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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 These are the copyright dates of the original Policy manual.
29 Since then, this manual has been updated by many others. No
30 comprehensive collection of copyright notices for subsequent
35 This manual is free software; you may redistribute it and/or
36 modify it under the terms of the GNU General Public License
37 as published by the Free Software Foundation; either version
38 2, or (at your option) any later version.
42 This is distributed in the hope that it will be useful, but
43 <em>without any warranty</em>; without even the implied
44 warranty of merchantability or fitness for a particular
45 purpose. See the GNU General Public License for more
50 A copy of the GNU General Public License is available as
51 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
52 distribution or on the World Wide Web at
53 <url id="http://www.gnu.org/copyleft/gpl.html"
54 name="the GNU General Public Licence">. You can also
55 obtain it by writing to the Free Software Foundation, Inc.,
56 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
64 <heading>About this manual</heading>
66 <heading>Scope</heading>
68 This manual describes the policy requirements for the Debian
69 GNU/Linux distribution. This includes the structure and
70 contents of the Debian archive and several design issues of the
71 operating system, as well as technical requirements that
72 each package must satisfy to be included in the
77 This manual also describes Debian policy as it relates to
78 creating Debian packages. It is not a tutorial on how to build
79 packages, nor is it exhaustive where it comes to describing
80 the behavior of the packaging system. Instead, this manual
81 attempts to define the interface to the package management
82 system that the developers have to be conversant with.<footnote>
83 Informally, the criteria used for inclusion is that the
84 material meet one of the following requirements:
85 <taglist compact="compact">
86 <tag>Standard interfaces</tag>
88 The material presented represents an interface to
89 the packaging system that is mandated for use, and
90 is used by, a significant number of packages, and
91 therefore should not be changed without peer
92 review. Package maintainers can then rely on this
93 interface not changing, and the package management
94 software authors need to ensure compatibility with
95 this interface definition. (Control file and
96 changelog file formats are examples.)
98 <tag>Chosen Convention</tag>
100 If there are a number of technically viable choices
101 that can be made, but one needs to select one of
102 these options for inter-operability. The version
103 number format is one example.
106 Please note that these are not mutually exclusive;
107 selected conventions often become parts of standard
113 The footnotes present in this manual are
114 merely informative, and are not part of Debian policy itself.
118 The appendices to this manual are not necessarily normative,
119 either. Please see <ref id="pkg-scope"> for more information.
123 In the normative part of this manual,
124 the words <em>must</em>, <em>should</em> and
125 <em>may</em>, and the adjectives <em>required</em>,
126 <em>recommended</em> and <em>optional</em>, are used to
127 distinguish the significance of the various guidelines in
128 this policy document. Packages that do not conform to the
129 guidelines denoted by <em>must</em> (or <em>required</em>)
130 will generally not be considered acceptable for the Debian
131 distribution. Non-conformance with guidelines denoted by
132 <em>should</em> (or <em>recommended</em>) will generally be
133 considered a bug, but will not necessarily render a package
134 unsuitable for distribution. Guidelines denoted by
135 <em>may</em> (or <em>optional</em>) are truly optional and
136 adherence is left to the maintainer's discretion.
140 These classifications are roughly equivalent to the bug
141 severities <em>serious</em> (for <em>must</em> or
142 <em>required</em> directive violations), <em>minor</em>,
143 <em>normal</em> or <em>important</em>
144 (for <em>should</em> or <em>recommended</em> directive
145 violations) and <em>wishlist</em> (for <em>optional</em>
148 Compare RFC 2119. Note, however, that these words are
149 used in a different way in this document.
154 Much of the information presented in this manual will be
155 useful even when building a package which is to be
156 distributed in some other way or is intended for local use
162 <heading>New versions of this document</heading>
165 This manual is distributed via the Debian package
166 <package><url name="debian-policy"
167 id="http://packages.debian.org/debian-policy"></package>
168 (<httpsite>packages.debian.org</httpsite>
169 <httppath>/debian-policy</httppath>).
173 The current version of this document is also available from
174 the Debian web mirrors at
175 <tt><url name="/doc/debian-policy/"
176 id="http://www.debian.org/doc/debian-policy/"></tt>.
178 <httpsite>www.debian.org</httpsite>
179 <httppath>/doc/debian-policy/</httppath>)
180 Also available from the same directory are several other
181 formats: <file>policy.html.tar.gz</file>
182 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
183 <file>policy.pdf.gz</file>
184 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
185 and <file>policy.ps.gz</file>
186 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
190 The <package>debian-policy</package> package also includes the file
191 <file>upgrading-checklist.txt.gz</file> which indicates policy
192 changes between versions of this document.
197 <heading>Authors and Maintainers</heading>
200 Originally called "Debian GNU/Linux Policy Manual", this
201 manual was initially written in 1996 by Ian Jackson.
202 It was revised on November 27th, 1996 by David A. Morris.
203 Christian Schwarz added new sections on March 15th, 1997,
204 and reworked/restructured it in April-July 1997.
205 Christoph Lameter contributed the "Web Standard".
206 Julian Gilbey largely restructured it in 2001.
210 Since September 1998, the responsibility for the contents of
211 this document lies on the <url name="debian-policy mailing list"
212 id="mailto:debian-policy@lists.debian.org">. Proposals
213 are discussed there and inserted into policy after a certain
214 consensus is established.
215 <!-- insert shameless policy-process plug here eventually -->
216 The actual editing is done by a group of maintainers that have
217 no editorial powers. These are the current maintainers:
220 <item>Julian Gilbey</item>
221 <item>Branden Robinson</item>
222 <item>Josip Rodin</item>
223 <item>Manoj Srivastava</item>
228 While the authors of this document have tried hard to avoid
229 typos and other errors, these do still occur. If you discover
230 an error in this manual or if you want to give any
231 comments, suggestions, or criticisms please send an email to
232 the Debian Policy List,
233 <email>debian-policy@lists.debian.org</email>, or submit a
234 bug report against the <tt>debian-policy</tt> package.
238 Please do not try to reach the individual authors or maintainers
239 of the Policy Manual regarding changes to the Policy.
244 <heading>Related documents</heading>
247 There are several other documents other than this Policy Manual
248 that are necessary to fully understand some Debian policies and
253 The external "sub-policy" documents are referred to in:
254 <list compact="compact">
255 <item><ref id="fhs"></item>
256 <item><ref id="virtual_pkg"></item>
257 <item><ref id="menus"></item>
258 <item><ref id="mime"></item>
259 <item><ref id="perl"></item>
260 <item><ref id="maintscriptprompt"></item>
261 <item><ref id="emacs"></item>
266 In addition to those, which carry the weight of policy, there
267 is the Debian Developer's Reference. This document describes
268 procedures and resources for Debian developers, but it is
269 <em>not</em> normative; rather, it includes things that don't
270 belong in the Policy, such as best practices for developers.
274 The Developer's Reference is available in the
275 <package>developers-reference</package> package.
276 It's also available from the Debian web mirrors at
277 <tt><url name="/doc/developers-reference/"
278 id="http://www.debian.org/doc/developers-reference/"></tt>.
282 <sect id="definitions">
283 <heading>Definitions</heading>
286 The following terms are used in this Policy Manual:
290 The character encoding specified by ANSI X3.4-1986 and its
291 predecessor standards, referred to in MIME as US-ASCII, and
292 corresponding to an encoding in eight bits per character of
293 the first 128 <url id="http://www.unicode.org/"
294 name="Unicode"> characters, with the eighth bit always zero.
298 The transformation format (sometimes called encoding) of
299 <url id="http://www.unicode.org/" name="Unicode"> defined by
300 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
301 name="RFC 3629">. UTF-8 has the useful property of having
302 ASCII as a subset, so any text encoded in ASCII is trivially
312 <heading>The Debian Archive</heading>
315 The Debian GNU/Linux system is maintained and distributed as a
316 collection of <em>packages</em>. Since there are so many of
317 them (currently well over 15000), they are split into
318 <em>sections</em> and given <em>priorities</em> to simplify
319 the handling of them.
323 The effort of the Debian project is to build a free operating
324 system, but not every package we want to make accessible is
325 <em>free</em> in our sense (see the Debian Free Software
326 Guidelines, below), or may be imported/exported without
327 restrictions. Thus, the archive is split into areas<footnote>
328 The Debian archive software uses the term "component" internally
329 and in the Release file format to refer to the division of an
330 archive. The Debian Social Contract simply refers to "areas."
331 This document uses terminology similar to the Social Contract.
332 </footnote> based on their licenses and other restrictions.
336 The aims of this are:
338 <list compact="compact">
339 <item>to allow us to make as much software available as we can</item>
340 <item>to allow us to encourage everyone to write free software,
342 <item>to allow us to make it easy for people to produce
343 CD-ROMs of our system without violating any licenses,
344 import/export restrictions, or any other laws.</item>
349 The <em>main</em> archive area forms the <em>Debian GNU/Linux
354 Packages in the other archive areas (<tt>contrib</tt>,
355 <tt>non-free</tt>) are not considered to be part of the Debian
356 distribution, although we support their use and provide
357 infrastructure for them (such as our bug-tracking system and
358 mailing lists). This Debian Policy Manual applies to these
363 <heading>The Debian Free Software Guidelines</heading>
365 The Debian Free Software Guidelines (DFSG) form our
366 definition of "free software". These are:
368 <tag>1. Free Redistribution
371 The license of a Debian component may not restrict any
372 party from selling or giving away the software as a
373 component of an aggregate software distribution
374 containing programs from several different
375 sources. The license may not require a royalty or
376 other fee for such sale.
381 The program must include source code, and must allow
382 distribution in source code as well as compiled form.
384 <tag>3. Derived Works
387 The license must allow modifications and derived
388 works, and must allow them to be distributed under the
389 same terms as the license of the original software.
391 <tag>4. Integrity of The Author's Source Code
394 The license may restrict source-code from being
395 distributed in modified form <em>only</em> if the
396 license allows the distribution of "patch files"
397 with the source code for the purpose of modifying the
398 program at build time. The license must explicitly
399 permit distribution of software built from modified
400 source code. The license may require derived works to
401 carry a different name or version number from the
402 original software. (This is a compromise. The Debian
403 Project encourages all authors to not restrict any
404 files, source or binary, from being modified.)
406 <tag>5. No Discrimination Against Persons or Groups
409 The license must not discriminate against any person
412 <tag>6. No Discrimination Against Fields of Endeavor
415 The license must not restrict anyone from making use
416 of the program in a specific field of endeavor. For
417 example, it may not restrict the program from being
418 used in a business, or from being used for genetic
421 <tag>7. Distribution of License
424 The rights attached to the program must apply to all
425 to whom the program is redistributed without the need
426 for execution of an additional license by those
429 <tag>8. License Must Not Be Specific to Debian
432 The rights attached to the program must not depend on
433 the program's being part of a Debian system. If the
434 program is extracted from Debian and used or
435 distributed without Debian but otherwise within the
436 terms of the program's license, all parties to whom
437 the program is redistributed must have the same
438 rights as those that are granted in conjunction with
441 <tag>9. License Must Not Contaminate Other Software
444 The license must not place restrictions on other
445 software that is distributed along with the licensed
446 software. For example, the license must not insist
447 that all other programs distributed on the same medium
448 must be free software.
450 <tag>10. Example Licenses
453 The "GPL," "BSD," and "Artistic" licenses are examples of
454 licenses that we consider <em>free</em>.
461 <heading>Archive areas</heading>
464 <heading>The main archive area</heading>
467 Every package in <em>main</em> must comply with the DFSG
468 (Debian Free Software Guidelines).
