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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></item>
261 <item><ref id="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 The <em>main</em> archive area comprises the Debian
469 distribution. Only the packages in this area are considered
470 part of the distribution. None of the packages in
471 the <em>main</em> archive area require software outside of
472 that area to function. Anyone may use, share, modify and
473 redistribute the packages in this archive area
475 See <url id="http://www.debian.org/intro/free"
476 name="What Does Free Mean?"> for
477 more about what we mean by free software.
482 Every package in <em>main</em> must comply with the DFSG
483 (Debian Free Software Guidelines).
487 In addition, the packages in <em>main</em>
488 <list compact="compact">
490 must not require or recommend a package outside
491 of <em>main</em> for compilation or execution (thus, the
492 package must not declare a "Pre-Depends", "Depends",
493 "Recommends", "Build-Depends", or "Build-Depends-Indep"
494 relationship on a non-<em>main</em> package),
497 must not be so buggy that we refuse to support them,
501 must meet all policy requirements presented in this
510 <heading>The contrib archive area</heading>
513 The <em>contrib</em> archive area contains supplemental
514 packages intended to work with the Debian distribution, but
515 which require software outside of the distribution to either
520 Every package in <em>contrib</em> must comply with the DFSG.
524 In addition, the packages in <em>contrib</em>
525 <list compact="compact">
527 must not be so buggy that we refuse to support them,
531 must meet all policy requirements presented in this
538 Examples of packages which would be included in
539 <em>contrib</em> are:
540 <list compact="compact">
542 free packages which require <em>contrib</em>,
543 <em>non-free</em> packages or packages which are not
544 in our archive at all for compilation or execution,
548 wrapper packages or other sorts of free accessories for
555 <sect1 id="non-free">
556 <heading>The non-free archive area</heading>
559 The <em>non-free</em> archive area contains supplemental
560 packages intended to work with the Debian distribution that do
561 not comply with the DFSG or have other problems that make
562 their distribution problematic. They may not comply with all
563 of the policy requirements in this manual due to restrictions
564 on modifications or other limitations.
568 Packages must be placed in <em>non-free</em> if they are
569 not compliant with the DFSG or are encumbered by patents
570 or other legal issues that make their distribution
575 In addition, the packages in <em>non-free</em>
576 <list compact="compact">
578 must not be so buggy that we refuse to support them,
582 must meet all policy requirements presented in this
583 manual that it is possible for them to meet.
585 It is possible that there are policy
586 requirements which the package is unable to
587 meet, for example, if the source is
588 unavailable. These situations will need to be
589 handled on a case-by-case basis.
598 <sect id="pkgcopyright">
599 <heading>Copyright considerations</heading>
602 Every package must be accompanied by a verbatim copy of its
603 copyright information and distribution license in the file
604 <file>/usr/share/doc/<var>package</var>/copyright</file>
605 (see <ref id="copyrightfile"> for further details).
609 We reserve the right to restrict files from being included
610 anywhere in our archives if
611 <list compact="compact">
613 their use or distribution would break a law,
616 there is an ethical conflict in their distribution or
620 we would have to sign a license for them, or
623 their distribution would conflict with other project
630 Programs whose authors encourage the user to make
631 donations are fine for the main distribution, provided
632 that the authors do not claim that not donating is
633 immoral, unethical, illegal or something similar; in such
634 a case they must go in <em>non-free</em>.
638 Packages whose copyright permission notices (or patent
639 problems) do not even allow redistribution of binaries
640 only, and where no special permission has been obtained,
641 must not be placed on the Debian FTP site and its mirrors
646 Note that under international copyright law (this applies
647 in the United States, too), <em>no</em> distribution or
648 modification of a work is allowed without an explicit
649 notice saying so. Therefore a program without a copyright
650 notice <em>is</em> copyrighted and you may not do anything
651 to it without risking being sued! Likewise if a program
652 has a copyright notice but no statement saying what is
653 permitted then nothing is permitted.
657 Many authors are unaware of the problems that restrictive
658 copyrights (or lack of copyright notices) can cause for
659 the users of their supposedly-free software. It is often
660 worthwhile contacting such authors diplomatically to ask
661 them to modify their license terms. However, this can be a
662 politically difficult thing to do and you should ask for
663 advice on the <tt>debian-legal</tt> mailing list first, as
668 When in doubt about a copyright, send mail to
669 <email>debian-legal@lists.debian.org</email>. Be prepared
670 to provide us with the copyright statement. Software
671 covered by the GPL, public domain software and BSD-like
672 copyrights are safe; be wary of the phrases "commercial
673 use prohibited" and "distribution restricted".
677 <sect id="subsections">
678 <heading>Sections</heading>
681 The packages in the archive areas <em>main</em>,
682 <em>contrib</em> and <em>non-free</em> are grouped further into
683 <em>sections</em> to simplify handling.
687 The archive area and section for each package should be
688 specified in the package's <tt>Section</tt> control record (see
689 <ref id="f-Section">). However, the maintainer of the Debian
690 archive may override this selection to ensure the consistency of
691 the Debian distribution. The <tt>Section</tt> field should be
693 <list compact="compact">
695 <em>section</em> if the package is in the
696 <em>main</em> archive area,
699 <em>area/section</em> if the package is in
700 the <em>contrib</em> or <em>non-free</em>
707 The Debian archive maintainers provide the authoritative
708 list of sections. At present, they are:
709 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
710 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
711 <em>education</em>, <em>electronics</em>, <em>embedded</em>,
712 <em>fonts</em>, <em>games</em>, <em>gnome</em>, <em>graphics</em>,
713 <em>gnu-r</em>, <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
714 <em>httpd</em>, <em>interpreters</em>, <em>introspection</em>,
715 <em>java</em>, <em>kde</em>, <em>kernel</em>, <em>libs</em>,
716 <em>libdevel</em>, <em>lisp</em>, <em>localization</em>,
717 <em>mail</em>, <em>math</em>, <em>metapackages</em>, <em>misc</em>,
718 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
719 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
720 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
721 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
722 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
723 <em>zope</em>. The additional section <em>debian-installer</em>
724 contains special packages used by the installer and is not used
725 for normal Debian packages.
729 For more information about the sections and their definitions,
730 see the <url id="http://packages.debian.org/unstable/"
731 name="list of sections in unstable">.
735 <sect id="priorities">
736 <heading>Priorities</heading>
739 Each package should have a <em>priority</em> value, which is
740 included in the package's <em>control record</em>
741 (see <ref id="f-Priority">).
742 This information is used by the Debian package management tools to
743 separate high-priority packages from less-important packages.
747 The following <em>priority levels</em> are recognized by the
748 Debian package management tools.
750 <tag><tt>required</tt></tag>
752 Packages which are necessary for the proper
753 functioning of the system (usually, this means that
754 dpkg functionality depends on these packages).
755 Removing a <tt>required</tt> package may cause your
756 system to become totally broken and you may not even
757 be able to use <prgn>dpkg</prgn> to put things back,
758 so only do so if you know what you are doing. Systems
759 with only the <tt>required</tt> packages are probably
760 unusable, but they do have enough functionality to
761 allow the sysadmin to boot and install more software.
763 <tag><tt>important</tt></tag>
765 Important programs, including those which one would
766 expect to find on any Unix-like system. If the
767 expectation is that an experienced Unix person who
768 found it missing would say "What on earth is going on,
769 where is <prgn>foo</prgn>?", it must be an
770 <tt>important</tt> package.<footnote>
771 This is an important criterion because we are
772 trying to produce, amongst other things, a free
775 Other packages without which the system will not run
776 well or be usable must also have priority
777 <tt>important</tt>. This does
778 <em>not</em> include Emacs, the X Window System, TeX
779 or any other large applications. The
780 <tt>important</tt> packages are just a bare minimum of
781 commonly-expected and necessary tools.
783 <tag><tt>standard</tt></tag>
785 These packages provide a reasonably small but not too
786 limited character-mode system. This is what will be
787 installed by default if the user doesn't select anything
788 else. It doesn't include many large applications.
790 <tag><tt>optional</tt></tag>
792 (In a sense everything that isn't required is
793 optional, but that's not what is meant here.) This is
794 all the software that you might reasonably want to
795 install if you didn't know what it was and don't have
796 specialized requirements. This is a much larger system
797 and includes the X Window System, a full TeX
798 distribution, and many applications. Note that
799 optional packages should not conflict with each other.
801 <tag><tt>extra</tt></tag>
803 This contains all packages that conflict with others
804 with required, important, standard or optional
805 priorities, or are only likely to be useful if you
806 already know what they are or have specialized
807 requirements (such as packages containing only detached
814 Packages must not depend on packages with lower priority
815 values (excluding build-time dependencies). In order to
816 ensure this, the priorities of one or more packages may need
825 <heading>Binary packages</heading>
828 The Debian distribution is based on the Debian
829 package management system, called <prgn>dpkg</prgn>. Thus,
830 all packages in the Debian distribution must be provided
831 in the <tt>.deb</tt> file format.
835 A <tt>.deb</tt> package contains two sets of files: a set of files
836 to install on the system when the package is installed, and a set
837 of files that provide additional metadata about the package or
838 which are executed when the package is installed or removed. This
839 second set of files is called <em>control information files</em>.
840 Among those files are the package maintainer scripts
841 and <file>control</file>, the <qref id="binarycontrolfiles">binary
842 package control file</qref> that contains the control fields for
843 the package. Other control information files include
844 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
845 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
846 used to store shared library dependency information and
847 the <file>conffiles</file> file that lists the package's
848 configuration files (described in <ref id="config-files">).
852 There is unfortunately a collision of terminology here between
853 control information files and files in the Debian control file
854 format. Throughout this document, a <em>control file</em> refers
855 to a file in the Debian control file format. These files are
856 documented in <ref id="controlfields">. Only files referred to
857 specifically as <em>control information files</em> are the files
858 included in the control information file member of
859 the <file>.deb</file> file format used by binary packages. Most
860 control information files are not in the Debian control file
865 <heading>The package name</heading>
868 Every package must have a name that's unique within the Debian
873 The package name is included in the control field
874 <tt>Package</tt>, the format of which is described
875 in <ref id="f-Package">.
876 The package name is also included as a part of the file name
877 of the <tt>.deb</tt> file.
882 <heading>The version of a package</heading>
885 Every package has a version number recorded in its
886 <tt>Version</tt> control file field, described in
887 <ref id="f-Version">.
891 The package management system imposes an ordering on version
892 numbers, so that it can tell whether packages are being up- or
893 downgraded and so that package system front end applications
894 can tell whether a package it finds available is newer than
895 the one installed on the system. The version number format
896 has the most significant parts (as far as comparison is
897 concerned) at the beginning.
901 If an upstream package has problematic version numbers they
902 should be converted to a sane form for use in the
903 <tt>Version</tt> field.
907 <heading>Version numbers based on dates</heading>
910 In general, Debian packages should use the same version
911 numbers as the upstream sources. However, upstream version
912 numbers based on some date formats (sometimes used for
913 development or "snapshot" releases) will not be ordered
914 correctly by the package management software. For
915 example, <prgn>dpkg</prgn> will consider "96May01" to be
916 greater than "96Dec24".
920 To prevent having to use epochs for every new upstream
921 version, the date-based portion of any upstream version number
922 should be given in a way that sorts correctly: four-digit year
923 first, followed by a two-digit numeric month, followed by a
924 two-digit numeric date, possibly with punctuation between the
929 Native Debian packages (i.e., packages which have been written
930 especially for Debian) whose version numbers include dates
931 should also follow these rules. If punctuation is desired
932 between the date components, remember that hyphen (<tt>-</tt>)
933 cannot be used in native package versions. Period
934 (<tt>.</tt>) is normally a good choice.
940 <sect id="maintainer">
941 <heading>The maintainer of a package</heading>
944 Every package must have a maintainer, except for orphaned
945 packages as described below. The maintainer may be one person
946 or a group of people reachable from a common email address, such
947 as a mailing list. The maintainer is responsible for
948 maintaining the Debian packaging files, evaluating and
949 responding appropriately to reported bugs, uploading new
950 versions of the package (either directly or through a sponsor),
951 ensuring that the package is placed in the appropriate archive
952 area and included in Debian releases as appropriate for the
953 stability and utility of the package, and requesting removal of
954 the package from the Debian distribution if it is no longer
955 useful or maintainable.
959 The maintainer must be specified in the <tt>Maintainer</tt>
960 control field with their correct name and a working email
961 address. The email address given in the <tt>Maintainer</tt>
962 control field must accept mail from those role accounts in
963 Debian used to send automated mails regarding the package. This
964 includes non-spam mail from the bug-tracking system, all mail
965 from the Debian archive maintenance software, and other role
966 accounts or automated processes that are commonly agreed on by
967 the project.<footnote>
968 A sample implementation of such a whitelist written for the
969 Mailman mailing list management software is used for mailing
970 lists hosted by alioth.debian.org.
972 If one person or team maintains several packages, they should
973 use the same form of their name and email address in
974 the <tt>Maintainer</tt> fields of those packages.
978 The format of the <tt>Maintainer</tt> control field is
979 described in <ref id="f-Maintainer">.
983 If the maintainer of the package is a team of people with a
984 shared email address, the <tt>Uploaders</tt> control field must
985 be present and must contain at least one human with their
986 personal email address. See <ref id="f-Uploaders"> for the
987 syntax of that field.
991 An orphaned package is one with no current maintainer. Orphaned
992 packages should have their <tt>Maintainer</tt> control field set
993 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
994 These packages are considered maintained by the Debian project
995 as a whole until someone else volunteers to take over
996 maintenance.<footnote>
997 The detailed procedure for gracefully orphaning a package can
998 be found in the Debian Developer's Reference
999 (see <ref id="related">).
1004 <sect id="descriptions">
1005 <heading>The description of a package</heading>
1008 Every Debian package must have a <tt>Description</tt> control
1009 field which contains a synopsis and extended description of the
1010 package. Technical information about the format of the
1011 <tt>Description</tt> field is in <ref id="f-Description">.
1015 The description should describe the package (the program) to a
1016 user (system administrator) who has never met it before so that
1017 they have enough information to decide whether they want to
1018 install it. This description should not just be copied verbatim
1019 from the program's documentation.
1023 Put important information first, both in the synopsis and
1024 extended description. Sometimes only the first part of the
1025 synopsis or of the description will be displayed. You can
1026 assume that there will usually be a way to see the whole
1027 extended description.
1031 The description should also give information about the
1032 significant dependencies and conflicts between this package
1033 and others, so that the user knows why these dependencies and
1034 conflicts have been declared.
1038 Instructions for configuring or using the package should
1039 not be included (that is what installation scripts,
1040 manual pages, info files, etc., are for). Copyright
1041 statements and other administrivia should not be included
1042 either (that is what the copyright file is for).
1045 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1048 The single line synopsis should be kept brief - certainly
1049 under 80 characters.
1053 Do not include the package name in the synopsis line. The
1054 display software knows how to display this already, and you
1055 do not need to state it. Remember that in many situations
1056 the user may only see the synopsis line - make it as
1057 informative as you can.
1062 <sect1 id="extendeddesc"><heading>The extended description</heading>
1065 Do not try to continue the single line synopsis into the
1066 extended description. This will not work correctly when
1067 the full description is displayed, and makes no sense
1068 where only the summary (the single line synopsis) is
1073 The extended description should describe what the package
1074 does and how it relates to the rest of the system (in terms
1075 of, for example, which subsystem it is which part of).
1079 The description field needs to make sense to anyone, even
1080 people who have no idea about any of the things the
1081 package deals with.<footnote>
1082 The blurb that comes with a program in its
1083 announcements and/or <prgn>README</prgn> files is
1084 rarely suitable for use in a description. It is
1085 usually aimed at people who are already in the
1086 community where the package is used.
1094 <sect id="dependencies">
1095 <heading>Dependencies</heading>
1098 Every package must specify the dependency information
1099 about other packages that are required for the first to
1104 For example, a dependency entry must be provided for any
1105 shared libraries required by a dynamically-linked executable
1106 binary in a package.
1110 Packages are not required to declare any dependencies they
1111 have on other packages which are marked <tt>Essential</tt>
1112 (see below), and should not do so unless they depend on a
1113 particular version of that package.<footnote>
1115 Essential is needed in part to avoid unresolvable dependency
1116 loops on upgrade. If packages add unnecessary dependencies
1117 on packages in this set, the chances that there
1118 <strong>will</strong> be an unresolvable dependency loop
1119 caused by forcing these Essential packages to be configured
1120 first before they need to be is greatly increased. It also
1121 increases the chances that frontends will be unable to
1122 <strong>calculate</strong> an upgrade path, even if one
1126 Also, functionality is rarely ever removed from the
1127 Essential set, but <em>packages</em> have been removed from
1128 the Essential set when the functionality moved to a
1129 different package. So depending on these packages <em>just
1130 in case</em> they stop being essential does way more harm
1137 Sometimes, unpacking one package requires that another package
1138 be first unpacked <em>and</em> configured. In this case, the
1139 depending package must specify this dependency in
1140 the <tt>Pre-Depends</tt> control field.
1144 You should not specify a <tt>Pre-Depends</tt> entry for a
1145 package before this has been discussed on the
1146 <tt>debian-devel</tt> mailing list and a consensus about
1147 doing that has been reached.
1151 The format of the package interrelationship control fields is
1152 described in <ref id="relationships">.
1156 <sect id="virtual_pkg">
1157 <heading>Virtual packages</heading>
1160 Sometimes, there are several packages which offer
1161 more-or-less the same functionality. In this case, it's
1162 useful to define a <em>virtual package</em> whose name
1163 describes that common functionality. (The virtual
1164 packages only exist logically, not physically; that's why
1165 they are called <em>virtual</em>.) The packages with this
1166 particular function will then <em>provide</em> the virtual
1167 package. Thus, any other package requiring that function
1168 can simply depend on the virtual package without having to
1169 specify all possible packages individually.
1173 All packages should use virtual package names where
1174 appropriate, and arrange to create new ones if necessary.
1175 They should not use virtual package names (except privately,
1176 amongst a cooperating group of packages) unless they have
1177 been agreed upon and appear in the list of virtual package
1178 names. (See also <ref id="virtual">)
1182 The latest version of the authoritative list of virtual
1183 package names can be found in the <tt>debian-policy</tt> package.
1184 It is also available from the Debian web mirrors at
1185 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1186 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1190 The procedure for updating the list is described in the preface
1197 <heading>Base system</heading>
1200 The <tt>base system</tt> is a minimum subset of the Debian
1201 system that is installed before everything else
1202 on a new system. Only very few packages are allowed to form
1203 part of the base system, in order to keep the required disk
1208 The base system consists of all those packages with priority
1209 <tt>required</tt> or <tt>important</tt>. Many of them will
1210 be tagged <tt>essential</tt> (see below).
1215 <heading>Essential packages</heading>
1218 Essential is defined as the minimal set of functionality that
1219 must be available and usable on the system at all times, even
1220 when packages are in an unconfigured (but unpacked) state.
1221 Packages are tagged <tt>essential</tt> for a system using the
1222 <tt>Essential</tt> control field. The format of the
1223 <tt>Essential</tt> control field is described in <ref
1228 Since these packages cannot be easily removed (one has to
1229 specify an extra <em>force option</em> to
1230 <prgn>dpkg</prgn> to do so), this flag must not be used
1231 unless absolutely necessary. A shared library package
1232 must not be tagged <tt>essential</tt>; dependencies will
1233 prevent its premature removal, and we need to be able to
1234 remove it when it has been superseded.
1238 Since dpkg will not prevent upgrading of other packages
1239 while an <tt>essential</tt> package is in an unconfigured
1240 state, all <tt>essential</tt> packages must supply all of
1241 their core functionality even when unconfigured. If the
1242 package cannot satisfy this requirement it must not be
1243 tagged as essential, and any packages depending on this
1244 package must instead have explicit dependency fields as
1249 Maintainers should take great care in adding any programs,
1250 interfaces, or functionality to <tt>essential</tt> packages.
1251 Packages may assume that functionality provided by
1252 <tt>essential</tt> packages is always available without
1253 declaring explicit dependencies, which means that removing
1254 functionality from the Essential set is very difficult and is
1255 almost never done. Any capability added to an
1256 <tt>essential</tt> package therefore creates an obligation to
1257 support that capability as part of the Essential set in
1262 You must not tag any packages <tt>essential</tt> before
1263 this has been discussed on the <tt>debian-devel</tt>
1264 mailing list and a consensus about doing that has been
1269 <sect id="maintscripts">
1270 <heading>Maintainer Scripts</heading>
1273 The package installation scripts should avoid producing
1274 output which is unnecessary for the user to see and
1275 should rely on <prgn>dpkg</prgn> to stave off boredom on
1276 the part of a user installing many packages. This means,
1277 amongst other things, using the <tt>--quiet</tt> option on
1278 <prgn>install-info</prgn>.
1282 Errors which occur during the execution of an installation
1283 script must be checked and the installation must not
1284 continue after an error.
1288 Note that in general <ref id="scripts"> applies to package
1289 maintainer scripts, too.
1293 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1294 to another package without consulting the maintainer of that
1295 package first. When adding or removing diversions, package
1296 maintainer scripts must provide the <tt>--package</tt> flag
1297 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1301 All packages which supply an instance of a common command
1302 name (or, in general, filename) should generally use
1303 <prgn>update-alternatives</prgn>, so that they may be
1304 installed together. If <prgn>update-alternatives</prgn>
1305 is not used, then each package must use
1306 <tt>Conflicts</tt> to ensure that other packages are
1307 de-installed. (In this case, it may be appropriate to
1308 specify a conflict against earlier versions of something
1309 that previously did not use
1310 <prgn>update-alternatives</prgn>; this is an exception to
1311 the usual rule that versioned conflicts should be
1315 <sect1 id="maintscriptprompt">
1316 <heading>Prompting in maintainer scripts</heading>
1318 Package maintainer scripts may prompt the user if
1319 necessary. Prompting must be done by communicating
1320 through a program, such as <prgn>debconf</prgn>, which
1321 conforms to the Debian Configuration Management
1322 Specification, version 2 or higher.
1326 Packages which are essential, or which are dependencies of
1327 essential packages, may fall back on another prompting method
1328 if no such interface is available when they are executed.
1332 The Debian Configuration Management Specification is included
1333 in the <file>debconf_specification</file> files in the
1334 <package>debian-policy</package> package.
1335 It is also available from the Debian web mirrors at
1336 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1337 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1341 Packages which use the Debian Configuration Management
1342 Specification may contain the additional control information
1343 files <file>config</file>
1344 and <file>templates</file>. <file>config</file> is an
1345 additional maintainer script used for package configuration,
1346 and <file>templates</file> contains templates used for user
1347 prompting. The <prgn>config</prgn> script might be run before
1348 the <prgn>preinst</prgn> script and before the package is
1349 unpacked or any of its dependencies or pre-dependencies are
1350 satisfied. Therefore it must work using only the tools
1351 present in <em>essential</em> packages.<footnote>
1352 <package>Debconf</package> or another tool that
1353 implements the Debian Configuration Management
1354 Specification will also be installed, and any
1355 versioned dependencies on it will be satisfied
1356 before preconfiguration begins.
1361 Packages which use the Debian Configuration Management
1362 Specification must allow for translation of their user-visible
1363 messages by using a gettext-based system such as the one
1364 provided by the <package>po-debconf</package> package.
1368 Packages should try to minimize the amount of prompting
1369 they need to do, and they should ensure that the user
1370 will only ever be asked each question once. This means
1371 that packages should try to use appropriate shared
1372 configuration files (such as <file>/etc/papersize</file> and
1373 <file>/etc/news/server</file>), and shared
1374 <package>debconf</package> variables rather than each
1375 prompting for their own list of required pieces of
1380 It also means that an upgrade should not ask the same
1381 questions again, unless the user has used
1382 <tt>dpkg --purge</tt> to remove the package's configuration.
1383 The answers to configuration questions should be stored in an
1384 appropriate place in <file>/etc</file> so that the user can
1385 modify them, and how this has been done should be
1390 If a package has a vitally important piece of
1391 information to pass to the user (such as "don't run me
1392 as I am, you must edit the following configuration files
1393 first or you risk your system emitting badly-formatted
1394 messages"), it should display this in the
1395 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1396 prompt the user to hit return to acknowledge the
1397 message. Copyright messages do not count as vitally
1398 important (they belong in
1399 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1400 neither do instructions on how to use a program (these
1401 should be in on-line documentation, where all the users
1406 Any necessary prompting should almost always be confined
1407 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1408 script. If it is done in the <prgn>postinst</prgn>, it
1409 should be protected with a conditional so that
1410 unnecessary prompting doesn't happen if a package's
1411 installation fails and the <prgn>postinst</prgn> is
1412 called with <tt>abort-upgrade</tt>,
1413 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1423 <heading>Source packages</heading>
1425 <sect id="standardsversion">
1426 <heading>Standards conformance</heading>
1429 Source packages should specify the most recent version number
1430 of this policy document with which your package complied
1431 when it was last updated.
1435 This information may be used to file bug reports
1436 automatically if your package becomes too much out of date.
1440 The version is specified in the <tt>Standards-Version</tt>
1442 The format of the <tt>Standards-Version</tt> field is
1443 described in <ref id="f-Standards-Version">.
1447 You should regularly, and especially if your package has
1448 become out of date, check for the newest Policy Manual
1449 available and update your package, if necessary. When your
1450 package complies with the new standards you should update the
1451 <tt>Standards-Version</tt> source package field and
1452 release it.<footnote>
1453 See the file <file>upgrading-checklist</file> for
1454 information about policy which has changed between
1455 different versions of this document.
1461 <sect id="pkg-relations">
1462 <heading>Package relationships</heading>
1465 Source packages should specify which binary packages they
1466 require to be installed or not to be installed in order to
1467 build correctly. For example, if building a package
1468 requires a certain compiler, then the compiler should be
1469 specified as a build-time dependency.
1473 It is not necessary to explicitly specify build-time
1474 relationships on a minimal set of packages that are always
1475 needed to compile, link and put in a Debian package a
1476 standard "Hello World!" program written in C or C++. The
1477 required packages are called <em>build-essential</em>, and
1478 an informational list can be found in
1479 <file>/usr/share/doc/build-essential/list</file> (which is
1480 contained in the <tt>build-essential</tt>
1483 <list compact="compact">
1485 This allows maintaining the list separately
1486 from the policy documents (the list does not
1487 need the kind of control that the policy
1491 Having a separate package allows one to install
1492 the build-essential packages on a machine, as
1493 well as allowing other packages such as tasks to
1494 require installation of the build-essential
1495 packages using the depends relation.
1498 The separate package allows bug reports against
1499 the list to be categorized separately from
1500 the policy management process in the BTS.
1507 When specifying the set of build-time dependencies, one
1508 should list only those packages explicitly required by the
1509 build. It is not necessary to list packages which are
1510 required merely because some other package in the list of
1511 build-time dependencies depends on them.<footnote>
1512 The reason for this is that dependencies change, and
1513 you should list all those packages, and <em>only</em>
1514 those packages that <em>you</em> need directly. What
1515 others need is their business. For example, if you
1516 only link against <file>libimlib</file>, you will need to
1517 build-depend on <package>libimlib2-dev</package> but
1518 not against any <tt>libjpeg*</tt> packages, even
1519 though <tt>libimlib2-dev</tt> currently depends on
1520 them: installation of <package>libimlib2-dev</package>
1521 will automatically ensure that all of its run-time
1522 dependencies are satisfied.
1527 If build-time dependencies are specified, it must be
1528 possible to build the package and produce working binaries
1529 on a system with only essential and build-essential
1530 packages installed and also those required to satisfy the
1531 build-time relationships (including any implied
1532 relationships). In particular, this means that version
1533 clauses should be used rigorously in build-time
1534 relationships so that one cannot produce bad or
1535 inconsistently configured packages when the relationships
1536 are properly satisfied.
1540 <ref id="relationships"> explains the technical details.
1545 <heading>Changes to the upstream sources</heading>
1548 If changes to the source code are made that are not
1549 specific to the needs of the Debian system, they should be
1550 sent to the upstream authors in whatever form they prefer
1551 so as to be included in the upstream version of the
1556 If you need to configure the package differently for
1557 Debian or for Linux, and the upstream source doesn't
1558 provide a way to do so, you should add such configuration
1559 facilities (for example, a new <prgn>autoconf</prgn> test
1560 or <tt>#define</tt>) and send the patch to the upstream
1561 authors, with the default set to the way they originally
1562 had it. You can then easily override the default in your
1563 <file>debian/rules</file> or wherever is appropriate.
1567 You should make sure that the <prgn>configure</prgn> utility
1568 detects the correct architecture specification string
1569 (refer to <ref id="arch-spec"> for details).
1573 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1574 <prgn>configure</prgn> scripts are used, you should edit the
1575 <file>.in</file> files rather than editing the
1576 <prgn>Makefile</prgn> directly. This allows the user to
1577 reconfigure the package if necessary. You should
1578 <em>not</em> configure the package and edit the generated
1579 <prgn>Makefile</prgn>! This makes it impossible for someone
1580 else to later reconfigure the package without losing the
1586 <sect id="dpkgchangelog">
1587 <heading>Debian changelog: <file>debian/changelog</file></heading>
1590 Changes in the Debian version of the package should be
1591 briefly explained in the Debian changelog file
1592 <file>debian/changelog</file>.<footnote>
1594 Mistakes in changelogs are usually best rectified by
1595 making a new changelog entry rather than "rewriting
1596 history" by editing old changelog entries.
1599 This includes modifications
1600 made in the Debian package compared to the upstream one
1601 as well as other changes and updates to the package.
1603 Although there is nothing stopping an author who is also
1604 the Debian maintainer from using this changelog for all
1605 their changes, it will have to be renamed if the Debian
1606 and upstream maintainers become different people. In such
1607 a case, however, it might be better to maintain the package
1608 as a non-native package.
1613 The format of the <file>debian/changelog</file> allows the
1614 package building tools to discover which version of the package
1615 is being built and find out other release-specific information.
1619 That format is a series of entries like this:
1621 <example compact="compact">
1622 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1624 [optional blank line(s), stripped]
1626 * <var>change details</var>
1627 <var>more change details</var>
1629 [blank line(s), included in output of dpkg-parsechangelog]
1631 * <var>even more change details</var>
1633 [optional blank line(s), stripped]
1635 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1640 <var>package</var> and <var>version</var> are the source
1641 package name and version number.
1645 <var>distribution(s)</var> lists the distributions where
1646 this version should be installed when it is uploaded - it
1647 is copied to the <tt>Distribution</tt> field in the
1648 <file>.changes</file> file. See <ref id="f-Distribution">.
1652 <var>urgency</var> is the value for the <tt>Urgency</tt>
1653 field in the <file>.changes</file> file for the upload
1654 (see <ref id="f-Urgency">). It is not possible to specify
1655 an urgency containing commas; commas are used to separate
1656 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1657 <prgn>dpkg</prgn> changelog format (though there is
1658 currently only one useful <var>keyword</var>,
1663 The change details may in fact be any series of lines
1664 starting with at least two spaces, but conventionally each
1665 change starts with an asterisk and a separating space and
1666 continuation lines are indented so as to bring them in
1667 line with the start of the text above. Blank lines may be
1668 used here to separate groups of changes, if desired.
1672 If this upload resolves bugs recorded in the Bug Tracking
1673 System (BTS), they may be automatically closed on the
1674 inclusion of this package into the Debian archive by
1675 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1676 in the change details.<footnote>
1677 To be precise, the string should match the following
1678 Perl regular expression:
1680 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1682 Then all of the bug numbers listed will be closed by the
1683 archive maintenance script (<prgn>katie</prgn>) using the
1684 <var>version</var> of the changelog entry.
1686 This information is conveyed via the <tt>Closes</tt> field
1687 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1691 The maintainer name and email address used in the changelog
1692 should be the details of the person uploading <em>this</em>
1693 version. They are <em>not</em> necessarily those of the
1694 usual package maintainer.<footnote>
1695 If the developer uploading the package is not one of the usual
1696 maintainers of the package (as listed in
1697 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1698 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1699 fields of the package), the first line of the changelog is
1700 conventionally used to explain why a non-maintainer is
1701 uploading the package. The Debian Developer's Reference
1702 (see <ref id="related">) documents the conventions
1704 The information here will be copied to the <tt>Changed-By</tt>
1705 field in the <tt>.changes</tt> file
1706 (see <ref id="f-Changed-By">), and then later used to send an
1707 acknowledgement when the upload has been installed.
1711 The <var>date</var> has the following format<footnote>
1712 This is the same as the format generated by <tt>date
1714 </footnote> (compatible and with the same semantics of
1715 RFC 2822 and RFC 5322):
1716 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1718 <list compact="compact">
1720 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1723 dd is a one- or two-digit day of the month (01-31)
1726 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1729 <item>yyyy is the four-digit year (e.g. 2010)</item>
1730 <item>hh is the two-digit hour (00-23)</item>
1731 <item>mm is the two-digit minutes (00-59)</item>
1732 <item>ss is the two-digit seconds (00-60)</item>
1734 +zzzz or -zzzz is the the time zone offset from Coordinated
1735 Universal Time (UTC). "+" indicates that the time is ahead
1736 of (i.e., east of) UTC and "-" indicates that the time is
1737 behind (i.e., west of) UTC. The first two digits indicate
1738 the hour difference from UTC and the last two digits
1739 indicate the number of additional minutes difference from
1740 UTC. The last two digits must be in the range 00-59.
1746 The first "title" line with the package name must start
1747 at the left hand margin. The "trailer" line with the
1748 maintainer and date details must be preceded by exactly
1749 one space. The maintainer details and the date must be
1750 separated by exactly two spaces.
1754 The entire changelog must be encoded in UTF-8.
1758 For more information on placement of the changelog files
1759 within binary packages, please see <ref id="changelogs">.
1763 <sect id="dpkgcopyright">
1764 <heading>Copyright: <file>debian/copyright</file></heading>
1766 Every package must be accompanied by a verbatim copy of its
1767 copyright information and distribution license in the file
1768 <file>/usr/share/doc/<var>package</var>/copyright</file>
1769 (see <ref id="copyrightfile"> for further details). Also see
1770 <ref id="pkgcopyright"> for further considerations related
1771 to copyrights for packages.
1775 <heading>Error trapping in makefiles</heading>
1778 When <prgn>make</prgn> invokes a command in a makefile
1779 (including your package's upstream makefiles and
1780 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1781 means that <prgn>sh</prgn>'s usual bad error handling
1782 properties apply: if you include a miniature script as one
1783 of the commands in your makefile you'll find that if you
1784 don't do anything about it then errors are not detected
1785 and <prgn>make</prgn> will blithely continue after
1790 Every time you put more than one shell command (this
1791 includes using a loop) in a makefile command you
1792 must make sure that errors are trapped. For
1793 simple compound commands, such as changing directory and
1794 then running a program, using <tt>&&</tt> rather
1795 than semicolon as a command separator is sufficient. For
1796 more complex commands including most loops and
1797 conditionals you should include a separate <tt>set -e</tt>
1798 command at the start of every makefile command that's
1799 actually one of these miniature shell scripts.
1803 <sect id="timestamps">
1804 <heading>Time Stamps</heading>
1806 Maintainers should preserve the modification times of the
1807 upstream source files in a package, as far as is reasonably
1809 The rationale is that there is some information conveyed
1810 by knowing the age of the file, for example, you could
1811 recognize that some documentation is very old by looking
1812 at the modification time, so it would be nice if the
1813 modification time of the upstream source would be
1819 <sect id="restrictions">
1820 <heading>Restrictions on objects in source packages</heading>
1823 The source package may not contain any hard links<footnote>
1825 This is not currently detected when building source
1826 packages, but only when extracting
1830 Hard links may be permitted at some point in the
1831 future, but would require a fair amount of
1834 </footnote>, device special files, sockets or setuid or
1835 setgid files.<footnote>
1836 Setgid directories are allowed.
1841 <sect id="debianrules">
1842 <heading>Main building script: <file>debian/rules</file></heading>
1845 This file must be an executable makefile, and contains the
1846 package-specific recipes for compiling the package and
1847 building binary package(s) from the source.
1851 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1852 so that it can be invoked by saying its name rather than
1853 invoking <prgn>make</prgn> explicitly. That is, invoking
1854 either of <tt>make -f debian/rules <em>args...</em></tt>
1855 or <tt>./debian/rules <em>args...</em></tt> must result in
1860 The following targets are required and must be implemented
1861 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1862 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1863 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1867 Since an interactive <file>debian/rules</file> script makes it
1868 impossible to auto-compile that package and also makes it hard
1869 for other people to reproduce the same binary package, all
1870 required targets must be non-interactive. It also follows that
1871 any target that these targets depend on must also be
1876 The targets are as follows:
1878 <tag><tt>build</tt> (required)</tag>
1881 The <tt>build</tt> target should perform all the
1882 configuration and compilation of the package.
1883 If a package has an interactive pre-build
1884 configuration routine, the Debian source package
1885 must either be built after this has taken place (so
1886 that the binary package can be built without rerunning
1887 the configuration) or the configuration routine
1888 modified to become non-interactive. (The latter is
1889 preferable if there are architecture-specific features
1890 detected by the configuration routine.)
1894 For some packages, notably ones where the same
1895 source tree is compiled in different ways to produce
1896 two binary packages, the <tt>build</tt> target
1897 does not make much sense. For these packages it is
1898 good enough to provide two (or more) targets
1899 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1900 for each of the ways of building the package, and a
1901 <tt>build</tt> target that does nothing. The
1902 <tt>binary</tt> target will have to build the
1903 package in each of the possible ways and make the
1904 binary package out of each.
1908 The <tt>build</tt> target must not do anything
1909 that might require root privilege.
1913 The <tt>build</tt> target may need to run the
1914 <tt>clean</tt> target first - see below.
