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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 These are the copyright dates of the original Policy manual.
29 Since then, this manual has been updated by many others. No
30 comprehensive collection of copyright notices for subsequent
35 This manual is free software; you may redistribute it and/or
36 modify it under the terms of the GNU General Public License
37 as published by the Free Software Foundation; either version
38 2, or (at your option) any later version.
42 This is distributed in the hope that it will be useful, but
43 <em>without any warranty</em>; without even the implied
44 warranty of merchantability or fitness for a particular
45 purpose. See the GNU General Public License for more
50 A copy of the GNU General Public License is available as
51 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
52 distribution or on the World Wide Web at
53 <url id="http://www.gnu.org/copyleft/gpl.html"
54 name="the GNU General Public Licence">. You can also
55 obtain it by writing to the Free Software Foundation, Inc.,
56 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
64 <heading>About this manual</heading>
66 <heading>Scope</heading>
68 This manual describes the policy requirements for the Debian
69 GNU/Linux distribution. This includes the structure and
70 contents of the Debian archive and several design issues of the
71 operating system, as well as technical requirements that
72 each package must satisfy to be included in the
77 This manual also describes Debian policy as it relates to
78 creating Debian packages. It is not a tutorial on how to build
79 packages, nor is it exhaustive where it comes to describing
80 the behavior of the packaging system. Instead, this manual
81 attempts to define the interface to the package management
82 system that the developers have to be conversant with.<footnote>
83 Informally, the criteria used for inclusion is that the
84 material meet one of the following requirements:
85 <taglist compact="compact">
86 <tag>Standard interfaces</tag>
88 The material presented represents an interface to
89 the packaging system that is mandated for use, and
90 is used by, a significant number of packages, and
91 therefore should not be changed without peer
92 review. Package maintainers can then rely on this
93 interface not changing, and the package management
94 software authors need to ensure compatibility with
95 this interface definition. (Control file and
96 changelog file formats are examples.)
98 <tag>Chosen Convention</tag>
100 If there are a number of technically viable choices
101 that can be made, but one needs to select one of
102 these options for inter-operability. The version
103 number format is one example.
106 Please note that these are not mutually exclusive;
107 selected conventions often become parts of standard
113 The footnotes present in this manual are
114 merely informative, and are not part of Debian policy itself.
118 The appendices to this manual are not necessarily normative,
119 either. Please see <ref id="pkg-scope"> for more information.
123 In the normative part of this manual,
124 the words <em>must</em>, <em>should</em> and
125 <em>may</em>, and the adjectives <em>required</em>,
126 <em>recommended</em> and <em>optional</em>, are used to
127 distinguish the significance of the various guidelines in
128 this policy document. Packages that do not conform to the
129 guidelines denoted by <em>must</em> (or <em>required</em>)
130 will generally not be considered acceptable for the Debian
131 distribution. Non-conformance with guidelines denoted by
132 <em>should</em> (or <em>recommended</em>) will generally be
133 considered a bug, but will not necessarily render a package
134 unsuitable for distribution. Guidelines denoted by
135 <em>may</em> (or <em>optional</em>) are truly optional and
136 adherence is left to the maintainer's discretion.
140 These classifications are roughly equivalent to the bug
141 severities <em>serious</em> (for <em>must</em> or
142 <em>required</em> directive violations), <em>minor</em>,
143 <em>normal</em> or <em>important</em>
144 (for <em>should</em> or <em>recommended</em> directive
145 violations) and <em>wishlist</em> (for <em>optional</em>
148 Compare RFC 2119. Note, however, that these words are
149 used in a different way in this document.
154 Much of the information presented in this manual will be
155 useful even when building a package which is to be
156 distributed in some other way or is intended for local use
162 <heading>New versions of this document</heading>
165 This manual is distributed via the Debian package
166 <package><url name="debian-policy"
167 id="http://packages.debian.org/debian-policy"></package>
168 (<httpsite>packages.debian.org</httpsite>
169 <httppath>/debian-policy</httppath>).
173 The current version of this document is also available from
174 the Debian web mirrors at
175 <tt><url name="/doc/debian-policy/"
176 id="http://www.debian.org/doc/debian-policy/"></tt>.
178 <httpsite>www.debian.org</httpsite>
179 <httppath>/doc/debian-policy/</httppath>)
180 Also available from the same directory are several other
181 formats: <file>policy.html.tar.gz</file>
182 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
183 <file>policy.pdf.gz</file>
184 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
185 and <file>policy.ps.gz</file>
186 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
190 The <package>debian-policy</package> package also includes the file
191 <file>upgrading-checklist.txt.gz</file> which indicates policy
192 changes between versions of this document.
197 <heading>Authors and Maintainers</heading>
200 Originally called "Debian GNU/Linux Policy Manual", this
201 manual was initially written in 1996 by Ian Jackson.
202 It was revised on November 27th, 1996 by David A. Morris.
203 Christian Schwarz added new sections on March 15th, 1997,
204 and reworked/restructured it in April-July 1997.
205 Christoph Lameter contributed the "Web Standard".
206 Julian Gilbey largely restructured it in 2001.
210 Since September 1998, the responsibility for the contents of
211 this document lies on the <url name="debian-policy mailing list"
212 id="mailto:debian-policy@lists.debian.org">. Proposals
213 are discussed there and inserted into policy after a certain
214 consensus is established.
215 <!-- insert shameless policy-process plug here eventually -->
216 The actual editing is done by a group of maintainers that have
217 no editorial powers. These are the current maintainers:
220 <item>Julian Gilbey</item>
221 <item>Branden Robinson</item>
222 <item>Josip Rodin</item>
223 <item>Manoj Srivastava</item>
228 While the authors of this document have tried hard to avoid
229 typos and other errors, these do still occur. If you discover
230 an error in this manual or if you want to give any
231 comments, suggestions, or criticisms please send an email to
232 the Debian Policy List,
233 <email>debian-policy@lists.debian.org</email>, or submit a
234 bug report against the <tt>debian-policy</tt> package.
238 Please do not try to reach the individual authors or maintainers
239 of the Policy Manual regarding changes to the Policy.
244 <heading>Related documents</heading>
247 There are several other documents other than this Policy Manual
248 that are necessary to fully understand some Debian policies and
253 The external "sub-policy" documents are referred to in:
254 <list compact="compact">
255 <item><ref id="fhs"></item>
256 <item><ref id="virtual_pkg"></item>
257 <item><ref id="menus"></item>
258 <item><ref id="mime"></item>
259 <item><ref id="perl"></item>
260 <item><ref id="maintscriptprompt"></item>
261 <item><ref id="emacs"></item>
266 In addition to those, which carry the weight of policy, there
267 is the Debian Developer's Reference. This document describes
268 procedures and resources for Debian developers, but it is
269 <em>not</em> normative; rather, it includes things that don't
270 belong in the Policy, such as best practices for developers.
274 The Developer's Reference is available in the
275 <package>developers-reference</package> package.
276 It's also available from the Debian web mirrors at
277 <tt><url name="/doc/developers-reference/"
278 id="http://www.debian.org/doc/developers-reference/"></tt>.
282 <sect id="definitions">
283 <heading>Definitions</heading>
286 The following terms are used in this Policy Manual:
290 The character encoding specified by ANSI X3.4-1986 and its
291 predecessor standards, referred to in MIME as US-ASCII, and
292 corresponding to an encoding in eight bits per character of
293 the first 128 <url id="http://www.unicode.org/"
294 name="Unicode"> characters, with the eighth bit always zero.
298 The transformation format (sometimes called encoding) of
299 <url id="http://www.unicode.org/" name="Unicode"> defined by
300 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
301 name="RFC 3629">. UTF-8 has the useful property of having
302 ASCII as a subset, so any text encoded in ASCII is trivially
312 <heading>The Debian Archive</heading>
315 The Debian GNU/Linux system is maintained and distributed as a
316 collection of <em>packages</em>. Since there are so many of
317 them (currently well over 15000), they are split into
318 <em>sections</em> and given <em>priorities</em> to simplify
319 the handling of them.
323 The effort of the Debian project is to build a free operating
324 system, but not every package we want to make accessible is
325 <em>free</em> in our sense (see the Debian Free Software
326 Guidelines, below), or may be imported/exported without
327 restrictions. Thus, the archive is split into areas<footnote>
328 The Debian archive software uses the term "component" internally
329 and in the Release file format to refer to the division of an
330 archive. The Debian Social Contract simply refers to "areas."
331 This document uses terminology similar to the Social Contract.
332 </footnote> based on their licenses and other restrictions.
336 The aims of this are:
338 <list compact="compact">
339 <item>to allow us to make as much software available as we can</item>
340 <item>to allow us to encourage everyone to write free software,
342 <item>to allow us to make it easy for people to produce
343 CD-ROMs of our system without violating any licenses,
344 import/export restrictions, or any other laws.</item>
349 The <em>main</em> archive area forms the <em>Debian GNU/Linux
354 Packages in the other archive areas (<tt>contrib</tt>,
355 <tt>non-free</tt>) are not considered to be part of the Debian
356 distribution, although we support their use and provide
357 infrastructure for them (such as our bug-tracking system and
358 mailing lists). This Debian Policy Manual applies to these
363 <heading>The Debian Free Software Guidelines</heading>
365 The Debian Free Software Guidelines (DFSG) form our
366 definition of "free software". These are:
368 <tag>1. Free Redistribution
371 The license of a Debian component may not restrict any
372 party from selling or giving away the software as a
373 component of an aggregate software distribution
374 containing programs from several different
375 sources. The license may not require a royalty or
376 other fee for such sale.
381 The program must include source code, and must allow
382 distribution in source code as well as compiled form.
384 <tag>3. Derived Works
387 The license must allow modifications and derived
388 works, and must allow them to be distributed under the
389 same terms as the license of the original software.
391 <tag>4. Integrity of The Author's Source Code
394 The license may restrict source-code from being
395 distributed in modified form <em>only</em> if the
396 license allows the distribution of "patch files"
397 with the source code for the purpose of modifying the
398 program at build time. The license must explicitly
399 permit distribution of software built from modified
400 source code. The license may require derived works to
401 carry a different name or version number from the
402 original software. (This is a compromise. The Debian
403 Project encourages all authors to not restrict any
404 files, source or binary, from being modified.)
406 <tag>5. No Discrimination Against Persons or Groups
409 The license must not discriminate against any person
412 <tag>6. No Discrimination Against Fields of Endeavor
415 The license must not restrict anyone from making use
416 of the program in a specific field of endeavor. For
417 example, it may not restrict the program from being
418 used in a business, or from being used for genetic
421 <tag>7. Distribution of License
424 The rights attached to the program must apply to all
425 to whom the program is redistributed without the need
426 for execution of an additional license by those
429 <tag>8. License Must Not Be Specific to Debian
432 The rights attached to the program must not depend on
433 the program's being part of a Debian system. If the
434 program is extracted from Debian and used or
435 distributed without Debian but otherwise within the
436 terms of the program's license, all parties to whom
437 the program is redistributed must have the same
438 rights as those that are granted in conjunction with
441 <tag>9. License Must Not Contaminate Other Software
444 The license must not place restrictions on other
445 software that is distributed along with the licensed
446 software. For example, the license must not insist
447 that all other programs distributed on the same medium
448 must be free software.
450 <tag>10. Example Licenses
453 The "GPL," "BSD," and "Artistic" licenses are examples of
454 licenses that we consider <em>free</em>.
461 <heading>Archive areas</heading>
464 <heading>The main archive area</heading>
467 Every package in <em>main</em> must comply with the DFSG
468 (Debian Free Software Guidelines).
472 In addition, the packages in <em>main</em>
473 <list compact="compact">
475 must not require a package outside of <em>main</em>
476 for compilation or execution (thus, the package must
477 not declare a "Depends", "Recommends", or
478 "Build-Depends" relationship on a non-<em>main</em>
482 must not be so buggy that we refuse to support them,
486 must meet all policy requirements presented in this
495 <heading>The contrib archive area</heading>
498 Every package in <em>contrib</em> must comply with the DFSG.
502 In addition, the packages in <em>contrib</em>
503 <list compact="compact">
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
517 Examples of packages which would be included in
518 <em>contrib</em> are:
519 <list compact="compact">
521 free packages which require <em>contrib</em>,
522 <em>non-free</em> packages or packages which are not
523 in our archive at all for compilation or execution,
527 wrapper packages or other sorts of free accessories for
534 <sect1 id="non-free">
535 <heading>The non-free archive area</heading>
538 Packages must be placed in <em>non-free</em> if they are
539 not compliant with the DFSG or are encumbered by patents
540 or other legal issues that make their distribution
545 In addition, the packages in <em>non-free</em>
546 <list compact="compact">
548 must not be so buggy that we refuse to support them,
552 must meet all policy requirements presented in this
553 manual that it is possible for them to meet.
555 It is possible that there are policy
556 requirements which the package is unable to
557 meet, for example, if the source is
558 unavailable. These situations will need to be
559 handled on a case-by-case basis.
568 <sect id="pkgcopyright">
569 <heading>Copyright considerations</heading>
572 Every package must be accompanied by a verbatim copy of its
573 copyright information and distribution license in the file
574 <file>/usr/share/doc/<var>package</var>/copyright</file>
575 (see <ref id="copyrightfile"> for further details).
579 We reserve the right to restrict files from being included
580 anywhere in our archives if
581 <list compact="compact">
583 their use or distribution would break a law,
586 there is an ethical conflict in their distribution or
590 we would have to sign a license for them, or
593 their distribution would conflict with other project
600 Programs whose authors encourage the user to make
601 donations are fine for the main distribution, provided
602 that the authors do not claim that not donating is
603 immoral, unethical, illegal or something similar; in such
604 a case they must go in <em>non-free</em>.
608 Packages whose copyright permission notices (or patent
609 problems) do not even allow redistribution of binaries
610 only, and where no special permission has been obtained,
611 must not be placed on the Debian FTP site and its mirrors
616 Note that under international copyright law (this applies
617 in the United States, too), <em>no</em> distribution or
618 modification of a work is allowed without an explicit
619 notice saying so. Therefore a program without a copyright
620 notice <em>is</em> copyrighted and you may not do anything
621 to it without risking being sued! Likewise if a program
622 has a copyright notice but no statement saying what is
623 permitted then nothing is permitted.
627 Many authors are unaware of the problems that restrictive
628 copyrights (or lack of copyright notices) can cause for
629 the users of their supposedly-free software. It is often
630 worthwhile contacting such authors diplomatically to ask
631 them to modify their license terms. However, this can be a
632 politically difficult thing to do and you should ask for
633 advice on the <tt>debian-legal</tt> mailing list first, as
638 When in doubt about a copyright, send mail to
639 <email>debian-legal@lists.debian.org</email>. Be prepared
640 to provide us with the copyright statement. Software
641 covered by the GPL, public domain software and BSD-like
642 copyrights are safe; be wary of the phrases "commercial
643 use prohibited" and "distribution restricted".
647 <sect id="subsections">
648 <heading>Sections</heading>
651 The packages in the archive areas <em>main</em>,
652 <em>contrib</em> and <em>non-free</em> are grouped further into
653 <em>sections</em> to simplify handling.
657 The archive area and section for each package should be
658 specified in the package's <tt>Section</tt> control record (see
659 <ref id="f-Section">). However, the maintainer of the Debian
660 archive may override this selection to ensure the consistency of
661 the Debian distribution. The <tt>Section</tt> field should be
663 <list compact="compact">
665 <em>section</em> if the package is in the
666 <em>main</em> archive area,
669 <em>area/section</em> if the package is in
670 the <em>contrib</em> or <em>non-free</em>
677 The Debian archive maintainers provide the authoritative
678 list of sections. At present, they are:
679 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
680 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
681 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
682 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
683 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
684 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
685 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
686 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
687 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
688 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
689 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
690 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
691 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
692 <em>zope</em>. The additional section <em>debian-installer</em>
693 contains special packages used by the installer and is not used
694 for normal Debian packages.
698 For more information about the sections and their definitions,
699 see the <url id="http://packages.debian.org/unstable/"
700 name="list of sections in unstable">.
704 <sect id="priorities">
705 <heading>Priorities</heading>
708 Each package should have a <em>priority</em> value, which is
709 included in the package's <em>control record</em>
710 (see <ref id="f-Priority">).
711 This information is used by the Debian package management tools to
712 separate high-priority packages from less-important packages.
716 The following <em>priority levels</em> are recognized by the
717 Debian package management tools.
719 <tag><tt>required</tt></tag>
721 Packages which are necessary for the proper
722 functioning of the system (usually, this means that
723 dpkg functionality depends on these packages).
724 Removing a <tt>required</tt> package may cause your
725 system to become totally broken and you may not even
726 be able to use <prgn>dpkg</prgn> to put things back,
727 so only do so if you know what you are doing. Systems
728 with only the <tt>required</tt> packages are probably
729 unusable, but they do have enough functionality to
730 allow the sysadmin to boot and install more software.
732 <tag><tt>important</tt></tag>
734 Important programs, including those which one would
735 expect to find on any Unix-like system. If the
736 expectation is that an experienced Unix person who
737 found it missing would say "What on earth is going on,
738 where is <prgn>foo</prgn>?", it must be an
739 <tt>important</tt> package.<footnote>
740 This is an important criterion because we are
741 trying to produce, amongst other things, a free
744 Other packages without which the system will not run
745 well or be usable must also have priority
746 <tt>important</tt>. This does
747 <em>not</em> include Emacs, the X Window System, TeX
748 or any other large applications. The
749 <tt>important</tt> packages are just a bare minimum of
750 commonly-expected and necessary tools.
752 <tag><tt>standard</tt></tag>
754 These packages provide a reasonably small but not too
755 limited character-mode system. This is what will be
756 installed by default if the user doesn't select anything
757 else. It doesn't include many large applications.
759 <tag><tt>optional</tt></tag>
761 (In a sense everything that isn't required is
762 optional, but that's not what is meant here.) This is
763 all the software that you might reasonably want to
764 install if you didn't know what it was and don't have
765 specialized requirements. This is a much larger system
766 and includes the X Window System, a full TeX
767 distribution, and many applications. Note that
768 optional packages should not conflict with each other.
770 <tag><tt>extra</tt></tag>
772 This contains all packages that conflict with others
773 with required, important, standard or optional
774 priorities, or are only likely to be useful if you
775 already know what they are or have specialized
776 requirements (such as packages containing only detached
783 Packages must not depend on packages with lower priority
784 values (excluding build-time dependencies). In order to
785 ensure this, the priorities of one or more packages may need
794 <heading>Binary packages</heading>
797 The Debian GNU/Linux distribution is based on the Debian
798 package management system, called <prgn>dpkg</prgn>. Thus,
799 all packages in the Debian distribution must be provided
800 in the <tt>.deb</tt> file format.
804 <heading>The package name</heading>
807 Every package must have a name that's unique within the Debian
812 The package name is included in the control field
813 <tt>Package</tt>, the format of which is described
814 in <ref id="f-Package">.
815 The package name is also included as a part of the file name
816 of the <tt>.deb</tt> file.
821 <heading>The version of a package</heading>
824 Every package has a version number recorded in its
825 <tt>Version</tt> control file field, described in
826 <ref id="f-Version">.
830 The package management system imposes an ordering on version
831 numbers, so that it can tell whether packages are being up- or
832 downgraded and so that package system front end applications
833 can tell whether a package it finds available is newer than
834 the one installed on the system. The version number format
835 has the most significant parts (as far as comparison is
836 concerned) at the beginning.
840 If an upstream package has problematic version numbers they
841 should be converted to a sane form for use in the
842 <tt>Version</tt> field.
846 <heading>Version numbers based on dates</heading>
849 In general, Debian packages should use the same version
850 numbers as the upstream sources.
854 However, in some cases where the upstream version number is
855 based on a date (e.g., a development "snapshot" release) the
856 package management system cannot handle these version
857 numbers without epochs. For example, dpkg will consider
858 "96May01" to be greater than "96Dec24".
862 To prevent having to use epochs for every new upstream
863 version, the date based portion of the version number
864 should be changed to the following format in such cases:
865 "19960501", "19961224". It is up to the maintainer whether
866 they want to bother the upstream maintainer to change
867 the version numbers upstream, too.
871 Note that other version formats based on dates which are
872 parsed correctly by the package management system should
873 <em>not</em> be changed.
877 Native Debian packages (i.e., packages which have been
878 written especially for Debian) whose version numbers include
879 dates should always use the "YYYYMMDD" format.
886 <heading>The maintainer of a package</heading>
889 Every package must have a Debian maintainer (the
890 maintainer may be one person or a group of people
891 reachable from a common email address, such as a mailing
892 list). The maintainer is responsible for ensuring that
893 the package is placed in the appropriate distributions.
897 The maintainer must be specified in the
898 <tt>Maintainer</tt> control field with their correct name
899 and a working email address. If one person maintains
900 several packages, they should try to avoid having
901 different forms of their name and email address in
902 the <tt>Maintainer</tt> fields of those packages.
906 The format of the <tt>Maintainer</tt> control field is
907 described in <ref id="f-Maintainer">.
911 If the maintainer of a package quits from the Debian
912 project, "Debian QA Group"
913 <email>packages@qa.debian.org</email> takes over the
914 maintainer-ship of the package until someone else
915 volunteers for that task. These packages are called
916 <em>orphaned packages</em>.<footnote>
917 The detailed procedure for doing this gracefully can
918 be found in the Debian Developer's Reference,
919 see <ref id="related">.
924 <sect id="descriptions">
925 <heading>The description of a package</heading>
928 Every Debian package must have an extended description
929 stored in the appropriate field of the control record.
930 The technical information about the format of the
931 <tt>Description</tt> field is in <ref id="f-Description">.
935 The description should describe the package (the program) to a
936 user (system administrator) who has never met it before so that
937 they have enough information to decide whether they want to
938 install it. This description should not just be copied verbatim
939 from the program's documentation.
943 Put important information first, both in the synopsis and
944 extended description. Sometimes only the first part of the
945 synopsis or of the description will be displayed. You can
946 assume that there will usually be a way to see the whole
947 extended description.
951 The description should also give information about the
952 significant dependencies and conflicts between this package
953 and others, so that the user knows why these dependencies and
954 conflicts have been declared.
958 Instructions for configuring or using the package should
959 not be included (that is what installation scripts,
960 manual pages, info files, etc., are for). Copyright
961 statements and other administrivia should not be included
962 either (that is what the copyright file is for).
965 <sect1 id="synopsis"><heading>The single line synopsis</heading>
968 The single line synopsis should be kept brief - certainly
973 Do not include the package name in the synopsis line. The
974 display software knows how to display this already, and you
975 do not need to state it. Remember that in many situations
976 the user may only see the synopsis line - make it as
977 informative as you can.
982 <sect1 id="extendeddesc"><heading>The extended description</heading>
985 Do not try to continue the single line synopsis into the
986 extended description. This will not work correctly when
987 the full description is displayed, and makes no sense
988 where only the summary (the single line synopsis) is
993 The extended description should describe what the package
994 does and how it relates to the rest of the system (in terms
995 of, for example, which subsystem it is which part of).
999 The description field needs to make sense to anyone, even
1000 people who have no idea about any of the things the
1001 package deals with.<footnote>
1002 The blurb that comes with a program in its
1003 announcements and/or <prgn>README</prgn> files is
1004 rarely suitable for use in a description. It is
1005 usually aimed at people who are already in the
1006 community where the package is used.
1015 <heading>Dependencies</heading>
1018 Every package must specify the dependency information
1019 about other packages that are required for the first to
1024 For example, a dependency entry must be provided for any
1025 shared libraries required by a dynamically-linked executable
1026 binary in a package.
1030 Packages are not required to declare any dependencies they
1031 have on other packages which are marked <tt>Essential</tt>
1032 (see below), and should not do so unless they depend on a
1033 particular version of that package.<footnote>
1035 Essential is needed in part to avoid unresolvable dependency
1036 loops on upgrade. If packages add unnecessary dependencies
1037 on packages in this set, the chances that there
1038 <strong>will</strong> be an unresolvable dependency loop
1039 caused by forcing these Essential packages to be configured
1040 first before they need to be is greatly increased. It also
1041 increases the chances that frontends will be unable to
1042 <strong>calculate</strong> an upgrade path, even if one
1046 Also, functionality is rarely ever removed from the
1047 Essential set, but <em>packages</em> have been removed from
1048 the Essential set when the functionality moved to a
1049 different package. So depending on these packages <em>just
1050 in case</em> they stop being essential does way more harm
1057 Sometimes, a package requires another package to be installed
1058 <em>and</em> configured before it can be installed. In this
1059 case, you must specify a <tt>Pre-Depends</tt> entry for
1064 You should not specify a <tt>Pre-Depends</tt> entry for a
1065 package before this has been discussed on the
1066 <tt>debian-devel</tt> mailing list and a consensus about
1067 doing that has been reached.
1071 The format of the package interrelationship control fields is
1072 described in <ref id="relationships">.
1076 <sect id="virtual_pkg">
1077 <heading>Virtual packages</heading>
1080 Sometimes, there are several packages which offer
1081 more-or-less the same functionality. In this case, it's
1082 useful to define a <em>virtual package</em> whose name
1083 describes that common functionality. (The virtual
1084 packages only exist logically, not physically; that's why
1085 they are called <em>virtual</em>.) The packages with this
1086 particular function will then <em>provide</em> the virtual
1087 package. Thus, any other package requiring that function
1088 can simply depend on the virtual package without having to
1089 specify all possible packages individually.
1093 All packages should use virtual package names where
1094 appropriate, and arrange to create new ones if necessary.
1095 They should not use virtual package names (except privately,
1096 amongst a cooperating group of packages) unless they have
1097 been agreed upon and appear in the list of virtual package
1098 names. (See also <ref id="virtual">)
1102 The latest version of the authoritative list of virtual
1103 package names can be found in the <tt>debian-policy</tt> package.
1104 It is also available from the Debian web mirrors at
1105 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1106 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1110 The procedure for updating the list is described in the preface
1117 <heading>Base system</heading>
1120 The <tt>base system</tt> is a minimum subset of the Debian
1121 GNU/Linux system that is installed before everything else
1122 on a new system. Only very few packages are allowed to form
1123 part of the base system, in order to keep the required disk
1128 The base system consists of all those packages with priority
1129 <tt>required</tt> or <tt>important</tt>. Many of them will
1130 be tagged <tt>essential</tt> (see below).
1135 <heading>Essential packages</heading>
1138 Essential is defined as the minimal set of functionality that
1139 must be available and usable on the system at all times, even
1140 when packages are in an unconfigured (but unpacked) state.
1141 Packages are tagged <tt>essential</tt> for a system using the
1142 <tt>Essential</tt> control file field. The format of the
1143 <tt>Essential</tt> control field is described in <ref
1148 Since these packages cannot be easily removed (one has to
1149 specify an extra <em>force option</em> to
1150 <prgn>dpkg</prgn> to do so), this flag must not be used
1151 unless absolutely necessary. A shared library package
1152 must not be tagged <tt>essential</tt>; dependencies will
1153 prevent its premature removal, and we need to be able to
1154 remove it when it has been superseded.
1158 Since dpkg will not prevent upgrading of other packages
1159 while an <tt>essential</tt> package is in an unconfigured
1160 state, all <tt>essential</tt> packages must supply all of
1161 their core functionality even when unconfigured. If the
1162 package cannot satisfy this requirement it must not be
1163 tagged as essential, and any packages depending on this
1164 package must instead have explicit dependency fields as
1169 Maintainers should take great care in adding any programs,
1170 interfaces, or functionality to <tt>essential</tt> packages.
1171 Packages may assume that functionality provided by
1172 <tt>essential</tt> packages is always available without
1173 declaring explicit dependencies, which means that removing
1174 functionality from the Essential set is very difficult and is
1175 almost never done. Any capability added to an
1176 <tt>essential</tt> package therefore creates an obligation to
1177 support that capability as part of the Essential set in
1182 You must not tag any packages <tt>essential</tt> before
1183 this has been discussed on the <tt>debian-devel</tt>
1184 mailing list and a consensus about doing that has been
1189 <sect id="maintscripts">
1190 <heading>Maintainer Scripts</heading>
1193 The package installation scripts should avoid producing
1194 output which is unnecessary for the user to see and
1195 should rely on <prgn>dpkg</prgn> to stave off boredom on
1196 the part of a user installing many packages. This means,
1197 amongst other things, using the <tt>--quiet</tt> option on
1198 <prgn>install-info</prgn>.
1202 Errors which occur during the execution of an installation
1203 script must be checked and the installation must not
1204 continue after an error.
1208 Note that in general <ref id="scripts"> applies to package
1209 maintainer scripts, too.
1213 You should not use <prgn>dpkg-divert</prgn> on a file
1214 belonging to another package without consulting the
1215 maintainer of that package first.
1219 All packages which supply an instance of a common command
1220 name (or, in general, filename) should generally use
1221 <prgn>update-alternatives</prgn>, so that they may be
1222 installed together. If <prgn>update-alternatives</prgn>
1223 is not used, then each package must use
1224 <tt>Conflicts</tt> to ensure that other packages are
1225 de-installed. (In this case, it may be appropriate to
1226 specify a conflict against earlier versions of something
1227 that previously did not use
1228 <prgn>update-alternatives</prgn>; this is an exception to
1229 the usual rule that versioned conflicts should be
1233 <sect1 id="maintscriptprompt">
1234 <heading>Prompting in maintainer scripts</heading>
1236 Package maintainer scripts may prompt the user if
1237 necessary. Prompting must be done by communicating
1238 through a program, such as <prgn>debconf</prgn>, which
1239 conforms to the Debian Configuration Management
1240 Specification, version 2 or higher.
1244 Packages which are essential, or which are dependencies of
1245 essential packages, may fall back on another prompting method
1246 if no such interface is available when they are executed.
1250 The Debian Configuration Management Specification is included
1251 in the <file>debconf_specification</file> files in the
1252 <package>debian-policy</package> package.
1253 It is also available from the Debian web mirrors at
1254 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1255 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1259 Packages which use the Debian Configuration Management
1260 Specification may contain an additional
1261 <prgn>config</prgn> script and a <tt>templates</tt>
1262 file in their control archive<footnote>
1263 The control.tar.gz inside the .deb.
1264 See <manref name="deb" section="5">.
1266 The <prgn>config</prgn> script might be run before the
1267 <prgn>preinst</prgn> script, and before the package is unpacked
1268 or any of its dependencies or pre-dependencies are satisfied.
1269 Therefore it must work using only the tools present in
1270 <em>essential</em> packages.<footnote>
1271 <package>Debconf</package> or another tool that
1272 implements the Debian Configuration Management
1273 Specification will also be installed, and any
1274 versioned dependencies on it will be satisfied
1275 before preconfiguration begins.
1280 Packages which use the Debian Configuration Management
1281 Specification must allow for translation of their user-visible
1282 messages by using a gettext-based system such as the one
1283 provided by the <package>po-debconf</package> package.
1287 Packages should try to minimize the amount of prompting
1288 they need to do, and they should ensure that the user
1289 will only ever be asked each question once. This means
1290 that packages should try to use appropriate shared
1291 configuration files (such as <file>/etc/papersize</file> and
1292 <file>/etc/news/server</file>), and shared
1293 <package>debconf</package> variables rather than each
1294 prompting for their own list of required pieces of
1299 It also means that an upgrade should not ask the same
1300 questions again, unless the user has used
1301 <tt>dpkg --purge</tt> to remove the package's configuration.
1302 The answers to configuration questions should be stored in an
1303 appropriate place in <file>/etc</file> so that the user can
1304 modify them, and how this has been done should be
1309 If a package has a vitally important piece of
1310 information to pass to the user (such as "don't run me
1311 as I am, you must edit the following configuration files
1312 first or you risk your system emitting badly-formatted
1313 messages"), it should display this in the
1314 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1315 prompt the user to hit return to acknowledge the
1316 message. Copyright messages do not count as vitally
1317 important (they belong in
1318 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1319 neither do instructions on how to use a program (these
1320 should be in on-line documentation, where all the users
1325 Any necessary prompting should almost always be confined
1326 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1327 script. If it is done in the <prgn>postinst</prgn>, it
1328 should be protected with a conditional so that
1329 unnecessary prompting doesn't happen if a package's
1330 installation fails and the <prgn>postinst</prgn> is
1331 called with <tt>abort-upgrade</tt>,
1332 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1342 <heading>Source packages</heading>
1344 <sect id="standardsversion">
1345 <heading>Standards conformance</heading>
1348 Source packages should specify the most recent version number
1349 of this policy document with which your package complied
1350 when it was last updated.
1354 This information may be used to file bug reports
1355 automatically if your package becomes too much out of date.
1359 The version is specified in the <tt>Standards-Version</tt>
1361 The format of the <tt>Standards-Version</tt> field is
1362 described in <ref id="f-Standards-Version">.
1366 You should regularly, and especially if your package has
1367 become out of date, check for the newest Policy Manual
1368 available and update your package, if necessary. When your
1369 package complies with the new standards you should update the
1370 <tt>Standards-Version</tt> source package field and
1371 release it.<footnote>
1372 See the file <file>upgrading-checklist</file> for
1373 information about policy which has changed between
1374 different versions of this document.
1380 <sect id="pkg-relations">
1381 <heading>Package relationships</heading>
1384 Source packages should specify which binary packages they
1385 require to be installed or not to be installed in order to
1386 build correctly. For example, if building a package
1387 requires a certain compiler, then the compiler should be
1388 specified as a build-time dependency.
1392 It is not necessary to explicitly specify build-time
1393 relationships on a minimal set of packages that are always
1394 needed to compile, link and put in a Debian package a
1395 standard "Hello World!" program written in C or C++. The
1396 required packages are called <em>build-essential</em>, and
1397 an informational list can be found in
1398 <file>/usr/share/doc/build-essential/list</file> (which is
1399 contained in the <tt>build-essential</tt>
1402 <list compact="compact">
1404 This allows maintaining the list separately
1405 from the policy documents (the list does not
1406 need the kind of control that the policy
1410 Having a separate package allows one to install
1411 the build-essential packages on a machine, as
1412 well as allowing other packages such as tasks to
1413 require installation of the build-essential
1414 packages using the depends relation.
1417 The separate package allows bug reports against
1418 the list to be categorized separately from
1419 the policy management process in the BTS.