472 In addition, the packages in <em>main</em>
473 <list compact="compact">
475 must not require a package outside of <em>main</em>
476 for compilation or execution (thus, the package must
477 not declare a "Depends", "Recommends", or
478 "Build-Depends" relationship on a non-<em>main</em>
482 must not be so buggy that we refuse to support them,
486 must meet all policy requirements presented in this
495 <heading>The contrib archive area</heading>
498 Every package in <em>contrib</em> must comply with the DFSG.
502 In addition, the packages in <em>contrib</em>
503 <list compact="compact">
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
517 Examples of packages which would be included in
518 <em>contrib</em> are:
519 <list compact="compact">
521 free packages which require <em>contrib</em>,
522 <em>non-free</em> packages or packages which are not
523 in our archive at all for compilation or execution,
527 wrapper packages or other sorts of free accessories for
534 <sect1 id="non-free">
535 <heading>The non-free archive area</heading>
538 Packages must be placed in <em>non-free</em> if they are
539 not compliant with the DFSG or are encumbered by patents
540 or other legal issues that make their distribution
545 In addition, the packages in <em>non-free</em>
546 <list compact="compact">
548 must not be so buggy that we refuse to support them,
552 must meet all policy requirements presented in this
553 manual that it is possible for them to meet.
555 It is possible that there are policy
556 requirements which the package is unable to
557 meet, for example, if the source is
558 unavailable. These situations will need to be
559 handled on a case-by-case basis.
568 <sect id="pkgcopyright">
569 <heading>Copyright considerations</heading>
572 Every package must be accompanied by a verbatim copy of its
573 copyright information and distribution license in the file
574 <file>/usr/share/doc/<var>package</var>/copyright</file>
575 (see <ref id="copyrightfile"> for further details).
579 We reserve the right to restrict files from being included
580 anywhere in our archives if
581 <list compact="compact">
583 their use or distribution would break a law,
586 there is an ethical conflict in their distribution or
590 we would have to sign a license for them, or
593 their distribution would conflict with other project
600 Programs whose authors encourage the user to make
601 donations are fine for the main distribution, provided
602 that the authors do not claim that not donating is
603 immoral, unethical, illegal or something similar; in such
604 a case they must go in <em>non-free</em>.
608 Packages whose copyright permission notices (or patent
609 problems) do not even allow redistribution of binaries
610 only, and where no special permission has been obtained,
611 must not be placed on the Debian FTP site and its mirrors
616 Note that under international copyright law (this applies
617 in the United States, too), <em>no</em> distribution or
618 modification of a work is allowed without an explicit
619 notice saying so. Therefore a program without a copyright
620 notice <em>is</em> copyrighted and you may not do anything
621 to it without risking being sued! Likewise if a program
622 has a copyright notice but no statement saying what is
623 permitted then nothing is permitted.
627 Many authors are unaware of the problems that restrictive
628 copyrights (or lack of copyright notices) can cause for
629 the users of their supposedly-free software. It is often
630 worthwhile contacting such authors diplomatically to ask
631 them to modify their license terms. However, this can be a
632 politically difficult thing to do and you should ask for
633 advice on the <tt>debian-legal</tt> mailing list first, as
638 When in doubt about a copyright, send mail to
639 <email>debian-legal@lists.debian.org</email>. Be prepared
640 to provide us with the copyright statement. Software
641 covered by the GPL, public domain software and BSD-like
642 copyrights are safe; be wary of the phrases "commercial
643 use prohibited" and "distribution restricted".
647 <sect id="subsections">
648 <heading>Sections</heading>
651 The packages in the archive areas <em>main</em>,
652 <em>contrib</em> and <em>non-free</em> are grouped further into
653 <em>sections</em> to simplify handling.
657 The archive area and section for each package should be
658 specified in the package's <tt>Section</tt> control record (see
659 <ref id="f-Section">). However, the maintainer of the Debian
660 archive may override this selection to ensure the consistency of
661 the Debian distribution. The <tt>Section</tt> field should be
663 <list compact="compact">
665 <em>section</em> if the package is in the
666 <em>main</em> archive area,
669 <em>area/section</em> if the package is in
670 the <em>contrib</em> or <em>non-free</em>
677 The Debian archive maintainers provide the authoritative
678 list of sections. At present, they are:
679 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
680 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
681 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
682 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
683 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
684 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
685 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
686 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
687 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
688 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
689 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
690 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
691 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
692 <em>zope</em>. The additional section <em>debian-installer</em>
693 contains special packages used by the installer and is not used
694 for normal Debian packages.
698 For more information about the sections and their definitions,
699 see the <url id="http://packages.debian.org/unstable/"
700 name="list of sections in unstable">.
704 <sect id="priorities">
705 <heading>Priorities</heading>
708 Each package should have a <em>priority</em> value, which is
709 included in the package's <em>control record</em>
710 (see <ref id="f-Priority">).
711 This information is used by the Debian package management tools to
712 separate high-priority packages from less-important packages.
716 The following <em>priority levels</em> are recognized by the
717 Debian package management tools.
719 <tag><tt>required</tt></tag>
721 Packages which are necessary for the proper
722 functioning of the system (usually, this means that
723 dpkg functionality depends on these packages).
724 Removing a <tt>required</tt> package may cause your
725 system to become totally broken and you may not even
726 be able to use <prgn>dpkg</prgn> to put things back,
727 so only do so if you know what you are doing. Systems
728 with only the <tt>required</tt> packages are probably
729 unusable, but they do have enough functionality to
730 allow the sysadmin to boot and install more software.
732 <tag><tt>important</tt></tag>
734 Important programs, including those which one would
735 expect to find on any Unix-like system. If the
736 expectation is that an experienced Unix person who
737 found it missing would say "What on earth is going on,
738 where is <prgn>foo</prgn>?", it must be an
739 <tt>important</tt> package.<footnote>
740 This is an important criterion because we are
741 trying to produce, amongst other things, a free
744 Other packages without which the system will not run
745 well or be usable must also have priority
746 <tt>important</tt>. This does
747 <em>not</em> include Emacs, the X Window System, TeX
748 or any other large applications. The
749 <tt>important</tt> packages are just a bare minimum of
750 commonly-expected and necessary tools.
752 <tag><tt>standard</tt></tag>
754 These packages provide a reasonably small but not too
755 limited character-mode system. This is what will be
756 installed by default if the user doesn't select anything
757 else. It doesn't include many large applications.
759 <tag><tt>optional</tt></tag>
761 (In a sense everything that isn't required is
762 optional, but that's not what is meant here.) This is
763 all the software that you might reasonably want to
764 install if you didn't know what it was and don't have
765 specialized requirements. This is a much larger system
766 and includes the X Window System, a full TeX
767 distribution, and many applications. Note that
768 optional packages should not conflict with each other.
770 <tag><tt>extra</tt></tag>
772 This contains all packages that conflict with others
773 with required, important, standard or optional
774 priorities, or are only likely to be useful if you
775 already know what they are or have specialized
776 requirements (such as packages containing only detached
783 Packages must not depend on packages with lower priority
784 values (excluding build-time dependencies). In order to
785 ensure this, the priorities of one or more packages may need
794 <heading>Binary packages</heading>
797 The Debian GNU/Linux distribution is based on the Debian
798 package management system, called <prgn>dpkg</prgn>. Thus,
799 all packages in the Debian distribution must be provided
800 in the <tt>.deb</tt> file format.
804 <heading>The package name</heading>
807 Every package must have a name that's unique within the Debian
812 The package name is included in the control field
813 <tt>Package</tt>, the format of which is described
814 in <ref id="f-Package">.
815 The package name is also included as a part of the file name
816 of the <tt>.deb</tt> file.
821 <heading>The version of a package</heading>
824 Every package has a version number recorded in its
825 <tt>Version</tt> control file field, described in
826 <ref id="f-Version">.
830 The package management system imposes an ordering on version
831 numbers, so that it can tell whether packages are being up- or
832 downgraded and so that package system front end applications
833 can tell whether a package it finds available is newer than
834 the one installed on the system. The version number format
835 has the most significant parts (as far as comparison is
836 concerned) at the beginning.
840 If an upstream package has problematic version numbers they
841 should be converted to a sane form for use in the
842 <tt>Version</tt> field.
846 <heading>Version numbers based on dates</heading>
849 In general, Debian packages should use the same version
850 numbers as the upstream sources.
854 However, in some cases where the upstream version number is
855 based on a date (e.g., a development "snapshot" release) the
856 package management system cannot handle these version
857 numbers without epochs. For example, dpkg will consider
858 "96May01" to be greater than "96Dec24".
862 To prevent having to use epochs for every new upstream
863 version, the date based portion of the version number
864 should be changed to the following format in such cases:
865 "19960501", "19961224". It is up to the maintainer whether
866 they want to bother the upstream maintainer to change
867 the version numbers upstream, too.
871 Note that other version formats based on dates which are
872 parsed correctly by the package management system should
873 <em>not</em> be changed.
877 Native Debian packages (i.e., packages which have been
878 written especially for Debian) whose version numbers include
879 dates should always use the "YYYYMMDD" format.
886 <heading>The maintainer of a package</heading>
889 Every package must have a Debian maintainer (the
890 maintainer may be one person or a group of people
891 reachable from a common email address, such as a mailing
892 list). The maintainer is responsible for ensuring that
893 the package is placed in the appropriate distributions.
897 The maintainer must be specified in the
898 <tt>Maintainer</tt> control field with their correct name
899 and a working email address. If one person maintains
900 several packages, they should try to avoid having
901 different forms of their name and email address in
902 the <tt>Maintainer</tt> fields of those packages.
906 The format of the <tt>Maintainer</tt> control field is
907 described in <ref id="f-Maintainer">.
911 If the maintainer of a package quits from the Debian
912 project, "Debian QA Group"
913 <email>packages@qa.debian.org</email> takes over the
914 maintainer-ship of the package until someone else
915 volunteers for that task. These packages are called
916 <em>orphaned packages</em>.<footnote>
917 The detailed procedure for doing this gracefully can
918 be found in the Debian Developer's Reference,
919 see <ref id="related">.
924 <sect id="descriptions">
925 <heading>The description of a package</heading>
928 Every Debian package must have an extended description
929 stored in the appropriate field of the control record.
930 The technical information about the format of the
931 <tt>Description</tt> field is in <ref id="f-Description">.
935 The description should describe the package (the program) to a
936 user (system administrator) who has never met it before so that
937 they have enough information to decide whether they want to
938 install it. This description should not just be copied verbatim
939 from the program's documentation.
943 Put important information first, both in the synopsis and
944 extended description. Sometimes only the first part of the
945 synopsis or of the description will be displayed. You can
946 assume that there will usually be a way to see the whole
947 extended description.
951 The description should also give information about the
952 significant dependencies and conflicts between this package
953 and others, so that the user knows why these dependencies and
954 conflicts have been declared.
958 Instructions for configuring or using the package should
959 not be included (that is what installation scripts,
960 manual pages, info files, etc., are for). Copyright
961 statements and other administrivia should not be included
962 either (that is what the copyright file is for).
965 <sect1 id="synopsis"><heading>The single line synopsis</heading>
968 The single line synopsis should be kept brief - certainly
973 Do not include the package name in the synopsis line. The
974 display software knows how to display this already, and you
975 do not need to state it. Remember that in many situations
976 the user may only see the synopsis line - make it as
977 informative as you can.
982 <sect1 id="extendeddesc"><heading>The extended description</heading>
985 Do not try to continue the single line synopsis into the
986 extended description. This will not work correctly when
987 the full description is displayed, and makes no sense
988 where only the summary (the single line synopsis) is
993 The extended description should describe what the package
994 does and how it relates to the rest of the system (in terms
995 of, for example, which subsystem it is which part of).
999 The description field needs to make sense to anyone, even
1000 people who have no idea about any of the things the
1001 package deals with.<footnote>
1002 The blurb that comes with a program in its
1003 announcements and/or <prgn>README</prgn> files is
1004 rarely suitable for use in a description. It is
1005 usually aimed at people who are already in the
1006 community where the package is used.
1015 <heading>Dependencies</heading>
1018 Every package must specify the dependency information
1019 about other packages that are required for the first to
1024 For example, a dependency entry must be provided for any
1025 shared libraries required by a dynamically-linked executable
1026 binary in a package.