1918 When a package has a configuration and build routine
1919 which takes a long time, or when the makefiles are
1920 poorly designed, or when <tt>build</tt> needs to
1921 run <tt>clean</tt> first, it is a good idea to
1922 <tt>touch build</tt> when the build process is
1923 complete. This will ensure that if <tt>debian/rules
1924 build</tt> is run again it will not rebuild the whole
1926 Another common way to do this is for <tt>build</tt>
1927 to depend on <prgn>build-stamp</prgn> and to do
1928 nothing else, and for the <prgn>build-stamp</prgn>
1929 target to do the building and to <tt>touch
1930 build-stamp</tt> on completion. This is
1931 especially useful if the build routine creates a
1932 file or directory called <tt>build</tt>; in such a
1933 case, <tt>build</tt> will need to be listed as
1934 a phony target (i.e., as a dependency of the
1935 <tt>.PHONY</tt> target). See the documentation of
1936 <prgn>make</prgn> for more information on phony
1942 <tag><tt>build-arch</tt> (optional),
1943 <tt>build-indep</tt> (optional)
1947 A package may also provide both of the targets
1948 <tt>build-arch</tt> and <tt>build-indep</tt>.
1949 The <tt>build-arch</tt> target, if provided, should
1950 perform all the configuration and compilation required for
1951 producing all architecture-dependant binary packages
1952 (those packages for which the body of the
1953 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1954 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1955 target, if provided, should perform all the configuration
1956 and compilation required for producing all
1957 architecture-independent binary packages (those packages
1958 for which the body of the <tt>Architecture</tt> field
1959 in <tt>debian/control</tt> is <tt>all</tt>).
1960 The <tt>build</tt> target should depend on those of the
1961 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1962 are provided in the rules file.<footnote>
1963 The intent of this split is so that binary-only builds
1964 need not install the dependencies required for
1965 the <tt>build-indep</tt> target. However, this is not
1966 yet used in practice since <tt>dpkg-buildpackage
1967 -B</tt>, and therefore the autobuilders,
1968 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1969 due to the difficulties in determining whether the
1970 optional <tt>build-arch</tt> target exists.
1975 If one or both of the targets <tt>build-arch</tt> and
1976 <tt>build-indep</tt> are not provided, then invoking
1977 <file>debian/rules</file> with one of the not-provided
1978 targets as arguments should produce a exit status code
1979 of 2. Usually this is provided automatically by make
1980 if the target is missing.
1984 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1985 must not do anything that might require root privilege.
1989 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1990 (required), <tt>binary-indep</tt> (required)
1994 The <tt>binary</tt> target must be all that is
1995 necessary for the user to build the binary package(s)
1996 produced from this source package. It is
1997 split into two parts: <prgn>binary-arch</prgn> builds
1998 the binary packages which are specific to a particular
1999 architecture, and <tt>binary-indep</tt> builds
2000 those which are not.
2003 <tt>binary</tt> may be (and commonly is) a target with
2004 no commands which simply depends on
2005 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2008 Both <tt>binary-*</tt> targets should depend on the
2009 <tt>build</tt> target, or on the appropriate
2010 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2011 provided, so that the package is built if it has not
2012 been already. It should then create the relevant
2013 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2014 make their control files and <prgn>dpkg-deb</prgn> to
2015 build them and place them in the parent of the top
2020 Both the <tt>binary-arch</tt> and
2021 <tt>binary-indep</tt> targets <em>must</em> exist.
2022 If one of them has nothing to do (which will always be
2023 the case if the source generates only a single binary
2024 package, whether architecture-dependent or not), it
2025 must still exist and must always succeed.
2029 The <tt>binary</tt> targets must be invoked as
2031 The <prgn>fakeroot</prgn> package often allows one
2032 to build a package correctly even without being
2038 <tag><tt>clean</tt> (required)</tag>
2041 This must undo any effects that the <tt>build</tt>
2042 and <tt>binary</tt> targets may have had, except
2043 that it should leave alone any output files created in
2044 the parent directory by a run of a <tt>binary</tt>
2049 If a <tt>build</tt> file is touched at the end of
2050 the <tt>build</tt> target, as suggested above, it
2051 should be removed as the first action that
2052 <tt>clean</tt> performs, so that running
2053 <tt>build</tt> again after an interrupted
2054 <tt>clean</tt> doesn't think that everything is
2059 The <tt>clean</tt> target may need to be
2060 invoked as root if <tt>binary</tt> has been
2061 invoked since the last <tt>clean</tt>, or if
2062 <tt>build</tt> has been invoked as root (since
2063 <tt>build</tt> may create directories, for
2068 <tag><tt>get-orig-source</tt> (optional)</tag>
2071 This target fetches the most recent version of the
2072 original source package from a canonical archive site
2073 (via FTP or WWW, for example), does any necessary
2074 rearrangement to turn it into the original source
2075 tar file format described below, and leaves it in the
2080 This target may be invoked in any directory, and
2081 should take care to clean up any temporary files it
2086 This target is optional, but providing it if
2087 possible is a good idea.
2091 <tag><tt>patch</tt> (optional)</tag>
2094 This target performs whatever additional actions are
2095 required to make the source ready for editing (unpacking
2096 additional upstream archives, applying patches, etc.).
2097 It is recommended to be implemented for any package where
2098 <tt>dpkg-source -x</tt> does not result in source ready
2099 for additional modification. See
2100 <ref id="readmesource">.
2106 The <tt>build</tt>, <tt>binary</tt> and
2107 <tt>clean</tt> targets must be invoked with the current
2108 directory being the package's top-level directory.
2113 Additional targets may exist in <file>debian/rules</file>,
2114 either as published or undocumented interfaces or for the
2115 package's internal use.
2119 The architectures we build on and build for are determined
2120 by <prgn>make</prgn> variables using the
2121 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2122 You can determine the Debian architecture and the GNU style
2123 architecture specification string for the build architecture as
2124 well as for the host architecture. The build architecture is
2125 the architecture on which <file>debian/rules</file> is run and
2126 the package build is performed. The host architecture is the
2127 architecture on which the resulting package will be installed
2128 and run. These are normally the same, but may be different in
2129 the case of cross-compilation (building packages for one
2130 architecture on machines of a different architecture).
2134 Here is a list of supported <prgn>make</prgn> variables:
2135 <list compact="compact">
2137 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2140 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2143 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2146 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2147 specification string)
2150 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2151 <tt>DEB_*_GNU_TYPE</tt>)
2154 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2155 <tt>DEB_*_GNU_TYPE</tt>)
2157 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2158 the build architecture or <tt>HOST</tt> for specification of the
2163 Backward compatibility can be provided in the rules file
2164 by setting the needed variables to suitable default
2165 values; please refer to the documentation of
2166 <prgn>dpkg-architecture</prgn> for details.
2170 It is important to understand that the <tt>DEB_*_ARCH</tt>
2171 string only determines which Debian architecture we are
2172 building on or for. It should not be used to get the CPU
2173 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2174 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2175 GNU style variables should generally only be used with upstream
2179 <sect1 id="debianrules-options">
2180 <heading><file>debian/rules</file> and
2181 <tt>DEB_BUILD_OPTIONS</tt></heading>
2184 Supporting the standardized environment variable
2185 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2186 contain several flags to change how a package is compiled and
2187 built. Each flag must be in the form <var>flag</var> or
2188 <var>flag</var>=<var>options</var>. If multiple flags are
2189 given, they must be separated by whitespace.<footnote>
2190 Some packages support any delimiter, but whitespace is the
2191 easiest to parse inside a makefile and avoids ambiguity with
2192 flag values that contain commas.
2194 <var>flag</var> must start with a lowercase letter
2195 (<tt>a-z</tt>) and consist only of lowercase letters,
2196 numbers (<tt>0-9</tt>), and the characters
2197 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2198 <var>options</var> must not contain whitespace. The same
2199 tag should not be given multiple times with conflicting
2200 values. Package maintainers may assume that
2201 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2205 The meaning of the following tags has been standardized:
2209 This tag says to not run any build-time test suite
2210 provided by the package.
2214 The presence of this tag means that the package should
2215 be compiled with a minimum of optimization. For C
2216 programs, it is best to add <tt>-O0</tt> to
2217 <tt>CFLAGS</tt> (although this is usually the default).
2218 Some programs might fail to build or run at this level
2219 of optimization; it may be necessary to use
2220 <tt>-O1</tt>, for example.
2224 This tag means that the debugging symbols should not be
2225 stripped from the binary during installation, so that
2226 debugging information may be included in the package.
2228 <tag>parallel=n</tag>
2230 This tag means that the package should be built using up
2231 to <tt>n</tt> parallel processes if the package build
2232 system supports this.<footnote>
2233 Packages built with <tt>make</tt> can often implement
2234 this by passing the <tt>-j</tt><var>n</var> option to
2237 If the package build system does not support parallel
2238 builds, this string must be ignored. If the package
2239 build system only supports a lower level of concurrency
2240 than <var>n</var>, the package should be built using as
2241 many parallel processes as the package build system
2242 supports. It is up to the package maintainer to decide
2243 whether the package build times are long enough and the
2244 package build system is robust enough to make supporting
2245 parallel builds worthwhile.
2251 Unknown flags must be ignored by <file>debian/rules</file>.
2255 The following makefile snippet is an example of how one may
2256 implement the build options; you will probably have to
2257 massage this example in order to make it work for your
2259 <example compact="compact">
2262 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2263 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2264 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2265 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2267 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2272 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2273 INSTALL_PROGRAM += -s
2275 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2276 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2277 MAKEFLAGS += -j$(NUMJOBS)
2282 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2283 # Code to run the package test suite.
2290 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2291 <sect id="substvars">
2292 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2295 When <prgn>dpkg-gencontrol</prgn>
2296 generates <qref id="binarycontrolfiles">binary package control
2297 files</qref> (<file>DEBIAN/control</file>), it performs variable
2298 substitutions on its output just before writing it. Variable
2299 substitutions have the form <tt>${<var>variable</var>}</tt>.
2300 The optional file <file>debian/substvars</file> contains
2301 variable substitutions to be used; variables can also be set
2302 directly from <file>debian/rules</file> using the <tt>-V</tt>
2303 option to the source packaging commands, and certain predefined
2304 variables are also available.
2308 The <file>debian/substvars</file> file is usually generated and
2309 modified dynamically by <file>debian/rules</file> targets, in
2310 which case it must be removed by the <tt>clean</tt> target.
2314 See <manref name="deb-substvars" section="5"> for full
2315 details about source variable substitutions, including the
2316 format of <file>debian/substvars</file>.</p>
2319 <sect id="debianwatch">
2320 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2323 This is an optional, recommended configuration file for the
2324 <tt>uscan</tt> utility which defines how to automatically scan
2325 ftp or http sites for newly available updates of the
2326 package. This is used
2327 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2328 tools to help with quality control and maintenance of the
2329 distribution as a whole.
2334 <sect id="debianfiles">
2335 <heading>Generated files list: <file>debian/files</file></heading>
2338 This file is not a permanent part of the source tree; it
2339 is used while building packages to record which files are
2340 being generated. <prgn>dpkg-genchanges</prgn> uses it
2341 when it generates a <file>.changes</file> file.
2345 It should not exist in a shipped source package, and so it
2346 (and any backup files or temporary files such as
2347 <file>files.new</file><footnote>
2348 <file>files.new</file> is used as a temporary file by
2349 <prgn>dpkg-gencontrol</prgn> and
2350 <prgn>dpkg-distaddfile</prgn> - they write a new
2351 version of <tt>files</tt> here before renaming it,
2352 to avoid leaving a corrupted copy if an error
2354 </footnote>) should be removed by the
2355 <tt>clean</tt> target. It may also be wise to
2356 ensure a fresh start by emptying or removing it at the
2357 start of the <tt>binary</tt> target.
2361 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2362 package, it adds an entry to <file>debian/files</file> for the
2363 <file>.deb</file> file that will be created when <tt>dpkg-deb
2364 --build</tt> is run for that binary package. So for most
2365 packages all that needs to be done with this file is to
2366 delete it in the <tt>clean</tt> target.
2370 If a package upload includes files besides the source
2371 package and any binary packages whose control files were
2372 made with <prgn>dpkg-gencontrol</prgn> then they should be
2373 placed in the parent of the package's top-level directory
2374 and <prgn>dpkg-distaddfile</prgn> should be called to add
2375 the file to the list in <file>debian/files</file>.</p>
2378 <sect id="embeddedfiles">
2379 <heading>Convenience copies of code</heading>
2382 Some software packages include in their distribution convenience
2383 copies of code from other software packages, generally so that
2384 users compiling from source don't have to download multiple
2385 packages. Debian packages should not make use of these
2386 convenience copies unless the included package is explicitly
2387 intended to be used in this way.<footnote>
2388 For example, parts of the GNU build system work like this.
2390 If the included code is already in the Debian archive in the
2391 form of a library, the Debian packaging should ensure that
2392 binary packages reference the libraries already in Debian and
2393 the convenience copy is not used. If the included code is not
2394 already in Debian, it should be packaged separately as a
2395 prerequisite if possible.
2397 Having multiple copies of the same code in Debian is
2398 inefficient, often creates either static linking or shared
2399 library conflicts, and, most importantly, increases the
2400 difficulty of handling security vulnerabilities in the
2406 <sect id="readmesource">
2407 <heading>Source package handling:
2408 <file>debian/README.source</file></heading>
2411 If running <prgn>dpkg-source -x</prgn> on a source package
2412 doesn't produce the source of the package, ready for editing,
2413 and allow one to make changes and run
2414 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2415 without taking any additional steps, creating a
2416 <file>debian/README.source</file> documentation file is
2417 recommended. This file should explain how to do all of the
2420 <item>Generate the fully patched source, in a form ready for
2421 editing, that would be built to create Debian
2422 packages. Doing this with a <tt>patch</tt> target in
2423 <file>debian/rules</file> is recommended; see
2424 <ref id="debianrules">.</item>
2425 <item>Modify the source and save those modifications so that
2426 they will be applied when building the package.</item>
2427 <item>Remove source modifications that are currently being
2428 applied when building the package.</item>
2429 <item>Optionally, document what steps are necessary to
2430 upgrade the Debian source package to a new upstream version,
2431 if applicable.</item>
2433 This explanation should include specific commands and mention
2434 any additional required Debian packages. It should not assume
2435 familiarity with any specific Debian packaging system or patch
2440 This explanation may refer to a documentation file installed by
2441 one of the package's build dependencies provided that the
2442 referenced documentation clearly explains these tasks and is not
2443 a general reference manual.
2447 <file>debian/README.source</file> may also include any other
2448 information that would be helpful to someone modifying the
2449 source package. Even if the package doesn't fit the above
2450 description, maintainers are encouraged to document in a
2451 <file>debian/README.source</file> file any source package with a
2452 particularly complex or unintuitive source layout or build
2453 system (for example, a package that builds the same source
2454 multiple times to generate different binary packages).
2460 <chapt id="controlfields">
2461 <heading>Control files and their fields</heading>
2464 The package management system manipulates data represented in
2465 a common format, known as <em>control data</em>, stored in
2466 <em>control files</em>.
2467 Control files are used for source packages, binary packages and
2468 the <file>.changes</file> files which control the installation
2469 of uploaded files<footnote>
2470 <prgn>dpkg</prgn>'s internal databases are in a similar
2475 <sect id="controlsyntax">
2476 <heading>Syntax of control files</heading>
2479 A control file consists of one or more paragraphs of
2481 The paragraphs are also sometimes referred to as stanzas.
2483 The paragraphs are separated by empty lines. Parsers may accept
2484 lines consisting solely of spaces and tabs as paragraph
2485 separators, but control files should use empty lines. Some control
2486 files allow only one paragraph; others allow several, in
2487 which case each paragraph usually refers to a different
2488 package. (For example, in source packages, the first
2489 paragraph refers to the source package, and later paragraphs
2490 refer to binary packages generated from the source.) The
2491 ordering of the paragraphs in control files is significant.
2495 Each paragraph consists of a series of data fields; each
2496 field consists of the field name, followed by a colon and
2497 then the data/value associated with that field. The field
2498 name is composed of printable ASCII characters (i.e.,
2499 characters that have values between 33 and 126, inclusive)
2500 except colon and must not with a begin with #. The
2501 field ends at the end of the line or at the end of the
2502 last continuation line (see below). Horizontal whitespace
2503 (spaces and tabs) may occur immediately before or after the
2504 value and is ignored there; it is conventional to put a
2505 single space after the colon. For example, a field might
2507 <example compact="compact">
2510 the field name is <tt>Package</tt> and the field value
2515 A paragraph must not contain more than one instance of a
2516 particular field name.
2520 There are three types of fields:
2524 The field, including its value, must be a single line. Folding
2525 of the field is not permitted. This is the default field type
2526 if the definition of the field does not specify a different
2531 The value of a folded field is a logical line that may span
2532 several lines. The lines after the first are called
2533 continuation lines and must start with a space or a tab.
2534 Whitespace, including any newlines, is not significant in the
2535 field values of folded fields.<footnote>
2536 This folding method is similar to RFC 5322, allowing control
2537 files that contain only one paragraph and no multiline fields
2538 to be read by parsers written for RFC 5322.
2541 <tag>multiline</tag>
2543 The value of a multiline field may comprise multiple continuation
2544 lines. The first line of the value, the part on the same line as
2545 the field name, often has special significance or may have to be
2546 empty. Other lines are added following the same syntax as the
2547 continuation lines of the folded fields. Whitespace, including newlines,
2548 is significant in the values of multiline fields.
2554 Whitespace must not appear
2555 inside names (of packages, architectures, files or anything
2556 else) or version numbers, or between the characters of
2557 multi-character version relationships.
2561 The presence and purpose of a field, and the syntax of its
2562 value may differ between types of control files.
2566 Field names are not case-sensitive, but it is usual to
2567 capitalize the field names using mixed case as shown below.
2568 Field values are case-sensitive unless the description of the
2569 field says otherwise.
2573 Paragraph separators (empty lines) and lines consisting only of
2574 spaces and tabs are not allowed within field values or between
2575 fields. Empty lines in field values are usually escaped by
2576 representing them by a space followed by a dot.
2580 Lines starting with # without any preceding whitespace are comments
2581 lines that are only permitted in source package control files
2582 (<file>debian/control</file>). These comment lines are ignored, even
2583 between two continuation lines. They do not end logical lines.
2587 All control files must be encoded in UTF-8.
2591 <sect id="sourcecontrolfiles">
2592 <heading>Source package control files -- <file>debian/control</file></heading>
2595 The <file>debian/control</file> file contains the most vital
2596 (and version-independent) information about the source package
2597 and about the binary packages it creates.
2601 The first paragraph of the control file contains information about
2602 the source package in general. The subsequent sets each describe a
2603 binary package that the source tree builds.
2607 The fields in the general paragraph (the first one, for the source
2610 <list compact="compact">
2611 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2614 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2615 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2616 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2617 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2618 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2619 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2624 The fields in the binary package paragraphs are:
2626 <list compact="compact">
2627 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2630 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2631 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2632 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2633 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2634 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2639 The syntax and semantics of the fields are described below.
2643 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2644 generate control files for binary packages (see below), by
2645 <prgn>dpkg-genchanges</prgn> to generate the
2646 <file>.changes</file> file to accompany the upload, and by
2647 <prgn>dpkg-source</prgn> when it creates the
2648 <file>.dsc</file> source control file as part of a source
2649 archive. Some fields are folded in <file>debian/control</file>,
2650 but not in any other control
2651 file. These tools are responsible for removing the line
2652 breaks from such fields when using fields from
2653 <file>debian/control</file> to generate other control files.
2657 The fields here may contain variable references - their
2658 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2659 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2660 when they generate output control files.
2661 See <ref id="substvars"> for details.
2665 <sect id="binarycontrolfiles">
2666 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2669 The <file>DEBIAN/control</file> file contains the most vital
2670 (and version-dependent) information about a binary package. It
2671 consists of a single paragraph.
2675 The fields in this file are:
2677 <list compact="compact">
2678 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2679 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2680 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2681 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2682 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2683 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2684 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2685 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2686 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2687 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2694 <sect id="debiansourcecontrolfiles">
2695 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2698 This file consists of a single paragraph, possibly surrounded by
2699 a PGP signature. The fields of that paragraph are listed below.
2700 Their syntax is described above, in <ref id="pkg-controlfields">.
2702 <list compact="compact">
2703 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2704 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2705 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2706 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2707 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2708 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2709 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2710 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2711 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2712 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2713 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2714 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2715 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2716 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2721 The Debian source control file is generated by
2722 <prgn>dpkg-source</prgn> when it builds the source
2723 archive, from other files in the source package,
2724 described above. When unpacking, it is checked against
2725 the files and directories in the other parts of the
2731 <sect id="debianchangesfiles">
2732 <heading>Debian changes files -- <file>.changes</file></heading>
2735 The <file>.changes</file> files are used by the Debian archive
2736 maintenance software to process updates to packages. They
2737 consist of a single paragraph, possibly surrounded by a PGP
2738 signature. That paragraph contains information from the
2739 <file>debian/control</file> file and other data about the
2740 source package gathered via <file>debian/changelog</file>
2741 and <file>debian/rules</file>.
2745 <file>.changes</file> files have a format version that is
2746 incremented whenever the documented fields or their meaning
2747 change. This document describes format &changesversion;.
2751 The fields in this file are:
2753 <list compact="compact">
2754 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2755 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2756 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2757 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2760 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2761 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2762 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2764 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2765 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2766 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2768 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2769 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2774 <sect id="controlfieldslist">
2775 <heading>List of fields</heading>
2777 <sect1 id="f-Source">
2778 <heading><tt>Source</tt></heading>
2781 This field identifies the source package name.
2785 In <file>debian/control</file> or a <file>.dsc</file> file,
2786 this field must contain only the name of the source package.
2790 In a binary package control file or a <file>.changes</file>
2791 file, the source package name may be followed by a version
2792 number in parentheses<footnote>
2793 It is customary to leave a space after the package name
2794 if a version number is specified.
2796 This version number may be omitted (and is, by
2797 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2798 the <tt>Version</tt> field of the binary package in
2799 question. The field itself may be omitted from a binary
2800 package control file when the source package has the same
2801 name and version as the binary package.
2805 Package names (both source and binary,
2806 see <ref id="f-Package">) must consist only of lower case
2807 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2808 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2809 (<tt>.</tt>). They must be at least two characters long and
2810 must start with an alphanumeric character.
2814 <sect1 id="f-Maintainer">
2815 <heading><tt>Maintainer</tt></heading>
2818 The package maintainer's name and email address. The name
2819 must come first, then the email address inside angle
2820 brackets <tt><></tt> (in RFC822 format).
2824 If the maintainer's name contains a full stop then the
2825 whole field will not work directly as an email address due
2826 to a misfeature in the syntax specified in RFC822; a
2827 program using this field as an address must check for this
2828 and correct the problem if necessary (for example by
2829 putting the name in round brackets and moving it to the
2830 end, and bringing the email address forward).
2834 See <ref id="maintainer"> for additional requirements and
2835 information about package maintainers.
2839 <sect1 id="f-Uploaders">
2840 <heading><tt>Uploaders</tt></heading>
2843 List of the names and email addresses of co-maintainers of the
2844 package, if any. If the package has other maintainers besides
2845 the one named in the <qref id="f-Maintainer">Maintainer
2846 field</qref>, their names and email addresses should be listed
2847 here. The format of each entry is the same as that of the
2848 Maintainer field, and multiple entries must be comma
2853 This is normally an optional field, but if
2854 the <tt>Maintainer</tt> control field names a group of people
2855 and a shared email address, the <tt>Uploaders</tt> field must
2856 be present and must contain at least one human with their
2857 personal email address.
2861 The Uploaders field in <file>debian/control</file> can be folded.
2865 <sect1 id="f-Changed-By">
2866 <heading><tt>Changed-By</tt></heading>
2869 The name and email address of the person who prepared this
2870 version of the package, usually a maintainer. The syntax is
2871 the same as for the <qref id="f-Maintainer">Maintainer
2876 <sect1 id="f-Section">
2877 <heading><tt>Section</tt></heading>
2880 This field specifies an application area into which the package
2881 has been classified. See <ref id="subsections">.
2885 When it appears in the <file>debian/control</file> file,
2886 it gives the value for the subfield of the same name in
2887 the <tt>Files</tt> field of the <file>.changes</file> file.
2888 It also gives the default for the same field in the binary
2893 <sect1 id="f-Priority">
2894 <heading><tt>Priority</tt></heading>
2897 This field represents how important it is that the user
2898 have the package installed. See <ref id="priorities">.
2902 When it appears in the <file>debian/control</file> file,
2903 it gives the value for the subfield of the same name in
2904 the <tt>Files</tt> field of the <file>.changes</file> file.
2905 It also gives the default for the same field in the binary
2910 <sect1 id="f-Package">
2911 <heading><tt>Package</tt></heading>
2914 The name of the binary package.
2918 Binary package names must follow the same syntax and
2919 restrictions as source package names. See <ref id="f-Source">
2924 <sect1 id="f-Architecture">
2925 <heading><tt>Architecture</tt></heading>
2928 Depending on context and the control file used, the
2929 <tt>Architecture</tt> field can include the following sets of
2933 A unique single word identifying a Debian machine
2934 architecture as described in <ref id="arch-spec">.
2937 An architecture wildcard identifying a set of Debian
2938 machine architectures, see <ref id="arch-wildcard-spec">.
2939 <tt>any</tt> matches all Debian machine architectures
2940 and is the most frequently used.
2943 <tt>all</tt>, which indicates an
2944 architecture-independent package.
2947 <tt>source</tt>, which indicates a source package.
2953 In the main <file>debian/control</file> file in the source
2954 package, this field may contain the special
2955 value <tt>all</tt>, the special architecture
2956 wildcard <tt>any</tt>, or a list of specific and wildcard
2957 architectures separated by spaces. If <tt>all</tt>
2958 or <tt>any</tt> appears, that value must be the entire
2959 contents of the field. Most packages will use
2960 either <tt>all</tt> or <tt>any</tt>.
2964 Specifying a specific list of architectures indicates that the
2965 source will build an architecture-dependent package only on
2966 architectures included in the list. Specifying a list of
2967 architecture wildcards indicates that the source will build an
2968 architecture-dependent package on only those architectures
2969 that match any of the specified architecture wildcards.
2970 Specifying a list of architectures or architecture wildcards
2971 other than <tt>any</tt> is for the minority of cases where a
2972 program is not portable or is not useful on some
2973 architectures. Where possible, the program should be made
2978 In the Debian source control file <file>.dsc</file>, this
2979 field contains a list of architectures and architecture
2980 wildcards separated by spaces. When the list contains the
2981 architecture wildcard <tt>any</tt>, the only other value
2982 allowed in the list is <tt>all</tt>.
2986 The list may include (or consist solely of) the special
2987 value <tt>all</tt>. In other words, in <file>.dsc</file>
2988 files unlike the <file>debian/control</file>, <tt>all</tt> may
2989 occur in combination with specific architectures.
2990 The <tt>Architecture</tt> field in the Debian source control
2991 file <file>.dsc</file> is generally constructed from
2992 the <tt>Architecture</tt> fields in
2993 the <file>debian/control</file> in the source package.
2997 Specifying only <tt>any</tt> indicates that the source package
2998 isn't dependent on any particular architecture and should
2999 compile fine on any one. The produced binary package(s)
3000 will be specific to whatever the current build architecture is.
3004 Specifying only <tt>all</tt> indicates that the source package
3005 will only build architecture-independent packages.
3009 Specifying <tt>any all</tt> indicates that the source package
3010 isn't dependent on any particular architecture. The set of
3011 produced binary packages will include at least one
3012 architecture-dependant package and one architecture-independent
3017 Specifying a list of architectures or architecture wildcards
3018 indicates that the source will build an architecture-dependent
3019 package, and will only work correctly on the listed or
3020 matching architectures. If the source package also builds at
3021 least one architecture-independent package, <tt>all</tt> will
3022 also be included in the list.
3026 In a <file>.changes</file> file, the <tt>Architecture</tt>
3027 field lists the architecture(s) of the package(s) currently
3028 being uploaded. This will be a list; if the source for the
3029 package is also being uploaded, the special
3030 entry <tt>source</tt> is also present. <tt>all</tt> will be
3031 present if any architecture-independent packages are being
3032 uploaded. Architecture wildcards such as <tt>any</tt> must
3033 never occur in the <tt>Architecture</tt> field in
3034 the <file>.changes</file> file.
3038 See <ref id="debianrules"> for information on how to get
3039 the architecture for the build process.
3043 <sect1 id="f-Essential">
3044 <heading><tt>Essential</tt></heading>
3047 This is a boolean field which may occur only in the
3048 control file of a binary package or in a per-package fields
3049 paragraph of a source package control file.
3053 If set to <tt>yes</tt> then the package management system
3054 will refuse to remove the package (upgrading and replacing
3055 it is still possible). The other possible value is <tt>no</tt>,
3056 which is the same as not having the field at all.
3061 <heading>Package interrelationship fields:
3062 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3063 <tt>Recommends</tt>, <tt>Suggests</tt>,
3064 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3065 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3069 These fields describe the package's relationships with
3070 other packages. Their syntax and semantics are described
3071 in <ref id="relationships">.</p>
3074 <sect1 id="f-Standards-Version">
3075 <heading><tt>Standards-Version</tt></heading>
3078 The most recent version of the standards (the policy
3079 manual and associated texts) with which the package
3084 The version number has four components: major and minor
3085 version number and major and minor patch level. When the
3086 standards change in a way that requires every package to
3087 change the major number will be changed. Significant
3088 changes that will require work in many packages will be
3089 signaled by a change to the minor number. The major patch
3090 level will be changed for any change to the meaning of the
3091 standards, however small; the minor patch level will be
3092 changed when only cosmetic, typographical or other edits
3093 are made which neither change the meaning of the document
3094 nor affect the contents of packages.
3098 Thus only the first three components of the policy version
3099 are significant in the <em>Standards-Version</em> control
3100 field, and so either these three components or all four
3101 components may be specified.<footnote>
3102 In the past, people specified the full version number
3103 in the Standards-Version field, for example "2.3.0.0".
3104 Since minor patch-level changes don't introduce new
3105 policy, it was thought it would be better to relax
3106 policy and only require the first 3 components to be
3107 specified, in this example "2.3.0". All four
3108 components may still be used if someone wishes to do so.
3114 <sect1 id="f-Version">
3115 <heading><tt>Version</tt></heading>
3118 The version number of a package. The format is:
3119 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3123 The three components here are:
3125 <tag><var>epoch</var></tag>
3128 This is a single (generally small) unsigned integer. It
3129 may be omitted, in which case zero is assumed. If it is
3130 omitted then the <var>upstream_version</var> may not
3135 It is provided to allow mistakes in the version numbers
3136 of older versions of a package, and also a package's
3137 previous version numbering schemes, to be left behind.
3141 <tag><var>upstream_version</var></tag>
3144 This is the main part of the version number. It is
3145 usually the version number of the original ("upstream")
3146 package from which the <file>.deb</file> file has been made,
3147 if this is applicable. Usually this will be in the same
3148 format as that specified by the upstream author(s);
3149 however, it may need to be reformatted to fit into the
3150 package management system's format and comparison
3155 The comparison behavior of the package management system
3156 with respect to the <var>upstream_version</var> is
3157 described below. The <var>upstream_version</var>
3158 portion of the version number is mandatory.
3162 The <var>upstream_version</var> may contain only
3163 alphanumerics<footnote>
3164 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3166 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3167 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3168 tilde) and should start with a digit. If there is no
3169 <var>debian_revision</var> then hyphens are not allowed;
3170 if there is no <var>epoch</var> then colons are not
3175 <tag><var>debian_revision</var></tag>
3178 This part of the version number specifies the version of
3179 the Debian package based on the upstream version. It
3180 may contain only alphanumerics and the characters
3181 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3182 tilde) and is compared in the same way as the
3183 <var>upstream_version</var> is.
3187 It is optional; if it isn't present then the
3188 <var>upstream_version</var> may not contain a hyphen.
3189 This format represents the case where a piece of
3190 software was written specifically to be a Debian
3191 package, where the Debian package source must always
3192 be identical to the pristine source and therefore no
3193 revision indication is required.
3197 It is conventional to restart the
3198 <var>debian_revision</var> at <tt>1</tt> each time the
3199 <var>upstream_version</var> is increased.
3203 The package management system will break the version
3204 number apart at the last hyphen in the string (if there
3205 is one) to determine the <var>upstream_version</var> and
3206 <var>debian_revision</var>. The absence of a
3207 <var>debian_revision</var> is equivalent to a
3208 <var>debian_revision</var> of <tt>0</tt>.
3215 When comparing two version numbers, first the <var>epoch</var>
3216 of each are compared, then the <var>upstream_version</var> if
3217 <var>epoch</var> is equal, and then <var>debian_revision</var>
3218 if <var>upstream_version</var> is also equal.
3219 <var>epoch</var> is compared numerically. The
3220 <var>upstream_version</var> and <var>debian_revision</var>
3221 parts are compared by the package management system using the
3222 following algorithm:
3226 The strings are compared from left to right.
3230 First the initial part of each string consisting entirely of
3231 non-digit characters is determined. These two parts (one of
3232 which may be empty) are compared lexically. If a difference
3233 is found it is returned. The lexical comparison is a
3234 comparison of ASCII values modified so that all the letters
3235 sort earlier than all the non-letters and so that a tilde
3236 sorts before anything, even the end of a part. For example,
3237 the following parts are in sorted order from earliest to
3238 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3239 <tt>a</tt>.<footnote>
3240 One common use of <tt>~</tt> is for upstream pre-releases.
3241 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3242 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3247 Then the initial part of the remainder of each string which
3248 consists entirely of digit characters is determined. The
3249 numerical values of these two parts are compared, and any
3250 difference found is returned as the result of the comparison.
3251 For these purposes an empty string (which can only occur at
3252 the end of one or both version strings being compared) counts
3257 These two steps (comparing and removing initial non-digit
3258 strings and initial digit strings) are repeated until a
3259 difference is found or both strings are exhausted.
3263 Note that the purpose of epochs is to allow us to leave behind
3264 mistakes in version numbering, and to cope with situations
3265 where the version numbering scheme changes. It is
3266 <em>not</em> intended to cope with version numbers containing
3267 strings of letters which the package management system cannot
3268 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3269 silly orderings.<footnote>
3270 The author of this manual has heard of a package whose
3271 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3272 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3278 <sect1 id="f-Description">
3279 <heading><tt>Description</tt></heading>
3282 In a source or binary control file, the <tt>Description</tt>
3283 field contains a description of the binary package, consisting
3284 of two parts, the synopsis or the short description, and the
3285 long description. It is a multiline field with the following
3291 Description: <single line synopsis>
3292 <extended description over several lines>
3297 The lines in the extended description can have these formats:
3303 Those starting with a single space are part of a paragraph.
3304 Successive lines of this form will be word-wrapped when
3305 displayed. The leading space will usually be stripped off.
3306 The line must contain at least one non-whitespace character.
3310 Those starting with two or more spaces. These will be
3311 displayed verbatim. If the display cannot be panned
3312 horizontally, the displaying program will line wrap them "hard"
3313 (i.e., without taking account of word breaks). If it can they
3314 will be allowed to trail off to the right. None, one or two
3315 initial spaces may be deleted, but the number of spaces
3316 deleted from each line will be the same (so that you can have
3317 indenting work correctly, for example). The line must
3318 contain at least one non-whitespace character.
3322 Those containing a single space followed by a single full stop
3323 character. These are rendered as blank lines. This is the
3324 <em>only</em> way to get a blank line<footnote>
3325 Completely empty lines will not be rendered as blank lines.
3326 Instead, they will cause the parser to think you're starting
3327 a whole new record in the control file, and will therefore
3328 likely abort with an error.
3333 Those containing a space, a full stop and some more characters.
3334 These are for future expansion. Do not use them.
3340 Do not use tab characters. Their effect is not predictable.
3344 See <ref id="descriptions"> for further information on this.
3348 In a <file>.changes</file> file, the <tt>Description</tt>
3349 field contains a summary of the descriptions for the packages
3350 being uploaded. For this case, the first line of the field
3351 value (the part on the same line as <tt>Description:</tt>) is
3352 always empty. It is a multiline field, with one
3353 line per package. Each line is
3354 indented by one space and contains the name of a binary
3355 package, a space, a hyphen (<tt>-</tt>), a space, and the
3356 short description line from that package.
3360 <sect1 id="f-Distribution">
3361 <heading><tt>Distribution</tt></heading>
3364 In a <file>.changes</file> file or parsed changelog output
3365 this contains the (space-separated) name(s) of the
3366 distribution(s) where this version of the package should
3367 be installed. Valid distributions are determined by the
3368 archive maintainers.<footnote>
3369 Example distribution names in the Debian archive used in
3370 <file>.changes</file> files are:
3371 <taglist compact="compact">
3372 <tag><em>unstable</em></tag>
3374 This distribution value refers to the
3375 <em>developmental</em> part of the Debian distribution
3376 tree. Most new packages, new upstream versions of
3377 packages and bug fixes go into the <em>unstable</em>
3381 <tag><em>experimental</em></tag>
3383 The packages with this distribution value are deemed
3384 by their maintainers to be high risk. Oftentimes they
3385 represent early beta or developmental packages from
3386 various sources that the maintainers want people to
3387 try, but are not ready to be a part of the other parts
3388 of the Debian distribution tree.
3393 Others are used for updating stable releases or for
3394 security uploads. More information is available in the
3395 Debian Developer's Reference, section "The Debian
3399 The Debian archive software only supports listing a single
3400 distribution. Migration of packages to other distributions is
3401 handled outside of the upload process.
3406 <heading><tt>Date</tt></heading>
3409 This field includes the date the package was built or last
3410 edited. It must be in the same format as the <var>date</var>
3411 in a <file>debian/changelog</file> entry.
3415 The value of this field is usually extracted from the
3416 <file>debian/changelog</file> file - see
3417 <ref id="dpkgchangelog">).
3421 <sect1 id="f-Format">
3422 <heading><tt>Format</tt></heading>
3425 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3426 files, this field declares the format version of that file.
3427 The syntax of the field value is the same as that of
3428 a <qref id="f-Version">package version number</qref> except
3429 that no epoch or Debian revision is allowed. The format
3430 described in this document is <tt>&changesversion;</tt>.
