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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a <tt>Pre-Depends</tt>, <tt>Depends</tt>,
480 <tt>Recommends</tt>, <tt>Build-Depends</tt>,
481 or <tt>Build-Depends-Indep</tt> relationship on a
482 non-<em>main</em> package unless a package
483 in <em>main</em> is listed as an alternative),
486 must not be so buggy that we refuse to support them,
490 must meet all policy requirements presented in this
499 <heading>The contrib archive area</heading>
502 Every package in <em>contrib</em> must comply with the DFSG.
506 In addition, the packages in <em>contrib</em>
507 <list compact="compact">
509 must not be so buggy that we refuse to support them,
513 must meet all policy requirements presented in this
521 Examples of packages which would be included in
522 <em>contrib</em> are:
523 <list compact="compact">
525 free packages which require <em>contrib</em>,
526 <em>non-free</em> packages or packages which are not
527 in our archive at all for compilation or execution,
531 wrapper packages or other sorts of free accessories for
538 <sect1 id="non-free">
539 <heading>The non-free archive area</heading>
542 Packages must be placed in <em>non-free</em> if they are
543 not compliant with the DFSG or are encumbered by patents
544 or other legal issues that make their distribution
549 In addition, the packages in <em>non-free</em>
550 <list compact="compact">
552 must not be so buggy that we refuse to support them,
556 must meet all policy requirements presented in this
557 manual that it is possible for them to meet.
559 It is possible that there are policy
560 requirements which the package is unable to
561 meet, for example, if the source is
562 unavailable. These situations will need to be
563 handled on a case-by-case basis.
572 <sect id="pkgcopyright">
573 <heading>Copyright considerations</heading>
576 Every package must be accompanied by a verbatim copy of its
577 copyright information and distribution license in the file
578 <file>/usr/share/doc/<var>package</var>/copyright</file>
579 (see <ref id="copyrightfile"> for further details).
583 We reserve the right to restrict files from being included
584 anywhere in our archives if
585 <list compact="compact">
587 their use or distribution would break a law,
590 there is an ethical conflict in their distribution or
594 we would have to sign a license for them, or
597 their distribution would conflict with other project
604 Programs whose authors encourage the user to make
605 donations are fine for the main distribution, provided
606 that the authors do not claim that not donating is
607 immoral, unethical, illegal or something similar; in such
608 a case they must go in <em>non-free</em>.
612 Packages whose copyright permission notices (or patent
613 problems) do not even allow redistribution of binaries
614 only, and where no special permission has been obtained,
615 must not be placed on the Debian FTP site and its mirrors
620 Note that under international copyright law (this applies
621 in the United States, too), <em>no</em> distribution or
622 modification of a work is allowed without an explicit
623 notice saying so. Therefore a program without a copyright
624 notice <em>is</em> copyrighted and you may not do anything
625 to it without risking being sued! Likewise if a program
626 has a copyright notice but no statement saying what is
627 permitted then nothing is permitted.
631 Many authors are unaware of the problems that restrictive
632 copyrights (or lack of copyright notices) can cause for
633 the users of their supposedly-free software. It is often
634 worthwhile contacting such authors diplomatically to ask
635 them to modify their license terms. However, this can be a
636 politically difficult thing to do and you should ask for
637 advice on the <tt>debian-legal</tt> mailing list first, as
642 When in doubt about a copyright, send mail to
643 <email>debian-legal@lists.debian.org</email>. Be prepared
644 to provide us with the copyright statement. Software
645 covered by the GPL, public domain software and BSD-like
646 copyrights are safe; be wary of the phrases "commercial
647 use prohibited" and "distribution restricted".
651 <sect id="subsections">
652 <heading>Sections</heading>
655 The packages in the archive areas <em>main</em>,
656 <em>contrib</em> and <em>non-free</em> are grouped further into
657 <em>sections</em> to simplify handling.
661 The archive area and section for each package should be
662 specified in the package's <tt>Section</tt> control record (see
663 <ref id="f-Section">). However, the maintainer of the Debian
664 archive may override this selection to ensure the consistency of
665 the Debian distribution. The <tt>Section</tt> field should be
667 <list compact="compact">
669 <em>section</em> if the package is in the
670 <em>main</em> archive area,
673 <em>area/section</em> if the package is in
674 the <em>contrib</em> or <em>non-free</em>
681 The Debian archive maintainers provide the authoritative
682 list of sections. At present, they are:
683 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
684 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
685 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
686 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
687 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
688 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
689 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
690 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
691 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
692 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
693 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
694 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
695 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
696 <em>zope</em>. The additional section <em>debian-installer</em>
697 contains special packages used by the installer and is not used
698 for normal Debian packages.
702 For more information about the sections and their definitions,
703 see the <url id="http://packages.debian.org/unstable/"
704 name="list of sections in unstable">.
708 <sect id="priorities">
709 <heading>Priorities</heading>
712 Each package should have a <em>priority</em> value, which is
713 included in the package's <em>control record</em>
714 (see <ref id="f-Priority">).
715 This information is used by the Debian package management tools to
716 separate high-priority packages from less-important packages.
720 The following <em>priority levels</em> are recognized by the
721 Debian package management tools.
723 <tag><tt>required</tt></tag>
725 Packages which are necessary for the proper
726 functioning of the system (usually, this means that
727 dpkg functionality depends on these packages).
728 Removing a <tt>required</tt> package may cause your
729 system to become totally broken and you may not even
730 be able to use <prgn>dpkg</prgn> to put things back,
731 so only do so if you know what you are doing. Systems
732 with only the <tt>required</tt> packages are probably
733 unusable, but they do have enough functionality to
734 allow the sysadmin to boot and install more software.
736 <tag><tt>important</tt></tag>
738 Important programs, including those which one would
739 expect to find on any Unix-like system. If the
740 expectation is that an experienced Unix person who
741 found it missing would say "What on earth is going on,
742 where is <prgn>foo</prgn>?", it must be an
743 <tt>important</tt> package.<footnote>
744 This is an important criterion because we are
745 trying to produce, amongst other things, a free
748 Other packages without which the system will not run
749 well or be usable must also have priority
750 <tt>important</tt>. This does
751 <em>not</em> include Emacs, the X Window System, TeX
752 or any other large applications. The
753 <tt>important</tt> packages are just a bare minimum of
754 commonly-expected and necessary tools.
756 <tag><tt>standard</tt></tag>
758 These packages provide a reasonably small but not too
759 limited character-mode system. This is what will be
760 installed by default if the user doesn't select anything
761 else. It doesn't include many large applications.
763 <tag><tt>optional</tt></tag>
765 (In a sense everything that isn't required is
766 optional, but that's not what is meant here.) This is
767 all the software that you might reasonably want to
768 install if you didn't know what it was and don't have
769 specialized requirements. This is a much larger system
770 and includes the X Window System, a full TeX
771 distribution, and many applications. Note that
772 optional packages should not conflict with each other.
774 <tag><tt>extra</tt></tag>
776 This contains all packages that conflict with others
777 with required, important, standard or optional
778 priorities, or are only likely to be useful if you
779 already know what they are or have specialized
780 requirements (such as packages containing only detached
787 Packages must not depend on packages with lower priority
788 values (excluding build-time dependencies). In order to
789 ensure this, the priorities of one or more packages may need
798 <heading>Binary packages</heading>
801 The Debian GNU/Linux distribution is based on the Debian
802 package management system, called <prgn>dpkg</prgn>. Thus,
803 all packages in the Debian distribution must be provided
804 in the <tt>.deb</tt> file format.
808 <heading>The package name</heading>
811 Every package must have a name that's unique within the Debian
816 The package name is included in the control field
817 <tt>Package</tt>, the format of which is described
818 in <ref id="f-Package">.
819 The package name is also included as a part of the file name
820 of the <tt>.deb</tt> file.
825 <heading>The version of a package</heading>
828 Every package has a version number recorded in its
829 <tt>Version</tt> control file field, described in
830 <ref id="f-Version">.
834 The package management system imposes an ordering on version
835 numbers, so that it can tell whether packages are being up- or
836 downgraded and so that package system front end applications
837 can tell whether a package it finds available is newer than
838 the one installed on the system. The version number format
839 has the most significant parts (as far as comparison is
840 concerned) at the beginning.
844 If an upstream package has problematic version numbers they
845 should be converted to a sane form for use in the
846 <tt>Version</tt> field.
850 <heading>Version numbers based on dates</heading>
853 In general, Debian packages should use the same version
854 numbers as the upstream sources.
858 However, in some cases where the upstream version number is
859 based on a date (e.g., a development "snapshot" release) the
860 package management system cannot handle these version
861 numbers without epochs. For example, dpkg will consider
862 "96May01" to be greater than "96Dec24".
866 To prevent having to use epochs for every new upstream
867 version, the date based portion of the version number
868 should be changed to the following format in such cases:
869 "19960501", "19961224". It is up to the maintainer whether
870 they want to bother the upstream maintainer to change
871 the version numbers upstream, too.
875 Note that other version formats based on dates which are
876 parsed correctly by the package management system should
877 <em>not</em> be changed.
881 Native Debian packages (i.e., packages which have been
882 written especially for Debian) whose version numbers include
883 dates should always use the "YYYYMMDD" format.
890 <heading>The maintainer of a package</heading>
893 Every package must have a Debian maintainer (the
894 maintainer may be one person or a group of people
895 reachable from a common email address, such as a mailing
896 list). The maintainer is responsible for ensuring that
897 the package is placed in the appropriate distributions.
901 The maintainer must be specified in the
902 <tt>Maintainer</tt> control field with their correct name
903 and a working email address. If one person maintains
904 several packages, they should try to avoid having
905 different forms of their name and email address in
906 the <tt>Maintainer</tt> fields of those packages.
910 The format of the <tt>Maintainer</tt> control field is
911 described in <ref id="f-Maintainer">.
915 If the maintainer of a package quits from the Debian
916 project, "Debian QA Group"
917 <email>packages@qa.debian.org</email> takes over the
918 maintainer-ship of the package until someone else
919 volunteers for that task. These packages are called
920 <em>orphaned packages</em>.<footnote>
921 The detailed procedure for doing this gracefully can
922 be found in the Debian Developer's Reference,
923 see <ref id="related">.
928 <sect id="descriptions">
929 <heading>The description of a package</heading>
932 Every Debian package must have an extended description
933 stored in the appropriate field of the control record.
934 The technical information about the format of the
935 <tt>Description</tt> field is in <ref id="f-Description">.
939 The description should describe the package (the program) to a
940 user (system administrator) who has never met it before so that
941 they have enough information to decide whether they want to
942 install it. This description should not just be copied verbatim
943 from the program's documentation.
947 Put important information first, both in the synopsis and
948 extended description. Sometimes only the first part of the
949 synopsis or of the description will be displayed. You can
950 assume that there will usually be a way to see the whole
951 extended description.
955 The description should also give information about the
956 significant dependencies and conflicts between this package
957 and others, so that the user knows why these dependencies and
958 conflicts have been declared.
962 Instructions for configuring or using the package should
963 not be included (that is what installation scripts,
964 manual pages, info files, etc., are for). Copyright
965 statements and other administrivia should not be included
966 either (that is what the copyright file is for).
969 <sect1 id="synopsis"><heading>The single line synopsis</heading>
972 The single line synopsis should be kept brief - certainly
977 Do not include the package name in the synopsis line. The
978 display software knows how to display this already, and you
979 do not need to state it. Remember that in many situations
980 the user may only see the synopsis line - make it as
981 informative as you can.
986 <sect1 id="extendeddesc"><heading>The extended description</heading>
989 Do not try to continue the single line synopsis into the
990 extended description. This will not work correctly when
991 the full description is displayed, and makes no sense
992 where only the summary (the single line synopsis) is
997 The extended description should describe what the package
998 does and how it relates to the rest of the system (in terms
999 of, for example, which subsystem it is which part of).
1003 The description field needs to make sense to anyone, even
1004 people who have no idea about any of the things the
1005 package deals with.<footnote>
1006 The blurb that comes with a program in its
1007 announcements and/or <prgn>README</prgn> files is
1008 rarely suitable for use in a description. It is
1009 usually aimed at people who are already in the
1010 community where the package is used.
1019 <heading>Dependencies</heading>
1022 Every package must specify the dependency information
1023 about other packages that are required for the first to
1028 For example, a dependency entry must be provided for any
1029 shared libraries required by a dynamically-linked executable
1030 binary in a package.
1034 Packages are not required to declare any dependencies they
1035 have on other packages which are marked <tt>Essential</tt>
1036 (see below), and should not do so unless they depend on a
1037 particular version of that package.<footnote>
1039 Essential is needed in part to avoid unresolvable dependency
1040 loops on upgrade. If packages add unnecessary dependencies
1041 on packages in this set, the chances that there
1042 <strong>will</strong> be an unresolvable dependency loop
1043 caused by forcing these Essential packages to be configured
1044 first before they need to be is greatly increased. It also
1045 increases the chances that frontends will be unable to
1046 <strong>calculate</strong> an upgrade path, even if one
1050 Also, functionality is rarely ever removed from the
1051 Essential set, but <em>packages</em> have been removed from
1052 the Essential set when the functionality moved to a
1053 different package. So depending on these packages <em>just
1054 in case</em> they stop being essential does way more harm
1061 Sometimes, a package requires another package to be installed
1062 <em>and</em> configured before it can be installed. In this
1063 case, you must specify a <tt>Pre-Depends</tt> entry for
1068 You should not specify a <tt>Pre-Depends</tt> entry for a
1069 package before this has been discussed on the
1070 <tt>debian-devel</tt> mailing list and a consensus about
1071 doing that has been reached.
1075 The format of the package interrelationship control fields is
1076 described in <ref id="relationships">.
1080 <sect id="virtual_pkg">
1081 <heading>Virtual packages</heading>
1084 Sometimes, there are several packages which offer
1085 more-or-less the same functionality. In this case, it's
1086 useful to define a <em>virtual package</em> whose name
1087 describes that common functionality. (The virtual
1088 packages only exist logically, not physically; that's why
1089 they are called <em>virtual</em>.) The packages with this
1090 particular function will then <em>provide</em> the virtual
1091 package. Thus, any other package requiring that function
1092 can simply depend on the virtual package without having to
1093 specify all possible packages individually.
1097 All packages should use virtual package names where
1098 appropriate, and arrange to create new ones if necessary.
1099 They should not use virtual package names (except privately,
1100 amongst a cooperating group of packages) unless they have
1101 been agreed upon and appear in the list of virtual package
1102 names. (See also <ref id="virtual">)
1106 The latest version of the authoritative list of virtual
1107 package names can be found in the <tt>debian-policy</tt> package.
1108 It is also available from the Debian web mirrors at
1109 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1110 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1114 The procedure for updating the list is described in the preface
1121 <heading>Base system</heading>
1124 The <tt>base system</tt> is a minimum subset of the Debian
1125 GNU/Linux system that is installed before everything else
1126 on a new system. Only very few packages are allowed to form
1127 part of the base system, in order to keep the required disk
1132 The base system consists of all those packages with priority
1133 <tt>required</tt> or <tt>important</tt>. Many of them will
1134 be tagged <tt>essential</tt> (see below).
1139 <heading>Essential packages</heading>
1142 Essential is defined as the minimal set of functionality that
1143 must be available and usable on the system at all times, even
1144 when packages are in an unconfigured (but unpacked) state.
1145 Packages are tagged <tt>essential</tt> for a system using the
1146 <tt>Essential</tt> control file field. The format of the
1147 <tt>Essential</tt> control field is described in <ref
1152 Since these packages cannot be easily removed (one has to
1153 specify an extra <em>force option</em> to
1154 <prgn>dpkg</prgn> to do so), this flag must not be used
1155 unless absolutely necessary. A shared library package
1156 must not be tagged <tt>essential</tt>; dependencies will
1157 prevent its premature removal, and we need to be able to
1158 remove it when it has been superseded.
1162 Since dpkg will not prevent upgrading of other packages
1163 while an <tt>essential</tt> package is in an unconfigured
1164 state, all <tt>essential</tt> packages must supply all of
1165 their core functionality even when unconfigured. If the
1166 package cannot satisfy this requirement it must not be
1167 tagged as essential, and any packages depending on this
1168 package must instead have explicit dependency fields as
1173 Maintainers should take great care in adding any programs,
1174 interfaces, or functionality to <tt>essential</tt> packages.
1175 Packages may assume that functionality provided by
1176 <tt>essential</tt> packages is always available without
1177 declaring explicit dependencies, which means that removing
1178 functionality from the Essential set is very difficult and is
1179 almost never done. Any capability added to an
1180 <tt>essential</tt> package therefore creates an obligation to
1181 support that capability as part of the Essential set in
1186 You must not tag any packages <tt>essential</tt> before
1187 this has been discussed on the <tt>debian-devel</tt>
1188 mailing list and a consensus about doing that has been
1193 <sect id="maintscripts">
1194 <heading>Maintainer Scripts</heading>
1197 The package installation scripts should avoid producing
1198 output which is unnecessary for the user to see and
1199 should rely on <prgn>dpkg</prgn> to stave off boredom on
1200 the part of a user installing many packages. This means,
1201 amongst other things, using the <tt>--quiet</tt> option on
1202 <prgn>install-info</prgn>.
1206 Errors which occur during the execution of an installation
1207 script must be checked and the installation must not
1208 continue after an error.
1212 Note that in general <ref id="scripts"> applies to package
1213 maintainer scripts, too.
1217 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1218 to another package without consulting the maintainer of that
1219 package first. When adding or removing diversions, package
1220 maintainer scripts must provide the <tt>--package</tt> flag
1221 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1225 All packages which supply an instance of a common command
1226 name (or, in general, filename) should generally use
1227 <prgn>update-alternatives</prgn>, so that they may be
1228 installed together. If <prgn>update-alternatives</prgn>
1229 is not used, then each package must use
1230 <tt>Conflicts</tt> to ensure that other packages are
1231 de-installed. (In this case, it may be appropriate to
1232 specify a conflict against earlier versions of something
1233 that previously did not use
1234 <prgn>update-alternatives</prgn>; this is an exception to
1235 the usual rule that versioned conflicts should be
1239 <sect1 id="maintscriptprompt">
1240 <heading>Prompting in maintainer scripts</heading>
1242 Package maintainer scripts may prompt the user if
1243 necessary. Prompting must be done by communicating
1244 through a program, such as <prgn>debconf</prgn>, which
1245 conforms to the Debian Configuration Management
1246 Specification, version 2 or higher.
1250 Packages which are essential, or which are dependencies of
1251 essential packages, may fall back on another prompting method
1252 if no such interface is available when they are executed.
1256 The Debian Configuration Management Specification is included
1257 in the <file>debconf_specification</file> files in the
1258 <package>debian-policy</package> package.
1259 It is also available from the Debian web mirrors at
1260 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1261 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1265 Packages which use the Debian Configuration Management
1266 Specification may contain an additional
1267 <prgn>config</prgn> script and a <tt>templates</tt>
1268 file in their control archive<footnote>
1269 The control.tar.gz inside the .deb.
1270 See <manref name="deb" section="5">.
1272 The <prgn>config</prgn> script might be run before the
1273 <prgn>preinst</prgn> script, and before the package is unpacked
1274 or any of its dependencies or pre-dependencies are satisfied.
1275 Therefore it must work using only the tools present in
1276 <em>essential</em> packages.<footnote>
1277 <package>Debconf</package> or another tool that
1278 implements the Debian Configuration Management
1279 Specification will also be installed, and any
1280 versioned dependencies on it will be satisfied
1281 before preconfiguration begins.
1286 Packages which use the Debian Configuration Management
1287 Specification must allow for translation of their user-visible
1288 messages by using a gettext-based system such as the one
1289 provided by the <package>po-debconf</package> package.
1293 Packages should try to minimize the amount of prompting
1294 they need to do, and they should ensure that the user
1295 will only ever be asked each question once. This means
1296 that packages should try to use appropriate shared
1297 configuration files (such as <file>/etc/papersize</file> and
1298 <file>/etc/news/server</file>), and shared
1299 <package>debconf</package> variables rather than each
1300 prompting for their own list of required pieces of
1305 It also means that an upgrade should not ask the same
1306 questions again, unless the user has used
1307 <tt>dpkg --purge</tt> to remove the package's configuration.
1308 The answers to configuration questions should be stored in an
1309 appropriate place in <file>/etc</file> so that the user can
1310 modify them, and how this has been done should be
1315 If a package has a vitally important piece of
1316 information to pass to the user (such as "don't run me
1317 as I am, you must edit the following configuration files
1318 first or you risk your system emitting badly-formatted
1319 messages"), it should display this in the
1320 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1321 prompt the user to hit return to acknowledge the
1322 message. Copyright messages do not count as vitally
1323 important (they belong in
1324 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1325 neither do instructions on how to use a program (these
1326 should be in on-line documentation, where all the users
1331 Any necessary prompting should almost always be confined
1332 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1333 script. If it is done in the <prgn>postinst</prgn>, it
1334 should be protected with a conditional so that
1335 unnecessary prompting doesn't happen if a package's
1336 installation fails and the <prgn>postinst</prgn> is
1337 called with <tt>abort-upgrade</tt>,
1338 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1348 <heading>Source packages</heading>
1350 <sect id="standardsversion">
1351 <heading>Standards conformance</heading>
1354 Source packages should specify the most recent version number
1355 of this policy document with which your package complied
1356 when it was last updated.
1360 This information may be used to file bug reports
1361 automatically if your package becomes too much out of date.
1365 The version is specified in the <tt>Standards-Version</tt>
1367 The format of the <tt>Standards-Version</tt> field is
1368 described in <ref id="f-Standards-Version">.
1372 You should regularly, and especially if your package has
1373 become out of date, check for the newest Policy Manual
1374 available and update your package, if necessary. When your
1375 package complies with the new standards you should update the
1376 <tt>Standards-Version</tt> source package field and
1377 release it.<footnote>
1378 See the file <file>upgrading-checklist</file> for
1379 information about policy which has changed between
1380 different versions of this document.
1386 <sect id="pkg-relations">
1387 <heading>Package relationships</heading>
1390 Source packages should specify which binary packages they
1391 require to be installed or not to be installed in order to
1392 build correctly. For example, if building a package
1393 requires a certain compiler, then the compiler should be
1394 specified as a build-time dependency.
1398 It is not necessary to explicitly specify build-time
1399 relationships on a minimal set of packages that are always
1400 needed to compile, link and put in a Debian package a
1401 standard "Hello World!" program written in C or C++. The
1402 required packages are called <em>build-essential</em>, and
1403 an informational list can be found in
1404 <file>/usr/share/doc/build-essential/list</file> (which is
1405 contained in the <tt>build-essential</tt>
1408 <list compact="compact">
1410 This allows maintaining the list separately
1411 from the policy documents (the list does not
1412 need the kind of control that the policy
1416 Having a separate package allows one to install
1417 the build-essential packages on a machine, as
1418 well as allowing other packages such as tasks to
1419 require installation of the build-essential
1420 packages using the depends relation.
1423 The separate package allows bug reports against
1424 the list to be categorized separately from
1425 the policy management process in the BTS.
1432 When specifying the set of build-time dependencies, one
1433 should list only those packages explicitly required by the
1434 build. It is not necessary to list packages which are
1435 required merely because some other package in the list of
1436 build-time dependencies depends on them.<footnote>
1437 The reason for this is that dependencies change, and
1438 you should list all those packages, and <em>only</em>
1439 those packages that <em>you</em> need directly. What
1440 others need is their business. For example, if you
1441 only link against <file>libimlib</file>, you will need to
1442 build-depend on <package>libimlib2-dev</package> but
1443 not against any <tt>libjpeg*</tt> packages, even
1444 though <tt>libimlib2-dev</tt> currently depends on
1445 them: installation of <package>libimlib2-dev</package>
1446 will automatically ensure that all of its run-time
1447 dependencies are satisfied.
1452 If build-time dependencies are specified, it must be
1453 possible to build the package and produce working binaries
1454 on a system with only essential and build-essential
1455 packages installed and also those required to satisfy the
1456 build-time relationships (including any implied
1457 relationships). In particular, this means that version
1458 clauses should be used rigorously in build-time
1459 relationships so that one cannot produce bad or
1460 inconsistently configured packages when the relationships
1461 are properly satisfied.
1465 <ref id="relationships"> explains the technical details.
1470 <heading>Changes to the upstream sources</heading>
1473 If changes to the source code are made that are not
1474 specific to the needs of the Debian system, they should be
1475 sent to the upstream authors in whatever form they prefer
1476 so as to be included in the upstream version of the
1481 If you need to configure the package differently for
1482 Debian or for Linux, and the upstream source doesn't
1483 provide a way to do so, you should add such configuration
1484 facilities (for example, a new <prgn>autoconf</prgn> test
1485 or <tt>#define</tt>) and send the patch to the upstream
1486 authors, with the default set to the way they originally
1487 had it. You can then easily override the default in your
1488 <file>debian/rules</file> or wherever is appropriate.
1492 You should make sure that the <prgn>configure</prgn> utility
1493 detects the correct architecture specification string
1494 (refer to <ref id="arch-spec"> for details).
1498 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1499 <prgn>configure</prgn> scripts are used, you should edit the
1500 <file>.in</file> files rather than editing the
1501 <prgn>Makefile</prgn> directly. This allows the user to
1502 reconfigure the package if necessary. You should
1503 <em>not</em> configure the package and edit the generated
1504 <prgn>Makefile</prgn>! This makes it impossible for someone
1505 else to later reconfigure the package without losing the
1511 <sect id="dpkgchangelog">
1512 <heading>Debian changelog: <file>debian/changelog</file></heading>
1515 Changes in the Debian version of the package should be
1516 briefly explained in the Debian changelog file
1517 <file>debian/changelog</file>.<footnote>
1519 Mistakes in changelogs are usually best rectified by
1520 making a new changelog entry rather than "rewriting
1521 history" by editing old changelog entries.
1524 This includes modifications
1525 made in the Debian package compared to the upstream one
1526 as well as other changes and updates to the package.
1528 Although there is nothing stopping an author who is also
1529 the Debian maintainer from using this changelog for all
1530 their changes, it will have to be renamed if the Debian
1531 and upstream maintainers become different people. In such
1532 a case, however, it might be better to maintain the package
1533 as a non-native package.
1538 The format of the <file>debian/changelog</file> allows the
1539 package building tools to discover which version of the package
1540 is being built and find out other release-specific information.
1544 That format is a series of entries like this:
1546 <example compact="compact">
1547 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1549 [optional blank line(s), stripped]
1551 * <var>change details</var>
1552 <var>more change details</var>
1554 [blank line(s), included in output of dpkg-parsechangelog]
1556 * <var>even more change details</var>
1558 [optional blank line(s), stripped]
1560 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1565 <var>package</var> and <var>version</var> are the source
1566 package name and version number.
1570 <var>distribution(s)</var> lists the distributions where
1571 this version should be installed when it is uploaded - it
1572 is copied to the <tt>Distribution</tt> field in the
1573 <file>.changes</file> file. See <ref id="f-Distribution">.
1577 <var>urgency</var> is the value for the <tt>Urgency</tt>
1578 field in the <file>.changes</file> file for the upload
1579 (see <ref id="f-Urgency">). It is not possible to specify
1580 an urgency containing commas; commas are used to separate
1581 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1582 <prgn>dpkg</prgn> changelog format (though there is
1583 currently only one useful <var>keyword</var>,
1588 The change details may in fact be any series of lines
1589 starting with at least two spaces, but conventionally each
1590 change starts with an asterisk and a separating space and
1591 continuation lines are indented so as to bring them in
1592 line with the start of the text above. Blank lines may be
1593 used here to separate groups of changes, if desired.
1597 If this upload resolves bugs recorded in the Bug Tracking
1598 System (BTS), they may be automatically closed on the
1599 inclusion of this package into the Debian archive by
1600 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1601 in the change details.<footnote>
1602 To be precise, the string should match the following
1603 Perl regular expression:
1605 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1607 Then all of the bug numbers listed will be closed by the
1608 archive maintenance script (<prgn>katie</prgn>) using the
1609 <var>version</var> of the changelog entry.
1611 This information is conveyed via the <tt>Closes</tt> field
1612 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1616 The maintainer name and email address used in the changelog
1617 should be the details of the person uploading <em>this</em>
1618 version. They are <em>not</em> necessarily those of the
1619 usual package maintainer. The information here will be
1620 copied to the <tt>Changed-By</tt> field in the
1621 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1622 and then later used to send an acknowledgement when the
1623 upload has been installed.
1627 The <var>date</var> has the following format<footnote>
1628 This is the same as the format generated by <tt>date
1630 </footnote> (compatible and with the same semantics of
1631 RFC 2822 and RFC 5322):
1632 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1634 <list compact="compact">
1636 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1639 dd is a one- or two-digit day of the month (01-31)
1642 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1645 <item>yyyy is the four-digit year (e.g. 2010)</item>
1646 <item>hh is the two-digit hour (00-23)</item>
1647 <item>mm is the two-digit minutes (00-59)</item>
1648 <item>ss is the two-digit seconds (00-60)</item>
1650 +zzzz or -zzzz is the the time zone offset from Coordinated
1651 Universal Time (UTC). "+" indicates that the time is ahead
1652 of (i.e., east of) UTC and "-" indicates that the time is
1653 behind (i.e., west of) UTC. The first two digits indicate
1654 the hour difference from UTC and the last two digits
1655 indicate the number of additional minutes difference from
1656 UTC. The last two digits must be in the range 00-59.
1662 The first "title" line with the package name must start
1663 at the left hand margin. The "trailer" line with the
1664 maintainer and date details must be preceded by exactly
1665 one space. The maintainer details and the date must be
1666 separated by exactly two spaces.
1670 The entire changelog must be encoded in UTF-8.
1674 For more information on placement of the changelog files
1675 within binary packages, please see <ref id="changelogs">.
1679 <sect id="dpkgcopyright">
1680 <heading>Copyright: <file>debian/copyright</file></heading>
1682 Every package must be accompanied by a verbatim copy of its
1683 copyright information and distribution license in the file
1684 <file>/usr/share/doc/<var>package</var>/copyright</file>
1685 (see <ref id="copyrightfile"> for further details). Also see
1686 <ref id="pkgcopyright"> for further considerations related
1687 to copyrights for packages.
1691 <heading>Error trapping in makefiles</heading>
1694 When <prgn>make</prgn> invokes a command in a makefile
1695 (including your package's upstream makefiles and
1696 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1697 means that <prgn>sh</prgn>'s usual bad error handling
1698 properties apply: if you include a miniature script as one
1699 of the commands in your makefile you'll find that if you
1700 don't do anything about it then errors are not detected
1701 and <prgn>make</prgn> will blithely continue after
1706 Every time you put more than one shell command (this
1707 includes using a loop) in a makefile command you
1708 must make sure that errors are trapped. For
1709 simple compound commands, such as changing directory and
1710 then running a program, using <tt>&&</tt> rather
1711 than semicolon as a command separator is sufficient. For
1712 more complex commands including most loops and
1713 conditionals you should include a separate <tt>set -e</tt>
1714 command at the start of every makefile command that's
1715 actually one of these miniature shell scripts.
1719 <sect id="timestamps">
1720 <heading>Time Stamps</heading>
1722 Maintainers should preserve the modification times of the
1723 upstream source files in a package, as far as is reasonably
1725 The rationale is that there is some information conveyed
1726 by knowing the age of the file, for example, you could
1727 recognize that some documentation is very old by looking
1728 at the modification time, so it would be nice if the
1729 modification time of the upstream source would be
1735 <sect id="restrictions">
1736 <heading>Restrictions on objects in source packages</heading>
1739 The source package may not contain any hard links<footnote>
1741 This is not currently detected when building source
1742 packages, but only when extracting
1746 Hard links may be permitted at some point in the
1747 future, but would require a fair amount of
1750 </footnote>, device special files, sockets or setuid or
1751 setgid files.<footnote>
1752 Setgid directories are allowed.
1757 <sect id="debianrules">
1758 <heading>Main building script: <file>debian/rules</file></heading>
1761 This file must be an executable makefile, and contains the
1762 package-specific recipes for compiling the package and
1763 building binary package(s) from the source.
1767 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1768 so that it can be invoked by saying its name rather than
1769 invoking <prgn>make</prgn> explicitly. That is, invoking
1770 either of <tt>make -f debian/rules <em>args...</em></tt>
1771 or <tt>./debian/rules <em>args...</em></tt> must result in
1776 Since an interactive <file>debian/rules</file> script makes it
1777 impossible to auto-compile that package and also makes it
1778 hard for other people to reproduce the same binary
1779 package, all <em>required targets</em> must be
1780 non-interactive. At a minimum, required targets are the
1781 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1782 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1783 <em>binary-indep</em>, and <em>build</em>. It also follows
1784 that any target that these targets depend on must also be
1789 The targets are as follows (required unless stated otherwise):
1791 <tag><tt>build</tt></tag>
1794 The <tt>build</tt> target should perform all the
1795 configuration and compilation of the package.
1796 If a package has an interactive pre-build
1797 configuration routine, the Debian source package
1798 must either be built after this has taken place (so
1799 that the binary package can be built without rerunning
1800 the configuration) or the configuration routine
1801 modified to become non-interactive. (The latter is
1802 preferable if there are architecture-specific features
1803 detected by the configuration routine.)
1807 For some packages, notably ones where the same
1808 source tree is compiled in different ways to produce
1809 two binary packages, the <tt>build</tt> target
1810 does not make much sense. For these packages it is
1811 good enough to provide two (or more) targets
1812 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1813 for each of the ways of building the package, and a
1814 <tt>build</tt> target that does nothing. The
1815 <tt>binary</tt> target will have to build the
1816 package in each of the possible ways and make the
1817 binary package out of each.
1821 The <tt>build</tt> target must not do anything
1822 that might require root privilege.
1826 The <tt>build</tt> target may need to run the
1827 <tt>clean</tt> target first - see below.