1030 Packages are not required to declare any dependencies they
1031 have on other packages which are marked <tt>Essential</tt>
1032 (see below), and should not do so unless they depend on a
1033 particular version of that package.<footnote>
1035 Essential is needed in part to avoid unresolvable dependency
1036 loops on upgrade. If packages add unnecessary dependencies
1037 on packages in this set, the chances that there
1038 <strong>will</strong> be an unresolvable dependency loop
1039 caused by forcing these Essential packages to be configured
1040 first before they need to be is greatly increased. It also
1041 increases the chances that frontends will be unable to
1042 <strong>calculate</strong> an upgrade path, even if one
1046 Also, functionality is rarely ever removed from the
1047 Essential set, but <em>packages</em> have been removed from
1048 the Essential set when the functionality moved to a
1049 different package. So depending on these packages <em>just
1050 in case</em> they stop being essential does way more harm
1057 Sometimes, a package requires another package to be installed
1058 <em>and</em> configured before it can be installed. In this
1059 case, you must specify a <tt>Pre-Depends</tt> entry for
1064 You should not specify a <tt>Pre-Depends</tt> entry for a
1065 package before this has been discussed on the
1066 <tt>debian-devel</tt> mailing list and a consensus about
1067 doing that has been reached.
1071 The format of the package interrelationship control fields is
1072 described in <ref id="relationships">.
1076 <sect id="virtual_pkg">
1077 <heading>Virtual packages</heading>
1080 Sometimes, there are several packages which offer
1081 more-or-less the same functionality. In this case, it's
1082 useful to define a <em>virtual package</em> whose name
1083 describes that common functionality. (The virtual
1084 packages only exist logically, not physically; that's why
1085 they are called <em>virtual</em>.) The packages with this
1086 particular function will then <em>provide</em> the virtual
1087 package. Thus, any other package requiring that function
1088 can simply depend on the virtual package without having to
1089 specify all possible packages individually.
1093 All packages should use virtual package names where
1094 appropriate, and arrange to create new ones if necessary.
1095 They should not use virtual package names (except privately,
1096 amongst a cooperating group of packages) unless they have
1097 been agreed upon and appear in the list of virtual package
1098 names. (See also <ref id="virtual">)
1102 The latest version of the authoritative list of virtual
1103 package names can be found in the <tt>debian-policy</tt> package.
1104 It is also available from the Debian web mirrors at
1105 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1106 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1110 The procedure for updating the list is described in the preface
1117 <heading>Base system</heading>
1120 The <tt>base system</tt> is a minimum subset of the Debian
1121 GNU/Linux system that is installed before everything else
1122 on a new system. Only very few packages are allowed to form
1123 part of the base system, in order to keep the required disk
1128 The base system consists of all those packages with priority
1129 <tt>required</tt> or <tt>important</tt>. Many of them will
1130 be tagged <tt>essential</tt> (see below).
1135 <heading>Essential packages</heading>
1138 Essential is defined as the minimal set of functionality that
1139 must be available and usable on the system at all times, even
1140 when packages are in an unconfigured (but unpacked) state.
1141 Packages are tagged <tt>essential</tt> for a system using the
1142 <tt>Essential</tt> control file field. The format of the
1143 <tt>Essential</tt> control field is described in <ref
1148 Since these packages cannot be easily removed (one has to
1149 specify an extra <em>force option</em> to
1150 <prgn>dpkg</prgn> to do so), this flag must not be used
1151 unless absolutely necessary. A shared library package
1152 must not be tagged <tt>essential</tt>; dependencies will
1153 prevent its premature removal, and we need to be able to
1154 remove it when it has been superseded.
1158 Since dpkg will not prevent upgrading of other packages
1159 while an <tt>essential</tt> package is in an unconfigured
1160 state, all <tt>essential</tt> packages must supply all of
1161 their core functionality even when unconfigured. If the
1162 package cannot satisfy this requirement it must not be
1163 tagged as essential, and any packages depending on this
1164 package must instead have explicit dependency fields as
1169 Maintainers should take great care in adding any programs,
1170 interfaces, or functionality to <tt>essential</tt> packages.
1171 Packages may assume that functionality provided by
1172 <tt>essential</tt> packages is always available without
1173 declaring explicit dependencies, which means that removing
1174 functionality from the Essential set is very difficult and is
1175 almost never done. Any capability added to an
1176 <tt>essential</tt> package therefore creates an obligation to
1177 support that capability as part of the Essential set in
1182 You must not tag any packages <tt>essential</tt> before
1183 this has been discussed on the <tt>debian-devel</tt>
1184 mailing list and a consensus about doing that has been
1189 <sect id="maintscripts">
1190 <heading>Maintainer Scripts</heading>
1193 The package installation scripts should avoid producing
1194 output which is unnecessary for the user to see and
1195 should rely on <prgn>dpkg</prgn> to stave off boredom on
1196 the part of a user installing many packages. This means,
1197 amongst other things, using the <tt>--quiet</tt> option on
1198 <prgn>install-info</prgn>.
1202 Errors which occur during the execution of an installation
1203 script must be checked and the installation must not
1204 continue after an error.
1208 Note that in general <ref id="scripts"> applies to package
1209 maintainer scripts, too.
1213 You should not use <prgn>dpkg-divert</prgn> on a file
1214 belonging to another package without consulting the
1215 maintainer of that package first.
1219 All packages which supply an instance of a common command
1220 name (or, in general, filename) should generally use
1221 <prgn>update-alternatives</prgn>, so that they may be
1222 installed together. If <prgn>update-alternatives</prgn>
1223 is not used, then each package must use
1224 <tt>Conflicts</tt> to ensure that other packages are
1225 de-installed. (In this case, it may be appropriate to
1226 specify a conflict against earlier versions of something
1227 that previously did not use
1228 <prgn>update-alternatives</prgn>; this is an exception to
1229 the usual rule that versioned conflicts should be
1233 <sect1 id="maintscriptprompt">
1234 <heading>Prompting in maintainer scripts</heading>
1236 Package maintainer scripts may prompt the user if
1237 necessary. Prompting must be done by communicating
1238 through a program, such as <prgn>debconf</prgn>, which
1239 conforms to the Debian Configuration Management
1240 Specification, version 2 or higher.
1244 Packages which are essential, or which are dependencies of
1245 essential packages, may fall back on another prompting method
1246 if no such interface is available when they are executed.
1250 The Debian Configuration Management Specification is included
1251 in the <file>debconf_specification</file> files in the
1252 <package>debian-policy</package> package.
1253 It is also available from the Debian web mirrors at
1254 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1255 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1259 Packages which use the Debian Configuration Management
1260 Specification may contain an additional
1261 <prgn>config</prgn> script and a <tt>templates</tt>
1262 file in their control archive<footnote>
1263 The control.tar.gz inside the .deb.
1264 See <manref name="deb" section="5">.
1266 The <prgn>config</prgn> script might be run before the
1267 <prgn>preinst</prgn> script, and before the package is unpacked
1268 or any of its dependencies or pre-dependencies are satisfied.
1269 Therefore it must work using only the tools present in
1270 <em>essential</em> packages.<footnote>
1271 <package>Debconf</package> or another tool that
1272 implements the Debian Configuration Management
1273 Specification will also be installed, and any
1274 versioned dependencies on it will be satisfied
1275 before preconfiguration begins.
1280 Packages which use the Debian Configuration Management
1281 Specification must allow for translation of their user-visible
1282 messages by using a gettext-based system such as the one
1283 provided by the <package>po-debconf</package> package.
1287 Packages should try to minimize the amount of prompting
1288 they need to do, and they should ensure that the user
1289 will only ever be asked each question once. This means
1290 that packages should try to use appropriate shared
1291 configuration files (such as <file>/etc/papersize</file> and
1292 <file>/etc/news/server</file>), and shared
1293 <package>debconf</package> variables rather than each
1294 prompting for their own list of required pieces of
1299 It also means that an upgrade should not ask the same
1300 questions again, unless the user has used
1301 <tt>dpkg --purge</tt> to remove the package's configuration.
1302 The answers to configuration questions should be stored in an
1303 appropriate place in <file>/etc</file> so that the user can
1304 modify them, and how this has been done should be
1309 If a package has a vitally important piece of
1310 information to pass to the user (such as "don't run me
1311 as I am, you must edit the following configuration files
1312 first or you risk your system emitting badly-formatted
1313 messages"), it should display this in the
1314 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1315 prompt the user to hit return to acknowledge the
1316 message. Copyright messages do not count as vitally
1317 important (they belong in
1318 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1319 neither do instructions on how to use a program (these
1320 should be in on-line documentation, where all the users
1325 Any necessary prompting should almost always be confined
1326 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1327 script. If it is done in the <prgn>postinst</prgn>, it
1328 should be protected with a conditional so that
1329 unnecessary prompting doesn't happen if a package's
1330 installation fails and the <prgn>postinst</prgn> is
1331 called with <tt>abort-upgrade</tt>,
1332 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1342 <heading>Source packages</heading>
1344 <sect id="standardsversion">
1345 <heading>Standards conformance</heading>
1348 Source packages should specify the most recent version number
1349 of this policy document with which your package complied
1350 when it was last updated.
1354 This information may be used to file bug reports
1355 automatically if your package becomes too much out of date.
1359 The version is specified in the <tt>Standards-Version</tt>
1361 The format of the <tt>Standards-Version</tt> field is
1362 described in <ref id="f-Standards-Version">.
1366 You should regularly, and especially if your package has
1367 become out of date, check for the newest Policy Manual
1368 available and update your package, if necessary. When your
1369 package complies with the new standards you should update the
1370 <tt>Standards-Version</tt> source package field and
1371 release it.<footnote>
1372 See the file <file>upgrading-checklist</file> for
1373 information about policy which has changed between
1374 different versions of this document.
1380 <sect id="pkg-relations">
1381 <heading>Package relationships</heading>
1384 Source packages should specify which binary packages they
1385 require to be installed or not to be installed in order to
1386 build correctly. For example, if building a package
1387 requires a certain compiler, then the compiler should be
1388 specified as a build-time dependency.
1392 It is not necessary to explicitly specify build-time
1393 relationships on a minimal set of packages that are always
1394 needed to compile, link and put in a Debian package a
1395 standard "Hello World!" program written in C or C++. The
1396 required packages are called <em>build-essential</em>, and
1397 an informational list can be found in
1398 <file>/usr/share/doc/build-essential/list</file> (which is
1399 contained in the <tt>build-essential</tt>
1402 <list compact="compact">
1404 This allows maintaining the list separately
1405 from the policy documents (the list does not
1406 need the kind of control that the policy
1410 Having a separate package allows one to install
1411 the build-essential packages on a machine, as
1412 well as allowing other packages such as tasks to
1413 require installation of the build-essential
1414 packages using the depends relation.
1417 The separate package allows bug reports against
1418 the list to be categorized separately from
1419 the policy management process in the BTS.
1426 When specifying the set of build-time dependencies, one
1427 should list only those packages explicitly required by the
1428 build. It is not necessary to list packages which are
1429 required merely because some other package in the list of
1430 build-time dependencies depends on them.<footnote>
1431 The reason for this is that dependencies change, and
1432 you should list all those packages, and <em>only</em>
1433 those packages that <em>you</em> need directly. What
1434 others need is their business. For example, if you
1435 only link against <file>libimlib</file>, you will need to
1436 build-depend on <package>libimlib2-dev</package> but
1437 not against any <tt>libjpeg*</tt> packages, even
1438 though <tt>libimlib2-dev</tt> currently depends on
1439 them: installation of <package>libimlib2-dev</package>
1440 will automatically ensure that all of its run-time
1441 dependencies are satisfied.
1446 If build-time dependencies are specified, it must be
1447 possible to build the package and produce working binaries
1448 on a system with only essential and build-essential
1449 packages installed and also those required to satisfy the
1450 build-time relationships (including any implied
1451 relationships). In particular, this means that version
1452 clauses should be used rigorously in build-time
1453 relationships so that one cannot produce bad or
1454 inconsistently configured packages when the relationships
1455 are properly satisfied.
1459 <ref id="relationships"> explains the technical details.