3434 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3435 Debian source control</qref> files, this field declares the
3436 format of the source package. The field value is used by
3437 programs acting on a source package to interpret the list of
3438 files in the source package and determine how to unpack it.
3439 The syntax of the field value is a numeric major revision, a
3440 period, a numeric minor revision, and then an optional subtype
3441 after whitespace, which if specified is an alphanumeric word
3442 in parentheses. The subtype is optional in the syntax but may
3443 be mandatory for particular source format revisions.
3445 The source formats currently supported by the Debian archive
3446 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3447 and <tt>3.0 (quilt)</tt>.
3452 <sect1 id="f-Urgency">
3453 <heading><tt>Urgency</tt></heading>
3456 This is a description of how important it is to upgrade to
3457 this version from previous ones. It consists of a single
3458 keyword taking one of the values <tt>low</tt>,
3459 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3460 <tt>critical</tt><footnote>
3461 Other urgency values are supported with configuration
3462 changes in the archive software but are not used in Debian.
3463 The urgency affects how quickly a package will be considered
3464 for inclusion into the <tt>testing</tt> distribution and
3465 gives an indication of the importance of any fixes included
3466 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3467 treated as synonymous.
3468 </footnote> (not case-sensitive) followed by an optional
3469 commentary (separated by a space) which is usually in
3470 parentheses. For example:
3473 Urgency: low (HIGH for users of diversions)
3479 The value of this field is usually extracted from the
3480 <file>debian/changelog</file> file - see
3481 <ref id="dpkgchangelog">.
3485 <sect1 id="f-Changes">
3486 <heading><tt>Changes</tt></heading>
3489 This multiline field contains the human-readable changes data, describing
3490 the differences between the last version and the current one.
3494 The first line of the field value (the part on the same line
3495 as <tt>Changes:</tt>) is always empty. The content of the
3496 field is expressed as continuation lines, with each line
3497 indented by at least one space. Blank lines must be
3498 represented by a line consisting only of a space and a full
3503 The value of this field is usually extracted from the
3504 <file>debian/changelog</file> file - see
3505 <ref id="dpkgchangelog">).
3509 Each version's change information should be preceded by a
3510 "title" line giving at least the version, distribution(s)
3511 and urgency, in a human-readable way.
3515 If data from several versions is being returned the entry
3516 for the most recent version should be returned first, and
3517 entries should be separated by the representation of a
3518 blank line (the "title" line may also be followed by the
3519 representation of a blank line).
3523 <sect1 id="f-Binary">
3524 <heading><tt>Binary</tt></heading>
3527 This folded field is a list of binary packages. Its syntax and
3528 meaning varies depending on the control file in which it
3533 When it appears in the <file>.dsc</file> file, it lists binary
3534 packages which a source package can produce, separated by
3536 A space after each comma is conventional.
3537 </footnote>. The source package
3538 does not necessarily produce all of these binary packages for
3539 every architecture. The source control file doesn't contain
3540 details of which architectures are appropriate for which of
3541 the binary packages.
3545 When it appears in a <file>.changes</file> file, it lists the
3546 names of the binary packages being uploaded, separated by
3547 whitespace (not commas).
3551 <sect1 id="f-Installed-Size">
3552 <heading><tt>Installed-Size</tt></heading>
3555 This field appears in the control files of binary packages,
3556 and in the <file>Packages</file> files. It gives an estimate
3557 of the total amount of disk space required to install the
3558 named package. Actual installed size may vary based on block
3559 size, file system properties, or actions taken by package
3564 The disk space is given as the integer value of the estimated
3565 installed size in bytes, divided by 1024 and rounded up.
3569 <sect1 id="f-Files">
3570 <heading><tt>Files</tt></heading>
3573 This field contains a list of files with information about
3574 each one. The exact information and syntax varies with
3579 In all cases, Files is a multiline field. The first line of
3580 the field value (the part on the same line as <tt>Files:</tt>)
3581 is always empty. The content of the field is expressed as
3582 continuation lines, one line per file. Each line must be
3583 indented by one space and contain a number of sub-fields,
3584 separated by spaces, as described below.
3588 In the <file>.dsc</file> file, each line contains the MD5
3589 checksum, size and filename of the tar file and (if
3590 applicable) diff file which make up the remainder of the
3591 source package<footnote>
3592 That is, the parts which are not the <tt>.dsc</tt>.
3593 </footnote>. For example:
3596 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3597 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3599 The exact forms of the filenames are described
3600 in <ref id="pkg-sourcearchives">.
3604 In the <file>.changes</file> file this contains one line per
3605 file being uploaded. Each line contains the MD5 checksum,
3606 size, section and priority and the filename. For example:
3609 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3610 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3611 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3612 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3614 The <qref id="f-Section">section</qref>
3615 and <qref id="f-Priority">priority</qref> are the values of
3616 the corresponding fields in the main source control file. If
3617 no section or priority is specified then <tt>-</tt> should be
3618 used, though section and priority values must be specified for
3619 new packages to be installed properly.
3623 The special value <tt>byhand</tt> for the section in a
3624 <tt>.changes</tt> file indicates that the file in question
3625 is not an ordinary package file and must by installed by
3626 hand by the distribution maintainers. If the section is
3627 <tt>byhand</tt> the priority should be <tt>-</tt>.
3631 If a new Debian revision of a package is being shipped and
3632 no new original source archive is being distributed the
3633 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3634 entry for the original source archive
3635 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3636 but the <file>.changes</file> file should leave it out. In
3637 this case the original source archive on the distribution
3638 site must match exactly, byte-for-byte, the original
3639 source archive which was used to generate the
3640 <file>.dsc</file> file and diff which are being uploaded.</p>
3643 <sect1 id="f-Closes">
3644 <heading><tt>Closes</tt></heading>
3647 A space-separated list of bug report numbers that the upload
3648 governed by the .changes file closes.
3652 <sect1 id="f-Homepage">
3653 <heading><tt>Homepage</tt></heading>
3656 The URL of the web site for this package, preferably (when
3657 applicable) the site from which the original source can be
3658 obtained and any additional upstream documentation or
3659 information may be found. The content of this field is a
3660 simple URL without any surrounding characters such as
3665 <sect1 id="f-Checksums">
3666 <heading><tt>Checksums-Sha1</tt>
3667 and <tt>Checksums-Sha256</tt></heading>
3670 These multiline fields contain a list of files with a checksum and size
3671 for each one. Both <tt>Checksums-Sha1</tt>
3672 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3673 only in the checksum algorithm used: SHA-1
3674 for <tt>Checksums-Sha1</tt> and SHA-256
3675 for <tt>Checksums-Sha256</tt>.
3679 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3680 multiline fields. The first line of the field value (the part
3681 on the same line as <tt>Checksums-Sha1:</tt>
3682 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3683 of the field is expressed as continuation lines, one line per
3684 file. Each line consists of the checksum, a space, the file
3685 size, a space, and the file name. For example (from
3686 a <file>.changes</file> file):
3689 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3690 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3691 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3692 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3694 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3695 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3696 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3697 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3702 In the <file>.dsc</file> file, these fields should list all
3703 files that make up the source package. In
3704 the <file>.changes</file> file, these fields should list all
3705 files being uploaded. The list of files in these fields
3706 must match the list of files in the <tt>Files</tt> field.
3710 <sect1 id="f-DM-Upload-Allowed">
3711 <heading><tt>DM-Upload-Allowed</tt></heading>
3714 The most recent version of a package uploaded to unstable or
3715 experimental must include the field <tt>DM-Upload-Allowed:
3716 yes</tt> in the source section of its source control file for
3717 the Debian archive to accept uploads signed with a key in the
3718 Debian Maintainer keyring. See the General
3719 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3720 name="Endorse the concept of Debian Maintainers"> for more
3727 <heading>User-defined fields</heading>
3730 Additional user-defined fields may be added to the
3731 source package control file. Such fields will be
3732 ignored, and not copied to (for example) binary or
3733 Debian source control files or upload control files.
3737 If you wish to add additional unsupported fields to
3738 these output files you should use the mechanism
3743 Fields in the main source control information file with
3744 names starting <tt>X</tt>, followed by one or more of
3745 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3746 be copied to the output files. Only the part of the
3747 field name after the hyphen will be used in the output
3748 file. Where the letter <tt>B</tt> is used the field
3749 will appear in binary package control files, where the
3750 letter <tt>S</tt> is used in Debian source control
3751 files and where <tt>C</tt> is used in upload control
3752 (<tt>.changes</tt>) files.
3756 For example, if the main source information control file
3759 XBS-Comment: I stand between the candle and the star.
3761 then the binary and Debian source control files will contain the
3764 Comment: I stand between the candle and the star.
3773 <chapt id="maintainerscripts">
3774 <heading>Package maintainer scripts and installation procedure</heading>
3777 <heading>Introduction to package maintainer scripts</heading>
3780 It is possible to supply scripts as part of a package which
3781 the package management system will run for you when your
3782 package is installed, upgraded or removed.
3786 These scripts are the control information
3787 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3788 and <prgn>postrm</prgn>. They must be proper executable files;
3789 if they are scripts (which is recommended), they must start with
3790 the usual <tt>#!</tt> convention. They should be readable and
3791 executable by anyone, and must not be world-writable.
3795 The package management system looks at the exit status from
3796 these scripts. It is important that they exit with a
3797 non-zero status if there is an error, so that the package
3798 management system can stop its processing. For shell
3799 scripts this means that you <em>almost always</em> need to
3800 use <tt>set -e</tt> (this is usually true when writing shell
3801 scripts, in fact). It is also important, of course, that
3802 they exit with a zero status if everything went well.
3806 Additionally, packages interacting with users
3807 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3808 should install a <prgn>config</prgn> script as a control
3809 information file. See <ref id="maintscriptprompt"> for details.
3813 When a package is upgraded a combination of the scripts from
3814 the old and new packages is called during the upgrade
3815 procedure. If your scripts are going to be at all
3816 complicated you need to be aware of this, and may need to
3817 check the arguments to your scripts.
3821 Broadly speaking the <prgn>preinst</prgn> is called before
3822 (a particular version of) a package is unpacked, and the
3823 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3824 before (a version of) a package is removed and the
3825 <prgn>postrm</prgn> afterwards.
3829 Programs called from maintainer scripts should not normally
3830 have a path prepended to them. Before installation is
3831 started, the package management system checks to see if the
3832 programs <prgn>ldconfig</prgn>,
3833 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3834 and <prgn>update-rc.d</prgn> can be found via the
3835 <tt>PATH</tt> environment variable. Those programs, and any
3836 other program that one would expect to be in the
3837 <tt>PATH</tt>, should thus be invoked without an absolute
3838 pathname. Maintainer scripts should also not reset the
3839 <tt>PATH</tt>, though they might choose to modify it by
3840 prepending or appending package-specific directories. These
3841 considerations really apply to all shell scripts.</p>
3844 <sect id="idempotency">
3845 <heading>Maintainer scripts idempotency</heading>
3848 It is necessary for the error recovery procedures that the
3849 scripts be idempotent. This means that if it is run
3850 successfully, and then it is called again, it doesn't bomb
3851 out or cause any harm, but just ensures that everything is
3852 the way it ought to be. If the first call failed, or
3853 aborted half way through for some reason, the second call
3854 should merely do the things that were left undone the first
3855 time, if any, and exit with a success status if everything
3857 This is so that if an error occurs, the user interrupts
3858 <prgn>dpkg</prgn> or some other unforeseen circumstance
3859 happens you don't leave the user with a badly-broken
3860 package when <prgn>dpkg</prgn> attempts to repeat the
3866 <sect id="controllingterminal">
3867 <heading>Controlling terminal for maintainer scripts</heading>
3870 Maintainer scripts are not guaranteed to run with a controlling
3871 terminal and may not be able to interact with the user. They
3872 must be able to fall back to noninteractive behavior if no
3873 controlling terminal is available. Maintainer scripts that
3874 prompt via a program conforming to the Debian Configuration
3875 Management Specification (see <ref id="maintscriptprompt">) may
3876 assume that program will handle falling back to noninteractive
3881 For high-priority prompts without a reasonable default answer,
3882 maintainer scripts may abort if there is no controlling
3883 terminal. However, this situation should be avoided if at all
3884 possible, since it prevents automated or unattended installs.
3885 In most cases, users will consider this to be a bug in the
3890 <sect id="exitstatus">
3891 <heading>Exit status</heading>
3894 Each script must return a zero exit status for
3895 success, or a nonzero one for failure, since the package
3896 management system looks for the exit status of these scripts
3897 and determines what action to take next based on that datum.
3901 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3906 What follows is a summary of all the ways in which maintainer
3907 scripts may be called along with what facilities those scripts
3908 may rely on being available at that time. Script names preceded
3909 by <var>new-</var> are the scripts from the new version of a
3910 package being installed, upgraded to, or downgraded to. Script
3911 names preceded by <var>old-</var> are the scripts from the old
3912 version of a package that is being upgraded from or downgraded
3917 The <prgn>preinst</prgn> script may be called in the following
3920 <tag><var>new-preinst</var> <tt>install</tt></tag>
3921 <tag><var>new-preinst</var> <tt>install</tt>
3922 <var>old-version</var></tag>
3923 <tag><var>new-preinst</var> <tt>upgrade</tt>
3924 <var>old-version</var></tag>
3926 The package will not yet be unpacked, so
3927 the <prgn>preinst</prgn> script cannot rely on any files
3928 included in its package. Only essential packages and
3929 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3930 available. Pre-dependencies will have been configured at
3931 least once, but at the time the <prgn>preinst</prgn> is
3932 called they may only be in an unpacked or "Half-Configured"
3933 state if a previous version of the pre-dependency was
3934 completely configured and has not been removed since then.
3937 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3938 <var>new-version</var></tag>
3940 Called during error handling of an upgrade that failed after
3941 unpacking the new package because the <tt>postrm
3942 upgrade</tt> action failed. The unpacked files may be
3943 partly from the new version or partly missing, so the script
3944 cannot rely on files included in the package. Package
3945 dependencies may not be available. Pre-dependencies will be
3946 at least unpacked following the same rules as above, except
3947 they may be only "Half-Installed" if an upgrade of the
3948 pre-dependency failed.<footnote>
3949 This can happen if the new version of the package no
3950 longer pre-depends on a package that had been partially
3958 The <prgn>postinst</prgn> script may be called in the following
3961 <tag><var>postinst</var> <tt>configure</tt>
3962 <var>most-recently-configured-version</var></tag>
3964 The files contained in the package will be unpacked. All
3965 package dependencies will at least be unpacked. If there
3966 are no circular dependencies involved, all package
3967 dependencies will be configured. For behavior in the case
3968 of circular dependencies, see the discussion
3969 in <ref id="binarydeps">.
3972 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3973 <var>new-version</var></tag>
3974 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3975 <tt>in-favour</tt> <var>package</var>
3976 <var>new-version</var></tag>
3977 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3978 <tag><var>deconfigured's-postinst</var>
3979 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3980 <var>failed-install-package</var> <var>version</var>
3981 [<tt>removing</tt> <var>conflicting-package</var>
3982 <var>version</var>]</tag>
3984 The files contained in the package will be unpacked. All
3985 package dependencies will at least be "Half-Installed" and
3986 will have previously been configured and not removed.
3987 However, dependencies may not be configured or even fully
3988 unpacked in some error situations.<footnote>
3989 For example, suppose packages foo and bar are installed
3990 with foo depending on bar. If an upgrade of bar were
3991 started and then aborted, and then an attempt to remove
3992 foo failed because its <prgn>prerm</prgn> script failed,
3993 foo's <tt>postinst abort-remove</tt> would be called with
3994 bar only "Half-Installed".
3996 The <prgn>postinst</prgn> should still attempt any actions
3997 for which its dependencies are required, since they will
3998 normally be available, but consider the correct error
3999 handling approach if those actions fail. Aborting
4000 the <prgn>postinst</prgn> action if commands or facilities
4001 from the package dependencies are not available is often the
4008 The <prgn>prerm</prgn> script may be called in the following
4011 <tag><var>prerm</var> <tt>remove</tt></tag>
4012 <tag><var>old-prerm</var>
4013 <tt>upgrade</tt><var>new-version</var></tag>
4014 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4015 <tt>in-favour</tt> <var>package</var>
4016 <var>new-version</var></tag>
4017 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4018 <tt>in-favour</tt> <var>package-being-installed</var>
4019 <var>version</var> [<tt>removing</tt>
4020 <var>conflicting-package</var> <var>version</var>]</tag>
4022 The package whose <prgn>prerm</prgn> is being called will be
4023 at least "Half-Installed". All package dependencies will at
4024 least be "Half-Installed" and will have previously been
4025 configured and not removed. If there was no error, all
4026 dependencies will at least be unpacked, but these actions
4027 may be called in various error states where dependencies are
4028 only "Half-Installed" due to a partial upgrade.
4031 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4032 <var>old-version</var></tag>
4034 Called during error handling when <tt>prerm upgrade</tt>
4035 fails. The new package will not yet be unpacked, and all
4036 the same constraints as for <tt>preinst upgrade</tt> apply.
4042 The <prgn>postrm</prgn> script may be called in the following
4045 <tag><var>postrm</var> <tt>remove</tt></tag>
4046 <tag><var>postrm</var> <tt>purge</tt></tag>
4047 <tag><var>old-postrm</var> <tt>upgrade</tt>
4048 <var>new-version</var></tag>
4049 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4050 <var>overwriter</var> <var>overwriter-version</var></tag>
4052 The <prgn>postrm</prgn> script is called after the package's
4053 files have been removed or replaced. The package
4054 whose <prgn>postrm</prgn> is being called may have
4055 previously been deconfigured and only be unpacked, at which
4056 point subsequent package changes do not consider its
4057 dependencies. Therefore, all <prgn>postrm</prgn> actions
4058 may only rely on essential packages and must gracefully skip
4059 any actions that require the package's dependencies if those
4060 dependencies are unavailable.<footnote>
4061 This is often done by checking whether the command or
4062 facility the <prgn>postrm</prgn> intends to call is
4063 available before calling it. For example:
4065 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4066 . /usr/share/debconf/confmodule
4070 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4071 configuration for the package
4072 if <package>debconf</package> is installed.
4076 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4077 <var>old-version</var></tag>
4079 Called when the old <tt>postrm upgrade</tt> action fails.
4080 The new package will be unpacked, but only essential
4081 packages and pre-dependencies can be relied on.
4082 Pre-dependencies will either be configured or will be
4083 "Unpacked" or "Half-Configured" but previously had been
4084 configured and was never removed.
4087 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4088 <tag><var>new-postrm</var> <tt>abort-install</tt>
4089 <var>old-version</var></tag>
4090 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4091 <var>old-version</var></tag>
4093 Called before unpacking the new package as part of the
4094 error handling of <prgn>preinst</prgn> failures. May assume
4095 the same state as <prgn>preinst</prgn> can assume.
4101 <sect id="unpackphase">
4102 <heading>Details of unpack phase of installation or upgrade</heading>
4105 The procedure on installation/upgrade/overwrite/disappear
4106 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4107 stage of <tt>dpkg --install</tt>) is as follows. In each
4108 case, if a major error occurs (unless listed below) the
4109 actions are, in general, run backwards - this means that the
4110 maintainer scripts are run with different arguments in
4111 reverse order. These are the "error unwind" calls listed
4118 If a version of the package is already installed, call
4119 <example compact="compact">
4120 <var>old-prerm</var> upgrade <var>new-version</var>
4124 If the script runs but exits with a non-zero
4125 exit status, <prgn>dpkg</prgn> will attempt:
4126 <example compact="compact">
4127 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4129 If this works, the upgrade continues. If this
4130 does not work, the error unwind:
4131 <example compact="compact">
4132 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4134 If this works, then the old-version is
4135 "Installed", if not, the old version is in a
4136 "Half-Configured" state.
4142 If a "conflicting" package is being removed at the same time,
4143 or if any package will be broken (due to <tt>Breaks</tt>):
4146 If <tt>--auto-deconfigure</tt> is
4147 specified, call, for each package to be deconfigured
4148 due to <tt>Breaks</tt>:
4149 <example compact="compact">
4150 <var>deconfigured's-prerm</var> deconfigure \
4151 in-favour <var>package-being-installed</var> <var>version</var>
4154 <example compact="compact">
4155 <var>deconfigured's-postinst</var> abort-deconfigure \
4156 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4158 The deconfigured packages are marked as
4159 requiring configuration, so that if
4160 <tt>--install</tt> is used they will be
4161 configured again if possible.
4164 If any packages depended on a conflicting
4165 package being removed and <tt>--auto-deconfigure</tt> is
4166 specified, call, for each such package:
4167 <example compact="compact">
4168 <var>deconfigured's-prerm</var> deconfigure \
4169 in-favour <var>package-being-installed</var> <var>version</var> \
4170 removing <var>conflicting-package</var> <var>version</var>
4173 <example compact="compact">
4174 <var>deconfigured's-postinst</var> abort-deconfigure \
4175 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4176 removing <var>conflicting-package</var> <var>version</var>
4178 The deconfigured packages are marked as
4179 requiring configuration, so that if
4180 <tt>--install</tt> is used they will be
4181 configured again if possible.
4184 To prepare for removal of each conflicting package, call:
4185 <example compact="compact">
4186 <var>conflictor's-prerm</var> remove \
4187 in-favour <var>package</var> <var>new-version</var>
4190 <example compact="compact">
4191 <var>conflictor's-postinst</var> abort-remove \
4192 in-favour <var>package</var> <var>new-version</var>
4201 If the package is being upgraded, call:
4202 <example compact="compact">
4203 <var>new-preinst</var> upgrade <var>old-version</var>
4205 If this fails, we call:
4207 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4214 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4216 is called. If this works, then the old version
4217 is in an "Installed" state, or else it is left
4218 in an "Unpacked" state.
4223 If it fails, then the old version is left
4224 in an "Half-Installed" state.
4231 Otherwise, if the package had some configuration
4232 files from a previous version installed (i.e., it
4233 is in the "configuration files only" state):
4234 <example compact="compact">
4235 <var>new-preinst</var> install <var>old-version</var>
4239 <var>new-postrm</var> abort-install <var>old-version</var>
4241 If this fails, the package is left in a
4242 "Half-Installed" state, which requires a
4243 reinstall. If it works, the packages is left in
4244 a "Config-Files" state.
4247 Otherwise (i.e., the package was completely purged):
4248 <example compact="compact">
4249 <var>new-preinst</var> install
4252 <example compact="compact">
4253 <var>new-postrm</var> abort-install
4255 If the error-unwind fails, the package is in a
4256 "Half-Installed" phase, and requires a
4257 reinstall. If the error unwind works, the
4258 package is in a not installed state.
4265 The new package's files are unpacked, overwriting any
4266 that may be on the system already, for example any
4267 from the old version of the same package or from
4268 another package. Backups of the old files are kept
4269 temporarily, and if anything goes wrong the package
4270 management system will attempt to put them back as
4271 part of the error unwind.
4275 It is an error for a package to contain files which
4276 are on the system in another package, unless
4277 <tt>Replaces</tt> is used (see <ref id="replaces">).
4279 The following paragraph is not currently the case:
4280 Currently the <tt>- - force-overwrite</tt> flag is
4281 enabled, downgrading it to a warning, but this may not
4287 It is a more serious error for a package to contain a
4288 plain file or other kind of non-directory where another
4289 package has a directory (again, unless
4290 <tt>Replaces</tt> is used). This error can be
4291 overridden if desired using
4292 <tt>--force-overwrite-dir</tt>, but this is not
4297 Packages which overwrite each other's files produce
4298 behavior which, though deterministic, is hard for the
4299 system administrator to understand. It can easily
4300 lead to "missing" programs if, for example, a package
4301 is unpacked which overwrites a file from another
4302 package, and is then removed again.<footnote>
4303 Part of the problem is due to what is arguably a
4304 bug in <prgn>dpkg</prgn>.
4309 A directory will never be replaced by a symbolic link
4310 to a directory or vice versa; instead, the existing
4311 state (symlink or not) will be left alone and
4312 <prgn>dpkg</prgn> will follow the symlink if there is
4321 If the package is being upgraded, call
4322 <example compact="compact">
4323 <var>old-postrm</var> upgrade <var>new-version</var>
4327 If this fails, <prgn>dpkg</prgn> will attempt:
4328 <example compact="compact">
4329 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4331 If this works, installation continues. If not,
4333 <example compact="compact">
4334 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4336 If this fails, the old version is left in a
4337 "Half-Installed" state. If it works, dpkg now
4339 <example compact="compact">
4340 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4342 If this fails, the old version is left in a
4343 "Half-Installed" state. If it works, dpkg now
4345 <example compact="compact">
4346 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4348 If this fails, the old version is in an
4355 This is the point of no return - if
4356 <prgn>dpkg</prgn> gets this far, it won't back off
4357 past this point if an error occurs. This will
4358 leave the package in a fairly bad state, which
4359 will require a successful re-installation to clear
4360 up, but it's when <prgn>dpkg</prgn> starts doing
4361 things that are irreversible.
4366 Any files which were in the old version of the package
4367 but not in the new are removed.
4371 The new file list replaces the old.
4375 The new maintainer scripts replace the old.
4379 Any packages all of whose files have been overwritten
4380 during the installation, and which aren't required for
4381 dependencies, are considered to have been removed.
4382 For each such package
4385 <prgn>dpkg</prgn> calls:
4386 <example compact="compact">
4387 <var>disappearer's-postrm</var> disappear \
4388 <var>overwriter</var> <var>overwriter-version</var>
4392 The package's maintainer scripts are removed.
4395 It is noted in the status database as being in a
4396 sane state, namely not installed (any conffiles
4397 it may have are ignored, rather than being
4398 removed by <prgn>dpkg</prgn>). Note that
4399 disappearing packages do not have their prerm
4400 called, because <prgn>dpkg</prgn> doesn't know
4401 in advance that the package is going to
4408 Any files in the package we're unpacking that are also
4409 listed in the file lists of other packages are removed
4410 from those lists. (This will lobotomize the file list
4411 of the "conflicting" package if there is one.)
4415 The backup files made during installation, above, are
4421 The new package's status is now sane, and recorded as
4426 Here is another point of no return - if the
4427 conflicting package's removal fails we do not unwind
4428 the rest of the installation; the conflicting package
4429 is left in a half-removed limbo.
4434 If there was a conflicting package we go and do the
4435 removal actions (described below), starting with the
4436 removal of the conflicting package's files (any that
4437 are also in the package being unpacked have already
4438 been removed from the conflicting package's file list,
4439 and so do not get removed now).
4445 <sect id="configdetails"><heading>Details of configuration</heading>
4448 When we configure a package (this happens with <tt>dpkg
4449 --install</tt> and <tt>dpkg --configure</tt>), we first
4450 update any <tt>conffile</tt>s and then call:
4451 <example compact="compact">
4452 <var>postinst</var> configure <var>most-recently-configured-version</var>
4457 No attempt is made to unwind after errors during
4458 configuration. If the configuration fails, the package is in
4459 a "Failed Config" state, and an error message is generated.
4463 If there is no most recently configured version
4464 <prgn>dpkg</prgn> will pass a null argument.
4467 Historical note: Truly ancient (pre-1997) versions of
4468 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4469 (including the angle brackets) in this case. Even older
4470 ones did not pass a second argument at all, under any
4471 circumstance. Note that upgrades using such an old dpkg
4472 version are unlikely to work for other reasons, even if
4473 this old argument behavior is handled by your postinst script.
4479 <sect id="removedetails"><heading>Details of removal and/or
4480 configuration purging</heading>
4486 <example compact="compact">
4487 <var>prerm</var> remove
4491 If prerm fails during replacement due to conflict
4493 <var>conflictor's-postinst</var> abort-remove \
4494 in-favour <var>package</var> <var>new-version</var>
4498 <var>postinst</var> abort-remove
4502 If this fails, the package is in a "Half-Configured"
4503 state, or else it remains "Installed".
4507 The package's files are removed (except <tt>conffile</tt>s).
4510 <example compact="compact">
4511 <var>postrm</var> remove
4515 If it fails, there's no error unwind, and the package is in
4516 an "Half-Installed" state.
4521 All the maintainer scripts except the <prgn>postrm</prgn>
4526 If we aren't purging the package we stop here. Note
4527 that packages which have no <prgn>postrm</prgn> and no
4528 <tt>conffile</tt>s are automatically purged when
4529 removed, as there is no difference except for the
4530 <prgn>dpkg</prgn> status.
4534 The <tt>conffile</tt>s and any backup files
4535 (<tt>~</tt>-files, <tt>#*#</tt> files,
4536 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4541 <example compact="compact">
4542 <var>postrm</var> purge
4546 If this fails, the package remains in a "Config-Files"
4551 The package's file list is removed.
4560 <chapt id="relationships">
4561 <heading>Declaring relationships between packages</heading>
4563 <sect id="depsyntax">
4564 <heading>Syntax of relationship fields</heading>
4567 These fields all have a uniform syntax. They are a list of
4568 package names separated by commas.
4572 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4573 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4574 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4575 control fields of the package, which declare
4576 dependencies on other packages, the package names listed may
4577 also include lists of alternative package names, separated
4578 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4579 if any one of the alternative packages is installed, that
4580 part of the dependency is considered to be satisfied.
4584 All of the fields except for <tt>Provides</tt> may restrict
4585 their applicability to particular versions of each named
4586 package. This is done in parentheses after each individual
4587 package name; the parentheses should contain a relation from
4588 the list below followed by a version number, in the format
4589 described in <ref id="f-Version">.
4593 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4594 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4595 strictly earlier, earlier or equal, exactly equal, later or
4596 equal and strictly later, respectively. The deprecated
4597 forms <tt><</tt> and <tt>></tt> were used to mean
4598 earlier/later or equal, rather than strictly earlier/later,
4599 so they should not appear in new packages (though
4600 <prgn>dpkg</prgn> still supports them).
4604 Whitespace may appear at any point in the version
4605 specification subject to the rules in <ref
4606 id="controlsyntax">, and must appear where it's necessary to
4607 disambiguate; it is not otherwise significant. All of the
4608 relationship fields can only be folded in source package control files. For
4609 consistency and in case of future changes to
4610 <prgn>dpkg</prgn> it is recommended that a single space be
4611 used after a version relationship and before a version
4612 number; it is also conventional to put a single space after
4613 each comma, on either side of each vertical bar, and before
4614 each open parenthesis. When opening a continuation line in a relationship field, it
4615 is conventional to do so after a comma and before the space
4616 following that comma.
4620 For example, a list of dependencies might appear as:
4621 <example compact="compact">
4624 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4629 Relationships may be restricted to a certain set of
4630 architectures. This is indicated in brackets after each
4631 individual package name and the optional version specification.
4632 The brackets enclose a non-empty list of Debian architecture names
4633 in the format described in <ref id="arch-spec">,
4634 separated by whitespace. Exclamation marks may be prepended to
4635 each of the names. (It is not permitted for some names to be
4636 prepended with exclamation marks while others aren't.)
4640 For build relationship fields
4641 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4642 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4643 the current Debian host architecture is not in this list and
4644 there are no exclamation marks in the list, or it is in the list
4645 with a prepended exclamation mark, the package name and the
4646 associated version specification are ignored completely for the
4647 purposes of defining the relationships.
4652 <example compact="compact">
4654 Build-Depends-Indep: texinfo
4655 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4656 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4658 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4659 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4660 <tt>gnumach-dev</tt> only on hurd-i386.
4664 For binary relationship fields, the architecture restriction
4665 syntax is only supported in the source package control
4666 file <file>debian/control</file>. When the corresponding binary
4667 package control file is generated, the relationship will either
4668 be omitted or included without the architecture restriction
4669 based on the architecture of the binary package. This means
4670 that architecture restrictions must not be used in binary
4671 relationship fields for architecture-independent packages
4672 (<tt>Architecture: all</tt>).
4677 <example compact="compact">
4678 Depends: foo [i386], bar [amd64]
4680 becomes <tt>Depends: foo</tt> when the package is built on
4681 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4682 package is built on the <tt>amd64</tt> architecture, and omitted
4683 entirely in binary packages built on all other architectures.
4687 If the architecture-restricted dependency is part of a set of
4688 alternatives using <tt>|</tt>, that alternative is ignored
4689 completely on architectures that do not match the restriction.
4691 <example compact="compact">
4692 Build-Depends: foo [!i386] | bar [!amd64]
4694 is equivalent to <tt>bar</tt> on the i386 architecture, to
4695 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4696 bar</tt> on all other architectures.
4700 Relationships may also be restricted to a certain set of
4701 architectures using architecture wildcards in the format
4702 described in <ref id="arch-wildcard-spec">. The syntax for
4703 declaring such restrictions is the same as declaring
4704 restrictions using a certain set of architectures without
4705 architecture wildcards. For example:
4706 <example compact="compact">
4707 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4709 is equivalent to <tt>foo</tt> on architectures using the Linux
4710 kernel and any cpu, <tt>bar</tt> on architectures using any
4711 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4712 using a kernel other than Linux.
4716 Note that the binary package relationship fields such as
4717 <tt>Depends</tt> appear in one of the binary package
4718 sections of the control file, whereas the build-time
4719 relationships such as <tt>Build-Depends</tt> appear in the
4720 source package section of the control file (which is the
4725 <sect id="binarydeps">
4726 <heading>Binary Dependencies - <tt>Depends</tt>,
4727 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4728 <tt>Pre-Depends</tt>
4732 Packages can declare in their control file that they have
4733 certain relationships to other packages - for example, that
4734 they may not be installed at the same time as certain other
4735 packages, and/or that they depend on the presence of others.
4739 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4740 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4741 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4742 <tt>Breaks</tt> is described in <ref id="breaks">, and
4743 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4744 rest are described below.
4748 These seven fields are used to declare a dependency
4749 relationship by one package on another. Except for
4750 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4751 depending (binary) package's control file.
4752 (<tt>Enhances</tt> appears in the recommending package's
4753 control file, and <tt>Breaks</tt> appears in the version of
4754 depended-on package which causes the named package to
4759 A <tt>Depends</tt> field takes effect <em>only</em> when a
4760 package is to be configured. It does not prevent a package
4761 being on the system in an unconfigured state while its
4762 dependencies are unsatisfied, and it is possible to replace
4763 a package whose dependencies are satisfied and which is
4764 properly installed with a different version whose
4765 dependencies are not and cannot be satisfied; when this is
4766 done the depending package will be left unconfigured (since
4767 attempts to configure it will give errors) and will not
4768 function properly. If it is necessary, a
4769 <tt>Pre-Depends</tt> field can be used, which has a partial
4770 effect even when a package is being unpacked, as explained
4771 in detail below. (The other three dependency fields,
4772 <tt>Recommends</tt>, <tt>Suggests</tt> and
4773 <tt>Enhances</tt>, are only used by the various front-ends
4774 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4775 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4779 Since <tt>Depends</tt> only places requirements on the order in
4780 which packages are configured, packages in an installation run
4781 are usually all unpacked first and all configured later.
4783 This approach makes dependency resolution easier. If two
4784 packages A and B are being upgraded, the installed package A
4785 depends on exactly the installed package B, and the new
4786 package A depends on exactly the new package B (a common
4787 situation when upgrading shared libraries and their
4788 corresponding development packages), satisfying the
4789 dependencies at every stage of the upgrade would be
4790 impossible. This relaxed restriction means that both new
4791 packages can be unpacked together and then configured in their
4797 If there is a circular dependency among packages being installed
4798 or removed, installation or removal order honoring the
4799 dependency order is impossible, requiring the dependency loop be
4800 broken at some point and the dependency requirements violated
4801 for at least one package. Packages involved in circular
4802 dependencies may not be able to rely on their dependencies being
4803 configured before they themselves are configured, depending on
4804 which side of the break of the circular dependency loop they
4805 happen to be on. If one of the packages in the loop has
4806 no <prgn>postinst</prgn> script, then the cycle will be broken
4807 at that package; this ensures that all <prgn>postinst</prgn>
4808 scripts are run with their dependencies properly configured if
4809 this is possible. Otherwise the breaking point is arbitrary.
4810 Packages should therefore avoid circular dependencies where
4811 possible, particularly if they have <prgn>postinst</prgn>
4816 The meaning of the five dependency fields is as follows:
4818 <tag><tt>Depends</tt></tag>
4821 This declares an absolute dependency. A package will
4822 not be configured unless all of the packages listed in
4823 its <tt>Depends</tt> field have been correctly
4824 configured (unless there is a circular dependency as
4829 The <tt>Depends</tt> field should be used if the
4830 depended-on package is required for the depending
4831 package to provide a significant amount of
4836 The <tt>Depends</tt> field should also be used if the
4837 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4838 require the depended-on package to be unpacked or
4839 configured in order to run. In the case of <tt>postinst
4840 configure</tt>, the depended-on packages will be unpacked
4841 and configured first. (If both packages are involved in a
4842 dependency loop, this might not work as expected; see the
4843 explanation a few paragraphs back.) In the case
4844 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4845 actions, the package dependencies will normally be at
4846 least unpacked, but they may be only "Half-Installed" if a
4847 previous upgrade of the dependency failed.
4851 Finally, the <tt>Depends</tt> field should be used if the
4852 depended-on package is needed by the <prgn>postrm</prgn>
4853 script to fully clean up after the package removal. There
4854 is no guarantee that package dependencies will be
4855 available when <prgn>postrm</prgn> is run, but the
4856 depended-on package is more likely to be available if the
4857 package declares a dependency (particularly in the case
4858 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4859 script must gracefully skip actions that require a
4860 dependency if that dependency isn't available.
4864 <tag><tt>Recommends</tt></tag>
4867 This declares a strong, but not absolute, dependency.
4871 The <tt>Recommends</tt> field should list packages
4872 that would be found together with this one in all but
4873 unusual installations.
4877 <tag><tt>Suggests</tt></tag>
4879 This is used to declare that one package may be more
4880 useful with one or more others. Using this field
4881 tells the packaging system and the user that the
4882 listed packages are related to this one and can
4883 perhaps enhance its usefulness, but that installing
4884 this one without them is perfectly reasonable.
