points,
6055 The version of this document referred here can be
6056 found in the <tt>debian-policy</tt> package or on <url
6057 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6058 name="FHS (Debian copy)"> alongside this manual (or, if
6059 you have the <package>debian-policy</package> installed,
6061 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6062 (local copy)">). The
6063 latest version, which may be a more recent version, may
6065 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6066 Specific questions about following the standard may be
6067 asked on the <tt>debian-devel</tt> mailing list, or
6068 referred to the FHS mailing list (see the
6069 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6075 <heading>Site-specific programs</heading>
6078 As mandated by the FHS, packages must not place any
6079 files in <file>/usr/local</file>, either by putting them in
6080 the file system archive to be unpacked by <prgn>dpkg</prgn>
6081 or by manipulating them in their maintainer scripts.
6085 However, the package may create empty directories below
6086 <file>/usr/local</file> so that the system administrator knows
6087 where to place site-specific files. These are not
6088 directories <em>in</em> <file>/usr/local</file>, but are
6089 children of directories in <file>/usr/local</file>. These
6090 directories (<file>/usr/local/*/dir/</file>)
6091 should be removed on package removal if they are
6096 Note that this applies only to
6097 directories <em>below</em> <file>/usr/local</file>,
6098 not <em>in</em> <file>/usr/local</file>. Packages must
6099 not create sub-directories in the
6100 directory <file>/usr/local</file> itself, except those
6101 listed in FHS, section 4.5. However, you may create
6102 directories below them as you wish. You must not remove
6103 any of the directories listed in 4.5, even if you created
6108 Since <file>/usr/local</file> can be mounted read-only from a
6109 remote server, these directories must be created and
6110 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6111 maintainer scripts and not be included in the
6112 <file>.deb</file> archive. These scripts must not fail if
6113 either of these operations fail.
6117 For example, the <tt>emacsen-common</tt> package could
6118 contain something like
6119 <example compact="compact">
6120 if [ ! -e /usr/local/share/emacs ]
6122 if mkdir /usr/local/share/emacs 2>/dev/null
6124 chown root:staff /usr/local/share/emacs
6125 chmod 2775 /usr/local/share/emacs
6129 in its <prgn>postinst</prgn> script, and
6130 <example compact="compact">
6131 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6132 rmdir /usr/local/share/emacs 2>/dev/null || true
6134 in the <prgn>prerm</prgn> script. (Note that this form is
6135 used to ensure that if the script is interrupted, the
6136 directory <file>/usr/local/share/emacs</file> will still be
6141 If you do create a directory in <file>/usr/local</file> for
6142 local additions to a package, you should ensure that
6143 settings in <file>/usr/local</file> take precedence over the
6144 equivalents in <file>/usr</file>.
6148 However, because <file>/usr/local</file> and its contents are
6149 for exclusive use of the local administrator, a package
6150 must not rely on the presence or absence of files or
6151 directories in <file>/usr/local</file> for normal operation.
6155 The <file>/usr/local</file> directory itself and all the
6156 subdirectories created by the package should (by default) have
6157 permissions 2775 (group-writable and set-group-id) and be
6158 owned by <tt>root:staff</tt>.
6163 <heading>The system-wide mail directory</heading>
6165 The system-wide mail directory
6166 is <file>/var/mail</file>. This directory is part of the
6167 base system and should not be owned by any particular mail
6168 agents. The use of the old
6169 location <file>/var/spool/mail</file> is deprecated, even
6170 though the spool may still be physically located there.
6176 <heading>Users and groups</heading>
6179 <heading>Introduction</heading>
6181 The Debian system can be configured to use either plain or
6186 Some user ids (UIDs) and group ids (GIDs) are reserved
6187 globally for use by certain packages. Because some
6188 packages need to include files which are owned by these
6189 users or groups, or need the ids compiled into binaries,
6190 these ids must be used on any Debian system only for the
6191 purpose for which they are allocated. This is a serious
6192 restriction, and we should avoid getting in the way of
6193 local administration policies. In particular, many sites
6194 allocate users and/or local system groups starting at 100.
6198 Apart from this we should have dynamically allocated ids,
6199 which should by default be arranged in some sensible
6200 order, but the behavior should be configurable.
6204 Packages other than <tt>base-passwd</tt> must not modify
6205 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6206 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6211 <heading>UID and GID classes</heading>
6213 The UID and GID numbers are divided into classes as
6219 Globally allocated by the Debian project, the same
6220 on every Debian system. These ids will appear in
6221 the <file>passwd</file> and <file>group</file> files of all
6222 Debian systems, new ids in this range being added
6223 automatically as the <tt>base-passwd</tt> package is
6228 Packages which need a single statically allocated
6229 uid or gid should use one of these; their
6230 maintainers should ask the <tt>base-passwd</tt>
6238 Dynamically allocated system users and groups.
6239 Packages which need a user or group, but can have
6240 this user or group allocated dynamically and
6241 differently on each system, should use <tt>adduser
6242 --system</tt> to create the group and/or user.
6243 <prgn>adduser</prgn> will check for the existence of
6244 the user or group, and if necessary choose an unused
6245 id based on the ranges specified in
6246 <file>adduser.conf</file>.
6250 <tag>1000-59999:</tag>
6253 Dynamically allocated user accounts. By default
6254 <prgn>adduser</prgn> will choose UIDs and GIDs for
6255 user accounts in this range, though
6256 <file>adduser.conf</file> may be used to modify this
6261 <tag>60000-64999:</tag>
6264 Globally allocated by the Debian project, but only
6265 created on demand. The ids are allocated centrally
6266 and statically, but the actual accounts are only
6267 created on users' systems on demand.
6271 These ids are for packages which are obscure or
6272 which require many statically-allocated ids. These
6273 packages should check for and create the accounts in
6274 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6275 <prgn>adduser</prgn> if it has this facility) if
6276 necessary. Packages which are likely to require
6277 further allocations should have a "hole" left after
6278 them in the allocation, to give them room to
6283 <tag>65000-65533:</tag>
6291 User <tt>nobody</tt>. The corresponding gid refers
6292 to the group <tt>nogroup</tt>.
6299 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6300 not</em> be used, because it is the error return
6309 <sect id="sysvinit">
6310 <heading>System run levels and <file>init.d</file> scripts</heading>
6312 <sect1 id="/etc/init.d">
6313 <heading>Introduction</heading>
6316 The <file>/etc/init.d</file> directory contains the scripts
6317 executed by <prgn>init</prgn> at boot time and when the
6318 init state (or "runlevel") is changed (see <manref
6319 name="init" section="8">).
6323 There are at least two different, yet functionally
6324 equivalent, ways of handling these scripts. For the sake
6325 of simplicity, this document describes only the symbolic
6326 link method. However, it must not be assumed by maintainer
6327 scripts that this method is being used, and any automated
6328 manipulation of the various runlevel behaviors by
6329 maintainer scripts must be performed using
6330 <prgn>update-rc.d</prgn> as described below and not by
6331 manually installing or removing symlinks. For information
6332 on the implementation details of the other method,
6333 implemented in the <tt>file-rc</tt> package, please refer
6334 to the documentation of that package.
6338 These scripts are referenced by symbolic links in the
6339 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6340 runlevels, <prgn>init</prgn> looks in the directory
6341 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6342 execute, where <tt><var>n</var></tt> is the runlevel that
6343 is being changed to, or <tt>S</tt> for the boot-up
6348 The names of the links all have the form
6349 <file>S<var>mm</var><var>script</var></file> or
6350 <file>K<var>mm</var><var>script</var></file> where
6351 <var>mm</var> is a two-digit number and <var>script</var>
6352 is the name of the script (this should be the same as the
6353 name of the actual script in <file>/etc/init.d</file>).
6357 When <prgn>init</prgn> changes runlevel first the targets
6358 of the links whose names start with a <tt>K</tt> are
6359 executed, each with the single argument <tt>stop</tt>,
6360 followed by the scripts prefixed with an <tt>S</tt>, each
6361 with the single argument <tt>start</tt>. (The links are
6362 those in the <file>/etc/rc<var>n</var>.d</file> directory
6363 corresponding to the new runlevel.) The <tt>K</tt> links
6364 are responsible for killing services and the <tt>S</tt>
6365 link for starting services upon entering the runlevel.
6369 For example, if we are changing from runlevel 2 to
6370 runlevel 3, init will first execute all of the <tt>K</tt>
6371 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6372 all of the <tt>S</tt> prefixed scripts in that directory.
6373 The links starting with <tt>K</tt> will cause the
6374 referred-to file to be executed with an argument of
6375 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6380 The two-digit number <var>mm</var> is used to determine
6381 the order in which to run the scripts: low-numbered links
6382 have their scripts run first. For example, the
6383 <tt>K20</tt> scripts will be executed before the
6384 <tt>K30</tt> scripts. This is used when a certain service
6385 must be started before another. For example, the name
6386 server <prgn>bind</prgn> might need to be started before
6387 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6388 can set up its access lists. In this case, the script
6389 that starts <prgn>bind</prgn> would have a lower number
6390 than the script that starts <prgn>inn</prgn> so that it
6392 <example compact="compact">
6399 The two runlevels 0 (halt) and 6 (reboot) are slightly
6400 different. In these runlevels, the links with an
6401 <tt>S</tt> prefix are still called after those with a
6402 <tt>K</tt> prefix, but they too are called with the single
6403 argument <tt>stop</tt>.
6407 <sect1 id="writing-init">
6408 <heading>Writing the scripts</heading>
6411 Packages that include daemons for system services should
6412 place scripts in <file>/etc/init.d</file> to start or stop
6413 services at boot time or during a change of runlevel.
6414 These scripts should be named
6415 <file>/etc/init.d/<var>package</var></file>, and they should
6416 accept one argument, saying what to do:
6419 <tag><tt>start</tt></tag>
6420 <item>start the service,</item>
6422 <tag><tt>stop</tt></tag>
6423 <item>stop the service,</item>
6425 <tag><tt>restart</tt></tag>
6426 <item>stop and restart the service if it's already running,
6427 otherwise start the service</item>
6429 <tag><tt>reload</tt></tag>
6430 <item><p>cause the configuration of the service to be
6431 reloaded without actually stopping and restarting
6434 <tag><tt>force-reload</tt></tag>
6435 <item>cause the configuration to be reloaded if the
6436 service supports this, otherwise restart the
6440 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6441 <tt>force-reload</tt> options should be supported by all
6442 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6447 The <file>init.d</file> scripts must ensure that they will
6448 behave sensibly (i.e., returning success and not starting
6449 multiple copies of a service) if invoked with <tt>start</tt>
6450 when the service is already running, or with <tt>stop</tt>
6451 when it isn't, and that they don't kill unfortunately-named
6452 user processes. The best way to achieve this is usually to
6453 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6458 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6459 scripts. Writing correct <file>init.d</file> scripts requires
6460 accepting various error exit statuses when daemons are already
6461 running or already stopped without aborting
6462 the <file>init.d</file> script, and common <file>init.d</file>
6463 function libraries are not safe to call with <tt>set -e</tt>
6465 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6466 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6467 in effect and echoing status messages to the console fails,
6469 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6470 to not use <tt>set -e</tt> and instead check the result of
6471 each command separately.
6475 If a service reloads its configuration automatically (as
6476 in the case of <prgn>cron</prgn>, for example), the
6477 <tt>reload</tt> option of the <file>init.d</file> script
6478 should behave as if the configuration has been reloaded
6483 The <file>/etc/init.d</file> scripts must be treated as
6484 configuration files, either (if they are present in the
6485 package, that is, in the .deb file) by marking them as
6486 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6487 by managing them correctly in the maintainer scripts (see
6488 <ref id="config-files">). This is important since we want
6489 to give the local system administrator the chance to adapt
6490 the scripts to the local system, e.g., to disable a
6491 service without de-installing the package, or to specify
6492 some special command line options when starting a service,
6493 while making sure their changes aren't lost during the next
6498 These scripts should not fail obscurely when the
6499 configuration files remain but the package has been
6500 removed, as configuration files remain on the system after
6501 the package has been removed. Only when <prgn>dpkg</prgn>
6502 is executed with the <tt>--purge</tt> option will
6503 configuration files be removed. In particular, as the
6504 <file>/etc/init.d/<var>package</var></file> script itself is
6505 usually a <tt>conffile</tt>, it will remain on the system
6506 if the package is removed but not purged. Therefore, you
6507 should include a <tt>test</tt> statement at the top of the
6509 <example compact="compact">
6510 test -f <var>program-executed-later-in-script</var> || exit 0
6515 Often there are some variables in the <file>init.d</file>
6516 scripts whose values control the behavior of the scripts,
6517 and which a system administrator is likely to want to
6518 change. As the scripts themselves are frequently
6519 <tt>conffile</tt>s, modifying them requires that the
6520 administrator merge in their changes each time the package
6521 is upgraded and the <tt>conffile</tt> changes. To ease
6522 the burden on the system administrator, such configurable
6523 values should not be placed directly in the script.
6524 Instead, they should be placed in a file in
6525 <file>/etc/default</file>, which typically will have the same
6526 base name as the <file>init.d</file> script. This extra file
6527 should be sourced by the script when the script runs. It
6528 must contain only variable settings and comments in SUSv3
6529 <prgn>sh</prgn> format. It may either be a
6530 <tt>conffile</tt> or a configuration file maintained by
6531 the package maintainer scripts. See <ref id="config-files">
6536 To ensure that vital configurable values are always
6537 available, the <file>init.d</file> script should set default
6538 values for each of the shell variables it uses, either
6539 before sourcing the <file>/etc/default/</file> file or
6540 afterwards using something like the <tt>:
6541 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6542 script must behave sensibly and not fail if the
6543 <file>/etc/default</file> file is deleted.
6547 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6548 as temporary filesystems<footnote>
6549 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6550 options in <file>/etc/default/rcS</file>.
6551 </footnote>, so the <file>init.d</file> scripts must handle this
6552 correctly. This will typically amount to creating any required
6553 subdirectories dynamically when the <file>init.d</file> script
6554 is run, rather than including them in the package and relying on
6555 <prgn>dpkg</prgn> to create them.
6560 <heading>Interfacing with the initscript system</heading>
6563 Maintainers should use the abstraction layer provided by
6564 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6565 programs to deal with initscripts in their packages'
6566 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6567 and <prgn>postrm</prgn>.
6571 Directly managing the /etc/rc?.d links and directly
6572 invoking the <file>/etc/init.d/</file> initscripts should
6573 be done only by packages providing the initscript
6574 subsystem (such as <prgn>sysv-rc</prgn> and
6575 <prgn>file-rc</prgn>).
6579 <heading>Managing the links</heading>
6582 The program <prgn>update-rc.d</prgn> is provided for
6583 package maintainers to arrange for the proper creation and
6584 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6585 or their functional equivalent if another method is being
6586 used. This may be used by maintainers in their packages'
6587 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6591 You must not include any <file>/etc/rc<var>n</var>.d</file>
6592 symbolic links in the actual archive or manually create or
6593 remove the symbolic links in maintainer scripts; you must
6594 use the <prgn>update-rc.d</prgn> program instead. (The
6595 former will fail if an alternative method of maintaining
6596 runlevel information is being used.) You must not include
6597 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6598 in the archive either. (Only the <tt>sysvinit</tt>
6603 By default <prgn>update-rc.d</prgn> will start services in
6604 each of the multi-user state runlevels (2, 3, 4, and 5)
6605 and stop them in the halt runlevel (0), the single-user
6606 runlevel (1) and the reboot runlevel (6). The system
6607 administrator will have the opportunity to customize
6608 runlevels by simply adding, moving, or removing the
6609 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6610 symbolic links are being used, or by modifying
6611 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6616 To get the default behavior for your package, put in your
6617 <prgn>postinst</prgn> script
6618 <example compact="compact">
6619 update-rc.d <var>package</var> defaults
6621 and in your <prgn>postrm</prgn>
6622 <example compact="compact">
6623 if [ "$1" = purge ]; then
6624 update-rc.d <var>package</var> remove
6626 </example>. Note that if your package changes runlevels
6627 or priority, you may have to remove and recreate the links,
6628 since otherwise the old links may persist. Refer to the
6629 documentation of <prgn>update-rc.d</prgn>.
6633 This will use a default sequence number of 20. If it does
6634 not matter when or in which order the <file>init.d</file>
6635 script is run, use this default. If it does, then you
6636 should talk to the maintainer of the <prgn>sysvinit</prgn>
6637 package or post to <tt>debian-devel</tt>, and they will
6638 help you choose a number.
6642 For more information about using <tt>update-rc.d</tt>,
6643 please consult its man page <manref name="update-rc.d"
6649 <heading>Running initscripts</heading>
6651 The program <prgn>invoke-rc.d</prgn> is provided to make
6652 it easier for package maintainers to properly invoke an
6653 initscript, obeying runlevel and other locally-defined
6654 constraints that might limit a package's right to start,
6655 stop and otherwise manage services. This program may be
6656 used by maintainers in their packages' scripts.