1464 <heading>Changes to the upstream sources</heading>
1467 If changes to the source code are made that are not
1468 specific to the needs of the Debian system, they should be
1469 sent to the upstream authors in whatever form they prefer
1470 so as to be included in the upstream version of the
1475 If you need to configure the package differently for
1476 Debian or for Linux, and the upstream source doesn't
1477 provide a way to do so, you should add such configuration
1478 facilities (for example, a new <prgn>autoconf</prgn> test
1479 or <tt>#define</tt>) and send the patch to the upstream
1480 authors, with the default set to the way they originally
1481 had it. You can then easily override the default in your
1482 <file>debian/rules</file> or wherever is appropriate.
1486 You should make sure that the <prgn>configure</prgn> utility
1487 detects the correct architecture specification string
1488 (refer to <ref id="arch-spec"> for details).
1492 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1493 <prgn>configure</prgn> scripts are used, you should edit the
1494 <file>.in</file> files rather than editing the
1495 <prgn>Makefile</prgn> directly. This allows the user to
1496 reconfigure the package if necessary. You should
1497 <em>not</em> configure the package and edit the generated
1498 <prgn>Makefile</prgn>! This makes it impossible for someone
1499 else to later reconfigure the package without losing the
1505 <sect id="dpkgchangelog">
1506 <heading>Debian changelog: <file>debian/changelog</file></heading>
1509 Changes in the Debian version of the package should be
1510 briefly explained in the Debian changelog file
1511 <file>debian/changelog</file>.<footnote>
1513 Mistakes in changelogs are usually best rectified by
1514 making a new changelog entry rather than "rewriting
1515 history" by editing old changelog entries.
1518 This includes modifications
1519 made in the Debian package compared to the upstream one
1520 as well as other changes and updates to the package.
1522 Although there is nothing stopping an author who is also
1523 the Debian maintainer from using this changelog for all
1524 their changes, it will have to be renamed if the Debian
1525 and upstream maintainers become different people. In such
1526 a case, however, it might be better to maintain the package
1527 as a non-native package.
1532 The format of the <file>debian/changelog</file> allows the
1533 package building tools to discover which version of the package
1534 is being built and find out other release-specific information.
1538 That format is a series of entries like this:
1540 <example compact="compact">
1541 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1543 [optional blank line(s), stripped]
1545 * <var>change details</var>
1546 <var>more change details</var>
1548 [blank line(s), included in output of dpkg-parsechangelog]
1550 * <var>even more change details</var>
1552 [optional blank line(s), stripped]
1554 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1559 <var>package</var> and <var>version</var> are the source
1560 package name and version number.
1564 <var>distribution(s)</var> lists the distributions where
1565 this version should be installed when it is uploaded - it
1566 is copied to the <tt>Distribution</tt> field in the
1567 <file>.changes</file> file. See <ref id="f-Distribution">.
1571 <var>urgency</var> is the value for the <tt>Urgency</tt>
1572 field in the <file>.changes</file> file for the upload
1573 (see <ref id="f-Urgency">). It is not possible to specify
1574 an urgency containing commas; commas are used to separate
1575 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1576 <prgn>dpkg</prgn> changelog format (though there is
1577 currently only one useful <var>keyword</var>,
1582 The change details may in fact be any series of lines
1583 starting with at least two spaces, but conventionally each
1584 change starts with an asterisk and a separating space and
1585 continuation lines are indented so as to bring them in
1586 line with the start of the text above. Blank lines may be
1587 used here to separate groups of changes, if desired.
1591 If this upload resolves bugs recorded in the Bug Tracking
1592 System (BTS), they may be automatically closed on the
1593 inclusion of this package into the Debian archive by
1594 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1595 in the change details.<footnote>
1596 To be precise, the string should match the following
1597 Perl regular expression:
1599 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1601 Then all of the bug numbers listed will be closed by the
1602 archive maintenance script (<prgn>katie</prgn>) using the
1603 <var>version</var> of the changelog entry.
1605 This information is conveyed via the <tt>Closes</tt> field
1606 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1610 The maintainer name and email address used in the changelog
1611 should be the details of the person uploading <em>this</em>
1612 version. They are <em>not</em> necessarily those of the
1613 usual package maintainer. The information here will be
1614 copied to the <tt>Changed-By</tt> field in the
1615 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1616 and then later used to send an acknowledgement when the
1617 upload has been installed.
1621 The <var>date</var> has the following format<footnote>
1622 This is the same as the format generated by <tt>date
1624 </footnote> (compatible and with the same semantics of
1625 RFC 2822 and RFC 5322):
1626 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1628 <list compact="compact">
1630 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1633 dd is a one- or two-digit day of the month (01-31)
1636 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1639 <item>yyyy is the four-digit year (e.g. 2010)</item>
1640 <item>hh is the two-digit hour (00-23)</item>
1641 <item>mm is the two-digit minutes (00-59)</item>
1642 <item>ss is the two-digit seconds (00-60)</item>
1644 +zzzz or -zzzz is the the time zone offset from Coordinated
1645 Universal Time (UTC). "+" indicates that the time is ahead
1646 of (i.e., east of) UTC and "-" indicates that the time is
1647 behind (i.e., west of) UTC. The first two digits indicate
1648 the hour difference from UTC and the last two digits
1649 indicate the number of additional minutes difference from
1650 UTC. The last two digits must be in the range 00-59.
1656 The first "title" line with the package name must start
1657 at the left hand margin. The "trailer" line with the
1658 maintainer and date details must be preceded by exactly
1659 one space. The maintainer details and the date must be
1660 separated by exactly two spaces.
1664 The entire changelog must be encoded in UTF-8.
1668 For more information on placement of the changelog files
1669 within binary packages, please see <ref id="changelogs">.
1673 <sect id="dpkgcopyright">
1674 <heading>Copyright: <file>debian/copyright</file></heading>
1676 Every package must be accompanied by a verbatim copy of its
1677 copyright information and distribution license in the file
1678 <file>/usr/share/doc/<var>package</var>/copyright</file>
1679 (see <ref id="copyrightfile"> for further details). Also see
1680 <ref id="pkgcopyright"> for further considerations related
1681 to copyrights for packages.
1685 <heading>Error trapping in makefiles</heading>
1688 When <prgn>make</prgn> invokes a command in a makefile
1689 (including your package's upstream makefiles and
1690 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1691 means that <prgn>sh</prgn>'s usual bad error handling
1692 properties apply: if you include a miniature script as one
1693 of the commands in your makefile you'll find that if you
1694 don't do anything about it then errors are not detected
1695 and <prgn>make</prgn> will blithely continue after
1700 Every time you put more than one shell command (this
1701 includes using a loop) in a makefile command you
1702 must make sure that errors are trapped. For
1703 simple compound commands, such as changing directory and
1704 then running a program, using <tt>&&</tt> rather
1705 than semicolon as a command separator is sufficient. For
1706 more complex commands including most loops and
1707 conditionals you should include a separate <tt>set -e</tt>
1708 command at the start of every makefile command that's
1709 actually one of these miniature shell scripts.
1713 <sect id="timestamps">
1714 <heading>Time Stamps</heading>
1716 Maintainers should preserve the modification times of the
1717 upstream source files in a package, as far as is reasonably
1719 The rationale is that there is some information conveyed
1720 by knowing the age of the file, for example, you could
1721 recognize that some documentation is very old by looking
1722 at the modification time, so it would be nice if the
1723 modification time of the upstream source would be
1729 <sect id="restrictions">
1730 <heading>Restrictions on objects in source packages</heading>
1733 The source package may not contain any hard links<footnote>
1735 This is not currently detected when building source
1736 packages, but only when extracting
1740 Hard links may be permitted at some point in the
1741 future, but would require a fair amount of
1744 </footnote>, device special files, sockets or setuid or
1745 setgid files.<footnote>
1746 Setgid directories are allowed.
1751 <sect id="debianrules">
1752 <heading>Main building script: <file>debian/rules</file></heading>
1755 This file must be an executable makefile, and contains the
1756 package-specific recipes for compiling the package and
1757 building binary package(s) from the source.
1761 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1762 so that it can be invoked by saying its name rather than
1763 invoking <prgn>make</prgn> explicitly. That is, invoking
1764 either of <tt>make -f debian/rules <em>args...</em></tt>
1765 or <tt>./debian/rules <em>args...</em></tt> must result in
1770 Since an interactive <file>debian/rules</file> script makes it
1771 impossible to auto-compile that package and also makes it
1772 hard for other people to reproduce the same binary
1773 package, all <em>required targets</em> must be
1774 non-interactive. At a minimum, required targets are the
1775 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1776 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1777 <em>binary-indep</em>, and <em>build</em>. It also follows
1778 that any target that these targets depend on must also be
1783 The targets are as follows (required unless stated otherwise):
1785 <tag><tt>build</tt></tag>
1788 The <tt>build</tt> target should perform all the
1789 configuration and compilation of the package.
1790 If a package has an interactive pre-build
1791 configuration routine, the Debian source package
1792 must either be built after this has taken place (so
1793 that the binary package can be built without rerunning
1794 the configuration) or the configuration routine
1795 modified to become non-interactive. (The latter is
1796 preferable if there are architecture-specific features
1797 detected by the configuration routine.)
1801 For some packages, notably ones where the same
1802 source tree is compiled in different ways to produce
1803 two binary packages, the <tt>build</tt> target
1804 does not make much sense. For these packages it is
1805 good enough to provide two (or more) targets
1806 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1807 for each of the ways of building the package, and a
1808 <tt>build</tt> target that does nothing. The
1809 <tt>binary</tt> target will have to build the
1810 package in each of the possible ways and make the
1811 binary package out of each.
1815 The <tt>build</tt> target must not do anything
1816 that might require root privilege.
1820 The <tt>build</tt> target may need to run the
1821 <tt>clean</tt> target first - see below.
1825 When a package has a configuration and build routine
1826 which takes a long time, or when the makefiles are
1827 poorly designed, or when <tt>build</tt> needs to
1828 run <tt>clean</tt> first, it is a good idea to
1829 <tt>touch build</tt> when the build process is
1830 complete. This will ensure that if <tt>debian/rules
1831 build</tt> is run again it will not rebuild the whole
1833 Another common way to do this is for <tt>build</tt>
1834 to depend on <prgn>build-stamp</prgn> and to do
1835 nothing else, and for the <prgn>build-stamp</prgn>
1836 target to do the building and to <tt>touch
1837 build-stamp</tt> on completion. This is
1838 especially useful if the build routine creates a
1839 file or directory called <tt>build</tt>; in such a
1840 case, <tt>build</tt> will need to be listed as
1841 a phony target (i.e., as a dependency of the
1842 <tt>.PHONY</tt> target). See the documentation of
1843 <prgn>make</prgn> for more information on phony
1849 <tag><tt>build-arch</tt> (optional),
1850 <tt>build-indep</tt> (optional)
1854 A package may also provide both of the targets
1855 <tt>build-arch</tt> and <tt>build-indep</tt>.
1856 The <tt>build-arch</tt> target, if provided, should
1857 perform all the configuration and compilation required for
1858 producing all architecture-dependant binary packages
1859 (those packages for which the body of the
1860 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1861 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1862 target, if provided, should perform all the configuration
1863 and compilation required for producing all
1864 architecture-independent binary packages (those packages
1865 for which the body of the <tt>Architecture</tt> field
1866 in <tt>debian/control</tt> is <tt>all</tt>).
1867 The <tt>build</tt> target should depend on those of the
1868 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1869 are provided in the rules file.<footnote>
1870 The intent of this split is so that binary-only builds
1871 need not install the dependencies required for
1872 the <tt>build-indep</tt> target. However, this is not
1873 yet used in practice since <tt>dpkg-buildpackage
1874 -B</tt>, and therefore the autobuilders,
1875 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1876 due to the difficulties in determining whether the
1877 optional <tt>build-arch</tt> target exists.