4887 <tag><tt>Enhances</tt></tag>
4889 This field is similar to Suggests but works in the
4890 opposite direction. It is used to declare that a
4891 package can enhance the functionality of another
4895 <tag><tt>Pre-Depends</tt></tag>
4898 This field is like <tt>Depends</tt>, except that it
4899 also forces <prgn>dpkg</prgn> to complete installation
4900 of the packages named before even starting the
4901 installation of the package which declares the
4902 pre-dependency, as follows:
4906 When a package declaring a pre-dependency is about to
4907 be <em>unpacked</em> the pre-dependency can be
4908 satisfied if the depended-on package is either fully
4909 configured, <em>or even if</em> the depended-on
4910 package(s) are only unpacked or in the "Half-Configured"
4911 state, provided that they have been configured
4912 correctly at some point in the past (and not removed
4913 or partially removed since). In this case, both the
4914 previously-configured and currently unpacked or
4915 "Half-Configured" versions must satisfy any version
4916 clause in the <tt>Pre-Depends</tt> field.
4920 When the package declaring a pre-dependency is about to
4921 be <em>configured</em>, the pre-dependency will be treated
4922 as a normal <tt>Depends</tt>. It will be considered
4923 satisfied only if the depended-on package has been
4924 correctly configured. However, unlike
4925 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4926 permit circular dependencies to be broken. If a circular
4927 dependency is encountered while attempting to honor
4928 <tt>Pre-Depends</tt>, the installation will be aborted.
4932 <tt>Pre-Depends</tt> are also required if the
4933 <prgn>preinst</prgn> script depends on the named package.
4934 It is best to avoid this situation if possible.
4938 <tt>Pre-Depends</tt> should be used sparingly,
4939 preferably only by packages whose premature upgrade or
4940 installation would hamper the ability of the system to
4941 continue with any upgrade that might be in progress.
4945 You should not specify a <tt>Pre-Depends</tt> entry for a
4946 package before this has been discussed on the
4947 <tt>debian-devel</tt> mailing list and a consensus about
4948 doing that has been reached. See <ref id="dependencies">.
4955 When selecting which level of dependency to use you should
4956 consider how important the depended-on package is to the
4957 functionality of the one declaring the dependency. Some
4958 packages are composed of components of varying degrees of
4959 importance. Such a package should list using
4960 <tt>Depends</tt> the package(s) which are required by the
4961 more important components. The other components'
4962 requirements may be mentioned as Suggestions or
4963 Recommendations, as appropriate to the components' relative
4969 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4972 When one binary package declares that it breaks another,
4973 <prgn>dpkg</prgn> will refuse to allow the package which
4974 declares <tt>Breaks</tt> to be unpacked unless the broken
4975 package is deconfigured first, and it will refuse to
4976 allow the broken package to be reconfigured.
4980 A package will not be regarded as causing breakage merely
4981 because its configuration files are still installed; it must
4982 be at least "Half-Installed".
4986 A special exception is made for packages which declare that
4987 they break their own package name or a virtual package which
4988 they provide (see below): this does not count as a real
4993 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4994 version clause; such a <tt>Breaks</tt> is introduced in the
4995 version of an (implicit or explicit) dependency which violates
4996 an assumption or reveals a bug in earlier versions of the broken
4997 package, or which takes over a file from earlier versions of the
4998 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4999 will inform higher-level package management tools that the
5000 broken package must be upgraded before the new one.
5004 If the breaking package also overwrites some files from the
5005 older package, it should use <tt>Replaces</tt> to ensure this
5006 goes smoothly. See <ref id="replaces"> for a full discussion
5007 of taking over files from other packages, including how to
5008 use <tt>Breaks</tt> in those cases.
5012 Many of the cases where <tt>Breaks</tt> should be used were
5013 previously handled with <tt>Conflicts</tt>
5014 because <tt>Breaks</tt> did not yet exist.
5015 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5016 See <ref id="conflicts"> for more information about the
5021 <sect id="conflicts">
5022 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5025 When one binary package declares a conflict with another using
5026 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5027 allow them to be unpacked on the system at the same time. This
5028 is a stronger restriction than <tt>Breaks</tt>, which prevents
5029 the broken package from being configured while the breaking
5030 package is in the "Unpacked" state but allows both packages to
5031 be unpacked at the same time.
5035 If one package is to be unpacked, the other must be removed
5036 first. If the package being unpacked is marked as replacing
5037 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5038 normally be used in this case) the one on the system, or the one
5039 on the system is marked as deselected, or both packages are
5040 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5041 automatically remove the package which is causing the conflict.
5042 Otherwise, it will halt the installation of the new package with
5043 an error. This mechanism is specifically designed to produce an
5044 error when the installed package is <tt>Essential</tt>, but the
5049 A package will not cause a conflict merely because its
5050 configuration files are still installed; it must be at least
5055 A special exception is made for packages which declare a
5056 conflict with their own package name, or with a virtual
5057 package which they provide (see below): this does not
5058 prevent their installation, and allows a package to conflict
5059 with others providing a replacement for it. You use this
5060 feature when you want the package in question to be the only
5061 package providing some feature.
5065 Normally, <tt>Breaks</tt> should be used instead
5066 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5067 stronger restriction on the ordering of package installation or
5068 upgrade and can make it more difficult for the package manager
5069 to find a correct solution to an upgrade or installation
5070 problem. <tt>Breaks</tt> should be used
5072 <item>when moving a file from one package to another (see
5073 <ref id="replaces">),</item>
5074 <item>when splitting a package (a special case of the previous
5076 <item>when the breaking package exposes a bug in or interacts
5077 badly with particular versions of the broken
5080 <tt>Conflicts</tt> should be used
5082 <item>when two packages provide the same file and will
5083 continue to do so,</item>
5084 <item>in conjunction with <tt>Provides</tt> when only one
5085 package providing a given virtual facility may be unpacked
5086 at a time (see <ref id="virtual">),</item>
5087 <item>in other cases where one must prevent simultaneous
5088 installation of two packages for reasons that are ongoing
5089 (not fixed in a later version of one of the packages) or
5090 that must prevent both packages from being unpacked at the
5091 same time, not just configured.</item>
5093 Be aware that adding <tt>Conflicts</tt> is normally not the best
5094 solution when two packages provide the same files. Depending on
5095 the reason for that conflict, using alternatives or renaming the
5096 files is often a better approach. See, for
5097 example, <ref id="binaries">.
5101 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5102 unless two packages cannot be installed at the same time or
5103 installing them both causes one of them to be broken or
5104 unusable. Having similar functionality or performing the same
5105 tasks as another package is not sufficient reason to
5106 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5110 A <tt>Conflicts</tt> entry may have an "earlier than" version
5111 clause if the reason for the conflict is corrected in a later
5112 version of one of the packages. However, normally the presence
5113 of an "earlier than" version clause is a sign
5114 that <tt>Breaks</tt> should have been used instead. An "earlier
5115 than" version clause in <tt>Conflicts</tt>
5116 prevents <prgn>dpkg</prgn> from upgrading or installing the
5117 package which declares such a conflict until the upgrade or
5118 removal of the conflicted-with package has been completed, which
5119 is a strong restriction.
5123 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5127 As well as the names of actual ("concrete") packages, the
5128 package relationship fields <tt>Depends</tt>,
5129 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5130 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5131 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5132 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5133 may mention "virtual packages".
5137 A <em>virtual package</em> is one which appears in the
5138 <tt>Provides</tt> control field of another package. The effect
5139 is as if the package(s) which provide a particular virtual
5140 package name had been listed by name everywhere the virtual
5141 package name appears. (See also <ref id="virtual_pkg">)
5145 If there are both concrete and virtual packages of the same
5146 name, then the dependency may be satisfied (or the conflict
5147 caused) by either the concrete package with the name in
5148 question or any other concrete package which provides the
5149 virtual package with the name in question. This is so that,
5150 for example, supposing we have
5151 <example compact="compact">
5154 </example> and someone else releases an enhanced version of
5155 the <tt>bar</tt> package they can say:
5156 <example compact="compact">
5160 and the <tt>bar-plus</tt> package will now also satisfy the
5161 dependency for the <tt>foo</tt> package.
5165 If a relationship field has a version number attached, only real
5166 packages will be considered to see whether the relationship is
5167 satisfied (or the prohibition violated, for a conflict or
5168 breakage). In other words, if a version number is specified,
5169 this is a request to ignore all <tt>Provides</tt> for that
5170 package name and consider only real packages. The package
5171 manager will assume that a package providing that virtual
5172 package is not of the "right" version. A <tt>Provides</tt>
5173 field may not contain version numbers, and the version number of
5174 the concrete package which provides a particular virtual package
5175 will not be considered when considering a dependency on or
5176 conflict with the virtual package name.<footnote>
5177 It is possible that a future release of <prgn>dpkg</prgn> may
5178 add the ability to specify a version number for each virtual
5179 package it provides. This feature is not yet present,
5180 however, and is expected to be used only infrequently.
5185 To specify which of a set of real packages should be the default
5186 to satisfy a particular dependency on a virtual package, list
5187 the real package as an alternative before the virtual one.
5191 If the virtual package represents a facility that can only be
5192 provided by one real package at a time, such as
5193 the <package>mail-transport-agent</package> virtual package that
5194 requires installation of a binary that would conflict with all
5195 other providers of that virtual package (see
5196 <ref id="mail-transport-agents">), all packages providing that
5197 virtual package should also declare a conflict with it
5198 using <tt>Conflicts</tt>. This will ensure that at most one
5199 provider of that virtual package is unpacked or installed at a
5204 <sect id="replaces"><heading>Overwriting files and replacing
5205 packages - <tt>Replaces</tt></heading>
5208 Packages can declare in their control file that they should
5209 overwrite files in certain other packages, or completely replace
5210 other packages. The <tt>Replaces</tt> control field has these
5211 two distinct purposes.
5214 <sect1><heading>Overwriting files in other packages</heading>
5217 It is usually an error for a package to contain files which
5218 are on the system in another package. However, if the
5219 overwriting package declares that it <tt>Replaces</tt> the one
5220 containing the file being overwritten, then <prgn>dpkg</prgn>
5221 will replace the file from the old package with that from the
5222 new. The file will no longer be listed as "owned" by the old
5223 package and will be taken over by the new package.
5224 Normally, <tt>Breaks</tt> should be used in conjunction
5225 with <tt>Replaces</tt>.<footnote>
5226 To see why <tt>Breaks</tt> is normally needed in addition
5227 to <tt>Replaces</tt>, consider the case of a file in the
5228 package <package>foo</package> being taken over by the
5229 package <package>foo-data</package>.
5230 <tt>Replaces</tt> will allow <package>foo-data</package> to
5231 be installed and take over that file. However,
5232 without <tt>Breaks</tt>, nothing
5233 requires <package>foo</package> to be upgraded to a newer
5234 version that knows it does not include that file and instead
5235 depends on <package>foo-data</package>. Nothing would
5236 prevent the new <package>foo-data</package> package from
5237 being installed and then removed, removing the file that it
5238 took over from <package>foo</package>. After that
5239 operation, the package manager would think the system was in
5240 a consistent state, but the <package>foo</package> package
5241 would be missing one of its files.
5246 For example, if a package <package>foo</package> is split
5247 into <package>foo</package> and <package>foo-data</package>
5248 starting at version 1.2-3, <package>foo-data</package> would
5250 <example compact="compact">
5251 Replaces: foo (<< 1.2-3)
5252 Breaks: foo (<< 1.2-3)
5254 in its control file. The new version of the
5255 package <package>foo</package> would normally have the field
5256 <example compact="compact">
5257 Depends: foo-data (>= 1.2-3)
5259 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5260 the files moved into <package>foo-data</package> are not
5261 required for normal operation).
5265 If a package is completely replaced in this way, so that
5266 <prgn>dpkg</prgn> does not know of any files it still
5267 contains, it is considered to have "disappeared". It will
5268 be marked as not wanted on the system (selected for
5269 removal) and not installed. Any <tt>conffile</tt>s
5270 details noted for the package will be ignored, as they
5271 will have been taken over by the overwriting package. The
5272 package's <prgn>postrm</prgn> script will be run with a
5273 special argument to allow the package to do any final
5274 cleanup required. See <ref id="mscriptsinstact">.
5276 Replaces is a one way relationship. You have to install
5277 the replacing package after the replaced package.
5282 For this usage of <tt>Replaces</tt>, virtual packages (see
5283 <ref id="virtual">) are not considered when looking at a
5284 <tt>Replaces</tt> field. The packages declared as being
5285 replaced must be mentioned by their real names.
5289 This usage of <tt>Replaces</tt> only takes effect when both
5290 packages are at least partially on the system at once. It is
5291 not relevant if the packages conflict unless the conflict has
5296 <sect1><heading>Replacing whole packages, forcing their
5300 Second, <tt>Replaces</tt> allows the packaging system to
5301 resolve which package should be removed when there is a
5302 conflict (see <ref id="conflicts">). This usage only takes
5303 effect when the two packages <em>do</em> conflict, so that the
5304 two usages of this field do not interfere with each other.
5308 In this situation, the package declared as being replaced
5309 can be a virtual package, so for example, all mail
5310 transport agents (MTAs) would have the following fields in
5311 their control files:
5312 <example compact="compact">
5313 Provides: mail-transport-agent
5314 Conflicts: mail-transport-agent
5315 Replaces: mail-transport-agent
5317 ensuring that only one MTA can be unpacked at any one
5318 time. See <ref id="virtual"> for more information about this
5323 <sect id="sourcebinarydeps">
5324 <heading>Relationships between source and binary packages -
5325 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5326 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5330 Source packages that require certain binary packages to be
5331 installed or absent at the time of building the package
5332 can declare relationships to those binary packages.
5336 This is done using the <tt>Build-Depends</tt>,
5337 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5338 <tt>Build-Conflicts-Indep</tt> control fields.
5342 Build-dependencies on "build-essential" binary packages can be
5343 omitted. Please see <ref id="pkg-relations"> for more information.
5347 The dependencies and conflicts they define must be satisfied
5348 (as defined earlier for binary packages) in order to invoke
5349 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5351 There is no Build-Depends-Arch; this role is essentially
5352 met with Build-Depends. Anyone building the
5353 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5354 assumed to be building the whole package, and therefore
5355 installation of all build dependencies is required.
5358 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5359 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5360 not yet know how to check for its existence, and
5361 <tt>binary-arch</tt>. The purpose of the original split
5362 between <tt>Build-Depends</tt> and
5363 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5364 wouldn't need to install extra packages needed only for the
5365 binary-indep targets. But without a build-arch/build-indep
5366 split, this didn't work, since most of the work is done in
5367 the build target, not in the binary target.
5371 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5372 <tt>binary-arch</tt></tag>
5374 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5375 fields must be satisfied when these targets are invoked.
5377 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5378 and <tt>binary-indep</tt></tag>
5380 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5381 <tt>Build-Depends-Indep</tt>, and
5382 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5383 these targets are invoked.
5391 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5394 Packages containing shared libraries must be constructed with
5395 a little care to make sure that the shared library is always
5396 available. This is especially important for packages whose
5397 shared libraries are vitally important, such as the C library
5398 (currently <tt>libc6</tt>).
5402 This section deals only with public shared libraries: shared
5403 libraries that are placed in directories searched by the dynamic
5404 linker by default or which are intended to be linked against
5405 normally and possibly used by other, independent packages. Shared
5406 libraries that are internal to a particular package or that are
5407 only loaded as dynamic modules are not covered by this section and
5408 are not subject to its requirements.
5412 A shared library is identified by the <tt>SONAME</tt> attribute
5413 stored in its dynamic section. When a binary is linked against a
5414 shared library, the <tt>SONAME</tt> of the shared library is
5415 recorded in the binary's <tt>NEEDED</tt> section so that the
5416 dynamic linker knows that library must be loaded at runtime. The
5417 shared library file's full name (which usually contains additional
5418 version information not needed in the <tt>SONAME</tt>) is
5419 therefore normally not referenced directly. Instead, the shared
5420 library is loaded by its <tt>SONAME</tt>, which exists on the file
5421 system as a symlink pointing to the full name of the shared
5422 library. This symlink must be provided by the
5423 package. <ref id="sharedlibs-runtime"> describes how to do this.
5425 This is a convention of shared library versioning, but not a
5426 requirement. Some libraries use the <tt>SONAME</tt> as the full
5427 library file name instead and therefore do not need a symlink.
5428 Most, however, encode additional information about
5429 backwards-compatible revisions as a minor version number in the
5430 file name. The <tt>SONAME</tt> itself only changes when
5431 binaries linked with the earlier version of the shared library
5432 may no longer work, but the filename may change with each
5433 release of the library. See <ref id="sharedlibs-runtime"> for
5439 When linking a binary or another shared library against a shared
5440 library, the <tt>SONAME</tt> for that shared library is not yet
5441 known. Instead, the shared library is found by looking for a file
5442 matching the library name with <tt>.so</tt> appended. This file
5443 exists on the file system as a symlink pointing to the shared
5448 Shared libraries are normally split into several binary packages.
5449 The <tt>SONAME</tt> symlink is installed by the runtime shared
5450 library package, and the bare <tt>.so</tt> symlink is installed in
5451 the development package since it's only used when linking binaries
5452 or shared libraries. However, there are some exceptions for
5453 unusual shared libraries or for shared libraries that are also
5454 loaded as dynamic modules by other programs.
5458 This section is primarily concerned with how the separation of
5459 shared libraries into multiple packages should be done and how
5460 dependencies on and between shared library binary packages are
5461 managed in Debian. <ref id="libraries"> should be read in
5462 conjunction with this section and contains additional rules for
5463 the files contained in the shared library packages.
5466 <sect id="sharedlibs-runtime">
5467 <heading>Run-time shared libraries</heading>
5470 The run-time shared library must be placed in a package
5471 whose name changes whenever the <tt>SONAME</tt> of the shared
5472 library changes. This allows several versions of the shared
5473 library to be installed at the same time, allowing installation
5474 of the new version of the shared library without immediately
5475 breaking binaries that depend on the old version. Normally, the
5476 run-time shared library and its <tt>SONAME</tt> symlink should
5477 be placed in a package named
5478 <package><var>libraryname</var><var>soversion</var></package>,
5479 where <var>soversion</var> is the version number in
5480 the <tt>SONAME</tt> of the shared library.
5481 See <ref id="shlibs"> for detailed information on how to
5482 determine this version. Alternatively, if it would be confusing
5483 to directly append <var>soversion</var>
5484 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5485 itself ends in a number), you should use
5486 <package><var>libraryname</var>-<var>soversion</var></package>
5491 If you have several shared libraries built from the same source
5492 tree, you may lump them all together into a single shared
5493 library package provided that all of their <tt>SONAME</tt>s will
5494 always change together. Be aware that this is not normally the
5495 case, and if the <tt>SONAME</tt>s do not change together,
5496 upgrading such a merged shared library package will be
5497 unnecessarily difficult because of file conflicts with the old
5498 version of the package. When in doubt, always split shared
5499 library packages so that each binary package installs a single
5504 Every time the shared library ABI changes in a way that may
5505 break binaries linked against older versions of the shared
5506 library, the <tt>SONAME</tt> of the library and the
5507 corresponding name for the binary package containing the runtime
5508 shared library should change. Normally, this means
5509 the <tt>SONAME</tt> should change any time an interface is
5510 removed from the shared library or the signature of an interface
5511 (the number of parameters or the types of parameters that it
5512 takes, for example) is changed. This practice is vital to
5513 allowing clean upgrades from older versions of the package and
5514 clean transitions between the old ABI and new ABI without having
5515 to upgrade every affected package simultaneously.
5519 The <tt>SONAME</tt> and binary package name need not, and indeed
5520 normally should not, change if new interfaces are added but none
5521 are removed or changed, since this will not break binaries
5522 linked against the old shared library. Correct versioning of
5523 dependencies on the newer shared library by binaries that use
5524 the new interfaces is handled via
5525 the <qref id="sharedlibs-symbols"><tt>symbols</tt> system</qref>
5526 or the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5531 The package should install the shared libraries under
5532 their normal names. For example, the <package>libgdbm3</package>
5533 package should install <file>libgdbm.so.3.0.0</file> as
5534 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5535 renamed or re-linked by any <prgn>prerm</prgn> or
5536 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5537 of renaming things safely without affecting running programs,
5538 and attempts to interfere with this are likely to lead to
5543 Shared libraries should not be installed executable, since
5544 the dynamic linker does not require this and trying to
5545 execute a shared library usually results in a core dump.
5549 The run-time library package should include the symbolic link for
5550 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5551 the shared libraries. For example,
5552 the <package>libgdbm3</package> package should include a symbolic
5553 link from <file>/usr/lib/libgdbm.so.3</file> to
5554 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5555 linker (for example <prgn>ld.so</prgn> or
5556 <prgn>ld-linux.so.*</prgn>) can find the library between the
5557 time that <prgn>dpkg</prgn> installs it and the time that
5558 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5560 The package management system requires the library to be
5561 placed before the symbolic link pointing to it in the
5562 <file>.deb</file> file. This is so that when
5563 <prgn>dpkg</prgn> comes to install the symlink
5564 (overwriting the previous symlink pointing at an older
5565 version of the library), the new shared library is already
5566 in place. In the past, this was achieved by creating the
5567 library in the temporary packaging directory before
5568 creating the symlink. Unfortunately, this was not always
5569 effective, since the building of the tar file in the
5570 <file>.deb</file> depended on the behavior of the underlying
5571 file system. Some file systems (such as reiserfs) reorder
5572 the files so that the order of creation is forgotten.
5573 Since version 1.7.0, <prgn>dpkg</prgn>
5574 reorders the files itself as necessary when building a
5575 package. Thus it is no longer important to concern
5576 oneself with the order of file creation.
5580 <sect1 id="ldconfig">
5581 <heading><tt>ldconfig</tt></heading>
5584 Any package installing shared libraries in one of the default
5585 library directories of the dynamic linker (which are currently
5586 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5587 listed in <file>/etc/ld.so.conf</file><footnote>
5588 These are currently <file>/usr/local/lib</file> plus
5589 directories under <file>/lib</file> and <file>/usr/lib</file>
5590 matching the multiarch triplet for the system architecture.
5592 must use <prgn>ldconfig</prgn> to update the shared library
5597 The package maintainer scripts must only call
5598 <prgn>ldconfig</prgn> under these circumstances:
5599 <list compact="compact">
5600 <item>When the <prgn>postinst</prgn> script is run with a
5601 first argument of <tt>configure</tt>, the script must call
5602 <prgn>ldconfig</prgn>, and may optionally invoke
5603 <prgn>ldconfig</prgn> at other times.
5605 <item>When the <prgn>postrm</prgn> script is run with a
5606 first argument of <tt>remove</tt>, the script should call
5607 <prgn>ldconfig</prgn>.
5612 During install or upgrade, the preinst is called before
5613 the new files are unpacked, so calling "ldconfig" is
5614 pointless. The preinst of an existing package can also be
5615 called if an upgrade fails. However, this happens during
5616 the critical time when a shared libs may exist on-disk
5617 under a temporary name. Thus, it is dangerous and
5618 forbidden by current policy to call "ldconfig" at this
5623 When a package is installed or upgraded, "postinst
5624 configure" runs after the new files are safely on-disk.
5625 Since it is perfectly safe to invoke ldconfig
5626 unconditionally in a postinst, it is OK for a package to
5627 simply put ldconfig in its postinst without checking the
5628 argument. The postinst can also be called to recover from
5629 a failed upgrade. This happens before any new files are
5630 unpacked, so there is no reason to call "ldconfig" at this
5635 For a package that is being removed, prerm is
5636 called with all the files intact, so calling ldconfig is
5637 useless. The other calls to "prerm" happen in the case of
5638 upgrade at a time when all the files of the old package
5639 are on-disk, so again calling "ldconfig" is pointless.
5643 postrm, on the other hand, is called with the "remove"
5644 argument just after the files are removed, so this is
5645 the proper time to call "ldconfig" to notify the system
5646 of the fact that the shared libraries from the package
5647 are removed. The postrm can be called at several other
5648 times. At the time of "postrm purge", "postrm
5649 abort-install", or "postrm abort-upgrade", calling
5650 "ldconfig" is useless because the shared lib files are
5651 not on-disk. However, when "postrm" is invoked with
5652 arguments "upgrade", "failed-upgrade", or "disappear", a
5653 shared lib may exist on-disk under a temporary filename.
5661 <sect id="sharedlibs-support-files">
5662 <heading>Shared library support files</heading>
5665 If your package contains files whose names do not change with
5666 each change in the library shared object version, you must not
5667 put them in the shared library package. Otherwise, several
5668 versions of the shared library cannot be installed at the same
5669 time without filename clashes, making upgrades and transitions
5670 unnecessarily difficult.
5674 It is recommended that supporting files and run-time support
5675 programs that do not need to be invoked manually by users, but
5676 are nevertheless required for the package to function, be placed
5677 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5678 preferably under <file>/usr/lib/</file><var>package-name</var>.
5679 If the program or file is architecture independent, the
5680 recommendation is for it to be placed in a subdirectory of
5681 <file>/usr/share</file> instead, preferably under
5682 <file>/usr/share/</file><var>package-name</var>. Following the
5683 <var>package-name</var> naming convention ensures that the file
5684 names change when the shared object version changes.
5688 Run-time support programs that use the shared library but are
5689 not required for the library to function or files used by the
5690 shared library that can be used by any version of the shared
5691 library package should instead be put in a separate package.
5692 This package might typically be named
5693 <package><var>libraryname</var>-tools</package>; note the
5694 absence of the <var>soversion</var> in the package name.
5698 Files and support programs only useful when compiling software
5699 against the library should be included in the development
5700 package for the library.<footnote>
5701 For example, a <file><var>package-name</var>-config</file>
5702 script or <package>pkg-config</package> configuration files.
5707 <sect id="sharedlibs-static">
5708 <heading>Static libraries</heading>
5711 The static library (<file><var>libraryname.a</var></file>)
5712 is usually provided in addition to the shared version.
5713 It is placed into the development package (see below).
5717 In some cases, it is acceptable for a library to be
5718 available in static form only; these cases include:
5720 <item>libraries for languages whose shared library support
5721 is immature or unstable</item>
5722 <item>libraries whose interfaces are in flux or under
5723 development (commonly the case when the library's
5724 major version number is zero, or where the ABI breaks
5725 across patchlevels)</item>
5726 <item>libraries which are explicitly intended to be
5727 available only in static form by their upstream
5732 <sect id="sharedlibs-dev">
5733 <heading>Development files</heading>
5736 If there are development files associated with a shared library,
5737 the source package needs to generate a binary development package
5738 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5739 or if you prefer only to support one development version at a
5740 time, <package><var>libraryname</var>-dev</package>. Installing
5741 the development package must result in installation of all the
5742 development files necessary for compiling programs against that
5743 shared library.<footnote>
5744 This wording allows the development files to be split into
5745 several packages, such as a separate architecture-independent
5746 <package><var>libraryname</var>-headers</package>, provided that
5747 the development package depends on all the required additional
5753 In case several development versions of a library exist, you may
5754 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5755 <ref id="conflicts">) to ensure that the user only installs one
5756 development version at a time (as different development versions are
5757 likely to have the same header files in them, which would cause a
5758 filename clash if both were unpacked).
5762 The development package should contain a symlink for the associated
5763 shared library without a version number. For example, the
5764 <package>libgdbm-dev</package> package should include a symlink
5765 from <file>/usr/lib/libgdbm.so</file> to
5766 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5767 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5768 <file>libgdbm.so</file> when compiling dynamically.
5772 If the package provides Ada Library Information
5773 (<file>*.ali</file>) files for use with GNAT, these files must be
5774 installed read-only (mode 0444) so that GNAT will not attempt to
5775 recompile them. This overrides the normal file mode requirements
5776 given in <ref id="permissions-owners">.
5780 <sect id="sharedlibs-intradeps">
5781 <heading>Dependencies between the packages of the same library</heading>
5784 Typically the development version should have an exact
5785 version dependency on the runtime library, to make sure that
5786 compilation and linking happens correctly. The
5787 <tt>${binary:Version}</tt> substitution variable can be
5788 useful for this purpose.
5790 Previously, <tt>${Source-Version}</tt> was used, but its name
5791 was confusing and it has been deprecated since dpkg 1.13.19.
5796 <sect id="sharedlibs-symbols">
5797 <heading>Dependencies between the library and other packages -
5798 the <tt>symbols</tt> system</heading>
5801 If a package contains a binary or library which links to a
5802 shared library, we must ensure that, when the package is
5803 installed on the system, all of the libraries needed are also
5804 installed. These dependencies must be added to the binary
5805 package when it is built, since they may change based on which
5806 version of a shared library the binary or library was linked
5807 with. To allow these dependencies to be constructed, shared
5808 libraries must provide either a <file>symbols</file> file or
5809 a <file>shlibs</file> file, which provide information on the
5810 package dependencies required to ensure the presence of this
5811 library. Any package which uses a shared library must use these
5812 files to determine the required dependencies when it is built.
5816 <file>shlibs</file> files were the original mechanism for
5817 handling library dependencies. They are documented
5818 in <ref id="sharedlibs-shlibdeps">. <file>symbols</file> files,
5819 documented in this section, are recommended for most packages,
5820 since they provide dependency information for each exported
5821 symbol and therefore generate more accurate dependencies for
5822 binaries that do not use symbols from newer versions of the
5823 shared library. However, <file>shlibs</file> files must be used
5824 for udebs. Packages which provide a <file>symbols</file> file
5825 are not required to provide a <file>shlibs</file> file.
5829 When a package that contains any shared libraries or compiled
5830 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
5831 each shared library and compiled binary to determine the
5832 libraries used and hence the dependencies needed by the
5834 <prgn>dpkg-shlibdeps</prgn> will use a program
5835 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find the
5836 libraries and the symbols in those libraries directly needed
5837 by the binaries or shared libraries in the package.
5842 We say that a binary <tt>foo</tt> <em>directly</em> uses a
5843 library <tt>libbar</tt> if it is explicitly linked with that
5844 library (that is, the library is listed in the
5845 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5846 to the link line when the binary is created). Other libraries
5847 that are needed by <tt>libbar</tt> are
5848 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5849 linker will load them automatically when it
5850 loads <tt>libbar</tt>. A package should depend on the libraries
5851 it directly uses, but not the libraries it indirectly uses. The
5852 dependencies for those libraries will automatically pull in the
5853 other libraries. <prgn>dpkg-shlibdeps</prgn> will handle this
5854 logic automatically, but package maintainers need to be aware of
5855 this distinction between directly and indirectly using a library
5856 if they have to override its results for some reason.
5858 A good example of where this helps is the following. We could
5859 update <tt>libimlib</tt> with a new version that supports a
5860 new graphics format called dgf (but retaining the same major
5861 version number) and depends on <tt>libdgf</tt>. If we
5862 used <prgn>ldd</prgn> to add dependencies for every library
5863 directly or indirectly linked with a binary, every package
5864 that uses <tt>libimlib</tt> would need to be recompiled so it
5865 would also depend on <tt>libdgf</tt> or it wouldn't run due to
5866 missing symbols. Since dependencies are only added based on
5867 ELF <tt>NEEDED</tt> attribute, packages
5868 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5869 having the dependency on <tt>libdgf</tt> and so they would not
5875 In the following sections, we will first describe where the
5876 various <file>symbols</file> files are to be found, then how to
5877 use <prgn>dpkg-shlibdeps</prgn>, and finally
5878 the <file>symbols</file> file format and how to create them if
5879 your package contains a shared library.
5882 <sect1 id="symbols-paths">
5883 <heading>The <file>symbols</file> files present on the
5887 <file>symbols</file> files for a shared library are normally
5888 provided by the shared library package, but there are several
5889 override paths that are checked first in case that information
5890 is wrong or missing. The following list gives them in the
5891 order in which they are read by <prgn>dpkg-shlibdeps</prgn>
5892 The first one that contains the required information is used.
5895 <p><file>debian/*/DEBIAN/symbols</file></p>
5898 During the package build, if the package itself contains
5899 shared libraries with <file>symbols</file> files, they
5900 will be generated in these staging directories
5901 by <prgn>dpkg-gensymbols</prgn>. <file>symbols</file>
5902 files found in the build tree take precedence
5903 over <file>symbols</file> files from other binary
5908 These files must exist
5909 before <prgn>dpkg-shlibdeps</prgn> is run or the
5910 dependencies of binaries and libraries from a source
5911 package on other libraries from that same source package
5912 will not be correct. In practice, this means
5913 that <prgn>dpkg-gensymbols</prgn> must be run
5914 before <prgn>dpkg-shlibdeps</prgn> during the package
5916 An example may clarify. Suppose the source
5917 package <tt>foo</tt> generates two binary
5918 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5919 When building the binary packages, the contents of the
5920 packages are staged in the
5921 directories <file>debian/libfoo2</file>
5922 and <file>debian/foo-runtime</file> respectively.
5923 (<file>debian/tmp</file> could be used instead of one
5924 of these.) Since <tt>libfoo2</tt> provides
5925 the <tt>libfoo</tt> shared library, it will contain
5926 a <tt>symbols</tt> file, which will be installed
5927 in <file>debian/libfoo2/DEBIAN/symbols</file>,
5928 eventually to be included as a control file in that
5929 package. When <prgn>dpkg-shlibdeps</prgn> is run on
5931 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5933 the <file>debian/libfoo2/DEBIAN/symbols</file> file to
5934 determine whether <tt>foo-prog</tt>'s library
5935 dependencies are satisfied by any of the libraries
5936 provided by <tt>libfoo2</tt>. Since those binaries
5937 were linked against the just-built shared library as
5938 part of the build process, the <file>symbols</file>
5939 file for the newly-built <tt>libfoo2</tt> must take
5940 precedence over a <file>symbols</file> file for any
5941 other <tt>libfoo2</tt> package already installed on
5949 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
5950 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
5954 Per-system overrides of shared library dependencies.
5955 These files normally do not exist. They are maintained
5956 by the local system administrator and must not be
5957 created by any Debian package.
5962 <p><file>symbols</file> control files for packages
5963 installed on the system</p>
5966 The <file>symbols</file> control files for all the
5967 packages currently installed on the system are searched
5968 last. This will be the most common source of shared
5969 library dependency information. These are normally
5970 found in <file>/var/lib/dpkg/info/*.symbols</file>, but
5971 packages should not rely on this and instead should
5972 use <tt>dpkg-query --control-path <var>package</var>
5973 symbols</tt> if for some reason these files need to be
5981 Be aware that if a <file>debian/shlibs.local</file> exists in
5982 the source package, it will override any <file>symbols</file>
5983 files. This is the only case where a <file>shlibs</file> is
5984 used despite <file>symbols</file> files being present. See
5985 <ref id="shlibs-paths"> and <ref id="sharedlibs-shlibdeps">
5986 for more information.
5990 <sect1 id="dpkg-shlibdeps">
5991 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5992 <tt>symbols</tt> files</heading>
5995 If your package contains any compiled binaries or shared
5996 libraries, put a call to <prgn>dpkg-shlibdeps</prgn> into
5997 your <file>debian/rules</file> file in the source package.
5998 List all of the compiled binaries, libraries, or loadable
5999 modules in your package.<footnote>
6000 The easiest way to do this is to use a package helper
6001 framework such as <tt>debhelper</tt>. If you are
6002 using <tt>debhelper</tt>, the <prgn>dh_shlibdeps</prgn>
6003 program will do this work for you. It will also correctly
6004 handle multi-binary packages.
6009 This command puts the dependency information into
6010 the <file>debian/substvars</file> file, which is then used
6011 by <prgn>dpkg-gencontrol</prgn>. You will need to place
6012 a <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6013 field in the control file of every binary package built by
6014 this source package that contains compiled binaries,
6015 libraries, or loadable modules. If you have multiple binary
6016 packages, you will need to call <prgn>dpkg-shlibdeps</prgn> on
6017 each one which contains compiled libraries or binaries, using
6018 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6019 specify a different <file>substvars</file> file for each
6020 binary package.<footnote>
6021 Again, <prgn>dh_shlibdeps</prgn>
6022 and <prgn>dh_gencontrol</prgn> will handle all of this for
6023 you if you're using <tt>debhelper</tt>, including generating
6024 separate <file>substvars</file> files for each binary
6025 package and calling <prgn>dpkg-gencontrol</prgn> with the
6031 For more details on <prgn>dpkg-shlibdeps</prgn>,
6032 see <manref name="dpkg-shlibdeps" section="1">.
6036 <sect1 id="symbols">
6037 <heading>The <file>symbols</file> File Format</heading>
6040 The following documents the format of the <file>symbols</file>
6041 control file as included in binary packages. These files are
6042 built from template <file>symbols</file> files in the source
6043 package by <prgn>dpkg-gensymbols</prgn>. The template files
6044 support a richer syntax that
6045 allows <prgn>dpkg-gensymbols</prgn> to do some of the tedious
6046 work involved in maintaining <file>symbols</file> files, such
6047 as handling C++ symbols or optional symbols that may not exist
6048 on particular architectures. When
6049 writing <file>symbols</file> files for a shared library
6050 package, refer to <manref name="dpkg-gensymbols" section="1">
6051 for the richer syntax.
6055 A <file>symbols</file> may contain one or more entries, one
6056 for each shared library contained in the package corresponding
6057 to that <file>symbols</file>. Each entry has the following
6063 <var>library-soname</var> <var>main-dependency-template</var>
6064 [| <var>alternative-dependency-template</var>]
6066 [* <var>field-name</var>: <var>field-value</var>]
6068 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6073 To explain this format, we'll use the the <tt>zlib1g</tt>
6074 package as an example, which (at the time of writing) installs
6075 the shared library <file>/usr/lib/libz.so.1.2.3.4</file>.
6076 Mandatory lines will be described first, followed by optional
6081 <var>library-soname</var> must contain exactly the value of
6082 the ELF <tt>SONAME</tt> attribute of the shared library. In
6083 our example, this is <tt>libz.so.1</tt>.<footnote>
6084 This can be determined by using the command
6085 <example compact="compact">
6086 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6092 <var>main-dependency-template</var> has the same syntax as a
6093 dependency field in a binary package control file, except that
6094 the string <tt>#MINVER#</tt> is replaced by a version
6095 restriction like <tt>(>= <var>version</var>)</tt> or by
6096 nothing if an unversioned dependency is deemed sufficient.
