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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
844 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
845 file</qref> used to store shared library dependency information
846 and the <file>conffiles</file> file that lists the package's
847 configuration files (described in <ref id="config-files">).
851 There is unfortunately a collision of terminology here between
852 control information files and files in the Debian control file
853 format. Throughout this document, a <em>control file</em> refers
854 to a file in the Debian control file format. These files are
855 documented in <ref id="controlfields">. Only files referred to
856 specifically as <em>control information files</em> are the files
857 included in the control information file member of
858 the <file>.deb</file> file format used by binary packages. Most
859 control information files are not in the Debian control file
864 <heading>The package name</heading>
867 Every package must have a name that's unique within the Debian
872 The package name is included in the control field
873 <tt>Package</tt>, the format of which is described
874 in <ref id="f-Package">.
875 The package name is also included as a part of the file name
876 of the <tt>.deb</tt> file.
881 <heading>The version of a package</heading>
884 Every package has a version number recorded in its
885 <tt>Version</tt> control file field, described in
886 <ref id="f-Version">.
890 The package management system imposes an ordering on version
891 numbers, so that it can tell whether packages are being up- or
892 downgraded and so that package system front end applications
893 can tell whether a package it finds available is newer than
894 the one installed on the system. The version number format
895 has the most significant parts (as far as comparison is
896 concerned) at the beginning.
900 If an upstream package has problematic version numbers they
901 should be converted to a sane form for use in the
902 <tt>Version</tt> field.
906 <heading>Version numbers based on dates</heading>
909 In general, Debian packages should use the same version
910 numbers as the upstream sources. However, upstream version
911 numbers based on some date formats (sometimes used for
912 development or "snapshot" releases) will not be ordered
913 correctly by the package management software. For
914 example, <prgn>dpkg</prgn> will consider "96May01" to be
915 greater than "96Dec24".
919 To prevent having to use epochs for every new upstream
920 version, the date-based portion of any upstream version number
921 should be given in a way that sorts correctly: four-digit year
922 first, followed by a two-digit numeric month, followed by a
923 two-digit numeric date, possibly with punctuation between the
928 Native Debian packages (i.e., packages which have been written
929 especially for Debian) whose version numbers include dates
930 should also follow these rules. If punctuation is desired
931 between the date components, remember that hyphen (<tt>-</tt>)
932 cannot be used in native package versions. Period
933 (<tt>.</tt>) is normally a good choice.
939 <sect id="maintainer">
940 <heading>The maintainer of a package</heading>
943 Every package must have a maintainer, except for orphaned
944 packages as described below. The maintainer may be one person
945 or a group of people reachable from a common email address, such
946 as a mailing list. The maintainer is responsible for
947 maintaining the Debian packaging files, evaluating and
948 responding appropriately to reported bugs, uploading new
949 versions of the package (either directly or through a sponsor),
950 ensuring that the package is placed in the appropriate archive
951 area and included in Debian releases as appropriate for the
952 stability and utility of the package, and requesting removal of
953 the package from the Debian distribution if it is no longer
954 useful or maintainable.
958 The maintainer must be specified in the <tt>Maintainer</tt>
959 control field with their correct name and a working email
960 address. The email address given in the <tt>Maintainer</tt>
961 control field must accept mail from those role accounts in
962 Debian used to send automated mails regarding the package. This
963 includes non-spam mail from the bug-tracking system, all mail
964 from the Debian archive maintenance software, and other role
965 accounts or automated processes that are commonly agreed on by
966 the project.<footnote>
967 A sample implementation of such a whitelist written for the
968 Mailman mailing list management software is used for mailing
969 lists hosted by alioth.debian.org.
971 If one person or team maintains several packages, they should
972 use the same form of their name and email address in
973 the <tt>Maintainer</tt> fields of those packages.
977 The format of the <tt>Maintainer</tt> control field is
978 described in <ref id="f-Maintainer">.
982 If the maintainer of the package is a team of people with a
983 shared email address, the <tt>Uploaders</tt> control field must
984 be present and must contain at least one human with their
985 personal email address. See <ref id="f-Uploaders"> for the
986 syntax of that field.
990 An orphaned package is one with no current maintainer. Orphaned
991 packages should have their <tt>Maintainer</tt> control field set
992 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
993 These packages are considered maintained by the Debian project
994 as a whole until someone else volunteers to take over
995 maintenance.<footnote>
996 The detailed procedure for gracefully orphaning a package can
997 be found in the Debian Developer's Reference
998 (see <ref id="related">).
1003 <sect id="descriptions">
1004 <heading>The description of a package</heading>
1007 Every Debian package must have a <tt>Description</tt> control
1008 field which contains a synopsis and extended description of the
1009 package. Technical information about the format of the
1010 <tt>Description</tt> field is in <ref id="f-Description">.
1014 The description should describe the package (the program) to a
1015 user (system administrator) who has never met it before so that
1016 they have enough information to decide whether they want to
1017 install it. This description should not just be copied verbatim
1018 from the program's documentation.
1022 Put important information first, both in the synopsis and
1023 extended description. Sometimes only the first part of the
1024 synopsis or of the description will be displayed. You can
1025 assume that there will usually be a way to see the whole
1026 extended description.
1030 The description should also give information about the
1031 significant dependencies and conflicts between this package
1032 and others, so that the user knows why these dependencies and
1033 conflicts have been declared.
1037 Instructions for configuring or using the package should
1038 not be included (that is what installation scripts,
1039 manual pages, info files, etc., are for). Copyright
1040 statements and other administrivia should not be included
1041 either (that is what the copyright file is for).
1044 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1047 The single line synopsis should be kept brief - certainly
1048 under 80 characters.
1052 Do not include the package name in the synopsis line. The
1053 display software knows how to display this already, and you
1054 do not need to state it. Remember that in many situations
1055 the user may only see the synopsis line - make it as
1056 informative as you can.
1061 <sect1 id="extendeddesc"><heading>The extended description</heading>
1064 Do not try to continue the single line synopsis into the
1065 extended description. This will not work correctly when
1066 the full description is displayed, and makes no sense
1067 where only the summary (the single line synopsis) is
1072 The extended description should describe what the package
1073 does and how it relates to the rest of the system (in terms
1074 of, for example, which subsystem it is which part of).
1078 The description field needs to make sense to anyone, even
1079 people who have no idea about any of the things the
1080 package deals with.<footnote>
1081 The blurb that comes with a program in its
1082 announcements and/or <prgn>README</prgn> files is
1083 rarely suitable for use in a description. It is
1084 usually aimed at people who are already in the
1085 community where the package is used.
1093 <sect id="dependencies">
1094 <heading>Dependencies</heading>
1097 Every package must specify the dependency information
1098 about other packages that are required for the first to
1103 For example, a dependency entry must be provided for any
1104 shared libraries required by a dynamically-linked executable
1105 binary in a package.
1109 Packages are not required to declare any dependencies they
1110 have on other packages which are marked <tt>Essential</tt>
1111 (see below), and should not do so unless they depend on a
1112 particular version of that package.<footnote>
1114 Essential is needed in part to avoid unresolvable dependency
1115 loops on upgrade. If packages add unnecessary dependencies
1116 on packages in this set, the chances that there
1117 <strong>will</strong> be an unresolvable dependency loop
1118 caused by forcing these Essential packages to be configured
1119 first before they need to be is greatly increased. It also
1120 increases the chances that frontends will be unable to
1121 <strong>calculate</strong> an upgrade path, even if one
1125 Also, functionality is rarely ever removed from the
1126 Essential set, but <em>packages</em> have been removed from
1127 the Essential set when the functionality moved to a
1128 different package. So depending on these packages <em>just
1129 in case</em> they stop being essential does way more harm
1136 Sometimes, unpacking one package requires that another package
1137 be first unpacked <em>and</em> configured. In this case, the
1138 depending package must specify this dependency in
1139 the <tt>Pre-Depends</tt> control field.
1143 You should not specify a <tt>Pre-Depends</tt> entry for a
1144 package before this has been discussed on the
1145 <tt>debian-devel</tt> mailing list and a consensus about
1146 doing that has been reached.
1150 The format of the package interrelationship control fields is
1151 described in <ref id="relationships">.
1155 <sect id="virtual_pkg">
1156 <heading>Virtual packages</heading>
1159 Sometimes, there are several packages which offer
1160 more-or-less the same functionality. In this case, it's
1161 useful to define a <em>virtual package</em> whose name
1162 describes that common functionality. (The virtual
1163 packages only exist logically, not physically; that's why
1164 they are called <em>virtual</em>.) The packages with this
1165 particular function will then <em>provide</em> the virtual
1166 package. Thus, any other package requiring that function
1167 can simply depend on the virtual package without having to
1168 specify all possible packages individually.
1172 All packages should use virtual package names where
1173 appropriate, and arrange to create new ones if necessary.
1174 They should not use virtual package names (except privately,
1175 amongst a cooperating group of packages) unless they have
1176 been agreed upon and appear in the list of virtual package
1177 names. (See also <ref id="virtual">)
1181 The latest version of the authoritative list of virtual
1182 package names can be found in the <tt>debian-policy</tt> package.
1183 It is also available from the Debian web mirrors at
1184 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1185 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1189 The procedure for updating the list is described in the preface
1196 <heading>Base system</heading>
1199 The <tt>base system</tt> is a minimum subset of the Debian
1200 system that is installed before everything else
1201 on a new system. Only very few packages are allowed to form
1202 part of the base system, in order to keep the required disk
1207 The base system consists of all those packages with priority
1208 <tt>required</tt> or <tt>important</tt>. Many of them will
1209 be tagged <tt>essential</tt> (see below).
1214 <heading>Essential packages</heading>
1217 Essential is defined as the minimal set of functionality that
1218 must be available and usable on the system at all times, even
1219 when packages are in an unconfigured (but unpacked) state.
1220 Packages are tagged <tt>essential</tt> for a system using the
1221 <tt>Essential</tt> control field. The format of the
1222 <tt>Essential</tt> control field is described in <ref
1227 Since these packages cannot be easily removed (one has to
1228 specify an extra <em>force option</em> to
1229 <prgn>dpkg</prgn> to do so), this flag must not be used
1230 unless absolutely necessary. A shared library package
1231 must not be tagged <tt>essential</tt>; dependencies will
1232 prevent its premature removal, and we need to be able to
1233 remove it when it has been superseded.
1237 Since dpkg will not prevent upgrading of other packages
1238 while an <tt>essential</tt> package is in an unconfigured
1239 state, all <tt>essential</tt> packages must supply all of
1240 their core functionality even when unconfigured. If the
1241 package cannot satisfy this requirement it must not be
1242 tagged as essential, and any packages depending on this
1243 package must instead have explicit dependency fields as
1248 Maintainers should take great care in adding any programs,
1249 interfaces, or functionality to <tt>essential</tt> packages.
1250 Packages may assume that functionality provided by
1251 <tt>essential</tt> packages is always available without
1252 declaring explicit dependencies, which means that removing
1253 functionality from the Essential set is very difficult and is
1254 almost never done. Any capability added to an
1255 <tt>essential</tt> package therefore creates an obligation to
1256 support that capability as part of the Essential set in
1261 You must not tag any packages <tt>essential</tt> before
1262 this has been discussed on the <tt>debian-devel</tt>
1263 mailing list and a consensus about doing that has been
1268 <sect id="maintscripts">
1269 <heading>Maintainer Scripts</heading>
1272 The package installation scripts should avoid producing
1273 output which is unnecessary for the user to see and
1274 should rely on <prgn>dpkg</prgn> to stave off boredom on
1275 the part of a user installing many packages. This means,
1276 amongst other things, using the <tt>--quiet</tt> option on
1277 <prgn>install-info</prgn>.
1281 Errors which occur during the execution of an installation
1282 script must be checked and the installation must not
1283 continue after an error.
1287 Note that in general <ref id="scripts"> applies to package
1288 maintainer scripts, too.
1292 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1293 to another package without consulting the maintainer of that
1294 package first. When adding or removing diversions, package
1295 maintainer scripts must provide the <tt>--package</tt> flag
1296 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1300 All packages which supply an instance of a common command
1301 name (or, in general, filename) should generally use
1302 <prgn>update-alternatives</prgn>, so that they may be
1303 installed together. If <prgn>update-alternatives</prgn>
1304 is not used, then each package must use
1305 <tt>Conflicts</tt> to ensure that other packages are
1306 de-installed. (In this case, it may be appropriate to
1307 specify a conflict against earlier versions of something
1308 that previously did not use
1309 <prgn>update-alternatives</prgn>; this is an exception to
1310 the usual rule that versioned conflicts should be
1314 <sect1 id="maintscriptprompt">
1315 <heading>Prompting in maintainer scripts</heading>
1317 Package maintainer scripts may prompt the user if
1318 necessary. Prompting must be done by communicating
1319 through a program, such as <prgn>debconf</prgn>, which
1320 conforms to the Debian Configuration Management
1321 Specification, version 2 or higher.
1325 Packages which are essential, or which are dependencies of
1326 essential packages, may fall back on another prompting method
1327 if no such interface is available when they are executed.
1331 The Debian Configuration Management Specification is included
1332 in the <file>debconf_specification</file> files in the
1333 <package>debian-policy</package> package.
1334 It is also available from the Debian web mirrors at
1335 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1336 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1340 Packages which use the Debian Configuration Management
1341 Specification may contain the additional control information
1342 files <file>config</file>
1343 and <file>templates</file>. <file>config</file> is an
1344 additional maintainer script used for package configuration,
1345 and <file>templates</file> contains templates used for user
1346 prompting. The <prgn>config</prgn> script might be run before
1347 the <prgn>preinst</prgn> script and before the package is
1348 unpacked or any of its dependencies or pre-dependencies are
1349 satisfied. Therefore it must work using only the tools
1350 present in <em>essential</em> packages.<footnote>
1351 <package>Debconf</package> or another tool that
1352 implements the Debian Configuration Management
1353 Specification will also be installed, and any
1354 versioned dependencies on it will be satisfied
1355 before preconfiguration begins.
1360 Packages which use the Debian Configuration Management
1361 Specification must allow for translation of their user-visible
1362 messages by using a gettext-based system such as the one
1363 provided by the <package>po-debconf</package> package.
1367 Packages should try to minimize the amount of prompting
1368 they need to do, and they should ensure that the user
1369 will only ever be asked each question once. This means
1370 that packages should try to use appropriate shared
1371 configuration files (such as <file>/etc/papersize</file> and
1372 <file>/etc/news/server</file>), and shared
1373 <package>debconf</package> variables rather than each
1374 prompting for their own list of required pieces of
1379 It also means that an upgrade should not ask the same
1380 questions again, unless the user has used
1381 <tt>dpkg --purge</tt> to remove the package's configuration.
1382 The answers to configuration questions should be stored in an
1383 appropriate place in <file>/etc</file> so that the user can
1384 modify them, and how this has been done should be
1389 If a package has a vitally important piece of
1390 information to pass to the user (such as "don't run me
1391 as I am, you must edit the following configuration files
1392 first or you risk your system emitting badly-formatted
1393 messages"), it should display this in the
1394 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1395 prompt the user to hit return to acknowledge the
1396 message. Copyright messages do not count as vitally
1397 important (they belong in
1398 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1399 neither do instructions on how to use a program (these
1400 should be in on-line documentation, where all the users
1405 Any necessary prompting should almost always be confined
1406 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1407 script. If it is done in the <prgn>postinst</prgn>, it
1408 should be protected with a conditional so that
1409 unnecessary prompting doesn't happen if a package's
1410 installation fails and the <prgn>postinst</prgn> is
1411 called with <tt>abort-upgrade</tt>,
1412 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1422 <heading>Source packages</heading>
1424 <sect id="standardsversion">
1425 <heading>Standards conformance</heading>
1428 Source packages should specify the most recent version number
1429 of this policy document with which your package complied
1430 when it was last updated.
1434 This information may be used to file bug reports
1435 automatically if your package becomes too much out of date.
1439 The version is specified in the <tt>Standards-Version</tt>
1441 The format of the <tt>Standards-Version</tt> field is
1442 described in <ref id="f-Standards-Version">.
1446 You should regularly, and especially if your package has
1447 become out of date, check for the newest Policy Manual
1448 available and update your package, if necessary. When your
1449 package complies with the new standards you should update the
1450 <tt>Standards-Version</tt> source package field and
1451 release it.<footnote>
1452 See the file <file>upgrading-checklist</file> for
1453 information about policy which has changed between
1454 different versions of this document.
1460 <sect id="pkg-relations">
1461 <heading>Package relationships</heading>
1464 Source packages should specify which binary packages they
1465 require to be installed or not to be installed in order to
1466 build correctly. For example, if building a package
1467 requires a certain compiler, then the compiler should be
1468 specified as a build-time dependency.
1472 It is not necessary to explicitly specify build-time
1473 relationships on a minimal set of packages that are always
1474 needed to compile, link and put in a Debian package a
1475 standard "Hello World!" program written in C or C++. The
1476 required packages are called <em>build-essential</em>, and
1477 an informational list can be found in
1478 <file>/usr/share/doc/build-essential/list</file> (which is
1479 contained in the <tt>build-essential</tt>
1482 <list compact="compact">
1484 This allows maintaining the list separately
1485 from the policy documents (the list does not
1486 need the kind of control that the policy
1490 Having a separate package allows one to install
1491 the build-essential packages on a machine, as
1492 well as allowing other packages such as tasks to
1493 require installation of the build-essential
1494 packages using the depends relation.
1497 The separate package allows bug reports against
1498 the list to be categorized separately from
1499 the policy management process in the BTS.
1506 When specifying the set of build-time dependencies, one
1507 should list only those packages explicitly required by the
1508 build. It is not necessary to list packages which are
1509 required merely because some other package in the list of
1510 build-time dependencies depends on them.<footnote>
1511 The reason for this is that dependencies change, and
1512 you should list all those packages, and <em>only</em>
1513 those packages that <em>you</em> need directly. What
1514 others need is their business. For example, if you
1515 only link against <file>libimlib</file>, you will need to
1516 build-depend on <package>libimlib2-dev</package> but
1517 not against any <tt>libjpeg*</tt> packages, even
1518 though <tt>libimlib2-dev</tt> currently depends on
1519 them: installation of <package>libimlib2-dev</package>
1520 will automatically ensure that all of its run-time
1521 dependencies are satisfied.
1526 If build-time dependencies are specified, it must be
1527 possible to build the package and produce working binaries
1528 on a system with only essential and build-essential
1529 packages installed and also those required to satisfy the
1530 build-time relationships (including any implied
1531 relationships). In particular, this means that version
1532 clauses should be used rigorously in build-time
1533 relationships so that one cannot produce bad or
1534 inconsistently configured packages when the relationships
1535 are properly satisfied.
1539 <ref id="relationships"> explains the technical details.
1544 <heading>Changes to the upstream sources</heading>
1547 If changes to the source code are made that are not
1548 specific to the needs of the Debian system, they should be
1549 sent to the upstream authors in whatever form they prefer
1550 so as to be included in the upstream version of the
1555 If you need to configure the package differently for
1556 Debian or for Linux, and the upstream source doesn't
1557 provide a way to do so, you should add such configuration
1558 facilities (for example, a new <prgn>autoconf</prgn> test
1559 or <tt>#define</tt>) and send the patch to the upstream
1560 authors, with the default set to the way they originally
1561 had it. You can then easily override the default in your
1562 <file>debian/rules</file> or wherever is appropriate.
1566 You should make sure that the <prgn>configure</prgn> utility
1567 detects the correct architecture specification string
1568 (refer to <ref id="arch-spec"> for details).
1572 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1573 <prgn>configure</prgn> scripts are used, you should edit the
1574 <file>.in</file> files rather than editing the
1575 <prgn>Makefile</prgn> directly. This allows the user to
1576 reconfigure the package if necessary. You should
1577 <em>not</em> configure the package and edit the generated
1578 <prgn>Makefile</prgn>! This makes it impossible for someone
1579 else to later reconfigure the package without losing the
1585 <sect id="dpkgchangelog">
1586 <heading>Debian changelog: <file>debian/changelog</file></heading>
1589 Changes in the Debian version of the package should be
1590 briefly explained in the Debian changelog file
1591 <file>debian/changelog</file>.<footnote>
1593 Mistakes in changelogs are usually best rectified by
1594 making a new changelog entry rather than "rewriting
1595 history" by editing old changelog entries.
1598 This includes modifications
1599 made in the Debian package compared to the upstream one
1600 as well as other changes and updates to the package.
1602 Although there is nothing stopping an author who is also
1603 the Debian maintainer from using this changelog for all
1604 their changes, it will have to be renamed if the Debian
1605 and upstream maintainers become different people. In such
1606 a case, however, it might be better to maintain the package
1607 as a non-native package.
1612 The format of the <file>debian/changelog</file> allows the
1613 package building tools to discover which version of the package
1614 is being built and find out other release-specific information.
1618 That format is a series of entries like this:
1620 <example compact="compact">
1621 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1623 [optional blank line(s), stripped]
1625 * <var>change details</var>
1626 <var>more change details</var>
1628 [blank line(s), included in output of dpkg-parsechangelog]
1630 * <var>even more change details</var>
1632 [optional blank line(s), stripped]
1634 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1639 <var>package</var> and <var>version</var> are the source
1640 package name and version number.
1644 <var>distribution(s)</var> lists the distributions where
1645 this version should be installed when it is uploaded - it
1646 is copied to the <tt>Distribution</tt> field in the
1647 <file>.changes</file> file. See <ref id="f-Distribution">.
1651 <var>urgency</var> is the value for the <tt>Urgency</tt>
1652 field in the <file>.changes</file> file for the upload
1653 (see <ref id="f-Urgency">). It is not possible to specify
1654 an urgency containing commas; commas are used to separate
1655 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1656 <prgn>dpkg</prgn> changelog format (though there is
1657 currently only one useful <var>keyword</var>,
1662 The change details may in fact be any series of lines
1663 starting with at least two spaces, but conventionally each
1664 change starts with an asterisk and a separating space and
1665 continuation lines are indented so as to bring them in
1666 line with the start of the text above. Blank lines may be
1667 used here to separate groups of changes, if desired.
1671 If this upload resolves bugs recorded in the Bug Tracking
1672 System (BTS), they may be automatically closed on the
1673 inclusion of this package into the Debian archive by
1674 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1675 in the change details.<footnote>
1676 To be precise, the string should match the following
1677 Perl regular expression:
1679 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1681 Then all of the bug numbers listed will be closed by the
1682 archive maintenance script (<prgn>katie</prgn>) using the
1683 <var>version</var> of the changelog entry.
1685 This information is conveyed via the <tt>Closes</tt> field
1686 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1690 The maintainer name and email address used in the changelog
1691 should be the details of the person uploading <em>this</em>
1692 version. They are <em>not</em> necessarily those of the
1693 usual package maintainer.<footnote>
1694 If the developer uploading the package is not one of the usual
1695 maintainers of the package (as listed in
1696 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1697 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1698 fields of the package), the first line of the changelog is
1699 conventionally used to explain why a non-maintainer is
1700 uploading the package. The Debian Developer's Reference
1701 (see <ref id="related">) documents the conventions
1703 The information here will be copied to the <tt>Changed-By</tt>
1704 field in the <tt>.changes</tt> file
1705 (see <ref id="f-Changed-By">), and then later used to send an
1706 acknowledgement when the upload has been installed.
1710 The <var>date</var> has the following format<footnote>
1711 This is the same as the format generated by <tt>date
1713 </footnote> (compatible and with the same semantics of
1714 RFC 2822 and RFC 5322):
1715 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1717 <list compact="compact">
1719 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1722 dd is a one- or two-digit day of the month (01-31)
1725 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1728 <item>yyyy is the four-digit year (e.g. 2010)</item>
1729 <item>hh is the two-digit hour (00-23)</item>
1730 <item>mm is the two-digit minutes (00-59)</item>
1731 <item>ss is the two-digit seconds (00-60)</item>
1733 +zzzz or -zzzz is the the time zone offset from Coordinated
1734 Universal Time (UTC). "+" indicates that the time is ahead
1735 of (i.e., east of) UTC and "-" indicates that the time is
1736 behind (i.e., west of) UTC. The first two digits indicate
1737 the hour difference from UTC and the last two digits
1738 indicate the number of additional minutes difference from
1739 UTC. The last two digits must be in the range 00-59.
1745 The first "title" line with the package name must start
1746 at the left hand margin. The "trailer" line with the
1747 maintainer and date details must be preceded by exactly
1748 one space. The maintainer details and the date must be
1749 separated by exactly two spaces.
1753 The entire changelog must be encoded in UTF-8.
1757 For more information on placement of the changelog files
1758 within binary packages, please see <ref id="changelogs">.
1762 <sect id="dpkgcopyright">
1763 <heading>Copyright: <file>debian/copyright</file></heading>
1765 Every package must be accompanied by a verbatim copy of its
1766 copyright information and distribution license in the file
1767 <file>/usr/share/doc/<var>package</var>/copyright</file>
1768 (see <ref id="copyrightfile"> for further details). Also see
1769 <ref id="pkgcopyright"> for further considerations related
1770 to copyrights for packages.
1774 <heading>Error trapping in makefiles</heading>
1777 When <prgn>make</prgn> invokes a command in a makefile
1778 (including your package's upstream makefiles and
1779 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1780 means that <prgn>sh</prgn>'s usual bad error handling
1781 properties apply: if you include a miniature script as one
1782 of the commands in your makefile you'll find that if you
1783 don't do anything about it then errors are not detected
1784 and <prgn>make</prgn> will blithely continue after
1789 Every time you put more than one shell command (this
1790 includes using a loop) in a makefile command you
1791 must make sure that errors are trapped. For
1792 simple compound commands, such as changing directory and
1793 then running a program, using <tt>&&</tt> rather
1794 than semicolon as a command separator is sufficient. For
1795 more complex commands including most loops and
1796 conditionals you should include a separate <tt>set -e</tt>
1797 command at the start of every makefile command that's
1798 actually one of these miniature shell scripts.
1802 <sect id="timestamps">
1803 <heading>Time Stamps</heading>
1805 Maintainers should preserve the modification times of the
1806 upstream source files in a package, as far as is reasonably
1808 The rationale is that there is some information conveyed
1809 by knowing the age of the file, for example, you could
1810 recognize that some documentation is very old by looking
1811 at the modification time, so it would be nice if the
1812 modification time of the upstream source would be
1818 <sect id="restrictions">
1819 <heading>Restrictions on objects in source packages</heading>
1822 The source package may not contain any hard links<footnote>
1824 This is not currently detected when building source
1825 packages, but only when extracting
1829 Hard links may be permitted at some point in the
1830 future, but would require a fair amount of
1833 </footnote>, device special files, sockets or setuid or
1834 setgid files.<footnote>
1835 Setgid directories are allowed.
1840 <sect id="debianrules">
1841 <heading>Main building script: <file>debian/rules</file></heading>
1844 This file must be an executable makefile, and contains the
1845 package-specific recipes for compiling the package and
1846 building binary package(s) from the source.
1850 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1851 so that it can be invoked by saying its name rather than
1852 invoking <prgn>make</prgn> explicitly. That is, invoking
1853 either of <tt>make -f debian/rules <em>args...</em></tt>
1854 or <tt>./debian/rules <em>args...</em></tt> must result in
1859 The following targets are required and must be implemented
1860 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1861 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1862 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1866 Since an interactive <file>debian/rules</file> script makes it
1867 impossible to auto-compile that package and also makes it hard
1868 for other people to reproduce the same binary package, all
1869 required targets must be non-interactive. It also follows that
1870 any target that these targets depend on must also be
1875 The targets are as follows:
1877 <tag><tt>build</tt> (required)</tag>
1880 The <tt>build</tt> target should perform all the
1881 configuration and compilation of the package.
1882 If a package has an interactive pre-build
1883 configuration routine, the Debian source package
1884 must either be built after this has taken place (so
1885 that the binary package can be built without rerunning
1886 the configuration) or the configuration routine
1887 modified to become non-interactive. (The latter is
1888 preferable if there are architecture-specific features
1889 detected by the configuration routine.)
1893 For some packages, notably ones where the same
1894 source tree is compiled in different ways to produce
1895 two binary packages, the <tt>build</tt> target
1896 does not make much sense. For these packages it is
1897 good enough to provide two (or more) targets
1898 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1899 for each of the ways of building the package, and a
1900 <tt>build</tt> target that does nothing. The
1901 <tt>binary</tt> target will have to build the
1902 package in each of the possible ways and make the
1903 binary package out of each.
1907 The <tt>build</tt> target must not do anything
1908 that might require root privilege.
1912 The <tt>build</tt> target may need to run the
1913 <tt>clean</tt> target first - see below.
1917 When a package has a configuration and build routine
1918 which takes a long time, or when the makefiles are
1919 poorly designed, or when <tt>build</tt> needs to
1920 run <tt>clean</tt> first, it is a good idea to
1921 <tt>touch build</tt> when the build process is
1922 complete. This will ensure that if <tt>debian/rules
1923 build</tt> is run again it will not rebuild the whole
1925 Another common way to do this is for <tt>build</tt>
1926 to depend on <prgn>build-stamp</prgn> and to do
1927 nothing else, and for the <prgn>build-stamp</prgn>
1928 target to do the building and to <tt>touch
1929 build-stamp</tt> on completion. This is
1930 especially useful if the build routine creates a
1931 file or directory called <tt>build</tt>; in such a
1932 case, <tt>build</tt> will need to be listed as
1933 a phony target (i.e., as a dependency of the
1934 <tt>.PHONY</tt> target). See the documentation of
1935 <prgn>make</prgn> for more information on phony
1941 <tag><tt>build-arch</tt> (optional),
1942 <tt>build-indep</tt> (optional)
1946 A package may also provide both of the targets
1947 <tt>build-arch</tt> and <tt>build-indep</tt>.
1948 The <tt>build-arch</tt> target, if provided, should
1949 perform all the configuration and compilation required for
1950 producing all architecture-dependant binary packages
1951 (those packages for which the body of the
1952 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1953 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1954 target, if provided, should perform all the configuration
1955 and compilation required for producing all
1956 architecture-independent binary packages (those packages
1957 for which the body of the <tt>Architecture</tt> field
1958 in <tt>debian/control</tt> is <tt>all</tt>).
1959 The <tt>build</tt> target should depend on those of the
1960 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1961 are provided in the rules file.<footnote>
1962 The intent of this split is so that binary-only builds
1963 need not install the dependencies required for
1964 the <tt>build-indep</tt> target. However, this is not
1965 yet used in practice since <tt>dpkg-buildpackage
1966 -B</tt>, and therefore the autobuilders,
1967 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1968 due to the difficulties in determining whether the
1969 optional <tt>build-arch</tt> target exists.
1974 If one or both of the targets <tt>build-arch</tt> and
1975 <tt>build-indep</tt> are not provided, then invoking
1976 <file>debian/rules</file> with one of the not-provided
1977 targets as arguments should produce a exit status code
1978 of 2. Usually this is provided automatically by make
1979 if the target is missing.
1983 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1984 must not do anything that might require root privilege.
1988 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1989 (required), <tt>binary-indep</tt> (required)
1993 The <tt>binary</tt> target must be all that is
1994 necessary for the user to build the binary package(s)
1995 produced from this source package. It is
1996 split into two parts: <prgn>binary-arch</prgn> builds
1997 the binary packages which are specific to a particular
1998 architecture, and <tt>binary-indep</tt> builds
1999 those which are not.
2002 <tt>binary</tt> may be (and commonly is) a target with
2003 no commands which simply depends on
2004 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2007 Both <tt>binary-*</tt> targets should depend on the
2008 <tt>build</tt> target, or on the appropriate
2009 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2010 provided, so that the package is built if it has not
2011 been already. It should then create the relevant
2012 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2013 make their control files and <prgn>dpkg-deb</prgn> to
2014 build them and place them in the parent of the top
2019 Both the <tt>binary-arch</tt> and
2020 <tt>binary-indep</tt> targets <em>must</em> exist.
2021 If one of them has nothing to do (which will always be
2022 the case if the source generates only a single binary
2023 package, whether architecture-dependent or not), it
2024 must still exist and must always succeed.
2028 The <tt>binary</tt> targets must be invoked as
2030 The <prgn>fakeroot</prgn> package often allows one
2031 to build a package correctly even without being
2037 <tag><tt>clean</tt> (required)</tag>
2040 This must undo any effects that the <tt>build</tt>
2041 and <tt>binary</tt> targets may have had, except
2042 that it should leave alone any output files created in
2043 the parent directory by a run of a <tt>binary</tt>
2048 If a <tt>build</tt> file is touched at the end of
2049 the <tt>build</tt> target, as suggested above, it
2050 should be removed as the first action that
2051 <tt>clean</tt> performs, so that running
2052 <tt>build</tt> again after an interrupted
2053 <tt>clean</tt> doesn't think that everything is
2058 The <tt>clean</tt> target may need to be
2059 invoked as root if <tt>binary</tt> has been
2060 invoked since the last <tt>clean</tt>, or if
2061 <tt>build</tt> has been invoked as root (since
2062 <tt>build</tt> may create directories, for
2067 <tag><tt>get-orig-source</tt> (optional)</tag>
2070 This target fetches the most recent version of the
2071 original source package from a canonical archive site
2072 (via FTP or WWW, for example), does any necessary
2073 rearrangement to turn it into the original source
2074 tar file format described below, and leaves it in the
2079 This target may be invoked in any directory, and
2080 should take care to clean up any temporary files it
2085 This target is optional, but providing it if
2086 possible is a good idea.
2090 <tag><tt>patch</tt> (optional)</tag>
2093 This target performs whatever additional actions are
2094 required to make the source ready for editing (unpacking
2095 additional upstream archives, applying patches, etc.).
2096 It is recommended to be implemented for any package where
2097 <tt>dpkg-source -x</tt> does not result in source ready
2098 for additional modification. See
2099 <ref id="readmesource">.
2105 The <tt>build</tt>, <tt>binary</tt> and
2106 <tt>clean</tt> targets must be invoked with the current
2107 directory being the package's top-level directory.
2112 Additional targets may exist in <file>debian/rules</file>,
2113 either as published or undocumented interfaces or for the
2114 package's internal use.
2118 The architectures we build on and build for are determined
2119 by <prgn>make</prgn> variables using the
2120 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2121 You can determine the Debian architecture and the GNU style
2122 architecture specification string for the build architecture as
2123 well as for the host architecture. The build architecture is
2124 the architecture on which <file>debian/rules</file> is run and
2125 the package build is performed. The host architecture is the
2126 architecture on which the resulting package will be installed
2127 and run. These are normally the same, but may be different in
2128 the case of cross-compilation (building packages for one
2129 architecture on machines of a different architecture).
2133 Here is a list of supported <prgn>make</prgn> variables:
2134 <list compact="compact">
2136 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2139 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2142 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2145 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2146 specification string)
2149 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2150 <tt>DEB_*_GNU_TYPE</tt>)
2153 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2154 <tt>DEB_*_GNU_TYPE</tt>)
2156 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2157 the build architecture or <tt>HOST</tt> for specification of the
2162 Backward compatibility can be provided in the rules file
2163 by setting the needed variables to suitable default
2164 values; please refer to the documentation of
2165 <prgn>dpkg-architecture</prgn> for details.