1882 If one or both of the targets <tt>build-arch</tt> and
1883 <tt>build-indep</tt> are not provided, then invoking
1884 <file>debian/rules</file> with one of the not-provided
1885 targets as arguments should produce a exit status code
1886 of 2. Usually this is provided automatically by make
1887 if the target is missing.
1891 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1892 must not do anything that might require root privilege.
1896 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1897 <tt>binary-indep</tt>
1901 The <tt>binary</tt> target must be all that is
1902 necessary for the user to build the binary package(s)
1903 produced from this source package. It is
1904 split into two parts: <prgn>binary-arch</prgn> builds
1905 the binary packages which are specific to a particular
1906 architecture, and <tt>binary-indep</tt> builds
1907 those which are not.
1910 <tt>binary</tt> may be (and commonly is) a target with
1911 no commands which simply depends on
1912 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1915 Both <tt>binary-*</tt> targets should depend on the
1916 <tt>build</tt> target, or on the appropriate
1917 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1918 provided, so that the package is built if it has not
1919 been already. It should then create the relevant
1920 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1921 make their control files and <prgn>dpkg-deb</prgn> to
1922 build them and place them in the parent of the top
1927 Both the <tt>binary-arch</tt> and
1928 <tt>binary-indep</tt> targets <em>must</em> exist.
1929 If one of them has nothing to do (which will always be
1930 the case if the source generates only a single binary
1931 package, whether architecture-dependent or not), it
1932 must still exist and must always succeed.
1936 The <tt>binary</tt> targets must be invoked as
1938 The <prgn>fakeroot</prgn> package often allows one
1939 to build a package correctly even without being
1945 <tag><tt>clean</tt></tag>
1948 This must undo any effects that the <tt>build</tt>
1949 and <tt>binary</tt> targets may have had, except
1950 that it should leave alone any output files created in
1951 the parent directory by a run of a <tt>binary</tt>
1956 If a <tt>build</tt> file is touched at the end of
1957 the <tt>build</tt> target, as suggested above, it
1958 should be removed as the first action that
1959 <tt>clean</tt> performs, so that running
1960 <tt>build</tt> again after an interrupted
1961 <tt>clean</tt> doesn't think that everything is
1966 The <tt>clean</tt> target may need to be
1967 invoked as root if <tt>binary</tt> has been
1968 invoked since the last <tt>clean</tt>, or if
1969 <tt>build</tt> has been invoked as root (since
1970 <tt>build</tt> may create directories, for
1975 <tag><tt>get-orig-source</tt> (optional)</tag>
1978 This target fetches the most recent version of the
1979 original source package from a canonical archive site
1980 (via FTP or WWW, for example), does any necessary
1981 rearrangement to turn it into the original source
1982 tar file format described below, and leaves it in the
1987 This target may be invoked in any directory, and
1988 should take care to clean up any temporary files it
1993 This target is optional, but providing it if
1994 possible is a good idea.
1998 <tag><tt>patch</tt> (optional)</tag>
2001 This target performs whatever additional actions are
2002 required to make the source ready for editing (unpacking
2003 additional upstream archives, applying patches, etc.).
2004 It is recommended to be implemented for any package where
2005 <tt>dpkg-source -x</tt> does not result in source ready
2006 for additional modification. See
2007 <ref id="readmesource">.
2013 The <tt>build</tt>, <tt>binary</tt> and
2014 <tt>clean</tt> targets must be invoked with the current
2015 directory being the package's top-level directory.
2020 Additional targets may exist in <file>debian/rules</file>,
2021 either as published or undocumented interfaces or for the
2022 package's internal use.
2026 The architectures we build on and build for are determined
2027 by <prgn>make</prgn> variables using the utility
2028 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2029 You can determine the
2030 Debian architecture and the GNU style architecture
2031 specification string for the build machine (the machine type
2032 we are building on) as well as for the host machine (the
2033 machine type we are building for). Here is a list of
2034 supported <prgn>make</prgn> variables:
2035 <list compact="compact">
2037 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2040 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2043 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2046 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2047 specification string)
2050 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2051 <tt>DEB_*_GNU_TYPE</tt>)
2054 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2055 <tt>DEB_*_GNU_TYPE</tt>)
2057 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2058 the build machine or <tt>HOST</tt> for specification of the
2063 Backward compatibility can be provided in the rules file
2064 by setting the needed variables to suitable default
2065 values; please refer to the documentation of
2066 <prgn>dpkg-architecture</prgn> for details.
2070 It is important to understand that the <tt>DEB_*_ARCH</tt>
2071 string only determines which Debian architecture we are
2072 building on or for. It should not be used to get the CPU
2073 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2074 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2075 GNU style variables should generally only be used with upstream
2079 <sect1 id="debianrules-options">
2080 <heading><file>debian/rules</file> and
2081 <tt>DEB_BUILD_OPTIONS</tt></heading>
2084 Supporting the standardized environment variable
2085 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2086 contain several flags to change how a package is compiled and
2087 built. Each flag must be in the form <var>flag</var> or
2088 <var>flag</var>=<var>options</var>. If multiple flags are
2089 given, they must be separated by whitespace.<footnote>
2090 Some packages support any delimiter, but whitespace is the
2091 easiest to parse inside a makefile and avoids ambiguity with
2092 flag values that contain commas.
2094 <var>flag</var> must start with a lowercase letter
2095 (<tt>a-z</tt>) and consist only of lowercase letters,
2096 numbers (<tt>0-9</tt>), and the characters
2097 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2098 <var>options</var> must not contain whitespace. The same
2099 tag should not be given multiple times with conflicting
2100 values. Package maintainers may assume that
2101 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2105 The meaning of the following tags has been standardized:
2109 This tag says to not run any build-time test suite
2110 provided by the package.
2114 The presence of this tag means that the package should
2115 be compiled with a minimum of optimization. For C
2116 programs, it is best to add <tt>-O0</tt> to
2117 <tt>CFLAGS</tt> (although this is usually the default).
2118 Some programs might fail to build or run at this level
2119 of optimization; it may be necessary to use
2120 <tt>-O1</tt>, for example.
2124 This tag means that the debugging symbols should not be
2125 stripped from the binary during installation, so that
2126 debugging information may be included in the package.
2128 <tag>parallel=n</tag>
2130 This tag means that the package should be built using up
2131 to <tt>n</tt> parallel processes if the package build
2132 system supports this.<footnote>
2133 Packages built with <tt>make</tt> can often implement
2134 this by passing the <tt>-j</tt><var>n</var> option to
2137 If the package build system does not support parallel
2138 builds, this string must be ignored. If the package
2139 build system only supports a lower level of concurrency
2140 than <var>n</var>, the package should be built using as
2141 many parallel processes as the package build system
2142 supports. It is up to the package maintainer to decide
2143 whether the package build times are long enough and the
2144 package build system is robust enough to make supporting
2145 parallel builds worthwhile.
2151 Unknown flags must be ignored by <file>debian/rules</file>.
2155 The following makefile snippet is an example of how one may
2156 implement the build options; you will probably have to
2157 massage this example in order to make it work for your
2159 <example compact="compact">
2162 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2163 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2164 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2165 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2167 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2172 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2173 INSTALL_PROGRAM += -s
2175 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2176 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2177 MAKEFLAGS += -j$(NUMJOBS)
2182 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2183 # Code to run the package test suite.
2190 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2191 <sect id="substvars">
2192 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2195 When <prgn>dpkg-gencontrol</prgn>,
2196 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2197 generate control files they perform variable substitutions
2198 on their output just before writing it. Variable
2199 substitutions have the form <tt>${<var>variable</var>}</tt>.
2200 The optional file <file>debian/substvars</file> contains
2201 variable substitutions to be used; variables can also be set
2202 directly from <file>debian/rules</file> using the <tt>-V</tt>
2203 option to the source packaging commands, and certain
2204 predefined variables are also available.
2208 The <file>debian/substvars</file> file is usually generated and
2209 modified dynamically by <file>debian/rules</file> targets, in
2210 which case it must be removed by the <tt>clean</tt> target.
2214 See <manref name="deb-substvars" section="5"> for full
2215 details about source variable substitutions, including the
2216 format of <file>debian/substvars</file>.</p>
2219 <sect id="debianwatch">
2220 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2223 This is an optional, recommended control file for the
2224 <tt>uscan</tt> utility which defines how to automatically
2225 scan ftp or http sites for newly available updates of the
2226 package. This is used by <url id="
2227 http://dehs.alioth.debian.org/"> and other Debian QA tools
2228 to help with quality control and maintenance of the
2229 distribution as a whole.
2234 <sect id="debianfiles">
2235 <heading>Generated files list: <file>debian/files</file></heading>
2238 This file is not a permanent part of the source tree; it
2239 is used while building packages to record which files are
2240 being generated. <prgn>dpkg-genchanges</prgn> uses it
2241 when it generates a <file>.changes</file> file.
2245 It should not exist in a shipped source package, and so it
2246 (and any backup files or temporary files such as
2247 <file>files.new</file><footnote>
2248 <file>files.new</file> is used as a temporary file by
2249 <prgn>dpkg-gencontrol</prgn> and
2250 <prgn>dpkg-distaddfile</prgn> - they write a new
2251 version of <tt>files</tt> here before renaming it,
2252 to avoid leaving a corrupted copy if an error
2254 </footnote>) should be removed by the
2255 <tt>clean</tt> target. It may also be wise to
2256 ensure a fresh start by emptying or removing it at the
2257 start of the <tt>binary</tt> target.
2261 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2262 package, it adds an entry to <file>debian/files</file> for the
2263 <file>.deb</file> file that will be created when <tt>dpkg-deb
2264 --build</tt> is run for that binary package. So for most
2265 packages all that needs to be done with this file is to
2266 delete it in the <tt>clean</tt> target.
2270 If a package upload includes files besides the source
2271 package and any binary packages whose control files were
2272 made with <prgn>dpkg-gencontrol</prgn> then they should be
2273 placed in the parent of the package's top-level directory
2274 and <prgn>dpkg-distaddfile</prgn> should be called to add
2275 the file to the list in <file>debian/files</file>.</p>
2278 <sect id="embeddedfiles">
2279 <heading>Convenience copies of code</heading>
2282 Some software packages include in their distribution convenience
2283 copies of code from other software packages, generally so that
2284 users compiling from source don't have to download multiple
2285 packages. Debian packages should not make use of these
2286 convenience copies unless the included package is explicitly
2287 intended to be used in this way.<footnote>
2288 For example, parts of the GNU build system work like this.
2290 If the included code is already in the Debian archive in the
2291 form of a library, the Debian packaging should ensure that
2292 binary packages reference the libraries already in Debian and
2293 the convenience copy is not used. If the included code is not
2294 already in Debian, it should be packaged separately as a
2295 prerequisite if possible.
2297 Having multiple copies of the same code in Debian is
2298 inefficient, often creates either static linking or shared
2299 library conflicts, and, most importantly, increases the
2300 difficulty of handling security vulnerabilities in the
2306 <sect id="readmesource">
2307 <heading>Source package handling:
2308 <file>debian/README.source</file></heading>
2311 If running <prgn>dpkg-source -x</prgn> on a source package
2312 doesn't produce the source of the package, ready for editing,
2313 and allow one to make changes and run
2314 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2315 without taking any additional steps, creating a
2316 <file>debian/README.source</file> documentation file is
2317 recommended. This file should explain how to do all of the
2320 <item>Generate the fully patched source, in a form ready for
2321 editing, that would be built to create Debian
2322 packages. Doing this with a <tt>patch</tt> target in
2323 <file>debian/rules</file> is recommended; see
2324 <ref id="debianrules">.</item>
2325 <item>Modify the source and save those modifications so that
2326 they will be applied when building the package.</item>
2327 <item>Remove source modifications that are currently being
2328 applied when building the package.</item>
2329 <item>Optionally, document what steps are necessary to
2330 upgrade the Debian source package to a new upstream version,
2331 if applicable.</item>
2333 This explanation should include specific commands and mention
2334 any additional required Debian packages. It should not assume
2335 familiarity with any specific Debian packaging system or patch
2340 This explanation may refer to a documentation file installed by
2341 one of the package's build dependencies provided that the
2342 referenced documentation clearly explains these tasks and is not
2343 a general reference manual.