6097 The version restriction will be based on which symbols from
6098 the shared library are referenced and the version at which
6099 they were introduced (see below). In nearly all
6100 cases, <var>main-dependency-template</var> will
6101 be <tt><var>package</var> #MINVER#</tt>,
6102 where <var>package</var> is the name of the binary package
6103 containing the shared library. This adds a simple,
6104 possibly-versioned dependency on the shared library package.
6105 In some rare cases, such as when multiple packages provide the
6106 same shared library ABI, the dependency template may need to
6111 In our example, the first line of
6112 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6113 <example compact="compact">
6114 libz.so.1 zlib1g #MINVER#
6119 Each public symbol exported by the shared library must have a
6120 corresponding symbol line, indented by one
6121 space. <var>symbol</var> is the exported symbol (which, for
6122 C++, means the mangled symbol) followed by <tt>@</tt> and the
6123 symbol version, or the string <tt>Base</tt> if there is no
6124 symbol version. <var>minimal-version</var> is the most recent
6125 version of the shared library that changed the behavior of
6126 that symbol, whether by adding it, changing its function
6127 signature (the parameters, their types, or the return type),
6128 or its behavior in a way that is visible to a
6129 caller. <var>id-of-dependency-template</var> is an optional
6130 field that references
6131 an <var>alternative-dependency-template</var>; see below for a
6136 For example, <tt>libz.so.1</tt> contains the
6137 symbols <tt>compress</tt>
6138 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6139 version and last changed its behavior in upstream
6140 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6141 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in upstream
6142 version <tt>1:1.2.0</tt>, and has not changed its behavior.
6143 Its <file>symbols</file> file therefore contains the lines:
6144 <example compact="compact">
6145 compress@Base 1:1.1.4
6146 compressBound@ZLIB_1.2.0 1:1.2.0
6148 Packages using only <tt>compress</tt> would then get a
6149 dependency of <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6150 using <tt>compressBound</tt> would get a dependency
6151 of <tt>zlib1g (>= 1:1.2.0)</tt>.
6155 One or more <var>alternative-dependency-template</var> lines
6156 may be provided. These are used in cases where some symbols
6157 in the shared library should use one dependency template while
6158 others should use a different template. The alternative
6159 dependency templates are used only if a symbol line contains
6160 the <var>id-of-dependency-template</var> field. The first
6161 alternative dependency template is numbered 1, the second 2,
6162 and so forth.<footnote>
6163 An example of where this may be needed is with a library
6164 that implements the libGL interface. All GL implementations
6165 provide the same set of base interfaces, and then may
6166 provide some additional interfaces only used by programs
6167 that require that specific GL implementation. So, for
6168 example, libgl1-mesa-glx may use the
6169 following <file>symbols</file> file:
6172 | libgl1-mesa-glx #MINVER#
6173 publicGlSymbol@Base 6.3-1
6175 implementationSpecificSymbol@Base 6.5.2-7 1
6178 Binaries or shared libraries using
6179 only <tt>publicGlSymbol</tt> would depend only
6180 on <tt>libgl1</tt> (which may be provided by multiple
6182 using <tt>implementationSpecificSymbol</tt> would get a
6183 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6188 Finally, the entry for the library may contain one or more
6189 metadata fields. Currently, the only
6190 supported <var>field-name</var>
6191 is <tt>Build-Depends-Package</tt>, whose value lists
6192 the <qref id="sharedlibs-dev">library development
6193 package</qref> on which packages using this shared library
6194 declare a build dependency. If this field is
6195 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6196 the resulting binary package dependency on the shared library
6197 is at least as strict as the source package dependency on the
6198 shared library development package.<footnote>
6199 This field should normally not be necessary, since if the
6200 behavior of any symbol has changed, the corresponding
6201 symbol <var>minimal-version</var> should have been
6202 increased. But including it makes the <tt>symbols</tt>
6203 system more robust by tightening the dependency in cases
6204 where the package using the shared library specifically
6205 requires at least a particular version of the shared library
6206 development package for some reason.
6208 For our example, the <tt>zlib1g</tt> <file>symbols</file> file
6210 <example compact="compact">
6211 * Build-Depends-Package: zlib1g-dev
6216 Also see <manref name="deb-symbols" section="5">.
6220 <sect1 id="providing-symbols">
6221 <heading>Providing a <file>symbols</file> file</heading>
6224 If your package provides a shared library, you should arrange
6225 to include a <file>symbols</file> control file following the
6226 format described above in that package. You must include
6227 either a <file>symbols</file> control file or
6228 a <file>shlibs</file> control file.
6232 Normally, this is done by creating a <file>symbols</file> in
6234 named <file>debian/<var>package</var>.symbols</file>
6235 or <file>debian/symbols</file>, possibly
6236 with <file>.<var>arch</var></file> appended if the symbols
6237 information varies by architecture. This file may use the
6238 extended syntax documented
6239 in <manref name="dpkg-gensymbols" section="1">. Then,
6240 call <prgn>dpkg-gensymbols</prgn> as part of the package build
6241 process. It will create <file>symbols</file> files in the
6242 package staging area based on the binaries and libraries in
6243 the package staging area and the <file>symbols</file> files in
6244 the source package.<footnote>
6246 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6247 take care of calling either <prgn>dpkg-gensymbols</prgn>
6248 or generating a <file>shlibs</file> file as appropriate.
6253 Packages that provide <file>symbols</file> files must keep
6254 them up-to-date to ensure correct dependencies in packages
6255 that use the shared libraries. This means updating
6256 the <file>symbols</file> file whenever a new public symbol is
6257 added, changing the <var>minimal-version</var> field whenever
6258 a symbol changes behavior or signature, and changing
6259 the <var>library-soname</var>
6260 and <var>main-dependency-template</var>, and probably all of
6261 the <var>minimal-version</var> fields, when the library
6262 changes <tt>SONAME</tt>. Removing a public symbol from
6263 the <file>symbols</file> file because it's no longer provided
6264 by the library normally requires changing the <tt>SONAME</tt>
6265 of the library. See <ref id="sharedlibs-runtime">.
6269 Special care should be taken in updating
6270 the <var>minimal-version</var> field when the behavior of a
6271 public symbol changes. This is easy to neglect, since there
6272 is no automated method of determining such changes, but
6273 failing to update <var>minimal-version</var> in this case may
6274 result in binary packages with too-weak dependencies that will
6275 fail at runtime, possibly in ways that can cause security
6276 vulnerabilities. If the package maintainer believes that a
6277 symbol behavior change may have occurred but isn't sure, it's
6278 safer to update the <var>minimal-version</var> of all possibly
6279 affected symbols to the current upstream version rather than
6280 leave them unmodified. This may result in unnecessarily
6281 strict dependencies, but it ensures that packages whose
6282 dependencies are satisfied will work properly.
6286 A common example of when a change
6287 to <var>minimal-version</var> is required is a function that
6288 takes an enum or struct argument that controls what the
6289 function does. For example:
6291 enum library_op { OP_FOO, OP_BAR };
6292 int library_do_operation(enum library_op);
6294 If a new operation, <tt>OP_BAZ</tt>, is added,
6295 the <var>minimal-version</var>
6296 of <tt>library_do_operation</tt> must be increased to the
6297 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6298 binary built against the new version of the library (having
6299 detected at compile-time that the library
6300 supports <tt>OP_BAZ</tt>) may be installed with a shared
6301 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6302 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6307 The <var>minimal-version</var> field normally should not
6308 contain the Debian revision of the package, since the library
6309 behavior is normally fixed for a particular upstream version
6310 and any Debian packaging of that upstream version will have
6311 the same behavior. In the rare case that the library behavior
6312 was changed in a particular Debian revision,
6313 appending <tt>~</tt> to the end of
6314 the <var>minimal-version</var> that includes the Debian
6315 revision is recommended, since this allows backports of the
6316 shared library package using the normal backport versioning
6317 convention to satisfy the dependency.
6322 <sect id="sharedlibs-shlibdeps">
6323 <heading>Dependencies between the library and other packages -
6324 the <tt>shlibs</tt> system</heading>
6327 The <tt>shlibs</tt> system is an alternative to
6328 the <tt>symbols</tt> system for declaring dependencies for
6329 shared libraries. It predated the <tt>symbols</tt> system and
6330 is therefore frequently seen in older packages. It is also
6331 required for udebs, which do not support <tt>symbols</tt>.
6335 <file>shlibs</file> files do not provide as detailed of
6336 information as <file>symbols</file> files. They only provide
6337 information about the library as a whole, not individual
6338 symbols, and therefore have to force tighter dependencies since
6339 they have no way of relaxing dependencies for binaries and
6340 libraries that only use symbols whose behavior has not changed.
6341 Because of this, and because of some problems with
6342 how <file>shlibs</file> files represent the
6343 library <tt>SONAME</tt>, <file>symbols</file> files are
6344 recommended instead for any shared library package that isn't a
6349 In the following sections, we will first describe where the
6350 various <file>shlibs</file> files are to be found, then how to
6351 use <prgn>dpkg-shlibdeps</prgn>, and finally
6352 the <file>shlibs</file> file format and how to create them if
6353 your package contains a shared library. Much of the information
6354 about <file>shlibs</file> files is the same as
6355 for <file>symbols</file> files, so only the differences will be
6359 <sect1 id="shlibs-paths">
6360 <heading>The <file>shlibs</file> files present on the
6364 There are several places where <tt>shlibs</tt> files are
6365 found. The following list gives them in the order in which
6366 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first one
6367 which gives the required information is used.)
6370 <p><file>debian/shlibs.local</file></p>
6373 This lists overrides for this package. This file should
6374 normally not be used, but may be needed temporarily in
6375 unusual situations to work around bugs in other
6376 packages, or in unusual cases where the normally
6377 declared dependency information in the
6378 installed <file>shlibs</file> file for a library cannot
6379 be used. This file overrides information obtained from
6385 <p><file>/etc/dpkg/shlibs.override</file></p>
6388 This lists global overrides. This list is normally
6389 empty. It is maintained by the local system
6395 <p><file>DEBIAN/shlibs</file> files in the "build
6399 These files are generated as part of the package build
6400 process and staged for inclusion as control files in the
6401 binary packages being built. They provide details of
6402 any shared libraries included in the same package.
6407 <p><file>shlibs</file> control files for packages
6408 installed on the system</p>
6411 The <file>shlibs</file> control files for all the
6412 packages currently installed on the system. These are
6414 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6415 packages should not rely on this and instead should
6416 use <tt>dpkg-query --control-path <var>package</var>
6417 shlibs</tt> if for some reason these files need to be
6423 <p><file>/etc/dpkg/shlibs.default</file></p>
6426 This file lists any shared libraries whose packages have
6427 failed to provide correct <file>shlibs</file> files. It
6428 was used when the <file>shlibs</file> setup was first
6429 introduced, but it is now normally empty. It is
6430 maintained by the <tt>dpkg</tt> maintainer.
6437 If a <file>symbols</file> file for a shared library package
6438 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6439 in preference to a <file>shlibs</file>, with the exception
6440 of <file>debian/shlibs.local</file>. The latter overrides any
6441 other <file>shlibs</file> or <file>symbols</file> files.
6446 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
6447 <file>shlibs</file> files</heading>
6450 Use of <prgn>dpkg-shlibdeps</prgn> with <file>shlibs</file>
6451 files is generally the same as with <file>symbols</file>
6452 files. See <ref id="dpkg-shlibdeps">.
6456 If you are creating a udeb for use in the Debian Installer,
6457 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6458 should use the dependency line of type <tt>udeb</tt> by
6459 adding the <tt>-tudeb</tt> option<footnote>
6460 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6461 will automatically add this option if it knows it is
6463 </footnote>. If there is no dependency line of
6464 type <tt>udeb</tt> in the <file>shlibs</file>
6465 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6466 regular dependency line.
6471 <heading>The <file>shlibs</file> File Format</heading>
6474 Each <file>shlibs</file> file has the same format. Lines
6475 beginning with <tt>#</tt> are considered to be comments and
6476 are ignored. Each line is of the form:
6477 <example compact="compact">
6478 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6483 We will explain this by reference to the example of the
6484 <tt>zlib1g</tt> package, which (at the time of writing)
6486 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6490 <var>type</var> is an optional element that indicates the type
6491 of package for which the line is valid. The only type
6492 currently in use is <tt>udeb</tt>. The colon and space after
6493 the type are required.
6497 <var>library-name</var> is the name of the shared library, in
6498 this case <tt>libz</tt>. (This must match the name part of
6499 the soname, see below.)
6503 <var>soname-version</var> is the version part of the
6504 ELF <tt>SONAME</tt> attribute of the library.
6505 The <tt>SONAME</tt> is the thing that must exactly match for
6506 the library to be recognized by the dynamic linker, and is
6508 form <tt><var>name</var>.so.<var>major-version</var></tt>, in
6509 our example, <tt>libz.so.1</tt>.
6510 The version part is the part which comes after
6511 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname
6512 may instead be of the
6513 form <tt><var>name</var>-<var>major-version</var>.so</tt>,
6514 such as <tt>libdb-5.1.so</tt>, in which case the name would
6515 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
6519 <var>dependencies</var> has the same syntax as a dependency
6520 field in a binary package control file. It should give
6521 details of which packages are required to satisfy a binary
6522 built against the version of the library contained in the
6523 package. See <ref id="depsyntax"> for details.
6527 In our example, if the last change to the <tt>zlib1g</tt>
6528 package that could change behavior for a client of that
6529 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6530 the <tt>shlibs</tt> entry for this library could say:
6531 <example compact="compact">
6532 libz 1 zlib1g (>= 1:1.2.3.3.dfsg-1)
6534 This version restriction must be new enough that any binary
6535 built against the current version of the library will work
6536 with any version of the shared library that satisfies that
6541 As zlib1g also provides a udeb containing the shared library,
6542 there would also be a second line:
6543 <example compact="compact">
6544 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg-1)
6550 <heading>Providing a <file>shlibs</file> file</heading>
6553 To provide a <file>shlibs</file> file for a shared library
6554 binary package, create a <file>shlibs</file> file following
6555 the format described above and place it in
6556 the <file>DEBIAN</file> directory for that package during the
6557 build. It will then be included as a control file for that
6559 This is what <prgn>dh_makeshlibs</prgn> in
6560 the <package>debhelper</package> suite does. If your package
6561 also has a udeb that provides a shared
6562 library, <prgn>dh_makeshlibs</prgn> can automatically
6563 generate the <tt>udeb:</tt> lines if you specify the name of
6564 the udeb with the <tt>--add-udeb</tt> option.
6569 Since <prgn>dpkg-shlibdeps</prgn> reads
6570 the <file>DEBIAN/shlibs</file> files in all of the binary
6571 packages being built from this source package, all of
6572 the <file>DEBIAN/shlibs</file> files should be installed
6573 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6581 <chapt id="opersys"><heading>The Operating System</heading>
6584 <heading>File system hierarchy</heading>
6588 <heading>File System Structure</heading>
6591 The location of all installed files and directories must
6592 comply with the Filesystem Hierarchy Standard (FHS),
6593 version 2.3, with the exceptions noted below, and except
6594 where doing so would violate other terms of Debian
6595 Policy. The following exceptions to the FHS apply:
6600 The optional rules related to user specific
6601 configuration files for applications are stored in
6602 the user's home directory are relaxed. It is
6603 recommended that such files start with the
6604 '<tt>.</tt>' character (a "dot file"), and if an
6605 application needs to create more than one dot file
6606 then the preferred placement is in a subdirectory
6607 with a name starting with a '.' character, (a "dot
6608 directory"). In this case it is recommended the
6609 configuration files not start with the '.'
6615 The requirement for amd64 to use <file>/lib64</file>
6616 for 64 bit binaries is removed.
6621 The requirement for object files, internal binaries, and
6622 libraries, including <file>libc.so.*</file>, to be located
6623 directly under <file>/lib{,32}</file> and
6624 <file>/usr/lib{,32}</file> is amended, permitting files
6625 to instead be installed to
6626 <file>/lib/<var>triplet</var></file> and
6627 <file>/usr/lib/<var>triplet</var></file>, where
6628 <tt><var>triplet</var></tt> is the value returned by
6629 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6630 architecture of the package. Packages may <em>not</em>
6631 install files to any <var>triplet</var> path other
6632 than the one matching the architecture of that package;
6633 for instance, an <tt>Architecture: amd64</tt> package
6634 containing 32-bit x86 libraries may not install these
6635 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6637 This is necessary in order to reserve the directories for
6638 use in cross-installation of library packages from other
6639 architectures, as part of the planned deployment of
6644 Applications may also use a single subdirectory under
6645 <file>/usr/lib/<var>triplet</var></file>.
6648 The execution time linker/loader, ld*, must still be made
6649 available in the existing location under /lib or /lib64
6650 since this is part of the ELF ABI for the architecture.
6655 The requirement that
6656 <file>/usr/local/share/man</file> be "synonymous"
6657 with <file>/usr/local/man</file> is relaxed to a
6662 The requirement that windowmanagers with a single
6663 configuration file call it <file>system.*wmrc</file>
6664 is removed, as is the restriction that the window
6665 manager subdirectory be named identically to the
6666 window manager name itself.
6671 The requirement that boot manager configuration
6672 files live in <file>/etc</file>, or at least are
6673 symlinked there, is relaxed to a recommendation.
6678 The additional directory <file>/run</file> in the root
6679 file system is allowed. <file>/run</file>
6680 replaces <file>/var/run</file>, and the
6681 subdirectory <file>/run/lock</file>
6682 replaces <file>/var/lock</file>, with
6683 the <file>/var</file> directories replaced by symlinks
6684 for backwards compatibility. <file>/run</file>
6685 and <file>/run/lock</file> must follow all of the
6686 requirements in the FHS for <file>/var/run</file>
6687 and <file>/var/lock</file>, respectively, such as file
6688 naming conventions, file format requirements, or the
6689 requirement that files be cleared during the boot
6690 process. Files and directories residing
6691 in <file>/run</file> should be stored on a temporary
6697 The following directories in the root filesystem are
6698 additionally allowed: <file>/sys</file> and
6699 <file>/selinux</file>. <footnote>These directories
6700 are used as mount points to mount virtual filesystems
6701 to get access to kernel information.</footnote>
6706 On GNU/Hurd systems, the following additional
6707 directories are allowed in the root
6708 filesystem: <file>/hurd</file>
6709 and <file>/servers</file>.<footnote>
6710 These directories are used to store translators and as
6711 a set of standard names for mount points,
6720 The version of this document referred here can be
6721 found in the <tt>debian-policy</tt> package or on <url
6722 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6723 name="FHS (Debian copy)"> alongside this manual (or, if
6724 you have the <package>debian-policy</package> installed,
6726 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6727 (local copy)">). The
6728 latest version, which may be a more recent version, may
6730 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6731 Specific questions about following the standard may be
6732 asked on the <tt>debian-devel</tt> mailing list, or
6733 referred to the FHS mailing list (see the
6734 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6740 <heading>Site-specific programs</heading>
6743 As mandated by the FHS, packages must not place any
6744 files in <file>/usr/local</file>, either by putting them in
6745 the file system archive to be unpacked by <prgn>dpkg</prgn>
6746 or by manipulating them in their maintainer scripts.
6750 However, the package may create empty directories below
6751 <file>/usr/local</file> so that the system administrator knows
6752 where to place site-specific files. These are not
6753 directories <em>in</em> <file>/usr/local</file>, but are
6754 children of directories in <file>/usr/local</file>. These
6755 directories (<file>/usr/local/*/dir/</file>)
6756 should be removed on package removal if they are
6761 Note that this applies only to
6762 directories <em>below</em> <file>/usr/local</file>,
6763 not <em>in</em> <file>/usr/local</file>. Packages must
6764 not create sub-directories in the
6765 directory <file>/usr/local</file> itself, except those
6766 listed in FHS, section 4.5. However, you may create
6767 directories below them as you wish. You must not remove
6768 any of the directories listed in 4.5, even if you created
6773 Since <file>/usr/local</file> can be mounted read-only from a
6774 remote server, these directories must be created and
6775 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6776 maintainer scripts and not be included in the
6777 <file>.deb</file> archive. These scripts must not fail if
6778 either of these operations fail.
6782 For example, the <tt>emacsen-common</tt> package could
6783 contain something like
6784 <example compact="compact">
6785 if [ ! -e /usr/local/share/emacs ]; then
6786 if mkdir /usr/local/share/emacs 2>/dev/null; then
6787 if chown root:staff /usr/local/share/emacs; then
6788 chmod 2775 /usr/local/share/emacs || true
6793 in its <prgn>postinst</prgn> script, and
6794 <example compact="compact">
6795 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6796 rmdir /usr/local/share/emacs 2>/dev/null || true
6798 in the <prgn>prerm</prgn> script. (Note that this form is
6799 used to ensure that if the script is interrupted, the
6800 directory <file>/usr/local/share/emacs</file> will still be
6805 If you do create a directory in <file>/usr/local</file> for
6806 local additions to a package, you should ensure that
6807 settings in <file>/usr/local</file> take precedence over the
6808 equivalents in <file>/usr</file>.
6812 However, because <file>/usr/local</file> and its contents are
6813 for exclusive use of the local administrator, a package
6814 must not rely on the presence or absence of files or
6815 directories in <file>/usr/local</file> for normal operation.
6819 The <file>/usr/local</file> directory itself and all the
6820 subdirectories created by the package should (by default) have
6821 permissions 2775 (group-writable and set-group-id) and be
6822 owned by <tt>root:staff</tt>.
6827 <heading>The system-wide mail directory</heading>
6829 The system-wide mail directory
6830 is <file>/var/mail</file>. This directory is part of the
6831 base system and should not be owned by any particular mail
6832 agents. The use of the old
6833 location <file>/var/spool/mail</file> is deprecated, even
6834 though the spool may still be physically located there.
6838 <sect1 id="fhs-run">
6839 <heading><file>/run</file> and <file>/run/lock</file></heading>
6842 The directory <file>/run</file> is cleared at boot, normally
6843 by being a mount point for a temporary file system. Packages
6844 therefore must not assume that any files or directories
6845 under <file>/run</file> other than <file>/run/lock</file>
6846 exist unless the package has arranged to create those files or
6847 directories since the last reboot. Normally, this is done by
6848 the package via an init script. See <ref id="writing-init">
6849 for more information.
6853 Packages must not include files or directories
6854 under <file>/run</file>, or under the
6855 older <file>/var/run</file> and <file>/var/lock<file> paths.
6856 The latter paths will normally be symlinks or other
6857 redirections to <file>/run</file> for backwards compatibility.
6863 <heading>Users and groups</heading>
6866 <heading>Introduction</heading>
6868 The Debian system can be configured to use either plain or
6873 Some user ids (UIDs) and group ids (GIDs) are reserved
6874 globally for use by certain packages. Because some
6875 packages need to include files which are owned by these
6876 users or groups, or need the ids compiled into binaries,
6877 these ids must be used on any Debian system only for the
6878 purpose for which they are allocated. This is a serious
6879 restriction, and we should avoid getting in the way of
6880 local administration policies. In particular, many sites
6881 allocate users and/or local system groups starting at 100.
6885 Apart from this we should have dynamically allocated ids,
6886 which should by default be arranged in some sensible
6887 order, but the behavior should be configurable.
6891 Packages other than <tt>base-passwd</tt> must not modify
6892 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6893 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6898 <heading>UID and GID classes</heading>
6900 The UID and GID numbers are divided into classes as
6906 Globally allocated by the Debian project, the same
6907 on every Debian system. These ids will appear in
6908 the <file>passwd</file> and <file>group</file> files of all
6909 Debian systems, new ids in this range being added
6910 automatically as the <tt>base-passwd</tt> package is
6915 Packages which need a single statically allocated
6916 uid or gid should use one of these; their
6917 maintainers should ask the <tt>base-passwd</tt>
6925 Dynamically allocated system users and groups.
6926 Packages which need a user or group, but can have
6927 this user or group allocated dynamically and
6928 differently on each system, should use <tt>adduser
6929 --system</tt> to create the group and/or user.
6930 <prgn>adduser</prgn> will check for the existence of
6931 the user or group, and if necessary choose an unused
6932 id based on the ranges specified in
6933 <file>adduser.conf</file>.
6937 <tag>1000-59999:</tag>
6940 Dynamically allocated user accounts. By default
6941 <prgn>adduser</prgn> will choose UIDs and GIDs for
6942 user accounts in this range, though
6943 <file>adduser.conf</file> may be used to modify this
6948 <tag>60000-64999:</tag>
6951 Globally allocated by the Debian project, but only
6952 created on demand. The ids are allocated centrally
6953 and statically, but the actual accounts are only
6954 created on users' systems on demand.
6958 These ids are for packages which are obscure or
6959 which require many statically-allocated ids. These
6960 packages should check for and create the accounts in
6961 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6962 <prgn>adduser</prgn> if it has this facility) if
6963 necessary. Packages which are likely to require
6964 further allocations should have a "hole" left after
6965 them in the allocation, to give them room to
6970 <tag>65000-65533:</tag>
6978 User <tt>nobody</tt>. The corresponding gid refers
6979 to the group <tt>nogroup</tt>.
6986 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6987 not</em> be used, because it is the error return
6996 <sect id="sysvinit">
6997 <heading>System run levels and <file>init.d</file> scripts</heading>
6999 <sect1 id="/etc/init.d">
7000 <heading>Introduction</heading>
7003 The <file>/etc/init.d</file> directory contains the scripts
7004 executed by <prgn>init</prgn> at boot time and when the
7005 init state (or "runlevel") is changed (see <manref
7006 name="init" section="8">).
7010 There are at least two different, yet functionally
7011 equivalent, ways of handling these scripts. For the sake
7012 of simplicity, this document describes only the symbolic
7013 link method. However, it must not be assumed by maintainer
7014 scripts that this method is being used, and any automated
7015 manipulation of the various runlevel behaviors by
7016 maintainer scripts must be performed using
7017 <prgn>update-rc.d</prgn> as described below and not by
7018 manually installing or removing symlinks. For information
7019 on the implementation details of the other method,
7020 implemented in the <tt>file-rc</tt> package, please refer
7021 to the documentation of that package.
7025 These scripts are referenced by symbolic links in the
7026 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7027 runlevels, <prgn>init</prgn> looks in the directory
7028 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7029 execute, where <tt><var>n</var></tt> is the runlevel that
7030 is being changed to, or <tt>S</tt> for the boot-up
7035 The names of the links all have the form
7036 <file>S<var>mm</var><var>script</var></file> or
7037 <file>K<var>mm</var><var>script</var></file> where
7038 <var>mm</var> is a two-digit number and <var>script</var>
7039 is the name of the script (this should be the same as the
7040 name of the actual script in <file>/etc/init.d</file>).
7044 When <prgn>init</prgn> changes runlevel first the targets
7045 of the links whose names start with a <tt>K</tt> are
7046 executed, each with the single argument <tt>stop</tt>,
7047 followed by the scripts prefixed with an <tt>S</tt>, each
7048 with the single argument <tt>start</tt>. (The links are
7049 those in the <file>/etc/rc<var>n</var>.d</file> directory
7050 corresponding to the new runlevel.) The <tt>K</tt> links
7051 are responsible for killing services and the <tt>S</tt>
7052 link for starting services upon entering the runlevel.
7056 For example, if we are changing from runlevel 2 to
7057 runlevel 3, init will first execute all of the <tt>K</tt>
7058 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7059 all of the <tt>S</tt> prefixed scripts in that directory.
7060 The links starting with <tt>K</tt> will cause the
7061 referred-to file to be executed with an argument of
7062 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7067 The two-digit number <var>mm</var> is used to determine
7068 the order in which to run the scripts: low-numbered links
7069 have their scripts run first. For example, the
7070 <tt>K20</tt> scripts will be executed before the
7071 <tt>K30</tt> scripts. This is used when a certain service
7072 must be started before another. For example, the name
7073 server <prgn>bind</prgn> might need to be started before
7074 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7075 can set up its access lists. In this case, the script
7076 that starts <prgn>bind</prgn> would have a lower number
7077 than the script that starts <prgn>inn</prgn> so that it
7079 <example compact="compact">
7086 The two runlevels 0 (halt) and 6 (reboot) are slightly
7087 different. In these runlevels, the links with an
7088 <tt>S</tt> prefix are still called after those with a
7089 <tt>K</tt> prefix, but they too are called with the single
7090 argument <tt>stop</tt>.
7094 <sect1 id="writing-init">
7095 <heading>Writing the scripts</heading>
7098 Packages that include daemons for system services should
7099 place scripts in <file>/etc/init.d</file> to start or stop
7100 services at boot time or during a change of runlevel.
7101 These scripts should be named
7102 <file>/etc/init.d/<var>package</var></file>, and they should
7103 accept one argument, saying what to do:
7106 <tag><tt>start</tt></tag>
7107 <item>start the service,</item>
7109 <tag><tt>stop</tt></tag>
7110 <item>stop the service,</item>
7112 <tag><tt>restart</tt></tag>
7113 <item>stop and restart the service if it's already running,
7114 otherwise start the service</item>
7116 <tag><tt>reload</tt></tag>
7117 <item><p>cause the configuration of the service to be
7118 reloaded without actually stopping and restarting
7121 <tag><tt>force-reload</tt></tag>
7122 <item>cause the configuration to be reloaded if the
7123 service supports this, otherwise restart the
7127 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7128 <tt>force-reload</tt> options should be supported by all
7129 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7134 The <file>init.d</file> scripts must ensure that they will
7135 behave sensibly (i.e., returning success and not starting
7136 multiple copies of a service) if invoked with <tt>start</tt>
7137 when the service is already running, or with <tt>stop</tt>
7138 when it isn't, and that they don't kill unfortunately-named
7139 user processes. The best way to achieve this is usually to
7140 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7145 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7146 scripts. Writing correct <file>init.d</file> scripts requires
7147 accepting various error exit statuses when daemons are already
7148 running or already stopped without aborting
7149 the <file>init.d</file> script, and common <file>init.d</file>
7150 function libraries are not safe to call with <tt>set -e</tt>
7152 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7153 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7154 in effect and echoing status messages to the console fails,
7156 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7157 to not use <tt>set -e</tt> and instead check the result of
7158 each command separately.
7162 If a service reloads its configuration automatically (as
7163 in the case of <prgn>cron</prgn>, for example), the
7164 <tt>reload</tt> option of the <file>init.d</file> script
7165 should behave as if the configuration has been reloaded
7170 The <file>/etc/init.d</file> scripts must be treated as
7171 configuration files, either (if they are present in the
7172 package, that is, in the .deb file) by marking them as
7173 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7174 by managing them correctly in the maintainer scripts (see
7175 <ref id="config-files">). This is important since we want
7176 to give the local system administrator the chance to adapt
7177 the scripts to the local system, e.g., to disable a
7178 service without de-installing the package, or to specify
7179 some special command line options when starting a service,
7180 while making sure their changes aren't lost during the next
7185 These scripts should not fail obscurely when the
7186 configuration files remain but the package has been
7187 removed, as configuration files remain on the system after
7188 the package has been removed. Only when <prgn>dpkg</prgn>
7189 is executed with the <tt>--purge</tt> option will
7190 configuration files be removed. In particular, as the
7191 <file>/etc/init.d/<var>package</var></file> script itself is
7192 usually a <tt>conffile</tt>, it will remain on the system
7193 if the package is removed but not purged. Therefore, you
7194 should include a <tt>test</tt> statement at the top of the
7196 <example compact="compact">
7197 test -f <var>program-executed-later-in-script</var> || exit 0
7202 Often there are some variables in the <file>init.d</file>
7203 scripts whose values control the behavior of the scripts,
7204 and which a system administrator is likely to want to
7205 change. As the scripts themselves are frequently
7206 <tt>conffile</tt>s, modifying them requires that the
7207 administrator merge in their changes each time the package
7208 is upgraded and the <tt>conffile</tt> changes. To ease
7209 the burden on the system administrator, such configurable
7210 values should not be placed directly in the script.
7211 Instead, they should be placed in a file in
7212 <file>/etc/default</file>, which typically will have the same
7213 base name as the <file>init.d</file> script. This extra file
7214 should be sourced by the script when the script runs. It
7215 must contain only variable settings and comments in SUSv3
7216 <prgn>sh</prgn> format. It may either be a
7217 <tt>conffile</tt> or a configuration file maintained by
7218 the package maintainer scripts. See <ref id="config-files">
7223 To ensure that vital configurable values are always
7224 available, the <file>init.d</file> script should set default
7225 values for each of the shell variables it uses, either
7226 before sourcing the <file>/etc/default/</file> file or
7227 afterwards using something like the <tt>:
7228 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7229 script must behave sensibly and not fail if the
7230 <file>/etc/default</file> file is deleted.
7234 Files and directories under <file>/run</file>, including ones
7235 referred to via the compatibility paths <file>/var/run</file>
7236 and <file>/var/lock</file>, are normally stored on a temporary
7237 filesystem and are normally not persistent across a reboot.
7238 The <file>init.d</file> scripts must handle this correctly.
7239 This will typically mean creating any required subdirectories
7240 dynamically when the <file>init.d</file> script is run.
7241 See <ref id="fhs-run"> for more information.
7246 <heading>Interfacing with the initscript system</heading>
7249 Maintainers should use the abstraction layer provided by
7250 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7251 programs to deal with initscripts in their packages'
7252 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7253 and <prgn>postrm</prgn>.
7257 Directly managing the /etc/rc?.d links and directly
7258 invoking the <file>/etc/init.d/</file> initscripts should
7259 be done only by packages providing the initscript
7260 subsystem (such as <prgn>sysv-rc</prgn> and
7261 <prgn>file-rc</prgn>).
7265 <heading>Managing the links</heading>
7268 The program <prgn>update-rc.d</prgn> is provided for
7269 package maintainers to arrange for the proper creation and
7270 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7271 or their functional equivalent if another method is being
7272 used. This may be used by maintainers in their packages'
7273 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7277 You must not include any <file>/etc/rc<var>n</var>.d</file>
7278 symbolic links in the actual archive or manually create or
7279 remove the symbolic links in maintainer scripts; you must
7280 use the <prgn>update-rc.d</prgn> program instead. (The
7281 former will fail if an alternative method of maintaining
7282 runlevel information is being used.) You must not include
7283 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7284 in the archive either. (Only the <tt>sysvinit</tt>
7289 By default <prgn>update-rc.d</prgn> will start services in
7290 each of the multi-user state runlevels (2, 3, 4, and 5)
7291 and stop them in the halt runlevel (0), the single-user
7292 runlevel (1) and the reboot runlevel (6). The system
7293 administrator will have the opportunity to customize
7294 runlevels by simply adding, moving, or removing the
7295 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7296 symbolic links are being used, or by modifying
7297 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7302 To get the default behavior for your package, put in your
7303 <prgn>postinst</prgn> script
7304 <example compact="compact">
7305 update-rc.d <var>package</var> defaults
7307 and in your <prgn>postrm</prgn>
7308 <example compact="compact">
7309 if [ "$1" = purge ]; then
7310 update-rc.d <var>package</var> remove
7312 </example>. Note that if your package changes runlevels
7313 or priority, you may have to remove and recreate the links,
7314 since otherwise the old links may persist. Refer to the
7315 documentation of <prgn>update-rc.d</prgn>.
7319 This will use a default sequence number of 20. If it does
7320 not matter when or in which order the <file>init.d</file>
7321 script is run, use this default. If it does, then you
7322 should talk to the maintainer of the <prgn>sysvinit</prgn>
7323 package or post to <tt>debian-devel</tt>, and they will
7324 help you choose a number.
7328 For more information about using <tt>update-rc.d</tt>,
7329 please consult its man page <manref name="update-rc.d"
7335 <heading>Running initscripts</heading>
7337 The program <prgn>invoke-rc.d</prgn> is provided to make
7338 it easier for package maintainers to properly invoke an
7339 initscript, obeying runlevel and other locally-defined
7340 constraints that might limit a package's right to start,
7341 stop and otherwise manage services. This program may be
7342 used by maintainers in their packages' scripts.
7346 The package maintainer scripts must use
7347 <prgn>invoke-rc.d</prgn> to invoke the
7348 <file>/etc/init.d/*</file> initscripts, instead of
7349 calling them directly.
7353 By default, <prgn>invoke-rc.d</prgn> will pass any
7354 action requests (start, stop, reload, restart...) to the
7355 <file>/etc/init.d</file> script, filtering out requests
7356 to start or restart a service out of its intended
7361 Most packages will simply need to change:
7362 <example compact="compact">/etc/init.d/<package>
7363 <action></example> in their <prgn>postinst</prgn>
7364 and <prgn>prerm</prgn> scripts to:
7365 <example compact="compact">
7366 if which invoke-rc.d >/dev/null 2>&1; then
7367 invoke-rc.d <var>package</var> <action>
7369 /etc/init.d/<var>package</var> <action>
7375 A package should register its initscript services using
7376 <prgn>update-rc.d</prgn> before it tries to invoke them
7377 using <prgn>invoke-rc.d</prgn>. Invocation of
7378 unregistered services may fail.
7382 For more information about using
7383 <prgn>invoke-rc.d</prgn>, please consult its man page
7384 <manref name="invoke-rc.d" section="8">.
7390 <heading>Boot-time initialization</heading>
7393 There used to be another directory, <file>/etc/rc.boot</file>,
7394 which contained scripts which were run once per machine
7395 boot. This has been deprecated in favour of links from
7396 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7397 described in <ref id="/etc/init.d">. Packages must not
7398 place files in <file>/etc/rc.boot</file>.
7403 <heading>Example</heading>
7406 An example on which you can base your
7407 <file>/etc/init.d</file> scripts is found in
7408 <file>/etc/init.d/skeleton</file>.
7415 <heading>Console messages from <file>init.d</file> scripts</heading>
7418 This section describes the formats to be used for messages
7419 written to standard output by the <file>/etc/init.d</file>
7420 scripts. The intent is to improve the consistency of
7421 Debian's startup and shutdown look and feel. For this
7422 reason, please look very carefully at the details. We want
7423 the messages to have the same format in terms of wording,
7424 spaces, punctuation and case of letters.