2169 It is important to understand that the <tt>DEB_*_ARCH</tt>
2170 string only determines which Debian architecture we are
2171 building on or for. It should not be used to get the CPU
2172 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2173 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2174 GNU style variables should generally only be used with upstream
2178 <sect1 id="debianrules-options">
2179 <heading><file>debian/rules</file> and
2180 <tt>DEB_BUILD_OPTIONS</tt></heading>
2183 Supporting the standardized environment variable
2184 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2185 contain several flags to change how a package is compiled and
2186 built. Each flag must be in the form <var>flag</var> or
2187 <var>flag</var>=<var>options</var>. If multiple flags are
2188 given, they must be separated by whitespace.<footnote>
2189 Some packages support any delimiter, but whitespace is the
2190 easiest to parse inside a makefile and avoids ambiguity with
2191 flag values that contain commas.
2193 <var>flag</var> must start with a lowercase letter
2194 (<tt>a-z</tt>) and consist only of lowercase letters,
2195 numbers (<tt>0-9</tt>), and the characters
2196 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2197 <var>options</var> must not contain whitespace. The same
2198 tag should not be given multiple times with conflicting
2199 values. Package maintainers may assume that
2200 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2204 The meaning of the following tags has been standardized:
2208 This tag says to not run any build-time test suite
2209 provided by the package.
2213 The presence of this tag means that the package should
2214 be compiled with a minimum of optimization. For C
2215 programs, it is best to add <tt>-O0</tt> to
2216 <tt>CFLAGS</tt> (although this is usually the default).
2217 Some programs might fail to build or run at this level
2218 of optimization; it may be necessary to use
2219 <tt>-O1</tt>, for example.
2223 This tag means that the debugging symbols should not be
2224 stripped from the binary during installation, so that
2225 debugging information may be included in the package.
2227 <tag>parallel=n</tag>
2229 This tag means that the package should be built using up
2230 to <tt>n</tt> parallel processes if the package build
2231 system supports this.<footnote>
2232 Packages built with <tt>make</tt> can often implement
2233 this by passing the <tt>-j</tt><var>n</var> option to
2236 If the package build system does not support parallel
2237 builds, this string must be ignored. If the package
2238 build system only supports a lower level of concurrency
2239 than <var>n</var>, the package should be built using as
2240 many parallel processes as the package build system
2241 supports. It is up to the package maintainer to decide
2242 whether the package build times are long enough and the
2243 package build system is robust enough to make supporting
2244 parallel builds worthwhile.
2250 Unknown flags must be ignored by <file>debian/rules</file>.
2254 The following makefile snippet is an example of how one may
2255 implement the build options; you will probably have to
2256 massage this example in order to make it work for your
2258 <example compact="compact">
2261 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2262 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2263 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2264 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2266 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2271 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2272 INSTALL_PROGRAM += -s
2274 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2275 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2276 MAKEFLAGS += -j$(NUMJOBS)
2281 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2282 # Code to run the package test suite.
2289 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2290 <sect id="substvars">
2291 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2294 When <prgn>dpkg-gencontrol</prgn>
2295 generates <qref id="binarycontrolfiles">binary package control
2296 files</qref> (<file>DEBIAN/control</file>), it performs variable
2297 substitutions on its output just before writing it. Variable
2298 substitutions have the form <tt>${<var>variable</var>}</tt>.
2299 The optional file <file>debian/substvars</file> contains
2300 variable substitutions to be used; variables can also be set
2301 directly from <file>debian/rules</file> using the <tt>-V</tt>
2302 option to the source packaging commands, and certain predefined
2303 variables are also available.
2307 The <file>debian/substvars</file> file is usually generated and
2308 modified dynamically by <file>debian/rules</file> targets, in
2309 which case it must be removed by the <tt>clean</tt> target.
2313 See <manref name="deb-substvars" section="5"> for full
2314 details about source variable substitutions, including the
2315 format of <file>debian/substvars</file>.</p>
2318 <sect id="debianwatch">
2319 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2322 This is an optional, recommended configuration file for the
2323 <tt>uscan</tt> utility which defines how to automatically scan
2324 ftp or http sites for newly available updates of the
2325 package. This is used
2326 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2327 tools to help with quality control and maintenance of the
2328 distribution as a whole.
2333 <sect id="debianfiles">
2334 <heading>Generated files list: <file>debian/files</file></heading>
2337 This file is not a permanent part of the source tree; it
2338 is used while building packages to record which files are
2339 being generated. <prgn>dpkg-genchanges</prgn> uses it
2340 when it generates a <file>.changes</file> file.
2344 It should not exist in a shipped source package, and so it
2345 (and any backup files or temporary files such as
2346 <file>files.new</file><footnote>
2347 <file>files.new</file> is used as a temporary file by
2348 <prgn>dpkg-gencontrol</prgn> and
2349 <prgn>dpkg-distaddfile</prgn> - they write a new
2350 version of <tt>files</tt> here before renaming it,
2351 to avoid leaving a corrupted copy if an error
2353 </footnote>) should be removed by the
2354 <tt>clean</tt> target. It may also be wise to
2355 ensure a fresh start by emptying or removing it at the
2356 start of the <tt>binary</tt> target.
2360 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2361 package, it adds an entry to <file>debian/files</file> for the
2362 <file>.deb</file> file that will be created when <tt>dpkg-deb
2363 --build</tt> is run for that binary package. So for most
2364 packages all that needs to be done with this file is to
2365 delete it in the <tt>clean</tt> target.
2369 If a package upload includes files besides the source
2370 package and any binary packages whose control files were
2371 made with <prgn>dpkg-gencontrol</prgn> then they should be
2372 placed in the parent of the package's top-level directory
2373 and <prgn>dpkg-distaddfile</prgn> should be called to add
2374 the file to the list in <file>debian/files</file>.</p>
2377 <sect id="embeddedfiles">
2378 <heading>Convenience copies of code</heading>
2381 Some software packages include in their distribution convenience
2382 copies of code from other software packages, generally so that
2383 users compiling from source don't have to download multiple
2384 packages. Debian packages should not make use of these
2385 convenience copies unless the included package is explicitly
2386 intended to be used in this way.<footnote>
2387 For example, parts of the GNU build system work like this.
2389 If the included code is already in the Debian archive in the
2390 form of a library, the Debian packaging should ensure that
2391 binary packages reference the libraries already in Debian and
2392 the convenience copy is not used. If the included code is not
2393 already in Debian, it should be packaged separately as a
2394 prerequisite if possible.
2396 Having multiple copies of the same code in Debian is
2397 inefficient, often creates either static linking or shared
2398 library conflicts, and, most importantly, increases the
2399 difficulty of handling security vulnerabilities in the
2405 <sect id="readmesource">
2406 <heading>Source package handling:
2407 <file>debian/README.source</file></heading>
2410 If running <prgn>dpkg-source -x</prgn> on a source package
2411 doesn't produce the source of the package, ready for editing,
2412 and allow one to make changes and run
2413 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2414 without taking any additional steps, creating a
2415 <file>debian/README.source</file> documentation file is
2416 recommended. This file should explain how to do all of the
2419 <item>Generate the fully patched source, in a form ready for
2420 editing, that would be built to create Debian
2421 packages. Doing this with a <tt>patch</tt> target in
2422 <file>debian/rules</file> is recommended; see
2423 <ref id="debianrules">.</item>
2424 <item>Modify the source and save those modifications so that
2425 they will be applied when building the package.</item>
2426 <item>Remove source modifications that are currently being
2427 applied when building the package.</item>
2428 <item>Optionally, document what steps are necessary to
2429 upgrade the Debian source package to a new upstream version,
2430 if applicable.</item>
2432 This explanation should include specific commands and mention
2433 any additional required Debian packages. It should not assume
2434 familiarity with any specific Debian packaging system or patch
2439 This explanation may refer to a documentation file installed by
2440 one of the package's build dependencies provided that the
2441 referenced documentation clearly explains these tasks and is not
2442 a general reference manual.
2446 <file>debian/README.source</file> may also include any other
2447 information that would be helpful to someone modifying the
2448 source package. Even if the package doesn't fit the above
2449 description, maintainers are encouraged to document in a
2450 <file>debian/README.source</file> file any source package with a
2451 particularly complex or unintuitive source layout or build
2452 system (for example, a package that builds the same source
2453 multiple times to generate different binary packages).
2459 <chapt id="controlfields">
2460 <heading>Control files and their fields</heading>
2463 The package management system manipulates data represented in
2464 a common format, known as <em>control data</em>, stored in
2465 <em>control files</em>.
2466 Control files are used for source packages, binary packages and
2467 the <file>.changes</file> files which control the installation
2468 of uploaded files<footnote>
2469 <prgn>dpkg</prgn>'s internal databases are in a similar
2474 <sect id="controlsyntax">
2475 <heading>Syntax of control files</heading>
2478 A control file consists of one or more paragraphs of
2480 The paragraphs are also sometimes referred to as stanzas.
2482 The paragraphs are separated by empty lines. Parsers may accept
2483 lines consisting solely of spaces and tabs as paragraph
2484 separators, but control files should use empty lines. Some control
2485 files allow only one paragraph; others allow several, in
2486 which case each paragraph usually refers to a different
2487 package. (For example, in source packages, the first
2488 paragraph refers to the source package, and later paragraphs
2489 refer to binary packages generated from the source.) The
2490 ordering of the paragraphs in control files is significant.
2494 Each paragraph consists of a series of data fields; each
2495 field consists of the field name, followed by a colon and
2496 then the data/value associated with that field. The field
2497 name is composed of printable ASCII characters (i.e.,
2498 characters that have values between 33 and 126, inclusive)
2499 except colon and must not with a begin with #. The
2500 field ends at the end of the line or at the end of the
2501 last continuation line (see below). Horizontal whitespace
2502 (spaces and tabs) may occur immediately before or after the
2503 value and is ignored there; it is conventional to put a
2504 single space after the colon. For example, a field might
2506 <example compact="compact">
2509 the field name is <tt>Package</tt> and the field value
2514 A paragraph must not contain more than one instance of a
2515 particular field name.
2519 There are three types of fields:
2523 The field, including its value, must be a single line. Folding
2524 of the field is not permitted. This is the default field type
2525 if the definition of the field does not specify a different
2530 The value of a folded field is a logical line that may span
2531 several lines. The lines after the first are called
2532 continuation lines and must start with a space or a tab.
2533 Whitespace, including any newlines, is not significant in the
2534 field values of folded fields.<footnote>
2535 This folding method is similar to RFC 5322, allowing control
2536 files that contain only one paragraph and no multiline fields
2537 to be read by parsers written for RFC 5322.
2540 <tag>multiline</tag>
2542 The value of a multiline field may comprise multiple continuation
2543 lines. The first line of the value, the part on the same line as
2544 the field name, often has special significance or may have to be
2545 empty. Other lines are added following the same syntax as the
2546 continuation lines of the folded fields. Whitespace, including newlines,
2547 is significant in the values of multiline fields.
2553 Whitespace must not appear
2554 inside names (of packages, architectures, files or anything
2555 else) or version numbers, or between the characters of
2556 multi-character version relationships.
2560 The presence and purpose of a field, and the syntax of its
2561 value may differ between types of control files.
2565 Field names are not case-sensitive, but it is usual to
2566 capitalize the field names using mixed case as shown below.
2567 Field values are case-sensitive unless the description of the
2568 field says otherwise.
2572 Paragraph separators (empty lines) and lines consisting only of
2573 spaces and tabs are not allowed within field values or between
2574 fields. Empty lines in field values are usually escaped by
2575 representing them by a space followed by a dot.
2579 Lines starting with # without any preceding whitespace are comments
2580 lines that are only permitted in source package control files
2581 (<file>debian/control</file>). These comment lines are ignored, even
2582 between two continuation lines. They do not end logical lines.
2586 All control files must be encoded in UTF-8.
2590 <sect id="sourcecontrolfiles">
2591 <heading>Source package control files -- <file>debian/control</file></heading>
2594 The <file>debian/control</file> file contains the most vital
2595 (and version-independent) information about the source package
2596 and about the binary packages it creates.
2600 The first paragraph of the control file contains information about
2601 the source package in general. The subsequent sets each describe a
2602 binary package that the source tree builds.
2606 The fields in the general paragraph (the first one, for the source
2609 <list compact="compact">
2610 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2611 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2613 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2614 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2615 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2616 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2617 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2618 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2623 The fields in the binary package paragraphs are:
2625 <list compact="compact">
2626 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2629 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2630 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2631 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2632 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2633 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2638 The syntax and semantics of the fields are described below.
2642 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2643 generate control files for binary packages (see below), by
2644 <prgn>dpkg-genchanges</prgn> to generate the
2645 <file>.changes</file> file to accompany the upload, and by
2646 <prgn>dpkg-source</prgn> when it creates the
2647 <file>.dsc</file> source control file as part of a source
2648 archive. Some fields are folded in <file>debian/control</file>,
2649 but not in any other control
2650 file. These tools are responsible for removing the line
2651 breaks from such fields when using fields from
2652 <file>debian/control</file> to generate other control files.
2656 The fields here may contain variable references - their
2657 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2658 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2659 when they generate output control files.
2660 See <ref id="substvars"> for details.
2664 <sect id="binarycontrolfiles">
2665 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2668 The <file>DEBIAN/control</file> file contains the most vital
2669 (and version-dependent) information about a binary package. It
2670 consists of a single paragraph.
2674 The fields in this file are:
2676 <list compact="compact">
2677 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2679 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2680 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2681 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2682 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2683 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2684 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2685 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2686 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2693 <sect id="debiansourcecontrolfiles">
2694 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2697 This file consists of a single paragraph, possibly surrounded by
2698 a PGP signature. The fields of that paragraph are listed below.
2699 Their syntax is described above, in <ref id="pkg-controlfields">.
2701 <list compact="compact">
2702 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2703 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2704 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2705 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2706 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2707 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2708 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2709 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2710 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2711 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2712 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2713 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2714 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2715 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2720 The Debian source control file is generated by
2721 <prgn>dpkg-source</prgn> when it builds the source
2722 archive, from other files in the source package,
2723 described above. When unpacking, it is checked against
2724 the files and directories in the other parts of the
2730 <sect id="debianchangesfiles">
2731 <heading>Debian changes files -- <file>.changes</file></heading>
2734 The <file>.changes</file> files are used by the Debian archive
2735 maintenance software to process updates to packages. They
2736 consist of a single paragraph, possibly surrounded by a PGP
2737 signature. That paragraph contains information from the
2738 <file>debian/control</file> file and other data about the
2739 source package gathered via <file>debian/changelog</file>
2740 and <file>debian/rules</file>.
2744 <file>.changes</file> files have a format version that is
2745 incremented whenever the documented fields or their meaning
2746 change. This document describes format &changesversion;.
2750 The fields in this file are:
2752 <list compact="compact">
2753 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2754 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2755 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2756 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2757 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2760 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2761 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2762 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2763 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2764 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2765 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2767 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2768 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2773 <sect id="controlfieldslist">
2774 <heading>List of fields</heading>
2776 <sect1 id="f-Source">
2777 <heading><tt>Source</tt></heading>
2780 This field identifies the source package name.
2784 In <file>debian/control</file> or a <file>.dsc</file> file,
2785 this field must contain only the name of the source package.
2789 In a binary package control file or a <file>.changes</file>
2790 file, the source package name may be followed by a version
2791 number in parentheses<footnote>
2792 It is customary to leave a space after the package name
2793 if a version number is specified.
2795 This version number may be omitted (and is, by
2796 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2797 the <tt>Version</tt> field of the binary package in
2798 question. The field itself may be omitted from a binary
2799 package control file when the source package has the same
2800 name and version as the binary package.
2804 Package names (both source and binary,
2805 see <ref id="f-Package">) must consist only of lower case
2806 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2807 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2808 (<tt>.</tt>). They must be at least two characters long and
2809 must start with an alphanumeric character.
2813 <sect1 id="f-Maintainer">
2814 <heading><tt>Maintainer</tt></heading>
2817 The package maintainer's name and email address. The name
2818 must come first, then the email address inside angle
2819 brackets <tt><></tt> (in RFC822 format).
2823 If the maintainer's name contains a full stop then the
2824 whole field will not work directly as an email address due
2825 to a misfeature in the syntax specified in RFC822; a
2826 program using this field as an address must check for this
2827 and correct the problem if necessary (for example by
2828 putting the name in round brackets and moving it to the
2829 end, and bringing the email address forward).
2833 See <ref id="maintainer"> for additional requirements and
2834 information about package maintainers.
2838 <sect1 id="f-Uploaders">
2839 <heading><tt>Uploaders</tt></heading>
2842 List of the names and email addresses of co-maintainers of the
2843 package, if any. If the package has other maintainers besides
2844 the one named in the <qref id="f-Maintainer">Maintainer
2845 field</qref>, their names and email addresses should be listed
2846 here. The format of each entry is the same as that of the
2847 Maintainer field, and multiple entries must be comma
2852 This is normally an optional field, but if
2853 the <tt>Maintainer</tt> control field names a group of people
2854 and a shared email address, the <tt>Uploaders</tt> field must
2855 be present and must contain at least one human with their
2856 personal email address.
2860 The Uploaders field in <file>debian/control</file> can be folded.
2864 <sect1 id="f-Changed-By">
2865 <heading><tt>Changed-By</tt></heading>
2868 The name and email address of the person who prepared this
2869 version of the package, usually a maintainer. The syntax is
2870 the same as for the <qref id="f-Maintainer">Maintainer
2875 <sect1 id="f-Section">
2876 <heading><tt>Section</tt></heading>
2879 This field specifies an application area into which the package
2880 has been classified. See <ref id="subsections">.
2884 When it appears in the <file>debian/control</file> file,
2885 it gives the value for the subfield of the same name in
2886 the <tt>Files</tt> field of the <file>.changes</file> file.
2887 It also gives the default for the same field in the binary
2892 <sect1 id="f-Priority">
2893 <heading><tt>Priority</tt></heading>
2896 This field represents how important it is that the user
2897 have the package installed. See <ref id="priorities">.
2901 When it appears in the <file>debian/control</file> file,
2902 it gives the value for the subfield of the same name in
2903 the <tt>Files</tt> field of the <file>.changes</file> file.
2904 It also gives the default for the same field in the binary
2909 <sect1 id="f-Package">
2910 <heading><tt>Package</tt></heading>
2913 The name of the binary package.
2917 Binary package names must follow the same syntax and
2918 restrictions as source package names. See <ref id="f-Source">
2923 <sect1 id="f-Architecture">
2924 <heading><tt>Architecture</tt></heading>
2927 Depending on context and the control file used, the
2928 <tt>Architecture</tt> field can include the following sets of
2932 A unique single word identifying a Debian machine
2933 architecture as described in <ref id="arch-spec">.
2936 An architecture wildcard identifying a set of Debian
2937 machine architectures, see <ref id="arch-wildcard-spec">.
2938 <tt>any</tt> matches all Debian machine architectures
2939 and is the most frequently used.
2942 <tt>all</tt>, which indicates an
2943 architecture-independent package.
2946 <tt>source</tt>, which indicates a source package.
2952 In the main <file>debian/control</file> file in the source
2953 package, this field may contain the special
2954 value <tt>all</tt>, the special architecture
2955 wildcard <tt>any</tt>, or a list of specific and wildcard
2956 architectures separated by spaces. If <tt>all</tt>
2957 or <tt>any</tt> appears, that value must be the entire
2958 contents of the field. Most packages will use
2959 either <tt>all</tt> or <tt>any</tt>.
2963 Specifying a specific list of architectures indicates that the
2964 source will build an architecture-dependent package only on
2965 architectures included in the list. Specifying a list of
2966 architecture wildcards indicates that the source will build an
2967 architecture-dependent package on only those architectures
2968 that match any of the specified architecture wildcards.
2969 Specifying a list of architectures or architecture wildcards
2970 other than <tt>any</tt> is for the minority of cases where a
2971 program is not portable or is not useful on some
2972 architectures. Where possible, the program should be made
2977 In the Debian source control file <file>.dsc</file>, this
2978 field contains a list of architectures and architecture
2979 wildcards separated by spaces. When the list contains the
2980 architecture wildcard <tt>any</tt>, the only other value
2981 allowed in the list is <tt>all</tt>.
2985 The list may include (or consist solely of) the special
2986 value <tt>all</tt>. In other words, in <file>.dsc</file>
2987 files unlike the <file>debian/control</file>, <tt>all</tt> may
2988 occur in combination with specific architectures.
2989 The <tt>Architecture</tt> field in the Debian source control
2990 file <file>.dsc</file> is generally constructed from
2991 the <tt>Architecture</tt> fields in
2992 the <file>debian/control</file> in the source package.
2996 Specifying only <tt>any</tt> indicates that the source package
2997 isn't dependent on any particular architecture and should
2998 compile fine on any one. The produced binary package(s)
2999 will be specific to whatever the current build architecture is.
3003 Specifying only <tt>all</tt> indicates that the source package
3004 will only build architecture-independent packages.
3008 Specifying <tt>any all</tt> indicates that the source package
3009 isn't dependent on any particular architecture. The set of
3010 produced binary packages will include at least one
3011 architecture-dependant package and one architecture-independent
3016 Specifying a list of architectures or architecture wildcards
3017 indicates that the source will build an architecture-dependent
3018 package, and will only work correctly on the listed or
3019 matching architectures. If the source package also builds at
3020 least one architecture-independent package, <tt>all</tt> will
3021 also be included in the list.
3025 In a <file>.changes</file> file, the <tt>Architecture</tt>
3026 field lists the architecture(s) of the package(s) currently
3027 being uploaded. This will be a list; if the source for the
3028 package is also being uploaded, the special
3029 entry <tt>source</tt> is also present. <tt>all</tt> will be
3030 present if any architecture-independent packages are being
3031 uploaded. Architecture wildcards such as <tt>any</tt> must
3032 never occur in the <tt>Architecture</tt> field in
3033 the <file>.changes</file> file.
3037 See <ref id="debianrules"> for information on how to get
3038 the architecture for the build process.
3042 <sect1 id="f-Essential">
3043 <heading><tt>Essential</tt></heading>
3046 This is a boolean field which may occur only in the
3047 control file of a binary package or in a per-package fields
3048 paragraph of a source package control file.
3052 If set to <tt>yes</tt> then the package management system
3053 will refuse to remove the package (upgrading and replacing
3054 it is still possible). The other possible value is <tt>no</tt>,
3055 which is the same as not having the field at all.
3060 <heading>Package interrelationship fields:
3061 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3062 <tt>Recommends</tt>, <tt>Suggests</tt>,
3063 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3064 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3068 These fields describe the package's relationships with
3069 other packages. Their syntax and semantics are described
3070 in <ref id="relationships">.</p>
3073 <sect1 id="f-Standards-Version">
3074 <heading><tt>Standards-Version</tt></heading>
3077 The most recent version of the standards (the policy
3078 manual and associated texts) with which the package
3083 The version number has four components: major and minor
3084 version number and major and minor patch level. When the
3085 standards change in a way that requires every package to
3086 change the major number will be changed. Significant
3087 changes that will require work in many packages will be
3088 signaled by a change to the minor number. The major patch
3089 level will be changed for any change to the meaning of the
3090 standards, however small; the minor patch level will be
3091 changed when only cosmetic, typographical or other edits
3092 are made which neither change the meaning of the document
3093 nor affect the contents of packages.
3097 Thus only the first three components of the policy version
3098 are significant in the <em>Standards-Version</em> control
3099 field, and so either these three components or all four
3100 components may be specified.<footnote>
3101 In the past, people specified the full version number
3102 in the Standards-Version field, for example "2.3.0.0".
3103 Since minor patch-level changes don't introduce new
3104 policy, it was thought it would be better to relax
3105 policy and only require the first 3 components to be
3106 specified, in this example "2.3.0". All four
3107 components may still be used if someone wishes to do so.
3113 <sect1 id="f-Version">
3114 <heading><tt>Version</tt></heading>
3117 The version number of a package. The format is:
3118 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3122 The three components here are:
3124 <tag><var>epoch</var></tag>
3127 This is a single (generally small) unsigned integer. It
3128 may be omitted, in which case zero is assumed. If it is
3129 omitted then the <var>upstream_version</var> may not
3134 It is provided to allow mistakes in the version numbers
3135 of older versions of a package, and also a package's
3136 previous version numbering schemes, to be left behind.
3140 <tag><var>upstream_version</var></tag>
3143 This is the main part of the version number. It is
3144 usually the version number of the original ("upstream")
3145 package from which the <file>.deb</file> file has been made,
3146 if this is applicable. Usually this will be in the same
3147 format as that specified by the upstream author(s);
3148 however, it may need to be reformatted to fit into the
3149 package management system's format and comparison
3154 The comparison behavior of the package management system
3155 with respect to the <var>upstream_version</var> is
3156 described below. The <var>upstream_version</var>
3157 portion of the version number is mandatory.
3161 The <var>upstream_version</var> may contain only
3162 alphanumerics<footnote>
3163 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3165 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3166 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3167 tilde) and should start with a digit. If there is no
3168 <var>debian_revision</var> then hyphens are not allowed;
3169 if there is no <var>epoch</var> then colons are not
3174 <tag><var>debian_revision</var></tag>
3177 This part of the version number specifies the version of
3178 the Debian package based on the upstream version. It
3179 may contain only alphanumerics and the characters
3180 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3181 tilde) and is compared in the same way as the
3182 <var>upstream_version</var> is.
3186 It is optional; if it isn't present then the
3187 <var>upstream_version</var> may not contain a hyphen.
3188 This format represents the case where a piece of
3189 software was written specifically to be a Debian
3190 package, where the Debian package source must always
3191 be identical to the pristine source and therefore no
3192 revision indication is required.
3196 It is conventional to restart the
3197 <var>debian_revision</var> at <tt>1</tt> each time the
3198 <var>upstream_version</var> is increased.
3202 The package management system will break the version
3203 number apart at the last hyphen in the string (if there
3204 is one) to determine the <var>upstream_version</var> and
3205 <var>debian_revision</var>. The absence of a
3206 <var>debian_revision</var> is equivalent to a
3207 <var>debian_revision</var> of <tt>0</tt>.
3214 When comparing two version numbers, first the <var>epoch</var>
3215 of each are compared, then the <var>upstream_version</var> if
3216 <var>epoch</var> is equal, and then <var>debian_revision</var>
3217 if <var>upstream_version</var> is also equal.
3218 <var>epoch</var> is compared numerically. The
3219 <var>upstream_version</var> and <var>debian_revision</var>
3220 parts are compared by the package management system using the
3221 following algorithm:
3225 The strings are compared from left to right.
3229 First the initial part of each string consisting entirely of
3230 non-digit characters is determined. These two parts (one of
3231 which may be empty) are compared lexically. If a difference
3232 is found it is returned. The lexical comparison is a
3233 comparison of ASCII values modified so that all the letters
3234 sort earlier than all the non-letters and so that a tilde
3235 sorts before anything, even the end of a part. For example,
3236 the following parts are in sorted order from earliest to
3237 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3238 <tt>a</tt>.<footnote>
3239 One common use of <tt>~</tt> is for upstream pre-releases.
3240 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3241 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3246 Then the initial part of the remainder of each string which
3247 consists entirely of digit characters is determined. The
3248 numerical values of these two parts are compared, and any
3249 difference found is returned as the result of the comparison.
3250 For these purposes an empty string (which can only occur at
3251 the end of one or both version strings being compared) counts
3256 These two steps (comparing and removing initial non-digit
3257 strings and initial digit strings) are repeated until a
3258 difference is found or both strings are exhausted.
3262 Note that the purpose of epochs is to allow us to leave behind
3263 mistakes in version numbering, and to cope with situations
3264 where the version numbering scheme changes. It is
3265 <em>not</em> intended to cope with version numbers containing
3266 strings of letters which the package management system cannot
3267 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3268 silly orderings.<footnote>
3269 The author of this manual has heard of a package whose
3270 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3271 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3277 <sect1 id="f-Description">
3278 <heading><tt>Description</tt></heading>
3281 In a source or binary control file, the <tt>Description</tt>
3282 field contains a description of the binary package, consisting
3283 of two parts, the synopsis or the short description, and the
3284 long description. It is a multiline field with the following
3290 Description: <single line synopsis>
3291 <extended description over several lines>
3296 The lines in the extended description can have these formats:
3302 Those starting with a single space are part of a paragraph.
3303 Successive lines of this form will be word-wrapped when
3304 displayed. The leading space will usually be stripped off.
3305 The line must contain at least one non-whitespace character.
3309 Those starting with two or more spaces. These will be
3310 displayed verbatim. If the display cannot be panned
3311 horizontally, the displaying program will line wrap them "hard"
3312 (i.e., without taking account of word breaks). If it can they
3313 will be allowed to trail off to the right. None, one or two
3314 initial spaces may be deleted, but the number of spaces
3315 deleted from each line will be the same (so that you can have
3316 indenting work correctly, for example). The line must
3317 contain at least one non-whitespace character.
3321 Those containing a single space followed by a single full stop
3322 character. These are rendered as blank lines. This is the
3323 <em>only</em> way to get a blank line<footnote>
3324 Completely empty lines will not be rendered as blank lines.
3325 Instead, they will cause the parser to think you're starting
3326 a whole new record in the control file, and will therefore
3327 likely abort with an error.
3332 Those containing a space, a full stop and some more characters.
3333 These are for future expansion. Do not use them.
3339 Do not use tab characters. Their effect is not predictable.
3343 See <ref id="descriptions"> for further information on this.
3347 In a <file>.changes</file> file, the <tt>Description</tt>
3348 field contains a summary of the descriptions for the packages
3349 being uploaded. For this case, the first line of the field
3350 value (the part on the same line as <tt>Description:</tt>) is
3351 always empty. It is a multiline field, with one
3352 line per package. Each line is
3353 indented by one space and contains the name of a binary
3354 package, a space, a hyphen (<tt>-</tt>), a space, and the
3355 short description line from that package.
3359 <sect1 id="f-Distribution">
3360 <heading><tt>Distribution</tt></heading>
3363 In a <file>.changes</file> file or parsed changelog output
3364 this contains the (space-separated) name(s) of the
3365 distribution(s) where this version of the package should
3366 be installed. Valid distributions are determined by the
3367 archive maintainers.<footnote>
3368 Example distribution names in the Debian archive used in
3369 <file>.changes</file> files are:
3370 <taglist compact="compact">
3371 <tag><em>unstable</em></tag>
3373 This distribution value refers to the
3374 <em>developmental</em> part of the Debian distribution
3375 tree. Most new packages, new upstream versions of
3376 packages and bug fixes go into the <em>unstable</em>
3380 <tag><em>experimental</em></tag>
3382 The packages with this distribution value are deemed
3383 by their maintainers to be high risk. Oftentimes they
3384 represent early beta or developmental packages from
3385 various sources that the maintainers want people to
3386 try, but are not ready to be a part of the other parts
3387 of the Debian distribution tree.
3392 Others are used for updating stable releases or for
3393 security uploads. More information is available in the
3394 Debian Developer's Reference, section "The Debian
3398 The Debian archive software only supports listing a single
3399 distribution. Migration of packages to other distributions is
3400 handled outside of the upload process.
3405 <heading><tt>Date</tt></heading>
3408 This field includes the date the package was built or last
3409 edited. It must be in the same format as the <var>date</var>
3410 in a <file>debian/changelog</file> entry.
3414 The value of this field is usually extracted from the
3415 <file>debian/changelog</file> file - see
3416 <ref id="dpkgchangelog">).
3420 <sect1 id="f-Format">
3421 <heading><tt>Format</tt></heading>
3424 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3425 files, this field declares the format version of that file.
3426 The syntax of the field value is the same as that of
3427 a <qref id="f-Version">package version number</qref> except
3428 that no epoch or Debian revision is allowed. The format
3429 described in this document is <tt>&changesversion;</tt>.
3433 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3434 Debian source control</qref> files, this field declares the
3435 format of the source package. The field value is used by
3436 programs acting on a source package to interpret the list of
3437 files in the source package and determine how to unpack it.
3438 The syntax of the field value is a numeric major revision, a
3439 period, a numeric minor revision, and then an optional subtype
3440 after whitespace, which if specified is an alphanumeric word
3441 in parentheses. The subtype is optional in the syntax but may
3442 be mandatory for particular source format revisions.
3444 The source formats currently supported by the Debian archive
3445 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3446 and <tt>3.0 (quilt)</tt>.
3451 <sect1 id="f-Urgency">
3452 <heading><tt>Urgency</tt></heading>
3455 This is a description of how important it is to upgrade to
3456 this version from previous ones. It consists of a single
3457 keyword taking one of the values <tt>low</tt>,
3458 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3459 <tt>critical</tt><footnote>
3460 Other urgency values are supported with configuration
3461 changes in the archive software but are not used in Debian.
3462 The urgency affects how quickly a package will be considered
3463 for inclusion into the <tt>testing</tt> distribution and
3464 gives an indication of the importance of any fixes included
3465 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3466 treated as synonymous.
3467 </footnote> (not case-sensitive) followed by an optional
3468 commentary (separated by a space) which is usually in
3469 parentheses. For example:
3472 Urgency: low (HIGH for users of diversions)
3478 The value of this field is usually extracted from the
3479 <file>debian/changelog</file> file - see
3480 <ref id="dpkgchangelog">.
3484 <sect1 id="f-Changes">
3485 <heading><tt>Changes</tt></heading>
3488 This multiline field contains the human-readable changes data, describing
3489 the differences between the last version and the current one.
3493 The first line of the field value (the part on the same line
3494 as <tt>Changes:</tt>) is always empty. The content of the
3495 field is expressed as continuation lines, with each line
3496 indented by at least one space. Blank lines must be
3497 represented by a line consisting only of a space and a full
3502 The value of this field is usually extracted from the
3503 <file>debian/changelog</file> file - see
3504 <ref id="dpkgchangelog">).
3508 Each version's change information should be preceded by a
3509 "title" line giving at least the version, distribution(s)
3510 and urgency, in a human-readable way.
3514 If data from several versions is being returned the entry
3515 for the most recent version should be returned first, and
3516 entries should be separated by the representation of a
3517 blank line (the "title" line may also be followed by the
3518 representation of a blank line).
3522 <sect1 id="f-Binary">
3523 <heading><tt>Binary</tt></heading>
3526 This folded field is a list of binary packages. Its syntax and
3527 meaning varies depending on the control file in which it
3532 When it appears in the <file>.dsc</file> file, it lists binary
3533 packages which a source package can produce, separated by
3535 A space after each comma is conventional.
3536 </footnote>. The source package
3537 does not necessarily produce all of these binary packages for
3538 every architecture. The source control file doesn't contain
3539 details of which architectures are appropriate for which of
3540 the binary packages.
3544 When it appears in a <file>.changes</file> file, it lists the
3545 names of the binary packages being uploaded, separated by
3546 whitespace (not commas).
3550 <sect1 id="f-Installed-Size">
3551 <heading><tt>Installed-Size</tt></heading>
3554 This field appears in the control files of binary packages,
3555 and in the <file>Packages</file> files. It gives an estimate
3556 of the total amount of disk space required to install the
3557 named package. Actual installed size may vary based on block
3558 size, file system properties, or actions taken by package
3563 The disk space is given as the integer value of the estimated
3564 installed size in bytes, divided by 1024 and rounded up.