2347 <file>debian/README.source</file> may also include any other
2348 information that would be helpful to someone modifying the
2349 source package. Even if the package doesn't fit the above
2350 description, maintainers are encouraged to document in a
2351 <file>debian/README.source</file> file any source package with a
2352 particularly complex or unintuitive source layout or build
2353 system (for example, a package that builds the same source
2354 multiple times to generate different binary packages).
2360 <chapt id="controlfields">
2361 <heading>Control files and their fields</heading>
2364 The package management system manipulates data represented in
2365 a common format, known as <em>control data</em>, stored in
2366 <em>control files</em>.
2367 Control files are used for source packages, binary packages and
2368 the <file>.changes</file> files which control the installation
2369 of uploaded files<footnote>
2370 <prgn>dpkg</prgn>'s internal databases are in a similar
2375 <sect id="controlsyntax">
2376 <heading>Syntax of control files</heading>
2379 A control file consists of one or more paragraphs of
2381 The paragraphs are also sometimes referred to as stanzas.
2383 The paragraphs are separated by blank lines. Some control
2384 files allow only one paragraph; others allow several, in
2385 which case each paragraph usually refers to a different
2386 package. (For example, in source packages, the first
2387 paragraph refers to the source package, and later paragraphs
2388 refer to binary packages generated from the source.)
2392 Each paragraph consists of a series of data fields; each
2393 field consists of the field name, followed by a colon and
2394 then the data/value associated with that field. It ends at
2395 the end of the (logical) line. Horizontal whitespace
2396 (spaces and tabs) may occur immediately before or after the
2397 value and is ignored there; it is conventional to put a
2398 single space after the colon. For example, a field might
2400 <example compact="compact">
2403 the field name is <tt>Package</tt> and the field value
2408 A paragraph must not contain more than one instance of a
2409 particular field name.
2413 Many fields' values may span several lines; in this case
2414 each continuation line must start with a space or a tab.
2415 Any trailing spaces or tabs at the end of individual
2416 lines of a field value are ignored.
2420 In fields where it is specified that lines may not wrap,
2421 only a single line of data is allowed and whitespace is not
2422 significant in a field body. Whitespace must not appear
2423 inside names (of packages, architectures, files or anything
2424 else) or version numbers, or between the characters of
2425 multi-character version relationships.
2429 Field names are not case-sensitive, but it is usual to
2430 capitalize the field names using mixed case as shown below.
2431 Field values are case-sensitive unless the description of the
2432 field says otherwise.
2436 Blank lines, or lines consisting only of spaces and tabs,
2437 are not allowed within field values or between fields - that
2438 would mean a new paragraph.
2442 All control files must be encoded in UTF-8.
2446 <sect id="sourcecontrolfiles">
2447 <heading>Source package control files -- <file>debian/control</file></heading>
2450 The <file>debian/control</file> file contains the most vital
2451 (and version-independent) information about the source package
2452 and about the binary packages it creates.
2456 The first paragraph of the control file contains information about
2457 the source package in general. The subsequent sets each describe a
2458 binary package that the source tree builds.
2462 The fields in the general paragraph (the first one, for the source
2465 <list compact="compact">
2466 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2467 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2468 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2469 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2470 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2471 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2472 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2473 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2478 The fields in the binary package paragraphs are:
2480 <list compact="compact">
2481 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2484 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2485 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2486 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2487 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2493 The syntax and semantics of the fields are described below.
2497 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2498 generate control files for binary packages (see below), by
2499 <prgn>dpkg-genchanges</prgn> to generate the
2500 <tt>.changes</tt> file to accompany the upload, and by
2501 <prgn>dpkg-source</prgn> when it creates the
2502 <file>.dsc</file> source control file as part of a source
2503 archive. Many fields are permitted to span multiple lines in
2504 <file>debian/control</file> but not in any other control
2505 file. These tools are responsible for removing the line
2506 breaks from such fields when using fields from
2507 <file>debian/control</file> to generate other control files.
2511 The fields here may contain variable references - their
2512 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2513 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2514 when they generate output control files.
2515 See <ref id="substvars"> for details.
2519 In addition to the control file syntax described <qref
2520 id="controlsyntax">above</qref>, this file may also contain
2521 comment lines starting with <tt>#</tt> without any preceding
2522 whitespace. All such lines are ignored, even in the middle of
2523 continuation lines for a multiline field, and do not end a
2529 <sect id="binarycontrolfiles">
2530 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2533 The <file>DEBIAN/control</file> file contains the most vital
2534 (and version-dependent) information about a binary package.
2538 The fields in this file are:
2540 <list compact="compact">
2541 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2542 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2543 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2544 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2545 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2546 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2548 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2549 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2550 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2557 <sect id="debiansourcecontrolfiles">
2558 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2561 This file contains a series of fields, identified and
2562 separated just like the fields in the control file of
2563 a binary package. The fields are listed below; their
2564 syntax is described above, in <ref id="pkg-controlfields">.
2566 <list compact="compact">
2567 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2568 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2570 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2571 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2574 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2575 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2576 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2577 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2578 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2579 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2584 The source package control file is generated by
2585 <prgn>dpkg-source</prgn> when it builds the source
2586 archive, from other files in the source package,
2587 described above. When unpacking, it is checked against
2588 the files and directories in the other parts of the
2594 <sect id="debianchangesfiles">
2595 <heading>Debian changes files -- <file>.changes</file></heading>
2598 The .changes files are used by the Debian archive maintenance
2599 software to process updates to packages. They contain one
2600 paragraph which contains information from the
2601 <tt>debian/control</tt> file and other data about the
2602 source package gathered via <tt>debian/changelog</tt>
2603 and <tt>debian/rules</tt>.
2607 The fields in this file are:
2609 <list compact="compact">
2610 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2611 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2614 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2616 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2618 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2620 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2622 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2624 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2625 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2630 <sect id="controlfieldslist">
2631 <heading>List of fields</heading>
2633 <sect1 id="f-Source">
2634 <heading><tt>Source</tt></heading>
2637 This field identifies the source package name.
2641 In <file>debian/control</file> or a <file>.dsc</file> file,
2642 this field must contain only the name of the source package.
2646 In a binary package control file or a <file>.changes</file>
2647 file, the source package name may be followed by a version
2648 number in parentheses<footnote>
2649 It is customary to leave a space after the package name
2650 if a version number is specified.
2652 This version number may be omitted (and is, by
2653 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2654 the <tt>Version</tt> field of the binary package in
2655 question. The field itself may be omitted from a binary
2656 package control file when the source package has the same
2657 name and version as the binary package.
2661 Package names (both source and binary,
2662 see <ref id="f-Package">) must consist only of lower case
2663 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2664 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2665 (<tt>.</tt>). They must be at least two characters long and
2666 must start with an alphanumeric character.
2670 <sect1 id="f-Maintainer">
2671 <heading><tt>Maintainer</tt></heading>
2674 The package maintainer's name and email address. The name
2675 must come first, then the email address inside angle
2676 brackets <tt><></tt> (in RFC822 format).
2680 If the maintainer's name contains a full stop then the
2681 whole field will not work directly as an email address due
2682 to a misfeature in the syntax specified in RFC822; a
2683 program using this field as an address must check for this
2684 and correct the problem if necessary (for example by
2685 putting the name in round brackets and moving it to the
2686 end, and bringing the email address forward).
2690 <sect1 id="f-Uploaders">
2691 <heading><tt>Uploaders</tt></heading>
2694 List of the names and email addresses of co-maintainers of
2695 the package, if any. If the package has other maintainers
2696 beside the one named in the
2697 <qref id="f-Maintainer">Maintainer field</qref>, their names
2698 and email addresses should be listed here. The format of each
2699 entry is the same as that of the Maintainer field, and
2700 multiple entries must be comma separated. This is an optional
2705 Any parser that interprets the Uploaders field in
2706 <file>debian/control</file> must permit it to span multiple
2707 lines. Line breaks in an Uploaders field that spans multiple
2708 lines are not significant and the semantics of the field are
2709 the same as if the line breaks had not been present.
2713 <sect1 id="f-Changed-By">
2714 <heading><tt>Changed-By</tt></heading>
2717 The name and email address of the person who prepared this
2718 version of the package, usually a maintainer. The syntax is
2719 the same as for the <qref id="f-Maintainer">Maintainer
2724 <sect1 id="f-Section">
2725 <heading><tt>Section</tt></heading>
2728 This field specifies an application area into which the package
2729 has been classified. See <ref id="subsections">.
2733 When it appears in the <file>debian/control</file> file,
2734 it gives the value for the subfield of the same name in
2735 the <tt>Files</tt> field of the <file>.changes</file> file.
2736 It also gives the default for the same field in the binary
2741 <sect1 id="f-Priority">
2742 <heading><tt>Priority</tt></heading>
2745 This field represents how important it is that the user
2746 have the package installed. See <ref id="priorities">.
2750 When it appears in the <file>debian/control</file> file,
2751 it gives the value for the subfield of the same name in
2752 the <tt>Files</tt> field of the <file>.changes</file> file.
2753 It also gives the default for the same field in the binary
2758 <sect1 id="f-Package">
2759 <heading><tt>Package</tt></heading>
2762 The name of the binary package.
2766 Binary package names must follow the same syntax and
2767 restrictions as source package names. See <ref id="f-Source">
2772 <sect1 id="f-Architecture">
2773 <heading><tt>Architecture</tt></heading>
2776 Depending on context and the control file used, the
2777 <tt>Architecture</tt> field can include the following sets of
2781 A unique single word identifying a Debian machine
2782 architecture as described in <ref id="arch-spec">.
2785 An architecture wildcard identifying a set of Debian
2786 machine architectures, see <ref id="arch-wildcard-spec">.
2787 <tt>any</tt> matches all Debian machine architectures
2788 and is the most frequently used.
2791 <tt>all</tt>, which indicates an
2792 architecture-independent package.
2795 <tt>source</tt>, which indicates a source package.
2801 In the main <file>debian/control</file> file in the source
2802 package, this field may contain the special
2803 value <tt>all</tt>, the special architecture
2804 wildcard <tt>any</tt>, or a list of specific and wildcard
2805 architectures separated by spaces. If <tt>all</tt>
2806 or <tt>any</tt> appears, that value must be the entire
2807 contents of the field. Most packages will use
2808 either <tt>all</tt> or <tt>any</tt>.
2812 Specifying a specific list of architectures indicates that the
2813 source will build an architecture-dependent package only on
2814 architectures included in the list. Specifying a list of
2815 architecture wildcards indicates that the source will build an
2816 architecture-dependent package on only those architectures
2817 that match any of the specified architecture wildcards.
2818 Specifying a list of architectures or architecture wildcards
2819 other than <tt>any</tt> is for the minority of cases where a
2820 program is not portable or is not useful on some
2821 architectures. Where possible, the program should be made
2826 In the source package control file <file>.dsc</file>, this
2827 field may contain either the architecture
2828 wildcard <tt>any</tt> or a list of architectures and
2829 architecture wildcards separated by spaces. If a list is
2830 given, it may include (or consist solely of) the special
2831 value <tt>all</tt>. In other words, in <file>.dsc</file>
2832 files unlike the <file>debian/control</file>, <tt>all</tt> may
2833 occur in combination with specific architectures.
2834 The <tt>Architecture</tt> field in the source package control
2835 file <file>.dsc</file> is generally constructed from
2836 the <tt>Architecture</tt> fields in
2837 the <file>debian/control</file> in the source package.
2841 Specifying <tt>any</tt> indicates that the source package
2842 isn't dependent on any particular architecture and should
2843 compile fine on any one. The produced binary package(s)
2844 will either be specific to whatever the current build
2845 architecture is or will be architecture-independent.
2849 Specifying only <tt>all</tt> indicates that the source package
2850 will only build architecture-independent packages. If this is
2851 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2852 <tt>any</tt> implies that the source package will build at
2853 least one architecture-dependent package.