7428 Here is a list of overall rules that should be used for
7429 messages generated by <file>/etc/init.d</file> scripts.
7435 The message should fit in one line (fewer than 80
7436 characters), start with a capital letter and end with
7437 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7441 If the script is performing some time consuming task in
7442 the background (not merely starting or stopping a
7443 program, for instance), an ellipsis (three dots:
7444 <tt>...</tt>) should be output to the screen, with no
7445 leading or tailing whitespace or line feeds.
7449 The messages should appear as if the computer is telling
7450 the user what it is doing (politely :-), but should not
7451 mention "it" directly. For example, instead of:
7452 <example compact="compact">
7453 I'm starting network daemons: nfsd mountd.
7455 the message should say
7456 <example compact="compact">
7457 Starting network daemons: nfsd mountd.
7464 <tt>init.d</tt> script should use the following standard
7465 message formats for the situations enumerated below.
7471 <p>When daemons are started</p>
7474 If the script starts one or more daemons, the output
7475 should look like this (a single line, no leading
7477 <example compact="compact">
7478 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7480 The <var>description</var> should describe the
7481 subsystem the daemon or set of daemons are part of,
7482 while <var>daemon-1</var> up to <var>daemon-n</var>
7483 denote each daemon's name (typically the file name of
7488 For example, the output of <file>/etc/init.d/lpd</file>
7490 <example compact="compact">
7491 Starting printer spooler: lpd.
7496 This can be achieved by saying
7497 <example compact="compact">
7498 echo -n "Starting printer spooler: lpd"
7499 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7502 in the script. If there are more than one daemon to
7503 start, the output should look like this:
7504 <example compact="compact">
7505 echo -n "Starting remote file system services:"
7506 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7507 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7508 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7511 This makes it possible for the user to see what is
7512 happening and when the final daemon has been started.
7513 Care should be taken in the placement of white spaces:
7514 in the example above the system administrators can
7515 easily comment out a line if they don't want to start
7516 a specific daemon, while the displayed message still
7522 <p>When a system parameter is being set</p>
7525 If you have to set up different system parameters
7526 during the system boot, you should use this format:
7527 <example compact="compact">
7528 Setting <var>parameter</var> to "<var>value</var>".
7533 You can use a statement such as the following to get
7535 <example compact="compact">
7536 echo "Setting DNS domainname to \"$domainname\"."
7541 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7542 for the left and right quotation marks. A grave accent
7543 (<tt>`</tt>) is not a quote character; neither is an
7544 apostrophe (<tt>'</tt>).
7549 <p>When a daemon is stopped or restarted</p>
7552 When you stop or restart a daemon, you should issue a
7553 message identical to the startup message, except that
7554 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7555 or <tt>Restarting</tt> respectively.
7559 For example, stopping the printer daemon will look like
7561 <example compact="compact">
7562 Stopping printer spooler: lpd.
7568 <p>When something is executed</p>
7571 There are several examples where you have to run a
7572 program at system startup or shutdown to perform a
7573 specific task, for example, setting the system's clock
7574 using <prgn>netdate</prgn> or killing all processes
7575 when the system shuts down. Your message should look
7577 <example compact="compact">
7578 Doing something very useful...done.
7580 You should print the <tt>done.</tt> immediately after
7581 the job has been completed, so that the user is
7582 informed why they have to wait. You can get this
7584 <example compact="compact">
7585 echo -n "Doing something very useful..."
7594 <p>When the configuration is reloaded</p>
7597 When a daemon is forced to reload its configuration
7598 files you should use the following format:
7599 <example compact="compact">
7600 Reloading <var>description</var> configuration...done.
7602 where <var>description</var> is the same as in the
7603 daemon starting message.
7610 <sect id="cron-jobs">
7611 <heading>Cron jobs</heading>
7614 Packages must not modify the configuration file
7615 <file>/etc/crontab</file>, and they must not modify the files in
7616 <file>/var/spool/cron/crontabs</file>.
7620 If a package wants to install a job that has to be executed via
7621 cron, it should place a file named as specified
7622 in <ref id="cron-files"> into one or more of the following
7624 <example compact="compact">
7630 As these directory names imply, the files within them are
7631 executed on an hourly, daily, weekly, or monthly basis,
7632 respectively. The exact times are listed in
7633 <file>/etc/crontab</file>.
7637 All files installed in any of these directories must be
7638 scripts (e.g., shell scripts or Perl scripts) so that they
7639 can easily be modified by the local system administrator.
7640 In addition, they must be treated as configuration files.
7644 If a certain job has to be executed at some other frequency or
7645 at a specific time, the package should install a file in
7646 <file>/etc/cron.d</file> with a name as specified
7647 in <ref id="cron-files">. This file uses the same syntax
7648 as <file>/etc/crontab</file> and is processed
7649 by <prgn>cron</prgn> automatically. The file must also be
7650 treated as a configuration file. (Note that entries in the
7651 <file>/etc/cron.d</file> directory are not handled by
7652 <prgn>anacron</prgn>. Thus, you should only use this
7653 directory for jobs which may be skipped if the system is not
7658 Unlike <file>crontab</file> files described in the IEEE Std
7659 1003.1-2008 (POSIX.1) available from
7660 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7661 name="The Open Group">, the files in
7662 <file>/etc/cron.d</file> and the file
7663 <file>/etc/crontab</file> have seven fields; namely:
7665 <item>Minute [0,59]</item>
7666 <item>Hour [0,23]</item>
7667 <item>Day of the month [1,31]</item>
7668 <item>Month of the year [1,12]</item>
7669 <item>Day of the week ([0,6] with 0=Sunday)</item>
7670 <item>Username</item>
7671 <item>Command to be run</item>
7673 Ranges of numbers are allowed. Ranges are two numbers
7674 separated with a hyphen. The specified range is inclusive.
7675 Lists are allowed. A list is a set of numbers (or ranges)
7676 separated by commas. Step values can be used in conjunction
7681 The scripts or <tt>crontab</tt> entries in these directories should
7682 check if all necessary programs are installed before they
7683 try to execute them. Otherwise, problems will arise when a
7684 package was removed but not purged since configuration files
7685 are kept on the system in this situation.
7689 Any <tt>cron</tt> daemon must provide
7690 <file>/usr/bin/crontab</file> and support normal
7691 <tt>crontab</tt> entries as specified in POSIX. The daemon
7692 must also support names for days and months, ranges, and
7693 step values. It has to support <file>/etc/crontab</file>,
7694 and correctly execute the scripts in
7695 <file>/etc/cron.d</file>. The daemon must also correctly
7697 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7700 <sect1 id="cron-files">
7701 <heading>Cron job file names</heading>
7704 The file name of a cron job file should normally match the
7705 name of the package from which it comes.
7709 If a package supplies multiple cron job files files in the
7710 same directory, the file names should all start with the name
7711 of the package (possibly modified as described below) followed
7712 by a hyphen (<tt>-</tt>) and a suitable suffix.
7716 A cron job file name must not include any period or plus
7717 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7718 cause cron to ignore the file. Underscores (<tt>_</tt>)
7719 should be used instead of <tt>.</tt> and <tt>+</tt>
7726 <heading>Menus</heading>
7729 The Debian <tt>menu</tt> package provides a standard
7730 interface between packages providing applications and
7731 <em>menu programs</em> (either X window managers or
7732 text-based menu programs such as <prgn>pdmenu</prgn>).
7736 All packages that provide applications that need not be
7737 passed any special command line arguments for normal
7738 operation should register a menu entry for those
7739 applications, so that users of the <tt>menu</tt> package
7740 will automatically get menu entries in their window
7741 managers, as well in shells like <tt>pdmenu</tt>.
7745 Menu entries should follow the current menu policy.
7749 The menu policy can be found in the <tt>menu-policy</tt>
7750 files in the <tt>debian-policy</tt> package.
7751 It is also available from the Debian web mirrors at
7752 <tt><url name="/doc/packaging-manuals/menu-policy/"
7753 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7757 Please also refer to the <em>Debian Menu System</em>
7758 documentation that comes with the <package>menu</package>
7759 package for information about how to register your
7765 <heading>Multimedia handlers</heading>
7768 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7769 is a mechanism for encoding files and data streams and
7770 providing meta-information about them, in particular their
7771 type (e.g. audio or video) and format (e.g. PNG, HTML,
7776 Registration of MIME type handlers allows programs like mail
7777 user agents and web browsers to invoke these handlers to
7778 view, edit or display MIME types they don't support directly.
7782 Packages which provide the ability to view/show/play,
7783 compose, edit or print MIME types should register themselves
7784 as such following the current MIME support policy.
7788 The <package>mime-support</package> package provides the
7789 <prgn>update-mime</prgn> program which allows packages to
7790 register programs that can show, compose, edit or print
7795 Packages containing such programs must register them
7796 with <prgn>update-mime</prgn> as documented in <manref
7797 name="update-mime" section="8">. They should <em>not</em> depend
7798 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7799 they should just put something like the following in the
7800 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7803 if [ -x /usr/sbin/update-mime ]; then
7812 <heading>Keyboard configuration</heading>
7815 To achieve a consistent keyboard configuration so that all
7816 applications interpret a keyboard event the same way, all
7817 programs in the Debian distribution must be configured to
7818 comply with the following guidelines.
7822 The following keys must have the specified interpretations:
7825 <tag><tt><--</tt></tag>
7826 <item>delete the character to the left of the cursor</item>
7828 <tag><tt>Delete</tt></tag>
7829 <item>delete the character to the right of the cursor</item>
7831 <tag><tt>Control+H</tt></tag>
7832 <item>emacs: the help prefix</item>
7835 The interpretation of any keyboard events should be
7836 independent of the terminal that is used, be it a virtual
7837 console, an X terminal emulator, an rlogin/telnet session,
7842 The following list explains how the different programs
7843 should be set up to achieve this:
7849 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7853 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7857 X translations are set up to make
7858 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7859 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7860 is the vt220 escape code for the "delete character"
7861 key). This must be done by loading the X resources
7862 using <prgn>xrdb</prgn> on all local X displays, not
7863 using the application defaults, so that the
7864 translation resources used correspond to the
7865 <prgn>xmodmap</prgn> settings.
7869 The Linux console is configured to make
7870 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7871 generate <tt>ESC [ 3 ~</tt>.
7875 X applications are configured so that <tt><</tt>
7876 deletes left, and <tt>Delete</tt> deletes right. Motif
7877 applications already work like this.
7881 Terminals should have <tt>stty erase ^?</tt> .
7885 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7886 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7887 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7891 Emacs is programmed to map <tt>KB_Backspace</tt> or
7892 the <tt>stty erase</tt> character to
7893 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7894 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7895 <tt>^H</tt> to <tt>help</tt> as always.
7899 Other applications use the <tt>stty erase</tt>
7900 character and <tt>kdch1</tt> for the two delete keys,
7901 with ASCII DEL being "delete previous character" and
7902 <tt>kdch1</tt> being "delete character under
7910 This will solve the problem except for the following
7917 Some terminals have a <tt><--</tt> key that cannot
7918 be made to produce anything except <tt>^H</tt>. On
7919 these terminals Emacs help will be unavailable on
7920 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7921 character takes precedence in Emacs, and has been set
7922 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7923 available) can be used instead.
7927 Some operating systems use <tt>^H</tt> for <tt>stty
7928 erase</tt>. However, modern telnet versions and all
7929 rlogin versions propagate <tt>stty</tt> settings, and
7930 almost all UNIX versions honour <tt>stty erase</tt>.
7931 Where the <tt>stty</tt> settings are not propagated
7932 correctly, things can be made to work by using
7933 <tt>stty</tt> manually.
7937 Some systems (including previous Debian versions) use
7938 <prgn>xmodmap</prgn> to arrange for both
7939 <tt><--</tt> and <tt>Delete</tt> to generate
7940 <tt>KB_Delete</tt>. We can change the behavior of
7941 their X clients using the same X resources that we use
7942 to do it for our own clients, or configure our clients
7943 using their resources when things are the other way
7944 around. On displays configured like this
7945 <tt>Delete</tt> will not work, but <tt><--</tt>
7950 Some operating systems have different <tt>kdch1</tt>
7951 settings in their <tt>terminfo</tt> database for
7952 <tt>xterm</tt> and others. On these systems the
7953 <tt>Delete</tt> key will not work correctly when you
7954 log in from a system conforming to our policy, but
7955 <tt><--</tt> will.
7962 <heading>Environment variables</heading>
7965 A program must not depend on environment variables to get
7966 reasonable defaults. (That's because these environment
7967 variables would have to be set in a system-wide
7968 configuration file like <file>/etc/profile</file>, which is not
7969 supported by all shells.)
7973 If a program usually depends on environment variables for its
7974 configuration, the program should be changed to fall back to
7975 a reasonable default configuration if these environment
7976 variables are not present. If this cannot be done easily
7977 (e.g., if the source code of a non-free program is not
7978 available), the program must be replaced by a small
7979 "wrapper" shell script which sets the environment variables
7980 if they are not already defined, and calls the original program.
7984 Here is an example of a wrapper script for this purpose:
7986 <example compact="compact">
7988 BAR=${BAR:-/var/lib/fubar}
7990 exec /usr/lib/foo/foo "$@"
7995 Furthermore, as <file>/etc/profile</file> is a configuration
7996 file of the <prgn>base-files</prgn> package, other packages must
7997 not put any environment variables or other commands into that
8002 <sect id="doc-base">
8003 <heading>Registering Documents using doc-base</heading>
8006 The <package>doc-base</package> package implements a
8007 flexible mechanism for handling and presenting
8008 documentation. The recommended practice is for every Debian
8009 package that provides online documentation (other than just
8010 manual pages) to register these documents with
8011 <package>doc-base</package> by installing a
8012 <package>doc-base</package> control file in
8013 <file>/usr/share/doc-base/</file>.
8016 Please refer to the documentation that comes with the
8017 <package>doc-base</package> package for information and
8026 <heading>Files</heading>
8028 <sect id="binaries">
8029 <heading>Binaries</heading>
8032 Two different packages must not install programs with
8033 different functionality but with the same filenames. (The
8034 case of two programs having the same functionality but
8035 different implementations is handled via "alternatives" or
8036 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8037 <ref id="conflicts"> respectively.) If this case happens,
8038 one of the programs must be renamed. The maintainers should
8039 report this to the <tt>debian-devel</tt> mailing list and
8040 try to find a consensus about which program will have to be
8041 renamed. If a consensus cannot be reached, <em>both</em>
8042 programs must be renamed.
8046 By default, when a package is being built, any binaries
8047 created should include debugging information, as well as
8048 being compiled with optimization. You should also turn on
8049 as many reasonable compilation warnings as possible; this
8050 makes life easier for porters, who can then look at build
8051 logs for possible problems. For the C programming language,
8052 this means the following compilation parameters should be
8054 <example compact="compact">
8056 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8058 INSTALL = install -s # (or use strip on the files in debian/tmp)
8063 Note that by default all installed binaries should be stripped,
8064 either by using the <tt>-s</tt> flag to
8065 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8066 the binaries after they have been copied into
8067 <file>debian/tmp</file> but before the tree is made into a
8072 Although binaries in the build tree should be compiled with
8073 debugging information by default, it can often be difficult to
8074 debug programs if they are also subjected to compiler
8075 optimization. For this reason, it is recommended to support the
8076 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8077 (see <ref id="debianrules-options">). This variable can contain
8078 several flags to change how a package is compiled and built.
8082 It is up to the package maintainer to decide what
8083 compilation options are best for the package. Certain
8084 binaries (such as computationally-intensive programs) will
8085 function better with certain flags (<tt>-O3</tt>, for
8086 example); feel free to use them. Please use good judgment
8087 here. Don't use flags for the sake of it; only use them
8088 if there is good reason to do so. Feel free to override
8089 the upstream author's ideas about which compilation
8090 options are best: they are often inappropriate for our
8096 <sect id="libraries">
8097 <heading>Libraries</heading>
8100 If the package is <strong>architecture: any</strong>, then
8101 the shared library compilation and linking flags must have
8102 <tt>-fPIC</tt>, or the package shall not build on some of
8103 the supported architectures<footnote>
8105 If you are using GCC, <tt>-fPIC</tt> produces code with
8106 relocatable position independent code, which is required for
8107 most architectures to create a shared library, with i386 and
8108 perhaps some others where non position independent code is
8109 permitted in a shared library.
8112 Position independent code may have a performance penalty,
8113 especially on <tt>i386</tt>. However, in most cases the
8114 speed penalty must be measured against the memory wasted on
8115 the few architectures where non position independent code is
8118 </footnote>. Any exception to this rule must be discussed on
8119 the mailing list <em>debian-devel@lists.debian.org</em>, and
8120 a rough consensus obtained. The reasons for not compiling
8121 with <tt>-fPIC</tt> flag must be recorded in the file
8122 <tt>README.Debian</tt>, and care must be taken to either
8123 restrict the architecture or arrange for <tt>-fPIC</tt> to
8124 be used on architectures where it is required.<footnote>
8126 Some of the reasons why this might be required is if the
8127 library contains hand crafted assembly code that is not
8128 relocatable, the speed penalty is excessive for compute
8129 intensive libs, and similar reasons.
8134 As to the static libraries, the common case is not to have
8135 relocatable code, since there is no benefit, unless in specific
8136 cases; therefore the static version must not be compiled
8137 with the <tt>-fPIC</tt> flag. Any exception to this rule
8138 should be discussed on the mailing list
8139 <em>debian-devel@lists.debian.org</em>, and the reasons for
8140 compiling with the <tt>-fPIC</tt> flag must be recorded in
8141 the file <tt>README.Debian</tt>. <footnote>
8143 Some of the reasons for linking static libraries with
8144 the <tt>-fPIC</tt> flag are if, for example, one needs a
8145 Perl API for a library that is under rapid development,
8146 and has an unstable API, so shared libraries are
8147 pointless at this phase of the library's development. In
8148 that case, since Perl needs a library with relocatable
8149 code, it may make sense to create a static library with
8150 relocatable code. Another reason cited is if you are
8151 distilling various libraries into a common shared
8152 library, like <tt>mklibs</tt> does in the Debian
8158 In other words, if both a shared and a static library is
8159 being built, each source unit (<tt>*.c</tt>, for example,
8160 for C files) will need to be compiled twice, for the normal
8165 Libraries should be built with threading support and to be
8166 thread-safe if the library supports this.
8170 Although not enforced by the build tools, shared libraries
8171 must be linked against all libraries that they use symbols from
8172 in the same way that binaries are. This ensures the correct
8173 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8174 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8175 systems and guarantees that all libraries can be safely opened
8176 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8177 option <tt>-Wl,-z,defs</tt> when building a shared library.
8178 Since this option enforces symbol resolution at build time,
8179 a missing library reference will be caught early as a fatal
8184 All installed shared libraries should be stripped with
8185 <example compact="compact">
8186 strip --strip-unneeded <var>your-lib</var>
8188 (The option <tt>--strip-unneeded</tt> makes
8189 <prgn>strip</prgn> remove only the symbols which aren't
8190 needed for relocation processing.) Shared libraries can
8191 function perfectly well when stripped, since the symbols for
8192 dynamic linking are in a separate part of the ELF object
8194 You might also want to use the options
8195 <tt>--remove-section=.comment</tt> and
8196 <tt>--remove-section=.note</tt> on both shared libraries
8197 and executables, and <tt>--strip-debug</tt> on static
8203 Note that under some circumstances it may be useful to
8204 install a shared library unstripped, for example when
8205 building a separate package to support debugging.
8209 Shared object files (often <file>.so</file> files) that are not
8210 public libraries, that is, they are not meant to be linked
8211 to by third party executables (binaries of other packages),
8212 should be installed in subdirectories of the
8213 <file>/usr/lib</file> directory. Such files are exempt from the
8214 rules that govern ordinary shared libraries, except that
8215 they must not be installed executable and should be
8217 A common example are the so-called "plug-ins",
8218 internal shared objects that are dynamically loaded by
8219 programs using <manref name="dlopen" section="3">.
8224 Packages that use <prgn>libtool</prgn> to create and install
8225 their shared libraries install a file containing additional
8226 metadata (ending in <file>.la</file>) alongside the library.
8227 For public libraries intended for use by other packages, these
8228 files normally should not be included in the Debian package,
8229 since the information they include is not necessary to link with
8230 the shared library on Debian and can add unnecessary additional
8231 dependencies to other programs or libraries.<footnote>
8232 These files store, among other things, all libraries on which
8233 that shared library depends. Unfortunately, if
8234 the <file>.la</file> file is present and contains that
8235 dependency information, using <prgn>libtool</prgn> when
8236 linking against that library will cause the resulting program
8237 or library to be linked against those dependencies as well,
8238 even if this is unnecessary. This can create unneeded
8239 dependencies on shared library packages that would otherwise
8240 be hidden behind the library ABI, and can make library
8241 transitions to new SONAMEs unnecessarily complicated and
8242 difficult to manage.
8244 If the <file>.la</file> file is required for that library (if,
8245 for instance, it's loaded via <tt>libltdl</tt> in a way that
8246 requires that meta-information), the <tt>dependency_libs</tt>
8247 setting in the <file>.la</file> file should normally be set to
8248 the empty string. If the shared library development package has
8249 historically included the <file>.la</file>, it must be retained
8250 in the development package (with <tt>dependency_libs</tt>
8251 emptied) until all libraries that depend on it have removed or
8252 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8253 files to prevent linking with those other libraries
8254 using <prgn>libtool</prgn> from failing.
8258 If the <file>.la</file> must be included, it should be included
8259 in the development (<tt>-dev</tt>) package, unless the library
8260 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8261 library. If it is intended for use with <tt>libltdl</tt>,
8262 the <file>.la</file> files must go in the run-time library
8267 These requirements for handling of <file>.la</file> files do not
8268 apply to loadable modules or libraries not installed in
8269 directories searched by default by the dynamic linker. Packages
8270 installing loadable modules will frequently need to install
8271 the <file>.la</file> files alongside the modules so that they
8272 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8273 does not need to be modified for libraries or modules that are
8274 not installed in directories searched by the dynamic linker by
8275 default and not intended for use by other packages.
8279 You must make sure that you use only released versions of
8280 shared libraries to build your packages; otherwise other
8281 users will not be able to run your binaries
8282 properly. Producing source packages that depend on
8283 unreleased compilers is also usually a bad
8290 <heading>Shared libraries</heading>
8292 This section has moved to <ref id="sharedlibs">.
8298 <heading>Scripts</heading>
8301 All command scripts, including the package maintainer
8302 scripts inside the package and used by <prgn>dpkg</prgn>,
8303 should have a <tt>#!</tt> line naming the shell to be used
8308 In the case of Perl scripts this should be
8309 <tt>#!/usr/bin/perl</tt>.
8313 When scripts are installed into a directory in the system
8314 PATH, the script name should not include an extension such
8315 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8316 language currently used to implement it.
8319 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8320 <file>init.d</file> scripts should almost certainly start
8321 with <tt>set -e</tt> so that errors are detected.
8322 <file>init.d</file> scripts are something of a special case, due
8323 to how frequently they need to call commands that are allowed to
8324 fail, and it may instead be easier to check the exit status of
8325 commands directly. See <ref id="writing-init"> for more
8326 information about writing <file>init.d</file> scripts.
8329 Every script should use <tt>set -e</tt> or check the exit status
8330 of <em>every</em> command.
8333 Scripts may assume that <file>/bin/sh</file> implements the
8334 SUSv3 Shell Command Language<footnote>
8335 Single UNIX Specification, version 3, which is also IEEE
8336 1003.1-2004 (POSIX), and is available on the World Wide Web
8337 from <url id="http://www.unix.org/version3/online.html"
8338 name="The Open Group"> after free
8339 registration.</footnote>
8340 plus the following additional features not mandated by
8342 These features are in widespread use in the Linux community
8343 and are implemented in all of bash, dash, and ksh, the most
8344 common shells users may wish to use as <file>/bin/sh</file>.
8347 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8348 must not generate a newline.</item>
8349 <item><tt>test</tt>, if implemented as a shell built-in, must
8350 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8352 <item><tt>local</tt> to create a scoped variable must be
8353 supported, including listing multiple variables in a single
8354 local command and assigning a value to a variable at the
8355 same time as localizing it. <tt>local</tt> may or
8356 may not preserve the variable value from an outer scope if
8357 no assignment is present. Uses such as:
8361 # ... use a, b, c, d ...
8364 must be supported and must set the value of <tt>c</tt> to
8367 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8368 -<var>signal</var></tt>, where <var>signal</var> is either
8369 the name of a signal or one of the numeric signals listed in
8370 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8371 supported if <prgn>kill</prgn> is implemented as a shell
8374 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8375 signals must be supported. In addition to the signal
8376 numbers listed in the extension, which are the same as for
8377 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8380 If a shell script requires non-SUSv3 features from the shell
8381 interpreter other than those listed above, the appropriate shell
8382 must be specified in the first line of the script (e.g.,
8383 <tt>#!/bin/bash</tt>) and the package must depend on the package
8384 providing the shell (unless the shell package is marked
8385 "Essential", as in the case of <prgn>bash</prgn>).
8389 You may wish to restrict your script to SUSv3 features plus the
8390 above set when possible so that it may use <file>/bin/sh</file>
8391 as its interpreter. If your script works with <prgn>dash</prgn>
8392 (originally called <prgn>ash</prgn>), it probably complies with
8393 the above requirements, but if you are in doubt, use
8394 <file>/bin/bash</file>.
8398 Perl scripts should check for errors when making any
8399 system calls, including <tt>open</tt>, <tt>print</tt>,
8400 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8404 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8405 scripting languages. See <em>Csh Programming Considered
8406 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8407 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8408 If an upstream package comes with <prgn>csh</prgn> scripts
8409 then you must make sure that they start with
8410 <tt>#!/bin/csh</tt> and make your package depend on the
8411 <prgn>c-shell</prgn> virtual package.
8415 Any scripts which create files in world-writeable
8416 directories (e.g., in <file>/tmp</file>) must use a
8417 mechanism which will fail atomically if a file with the same
8418 name already exists.
8422 The Debian base system provides the <prgn>tempfile</prgn>
8423 and <prgn>mktemp</prgn> utilities for use by scripts for
8430 <heading>Symbolic links</heading>
8433 In general, symbolic links within a top-level directory should
8434 be relative, and symbolic links pointing from one top-level
8435 directory to or into another should be absolute. (A top-level
8436 directory is a sub-directory of the root
8437 directory <file>/</file>.) For example, a symbolic link
8438 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8439 should be relative (<file>../share/bar</file>), but a symbolic
8440 link from <file>/var/run</file> to <file>/run</file> should be
8442 This is necessary to allow top-level directories to be
8443 symlinks. If linking <file>/var/run</file>
8444 to <file>/run</file> were done with the relative symbolic
8445 link <file>../run</file>, but <file>/var</file> were a
8446 symbolic link to <file>/srv/disk1</file>, the symbolic link
8447 would point to <file>/srv/run</file> rather than the intended
8453 In addition, symbolic links should be specified as short as
8454 possible, i.e., link targets like <file>foo/../bar</file> are
8459 Note that when creating a relative link using
8460 <prgn>ln</prgn> it is not necessary for the target of the
8461 link to exist relative to the working directory you're
8462 running <prgn>ln</prgn> from, nor is it necessary to change
8463 directory to the directory where the link is to be made.
8464 Simply include the string that should appear as the target
8465 of the link (this will be a pathname relative to the
8466 directory in which the link resides) as the first argument
8471 For example, in your <prgn>Makefile</prgn> or
8472 <file>debian/rules</file>, you can do things like:
8473 <example compact="compact">
8474 ln -fs gcc $(prefix)/bin/cc
8475 ln -fs gcc debian/tmp/usr/bin/cc
8476 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8477 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8482 A symbolic link pointing to a compressed file should always
8483 have the same file extension as the referenced file. (For
8484 example, if a file <file>foo.gz</file> is referenced by a
8485 symbolic link, the filename of the link has to end with
8486 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8491 <heading>Device files</heading>
8494 Packages must not include device files or named pipes in the
8499 If a package needs any special device files that are not
8500 included in the base system, it must call
8501 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8502 after notifying the user<footnote>
8503 This notification could be done via a (low-priority)
8504 debconf message, or an echo (printf) statement.
8509 Packages must not remove any device files in the
8510 <prgn>postrm</prgn> or any other script. This is left to the
8511 system administrator.
8515 Debian uses the serial devices
8516 <file>/dev/ttyS*</file>. Programs using the old
8517 <file>/dev/cu*</file> devices should be changed to use
8518 <file>/dev/ttyS*</file>.
8522 Named pipes needed by the package must be created in
8523 the <prgn>postinst</prgn> script<footnote>
8524 It's better to use <prgn>mkfifo</prgn> rather
8525 than <prgn>mknod</prgn> to create named pipes so that
8526 automated checks for packages incorrectly creating device
8527 files with <prgn>mknod</prgn> won't have false positives.
8528 </footnote> and removed in
8529 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8534 <sect id="config-files">
8535 <heading>Configuration files</heading>
8538 <heading>Definitions</heading>
8542 <tag>configuration file</tag>
8544 A file that affects the operation of a program, or
8545 provides site- or host-specific information, or
8546 otherwise customizes the behavior of a program.
8547 Typically, configuration files are intended to be
8548 modified by the system administrator (if needed or
8549 desired) to conform to local policy or to provide
8550 more useful site-specific behavior.
8553 <tag><tt>conffile</tt></tag>
8555 A file listed in a package's <tt>conffiles</tt>
8556 file, and is treated specially by <prgn>dpkg</prgn>
8557 (see <ref id="configdetails">).
8563 The distinction between these two is important; they are
8564 not interchangeable concepts. Almost all
8565 <tt>conffile</tt>s are configuration files, but many
8566 configuration files are not <tt>conffiles</tt>.
8570 As noted elsewhere, <file>/etc/init.d</file> scripts,
8571 <file>/etc/default</file> files, scripts installed in
8572 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8573 configuration installed in <file>/etc/cron.d</file> must be
8574 treated as configuration files. In general, any script that
8575 embeds configuration information is de-facto a configuration
8576 file and should be treated as such.
8581 <heading>Location</heading>
8584 Any configuration files created or used by your package
8585 must reside in <file>/etc</file>. If there are several,
8586 consider creating a subdirectory of <file>/etc</file>
8587 named after your package.
8591 If your package creates or uses configuration files
8592 outside of <file>/etc</file>, and it is not feasible to modify
8593 the package to use <file>/etc</file> directly, put the files
8594 in <file>/etc</file> and create symbolic links to those files
8595 from the location that the package requires.
8600 <heading>Behavior</heading>
8603 Configuration file handling must conform to the following
8605 <list compact="compact">
8607 local changes must be preserved during a package
8611 configuration files must be preserved when the
8612 package is removed, and only deleted when the
8616 Obsolete configuration files without local changes may be
8617 removed by the package during upgrade.
8621 The easy way to achieve this behavior is to make the
8622 configuration file a <tt>conffile</tt>. This is
8623 appropriate only if it is possible to distribute a default
8624 version that will work for most installations, although
8625 some system administrators may choose to modify it. This
8626 implies that the default version will be part of the
8627 package distribution, and must not be modified by the
8628 maintainer scripts during installation (or at any other
8633 In order to ensure that local changes are preserved
8634 correctly, no package may contain or make hard links to
8635 conffiles.<footnote>
8636 Rationale: There are two problems with hard links.
8637 The first is that some editors break the link while
8638 editing one of the files, so that the two files may
8639 unwittingly become unlinked and different. The second
8640 is that <prgn>dpkg</prgn> might break the hard link
8641 while upgrading <tt>conffile</tt>s.
8646 The other way to do it is via the maintainer scripts. In
8647 this case, the configuration file must not be listed as a
8648 <tt>conffile</tt> and must not be part of the package
8649 distribution. If the existence of a file is required for
8650 the package to be sensibly configured it is the
8651 responsibility of the package maintainer to provide
8652 maintainer scripts which correctly create, update and
8653 maintain the file and remove it on purge. (See <ref
8654 id="maintainerscripts"> for more information.) These
8655 scripts must be idempotent (i.e., must work correctly if
8656 <prgn>dpkg</prgn> needs to re-run them due to errors
8657 during installation or removal), must cope with all the
8658 variety of ways <prgn>dpkg</prgn> can call maintainer
8659 scripts, must not overwrite or otherwise mangle the user's
8660 configuration without asking, must not ask unnecessary
8661 questions (particularly during upgrades), and must
8662 otherwise be good citizens.
8666 The scripts are not required to configure every possible
8667 option for the package, but only those necessary to get
8668 the package running on a given system. Ideally the
8669 sysadmin should not have to do any configuration other
8670 than that done (semi-)automatically by the
8671 <prgn>postinst</prgn> script.
8675 A common practice is to create a script called
8676 <file><var>package</var>-configure</file> and have the
8677 package's <prgn>postinst</prgn> call it if and only if the
8678 configuration file does not already exist. In certain
8679 cases it is useful for there to be an example or template
8680 file which the maintainer scripts use. Such files should
8681 be in <file>/usr/share/<var>package</var></file> or
8682 <file>/usr/lib/<var>package</var></file> (depending on whether
8683 they are architecture-independent or not). There should
8684 be symbolic links to them from
8685 <file>/usr/share/doc/<var>package</var>/examples</file> if
8686 they are examples, and should be perfectly ordinary
8687 <prgn>dpkg</prgn>-handled files (<em>not</em>
8688 configuration files).
8692 These two styles of configuration file handling must
8693 not be mixed, for that way lies madness:
8694 <prgn>dpkg</prgn> will ask about overwriting the file
8695 every time the package is upgraded.
8700 <heading>Sharing configuration files</heading>
8703 If two or more packages use the same configuration file
8704 and it is reasonable for both to be installed at the same
8705 time, one of these packages must be defined as
8706 <em>owner</em> of the configuration file, i.e., it will be
8707 the package which handles that file as a configuration
8708 file. Other packages that use the configuration file must
8709 depend on the owning package if they require the
8710 configuration file to operate. If the other package will
8711 use the configuration file if present, but is capable of
8712 operating without it, no dependency need be declared.
8716 If it is desirable for two or more related packages to
8717 share a configuration file <em>and</em> for all of the
8718 related packages to be able to modify that configuration
8719 file, then the following should be done:
8720 <enumlist compact="compact">
8722 One of the related packages (the "owning" package)
8723 will manage the configuration file with maintainer
8724 scripts as described in the previous section.
8727 The owning package should also provide a program
8728 that the other packages may use to modify the
8732 The related packages must use the provided program
8733 to make any desired modifications to the
8734 configuration file. They should either depend on
8735 the core package to guarantee that the configuration
8736 modifier program is available or accept gracefully
8737 that they cannot modify the configuration file if it
8738 is not. (This is in addition to the fact that the
8739 configuration file may not even be present in the
8746 Sometimes it's appropriate to create a new package which
8747 provides the basic infrastructure for the other packages
8748 and which manages the shared configuration files. (The
8749 <tt>sgml-base</tt> package is a good example.)
8753 If the configuration file cannot be shared as described above,
8754 the packages must be marked as conflicting with each other.
8755 Two packages that specify the same file as
8756 a <tt>conffile</tt> must conflict. This is an instance of the
8757 general rule about not sharing files. Neither alternatives
8758 nor diversions are likely to be appropriate in this case; in
8759 particular, <prgn>dpkg</prgn> does not handle diverted
8760 <tt>conffile</tt>s well.
8764 When two packages both declare the same <tt>conffile</tt>, they
8765 may see left-over configuration files from each other even
8766 though they conflict with each other. If a user removes
8767 (without purging) one of the packages and installs the other,
8768 the new package will take over the <tt>conffile</tt> from the
8769 old package. If the file was modified by the user, it will be
8770 treated the same as any other locally
8771 modified <tt>conffile</tt> during an upgrade.
8775 The maintainer scripts must not alter a <tt>conffile</tt>
8776 of <em>any</em> package, including the one the scripts
8782 <heading>User configuration files ("dotfiles")</heading>
8785 The files in <file>/etc/skel</file> will automatically be
8786 copied into new user accounts by <prgn>adduser</prgn>.
8787 No other program should reference the files in
8788 <file>/etc/skel</file>.
8792 Therefore, if a program needs a dotfile to exist in
8793 advance in <file>$HOME</file> to work sensibly, that dotfile
8794 should be installed in <file>/etc/skel</file> and treated as a
8799 However, programs that require dotfiles in order to
8800 operate sensibly are a bad thing, unless they do create
8801 the dotfiles themselves automatically.
8805 Furthermore, programs should be configured by the Debian
8806 default installation to behave as closely to the upstream
8807 default behavior as possible.
8811 Therefore, if a program in a Debian package needs to be
8812 configured in some way in order to operate sensibly, that
8813 should be done using a site-wide configuration file placed
8814 in <file>/etc</file>. Only if the program doesn't support a
8815 site-wide default configuration and the package maintainer
8816 doesn't have time to add it may a default per-user file be
8817 placed in <file>/etc/skel</file>.
8821 <file>/etc/skel</file> should be as empty as we can make it.
8822 This is particularly true because there is no easy (or
8823 necessarily desirable) mechanism for ensuring that the
8824 appropriate dotfiles are copied into the accounts of
8825 existing users when a package is installed.
8831 <heading>Log files</heading>
8833 Log files should usually be named
8834 <file>/var/log/<var>package</var>.log</file>. If you have many
8835 log files, or need a separate directory for permission
8836 reasons (<file>/var/log</file> is writable only by
8837 <file>root</file>), you should usually create a directory named
8838 <file>/var/log/<var>package</var></file> and place your log
8843 Log files must be rotated occasionally so that they don't grow
8844 indefinitely. The best way to do this is to install a log
8845 rotation configuration file in the
8846 directory <file>/etc/logrotate.d</file>, normally
8847 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8848 the facilities provided by <prgn>logrotate</prgn>.
8851 The traditional approach to log files has been to set up
8852 <em>ad hoc</em> log rotation schemes using simple shell
8853 scripts and cron. While this approach is highly
8854 customizable, it requires quite a lot of sysadmin work.
