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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="mime"></item>
262 <item><ref id="perl"></item>
263 <item><ref id="maintscriptprompt"></item>
264 <item><ref id="emacs"></item>
269 In addition to those, which carry the weight of policy, there
270 is the Debian Developer's Reference. This document describes
271 procedures and resources for Debian developers, but it is
272 <em>not</em> normative; rather, it includes things that don't
273 belong in the Policy, such as best practices for developers.
277 The Developer's Reference is available in the
278 <package>developers-reference</package> package.
279 It's also available from the Debian web mirrors at
280 <tt><url name="/doc/developers-reference/"
281 id="http://www.debian.org/doc/developers-reference/"></tt>.
285 <sect id="definitions">
286 <heading>Definitions</heading>
289 The following terms are used in this Policy Manual:
293 The character encoding specified by ANSI X3.4-1986 and its
294 predecessor standards, referred to in MIME as US-ASCII, and
295 corresponding to an encoding in eight bits per character of
296 the first 128 <url id="http://www.unicode.org/"
297 name="Unicode"> characters, with the eighth bit always zero.
301 The transformation format (sometimes called encoding) of
302 <url id="http://www.unicode.org/" name="Unicode"> defined by
303 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
304 name="RFC 3629">. UTF-8 has the useful property of having
305 ASCII as a subset, so any text encoded in ASCII is trivially
315 <heading>The Debian Archive</heading>
318 The Debian system is maintained and distributed as a
319 collection of <em>packages</em>. Since there are so many of
320 them (currently well over 15000), they are split into
321 <em>sections</em> and given <em>priorities</em> to simplify
322 the handling of them.
326 The effort of the Debian project is to build a free operating
327 system, but not every package we want to make accessible is
328 <em>free</em> in our sense (see the Debian Free Software
329 Guidelines, below), or may be imported/exported without
330 restrictions. Thus, the archive is split into areas<footnote>
331 The Debian archive software uses the term "component" internally
332 and in the Release file format to refer to the division of an
333 archive. The Debian Social Contract simply refers to "areas."
334 This document uses terminology similar to the Social Contract.
335 </footnote> based on their licenses and other restrictions.
339 The aims of this are:
341 <list compact="compact">
342 <item>to allow us to make as much software available as we can</item>
343 <item>to allow us to encourage everyone to write free software,
345 <item>to allow us to make it easy for people to produce
346 CD-ROMs of our system without violating any licenses,
347 import/export restrictions, or any other laws.</item>
352 The <em>main</em> archive area forms the <em>Debian distribution</em>.
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 The <em>main</em> archive area comprises the Debian
470 distribution. Only the packages in this area are considered
471 part of the distribution. None of the packages in
472 the <em>main</em> archive area require software outside of
473 that area to function. Anyone may use, share, modify and
474 redistribute the packages in this archive area
476 See <url id="http://www.debian.org/intro/free"
477 name="What Does Free Mean?"> for
478 more about what we mean by free software.
483 Every package in <em>main</em> must comply with the DFSG
484 (Debian Free Software Guidelines).
488 In addition, the packages in <em>main</em>
489 <list compact="compact">
491 must not require a package outside of <em>main</em>
492 for compilation or execution (thus, the package must
493 not declare a "Depends", "Recommends", or
494 "Build-Depends" relationship on a non-<em>main</em>
498 must not be so buggy that we refuse to support them,
502 must meet all policy requirements presented in this
511 <heading>The contrib archive area</heading>
514 The <em>contrib</em> archive area contains supplemental
515 packages intended to work with the Debian distribution, but
516 which require software outside of the distribution to either
521 Every package in <em>contrib</em> must comply with the DFSG.
525 In addition, the packages in <em>contrib</em>
526 <list compact="compact">
528 must not be so buggy that we refuse to support them,
532 must meet all policy requirements presented in this
539 Examples of packages which would be included in
540 <em>contrib</em> are:
541 <list compact="compact">
543 free packages which require <em>contrib</em>,
544 <em>non-free</em> packages or packages which are not
545 in our archive at all for compilation or execution,
549 wrapper packages or other sorts of free accessories for
556 <sect1 id="non-free">
557 <heading>The non-free archive area</heading>
560 The <em>non-free</em> archive area contains supplemental
561 packages intended to work with the Debian distribution that do
562 not comply with the DFSG or have other problems that make
563 their distribution problematic. They may not comply with all
564 of the policy requirements in this manual due to restrictions
565 on modifications or other limitations.
569 Packages must be placed in <em>non-free</em> if they are
570 not compliant with the DFSG or are encumbered by patents
571 or other legal issues that make their distribution
576 In addition, the packages in <em>non-free</em>
577 <list compact="compact">
579 must not be so buggy that we refuse to support them,
583 must meet all policy requirements presented in this
584 manual that it is possible for them to meet.
586 It is possible that there are policy
587 requirements which the package is unable to
588 meet, for example, if the source is
589 unavailable. These situations will need to be
590 handled on a case-by-case basis.
599 <sect id="pkgcopyright">
600 <heading>Copyright considerations</heading>
603 Every package must be accompanied by a verbatim copy of its
604 copyright information and distribution license in the file
605 <file>/usr/share/doc/<var>package</var>/copyright</file>
606 (see <ref id="copyrightfile"> for further details).
610 We reserve the right to restrict files from being included
611 anywhere in our archives if
612 <list compact="compact">
614 their use or distribution would break a law,
617 there is an ethical conflict in their distribution or
621 we would have to sign a license for them, or
624 their distribution would conflict with other project
631 Programs whose authors encourage the user to make
632 donations are fine for the main distribution, provided
633 that the authors do not claim that not donating is
634 immoral, unethical, illegal or something similar; in such
635 a case they must go in <em>non-free</em>.
639 Packages whose copyright permission notices (or patent
640 problems) do not even allow redistribution of binaries
641 only, and where no special permission has been obtained,
642 must not be placed on the Debian FTP site and its mirrors
647 Note that under international copyright law (this applies
648 in the United States, too), <em>no</em> distribution or
649 modification of a work is allowed without an explicit
650 notice saying so. Therefore a program without a copyright
651 notice <em>is</em> copyrighted and you may not do anything
652 to it without risking being sued! Likewise if a program
653 has a copyright notice but no statement saying what is
654 permitted then nothing is permitted.
658 Many authors are unaware of the problems that restrictive
659 copyrights (or lack of copyright notices) can cause for
660 the users of their supposedly-free software. It is often
661 worthwhile contacting such authors diplomatically to ask
662 them to modify their license terms. However, this can be a
663 politically difficult thing to do and you should ask for
664 advice on the <tt>debian-legal</tt> mailing list first, as
669 When in doubt about a copyright, send mail to
670 <email>debian-legal@lists.debian.org</email>. Be prepared
671 to provide us with the copyright statement. Software
672 covered by the GPL, public domain software and BSD-like
673 copyrights are safe; be wary of the phrases "commercial
674 use prohibited" and "distribution restricted".
678 <sect id="subsections">
679 <heading>Sections</heading>
682 The packages in the archive areas <em>main</em>,
683 <em>contrib</em> and <em>non-free</em> are grouped further into
684 <em>sections</em> to simplify handling.
688 The archive area and section for each package should be
689 specified in the package's <tt>Section</tt> control record (see
690 <ref id="f-Section">). However, the maintainer of the Debian
691 archive may override this selection to ensure the consistency of
692 the Debian distribution. The <tt>Section</tt> field should be
694 <list compact="compact">
696 <em>section</em> if the package is in the
697 <em>main</em> archive area,
700 <em>area/section</em> if the package is in
701 the <em>contrib</em> or <em>non-free</em>
708 The Debian archive maintainers provide the authoritative
709 list of sections. At present, they are:
710 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
711 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
712 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
713 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
714 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
715 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
716 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
717 <em>localization</em>, <em>mail</em>, <em>math</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.
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, a package requires another package to be installed
1137 <em>and</em> configured before it can be installed. In this
1138 case, you must specify a <tt>Pre-Depends</tt> entry for
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 blank lines. Some control
2483 files allow only one paragraph; others allow several, in
2484 which case each paragraph usually refers to a different
2485 package. (For example, in source packages, the first
2486 paragraph refers to the source package, and later paragraphs
2487 refer to binary packages generated from the source.)
2491 Each paragraph consists of a series of data fields; each
2492 field consists of the field name, followed by a colon and
2493 then the data/value associated with that field. It ends at
2494 the end of the (logical) line. Horizontal whitespace
2495 (spaces and tabs) may occur immediately before or after the
2496 value and is ignored there; it is conventional to put a
2497 single space after the colon. For example, a field might
2499 <example compact="compact">
2502 the field name is <tt>Package</tt> and the field value
2507 A paragraph must not contain more than one instance of a
2508 particular field name.
2512 Many fields' values may span several lines; in this case
2513 each continuation line must start with a space or a tab.
2514 Any trailing spaces or tabs at the end of individual
2515 lines of a field value are ignored.
2519 In fields where it is specified that lines may not wrap,
2520 only a single line of data is allowed and whitespace is not
2521 significant in a field body. Whitespace must not appear
2522 inside names (of packages, architectures, files or anything
2523 else) or version numbers, or between the characters of
2524 multi-character version relationships.
2528 Field names are not case-sensitive, but it is usual to
2529 capitalize the field names using mixed case as shown below.
2530 Field values are case-sensitive unless the description of the
2531 field says otherwise.
2535 Blank lines, or lines consisting only of spaces and tabs,
2536 are not allowed within field values or between fields - that
2537 would mean a new paragraph.
2541 All control files must be encoded in UTF-8.
2545 <sect id="sourcecontrolfiles">
2546 <heading>Source package control files -- <file>debian/control</file></heading>
2549 The <file>debian/control</file> file contains the most vital
2550 (and version-independent) information about the source package
2551 and about the binary packages it creates.
2555 The first paragraph of the control file contains information about
2556 the source package in general. The subsequent sets each describe a
2557 binary package that the source tree builds.
2561 The fields in the general paragraph (the first one, for the source
2564 <list compact="compact">
2565 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2566 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2567 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2568 <item><qref id="f-DM-Upload-Allowed"<tt>DM-Upload-Allowed</tt></qref></item>
2569 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2570 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2571 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2572 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2573 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2578 The fields in the binary package paragraphs are:
2580 <list compact="compact">
2581 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2582 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2583 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2584 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2585 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2586 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2587 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2588 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2593 The syntax and semantics of the fields are described below.
2597 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2598 generate control files for binary packages (see below), by
2599 <prgn>dpkg-genchanges</prgn> to generate the
2600 <file>.changes</file> file to accompany the upload, and by
2601 <prgn>dpkg-source</prgn> when it creates the
2602 <file>.dsc</file> source control file as part of a source
2603 archive. Many fields are permitted to span multiple lines in
2604 <file>debian/control</file> but not in any other control
2605 file. These tools are responsible for removing the line
2606 breaks from such fields when using fields from
2607 <file>debian/control</file> to generate other control files.
2611 The fields here may contain variable references - their
2612 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2613 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2614 when they generate output control files.
2615 See <ref id="substvars"> for details.
2619 In addition to the control file syntax described <qref
2620 id="controlsyntax">above</qref>, this file may also contain
2621 comment lines starting with <tt>#</tt> without any preceding
2622 whitespace. All such lines are ignored, even in the middle of
2623 continuation lines for a multiline field, and do not end a
2629 <sect id="binarycontrolfiles">
2630 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2633 The <file>DEBIAN/control</file> file contains the most vital
2634 (and version-dependent) information about a binary package. It
2635 consists of a single paragraph.
2639 The fields in this file are:
2641 <list compact="compact">
2642 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2644 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2646 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2649 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2650 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2658 <sect id="debiansourcecontrolfiles">
2659 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2662 This file consists of a single paragraph, possibly surrounded by
2663 a PGP signature. The fields of that paragraph are listed below.
2664 Their syntax is described above, in <ref id="pkg-controlfields">.
2666 <list compact="compact">
2667 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2668 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2669 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2670 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2671 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2672 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2673 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2674 <item><qref id="f-DM-Upload-Allowed"<tt>DM-Upload-Allowed</tt></qref></item>
2675 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2676 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2677 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2678 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2679 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2680 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2685 The source package control file is generated by
2686 <prgn>dpkg-source</prgn> when it builds the source
2687 archive, from other files in the source package,
2688 described above. When unpacking, it is checked against
2689 the files and directories in the other parts of the
2695 <sect id="debianchangesfiles">
2696 <heading>Debian changes files -- <file>.changes</file></heading>
2699 The <file>.changes</file> files are used by the Debian archive
2700 maintenance software to process updates to packages. They
2701 consist of a single paragraph, possibly surrounded by a PGP
2702 signature. That paragraph contains information from the
2703 <file>debian/control</file> file and other data about the
2704 source package gathered via <file>debian/changelog</file>
2705 and <file>debian/rules</file>.
2709 <file>.changes</file> files have a format version that is
2710 incremented whenever the documented fields or their meaning
2711 change. This document describes format &changesversion;.
2715 The fields in this file are:
2717 <list compact="compact">
2718 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2721 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2722 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2724 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2725 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2726 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2727 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2728 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2730 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2731 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2732 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2733 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2738 <sect id="controlfieldslist">
2739 <heading>List of fields</heading>
2741 <sect1 id="f-Source">
2742 <heading><tt>Source</tt></heading>
2745 This field identifies the source package name.
2749 In <file>debian/control</file> or a <file>.dsc</file> file,
2750 this field must contain only the name of the source package.
2754 In a binary package control file or a <file>.changes</file>
2755 file, the source package name may be followed by a version
2756 number in parentheses<footnote>
2757 It is customary to leave a space after the package name
2758 if a version number is specified.
2760 This version number may be omitted (and is, by
2761 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2762 the <tt>Version</tt> field of the binary package in
2763 question. The field itself may be omitted from a binary
2764 package control file when the source package has the same
2765 name and version as the binary package.
2769 Package names (both source and binary,
2770 see <ref id="f-Package">) must consist only of lower case
2771 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2772 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2773 (<tt>.</tt>). They must be at least two characters long and
2774 must start with an alphanumeric character.
2778 <sect1 id="f-Maintainer">
2779 <heading><tt>Maintainer</tt></heading>
2782 The package maintainer's name and email address. The name
2783 must come first, then the email address inside angle
2784 brackets <tt><></tt> (in RFC822 format).
2788 If the maintainer's name contains a full stop then the
2789 whole field will not work directly as an email address due
2790 to a misfeature in the syntax specified in RFC822; a
2791 program using this field as an address must check for this
2792 and correct the problem if necessary (for example by
2793 putting the name in round brackets and moving it to the
2794 end, and bringing the email address forward).
2798 See <ref id="maintainer"> for additional requirements and
2799 information about package maintainers.
2803 <sect1 id="f-Uploaders">
2804 <heading><tt>Uploaders</tt></heading>
2807 List of the names and email addresses of co-maintainers of the
2808 package, if any. If the package has other maintainers besides
2809 the one named in the <qref id="f-Maintainer">Maintainer
2810 field</qref>, their names and email addresses should be listed
2811 here. The format of each entry is the same as that of the
2812 Maintainer field, and multiple entries must be comma
2817 This is normally an optional field, but if
2818 the <tt>Maintainer</tt> control field names a group of people
2819 and a shared email address, the <tt>Uploaders</tt> field must
2820 be present and must contain at least one human with their
2821 personal email address.
2825 Any parser that interprets the Uploaders field in
2826 <file>debian/control</file> must permit it to span multiple
2827 lines. Line breaks in an Uploaders field that spans multiple
2828 lines are not significant and the semantics of the field are
2829 the same as if the line breaks had not been present.
2833 <sect1 id="f-Changed-By">
2834 <heading><tt>Changed-By</tt></heading>
2837 The name and email address of the person who prepared this
2838 version of the package, usually a maintainer. The syntax is
2839 the same as for the <qref id="f-Maintainer">Maintainer
2844 <sect1 id="f-Section">
2845 <heading><tt>Section</tt></heading>
2848 This field specifies an application area into which the package
2849 has been classified. See <ref id="subsections">.
2853 When it appears in the <file>debian/control</file> file,
2854 it gives the value for the subfield of the same name in
2855 the <tt>Files</tt> field of the <file>.changes</file> file.
2856 It also gives the default for the same field in the binary
2861 <sect1 id="f-Priority">
2862 <heading><tt>Priority</tt></heading>
2865 This field represents how important it is that the user
2866 have the package installed. See <ref id="priorities">.
2870 When it appears in the <file>debian/control</file> file,
2871 it gives the value for the subfield of the same name in
2872 the <tt>Files</tt> field of the <file>.changes</file> file.
2873 It also gives the default for the same field in the binary
2878 <sect1 id="f-Package">
2879 <heading><tt>Package</tt></heading>
2882 The name of the binary package.
2886 Binary package names must follow the same syntax and
2887 restrictions as source package names. See <ref id="f-Source">
2892 <sect1 id="f-Architecture">
2893 <heading><tt>Architecture</tt></heading>
2896 Depending on context and the control file used, the
2897 <tt>Architecture</tt> field can include the following sets of
2901 A unique single word identifying a Debian machine
2902 architecture as described in <ref id="arch-spec">.
2905 An architecture wildcard identifying a set of Debian
2906 machine architectures, see <ref id="arch-wildcard-spec">.
2907 <tt>any</tt> matches all Debian machine architectures
2908 and is the most frequently used.
2911 <tt>all</tt>, which indicates an
2912 architecture-independent package.
2915 <tt>source</tt>, which indicates a source package.
2921 In the main <file>debian/control</file> file in the source
2922 package, this field may contain the special
2923 value <tt>all</tt>, the special architecture
2924 wildcard <tt>any</tt>, or a list of specific and wildcard
2925 architectures separated by spaces. If <tt>all</tt>
2926 or <tt>any</tt> appears, that value must be the entire
2927 contents of the field. Most packages will use
2928 either <tt>all</tt> or <tt>any</tt>.
2932 Specifying a specific list of architectures indicates that the
2933 source will build an architecture-dependent package only on
2934 architectures included in the list. Specifying a list of
2935 architecture wildcards indicates that the source will build an
2936 architecture-dependent package on only those architectures
2937 that match any of the specified architecture wildcards.
2938 Specifying a list of architectures or architecture wildcards
2939 other than <tt>any</tt> is for the minority of cases where a
2940 program is not portable or is not useful on some
2941 architectures. Where possible, the program should be made
2946 In the source package control file <file>.dsc</file>, this
2947 field may contain either the architecture
2948 wildcard <tt>any</tt> or a list of architectures and
2949 architecture wildcards separated by spaces. If a list is
2950 given, it may include (or consist solely of) the special
2951 value <tt>all</tt>. In other words, in <file>.dsc</file>
2952 files unlike the <file>debian/control</file>, <tt>all</tt> may
2953 occur in combination with specific architectures.
2954 The <tt>Architecture</tt> field in the source package control
2955 file <file>.dsc</file> is generally constructed from
2956 the <tt>Architecture</tt> fields in
2957 the <file>debian/control</file> in the source package.
2961 Specifying <tt>any</tt> indicates that the source package
2962 isn't dependent on any particular architecture and should
2963 compile fine on any one. The produced binary package(s)
2964 will either be specific to whatever the current build
2965 architecture is or will be architecture-independent.
2969 Specifying only <tt>all</tt> indicates that the source package
2970 will only build architecture-independent packages. If this is
2971 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2972 <tt>any</tt> implies that the source package will build at
2973 least one architecture-dependent package.
2977 Specifying a list of architectures or architecture wildcards
2978 indicates that the source will build an architecture-dependent
2979 package, and will only work correctly on the listed or
2980 matching architectures. If the source package also builds at
2981 least one architecture-independent package, <tt>all</tt> will
2982 also be included in the list.
2986 In a <file>.changes</file> file, the <tt>Architecture</tt>
2987 field lists the architecture(s) of the package(s) currently
2988 being uploaded. This will be a list; if the source for the
2989 package is also being uploaded, the special
2990 entry <tt>source</tt> is also present. <tt>all</tt> will be
2991 present if any architecture-independent packages are being
2992 uploaded. Architecture wildcards such as <tt>any</tt> must
2993 never occur in the <tt>Architecture</tt> field in
2994 the <file>.changes</file> file.
2998 See <ref id="debianrules"> for information on how to get
2999 the architecture for the build process.
3003 <sect1 id="f-Essential">
3004 <heading><tt>Essential</tt></heading>
3007 This is a boolean field which may occur only in the
3008 control file of a binary package or in a per-package fields
3009 paragraph of a main source control data file.
3013 If set to <tt>yes</tt> then the package management system
3014 will refuse to remove the package (upgrading and replacing
3015 it is still possible). The other possible value is <tt>no</tt>,
3016 which is the same as not having the field at all.
3021 <heading>Package interrelationship fields:
3022 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3023 <tt>Recommends</tt>, <tt>Suggests</tt>,
3024 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3025 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3029 These fields describe the package's relationships with
3030 other packages. Their syntax and semantics are described
3031 in <ref id="relationships">.</p>
3034 <sect1 id="f-Standards-Version">
3035 <heading><tt>Standards-Version</tt></heading>
3038 The most recent version of the standards (the policy
3039 manual and associated texts) with which the package
3044 The version number has four components: major and minor
3045 version number and major and minor patch level. When the
3046 standards change in a way that requires every package to
3047 change the major number will be changed. Significant
3048 changes that will require work in many packages will be
3049 signaled by a change to the minor number. The major patch
3050 level will be changed for any change to the meaning of the
3051 standards, however small; the minor patch level will be
3052 changed when only cosmetic, typographical or other edits
3053 are made which neither change the meaning of the document
3054 nor affect the contents of packages.
3058 Thus only the first three components of the policy version
3059 are significant in the <em>Standards-Version</em> control
3060 field, and so either these three components or all four
3061 components may be specified.<footnote>
3062 In the past, people specified the full version number
3063 in the Standards-Version field, for example "2.3.0.0".
3064 Since minor patch-level changes don't introduce new
3065 policy, it was thought it would be better to relax
3066 policy and only require the first 3 components to be
3067 specified, in this example "2.3.0". All four
3068 components may still be used if someone wishes to do so.
3074 <sect1 id="f-Version">
3075 <heading><tt>Version</tt></heading>
3078 The version number of a package. The format is:
3079 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3083 The three components here are:
3085 <tag><var>epoch</var></tag>
3088 This is a single (generally small) unsigned integer. It
3089 may be omitted, in which case zero is assumed. If it is
3090 omitted then the <var>upstream_version</var> may not
3095 It is provided to allow mistakes in the version numbers
3096 of older versions of a package, and also a package's
3097 previous version numbering schemes, to be left behind.
3101 <tag><var>upstream_version</var></tag>
3104 This is the main part of the version number. It is
3105 usually the version number of the original ("upstream")
3106 package from which the <file>.deb</file> file has been made,
3107 if this is applicable. Usually this will be in the same
3108 format as that specified by the upstream author(s);
3109 however, it may need to be reformatted to fit into the
3110 package management system's format and comparison
3115 The comparison behavior of the package management system
3116 with respect to the <var>upstream_version</var> is
3117 described below. The <var>upstream_version</var>
3118 portion of the version number is mandatory.
3122 The <var>upstream_version</var> may contain only
3123 alphanumerics<footnote>
3124 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3126 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3127 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3128 tilde) and should start with a digit. If there is no
3129 <var>debian_revision</var> then hyphens are not allowed;
3130 if there is no <var>epoch</var> then colons are not
3135 <tag><var>debian_revision</var></tag>
3138 This part of the version number specifies the version of
3139 the Debian package based on the upstream version. It
3140 may contain only alphanumerics and the characters
3141 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3142 tilde) and is compared in the same way as the
3143 <var>upstream_version</var> is.
3147 It is optional; if it isn't present then the
3148 <var>upstream_version</var> may not contain a hyphen.
3149 This format represents the case where a piece of
3150 software was written specifically to be a Debian
3151 package, where the Debian package source must always
3152 be identical to the pristine source and therefore no
3153 revision indication is required.
3157 It is conventional to restart the
3158 <var>debian_revision</var> at <tt>1</tt> each time the
3159 <var>upstream_version</var> is increased.
3163 The package management system will break the version
3164 number apart at the last hyphen in the string (if there
3165 is one) to determine the <var>upstream_version</var> and
3166 <var>debian_revision</var>. The absence of a
3167 <var>debian_revision</var> is equivalent to a
3168 <var>debian_revision</var> of <tt>0</tt>.
3175 When comparing two version numbers, first the <var>epoch</var>
3176 of each are compared, then the <var>upstream_version</var> if
3177 <var>epoch</var> is equal, and then <var>debian_revision</var>
3178 if <var>upstream_version</var> is also equal.
3179 <var>epoch</var> is compared numerically. The
3180 <var>upstream_version</var> and <var>debian_revision</var>
3181 parts are compared by the package management system using the
3182 following algorithm:
3186 The strings are compared from left to right.
3190 First the initial part of each string consisting entirely of
3191 non-digit characters is determined. These two parts (one of
3192 which may be empty) are compared lexically. If a difference
3193 is found it is returned. The lexical comparison is a
3194 comparison of ASCII values modified so that all the letters
3195 sort earlier than all the non-letters and so that a tilde
3196 sorts before anything, even the end of a part. For example,
3197 the following parts are in sorted order from earliest to
3198 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3199 <tt>a</tt>.<footnote>
3200 One common use of <tt>~</tt> is for upstream pre-releases.
3201 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3202 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3207 Then the initial part of the remainder of each string which
3208 consists entirely of digit characters is determined. The
3209 numerical values of these two parts are compared, and any
3210 difference found is returned as the result of the comparison.
3211 For these purposes an empty string (which can only occur at
3212 the end of one or both version strings being compared) counts
3217 These two steps (comparing and removing initial non-digit
3218 strings and initial digit strings) are repeated until a
3219 difference is found or both strings are exhausted.
3223 Note that the purpose of epochs is to allow us to leave behind
3224 mistakes in version numbering, and to cope with situations
3225 where the version numbering scheme changes. It is
3226 <em>not</em> intended to cope with version numbers containing
3227 strings of letters which the package management system cannot
3228 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3229 silly orderings.<footnote>
3230 The author of this manual has heard of a package whose
3231 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3232 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3238 <sect1 id="f-Description">
3239 <heading><tt>Description</tt></heading>
3242 In a source or binary control file, the <tt>Description</tt>
3243 field contains a description of the binary package, consisting
3244 of two parts, the synopsis or the short description, and the
3245 long description. The field's format is as follows:
3250 Description: <single line synopsis>
3251 <extended description over several lines>
3256 The lines in the extended description can have these formats:
3262 Those starting with a single space are part of a paragraph.
3263 Successive lines of this form will be word-wrapped when
3264 displayed. The leading space will usually be stripped off.
3268 Those starting with two or more spaces. These will be
3269 displayed verbatim. If the display cannot be panned
3270 horizontally, the displaying program will line wrap them "hard"
3271 (i.e., without taking account of word breaks). If it can they
3272 will be allowed to trail off to the right. None, one or two
3273 initial spaces may be deleted, but the number of spaces
3274 deleted from each line will be the same (so that you can have
3275 indenting work correctly, for example).
3279 Those containing a single space followed by a single full stop
3280 character. These are rendered as blank lines. This is the
3281 <em>only</em> way to get a blank line<footnote>
3282 Completely empty lines will not be rendered as blank lines.
3283 Instead, they will cause the parser to think you're starting
3284 a whole new record in the control file, and will therefore
3285 likely abort with an error.
3290 Those containing a space, a full stop and some more characters.
3291 These are for future expansion. Do not use them.
3297 Do not use tab characters. Their effect is not predictable.
3301 See <ref id="descriptions"> for further information on this.
3305 In a <file>.changes</file> file, the <tt>Description</tt>
3306 field contains a summary of the descriptions for the packages
3307 being uploaded. For this case, the first line of the field
3308 value (the part on the same line as <tt>Description:</tt>) is
3309 always empty. The content of the field is expressed as
3310 continuation lines, one line per package. Each line is
3311 indented by one space and contains the name of a binary
3312 package, a space, a hyphen (<tt>-</tt>), a space, and the
3313 short description line from that package.
3317 <sect1 id="f-Distribution">
3318 <heading><tt>Distribution</tt></heading>
3321 In a <file>.changes</file> file or parsed changelog output
3322 this contains the (space-separated) name(s) of the
3323 distribution(s) where this version of the package should
3324 be installed. Valid distributions are determined by the
3325 archive maintainers.<footnote>
3326 Example distribution names in the Debian archive used in
3327 <file>.changes</file> files are:
3328 <taglist compact="compact">
3329 <tag><em>unstable</em></tag>
3331 This distribution value refers to the
3332 <em>developmental</em> part of the Debian distribution
3333 tree. Most new packages, new upstream versions of
3334 packages and bug fixes go into the <em>unstable</em>
3338 <tag><em>experimental</em></tag>
3340 The packages with this distribution value are deemed
3341 by their maintainers to be high risk. Oftentimes they
3342 represent early beta or developmental packages from
3343 various sources that the maintainers want people to
3344 try, but are not ready to be a part of the other parts
3345 of the Debian distribution tree.
3350 Others are used for updating stable releases or for
3351 security uploads. More information is available in the
3352 Debian Developer's Reference, section "The Debian
3356 The Debian archive software only supports listing a single
3357 distribution. Migration of packages to other distributions is
3358 handled outside of the upload process.
3363 <heading><tt>Date</tt></heading>
3366 This field includes the date the package was built or last
3367 edited. It must be in the same format as the <var>date</var>
3368 in a <file>debian/changelog</file> entry.
3372 The value of this field is usually extracted from the
3373 <file>debian/changelog</file> file - see
3374 <ref id="dpkgchangelog">).