3568 <sect1 id="f-Files">
3569 <heading><tt>Files</tt></heading>
3572 This field contains a list of files with information about
3573 each one. The exact information and syntax varies with
3578 In all cases, Files is a multiline field. The first line of
3579 the field value (the part on the same line as <tt>Files:</tt>)
3580 is always empty. The content of the field is expressed as
3581 continuation lines, one line per file. Each line must be
3582 indented by one space and contain a number of sub-fields,
3583 separated by spaces, as described below.
3587 In the <file>.dsc</file> file, each line contains the MD5
3588 checksum, size and filename of the tar file and (if
3589 applicable) diff file which make up the remainder of the
3590 source package<footnote>
3591 That is, the parts which are not the <tt>.dsc</tt>.
3592 </footnote>. For example:
3595 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3596 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3598 The exact forms of the filenames are described
3599 in <ref id="pkg-sourcearchives">.
3603 In the <file>.changes</file> file this contains one line per
3604 file being uploaded. Each line contains the MD5 checksum,
3605 size, section and priority and the filename. For example:
3608 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3609 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3610 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3611 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3613 The <qref id="f-Section">section</qref>
3614 and <qref id="f-Priority">priority</qref> are the values of
3615 the corresponding fields in the main source control file. If
3616 no section or priority is specified then <tt>-</tt> should be
3617 used, though section and priority values must be specified for
3618 new packages to be installed properly.
3622 The special value <tt>byhand</tt> for the section in a
3623 <tt>.changes</tt> file indicates that the file in question
3624 is not an ordinary package file and must by installed by
3625 hand by the distribution maintainers. If the section is
3626 <tt>byhand</tt> the priority should be <tt>-</tt>.
3630 If a new Debian revision of a package is being shipped and
3631 no new original source archive is being distributed the
3632 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3633 entry for the original source archive
3634 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3635 but the <file>.changes</file> file should leave it out. In
3636 this case the original source archive on the distribution
3637 site must match exactly, byte-for-byte, the original
3638 source archive which was used to generate the
3639 <file>.dsc</file> file and diff which are being uploaded.</p>
3642 <sect1 id="f-Closes">
3643 <heading><tt>Closes</tt></heading>
3646 A space-separated list of bug report numbers that the upload
3647 governed by the .changes file closes.
3651 <sect1 id="f-Homepage">
3652 <heading><tt>Homepage</tt></heading>
3655 The URL of the web site for this package, preferably (when
3656 applicable) the site from which the original source can be
3657 obtained and any additional upstream documentation or
3658 information may be found. The content of this field is a
3659 simple URL without any surrounding characters such as
3664 <sect1 id="f-Checksums">
3665 <heading><tt>Checksums-Sha1</tt>
3666 and <tt>Checksums-Sha256</tt></heading>
3669 These multiline fields contain a list of files with a checksum and size
3670 for each one. Both <tt>Checksums-Sha1</tt>
3671 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3672 only in the checksum algorithm used: SHA-1
3673 for <tt>Checksums-Sha1</tt> and SHA-256
3674 for <tt>Checksums-Sha256</tt>.
3678 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3679 multiline fields. The first line of the field value (the part
3680 on the same line as <tt>Checksums-Sha1:</tt>
3681 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3682 of the field is expressed as continuation lines, one line per
3683 file. Each line consists of the checksum, a space, the file
3684 size, a space, and the file name. For example (from
3685 a <file>.changes</file> file):
3688 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3689 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3690 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3691 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3693 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3694 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3695 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3696 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3701 In the <file>.dsc</file> file, these fields should list all
3702 files that make up the source package. In
3703 the <file>.changes</file> file, these fields should list all
3704 files being uploaded. The list of files in these fields
3705 must match the list of files in the <tt>Files</tt> field.
3709 <sect1 id="f-DM-Upload-Allowed">
3710 <heading><tt>DM-Upload-Allowed</tt></heading>
3713 The most recent version of a package uploaded to unstable or
3714 experimental must include the field <tt>DM-Upload-Allowed:
3715 yes</tt> in the source section of its source control file for
3716 the Debian archive to accept uploads signed with a key in the
3717 Debian Maintainer keyring. See the General
3718 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3719 name="Endorse the concept of Debian Maintainers"> for more
3726 <heading>User-defined fields</heading>
3729 Additional user-defined fields may be added to the
3730 source package control file. Such fields will be
3731 ignored, and not copied to (for example) binary or
3732 Debian source control files or upload control files.
3736 If you wish to add additional unsupported fields to
3737 these output files you should use the mechanism
3742 Fields in the main source control information file with
3743 names starting <tt>X</tt>, followed by one or more of
3744 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3745 be copied to the output files. Only the part of the
3746 field name after the hyphen will be used in the output
3747 file. Where the letter <tt>B</tt> is used the field
3748 will appear in binary package control files, where the
3749 letter <tt>S</tt> is used in Debian source control
3750 files and where <tt>C</tt> is used in upload control
3751 (<tt>.changes</tt>) files.
3755 For example, if the main source information control file
3758 XBS-Comment: I stand between the candle and the star.
3760 then the binary and Debian source control files will contain the
3763 Comment: I stand between the candle and the star.
3772 <chapt id="maintainerscripts">
3773 <heading>Package maintainer scripts and installation procedure</heading>
3776 <heading>Introduction to package maintainer scripts</heading>
3779 It is possible to supply scripts as part of a package which
3780 the package management system will run for you when your
3781 package is installed, upgraded or removed.
3785 These scripts are the control information
3786 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3787 and <prgn>postrm</prgn>. They must be proper executable files;
3788 if they are scripts (which is recommended), they must start with
3789 the usual <tt>#!</tt> convention. They should be readable and
3790 executable by anyone, and must not be world-writable.
3794 The package management system looks at the exit status from
3795 these scripts. It is important that they exit with a
3796 non-zero status if there is an error, so that the package
3797 management system can stop its processing. For shell
3798 scripts this means that you <em>almost always</em> need to
3799 use <tt>set -e</tt> (this is usually true when writing shell
3800 scripts, in fact). It is also important, of course, that
3801 they exit with a zero status if everything went well.
3805 Additionally, packages interacting with users
3806 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3807 should install a <prgn>config</prgn> script as a control
3808 information file. See <ref id="maintscriptprompt"> for details.
3812 When a package is upgraded a combination of the scripts from
3813 the old and new packages is called during the upgrade
3814 procedure. If your scripts are going to be at all
3815 complicated you need to be aware of this, and may need to
3816 check the arguments to your scripts.
3820 Broadly speaking the <prgn>preinst</prgn> is called before
3821 (a particular version of) a package is unpacked, and the
3822 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3823 before (a version of) a package is removed and the
3824 <prgn>postrm</prgn> afterwards.
3828 Programs called from maintainer scripts should not normally
3829 have a path prepended to them. Before installation is
3830 started, the package management system checks to see if the
3831 programs <prgn>ldconfig</prgn>,
3832 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3833 and <prgn>update-rc.d</prgn> can be found via the
3834 <tt>PATH</tt> environment variable. Those programs, and any
3835 other program that one would expect to be in the
3836 <tt>PATH</tt>, should thus be invoked without an absolute
3837 pathname. Maintainer scripts should also not reset the
3838 <tt>PATH</tt>, though they might choose to modify it by
3839 prepending or appending package-specific directories. These
3840 considerations really apply to all shell scripts.</p>
3843 <sect id="idempotency">
3844 <heading>Maintainer scripts idempotency</heading>
3847 It is necessary for the error recovery procedures that the
3848 scripts be idempotent. This means that if it is run
3849 successfully, and then it is called again, it doesn't bomb
3850 out or cause any harm, but just ensures that everything is
3851 the way it ought to be. If the first call failed, or
3852 aborted half way through for some reason, the second call
3853 should merely do the things that were left undone the first
3854 time, if any, and exit with a success status if everything
3856 This is so that if an error occurs, the user interrupts
3857 <prgn>dpkg</prgn> or some other unforeseen circumstance
3858 happens you don't leave the user with a badly-broken
3859 package when <prgn>dpkg</prgn> attempts to repeat the
3865 <sect id="controllingterminal">
3866 <heading>Controlling terminal for maintainer scripts</heading>
3869 Maintainer scripts are not guaranteed to run with a controlling
3870 terminal and may not be able to interact with the user. They
3871 must be able to fall back to noninteractive behavior if no
3872 controlling terminal is available. Maintainer scripts that
3873 prompt via a program conforming to the Debian Configuration
3874 Management Specification (see <ref id="maintscriptprompt">) may
3875 assume that program will handle falling back to noninteractive
3880 For high-priority prompts without a reasonable default answer,
3881 maintainer scripts may abort if there is no controlling
3882 terminal. However, this situation should be avoided if at all
3883 possible, since it prevents automated or unattended installs.
3884 In most cases, users will consider this to be a bug in the
3889 <sect id="exitstatus">
3890 <heading>Exit status</heading>
3893 Each script must return a zero exit status for
3894 success, or a nonzero one for failure, since the package
3895 management system looks for the exit status of these scripts
3896 and determines what action to take next based on that datum.
3900 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3905 What follows is a summary of all the ways in which maintainer
3906 scripts may be called along with what facilities those scripts
3907 may rely on being available at that time. Script names preceded
3908 by <var>new-</var> are the scripts from the new version of a
3909 package being installed, upgraded to, or downgraded to. Script
3910 names preceded by <var>old-</var> are the scripts from the old
3911 version of a package that is being upgraded from or downgraded
3916 The <prgn>preinst</prgn> script may be called in the following
3919 <tag><var>new-preinst</var> <tt>install</tt></tag>
3920 <tag><var>new-preinst</var> <tt>install</tt>
3921 <var>old-version</var></tag>
3922 <tag><var>new-preinst</var> <tt>upgrade</tt>
3923 <var>old-version</var></tag>
3925 The package will not yet be unpacked, so
3926 the <prgn>preinst</prgn> script cannot rely on any files
3927 included in its package. Only essential packages and
3928 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3929 available. Pre-dependencies will have been configured at
3930 least once, but at the time the <prgn>preinst</prgn> is
3931 called they may only be in an unpacked or "Half-Configured"
3932 state if a previous version of the pre-dependency was
3933 completely configured and has not been removed since then.
3936 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3937 <var>new-version</var></tag>
3939 Called during error handling of an upgrade that failed after
3940 unpacking the new package because the <tt>postrm
3941 upgrade</tt> action failed. The unpacked files may be
3942 partly from the new version or partly missing, so the script
3943 cannot rely on files included in the package. Package
3944 dependencies may not be available. Pre-dependencies will be
3945 at least unpacked following the same rules as above, except
3946 they may be only "Half-Installed" if an upgrade of the
3947 pre-dependency failed.<footnote>
3948 This can happen if the new version of the package no
3949 longer pre-depends on a package that had been partially
3957 The <prgn>postinst</prgn> script may be called in the following
3960 <tag><var>postinst</var> <tt>configure</tt>
3961 <var>most-recently-configured-version</var></tag>
3963 The files contained in the package will be unpacked. All
3964 package dependencies will at least be unpacked. If there
3965 are no circular dependencies involved, all package
3966 dependencies will be configured. For behavior in the case
3967 of circular dependencies, see the discussion
3968 in <ref id="binarydeps">.
3971 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3972 <var>new-version</var></tag>
3973 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3974 <tt>in-favour</tt> <var>package</var>
3975 <var>new-version</var></tag>
3976 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3977 <tag><var>deconfigured's-postinst</var>
3978 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3979 <var>failed-install-package</var> <var>version</var>
3980 [<tt>removing</tt> <var>conflicting-package</var>
3981 <var>version</var>]</tag>
3983 The files contained in the package will be unpacked. All
3984 package dependencies will at least be "Half-Installed" and
3985 will have previously been configured and not removed.
3986 However, dependencies may not be configured or even fully
3987 unpacked in some error situations.<footnote>
3988 For example, suppose packages foo and bar are installed
3989 with foo depending on bar. If an upgrade of bar were
3990 started and then aborted, and then an attempt to remove
3991 foo failed because its <prgn>prerm</prgn> script failed,
3992 foo's <tt>postinst abort-remove</tt> would be called with
3993 bar only "Half-Installed".
3995 The <prgn>postinst</prgn> should still attempt any actions
3996 for which its dependencies are required, since they will
3997 normally be available, but consider the correct error
3998 handling approach if those actions fail. Aborting
3999 the <prgn>postinst</prgn> action if commands or facilities
4000 from the package dependencies are not available is often the
4007 The <prgn>prerm</prgn> script may be called in the following
4010 <tag><var>prerm</var> <tt>remove</tt></tag>
4011 <tag><var>old-prerm</var>
4012 <tt>upgrade</tt><var>new-version</var></tag>
4013 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4014 <tt>in-favour</tt> <var>package</var>
4015 <var>new-version</var></tag>
4016 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4017 <tt>in-favour</tt> <var>package-being-installed</var>
4018 <var>version</var> [<tt>removing</tt>
4019 <var>conflicting-package</var> <var>version</var>]</tag>
4021 The package whose <prgn>prerm</prgn> is being called will be
4022 at least "Half-Installed". All package dependencies will at
4023 least be "Half-Installed" and will have previously been
4024 configured and not removed. If there was no error, all
4025 dependencies will at least be unpacked, but these actions
4026 may be called in various error states where dependencies are
4027 only "Half-Installed" due to a partial upgrade.
4030 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4031 <var>old-version</var></tag>
4033 Called during error handling when <tt>prerm upgrade</tt>
4034 fails. The new package will not yet be unpacked, and all
4035 the same constraints as for <tt>preinst upgrade</tt> apply.
4041 The <prgn>postrm</prgn> script may be called in the following
4044 <tag><var>postrm</var> <tt>remove</tt></tag>
4045 <tag><var>postrm</var> <tt>purge</tt></tag>
4046 <tag><var>old-postrm</var> <tt>upgrade</tt>
4047 <var>new-version</var></tag>
4048 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4049 <var>overwriter</var> <var>overwriter-version</var></tag>
4051 The <prgn>postrm</prgn> script is called after the package's
4052 files have been removed or replaced. The package
4053 whose <prgn>postrm</prgn> is being called may have
4054 previously been deconfigured and only be unpacked, at which
4055 point subsequent package changes do not consider its
4056 dependencies. Therefore, all <prgn>postrm</prgn> actions
4057 may only rely on essential packages and must gracefully skip
4058 any actions that require the package's dependencies if those
4059 dependencies are unavailable.<footnote>
4060 This is often done by checking whether the command or
4061 facility the <prgn>postrm</prgn> intends to call is
4062 available before calling it. For example:
4064 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4065 . /usr/share/debconf/confmodule
4069 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4070 configuration for the package
4071 if <package>debconf</package> is installed.
4075 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4076 <var>old-version</var></tag>
4078 Called when the old <tt>postrm upgrade</tt> action fails.
4079 The new package will be unpacked, but only essential
4080 packages and pre-dependencies can be relied on.
4081 Pre-dependencies will either be configured or will be
4082 "Unpacked" or "Half-Configured" but previously had been
4083 configured and was never removed.
4086 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4087 <tag><var>new-postrm</var> <tt>abort-install</tt>
4088 <var>old-version</var></tag>
4089 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4090 <var>old-version</var></tag>
4092 Called before unpacking the new package as part of the
4093 error handling of <prgn>preinst</prgn> failures. May assume
4094 the same state as <prgn>preinst</prgn> can assume.
4100 <sect id="unpackphase">
4101 <heading>Details of unpack phase of installation or upgrade</heading>
4104 The procedure on installation/upgrade/overwrite/disappear
4105 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4106 stage of <tt>dpkg --install</tt>) is as follows. In each
4107 case, if a major error occurs (unless listed below) the
4108 actions are, in general, run backwards - this means that the
4109 maintainer scripts are run with different arguments in
4110 reverse order. These are the "error unwind" calls listed
4117 If a version of the package is already installed, call
4118 <example compact="compact">
4119 <var>old-prerm</var> upgrade <var>new-version</var>
4123 If the script runs but exits with a non-zero
4124 exit status, <prgn>dpkg</prgn> will attempt:
4125 <example compact="compact">
4126 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4128 If this works, the upgrade continues. If this
4129 does not work, the error unwind:
4130 <example compact="compact">
4131 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4133 If this works, then the old-version is
4134 "Installed", if not, the old version is in a
4135 "Half-Configured" state.
4141 If a "conflicting" package is being removed at the same time,
4142 or if any package will be broken (due to <tt>Breaks</tt>):
4145 If <tt>--auto-deconfigure</tt> is
4146 specified, call, for each package to be deconfigured
4147 due to <tt>Breaks</tt>:
4148 <example compact="compact">
4149 <var>deconfigured's-prerm</var> deconfigure \
4150 in-favour <var>package-being-installed</var> <var>version</var>
4153 <example compact="compact">
4154 <var>deconfigured's-postinst</var> abort-deconfigure \
4155 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4157 The deconfigured packages are marked as
4158 requiring configuration, so that if
4159 <tt>--install</tt> is used they will be
4160 configured again if possible.
4163 If any packages depended on a conflicting
4164 package being removed and <tt>--auto-deconfigure</tt> is
4165 specified, call, for each such package:
4166 <example compact="compact">
4167 <var>deconfigured's-prerm</var> deconfigure \
4168 in-favour <var>package-being-installed</var> <var>version</var> \
4169 removing <var>conflicting-package</var> <var>version</var>
4172 <example compact="compact">
4173 <var>deconfigured's-postinst</var> abort-deconfigure \
4174 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4175 removing <var>conflicting-package</var> <var>version</var>
4177 The deconfigured packages are marked as
4178 requiring configuration, so that if
4179 <tt>--install</tt> is used they will be
4180 configured again if possible.
4183 To prepare for removal of each conflicting package, call:
4184 <example compact="compact">
4185 <var>conflictor's-prerm</var> remove \
4186 in-favour <var>package</var> <var>new-version</var>
4189 <example compact="compact">
4190 <var>conflictor's-postinst</var> abort-remove \
4191 in-favour <var>package</var> <var>new-version</var>
4200 If the package is being upgraded, call:
4201 <example compact="compact">
4202 <var>new-preinst</var> upgrade <var>old-version</var>
4204 If this fails, we call:
4206 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4213 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4215 is called. If this works, then the old version
4216 is in an "Installed" state, or else it is left
4217 in an "Unpacked" state.
4222 If it fails, then the old version is left
4223 in an "Half-Installed" state.
4230 Otherwise, if the package had some configuration
4231 files from a previous version installed (i.e., it
4232 is in the "configuration files only" state):
4233 <example compact="compact">
4234 <var>new-preinst</var> install <var>old-version</var>
4238 <var>new-postrm</var> abort-install <var>old-version</var>
4240 If this fails, the package is left in a
4241 "Half-Installed" state, which requires a
4242 reinstall. If it works, the packages is left in
4243 a "Config-Files" state.
4246 Otherwise (i.e., the package was completely purged):
4247 <example compact="compact">
4248 <var>new-preinst</var> install
4251 <example compact="compact">
4252 <var>new-postrm</var> abort-install
4254 If the error-unwind fails, the package is in a
4255 "Half-Installed" phase, and requires a
4256 reinstall. If the error unwind works, the
4257 package is in a not installed state.
4264 The new package's files are unpacked, overwriting any
4265 that may be on the system already, for example any
4266 from the old version of the same package or from
4267 another package. Backups of the old files are kept
4268 temporarily, and if anything goes wrong the package
4269 management system will attempt to put them back as
4270 part of the error unwind.
4274 It is an error for a package to contain files which
4275 are on the system in another package, unless
4276 <tt>Replaces</tt> is used (see <ref id="replaces">).
4278 The following paragraph is not currently the case:
4279 Currently the <tt>- - force-overwrite</tt> flag is
4280 enabled, downgrading it to a warning, but this may not
4286 It is a more serious error for a package to contain a
4287 plain file or other kind of non-directory where another
4288 package has a directory (again, unless
4289 <tt>Replaces</tt> is used). This error can be
4290 overridden if desired using
4291 <tt>--force-overwrite-dir</tt>, but this is not
4296 Packages which overwrite each other's files produce
4297 behavior which, though deterministic, is hard for the
4298 system administrator to understand. It can easily
4299 lead to "missing" programs if, for example, a package
4300 is unpacked which overwrites a file from another
4301 package, and is then removed again.<footnote>
4302 Part of the problem is due to what is arguably a
4303 bug in <prgn>dpkg</prgn>.
4308 A directory will never be replaced by a symbolic link
4309 to a directory or vice versa; instead, the existing
4310 state (symlink or not) will be left alone and
4311 <prgn>dpkg</prgn> will follow the symlink if there is
4320 If the package is being upgraded, call
4321 <example compact="compact">
4322 <var>old-postrm</var> upgrade <var>new-version</var>
4326 If this fails, <prgn>dpkg</prgn> will attempt:
4327 <example compact="compact">
4328 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4330 If this works, installation continues. If not,
4332 <example compact="compact">
4333 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4335 If this fails, the old version is left in a
4336 "Half-Installed" state. If it works, dpkg now
4338 <example compact="compact">
4339 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4341 If this fails, the old version is left in a
4342 "Half-Installed" state. If it works, dpkg now
4344 <example compact="compact">
4345 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4347 If this fails, the old version is in an
4354 This is the point of no return - if
4355 <prgn>dpkg</prgn> gets this far, it won't back off
4356 past this point if an error occurs. This will
4357 leave the package in a fairly bad state, which
4358 will require a successful re-installation to clear
4359 up, but it's when <prgn>dpkg</prgn> starts doing
4360 things that are irreversible.
4365 Any files which were in the old version of the package
4366 but not in the new are removed.
4370 The new file list replaces the old.
4374 The new maintainer scripts replace the old.
4378 Any packages all of whose files have been overwritten
4379 during the installation, and which aren't required for
4380 dependencies, are considered to have been removed.
4381 For each such package
4384 <prgn>dpkg</prgn> calls:
4385 <example compact="compact">
4386 <var>disappearer's-postrm</var> disappear \
4387 <var>overwriter</var> <var>overwriter-version</var>
4391 The package's maintainer scripts are removed.
4394 It is noted in the status database as being in a
4395 sane state, namely not installed (any conffiles
4396 it may have are ignored, rather than being
4397 removed by <prgn>dpkg</prgn>). Note that
4398 disappearing packages do not have their prerm
4399 called, because <prgn>dpkg</prgn> doesn't know
4400 in advance that the package is going to
4407 Any files in the package we're unpacking that are also
4408 listed in the file lists of other packages are removed
4409 from those lists. (This will lobotomize the file list
4410 of the "conflicting" package if there is one.)
4414 The backup files made during installation, above, are
4420 The new package's status is now sane, and recorded as
4425 Here is another point of no return - if the
4426 conflicting package's removal fails we do not unwind
4427 the rest of the installation; the conflicting package
4428 is left in a half-removed limbo.
4433 If there was a conflicting package we go and do the
4434 removal actions (described below), starting with the
4435 removal of the conflicting package's files (any that
4436 are also in the package being unpacked have already
4437 been removed from the conflicting package's file list,
4438 and so do not get removed now).
4444 <sect id="configdetails"><heading>Details of configuration</heading>
4447 When we configure a package (this happens with <tt>dpkg
4448 --install</tt> and <tt>dpkg --configure</tt>), we first
4449 update any <tt>conffile</tt>s and then call:
4450 <example compact="compact">
4451 <var>postinst</var> configure <var>most-recently-configured-version</var>
4456 No attempt is made to unwind after errors during
4457 configuration. If the configuration fails, the package is in
4458 a "Failed Config" state, and an error message is generated.
4462 If there is no most recently configured version
4463 <prgn>dpkg</prgn> will pass a null argument.
4466 Historical note: Truly ancient (pre-1997) versions of
4467 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4468 (including the angle brackets) in this case. Even older
4469 ones did not pass a second argument at all, under any
4470 circumstance. Note that upgrades using such an old dpkg
4471 version are unlikely to work for other reasons, even if
4472 this old argument behavior is handled by your postinst script.
4478 <sect id="removedetails"><heading>Details of removal and/or
4479 configuration purging</heading>
4485 <example compact="compact">
4486 <var>prerm</var> remove
4490 If prerm fails during replacement due to conflict
4492 <var>conflictor's-postinst</var> abort-remove \
4493 in-favour <var>package</var> <var>new-version</var>
4497 <var>postinst</var> abort-remove
4501 If this fails, the package is in a "Half-Configured"
4502 state, or else it remains "Installed".
4506 The package's files are removed (except <tt>conffile</tt>s).
4509 <example compact="compact">
4510 <var>postrm</var> remove
4514 If it fails, there's no error unwind, and the package is in
4515 an "Half-Installed" state.
4520 All the maintainer scripts except the <prgn>postrm</prgn>
4525 If we aren't purging the package we stop here. Note
4526 that packages which have no <prgn>postrm</prgn> and no
4527 <tt>conffile</tt>s are automatically purged when
4528 removed, as there is no difference except for the
4529 <prgn>dpkg</prgn> status.
4533 The <tt>conffile</tt>s and any backup files
4534 (<tt>~</tt>-files, <tt>#*#</tt> files,
4535 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4540 <example compact="compact">
4541 <var>postrm</var> purge
4545 If this fails, the package remains in a "Config-Files"
4550 The package's file list is removed.
4559 <chapt id="relationships">
4560 <heading>Declaring relationships between packages</heading>
4562 <sect id="depsyntax">
4563 <heading>Syntax of relationship fields</heading>
4566 These fields all have a uniform syntax. They are a list of
4567 package names separated by commas.
4571 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4572 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4573 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4574 control fields of the package, which declare
4575 dependencies on other packages, the package names listed may
4576 also include lists of alternative package names, separated
4577 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4578 if any one of the alternative packages is installed, that
4579 part of the dependency is considered to be satisfied.
4583 All of the fields except for <tt>Provides</tt> may restrict
4584 their applicability to particular versions of each named
4585 package. This is done in parentheses after each individual
4586 package name; the parentheses should contain a relation from
4587 the list below followed by a version number, in the format
4588 described in <ref id="f-Version">.
4592 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4593 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4594 strictly earlier, earlier or equal, exactly equal, later or
4595 equal and strictly later, respectively. The deprecated
4596 forms <tt><</tt> and <tt>></tt> were used to mean
4597 earlier/later or equal, rather than strictly earlier/later,
4598 so they should not appear in new packages (though
4599 <prgn>dpkg</prgn> still supports them).
4603 Whitespace may appear at any point in the version
4604 specification subject to the rules in <ref
4605 id="controlsyntax">, and must appear where it's necessary to
4606 disambiguate; it is not otherwise significant. All of the
4607 relationship fields can only be folded in source package control files. For
4608 consistency and in case of future changes to
4609 <prgn>dpkg</prgn> it is recommended that a single space be
4610 used after a version relationship and before a version
4611 number; it is also conventional to put a single space after
4612 each comma, on either side of each vertical bar, and before
4613 each open parenthesis. When opening a continuation line in a relationship field, it
4614 is conventional to do so after a comma and before the space
4615 following that comma.
4619 For example, a list of dependencies might appear as:
4620 <example compact="compact">
4623 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4628 Relationships may be restricted to a certain set of
4629 architectures. This is indicated in brackets after each
4630 individual package name and the optional version specification.
4631 The brackets enclose a non-empty list of Debian architecture names
4632 in the format described in <ref id="arch-spec">,
4633 separated by whitespace. Exclamation marks may be prepended to
4634 each of the names. (It is not permitted for some names to be
4635 prepended with exclamation marks while others aren't.)
4639 For build relationship fields
4640 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4641 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4642 the current Debian host architecture is not in this list and
4643 there are no exclamation marks in the list, or it is in the list
4644 with a prepended exclamation mark, the package name and the
4645 associated version specification are ignored completely for the
4646 purposes of defining the relationships.
4651 <example compact="compact">
4653 Build-Depends-Indep: texinfo
4654 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4655 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4657 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4658 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4659 <tt>gnumach-dev</tt> only on hurd-i386.
4663 For binary relationship fields, the architecture restriction
4664 syntax is only supported in the source package control
4665 file <file>debian/control</file>. When the corresponding binary
4666 package control file is generated, the relationship will either
4667 be omitted or included without the architecture restriction
4668 based on the architecture of the binary package. This means
4669 that architecture restrictions must not be used in binary
4670 relationship fields for architecture-independent packages
4671 (<tt>Architecture: all</tt>).
4676 <example compact="compact">
4677 Depends: foo [i386], bar [amd64]
4679 becomes <tt>Depends: foo</tt> when the package is built on
4680 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4681 package is built on the <tt>amd64</tt> architecture, and omitted
4682 entirely in binary packages built on all other architectures.
4686 If the architecture-restricted dependency is part of a set of
4687 alternatives using <tt>|</tt>, that alternative is ignored
4688 completely on architectures that do not match the restriction.
4690 <example compact="compact">
4691 Build-Depends: foo [!i386] | bar [!amd64]
4693 is equivalent to <tt>bar</tt> on the i386 architecture, to
4694 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4695 bar</tt> on all other architectures.
4699 Relationships may also be restricted to a certain set of
4700 architectures using architecture wildcards in the format
4701 described in <ref id="arch-wildcard-spec">. The syntax for
4702 declaring such restrictions is the same as declaring
4703 restrictions using a certain set of architectures without
4704 architecture wildcards. For example:
4705 <example compact="compact">
4706 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4708 is equivalent to <tt>foo</tt> on architectures using the Linux
4709 kernel and any cpu, <tt>bar</tt> on architectures using any
4710 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4711 using a kernel other than Linux.
4715 Note that the binary package relationship fields such as
4716 <tt>Depends</tt> appear in one of the binary package
4717 sections of the control file, whereas the build-time
4718 relationships such as <tt>Build-Depends</tt> appear in the
4719 source package section of the control file (which is the
4724 <sect id="binarydeps">
4725 <heading>Binary Dependencies - <tt>Depends</tt>,
4726 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4727 <tt>Pre-Depends</tt>
4731 Packages can declare in their control file that they have
4732 certain relationships to other packages - for example, that
4733 they may not be installed at the same time as certain other
4734 packages, and/or that they depend on the presence of others.
4738 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4739 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4740 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4741 <tt>Breaks</tt> is described in <ref id="breaks">, and
4742 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4743 rest are described below.
4747 These seven fields are used to declare a dependency
4748 relationship by one package on another. Except for
4749 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4750 depending (binary) package's control file.
4751 (<tt>Enhances</tt> appears in the recommending package's
4752 control file, and <tt>Breaks</tt> appears in the version of
4753 depended-on package which causes the named package to
4758 A <tt>Depends</tt> field takes effect <em>only</em> when a
4759 package is to be configured. It does not prevent a package
4760 being on the system in an unconfigured state while its
4761 dependencies are unsatisfied, and it is possible to replace
4762 a package whose dependencies are satisfied and which is
4763 properly installed with a different version whose
4764 dependencies are not and cannot be satisfied; when this is
4765 done the depending package will be left unconfigured (since
4766 attempts to configure it will give errors) and will not
4767 function properly. If it is necessary, a
4768 <tt>Pre-Depends</tt> field can be used, which has a partial
4769 effect even when a package is being unpacked, as explained
4770 in detail below. (The other three dependency fields,
4771 <tt>Recommends</tt>, <tt>Suggests</tt> and
4772 <tt>Enhances</tt>, are only used by the various front-ends
4773 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4774 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4778 Since <tt>Depends</tt> only places requirements on the order in
4779 which packages are configured, packages in an installation run
4780 are usually all unpacked first and all configured later.
4782 This approach makes dependency resolution easier. If two
4783 packages A and B are being upgraded, the installed package A
4784 depends on exactly the installed package B, and the new
4785 package A depends on exactly the new package B (a common
4786 situation when upgrading shared libraries and their
4787 corresponding development packages), satisfying the
4788 dependencies at every stage of the upgrade would be
4789 impossible. This relaxed restriction means that both new
4790 packages can be unpacked together and then configured in their
4796 If there is a circular dependency among packages being installed
4797 or removed, installation or removal order honoring the
4798 dependency order is impossible, requiring the dependency loop be
4799 broken at some point and the dependency requirements violated
4800 for at least one package. Packages involved in circular
4801 dependencies may not be able to rely on their dependencies being
4802 configured before they themselves are configured, depending on
4803 which side of the break of the circular dependency loop they
4804 happen to be on. If one of the packages in the loop has
4805 no <prgn>postinst</prgn> script, then the cycle will be broken
4806 at that package; this ensures that all <prgn>postinst</prgn>
4807 scripts are run with their dependencies properly configured if
4808 this is possible. Otherwise the breaking point is arbitrary.
4809 Packages should therefore avoid circular dependencies where
4810 possible, particularly if they have <prgn>postinst</prgn>
4815 The meaning of the five dependency fields is as follows:
4817 <tag><tt>Depends</tt></tag>
4820 This declares an absolute dependency. A package will
4821 not be configured unless all of the packages listed in
4822 its <tt>Depends</tt> field have been correctly
4823 configured (unless there is a circular dependency as
4828 The <tt>Depends</tt> field should be used if the
4829 depended-on package is required for the depending
4830 package to provide a significant amount of
4835 The <tt>Depends</tt> field should also be used if the
4836 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4837 require the depended-on package to be unpacked or
4838 configured in order to run. In the case of <tt>postinst
4839 configure</tt>, the depended-on packages will be unpacked
4840 and configured first. (If both packages are involved in a
4841 dependency loop, this might not work as expected; see the
4842 explanation a few paragraphs back.) In the case
4843 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4844 actions, the package dependencies will normally be at
4845 least unpacked, but they may be only "Half-Installed" if a
4846 previous upgrade of the dependency failed.
4850 Finally, the <tt>Depends</tt> field should be used if the
4851 depended-on package is needed by the <prgn>postrm</prgn>
4852 script to fully clean up after the package removal. There
4853 is no guarantee that package dependencies will be
4854 available when <prgn>postrm</prgn> is run, but the
4855 depended-on package is more likely to be available if the
4856 package declares a dependency (particularly in the case
4857 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4858 script must gracefully skip actions that require a
4859 dependency if that dependency isn't available.
4863 <tag><tt>Recommends</tt></tag>
4866 This declares a strong, but not absolute, dependency.
4870 The <tt>Recommends</tt> field should list packages
4871 that would be found together with this one in all but
4872 unusual installations.
4876 <tag><tt>Suggests</tt></tag>
4878 This is used to declare that one package may be more
4879 useful with one or more others. Using this field
4880 tells the packaging system and the user that the
4881 listed packages are related to this one and can
4882 perhaps enhance its usefulness, but that installing
4883 this one without them is perfectly reasonable.
4886 <tag><tt>Enhances</tt></tag>
4888 This field is similar to Suggests but works in the
4889 opposite direction. It is used to declare that a
4890 package can enhance the functionality of another
4894 <tag><tt>Pre-Depends</tt></tag>
4897 This field is like <tt>Depends</tt>, except that it
4898 also forces <prgn>dpkg</prgn> to complete installation
4899 of the packages named before even starting the
4900 installation of the package which declares the
4901 pre-dependency, as follows:
4905 When a package declaring a pre-dependency is about to
4906 be <em>unpacked</em> the pre-dependency can be
4907 satisfied if the depended-on package is either fully
4908 configured, <em>or even if</em> the depended-on
4909 package(s) are only unpacked or in the "Half-Configured"
4910 state, provided that they have been configured
4911 correctly at some point in the past (and not removed
4912 or partially removed since). In this case, both the
4913 previously-configured and currently unpacked or
4914 "Half-Configured" versions must satisfy any version
4915 clause in the <tt>Pre-Depends</tt> field.