1426 When specifying the set of build-time dependencies, one
1427 should list only those packages explicitly required by the
1428 build. It is not necessary to list packages which are
1429 required merely because some other package in the list of
1430 build-time dependencies depends on them.<footnote>
1431 The reason for this is that dependencies change, and
1432 you should list all those packages, and <em>only</em>
1433 those packages that <em>you</em> need directly. What
1434 others need is their business. For example, if you
1435 only link against <file>libimlib</file>, you will need to
1436 build-depend on <package>libimlib2-dev</package> but
1437 not against any <tt>libjpeg*</tt> packages, even
1438 though <tt>libimlib2-dev</tt> currently depends on
1439 them: installation of <package>libimlib2-dev</package>
1440 will automatically ensure that all of its run-time
1441 dependencies are satisfied.
1446 If build-time dependencies are specified, it must be
1447 possible to build the package and produce working binaries
1448 on a system with only essential and build-essential
1449 packages installed and also those required to satisfy the
1450 build-time relationships (including any implied
1451 relationships). In particular, this means that version
1452 clauses should be used rigorously in build-time
1453 relationships so that one cannot produce bad or
1454 inconsistently configured packages when the relationships
1455 are properly satisfied.
1459 <ref id="relationships"> explains the technical details.
1464 <heading>Changes to the upstream sources</heading>
1467 If changes to the source code are made that are not
1468 specific to the needs of the Debian system, they should be
1469 sent to the upstream authors in whatever form they prefer
1470 so as to be included in the upstream version of the
1475 If you need to configure the package differently for
1476 Debian or for Linux, and the upstream source doesn't
1477 provide a way to do so, you should add such configuration
1478 facilities (for example, a new <prgn>autoconf</prgn> test
1479 or <tt>#define</tt>) and send the patch to the upstream
1480 authors, with the default set to the way they originally
1481 had it. You can then easily override the default in your
1482 <file>debian/rules</file> or wherever is appropriate.
1486 You should make sure that the <prgn>configure</prgn> utility
1487 detects the correct architecture specification string
1488 (refer to <ref id="arch-spec"> for details).
1492 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1493 <prgn>configure</prgn> scripts are used, you should edit the
1494 <file>.in</file> files rather than editing the
1495 <prgn>Makefile</prgn> directly. This allows the user to
1496 reconfigure the package if necessary. You should
1497 <em>not</em> configure the package and edit the generated
1498 <prgn>Makefile</prgn>! This makes it impossible for someone
1499 else to later reconfigure the package without losing the
1505 <sect id="dpkgchangelog">
1506 <heading>Debian changelog: <file>debian/changelog</file></heading>
1509 Changes in the Debian version of the package should be
1510 briefly explained in the Debian changelog file
1511 <file>debian/changelog</file>.<footnote>
1513 Mistakes in changelogs are usually best rectified by
1514 making a new changelog entry rather than "rewriting
1515 history" by editing old changelog entries.
1518 This includes modifications
1519 made in the Debian package compared to the upstream one
1520 as well as other changes and updates to the package.
1522 Although there is nothing stopping an author who is also
1523 the Debian maintainer from using this changelog for all
1524 their changes, it will have to be renamed if the Debian
1525 and upstream maintainers become different people. In such
1526 a case, however, it might be better to maintain the package
1527 as a non-native package.
1532 The format of the <file>debian/changelog</file> allows the
1533 package building tools to discover which version of the package
1534 is being built and find out other release-specific information.
1538 That format is a series of entries like this:
1540 <example compact="compact">
1541 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1543 [optional blank line(s), stripped]
1545 * <var>change details</var>
1546 <var>more change details</var>
1548 [blank line(s), included in output of dpkg-parsechangelog]
1550 * <var>even more change details</var>
1552 [optional blank line(s), stripped]
1554 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1559 <var>package</var> and <var>version</var> are the source
1560 package name and version number.
1564 <var>distribution(s)</var> lists the distributions where
1565 this version should be installed when it is uploaded - it
1566 is copied to the <tt>Distribution</tt> field in the
1567 <file>.changes</file> file. See <ref id="f-Distribution">.
1571 <var>urgency</var> is the value for the <tt>Urgency</tt>
1572 field in the <file>.changes</file> file for the upload
1573 (see <ref id="f-Urgency">). It is not possible to specify
1574 an urgency containing commas; commas are used to separate
1575 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1576 <prgn>dpkg</prgn> changelog format (though there is
1577 currently only one useful <var>keyword</var>,
1582 The change details may in fact be any series of lines
1583 starting with at least two spaces, but conventionally each
1584 change starts with an asterisk and a separating space and
1585 continuation lines are indented so as to bring them in
1586 line with the start of the text above. Blank lines may be
1587 used here to separate groups of changes, if desired.
1591 If this upload resolves bugs recorded in the Bug Tracking
1592 System (BTS), they may be automatically closed on the
1593 inclusion of this package into the Debian archive by
1594 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1595 in the change details.<footnote>
1596 To be precise, the string should match the following
1597 Perl regular expression:
1599 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1601 Then all of the bug numbers listed will be closed by the
1602 archive maintenance script (<prgn>katie</prgn>) using the
1603 <var>version</var> of the changelog entry.
1605 This information is conveyed via the <tt>Closes</tt> field
1606 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1610 The maintainer name and email address used in the changelog
1611 should be the details of the person uploading <em>this</em>
1612 version. They are <em>not</em> necessarily those of the
1613 usual package maintainer. The information here will be
1614 copied to the <tt>Changed-By</tt> field in the
1615 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1616 and then later used to send an acknowledgement when the
1617 upload has been installed.
1621 The <var>date</var> must be in RFC822 format<footnote>
1622 This is generated by <tt>date -R</tt>.
1623 </footnote>; it must include the time zone specified
1624 numerically, with the time zone name or abbreviation
1625 optionally present as a comment in parentheses.
1629 The first "title" line with the package name must start
1630 at the left hand margin. The "trailer" line with the
1631 maintainer and date details must be preceded by exactly
1632 one space. The maintainer details and the date must be
1633 separated by exactly two spaces.
1637 The entire changelog must be encoded in UTF-8.
1641 For more information on placement of the changelog files
1642 within binary packages, please see <ref id="changelogs">.
1646 <sect id="dpkgcopyright">
1647 <heading>Copyright: <file>debian/copyright</file></heading>
1649 Every package must be accompanied by a verbatim copy of its
1650 copyright information and distribution license in the file
1651 <file>/usr/share/doc/<var>package</var>/copyright</file>
1652 (see <ref id="copyrightfile"> for further details). Also see
1653 <ref id="pkgcopyright"> for further considerations related
1654 to copyrights for packages.
1658 <heading>Error trapping in makefiles</heading>
1661 When <prgn>make</prgn> invokes a command in a makefile
1662 (including your package's upstream makefiles and
1663 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1664 means that <prgn>sh</prgn>'s usual bad error handling
1665 properties apply: if you include a miniature script as one
1666 of the commands in your makefile you'll find that if you
1667 don't do anything about it then errors are not detected
1668 and <prgn>make</prgn> will blithely continue after
1673 Every time you put more than one shell command (this
1674 includes using a loop) in a makefile command you
1675 must make sure that errors are trapped. For
1676 simple compound commands, such as changing directory and
1677 then running a program, using <tt>&&</tt> rather
1678 than semicolon as a command separator is sufficient. For
1679 more complex commands including most loops and
1680 conditionals you should include a separate <tt>set -e</tt>
1681 command at the start of every makefile command that's
1682 actually one of these miniature shell scripts.
1686 <sect id="timestamps">
1687 <heading>Time Stamps</heading>
1689 Maintainers should preserve the modification times of the
1690 upstream source files in a package, as far as is reasonably
1692 The rationale is that there is some information conveyed
1693 by knowing the age of the file, for example, you could
1694 recognize that some documentation is very old by looking
1695 at the modification time, so it would be nice if the
1696 modification time of the upstream source would be
1702 <sect id="restrictions">
1703 <heading>Restrictions on objects in source packages</heading>
1706 The source package may not contain any hard links<footnote>
1708 This is not currently detected when building source
1709 packages, but only when extracting
1713 Hard links may be permitted at some point in the
1714 future, but would require a fair amount of
1717 </footnote>, device special files, sockets or setuid or
1718 setgid files.<footnote>
1719 Setgid directories are allowed.
1724 <sect id="debianrules">
1725 <heading>Main building script: <file>debian/rules</file></heading>
1728 This file must be an executable makefile, and contains the
1729 package-specific recipes for compiling the package and
1730 building binary package(s) from the source.
1734 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1735 so that it can be invoked by saying its name rather than
1736 invoking <prgn>make</prgn> explicitly. That is, invoking
1737 either of <tt>make -f debian/rules <em>args...</em></tt>
1738 or <tt>./debian/rules <em>args...</em></tt> must result in
1743 Since an interactive <file>debian/rules</file> script makes it
1744 impossible to auto-compile that package and also makes it
1745 hard for other people to reproduce the same binary
1746 package, all <em>required targets</em> must be
1747 non-interactive. At a minimum, required targets are the
1748 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1749 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1750 <em>binary-indep</em>, and <em>build</em>. It also follows
1751 that any target that these targets depend on must also be
1756 The targets are as follows (required unless stated otherwise):
1758 <tag><tt>build</tt></tag>
1761 The <tt>build</tt> target should perform all the
1762 configuration and compilation of the package.
1763 If a package has an interactive pre-build
1764 configuration routine, the Debianized source package
1765 must either be built after this has taken place (so
1766 that the binary package can be built without rerunning
1767 the configuration) or the configuration routine
1768 modified to become non-interactive. (The latter is
1769 preferable if there are architecture-specific features
1770 detected by the configuration routine.)
1774 For some packages, notably ones where the same
1775 source tree is compiled in different ways to produce
1776 two binary packages, the <tt>build</tt> target
1777 does not make much sense. For these packages it is
1778 good enough to provide two (or more) targets
1779 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1780 for each of the ways of building the package, and a
1781 <tt>build</tt> target that does nothing. The
1782 <tt>binary</tt> target will have to build the
1783 package in each of the possible ways and make the
1784 binary package out of each.
1788 The <tt>build</tt> target must not do anything
1789 that might require root privilege.
1793 The <tt>build</tt> target may need to run the
1794 <tt>clean</tt> target first - see below.
1798 When a package has a configuration and build routine
1799 which takes a long time, or when the makefiles are
1800 poorly designed, or when <tt>build</tt> needs to
1801 run <tt>clean</tt> first, it is a good idea to
1802 <tt>touch build</tt> when the build process is
1803 complete. This will ensure that if <tt>debian/rules
1804 build</tt> is run again it will not rebuild the whole
1806 Another common way to do this is for <tt>build</tt>
1807 to depend on <prgn>build-stamp</prgn> and to do
1808 nothing else, and for the <prgn>build-stamp</prgn>
1809 target to do the building and to <tt>touch
1810 build-stamp</tt> on completion. This is
1811 especially useful if the build routine creates a
1812 file or directory called <tt>build</tt>; in such a
1813 case, <tt>build</tt> will need to be listed as
1814 a phony target (i.e., as a dependency of the
1815 <tt>.PHONY</tt> target). See the documentation of
1816 <prgn>make</prgn> for more information on phony
1822 <tag><tt>build-arch</tt> (optional),
1823 <tt>build-indep</tt> (optional)
1827 A package may also provide both of the targets
1828 <tt>build-arch</tt> and <tt>build-indep</tt>.
1829 The <tt>build-arch</tt> target, if provided, should
1830 perform all the configuration and compilation required
1831 for producing all architecture-dependant binary packages
1832 (those packages for which the body of the
1833 <tt>Architecture</tt> field in <tt>debian/control</tt>
1834 is not <tt>all</tt>).
1835 Similarly, the <tt>build-indep</tt> target, if
1836 provided, should perform all the configuration and
1837 compilation required for producing all
1838 architecture-independent binary packages
1839 (those packages for which the body of the
1840 <tt>Architecture</tt> field in <tt>debian/control</tt>
1842 The <tt>build</tt> target should depend on those of the
1843 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1844 are provided in the rules file.
1848 If one or both of the targets <tt>build-arch</tt> and
1849 <tt>build-indep</tt> are not provided, then invoking
1850 <file>debian/rules</file> with one of the not-provided
1851 targets as arguments should produce a exit status code
1852 of 2. Usually this is provided automatically by make
1853 if the target is missing.
1857 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1858 must not do anything that might require root privilege.
1862 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1863 <tt>binary-indep</tt>
1867 The <tt>binary</tt> target must be all that is
1868 necessary for the user to build the binary package(s)
1869 produced from this source package. It is
1870 split into two parts: <prgn>binary-arch</prgn> builds
1871 the binary packages which are specific to a particular
1872 architecture, and <tt>binary-indep</tt> builds
1873 those which are not.
1876 <tt>binary</tt> may be (and commonly is) a target with
1877 no commands which simply depends on
1878 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1881 Both <tt>binary-*</tt> targets should depend on the
1882 <tt>build</tt> target, or on the appropriate
1883 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1884 provided, so that the package is built if it has not
1885 been already. It should then create the relevant
1886 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1887 make their control files and <prgn>dpkg-deb</prgn> to
1888 build them and place them in the parent of the top
1893 Both the <tt>binary-arch</tt> and
1894 <tt>binary-indep</tt> targets <em>must</em> exist.
1895 If one of them has nothing to do (which will always be
1896 the case if the source generates only a single binary
1897 package, whether architecture-dependent or not), it
1898 must still exist and must always succeed.
1902 The <tt>binary</tt> targets must be invoked as
1904 The <prgn>fakeroot</prgn> package often allows one
1905 to build a package correctly even without being
1911 <tag><tt>clean</tt></tag>
1914 This must undo any effects that the <tt>build</tt>
1915 and <tt>binary</tt> targets may have had, except
1916 that it should leave alone any output files created in
1917 the parent directory by a run of a <tt>binary</tt>
1922 If a <tt>build</tt> file is touched at the end of
1923 the <tt>build</tt> target, as suggested above, it
1924 should be removed as the first action that
1925 <tt>clean</tt> performs, so that running
1926 <tt>build</tt> again after an interrupted
1927 <tt>clean</tt> doesn't think that everything is
1932 The <tt>clean</tt> target may need to be
1933 invoked as root if <tt>binary</tt> has been
1934 invoked since the last <tt>clean</tt>, or if
1935 <tt>build</tt> has been invoked as root (since
1936 <tt>build</tt> may create directories, for
1941 <tag><tt>get-orig-source</tt> (optional)</tag>
1944 This target fetches the most recent version of the
1945 original source package from a canonical archive site
1946 (via FTP or WWW, for example), does any necessary
1947 rearrangement to turn it into the original source
1948 tar file format described below, and leaves it in the
1953 This target may be invoked in any directory, and
1954 should take care to clean up any temporary files it
1959 This target is optional, but providing it if
1960 possible is a good idea.
1964 <tag><tt>patch</tt> (optional)</tag>
1967 This target performs whatever additional actions are
1968 required to make the source ready for editing (unpacking
1969 additional upstream archives, applying patches, etc.).
1970 It is recommended to be implemented for any package where
1971 <tt>dpkg-source -x</tt> does not result in source ready
1972 for additional modification. See
1973 <ref id="readmesource">.
1979 The <tt>build</tt>, <tt>binary</tt> and
1980 <tt>clean</tt> targets must be invoked with the current
1981 directory being the package's top-level directory.
1986 Additional targets may exist in <file>debian/rules</file>,
1987 either as published or undocumented interfaces or for the
1988 package's internal use.
1992 The architectures we build on and build for are determined
1993 by <prgn>make</prgn> variables using the utility
1994 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1995 You can determine the
1996 Debian architecture and the GNU style architecture
1997 specification string for the build machine (the machine type
1998 we are building on) as well as for the host machine (the
1999 machine type we are building for). Here is a list of
2000 supported <prgn>make</prgn> variables:
2001 <list compact="compact">
2003 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2006 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2009 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2012 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2013 specification string)
2016 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2017 <tt>DEB_*_GNU_TYPE</tt>)
2020 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2021 <tt>DEB_*_GNU_TYPE</tt>)
2023 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2024 the build machine or <tt>HOST</tt> for specification of the
2029 Backward compatibility can be provided in the rules file
2030 by setting the needed variables to suitable default
2031 values; please refer to the documentation of
2032 <prgn>dpkg-architecture</prgn> for details.
2036 It is important to understand that the <tt>DEB_*_ARCH</tt>
2037 string only determines which Debian architecture we are
2038 building on or for. It should not be used to get the CPU
2039 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2040 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2041 GNU style variables should generally only be used with upstream
2045 <sect1 id="debianrules-options">
2046 <heading><file>debian/rules</file> and
2047 <tt>DEB_BUILD_OPTIONS</tt></heading>
2050 Supporting the standardized environment variable
2051 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2052 contain several flags to change how a package is compiled and
2053 built. Each flag must be in the form <var>flag</var> or
2054 <var>flag</var>=<var>options</var>. If multiple flags are
2055 given, they must be separated by whitespace.<footnote>
2056 Some packages support any delimiter, but whitespace is the
2057 easiest to parse inside a makefile and avoids ambiguity with
2058 flag values that contain commas.
2060 <var>flag</var> must start with a lowercase letter
2061 (<tt>a-z</tt>) and consist only of lowercase letters,
2062 numbers (<tt>0-9</tt>), and the characters
2063 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2064 <var>options</var> must not contain whitespace. The same
2065 tag should not be given multiple times with conflicting
2066 values. Package maintainers may assume that
2067 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2071 The meaning of the following tags has been standardized:
2075 This tag says to not run any build-time test suite
2076 provided by the package.
2080 The presence of this tag means that the package should
2081 be compiled with a minimum of optimization. For C
2082 programs, it is best to add <tt>-O0</tt> to
2083 <tt>CFLAGS</tt> (although this is usually the default).
2084 Some programs might fail to build or run at this level
2085 of optimization; it may be necessary to use
2086 <tt>-O1</tt>, for example.
2090 This tag means that the debugging symbols should not be
2091 stripped from the binary during installation, so that
2092 debugging information may be included in the package.
2094 <tag>parallel=n</tag>
2096 This tag means that the package should be built using up
2097 to <tt>n</tt> parallel processes if the package build
2098 system supports this.<footnote>
2099 Packages built with <tt>make</tt> can often implement
2100 this by passing the <tt>-j</tt><var>n</var> option to
2103 If the package build system does not support parallel
2104 builds, this string must be ignored. If the package
2105 build system only supports a lower level of concurrency
2106 than <var>n</var>, the package should be built using as
2107 many parallel processes as the package build system
2108 supports. It is up to the package maintainer to decide
2109 whether the package build times are long enough and the
2110 package build system is robust enough to make supporting
2111 parallel builds worthwhile.
2117 Unknown flags must be ignored by <file>debian/rules</file>.
2121 The following makefile snippet is an example of how one may
2122 implement the build options; you will probably have to
2123 massage this example in order to make it work for your
2125 <example compact="compact">
2128 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2129 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2130 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2131 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2133 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2138 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2139 INSTALL_PROGRAM += -s
2141 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2142 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2143 MAKEFLAGS += -j$(NUMJOBS)
2148 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2149 # Code to run the package test suite.
2156 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2157 <sect id="substvars">
2158 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2161 When <prgn>dpkg-gencontrol</prgn>,
2162 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2163 generate control files they perform variable substitutions
2164 on their output just before writing it. Variable
2165 substitutions have the form <tt>${<var>variable</var>}</tt>.
2166 The optional file <file>debian/substvars</file> contains
2167 variable substitutions to be used; variables can also be set
2168 directly from <file>debian/rules</file> using the <tt>-V</tt>
2169 option to the source packaging commands, and certain
2170 predefined variables are also available.
2174 The <file>debian/substvars</file> file is usually generated and
2175 modified dynamically by <file>debian/rules</file> targets, in
2176 which case it must be removed by the <tt>clean</tt> target.
2180 See <manref name="deb-substvars" section="5"> for full
2181 details about source variable substitutions, including the
2182 format of <file>debian/substvars</file>.</p>
2185 <sect id="debianwatch">
2186 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2189 This is an optional, recommended control file for the
2190 <tt>uscan</tt> utility which defines how to automatically
2191 scan ftp or http sites for newly available updates of the
2192 package. This is used by <url id="
2193 http://dehs.alioth.debian.org/"> and other Debian QA tools
2194 to help with quality control and maintenance of the
2195 distribution as a whole.
2200 <sect id="debianfiles">
2201 <heading>Generated files list: <file>debian/files</file></heading>
2204 This file is not a permanent part of the source tree; it
2205 is used while building packages to record which files are
2206 being generated. <prgn>dpkg-genchanges</prgn> uses it
2207 when it generates a <file>.changes</file> file.
2211 It should not exist in a shipped source package, and so it
2212 (and any backup files or temporary files such as
2213 <file>files.new</file><footnote>
2214 <file>files.new</file> is used as a temporary file by
2215 <prgn>dpkg-gencontrol</prgn> and
2216 <prgn>dpkg-distaddfile</prgn> - they write a new
2217 version of <tt>files</tt> here before renaming it,
2218 to avoid leaving a corrupted copy if an error
2220 </footnote>) should be removed by the
2221 <tt>clean</tt> target. It may also be wise to
2222 ensure a fresh start by emptying or removing it at the
2223 start of the <tt>binary</tt> target.
2227 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2228 package, it adds an entry to <file>debian/files</file> for the
2229 <file>.deb</file> file that will be created when <tt>dpkg-deb
2230 --build</tt> is run for that binary package. So for most
2231 packages all that needs to be done with this file is to
2232 delete it in the <tt>clean</tt> target.
2236 If a package upload includes files besides the source
2237 package and any binary packages whose control files were
2238 made with <prgn>dpkg-gencontrol</prgn> then they should be
2239 placed in the parent of the package's top-level directory
2240 and <prgn>dpkg-distaddfile</prgn> should be called to add
2241 the file to the list in <file>debian/files</file>.</p>
2244 <sect id="embeddedfiles">
2245 <heading>Convenience copies of code</heading>
2248 Some software packages include in their distribution convenience
2249 copies of code from other software packages, generally so that
2250 users compiling from source don't have to download multiple
2251 packages. Debian packages should not make use of these
2252 convenience copies unless the included package is explicitly
2253 intended to be used in this way.<footnote>
2254 For example, parts of the GNU build system work like this.
2256 If the included code is already in the Debian archive in the
2257 form of a library, the Debian packaging should ensure that
2258 binary packages reference the libraries already in Debian and
2259 the convenience copy is not used. If the included code is not
2260 already in Debian, it should be packaged separately as a
2261 prerequisite if possible.
2263 Having multiple copies of the same code in Debian is
2264 inefficient, often creates either static linking or shared
2265 library conflicts, and, most importantly, increases the
2266 difficulty of handling security vulnerabilities in the
2272 <sect id="readmesource">
2273 <heading>Source package handling:
2274 <file>debian/README.source</file></heading>
2277 If running <prgn>dpkg-source -x</prgn> on a source package
2278 doesn't produce the source of the package, ready for editing,
2279 and allow one to make changes and run
2280 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2281 without taking any additional steps, creating a
2282 <file>debian/README.source</file> documentation file is
2283 recommended. This file should explain how to do all of the
2286 <item>Generate the fully patched source, in a form ready for
2287 editing, that would be built to create Debian
2288 packages. Doing this with a <tt>patch</tt> target in
2289 <file>debian/rules</file> is recommended; see
2290 <ref id="debianrules">.</item>
2291 <item>Modify the source and save those modifications so that
2292 they will be applied when building the package.</item>
2293 <item>Remove source modifications that are currently being
2294 applied when building the package.</item>
2295 <item>Optionally, document what steps are necessary to
2296 upgrade the Debian source package to a new upstream version,
2297 if applicable.</item>
2299 This explanation should include specific commands and mention
2300 any additional required Debian packages. It should not assume
2301 familiarity with any specific Debian packaging system or patch
2306 This explanation may refer to a documentation file installed by
2307 one of the package's build dependencies provided that the
2308 referenced documentation clearly explains these tasks and is not
2309 a general reference manual.
2313 <file>debian/README.source</file> may also include any other
2314 information that would be helpful to someone modifying the
2315 source package. Even if the package doesn't fit the above
2316 description, maintainers are encouraged to document in a
2317 <file>debian/README.source</file> file any source package with a
2318 particularly complex or unintuitive source layout or build
2319 system (for example, a package that builds the same source
2320 multiple times to generate different binary packages).
2326 <chapt id="controlfields">
2327 <heading>Control files and their fields</heading>
2330 The package management system manipulates data represented in
2331 a common format, known as <em>control data</em>, stored in
2332 <em>control files</em>.
2333 Control files are used for source packages, binary packages and
2334 the <file>.changes</file> files which control the installation
2335 of uploaded files<footnote>
2336 <prgn>dpkg</prgn>'s internal databases are in a similar
2341 <sect id="controlsyntax">
2342 <heading>Syntax of control files</heading>
2345 A control file consists of one or more paragraphs of
2347 The paragraphs are also sometimes referred to as stanzas.
2349 The paragraphs are separated by blank lines. Some control
2350 files allow only one paragraph; others allow several, in
2351 which case each paragraph usually refers to a different
2352 package. (For example, in source packages, the first
2353 paragraph refers to the source package, and later paragraphs
2354 refer to binary packages generated from the source.)
2358 Each paragraph consists of a series of data fields; each
2359 field consists of the field name, followed by a colon and
2360 then the data/value associated with that field. It ends at
2361 the end of the (logical) line. Horizontal whitespace
2362 (spaces and tabs) may occur immediately before or after the
2363 value and is ignored there; it is conventional to put a
2364 single space after the colon. For example, a field might
2366 <example compact="compact">
2369 the field name is <tt>Package</tt> and the field value
2374 Many fields' values may span several lines; in this case
2375 each continuation line must start with a space or a tab.
2376 Any trailing spaces or tabs at the end of individual
2377 lines of a field value are ignored.
2381 In fields where it is specified that lines may not wrap,
2382 only a single line of data is allowed and whitespace is not
2383 significant in a field body. Whitespace must not appear
2384 inside names (of packages, architectures, files or anything
2385 else) or version numbers, or between the characters of
2386 multi-character version relationships.
2390 Field names are not case-sensitive, but it is usual to
2391 capitalize the field names using mixed case as shown below.
2392 Field values are case-sensitive unless the description of the
2393 field says otherwise.
2397 Blank lines, or lines consisting only of spaces and tabs,
2398 are not allowed within field values or between fields - that
2399 would mean a new paragraph.
2403 All control files must be encoded in UTF-8.
2407 <sect id="sourcecontrolfiles">
2408 <heading>Source package control files -- <file>debian/control</file></heading>
2411 The <file>debian/control</file> file contains the most vital
2412 (and version-independent) information about the source package
2413 and about the binary packages it creates.
2417 The first paragraph of the control file contains information about
2418 the source package in general. The subsequent sets each describe a
2419 binary package that the source tree builds.
2423 The fields in the general paragraph (the first one, for the source
2426 <list compact="compact">
2427 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2428 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2429 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2430 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2431 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2432 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2433 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2434 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2439 The fields in the binary package paragraphs are:
2441 <list compact="compact">
2442 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2443 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2444 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2445 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2446 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2447 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2448 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2449 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2454 The syntax and semantics of the fields are described below.
2460 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2461 generate control files for binary packages (see below), by
2462 <prgn>dpkg-genchanges</prgn> to generate the
2463 <tt>.changes</tt> file to accompany the upload, and by
2464 <prgn>dpkg-source</prgn> when it creates the
2465 <file>.dsc</file> source control file as part of a source
2466 archive. Many fields are permitted to span multiple lines in
2467 <file>debian/control</file> but not in any other control
2468 file. These tools are responsible for removing the line
2469 breaks from such fields when using fields from
2470 <file>debian/control</file> to generate other control files.
2474 The fields here may contain variable references - their
2475 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2476 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2477 when they generate output control files.
2478 See <ref id="substvars"> for details.
2482 In addition to the control file syntax described <qref
2483 id="controlsyntax">above</qref>, this file may also contain
2484 comment lines starting with <tt>#</tt> without any preceding
2485 whitespace. All such lines are ignored, even in the middle of
2486 continuation lines for a multiline field, and do not end a
2492 <sect id="binarycontrolfiles">
2493 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2496 The <file>DEBIAN/control</file> file contains the most vital
2497 (and version-dependent) information about a binary package.
2501 The fields in this file are:
2503 <list compact="compact">
2504 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2506 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2507 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2508 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2509 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2510 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2511 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2512 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2513 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2520 <sect id="debiansourcecontrolfiles">
2521 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2524 This file contains a series of fields, identified and
2525 separated just like the fields in the control file of
2526 a binary package. The fields are listed below; their
2527 syntax is described above, in <ref id="pkg-controlfields">.
2529 <list compact="compact">
2530 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2531 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2532 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2533 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2534 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2535 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2536 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2537 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2538 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2539 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2540 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2545 The source package control file is generated by
2546 <prgn>dpkg-source</prgn> when it builds the source
2547 archive, from other files in the source package,
2548 described above. When unpacking, it is checked against
2549 the files and directories in the other parts of the
2555 <sect id="debianchangesfiles">
2556 <heading>Debian changes files -- <file>.changes</file></heading>
2559 The .changes files are used by the Debian archive maintenance
2560 software to process updates to packages. They contain one
2561 paragraph which contains information from the
2562 <tt>debian/control</tt> file and other data about the
2563 source package gathered via <tt>debian/changelog</tt>
2564 and <tt>debian/rules</tt>.
2568 The fields in this file are:
2570 <list compact="compact">
2571 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2575 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2576 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2579 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2580 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2581 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2582 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2583 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2584 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2589 <sect id="controlfieldslist">
2590 <heading>List of fields</heading>
2592 <sect1 id="f-Source">
2593 <heading><tt>Source</tt></heading>
2596 This field identifies the source package name.
2600 In <file>debian/control</file> or a <file>.dsc</file> file,
2601 this field must contain only the name of the source package.
2605 In a binary package control file or a <file>.changes</file>
2606 file, the source package name may be followed by a version
2607 number in parentheses<footnote>
2608 It is customary to leave a space after the package name
2609 if a version number is specified.
2611 This version number may be omitted (and is, by
2612 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2613 the <tt>Version</tt> field of the binary package in
2614 question. The field itself may be omitted from a binary
2615 package control file when the source package has the same
2616 name and version as the binary package.
2620 Package names (both source and binary,
2621 see <ref id="f-Package">) must consist only of lower case
2622 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2623 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2624 (<tt>.</tt>). They must be at least two characters long and
2625 must start with an alphanumeric character.
2629 <sect1 id="f-Maintainer">
2630 <heading><tt>Maintainer</tt></heading>
2633 The package maintainer's name and email address. The name
2634 should come first, then the email address inside angle
2635 brackets <tt><></tt> (in RFC822 format).
2639 If the maintainer's name contains a full stop then the
2640 whole field will not work directly as an email address due
2641 to a misfeature in the syntax specified in RFC822; a
2642 program using this field as an address must check for this
2643 and correct the problem if necessary (for example by
2644 putting the name in round brackets and moving it to the
2645 end, and bringing the email address forward).
2649 <sect1 id="f-Uploaders">
2650 <heading><tt>Uploaders</tt></heading>
2653 List of the names and email addresses of co-maintainers of
2654 the package, if any. If the package has other maintainers
2655 beside the one named in the
2656 <qref id="f-Maintainer">Maintainer field</qref>, their
2657 names and email addresses should be listed here. The
2658 format is the same as that of the Maintainer tag, and
2659 multiple entries should be comma separated. Currently,
2660 this field is restricted to a single line of data. This
2661 is an optional field.
2664 Any parser that interprets the Uploaders field in
2665 <file>debian/control</file> must permit it to span multiple
2666 lines. Line breaks in an Uploaders field that spans multiple
2667 lines are not significant and the semantics of the field are
2668 the same as if the line breaks had not been present.
2672 <sect1 id="f-Changed-By">
2673 <heading><tt>Changed-By</tt></heading>
2676 The name and email address of the person who changed the
2677 said package. Usually the name of the maintainer.
2678 All the rules for the Maintainer field apply here, too.
2682 <sect1 id="f-Section">
2683 <heading><tt>Section</tt></heading>
2686 This field specifies an application area into which the package
2687 has been classified. See <ref id="subsections">.
2691 When it appears in the <file>debian/control</file> file,
2692 it gives the value for the subfield of the same name in
2693 the <tt>Files</tt> field of the <file>.changes</file> file.
2694 It also gives the default for the same field in the binary
2699 <sect1 id="f-Priority">
2700 <heading><tt>Priority</tt></heading>
2703 This field represents how important it is that the user
2704 have the package installed. See <ref id="priorities">.
2708 When it appears in the <file>debian/control</file> file,
2709 it gives the value for the subfield of the same name in
2710 the <tt>Files</tt> field of the <file>.changes</file> file.
2711 It also gives the default for the same field in the binary
2716 <sect1 id="f-Package">
2717 <heading><tt>Package</tt></heading>
2720 The name of the binary package.
2724 Binary package names must follow the same syntax and
2725 restrictions as source package names. See <ref id="f-Source">
2730 <sect1 id="f-Architecture">
2731 <heading><tt>Architecture</tt></heading>
2734 Depending on context and the control file used, the
2735 <tt>Architecture</tt> field can include the following sets of
2738 <item>A unique single word identifying a Debian machine
2739 architecture as described in <ref id="arch-spec">.
2740 <item><tt>all</tt>, which indicates an
2741 architecture-independent package.
2742 <item><tt>any</tt>, which indicates a package available
2743 for building on any architecture.
2744 <item><tt>source</tt>, which indicates a source package.
2749 In the main <file>debian/control</file> file in the source
2750 package, this field may contain the special value
2751 <tt>any</tt>, the special value <tt>all</tt>, or a list of
2752 architectures separated by spaces. If <tt>any</tt> or
2753 <tt>all</tt> appear, they must be the entire contents of the
2754 field. Most packages will use either <tt>any</tt> or
2755 <tt>all</tt>. Specifying a specific list of architectures is
2756 for the minority of cases where a program is not portable or
2757 is not useful on some architectures, and where possible the
2758 program should be made portable instead.
2762 In the source package control file <file>.dsc</file>, this
2763 field may contain either the special value <tt>any</tt> or a
2764 list of architectures separated by spaces. If a list is given,
2765 it may include (or consist solely of) the special value
2766 <tt>all</tt>. In other words, in <file>.dsc</file> files
2767 unlike the <file>debian/control</file>, <tt>all</tt> may occur
2768 in combination with specific architectures. The
2769 <tt>Architecture</tt> field in the source package control file
2770 <file>.dsc</file> is generally constructed from the
2771 <tt>Architecture</tt> fields in the
2772 <file>debian/control</file> in the source package.