3378 <sect1 id="f-Format">
3379 <heading><tt>Format</tt></heading>
3382 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3383 files, this field declares the format version of that file.
3384 The syntax of the field value is the same as that of
3385 a <qref id="f-Version">package version number</qref> except
3386 that no epoch or Debian revision is allowed. The format
3387 described in this document is <tt>&changesversion;</tt>.
3391 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3392 Debian source control</qref> files, this field declares the
3393 format of the source package. The field value is used by
3394 programs acting on a source package to interpret the list of
3395 files in the source package and determine how to unpack it.
3396 The syntax of the field value is a numeric major revision, a
3397 period, a numeric minor revision, and then an optional subtype
3398 after whitespace, which if specified is an alphanumeric word
3399 in parentheses. The subtype is optional in the syntax but may
3400 be mandatory for particular source format revisions.
3402 The source formats currently supported by the Debian archive
3403 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3404 and <tt>3.0 (quilt)</tt>.
3409 <sect1 id="f-Urgency">
3410 <heading><tt>Urgency</tt></heading>
3413 This is a description of how important it is to upgrade to
3414 this version from previous ones. It consists of a single
3415 keyword taking one of the values <tt>low</tt>,
3416 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3417 <tt>critical</tt><footnote>
3418 Other urgency values are supported with configuration
3419 changes in the archive software but are not used in Debian.
3420 The urgency affects how quickly a package will be considered
3421 for inclusion into the <tt>testing</tt> distribution and
3422 gives an indication of the importance of any fixes included
3423 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3424 treated as synonymous.
3425 </footnote> (not case-sensitive) followed by an optional
3426 commentary (separated by a space) which is usually in
3427 parentheses. For example:
3430 Urgency: low (HIGH for users of diversions)
3436 The value of this field is usually extracted from the
3437 <file>debian/changelog</file> file - see
3438 <ref id="dpkgchangelog">.
3442 <sect1 id="f-Changes">
3443 <heading><tt>Changes</tt></heading>
3446 This field contains the human-readable changes data, describing
3447 the differences between the last version and the current one.
3451 The first line of the field value (the part on the same line
3452 as <tt>Changes:</tt>) is always empty. The content of the
3453 field is expressed as continuation lines, with each line
3454 indented by at least one space. Blank lines must be
3455 represented by a line consisting only of a space and a full
3460 The value of this field is usually extracted from the
3461 <file>debian/changelog</file> file - see
3462 <ref id="dpkgchangelog">).
3466 Each version's change information should be preceded by a
3467 "title" line giving at least the version, distribution(s)
3468 and urgency, in a human-readable way.
3472 If data from several versions is being returned the entry
3473 for the most recent version should be returned first, and
3474 entries should be separated by the representation of a
3475 blank line (the "title" line may also be followed by the
3476 representation of a blank line).
3480 <sect1 id="f-Binary">
3481 <heading><tt>Binary</tt></heading>
3484 This field is a list of binary packages. Its syntax and
3485 meaning varies depending on the control file in which it
3490 When it appears in the <file>.dsc</file> file, it lists binary
3491 packages which a source package can produce, separated by
3493 A space after each comma is conventional.
3494 </footnote>. It may span multiple lines. The source package
3495 does not necessarily produce all of these binary packages for
3496 every architecture. The source control file doesn't contain
3497 details of which architectures are appropriate for which of
3498 the binary packages.
3502 When it appears in a <file>.changes</file> file, it lists the
3503 names of the binary packages being uploaded, separated by
3504 whitespace (not commas). It may span multiple lines.
3508 <sect1 id="f-Installed-Size">
3509 <heading><tt>Installed-Size</tt></heading>
3512 This field appears in the control files of binary packages,
3513 and in the <file>Packages</file> files. It gives an estimate
3514 of the total amount of disk space required to install the
3515 named package. Actual installed size may vary based on block
3516 size, file system properties, or actions taken by package
3521 The disk space is given as the integer value of the estimated
3522 installed size in bytes, divided by 1024 and rounded up.
3526 <sect1 id="f-Files">
3527 <heading><tt>Files</tt></heading>
3530 This field contains a list of files with information about
3531 each one. The exact information and syntax varies with
3536 In all cases, Files is a multiline field. The first line of
3537 the field value (the part on the same line as <tt>Files:</tt>)
3538 is always empty. The content of the field is expressed as
3539 continuation lines, one line per file. Each line must be
3540 indented by one space and contain a number of sub-fields,
3541 separated by spaces, as described below.
3545 In the <file>.dsc</file> file, each line contains the MD5
3546 checksum, size and filename of the tar file and (if
3547 applicable) diff file which make up the remainder of the
3548 source package<footnote>
3549 That is, the parts which are not the <tt>.dsc</tt>.
3550 </footnote>. For example:
3553 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3554 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3556 The exact forms of the filenames are described
3557 in <ref id="pkg-sourcearchives">.
3561 In the <file>.changes</file> file this contains one line per
3562 file being uploaded. Each line contains the MD5 checksum,
3563 size, section and priority and the filename. For example:
3566 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3567 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3568 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3569 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3571 The <qref id="f-Section">section</qref>
3572 and <qref id="f-Priority">priority</qref> are the values of
3573 the corresponding fields in the main source control file. If
3574 no section or priority is specified then <tt>-</tt> should be
3575 used, though section and priority values must be specified for
3576 new packages to be installed properly.
3580 The special value <tt>byhand</tt> for the section in a
3581 <tt>.changes</tt> file indicates that the file in question
3582 is not an ordinary package file and must by installed by
3583 hand by the distribution maintainers. If the section is
3584 <tt>byhand</tt> the priority should be <tt>-</tt>.
3588 If a new Debian revision of a package is being shipped and
3589 no new original source archive is being distributed the
3590 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3591 entry for the original source archive
3592 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3593 but the <file>.changes</file> file should leave it out. In
3594 this case the original source archive on the distribution
3595 site must match exactly, byte-for-byte, the original
3596 source archive which was used to generate the
3597 <file>.dsc</file> file and diff which are being uploaded.</p>
3600 <sect1 id="f-Closes">
3601 <heading><tt>Closes</tt></heading>
3604 A space-separated list of bug report numbers that the upload
3605 governed by the .changes file closes.
3609 <sect1 id="f-Homepage">
3610 <heading><tt>Homepage</tt></heading>
3613 The URL of the web site for this package, preferably (when
3614 applicable) the site from which the original source can be
3615 obtained and any additional upstream documentation or
3616 information may be found. The content of this field is a
3617 simple URL without any surrounding characters such as
3622 <sect1 id="f-Checksums">
3623 <heading><tt>Checksums-Sha1</tt>
3624 and <tt>Checksums-Sha256</tt></heading>
3627 These fields contain a list of files with a checksum and size
3628 for each one. Both <tt>Checksums-Sha1</tt>
3629 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3630 only in the checksum algorithm used: SHA-1
3631 for <tt>Checksums-Sha1</tt> and SHA-256
3632 for <tt>Checksums-Sha256</tt>.
3636 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3637 multiline fields. The first line of the field value (the part
3638 on the same line as <tt>Checksums-Sha1:</tt>
3639 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3640 of the field is expressed as continuation lines, one line per
3641 file. Each line consists of the checksum, a space, the file
3642 size, a space, and the file name. For example (from
3643 a <file>.changes</file> file):
3646 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3647 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3648 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3649 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3651 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3652 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3653 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3654 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3659 In the <file>.dsc</file> file, these fields should list all
3660 files that make up the source package. In
3661 the <file>.changes</file> file, these fields should list all
3662 files being uploaded. The list of files in these fields
3663 must match the list of files in the <tt>Files</tt> field.
3667 <sect1 id="f-DM-Upload-Allowed">
3668 <heading><tt>DM-Upload-Allowed</tt></heading>
3671 The most recent version of a package uploaded to unstable or
3672 experimental must include the field <tt>DM-Upload-Allowed:
3673 yes</tt> in the source section of its source control file for
3674 the Debian archive to accept uploads signed with a key in the
3675 Debian Maintainer keyring. See the General
3676 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3677 name="Endorse the concept of Debian Maintainers"> for more
3684 <heading>User-defined fields</heading>
3687 Additional user-defined fields may be added to the
3688 source package control file. Such fields will be
3689 ignored, and not copied to (for example) binary or
3690 source package control files or upload control files.
3694 If you wish to add additional unsupported fields to
3695 these output files you should use the mechanism
3700 Fields in the main source control information file with
3701 names starting <tt>X</tt>, followed by one or more of
3702 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3703 be copied to the output files. Only the part of the
3704 field name after the hyphen will be used in the output
3705 file. Where the letter <tt>B</tt> is used the field
3706 will appear in binary package control files, where the
3707 letter <tt>S</tt> is used in source package control
3708 files and where <tt>C</tt> is used in upload control
3709 (<tt>.changes</tt>) files.
3713 For example, if the main source information control file
3716 XBS-Comment: I stand between the candle and the star.
3718 then the binary and source package control files will contain the
3721 Comment: I stand between the candle and the star.
3730 <chapt id="maintainerscripts">
3731 <heading>Package maintainer scripts and installation procedure</heading>
3734 <heading>Introduction to package maintainer scripts</heading>
3737 It is possible to supply scripts as part of a package which
3738 the package management system will run for you when your
3739 package is installed, upgraded or removed.
3743 These scripts are the control information
3744 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3745 and <prgn>postrm</prgn>. They must be proper executable files;
3746 if they are scripts (which is recommended), they must start with
3747 the usual <tt>#!</tt> convention. They should be readable and
3748 executable by anyone, and must not be world-writable.
3752 The package management system looks at the exit status from
3753 these scripts. It is important that they exit with a
3754 non-zero status if there is an error, so that the package
3755 management system can stop its processing. For shell
3756 scripts this means that you <em>almost always</em> need to
3757 use <tt>set -e</tt> (this is usually true when writing shell
3758 scripts, in fact). It is also important, of course, that
3759 they exit with a zero status if everything went well.
3763 Additionally, packages interacting with users
3764 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3765 should install a <prgn>config</prgn> script as a control
3766 information file. See <ref id="maintscriptprompt"> for details.
3770 When a package is upgraded a combination of the scripts from
3771 the old and new packages is called during the upgrade
3772 procedure. If your scripts are going to be at all
3773 complicated you need to be aware of this, and may need to
3774 check the arguments to your scripts.
3778 Broadly speaking the <prgn>preinst</prgn> is called before
3779 (a particular version of) a package is installed, and the
3780 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3781 before (a version of) a package is removed and the
3782 <prgn>postrm</prgn> afterwards.
3786 Programs called from maintainer scripts should not normally
3787 have a path prepended to them. Before installation is
3788 started, the package management system checks to see if the
3789 programs <prgn>ldconfig</prgn>,
3790 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3791 and <prgn>update-rc.d</prgn> can be found via the
3792 <tt>PATH</tt> environment variable. Those programs, and any
3793 other program that one would expect to be in the
3794 <tt>PATH</tt>, should thus be invoked without an absolute
3795 pathname. Maintainer scripts should also not reset the
3796 <tt>PATH</tt>, though they might choose to modify it by
3797 prepending or appending package-specific directories. These
3798 considerations really apply to all shell scripts.</p>
3801 <sect id="idempotency">
3802 <heading>Maintainer scripts idempotency</heading>
3805 It is necessary for the error recovery procedures that the
3806 scripts be idempotent. This means that if it is run
3807 successfully, and then it is called again, it doesn't bomb
3808 out or cause any harm, but just ensures that everything is
3809 the way it ought to be. If the first call failed, or
3810 aborted half way through for some reason, the second call
3811 should merely do the things that were left undone the first
3812 time, if any, and exit with a success status if everything
3814 This is so that if an error occurs, the user interrupts
3815 <prgn>dpkg</prgn> or some other unforeseen circumstance
3816 happens you don't leave the user with a badly-broken
3817 package when <prgn>dpkg</prgn> attempts to repeat the
3823 <sect id="controllingterminal">
3824 <heading>Controlling terminal for maintainer scripts</heading>
3827 Maintainer scripts are not guaranteed to run with a controlling
3828 terminal and may not be able to interact with the user. They
3829 must be able to fall back to noninteractive behavior if no
3830 controlling terminal is available. Maintainer scripts that
3831 prompt via a program conforming to the Debian Configuration
3832 Management Specification (see <ref id="maintscriptprompt">) may
3833 assume that program will handle falling back to noninteractive
3838 For high-priority prompts without a reasonable default answer,
3839 maintainer scripts may abort if there is no controlling
3840 terminal. However, this situation should be avoided if at all
3841 possible, since it prevents automated or unattended installs.
3842 In most cases, users will consider this to be a bug in the
3847 <sect id="exitstatus">
3848 <heading>Exit status</heading>
3851 Each script must return a zero exit status for
3852 success, or a nonzero one for failure, since the package
3853 management system looks for the exit status of these scripts
3854 and determines what action to take next based on that datum.
3858 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3863 <list compact="compact">
3865 <var>new-preinst</var> <tt>install</tt>
3868 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3871 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3874 <var>old-preinst</var> <tt>abort-upgrade</tt>
3875 <var>new-version</var>
3880 <list compact="compact">
3882 <var>postinst</var> <tt>configure</tt>
3883 <var>most-recently-configured-version</var>
3886 <var>old-postinst</var> <tt>abort-upgrade</tt>
3887 <var>new-version</var>
3890 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3891 <tt>in-favour</tt> <var>package</var>
3892 <var>new-version</var>
3895 <var>postinst</var> <tt>abort-remove</tt>
3898 <var>deconfigured's-postinst</var>
3899 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3900 <var>failed-install-package</var> <var>version</var>
3901 [<tt>removing</tt> <var>conflicting-package</var>
3907 <list compact="compact">
3909 <var>prerm</var> <tt>remove</tt>
3912 <var>old-prerm</var> <tt>upgrade</tt>
3913 <var>new-version</var>
3916 <var>new-prerm</var> <tt>failed-upgrade</tt>
3917 <var>old-version</var>
3920 <var>conflictor's-prerm</var> <tt>remove</tt>
3921 <tt>in-favour</tt> <var>package</var>
3922 <var>new-version</var>
3925 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3926 <tt>in-favour</tt> <var>package-being-installed</var>
3927 <var>version</var> [<tt>removing</tt>
3928 <var>conflicting-package</var>
3934 <list compact="compact">
3936 <var>postrm</var> <tt>remove</tt>
3939 <var>postrm</var> <tt>purge</tt>
3942 <var>old-postrm</var> <tt>upgrade</tt>
3943 <var>new-version</var>
3946 <var>new-postrm</var> <tt>failed-upgrade</tt>
3947 <var>old-version</var>
3950 <var>new-postrm</var> <tt>abort-install</tt>
3953 <var>new-postrm</var> <tt>abort-install</tt>
3954 <var>old-version</var>
3957 <var>new-postrm</var> <tt>abort-upgrade</tt>
3958 <var>old-version</var>
3961 <var>disappearer's-postrm</var> <tt>disappear</tt>
3962 <var>overwriter</var>
3963 <var>overwriter-version</var>
3969 <sect id="unpackphase">
3970 <heading>Details of unpack phase of installation or upgrade</heading>
3973 The procedure on installation/upgrade/overwrite/disappear
3974 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3975 stage of <tt>dpkg --install</tt>) is as follows. In each
3976 case, if a major error occurs (unless listed below) the
3977 actions are, in general, run backwards - this means that the
3978 maintainer scripts are run with different arguments in
3979 reverse order. These are the "error unwind" calls listed
3986 If a version of the package is already installed, call
3987 <example compact="compact">
3988 <var>old-prerm</var> upgrade <var>new-version</var>
3992 If the script runs but exits with a non-zero
3993 exit status, <prgn>dpkg</prgn> will attempt:
3994 <example compact="compact">
3995 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3997 If this works, the upgrade continues. If this
3998 does not work, the error unwind:
3999 <example compact="compact">
4000 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4002 If this works, then the old-version is
4003 "Installed", if not, the old version is in a
4004 "Half-Configured" state.
4010 If a "conflicting" package is being removed at the same time,
4011 or if any package will be broken (due to <tt>Breaks</tt>):
4014 If <tt>--auto-deconfigure</tt> is
4015 specified, call, for each package to be deconfigured
4016 due to <tt>Breaks</tt>:
4017 <example compact="compact">
4018 <var>deconfigured's-prerm</var> deconfigure \
4019 in-favour <var>package-being-installed</var> <var>version</var>
4022 <example compact="compact">
4023 <var>deconfigured's-postinst</var> abort-deconfigure \
4024 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4026 The deconfigured packages are marked as
4027 requiring configuration, so that if
4028 <tt>--install</tt> is used they will be
4029 configured again if possible.
4032 If any packages depended on a conflicting
4033 package being removed and <tt>--auto-deconfigure</tt> is
4034 specified, call, for each such package:
4035 <example compact="compact">
4036 <var>deconfigured's-prerm</var> deconfigure \
4037 in-favour <var>package-being-installed</var> <var>version</var> \
4038 removing <var>conflicting-package</var> <var>version</var>
4041 <example compact="compact">
4042 <var>deconfigured's-postinst</var> abort-deconfigure \
4043 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4044 removing <var>conflicting-package</var> <var>version</var>
4046 The deconfigured packages are marked as
4047 requiring configuration, so that if
4048 <tt>--install</tt> is used they will be
4049 configured again if possible.
4052 To prepare for removal of each conflicting package, call:
4053 <example compact="compact">
4054 <var>conflictor's-prerm</var> remove \
4055 in-favour <var>package</var> <var>new-version</var>
4058 <example compact="compact">
4059 <var>conflictor's-postinst</var> abort-remove \
4060 in-favour <var>package</var> <var>new-version</var>
4069 If the package is being upgraded, call:
4070 <example compact="compact">
4071 <var>new-preinst</var> upgrade <var>old-version</var>
4073 If this fails, we call:
4075 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4082 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4084 is called. If this works, then the old version
4085 is in an "Installed" state, or else it is left
4086 in an "Unpacked" state.
4091 If it fails, then the old version is left
4092 in an "Half-Installed" state.
4099 Otherwise, if the package had some configuration
4100 files from a previous version installed (i.e., it
4101 is in the "configuration files only" state):
4102 <example compact="compact">
4103 <var>new-preinst</var> install <var>old-version</var>
4107 <var>new-postrm</var> abort-install <var>old-version</var>
4109 If this fails, the package is left in a
4110 "Half-Installed" state, which requires a
4111 reinstall. If it works, the packages is left in
4112 a "Config-Files" state.
4115 Otherwise (i.e., the package was completely purged):
4116 <example compact="compact">
4117 <var>new-preinst</var> install
4120 <example compact="compact">
4121 <var>new-postrm</var> abort-install
4123 If the error-unwind fails, the package is in a
4124 "Half-Installed" phase, and requires a
4125 reinstall. If the error unwind works, the
4126 package is in a not installed state.
4133 The new package's files are unpacked, overwriting any
4134 that may be on the system already, for example any
4135 from the old version of the same package or from
4136 another package. Backups of the old files are kept
4137 temporarily, and if anything goes wrong the package
4138 management system will attempt to put them back as
4139 part of the error unwind.
4143 It is an error for a package to contain files which
4144 are on the system in another package, unless
4145 <tt>Replaces</tt> is used (see <ref id="replaces">).
4147 The following paragraph is not currently the case:
4148 Currently the <tt>- - force-overwrite</tt> flag is
4149 enabled, downgrading it to a warning, but this may not
4155 It is a more serious error for a package to contain a
4156 plain file or other kind of non-directory where another
4157 package has a directory (again, unless
4158 <tt>Replaces</tt> is used). This error can be
4159 overridden if desired using
4160 <tt>--force-overwrite-dir</tt>, but this is not
4165 Packages which overwrite each other's files produce
4166 behavior which, though deterministic, is hard for the
4167 system administrator to understand. It can easily
4168 lead to "missing" programs if, for example, a package
4169 is installed which overwrites a file from another
4170 package, and is then removed again.<footnote>
4171 Part of the problem is due to what is arguably a
4172 bug in <prgn>dpkg</prgn>.
4177 A directory will never be replaced by a symbolic link
4178 to a directory or vice versa; instead, the existing
4179 state (symlink or not) will be left alone and
4180 <prgn>dpkg</prgn> will follow the symlink if there is
4189 If the package is being upgraded, call
4190 <example compact="compact">
4191 <var>old-postrm</var> upgrade <var>new-version</var>
4195 If this fails, <prgn>dpkg</prgn> will attempt:
4196 <example compact="compact">
4197 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4199 If this works, installation continues. If not,
4201 <example compact="compact">
4202 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4204 If this fails, the old version is left in a
4205 "Half-Installed" state. If it works, dpkg now
4207 <example compact="compact">
4208 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4210 If this fails, the old version is left in a
4211 "Half-Installed" state. If it works, dpkg now
4213 <example compact="compact">
4214 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4216 If this fails, the old version is in an
4223 This is the point of no return - if
4224 <prgn>dpkg</prgn> gets this far, it won't back off
4225 past this point if an error occurs. This will
4226 leave the package in a fairly bad state, which
4227 will require a successful re-installation to clear
4228 up, but it's when <prgn>dpkg</prgn> starts doing
4229 things that are irreversible.
4234 Any files which were in the old version of the package
4235 but not in the new are removed.
4239 The new file list replaces the old.
4243 The new maintainer scripts replace the old.
4247 Any packages all of whose files have been overwritten
4248 during the installation, and which aren't required for
4249 dependencies, are considered to have been removed.
4250 For each such package
4253 <prgn>dpkg</prgn> calls:
4254 <example compact="compact">
4255 <var>disappearer's-postrm</var> disappear \
4256 <var>overwriter</var> <var>overwriter-version</var>
4260 The package's maintainer scripts are removed.
4263 It is noted in the status database as being in a
4264 sane state, namely not installed (any conffiles
4265 it may have are ignored, rather than being
4266 removed by <prgn>dpkg</prgn>). Note that
4267 disappearing packages do not have their prerm
4268 called, because <prgn>dpkg</prgn> doesn't know
4269 in advance that the package is going to
4276 Any files in the package we're unpacking that are also
4277 listed in the file lists of other packages are removed
4278 from those lists. (This will lobotomize the file list
4279 of the "conflicting" package if there is one.)
4283 The backup files made during installation, above, are
4289 The new package's status is now sane, and recorded as
4294 Here is another point of no return - if the
4295 conflicting package's removal fails we do not unwind
4296 the rest of the installation; the conflicting package
4297 is left in a half-removed limbo.
4302 If there was a conflicting package we go and do the
4303 removal actions (described below), starting with the
4304 removal of the conflicting package's files (any that
4305 are also in the package being installed have already
4306 been removed from the conflicting package's file list,
4307 and so do not get removed now).
4313 <sect id="configdetails"><heading>Details of configuration</heading>
4316 When we configure a package (this happens with <tt>dpkg
4317 --install</tt> and <tt>dpkg --configure</tt>), we first
4318 update any <tt>conffile</tt>s and then call:
4319 <example compact="compact">
4320 <var>postinst</var> configure <var>most-recently-configured-version</var>
4325 No attempt is made to unwind after errors during
4326 configuration. If the configuration fails, the package is in
4327 a "Failed Config" state, and an error message is generated.
4331 If there is no most recently configured version
4332 <prgn>dpkg</prgn> will pass a null argument.
4335 Historical note: Truly ancient (pre-1997) versions of
4336 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4337 (including the angle brackets) in this case. Even older
4338 ones did not pass a second argument at all, under any
4339 circumstance. Note that upgrades using such an old dpkg
4340 version are unlikely to work for other reasons, even if
4341 this old argument behavior is handled by your postinst script.
4347 <sect id="removedetails"><heading>Details of removal and/or
4348 configuration purging</heading>
4354 <example compact="compact">
4355 <var>prerm</var> remove
4359 If prerm fails during replacement due to conflict
4361 <var>conflictor's-postinst</var> abort-remove \
4362 in-favour <var>package</var> <var>new-version</var>
4366 <var>postinst</var> abort-remove
4370 If this fails, the package is in a "Half-Configured"
4371 state, or else it remains "Installed".
4375 The package's files are removed (except <tt>conffile</tt>s).
4378 <example compact="compact">
4379 <var>postrm</var> remove
4383 If it fails, there's no error unwind, and the package is in
4384 an "Half-Installed" state.
4389 All the maintainer scripts except the <prgn>postrm</prgn>
4394 If we aren't purging the package we stop here. Note
4395 that packages which have no <prgn>postrm</prgn> and no
4396 <tt>conffile</tt>s are automatically purged when
4397 removed, as there is no difference except for the
4398 <prgn>dpkg</prgn> status.
4402 The <tt>conffile</tt>s and any backup files
4403 (<tt>~</tt>-files, <tt>#*#</tt> files,
4404 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4409 <example compact="compact">
4410 <var>postrm</var> purge
4414 If this fails, the package remains in a "Config-Files"
4419 The package's file list is removed.
4428 <chapt id="relationships">
4429 <heading>Declaring relationships between packages</heading>
4431 <sect id="depsyntax">
4432 <heading>Syntax of relationship fields</heading>
4435 These fields all have a uniform syntax. They are a list of
4436 package names separated by commas.
4440 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4441 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4442 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4443 control fields of the package, which declare
4444 dependencies on other packages, the package names listed may
4445 also include lists of alternative package names, separated
4446 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4447 if any one of the alternative packages is installed, that
4448 part of the dependency is considered to be satisfied.
4452 All of the fields except for <tt>Provides</tt> may restrict
4453 their applicability to particular versions of each named
4454 package. This is done in parentheses after each individual
4455 package name; the parentheses should contain a relation from
4456 the list below followed by a version number, in the format
4457 described in <ref id="f-Version">.
4461 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4462 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4463 strictly earlier, earlier or equal, exactly equal, later or
4464 equal and strictly later, respectively. The deprecated
4465 forms <tt><</tt> and <tt>></tt> were used to mean
4466 earlier/later or equal, rather than strictly earlier/later,
4467 so they should not appear in new packages (though
4468 <prgn>dpkg</prgn> still supports them).
4472 Whitespace may appear at any point in the version
4473 specification subject to the rules in <ref
4474 id="controlsyntax">, and must appear where it's necessary to
4475 disambiguate; it is not otherwise significant. All of the
4476 relationship fields may span multiple lines. For
4477 consistency and in case of future changes to
4478 <prgn>dpkg</prgn> it is recommended that a single space be
4479 used after a version relationship and before a version
4480 number; it is also conventional to put a single space after
4481 each comma, on either side of each vertical bar, and before
4482 each open parenthesis. When wrapping a relationship field, it
4483 is conventional to do so after a comma and before the space
4484 following that comma.
4488 For example, a list of dependencies might appear as:
4489 <example compact="compact">
4492 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4497 Relationships may be restricted to a certain set of
4498 architectures. This is indicated in brackets after each
4499 individual package name and the optional version specification.
4500 The brackets enclose a list of Debian architecture names
4501 separated by whitespace. Exclamation marks may be prepended to
4502 each of the names. (It is not permitted for some names to be
4503 prepended with exclamation marks while others aren't.)
4507 For build relationship fields
4508 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4509 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4510 the current Debian host architecture is not in this list and
4511 there are no exclamation marks in the list, or it is in the list
4512 with a prepended exclamation mark, the package name and the
4513 associated version specification are ignored completely for the
4514 purposes of defining the relationships.
4519 <example compact="compact">
4521 Build-Depends-Indep: texinfo
4522 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4523 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4525 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4526 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4527 <tt>gnumach-dev</tt> only on hurd-i386.
4531 For binary relationship fields, the architecture restriction
4532 syntax is only supported in the source package control
4533 file <file>debian/control</file>. When the corresponding binary
4534 package control file is generated, the relationship will either
4535 be omitted or included without the architecture restriction
4536 based on the architecture of the binary package. This means
4537 that architecture restrictions must not be used in binary
4538 relationship fields for architecture-independent packages
4539 (<tt>Architecture: all</tt>).
4544 <example compact="compact">
4545 Depends: foo [i386], bar [amd64]
4547 becomes <tt>Depends: foo</tt> when the package is built on
4548 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4549 package is built on the <tt>amd64</tt> architecture, and omitted
4550 entirely in binary packages built on all other architectures.
4554 If the architecture-restricted dependency is part of a set of
4555 alternatives using <tt>|</tt>, that alternative is ignored
4556 completely on architectures that do not match the restriction.
4558 <example compact="compact">
4559 Build-Depends: foo [!i386] | bar [!amd64]
4561 is equivalent to <tt>bar</tt> on the i386 architecture, to
4562 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4563 bar</tt> on all other architectures.
4567 Relationships may also be restricted to a certain set of
4568 architectures using architecture wildcards. The syntax for
4569 declaring such restrictions is the same as declaring
4570 restrictions using a certain set of architectures without
4571 architecture wildcards. For example:
4572 <example compact="compact">
4573 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4575 is equivalent to <tt>foo</tt> on architectures using the Linux
4576 kernel and any cpu, <tt>bar</tt> on architectures using any
4577 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4578 using a kernel other than Linux.
4582 Note that the binary package relationship fields such as
4583 <tt>Depends</tt> appear in one of the binary package
4584 sections of the control file, whereas the build-time
4585 relationships such as <tt>Build-Depends</tt> appear in the
4586 source package section of the control file (which is the
4591 <sect id="binarydeps">
4592 <heading>Binary Dependencies - <tt>Depends</tt>,
4593 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4594 <tt>Pre-Depends</tt>
4598 Packages can declare in their control file that they have
4599 certain relationships to other packages - for example, that
4600 they may not be installed at the same time as certain other
4601 packages, and/or that they depend on the presence of others.
4605 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4606 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4607 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4608 <tt>Breaks</tt> is described in <ref id="breaks">, and
4609 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4610 rest are described below.