4919 When the package declaring a pre-dependency is about to
4920 be <em>configured</em>, the pre-dependency will be treated
4921 as a normal <tt>Depends</tt>. It will be considered
4922 satisfied only if the depended-on package has been
4923 correctly configured. However, unlike
4924 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4925 permit circular dependencies to be broken. If a circular
4926 dependency is encountered while attempting to honor
4927 <tt>Pre-Depends</tt>, the installation will be aborted.
4931 <tt>Pre-Depends</tt> are also required if the
4932 <prgn>preinst</prgn> script depends on the named package.
4933 It is best to avoid this situation if possible.
4937 <tt>Pre-Depends</tt> should be used sparingly,
4938 preferably only by packages whose premature upgrade or
4939 installation would hamper the ability of the system to
4940 continue with any upgrade that might be in progress.
4944 You should not specify a <tt>Pre-Depends</tt> entry for a
4945 package before this has been discussed on the
4946 <tt>debian-devel</tt> mailing list and a consensus about
4947 doing that has been reached. See <ref id="dependencies">.
4954 When selecting which level of dependency to use you should
4955 consider how important the depended-on package is to the
4956 functionality of the one declaring the dependency. Some
4957 packages are composed of components of varying degrees of
4958 importance. Such a package should list using
4959 <tt>Depends</tt> the package(s) which are required by the
4960 more important components. The other components'
4961 requirements may be mentioned as Suggestions or
4962 Recommendations, as appropriate to the components' relative
4968 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4971 When one binary package declares that it breaks another,
4972 <prgn>dpkg</prgn> will refuse to allow the package which
4973 declares <tt>Breaks</tt> to be unpacked unless the broken
4974 package is deconfigured first, and it will refuse to
4975 allow the broken package to be reconfigured.
4979 A package will not be regarded as causing breakage merely
4980 because its configuration files are still installed; it must
4981 be at least "Half-Installed".
4985 A special exception is made for packages which declare that
4986 they break their own package name or a virtual package which
4987 they provide (see below): this does not count as a real
4992 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4993 version clause; such a <tt>Breaks</tt> is introduced in the
4994 version of an (implicit or explicit) dependency which violates
4995 an assumption or reveals a bug in earlier versions of the broken
4996 package, or which takes over a file from earlier versions of the
4997 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4998 will inform higher-level package management tools that the
4999 broken package must be upgraded before the new one.
5003 If the breaking package also overwrites some files from the
5004 older package, it should use <tt>Replaces</tt> to ensure this
5005 goes smoothly. See <ref id="replaces"> for a full discussion
5006 of taking over files from other packages, including how to
5007 use <tt>Breaks</tt> in those cases.
5011 Many of the cases where <tt>Breaks</tt> should be used were
5012 previously handled with <tt>Conflicts</tt>
5013 because <tt>Breaks</tt> did not yet exist.
5014 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5015 See <ref id="conflicts"> for more information about the
5020 <sect id="conflicts">
5021 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5024 When one binary package declares a conflict with another using
5025 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5026 allow them to be unpacked on the system at the same time. This
5027 is a stronger restriction than <tt>Breaks</tt>, which prevents
5028 the broken package from being configured while the breaking
5029 package is in the "Unpacked" state but allows both packages to
5030 be unpacked at the same time.
5034 If one package is to be unpacked, the other must be removed
5035 first. If the package being unpacked is marked as replacing
5036 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5037 normally be used in this case) the one on the system, or the one
5038 on the system is marked as deselected, or both packages are
5039 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5040 automatically remove the package which is causing the conflict.
5041 Otherwise, it will halt the installation of the new package with
5042 an error. This mechanism is specifically designed to produce an
5043 error when the installed package is <tt>Essential</tt>, but the
5048 A package will not cause a conflict merely because its
5049 configuration files are still installed; it must be at least
5054 A special exception is made for packages which declare a
5055 conflict with their own package name, or with a virtual
5056 package which they provide (see below): this does not
5057 prevent their installation, and allows a package to conflict
5058 with others providing a replacement for it. You use this
5059 feature when you want the package in question to be the only
5060 package providing some feature.
5064 Normally, <tt>Breaks</tt> should be used instead
5065 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5066 stronger restriction on the ordering of package installation or
5067 upgrade and can make it more difficult for the package manager
5068 to find a correct solution to an upgrade or installation
5069 problem. <tt>Breaks</tt> should be used
5071 <item>when moving a file from one package to another (see
5072 <ref id="replaces">),</item>
5073 <item>when splitting a package (a special case of the previous
5075 <item>when the breaking package exposes a bug in or interacts
5076 badly with particular versions of the broken
5079 <tt>Conflicts</tt> should be used
5081 <item>when two packages provide the same file and will
5082 continue to do so,</item>
5083 <item>in conjunction with <tt>Provides</tt> when only one
5084 package providing a given virtual facility may be unpacked
5085 at a time (see <ref id="virtual">),</item>
5086 <item>in other cases where one must prevent simultaneous
5087 installation of two packages for reasons that are ongoing
5088 (not fixed in a later version of one of the packages) or
5089 that must prevent both packages from being unpacked at the
5090 same time, not just configured.</item>
5092 Be aware that adding <tt>Conflicts</tt> is normally not the best
5093 solution when two packages provide the same files. Depending on
5094 the reason for that conflict, using alternatives or renaming the
5095 files is often a better approach. See, for
5096 example, <ref id="binaries">.
5100 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5101 unless two packages cannot be installed at the same time or
5102 installing them both causes one of them to be broken or
5103 unusable. Having similar functionality or performing the same
5104 tasks as another package is not sufficient reason to
5105 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5109 A <tt>Conflicts</tt> entry may have an "earlier than" version
5110 clause if the reason for the conflict is corrected in a later
5111 version of one of the packages. However, normally the presence
5112 of an "earlier than" version clause is a sign
5113 that <tt>Breaks</tt> should have been used instead. An "earlier
5114 than" version clause in <tt>Conflicts</tt>
5115 prevents <prgn>dpkg</prgn> from upgrading or installing the
5116 package which declares such a conflict until the upgrade or
5117 removal of the conflicted-with package has been completed, which
5118 is a strong restriction.
5122 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5126 As well as the names of actual ("concrete") packages, the
5127 package relationship fields <tt>Depends</tt>,
5128 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5129 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5130 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5131 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5132 may mention "virtual packages".
5136 A <em>virtual package</em> is one which appears in the
5137 <tt>Provides</tt> control field of another package. The effect
5138 is as if the package(s) which provide a particular virtual
5139 package name had been listed by name everywhere the virtual
5140 package name appears. (See also <ref id="virtual_pkg">)
5144 If there are both concrete and virtual packages of the same
5145 name, then the dependency may be satisfied (or the conflict
5146 caused) by either the concrete package with the name in
5147 question or any other concrete package which provides the
5148 virtual package with the name in question. This is so that,
5149 for example, supposing we have
5150 <example compact="compact">
5153 </example> and someone else releases an enhanced version of
5154 the <tt>bar</tt> package they can say:
5155 <example compact="compact">
5159 and the <tt>bar-plus</tt> package will now also satisfy the
5160 dependency for the <tt>foo</tt> package.
5164 If a relationship field has a version number attached, only real
5165 packages will be considered to see whether the relationship is
5166 satisfied (or the prohibition violated, for a conflict or
5167 breakage). In other words, if a version number is specified,
5168 this is a request to ignore all <tt>Provides</tt> for that
5169 package name and consider only real packages. The package
5170 manager will assume that a package providing that virtual
5171 package is not of the "right" version. A <tt>Provides</tt>
5172 field may not contain version numbers, and the version number of
5173 the concrete package which provides a particular virtual package
5174 will not be considered when considering a dependency on or
5175 conflict with the virtual package name.<footnote>
5176 It is possible that a future release of <prgn>dpkg</prgn> may
5177 add the ability to specify a version number for each virtual
5178 package it provides. This feature is not yet present,
5179 however, and is expected to be used only infrequently.
5184 To specify which of a set of real packages should be the default
5185 to satisfy a particular dependency on a virtual package, list
5186 the real package as an alternative before the virtual one.
5190 If the virtual package represents a facility that can only be
5191 provided by one real package at a time, such as
5192 the <package>mail-transport-agent</package> virtual package that
5193 requires installation of a binary that would conflict with all
5194 other providers of that virtual package (see
5195 <ref id="mail-transport-agents">), all packages providing that
5196 virtual package should also declare a conflict with it
5197 using <tt>Conflicts</tt>. This will ensure that at most one
5198 provider of that virtual package is unpacked or installed at a
5203 <sect id="replaces"><heading>Overwriting files and replacing
5204 packages - <tt>Replaces</tt></heading>
5207 Packages can declare in their control file that they should
5208 overwrite files in certain other packages, or completely replace
5209 other packages. The <tt>Replaces</tt> control field has these
5210 two distinct purposes.
5213 <sect1><heading>Overwriting files in other packages</heading>
5216 It is usually an error for a package to contain files which
5217 are on the system in another package. However, if the
5218 overwriting package declares that it <tt>Replaces</tt> the one
5219 containing the file being overwritten, then <prgn>dpkg</prgn>
5220 will replace the file from the old package with that from the
5221 new. The file will no longer be listed as "owned" by the old
5222 package and will be taken over by the new package.
5223 Normally, <tt>Breaks</tt> should be used in conjunction
5224 with <tt>Replaces</tt>.<footnote>
5225 To see why <tt>Breaks</tt> is normally needed in addition
5226 to <tt>Replaces</tt>, consider the case of a file in the
5227 package <package>foo</package> being taken over by the
5228 package <package>foo-data</package>.
5229 <tt>Replaces</tt> will allow <package>foo-data</package> to
5230 be installed and take over that file. However,
5231 without <tt>Breaks</tt>, nothing
5232 requires <package>foo</package> to be upgraded to a newer
5233 version that knows it does not include that file and instead
5234 depends on <package>foo-data</package>. Nothing would
5235 prevent the new <package>foo-data</package> package from
5236 being installed and then removed, removing the file that it
5237 took over from <package>foo</package>. After that
5238 operation, the package manager would think the system was in
5239 a consistent state, but the <package>foo</package> package
5240 would be missing one of its files.
5245 For example, if a package <package>foo</package> is split
5246 into <package>foo</package> and <package>foo-data</package>
5247 starting at version 1.2-3, <package>foo-data</package> would
5249 <example compact="compact">
5250 Replaces: foo (<< 1.2-3)
5251 Breaks: foo (<< 1.2-3)
5253 in its control file. The new version of the
5254 package <package>foo</package> would normally have the field
5255 <example compact="compact">
5256 Depends: foo-data (>= 1.2-3)
5258 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5259 the files moved into <package>foo-data</package> are not
5260 required for normal operation).
5264 If a package is completely replaced in this way, so that
5265 <prgn>dpkg</prgn> does not know of any files it still
5266 contains, it is considered to have "disappeared". It will
5267 be marked as not wanted on the system (selected for
5268 removal) and not installed. Any <tt>conffile</tt>s
5269 details noted for the package will be ignored, as they
5270 will have been taken over by the overwriting package. The
5271 package's <prgn>postrm</prgn> script will be run with a
5272 special argument to allow the package to do any final
5273 cleanup required. See <ref id="mscriptsinstact">.
5275 Replaces is a one way relationship. You have to install
5276 the replacing package after the replaced package.
5281 For this usage of <tt>Replaces</tt>, virtual packages (see
5282 <ref id="virtual">) are not considered when looking at a
5283 <tt>Replaces</tt> field. The packages declared as being
5284 replaced must be mentioned by their real names.
5288 This usage of <tt>Replaces</tt> only takes effect when both
5289 packages are at least partially on the system at once. It is
5290 not relevant if the packages conflict unless the conflict has
5295 <sect1><heading>Replacing whole packages, forcing their
5299 Second, <tt>Replaces</tt> allows the packaging system to
5300 resolve which package should be removed when there is a
5301 conflict (see <ref id="conflicts">). This usage only takes
5302 effect when the two packages <em>do</em> conflict, so that the
5303 two usages of this field do not interfere with each other.
5307 In this situation, the package declared as being replaced
5308 can be a virtual package, so for example, all mail
5309 transport agents (MTAs) would have the following fields in
5310 their control files:
5311 <example compact="compact">
5312 Provides: mail-transport-agent
5313 Conflicts: mail-transport-agent
5314 Replaces: mail-transport-agent
5316 ensuring that only one MTA can be unpacked at any one
5317 time. See <ref id="virtual"> for more information about this
5322 <sect id="sourcebinarydeps">
5323 <heading>Relationships between source and binary packages -
5324 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5325 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5329 Source packages that require certain binary packages to be
5330 installed or absent at the time of building the package
5331 can declare relationships to those binary packages.
5335 This is done using the <tt>Build-Depends</tt>,
5336 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5337 <tt>Build-Conflicts-Indep</tt> control fields.
5341 Build-dependencies on "build-essential" binary packages can be
5342 omitted. Please see <ref id="pkg-relations"> for more information.
5346 The dependencies and conflicts they define must be satisfied
5347 (as defined earlier for binary packages) in order to invoke
5348 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5350 There is no Build-Depends-Arch; this role is essentially
5351 met with Build-Depends. Anyone building the
5352 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5353 assumed to be building the whole package, and therefore
5354 installation of all build dependencies is required.
5357 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5358 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5359 not yet know how to check for its existence, and
5360 <tt>binary-arch</tt>. The purpose of the original split
5361 between <tt>Build-Depends</tt> and
5362 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5363 wouldn't need to install extra packages needed only for the
5364 binary-indep targets. But without a build-arch/build-indep
5365 split, this didn't work, since most of the work is done in
5366 the build target, not in the binary target.
5370 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5371 <tt>binary-arch</tt></tag>
5373 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5374 fields must be satisfied when these targets are invoked.
5376 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5377 and <tt>binary-indep</tt></tag>
5379 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5380 <tt>Build-Depends-Indep</tt>, and
5381 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5382 these targets are invoked.
5390 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5393 Packages containing shared libraries must be constructed with
5394 a little care to make sure that the shared library is always
5395 available. This is especially important for packages whose
5396 shared libraries are vitally important, such as the C library
5397 (currently <tt>libc6</tt>).
5401 This section deals only with public shared libraries: shared
5402 libraries that are placed in directories searched by the dynamic
5403 linker by default or which are intended to be linked against
5404 normally and possibly used by other, independent packages. Shared
5405 libraries that are internal to a particular package or that are
5406 only loaded as dynamic modules are not covered by this section and
5407 are not subject to its requirements.
5411 A shared library is identified by the <tt>SONAME</tt> attribute
5412 stored in its dynamic section. When a binary is linked against a
5413 shared library, the <tt>SONAME</tt> of the shared library is
5414 recorded in the binary's <tt>NEEDED</tt> section so that the
5415 dynamic linker knows that library must be loaded at runtime. The
5416 shared library file's full name (which usually contains additional
5417 version information not needed in the <tt>SONAME</tt>) is
5418 therefore normally not referenced directly. Instead, the shared
5419 library is loaded by its <tt>SONAME</tt>, which exists on the file
5420 system as a symlink pointing to the full name of the shared
5421 library. This symlink must be provided by the
5422 package. <ref id="sharedlibs-runtime"> describes how to do this.
5424 This is a convention of shared library versioning, but not a
5425 requirement. Some libraries use the <tt>SONAME</tt> as the full
5426 library file name instead and therefore do not need a symlink.
5427 Most, however, encode additional information about
5428 backwards-compatible revisions as a minor version number in the
5429 file name. The <tt>SONAME</tt> itself only changes when
5430 binaries linked with the earlier version of the shared library
5431 may no longer work, but the filename may change with each
5432 release of the library. See <ref id="sharedlibs-runtime"> for
5438 When linking a binary or another shared library against a shared
5439 library, the <tt>SONAME</tt> for that shared library is not yet
5440 known. Instead, the shared library is found by looking for a file
5441 matching the library name with <tt>.so</tt> appended. This file
5442 exists on the file system as a symlink pointing to the shared
5447 Shared libraries are normally split into several binary packages.
5448 The <tt>SONAME</tt> symlink is installed by the runtime shared
5449 library package, and the bare <tt>.so</tt> symlink is installed in
5450 the development package since it's only used when linking binaries
5451 or shared libraries. However, there are some exceptions for
5452 unusual shared libraries or for shared libraries that are also
5453 loaded as dynamic modules by other programs.
5457 This section is primarily concerned with how the separation of
5458 shared libraries into multiple packages should be done and how
5459 dependencies on and between shared library binary packages are
5460 managed in Debian. <ref id="libraries"> should be read in
5461 conjunction with this section and contains additional rules for
5462 the files contained in the shared library packages.
5465 <sect id="sharedlibs-runtime">
5466 <heading>Run-time shared libraries</heading>
5469 The run-time shared library must be placed in a package
5470 whose name changes whenever the <tt>SONAME</tt> of the shared
5471 library changes. This allows several versions of the shared
5472 library to be installed at the same time, allowing installation
5473 of the new version of the shared library without immediately
5474 breaking binaries that depend on the old version. Normally, the
5475 run-time shared library and its <tt>SONAME</tt> symlink should
5476 be placed in a package named
5477 <package><var>libraryname</var><var>soversion</var></package>,
5478 where <var>soversion</var> is the version number in
5479 the <tt>SONAME</tt> of the shared library.
5480 See <ref id="shlibs"> for detailed information on how to
5481 determine this version. Alternatively, if it would be confusing
5482 to directly append <var>soversion</var>
5483 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5484 itself ends in a number), you should use
5485 <package><var>libraryname</var>-<var>soversion</var></package>
5490 If you have several shared libraries built from the same source
5491 tree, you may lump them all together into a single shared
5492 library package provided that all of their <tt>SONAME</tt>s will
5493 always change together. Be aware that this is not normally the
5494 case, and if the <tt>SONAME</tt>s do not change together,
5495 upgrading such a merged shared library package will be
5496 unnecessarily difficult because of file conflicts with the old
5497 version of the package. When in doubt, always split shared
5498 library packages so that each binary package installs a single
5503 Every time the shared library ABI changes in a way that may
5504 break binaries linked against older versions of the shared
5505 library, the <tt>SONAME</tt> of the library and the
5506 corresponding name for the binary package containing the runtime
5507 shared library should change. Normally, this means
5508 the <tt>SONAME</tt> should change any time an interface is
5509 removed from the shared library or the signature of an interface
5510 (the number of parameters or the types of parameters that it
5511 takes, for example) is changed. This practice is vital to
5512 allowing clean upgrades from older versions of the package and
5513 clean transitions between the old ABI and new ABI without having
5514 to upgrade every affected package simultaneously.
5518 The <tt>SONAME</tt> and binary package name need not, and indeed
5519 normally should not, change if new interfaces are added but none
5520 are removed or changed, since this will not break binaries
5521 linked against the old shared library. Correct versioning of
5522 dependencies on the newer shared library by binaries that use
5523 the new interfaces is handled via
5524 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5525 system</qref> or via symbols files (see
5526 <manref name="deb-symbols" section="5">).
5530 The package should install the shared libraries under
5531 their normal names. For example, the <package>libgdbm3</package>
5532 package should install <file>libgdbm.so.3.0.0</file> as
5533 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5534 renamed or re-linked by any <prgn>prerm</prgn> or
5535 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5536 of renaming things safely without affecting running programs,
5537 and attempts to interfere with this are likely to lead to
5542 Shared libraries should not be installed executable, since
5543 the dynamic linker does not require this and trying to
5544 execute a shared library usually results in a core dump.
5548 The run-time library package should include the symbolic link for
5549 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5550 the shared libraries. For example,
5551 the <package>libgdbm3</package> package should include a symbolic
5552 link from <file>/usr/lib/libgdbm.so.3</file> to
5553 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5554 linker (for example <prgn>ld.so</prgn> or
5555 <prgn>ld-linux.so.*</prgn>) can find the library between the
5556 time that <prgn>dpkg</prgn> installs it and the time that
5557 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5559 The package management system requires the library to be
5560 placed before the symbolic link pointing to it in the
5561 <file>.deb</file> file. This is so that when
5562 <prgn>dpkg</prgn> comes to install the symlink
5563 (overwriting the previous symlink pointing at an older
5564 version of the library), the new shared library is already
5565 in place. In the past, this was achieved by creating the
5566 library in the temporary packaging directory before
5567 creating the symlink. Unfortunately, this was not always
5568 effective, since the building of the tar file in the
5569 <file>.deb</file> depended on the behavior of the underlying
5570 file system. Some file systems (such as reiserfs) reorder
5571 the files so that the order of creation is forgotten.
5572 Since version 1.7.0, <prgn>dpkg</prgn>
5573 reorders the files itself as necessary when building a
5574 package. Thus it is no longer important to concern
5575 oneself with the order of file creation.
5579 <sect1 id="ldconfig">
5580 <heading><tt>ldconfig</tt></heading>
5583 Any package installing shared libraries in one of the default
5584 library directories of the dynamic linker (which are currently
5585 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5586 listed in <file>/etc/ld.so.conf</file><footnote>
5587 These are currently <file>/usr/local/lib</file> plus
5588 directories under <file>/lib</file> and <file>/usr/lib</file>
5589 matching the multiarch triplet for the system architecture.
5591 must use <prgn>ldconfig</prgn> to update the shared library
5596 The package maintainer scripts must only call
5597 <prgn>ldconfig</prgn> under these circumstances:
5598 <list compact="compact">
5599 <item>When the <prgn>postinst</prgn> script is run with a
5600 first argument of <tt>configure</tt>, the script must call
5601 <prgn>ldconfig</prgn>, and may optionally invoke
5602 <prgn>ldconfig</prgn> at other times.
5604 <item>When the <prgn>postrm</prgn> script is run with a
5605 first argument of <tt>remove</tt>, the script should call
5606 <prgn>ldconfig</prgn>.
5611 During install or upgrade, the preinst is called before
5612 the new files are unpacked, so calling "ldconfig" is
5613 pointless. The preinst of an existing package can also be
5614 called if an upgrade fails. However, this happens during
5615 the critical time when a shared libs may exist on-disk
5616 under a temporary name. Thus, it is dangerous and
5617 forbidden by current policy to call "ldconfig" at this
5622 When a package is installed or upgraded, "postinst
5623 configure" runs after the new files are safely on-disk.
5624 Since it is perfectly safe to invoke ldconfig
5625 unconditionally in a postinst, it is OK for a package to
5626 simply put ldconfig in its postinst without checking the
5627 argument. The postinst can also be called to recover from
5628 a failed upgrade. This happens before any new files are
5629 unpacked, so there is no reason to call "ldconfig" at this
5634 For a package that is being removed, prerm is
5635 called with all the files intact, so calling ldconfig is
5636 useless. The other calls to "prerm" happen in the case of
5637 upgrade at a time when all the files of the old package
5638 are on-disk, so again calling "ldconfig" is pointless.
5642 postrm, on the other hand, is called with the "remove"
5643 argument just after the files are removed, so this is
5644 the proper time to call "ldconfig" to notify the system
5645 of the fact that the shared libraries from the package
5646 are removed. The postrm can be called at several other
5647 times. At the time of "postrm purge", "postrm
5648 abort-install", or "postrm abort-upgrade", calling
5649 "ldconfig" is useless because the shared lib files are
5650 not on-disk. However, when "postrm" is invoked with
5651 arguments "upgrade", "failed-upgrade", or "disappear", a
5652 shared lib may exist on-disk under a temporary filename.
5660 <sect id="sharedlibs-support-files">
5661 <heading>Shared library support files</heading>
5664 If your package contains files whose names do not change with
5665 each change in the library shared object version, you must not
5666 put them in the shared library package. Otherwise, several
5667 versions of the shared library cannot be installed at the same
5668 time without filename clashes, making upgrades and transitions
5669 unnecessarily difficult.
5673 It is recommended that supporting files and run-time support
5674 programs that do not need to be invoked manually by users, but
5675 are nevertheless required for the package to function, be placed
5676 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5677 preferably under <file>/usr/lib/</file><var>package-name</var>.
5678 If the program or file is architecture independent, the
5679 recommendation is for it to be placed in a subdirectory of
5680 <file>/usr/share</file> instead, preferably under
5681 <file>/usr/share/</file><var>package-name</var>. Following the
5682 <var>package-name</var> naming convention ensures that the file
5683 names change when the shared object version changes.
5687 Run-time support programs that use the shared library but are
5688 not required for the library to function or files used by the
5689 shared library that can be used by any version of the shared
5690 library package should instead be put in a separate package.
5691 This package might typically be named
5692 <package><var>libraryname</var>-tools</package>; note the
5693 absence of the <var>soversion</var> in the package name.
5697 Files and support programs only useful when compiling software
5698 against the library should be included in the development
5699 package for the library.<footnote>
5700 For example, a <file><var>package-name</var>-config</file>
5701 script or <package>pkg-config</package> configuration files.
5706 <sect id="sharedlibs-static">
5707 <heading>Static libraries</heading>
5710 The static library (<file><var>libraryname.a</var></file>)
5711 is usually provided in addition to the shared version.
5712 It is placed into the development package (see below).
5716 In some cases, it is acceptable for a library to be
5717 available in static form only; these cases include:
5719 <item>libraries for languages whose shared library support
5720 is immature or unstable</item>
5721 <item>libraries whose interfaces are in flux or under
5722 development (commonly the case when the library's
5723 major version number is zero, or where the ABI breaks
5724 across patchlevels)</item>
5725 <item>libraries which are explicitly intended to be
5726 available only in static form by their upstream
5731 <sect id="sharedlibs-dev">
5732 <heading>Development files</heading>
5735 If there are development files associated with a shared library,
5736 the source package needs to generate a binary development package
5737 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5738 or if you prefer only to support one development version at a
5739 time, <package><var>libraryname</var>-dev</package>. Installing
5740 the development package must result in installation of all the
5741 development files necessary for compiling programs against that
5742 shared library.<footnote>
5743 This wording allows the development files to be split into
5744 several packages, such as a separate architecture-independent
5745 <package><var>libraryname</var>-headers</package>, provided that
5746 the development package depends on all the required additional
5752 In case several development versions of a library exist, you may
5753 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5754 <ref id="conflicts">) to ensure that the user only installs one
5755 development version at a time (as different development versions are
5756 likely to have the same header files in them, which would cause a
5757 filename clash if both were unpacked).
5761 The development package should contain a symlink for the associated
5762 shared library without a version number. For example, the
5763 <package>libgdbm-dev</package> package should include a symlink
5764 from <file>/usr/lib/libgdbm.so</file> to
5765 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5766 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5767 <file>libgdbm.so</file> when compiling dynamically.
5771 If the package provides Ada Library Information
5772 (<file>*.ali</file>) files for use with GNAT, these files must be
5773 installed read-only (mode 0444) so that GNAT will not attempt to
5774 recompile them. This overrides the normal file mode requirements
5775 given in <ref id="permissions-owners">.
5779 <sect id="sharedlibs-intradeps">
5780 <heading>Dependencies between the packages of the same library</heading>
5783 Typically the development version should have an exact
5784 version dependency on the runtime library, to make sure that
5785 compilation and linking happens correctly. The
5786 <tt>${binary:Version}</tt> substitution variable can be
5787 useful for this purpose.
5789 Previously, <tt>${Source-Version}</tt> was used, but its name
5790 was confusing and it has been deprecated since dpkg 1.13.19.
5795 <sect id="sharedlibs-shlibdeps">
5796 <heading>Dependencies between the library and other packages -
5797 the <tt>shlibs</tt> system</heading>
5800 If a package contains a binary or library which links to a
5801 shared library, we must ensure that when the package is
5802 installed on the system, all of the libraries needed are
5803 also installed. This requirement led to the creation of the
5804 <tt>shlibs</tt> system, which is very simple in its design:
5805 any package which <em>provides</em> a shared library also
5806 provides information on the package dependencies required to
5807 ensure the presence of this library, and any package which
5808 <em>uses</em> a shared library uses this information to
5809 determine the dependencies it requires. The files which
5810 contain the mapping from shared libraries to the necessary
5811 dependency information are called <file>shlibs</file> files.
5815 When a package is built which contains any shared libraries, it
5816 must provide a <file>shlibs</file> file for other packages to
5817 use. When a package is built which contains any shared
5818 libraries or compiled binaries, it must run
5819 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5820 on these to determine the libraries used and hence the
5821 dependencies needed by this package.<footnote>
5823 <prgn>dpkg-shlibdeps</prgn> will use a program
5824 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5825 the libraries directly needed by the binaries or shared
5826 libraries in the package.
5830 We say that a binary <tt>foo</tt> <em>directly</em> uses
5831 a library <tt>libbar</tt> if it is explicitly linked
5832 with that library (that is, the library is listed in the ELF
5833 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5834 to the link line when the binary is created). Other
5835 libraries that are needed by <tt>libbar</tt> are linked
5836 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5837 linker will load them automatically when it loads
5838 <tt>libbar</tt>. A package should depend on the libraries
5839 it directly uses, but not the libraries it indirectly uses.
5840 The dependencies for those libraries will automatically pull
5841 in the other libraries.
5845 A good example of where this helps is the following. We
5846 could update <tt>libimlib</tt> with a new version that
5847 supports a new graphics format called dgf (but retaining the
5848 same major version number) and depends on <tt>libdgf</tt>.
5849 If we used <prgn>ldd</prgn> to add dependencies for every
5850 library directly or indirectly linked with a binary, every
5851 package that uses <tt>libimlib</tt> would need to be
5852 recompiled so it would also depend on <tt>libdgf</tt> or it
5853 wouldn't run due to missing symbols. Since dependencies are
5854 only added based on ELF <tt>NEEDED</tt> attribute, packages
5855 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5856 having the dependency on <tt>libdgf</tt> and so they would
5857 not need rebuilding.
5863 In the following sections, we will first describe where the
5864 various <tt>shlibs</tt> files are to be found, then how to
5865 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5866 file format and how to create them if your package contains a
5871 <heading>The <tt>shlibs</tt> files present on the system</heading>
5874 There are several places where <tt>shlibs</tt> files are
5875 found. The following list gives them in the order in which
5877 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5878 (The first one which gives the required information is used.)
5884 <p><file>debian/shlibs.local</file></p>
5887 This lists overrides for this package. This file should
5888 normally not be used, but may be needed temporarily in
5889 unusual situations to work around bugs in other packages,
5890 or in unusual cases where the normally declared dependency
5891 information in the installed <file>shlibs</file> file for
5892 a library cannot be used. This file overrides information
5893 obtained from any other source.
5898 <p><file>/etc/dpkg/shlibs.override</file></p>
5901 This lists global overrides. This list is normally
5902 empty. It is maintained by the local system
5908 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5911 When packages are being built,
5912 any <file>debian/shlibs</file> files are copied into the
5913 control information file area of the temporary build
5914 directory and given the name <file>shlibs</file>. These
5915 files give details of any shared libraries included in the
5916 same package.<footnote>
5917 An example may help here. Let us say that the source
5918 package <tt>foo</tt> generates two binary
5919 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5920 When building the binary packages, the two packages are
5921 created in the directories <file>debian/libfoo2</file>
5922 and <file>debian/foo-runtime</file> respectively.
5923 (<file>debian/tmp</file> could be used instead of one of
5924 these.) Since <tt>libfoo2</tt> provides the
5925 <tt>libfoo</tt> shared library, it will require a
5926 <tt>shlibs</tt> file, which will be installed in
5927 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5928 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5929 When <prgn>dpkg-shlibdeps</prgn> is run on the
5930 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5932 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5933 determine whether <tt>foo-prog</tt>'s library
5934 dependencies are satisfied by any of the libraries
5935 provided by <tt>libfoo2</tt>. For this reason,
5936 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5937 the individual binary packages' <tt>shlibs</tt> files
5938 have been installed into the build directory.
5944 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5947 These are the <file>shlibs</file> files corresponding to
5948 all of the packages installed on the system, and are
5949 maintained by the relevant package maintainers.
5954 <p><file>/etc/dpkg/shlibs.default</file></p>
5957 This file lists any shared libraries whose packages
5958 have failed to provide correct <file>shlibs</file> files.
5959 It was used when the <file>shlibs</file> setup was first
5960 introduced, but it is now normally empty. It is
5961 maintained by the <tt>dpkg</tt> maintainer.
5969 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5970 <file>shlibs</file> files</heading>
5974 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5975 into your <file>debian/rules</file> file. If your package
5976 contains only compiled binaries and libraries (but no scripts),
5977 you can use a command such as:
5978 <example compact="compact">
5979 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5980 debian/tmp/usr/lib/*
5982 Otherwise, you will need to explicitly list the compiled
5983 binaries and libraries.<footnote>
5984 If you are using <tt>debhelper</tt>, the
5985 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5986 It will also correctly handle multi-binary packages.
5991 This command puts the dependency information into the
5992 <file>debian/substvars</file> file, which is then used by
5993 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5994 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5995 field in the control file for this to work.
5999 If you have multiple binary packages, you will need to call
6000 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6001 compiled libraries or binaries. In such a case, you will
6002 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6003 utilities to specify a different <file>substvars</file> file.
6007 If you are creating a udeb for use in the Debian Installer,
6008 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6009 should use the dependency line of type <tt>udeb</tt> by
6010 adding the <tt>-tudeb</tt> option<footnote>
6011 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6012 will automatically add this option if it knows it is
6014 </footnote>. If there is no dependency line of
6015 type <tt>udeb</tt> in the <file>shlibs</file>
6016 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6021 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6022 <ref id="pkg-dpkg-shlibdeps"> and
6023 <manref name="dpkg-shlibdeps" section="1">.
6028 <heading>The <file>shlibs</file> File Format</heading>
6031 Each <file>shlibs</file> file has the same format. Lines
6032 beginning with <tt>#</tt> are considered to be comments and
6033 are ignored. Each line is of the form:
6034 <example compact="compact">
6035 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6040 We will explain this by reference to the example of the
6041 <tt>zlib1g</tt> package, which (at the time of writing)
6042 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6046 <var>type</var> is an optional element that indicates the type
6047 of package for which the line is valid. The only type currently
6048 in use is <tt>udeb</tt>. The colon and space after the type are
6053 <var>library-name</var> is the name of the shared library,
6054 in this case <tt>libz</tt>. (This must match the name part
6055 of the soname, see below.)
6059 <var>soname-version</var> is the version part of the soname of
6060 the library. The soname is the thing that must exactly match
6061 for the library to be recognized by the dynamic linker, and is
6063 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6064 example, <tt>libz.so.1</tt>.<footnote>
6065 This can be determined using the command
6066 <example compact="compact">
6067 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6070 The version part is the part which comes after
6071 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6072 instead be of the form
6073 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6074 as <tt>libdb-4.8.so</tt>, in which case the name would
6075 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6079 <var>dependencies</var> has the same syntax as a dependency
6080 field in a binary package control file. It should give
6081 details of which packages are required to satisfy a binary
6082 built against the version of the library contained in the
6083 package. See <ref id="depsyntax"> for details.
6087 In our example, if the first version of the <tt>zlib1g</tt>
6088 package which contained a minor number of at least
6089 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6090 <tt>shlibs</tt> entry for this library could say:
6091 <example compact="compact">
6092 libz 1 zlib1g (>= 1:1.1.3)
6094 The version-specific dependency is to avoid warnings from
6095 the dynamic linker about using older shared libraries with
6100 As zlib1g also provides a udeb containing the shared library,
6101 there would also be a second line:
6102 <example compact="compact">
6103 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6109 <heading>Providing a <file>shlibs</file> file</heading>
6112 If your package provides a shared library, you need to create
6113 a <file>shlibs</file> file following the format described above.