2776 Specifying <tt>any</tt> indicates that the source package
2777 isn't dependent on any particular architecture and should
2778 compile fine on any one. The produced binary package(s)
2779 will either be specific to whatever the current build
2780 architecture is or will be architecture-independent.
2784 Specifying only <tt>all</tt> indicates that the source package
2785 will only build architecture-independent packages. If this is
2786 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2787 <tt>any</tt> implies that the source package will build at
2788 least one architecture-dependent package.
2792 Specifying a list of architectures indicates that the source
2793 will build an architecture-dependent package, and will only
2794 work correctly on the listed architectures. If the source
2795 package also builds at least one architecture-independent
2796 package, <tt>all</tt> will also be included in the list.
2800 In a <file>.changes</file> file, the <tt>Architecture</tt>
2801 field lists the architecture(s) of the package(s)
2802 currently being uploaded. This will be a list; if the
2803 source for the package is also being uploaded, the special
2804 entry <tt>source</tt> is also present. <tt>all</tt> will be
2805 present if any architecture-independent packages are being
2806 uploaded. <tt>any</tt> may never occur in the
2807 <tt>Architecture</tt> field in the <file>.changes</file>
2812 See <ref id="debianrules"> for information on how to get
2813 the architecture for the build process.
2817 <sect1 id="f-Essential">
2818 <heading><tt>Essential</tt></heading>
2821 This is a boolean field which may occur only in the
2822 control file of a binary package or in a per-package fields
2823 paragraph of a main source control data file.
2827 If set to <tt>yes</tt> then the package management system
2828 will refuse to remove the package (upgrading and replacing
2829 it is still possible). The other possible value is <tt>no</tt>,
2830 which is the same as not having the field at all.
2835 <heading>Package interrelationship fields:
2836 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2837 <tt>Recommends</tt>, <tt>Suggests</tt>,
2838 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2839 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2843 These fields describe the package's relationships with
2844 other packages. Their syntax and semantics are described
2845 in <ref id="relationships">.</p>
2848 <sect1 id="f-Standards-Version">
2849 <heading><tt>Standards-Version</tt></heading>
2852 The most recent version of the standards (the policy
2853 manual and associated texts) with which the package
2858 The version number has four components: major and minor
2859 version number and major and minor patch level. When the
2860 standards change in a way that requires every package to
2861 change the major number will be changed. Significant
2862 changes that will require work in many packages will be
2863 signaled by a change to the minor number. The major patch
2864 level will be changed for any change to the meaning of the
2865 standards, however small; the minor patch level will be
2866 changed when only cosmetic, typographical or other edits
2867 are made which neither change the meaning of the document
2868 nor affect the contents of packages.
2872 Thus only the first three components of the policy version
2873 are significant in the <em>Standards-Version</em> control
2874 field, and so either these three components or all four
2875 components may be specified.<footnote>
2876 In the past, people specified the full version number
2877 in the Standards-Version field, for example "2.3.0.0".
2878 Since minor patch-level changes don't introduce new
2879 policy, it was thought it would be better to relax
2880 policy and only require the first 3 components to be
2881 specified, in this example "2.3.0". All four
2882 components may still be used if someone wishes to do so.
2888 <sect1 id="f-Version">
2889 <heading><tt>Version</tt></heading>
2892 The version number of a package. The format is:
2893 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2897 The three components here are:
2899 <tag><var>epoch</var></tag>
2902 This is a single (generally small) unsigned integer. It
2903 may be omitted, in which case zero is assumed. If it is
2904 omitted then the <var>upstream_version</var> may not
2909 It is provided to allow mistakes in the version numbers
2910 of older versions of a package, and also a package's
2911 previous version numbering schemes, to be left behind.
2915 <tag><var>upstream_version</var></tag>
2918 This is the main part of the version number. It is
2919 usually the version number of the original ("upstream")
2920 package from which the <file>.deb</file> file has been made,
2921 if this is applicable. Usually this will be in the same
2922 format as that specified by the upstream author(s);
2923 however, it may need to be reformatted to fit into the
2924 package management system's format and comparison
2929 The comparison behavior of the package management system
2930 with respect to the <var>upstream_version</var> is
2931 described below. The <var>upstream_version</var>
2932 portion of the version number is mandatory.
2936 The <var>upstream_version</var> may contain only
2937 alphanumerics<footnote>
2938 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2940 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2941 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2942 tilde) and should start with a digit. If there is no
2943 <var>debian_revision</var> then hyphens are not allowed;
2944 if there is no <var>epoch</var> then colons are not
2949 <tag><var>debian_revision</var></tag>
2952 This part of the version number specifies the version of
2953 the Debian package based on the upstream version. It
2954 may contain only alphanumerics and the characters
2955 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2956 tilde) and is compared in the same way as the
2957 <var>upstream_version</var> is.
2961 It is optional; if it isn't present then the
2962 <var>upstream_version</var> may not contain a hyphen.
2963 This format represents the case where a piece of
2964 software was written specifically to be turned into a
2965 Debian package, and so there is only one "debianisation"
2966 of it and therefore no revision indication is required.
2970 It is conventional to restart the
2971 <var>debian_revision</var> at <tt>1</tt> each time the
2972 <var>upstream_version</var> is increased.
2976 The package management system will break the version
2977 number apart at the last hyphen in the string (if there
2978 is one) to determine the <var>upstream_version</var> and
2979 <var>debian_revision</var>. The absence of a
2980 <var>debian_revision</var> is equivalent to a
2981 <var>debian_revision</var> of <tt>0</tt>.
2988 When comparing two version numbers, first the <var>epoch</var>
2989 of each are compared, then the <var>upstream_version</var> if
2990 <var>epoch</var> is equal, and then <var>debian_revision</var>
2991 if <var>upstream_version</var> is also equal.
2992 <var>epoch</var> is compared numerically. The
2993 <var>upstream_version</var> and <var>debian_revision</var>
2994 parts are compared by the package management system using the
2995 following algorithm:
2999 The strings are compared from left to right.
3003 First the initial part of each string consisting entirely of
3004 non-digit characters is determined. These two parts (one of
3005 which may be empty) are compared lexically. If a difference
3006 is found it is returned. The lexical comparison is a
3007 comparison of ASCII values modified so that all the letters
3008 sort earlier than all the non-letters and so that a tilde
3009 sorts before anything, even the end of a part. For example,
3010 the following parts are in sorted order from earliest to
3011 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3012 <tt>a</tt>.<footnote>
3013 One common use of <tt>~</tt> is for upstream pre-releases.
3014 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3015 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3020 Then the initial part of the remainder of each string which
3021 consists entirely of digit characters is determined. The
3022 numerical values of these two parts are compared, and any
3023 difference found is returned as the result of the comparison.
3024 For these purposes an empty string (which can only occur at
3025 the end of one or both version strings being compared) counts
3030 These two steps (comparing and removing initial non-digit
3031 strings and initial digit strings) are repeated until a
3032 difference is found or both strings are exhausted.
3036 Note that the purpose of epochs is to allow us to leave behind
3037 mistakes in version numbering, and to cope with situations
3038 where the version numbering scheme changes. It is
3039 <em>not</em> intended to cope with version numbers containing
3040 strings of letters which the package management system cannot
3041 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3042 silly orderings (the author of this manual has heard of a
3043 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
3044 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
3045 <tt>2</tt> and so forth).
3049 <sect1 id="f-Description">
3050 <heading><tt>Description</tt></heading>
3053 In a source or binary control file, the <tt>Description</tt>
3054 field contains a description of the binary package, consisting
3055 of two parts, the synopsis or the short description, and the
3056 long description. The field's format is as follows:
3061 Description: <single line synopsis>
3062 <extended description over several lines>
3067 The lines in the extended description can have these formats:
3073 Those starting with a single space are part of a paragraph.
3074 Successive lines of this form will be word-wrapped when
3075 displayed. The leading space will usually be stripped off.
3079 Those starting with two or more spaces. These will be
3080 displayed verbatim. If the display cannot be panned
3081 horizontally, the displaying program will line wrap them "hard"
3082 (i.e., without taking account of word breaks). If it can they
3083 will be allowed to trail off to the right. None, one or two
3084 initial spaces may be deleted, but the number of spaces
3085 deleted from each line will be the same (so that you can have
3086 indenting work correctly, for example).
3090 Those containing a single space followed by a single full stop
3091 character. These are rendered as blank lines. This is the
3092 <em>only</em> way to get a blank line<footnote>
3093 Completely empty lines will not be rendered as blank lines.
3094 Instead, they will cause the parser to think you're starting
3095 a whole new record in the control file, and will therefore
3096 likely abort with an error.
3101 Those containing a space, a full stop and some more characters.
3102 These are for future expansion. Do not use them.
3108 Do not use tab characters. Their effect is not predictable.
3112 See <ref id="descriptions"> for further information on this.
3116 In a <file>.changes</file> file, the <tt>Description</tt>
3117 field contains a summary of the descriptions for the packages
3118 being uploaded. For this case, the first line of the field
3119 value (the part on the same line as <tt>Description:</tt>) is
3120 always empty. The content of the field is expressed as
3121 continuation lines, one line per package. Each line is
3122 indented by one space and contains the name of a binary
3123 package, a space, a hyphen (<tt>-</tt>), a space, and the
3124 short description line from that package.
3128 <sect1 id="f-Distribution">
3129 <heading><tt>Distribution</tt></heading>
3132 In a <file>.changes</file> file or parsed changelog output
3133 this contains the (space-separated) name(s) of the
3134 distribution(s) where this version of the package should
3135 be installed. Valid distributions are determined by the
3136 archive maintainers.<footnote>
3137 Example distribution names in the Debian archive used in
3138 <file>.changes</file> files are:
3139 <taglist compact="compact">
3140 <tag><em>unstable</em></tag>
3142 This distribution value refers to the
3143 <em>developmental</em> part of the Debian distribution
3144 tree. Most new packages, new upstream versions of
3145 packages and bug fixes go into the <em>unstable</em>
3149 <tag><em>experimental</em></tag>
3151 The packages with this distribution value are deemed
3152 by their maintainers to be high risk. Oftentimes they
3153 represent early beta or developmental packages from
3154 various sources that the maintainers want people to
3155 try, but are not ready to be a part of the other parts
3156 of the Debian distribution tree.
3161 Others are used for updating stable releases or for
3162 security uploads. More information is available in the
3163 Debian Developer's Reference, section "The Debian
3167 The Debian archive software only supports listing a single
3168 distribution. Migration of packages to other distributions is
3169 handled outside of the upload process.
3174 <heading><tt>Date</tt></heading>
3177 This field includes the date the package was built or last edited.
3181 The value of this field is usually extracted from the
3182 <file>debian/changelog</file> file - see
3183 <ref id="dpkgchangelog">).
3187 <sect1 id="f-Format">
3188 <heading><tt>Format</tt></heading>
3191 This field specifies a format revision for the file.
3192 The most current format described in the Policy Manual
3193 is version <strong>1.5</strong>. The syntax of the
3194 format value is the same as that of a package version
3195 number except that no epoch or Debian revision is allowed
3196 - see <ref id="f-Version">.
3200 <sect1 id="f-Urgency">
3201 <heading><tt>Urgency</tt></heading>
3204 This is a description of how important it is to upgrade to
3205 this version from previous ones. It consists of a single
3206 keyword taking one of the values <tt>low</tt>,
3207 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3208 <tt>critical</tt><footnote>
3209 Other urgency values are supported with configuration
3210 changes in the archive software but are not used in Debian.
3211 The urgency affects how quickly a package will be considered
3212 for inclusion into the <tt>testing</tt> distribution and
3213 gives an indication of the importance of any fixes included
3214 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3215 treated as synonymous.
3216 </footnote> (not case-sensitive) followed by an optional
3217 commentary (separated by a space) which is usually in
3218 parentheses. For example:
3221 Urgency: low (HIGH for users of diversions)
3227 The value of this field is usually extracted from the
3228 <file>debian/changelog</file> file - see
3229 <ref id="dpkgchangelog">.
3233 <sect1 id="f-Changes">
3234 <heading><tt>Changes</tt></heading>
3237 This field contains the human-readable changes data, describing
3238 the differences between the last version and the current one.
3242 The first line of the field value (the part on the same line
3243 as <tt>Changes:</tt>) is always empty. The content of the
3244 field is expressed as continuation lines, with each line
3245 indented by at least one space. Blank lines must be
3246 represented by a line consisting only of a space and a full
3251 The value of this field is usually extracted from the
3252 <file>debian/changelog</file> file - see
3253 <ref id="dpkgchangelog">).
3257 Each version's change information should be preceded by a
3258 "title" line giving at least the version, distribution(s)
3259 and urgency, in a human-readable way.
3263 If data from several versions is being returned the entry
3264 for the most recent version should be returned first, and
3265 entries should be separated by the representation of a
3266 blank line (the "title" line may also be followed by the
3267 representation of a blank line).
3271 <sect1 id="f-Binary">
3272 <heading><tt>Binary</tt></heading>
3275 This field is a list of binary packages. Its syntax and
3276 meaning varies depending on the control file in which it
3281 When it appears in the <file>.dsc</file> file, it lists binary
3282 packages which a source package can produce, separated by
3284 A space after each comma is conventional.
3285 </footnote>. It may span multiple lines. The source package
3286 does not necessarily produce all of these binary packages for
3287 every architecture. The source control file doesn't contain
3288 details of which architectures are appropriate for which of
3289 the binary packages.
3293 When it appears in a <file>.changes</file> file, it lists the
3294 names of the binary packages being uploaded, separated by
3295 whitespace (not commas). It may span multiple lines.
3299 <sect1 id="f-Installed-Size">
3300 <heading><tt>Installed-Size</tt></heading>
3303 This field appears in the control files of binary packages,
3304 and in the <file>Packages</file> files. It gives an estimate
3305 of the total amount of disk space required to install the
3306 named package. Actual installed size may vary based on block
3307 size, file system properties, or actions taken by package
3312 The disk space is given as the integer value of the estimated
3313 installed size in bytes, divided by 1024 and rounded up.
3317 <sect1 id="f-Files">
3318 <heading><tt>Files</tt></heading>
3321 This field contains a list of files with information about
3322 each one. The exact information and syntax varies with
3327 In all cases, Files is a multiline field. The first line of
3328 the field value (the part on the same line as <tt>Files:</tt>)
3329 is always empty. The content of the field is expressed as
3330 continuation lines, one line per file. Each line must be
3331 indented by one space and contain a number of sub-fields,
3332 separated by spaces, as described below.
3336 In the <file>.dsc</file> file, each line contains the MD5
3337 checksum, size and filename of the tar file and (if
3338 applicable) diff file which make up the remainder of the
3339 source package<footnote>
3340 That is, the parts which are not the <tt>.dsc</tt>.
3341 </footnote>. For example:
3344 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3345 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3347 The exact forms of the filenames are described
3348 in <ref id="pkg-sourcearchives">.
3352 In the <file>.changes</file> file this contains one line per
3353 file being uploaded. Each line contains the MD5 checksum,
3354 size, section and priority and the filename. For example:
3357 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3358 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3359 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3360 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3362 The <qref id="f-Section">section</qref>
3363 and <qref id="f-Priority">priority</qref> are the values of
3364 the corresponding fields in the main source control file. If
3365 no section or priority is specified then <tt>-</tt> should be
3366 used, though section and priority values must be specified for
3367 new packages to be installed properly.
3371 The special value <tt>byhand</tt> for the section in a
3372 <tt>.changes</tt> file indicates that the file in question
3373 is not an ordinary package file and must by installed by
3374 hand by the distribution maintainers. If the section is
3375 <tt>byhand</tt> the priority should be <tt>-</tt>.
3379 If a new Debian revision of a package is being shipped and
3380 no new original source archive is being distributed the
3381 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3382 entry for the original source archive
3383 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3384 but the <file>.changes</file> file should leave it out. In
3385 this case the original source archive on the distribution
3386 site must match exactly, byte-for-byte, the original
3387 source archive which was used to generate the
3388 <file>.dsc</file> file and diff which are being uploaded.</p>
3391 <sect1 id="f-Closes">
3392 <heading><tt>Closes</tt></heading>
3395 A space-separated list of bug report numbers that the upload
3396 governed by the .changes file closes.
3400 <sect1 id="f-Homepage">
3401 <heading><tt>Homepage</tt></heading>
3404 The URL of the web site for this package, preferably (when
3405 applicable) the site from which the original source can be
3406 obtained and any additional upstream documentation or
3407 information may be found. The content of this field is a
3408 simple URL without any surrounding characters such as
3416 <heading>User-defined fields</heading>
3419 Additional user-defined fields may be added to the
3420 source package control file. Such fields will be
3421 ignored, and not copied to (for example) binary or
3422 source package control files or upload control files.
3426 If you wish to add additional unsupported fields to
3427 these output files you should use the mechanism
3432 Fields in the main source control information file with
3433 names starting <tt>X</tt>, followed by one or more of
3434 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3435 be copied to the output files. Only the part of the
3436 field name after the hyphen will be used in the output
3437 file. Where the letter <tt>B</tt> is used the field
3438 will appear in binary package control files, where the
3439 letter <tt>S</tt> is used in source package control
3440 files and where <tt>C</tt> is used in upload control
3441 (<tt>.changes</tt>) files.
3445 For example, if the main source information control file
3448 XBS-Comment: I stand between the candle and the star.
3450 then the binary and source package control files will contain the
3453 Comment: I stand between the candle and the star.
3462 <chapt id="maintainerscripts">
3463 <heading>Package maintainer scripts and installation procedure</heading>
3466 <heading>Introduction to package maintainer scripts</heading>
3469 It is possible to supply scripts as part of a package which
3470 the package management system will run for you when your
3471 package is installed, upgraded or removed.
3475 These scripts are the files <prgn>preinst</prgn>,
3476 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3477 <prgn>postrm</prgn> in the control area of the package.
3478 They must be proper executable files; if they are scripts
3479 (which is recommended), they must start with the usual
3480 <tt>#!</tt> convention. They should be readable and
3481 executable by anyone, and must not be world-writable.
3485 The package management system looks at the exit status from
3486 these scripts. It is important that they exit with a
3487 non-zero status if there is an error, so that the package
3488 management system can stop its processing. For shell
3489 scripts this means that you <em>almost always</em> need to
3490 use <tt>set -e</tt> (this is usually true when writing shell
3491 scripts, in fact). It is also important, of course, that
3492 they exit with a zero status if everything went well.
3496 Additionally, packages interacting with users using
3497 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3498 install a <prgn>config</prgn> script in the control area,
3499 see <ref id="maintscriptprompt"> for details.
3503 When a package is upgraded a combination of the scripts from
3504 the old and new packages is called during the upgrade
3505 procedure. If your scripts are going to be at all
3506 complicated you need to be aware of this, and may need to
3507 check the arguments to your scripts.
3511 Broadly speaking the <prgn>preinst</prgn> is called before
3512 (a particular version of) a package is installed, and the
3513 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3514 before (a version of) a package is removed and the
3515 <prgn>postrm</prgn> afterwards.
3519 Programs called from maintainer scripts should not normally
3520 have a path prepended to them. Before installation is
3521 started, the package management system checks to see if the
3522 programs <prgn>ldconfig</prgn>,
3523 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3524 and <prgn>update-rc.d</prgn> can be found via the
3525 <tt>PATH</tt> environment variable. Those programs, and any
3526 other program that one would expect to be in the
3527 <tt>PATH</tt>, should thus be invoked without an absolute
3528 pathname. Maintainer scripts should also not reset the
3529 <tt>PATH</tt>, though they might choose to modify it by
3530 prepending or appending package-specific directories. These
3531 considerations really apply to all shell scripts.</p>
3534 <sect id="idempotency">
3535 <heading>Maintainer scripts idempotency</heading>
3538 It is necessary for the error recovery procedures that the
3539 scripts be idempotent. This means that if it is run
3540 successfully, and then it is called again, it doesn't bomb
3541 out or cause any harm, but just ensures that everything is
3542 the way it ought to be. If the first call failed, or
3543 aborted half way through for some reason, the second call
3544 should merely do the things that were left undone the first
3545 time, if any, and exit with a success status if everything
3547 This is so that if an error occurs, the user interrupts
3548 <prgn>dpkg</prgn> or some other unforeseen circumstance
3549 happens you don't leave the user with a badly-broken
3550 package when <prgn>dpkg</prgn> attempts to repeat the
3556 <sect id="controllingterminal">
3557 <heading>Controlling terminal for maintainer scripts</heading>
3560 Maintainer scripts are not guaranteed to run with a controlling
3561 terminal and may not be able to interact with the user. They
3562 must be able to fall back to noninteractive behavior if no
3563 controlling terminal is available. Maintainer scripts that
3564 prompt via a program conforming to the Debian Configuration
3565 Management Specification (see <ref id="maintscriptprompt">) may
3566 assume that program will handle falling back to noninteractive
3571 <sect id="exitstatus">
3572 <heading>Exit status</heading>
3575 Each script must return a zero exit status for
3576 success, or a nonzero one for failure, since the package
3577 management system looks for the exit status of these scripts
3578 and determines what action to take next based on that datum.
3582 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3587 <list compact="compact">
3589 <var>new-preinst</var> <tt>install</tt>
3592 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3595 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3598 <var>old-preinst</var> <tt>abort-upgrade</tt>
3599 <var>new-version</var>
3604 <list compact="compact">
3606 <var>postinst</var> <tt>configure</tt>
3607 <var>most-recently-configured-version</var>
3610 <var>old-postinst</var> <tt>abort-upgrade</tt>
3611 <var>new-version</var>
3614 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3615 <tt>in-favour</tt> <var>package</var>
3616 <var>new-version</var>
3619 <var>postinst</var> <tt>abort-remove</tt>
3622 <var>deconfigured's-postinst</var>
3623 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3624 <var>failed-install-package</var> <var>version</var>
3625 [<tt>removing</tt> <var>conflicting-package</var>
3631 <list compact="compact">
3633 <var>prerm</var> <tt>remove</tt>
3636 <var>old-prerm</var> <tt>upgrade</tt>
3637 <var>new-version</var>
3640 <var>new-prerm</var> <tt>failed-upgrade</tt>
3641 <var>old-version</var>
3644 <var>conflictor's-prerm</var> <tt>remove</tt>
3645 <tt>in-favour</tt> <var>package</var>
3646 <var>new-version</var>
3649 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3650 <tt>in-favour</tt> <var>package-being-installed</var>
3651 <var>version</var> [<tt>removing</tt>
3652 <var>conflicting-package</var>
3658 <list compact="compact">
3660 <var>postrm</var> <tt>remove</tt>
3663 <var>postrm</var> <tt>purge</tt>
3666 <var>old-postrm</var> <tt>upgrade</tt>
3667 <var>new-version</var>
3670 <var>new-postrm</var> <tt>failed-upgrade</tt>
3671 <var>old-version</var>
3674 <var>new-postrm</var> <tt>abort-install</tt>
3677 <var>new-postrm</var> <tt>abort-install</tt>
3678 <var>old-version</var>
3681 <var>new-postrm</var> <tt>abort-upgrade</tt>
3682 <var>old-version</var>
3685 <var>disappearer's-postrm</var> <tt>disappear</tt>
3686 <var>overwriter</var>
3687 <var>overwriter-version</var>
3693 <sect id="unpackphase">
3694 <heading>Details of unpack phase of installation or upgrade</heading>
3697 The procedure on installation/upgrade/overwrite/disappear
3698 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3699 stage of <tt>dpkg --install</tt>) is as follows. In each
3700 case, if a major error occurs (unless listed below) the
3701 actions are, in general, run backwards - this means that the
3702 maintainer scripts are run with different arguments in
3703 reverse order. These are the "error unwind" calls listed
3710 If a version of the package is already installed, call
3711 <example compact="compact">
3712 <var>old-prerm</var> upgrade <var>new-version</var>
3716 If the script runs but exits with a non-zero
3717 exit status, <prgn>dpkg</prgn> will attempt:
3718 <example compact="compact">
3719 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3721 If this works, the upgrade continues. If this
3722 does not work, the error unwind:
3723 <example compact="compact">
3724 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3726 If this works, then the old-version is
3727 "Installed", if not, the old version is in a
3728 "Half-Configured" state.
3734 If a "conflicting" package is being removed at the same time,
3735 or if any package will be broken (due to <tt>Breaks</tt>):
3738 If <tt>--auto-deconfigure</tt> is
3739 specified, call, for each package to be deconfigured
3740 due to <tt>Breaks</tt>:
3741 <example compact="compact">
3742 <var>deconfigured's-prerm</var> deconfigure \
3743 in-favour <var>package-being-installed</var> <var>version</var>
3746 <example compact="compact">
3747 <var>deconfigured's-postinst</var> abort-deconfigure \
3748 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3750 The deconfigured packages are marked as
3751 requiring configuration, so that if
3752 <tt>--install</tt> is used they will be
3753 configured again if possible.
3756 If any packages depended on a conflicting
3757 package being removed and <tt>--auto-deconfigure</tt> is
3758 specified, call, for each such package:
3759 <example compact="compact">
3760 <var>deconfigured's-prerm</var> deconfigure \
3761 in-favour <var>package-being-installed</var> <var>version</var> \
3762 removing <var>conflicting-package</var> <var>version</var>
3765 <example compact="compact">
3766 <var>deconfigured's-postinst</var> abort-deconfigure \
3767 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3768 removing <var>conflicting-package</var> <var>version</var>
3770 The deconfigured packages are marked as
3771 requiring configuration, so that if
3772 <tt>--install</tt> is used they will be
3773 configured again if possible.
3776 To prepare for removal of each conflicting package, call:
3777 <example compact="compact">
3778 <var>conflictor's-prerm</var> remove \
3779 in-favour <var>package</var> <var>new-version</var>
3782 <example compact="compact">
3783 <var>conflictor's-postinst</var> abort-remove \
3784 in-favour <var>package</var> <var>new-version</var>
3793 If the package is being upgraded, call:
3794 <example compact="compact">
3795 <var>new-preinst</var> upgrade <var>old-version</var>
3797 If this fails, we call:
3799 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3806 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3808 is called. If this works, then the old version
3809 is in an "Installed" state, or else it is left
3810 in an "Unpacked" state.
3815 If it fails, then the old version is left
3816 in an "Half-Installed" state.
3823 Otherwise, if the package had some configuration
3824 files from a previous version installed (i.e., it
3825 is in the "configuration files only" state):
3826 <example compact="compact">
3827 <var>new-preinst</var> install <var>old-version</var>
3831 <var>new-postrm</var> abort-install <var>old-version</var>
3833 If this fails, the package is left in a
3834 "Half-Installed" state, which requires a
3835 reinstall. If it works, the packages is left in
3836 a "Config-Files" state.
3839 Otherwise (i.e., the package was completely purged):
3840 <example compact="compact">
3841 <var>new-preinst</var> install
3844 <example compact="compact">
3845 <var>new-postrm</var> abort-install
3847 If the error-unwind fails, the package is in a
3848 "Half-Installed" phase, and requires a
3849 reinstall. If the error unwind works, the
3850 package is in a not installed state.
3857 The new package's files are unpacked, overwriting any
3858 that may be on the system already, for example any
3859 from the old version of the same package or from
3860 another package. Backups of the old files are kept
3861 temporarily, and if anything goes wrong the package
3862 management system will attempt to put them back as
3863 part of the error unwind.
3867 It is an error for a package to contain files which
3868 are on the system in another package, unless
3869 <tt>Replaces</tt> is used (see <ref id="replaces">).
3871 The following paragraph is not currently the case:
3872 Currently the <tt>- - force-overwrite</tt> flag is
3873 enabled, downgrading it to a warning, but this may not
3879 It is a more serious error for a package to contain a
3880 plain file or other kind of non-directory where another
3881 package has a directory (again, unless
3882 <tt>Replaces</tt> is used). This error can be
3883 overridden if desired using
3884 <tt>--force-overwrite-dir</tt>, but this is not
3889 Packages which overwrite each other's files produce
3890 behavior which, though deterministic, is hard for the
3891 system administrator to understand. It can easily
3892 lead to "missing" programs if, for example, a package
3893 is installed which overwrites a file from another
3894 package, and is then removed again.<footnote>
3895 Part of the problem is due to what is arguably a
3896 bug in <prgn>dpkg</prgn>.
3901 A directory will never be replaced by a symbolic link
3902 to a directory or vice versa; instead, the existing
3903 state (symlink or not) will be left alone and
3904 <prgn>dpkg</prgn> will follow the symlink if there is
3913 If the package is being upgraded, call
3914 <example compact="compact">
3915 <var>old-postrm</var> upgrade <var>new-version</var>
3919 If this fails, <prgn>dpkg</prgn> will attempt:
3920 <example compact="compact">
3921 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3923 If this works, installation continues. If not,
3925 <example compact="compact">
3926 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3928 If this fails, the old version is left in a
3929 "Half-Installed" state. If it works, dpkg now
3931 <example compact="compact">
3932 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3934 If this fails, the old version is left in a
3935 "Half-Installed" state. If it works, dpkg now
3937 <example compact="compact">
3938 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3940 If this fails, the old version is in an
3947 This is the point of no return - if
3948 <prgn>dpkg</prgn> gets this far, it won't back off
3949 past this point if an error occurs. This will
3950 leave the package in a fairly bad state, which
3951 will require a successful re-installation to clear
3952 up, but it's when <prgn>dpkg</prgn> starts doing
3953 things that are irreversible.
3958 Any files which were in the old version of the package
3959 but not in the new are removed.
3963 The new file list replaces the old.
3967 The new maintainer scripts replace the old.
3971 Any packages all of whose files have been overwritten
3972 during the installation, and which aren't required for
3973 dependencies, are considered to have been removed.
3974 For each such package
3977 <prgn>dpkg</prgn> calls:
3978 <example compact="compact">
3979 <var>disappearer's-postrm</var> disappear \
3980 <var>overwriter</var> <var>overwriter-version</var>
3984 The package's maintainer scripts are removed.
3987 It is noted in the status database as being in a
3988 sane state, namely not installed (any conffiles
3989 it may have are ignored, rather than being
3990 removed by <prgn>dpkg</prgn>). Note that
3991 disappearing packages do not have their prerm
3992 called, because <prgn>dpkg</prgn> doesn't know
3993 in advance that the package is going to
4000 Any files in the package we're unpacking that are also
4001 listed in the file lists of other packages are removed
4002 from those lists. (This will lobotomize the file list
4003 of the "conflicting" package if there is one.)
4007 The backup files made during installation, above, are
4013 The new package's status is now sane, and recorded as
4018 Here is another point of no return - if the
4019 conflicting package's removal fails we do not unwind
4020 the rest of the installation; the conflicting package
4021 is left in a half-removed limbo.
4026 If there was a conflicting package we go and do the
4027 removal actions (described below), starting with the
4028 removal of the conflicting package's files (any that
4029 are also in the package being installed have already
4030 been removed from the conflicting package's file list,
4031 and so do not get removed now).
4037 <sect id="configdetails"><heading>Details of configuration</heading>
4040 When we configure a package (this happens with <tt>dpkg
4041 --install</tt> and <tt>dpkg --configure</tt>), we first
4042 update any <tt>conffile</tt>s and then call:
4043 <example compact="compact">
4044 <var>postinst</var> configure <var>most-recently-configured-version</var>
4049 No attempt is made to unwind after errors during
4050 configuration. If the configuration fails, the package is in
4051 a "Failed Config" state, and an error message is generated.
4055 If there is no most recently configured version
4056 <prgn>dpkg</prgn> will pass a null argument.
4059 Historical note: Truly ancient (pre-1997) versions of
4060 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4061 (including the angle brackets) in this case. Even older
4062 ones did not pass a second argument at all, under any
4063 circumstance. Note that upgrades using such an old dpkg
4064 version are unlikely to work for other reasons, even if
4065 this old argument behavior is handled by your postinst script.
4071 <sect id="removedetails"><heading>Details of removal and/or
4072 configuration purging</heading>
4078 <example compact="compact">
4079 <var>prerm</var> remove
4083 If prerm fails during replacement due to conflict
4085 <var>conflictor's-postinst</var> abort-remove \
4086 in-favour <var>package</var> <var>new-version</var>
4090 <var>postinst</var> abort-remove
4094 If this fails, the package is in a "Half-Configured"
4095 state, or else it remains "Installed".
4099 The package's files are removed (except <tt>conffile</tt>s).
4102 <example compact="compact">
4103 <var>postrm</var> remove
4107 If it fails, there's no error unwind, and the package is in
4108 an "Half-Installed" state.
4113 All the maintainer scripts except the <prgn>postrm</prgn>
4118 If we aren't purging the package we stop here. Note
4119 that packages which have no <prgn>postrm</prgn> and no
4120 <tt>conffile</tt>s are automatically purged when
4121 removed, as there is no difference except for the
4122 <prgn>dpkg</prgn> status.
4126 The <tt>conffile</tt>s and any backup files
4127 (<tt>~</tt>-files, <tt>#*#</tt> files,
4128 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4133 <example compact="compact">
4134 <var>postrm</var> purge
4138 If this fails, the package remains in a "Config-Files"
4143 The package's file list is removed.
4152 <chapt id="relationships">
4153 <heading>Declaring relationships between packages</heading>
4155 <sect id="depsyntax">
4156 <heading>Syntax of relationship fields</heading>
4159 These fields all have a uniform syntax. They are a list of
4160 package names separated by commas.
4164 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4165 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4166 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4167 control file fields of the package, which declare
4168 dependencies on other packages, the package names listed may
4169 also include lists of alternative package names, separated
4170 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4171 if any one of the alternative packages is installed, that
4172 part of the dependency is considered to be satisfied.
4176 All of the fields except for <tt>Provides</tt> may restrict
4177 their applicability to particular versions of each named
4178 package. This is done in parentheses after each individual
4179 package name; the parentheses should contain a relation from
4180 the list below followed by a version number, in the format
4181 described in <ref id="f-Version">.
4185 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4186 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4187 strictly earlier, earlier or equal, exactly equal, later or
4188 equal and strictly later, respectively. The deprecated
4189 forms <tt><</tt> and <tt>></tt> were used to mean
4190 earlier/later or equal, rather than strictly earlier/later,
4191 so they should not appear in new packages (though
4192 <prgn>dpkg</prgn> still supports them).