8855 Even though the original Debian system helped a little
8856 by automatically installing a system which can be used
8857 as a template, this was deemed not enough.
8861 The use of <prgn>logrotate</prgn>, a program developed
8862 by Red Hat, is better, as it centralizes log management.
8863 It has both a configuration file
8864 (<file>/etc/logrotate.conf</file>) and a directory where
8865 packages can drop their individual log rotation
8866 configurations (<file>/etc/logrotate.d</file>).
8869 Here is a good example for a logrotate config
8870 file (for more information see <manref name="logrotate"
8872 <example compact="compact">
8873 /var/log/foo/*.log {
8879 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8883 This rotates all files under <file>/var/log/foo</file>, saves 12
8884 compressed generations, and tells the daemon to reopen its log
8885 files after the log rotation. It skips this log rotation
8886 (via <tt>missingok</tt>) if no such log file is present, which
8887 avoids errors if the package is removed but not purged.
8891 Log files should be removed when the package is
8892 purged (but not when it is only removed). This should be
8893 done by the <prgn>postrm</prgn> script when it is called
8894 with the argument <tt>purge</tt> (see <ref
8895 id="removedetails">).
8899 <sect id="permissions-owners">
8900 <heading>Permissions and owners</heading>
8903 The rules in this section are guidelines for general use.
8904 If necessary you may deviate from the details below.
8905 However, if you do so you must make sure that what is done
8906 is secure and you should try to be as consistent as possible
8907 with the rest of the system. You should probably also
8908 discuss it on <prgn>debian-devel</prgn> first.
8912 Files should be owned by <tt>root:root</tt>, and made
8913 writable only by the owner and universally readable (and
8914 executable, if appropriate), that is mode 644 or 755.
8918 Directories should be mode 755 or (for group-writability)
8919 mode 2775. The ownership of the directory should be
8920 consistent with its mode: if a directory is mode 2775, it
8921 should be owned by the group that needs write access to
8924 When a package is upgraded, and the owner or permissions
8925 of a file included in the package has changed, dpkg
8926 arranges for the ownership and permissions to be
8927 correctly set upon installation. However, this does not
8928 extend to directories; the permissions and ownership of
8929 directories already on the system does not change on
8930 install or upgrade of packages. This makes sense, since
8931 otherwise common directories like <tt>/usr</tt> would
8932 always be in flux. To correctly change permissions of a
8933 directory the package owns, explicit action is required,
8934 usually in the <tt>postinst</tt> script. Care must be
8935 taken to handle downgrades as well, in that case.
8941 Control information files should be owned by <tt>root:root</tt>
8942 and either mode 644 (for most files) or mode 755 (for
8943 executables such as <qref id="maintscripts">maintainer
8948 Setuid and setgid executables should be mode 4755 or 2755
8949 respectively, and owned by the appropriate user or group.
8950 They should not be made unreadable (modes like 4711 or
8951 2711 or even 4111); doing so achieves no extra security,
8952 because anyone can find the binary in the freely available
8953 Debian package; it is merely inconvenient. For the same
8954 reason you should not restrict read or execute permissions
8955 on non-set-id executables.
8959 Some setuid programs need to be restricted to particular
8960 sets of users, using file permissions. In this case they
8961 should be owned by the uid to which they are set-id, and by
8962 the group which should be allowed to execute them. They
8963 should have mode 4754; again there is no point in making
8964 them unreadable to those users who must not be allowed to
8969 It is possible to arrange that the system administrator can
8970 reconfigure the package to correspond to their local
8971 security policy by changing the permissions on a binary:
8972 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8973 described below.<footnote>
8974 Ordinary files installed by <prgn>dpkg</prgn> (as
8975 opposed to <tt>conffile</tt>s and other similar objects)
8976 normally have their permissions reset to the distributed
8977 permissions when the package is reinstalled. However,
8978 the use of <prgn>dpkg-statoverride</prgn> overrides this
8981 Another method you should consider is to create a group for
8982 people allowed to use the program(s) and make any setuid
8983 executables executable only by that group.
8987 If you need to create a new user or group for your package
8988 there are two possibilities. Firstly, you may need to
8989 make some files in the binary package be owned by this
8990 user or group, or you may need to compile the user or
8991 group id (rather than just the name) into the binary
8992 (though this latter should be avoided if possible, as in
8993 this case you need a statically allocated id).</p>
8996 If you need a statically allocated id, you must ask for a
8997 user or group id from the <tt>base-passwd</tt> maintainer,
8998 and must not release the package until you have been
8999 allocated one. Once you have been allocated one you must
9000 either make the package depend on a version of the
9001 <tt>base-passwd</tt> package with the id present in
9002 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9003 your package to create the user or group itself with the
9004 correct id (using <tt>adduser</tt>) in its
9005 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9006 the <prgn>postinst</prgn> is to be preferred if it is
9007 possible, otherwise a pre-dependency will be needed on the
9008 <tt>adduser</tt> package.)
9012 On the other hand, the program might be able to determine
9013 the uid or gid from the user or group name at runtime, so
9014 that a dynamically allocated id can be used. In this case
9015 you should choose an appropriate user or group name,
9016 discussing this on <prgn>debian-devel</prgn> and checking
9017 with the <package/base-passwd/ maintainer that it is unique and that
9018 they do not wish you to use a statically allocated id
9019 instead. When this has been checked you must arrange for
9020 your package to create the user or group if necessary using
9021 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9022 <prgn>postinst</prgn> script (again, the latter is to be
9023 preferred if it is possible).
9027 Note that changing the numeric value of an id associated
9028 with a name is very difficult, and involves searching the
9029 file system for all appropriate files. You need to think
9030 carefully whether a static or dynamic id is required, since
9031 changing your mind later will cause problems.
9034 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9036 This section is not intended as policy, but as a
9037 description of the use of <prgn>dpkg-statoverride</prgn>.
9041 If a system administrator wishes to have a file (or
9042 directory or other such thing) installed with owner and
9043 permissions different from those in the distributed Debian
9044 package, they can use the <prgn>dpkg-statoverride</prgn>
9045 program to instruct <prgn>dpkg</prgn> to use the different
9046 settings every time the file is installed. Thus the
9047 package maintainer should distribute the files with their
9048 normal permissions, and leave it for the system
9049 administrator to make any desired changes. For example, a
9050 daemon which is normally required to be setuid root, but
9051 in certain situations could be used without being setuid,
9052 should be installed setuid in the <tt>.deb</tt>. Then the
9053 local system administrator can change this if they wish.
9054 If there are two standard ways of doing it, the package
9055 maintainer can use <tt>debconf</tt> to find out the
9056 preference, and call <prgn>dpkg-statoverride</prgn> in the
9057 maintainer script if necessary to accommodate the system
9058 administrator's choice. Care must be taken during
9059 upgrades to not override an existing setting.
9063 Given the above, <prgn>dpkg-statoverride</prgn> is
9064 essentially a tool for system administrators and would not
9065 normally be needed in the maintainer scripts. There is
9066 one type of situation, though, where calls to
9067 <prgn>dpkg-statoverride</prgn> would be needed in the
9068 maintainer scripts, and that involves packages which use
9069 dynamically allocated user or group ids. In such a
9070 situation, something like the following idiom can be very
9071 helpful in the package's <prgn>postinst</prgn>, where
9072 <tt>sysuser</tt> is a dynamically allocated id:
9074 for i in /usr/bin/foo /usr/sbin/bar
9076 # only do something when no setting exists
9077 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9079 #include: debconf processing, question about foo and bar
9080 if [ "$RET" = "true" ] ; then
9081 dpkg-statoverride --update --add sysuser root 4755 $i
9086 The corresponding code to remove the override when the package
9089 for i in /usr/bin/foo /usr/sbin/bar
9091 if dpkg-statoverride --list $i >/dev/null 2>&1
9093 dpkg-statoverride --remove $i
9103 <chapt id="customized-programs">
9104 <heading>Customized programs</heading>
9106 <sect id="arch-spec">
9107 <heading>Architecture specification strings</heading>
9110 If a program needs to specify an <em>architecture specification
9111 string</em> in some place, it should select one of the strings
9112 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9113 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9114 part is sometimes elided, as when the OS is Linux.
9118 Note that we don't want to use
9119 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9120 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9121 since this would make our programs incompatible with other
9122 Linux distributions. We also don't use something like
9123 <tt><var>arch</var>-unknown-linux</tt>, since the
9124 <tt>unknown</tt> does not look very good.
9127 <sect1 id="arch-wildcard-spec">
9128 <heading>Architecture wildcards</heading>
9131 A package may specify an architecture wildcard. Architecture
9132 wildcards are in the format <tt>any</tt> (which matches every
9133 architecture), <tt><var>os</var></tt>-any, or
9134 any-<tt><var>cpu</var></tt>. <footnote>
9135 Internally, the package system normalizes the GNU triplets
9136 and the Debian arches into Debian arch triplets (which are
9137 kind of inverted GNU triplets), with the first component of
9138 the triplet representing the libc and ABI in use, and then
9139 does matching against those triplets. However, such
9140 triplets are an internal implementation detail that should
9141 not be used by packages directly. The libc and ABI portion
9142 is handled internally by the package system based on
9143 the <var>os</var> and <var>cpu</var>.
9150 <heading>Daemons</heading>
9153 The configuration files <file>/etc/services</file>,
9154 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9155 by the <prgn>netbase</prgn> package and must not be modified
9160 If a package requires a new entry in one of these files, the
9161 maintainer should get in contact with the
9162 <prgn>netbase</prgn> maintainer, who will add the entries
9163 and release a new version of the <prgn>netbase</prgn>
9168 The configuration file <file>/etc/inetd.conf</file> must not be
9169 modified by the package's scripts except via the
9170 <prgn>update-inetd</prgn> script or the
9171 <file>DebianNet.pm</file> Perl module. See their documentation
9172 for details on how to add entries.
9176 If a package wants to install an example entry into
9177 <file>/etc/inetd.conf</file>, the entry must be preceded with
9178 exactly one hash character (<tt>#</tt>). Such lines are
9179 treated as "commented out by user" by the
9180 <prgn>update-inetd</prgn> script and are not changed or
9181 activated during package updates.
9186 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9190 Some programs need to create pseudo-ttys. This should be done
9191 using Unix98 ptys if the C library supports it. The resulting
9192 program must not be installed setuid root, unless that
9193 is required for other functionality.
9197 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9198 <file>/var/log/lastlog</file> must be installed writable by
9199 group <tt>utmp</tt>. Programs which need to modify those
9200 files must be installed setgid <tt>utmp</tt>.
9205 <heading>Editors and pagers</heading>
9208 Some programs have the ability to launch an editor or pager
9209 program to edit or display a text document. Since there are
9210 lots of different editors and pagers available in the Debian
9211 distribution, the system administrator and each user should
9212 have the possibility to choose their preferred editor and
9217 In addition, every program should choose a good default
9218 editor/pager if none is selected by the user or system
9223 Thus, every program that launches an editor or pager must
9224 use the EDITOR or PAGER environment variable to determine
9225 the editor or pager the user wishes to use. If these
9226 variables are not set, the programs <file>/usr/bin/editor</file>
9227 and <file>/usr/bin/pager</file> should be used, respectively.
9231 These two files are managed through the <prgn>dpkg</prgn>
9232 "alternatives" mechanism. Every package providing an editor or
9233 pager must call the <prgn>update-alternatives</prgn> script to
9234 register as an alternative for <file>/usr/bin/editor</file>
9235 or <file>/usr/bin/pager</file> as appropriate. The alternative
9236 should have a slave alternative
9237 for <file>/usr/share/man/man1/editor.1.gz</file>
9238 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9239 corresponding manual page.
9243 If it is very hard to adapt a program to make use of the
9244 EDITOR or PAGER variables, that program may be configured to
9245 use <file>/usr/bin/sensible-editor</file> and
9246 <file>/usr/bin/sensible-pager</file> as the editor or pager
9247 program respectively. These are two scripts provided in the
9248 <package>sensible-utils</package> package that check the EDITOR
9249 and PAGER variables and launch the appropriate program, and fall
9250 back to <file>/usr/bin/editor</file>
9251 and <file>/usr/bin/pager</file> if the variable is not set.
9255 A program may also use the VISUAL environment variable to
9256 determine the user's choice of editor. If it exists, it
9257 should take precedence over EDITOR. This is in fact what
9258 <file>/usr/bin/sensible-editor</file> does.
9262 It is not required for a package to depend on
9263 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9264 package to provide such virtual packages.<footnote>
9265 The Debian base system already provides an editor and a
9271 <sect id="web-appl">
9272 <heading>Web servers and applications</heading>
9275 This section describes the locations and URLs that should
9276 be used by all web servers and web applications in the
9283 Cgi-bin executable files are installed in the
9285 <example compact="compact">
9286 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
9288 or a subdirectory of that directory, and should be
9290 <example compact="compact">
9291 http://localhost/cgi-bin/<var>cgi-bin-name</var>
9293 (possibly with a subdirectory name
9294 before <var>cgi-bin-name</var>).
9298 <p>Access to HTML documents</p>
9301 HTML documents for a package are stored in
9302 <file>/usr/share/doc/<var>package</var></file>
9303 and can be referred to as
9304 <example compact="compact">
9305 http://localhost/doc/<var>package</var>/<var>filename</var>
9310 The web server should restrict access to the document
9311 tree so that only clients on the same host can read
9312 the documents. If the web server does not support such
9313 access controls, then it should not provide access at
9314 all, or ask about providing access during installation.
9319 <p>Access to images</p>
9321 It is recommended that images for a package be stored
9322 in <tt>/usr/share/images/<var>package</var></tt> and
9323 may be referred to through an alias <tt>/images/</tt>
9326 http://localhost/images/<package>/<filename>
9333 <p>Web Document Root</p>
9336 Web Applications should try to avoid storing files in
9337 the Web Document Root. Instead they should use the
9338 /usr/share/doc/<var>package</var> directory for
9339 documents and register the Web Application via the
9340 <package>doc-base</package> package. If access to the
9341 web document root is unavoidable then use
9342 <example compact="compact">
9345 as the Document Root. This might be just a symbolic
9346 link to the location where the system administrator
9347 has put the real document root.
9350 <item><p>Providing httpd and/or httpd-cgi</p>
9352 All web servers should provide the virtual package
9353 <tt>httpd</tt>. If a web server has CGI support it should
9354 provide <tt>httpd-cgi</tt> additionally.
9357 All web applications which do not contain CGI scripts should
9358 depend on <tt>httpd</tt>, all those web applications which
9359 <tt>do</tt> contain CGI scripts, should depend on
9367 <sect id="mail-transport-agents">
9368 <heading>Mail transport, delivery and user agents</heading>
9371 Debian packages which process electronic mail, whether mail
9372 user agents (MUAs) or mail transport agents (MTAs), must
9373 ensure that they are compatible with the configuration
9374 decisions below. Failure to do this may result in lost
9375 mail, broken <tt>From:</tt> lines, and other serious brain
9380 The mail spool is <file>/var/mail</file> and the interface to
9381 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9382 the FHS). On older systems, the mail spool may be
9383 physically located in <file>/var/spool/mail</file>, but all
9384 access to the mail spool should be via the
9385 <file>/var/mail</file> symlink. The mail spool is part of the
9386 base system and not part of the MTA package.
9390 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9391 programs (such as IMAP daemons) must lock the mailbox in an
9392 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9393 be combined with dot locking. To avoid deadlocks, a program
9394 should use <tt>fcntl()</tt> first and dot locking after
9395 this, or alternatively implement the two locking methods in
9396 a non blocking way<footnote>
9397 If it is not possible to establish both locks, the
9398 system shouldn't wait for the second lock to be
9399 established, but remove the first lock, wait a (random)
9400 time, and start over locking again.
9401 </footnote>. Using the functions <tt>maillock</tt> and
9402 <tt>mailunlock</tt> provided by the
9403 <tt>liblockfile*</tt><footnote>
9404 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9405 to use these functions.
9406 </footnote> packages is the recommended way to realize this.
9410 Mailboxes are generally either mode 600 and owned by
9411 <var>user</var> or mode 660 and owned by
9412 <tt><var>user</var>:mail</tt><footnote>
9413 There are two traditional permission schemes for mail spools:
9414 mode 600 with all mail delivery done by processes running as
9415 the destination user, or mode 660 and owned by group mail with
9416 mail delivery done by a process running as a system user in
9417 group mail. Historically, Debian required mode 660 mail
9418 spools to enable the latter model, but that model has become
9419 increasingly uncommon and the principle of least privilege
9420 indicates that mail systems that use the first model should
9421 use permissions of 600. If delivery to programs is permitted,
9422 it's easier to keep the mail system secure if the delivery
9423 agent runs as the destination user. Debian Policy therefore
9424 permits either scheme.
9425 </footnote>. The local system administrator may choose a
9426 different permission scheme; packages should not make
9427 assumptions about the permission and ownership of mailboxes
9428 unless required (such as when creating a new mailbox). A MUA
9429 may remove a mailbox (unless it has nonstandard permissions) in
9430 which case the MTA or another MUA must recreate it if needed.
9434 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9435 be setgid mail to do the locking mentioned above (and
9436 must obviously avoid accessing other users' mailboxes
9437 using this privilege).</p>
9440 <file>/etc/aliases</file> is the source file for the system mail
9441 aliases (e.g., postmaster, usenet, etc.), it is the one
9442 which the sysadmin and <prgn>postinst</prgn> scripts may
9443 edit. After <file>/etc/aliases</file> is edited the program or
9444 human editing it must call <prgn>newaliases</prgn>. All MTA
9445 packages must come with a <prgn>newaliases</prgn> program,
9446 even if it does nothing, but older MTA packages did not do
9447 this so programs should not fail if <prgn>newaliases</prgn>
9448 cannot be found. Note that because of this, all MTA
9449 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9450 <tt>Replaces: mail-transport-agent</tt> control fields.
9454 The convention of writing <tt>forward to
9455 <var>address</var></tt> in the mailbox itself is not
9456 supported. Use a <tt>.forward</tt> file instead.</p>
9459 The <prgn>rmail</prgn> program used by UUCP
9460 for incoming mail should be <file>/usr/sbin/rmail</file>.
9461 Likewise, <prgn>rsmtp</prgn>, for receiving
9462 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9466 If your package needs to know what hostname to use on (for
9467 example) outgoing news and mail messages which are generated
9468 locally, you should use the file <file>/etc/mailname</file>. It
9469 will contain the portion after the username and <tt>@</tt>
9470 (at) sign for email addresses of users on the machine
9471 (followed by a newline).
9475 Such a package should check for the existence of this file
9476 when it is being configured. If it exists, it should be
9477 used without comment, although an MTA's configuration script
9478 may wish to prompt the user even if it finds that this file
9479 exists. If the file does not exist, the package should
9480 prompt the user for the value (preferably using
9481 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9482 as well as using it in the package's configuration. The
9483 prompt should make it clear that the name will not just be
9484 used by that package. For example, in this situation the
9485 <tt>inn</tt> package could say something like:
9486 <example compact="compact">
9487 Please enter the "mail name" of your system. This is the
9488 hostname portion of the address to be shown on outgoing
9489 news and mail messages. The default is
9490 <var>syshostname</var>, your system's host name. Mail
9491 name ["<var>syshostname</var>"]:
9493 where <var>syshostname</var> is the output of <tt>hostname
9499 <heading>News system configuration</heading>
9502 All the configuration files related to the NNTP (news)
9503 servers and clients should be located under
9504 <file>/etc/news</file>.</p>
9507 There are some configuration issues that apply to a number
9508 of news clients and server packages on the machine. These
9512 <tag><file>/etc/news/organization</file></tag>
9514 A string which should appear as the
9515 organization header for all messages posted
9516 by NNTP clients on the machine
9519 <tag><file>/etc/news/server</file></tag>
9521 Contains the FQDN of the upstream NNTP
9522 server, or localhost if the local machine is
9527 Other global files may be added as required for cross-package news
9534 <heading>Programs for the X Window System</heading>
9537 <heading>Providing X support and package priorities</heading>
9540 Programs that can be configured with support for the X
9541 Window System must be configured to do so and must declare
9542 any package dependencies necessary to satisfy their
9543 runtime requirements when using the X Window System. If
9544 such a package is of higher priority than the X packages
9545 on which it depends, it is required that either the
9546 X-specific components be split into a separate package, or
9547 that an alternative version of the package, which includes
9548 X support, be provided, or that the package's priority be
9554 <heading>Packages providing an X server</heading>
9557 Packages that provide an X server that, directly or
9558 indirectly, communicates with real input and display
9559 hardware should declare in their <tt>Provides</tt> control
9560 field that they provide the virtual
9561 package <tt>xserver</tt>.<footnote>
9562 This implements current practice, and provides an
9563 actual policy for usage of the <tt>xserver</tt>
9564 virtual package which appears in the virtual packages
9565 list. In a nutshell, X servers that interface
9566 directly with the display and input hardware or via
9567 another subsystem (e.g., GGI) should provide
9568 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9569 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9575 <heading>Packages providing a terminal emulator</heading>
9578 Packages that provide a terminal emulator for the X Window
9579 System which meet the criteria listed below should declare in
9580 their <tt>Provides</tt> control field that they provide the
9581 virtual package <tt>x-terminal-emulator</tt>. They should
9582 also register themselves as an alternative for
9583 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9584 20. That alternative should have a slave alternative
9585 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9586 pointing to the corresponding manual page.
9590 To be an <tt>x-terminal-emulator</tt>, a program must:
9591 <list compact="compact">
9593 Be able to emulate a DEC VT100 terminal, or a
9594 compatible terminal.
9598 Support the command-line option <tt>-e
9599 <var>command</var></tt>, which creates a new
9600 terminal window<footnote>
9601 "New terminal window" does not necessarily mean
9602 a new top-level X window directly parented by
9603 the window manager; it could, if the terminal
9604 emulator application were so coded, be a new
9605 "view" in a multiple-document interface (MDI).
9607 and runs the specified <var>command</var>,
9608 interpreting the entirety of the rest of the command
9609 line as a command to pass straight to exec, in the
9610 manner that <tt>xterm</tt> does.
9614 Support the command-line option <tt>-T
9615 <var>title</var></tt>, which creates a new terminal
9616 window with the window title <var>title</var>.
9623 <heading>Packages providing a window manager</heading>
9626 Packages that provide a window manager should declare in
9627 their <tt>Provides</tt> control field that they provide the
9628 virtual package <tt>x-window-manager</tt>. They should also
9629 register themselves as an alternative for
9630 <file>/usr/bin/x-window-manager</file>, with a priority
9631 calculated as follows:
9632 <list compact="compact">
9634 Start with a priority of 20.
9638 If the window manager supports the Debian menu
9639 system, add 20 points if this support is available
9640 in the package's default configuration (i.e., no
9641 configuration files belonging to the system or user
9642 have to be edited to activate the feature); if
9643 configuration files must be modified, add only 10
9649 If the window manager complies with <url
9650 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9651 name="The Window Manager Specification Project">,
9652 written by the <url id="http://www.freedesktop.org/wiki/"
9653 name="Free Desktop Group">, add 40 points.
9657 If the window manager permits the X session to be
9658 restarted using a <em>different</em> window manager
9659 (without killing the X server) in its default
9660 configuration, add 10 points; otherwise add none.
9663 That alternative should have a slave alternative
9664 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9665 pointing to the corresponding manual page.
9670 <heading>Packages providing fonts</heading>
9673 Packages that provide fonts for the X Window
9675 For the purposes of Debian Policy, a "font for the X
9676 Window System" is one which is accessed via X protocol
9677 requests. Fonts for the Linux console, for PostScript
9678 renderer, or any other purpose, do not fit this
9679 definition. Any tool which makes such fonts available
9680 to the X Window System, however, must abide by this
9683 must do a number of things to ensure that they are both
9684 available without modification of the X or font server
9685 configuration, and that they do not corrupt files used by
9686 other font packages to register information about
9690 Fonts of any type supported by the X Window System
9691 must be in a separate binary package from any
9692 executables, libraries, or documentation (except
9693 that specific to the fonts shipped, such as their
9694 license information). If one or more of the fonts
9695 so packaged are necessary for proper operation of
9696 the package with which they are associated the font
9697 package may be Recommended; if the fonts merely
9698 provide an enhancement, a Suggests relationship may
9699 be used. Packages must not Depend on font
9701 This is because the X server may retrieve fonts
9702 from the local file system or over the network
9703 from an X font server; the Debian package system
9704 is empowered to deal only with the local
9710 BDF fonts must be converted to PCF fonts with the
9711 <prgn>bdftopcf</prgn> utility (available in the
9712 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9713 placed in a directory that corresponds to their
9715 <list compact="compact">
9717 100 dpi fonts must be placed in
9718 <file>/usr/share/fonts/X11/100dpi/</file>.
9722 75 dpi fonts must be placed in
9723 <file>/usr/share/fonts/X11/75dpi/</file>.
9727 Character-cell fonts, cursor fonts, and other
9728 low-resolution fonts must be placed in
9729 <file>/usr/share/fonts/X11/misc/</file>.
9735 Type 1 fonts must be placed in
9736 <file>/usr/share/fonts/X11/Type1/</file>. If font
9737 metric files are available, they must be placed here
9742 Subdirectories of <file>/usr/share/fonts/X11/</file>
9743 other than those listed above must be neither
9744 created nor used. (The <file>PEX</file>, <file>CID</file>,
9745 <file>Speedo</file>, and <file>cyrillic</file> directories
9746 are excepted for historical reasons, but installation of
9747 files into these directories remains discouraged.)
9751 Font packages may, instead of placing files directly
9752 in the X font directories listed above, provide
9753 symbolic links in that font directory pointing to
9754 the files' actual location in the filesystem. Such
9755 a location must comply with the FHS.
9759 Font packages should not contain both 75dpi and
9760 100dpi versions of a font. If both are available,
9761 they should be provided in separate binary packages
9762 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9763 the names of the packages containing the
9764 corresponding fonts.
9768 Fonts destined for the <file>misc</file> subdirectory
9769 should not be included in the same package as 75dpi
9770 or 100dpi fonts; instead, they should be provided in
9771 a separate package with <tt>-misc</tt> appended to
9776 Font packages must not provide the files
9777 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9778 <file>fonts.scale</file> in a font directory:
9781 <file>fonts.dir</file> files must not be provided at all.
9785 <file>fonts.alias</file> and <file>fonts.scale</file>
9786 files, if needed, should be provided in the
9788 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9789 where <var>fontdir</var> is the name of the
9791 <file>/usr/share/fonts/X11/</file> where the
9792 package's corresponding fonts are stored
9793 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9794 <var>package</var> is the name of the package
9795 that provides these fonts, and
9796 <var>extension</var> is either <tt>scale</tt>
9797 or <tt>alias</tt>, whichever corresponds to
9804 Font packages must declare a dependency on
9805 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9806 or <tt>Pre-Depends</tt> control field.
9810 Font packages that provide one or more
9811 <file>fonts.scale</file> files as described above must
9812 invoke <prgn>update-fonts-scale</prgn> on each
9813 directory into which they installed fonts
9814 <em>before</em> invoking
9815 <prgn>update-fonts-dir</prgn> on that directory.
9816 This invocation must occur in both the
9817 <prgn>postinst</prgn> (for all arguments) and
9818 <prgn>postrm</prgn> (for all arguments except
9819 <tt>upgrade</tt>) scripts.
9823 Font packages that provide one or more
9824 <file>fonts.alias</file> files as described above must
9825 invoke <prgn>update-fonts-alias</prgn> on each
9826 directory into which they installed fonts. This
9827 invocation must occur in both the
9828 <prgn>postinst</prgn> (for all arguments) and
9829 <prgn>postrm</prgn> (for all arguments except
9830 <tt>upgrade</tt>) scripts.
9834 Font packages must invoke
9835 <prgn>update-fonts-dir</prgn> on each directory into
9836 which they installed fonts. This invocation must
9837 occur in both the <prgn>postinst</prgn> (for all
9838 arguments) and <prgn>postrm</prgn> (for all
9839 arguments except <tt>upgrade</tt>) scripts.
9843 Font packages must not provide alias names for the
9844 fonts they include which collide with alias names
9845 already in use by fonts already packaged.
9849 Font packages must not provide fonts with the same
9850 XLFD registry name as another font already packaged.
9856 <sect1 id="appdefaults">
9857 <heading>Application defaults files</heading>
9860 Application defaults files must be installed in the
9861 directory <file>/etc/X11/app-defaults/</file> (use of a
9862 localized subdirectory of <file>/etc/X11/</file> as described
9863 in the <em>X Toolkit Intrinsics - C Language
9864 Interface</em> manual is also permitted). They must be
9865 registered as <tt>conffile</tt>s or handled as
9866 configuration files.
9870 Customization of programs' X resources may also be
9871 supported with the provision of a file with the same name
9872 as that of the package placed in
9873 the <file>/etc/X11/Xresources/</file> directory, which
9874 must be registered as a <tt>conffile</tt> or handled as a
9875 configuration file.<footnote>
9876 Note that this mechanism is not the same as using
9877 app-defaults; app-defaults are tied to the client
9878 binary on the local file system, whereas X resources
9879 are stored in the X server and affect all connecting
9886 <heading>Installation directory issues</heading>
9889 Historically, packages using the X Window System used a
9890 separate set of installation directories from other packages.
9891 This practice has been discontinued and packages using the X
9892 Window System should now generally be installed in the same
9893 directories as any other package. Specifically, packages must
9894 not install files under the <file>/usr/X11R6/</file> directory
9895 and the <file>/usr/X11R6/</file> directory hierarchy should be
9896 regarded as obsolete.
9900 Include files previously installed under
9901 <file>/usr/X11R6/include/X11/</file> should be installed into
9902 <file>/usr/include/X11/</file>. For files previously
9903 installed into subdirectories of
9904 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9905 determine if subdirectories of <file>/usr/lib/</file> and
9906 <file>/usr/share/</file> can be used. If not, a subdirectory
9907 of <file>/usr/lib/X11/</file> should be used.
9911 Configuration files for window, display, or session managers
9912 or other applications that are tightly integrated with the X
9913 Window System may be placed in a subdirectory
9914 of <file>/etc/X11/</file> corresponding to the package name.
9915 Other X Window System applications should use
9916 the <file>/etc/</file> directory unless otherwise mandated by
9917 policy (such as for <ref id="appdefaults">).
9923 <heading>Perl programs and modules</heading>
9926 Perl programs and modules should follow the current Perl policy.
9930 The Perl policy can be found in the <tt>perl-policy</tt>
9931 files in the <tt>debian-policy</tt> package.
9932 It is also available from the Debian web mirrors at
9933 <tt><url name="/doc/packaging-manuals/perl-policy/"
9934 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9939 <heading>Emacs lisp programs</heading>
9942 Please refer to the "Debian Emacs Policy" for details of how to
9943 package emacs lisp programs.
9947 The Emacs policy is available in
9948 <file>debian-emacs-policy.gz</file> of the
9949 <package>emacsen-common</package> package.
9950 It is also available from the Debian web mirrors at
9951 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9952 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9957 <heading>Games</heading>
9960 The permissions on <file>/var/games</file> are mode 755, owner
9961 <tt>root</tt> and group <tt>root</tt>.
9965 Each game decides on its own security policy.</p>
9968 Games which require protected, privileged access to
9969 high-score files, saved games, etc., may be made
9970 set-<em>group</em>-id (mode 2755) and owned by
9971 <tt>root:games</tt>, and use files and directories with
9972 appropriate permissions (770 <tt>root:games</tt>, for
9973 example). They must not be made
9974 set-<em>user</em>-id, as this causes security problems. (If
9975 an attacker can subvert any set-user-id game they can
9976 overwrite the executable of any other, causing other players
9977 of these games to run a Trojan horse program. With a
9978 set-group-id game the attacker only gets access to less
9979 important game data, and if they can get at the other
9980 players' accounts at all it will take considerably more
9984 Some packages, for example some fortune cookie programs, are
9985 configured by the upstream authors to install with their
9986 data files or other static information made unreadable so
9987 that they can only be accessed through set-id programs
9988 provided. You should not do this in a Debian package: anyone can
9989 download the <file>.deb</file> file and read the data from it,
9990 so there is no point making the files unreadable. Not
9991 making the files unreadable also means that you don't have
9992 to make so many programs set-id, which reduces the risk of a
9996 As described in the FHS, binaries of games should be
9997 installed in the directory <file>/usr/games</file>. This also
9998 applies to games that use the X Window System. Manual pages
9999 for games (X and non-X games) should be installed in
10000 <file>/usr/share/man/man6</file>.</p>
10006 <heading>Documentation</heading>
10009 <heading>Manual pages</heading>
10012 You should install manual pages in <prgn>nroff</prgn> source
10013 form, in appropriate places under <file>/usr/share/man</file>.
10014 You should only use sections 1 to 9 (see the FHS for more
10015 details). You must not install a pre-formatted "cat page".
10019 Each program, utility, and function should have an
10020 associated manual page included in the same package. It is
10021 suggested that all configuration files also have a manual
10022 page included as well. Manual pages for protocols and other
10023 auxiliary things are optional.
10027 If no manual page is available, this is considered as a bug
10028 and should be reported to the Debian Bug Tracking System (the
10029 maintainer of the package is allowed to write this bug report
10030 themselves, if they so desire). Do not close the bug report
10031 until a proper man page is available.<footnote>
10032 It is not very hard to write a man page. See the
10033 <url id="http://www.schweikhardt.net/man_page_howto.html"
10034 name="Man-Page-HOWTO">,
10035 <manref name="man" section="7">, the examples created
10036 by <prgn>dh_make</prgn>, the helper
10037 program <prgn>help2man</prgn>, or the
10038 directory <file>/usr/share/doc/man-db/examples</file>.
10043 You may forward a complaint about a missing man page to the
10044 upstream authors, and mark the bug as forwarded in the
10045 Debian bug tracking system. Even though the GNU Project do
10046 not in general consider the lack of a man page to be a bug,
10047 we do; if they tell you that they don't consider it a bug
10048 you should leave the bug in our bug tracking system open
10053 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10057 If one man page needs to be accessible via several names it
10058 is better to use a symbolic link than the <file>.so</file>
10059 feature, but there is no need to fiddle with the relevant
10060 parts of the upstream source to change from <file>.so</file> to
10061 symlinks: don't do it unless it's easy. You should not
10062 create hard links in the manual page directories, nor put
10063 absolute filenames in <file>.so</file> directives. The filename
10064 in a <file>.so</file> in a man page should be relative to the
10065 base of the man page tree (usually
10066 <file>/usr/share/man</file>). If you do not create any links
10067 (whether symlinks, hard links, or <tt>.so</tt> directives)
10068 in the file system to the alternate names of the man page,
10069 then you should not rely on <prgn>man</prgn> finding your
10070 man page under those names based solely on the information in
10071 the man page's header.<footnote>
10072 Supporting this in <prgn>man</prgn> often requires
10073 unreasonable processing time to find a manual page or to
10074 report that none exists, and moves knowledge into man's
10075 database that would be better left in the file system.
10076 This support is therefore deprecated and will cease to
10077 be present in the future.
10082 Manual pages in locale-specific subdirectories of
10083 <file>/usr/share/man</file> should use either UTF-8 or the usual
10084 legacy encoding for that language (normally the one corresponding
10085 to the shortest relevant locale name in
10086 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10087 <file>/usr/share/man/fr</file> should use either UTF-8 or
10088 ISO-8859-1.<footnote>
10089 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10090 use. In future, all manual pages will be required to use
10096 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10097 included in the subdirectory name unless it indicates a
10098 significant difference in the language, as this excludes
10099 speakers of the language in other countries.<footnote>
10100 At the time of writing, Chinese and Portuguese are the main
10101 languages with such differences, so <file>pt_BR</file>,
10102 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10107 If a localized version of a manual page is provided, it should
10108 either be up-to-date or it should be obvious to the reader that
10109 it is outdated and the original manual page should be used
10110 instead. This can be done either by a note at the beginning of
10111 the manual page or by showing the missing or changed portions in
10112 the original language instead of the target language.
10117 <heading>Info documents</heading>
10120 Info documents should be installed in <file>/usr/share/info</file>.
10121 They should be compressed with <tt>gzip -9</tt>.
10125 The <prgn>install-info</prgn> program maintains a directory of
10126 installed info documents in <file>/usr/share/info/dir</file> for
10127 the use of info readers.<footnote>
10128 It was previously necessary for packages installing info
10129 documents to run <prgn>install-info</prgn> from maintainer
10130 scripts. This is no longer necessary. The installation
10131 system now uses dpkg triggers.
10133 This file must not be included in packages. Packages containing
10134 info documents should depend on <tt>dpkg (>= 1.15.4) |
10135 install-info</tt> to ensure that the directory file is properly
10136 rebuilt during partial upgrades from Debian 5.0 (lenny) and
10141 Info documents should contain section and directory entry
10142 information in the document for the use
10143 of <prgn>install-info</prgn>. The section should be specified
10144 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10145 space and the section of this info page. The directory entry or
10146 entries should be included between
10147 a <tt>START-INFO-DIR-ENTRY</tt> line and
10148 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10150 INFO-DIR-SECTION Individual utilities
10151 START-INFO-DIR-ENTRY
10152 * example: (example). An example info directory entry.
10155 To determine which section to use, you should look
10156 at <file>/usr/share/info/dir</file> on your system and choose
10157 the most relevant (or create a new section if none of the
10158 current sections are relevant).<footnote>
10159 Normally, info documents are generated from Texinfo source.
10160 To include this information in the generated info document, if
10161 it is absent, add commands like:
10163 @dircategory Individual utilities
10165 * example: (example). An example info directory entry.
10168 to the Texinfo source of the document and ensure that the info
10169 documents are rebuilt from source during the package build.
10175 <heading>Additional documentation</heading>
10178 Any additional documentation that comes with the package may
10179 be installed at the discretion of the package maintainer.
10180 Plain text documentation should be installed in the directory
10181 <file>/usr/share/doc/<var>package</var></file>, where
10182 <var>package</var> is the name of the package, and
10183 compressed with <tt>gzip -9</tt> unless it is small.