6114 It is usual to call this file <file>debian/shlibs</file> (but if
6115 you have multiple binary packages, you might want to call it
6116 <file>debian/shlibs.<var>package</var></file> instead). Then
6117 let <file>debian/rules</file> install it in the control
6118 information file area:
6119 <example compact="compact">
6120 install -m644 debian/shlibs debian/tmp/DEBIAN
6122 or, in the case of a multi-binary package:
6123 <example compact="compact">
6124 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6126 An alternative way of doing this is to create the
6127 <file>shlibs</file> file in the control information file area
6128 directly from <file>debian/rules</file> without using
6129 a <file>debian/shlibs</file> file at all,<footnote>
6130 This is what <prgn>dh_makeshlibs</prgn> in
6131 the <package>debhelper</package> suite does. If your package
6132 also has a udeb that provides a shared
6133 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6134 the <tt>udeb:</tt> lines if you specify the name of the udeb
6135 with the <tt>--add-udeb</tt> option.
6137 since the <file>debian/shlibs</file> file itself is ignored by
6138 <prgn>dpkg-shlibdeps</prgn>.
6142 As <prgn>dpkg-shlibdeps</prgn> reads the
6143 <file>DEBIAN/shlibs</file> files in all of the binary packages
6144 being built from this source package, all of the
6145 <file>DEBIAN/shlibs</file> files should be installed before
6146 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6154 <chapt id="opersys"><heading>The Operating System</heading>
6157 <heading>File system hierarchy</heading>
6161 <heading>File System Structure</heading>
6164 The location of all installed files and directories must
6165 comply with the Filesystem Hierarchy Standard (FHS),
6166 version 2.3, with the exceptions noted below, and except
6167 where doing so would violate other terms of Debian
6168 Policy. The following exceptions to the FHS apply:
6173 The optional rules related to user specific
6174 configuration files for applications are stored in
6175 the user's home directory are relaxed. It is
6176 recommended that such files start with the
6177 '<tt>.</tt>' character (a "dot file"), and if an
6178 application needs to create more than one dot file
6179 then the preferred placement is in a subdirectory
6180 with a name starting with a '.' character, (a "dot
6181 directory"). In this case it is recommended the
6182 configuration files not start with the '.'
6188 The requirement for amd64 to use <file>/lib64</file>
6189 for 64 bit binaries is removed.
6194 The requirement for object files, internal binaries, and
6195 libraries, including <file>libc.so.*</file>, to be located
6196 directly under <file>/lib{,32}</file> and
6197 <file>/usr/lib{,32}</file> is amended, permitting files
6198 to instead be installed to
6199 <file>/lib/<var>triplet</var></file> and
6200 <file>/usr/lib/<var>triplet</var></file>, where
6201 <tt><var>triplet</var></tt> is the value returned by
6202 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6203 architecture of the package. Packages may <em>not</em>
6204 install files to any <var>triplet</var> path other
6205 than the one matching the architecture of that package;
6206 for instance, an <tt>Architecture: amd64</tt> package
6207 containing 32-bit x86 libraries may not install these
6208 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6210 This is necessary in order to reserve the directories for
6211 use in cross-installation of library packages from other
6212 architectures, as part of the planned deployment of
6217 Applications may also use a single subdirectory under
6218 <file>/usr/lib/<var>triplet</var></file>.
6221 The execution time linker/loader, ld*, must still be made
6222 available in the existing location under /lib or /lib64
6223 since this is part of the ELF ABI for the architecture.
6228 The requirement that
6229 <file>/usr/local/share/man</file> be "synonymous"
6230 with <file>/usr/local/man</file> is relaxed to a
6235 The requirement that windowmanagers with a single
6236 configuration file call it <file>system.*wmrc</file>
6237 is removed, as is the restriction that the window
6238 manager subdirectory be named identically to the
6239 window manager name itself.
6244 The requirement that boot manager configuration
6245 files live in <file>/etc</file>, or at least are
6246 symlinked there, is relaxed to a recommendation.
6251 The additional directory <file>/run</file> in the root
6252 file system is allowed. <file>/run</file>
6253 replaces <file>/var/run</file>, and the
6254 subdirectory <file>/run/lock</file>
6255 replaces <file>/var/lock</file>, with
6256 the <file>/var</file> directories replaced by symlinks
6257 for backwards compatibility. <file>/run</file>
6258 and <file>/run/lock</file> must follow all of the
6259 requirements in the FHS for <file>/var/run</file>
6260 and <file>/var/lock</file>, respectively, such as file
6261 naming conventions, file format requirements, or the
6262 requirement that files be cleared during the boot
6263 process. Files and directories residing
6264 in <file>/run</file> should be stored on a temporary
6270 The following directories in the root filesystem are
6271 additionally allowed: <file>/sys</file> and
6272 <file>/selinux</file>. <footnote>These directories
6273 are used as mount points to mount virtual filesystems
6274 to get access to kernel information.</footnote>
6279 On GNU/Hurd systems, the following additional
6280 directories are allowed in the root
6281 filesystem: <file>/hurd</file>
6282 and <file>/servers</file>.<footnote>
6283 These directories are used to store translators and as
6284 a set of standard names for mount points,
6293 The version of this document referred here can be
6294 found in the <tt>debian-policy</tt> package or on <url
6295 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6296 name="FHS (Debian copy)"> alongside this manual (or, if
6297 you have the <package>debian-policy</package> installed,
6299 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6300 (local copy)">). The
6301 latest version, which may be a more recent version, may
6303 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6304 Specific questions about following the standard may be
6305 asked on the <tt>debian-devel</tt> mailing list, or
6306 referred to the FHS mailing list (see the
6307 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6313 <heading>Site-specific programs</heading>
6316 As mandated by the FHS, packages must not place any
6317 files in <file>/usr/local</file>, either by putting them in
6318 the file system archive to be unpacked by <prgn>dpkg</prgn>
6319 or by manipulating them in their maintainer scripts.
6323 However, the package may create empty directories below
6324 <file>/usr/local</file> so that the system administrator knows
6325 where to place site-specific files. These are not
6326 directories <em>in</em> <file>/usr/local</file>, but are
6327 children of directories in <file>/usr/local</file>. These
6328 directories (<file>/usr/local/*/dir/</file>)
6329 should be removed on package removal if they are
6334 Note that this applies only to
6335 directories <em>below</em> <file>/usr/local</file>,
6336 not <em>in</em> <file>/usr/local</file>. Packages must
6337 not create sub-directories in the
6338 directory <file>/usr/local</file> itself, except those
6339 listed in FHS, section 4.5. However, you may create
6340 directories below them as you wish. You must not remove
6341 any of the directories listed in 4.5, even if you created
6346 Since <file>/usr/local</file> can be mounted read-only from a
6347 remote server, these directories must be created and
6348 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6349 maintainer scripts and not be included in the
6350 <file>.deb</file> archive. These scripts must not fail if
6351 either of these operations fail.
6355 For example, the <tt>emacsen-common</tt> package could
6356 contain something like
6357 <example compact="compact">
6358 if [ ! -e /usr/local/share/emacs ]; then
6359 if mkdir /usr/local/share/emacs 2>/dev/null; then
6360 if chown root:staff /usr/local/share/emacs; then
6361 chmod 2775 /usr/local/share/emacs || true
6366 in its <prgn>postinst</prgn> script, and
6367 <example compact="compact">
6368 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6369 rmdir /usr/local/share/emacs 2>/dev/null || true
6371 in the <prgn>prerm</prgn> script. (Note that this form is
6372 used to ensure that if the script is interrupted, the
6373 directory <file>/usr/local/share/emacs</file> will still be
6378 If you do create a directory in <file>/usr/local</file> for
6379 local additions to a package, you should ensure that
6380 settings in <file>/usr/local</file> take precedence over the
6381 equivalents in <file>/usr</file>.
6385 However, because <file>/usr/local</file> and its contents are
6386 for exclusive use of the local administrator, a package
6387 must not rely on the presence or absence of files or
6388 directories in <file>/usr/local</file> for normal operation.
6392 The <file>/usr/local</file> directory itself and all the
6393 subdirectories created by the package should (by default) have
6394 permissions 2775 (group-writable and set-group-id) and be
6395 owned by <tt>root:staff</tt>.
6400 <heading>The system-wide mail directory</heading>
6402 The system-wide mail directory
6403 is <file>/var/mail</file>. This directory is part of the
6404 base system and should not be owned by any particular mail
6405 agents. The use of the old
6406 location <file>/var/spool/mail</file> is deprecated, even
6407 though the spool may still be physically located there.
6411 <sect1 id="fhs-run">
6412 <heading><file>/run</file> and <file>/run/lock</file></heading>
6415 The directory <file>/run</file> is cleared at boot, normally
6416 by being a mount point for a temporary file system. Packages
6417 therefore must not assume that any files or directories
6418 under <file>/run</file> other than <file>/run/lock</file>
6419 exist unless the package has arranged to create those files or
6420 directories since the last reboot. Normally, this is done by
6421 the package via an init script. See <ref id="writing-init">
6422 for more information.
6426 Packages must not include files or directories
6427 under <file>/run</file>, or under the
6428 older <file>/var/run</file> and <file>/var/lock</file> paths.
6429 The latter paths will normally be symlinks or other
6430 redirections to <file>/run</file> for backwards compatibility.
6436 <heading>Users and groups</heading>
6439 <heading>Introduction</heading>
6441 The Debian system can be configured to use either plain or
6446 Some user ids (UIDs) and group ids (GIDs) are reserved
6447 globally for use by certain packages. Because some
6448 packages need to include files which are owned by these
6449 users or groups, or need the ids compiled into binaries,
6450 these ids must be used on any Debian system only for the
6451 purpose for which they are allocated. This is a serious
6452 restriction, and we should avoid getting in the way of
6453 local administration policies. In particular, many sites
6454 allocate users and/or local system groups starting at 100.
6458 Apart from this we should have dynamically allocated ids,
6459 which should by default be arranged in some sensible
6460 order, but the behavior should be configurable.
6464 Packages other than <tt>base-passwd</tt> must not modify
6465 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6466 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6471 <heading>UID and GID classes</heading>
6473 The UID and GID numbers are divided into classes as
6479 Globally allocated by the Debian project, the same
6480 on every Debian system. These ids will appear in
6481 the <file>passwd</file> and <file>group</file> files of all
6482 Debian systems, new ids in this range being added
6483 automatically as the <tt>base-passwd</tt> package is
6488 Packages which need a single statically allocated
6489 uid or gid should use one of these; their
6490 maintainers should ask the <tt>base-passwd</tt>
6498 Dynamically allocated system users and groups.
6499 Packages which need a user or group, but can have
6500 this user or group allocated dynamically and
6501 differently on each system, should use <tt>adduser
6502 --system</tt> to create the group and/or user.
6503 <prgn>adduser</prgn> will check for the existence of
6504 the user or group, and if necessary choose an unused
6505 id based on the ranges specified in
6506 <file>adduser.conf</file>.
6510 <tag>1000-59999:</tag>
6513 Dynamically allocated user accounts. By default
6514 <prgn>adduser</prgn> will choose UIDs and GIDs for
6515 user accounts in this range, though
6516 <file>adduser.conf</file> may be used to modify this
6521 <tag>60000-64999:</tag>
6524 Globally allocated by the Debian project, but only
6525 created on demand. The ids are allocated centrally
6526 and statically, but the actual accounts are only
6527 created on users' systems on demand.
6531 These ids are for packages which are obscure or
6532 which require many statically-allocated ids. These
6533 packages should check for and create the accounts in
6534 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6535 <prgn>adduser</prgn> if it has this facility) if
6536 necessary. Packages which are likely to require
6537 further allocations should have a "hole" left after
6538 them in the allocation, to give them room to
6543 <tag>65000-65533:</tag>
6551 User <tt>nobody</tt>. The corresponding gid refers
6552 to the group <tt>nogroup</tt>.
6559 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6560 not</em> be used, because it is the error return
6569 <sect id="sysvinit">
6570 <heading>System run levels and <file>init.d</file> scripts</heading>
6572 <sect1 id="/etc/init.d">
6573 <heading>Introduction</heading>
6576 The <file>/etc/init.d</file> directory contains the scripts
6577 executed by <prgn>init</prgn> at boot time and when the
6578 init state (or "runlevel") is changed (see <manref
6579 name="init" section="8">).
6583 There are at least two different, yet functionally
6584 equivalent, ways of handling these scripts. For the sake
6585 of simplicity, this document describes only the symbolic
6586 link method. However, it must not be assumed by maintainer
6587 scripts that this method is being used, and any automated
6588 manipulation of the various runlevel behaviors by
6589 maintainer scripts must be performed using
6590 <prgn>update-rc.d</prgn> as described below and not by
6591 manually installing or removing symlinks. For information
6592 on the implementation details of the other method,
6593 implemented in the <tt>file-rc</tt> package, please refer
6594 to the documentation of that package.
6598 These scripts are referenced by symbolic links in the
6599 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6600 runlevels, <prgn>init</prgn> looks in the directory
6601 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6602 execute, where <tt><var>n</var></tt> is the runlevel that
6603 is being changed to, or <tt>S</tt> for the boot-up
6608 The names of the links all have the form
6609 <file>S<var>mm</var><var>script</var></file> or
6610 <file>K<var>mm</var><var>script</var></file> where
6611 <var>mm</var> is a two-digit number and <var>script</var>
6612 is the name of the script (this should be the same as the
6613 name of the actual script in <file>/etc/init.d</file>).
6617 When <prgn>init</prgn> changes runlevel first the targets
6618 of the links whose names start with a <tt>K</tt> are
6619 executed, each with the single argument <tt>stop</tt>,
6620 followed by the scripts prefixed with an <tt>S</tt>, each
6621 with the single argument <tt>start</tt>. (The links are
6622 those in the <file>/etc/rc<var>n</var>.d</file> directory
6623 corresponding to the new runlevel.) The <tt>K</tt> links
6624 are responsible for killing services and the <tt>S</tt>
6625 link for starting services upon entering the runlevel.
6629 For example, if we are changing from runlevel 2 to
6630 runlevel 3, init will first execute all of the <tt>K</tt>
6631 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6632 all of the <tt>S</tt> prefixed scripts in that directory.
6633 The links starting with <tt>K</tt> will cause the
6634 referred-to file to be executed with an argument of
6635 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6640 The two-digit number <var>mm</var> is used to determine
6641 the order in which to run the scripts: low-numbered links
6642 have their scripts run first. For example, the
6643 <tt>K20</tt> scripts will be executed before the
6644 <tt>K30</tt> scripts. This is used when a certain service
6645 must be started before another. For example, the name
6646 server <prgn>bind</prgn> might need to be started before
6647 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6648 can set up its access lists. In this case, the script
6649 that starts <prgn>bind</prgn> would have a lower number
6650 than the script that starts <prgn>inn</prgn> so that it
6652 <example compact="compact">
6659 The two runlevels 0 (halt) and 6 (reboot) are slightly
6660 different. In these runlevels, the links with an
6661 <tt>S</tt> prefix are still called after those with a
6662 <tt>K</tt> prefix, but they too are called with the single
6663 argument <tt>stop</tt>.
6667 <sect1 id="writing-init">
6668 <heading>Writing the scripts</heading>
6671 Packages that include daemons for system services should
6672 place scripts in <file>/etc/init.d</file> to start or stop
6673 services at boot time or during a change of runlevel.
6674 These scripts should be named
6675 <file>/etc/init.d/<var>package</var></file>, and they should
6676 accept one argument, saying what to do:
6679 <tag><tt>start</tt></tag>
6680 <item>start the service,</item>
6682 <tag><tt>stop</tt></tag>
6683 <item>stop the service,</item>
6685 <tag><tt>restart</tt></tag>
6686 <item>stop and restart the service if it's already running,
6687 otherwise start the service</item>
6689 <tag><tt>reload</tt></tag>
6690 <item><p>cause the configuration of the service to be
6691 reloaded without actually stopping and restarting
6694 <tag><tt>force-reload</tt></tag>
6695 <item>cause the configuration to be reloaded if the
6696 service supports this, otherwise restart the
6700 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6701 <tt>force-reload</tt> options should be supported by all
6702 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6707 The <file>init.d</file> scripts must ensure that they will
6708 behave sensibly (i.e., returning success and not starting
6709 multiple copies of a service) if invoked with <tt>start</tt>
6710 when the service is already running, or with <tt>stop</tt>
6711 when it isn't, and that they don't kill unfortunately-named
6712 user processes. The best way to achieve this is usually to
6713 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6718 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6719 scripts. Writing correct <file>init.d</file> scripts requires
6720 accepting various error exit statuses when daemons are already
6721 running or already stopped without aborting
6722 the <file>init.d</file> script, and common <file>init.d</file>
6723 function libraries are not safe to call with <tt>set -e</tt>
6725 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6726 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6727 in effect and echoing status messages to the console fails,
6729 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6730 to not use <tt>set -e</tt> and instead check the result of
6731 each command separately.
6735 If a service reloads its configuration automatically (as
6736 in the case of <prgn>cron</prgn>, for example), the
6737 <tt>reload</tt> option of the <file>init.d</file> script
6738 should behave as if the configuration has been reloaded
6743 The <file>/etc/init.d</file> scripts must be treated as
6744 configuration files, either (if they are present in the
6745 package, that is, in the .deb file) by marking them as
6746 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6747 by managing them correctly in the maintainer scripts (see
6748 <ref id="config-files">). This is important since we want
6749 to give the local system administrator the chance to adapt
6750 the scripts to the local system, e.g., to disable a
6751 service without de-installing the package, or to specify
6752 some special command line options when starting a service,
6753 while making sure their changes aren't lost during the next
6758 These scripts should not fail obscurely when the
6759 configuration files remain but the package has been
6760 removed, as configuration files remain on the system after
6761 the package has been removed. Only when <prgn>dpkg</prgn>
6762 is executed with the <tt>--purge</tt> option will
6763 configuration files be removed. In particular, as the
6764 <file>/etc/init.d/<var>package</var></file> script itself is
6765 usually a <tt>conffile</tt>, it will remain on the system
6766 if the package is removed but not purged. Therefore, you
6767 should include a <tt>test</tt> statement at the top of the
6769 <example compact="compact">
6770 test -f <var>program-executed-later-in-script</var> || exit 0
6775 Often there are some variables in the <file>init.d</file>
6776 scripts whose values control the behavior of the scripts,
6777 and which a system administrator is likely to want to
6778 change. As the scripts themselves are frequently
6779 <tt>conffile</tt>s, modifying them requires that the
6780 administrator merge in their changes each time the package
6781 is upgraded and the <tt>conffile</tt> changes. To ease
6782 the burden on the system administrator, such configurable
6783 values should not be placed directly in the script.
6784 Instead, they should be placed in a file in
6785 <file>/etc/default</file>, which typically will have the same
6786 base name as the <file>init.d</file> script. This extra file
6787 should be sourced by the script when the script runs. It
6788 must contain only variable settings and comments in SUSv3
6789 <prgn>sh</prgn> format. It may either be a
6790 <tt>conffile</tt> or a configuration file maintained by
6791 the package maintainer scripts. See <ref id="config-files">
6796 To ensure that vital configurable values are always
6797 available, the <file>init.d</file> script should set default
6798 values for each of the shell variables it uses, either
6799 before sourcing the <file>/etc/default/</file> file or
6800 afterwards using something like the <tt>:
6801 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6802 script must behave sensibly and not fail if the
6803 <file>/etc/default</file> file is deleted.
6807 Files and directories under <file>/run</file>, including ones
6808 referred to via the compatibility paths <file>/var/run</file>
6809 and <file>/var/lock</file>, are normally stored on a temporary
6810 filesystem and are normally not persistent across a reboot.
6811 The <file>init.d</file> scripts must handle this correctly.
6812 This will typically mean creating any required subdirectories
6813 dynamically when the <file>init.d</file> script is run.
6814 See <ref id="fhs-run"> for more information.
6819 <heading>Interfacing with the initscript system</heading>
6822 Maintainers should use the abstraction layer provided by
6823 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6824 programs to deal with initscripts in their packages'
6825 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6826 and <prgn>postrm</prgn>.
6830 Directly managing the /etc/rc?.d links and directly
6831 invoking the <file>/etc/init.d/</file> initscripts should
6832 be done only by packages providing the initscript
6833 subsystem (such as <prgn>sysv-rc</prgn> and
6834 <prgn>file-rc</prgn>).
6838 <heading>Managing the links</heading>
6841 The program <prgn>update-rc.d</prgn> is provided for
6842 package maintainers to arrange for the proper creation and
6843 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6844 or their functional equivalent if another method is being
6845 used. This may be used by maintainers in their packages'
6846 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6850 You must not include any <file>/etc/rc<var>n</var>.d</file>
6851 symbolic links in the actual archive or manually create or
6852 remove the symbolic links in maintainer scripts; you must
6853 use the <prgn>update-rc.d</prgn> program instead. (The
6854 former will fail if an alternative method of maintaining
6855 runlevel information is being used.) You must not include
6856 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6857 in the archive either. (Only the <tt>sysvinit</tt>
6862 By default <prgn>update-rc.d</prgn> will start services in
6863 each of the multi-user state runlevels (2, 3, 4, and 5)
6864 and stop them in the halt runlevel (0), the single-user
6865 runlevel (1) and the reboot runlevel (6). The system
6866 administrator will have the opportunity to customize
6867 runlevels by simply adding, moving, or removing the
6868 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6869 symbolic links are being used, or by modifying
6870 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6875 To get the default behavior for your package, put in your
6876 <prgn>postinst</prgn> script
6877 <example compact="compact">
6878 update-rc.d <var>package</var> defaults
6880 and in your <prgn>postrm</prgn>
6881 <example compact="compact">
6882 if [ "$1" = purge ]; then
6883 update-rc.d <var>package</var> remove
6885 </example>. Note that if your package changes runlevels
6886 or priority, you may have to remove and recreate the links,
6887 since otherwise the old links may persist. Refer to the
6888 documentation of <prgn>update-rc.d</prgn>.
6892 This will use a default sequence number of 20. If it does
6893 not matter when or in which order the <file>init.d</file>
6894 script is run, use this default. If it does, then you
6895 should talk to the maintainer of the <prgn>sysvinit</prgn>
6896 package or post to <tt>debian-devel</tt>, and they will
6897 help you choose a number.
6901 For more information about using <tt>update-rc.d</tt>,
6902 please consult its man page <manref name="update-rc.d"
6908 <heading>Running initscripts</heading>
6910 The program <prgn>invoke-rc.d</prgn> is provided to make
6911 it easier for package maintainers to properly invoke an
6912 initscript, obeying runlevel and other locally-defined
6913 constraints that might limit a package's right to start,
6914 stop and otherwise manage services. This program may be
6915 used by maintainers in their packages' scripts.
6919 The package maintainer scripts must use
6920 <prgn>invoke-rc.d</prgn> to invoke the
6921 <file>/etc/init.d/*</file> initscripts, instead of
6922 calling them directly.
6926 By default, <prgn>invoke-rc.d</prgn> will pass any
6927 action requests (start, stop, reload, restart...) to the
6928 <file>/etc/init.d</file> script, filtering out requests
6929 to start or restart a service out of its intended
6934 Most packages will simply need to change:
6935 <example compact="compact">/etc/init.d/<package>
6936 <action></example> in their <prgn>postinst</prgn>
6937 and <prgn>prerm</prgn> scripts to:
6938 <example compact="compact">
6939 if which invoke-rc.d >/dev/null 2>&1; then
6940 invoke-rc.d <var>package</var> <action>
6942 /etc/init.d/<var>package</var> <action>
6948 A package should register its initscript services using
6949 <prgn>update-rc.d</prgn> before it tries to invoke them
6950 using <prgn>invoke-rc.d</prgn>. Invocation of
6951 unregistered services may fail.
6955 For more information about using
6956 <prgn>invoke-rc.d</prgn>, please consult its man page
6957 <manref name="invoke-rc.d" section="8">.
6963 <heading>Boot-time initialization</heading>
6966 There used to be another directory, <file>/etc/rc.boot</file>,
6967 which contained scripts which were run once per machine
6968 boot. This has been deprecated in favour of links from
6969 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6970 described in <ref id="/etc/init.d">. Packages must not
6971 place files in <file>/etc/rc.boot</file>.
6976 <heading>Example</heading>
6979 An example on which you can base your
6980 <file>/etc/init.d</file> scripts is found in
6981 <file>/etc/init.d/skeleton</file>.
6988 <heading>Console messages from <file>init.d</file> scripts</heading>
6991 This section describes the formats to be used for messages
6992 written to standard output by the <file>/etc/init.d</file>
6993 scripts. The intent is to improve the consistency of
6994 Debian's startup and shutdown look and feel. For this
6995 reason, please look very carefully at the details. We want
6996 the messages to have the same format in terms of wording,
6997 spaces, punctuation and case of letters.
7001 Here is a list of overall rules that should be used for
7002 messages generated by <file>/etc/init.d</file> scripts.
7008 The message should fit in one line (fewer than 80
7009 characters), start with a capital letter and end with
7010 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7014 If the script is performing some time consuming task in
7015 the background (not merely starting or stopping a
7016 program, for instance), an ellipsis (three dots:
7017 <tt>...</tt>) should be output to the screen, with no
7018 leading or tailing whitespace or line feeds.
7022 The messages should appear as if the computer is telling
7023 the user what it is doing (politely :-), but should not
7024 mention "it" directly. For example, instead of:
7025 <example compact="compact">
7026 I'm starting network daemons: nfsd mountd.
7028 the message should say
7029 <example compact="compact">
7030 Starting network daemons: nfsd mountd.
7037 <tt>init.d</tt> script should use the following standard
7038 message formats for the situations enumerated below.
7044 <p>When daemons are started</p>
7047 If the script starts one or more daemons, the output
7048 should look like this (a single line, no leading
7050 <example compact="compact">
7051 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7053 The <var>description</var> should describe the
7054 subsystem the daemon or set of daemons are part of,
7055 while <var>daemon-1</var> up to <var>daemon-n</var>
7056 denote each daemon's name (typically the file name of
7061 For example, the output of <file>/etc/init.d/lpd</file>
7063 <example compact="compact">
7064 Starting printer spooler: lpd.
7069 This can be achieved by saying
7070 <example compact="compact">
7071 echo -n "Starting printer spooler: lpd"
7072 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7075 in the script. If there are more than one daemon to
7076 start, the output should look like this:
7077 <example compact="compact">
7078 echo -n "Starting remote file system services:"
7079 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7080 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7081 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7084 This makes it possible for the user to see what is
7085 happening and when the final daemon has been started.
7086 Care should be taken in the placement of white spaces:
7087 in the example above the system administrators can
7088 easily comment out a line if they don't want to start
7089 a specific daemon, while the displayed message still
7095 <p>When a system parameter is being set</p>
7098 If you have to set up different system parameters
7099 during the system boot, you should use this format:
7100 <example compact="compact">
7101 Setting <var>parameter</var> to "<var>value</var>".
7106 You can use a statement such as the following to get
7108 <example compact="compact">
7109 echo "Setting DNS domainname to \"$domainname\"."
7114 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7115 for the left and right quotation marks. A grave accent
7116 (<tt>`</tt>) is not a quote character; neither is an
7117 apostrophe (<tt>'</tt>).
7122 <p>When a daemon is stopped or restarted</p>
7125 When you stop or restart a daemon, you should issue a
7126 message identical to the startup message, except that
7127 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7128 or <tt>Restarting</tt> respectively.
7132 For example, stopping the printer daemon will look like
7134 <example compact="compact">
7135 Stopping printer spooler: lpd.
7141 <p>When something is executed</p>
7144 There are several examples where you have to run a
7145 program at system startup or shutdown to perform a
7146 specific task, for example, setting the system's clock
7147 using <prgn>netdate</prgn> or killing all processes
7148 when the system shuts down. Your message should look
7150 <example compact="compact">
7151 Doing something very useful...done.
7153 You should print the <tt>done.</tt> immediately after
7154 the job has been completed, so that the user is
7155 informed why they have to wait. You can get this
7157 <example compact="compact">
7158 echo -n "Doing something very useful..."
7167 <p>When the configuration is reloaded</p>
7170 When a daemon is forced to reload its configuration
7171 files you should use the following format:
7172 <example compact="compact">
7173 Reloading <var>description</var> configuration...done.
7175 where <var>description</var> is the same as in the
7176 daemon starting message.
7183 <sect id="cron-jobs">
7184 <heading>Cron jobs</heading>
7187 Packages must not modify the configuration file
7188 <file>/etc/crontab</file>, and they must not modify the files in
7189 <file>/var/spool/cron/crontabs</file>.
7193 If a package wants to install a job that has to be executed via
7194 cron, it should place a file named as specified
7195 in <ref id="cron-files"> into one or more of the following
7197 <example compact="compact">
7203 As these directory names imply, the files within them are
7204 executed on an hourly, daily, weekly, or monthly basis,
7205 respectively. The exact times are listed in
7206 <file>/etc/crontab</file>.
7210 All files installed in any of these directories must be
7211 scripts (e.g., shell scripts or Perl scripts) so that they
7212 can easily be modified by the local system administrator.
7213 In addition, they must be treated as configuration files.
7217 If a certain job has to be executed at some other frequency or
7218 at a specific time, the package should install a file in
7219 <file>/etc/cron.d</file> with a name as specified
7220 in <ref id="cron-files">. This file uses the same syntax
7221 as <file>/etc/crontab</file> and is processed
7222 by <prgn>cron</prgn> automatically. The file must also be
7223 treated as a configuration file. (Note that entries in the
7224 <file>/etc/cron.d</file> directory are not handled by
7225 <prgn>anacron</prgn>. Thus, you should only use this
7226 directory for jobs which may be skipped if the system is not
7231 Unlike <file>crontab</file> files described in the IEEE Std
7232 1003.1-2008 (POSIX.1) available from
7233 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7234 name="The Open Group">, the files in
7235 <file>/etc/cron.d</file> and the file
7236 <file>/etc/crontab</file> have seven fields; namely:
7238 <item>Minute [0,59]</item>
7239 <item>Hour [0,23]</item>
7240 <item>Day of the month [1,31]</item>
7241 <item>Month of the year [1,12]</item>
7242 <item>Day of the week ([0,6] with 0=Sunday)</item>
7243 <item>Username</item>
7244 <item>Command to be run</item>
7246 Ranges of numbers are allowed. Ranges are two numbers
7247 separated with a hyphen. The specified range is inclusive.
7248 Lists are allowed. A list is a set of numbers (or ranges)
7249 separated by commas. Step values can be used in conjunction
7254 The scripts or <tt>crontab</tt> entries in these directories should
7255 check if all necessary programs are installed before they
7256 try to execute them. Otherwise, problems will arise when a
7257 package was removed but not purged since configuration files
7258 are kept on the system in this situation.
7262 Any <tt>cron</tt> daemon must provide
7263 <file>/usr/bin/crontab</file> and support normal
7264 <tt>crontab</tt> entries as specified in POSIX. The daemon
7265 must also support names for days and months, ranges, and
7266 step values. It has to support <file>/etc/crontab</file>,
7267 and correctly execute the scripts in
7268 <file>/etc/cron.d</file>. The daemon must also correctly
7270 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7273 <sect1 id="cron-files">
7274 <heading>Cron job file names</heading>
7277 The file name of a cron job file should normally match the
7278 name of the package from which it comes.
7282 If a package supplies multiple cron job files files in the
7283 same directory, the file names should all start with the name
7284 of the package (possibly modified as described below) followed
7285 by a hyphen (<tt>-</tt>) and a suitable suffix.
7289 A cron job file name must not include any period or plus
7290 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7291 cause cron to ignore the file. Underscores (<tt>_</tt>)
7292 should be used instead of <tt>.</tt> and <tt>+</tt>
7299 <heading>Menus</heading>
7302 The Debian <tt>menu</tt> package provides a standard
7303 interface between packages providing applications and
7304 <em>menu programs</em> (either X window managers or
7305 text-based menu programs such as <prgn>pdmenu</prgn>).
7309 All packages that provide applications that need not be
7310 passed any special command line arguments for normal
7311 operation should register a menu entry for those
7312 applications, so that users of the <tt>menu</tt> package
7313 will automatically get menu entries in their window
7314 managers, as well in shells like <tt>pdmenu</tt>.
7318 Menu entries should follow the current menu policy.
7322 The menu policy can be found in the <tt>menu-policy</tt>
7323 files in the <tt>debian-policy</tt> package.
7324 It is also available from the Debian web mirrors at
7325 <tt><url name="/doc/packaging-manuals/menu-policy/"
7326 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7330 Please also refer to the <em>Debian Menu System</em>
7331 documentation that comes with the <package>menu</package>
7332 package for information about how to register your
7338 <heading>Multimedia handlers</heading>
7341 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7342 is a mechanism for encoding files and data streams and
7343 providing meta-information about them, in particular their
7344 type (e.g. audio or video) and format (e.g. PNG, HTML,
7349 Registration of MIME type handlers allows programs like mail
7350 user agents and web browsers to invoke these handlers to
7351 view, edit or display MIME types they don't support directly.
7355 Packages which provide the ability to view/show/play,
7356 compose, edit or print MIME types should register themselves
7357 as such following the current MIME support policy.
7361 The <package>mime-support</package> package provides the
7362 <prgn>update-mime</prgn> program which allows packages to
7363 register programs that can show, compose, edit or print
7368 Packages containing such programs must register them
7369 with <prgn>update-mime</prgn> as documented in <manref
7370 name="update-mime" section="8">. They should <em>not</em> depend
7371 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7372 they should just put something like the following in the
7373 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7376 if [ -x /usr/sbin/update-mime ]; then
7385 <heading>Keyboard configuration</heading>
7388 To achieve a consistent keyboard configuration so that all
7389 applications interpret a keyboard event the same way, all
7390 programs in the Debian distribution must be configured to
7391 comply with the following guidelines.
7395 The following keys must have the specified interpretations:
7398 <tag><tt><--</tt></tag>
7399 <item>delete the character to the left of the cursor</item>
7401 <tag><tt>Delete</tt></tag>
7402 <item>delete the character to the right of the cursor</item>
7404 <tag><tt>Control+H</tt></tag>
7405 <item>emacs: the help prefix</item>
7408 The interpretation of any keyboard events should be
7409 independent of the terminal that is used, be it a virtual
7410 console, an X terminal emulator, an rlogin/telnet session,
7415 The following list explains how the different programs
7416 should be set up to achieve this:
7422 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7426 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7430 X translations are set up to make
7431 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7432 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7433 is the vt220 escape code for the "delete character"
7434 key). This must be done by loading the X resources
7435 using <prgn>xrdb</prgn> on all local X displays, not
7436 using the application defaults, so that the
7437 translation resources used correspond to the
7438 <prgn>xmodmap</prgn> settings.
7442 The Linux console is configured to make
7443 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7444 generate <tt>ESC [ 3 ~</tt>.
7448 X applications are configured so that <tt><</tt>
7449 deletes left, and <tt>Delete</tt> deletes right. Motif
7450 applications already work like this.