6660 The package maintainer scripts must use
6661 <prgn>invoke-rc.d</prgn> to invoke the
6662 <file>/etc/init.d/*</file> initscripts, instead of
6663 calling them directly.
6667 By default, <prgn>invoke-rc.d</prgn> will pass any
6668 action requests (start, stop, reload, restart...) to the
6669 <file>/etc/init.d</file> script, filtering out requests
6670 to start or restart a service out of its intended
6675 Most packages will simply need to change:
6676 <example compact="compact">/etc/init.d/<package>
6677 <action></example> in their <prgn>postinst</prgn>
6678 and <prgn>prerm</prgn> scripts to:
6679 <example compact="compact">
6680 if which invoke-rc.d >/dev/null 2>&1; then
6681 invoke-rc.d <var>package</var> <action>
6683 /etc/init.d/<var>package</var> <action>
6689 A package should register its initscript services using
6690 <prgn>update-rc.d</prgn> before it tries to invoke them
6691 using <prgn>invoke-rc.d</prgn>. Invocation of
6692 unregistered services may fail.
6696 For more information about using
6697 <prgn>invoke-rc.d</prgn>, please consult its man page
6698 <manref name="invoke-rc.d" section="8">.
6704 <heading>Boot-time initialization</heading>
6707 There used to be another directory, <file>/etc/rc.boot</file>,
6708 which contained scripts which were run once per machine
6709 boot. This has been deprecated in favour of links from
6710 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6711 described in <ref id="/etc/init.d">. Packages must not
6712 place files in <file>/etc/rc.boot</file>.
6717 <heading>Example</heading>
6720 An example on which you can base your
6721 <file>/etc/init.d</file> scripts is found in
6722 <file>/etc/init.d/skeleton</file>.
6729 <heading>Console messages from <file>init.d</file> scripts</heading>
6732 This section describes the formats to be used for messages
6733 written to standard output by the <file>/etc/init.d</file>
6734 scripts. The intent is to improve the consistency of
6735 Debian's startup and shutdown look and feel. For this
6736 reason, please look very carefully at the details. We want
6737 the messages to have the same format in terms of wording,
6738 spaces, punctuation and case of letters.
6742 Here is a list of overall rules that should be used for
6743 messages generated by <file>/etc/init.d</file> scripts.
6749 The message should fit in one line (fewer than 80
6750 characters), start with a capital letter and end with
6751 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6755 If the script is performing some time consuming task in
6756 the background (not merely starting or stopping a
6757 program, for instance), an ellipsis (three dots:
6758 <tt>...</tt>) should be output to the screen, with no
6759 leading or tailing whitespace or line feeds.
6763 The messages should appear as if the computer is telling
6764 the user what it is doing (politely :-), but should not
6765 mention "it" directly. For example, instead of:
6766 <example compact="compact">
6767 I'm starting network daemons: nfsd mountd.
6769 the message should say
6770 <example compact="compact">
6771 Starting network daemons: nfsd mountd.
6778 <tt>init.d</tt> script should use the following standard
6779 message formats for the situations enumerated below.
6785 <p>When daemons are started</p>
6788 If the script starts one or more daemons, the output
6789 should look like this (a single line, no leading
6791 <example compact="compact">
6792 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6794 The <var>description</var> should describe the
6795 subsystem the daemon or set of daemons are part of,
6796 while <var>daemon-1</var> up to <var>daemon-n</var>
6797 denote each daemon's name (typically the file name of
6802 For example, the output of <file>/etc/init.d/lpd</file>
6804 <example compact="compact">
6805 Starting printer spooler: lpd.
6810 This can be achieved by saying
6811 <example compact="compact">
6812 echo -n "Starting printer spooler: lpd"
6813 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6816 in the script. If there are more than one daemon to
6817 start, the output should look like this:
6818 <example compact="compact">
6819 echo -n "Starting remote file system services:"
6820 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6821 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6822 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6825 This makes it possible for the user to see what is
6826 happening and when the final daemon has been started.
6827 Care should be taken in the placement of white spaces:
6828 in the example above the system administrators can
6829 easily comment out a line if they don't want to start
6830 a specific daemon, while the displayed message still
6836 <p>When a system parameter is being set</p>
6839 If you have to set up different system parameters
6840 during the system boot, you should use this format:
6841 <example compact="compact">
6842 Setting <var>parameter</var> to "<var>value</var>".
6847 You can use a statement such as the following to get
6849 <example compact="compact">
6850 echo "Setting DNS domainname to \"$domainname\"."
6855 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6856 for the left and right quotation marks. A grave accent
6857 (<tt>`</tt>) is not a quote character; neither is an
6858 apostrophe (<tt>'</tt>).
6863 <p>When a daemon is stopped or restarted</p>
6866 When you stop or restart a daemon, you should issue a
6867 message identical to the startup message, except that
6868 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6869 or <tt>Restarting</tt> respectively.
6873 For example, stopping the printer daemon will look like
6875 <example compact="compact">
6876 Stopping printer spooler: lpd.
6882 <p>When something is executed</p>
6885 There are several examples where you have to run a
6886 program at system startup or shutdown to perform a
6887 specific task, for example, setting the system's clock
6888 using <prgn>netdate</prgn> or killing all processes
6889 when the system shuts down. Your message should look
6891 <example compact="compact">
6892 Doing something very useful...done.
6894 You should print the <tt>done.</tt> immediately after
6895 the job has been completed, so that the user is
6896 informed why they have to wait. You can get this
6898 <example compact="compact">
6899 echo -n "Doing something very useful..."
6908 <p>When the configuration is reloaded</p>
6911 When a daemon is forced to reload its configuration
6912 files you should use the following format:
6913 <example compact="compact">
6914 Reloading <var>description</var> configuration...done.
6916 where <var>description</var> is the same as in the
6917 daemon starting message.
6925 <heading>Cron jobs</heading>
6928 Packages must not modify the configuration file
6929 <file>/etc/crontab</file>, and they must not modify the files in
6930 <file>/var/spool/cron/crontabs</file>.</p>
6933 If a package wants to install a job that has to be executed
6934 via cron, it should place a file with the name of the
6935 package in one or more of the following directories:
6936 <example compact="compact">
6942 As these directory names imply, the files within them are
6943 executed on an hourly, daily, weekly, or monthly basis,
6944 respectively. The exact times are listed in
6945 <file>/etc/crontab</file>.</p>
6948 All files installed in any of these directories must be
6949 scripts (e.g., shell scripts or Perl scripts) so that they
6950 can easily be modified by the local system administrator.
6951 In addition, they must be treated as configuration files.
6955 If a certain job has to be executed at some other frequency or
6956 at a specific time, the package should install a file
6957 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6958 same syntax as <file>/etc/crontab</file> and is processed by
6959 <prgn>cron</prgn> automatically. The file must also be
6960 treated as a configuration file. (Note that entries in the
6961 <file>/etc/cron.d</file> directory are not handled by
6962 <prgn>anacron</prgn>. Thus, you should only use this
6963 directory for jobs which may be skipped if the system is not
6966 Unlike <file>crontab</file> files described in the IEEE Std
6967 1003.1-2008 (POSIX.1) available from
6968 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6969 name="The Open Group">, the files in
6970 <file>/etc/cron.d</file> and the file
6971 <file>/etc/crontab</file> have seven fields; namely:
6973 <item>Minute [0,59]</item>
6974 <item>Hour [0,23]</item>
6975 <item>Day of the month [1,31]</item>
6976 <item>Month of the year [1,12]</item>
6977 <item>Day of the week ([0,6] with 0=Sunday)</item>
6978 <item>Username</item>
6979 <item>Command to be run</item>
6981 Ranges of numbers are allowed. Ranges are two numbers
6982 separated with a hyphen. The specified range is inclusive.
6983 Lists are allowed. A list is a set of numbers (or ranges)
6984 separated by commas. Step values can be used in conjunction
6989 The scripts or <tt>crontab</tt> entries in these directories should
6990 check if all necessary programs are installed before they
6991 try to execute them. Otherwise, problems will arise when a
6992 package was removed but not purged since configuration files
6993 are kept on the system in this situation.
6997 Any <tt>cron</tt> daemon must provide
6998 <file>/usr/bin/crontab</file> and support normal
6999 <tt>crontab</tt> entries as specified in POSIX. The daemon
7000 must also support names for days and months, ranges, and
7001 step values. It has to support <file>/etc/crontab</file>,
7002 and correctly execute the scripts in
7003 <file>/etc/cron.d</file>. The daemon must also correctly
7005 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7010 <heading>Menus</heading>
7013 The Debian <tt>menu</tt> package provides a standard
7014 interface between packages providing applications and
7015 <em>menu programs</em> (either X window managers or
7016 text-based menu programs such as <prgn>pdmenu</prgn>).
7020 All packages that provide applications that need not be
7021 passed any special command line arguments for normal
7022 operation should register a menu entry for those
7023 applications, so that users of the <tt>menu</tt> package
7024 will automatically get menu entries in their window
7025 managers, as well in shells like <tt>pdmenu</tt>.
7029 Menu entries should follow the current menu policy.
7033 The menu policy can be found in the <tt>menu-policy</tt>
7034 files in the <tt>debian-policy</tt> package.
7035 It is also available from the Debian web mirrors at
7036 <tt><url name="/doc/packaging-manuals/menu-policy/"
7037 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7041 Please also refer to the <em>Debian Menu System</em>
7042 documentation that comes with the <package>menu</package>
7043 package for information about how to register your
7049 <heading>Multimedia handlers</heading>
7052 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7053 is a mechanism for encoding files and data streams and
7054 providing meta-information about them, in particular their
7055 type (e.g. audio or video) and format (e.g. PNG, HTML,
7060 Registration of MIME type handlers allows programs like mail
7061 user agents and web browsers to invoke these handlers to
7062 view, edit or display MIME types they don't support directly.
7066 Packages which provide the ability to view/show/play,
7067 compose, edit or print MIME types should register themselves
7068 as such following the current MIME support policy.
7072 The MIME support policy can be found in the <tt>mime-policy</tt>
7073 files in the <tt>debian-policy</tt> package.
7074 It is also available from the Debian web mirrors at
7075 <tt><url name="/doc/packaging-manuals/mime-policy/"
7076 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7082 <heading>Keyboard configuration</heading>
7085 To achieve a consistent keyboard configuration so that all
7086 applications interpret a keyboard event the same way, all
7087 programs in the Debian distribution must be configured to
7088 comply with the following guidelines.
7092 The following keys must have the specified interpretations:
7095 <tag><tt><--</tt></tag>
7096 <item>delete the character to the left of the cursor</item>
7098 <tag><tt>Delete</tt></tag>
7099 <item>delete the character to the right of the cursor</item>
7101 <tag><tt>Control+H</tt></tag>
7102 <item>emacs: the help prefix</item>
7105 The interpretation of any keyboard events should be
7106 independent of the terminal that is used, be it a virtual
7107 console, an X terminal emulator, an rlogin/telnet session,
7112 The following list explains how the different programs
7113 should be set up to achieve this:
7119 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7123 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7127 X translations are set up to make
7128 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7129 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7130 is the vt220 escape code for the "delete character"
7131 key). This must be done by loading the X resources
7132 using <prgn>xrdb</prgn> on all local X displays, not
7133 using the application defaults, so that the
7134 translation resources used correspond to the
7135 <prgn>xmodmap</prgn> settings.
7139 The Linux console is configured to make
7140 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7141 generate <tt>ESC [ 3 ~</tt>.
7145 X applications are configured so that <tt><</tt>
7146 deletes left, and <tt>Delete</tt> deletes right. Motif
7147 applications already work like this.
7151 Terminals should have <tt>stty erase ^?</tt> .
7155 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7156 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7157 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7161 Emacs is programmed to map <tt>KB_Backspace</tt> or
7162 the <tt>stty erase</tt> character to
7163 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7164 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7165 <tt>^H</tt> to <tt>help</tt> as always.
7169 Other applications use the <tt>stty erase</tt>
7170 character and <tt>kdch1</tt> for the two delete keys,
7171 with ASCII DEL being "delete previous character" and
7172 <tt>kdch1</tt> being "delete character under
7180 This will solve the problem except for the following
7187 Some terminals have a <tt><--</tt> key that cannot
7188 be made to produce anything except <tt>^H</tt>. On
7189 these terminals Emacs help will be unavailable on
7190 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7191 character takes precedence in Emacs, and has been set
7192 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7193 available) can be used instead.
7197 Some operating systems use <tt>^H</tt> for <tt>stty
7198 erase</tt>. However, modern telnet versions and all
7199 rlogin versions propagate <tt>stty</tt> settings, and
7200 almost all UNIX versions honour <tt>stty erase</tt>.
7201 Where the <tt>stty</tt> settings are not propagated
7202 correctly, things can be made to work by using
7203 <tt>stty</tt> manually.
7207 Some systems (including previous Debian versions) use
7208 <prgn>xmodmap</prgn> to arrange for both
7209 <tt><--</tt> and <tt>Delete</tt> to generate
7210 <tt>KB_Delete</tt>. We can change the behavior of
7211 their X clients using the same X resources that we use
7212 to do it for our own clients, or configure our clients
7213 using their resources when things are the other way
7214 around. On displays configured like this
7215 <tt>Delete</tt> will not work, but <tt><--</tt>
7220 Some operating systems have different <tt>kdch1</tt>
7221 settings in their <tt>terminfo</tt> database for
7222 <tt>xterm</tt> and others. On these systems the
7223 <tt>Delete</tt> key will not work correctly when you
7224 log in from a system conforming to our policy, but
7225 <tt><--</tt> will.
7232 <heading>Environment variables</heading>
7235 A program must not depend on environment variables to get
7236 reasonable defaults. (That's because these environment
7237 variables would have to be set in a system-wide
7238 configuration file like <file>/etc/profile</file>, which is not
7239 supported by all shells.)
7243 If a program usually depends on environment variables for its
7244 configuration, the program should be changed to fall back to
7245 a reasonable default configuration if these environment
7246 variables are not present. If this cannot be done easily
7247 (e.g., if the source code of a non-free program is not
7248 available), the program must be replaced by a small
7249 "wrapper" shell script which sets the environment variables
7250 if they are not already defined, and calls the original program.
7254 Here is an example of a wrapper script for this purpose:
7256 <example compact="compact">
7258 BAR=${BAR:-/var/lib/fubar}
7260 exec /usr/lib/foo/foo "$@"
7265 Furthermore, as <file>/etc/profile</file> is a configuration
7266 file of the <prgn>base-files</prgn> package, other packages must
7267 not put any environment variables or other commands into that
7272 <sect id="doc-base">
7273 <heading>Registering Documents using doc-base</heading>
7276 The <package>doc-base</package> package implements a
7277 flexible mechanism for handling and presenting
7278 documentation. The recommended practice is for every Debian
7279 package that provides online documentation (other than just
7280 manual pages) to register these documents with
7281 <package>doc-base</package> by installing a
7282 <package>doc-base</package> control file via the
7283 <prgn/install-docs/ script at installation time and
7284 de-register the manuals again when the package is removed.
7287 Please refer to the documentation that comes with the
7288 <package>doc-base</package> package for information and
7297 <heading>Files</heading>
7299 <sect id="binaries">
7300 <heading>Binaries</heading>
7303 Two different packages must not install programs with
7304 different functionality but with the same filenames. (The
7305 case of two programs having the same functionality but
7306 different implementations is handled via "alternatives" or
7307 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7308 <ref id="conflicts"> respectively.) If this case happens,
7309 one of the programs must be renamed. The maintainers should
7310 report this to the <tt>debian-devel</tt> mailing list and
7311 try to find a consensus about which program will have to be
7312 renamed. If a consensus cannot be reached, <em>both</em>
7313 programs must be renamed.
7317 By default, when a package is being built, any binaries
7318 created should include debugging information, as well as
7319 being compiled with optimization. You should also turn on
7320 as many reasonable compilation warnings as possible; this
7321 makes life easier for porters, who can then look at build
7322 logs for possible problems. For the C programming language,
7323 this means the following compilation parameters should be
7325 <example compact="compact">
7327 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7329 INSTALL = install -s # (or use strip on the files in debian/tmp)
7334 Note that by default all installed binaries should be stripped,
7335 either by using the <tt>-s</tt> flag to
7336 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7337 the binaries after they have been copied into
7338 <file>debian/tmp</file> but before the tree is made into a
7343 Although binaries in the build tree should be compiled with
7344 debugging information by default, it can often be difficult to
7345 debug programs if they are also subjected to compiler
7346 optimization. For this reason, it is recommended to support the
7347 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7348 (see <ref id="debianrules-options">). This variable can contain
7349 several flags to change how a package is compiled and built.