1831 When a package has a configuration and build routine
1832 which takes a long time, or when the makefiles are
1833 poorly designed, or when <tt>build</tt> needs to
1834 run <tt>clean</tt> first, it is a good idea to
1835 <tt>touch build</tt> when the build process is
1836 complete. This will ensure that if <tt>debian/rules
1837 build</tt> is run again it will not rebuild the whole
1839 Another common way to do this is for <tt>build</tt>
1840 to depend on <prgn>build-stamp</prgn> and to do
1841 nothing else, and for the <prgn>build-stamp</prgn>
1842 target to do the building and to <tt>touch
1843 build-stamp</tt> on completion. This is
1844 especially useful if the build routine creates a
1845 file or directory called <tt>build</tt>; in such a
1846 case, <tt>build</tt> will need to be listed as
1847 a phony target (i.e., as a dependency of the
1848 <tt>.PHONY</tt> target). See the documentation of
1849 <prgn>make</prgn> for more information on phony
1855 <tag><tt>build-arch</tt> (optional),
1856 <tt>build-indep</tt> (optional)
1860 A package may also provide both of the targets
1861 <tt>build-arch</tt> and <tt>build-indep</tt>.
1862 The <tt>build-arch</tt> target, if provided, should
1863 perform all the configuration and compilation required for
1864 producing all architecture-dependant binary packages
1865 (those packages for which the body of the
1866 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1867 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1868 target, if provided, should perform all the configuration
1869 and compilation required for producing all
1870 architecture-independent binary packages (those packages
1871 for which the body of the <tt>Architecture</tt> field
1872 in <tt>debian/control</tt> is <tt>all</tt>).
1873 The <tt>build</tt> target should depend on those of the
1874 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1875 are provided in the rules file.<footnote>
1876 The intent of this split is so that binary-only builds
1877 need not install the dependencies required for
1878 the <tt>build-indep</tt> target. However, this is not
1879 yet used in practice since <tt>dpkg-buildpackage
1880 -B</tt>, and therefore the autobuilders,
1881 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1882 due to the difficulties in determining whether the
1883 optional <tt>build-arch</tt> target exists.
1888 If one or both of the targets <tt>build-arch</tt> and
1889 <tt>build-indep</tt> are not provided, then invoking
1890 <file>debian/rules</file> with one of the not-provided
1891 targets as arguments should produce a exit status code
1892 of 2. Usually this is provided automatically by make
1893 if the target is missing.
1897 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1898 must not do anything that might require root privilege.
1902 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1903 <tt>binary-indep</tt>
1907 The <tt>binary</tt> target must be all that is
1908 necessary for the user to build the binary package(s)
1909 produced from this source package. It is
1910 split into two parts: <prgn>binary-arch</prgn> builds
1911 the binary packages which are specific to a particular
1912 architecture, and <tt>binary-indep</tt> builds
1913 those which are not.
1916 <tt>binary</tt> may be (and commonly is) a target with
1917 no commands which simply depends on
1918 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1921 Both <tt>binary-*</tt> targets should depend on the
1922 <tt>build</tt> target, or on the appropriate
1923 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1924 provided, so that the package is built if it has not
1925 been already. It should then create the relevant
1926 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1927 make their control files and <prgn>dpkg-deb</prgn> to
1928 build them and place them in the parent of the top
1933 Both the <tt>binary-arch</tt> and
1934 <tt>binary-indep</tt> targets <em>must</em> exist.
1935 If one of them has nothing to do (which will always be
1936 the case if the source generates only a single binary
1937 package, whether architecture-dependent or not), it
1938 must still exist and must always succeed.
1942 The <tt>binary</tt> targets must be invoked as
1944 The <prgn>fakeroot</prgn> package often allows one
1945 to build a package correctly even without being
1951 <tag><tt>clean</tt></tag>
1954 This must undo any effects that the <tt>build</tt>
1955 and <tt>binary</tt> targets may have had, except
1956 that it should leave alone any output files created in
1957 the parent directory by a run of a <tt>binary</tt>
1962 If a <tt>build</tt> file is touched at the end of
1963 the <tt>build</tt> target, as suggested above, it
1964 should be removed as the first action that
1965 <tt>clean</tt> performs, so that running
1966 <tt>build</tt> again after an interrupted
1967 <tt>clean</tt> doesn't think that everything is
1972 The <tt>clean</tt> target may need to be
1973 invoked as root if <tt>binary</tt> has been
1974 invoked since the last <tt>clean</tt>, or if
1975 <tt>build</tt> has been invoked as root (since
1976 <tt>build</tt> may create directories, for
1981 <tag><tt>get-orig-source</tt> (optional)</tag>
1984 This target fetches the most recent version of the
1985 original source package from a canonical archive site
1986 (via FTP or WWW, for example), does any necessary
1987 rearrangement to turn it into the original source
1988 tar file format described below, and leaves it in the
1993 This target may be invoked in any directory, and
1994 should take care to clean up any temporary files it
1999 This target is optional, but providing it if
2000 possible is a good idea.
2004 <tag><tt>patch</tt> (optional)</tag>
2007 This target performs whatever additional actions are
2008 required to make the source ready for editing (unpacking
2009 additional upstream archives, applying patches, etc.).
2010 It is recommended to be implemented for any package where
2011 <tt>dpkg-source -x</tt> does not result in source ready
2012 for additional modification. See
2013 <ref id="readmesource">.
2019 The <tt>build</tt>, <tt>binary</tt> and
2020 <tt>clean</tt> targets must be invoked with the current
2021 directory being the package's top-level directory.
2026 Additional targets may exist in <file>debian/rules</file>,
2027 either as published or undocumented interfaces or for the
2028 package's internal use.
2032 The architectures we build on and build for are determined
2033 by <prgn>make</prgn> variables using the utility
2034 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2035 You can determine the
2036 Debian architecture and the GNU style architecture
2037 specification string for the build machine (the machine type
2038 we are building on) as well as for the host machine (the
2039 machine type we are building for). Here is a list of
2040 supported <prgn>make</prgn> variables:
2041 <list compact="compact">
2043 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2046 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2049 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2052 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2053 specification string)
2056 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2057 <tt>DEB_*_GNU_TYPE</tt>)
2060 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2061 <tt>DEB_*_GNU_TYPE</tt>)
2063 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2064 the build machine or <tt>HOST</tt> for specification of the
2069 Backward compatibility can be provided in the rules file
2070 by setting the needed variables to suitable default
2071 values; please refer to the documentation of
2072 <prgn>dpkg-architecture</prgn> for details.
2076 It is important to understand that the <tt>DEB_*_ARCH</tt>
2077 string only determines which Debian architecture we are
2078 building on or for. It should not be used to get the CPU
2079 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2080 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2081 GNU style variables should generally only be used with upstream
2085 <sect1 id="debianrules-options">
2086 <heading><file>debian/rules</file> and
2087 <tt>DEB_BUILD_OPTIONS</tt></heading>
2090 Supporting the standardized environment variable
2091 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2092 contain several flags to change how a package is compiled and
2093 built. Each flag must be in the form <var>flag</var> or
2094 <var>flag</var>=<var>options</var>. If multiple flags are
2095 given, they must be separated by whitespace.<footnote>
2096 Some packages support any delimiter, but whitespace is the
2097 easiest to parse inside a makefile and avoids ambiguity with
2098 flag values that contain commas.
2100 <var>flag</var> must start with a lowercase letter
2101 (<tt>a-z</tt>) and consist only of lowercase letters,
2102 numbers (<tt>0-9</tt>), and the characters
2103 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2104 <var>options</var> must not contain whitespace. The same
2105 tag should not be given multiple times with conflicting
2106 values. Package maintainers may assume that
2107 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2111 The meaning of the following tags has been standardized:
2115 This tag says to not run any build-time test suite
2116 provided by the package.
2120 The presence of this tag means that the package should
2121 be compiled with a minimum of optimization. For C
2122 programs, it is best to add <tt>-O0</tt> to
2123 <tt>CFLAGS</tt> (although this is usually the default).
2124 Some programs might fail to build or run at this level
2125 of optimization; it may be necessary to use
2126 <tt>-O1</tt>, for example.
2130 This tag means that the debugging symbols should not be
2131 stripped from the binary during installation, so that
2132 debugging information may be included in the package.
2134 <tag>parallel=n</tag>
2136 This tag means that the package should be built using up
2137 to <tt>n</tt> parallel processes if the package build
2138 system supports this.<footnote>
2139 Packages built with <tt>make</tt> can often implement
2140 this by passing the <tt>-j</tt><var>n</var> option to
2143 If the package build system does not support parallel
2144 builds, this string must be ignored. If the package
2145 build system only supports a lower level of concurrency
2146 than <var>n</var>, the package should be built using as
2147 many parallel processes as the package build system
2148 supports. It is up to the package maintainer to decide
2149 whether the package build times are long enough and the
2150 package build system is robust enough to make supporting
2151 parallel builds worthwhile.
2157 Unknown flags must be ignored by <file>debian/rules</file>.
2161 The following makefile snippet is an example of how one may
2162 implement the build options; you will probably have to
2163 massage this example in order to make it work for your
2165 <example compact="compact">
2168 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2169 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2170 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2171 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2173 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2178 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2179 INSTALL_PROGRAM += -s
2181 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2182 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2183 MAKEFLAGS += -j$(NUMJOBS)
2188 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2189 # Code to run the package test suite.
2196 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2197 <sect id="substvars">
2198 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2201 When <prgn>dpkg-gencontrol</prgn>,
2202 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2203 generate control files they perform variable substitutions
2204 on their output just before writing it. Variable
2205 substitutions have the form <tt>${<var>variable</var>}</tt>.
2206 The optional file <file>debian/substvars</file> contains
2207 variable substitutions to be used; variables can also be set
2208 directly from <file>debian/rules</file> using the <tt>-V</tt>
2209 option to the source packaging commands, and certain
2210 predefined variables are also available.
2214 The <file>debian/substvars</file> file is usually generated and
2215 modified dynamically by <file>debian/rules</file> targets, in
2216 which case it must be removed by the <tt>clean</tt> target.
2220 See <manref name="deb-substvars" section="5"> for full
2221 details about source variable substitutions, including the
2222 format of <file>debian/substvars</file>.</p>
2225 <sect id="debianwatch">
2226 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2229 This is an optional, recommended control file for the
2230 <tt>uscan</tt> utility which defines how to automatically
2231 scan ftp or http sites for newly available updates of the
2232 package. This is used by <url id="
2233 http://dehs.alioth.debian.org/"> and other Debian QA tools
2234 to help with quality control and maintenance of the
2235 distribution as a whole.
2240 <sect id="debianfiles">
2241 <heading>Generated files list: <file>debian/files</file></heading>
2244 This file is not a permanent part of the source tree; it
2245 is used while building packages to record which files are
2246 being generated. <prgn>dpkg-genchanges</prgn> uses it
2247 when it generates a <file>.changes</file> file.
2251 It should not exist in a shipped source package, and so it
2252 (and any backup files or temporary files such as
2253 <file>files.new</file><footnote>
2254 <file>files.new</file> is used as a temporary file by
2255 <prgn>dpkg-gencontrol</prgn> and
2256 <prgn>dpkg-distaddfile</prgn> - they write a new
2257 version of <tt>files</tt> here before renaming it,
2258 to avoid leaving a corrupted copy if an error
2260 </footnote>) should be removed by the
2261 <tt>clean</tt> target. It may also be wise to
2262 ensure a fresh start by emptying or removing it at the
2263 start of the <tt>binary</tt> target.
2267 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2268 package, it adds an entry to <file>debian/files</file> for the
2269 <file>.deb</file> file that will be created when <tt>dpkg-deb
2270 --build</tt> is run for that binary package. So for most
2271 packages all that needs to be done with this file is to
2272 delete it in the <tt>clean</tt> target.
2276 If a package upload includes files besides the source
2277 package and any binary packages whose control files were
2278 made with <prgn>dpkg-gencontrol</prgn> then they should be
2279 placed in the parent of the package's top-level directory
2280 and <prgn>dpkg-distaddfile</prgn> should be called to add
2281 the file to the list in <file>debian/files</file>.</p>
2284 <sect id="embeddedfiles">
2285 <heading>Convenience copies of code</heading>
2288 Some software packages include in their distribution convenience
2289 copies of code from other software packages, generally so that
2290 users compiling from source don't have to download multiple
2291 packages. Debian packages should not make use of these
2292 convenience copies unless the included package is explicitly
2293 intended to be used in this way.<footnote>
2294 For example, parts of the GNU build system work like this.
2296 If the included code is already in the Debian archive in the
2297 form of a library, the Debian packaging should ensure that
2298 binary packages reference the libraries already in Debian and
2299 the convenience copy is not used. If the included code is not
2300 already in Debian, it should be packaged separately as a
2301 prerequisite if possible.
2303 Having multiple copies of the same code in Debian is
2304 inefficient, often creates either static linking or shared
2305 library conflicts, and, most importantly, increases the
2306 difficulty of handling security vulnerabilities in the
2312 <sect id="readmesource">
2313 <heading>Source package handling:
2314 <file>debian/README.source</file></heading>
2317 If running <prgn>dpkg-source -x</prgn> on a source package
2318 doesn't produce the source of the package, ready for editing,
2319 and allow one to make changes and run
2320 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2321 without taking any additional steps, creating a
2322 <file>debian/README.source</file> documentation file is
2323 recommended. This file should explain how to do all of the
2326 <item>Generate the fully patched source, in a form ready for
2327 editing, that would be built to create Debian
2328 packages. Doing this with a <tt>patch</tt> target in
2329 <file>debian/rules</file> is recommended; see
2330 <ref id="debianrules">.</item>
2331 <item>Modify the source and save those modifications so that
2332 they will be applied when building the package.</item>
2333 <item>Remove source modifications that are currently being
2334 applied when building the package.</item>
2335 <item>Optionally, document what steps are necessary to
2336 upgrade the Debian source package to a new upstream version,
2337 if applicable.</item>
2339 This explanation should include specific commands and mention
2340 any additional required Debian packages. It should not assume
2341 familiarity with any specific Debian packaging system or patch
2346 This explanation may refer to a documentation file installed by
2347 one of the package's build dependencies provided that the
2348 referenced documentation clearly explains these tasks and is not
2349 a general reference manual.
2353 <file>debian/README.source</file> may also include any other
2354 information that would be helpful to someone modifying the
2355 source package. Even if the package doesn't fit the above
2356 description, maintainers are encouraged to document in a
2357 <file>debian/README.source</file> file any source package with a
2358 particularly complex or unintuitive source layout or build
2359 system (for example, a package that builds the same source
2360 multiple times to generate different binary packages).
2366 <chapt id="controlfields">
2367 <heading>Control files and their fields</heading>
2370 The package management system manipulates data represented in
2371 a common format, known as <em>control data</em>, stored in
2372 <em>control files</em>.
2373 Control files are used for source packages, binary packages and
2374 the <file>.changes</file> files which control the installation
2375 of uploaded files<footnote>
2376 <prgn>dpkg</prgn>'s internal databases are in a similar
2381 <sect id="controlsyntax">
2382 <heading>Syntax of control files</heading>
2385 A control file consists of one or more paragraphs of
2387 The paragraphs are also sometimes referred to as stanzas.
2389 The paragraphs are separated by blank lines. Some control
2390 files allow only one paragraph; others allow several, in
2391 which case each paragraph usually refers to a different
2392 package. (For example, in source packages, the first
2393 paragraph refers to the source package, and later paragraphs
2394 refer to binary packages generated from the source.)
2398 Each paragraph consists of a series of data fields; each
2399 field consists of the field name, followed by a colon and
2400 then the data/value associated with that field. It ends at
2401 the end of the (logical) line. Horizontal whitespace
2402 (spaces and tabs) may occur immediately before or after the
2403 value and is ignored there; it is conventional to put a
2404 single space after the colon. For example, a field might
2406 <example compact="compact">
2409 the field name is <tt>Package</tt> and the field value
2414 A paragraph must not contain more than one instance of a
2415 particular field name.
2419 Many fields' values may span several lines; in this case
2420 each continuation line must start with a space or a tab.
2421 Any trailing spaces or tabs at the end of individual
2422 lines of a field value are ignored.
2426 In fields where it is specified that lines may not wrap,
2427 only a single line of data is allowed and whitespace is not
2428 significant in a field body. Whitespace must not appear
2429 inside names (of packages, architectures, files or anything
2430 else) or version numbers, or between the characters of
2431 multi-character version relationships.
2435 Field names are not case-sensitive, but it is usual to
2436 capitalize the field names using mixed case as shown below.
2437 Field values are case-sensitive unless the description of the
2438 field says otherwise.
2442 Blank lines, or lines consisting only of spaces and tabs,
2443 are not allowed within field values or between fields - that
2444 would mean a new paragraph.
2448 All control files must be encoded in UTF-8.
2452 <sect id="sourcecontrolfiles">
2453 <heading>Source package control files -- <file>debian/control</file></heading>
2456 The <file>debian/control</file> file contains the most vital
2457 (and version-independent) information about the source package
2458 and about the binary packages it creates.
2462 The first paragraph of the control file contains information about
2463 the source package in general. The subsequent sets each describe a
2464 binary package that the source tree builds.
2468 The fields in the general paragraph (the first one, for the source
2471 <list compact="compact">
2472 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2474 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2475 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2476 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2477 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2478 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2479 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2484 The fields in the binary package paragraphs are:
2486 <list compact="compact">
2487 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2490 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2491 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2492 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2493 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2499 The syntax and semantics of the fields are described below.
2503 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2504 generate control files for binary packages (see below), by
2505 <prgn>dpkg-genchanges</prgn> to generate the
2506 <file>.changes</file> file to accompany the upload, and by
2507 <prgn>dpkg-source</prgn> when it creates the
2508 <file>.dsc</file> source control file as part of a source
2509 archive. Many fields are permitted to span multiple lines in
2510 <file>debian/control</file> but not in any other control
2511 file. These tools are responsible for removing the line
2512 breaks from such fields when using fields from
2513 <file>debian/control</file> to generate other control files.
2517 The fields here may contain variable references - their
2518 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2519 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2520 when they generate output control files.
2521 See <ref id="substvars"> for details.
2525 In addition to the control file syntax described <qref
2526 id="controlsyntax">above</qref>, this file may also contain
2527 comment lines starting with <tt>#</tt> without any preceding
2528 whitespace. All such lines are ignored, even in the middle of
2529 continuation lines for a multiline field, and do not end a
2535 <sect id="binarycontrolfiles">
2536 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2539 The <file>DEBIAN/control</file> file contains the most vital
2540 (and version-dependent) information about a binary package. It
2541 consists of a single paragraph.
2545 The fields in this file are:
2547 <list compact="compact">
2548 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2550 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2552 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2553 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2554 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2555 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2556 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2557 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2558 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2559 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2564 <sect id="debiansourcecontrolfiles">
2565 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2568 This file consists of a single paragraph, possibly surrounded by
2569 a PGP signature. The fields of that paragraph are listed below.
2570 Their syntax is described above, in <ref id="pkg-controlfields">.
2572 <list compact="compact">
2573 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2575 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2576 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2577 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2580 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2581 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2582 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2583 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2584 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2585 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2590 The source package control file is generated by
2591 <prgn>dpkg-source</prgn> when it builds the source
2592 archive, from other files in the source package,
2593 described above. When unpacking, it is checked against
2594 the files and directories in the other parts of the
2600 <sect id="debianchangesfiles">
2601 <heading>Debian changes files -- <file>.changes</file></heading>
2604 The <file>.changes</file> files are used by the Debian archive
2605 maintenance software to process updates to packages. They
2606 consist of a single paragraph, possibly surrounded by a PGP
2607 signature. That paragraph contains information from the
2608 <file>debian/control</file> file and other data about the
2609 source package gathered via <file>debian/changelog</file>
2610 and <file>debian/rules</file>.
2614 <file>.changes</file> files have a format version that is
2615 incremented whenever the documented fields or their meaning
2616 change. This document describes format &changesversion;.
2620 The fields in this file are:
2622 <list compact="compact">
2623 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2631 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2633 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2634 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2635 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2636 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2637 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2638 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2643 <sect id="controlfieldslist">
2644 <heading>List of fields</heading>
2646 <sect1 id="f-Source">
2647 <heading><tt>Source</tt></heading>
2650 This field identifies the source package name.
2654 In <file>debian/control</file> or a <file>.dsc</file> file,
2655 this field must contain only the name of the source package.
2659 In a binary package control file or a <file>.changes</file>
2660 file, the source package name may be followed by a version
2661 number in parentheses<footnote>
2662 It is customary to leave a space after the package name
2663 if a version number is specified.
2665 This version number may be omitted (and is, by
2666 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2667 the <tt>Version</tt> field of the binary package in
2668 question. The field itself may be omitted from a binary
2669 package control file when the source package has the same
2670 name and version as the binary package.
2674 Package names (both source and binary,
2675 see <ref id="f-Package">) must consist only of lower case
2676 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2677 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2678 (<tt>.</tt>). They must be at least two characters long and
2679 must start with an alphanumeric character.
2683 <sect1 id="f-Maintainer">
2684 <heading><tt>Maintainer</tt></heading>
2687 The package maintainer's name and email address. The name
2688 must come first, then the email address inside angle
2689 brackets <tt><></tt> (in RFC822 format).
2693 If the maintainer's name contains a full stop then the
2694 whole field will not work directly as an email address due
2695 to a misfeature in the syntax specified in RFC822; a
2696 program using this field as an address must check for this
2697 and correct the problem if necessary (for example by
2698 putting the name in round brackets and moving it to the
2699 end, and bringing the email address forward).
2703 <sect1 id="f-Uploaders">
2704 <heading><tt>Uploaders</tt></heading>
2707 List of the names and email addresses of co-maintainers of
2708 the package, if any. If the package has other maintainers
2709 beside the one named in the
2710 <qref id="f-Maintainer">Maintainer field</qref>, their names
2711 and email addresses should be listed here. The format of each
2712 entry is the same as that of the Maintainer field, and
2713 multiple entries must be comma separated. This is an optional
2718 Any parser that interprets the Uploaders field in
2719 <file>debian/control</file> must permit it to span multiple
2720 lines. Line breaks in an Uploaders field that spans multiple
2721 lines are not significant and the semantics of the field are
2722 the same as if the line breaks had not been present.
2726 <sect1 id="f-Changed-By">
2727 <heading><tt>Changed-By</tt></heading>
2730 The name and email address of the person who prepared this
2731 version of the package, usually a maintainer. The syntax is
2732 the same as for the <qref id="f-Maintainer">Maintainer
2737 <sect1 id="f-Section">
2738 <heading><tt>Section</tt></heading>
2741 This field specifies an application area into which the package
2742 has been classified. See <ref id="subsections">.
2746 When it appears in the <file>debian/control</file> file,
2747 it gives the value for the subfield of the same name in
2748 the <tt>Files</tt> field of the <file>.changes</file> file.
2749 It also gives the default for the same field in the binary
2754 <sect1 id="f-Priority">
2755 <heading><tt>Priority</tt></heading>
2758 This field represents how important it is that the user
2759 have the package installed. See <ref id="priorities">.
2763 When it appears in the <file>debian/control</file> file,
2764 it gives the value for the subfield of the same name in
2765 the <tt>Files</tt> field of the <file>.changes</file> file.
2766 It also gives the default for the same field in the binary
2771 <sect1 id="f-Package">
2772 <heading><tt>Package</tt></heading>
2775 The name of the binary package.
2779 Binary package names must follow the same syntax and
2780 restrictions as source package names. See <ref id="f-Source">
2785 <sect1 id="f-Architecture">
2786 <heading><tt>Architecture</tt></heading>
2789 Depending on context and the control file used, the
2790 <tt>Architecture</tt> field can include the following sets of
2794 A unique single word identifying a Debian machine
2795 architecture as described in <ref id="arch-spec">.
2798 An architecture wildcard identifying a set of Debian
2799 machine architectures, see <ref id="arch-wildcard-spec">.
2800 <tt>any</tt> matches all Debian machine architectures
2801 and is the most frequently used.
2804 <tt>all</tt>, which indicates an
2805 architecture-independent package.
2808 <tt>source</tt>, which indicates a source package.
2814 In the main <file>debian/control</file> file in the source
2815 package, this field may contain the special
2816 value <tt>all</tt>, the special architecture
2817 wildcard <tt>any</tt>, or a list of specific and wildcard
2818 architectures separated by spaces. If <tt>all</tt>
2819 or <tt>any</tt> appears, that value must be the entire
2820 contents of the field. Most packages will use
2821 either <tt>all</tt> or <tt>any</tt>.
2825 Specifying a specific list of architectures indicates that the
2826 source will build an architecture-dependent package only on
2827 architectures included in the list. Specifying a list of
2828 architecture wildcards indicates that the source will build an
2829 architecture-dependent package on only those architectures
2830 that match any of the specified architecture wildcards.
2831 Specifying a list of architectures or architecture wildcards
2832 other than <tt>any</tt> is for the minority of cases where a
2833 program is not portable or is not useful on some
2834 architectures. Where possible, the program should be made
2839 In the source package control file <file>.dsc</file>, this
2840 field may contain either the architecture
2841 wildcard <tt>any</tt> or a list of architectures and
2842 architecture wildcards separated by spaces. If a list is
2843 given, it may include (or consist solely of) the special
2844 value <tt>all</tt>. In other words, in <file>.dsc</file>
2845 files unlike the <file>debian/control</file>, <tt>all</tt> may
2846 occur in combination with specific architectures.
2847 The <tt>Architecture</tt> field in the source package control
2848 file <file>.dsc</file> is generally constructed from
2849 the <tt>Architecture</tt> fields in
2850 the <file>debian/control</file> in the source package.
2854 Specifying <tt>any</tt> indicates that the source package
2855 isn't dependent on any particular architecture and should
2856 compile fine on any one. The produced binary package(s)
2857 will either be specific to whatever the current build
2858 architecture is or will be architecture-independent.
2862 Specifying only <tt>all</tt> indicates that the source package
2863 will only build architecture-independent packages. If this is
2864 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2865 <tt>any</tt> implies that the source package will build at
2866 least one architecture-dependent package.
2870 Specifying a list of architectures or architecture wildcards
2871 indicates that the source will build an architecture-dependent
2872 package, and will only work correctly on the listed or
2873 matching architectures. If the source package also builds at
2874 least one architecture-independent package, <tt>all</tt> will
2875 also be included in the list.
2879 In a <file>.changes</file> file, the <tt>Architecture</tt>
2880 field lists the architecture(s) of the package(s) currently
2881 being uploaded. This will be a list; if the source for the
2882 package is also being uploaded, the special
2883 entry <tt>source</tt> is also present. <tt>all</tt> will be
2884 present if any architecture-independent packages are being
2885 uploaded. Architecture wildcards such as <tt>any</tt> must
2886 never occur in the <tt>Architecture</tt> field in
2887 the <file>.changes</file> file.
2891 See <ref id="debianrules"> for information on how to get
2892 the architecture for the build process.
2896 <sect1 id="f-Essential">
2897 <heading><tt>Essential</tt></heading>
2900 This is a boolean field which may occur only in the
2901 control file of a binary package or in a per-package fields
2902 paragraph of a main source control data file.
2906 If set to <tt>yes</tt> then the package management system
2907 will refuse to remove the package (upgrading and replacing
2908 it is still possible). The other possible value is <tt>no</tt>,
2909 which is the same as not having the field at all.
2914 <heading>Package interrelationship fields:
2915 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2916 <tt>Recommends</tt>, <tt>Suggests</tt>,
2917 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2918 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2922 These fields describe the package's relationships with
2923 other packages. Their syntax and semantics are described
2924 in <ref id="relationships">.</p>
2927 <sect1 id="f-Standards-Version">
2928 <heading><tt>Standards-Version</tt></heading>
2931 The most recent version of the standards (the policy
2932 manual and associated texts) with which the package
2937 The version number has four components: major and minor
2938 version number and major and minor patch level. When the
2939 standards change in a way that requires every package to
2940 change the major number will be changed. Significant
2941 changes that will require work in many packages will be
2942 signaled by a change to the minor number. The major patch
2943 level will be changed for any change to the meaning of the
2944 standards, however small; the minor patch level will be
2945 changed when only cosmetic, typographical or other edits
2946 are made which neither change the meaning of the document
2947 nor affect the contents of packages.
2951 Thus only the first three components of the policy version
2952 are significant in the <em>Standards-Version</em> control
2953 field, and so either these three components or all four
2954 components may be specified.<footnote>
2955 In the past, people specified the full version number
2956 in the Standards-Version field, for example "2.3.0.0".
2957 Since minor patch-level changes don't introduce new
2958 policy, it was thought it would be better to relax
2959 policy and only require the first 3 components to be
2960 specified, in this example "2.3.0". All four
2961 components may still be used if someone wishes to do so.
2967 <sect1 id="f-Version">
2968 <heading><tt>Version</tt></heading>
2971 The version number of a package. The format is:
2972 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2976 The three components here are:
2978 <tag><var>epoch</var></tag>
2981 This is a single (generally small) unsigned integer. It
2982 may be omitted, in which case zero is assumed. If it is
2983 omitted then the <var>upstream_version</var> may not
2988 It is provided to allow mistakes in the version numbers
2989 of older versions of a package, and also a package's
2990 previous version numbering schemes, to be left behind.
2994 <tag><var>upstream_version</var></tag>
2997 This is the main part of the version number. It is
2998 usually the version number of the original ("upstream")
2999 package from which the <file>.deb</file> file has been made,
3000 if this is applicable. Usually this will be in the same
3001 format as that specified by the upstream author(s);
3002 however, it may need to be reformatted to fit into the
3003 package management system's format and comparison
3008 The comparison behavior of the package management system
3009 with respect to the <var>upstream_version</var> is
3010 described below. The <var>upstream_version</var>
3011 portion of the version number is mandatory.
3015 The <var>upstream_version</var> may contain only
3016 alphanumerics<footnote>
3017 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3019 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3020 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3021 tilde) and should start with a digit. If there is no
3022 <var>debian_revision</var> then hyphens are not allowed;
3023 if there is no <var>epoch</var> then colons are not
3028 <tag><var>debian_revision</var></tag>
3031 This part of the version number specifies the version of
3032 the Debian package based on the upstream version. It
3033 may contain only alphanumerics and the characters
3034 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3035 tilde) and is compared in the same way as the
3036 <var>upstream_version</var> is.
3040 It is optional; if it isn't present then the
3041 <var>upstream_version</var> may not contain a hyphen.
3042 This format represents the case where a piece of
3043 software was written specifically to be a Debian
3044 package, where the Debian package source must always
3045 be identical to the pristine source and therefore no
3046 revision indication is required.
3050 It is conventional to restart the
3051 <var>debian_revision</var> at <tt>1</tt> each time the
3052 <var>upstream_version</var> is increased.
3056 The package management system will break the version
3057 number apart at the last hyphen in the string (if there
3058 is one) to determine the <var>upstream_version</var> and
3059 <var>debian_revision</var>. The absence of a
3060 <var>debian_revision</var> is equivalent to a
3061 <var>debian_revision</var> of <tt>0</tt>.
3068 When comparing two version numbers, first the <var>epoch</var>
3069 of each are compared, then the <var>upstream_version</var> if
3070 <var>epoch</var> is equal, and then <var>debian_revision</var>
3071 if <var>upstream_version</var> is also equal.
3072 <var>epoch</var> is compared numerically. The
3073 <var>upstream_version</var> and <var>debian_revision</var>
3074 parts are compared by the package management system using the
3075 following algorithm:
3079 The strings are compared from left to right.
3083 First the initial part of each string consisting entirely of
3084 non-digit characters is determined. These two parts (one of
3085 which may be empty) are compared lexically. If a difference
3086 is found it is returned. The lexical comparison is a
3087 comparison of ASCII values modified so that all the letters
3088 sort earlier than all the non-letters and so that a tilde
3089 sorts before anything, even the end of a part. For example,
3090 the following parts are in sorted order from earliest to
3091 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3092 <tt>a</tt>.<footnote>
3093 One common use of <tt>~</tt> is for upstream pre-releases.
3094 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3095 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3100 Then the initial part of the remainder of each string which
3101 consists entirely of digit characters is determined. The
3102 numerical values of these two parts are compared, and any
3103 difference found is returned as the result of the comparison.
3104 For these purposes an empty string (which can only occur at
3105 the end of one or both version strings being compared) counts
3110 These two steps (comparing and removing initial non-digit
3111 strings and initial digit strings) are repeated until a
3112 difference is found or both strings are exhausted.
3116 Note that the purpose of epochs is to allow us to leave behind
3117 mistakes in version numbering, and to cope with situations
3118 where the version numbering scheme changes. It is
3119 <em>not</em> intended to cope with version numbers containing
3120 strings of letters which the package management system cannot
3121 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3122 silly orderings.<footnote>
3123 The author of this manual has heard of a package whose
3124 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3125 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3131 <sect1 id="f-Description">
3132 <heading><tt>Description</tt></heading>
3135 In a source or binary control file, the <tt>Description</tt>
3136 field contains a description of the binary package, consisting
3137 of two parts, the synopsis or the short description, and the
3138 long description. The field's format is as follows:
3143 Description: <single line synopsis>
3144 <extended description over several lines>
3149 The lines in the extended description can have these formats:
3155 Those starting with a single space are part of a paragraph.
3156 Successive lines of this form will be word-wrapped when
3157 displayed. The leading space will usually be stripped off.
3161 Those starting with two or more spaces. These will be
3162 displayed verbatim. If the display cannot be panned
3163 horizontally, the displaying program will line wrap them "hard"
3164 (i.e., without taking account of word breaks). If it can they
3165 will be allowed to trail off to the right. None, one or two
3166 initial spaces may be deleted, but the number of spaces
3167 deleted from each line will be the same (so that you can have
3168 indenting work correctly, for example).
3172 Those containing a single space followed by a single full stop
3173 character. These are rendered as blank lines. This is the
3174 <em>only</em> way to get a blank line<footnote>
3175 Completely empty lines will not be rendered as blank lines.
3176 Instead, they will cause the parser to think you're starting
3177 a whole new record in the control file, and will therefore
3178 likely abort with an error.