4196 Whitespace may appear at any point in the version
4197 specification subject to the rules in <ref
4198 id="controlsyntax">, and must appear where it's necessary to
4199 disambiguate; it is not otherwise significant. All of the
4200 relationship fields may span multiple lines. For
4201 consistency and in case of future changes to
4202 <prgn>dpkg</prgn> it is recommended that a single space be
4203 used after a version relationship and before a version
4204 number; it is also conventional to put a single space after
4205 each comma, on either side of each vertical bar, and before
4206 each open parenthesis. When wrapping a relationship field, it
4207 is conventional to do so after a comma and before the space
4208 following that comma.
4212 For example, a list of dependencies might appear as:
4213 <example compact="compact">
4216 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4221 All fields that specify build-time relationships
4222 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4223 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4224 may be restricted to a certain set of architectures. This
4225 is indicated in brackets after each individual package name and
4226 the optional version specification. The brackets enclose a
4227 list of Debian architecture names separated by whitespace.
4228 Exclamation marks may be prepended to each of the names.
4229 (It is not permitted for some names to be prepended with
4230 exclamation marks while others aren't.) If the current Debian
4231 host architecture is not in this list and there are no
4232 exclamation marks in the list, or it is in the list with a
4233 prepended exclamation mark, the package name and the
4234 associated version specification are ignored completely for
4235 the purposes of defining the relationships.
4240 <example compact="compact">
4242 Build-Depends-Indep: texinfo
4243 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4244 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4246 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4247 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4248 <tt>gnumach-dev</tt> only on hurd-i386.
4252 If the architecture-restricted dependency is part of a set of
4253 alternatives using <tt>|</tt>, that alternative is ignored
4254 completely on architectures that do not match the restriction.
4256 <example compact="compact">
4257 Build-Depends: foo [!i386] | bar [!amd64]
4259 is equivalent to <tt>bar</tt> on the i386 architecture, to
4260 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4261 bar</tt> on all other architectures.
4265 Note that the binary package relationship fields such as
4266 <tt>Depends</tt> appear in one of the binary package
4267 sections of the control file, whereas the build-time
4268 relationships such as <tt>Build-Depends</tt> appear in the
4269 source package section of the control file (which is the
4274 <sect id="binarydeps">
4275 <heading>Binary Dependencies - <tt>Depends</tt>,
4276 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4277 <tt>Pre-Depends</tt>
4281 Packages can declare in their control file that they have
4282 certain relationships to other packages - for example, that
4283 they may not be installed at the same time as certain other
4284 packages, and/or that they depend on the presence of others.
4288 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4289 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4290 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4291 <tt>Breaks</tt> is described in <ref id="breaks">, and
4292 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4293 rest are described below.
4297 These seven fields are used to declare a dependency
4298 relationship by one package on another. Except for
4299 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4300 depending (binary) package's control file.
4301 (<tt>Enhances</tt> appears in the recommending package's
4302 control file, and <tt>Breaks</tt> appears in the version of
4303 depended-on package which causes the named package to
4308 A <tt>Depends</tt> field takes effect <em>only</em> when a
4309 package is to be configured. It does not prevent a package
4310 being on the system in an unconfigured state while its
4311 dependencies are unsatisfied, and it is possible to replace
4312 a package whose dependencies are satisfied and which is
4313 properly installed with a different version whose
4314 dependencies are not and cannot be satisfied; when this is
4315 done the depending package will be left unconfigured (since
4316 attempts to configure it will give errors) and will not
4317 function properly. If it is necessary, a
4318 <tt>Pre-Depends</tt> field can be used, which has a partial
4319 effect even when a package is being unpacked, as explained
4320 in detail below. (The other three dependency fields,
4321 <tt>Recommends</tt>, <tt>Suggests</tt> and
4322 <tt>Enhances</tt>, are only used by the various front-ends
4323 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4324 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4328 For this reason packages in an installation run are usually
4329 all unpacked first and all configured later; this gives
4330 later versions of packages with dependencies on later
4331 versions of other packages the opportunity to have their
4332 dependencies satisfied.
4336 In case of circular dependencies, since installation or
4337 removal order honoring the dependency order can't be
4338 established, dependency loops are broken at some point
4339 (based on rules below), and some packages may not be able to
4340 rely on their dependencies being present when being
4341 installed or removed, depending on which side of the break
4342 of the circular dependency loop they happen to be on. If one
4343 of the packages in the loop has no postinst script, then the
4344 cycle will be broken at that package, so as to ensure that
4345 all postinst scripts run with the dependencies properly
4346 configured if this is possible. Otherwise the breaking point
4351 The <tt>Depends</tt> field thus allows package maintainers
4352 to impose an order in which packages should be configured.
4356 The meaning of the five dependency fields is as follows:
4358 <tag><tt>Depends</tt></tag>
4361 This declares an absolute dependency. A package will
4362 not be configured unless all of the packages listed in
4363 its <tt>Depends</tt> field have been correctly
4368 The <tt>Depends</tt> field should be used if the
4369 depended-on package is required for the depending
4370 package to provide a significant amount of
4375 The <tt>Depends</tt> field should also be used if the
4376 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4377 <prgn>postrm</prgn> scripts require the package to be
4378 present in order to run. Note, however, that the
4379 <prgn>postrm</prgn> cannot rely on any non-essential
4380 packages to be present during the <tt>purge</tt>
4384 <tag><tt>Recommends</tt></tag>
4387 This declares a strong, but not absolute, dependency.
4391 The <tt>Recommends</tt> field should list packages
4392 that would be found together with this one in all but
4393 unusual installations.
4397 <tag><tt>Suggests</tt></tag>
4399 This is used to declare that one package may be more
4400 useful with one or more others. Using this field
4401 tells the packaging system and the user that the
4402 listed packages are related to this one and can
4403 perhaps enhance its usefulness, but that installing
4404 this one without them is perfectly reasonable.
4407 <tag><tt>Enhances</tt></tag>
4409 This field is similar to Suggests but works in the
4410 opposite direction. It is used to declare that a
4411 package can enhance the functionality of another
4415 <tag><tt>Pre-Depends</tt></tag>
4418 This field is like <tt>Depends</tt>, except that it
4419 also forces <prgn>dpkg</prgn> to complete installation
4420 of the packages named before even starting the
4421 installation of the package which declares the
4422 pre-dependency, as follows:
4426 When a package declaring a pre-dependency is about to
4427 be <em>unpacked</em> the pre-dependency can be
4428 satisfied if the depended-on package is either fully
4429 configured, <em>or even if</em> the depended-on
4430 package(s) are only unpacked or in the "Half-Configured"
4431 state, provided that they have been configured
4432 correctly at some point in the past (and not removed
4433 or partially removed since). In this case, both the
4434 previously-configured and currently unpacked or
4435 "Half-Configured" versions must satisfy any version
4436 clause in the <tt>Pre-Depends</tt> field.
4440 When the package declaring a pre-dependency is about
4441 to be <em>configured</em>, the pre-dependency will be
4442 treated as a normal <tt>Depends</tt>, that is, it will
4443 be considered satisfied only if the depended-on
4444 package has been correctly configured.
4448 <tt>Pre-Depends</tt> should be used sparingly,
4449 preferably only by packages whose premature upgrade or
4450 installation would hamper the ability of the system to
4451 continue with any upgrade that might be in progress.
4455 <tt>Pre-Depends</tt> are also required if the
4456 <prgn>preinst</prgn> script depends on the named
4457 package. It is best to avoid this situation if
4465 When selecting which level of dependency to use you should
4466 consider how important the depended-on package is to the
4467 functionality of the one declaring the dependency. Some
4468 packages are composed of components of varying degrees of
4469 importance. Such a package should list using
4470 <tt>Depends</tt> the package(s) which are required by the
4471 more important components. The other components'
4472 requirements may be mentioned as Suggestions or
4473 Recommendations, as appropriate to the components' relative
4479 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4482 When one binary package declares that it breaks another,
4483 <prgn>dpkg</prgn> will refuse to allow the package which
4484 declares <tt>Breaks</tt> be installed unless the broken
4485 package is deconfigured first, and it will refuse to
4486 allow the broken package to be reconfigured.
4490 A package will not be regarded as causing breakage merely
4491 because its configuration files are still installed; it must
4492 be at least "Half-Installed".
4496 A special exception is made for packages which declare that
4497 they break their own package name or a virtual package which
4498 they provide (see below): this does not count as a real
4503 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4504 version clause; such a <tt>Breaks</tt> is introduced in the
4505 version of an (implicit or explicit) dependency which
4506 violates an assumption or reveals a bug in earlier versions
4507 of the broken package. This use of <tt>Breaks</tt> will
4508 inform higher-level package management tools that broken
4509 package must be upgraded before the new one.
4513 If the breaking package also overwrites some files from the
4514 older package, it should use <tt>Replaces</tt> (not
4515 <tt>Conflicts</tt>) to ensure this goes smoothly.
4519 <sect id="conflicts">
4520 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4523 When one binary package declares a conflict with another
4524 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4525 refuse to allow them to be installed on the system at the
4530 If one package is to be installed, the other must be removed
4531 first - if the package being installed is marked as
4532 replacing (see <ref id="replaces">) the one on the system,
4533 or the one on the system is marked as deselected, or both
4534 packages are marked <tt>Essential</tt>, then
4535 <prgn>dpkg</prgn> will automatically remove the package
4536 which is causing the conflict, otherwise it will halt the
4537 installation of the new package with an error. This
4538 mechanism is specifically designed to produce an error when
4539 the installed package is <tt>Essential</tt>, but the new
4544 A package will not cause a conflict merely because its
4545 configuration files are still installed; it must be at least
4550 A special exception is made for packages which declare a
4551 conflict with their own package name, or with a virtual
4552 package which they provide (see below): this does not
4553 prevent their installation, and allows a package to conflict
4554 with others providing a replacement for it. You use this
4555 feature when you want the package in question to be the only
4556 package providing some feature.
4560 A <tt>Conflicts</tt> entry should almost never have an
4561 "earlier than" version clause. This would prevent
4562 <prgn>dpkg</prgn> from upgrading or installing the package
4563 which declared such a conflict until the upgrade or removal
4564 of the conflicted-with package had been completed. Instead,
4565 <tt>Breaks</tt> may be used.
4569 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4573 As well as the names of actual ("concrete") packages, the
4574 package relationship fields <tt>Depends</tt>,
4575 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4576 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4577 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4578 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4579 may mention "virtual packages".
4583 A <em>virtual package</em> is one which appears in the
4584 <tt>Provides</tt> control file field of another package.
4585 The effect is as if the package(s) which provide a
4586 particular virtual package name had been listed by name
4587 everywhere the virtual package name appears. (See also <ref
4592 If there are both concrete and virtual packages of the same
4593 name, then the dependency may be satisfied (or the conflict
4594 caused) by either the concrete package with the name in
4595 question or any other concrete package which provides the
4596 virtual package with the name in question. This is so that,
4597 for example, supposing we have
4598 <example compact="compact">
4601 </example> and someone else releases an enhanced version of
4602 the <tt>bar</tt> package they can say:
4603 <example compact="compact">
4607 and the <tt>bar-plus</tt> package will now also satisfy the
4608 dependency for the <tt>foo</tt> package.
4612 If a relationship field has a version number attached
4613 then only real packages will be considered to see whether
4614 the relationship is satisfied (or the prohibition violated,
4615 for a conflict or breakage) - it is assumed that a real
4616 package which provides the virtual package is not of the
4617 "right" version. So, a <tt>Provides</tt> field may not
4618 contain version numbers, and the version number of the
4619 concrete package which provides a particular virtual package
4620 will not be looked at when considering a dependency on or
4621 conflict with the virtual package name.
4625 It is likely that the ability will be added in a future
4626 release of <prgn>dpkg</prgn> to specify a version number for
4627 each virtual package it provides. This feature is not yet
4628 present, however, and is expected to be used only
4633 If you want to specify which of a set of real packages
4634 should be the default to satisfy a particular dependency on
4635 a virtual package, you should list the real package as an
4636 alternative before the virtual one.
4641 <sect id="replaces"><heading>Overwriting files and replacing
4642 packages - <tt>Replaces</tt></heading>
4645 Packages can declare in their control file that they should
4646 overwrite files in certain other packages, or completely
4647 replace other packages. The <tt>Replaces</tt> control file
4648 field has these two distinct purposes.
4651 <sect1><heading>Overwriting files in other packages</heading>
4654 Firstly, as mentioned before, it is usually an error for a
4655 package to contain files which are on the system in
4660 However, if the overwriting package declares that it
4661 <tt>Replaces</tt> the one containing the file being
4662 overwritten, then <prgn>dpkg</prgn> will replace the file
4663 from the old package with that from the new. The file
4664 will no longer be listed as "owned" by the old package.
4668 If a package is completely replaced in this way, so that
4669 <prgn>dpkg</prgn> does not know of any files it still
4670 contains, it is considered to have "disappeared". It will
4671 be marked as not wanted on the system (selected for
4672 removal) and not installed. Any <tt>conffile</tt>s
4673 details noted for the package will be ignored, as they
4674 will have been taken over by the overwriting package. The
4675 package's <prgn>postrm</prgn> script will be run with a
4676 special argument to allow the package to do any final
4677 cleanup required. See <ref id="mscriptsinstact">.
4680 Replaces is a one way relationship -- you have to
4681 install the replacing package after the replaced
4688 For this usage of <tt>Replaces</tt>, virtual packages (see
4689 <ref id="virtual">) are not considered when looking at a
4690 <tt>Replaces</tt> field - the packages declared as being
4691 replaced must be mentioned by their real names.
4695 Furthermore, this usage of <tt>Replaces</tt> only takes
4696 effect when both packages are at least partially on the
4697 system at once, so that it can only happen if they do not
4698 conflict or if the conflict has been overridden.
4703 <sect1><heading>Replacing whole packages, forcing their
4707 Secondly, <tt>Replaces</tt> allows the packaging system to
4708 resolve which package should be removed when there is a
4709 conflict - see <ref id="conflicts">. This usage only
4710 takes effect when the two packages <em>do</em> conflict,
4711 so that the two usages of this field do not interfere with
4716 In this situation, the package declared as being replaced
4717 can be a virtual package, so for example, all mail
4718 transport agents (MTAs) would have the following fields in
4719 their control files:
4720 <example compact="compact">
4721 Provides: mail-transport-agent
4722 Conflicts: mail-transport-agent
4723 Replaces: mail-transport-agent
4725 ensuring that only one MTA can be installed at any one
4730 <sect id="sourcebinarydeps">
4731 <heading>Relationships between source and binary packages -
4732 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4733 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4737 Source packages that require certain binary packages to be
4738 installed or absent at the time of building the package
4739 can declare relationships to those binary packages.
4743 This is done using the <tt>Build-Depends</tt>,
4744 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4745 <tt>Build-Conflicts-Indep</tt> control file fields.
4749 Build-dependencies on "build-essential" binary packages can be
4750 omitted. Please see <ref id="pkg-relations"> for more information.
4754 The dependencies and conflicts they define must be satisfied
4755 (as defined earlier for binary packages) in order to invoke
4756 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4758 If you make "build-arch" or "binary-arch", you need
4759 Build-Depends. If you make "build-indep" or
4760 "binary-indep", you need Build-Depends and
4761 Build-Depends-Indep. If you make "build" or "binary",
4765 There is no Build-Depends-Arch; this role is essentially
4766 met with Build-Depends. Anyone building the
4767 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4768 is basically assumed to be building the whole package
4769 anyway and so installs all build dependencies. The
4770 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4771 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4772 does not yet know how to check for its existence) and
4773 <tt>binary-arch</tt>.
4776 The purpose of the original split, I recall, was so that
4777 the autobuilders wouldn't need to install extra packages
4778 needed only for the binary-indep targets. But without a
4779 build-arch/build-indep split, this didn't work, since
4780 most of the work is done in the build target, not in the
4786 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4788 The <tt>Build-Depends</tt> and
4789 <tt>Build-Conflicts</tt> fields must be satisfied when
4790 any of the following targets is invoked:
4791 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4792 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4793 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4795 <tag><tt>Build-Depends-Indep</tt>,
4796 <tt>Build-Conflicts-Indep</tt></tag>
4798 The <tt>Build-Depends-Indep</tt> and
4799 <tt>Build-Conflicts-Indep</tt> fields must be
4800 satisfied when any of the following targets is
4801 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4802 <tt>binary</tt> and <tt>binary-indep</tt>.
4812 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4815 Packages containing shared libraries must be constructed with
4816 a little care to make sure that the shared library is always
4817 available. This is especially important for packages whose
4818 shared libraries are vitally important, such as the C library
4819 (currently <tt>libc6</tt>).
4823 Packages involving shared libraries should be split up into
4824 several binary packages. This section mostly deals with how
4825 this separation is to be accomplished; rules for files within
4826 the shared library packages are in <ref id="libraries"> instead.
4829 <sect id="sharedlibs-runtime">
4830 <heading>Run-time shared libraries</heading>
4833 The run-time shared library needs to be placed in a package
4834 whose name changes whenever the shared object version
4837 Since it is common place to install several versions of a
4838 package that just provides shared libraries, it is a
4839 good idea that the library package should not
4840 contain any extraneous non-versioned files, unless they
4841 happen to be in versioned directories.</p>
4843 The most common mechanism is to place it in a package
4845 <package><var>libraryname</var><var>soversion</var></package>,
4846 where <file><var>soversion</var></file> is the version number
4847 in the soname of the shared library<footnote>
4848 The soname is the shared object name: it's the thing
4849 that has to match exactly between building an executable
4850 and running it for the dynamic linker to be able run the
4851 program. For example, if the soname of the library is
4852 <file>libfoo.so.6</file>, the library package would be
4853 called <file>libfoo6</file>.
4855 Alternatively, if it would be confusing to directly append
4856 <var>soversion</var> to <var>libraryname</var> (e.g. because
4857 <var>libraryname</var> itself ends in a number), you may use
4858 <package><var>libraryname</var>-<var>soversion</var></package> and
4859 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4864 If you have several shared libraries built from the same
4865 source tree you may lump them all together into a single
4866 shared library package, provided that you change all of
4867 their sonames at once (so that you don't get filename
4868 clashes if you try to install different versions of the
4869 combined shared libraries package).
4873 The package should install the shared libraries under
4874 their normal names. For example, the <package>libgdbm3</package>
4875 package should install <file>libgdbm.so.3.0.0</file> as
4876 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4877 renamed or re-linked by any <prgn>prerm</prgn> or
4878 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4879 of renaming things safely without affecting running programs,
4880 and attempts to interfere with this are likely to lead to
4885 Shared libraries should not be installed executable, since
4886 the dynamic linker does not require this and trying to
4887 execute a shared library usually results in a core dump.
4891 The run-time library package should include the symbolic link that
4892 <prgn>ldconfig</prgn> would create for the shared libraries.
4893 For example, the <package>libgdbm3</package> package should include
4894 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4895 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4896 linker (for example <prgn>ld.so</prgn> or
4897 <prgn>ld-linux.so.*</prgn>) can find the library between the
4898 time that <prgn>dpkg</prgn> installs it and the time that
4899 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4901 The package management system requires the library to be
4902 placed before the symbolic link pointing to it in the
4903 <file>.deb</file> file. This is so that when
4904 <prgn>dpkg</prgn> comes to install the symlink
4905 (overwriting the previous symlink pointing at an older
4906 version of the library), the new shared library is already
4907 in place. In the past, this was achieved by creating the
4908 library in the temporary packaging directory before
4909 creating the symlink. Unfortunately, this was not always
4910 effective, since the building of the tar file in the
4911 <file>.deb</file> depended on the behavior of the underlying
4912 file system. Some file systems (such as reiserfs) reorder
4913 the files so that the order of creation is forgotten.
4914 Since version 1.7.0, <prgn>dpkg</prgn>
4915 reorders the files itself as necessary when building a
4916 package. Thus it is no longer important to concern
4917 oneself with the order of file creation.
4921 <sect1 id="ldconfig">
4922 <heading><tt>ldconfig</tt></heading>
4925 Any package installing shared libraries in one of the default
4926 library directories of the dynamic linker (which are currently
4927 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4928 listed in <file>/etc/ld.so.conf</file><footnote>
4930 <list compact="compact">
4931 <item>/usr/local/lib</item>
4932 <item>/usr/lib/libc5-compat</item>
4933 <item>/lib/libc5-compat</item>
4936 must use <prgn>ldconfig</prgn> to update the shared library
4941 The package maintainer scripts must only call
4942 <prgn>ldconfig</prgn> under these circumstances:
4943 <list compact="compact">
4944 <item>When the <prgn>postinst</prgn> script is run with a
4945 first argument of <tt>configure</tt>, the script must call
4946 <prgn>ldconfig</prgn>, and may optionally invoke
4947 <prgn>ldconfig</prgn> at other times.
4949 <item>When the <prgn>postrm</prgn> script is run with a
4950 first argument of <tt>remove</tt>, the script should call
4951 <prgn>ldconfig</prgn>.
4956 During install or upgrade, the preinst is called before
4957 the new files are installed, so calling "ldconfig" is
4958 pointless. The preinst of an existing package can also be
4959 called if an upgrade fails. However, this happens during
4960 the critical time when a shared libs may exist on-disk
4961 under a temporary name. Thus, it is dangerous and
4962 forbidden by current policy to call "ldconfig" at this
4967 When a package is installed or upgraded, "postinst
4968 configure" runs after the new files are safely on-disk.
4969 Since it is perfectly safe to invoke ldconfig
4970 unconditionally in a postinst, it is OK for a package to
4971 simply put ldconfig in its postinst without checking the
4972 argument. The postinst can also be called to recover from
4973 a failed upgrade. This happens before any new files are
4974 unpacked, so there is no reason to call "ldconfig" at this
4979 For a package that is being removed, prerm is
4980 called with all the files intact, so calling ldconfig is
4981 useless. The other calls to "prerm" happen in the case of
4982 upgrade at a time when all the files of the old package
4983 are on-disk, so again calling "ldconfig" is pointless.
4987 postrm, on the other hand, is called with the "remove"
4988 argument just after the files are removed, so this is
4989 the proper time to call "ldconfig" to notify the system
4990 of the fact that the shared libraries from the package
4991 are removed. The postrm can be called at several other
4992 times. At the time of "postrm purge", "postrm
4993 abort-install", or "postrm abort-upgrade", calling
4994 "ldconfig" is useless because the shared lib files are
4995 not on-disk. However, when "postrm" is invoked with
4996 arguments "upgrade", "failed-upgrade", or "disappear", a
4997 shared lib may exist on-disk under a temporary filename.
5005 <sect id="sharedlibs-support-files">
5006 <heading>Shared library support files</heading>
5009 If your package contains files whose names do not change with
5010 each change in the library shared object version, you must not
5011 put them in the shared library package. Otherwise, several
5012 versions of the shared library cannot be installed at the same
5013 time without filename clashes, making upgrades and transitions
5014 unnecessarily difficult.
5018 It is recommended that supporting files and run-time support
5019 programs that do not need to be invoked manually by users, but
5020 are nevertheless required for the package to function, be placed
5021 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5022 preferably under <file>/usr/lib/</file><var>package-name</var>.
5023 If the program or file is architecture independent, the
5024 recommendation is for it to be placed in a subdirectory of
5025 <file>/usr/share</file> instead, preferably under
5026 <file>/usr/share/</file><var>package-name</var>. Following the
5027 <var>package-name</var> naming convention ensures that the file
5028 names change when the shared object version changes.
5032 Run-time support programs that use the shared library but are
5033 not required for the library to function or files used by the
5034 shared library that can be used by any version of the shared
5035 library package should instead be put in a separate package.
5036 This package might typically be named
5037 <package><var>libraryname</var>-tools</package>; note the
5038 absence of the <var>soversion</var> in the package name.
5042 Files and support programs only useful when compiling software
5043 against the library should be included in the development
5044 package for the library.<footnote>
5045 For example, a <file><var>package-name</var>-config</file>
5046 script or <package>pkg-config</package> configuration files.
5051 <sect id="sharedlibs-static">
5052 <heading>Static libraries</heading>
5055 The static library (<file><var>libraryname.a</var></file>)
5056 is usually provided in addition to the shared version.
5057 It is placed into the development package (see below).
5061 In some cases, it is acceptable for a library to be
5062 available in static form only; these cases include:
5064 <item>libraries for languages whose shared library support
5065 is immature or unstable</item>
5066 <item>libraries whose interfaces are in flux or under
5067 development (commonly the case when the library's
5068 major version number is zero, or where the ABI breaks
5069 across patchlevels)</item>
5070 <item>libraries which are explicitly intended to be
5071 available only in static form by their upstream
5076 <sect id="sharedlibs-dev">
5077 <heading>Development files</heading>
5080 The development files associated to a shared library need to be
5081 placed in a package called
5082 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5083 or if you prefer only to support one development version at a
5084 time, <package><var>libraryname</var>-dev</package>.
5088 In case several development versions of a library exist, you may
5089 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5090 <ref id="conflicts">) to ensure that the user only installs one
5091 development version at a time (as different development versions are
5092 likely to have the same header files in them, which would cause a
5093 filename clash if both were installed).
5097 The development package should contain a symlink for the associated
5098 shared library without a version number. For example, the
5099 <package>libgdbm-dev</package> package should include a symlink
5100 from <file>/usr/lib/libgdbm.so</file> to
5101 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5102 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5103 <file>libgdbm.so</file> when compiling dynamically.
5107 <sect id="sharedlibs-intradeps">
5108 <heading>Dependencies between the packages of the same library</heading>
5111 Typically the development version should have an exact
5112 version dependency on the runtime library, to make sure that
5113 compilation and linking happens correctly. The
5114 <tt>${binary:Version}</tt> substitution variable can be
5115 useful for this purpose.
5117 Previously, <tt>${Source-Version}</tt> was used, but its name
5118 was confusing and it has been deprecated since dpkg 1.13.19.
5123 <sect id="sharedlibs-shlibdeps">
5124 <heading>Dependencies between the library and other packages -
5125 the <tt>shlibs</tt> system</heading>
5128 If a package contains a binary or library which links to a
5129 shared library, we must ensure that when the package is
5130 installed on the system, all of the libraries needed are
5131 also installed. This requirement led to the creation of the
5132 <tt>shlibs</tt> system, which is very simple in its design:
5133 any package which <em>provides</em> a shared library also
5134 provides information on the package dependencies required to
5135 ensure the presence of this library, and any package which
5136 <em>uses</em> a shared library uses this information to
5137 determine the dependencies it requires. The files which
5138 contain the mapping from shared libraries to the necessary
5139 dependency information are called <file>shlibs</file> files.
5143 Thus, when a package is built which contains any shared
5144 libraries, it must provide a <file>shlibs</file> file for other
5145 packages to use, and when a package is built which contains
5146 any shared libraries or compiled binaries, it must run
5147 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5148 on these to determine the libraries used and hence the
5149 dependencies needed by this package.<footnote>
5151 In the past, the shared libraries linked to were
5152 determined by calling <prgn>ldd</prgn>, but now
5153 <prgn>objdump</prgn> is used to do this. The only
5154 change this makes to package building is that
5155 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5156 libraries, whereas in the past this was unnecessary.
5157 The rest of this footnote explains the advantage that
5162 We say that a binary <tt>foo</tt> <em>directly</em> uses
5163 a library <tt>libbar</tt> if it is explicitly linked
5164 with that library (that is, it uses the flag
5165 <tt>-lbar</tt> during the linking stage). Other
5166 libraries that are needed by <tt>libbar</tt> are linked
5167 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5168 linker will load them automatically when it loads
5169 <tt>libbar</tt>. A package should depend on
5170 the libraries it directly uses, and the dependencies for
5171 those libraries should automatically pull in the other
5176 Unfortunately, the <prgn>ldd</prgn> program shows both
5177 the directly and indirectly used libraries, meaning that
5178 the dependencies determined included both direct and
5179 indirect dependencies. The use of <prgn>objdump</prgn>
5180 avoids this problem by determining only the directly
5185 A good example of where this helps is the following. We
5186 could update <tt>libimlib</tt> with a new version that
5187 supports a new graphics format called dgf (but retaining
5188 the same major version number). If we used the old
5189 <prgn>ldd</prgn> method, every package that uses
5190 <tt>libimlib</tt> would need to be recompiled so it
5191 would also depend on <tt>libdgf</tt> or it wouldn't run
5192 due to missing symbols. However with the new system,
5193 packages using <tt>libimlib</tt> can rely on
5194 <tt>libimlib</tt> itself having the dependency on
5195 <tt>libdgf</tt> and so they would not need rebuilding.
5201 In the following sections, we will first describe where the
5202 various <tt>shlibs</tt> files are to be found, then how to
5203 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5204 file format and how to create them if your package contains a
5209 <heading>The <tt>shlibs</tt> files present on the system</heading>
5212 There are several places where <tt>shlibs</tt> files are
5213 found. The following list gives them in the order in which
5215 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5216 (The first one which gives the required information is used.)
5222 <p><file>debian/shlibs.local</file></p>
5225 This lists overrides for this package. Its use is
5226 described below (see <ref id="shlibslocal">).
5231 <p><file>/etc/dpkg/shlibs.override</file></p>
5234 This lists global overrides. This list is normally
5235 empty. It is maintained by the local system
5241 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5244 When packages are being built, any
5245 <file>debian/shlibs</file> files are copied into the
5246 control file area of the temporary build directory and
5247 given the name <file>shlibs</file>. These files give
5248 details of any shared libraries included in the
5250 An example may help here. Let us say that the
5251 source package <tt>foo</tt> generates two binary
5252 packages, <tt>libfoo2</tt> and
5253 <tt>foo-runtime</tt>. When building the binary
5254 packages, the two packages are created in the
5255 directories <file>debian/libfoo2</file> and
5256 <file>debian/foo-runtime</file> respectively.
5257 (<file>debian/tmp</file> could be used instead of one
5258 of these.) Since <tt>libfoo2</tt> provides the
5259 <tt>libfoo</tt> shared library, it will require a
5260 <tt>shlibs</tt> file, which will be installed in
5261 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5263 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5264 when <prgn>dpkg-shlibdeps</prgn> is run on the
5266 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5268 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5269 determine whether <tt>foo-prog</tt>'s library
5270 dependencies are satisfied by any of the libraries
5271 provided by <tt>libfoo2</tt>. For this reason,
5272 <prgn>dpkg-shlibdeps</prgn> must only be run once
5273 all of the individual binary packages'
5274 <tt>shlibs</tt> files have been installed into the
5281 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5284 These are the <file>shlibs</file> files corresponding to
5285 all of the packages installed on the system, and are
5286 maintained by the relevant package maintainers.
5291 <p><file>/etc/dpkg/shlibs.default</file></p>
5294 This file lists any shared libraries whose packages
5295 have failed to provide correct <file>shlibs</file> files.
5296 It was used when the <file>shlibs</file> setup was first
5297 introduced, but it is now normally empty. It is
5298 maintained by the <tt>dpkg</tt> maintainer.
5306 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5307 <file>shlibs</file> files</heading>
5311 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5312 into your <file>debian/rules</file> file. If your package
5313 contains only compiled binaries and libraries (but no scripts),
5314 you can use a command such as:
5315 <example compact="compact">
5316 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5317 debian/tmp/usr/lib/*
5319 Otherwise, you will need to explicitly list the compiled
5320 binaries and libraries.<footnote>
5321 If you are using <tt>debhelper</tt>, the
5322 <prgn>dh_shlibdeps</prgn> program will do this work for
5323 you. It will also correctly handle multi-binary
5329 This command puts the dependency information into the
5330 <file>debian/substvars</file> file, which is then used by
5331 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5332 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5333 field in the control file for this to work.
5337 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5338 done. If it does complain you might need to create your own
5339 <file>debian/shlibs.local</file> file, as explained below (see
5340 <ref id="shlibslocal">).
5344 If you have multiple binary packages, you will need to call
5345 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5346 compiled libraries or binaries. In such a case, you will
5347 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5348 utilities to specify a different <file>substvars</file> file.
5352 If you are creating a udeb for use in the Debian Installer,
5353 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5354 should use the dependency line of type <tt>udeb</tt> by
5355 adding the <tt>-tudeb</tt> option<footnote>
5356 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5357 will automatically add this option if it knows it is
5359 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5360 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5361 fall back to the regular dependency line.
5365 For more details on dpkg-shlibdeps, please see
5366 <ref id="pkg-dpkg-shlibdeps"> and
5367 <manref name="dpkg-shlibdeps" section="1">.
5372 <heading>The <file>shlibs</file> File Format</heading>
5375 Each <file>shlibs</file> file has the same format. Lines
5376 beginning with <tt>#</tt> are considered to be comments and
5377 are ignored. Each line is of the form:
5378 <example compact="compact">
5379 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5384 We will explain this by reference to the example of the
5385 <tt>zlib1g</tt> package, which (at the time of writing)
5386 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5390 <var>type</var> is an optional element that indicates the type
5391 of package for which the line is valid. The only type currently
5392 in use is <tt>udeb</tt>. The colon and space after the type are
5397 <var>library-name</var> is the name of the shared library,
5398 in this case <tt>libz</tt>. (This must match the name part
5399 of the soname, see below.)
5403 <var>soname-version</var> is the version part of the soname of
5404 the library. The soname is the thing that must exactly match
5405 for the library to be recognized by the dynamic linker, and is
5407 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5408 example, <tt>libz.so.1</tt>.<footnote>
5409 This can be determined using the command
5410 <example compact="compact">
5411 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5414 The version part is the part which comes after
5415 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5419 <var>dependencies</var> has the same syntax as a dependency
5420 field in a binary package control file. It should give
5421 details of which packages are required to satisfy a binary
5422 built against the version of the library contained in the
5423 package. See <ref id="depsyntax"> for details.
5427 In our example, if the first version of the <tt>zlib1g</tt>
5428 package which contained a minor number of at least
5429 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5430 <tt>shlibs</tt> entry for this library could say:
5431 <example compact="compact">
5432 libz 1 zlib1g (>= 1:1.1.3)
5434 The version-specific dependency is to avoid warnings from
5435 the dynamic linker about using older shared libraries with
5440 As zlib1g also provides a udeb containing the shared library,
5441 there would also be a second line:
5442 <example compact="compact">
5443 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5449 <heading>Providing a <file>shlibs</file> file</heading>
5452 If your package provides a shared library, you need to create
5453 a <file>shlibs</file> file following the format described above.