7353 It is up to the package maintainer to decide what
7354 compilation options are best for the package. Certain
7355 binaries (such as computationally-intensive programs) will
7356 function better with certain flags (<tt>-O3</tt>, for
7357 example); feel free to use them. Please use good judgment
7358 here. Don't use flags for the sake of it; only use them
7359 if there is good reason to do so. Feel free to override
7360 the upstream author's ideas about which compilation
7361 options are best: they are often inappropriate for our
7367 <sect id="libraries">
7368 <heading>Libraries</heading>
7371 If the package is <strong>architecture: any</strong>, then
7372 the shared library compilation and linking flags must have
7373 <tt>-fPIC</tt>, or the package shall not build on some of
7374 the supported architectures<footnote>
7376 If you are using GCC, <tt>-fPIC</tt> produces code with
7377 relocatable position independent code, which is required for
7378 most architectures to create a shared library, with i386 and
7379 perhaps some others where non position independent code is
7380 permitted in a shared library.
7383 Position independent code may have a performance penalty,
7384 especially on <tt>i386</tt>. However, in most cases the
7385 speed penalty must be measured against the memory wasted on
7386 the few architectures where non position independent code is
7389 </footnote>. Any exception to this rule must be discussed on
7390 the mailing list <em>debian-devel@lists.debian.org</em>, and
7391 a rough consensus obtained. The reasons for not compiling
7392 with <tt>-fPIC</tt> flag must be recorded in the file
7393 <tt>README.Debian</tt>, and care must be taken to either
7394 restrict the architecture or arrange for <tt>-fPIC</tt> to
7395 be used on architectures where it is required.<footnote>
7397 Some of the reasons why this might be required is if the
7398 library contains hand crafted assembly code that is not
7399 relocatable, the speed penalty is excessive for compute
7400 intensive libs, and similar reasons.
7405 As to the static libraries, the common case is not to have
7406 relocatable code, since there is no benefit, unless in specific
7407 cases; therefore the static version must not be compiled
7408 with the <tt>-fPIC</tt> flag. Any exception to this rule
7409 should be discussed on the mailing list
7410 <em>debian-devel@lists.debian.org</em>, and the reasons for
7411 compiling with the <tt>-fPIC</tt> flag must be recorded in
7412 the file <tt>README.Debian</tt>. <footnote>
7414 Some of the reasons for linking static libraries with
7415 the <tt>-fPIC</tt> flag are if, for example, one needs a
7416 Perl API for a library that is under rapid development,
7417 and has an unstable API, so shared libraries are
7418 pointless at this phase of the library's development. In
7419 that case, since Perl needs a library with relocatable
7420 code, it may make sense to create a static library with
7421 relocatable code. Another reason cited is if you are
7422 distilling various libraries into a common shared
7423 library, like <tt>mklibs</tt> does in the Debian
7429 In other words, if both a shared and a static library is
7430 being built, each source unit (<tt>*.c</tt>, for example,
7431 for C files) will need to be compiled twice, for the normal
7436 Libraries should be built with threading support and to be
7437 thread-safe if the library supports this.
7441 Although not enforced by the build tools, shared libraries
7442 must be linked against all libraries that they use symbols from
7443 in the same way that binaries are. This ensures the correct
7444 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7445 system and guarantees that all libraries can be safely opened
7446 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7447 option <tt>-Wl,-z,defs</tt> when building a shared library.
7448 Since this option enforces symbol resolution at build time,
7449 a missing library reference will be caught early as a fatal
7454 All installed shared libraries should be stripped with
7455 <example compact="compact">
7456 strip --strip-unneeded <var>your-lib</var>
7458 (The option <tt>--strip-unneeded</tt> makes
7459 <prgn>strip</prgn> remove only the symbols which aren't
7460 needed for relocation processing.) Shared libraries can
7461 function perfectly well when stripped, since the symbols for
7462 dynamic linking are in a separate part of the ELF object
7464 You might also want to use the options
7465 <tt>--remove-section=.comment</tt> and
7466 <tt>--remove-section=.note</tt> on both shared libraries
7467 and executables, and <tt>--strip-debug</tt> on static
7473 Note that under some circumstances it may be useful to
7474 install a shared library unstripped, for example when
7475 building a separate package to support debugging.
7479 Shared object files (often <file>.so</file> files) that are not
7480 public libraries, that is, they are not meant to be linked
7481 to by third party executables (binaries of other packages),
7482 should be installed in subdirectories of the
7483 <file>/usr/lib</file> directory. Such files are exempt from the
7484 rules that govern ordinary shared libraries, except that
7485 they must not be installed executable and should be
7487 A common example are the so-called "plug-ins",
7488 internal shared objects that are dynamically loaded by
7489 programs using <manref name="dlopen" section="3">.
7494 Packages that use <prgn>libtool</prgn> to create and install
7495 their shared libraries install a file containing additional
7496 metadata (ending in <file>.la</file>) alongside the library.
7497 For public libraries intended for use by other packages, these
7498 files normally should not be included in the Debian package,
7499 since the information they include is not necessary to link with
7500 the shared library on Debian and can add unnecessary additional
7501 dependencies to other programs or libraries.<footnote>
7502 These files store, among other things, all libraries on which
7503 that shared library depends. Unfortunately, if
7504 the <file>.la</file> file is present and contains that
7505 dependency information, using <prgn>libtool</prgn> when
7506 linking against that library will cause the resulting program
7507 or library to be linked against those dependencies as well,
7508 even if this is unnecessary. This can create unneeded
7509 dependencies on shared library packages that would otherwise
7510 be hidden behind the library ABI, and can make library
7511 transitions to new SONAMEs unnecessarily complicated and
7512 difficult to manage.
7514 If the <file>.la</file> file is required for that library (if,
7515 for instance, it's loaded via <tt>libltdl</tt> in a way that
7516 requires that meta-information), the <tt>dependency_libs</tt>
7517 setting in the <file>.la</file> file should normally be set to
7518 the empty string. If the shared library development package has
7519 historically included the <file>.la</file>, it must be retained
7520 in the development package (with <tt>dependency_libs</tt>
7521 emptied) until all libraries that depend on it have removed or
7522 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7523 files to prevent linking with those other libraries
7524 using <prgn>libtool</prgn> from failing.
7528 If the <file>.la</file> must be included, it should be included
7529 in the development (<tt>-dev</tt>) package, unless the library
7530 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7531 library. If it is intended for use with <tt>libltdl</tt>,
7532 the <file>.la</file> files must go in the run-time library
7537 These requirements for handling of <file>.la</file> files do not
7538 apply to loadable modules or libraries not installed in
7539 directories searched by default by the dynamic linker. Packages
7540 installing loadable modules will frequently need to install
7541 the <file>.la</file> files alongside the modules so that they
7542 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7543 does not need to be modified for libraries or modules that are
7544 not installed in directories searched by the dynamic linker by
7545 default and not intended for use by other packages.
7549 You must make sure that you use only released versions of
7550 shared libraries to build your packages; otherwise other
7551 users will not be able to run your binaries
7552 properly. Producing source packages that depend on
7553 unreleased compilers is also usually a bad
7560 <heading>Shared libraries</heading>
7562 This section has moved to <ref id="sharedlibs">.
7568 <heading>Scripts</heading>
7571 All command scripts, including the package maintainer
7572 scripts inside the package and used by <prgn>dpkg</prgn>,
7573 should have a <tt>#!</tt> line naming the shell to be used
7578 In the case of Perl scripts this should be
7579 <tt>#!/usr/bin/perl</tt>.
7583 When scripts are installed into a directory in the system
7584 PATH, the script name should not include an extension such
7585 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7586 language currently used to implement it.
7589 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7590 <file>init.d</file> scripts should almost certainly start
7591 with <tt>set -e</tt> so that errors are detected.
7592 <file>init.d</file> scripts are something of a special case, due
7593 to how frequently they need to call commands that are allowed to
7594 fail, and it may instead be easier to check the exit status of
7595 commands directly. See <ref id="writing-init"> for more
7596 information about writing <file>init.d</file> scripts.
7599 Every script should use <tt>set -e</tt> or check the exit status
7600 of <em>every</em> command.
7603 Scripts may assume that <file>/bin/sh</file> implements the
7604 SUSv3 Shell Command Language<footnote>
7605 Single UNIX Specification, version 3, which is also IEEE
7606 1003.1-2004 (POSIX), and is available on the World Wide Web
7607 from <url id="http://www.unix.org/version3/online.html"
7608 name="The Open Group"> after free
7609 registration.</footnote>
7610 plus the following additional features not mandated by
7612 These features are in widespread use in the Linux community
7613 and are implemented in all of bash, dash, and ksh, the most
7614 common shells users may wish to use as <file>/bin/sh</file>.
7617 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7618 must not generate a newline.</item>
7619 <item><tt>test</tt>, if implemented as a shell built-in, must
7620 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7622 <item><tt>local</tt> to create a scoped variable must be
7623 supported, including listing multiple variables in a single
7624 local command and assigning a value to a variable at the
7625 same time as localizing it. <tt>local</tt> may or
7626 may not preserve the variable value from an outer scope if
7627 no assignment is present. Uses such as:
7631 # ... use a, b, c, d ...
7634 must be supported and must set the value of <tt>c</tt> to
7637 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7638 -<var>signal</var></tt>, where <var>signal</var> is either
7639 the name of a signal or one of the numeric signals listed in
7640 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7641 supported if <prgn>kill</prgn> is implemented as a shell
7644 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7645 signals must be supported. In addition to the signal
7646 numbers listed in the extension, which are the same as for
7647 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7650 If a shell script requires non-SUSv3 features from the shell
7651 interpreter other than those listed above, the appropriate shell
7652 must be specified in the first line of the script (e.g.,
7653 <tt>#!/bin/bash</tt>) and the package must depend on the package
7654 providing the shell (unless the shell package is marked
7655 "Essential", as in the case of <prgn>bash</prgn>).
7659 You may wish to restrict your script to SUSv3 features plus the
7660 above set when possible so that it may use <file>/bin/sh</file>
7661 as its interpreter. If your script works with <prgn>dash</prgn>
7662 (originally called <prgn>ash</prgn>), it probably complies with
7663 the above requirements, but if you are in doubt, use
7664 <file>/bin/bash</file>.
7668 Perl scripts should check for errors when making any
7669 system calls, including <tt>open</tt>, <tt>print</tt>,
7670 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7674 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7675 scripting languages. See <em>Csh Programming Considered
7676 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7677 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7678 If an upstream package comes with <prgn>csh</prgn> scripts
7679 then you must make sure that they start with
7680 <tt>#!/bin/csh</tt> and make your package depend on the
7681 <prgn>c-shell</prgn> virtual package.
7685 Any scripts which create files in world-writeable
7686 directories (e.g., in <file>/tmp</file>) must use a
7687 mechanism which will fail atomically if a file with the same
7688 name already exists.
7692 The Debian base system provides the <prgn>tempfile</prgn>
7693 and <prgn>mktemp</prgn> utilities for use by scripts for
7700 <heading>Symbolic links</heading>
7703 In general, symbolic links within a top-level directory
7704 should be relative, and symbolic links pointing from one
7705 top-level directory into another should be absolute. (A
7706 top-level directory is a sub-directory of the root
7707 directory <file>/</file>.)
7711 In addition, symbolic links should be specified as short as
7712 possible, i.e., link targets like <file>foo/../bar</file> are
7717 Note that when creating a relative link using
7718 <prgn>ln</prgn> it is not necessary for the target of the
7719 link to exist relative to the working directory you're
7720 running <prgn>ln</prgn> from, nor is it necessary to change
7721 directory to the directory where the link is to be made.
7722 Simply include the string that should appear as the target
7723 of the link (this will be a pathname relative to the
7724 directory in which the link resides) as the first argument
7729 For example, in your <prgn>Makefile</prgn> or
7730 <file>debian/rules</file>, you can do things like:
7731 <example compact="compact">
7732 ln -fs gcc $(prefix)/bin/cc
7733 ln -fs gcc debian/tmp/usr/bin/cc
7734 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7735 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7740 A symbolic link pointing to a compressed file should always
7741 have the same file extension as the referenced file. (For
7742 example, if a file <file>foo.gz</file> is referenced by a
7743 symbolic link, the filename of the link has to end with
7744 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7749 <heading>Device files</heading>
7752 Packages must not include device files or named pipes in the
7757 If a package needs any special device files that are not
7758 included in the base system, it must call
7759 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7760 after notifying the user<footnote>
7761 This notification could be done via a (low-priority)
7762 debconf message, or an echo (printf) statement.
7767 Packages must not remove any device files in the
7768 <prgn>postrm</prgn> or any other script. This is left to the
7769 system administrator.
7773 Debian uses the serial devices
7774 <file>/dev/ttyS*</file>. Programs using the old
7775 <file>/dev/cu*</file> devices should be changed to use
7776 <file>/dev/ttyS*</file>.
7780 Named pipes needed by the package must be created in
7781 the <prgn>postinst</prgn> script<footnote>
7782 It's better to use <prgn>mkfifo</prgn> rather
7783 than <prgn>mknod</prgn> to create named pipes so that
7784 automated checks for packages incorrectly creating device
7785 files with <prgn>mknod</prgn> won't have false positives.
7786 </footnote> and removed in
7787 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7792 <sect id="config-files">
7793 <heading>Configuration files</heading>
7796 <heading>Definitions</heading>
7800 <tag>configuration file</tag>
7802 A file that affects the operation of a program, or
7803 provides site- or host-specific information, or
7804 otherwise customizes the behavior of a program.
7805 Typically, configuration files are intended to be
7806 modified by the system administrator (if needed or
7807 desired) to conform to local policy or to provide
7808 more useful site-specific behavior.
7811 <tag><tt>conffile</tt></tag>
7813 A file listed in a package's <tt>conffiles</tt>
7814 file, and is treated specially by <prgn>dpkg</prgn>
7815 (see <ref id="configdetails">).
7821 The distinction between these two is important; they are
7822 not interchangeable concepts. Almost all
7823 <tt>conffile</tt>s are configuration files, but many
7824 configuration files are not <tt>conffiles</tt>.
7828 As noted elsewhere, <file>/etc/init.d</file> scripts,
7829 <file>/etc/default</file> files, scripts installed in
7830 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7831 configuration installed in <file>/etc/cron.d</file> must be
7832 treated as configuration files. In general, any script that
7833 embeds configuration information is de-facto a configuration
7834 file and should be treated as such.
7839 <heading>Location</heading>
7842 Any configuration files created or used by your package
7843 must reside in <file>/etc</file>. If there are several,
7844 consider creating a subdirectory of <file>/etc</file>
7845 named after your package.
7849 If your package creates or uses configuration files
7850 outside of <file>/etc</file>, and it is not feasible to modify
7851 the package to use <file>/etc</file> directly, put the files
7852 in <file>/etc</file> and create symbolic links to those files
7853 from the location that the package requires.
7858 <heading>Behavior</heading>
7861 Configuration file handling must conform to the following
7863 <list compact="compact">
7865 local changes must be preserved during a package
7869 configuration files must be preserved when the
7870 package is removed, and only deleted when the
7874 Obsolete configuration files without local changes may be
7875 removed by the package during upgrade.
7879 The easy way to achieve this behavior is to make the
7880 configuration file a <tt>conffile</tt>. This is
7881 appropriate only if it is possible to distribute a default
7882 version that will work for most installations, although
7883 some system administrators may choose to modify it. This
7884 implies that the default version will be part of the
7885 package distribution, and must not be modified by the
7886 maintainer scripts during installation (or at any other
7891 In order to ensure that local changes are preserved
7892 correctly, no package may contain or make hard links to
7893 conffiles.<footnote>
7894 Rationale: There are two problems with hard links.
7895 The first is that some editors break the link while
7896 editing one of the files, so that the two files may
7897 unwittingly become unlinked and different. The second
7898 is that <prgn>dpkg</prgn> might break the hard link
7899 while upgrading <tt>conffile</tt>s.
7904 The other way to do it is via the maintainer scripts. In
7905 this case, the configuration file must not be listed as a
7906 <tt>conffile</tt> and must not be part of the package
7907 distribution. If the existence of a file is required for
7908 the package to be sensibly configured it is the
7909 responsibility of the package maintainer to provide
7910 maintainer scripts which correctly create, update and
7911 maintain the file and remove it on purge. (See <ref
7912 id="maintainerscripts"> for more information.) These
7913 scripts must be idempotent (i.e., must work correctly if
7914 <prgn>dpkg</prgn> needs to re-run them due to errors
7915 during installation or removal), must cope with all the
7916 variety of ways <prgn>dpkg</prgn> can call maintainer
7917 scripts, must not overwrite or otherwise mangle the user's
7918 configuration without asking, must not ask unnecessary
7919 questions (particularly during upgrades), and must
7920 otherwise be good citizens.
7924 The scripts are not required to configure every possible
7925 option for the package, but only those necessary to get
7926 the package running on a given system. Ideally the
7927 sysadmin should not have to do any configuration other
7928 than that done (semi-)automatically by the
7929 <prgn>postinst</prgn> script.
7933 A common practice is to create a script called
7934 <file><var>package</var>-configure</file> and have the
7935 package's <prgn>postinst</prgn> call it if and only if the
7936 configuration file does not already exist. In certain
7937 cases it is useful for there to be an example or template
7938 file which the maintainer scripts use. Such files should
7939 be in <file>/usr/share/<var>package</var></file> or
7940 <file>/usr/lib/<var>package</var></file> (depending on whether
7941 they are architecture-independent or not). There should
7942 be symbolic links to them from
7943 <file>/usr/share/doc/<var>package</var>/examples</file> if
7944 they are examples, and should be perfectly ordinary
7945 <prgn>dpkg</prgn>-handled files (<em>not</em>
7946 configuration files).