3183 Those containing a space, a full stop and some more characters.
3184 These are for future expansion. Do not use them.
3190 Do not use tab characters. Their effect is not predictable.
3194 See <ref id="descriptions"> for further information on this.
3198 In a <file>.changes</file> file, the <tt>Description</tt>
3199 field contains a summary of the descriptions for the packages
3200 being uploaded. For this case, the first line of the field
3201 value (the part on the same line as <tt>Description:</tt>) is
3202 always empty. The content of the field is expressed as
3203 continuation lines, one line per package. Each line is
3204 indented by one space and contains the name of a binary
3205 package, a space, a hyphen (<tt>-</tt>), a space, and the
3206 short description line from that package.
3210 <sect1 id="f-Distribution">
3211 <heading><tt>Distribution</tt></heading>
3214 In a <file>.changes</file> file or parsed changelog output
3215 this contains the (space-separated) name(s) of the
3216 distribution(s) where this version of the package should
3217 be installed. Valid distributions are determined by the
3218 archive maintainers.<footnote>
3219 Example distribution names in the Debian archive used in
3220 <file>.changes</file> files are:
3221 <taglist compact="compact">
3222 <tag><em>unstable</em></tag>
3224 This distribution value refers to the
3225 <em>developmental</em> part of the Debian distribution
3226 tree. Most new packages, new upstream versions of
3227 packages and bug fixes go into the <em>unstable</em>
3231 <tag><em>experimental</em></tag>
3233 The packages with this distribution value are deemed
3234 by their maintainers to be high risk. Oftentimes they
3235 represent early beta or developmental packages from
3236 various sources that the maintainers want people to
3237 try, but are not ready to be a part of the other parts
3238 of the Debian distribution tree.
3243 Others are used for updating stable releases or for
3244 security uploads. More information is available in the
3245 Debian Developer's Reference, section "The Debian
3249 The Debian archive software only supports listing a single
3250 distribution. Migration of packages to other distributions is
3251 handled outside of the upload process.
3256 <heading><tt>Date</tt></heading>
3259 This field includes the date the package was built or last
3260 edited. It must be in the same format as the <var>date</var>
3261 in a <file>debian/changelog</file> entry.
3265 The value of this field is usually extracted from the
3266 <file>debian/changelog</file> file - see
3267 <ref id="dpkgchangelog">).
3271 <sect1 id="f-Format">
3272 <heading><tt>Format</tt></heading>
3275 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3276 files, this field declares the format version of that file.
3277 The syntax of the field value is the same as that of
3278 a <qref id="f-Version">package version number</qref> except
3279 that no epoch or Debian revision is allowed. The format
3280 described in this document is <tt>&changesversion;</tt>.
3284 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3285 Debian source control</qref> files, this field declares the
3286 format of the source package. The field value is used by
3287 programs acting on a source package to interpret the list of
3288 files in the source package and determine how to unpack it.
3289 The syntax of the field value is a numeric major revision, a
3290 period, a numeric minor revision, and then an optional subtype
3291 after whitespace, which if specified is an alphanumeric word
3292 in parentheses. The subtype is optional in the syntax but may
3293 be mandatory for particular source format revisions.
3295 The source formats currently supported by the Debian archive
3296 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3297 and <tt>3.0 (quilt)</tt>.
3302 <sect1 id="f-Urgency">
3303 <heading><tt>Urgency</tt></heading>
3306 This is a description of how important it is to upgrade to
3307 this version from previous ones. It consists of a single
3308 keyword taking one of the values <tt>low</tt>,
3309 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3310 <tt>critical</tt><footnote>
3311 Other urgency values are supported with configuration
3312 changes in the archive software but are not used in Debian.
3313 The urgency affects how quickly a package will be considered
3314 for inclusion into the <tt>testing</tt> distribution and
3315 gives an indication of the importance of any fixes included
3316 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3317 treated as synonymous.
3318 </footnote> (not case-sensitive) followed by an optional
3319 commentary (separated by a space) which is usually in
3320 parentheses. For example:
3323 Urgency: low (HIGH for users of diversions)
3329 The value of this field is usually extracted from the
3330 <file>debian/changelog</file> file - see
3331 <ref id="dpkgchangelog">.
3335 <sect1 id="f-Changes">
3336 <heading><tt>Changes</tt></heading>
3339 This field contains the human-readable changes data, describing
3340 the differences between the last version and the current one.
3344 The first line of the field value (the part on the same line
3345 as <tt>Changes:</tt>) is always empty. The content of the
3346 field is expressed as continuation lines, with each line
3347 indented by at least one space. Blank lines must be
3348 represented by a line consisting only of a space and a full
3353 The value of this field is usually extracted from the
3354 <file>debian/changelog</file> file - see
3355 <ref id="dpkgchangelog">).
3359 Each version's change information should be preceded by a
3360 "title" line giving at least the version, distribution(s)
3361 and urgency, in a human-readable way.
3365 If data from several versions is being returned the entry
3366 for the most recent version should be returned first, and
3367 entries should be separated by the representation of a
3368 blank line (the "title" line may also be followed by the
3369 representation of a blank line).
3373 <sect1 id="f-Binary">
3374 <heading><tt>Binary</tt></heading>
3377 This field is a list of binary packages. Its syntax and
3378 meaning varies depending on the control file in which it
3383 When it appears in the <file>.dsc</file> file, it lists binary
3384 packages which a source package can produce, separated by
3386 A space after each comma is conventional.
3387 </footnote>. It may span multiple lines. The source package
3388 does not necessarily produce all of these binary packages for
3389 every architecture. The source control file doesn't contain
3390 details of which architectures are appropriate for which of
3391 the binary packages.
3395 When it appears in a <file>.changes</file> file, it lists the
3396 names of the binary packages being uploaded, separated by
3397 whitespace (not commas). It may span multiple lines.
3401 <sect1 id="f-Installed-Size">
3402 <heading><tt>Installed-Size</tt></heading>
3405 This field appears in the control files of binary packages,
3406 and in the <file>Packages</file> files. It gives an estimate
3407 of the total amount of disk space required to install the
3408 named package. Actual installed size may vary based on block
3409 size, file system properties, or actions taken by package
3414 The disk space is given as the integer value of the estimated
3415 installed size in bytes, divided by 1024 and rounded up.
3419 <sect1 id="f-Files">
3420 <heading><tt>Files</tt></heading>
3423 This field contains a list of files with information about
3424 each one. The exact information and syntax varies with
3429 In all cases, Files is a multiline field. The first line of
3430 the field value (the part on the same line as <tt>Files:</tt>)
3431 is always empty. The content of the field is expressed as
3432 continuation lines, one line per file. Each line must be
3433 indented by one space and contain a number of sub-fields,
3434 separated by spaces, as described below.
3438 In the <file>.dsc</file> file, each line contains the MD5
3439 checksum, size and filename of the tar file and (if
3440 applicable) diff file which make up the remainder of the
3441 source package<footnote>
3442 That is, the parts which are not the <tt>.dsc</tt>.
3443 </footnote>. For example:
3446 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3447 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3449 The exact forms of the filenames are described
3450 in <ref id="pkg-sourcearchives">.
3454 In the <file>.changes</file> file this contains one line per
3455 file being uploaded. Each line contains the MD5 checksum,
3456 size, section and priority and the filename. For example:
3459 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3460 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3461 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3462 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3464 The <qref id="f-Section">section</qref>
3465 and <qref id="f-Priority">priority</qref> are the values of
3466 the corresponding fields in the main source control file. If
3467 no section or priority is specified then <tt>-</tt> should be
3468 used, though section and priority values must be specified for
3469 new packages to be installed properly.
3473 The special value <tt>byhand</tt> for the section in a
3474 <tt>.changes</tt> file indicates that the file in question
3475 is not an ordinary package file and must by installed by
3476 hand by the distribution maintainers. If the section is
3477 <tt>byhand</tt> the priority should be <tt>-</tt>.
3481 If a new Debian revision of a package is being shipped and
3482 no new original source archive is being distributed the
3483 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3484 entry for the original source archive
3485 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3486 but the <file>.changes</file> file should leave it out. In
3487 this case the original source archive on the distribution
3488 site must match exactly, byte-for-byte, the original
3489 source archive which was used to generate the
3490 <file>.dsc</file> file and diff which are being uploaded.</p>
3493 <sect1 id="f-Closes">
3494 <heading><tt>Closes</tt></heading>
3497 A space-separated list of bug report numbers that the upload
3498 governed by the .changes file closes.
3502 <sect1 id="f-Homepage">
3503 <heading><tt>Homepage</tt></heading>
3506 The URL of the web site for this package, preferably (when
3507 applicable) the site from which the original source can be
3508 obtained and any additional upstream documentation or
3509 information may be found. The content of this field is a
3510 simple URL without any surrounding characters such as
3515 <sect1 id="f-Checksums">
3516 <heading><tt>Checksums-Sha1</tt>
3517 and <tt>Checksums-Sha256</tt></heading>
3520 These fields contain a list of files with a checksum and size
3521 for each one. Both <tt>Checksums-Sha1</tt>
3522 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3523 only in the checksum algorithm used: SHA-1
3524 for <tt>Checksums-Sha1</tt> and SHA-256
3525 for <tt>Checksums-Sha256</tt>.
3529 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3530 multiline fields. The first line of the field value (the part
3531 on the same line as <tt>Checksums-Sha1:</tt>
3532 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3533 of the field is expressed as continuation lines, one line per
3534 file. Each line consists of the checksum, a space, the file
3535 size, a space, and the file name. For example (from
3536 a <file>.changes</file> file):
3539 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3540 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3541 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3542 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3544 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3545 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3546 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3547 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3552 In the <file>.dsc</file> file, these fields should list all
3553 files that make up the source package. In
3554 the <file>.changes</file> file, these fields should list all
3555 files being uploaded. The list of files in these fields
3556 must match the list of files in the <tt>Files</tt> field.
3562 <heading>User-defined fields</heading>
3565 Additional user-defined fields may be added to the
3566 source package control file. Such fields will be
3567 ignored, and not copied to (for example) binary or
3568 source package control files or upload control files.
3572 If you wish to add additional unsupported fields to
3573 these output files you should use the mechanism
3578 Fields in the main source control information file with
3579 names starting <tt>X</tt>, followed by one or more of
3580 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3581 be copied to the output files. Only the part of the
3582 field name after the hyphen will be used in the output
3583 file. Where the letter <tt>B</tt> is used the field
3584 will appear in binary package control files, where the
3585 letter <tt>S</tt> is used in source package control
3586 files and where <tt>C</tt> is used in upload control
3587 (<tt>.changes</tt>) files.
3591 For example, if the main source information control file
3594 XBS-Comment: I stand between the candle and the star.
3596 then the binary and source package control files will contain the
3599 Comment: I stand between the candle and the star.
3608 <chapt id="maintainerscripts">
3609 <heading>Package maintainer scripts and installation procedure</heading>
3612 <heading>Introduction to package maintainer scripts</heading>
3615 It is possible to supply scripts as part of a package which
3616 the package management system will run for you when your
3617 package is installed, upgraded or removed.
3621 These scripts are the files <prgn>preinst</prgn>,
3622 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3623 <prgn>postrm</prgn> in the control area of the package.
3624 They must be proper executable files; if they are scripts
3625 (which is recommended), they must start with the usual
3626 <tt>#!</tt> convention. They should be readable and
3627 executable by anyone, and must not be world-writable.
3631 The package management system looks at the exit status from
3632 these scripts. It is important that they exit with a
3633 non-zero status if there is an error, so that the package
3634 management system can stop its processing. For shell
3635 scripts this means that you <em>almost always</em> need to
3636 use <tt>set -e</tt> (this is usually true when writing shell
3637 scripts, in fact). It is also important, of course, that
3638 they exit with a zero status if everything went well.
3642 Additionally, packages interacting with users using
3643 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3644 install a <prgn>config</prgn> script in the control area,
3645 see <ref id="maintscriptprompt"> for details.
3649 When a package is upgraded a combination of the scripts from
3650 the old and new packages is called during the upgrade
3651 procedure. If your scripts are going to be at all
3652 complicated you need to be aware of this, and may need to
3653 check the arguments to your scripts.
3657 Broadly speaking the <prgn>preinst</prgn> is called before
3658 (a particular version of) a package is installed, and the
3659 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3660 before (a version of) a package is removed and the
3661 <prgn>postrm</prgn> afterwards.
3665 Programs called from maintainer scripts should not normally
3666 have a path prepended to them. Before installation is
3667 started, the package management system checks to see if the
3668 programs <prgn>ldconfig</prgn>,
3669 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3670 and <prgn>update-rc.d</prgn> can be found via the
3671 <tt>PATH</tt> environment variable. Those programs, and any
3672 other program that one would expect to be in the
3673 <tt>PATH</tt>, should thus be invoked without an absolute
3674 pathname. Maintainer scripts should also not reset the
3675 <tt>PATH</tt>, though they might choose to modify it by
3676 prepending or appending package-specific directories. These
3677 considerations really apply to all shell scripts.</p>
3680 <sect id="idempotency">
3681 <heading>Maintainer scripts idempotency</heading>
3684 It is necessary for the error recovery procedures that the
3685 scripts be idempotent. This means that if it is run
3686 successfully, and then it is called again, it doesn't bomb
3687 out or cause any harm, but just ensures that everything is
3688 the way it ought to be. If the first call failed, or
3689 aborted half way through for some reason, the second call
3690 should merely do the things that were left undone the first
3691 time, if any, and exit with a success status if everything
3693 This is so that if an error occurs, the user interrupts
3694 <prgn>dpkg</prgn> or some other unforeseen circumstance
3695 happens you don't leave the user with a badly-broken
3696 package when <prgn>dpkg</prgn> attempts to repeat the
3702 <sect id="controllingterminal">
3703 <heading>Controlling terminal for maintainer scripts</heading>
3706 Maintainer scripts are not guaranteed to run with a controlling
3707 terminal and may not be able to interact with the user. They
3708 must be able to fall back to noninteractive behavior if no
3709 controlling terminal is available. Maintainer scripts that
3710 prompt via a program conforming to the Debian Configuration
3711 Management Specification (see <ref id="maintscriptprompt">) may
3712 assume that program will handle falling back to noninteractive
3717 For high-priority prompts without a reasonable default answer,
3718 maintainer scripts may abort if there is no controlling
3719 terminal. However, this situation should be avoided if at all
3720 possible, since it prevents automated or unattended installs.
3721 In most cases, users will consider this to be a bug in the
3726 <sect id="exitstatus">
3727 <heading>Exit status</heading>
3730 Each script must return a zero exit status for
3731 success, or a nonzero one for failure, since the package
3732 management system looks for the exit status of these scripts
3733 and determines what action to take next based on that datum.
3737 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3742 <list compact="compact">
3744 <var>new-preinst</var> <tt>install</tt>
3747 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3750 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3753 <var>old-preinst</var> <tt>abort-upgrade</tt>
3754 <var>new-version</var>
3759 <list compact="compact">
3761 <var>postinst</var> <tt>configure</tt>
3762 <var>most-recently-configured-version</var>
3765 <var>old-postinst</var> <tt>abort-upgrade</tt>
3766 <var>new-version</var>
3769 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3770 <tt>in-favour</tt> <var>package</var>
3771 <var>new-version</var>
3774 <var>postinst</var> <tt>abort-remove</tt>
3777 <var>deconfigured's-postinst</var>
3778 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3779 <var>failed-install-package</var> <var>version</var>
3780 [<tt>removing</tt> <var>conflicting-package</var>
3786 <list compact="compact">
3788 <var>prerm</var> <tt>remove</tt>
3791 <var>old-prerm</var> <tt>upgrade</tt>
3792 <var>new-version</var>
3795 <var>new-prerm</var> <tt>failed-upgrade</tt>
3796 <var>old-version</var>
3799 <var>conflictor's-prerm</var> <tt>remove</tt>
3800 <tt>in-favour</tt> <var>package</var>
3801 <var>new-version</var>
3804 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3805 <tt>in-favour</tt> <var>package-being-installed</var>
3806 <var>version</var> [<tt>removing</tt>
3807 <var>conflicting-package</var>
3813 <list compact="compact">
3815 <var>postrm</var> <tt>remove</tt>
3818 <var>postrm</var> <tt>purge</tt>
3821 <var>old-postrm</var> <tt>upgrade</tt>
3822 <var>new-version</var>
3825 <var>new-postrm</var> <tt>failed-upgrade</tt>
3826 <var>old-version</var>
3829 <var>new-postrm</var> <tt>abort-install</tt>
3832 <var>new-postrm</var> <tt>abort-install</tt>
3833 <var>old-version</var>
3836 <var>new-postrm</var> <tt>abort-upgrade</tt>
3837 <var>old-version</var>
3840 <var>disappearer's-postrm</var> <tt>disappear</tt>
3841 <var>overwriter</var>
3842 <var>overwriter-version</var>
3848 <sect id="unpackphase">
3849 <heading>Details of unpack phase of installation or upgrade</heading>
3852 The procedure on installation/upgrade/overwrite/disappear
3853 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3854 stage of <tt>dpkg --install</tt>) is as follows. In each
3855 case, if a major error occurs (unless listed below) the
3856 actions are, in general, run backwards - this means that the
3857 maintainer scripts are run with different arguments in
3858 reverse order. These are the "error unwind" calls listed
3865 If a version of the package is already installed, call
3866 <example compact="compact">
3867 <var>old-prerm</var> upgrade <var>new-version</var>
3871 If the script runs but exits with a non-zero
3872 exit status, <prgn>dpkg</prgn> will attempt:
3873 <example compact="compact">
3874 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3876 If this works, the upgrade continues. If this
3877 does not work, the error unwind:
3878 <example compact="compact">
3879 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3881 If this works, then the old-version is
3882 "Installed", if not, the old version is in a
3883 "Half-Configured" state.
3889 If a "conflicting" package is being removed at the same time,
3890 or if any package will be broken (due to <tt>Breaks</tt>):
3893 If <tt>--auto-deconfigure</tt> is
3894 specified, call, for each package to be deconfigured
3895 due to <tt>Breaks</tt>:
3896 <example compact="compact">
3897 <var>deconfigured's-prerm</var> deconfigure \
3898 in-favour <var>package-being-installed</var> <var>version</var>
3901 <example compact="compact">
3902 <var>deconfigured's-postinst</var> abort-deconfigure \
3903 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3905 The deconfigured packages are marked as
3906 requiring configuration, so that if
3907 <tt>--install</tt> is used they will be
3908 configured again if possible.
3911 If any packages depended on a conflicting
3912 package being removed and <tt>--auto-deconfigure</tt> is
3913 specified, call, for each such package:
3914 <example compact="compact">
3915 <var>deconfigured's-prerm</var> deconfigure \
3916 in-favour <var>package-being-installed</var> <var>version</var> \
3917 removing <var>conflicting-package</var> <var>version</var>
3920 <example compact="compact">
3921 <var>deconfigured's-postinst</var> abort-deconfigure \
3922 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3923 removing <var>conflicting-package</var> <var>version</var>
3925 The deconfigured packages are marked as
3926 requiring configuration, so that if
3927 <tt>--install</tt> is used they will be
3928 configured again if possible.
3931 To prepare for removal of each conflicting package, call:
3932 <example compact="compact">
3933 <var>conflictor's-prerm</var> remove \
3934 in-favour <var>package</var> <var>new-version</var>
3937 <example compact="compact">
3938 <var>conflictor's-postinst</var> abort-remove \
3939 in-favour <var>package</var> <var>new-version</var>
3948 If the package is being upgraded, call:
3949 <example compact="compact">
3950 <var>new-preinst</var> upgrade <var>old-version</var>
3952 If this fails, we call:
3954 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3961 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3963 is called. If this works, then the old version
3964 is in an "Installed" state, or else it is left
3965 in an "Unpacked" state.
3970 If it fails, then the old version is left
3971 in an "Half-Installed" state.
3978 Otherwise, if the package had some configuration
3979 files from a previous version installed (i.e., it
3980 is in the "configuration files only" state):
3981 <example compact="compact">
3982 <var>new-preinst</var> install <var>old-version</var>
3986 <var>new-postrm</var> abort-install <var>old-version</var>
3988 If this fails, the package is left in a
3989 "Half-Installed" state, which requires a
3990 reinstall. If it works, the packages is left in
3991 a "Config-Files" state.
3994 Otherwise (i.e., the package was completely purged):
3995 <example compact="compact">
3996 <var>new-preinst</var> install
3999 <example compact="compact">
4000 <var>new-postrm</var> abort-install
4002 If the error-unwind fails, the package is in a
4003 "Half-Installed" phase, and requires a
4004 reinstall. If the error unwind works, the
4005 package is in a not installed state.
4012 The new package's files are unpacked, overwriting any
4013 that may be on the system already, for example any
4014 from the old version of the same package or from
4015 another package. Backups of the old files are kept
4016 temporarily, and if anything goes wrong the package
4017 management system will attempt to put them back as
4018 part of the error unwind.
4022 It is an error for a package to contain files which
4023 are on the system in another package, unless
4024 <tt>Replaces</tt> is used (see <ref id="replaces">).
4026 The following paragraph is not currently the case:
4027 Currently the <tt>- - force-overwrite</tt> flag is
4028 enabled, downgrading it to a warning, but this may not
4034 It is a more serious error for a package to contain a
4035 plain file or other kind of non-directory where another
4036 package has a directory (again, unless
4037 <tt>Replaces</tt> is used). This error can be
4038 overridden if desired using
4039 <tt>--force-overwrite-dir</tt>, but this is not
4044 Packages which overwrite each other's files produce
4045 behavior which, though deterministic, is hard for the
4046 system administrator to understand. It can easily
4047 lead to "missing" programs if, for example, a package
4048 is installed which overwrites a file from another
4049 package, and is then removed again.<footnote>
4050 Part of the problem is due to what is arguably a
4051 bug in <prgn>dpkg</prgn>.
4056 A directory will never be replaced by a symbolic link
4057 to a directory or vice versa; instead, the existing
4058 state (symlink or not) will be left alone and
4059 <prgn>dpkg</prgn> will follow the symlink if there is
4068 If the package is being upgraded, call
4069 <example compact="compact">
4070 <var>old-postrm</var> upgrade <var>new-version</var>
4074 If this fails, <prgn>dpkg</prgn> will attempt:
4075 <example compact="compact">
4076 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4078 If this works, installation continues. If not,
4080 <example compact="compact">
4081 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4083 If this fails, the old version is left in a
4084 "Half-Installed" state. If it works, dpkg now
4086 <example compact="compact">
4087 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4089 If this fails, the old version is left in a
4090 "Half-Installed" state. If it works, dpkg now
4092 <example compact="compact">
4093 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4095 If this fails, the old version is in an
4102 This is the point of no return - if
4103 <prgn>dpkg</prgn> gets this far, it won't back off
4104 past this point if an error occurs. This will
4105 leave the package in a fairly bad state, which
4106 will require a successful re-installation to clear
4107 up, but it's when <prgn>dpkg</prgn> starts doing
4108 things that are irreversible.
4113 Any files which were in the old version of the package
4114 but not in the new are removed.
4118 The new file list replaces the old.
4122 The new maintainer scripts replace the old.
4126 Any packages all of whose files have been overwritten
4127 during the installation, and which aren't required for
4128 dependencies, are considered to have been removed.
4129 For each such package
4132 <prgn>dpkg</prgn> calls:
4133 <example compact="compact">
4134 <var>disappearer's-postrm</var> disappear \
4135 <var>overwriter</var> <var>overwriter-version</var>
4139 The package's maintainer scripts are removed.
4142 It is noted in the status database as being in a
4143 sane state, namely not installed (any conffiles
4144 it may have are ignored, rather than being
4145 removed by <prgn>dpkg</prgn>). Note that
4146 disappearing packages do not have their prerm
4147 called, because <prgn>dpkg</prgn> doesn't know
4148 in advance that the package is going to
4155 Any files in the package we're unpacking that are also
4156 listed in the file lists of other packages are removed
4157 from those lists. (This will lobotomize the file list
4158 of the "conflicting" package if there is one.)
4162 The backup files made during installation, above, are
4168 The new package's status is now sane, and recorded as
4173 Here is another point of no return - if the
4174 conflicting package's removal fails we do not unwind
4175 the rest of the installation; the conflicting package
4176 is left in a half-removed limbo.
4181 If there was a conflicting package we go and do the
4182 removal actions (described below), starting with the
4183 removal of the conflicting package's files (any that
4184 are also in the package being installed have already
4185 been removed from the conflicting package's file list,
4186 and so do not get removed now).
4192 <sect id="configdetails"><heading>Details of configuration</heading>
4195 When we configure a package (this happens with <tt>dpkg
4196 --install</tt> and <tt>dpkg --configure</tt>), we first
4197 update any <tt>conffile</tt>s and then call:
4198 <example compact="compact">
4199 <var>postinst</var> configure <var>most-recently-configured-version</var>
4204 No attempt is made to unwind after errors during
4205 configuration. If the configuration fails, the package is in
4206 a "Failed Config" state, and an error message is generated.
4210 If there is no most recently configured version
4211 <prgn>dpkg</prgn> will pass a null argument.
4214 Historical note: Truly ancient (pre-1997) versions of
4215 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4216 (including the angle brackets) in this case. Even older
4217 ones did not pass a second argument at all, under any
4218 circumstance. Note that upgrades using such an old dpkg
4219 version are unlikely to work for other reasons, even if
4220 this old argument behavior is handled by your postinst script.
4226 <sect id="removedetails"><heading>Details of removal and/or
4227 configuration purging</heading>
4233 <example compact="compact">
4234 <var>prerm</var> remove
4238 If prerm fails during replacement due to conflict
4240 <var>conflictor's-postinst</var> abort-remove \
4241 in-favour <var>package</var> <var>new-version</var>
4245 <var>postinst</var> abort-remove
4249 If this fails, the package is in a "Half-Configured"
4250 state, or else it remains "Installed".
4254 The package's files are removed (except <tt>conffile</tt>s).
4257 <example compact="compact">
4258 <var>postrm</var> remove
4262 If it fails, there's no error unwind, and the package is in
4263 an "Half-Installed" state.
4268 All the maintainer scripts except the <prgn>postrm</prgn>
4273 If we aren't purging the package we stop here. Note
4274 that packages which have no <prgn>postrm</prgn> and no
4275 <tt>conffile</tt>s are automatically purged when
4276 removed, as there is no difference except for the
4277 <prgn>dpkg</prgn> status.
4281 The <tt>conffile</tt>s and any backup files
4282 (<tt>~</tt>-files, <tt>#*#</tt> files,
4283 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4288 <example compact="compact">
4289 <var>postrm</var> purge
4293 If this fails, the package remains in a "Config-Files"
4298 The package's file list is removed.
4307 <chapt id="relationships">
4308 <heading>Declaring relationships between packages</heading>
4310 <sect id="depsyntax">
4311 <heading>Syntax of relationship fields</heading>
4314 These fields all have a uniform syntax. They are a list of
4315 package names separated by commas.
4319 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4320 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4321 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4322 control file fields of the package, which declare
4323 dependencies on other packages, the package names listed may
4324 also include lists of alternative package names, separated
4325 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4326 if any one of the alternative packages is installed, that
4327 part of the dependency is considered to be satisfied.
4331 All of the fields except for <tt>Provides</tt> may restrict
4332 their applicability to particular versions of each named
4333 package. This is done in parentheses after each individual
4334 package name; the parentheses should contain a relation from
4335 the list below followed by a version number, in the format
4336 described in <ref id="f-Version">.
4340 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4341 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4342 strictly earlier, earlier or equal, exactly equal, later or
4343 equal and strictly later, respectively. The deprecated
4344 forms <tt><</tt> and <tt>></tt> were used to mean
4345 earlier/later or equal, rather than strictly earlier/later,
4346 so they should not appear in new packages (though
4347 <prgn>dpkg</prgn> still supports them).
4351 Whitespace may appear at any point in the version
4352 specification subject to the rules in <ref
4353 id="controlsyntax">, and must appear where it's necessary to
4354 disambiguate; it is not otherwise significant. All of the
4355 relationship fields may span multiple lines. For
4356 consistency and in case of future changes to
4357 <prgn>dpkg</prgn> it is recommended that a single space be
4358 used after a version relationship and before a version
4359 number; it is also conventional to put a single space after
4360 each comma, on either side of each vertical bar, and before
4361 each open parenthesis. When wrapping a relationship field, it
4362 is conventional to do so after a comma and before the space
4363 following that comma.
4367 For example, a list of dependencies might appear as:
4368 <example compact="compact">
4371 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4376 All fields that specify build-time relationships
4377 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4378 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4379 may be restricted to a certain set of architectures. This
4380 is indicated in brackets after each individual package name and
4381 the optional version specification. The brackets enclose a
4382 list of Debian architecture names separated by whitespace.
4383 Exclamation marks may be prepended to each of the names.
4384 (It is not permitted for some names to be prepended with
4385 exclamation marks while others aren't.) If the current Debian
4386 host architecture is not in this list and there are no
4387 exclamation marks in the list, or it is in the list with a
4388 prepended exclamation mark, the package name and the
4389 associated version specification are ignored completely for
4390 the purposes of defining the relationships.
4395 <example compact="compact">
4397 Build-Depends-Indep: texinfo
4398 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4399 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4401 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4402 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4403 <tt>gnumach-dev</tt> only on hurd-i386.
4407 If the architecture-restricted dependency is part of a set of
4408 alternatives using <tt>|</tt>, that alternative is ignored
4409 completely on architectures that do not match the restriction.
4411 <example compact="compact">
4412 Build-Depends: foo [!i386] | bar [!amd64]
4414 is equivalent to <tt>bar</tt> on the i386 architecture, to
4415 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4416 bar</tt> on all other architectures.
4420 All fields that specify build-time relationships may also be
4421 restricted to a certain set of architectures using architecture
4422 wildcards. The syntax for declaring such restrictions is the
4423 same as declaring restrictions using a certain set of
4424 architectures without architecture wildcards. For example:
4425 <example compact="compact">
4426 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4428 is equivalent to <tt>foo</tt> on architectures using the Linux
4429 kernel and any cpu, <tt>bar</tt> on architectures using any
4430 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4431 using a kernel other than Linux.
4435 Note that the binary package relationship fields such as
4436 <tt>Depends</tt> appear in one of the binary package
4437 sections of the control file, whereas the build-time
4438 relationships such as <tt>Build-Depends</tt> appear in the
4439 source package section of the control file (which is the
4444 <sect id="binarydeps">
4445 <heading>Binary Dependencies - <tt>Depends</tt>,
4446 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4447 <tt>Pre-Depends</tt>
4451 Packages can declare in their control file that they have
4452 certain relationships to other packages - for example, that
4453 they may not be installed at the same time as certain other
4454 packages, and/or that they depend on the presence of others.
4458 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4459 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4460 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4461 <tt>Breaks</tt> is described in <ref id="breaks">, and
4462 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4463 rest are described below.
4467 These seven fields are used to declare a dependency
4468 relationship by one package on another. Except for
4469 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4470 depending (binary) package's control file.
4471 (<tt>Enhances</tt> appears in the recommending package's
4472 control file, and <tt>Breaks</tt> appears in the version of
4473 depended-on package which causes the named package to
4478 A <tt>Depends</tt> field takes effect <em>only</em> when a
4479 package is to be configured. It does not prevent a package
4480 being on the system in an unconfigured state while its
4481 dependencies are unsatisfied, and it is possible to replace
4482 a package whose dependencies are satisfied and which is
4483 properly installed with a different version whose
4484 dependencies are not and cannot be satisfied; when this is
4485 done the depending package will be left unconfigured (since
4486 attempts to configure it will give errors) and will not
4487 function properly. If it is necessary, a
4488 <tt>Pre-Depends</tt> field can be used, which has a partial
4489 effect even when a package is being unpacked, as explained
4490 in detail below. (The other three dependency fields,
4491 <tt>Recommends</tt>, <tt>Suggests</tt> and
4492 <tt>Enhances</tt>, are only used by the various front-ends
4493 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4494 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4498 For this reason packages in an installation run are usually
4499 all unpacked first and all configured later; this gives
4500 later versions of packages with dependencies on later
4501 versions of other packages the opportunity to have their
4502 dependencies satisfied.
4506 In case of circular dependencies, since installation or
4507 removal order honoring the dependency order can't be
4508 established, dependency loops are broken at some point
4509 (based on rules below), and some packages may not be able to
4510 rely on their dependencies being present when being
4511 installed or removed, depending on which side of the break
4512 of the circular dependency loop they happen to be on. If one
4513 of the packages in the loop has no postinst script, then the
4514 cycle will be broken at that package, so as to ensure that
4515 all postinst scripts run with the dependencies properly
4516 configured if this is possible. Otherwise the breaking point
4521 The <tt>Depends</tt> field thus allows package maintainers
4522 to impose an order in which packages should be configured.
4526 The meaning of the five dependency fields is as follows:
4528 <tag><tt>Depends</tt></tag>
4531 This declares an absolute dependency. A package will
4532 not be configured unless all of the packages listed in
4533 its <tt>Depends</tt> field have been correctly
4538 The <tt>Depends</tt> field should be used if the
4539 depended-on package is required for the depending
4540 package to provide a significant amount of
4545 The <tt>Depends</tt> field should also be used if the
4546 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4547 <prgn>postrm</prgn> scripts require the package to be
4548 present in order to run. Note, however, that the
4549 <prgn>postrm</prgn> cannot rely on any non-essential
4550 packages to be present during the <tt>purge</tt>
4554 <tag><tt>Recommends</tt></tag>
4557 This declares a strong, but not absolute, dependency.
4561 The <tt>Recommends</tt> field should list packages
4562 that would be found together with this one in all but
4563 unusual installations.
4567 <tag><tt>Suggests</tt></tag>
4569 This is used to declare that one package may be more
4570 useful with one or more others. Using this field
4571 tells the packaging system and the user that the
4572 listed packages are related to this one and can
4573 perhaps enhance its usefulness, but that installing
4574 this one without them is perfectly reasonable.