5454 It is usual to call this file <file>debian/shlibs</file> (but if
5455 you have multiple binary packages, you might want to call it
5456 <file>debian/shlibs.<var>package</var></file> instead). Then
5457 let <file>debian/rules</file> install it in the control area:
5458 <example compact="compact">
5459 install -m644 debian/shlibs debian/tmp/DEBIAN
5461 or, in the case of a multi-binary package:
5462 <example compact="compact">
5463 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5465 An alternative way of doing this is to create the
5466 <file>shlibs</file> file in the control area directly from
5467 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5468 file at all,<footnote>
5469 This is what <prgn>dh_makeshlibs</prgn> in the
5470 <tt>debhelper</tt> suite does. If your package also has a udeb
5471 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5472 automatically generate the <tt>udeb:</tt> lines if you specify
5473 the name of the udeb with the <tt>--add-udeb</tt> option.
5475 since the <file>debian/shlibs</file> file itself is ignored by
5476 <prgn>dpkg-shlibdeps</prgn>.
5480 As <prgn>dpkg-shlibdeps</prgn> reads the
5481 <file>DEBIAN/shlibs</file> files in all of the binary packages
5482 being built from this source package, all of the
5483 <file>DEBIAN/shlibs</file> files should be installed before
5484 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5489 <sect1 id="shlibslocal">
5490 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5493 This file is intended only as a <em>temporary</em> fix if
5494 your binaries or libraries depend on a library whose package
5495 does not yet provide a correct <file>shlibs</file> file.
5499 We will assume that you are trying to package a binary
5500 <tt>foo</tt>. When you try running
5501 <prgn>dpkg-shlibdeps</prgn> you get the following error
5502 message (<tt>-O</tt> displays the dependency information on
5503 <tt>stdout</tt> instead of writing it to
5504 <tt>debian/substvars</tt>, and the lines have been wrapped
5505 for ease of reading):
5506 <example compact="compact">
5507 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5508 dpkg-shlibdeps: warning: unable to find dependency
5509 information for shared library libbar (soname 1,
5510 path /usr/lib/libbar.so.1, dependency field Depends)
5511 shlibs:Depends=libc6 (>= 2.2.2-2)
5513 You can then run <prgn>ldd</prgn> on the binary to find the
5514 full location of the library concerned:
5515 <example compact="compact">
5517 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5518 libc.so.6 => /lib/libc.so.6 (0x40032000)
5519 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5521 So the <prgn>foo</prgn> binary depends on the
5522 <prgn>libbar</prgn> shared library, but no package seems to
5523 provide a <file>*.shlibs</file> file handling
5524 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5525 determine the package responsible:
5526 <example compact="compact">
5527 $ dpkg -S /usr/lib/libbar.so.1
5528 bar1: /usr/lib/libbar.so.1
5529 $ dpkg -s bar1 | grep Version
5532 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5533 is the one we are using. Now we can file a bug against the
5534 <tt>bar1</tt> package and create our own
5535 <file>debian/shlibs.local</file> to locally fix the problem.
5536 Including the following line into your
5537 <file>debian/shlibs.local</file> file:
5538 <example compact="compact">
5539 libbar 1 bar1 (>= 1.0-1)
5541 should allow the package build to work.
5545 As soon as the maintainer of <tt>bar1</tt> provides a
5546 correct <file>shlibs</file> file, you should remove this line
5547 from your <file>debian/shlibs.local</file> file. (You should
5548 probably also then have a versioned <tt>Build-Depends</tt>
5549 on <tt>bar1</tt> to help ensure that others do not have the
5550 same problem building your package.)
5559 <chapt id="opersys"><heading>The Operating System</heading>
5562 <heading>File system hierarchy</heading>
5566 <heading>File System Structure</heading>
5569 The location of all installed files and directories must
5570 comply with the Filesystem Hierarchy Standard (FHS),
5571 version 2.3, with the exceptions noted below, and except
5572 where doing so would violate other terms of Debian
5573 Policy. The following exceptions to the FHS apply:
5578 The optional rules related to user specific
5579 configuration files for applications are stored in
5580 the user's home directory are relaxed. It is
5581 recommended that such files start with the
5582 '<tt>.</tt>' character (a "dot file"), and if an
5583 application needs to create more than one dot file
5584 then the preferred placement is in a subdirectory
5585 with a name starting with a '.' character, (a "dot
5586 directory"). In this case it is recommended the
5587 configuration files not start with the '.'
5593 The requirement for amd64 to use <file>/lib64</file>
5594 for 64 bit binaries is removed.
5599 The requirement for object files, internal binaries, and
5600 libraries, including <file>libc.so.*</file>, to be located
5601 directly under <file>/lib{,32}</file> and
5602 <file>/usr/lib{,32}</file> is amended, permitting files
5603 to instead be installed to
5604 <file>/lib/<var>triplet</var></file> and
5605 <file>/usr/lib/<var>triplet</var></file>, where
5606 <tt><var>triplet</var></tt> is the value returned by
5607 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5608 architecture of the package. Packages may <em>not</em>
5609 install files to any <var>triplet</var> path other
5610 than the one matching the architecture of that package;
5611 for instance, an <tt>Architecture: amd64</tt> package
5612 containing 32-bit x86 libraries may not install these
5613 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5615 This is necessary in order to reserve the directories for
5616 use in cross-installation of library packages from other
5617 architectures, as part of the planned deployment of
5622 Applications may also use a single subdirectory under
5623 <file>/usr/lib/<var>triplet</var></file>.
5626 The execution time linker/loader, ld*, must still be made
5627 available in the existing location under /lib or /lib64
5628 since this is part of the ELF ABI for the architecture.
5633 The requirement that
5634 <file>/usr/local/share/man</file> be "synonymous"
5635 with <file>/usr/local/man</file> is relaxed to a
5640 The requirement that windowmanagers with a single
5641 configuration file call it <file>system.*wmrc</file>
5642 is removed, as is the restriction that the window
5643 manager subdirectory be named identically to the
5644 window manager name itself.
5649 The requirement that boot manager configuration
5650 files live in <file>/etc</file>, or at least are
5651 symlinked there, is relaxed to a recommendation.
5656 The following directories in the root filesystem are
5657 additionally allowed: <file>/sys</file> and
5658 <file>/selinux</file>. <footnote>These directories
5659 are used as mount points to mount virtual filesystems
5660 to get access to kernel information.</footnote>
5667 The version of this document referred here can be
5668 found in the <tt>debian-policy</tt> package or on <url
5669 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5670 name="FHS (Debian copy)"> alongside this manual (or, if
5671 you have the <package>debian-policy</package> installed,
5673 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5674 (local copy)">). The
5675 latest version, which may be a more recent version, may
5677 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5678 Specific questions about following the standard may be
5679 asked on the <tt>debian-devel</tt> mailing list, or
5680 referred to the FHS mailing list (see the
5681 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5687 <heading>Site-specific programs</heading>
5690 As mandated by the FHS, packages must not place any
5691 files in <file>/usr/local</file>, either by putting them in
5692 the file system archive to be unpacked by <prgn>dpkg</prgn>
5693 or by manipulating them in their maintainer scripts.
5697 However, the package may create empty directories below
5698 <file>/usr/local</file> so that the system administrator knows
5699 where to place site-specific files. These are not
5700 directories <em>in</em> <file>/usr/local</file>, but are
5701 children of directories in <file>/usr/local</file>. These
5702 directories (<file>/usr/local/*/dir/</file>)
5703 should be removed on package removal if they are
5708 Note that this applies only to
5709 directories <em>below</em> <file>/usr/local</file>,
5710 not <em>in</em> <file>/usr/local</file>. Packages must
5711 not create sub-directories in the
5712 directory <file>/usr/local</file> itself, except those
5713 listed in FHS, section 4.5. However, you may create
5714 directories below them as you wish. You must not remove
5715 any of the directories listed in 4.5, even if you created
5720 Since <file>/usr/local</file> can be mounted read-only from a
5721 remote server, these directories must be created and
5722 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5723 maintainer scripts and not be included in the
5724 <file>.deb</file> archive. These scripts must not fail if
5725 either of these operations fail.
5729 For example, the <tt>emacsen-common</tt> package could
5730 contain something like
5731 <example compact="compact">
5732 if [ ! -e /usr/local/share/emacs ]
5734 if mkdir /usr/local/share/emacs 2>/dev/null
5736 chown root:staff /usr/local/share/emacs
5737 chmod 2775 /usr/local/share/emacs
5741 in its <prgn>postinst</prgn> script, and
5742 <example compact="compact">
5743 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5744 rmdir /usr/local/share/emacs 2>/dev/null || true
5746 in the <prgn>prerm</prgn> script. (Note that this form is
5747 used to ensure that if the script is interrupted, the
5748 directory <file>/usr/local/share/emacs</file> will still be
5753 If you do create a directory in <file>/usr/local</file> for
5754 local additions to a package, you should ensure that
5755 settings in <file>/usr/local</file> take precedence over the
5756 equivalents in <file>/usr</file>.
5760 However, because <file>/usr/local</file> and its contents are
5761 for exclusive use of the local administrator, a package
5762 must not rely on the presence or absence of files or
5763 directories in <file>/usr/local</file> for normal operation.
5767 The <file>/usr/local</file> directory itself and all the
5768 subdirectories created by the package should (by default) have
5769 permissions 2775 (group-writable and set-group-id) and be
5770 owned by <tt>root:staff</tt>.
5775 <heading>The system-wide mail directory</heading>
5777 The system-wide mail directory
5778 is <file>/var/mail</file>. This directory is part of the
5779 base system and should not be owned by any particular mail
5780 agents. The use of the old
5781 location <file>/var/spool/mail</file> is deprecated, even
5782 though the spool may still be physically located there.
5788 <heading>Users and groups</heading>
5791 <heading>Introduction</heading>
5793 The Debian system can be configured to use either plain or
5798 Some user ids (UIDs) and group ids (GIDs) are reserved
5799 globally for use by certain packages. Because some
5800 packages need to include files which are owned by these
5801 users or groups, or need the ids compiled into binaries,
5802 these ids must be used on any Debian system only for the
5803 purpose for which they are allocated. This is a serious
5804 restriction, and we should avoid getting in the way of
5805 local administration policies. In particular, many sites
5806 allocate users and/or local system groups starting at 100.
5810 Apart from this we should have dynamically allocated ids,
5811 which should by default be arranged in some sensible
5812 order, but the behavior should be configurable.
5816 Packages other than <tt>base-passwd</tt> must not modify
5817 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5818 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5823 <heading>UID and GID classes</heading>
5825 The UID and GID numbers are divided into classes as
5831 Globally allocated by the Debian project, the same
5832 on every Debian system. These ids will appear in
5833 the <file>passwd</file> and <file>group</file> files of all
5834 Debian systems, new ids in this range being added
5835 automatically as the <tt>base-passwd</tt> package is
5840 Packages which need a single statically allocated
5841 uid or gid should use one of these; their
5842 maintainers should ask the <tt>base-passwd</tt>
5850 Dynamically allocated system users and groups.
5851 Packages which need a user or group, but can have
5852 this user or group allocated dynamically and
5853 differently on each system, should use <tt>adduser
5854 --system</tt> to create the group and/or user.
5855 <prgn>adduser</prgn> will check for the existence of
5856 the user or group, and if necessary choose an unused
5857 id based on the ranges specified in
5858 <file>adduser.conf</file>.
5862 <tag>1000-59999:</tag>
5865 Dynamically allocated user accounts. By default
5866 <prgn>adduser</prgn> will choose UIDs and GIDs for
5867 user accounts in this range, though
5868 <file>adduser.conf</file> may be used to modify this
5873 <tag>60000-64999:</tag>
5876 Globally allocated by the Debian project, but only
5877 created on demand. The ids are allocated centrally
5878 and statically, but the actual accounts are only
5879 created on users' systems on demand.
5883 These ids are for packages which are obscure or
5884 which require many statically-allocated ids. These
5885 packages should check for and create the accounts in
5886 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5887 <prgn>adduser</prgn> if it has this facility) if
5888 necessary. Packages which are likely to require
5889 further allocations should have a "hole" left after
5890 them in the allocation, to give them room to
5895 <tag>65000-65533:</tag>
5903 User <tt>nobody</tt>. The corresponding gid refers
5904 to the group <tt>nogroup</tt>.
5911 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5912 not</em> be used, because it is the error return
5921 <sect id="sysvinit">
5922 <heading>System run levels and <file>init.d</file> scripts</heading>
5924 <sect1 id="/etc/init.d">
5925 <heading>Introduction</heading>
5928 The <file>/etc/init.d</file> directory contains the scripts
5929 executed by <prgn>init</prgn> at boot time and when the
5930 init state (or "runlevel") is changed (see <manref
5931 name="init" section="8">).
5935 There are at least two different, yet functionally
5936 equivalent, ways of handling these scripts. For the sake
5937 of simplicity, this document describes only the symbolic
5938 link method. However, it must not be assumed by maintainer
5939 scripts that this method is being used, and any automated
5940 manipulation of the various runlevel behaviors by
5941 maintainer scripts must be performed using
5942 <prgn>update-rc.d</prgn> as described below and not by
5943 manually installing or removing symlinks. For information
5944 on the implementation details of the other method,
5945 implemented in the <tt>file-rc</tt> package, please refer
5946 to the documentation of that package.
5950 These scripts are referenced by symbolic links in the
5951 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5952 runlevels, <prgn>init</prgn> looks in the directory
5953 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5954 execute, where <tt><var>n</var></tt> is the runlevel that
5955 is being changed to, or <tt>S</tt> for the boot-up
5960 The names of the links all have the form
5961 <file>S<var>mm</var><var>script</var></file> or
5962 <file>K<var>mm</var><var>script</var></file> where
5963 <var>mm</var> is a two-digit number and <var>script</var>
5964 is the name of the script (this should be the same as the
5965 name of the actual script in <file>/etc/init.d</file>).
5969 When <prgn>init</prgn> changes runlevel first the targets
5970 of the links whose names start with a <tt>K</tt> are
5971 executed, each with the single argument <tt>stop</tt>,
5972 followed by the scripts prefixed with an <tt>S</tt>, each
5973 with the single argument <tt>start</tt>. (The links are
5974 those in the <file>/etc/rc<var>n</var>.d</file> directory
5975 corresponding to the new runlevel.) The <tt>K</tt> links
5976 are responsible for killing services and the <tt>S</tt>
5977 link for starting services upon entering the runlevel.
5981 For example, if we are changing from runlevel 2 to
5982 runlevel 3, init will first execute all of the <tt>K</tt>
5983 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5984 all of the <tt>S</tt> prefixed scripts in that directory.
5985 The links starting with <tt>K</tt> will cause the
5986 referred-to file to be executed with an argument of
5987 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5992 The two-digit number <var>mm</var> is used to determine
5993 the order in which to run the scripts: low-numbered links
5994 have their scripts run first. For example, the
5995 <tt>K20</tt> scripts will be executed before the
5996 <tt>K30</tt> scripts. This is used when a certain service
5997 must be started before another. For example, the name
5998 server <prgn>bind</prgn> might need to be started before
5999 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6000 can set up its access lists. In this case, the script
6001 that starts <prgn>bind</prgn> would have a lower number
6002 than the script that starts <prgn>inn</prgn> so that it
6004 <example compact="compact">
6011 The two runlevels 0 (halt) and 6 (reboot) are slightly
6012 different. In these runlevels, the links with an
6013 <tt>S</tt> prefix are still called after those with a
6014 <tt>K</tt> prefix, but they too are called with the single
6015 argument <tt>stop</tt>.
6019 <sect1 id="writing-init">
6020 <heading>Writing the scripts</heading>
6023 Packages that include daemons for system services should
6024 place scripts in <file>/etc/init.d</file> to start or stop
6025 services at boot time or during a change of runlevel.
6026 These scripts should be named
6027 <file>/etc/init.d/<var>package</var></file>, and they should
6028 accept one argument, saying what to do:
6031 <tag><tt>start</tt></tag>
6032 <item>start the service,</item>
6034 <tag><tt>stop</tt></tag>
6035 <item>stop the service,</item>
6037 <tag><tt>restart</tt></tag>
6038 <item>stop and restart the service if it's already running,
6039 otherwise start the service</item>
6041 <tag><tt>reload</tt></tag>
6042 <item><p>cause the configuration of the service to be
6043 reloaded without actually stopping and restarting
6046 <tag><tt>force-reload</tt></tag>
6047 <item>cause the configuration to be reloaded if the
6048 service supports this, otherwise restart the
6052 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6053 <tt>force-reload</tt> options should be supported by all
6054 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6059 The <file>init.d</file> scripts must ensure that they will
6060 behave sensibly (i.e., returning success and not starting
6061 multiple copies of a service) if invoked with <tt>start</tt>
6062 when the service is already running, or with <tt>stop</tt>
6063 when it isn't, and that they don't kill unfortunately-named
6064 user processes. The best way to achieve this is usually to
6065 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6070 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6071 scripts. Writing correct <file>init.d</file> scripts requires
6072 accepting various error exit statuses when daemons are already
6073 running or already stopped without aborting
6074 the <file>init.d</file> script, and common <file>init.d</file>
6075 function libraries are not safe to call with <tt>set -e</tt>
6077 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6078 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6079 in effect and echoing status messages to the console fails,
6081 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6082 to not use <tt>set -e</tt> and instead check the result of
6083 each command separately.
6087 If a service reloads its configuration automatically (as
6088 in the case of <prgn>cron</prgn>, for example), the
6089 <tt>reload</tt> option of the <file>init.d</file> script
6090 should behave as if the configuration has been reloaded
6095 The <file>/etc/init.d</file> scripts must be treated as
6096 configuration files, either (if they are present in the
6097 package, that is, in the .deb file) by marking them as
6098 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6099 by managing them correctly in the maintainer scripts (see
6100 <ref id="config-files">). This is important since we want
6101 to give the local system administrator the chance to adapt
6102 the scripts to the local system, e.g., to disable a
6103 service without de-installing the package, or to specify
6104 some special command line options when starting a service,
6105 while making sure their changes aren't lost during the next
6110 These scripts should not fail obscurely when the
6111 configuration files remain but the package has been
6112 removed, as configuration files remain on the system after
6113 the package has been removed. Only when <prgn>dpkg</prgn>
6114 is executed with the <tt>--purge</tt> option will
6115 configuration files be removed. In particular, as the
6116 <file>/etc/init.d/<var>package</var></file> script itself is
6117 usually a <tt>conffile</tt>, it will remain on the system
6118 if the package is removed but not purged. Therefore, you
6119 should include a <tt>test</tt> statement at the top of the
6121 <example compact="compact">
6122 test -f <var>program-executed-later-in-script</var> || exit 0
6127 Often there are some variables in the <file>init.d</file>
6128 scripts whose values control the behavior of the scripts,
6129 and which a system administrator is likely to want to
6130 change. As the scripts themselves are frequently
6131 <tt>conffile</tt>s, modifying them requires that the
6132 administrator merge in their changes each time the package
6133 is upgraded and the <tt>conffile</tt> changes. To ease
6134 the burden on the system administrator, such configurable
6135 values should not be placed directly in the script.
6136 Instead, they should be placed in a file in
6137 <file>/etc/default</file>, which typically will have the same
6138 base name as the <file>init.d</file> script. This extra file
6139 should be sourced by the script when the script runs. It
6140 must contain only variable settings and comments in SUSv3
6141 <prgn>sh</prgn> format. It may either be a
6142 <tt>conffile</tt> or a configuration file maintained by
6143 the package maintainer scripts. See <ref id="config-files">
6148 To ensure that vital configurable values are always
6149 available, the <file>init.d</file> script should set default
6150 values for each of the shell variables it uses, either
6151 before sourcing the <file>/etc/default/</file> file or
6152 afterwards using something like the <tt>:
6153 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6154 script must behave sensibly and not fail if the
6155 <file>/etc/default</file> file is deleted.
6159 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6160 as temporary filesystems<footnote>
6161 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6162 options in <file>/etc/default/rcS</file>.
6163 </footnote>, so the <file>init.d</file> scripts must handle this
6164 correctly. This will typically amount to creating any required
6165 subdirectories dynamically when the <file>init.d</file> script
6166 is run, rather than including them in the package and relying on
6167 <prgn>dpkg</prgn> to create them.
6172 <heading>Interfacing with the initscript system</heading>
6175 Maintainers should use the abstraction layer provided by
6176 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6177 programs to deal with initscripts in their packages'
6178 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6179 and <prgn>postrm</prgn>.
6183 Directly managing the /etc/rc?.d links and directly
6184 invoking the <file>/etc/init.d/</file> initscripts should
6185 be done only by packages providing the initscript
6186 subsystem (such as <prgn>sysv-rc</prgn> and
6187 <prgn>file-rc</prgn>).
6191 <heading>Managing the links</heading>
6194 The program <prgn>update-rc.d</prgn> is provided for
6195 package maintainers to arrange for the proper creation and
6196 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6197 or their functional equivalent if another method is being
6198 used. This may be used by maintainers in their packages'
6199 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6203 You must not include any <file>/etc/rc<var>n</var>.d</file>
6204 symbolic links in the actual archive or manually create or
6205 remove the symbolic links in maintainer scripts; you must
6206 use the <prgn>update-rc.d</prgn> program instead. (The
6207 former will fail if an alternative method of maintaining
6208 runlevel information is being used.) You must not include
6209 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6210 in the archive either. (Only the <tt>sysvinit</tt>
6215 By default <prgn>update-rc.d</prgn> will start services in
6216 each of the multi-user state runlevels (2, 3, 4, and 5)
6217 and stop them in the halt runlevel (0), the single-user
6218 runlevel (1) and the reboot runlevel (6). The system
6219 administrator will have the opportunity to customize
6220 runlevels by simply adding, moving, or removing the
6221 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6222 symbolic links are being used, or by modifying
6223 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6228 To get the default behavior for your package, put in your
6229 <prgn>postinst</prgn> script
6230 <example compact="compact">
6231 update-rc.d <var>package</var> defaults
6233 and in your <prgn>postrm</prgn>
6234 <example compact="compact">
6235 if [ "$1" = purge ]; then
6236 update-rc.d <var>package</var> remove
6238 </example>. Note that if your package changes runlevels
6239 or priority, you may have to remove and recreate the links,
6240 since otherwise the old links may persist. Refer to the
6241 documentation of <prgn>update-rc.d</prgn>.
6245 This will use a default sequence number of 20. If it does
6246 not matter when or in which order the <file>init.d</file>
6247 script is run, use this default. If it does, then you
6248 should talk to the maintainer of the <prgn>sysvinit</prgn>
6249 package or post to <tt>debian-devel</tt>, and they will
6250 help you choose a number.
6254 For more information about using <tt>update-rc.d</tt>,
6255 please consult its man page <manref name="update-rc.d"
6261 <heading>Running initscripts</heading>
6263 The program <prgn>invoke-rc.d</prgn> is provided to make
6264 it easier for package maintainers to properly invoke an
6265 initscript, obeying runlevel and other locally-defined
6266 constraints that might limit a package's right to start,
6267 stop and otherwise manage services. This program may be
6268 used by maintainers in their packages' scripts.
6272 The package maintainer scripts must use
6273 <prgn>invoke-rc.d</prgn> to invoke the
6274 <file>/etc/init.d/*</file> initscripts, instead of
6275 calling them directly.
6279 By default, <prgn>invoke-rc.d</prgn> will pass any
6280 action requests (start, stop, reload, restart...) to the
6281 <file>/etc/init.d</file> script, filtering out requests
6282 to start or restart a service out of its intended
6287 Most packages will simply need to change:
6288 <example compact="compact">/etc/init.d/<package>
6289 <action></example> in their <prgn>postinst</prgn>
6290 and <prgn>prerm</prgn> scripts to:
6291 <example compact="compact">
6292 if which invoke-rc.d >/dev/null 2>&1; then
6293 invoke-rc.d <var>package</var> <action>
6295 /etc/init.d/<var>package</var> <action>
6301 A package should register its initscript services using
6302 <prgn>update-rc.d</prgn> before it tries to invoke them
6303 using <prgn>invoke-rc.d</prgn>. Invocation of
6304 unregistered services may fail.
6308 For more information about using
6309 <prgn>invoke-rc.d</prgn>, please consult its man page
6310 <manref name="invoke-rc.d" section="8">.
6316 <heading>Boot-time initialization</heading>
6319 There used to be another directory, <file>/etc/rc.boot</file>,
6320 which contained scripts which were run once per machine
6321 boot. This has been deprecated in favour of links from
6322 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6323 described in <ref id="/etc/init.d">. Packages must not
6324 place files in <file>/etc/rc.boot</file>.
6329 <heading>Example</heading>
6332 An example on which you can base your
6333 <file>/etc/init.d</file> scripts is found in
6334 <file>/etc/init.d/skeleton</file>.
6341 <heading>Console messages from <file>init.d</file> scripts</heading>
6344 This section describes the formats to be used for messages
6345 written to standard output by the <file>/etc/init.d</file>
6346 scripts. The intent is to improve the consistency of
6347 Debian's startup and shutdown look and feel. For this
6348 reason, please look very carefully at the details. We want
6349 the messages to have the same format in terms of wording,
6350 spaces, punctuation and case of letters.
6354 Here is a list of overall rules that should be used for
6355 messages generated by <file>/etc/init.d</file> scripts.
6361 The message should fit in one line (fewer than 80
6362 characters), start with a capital letter and end with
6363 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6367 If the script is performing some time consuming task in
6368 the background (not merely starting or stopping a
6369 program, for instance), an ellipsis (three dots:
6370 <tt>...</tt>) should be output to the screen, with no
6371 leading or tailing whitespace or line feeds.
6375 The messages should appear as if the computer is telling
6376 the user what it is doing (politely :-), but should not
6377 mention "it" directly. For example, instead of:
6378 <example compact="compact">
6379 I'm starting network daemons: nfsd mountd.
6381 the message should say
6382 <example compact="compact">
6383 Starting network daemons: nfsd mountd.
6390 <tt>init.d</tt> script should use the following standard
6391 message formats for the situations enumerated below.
6397 <p>When daemons are started</p>
6400 If the script starts one or more daemons, the output
6401 should look like this (a single line, no leading
6403 <example compact="compact">
6404 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6406 The <var>description</var> should describe the
6407 subsystem the daemon or set of daemons are part of,
6408 while <var>daemon-1</var> up to <var>daemon-n</var>
6409 denote each daemon's name (typically the file name of
6414 For example, the output of <file>/etc/init.d/lpd</file>
6416 <example compact="compact">
6417 Starting printer spooler: lpd.
6422 This can be achieved by saying
6423 <example compact="compact">
6424 echo -n "Starting printer spooler: lpd"
6425 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6428 in the script. If there are more than one daemon to
6429 start, the output should look like this:
6430 <example compact="compact">
6431 echo -n "Starting remote file system services:"
6432 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6433 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6434 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6437 This makes it possible for the user to see what is
6438 happening and when the final daemon has been started.
6439 Care should be taken in the placement of white spaces:
6440 in the example above the system administrators can
6441 easily comment out a line if they don't want to start
6442 a specific daemon, while the displayed message still
6448 <p>When a system parameter is being set</p>
6451 If you have to set up different system parameters
6452 during the system boot, you should use this format:
6453 <example compact="compact">
6454 Setting <var>parameter</var> to "<var>value</var>".
6459 You can use a statement such as the following to get
6461 <example compact="compact">
6462 echo "Setting DNS domainname to \"$domainname\"."
6467 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6468 for the left and right quotation marks. A grave accent
6469 (<tt>`</tt>) is not a quote character; neither is an
6470 apostrophe (<tt>'</tt>).
6475 <p>When a daemon is stopped or restarted</p>
6478 When you stop or restart a daemon, you should issue a
6479 message identical to the startup message, except that
6480 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6481 or <tt>Restarting</tt> respectively.
6485 For example, stopping the printer daemon will look like
6487 <example compact="compact">
6488 Stopping printer spooler: lpd.
6494 <p>When something is executed</p>
6497 There are several examples where you have to run a
6498 program at system startup or shutdown to perform a
6499 specific task, for example, setting the system's clock
6500 using <prgn>netdate</prgn> or killing all processes
6501 when the system shuts down. Your message should look
6503 <example compact="compact">
6504 Doing something very useful...done.
6506 You should print the <tt>done.</tt> immediately after
6507 the job has been completed, so that the user is
6508 informed why they have to wait. You can get this
6510 <example compact="compact">
6511 echo -n "Doing something very useful..."
6520 <p>When the configuration is reloaded</p>
6523 When a daemon is forced to reload its configuration
6524 files you should use the following format:
6525 <example compact="compact">
6526 Reloading <var>description</var> configuration...done.
6528 where <var>description</var> is the same as in the
6529 daemon starting message.
6537 <heading>Cron jobs</heading>
6540 Packages must not modify the configuration file
6541 <file>/etc/crontab</file>, and they must not modify the files in
6542 <file>/var/spool/cron/crontabs</file>.</p>
6545 If a package wants to install a job that has to be executed
6546 via cron, it should place a file with the name of the
6547 package in one or more of the following directories:
6548 <example compact="compact">
6554 As these directory names imply, the files within them are
6555 executed on an hourly, daily, weekly, or monthly basis,
6556 respectively. The exact times are listed in
6557 <file>/etc/crontab</file>.</p>
6560 All files installed in any of these directories must be
6561 scripts (e.g., shell scripts or Perl scripts) so that they
6562 can easily be modified by the local system administrator.
6563 In addition, they must be treated as configuration files.
6567 If a certain job has to be executed at some other frequency or
6568 at a specific time, the package should install a file
6569 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6570 same syntax as <file>/etc/crontab</file> and is processed by
6571 <prgn>cron</prgn> automatically. The file must also be
6572 treated as a configuration file. (Note that entries in the
6573 <file>/etc/cron.d</file> directory are not handled by
6574 <prgn>anacron</prgn>. Thus, you should only use this
6575 directory for jobs which may be skipped if the system is not
6578 Unlike <file>crontab</file> files described in the IEEE Std
6579 1003.1-2008 (POSIX.1) available from
6580 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6581 name="The Open Group">, the files in
6582 <file>/etc/cron.d</file> and the file
6583 <file>/etc/crontab</file> have seven fields; namely:
6585 <item>Minute [0,59]</item>
6586 <item>Hour [0,23]</item>
6587 <item>Day of the month [1,31]</item>
6588 <item>Month of the year [1,12]</item>
6589 <item>Day of the week ([0,6] with 0=Sunday)</item>
6590 <item>Username</item>
6591 <item>Command to be run</item>
6593 Ranges of numbers are allowed. Ranges are two numbers
6594 separated with a hyphen. The specified range is inclusive.
6595 Lists are allowed. A list is a set of numbers (or ranges)
6596 separated by commas. Step values can be used in conjunction
6601 The scripts or <tt>crontab</tt> entries in these directories should
6602 check if all necessary programs are installed before they
6603 try to execute them. Otherwise, problems will arise when a
6604 package was removed but not purged since configuration files
6605 are kept on the system in this situation.
6609 Any <tt>cron</tt> daemon must provide
6610 <file>/usr/bin/crontab</file> and support normal
6611 <tt>crontab</tt> entries as specified in POSIX. The daemon
6612 must also support names for days and months, ranges, and
6613 step values. It has to support <file>/etc/crontab</file>,
6614 and correctly execute the scripts in
6615 <file>/etc/cron.d</file>. The daemon must also correctly
6617 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6622 <heading>Menus</heading>
6625 The Debian <tt>menu</tt> package provides a standard
6626 interface between packages providing applications and
6627 <em>menu programs</em> (either X window managers or
6628 text-based menu programs such as <prgn>pdmenu</prgn>).
6632 All packages that provide applications that need not be
6633 passed any special command line arguments for normal
6634 operation should register a menu entry for those
6635 applications, so that users of the <tt>menu</tt> package
6636 will automatically get menu entries in their window
6637 managers, as well in shells like <tt>pdmenu</tt>.
6641 Menu entries should follow the current menu policy.
6645 The menu policy can be found in the <tt>menu-policy</tt>
6646 files in the <tt>debian-policy</tt> package.
6647 It is also available from the Debian web mirrors at
6648 <tt><url name="/doc/packaging-manuals/menu-policy/"
6649 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6653 Please also refer to the <em>Debian Menu System</em>
6654 documentation that comes with the <package>menu</package>
6655 package for information about how to register your
6661 <heading>Multimedia handlers</heading>
6664 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6665 is a mechanism for encoding files and data streams and
6666 providing meta-information about them, in particular their
6667 type (e.g. audio or video) and format (e.g. PNG, HTML,
6672 Registration of MIME type handlers allows programs like mail
6673 user agents and web browsers to invoke these handlers to
6674 view, edit or display MIME types they don't support directly.
6678 Packages which provide the ability to view/show/play,
6679 compose, edit or print MIME types should register themselves
6680 as such following the current MIME support policy.
6684 The MIME support policy can be found in the <tt>mime-policy</tt>
6685 files in the <tt>debian-policy</tt> package.
6686 It is also available from the Debian web mirrors at
6687 <tt><url name="/doc/packaging-manuals/mime-policy/"
6688 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6694 <heading>Keyboard configuration</heading>
6697 To achieve a consistent keyboard configuration so that all
6698 applications interpret a keyboard event the same way, all
6699 programs in the Debian distribution must be configured to
6700 comply with the following guidelines.
6704 The following keys must have the specified interpretations:
6707 <tag><tt><--</tt></tag>
6708 <item>delete the character to the left of the cursor</item>
6710 <tag><tt>Delete</tt></tag>
6711 <item>delete the character to the right of the cursor</item>
6713 <tag><tt>Control+H</tt></tag>
6714 <item>emacs: the help prefix</item>
6717 The interpretation of any keyboard events should be
6718 independent of the terminal that is used, be it a virtual
6719 console, an X terminal emulator, an rlogin/telnet session,
6724 The following list explains how the different programs
6725 should be set up to achieve this:
6731 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6735 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6739 X translations are set up to make
6740 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6741 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6742 is the vt220 escape code for the "delete character"
6743 key). This must be done by loading the X resources
6744 using <prgn>xrdb</prgn> on all local X displays, not
6745 using the application defaults, so that the
6746 translation resources used correspond to the
6747 <prgn>xmodmap</prgn> settings.
6751 The Linux console is configured to make
6752 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6753 generate <tt>ESC [ 3 ~</tt>.
6757 X applications are configured so that <tt><</tt>
6758 deletes left, and <tt>Delete</tt> deletes right. Motif
6759 applications already work like this.
6763 Terminals should have <tt>stty erase ^?</tt> .
6767 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6768 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6769 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6773 Emacs is programmed to map <tt>KB_Backspace</tt> or
6774 the <tt>stty erase</tt> character to
6775 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6776 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6777 <tt>^H</tt> to <tt>help</tt> as always.