7950 These two styles of configuration file handling must
7951 not be mixed, for that way lies madness:
7952 <prgn>dpkg</prgn> will ask about overwriting the file
7953 every time the package is upgraded.
7958 <heading>Sharing configuration files</heading>
7961 If two or more packages use the same configuration file
7962 and it is reasonable for both to be installed at the same
7963 time, one of these packages must be defined as
7964 <em>owner</em> of the configuration file, i.e., it will be
7965 the package which handles that file as a configuration
7966 file. Other packages that use the configuration file must
7967 depend on the owning package if they require the
7968 configuration file to operate. If the other package will
7969 use the configuration file if present, but is capable of
7970 operating without it, no dependency need be declared.
7974 If it is desirable for two or more related packages to
7975 share a configuration file <em>and</em> for all of the
7976 related packages to be able to modify that configuration
7977 file, then the following should be done:
7978 <enumlist compact="compact">
7980 One of the related packages (the "owning" package)
7981 will manage the configuration file with maintainer
7982 scripts as described in the previous section.
7985 The owning package should also provide a program
7986 that the other packages may use to modify the
7990 The related packages must use the provided program
7991 to make any desired modifications to the
7992 configuration file. They should either depend on
7993 the core package to guarantee that the configuration
7994 modifier program is available or accept gracefully
7995 that they cannot modify the configuration file if it
7996 is not. (This is in addition to the fact that the
7997 configuration file may not even be present in the
8004 Sometimes it's appropriate to create a new package which
8005 provides the basic infrastructure for the other packages
8006 and which manages the shared configuration files. (The
8007 <tt>sgml-base</tt> package is a good example.)
8011 If the configuration file cannot be shared as described above,
8012 the packages must be marked as conflicting with each other.
8013 Two packages that specify the same file as
8014 a <tt>conffile</tt> must conflict. This is an instance of the
8015 general rule about not sharing files. Neither alternatives
8016 nor diversions are likely to be appropriate in this case; in
8017 particular, <prgn>dpkg</prgn> does not handle diverted
8018 <tt>conffile</tt>s well.
8022 When two packages both declare the same <tt>conffile</tt>, they
8023 may see left-over configuration files from each other even
8024 though they conflict with each other. If a user removes
8025 (without purging) one of the packages and installs the other,
8026 the new package will take over the <tt>conffile</tt> from the
8027 old package. If the file was modified by the user, it will be
8028 treated the same as any other locally
8029 modified <tt>conffile</tt> during an upgrade.
8033 The maintainer scripts must not alter a <tt>conffile</tt>
8034 of <em>any</em> package, including the one the scripts
8040 <heading>User configuration files ("dotfiles")</heading>
8043 The files in <file>/etc/skel</file> will automatically be
8044 copied into new user accounts by <prgn>adduser</prgn>.
8045 No other program should reference the files in
8046 <file>/etc/skel</file>.
8050 Therefore, if a program needs a dotfile to exist in
8051 advance in <file>$HOME</file> to work sensibly, that dotfile
8052 should be installed in <file>/etc/skel</file> and treated as a
8057 However, programs that require dotfiles in order to
8058 operate sensibly are a bad thing, unless they do create
8059 the dotfiles themselves automatically.
8063 Furthermore, programs should be configured by the Debian
8064 default installation to behave as closely to the upstream
8065 default behavior as possible.
8069 Therefore, if a program in a Debian package needs to be
8070 configured in some way in order to operate sensibly, that
8071 should be done using a site-wide configuration file placed
8072 in <file>/etc</file>. Only if the program doesn't support a
8073 site-wide default configuration and the package maintainer
8074 doesn't have time to add it may a default per-user file be
8075 placed in <file>/etc/skel</file>.
8079 <file>/etc/skel</file> should be as empty as we can make it.
8080 This is particularly true because there is no easy (or
8081 necessarily desirable) mechanism for ensuring that the
8082 appropriate dotfiles are copied into the accounts of
8083 existing users when a package is installed.
8089 <heading>Log files</heading>
8091 Log files should usually be named
8092 <file>/var/log/<var>package</var>.log</file>. If you have many
8093 log files, or need a separate directory for permission
8094 reasons (<file>/var/log</file> is writable only by
8095 <file>root</file>), you should usually create a directory named
8096 <file>/var/log/<var>package</var></file> and place your log
8101 Log files must be rotated occasionally so that they don't grow
8102 indefinitely. The best way to do this is to install a log
8103 rotation configuration file in the
8104 directory <file>/etc/logrotate.d</file>, normally
8105 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8106 the facilities provided by <prgn>logrotate</prgn>.
8109 The traditional approach to log files has been to set up
8110 <em>ad hoc</em> log rotation schemes using simple shell
8111 scripts and cron. While this approach is highly
8112 customizable, it requires quite a lot of sysadmin work.
8113 Even though the original Debian system helped a little
8114 by automatically installing a system which can be used
8115 as a template, this was deemed not enough.
8119 The use of <prgn>logrotate</prgn>, a program developed
8120 by Red Hat, is better, as it centralizes log management.
8121 It has both a configuration file
8122 (<file>/etc/logrotate.conf</file>) and a directory where
8123 packages can drop their individual log rotation
8124 configurations (<file>/etc/logrotate.d</file>).
8127 Here is a good example for a logrotate config
8128 file (for more information see <manref name="logrotate"
8130 <example compact="compact">
8131 /var/log/foo/*.log {
8137 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8141 This rotates all files under <file>/var/log/foo</file>, saves 12
8142 compressed generations, and tells the daemon to reopen its log
8143 files after the log rotation. It skips this log rotation
8144 (via <tt>missingok</tt>) if no such log file is present, which
8145 avoids errors if the package is removed but not purged.
8149 Log files should be removed when the package is
8150 purged (but not when it is only removed). This should be
8151 done by the <prgn>postrm</prgn> script when it is called
8152 with the argument <tt>purge</tt> (see <ref
8153 id="removedetails">).
8157 <sect id="permissions-owners">
8158 <heading>Permissions and owners</heading>
8161 The rules in this section are guidelines for general use.
8162 If necessary you may deviate from the details below.
8163 However, if you do so you must make sure that what is done
8164 is secure and you should try to be as consistent as possible
8165 with the rest of the system. You should probably also
8166 discuss it on <prgn>debian-devel</prgn> first.
8170 Files should be owned by <tt>root:root</tt>, and made
8171 writable only by the owner and universally readable (and
8172 executable, if appropriate), that is mode 644 or 755.
8176 Directories should be mode 755 or (for group-writability)
8177 mode 2775. The ownership of the directory should be
8178 consistent with its mode: if a directory is mode 2775, it
8179 should be owned by the group that needs write access to
8182 When a package is upgraded, and the owner or permissions
8183 of a file included in the package has changed, dpkg
8184 arranges for the ownership and permissions to be
8185 correctly set upon installation. However, this does not
8186 extend to directories; the permissions and ownership of
8187 directories already on the system does not change on
8188 install or upgrade of packages. This makes sense, since
8189 otherwise common directories like <tt>/usr</tt> would
8190 always be in flux. To correctly change permissions of a
8191 directory the package owns, explicit action is required,
8192 usually in the <tt>postinst</tt> script. Care must be
8193 taken to handle downgrades as well, in that case.
8199 Control information files should be owned by <tt>root:root</tt>
8200 and either mode 644 (for most files) or mode 755 (for
8201 executables such as <qref id="maintscripts">maintainer
8206 Setuid and setgid executables should be mode 4755 or 2755
8207 respectively, and owned by the appropriate user or group.
8208 They should not be made unreadable (modes like 4711 or
8209 2711 or even 4111); doing so achieves no extra security,
8210 because anyone can find the binary in the freely available
8211 Debian package; it is merely inconvenient. For the same
8212 reason you should not restrict read or execute permissions
8213 on non-set-id executables.
8217 Some setuid programs need to be restricted to particular
8218 sets of users, using file permissions. In this case they
8219 should be owned by the uid to which they are set-id, and by
8220 the group which should be allowed to execute them. They
8221 should have mode 4754; again there is no point in making
8222 them unreadable to those users who must not be allowed to
8227 It is possible to arrange that the system administrator can
8228 reconfigure the package to correspond to their local
8229 security policy by changing the permissions on a binary:
8230 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8231 described below.<footnote>
8232 Ordinary files installed by <prgn>dpkg</prgn> (as
8233 opposed to <tt>conffile</tt>s and other similar objects)
8234 normally have their permissions reset to the distributed
8235 permissions when the package is reinstalled. However,
8236 the use of <prgn>dpkg-statoverride</prgn> overrides this
8239 Another method you should consider is to create a group for
8240 people allowed to use the program(s) and make any setuid
8241 executables executable only by that group.
8245 If you need to create a new user or group for your package
8246 there are two possibilities. Firstly, you may need to
8247 make some files in the binary package be owned by this
8248 user or group, or you may need to compile the user or
8249 group id (rather than just the name) into the binary
8250 (though this latter should be avoided if possible, as in
8251 this case you need a statically allocated id).</p>
8254 If you need a statically allocated id, you must ask for a
8255 user or group id from the <tt>base-passwd</tt> maintainer,
8256 and must not release the package until you have been
8257 allocated one. Once you have been allocated one you must
8258 either make the package depend on a version of the
8259 <tt>base-passwd</tt> package with the id present in
8260 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8261 your package to create the user or group itself with the
8262 correct id (using <tt>adduser</tt>) in its
8263 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8264 the <prgn>postinst</prgn> is to be preferred if it is
8265 possible, otherwise a pre-dependency will be needed on the
8266 <tt>adduser</tt> package.)
8270 On the other hand, the program might be able to determine
8271 the uid or gid from the user or group name at runtime, so
8272 that a dynamically allocated id can be used. In this case
8273 you should choose an appropriate user or group name,
8274 discussing this on <prgn>debian-devel</prgn> and checking
8275 with the <package/base-passwd/ maintainer that it is unique and that
8276 they do not wish you to use a statically allocated id
8277 instead. When this has been checked you must arrange for
8278 your package to create the user or group if necessary using
8279 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8280 <prgn>postinst</prgn> script (again, the latter is to be
8281 preferred if it is possible).
8285 Note that changing the numeric value of an id associated
8286 with a name is very difficult, and involves searching the
8287 file system for all appropriate files. You need to think
8288 carefully whether a static or dynamic id is required, since
8289 changing your mind later will cause problems.
8292 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8294 This section is not intended as policy, but as a
8295 description of the use of <prgn>dpkg-statoverride</prgn>.
8299 If a system administrator wishes to have a file (or
8300 directory or other such thing) installed with owner and
8301 permissions different from those in the distributed Debian
8302 package, they can use the <prgn>dpkg-statoverride</prgn>
8303 program to instruct <prgn>dpkg</prgn> to use the different
8304 settings every time the file is installed. Thus the
8305 package maintainer should distribute the files with their
8306 normal permissions, and leave it for the system
8307 administrator to make any desired changes. For example, a
8308 daemon which is normally required to be setuid root, but
8309 in certain situations could be used without being setuid,
8310 should be installed setuid in the <tt>.deb</tt>. Then the
8311 local system administrator can change this if they wish.
8312 If there are two standard ways of doing it, the package
8313 maintainer can use <tt>debconf</tt> to find out the
8314 preference, and call <prgn>dpkg-statoverride</prgn> in the
8315 maintainer script if necessary to accommodate the system
8316 administrator's choice. Care must be taken during
8317 upgrades to not override an existing setting.
8321 Given the above, <prgn>dpkg-statoverride</prgn> is
8322 essentially a tool for system administrators and would not
8323 normally be needed in the maintainer scripts. There is
8324 one type of situation, though, where calls to
8325 <prgn>dpkg-statoverride</prgn> would be needed in the
8326 maintainer scripts, and that involves packages which use
8327 dynamically allocated user or group ids. In such a
8328 situation, something like the following idiom can be very
8329 helpful in the package's <prgn>postinst</prgn>, where
8330 <tt>sysuser</tt> is a dynamically allocated id:
8332 for i in /usr/bin/foo /usr/sbin/bar
8334 # only do something when no setting exists
8335 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8337 #include: debconf processing, question about foo and bar
8338 if [ "$RET" = "true" ] ; then
8339 dpkg-statoverride --update --add sysuser root 4755 $i
8344 The corresponding code to remove the override when the package
8347 for i in /usr/bin/foo /usr/sbin/bar
8349 if dpkg-statoverride --list $i >/dev/null 2>&1
8351 dpkg-statoverride --remove $i
8361 <chapt id="customized-programs">
8362 <heading>Customized programs</heading>
8364 <sect id="arch-spec">
8365 <heading>Architecture specification strings</heading>
8368 If a program needs to specify an <em>architecture specification
8369 string</em> in some place, it should select one of the strings
8370 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8371 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8372 part is sometimes elided, as when the OS is Linux.
8376 Note that we don't want to use
8377 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8378 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8379 since this would make our programs incompatible with other
8380 Linux distributions. We also don't use something like
8381 <tt><var>arch</var>-unknown-linux</tt>, since the
8382 <tt>unknown</tt> does not look very good.
8385 <sect1 id="arch-wildcard-spec">
8386 <heading>Architecture wildcards</heading>
8389 A package may specify an architecture wildcard. Architecture
8390 wildcards are in the format <tt>any</tt> (which matches every
8391 architecture), <tt><var>os</var></tt>-any, or
8392 any-<tt><var>cpu</var></tt>. <footnote>
8393 Internally, the package system normalizes the GNU triplets
8394 and the Debian arches into Debian arch triplets (which are
8395 kind of inverted GNU triplets), with the first component of
8396 the triplet representing the libc and ABI in use, and then
8397 does matching against those triplets. However, such
8398 triplets are an internal implementation detail that should
8399 not be used by packages directly. The libc and ABI portion
8400 is handled internally by the package system based on
8401 the <var>os</var> and <var>cpu</var>.
8408 <heading>Daemons</heading>
8411 The configuration files <file>/etc/services</file>,
8412 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8413 by the <prgn>netbase</prgn> package and must not be modified
8418 If a package requires a new entry in one of these files, the
8419 maintainer should get in contact with the
8420 <prgn>netbase</prgn> maintainer, who will add the entries
8421 and release a new version of the <prgn>netbase</prgn>
8426 The configuration file <file>/etc/inetd.conf</file> must not be
8427 modified by the package's scripts except via the
8428 <prgn>update-inetd</prgn> script or the
8429 <file>DebianNet.pm</file> Perl module. See their documentation
8430 for details on how to add entries.
8434 If a package wants to install an example entry into
8435 <file>/etc/inetd.conf</file>, the entry must be preceded with
8436 exactly one hash character (<tt>#</tt>). Such lines are
8437 treated as "commented out by user" by the
8438 <prgn>update-inetd</prgn> script and are not changed or
8439 activated during package updates.
8444 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8448 Some programs need to create pseudo-ttys. This should be done
8449 using Unix98 ptys if the C library supports it. The resulting
8450 program must not be installed setuid root, unless that
8451 is required for other functionality.
8455 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8456 <file>/var/log/lastlog</file> must be installed writable by
8457 group <tt>utmp</tt>. Programs which need to modify those
8458 files must be installed setgid <tt>utmp</tt>.
8463 <heading>Editors and pagers</heading>
8466 Some programs have the ability to launch an editor or pager
8467 program to edit or display a text document. Since there are
8468 lots of different editors and pagers available in the Debian
8469 distribution, the system administrator and each user should
8470 have the possibility to choose their preferred editor and
8475 In addition, every program should choose a good default
8476 editor/pager if none is selected by the user or system
8481 Thus, every program that launches an editor or pager must
8482 use the EDITOR or PAGER environment variable to determine
8483 the editor or pager the user wishes to use. If these
8484 variables are not set, the programs <file>/usr/bin/editor</file>
8485 and <file>/usr/bin/pager</file> should be used, respectively.
8489 These two files are managed through the <prgn>dpkg</prgn>
8490 "alternatives" mechanism. Every package providing an editor or
8491 pager must call the <prgn>update-alternatives</prgn> script to
8492 register as an alternative for <file>/usr/bin/editor</file>
8493 or <file>/usr/bin/pager</file> as appropriate. The alternative
8494 should have a slave alternative
8495 for <file>/usr/share/man/man1/editor.1.gz</file>
8496 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8497 corresponding manual page.
8501 If it is very hard to adapt a program to make use of the
8502 EDITOR or PAGER variables, that program may be configured to
8503 use <file>/usr/bin/sensible-editor</file> and
8504 <file>/usr/bin/sensible-pager</file> as the editor or pager
8505 program respectively. These are two scripts provided in the
8506 <package>sensible-utils</package> package that check the EDITOR
8507 and PAGER variables and launch the appropriate program, and fall
8508 back to <file>/usr/bin/editor</file>
8509 and <file>/usr/bin/pager</file> if the variable is not set.