4577 <tag><tt>Enhances</tt></tag>
4579 This field is similar to Suggests but works in the
4580 opposite direction. It is used to declare that a
4581 package can enhance the functionality of another
4585 <tag><tt>Pre-Depends</tt></tag>
4588 This field is like <tt>Depends</tt>, except that it
4589 also forces <prgn>dpkg</prgn> to complete installation
4590 of the packages named before even starting the
4591 installation of the package which declares the
4592 pre-dependency, as follows:
4596 When a package declaring a pre-dependency is about to
4597 be <em>unpacked</em> the pre-dependency can be
4598 satisfied if the depended-on package is either fully
4599 configured, <em>or even if</em> the depended-on
4600 package(s) are only unpacked or in the "Half-Configured"
4601 state, provided that they have been configured
4602 correctly at some point in the past (and not removed
4603 or partially removed since). In this case, both the
4604 previously-configured and currently unpacked or
4605 "Half-Configured" versions must satisfy any version
4606 clause in the <tt>Pre-Depends</tt> field.
4610 When the package declaring a pre-dependency is about
4611 to be <em>configured</em>, the pre-dependency will be
4612 treated as a normal <tt>Depends</tt>, that is, it will
4613 be considered satisfied only if the depended-on
4614 package has been correctly configured.
4618 <tt>Pre-Depends</tt> should be used sparingly,
4619 preferably only by packages whose premature upgrade or
4620 installation would hamper the ability of the system to
4621 continue with any upgrade that might be in progress.
4625 <tt>Pre-Depends</tt> are also required if the
4626 <prgn>preinst</prgn> script depends on the named
4627 package. It is best to avoid this situation if
4635 When selecting which level of dependency to use you should
4636 consider how important the depended-on package is to the
4637 functionality of the one declaring the dependency. Some
4638 packages are composed of components of varying degrees of
4639 importance. Such a package should list using
4640 <tt>Depends</tt> the package(s) which are required by the
4641 more important components. The other components'
4642 requirements may be mentioned as Suggestions or
4643 Recommendations, as appropriate to the components' relative
4649 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4652 When one binary package declares that it breaks another,
4653 <prgn>dpkg</prgn> will refuse to allow the package which
4654 declares <tt>Breaks</tt> be installed unless the broken
4655 package is deconfigured first, and it will refuse to
4656 allow the broken package to be reconfigured.
4660 A package will not be regarded as causing breakage merely
4661 because its configuration files are still installed; it must
4662 be at least "Half-Installed".
4666 A special exception is made for packages which declare that
4667 they break their own package name or a virtual package which
4668 they provide (see below): this does not count as a real
4673 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4674 version clause; such a <tt>Breaks</tt> is introduced in the
4675 version of an (implicit or explicit) dependency which violates
4676 an assumption or reveals a bug in earlier versions of the broken
4677 package, or which takes over a file from earlier versions of the
4678 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4679 will inform higher-level package management tools that the
4680 broken package must be upgraded before the new one.
4684 If the breaking package also overwrites some files from the
4685 older package, it should use <tt>Replaces</tt> to ensure this
4686 goes smoothly. See <ref id="replaces"> for a full discussion
4687 of taking over files from other packages, including how to
4688 use <tt>Breaks</tt> in those cases.
4692 Many of the cases where <tt>Breaks</tt> should be used were
4693 previously handled with <tt>Conflicts</tt>
4694 because <tt>Breaks</tt> did not yet exist.
4695 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4696 See <ref id="conflicts"> for more information about the
4701 <sect id="conflicts">
4702 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4705 When one binary package declares a conflict with another
4706 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4707 refuse to allow them to be installed on the system at the
4708 same time. This is a stronger restriction than <tt>Breaks</tt>,
4709 which just prevents both packages from being configured at the
4710 same time. Conflicting packages cannot be unpacked on the
4711 system at the same time.
4715 If one package is to be installed, the other must be removed
4716 first. If the package being installed is marked as replacing
4717 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4718 normally be used in this case) the one on the system, or the one
4719 on the system is marked as deselected, or both packages are
4720 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4721 automatically remove the package which is causing the conflict.
4722 Otherwise, it will halt the installation of the new package with
4723 an error. This mechanism is specifically designed to produce an
4724 error when the installed package is <tt>Essential</tt>, but the
4729 A package will not cause a conflict merely because its
4730 configuration files are still installed; it must be at least
4735 A special exception is made for packages which declare a
4736 conflict with their own package name, or with a virtual
4737 package which they provide (see below): this does not
4738 prevent their installation, and allows a package to conflict
4739 with others providing a replacement for it. You use this
4740 feature when you want the package in question to be the only
4741 package providing some feature.
4745 Normally, <tt>Breaks</tt> should be used instead
4746 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4747 stronger restriction on the ordering of package installation or
4748 upgrade and can make it more difficult for the package manager
4749 to find a correct solution to an upgrade or installation
4750 problem. <tt>Breaks</tt> should be used
4752 <item>when moving a file from one package to another (see
4753 <ref id="replaces">),</item>
4754 <item>when splitting a package (a special case of the previous
4756 <item>when the breaking package exposes a bug in or interacts
4757 badly with particular versions of the broken
4760 <tt>Conflicts</tt> should be used
4762 <item>when two packages provide the same file and will
4763 continue to do so,</item>
4764 <item>in conjunction with <tt>Provides</tt> when only one
4765 package providing a given virtual facility may be installed
4766 at a time (see <ref id="virtual">),</item>
4767 <item>in other cases where one must prevent simultaneous
4768 installation of two packages for reasons that are ongoing
4769 (not fixed in a later version of one of the packages) or
4770 that must prevent both packages from being unpacked at the
4771 same time, not just configured.</item>
4773 Be aware that adding <tt>Conflicts</tt> is normally not the best
4774 solution when two packages provide the same files. Depending on
4775 the reason for that conflict, using alternatives or renaming the
4776 files is often a better approach. See, for
4777 example, <ref id="binaries">.
4781 A <tt>Conflicts</tt> entry may have an "earlier than" version
4782 clause if the reason for the conflict is corrected in a later
4783 version of one of the packages. However, normally the presence
4784 of an "earlier than" version clause is a sign
4785 that <tt>Breaks</tt> should have been used instead. An "earlier
4786 than" version clause in <tt>Conflicts</tt>
4787 prevents <prgn>dpkg</prgn> from upgrading or installing the
4788 package which declares such a conflict until the upgrade or
4789 removal of the conflicted-with package has been completed, which
4790 is a strong restriction.
4794 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4798 As well as the names of actual ("concrete") packages, the
4799 package relationship fields <tt>Depends</tt>,
4800 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4801 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4802 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4803 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4804 may mention "virtual packages".
4808 A <em>virtual package</em> is one which appears in the
4809 <tt>Provides</tt> control file field of another package.
4810 The effect is as if the package(s) which provide a
4811 particular virtual package name had been listed by name
4812 everywhere the virtual package name appears. (See also <ref
4817 If there are both concrete and virtual packages of the same
4818 name, then the dependency may be satisfied (or the conflict
4819 caused) by either the concrete package with the name in
4820 question or any other concrete package which provides the
4821 virtual package with the name in question. This is so that,
4822 for example, supposing we have
4823 <example compact="compact">
4826 </example> and someone else releases an enhanced version of
4827 the <tt>bar</tt> package they can say:
4828 <example compact="compact">
4832 and the <tt>bar-plus</tt> package will now also satisfy the
4833 dependency for the <tt>foo</tt> package.
4837 If a relationship field has a version number attached, only real
4838 packages will be considered to see whether the relationship is
4839 satisfied (or the prohibition violated, for a conflict or
4840 breakage). In other words, if a version number is specified,
4841 this is a request to ignore all <tt>Provides</tt> for that
4842 package name and consider only real packages. The package
4843 manager will assume that a package providing that virtual
4844 package is not of the "right" version. A <tt>Provides</tt>
4845 field may not contain version numbers, and the version number of
4846 the concrete package which provides a particular virtual package
4847 will not be considered when considering a dependency on or
4848 conflict with the virtual package name.<footnote>
4849 It is possible that a future release of <prgn>dpkg</prgn> may
4850 add the ability to specify a version number for each virtual
4851 package it provides. This feature is not yet present,
4852 however, and is expected to be used only infrequently.
4857 To specify which of a set of real packages should be the default
4858 to satisfy a particular dependency on a virtual package, list
4859 the real package as an alternative before the virtual one.
4863 If the virtual package represents a facility that can only be
4864 provided by one real package at a time, such as
4865 the <package>mail-transport-agent</package> virtual package that
4866 requires installation of a binary that would conflict with all
4867 other providers of that virtual package (see
4868 <ref id="mail-transport-agents">), all packages providing that
4869 virtual package should also declare a conflict with it
4870 using <tt>Conflicts</tt>. This will ensure that at most one
4871 provider of that virtual package is unpacked or installed at a
4876 <sect id="replaces"><heading>Overwriting files and replacing
4877 packages - <tt>Replaces</tt></heading>
4880 Packages can declare in their control file that they should
4881 overwrite files in certain other packages, or completely
4882 replace other packages. The <tt>Replaces</tt> control file
4883 field has these two distinct purposes.
4886 <sect1><heading>Overwriting files in other packages</heading>
4889 It is usually an error for a package to contain files which
4890 are on the system in another package. However, if the
4891 overwriting package declares that it <tt>Replaces</tt> the one
4892 containing the file being overwritten, then <prgn>dpkg</prgn>
4893 will replace the file from the old package with that from the
4894 new. The file will no longer be listed as "owned" by the old
4895 package and will be taken over by the new package.
4896 Normally, <tt>Breaks</tt> should be used in conjunction
4897 with <tt>Replaces</tt>.<footnote>
4898 To see why <tt>Breaks</tt> is normally needed in addition
4899 to <tt>Replaces</tt>, consider the case of a file in the
4900 package <package>foo</package> being taken over by the
4901 package <package>foo-data</package>.
4902 <tt>Replaces</tt> will allow <package>foo-data</package> to
4903 be installed and take over that file. However,
4904 without <tt>Breaks</tt>, nothing
4905 requires <package>foo</package> to be upgraded to a newer
4906 version that knows it does not include that file and instead
4907 depends on <package>foo-data</package>. Nothing would
4908 prevent the new <package>foo-data</package> package from
4909 being installed and then removed, removing the file that it
4910 took over from <package>foo</package>. After that
4911 operation, the package manager would think the system was in
4912 a consistent state, but the <package>foo</package> package
4913 would be missing one of its files.
4918 For example, if a package <package>foo</package> is split
4919 into <package>foo</package> and <package>foo-data</package>
4920 starting at version 1.2-3, <package>foo-data</package> would
4922 <example compact="compact">
4923 Replaces: foo (<< 1.2-3)
4924 Breaks: foo (<< 1.2-3)
4926 in its control file. The new version of the
4927 package <package>foo</package> would normally have the field
4928 <example compact="compact">
4929 Depends: foo-data (>= 1.2-3)
4931 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4932 the files moved into <package>foo-data</package> are not
4933 required for normal operation).
4937 If a package is completely replaced in this way, so that
4938 <prgn>dpkg</prgn> does not know of any files it still
4939 contains, it is considered to have "disappeared". It will
4940 be marked as not wanted on the system (selected for
4941 removal) and not installed. Any <tt>conffile</tt>s
4942 details noted for the package will be ignored, as they
4943 will have been taken over by the overwriting package. The
4944 package's <prgn>postrm</prgn> script will be run with a
4945 special argument to allow the package to do any final
4946 cleanup required. See <ref id="mscriptsinstact">.
4948 Replaces is a one way relationship. You have to install
4949 the replacing package after the replaced package.
4954 For this usage of <tt>Replaces</tt>, virtual packages (see
4955 <ref id="virtual">) are not considered when looking at a
4956 <tt>Replaces</tt> field. The packages declared as being
4957 replaced must be mentioned by their real names.
4961 This usage of <tt>Replaces</tt> only takes effect when both
4962 packages are at least partially on the system at once. It is
4963 not relevant if the packages conflict unless the conflict has
4968 <sect1><heading>Replacing whole packages, forcing their
4972 Second, <tt>Replaces</tt> allows the packaging system to
4973 resolve which package should be removed when there is a
4974 conflict (see <ref id="conflicts">). This usage only takes
4975 effect when the two packages <em>do</em> conflict, so that the
4976 two usages of this field do not interfere with each other.
4980 In this situation, the package declared as being replaced
4981 can be a virtual package, so for example, all mail
4982 transport agents (MTAs) would have the following fields in
4983 their control files:
4984 <example compact="compact">
4985 Provides: mail-transport-agent
4986 Conflicts: mail-transport-agent
4987 Replaces: mail-transport-agent
4989 ensuring that only one MTA can be installed at any one
4990 time. See <ref id="virtual"> for more information about this
4995 <sect id="sourcebinarydeps">
4996 <heading>Relationships between source and binary packages -
4997 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4998 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5002 Source packages that require certain binary packages to be
5003 installed or absent at the time of building the package
5004 can declare relationships to those binary packages.
5008 This is done using the <tt>Build-Depends</tt>,
5009 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5010 <tt>Build-Conflicts-Indep</tt> control file fields.
5014 Build-dependencies on "build-essential" binary packages can be
5015 omitted. Please see <ref id="pkg-relations"> for more information.
5019 The dependencies and conflicts they define must be satisfied
5020 (as defined earlier for binary packages) in order to invoke
5021 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5023 There is no Build-Depends-Arch; this role is essentially
5024 met with Build-Depends. Anyone building the
5025 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5026 assumed to be building the whole package, and therefore
5027 installation of all build dependencies is required.
5030 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5031 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5032 not yet know how to check for its existence, and
5033 <tt>binary-arch</tt>. The purpose of the original split
5034 between <tt>Build-Depends</tt> and
5035 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5036 wouldn't need to install extra packages needed only for the
5037 binary-indep targets. But without a build-arch/build-indep
5038 split, this didn't work, since most of the work is done in
5039 the build target, not in the binary target.
5043 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5044 <tt>binary-arch</tt></tag>
5046 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5047 fields must be satisfied when these targets are invoked.
5049 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5050 and <tt>binary-indep</tt></tag>
5052 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5053 <tt>Build-Depends-Indep</tt>, and
5054 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5055 these targets are invoked.
5063 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5066 Packages containing shared libraries must be constructed with
5067 a little care to make sure that the shared library is always
5068 available. This is especially important for packages whose
5069 shared libraries are vitally important, such as the C library
5070 (currently <tt>libc6</tt>).
5074 Packages involving shared libraries should be split up into
5075 several binary packages. This section mostly deals with how
5076 this separation is to be accomplished; rules for files within
5077 the shared library packages are in <ref id="libraries"> instead.
5080 <sect id="sharedlibs-runtime">
5081 <heading>Run-time shared libraries</heading>
5084 The run-time shared library needs to be placed in a package
5085 whose name changes whenever the shared object version
5088 Since it is common place to install several versions of a
5089 package that just provides shared libraries, it is a
5090 good idea that the library package should not
5091 contain any extraneous non-versioned files, unless they
5092 happen to be in versioned directories.</p>
5094 The most common mechanism is to place it in a package
5096 <package><var>libraryname</var><var>soversion</var></package>,
5097 where <file><var>soversion</var></file> is the version number
5098 in the soname of the shared library<footnote>
5099 The soname is the shared object name: it's the thing
5100 that has to match exactly between building an executable
5101 and running it for the dynamic linker to be able run the
5102 program. For example, if the soname of the library is
5103 <file>libfoo.so.6</file>, the library package would be
5104 called <file>libfoo6</file>.
5106 Alternatively, if it would be confusing to directly append
5107 <var>soversion</var> to <var>libraryname</var> (e.g. because
5108 <var>libraryname</var> itself ends in a number), you may use
5109 <package><var>libraryname</var>-<var>soversion</var></package> and
5110 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5115 If you have several shared libraries built from the same
5116 source tree you may lump them all together into a single
5117 shared library package, provided that you change all of
5118 their sonames at once (so that you don't get filename
5119 clashes if you try to install different versions of the
5120 combined shared libraries package).
5124 The package should install the shared libraries under
5125 their normal names. For example, the <package>libgdbm3</package>
5126 package should install <file>libgdbm.so.3.0.0</file> as
5127 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5128 renamed or re-linked by any <prgn>prerm</prgn> or
5129 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5130 of renaming things safely without affecting running programs,
5131 and attempts to interfere with this are likely to lead to
5136 Shared libraries should not be installed executable, since
5137 the dynamic linker does not require this and trying to
5138 execute a shared library usually results in a core dump.
5142 The run-time library package should include the symbolic link that
5143 <prgn>ldconfig</prgn> would create for the shared libraries.
5144 For example, the <package>libgdbm3</package> package should include
5145 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5146 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5147 linker (for example <prgn>ld.so</prgn> or
5148 <prgn>ld-linux.so.*</prgn>) can find the library between the
5149 time that <prgn>dpkg</prgn> installs it and the time that
5150 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5152 The package management system requires the library to be
5153 placed before the symbolic link pointing to it in the
5154 <file>.deb</file> file. This is so that when
5155 <prgn>dpkg</prgn> comes to install the symlink
5156 (overwriting the previous symlink pointing at an older
5157 version of the library), the new shared library is already
5158 in place. In the past, this was achieved by creating the
5159 library in the temporary packaging directory before
5160 creating the symlink. Unfortunately, this was not always
5161 effective, since the building of the tar file in the
5162 <file>.deb</file> depended on the behavior of the underlying
5163 file system. Some file systems (such as reiserfs) reorder
5164 the files so that the order of creation is forgotten.
5165 Since version 1.7.0, <prgn>dpkg</prgn>
5166 reorders the files itself as necessary when building a
5167 package. Thus it is no longer important to concern
5168 oneself with the order of file creation.
5172 <sect1 id="ldconfig">
5173 <heading><tt>ldconfig</tt></heading>
5176 Any package installing shared libraries in one of the default
5177 library directories of the dynamic linker (which are currently
5178 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5179 listed in <file>/etc/ld.so.conf</file><footnote>
5181 <list compact="compact">
5182 <item>/usr/local/lib</item>
5183 <item>/usr/lib/libc5-compat</item>
5184 <item>/lib/libc5-compat</item>
5187 must use <prgn>ldconfig</prgn> to update the shared library
5192 The package maintainer scripts must only call
5193 <prgn>ldconfig</prgn> under these circumstances:
5194 <list compact="compact">
5195 <item>When the <prgn>postinst</prgn> script is run with a
5196 first argument of <tt>configure</tt>, the script must call
5197 <prgn>ldconfig</prgn>, and may optionally invoke
5198 <prgn>ldconfig</prgn> at other times.
5200 <item>When the <prgn>postrm</prgn> script is run with a
5201 first argument of <tt>remove</tt>, the script should call
5202 <prgn>ldconfig</prgn>.
5207 During install or upgrade, the preinst is called before
5208 the new files are installed, so calling "ldconfig" is
5209 pointless. The preinst of an existing package can also be
5210 called if an upgrade fails. However, this happens during
5211 the critical time when a shared libs may exist on-disk
5212 under a temporary name. Thus, it is dangerous and
5213 forbidden by current policy to call "ldconfig" at this
5218 When a package is installed or upgraded, "postinst
5219 configure" runs after the new files are safely on-disk.
5220 Since it is perfectly safe to invoke ldconfig
5221 unconditionally in a postinst, it is OK for a package to
5222 simply put ldconfig in its postinst without checking the
5223 argument. The postinst can also be called to recover from
5224 a failed upgrade. This happens before any new files are
5225 unpacked, so there is no reason to call "ldconfig" at this
5230 For a package that is being removed, prerm is
5231 called with all the files intact, so calling ldconfig is
5232 useless. The other calls to "prerm" happen in the case of
5233 upgrade at a time when all the files of the old package
5234 are on-disk, so again calling "ldconfig" is pointless.
5238 postrm, on the other hand, is called with the "remove"
5239 argument just after the files are removed, so this is
5240 the proper time to call "ldconfig" to notify the system
5241 of the fact that the shared libraries from the package
5242 are removed. The postrm can be called at several other
5243 times. At the time of "postrm purge", "postrm
5244 abort-install", or "postrm abort-upgrade", calling
5245 "ldconfig" is useless because the shared lib files are
5246 not on-disk. However, when "postrm" is invoked with
5247 arguments "upgrade", "failed-upgrade", or "disappear", a
5248 shared lib may exist on-disk under a temporary filename.
5256 <sect id="sharedlibs-support-files">
5257 <heading>Shared library support files</heading>
5260 If your package contains files whose names do not change with
5261 each change in the library shared object version, you must not
5262 put them in the shared library package. Otherwise, several
5263 versions of the shared library cannot be installed at the same
5264 time without filename clashes, making upgrades and transitions
5265 unnecessarily difficult.
5269 It is recommended that supporting files and run-time support
5270 programs that do not need to be invoked manually by users, but
5271 are nevertheless required for the package to function, be placed
5272 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5273 preferably under <file>/usr/lib/</file><var>package-name</var>.
5274 If the program or file is architecture independent, the
5275 recommendation is for it to be placed in a subdirectory of
5276 <file>/usr/share</file> instead, preferably under
5277 <file>/usr/share/</file><var>package-name</var>. Following the
5278 <var>package-name</var> naming convention ensures that the file
5279 names change when the shared object version changes.
5283 Run-time support programs that use the shared library but are
5284 not required for the library to function or files used by the
5285 shared library that can be used by any version of the shared
5286 library package should instead be put in a separate package.
5287 This package might typically be named
5288 <package><var>libraryname</var>-tools</package>; note the
5289 absence of the <var>soversion</var> in the package name.
5293 Files and support programs only useful when compiling software
5294 against the library should be included in the development
5295 package for the library.<footnote>
5296 For example, a <file><var>package-name</var>-config</file>
5297 script or <package>pkg-config</package> configuration files.
5302 <sect id="sharedlibs-static">
5303 <heading>Static libraries</heading>
5306 The static library (<file><var>libraryname.a</var></file>)
5307 is usually provided in addition to the shared version.
5308 It is placed into the development package (see below).
5312 In some cases, it is acceptable for a library to be
5313 available in static form only; these cases include:
5315 <item>libraries for languages whose shared library support
5316 is immature or unstable</item>
5317 <item>libraries whose interfaces are in flux or under
5318 development (commonly the case when the library's
5319 major version number is zero, or where the ABI breaks
5320 across patchlevels)</item>
5321 <item>libraries which are explicitly intended to be
5322 available only in static form by their upstream
5327 <sect id="sharedlibs-dev">
5328 <heading>Development files</heading>
5331 If there are development files associated with a shared library,
5332 the source package needs to generate a binary development package
5333 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5334 or if you prefer only to support one development version at a
5335 time, <package><var>libraryname</var>-dev</package>. Installing
5336 the development package must result in installation of all the
5337 development files necessary for compiling programs against that
5338 shared library.<footnote>
5339 This wording allows the development files to be split into
5340 several packages, such as a separate architecture-independent
5341 <package><var>libraryname</var>-headers</package>, provided that
5342 the development package depends on all the required additional
5348 In case several development versions of a library exist, you may
5349 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5350 <ref id="conflicts">) to ensure that the user only installs one
5351 development version at a time (as different development versions are
5352 likely to have the same header files in them, which would cause a
5353 filename clash if both were installed).
5357 The development package should contain a symlink for the associated
5358 shared library without a version number. For example, the
5359 <package>libgdbm-dev</package> package should include a symlink
5360 from <file>/usr/lib/libgdbm.so</file> to
5361 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5362 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5363 <file>libgdbm.so</file> when compiling dynamically.
5367 <sect id="sharedlibs-intradeps">
5368 <heading>Dependencies between the packages of the same library</heading>
5371 Typically the development version should have an exact
5372 version dependency on the runtime library, to make sure that
5373 compilation and linking happens correctly. The
5374 <tt>${binary:Version}</tt> substitution variable can be
5375 useful for this purpose.
5377 Previously, <tt>${Source-Version}</tt> was used, but its name
5378 was confusing and it has been deprecated since dpkg 1.13.19.
5383 <sect id="sharedlibs-shlibdeps">
5384 <heading>Dependencies between the library and other packages -
5385 the <tt>shlibs</tt> system</heading>
5388 If a package contains a binary or library which links to a
5389 shared library, we must ensure that when the package is
5390 installed on the system, all of the libraries needed are
5391 also installed. This requirement led to the creation of the
5392 <tt>shlibs</tt> system, which is very simple in its design:
5393 any package which <em>provides</em> a shared library also
5394 provides information on the package dependencies required to
5395 ensure the presence of this library, and any package which
5396 <em>uses</em> a shared library uses this information to
5397 determine the dependencies it requires. The files which
5398 contain the mapping from shared libraries to the necessary
5399 dependency information are called <file>shlibs</file> files.
5403 When a package is built which contains any shared libraries, it
5404 must provide a <file>shlibs</file> file for other packages to
5405 use. When a package is built which contains any shared
5406 libraries or compiled binaries, it must run
5407 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5408 on these to determine the libraries used and hence the
5409 dependencies needed by this package.<footnote>
5411 <prgn>dpkg-shlibdeps</prgn> will use a program
5412 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5413 the libraries directly needed by the binaries or shared
5414 libraries in the package.
5418 We say that a binary <tt>foo</tt> <em>directly</em> uses
5419 a library <tt>libbar</tt> if it is explicitly linked
5420 with that library (that is, the library is listed in the ELF
5421 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5422 to the link line when the binary is created). Other
5423 libraries that are needed by <tt>libbar</tt> are linked
5424 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5425 linker will load them automatically when it loads
5426 <tt>libbar</tt>. A package should depend on the libraries
5427 it directly uses, but not the libraries it indirectly uses.
5428 The dependencies for those libraries will automatically pull
5429 in the other libraries.
5433 A good example of where this helps is the following. We
5434 could update <tt>libimlib</tt> with a new version that
5435 supports a new graphics format called dgf (but retaining the
5436 same major version number) and depends on <tt>libdgf</tt>.
5437 If we used <prgn>ldd</prgn> to add dependencies for every
5438 library directly or indirectly linked with a binary, every
5439 package that uses <tt>libimlib</tt> would need to be
5440 recompiled so it would also depend on <tt>libdgf</tt> or it
5441 wouldn't run due to missing symbols. Since dependencies are
5442 only added based on ELF <tt>NEEDED</tt> attribute, packages
5443 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5444 having the dependency on <tt>libdgf</tt> and so they would
5445 not need rebuilding.
5451 In the following sections, we will first describe where the
5452 various <tt>shlibs</tt> files are to be found, then how to
5453 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5454 file format and how to create them if your package contains a
5459 <heading>The <tt>shlibs</tt> files present on the system</heading>
5462 There are several places where <tt>shlibs</tt> files are
5463 found. The following list gives them in the order in which
5465 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5466 (The first one which gives the required information is used.)
5472 <p><file>debian/shlibs.local</file></p>
5475 This lists overrides for this package. This file should
5476 normally not be used, but may be needed temporarily in
5477 unusual situations to work around bugs in other packages,
5478 or in unusual cases where the normally declared dependency
5479 information in the installed <file>shlibs</file> file for
5480 a library cannot be used. The contents of this file
5481 override information obtained from any other source.
5486 <p><file>/etc/dpkg/shlibs.override</file></p>
5489 This lists global overrides. This list is normally
5490 empty. It is maintained by the local system
5496 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5499 When packages are being built,
5500 any <file>debian/shlibs</file> files are copied into the
5501 control file area of the temporary build directory and
5502 given the name <file>shlibs</file>. These files give
5503 details of any shared libraries included in the same
5505 An example may help here. Let us say that the source
5506 package <tt>foo</tt> generates two binary
5507 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5508 When building the binary packages, the two packages are
5509 created in the directories <file>debian/libfoo2</file>
5510 and <file>debian/foo-runtime</file> respectively.
5511 (<file>debian/tmp</file> could be used instead of one of
5512 these.) Since <tt>libfoo2</tt> provides the
5513 <tt>libfoo</tt> shared library, it will require a
5514 <tt>shlibs</tt> file, which will be installed in
5515 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5516 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5517 When <prgn>dpkg-shlibdeps</prgn> is run on the
5518 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5520 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5521 determine whether <tt>foo-prog</tt>'s library
5522 dependencies are satisfied by any of the libraries
5523 provided by <tt>libfoo2</tt>. For this reason,
5524 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5525 the individual binary packages' <tt>shlibs</tt> files
5526 have been installed into the build directory.
5532 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5535 These are the <file>shlibs</file> files corresponding to
5536 all of the packages installed on the system, and are
5537 maintained by the relevant package maintainers.
5542 <p><file>/etc/dpkg/shlibs.default</file></p>
5545 This file lists any shared libraries whose packages
5546 have failed to provide correct <file>shlibs</file> files.
5547 It was used when the <file>shlibs</file> setup was first
5548 introduced, but it is now normally empty. It is
5549 maintained by the <tt>dpkg</tt> maintainer.
5557 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5558 <file>shlibs</file> files</heading>
5562 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5563 into your <file>debian/rules</file> file. If your package
5564 contains only compiled binaries and libraries (but no scripts),
5565 you can use a command such as:
5566 <example compact="compact">
5567 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5568 debian/tmp/usr/lib/*
5570 Otherwise, you will need to explicitly list the compiled
5571 binaries and libraries.<footnote>
5572 If you are using <tt>debhelper</tt>, the
5573 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5574 It will also correctly handle multi-binary packages.
5579 This command puts the dependency information into the
5580 <file>debian/substvars</file> file, which is then used by
5581 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5582 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5583 field in the control file for this to work.
5587 If you have multiple binary packages, you will need to call
5588 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5589 compiled libraries or binaries. In such a case, you will
5590 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5591 utilities to specify a different <file>substvars</file> file.
5595 If you are creating a udeb for use in the Debian Installer,
5596 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5597 should use the dependency line of type <tt>udeb</tt> by
5598 adding the <tt>-tudeb</tt> option<footnote>
5599 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5600 will automatically add this option if it knows it is
5602 </footnote>. If there is no dependency line of
5603 type <tt>udeb</tt> in the <file>shlibs</file>
5604 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5609 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5610 <ref id="pkg-dpkg-shlibdeps"> and
5611 <manref name="dpkg-shlibdeps" section="1">.
5616 <heading>The <file>shlibs</file> File Format</heading>
5619 Each <file>shlibs</file> file has the same format. Lines
5620 beginning with <tt>#</tt> are considered to be comments and
5621 are ignored. Each line is of the form:
5622 <example compact="compact">
5623 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5628 We will explain this by reference to the example of the
5629 <tt>zlib1g</tt> package, which (at the time of writing)
5630 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5634 <var>type</var> is an optional element that indicates the type
5635 of package for which the line is valid. The only type currently
5636 in use is <tt>udeb</tt>. The colon and space after the type are
5641 <var>library-name</var> is the name of the shared library,
5642 in this case <tt>libz</tt>. (This must match the name part
5643 of the soname, see below.)
5647 <var>soname-version</var> is the version part of the soname of
5648 the library. The soname is the thing that must exactly match
5649 for the library to be recognized by the dynamic linker, and is
5651 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5652 example, <tt>libz.so.1</tt>.<footnote>
5653 This can be determined using the command
5654 <example compact="compact">
5655 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5658 The version part is the part which comes after
5659 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5660 instead be of the form
5661 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5662 as <tt>libdb-4.8.so</tt>, in which case the name would
5663 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5667 <var>dependencies</var> has the same syntax as a dependency
5668 field in a binary package control file. It should give
5669 details of which packages are required to satisfy a binary
5670 built against the version of the library contained in the
5671 package. See <ref id="depsyntax"> for details.
5675 In our example, if the first version of the <tt>zlib1g</tt>
5676 package which contained a minor number of at least
5677 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5678 <tt>shlibs</tt> entry for this library could say:
5679 <example compact="compact">
5680 libz 1 zlib1g (>= 1:1.1.3)
5682 The version-specific dependency is to avoid warnings from
5683 the dynamic linker about using older shared libraries with
5688 As zlib1g also provides a udeb containing the shared library,
5689 there would also be a second line:
5690 <example compact="compact">
5691 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5697 <heading>Providing a <file>shlibs</file> file</heading>
5700 If your package provides a shared library, you need to create
5701 a <file>shlibs</file> file following the format described above.
5702 It is usual to call this file <file>debian/shlibs</file> (but if
5703 you have multiple binary packages, you might want to call it
5704 <file>debian/shlibs.<var>package</var></file> instead). Then
5705 let <file>debian/rules</file> install it in the control area:
5706 <example compact="compact">
5707 install -m644 debian/shlibs debian/tmp/DEBIAN
5709 or, in the case of a multi-binary package:
5710 <example compact="compact">
5711 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5713 An alternative way of doing this is to create the
5714 <file>shlibs</file> file in the control area directly from
5715 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5716 file at all,<footnote>
5717 This is what <prgn>dh_makeshlibs</prgn> in
5718 the <package>debhelper</package> suite does. If your package
5719 also has a udeb that provides a shared
5720 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5721 the <tt>udeb:</tt> lines if you specify the name of the udeb
5722 with the <tt>--add-udeb</tt> option.
5724 since the <file>debian/shlibs</file> file itself is ignored by
5725 <prgn>dpkg-shlibdeps</prgn>.
5729 As <prgn>dpkg-shlibdeps</prgn> reads the
5730 <file>DEBIAN/shlibs</file> files in all of the binary packages
5731 being built from this source package, all of the
5732 <file>DEBIAN/shlibs</file> files should be installed before
5733 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5741 <chapt id="opersys"><heading>The Operating System</heading>
5744 <heading>File system hierarchy</heading>
5748 <heading>File System Structure</heading>
5751 The location of all installed files and directories must
5752 comply with the Filesystem Hierarchy Standard (FHS),
5753 version 2.3, with the exceptions noted below, and except
5754 where doing so would violate other terms of Debian
5755 Policy. The following exceptions to the FHS apply:
5760 The optional rules related to user specific
5761 configuration files for applications are stored in
5762 the user's home directory are relaxed. It is
5763 recommended that such files start with the
5764 '<tt>.</tt>' character (a "dot file"), and if an
5765 application needs to create more than one dot file
5766 then the preferred placement is in a subdirectory
5767 with a name starting with a '.' character, (a "dot
5768 directory"). In this case it is recommended the
5769 configuration files not start with the '.'