4614 These seven fields are used to declare a dependency
4615 relationship by one package on another. Except for
4616 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4617 depending (binary) package's control file.
4618 (<tt>Enhances</tt> appears in the recommending package's
4619 control file, and <tt>Breaks</tt> appears in the version of
4620 depended-on package which causes the named package to
4625 A <tt>Depends</tt> field takes effect <em>only</em> when a
4626 package is to be configured. It does not prevent a package
4627 being on the system in an unconfigured state while its
4628 dependencies are unsatisfied, and it is possible to replace
4629 a package whose dependencies are satisfied and which is
4630 properly installed with a different version whose
4631 dependencies are not and cannot be satisfied; when this is
4632 done the depending package will be left unconfigured (since
4633 attempts to configure it will give errors) and will not
4634 function properly. If it is necessary, a
4635 <tt>Pre-Depends</tt> field can be used, which has a partial
4636 effect even when a package is being unpacked, as explained
4637 in detail below. (The other three dependency fields,
4638 <tt>Recommends</tt>, <tt>Suggests</tt> and
4639 <tt>Enhances</tt>, are only used by the various front-ends
4640 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4641 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4645 For this reason packages in an installation run are usually
4646 all unpacked first and all configured later; this gives
4647 later versions of packages with dependencies on later
4648 versions of other packages the opportunity to have their
4649 dependencies satisfied.
4653 In case of circular dependencies, since installation or
4654 removal order honoring the dependency order can't be
4655 established, dependency loops are broken at some point
4656 (based on rules below), and some packages may not be able to
4657 rely on their dependencies being present when being
4658 installed or removed, depending on which side of the break
4659 of the circular dependency loop they happen to be on. If one
4660 of the packages in the loop has no postinst script, then the
4661 cycle will be broken at that package, so as to ensure that
4662 all postinst scripts run with the dependencies properly
4663 configured if this is possible. Otherwise the breaking point
4668 The <tt>Depends</tt> field thus allows package maintainers
4669 to impose an order in which packages should be configured.
4673 The meaning of the five dependency fields is as follows:
4675 <tag><tt>Depends</tt></tag>
4678 This declares an absolute dependency. A package will
4679 not be configured unless all of the packages listed in
4680 its <tt>Depends</tt> field have been correctly
4685 The <tt>Depends</tt> field should be used if the
4686 depended-on package is required for the depending
4687 package to provide a significant amount of
4692 The <tt>Depends</tt> field should also be used if the
4693 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4694 <prgn>postrm</prgn> scripts require the package to be
4695 present in order to run. Note, however, that the
4696 <prgn>postrm</prgn> cannot rely on any non-essential
4697 packages to be present during the <tt>purge</tt>
4701 <tag><tt>Recommends</tt></tag>
4704 This declares a strong, but not absolute, dependency.
4708 The <tt>Recommends</tt> field should list packages
4709 that would be found together with this one in all but
4710 unusual installations.
4714 <tag><tt>Suggests</tt></tag>
4716 This is used to declare that one package may be more
4717 useful with one or more others. Using this field
4718 tells the packaging system and the user that the
4719 listed packages are related to this one and can
4720 perhaps enhance its usefulness, but that installing
4721 this one without them is perfectly reasonable.
4724 <tag><tt>Enhances</tt></tag>
4726 This field is similar to Suggests but works in the
4727 opposite direction. It is used to declare that a
4728 package can enhance the functionality of another
4732 <tag><tt>Pre-Depends</tt></tag>
4735 This field is like <tt>Depends</tt>, except that it
4736 also forces <prgn>dpkg</prgn> to complete installation
4737 of the packages named before even starting the
4738 installation of the package which declares the
4739 pre-dependency, as follows:
4743 When a package declaring a pre-dependency is about to
4744 be <em>unpacked</em> the pre-dependency can be
4745 satisfied if the depended-on package is either fully
4746 configured, <em>or even if</em> the depended-on
4747 package(s) are only unpacked or in the "Half-Configured"
4748 state, provided that they have been configured
4749 correctly at some point in the past (and not removed
4750 or partially removed since). In this case, both the
4751 previously-configured and currently unpacked or
4752 "Half-Configured" versions must satisfy any version
4753 clause in the <tt>Pre-Depends</tt> field.
4757 When the package declaring a pre-dependency is about
4758 to be <em>configured</em>, the pre-dependency will be
4759 treated as a normal <tt>Depends</tt>, that is, it will
4760 be considered satisfied only if the depended-on
4761 package has been correctly configured.
4765 <tt>Pre-Depends</tt> should be used sparingly,
4766 preferably only by packages whose premature upgrade or
4767 installation would hamper the ability of the system to
4768 continue with any upgrade that might be in progress.
4772 <tt>Pre-Depends</tt> are also required if the
4773 <prgn>preinst</prgn> script depends on the named
4774 package. It is best to avoid this situation if
4782 When selecting which level of dependency to use you should
4783 consider how important the depended-on package is to the
4784 functionality of the one declaring the dependency. Some
4785 packages are composed of components of varying degrees of
4786 importance. Such a package should list using
4787 <tt>Depends</tt> the package(s) which are required by the
4788 more important components. The other components'
4789 requirements may be mentioned as Suggestions or
4790 Recommendations, as appropriate to the components' relative
4796 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4799 When one binary package declares that it breaks another,
4800 <prgn>dpkg</prgn> will refuse to allow the package which
4801 declares <tt>Breaks</tt> be installed unless the broken
4802 package is deconfigured first, and it will refuse to
4803 allow the broken package to be reconfigured.
4807 A package will not be regarded as causing breakage merely
4808 because its configuration files are still installed; it must
4809 be at least "Half-Installed".
4813 A special exception is made for packages which declare that
4814 they break their own package name or a virtual package which
4815 they provide (see below): this does not count as a real
4820 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4821 version clause; such a <tt>Breaks</tt> is introduced in the
4822 version of an (implicit or explicit) dependency which violates
4823 an assumption or reveals a bug in earlier versions of the broken
4824 package, or which takes over a file from earlier versions of the
4825 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4826 will inform higher-level package management tools that the
4827 broken package must be upgraded before the new one.
4831 If the breaking package also overwrites some files from the
4832 older package, it should use <tt>Replaces</tt> to ensure this
4833 goes smoothly. See <ref id="replaces"> for a full discussion
4834 of taking over files from other packages, including how to
4835 use <tt>Breaks</tt> in those cases.
4839 Many of the cases where <tt>Breaks</tt> should be used were
4840 previously handled with <tt>Conflicts</tt>
4841 because <tt>Breaks</tt> did not yet exist.
4842 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4843 See <ref id="conflicts"> for more information about the
4848 <sect id="conflicts">
4849 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4852 When one binary package declares a conflict with another
4853 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4854 refuse to allow them to be installed on the system at the
4855 same time. This is a stronger restriction than <tt>Breaks</tt>,
4856 which just prevents both packages from being configured at the
4857 same time. Conflicting packages cannot be unpacked on the
4858 system at the same time.
4862 If one package is to be installed, the other must be removed
4863 first. If the package being installed is marked as replacing
4864 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4865 normally be used in this case) the one on the system, or the one
4866 on the system is marked as deselected, or both packages are
4867 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4868 automatically remove the package which is causing the conflict.
4869 Otherwise, it will halt the installation of the new package with
4870 an error. This mechanism is specifically designed to produce an
4871 error when the installed package is <tt>Essential</tt>, but the
4876 A package will not cause a conflict merely because its
4877 configuration files are still installed; it must be at least
4882 A special exception is made for packages which declare a
4883 conflict with their own package name, or with a virtual
4884 package which they provide (see below): this does not
4885 prevent their installation, and allows a package to conflict
4886 with others providing a replacement for it. You use this
4887 feature when you want the package in question to be the only
4888 package providing some feature.
4892 Normally, <tt>Breaks</tt> should be used instead
4893 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4894 stronger restriction on the ordering of package installation or
4895 upgrade and can make it more difficult for the package manager
4896 to find a correct solution to an upgrade or installation
4897 problem. <tt>Breaks</tt> should be used
4899 <item>when moving a file from one package to another (see
4900 <ref id="replaces">),</item>
4901 <item>when splitting a package (a special case of the previous
4903 <item>when the breaking package exposes a bug in or interacts
4904 badly with particular versions of the broken
4907 <tt>Conflicts</tt> should be used
4909 <item>when two packages provide the same file and will
4910 continue to do so,</item>
4911 <item>in conjunction with <tt>Provides</tt> when only one
4912 package providing a given virtual facility may be installed
4913 at a time (see <ref id="virtual">),</item>
4914 <item>in other cases where one must prevent simultaneous
4915 installation of two packages for reasons that are ongoing
4916 (not fixed in a later version of one of the packages) or
4917 that must prevent both packages from being unpacked at the
4918 same time, not just configured.</item>
4920 Be aware that adding <tt>Conflicts</tt> is normally not the best
4921 solution when two packages provide the same files. Depending on
4922 the reason for that conflict, using alternatives or renaming the
4923 files is often a better approach. See, for
4924 example, <ref id="binaries">.
4928 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4929 unless two packages cannot be installed at the same time or
4930 installing them both causes one of them to be broken or
4931 unusable. Having similar functionality or performing the same
4932 tasks as another package is not sufficient reason to
4933 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4937 A <tt>Conflicts</tt> entry may have an "earlier than" version
4938 clause if the reason for the conflict is corrected in a later
4939 version of one of the packages. However, normally the presence
4940 of an "earlier than" version clause is a sign
4941 that <tt>Breaks</tt> should have been used instead. An "earlier
4942 than" version clause in <tt>Conflicts</tt>
4943 prevents <prgn>dpkg</prgn> from upgrading or installing the
4944 package which declares such a conflict until the upgrade or
4945 removal of the conflicted-with package has been completed, which
4946 is a strong restriction.
4950 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4954 As well as the names of actual ("concrete") packages, the
4955 package relationship fields <tt>Depends</tt>,
4956 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4957 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4958 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4959 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4960 may mention "virtual packages".
4964 A <em>virtual package</em> is one which appears in the
4965 <tt>Provides</tt> control field of another package. The effect
4966 is as if the package(s) which provide a particular virtual
4967 package name had been listed by name everywhere the virtual
4968 package name appears. (See also <ref id="virtual_pkg">)
4972 If there are both concrete and virtual packages of the same
4973 name, then the dependency may be satisfied (or the conflict
4974 caused) by either the concrete package with the name in
4975 question or any other concrete package which provides the
4976 virtual package with the name in question. This is so that,
4977 for example, supposing we have
4978 <example compact="compact">
4981 </example> and someone else releases an enhanced version of
4982 the <tt>bar</tt> package they can say:
4983 <example compact="compact">
4987 and the <tt>bar-plus</tt> package will now also satisfy the
4988 dependency for the <tt>foo</tt> package.
4992 If a relationship field has a version number attached, only real
4993 packages will be considered to see whether the relationship is
4994 satisfied (or the prohibition violated, for a conflict or
4995 breakage). In other words, if a version number is specified,
4996 this is a request to ignore all <tt>Provides</tt> for that
4997 package name and consider only real packages. The package
4998 manager will assume that a package providing that virtual
4999 package is not of the "right" version. A <tt>Provides</tt>
5000 field may not contain version numbers, and the version number of
5001 the concrete package which provides a particular virtual package
5002 will not be considered when considering a dependency on or
5003 conflict with the virtual package name.<footnote>
5004 It is possible that a future release of <prgn>dpkg</prgn> may
5005 add the ability to specify a version number for each virtual
5006 package it provides. This feature is not yet present,
5007 however, and is expected to be used only infrequently.
5012 To specify which of a set of real packages should be the default
5013 to satisfy a particular dependency on a virtual package, list
5014 the real package as an alternative before the virtual one.
5018 If the virtual package represents a facility that can only be
5019 provided by one real package at a time, such as
5020 the <package>mail-transport-agent</package> virtual package that
5021 requires installation of a binary that would conflict with all
5022 other providers of that virtual package (see
5023 <ref id="mail-transport-agents">), all packages providing that
5024 virtual package should also declare a conflict with it
5025 using <tt>Conflicts</tt>. This will ensure that at most one
5026 provider of that virtual package is unpacked or installed at a
5031 <sect id="replaces"><heading>Overwriting files and replacing
5032 packages - <tt>Replaces</tt></heading>
5035 Packages can declare in their control file that they should
5036 overwrite files in certain other packages, or completely replace
5037 other packages. The <tt>Replaces</tt> control field has these
5038 two distinct purposes.
5041 <sect1><heading>Overwriting files in other packages</heading>
5044 It is usually an error for a package to contain files which
5045 are on the system in another package. However, if the
5046 overwriting package declares that it <tt>Replaces</tt> the one
5047 containing the file being overwritten, then <prgn>dpkg</prgn>
5048 will replace the file from the old package with that from the
5049 new. The file will no longer be listed as "owned" by the old
5050 package and will be taken over by the new package.
5051 Normally, <tt>Breaks</tt> should be used in conjunction
5052 with <tt>Replaces</tt>.<footnote>
5053 To see why <tt>Breaks</tt> is normally needed in addition
5054 to <tt>Replaces</tt>, consider the case of a file in the
5055 package <package>foo</package> being taken over by the
5056 package <package>foo-data</package>.
5057 <tt>Replaces</tt> will allow <package>foo-data</package> to
5058 be installed and take over that file. However,
5059 without <tt>Breaks</tt>, nothing
5060 requires <package>foo</package> to be upgraded to a newer
5061 version that knows it does not include that file and instead
5062 depends on <package>foo-data</package>. Nothing would
5063 prevent the new <package>foo-data</package> package from
5064 being installed and then removed, removing the file that it
5065 took over from <package>foo</package>. After that
5066 operation, the package manager would think the system was in
5067 a consistent state, but the <package>foo</package> package
5068 would be missing one of its files.
5073 For example, if a package <package>foo</package> is split
5074 into <package>foo</package> and <package>foo-data</package>
5075 starting at version 1.2-3, <package>foo-data</package> would
5077 <example compact="compact">
5078 Replaces: foo (<< 1.2-3)
5079 Breaks: foo (<< 1.2-3)
5081 in its control file. The new version of the
5082 package <package>foo</package> would normally have the field
5083 <example compact="compact">
5084 Depends: foo-data (>= 1.2-3)
5086 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5087 the files moved into <package>foo-data</package> are not
5088 required for normal operation).
5092 If a package is completely replaced in this way, so that
5093 <prgn>dpkg</prgn> does not know of any files it still
5094 contains, it is considered to have "disappeared". It will
5095 be marked as not wanted on the system (selected for
5096 removal) and not installed. Any <tt>conffile</tt>s
5097 details noted for the package will be ignored, as they
5098 will have been taken over by the overwriting package. The
5099 package's <prgn>postrm</prgn> script will be run with a
5100 special argument to allow the package to do any final
5101 cleanup required. See <ref id="mscriptsinstact">.
5103 Replaces is a one way relationship. You have to install
5104 the replacing package after the replaced package.
5109 For this usage of <tt>Replaces</tt>, virtual packages (see
5110 <ref id="virtual">) are not considered when looking at a
5111 <tt>Replaces</tt> field. The packages declared as being
5112 replaced must be mentioned by their real names.
5116 This usage of <tt>Replaces</tt> only takes effect when both
5117 packages are at least partially on the system at once. It is
5118 not relevant if the packages conflict unless the conflict has
5123 <sect1><heading>Replacing whole packages, forcing their
5127 Second, <tt>Replaces</tt> allows the packaging system to
5128 resolve which package should be removed when there is a
5129 conflict (see <ref id="conflicts">). This usage only takes
5130 effect when the two packages <em>do</em> conflict, so that the
5131 two usages of this field do not interfere with each other.
5135 In this situation, the package declared as being replaced
5136 can be a virtual package, so for example, all mail
5137 transport agents (MTAs) would have the following fields in
5138 their control files:
5139 <example compact="compact">
5140 Provides: mail-transport-agent
5141 Conflicts: mail-transport-agent
5142 Replaces: mail-transport-agent
5144 ensuring that only one MTA can be installed at any one
5145 time. See <ref id="virtual"> for more information about this
5150 <sect id="sourcebinarydeps">
5151 <heading>Relationships between source and binary packages -
5152 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5153 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5157 Source packages that require certain binary packages to be
5158 installed or absent at the time of building the package
5159 can declare relationships to those binary packages.
5163 This is done using the <tt>Build-Depends</tt>,
5164 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5165 <tt>Build-Conflicts-Indep</tt> control fields.
5169 Build-dependencies on "build-essential" binary packages can be
5170 omitted. Please see <ref id="pkg-relations"> for more information.
5174 The dependencies and conflicts they define must be satisfied
5175 (as defined earlier for binary packages) in order to invoke
5176 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5178 There is no Build-Depends-Arch; this role is essentially
5179 met with Build-Depends. Anyone building the
5180 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5181 assumed to be building the whole package, and therefore
5182 installation of all build dependencies is required.
5185 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5186 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5187 not yet know how to check for its existence, and
5188 <tt>binary-arch</tt>. The purpose of the original split
5189 between <tt>Build-Depends</tt> and
5190 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5191 wouldn't need to install extra packages needed only for the
5192 binary-indep targets. But without a build-arch/build-indep
5193 split, this didn't work, since most of the work is done in
5194 the build target, not in the binary target.
5198 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5199 <tt>binary-arch</tt></tag>
5201 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5202 fields must be satisfied when these targets are invoked.
5204 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5205 and <tt>binary-indep</tt></tag>
5207 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5208 <tt>Build-Depends-Indep</tt>, and
5209 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5210 these targets are invoked.
5218 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5221 Packages containing shared libraries must be constructed with
5222 a little care to make sure that the shared library is always
5223 available. This is especially important for packages whose
5224 shared libraries are vitally important, such as the C library
5225 (currently <tt>libc6</tt>).
5229 This section deals only with public shared libraries: shared
5230 libraries that are placed in directories searched by the dynamic
5231 linker by default or which are intended to be linked against
5232 normally and possibly used by other, independent packages. Shared
5233 libraries that are internal to a particular package or that are
5234 only loaded as dynamic modules are not covered by this section and
5235 are not subject to its requirements.
5239 A shared library is identified by the <tt>SONAME</tt> attribute
5240 stored in its dynamic section. When a binary is linked against a
5241 shared library, the <tt>SONAME</tt> of the shared library is
5242 recorded in the binary's <tt>NEEDED</tt> section so that the
5243 dynamic linker knows that library must be loaded at runtime. The
5244 shared library file's full name (which usually contains additional
5245 version information not needed in the <tt>SONAME</tt>) is
5246 therefore normally not referenced directly. Instead, the shared
5247 library is loaded by its <tt>SONAME</tt>, which exists on the file
5248 system as a symlink pointing to the full name of the shared
5249 library. This symlink must be provided by the
5250 package. <ref id="sharedlibs-runtime"> describes how to do this.
5252 This is a convention of shared library versioning, but not a
5253 requirement. Some libraries use the <tt>SONAME</tt> as the full
5254 library file name instead and therefore do not need a symlink.
5255 Most, however, encode additional information about
5256 backwards-compatible revisions as a minor version number in the
5257 file name. The <tt>SONAME</tt> itself only changes when
5258 binaries linked with the earlier version of the shared library
5259 may no longer work, but the filename may change with each
5260 release of the library. See <ref id="sharedlibs-runtime"> for
5266 When linking a binary or another shared library against a shared
5267 library, the <tt>SONAME</tt> for that shared library is not yet
5268 known. Instead, the shared library is found by looking for a file
5269 matching the library name with <tt>.so</tt> appended. This file
5270 exists on the file system as a symlink pointing to the shared
5275 Shared libraries are normally split into several binary packages.
5276 The <tt>SONAME</tt> symlink is installed by the runtime shared
5277 library package, and the bare <tt>.so</tt> symlink is installed in
5278 the development package since it's only used when linking binaries
5279 or shared libraries. However, there are some exceptions for
5280 unusual shared libraries or for shared libraries that are also
5281 loaded as dynamic modules by other programs.
5285 This section is primarily concerned with how the separation of
5286 shared libraries into multiple packages should be done and how
5287 dependencies on and between shared library binary packages are
5288 managed in Debian. <ref id="libraries"> should be read in
5289 conjunction with this section and contains additional rules for
5290 the files contained in the shared library packages.
5293 <sect id="sharedlibs-runtime">
5294 <heading>Run-time shared libraries</heading>
5297 The run-time shared library must be placed in a package
5298 whose name changes whenever the <tt>SONAME</tt> of the shared
5299 library changes. This allows several versions of the shared
5300 library to be installed at the same time, allowing installation
5301 of the new version of the shared library without immediately
5302 breaking binaries that depend on the old version. Normally, the
5303 run-time shared library and its <tt>SONAME</tt> symlink should
5304 be placed in a package named
5305 <package><var>libraryname</var><var>soversion</var></package>,
5306 where <var>soversion</var> is the version number in
5307 the <tt>SONAME</tt> of the shared library.
5308 See <ref id="shlibs"> for detailed information on how to
5309 determine this version. Alternatively, if it would be confusing
5310 to directly append <var>soversion</var>
5311 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5312 itself ends in a number), you should use
5313 <package><var>libraryname</var>-<var>soversion</var></package>
5318 If you have several shared libraries built from the same source
5319 tree, you may lump them all together into a single shared
5320 library package provided that all of their <tt>SONAME</tt>s will
5321 always change together. Be aware that this is not normally the
5322 case, and if the <tt>SONAME</tt>s do not change together,
5323 upgrading such a merged shared library package will be
5324 unnecessarily difficult because of file conflicts with the old
5325 version of the package. When in doubt, always split shared
5326 library packages so that each binary package installs a single
5331 Every time the shared library ABI changes in a way that may
5332 break binaries linked against older versions of the shared
5333 library, the <tt>SONAME</tt> of the library and the
5334 corresponding name for the binary package containing the runtime
5335 shared library should change. Normally, this means
5336 the <tt>SONAME</tt> should change any time an interface is
5337 removed from the shared library or the signature of an interface
5338 (the number of parameters or the types of parameters that it
5339 takes, for example) is changed. This practice is vital to
5340 allowing clean upgrades from older versions of the package and
5341 clean transitions between the old ABI and new ABI without having
5342 to upgrade every affected package simultaneously.
5346 The <tt>SONAME</tt> and binary package name need not, and indeed
5347 normally should not, change if new interfaces are added but none
5348 are removed or changed, since this will not break binaries
5349 linked against the old shared library. Correct versioning of
5350 dependencies on the newer shared library by binaries that use
5351 the new interfaces is handled via
5352 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5353 system</qref> or via symbols files (see
5354 <manref name="deb-symbols" section="5">).
5358 The package should install the shared libraries under
5359 their normal names. For example, the <package>libgdbm3</package>
5360 package should install <file>libgdbm.so.3.0.0</file> as
5361 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5362 renamed or re-linked by any <prgn>prerm</prgn> or
5363 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5364 of renaming things safely without affecting running programs,
5365 and attempts to interfere with this are likely to lead to
5370 Shared libraries should not be installed executable, since
5371 the dynamic linker does not require this and trying to
5372 execute a shared library usually results in a core dump.
5376 The run-time library package should include the symbolic link for
5377 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5378 the shared libraries. For example,
5379 the <package>libgdbm3</package> package should include a symbolic
5380 link from <file>/usr/lib/libgdbm.so.3</file> to
5381 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5382 linker (for example <prgn>ld.so</prgn> or
5383 <prgn>ld-linux.so.*</prgn>) can find the library between the
5384 time that <prgn>dpkg</prgn> installs it and the time that
5385 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5387 The package management system requires the library to be
5388 placed before the symbolic link pointing to it in the
5389 <file>.deb</file> file. This is so that when
5390 <prgn>dpkg</prgn> comes to install the symlink
5391 (overwriting the previous symlink pointing at an older
5392 version of the library), the new shared library is already
5393 in place. In the past, this was achieved by creating the
5394 library in the temporary packaging directory before
5395 creating the symlink. Unfortunately, this was not always
5396 effective, since the building of the tar file in the
5397 <file>.deb</file> depended on the behavior of the underlying
5398 file system. Some file systems (such as reiserfs) reorder
5399 the files so that the order of creation is forgotten.
5400 Since version 1.7.0, <prgn>dpkg</prgn>
5401 reorders the files itself as necessary when building a
5402 package. Thus it is no longer important to concern
5403 oneself with the order of file creation.
5407 <sect1 id="ldconfig">
5408 <heading><tt>ldconfig</tt></heading>
5411 Any package installing shared libraries in one of the default
5412 library directories of the dynamic linker (which are currently
5413 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5414 listed in <file>/etc/ld.so.conf</file><footnote>
5415 These are currently <file>/usr/local/lib</file> plus
5416 directories under <file>/lib</file> and <file>/usr/lib</file>
5417 matching the multiarch triplet for the system architecture.
5419 must use <prgn>ldconfig</prgn> to update the shared library
5424 The package maintainer scripts must only call
5425 <prgn>ldconfig</prgn> under these circumstances:
5426 <list compact="compact">
5427 <item>When the <prgn>postinst</prgn> script is run with a
5428 first argument of <tt>configure</tt>, the script must call
5429 <prgn>ldconfig</prgn>, and may optionally invoke
5430 <prgn>ldconfig</prgn> at other times.
5432 <item>When the <prgn>postrm</prgn> script is run with a
5433 first argument of <tt>remove</tt>, the script should call
5434 <prgn>ldconfig</prgn>.
5439 During install or upgrade, the preinst is called before
5440 the new files are installed, so calling "ldconfig" is
5441 pointless. The preinst of an existing package can also be
5442 called if an upgrade fails. However, this happens during
5443 the critical time when a shared libs may exist on-disk
5444 under a temporary name. Thus, it is dangerous and
5445 forbidden by current policy to call "ldconfig" at this
5450 When a package is installed or upgraded, "postinst
5451 configure" runs after the new files are safely on-disk.
5452 Since it is perfectly safe to invoke ldconfig
5453 unconditionally in a postinst, it is OK for a package to
5454 simply put ldconfig in its postinst without checking the
5455 argument. The postinst can also be called to recover from
5456 a failed upgrade. This happens before any new files are
5457 unpacked, so there is no reason to call "ldconfig" at this
5462 For a package that is being removed, prerm is
5463 called with all the files intact, so calling ldconfig is
5464 useless. The other calls to "prerm" happen in the case of
5465 upgrade at a time when all the files of the old package
5466 are on-disk, so again calling "ldconfig" is pointless.
5470 postrm, on the other hand, is called with the "remove"
5471 argument just after the files are removed, so this is
5472 the proper time to call "ldconfig" to notify the system
5473 of the fact that the shared libraries from the package
5474 are removed. The postrm can be called at several other
5475 times. At the time of "postrm purge", "postrm
5476 abort-install", or "postrm abort-upgrade", calling
5477 "ldconfig" is useless because the shared lib files are
5478 not on-disk. However, when "postrm" is invoked with
5479 arguments "upgrade", "failed-upgrade", or "disappear", a
5480 shared lib may exist on-disk under a temporary filename.
5488 <sect id="sharedlibs-support-files">
5489 <heading>Shared library support files</heading>
5492 If your package contains files whose names do not change with
5493 each change in the library shared object version, you must not
5494 put them in the shared library package. Otherwise, several
5495 versions of the shared library cannot be installed at the same
5496 time without filename clashes, making upgrades and transitions
5497 unnecessarily difficult.
5501 It is recommended that supporting files and run-time support
5502 programs that do not need to be invoked manually by users, but
5503 are nevertheless required for the package to function, be placed
5504 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5505 preferably under <file>/usr/lib/</file><var>package-name</var>.
5506 If the program or file is architecture independent, the
5507 recommendation is for it to be placed in a subdirectory of
5508 <file>/usr/share</file> instead, preferably under
5509 <file>/usr/share/</file><var>package-name</var>. Following the
5510 <var>package-name</var> naming convention ensures that the file
5511 names change when the shared object version changes.
5515 Run-time support programs that use the shared library but are
5516 not required for the library to function or files used by the
5517 shared library that can be used by any version of the shared
5518 library package should instead be put in a separate package.
5519 This package might typically be named
5520 <package><var>libraryname</var>-tools</package>; note the
5521 absence of the <var>soversion</var> in the package name.
5525 Files and support programs only useful when compiling software
5526 against the library should be included in the development
5527 package for the library.<footnote>
5528 For example, a <file><var>package-name</var>-config</file>
5529 script or <package>pkg-config</package> configuration files.
5534 <sect id="sharedlibs-static">
5535 <heading>Static libraries</heading>
5538 The static library (<file><var>libraryname.a</var></file>)
5539 is usually provided in addition to the shared version.
5540 It is placed into the development package (see below).
5544 In some cases, it is acceptable for a library to be
5545 available in static form only; these cases include:
5547 <item>libraries for languages whose shared library support
5548 is immature or unstable</item>
5549 <item>libraries whose interfaces are in flux or under
5550 development (commonly the case when the library's
5551 major version number is zero, or where the ABI breaks
5552 across patchlevels)</item>
5553 <item>libraries which are explicitly intended to be
5554 available only in static form by their upstream
5559 <sect id="sharedlibs-dev">
5560 <heading>Development files</heading>
5563 If there are development files associated with a shared library,
5564 the source package needs to generate a binary development package
5565 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5566 or if you prefer only to support one development version at a
5567 time, <package><var>libraryname</var>-dev</package>. Installing
5568 the development package must result in installation of all the
5569 development files necessary for compiling programs against that
5570 shared library.<footnote>
5571 This wording allows the development files to be split into
5572 several packages, such as a separate architecture-independent
5573 <package><var>libraryname</var>-headers</package>, provided that
5574 the development package depends on all the required additional
5580 In case several development versions of a library exist, you may
5581 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5582 <ref id="conflicts">) to ensure that the user only installs one
5583 development version at a time (as different development versions are
5584 likely to have the same header files in them, which would cause a
5585 filename clash if both were installed).