2857 Specifying a list of architectures or architecture wildcards
2858 indicates that the source will build an architecture-dependent
2859 package, and will only work correctly on the listed or
2860 matching architectures. If the source package also builds at
2861 least one architecture-independent package, <tt>all</tt> will
2862 also be included in the list.
2866 In a <file>.changes</file> file, the <tt>Architecture</tt>
2867 field lists the architecture(s) of the package(s) currently
2868 being uploaded. This will be a list; if the source for the
2869 package is also being uploaded, the special
2870 entry <tt>source</tt> is also present. <tt>all</tt> will be
2871 present if any architecture-independent packages are being
2872 uploaded. Architecture wildcards such as <tt>any</tt> must
2873 never occur in the <tt>Architecture</tt> field in
2874 the <file>.changes</file> file.
2878 See <ref id="debianrules"> for information on how to get
2879 the architecture for the build process.
2883 <sect1 id="f-Essential">
2884 <heading><tt>Essential</tt></heading>
2887 This is a boolean field which may occur only in the
2888 control file of a binary package or in a per-package fields
2889 paragraph of a main source control data file.
2893 If set to <tt>yes</tt> then the package management system
2894 will refuse to remove the package (upgrading and replacing
2895 it is still possible). The other possible value is <tt>no</tt>,
2896 which is the same as not having the field at all.
2901 <heading>Package interrelationship fields:
2902 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2903 <tt>Recommends</tt>, <tt>Suggests</tt>,
2904 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2905 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2909 These fields describe the package's relationships with
2910 other packages. Their syntax and semantics are described
2911 in <ref id="relationships">.</p>
2914 <sect1 id="f-Standards-Version">
2915 <heading><tt>Standards-Version</tt></heading>
2918 The most recent version of the standards (the policy
2919 manual and associated texts) with which the package
2924 The version number has four components: major and minor
2925 version number and major and minor patch level. When the
2926 standards change in a way that requires every package to
2927 change the major number will be changed. Significant
2928 changes that will require work in many packages will be
2929 signaled by a change to the minor number. The major patch
2930 level will be changed for any change to the meaning of the
2931 standards, however small; the minor patch level will be
2932 changed when only cosmetic, typographical or other edits
2933 are made which neither change the meaning of the document
2934 nor affect the contents of packages.
2938 Thus only the first three components of the policy version
2939 are significant in the <em>Standards-Version</em> control
2940 field, and so either these three components or all four
2941 components may be specified.<footnote>
2942 In the past, people specified the full version number
2943 in the Standards-Version field, for example "2.3.0.0".
2944 Since minor patch-level changes don't introduce new
2945 policy, it was thought it would be better to relax
2946 policy and only require the first 3 components to be
2947 specified, in this example "2.3.0". All four
2948 components may still be used if someone wishes to do so.
2954 <sect1 id="f-Version">
2955 <heading><tt>Version</tt></heading>
2958 The version number of a package. The format is:
2959 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2963 The three components here are:
2965 <tag><var>epoch</var></tag>
2968 This is a single (generally small) unsigned integer. It
2969 may be omitted, in which case zero is assumed. If it is
2970 omitted then the <var>upstream_version</var> may not
2975 It is provided to allow mistakes in the version numbers
2976 of older versions of a package, and also a package's
2977 previous version numbering schemes, to be left behind.
2981 <tag><var>upstream_version</var></tag>
2984 This is the main part of the version number. It is
2985 usually the version number of the original ("upstream")
2986 package from which the <file>.deb</file> file has been made,
2987 if this is applicable. Usually this will be in the same
2988 format as that specified by the upstream author(s);
2989 however, it may need to be reformatted to fit into the
2990 package management system's format and comparison
2995 The comparison behavior of the package management system
2996 with respect to the <var>upstream_version</var> is
2997 described below. The <var>upstream_version</var>
2998 portion of the version number is mandatory.
3002 The <var>upstream_version</var> may contain only
3003 alphanumerics<footnote>
3004 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3006 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3007 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3008 tilde) and should start with a digit. If there is no
3009 <var>debian_revision</var> then hyphens are not allowed;
3010 if there is no <var>epoch</var> then colons are not
3015 <tag><var>debian_revision</var></tag>
3018 This part of the version number specifies the version of
3019 the Debian package based on the upstream version. It
3020 may contain only alphanumerics and the characters
3021 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3022 tilde) and is compared in the same way as the
3023 <var>upstream_version</var> is.
3027 It is optional; if it isn't present then the
3028 <var>upstream_version</var> may not contain a hyphen.
3029 This format represents the case where a piece of
3030 software was written specifically to be a Debian
3031 package, where the Debian package source must always
3032 be identical to the pristine source and therefore no
3033 revision indication is required.
3037 It is conventional to restart the
3038 <var>debian_revision</var> at <tt>1</tt> each time the
3039 <var>upstream_version</var> is increased.
3043 The package management system will break the version
3044 number apart at the last hyphen in the string (if there
3045 is one) to determine the <var>upstream_version</var> and
3046 <var>debian_revision</var>. The absence of a
3047 <var>debian_revision</var> is equivalent to a
3048 <var>debian_revision</var> of <tt>0</tt>.
3055 When comparing two version numbers, first the <var>epoch</var>
3056 of each are compared, then the <var>upstream_version</var> if
3057 <var>epoch</var> is equal, and then <var>debian_revision</var>
3058 if <var>upstream_version</var> is also equal.
3059 <var>epoch</var> is compared numerically. The
3060 <var>upstream_version</var> and <var>debian_revision</var>
3061 parts are compared by the package management system using the
3062 following algorithm:
3066 The strings are compared from left to right.
3070 First the initial part of each string consisting entirely of
3071 non-digit characters is determined. These two parts (one of
3072 which may be empty) are compared lexically. If a difference
3073 is found it is returned. The lexical comparison is a
3074 comparison of ASCII values modified so that all the letters
3075 sort earlier than all the non-letters and so that a tilde
3076 sorts before anything, even the end of a part. For example,
3077 the following parts are in sorted order from earliest to
3078 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3079 <tt>a</tt>.<footnote>
3080 One common use of <tt>~</tt> is for upstream pre-releases.
3081 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3082 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3087 Then the initial part of the remainder of each string which
3088 consists entirely of digit characters is determined. The
3089 numerical values of these two parts are compared, and any
3090 difference found is returned as the result of the comparison.
3091 For these purposes an empty string (which can only occur at
3092 the end of one or both version strings being compared) counts
3097 These two steps (comparing and removing initial non-digit
3098 strings and initial digit strings) are repeated until a
3099 difference is found or both strings are exhausted.
3103 Note that the purpose of epochs is to allow us to leave behind
3104 mistakes in version numbering, and to cope with situations
3105 where the version numbering scheme changes. It is
3106 <em>not</em> intended to cope with version numbers containing
3107 strings of letters which the package management system cannot
3108 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3109 silly orderings.<footnote>
3110 The author of this manual has heard of a package whose
3111 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3112 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3118 <sect1 id="f-Description">
3119 <heading><tt>Description</tt></heading>
3122 In a source or binary control file, the <tt>Description</tt>
3123 field contains a description of the binary package, consisting
3124 of two parts, the synopsis or the short description, and the
3125 long description. The field's format is as follows:
3130 Description: <single line synopsis>
3131 <extended description over several lines>
3136 The lines in the extended description can have these formats:
3142 Those starting with a single space are part of a paragraph.
3143 Successive lines of this form will be word-wrapped when
3144 displayed. The leading space will usually be stripped off.
3148 Those starting with two or more spaces. These will be
3149 displayed verbatim. If the display cannot be panned
3150 horizontally, the displaying program will line wrap them "hard"
3151 (i.e., without taking account of word breaks). If it can they
3152 will be allowed to trail off to the right. None, one or two
3153 initial spaces may be deleted, but the number of spaces
3154 deleted from each line will be the same (so that you can have
3155 indenting work correctly, for example).
3159 Those containing a single space followed by a single full stop
3160 character. These are rendered as blank lines. This is the
3161 <em>only</em> way to get a blank line<footnote>
3162 Completely empty lines will not be rendered as blank lines.
3163 Instead, they will cause the parser to think you're starting
3164 a whole new record in the control file, and will therefore
3165 likely abort with an error.
3170 Those containing a space, a full stop and some more characters.
3171 These are for future expansion. Do not use them.
3177 Do not use tab characters. Their effect is not predictable.
3181 See <ref id="descriptions"> for further information on this.
3185 In a <file>.changes</file> file, the <tt>Description</tt>
3186 field contains a summary of the descriptions for the packages
3187 being uploaded. For this case, the first line of the field
3188 value (the part on the same line as <tt>Description:</tt>) is
3189 always empty. The content of the field is expressed as
3190 continuation lines, one line per package. Each line is
3191 indented by one space and contains the name of a binary
3192 package, a space, a hyphen (<tt>-</tt>), a space, and the
3193 short description line from that package.
3197 <sect1 id="f-Distribution">
3198 <heading><tt>Distribution</tt></heading>
3201 In a <file>.changes</file> file or parsed changelog output
3202 this contains the (space-separated) name(s) of the
3203 distribution(s) where this version of the package should
3204 be installed. Valid distributions are determined by the
3205 archive maintainers.<footnote>
3206 Example distribution names in the Debian archive used in
3207 <file>.changes</file> files are:
3208 <taglist compact="compact">
3209 <tag><em>unstable</em></tag>
3211 This distribution value refers to the
3212 <em>developmental</em> part of the Debian distribution
3213 tree. Most new packages, new upstream versions of
3214 packages and bug fixes go into the <em>unstable</em>
3218 <tag><em>experimental</em></tag>
3220 The packages with this distribution value are deemed
3221 by their maintainers to be high risk. Oftentimes they
3222 represent early beta or developmental packages from
3223 various sources that the maintainers want people to
3224 try, but are not ready to be a part of the other parts
3225 of the Debian distribution tree.
3230 Others are used for updating stable releases or for
3231 security uploads. More information is available in the
3232 Debian Developer's Reference, section "The Debian
3236 The Debian archive software only supports listing a single
3237 distribution. Migration of packages to other distributions is
3238 handled outside of the upload process.
3243 <heading><tt>Date</tt></heading>
3246 This field includes the date the package was built or last
3247 edited. It must be in the same format as the <var>date</var>
3248 in a <file>debian/changelog</file> entry.
3252 The value of this field is usually extracted from the
3253 <file>debian/changelog</file> file - see
3254 <ref id="dpkgchangelog">).
3258 <sect1 id="f-Format">
3259 <heading><tt>Format</tt></heading>
3262 This field specifies a format revision for the file.
3263 The most current format described in the Policy Manual
3264 is version <strong>1.5</strong>. The syntax of the
3265 format value is the same as that of a package version
3266 number except that no epoch or Debian revision is allowed
3267 - see <ref id="f-Version">.
3271 <sect1 id="f-Urgency">
3272 <heading><tt>Urgency</tt></heading>
3275 This is a description of how important it is to upgrade to
3276 this version from previous ones. It consists of a single
3277 keyword taking one of the values <tt>low</tt>,
3278 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3279 <tt>critical</tt><footnote>
3280 Other urgency values are supported with configuration
3281 changes in the archive software but are not used in Debian.
3282 The urgency affects how quickly a package will be considered
3283 for inclusion into the <tt>testing</tt> distribution and
3284 gives an indication of the importance of any fixes included
3285 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3286 treated as synonymous.
3287 </footnote> (not case-sensitive) followed by an optional
3288 commentary (separated by a space) which is usually in
3289 parentheses. For example:
3292 Urgency: low (HIGH for users of diversions)
3298 The value of this field is usually extracted from the
3299 <file>debian/changelog</file> file - see
3300 <ref id="dpkgchangelog">.
3304 <sect1 id="f-Changes">
3305 <heading><tt>Changes</tt></heading>
3308 This field contains the human-readable changes data, describing
3309 the differences between the last version and the current one.