10187 If a package comes with large amounts of documentation which
10188 many users of the package will not require you should create
10189 a separate binary package to contain it, so that it does not
10190 take up disk space on the machines of users who do not need
10191 or want it installed.</p>
10194 It is often a good idea to put text information files
10195 (<file>README</file>s, changelogs, and so forth) that come with
10196 the source package in <file>/usr/share/doc/<var>package</var></file>
10197 in the binary package. However, you don't need to install
10198 the instructions for building and installing the package, of
10202 Packages must not require the existence of any files in
10203 <file>/usr/share/doc/</file> in order to function
10205 The system administrator should be able to
10206 delete files in <file>/usr/share/doc/</file> without causing
10207 any programs to break.
10209 Any files that are referenced by programs but are also
10210 useful as stand alone documentation should be installed under
10211 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10212 <file>/usr/share/doc/<var>package</var></file>.
10216 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10217 link to another directory in <file>/usr/share/doc</file> only if
10218 the two packages both come from the same source and the
10219 first package Depends on the second.<footnote>
10221 Please note that this does not override the section on
10222 changelog files below, so the file
10223 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10224 must refer to the changelog for the current version of
10225 <var>package</var> in question. In practice, this means
10226 that the sources of the target and the destination of the
10227 symlink must be the same (same source package and
10234 Former Debian releases placed all additional documentation
10235 in <file>/usr/doc/<var>package</var></file>. This has been
10236 changed to <file>/usr/share/doc/<var>package</var></file>,
10237 and packages must not put documentation in the directory
10238 <file>/usr/doc/<var>package</var></file>. <footnote>
10239 At this phase of the transition, we no longer require a
10240 symbolic link in <file>/usr/doc/</file>. At a later point,
10241 policy shall change to make the symbolic links a bug.
10247 <heading>Preferred documentation formats</heading>
10250 The unification of Debian documentation is being carried out
10254 If your package comes with extensive documentation in a
10255 markup format that can be converted to various other formats
10256 you should if possible ship HTML versions in a binary
10257 package, in the directory
10258 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10259 its subdirectories.<footnote>
10260 The rationale: The important thing here is that HTML
10261 docs should be available in <em>some</em> package, not
10262 necessarily in the main binary package.
10267 Other formats such as PostScript may be provided at the
10268 package maintainer's discretion.
10272 <sect id="copyrightfile">
10273 <heading>Copyright information</heading>
10276 Every package must be accompanied by a verbatim copy of its
10277 copyright information and distribution license in the file
10278 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10279 file must neither be compressed nor be a symbolic link.
10283 In addition, the copyright file must say where the upstream
10284 sources (if any) were obtained, and should name the original
10289 Packages in the <em>contrib</em> or <em>non-free</em> archive
10290 areas should state in the copyright file that the package is not
10291 part of the Debian distribution and briefly explain why.
10295 A copy of the file which will be installed in
10296 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10297 be in <file>debian/copyright</file> in the source package.
10301 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10302 link to another directory in <file>/usr/share/doc</file> only if
10303 the two packages both come from the same source and the
10304 first package Depends on the second. These rules are important
10305 because <file>copyright</file> files must be extractable by
10310 Packages distributed under the Apache license (version 2.0), the
10311 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10312 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10313 1.3) should refer to the corresponding files
10314 under <file>/usr/share/common-licenses</file>,<footnote>
10317 <file>/usr/share/common-licenses/Apache-2.0</file>,
10318 <file>/usr/share/common-licenses/Artistic</file>,
10319 <file>/usr/share/common-licenses/GPL-1</file>,
10320 <file>/usr/share/common-licenses/GPL-2</file>,
10321 <file>/usr/share/common-licenses/GPL-3</file>,
10322 <file>/usr/share/common-licenses/LGPL-2</file>,
10323 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10324 <file>/usr/share/common-licenses/LGPL-3</file>,
10325 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10326 <file>/usr/share/common-licenses/GFDL-1.3</file>
10327 respectively. The University of California BSD license is
10328 also included in <package>base-files</package> as
10329 <file>/usr/share/common-licenses/BSD</file>, but given the
10330 brevity of this license, its specificity to code whose
10331 copyright is held by the Regents of the University of
10332 California, and the frequency of minor wording changes, its
10333 text should be included in the copyright file rather than
10334 referencing this file.
10336 </footnote> rather than quoting them in the copyright
10341 You should not use the copyright file as a general <file>README</file>
10342 file. If your package has such a file it should be
10343 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10344 <file>README.Debian</file> or some other appropriate place.</p>
10348 <heading>Examples</heading>
10351 Any examples (configurations, source files, whatever),
10352 should be installed in a directory
10353 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10354 files should not be referenced by any program: they're there
10355 for the benefit of the system administrator and users as
10356 documentation only. Architecture-specific example files
10357 should be installed in a directory
10358 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10360 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10361 latter directory itself may be a symbolic link to the
10366 If the purpose of a package is to provide examples, then the
10367 example files may be installed into
10368 <file>/usr/share/doc/<var>package</var></file>.
10372 <sect id="changelogs">
10373 <heading>Changelog files</heading>
10376 Packages that are not Debian-native must contain a
10377 compressed copy of the <file>debian/changelog</file> file from
10378 the Debian source tree in
10379 <file>/usr/share/doc/<var>package</var></file> with the name
10380 <file>changelog.Debian.gz</file>.
10384 If an upstream changelog is available, it should be accessible as
10385 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10386 plain text. If the upstream changelog is distributed in
10387 HTML, it should be made available in that form as
10388 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10389 and a plain text <file>changelog.gz</file> should be generated
10390 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10391 the upstream changelog files do not already conform to this
10392 naming convention, then this may be achieved either by
10393 renaming the files, or by adding a symbolic link, at the
10394 maintainer's discretion.<footnote>
10395 Rationale: People should not have to look in places for
10396 upstream changelogs merely because they are given
10397 different names or are distributed in HTML format.
10402 All of these files should be installed compressed using
10403 <tt>gzip -9</tt>, as they will become large with time even
10404 if they start out small.
10408 If the package has only one changelog which is used both as
10409 the Debian changelog and the upstream one because there is
10410 no separate upstream maintainer then that changelog should
10411 usually be installed as
10412 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10413 there is a separate upstream maintainer, but no upstream
10414 changelog, then the Debian changelog should still be called
10415 <file>changelog.Debian.gz</file>.
10419 For details about the format and contents of the Debian
10420 changelog file, please see <ref id="dpkgchangelog">.
10425 <appendix id="pkg-scope">
10426 <heading>Introduction and scope of these appendices</heading>
10429 These appendices are taken essentially verbatim from the
10430 now-deprecated Packaging Manual, version 3.2.1.0. They are
10431 the chapters which are likely to be of use to package
10432 maintainers and which have not already been included in the
10433 policy document itself. Most of these sections are very likely
10434 not relevant to policy; they should be treated as
10435 documentation for the packaging system. Please note that these
10436 appendices are included for convenience, and for historical
10437 reasons: they used to be part of policy package, and they have
10438 not yet been incorporated into dpkg documentation. However,
10439 they still have value, and hence they are presented here.
10443 They have not yet been checked to ensure that they are
10444 compatible with the contents of policy, and if there are any
10445 contradictions, the version in the main policy document takes
10446 precedence. The remaining chapters of the old Packaging
10447 Manual have also not been read in detail to ensure that there
10448 are not parts which have been left out. Both of these will be
10449 done in due course.
10453 Certain parts of the Packaging manual were integrated into the
10454 Policy Manual proper, and removed from the appendices. Links
10455 have been placed from the old locations to the new ones.
10459 <prgn>dpkg</prgn> is a suite of programs for creating binary
10460 package files and installing and removing them on Unix
10462 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10463 work on or be ported to other systems.
10468 The binary packages are designed for the management of
10469 installed executable programs (usually compiled binaries) and
10470 their associated data, though source code examples and
10471 documentation are provided as part of some packages.</p>
10474 This manual describes the technical aspects of creating Debian
10475 binary packages (<file>.deb</file> files). It documents the
10476 behavior of the package management programs
10477 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10478 they interact with packages.</p>
10481 It also documents the interaction between
10482 <prgn>dselect</prgn>'s core and the access method scripts it
10483 uses to actually install the selected packages, and describes
10484 how to create a new access method.</p>
10487 This manual does not go into detail about the options and
10488 usage of the package building and installation tools. It
10489 should therefore be read in conjunction with those programs'
10494 The utility programs which are provided with <prgn>dpkg</prgn>
10495 for managing various system configuration and similar issues,
10496 such as <prgn>update-rc.d</prgn> and
10497 <prgn>install-info</prgn>, are not described in detail here -
10498 please see their man pages.
10502 It is assumed that the reader is reasonably familiar with the
10503 <prgn>dpkg</prgn> System Administrators' manual.
10504 Unfortunately this manual does not yet exist.
10508 The Debian version of the FSF's GNU hello program is provided as
10509 an example for people wishing to create Debian packages. However,
10510 while the examples are helpful, they do not replace the need to
10511 read and follow the Policy and Programmer's Manual.</p>
10514 <appendix id="pkg-binarypkg">
10515 <heading>Binary packages (from old Packaging Manual)</heading>
10518 The binary package has two main sections. The first part
10519 consists of various control information files and scripts used
10520 by <prgn>dpkg</prgn> when installing and removing. See <ref
10521 id="pkg-controlarea">.
10525 The second part is an archive containing the files and
10526 directories to be installed.
10530 In the future binary packages may also contain other
10531 components, such as checksums and digital signatures. The
10532 format for the archive is described in full in the
10533 <file>deb(5)</file> man page.
10537 <sect id="pkg-bincreating"><heading>Creating package files -
10538 <prgn>dpkg-deb</prgn>
10542 All manipulation of binary package files is done by
10543 <prgn>dpkg-deb</prgn>; it's the only program that has
10544 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10545 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10546 will spot that the options requested are appropriate to
10547 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10552 In order to create a binary package you must make a
10553 directory tree which contains all the files and directories
10554 you want to have in the file system data part of the package.
10555 In Debian-format source packages this directory is usually
10556 <file>debian/tmp</file>, relative to the top of the package's
10561 They should have the locations (relative to the root of the
10562 directory tree you're constructing) ownerships and
10563 permissions which you want them to have on the system when
10564 they are installed.
10568 With current versions of <prgn>dpkg</prgn> the uid/username
10569 and gid/groupname mappings for the users and groups being
10570 used should be the same on the system where the package is
10571 built and the one where it is installed.
10575 You need to add one special directory to the root of the
10576 miniature file system tree you're creating:
10577 <prgn>DEBIAN</prgn>. It should contain the control
10578 information files, notably the binary package control file
10579 (see <ref id="pkg-controlfile">).
10583 The <prgn>DEBIAN</prgn> directory will not appear in the
10584 file system archive of the package, and so won't be installed
10585 by <prgn>dpkg</prgn> when the package is unpacked.
10589 When you've prepared the package, you should invoke:
10591 dpkg --build <var>directory</var>
10596 This will build the package in
10597 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10598 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10599 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10600 build the package.)
10604 See the man page <manref name="dpkg-deb" section="8"> for details of how
10605 to examine the contents of this newly-created file. You may find the
10606 output of following commands enlightening:
10608 dpkg-deb --info <var>filename</var>.deb
10609 dpkg-deb --contents <var>filename</var>.deb
10610 dpkg --contents <var>filename</var>.deb
10612 To view the copyright file for a package you could use this command:
10614 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10619 <sect id="pkg-controlarea">
10620 <heading>Package control information files</heading>
10623 The control information portion of a binary package is a
10624 collection of files with names known to <prgn>dpkg</prgn>.
10625 It will treat the contents of these files specially - some
10626 of them contain information used by <prgn>dpkg</prgn> when
10627 installing or removing the package; others are scripts which
10628 the package maintainer wants <prgn>dpkg</prgn> to run.
10632 It is possible to put other files in the package control
10633 information file area, but this is not generally a good idea
10634 (though they will largely be ignored).
10638 Here is a brief list of the control information files supported
10639 by <prgn>dpkg</prgn> and a summary of what they're used for.
10644 <tag><tt>control</tt>
10647 This is the key description file used by
10648 <prgn>dpkg</prgn>. It specifies the package's name
10649 and version, gives its description for the user,
10650 states its relationships with other packages, and so
10651 forth. See <ref id="sourcecontrolfiles"> and
10652 <ref id="binarycontrolfiles">.
10656 It is usually generated automatically from information
10657 in the source package by the
10658 <prgn>dpkg-gencontrol</prgn> program, and with
10659 assistance from <prgn>dpkg-shlibdeps</prgn>.
10660 See <ref id="pkg-sourcetools">.
10664 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10669 These are executable files (usually scripts) which
10670 <prgn>dpkg</prgn> runs during installation, upgrade
10671 and removal of packages. They allow the package to
10672 deal with matters which are particular to that package
10673 or require more complicated processing than that
10674 provided by <prgn>dpkg</prgn>. Details of when and
10675 how they are called are in <ref id="maintainerscripts">.
10679 It is very important to make these scripts idempotent.
10680 See <ref id="idempotency">.
10684 The maintainer scripts are not guaranteed to run with a
10685 controlling terminal and may not be able to interact with
10686 the user. See <ref id="controllingterminal">.
10690 <tag><tt>conffiles</tt>
10693 This file contains a list of configuration files which
10694 are to be handled automatically by <prgn>dpkg</prgn>
10695 (see <ref id="pkg-conffiles">). Note that not necessarily
10696 every configuration file should be listed here.
10699 <tag><tt>shlibs</tt>
10702 This file contains a list of the shared libraries
10703 supplied by the package, with dependency details for
10704 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10705 when it determines what dependencies are required in a
10706 package control file. The <tt>shlibs</tt> file format
10707 is described on <ref id="shlibs">.
10712 <sect id="pkg-controlfile">
10713 <heading>The main control information file: <tt>control</tt></heading>
10716 The most important control information file used by
10717 <prgn>dpkg</prgn> when it installs a package is
10718 <tt>control</tt>. It contains all the package's "vital
10723 The binary package control files of packages built from
10724 Debian sources are made by a special tool,
10725 <prgn>dpkg-gencontrol</prgn>, which reads
10726 <file>debian/control</file> and <file>debian/changelog</file> to
10727 find the information it needs. See <ref id="pkg-sourcepkg"> for
10732 The fields in binary package control files are listed in
10733 <ref id="binarycontrolfiles">.
10737 A description of the syntax of control files and the purpose
10738 of the fields is available in <ref id="controlfields">.
10743 <heading>Time Stamps</heading>
10746 See <ref id="timestamps">.
10751 <appendix id="pkg-sourcepkg">
10752 <heading>Source packages (from old Packaging Manual) </heading>
10755 The Debian binary packages in the distribution are generated
10756 from Debian sources, which are in a special format to assist
10757 the easy and automatic building of binaries.
10760 <sect id="pkg-sourcetools">
10761 <heading>Tools for processing source packages</heading>
10764 Various tools are provided for manipulating source packages;
10765 they pack and unpack sources and help build of binary
10766 packages and help manage the distribution of new versions.
10770 They are introduced and typical uses described here; see
10771 <manref name="dpkg-source" section="1"> for full
10772 documentation about their arguments and operation.
10776 For examples of how to construct a Debian source package,
10777 and how to use those utilities that are used by Debian
10778 source packages, please see the <prgn>hello</prgn> example
10782 <sect1 id="pkg-dpkg-source">
10784 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10789 This program is frequently used by hand, and is also
10790 called from package-independent automated building scripts
10791 such as <prgn>dpkg-buildpackage</prgn>.
10795 To unpack a package it is typically invoked with
10797 dpkg-source -x <var>.../path/to/filename</var>.dsc
10802 with the <file><var>filename</var>.tar.gz</file> and
10803 <file><var>filename</var>.diff.gz</file> (if applicable) in
10804 the same directory. It unpacks into
10805 <file><var>package</var>-<var>version</var></file>, and if
10807 <file><var>package</var>-<var>version</var>.orig</file>, in
10808 the current directory.
10812 To create a packed source archive it is typically invoked:
10814 dpkg-source -b <var>package</var>-<var>version</var>
10819 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10820 <file>.diff.gz</file> (if appropriate) in the current
10821 directory. <prgn>dpkg-source</prgn> does not clean the
10822 source tree first - this must be done separately if it is
10827 See also <ref id="pkg-sourcearchives">.</p>
10831 <sect1 id="pkg-dpkg-buildpackage">
10833 <prgn>dpkg-buildpackage</prgn> - overall package-building
10838 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10839 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10840 targets <tt>clean</tt>, <tt>build</tt> and
10841 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10842 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10843 source and binary package upload.
10847 It is usually invoked by hand from the top level of the
10848 built or unbuilt source directory. It may be invoked with
10849 no arguments; useful arguments include:
10850 <taglist compact="compact">
10851 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10854 Do not sign the <tt>.changes</tt> file or the
10855 source package <tt>.dsc</tt> file, respectively.</p>
10857 <tag><tt>-p<var>sign-command</var></tt></tag>
10860 Invoke <var>sign-command</var> instead of finding
10861 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10862 <var>sign-command</var> must behave just like
10863 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10865 <tag><tt>-r<var>root-command</var></tt></tag>
10868 When root privilege is required, invoke the command
10869 <var>root-command</var>. <var>root-command</var>
10870 should invoke its first argument as a command, from
10871 the <prgn>PATH</prgn> if necessary, and pass its
10872 second and subsequent arguments to the command it
10873 calls. If no <var>root-command</var> is supplied
10874 then <var>dpkg-buildpackage</var> will take no
10875 special action to gain root privilege, so that for
10876 most packages it will have to be invoked as root to
10879 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10882 Two types of binary-only build and upload - see
10883 <manref name="dpkg-source" section="1">.
10890 <sect1 id="pkg-dpkg-gencontrol">
10892 <prgn>dpkg-gencontrol</prgn> - generates binary package
10897 This program is usually called from <file>debian/rules</file>
10898 (see <ref id="pkg-sourcetree">) in the top level of the source
10903 This is usually done just before the files and directories in the
10904 temporary directory tree where the package is being built have their
10905 permissions and ownerships set and the package is constructed using
10906 <prgn>dpkg-deb/</prgn>
10908 This is so that the control file which is produced has
10909 the right permissions
10914 <prgn>dpkg-gencontrol</prgn> must be called after all the
10915 files which are to go into the package have been placed in
10916 the temporary build directory, so that its calculation of
10917 the installed size of a package is correct.
10921 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10922 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10923 variable substitutions created by
10924 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10929 For a package which generates only one binary package, and
10930 which builds it in <file>debian/tmp</file> relative to the top
10931 of the source package, it is usually sufficient to call
10932 <prgn>dpkg-gencontrol</prgn>.
10936 Sources which build several binaries will typically need
10939 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10940 </example> The <tt>-P</tt> tells
10941 <prgn>dpkg-gencontrol</prgn> that the package is being
10942 built in a non-default directory, and the <tt>-p</tt>
10943 tells it which package's control file should be generated.
10947 <prgn>dpkg-gencontrol</prgn> also adds information to the
10948 list of files in <file>debian/files</file>, for the benefit of
10949 (for example) a future invocation of
10950 <prgn>dpkg-genchanges</prgn>.</p>
10953 <sect1 id="pkg-dpkg-distaddfile">
10955 <prgn>dpkg-distaddfile</prgn> - adds a file to
10956 <file>debian/files</file>
10960 Some packages' uploads need to include files other than
10961 the source and binary package files.
10965 <prgn>dpkg-distaddfile</prgn> adds a file to the
10966 <file>debian/files</file> file so that it will be included in
10967 the <file>.changes</file> file when
10968 <prgn>dpkg-genchanges</prgn> is run.
10972 It is usually invoked from the <tt>binary</tt> target of
10973 <file>debian/rules</file>:
10975 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10977 The <var>filename</var> is relative to the directory where
10978 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10979 is usually the directory above the top level of the source
10980 tree. The <file>debian/rules</file> target should put the
10981 file there just before or just after calling
10982 <prgn>dpkg-distaddfile</prgn>.
10986 The <var>section</var> and <var>priority</var> are passed
10987 unchanged into the resulting <file>.changes</file> file.
10992 <sect1 id="pkg-dpkg-genchanges">
10994 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10995 upload control file
10999 This program is usually called by package-independent
11000 automatic building scripts such as
11001 <prgn>dpkg-buildpackage</prgn>, but it may also be called
11006 It is usually called in the top level of a built source
11007 tree, and when invoked with no arguments will print out a
11008 straightforward <file>.changes</file> file based on the
11009 information in the source package's changelog and control
11010 file and the binary and source packages which should have
11016 <sect1 id="pkg-dpkg-parsechangelog">
11018 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11019 representation of a changelog
11023 This program is used internally by
11024 <prgn>dpkg-source</prgn> et al. It may also occasionally
11025 be useful in <file>debian/rules</file> and elsewhere. It
11026 parses a changelog, <file>debian/changelog</file> by default,
11027 and prints a control-file format representation of the
11028 information in it to standard output.
11032 <sect1 id="pkg-dpkg-architecture">
11034 <prgn>dpkg-architecture</prgn> - information about the build and
11039 This program can be used manually, but is also invoked by
11040 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
11041 environment or make variables which specify the build and host
11042 architecture for the package building process.
11047 <sect id="pkg-sourcetree">
11048 <heading>The Debian package source tree</heading>
11051 The source archive scheme described later is intended to
11052 allow a Debian package source tree with some associated
11053 control information to be reproduced and transported easily.
11054 The Debian package source tree is a version of the original
11055 program with certain files added for the benefit of the
11056 packaging process, and with any other changes required
11057 made to the rest of the source code and installation
11062 The extra files created for Debian are in the subdirectory
11063 <file>debian</file> of the top level of the Debian package
11064 source tree. They are described below.
11067 <sect1 id="pkg-debianrules">
11068 <heading><file>debian/rules</file> - the main building script</heading>
11071 See <ref id="debianrules">.
11075 <sect1 id="pkg-srcsubstvars">
11076 <heading><file>debian/substvars</file> and variable substitutions</heading>
11079 See <ref id="substvars">.
11085 <heading><file>debian/files</file></heading>
11088 See <ref id="debianfiles">.
11092 <sect1><heading><file>debian/tmp</file>
11096 This is the canonical temporary location for the
11097 construction of binary packages by the <tt>binary</tt>
11098 target. The directory <file>tmp</file> serves as the root of
11099 the file system tree as it is being constructed (for
11100 example, by using the package's upstream makefiles install
11101 targets and redirecting the output there), and it also
11102 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11103 id="pkg-bincreating">.
11107 If several binary packages are generated from the same
11108 source tree it is usual to use several
11109 <file>debian/tmp<var>something</var></file> directories, for
11110 example <file>tmp-a</file> or <file>tmp-doc</file>.
11114 Whatever <file>tmp</file> directories are created and used by
11115 <tt>binary</tt> must of course be removed by the
11116 <tt>clean</tt> target.</p></sect1>
11120 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11124 As it exists on the FTP site, a Debian source package
11125 consists of three related files. You must have the right
11126 versions of all three to be able to use them.
11131 <tag>Debian source control file - <tt>.dsc</tt></tag>
11133 This file is a control file used by <prgn>dpkg-source</prgn>
11134 to extract a source package.
11135 See <ref id="debiansourcecontrolfiles">.
11139 Original source archive -
11141 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11147 This is a compressed (with <tt>gzip -9</tt>)
11148 <prgn>tar</prgn> file containing the source code from
11149 the upstream authors of the program.
11154 Debian package diff -
11156 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11162 This is a unified context diff (<tt>diff -u</tt>)
11163 giving the changes which are required to turn the
11164 original source into the Debian source. These changes
11165 may only include editing and creating plain files.
11166 The permissions of files, the targets of symbolic
11167 links and the characteristics of special files or
11168 pipes may not be changed and no files may be removed
11173 All the directories in the diff must exist, except the
11174 <file>debian</file> subdirectory of the top of the source
11175 tree, which will be created by
11176 <prgn>dpkg-source</prgn> if necessary when unpacking.
11180 The <prgn>dpkg-source</prgn> program will
11181 automatically make the <file>debian/rules</file> file
11182 executable (see below).</p></item>
11187 If there is no original source code - for example, if the
11188 package is specially prepared for Debian or the Debian
11189 maintainer is the same as the upstream maintainer - the
11190 format is slightly different: then there is no diff, and the
11192 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11193 and preferably contains a directory named
11194 <file><var>package</var>-<var>version</var></file>.
11199 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11202 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11203 Debian source package. However, if it is not available it
11204 is possible to unpack a Debian source archive as follows:
11205 <enumlist compact="compact">
11208 Untar the tarfile, which will create a <file>.orig</file>
11212 <p>Rename the <file>.orig</file> directory to
11213 <file><var>package</var>-<var>version</var></file>.</p>
11217 Create the subdirectory <file>debian</file> at the top of
11218 the source tree.</p>
11220 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11222 <item><p>Untar the tarfile again if you want a copy of the original
11223 source code alongside the Debian version.</p>
11228 It is not possible to generate a valid Debian source archive
11229 without using <prgn>dpkg-source</prgn>. In particular,
11230 attempting to use <prgn>diff</prgn> directly to generate the
11231 <file>.diff.gz</file> file will not work.
11235 <heading>Restrictions on objects in source packages</heading>
11238 The source package may not contain any hard links
11240 This is not currently detected when building source
11241 packages, but only when extracting
11245 Hard links may be permitted at some point in the
11246 future, but would require a fair amount of
11248 </footnote>, device special files, sockets or setuid or
11251 Setgid directories are allowed.
11256 The source packaging tools manage the changes between the
11257 original and Debian source using <prgn>diff</prgn> and
11258 <prgn>patch</prgn>. Turning the original source tree as
11259 included in the <file>.orig.tar.gz</file> into the Debian
11260 package source must not involve any changes which cannot be
11261 handled by these tools. Problematic changes which cause
11262 <prgn>dpkg-source</prgn> to halt with an error when
11263 building the source package are:
11264 <list compact="compact">
11265 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11267 <item><p>Changing the targets of symbolic links.</p>
11269 <item><p>Creating directories, other than <file>debian</file>.</p>
11271 <item><p>Changes to the contents of binary files.</p></item>
11272 </list> Changes which cause <prgn>dpkg-source</prgn> to
11273 print a warning but continue anyway are:
11274 <list compact="compact">
11277 Removing files, directories or symlinks.
11279 Renaming a file is not treated specially - it is
11280 seen as the removal of the old file (which
11281 generates a warning, but is otherwise ignored),
11282 and the creation of the new one.
11288 Changed text files which are missing the usual final
11289 newline (either in the original or the modified
11294 Changes which are not represented, but which are not detected by
11295 <prgn>dpkg-source</prgn>, are:
11296 <list compact="compact">
11297 <item><p>Changing the permissions of files (other than
11298 <file>debian/rules</file>) and directories.</p></item>
11303 The <file>debian</file> directory and <file>debian/rules</file>
11304 are handled specially by <prgn>dpkg-source</prgn> - before
11305 applying the changes it will create the <file>debian</file>
11306 directory, and afterwards it will make
11307 <file>debian/rules</file> world-executable.
11313 <appendix id="pkg-controlfields">
11314 <heading>Control files and their fields (from old Packaging Manual)</heading>
11317 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11318 data in a common format, known as control files. Binary and
11319 source packages have control data as do the <file>.changes</file>
11320 files which control the installation of uploaded files, and
11321 <prgn>dpkg</prgn>'s internal databases are in a similar
11326 <heading>Syntax of control files</heading>
11329 See <ref id="controlsyntax">.
11333 It is important to note that there are several fields which
11334 are optional as far as <prgn>dpkg</prgn> and the related
11335 tools are concerned, but which must appear in every Debian
11336 package, or whose omission may cause problems.
11341 <heading>List of fields</heading>
11344 See <ref id="controlfieldslist">.
11348 This section now contains only the fields that didn't belong
11349 to the Policy manual.
11352 <sect1 id="pkg-f-Filename">
11353 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11356 These fields in <tt>Packages</tt> files give the
11357 filename(s) of (the parts of) a package in the
11358 distribution directories, relative to the root of the
11359 Debian hierarchy. If the package has been split into
11360 several parts the parts are all listed in order, separated
11365 <sect1 id="pkg-f-Size">
11366 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11369 These fields in <file>Packages</file> files give the size (in
11370 bytes, expressed in decimal) and MD5 checksum of the
11371 file(s) which make(s) up a binary package in the
11372 distribution. If the package is split into several parts
11373 the values for the parts are listed in order, separated by
11378 <sect1 id="pkg-f-Status">
11379 <heading><tt>Status</tt></heading>
11382 This field in <prgn>dpkg</prgn>'s status file records
11383 whether the user wants a package installed, removed or
11384 left alone, whether it is broken (requiring
11385 re-installation) or not and what its current state on the
11386 system is. Each of these pieces of information is a
11391 <sect1 id="pkg-f-Config-Version">
11392 <heading><tt>Config-Version</tt></heading>
11395 If a package is not installed or not configured, this
11396 field in <prgn>dpkg</prgn>'s status file records the last
11397 version of the package which was successfully
11402 <sect1 id="pkg-f-Conffiles">
11403 <heading><tt>Conffiles</tt></heading>
11406 This field in <prgn>dpkg</prgn>'s status file contains
11407 information about the automatically-managed configuration
11408 files held by a package. This field should <em>not</em>
11409 appear anywhere in a package!
11414 <heading>Obsolete fields</heading>
11417 These are still recognized by <prgn>dpkg</prgn> but should
11418 not appear anywhere any more.
11420 <taglist compact="compact">
11422 <tag><tt>Revision</tt></tag>
11423 <tag><tt>Package-Revision</tt></tag>
11424 <tag><tt>Package_Revision</tt></tag>
11426 The Debian revision part of the package version was
11427 at one point in a separate control field. This
11428 field went through several names.
11431 <tag><tt>Recommended</tt></tag>
11432 <item>Old name for <tt>Recommends</tt>.</item>
11434 <tag><tt>Optional</tt></tag>
11435 <item>Old name for <tt>Suggests</tt>.</item>
11437 <tag><tt>Class</tt></tag>
11438 <item>Old name for <tt>Priority</tt>.</item>
11447 <appendix id="pkg-conffiles">
11448 <heading>Configuration file handling (from old Packaging Manual)</heading>
11451 <prgn>dpkg</prgn> can do a certain amount of automatic
11452 handling of package configuration files.
11456 Whether this mechanism is appropriate depends on a number of
11457 factors, but basically there are two approaches to any
11458 particular configuration file.
11462 The easy method is to ship a best-effort configuration in the
11463 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11464 handle updates. If the user is unlikely to want to edit the
11465 file, but you need them to be able to without losing their
11466 changes, and a new package with a changed version of the file
11467 is only released infrequently, this is a good approach.
11471 The hard method is to build the configuration file from
11472 scratch in the <prgn>postinst</prgn> script, and to take the
11473 responsibility for fixing any mistakes made in earlier
11474 versions of the package automatically. This will be
11475 appropriate if the file is likely to need to be different on
11479 <sect><heading>Automatic handling of configuration files by
11484 A package may contain a control information file called
11485 <tt>conffiles</tt>. This file should be a list of filenames
11486 of configuration files needing automatic handling, separated
11487 by newlines. The filenames should be absolute pathnames,
11488 and the files referred to should actually exist in the
11493 When a package is upgraded <prgn>dpkg</prgn> will process
11494 the configuration files during the configuration stage,
11495 shortly before it runs the package's <prgn>postinst</prgn>
11500 For each file it checks to see whether the version of the
11501 file included in the package is the same as the one that was
11502 included in the last version of the package (the one that is
11503 being upgraded from); it also compares the version currently
11504 installed on the system with the one shipped with the last
11509 If neither the user nor the package maintainer has changed
11510 the file, it is left alone. If one or the other has changed
11511 their version, then the changed version is preferred - i.e.,
11512 if the user edits their file, but the package maintainer
11513 doesn't ship a different version, the user's changes will
11514 stay, silently, but if the maintainer ships a new version
11515 and the user hasn't edited it the new version will be
11516 installed (with an informative message). If both have
11517 changed their version the user is prompted about the problem
11518 and must resolve the differences themselves.
11522 The comparisons are done by calculating the MD5 message
11523 digests of the files, and storing the MD5 of the file as it
11524 was included in the most recent version of the package.
11528 When a package is installed for the first time
11529 <prgn>dpkg</prgn> will install the file that comes with it,
11530 unless that would mean overwriting a file already on the
11535 However, note that <prgn>dpkg</prgn> will <em>not</em>
11536 replace a conffile that was removed by the user (or by a
11537 script). This is necessary because with some programs a
11538 missing file produces an effect hard or impossible to
11539 achieve in another way, so that a missing file needs to be
11540 kept that way if the user did it.
11544 Note that a package should <em>not</em> modify a
11545 <prgn>dpkg</prgn>-handled conffile in its maintainer
11546 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11547 the user confusing and possibly dangerous options for
11548 conffile update when the package is upgraded.</p>
11551 <sect><heading>Fully-featured maintainer script configuration
11556 For files which contain site-specific information such as
11557 the hostname and networking details and so forth, it is
11558 better to create the file in the package's
11559 <prgn>postinst</prgn> script.
11563 This will typically involve examining the state of the rest
11564 of the system to determine values and other information, and
11565 may involve prompting the user for some information which
11566 can't be obtained some other way.
11570 When using this method there are a couple of important
11571 issues which should be considered:
11575 If you discover a bug in the program which generates the
11576 configuration file, or if the format of the file changes
11577 from one version to the next, you will have to arrange for
11578 the postinst script to do something sensible - usually this
11579 will mean editing the installed configuration file to remove
11580 the problem or change the syntax. You will have to do this
11581 very carefully, since the user may have changed the file,
11582 perhaps to fix the very problem that your script is trying
11583 to deal with - you will have to detect these situations and
11584 deal with them correctly.
11588 If you do go down this route it's probably a good idea to
11589 make the program that generates the configuration file(s) a
11590 separate program in <file>/usr/sbin</file>, by convention called
11591 <file><var>package</var>config</file> and then run that if
11592 appropriate from the post-installation script. The
11593 <tt><var>package</var>config</tt> program should not
11594 unquestioningly overwrite an existing configuration - if its
11595 mode of operation is geared towards setting up a package for
11596 the first time (rather than any arbitrary reconfiguration
11597 later) you should have it check whether the configuration
11598 already exists, and require a <tt>--force</tt> flag to
11599 overwrite it.</p></sect>
11602 <appendix id="pkg-alternatives"><heading>Alternative versions of
11603 an interface - <prgn>update-alternatives</prgn> (from old
11608 When several packages all provide different versions of the
11609 same program or file it is useful to have the system select a
11610 default, but to allow the system administrator to change it
11611 and have their decisions respected.
11615 For example, there are several versions of the <prgn>vi</prgn>
11616 editor, and there is no reason to prevent all of them from
11617 being installed at once, each under their own name
11618 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11619 Nevertheless it is desirable to have the name <tt>vi</tt>
11620 refer to something, at least by default.
11624 If all the packages involved cooperate, this can be done with
11625 <prgn>update-alternatives</prgn>.
11629 Each package provides its own version under its own name, and
11630 calls <prgn>update-alternatives</prgn> in its postinst to
11631 register its version (and again in its prerm to deregister
11636 See the man page <manref name="update-alternatives"
11637 section="8"> for details.
11641 If <prgn>update-alternatives</prgn> does not seem appropriate
11642 you may wish to consider using diversions instead.</p>
11645 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11646 package's version of a file (from old Packaging Manual)
11650 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11651 when it reinstalls the package it belongs to, and to have it
11652 put the file from the package somewhere else instead.
11656 This can be used locally to override a package's version of a
11657 file, or by one package to override another's version (or
11658 provide a wrapper for it).
11662 Before deciding to use a diversion, read <ref
11663 id="pkg-alternatives"> to see if you really want a diversion
11664 rather than several alternative versions of a program.
11668 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11669 and updated by a special program <prgn>dpkg-divert</prgn>.
11670 Please see <manref name="dpkg-divert" section="8"> for full
11671 details of its operation.
11675 When a package wishes to divert a file from another, it should
11676 call <prgn>dpkg-divert</prgn> in its preinst to add the
11677 diversion and rename the existing file. For example,
11678 supposing that a <prgn>smailwrapper</prgn> package wishes to
11679 install a wrapper around <file>/usr/sbin/smail</file>:
11681 dpkg-divert --package smailwrapper --add --rename \
11682 --divert /usr/sbin/smail.real /usr/sbin/smail
11683 </example> The <tt>--package smailwrapper</tt> ensures that
11684 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11685 can bypass the diversion and get installed as the true version.
11686 It's safe to add the diversion unconditionally on upgrades since
11687 it will be left unchanged if it already exists, but
11688 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11689 message, make the command conditional on the version from which
11690 the package is being upgraded:
11692 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11693 dpkg-divert --package smailwrapper --add --rename \
11694 --divert /usr/sbin/smail.real /usr/sbin/smail
11696 </example> where <tt>1.0-2</tt> is the version at which the
11697 diversion was first added to the package. Running the command
11698 during abort-upgrade is pointless but harmless.
11702 The postrm has to do the reverse:
11704 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11705 dpkg-divert --package smailwrapper --remove --rename \
11706 --divert /usr/sbin/smail.real /usr/sbin/smail
11708 </example> If the diversion was added at a particular version, the
11709 postrm should also handle the failure case of upgrading from an
11710 older version (unless the older version is so old that direct
11711 upgrades are no longer supported):
11713 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11714 dpkg-divert --package smailwrapper --remove --rename \
11715 --divert /usr/sbin/smail.real /usr/sbin/smail
11717 </example> where <tt>1.0-2</tt> is the version at which the
11718 diversion was first added to the package. The postrm should not
11719 remove the diversion on upgrades both because there's no reason to
11720 remove the diversion only to immediately re-add it and since the
11721 postrm of the old package is run after unpacking so the removal of
11722 the diversion will fail.
11726 Do not attempt to divert a file which is vitally important for
11727 the system's operation - when using <prgn>dpkg-divert</prgn>
11728 there is a time, after it has been diverted but before
11729 <prgn>dpkg</prgn> has installed the new version, when the file
11730 does not exist.</p>
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