5589 The development package should contain a symlink for the associated
5590 shared library without a version number. For example, the
5591 <package>libgdbm-dev</package> package should include a symlink
5592 from <file>/usr/lib/libgdbm.so</file> to
5593 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5594 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5595 <file>libgdbm.so</file> when compiling dynamically.
5599 If the package provides Ada Library Information
5600 (<file>*.ali</file>) files for use with GNAT, these files must be
5601 installed read-only (mode 0444) so that GNAT will not attempt to
5602 recompile them. This overrides the normal file mode requirements
5603 given in <ref id="permissions-owners">.
5607 <sect id="sharedlibs-intradeps">
5608 <heading>Dependencies between the packages of the same library</heading>
5611 Typically the development version should have an exact
5612 version dependency on the runtime library, to make sure that
5613 compilation and linking happens correctly. The
5614 <tt>${binary:Version}</tt> substitution variable can be
5615 useful for this purpose.
5617 Previously, <tt>${Source-Version}</tt> was used, but its name
5618 was confusing and it has been deprecated since dpkg 1.13.19.
5623 <sect id="sharedlibs-shlibdeps">
5624 <heading>Dependencies between the library and other packages -
5625 the <tt>shlibs</tt> system</heading>
5628 If a package contains a binary or library which links to a
5629 shared library, we must ensure that when the package is
5630 installed on the system, all of the libraries needed are
5631 also installed. This requirement led to the creation of the
5632 <tt>shlibs</tt> system, which is very simple in its design:
5633 any package which <em>provides</em> a shared library also
5634 provides information on the package dependencies required to
5635 ensure the presence of this library, and any package which
5636 <em>uses</em> a shared library uses this information to
5637 determine the dependencies it requires. The files which
5638 contain the mapping from shared libraries to the necessary
5639 dependency information are called <file>shlibs</file> files.
5643 When a package is built which contains any shared libraries, it
5644 must provide a <file>shlibs</file> file for other packages to
5645 use. When a package is built which contains any shared
5646 libraries or compiled binaries, it must run
5647 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5648 on these to determine the libraries used and hence the
5649 dependencies needed by this package.<footnote>
5651 <prgn>dpkg-shlibdeps</prgn> will use a program
5652 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5653 the libraries directly needed by the binaries or shared
5654 libraries in the package.
5658 We say that a binary <tt>foo</tt> <em>directly</em> uses
5659 a library <tt>libbar</tt> if it is explicitly linked
5660 with that library (that is, the library is listed in the ELF
5661 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5662 to the link line when the binary is created). Other
5663 libraries that are needed by <tt>libbar</tt> are linked
5664 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5665 linker will load them automatically when it loads
5666 <tt>libbar</tt>. A package should depend on the libraries
5667 it directly uses, but not the libraries it indirectly uses.
5668 The dependencies for those libraries will automatically pull
5669 in the other libraries.
5673 A good example of where this helps is the following. We
5674 could update <tt>libimlib</tt> with a new version that
5675 supports a new graphics format called dgf (but retaining the
5676 same major version number) and depends on <tt>libdgf</tt>.
5677 If we used <prgn>ldd</prgn> to add dependencies for every
5678 library directly or indirectly linked with a binary, every
5679 package that uses <tt>libimlib</tt> would need to be
5680 recompiled so it would also depend on <tt>libdgf</tt> or it
5681 wouldn't run due to missing symbols. Since dependencies are
5682 only added based on ELF <tt>NEEDED</tt> attribute, packages
5683 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5684 having the dependency on <tt>libdgf</tt> and so they would
5685 not need rebuilding.
5691 In the following sections, we will first describe where the
5692 various <tt>shlibs</tt> files are to be found, then how to
5693 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5694 file format and how to create them if your package contains a
5699 <heading>The <tt>shlibs</tt> files present on the system</heading>
5702 There are several places where <tt>shlibs</tt> files are
5703 found. The following list gives them in the order in which
5705 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5706 (The first one which gives the required information is used.)
5712 <p><file>debian/shlibs.local</file></p>
5715 This lists overrides for this package. This file should
5716 normally not be used, but may be needed temporarily in
5717 unusual situations to work around bugs in other packages,
5718 or in unusual cases where the normally declared dependency
5719 information in the installed <file>shlibs</file> file for
5720 a library cannot be used. This file overrides information
5721 obtained from any other source.
5726 <p><file>/etc/dpkg/shlibs.override</file></p>
5729 This lists global overrides. This list is normally
5730 empty. It is maintained by the local system
5736 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5739 When packages are being built,
5740 any <file>debian/shlibs</file> files are copied into the
5741 control information file area of the temporary build
5742 directory and given the name <file>shlibs</file>. These
5743 files give details of any shared libraries included in the
5744 same package.<footnote>
5745 An example may help here. Let us say that the source
5746 package <tt>foo</tt> generates two binary
5747 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5748 When building the binary packages, the two packages are
5749 created in the directories <file>debian/libfoo2</file>
5750 and <file>debian/foo-runtime</file> respectively.
5751 (<file>debian/tmp</file> could be used instead of one of
5752 these.) Since <tt>libfoo2</tt> provides the
5753 <tt>libfoo</tt> shared library, it will require a
5754 <tt>shlibs</tt> file, which will be installed in
5755 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5756 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5757 When <prgn>dpkg-shlibdeps</prgn> is run on the
5758 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5760 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5761 determine whether <tt>foo-prog</tt>'s library
5762 dependencies are satisfied by any of the libraries
5763 provided by <tt>libfoo2</tt>. For this reason,
5764 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5765 the individual binary packages' <tt>shlibs</tt> files
5766 have been installed into the build directory.
5772 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5775 These are the <file>shlibs</file> files corresponding to
5776 all of the packages installed on the system, and are
5777 maintained by the relevant package maintainers.
5782 <p><file>/etc/dpkg/shlibs.default</file></p>
5785 This file lists any shared libraries whose packages
5786 have failed to provide correct <file>shlibs</file> files.
5787 It was used when the <file>shlibs</file> setup was first
5788 introduced, but it is now normally empty. It is
5789 maintained by the <tt>dpkg</tt> maintainer.
5797 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5798 <file>shlibs</file> files</heading>
5802 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5803 into your <file>debian/rules</file> file. If your package
5804 contains only compiled binaries and libraries (but no scripts),
5805 you can use a command such as:
5806 <example compact="compact">
5807 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5808 debian/tmp/usr/lib/*
5810 Otherwise, you will need to explicitly list the compiled
5811 binaries and libraries.<footnote>
5812 If you are using <tt>debhelper</tt>, the
5813 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5814 It will also correctly handle multi-binary packages.
5819 This command puts the dependency information into the
5820 <file>debian/substvars</file> file, which is then used by
5821 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5822 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5823 field in the control file for this to work.
5827 If you have multiple binary packages, you will need to call
5828 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5829 compiled libraries or binaries. In such a case, you will
5830 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5831 utilities to specify a different <file>substvars</file> file.
5835 If you are creating a udeb for use in the Debian Installer,
5836 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5837 should use the dependency line of type <tt>udeb</tt> by
5838 adding the <tt>-tudeb</tt> option<footnote>
5839 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5840 will automatically add this option if it knows it is
5842 </footnote>. If there is no dependency line of
5843 type <tt>udeb</tt> in the <file>shlibs</file>
5844 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5849 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5850 <ref id="pkg-dpkg-shlibdeps"> and
5851 <manref name="dpkg-shlibdeps" section="1">.
5856 <heading>The <file>shlibs</file> File Format</heading>
5859 Each <file>shlibs</file> file has the same format. Lines
5860 beginning with <tt>#</tt> are considered to be comments and
5861 are ignored. Each line is of the form:
5862 <example compact="compact">
5863 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5868 We will explain this by reference to the example of the
5869 <tt>zlib1g</tt> package, which (at the time of writing)
5870 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5874 <var>type</var> is an optional element that indicates the type
5875 of package for which the line is valid. The only type currently
5876 in use is <tt>udeb</tt>. The colon and space after the type are
5881 <var>library-name</var> is the name of the shared library,
5882 in this case <tt>libz</tt>. (This must match the name part
5883 of the soname, see below.)
5887 <var>soname-version</var> is the version part of the soname of
5888 the library. The soname is the thing that must exactly match
5889 for the library to be recognized by the dynamic linker, and is
5891 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5892 example, <tt>libz.so.1</tt>.<footnote>
5893 This can be determined using the command
5894 <example compact="compact">
5895 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5898 The version part is the part which comes after
5899 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5900 instead be of the form
5901 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5902 as <tt>libdb-4.8.so</tt>, in which case the name would
5903 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5907 <var>dependencies</var> has the same syntax as a dependency
5908 field in a binary package control file. It should give
5909 details of which packages are required to satisfy a binary
5910 built against the version of the library contained in the
5911 package. See <ref id="depsyntax"> for details.
5915 In our example, if the first version of the <tt>zlib1g</tt>
5916 package which contained a minor number of at least
5917 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5918 <tt>shlibs</tt> entry for this library could say:
5919 <example compact="compact">
5920 libz 1 zlib1g (>= 1:1.1.3)
5922 The version-specific dependency is to avoid warnings from
5923 the dynamic linker about using older shared libraries with
5928 As zlib1g also provides a udeb containing the shared library,
5929 there would also be a second line:
5930 <example compact="compact">
5931 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5937 <heading>Providing a <file>shlibs</file> file</heading>
5940 If your package provides a shared library, you need to create
5941 a <file>shlibs</file> file following the format described above.
5942 It is usual to call this file <file>debian/shlibs</file> (but if
5943 you have multiple binary packages, you might want to call it
5944 <file>debian/shlibs.<var>package</var></file> instead). Then
5945 let <file>debian/rules</file> install it in the control
5946 information file area:
5947 <example compact="compact">
5948 install -m644 debian/shlibs debian/tmp/DEBIAN
5950 or, in the case of a multi-binary package:
5951 <example compact="compact">
5952 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5954 An alternative way of doing this is to create the
5955 <file>shlibs</file> file in the control information file area
5956 directly from <file>debian/rules</file> without using
5957 a <file>debian/shlibs</file> file at all,<footnote>
5958 This is what <prgn>dh_makeshlibs</prgn> in
5959 the <package>debhelper</package> suite does. If your package
5960 also has a udeb that provides a shared
5961 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5962 the <tt>udeb:</tt> lines if you specify the name of the udeb
5963 with the <tt>--add-udeb</tt> option.
5965 since the <file>debian/shlibs</file> file itself is ignored by
5966 <prgn>dpkg-shlibdeps</prgn>.
5970 As <prgn>dpkg-shlibdeps</prgn> reads the
5971 <file>DEBIAN/shlibs</file> files in all of the binary packages
5972 being built from this source package, all of the
5973 <file>DEBIAN/shlibs</file> files should be installed before
5974 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5982 <chapt id="opersys"><heading>The Operating System</heading>
5985 <heading>File system hierarchy</heading>
5989 <heading>File System Structure</heading>
5992 The location of all installed files and directories must
5993 comply with the Filesystem Hierarchy Standard (FHS),
5994 version 2.3, with the exceptions noted below, and except
5995 where doing so would violate other terms of Debian
5996 Policy. The following exceptions to the FHS apply:
6001 The optional rules related to user specific
6002 configuration files for applications are stored in
6003 the user's home directory are relaxed. It is
6004 recommended that such files start with the
6005 '<tt>.</tt>' character (a "dot file"), and if an
6006 application needs to create more than one dot file
6007 then the preferred placement is in a subdirectory
6008 with a name starting with a '.' character, (a "dot
6009 directory"). In this case it is recommended the
6010 configuration files not start with the '.'
6016 The requirement for amd64 to use <file>/lib64</file>
6017 for 64 bit binaries is removed.
6022 The requirement for object files, internal binaries, and
6023 libraries, including <file>libc.so.*</file>, to be located
6024 directly under <file>/lib{,32}</file> and
6025 <file>/usr/lib{,32}</file> is amended, permitting files
6026 to instead be installed to
6027 <file>/lib/<var>triplet</var></file> and
6028 <file>/usr/lib/<var>triplet</var></file>, where
6029 <tt><var>triplet</var></tt> is the value returned by
6030 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
6031 architecture of the package. Packages may <em>not</em>
6032 install files to any <var>triplet</var> path other
6033 than the one matching the architecture of that package;
6034 for instance, an <tt>Architecture: amd64</tt> package
6035 containing 32-bit x86 libraries may not install these
6036 libraries to <file>/usr/lib/i486-linux-gnu</file>.
6038 This is necessary in order to reserve the directories for
6039 use in cross-installation of library packages from other
6040 architectures, as part of the planned deployment of
6045 Applications may also use a single subdirectory under
6046 <file>/usr/lib/<var>triplet</var></file>.
6049 The execution time linker/loader, ld*, must still be made
6050 available in the existing location under /lib or /lib64
6051 since this is part of the ELF ABI for the architecture.
6056 The requirement that
6057 <file>/usr/local/share/man</file> be "synonymous"
6058 with <file>/usr/local/man</file> is relaxed to a
6063 The requirement that windowmanagers with a single
6064 configuration file call it <file>system.*wmrc</file>
6065 is removed, as is the restriction that the window
6066 manager subdirectory be named identically to the
6067 window manager name itself.
6072 The requirement that boot manager configuration
6073 files live in <file>/etc</file>, or at least are
6074 symlinked there, is relaxed to a recommendation.
6079 The following directories in the root filesystem are
6080 additionally allowed: <file>/sys</file> and
6081 <file>/selinux</file>. <footnote>These directories
6082 are used as mount points to mount virtual filesystems
6083 to get access to kernel information.</footnote>
6088 On GNU/Hurd systems, the following additional
6089 directories are allowed in the root
6090 filesystem: <file>/hurd</file>
6091 and <file>/servers</file>.<footnote>
6092 These directories are used to store translators and as
6093 a set of standard names for mount points,
6102 The version of this document referred here can be
6103 found in the <tt>debian-policy</tt> package or on <url
6104 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6105 name="FHS (Debian copy)"> alongside this manual (or, if
6106 you have the <package>debian-policy</package> installed,
6108 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6109 (local copy)">). The
6110 latest version, which may be a more recent version, may
6112 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6113 Specific questions about following the standard may be
6114 asked on the <tt>debian-devel</tt> mailing list, or
6115 referred to the FHS mailing list (see the
6116 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6122 <heading>Site-specific programs</heading>
6125 As mandated by the FHS, packages must not place any
6126 files in <file>/usr/local</file>, either by putting them in
6127 the file system archive to be unpacked by <prgn>dpkg</prgn>
6128 or by manipulating them in their maintainer scripts.
6132 However, the package may create empty directories below
6133 <file>/usr/local</file> so that the system administrator knows
6134 where to place site-specific files. These are not
6135 directories <em>in</em> <file>/usr/local</file>, but are
6136 children of directories in <file>/usr/local</file>. These
6137 directories (<file>/usr/local/*/dir/</file>)
6138 should be removed on package removal if they are
6143 Note that this applies only to
6144 directories <em>below</em> <file>/usr/local</file>,
6145 not <em>in</em> <file>/usr/local</file>. Packages must
6146 not create sub-directories in the
6147 directory <file>/usr/local</file> itself, except those
6148 listed in FHS, section 4.5. However, you may create
6149 directories below them as you wish. You must not remove
6150 any of the directories listed in 4.5, even if you created
6155 Since <file>/usr/local</file> can be mounted read-only from a
6156 remote server, these directories must be created and
6157 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6158 maintainer scripts and not be included in the
6159 <file>.deb</file> archive. These scripts must not fail if
6160 either of these operations fail.
6164 For example, the <tt>emacsen-common</tt> package could
6165 contain something like
6166 <example compact="compact">
6167 if [ ! -e /usr/local/share/emacs ]
6169 if mkdir /usr/local/share/emacs 2>/dev/null
6171 chown root:staff /usr/local/share/emacs
6172 chmod 2775 /usr/local/share/emacs
6176 in its <prgn>postinst</prgn> script, and
6177 <example compact="compact">
6178 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6179 rmdir /usr/local/share/emacs 2>/dev/null || true
6181 in the <prgn>prerm</prgn> script. (Note that this form is
6182 used to ensure that if the script is interrupted, the
6183 directory <file>/usr/local/share/emacs</file> will still be
6188 If you do create a directory in <file>/usr/local</file> for
6189 local additions to a package, you should ensure that
6190 settings in <file>/usr/local</file> take precedence over the
6191 equivalents in <file>/usr</file>.
6195 However, because <file>/usr/local</file> and its contents are
6196 for exclusive use of the local administrator, a package
6197 must not rely on the presence or absence of files or
6198 directories in <file>/usr/local</file> for normal operation.
6202 The <file>/usr/local</file> directory itself and all the
6203 subdirectories created by the package should (by default) have
6204 permissions 2775 (group-writable and set-group-id) and be
6205 owned by <tt>root:staff</tt>.
6210 <heading>The system-wide mail directory</heading>
6212 The system-wide mail directory
6213 is <file>/var/mail</file>. This directory is part of the
6214 base system and should not be owned by any particular mail
6215 agents. The use of the old
6216 location <file>/var/spool/mail</file> is deprecated, even
6217 though the spool may still be physically located there.
6223 <heading>Users and groups</heading>
6226 <heading>Introduction</heading>
6228 The Debian system can be configured to use either plain or
6233 Some user ids (UIDs) and group ids (GIDs) are reserved
6234 globally for use by certain packages. Because some
6235 packages need to include files which are owned by these
6236 users or groups, or need the ids compiled into binaries,
6237 these ids must be used on any Debian system only for the
6238 purpose for which they are allocated. This is a serious
6239 restriction, and we should avoid getting in the way of
6240 local administration policies. In particular, many sites
6241 allocate users and/or local system groups starting at 100.
6245 Apart from this we should have dynamically allocated ids,
6246 which should by default be arranged in some sensible
6247 order, but the behavior should be configurable.
6251 Packages other than <tt>base-passwd</tt> must not modify
6252 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6253 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6258 <heading>UID and GID classes</heading>
6260 The UID and GID numbers are divided into classes as
6266 Globally allocated by the Debian project, the same
6267 on every Debian system. These ids will appear in
6268 the <file>passwd</file> and <file>group</file> files of all
6269 Debian systems, new ids in this range being added
6270 automatically as the <tt>base-passwd</tt> package is
6275 Packages which need a single statically allocated
6276 uid or gid should use one of these; their
6277 maintainers should ask the <tt>base-passwd</tt>
6285 Dynamically allocated system users and groups.
6286 Packages which need a user or group, but can have
6287 this user or group allocated dynamically and
6288 differently on each system, should use <tt>adduser
6289 --system</tt> to create the group and/or user.
6290 <prgn>adduser</prgn> will check for the existence of
6291 the user or group, and if necessary choose an unused
6292 id based on the ranges specified in
6293 <file>adduser.conf</file>.
6297 <tag>1000-59999:</tag>
6300 Dynamically allocated user accounts. By default
6301 <prgn>adduser</prgn> will choose UIDs and GIDs for
6302 user accounts in this range, though
6303 <file>adduser.conf</file> may be used to modify this
6308 <tag>60000-64999:</tag>
6311 Globally allocated by the Debian project, but only
6312 created on demand. The ids are allocated centrally
6313 and statically, but the actual accounts are only
6314 created on users' systems on demand.
6318 These ids are for packages which are obscure or
6319 which require many statically-allocated ids. These
6320 packages should check for and create the accounts in
6321 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6322 <prgn>adduser</prgn> if it has this facility) if
6323 necessary. Packages which are likely to require
6324 further allocations should have a "hole" left after
6325 them in the allocation, to give them room to
6330 <tag>65000-65533:</tag>
6338 User <tt>nobody</tt>. The corresponding gid refers
6339 to the group <tt>nogroup</tt>.
6346 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6347 not</em> be used, because it is the error return
6356 <sect id="sysvinit">
6357 <heading>System run levels and <file>init.d</file> scripts</heading>
6359 <sect1 id="/etc/init.d">
6360 <heading>Introduction</heading>
6363 The <file>/etc/init.d</file> directory contains the scripts
6364 executed by <prgn>init</prgn> at boot time and when the
6365 init state (or "runlevel") is changed (see <manref
6366 name="init" section="8">).
6370 There are at least two different, yet functionally
6371 equivalent, ways of handling these scripts. For the sake
6372 of simplicity, this document describes only the symbolic
6373 link method. However, it must not be assumed by maintainer
6374 scripts that this method is being used, and any automated
6375 manipulation of the various runlevel behaviors by
6376 maintainer scripts must be performed using
6377 <prgn>update-rc.d</prgn> as described below and not by
6378 manually installing or removing symlinks. For information
6379 on the implementation details of the other method,
6380 implemented in the <tt>file-rc</tt> package, please refer
6381 to the documentation of that package.
6385 These scripts are referenced by symbolic links in the
6386 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6387 runlevels, <prgn>init</prgn> looks in the directory
6388 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6389 execute, where <tt><var>n</var></tt> is the runlevel that
6390 is being changed to, or <tt>S</tt> for the boot-up
6395 The names of the links all have the form
6396 <file>S<var>mm</var><var>script</var></file> or
6397 <file>K<var>mm</var><var>script</var></file> where
6398 <var>mm</var> is a two-digit number and <var>script</var>
6399 is the name of the script (this should be the same as the
6400 name of the actual script in <file>/etc/init.d</file>).
6404 When <prgn>init</prgn> changes runlevel first the targets
6405 of the links whose names start with a <tt>K</tt> are
6406 executed, each with the single argument <tt>stop</tt>,
6407 followed by the scripts prefixed with an <tt>S</tt>, each
6408 with the single argument <tt>start</tt>. (The links are
6409 those in the <file>/etc/rc<var>n</var>.d</file> directory
6410 corresponding to the new runlevel.) The <tt>K</tt> links
6411 are responsible for killing services and the <tt>S</tt>
6412 link for starting services upon entering the runlevel.
6416 For example, if we are changing from runlevel 2 to
6417 runlevel 3, init will first execute all of the <tt>K</tt>
6418 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6419 all of the <tt>S</tt> prefixed scripts in that directory.
6420 The links starting with <tt>K</tt> will cause the
6421 referred-to file to be executed with an argument of
6422 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6427 The two-digit number <var>mm</var> is used to determine
6428 the order in which to run the scripts: low-numbered links
6429 have their scripts run first. For example, the
6430 <tt>K20</tt> scripts will be executed before the
6431 <tt>K30</tt> scripts. This is used when a certain service
6432 must be started before another. For example, the name
6433 server <prgn>bind</prgn> might need to be started before
6434 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6435 can set up its access lists. In this case, the script
6436 that starts <prgn>bind</prgn> would have a lower number
6437 than the script that starts <prgn>inn</prgn> so that it
6439 <example compact="compact">
6446 The two runlevels 0 (halt) and 6 (reboot) are slightly
6447 different. In these runlevels, the links with an
6448 <tt>S</tt> prefix are still called after those with a
6449 <tt>K</tt> prefix, but they too are called with the single
6450 argument <tt>stop</tt>.
6454 <sect1 id="writing-init">
6455 <heading>Writing the scripts</heading>
6458 Packages that include daemons for system services should
6459 place scripts in <file>/etc/init.d</file> to start or stop
6460 services at boot time or during a change of runlevel.
6461 These scripts should be named
6462 <file>/etc/init.d/<var>package</var></file>, and they should
6463 accept one argument, saying what to do:
6466 <tag><tt>start</tt></tag>
6467 <item>start the service,</item>
6469 <tag><tt>stop</tt></tag>
6470 <item>stop the service,</item>
6472 <tag><tt>restart</tt></tag>
6473 <item>stop and restart the service if it's already running,
6474 otherwise start the service</item>
6476 <tag><tt>reload</tt></tag>
6477 <item><p>cause the configuration of the service to be
6478 reloaded without actually stopping and restarting
6481 <tag><tt>force-reload</tt></tag>
6482 <item>cause the configuration to be reloaded if the
6483 service supports this, otherwise restart the
6487 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6488 <tt>force-reload</tt> options should be supported by all
6489 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6494 The <file>init.d</file> scripts must ensure that they will
6495 behave sensibly (i.e., returning success and not starting
6496 multiple copies of a service) if invoked with <tt>start</tt>
6497 when the service is already running, or with <tt>stop</tt>
6498 when it isn't, and that they don't kill unfortunately-named
6499 user processes. The best way to achieve this is usually to
6500 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6505 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6506 scripts. Writing correct <file>init.d</file> scripts requires
6507 accepting various error exit statuses when daemons are already
6508 running or already stopped without aborting
6509 the <file>init.d</file> script, and common <file>init.d</file>
6510 function libraries are not safe to call with <tt>set -e</tt>
6512 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6513 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6514 in effect and echoing status messages to the console fails,
6516 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6517 to not use <tt>set -e</tt> and instead check the result of
6518 each command separately.
6522 If a service reloads its configuration automatically (as
6523 in the case of <prgn>cron</prgn>, for example), the
6524 <tt>reload</tt> option of the <file>init.d</file> script
6525 should behave as if the configuration has been reloaded
6530 The <file>/etc/init.d</file> scripts must be treated as
6531 configuration files, either (if they are present in the
6532 package, that is, in the .deb file) by marking them as
6533 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6534 by managing them correctly in the maintainer scripts (see
6535 <ref id="config-files">). This is important since we want
6536 to give the local system administrator the chance to adapt
6537 the scripts to the local system, e.g., to disable a
6538 service without de-installing the package, or to specify
6539 some special command line options when starting a service,
6540 while making sure their changes aren't lost during the next
6545 These scripts should not fail obscurely when the
6546 configuration files remain but the package has been
6547 removed, as configuration files remain on the system after
6548 the package has been removed. Only when <prgn>dpkg</prgn>
6549 is executed with the <tt>--purge</tt> option will
6550 configuration files be removed. In particular, as the
6551 <file>/etc/init.d/<var>package</var></file> script itself is
6552 usually a <tt>conffile</tt>, it will remain on the system
6553 if the package is removed but not purged. Therefore, you
6554 should include a <tt>test</tt> statement at the top of the
6556 <example compact="compact">
6557 test -f <var>program-executed-later-in-script</var> || exit 0
6562 Often there are some variables in the <file>init.d</file>
6563 scripts whose values control the behavior of the scripts,
6564 and which a system administrator is likely to want to
6565 change. As the scripts themselves are frequently
6566 <tt>conffile</tt>s, modifying them requires that the
6567 administrator merge in their changes each time the package
6568 is upgraded and the <tt>conffile</tt> changes. To ease
6569 the burden on the system administrator, such configurable
6570 values should not be placed directly in the script.
6571 Instead, they should be placed in a file in
6572 <file>/etc/default</file>, which typically will have the same
6573 base name as the <file>init.d</file> script. This extra file
6574 should be sourced by the script when the script runs. It
6575 must contain only variable settings and comments in SUSv3
6576 <prgn>sh</prgn> format. It may either be a
6577 <tt>conffile</tt> or a configuration file maintained by
6578 the package maintainer scripts. See <ref id="config-files">
6583 To ensure that vital configurable values are always
6584 available, the <file>init.d</file> script should set default
6585 values for each of the shell variables it uses, either
6586 before sourcing the <file>/etc/default/</file> file or
6587 afterwards using something like the <tt>:
6588 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6589 script must behave sensibly and not fail if the
6590 <file>/etc/default</file> file is deleted.
6594 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6595 as temporary filesystems<footnote>
6596 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6597 options in <file>/etc/default/rcS</file>.
6598 </footnote>, so the <file>init.d</file> scripts must handle this
6599 correctly. This will typically amount to creating any required
6600 subdirectories dynamically when the <file>init.d</file> script
6601 is run, rather than including them in the package and relying on
6602 <prgn>dpkg</prgn> to create them.
6607 <heading>Interfacing with the initscript system</heading>
6610 Maintainers should use the abstraction layer provided by
6611 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6612 programs to deal with initscripts in their packages'
6613 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6614 and <prgn>postrm</prgn>.
6618 Directly managing the /etc/rc?.d links and directly
6619 invoking the <file>/etc/init.d/</file> initscripts should
6620 be done only by packages providing the initscript
6621 subsystem (such as <prgn>sysv-rc</prgn> and
6622 <prgn>file-rc</prgn>).
6626 <heading>Managing the links</heading>
6629 The program <prgn>update-rc.d</prgn> is provided for
6630 package maintainers to arrange for the proper creation and
6631 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6632 or their functional equivalent if another method is being
6633 used. This may be used by maintainers in their packages'
6634 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6638 You must not include any <file>/etc/rc<var>n</var>.d</file>
6639 symbolic links in the actual archive or manually create or
6640 remove the symbolic links in maintainer scripts; you must
6641 use the <prgn>update-rc.d</prgn> program instead. (The
6642 former will fail if an alternative method of maintaining
6643 runlevel information is being used.) You must not include
6644 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6645 in the archive either. (Only the <tt>sysvinit</tt>
6650 By default <prgn>update-rc.d</prgn> will start services in
6651 each of the multi-user state runlevels (2, 3, 4, and 5)
6652 and stop them in the halt runlevel (0), the single-user
6653 runlevel (1) and the reboot runlevel (6). The system
6654 administrator will have the opportunity to customize
6655 runlevels by simply adding, moving, or removing the
6656 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6657 symbolic links are being used, or by modifying
6658 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6663 To get the default behavior for your package, put in your
6664 <prgn>postinst</prgn> script
6665 <example compact="compact">
6666 update-rc.d <var>package</var> defaults
6668 and in your <prgn>postrm</prgn>
6669 <example compact="compact">
6670 if [ "$1" = purge ]; then
6671 update-rc.d <var>package</var> remove
6673 </example>. Note that if your package changes runlevels
6674 or priority, you may have to remove and recreate the links,
6675 since otherwise the old links may persist. Refer to the
6676 documentation of <prgn>update-rc.d</prgn>.