6781 Other applications use the <tt>stty erase</tt>
6782 character and <tt>kdch1</tt> for the two delete keys,
6783 with ASCII DEL being "delete previous character" and
6784 <tt>kdch1</tt> being "delete character under
6792 This will solve the problem except for the following
6799 Some terminals have a <tt><--</tt> key that cannot
6800 be made to produce anything except <tt>^H</tt>. On
6801 these terminals Emacs help will be unavailable on
6802 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6803 character takes precedence in Emacs, and has been set
6804 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6805 available) can be used instead.
6809 Some operating systems use <tt>^H</tt> for <tt>stty
6810 erase</tt>. However, modern telnet versions and all
6811 rlogin versions propagate <tt>stty</tt> settings, and
6812 almost all UNIX versions honour <tt>stty erase</tt>.
6813 Where the <tt>stty</tt> settings are not propagated
6814 correctly, things can be made to work by using
6815 <tt>stty</tt> manually.
6819 Some systems (including previous Debian versions) use
6820 <prgn>xmodmap</prgn> to arrange for both
6821 <tt><--</tt> and <tt>Delete</tt> to generate
6822 <tt>KB_Delete</tt>. We can change the behavior of
6823 their X clients using the same X resources that we use
6824 to do it for our own clients, or configure our clients
6825 using their resources when things are the other way
6826 around. On displays configured like this
6827 <tt>Delete</tt> will not work, but <tt><--</tt>
6832 Some operating systems have different <tt>kdch1</tt>
6833 settings in their <tt>terminfo</tt> database for
6834 <tt>xterm</tt> and others. On these systems the
6835 <tt>Delete</tt> key will not work correctly when you
6836 log in from a system conforming to our policy, but
6837 <tt><--</tt> will.
6844 <heading>Environment variables</heading>
6847 A program must not depend on environment variables to get
6848 reasonable defaults. (That's because these environment
6849 variables would have to be set in a system-wide
6850 configuration file like <file>/etc/profile</file>, which is not
6851 supported by all shells.)
6855 If a program usually depends on environment variables for its
6856 configuration, the program should be changed to fall back to
6857 a reasonable default configuration if these environment
6858 variables are not present. If this cannot be done easily
6859 (e.g., if the source code of a non-free program is not
6860 available), the program must be replaced by a small
6861 "wrapper" shell script which sets the environment variables
6862 if they are not already defined, and calls the original program.
6866 Here is an example of a wrapper script for this purpose:
6868 <example compact="compact">
6870 BAR=${BAR:-/var/lib/fubar}
6872 exec /usr/lib/foo/foo "$@"
6877 Furthermore, as <file>/etc/profile</file> is a configuration
6878 file of the <prgn>base-files</prgn> package, other packages must
6879 not put any environment variables or other commands into that
6884 <sect id="doc-base">
6885 <heading>Registering Documents using doc-base</heading>
6888 The <package>doc-base</package> package implements a
6889 flexible mechanism for handling and presenting
6890 documentation. The recommended practice is for every Debian
6891 package that provides online documentation (other than just
6892 manual pages) to register these documents with
6893 <package>doc-base</package> by installing a
6894 <package>doc-base</package> control file via the
6895 <prgn/install-docs/ script at installation time and
6896 de-register the manuals again when the package is removed.
6899 Please refer to the documentation that comes with the
6900 <package>doc-base</package> package for information and
6909 <heading>Files</heading>
6912 <heading>Binaries</heading>
6915 Two different packages must not install programs with
6916 different functionality but with the same filenames. (The
6917 case of two programs having the same functionality but
6918 different implementations is handled via "alternatives" or
6919 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6920 <ref id="conflicts"> respectively.) If this case happens,
6921 one of the programs must be renamed. The maintainers should
6922 report this to the <tt>debian-devel</tt> mailing list and
6923 try to find a consensus about which program will have to be
6924 renamed. If a consensus cannot be reached, <em>both</em>
6925 programs must be renamed.
6929 By default, when a package is being built, any binaries
6930 created should include debugging information, as well as
6931 being compiled with optimization. You should also turn on
6932 as many reasonable compilation warnings as possible; this
6933 makes life easier for porters, who can then look at build
6934 logs for possible problems. For the C programming language,
6935 this means the following compilation parameters should be
6937 <example compact="compact">
6939 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6941 INSTALL = install -s # (or use strip on the files in debian/tmp)
6946 Note that by default all installed binaries should be stripped,
6947 either by using the <tt>-s</tt> flag to
6948 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6949 the binaries after they have been copied into
6950 <file>debian/tmp</file> but before the tree is made into a
6955 Although binaries in the build tree should be compiled with
6956 debugging information by default, it can often be difficult to
6957 debug programs if they are also subjected to compiler
6958 optimization. For this reason, it is recommended to support the
6959 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6960 (see <ref id="debianrules-options">). This variable can contain
6961 several flags to change how a package is compiled and built.
6965 It is up to the package maintainer to decide what
6966 compilation options are best for the package. Certain
6967 binaries (such as computationally-intensive programs) will
6968 function better with certain flags (<tt>-O3</tt>, for
6969 example); feel free to use them. Please use good judgment
6970 here. Don't use flags for the sake of it; only use them
6971 if there is good reason to do so. Feel free to override
6972 the upstream author's ideas about which compilation
6973 options are best: they are often inappropriate for our
6979 <sect id="libraries">
6980 <heading>Libraries</heading>
6983 If the package is <strong>architecture: any</strong>, then
6984 the shared library compilation and linking flags must have
6985 <tt>-fPIC</tt>, or the package shall not build on some of
6986 the supported architectures<footnote>
6988 If you are using GCC, <tt>-fPIC</tt> produces code with
6989 relocatable position independent code, which is required for
6990 most architectures to create a shared library, with i386 and
6991 perhaps some others where non position independent code is
6992 permitted in a shared library.
6995 Position independent code may have a performance penalty,
6996 especially on <tt>i386</tt>. However, in most cases the
6997 speed penalty must be measured against the memory wasted on
6998 the few architectures where non position independent code is
7001 </footnote>. Any exception to this rule must be discussed on
7002 the mailing list <em>debian-devel@lists.debian.org</em>, and
7003 a rough consensus obtained. The reasons for not compiling
7004 with <tt>-fPIC</tt> flag must be recorded in the file
7005 <tt>README.Debian</tt>, and care must be taken to either
7006 restrict the architecture or arrange for <tt>-fPIC</tt> to
7007 be used on architectures where it is required.<footnote>
7009 Some of the reasons why this might be required is if the
7010 library contains hand crafted assembly code that is not
7011 relocatable, the speed penalty is excessive for compute
7012 intensive libs, and similar reasons.
7017 As to the static libraries, the common case is not to have
7018 relocatable code, since there is no benefit, unless in specific
7019 cases; therefore the static version must not be compiled
7020 with the <tt>-fPIC</tt> flag. Any exception to this rule
7021 should be discussed on the mailing list
7022 <em>debian-devel@lists.debian.org</em>, and the reasons for
7023 compiling with the <tt>-fPIC</tt> flag must be recorded in
7024 the file <tt>README.Debian</tt>. <footnote>
7026 Some of the reasons for linking static libraries with
7027 the <tt>-fPIC</tt> flag are if, for example, one needs a
7028 Perl API for a library that is under rapid development,
7029 and has an unstable API, so shared libraries are
7030 pointless at this phase of the library's development. In
7031 that case, since Perl needs a library with relocatable
7032 code, it may make sense to create a static library with
7033 relocatable code. Another reason cited is if you are
7034 distilling various libraries into a common shared
7035 library, like <tt>mklibs</tt> does in the Debian
7041 In other words, if both a shared and a static library is
7042 being built, each source unit (<tt>*.c</tt>, for example,
7043 for C files) will need to be compiled twice, for the normal
7047 You must specify the gcc option <tt>-D_REENTRANT</tt>
7048 when building a library (either static or shared) to make
7049 the library compatible with LinuxThreads.
7053 Although not enforced by the build tools, shared libraries
7054 must be linked against all libraries that they use symbols from
7055 in the same way that binaries are. This ensures the correct
7056 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7057 system and guarantees that all libraries can be safely opened
7058 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7059 option <tt>-Wl,-z,defs</tt> when building a shared library.
7060 Since this option enforces symbol resolution at build time,
7061 a missing library reference will be caught early as a fatal
7066 All installed shared libraries should be stripped with
7067 <example compact="compact">
7068 strip --strip-unneeded <var>your-lib</var>
7070 (The option <tt>--strip-unneeded</tt> makes
7071 <prgn>strip</prgn> remove only the symbols which aren't
7072 needed for relocation processing.) Shared libraries can
7073 function perfectly well when stripped, since the symbols for
7074 dynamic linking are in a separate part of the ELF object
7076 You might also want to use the options
7077 <tt>--remove-section=.comment</tt> and
7078 <tt>--remove-section=.note</tt> on both shared libraries
7079 and executables, and <tt>--strip-debug</tt> on static
7085 Note that under some circumstances it may be useful to
7086 install a shared library unstripped, for example when
7087 building a separate package to support debugging.
7091 Shared object files (often <file>.so</file> files) that are not
7092 public libraries, that is, they are not meant to be linked
7093 to by third party executables (binaries of other packages),
7094 should be installed in subdirectories of the
7095 <file>/usr/lib</file> directory. Such files are exempt from the
7096 rules that govern ordinary shared libraries, except that
7097 they must not be installed executable and should be
7099 A common example are the so-called "plug-ins",
7100 internal shared objects that are dynamically loaded by
7101 programs using <manref name="dlopen" section="3">.
7106 An ever increasing number of packages are using
7107 <prgn>libtool</prgn> to do their linking. The latest GNU
7108 libtools (>= 1.3a) can take advantage of the metadata in the
7109 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7110 files). The main advantage of <prgn>libtool</prgn>'s
7111 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7112 store and subsequently access metadata with respect to the
7113 libraries it builds. <prgn>libtool</prgn> will search for
7114 those files, which contain a lot of useful information about
7115 a library (such as library dependency information for static
7116 linking). Also, they're <em>essential</em> for programs
7117 using <tt>libltdl</tt>.<footnote>
7118 Although <prgn>libtool</prgn> is fully capable of
7119 linking against shared libraries which don't have
7120 <tt>.la</tt> files, as it is a mere shell script it can
7121 add considerably to the build time of a
7122 <prgn>libtool</prgn>-using package if that shell script
7123 has to derive all this information from first principles
7124 for each library every time it is linked. With the
7125 advent of <prgn>libtool</prgn> version 1.4 (and to a
7126 lesser extent <prgn>libtool</prgn> version 1.3), the
7127 <file>.la</file> files also store information about
7128 inter-library dependencies which cannot necessarily be
7129 derived after the <file>.la</file> file is deleted.
7134 Packages that use <prgn>libtool</prgn> to create shared
7135 libraries should include the <file>.la</file> files in the
7136 <tt>-dev</tt> package, unless the package relies on
7137 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7138 the <tt>.la</tt> files must go in the run-time library
7143 You must make sure that you use only released versions of
7144 shared libraries to build your packages; otherwise other
7145 users will not be able to run your binaries
7146 properly. Producing source packages that depend on
7147 unreleased compilers is also usually a bad
7154 <heading>Shared libraries</heading>
7156 This section has moved to <ref id="sharedlibs">.
7162 <heading>Scripts</heading>
7165 All command scripts, including the package maintainer
7166 scripts inside the package and used by <prgn>dpkg</prgn>,
7167 should have a <tt>#!</tt> line naming the shell to be used
7172 In the case of Perl scripts this should be
7173 <tt>#!/usr/bin/perl</tt>.
7177 When scripts are installed into a directory in the system
7178 PATH, the script name should not include an extension such
7179 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7180 language currently used to implement it.
7183 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7184 <file>init.d</file> scripts should almost certainly start
7185 with <tt>set -e</tt> so that errors are detected.
7186 <file>init.d</file> scripts are something of a special case, due
7187 to how frequently they need to call commands that are allowed to
7188 fail, and it may instead be easier to check the exit status of
7189 commands directly. See <ref id="writing-init"> for more
7190 information about writing <file>init.d</file> scripts.
7193 Every script should use <tt>set -e</tt> or check the exit status
7194 of <em>every</em> command.
7197 Scripts may assume that <file>/bin/sh</file> implements the
7198 SUSv3 Shell Command Language<footnote>
7199 Single UNIX Specification, version 3, which is also IEEE
7200 1003.1-2004 (POSIX), and is available on the World Wide Web
7201 from <url id="http://www.unix.org/version3/online.html"
7202 name="The Open Group"> after free
7203 registration.</footnote>
7204 plus the following additional features not mandated by
7206 These features are in widespread use in the Linux community
7207 and are implemented in all of bash, dash, and ksh, the most
7208 common shells users may wish to use as <file>/bin/sh</file>.
7211 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7212 must not generate a newline.</item>
7213 <item><tt>test</tt>, if implemented as a shell built-in, must
7214 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7216 <item><tt>local</tt> to create a scoped variable must be
7217 supported, including listing multiple variables in a single
7218 local command and assigning a value to a variable at the
7219 same time as localizing it. <tt>local</tt> may or
7220 may not preserve the variable value from an outer scope if
7221 no assignment is present. Uses such as:
7225 # ... use a, b, c, d ...
7228 must be supported and must set the value of <tt>c</tt> to
7232 If a shell script requires non-SUSv3 features from the shell
7233 interpreter other than those listed above, the appropriate shell
7234 must be specified in the first line of the script (e.g.,
7235 <tt>#!/bin/bash</tt>) and the package must depend on the package
7236 providing the shell (unless the shell package is marked
7237 "Essential", as in the case of <prgn>bash</prgn>).
7241 You may wish to restrict your script to SUSv3 features plus the
7242 above set when possible so that it may use <file>/bin/sh</file>
7243 as its interpreter. If your script works with <prgn>dash</prgn>
7244 (originally called <prgn>ash</prgn>), it probably complies with
7245 the above requirements, but if you are in doubt, use
7246 <file>/bin/bash</file>.
7250 Perl scripts should check for errors when making any
7251 system calls, including <tt>open</tt>, <tt>print</tt>,
7252 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7256 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7257 scripting languages. See <em>Csh Programming Considered
7258 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7259 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7260 If an upstream package comes with <prgn>csh</prgn> scripts
7261 then you must make sure that they start with
7262 <tt>#!/bin/csh</tt> and make your package depend on the
7263 <prgn>c-shell</prgn> virtual package.
7267 Any scripts which create files in world-writeable
7268 directories (e.g., in <file>/tmp</file>) must use a
7269 mechanism which will fail atomically if a file with the same
7270 name already exists.
7274 The Debian base system provides the <prgn>tempfile</prgn>
7275 and <prgn>mktemp</prgn> utilities for use by scripts for
7282 <heading>Symbolic links</heading>
7285 In general, symbolic links within a top-level directory
7286 should be relative, and symbolic links pointing from one
7287 top-level directory into another should be absolute. (A
7288 top-level directory is a sub-directory of the root
7289 directory <file>/</file>.)
7293 In addition, symbolic links should be specified as short as
7294 possible, i.e., link targets like <file>foo/../bar</file> are
7299 Note that when creating a relative link using
7300 <prgn>ln</prgn> it is not necessary for the target of the
7301 link to exist relative to the working directory you're
7302 running <prgn>ln</prgn> from, nor is it necessary to change
7303 directory to the directory where the link is to be made.
7304 Simply include the string that should appear as the target
7305 of the link (this will be a pathname relative to the
7306 directory in which the link resides) as the first argument
7311 For example, in your <prgn>Makefile</prgn> or
7312 <file>debian/rules</file>, you can do things like:
7313 <example compact="compact">
7314 ln -fs gcc $(prefix)/bin/cc
7315 ln -fs gcc debian/tmp/usr/bin/cc
7316 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7317 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7322 A symbolic link pointing to a compressed file should always
7323 have the same file extension as the referenced file. (For
7324 example, if a file <file>foo.gz</file> is referenced by a
7325 symbolic link, the filename of the link has to end with
7326 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7331 <heading>Device files</heading>
7334 Packages must not include device files or named pipes in the
7339 If a package needs any special device files that are not
7340 included in the base system, it must call
7341 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7342 after notifying the user<footnote>
7343 This notification could be done via a (low-priority)
7344 debconf message, or an echo (printf) statement.
7349 Packages must not remove any device files in the
7350 <prgn>postrm</prgn> or any other script. This is left to the
7351 system administrator.
7355 Debian uses the serial devices
7356 <file>/dev/ttyS*</file>. Programs using the old
7357 <file>/dev/cu*</file> devices should be changed to use
7358 <file>/dev/ttyS*</file>.
7362 Named pipes needed by the package must be created in
7363 the <prgn>postinst</prgn> script<footnote>
7364 It's better to use <prgn>mkfifo</prgn> rather
7365 than <prgn>mknod</prgn> to create named pipes so that
7366 automated checks for packages incorrectly creating device
7367 files with <prgn>mknod</prgn> won't have false positives.
7368 </footnote> and removed in
7369 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7374 <sect id="config-files">
7375 <heading>Configuration files</heading>
7378 <heading>Definitions</heading>
7382 <tag>configuration file</tag>
7384 A file that affects the operation of a program, or
7385 provides site- or host-specific information, or
7386 otherwise customizes the behavior of a program.
7387 Typically, configuration files are intended to be
7388 modified by the system administrator (if needed or
7389 desired) to conform to local policy or to provide
7390 more useful site-specific behavior.
7393 <tag><tt>conffile</tt></tag>
7395 A file listed in a package's <tt>conffiles</tt>
7396 file, and is treated specially by <prgn>dpkg</prgn>
7397 (see <ref id="configdetails">).
7403 The distinction between these two is important; they are
7404 not interchangeable concepts. Almost all
7405 <tt>conffile</tt>s are configuration files, but many
7406 configuration files are not <tt>conffiles</tt>.
7410 As noted elsewhere, <file>/etc/init.d</file> scripts,
7411 <file>/etc/default</file> files, scripts installed in
7412 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7413 configuration installed in <file>/etc/cron.d</file> must be
7414 treated as configuration files. In general, any script that
7415 embeds configuration information is de-facto a configuration
7416 file and should be treated as such.
7421 <heading>Location</heading>
7424 Any configuration files created or used by your package
7425 must reside in <file>/etc</file>. If there are several,
7426 consider creating a subdirectory of <file>/etc</file>
7427 named after your package.
7431 If your package creates or uses configuration files
7432 outside of <file>/etc</file>, and it is not feasible to modify
7433 the package to use <file>/etc</file> directly, put the files
7434 in <file>/etc</file> and create symbolic links to those files
7435 from the location that the package requires.
7440 <heading>Behavior</heading>
7443 Configuration file handling must conform to the following
7445 <list compact="compact">
7447 local changes must be preserved during a package
7451 configuration files must be preserved when the
7452 package is removed, and only deleted when the
7459 The easy way to achieve this behavior is to make the
7460 configuration file a <tt>conffile</tt>. This is
7461 appropriate only if it is possible to distribute a default
7462 version that will work for most installations, although
7463 some system administrators may choose to modify it. This
7464 implies that the default version will be part of the
7465 package distribution, and must not be modified by the
7466 maintainer scripts during installation (or at any other
7471 In order to ensure that local changes are preserved
7472 correctly, no package may contain or make hard links to
7473 conffiles.<footnote>
7474 Rationale: There are two problems with hard links.
7475 The first is that some editors break the link while
7476 editing one of the files, so that the two files may
7477 unwittingly become unlinked and different. The second
7478 is that <prgn>dpkg</prgn> might break the hard link
7479 while upgrading <tt>conffile</tt>s.
7484 The other way to do it is via the maintainer scripts. In
7485 this case, the configuration file must not be listed as a
7486 <tt>conffile</tt> and must not be part of the package
7487 distribution. If the existence of a file is required for
7488 the package to be sensibly configured it is the
7489 responsibility of the package maintainer to provide
7490 maintainer scripts which correctly create, update and
7491 maintain the file and remove it on purge. (See <ref
7492 id="maintainerscripts"> for more information.) These
7493 scripts must be idempotent (i.e., must work correctly if
7494 <prgn>dpkg</prgn> needs to re-run them due to errors
7495 during installation or removal), must cope with all the
7496 variety of ways <prgn>dpkg</prgn> can call maintainer
7497 scripts, must not overwrite or otherwise mangle the user's
7498 configuration without asking, must not ask unnecessary
7499 questions (particularly during upgrades), and must
7500 otherwise be good citizens.
7504 The scripts are not required to configure every possible
7505 option for the package, but only those necessary to get
7506 the package running on a given system. Ideally the
7507 sysadmin should not have to do any configuration other
7508 than that done (semi-)automatically by the
7509 <prgn>postinst</prgn> script.
7513 A common practice is to create a script called
7514 <file><var>package</var>-configure</file> and have the
7515 package's <prgn>postinst</prgn> call it if and only if the
7516 configuration file does not already exist. In certain
7517 cases it is useful for there to be an example or template
7518 file which the maintainer scripts use. Such files should
7519 be in <file>/usr/share/<var>package</var></file> or
7520 <file>/usr/lib/<var>package</var></file> (depending on whether
7521 they are architecture-independent or not). There should
7522 be symbolic links to them from
7523 <file>/usr/share/doc/<var>package</var>/examples</file> if
7524 they are examples, and should be perfectly ordinary
7525 <prgn>dpkg</prgn>-handled files (<em>not</em>
7526 configuration files).
7530 These two styles of configuration file handling must
7531 not be mixed, for that way lies madness:
7532 <prgn>dpkg</prgn> will ask about overwriting the file
7533 every time the package is upgraded.
7538 <heading>Sharing configuration files</heading>
7541 Packages which specify the same file as a
7542 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7543 with each other. (This is an instance of the general rule
7544 about not sharing files. Note that neither alternatives
7545 nor diversions are likely to be appropriate in this case;
7546 in particular, <prgn>dpkg</prgn> does not handle diverted
7547 <tt>conffile</tt>s well.)
7551 The maintainer scripts must not alter a <tt>conffile</tt>
7552 of <em>any</em> package, including the one the scripts
7557 If two or more packages use the same configuration file
7558 and it is reasonable for both to be installed at the same
7559 time, one of these packages must be defined as
7560 <em>owner</em> of the configuration file, i.e., it will be
7561 the package which handles that file as a configuration
7562 file. Other packages that use the configuration file must
7563 depend on the owning package if they require the
7564 configuration file to operate. If the other package will
7565 use the configuration file if present, but is capable of
7566 operating without it, no dependency need be declared.
7570 If it is desirable for two or more related packages to
7571 share a configuration file <em>and</em> for all of the
7572 related packages to be able to modify that configuration
7573 file, then the following should be done:
7574 <enumlist compact="compact">
7576 One of the related packages (the "owning" package)
7577 will manage the configuration file with maintainer
7578 scripts as described in the previous section.
7581 The owning package should also provide a program
7582 that the other packages may use to modify the
7586 The related packages must use the provided program
7587 to make any desired modifications to the
7588 configuration file. They should either depend on
7589 the core package to guarantee that the configuration
7590 modifier program is available or accept gracefully
7591 that they cannot modify the configuration file if it
7592 is not. (This is in addition to the fact that the
7593 configuration file may not even be present in the
7600 Sometimes it's appropriate to create a new package which
7601 provides the basic infrastructure for the other packages
7602 and which manages the shared configuration files. (The
7603 <tt>sgml-base</tt> package is a good example.)
7608 <heading>User configuration files ("dotfiles")</heading>
7611 The files in <file>/etc/skel</file> will automatically be
7612 copied into new user accounts by <prgn>adduser</prgn>.
7613 No other program should reference the files in
7614 <file>/etc/skel</file>.
7618 Therefore, if a program needs a dotfile to exist in
7619 advance in <file>$HOME</file> to work sensibly, that dotfile
7620 should be installed in <file>/etc/skel</file> and treated as a
7625 However, programs that require dotfiles in order to
7626 operate sensibly are a bad thing, unless they do create
7627 the dotfiles themselves automatically.
7631 Furthermore, programs should be configured by the Debian
7632 default installation to behave as closely to the upstream
7633 default behavior as possible.
7637 Therefore, if a program in a Debian package needs to be
7638 configured in some way in order to operate sensibly, that
7639 should be done using a site-wide configuration file placed
7640 in <file>/etc</file>. Only if the program doesn't support a
7641 site-wide default configuration and the package maintainer
7642 doesn't have time to add it may a default per-user file be
7643 placed in <file>/etc/skel</file>.
7647 <file>/etc/skel</file> should be as empty as we can make it.
7648 This is particularly true because there is no easy (or
7649 necessarily desirable) mechanism for ensuring that the
7650 appropriate dotfiles are copied into the accounts of
7651 existing users when a package is installed.
7657 <heading>Log files</heading>
7659 Log files should usually be named
7660 <file>/var/log/<var>package</var>.log</file>. If you have many
7661 log files, or need a separate directory for permission
7662 reasons (<file>/var/log</file> is writable only by
7663 <file>root</file>), you should usually create a directory named
7664 <file>/var/log/<var>package</var></file> and place your log
7669 Log files must be rotated occasionally so that they don't
7670 grow indefinitely; the best way to do this is to drop a log
7671 rotation configuration file into the directory
7672 <file>/etc/logrotate.d</file> and use the facilities provided by
7673 logrotate.<footnote>
7675 The traditional approach to log files has been to set up
7676 <em>ad hoc</em> log rotation schemes using simple shell
7677 scripts and cron. While this approach is highly
7678 customizable, it requires quite a lot of sysadmin work.
7679 Even though the original Debian system helped a little
7680 by automatically installing a system which can be used
7681 as a template, this was deemed not enough.
7685 The use of <prgn>logrotate</prgn>, a program developed
7686 by Red Hat, is better, as it centralizes log management.
7687 It has both a configuration file
7688 (<file>/etc/logrotate.conf</file>) and a directory where
7689 packages can drop their individual log rotation
7690 configurations (<file>/etc/logrotate.d</file>).
7693 Here is a good example for a logrotate config
7694 file (for more information see <manref name="logrotate"
7696 <example compact="compact">
7697 /var/log/foo/*.log {
7702 /etc/init.d/foo force-reload
7706 This rotates all files under <file>/var/log/foo</file>, saves 12
7707 compressed generations, and forces the daemon to reload its
7708 configuration information after the log rotation.
7712 Log files should be removed when the package is
7713 purged (but not when it is only removed). This should be
7714 done by the <prgn>postrm</prgn> script when it is called
7715 with the argument <tt>purge</tt> (see <ref
7716 id="removedetails">).
7721 <heading>Permissions and owners</heading>
7724 The rules in this section are guidelines for general use.
7725 If necessary you may deviate from the details below.
7726 However, if you do so you must make sure that what is done
7727 is secure and you should try to be as consistent as possible
7728 with the rest of the system. You should probably also
7729 discuss it on <prgn>debian-devel</prgn> first.
7733 Files should be owned by <tt>root:root</tt>, and made
7734 writable only by the owner and universally readable (and
7735 executable, if appropriate), that is mode 644 or 755.
7739 Directories should be mode 755 or (for group-writability)
7740 mode 2775. The ownership of the directory should be
7741 consistent with its mode: if a directory is mode 2775, it
7742 should be owned by the group that needs write access to
7745 When a package is upgraded, and the owner or permissions
7746 of a file included in the package has changed, dpkg
7747 arranges for the ownership and permissions to be
7748 correctly set upon installation. However, this does not
7749 extend to directories; the permissions and ownership of
7750 directories already on the system does not change on
7751 install or upgrade of packages. This makes sense, since
7752 otherwise common directories like <tt>/usr</tt> would
7753 always be in flux. To correctly change permissions of a
7754 directory the package owns, explicit action is required,
7755 usually in the <tt>postinst</tt> script. Care must be
7756 taken to handle downgrades as well, in that case.
7763 Setuid and setgid executables should be mode 4755 or 2755
7764 respectively, and owned by the appropriate user or group.
7765 They should not be made unreadable (modes like 4711 or
7766 2711 or even 4111); doing so achieves no extra security,
7767 because anyone can find the binary in the freely available
7768 Debian package; it is merely inconvenient. For the same
7769 reason you should not restrict read or execute permissions
7770 on non-set-id executables.
7774 Some setuid programs need to be restricted to particular
7775 sets of users, using file permissions. In this case they
7776 should be owned by the uid to which they are set-id, and by
7777 the group which should be allowed to execute them. They
7778 should have mode 4754; again there is no point in making
7779 them unreadable to those users who must not be allowed to
7784 It is possible to arrange that the system administrator can
7785 reconfigure the package to correspond to their local
7786 security policy by changing the permissions on a binary:
7787 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7788 described below.<footnote>
7789 Ordinary files installed by <prgn>dpkg</prgn> (as
7790 opposed to <tt>conffile</tt>s and other similar objects)
7791 normally have their permissions reset to the distributed
7792 permissions when the package is reinstalled. However,
7793 the use of <prgn>dpkg-statoverride</prgn> overrides this
7796 Another method you should consider is to create a group for
7797 people allowed to use the program(s) and make any setuid
7798 executables executable only by that group.
7802 If you need to create a new user or group for your package
7803 there are two possibilities. Firstly, you may need to
7804 make some files in the binary package be owned by this
7805 user or group, or you may need to compile the user or
7806 group id (rather than just the name) into the binary
7807 (though this latter should be avoided if possible, as in
7808 this case you need a statically allocated id).</p>
7811 If you need a statically allocated id, you must ask for a
7812 user or group id from the <tt>base-passwd</tt> maintainer,
7813 and must not release the package until you have been
7814 allocated one. Once you have been allocated one you must
7815 either make the package depend on a version of the
7816 <tt>base-passwd</tt> package with the id present in
7817 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7818 your package to create the user or group itself with the
7819 correct id (using <tt>adduser</tt>) in its
7820 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7821 the <prgn>postinst</prgn> is to be preferred if it is
7822 possible, otherwise a pre-dependency will be needed on the
7823 <tt>adduser</tt> package.)
7827 On the other hand, the program might be able to determine
7828 the uid or gid from the user or group name at runtime, so
7829 that a dynamically allocated id can be used. In this case
7830 you should choose an appropriate user or group name,
7831 discussing this on <prgn>debian-devel</prgn> and checking
7832 with the <package/base-passwd/ maintainer that it is unique and that
7833 they do not wish you to use a statically allocated id
7834 instead. When this has been checked you must arrange for
7835 your package to create the user or group if necessary using
7836 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7837 <prgn>postinst</prgn> script (again, the latter is to be
7838 preferred if it is possible).
7842 Note that changing the numeric value of an id associated
7843 with a name is very difficult, and involves searching the
7844 file system for all appropriate files. You need to think
7845 carefully whether a static or dynamic id is required, since
7846 changing your mind later will cause problems.
7849 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7851 This section is not intended as policy, but as a
7852 description of the use of <prgn>dpkg-statoverride</prgn>.
7856 If a system administrator wishes to have a file (or
7857 directory or other such thing) installed with owner and
7858 permissions different from those in the distributed Debian
7859 package, they can use the <prgn>dpkg-statoverride</prgn>
7860 program to instruct <prgn>dpkg</prgn> to use the different
7861 settings every time the file is installed. Thus the
7862 package maintainer should distribute the files with their
7863 normal permissions, and leave it for the system
7864 administrator to make any desired changes. For example, a
7865 daemon which is normally required to be setuid root, but
7866 in certain situations could be used without being setuid,
7867 should be installed setuid in the <tt>.deb</tt>. Then the
7868 local system administrator can change this if they wish.
7869 If there are two standard ways of doing it, the package
7870 maintainer can use <tt>debconf</tt> to find out the
7871 preference, and call <prgn>dpkg-statoverride</prgn> in the
7872 maintainer script if necessary to accommodate the system
7873 administrator's choice. Care must be taken during
7874 upgrades to not override an existing setting.
7878 Given the above, <prgn>dpkg-statoverride</prgn> is
7879 essentially a tool for system administrators and would not
7880 normally be needed in the maintainer scripts. There is
7881 one type of situation, though, where calls to
7882 <prgn>dpkg-statoverride</prgn> would be needed in the
7883 maintainer scripts, and that involves packages which use
7884 dynamically allocated user or group ids. In such a
7885 situation, something like the following idiom can be very
7886 helpful in the package's <prgn>postinst</prgn>, where
7887 <tt>sysuser</tt> is a dynamically allocated id:
7889 for i in /usr/bin/foo /usr/sbin/bar
7891 # only do something when no setting exists
7892 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7894 #include: debconf processing, question about foo and bar
7895 if [ "$RET" = "true" ] ; then
7896 dpkg-statoverride --update --add sysuser root 4755 $i
7901 The corresponding code to remove the override when the package
7904 for i in /usr/bin/foo /usr/sbin/bar
7906 if dpkg-statoverride --list $i >/dev/null 2>&1
7908 dpkg-statoverride --remove $i
7918 <chapt id="customized-programs">
7919 <heading>Customized programs</heading>
7921 <sect id="arch-spec">
7922 <heading>Architecture specification strings</heading>
7925 If a program needs to specify an <em>architecture specification
7926 string</em> in some place, it should select one of the
7927 strings provided by <tt>dpkg-architecture -L</tt>. The
7928 strings are in the format
7929 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7930 is sometimes elided, as when the OS is Linux.<footnote>
7931 <p>Currently, the strings are:
7932 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7933 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7934 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7935 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7936 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7937 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7938 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7939 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7940 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7941 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7942 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7943 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7944 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7945 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7946 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7947 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7948 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7949 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7950 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7951 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7952 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7953 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7954 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7955 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7956 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7957 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7958 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7959 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7960 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7961 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7962 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7963 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7964 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7965 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7966 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7967 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7968 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7974 Note that we don't want to use
7975 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7976 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7977 since this would make our programs incompatible with other
7978 Linux distributions. We also don't use something like
7979 <tt><var>arch</var>-unknown-linux</tt>, since the
7980 <tt>unknown</tt> does not look very good.
7985 <heading>Daemons</heading>
7988 The configuration files <file>/etc/services</file>,
7989 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7990 by the <prgn>netbase</prgn> package and must not be modified
7995 If a package requires a new entry in one of these files, the
7996 maintainer should get in contact with the
7997 <prgn>netbase</prgn> maintainer, who will add the entries
7998 and release a new version of the <prgn>netbase</prgn>
8003 The configuration file <file>/etc/inetd.conf</file> must not be
8004 modified by the package's scripts except via the
8005 <prgn>update-inetd</prgn> script or the
8006 <file>DebianNet.pm</file> Perl module. See their documentation
8007 for details on how to add entries.