8513 A program may also use the VISUAL environment variable to
8514 determine the user's choice of editor. If it exists, it
8515 should take precedence over EDITOR. This is in fact what
8516 <file>/usr/bin/sensible-editor</file> does.
8520 It is not required for a package to depend on
8521 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8522 package to provide such virtual packages.<footnote>
8523 The Debian base system already provides an editor and a
8529 <sect id="web-appl">
8530 <heading>Web servers and applications</heading>
8533 This section describes the locations and URLs that should
8534 be used by all web servers and web applications in the
8541 Cgi-bin executable files are installed in the
8543 <example compact="compact">
8544 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8546 or a subdirectory of that directory, and should be
8548 <example compact="compact">
8549 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8551 (possibly with a subdirectory name
8552 before <var>cgi-bin-name</var>).
8556 <p>Access to HTML documents</p>
8559 HTML documents for a package are stored in
8560 <file>/usr/share/doc/<var>package</var></file>
8561 and can be referred to as
8562 <example compact="compact">
8563 http://localhost/doc/<var>package</var>/<var>filename</var>
8568 The web server should restrict access to the document
8569 tree so that only clients on the same host can read
8570 the documents. If the web server does not support such
8571 access controls, then it should not provide access at
8572 all, or ask about providing access during installation.
8577 <p>Access to images</p>
8579 It is recommended that images for a package be stored
8580 in <tt>/usr/share/images/<var>package</var></tt> and
8581 may be referred to through an alias <tt>/images/</tt>
8584 http://localhost/images/<package>/<filename>
8591 <p>Web Document Root</p>
8594 Web Applications should try to avoid storing files in
8595 the Web Document Root. Instead they should use the
8596 /usr/share/doc/<var>package</var> directory for
8597 documents and register the Web Application via the
8598 <package>doc-base</package> package. If access to the
8599 web document root is unavoidable then use
8600 <example compact="compact">
8603 as the Document Root. This might be just a symbolic
8604 link to the location where the system administrator
8605 has put the real document root.
8608 <item><p>Providing httpd and/or httpd-cgi</p>
8610 All web servers should provide the virtual package
8611 <tt>httpd</tt>. If a web server has CGI support it should
8612 provide <tt>httpd-cgi</tt> additionally.
8615 All web applications which do not contain CGI scripts should
8616 depend on <tt>httpd</tt>, all those web applications which
8617 <tt>do</tt> contain CGI scripts, should depend on
8625 <sect id="mail-transport-agents">
8626 <heading>Mail transport, delivery and user agents</heading>
8629 Debian packages which process electronic mail, whether mail
8630 user agents (MUAs) or mail transport agents (MTAs), must
8631 ensure that they are compatible with the configuration
8632 decisions below. Failure to do this may result in lost
8633 mail, broken <tt>From:</tt> lines, and other serious brain
8638 The mail spool is <file>/var/mail</file> and the interface to
8639 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8640 the FHS). On older systems, the mail spool may be
8641 physically located in <file>/var/spool/mail</file>, but all
8642 access to the mail spool should be via the
8643 <file>/var/mail</file> symlink. The mail spool is part of the
8644 base system and not part of the MTA package.
8648 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8649 programs (such as IMAP daemons) must lock the mailbox in an
8650 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8651 be combined with dot locking. To avoid deadlocks, a program
8652 should use <tt>fcntl()</tt> first and dot locking after
8653 this, or alternatively implement the two locking methods in
8654 a non blocking way<footnote>
8655 If it is not possible to establish both locks, the
8656 system shouldn't wait for the second lock to be
8657 established, but remove the first lock, wait a (random)
8658 time, and start over locking again.
8659 </footnote>. Using the functions <tt>maillock</tt> and
8660 <tt>mailunlock</tt> provided by the
8661 <tt>liblockfile*</tt><footnote>
8662 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8663 to use these functions.
8664 </footnote> packages is the recommended way to realize this.
8668 Mailboxes are generally either mode 600 and owned by
8669 <var>user</var> or mode 660 and owned by
8670 <tt><var>user</var>:mail</tt><footnote>
8671 There are two traditional permission schemes for mail spools:
8672 mode 600 with all mail delivery done by processes running as
8673 the destination user, or mode 660 and owned by group mail with
8674 mail delivery done by a process running as a system user in
8675 group mail. Historically, Debian required mode 660 mail
8676 spools to enable the latter model, but that model has become
8677 increasingly uncommon and the principle of least privilege
8678 indicates that mail systems that use the first model should
8679 use permissions of 600. If delivery to programs is permitted,
8680 it's easier to keep the mail system secure if the delivery
8681 agent runs as the destination user. Debian Policy therefore
8682 permits either scheme.
8683 </footnote>. The local system administrator may choose a
8684 different permission scheme; packages should not make
8685 assumptions about the permission and ownership of mailboxes
8686 unless required (such as when creating a new mailbox). A MUA
8687 may remove a mailbox (unless it has nonstandard permissions) in
8688 which case the MTA or another MUA must recreate it if needed.
8692 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8693 be setgid mail to do the locking mentioned above (and
8694 must obviously avoid accessing other users' mailboxes
8695 using this privilege).</p>
8698 <file>/etc/aliases</file> is the source file for the system mail
8699 aliases (e.g., postmaster, usenet, etc.), it is the one
8700 which the sysadmin and <prgn>postinst</prgn> scripts may
8701 edit. After <file>/etc/aliases</file> is edited the program or
8702 human editing it must call <prgn>newaliases</prgn>. All MTA
8703 packages must come with a <prgn>newaliases</prgn> program,
8704 even if it does nothing, but older MTA packages did not do
8705 this so programs should not fail if <prgn>newaliases</prgn>
8706 cannot be found. Note that because of this, all MTA
8707 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8708 <tt>Replaces: mail-transport-agent</tt> control fields.
8712 The convention of writing <tt>forward to
8713 <var>address</var></tt> in the mailbox itself is not
8714 supported. Use a <tt>.forward</tt> file instead.</p>
8717 The <prgn>rmail</prgn> program used by UUCP
8718 for incoming mail should be <file>/usr/sbin/rmail</file>.
8719 Likewise, <prgn>rsmtp</prgn>, for receiving
8720 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8724 If your package needs to know what hostname to use on (for
8725 example) outgoing news and mail messages which are generated
8726 locally, you should use the file <file>/etc/mailname</file>. It
8727 will contain the portion after the username and <tt>@</tt>
8728 (at) sign for email addresses of users on the machine
8729 (followed by a newline).
8733 Such a package should check for the existence of this file
8734 when it is being configured. If it exists, it should be
8735 used without comment, although an MTA's configuration script
8736 may wish to prompt the user even if it finds that this file
8737 exists. If the file does not exist, the package should
8738 prompt the user for the value (preferably using
8739 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8740 as well as using it in the package's configuration. The
8741 prompt should make it clear that the name will not just be
8742 used by that package. For example, in this situation the
8743 <tt>inn</tt> package could say something like:
8744 <example compact="compact">
8745 Please enter the "mail name" of your system. This is the
8746 hostname portion of the address to be shown on outgoing
8747 news and mail messages. The default is
8748 <var>syshostname</var>, your system's host name. Mail
8749 name ["<var>syshostname</var>"]:
8751 where <var>syshostname</var> is the output of <tt>hostname
8757 <heading>News system configuration</heading>
8760 All the configuration files related to the NNTP (news)
8761 servers and clients should be located under
8762 <file>/etc/news</file>.</p>
8765 There are some configuration issues that apply to a number
8766 of news clients and server packages on the machine. These
8770 <tag><file>/etc/news/organization</file></tag>
8772 A string which should appear as the
8773 organization header for all messages posted
8774 by NNTP clients on the machine
8777 <tag><file>/etc/news/server</file></tag>
8779 Contains the FQDN of the upstream NNTP
8780 server, or localhost if the local machine is
8785 Other global files may be added as required for cross-package news
8792 <heading>Programs for the X Window System</heading>
8795 <heading>Providing X support and package priorities</heading>
8798 Programs that can be configured with support for the X
8799 Window System must be configured to do so and must declare
8800 any package dependencies necessary to satisfy their
8801 runtime requirements when using the X Window System. If
8802 such a package is of higher priority than the X packages
8803 on which it depends, it is required that either the
8804 X-specific components be split into a separate package, or
8805 that an alternative version of the package, which includes
8806 X support, be provided, or that the package's priority be
8812 <heading>Packages providing an X server</heading>
8815 Packages that provide an X server that, directly or
8816 indirectly, communicates with real input and display
8817 hardware should declare in their <tt>Provides</tt> control
8818 field that they provide the virtual
8819 package <tt>xserver</tt>.<footnote>
8820 This implements current practice, and provides an
8821 actual policy for usage of the <tt>xserver</tt>
8822 virtual package which appears in the virtual packages
8823 list. In a nutshell, X servers that interface
8824 directly with the display and input hardware or via
8825 another subsystem (e.g., GGI) should provide
8826 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8827 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8833 <heading>Packages providing a terminal emulator</heading>
8836 Packages that provide a terminal emulator for the X Window
8837 System which meet the criteria listed below should declare in
8838 their <tt>Provides</tt> control field that they provide the
8839 virtual package <tt>x-terminal-emulator</tt>. They should
8840 also register themselves as an alternative for
8841 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8842 20. That alternative should have a slave alternative
8843 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8844 pointing to the corresponding manual page.
8848 To be an <tt>x-terminal-emulator</tt>, a program must:
8849 <list compact="compact">
8851 Be able to emulate a DEC VT100 terminal, or a
8852 compatible terminal.
8856 Support the command-line option <tt>-e
8857 <var>command</var></tt>, which creates a new
8858 terminal window<footnote>
8859 "New terminal window" does not necessarily mean
8860 a new top-level X window directly parented by
8861 the window manager; it could, if the terminal
8862 emulator application were so coded, be a new
8863 "view" in a multiple-document interface (MDI).
8865 and runs the specified <var>command</var>,
8866 interpreting the entirety of the rest of the command
8867 line as a command to pass straight to exec, in the
8868 manner that <tt>xterm</tt> does.
8872 Support the command-line option <tt>-T
8873 <var>title</var></tt>, which creates a new terminal
8874 window with the window title <var>title</var>.
8881 <heading>Packages providing a window manager</heading>
8884 Packages that provide a window manager should declare in
8885 their <tt>Provides</tt> control field that they provide the
8886 virtual package <tt>x-window-manager</tt>. They should also
8887 register themselves as an alternative for
8888 <file>/usr/bin/x-window-manager</file>, with a priority
8889 calculated as follows:
8890 <list compact="compact">
8892 Start with a priority of 20.
8896 If the window manager supports the Debian menu
8897 system, add 20 points if this support is available
8898 in the package's default configuration (i.e., no
8899 configuration files belonging to the system or user
8900 have to be edited to activate the feature); if
8901 configuration files must be modified, add only 10
8907 If the window manager complies with <url
8908 id="http://www.freedesktop.org/Standards/wm-spec"
8909 name="The Window Manager Specification Project">,
8910 written by the <url id="http://www.freedesktop.org/"
8911 name="Free Desktop Group">, add 40 points.
8915 If the window manager permits the X session to be
8916 restarted using a <em>different</em> window manager
8917 (without killing the X server) in its default
8918 configuration, add 10 points; otherwise add none.
8921 That alternative should have a slave alternative
8922 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8923 pointing to the corresponding manual page.
8928 <heading>Packages providing fonts</heading>
8931 Packages that provide fonts for the X Window
8933 For the purposes of Debian Policy, a "font for the X
8934 Window System" is one which is accessed via X protocol
8935 requests. Fonts for the Linux console, for PostScript
8936 renderer, or any other purpose, do not fit this
8937 definition. Any tool which makes such fonts available
8938 to the X Window System, however, must abide by this
8941 must do a number of things to ensure that they are both
8942 available without modification of the X or font server
8943 configuration, and that they do not corrupt files used by
8944 other font packages to register information about
8948 Fonts of any type supported by the X Window System
8949 must be in a separate binary package from any
8950 executables, libraries, or documentation (except
8951 that specific to the fonts shipped, such as their
8952 license information). If one or more of the fonts
8953 so packaged are necessary for proper operation of
8954 the package with which they are associated the font
8955 package may be Recommended; if the fonts merely
8956 provide an enhancement, a Suggests relationship may
8957 be used. Packages must not Depend on font
8959 This is because the X server may retrieve fonts
8960 from the local file system or over the network
8961 from an X font server; the Debian package system
8962 is empowered to deal only with the local
8968 BDF fonts must be converted to PCF fonts with the
8969 <prgn>bdftopcf</prgn> utility (available in the
8970 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8971 placed in a directory that corresponds to their
8973 <list compact="compact">
8975 100 dpi fonts must be placed in
8976 <file>/usr/share/fonts/X11/100dpi/</file>.
8980 75 dpi fonts must be placed in
8981 <file>/usr/share/fonts/X11/75dpi/</file>.
8985 Character-cell fonts, cursor fonts, and other
8986 low-resolution fonts must be placed in
8987 <file>/usr/share/fonts/X11/misc/</file>.
8993 Type 1 fonts must be placed in
8994 <file>/usr/share/fonts/X11/Type1/</file>. If font
8995 metric files are available, they must be placed here
9000 Subdirectories of <file>/usr/share/fonts/X11/</file>
9001 other than those listed above must be neither
9002 created nor used. (The <file>PEX</file>, <file>CID</file>,
9003 <file>Speedo</file>, and <file>cyrillic</file> directories
9004 are excepted for historical reasons, but installation of
9005 files into these directories remains discouraged.)
9009 Font packages may, instead of placing files directly
9010 in the X font directories listed above, provide
9011 symbolic links in that font directory pointing to
9012 the files' actual location in the filesystem. Such
9013 a location must comply with the FHS.
9017 Font packages should not contain both 75dpi and
9018 100dpi versions of a font. If both are available,
9019 they should be provided in separate binary packages
9020 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9021 the names of the packages containing the
9022 corresponding fonts.
9026 Fonts destined for the <file>misc</file> subdirectory
9027 should not be included in the same package as 75dpi
9028 or 100dpi fonts; instead, they should be provided in
9029 a separate package with <tt>-misc</tt> appended to
9034 Font packages must not provide the files
9035 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9036 <file>fonts.scale</file> in a font directory:
9039 <file>fonts.dir</file> files must not be provided at all.
9043 <file>fonts.alias</file> and <file>fonts.scale</file>
9044 files, if needed, should be provided in the
9046 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9047 where <var>fontdir</var> is the name of the
9049 <file>/usr/share/fonts/X11/</file> where the
9050 package's corresponding fonts are stored
9051 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9052 <var>package</var> is the name of the package
9053 that provides these fonts, and
9054 <var>extension</var> is either <tt>scale</tt>
9055 or <tt>alias</tt>, whichever corresponds to
9062 Font packages must declare a dependency on
9063 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9064 or <tt>Pre-Depends</tt> control field.
9068 Font packages that provide one or more
9069 <file>fonts.scale</file> files as described above must
9070 invoke <prgn>update-fonts-scale</prgn> on each
9071 directory into which they installed fonts
9072 <em>before</em> invoking
9073 <prgn>update-fonts-dir</prgn> on that directory.
9074 This invocation must occur in both the
9075 <prgn>postinst</prgn> (for all arguments) and
9076 <prgn>postrm</prgn> (for all arguments except
9077 <tt>upgrade</tt>) scripts.
9081 Font packages that provide one or more
9082 <file>fonts.alias</file> files as described above must
9083 invoke <prgn>update-fonts-alias</prgn> on each
9084 directory into which they installed fonts. This
9085 invocation must occur in both the
9086 <prgn>postinst</prgn> (for all arguments) and
9087 <prgn>postrm</prgn> (for all arguments except
9088 <tt>upgrade</tt>) scripts.
9092 Font packages must invoke
9093 <prgn>update-fonts-dir</prgn> on each directory into
9094 which they installed fonts. This invocation must
9095 occur in both the <prgn>postinst</prgn> (for all
9096 arguments) and <prgn>postrm</prgn> (for all
9097 arguments except <tt>upgrade</tt>) scripts.
9101 Font packages must not provide alias names for the
9102 fonts they include which collide with alias names
9103 already in use by fonts already packaged.
9107 Font packages must not provide fonts with the same
9108 XLFD registry name as another font already packaged.
9114 <sect1 id="appdefaults">
9115 <heading>Application defaults files</heading>
9118 Application defaults files must be installed in the
9119 directory <file>/etc/X11/app-defaults/</file> (use of a
9120 localized subdirectory of <file>/etc/X11/</file> as described
9121 in the <em>X Toolkit Intrinsics - C Language
9122 Interface</em> manual is also permitted). They must be
9123 registered as <tt>conffile</tt>s or handled as
9124 configuration files.