6680 This will use a default sequence number of 20. If it does
6681 not matter when or in which order the <file>init.d</file>
6682 script is run, use this default. If it does, then you
6683 should talk to the maintainer of the <prgn>sysvinit</prgn>
6684 package or post to <tt>debian-devel</tt>, and they will
6685 help you choose a number.
6689 For more information about using <tt>update-rc.d</tt>,
6690 please consult its man page <manref name="update-rc.d"
6696 <heading>Running initscripts</heading>
6698 The program <prgn>invoke-rc.d</prgn> is provided to make
6699 it easier for package maintainers to properly invoke an
6700 initscript, obeying runlevel and other locally-defined
6701 constraints that might limit a package's right to start,
6702 stop and otherwise manage services. This program may be
6703 used by maintainers in their packages' scripts.
6707 The package maintainer scripts must use
6708 <prgn>invoke-rc.d</prgn> to invoke the
6709 <file>/etc/init.d/*</file> initscripts, instead of
6710 calling them directly.
6714 By default, <prgn>invoke-rc.d</prgn> will pass any
6715 action requests (start, stop, reload, restart...) to the
6716 <file>/etc/init.d</file> script, filtering out requests
6717 to start or restart a service out of its intended
6722 Most packages will simply need to change:
6723 <example compact="compact">/etc/init.d/<package>
6724 <action></example> in their <prgn>postinst</prgn>
6725 and <prgn>prerm</prgn> scripts to:
6726 <example compact="compact">
6727 if which invoke-rc.d >/dev/null 2>&1; then
6728 invoke-rc.d <var>package</var> <action>
6730 /etc/init.d/<var>package</var> <action>
6736 A package should register its initscript services using
6737 <prgn>update-rc.d</prgn> before it tries to invoke them
6738 using <prgn>invoke-rc.d</prgn>. Invocation of
6739 unregistered services may fail.
6743 For more information about using
6744 <prgn>invoke-rc.d</prgn>, please consult its man page
6745 <manref name="invoke-rc.d" section="8">.
6751 <heading>Boot-time initialization</heading>
6754 There used to be another directory, <file>/etc/rc.boot</file>,
6755 which contained scripts which were run once per machine
6756 boot. This has been deprecated in favour of links from
6757 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6758 described in <ref id="/etc/init.d">. Packages must not
6759 place files in <file>/etc/rc.boot</file>.
6764 <heading>Example</heading>
6767 An example on which you can base your
6768 <file>/etc/init.d</file> scripts is found in
6769 <file>/etc/init.d/skeleton</file>.
6776 <heading>Console messages from <file>init.d</file> scripts</heading>
6779 This section describes the formats to be used for messages
6780 written to standard output by the <file>/etc/init.d</file>
6781 scripts. The intent is to improve the consistency of
6782 Debian's startup and shutdown look and feel. For this
6783 reason, please look very carefully at the details. We want
6784 the messages to have the same format in terms of wording,
6785 spaces, punctuation and case of letters.
6789 Here is a list of overall rules that should be used for
6790 messages generated by <file>/etc/init.d</file> scripts.
6796 The message should fit in one line (fewer than 80
6797 characters), start with a capital letter and end with
6798 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6802 If the script is performing some time consuming task in
6803 the background (not merely starting or stopping a
6804 program, for instance), an ellipsis (three dots:
6805 <tt>...</tt>) should be output to the screen, with no
6806 leading or tailing whitespace or line feeds.
6810 The messages should appear as if the computer is telling
6811 the user what it is doing (politely :-), but should not
6812 mention "it" directly. For example, instead of:
6813 <example compact="compact">
6814 I'm starting network daemons: nfsd mountd.
6816 the message should say
6817 <example compact="compact">
6818 Starting network daemons: nfsd mountd.
6825 <tt>init.d</tt> script should use the following standard
6826 message formats for the situations enumerated below.
6832 <p>When daemons are started</p>
6835 If the script starts one or more daemons, the output
6836 should look like this (a single line, no leading
6838 <example compact="compact">
6839 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6841 The <var>description</var> should describe the
6842 subsystem the daemon or set of daemons are part of,
6843 while <var>daemon-1</var> up to <var>daemon-n</var>
6844 denote each daemon's name (typically the file name of
6849 For example, the output of <file>/etc/init.d/lpd</file>
6851 <example compact="compact">
6852 Starting printer spooler: lpd.
6857 This can be achieved by saying
6858 <example compact="compact">
6859 echo -n "Starting printer spooler: lpd"
6860 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6863 in the script. If there are more than one daemon to
6864 start, the output should look like this:
6865 <example compact="compact">
6866 echo -n "Starting remote file system services:"
6867 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6868 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6869 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6872 This makes it possible for the user to see what is
6873 happening and when the final daemon has been started.
6874 Care should be taken in the placement of white spaces:
6875 in the example above the system administrators can
6876 easily comment out a line if they don't want to start
6877 a specific daemon, while the displayed message still
6883 <p>When a system parameter is being set</p>
6886 If you have to set up different system parameters
6887 during the system boot, you should use this format:
6888 <example compact="compact">
6889 Setting <var>parameter</var> to "<var>value</var>".
6894 You can use a statement such as the following to get
6896 <example compact="compact">
6897 echo "Setting DNS domainname to \"$domainname\"."
6902 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6903 for the left and right quotation marks. A grave accent
6904 (<tt>`</tt>) is not a quote character; neither is an
6905 apostrophe (<tt>'</tt>).
6910 <p>When a daemon is stopped or restarted</p>
6913 When you stop or restart a daemon, you should issue a
6914 message identical to the startup message, except that
6915 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6916 or <tt>Restarting</tt> respectively.
6920 For example, stopping the printer daemon will look like
6922 <example compact="compact">
6923 Stopping printer spooler: lpd.
6929 <p>When something is executed</p>
6932 There are several examples where you have to run a
6933 program at system startup or shutdown to perform a
6934 specific task, for example, setting the system's clock
6935 using <prgn>netdate</prgn> or killing all processes
6936 when the system shuts down. Your message should look
6938 <example compact="compact">
6939 Doing something very useful...done.
6941 You should print the <tt>done.</tt> immediately after
6942 the job has been completed, so that the user is
6943 informed why they have to wait. You can get this
6945 <example compact="compact">
6946 echo -n "Doing something very useful..."
6955 <p>When the configuration is reloaded</p>
6958 When a daemon is forced to reload its configuration
6959 files you should use the following format:
6960 <example compact="compact">
6961 Reloading <var>description</var> configuration...done.
6963 where <var>description</var> is the same as in the
6964 daemon starting message.
6972 <heading>Cron jobs</heading>
6975 Packages must not modify the configuration file
6976 <file>/etc/crontab</file>, and they must not modify the files in
6977 <file>/var/spool/cron/crontabs</file>.</p>
6980 If a package wants to install a job that has to be executed
6981 via cron, it should place a file with the name of the
6982 package in one or more of the following directories:
6983 <example compact="compact">
6989 As these directory names imply, the files within them are
6990 executed on an hourly, daily, weekly, or monthly basis,
6991 respectively. The exact times are listed in
6992 <file>/etc/crontab</file>.</p>
6995 All files installed in any of these directories must be
6996 scripts (e.g., shell scripts or Perl scripts) so that they
6997 can easily be modified by the local system administrator.
6998 In addition, they must be treated as configuration files.
7002 If a certain job has to be executed at some other frequency or
7003 at a specific time, the package should install a file
7004 <file>/etc/cron.d/<var>package</var></file>. This file uses the
7005 same syntax as <file>/etc/crontab</file> and is processed by
7006 <prgn>cron</prgn> automatically. The file must also be
7007 treated as a configuration file. (Note that entries in the
7008 <file>/etc/cron.d</file> directory are not handled by
7009 <prgn>anacron</prgn>. Thus, you should only use this
7010 directory for jobs which may be skipped if the system is not
7013 Unlike <file>crontab</file> files described in the IEEE Std
7014 1003.1-2008 (POSIX.1) available from
7015 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7016 name="The Open Group">, the files in
7017 <file>/etc/cron.d</file> and the file
7018 <file>/etc/crontab</file> have seven fields; namely:
7020 <item>Minute [0,59]</item>
7021 <item>Hour [0,23]</item>
7022 <item>Day of the month [1,31]</item>
7023 <item>Month of the year [1,12]</item>
7024 <item>Day of the week ([0,6] with 0=Sunday)</item>
7025 <item>Username</item>
7026 <item>Command to be run</item>
7028 Ranges of numbers are allowed. Ranges are two numbers
7029 separated with a hyphen. The specified range is inclusive.
7030 Lists are allowed. A list is a set of numbers (or ranges)
7031 separated by commas. Step values can be used in conjunction
7036 The scripts or <tt>crontab</tt> entries in these directories should
7037 check if all necessary programs are installed before they
7038 try to execute them. Otherwise, problems will arise when a
7039 package was removed but not purged since configuration files
7040 are kept on the system in this situation.
7044 Any <tt>cron</tt> daemon must provide
7045 <file>/usr/bin/crontab</file> and support normal
7046 <tt>crontab</tt> entries as specified in POSIX. The daemon
7047 must also support names for days and months, ranges, and
7048 step values. It has to support <file>/etc/crontab</file>,
7049 and correctly execute the scripts in
7050 <file>/etc/cron.d</file>. The daemon must also correctly
7052 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7057 <heading>Menus</heading>
7060 The Debian <tt>menu</tt> package provides a standard
7061 interface between packages providing applications and
7062 <em>menu programs</em> (either X window managers or
7063 text-based menu programs such as <prgn>pdmenu</prgn>).
7067 All packages that provide applications that need not be
7068 passed any special command line arguments for normal
7069 operation should register a menu entry for those
7070 applications, so that users of the <tt>menu</tt> package
7071 will automatically get menu entries in their window
7072 managers, as well in shells like <tt>pdmenu</tt>.
7076 Menu entries should follow the current menu policy.
7080 The menu policy can be found in the <tt>menu-policy</tt>
7081 files in the <tt>debian-policy</tt> package.
7082 It is also available from the Debian web mirrors at
7083 <tt><url name="/doc/packaging-manuals/menu-policy/"
7084 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7088 Please also refer to the <em>Debian Menu System</em>
7089 documentation that comes with the <package>menu</package>
7090 package for information about how to register your
7096 <heading>Multimedia handlers</heading>
7099 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7100 is a mechanism for encoding files and data streams and
7101 providing meta-information about them, in particular their
7102 type (e.g. audio or video) and format (e.g. PNG, HTML,
7107 Registration of MIME type handlers allows programs like mail
7108 user agents and web browsers to invoke these handlers to
7109 view, edit or display MIME types they don't support directly.
7113 Packages which provide the ability to view/show/play,
7114 compose, edit or print MIME types should register themselves
7115 as such following the current MIME support policy.
7119 The MIME support policy can be found in the <tt>mime-policy</tt>
7120 files in the <tt>debian-policy</tt> package.
7121 It is also available from the Debian web mirrors at
7122 <tt><url name="/doc/packaging-manuals/mime-policy/"
7123 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7129 <heading>Keyboard configuration</heading>
7132 To achieve a consistent keyboard configuration so that all
7133 applications interpret a keyboard event the same way, all
7134 programs in the Debian distribution must be configured to
7135 comply with the following guidelines.
7139 The following keys must have the specified interpretations:
7142 <tag><tt><--</tt></tag>
7143 <item>delete the character to the left of the cursor</item>
7145 <tag><tt>Delete</tt></tag>
7146 <item>delete the character to the right of the cursor</item>
7148 <tag><tt>Control+H</tt></tag>
7149 <item>emacs: the help prefix</item>
7152 The interpretation of any keyboard events should be
7153 independent of the terminal that is used, be it a virtual
7154 console, an X terminal emulator, an rlogin/telnet session,
7159 The following list explains how the different programs
7160 should be set up to achieve this:
7166 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7170 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7174 X translations are set up to make
7175 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7176 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7177 is the vt220 escape code for the "delete character"
7178 key). This must be done by loading the X resources
7179 using <prgn>xrdb</prgn> on all local X displays, not
7180 using the application defaults, so that the
7181 translation resources used correspond to the
7182 <prgn>xmodmap</prgn> settings.
7186 The Linux console is configured to make
7187 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7188 generate <tt>ESC [ 3 ~</tt>.
7192 X applications are configured so that <tt><</tt>
7193 deletes left, and <tt>Delete</tt> deletes right. Motif
7194 applications already work like this.
7198 Terminals should have <tt>stty erase ^?</tt> .
7202 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7203 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7204 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7208 Emacs is programmed to map <tt>KB_Backspace</tt> or
7209 the <tt>stty erase</tt> character to
7210 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7211 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7212 <tt>^H</tt> to <tt>help</tt> as always.
7216 Other applications use the <tt>stty erase</tt>
7217 character and <tt>kdch1</tt> for the two delete keys,
7218 with ASCII DEL being "delete previous character" and
7219 <tt>kdch1</tt> being "delete character under
7227 This will solve the problem except for the following
7234 Some terminals have a <tt><--</tt> key that cannot
7235 be made to produce anything except <tt>^H</tt>. On
7236 these terminals Emacs help will be unavailable on
7237 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7238 character takes precedence in Emacs, and has been set
7239 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7240 available) can be used instead.
7244 Some operating systems use <tt>^H</tt> for <tt>stty
7245 erase</tt>. However, modern telnet versions and all
7246 rlogin versions propagate <tt>stty</tt> settings, and
7247 almost all UNIX versions honour <tt>stty erase</tt>.
7248 Where the <tt>stty</tt> settings are not propagated
7249 correctly, things can be made to work by using
7250 <tt>stty</tt> manually.
7254 Some systems (including previous Debian versions) use
7255 <prgn>xmodmap</prgn> to arrange for both
7256 <tt><--</tt> and <tt>Delete</tt> to generate
7257 <tt>KB_Delete</tt>. We can change the behavior of
7258 their X clients using the same X resources that we use
7259 to do it for our own clients, or configure our clients
7260 using their resources when things are the other way
7261 around. On displays configured like this
7262 <tt>Delete</tt> will not work, but <tt><--</tt>
7267 Some operating systems have different <tt>kdch1</tt>
7268 settings in their <tt>terminfo</tt> database for
7269 <tt>xterm</tt> and others. On these systems the
7270 <tt>Delete</tt> key will not work correctly when you
7271 log in from a system conforming to our policy, but
7272 <tt><--</tt> will.
7279 <heading>Environment variables</heading>
7282 A program must not depend on environment variables to get
7283 reasonable defaults. (That's because these environment
7284 variables would have to be set in a system-wide
7285 configuration file like <file>/etc/profile</file>, which is not
7286 supported by all shells.)
7290 If a program usually depends on environment variables for its
7291 configuration, the program should be changed to fall back to
7292 a reasonable default configuration if these environment
7293 variables are not present. If this cannot be done easily
7294 (e.g., if the source code of a non-free program is not
7295 available), the program must be replaced by a small
7296 "wrapper" shell script which sets the environment variables
7297 if they are not already defined, and calls the original program.
7301 Here is an example of a wrapper script for this purpose:
7303 <example compact="compact">
7305 BAR=${BAR:-/var/lib/fubar}
7307 exec /usr/lib/foo/foo "$@"
7312 Furthermore, as <file>/etc/profile</file> is a configuration
7313 file of the <prgn>base-files</prgn> package, other packages must
7314 not put any environment variables or other commands into that
7319 <sect id="doc-base">
7320 <heading>Registering Documents using doc-base</heading>
7323 The <package>doc-base</package> package implements a
7324 flexible mechanism for handling and presenting
7325 documentation. The recommended practice is for every Debian
7326 package that provides online documentation (other than just
7327 manual pages) to register these documents with
7328 <package>doc-base</package> by installing a
7329 <package>doc-base</package> control file via the
7330 <prgn/install-docs/ script at installation time and
7331 de-register the manuals again when the package is removed.
7334 Please refer to the documentation that comes with the
7335 <package>doc-base</package> package for information and
7344 <heading>Files</heading>
7346 <sect id="binaries">
7347 <heading>Binaries</heading>
7350 Two different packages must not install programs with
7351 different functionality but with the same filenames. (The
7352 case of two programs having the same functionality but
7353 different implementations is handled via "alternatives" or
7354 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7355 <ref id="conflicts"> respectively.) If this case happens,
7356 one of the programs must be renamed. The maintainers should
7357 report this to the <tt>debian-devel</tt> mailing list and
7358 try to find a consensus about which program will have to be
7359 renamed. If a consensus cannot be reached, <em>both</em>
7360 programs must be renamed.
7364 By default, when a package is being built, any binaries
7365 created should include debugging information, as well as
7366 being compiled with optimization. You should also turn on
7367 as many reasonable compilation warnings as possible; this
7368 makes life easier for porters, who can then look at build
7369 logs for possible problems. For the C programming language,
7370 this means the following compilation parameters should be
7372 <example compact="compact">
7374 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7376 INSTALL = install -s # (or use strip on the files in debian/tmp)
7381 Note that by default all installed binaries should be stripped,
7382 either by using the <tt>-s</tt> flag to
7383 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7384 the binaries after they have been copied into
7385 <file>debian/tmp</file> but before the tree is made into a
7390 Although binaries in the build tree should be compiled with
7391 debugging information by default, it can often be difficult to
7392 debug programs if they are also subjected to compiler
7393 optimization. For this reason, it is recommended to support the
7394 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7395 (see <ref id="debianrules-options">). This variable can contain
7396 several flags to change how a package is compiled and built.
7400 It is up to the package maintainer to decide what
7401 compilation options are best for the package. Certain
7402 binaries (such as computationally-intensive programs) will
7403 function better with certain flags (<tt>-O3</tt>, for
7404 example); feel free to use them. Please use good judgment
7405 here. Don't use flags for the sake of it; only use them
7406 if there is good reason to do so. Feel free to override
7407 the upstream author's ideas about which compilation
7408 options are best: they are often inappropriate for our
7414 <sect id="libraries">
7415 <heading>Libraries</heading>
7418 If the package is <strong>architecture: any</strong>, then
7419 the shared library compilation and linking flags must have
7420 <tt>-fPIC</tt>, or the package shall not build on some of
7421 the supported architectures<footnote>
7423 If you are using GCC, <tt>-fPIC</tt> produces code with
7424 relocatable position independent code, which is required for
7425 most architectures to create a shared library, with i386 and
7426 perhaps some others where non position independent code is
7427 permitted in a shared library.
7430 Position independent code may have a performance penalty,
7431 especially on <tt>i386</tt>. However, in most cases the
7432 speed penalty must be measured against the memory wasted on
7433 the few architectures where non position independent code is
7436 </footnote>. Any exception to this rule must be discussed on
7437 the mailing list <em>debian-devel@lists.debian.org</em>, and
7438 a rough consensus obtained. The reasons for not compiling
7439 with <tt>-fPIC</tt> flag must be recorded in the file
7440 <tt>README.Debian</tt>, and care must be taken to either
7441 restrict the architecture or arrange for <tt>-fPIC</tt> to
7442 be used on architectures where it is required.<footnote>
7444 Some of the reasons why this might be required is if the
7445 library contains hand crafted assembly code that is not
7446 relocatable, the speed penalty is excessive for compute
7447 intensive libs, and similar reasons.
7452 As to the static libraries, the common case is not to have
7453 relocatable code, since there is no benefit, unless in specific
7454 cases; therefore the static version must not be compiled
7455 with the <tt>-fPIC</tt> flag. Any exception to this rule
7456 should be discussed on the mailing list
7457 <em>debian-devel@lists.debian.org</em>, and the reasons for
7458 compiling with the <tt>-fPIC</tt> flag must be recorded in
7459 the file <tt>README.Debian</tt>. <footnote>
7461 Some of the reasons for linking static libraries with
7462 the <tt>-fPIC</tt> flag are if, for example, one needs a
7463 Perl API for a library that is under rapid development,
7464 and has an unstable API, so shared libraries are
7465 pointless at this phase of the library's development. In
7466 that case, since Perl needs a library with relocatable
7467 code, it may make sense to create a static library with
7468 relocatable code. Another reason cited is if you are
7469 distilling various libraries into a common shared
7470 library, like <tt>mklibs</tt> does in the Debian
7476 In other words, if both a shared and a static library is
7477 being built, each source unit (<tt>*.c</tt>, for example,
7478 for C files) will need to be compiled twice, for the normal
7483 Libraries should be built with threading support and to be
7484 thread-safe if the library supports this.
7488 Although not enforced by the build tools, shared libraries
7489 must be linked against all libraries that they use symbols from
7490 in the same way that binaries are. This ensures the correct
7491 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7492 system and guarantees that all libraries can be safely opened
7493 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7494 option <tt>-Wl,-z,defs</tt> when building a shared library.
7495 Since this option enforces symbol resolution at build time,
7496 a missing library reference will be caught early as a fatal
7501 All installed shared libraries should be stripped with
7502 <example compact="compact">
7503 strip --strip-unneeded <var>your-lib</var>
7505 (The option <tt>--strip-unneeded</tt> makes
7506 <prgn>strip</prgn> remove only the symbols which aren't
7507 needed for relocation processing.) Shared libraries can
7508 function perfectly well when stripped, since the symbols for
7509 dynamic linking are in a separate part of the ELF object
7511 You might also want to use the options
7512 <tt>--remove-section=.comment</tt> and
7513 <tt>--remove-section=.note</tt> on both shared libraries
7514 and executables, and <tt>--strip-debug</tt> on static
7520 Note that under some circumstances it may be useful to
7521 install a shared library unstripped, for example when
7522 building a separate package to support debugging.
7526 Shared object files (often <file>.so</file> files) that are not
7527 public libraries, that is, they are not meant to be linked
7528 to by third party executables (binaries of other packages),
7529 should be installed in subdirectories of the
7530 <file>/usr/lib</file> directory. Such files are exempt from the
7531 rules that govern ordinary shared libraries, except that
7532 they must not be installed executable and should be
7534 A common example are the so-called "plug-ins",
7535 internal shared objects that are dynamically loaded by
7536 programs using <manref name="dlopen" section="3">.
7541 Packages that use <prgn>libtool</prgn> to create and install
7542 their shared libraries install a file containing additional
7543 metadata (ending in <file>.la</file>) alongside the library.
7544 For public libraries intended for use by other packages, these
7545 files normally should not be included in the Debian package,
7546 since the information they include is not necessary to link with
7547 the shared library on Debian and can add unnecessary additional
7548 dependencies to other programs or libraries.<footnote>
7549 These files store, among other things, all libraries on which
7550 that shared library depends. Unfortunately, if
7551 the <file>.la</file> file is present and contains that
7552 dependency information, using <prgn>libtool</prgn> when
7553 linking against that library will cause the resulting program
7554 or library to be linked against those dependencies as well,
7555 even if this is unnecessary. This can create unneeded
7556 dependencies on shared library packages that would otherwise
7557 be hidden behind the library ABI, and can make library
7558 transitions to new SONAMEs unnecessarily complicated and
7559 difficult to manage.
7561 If the <file>.la</file> file is required for that library (if,
7562 for instance, it's loaded via <tt>libltdl</tt> in a way that
7563 requires that meta-information), the <tt>dependency_libs</tt>
7564 setting in the <file>.la</file> file should normally be set to
7565 the empty string. If the shared library development package has
7566 historically included the <file>.la</file>, it must be retained
7567 in the development package (with <tt>dependency_libs</tt>
7568 emptied) until all libraries that depend on it have removed or
7569 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7570 files to prevent linking with those other libraries
7571 using <prgn>libtool</prgn> from failing.
7575 If the <file>.la</file> must be included, it should be included
7576 in the development (<tt>-dev</tt>) package, unless the library
7577 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7578 library. If it is intended for use with <tt>libltdl</tt>,
7579 the <file>.la</file> files must go in the run-time library
7584 These requirements for handling of <file>.la</file> files do not
7585 apply to loadable modules or libraries not installed in
7586 directories searched by default by the dynamic linker. Packages
7587 installing loadable modules will frequently need to install
7588 the <file>.la</file> files alongside the modules so that they
7589 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7590 does not need to be modified for libraries or modules that are
7591 not installed in directories searched by the dynamic linker by
7592 default and not intended for use by other packages.
7596 You must make sure that you use only released versions of
7597 shared libraries to build your packages; otherwise other
7598 users will not be able to run your binaries
7599 properly. Producing source packages that depend on
7600 unreleased compilers is also usually a bad
7607 <heading>Shared libraries</heading>
7609 This section has moved to <ref id="sharedlibs">.
7615 <heading>Scripts</heading>
7618 All command scripts, including the package maintainer
7619 scripts inside the package and used by <prgn>dpkg</prgn>,
7620 should have a <tt>#!</tt> line naming the shell to be used
7625 In the case of Perl scripts this should be
7626 <tt>#!/usr/bin/perl</tt>.
7630 When scripts are installed into a directory in the system
7631 PATH, the script name should not include an extension such
7632 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7633 language currently used to implement it.
7636 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7637 <file>init.d</file> scripts should almost certainly start
7638 with <tt>set -e</tt> so that errors are detected.
7639 <file>init.d</file> scripts are something of a special case, due
7640 to how frequently they need to call commands that are allowed to
7641 fail, and it may instead be easier to check the exit status of
7642 commands directly. See <ref id="writing-init"> for more
7643 information about writing <file>init.d</file> scripts.
7646 Every script should use <tt>set -e</tt> or check the exit status
7647 of <em>every</em> command.
7650 Scripts may assume that <file>/bin/sh</file> implements the
7651 SUSv3 Shell Command Language<footnote>
7652 Single UNIX Specification, version 3, which is also IEEE
7653 1003.1-2004 (POSIX), and is available on the World Wide Web
7654 from <url id="http://www.unix.org/version3/online.html"
7655 name="The Open Group"> after free
7656 registration.</footnote>
7657 plus the following additional features not mandated by
7659 These features are in widespread use in the Linux community
7660 and are implemented in all of bash, dash, and ksh, the most
7661 common shells users may wish to use as <file>/bin/sh</file>.
7664 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7665 must not generate a newline.</item>
7666 <item><tt>test</tt>, if implemented as a shell built-in, must
7667 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7669 <item><tt>local</tt> to create a scoped variable must be
7670 supported, including listing multiple variables in a single
7671 local command and assigning a value to a variable at the
7672 same time as localizing it. <tt>local</tt> may or
7673 may not preserve the variable value from an outer scope if
7674 no assignment is present. Uses such as:
7678 # ... use a, b, c, d ...
7681 must be supported and must set the value of <tt>c</tt> to
7684 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7685 -<var>signal</var></tt>, where <var>signal</var> is either
7686 the name of a signal or one of the numeric signals listed in
7687 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7688 supported if <prgn>kill</prgn> is implemented as a shell
7691 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7692 signals must be supported. In addition to the signal
7693 numbers listed in the extension, which are the same as for
7694 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7697 If a shell script requires non-SUSv3 features from the shell
7698 interpreter other than those listed above, the appropriate shell
7699 must be specified in the first line of the script (e.g.,
7700 <tt>#!/bin/bash</tt>) and the package must depend on the package
7701 providing the shell (unless the shell package is marked
7702 "Essential", as in the case of <prgn>bash</prgn>).
7706 You may wish to restrict your script to SUSv3 features plus the
7707 above set when possible so that it may use <file>/bin/sh</file>
7708 as its interpreter. If your script works with <prgn>dash</prgn>
7709 (originally called <prgn>ash</prgn>), it probably complies with
7710 the above requirements, but if you are in doubt, use
7711 <file>/bin/bash</file>.
7715 Perl scripts should check for errors when making any
7716 system calls, including <tt>open</tt>, <tt>print</tt>,
7717 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7721 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7722 scripting languages. See <em>Csh Programming Considered
7723 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7724 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7725 If an upstream package comes with <prgn>csh</prgn> scripts
7726 then you must make sure that they start with
7727 <tt>#!/bin/csh</tt> and make your package depend on the
7728 <prgn>c-shell</prgn> virtual package.
7732 Any scripts which create files in world-writeable
7733 directories (e.g., in <file>/tmp</file>) must use a
7734 mechanism which will fail atomically if a file with the same
7735 name already exists.
7739 The Debian base system provides the <prgn>tempfile</prgn>
7740 and <prgn>mktemp</prgn> utilities for use by scripts for
7747 <heading>Symbolic links</heading>
7750 In general, symbolic links within a top-level directory
7751 should be relative, and symbolic links pointing from one
7752 top-level directory into another should be absolute. (A
7753 top-level directory is a sub-directory of the root
7754 directory <file>/</file>.)
7758 In addition, symbolic links should be specified as short as
7759 possible, i.e., link targets like <file>foo/../bar</file> are
7764 Note that when creating a relative link using
7765 <prgn>ln</prgn> it is not necessary for the target of the
7766 link to exist relative to the working directory you're
7767 running <prgn>ln</prgn> from, nor is it necessary to change
7768 directory to the directory where the link is to be made.
7769 Simply include the string that should appear as the target
7770 of the link (this will be a pathname relative to the
7771 directory in which the link resides) as the first argument
7776 For example, in your <prgn>Makefile</prgn> or
7777 <file>debian/rules</file>, you can do things like:
7778 <example compact="compact">
7779 ln -fs gcc $(prefix)/bin/cc
7780 ln -fs gcc debian/tmp/usr/bin/cc
7781 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7782 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7787 A symbolic link pointing to a compressed file should always
7788 have the same file extension as the referenced file. (For
7789 example, if a file <file>foo.gz</file> is referenced by a
7790 symbolic link, the filename of the link has to end with
7791 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7796 <heading>Device files</heading>
7799 Packages must not include device files or named pipes in the
7804 If a package needs any special device files that are not
7805 included in the base system, it must call
7806 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7807 after notifying the user<footnote>
7808 This notification could be done via a (low-priority)
7809 debconf message, or an echo (printf) statement.