5775 The requirement for amd64 to use <file>/lib64</file>
5776 for 64 bit binaries is removed.
5781 The requirement for object files, internal binaries, and
5782 libraries, including <file>libc.so.*</file>, to be located
5783 directly under <file>/lib{,32}</file> and
5784 <file>/usr/lib{,32}</file> is amended, permitting files
5785 to instead be installed to
5786 <file>/lib/<var>triplet</var></file> and
5787 <file>/usr/lib/<var>triplet</var></file>, where
5788 <tt><var>triplet</var></tt> is the value returned by
5789 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5790 architecture of the package. Packages may <em>not</em>
5791 install files to any <var>triplet</var> path other
5792 than the one matching the architecture of that package;
5793 for instance, an <tt>Architecture: amd64</tt> package
5794 containing 32-bit x86 libraries may not install these
5795 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5797 This is necessary in order to reserve the directories for
5798 use in cross-installation of library packages from other
5799 architectures, as part of the planned deployment of
5804 Applications may also use a single subdirectory under
5805 <file>/usr/lib/<var>triplet</var></file>.
5808 The execution time linker/loader, ld*, must still be made
5809 available in the existing location under /lib or /lib64
5810 since this is part of the ELF ABI for the architecture.
5815 The requirement that
5816 <file>/usr/local/share/man</file> be "synonymous"
5817 with <file>/usr/local/man</file> is relaxed to a
5822 The requirement that windowmanagers with a single
5823 configuration file call it <file>system.*wmrc</file>
5824 is removed, as is the restriction that the window
5825 manager subdirectory be named identically to the
5826 window manager name itself.
5831 The requirement that boot manager configuration
5832 files live in <file>/etc</file>, or at least are
5833 symlinked there, is relaxed to a recommendation.
5838 The following directories in the root filesystem are
5839 additionally allowed: <file>/sys</file> and
5840 <file>/selinux</file>. <footnote>These directories
5841 are used as mount points to mount virtual filesystems
5842 to get access to kernel information.</footnote>
5849 The version of this document referred here can be
5850 found in the <tt>debian-policy</tt> package or on <url
5851 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5852 name="FHS (Debian copy)"> alongside this manual (or, if
5853 you have the <package>debian-policy</package> installed,
5855 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5856 (local copy)">). The
5857 latest version, which may be a more recent version, may
5859 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5860 Specific questions about following the standard may be
5861 asked on the <tt>debian-devel</tt> mailing list, or
5862 referred to the FHS mailing list (see the
5863 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5869 <heading>Site-specific programs</heading>
5872 As mandated by the FHS, packages must not place any
5873 files in <file>/usr/local</file>, either by putting them in
5874 the file system archive to be unpacked by <prgn>dpkg</prgn>
5875 or by manipulating them in their maintainer scripts.
5879 However, the package may create empty directories below
5880 <file>/usr/local</file> so that the system administrator knows
5881 where to place site-specific files. These are not
5882 directories <em>in</em> <file>/usr/local</file>, but are
5883 children of directories in <file>/usr/local</file>. These
5884 directories (<file>/usr/local/*/dir/</file>)
5885 should be removed on package removal if they are
5890 Note that this applies only to
5891 directories <em>below</em> <file>/usr/local</file>,
5892 not <em>in</em> <file>/usr/local</file>. Packages must
5893 not create sub-directories in the
5894 directory <file>/usr/local</file> itself, except those
5895 listed in FHS, section 4.5. However, you may create
5896 directories below them as you wish. You must not remove
5897 any of the directories listed in 4.5, even if you created
5902 Since <file>/usr/local</file> can be mounted read-only from a
5903 remote server, these directories must be created and
5904 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5905 maintainer scripts and not be included in the
5906 <file>.deb</file> archive. These scripts must not fail if
5907 either of these operations fail.
5911 For example, the <tt>emacsen-common</tt> package could
5912 contain something like
5913 <example compact="compact">
5914 if [ ! -e /usr/local/share/emacs ]
5916 if mkdir /usr/local/share/emacs 2>/dev/null
5918 chown root:staff /usr/local/share/emacs
5919 chmod 2775 /usr/local/share/emacs
5923 in its <prgn>postinst</prgn> script, and
5924 <example compact="compact">
5925 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5926 rmdir /usr/local/share/emacs 2>/dev/null || true
5928 in the <prgn>prerm</prgn> script. (Note that this form is
5929 used to ensure that if the script is interrupted, the
5930 directory <file>/usr/local/share/emacs</file> will still be
5935 If you do create a directory in <file>/usr/local</file> for
5936 local additions to a package, you should ensure that
5937 settings in <file>/usr/local</file> take precedence over the
5938 equivalents in <file>/usr</file>.
5942 However, because <file>/usr/local</file> and its contents are
5943 for exclusive use of the local administrator, a package
5944 must not rely on the presence or absence of files or
5945 directories in <file>/usr/local</file> for normal operation.
5949 The <file>/usr/local</file> directory itself and all the
5950 subdirectories created by the package should (by default) have
5951 permissions 2775 (group-writable and set-group-id) and be
5952 owned by <tt>root:staff</tt>.
5957 <heading>The system-wide mail directory</heading>
5959 The system-wide mail directory
5960 is <file>/var/mail</file>. This directory is part of the
5961 base system and should not be owned by any particular mail
5962 agents. The use of the old
5963 location <file>/var/spool/mail</file> is deprecated, even
5964 though the spool may still be physically located there.
5970 <heading>Users and groups</heading>
5973 <heading>Introduction</heading>
5975 The Debian system can be configured to use either plain or
5980 Some user ids (UIDs) and group ids (GIDs) are reserved
5981 globally for use by certain packages. Because some
5982 packages need to include files which are owned by these
5983 users or groups, or need the ids compiled into binaries,
5984 these ids must be used on any Debian system only for the
5985 purpose for which they are allocated. This is a serious
5986 restriction, and we should avoid getting in the way of
5987 local administration policies. In particular, many sites
5988 allocate users and/or local system groups starting at 100.
5992 Apart from this we should have dynamically allocated ids,
5993 which should by default be arranged in some sensible
5994 order, but the behavior should be configurable.
5998 Packages other than <tt>base-passwd</tt> must not modify
5999 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6000 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6005 <heading>UID and GID classes</heading>
6007 The UID and GID numbers are divided into classes as
6013 Globally allocated by the Debian project, the same
6014 on every Debian system. These ids will appear in
6015 the <file>passwd</file> and <file>group</file> files of all
6016 Debian systems, new ids in this range being added
6017 automatically as the <tt>base-passwd</tt> package is
6022 Packages which need a single statically allocated
6023 uid or gid should use one of these; their
6024 maintainers should ask the <tt>base-passwd</tt>
6032 Dynamically allocated system users and groups.
6033 Packages which need a user or group, but can have
6034 this user or group allocated dynamically and
6035 differently on each system, should use <tt>adduser
6036 --system</tt> to create the group and/or user.
6037 <prgn>adduser</prgn> will check for the existence of
6038 the user or group, and if necessary choose an unused
6039 id based on the ranges specified in
6040 <file>adduser.conf</file>.
6044 <tag>1000-59999:</tag>
6047 Dynamically allocated user accounts. By default
6048 <prgn>adduser</prgn> will choose UIDs and GIDs for
6049 user accounts in this range, though
6050 <file>adduser.conf</file> may be used to modify this
6055 <tag>60000-64999:</tag>
6058 Globally allocated by the Debian project, but only
6059 created on demand. The ids are allocated centrally
6060 and statically, but the actual accounts are only
6061 created on users' systems on demand.
6065 These ids are for packages which are obscure or
6066 which require many statically-allocated ids. These
6067 packages should check for and create the accounts in
6068 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6069 <prgn>adduser</prgn> if it has this facility) if
6070 necessary. Packages which are likely to require
6071 further allocations should have a "hole" left after
6072 them in the allocation, to give them room to
6077 <tag>65000-65533:</tag>
6085 User <tt>nobody</tt>. The corresponding gid refers
6086 to the group <tt>nogroup</tt>.
6093 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6094 not</em> be used, because it is the error return
6103 <sect id="sysvinit">
6104 <heading>System run levels and <file>init.d</file> scripts</heading>
6106 <sect1 id="/etc/init.d">
6107 <heading>Introduction</heading>
6110 The <file>/etc/init.d</file> directory contains the scripts
6111 executed by <prgn>init</prgn> at boot time and when the
6112 init state (or "runlevel") is changed (see <manref
6113 name="init" section="8">).
6117 There are at least two different, yet functionally
6118 equivalent, ways of handling these scripts. For the sake
6119 of simplicity, this document describes only the symbolic
6120 link method. However, it must not be assumed by maintainer
6121 scripts that this method is being used, and any automated
6122 manipulation of the various runlevel behaviors by
6123 maintainer scripts must be performed using
6124 <prgn>update-rc.d</prgn> as described below and not by
6125 manually installing or removing symlinks. For information
6126 on the implementation details of the other method,
6127 implemented in the <tt>file-rc</tt> package, please refer
6128 to the documentation of that package.
6132 These scripts are referenced by symbolic links in the
6133 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6134 runlevels, <prgn>init</prgn> looks in the directory
6135 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6136 execute, where <tt><var>n</var></tt> is the runlevel that
6137 is being changed to, or <tt>S</tt> for the boot-up
6142 The names of the links all have the form
6143 <file>S<var>mm</var><var>script</var></file> or
6144 <file>K<var>mm</var><var>script</var></file> where
6145 <var>mm</var> is a two-digit number and <var>script</var>
6146 is the name of the script (this should be the same as the
6147 name of the actual script in <file>/etc/init.d</file>).
6151 When <prgn>init</prgn> changes runlevel first the targets
6152 of the links whose names start with a <tt>K</tt> are
6153 executed, each with the single argument <tt>stop</tt>,
6154 followed by the scripts prefixed with an <tt>S</tt>, each
6155 with the single argument <tt>start</tt>. (The links are
6156 those in the <file>/etc/rc<var>n</var>.d</file> directory
6157 corresponding to the new runlevel.) The <tt>K</tt> links
6158 are responsible for killing services and the <tt>S</tt>
6159 link for starting services upon entering the runlevel.
6163 For example, if we are changing from runlevel 2 to
6164 runlevel 3, init will first execute all of the <tt>K</tt>
6165 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6166 all of the <tt>S</tt> prefixed scripts in that directory.
6167 The links starting with <tt>K</tt> will cause the
6168 referred-to file to be executed with an argument of
6169 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6174 The two-digit number <var>mm</var> is used to determine
6175 the order in which to run the scripts: low-numbered links
6176 have their scripts run first. For example, the
6177 <tt>K20</tt> scripts will be executed before the
6178 <tt>K30</tt> scripts. This is used when a certain service
6179 must be started before another. For example, the name
6180 server <prgn>bind</prgn> might need to be started before
6181 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6182 can set up its access lists. In this case, the script
6183 that starts <prgn>bind</prgn> would have a lower number
6184 than the script that starts <prgn>inn</prgn> so that it
6186 <example compact="compact">
6193 The two runlevels 0 (halt) and 6 (reboot) are slightly
6194 different. In these runlevels, the links with an
6195 <tt>S</tt> prefix are still called after those with a
6196 <tt>K</tt> prefix, but they too are called with the single
6197 argument <tt>stop</tt>.
6201 <sect1 id="writing-init">
6202 <heading>Writing the scripts</heading>
6205 Packages that include daemons for system services should
6206 place scripts in <file>/etc/init.d</file> to start or stop
6207 services at boot time or during a change of runlevel.
6208 These scripts should be named
6209 <file>/etc/init.d/<var>package</var></file>, and they should
6210 accept one argument, saying what to do:
6213 <tag><tt>start</tt></tag>
6214 <item>start the service,</item>
6216 <tag><tt>stop</tt></tag>
6217 <item>stop the service,</item>
6219 <tag><tt>restart</tt></tag>
6220 <item>stop and restart the service if it's already running,
6221 otherwise start the service</item>
6223 <tag><tt>reload</tt></tag>
6224 <item><p>cause the configuration of the service to be
6225 reloaded without actually stopping and restarting
6228 <tag><tt>force-reload</tt></tag>
6229 <item>cause the configuration to be reloaded if the
6230 service supports this, otherwise restart the
6234 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6235 <tt>force-reload</tt> options should be supported by all
6236 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6241 The <file>init.d</file> scripts must ensure that they will
6242 behave sensibly (i.e., returning success and not starting
6243 multiple copies of a service) if invoked with <tt>start</tt>
6244 when the service is already running, or with <tt>stop</tt>
6245 when it isn't, and that they don't kill unfortunately-named
6246 user processes. The best way to achieve this is usually to
6247 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6252 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6253 scripts. Writing correct <file>init.d</file> scripts requires
6254 accepting various error exit statuses when daemons are already
6255 running or already stopped without aborting
6256 the <file>init.d</file> script, and common <file>init.d</file>
6257 function libraries are not safe to call with <tt>set -e</tt>
6259 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6260 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6261 in effect and echoing status messages to the console fails,
6263 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6264 to not use <tt>set -e</tt> and instead check the result of
6265 each command separately.
6269 If a service reloads its configuration automatically (as
6270 in the case of <prgn>cron</prgn>, for example), the
6271 <tt>reload</tt> option of the <file>init.d</file> script
6272 should behave as if the configuration has been reloaded
6277 The <file>/etc/init.d</file> scripts must be treated as
6278 configuration files, either (if they are present in the
6279 package, that is, in the .deb file) by marking them as
6280 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6281 by managing them correctly in the maintainer scripts (see
6282 <ref id="config-files">). This is important since we want
6283 to give the local system administrator the chance to adapt
6284 the scripts to the local system, e.g., to disable a
6285 service without de-installing the package, or to specify
6286 some special command line options when starting a service,
6287 while making sure their changes aren't lost during the next
6292 These scripts should not fail obscurely when the
6293 configuration files remain but the package has been
6294 removed, as configuration files remain on the system after
6295 the package has been removed. Only when <prgn>dpkg</prgn>
6296 is executed with the <tt>--purge</tt> option will
6297 configuration files be removed. In particular, as the
6298 <file>/etc/init.d/<var>package</var></file> script itself is
6299 usually a <tt>conffile</tt>, it will remain on the system
6300 if the package is removed but not purged. Therefore, you
6301 should include a <tt>test</tt> statement at the top of the
6303 <example compact="compact">
6304 test -f <var>program-executed-later-in-script</var> || exit 0
6309 Often there are some variables in the <file>init.d</file>
6310 scripts whose values control the behavior of the scripts,
6311 and which a system administrator is likely to want to
6312 change. As the scripts themselves are frequently
6313 <tt>conffile</tt>s, modifying them requires that the
6314 administrator merge in their changes each time the package
6315 is upgraded and the <tt>conffile</tt> changes. To ease
6316 the burden on the system administrator, such configurable
6317 values should not be placed directly in the script.
6318 Instead, they should be placed in a file in
6319 <file>/etc/default</file>, which typically will have the same
6320 base name as the <file>init.d</file> script. This extra file
6321 should be sourced by the script when the script runs. It
6322 must contain only variable settings and comments in SUSv3
6323 <prgn>sh</prgn> format. It may either be a
6324 <tt>conffile</tt> or a configuration file maintained by
6325 the package maintainer scripts. See <ref id="config-files">
6330 To ensure that vital configurable values are always
6331 available, the <file>init.d</file> script should set default
6332 values for each of the shell variables it uses, either
6333 before sourcing the <file>/etc/default/</file> file or
6334 afterwards using something like the <tt>:
6335 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6336 script must behave sensibly and not fail if the
6337 <file>/etc/default</file> file is deleted.
6341 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6342 as temporary filesystems<footnote>
6343 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6344 options in <file>/etc/default/rcS</file>.
6345 </footnote>, so the <file>init.d</file> scripts must handle this
6346 correctly. This will typically amount to creating any required
6347 subdirectories dynamically when the <file>init.d</file> script
6348 is run, rather than including them in the package and relying on
6349 <prgn>dpkg</prgn> to create them.
6354 <heading>Interfacing with the initscript system</heading>
6357 Maintainers should use the abstraction layer provided by
6358 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6359 programs to deal with initscripts in their packages'
6360 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6361 and <prgn>postrm</prgn>.
6365 Directly managing the /etc/rc?.d links and directly
6366 invoking the <file>/etc/init.d/</file> initscripts should
6367 be done only by packages providing the initscript
6368 subsystem (such as <prgn>sysv-rc</prgn> and
6369 <prgn>file-rc</prgn>).
6373 <heading>Managing the links</heading>
6376 The program <prgn>update-rc.d</prgn> is provided for
6377 package maintainers to arrange for the proper creation and
6378 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6379 or their functional equivalent if another method is being
6380 used. This may be used by maintainers in their packages'
6381 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6385 You must not include any <file>/etc/rc<var>n</var>.d</file>
6386 symbolic links in the actual archive or manually create or
6387 remove the symbolic links in maintainer scripts; you must
6388 use the <prgn>update-rc.d</prgn> program instead. (The
6389 former will fail if an alternative method of maintaining
6390 runlevel information is being used.) You must not include
6391 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6392 in the archive either. (Only the <tt>sysvinit</tt>
6397 By default <prgn>update-rc.d</prgn> will start services in
6398 each of the multi-user state runlevels (2, 3, 4, and 5)
6399 and stop them in the halt runlevel (0), the single-user
6400 runlevel (1) and the reboot runlevel (6). The system
6401 administrator will have the opportunity to customize
6402 runlevels by simply adding, moving, or removing the
6403 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6404 symbolic links are being used, or by modifying
6405 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6410 To get the default behavior for your package, put in your
6411 <prgn>postinst</prgn> script
6412 <example compact="compact">
6413 update-rc.d <var>package</var> defaults
6415 and in your <prgn>postrm</prgn>
6416 <example compact="compact">
6417 if [ "$1" = purge ]; then
6418 update-rc.d <var>package</var> remove
6420 </example>. Note that if your package changes runlevels
6421 or priority, you may have to remove and recreate the links,
6422 since otherwise the old links may persist. Refer to the
6423 documentation of <prgn>update-rc.d</prgn>.
6427 This will use a default sequence number of 20. If it does
6428 not matter when or in which order the <file>init.d</file>
6429 script is run, use this default. If it does, then you
6430 should talk to the maintainer of the <prgn>sysvinit</prgn>
6431 package or post to <tt>debian-devel</tt>, and they will
6432 help you choose a number.
6436 For more information about using <tt>update-rc.d</tt>,
6437 please consult its man page <manref name="update-rc.d"
6443 <heading>Running initscripts</heading>
6445 The program <prgn>invoke-rc.d</prgn> is provided to make
6446 it easier for package maintainers to properly invoke an
6447 initscript, obeying runlevel and other locally-defined
6448 constraints that might limit a package's right to start,
6449 stop and otherwise manage services. This program may be
6450 used by maintainers in their packages' scripts.
6454 The package maintainer scripts must use
6455 <prgn>invoke-rc.d</prgn> to invoke the
6456 <file>/etc/init.d/*</file> initscripts, instead of
6457 calling them directly.
6461 By default, <prgn>invoke-rc.d</prgn> will pass any
6462 action requests (start, stop, reload, restart...) to the
6463 <file>/etc/init.d</file> script, filtering out requests
6464 to start or restart a service out of its intended
6469 Most packages will simply need to change:
6470 <example compact="compact">/etc/init.d/<package>
6471 <action></example> in their <prgn>postinst</prgn>
6472 and <prgn>prerm</prgn> scripts to:
6473 <example compact="compact">
6474 if which invoke-rc.d >/dev/null 2>&1; then
6475 invoke-rc.d <var>package</var> <action>
6477 /etc/init.d/<var>package</var> <action>
6483 A package should register its initscript services using
6484 <prgn>update-rc.d</prgn> before it tries to invoke them
6485 using <prgn>invoke-rc.d</prgn>. Invocation of
6486 unregistered services may fail.
6490 For more information about using
6491 <prgn>invoke-rc.d</prgn>, please consult its man page
6492 <manref name="invoke-rc.d" section="8">.
6498 <heading>Boot-time initialization</heading>
6501 There used to be another directory, <file>/etc/rc.boot</file>,
6502 which contained scripts which were run once per machine
6503 boot. This has been deprecated in favour of links from
6504 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6505 described in <ref id="/etc/init.d">. Packages must not
6506 place files in <file>/etc/rc.boot</file>.
6511 <heading>Example</heading>
6514 An example on which you can base your
6515 <file>/etc/init.d</file> scripts is found in
6516 <file>/etc/init.d/skeleton</file>.
6523 <heading>Console messages from <file>init.d</file> scripts</heading>
6526 This section describes the formats to be used for messages
6527 written to standard output by the <file>/etc/init.d</file>
6528 scripts. The intent is to improve the consistency of
6529 Debian's startup and shutdown look and feel. For this
6530 reason, please look very carefully at the details. We want
6531 the messages to have the same format in terms of wording,
6532 spaces, punctuation and case of letters.
6536 Here is a list of overall rules that should be used for
6537 messages generated by <file>/etc/init.d</file> scripts.
6543 The message should fit in one line (fewer than 80
6544 characters), start with a capital letter and end with
6545 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6549 If the script is performing some time consuming task in
6550 the background (not merely starting or stopping a
6551 program, for instance), an ellipsis (three dots:
6552 <tt>...</tt>) should be output to the screen, with no
6553 leading or tailing whitespace or line feeds.
6557 The messages should appear as if the computer is telling
6558 the user what it is doing (politely :-), but should not
6559 mention "it" directly. For example, instead of:
6560 <example compact="compact">
6561 I'm starting network daemons: nfsd mountd.
6563 the message should say
6564 <example compact="compact">
6565 Starting network daemons: nfsd mountd.
6572 <tt>init.d</tt> script should use the following standard
6573 message formats for the situations enumerated below.
6579 <p>When daemons are started</p>
6582 If the script starts one or more daemons, the output
6583 should look like this (a single line, no leading
6585 <example compact="compact">
6586 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6588 The <var>description</var> should describe the
6589 subsystem the daemon or set of daemons are part of,
6590 while <var>daemon-1</var> up to <var>daemon-n</var>
6591 denote each daemon's name (typically the file name of
6596 For example, the output of <file>/etc/init.d/lpd</file>
6598 <example compact="compact">
6599 Starting printer spooler: lpd.
6604 This can be achieved by saying
6605 <example compact="compact">
6606 echo -n "Starting printer spooler: lpd"
6607 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6610 in the script. If there are more than one daemon to
6611 start, the output should look like this:
6612 <example compact="compact">
6613 echo -n "Starting remote file system services:"
6614 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6615 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6616 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6619 This makes it possible for the user to see what is
6620 happening and when the final daemon has been started.
6621 Care should be taken in the placement of white spaces:
6622 in the example above the system administrators can
6623 easily comment out a line if they don't want to start
6624 a specific daemon, while the displayed message still
6630 <p>When a system parameter is being set</p>
6633 If you have to set up different system parameters
6634 during the system boot, you should use this format:
6635 <example compact="compact">
6636 Setting <var>parameter</var> to "<var>value</var>".
6641 You can use a statement such as the following to get
6643 <example compact="compact">
6644 echo "Setting DNS domainname to \"$domainname\"."
6649 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6650 for the left and right quotation marks. A grave accent
6651 (<tt>`</tt>) is not a quote character; neither is an
6652 apostrophe (<tt>'</tt>).
6657 <p>When a daemon is stopped or restarted</p>
6660 When you stop or restart a daemon, you should issue a
6661 message identical to the startup message, except that
6662 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6663 or <tt>Restarting</tt> respectively.
6667 For example, stopping the printer daemon will look like
6669 <example compact="compact">
6670 Stopping printer spooler: lpd.
6676 <p>When something is executed</p>
6679 There are several examples where you have to run a
6680 program at system startup or shutdown to perform a
6681 specific task, for example, setting the system's clock
6682 using <prgn>netdate</prgn> or killing all processes
6683 when the system shuts down. Your message should look
6685 <example compact="compact">
6686 Doing something very useful...done.
6688 You should print the <tt>done.</tt> immediately after
6689 the job has been completed, so that the user is
6690 informed why they have to wait. You can get this
6692 <example compact="compact">
6693 echo -n "Doing something very useful..."
6702 <p>When the configuration is reloaded</p>
6705 When a daemon is forced to reload its configuration
6706 files you should use the following format:
6707 <example compact="compact">
6708 Reloading <var>description</var> configuration...done.
6710 where <var>description</var> is the same as in the
6711 daemon starting message.
6719 <heading>Cron jobs</heading>
6722 Packages must not modify the configuration file
6723 <file>/etc/crontab</file>, and they must not modify the files in
6724 <file>/var/spool/cron/crontabs</file>.</p>
6727 If a package wants to install a job that has to be executed
6728 via cron, it should place a file with the name of the
6729 package in one or more of the following directories:
6730 <example compact="compact">
6736 As these directory names imply, the files within them are
6737 executed on an hourly, daily, weekly, or monthly basis,
6738 respectively. The exact times are listed in
6739 <file>/etc/crontab</file>.</p>
6742 All files installed in any of these directories must be
6743 scripts (e.g., shell scripts or Perl scripts) so that they
6744 can easily be modified by the local system administrator.
6745 In addition, they must be treated as configuration files.
6749 If a certain job has to be executed at some other frequency or
6750 at a specific time, the package should install a file
6751 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6752 same syntax as <file>/etc/crontab</file> and is processed by
6753 <prgn>cron</prgn> automatically. The file must also be
6754 treated as a configuration file. (Note that entries in the
6755 <file>/etc/cron.d</file> directory are not handled by
6756 <prgn>anacron</prgn>. Thus, you should only use this
6757 directory for jobs which may be skipped if the system is not
6760 Unlike <file>crontab</file> files described in the IEEE Std
6761 1003.1-2008 (POSIX.1) available from
6762 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6763 name="The Open Group">, the files in
6764 <file>/etc/cron.d</file> and the file
6765 <file>/etc/crontab</file> have seven fields; namely:
6767 <item>Minute [0,59]</item>
6768 <item>Hour [0,23]</item>
6769 <item>Day of the month [1,31]</item>
6770 <item>Month of the year [1,12]</item>
6771 <item>Day of the week ([0,6] with 0=Sunday)</item>
6772 <item>Username</item>
6773 <item>Command to be run</item>
6775 Ranges of numbers are allowed. Ranges are two numbers
6776 separated with a hyphen. The specified range is inclusive.
6777 Lists are allowed. A list is a set of numbers (or ranges)
6778 separated by commas. Step values can be used in conjunction
6783 The scripts or <tt>crontab</tt> entries in these directories should
6784 check if all necessary programs are installed before they
6785 try to execute them. Otherwise, problems will arise when a
6786 package was removed but not purged since configuration files
6787 are kept on the system in this situation.
6791 Any <tt>cron</tt> daemon must provide
6792 <file>/usr/bin/crontab</file> and support normal
6793 <tt>crontab</tt> entries as specified in POSIX. The daemon
6794 must also support names for days and months, ranges, and
6795 step values. It has to support <file>/etc/crontab</file>,
6796 and correctly execute the scripts in
6797 <file>/etc/cron.d</file>. The daemon must also correctly
6799 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6804 <heading>Menus</heading>
6807 The Debian <tt>menu</tt> package provides a standard
6808 interface between packages providing applications and
6809 <em>menu programs</em> (either X window managers or
6810 text-based menu programs such as <prgn>pdmenu</prgn>).
6814 All packages that provide applications that need not be
6815 passed any special command line arguments for normal
6816 operation should register a menu entry for those
6817 applications, so that users of the <tt>menu</tt> package
6818 will automatically get menu entries in their window
6819 managers, as well in shells like <tt>pdmenu</tt>.
6823 Menu entries should follow the current menu policy.
6827 The menu policy can be found in the <tt>menu-policy</tt>
6828 files in the <tt>debian-policy</tt> package.
6829 It is also available from the Debian web mirrors at
6830 <tt><url name="/doc/packaging-manuals/menu-policy/"
6831 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6835 Please also refer to the <em>Debian Menu System</em>
6836 documentation that comes with the <package>menu</package>
6837 package for information about how to register your
6843 <heading>Multimedia handlers</heading>
6846 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6847 is a mechanism for encoding files and data streams and
6848 providing meta-information about them, in particular their
6849 type (e.g. audio or video) and format (e.g. PNG, HTML,
6854 Registration of MIME type handlers allows programs like mail
6855 user agents and web browsers to invoke these handlers to
6856 view, edit or display MIME types they don't support directly.
6860 Packages which provide the ability to view/show/play,
6861 compose, edit or print MIME types should register themselves
6862 as such following the current MIME support policy.
6866 The MIME support policy can be found in the <tt>mime-policy</tt>
6867 files in the <tt>debian-policy</tt> package.
6868 It is also available from the Debian web mirrors at
6869 <tt><url name="/doc/packaging-manuals/mime-policy/"
6870 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6876 <heading>Keyboard configuration</heading>
6879 To achieve a consistent keyboard configuration so that all
6880 applications interpret a keyboard event the same way, all
6881 programs in the Debian distribution must be configured to
6882 comply with the following guidelines.
6886 The following keys must have the specified interpretations:
6889 <tag><tt><--</tt></tag>
6890 <item>delete the character to the left of the cursor</item>
6892 <tag><tt>Delete</tt></tag>
6893 <item>delete the character to the right of the cursor</item>
6895 <tag><tt>Control+H</tt></tag>
6896 <item>emacs: the help prefix</item>
6899 The interpretation of any keyboard events should be
6900 independent of the terminal that is used, be it a virtual
6901 console, an X terminal emulator, an rlogin/telnet session,
6906 The following list explains how the different programs
6907 should be set up to achieve this:
6913 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6917 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6921 X translations are set up to make
6922 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6923 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6924 is the vt220 escape code for the "delete character"
6925 key). This must be done by loading the X resources
6926 using <prgn>xrdb</prgn> on all local X displays, not
6927 using the application defaults, so that the
6928 translation resources used correspond to the
6929 <prgn>xmodmap</prgn> settings.
6933 The Linux console is configured to make
6934 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6935 generate <tt>ESC [ 3 ~</tt>.
6939 X applications are configured so that <tt><</tt>
6940 deletes left, and <tt>Delete</tt> deletes right. Motif
6941 applications already work like this.
6945 Terminals should have <tt>stty erase ^?</tt> .
6949 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6950 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6951 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6955 Emacs is programmed to map <tt>KB_Backspace</tt> or
6956 the <tt>stty erase</tt> character to
6957 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6958 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6959 <tt>^H</tt> to <tt>help</tt> as always.
6963 Other applications use the <tt>stty erase</tt>
6964 character and <tt>kdch1</tt> for the two delete keys,
6965 with ASCII DEL being "delete previous character" and
6966 <tt>kdch1</tt> being "delete character under
6974 This will solve the problem except for the following
6981 Some terminals have a <tt><--</tt> key that cannot
6982 be made to produce anything except <tt>^H</tt>. On
6983 these terminals Emacs help will be unavailable on
6984 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6985 character takes precedence in Emacs, and has been set
6986 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6987 available) can be used instead.
6991 Some operating systems use <tt>^H</tt> for <tt>stty
6992 erase</tt>. However, modern telnet versions and all
6993 rlogin versions propagate <tt>stty</tt> settings, and
6994 almost all UNIX versions honour <tt>stty erase</tt>.
6995 Where the <tt>stty</tt> settings are not propagated
6996 correctly, things can be made to work by using
6997 <tt>stty</tt> manually.
7001 Some systems (including previous Debian versions) use
7002 <prgn>xmodmap</prgn> to arrange for both
7003 <tt><--</tt> and <tt>Delete</tt> to generate
7004 <tt>KB_Delete</tt>. We can change the behavior of
7005 their X clients using the same X resources that we use
7006 to do it for our own clients, or configure our clients
7007 using their resources when things are the other way
7008 around. On displays configured like this
7009 <tt>Delete</tt> will not work, but <tt><--</tt>
7014 Some operating systems have different <tt>kdch1</tt>
7015 settings in their <tt>terminfo</tt> database for
7016 <tt>xterm</tt> and others. On these systems the
7017 <tt>Delete</tt> key will not work correctly when you
7018 log in from a system conforming to our policy, but
7019 <tt><--</tt> will.
7026 <heading>Environment variables</heading>
7029 A program must not depend on environment variables to get
7030 reasonable defaults. (That's because these environment
7031 variables would have to be set in a system-wide
7032 configuration file like <file>/etc/profile</file>, which is not
7033 supported by all shells.)
7037 If a program usually depends on environment variables for its
7038 configuration, the program should be changed to fall back to
7039 a reasonable default configuration if these environment
7040 variables are not present. If this cannot be done easily
7041 (e.g., if the source code of a non-free program is not
7042 available), the program must be replaced by a small
7043 "wrapper" shell script which sets the environment variables
7044 if they are not already defined, and calls the original program.
7048 Here is an example of a wrapper script for this purpose:
7050 <example compact="compact">
7052 BAR=${BAR:-/var/lib/fubar}
7054 exec /usr/lib/foo/foo "$@"
7059 Furthermore, as <file>/etc/profile</file> is a configuration
7060 file of the <prgn>base-files</prgn> package, other packages must
7061 not put any environment variables or other commands into that
7066 <sect id="doc-base">
7067 <heading>Registering Documents using doc-base</heading>
7070 The <package>doc-base</package> package implements a
7071 flexible mechanism for handling and presenting
7072 documentation. The recommended practice is for every Debian
7073 package that provides online documentation (other than just
7074 manual pages) to register these documents with
7075 <package>doc-base</package> by installing a
7076 <package>doc-base</package> control file via the
7077 <prgn/install-docs/ script at installation time and
7078 de-register the manuals again when the package is removed.