7454 Terminals should have <tt>stty erase ^?</tt> .
7458 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7459 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7460 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7464 Emacs is programmed to map <tt>KB_Backspace</tt> or
7465 the <tt>stty erase</tt> character to
7466 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7467 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7468 <tt>^H</tt> to <tt>help</tt> as always.
7472 Other applications use the <tt>stty erase</tt>
7473 character and <tt>kdch1</tt> for the two delete keys,
7474 with ASCII DEL being "delete previous character" and
7475 <tt>kdch1</tt> being "delete character under
7483 This will solve the problem except for the following
7490 Some terminals have a <tt><--</tt> key that cannot
7491 be made to produce anything except <tt>^H</tt>. On
7492 these terminals Emacs help will be unavailable on
7493 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7494 character takes precedence in Emacs, and has been set
7495 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7496 available) can be used instead.
7500 Some operating systems use <tt>^H</tt> for <tt>stty
7501 erase</tt>. However, modern telnet versions and all
7502 rlogin versions propagate <tt>stty</tt> settings, and
7503 almost all UNIX versions honour <tt>stty erase</tt>.
7504 Where the <tt>stty</tt> settings are not propagated
7505 correctly, things can be made to work by using
7506 <tt>stty</tt> manually.
7510 Some systems (including previous Debian versions) use
7511 <prgn>xmodmap</prgn> to arrange for both
7512 <tt><--</tt> and <tt>Delete</tt> to generate
7513 <tt>KB_Delete</tt>. We can change the behavior of
7514 their X clients using the same X resources that we use
7515 to do it for our own clients, or configure our clients
7516 using their resources when things are the other way
7517 around. On displays configured like this
7518 <tt>Delete</tt> will not work, but <tt><--</tt>
7523 Some operating systems have different <tt>kdch1</tt>
7524 settings in their <tt>terminfo</tt> database for
7525 <tt>xterm</tt> and others. On these systems the
7526 <tt>Delete</tt> key will not work correctly when you
7527 log in from a system conforming to our policy, but
7528 <tt><--</tt> will.
7535 <heading>Environment variables</heading>
7538 A program must not depend on environment variables to get
7539 reasonable defaults. (That's because these environment
7540 variables would have to be set in a system-wide
7541 configuration file like <file>/etc/profile</file>, which is not
7542 supported by all shells.)
7546 If a program usually depends on environment variables for its
7547 configuration, the program should be changed to fall back to
7548 a reasonable default configuration if these environment
7549 variables are not present. If this cannot be done easily
7550 (e.g., if the source code of a non-free program is not
7551 available), the program must be replaced by a small
7552 "wrapper" shell script which sets the environment variables
7553 if they are not already defined, and calls the original program.
7557 Here is an example of a wrapper script for this purpose:
7559 <example compact="compact">
7561 BAR=${BAR:-/var/lib/fubar}
7563 exec /usr/lib/foo/foo "$@"
7568 Furthermore, as <file>/etc/profile</file> is a configuration
7569 file of the <prgn>base-files</prgn> package, other packages must
7570 not put any environment variables or other commands into that
7575 <sect id="doc-base">
7576 <heading>Registering Documents using doc-base</heading>
7579 The <package>doc-base</package> package implements a
7580 flexible mechanism for handling and presenting
7581 documentation. The recommended practice is for every Debian
7582 package that provides online documentation (other than just
7583 manual pages) to register these documents with
7584 <package>doc-base</package> by installing a
7585 <package>doc-base</package> control file in
7586 <file>/usr/share/doc-base/</file>.
7589 Please refer to the documentation that comes with the
7590 <package>doc-base</package> package for information and
7599 <heading>Files</heading>
7601 <sect id="binaries">
7602 <heading>Binaries</heading>
7605 Two different packages must not install programs with
7606 different functionality but with the same filenames. (The
7607 case of two programs having the same functionality but
7608 different implementations is handled via "alternatives" or
7609 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7610 <ref id="conflicts"> respectively.) If this case happens,
7611 one of the programs must be renamed. The maintainers should
7612 report this to the <tt>debian-devel</tt> mailing list and
7613 try to find a consensus about which program will have to be
7614 renamed. If a consensus cannot be reached, <em>both</em>
7615 programs must be renamed.
7619 By default, when a package is being built, any binaries
7620 created should include debugging information, as well as
7621 being compiled with optimization. You should also turn on
7622 as many reasonable compilation warnings as possible; this
7623 makes life easier for porters, who can then look at build
7624 logs for possible problems. For the C programming language,
7625 this means the following compilation parameters should be
7627 <example compact="compact">
7629 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7631 INSTALL = install -s # (or use strip on the files in debian/tmp)
7636 Note that by default all installed binaries should be stripped,
7637 either by using the <tt>-s</tt> flag to
7638 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7639 the binaries after they have been copied into
7640 <file>debian/tmp</file> but before the tree is made into a
7645 Although binaries in the build tree should be compiled with
7646 debugging information by default, it can often be difficult to
7647 debug programs if they are also subjected to compiler
7648 optimization. For this reason, it is recommended to support the
7649 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7650 (see <ref id="debianrules-options">). This variable can contain
7651 several flags to change how a package is compiled and built.
7655 It is up to the package maintainer to decide what
7656 compilation options are best for the package. Certain
7657 binaries (such as computationally-intensive programs) will
7658 function better with certain flags (<tt>-O3</tt>, for
7659 example); feel free to use them. Please use good judgment
7660 here. Don't use flags for the sake of it; only use them
7661 if there is good reason to do so. Feel free to override
7662 the upstream author's ideas about which compilation
7663 options are best: they are often inappropriate for our
7669 <sect id="libraries">
7670 <heading>Libraries</heading>
7673 If the package is <strong>architecture: any</strong>, then
7674 the shared library compilation and linking flags must have
7675 <tt>-fPIC</tt>, or the package shall not build on some of
7676 the supported architectures<footnote>
7678 If you are using GCC, <tt>-fPIC</tt> produces code with
7679 relocatable position independent code, which is required for
7680 most architectures to create a shared library, with i386 and
7681 perhaps some others where non position independent code is
7682 permitted in a shared library.
7685 Position independent code may have a performance penalty,
7686 especially on <tt>i386</tt>. However, in most cases the
7687 speed penalty must be measured against the memory wasted on
7688 the few architectures where non position independent code is
7691 </footnote>. Any exception to this rule must be discussed on
7692 the mailing list <em>debian-devel@lists.debian.org</em>, and
7693 a rough consensus obtained. The reasons for not compiling
7694 with <tt>-fPIC</tt> flag must be recorded in the file
7695 <tt>README.Debian</tt>, and care must be taken to either
7696 restrict the architecture or arrange for <tt>-fPIC</tt> to
7697 be used on architectures where it is required.<footnote>
7699 Some of the reasons why this might be required is if the
7700 library contains hand crafted assembly code that is not
7701 relocatable, the speed penalty is excessive for compute
7702 intensive libs, and similar reasons.
7707 As to the static libraries, the common case is not to have
7708 relocatable code, since there is no benefit, unless in specific
7709 cases; therefore the static version must not be compiled
7710 with the <tt>-fPIC</tt> flag. Any exception to this rule
7711 should be discussed on the mailing list
7712 <em>debian-devel@lists.debian.org</em>, and the reasons for
7713 compiling with the <tt>-fPIC</tt> flag must be recorded in
7714 the file <tt>README.Debian</tt>. <footnote>
7716 Some of the reasons for linking static libraries with
7717 the <tt>-fPIC</tt> flag are if, for example, one needs a
7718 Perl API for a library that is under rapid development,
7719 and has an unstable API, so shared libraries are
7720 pointless at this phase of the library's development. In
7721 that case, since Perl needs a library with relocatable
7722 code, it may make sense to create a static library with
7723 relocatable code. Another reason cited is if you are
7724 distilling various libraries into a common shared
7725 library, like <tt>mklibs</tt> does in the Debian
7731 In other words, if both a shared and a static library is
7732 being built, each source unit (<tt>*.c</tt>, for example,
7733 for C files) will need to be compiled twice, for the normal
7738 Libraries should be built with threading support and to be
7739 thread-safe if the library supports this.
7743 Although not enforced by the build tools, shared libraries
7744 must be linked against all libraries that they use symbols from
7745 in the same way that binaries are. This ensures the correct
7746 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7747 system and guarantees that all libraries can be safely opened
7748 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7749 option <tt>-Wl,-z,defs</tt> when building a shared library.
7750 Since this option enforces symbol resolution at build time,
7751 a missing library reference will be caught early as a fatal
7756 All installed shared libraries should be stripped with
7757 <example compact="compact">
7758 strip --strip-unneeded <var>your-lib</var>
7760 (The option <tt>--strip-unneeded</tt> makes
7761 <prgn>strip</prgn> remove only the symbols which aren't
7762 needed for relocation processing.) Shared libraries can
7763 function perfectly well when stripped, since the symbols for
7764 dynamic linking are in a separate part of the ELF object
7766 You might also want to use the options
7767 <tt>--remove-section=.comment</tt> and
7768 <tt>--remove-section=.note</tt> on both shared libraries
7769 and executables, and <tt>--strip-debug</tt> on static
7775 Note that under some circumstances it may be useful to
7776 install a shared library unstripped, for example when
7777 building a separate package to support debugging.
7781 Shared object files (often <file>.so</file> files) that are not
7782 public libraries, that is, they are not meant to be linked
7783 to by third party executables (binaries of other packages),
7784 should be installed in subdirectories of the
7785 <file>/usr/lib</file> directory. Such files are exempt from the
7786 rules that govern ordinary shared libraries, except that
7787 they must not be installed executable and should be
7789 A common example are the so-called "plug-ins",
7790 internal shared objects that are dynamically loaded by
7791 programs using <manref name="dlopen" section="3">.
7796 Packages that use <prgn>libtool</prgn> to create and install
7797 their shared libraries install a file containing additional
7798 metadata (ending in <file>.la</file>) alongside the library.
7799 For public libraries intended for use by other packages, these
7800 files normally should not be included in the Debian package,
7801 since the information they include is not necessary to link with
7802 the shared library on Debian and can add unnecessary additional
7803 dependencies to other programs or libraries.<footnote>
7804 These files store, among other things, all libraries on which
7805 that shared library depends. Unfortunately, if
7806 the <file>.la</file> file is present and contains that
7807 dependency information, using <prgn>libtool</prgn> when
7808 linking against that library will cause the resulting program
7809 or library to be linked against those dependencies as well,
7810 even if this is unnecessary. This can create unneeded
7811 dependencies on shared library packages that would otherwise
7812 be hidden behind the library ABI, and can make library
7813 transitions to new SONAMEs unnecessarily complicated and
7814 difficult to manage.
7816 If the <file>.la</file> file is required for that library (if,
7817 for instance, it's loaded via <tt>libltdl</tt> in a way that
7818 requires that meta-information), the <tt>dependency_libs</tt>
7819 setting in the <file>.la</file> file should normally be set to
7820 the empty string. If the shared library development package has
7821 historically included the <file>.la</file>, it must be retained
7822 in the development package (with <tt>dependency_libs</tt>
7823 emptied) until all libraries that depend on it have removed or
7824 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7825 files to prevent linking with those other libraries
7826 using <prgn>libtool</prgn> from failing.
7830 If the <file>.la</file> must be included, it should be included
7831 in the development (<tt>-dev</tt>) package, unless the library
7832 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7833 library. If it is intended for use with <tt>libltdl</tt>,
7834 the <file>.la</file> files must go in the run-time library
7839 These requirements for handling of <file>.la</file> files do not
7840 apply to loadable modules or libraries not installed in
7841 directories searched by default by the dynamic linker. Packages
7842 installing loadable modules will frequently need to install
7843 the <file>.la</file> files alongside the modules so that they
7844 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7845 does not need to be modified for libraries or modules that are
7846 not installed in directories searched by the dynamic linker by
7847 default and not intended for use by other packages.
7851 You must make sure that you use only released versions of
7852 shared libraries to build your packages; otherwise other
7853 users will not be able to run your binaries
7854 properly. Producing source packages that depend on
7855 unreleased compilers is also usually a bad
7862 <heading>Shared libraries</heading>
7864 This section has moved to <ref id="sharedlibs">.
7870 <heading>Scripts</heading>
7873 All command scripts, including the package maintainer
7874 scripts inside the package and used by <prgn>dpkg</prgn>,
7875 should have a <tt>#!</tt> line naming the shell to be used
7880 In the case of Perl scripts this should be
7881 <tt>#!/usr/bin/perl</tt>.
7885 When scripts are installed into a directory in the system
7886 PATH, the script name should not include an extension such
7887 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7888 language currently used to implement it.
7891 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7892 <file>init.d</file> scripts should almost certainly start
7893 with <tt>set -e</tt> so that errors are detected.
7894 <file>init.d</file> scripts are something of a special case, due
7895 to how frequently they need to call commands that are allowed to
7896 fail, and it may instead be easier to check the exit status of
7897 commands directly. See <ref id="writing-init"> for more
7898 information about writing <file>init.d</file> scripts.
7901 Every script should use <tt>set -e</tt> or check the exit status
7902 of <em>every</em> command.
7905 Scripts may assume that <file>/bin/sh</file> implements the
7906 SUSv3 Shell Command Language<footnote>
7907 Single UNIX Specification, version 3, which is also IEEE
7908 1003.1-2004 (POSIX), and is available on the World Wide Web
7909 from <url id="http://www.unix.org/version3/online.html"
7910 name="The Open Group"> after free
7911 registration.</footnote>
7912 plus the following additional features not mandated by
7914 These features are in widespread use in the Linux community
7915 and are implemented in all of bash, dash, and ksh, the most
7916 common shells users may wish to use as <file>/bin/sh</file>.
7919 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7920 must not generate a newline.</item>
7921 <item><tt>test</tt>, if implemented as a shell built-in, must
7922 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7924 <item><tt>local</tt> to create a scoped variable must be
7925 supported, including listing multiple variables in a single
7926 local command and assigning a value to a variable at the
7927 same time as localizing it. <tt>local</tt> may or
7928 may not preserve the variable value from an outer scope if
7929 no assignment is present. Uses such as:
7933 # ... use a, b, c, d ...
7936 must be supported and must set the value of <tt>c</tt> to
7939 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7940 -<var>signal</var></tt>, where <var>signal</var> is either
7941 the name of a signal or one of the numeric signals listed in
7942 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7943 supported if <prgn>kill</prgn> is implemented as a shell
7946 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7947 signals must be supported. In addition to the signal
7948 numbers listed in the extension, which are the same as for
7949 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7952 If a shell script requires non-SUSv3 features from the shell
7953 interpreter other than those listed above, the appropriate shell
7954 must be specified in the first line of the script (e.g.,
7955 <tt>#!/bin/bash</tt>) and the package must depend on the package
7956 providing the shell (unless the shell package is marked
7957 "Essential", as in the case of <prgn>bash</prgn>).
7961 You may wish to restrict your script to SUSv3 features plus the
7962 above set when possible so that it may use <file>/bin/sh</file>
7963 as its interpreter. If your script works with <prgn>dash</prgn>
7964 (originally called <prgn>ash</prgn>), it probably complies with
7965 the above requirements, but if you are in doubt, use
7966 <file>/bin/bash</file>.
7970 Perl scripts should check for errors when making any
7971 system calls, including <tt>open</tt>, <tt>print</tt>,
7972 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7976 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7977 scripting languages. See <em>Csh Programming Considered
7978 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7979 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7980 If an upstream package comes with <prgn>csh</prgn> scripts
7981 then you must make sure that they start with
7982 <tt>#!/bin/csh</tt> and make your package depend on the
7983 <prgn>c-shell</prgn> virtual package.
7987 Any scripts which create files in world-writeable
7988 directories (e.g., in <file>/tmp</file>) must use a
7989 mechanism which will fail atomically if a file with the same
7990 name already exists.
7994 The Debian base system provides the <prgn>tempfile</prgn>
7995 and <prgn>mktemp</prgn> utilities for use by scripts for
8002 <heading>Symbolic links</heading>
8005 In general, symbolic links within a top-level directory should
8006 be relative, and symbolic links pointing from one top-level
8007 directory to or into another should be absolute. (A top-level
8008 directory is a sub-directory of the root
8009 directory <file>/</file>.) For example, a symbolic link
8010 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8011 should be relative (<file>../share/bar</file>), but a symbolic
8012 link from <file>/var/run</file> to <file>/run</file> should be
8014 This is necessary to allow top-level directories to be
8015 symlinks. If linking <file>/var/run</file>
8016 to <file>/run</file> were done with the relative symbolic
8017 link <file>../run</file>, but <file>/var</file> were a
8018 symbolic link to <file>/srv/disk1</file>, the symbolic link
8019 would point to <file>/srv/run</file> rather than the intended
8025 In addition, symbolic links should be specified as short as
8026 possible, i.e., link targets like <file>foo/../bar</file> are
8031 Note that when creating a relative link using
8032 <prgn>ln</prgn> it is not necessary for the target of the
8033 link to exist relative to the working directory you're
8034 running <prgn>ln</prgn> from, nor is it necessary to change
8035 directory to the directory where the link is to be made.
8036 Simply include the string that should appear as the target
8037 of the link (this will be a pathname relative to the
8038 directory in which the link resides) as the first argument
8043 For example, in your <prgn>Makefile</prgn> or
8044 <file>debian/rules</file>, you can do things like:
8045 <example compact="compact">
8046 ln -fs gcc $(prefix)/bin/cc
8047 ln -fs gcc debian/tmp/usr/bin/cc
8048 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8049 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8054 A symbolic link pointing to a compressed file should always
8055 have the same file extension as the referenced file. (For
8056 example, if a file <file>foo.gz</file> is referenced by a
8057 symbolic link, the filename of the link has to end with
8058 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8063 <heading>Device files</heading>
8066 Packages must not include device files or named pipes in the
8071 If a package needs any special device files that are not
8072 included in the base system, it must call
8073 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8074 after notifying the user<footnote>
8075 This notification could be done via a (low-priority)
8076 debconf message, or an echo (printf) statement.
8081 Packages must not remove any device files in the
8082 <prgn>postrm</prgn> or any other script. This is left to the
8083 system administrator.
8087 Debian uses the serial devices
8088 <file>/dev/ttyS*</file>. Programs using the old
8089 <file>/dev/cu*</file> devices should be changed to use
8090 <file>/dev/ttyS*</file>.
8094 Named pipes needed by the package must be created in
8095 the <prgn>postinst</prgn> script<footnote>
8096 It's better to use <prgn>mkfifo</prgn> rather
8097 than <prgn>mknod</prgn> to create named pipes so that
8098 automated checks for packages incorrectly creating device
8099 files with <prgn>mknod</prgn> won't have false positives.
8100 </footnote> and removed in
8101 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8106 <sect id="config-files">
8107 <heading>Configuration files</heading>
8110 <heading>Definitions</heading>
8114 <tag>configuration file</tag>
8116 A file that affects the operation of a program, or
8117 provides site- or host-specific information, or
8118 otherwise customizes the behavior of a program.
8119 Typically, configuration files are intended to be
8120 modified by the system administrator (if needed or
8121 desired) to conform to local policy or to provide
8122 more useful site-specific behavior.
8125 <tag><tt>conffile</tt></tag>
8127 A file listed in a package's <tt>conffiles</tt>
8128 file, and is treated specially by <prgn>dpkg</prgn>
8129 (see <ref id="configdetails">).
8135 The distinction between these two is important; they are
8136 not interchangeable concepts. Almost all
8137 <tt>conffile</tt>s are configuration files, but many
8138 configuration files are not <tt>conffiles</tt>.
8142 As noted elsewhere, <file>/etc/init.d</file> scripts,
8143 <file>/etc/default</file> files, scripts installed in
8144 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8145 configuration installed in <file>/etc/cron.d</file> must be
8146 treated as configuration files. In general, any script that
8147 embeds configuration information is de-facto a configuration
8148 file and should be treated as such.
8153 <heading>Location</heading>
8156 Any configuration files created or used by your package
8157 must reside in <file>/etc</file>. If there are several,
8158 consider creating a subdirectory of <file>/etc</file>
8159 named after your package.
8163 If your package creates or uses configuration files
8164 outside of <file>/etc</file>, and it is not feasible to modify
8165 the package to use <file>/etc</file> directly, put the files
8166 in <file>/etc</file> and create symbolic links to those files
8167 from the location that the package requires.
8172 <heading>Behavior</heading>
8175 Configuration file handling must conform to the following
8177 <list compact="compact">
8179 local changes must be preserved during a package
8183 configuration files must be preserved when the
8184 package is removed, and only deleted when the
8188 Obsolete configuration files without local changes may be
8189 removed by the package during upgrade.
8193 The easy way to achieve this behavior is to make the
8194 configuration file a <tt>conffile</tt>. This is
8195 appropriate only if it is possible to distribute a default
8196 version that will work for most installations, although
8197 some system administrators may choose to modify it. This
8198 implies that the default version will be part of the
8199 package distribution, and must not be modified by the
8200 maintainer scripts during installation (or at any other
8205 In order to ensure that local changes are preserved
8206 correctly, no package may contain or make hard links to
8207 conffiles.<footnote>
8208 Rationale: There are two problems with hard links.
8209 The first is that some editors break the link while
8210 editing one of the files, so that the two files may
8211 unwittingly become unlinked and different. The second
8212 is that <prgn>dpkg</prgn> might break the hard link
8213 while upgrading <tt>conffile</tt>s.
8218 The other way to do it is via the maintainer scripts. In
8219 this case, the configuration file must not be listed as a
8220 <tt>conffile</tt> and must not be part of the package
8221 distribution. If the existence of a file is required for
8222 the package to be sensibly configured it is the
8223 responsibility of the package maintainer to provide
8224 maintainer scripts which correctly create, update and
8225 maintain the file and remove it on purge. (See <ref
8226 id="maintainerscripts"> for more information.) These
8227 scripts must be idempotent (i.e., must work correctly if
8228 <prgn>dpkg</prgn> needs to re-run them due to errors
8229 during installation or removal), must cope with all the
8230 variety of ways <prgn>dpkg</prgn> can call maintainer
8231 scripts, must not overwrite or otherwise mangle the user's
8232 configuration without asking, must not ask unnecessary
8233 questions (particularly during upgrades), and must
8234 otherwise be good citizens.
8238 The scripts are not required to configure every possible
8239 option for the package, but only those necessary to get
8240 the package running on a given system. Ideally the
8241 sysadmin should not have to do any configuration other
8242 than that done (semi-)automatically by the
8243 <prgn>postinst</prgn> script.
8247 A common practice is to create a script called
8248 <file><var>package</var>-configure</file> and have the
8249 package's <prgn>postinst</prgn> call it if and only if the
8250 configuration file does not already exist. In certain
8251 cases it is useful for there to be an example or template
8252 file which the maintainer scripts use. Such files should
8253 be in <file>/usr/share/<var>package</var></file> or
8254 <file>/usr/lib/<var>package</var></file> (depending on whether
8255 they are architecture-independent or not). There should
8256 be symbolic links to them from
8257 <file>/usr/share/doc/<var>package</var>/examples</file> if
8258 they are examples, and should be perfectly ordinary
8259 <prgn>dpkg</prgn>-handled files (<em>not</em>
8260 configuration files).
8264 These two styles of configuration file handling must
8265 not be mixed, for that way lies madness:
8266 <prgn>dpkg</prgn> will ask about overwriting the file
8267 every time the package is upgraded.
8272 <heading>Sharing configuration files</heading>
8275 If two or more packages use the same configuration file
8276 and it is reasonable for both to be installed at the same
8277 time, one of these packages must be defined as
8278 <em>owner</em> of the configuration file, i.e., it will be
8279 the package which handles that file as a configuration
8280 file. Other packages that use the configuration file must
8281 depend on the owning package if they require the
8282 configuration file to operate. If the other package will
8283 use the configuration file if present, but is capable of
8284 operating without it, no dependency need be declared.
8288 If it is desirable for two or more related packages to
8289 share a configuration file <em>and</em> for all of the
8290 related packages to be able to modify that configuration
8291 file, then the following should be done:
8292 <enumlist compact="compact">
8294 One of the related packages (the "owning" package)
8295 will manage the configuration file with maintainer
8296 scripts as described in the previous section.
8299 The owning package should also provide a program
8300 that the other packages may use to modify the
8304 The related packages must use the provided program
8305 to make any desired modifications to the
8306 configuration file. They should either depend on
8307 the core package to guarantee that the configuration
8308 modifier program is available or accept gracefully
8309 that they cannot modify the configuration file if it
8310 is not. (This is in addition to the fact that the
8311 configuration file may not even be present in the
8318 Sometimes it's appropriate to create a new package which
8319 provides the basic infrastructure for the other packages
8320 and which manages the shared configuration files. (The
8321 <tt>sgml-base</tt> package is a good example.)
8325 If the configuration file cannot be shared as described above,
8326 the packages must be marked as conflicting with each other.
8327 Two packages that specify the same file as
8328 a <tt>conffile</tt> must conflict. This is an instance of the
8329 general rule about not sharing files. Neither alternatives
8330 nor diversions are likely to be appropriate in this case; in
8331 particular, <prgn>dpkg</prgn> does not handle diverted
8332 <tt>conffile</tt>s well.
8336 When two packages both declare the same <tt>conffile</tt>, they
8337 may see left-over configuration files from each other even
8338 though they conflict with each other. If a user removes
8339 (without purging) one of the packages and installs the other,
8340 the new package will take over the <tt>conffile</tt> from the
8341 old package. If the file was modified by the user, it will be
8342 treated the same as any other locally
8343 modified <tt>conffile</tt> during an upgrade.
8347 The maintainer scripts must not alter a <tt>conffile</tt>
8348 of <em>any</em> package, including the one the scripts
8354 <heading>User configuration files ("dotfiles")</heading>
8357 The files in <file>/etc/skel</file> will automatically be
8358 copied into new user accounts by <prgn>adduser</prgn>.
8359 No other program should reference the files in
8360 <file>/etc/skel</file>.
8364 Therefore, if a program needs a dotfile to exist in
8365 advance in <file>$HOME</file> to work sensibly, that dotfile
8366 should be installed in <file>/etc/skel</file> and treated as a
8371 However, programs that require dotfiles in order to
8372 operate sensibly are a bad thing, unless they do create
8373 the dotfiles themselves automatically.
8377 Furthermore, programs should be configured by the Debian
8378 default installation to behave as closely to the upstream
8379 default behavior as possible.
8383 Therefore, if a program in a Debian package needs to be
8384 configured in some way in order to operate sensibly, that
8385 should be done using a site-wide configuration file placed
8386 in <file>/etc</file>. Only if the program doesn't support a
8387 site-wide default configuration and the package maintainer
8388 doesn't have time to add it may a default per-user file be
8389 placed in <file>/etc/skel</file>.
8393 <file>/etc/skel</file> should be as empty as we can make it.
8394 This is particularly true because there is no easy (or
8395 necessarily desirable) mechanism for ensuring that the
8396 appropriate dotfiles are copied into the accounts of
8397 existing users when a package is installed.
8403 <heading>Log files</heading>
8405 Log files should usually be named
8406 <file>/var/log/<var>package</var>.log</file>. If you have many
8407 log files, or need a separate directory for permission
8408 reasons (<file>/var/log</file> is writable only by
8409 <file>root</file>), you should usually create a directory named
8410 <file>/var/log/<var>package</var></file> and place your log
8415 Log files must be rotated occasionally so that they don't grow
8416 indefinitely. The best way to do this is to install a log
8417 rotation configuration file in the
8418 directory <file>/etc/logrotate.d</file>, normally
8419 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8420 the facilities provided by <prgn>logrotate</prgn>.
8423 The traditional approach to log files has been to set up
8424 <em>ad hoc</em> log rotation schemes using simple shell
8425 scripts and cron. While this approach is highly
8426 customizable, it requires quite a lot of sysadmin work.
8427 Even though the original Debian system helped a little
8428 by automatically installing a system which can be used
8429 as a template, this was deemed not enough.
8433 The use of <prgn>logrotate</prgn>, a program developed
8434 by Red Hat, is better, as it centralizes log management.
8435 It has both a configuration file
8436 (<file>/etc/logrotate.conf</file>) and a directory where
8437 packages can drop their individual log rotation
8438 configurations (<file>/etc/logrotate.d</file>).
8441 Here is a good example for a logrotate config
8442 file (for more information see <manref name="logrotate"
8444 <example compact="compact">
8445 /var/log/foo/*.log {
8451 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8455 This rotates all files under <file>/var/log/foo</file>, saves 12
8456 compressed generations, and tells the daemon to reopen its log
8457 files after the log rotation. It skips this log rotation
8458 (via <tt>missingok</tt>) if no such log file is present, which
8459 avoids errors if the package is removed but not purged.
8463 Log files should be removed when the package is
8464 purged (but not when it is only removed). This should be
8465 done by the <prgn>postrm</prgn> script when it is called
8466 with the argument <tt>purge</tt> (see <ref
8467 id="removedetails">).
8471 <sect id="permissions-owners">
8472 <heading>Permissions and owners</heading>
8475 The rules in this section are guidelines for general use.
8476 If necessary you may deviate from the details below.
8477 However, if you do so you must make sure that what is done
8478 is secure and you should try to be as consistent as possible
8479 with the rest of the system. You should probably also
8480 discuss it on <prgn>debian-devel</prgn> first.
8484 Files should be owned by <tt>root:root</tt>, and made
8485 writable only by the owner and universally readable (and
8486 executable, if appropriate), that is mode 644 or 755.
8490 Directories should be mode 755 or (for group-writability)
8491 mode 2775. The ownership of the directory should be
8492 consistent with its mode: if a directory is mode 2775, it
8493 should be owned by the group that needs write access to
8496 When a package is upgraded, and the owner or permissions
8497 of a file included in the package has changed, dpkg
8498 arranges for the ownership and permissions to be
8499 correctly set upon installation. However, this does not
8500 extend to directories; the permissions and ownership of
8501 directories already on the system does not change on
8502 install or upgrade of packages. This makes sense, since
8503 otherwise common directories like <tt>/usr</tt> would
8504 always be in flux. To correctly change permissions of a
8505 directory the package owns, explicit action is required,
8506 usually in the <tt>postinst</tt> script. Care must be
8507 taken to handle downgrades as well, in that case.
8513 Control information files should be owned by <tt>root:root</tt>
8514 and either mode 644 (for most files) or mode 755 (for
8515 executables such as <qref id="maintscripts">maintainer
8520 Setuid and setgid executables should be mode 4755 or 2755
8521 respectively, and owned by the appropriate user or group.
8522 They should not be made unreadable (modes like 4711 or
8523 2711 or even 4111); doing so achieves no extra security,
8524 because anyone can find the binary in the freely available
8525 Debian package; it is merely inconvenient. For the same
8526 reason you should not restrict read or execute permissions
8527 on non-set-id executables.
8531 Some setuid programs need to be restricted to particular
8532 sets of users, using file permissions. In this case they
8533 should be owned by the uid to which they are set-id, and by
8534 the group which should be allowed to execute them. They
8535 should have mode 4754; again there is no point in making
8536 them unreadable to those users who must not be allowed to
8541 It is possible to arrange that the system administrator can
8542 reconfigure the package to correspond to their local
8543 security policy by changing the permissions on a binary:
8544 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8545 described below.<footnote>
8546 Ordinary files installed by <prgn>dpkg</prgn> (as
8547 opposed to <tt>conffile</tt>s and other similar objects)
8548 normally have their permissions reset to the distributed
8549 permissions when the package is reinstalled. However,
8550 the use of <prgn>dpkg-statoverride</prgn> overrides this
8553 Another method you should consider is to create a group for
8554 people allowed to use the program(s) and make any setuid
8555 executables executable only by that group.
8559 If you need to create a new user or group for your package
8560 there are two possibilities. Firstly, you may need to
8561 make some files in the binary package be owned by this
8562 user or group, or you may need to compile the user or
8563 group id (rather than just the name) into the binary
8564 (though this latter should be avoided if possible, as in
8565 this case you need a statically allocated id).</p>
8568 If you need a statically allocated id, you must ask for a
8569 user or group id from the <tt>base-passwd</tt> maintainer,
8570 and must not release the package until you have been
8571 allocated one. Once you have been allocated one you must
8572 either make the package depend on a version of the
8573 <tt>base-passwd</tt> package with the id present in
8574 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8575 your package to create the user or group itself with the
8576 correct id (using <tt>adduser</tt>) in its
8577 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8578 the <prgn>postinst</prgn> is to be preferred if it is
8579 possible, otherwise a pre-dependency will be needed on the
8580 <tt>adduser</tt> package.)
8584 On the other hand, the program might be able to determine
8585 the uid or gid from the user or group name at runtime, so
8586 that a dynamically allocated id can be used. In this case
8587 you should choose an appropriate user or group name,
8588 discussing this on <prgn>debian-devel</prgn> and checking
8589 with the <package/base-passwd/ maintainer that it is unique and that
8590 they do not wish you to use a statically allocated id
8591 instead. When this has been checked you must arrange for
8592 your package to create the user or group if necessary using
8593 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8594 <prgn>postinst</prgn> script (again, the latter is to be
8595 preferred if it is possible).
8599 Note that changing the numeric value of an id associated
8600 with a name is very difficult, and involves searching the
8601 file system for all appropriate files. You need to think
8602 carefully whether a static or dynamic id is required, since
8603 changing your mind later will cause problems.
8606 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8608 This section is not intended as policy, but as a
8609 description of the use of <prgn>dpkg-statoverride</prgn>.
8613 If a system administrator wishes to have a file (or
8614 directory or other such thing) installed with owner and
8615 permissions different from those in the distributed Debian
8616 package, they can use the <prgn>dpkg-statoverride</prgn>
8617 program to instruct <prgn>dpkg</prgn> to use the different
8618 settings every time the file is installed. Thus the
8619 package maintainer should distribute the files with their
8620 normal permissions, and leave it for the system
8621 administrator to make any desired changes. For example, a
8622 daemon which is normally required to be setuid root, but
8623 in certain situations could be used without being setuid,
8624 should be installed setuid in the <tt>.deb</tt>. Then the
8625 local system administrator can change this if they wish.
8626 If there are two standard ways of doing it, the package
8627 maintainer can use <tt>debconf</tt> to find out the
8628 preference, and call <prgn>dpkg-statoverride</prgn> in the
8629 maintainer script if necessary to accommodate the system
8630 administrator's choice. Care must be taken during
8631 upgrades to not override an existing setting.
8635 Given the above, <prgn>dpkg-statoverride</prgn> is
8636 essentially a tool for system administrators and would not
8637 normally be needed in the maintainer scripts. There is
8638 one type of situation, though, where calls to
8639 <prgn>dpkg-statoverride</prgn> would be needed in the
8640 maintainer scripts, and that involves packages which use
8641 dynamically allocated user or group ids. In such a
8642 situation, something like the following idiom can be very
8643 helpful in the package's <prgn>postinst</prgn>, where
8644 <tt>sysuser</tt> is a dynamically allocated id:
8646 for i in /usr/bin/foo /usr/sbin/bar
8648 # only do something when no setting exists
8649 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8651 #include: debconf processing, question about foo and bar
8652 if [ "$RET" = "true" ] ; then
8653 dpkg-statoverride --update --add sysuser root 4755 $i
8658 The corresponding code to remove the override when the package
8661 for i in /usr/bin/foo /usr/sbin/bar
8663 if dpkg-statoverride --list $i >/dev/null 2>&1
8665 dpkg-statoverride --remove $i
8675 <chapt id="customized-programs">
8676 <heading>Customized programs</heading>
8678 <sect id="arch-spec">
8679 <heading>Architecture specification strings</heading>
8682 If a program needs to specify an <em>architecture specification
8683 string</em> in some place, it should select one of the strings
8684 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8685 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8686 part is sometimes elided, as when the OS is Linux.