9128 Customization of programs' X resources may also be
9129 supported with the provision of a file with the same name
9130 as that of the package placed in
9131 the <file>/etc/X11/Xresources/</file> directory, which
9132 must be registered as a <tt>conffile</tt> or handled as a
9133 configuration file.<footnote>
9134 Note that this mechanism is not the same as using
9135 app-defaults; app-defaults are tied to the client
9136 binary on the local file system, whereas X resources
9137 are stored in the X server and affect all connecting
9144 <heading>Installation directory issues</heading>
9147 Historically, packages using the X Window System used a
9148 separate set of installation directories from other packages.
9149 This practice has been discontinued and packages using the X
9150 Window System should now generally be installed in the same
9151 directories as any other package. Specifically, packages must
9152 not install files under the <file>/usr/X11R6/</file> directory
9153 and the <file>/usr/X11R6/</file> directory hierarchy should be
9154 regarded as obsolete.
9158 Include files previously installed under
9159 <file>/usr/X11R6/include/X11/</file> should be installed into
9160 <file>/usr/include/X11/</file>. For files previously
9161 installed into subdirectories of
9162 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9163 determine if subdirectories of <file>/usr/lib/</file> and
9164 <file>/usr/share/</file> can be used. If not, a subdirectory
9165 of <file>/usr/lib/X11/</file> should be used.
9169 Configuration files for window, display, or session managers
9170 or other applications that are tightly integrated with the X
9171 Window System may be placed in a subdirectory
9172 of <file>/etc/X11/</file> corresponding to the package name.
9173 Other X Window System applications should use
9174 the <file>/etc/</file> directory unless otherwise mandated by
9175 policy (such as for <ref id="appdefaults">).
9180 <heading>The OSF/Motif and OpenMotif libraries</heading>
9183 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9184 OpenMotif libraries</em><footnote>
9185 OSF/Motif and OpenMotif are collectively referred to as
9186 "Motif" in this policy document.
9188 should be compiled against and tested with LessTif (a free
9189 re-implementation of Motif) instead. If the maintainer
9190 judges that the program or programs do not work
9191 sufficiently well with LessTif to be distributed and
9192 supported, but do so when compiled against Motif, then two
9193 versions of the package should be created; one linked
9194 statically against Motif and with <tt>-smotif</tt>
9195 appended to the package name, and one linked dynamically
9196 against Motif and with <tt>-dmotif</tt> appended to the
9201 Both Motif-linked versions are dependent
9202 upon non-DFSG-compliant software and thus cannot be
9203 uploaded to the <em>main</em> distribution; if the
9204 software is itself DFSG-compliant it may be uploaded to
9205 the <em>contrib</em> distribution. While known existing
9206 versions of Motif permit unlimited redistribution of
9207 binaries linked against the library (whether statically or
9208 dynamically), it is the package maintainer's
9209 responsibility to determine whether this is permitted by
9210 the license of the copy of Motif in their possession.
9216 <heading>Perl programs and modules</heading>
9219 Perl programs and modules should follow the current Perl policy.
9223 The Perl policy can be found in the <tt>perl-policy</tt>
9224 files in the <tt>debian-policy</tt> package.
9225 It is also available from the Debian web mirrors at
9226 <tt><url name="/doc/packaging-manuals/perl-policy/"
9227 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9232 <heading>Emacs lisp programs</heading>
9235 Please refer to the "Debian Emacs Policy" for details of how to
9236 package emacs lisp programs.
9240 The Emacs policy is available in
9241 <file>debian-emacs-policy.gz</file> of the
9242 <package>emacsen-common</package> package.
9243 It is also available from the Debian web mirrors at
9244 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9245 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9250 <heading>Games</heading>
9253 The permissions on <file>/var/games</file> are mode 755, owner
9254 <tt>root</tt> and group <tt>root</tt>.
9258 Each game decides on its own security policy.</p>
9261 Games which require protected, privileged access to
9262 high-score files, saved games, etc., may be made
9263 set-<em>group</em>-id (mode 2755) and owned by
9264 <tt>root:games</tt>, and use files and directories with
9265 appropriate permissions (770 <tt>root:games</tt>, for
9266 example). They must not be made
9267 set-<em>user</em>-id, as this causes security problems. (If
9268 an attacker can subvert any set-user-id game they can
9269 overwrite the executable of any other, causing other players
9270 of these games to run a Trojan horse program. With a
9271 set-group-id game the attacker only gets access to less
9272 important game data, and if they can get at the other
9273 players' accounts at all it will take considerably more
9277 Some packages, for example some fortune cookie programs, are
9278 configured by the upstream authors to install with their
9279 data files or other static information made unreadable so
9280 that they can only be accessed through set-id programs
9281 provided. You should not do this in a Debian package: anyone can
9282 download the <file>.deb</file> file and read the data from it,
9283 so there is no point making the files unreadable. Not
9284 making the files unreadable also means that you don't have
9285 to make so many programs set-id, which reduces the risk of a
9289 As described in the FHS, binaries of games should be
9290 installed in the directory <file>/usr/games</file>. This also
9291 applies to games that use the X Window System. Manual pages
9292 for games (X and non-X games) should be installed in
9293 <file>/usr/share/man/man6</file>.</p>
9299 <heading>Documentation</heading>
9302 <heading>Manual pages</heading>
9305 You should install manual pages in <prgn>nroff</prgn> source
9306 form, in appropriate places under <file>/usr/share/man</file>.
9307 You should only use sections 1 to 9 (see the FHS for more
9308 details). You must not install a pre-formatted "cat page".
9312 Each program, utility, and function should have an
9313 associated manual page included in the same package. It is
9314 suggested that all configuration files also have a manual
9315 page included as well. Manual pages for protocols and other
9316 auxiliary things are optional.
9320 If no manual page is available, this is considered as a bug
9321 and should be reported to the Debian Bug Tracking System (the
9322 maintainer of the package is allowed to write this bug report
9323 themselves, if they so desire). Do not close the bug report
9324 until a proper man page is available.<footnote>
9325 It is not very hard to write a man page. See the
9326 <url id="http://www.schweikhardt.net/man_page_howto.html"
9327 name="Man-Page-HOWTO">,
9328 <manref name="man" section="7">, the examples
9329 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9330 the helper program <prgn>help2man</prgn>, or the
9331 directory <file>/usr/share/doc/man-db/examples</file>.
9336 You may forward a complaint about a missing man page to the
9337 upstream authors, and mark the bug as forwarded in the
9338 Debian bug tracking system. Even though the GNU Project do
9339 not in general consider the lack of a man page to be a bug,
9340 we do; if they tell you that they don't consider it a bug
9341 you should leave the bug in our bug tracking system open
9346 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9350 If one man page needs to be accessible via several names it
9351 is better to use a symbolic link than the <file>.so</file>
9352 feature, but there is no need to fiddle with the relevant
9353 parts of the upstream source to change from <file>.so</file> to
9354 symlinks: don't do it unless it's easy. You should not
9355 create hard links in the manual page directories, nor put
9356 absolute filenames in <file>.so</file> directives. The filename
9357 in a <file>.so</file> in a man page should be relative to the
9358 base of the man page tree (usually
9359 <file>/usr/share/man</file>). If you do not create any links
9360 (whether symlinks, hard links, or <tt>.so</tt> directives)
9361 in the file system to the alternate names of the man page,
9362 then you should not rely on <prgn>man</prgn> finding your
9363 man page under those names based solely on the information in
9364 the man page's header.<footnote>
9365 Supporting this in <prgn>man</prgn> often requires
9366 unreasonable processing time to find a manual page or to
9367 report that none exists, and moves knowledge into man's
9368 database that would be better left in the file system.
9369 This support is therefore deprecated and will cease to
9370 be present in the future.
9375 Manual pages in locale-specific subdirectories of
9376 <file>/usr/share/man</file> should use either UTF-8 or the usual
9377 legacy encoding for that language (normally the one corresponding
9378 to the shortest relevant locale name in
9379 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9380 <file>/usr/share/man/fr</file> should use either UTF-8 or
9381 ISO-8859-1.<footnote>
9382 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9383 use. In future, all manual pages will be required to use
9389 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9390 included in the subdirectory name unless it indicates a
9391 significant difference in the language, as this excludes
9392 speakers of the language in other countries.<footnote>
9393 At the time of writing, Chinese and Portuguese are the main
9394 languages with such differences, so <file>pt_BR</file>,
9395 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9400 If a localized version of a manual page is provided, it should
9401 either be up-to-date or it should be obvious to the reader that
9402 it is outdated and the original manual page should be used
9403 instead. This can be done either by a note at the beginning of
9404 the manual page or by showing the missing or changed portions in
9405 the original language instead of the target language.
9410 <heading>Info documents</heading>
9413 Info documents should be installed in <file>/usr/share/info</file>.
9414 They should be compressed with <tt>gzip -9</tt>.
9418 The <prgn>install-info</prgn> program maintains a directory of
9419 installed info documents in <file>/usr/share/info/dir</file> for
9420 the use of info readers.<footnote>
9421 It was previously necessary for packages installing info
9422 documents to run <prgn>install-info</prgn> from maintainer
9423 scripts. This is no longer necessary. The installation
9424 system now uses dpkg triggers.
9426 This file must not be included in packages. Packages containing
9427 info documents should depend on <tt>dpkg (>= 1.15.4) |
9428 install-info</tt> to ensure that the directory file is properly
9429 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9434 Info documents should contain section and directory entry
9435 information in the document for the use
9436 of <prgn>install-info</prgn>. The section should be specified
9437 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9438 space and the section of this info page. The directory entry or
9439 entries should be included between
9440 a <tt>START-INFO-DIR-ENTRY</tt> line and
9441 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9443 INFO-DIR-SECTION Individual utilities
9444 START-INFO-DIR-ENTRY
9445 * example: (example). An example info directory entry.
9448 To determine which section to use, you should look
9449 at <file>/usr/share/info/dir</file> on your system and choose
9450 the most relevant (or create a new section if none of the
9451 current sections are relevant).<footnote>
9452 Normally, info documents are generated from Texinfo source.
9453 To include this information in the generated info document, if
9454 it is absent, add commands like:
9456 @dircategory Individual utilities
9458 * example: (example). An example info directory entry.
9461 to the Texinfo source of the document and ensure that the info
9462 documents are rebuilt from source during the package build.
9468 <heading>Additional documentation</heading>
9471 Any additional documentation that comes with the package may
9472 be installed at the discretion of the package maintainer.
9473 Plain text documentation should be installed in the directory
9474 <file>/usr/share/doc/<var>package</var></file>, where
9475 <var>package</var> is the name of the package, and
9476 compressed with <tt>gzip -9</tt> unless it is small.
9480 If a package comes with large amounts of documentation which
9481 many users of the package will not require you should create
9482 a separate binary package to contain it, so that it does not
9483 take up disk space on the machines of users who do not need
9484 or want it installed.</p>
9487 It is often a good idea to put text information files
9488 (<file>README</file>s, changelogs, and so forth) that come with
9489 the source package in <file>/usr/share/doc/<var>package</var></file>
9490 in the binary package. However, you don't need to install
9491 the instructions for building and installing the package, of
9495 Packages must not require the existence of any files in
9496 <file>/usr/share/doc/</file> in order to function
9498 The system administrator should be able to
9499 delete files in <file>/usr/share/doc/</file> without causing
9500 any programs to break.
9502 Any files that are referenced by programs but are also
9503 useful as stand alone documentation should be installed under
9504 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9505 <file>/usr/share/doc/<var>package</var></file>.
9509 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9510 link to another directory in <file>/usr/share/doc</file> only if
9511 the two packages both come from the same source and the
9512 first package Depends on the second.<footnote>
9514 Please note that this does not override the section on
9515 changelog files below, so the file
9516 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9517 must refer to the changelog for the current version of
9518 <var>package</var> in question. In practice, this means
9519 that the sources of the target and the destination of the
9520 symlink must be the same (same source package and
9527 Former Debian releases placed all additional documentation
9528 in <file>/usr/doc/<var>package</var></file>. This has been
9529 changed to <file>/usr/share/doc/<var>package</var></file>,
9530 and packages must not put documentation in the directory
9531 <file>/usr/doc/<var>package</var></file>. <footnote>
9532 At this phase of the transition, we no longer require a
9533 symbolic link in <file>/usr/doc/</file>. At a later point,
9534 policy shall change to make the symbolic links a bug.
9540 <heading>Preferred documentation formats</heading>
9543 The unification of Debian documentation is being carried out
9547 If your package comes with extensive documentation in a
9548 markup format that can be converted to various other formats
9549 you should if possible ship HTML versions in a binary
9550 package, in the directory
9551 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9552 its subdirectories.<footnote>
9553 The rationale: The important thing here is that HTML
9554 docs should be available in <em>some</em> package, not
9555 necessarily in the main binary package.
9560 Other formats such as PostScript may be provided at the
9561 package maintainer's discretion.
9565 <sect id="copyrightfile">
9566 <heading>Copyright information</heading>
9569 Every package must be accompanied by a verbatim copy of its
9570 copyright information and distribution license in the file
9571 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9572 file must neither be compressed nor be a symbolic link.
9576 In addition, the copyright file must say where the upstream
9577 sources (if any) were obtained. It should name the original
9578 authors of the package and the Debian maintainer(s) who were
9579 involved with its creation.
9583 Packages in the <em>contrib</em> or <em>non-free</em> archive
9584 areas should state in the copyright file that the package is not
9585 part of the Debian distribution and briefly explain why.
9589 A copy of the file which will be installed in
9590 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9591 be in <file>debian/copyright</file> in the source package.
9595 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9596 link to another directory in <file>/usr/share/doc</file> only if
9597 the two packages both come from the same source and the
9598 first package Depends on the second. These rules are
9599 important because copyrights must be extractable by
9604 Packages distributed under the Apache license (version 2.0), the
9605 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9606 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9607 1.3) should refer to the corresponding files
9608 under <file>/usr/share/common-licenses</file>,<footnote>
9611 <file>/usr/share/common-licenses/Apache-2.0</file>,
9612 <file>/usr/share/common-licenses/Artistic</file>,
9613 <file>/usr/share/common-licenses/GPL-1</file>,
9614 <file>/usr/share/common-licenses/GPL-2</file>,
9615 <file>/usr/share/common-licenses/GPL-3</file>,
9616 <file>/usr/share/common-licenses/LGPL-2</file>,
9617 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9618 <file>/usr/share/common-licenses/LGPL-3</file>,
9619 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9620 <file>/usr/share/common-licenses/GFDL-1.3</file>
9621 respectively. The University of California BSD license is
9622 also included in <package>base-files</package> as
9623 <file>/usr/share/common-licenses/BSD</file>, but given the
9624 brevity of this license, its specificity to code whose
9625 copyright is held by the Regents of the University of
9626 California, and the frequency of minor wording changes, its
9627 text should be included in the copyright file rather than
9628 referencing this file.
9630 </footnote> rather than quoting them in the copyright
9635 You should not use the copyright file as a general <file>README</file>
9636 file. If your package has such a file it should be
9637 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9638 <file>README.Debian</file> or some other appropriate place.</p>
9642 <heading>Examples</heading>
9645 Any examples (configurations, source files, whatever),
9646 should be installed in a directory
9647 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9648 files should not be referenced by any program: they're there
9649 for the benefit of the system administrator and users as
9650 documentation only. Architecture-specific example files
9651 should be installed in a directory
9652 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9654 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9655 latter directory itself may be a symbolic link to the
9660 If the purpose of a package is to provide examples, then the
9661 example files may be installed into
9662 <file>/usr/share/doc/<var>package</var></file>.
9666 <sect id="changelogs">
9667 <heading>Changelog files</heading>
9670 Packages that are not Debian-native must contain a
9671 compressed copy of the <file>debian/changelog</file> file from
9672 the Debian source tree in
9673 <file>/usr/share/doc/<var>package</var></file> with the name
9674 <file>changelog.Debian.gz</file>.
9678 If an upstream changelog is available, it should be accessible as
9679 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9680 plain text. If the upstream changelog is distributed in
9681 HTML, it should be made available in that form as
9682 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9683 and a plain text <file>changelog.gz</file> should be generated
9684 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9685 the upstream changelog files do not already conform to this
9686 naming convention, then this may be achieved either by
9687 renaming the files, or by adding a symbolic link, at the
9688 maintainer's discretion.<footnote>
9689 Rationale: People should not have to look in places for
9690 upstream changelogs merely because they are given
9691 different names or are distributed in HTML format.
9696 All of these files should be installed compressed using
9697 <tt>gzip -9</tt>, as they will become large with time even
9698 if they start out small.
9702 If the package has only one changelog which is used both as
9703 the Debian changelog and the upstream one because there is
9704 no separate upstream maintainer then that changelog should
9705 usually be installed as
9706 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9707 there is a separate upstream maintainer, but no upstream
9708 changelog, then the Debian changelog should still be called
9709 <file>changelog.Debian.gz</file>.
9713 For details about the format and contents of the Debian
9714 changelog file, please see <ref id="dpkgchangelog">.