7081 Please refer to the documentation that comes with the
7082 <package>doc-base</package> package for information and
7091 <heading>Files</heading>
7093 <sect id="binaries">
7094 <heading>Binaries</heading>
7097 Two different packages must not install programs with
7098 different functionality but with the same filenames. (The
7099 case of two programs having the same functionality but
7100 different implementations is handled via "alternatives" or
7101 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7102 <ref id="conflicts"> respectively.) If this case happens,
7103 one of the programs must be renamed. The maintainers should
7104 report this to the <tt>debian-devel</tt> mailing list and
7105 try to find a consensus about which program will have to be
7106 renamed. If a consensus cannot be reached, <em>both</em>
7107 programs must be renamed.
7111 By default, when a package is being built, any binaries
7112 created should include debugging information, as well as
7113 being compiled with optimization. You should also turn on
7114 as many reasonable compilation warnings as possible; this
7115 makes life easier for porters, who can then look at build
7116 logs for possible problems. For the C programming language,
7117 this means the following compilation parameters should be
7119 <example compact="compact">
7121 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7123 INSTALL = install -s # (or use strip on the files in debian/tmp)
7128 Note that by default all installed binaries should be stripped,
7129 either by using the <tt>-s</tt> flag to
7130 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7131 the binaries after they have been copied into
7132 <file>debian/tmp</file> but before the tree is made into a
7137 Although binaries in the build tree should be compiled with
7138 debugging information by default, it can often be difficult to
7139 debug programs if they are also subjected to compiler
7140 optimization. For this reason, it is recommended to support the
7141 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7142 (see <ref id="debianrules-options">). This variable can contain
7143 several flags to change how a package is compiled and built.
7147 It is up to the package maintainer to decide what
7148 compilation options are best for the package. Certain
7149 binaries (such as computationally-intensive programs) will
7150 function better with certain flags (<tt>-O3</tt>, for
7151 example); feel free to use them. Please use good judgment
7152 here. Don't use flags for the sake of it; only use them
7153 if there is good reason to do so. Feel free to override
7154 the upstream author's ideas about which compilation
7155 options are best: they are often inappropriate for our
7161 <sect id="libraries">
7162 <heading>Libraries</heading>
7165 If the package is <strong>architecture: any</strong>, then
7166 the shared library compilation and linking flags must have
7167 <tt>-fPIC</tt>, or the package shall not build on some of
7168 the supported architectures<footnote>
7170 If you are using GCC, <tt>-fPIC</tt> produces code with
7171 relocatable position independent code, which is required for
7172 most architectures to create a shared library, with i386 and
7173 perhaps some others where non position independent code is
7174 permitted in a shared library.
7177 Position independent code may have a performance penalty,
7178 especially on <tt>i386</tt>. However, in most cases the
7179 speed penalty must be measured against the memory wasted on
7180 the few architectures where non position independent code is
7183 </footnote>. Any exception to this rule must be discussed on
7184 the mailing list <em>debian-devel@lists.debian.org</em>, and
7185 a rough consensus obtained. The reasons for not compiling
7186 with <tt>-fPIC</tt> flag must be recorded in the file
7187 <tt>README.Debian</tt>, and care must be taken to either
7188 restrict the architecture or arrange for <tt>-fPIC</tt> to
7189 be used on architectures where it is required.<footnote>
7191 Some of the reasons why this might be required is if the
7192 library contains hand crafted assembly code that is not
7193 relocatable, the speed penalty is excessive for compute
7194 intensive libs, and similar reasons.
7199 As to the static libraries, the common case is not to have
7200 relocatable code, since there is no benefit, unless in specific
7201 cases; therefore the static version must not be compiled
7202 with the <tt>-fPIC</tt> flag. Any exception to this rule
7203 should be discussed on the mailing list
7204 <em>debian-devel@lists.debian.org</em>, and the reasons for
7205 compiling with the <tt>-fPIC</tt> flag must be recorded in
7206 the file <tt>README.Debian</tt>. <footnote>
7208 Some of the reasons for linking static libraries with
7209 the <tt>-fPIC</tt> flag are if, for example, one needs a
7210 Perl API for a library that is under rapid development,
7211 and has an unstable API, so shared libraries are
7212 pointless at this phase of the library's development. In
7213 that case, since Perl needs a library with relocatable
7214 code, it may make sense to create a static library with
7215 relocatable code. Another reason cited is if you are
7216 distilling various libraries into a common shared
7217 library, like <tt>mklibs</tt> does in the Debian
7223 In other words, if both a shared and a static library is
7224 being built, each source unit (<tt>*.c</tt>, for example,
7225 for C files) will need to be compiled twice, for the normal
7229 You must specify the gcc option <tt>-D_REENTRANT</tt>
7230 when building a library (either static or shared) to make
7231 the library compatible with LinuxThreads.
7235 Although not enforced by the build tools, shared libraries
7236 must be linked against all libraries that they use symbols from
7237 in the same way that binaries are. This ensures the correct
7238 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7239 system and guarantees that all libraries can be safely opened
7240 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7241 option <tt>-Wl,-z,defs</tt> when building a shared library.
7242 Since this option enforces symbol resolution at build time,
7243 a missing library reference will be caught early as a fatal
7248 All installed shared libraries should be stripped with
7249 <example compact="compact">
7250 strip --strip-unneeded <var>your-lib</var>
7252 (The option <tt>--strip-unneeded</tt> makes
7253 <prgn>strip</prgn> remove only the symbols which aren't
7254 needed for relocation processing.) Shared libraries can
7255 function perfectly well when stripped, since the symbols for
7256 dynamic linking are in a separate part of the ELF object
7258 You might also want to use the options
7259 <tt>--remove-section=.comment</tt> and
7260 <tt>--remove-section=.note</tt> on both shared libraries
7261 and executables, and <tt>--strip-debug</tt> on static
7267 Note that under some circumstances it may be useful to
7268 install a shared library unstripped, for example when
7269 building a separate package to support debugging.
7273 Shared object files (often <file>.so</file> files) that are not
7274 public libraries, that is, they are not meant to be linked
7275 to by third party executables (binaries of other packages),
7276 should be installed in subdirectories of the
7277 <file>/usr/lib</file> directory. Such files are exempt from the
7278 rules that govern ordinary shared libraries, except that
7279 they must not be installed executable and should be
7281 A common example are the so-called "plug-ins",
7282 internal shared objects that are dynamically loaded by
7283 programs using <manref name="dlopen" section="3">.
7288 Packages that use <prgn>libtool</prgn> to create and install
7289 their shared libraries install a file containing additional
7290 metadata (ending in <file>.la</file>) alongside the library.
7291 For public libraries intended for use by other packages, these
7292 files normally should not be included in the Debian package,
7293 since the information they include is not necessary to link with
7294 the shared library on Debian and can add unnecessary additional
7295 dependencies to other programs or libraries.<footnote>
7296 These files store, among other things, all libraries on which
7297 that shared library depends. Unfortunately, if
7298 the <file>.la</file> file is present and contains that
7299 dependency information, using <prgn>libtool</prgn> when
7300 linking against that library will cause the resulting program
7301 or library to be linked against those dependencies as well,
7302 even if this is unnecessary. This can create unneeded
7303 dependencies on shared library packages that would otherwise
7304 be hidden behind the library ABI, and can make library
7305 transitions to new SONAMEs unnecessarily complicated and
7306 difficult to manage.
7308 If the <file>.la</file> file is required for that library (if,
7309 for instance, it's loaded via <tt>libltdl</tt> in a way that
7310 requires that meta-information), the <tt>dependency_libs</tt>
7311 setting in the <file>.la</file> file should normally be set to
7312 the empty string. If the shared library development package has
7313 historically included the <file>.la</file>, it must be retained
7314 in the development package (with <tt>dependency_libs</tt>
7315 emptied) until all libraries that depend on it have removed or
7316 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7317 files to prevent linking with those other libraries
7318 using <prgn>libtool</prgn> from failing.
7322 If the <file>.la</file> must be included, it should be included
7323 in the development (<tt>-dev</tt>) package, unless the library
7324 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7325 library. If it is intended for use with <tt>libltdl</tt>,
7326 the <file>.la</file> files must go in the run-time library
7331 These requirements for handling of <file>.la</file> files do not
7332 apply to loadable modules or libraries not installed in
7333 directories searched by default by the dynamic linker. Packages
7334 installing loadable modules will frequently need to install
7335 the <file>.la</file> files alongside the modules so that they
7336 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7337 does not need to be modified for libraries or modules that are
7338 not installed in directories searched by the dynamic linker by
7339 default and not intended for use by other packages.
7343 You must make sure that you use only released versions of
7344 shared libraries to build your packages; otherwise other
7345 users will not be able to run your binaries
7346 properly. Producing source packages that depend on
7347 unreleased compilers is also usually a bad
7354 <heading>Shared libraries</heading>
7356 This section has moved to <ref id="sharedlibs">.
7362 <heading>Scripts</heading>
7365 All command scripts, including the package maintainer
7366 scripts inside the package and used by <prgn>dpkg</prgn>,
7367 should have a <tt>#!</tt> line naming the shell to be used
7372 In the case of Perl scripts this should be
7373 <tt>#!/usr/bin/perl</tt>.
7377 When scripts are installed into a directory in the system
7378 PATH, the script name should not include an extension such
7379 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7380 language currently used to implement it.
7383 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7384 <file>init.d</file> scripts should almost certainly start
7385 with <tt>set -e</tt> so that errors are detected.
7386 <file>init.d</file> scripts are something of a special case, due
7387 to how frequently they need to call commands that are allowed to
7388 fail, and it may instead be easier to check the exit status of
7389 commands directly. See <ref id="writing-init"> for more
7390 information about writing <file>init.d</file> scripts.
7393 Every script should use <tt>set -e</tt> or check the exit status
7394 of <em>every</em> command.
7397 Scripts may assume that <file>/bin/sh</file> implements the
7398 SUSv3 Shell Command Language<footnote>
7399 Single UNIX Specification, version 3, which is also IEEE
7400 1003.1-2004 (POSIX), and is available on the World Wide Web
7401 from <url id="http://www.unix.org/version3/online.html"
7402 name="The Open Group"> after free
7403 registration.</footnote>
7404 plus the following additional features not mandated by
7406 These features are in widespread use in the Linux community
7407 and are implemented in all of bash, dash, and ksh, the most
7408 common shells users may wish to use as <file>/bin/sh</file>.
7411 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7412 must not generate a newline.</item>
7413 <item><tt>test</tt>, if implemented as a shell built-in, must
7414 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7416 <item><tt>local</tt> to create a scoped variable must be
7417 supported, including listing multiple variables in a single
7418 local command and assigning a value to a variable at the
7419 same time as localizing it. <tt>local</tt> may or
7420 may not preserve the variable value from an outer scope if
7421 no assignment is present. Uses such as:
7425 # ... use a, b, c, d ...
7428 must be supported and must set the value of <tt>c</tt> to
7432 If a shell script requires non-SUSv3 features from the shell
7433 interpreter other than those listed above, the appropriate shell
7434 must be specified in the first line of the script (e.g.,
7435 <tt>#!/bin/bash</tt>) and the package must depend on the package
7436 providing the shell (unless the shell package is marked
7437 "Essential", as in the case of <prgn>bash</prgn>).
7441 You may wish to restrict your script to SUSv3 features plus the
7442 above set when possible so that it may use <file>/bin/sh</file>
7443 as its interpreter. If your script works with <prgn>dash</prgn>
7444 (originally called <prgn>ash</prgn>), it probably complies with
7445 the above requirements, but if you are in doubt, use
7446 <file>/bin/bash</file>.
7450 Perl scripts should check for errors when making any
7451 system calls, including <tt>open</tt>, <tt>print</tt>,
7452 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7456 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7457 scripting languages. See <em>Csh Programming Considered
7458 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7459 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7460 If an upstream package comes with <prgn>csh</prgn> scripts
7461 then you must make sure that they start with
7462 <tt>#!/bin/csh</tt> and make your package depend on the
7463 <prgn>c-shell</prgn> virtual package.
7467 Any scripts which create files in world-writeable
7468 directories (e.g., in <file>/tmp</file>) must use a
7469 mechanism which will fail atomically if a file with the same
7470 name already exists.
7474 The Debian base system provides the <prgn>tempfile</prgn>
7475 and <prgn>mktemp</prgn> utilities for use by scripts for
7482 <heading>Symbolic links</heading>
7485 In general, symbolic links within a top-level directory
7486 should be relative, and symbolic links pointing from one
7487 top-level directory into another should be absolute. (A
7488 top-level directory is a sub-directory of the root
7489 directory <file>/</file>.)
7493 In addition, symbolic links should be specified as short as
7494 possible, i.e., link targets like <file>foo/../bar</file> are
7499 Note that when creating a relative link using
7500 <prgn>ln</prgn> it is not necessary for the target of the
7501 link to exist relative to the working directory you're
7502 running <prgn>ln</prgn> from, nor is it necessary to change
7503 directory to the directory where the link is to be made.
7504 Simply include the string that should appear as the target
7505 of the link (this will be a pathname relative to the
7506 directory in which the link resides) as the first argument
7511 For example, in your <prgn>Makefile</prgn> or
7512 <file>debian/rules</file>, you can do things like:
7513 <example compact="compact">
7514 ln -fs gcc $(prefix)/bin/cc
7515 ln -fs gcc debian/tmp/usr/bin/cc
7516 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7517 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7522 A symbolic link pointing to a compressed file should always
7523 have the same file extension as the referenced file. (For
7524 example, if a file <file>foo.gz</file> is referenced by a
7525 symbolic link, the filename of the link has to end with
7526 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7531 <heading>Device files</heading>
7534 Packages must not include device files or named pipes in the
7539 If a package needs any special device files that are not
7540 included in the base system, it must call
7541 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7542 after notifying the user<footnote>
7543 This notification could be done via a (low-priority)
7544 debconf message, or an echo (printf) statement.
7549 Packages must not remove any device files in the
7550 <prgn>postrm</prgn> or any other script. This is left to the
7551 system administrator.
7555 Debian uses the serial devices
7556 <file>/dev/ttyS*</file>. Programs using the old
7557 <file>/dev/cu*</file> devices should be changed to use
7558 <file>/dev/ttyS*</file>.
7562 Named pipes needed by the package must be created in
7563 the <prgn>postinst</prgn> script<footnote>
7564 It's better to use <prgn>mkfifo</prgn> rather
7565 than <prgn>mknod</prgn> to create named pipes so that
7566 automated checks for packages incorrectly creating device
7567 files with <prgn>mknod</prgn> won't have false positives.
7568 </footnote> and removed in
7569 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7574 <sect id="config-files">
7575 <heading>Configuration files</heading>
7578 <heading>Definitions</heading>
7582 <tag>configuration file</tag>
7584 A file that affects the operation of a program, or
7585 provides site- or host-specific information, or
7586 otherwise customizes the behavior of a program.
7587 Typically, configuration files are intended to be
7588 modified by the system administrator (if needed or
7589 desired) to conform to local policy or to provide
7590 more useful site-specific behavior.
7593 <tag><tt>conffile</tt></tag>
7595 A file listed in a package's <tt>conffiles</tt>
7596 file, and is treated specially by <prgn>dpkg</prgn>
7597 (see <ref id="configdetails">).
7603 The distinction between these two is important; they are
7604 not interchangeable concepts. Almost all
7605 <tt>conffile</tt>s are configuration files, but many
7606 configuration files are not <tt>conffiles</tt>.
7610 As noted elsewhere, <file>/etc/init.d</file> scripts,
7611 <file>/etc/default</file> files, scripts installed in
7612 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7613 configuration installed in <file>/etc/cron.d</file> must be
7614 treated as configuration files. In general, any script that
7615 embeds configuration information is de-facto a configuration
7616 file and should be treated as such.
7621 <heading>Location</heading>
7624 Any configuration files created or used by your package
7625 must reside in <file>/etc</file>. If there are several,
7626 consider creating a subdirectory of <file>/etc</file>
7627 named after your package.
7631 If your package creates or uses configuration files
7632 outside of <file>/etc</file>, and it is not feasible to modify
7633 the package to use <file>/etc</file> directly, put the files
7634 in <file>/etc</file> and create symbolic links to those files
7635 from the location that the package requires.
7640 <heading>Behavior</heading>
7643 Configuration file handling must conform to the following
7645 <list compact="compact">
7647 local changes must be preserved during a package
7651 configuration files must be preserved when the
7652 package is removed, and only deleted when the
7656 Obsolete configuration files without local changes may be
7657 removed by the package during upgrade.
7661 The easy way to achieve this behavior is to make the
7662 configuration file a <tt>conffile</tt>. This is
7663 appropriate only if it is possible to distribute a default
7664 version that will work for most installations, although
7665 some system administrators may choose to modify it. This
7666 implies that the default version will be part of the
7667 package distribution, and must not be modified by the
7668 maintainer scripts during installation (or at any other
7673 In order to ensure that local changes are preserved
7674 correctly, no package may contain or make hard links to
7675 conffiles.<footnote>
7676 Rationale: There are two problems with hard links.
7677 The first is that some editors break the link while
7678 editing one of the files, so that the two files may
7679 unwittingly become unlinked and different. The second
7680 is that <prgn>dpkg</prgn> might break the hard link
7681 while upgrading <tt>conffile</tt>s.
7686 The other way to do it is via the maintainer scripts. In
7687 this case, the configuration file must not be listed as a
7688 <tt>conffile</tt> and must not be part of the package
7689 distribution. If the existence of a file is required for
7690 the package to be sensibly configured it is the
7691 responsibility of the package maintainer to provide
7692 maintainer scripts which correctly create, update and
7693 maintain the file and remove it on purge. (See <ref
7694 id="maintainerscripts"> for more information.) These
7695 scripts must be idempotent (i.e., must work correctly if
7696 <prgn>dpkg</prgn> needs to re-run them due to errors
7697 during installation or removal), must cope with all the
7698 variety of ways <prgn>dpkg</prgn> can call maintainer
7699 scripts, must not overwrite or otherwise mangle the user's
7700 configuration without asking, must not ask unnecessary
7701 questions (particularly during upgrades), and must
7702 otherwise be good citizens.
7706 The scripts are not required to configure every possible
7707 option for the package, but only those necessary to get
7708 the package running on a given system. Ideally the
7709 sysadmin should not have to do any configuration other
7710 than that done (semi-)automatically by the
7711 <prgn>postinst</prgn> script.
7715 A common practice is to create a script called
7716 <file><var>package</var>-configure</file> and have the
7717 package's <prgn>postinst</prgn> call it if and only if the
7718 configuration file does not already exist. In certain
7719 cases it is useful for there to be an example or template
7720 file which the maintainer scripts use. Such files should
7721 be in <file>/usr/share/<var>package</var></file> or
7722 <file>/usr/lib/<var>package</var></file> (depending on whether
7723 they are architecture-independent or not). There should
7724 be symbolic links to them from
7725 <file>/usr/share/doc/<var>package</var>/examples</file> if
7726 they are examples, and should be perfectly ordinary
7727 <prgn>dpkg</prgn>-handled files (<em>not</em>
7728 configuration files).
7732 These two styles of configuration file handling must
7733 not be mixed, for that way lies madness:
7734 <prgn>dpkg</prgn> will ask about overwriting the file
7735 every time the package is upgraded.
7740 <heading>Sharing configuration files</heading>
7743 Packages which specify the same file as a
7744 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7745 with each other. (This is an instance of the general rule
7746 about not sharing files. Note that neither alternatives
7747 nor diversions are likely to be appropriate in this case;
7748 in particular, <prgn>dpkg</prgn> does not handle diverted
7749 <tt>conffile</tt>s well.)
7753 The maintainer scripts must not alter a <tt>conffile</tt>
7754 of <em>any</em> package, including the one the scripts
7759 If two or more packages use the same configuration file
7760 and it is reasonable for both to be installed at the same
7761 time, one of these packages must be defined as
7762 <em>owner</em> of the configuration file, i.e., it will be
7763 the package which handles that file as a configuration
7764 file. Other packages that use the configuration file must
7765 depend on the owning package if they require the
7766 configuration file to operate. If the other package will
7767 use the configuration file if present, but is capable of
7768 operating without it, no dependency need be declared.
7772 If it is desirable for two or more related packages to
7773 share a configuration file <em>and</em> for all of the
7774 related packages to be able to modify that configuration
7775 file, then the following should be done:
7776 <enumlist compact="compact">
7778 One of the related packages (the "owning" package)
7779 will manage the configuration file with maintainer
7780 scripts as described in the previous section.
7783 The owning package should also provide a program
7784 that the other packages may use to modify the
7788 The related packages must use the provided program
7789 to make any desired modifications to the
7790 configuration file. They should either depend on
7791 the core package to guarantee that the configuration
7792 modifier program is available or accept gracefully
7793 that they cannot modify the configuration file if it
7794 is not. (This is in addition to the fact that the
7795 configuration file may not even be present in the
7802 Sometimes it's appropriate to create a new package which
7803 provides the basic infrastructure for the other packages
7804 and which manages the shared configuration files. (The
7805 <tt>sgml-base</tt> package is a good example.)
7810 <heading>User configuration files ("dotfiles")</heading>
7813 The files in <file>/etc/skel</file> will automatically be
7814 copied into new user accounts by <prgn>adduser</prgn>.
7815 No other program should reference the files in
7816 <file>/etc/skel</file>.
7820 Therefore, if a program needs a dotfile to exist in
7821 advance in <file>$HOME</file> to work sensibly, that dotfile
7822 should be installed in <file>/etc/skel</file> and treated as a
7827 However, programs that require dotfiles in order to
7828 operate sensibly are a bad thing, unless they do create
7829 the dotfiles themselves automatically.
7833 Furthermore, programs should be configured by the Debian
7834 default installation to behave as closely to the upstream
7835 default behavior as possible.
7839 Therefore, if a program in a Debian package needs to be
7840 configured in some way in order to operate sensibly, that
7841 should be done using a site-wide configuration file placed
7842 in <file>/etc</file>. Only if the program doesn't support a
7843 site-wide default configuration and the package maintainer
7844 doesn't have time to add it may a default per-user file be
7845 placed in <file>/etc/skel</file>.
7849 <file>/etc/skel</file> should be as empty as we can make it.
7850 This is particularly true because there is no easy (or
7851 necessarily desirable) mechanism for ensuring that the
7852 appropriate dotfiles are copied into the accounts of
7853 existing users when a package is installed.
7859 <heading>Log files</heading>
7861 Log files should usually be named
7862 <file>/var/log/<var>package</var>.log</file>. If you have many
7863 log files, or need a separate directory for permission
7864 reasons (<file>/var/log</file> is writable only by
7865 <file>root</file>), you should usually create a directory named
7866 <file>/var/log/<var>package</var></file> and place your log
7871 Log files must be rotated occasionally so that they don't
7872 grow indefinitely; the best way to do this is to drop a log
7873 rotation configuration file into the directory
7874 <file>/etc/logrotate.d</file> and use the facilities provided by
7875 logrotate.<footnote>
7877 The traditional approach to log files has been to set up
7878 <em>ad hoc</em> log rotation schemes using simple shell
7879 scripts and cron. While this approach is highly
7880 customizable, it requires quite a lot of sysadmin work.
7881 Even though the original Debian system helped a little
7882 by automatically installing a system which can be used
7883 as a template, this was deemed not enough.
7887 The use of <prgn>logrotate</prgn>, a program developed
7888 by Red Hat, is better, as it centralizes log management.
7889 It has both a configuration file
7890 (<file>/etc/logrotate.conf</file>) and a directory where
7891 packages can drop their individual log rotation
7892 configurations (<file>/etc/logrotate.d</file>).
7895 Here is a good example for a logrotate config
7896 file (for more information see <manref name="logrotate"
7898 <example compact="compact">
7899 /var/log/foo/*.log {
7904 /etc/init.d/foo force-reload
7908 This rotates all files under <file>/var/log/foo</file>, saves 12
7909 compressed generations, and forces the daemon to reload its
7910 configuration information after the log rotation.
7914 Log files should be removed when the package is
7915 purged (but not when it is only removed). This should be
7916 done by the <prgn>postrm</prgn> script when it is called
7917 with the argument <tt>purge</tt> (see <ref
7918 id="removedetails">).
7923 <heading>Permissions and owners</heading>
7926 The rules in this section are guidelines for general use.
7927 If necessary you may deviate from the details below.
7928 However, if you do so you must make sure that what is done
7929 is secure and you should try to be as consistent as possible
7930 with the rest of the system. You should probably also
7931 discuss it on <prgn>debian-devel</prgn> first.
7935 Files should be owned by <tt>root:root</tt>, and made
7936 writable only by the owner and universally readable (and
7937 executable, if appropriate), that is mode 644 or 755.
7941 Directories should be mode 755 or (for group-writability)
7942 mode 2775. The ownership of the directory should be
7943 consistent with its mode: if a directory is mode 2775, it
7944 should be owned by the group that needs write access to
7947 When a package is upgraded, and the owner or permissions
7948 of a file included in the package has changed, dpkg
7949 arranges for the ownership and permissions to be
7950 correctly set upon installation. However, this does not
7951 extend to directories; the permissions and ownership of
7952 directories already on the system does not change on
7953 install or upgrade of packages. This makes sense, since
7954 otherwise common directories like <tt>/usr</tt> would
7955 always be in flux. To correctly change permissions of a
7956 directory the package owns, explicit action is required,
7957 usually in the <tt>postinst</tt> script. Care must be
7958 taken to handle downgrades as well, in that case.
7965 Setuid and setgid executables should be mode 4755 or 2755
7966 respectively, and owned by the appropriate user or group.
7967 They should not be made unreadable (modes like 4711 or
7968 2711 or even 4111); doing so achieves no extra security,
7969 because anyone can find the binary in the freely available
7970 Debian package; it is merely inconvenient. For the same
7971 reason you should not restrict read or execute permissions
7972 on non-set-id executables.
7976 Some setuid programs need to be restricted to particular
7977 sets of users, using file permissions. In this case they
7978 should be owned by the uid to which they are set-id, and by
7979 the group which should be allowed to execute them. They
7980 should have mode 4754; again there is no point in making
7981 them unreadable to those users who must not be allowed to
7986 It is possible to arrange that the system administrator can
7987 reconfigure the package to correspond to their local
7988 security policy by changing the permissions on a binary:
7989 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7990 described below.<footnote>
7991 Ordinary files installed by <prgn>dpkg</prgn> (as
7992 opposed to <tt>conffile</tt>s and other similar objects)
7993 normally have their permissions reset to the distributed
7994 permissions when the package is reinstalled. However,
7995 the use of <prgn>dpkg-statoverride</prgn> overrides this
7998 Another method you should consider is to create a group for
7999 people allowed to use the program(s) and make any setuid
8000 executables executable only by that group.
8004 If you need to create a new user or group for your package
8005 there are two possibilities. Firstly, you may need to
8006 make some files in the binary package be owned by this
8007 user or group, or you may need to compile the user or
8008 group id (rather than just the name) into the binary
8009 (though this latter should be avoided if possible, as in
8010 this case you need a statically allocated id).</p>
8013 If you need a statically allocated id, you must ask for a
8014 user or group id from the <tt>base-passwd</tt> maintainer,
8015 and must not release the package until you have been
8016 allocated one. Once you have been allocated one you must
8017 either make the package depend on a version of the
8018 <tt>base-passwd</tt> package with the id present in
8019 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8020 your package to create the user or group itself with the
8021 correct id (using <tt>adduser</tt>) in its
8022 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8023 the <prgn>postinst</prgn> is to be preferred if it is
8024 possible, otherwise a pre-dependency will be needed on the
8025 <tt>adduser</tt> package.)
8029 On the other hand, the program might be able to determine
8030 the uid or gid from the user or group name at runtime, so
8031 that a dynamically allocated id can be used. In this case
8032 you should choose an appropriate user or group name,
8033 discussing this on <prgn>debian-devel</prgn> and checking
8034 with the <package/base-passwd/ maintainer that it is unique and that
8035 they do not wish you to use a statically allocated id
8036 instead. When this has been checked you must arrange for
8037 your package to create the user or group if necessary using
8038 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8039 <prgn>postinst</prgn> script (again, the latter is to be
8040 preferred if it is possible).
8044 Note that changing the numeric value of an id associated
8045 with a name is very difficult, and involves searching the
8046 file system for all appropriate files. You need to think
8047 carefully whether a static or dynamic id is required, since
8048 changing your mind later will cause problems.
8051 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8053 This section is not intended as policy, but as a
8054 description of the use of <prgn>dpkg-statoverride</prgn>.
8058 If a system administrator wishes to have a file (or
8059 directory or other such thing) installed with owner and
8060 permissions different from those in the distributed Debian
8061 package, they can use the <prgn>dpkg-statoverride</prgn>
8062 program to instruct <prgn>dpkg</prgn> to use the different
8063 settings every time the file is installed. Thus the
8064 package maintainer should distribute the files with their
8065 normal permissions, and leave it for the system
8066 administrator to make any desired changes. For example, a
8067 daemon which is normally required to be setuid root, but
8068 in certain situations could be used without being setuid,
8069 should be installed setuid in the <tt>.deb</tt>. Then the
8070 local system administrator can change this if they wish.
8071 If there are two standard ways of doing it, the package
8072 maintainer can use <tt>debconf</tt> to find out the
8073 preference, and call <prgn>dpkg-statoverride</prgn> in the
8074 maintainer script if necessary to accommodate the system
8075 administrator's choice. Care must be taken during
8076 upgrades to not override an existing setting.
8080 Given the above, <prgn>dpkg-statoverride</prgn> is
8081 essentially a tool for system administrators and would not
8082 normally be needed in the maintainer scripts. There is
8083 one type of situation, though, where calls to
8084 <prgn>dpkg-statoverride</prgn> would be needed in the
8085 maintainer scripts, and that involves packages which use
8086 dynamically allocated user or group ids. In such a
8087 situation, something like the following idiom can be very
8088 helpful in the package's <prgn>postinst</prgn>, where
8089 <tt>sysuser</tt> is a dynamically allocated id:
8091 for i in /usr/bin/foo /usr/sbin/bar
8093 # only do something when no setting exists
8094 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8096 #include: debconf processing, question about foo and bar
8097 if [ "$RET" = "true" ] ; then
8098 dpkg-statoverride --update --add sysuser root 4755 $i
8103 The corresponding code to remove the override when the package
8106 for i in /usr/bin/foo /usr/sbin/bar
8108 if dpkg-statoverride --list $i >/dev/null 2>&1
8110 dpkg-statoverride --remove $i
8120 <chapt id="customized-programs">
8121 <heading>Customized programs</heading>
8123 <sect id="arch-spec">
8124 <heading>Architecture specification strings</heading>
8127 If a program needs to specify an <em>architecture specification
8128 string</em> in some place, it should select one of the strings
8129 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8130 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8131 part is sometimes elided, as when the OS is Linux.
8135 Note that we don't want to use
8136 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8137 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8138 since this would make our programs incompatible with other
8139 Linux distributions. We also don't use something like
8140 <tt><var>arch</var>-unknown-linux</tt>, since the
8141 <tt>unknown</tt> does not look very good.
8144 <sect1 id="arch-wildcard-spec">
8145 <heading>Architecture wildcards</heading>
8148 A package may specify an architecture wildcard. Architecture
8149 wildcards are in the format <tt>any</tt> (which matches every
8150 architecture), <tt><var>os</var></tt>-any, or
8151 any-<tt><var>cpu</var></tt>. <footnote>
8152 Internally, the package system normalizes the GNU triplets
8153 and the Debian arches into Debian arch triplets (which are
8154 kind of inverted GNU triplets), with the first component of
8155 the triplet representing the libc and ABI in use, and then
8156 does matching against those triplets. However, such
8157 triplets are an internal implementation detail that should
8158 not be used by packages directly. The libc and ABI portion
8159 is handled internally by the package system based on
8160 the <var>os</var> and <var>cpu</var>.
8167 <heading>Daemons</heading>
8170 The configuration files <file>/etc/services</file>,
8171 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8172 by the <prgn>netbase</prgn> package and must not be modified
8177 If a package requires a new entry in one of these files, the
8178 maintainer should get in contact with the
8179 <prgn>netbase</prgn> maintainer, who will add the entries
8180 and release a new version of the <prgn>netbase</prgn>
8185 The configuration file <file>/etc/inetd.conf</file> must not be
8186 modified by the package's scripts except via the
8187 <prgn>update-inetd</prgn> script or the
8188 <file>DebianNet.pm</file> Perl module. See their documentation
8189 for details on how to add entries.
8193 If a package wants to install an example entry into
8194 <file>/etc/inetd.conf</file>, the entry must be preceded with
8195 exactly one hash character (<tt>#</tt>). Such lines are
8196 treated as "commented out by user" by the
8197 <prgn>update-inetd</prgn> script and are not changed or
8198 activated during package updates.
8203 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8207 Some programs need to create pseudo-ttys. This should be done
8208 using Unix98 ptys if the C library supports it. The resulting
8209 program must not be installed setuid root, unless that
8210 is required for other functionality.
8214 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8215 <file>/var/log/lastlog</file> must be installed writable by
8216 group <tt>utmp</tt>. Programs which need to modify those
8217 files must be installed setgid <tt>utmp</tt>.
8222 <heading>Editors and pagers</heading>
8225 Some programs have the ability to launch an editor or pager
8226 program to edit or display a text document. Since there are
8227 lots of different editors and pagers available in the Debian
8228 distribution, the system administrator and each user should
8229 have the possibility to choose their preferred editor and
8234 In addition, every program should choose a good default
8235 editor/pager if none is selected by the user or system
8240 Thus, every program that launches an editor or pager must
8241 use the EDITOR or PAGER environment variable to determine
8242 the editor or pager the user wishes to use. If these
8243 variables are not set, the programs <file>/usr/bin/editor</file>
8244 and <file>/usr/bin/pager</file> should be used, respectively.