7814 Packages must not remove any device files in the
7815 <prgn>postrm</prgn> or any other script. This is left to the
7816 system administrator.
7820 Debian uses the serial devices
7821 <file>/dev/ttyS*</file>. Programs using the old
7822 <file>/dev/cu*</file> devices should be changed to use
7823 <file>/dev/ttyS*</file>.
7827 Named pipes needed by the package must be created in
7828 the <prgn>postinst</prgn> script<footnote>
7829 It's better to use <prgn>mkfifo</prgn> rather
7830 than <prgn>mknod</prgn> to create named pipes so that
7831 automated checks for packages incorrectly creating device
7832 files with <prgn>mknod</prgn> won't have false positives.
7833 </footnote> and removed in
7834 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7839 <sect id="config-files">
7840 <heading>Configuration files</heading>
7843 <heading>Definitions</heading>
7847 <tag>configuration file</tag>
7849 A file that affects the operation of a program, or
7850 provides site- or host-specific information, or
7851 otherwise customizes the behavior of a program.
7852 Typically, configuration files are intended to be
7853 modified by the system administrator (if needed or
7854 desired) to conform to local policy or to provide
7855 more useful site-specific behavior.
7858 <tag><tt>conffile</tt></tag>
7860 A file listed in a package's <tt>conffiles</tt>
7861 file, and is treated specially by <prgn>dpkg</prgn>
7862 (see <ref id="configdetails">).
7868 The distinction between these two is important; they are
7869 not interchangeable concepts. Almost all
7870 <tt>conffile</tt>s are configuration files, but many
7871 configuration files are not <tt>conffiles</tt>.
7875 As noted elsewhere, <file>/etc/init.d</file> scripts,
7876 <file>/etc/default</file> files, scripts installed in
7877 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7878 configuration installed in <file>/etc/cron.d</file> must be
7879 treated as configuration files. In general, any script that
7880 embeds configuration information is de-facto a configuration
7881 file and should be treated as such.
7886 <heading>Location</heading>
7889 Any configuration files created or used by your package
7890 must reside in <file>/etc</file>. If there are several,
7891 consider creating a subdirectory of <file>/etc</file>
7892 named after your package.
7896 If your package creates or uses configuration files
7897 outside of <file>/etc</file>, and it is not feasible to modify
7898 the package to use <file>/etc</file> directly, put the files
7899 in <file>/etc</file> and create symbolic links to those files
7900 from the location that the package requires.
7905 <heading>Behavior</heading>
7908 Configuration file handling must conform to the following
7910 <list compact="compact">
7912 local changes must be preserved during a package
7916 configuration files must be preserved when the
7917 package is removed, and only deleted when the
7921 Obsolete configuration files without local changes may be
7922 removed by the package during upgrade.
7926 The easy way to achieve this behavior is to make the
7927 configuration file a <tt>conffile</tt>. This is
7928 appropriate only if it is possible to distribute a default
7929 version that will work for most installations, although
7930 some system administrators may choose to modify it. This
7931 implies that the default version will be part of the
7932 package distribution, and must not be modified by the
7933 maintainer scripts during installation (or at any other
7938 In order to ensure that local changes are preserved
7939 correctly, no package may contain or make hard links to
7940 conffiles.<footnote>
7941 Rationale: There are two problems with hard links.
7942 The first is that some editors break the link while
7943 editing one of the files, so that the two files may
7944 unwittingly become unlinked and different. The second
7945 is that <prgn>dpkg</prgn> might break the hard link
7946 while upgrading <tt>conffile</tt>s.
7951 The other way to do it is via the maintainer scripts. In
7952 this case, the configuration file must not be listed as a
7953 <tt>conffile</tt> and must not be part of the package
7954 distribution. If the existence of a file is required for
7955 the package to be sensibly configured it is the
7956 responsibility of the package maintainer to provide
7957 maintainer scripts which correctly create, update and
7958 maintain the file and remove it on purge. (See <ref
7959 id="maintainerscripts"> for more information.) These
7960 scripts must be idempotent (i.e., must work correctly if
7961 <prgn>dpkg</prgn> needs to re-run them due to errors
7962 during installation or removal), must cope with all the
7963 variety of ways <prgn>dpkg</prgn> can call maintainer
7964 scripts, must not overwrite or otherwise mangle the user's
7965 configuration without asking, must not ask unnecessary
7966 questions (particularly during upgrades), and must
7967 otherwise be good citizens.
7971 The scripts are not required to configure every possible
7972 option for the package, but only those necessary to get
7973 the package running on a given system. Ideally the
7974 sysadmin should not have to do any configuration other
7975 than that done (semi-)automatically by the
7976 <prgn>postinst</prgn> script.
7980 A common practice is to create a script called
7981 <file><var>package</var>-configure</file> and have the
7982 package's <prgn>postinst</prgn> call it if and only if the
7983 configuration file does not already exist. In certain
7984 cases it is useful for there to be an example or template
7985 file which the maintainer scripts use. Such files should
7986 be in <file>/usr/share/<var>package</var></file> or
7987 <file>/usr/lib/<var>package</var></file> (depending on whether
7988 they are architecture-independent or not). There should
7989 be symbolic links to them from
7990 <file>/usr/share/doc/<var>package</var>/examples</file> if
7991 they are examples, and should be perfectly ordinary
7992 <prgn>dpkg</prgn>-handled files (<em>not</em>
7993 configuration files).
7997 These two styles of configuration file handling must
7998 not be mixed, for that way lies madness:
7999 <prgn>dpkg</prgn> will ask about overwriting the file
8000 every time the package is upgraded.
8005 <heading>Sharing configuration files</heading>
8008 Packages which specify the same file as a
8009 <tt>conffile</tt> must be tagged as <em>conflicting</em>
8010 with each other. (This is an instance of the general rule
8011 about not sharing files. Note that neither alternatives
8012 nor diversions are likely to be appropriate in this case;
8013 in particular, <prgn>dpkg</prgn> does not handle diverted
8014 <tt>conffile</tt>s well.)
8018 The maintainer scripts must not alter a <tt>conffile</tt>
8019 of <em>any</em> package, including the one the scripts
8024 If two or more packages use the same configuration file
8025 and it is reasonable for both to be installed at the same
8026 time, one of these packages must be defined as
8027 <em>owner</em> of the configuration file, i.e., it will be
8028 the package which handles that file as a configuration
8029 file. Other packages that use the configuration file must
8030 depend on the owning package if they require the
8031 configuration file to operate. If the other package will
8032 use the configuration file if present, but is capable of
8033 operating without it, no dependency need be declared.
8037 If it is desirable for two or more related packages to
8038 share a configuration file <em>and</em> for all of the
8039 related packages to be able to modify that configuration
8040 file, then the following should be done:
8041 <enumlist compact="compact">
8043 One of the related packages (the "owning" package)
8044 will manage the configuration file with maintainer
8045 scripts as described in the previous section.
8048 The owning package should also provide a program
8049 that the other packages may use to modify the
8053 The related packages must use the provided program
8054 to make any desired modifications to the
8055 configuration file. They should either depend on
8056 the core package to guarantee that the configuration
8057 modifier program is available or accept gracefully
8058 that they cannot modify the configuration file if it
8059 is not. (This is in addition to the fact that the
8060 configuration file may not even be present in the
8067 Sometimes it's appropriate to create a new package which
8068 provides the basic infrastructure for the other packages
8069 and which manages the shared configuration files. (The
8070 <tt>sgml-base</tt> package is a good example.)
8075 <heading>User configuration files ("dotfiles")</heading>
8078 The files in <file>/etc/skel</file> will automatically be
8079 copied into new user accounts by <prgn>adduser</prgn>.
8080 No other program should reference the files in
8081 <file>/etc/skel</file>.
8085 Therefore, if a program needs a dotfile to exist in
8086 advance in <file>$HOME</file> to work sensibly, that dotfile
8087 should be installed in <file>/etc/skel</file> and treated as a
8092 However, programs that require dotfiles in order to
8093 operate sensibly are a bad thing, unless they do create
8094 the dotfiles themselves automatically.
8098 Furthermore, programs should be configured by the Debian
8099 default installation to behave as closely to the upstream
8100 default behavior as possible.
8104 Therefore, if a program in a Debian package needs to be
8105 configured in some way in order to operate sensibly, that
8106 should be done using a site-wide configuration file placed
8107 in <file>/etc</file>. Only if the program doesn't support a
8108 site-wide default configuration and the package maintainer
8109 doesn't have time to add it may a default per-user file be
8110 placed in <file>/etc/skel</file>.
8114 <file>/etc/skel</file> should be as empty as we can make it.
8115 This is particularly true because there is no easy (or
8116 necessarily desirable) mechanism for ensuring that the
8117 appropriate dotfiles are copied into the accounts of
8118 existing users when a package is installed.
8124 <heading>Log files</heading>
8126 Log files should usually be named
8127 <file>/var/log/<var>package</var>.log</file>. If you have many
8128 log files, or need a separate directory for permission
8129 reasons (<file>/var/log</file> is writable only by
8130 <file>root</file>), you should usually create a directory named
8131 <file>/var/log/<var>package</var></file> and place your log
8136 Log files must be rotated occasionally so that they don't grow
8137 indefinitely. The best way to do this is to install a log
8138 rotation configuration file in the
8139 directory <file>/etc/logrotate.d</file>, normally
8140 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8141 the facilities provided by <prgn>logrotate</prgn>.
8144 The traditional approach to log files has been to set up
8145 <em>ad hoc</em> log rotation schemes using simple shell
8146 scripts and cron. While this approach is highly
8147 customizable, it requires quite a lot of sysadmin work.
8148 Even though the original Debian system helped a little
8149 by automatically installing a system which can be used
8150 as a template, this was deemed not enough.
8154 The use of <prgn>logrotate</prgn>, a program developed
8155 by Red Hat, is better, as it centralizes log management.
8156 It has both a configuration file
8157 (<file>/etc/logrotate.conf</file>) and a directory where
8158 packages can drop their individual log rotation
8159 configurations (<file>/etc/logrotate.d</file>).
8162 Here is a good example for a logrotate config
8163 file (for more information see <manref name="logrotate"
8165 <example compact="compact">
8166 /var/log/foo/*.log {
8172 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8176 This rotates all files under <file>/var/log/foo</file>, saves 12
8177 compressed generations, and tells the daemon to reopen its log
8178 files after the log rotation. It skips this log rotation
8179 (via <tt>missingok</tt>) if no such log file is present, which
8180 avoids errors if the package is removed but not purged.
8184 Log files should be removed when the package is
8185 purged (but not when it is only removed). This should be
8186 done by the <prgn>postrm</prgn> script when it is called
8187 with the argument <tt>purge</tt> (see <ref
8188 id="removedetails">).
8192 <sect id="permissions-owners">
8193 <heading>Permissions and owners</heading>
8196 The rules in this section are guidelines for general use.
8197 If necessary you may deviate from the details below.
8198 However, if you do so you must make sure that what is done
8199 is secure and you should try to be as consistent as possible
8200 with the rest of the system. You should probably also
8201 discuss it on <prgn>debian-devel</prgn> first.
8205 Files should be owned by <tt>root:root</tt>, and made
8206 writable only by the owner and universally readable (and
8207 executable, if appropriate), that is mode 644 or 755.
8211 Directories should be mode 755 or (for group-writability)
8212 mode 2775. The ownership of the directory should be
8213 consistent with its mode: if a directory is mode 2775, it
8214 should be owned by the group that needs write access to
8217 When a package is upgraded, and the owner or permissions
8218 of a file included in the package has changed, dpkg
8219 arranges for the ownership and permissions to be
8220 correctly set upon installation. However, this does not
8221 extend to directories; the permissions and ownership of
8222 directories already on the system does not change on
8223 install or upgrade of packages. This makes sense, since
8224 otherwise common directories like <tt>/usr</tt> would
8225 always be in flux. To correctly change permissions of a
8226 directory the package owns, explicit action is required,
8227 usually in the <tt>postinst</tt> script. Care must be
8228 taken to handle downgrades as well, in that case.
8234 Control information files should be owned by <tt>root:root</tt>
8235 and either mode 644 (for most files) or mode 755 (for
8236 executables such as <qref id="maintscripts">maintainer
8241 Setuid and setgid executables should be mode 4755 or 2755
8242 respectively, and owned by the appropriate user or group.
8243 They should not be made unreadable (modes like 4711 or
8244 2711 or even 4111); doing so achieves no extra security,
8245 because anyone can find the binary in the freely available
8246 Debian package; it is merely inconvenient. For the same
8247 reason you should not restrict read or execute permissions
8248 on non-set-id executables.
8252 Some setuid programs need to be restricted to particular
8253 sets of users, using file permissions. In this case they
8254 should be owned by the uid to which they are set-id, and by
8255 the group which should be allowed to execute them. They
8256 should have mode 4754; again there is no point in making
8257 them unreadable to those users who must not be allowed to
8262 It is possible to arrange that the system administrator can
8263 reconfigure the package to correspond to their local
8264 security policy by changing the permissions on a binary:
8265 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8266 described below.<footnote>
8267 Ordinary files installed by <prgn>dpkg</prgn> (as
8268 opposed to <tt>conffile</tt>s and other similar objects)
8269 normally have their permissions reset to the distributed
8270 permissions when the package is reinstalled. However,
8271 the use of <prgn>dpkg-statoverride</prgn> overrides this
8274 Another method you should consider is to create a group for
8275 people allowed to use the program(s) and make any setuid
8276 executables executable only by that group.
8280 If you need to create a new user or group for your package
8281 there are two possibilities. Firstly, you may need to
8282 make some files in the binary package be owned by this
8283 user or group, or you may need to compile the user or
8284 group id (rather than just the name) into the binary
8285 (though this latter should be avoided if possible, as in
8286 this case you need a statically allocated id).</p>
8289 If you need a statically allocated id, you must ask for a
8290 user or group id from the <tt>base-passwd</tt> maintainer,
8291 and must not release the package until you have been
8292 allocated one. Once you have been allocated one you must
8293 either make the package depend on a version of the
8294 <tt>base-passwd</tt> package with the id present in
8295 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8296 your package to create the user or group itself with the
8297 correct id (using <tt>adduser</tt>) in its
8298 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8299 the <prgn>postinst</prgn> is to be preferred if it is
8300 possible, otherwise a pre-dependency will be needed on the
8301 <tt>adduser</tt> package.)
8305 On the other hand, the program might be able to determine
8306 the uid or gid from the user or group name at runtime, so
8307 that a dynamically allocated id can be used. In this case
8308 you should choose an appropriate user or group name,
8309 discussing this on <prgn>debian-devel</prgn> and checking
8310 with the <package/base-passwd/ maintainer that it is unique and that
8311 they do not wish you to use a statically allocated id
8312 instead. When this has been checked you must arrange for
8313 your package to create the user or group if necessary using
8314 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8315 <prgn>postinst</prgn> script (again, the latter is to be
8316 preferred if it is possible).
8320 Note that changing the numeric value of an id associated
8321 with a name is very difficult, and involves searching the
8322 file system for all appropriate files. You need to think
8323 carefully whether a static or dynamic id is required, since
8324 changing your mind later will cause problems.
8327 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8329 This section is not intended as policy, but as a
8330 description of the use of <prgn>dpkg-statoverride</prgn>.
8334 If a system administrator wishes to have a file (or
8335 directory or other such thing) installed with owner and
8336 permissions different from those in the distributed Debian
8337 package, they can use the <prgn>dpkg-statoverride</prgn>
8338 program to instruct <prgn>dpkg</prgn> to use the different
8339 settings every time the file is installed. Thus the
8340 package maintainer should distribute the files with their
8341 normal permissions, and leave it for the system
8342 administrator to make any desired changes. For example, a
8343 daemon which is normally required to be setuid root, but
8344 in certain situations could be used without being setuid,
8345 should be installed setuid in the <tt>.deb</tt>. Then the
8346 local system administrator can change this if they wish.
8347 If there are two standard ways of doing it, the package
8348 maintainer can use <tt>debconf</tt> to find out the
8349 preference, and call <prgn>dpkg-statoverride</prgn> in the
8350 maintainer script if necessary to accommodate the system
8351 administrator's choice. Care must be taken during
8352 upgrades to not override an existing setting.
8356 Given the above, <prgn>dpkg-statoverride</prgn> is
8357 essentially a tool for system administrators and would not
8358 normally be needed in the maintainer scripts. There is
8359 one type of situation, though, where calls to
8360 <prgn>dpkg-statoverride</prgn> would be needed in the
8361 maintainer scripts, and that involves packages which use
8362 dynamically allocated user or group ids. In such a
8363 situation, something like the following idiom can be very
8364 helpful in the package's <prgn>postinst</prgn>, where
8365 <tt>sysuser</tt> is a dynamically allocated id:
8367 for i in /usr/bin/foo /usr/sbin/bar
8369 # only do something when no setting exists
8370 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8372 #include: debconf processing, question about foo and bar
8373 if [ "$RET" = "true" ] ; then
8374 dpkg-statoverride --update --add sysuser root 4755 $i
8379 The corresponding code to remove the override when the package
8382 for i in /usr/bin/foo /usr/sbin/bar
8384 if dpkg-statoverride --list $i >/dev/null 2>&1
8386 dpkg-statoverride --remove $i
8396 <chapt id="customized-programs">
8397 <heading>Customized programs</heading>
8399 <sect id="arch-spec">
8400 <heading>Architecture specification strings</heading>
8403 If a program needs to specify an <em>architecture specification
8404 string</em> in some place, it should select one of the strings
8405 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8406 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8407 part is sometimes elided, as when the OS is Linux.
8411 Note that we don't want to use
8412 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8413 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8414 since this would make our programs incompatible with other
8415 Linux distributions. We also don't use something like
8416 <tt><var>arch</var>-unknown-linux</tt>, since the
8417 <tt>unknown</tt> does not look very good.
8420 <sect1 id="arch-wildcard-spec">
8421 <heading>Architecture wildcards</heading>
8424 A package may specify an architecture wildcard. Architecture
8425 wildcards are in the format <tt>any</tt> (which matches every
8426 architecture), <tt><var>os</var></tt>-any, or
8427 any-<tt><var>cpu</var></tt>. <footnote>
8428 Internally, the package system normalizes the GNU triplets
8429 and the Debian arches into Debian arch triplets (which are
8430 kind of inverted GNU triplets), with the first component of
8431 the triplet representing the libc and ABI in use, and then
8432 does matching against those triplets. However, such
8433 triplets are an internal implementation detail that should
8434 not be used by packages directly. The libc and ABI portion
8435 is handled internally by the package system based on
8436 the <var>os</var> and <var>cpu</var>.
8443 <heading>Daemons</heading>
8446 The configuration files <file>/etc/services</file>,
8447 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8448 by the <prgn>netbase</prgn> package and must not be modified
8453 If a package requires a new entry in one of these files, the
8454 maintainer should get in contact with the
8455 <prgn>netbase</prgn> maintainer, who will add the entries
8456 and release a new version of the <prgn>netbase</prgn>
8461 The configuration file <file>/etc/inetd.conf</file> must not be
8462 modified by the package's scripts except via the
8463 <prgn>update-inetd</prgn> script or the
8464 <file>DebianNet.pm</file> Perl module. See their documentation
8465 for details on how to add entries.
8469 If a package wants to install an example entry into
8470 <file>/etc/inetd.conf</file>, the entry must be preceded with
8471 exactly one hash character (<tt>#</tt>). Such lines are
8472 treated as "commented out by user" by the
8473 <prgn>update-inetd</prgn> script and are not changed or
8474 activated during package updates.
8479 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8483 Some programs need to create pseudo-ttys. This should be done
8484 using Unix98 ptys if the C library supports it. The resulting
8485 program must not be installed setuid root, unless that
8486 is required for other functionality.
8490 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8491 <file>/var/log/lastlog</file> must be installed writable by
8492 group <tt>utmp</tt>. Programs which need to modify those
8493 files must be installed setgid <tt>utmp</tt>.
8498 <heading>Editors and pagers</heading>
8501 Some programs have the ability to launch an editor or pager
8502 program to edit or display a text document. Since there are
8503 lots of different editors and pagers available in the Debian
8504 distribution, the system administrator and each user should
8505 have the possibility to choose their preferred editor and
8510 In addition, every program should choose a good default
8511 editor/pager if none is selected by the user or system
8516 Thus, every program that launches an editor or pager must
8517 use the EDITOR or PAGER environment variable to determine
8518 the editor or pager the user wishes to use. If these
8519 variables are not set, the programs <file>/usr/bin/editor</file>
8520 and <file>/usr/bin/pager</file> should be used, respectively.
8524 These two files are managed through the <prgn>dpkg</prgn>
8525 "alternatives" mechanism. Every package providing an editor or
8526 pager must call the <prgn>update-alternatives</prgn> script to
8527 register as an alternative for <file>/usr/bin/editor</file>
8528 or <file>/usr/bin/pager</file> as appropriate. The alternative
8529 should have a slave alternative
8530 for <file>/usr/share/man/man1/editor.1.gz</file>
8531 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8532 corresponding manual page.
8536 If it is very hard to adapt a program to make use of the
8537 EDITOR or PAGER variables, that program may be configured to
8538 use <file>/usr/bin/sensible-editor</file> and
8539 <file>/usr/bin/sensible-pager</file> as the editor or pager
8540 program respectively. These are two scripts provided in the
8541 <package>sensible-utils</package> package that check the EDITOR
8542 and PAGER variables and launch the appropriate program, and fall
8543 back to <file>/usr/bin/editor</file>
8544 and <file>/usr/bin/pager</file> if the variable is not set.
8548 A program may also use the VISUAL environment variable to
8549 determine the user's choice of editor. If it exists, it
8550 should take precedence over EDITOR. This is in fact what
8551 <file>/usr/bin/sensible-editor</file> does.
8555 It is not required for a package to depend on
8556 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8557 package to provide such virtual packages.<footnote>
8558 The Debian base system already provides an editor and a
8564 <sect id="web-appl">
8565 <heading>Web servers and applications</heading>
8568 This section describes the locations and URLs that should
8569 be used by all web servers and web applications in the
8576 Cgi-bin executable files are installed in the
8578 <example compact="compact">
8579 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8581 or a subdirectory of that directory, and should be
8583 <example compact="compact">
8584 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8586 (possibly with a subdirectory name
8587 before <var>cgi-bin-name</var>).
8591 <p>Access to HTML documents</p>
8594 HTML documents for a package are stored in
8595 <file>/usr/share/doc/<var>package</var></file>
8596 and can be referred to as
8597 <example compact="compact">
8598 http://localhost/doc/<var>package</var>/<var>filename</var>
8603 The web server should restrict access to the document
8604 tree so that only clients on the same host can read
8605 the documents. If the web server does not support such
8606 access controls, then it should not provide access at
8607 all, or ask about providing access during installation.
8612 <p>Access to images</p>
8614 It is recommended that images for a package be stored
8615 in <tt>/usr/share/images/<var>package</var></tt> and
8616 may be referred to through an alias <tt>/images/</tt>
8619 http://localhost/images/<package>/<filename>
8626 <p>Web Document Root</p>
8629 Web Applications should try to avoid storing files in
8630 the Web Document Root. Instead they should use the
8631 /usr/share/doc/<var>package</var> directory for
8632 documents and register the Web Application via the
8633 <package>doc-base</package> package. If access to the
8634 web document root is unavoidable then use
8635 <example compact="compact">
8638 as the Document Root. This might be just a symbolic
8639 link to the location where the system administrator
8640 has put the real document root.
8643 <item><p>Providing httpd and/or httpd-cgi</p>
8645 All web servers should provide the virtual package
8646 <tt>httpd</tt>. If a web server has CGI support it should
8647 provide <tt>httpd-cgi</tt> additionally.
8650 All web applications which do not contain CGI scripts should
8651 depend on <tt>httpd</tt>, all those web applications which
8652 <tt>do</tt> contain CGI scripts, should depend on
8660 <sect id="mail-transport-agents">
8661 <heading>Mail transport, delivery and user agents</heading>
8664 Debian packages which process electronic mail, whether mail
8665 user agents (MUAs) or mail transport agents (MTAs), must
8666 ensure that they are compatible with the configuration
8667 decisions below. Failure to do this may result in lost
8668 mail, broken <tt>From:</tt> lines, and other serious brain
8673 The mail spool is <file>/var/mail</file> and the interface to
8674 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8675 the FHS). On older systems, the mail spool may be
8676 physically located in <file>/var/spool/mail</file>, but all
8677 access to the mail spool should be via the
8678 <file>/var/mail</file> symlink. The mail spool is part of the
8679 base system and not part of the MTA package.
8683 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8684 programs (such as IMAP daemons) must lock the mailbox in an
8685 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8686 be combined with dot locking. To avoid deadlocks, a program
8687 should use <tt>fcntl()</tt> first and dot locking after
8688 this, or alternatively implement the two locking methods in
8689 a non blocking way<footnote>
8690 If it is not possible to establish both locks, the
8691 system shouldn't wait for the second lock to be
8692 established, but remove the first lock, wait a (random)
8693 time, and start over locking again.
8694 </footnote>. Using the functions <tt>maillock</tt> and
8695 <tt>mailunlock</tt> provided by the
8696 <tt>liblockfile*</tt><footnote>
8697 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8698 to use these functions.
8699 </footnote> packages is the recommended way to realize this.
8703 Mailboxes are generally either mode 600 and owned by
8704 <var>user</var> or mode 660 and owned by
8705 <tt><var>user</var>:mail</tt><footnote>
8706 There are two traditional permission schemes for mail spools:
8707 mode 600 with all mail delivery done by processes running as
8708 the destination user, or mode 660 and owned by group mail with
8709 mail delivery done by a process running as a system user in
8710 group mail. Historically, Debian required mode 660 mail
8711 spools to enable the latter model, but that model has become
8712 increasingly uncommon and the principle of least privilege
8713 indicates that mail systems that use the first model should
8714 use permissions of 600. If delivery to programs is permitted,
8715 it's easier to keep the mail system secure if the delivery
8716 agent runs as the destination user. Debian Policy therefore
8717 permits either scheme.
8718 </footnote>. The local system administrator may choose a
8719 different permission scheme; packages should not make
8720 assumptions about the permission and ownership of mailboxes
8721 unless required (such as when creating a new mailbox). A MUA
8722 may remove a mailbox (unless it has nonstandard permissions) in
8723 which case the MTA or another MUA must recreate it if needed.
8727 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8728 be setgid mail to do the locking mentioned above (and
8729 must obviously avoid accessing other users' mailboxes
8730 using this privilege).</p>
8733 <file>/etc/aliases</file> is the source file for the system mail
8734 aliases (e.g., postmaster, usenet, etc.), it is the one
8735 which the sysadmin and <prgn>postinst</prgn> scripts may
8736 edit. After <file>/etc/aliases</file> is edited the program or
8737 human editing it must call <prgn>newaliases</prgn>. All MTA
8738 packages must come with a <prgn>newaliases</prgn> program,
8739 even if it does nothing, but older MTA packages did not do
8740 this so programs should not fail if <prgn>newaliases</prgn>
8741 cannot be found. Note that because of this, all MTA
8742 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8743 <tt>Replaces: mail-transport-agent</tt> control fields.
8747 The convention of writing <tt>forward to
8748 <var>address</var></tt> in the mailbox itself is not
8749 supported. Use a <tt>.forward</tt> file instead.</p>
8752 The <prgn>rmail</prgn> program used by UUCP
8753 for incoming mail should be <file>/usr/sbin/rmail</file>.
8754 Likewise, <prgn>rsmtp</prgn>, for receiving
8755 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8759 If your package needs to know what hostname to use on (for
8760 example) outgoing news and mail messages which are generated
8761 locally, you should use the file <file>/etc/mailname</file>. It
8762 will contain the portion after the username and <tt>@</tt>
8763 (at) sign for email addresses of users on the machine
8764 (followed by a newline).
8768 Such a package should check for the existence of this file
8769 when it is being configured. If it exists, it should be
8770 used without comment, although an MTA's configuration script
8771 may wish to prompt the user even if it finds that this file
8772 exists. If the file does not exist, the package should
8773 prompt the user for the value (preferably using
8774 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8775 as well as using it in the package's configuration. The
8776 prompt should make it clear that the name will not just be
8777 used by that package. For example, in this situation the
8778 <tt>inn</tt> package could say something like:
8779 <example compact="compact">
8780 Please enter the "mail name" of your system. This is the
8781 hostname portion of the address to be shown on outgoing
8782 news and mail messages. The default is
8783 <var>syshostname</var>, your system's host name. Mail
8784 name ["<var>syshostname</var>"]:
8786 where <var>syshostname</var> is the output of <tt>hostname
8792 <heading>News system configuration</heading>
8795 All the configuration files related to the NNTP (news)
8796 servers and clients should be located under
8797 <file>/etc/news</file>.</p>
8800 There are some configuration issues that apply to a number
8801 of news clients and server packages on the machine. These
8805 <tag><file>/etc/news/organization</file></tag>
8807 A string which should appear as the
8808 organization header for all messages posted
8809 by NNTP clients on the machine
8812 <tag><file>/etc/news/server</file></tag>
8814 Contains the FQDN of the upstream NNTP
8815 server, or localhost if the local machine is
8820 Other global files may be added as required for cross-package news
8827 <heading>Programs for the X Window System</heading>
8830 <heading>Providing X support and package priorities</heading>
8833 Programs that can be configured with support for the X
8834 Window System must be configured to do so and must declare
8835 any package dependencies necessary to satisfy their
8836 runtime requirements when using the X Window System. If
8837 such a package is of higher priority than the X packages
8838 on which it depends, it is required that either the
8839 X-specific components be split into a separate package, or
8840 that an alternative version of the package, which includes
8841 X support, be provided, or that the package's priority be
8847 <heading>Packages providing an X server</heading>
8850 Packages that provide an X server that, directly or
8851 indirectly, communicates with real input and display
8852 hardware should declare in their <tt>Provides</tt> control
8853 field that they provide the virtual
8854 package <tt>xserver</tt>.<footnote>
8855 This implements current practice, and provides an
8856 actual policy for usage of the <tt>xserver</tt>
8857 virtual package which appears in the virtual packages
8858 list. In a nutshell, X servers that interface
8859 directly with the display and input hardware or via
8860 another subsystem (e.g., GGI) should provide
8861 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8862 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8868 <heading>Packages providing a terminal emulator</heading>
8871 Packages that provide a terminal emulator for the X Window
8872 System which meet the criteria listed below should declare in
8873 their <tt>Provides</tt> control field that they provide the
8874 virtual package <tt>x-terminal-emulator</tt>. They should
8875 also register themselves as an alternative for
8876 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8877 20. That alternative should have a slave alternative
8878 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8879 pointing to the corresponding manual page.