9719 <appendix id="pkg-scope">
9720 <heading>Introduction and scope of these appendices</heading>
9723 These appendices are taken essentially verbatim from the
9724 now-deprecated Packaging Manual, version 3.2.1.0. They are
9725 the chapters which are likely to be of use to package
9726 maintainers and which have not already been included in the
9727 policy document itself. Most of these sections are very likely
9728 not relevant to policy; they should be treated as
9729 documentation for the packaging system. Please note that these
9730 appendices are included for convenience, and for historical
9731 reasons: they used to be part of policy package, and they have
9732 not yet been incorporated into dpkg documentation. However,
9733 they still have value, and hence they are presented here.
9737 They have not yet been checked to ensure that they are
9738 compatible with the contents of policy, and if there are any
9739 contradictions, the version in the main policy document takes
9740 precedence. The remaining chapters of the old Packaging
9741 Manual have also not been read in detail to ensure that there
9742 are not parts which have been left out. Both of these will be
9747 Certain parts of the Packaging manual were integrated into the
9748 Policy Manual proper, and removed from the appendices. Links
9749 have been placed from the old locations to the new ones.
9753 <prgn>dpkg</prgn> is a suite of programs for creating binary
9754 package files and installing and removing them on Unix
9756 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
9757 work on or be ported to other systems.
9762 The binary packages are designed for the management of
9763 installed executable programs (usually compiled binaries) and
9764 their associated data, though source code examples and
9765 documentation are provided as part of some packages.</p>
9768 This manual describes the technical aspects of creating Debian
9769 binary packages (<file>.deb</file> files). It documents the
9770 behavior of the package management programs
9771 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9772 they interact with packages.</p>
9775 It also documents the interaction between
9776 <prgn>dselect</prgn>'s core and the access method scripts it
9777 uses to actually install the selected packages, and describes
9778 how to create a new access method.</p>
9781 This manual does not go into detail about the options and
9782 usage of the package building and installation tools. It
9783 should therefore be read in conjunction with those programs'
9788 The utility programs which are provided with <prgn>dpkg</prgn>
9789 for managing various system configuration and similar issues,
9790 such as <prgn>update-rc.d</prgn> and
9791 <prgn>install-info</prgn>, are not described in detail here -
9792 please see their man pages.
9796 It is assumed that the reader is reasonably familiar with the
9797 <prgn>dpkg</prgn> System Administrators' manual.
9798 Unfortunately this manual does not yet exist.
9802 The Debian version of the FSF's GNU hello program is provided
9803 as an example for people wishing to create Debian
9804 packages. The Debian <prgn>debmake</prgn> package is
9805 recommended as a very helpful tool in creating and maintaining
9806 Debian packages. However, while the tools and examples are
9807 helpful, they do not replace the need to read and follow the
9808 Policy and Programmer's Manual.</p>
9811 <appendix id="pkg-binarypkg">
9812 <heading>Binary packages (from old Packaging Manual)</heading>
9815 The binary package has two main sections. The first part
9816 consists of various control information files and scripts used
9817 by <prgn>dpkg</prgn> when installing and removing. See <ref
9818 id="pkg-controlarea">.
9822 The second part is an archive containing the files and
9823 directories to be installed.
9827 In the future binary packages may also contain other
9828 components, such as checksums and digital signatures. The
9829 format for the archive is described in full in the
9830 <file>deb(5)</file> man page.
9834 <sect id="pkg-bincreating"><heading>Creating package files -
9835 <prgn>dpkg-deb</prgn>
9839 All manipulation of binary package files is done by
9840 <prgn>dpkg-deb</prgn>; it's the only program that has
9841 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9842 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9843 will spot that the options requested are appropriate to
9844 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9849 In order to create a binary package you must make a
9850 directory tree which contains all the files and directories
9851 you want to have in the file system data part of the package.
9852 In Debian-format source packages this directory is usually
9853 <file>debian/tmp</file>, relative to the top of the package's
9858 They should have the locations (relative to the root of the
9859 directory tree you're constructing) ownerships and
9860 permissions which you want them to have on the system when
9865 With current versions of <prgn>dpkg</prgn> the uid/username
9866 and gid/groupname mappings for the users and groups being
9867 used should be the same on the system where the package is
9868 built and the one where it is installed.
9872 You need to add one special directory to the root of the
9873 miniature file system tree you're creating:
9874 <prgn>DEBIAN</prgn>. It should contain the control
9875 information files, notably the binary package control file
9876 (see <ref id="pkg-controlfile">).
9880 The <prgn>DEBIAN</prgn> directory will not appear in the
9881 file system archive of the package, and so won't be installed
9882 by <prgn>dpkg</prgn> when the package is installed.
9886 When you've prepared the package, you should invoke:
9888 dpkg --build <var>directory</var>
9893 This will build the package in
9894 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9895 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9896 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9901 See the man page <manref name="dpkg-deb" section="8"> for details of how
9902 to examine the contents of this newly-created file. You may find the
9903 output of following commands enlightening:
9905 dpkg-deb --info <var>filename</var>.deb
9906 dpkg-deb --contents <var>filename</var>.deb
9907 dpkg --contents <var>filename</var>.deb
9909 To view the copyright file for a package you could use this command:
9911 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9916 <sect id="pkg-controlarea">
9917 <heading>Package control information files</heading>
9920 The control information portion of a binary package is a
9921 collection of files with names known to <prgn>dpkg</prgn>.
9922 It will treat the contents of these files specially - some
9923 of them contain information used by <prgn>dpkg</prgn> when
9924 installing or removing the package; others are scripts which
9925 the package maintainer wants <prgn>dpkg</prgn> to run.
9929 It is possible to put other files in the package control
9930 information file area, but this is not generally a good idea
9931 (though they will largely be ignored).
9935 Here is a brief list of the control information files supported
9936 by <prgn>dpkg</prgn> and a summary of what they're used for.
9941 <tag><tt>control</tt>
9944 This is the key description file used by
9945 <prgn>dpkg</prgn>. It specifies the package's name
9946 and version, gives its description for the user,
9947 states its relationships with other packages, and so
9948 forth. See <ref id="sourcecontrolfiles"> and
9949 <ref id="binarycontrolfiles">.
9953 It is usually generated automatically from information
9954 in the source package by the
9955 <prgn>dpkg-gencontrol</prgn> program, and with
9956 assistance from <prgn>dpkg-shlibdeps</prgn>.
9957 See <ref id="pkg-sourcetools">.
9961 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9966 These are executable files (usually scripts) which
9967 <prgn>dpkg</prgn> runs during installation, upgrade
9968 and removal of packages. They allow the package to
9969 deal with matters which are particular to that package
9970 or require more complicated processing than that
9971 provided by <prgn>dpkg</prgn>. Details of when and
9972 how they are called are in <ref id="maintainerscripts">.
9976 It is very important to make these scripts idempotent.
9977 See <ref id="idempotency">.
9981 The maintainer scripts are not guaranteed to run with a
9982 controlling terminal and may not be able to interact with
9983 the user. See <ref id="controllingterminal">.
9987 <tag><tt>conffiles</tt>
9990 This file contains a list of configuration files which
9991 are to be handled automatically by <prgn>dpkg</prgn>
9992 (see <ref id="pkg-conffiles">). Note that not necessarily
9993 every configuration file should be listed here.
9996 <tag><tt>shlibs</tt>
9999 This file contains a list of the shared libraries
10000 supplied by the package, with dependency details for
10001 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10002 when it determines what dependencies are required in a
10003 package control file. The <tt>shlibs</tt> file format
10004 is described on <ref id="shlibs">.
10009 <sect id="pkg-controlfile">
10010 <heading>The main control information file: <tt>control</tt></heading>
10013 The most important control information file used by
10014 <prgn>dpkg</prgn> when it installs a package is
10015 <tt>control</tt>. It contains all the package's "vital
10020 The binary package control files of packages built from
10021 Debian sources are made by a special tool,
10022 <prgn>dpkg-gencontrol</prgn>, which reads
10023 <file>debian/control</file> and <file>debian/changelog</file> to
10024 find the information it needs. See <ref id="pkg-sourcepkg"> for
10029 The fields in binary package control files are listed in
10030 <ref id="binarycontrolfiles">.
10034 A description of the syntax of control files and the purpose
10035 of the fields is available in <ref id="controlfields">.
10040 <heading>Time Stamps</heading>
10043 See <ref id="timestamps">.
10048 <appendix id="pkg-sourcepkg">
10049 <heading>Source packages (from old Packaging Manual) </heading>
10052 The Debian binary packages in the distribution are generated
10053 from Debian sources, which are in a special format to assist
10054 the easy and automatic building of binaries.
10057 <sect id="pkg-sourcetools">
10058 <heading>Tools for processing source packages</heading>
10061 Various tools are provided for manipulating source packages;
10062 they pack and unpack sources and help build of binary
10063 packages and help manage the distribution of new versions.
10067 They are introduced and typical uses described here; see
10068 <manref name="dpkg-source" section="1"> for full
10069 documentation about their arguments and operation.
10073 For examples of how to construct a Debian source package,
10074 and how to use those utilities that are used by Debian
10075 source packages, please see the <prgn>hello</prgn> example
10079 <sect1 id="pkg-dpkg-source">
10081 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10086 This program is frequently used by hand, and is also
10087 called from package-independent automated building scripts
10088 such as <prgn>dpkg-buildpackage</prgn>.
10092 To unpack a package it is typically invoked with
10094 dpkg-source -x <var>.../path/to/filename</var>.dsc
10099 with the <file><var>filename</var>.tar.gz</file> and
10100 <file><var>filename</var>.diff.gz</file> (if applicable) in
10101 the same directory. It unpacks into
10102 <file><var>package</var>-<var>version</var></file>, and if
10104 <file><var>package</var>-<var>version</var>.orig</file>, in
10105 the current directory.
10109 To create a packed source archive it is typically invoked:
10111 dpkg-source -b <var>package</var>-<var>version</var>
10116 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10117 <file>.diff.gz</file> (if appropriate) in the current
10118 directory. <prgn>dpkg-source</prgn> does not clean the
10119 source tree first - this must be done separately if it is
10124 See also <ref id="pkg-sourcearchives">.</p>
10128 <sect1 id="pkg-dpkg-buildpackage">
10130 <prgn>dpkg-buildpackage</prgn> - overall package-building
10135 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10136 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10137 targets <tt>clean</tt>, <tt>build</tt> and
10138 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10139 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10140 source and binary package upload.
10144 It is usually invoked by hand from the top level of the
10145 built or unbuilt source directory. It may be invoked with
10146 no arguments; useful arguments include:
10147 <taglist compact="compact">
10148 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10151 Do not sign the <tt>.changes</tt> file or the
10152 source package <tt>.dsc</tt> file, respectively.</p>
10154 <tag><tt>-p<var>sign-command</var></tt></tag>
10157 Invoke <var>sign-command</var> instead of finding
10158 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10159 <var>sign-command</var> must behave just like
10160 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10162 <tag><tt>-r<var>root-command</var></tt></tag>
10165 When root privilege is required, invoke the command
10166 <var>root-command</var>. <var>root-command</var>
10167 should invoke its first argument as a command, from
10168 the <prgn>PATH</prgn> if necessary, and pass its
10169 second and subsequent arguments to the command it
10170 calls. If no <var>root-command</var> is supplied
10171 then <var>dpkg-buildpackage</var> will take no
10172 special action to gain root privilege, so that for
10173 most packages it will have to be invoked as root to
10176 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10179 Two types of binary-only build and upload - see
10180 <manref name="dpkg-source" section="1">.
10187 <sect1 id="pkg-dpkg-gencontrol">
10189 <prgn>dpkg-gencontrol</prgn> - generates binary package
10194 This program is usually called from <file>debian/rules</file>
10195 (see <ref id="pkg-sourcetree">) in the top level of the source
10200 This is usually done just before the files and directories in the
10201 temporary directory tree where the package is being built have their
10202 permissions and ownerships set and the package is constructed using
10203 <prgn>dpkg-deb/</prgn>
10205 This is so that the control file which is produced has
10206 the right permissions
10211 <prgn>dpkg-gencontrol</prgn> must be called after all the
10212 files which are to go into the package have been placed in
10213 the temporary build directory, so that its calculation of
10214 the installed size of a package is correct.
10218 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10219 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10220 variable substitutions created by
10221 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10226 For a package which generates only one binary package, and
10227 which builds it in <file>debian/tmp</file> relative to the top
10228 of the source package, it is usually sufficient to call
10229 <prgn>dpkg-gencontrol</prgn>.
10233 Sources which build several binaries will typically need
10236 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10237 </example> The <tt>-P</tt> tells
10238 <prgn>dpkg-gencontrol</prgn> that the package is being
10239 built in a non-default directory, and the <tt>-p</tt>
10240 tells it which package's control file should be generated.
10244 <prgn>dpkg-gencontrol</prgn> also adds information to the
10245 list of files in <file>debian/files</file>, for the benefit of
10246 (for example) a future invocation of
10247 <prgn>dpkg-genchanges</prgn>.</p>
10250 <sect1 id="pkg-dpkg-shlibdeps">
10252 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10257 This program is usually called from <file>debian/rules</file>
10258 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10259 id="pkg-sourcetree">), in the top level of the source tree.
10263 Its arguments are executables and shared libraries
10266 They may be specified either in the locations in the
10267 source tree where they are created or in the locations
10268 in the temporary build tree where they are installed
10269 prior to binary package creation.
10271 </footnote> for which shared library dependencies should
10272 be included in the binary package's control file.
10276 If some of the found shared libraries should only
10277 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10278 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10279 by using the <tt>-d<var>dependency-field</var></tt> option
10280 before those executable(s). (Each <tt>-d</tt> option
10281 takes effect until the next <tt>-d</tt>.)
10285 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10286 output control file to be modified. Instead by default it
10287 adds to the <file>debian/substvars</file> file variable
10288 settings like <tt>shlibs:Depends</tt>. These variable
10289 settings must be referenced in dependency fields in the
10290 appropriate per-binary-package sections of the source
10295 For example, a package that generates an essential part
10296 which requires dependencies, and optional parts that
10297 which only require a recommendation, would separate those
10298 two sets of dependencies into two different fields.<footnote>
10299 At the time of writing, an example for this was the
10300 <package/xmms/ package, with Depends used for the xmms
10301 executable, Recommends for the plug-ins and Suggests for
10302 even more optional features provided by unzip.
10304 It can say in its <file>debian/rules</file>:
10306 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10307 -dRecommends <var>optionalpart anotheroptionalpart</var>
10309 and then in its main control file <file>debian/control</file>:
10312 Depends: ${shlibs:Depends}
10313 Recommends: ${shlibs:Recommends}
10319 Sources which produce several binary packages with
10320 different shared library dependency requirements can use
10321 the <tt>-p<var>varnameprefix</var></tt> option to override
10322 the default <tt>shlibs:</tt> prefix (one invocation of
10323 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10324 They can thus produce several sets of dependency
10325 variables, each of the form
10326 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10327 which can be referred to in the appropriate parts of the
10328 binary package control files.
10333 <sect1 id="pkg-dpkg-distaddfile">
10335 <prgn>dpkg-distaddfile</prgn> - adds a file to
10336 <file>debian/files</file>
10340 Some packages' uploads need to include files other than
10341 the source and binary package files.
10345 <prgn>dpkg-distaddfile</prgn> adds a file to the
10346 <file>debian/files</file> file so that it will be included in
10347 the <file>.changes</file> file when
10348 <prgn>dpkg-genchanges</prgn> is run.
10352 It is usually invoked from the <tt>binary</tt> target of
10353 <file>debian/rules</file>:
10355 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10357 The <var>filename</var> is relative to the directory where
10358 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10359 is usually the directory above the top level of the source
10360 tree. The <file>debian/rules</file> target should put the
10361 file there just before or just after calling
10362 <prgn>dpkg-distaddfile</prgn>.
10366 The <var>section</var> and <var>priority</var> are passed
10367 unchanged into the resulting <file>.changes</file> file.
10372 <sect1 id="pkg-dpkg-genchanges">
10374 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10375 upload control file
10379 This program is usually called by package-independent
10380 automatic building scripts such as
10381 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10386 It is usually called in the top level of a built source
10387 tree, and when invoked with no arguments will print out a
10388 straightforward <file>.changes</file> file based on the
10389 information in the source package's changelog and control
10390 file and the binary and source packages which should have
10396 <sect1 id="pkg-dpkg-parsechangelog">
10398 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10399 representation of a changelog
10403 This program is used internally by
10404 <prgn>dpkg-source</prgn> et al. It may also occasionally
10405 be useful in <file>debian/rules</file> and elsewhere. It
10406 parses a changelog, <file>debian/changelog</file> by default,
10407 and prints a control-file format representation of the
10408 information in it to standard output.
10412 <sect1 id="pkg-dpkg-architecture">
10414 <prgn>dpkg-architecture</prgn> - information about the build and
10419 This program can be used manually, but is also invoked by
10420 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10421 environment or make variables which specify the build and host
10422 architecture for the package building process.
10427 <sect id="pkg-sourcetree">
10428 <heading>The Debian package source tree</heading>
10431 The source archive scheme described later is intended to
10432 allow a Debian package source tree with some associated
10433 control information to be reproduced and transported easily.