8248 These two files are managed through the <prgn>dpkg</prgn>
8249 "alternatives" mechanism. Thus every package providing an
8250 editor or pager must call the
8251 <prgn>update-alternatives</prgn> script to register these
8256 If it is very hard to adapt a program to make use of the
8257 EDITOR or PAGER variables, that program may be configured to
8258 use <file>/usr/bin/sensible-editor</file> and
8259 <file>/usr/bin/sensible-pager</file> as the editor or pager
8260 program respectively. These are two scripts provided in the
8261 <package>sensible-utils</package> package that check the EDITOR
8262 and PAGER variables and launch the appropriate program, and fall
8263 back to <file>/usr/bin/editor</file>
8264 and <file>/usr/bin/pager</file> if the variable is not set.
8268 A program may also use the VISUAL environment variable to
8269 determine the user's choice of editor. If it exists, it
8270 should take precedence over EDITOR. This is in fact what
8271 <file>/usr/bin/sensible-editor</file> does.
8275 It is not required for a package to depend on
8276 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8277 package to provide such virtual packages.<footnote>
8278 The Debian base system already provides an editor and a
8284 <sect id="web-appl">
8285 <heading>Web servers and applications</heading>
8288 This section describes the locations and URLs that should
8289 be used by all web servers and web applications in the
8296 Cgi-bin executable files are installed in the
8298 <example compact="compact">
8299 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8301 and should be referred to as
8302 <example compact="compact">
8303 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8309 <p>Access to HTML documents</p>
8312 HTML documents for a package are stored in
8313 <file>/usr/share/doc/<var>package</var></file>
8314 and can be referred to as
8315 <example compact="compact">
8316 http://localhost/doc/<var>package</var>/<var>filename</var>
8321 The web server should restrict access to the document
8322 tree so that only clients on the same host can read
8323 the documents. If the web server does not support such
8324 access controls, then it should not provide access at
8325 all, or ask about providing access during installation.
8330 <p>Access to images</p>
8332 It is recommended that images for a package be stored
8333 in <tt>/usr/share/images/<var>package</var></tt> and
8334 may be referred to through an alias <tt>/images/</tt>
8337 http://localhost/images/<package>/<filename>
8344 <p>Web Document Root</p>
8347 Web Applications should try to avoid storing files in
8348 the Web Document Root. Instead they should use the
8349 /usr/share/doc/<var>package</var> directory for
8350 documents and register the Web Application via the
8351 <package>doc-base</package> package. If access to the
8352 web document root is unavoidable then use
8353 <example compact="compact">
8356 as the Document Root. This might be just a symbolic
8357 link to the location where the system administrator
8358 has put the real document root.
8361 <item><p>Providing httpd and/or httpd-cgi</p>
8363 All web servers should provide the virtual package
8364 <tt>httpd</tt>. If a web server has CGI support it should
8365 provide <tt>httpd-cgi</tt> additionally.
8368 All web applications which do not contain CGI scripts should
8369 depend on <tt>httpd</tt>, all those web applications which
8370 <tt>do</tt> contain CGI scripts, should depend on
8378 <sect id="mail-transport-agents">
8379 <heading>Mail transport, delivery and user agents</heading>
8382 Debian packages which process electronic mail, whether mail
8383 user agents (MUAs) or mail transport agents (MTAs), must
8384 ensure that they are compatible with the configuration
8385 decisions below. Failure to do this may result in lost
8386 mail, broken <tt>From:</tt> lines, and other serious brain
8391 The mail spool is <file>/var/mail</file> and the interface to
8392 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8393 the FHS). On older systems, the mail spool may be
8394 physically located in <file>/var/spool/mail</file>, but all
8395 access to the mail spool should be via the
8396 <file>/var/mail</file> symlink. The mail spool is part of the
8397 base system and not part of the MTA package.
8401 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8402 programs (such as IMAP daemons) must lock the mailbox in an
8403 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8404 be combined with dot locking. To avoid deadlocks, a program
8405 should use <tt>fcntl()</tt> first and dot locking after
8406 this, or alternatively implement the two locking methods in
8407 a non blocking way<footnote>
8408 If it is not possible to establish both locks, the
8409 system shouldn't wait for the second lock to be
8410 established, but remove the first lock, wait a (random)
8411 time, and start over locking again.
8412 </footnote>. Using the functions <tt>maillock</tt> and
8413 <tt>mailunlock</tt> provided by the
8414 <tt>liblockfile*</tt><footnote>
8415 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8416 to use these functions.
8417 </footnote> packages is the recommended way to realize this.
8421 Mailboxes are generally either mode 600 and owned by
8422 <var>user</var> or mode 660 and owned by
8423 <tt><var>user</var>:mail</tt><footnote>
8424 There are two traditional permission schemes for mail spools:
8425 mode 600 with all mail delivery done by processes running as
8426 the destination user, or mode 660 and owned by group mail with
8427 mail delivery done by a process running as a system user in
8428 group mail. Historically, Debian required mode 660 mail
8429 spools to enable the latter model, but that model has become
8430 increasingly uncommon and the principle of least privilege
8431 indicates that mail systems that use the first model should
8432 use permissions of 600. If delivery to programs is permitted,
8433 it's easier to keep the mail system secure if the delivery
8434 agent runs as the destination user. Debian Policy therefore
8435 permits either scheme.
8436 </footnote>. The local system administrator may choose a
8437 different permission scheme; packages should not make
8438 assumptions about the permission and ownership of mailboxes
8439 unless required (such as when creating a new mailbox). A MUA
8440 may remove a mailbox (unless it has nonstandard permissions) in
8441 which case the MTA or another MUA must recreate it if needed.
8445 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8446 be setgid mail to do the locking mentioned above (and
8447 must obviously avoid accessing other users' mailboxes
8448 using this privilege).</p>
8451 <file>/etc/aliases</file> is the source file for the system mail
8452 aliases (e.g., postmaster, usenet, etc.), it is the one
8453 which the sysadmin and <prgn>postinst</prgn> scripts may
8454 edit. After <file>/etc/aliases</file> is edited the program or
8455 human editing it must call <prgn>newaliases</prgn>. All MTA
8456 packages must come with a <prgn>newaliases</prgn> program,
8457 even if it does nothing, but older MTA packages did not do
8458 this so programs should not fail if <prgn>newaliases</prgn>
8459 cannot be found. Note that because of this, all MTA
8460 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8461 <tt>Replaces: mail-transport-agent</tt> control file
8466 The convention of writing <tt>forward to
8467 <var>address</var></tt> in the mailbox itself is not
8468 supported. Use a <tt>.forward</tt> file instead.</p>
8471 The <prgn>rmail</prgn> program used by UUCP
8472 for incoming mail should be <file>/usr/sbin/rmail</file>.
8473 Likewise, <prgn>rsmtp</prgn>, for receiving
8474 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8478 If your package needs to know what hostname to use on (for
8479 example) outgoing news and mail messages which are generated
8480 locally, you should use the file <file>/etc/mailname</file>. It
8481 will contain the portion after the username and <tt>@</tt>
8482 (at) sign for email addresses of users on the machine
8483 (followed by a newline).
8487 Such a package should check for the existence of this file
8488 when it is being configured. If it exists, it should be
8489 used without comment, although an MTA's configuration script
8490 may wish to prompt the user even if it finds that this file
8491 exists. If the file does not exist, the package should
8492 prompt the user for the value (preferably using
8493 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8494 as well as using it in the package's configuration. The
8495 prompt should make it clear that the name will not just be
8496 used by that package. For example, in this situation the
8497 <tt>inn</tt> package could say something like:
8498 <example compact="compact">
8499 Please enter the "mail name" of your system. This is the
8500 hostname portion of the address to be shown on outgoing
8501 news and mail messages. The default is
8502 <var>syshostname</var>, your system's host name. Mail
8503 name ["<var>syshostname</var>"]:
8505 where <var>syshostname</var> is the output of <tt>hostname
8511 <heading>News system configuration</heading>
8514 All the configuration files related to the NNTP (news)
8515 servers and clients should be located under
8516 <file>/etc/news</file>.</p>
8519 There are some configuration issues that apply to a number
8520 of news clients and server packages on the machine. These
8524 <tag><file>/etc/news/organization</file></tag>
8526 A string which should appear as the
8527 organization header for all messages posted
8528 by NNTP clients on the machine
8531 <tag><file>/etc/news/server</file></tag>
8533 Contains the FQDN of the upstream NNTP
8534 server, or localhost if the local machine is
8539 Other global files may be added as required for cross-package news
8546 <heading>Programs for the X Window System</heading>
8549 <heading>Providing X support and package priorities</heading>
8552 Programs that can be configured with support for the X
8553 Window System must be configured to do so and must declare
8554 any package dependencies necessary to satisfy their
8555 runtime requirements when using the X Window System. If
8556 such a package is of higher priority than the X packages
8557 on which it depends, it is required that either the
8558 X-specific components be split into a separate package, or
8559 that an alternative version of the package, which includes
8560 X support, be provided, or that the package's priority be
8566 <heading>Packages providing an X server</heading>
8569 Packages that provide an X server that, directly or
8570 indirectly, communicates with real input and display
8571 hardware should declare in their control data that they
8572 provide the virtual package <tt>xserver</tt>.<footnote>
8573 This implements current practice, and provides an
8574 actual policy for usage of the <tt>xserver</tt>
8575 virtual package which appears in the virtual packages
8576 list. In a nutshell, X servers that interface
8577 directly with the display and input hardware or via
8578 another subsystem (e.g., GGI) should provide
8579 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8580 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8586 <heading>Packages providing a terminal emulator</heading>
8589 Packages that provide a terminal emulator for the X Window
8590 System which meet the criteria listed below should declare
8591 in their control data that they provide the virtual
8592 package <tt>x-terminal-emulator</tt>. They should also
8593 register themselves as an alternative for
8594 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8599 To be an <tt>x-terminal-emulator</tt>, a program must:
8600 <list compact="compact">
8602 Be able to emulate a DEC VT100 terminal, or a
8603 compatible terminal.
8607 Support the command-line option <tt>-e
8608 <var>command</var></tt>, which creates a new
8609 terminal window<footnote>
8610 "New terminal window" does not necessarily mean
8611 a new top-level X window directly parented by
8612 the window manager; it could, if the terminal
8613 emulator application were so coded, be a new
8614 "view" in a multiple-document interface (MDI).
8616 and runs the specified <var>command</var>,
8617 interpreting the entirety of the rest of the command
8618 line as a command to pass straight to exec, in the
8619 manner that <tt>xterm</tt> does.
8623 Support the command-line option <tt>-T
8624 <var>title</var></tt>, which creates a new terminal
8625 window with the window title <var>title</var>.
8632 <heading>Packages providing a window manager</heading>
8635 Packages that provide a window manager should declare in
8636 their control data that they provide the virtual package
8637 <tt>x-window-manager</tt>. They should also register
8638 themselves as an alternative for
8639 <file>/usr/bin/x-window-manager</file>, with a priority
8640 calculated as follows:
8641 <list compact="compact">
8643 Start with a priority of 20.
8647 If the window manager supports the Debian menu
8648 system, add 20 points if this support is available
8649 in the package's default configuration (i.e., no
8650 configuration files belonging to the system or user
8651 have to be edited to activate the feature); if
8652 configuration files must be modified, add only 10
8658 If the window manager complies with <url
8659 id="http://www.freedesktop.org/Standards/wm-spec"
8660 name="The Window Manager Specification Project">,
8661 written by the <url id="http://www.freedesktop.org/"
8662 name="Free Desktop Group">, add 40 points.
8666 If the window manager permits the X session to be
8667 restarted using a <em>different</em> window manager
8668 (without killing the X server) in its default
8669 configuration, add 10 points; otherwise add none.
8676 <heading>Packages providing fonts</heading>
8679 Packages that provide fonts for the X Window
8681 For the purposes of Debian Policy, a "font for the X
8682 Window System" is one which is accessed via X protocol
8683 requests. Fonts for the Linux console, for PostScript
8684 renderer, or any other purpose, do not fit this
8685 definition. Any tool which makes such fonts available
8686 to the X Window System, however, must abide by this
8689 must do a number of things to ensure that they are both
8690 available without modification of the X or font server
8691 configuration, and that they do not corrupt files used by
8692 other font packages to register information about
8696 Fonts of any type supported by the X Window System
8697 must be in a separate binary package from any
8698 executables, libraries, or documentation (except
8699 that specific to the fonts shipped, such as their
8700 license information). If one or more of the fonts
8701 so packaged are necessary for proper operation of
8702 the package with which they are associated the font
8703 package may be Recommended; if the fonts merely
8704 provide an enhancement, a Suggests relationship may
8705 be used. Packages must not Depend on font
8707 This is because the X server may retrieve fonts
8708 from the local file system or over the network
8709 from an X font server; the Debian package system
8710 is empowered to deal only with the local
8716 BDF fonts must be converted to PCF fonts with the
8717 <prgn>bdftopcf</prgn> utility (available in the
8718 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8719 placed in a directory that corresponds to their
8721 <list compact="compact">
8723 100 dpi fonts must be placed in
8724 <file>/usr/share/fonts/X11/100dpi/</file>.
8728 75 dpi fonts must be placed in
8729 <file>/usr/share/fonts/X11/75dpi/</file>.
8733 Character-cell fonts, cursor fonts, and other
8734 low-resolution fonts must be placed in
8735 <file>/usr/share/fonts/X11/misc/</file>.
8741 Type 1 fonts must be placed in
8742 <file>/usr/share/fonts/X11/Type1/</file>. If font
8743 metric files are available, they must be placed here
8748 Subdirectories of <file>/usr/share/fonts/X11/</file>
8749 other than those listed above must be neither
8750 created nor used. (The <file>PEX</file>, <file>CID</file>,
8751 <file>Speedo</file>, and <file>cyrillic</file> directories
8752 are excepted for historical reasons, but installation of
8753 files into these directories remains discouraged.)
8757 Font packages may, instead of placing files directly
8758 in the X font directories listed above, provide
8759 symbolic links in that font directory pointing to
8760 the files' actual location in the filesystem. Such
8761 a location must comply with the FHS.
8765 Font packages should not contain both 75dpi and
8766 100dpi versions of a font. If both are available,
8767 they should be provided in separate binary packages
8768 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8769 the names of the packages containing the
8770 corresponding fonts.
8774 Fonts destined for the <file>misc</file> subdirectory
8775 should not be included in the same package as 75dpi
8776 or 100dpi fonts; instead, they should be provided in
8777 a separate package with <tt>-misc</tt> appended to
8782 Font packages must not provide the files
8783 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8784 <file>fonts.scale</file> in a font directory:
8787 <file>fonts.dir</file> files must not be provided at all.
8791 <file>fonts.alias</file> and <file>fonts.scale</file>
8792 files, if needed, should be provided in the
8794 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8795 where <var>fontdir</var> is the name of the
8797 <file>/usr/share/fonts/X11/</file> where the
8798 package's corresponding fonts are stored
8799 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8800 <var>package</var> is the name of the package
8801 that provides these fonts, and
8802 <var>extension</var> is either <tt>scale</tt>
8803 or <tt>alias</tt>, whichever corresponds to
8810 Font packages must declare a dependency on
8811 <tt>xfonts-utils</tt> in their control
8816 Font packages that provide one or more
8817 <file>fonts.scale</file> files as described above must
8818 invoke <prgn>update-fonts-scale</prgn> on each
8819 directory into which they installed fonts
8820 <em>before</em> invoking
8821 <prgn>update-fonts-dir</prgn> on that directory.
8822 This invocation must occur in both the
8823 <prgn>postinst</prgn> (for all arguments) and
8824 <prgn>postrm</prgn> (for all arguments except
8825 <tt>upgrade</tt>) scripts.
8829 Font packages that provide one or more
8830 <file>fonts.alias</file> files as described above must
8831 invoke <prgn>update-fonts-alias</prgn> on each
8832 directory into which they installed fonts. This
8833 invocation must occur in both the
8834 <prgn>postinst</prgn> (for all arguments) and
8835 <prgn>postrm</prgn> (for all arguments except
8836 <tt>upgrade</tt>) scripts.
8840 Font packages must invoke
8841 <prgn>update-fonts-dir</prgn> on each directory into
8842 which they installed fonts. This invocation must
8843 occur in both the <prgn>postinst</prgn> (for all
8844 arguments) and <prgn>postrm</prgn> (for all
8845 arguments except <tt>upgrade</tt>) scripts.
8849 Font packages must not provide alias names for the
8850 fonts they include which collide with alias names
8851 already in use by fonts already packaged.
8855 Font packages must not provide fonts with the same
8856 XLFD registry name as another font already packaged.
8862 <sect1 id="appdefaults">
8863 <heading>Application defaults files</heading>
8866 Application defaults files must be installed in the
8867 directory <file>/etc/X11/app-defaults/</file> (use of a
8868 localized subdirectory of <file>/etc/X11/</file> as described
8869 in the <em>X Toolkit Intrinsics - C Language
8870 Interface</em> manual is also permitted). They must be
8871 registered as <tt>conffile</tt>s or handled as
8872 configuration files.
8876 Customization of programs' X resources may also be
8877 supported with the provision of a file with the same name
8878 as that of the package placed in
8879 the <file>/etc/X11/Xresources/</file> directory, which
8880 must be registered as a <tt>conffile</tt> or handled as a
8881 configuration file.<footnote>
8882 Note that this mechanism is not the same as using
8883 app-defaults; app-defaults are tied to the client
8884 binary on the local file system, whereas X resources
8885 are stored in the X server and affect all connecting
8892 <heading>Installation directory issues</heading>
8895 Historically, packages using the X Window System used a
8896 separate set of installation directories from other packages.
8897 This practice has been discontinued and packages using the X
8898 Window System should now generally be installed in the same
8899 directories as any other package. Specifically, packages must
8900 not install files under the <file>/usr/X11R6/</file> directory
8901 and the <file>/usr/X11R6/</file> directory hierarchy should be
8902 regarded as obsolete.
8906 Include files previously installed under
8907 <file>/usr/X11R6/include/X11/</file> should be installed into
8908 <file>/usr/include/X11/</file>. For files previously
8909 installed into subdirectories of
8910 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8911 determine if subdirectories of <file>/usr/lib/</file> and
8912 <file>/usr/share/</file> can be used. If not, a subdirectory
8913 of <file>/usr/lib/X11/</file> should be used.
8917 Configuration files for window, display, or session managers
8918 or other applications that are tightly integrated with the X
8919 Window System may be placed in a subdirectory
8920 of <file>/etc/X11/</file> corresponding to the package name.
8921 Other X Window System applications should use
8922 the <file>/etc/</file> directory unless otherwise mandated by
8923 policy (such as for <ref id="appdefaults">).
8928 <heading>The OSF/Motif and OpenMotif libraries</heading>
8931 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8932 OpenMotif libraries</em><footnote>
8933 OSF/Motif and OpenMotif are collectively referred to as
8934 "Motif" in this policy document.
8936 should be compiled against and tested with LessTif (a free
8937 re-implementation of Motif) instead. If the maintainer
8938 judges that the program or programs do not work
8939 sufficiently well with LessTif to be distributed and
8940 supported, but do so when compiled against Motif, then two
8941 versions of the package should be created; one linked
8942 statically against Motif and with <tt>-smotif</tt>
8943 appended to the package name, and one linked dynamically
8944 against Motif and with <tt>-dmotif</tt> appended to the
8949 Both Motif-linked versions are dependent
8950 upon non-DFSG-compliant software and thus cannot be
8951 uploaded to the <em>main</em> distribution; if the
8952 software is itself DFSG-compliant it may be uploaded to
8953 the <em>contrib</em> distribution. While known existing
8954 versions of Motif permit unlimited redistribution of
8955 binaries linked against the library (whether statically or
8956 dynamically), it is the package maintainer's
8957 responsibility to determine whether this is permitted by
8958 the license of the copy of Motif in their possession.
8964 <heading>Perl programs and modules</heading>
8967 Perl programs and modules should follow the current Perl policy.
8971 The Perl policy can be found in the <tt>perl-policy</tt>
8972 files in the <tt>debian-policy</tt> package.
8973 It is also available from the Debian web mirrors at
8974 <tt><url name="/doc/packaging-manuals/perl-policy/"
8975 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8980 <heading>Emacs lisp programs</heading>
8983 Please refer to the "Debian Emacs Policy" for details of how to
8984 package emacs lisp programs.
8988 The Emacs policy is available in
8989 <file>debian-emacs-policy.gz</file> of the
8990 <package>emacsen-common</package> package.
8991 It is also available from the Debian web mirrors at
8992 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8993 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8998 <heading>Games</heading>
9001 The permissions on <file>/var/games</file> are mode 755, owner
9002 <tt>root</tt> and group <tt>root</tt>.
9006 Each game decides on its own security policy.</p>
9009 Games which require protected, privileged access to
9010 high-score files, saved games, etc., may be made
9011 set-<em>group</em>-id (mode 2755) and owned by
9012 <tt>root:games</tt>, and use files and directories with
9013 appropriate permissions (770 <tt>root:games</tt>, for
9014 example). They must not be made
9015 set-<em>user</em>-id, as this causes security problems. (If
9016 an attacker can subvert any set-user-id game they can
9017 overwrite the executable of any other, causing other players
9018 of these games to run a Trojan horse program. With a
9019 set-group-id game the attacker only gets access to less
9020 important game data, and if they can get at the other
9021 players' accounts at all it will take considerably more
9025 Some packages, for example some fortune cookie programs, are
9026 configured by the upstream authors to install with their
9027 data files or other static information made unreadable so
9028 that they can only be accessed through set-id programs
9029 provided. You should not do this in a Debian package: anyone can
9030 download the <file>.deb</file> file and read the data from it,
9031 so there is no point making the files unreadable. Not
9032 making the files unreadable also means that you don't have
9033 to make so many programs set-id, which reduces the risk of a
9037 As described in the FHS, binaries of games should be
9038 installed in the directory <file>/usr/games</file>. This also
9039 applies to games that use the X Window System. Manual pages
9040 for games (X and non-X games) should be installed in
9041 <file>/usr/share/man/man6</file>.</p>
9047 <heading>Documentation</heading>
9050 <heading>Manual pages</heading>
9053 You should install manual pages in <prgn>nroff</prgn> source
9054 form, in appropriate places under <file>/usr/share/man</file>.
9055 You should only use sections 1 to 9 (see the FHS for more
9056 details). You must not install a pre-formatted "cat page".
9060 Each program, utility, and function should have an
9061 associated manual page included in the same package. It is
9062 suggested that all configuration files also have a manual
9063 page included as well. Manual pages for protocols and other
9064 auxiliary things are optional.
9068 If no manual page is available, this is considered as a bug
9069 and should be reported to the Debian Bug Tracking System (the
9070 maintainer of the package is allowed to write this bug report
9071 themselves, if they so desire). Do not close the bug report
9072 until a proper man page is available.<footnote>
9073 It is not very hard to write a man page. See the
9074 <url id="http://www.schweikhardt.net/man_page_howto.html"
9075 name="Man-Page-HOWTO">,
9076 <manref name="man" section="7">, the examples
9077 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9078 the helper program <prgn>help2man</prgn>, or the
9079 directory <file>/usr/share/doc/man-db/examples</file>.
9084 You may forward a complaint about a missing man page to the
9085 upstream authors, and mark the bug as forwarded in the
9086 Debian bug tracking system. Even though the GNU Project do
9087 not in general consider the lack of a man page to be a bug,
9088 we do; if they tell you that they don't consider it a bug
9089 you should leave the bug in our bug tracking system open
9094 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9098 If one man page needs to be accessible via several names it
9099 is better to use a symbolic link than the <file>.so</file>
9100 feature, but there is no need to fiddle with the relevant
9101 parts of the upstream source to change from <file>.so</file> to
9102 symlinks: don't do it unless it's easy. You should not
9103 create hard links in the manual page directories, nor put
9104 absolute filenames in <file>.so</file> directives. The filename
9105 in a <file>.so</file> in a man page should be relative to the
9106 base of the man page tree (usually
9107 <file>/usr/share/man</file>). If you do not create any links
9108 (whether symlinks, hard links, or <tt>.so</tt> directives)
9109 in the file system to the alternate names of the man page,
9110 then you should not rely on <prgn>man</prgn> finding your
9111 man page under those names based solely on the information in
9112 the man page's header.<footnote>
9113 Supporting this in <prgn>man</prgn> often requires
9114 unreasonable processing time to find a manual page or to
9115 report that none exists, and moves knowledge into man's
9116 database that would be better left in the file system.
9117 This support is therefore deprecated and will cease to
9118 be present in the future.
9123 Manual pages in locale-specific subdirectories of
9124 <file>/usr/share/man</file> should use either UTF-8 or the usual
9125 legacy encoding for that language (normally the one corresponding
9126 to the shortest relevant locale name in
9127 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9128 <file>/usr/share/man/fr</file> should use either UTF-8 or
9129 ISO-8859-1.<footnote>
9130 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9131 use. In future, all manual pages will be required to use
9137 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9138 included in the subdirectory name unless it indicates a
9139 significant difference in the language, as this excludes
9140 speakers of the language in other countries.<footnote>
9141 At the time of writing, Chinese and Portuguese are the main
9142 languages with such differences, so <file>pt_BR</file>,
9143 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9148 If a localized version of a manual page is provided, it should
9149 either be up-to-date or it should be obvious to the reader that
9150 it is outdated and the original manual page should be used
9151 instead. This can be done either by a note at the beginning of
9152 the manual page or by showing the missing or changed portions in
9153 the original language instead of the target language.
9158 <heading>Info documents</heading>
9161 Info documents should be installed in <file>/usr/share/info</file>.
9162 They should be compressed with <tt>gzip -9</tt>.
9166 The <prgn>install-info</prgn> program maintains a directory of
9167 installed info documents in <file>/usr/share/info/dir</file> for
9168 the use of info readers.<footnote>
9169 It was previously necessary for packages installing info
9170 documents to run <prgn>install-info</prgn> from maintainer
9171 scripts. This is no longer necessary. The installation
9172 system now uses dpkg triggers.
9174 This file must not be included in packages. Packages containing
9175 info documents should depend on <tt>dpkg (>= 1.15.4) |
9176 install-info</tt> to ensure that the directory file is properly
9177 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9182 Info documents should contain section and directory entry
9183 information in the document for the use
9184 of <prgn>install-info</prgn>. The section should be specified
9185 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9186 space and the section of this info page. The directory entry or
9187 entries should be included between
9188 a <tt>START-INFO-DIR-ENTRY</tt> line and
9189 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9191 INFO-DIR-SECTION Individual utilities
9192 START-INFO-DIR-ENTRY
9193 * example: (example). An example info directory entry.
9196 To determine which section to use, you should look
9197 at <file>/usr/share/info/dir</file> on your system and choose
9198 the most relevant (or create a new section if none of the
9199 current sections are relevant).<footnote>
9200 Normally, info documents are generated from Texinfo source.
9201 To include this information in the generated info document, if
9202 it is absent, add commands like:
9204 @dircategory Individual utilities
9206 * example: (example). An example info directory entry.
9209 to the Texinfo source of the document and ensure that the info
9210 documents are rebuilt from source during the package build.
9216 <heading>Additional documentation</heading>
9219 Any additional documentation that comes with the package may
9220 be installed at the discretion of the package maintainer.
9221 Plain text documentation should be installed in the directory
9222 <file>/usr/share/doc/<var>package</var></file>, where
9223 <var>package</var> is the name of the package, and
9224 compressed with <tt>gzip -9</tt> unless it is small.
9228 If a package comes with large amounts of documentation which
9229 many users of the package will not require you should create
9230 a separate binary package to contain it, so that it does not
9231 take up disk space on the machines of users who do not need
9232 or want it installed.</p>
9235 It is often a good idea to put text information files
9236 (<file>README</file>s, changelogs, and so forth) that come with
9237 the source package in <file>/usr/share/doc/<var>package</var></file>
9238 in the binary package. However, you don't need to install
9239 the instructions for building and installing the package, of
9243 Packages must not require the existence of any files in
9244 <file>/usr/share/doc/</file> in order to function
9246 The system administrator should be able to
9247 delete files in <file>/usr/share/doc/</file> without causing
9248 any programs to break.
9250 Any files that are referenced by programs but are also
9251 useful as stand alone documentation should be installed under
9252 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9253 <file>/usr/share/doc/<var>package</var></file>.
9257 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9258 link to another directory in <file>/usr/share/doc</file> only if
9259 the two packages both come from the same source and the
9260 first package Depends on the second.<footnote>
9262 Please note that this does not override the section on
9263 changelog files below, so the file
9264 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9265 must refer to the changelog for the current version of
9266 <var>package</var> in question. In practice, this means
9267 that the sources of the target and the destination of the
9268 symlink must be the same (same source package and
9275 Former Debian releases placed all additional documentation
9276 in <file>/usr/doc/<var>package</var></file>. This has been
9277 changed to <file>/usr/share/doc/<var>package</var></file>,
9278 and packages must not put documentation in the directory
9279 <file>/usr/doc/<var>package</var></file>. <footnote>
9280 At this phase of the transition, we no longer require a
9281 symbolic link in <file>/usr/doc/</file>. At a later point,
9282 policy shall change to make the symbolic links a bug.
9288 <heading>Preferred documentation formats</heading>
9291 The unification of Debian documentation is being carried out
9295 If your package comes with extensive documentation in a
9296 markup format that can be converted to various other formats
9297 you should if possible ship HTML versions in a binary
9298 package, in the directory
9299 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9300 its subdirectories.<footnote>
9301 The rationale: The important thing here is that HTML
9302 docs should be available in <em>some</em> package, not
9303 necessarily in the main binary package.
9308 Other formats such as PostScript may be provided at the
9309 package maintainer's discretion.
9313 <sect id="copyrightfile">
9314 <heading>Copyright information</heading>
9317 Every package must be accompanied by a verbatim copy of its
9318 copyright information and distribution license in the file
9319 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9320 file must neither be compressed nor be a symbolic link.
9324 In addition, the copyright file must say where the upstream
9325 sources (if any) were obtained. It should name the original
9326 authors of the package and the Debian maintainer(s) who were
9327 involved with its creation.
9331 Packages in the <em>contrib</em> or <em>non-free</em> archive
9332 areas should state in the copyright file that the package is not
9333 part of the Debian GNU/Linux distribution and briefly explain
9338 A copy of the file which will be installed in
9339 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9340 be in <file>debian/copyright</file> in the source package.
9344 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9345 link to another directory in <file>/usr/share/doc</file> only if
9346 the two packages both come from the same source and the
9347 first package Depends on the second. These rules are
9348 important because copyrights must be extractable by
9353 Packages distributed under the Apache license (version 2.0), the
9354 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9355 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9356 1.3) should refer to the corresponding files
9357 under <file>/usr/share/common-licenses</file>,<footnote>
9360 <file>/usr/share/common-licenses/Apache-2.0</file>,
9361 <file>/usr/share/common-licenses/Artistic</file>,
9362 <file>/usr/share/common-licenses/GPL-1</file>,
9363 <file>/usr/share/common-licenses/GPL-2</file>,
9364 <file>/usr/share/common-licenses/GPL-3</file>,
9365 <file>/usr/share/common-licenses/LGPL-2</file>,
9366 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9367 <file>/usr/share/common-licenses/LGPL-3</file>,
9368 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9369 <file>/usr/share/common-licenses/GFDL-1.3</file>
9370 respectively. The University of California BSD license is
9371 also included in <package>base-files</package> as
9372 <file>/usr/share/common-licenses/BSD</file>, but given the
9373 brevity of this license, its specificity to code whose
9374 copyright is held by the Regents of the University of
9375 California, and the frequency of minor wording changes, its
9376 text should be included in the copyright file rather than
9377 referencing this file.
9379 </footnote> rather than quoting them in the copyright
9384 You should not use the copyright file as a general <file>README</file>
9385 file. If your package has such a file it should be
9386 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9387 <file>README.Debian</file> or some other appropriate place.</p>
9391 <heading>Examples</heading>
9394 Any examples (configurations, source files, whatever),
9395 should be installed in a directory
9396 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9397 files should not be referenced by any program: they're there
9398 for the benefit of the system administrator and users as
9399 documentation only. Architecture-specific example files
9400 should be installed in a directory
9401 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9403 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9404 latter directory itself may be a symbolic link to the
9409 If the purpose of a package is to provide examples, then the
9410 example files may be installed into
9411 <file>/usr/share/doc/<var>package</var></file>.
9415 <sect id="changelogs">
9416 <heading>Changelog files</heading>
9419 Packages that are not Debian-native must contain a
9420 compressed copy of the <file>debian/changelog</file> file from
9421 the Debian source tree in
9422 <file>/usr/share/doc/<var>package</var></file> with the name
9423 <file>changelog.Debian.gz</file>.
9427 If an upstream changelog is available, it should be accessible as
9428 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9429 plain text. If the upstream changelog is distributed in
9430 HTML, it should be made available in that form as
9431 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9432 and a plain text <file>changelog.gz</file> should be generated
9433 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9434 the upstream changelog files do not already conform to this
9435 naming convention, then this may be achieved either by
9436 renaming the files, or by adding a symbolic link, at the
9437 maintainer's discretion.<footnote>
9438 Rationale: People should not have to look in places for
9439 upstream changelogs merely because they are given
9440 different names or are distributed in HTML format.
9445 All of these files should be installed compressed using
9446 <tt>gzip -9</tt>, as they will become large with time even
9447 if they start out small.
9451 If the package has only one changelog which is used both as
9452 the Debian changelog and the upstream one because there is
9453 no separate upstream maintainer then that changelog should
9454 usually be installed as
9455 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9456 there is a separate upstream maintainer, but no upstream
9457 changelog, then the Debian changelog should still be called
9458 <file>changelog.Debian.gz</file>.
9462 For details about the format and contents of the Debian
9463 changelog file, please see <ref id="dpkgchangelog">.