8883 To be an <tt>x-terminal-emulator</tt>, a program must:
8884 <list compact="compact">
8886 Be able to emulate a DEC VT100 terminal, or a
8887 compatible terminal.
8891 Support the command-line option <tt>-e
8892 <var>command</var></tt>, which creates a new
8893 terminal window<footnote>
8894 "New terminal window" does not necessarily mean
8895 a new top-level X window directly parented by
8896 the window manager; it could, if the terminal
8897 emulator application were so coded, be a new
8898 "view" in a multiple-document interface (MDI).
8900 and runs the specified <var>command</var>,
8901 interpreting the entirety of the rest of the command
8902 line as a command to pass straight to exec, in the
8903 manner that <tt>xterm</tt> does.
8907 Support the command-line option <tt>-T
8908 <var>title</var></tt>, which creates a new terminal
8909 window with the window title <var>title</var>.
8916 <heading>Packages providing a window manager</heading>
8919 Packages that provide a window manager should declare in
8920 their <tt>Provides</tt> control field that they provide the
8921 virtual package <tt>x-window-manager</tt>. They should also
8922 register themselves as an alternative for
8923 <file>/usr/bin/x-window-manager</file>, with a priority
8924 calculated as follows:
8925 <list compact="compact">
8927 Start with a priority of 20.
8931 If the window manager supports the Debian menu
8932 system, add 20 points if this support is available
8933 in the package's default configuration (i.e., no
8934 configuration files belonging to the system or user
8935 have to be edited to activate the feature); if
8936 configuration files must be modified, add only 10
8942 If the window manager complies with <url
8943 id="http://www.freedesktop.org/Standards/wm-spec"
8944 name="The Window Manager Specification Project">,
8945 written by the <url id="http://www.freedesktop.org/"
8946 name="Free Desktop Group">, add 40 points.
8950 If the window manager permits the X session to be
8951 restarted using a <em>different</em> window manager
8952 (without killing the X server) in its default
8953 configuration, add 10 points; otherwise add none.
8956 That alternative should have a slave alternative
8957 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8958 pointing to the corresponding manual page.
8963 <heading>Packages providing fonts</heading>
8966 Packages that provide fonts for the X Window
8968 For the purposes of Debian Policy, a "font for the X
8969 Window System" is one which is accessed via X protocol
8970 requests. Fonts for the Linux console, for PostScript
8971 renderer, or any other purpose, do not fit this
8972 definition. Any tool which makes such fonts available
8973 to the X Window System, however, must abide by this
8976 must do a number of things to ensure that they are both
8977 available without modification of the X or font server
8978 configuration, and that they do not corrupt files used by
8979 other font packages to register information about
8983 Fonts of any type supported by the X Window System
8984 must be in a separate binary package from any
8985 executables, libraries, or documentation (except
8986 that specific to the fonts shipped, such as their
8987 license information). If one or more of the fonts
8988 so packaged are necessary for proper operation of
8989 the package with which they are associated the font
8990 package may be Recommended; if the fonts merely
8991 provide an enhancement, a Suggests relationship may
8992 be used. Packages must not Depend on font
8994 This is because the X server may retrieve fonts
8995 from the local file system or over the network
8996 from an X font server; the Debian package system
8997 is empowered to deal only with the local
9003 BDF fonts must be converted to PCF fonts with the
9004 <prgn>bdftopcf</prgn> utility (available in the
9005 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9006 placed in a directory that corresponds to their
9008 <list compact="compact">
9010 100 dpi fonts must be placed in
9011 <file>/usr/share/fonts/X11/100dpi/</file>.
9015 75 dpi fonts must be placed in
9016 <file>/usr/share/fonts/X11/75dpi/</file>.
9020 Character-cell fonts, cursor fonts, and other
9021 low-resolution fonts must be placed in
9022 <file>/usr/share/fonts/X11/misc/</file>.
9028 Type 1 fonts must be placed in
9029 <file>/usr/share/fonts/X11/Type1/</file>. If font
9030 metric files are available, they must be placed here
9035 Subdirectories of <file>/usr/share/fonts/X11/</file>
9036 other than those listed above must be neither
9037 created nor used. (The <file>PEX</file>, <file>CID</file>,
9038 <file>Speedo</file>, and <file>cyrillic</file> directories
9039 are excepted for historical reasons, but installation of
9040 files into these directories remains discouraged.)
9044 Font packages may, instead of placing files directly
9045 in the X font directories listed above, provide
9046 symbolic links in that font directory pointing to
9047 the files' actual location in the filesystem. Such
9048 a location must comply with the FHS.
9052 Font packages should not contain both 75dpi and
9053 100dpi versions of a font. If both are available,
9054 they should be provided in separate binary packages
9055 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9056 the names of the packages containing the
9057 corresponding fonts.
9061 Fonts destined for the <file>misc</file> subdirectory
9062 should not be included in the same package as 75dpi
9063 or 100dpi fonts; instead, they should be provided in
9064 a separate package with <tt>-misc</tt> appended to
9069 Font packages must not provide the files
9070 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9071 <file>fonts.scale</file> in a font directory:
9074 <file>fonts.dir</file> files must not be provided at all.
9078 <file>fonts.alias</file> and <file>fonts.scale</file>
9079 files, if needed, should be provided in the
9081 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9082 where <var>fontdir</var> is the name of the
9084 <file>/usr/share/fonts/X11/</file> where the
9085 package's corresponding fonts are stored
9086 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9087 <var>package</var> is the name of the package
9088 that provides these fonts, and
9089 <var>extension</var> is either <tt>scale</tt>
9090 or <tt>alias</tt>, whichever corresponds to
9097 Font packages must declare a dependency on
9098 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9099 or <tt>Pre-Depends</tt> control field.
9103 Font packages that provide one or more
9104 <file>fonts.scale</file> files as described above must
9105 invoke <prgn>update-fonts-scale</prgn> on each
9106 directory into which they installed fonts
9107 <em>before</em> invoking
9108 <prgn>update-fonts-dir</prgn> on that directory.
9109 This invocation must occur in both the
9110 <prgn>postinst</prgn> (for all arguments) and
9111 <prgn>postrm</prgn> (for all arguments except
9112 <tt>upgrade</tt>) scripts.
9116 Font packages that provide one or more
9117 <file>fonts.alias</file> files as described above must
9118 invoke <prgn>update-fonts-alias</prgn> on each
9119 directory into which they installed fonts. This
9120 invocation must occur in both the
9121 <prgn>postinst</prgn> (for all arguments) and
9122 <prgn>postrm</prgn> (for all arguments except
9123 <tt>upgrade</tt>) scripts.
9127 Font packages must invoke
9128 <prgn>update-fonts-dir</prgn> on each directory into
9129 which they installed fonts. This invocation must
9130 occur in both the <prgn>postinst</prgn> (for all
9131 arguments) and <prgn>postrm</prgn> (for all
9132 arguments except <tt>upgrade</tt>) scripts.
9136 Font packages must not provide alias names for the
9137 fonts they include which collide with alias names
9138 already in use by fonts already packaged.
9142 Font packages must not provide fonts with the same
9143 XLFD registry name as another font already packaged.
9149 <sect1 id="appdefaults">
9150 <heading>Application defaults files</heading>
9153 Application defaults files must be installed in the
9154 directory <file>/etc/X11/app-defaults/</file> (use of a
9155 localized subdirectory of <file>/etc/X11/</file> as described
9156 in the <em>X Toolkit Intrinsics - C Language
9157 Interface</em> manual is also permitted). They must be
9158 registered as <tt>conffile</tt>s or handled as
9159 configuration files.
9163 Customization of programs' X resources may also be
9164 supported with the provision of a file with the same name
9165 as that of the package placed in
9166 the <file>/etc/X11/Xresources/</file> directory, which
9167 must be registered as a <tt>conffile</tt> or handled as a
9168 configuration file.<footnote>
9169 Note that this mechanism is not the same as using
9170 app-defaults; app-defaults are tied to the client
9171 binary on the local file system, whereas X resources
9172 are stored in the X server and affect all connecting
9179 <heading>Installation directory issues</heading>
9182 Historically, packages using the X Window System used a
9183 separate set of installation directories from other packages.
9184 This practice has been discontinued and packages using the X
9185 Window System should now generally be installed in the same
9186 directories as any other package. Specifically, packages must
9187 not install files under the <file>/usr/X11R6/</file> directory
9188 and the <file>/usr/X11R6/</file> directory hierarchy should be
9189 regarded as obsolete.
9193 Include files previously installed under
9194 <file>/usr/X11R6/include/X11/</file> should be installed into
9195 <file>/usr/include/X11/</file>. For files previously
9196 installed into subdirectories of
9197 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9198 determine if subdirectories of <file>/usr/lib/</file> and
9199 <file>/usr/share/</file> can be used. If not, a subdirectory
9200 of <file>/usr/lib/X11/</file> should be used.
9204 Configuration files for window, display, or session managers
9205 or other applications that are tightly integrated with the X
9206 Window System may be placed in a subdirectory
9207 of <file>/etc/X11/</file> corresponding to the package name.
9208 Other X Window System applications should use
9209 the <file>/etc/</file> directory unless otherwise mandated by
9210 policy (such as for <ref id="appdefaults">).
9215 <heading>The OSF/Motif and OpenMotif libraries</heading>
9218 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9219 OpenMotif libraries</em><footnote>
9220 OSF/Motif and OpenMotif are collectively referred to as
9221 "Motif" in this policy document.
9223 should be compiled against and tested with LessTif (a free
9224 re-implementation of Motif) instead. If the maintainer
9225 judges that the program or programs do not work
9226 sufficiently well with LessTif to be distributed and
9227 supported, but do so when compiled against Motif, then two
9228 versions of the package should be created; one linked
9229 statically against Motif and with <tt>-smotif</tt>
9230 appended to the package name, and one linked dynamically
9231 against Motif and with <tt>-dmotif</tt> appended to the
9236 Both Motif-linked versions are dependent
9237 upon non-DFSG-compliant software and thus cannot be
9238 uploaded to the <em>main</em> distribution; if the
9239 software is itself DFSG-compliant it may be uploaded to
9240 the <em>contrib</em> distribution. While known existing
9241 versions of Motif permit unlimited redistribution of
9242 binaries linked against the library (whether statically or
9243 dynamically), it is the package maintainer's
9244 responsibility to determine whether this is permitted by
9245 the license of the copy of Motif in their possession.
9251 <heading>Perl programs and modules</heading>
9254 Perl programs and modules should follow the current Perl policy.
9258 The Perl policy can be found in the <tt>perl-policy</tt>
9259 files in the <tt>debian-policy</tt> package.
9260 It is also available from the Debian web mirrors at
9261 <tt><url name="/doc/packaging-manuals/perl-policy/"
9262 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9267 <heading>Emacs lisp programs</heading>
9270 Please refer to the "Debian Emacs Policy" for details of how to
9271 package emacs lisp programs.
9275 The Emacs policy is available in
9276 <file>debian-emacs-policy.gz</file> of the
9277 <package>emacsen-common</package> package.
9278 It is also available from the Debian web mirrors at
9279 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9280 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9285 <heading>Games</heading>
9288 The permissions on <file>/var/games</file> are mode 755, owner
9289 <tt>root</tt> and group <tt>root</tt>.
9293 Each game decides on its own security policy.</p>
9296 Games which require protected, privileged access to
9297 high-score files, saved games, etc., may be made
9298 set-<em>group</em>-id (mode 2755) and owned by
9299 <tt>root:games</tt>, and use files and directories with
9300 appropriate permissions (770 <tt>root:games</tt>, for
9301 example). They must not be made
9302 set-<em>user</em>-id, as this causes security problems. (If
9303 an attacker can subvert any set-user-id game they can
9304 overwrite the executable of any other, causing other players
9305 of these games to run a Trojan horse program. With a
9306 set-group-id game the attacker only gets access to less
9307 important game data, and if they can get at the other
9308 players' accounts at all it will take considerably more
9312 Some packages, for example some fortune cookie programs, are
9313 configured by the upstream authors to install with their
9314 data files or other static information made unreadable so
9315 that they can only be accessed through set-id programs
9316 provided. You should not do this in a Debian package: anyone can
9317 download the <file>.deb</file> file and read the data from it,
9318 so there is no point making the files unreadable. Not
9319 making the files unreadable also means that you don't have
9320 to make so many programs set-id, which reduces the risk of a
9324 As described in the FHS, binaries of games should be
9325 installed in the directory <file>/usr/games</file>. This also
9326 applies to games that use the X Window System. Manual pages
9327 for games (X and non-X games) should be installed in
9328 <file>/usr/share/man/man6</file>.</p>
9334 <heading>Documentation</heading>
9337 <heading>Manual pages</heading>
9340 You should install manual pages in <prgn>nroff</prgn> source
9341 form, in appropriate places under <file>/usr/share/man</file>.
9342 You should only use sections 1 to 9 (see the FHS for more
9343 details). You must not install a pre-formatted "cat page".
9347 Each program, utility, and function should have an
9348 associated manual page included in the same package. It is
9349 suggested that all configuration files also have a manual
9350 page included as well. Manual pages for protocols and other
9351 auxiliary things are optional.
9355 If no manual page is available, this is considered as a bug
9356 and should be reported to the Debian Bug Tracking System (the
9357 maintainer of the package is allowed to write this bug report
9358 themselves, if they so desire). Do not close the bug report
9359 until a proper man page is available.<footnote>
9360 It is not very hard to write a man page. See the
9361 <url id="http://www.schweikhardt.net/man_page_howto.html"
9362 name="Man-Page-HOWTO">,
9363 <manref name="man" section="7">, the examples
9364 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9365 the helper program <prgn>help2man</prgn>, or the
9366 directory <file>/usr/share/doc/man-db/examples</file>.
9371 You may forward a complaint about a missing man page to the
9372 upstream authors, and mark the bug as forwarded in the
9373 Debian bug tracking system. Even though the GNU Project do
9374 not in general consider the lack of a man page to be a bug,
9375 we do; if they tell you that they don't consider it a bug
9376 you should leave the bug in our bug tracking system open
9381 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9385 If one man page needs to be accessible via several names it
9386 is better to use a symbolic link than the <file>.so</file>
9387 feature, but there is no need to fiddle with the relevant
9388 parts of the upstream source to change from <file>.so</file> to
9389 symlinks: don't do it unless it's easy. You should not
9390 create hard links in the manual page directories, nor put
9391 absolute filenames in <file>.so</file> directives. The filename
9392 in a <file>.so</file> in a man page should be relative to the
9393 base of the man page tree (usually
9394 <file>/usr/share/man</file>). If you do not create any links
9395 (whether symlinks, hard links, or <tt>.so</tt> directives)
9396 in the file system to the alternate names of the man page,
9397 then you should not rely on <prgn>man</prgn> finding your
9398 man page under those names based solely on the information in
9399 the man page's header.<footnote>
9400 Supporting this in <prgn>man</prgn> often requires
9401 unreasonable processing time to find a manual page or to
9402 report that none exists, and moves knowledge into man's
9403 database that would be better left in the file system.
9404 This support is therefore deprecated and will cease to
9405 be present in the future.
9410 Manual pages in locale-specific subdirectories of
9411 <file>/usr/share/man</file> should use either UTF-8 or the usual
9412 legacy encoding for that language (normally the one corresponding
9413 to the shortest relevant locale name in
9414 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9415 <file>/usr/share/man/fr</file> should use either UTF-8 or
9416 ISO-8859-1.<footnote>
9417 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9418 use. In future, all manual pages will be required to use
9424 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9425 included in the subdirectory name unless it indicates a
9426 significant difference in the language, as this excludes
9427 speakers of the language in other countries.<footnote>
9428 At the time of writing, Chinese and Portuguese are the main
9429 languages with such differences, so <file>pt_BR</file>,
9430 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9435 If a localized version of a manual page is provided, it should
9436 either be up-to-date or it should be obvious to the reader that
9437 it is outdated and the original manual page should be used
9438 instead. This can be done either by a note at the beginning of
9439 the manual page or by showing the missing or changed portions in
9440 the original language instead of the target language.
9445 <heading>Info documents</heading>
9448 Info documents should be installed in <file>/usr/share/info</file>.
9449 They should be compressed with <tt>gzip -9</tt>.
9453 The <prgn>install-info</prgn> program maintains a directory of
9454 installed info documents in <file>/usr/share/info/dir</file> for
9455 the use of info readers.<footnote>
9456 It was previously necessary for packages installing info
9457 documents to run <prgn>install-info</prgn> from maintainer
9458 scripts. This is no longer necessary. The installation
9459 system now uses dpkg triggers.
9461 This file must not be included in packages. Packages containing
9462 info documents should depend on <tt>dpkg (>= 1.15.4) |
9463 install-info</tt> to ensure that the directory file is properly
9464 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9469 Info documents should contain section and directory entry
9470 information in the document for the use
9471 of <prgn>install-info</prgn>. The section should be specified
9472 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9473 space and the section of this info page. The directory entry or
9474 entries should be included between
9475 a <tt>START-INFO-DIR-ENTRY</tt> line and
9476 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9478 INFO-DIR-SECTION Individual utilities
9479 START-INFO-DIR-ENTRY
9480 * example: (example). An example info directory entry.
9483 To determine which section to use, you should look
9484 at <file>/usr/share/info/dir</file> on your system and choose
9485 the most relevant (or create a new section if none of the
9486 current sections are relevant).<footnote>
9487 Normally, info documents are generated from Texinfo source.
9488 To include this information in the generated info document, if
9489 it is absent, add commands like:
9491 @dircategory Individual utilities
9493 * example: (example). An example info directory entry.
9496 to the Texinfo source of the document and ensure that the info
9497 documents are rebuilt from source during the package build.
9503 <heading>Additional documentation</heading>
9506 Any additional documentation that comes with the package may
9507 be installed at the discretion of the package maintainer.
9508 Plain text documentation should be installed in the directory
9509 <file>/usr/share/doc/<var>package</var></file>, where
9510 <var>package</var> is the name of the package, and
9511 compressed with <tt>gzip -9</tt> unless it is small.
9515 If a package comes with large amounts of documentation which
9516 many users of the package will not require you should create
9517 a separate binary package to contain it, so that it does not
9518 take up disk space on the machines of users who do not need
9519 or want it installed.</p>
9522 It is often a good idea to put text information files
9523 (<file>README</file>s, changelogs, and so forth) that come with
9524 the source package in <file>/usr/share/doc/<var>package</var></file>
9525 in the binary package. However, you don't need to install
9526 the instructions for building and installing the package, of
9530 Packages must not require the existence of any files in
9531 <file>/usr/share/doc/</file> in order to function
9533 The system administrator should be able to
9534 delete files in <file>/usr/share/doc/</file> without causing
9535 any programs to break.
9537 Any files that are referenced by programs but are also
9538 useful as stand alone documentation should be installed under
9539 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9540 <file>/usr/share/doc/<var>package</var></file>.
9544 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9545 link to another directory in <file>/usr/share/doc</file> only if
9546 the two packages both come from the same source and the
9547 first package Depends on the second.<footnote>
9549 Please note that this does not override the section on
9550 changelog files below, so the file
9551 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9552 must refer to the changelog for the current version of
9553 <var>package</var> in question. In practice, this means
9554 that the sources of the target and the destination of the
9555 symlink must be the same (same source package and
9562 Former Debian releases placed all additional documentation
9563 in <file>/usr/doc/<var>package</var></file>. This has been
9564 changed to <file>/usr/share/doc/<var>package</var></file>,
9565 and packages must not put documentation in the directory
9566 <file>/usr/doc/<var>package</var></file>. <footnote>
9567 At this phase of the transition, we no longer require a
9568 symbolic link in <file>/usr/doc/</file>. At a later point,
9569 policy shall change to make the symbolic links a bug.
9575 <heading>Preferred documentation formats</heading>
9578 The unification of Debian documentation is being carried out
9582 If your package comes with extensive documentation in a
9583 markup format that can be converted to various other formats
9584 you should if possible ship HTML versions in a binary
9585 package, in the directory
9586 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9587 its subdirectories.<footnote>
9588 The rationale: The important thing here is that HTML
9589 docs should be available in <em>some</em> package, not
9590 necessarily in the main binary package.
9595 Other formats such as PostScript may be provided at the
9596 package maintainer's discretion.
9600 <sect id="copyrightfile">
9601 <heading>Copyright information</heading>
9604 Every package must be accompanied by a verbatim copy of its
9605 copyright information and distribution license in the file
9606 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9607 file must neither be compressed nor be a symbolic link.
9611 In addition, the copyright file must say where the upstream
9612 sources (if any) were obtained. It should name the original
9613 authors of the package and the Debian maintainer(s) who were
9614 involved with its creation.
9618 Packages in the <em>contrib</em> or <em>non-free</em> archive
9619 areas should state in the copyright file that the package is not
9620 part of the Debian distribution and briefly explain why.
9624 A copy of the file which will be installed in
9625 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9626 be in <file>debian/copyright</file> in the source package.
9630 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9631 link to another directory in <file>/usr/share/doc</file> only if
9632 the two packages both come from the same source and the
9633 first package Depends on the second. These rules are
9634 important because copyrights must be extractable by
9639 Packages distributed under the Apache license (version 2.0), the
9640 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9641 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9642 1.3) should refer to the corresponding files
9643 under <file>/usr/share/common-licenses</file>,<footnote>
9646 <file>/usr/share/common-licenses/Apache-2.0</file>,
9647 <file>/usr/share/common-licenses/Artistic</file>,
9648 <file>/usr/share/common-licenses/GPL-1</file>,
9649 <file>/usr/share/common-licenses/GPL-2</file>,
9650 <file>/usr/share/common-licenses/GPL-3</file>,
9651 <file>/usr/share/common-licenses/LGPL-2</file>,
9652 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9653 <file>/usr/share/common-licenses/LGPL-3</file>,
9654 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9655 <file>/usr/share/common-licenses/GFDL-1.3</file>
9656 respectively. The University of California BSD license is
9657 also included in <package>base-files</package> as
9658 <file>/usr/share/common-licenses/BSD</file>, but given the
9659 brevity of this license, its specificity to code whose
9660 copyright is held by the Regents of the University of
9661 California, and the frequency of minor wording changes, its
9662 text should be included in the copyright file rather than
9663 referencing this file.
9665 </footnote> rather than quoting them in the copyright
9670 You should not use the copyright file as a general <file>README</file>
9671 file. If your package has such a file it should be
9672 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9673 <file>README.Debian</file> or some other appropriate place.</p>
9677 <heading>Examples</heading>
9680 Any examples (configurations, source files, whatever),
9681 should be installed in a directory
9682 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9683 files should not be referenced by any program: they're there
9684 for the benefit of the system administrator and users as
9685 documentation only. Architecture-specific example files
9686 should be installed in a directory
9687 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9689 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9690 latter directory itself may be a symbolic link to the
9695 If the purpose of a package is to provide examples, then the
9696 example files may be installed into
9697 <file>/usr/share/doc/<var>package</var></file>.
9701 <sect id="changelogs">
9702 <heading>Changelog files</heading>
9705 Packages that are not Debian-native must contain a
9706 compressed copy of the <file>debian/changelog</file> file from
9707 the Debian source tree in
9708 <file>/usr/share/doc/<var>package</var></file> with the name
9709 <file>changelog.Debian.gz</file>.
9713 If an upstream changelog is available, it should be accessible as
9714 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9715 plain text. If the upstream changelog is distributed in
9716 HTML, it should be made available in that form as
9717 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9718 and a plain text <file>changelog.gz</file> should be generated
9719 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9720 the upstream changelog files do not already conform to this
9721 naming convention, then this may be achieved either by
9722 renaming the files, or by adding a symbolic link, at the
9723 maintainer's discretion.<footnote>
9724 Rationale: People should not have to look in places for
9725 upstream changelogs merely because they are given
9726 different names or are distributed in HTML format.
9731 All of these files should be installed compressed using
9732 <tt>gzip -9</tt>, as they will become large with time even
9733 if they start out small.
9737 If the package has only one changelog which is used both as
9738 the Debian changelog and the upstream one because there is
9739 no separate upstream maintainer then that changelog should
9740 usually be installed as
9741 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9742 there is a separate upstream maintainer, but no upstream
9743 changelog, then the Debian changelog should still be called
9744 <file>changelog.Debian.gz</file>.
9748 For details about the format and contents of the Debian
9749 changelog file, please see <ref id="dpkgchangelog">.
9754 <appendix id="pkg-scope">
9755 <heading>Introduction and scope of these appendices</heading>
9758 These appendices are taken essentially verbatim from the
9759 now-deprecated Packaging Manual, version 3.2.1.0. They are
9760 the chapters which are likely to be of use to package
9761 maintainers and which have not already been included in the
9762 policy document itself. Most of these sections are very likely
9763 not relevant to policy; they should be treated as
9764 documentation for the packaging system. Please note that these
9765 appendices are included for convenience, and for historical
9766 reasons: they used to be part of policy package, and they have
9767 not yet been incorporated into dpkg documentation. However,
9768 they still have value, and hence they are presented here.
9772 They have not yet been checked to ensure that they are
9773 compatible with the contents of policy, and if there are any
9774 contradictions, the version in the main policy document takes
9775 precedence. The remaining chapters of the old Packaging
9776 Manual have also not been read in detail to ensure that there
9777 are not parts which have been left out. Both of these will be
9782 Certain parts of the Packaging manual were integrated into the
9783 Policy Manual proper, and removed from the appendices. Links
9784 have been placed from the old locations to the new ones.
9788 <prgn>dpkg</prgn> is a suite of programs for creating binary
9789 package files and installing and removing them on Unix
9791 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
9792 work on or be ported to other systems.
9797 The binary packages are designed for the management of
9798 installed executable programs (usually compiled binaries) and
9799 their associated data, though source code examples and
9800 documentation are provided as part of some packages.</p>
9803 This manual describes the technical aspects of creating Debian
9804 binary packages (<file>.deb</file> files). It documents the
9805 behavior of the package management programs
9806 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9807 they interact with packages.</p>
9810 It also documents the interaction between
9811 <prgn>dselect</prgn>'s core and the access method scripts it
9812 uses to actually install the selected packages, and describes
9813 how to create a new access method.</p>
9816 This manual does not go into detail about the options and
9817 usage of the package building and installation tools. It
9818 should therefore be read in conjunction with those programs'
9823 The utility programs which are provided with <prgn>dpkg</prgn>
9824 for managing various system configuration and similar issues,
9825 such as <prgn>update-rc.d</prgn> and
9826 <prgn>install-info</prgn>, are not described in detail here -
9827 please see their man pages.
9831 It is assumed that the reader is reasonably familiar with the
9832 <prgn>dpkg</prgn> System Administrators' manual.
9833 Unfortunately this manual does not yet exist.
9837 The Debian version of the FSF's GNU hello program is provided
9838 as an example for people wishing to create Debian
9839 packages. The Debian <prgn>debmake</prgn> package is
9840 recommended as a very helpful tool in creating and maintaining
9841 Debian packages. However, while the tools and examples are
9842 helpful, they do not replace the need to read and follow the
9843 Policy and Programmer's Manual.</p>
9846 <appendix id="pkg-binarypkg">
9847 <heading>Binary packages (from old Packaging Manual)</heading>
9850 The binary package has two main sections. The first part
9851 consists of various control information files and scripts used
9852 by <prgn>dpkg</prgn> when installing and removing. See <ref
9853 id="pkg-controlarea">.
9857 The second part is an archive containing the files and
9858 directories to be installed.
9862 In the future binary packages may also contain other
9863 components, such as checksums and digital signatures. The
9864 format for the archive is described in full in the
9865 <file>deb(5)</file> man page.
9869 <sect id="pkg-bincreating"><heading>Creating package files -
9870 <prgn>dpkg-deb</prgn>
9874 All manipulation of binary package files is done by
9875 <prgn>dpkg-deb</prgn>; it's the only program that has
9876 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9877 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9878 will spot that the options requested are appropriate to
9879 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9884 In order to create a binary package you must make a
9885 directory tree which contains all the files and directories
9886 you want to have in the file system data part of the package.
9887 In Debian-format source packages this directory is usually
9888 <file>debian/tmp</file>, relative to the top of the package's
9893 They should have the locations (relative to the root of the
9894 directory tree you're constructing) ownerships and
9895 permissions which you want them to have on the system when
9900 With current versions of <prgn>dpkg</prgn> the uid/username
9901 and gid/groupname mappings for the users and groups being
9902 used should be the same on the system where the package is
9903 built and the one where it is installed.
9907 You need to add one special directory to the root of the
9908 miniature file system tree you're creating:
9909 <prgn>DEBIAN</prgn>. It should contain the control
9910 information files, notably the binary package control file
9911 (see <ref id="pkg-controlfile">).