8690 Note that we don't want to use
8691 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8692 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8693 since this would make our programs incompatible with other
8694 Linux distributions. We also don't use something like
8695 <tt><var>arch</var>-unknown-linux</tt>, since the
8696 <tt>unknown</tt> does not look very good.
8699 <sect1 id="arch-wildcard-spec">
8700 <heading>Architecture wildcards</heading>
8703 A package may specify an architecture wildcard. Architecture
8704 wildcards are in the format <tt>any</tt> (which matches every
8705 architecture), <tt><var>os</var></tt>-any, or
8706 any-<tt><var>cpu</var></tt>. <footnote>
8707 Internally, the package system normalizes the GNU triplets
8708 and the Debian arches into Debian arch triplets (which are
8709 kind of inverted GNU triplets), with the first component of
8710 the triplet representing the libc and ABI in use, and then
8711 does matching against those triplets. However, such
8712 triplets are an internal implementation detail that should
8713 not be used by packages directly. The libc and ABI portion
8714 is handled internally by the package system based on
8715 the <var>os</var> and <var>cpu</var>.
8722 <heading>Daemons</heading>
8725 The configuration files <file>/etc/services</file>,
8726 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8727 by the <prgn>netbase</prgn> package and must not be modified
8732 If a package requires a new entry in one of these files, the
8733 maintainer should get in contact with the
8734 <prgn>netbase</prgn> maintainer, who will add the entries
8735 and release a new version of the <prgn>netbase</prgn>
8740 The configuration file <file>/etc/inetd.conf</file> must not be
8741 modified by the package's scripts except via the
8742 <prgn>update-inetd</prgn> script or the
8743 <file>DebianNet.pm</file> Perl module. See their documentation
8744 for details on how to add entries.
8748 If a package wants to install an example entry into
8749 <file>/etc/inetd.conf</file>, the entry must be preceded with
8750 exactly one hash character (<tt>#</tt>). Such lines are
8751 treated as "commented out by user" by the
8752 <prgn>update-inetd</prgn> script and are not changed or
8753 activated during package updates.
8758 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8762 Some programs need to create pseudo-ttys. This should be done
8763 using Unix98 ptys if the C library supports it. The resulting
8764 program must not be installed setuid root, unless that
8765 is required for other functionality.
8769 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8770 <file>/var/log/lastlog</file> must be installed writable by
8771 group <tt>utmp</tt>. Programs which need to modify those
8772 files must be installed setgid <tt>utmp</tt>.
8777 <heading>Editors and pagers</heading>
8780 Some programs have the ability to launch an editor or pager
8781 program to edit or display a text document. Since there are
8782 lots of different editors and pagers available in the Debian
8783 distribution, the system administrator and each user should
8784 have the possibility to choose their preferred editor and
8789 In addition, every program should choose a good default
8790 editor/pager if none is selected by the user or system
8795 Thus, every program that launches an editor or pager must
8796 use the EDITOR or PAGER environment variable to determine
8797 the editor or pager the user wishes to use. If these
8798 variables are not set, the programs <file>/usr/bin/editor</file>
8799 and <file>/usr/bin/pager</file> should be used, respectively.
8803 These two files are managed through the <prgn>dpkg</prgn>
8804 "alternatives" mechanism. Every package providing an editor or
8805 pager must call the <prgn>update-alternatives</prgn> script to
8806 register as an alternative for <file>/usr/bin/editor</file>
8807 or <file>/usr/bin/pager</file> as appropriate. The alternative
8808 should have a slave alternative
8809 for <file>/usr/share/man/man1/editor.1.gz</file>
8810 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8811 corresponding manual page.
8815 If it is very hard to adapt a program to make use of the
8816 EDITOR or PAGER variables, that program may be configured to
8817 use <file>/usr/bin/sensible-editor</file> and
8818 <file>/usr/bin/sensible-pager</file> as the editor or pager
8819 program respectively. These are two scripts provided in the
8820 <package>sensible-utils</package> package that check the EDITOR
8821 and PAGER variables and launch the appropriate program, and fall
8822 back to <file>/usr/bin/editor</file>
8823 and <file>/usr/bin/pager</file> if the variable is not set.
8827 A program may also use the VISUAL environment variable to
8828 determine the user's choice of editor. If it exists, it
8829 should take precedence over EDITOR. This is in fact what
8830 <file>/usr/bin/sensible-editor</file> does.
8834 It is not required for a package to depend on
8835 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8836 package to provide such virtual packages.<footnote>
8837 The Debian base system already provides an editor and a
8843 <sect id="web-appl">
8844 <heading>Web servers and applications</heading>
8847 This section describes the locations and URLs that should
8848 be used by all web servers and web applications in the
8855 Cgi-bin executable files are installed in the
8857 <example compact="compact">
8858 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8860 or a subdirectory of that directory, and should be
8862 <example compact="compact">
8863 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8865 (possibly with a subdirectory name
8866 before <var>cgi-bin-name</var>).
8870 <p>Access to HTML documents</p>
8873 HTML documents for a package are stored in
8874 <file>/usr/share/doc/<var>package</var></file>
8875 and can be referred to as
8876 <example compact="compact">
8877 http://localhost/doc/<var>package</var>/<var>filename</var>
8882 The web server should restrict access to the document
8883 tree so that only clients on the same host can read
8884 the documents. If the web server does not support such
8885 access controls, then it should not provide access at
8886 all, or ask about providing access during installation.
8891 <p>Access to images</p>
8893 It is recommended that images for a package be stored
8894 in <tt>/usr/share/images/<var>package</var></tt> and
8895 may be referred to through an alias <tt>/images/</tt>
8898 http://localhost/images/<package>/<filename>
8905 <p>Web Document Root</p>
8908 Web Applications should try to avoid storing files in
8909 the Web Document Root. Instead they should use the
8910 /usr/share/doc/<var>package</var> directory for
8911 documents and register the Web Application via the
8912 <package>doc-base</package> package. If access to the
8913 web document root is unavoidable then use
8914 <example compact="compact">
8917 as the Document Root. This might be just a symbolic
8918 link to the location where the system administrator
8919 has put the real document root.
8922 <item><p>Providing httpd and/or httpd-cgi</p>
8924 All web servers should provide the virtual package
8925 <tt>httpd</tt>. If a web server has CGI support it should
8926 provide <tt>httpd-cgi</tt> additionally.
8929 All web applications which do not contain CGI scripts should
8930 depend on <tt>httpd</tt>, all those web applications which
8931 <tt>do</tt> contain CGI scripts, should depend on
8939 <sect id="mail-transport-agents">
8940 <heading>Mail transport, delivery and user agents</heading>
8943 Debian packages which process electronic mail, whether mail
8944 user agents (MUAs) or mail transport agents (MTAs), must
8945 ensure that they are compatible with the configuration
8946 decisions below. Failure to do this may result in lost
8947 mail, broken <tt>From:</tt> lines, and other serious brain
8952 The mail spool is <file>/var/mail</file> and the interface to
8953 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8954 the FHS). On older systems, the mail spool may be
8955 physically located in <file>/var/spool/mail</file>, but all
8956 access to the mail spool should be via the
8957 <file>/var/mail</file> symlink. The mail spool is part of the
8958 base system and not part of the MTA package.
8962 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8963 programs (such as IMAP daemons) must lock the mailbox in an
8964 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8965 be combined with dot locking. To avoid deadlocks, a program
8966 should use <tt>fcntl()</tt> first and dot locking after
8967 this, or alternatively implement the two locking methods in
8968 a non blocking way<footnote>
8969 If it is not possible to establish both locks, the
8970 system shouldn't wait for the second lock to be
8971 established, but remove the first lock, wait a (random)
8972 time, and start over locking again.
8973 </footnote>. Using the functions <tt>maillock</tt> and
8974 <tt>mailunlock</tt> provided by the
8975 <tt>liblockfile*</tt><footnote>
8976 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8977 to use these functions.
8978 </footnote> packages is the recommended way to realize this.
8982 Mailboxes are generally either mode 600 and owned by
8983 <var>user</var> or mode 660 and owned by
8984 <tt><var>user</var>:mail</tt><footnote>
8985 There are two traditional permission schemes for mail spools:
8986 mode 600 with all mail delivery done by processes running as
8987 the destination user, or mode 660 and owned by group mail with
8988 mail delivery done by a process running as a system user in
8989 group mail. Historically, Debian required mode 660 mail
8990 spools to enable the latter model, but that model has become
8991 increasingly uncommon and the principle of least privilege
8992 indicates that mail systems that use the first model should
8993 use permissions of 600. If delivery to programs is permitted,
8994 it's easier to keep the mail system secure if the delivery
8995 agent runs as the destination user. Debian Policy therefore
8996 permits either scheme.
8997 </footnote>. The local system administrator may choose a
8998 different permission scheme; packages should not make
8999 assumptions about the permission and ownership of mailboxes
9000 unless required (such as when creating a new mailbox). A MUA
9001 may remove a mailbox (unless it has nonstandard permissions) in
9002 which case the MTA or another MUA must recreate it if needed.
9006 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9007 be setgid mail to do the locking mentioned above (and
9008 must obviously avoid accessing other users' mailboxes
9009 using this privilege).</p>
9012 <file>/etc/aliases</file> is the source file for the system mail
9013 aliases (e.g., postmaster, usenet, etc.), it is the one
9014 which the sysadmin and <prgn>postinst</prgn> scripts may
9015 edit. After <file>/etc/aliases</file> is edited the program or
9016 human editing it must call <prgn>newaliases</prgn>. All MTA
9017 packages must come with a <prgn>newaliases</prgn> program,
9018 even if it does nothing, but older MTA packages did not do
9019 this so programs should not fail if <prgn>newaliases</prgn>
9020 cannot be found. Note that because of this, all MTA
9021 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9022 <tt>Replaces: mail-transport-agent</tt> control fields.
9026 The convention of writing <tt>forward to
9027 <var>address</var></tt> in the mailbox itself is not
9028 supported. Use a <tt>.forward</tt> file instead.</p>
9031 The <prgn>rmail</prgn> program used by UUCP
9032 for incoming mail should be <file>/usr/sbin/rmail</file>.
9033 Likewise, <prgn>rsmtp</prgn>, for receiving
9034 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9038 If your package needs to know what hostname to use on (for
9039 example) outgoing news and mail messages which are generated
9040 locally, you should use the file <file>/etc/mailname</file>. It
9041 will contain the portion after the username and <tt>@</tt>
9042 (at) sign for email addresses of users on the machine
9043 (followed by a newline).
9047 Such a package should check for the existence of this file
9048 when it is being configured. If it exists, it should be
9049 used without comment, although an MTA's configuration script
9050 may wish to prompt the user even if it finds that this file
9051 exists. If the file does not exist, the package should
9052 prompt the user for the value (preferably using
9053 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9054 as well as using it in the package's configuration. The
9055 prompt should make it clear that the name will not just be
9056 used by that package. For example, in this situation the
9057 <tt>inn</tt> package could say something like:
9058 <example compact="compact">
9059 Please enter the "mail name" of your system. This is the
9060 hostname portion of the address to be shown on outgoing
9061 news and mail messages. The default is
9062 <var>syshostname</var>, your system's host name. Mail
9063 name ["<var>syshostname</var>"]:
9065 where <var>syshostname</var> is the output of <tt>hostname
9071 <heading>News system configuration</heading>
9074 All the configuration files related to the NNTP (news)
9075 servers and clients should be located under
9076 <file>/etc/news</file>.</p>
9079 There are some configuration issues that apply to a number
9080 of news clients and server packages on the machine. These
9084 <tag><file>/etc/news/organization</file></tag>
9086 A string which should appear as the
9087 organization header for all messages posted
9088 by NNTP clients on the machine
9091 <tag><file>/etc/news/server</file></tag>
9093 Contains the FQDN of the upstream NNTP
9094 server, or localhost if the local machine is
9099 Other global files may be added as required for cross-package news
9106 <heading>Programs for the X Window System</heading>
9109 <heading>Providing X support and package priorities</heading>
9112 Programs that can be configured with support for the X
9113 Window System must be configured to do so and must declare
9114 any package dependencies necessary to satisfy their
9115 runtime requirements when using the X Window System. If
9116 such a package is of higher priority than the X packages
9117 on which it depends, it is required that either the
9118 X-specific components be split into a separate package, or
9119 that an alternative version of the package, which includes
9120 X support, be provided, or that the package's priority be
9126 <heading>Packages providing an X server</heading>
9129 Packages that provide an X server that, directly or
9130 indirectly, communicates with real input and display
9131 hardware should declare in their <tt>Provides</tt> control
9132 field that they provide the virtual
9133 package <tt>xserver</tt>.<footnote>
9134 This implements current practice, and provides an
9135 actual policy for usage of the <tt>xserver</tt>
9136 virtual package which appears in the virtual packages
9137 list. In a nutshell, X servers that interface
9138 directly with the display and input hardware or via
9139 another subsystem (e.g., GGI) should provide
9140 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9141 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9147 <heading>Packages providing a terminal emulator</heading>
9150 Packages that provide a terminal emulator for the X Window
9151 System which meet the criteria listed below should declare in
9152 their <tt>Provides</tt> control field that they provide the
9153 virtual package <tt>x-terminal-emulator</tt>. They should
9154 also register themselves as an alternative for
9155 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9156 20. That alternative should have a slave alternative
9157 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9158 pointing to the corresponding manual page.
9162 To be an <tt>x-terminal-emulator</tt>, a program must:
9163 <list compact="compact">
9165 Be able to emulate a DEC VT100 terminal, or a
9166 compatible terminal.
9170 Support the command-line option <tt>-e
9171 <var>command</var></tt>, which creates a new
9172 terminal window<footnote>
9173 "New terminal window" does not necessarily mean
9174 a new top-level X window directly parented by
9175 the window manager; it could, if the terminal
9176 emulator application were so coded, be a new
9177 "view" in a multiple-document interface (MDI).
9179 and runs the specified <var>command</var>,
9180 interpreting the entirety of the rest of the command
9181 line as a command to pass straight to exec, in the
9182 manner that <tt>xterm</tt> does.
9186 Support the command-line option <tt>-T
9187 <var>title</var></tt>, which creates a new terminal
9188 window with the window title <var>title</var>.
9195 <heading>Packages providing a window manager</heading>
9198 Packages that provide a window manager should declare in
9199 their <tt>Provides</tt> control field that they provide the
9200 virtual package <tt>x-window-manager</tt>. They should also
9201 register themselves as an alternative for
9202 <file>/usr/bin/x-window-manager</file>, with a priority
9203 calculated as follows:
9204 <list compact="compact">
9206 Start with a priority of 20.
9210 If the window manager supports the Debian menu
9211 system, add 20 points if this support is available
9212 in the package's default configuration (i.e., no
9213 configuration files belonging to the system or user
9214 have to be edited to activate the feature); if
9215 configuration files must be modified, add only 10
9221 If the window manager complies with <url
9222 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9223 name="The Window Manager Specification Project">,
9224 written by the <url id="http://www.freedesktop.org/wiki/"
9225 name="Free Desktop Group">, add 40 points.
9229 If the window manager permits the X session to be
9230 restarted using a <em>different</em> window manager
9231 (without killing the X server) in its default
9232 configuration, add 10 points; otherwise add none.
9235 That alternative should have a slave alternative
9236 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9237 pointing to the corresponding manual page.
9242 <heading>Packages providing fonts</heading>
9245 Packages that provide fonts for the X Window
9247 For the purposes of Debian Policy, a "font for the X
9248 Window System" is one which is accessed via X protocol
9249 requests. Fonts for the Linux console, for PostScript
9250 renderer, or any other purpose, do not fit this
9251 definition. Any tool which makes such fonts available
9252 to the X Window System, however, must abide by this
9255 must do a number of things to ensure that they are both
9256 available without modification of the X or font server
9257 configuration, and that they do not corrupt files used by
9258 other font packages to register information about
9262 Fonts of any type supported by the X Window System
9263 must be in a separate binary package from any
9264 executables, libraries, or documentation (except
9265 that specific to the fonts shipped, such as their
9266 license information). If one or more of the fonts
9267 so packaged are necessary for proper operation of
9268 the package with which they are associated the font
9269 package may be Recommended; if the fonts merely
9270 provide an enhancement, a Suggests relationship may
9271 be used. Packages must not Depend on font
9273 This is because the X server may retrieve fonts
9274 from the local file system or over the network
9275 from an X font server; the Debian package system
9276 is empowered to deal only with the local
9282 BDF fonts must be converted to PCF fonts with the
9283 <prgn>bdftopcf</prgn> utility (available in the
9284 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9285 placed in a directory that corresponds to their
9287 <list compact="compact">
9289 100 dpi fonts must be placed in
9290 <file>/usr/share/fonts/X11/100dpi/</file>.
9294 75 dpi fonts must be placed in
9295 <file>/usr/share/fonts/X11/75dpi/</file>.
9299 Character-cell fonts, cursor fonts, and other
9300 low-resolution fonts must be placed in
9301 <file>/usr/share/fonts/X11/misc/</file>.
9307 Type 1 fonts must be placed in
9308 <file>/usr/share/fonts/X11/Type1/</file>. If font
9309 metric files are available, they must be placed here
9314 Subdirectories of <file>/usr/share/fonts/X11/</file>
9315 other than those listed above must be neither
9316 created nor used. (The <file>PEX</file>, <file>CID</file>,
9317 <file>Speedo</file>, and <file>cyrillic</file> directories
9318 are excepted for historical reasons, but installation of
9319 files into these directories remains discouraged.)
9323 Font packages may, instead of placing files directly
9324 in the X font directories listed above, provide
9325 symbolic links in that font directory pointing to
9326 the files' actual location in the filesystem. Such
9327 a location must comply with the FHS.
9331 Font packages should not contain both 75dpi and
9332 100dpi versions of a font. If both are available,
9333 they should be provided in separate binary packages
9334 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9335 the names of the packages containing the
9336 corresponding fonts.
9340 Fonts destined for the <file>misc</file> subdirectory
9341 should not be included in the same package as 75dpi
9342 or 100dpi fonts; instead, they should be provided in
9343 a separate package with <tt>-misc</tt> appended to
9348 Font packages must not provide the files
9349 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9350 <file>fonts.scale</file> in a font directory:
9353 <file>fonts.dir</file> files must not be provided at all.
9357 <file>fonts.alias</file> and <file>fonts.scale</file>
9358 files, if needed, should be provided in the
9360 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9361 where <var>fontdir</var> is the name of the
9363 <file>/usr/share/fonts/X11/</file> where the
9364 package's corresponding fonts are stored
9365 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9366 <var>package</var> is the name of the package
9367 that provides these fonts, and
9368 <var>extension</var> is either <tt>scale</tt>
9369 or <tt>alias</tt>, whichever corresponds to
9376 Font packages must declare a dependency on
9377 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9378 or <tt>Pre-Depends</tt> control field.
9382 Font packages that provide one or more
9383 <file>fonts.scale</file> files as described above must
9384 invoke <prgn>update-fonts-scale</prgn> on each
9385 directory into which they installed fonts
9386 <em>before</em> invoking
9387 <prgn>update-fonts-dir</prgn> on that directory.
9388 This invocation must occur in both the
9389 <prgn>postinst</prgn> (for all arguments) and
9390 <prgn>postrm</prgn> (for all arguments except
9391 <tt>upgrade</tt>) scripts.
9395 Font packages that provide one or more
9396 <file>fonts.alias</file> files as described above must
9397 invoke <prgn>update-fonts-alias</prgn> on each
9398 directory into which they installed fonts. This
9399 invocation must occur in both the
9400 <prgn>postinst</prgn> (for all arguments) and
9401 <prgn>postrm</prgn> (for all arguments except
9402 <tt>upgrade</tt>) scripts.
9406 Font packages must invoke
9407 <prgn>update-fonts-dir</prgn> on each directory into
9408 which they installed fonts. This invocation must
9409 occur in both the <prgn>postinst</prgn> (for all
9410 arguments) and <prgn>postrm</prgn> (for all
9411 arguments except <tt>upgrade</tt>) scripts.
9415 Font packages must not provide alias names for the
9416 fonts they include which collide with alias names
9417 already in use by fonts already packaged.
9421 Font packages must not provide fonts with the same
9422 XLFD registry name as another font already packaged.
9428 <sect1 id="appdefaults">
9429 <heading>Application defaults files</heading>
9432 Application defaults files must be installed in the
9433 directory <file>/etc/X11/app-defaults/</file> (use of a
9434 localized subdirectory of <file>/etc/X11/</file> as described
9435 in the <em>X Toolkit Intrinsics - C Language
9436 Interface</em> manual is also permitted). They must be
9437 registered as <tt>conffile</tt>s or handled as
9438 configuration files.
9442 Customization of programs' X resources may also be
9443 supported with the provision of a file with the same name
9444 as that of the package placed in
9445 the <file>/etc/X11/Xresources/</file> directory, which
9446 must be registered as a <tt>conffile</tt> or handled as a
9447 configuration file.<footnote>
9448 Note that this mechanism is not the same as using
9449 app-defaults; app-defaults are tied to the client
9450 binary on the local file system, whereas X resources
9451 are stored in the X server and affect all connecting
9458 <heading>Installation directory issues</heading>
9461 Historically, packages using the X Window System used a
9462 separate set of installation directories from other packages.
9463 This practice has been discontinued and packages using the X
9464 Window System should now generally be installed in the same
9465 directories as any other package. Specifically, packages must
9466 not install files under the <file>/usr/X11R6/</file> directory
9467 and the <file>/usr/X11R6/</file> directory hierarchy should be
9468 regarded as obsolete.
9472 Include files previously installed under
9473 <file>/usr/X11R6/include/X11/</file> should be installed into
9474 <file>/usr/include/X11/</file>. For files previously
9475 installed into subdirectories of
9476 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9477 determine if subdirectories of <file>/usr/lib/</file> and
9478 <file>/usr/share/</file> can be used. If not, a subdirectory
9479 of <file>/usr/lib/X11/</file> should be used.
9483 Configuration files for window, display, or session managers
9484 or other applications that are tightly integrated with the X
9485 Window System may be placed in a subdirectory
9486 of <file>/etc/X11/</file> corresponding to the package name.
9487 Other X Window System applications should use
9488 the <file>/etc/</file> directory unless otherwise mandated by
9489 policy (such as for <ref id="appdefaults">).
9495 <heading>Perl programs and modules</heading>
9498 Perl programs and modules should follow the current Perl policy.
9502 The Perl policy can be found in the <tt>perl-policy</tt>
9503 files in the <tt>debian-policy</tt> package.
9504 It is also available from the Debian web mirrors at
9505 <tt><url name="/doc/packaging-manuals/perl-policy/"
9506 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9511 <heading>Emacs lisp programs</heading>
9514 Please refer to the "Debian Emacs Policy" for details of how to
9515 package emacs lisp programs.
9519 The Emacs policy is available in
9520 <file>debian-emacs-policy.gz</file> of the
9521 <package>emacsen-common</package> package.
9522 It is also available from the Debian web mirrors at
9523 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9524 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9529 <heading>Games</heading>
9532 The permissions on <file>/var/games</file> are mode 755, owner
9533 <tt>root</tt> and group <tt>root</tt>.
9537 Each game decides on its own security policy.</p>
9540 Games which require protected, privileged access to
9541 high-score files, saved games, etc., may be made
9542 set-<em>group</em>-id (mode 2755) and owned by
9543 <tt>root:games</tt>, and use files and directories with
9544 appropriate permissions (770 <tt>root:games</tt>, for
9545 example). They must not be made
9546 set-<em>user</em>-id, as this causes security problems. (If
9547 an attacker can subvert any set-user-id game they can
9548 overwrite the executable of any other, causing other players
9549 of these games to run a Trojan horse program. With a
9550 set-group-id game the attacker only gets access to less
9551 important game data, and if they can get at the other
9552 players' accounts at all it will take considerably more
9556 Some packages, for example some fortune cookie programs, are
9557 configured by the upstream authors to install with their
9558 data files or other static information made unreadable so
9559 that they can only be accessed through set-id programs
9560 provided. You should not do this in a Debian package: anyone can
9561 download the <file>.deb</file> file and read the data from it,
9562 so there is no point making the files unreadable. Not
9563 making the files unreadable also means that you don't have
9564 to make so many programs set-id, which reduces the risk of a
9568 As described in the FHS, binaries of games should be
9569 installed in the directory <file>/usr/games</file>. This also
9570 applies to games that use the X Window System. Manual pages
9571 for games (X and non-X games) should be installed in
9572 <file>/usr/share/man/man6</file>.</p>
9578 <heading>Documentation</heading>
9581 <heading>Manual pages</heading>
9584 You should install manual pages in <prgn>nroff</prgn> source
9585 form, in appropriate places under <file>/usr/share/man</file>.
9586 You should only use sections 1 to 9 (see the FHS for more
9587 details). You must not install a pre-formatted "cat page".
9591 Each program, utility, and function should have an
9592 associated manual page included in the same package. It is
9593 suggested that all configuration files also have a manual
9594 page included as well. Manual pages for protocols and other
9595 auxiliary things are optional.
9599 If no manual page is available, this is considered as a bug
9600 and should be reported to the Debian Bug Tracking System (the
9601 maintainer of the package is allowed to write this bug report
9602 themselves, if they so desire). Do not close the bug report
9603 until a proper man page is available.<footnote>
9604 It is not very hard to write a man page. See the
9605 <url id="http://www.schweikhardt.net/man_page_howto.html"
9606 name="Man-Page-HOWTO">,
9607 <manref name="man" section="7">, the examples created
9608 by <prgn>dh_make</prgn>, the helper
9609 program <prgn>help2man</prgn>, or the
9610 directory <file>/usr/share/doc/man-db/examples</file>.
9615 You may forward a complaint about a missing man page to the
9616 upstream authors, and mark the bug as forwarded in the
9617 Debian bug tracking system. Even though the GNU Project do
9618 not in general consider the lack of a man page to be a bug,
9619 we do; if they tell you that they don't consider it a bug
9620 you should leave the bug in our bug tracking system open
9625 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9629 If one man page needs to be accessible via several names it
9630 is better to use a symbolic link than the <file>.so</file>
9631 feature, but there is no need to fiddle with the relevant
9632 parts of the upstream source to change from <file>.so</file> to
9633 symlinks: don't do it unless it's easy. You should not
9634 create hard links in the manual page directories, nor put
9635 absolute filenames in <file>.so</file> directives. The filename
9636 in a <file>.so</file> in a man page should be relative to the
9637 base of the man page tree (usually
9638 <file>/usr/share/man</file>). If you do not create any links
9639 (whether symlinks, hard links, or <tt>.so</tt> directives)
9640 in the file system to the alternate names of the man page,
9641 then you should not rely on <prgn>man</prgn> finding your
9642 man page under those names based solely on the information in
9643 the man page's header.<footnote>
9644 Supporting this in <prgn>man</prgn> often requires
9645 unreasonable processing time to find a manual page or to
9646 report that none exists, and moves knowledge into man's
9647 database that would be better left in the file system.
9648 This support is therefore deprecated and will cease to
9649 be present in the future.
9654 Manual pages in locale-specific subdirectories of
9655 <file>/usr/share/man</file> should use either UTF-8 or the usual
9656 legacy encoding for that language (normally the one corresponding
9657 to the shortest relevant locale name in
9658 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9659 <file>/usr/share/man/fr</file> should use either UTF-8 or
9660 ISO-8859-1.<footnote>
9661 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9662 use. In future, all manual pages will be required to use
9668 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9669 included in the subdirectory name unless it indicates a
9670 significant difference in the language, as this excludes
9671 speakers of the language in other countries.<footnote>
9672 At the time of writing, Chinese and Portuguese are the main
9673 languages with such differences, so <file>pt_BR</file>,
9674 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9679 If a localized version of a manual page is provided, it should
9680 either be up-to-date or it should be obvious to the reader that
9681 it is outdated and the original manual page should be used
9682 instead. This can be done either by a note at the beginning of
9683 the manual page or by showing the missing or changed portions in
9684 the original language instead of the target language.
9689 <heading>Info documents</heading>
9692 Info documents should be installed in <file>/usr/share/info</file>.
9693 They should be compressed with <tt>gzip -9</tt>.
9697 The <prgn>install-info</prgn> program maintains a directory of
9698 installed info documents in <file>/usr/share/info/dir</file> for
9699 the use of info readers.<footnote>
9700 It was previously necessary for packages installing info
9701 documents to run <prgn>install-info</prgn> from maintainer
9702 scripts. This is no longer necessary. The installation
9703 system now uses dpkg triggers.
9705 This file must not be included in packages. Packages containing
9706 info documents should depend on <tt>dpkg (>= 1.15.4) |
9707 install-info</tt> to ensure that the directory file is properly
9708 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9713 Info documents should contain section and directory entry
9714 information in the document for the use
9715 of <prgn>install-info</prgn>. The section should be specified
9716 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9717 space and the section of this info page. The directory entry or
9718 entries should be included between
9719 a <tt>START-INFO-DIR-ENTRY</tt> line and
9720 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9722 INFO-DIR-SECTION Individual utilities
9723 START-INFO-DIR-ENTRY
9724 * example: (example). An example info directory entry.
9727 To determine which section to use, you should look
9728 at <file>/usr/share/info/dir</file> on your system and choose
9729 the most relevant (or create a new section if none of the
9730 current sections are relevant).<footnote>
9731 Normally, info documents are generated from Texinfo source.
9732 To include this information in the generated info document, if
9733 it is absent, add commands like:
9735 @dircategory Individual utilities
9737 * example: (example). An example info directory entry.
9740 to the Texinfo source of the document and ensure that the info
9741 documents are rebuilt from source during the package build.
9747 <heading>Additional documentation</heading>
9750 Any additional documentation that comes with the package may
9751 be installed at the discretion of the package maintainer.
9752 Plain text documentation should be installed in the directory
9753 <file>/usr/share/doc/<var>package</var></file>, where
9754 <var>package</var> is the name of the package, and
9755 compressed with <tt>gzip -9</tt> unless it is small.
9759 If a package comes with large amounts of documentation which
9760 many users of the package will not require you should create
9761 a separate binary package to contain it, so that it does not
9762 take up disk space on the machines of users who do not need
9763 or want it installed.</p>
9766 It is often a good idea to put text information files
9767 (<file>README</file>s, changelogs, and so forth) that come with
9768 the source package in <file>/usr/share/doc/<var>package</var></file>
9769 in the binary package. However, you don't need to install
9770 the instructions for building and installing the package, of
9774 Packages must not require the existence of any files in
9775 <file>/usr/share/doc/</file> in order to function
9777 The system administrator should be able to
9778 delete files in <file>/usr/share/doc/</file> without causing
9779 any programs to break.
9781 Any files that are referenced by programs but are also
9782 useful as stand alone documentation should be installed under
9783 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9784 <file>/usr/share/doc/<var>package</var></file>.
9788 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9789 link to another directory in <file>/usr/share/doc</file> only if
9790 the two packages both come from the same source and the
9791 first package Depends on the second.<footnote>
9793 Please note that this does not override the section on
9794 changelog files below, so the file
9795 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9796 must refer to the changelog for the current version of
9797 <var>package</var> in question. In practice, this means
9798 that the sources of the target and the destination of the
9799 symlink must be the same (same source package and
9806 Former Debian releases placed all additional documentation
9807 in <file>/usr/doc/<var>package</var></file>. This has been
9808 changed to <file>/usr/share/doc/<var>package</var></file>,
9809 and packages must not put documentation in the directory
9810 <file>/usr/doc/<var>package</var></file>. <footnote>
9811 At this phase of the transition, we no longer require a
9812 symbolic link in <file>/usr/doc/</file>. At a later point,
9813 policy shall change to make the symbolic links a bug.
9819 <heading>Preferred documentation formats</heading>
9822 The unification of Debian documentation is being carried out
9826 If your package comes with extensive documentation in a
9827 markup format that can be converted to various other formats
9828 you should if possible ship HTML versions in a binary
9829 package, in the directory
9830 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9831 its subdirectories.<footnote>
9832 The rationale: The important thing here is that HTML
9833 docs should be available in <em>some</em> package, not
9834 necessarily in the main binary package.
9839 Other formats such as PostScript may be provided at the
9840 package maintainer's discretion.
9844 <sect id="copyrightfile">
9845 <heading>Copyright information</heading>
9848 Every package must be accompanied by a verbatim copy of its
9849 copyright information and distribution license in the file
9850 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9851 file must neither be compressed nor be a symbolic link.
9855 In addition, the copyright file must say where the upstream
9856 sources (if any) were obtained, and should name the original
9861 Packages in the <em>contrib</em> or <em>non-free</em> archive
9862 areas should state in the copyright file that the package is not
9863 part of the Debian distribution and briefly explain why.
9867 A copy of the file which will be installed in
9868 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9869 be in <file>debian/copyright</file> in the source package.
9873 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9874 link to another directory in <file>/usr/share/doc</file> only if
9875 the two packages both come from the same source and the
9876 first package Depends on the second. These rules are important
9877 because <file>copyright</file> files must be extractable by
9882 Packages distributed under the Apache license (version 2.0), the
9883 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9884 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9885 1.3) should refer to the corresponding files
9886 under <file>/usr/share/common-licenses</file>,<footnote>
9889 <file>/usr/share/common-licenses/Apache-2.0</file>,
9890 <file>/usr/share/common-licenses/Artistic</file>,
9891 <file>/usr/share/common-licenses/GPL-1</file>,
9892 <file>/usr/share/common-licenses/GPL-2</file>,
9893 <file>/usr/share/common-licenses/GPL-3</file>,
9894 <file>/usr/share/common-licenses/LGPL-2</file>,
9895 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9896 <file>/usr/share/common-licenses/LGPL-3</file>,
9897 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9898 <file>/usr/share/common-licenses/GFDL-1.3</file>
9899 respectively. The University of California BSD license is
9900 also included in <package>base-files</package> as
9901 <file>/usr/share/common-licenses/BSD</file>, but given the
9902 brevity of this license, its specificity to code whose
9903 copyright is held by the Regents of the University of
9904 California, and the frequency of minor wording changes, its
9905 text should be included in the copyright file rather than
9906 referencing this file.
9908 </footnote> rather than quoting them in the copyright
9913 You should not use the copyright file as a general <file>README</file>
9914 file. If your package has such a file it should be
9915 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9916 <file>README.Debian</file> or some other appropriate place.</p>
9920 <heading>Examples</heading>
9923 Any examples (configurations, source files, whatever),
9924 should be installed in a directory
9925 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9926 files should not be referenced by any program: they're there
9927 for the benefit of the system administrator and users as
9928 documentation only. Architecture-specific example files
9929 should be installed in a directory
9930 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9932 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9933 latter directory itself may be a symbolic link to the
9938 If the purpose of a package is to provide examples, then the
9939 example files may be installed into
9940 <file>/usr/share/doc/<var>package</var></file>.