8011 If a package wants to install an example entry into
8012 <file>/etc/inetd.conf</file>, the entry must be preceded with
8013 exactly one hash character (<tt>#</tt>). Such lines are
8014 treated as "commented out by user" by the
8015 <prgn>update-inetd</prgn> script and are not changed or
8016 activated during package updates.
8021 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8025 Some programs need to create pseudo-ttys. This should be done
8026 using Unix98 ptys if the C library supports it. The resulting
8027 program must not be installed setuid root, unless that
8028 is required for other functionality.
8032 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8033 <file>/var/log/lastlog</file> must be installed writable by
8034 group <tt>utmp</tt>. Programs which need to modify those
8035 files must be installed setgid <tt>utmp</tt>.
8040 <heading>Editors and pagers</heading>
8043 Some programs have the ability to launch an editor or pager
8044 program to edit or display a text document. Since there are
8045 lots of different editors and pagers available in the Debian
8046 distribution, the system administrator and each user should
8047 have the possibility to choose their preferred editor and
8052 In addition, every program should choose a good default
8053 editor/pager if none is selected by the user or system
8058 Thus, every program that launches an editor or pager must
8059 use the EDITOR or PAGER environment variable to determine
8060 the editor or pager the user wishes to use. If these
8061 variables are not set, the programs <file>/usr/bin/editor</file>
8062 and <file>/usr/bin/pager</file> should be used, respectively.
8066 These two files are managed through the <prgn>dpkg</prgn>
8067 "alternatives" mechanism. Thus every package providing an
8068 editor or pager must call the
8069 <prgn>update-alternatives</prgn> script to register these
8074 If it is very hard to adapt a program to make use of the
8075 EDITOR or PAGER variables, that program may be configured to
8076 use <file>/usr/bin/sensible-editor</file> and
8077 <file>/usr/bin/sensible-pager</file> as the editor or pager
8078 program respectively. These are two scripts provided in the
8079 <package>sensible-utils</package> package that check the EDITOR
8080 and PAGER variables and launch the appropriate program, and fall
8081 back to <file>/usr/bin/editor</file>
8082 and <file>/usr/bin/pager</file> if the variable is not set.
8086 A program may also use the VISUAL environment variable to
8087 determine the user's choice of editor. If it exists, it
8088 should take precedence over EDITOR. This is in fact what
8089 <file>/usr/bin/sensible-editor</file> does.
8093 It is not required for a package to depend on
8094 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8095 package to provide such virtual packages.<footnote>
8096 The Debian base system already provides an editor and a
8102 <sect id="web-appl">
8103 <heading>Web servers and applications</heading>
8106 This section describes the locations and URLs that should
8107 be used by all web servers and web applications in the
8114 Cgi-bin executable files are installed in the
8116 <example compact="compact">
8117 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8119 and should be referred to as
8120 <example compact="compact">
8121 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8127 <p>Access to HTML documents</p>
8130 HTML documents for a package are stored in
8131 <file>/usr/share/doc/<var>package</var></file>
8132 and can be referred to as
8133 <example compact="compact">
8134 http://localhost/doc/<var>package</var>/<var>filename</var>
8139 The web server should restrict access to the document
8140 tree so that only clients on the same host can read
8141 the documents. If the web server does not support such
8142 access controls, then it should not provide access at
8143 all, or ask about providing access during installation.
8148 <p>Access to images</p>
8150 It is recommended that images for a package be stored
8151 in <tt>/usr/share/images/<var>package</var></tt> and
8152 may be referred to through an alias <tt>/images/</tt>
8155 http://localhost/images/<package>/<filename>
8162 <p>Web Document Root</p>
8165 Web Applications should try to avoid storing files in
8166 the Web Document Root. Instead they should use the
8167 /usr/share/doc/<var>package</var> directory for
8168 documents and register the Web Application via the
8169 <package>doc-base</package> package. If access to the
8170 web document root is unavoidable then use
8171 <example compact="compact">
8174 as the Document Root. This might be just a symbolic
8175 link to the location where the system administrator
8176 has put the real document root.
8179 <item><p>Providing httpd and/or httpd-cgi</p>
8181 All web servers should provide the virtual package
8182 <tt>httpd</tt>. If a web server has CGI support it should
8183 provide <tt>httpd-cgi</tt> additionally.
8186 All web applications which do not contain CGI scripts should
8187 depend on <tt>httpd</tt>, all those web applications which
8188 <tt>do</tt> contain CGI scripts, should depend on
8196 <sect id="mail-transport-agents">
8197 <heading>Mail transport, delivery and user agents</heading>
8200 Debian packages which process electronic mail, whether mail
8201 user agents (MUAs) or mail transport agents (MTAs), must
8202 ensure that they are compatible with the configuration
8203 decisions below. Failure to do this may result in lost
8204 mail, broken <tt>From:</tt> lines, and other serious brain
8209 The mail spool is <file>/var/mail</file> and the interface to
8210 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8211 the FHS). On older systems, the mail spool may be
8212 physically located in <file>/var/spool/mail</file>, but all
8213 access to the mail spool should be via the
8214 <file>/var/mail</file> symlink. The mail spool is part of the
8215 base system and not part of the MTA package.
8219 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8220 programs (such as IMAP daemons) must lock the mailbox in an
8221 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8222 be combined with dot locking. To avoid deadlocks, a program
8223 should use <tt>fcntl()</tt> first and dot locking after
8224 this, or alternatively implement the two locking methods in
8225 a non blocking way<footnote>
8226 If it is not possible to establish both locks, the
8227 system shouldn't wait for the second lock to be
8228 established, but remove the first lock, wait a (random)
8229 time, and start over locking again.
8230 </footnote>. Using the functions <tt>maillock</tt> and
8231 <tt>mailunlock</tt> provided by the
8232 <tt>liblockfile*</tt><footnote>
8233 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8234 to use these functions.
8235 </footnote> packages is the recommended way to realize this.
8239 Mailboxes are generally either mode 600 and owned by
8240 <var>user</var> or mode 660 and owned by
8241 <tt><var>user</var>:mail</tt><footnote>
8242 There are two traditional permission schemes for mail spools:
8243 mode 600 with all mail delivery done by processes running as
8244 the destination user, or mode 660 and owned by group mail with
8245 mail delivery done by a process running as a system user in
8246 group mail. Historically, Debian required mode 660 mail
8247 spools to enable the latter model, but that model has become
8248 increasingly uncommon and the principle of least privilege
8249 indicates that mail systems that use the first model should
8250 use permissions of 600. If delivery to programs is permitted,
8251 it's easier to keep the mail system secure if the delivery
8252 agent runs as the destination user. Debian Policy therefore
8253 permits either scheme.
8254 </footnote>. The local system administrator may choose a
8255 different permission scheme; packages should not make
8256 assumptions about the permission and ownership of mailboxes
8257 unless required (such as when creating a new mailbox). A MUA
8258 may remove a mailbox (unless it has nonstandard permissions) in
8259 which case the MTA or another MUA must recreate it if needed.
8263 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8264 be setgid mail to do the locking mentioned above (and
8265 must obviously avoid accessing other users' mailboxes
8266 using this privilege).</p>
8269 <file>/etc/aliases</file> is the source file for the system mail
8270 aliases (e.g., postmaster, usenet, etc.), it is the one
8271 which the sysadmin and <prgn>postinst</prgn> scripts may
8272 edit. After <file>/etc/aliases</file> is edited the program or
8273 human editing it must call <prgn>newaliases</prgn>. All MTA
8274 packages must come with a <prgn>newaliases</prgn> program,
8275 even if it does nothing, but older MTA packages did not do
8276 this so programs should not fail if <prgn>newaliases</prgn>
8277 cannot be found. Note that because of this, all MTA
8278 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8279 <tt>Replaces: mail-transport-agent</tt> control file
8284 The convention of writing <tt>forward to
8285 <var>address</var></tt> in the mailbox itself is not
8286 supported. Use a <tt>.forward</tt> file instead.</p>
8289 The <prgn>rmail</prgn> program used by UUCP
8290 for incoming mail should be <file>/usr/sbin/rmail</file>.
8291 Likewise, <prgn>rsmtp</prgn>, for receiving
8292 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8296 If your package needs to know what hostname to use on (for
8297 example) outgoing news and mail messages which are generated
8298 locally, you should use the file <file>/etc/mailname</file>. It
8299 will contain the portion after the username and <tt>@</tt>
8300 (at) sign for email addresses of users on the machine
8301 (followed by a newline).
8305 Such a package should check for the existence of this file
8306 when it is being configured. If it exists, it should be
8307 used without comment, although an MTA's configuration script
8308 may wish to prompt the user even if it finds that this file
8309 exists. If the file does not exist, the package should
8310 prompt the user for the value (preferably using
8311 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8312 as well as using it in the package's configuration. The
8313 prompt should make it clear that the name will not just be
8314 used by that package. For example, in this situation the
8315 <tt>inn</tt> package could say something like:
8316 <example compact="compact">
8317 Please enter the "mail name" of your system. This is the
8318 hostname portion of the address to be shown on outgoing
8319 news and mail messages. The default is
8320 <var>syshostname</var>, your system's host name. Mail
8321 name ["<var>syshostname</var>"]:
8323 where <var>syshostname</var> is the output of <tt>hostname
8329 <heading>News system configuration</heading>
8332 All the configuration files related to the NNTP (news)
8333 servers and clients should be located under
8334 <file>/etc/news</file>.</p>
8337 There are some configuration issues that apply to a number
8338 of news clients and server packages on the machine. These
8342 <tag><file>/etc/news/organization</file></tag>
8344 A string which should appear as the
8345 organization header for all messages posted
8346 by NNTP clients on the machine
8349 <tag><file>/etc/news/server</file></tag>
8351 Contains the FQDN of the upstream NNTP
8352 server, or localhost if the local machine is
8357 Other global files may be added as required for cross-package news
8364 <heading>Programs for the X Window System</heading>
8367 <heading>Providing X support and package priorities</heading>
8370 Programs that can be configured with support for the X
8371 Window System must be configured to do so and must declare
8372 any package dependencies necessary to satisfy their
8373 runtime requirements when using the X Window System. If
8374 such a package is of higher priority than the X packages
8375 on which it depends, it is required that either the
8376 X-specific components be split into a separate package, or
8377 that an alternative version of the package, which includes
8378 X support, be provided, or that the package's priority be
8384 <heading>Packages providing an X server</heading>
8387 Packages that provide an X server that, directly or
8388 indirectly, communicates with real input and display
8389 hardware should declare in their control data that they
8390 provide the virtual package <tt>xserver</tt>.<footnote>
8391 This implements current practice, and provides an
8392 actual policy for usage of the <tt>xserver</tt>
8393 virtual package which appears in the virtual packages
8394 list. In a nutshell, X servers that interface
8395 directly with the display and input hardware or via
8396 another subsystem (e.g., GGI) should provide
8397 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8398 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8404 <heading>Packages providing a terminal emulator</heading>
8407 Packages that provide a terminal emulator for the X Window
8408 System which meet the criteria listed below should declare
8409 in their control data that they provide the virtual
8410 package <tt>x-terminal-emulator</tt>. They should also
8411 register themselves as an alternative for
8412 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8417 To be an <tt>x-terminal-emulator</tt>, a program must:
8418 <list compact="compact">
8420 Be able to emulate a DEC VT100 terminal, or a
8421 compatible terminal.
8425 Support the command-line option <tt>-e
8426 <var>command</var></tt>, which creates a new
8427 terminal window<footnote>
8428 "New terminal window" does not necessarily mean
8429 a new top-level X window directly parented by
8430 the window manager; it could, if the terminal
8431 emulator application were so coded, be a new
8432 "view" in a multiple-document interface (MDI).
8434 and runs the specified <var>command</var>,
8435 interpreting the entirety of the rest of the command
8436 line as a command to pass straight to exec, in the
8437 manner that <tt>xterm</tt> does.
8441 Support the command-line option <tt>-T
8442 <var>title</var></tt>, which creates a new terminal
8443 window with the window title <var>title</var>.
8450 <heading>Packages providing a window manager</heading>
8453 Packages that provide a window manager should declare in
8454 their control data that they provide the virtual package
8455 <tt>x-window-manager</tt>. They should also register
8456 themselves as an alternative for
8457 <file>/usr/bin/x-window-manager</file>, with a priority
8458 calculated as follows:
8459 <list compact="compact">
8461 Start with a priority of 20.
8465 If the window manager supports the Debian menu
8466 system, add 20 points if this support is available
8467 in the package's default configuration (i.e., no
8468 configuration files belonging to the system or user
8469 have to be edited to activate the feature); if
8470 configuration files must be modified, add only 10
8476 If the window manager complies with <url
8477 id="http://www.freedesktop.org/Standards/wm-spec"
8478 name="The Window Manager Specification Project">,
8479 written by the <url id="http://www.freedesktop.org/"
8480 name="Free Desktop Group">, add 40 points.
8484 If the window manager permits the X session to be
8485 restarted using a <em>different</em> window manager
8486 (without killing the X server) in its default
8487 configuration, add 10 points; otherwise add none.
8494 <heading>Packages providing fonts</heading>
8497 Packages that provide fonts for the X Window
8499 For the purposes of Debian Policy, a "font for the X
8500 Window System" is one which is accessed via X protocol
8501 requests. Fonts for the Linux console, for PostScript
8502 renderer, or any other purpose, do not fit this
8503 definition. Any tool which makes such fonts available
8504 to the X Window System, however, must abide by this
8507 must do a number of things to ensure that they are both
8508 available without modification of the X or font server
8509 configuration, and that they do not corrupt files used by
8510 other font packages to register information about
8514 Fonts of any type supported by the X Window System
8515 must be in a separate binary package from any
8516 executables, libraries, or documentation (except
8517 that specific to the fonts shipped, such as their
8518 license information). If one or more of the fonts
8519 so packaged are necessary for proper operation of
8520 the package with which they are associated the font
8521 package may be Recommended; if the fonts merely
8522 provide an enhancement, a Suggests relationship may
8523 be used. Packages must not Depend on font
8525 This is because the X server may retrieve fonts
8526 from the local file system or over the network
8527 from an X font server; the Debian package system
8528 is empowered to deal only with the local
8534 BDF fonts must be converted to PCF fonts with the
8535 <prgn>bdftopcf</prgn> utility (available in the
8536 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8537 placed in a directory that corresponds to their
8539 <list compact="compact">
8541 100 dpi fonts must be placed in
8542 <file>/usr/share/fonts/X11/100dpi/</file>.
8546 75 dpi fonts must be placed in
8547 <file>/usr/share/fonts/X11/75dpi/</file>.
8551 Character-cell fonts, cursor fonts, and other
8552 low-resolution fonts must be placed in
8553 <file>/usr/share/fonts/X11/misc/</file>.
8559 Type 1 fonts must be placed in
8560 <file>/usr/share/fonts/X11/Type1/</file>. If font
8561 metric files are available, they must be placed here
8566 Subdirectories of <file>/usr/share/fonts/X11/</file>
8567 other than those listed above must be neither
8568 created nor used. (The <file>PEX</file>, <file>CID</file>,
8569 <file>Speedo</file>, and <file>cyrillic</file> directories
8570 are excepted for historical reasons, but installation of
8571 files into these directories remains discouraged.)
8575 Font packages may, instead of placing files directly
8576 in the X font directories listed above, provide
8577 symbolic links in that font directory pointing to
8578 the files' actual location in the filesystem. Such
8579 a location must comply with the FHS.
8583 Font packages should not contain both 75dpi and
8584 100dpi versions of a font. If both are available,
8585 they should be provided in separate binary packages
8586 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8587 the names of the packages containing the
8588 corresponding fonts.
8592 Fonts destined for the <file>misc</file> subdirectory
8593 should not be included in the same package as 75dpi
8594 or 100dpi fonts; instead, they should be provided in
8595 a separate package with <tt>-misc</tt> appended to
8600 Font packages must not provide the files
8601 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8602 <file>fonts.scale</file> in a font directory:
8605 <file>fonts.dir</file> files must not be provided at all.
8609 <file>fonts.alias</file> and <file>fonts.scale</file>
8610 files, if needed, should be provided in the
8612 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8613 where <var>fontdir</var> is the name of the
8615 <file>/usr/share/fonts/X11/</file> where the
8616 package's corresponding fonts are stored
8617 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8618 <var>package</var> is the name of the package
8619 that provides these fonts, and
8620 <var>extension</var> is either <tt>scale</tt>
8621 or <tt>alias</tt>, whichever corresponds to
8628 Font packages must declare a dependency on
8629 <tt>xfonts-utils</tt> in their control
8634 Font packages that provide one or more
8635 <file>fonts.scale</file> files as described above must
8636 invoke <prgn>update-fonts-scale</prgn> on each
8637 directory into which they installed fonts
8638 <em>before</em> invoking
8639 <prgn>update-fonts-dir</prgn> on that directory.
8640 This invocation must occur in both the
8641 <prgn>postinst</prgn> (for all arguments) and
8642 <prgn>postrm</prgn> (for all arguments except
8643 <tt>upgrade</tt>) scripts.
8647 Font packages that provide one or more
8648 <file>fonts.alias</file> files as described above must
8649 invoke <prgn>update-fonts-alias</prgn> on each
8650 directory into which they installed fonts. This
8651 invocation must occur in both the
8652 <prgn>postinst</prgn> (for all arguments) and
8653 <prgn>postrm</prgn> (for all arguments except
8654 <tt>upgrade</tt>) scripts.
8658 Font packages must invoke
8659 <prgn>update-fonts-dir</prgn> on each directory into
8660 which they installed fonts. This invocation must
8661 occur in both the <prgn>postinst</prgn> (for all
8662 arguments) and <prgn>postrm</prgn> (for all
8663 arguments except <tt>upgrade</tt>) scripts.
8667 Font packages must not provide alias names for the
8668 fonts they include which collide with alias names
8669 already in use by fonts already packaged.
8673 Font packages must not provide fonts with the same
8674 XLFD registry name as another font already packaged.
8680 <sect1 id="appdefaults">
8681 <heading>Application defaults files</heading>
8684 Application defaults files must be installed in the
8685 directory <file>/etc/X11/app-defaults/</file> (use of a
8686 localized subdirectory of <file>/etc/X11/</file> as described
8687 in the <em>X Toolkit Intrinsics - C Language
8688 Interface</em> manual is also permitted). They must be
8689 registered as <tt>conffile</tt>s or handled as
8690 configuration files.
8694 Customization of programs' X resources may also be
8695 supported with the provision of a file with the same name
8696 as that of the package placed in
8697 the <file>/etc/X11/Xresources/</file> directory, which
8698 must be registered as a <tt>conffile</tt> or handled as a
8699 configuration file.<footnote>
8700 Note that this mechanism is not the same as using
8701 app-defaults; app-defaults are tied to the client
8702 binary on the local file system, whereas X resources
8703 are stored in the X server and affect all connecting
8710 <heading>Installation directory issues</heading>
8713 Historically, packages using the X Window System used a
8714 separate set of installation directories from other packages.
8715 This practice has been discontinued and packages using the X
8716 Window System should now generally be installed in the same
8717 directories as any other package. Specifically, packages must
8718 not install files under the <file>/usr/X11R6/</file> directory
8719 and the <file>/usr/X11R6/</file> directory hierarchy should be
8720 regarded as obsolete.
8724 Include files previously installed under
8725 <file>/usr/X11R6/include/X11/</file> should be installed into
8726 <file>/usr/include/X11/</file>. For files previously
8727 installed into subdirectories of
8728 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8729 determine if subdirectories of <file>/usr/lib/</file> and
8730 <file>/usr/share/</file> can be used. If not, a subdirectory
8731 of <file>/usr/lib/X11/</file> should be used.
8735 Configuration files for window, display, or session managers
8736 or other applications that are tightly integrated with the X
8737 Window System may be placed in a subdirectory
8738 of <file>/etc/X11/</file> corresponding to the package name.
8739 Other X Window System applications should use
8740 the <file>/etc/</file> directory unless otherwise mandated by
8741 policy (such as for <ref id="appdefaults">).
8746 <heading>The OSF/Motif and OpenMotif libraries</heading>
8749 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8750 OpenMotif libraries</em><footnote>
8751 OSF/Motif and OpenMotif are collectively referred to as
8752 "Motif" in this policy document.
8754 should be compiled against and tested with LessTif (a free
8755 re-implementation of Motif) instead. If the maintainer
8756 judges that the program or programs do not work
8757 sufficiently well with LessTif to be distributed and
8758 supported, but do so when compiled against Motif, then two
8759 versions of the package should be created; one linked
8760 statically against Motif and with <tt>-smotif</tt>
8761 appended to the package name, and one linked dynamically
8762 against Motif and with <tt>-dmotif</tt> appended to the
8767 Both Motif-linked versions are dependent
8768 upon non-DFSG-compliant software and thus cannot be
8769 uploaded to the <em>main</em> distribution; if the
8770 software is itself DFSG-compliant it may be uploaded to
8771 the <em>contrib</em> distribution. While known existing
8772 versions of Motif permit unlimited redistribution of
8773 binaries linked against the library (whether statically or
8774 dynamically), it is the package maintainer's
8775 responsibility to determine whether this is permitted by
8776 the license of the copy of Motif in their possession.
8782 <heading>Perl programs and modules</heading>
8785 Perl programs and modules should follow the current Perl policy.
8789 The Perl policy can be found in the <tt>perl-policy</tt>
8790 files in the <tt>debian-policy</tt> package.
8791 It is also available from the Debian web mirrors at
8792 <tt><url name="/doc/packaging-manuals/perl-policy/"
8793 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8798 <heading>Emacs lisp programs</heading>
8801 Please refer to the "Debian Emacs Policy" for details of how to
8802 package emacs lisp programs.
8806 The Emacs policy is available in
8807 <file>debian-emacs-policy.gz</file> of the
8808 <package>emacsen-common</package> package.
8809 It is also available from the Debian web mirrors at
8810 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8811 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8816 <heading>Games</heading>
8819 The permissions on <file>/var/games</file> are mode 755, owner
8820 <tt>root</tt> and group <tt>root</tt>.
8824 Each game decides on its own security policy.</p>
8827 Games which require protected, privileged access to
8828 high-score files, saved games, etc., may be made
8829 set-<em>group</em>-id (mode 2755) and owned by
8830 <tt>root:games</tt>, and use files and directories with
8831 appropriate permissions (770 <tt>root:games</tt>, for
8832 example). They must not be made
8833 set-<em>user</em>-id, as this causes security problems. (If
8834 an attacker can subvert any set-user-id game they can
8835 overwrite the executable of any other, causing other players
8836 of these games to run a Trojan horse program. With a
8837 set-group-id game the attacker only gets access to less
8838 important game data, and if they can get at the other
8839 players' accounts at all it will take considerably more
8843 Some packages, for example some fortune cookie programs, are
8844 configured by the upstream authors to install with their
8845 data files or other static information made unreadable so
8846 that they can only be accessed through set-id programs
8847 provided. You should not do this in a Debian package: anyone can
8848 download the <file>.deb</file> file and read the data from it,
8849 so there is no point making the files unreadable. Not
8850 making the files unreadable also means that you don't have
8851 to make so many programs set-id, which reduces the risk of a
8855 As described in the FHS, binaries of games should be
8856 installed in the directory <file>/usr/games</file>. This also
8857 applies to games that use the X Window System. Manual pages
8858 for games (X and non-X games) should be installed in
8859 <file>/usr/share/man/man6</file>.</p>
8865 <heading>Documentation</heading>
8868 <heading>Manual pages</heading>
8871 You should install manual pages in <prgn>nroff</prgn> source
8872 form, in appropriate places under <file>/usr/share/man</file>.
8873 You should only use sections 1 to 9 (see the FHS for more
8874 details). You must not install a pre-formatted "cat page".
8878 Each program, utility, and function should have an
8879 associated manual page included in the same package. It is
8880 suggested that all configuration files also have a manual
8881 page included as well. Manual pages for protocols and other
8882 auxiliary things are optional.
8886 If no manual page is available, this is considered as a bug
8887 and should be reported to the Debian Bug Tracking System (the
8888 maintainer of the package is allowed to write this bug report
8889 themselves, if they so desire). Do not close the bug report
8890 until a proper man page is available.<footnote>
8891 It is not very hard to write a man page. See the
8892 <url id="http://www.schweikhardt.net/man_page_howto.html"
8893 name="Man-Page-HOWTO">,
8894 <manref name="man" section="7">, the examples
8895 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8896 the helper programs <prgn>help2man</prgn>, or the
8897 directory <file>/usr/share/doc/man-db/examples</file>.
8902 You may forward a complaint about a missing man page to the
8903 upstream authors, and mark the bug as forwarded in the
8904 Debian bug tracking system. Even though the GNU Project do
8905 not in general consider the lack of a man page to be a bug,
8906 we do; if they tell you that they don't consider it a bug
8907 you should leave the bug in our bug tracking system open
8912 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8916 If one man page needs to be accessible via several names it
8917 is better to use a symbolic link than the <file>.so</file>
8918 feature, but there is no need to fiddle with the relevant
8919 parts of the upstream source to change from <file>.so</file> to
8920 symlinks: don't do it unless it's easy. You should not
8921 create hard links in the manual page directories, nor put
8922 absolute filenames in <file>.so</file> directives. The filename
8923 in a <file>.so</file> in a man page should be relative to the
8924 base of the man page tree (usually
8925 <file>/usr/share/man</file>). If you do not create any links
8926 (whether symlinks, hard links, or <tt>.so</tt> directives)
8927 in the file system to the alternate names of the man page,
8928 then you should not rely on <prgn>man</prgn> finding your
8929 man page under those names based solely on the information in
8930 the man page's header.<footnote>
8931 Supporting this in <prgn>man</prgn> often requires
8932 unreasonable processing time to find a manual page or to
8933 report that none exists, and moves knowledge into man's
8934 database that would be better left in the file system.
8935 This support is therefore deprecated and will cease to
8936 be present in the future.
8941 Manual pages in locale-specific subdirectories of
8942 <file>/usr/share/man</file> should use either UTF-8 or the usual
8943 legacy encoding for that language (normally the one corresponding
8944 to the shortest relevant locale name in
8945 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8946 <file>/usr/share/man/fr</file> should use either UTF-8 or
8947 ISO-8859-1.<footnote>
8948 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8949 use. In future, all manual pages will be required to use
8955 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8956 included in the subdirectory name unless it indicates a
8957 significant difference in the language, as this excludes
8958 speakers of the language in other countries.<footnote>
8959 At the time of writing, Chinese and Portuguese are the main
8960 languages with such differences, so <file>pt_BR</file>,
8961 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8966 If a localized version of a manual page is provided, it should
8967 either be up-to-date or it should be obvious to the reader that
8968 it is outdated and the original manual page should be used
8969 instead. This can be done either by a note at the beginning of
8970 the manual page or by showing the missing or changed portions in
8971 the original language instead of the target language.
8976 <heading>Info documents</heading>
8979 Info documents should be installed in <file>/usr/share/info</file>.
8980 They should be compressed with <tt>gzip -9</tt>.
8984 The <prgn>install-info</prgn> program maintains a directory of
8985 installed info documents in <file>/usr/share/info/dir</file> for
8986 the use of info readers.<footnote>
8987 It was previously necessary for packages installing info
8988 documents to run <prgn>install-info</prgn> from maintainer
8989 scripts. This is no longer necessary. The installation
8990 system now uses dpkg triggers.
8992 This file must not be included in packages. Packages containing
8993 info documents should depend on <tt>dpkg (>= 1.15.4) |
8994 install-info</tt> to ensure that the directory file is properly
8995 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9000 Info documents should contain section and directory entry
9001 information in the document for the use
9002 of <prgn>install-info</prgn>. The section should be specified
9003 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9004 space and the section of this info page. The directory entry or
9005 entries should be included between
9006 a <tt>START-INFO-DIR-ENTRY</tt> line and
9007 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9009 INFO-DIR-SECTION Individual utilities
9010 START-INFO-DIR-ENTRY
9011 * example: (example). An example info directory entry.
9014 To determine which section to use, you should look
9015 at <file>/usr/share/info/dir</file> on your system and choose
9016 the most relevant (or create a new section if none of the
9017 current sections are relevant).<footnote>
9018 Normally, info documents are generated from Texinfo source.
9019 To include this information in the generated info document, if
9020 it is absent, add commands like:
9022 @dircategory Individual utilities
9024 * example: (example). An example info directory entry.
9027 to the Texinfo source of the document and ensure that the info
9028 documents are rebuilt from source during the package build.
9034 <heading>Additional documentation</heading>
9037 Any additional documentation that comes with the package may
9038 be installed at the discretion of the package maintainer.
9039 Plain text documentation should be installed in the directory
9040 <file>/usr/share/doc/<var>package</var></file>, where
9041 <var>package</var> is the name of the package, and
9042 compressed with <tt>gzip -9</tt> unless it is small.
9046 If a package comes with large amounts of documentation which
9047 many users of the package will not require you should create
9048 a separate binary package to contain it, so that it does not
9049 take up disk space on the machines of users who do not need
9050 or want it installed.</p>
9053 It is often a good idea to put text information files
9054 (<file>README</file>s, changelogs, and so forth) that come with
9055 the source package in <file>/usr/share/doc/<var>package</var></file>
9056 in the binary package. However, you don't need to install
9057 the instructions for building and installing the package, of
9061 Packages must not require the existence of any files in
9062 <file>/usr/share/doc/</file> in order to function
9064 The system administrator should be able to
9065 delete files in <file>/usr/share/doc/</file> without causing
9066 any programs to break.
9068 Any files that are referenced by programs but are also
9069 useful as stand alone documentation should be installed under
9070 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9071 <file>/usr/share/doc/<var>package</var></file>.
9075 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9076 link to another directory in <file>/usr/share/doc</file> only if
9077 the two packages both come from the same source and the
9078 first package Depends on the second.<footnote>
9080 Please note that this does not override the section on
9081 changelog files below, so the file
9082 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9083 must refer to the changelog for the current version of
9084 <var>package</var> in question. In practice, this means
9085 that the sources of the target and the destination of the
9086 symlink must be the same (same source package and
9093 Former Debian releases placed all additional documentation
9094 in <file>/usr/doc/<var>package</var></file>. This has been
9095 changed to <file>/usr/share/doc/<var>package</var></file>,
9096 and packages must not put documentation in the directory
9097 <file>/usr/doc/<var>package</var></file>. <footnote>
9098 At this phase of the transition, we no longer require a
9099 symbolic link in <file>/usr/doc/</file>. At a later point,
9100 policy shall change to make the symbolic links a bug.
9106 <heading>Preferred documentation formats</heading>
9109 The unification of Debian documentation is being carried out
9113 If your package comes with extensive documentation in a
9114 markup format that can be converted to various other formats
9115 you should if possible ship HTML versions in a binary
9116 package, in the directory
9117 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9118 its subdirectories.<footnote>
9119 The rationale: The important thing here is that HTML
9120 docs should be available in <em>some</em> package, not
9121 necessarily in the main binary package.
9126 Other formats such as PostScript may be provided at the
9127 package maintainer's discretion.
9131 <sect id="copyrightfile">
9132 <heading>Copyright information</heading>
9135 Every package must be accompanied by a verbatim copy of its
9136 copyright information and distribution license in the file
9137 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9138 file must neither be compressed nor be a symbolic link.
9142 In addition, the copyright file must say where the upstream
9143 sources (if any) were obtained. It should name the original
9144 authors of the package and the Debian maintainer(s) who were
9145 involved with its creation.
9149 Packages in the <em>contrib</em> or <em>non-free</em> archive
9150 areas should state in the copyright file that the package is not
9151 part of the Debian GNU/Linux distribution and briefly explain
9156 A copy of the file which will be installed in
9157 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9158 be in <file>debian/copyright</file> in the source package.
9162 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9163 link to another directory in <file>/usr/share/doc</file> only if
9164 the two packages both come from the same source and the
9165 first package Depends on the second. These rules are
9166 important because copyrights must be extractable by
9171 Packages distributed under the UCB BSD license, the Apache
9172 license (version 2.0), the Artistic license, the GNU GPL
9173 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and the
9174 GNU FDL (versions 1.2 or 1.3) should refer to the corresponding
9175 files under <file>/usr/share/common-licenses</file>,<footnote>
9178 <file>/usr/share/common-licenses/BSD</file>,
9179 <file>/usr/share/common-licenses/Apache-2.0</file>,
9180 <file>/usr/share/common-licenses/Artistic</file>,
9181 <file>/usr/share/common-licenses/GPL-2</file>,
9182 <file>/usr/share/common-licenses/GPL-3</file>,
9183 <file>/usr/share/common-licenses/LGPL-2</file>,
9184 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9185 <file>/usr/share/common-licenses/LGPL-3</file>,
9186 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9187 <file>/usr/share/common-licenses/GFDL-1.3</file>
9190 </footnote> rather than quoting them in the copyright
9195 You should not use the copyright file as a general <file>README</file>
9196 file. If your package has such a file it should be
9197 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9198 <file>README.Debian</file> or some other appropriate place.</p>
9202 <heading>Examples</heading>
9205 Any examples (configurations, source files, whatever),
9206 should be installed in a directory
9207 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9208 files should not be referenced by any program: they're there
9209 for the benefit of the system administrator and users as
9210 documentation only. Architecture-specific example files
9211 should be installed in a directory
9212 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9214 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9215 latter directory itself may be a symbolic link to the
9220 If the purpose of a package is to provide examples, then the
9221 example files may be installed into
9222 <file>/usr/share/doc/<var>package</var></file>.
9226 <sect id="changelogs">
9227 <heading>Changelog files</heading>
9230 Packages that are not Debian-native must contain a
9231 compressed copy of the <file>debian/changelog</file> file from
9232 the Debian source tree in
9233 <file>/usr/share/doc/<var>package</var></file> with the name
9234 <file>changelog.Debian.gz</file>.
9238 If an upstream changelog is available, it should be accessible as
9239 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9240 plain text. If the upstream changelog is distributed in
9241 HTML, it should be made available in that form as
9242 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9243 and a plain text <file>changelog.gz</file> should be generated
9244 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9245 the upstream changelog files do not already conform to this
9246 naming convention, then this may be achieved either by
9247 renaming the files, or by adding a symbolic link, at the
9248 maintainer's discretion.<footnote>
9249 Rationale: People should not have to look in places for
9250 upstream changelogs merely because they are given
9251 different names or are distributed in HTML format.
9256 All of these files should be installed compressed using
9257 <tt>gzip -9</tt>, as they will become large with time even
9258 if they start out small.