9915 The <prgn>DEBIAN</prgn> directory will not appear in the
9916 file system archive of the package, and so won't be installed
9917 by <prgn>dpkg</prgn> when the package is installed.
9921 When you've prepared the package, you should invoke:
9923 dpkg --build <var>directory</var>
9928 This will build the package in
9929 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9930 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9931 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9936 See the man page <manref name="dpkg-deb" section="8"> for details of how
9937 to examine the contents of this newly-created file. You may find the
9938 output of following commands enlightening:
9940 dpkg-deb --info <var>filename</var>.deb
9941 dpkg-deb --contents <var>filename</var>.deb
9942 dpkg --contents <var>filename</var>.deb
9944 To view the copyright file for a package you could use this command:
9946 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9951 <sect id="pkg-controlarea">
9952 <heading>Package control information files</heading>
9955 The control information portion of a binary package is a
9956 collection of files with names known to <prgn>dpkg</prgn>.
9957 It will treat the contents of these files specially - some
9958 of them contain information used by <prgn>dpkg</prgn> when
9959 installing or removing the package; others are scripts which
9960 the package maintainer wants <prgn>dpkg</prgn> to run.
9964 It is possible to put other files in the package control
9965 information file area, but this is not generally a good idea
9966 (though they will largely be ignored).
9970 Here is a brief list of the control information files supported
9971 by <prgn>dpkg</prgn> and a summary of what they're used for.
9976 <tag><tt>control</tt>
9979 This is the key description file used by
9980 <prgn>dpkg</prgn>. It specifies the package's name
9981 and version, gives its description for the user,
9982 states its relationships with other packages, and so
9983 forth. See <ref id="sourcecontrolfiles"> and
9984 <ref id="binarycontrolfiles">.
9988 It is usually generated automatically from information
9989 in the source package by the
9990 <prgn>dpkg-gencontrol</prgn> program, and with
9991 assistance from <prgn>dpkg-shlibdeps</prgn>.
9992 See <ref id="pkg-sourcetools">.
9996 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10001 These are executable files (usually scripts) which
10002 <prgn>dpkg</prgn> runs during installation, upgrade
10003 and removal of packages. They allow the package to
10004 deal with matters which are particular to that package
10005 or require more complicated processing than that
10006 provided by <prgn>dpkg</prgn>. Details of when and
10007 how they are called are in <ref id="maintainerscripts">.
10011 It is very important to make these scripts idempotent.
10012 See <ref id="idempotency">.
10016 The maintainer scripts are not guaranteed to run with a
10017 controlling terminal and may not be able to interact with
10018 the user. See <ref id="controllingterminal">.
10022 <tag><tt>conffiles</tt>
10025 This file contains a list of configuration files which
10026 are to be handled automatically by <prgn>dpkg</prgn>
10027 (see <ref id="pkg-conffiles">). Note that not necessarily
10028 every configuration file should be listed here.
10031 <tag><tt>shlibs</tt>
10034 This file contains a list of the shared libraries
10035 supplied by the package, with dependency details for
10036 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10037 when it determines what dependencies are required in a
10038 package control file. The <tt>shlibs</tt> file format
10039 is described on <ref id="shlibs">.
10044 <sect id="pkg-controlfile">
10045 <heading>The main control information file: <tt>control</tt></heading>
10048 The most important control information file used by
10049 <prgn>dpkg</prgn> when it installs a package is
10050 <tt>control</tt>. It contains all the package's "vital
10055 The binary package control files of packages built from
10056 Debian sources are made by a special tool,
10057 <prgn>dpkg-gencontrol</prgn>, which reads
10058 <file>debian/control</file> and <file>debian/changelog</file> to
10059 find the information it needs. See <ref id="pkg-sourcepkg"> for
10064 The fields in binary package control files are listed in
10065 <ref id="binarycontrolfiles">.
10069 A description of the syntax of control files and the purpose
10070 of the fields is available in <ref id="controlfields">.
10075 <heading>Time Stamps</heading>
10078 See <ref id="timestamps">.
10083 <appendix id="pkg-sourcepkg">
10084 <heading>Source packages (from old Packaging Manual) </heading>
10087 The Debian binary packages in the distribution are generated
10088 from Debian sources, which are in a special format to assist
10089 the easy and automatic building of binaries.
10092 <sect id="pkg-sourcetools">
10093 <heading>Tools for processing source packages</heading>
10096 Various tools are provided for manipulating source packages;
10097 they pack and unpack sources and help build of binary
10098 packages and help manage the distribution of new versions.
10102 They are introduced and typical uses described here; see
10103 <manref name="dpkg-source" section="1"> for full
10104 documentation about their arguments and operation.
10108 For examples of how to construct a Debian source package,
10109 and how to use those utilities that are used by Debian
10110 source packages, please see the <prgn>hello</prgn> example
10114 <sect1 id="pkg-dpkg-source">
10116 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10121 This program is frequently used by hand, and is also
10122 called from package-independent automated building scripts
10123 such as <prgn>dpkg-buildpackage</prgn>.
10127 To unpack a package it is typically invoked with
10129 dpkg-source -x <var>.../path/to/filename</var>.dsc
10134 with the <file><var>filename</var>.tar.gz</file> and
10135 <file><var>filename</var>.diff.gz</file> (if applicable) in
10136 the same directory. It unpacks into
10137 <file><var>package</var>-<var>version</var></file>, and if
10139 <file><var>package</var>-<var>version</var>.orig</file>, in
10140 the current directory.
10144 To create a packed source archive it is typically invoked:
10146 dpkg-source -b <var>package</var>-<var>version</var>
10151 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10152 <file>.diff.gz</file> (if appropriate) in the current
10153 directory. <prgn>dpkg-source</prgn> does not clean the
10154 source tree first - this must be done separately if it is
10159 See also <ref id="pkg-sourcearchives">.</p>
10163 <sect1 id="pkg-dpkg-buildpackage">
10165 <prgn>dpkg-buildpackage</prgn> - overall package-building
10170 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10171 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10172 targets <tt>clean</tt>, <tt>build</tt> and
10173 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10174 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10175 source and binary package upload.
10179 It is usually invoked by hand from the top level of the
10180 built or unbuilt source directory. It may be invoked with
10181 no arguments; useful arguments include:
10182 <taglist compact="compact">
10183 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10186 Do not sign the <tt>.changes</tt> file or the
10187 source package <tt>.dsc</tt> file, respectively.</p>
10189 <tag><tt>-p<var>sign-command</var></tt></tag>
10192 Invoke <var>sign-command</var> instead of finding
10193 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10194 <var>sign-command</var> must behave just like
10195 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10197 <tag><tt>-r<var>root-command</var></tt></tag>
10200 When root privilege is required, invoke the command
10201 <var>root-command</var>. <var>root-command</var>
10202 should invoke its first argument as a command, from
10203 the <prgn>PATH</prgn> if necessary, and pass its
10204 second and subsequent arguments to the command it
10205 calls. If no <var>root-command</var> is supplied
10206 then <var>dpkg-buildpackage</var> will take no
10207 special action to gain root privilege, so that for
10208 most packages it will have to be invoked as root to
10211 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10214 Two types of binary-only build and upload - see
10215 <manref name="dpkg-source" section="1">.
10222 <sect1 id="pkg-dpkg-gencontrol">
10224 <prgn>dpkg-gencontrol</prgn> - generates binary package
10229 This program is usually called from <file>debian/rules</file>
10230 (see <ref id="pkg-sourcetree">) in the top level of the source
10235 This is usually done just before the files and directories in the
10236 temporary directory tree where the package is being built have their
10237 permissions and ownerships set and the package is constructed using
10238 <prgn>dpkg-deb/</prgn>
10240 This is so that the control file which is produced has
10241 the right permissions
10246 <prgn>dpkg-gencontrol</prgn> must be called after all the
10247 files which are to go into the package have been placed in
10248 the temporary build directory, so that its calculation of
10249 the installed size of a package is correct.
10253 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10254 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10255 variable substitutions created by
10256 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10261 For a package which generates only one binary package, and
10262 which builds it in <file>debian/tmp</file> relative to the top
10263 of the source package, it is usually sufficient to call
10264 <prgn>dpkg-gencontrol</prgn>.
10268 Sources which build several binaries will typically need
10271 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10272 </example> The <tt>-P</tt> tells
10273 <prgn>dpkg-gencontrol</prgn> that the package is being
10274 built in a non-default directory, and the <tt>-p</tt>
10275 tells it which package's control file should be generated.
10279 <prgn>dpkg-gencontrol</prgn> also adds information to the
10280 list of files in <file>debian/files</file>, for the benefit of
10281 (for example) a future invocation of
10282 <prgn>dpkg-genchanges</prgn>.</p>
10285 <sect1 id="pkg-dpkg-shlibdeps">
10287 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10292 This program is usually called from <file>debian/rules</file>
10293 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10294 id="pkg-sourcetree">), in the top level of the source tree.
10298 Its arguments are executables and shared libraries
10301 They may be specified either in the locations in the
10302 source tree where they are created or in the locations
10303 in the temporary build tree where they are installed
10304 prior to binary package creation.
10306 </footnote> for which shared library dependencies should
10307 be included in the binary package's control file.
10311 If some of the found shared libraries should only
10312 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10313 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10314 by using the <tt>-d<var>dependency-field</var></tt> option
10315 before those executable(s). (Each <tt>-d</tt> option
10316 takes effect until the next <tt>-d</tt>.)
10320 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10321 output control file to be modified. Instead by default it
10322 adds to the <file>debian/substvars</file> file variable
10323 settings like <tt>shlibs:Depends</tt>. These variable
10324 settings must be referenced in dependency fields in the
10325 appropriate per-binary-package sections of the source
10330 For example, a package that generates an essential part
10331 which requires dependencies, and optional parts that
10332 which only require a recommendation, would separate those
10333 two sets of dependencies into two different fields.<footnote>
10334 At the time of writing, an example for this was the
10335 <package/xmms/ package, with Depends used for the xmms
10336 executable, Recommends for the plug-ins and Suggests for
10337 even more optional features provided by unzip.
10339 It can say in its <file>debian/rules</file>:
10341 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10342 -dRecommends <var>optionalpart anotheroptionalpart</var>
10344 and then in its main control file <file>debian/control</file>:
10347 Depends: ${shlibs:Depends}
10348 Recommends: ${shlibs:Recommends}
10354 Sources which produce several binary packages with
10355 different shared library dependency requirements can use
10356 the <tt>-p<var>varnameprefix</var></tt> option to override
10357 the default <tt>shlibs:</tt> prefix (one invocation of
10358 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10359 They can thus produce several sets of dependency
10360 variables, each of the form
10361 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10362 which can be referred to in the appropriate parts of the
10363 binary package control files.
10368 <sect1 id="pkg-dpkg-distaddfile">
10370 <prgn>dpkg-distaddfile</prgn> - adds a file to
10371 <file>debian/files</file>
10375 Some packages' uploads need to include files other than
10376 the source and binary package files.
10380 <prgn>dpkg-distaddfile</prgn> adds a file to the
10381 <file>debian/files</file> file so that it will be included in
10382 the <file>.changes</file> file when
10383 <prgn>dpkg-genchanges</prgn> is run.
10387 It is usually invoked from the <tt>binary</tt> target of
10388 <file>debian/rules</file>:
10390 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10392 The <var>filename</var> is relative to the directory where
10393 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10394 is usually the directory above the top level of the source
10395 tree. The <file>debian/rules</file> target should put the
10396 file there just before or just after calling
10397 <prgn>dpkg-distaddfile</prgn>.
10401 The <var>section</var> and <var>priority</var> are passed
10402 unchanged into the resulting <file>.changes</file> file.
10407 <sect1 id="pkg-dpkg-genchanges">
10409 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10410 upload control file
10414 This program is usually called by package-independent
10415 automatic building scripts such as
10416 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10421 It is usually called in the top level of a built source
10422 tree, and when invoked with no arguments will print out a
10423 straightforward <file>.changes</file> file based on the
10424 information in the source package's changelog and control
10425 file and the binary and source packages which should have
10431 <sect1 id="pkg-dpkg-parsechangelog">
10433 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10434 representation of a changelog
10438 This program is used internally by
10439 <prgn>dpkg-source</prgn> et al. It may also occasionally
10440 be useful in <file>debian/rules</file> and elsewhere. It
10441 parses a changelog, <file>debian/changelog</file> by default,
10442 and prints a control-file format representation of the
10443 information in it to standard output.
10447 <sect1 id="pkg-dpkg-architecture">
10449 <prgn>dpkg-architecture</prgn> - information about the build and
10454 This program can be used manually, but is also invoked by
10455 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10456 environment or make variables which specify the build and host
10457 architecture for the package building process.
10462 <sect id="pkg-sourcetree">
10463 <heading>The Debian package source tree</heading>
10466 The source archive scheme described later is intended to
10467 allow a Debian package source tree with some associated
10468 control information to be reproduced and transported easily.
10469 The Debian package source tree is a version of the original
10470 program with certain files added for the benefit of the
10471 packaging process, and with any other changes required
10472 made to the rest of the source code and installation
10477 The extra files created for Debian are in the subdirectory
10478 <file>debian</file> of the top level of the Debian package
10479 source tree. They are described below.
10482 <sect1 id="pkg-debianrules">
10483 <heading><file>debian/rules</file> - the main building script</heading>
10486 See <ref id="debianrules">.
10490 <sect1 id="pkg-srcsubstvars">
10491 <heading><file>debian/substvars</file> and variable substitutions</heading>
10494 See <ref id="substvars">.
10500 <heading><file>debian/files</file></heading>
10503 See <ref id="debianfiles">.
10507 <sect1><heading><file>debian/tmp</file>
10511 This is the canonical temporary location for the
10512 construction of binary packages by the <tt>binary</tt>
10513 target. The directory <file>tmp</file> serves as the root of
10514 the file system tree as it is being constructed (for
10515 example, by using the package's upstream makefiles install
10516 targets and redirecting the output there), and it also
10517 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10518 id="pkg-bincreating">.
10522 If several binary packages are generated from the same
10523 source tree it is usual to use several
10524 <file>debian/tmp<var>something</var></file> directories, for
10525 example <file>tmp-a</file> or <file>tmp-doc</file>.
10529 Whatever <file>tmp</file> directories are created and used by
10530 <tt>binary</tt> must of course be removed by the
10531 <tt>clean</tt> target.</p></sect1>
10535 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10539 As it exists on the FTP site, a Debian source package
10540 consists of three related files. You must have the right
10541 versions of all three to be able to use them.
10546 <tag>Debian source control file - <tt>.dsc</tt></tag>
10548 This file is a control file used by <prgn>dpkg-source</prgn>
10549 to extract a source package.
10550 See <ref id="debiansourcecontrolfiles">.
10554 Original source archive -
10556 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10562 This is a compressed (with <tt>gzip -9</tt>)
10563 <prgn>tar</prgn> file containing the source code from
10564 the upstream authors of the program.
10569 Debian package diff -
10571 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10577 This is a unified context diff (<tt>diff -u</tt>)
10578 giving the changes which are required to turn the
10579 original source into the Debian source. These changes
10580 may only include editing and creating plain files.
10581 The permissions of files, the targets of symbolic
10582 links and the characteristics of special files or
10583 pipes may not be changed and no files may be removed
10588 All the directories in the diff must exist, except the
10589 <file>debian</file> subdirectory of the top of the source
10590 tree, which will be created by
10591 <prgn>dpkg-source</prgn> if necessary when unpacking.
10595 The <prgn>dpkg-source</prgn> program will
10596 automatically make the <file>debian/rules</file> file
10597 executable (see below).</p></item>
10602 If there is no original source code - for example, if the
10603 package is specially prepared for Debian or the Debian
10604 maintainer is the same as the upstream maintainer - the
10605 format is slightly different: then there is no diff, and the
10607 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10608 and preferably contains a directory named
10609 <file><var>package</var>-<var>version</var></file>.
10614 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10617 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10618 Debian source package. However, if it is not available it
10619 is possible to unpack a Debian source archive as follows:
10620 <enumlist compact="compact">
10623 Untar the tarfile, which will create a <file>.orig</file>
10627 <p>Rename the <file>.orig</file> directory to
10628 <file><var>package</var>-<var>version</var></file>.</p>
10632 Create the subdirectory <file>debian</file> at the top of
10633 the source tree.</p>
10635 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10637 <item><p>Untar the tarfile again if you want a copy of the original
10638 source code alongside the Debian version.</p>
10643 It is not possible to generate a valid Debian source archive
10644 without using <prgn>dpkg-source</prgn>. In particular,
10645 attempting to use <prgn>diff</prgn> directly to generate the
10646 <file>.diff.gz</file> file will not work.
10650 <heading>Restrictions on objects in source packages</heading>
10653 The source package may not contain any hard links
10655 This is not currently detected when building source
10656 packages, but only when extracting
10660 Hard links may be permitted at some point in the
10661 future, but would require a fair amount of
10663 </footnote>, device special files, sockets or setuid or
10666 Setgid directories are allowed.
10671 The source packaging tools manage the changes between the
10672 original and Debian source using <prgn>diff</prgn> and
10673 <prgn>patch</prgn>. Turning the original source tree as
10674 included in the <file>.orig.tar.gz</file> into the Debian
10675 package source must not involve any changes which cannot be
10676 handled by these tools. Problematic changes which cause
10677 <prgn>dpkg-source</prgn> to halt with an error when
10678 building the source package are:
10679 <list compact="compact">
10680 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10682 <item><p>Changing the targets of symbolic links.</p>
10684 <item><p>Creating directories, other than <file>debian</file>.</p>
10686 <item><p>Changes to the contents of binary files.</p></item>
10687 </list> Changes which cause <prgn>dpkg-source</prgn> to
10688 print a warning but continue anyway are:
10689 <list compact="compact">
10692 Removing files, directories or symlinks.
10694 Renaming a file is not treated specially - it is
10695 seen as the removal of the old file (which
10696 generates a warning, but is otherwise ignored),
10697 and the creation of the new one.
10703 Changed text files which are missing the usual final
10704 newline (either in the original or the modified
10709 Changes which are not represented, but which are not detected by
10710 <prgn>dpkg-source</prgn>, are:
10711 <list compact="compact">
10712 <item><p>Changing the permissions of files (other than
10713 <file>debian/rules</file>) and directories.</p></item>
10718 The <file>debian</file> directory and <file>debian/rules</file>
10719 are handled specially by <prgn>dpkg-source</prgn> - before
10720 applying the changes it will create the <file>debian</file>
10721 directory, and afterwards it will make
10722 <file>debian/rules</file> world-executable.
10728 <appendix id="pkg-controlfields">
10729 <heading>Control files and their fields (from old Packaging Manual)</heading>
10732 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10733 data in a common format, known as control files. Binary and
10734 source packages have control data as do the <file>.changes</file>
10735 files which control the installation of uploaded files, and
10736 <prgn>dpkg</prgn>'s internal databases are in a similar
10741 <heading>Syntax of control files</heading>
10744 See <ref id="controlsyntax">.
10748 It is important to note that there are several fields which
10749 are optional as far as <prgn>dpkg</prgn> and the related
10750 tools are concerned, but which must appear in every Debian
10751 package, or whose omission may cause problems.
10756 <heading>List of fields</heading>
10759 See <ref id="controlfieldslist">.
10763 This section now contains only the fields that didn't belong
10764 to the Policy manual.
10767 <sect1 id="pkg-f-Filename">
10768 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10771 These fields in <tt>Packages</tt> files give the
10772 filename(s) of (the parts of) a package in the
10773 distribution directories, relative to the root of the
10774 Debian hierarchy. If the package has been split into
10775 several parts the parts are all listed in order, separated
10780 <sect1 id="pkg-f-Size">
10781 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10784 These fields in <file>Packages</file> files give the size (in
10785 bytes, expressed in decimal) and MD5 checksum of the
10786 file(s) which make(s) up a binary package in the
10787 distribution. If the package is split into several parts
10788 the values for the parts are listed in order, separated by
10793 <sect1 id="pkg-f-Status">
10794 <heading><tt>Status</tt></heading>
10797 This field in <prgn>dpkg</prgn>'s status file records
10798 whether the user wants a package installed, removed or
10799 left alone, whether it is broken (requiring
10800 re-installation) or not and what its current state on the
10801 system is. Each of these pieces of information is a
10806 <sect1 id="pkg-f-Config-Version">
10807 <heading><tt>Config-Version</tt></heading>
10810 If a package is not installed or not configured, this
10811 field in <prgn>dpkg</prgn>'s status file records the last
10812 version of the package which was successfully
10817 <sect1 id="pkg-f-Conffiles">
10818 <heading><tt>Conffiles</tt></heading>
10821 This field in <prgn>dpkg</prgn>'s status file contains
10822 information about the automatically-managed configuration
10823 files held by a package. This field should <em>not</em>
10824 appear anywhere in a package!
10829 <heading>Obsolete fields</heading>
10832 These are still recognized by <prgn>dpkg</prgn> but should
10833 not appear anywhere any more.
10835 <taglist compact="compact">
10837 <tag><tt>Revision</tt></tag>
10838 <tag><tt>Package-Revision</tt></tag>
10839 <tag><tt>Package_Revision</tt></tag>
10841 The Debian revision part of the package version was
10842 at one point in a separate control field. This
10843 field went through several names.
10846 <tag><tt>Recommended</tt></tag>
10847 <item>Old name for <tt>Recommends</tt>.</item>
10849 <tag><tt>Optional</tt></tag>
10850 <item>Old name for <tt>Suggests</tt>.</item>
10852 <tag><tt>Class</tt></tag>
10853 <item>Old name for <tt>Priority</tt>.</item>
10862 <appendix id="pkg-conffiles">
10863 <heading>Configuration file handling (from old Packaging Manual)</heading>
10866 <prgn>dpkg</prgn> can do a certain amount of automatic
10867 handling of package configuration files.
10871 Whether this mechanism is appropriate depends on a number of
10872 factors, but basically there are two approaches to any
10873 particular configuration file.
10877 The easy method is to ship a best-effort configuration in the
10878 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10879 handle updates. If the user is unlikely to want to edit the
10880 file, but you need them to be able to without losing their
10881 changes, and a new package with a changed version of the file
10882 is only released infrequently, this is a good approach.
10886 The hard method is to build the configuration file from
10887 scratch in the <prgn>postinst</prgn> script, and to take the
10888 responsibility for fixing any mistakes made in earlier
10889 versions of the package automatically. This will be
10890 appropriate if the file is likely to need to be different on
10894 <sect><heading>Automatic handling of configuration files by
10899 A package may contain a control information file called
10900 <tt>conffiles</tt>. This file should be a list of filenames
10901 of configuration files needing automatic handling, separated
10902 by newlines. The filenames should be absolute pathnames,
10903 and the files referred to should actually exist in the
10908 When a package is upgraded <prgn>dpkg</prgn> will process
10909 the configuration files during the configuration stage,
10910 shortly before it runs the package's <prgn>postinst</prgn>
10915 For each file it checks to see whether the version of the
10916 file included in the package is the same as the one that was
10917 included in the last version of the package (the one that is
10918 being upgraded from); it also compares the version currently
10919 installed on the system with the one shipped with the last
10924 If neither the user nor the package maintainer has changed
10925 the file, it is left alone. If one or the other has changed
10926 their version, then the changed version is preferred - i.e.,
10927 if the user edits their file, but the package maintainer
10928 doesn't ship a different version, the user's changes will
10929 stay, silently, but if the maintainer ships a new version
10930 and the user hasn't edited it the new version will be
10931 installed (with an informative message). If both have
10932 changed their version the user is prompted about the problem
10933 and must resolve the differences themselves.
10937 The comparisons are done by calculating the MD5 message
10938 digests of the files, and storing the MD5 of the file as it
10939 was included in the most recent version of the package.
10943 When a package is installed for the first time
10944 <prgn>dpkg</prgn> will install the file that comes with it,
10945 unless that would mean overwriting a file already on the
10950 However, note that <prgn>dpkg</prgn> will <em>not</em>
10951 replace a conffile that was removed by the user (or by a
10952 script). This is necessary because with some programs a
10953 missing file produces an effect hard or impossible to
10954 achieve in another way, so that a missing file needs to be
10955 kept that way if the user did it.
10959 Note that a package should <em>not</em> modify a
10960 <prgn>dpkg</prgn>-handled conffile in its maintainer
10961 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10962 the user confusing and possibly dangerous options for
10963 conffile update when the package is upgraded.</p>
10966 <sect><heading>Fully-featured maintainer script configuration
10971 For files which contain site-specific information such as
10972 the hostname and networking details and so forth, it is
10973 better to create the file in the package's
10974 <prgn>postinst</prgn> script.
10978 This will typically involve examining the state of the rest
10979 of the system to determine values and other information, and
10980 may involve prompting the user for some information which
10981 can't be obtained some other way.
10985 When using this method there are a couple of important
10986 issues which should be considered:
10990 If you discover a bug in the program which generates the
10991 configuration file, or if the format of the file changes
10992 from one version to the next, you will have to arrange for
10993 the postinst script to do something sensible - usually this
10994 will mean editing the installed configuration file to remove
10995 the problem or change the syntax. You will have to do this
10996 very carefully, since the user may have changed the file,
10997 perhaps to fix the very problem that your script is trying
10998 to deal with - you will have to detect these situations and
10999 deal with them correctly.
11003 If you do go down this route it's probably a good idea to
11004 make the program that generates the configuration file(s) a
11005 separate program in <file>/usr/sbin</file>, by convention called
11006 <file><var>package</var>config</file> and then run that if
11007 appropriate from the post-installation script. The
11008 <tt><var>package</var>config</tt> program should not
11009 unquestioningly overwrite an existing configuration - if its
11010 mode of operation is geared towards setting up a package for
11011 the first time (rather than any arbitrary reconfiguration
11012 later) you should have it check whether the configuration
11013 already exists, and require a <tt>--force</tt> flag to
11014 overwrite it.</p></sect>
11017 <appendix id="pkg-alternatives"><heading>Alternative versions of
11018 an interface - <prgn>update-alternatives</prgn> (from old
11023 When several packages all provide different versions of the
11024 same program or file it is useful to have the system select a
11025 default, but to allow the system administrator to change it
11026 and have their decisions respected.
11030 For example, there are several versions of the <prgn>vi</prgn>
11031 editor, and there is no reason to prevent all of them from
11032 being installed at once, each under their own name
11033 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11034 Nevertheless it is desirable to have the name <tt>vi</tt>
11035 refer to something, at least by default.
11039 If all the packages involved cooperate, this can be done with
11040 <prgn>update-alternatives</prgn>.
11044 Each package provides its own version under its own name, and
11045 calls <prgn>update-alternatives</prgn> in its postinst to
11046 register its version (and again in its prerm to deregister
11051 See the man page <manref name="update-alternatives"
11052 section="8"> for details.
11056 If <prgn>update-alternatives</prgn> does not seem appropriate
11057 you may wish to consider using diversions instead.</p>
11060 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11061 package's version of a file (from old Packaging Manual)
11065 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11066 when it reinstalls the package it belongs to, and to have it
11067 put the file from the package somewhere else instead.
11071 This can be used locally to override a package's version of a
11072 file, or by one package to override another's version (or
11073 provide a wrapper for it).
11077 Before deciding to use a diversion, read <ref
11078 id="pkg-alternatives"> to see if you really want a diversion
11079 rather than several alternative versions of a program.
11083 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11084 and updated by a special program <prgn>dpkg-divert</prgn>.
11085 Please see <manref name="dpkg-divert" section="8"> for full
11086 details of its operation.
11090 When a package wishes to divert a file from another, it should
11091 call <prgn>dpkg-divert</prgn> in its preinst to add the
11092 diversion and rename the existing file. For example,
11093 supposing that a <prgn>smailwrapper</prgn> package wishes to
11094 install a wrapper around <file>/usr/sbin/smail</file>:
11096 dpkg-divert --package smailwrapper --add --rename \
11097 --divert /usr/sbin/smail.real /usr/sbin/smail
11098 </example> The <tt>--package smailwrapper</tt> ensures that
11099 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11100 can bypass the diversion and get installed as the true version.
11101 It's safe to add the diversion unconditionally on upgrades since
11102 it will be left unchanged if it already exists, but
11103 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11104 message, make the command conditional on the version from which
11105 the package is being upgraded:
11107 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11108 dpkg-divert --package smailwrapper --add --rename \
11109 --divert /usr/sbin/smail.real /usr/sbin/smail
11111 </example> where <tt>1.0-2</tt> is the version at which the
11112 diversion was first added to the package. Running the command
11113 during abort-upgrade is pointless but harmless.
11117 The postrm has to do the reverse:
11119 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11120 dpkg-divert --package smailwrapper --remove --rename \
11121 --divert /usr/sbin/smail.real /usr/sbin/smail
11123 </example> If the diversion was added at a particular version, the
11124 postrm should also handle the failure case of upgrading from an
11125 older version (unless the older version is so old that direct
11126 upgrades are no longer supported):
11128 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11129 dpkg-divert --package smailwrapper --remove --rename \
11130 --divert /usr/sbin/smail.real /usr/sbin/smail
11132 </example> where <tt>1.02-2</tt> is the version at which the
11133 diversion was first added to the package. The postrm should not
11134 remove the diversion on upgrades both because there's no reason to
11135 remove the diversion only to immediately re-add it and since the
11136 postrm of the old package is run after unpacking so the removal of
11137 the diversion will fail.
11141 Do not attempt to divert a file which is vitally important for
11142 the system's operation - when using <prgn>dpkg-divert</prgn>
11143 there is a time, after it has been diverted but before
11144 <prgn>dpkg</prgn> has installed the new version, when the file
11145 does not exist.</p>
11150 <!-- Local variables: -->
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