10434 The Debian package source tree is a version of the original
10435 program with certain files added for the benefit of the
10436 packaging process, and with any other changes required
10437 made to the rest of the source code and installation
10442 The extra files created for Debian are in the subdirectory
10443 <file>debian</file> of the top level of the Debian package
10444 source tree. They are described below.
10447 <sect1 id="pkg-debianrules">
10448 <heading><file>debian/rules</file> - the main building script</heading>
10451 See <ref id="debianrules">.
10455 <sect1 id="pkg-srcsubstvars">
10456 <heading><file>debian/substvars</file> and variable substitutions</heading>
10459 See <ref id="substvars">.
10465 <heading><file>debian/files</file></heading>
10468 See <ref id="debianfiles">.
10472 <sect1><heading><file>debian/tmp</file>
10476 This is the canonical temporary location for the
10477 construction of binary packages by the <tt>binary</tt>
10478 target. The directory <file>tmp</file> serves as the root of
10479 the file system tree as it is being constructed (for
10480 example, by using the package's upstream makefiles install
10481 targets and redirecting the output there), and it also
10482 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10483 id="pkg-bincreating">.
10487 If several binary packages are generated from the same
10488 source tree it is usual to use several
10489 <file>debian/tmp<var>something</var></file> directories, for
10490 example <file>tmp-a</file> or <file>tmp-doc</file>.
10494 Whatever <file>tmp</file> directories are created and used by
10495 <tt>binary</tt> must of course be removed by the
10496 <tt>clean</tt> target.</p></sect1>
10500 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10504 As it exists on the FTP site, a Debian source package
10505 consists of three related files. You must have the right
10506 versions of all three to be able to use them.
10511 <tag>Debian source control file - <tt>.dsc</tt></tag>
10513 This file is a control file used by <prgn>dpkg-source</prgn>
10514 to extract a source package.
10515 See <ref id="debiansourcecontrolfiles">.
10519 Original source archive -
10521 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10527 This is a compressed (with <tt>gzip -9</tt>)
10528 <prgn>tar</prgn> file containing the source code from
10529 the upstream authors of the program.
10534 Debian package diff -
10536 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10542 This is a unified context diff (<tt>diff -u</tt>)
10543 giving the changes which are required to turn the
10544 original source into the Debian source. These changes
10545 may only include editing and creating plain files.
10546 The permissions of files, the targets of symbolic
10547 links and the characteristics of special files or
10548 pipes may not be changed and no files may be removed
10553 All the directories in the diff must exist, except the
10554 <file>debian</file> subdirectory of the top of the source
10555 tree, which will be created by
10556 <prgn>dpkg-source</prgn> if necessary when unpacking.
10560 The <prgn>dpkg-source</prgn> program will
10561 automatically make the <file>debian/rules</file> file
10562 executable (see below).</p></item>
10567 If there is no original source code - for example, if the
10568 package is specially prepared for Debian or the Debian
10569 maintainer is the same as the upstream maintainer - the
10570 format is slightly different: then there is no diff, and the
10572 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10573 and preferably contains a directory named
10574 <file><var>package</var>-<var>version</var></file>.
10579 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10582 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10583 Debian source package. However, if it is not available it
10584 is possible to unpack a Debian source archive as follows:
10585 <enumlist compact="compact">
10588 Untar the tarfile, which will create a <file>.orig</file>
10592 <p>Rename the <file>.orig</file> directory to
10593 <file><var>package</var>-<var>version</var></file>.</p>
10597 Create the subdirectory <file>debian</file> at the top of
10598 the source tree.</p>
10600 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10602 <item><p>Untar the tarfile again if you want a copy of the original
10603 source code alongside the Debian version.</p>
10608 It is not possible to generate a valid Debian source archive
10609 without using <prgn>dpkg-source</prgn>. In particular,
10610 attempting to use <prgn>diff</prgn> directly to generate the
10611 <file>.diff.gz</file> file will not work.
10615 <heading>Restrictions on objects in source packages</heading>
10618 The source package may not contain any hard links
10620 This is not currently detected when building source
10621 packages, but only when extracting
10625 Hard links may be permitted at some point in the
10626 future, but would require a fair amount of
10628 </footnote>, device special files, sockets or setuid or
10631 Setgid directories are allowed.
10636 The source packaging tools manage the changes between the
10637 original and Debian source using <prgn>diff</prgn> and
10638 <prgn>patch</prgn>. Turning the original source tree as
10639 included in the <file>.orig.tar.gz</file> into the Debian
10640 package source must not involve any changes which cannot be
10641 handled by these tools. Problematic changes which cause
10642 <prgn>dpkg-source</prgn> to halt with an error when
10643 building the source package are:
10644 <list compact="compact">
10645 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10647 <item><p>Changing the targets of symbolic links.</p>
10649 <item><p>Creating directories, other than <file>debian</file>.</p>
10651 <item><p>Changes to the contents of binary files.</p></item>
10652 </list> Changes which cause <prgn>dpkg-source</prgn> to
10653 print a warning but continue anyway are:
10654 <list compact="compact">
10657 Removing files, directories or symlinks.
10659 Renaming a file is not treated specially - it is
10660 seen as the removal of the old file (which
10661 generates a warning, but is otherwise ignored),
10662 and the creation of the new one.
10668 Changed text files which are missing the usual final
10669 newline (either in the original or the modified
10674 Changes which are not represented, but which are not detected by
10675 <prgn>dpkg-source</prgn>, are:
10676 <list compact="compact">
10677 <item><p>Changing the permissions of files (other than
10678 <file>debian/rules</file>) and directories.</p></item>
10683 The <file>debian</file> directory and <file>debian/rules</file>
10684 are handled specially by <prgn>dpkg-source</prgn> - before
10685 applying the changes it will create the <file>debian</file>
10686 directory, and afterwards it will make
10687 <file>debian/rules</file> world-executable.
10693 <appendix id="pkg-controlfields">
10694 <heading>Control files and their fields (from old Packaging Manual)</heading>
10697 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10698 data in a common format, known as control files. Binary and
10699 source packages have control data as do the <file>.changes</file>
10700 files which control the installation of uploaded files, and
10701 <prgn>dpkg</prgn>'s internal databases are in a similar
10706 <heading>Syntax of control files</heading>
10709 See <ref id="controlsyntax">.
10713 It is important to note that there are several fields which
10714 are optional as far as <prgn>dpkg</prgn> and the related
10715 tools are concerned, but which must appear in every Debian
10716 package, or whose omission may cause problems.
10721 <heading>List of fields</heading>
10724 See <ref id="controlfieldslist">.
10728 This section now contains only the fields that didn't belong
10729 to the Policy manual.
10732 <sect1 id="pkg-f-Filename">
10733 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10736 These fields in <tt>Packages</tt> files give the
10737 filename(s) of (the parts of) a package in the
10738 distribution directories, relative to the root of the
10739 Debian hierarchy. If the package has been split into
10740 several parts the parts are all listed in order, separated
10745 <sect1 id="pkg-f-Size">
10746 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10749 These fields in <file>Packages</file> files give the size (in
10750 bytes, expressed in decimal) and MD5 checksum of the
10751 file(s) which make(s) up a binary package in the
10752 distribution. If the package is split into several parts
10753 the values for the parts are listed in order, separated by
10758 <sect1 id="pkg-f-Status">
10759 <heading><tt>Status</tt></heading>
10762 This field in <prgn>dpkg</prgn>'s status file records
10763 whether the user wants a package installed, removed or
10764 left alone, whether it is broken (requiring
10765 re-installation) or not and what its current state on the
10766 system is. Each of these pieces of information is a
10771 <sect1 id="pkg-f-Config-Version">
10772 <heading><tt>Config-Version</tt></heading>
10775 If a package is not installed or not configured, this
10776 field in <prgn>dpkg</prgn>'s status file records the last
10777 version of the package which was successfully
10782 <sect1 id="pkg-f-Conffiles">
10783 <heading><tt>Conffiles</tt></heading>
10786 This field in <prgn>dpkg</prgn>'s status file contains
10787 information about the automatically-managed configuration
10788 files held by a package. This field should <em>not</em>
10789 appear anywhere in a package!
10794 <heading>Obsolete fields</heading>
10797 These are still recognized by <prgn>dpkg</prgn> but should
10798 not appear anywhere any more.
10800 <taglist compact="compact">
10802 <tag><tt>Revision</tt></tag>
10803 <tag><tt>Package-Revision</tt></tag>
10804 <tag><tt>Package_Revision</tt></tag>
10806 The Debian revision part of the package version was
10807 at one point in a separate control field. This
10808 field went through several names.
10811 <tag><tt>Recommended</tt></tag>
10812 <item>Old name for <tt>Recommends</tt>.</item>
10814 <tag><tt>Optional</tt></tag>
10815 <item>Old name for <tt>Suggests</tt>.</item>
10817 <tag><tt>Class</tt></tag>
10818 <item>Old name for <tt>Priority</tt>.</item>
10827 <appendix id="pkg-conffiles">
10828 <heading>Configuration file handling (from old Packaging Manual)</heading>
10831 <prgn>dpkg</prgn> can do a certain amount of automatic
10832 handling of package configuration files.
10836 Whether this mechanism is appropriate depends on a number of
10837 factors, but basically there are two approaches to any
10838 particular configuration file.
10842 The easy method is to ship a best-effort configuration in the
10843 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10844 handle updates. If the user is unlikely to want to edit the
10845 file, but you need them to be able to without losing their
10846 changes, and a new package with a changed version of the file
10847 is only released infrequently, this is a good approach.
10851 The hard method is to build the configuration file from
10852 scratch in the <prgn>postinst</prgn> script, and to take the
10853 responsibility for fixing any mistakes made in earlier
10854 versions of the package automatically. This will be
10855 appropriate if the file is likely to need to be different on
10859 <sect><heading>Automatic handling of configuration files by
10864 A package may contain a control information file called
10865 <tt>conffiles</tt>. This file should be a list of filenames
10866 of configuration files needing automatic handling, separated
10867 by newlines. The filenames should be absolute pathnames,
10868 and the files referred to should actually exist in the
10873 When a package is upgraded <prgn>dpkg</prgn> will process
10874 the configuration files during the configuration stage,
10875 shortly before it runs the package's <prgn>postinst</prgn>
10880 For each file it checks to see whether the version of the
10881 file included in the package is the same as the one that was
10882 included in the last version of the package (the one that is
10883 being upgraded from); it also compares the version currently
10884 installed on the system with the one shipped with the last
10889 If neither the user nor the package maintainer has changed
10890 the file, it is left alone. If one or the other has changed
10891 their version, then the changed version is preferred - i.e.,
10892 if the user edits their file, but the package maintainer
10893 doesn't ship a different version, the user's changes will
10894 stay, silently, but if the maintainer ships a new version
10895 and the user hasn't edited it the new version will be
10896 installed (with an informative message). If both have
10897 changed their version the user is prompted about the problem
10898 and must resolve the differences themselves.
10902 The comparisons are done by calculating the MD5 message
10903 digests of the files, and storing the MD5 of the file as it
10904 was included in the most recent version of the package.
10908 When a package is installed for the first time
10909 <prgn>dpkg</prgn> will install the file that comes with it,
10910 unless that would mean overwriting a file already on the
10915 However, note that <prgn>dpkg</prgn> will <em>not</em>
10916 replace a conffile that was removed by the user (or by a
10917 script). This is necessary because with some programs a
10918 missing file produces an effect hard or impossible to
10919 achieve in another way, so that a missing file needs to be
10920 kept that way if the user did it.
10924 Note that a package should <em>not</em> modify a
10925 <prgn>dpkg</prgn>-handled conffile in its maintainer
10926 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10927 the user confusing and possibly dangerous options for
10928 conffile update when the package is upgraded.</p>
10931 <sect><heading>Fully-featured maintainer script configuration
10936 For files which contain site-specific information such as
10937 the hostname and networking details and so forth, it is
10938 better to create the file in the package's
10939 <prgn>postinst</prgn> script.
10943 This will typically involve examining the state of the rest
10944 of the system to determine values and other information, and
10945 may involve prompting the user for some information which
10946 can't be obtained some other way.
10950 When using this method there are a couple of important
10951 issues which should be considered:
10955 If you discover a bug in the program which generates the
10956 configuration file, or if the format of the file changes
10957 from one version to the next, you will have to arrange for
10958 the postinst script to do something sensible - usually this
10959 will mean editing the installed configuration file to remove
10960 the problem or change the syntax. You will have to do this
10961 very carefully, since the user may have changed the file,
10962 perhaps to fix the very problem that your script is trying
10963 to deal with - you will have to detect these situations and
10964 deal with them correctly.
10968 If you do go down this route it's probably a good idea to
10969 make the program that generates the configuration file(s) a
10970 separate program in <file>/usr/sbin</file>, by convention called
10971 <file><var>package</var>config</file> and then run that if
10972 appropriate from the post-installation script. The
10973 <tt><var>package</var>config</tt> program should not
10974 unquestioningly overwrite an existing configuration - if its
10975 mode of operation is geared towards setting up a package for
10976 the first time (rather than any arbitrary reconfiguration
10977 later) you should have it check whether the configuration
10978 already exists, and require a <tt>--force</tt> flag to
10979 overwrite it.</p></sect>
10982 <appendix id="pkg-alternatives"><heading>Alternative versions of
10983 an interface - <prgn>update-alternatives</prgn> (from old
10988 When several packages all provide different versions of the
10989 same program or file it is useful to have the system select a
10990 default, but to allow the system administrator to change it
10991 and have their decisions respected.
10995 For example, there are several versions of the <prgn>vi</prgn>
10996 editor, and there is no reason to prevent all of them from
10997 being installed at once, each under their own name
10998 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10999 Nevertheless it is desirable to have the name <tt>vi</tt>
11000 refer to something, at least by default.
11004 If all the packages involved cooperate, this can be done with
11005 <prgn>update-alternatives</prgn>.
11009 Each package provides its own version under its own name, and
11010 calls <prgn>update-alternatives</prgn> in its postinst to
11011 register its version (and again in its prerm to deregister
11016 See the man page <manref name="update-alternatives"
11017 section="8"> for details.
11021 If <prgn>update-alternatives</prgn> does not seem appropriate
11022 you may wish to consider using diversions instead.</p>
11025 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11026 package's version of a file (from old Packaging Manual)
11030 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11031 when it reinstalls the package it belongs to, and to have it
11032 put the file from the package somewhere else instead.
11036 This can be used locally to override a package's version of a
11037 file, or by one package to override another's version (or
11038 provide a wrapper for it).
11042 Before deciding to use a diversion, read <ref
11043 id="pkg-alternatives"> to see if you really want a diversion
11044 rather than several alternative versions of a program.
11048 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11049 and updated by a special program <prgn>dpkg-divert</prgn>.
11050 Please see <manref name="dpkg-divert" section="8"> for full
11051 details of its operation.
11055 When a package wishes to divert a file from another, it should
11056 call <prgn>dpkg-divert</prgn> in its preinst to add the
11057 diversion and rename the existing file. For example,
11058 supposing that a <prgn>smailwrapper</prgn> package wishes to
11059 install a wrapper around <file>/usr/sbin/smail</file>:
11061 dpkg-divert --package smailwrapper --add --rename \
11062 --divert /usr/sbin/smail.real /usr/sbin/smail
11063 </example> The <tt>--package smailwrapper</tt> ensures that
11064 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11065 can bypass the diversion and get installed as the true version.
11066 It's safe to add the diversion unconditionally on upgrades since
11067 it will be left unchanged if it already exists, but
11068 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11069 message, make the command conditional on the version from which
11070 the package is being upgraded:
11072 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11073 dpkg-divert --package smailwrapper --add --rename \
11074 --divert /usr/sbin/smail.real /usr/sbin/smail
11076 </example> where <tt>1.0-2</tt> is the version at which the
11077 diversion was first added to the package. Running the command
11078 during abort-upgrade is pointless but harmless.
11082 The postrm has to do the reverse:
11084 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11085 dpkg-divert --package smailwrapper --remove --rename \
11086 --divert /usr/sbin/smail.real /usr/sbin/smail
11088 </example> If the diversion was added at a particular version, the
11089 postrm should also handle the failure case of upgrading from an
11090 older version (unless the older version is so old that direct
11091 upgrades are no longer supported):
11093 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11094 dpkg-divert --package smailwrapper --remove --rename \
11095 --divert /usr/sbin/smail.real /usr/sbin/smail
11097 </example> where <tt>1.02-2</tt> is the version at which the
11098 diversion was first added to the package. The postrm should not
11099 remove the diversion on upgrades both because there's no reason to
11100 remove the diversion only to immediately re-add it and since the
11101 postrm of the old package is run after unpacking so the removal of
11102 the diversion will fail.
11106 Do not attempt to divert a file which is vitally important for
11107 the system's operation - when using <prgn>dpkg-divert</prgn>
11108 there is a time, after it has been diverted but before
11109 <prgn>dpkg</prgn> has installed the new version, when the file
11110 does not exist.</p>
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