9262 If the package has only one changelog which is used both as
9263 the Debian changelog and the upstream one because there is
9264 no separate upstream maintainer then that changelog should
9265 usually be installed as
9266 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9267 there is a separate upstream maintainer, but no upstream
9268 changelog, then the Debian changelog should still be called
9269 <file>changelog.Debian.gz</file>.
9273 For details about the format and contents of the Debian
9274 changelog file, please see <ref id="dpkgchangelog">.
9279 <appendix id="pkg-scope">
9280 <heading>Introduction and scope of these appendices</heading>
9283 These appendices are taken essentially verbatim from the
9284 now-deprecated Packaging Manual, version 3.2.1.0. They are
9285 the chapters which are likely to be of use to package
9286 maintainers and which have not already been included in the
9287 policy document itself. Most of these sections are very likely
9288 not relevant to policy; they should be treated as
9289 documentation for the packaging system. Please note that these
9290 appendices are included for convenience, and for historical
9291 reasons: they used to be part of policy package, and they have
9292 not yet been incorporated into dpkg documentation. However,
9293 they still have value, and hence they are presented here.
9297 They have not yet been checked to ensure that they are
9298 compatible with the contents of policy, and if there are any
9299 contradictions, the version in the main policy document takes
9300 precedence. The remaining chapters of the old Packaging
9301 Manual have also not been read in detail to ensure that there
9302 are not parts which have been left out. Both of these will be
9307 Certain parts of the Packaging manual were integrated into the
9308 Policy Manual proper, and removed from the appendices. Links
9309 have been placed from the old locations to the new ones.
9313 <prgn>dpkg</prgn> is a suite of programs for creating binary
9314 package files and installing and removing them on Unix
9316 <prgn>dpkg</prgn> is targeted primarily at Debian
9317 GNU/Linux, but may work on or be ported to other
9323 The binary packages are designed for the management of
9324 installed executable programs (usually compiled binaries) and
9325 their associated data, though source code examples and
9326 documentation are provided as part of some packages.</p>
9329 This manual describes the technical aspects of creating Debian
9330 binary packages (<file>.deb</file> files). It documents the
9331 behavior of the package management programs
9332 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9333 they interact with packages.</p>
9336 It also documents the interaction between
9337 <prgn>dselect</prgn>'s core and the access method scripts it
9338 uses to actually install the selected packages, and describes
9339 how to create a new access method.</p>
9342 This manual does not go into detail about the options and
9343 usage of the package building and installation tools. It
9344 should therefore be read in conjunction with those programs'
9349 The utility programs which are provided with <prgn>dpkg</prgn>
9350 for managing various system configuration and similar issues,
9351 such as <prgn>update-rc.d</prgn> and
9352 <prgn>install-info</prgn>, are not described in detail here -
9353 please see their man pages.
9357 It is assumed that the reader is reasonably familiar with the
9358 <prgn>dpkg</prgn> System Administrators' manual.
9359 Unfortunately this manual does not yet exist.
9363 The Debian version of the FSF's GNU hello program is provided
9364 as an example for people wishing to create Debian
9365 packages. The Debian <prgn>debmake</prgn> package is
9366 recommended as a very helpful tool in creating and maintaining
9367 Debian packages. However, while the tools and examples are
9368 helpful, they do not replace the need to read and follow the
9369 Policy and Programmer's Manual.</p>
9372 <appendix id="pkg-binarypkg">
9373 <heading>Binary packages (from old Packaging Manual)</heading>
9376 The binary package has two main sections. The first part
9377 consists of various control information files and scripts used
9378 by <prgn>dpkg</prgn> when installing and removing. See <ref
9379 id="pkg-controlarea">.
9383 The second part is an archive containing the files and
9384 directories to be installed.
9388 In the future binary packages may also contain other
9389 components, such as checksums and digital signatures. The
9390 format for the archive is described in full in the
9391 <file>deb(5)</file> man page.
9395 <sect id="pkg-bincreating"><heading>Creating package files -
9396 <prgn>dpkg-deb</prgn>
9400 All manipulation of binary package files is done by
9401 <prgn>dpkg-deb</prgn>; it's the only program that has
9402 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9403 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9404 will spot that the options requested are appropriate to
9405 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9410 In order to create a binary package you must make a
9411 directory tree which contains all the files and directories
9412 you want to have in the file system data part of the package.
9413 In Debian-format source packages this directory is usually
9414 <file>debian/tmp</file>, relative to the top of the package's
9419 They should have the locations (relative to the root of the
9420 directory tree you're constructing) ownerships and
9421 permissions which you want them to have on the system when
9426 With current versions of <prgn>dpkg</prgn> the uid/username
9427 and gid/groupname mappings for the users and groups being
9428 used should be the same on the system where the package is
9429 built and the one where it is installed.
9433 You need to add one special directory to the root of the
9434 miniature file system tree you're creating:
9435 <prgn>DEBIAN</prgn>. It should contain the control
9436 information files, notably the binary package control file
9437 (see <ref id="pkg-controlfile">).
9441 The <prgn>DEBIAN</prgn> directory will not appear in the
9442 file system archive of the package, and so won't be installed
9443 by <prgn>dpkg</prgn> when the package is installed.
9447 When you've prepared the package, you should invoke:
9449 dpkg --build <var>directory</var>
9454 This will build the package in
9455 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9456 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9457 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9462 See the man page <manref name="dpkg-deb" section="8"> for details of how
9463 to examine the contents of this newly-created file. You may find the
9464 output of following commands enlightening:
9466 dpkg-deb --info <var>filename</var>.deb
9467 dpkg-deb --contents <var>filename</var>.deb
9468 dpkg --contents <var>filename</var>.deb
9470 To view the copyright file for a package you could use this command:
9472 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9477 <sect id="pkg-controlarea">
9478 <heading>Package control information files</heading>
9481 The control information portion of a binary package is a
9482 collection of files with names known to <prgn>dpkg</prgn>.
9483 It will treat the contents of these files specially - some
9484 of them contain information used by <prgn>dpkg</prgn> when
9485 installing or removing the package; others are scripts which
9486 the package maintainer wants <prgn>dpkg</prgn> to run.
9490 It is possible to put other files in the package control
9491 area, but this is not generally a good idea (though they
9492 will largely be ignored).
9496 Here is a brief list of the control info files supported by
9497 <prgn>dpkg</prgn> and a summary of what they're used for.
9502 <tag><tt>control</tt>
9505 This is the key description file used by
9506 <prgn>dpkg</prgn>. It specifies the package's name
9507 and version, gives its description for the user,
9508 states its relationships with other packages, and so
9509 forth. See <ref id="sourcecontrolfiles"> and
9510 <ref id="binarycontrolfiles">.
9514 It is usually generated automatically from information
9515 in the source package by the
9516 <prgn>dpkg-gencontrol</prgn> program, and with
9517 assistance from <prgn>dpkg-shlibdeps</prgn>.
9518 See <ref id="pkg-sourcetools">.
9522 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9527 These are executable files (usually scripts) which
9528 <prgn>dpkg</prgn> runs during installation, upgrade
9529 and removal of packages. They allow the package to
9530 deal with matters which are particular to that package
9531 or require more complicated processing than that
9532 provided by <prgn>dpkg</prgn>. Details of when and
9533 how they are called are in <ref id="maintainerscripts">.
9537 It is very important to make these scripts idempotent.
9538 See <ref id="idempotency">.
9542 The maintainer scripts are not guaranteed to run with a
9543 controlling terminal and may not be able to interact with
9544 the user. See <ref id="controllingterminal">.
9548 <tag><tt>conffiles</tt>
9551 This file contains a list of configuration files which
9552 are to be handled automatically by <prgn>dpkg</prgn>
9553 (see <ref id="pkg-conffiles">). Note that not necessarily
9554 every configuration file should be listed here.
9557 <tag><tt>shlibs</tt>
9560 This file contains a list of the shared libraries
9561 supplied by the package, with dependency details for
9562 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9563 when it determines what dependencies are required in a
9564 package control file. The <tt>shlibs</tt> file format
9565 is described on <ref id="shlibs">.
9570 <sect id="pkg-controlfile">
9571 <heading>The main control information file: <tt>control</tt></heading>
9574 The most important control information file used by
9575 <prgn>dpkg</prgn> when it installs a package is
9576 <tt>control</tt>. It contains all the package's "vital
9581 The binary package control files of packages built from
9582 Debian sources are made by a special tool,
9583 <prgn>dpkg-gencontrol</prgn>, which reads
9584 <file>debian/control</file> and <file>debian/changelog</file> to
9585 find the information it needs. See <ref id="pkg-sourcepkg"> for
9590 The fields in binary package control files are listed in
9591 <ref id="binarycontrolfiles">.
9595 A description of the syntax of control files and the purpose
9596 of the fields is available in <ref id="controlfields">.
9601 <heading>Time Stamps</heading>
9604 See <ref id="timestamps">.
9609 <appendix id="pkg-sourcepkg">
9610 <heading>Source packages (from old Packaging Manual) </heading>
9613 The Debian binary packages in the distribution are generated
9614 from Debian sources, which are in a special format to assist
9615 the easy and automatic building of binaries.
9618 <sect id="pkg-sourcetools">
9619 <heading>Tools for processing source packages</heading>
9622 Various tools are provided for manipulating source packages;
9623 they pack and unpack sources and help build of binary
9624 packages and help manage the distribution of new versions.
9628 They are introduced and typical uses described here; see
9629 <manref name="dpkg-source" section="1"> for full
9630 documentation about their arguments and operation.
9634 For examples of how to construct a Debian source package,
9635 and how to use those utilities that are used by Debian
9636 source packages, please see the <prgn>hello</prgn> example
9640 <sect1 id="pkg-dpkg-source">
9642 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9647 This program is frequently used by hand, and is also
9648 called from package-independent automated building scripts
9649 such as <prgn>dpkg-buildpackage</prgn>.
9653 To unpack a package it is typically invoked with
9655 dpkg-source -x <var>.../path/to/filename</var>.dsc
9660 with the <file><var>filename</var>.tar.gz</file> and
9661 <file><var>filename</var>.diff.gz</file> (if applicable) in
9662 the same directory. It unpacks into
9663 <file><var>package</var>-<var>version</var></file>, and if
9665 <file><var>package</var>-<var>version</var>.orig</file>, in
9666 the current directory.
9670 To create a packed source archive it is typically invoked:
9672 dpkg-source -b <var>package</var>-<var>version</var>
9677 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9678 <file>.diff.gz</file> (if appropriate) in the current
9679 directory. <prgn>dpkg-source</prgn> does not clean the
9680 source tree first - this must be done separately if it is
9685 See also <ref id="pkg-sourcearchives">.</p>
9689 <sect1 id="pkg-dpkg-buildpackage">
9691 <prgn>dpkg-buildpackage</prgn> - overall package-building
9696 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9697 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9698 targets <tt>clean</tt>, <tt>build</tt> and
9699 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9700 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9701 source and binary package upload.
9705 It is usually invoked by hand from the top level of the
9706 built or unbuilt source directory. It may be invoked with
9707 no arguments; useful arguments include:
9708 <taglist compact="compact">
9709 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9712 Do not sign the <tt>.changes</tt> file or the
9713 source package <tt>.dsc</tt> file, respectively.</p>
9715 <tag><tt>-p<var>sign-command</var></tt></tag>
9718 Invoke <var>sign-command</var> instead of finding
9719 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9720 <var>sign-command</var> must behave just like
9721 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9723 <tag><tt>-r<var>root-command</var></tt></tag>
9726 When root privilege is required, invoke the command
9727 <var>root-command</var>. <var>root-command</var>
9728 should invoke its first argument as a command, from
9729 the <prgn>PATH</prgn> if necessary, and pass its
9730 second and subsequent arguments to the command it
9731 calls. If no <var>root-command</var> is supplied
9732 then <var>dpkg-buildpackage</var> will take no
9733 special action to gain root privilege, so that for
9734 most packages it will have to be invoked as root to
9737 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9740 Two types of binary-only build and upload - see
9741 <manref name="dpkg-source" section="1">.
9748 <sect1 id="pkg-dpkg-gencontrol">
9750 <prgn>dpkg-gencontrol</prgn> - generates binary package
9755 This program is usually called from <file>debian/rules</file>
9756 (see <ref id="pkg-sourcetree">) in the top level of the source
9761 This is usually done just before the files and directories in the
9762 temporary directory tree where the package is being built have their
9763 permissions and ownerships set and the package is constructed using
9764 <prgn>dpkg-deb/</prgn>
9766 This is so that the control file which is produced has
9767 the right permissions
9772 <prgn>dpkg-gencontrol</prgn> must be called after all the
9773 files which are to go into the package have been placed in
9774 the temporary build directory, so that its calculation of
9775 the installed size of a package is correct.
9779 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9780 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9781 variable substitutions created by
9782 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9787 For a package which generates only one binary package, and
9788 which builds it in <file>debian/tmp</file> relative to the top
9789 of the source package, it is usually sufficient to call
9790 <prgn>dpkg-gencontrol</prgn>.
9794 Sources which build several binaries will typically need
9797 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9798 </example> The <tt>-P</tt> tells
9799 <prgn>dpkg-gencontrol</prgn> that the package is being
9800 built in a non-default directory, and the <tt>-p</tt>
9801 tells it which package's control file should be generated.
9805 <prgn>dpkg-gencontrol</prgn> also adds information to the
9806 list of files in <file>debian/files</file>, for the benefit of
9807 (for example) a future invocation of
9808 <prgn>dpkg-genchanges</prgn>.</p>
9811 <sect1 id="pkg-dpkg-shlibdeps">
9813 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9818 This program is usually called from <file>debian/rules</file>
9819 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9820 id="pkg-sourcetree">), in the top level of the source tree.
9824 Its arguments are executables and shared libraries
9827 They may be specified either in the locations in the
9828 source tree where they are created or in the locations
9829 in the temporary build tree where they are installed
9830 prior to binary package creation.
9832 </footnote> for which shared library dependencies should
9833 be included in the binary package's control file.
9837 If some of the found shared libraries should only
9838 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9839 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9840 by using the <tt>-d<var>dependency-field</var></tt> option
9841 before those executable(s). (Each <tt>-d</tt> option
9842 takes effect until the next <tt>-d</tt>.)
9846 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9847 output control file to be modified. Instead by default it
9848 adds to the <file>debian/substvars</file> file variable
9849 settings like <tt>shlibs:Depends</tt>. These variable
9850 settings must be referenced in dependency fields in the
9851 appropriate per-binary-package sections of the source
9856 For example, a package that generates an essential part
9857 which requires dependencies, and optional parts that
9858 which only require a recommendation, would separate those
9859 two sets of dependencies into two different fields.<footnote>
9860 At the time of writing, an example for this was the
9861 <package/xmms/ package, with Depends used for the xmms
9862 executable, Recommends for the plug-ins and Suggests for
9863 even more optional features provided by unzip.
9865 It can say in its <file>debian/rules</file>:
9867 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9868 -dRecommends <var>optionalpart anotheroptionalpart</var>
9870 and then in its main control file <file>debian/control</file>:
9873 Depends: ${shlibs:Depends}
9874 Recommends: ${shlibs:Recommends}
9880 Sources which produce several binary packages with
9881 different shared library dependency requirements can use
9882 the <tt>-p<var>varnameprefix</var></tt> option to override
9883 the default <tt>shlibs:</tt> prefix (one invocation of
9884 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9885 They can thus produce several sets of dependency
9886 variables, each of the form
9887 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9888 which can be referred to in the appropriate parts of the
9889 binary package control files.
9894 <sect1 id="pkg-dpkg-distaddfile">
9896 <prgn>dpkg-distaddfile</prgn> - adds a file to
9897 <file>debian/files</file>
9901 Some packages' uploads need to include files other than
9902 the source and binary package files.
9906 <prgn>dpkg-distaddfile</prgn> adds a file to the
9907 <file>debian/files</file> file so that it will be included in
9908 the <file>.changes</file> file when
9909 <prgn>dpkg-genchanges</prgn> is run.
9913 It is usually invoked from the <tt>binary</tt> target of
9914 <file>debian/rules</file>:
9916 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9918 The <var>filename</var> is relative to the directory where
9919 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9920 is usually the directory above the top level of the source
9921 tree. The <file>debian/rules</file> target should put the
9922 file there just before or just after calling
9923 <prgn>dpkg-distaddfile</prgn>.
9927 The <var>section</var> and <var>priority</var> are passed
9928 unchanged into the resulting <file>.changes</file> file.
9933 <sect1 id="pkg-dpkg-genchanges">
9935 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9940 This program is usually called by package-independent
9941 automatic building scripts such as
9942 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9947 It is usually called in the top level of a built source
9948 tree, and when invoked with no arguments will print out a
9949 straightforward <file>.changes</file> file based on the
9950 information in the source package's changelog and control
9951 file and the binary and source packages which should have
9957 <sect1 id="pkg-dpkg-parsechangelog">
9959 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9960 representation of a changelog
9964 This program is used internally by
9965 <prgn>dpkg-source</prgn> et al. It may also occasionally
9966 be useful in <file>debian/rules</file> and elsewhere. It
9967 parses a changelog, <file>debian/changelog</file> by default,
9968 and prints a control-file format representation of the
9969 information in it to standard output.
9973 <sect1 id="pkg-dpkg-architecture">
9975 <prgn>dpkg-architecture</prgn> - information about the build and
9980 This program can be used manually, but is also invoked by
9981 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9982 environment or make variables which specify the build and host
9983 architecture for the package building process.
9988 <sect id="pkg-sourcetree">
9989 <heading>The Debianised source tree</heading>
9992 The source archive scheme described later is intended to
9993 allow a Debianised source tree with some associated control
9994 information to be reproduced and transported easily. The
9995 Debianised source tree is a version of the original program
9996 with certain files added for the benefit of the
9997 Debianisation process, and with any other changes required
9998 made to the rest of the source code and installation
10003 The extra files created for Debian are in the subdirectory
10004 <file>debian</file> of the top level of the Debianised source
10005 tree. They are described below.
10008 <sect1 id="pkg-debianrules">
10009 <heading><file>debian/rules</file> - the main building script</heading>
10012 See <ref id="debianrules">.
10016 <sect1 id="pkg-srcsubstvars">
10017 <heading><file>debian/substvars</file> and variable substitutions</heading>
10020 See <ref id="substvars">.
10026 <heading><file>debian/files</file></heading>
10029 See <ref id="debianfiles">.
10033 <sect1><heading><file>debian/tmp</file>
10037 This is the canonical temporary location for the
10038 construction of binary packages by the <tt>binary</tt>
10039 target. The directory <file>tmp</file> serves as the root of
10040 the file system tree as it is being constructed (for
10041 example, by using the package's upstream makefiles install
10042 targets and redirecting the output there), and it also
10043 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10044 id="pkg-bincreating">.
10048 If several binary packages are generated from the same
10049 source tree it is usual to use several
10050 <file>debian/tmp<var>something</var></file> directories, for
10051 example <file>tmp-a</file> or <file>tmp-doc</file>.
10055 Whatever <file>tmp</file> directories are created and used by
10056 <tt>binary</tt> must of course be removed by the
10057 <tt>clean</tt> target.</p></sect1>
10061 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10065 As it exists on the FTP site, a Debian source package
10066 consists of three related files. You must have the right
10067 versions of all three to be able to use them.
10072 <tag>Debian source control file - <tt>.dsc</tt></tag>
10074 This file is a control file used by <prgn>dpkg-source</prgn>
10075 to extract a source package.
10076 See <ref id="debiansourcecontrolfiles">.
10080 Original source archive -
10082 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10088 This is a compressed (with <tt>gzip -9</tt>)
10089 <prgn>tar</prgn> file containing the source code from
10090 the upstream authors of the program.
10095 Debianisation diff -
10097 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10103 This is a unified context diff (<tt>diff -u</tt>)
10104 giving the changes which are required to turn the
10105 original source into the Debian source. These changes
10106 may only include editing and creating plain files.
10107 The permissions of files, the targets of symbolic
10108 links and the characteristics of special files or
10109 pipes may not be changed and no files may be removed
10114 All the directories in the diff must exist, except the
10115 <file>debian</file> subdirectory of the top of the source
10116 tree, which will be created by
10117 <prgn>dpkg-source</prgn> if necessary when unpacking.
10121 The <prgn>dpkg-source</prgn> program will
10122 automatically make the <file>debian/rules</file> file
10123 executable (see below).</p></item>
10128 If there is no original source code - for example, if the
10129 package is specially prepared for Debian or the Debian
10130 maintainer is the same as the upstream maintainer - the
10131 format is slightly different: then there is no diff, and the
10133 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10134 and preferably contains a directory named
10135 <file><var>package</var>-<var>version</var></file>.
10140 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10143 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10144 Debian source package. However, if it is not available it
10145 is possible to unpack a Debian source archive as follows:
10146 <enumlist compact="compact">
10149 Untar the tarfile, which will create a <file>.orig</file>
10153 <p>Rename the <file>.orig</file> directory to
10154 <file><var>package</var>-<var>version</var></file>.</p>
10158 Create the subdirectory <file>debian</file> at the top of
10159 the source tree.</p>
10161 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10163 <item><p>Untar the tarfile again if you want a copy of the original
10164 source code alongside the Debianised version.</p>
10169 It is not possible to generate a valid Debian source archive
10170 without using <prgn>dpkg-source</prgn>. In particular,
10171 attempting to use <prgn>diff</prgn> directly to generate the
10172 <file>.diff.gz</file> file will not work.
10176 <heading>Restrictions on objects in source packages</heading>
10179 The source package may not contain any hard links
10181 This is not currently detected when building source
10182 packages, but only when extracting
10186 Hard links may be permitted at some point in the
10187 future, but would require a fair amount of
10189 </footnote>, device special files, sockets or setuid or
10192 Setgid directories are allowed.
10197 The source packaging tools manage the changes between the
10198 original and Debianised source using <prgn>diff</prgn> and
10199 <prgn>patch</prgn>. Turning the original source tree as
10200 included in the <file>.orig.tar.gz</file> into the debianised
10201 source must not involve any changes which cannot be
10202 handled by these tools. Problematic changes which cause
10203 <prgn>dpkg-source</prgn> to halt with an error when
10204 building the source package are:
10205 <list compact="compact">
10206 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10208 <item><p>Changing the targets of symbolic links.</p>
10210 <item><p>Creating directories, other than <file>debian</file>.</p>
10212 <item><p>Changes to the contents of binary files.</p></item>
10213 </list> Changes which cause <prgn>dpkg-source</prgn> to
10214 print a warning but continue anyway are:
10215 <list compact="compact">
10218 Removing files, directories or symlinks.
10220 Renaming a file is not treated specially - it is
10221 seen as the removal of the old file (which
10222 generates a warning, but is otherwise ignored),
10223 and the creation of the new one.
10229 Changed text files which are missing the usual final
10230 newline (either in the original or the modified
10235 Changes which are not represented, but which are not detected by
10236 <prgn>dpkg-source</prgn>, are:
10237 <list compact="compact">
10238 <item><p>Changing the permissions of files (other than
10239 <file>debian/rules</file>) and directories.</p></item>
10244 The <file>debian</file> directory and <file>debian/rules</file>
10245 are handled specially by <prgn>dpkg-source</prgn> - before
10246 applying the changes it will create the <file>debian</file>
10247 directory, and afterwards it will make
10248 <file>debian/rules</file> world-executable.
10254 <appendix id="pkg-controlfields">
10255 <heading>Control files and their fields (from old Packaging Manual)</heading>
10258 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10259 data in a common format, known as control files. Binary and
10260 source packages have control data as do the <file>.changes</file>
10261 files which control the installation of uploaded files, and
10262 <prgn>dpkg</prgn>'s internal databases are in a similar
10267 <heading>Syntax of control files</heading>
10270 See <ref id="controlsyntax">.
10274 It is important to note that there are several fields which
10275 are optional as far as <prgn>dpkg</prgn> and the related
10276 tools are concerned, but which must appear in every Debian
10277 package, or whose omission may cause problems.
10282 <heading>List of fields</heading>
10285 See <ref id="controlfieldslist">.
10289 This section now contains only the fields that didn't belong
10290 to the Policy manual.
10293 <sect1 id="pkg-f-Filename">
10294 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10297 These fields in <tt>Packages</tt> files give the
10298 filename(s) of (the parts of) a package in the
10299 distribution directories, relative to the root of the
10300 Debian hierarchy. If the package has been split into
10301 several parts the parts are all listed in order, separated
10306 <sect1 id="pkg-f-Size">
10307 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10310 These fields in <file>Packages</file> files give the size (in
10311 bytes, expressed in decimal) and MD5 checksum of the
10312 file(s) which make(s) up a binary package in the
10313 distribution. If the package is split into several parts
10314 the values for the parts are listed in order, separated by
10319 <sect1 id="pkg-f-Status">
10320 <heading><tt>Status</tt></heading>
10323 This field in <prgn>dpkg</prgn>'s status file records
10324 whether the user wants a package installed, removed or
10325 left alone, whether it is broken (requiring
10326 re-installation) or not and what its current state on the
10327 system is. Each of these pieces of information is a
10332 <sect1 id="pkg-f-Config-Version">
10333 <heading><tt>Config-Version</tt></heading>
10336 If a package is not installed or not configured, this
10337 field in <prgn>dpkg</prgn>'s status file records the last
10338 version of the package which was successfully
10343 <sect1 id="pkg-f-Conffiles">
10344 <heading><tt>Conffiles</tt></heading>
10347 This field in <prgn>dpkg</prgn>'s status file contains
10348 information about the automatically-managed configuration
10349 files held by a package. This field should <em>not</em>
10350 appear anywhere in a package!
10355 <heading>Obsolete fields</heading>
10358 These are still recognized by <prgn>dpkg</prgn> but should
10359 not appear anywhere any more.
10361 <taglist compact="compact">
10363 <tag><tt>Revision</tt></tag>
10364 <tag><tt>Package-Revision</tt></tag>
10365 <tag><tt>Package_Revision</tt></tag>
10367 The Debian revision part of the package version was
10368 at one point in a separate control file field. This
10369 field went through several names.
10372 <tag><tt>Recommended</tt></tag>
10373 <item>Old name for <tt>Recommends</tt>.</item>
10375 <tag><tt>Optional</tt></tag>
10376 <item>Old name for <tt>Suggests</tt>.</item>
10378 <tag><tt>Class</tt></tag>
10379 <item>Old name for <tt>Priority</tt>.</item>
10388 <appendix id="pkg-conffiles">
10389 <heading>Configuration file handling (from old Packaging Manual)</heading>
10392 <prgn>dpkg</prgn> can do a certain amount of automatic
10393 handling of package configuration files.
10397 Whether this mechanism is appropriate depends on a number of
10398 factors, but basically there are two approaches to any
10399 particular configuration file.
10403 The easy method is to ship a best-effort configuration in the
10404 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10405 handle updates. If the user is unlikely to want to edit the
10406 file, but you need them to be able to without losing their
10407 changes, and a new package with a changed version of the file
10408 is only released infrequently, this is a good approach.
10412 The hard method is to build the configuration file from
10413 scratch in the <prgn>postinst</prgn> script, and to take the
10414 responsibility for fixing any mistakes made in earlier
10415 versions of the package automatically. This will be
10416 appropriate if the file is likely to need to be different on
10420 <sect><heading>Automatic handling of configuration files by
10425 A package may contain a control area file called
10426 <tt>conffiles</tt>. This file should be a list of filenames
10427 of configuration files needing automatic handling, separated
10428 by newlines. The filenames should be absolute pathnames,
10429 and the files referred to should actually exist in the
10434 When a package is upgraded <prgn>dpkg</prgn> will process
10435 the configuration files during the configuration stage,
10436 shortly before it runs the package's <prgn>postinst</prgn>
10441 For each file it checks to see whether the version of the
10442 file included in the package is the same as the one that was
10443 included in the last version of the package (the one that is
10444 being upgraded from); it also compares the version currently
10445 installed on the system with the one shipped with the last
10450 If neither the user nor the package maintainer has changed
10451 the file, it is left alone. If one or the other has changed
10452 their version, then the changed version is preferred - i.e.,
10453 if the user edits their file, but the package maintainer
10454 doesn't ship a different version, the user's changes will
10455 stay, silently, but if the maintainer ships a new version
10456 and the user hasn't edited it the new version will be
10457 installed (with an informative message). If both have
10458 changed their version the user is prompted about the problem
10459 and must resolve the differences themselves.
10463 The comparisons are done by calculating the MD5 message
10464 digests of the files, and storing the MD5 of the file as it
10465 was included in the most recent version of the package.
10469 When a package is installed for the first time
10470 <prgn>dpkg</prgn> will install the file that comes with it,
10471 unless that would mean overwriting a file already on the
10476 However, note that <prgn>dpkg</prgn> will <em>not</em>
10477 replace a conffile that was removed by the user (or by a
10478 script). This is necessary because with some programs a
10479 missing file produces an effect hard or impossible to
10480 achieve in another way, so that a missing file needs to be
10481 kept that way if the user did it.
10485 Note that a package should <em>not</em> modify a
10486 <prgn>dpkg</prgn>-handled conffile in its maintainer
10487 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10488 the user confusing and possibly dangerous options for
10489 conffile update when the package is upgraded.</p>
10492 <sect><heading>Fully-featured maintainer script configuration
10497 For files which contain site-specific information such as
10498 the hostname and networking details and so forth, it is
10499 better to create the file in the package's
10500 <prgn>postinst</prgn> script.
10504 This will typically involve examining the state of the rest
10505 of the system to determine values and other information, and
10506 may involve prompting the user for some information which
10507 can't be obtained some other way.
10511 When using this method there are a couple of important
10512 issues which should be considered:
10516 If you discover a bug in the program which generates the
10517 configuration file, or if the format of the file changes
10518 from one version to the next, you will have to arrange for
10519 the postinst script to do something sensible - usually this
10520 will mean editing the installed configuration file to remove
10521 the problem or change the syntax. You will have to do this
10522 very carefully, since the user may have changed the file,
10523 perhaps to fix the very problem that your script is trying
10524 to deal with - you will have to detect these situations and
10525 deal with them correctly.
10529 If you do go down this route it's probably a good idea to
10530 make the program that generates the configuration file(s) a
10531 separate program in <file>/usr/sbin</file>, by convention called
10532 <file><var>package</var>config</file> and then run that if
10533 appropriate from the post-installation script. The
10534 <tt><var>package</var>config</tt> program should not
10535 unquestioningly overwrite an existing configuration - if its
10536 mode of operation is geared towards setting up a package for
10537 the first time (rather than any arbitrary reconfiguration
10538 later) you should have it check whether the configuration
10539 already exists, and require a <tt>--force</tt> flag to
10540 overwrite it.</p></sect>
10543 <appendix id="pkg-alternatives"><heading>Alternative versions of
10544 an interface - <prgn>update-alternatives</prgn> (from old
10549 When several packages all provide different versions of the
10550 same program or file it is useful to have the system select a
10551 default, but to allow the system administrator to change it
10552 and have their decisions respected.
10556 For example, there are several versions of the <prgn>vi</prgn>
10557 editor, and there is no reason to prevent all of them from
10558 being installed at once, each under their own name
10559 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10560 Nevertheless it is desirable to have the name <tt>vi</tt>
10561 refer to something, at least by default.
10565 If all the packages involved cooperate, this can be done with
10566 <prgn>update-alternatives</prgn>.
10570 Each package provides its own version under its own name, and
10571 calls <prgn>update-alternatives</prgn> in its postinst to
10572 register its version (and again in its prerm to deregister
10577 See the man page <manref name="update-alternatives"
10578 section="8"> for details.
10582 If <prgn>update-alternatives</prgn> does not seem appropriate
10583 you may wish to consider using diversions instead.</p>
10586 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10587 package's version of a file (from old Packaging Manual)
10591 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10592 when it reinstalls the package it belongs to, and to have it
10593 put the file from the package somewhere else instead.
10597 This can be used locally to override a package's version of a
10598 file, or by one package to override another's version (or
10599 provide a wrapper for it).
10603 Before deciding to use a diversion, read <ref
10604 id="pkg-alternatives"> to see if you really want a diversion
10605 rather than several alternative versions of a program.
10609 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10610 and updated by a special program <prgn>dpkg-divert</prgn>.
10611 Please see <manref name="dpkg-divert" section="8"> for full
10612 details of its operation.
10616 When a package wishes to divert a file from another, it should
10617 call <prgn>dpkg-divert</prgn> in its preinst to add the
10618 diversion and rename the existing file. For example,
10619 supposing that a <prgn>smailwrapper</prgn> package wishes to
10620 install a wrapper around <file>/usr/sbin/smail</file>:
10622 dpkg-divert --package smailwrapper --add --rename \
10623 --divert /usr/sbin/smail.real /usr/sbin/smail
10624 </example> The <tt>--package smailwrapper</tt> ensures that
10625 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10626 can bypass the diversion and get installed as the true version.
10627 It's safe to add the diversion unconditionally on upgrades since
10628 it will be left unchanged if it already exists, but
10629 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10630 message, make the command conditional on the version from which
10631 the package is being upgraded:
10633 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10634 dpkg-divert --package smailwrapper --add --rename \
10635 --divert /usr/sbin/smail.real /usr/sbin/smail
10637 </example> where <tt>1.0-2</tt> is the version at which the
10638 diversion was first added to the package. Running the command
10639 during abort-upgrade is pointless but harmless.
10643 The postrm has to do the reverse:
10645 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10646 dpkg-divert --package smailwrapper --remove --rename \
10647 --divert /usr/sbin/smail.real /usr/sbin/smail
10649 </example> If the diversion was added at a particular version, the
10650 postrm should also handle the failure case of upgrading from an
10651 older version (unless the older version is so old that direct
10652 upgrades are no longer supported):
10654 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10655 dpkg-divert --package smailwrapper --remove --rename \
10656 --divert /usr/sbin/smail.real /usr/sbin/smail
10658 </example> where <tt>1.02-2</tt> is the version at which the
10659 diversion was first added to the package. The postrm should not
10660 remove the diversion on upgrades both because there's no reason to
10661 remove the diversion only to immediately re-add it and since the
10662 postrm of the old package is run after unpacking so the removal of
10663 the diversion will fail.
10667 Do not attempt to divert a file which is vitally important for
10668 the system's operation - when using <prgn>dpkg-divert</prgn>
10669 there is a time, after it has been diverted but before
10670 <prgn>dpkg</prgn> has installed the new version, when the file
10671 does not exist.</p>
10676 <!-- Local variables: -->
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