9944 <sect id="changelogs">
9945 <heading>Changelog files</heading>
9948 Packages that are not Debian-native must contain a
9949 compressed copy of the <file>debian/changelog</file> file from
9950 the Debian source tree in
9951 <file>/usr/share/doc/<var>package</var></file> with the name
9952 <file>changelog.Debian.gz</file>.
9956 If an upstream changelog is available, it should be accessible as
9957 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9958 plain text. If the upstream changelog is distributed in
9959 HTML, it should be made available in that form as
9960 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9961 and a plain text <file>changelog.gz</file> should be generated
9962 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9963 the upstream changelog files do not already conform to this
9964 naming convention, then this may be achieved either by
9965 renaming the files, or by adding a symbolic link, at the
9966 maintainer's discretion.<footnote>
9967 Rationale: People should not have to look in places for
9968 upstream changelogs merely because they are given
9969 different names or are distributed in HTML format.
9974 All of these files should be installed compressed using
9975 <tt>gzip -9</tt>, as they will become large with time even
9976 if they start out small.
9980 If the package has only one changelog which is used both as
9981 the Debian changelog and the upstream one because there is
9982 no separate upstream maintainer then that changelog should
9983 usually be installed as
9984 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9985 there is a separate upstream maintainer, but no upstream
9986 changelog, then the Debian changelog should still be called
9987 <file>changelog.Debian.gz</file>.
9991 For details about the format and contents of the Debian
9992 changelog file, please see <ref id="dpkgchangelog">.
9997 <appendix id="pkg-scope">
9998 <heading>Introduction and scope of these appendices</heading>
10001 These appendices are taken essentially verbatim from the
10002 now-deprecated Packaging Manual, version 3.2.1.0. They are
10003 the chapters which are likely to be of use to package
10004 maintainers and which have not already been included in the
10005 policy document itself. Most of these sections are very likely
10006 not relevant to policy; they should be treated as
10007 documentation for the packaging system. Please note that these
10008 appendices are included for convenience, and for historical
10009 reasons: they used to be part of policy package, and they have
10010 not yet been incorporated into dpkg documentation. However,
10011 they still have value, and hence they are presented here.
10015 They have not yet been checked to ensure that they are
10016 compatible with the contents of policy, and if there are any
10017 contradictions, the version in the main policy document takes
10018 precedence. The remaining chapters of the old Packaging
10019 Manual have also not been read in detail to ensure that there
10020 are not parts which have been left out. Both of these will be
10021 done in due course.
10025 Certain parts of the Packaging manual were integrated into the
10026 Policy Manual proper, and removed from the appendices. Links
10027 have been placed from the old locations to the new ones.
10031 <prgn>dpkg</prgn> is a suite of programs for creating binary
10032 package files and installing and removing them on Unix
10034 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10035 work on or be ported to other systems.
10040 The binary packages are designed for the management of
10041 installed executable programs (usually compiled binaries) and
10042 their associated data, though source code examples and
10043 documentation are provided as part of some packages.</p>
10046 This manual describes the technical aspects of creating Debian
10047 binary packages (<file>.deb</file> files). It documents the
10048 behavior of the package management programs
10049 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10050 they interact with packages.</p>
10053 It also documents the interaction between
10054 <prgn>dselect</prgn>'s core and the access method scripts it
10055 uses to actually install the selected packages, and describes
10056 how to create a new access method.</p>
10059 This manual does not go into detail about the options and
10060 usage of the package building and installation tools. It
10061 should therefore be read in conjunction with those programs'
10066 The utility programs which are provided with <prgn>dpkg</prgn>
10067 for managing various system configuration and similar issues,
10068 such as <prgn>update-rc.d</prgn> and
10069 <prgn>install-info</prgn>, are not described in detail here -
10070 please see their man pages.
10074 It is assumed that the reader is reasonably familiar with the
10075 <prgn>dpkg</prgn> System Administrators' manual.
10076 Unfortunately this manual does not yet exist.
10080 The Debian version of the FSF's GNU hello program is provided as
10081 an example for people wishing to create Debian packages. However,
10082 while the examples are helpful, they do not replace the need to
10083 read and follow the Policy and Programmer's Manual.</p>
10086 <appendix id="pkg-binarypkg">
10087 <heading>Binary packages (from old Packaging Manual)</heading>
10090 The binary package has two main sections. The first part
10091 consists of various control information files and scripts used
10092 by <prgn>dpkg</prgn> when installing and removing. See <ref
10093 id="pkg-controlarea">.
10097 The second part is an archive containing the files and
10098 directories to be installed.
10102 In the future binary packages may also contain other
10103 components, such as checksums and digital signatures. The
10104 format for the archive is described in full in the
10105 <file>deb(5)</file> man page.
10109 <sect id="pkg-bincreating"><heading>Creating package files -
10110 <prgn>dpkg-deb</prgn>
10114 All manipulation of binary package files is done by
10115 <prgn>dpkg-deb</prgn>; it's the only program that has
10116 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10117 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10118 will spot that the options requested are appropriate to
10119 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10124 In order to create a binary package you must make a
10125 directory tree which contains all the files and directories
10126 you want to have in the file system data part of the package.
10127 In Debian-format source packages this directory is usually
10128 <file>debian/tmp</file>, relative to the top of the package's
10133 They should have the locations (relative to the root of the
10134 directory tree you're constructing) ownerships and
10135 permissions which you want them to have on the system when
10136 they are installed.
10140 With current versions of <prgn>dpkg</prgn> the uid/username
10141 and gid/groupname mappings for the users and groups being
10142 used should be the same on the system where the package is
10143 built and the one where it is installed.
10147 You need to add one special directory to the root of the
10148 miniature file system tree you're creating:
10149 <prgn>DEBIAN</prgn>. It should contain the control
10150 information files, notably the binary package control file
10151 (see <ref id="pkg-controlfile">).
10155 The <prgn>DEBIAN</prgn> directory will not appear in the
10156 file system archive of the package, and so won't be installed
10157 by <prgn>dpkg</prgn> when the package is unpacked.
10161 When you've prepared the package, you should invoke:
10163 dpkg --build <var>directory</var>
10168 This will build the package in
10169 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10170 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10171 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10172 build the package.)
10176 See the man page <manref name="dpkg-deb" section="8"> for details of how
10177 to examine the contents of this newly-created file. You may find the
10178 output of following commands enlightening:
10180 dpkg-deb --info <var>filename</var>.deb
10181 dpkg-deb --contents <var>filename</var>.deb
10182 dpkg --contents <var>filename</var>.deb
10184 To view the copyright file for a package you could use this command:
10186 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10191 <sect id="pkg-controlarea">
10192 <heading>Package control information files</heading>
10195 The control information portion of a binary package is a
10196 collection of files with names known to <prgn>dpkg</prgn>.
10197 It will treat the contents of these files specially - some
10198 of them contain information used by <prgn>dpkg</prgn> when
10199 installing or removing the package; others are scripts which
10200 the package maintainer wants <prgn>dpkg</prgn> to run.
10204 It is possible to put other files in the package control
10205 information file area, but this is not generally a good idea
10206 (though they will largely be ignored).
10210 Here is a brief list of the control information files supported
10211 by <prgn>dpkg</prgn> and a summary of what they're used for.
10216 <tag><tt>control</tt>
10219 This is the key description file used by
10220 <prgn>dpkg</prgn>. It specifies the package's name
10221 and version, gives its description for the user,
10222 states its relationships with other packages, and so
10223 forth. See <ref id="sourcecontrolfiles"> and
10224 <ref id="binarycontrolfiles">.
10228 It is usually generated automatically from information
10229 in the source package by the
10230 <prgn>dpkg-gencontrol</prgn> program, and with
10231 assistance from <prgn>dpkg-shlibdeps</prgn>.
10232 See <ref id="pkg-sourcetools">.
10236 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10241 These are executable files (usually scripts) which
10242 <prgn>dpkg</prgn> runs during installation, upgrade
10243 and removal of packages. They allow the package to
10244 deal with matters which are particular to that package
10245 or require more complicated processing than that
10246 provided by <prgn>dpkg</prgn>. Details of when and
10247 how they are called are in <ref id="maintainerscripts">.
10251 It is very important to make these scripts idempotent.
10252 See <ref id="idempotency">.
10256 The maintainer scripts are not guaranteed to run with a
10257 controlling terminal and may not be able to interact with
10258 the user. See <ref id="controllingterminal">.
10262 <tag><tt>conffiles</tt>
10265 This file contains a list of configuration files which
10266 are to be handled automatically by <prgn>dpkg</prgn>
10267 (see <ref id="pkg-conffiles">). Note that not necessarily
10268 every configuration file should be listed here.
10271 <tag><tt>shlibs</tt>
10274 This file contains a list of the shared libraries
10275 supplied by the package, with dependency details for
10276 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10277 when it determines what dependencies are required in a
10278 package control file. The <tt>shlibs</tt> file format
10279 is described on <ref id="shlibs">.
10284 <sect id="pkg-controlfile">
10285 <heading>The main control information file: <tt>control</tt></heading>
10288 The most important control information file used by
10289 <prgn>dpkg</prgn> when it installs a package is
10290 <tt>control</tt>. It contains all the package's "vital
10295 The binary package control files of packages built from
10296 Debian sources are made by a special tool,
10297 <prgn>dpkg-gencontrol</prgn>, which reads
10298 <file>debian/control</file> and <file>debian/changelog</file> to
10299 find the information it needs. See <ref id="pkg-sourcepkg"> for
10304 The fields in binary package control files are listed in
10305 <ref id="binarycontrolfiles">.
10309 A description of the syntax of control files and the purpose
10310 of the fields is available in <ref id="controlfields">.
10315 <heading>Time Stamps</heading>
10318 See <ref id="timestamps">.
10323 <appendix id="pkg-sourcepkg">
10324 <heading>Source packages (from old Packaging Manual) </heading>
10327 The Debian binary packages in the distribution are generated
10328 from Debian sources, which are in a special format to assist
10329 the easy and automatic building of binaries.
10332 <sect id="pkg-sourcetools">
10333 <heading>Tools for processing source packages</heading>
10336 Various tools are provided for manipulating source packages;
10337 they pack and unpack sources and help build of binary
10338 packages and help manage the distribution of new versions.
10342 They are introduced and typical uses described here; see
10343 <manref name="dpkg-source" section="1"> for full
10344 documentation about their arguments and operation.
10348 For examples of how to construct a Debian source package,
10349 and how to use those utilities that are used by Debian
10350 source packages, please see the <prgn>hello</prgn> example
10354 <sect1 id="pkg-dpkg-source">
10356 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10361 This program is frequently used by hand, and is also
10362 called from package-independent automated building scripts
10363 such as <prgn>dpkg-buildpackage</prgn>.
10367 To unpack a package it is typically invoked with
10369 dpkg-source -x <var>.../path/to/filename</var>.dsc
10374 with the <file><var>filename</var>.tar.gz</file> and
10375 <file><var>filename</var>.diff.gz</file> (if applicable) in
10376 the same directory. It unpacks into
10377 <file><var>package</var>-<var>version</var></file>, and if
10379 <file><var>package</var>-<var>version</var>.orig</file>, in
10380 the current directory.
10384 To create a packed source archive it is typically invoked:
10386 dpkg-source -b <var>package</var>-<var>version</var>
10391 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10392 <file>.diff.gz</file> (if appropriate) in the current
10393 directory. <prgn>dpkg-source</prgn> does not clean the
10394 source tree first - this must be done separately if it is
10399 See also <ref id="pkg-sourcearchives">.</p>
10403 <sect1 id="pkg-dpkg-buildpackage">
10405 <prgn>dpkg-buildpackage</prgn> - overall package-building
10410 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10411 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10412 targets <tt>clean</tt>, <tt>build</tt> and
10413 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10414 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10415 source and binary package upload.
10419 It is usually invoked by hand from the top level of the
10420 built or unbuilt source directory. It may be invoked with
10421 no arguments; useful arguments include:
10422 <taglist compact="compact">
10423 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10426 Do not sign the <tt>.changes</tt> file or the
10427 source package <tt>.dsc</tt> file, respectively.</p>
10429 <tag><tt>-p<var>sign-command</var></tt></tag>
10432 Invoke <var>sign-command</var> instead of finding
10433 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10434 <var>sign-command</var> must behave just like
10435 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10437 <tag><tt>-r<var>root-command</var></tt></tag>
10440 When root privilege is required, invoke the command
10441 <var>root-command</var>. <var>root-command</var>
10442 should invoke its first argument as a command, from
10443 the <prgn>PATH</prgn> if necessary, and pass its
10444 second and subsequent arguments to the command it
10445 calls. If no <var>root-command</var> is supplied
10446 then <var>dpkg-buildpackage</var> will take no
10447 special action to gain root privilege, so that for
10448 most packages it will have to be invoked as root to
10451 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10454 Two types of binary-only build and upload - see
10455 <manref name="dpkg-source" section="1">.
10462 <sect1 id="pkg-dpkg-gencontrol">
10464 <prgn>dpkg-gencontrol</prgn> - generates binary package
10469 This program is usually called from <file>debian/rules</file>
10470 (see <ref id="pkg-sourcetree">) in the top level of the source
10475 This is usually done just before the files and directories in the
10476 temporary directory tree where the package is being built have their
10477 permissions and ownerships set and the package is constructed using
10478 <prgn>dpkg-deb/</prgn>
10480 This is so that the control file which is produced has
10481 the right permissions
10486 <prgn>dpkg-gencontrol</prgn> must be called after all the
10487 files which are to go into the package have been placed in
10488 the temporary build directory, so that its calculation of
10489 the installed size of a package is correct.
10493 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10494 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10495 variable substitutions created by
10496 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10501 For a package which generates only one binary package, and
10502 which builds it in <file>debian/tmp</file> relative to the top
10503 of the source package, it is usually sufficient to call
10504 <prgn>dpkg-gencontrol</prgn>.
10508 Sources which build several binaries will typically need
10511 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10512 </example> The <tt>-P</tt> tells
10513 <prgn>dpkg-gencontrol</prgn> that the package is being
10514 built in a non-default directory, and the <tt>-p</tt>
10515 tells it which package's control file should be generated.
10519 <prgn>dpkg-gencontrol</prgn> also adds information to the
10520 list of files in <file>debian/files</file>, for the benefit of
10521 (for example) a future invocation of
10522 <prgn>dpkg-genchanges</prgn>.</p>
10525 <sect1 id="pkg-dpkg-shlibdeps">
10527 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10532 This program is usually called from <file>debian/rules</file>
10533 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10534 id="pkg-sourcetree">), in the top level of the source tree.
10538 Its arguments are executables and shared libraries
10541 They may be specified either in the locations in the
10542 source tree where they are created or in the locations
10543 in the temporary build tree where they are installed
10544 prior to binary package creation.
10546 </footnote> for which shared library dependencies should
10547 be included in the binary package's control file.
10551 If some of the found shared libraries should only
10552 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10553 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10554 by using the <tt>-d<var>dependency-field</var></tt> option
10555 before those executable(s). (Each <tt>-d</tt> option
10556 takes effect until the next <tt>-d</tt>.)
10560 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10561 output control file to be modified. Instead by default it
10562 adds to the <file>debian/substvars</file> file variable
10563 settings like <tt>shlibs:Depends</tt>. These variable
10564 settings must be referenced in dependency fields in the
10565 appropriate per-binary-package sections of the source
10570 For example, a package that generates an essential part
10571 which requires dependencies, and optional parts that
10572 which only require a recommendation, would separate those
10573 two sets of dependencies into two different fields.<footnote>
10574 At the time of writing, an example for this was the
10575 <package/xmms/ package, with Depends used for the xmms
10576 executable, Recommends for the plug-ins and Suggests for
10577 even more optional features provided by unzip.
10579 It can say in its <file>debian/rules</file>:
10581 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10582 -dRecommends <var>optionalpart anotheroptionalpart</var>
10584 and then in its main control file <file>debian/control</file>:
10587 Depends: ${shlibs:Depends}
10588 Recommends: ${shlibs:Recommends}
10594 Sources which produce several binary packages with
10595 different shared library dependency requirements can use
10596 the <tt>-p<var>varnameprefix</var></tt> option to override
10597 the default <tt>shlibs:</tt> prefix (one invocation of
10598 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10599 They can thus produce several sets of dependency
10600 variables, each of the form
10601 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10602 which can be referred to in the appropriate parts of the
10603 binary package control files.
10608 <sect1 id="pkg-dpkg-distaddfile">
10610 <prgn>dpkg-distaddfile</prgn> - adds a file to
10611 <file>debian/files</file>
10615 Some packages' uploads need to include files other than
10616 the source and binary package files.
10620 <prgn>dpkg-distaddfile</prgn> adds a file to the
10621 <file>debian/files</file> file so that it will be included in
10622 the <file>.changes</file> file when
10623 <prgn>dpkg-genchanges</prgn> is run.
10627 It is usually invoked from the <tt>binary</tt> target of
10628 <file>debian/rules</file>:
10630 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10632 The <var>filename</var> is relative to the directory where
10633 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10634 is usually the directory above the top level of the source
10635 tree. The <file>debian/rules</file> target should put the
10636 file there just before or just after calling
10637 <prgn>dpkg-distaddfile</prgn>.
10641 The <var>section</var> and <var>priority</var> are passed
10642 unchanged into the resulting <file>.changes</file> file.
10647 <sect1 id="pkg-dpkg-genchanges">
10649 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10650 upload control file
10654 This program is usually called by package-independent
10655 automatic building scripts such as
10656 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10661 It is usually called in the top level of a built source
10662 tree, and when invoked with no arguments will print out a
10663 straightforward <file>.changes</file> file based on the
10664 information in the source package's changelog and control
10665 file and the binary and source packages which should have
10671 <sect1 id="pkg-dpkg-parsechangelog">
10673 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10674 representation of a changelog
10678 This program is used internally by
10679 <prgn>dpkg-source</prgn> et al. It may also occasionally
10680 be useful in <file>debian/rules</file> and elsewhere. It
10681 parses a changelog, <file>debian/changelog</file> by default,
10682 and prints a control-file format representation of the
10683 information in it to standard output.
10687 <sect1 id="pkg-dpkg-architecture">
10689 <prgn>dpkg-architecture</prgn> - information about the build and
10694 This program can be used manually, but is also invoked by
10695 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10696 environment or make variables which specify the build and host
10697 architecture for the package building process.
10702 <sect id="pkg-sourcetree">
10703 <heading>The Debian package source tree</heading>
10706 The source archive scheme described later is intended to
10707 allow a Debian package source tree with some associated
10708 control information to be reproduced and transported easily.
10709 The Debian package source tree is a version of the original
10710 program with certain files added for the benefit of the
10711 packaging process, and with any other changes required
10712 made to the rest of the source code and installation
10717 The extra files created for Debian are in the subdirectory
10718 <file>debian</file> of the top level of the Debian package
10719 source tree. They are described below.
10722 <sect1 id="pkg-debianrules">
10723 <heading><file>debian/rules</file> - the main building script</heading>
10726 See <ref id="debianrules">.
10730 <sect1 id="pkg-srcsubstvars">
10731 <heading><file>debian/substvars</file> and variable substitutions</heading>
10734 See <ref id="substvars">.
10740 <heading><file>debian/files</file></heading>
10743 See <ref id="debianfiles">.
10747 <sect1><heading><file>debian/tmp</file>
10751 This is the canonical temporary location for the
10752 construction of binary packages by the <tt>binary</tt>
10753 target. The directory <file>tmp</file> serves as the root of
10754 the file system tree as it is being constructed (for
10755 example, by using the package's upstream makefiles install
10756 targets and redirecting the output there), and it also
10757 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10758 id="pkg-bincreating">.
10762 If several binary packages are generated from the same
10763 source tree it is usual to use several
10764 <file>debian/tmp<var>something</var></file> directories, for
10765 example <file>tmp-a</file> or <file>tmp-doc</file>.
10769 Whatever <file>tmp</file> directories are created and used by
10770 <tt>binary</tt> must of course be removed by the
10771 <tt>clean</tt> target.</p></sect1>
10775 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10779 As it exists on the FTP site, a Debian source package
10780 consists of three related files. You must have the right
10781 versions of all three to be able to use them.
10786 <tag>Debian source control file - <tt>.dsc</tt></tag>
10788 This file is a control file used by <prgn>dpkg-source</prgn>
10789 to extract a source package.
10790 See <ref id="debiansourcecontrolfiles">.
10794 Original source archive -
10796 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10802 This is a compressed (with <tt>gzip -9</tt>)
10803 <prgn>tar</prgn> file containing the source code from
10804 the upstream authors of the program.
10809 Debian package diff -
10811 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10817 This is a unified context diff (<tt>diff -u</tt>)
10818 giving the changes which are required to turn the
10819 original source into the Debian source. These changes
10820 may only include editing and creating plain files.
10821 The permissions of files, the targets of symbolic
10822 links and the characteristics of special files or
10823 pipes may not be changed and no files may be removed
10828 All the directories in the diff must exist, except the
10829 <file>debian</file> subdirectory of the top of the source
10830 tree, which will be created by
10831 <prgn>dpkg-source</prgn> if necessary when unpacking.
10835 The <prgn>dpkg-source</prgn> program will
10836 automatically make the <file>debian/rules</file> file
10837 executable (see below).</p></item>
10842 If there is no original source code - for example, if the
10843 package is specially prepared for Debian or the Debian
10844 maintainer is the same as the upstream maintainer - the
10845 format is slightly different: then there is no diff, and the
10847 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10848 and preferably contains a directory named
10849 <file><var>package</var>-<var>version</var></file>.
10854 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10857 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10858 Debian source package. However, if it is not available it
10859 is possible to unpack a Debian source archive as follows:
10860 <enumlist compact="compact">
10863 Untar the tarfile, which will create a <file>.orig</file>
10867 <p>Rename the <file>.orig</file> directory to
10868 <file><var>package</var>-<var>version</var></file>.</p>
10872 Create the subdirectory <file>debian</file> at the top of
10873 the source tree.</p>
10875 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10877 <item><p>Untar the tarfile again if you want a copy of the original
10878 source code alongside the Debian version.</p>
10883 It is not possible to generate a valid Debian source archive
10884 without using <prgn>dpkg-source</prgn>. In particular,
10885 attempting to use <prgn>diff</prgn> directly to generate the
10886 <file>.diff.gz</file> file will not work.
10890 <heading>Restrictions on objects in source packages</heading>
10893 The source package may not contain any hard links
10895 This is not currently detected when building source
10896 packages, but only when extracting
10900 Hard links may be permitted at some point in the
10901 future, but would require a fair amount of
10903 </footnote>, device special files, sockets or setuid or
10906 Setgid directories are allowed.
10911 The source packaging tools manage the changes between the
10912 original and Debian source using <prgn>diff</prgn> and
10913 <prgn>patch</prgn>. Turning the original source tree as
10914 included in the <file>.orig.tar.gz</file> into the Debian
10915 package source must not involve any changes which cannot be
10916 handled by these tools. Problematic changes which cause
10917 <prgn>dpkg-source</prgn> to halt with an error when
10918 building the source package are:
10919 <list compact="compact">
10920 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10922 <item><p>Changing the targets of symbolic links.</p>
10924 <item><p>Creating directories, other than <file>debian</file>.</p>
10926 <item><p>Changes to the contents of binary files.</p></item>
10927 </list> Changes which cause <prgn>dpkg-source</prgn> to
10928 print a warning but continue anyway are:
10929 <list compact="compact">
10932 Removing files, directories or symlinks.
10934 Renaming a file is not treated specially - it is
10935 seen as the removal of the old file (which
10936 generates a warning, but is otherwise ignored),
10937 and the creation of the new one.
10943 Changed text files which are missing the usual final
10944 newline (either in the original or the modified
10949 Changes which are not represented, but which are not detected by
10950 <prgn>dpkg-source</prgn>, are:
10951 <list compact="compact">
10952 <item><p>Changing the permissions of files (other than
10953 <file>debian/rules</file>) and directories.</p></item>
10958 The <file>debian</file> directory and <file>debian/rules</file>
10959 are handled specially by <prgn>dpkg-source</prgn> - before
10960 applying the changes it will create the <file>debian</file>
10961 directory, and afterwards it will make
10962 <file>debian/rules</file> world-executable.
10968 <appendix id="pkg-controlfields">
10969 <heading>Control files and their fields (from old Packaging Manual)</heading>
10972 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10973 data in a common format, known as control files. Binary and
10974 source packages have control data as do the <file>.changes</file>
10975 files which control the installation of uploaded files, and
10976 <prgn>dpkg</prgn>'s internal databases are in a similar
10981 <heading>Syntax of control files</heading>
10984 See <ref id="controlsyntax">.
10988 It is important to note that there are several fields which
10989 are optional as far as <prgn>dpkg</prgn> and the related
10990 tools are concerned, but which must appear in every Debian
10991 package, or whose omission may cause problems.
10996 <heading>List of fields</heading>
10999 See <ref id="controlfieldslist">.
11003 This section now contains only the fields that didn't belong
11004 to the Policy manual.
11007 <sect1 id="pkg-f-Filename">
11008 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11011 These fields in <tt>Packages</tt> files give the
11012 filename(s) of (the parts of) a package in the
11013 distribution directories, relative to the root of the
11014 Debian hierarchy. If the package has been split into
11015 several parts the parts are all listed in order, separated
11020 <sect1 id="pkg-f-Size">
11021 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11024 These fields in <file>Packages</file> files give the size (in
11025 bytes, expressed in decimal) and MD5 checksum of the
11026 file(s) which make(s) up a binary package in the
11027 distribution. If the package is split into several parts
11028 the values for the parts are listed in order, separated by
11033 <sect1 id="pkg-f-Status">
11034 <heading><tt>Status</tt></heading>
11037 This field in <prgn>dpkg</prgn>'s status file records
11038 whether the user wants a package installed, removed or
11039 left alone, whether it is broken (requiring
11040 re-installation) or not and what its current state on the
11041 system is. Each of these pieces of information is a
11046 <sect1 id="pkg-f-Config-Version">
11047 <heading><tt>Config-Version</tt></heading>
11050 If a package is not installed or not configured, this
11051 field in <prgn>dpkg</prgn>'s status file records the last
11052 version of the package which was successfully
11057 <sect1 id="pkg-f-Conffiles">
11058 <heading><tt>Conffiles</tt></heading>
11061 This field in <prgn>dpkg</prgn>'s status file contains
11062 information about the automatically-managed configuration
11063 files held by a package. This field should <em>not</em>
11064 appear anywhere in a package!
11069 <heading>Obsolete fields</heading>
11072 These are still recognized by <prgn>dpkg</prgn> but should
11073 not appear anywhere any more.
11075 <taglist compact="compact">
11077 <tag><tt>Revision</tt></tag>
11078 <tag><tt>Package-Revision</tt></tag>
11079 <tag><tt>Package_Revision</tt></tag>
11081 The Debian revision part of the package version was
11082 at one point in a separate control field. This
11083 field went through several names.
11086 <tag><tt>Recommended</tt></tag>
11087 <item>Old name for <tt>Recommends</tt>.</item>
11089 <tag><tt>Optional</tt></tag>
11090 <item>Old name for <tt>Suggests</tt>.</item>
11092 <tag><tt>Class</tt></tag>
11093 <item>Old name for <tt>Priority</tt>.</item>
11102 <appendix id="pkg-conffiles">
11103 <heading>Configuration file handling (from old Packaging Manual)</heading>
11106 <prgn>dpkg</prgn> can do a certain amount of automatic
11107 handling of package configuration files.
11111 Whether this mechanism is appropriate depends on a number of
11112 factors, but basically there are two approaches to any
11113 particular configuration file.
11117 The easy method is to ship a best-effort configuration in the
11118 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11119 handle updates. If the user is unlikely to want to edit the
11120 file, but you need them to be able to without losing their
11121 changes, and a new package with a changed version of the file
11122 is only released infrequently, this is a good approach.
11126 The hard method is to build the configuration file from
11127 scratch in the <prgn>postinst</prgn> script, and to take the
11128 responsibility for fixing any mistakes made in earlier
11129 versions of the package automatically. This will be
11130 appropriate if the file is likely to need to be different on
11134 <sect><heading>Automatic handling of configuration files by
11139 A package may contain a control information file called
11140 <tt>conffiles</tt>. This file should be a list of filenames
11141 of configuration files needing automatic handling, separated
11142 by newlines. The filenames should be absolute pathnames,
11143 and the files referred to should actually exist in the
11148 When a package is upgraded <prgn>dpkg</prgn> will process
11149 the configuration files during the configuration stage,
11150 shortly before it runs the package's <prgn>postinst</prgn>
11155 For each file it checks to see whether the version of the
11156 file included in the package is the same as the one that was
11157 included in the last version of the package (the one that is
11158 being upgraded from); it also compares the version currently
11159 installed on the system with the one shipped with the last
11164 If neither the user nor the package maintainer has changed
11165 the file, it is left alone. If one or the other has changed
11166 their version, then the changed version is preferred - i.e.,
11167 if the user edits their file, but the package maintainer
11168 doesn't ship a different version, the user's changes will
11169 stay, silently, but if the maintainer ships a new version
11170 and the user hasn't edited it the new version will be
11171 installed (with an informative message). If both have
11172 changed their version the user is prompted about the problem
11173 and must resolve the differences themselves.
11177 The comparisons are done by calculating the MD5 message
11178 digests of the files, and storing the MD5 of the file as it
11179 was included in the most recent version of the package.
11183 When a package is installed for the first time
11184 <prgn>dpkg</prgn> will install the file that comes with it,
11185 unless that would mean overwriting a file already on the
11190 However, note that <prgn>dpkg</prgn> will <em>not</em>
11191 replace a conffile that was removed by the user (or by a
11192 script). This is necessary because with some programs a
11193 missing file produces an effect hard or impossible to
11194 achieve in another way, so that a missing file needs to be
11195 kept that way if the user did it.
11199 Note that a package should <em>not</em> modify a
11200 <prgn>dpkg</prgn>-handled conffile in its maintainer
11201 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11202 the user confusing and possibly dangerous options for
11203 conffile update when the package is upgraded.</p>
11206 <sect><heading>Fully-featured maintainer script configuration
11211 For files which contain site-specific information such as
11212 the hostname and networking details and so forth, it is
11213 better to create the file in the package's
11214 <prgn>postinst</prgn> script.
11218 This will typically involve examining the state of the rest
11219 of the system to determine values and other information, and
11220 may involve prompting the user for some information which
11221 can't be obtained some other way.
11225 When using this method there are a couple of important
11226 issues which should be considered:
11230 If you discover a bug in the program which generates the
11231 configuration file, or if the format of the file changes
11232 from one version to the next, you will have to arrange for
11233 the postinst script to do something sensible - usually this
11234 will mean editing the installed configuration file to remove
11235 the problem or change the syntax. You will have to do this
11236 very carefully, since the user may have changed the file,
11237 perhaps to fix the very problem that your script is trying
11238 to deal with - you will have to detect these situations and
11239 deal with them correctly.
11243 If you do go down this route it's probably a good idea to
11244 make the program that generates the configuration file(s) a
11245 separate program in <file>/usr/sbin</file>, by convention called
11246 <file><var>package</var>config</file> and then run that if
11247 appropriate from the post-installation script. The
11248 <tt><var>package</var>config</tt> program should not
11249 unquestioningly overwrite an existing configuration - if its
11250 mode of operation is geared towards setting up a package for
11251 the first time (rather than any arbitrary reconfiguration
11252 later) you should have it check whether the configuration
11253 already exists, and require a <tt>--force</tt> flag to
11254 overwrite it.</p></sect>
11257 <appendix id="pkg-alternatives"><heading>Alternative versions of
11258 an interface - <prgn>update-alternatives</prgn> (from old
11263 When several packages all provide different versions of the
11264 same program or file it is useful to have the system select a
11265 default, but to allow the system administrator to change it
11266 and have their decisions respected.
11270 For example, there are several versions of the <prgn>vi</prgn>
11271 editor, and there is no reason to prevent all of them from
11272 being installed at once, each under their own name
11273 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11274 Nevertheless it is desirable to have the name <tt>vi</tt>
11275 refer to something, at least by default.
11279 If all the packages involved cooperate, this can be done with
11280 <prgn>update-alternatives</prgn>.
11284 Each package provides its own version under its own name, and
11285 calls <prgn>update-alternatives</prgn> in its postinst to
11286 register its version (and again in its prerm to deregister
11291 See the man page <manref name="update-alternatives"
11292 section="8"> for details.
11296 If <prgn>update-alternatives</prgn> does not seem appropriate
11297 you may wish to consider using diversions instead.</p>
11300 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11301 package's version of a file (from old Packaging Manual)
11305 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11306 when it reinstalls the package it belongs to, and to have it
11307 put the file from the package somewhere else instead.
11311 This can be used locally to override a package's version of a
11312 file, or by one package to override another's version (or
11313 provide a wrapper for it).
11317 Before deciding to use a diversion, read <ref
11318 id="pkg-alternatives"> to see if you really want a diversion
11319 rather than several alternative versions of a program.
11323 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11324 and updated by a special program <prgn>dpkg-divert</prgn>.
11325 Please see <manref name="dpkg-divert" section="8"> for full
11326 details of its operation.
11330 When a package wishes to divert a file from another, it should
11331 call <prgn>dpkg-divert</prgn> in its preinst to add the
11332 diversion and rename the existing file. For example,
11333 supposing that a <prgn>smailwrapper</prgn> package wishes to
11334 install a wrapper around <file>/usr/sbin/smail</file>:
11336 dpkg-divert --package smailwrapper --add --rename \
11337 --divert /usr/sbin/smail.real /usr/sbin/smail
11338 </example> The <tt>--package smailwrapper</tt> ensures that
11339 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11340 can bypass the diversion and get installed as the true version.
11341 It's safe to add the diversion unconditionally on upgrades since
11342 it will be left unchanged if it already exists, but
11343 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11344 message, make the command conditional on the version from which
11345 the package is being upgraded:
11347 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11348 dpkg-divert --package smailwrapper --add --rename \
11349 --divert /usr/sbin/smail.real /usr/sbin/smail
11351 </example> where <tt>1.0-2</tt> is the version at which the
11352 diversion was first added to the package. Running the command
11353 during abort-upgrade is pointless but harmless.
11357 The postrm has to do the reverse:
11359 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11360 dpkg-divert --package smailwrapper --remove --rename \
11361 --divert /usr/sbin/smail.real /usr/sbin/smail
11363 </example> If the diversion was added at a particular version, the
11364 postrm should also handle the failure case of upgrading from an
11365 older version (unless the older version is so old that direct
11366 upgrades are no longer supported):
11368 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11369 dpkg-divert --package smailwrapper --remove --rename \
11370 --divert /usr/sbin/smail.real /usr/sbin/smail
11372 </example> where <tt>1.0-2</tt> is the version at which the
11373 diversion was first added to the package. The postrm should not
11374 remove the diversion on upgrades both because there's no reason to
11375 remove the diversion only to immediately re-add it and since the
11376 postrm of the old package is run after unpacking so the removal of
11377 the diversion will fail.
11381 Do not attempt to divert a file which is vitally important for
11382 the system's operation - when using <prgn>dpkg-divert</prgn>
11383 there is a time, after it has been diverted but before
11384 <prgn>dpkg</prgn> has installed the new version, when the file
11385 does not exist.</p>
11390 <!-- Local variables: -->
11391 <!-- indent-tabs-mode: t -->
11393 <!-- vim:set ai sts=2 sw=2 tw=76: -->