9468 <appendix id="pkg-scope">
9469 <heading>Introduction and scope of these appendices</heading>
9472 These appendices are taken essentially verbatim from the
9473 now-deprecated Packaging Manual, version 3.2.1.0. They are
9474 the chapters which are likely to be of use to package
9475 maintainers and which have not already been included in the
9476 policy document itself. Most of these sections are very likely
9477 not relevant to policy; they should be treated as
9478 documentation for the packaging system. Please note that these
9479 appendices are included for convenience, and for historical
9480 reasons: they used to be part of policy package, and they have
9481 not yet been incorporated into dpkg documentation. However,
9482 they still have value, and hence they are presented here.
9486 They have not yet been checked to ensure that they are
9487 compatible with the contents of policy, and if there are any
9488 contradictions, the version in the main policy document takes
9489 precedence. The remaining chapters of the old Packaging
9490 Manual have also not been read in detail to ensure that there
9491 are not parts which have been left out. Both of these will be
9496 Certain parts of the Packaging manual were integrated into the
9497 Policy Manual proper, and removed from the appendices. Links
9498 have been placed from the old locations to the new ones.
9502 <prgn>dpkg</prgn> is a suite of programs for creating binary
9503 package files and installing and removing them on Unix
9505 <prgn>dpkg</prgn> is targeted primarily at Debian
9506 GNU/Linux, but may work on or be ported to other
9512 The binary packages are designed for the management of
9513 installed executable programs (usually compiled binaries) and
9514 their associated data, though source code examples and
9515 documentation are provided as part of some packages.</p>
9518 This manual describes the technical aspects of creating Debian
9519 binary packages (<file>.deb</file> files). It documents the
9520 behavior of the package management programs
9521 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9522 they interact with packages.</p>
9525 It also documents the interaction between
9526 <prgn>dselect</prgn>'s core and the access method scripts it
9527 uses to actually install the selected packages, and describes
9528 how to create a new access method.</p>
9531 This manual does not go into detail about the options and
9532 usage of the package building and installation tools. It
9533 should therefore be read in conjunction with those programs'
9538 The utility programs which are provided with <prgn>dpkg</prgn>
9539 for managing various system configuration and similar issues,
9540 such as <prgn>update-rc.d</prgn> and
9541 <prgn>install-info</prgn>, are not described in detail here -
9542 please see their man pages.
9546 It is assumed that the reader is reasonably familiar with the
9547 <prgn>dpkg</prgn> System Administrators' manual.
9548 Unfortunately this manual does not yet exist.
9552 The Debian version of the FSF's GNU hello program is provided
9553 as an example for people wishing to create Debian
9554 packages. The Debian <prgn>debmake</prgn> package is
9555 recommended as a very helpful tool in creating and maintaining
9556 Debian packages. However, while the tools and examples are
9557 helpful, they do not replace the need to read and follow the
9558 Policy and Programmer's Manual.</p>
9561 <appendix id="pkg-binarypkg">
9562 <heading>Binary packages (from old Packaging Manual)</heading>
9565 The binary package has two main sections. The first part
9566 consists of various control information files and scripts used
9567 by <prgn>dpkg</prgn> when installing and removing. See <ref
9568 id="pkg-controlarea">.
9572 The second part is an archive containing the files and
9573 directories to be installed.
9577 In the future binary packages may also contain other
9578 components, such as checksums and digital signatures. The
9579 format for the archive is described in full in the
9580 <file>deb(5)</file> man page.
9584 <sect id="pkg-bincreating"><heading>Creating package files -
9585 <prgn>dpkg-deb</prgn>
9589 All manipulation of binary package files is done by
9590 <prgn>dpkg-deb</prgn>; it's the only program that has
9591 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9592 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9593 will spot that the options requested are appropriate to
9594 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9599 In order to create a binary package you must make a
9600 directory tree which contains all the files and directories
9601 you want to have in the file system data part of the package.
9602 In Debian-format source packages this directory is usually
9603 <file>debian/tmp</file>, relative to the top of the package's
9608 They should have the locations (relative to the root of the
9609 directory tree you're constructing) ownerships and
9610 permissions which you want them to have on the system when
9615 With current versions of <prgn>dpkg</prgn> the uid/username
9616 and gid/groupname mappings for the users and groups being
9617 used should be the same on the system where the package is
9618 built and the one where it is installed.
9622 You need to add one special directory to the root of the
9623 miniature file system tree you're creating:
9624 <prgn>DEBIAN</prgn>. It should contain the control
9625 information files, notably the binary package control file
9626 (see <ref id="pkg-controlfile">).
9630 The <prgn>DEBIAN</prgn> directory will not appear in the
9631 file system archive of the package, and so won't be installed
9632 by <prgn>dpkg</prgn> when the package is installed.
9636 When you've prepared the package, you should invoke:
9638 dpkg --build <var>directory</var>
9643 This will build the package in
9644 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9645 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9646 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9651 See the man page <manref name="dpkg-deb" section="8"> for details of how
9652 to examine the contents of this newly-created file. You may find the
9653 output of following commands enlightening:
9655 dpkg-deb --info <var>filename</var>.deb
9656 dpkg-deb --contents <var>filename</var>.deb
9657 dpkg --contents <var>filename</var>.deb
9659 To view the copyright file for a package you could use this command:
9661 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9666 <sect id="pkg-controlarea">
9667 <heading>Package control information files</heading>
9670 The control information portion of a binary package is a
9671 collection of files with names known to <prgn>dpkg</prgn>.
9672 It will treat the contents of these files specially - some
9673 of them contain information used by <prgn>dpkg</prgn> when
9674 installing or removing the package; others are scripts which
9675 the package maintainer wants <prgn>dpkg</prgn> to run.
9679 It is possible to put other files in the package control
9680 area, but this is not generally a good idea (though they
9681 will largely be ignored).
9685 Here is a brief list of the control info files supported by
9686 <prgn>dpkg</prgn> and a summary of what they're used for.
9691 <tag><tt>control</tt>
9694 This is the key description file used by
9695 <prgn>dpkg</prgn>. It specifies the package's name
9696 and version, gives its description for the user,
9697 states its relationships with other packages, and so
9698 forth. See <ref id="sourcecontrolfiles"> and
9699 <ref id="binarycontrolfiles">.
9703 It is usually generated automatically from information
9704 in the source package by the
9705 <prgn>dpkg-gencontrol</prgn> program, and with
9706 assistance from <prgn>dpkg-shlibdeps</prgn>.
9707 See <ref id="pkg-sourcetools">.
9711 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9716 These are executable files (usually scripts) which
9717 <prgn>dpkg</prgn> runs during installation, upgrade
9718 and removal of packages. They allow the package to
9719 deal with matters which are particular to that package
9720 or require more complicated processing than that
9721 provided by <prgn>dpkg</prgn>. Details of when and
9722 how they are called are in <ref id="maintainerscripts">.
9726 It is very important to make these scripts idempotent.
9727 See <ref id="idempotency">.
9731 The maintainer scripts are not guaranteed to run with a
9732 controlling terminal and may not be able to interact with
9733 the user. See <ref id="controllingterminal">.
9737 <tag><tt>conffiles</tt>
9740 This file contains a list of configuration files which
9741 are to be handled automatically by <prgn>dpkg</prgn>
9742 (see <ref id="pkg-conffiles">). Note that not necessarily
9743 every configuration file should be listed here.
9746 <tag><tt>shlibs</tt>
9749 This file contains a list of the shared libraries
9750 supplied by the package, with dependency details for
9751 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9752 when it determines what dependencies are required in a
9753 package control file. The <tt>shlibs</tt> file format
9754 is described on <ref id="shlibs">.
9759 <sect id="pkg-controlfile">
9760 <heading>The main control information file: <tt>control</tt></heading>
9763 The most important control information file used by
9764 <prgn>dpkg</prgn> when it installs a package is
9765 <tt>control</tt>. It contains all the package's "vital
9770 The binary package control files of packages built from
9771 Debian sources are made by a special tool,
9772 <prgn>dpkg-gencontrol</prgn>, which reads
9773 <file>debian/control</file> and <file>debian/changelog</file> to
9774 find the information it needs. See <ref id="pkg-sourcepkg"> for
9779 The fields in binary package control files are listed in
9780 <ref id="binarycontrolfiles">.
9784 A description of the syntax of control files and the purpose
9785 of the fields is available in <ref id="controlfields">.
9790 <heading>Time Stamps</heading>
9793 See <ref id="timestamps">.
9798 <appendix id="pkg-sourcepkg">
9799 <heading>Source packages (from old Packaging Manual) </heading>
9802 The Debian binary packages in the distribution are generated
9803 from Debian sources, which are in a special format to assist
9804 the easy and automatic building of binaries.
9807 <sect id="pkg-sourcetools">
9808 <heading>Tools for processing source packages</heading>
9811 Various tools are provided for manipulating source packages;
9812 they pack and unpack sources and help build of binary
9813 packages and help manage the distribution of new versions.
9817 They are introduced and typical uses described here; see
9818 <manref name="dpkg-source" section="1"> for full
9819 documentation about their arguments and operation.
9823 For examples of how to construct a Debian source package,
9824 and how to use those utilities that are used by Debian
9825 source packages, please see the <prgn>hello</prgn> example
9829 <sect1 id="pkg-dpkg-source">
9831 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9836 This program is frequently used by hand, and is also
9837 called from package-independent automated building scripts
9838 such as <prgn>dpkg-buildpackage</prgn>.
9842 To unpack a package it is typically invoked with
9844 dpkg-source -x <var>.../path/to/filename</var>.dsc
9849 with the <file><var>filename</var>.tar.gz</file> and
9850 <file><var>filename</var>.diff.gz</file> (if applicable) in
9851 the same directory. It unpacks into
9852 <file><var>package</var>-<var>version</var></file>, and if
9854 <file><var>package</var>-<var>version</var>.orig</file>, in
9855 the current directory.
9859 To create a packed source archive it is typically invoked:
9861 dpkg-source -b <var>package</var>-<var>version</var>
9866 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9867 <file>.diff.gz</file> (if appropriate) in the current
9868 directory. <prgn>dpkg-source</prgn> does not clean the
9869 source tree first - this must be done separately if it is
9874 See also <ref id="pkg-sourcearchives">.</p>
9878 <sect1 id="pkg-dpkg-buildpackage">
9880 <prgn>dpkg-buildpackage</prgn> - overall package-building
9885 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9886 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9887 targets <tt>clean</tt>, <tt>build</tt> and
9888 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9889 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9890 source and binary package upload.
9894 It is usually invoked by hand from the top level of the
9895 built or unbuilt source directory. It may be invoked with
9896 no arguments; useful arguments include:
9897 <taglist compact="compact">
9898 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9901 Do not sign the <tt>.changes</tt> file or the
9902 source package <tt>.dsc</tt> file, respectively.</p>
9904 <tag><tt>-p<var>sign-command</var></tt></tag>
9907 Invoke <var>sign-command</var> instead of finding
9908 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9909 <var>sign-command</var> must behave just like
9910 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9912 <tag><tt>-r<var>root-command</var></tt></tag>
9915 When root privilege is required, invoke the command
9916 <var>root-command</var>. <var>root-command</var>
9917 should invoke its first argument as a command, from
9918 the <prgn>PATH</prgn> if necessary, and pass its
9919 second and subsequent arguments to the command it
9920 calls. If no <var>root-command</var> is supplied
9921 then <var>dpkg-buildpackage</var> will take no
9922 special action to gain root privilege, so that for
9923 most packages it will have to be invoked as root to
9926 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9929 Two types of binary-only build and upload - see
9930 <manref name="dpkg-source" section="1">.
9937 <sect1 id="pkg-dpkg-gencontrol">
9939 <prgn>dpkg-gencontrol</prgn> - generates binary package
9944 This program is usually called from <file>debian/rules</file>
9945 (see <ref id="pkg-sourcetree">) in the top level of the source
9950 This is usually done just before the files and directories in the
9951 temporary directory tree where the package is being built have their
9952 permissions and ownerships set and the package is constructed using
9953 <prgn>dpkg-deb/</prgn>
9955 This is so that the control file which is produced has
9956 the right permissions
9961 <prgn>dpkg-gencontrol</prgn> must be called after all the
9962 files which are to go into the package have been placed in
9963 the temporary build directory, so that its calculation of
9964 the installed size of a package is correct.
9968 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9969 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9970 variable substitutions created by
9971 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9976 For a package which generates only one binary package, and
9977 which builds it in <file>debian/tmp</file> relative to the top
9978 of the source package, it is usually sufficient to call
9979 <prgn>dpkg-gencontrol</prgn>.
9983 Sources which build several binaries will typically need
9986 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9987 </example> The <tt>-P</tt> tells
9988 <prgn>dpkg-gencontrol</prgn> that the package is being
9989 built in a non-default directory, and the <tt>-p</tt>
9990 tells it which package's control file should be generated.
9994 <prgn>dpkg-gencontrol</prgn> also adds information to the
9995 list of files in <file>debian/files</file>, for the benefit of
9996 (for example) a future invocation of
9997 <prgn>dpkg-genchanges</prgn>.</p>
10000 <sect1 id="pkg-dpkg-shlibdeps">
10002 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10007 This program is usually called from <file>debian/rules</file>
10008 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10009 id="pkg-sourcetree">), in the top level of the source tree.
10013 Its arguments are executables and shared libraries
10016 They may be specified either in the locations in the
10017 source tree where they are created or in the locations
10018 in the temporary build tree where they are installed
10019 prior to binary package creation.
10021 </footnote> for which shared library dependencies should
10022 be included in the binary package's control file.
10026 If some of the found shared libraries should only
10027 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10028 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10029 by using the <tt>-d<var>dependency-field</var></tt> option
10030 before those executable(s). (Each <tt>-d</tt> option
10031 takes effect until the next <tt>-d</tt>.)
10035 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10036 output control file to be modified. Instead by default it
10037 adds to the <file>debian/substvars</file> file variable
10038 settings like <tt>shlibs:Depends</tt>. These variable
10039 settings must be referenced in dependency fields in the
10040 appropriate per-binary-package sections of the source
10045 For example, a package that generates an essential part
10046 which requires dependencies, and optional parts that
10047 which only require a recommendation, would separate those
10048 two sets of dependencies into two different fields.<footnote>
10049 At the time of writing, an example for this was the
10050 <package/xmms/ package, with Depends used for the xmms
10051 executable, Recommends for the plug-ins and Suggests for
10052 even more optional features provided by unzip.
10054 It can say in its <file>debian/rules</file>:
10056 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10057 -dRecommends <var>optionalpart anotheroptionalpart</var>
10059 and then in its main control file <file>debian/control</file>:
10062 Depends: ${shlibs:Depends}
10063 Recommends: ${shlibs:Recommends}
10069 Sources which produce several binary packages with
10070 different shared library dependency requirements can use
10071 the <tt>-p<var>varnameprefix</var></tt> option to override
10072 the default <tt>shlibs:</tt> prefix (one invocation of
10073 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10074 They can thus produce several sets of dependency
10075 variables, each of the form
10076 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10077 which can be referred to in the appropriate parts of the
10078 binary package control files.
10083 <sect1 id="pkg-dpkg-distaddfile">
10085 <prgn>dpkg-distaddfile</prgn> - adds a file to
10086 <file>debian/files</file>
10090 Some packages' uploads need to include files other than
10091 the source and binary package files.
10095 <prgn>dpkg-distaddfile</prgn> adds a file to the
10096 <file>debian/files</file> file so that it will be included in
10097 the <file>.changes</file> file when
10098 <prgn>dpkg-genchanges</prgn> is run.
10102 It is usually invoked from the <tt>binary</tt> target of
10103 <file>debian/rules</file>:
10105 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10107 The <var>filename</var> is relative to the directory where
10108 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10109 is usually the directory above the top level of the source
10110 tree. The <file>debian/rules</file> target should put the
10111 file there just before or just after calling
10112 <prgn>dpkg-distaddfile</prgn>.
10116 The <var>section</var> and <var>priority</var> are passed
10117 unchanged into the resulting <file>.changes</file> file.
10122 <sect1 id="pkg-dpkg-genchanges">
10124 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10125 upload control file
10129 This program is usually called by package-independent
10130 automatic building scripts such as
10131 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10136 It is usually called in the top level of a built source
10137 tree, and when invoked with no arguments will print out a
10138 straightforward <file>.changes</file> file based on the
10139 information in the source package's changelog and control
10140 file and the binary and source packages which should have
10146 <sect1 id="pkg-dpkg-parsechangelog">
10148 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10149 representation of a changelog
10153 This program is used internally by
10154 <prgn>dpkg-source</prgn> et al. It may also occasionally
10155 be useful in <file>debian/rules</file> and elsewhere. It
10156 parses a changelog, <file>debian/changelog</file> by default,
10157 and prints a control-file format representation of the
10158 information in it to standard output.
10162 <sect1 id="pkg-dpkg-architecture">
10164 <prgn>dpkg-architecture</prgn> - information about the build and
10169 This program can be used manually, but is also invoked by
10170 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10171 environment or make variables which specify the build and host
10172 architecture for the package building process.
10177 <sect id="pkg-sourcetree">
10178 <heading>The Debian package source tree</heading>
10181 The source archive scheme described later is intended to
10182 allow a Debian package source tree with some associated
10183 control information to be reproduced and transported easily.
10184 The Debian package source tree is a version of the original
10185 program with certain files added for the benefit of the
10186 packaging process, and with any other changes required
10187 made to the rest of the source code and installation
10192 The extra files created for Debian are in the subdirectory
10193 <file>debian</file> of the top level of the Debian package
10194 source tree. They are described below.
10197 <sect1 id="pkg-debianrules">
10198 <heading><file>debian/rules</file> - the main building script</heading>
10201 See <ref id="debianrules">.
10205 <sect1 id="pkg-srcsubstvars">
10206 <heading><file>debian/substvars</file> and variable substitutions</heading>
10209 See <ref id="substvars">.
10215 <heading><file>debian/files</file></heading>
10218 See <ref id="debianfiles">.
10222 <sect1><heading><file>debian/tmp</file>
10226 This is the canonical temporary location for the
10227 construction of binary packages by the <tt>binary</tt>
10228 target. The directory <file>tmp</file> serves as the root of
10229 the file system tree as it is being constructed (for
10230 example, by using the package's upstream makefiles install
10231 targets and redirecting the output there), and it also
10232 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10233 id="pkg-bincreating">.
10237 If several binary packages are generated from the same
10238 source tree it is usual to use several
10239 <file>debian/tmp<var>something</var></file> directories, for
10240 example <file>tmp-a</file> or <file>tmp-doc</file>.
10244 Whatever <file>tmp</file> directories are created and used by
10245 <tt>binary</tt> must of course be removed by the
10246 <tt>clean</tt> target.</p></sect1>
10250 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10254 As it exists on the FTP site, a Debian source package
10255 consists of three related files. You must have the right
10256 versions of all three to be able to use them.
10261 <tag>Debian source control file - <tt>.dsc</tt></tag>
10263 This file is a control file used by <prgn>dpkg-source</prgn>
10264 to extract a source package.
10265 See <ref id="debiansourcecontrolfiles">.
10269 Original source archive -
10271 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10277 This is a compressed (with <tt>gzip -9</tt>)
10278 <prgn>tar</prgn> file containing the source code from
10279 the upstream authors of the program.
10284 Debian package diff -
10286 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10292 This is a unified context diff (<tt>diff -u</tt>)
10293 giving the changes which are required to turn the
10294 original source into the Debian source. These changes
10295 may only include editing and creating plain files.
10296 The permissions of files, the targets of symbolic
10297 links and the characteristics of special files or
10298 pipes may not be changed and no files may be removed
10303 All the directories in the diff must exist, except the
10304 <file>debian</file> subdirectory of the top of the source
10305 tree, which will be created by
10306 <prgn>dpkg-source</prgn> if necessary when unpacking.
10310 The <prgn>dpkg-source</prgn> program will
10311 automatically make the <file>debian/rules</file> file
10312 executable (see below).</p></item>
10317 If there is no original source code - for example, if the
10318 package is specially prepared for Debian or the Debian
10319 maintainer is the same as the upstream maintainer - the
10320 format is slightly different: then there is no diff, and the
10322 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10323 and preferably contains a directory named
10324 <file><var>package</var>-<var>version</var></file>.
10329 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10332 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10333 Debian source package. However, if it is not available it
10334 is possible to unpack a Debian source archive as follows:
10335 <enumlist compact="compact">
10338 Untar the tarfile, which will create a <file>.orig</file>
10342 <p>Rename the <file>.orig</file> directory to
10343 <file><var>package</var>-<var>version</var></file>.</p>
10347 Create the subdirectory <file>debian</file> at the top of
10348 the source tree.</p>
10350 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10352 <item><p>Untar the tarfile again if you want a copy of the original
10353 source code alongside the Debian version.</p>
10358 It is not possible to generate a valid Debian source archive
10359 without using <prgn>dpkg-source</prgn>. In particular,
10360 attempting to use <prgn>diff</prgn> directly to generate the
10361 <file>.diff.gz</file> file will not work.
10365 <heading>Restrictions on objects in source packages</heading>
10368 The source package may not contain any hard links
10370 This is not currently detected when building source
10371 packages, but only when extracting
10375 Hard links may be permitted at some point in the
10376 future, but would require a fair amount of
10378 </footnote>, device special files, sockets or setuid or
10381 Setgid directories are allowed.
10386 The source packaging tools manage the changes between the
10387 original and Debian source using <prgn>diff</prgn> and
10388 <prgn>patch</prgn>. Turning the original source tree as
10389 included in the <file>.orig.tar.gz</file> into the Debian
10390 package source must not involve any changes which cannot be
10391 handled by these tools. Problematic changes which cause
10392 <prgn>dpkg-source</prgn> to halt with an error when
10393 building the source package are:
10394 <list compact="compact">
10395 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10397 <item><p>Changing the targets of symbolic links.</p>
10399 <item><p>Creating directories, other than <file>debian</file>.</p>
10401 <item><p>Changes to the contents of binary files.</p></item>
10402 </list> Changes which cause <prgn>dpkg-source</prgn> to
10403 print a warning but continue anyway are:
10404 <list compact="compact">
10407 Removing files, directories or symlinks.
10409 Renaming a file is not treated specially - it is
10410 seen as the removal of the old file (which
10411 generates a warning, but is otherwise ignored),
10412 and the creation of the new one.
10418 Changed text files which are missing the usual final
10419 newline (either in the original or the modified
10424 Changes which are not represented, but which are not detected by
10425 <prgn>dpkg-source</prgn>, are:
10426 <list compact="compact">
10427 <item><p>Changing the permissions of files (other than
10428 <file>debian/rules</file>) and directories.</p></item>
10433 The <file>debian</file> directory and <file>debian/rules</file>
10434 are handled specially by <prgn>dpkg-source</prgn> - before
10435 applying the changes it will create the <file>debian</file>
10436 directory, and afterwards it will make
10437 <file>debian/rules</file> world-executable.
10443 <appendix id="pkg-controlfields">
10444 <heading>Control files and their fields (from old Packaging Manual)</heading>
10447 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10448 data in a common format, known as control files. Binary and
10449 source packages have control data as do the <file>.changes</file>
10450 files which control the installation of uploaded files, and
10451 <prgn>dpkg</prgn>'s internal databases are in a similar
10456 <heading>Syntax of control files</heading>
10459 See <ref id="controlsyntax">.
10463 It is important to note that there are several fields which
10464 are optional as far as <prgn>dpkg</prgn> and the related
10465 tools are concerned, but which must appear in every Debian
10466 package, or whose omission may cause problems.
10471 <heading>List of fields</heading>
10474 See <ref id="controlfieldslist">.
10478 This section now contains only the fields that didn't belong
10479 to the Policy manual.
10482 <sect1 id="pkg-f-Filename">
10483 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10486 These fields in <tt>Packages</tt> files give the
10487 filename(s) of (the parts of) a package in the
10488 distribution directories, relative to the root of the
10489 Debian hierarchy. If the package has been split into
10490 several parts the parts are all listed in order, separated
10495 <sect1 id="pkg-f-Size">
10496 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10499 These fields in <file>Packages</file> files give the size (in
10500 bytes, expressed in decimal) and MD5 checksum of the
10501 file(s) which make(s) up a binary package in the
10502 distribution. If the package is split into several parts
10503 the values for the parts are listed in order, separated by
10508 <sect1 id="pkg-f-Status">
10509 <heading><tt>Status</tt></heading>
10512 This field in <prgn>dpkg</prgn>'s status file records
10513 whether the user wants a package installed, removed or
10514 left alone, whether it is broken (requiring
10515 re-installation) or not and what its current state on the
10516 system is. Each of these pieces of information is a
10521 <sect1 id="pkg-f-Config-Version">
10522 <heading><tt>Config-Version</tt></heading>
10525 If a package is not installed or not configured, this
10526 field in <prgn>dpkg</prgn>'s status file records the last
10527 version of the package which was successfully
10532 <sect1 id="pkg-f-Conffiles">
10533 <heading><tt>Conffiles</tt></heading>
10536 This field in <prgn>dpkg</prgn>'s status file contains
10537 information about the automatically-managed configuration
10538 files held by a package. This field should <em>not</em>
10539 appear anywhere in a package!
10544 <heading>Obsolete fields</heading>
10547 These are still recognized by <prgn>dpkg</prgn> but should
10548 not appear anywhere any more.
10550 <taglist compact="compact">
10552 <tag><tt>Revision</tt></tag>
10553 <tag><tt>Package-Revision</tt></tag>
10554 <tag><tt>Package_Revision</tt></tag>
10556 The Debian revision part of the package version was
10557 at one point in a separate control file field. This
10558 field went through several names.
10561 <tag><tt>Recommended</tt></tag>
10562 <item>Old name for <tt>Recommends</tt>.</item>
10564 <tag><tt>Optional</tt></tag>
10565 <item>Old name for <tt>Suggests</tt>.</item>
10567 <tag><tt>Class</tt></tag>
10568 <item>Old name for <tt>Priority</tt>.</item>
10577 <appendix id="pkg-conffiles">
10578 <heading>Configuration file handling (from old Packaging Manual)</heading>
10581 <prgn>dpkg</prgn> can do a certain amount of automatic
10582 handling of package configuration files.
10586 Whether this mechanism is appropriate depends on a number of
10587 factors, but basically there are two approaches to any
10588 particular configuration file.
10592 The easy method is to ship a best-effort configuration in the
10593 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10594 handle updates. If the user is unlikely to want to edit the
10595 file, but you need them to be able to without losing their
10596 changes, and a new package with a changed version of the file
10597 is only released infrequently, this is a good approach.
10601 The hard method is to build the configuration file from
10602 scratch in the <prgn>postinst</prgn> script, and to take the
10603 responsibility for fixing any mistakes made in earlier
10604 versions of the package automatically. This will be
10605 appropriate if the file is likely to need to be different on
10609 <sect><heading>Automatic handling of configuration files by
10614 A package may contain a control area file called
10615 <tt>conffiles</tt>. This file should be a list of filenames
10616 of configuration files needing automatic handling, separated
10617 by newlines. The filenames should be absolute pathnames,
10618 and the files referred to should actually exist in the
10623 When a package is upgraded <prgn>dpkg</prgn> will process
10624 the configuration files during the configuration stage,
10625 shortly before it runs the package's <prgn>postinst</prgn>
10630 For each file it checks to see whether the version of the
10631 file included in the package is the same as the one that was
10632 included in the last version of the package (the one that is
10633 being upgraded from); it also compares the version currently
10634 installed on the system with the one shipped with the last
10639 If neither the user nor the package maintainer has changed
10640 the file, it is left alone. If one or the other has changed
10641 their version, then the changed version is preferred - i.e.,
10642 if the user edits their file, but the package maintainer
10643 doesn't ship a different version, the user's changes will
10644 stay, silently, but if the maintainer ships a new version
10645 and the user hasn't edited it the new version will be
10646 installed (with an informative message). If both have
10647 changed their version the user is prompted about the problem
10648 and must resolve the differences themselves.
10652 The comparisons are done by calculating the MD5 message
10653 digests of the files, and storing the MD5 of the file as it
10654 was included in the most recent version of the package.
10658 When a package is installed for the first time
10659 <prgn>dpkg</prgn> will install the file that comes with it,
10660 unless that would mean overwriting a file already on the
10665 However, note that <prgn>dpkg</prgn> will <em>not</em>
10666 replace a conffile that was removed by the user (or by a
10667 script). This is necessary because with some programs a
10668 missing file produces an effect hard or impossible to
10669 achieve in another way, so that a missing file needs to be
10670 kept that way if the user did it.
10674 Note that a package should <em>not</em> modify a
10675 <prgn>dpkg</prgn>-handled conffile in its maintainer
10676 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10677 the user confusing and possibly dangerous options for
10678 conffile update when the package is upgraded.</p>
10681 <sect><heading>Fully-featured maintainer script configuration
10686 For files which contain site-specific information such as
10687 the hostname and networking details and so forth, it is
10688 better to create the file in the package's
10689 <prgn>postinst</prgn> script.
10693 This will typically involve examining the state of the rest
10694 of the system to determine values and other information, and
10695 may involve prompting the user for some information which
10696 can't be obtained some other way.
10700 When using this method there are a couple of important
10701 issues which should be considered:
10705 If you discover a bug in the program which generates the
10706 configuration file, or if the format of the file changes
10707 from one version to the next, you will have to arrange for
10708 the postinst script to do something sensible - usually this
10709 will mean editing the installed configuration file to remove
10710 the problem or change the syntax. You will have to do this
10711 very carefully, since the user may have changed the file,
10712 perhaps to fix the very problem that your script is trying
10713 to deal with - you will have to detect these situations and
10714 deal with them correctly.
10718 If you do go down this route it's probably a good idea to
10719 make the program that generates the configuration file(s) a
10720 separate program in <file>/usr/sbin</file>, by convention called
10721 <file><var>package</var>config</file> and then run that if
10722 appropriate from the post-installation script. The
10723 <tt><var>package</var>config</tt> program should not
10724 unquestioningly overwrite an existing configuration - if its
10725 mode of operation is geared towards setting up a package for
10726 the first time (rather than any arbitrary reconfiguration
10727 later) you should have it check whether the configuration
10728 already exists, and require a <tt>--force</tt> flag to
10729 overwrite it.</p></sect>
10732 <appendix id="pkg-alternatives"><heading>Alternative versions of
10733 an interface - <prgn>update-alternatives</prgn> (from old
10738 When several packages all provide different versions of the
10739 same program or file it is useful to have the system select a
10740 default, but to allow the system administrator to change it
10741 and have their decisions respected.
10745 For example, there are several versions of the <prgn>vi</prgn>
10746 editor, and there is no reason to prevent all of them from
10747 being installed at once, each under their own name
10748 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10749 Nevertheless it is desirable to have the name <tt>vi</tt>
10750 refer to something, at least by default.
10754 If all the packages involved cooperate, this can be done with
10755 <prgn>update-alternatives</prgn>.
10759 Each package provides its own version under its own name, and
10760 calls <prgn>update-alternatives</prgn> in its postinst to
10761 register its version (and again in its prerm to deregister
10766 See the man page <manref name="update-alternatives"
10767 section="8"> for details.
10771 If <prgn>update-alternatives</prgn> does not seem appropriate
10772 you may wish to consider using diversions instead.</p>
10775 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10776 package's version of a file (from old Packaging Manual)
10780 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10781 when it reinstalls the package it belongs to, and to have it
10782 put the file from the package somewhere else instead.
10786 This can be used locally to override a package's version of a
10787 file, or by one package to override another's version (or
10788 provide a wrapper for it).
10792 Before deciding to use a diversion, read <ref
10793 id="pkg-alternatives"> to see if you really want a diversion
10794 rather than several alternative versions of a program.
10798 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10799 and updated by a special program <prgn>dpkg-divert</prgn>.
10800 Please see <manref name="dpkg-divert" section="8"> for full
10801 details of its operation.
10805 When a package wishes to divert a file from another, it should
10806 call <prgn>dpkg-divert</prgn> in its preinst to add the
10807 diversion and rename the existing file. For example,
10808 supposing that a <prgn>smailwrapper</prgn> package wishes to
10809 install a wrapper around <file>/usr/sbin/smail</file>:
10811 dpkg-divert --package smailwrapper --add --rename \
10812 --divert /usr/sbin/smail.real /usr/sbin/smail
10813 </example> The <tt>--package smailwrapper</tt> ensures that
10814 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10815 can bypass the diversion and get installed as the true version.
10816 It's safe to add the diversion unconditionally on upgrades since
10817 it will be left unchanged if it already exists, but
10818 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10819 message, make the command conditional on the version from which
10820 the package is being upgraded:
10822 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10823 dpkg-divert --package smailwrapper --add --rename \
10824 --divert /usr/sbin/smail.real /usr/sbin/smail
10826 </example> where <tt>1.0-2</tt> is the version at which the
10827 diversion was first added to the package. Running the command
10828 during abort-upgrade is pointless but harmless.
10832 The postrm has to do the reverse:
10834 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10835 dpkg-divert --package smailwrapper --remove --rename \
10836 --divert /usr/sbin/smail.real /usr/sbin/smail
10838 </example> If the diversion was added at a particular version, the
10839 postrm should also handle the failure case of upgrading from an
10840 older version (unless the older version is so old that direct
10841 upgrades are no longer supported):
10843 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10844 dpkg-divert --package smailwrapper --remove --rename \
10845 --divert /usr/sbin/smail.real /usr/sbin/smail
10847 </example> where <tt>1.02-2</tt> is the version at which the
10848 diversion was first added to the package. The postrm should not
10849 remove the diversion on upgrades both because there's no reason to
10850 remove the diversion only to immediately re-add it and since the
10851 postrm of the old package is run after unpacking so the removal of
10852 the diversion will fail.
10856 Do not attempt to divert a file which is vitally important for
10857 the system's operation - when using <prgn>dpkg-divert</prgn>
10858 there is a time, after it has been diverted but before
10859 <prgn>dpkg</prgn> has installed the new version, when the file
10860 does not exist.</p>
10865 <!-- Local variables: -->
10866 <!-- indent-tabs-mode: t -->
10868 <!-- vim:set ai et sts=2 sw=2 tw=76: -->