3313 The first line of the field value (the part on the same line
3314 as <tt>Changes:</tt>) is always empty. The content of the
3315 field is expressed as continuation lines, with each line
3316 indented by at least one space. Blank lines must be
3317 represented by a line consisting only of a space and a full
3322 The value of this field is usually extracted from the
3323 <file>debian/changelog</file> file - see
3324 <ref id="dpkgchangelog">).
3328 Each version's change information should be preceded by a
3329 "title" line giving at least the version, distribution(s)
3330 and urgency, in a human-readable way.
3334 If data from several versions is being returned the entry
3335 for the most recent version should be returned first, and
3336 entries should be separated by the representation of a
3337 blank line (the "title" line may also be followed by the
3338 representation of a blank line).
3342 <sect1 id="f-Binary">
3343 <heading><tt>Binary</tt></heading>
3346 This field is a list of binary packages. Its syntax and
3347 meaning varies depending on the control file in which it
3352 When it appears in the <file>.dsc</file> file, it lists binary
3353 packages which a source package can produce, separated by
3355 A space after each comma is conventional.
3356 </footnote>. It may span multiple lines. The source package
3357 does not necessarily produce all of these binary packages for
3358 every architecture. The source control file doesn't contain
3359 details of which architectures are appropriate for which of
3360 the binary packages.
3364 When it appears in a <file>.changes</file> file, it lists the
3365 names of the binary packages being uploaded, separated by
3366 whitespace (not commas). It may span multiple lines.
3370 <sect1 id="f-Installed-Size">
3371 <heading><tt>Installed-Size</tt></heading>
3374 This field appears in the control files of binary packages,
3375 and in the <file>Packages</file> files. It gives an estimate
3376 of the total amount of disk space required to install the
3377 named package. Actual installed size may vary based on block
3378 size, file system properties, or actions taken by package
3383 The disk space is given as the integer value of the estimated
3384 installed size in bytes, divided by 1024 and rounded up.
3388 <sect1 id="f-Files">
3389 <heading><tt>Files</tt></heading>
3392 This field contains a list of files with information about
3393 each one. The exact information and syntax varies with
3398 In all cases, Files is a multiline field. The first line of
3399 the field value (the part on the same line as <tt>Files:</tt>)
3400 is always empty. The content of the field is expressed as
3401 continuation lines, one line per file. Each line must be
3402 indented by one space and contain a number of sub-fields,
3403 separated by spaces, as described below.
3407 In the <file>.dsc</file> file, each line contains the MD5
3408 checksum, size and filename of the tar file and (if
3409 applicable) diff file which make up the remainder of the
3410 source package<footnote>
3411 That is, the parts which are not the <tt>.dsc</tt>.
3412 </footnote>. For example:
3415 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3416 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3418 The exact forms of the filenames are described
3419 in <ref id="pkg-sourcearchives">.
3423 In the <file>.changes</file> file this contains one line per
3424 file being uploaded. Each line contains the MD5 checksum,
3425 size, section and priority and the filename. For example:
3428 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3429 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3430 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3431 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3433 The <qref id="f-Section">section</qref>
3434 and <qref id="f-Priority">priority</qref> are the values of
3435 the corresponding fields in the main source control file. If
3436 no section or priority is specified then <tt>-</tt> should be
3437 used, though section and priority values must be specified for
3438 new packages to be installed properly.
3442 The special value <tt>byhand</tt> for the section in a
3443 <tt>.changes</tt> file indicates that the file in question
3444 is not an ordinary package file and must by installed by
3445 hand by the distribution maintainers. If the section is
3446 <tt>byhand</tt> the priority should be <tt>-</tt>.
3450 If a new Debian revision of a package is being shipped and
3451 no new original source archive is being distributed the
3452 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3453 entry for the original source archive
3454 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3455 but the <file>.changes</file> file should leave it out. In
3456 this case the original source archive on the distribution
3457 site must match exactly, byte-for-byte, the original
3458 source archive which was used to generate the
3459 <file>.dsc</file> file and diff which are being uploaded.</p>
3462 <sect1 id="f-Closes">
3463 <heading><tt>Closes</tt></heading>
3466 A space-separated list of bug report numbers that the upload
3467 governed by the .changes file closes.
3471 <sect1 id="f-Homepage">
3472 <heading><tt>Homepage</tt></heading>
3475 The URL of the web site for this package, preferably (when
3476 applicable) the site from which the original source can be
3477 obtained and any additional upstream documentation or
3478 information may be found. The content of this field is a
3479 simple URL without any surrounding characters such as
3484 <sect1 id="f-Checksums">
3485 <heading><tt>Checksums-Sha1</tt>
3486 and <tt>Checksums-Sha256</tt></heading>
3489 These fields contain a list of files with a checksum and size
3490 for each one. Both <tt>Checksums-Sha1</tt>
3491 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3492 only in the checksum algorithm used: SHA-1
3493 for <tt>Checksums-Sha1</tt> and SHA-256
3494 for <tt>Checksums-Sha256</tt>.
3498 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3499 multiline fields. The first line of the field value (the part
3500 on the same line as <tt>Checksums-Sha1:</tt>
3501 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3502 of the field is expressed as continuation lines, one line per
3503 file. Each line consists of the checksum, a space, the file
3504 size, a space, and the file name. For example (from
3505 a <file>.changes</file> file):
3508 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3509 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3510 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3511 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3513 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3514 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3515 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3516 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3521 In the <file>.dsc</file> file, these fields should list all
3522 files that make up the source package. In
3523 the <file>.changes</file> file, these fields should list all
3524 files being uploaded. The list of files in these fields
3525 must match the list of files in the <tt>Files</tt> field.
3532 <heading>User-defined fields</heading>
3535 Additional user-defined fields may be added to the
3536 source package control file. Such fields will be
3537 ignored, and not copied to (for example) binary or
3538 source package control files or upload control files.
3542 If you wish to add additional unsupported fields to
3543 these output files you should use the mechanism
3548 Fields in the main source control information file with
3549 names starting <tt>X</tt>, followed by one or more of
3550 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3551 be copied to the output files. Only the part of the
3552 field name after the hyphen will be used in the output
3553 file. Where the letter <tt>B</tt> is used the field
3554 will appear in binary package control files, where the
3555 letter <tt>S</tt> is used in source package control
3556 files and where <tt>C</tt> is used in upload control
3557 (<tt>.changes</tt>) files.
3561 For example, if the main source information control file
3564 XBS-Comment: I stand between the candle and the star.
3566 then the binary and source package control files will contain the
3569 Comment: I stand between the candle and the star.
3578 <chapt id="maintainerscripts">
3579 <heading>Package maintainer scripts and installation procedure</heading>
3582 <heading>Introduction to package maintainer scripts</heading>
3585 It is possible to supply scripts as part of a package which
3586 the package management system will run for you when your
3587 package is installed, upgraded or removed.
3591 These scripts are the files <prgn>preinst</prgn>,
3592 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3593 <prgn>postrm</prgn> in the control area of the package.
3594 They must be proper executable files; if they are scripts
3595 (which is recommended), they must start with the usual
3596 <tt>#!</tt> convention. They should be readable and
3597 executable by anyone, and must not be world-writable.
3601 The package management system looks at the exit status from
3602 these scripts. It is important that they exit with a
3603 non-zero status if there is an error, so that the package
3604 management system can stop its processing. For shell
3605 scripts this means that you <em>almost always</em> need to
3606 use <tt>set -e</tt> (this is usually true when writing shell
3607 scripts, in fact). It is also important, of course, that
3608 they exit with a zero status if everything went well.
3612 Additionally, packages interacting with users using
3613 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3614 install a <prgn>config</prgn> script in the control area,
3615 see <ref id="maintscriptprompt"> for details.
3619 When a package is upgraded a combination of the scripts from
3620 the old and new packages is called during the upgrade
3621 procedure. If your scripts are going to be at all
3622 complicated you need to be aware of this, and may need to
3623 check the arguments to your scripts.
3627 Broadly speaking the <prgn>preinst</prgn> is called before
3628 (a particular version of) a package is installed, and the
3629 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3630 before (a version of) a package is removed and the
3631 <prgn>postrm</prgn> afterwards.
3635 Programs called from maintainer scripts should not normally
3636 have a path prepended to them. Before installation is
3637 started, the package management system checks to see if the
3638 programs <prgn>ldconfig</prgn>,
3639 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3640 and <prgn>update-rc.d</prgn> can be found via the
3641 <tt>PATH</tt> environment variable. Those programs, and any
3642 other program that one would expect to be in the
3643 <tt>PATH</tt>, should thus be invoked without an absolute
3644 pathname. Maintainer scripts should also not reset the
3645 <tt>PATH</tt>, though they might choose to modify it by
3646 prepending or appending package-specific directories. These
3647 considerations really apply to all shell scripts.</p>
3650 <sect id="idempotency">
3651 <heading>Maintainer scripts idempotency</heading>
3654 It is necessary for the error recovery procedures that the
3655 scripts be idempotent. This means that if it is run
3656 successfully, and then it is called again, it doesn't bomb
3657 out or cause any harm, but just ensures that everything is
3658 the way it ought to be. If the first call failed, or
3659 aborted half way through for some reason, the second call
3660 should merely do the things that were left undone the first
3661 time, if any, and exit with a success status if everything
3663 This is so that if an error occurs, the user interrupts
3664 <prgn>dpkg</prgn> or some other unforeseen circumstance
3665 happens you don't leave the user with a badly-broken
3666 package when <prgn>dpkg</prgn> attempts to repeat the
3672 <sect id="controllingterminal">
3673 <heading>Controlling terminal for maintainer scripts</heading>
3676 Maintainer scripts are not guaranteed to run with a controlling
3677 terminal and may not be able to interact with the user. They
3678 must be able to fall back to noninteractive behavior if no
3679 controlling terminal is available. Maintainer scripts that
3680 prompt via a program conforming to the Debian Configuration
3681 Management Specification (see <ref id="maintscriptprompt">) may
3682 assume that program will handle falling back to noninteractive
3687 For high-priority prompts without a reasonable default answer,
3688 maintainer scripts may abort if there is no controlling
3689 terminal. However, this situation should be avoided if at all
3690 possible, since it prevents automated or unattended installs.
3691 In most cases, users will consider this to be a bug in the
3696 <sect id="exitstatus">
3697 <heading>Exit status</heading>
3700 Each script must return a zero exit status for
3701 success, or a nonzero one for failure, since the package
3702 management system looks for the exit status of these scripts
3703 and determines what action to take next based on that datum.
3707 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3712 <list compact="compact">
3714 <var>new-preinst</var> <tt>install</tt>
3717 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3720 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3723 <var>old-preinst</var> <tt>abort-upgrade</tt>
3724 <var>new-version</var>
3729 <list compact="compact">
3731 <var>postinst</var> <tt>configure</tt>
3732 <var>most-recently-configured-version</var>
3735 <var>old-postinst</var> <tt>abort-upgrade</tt>
3736 <var>new-version</var>
3739 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3740 <tt>in-favour</tt> <var>package</var>
3741 <var>new-version</var>
3744 <var>postinst</var> <tt>abort-remove</tt>
3747 <var>deconfigured's-postinst</var>
3748 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3749 <var>failed-install-package</var> <var>version</var>
3750 [<tt>removing</tt> <var>conflicting-package</var>
3756 <list compact="compact">
3758 <var>prerm</var> <tt>remove</tt>
3761 <var>old-prerm</var> <tt>upgrade</tt>
3762 <var>new-version</var>
3765 <var>new-prerm</var> <tt>failed-upgrade</tt>
3766 <var>old-version</var>
3769 <var>conflictor's-prerm</var> <tt>remove</tt>
3770 <tt>in-favour</tt> <var>package</var>
3771 <var>new-version</var>
3774 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3775 <tt>in-favour</tt> <var>package-being-installed</var>
3776 <var>version</var> [<tt>removing</tt>
3777 <var>conflicting-package</var>
3783 <list compact="compact">
3785 <var>postrm</var> <tt>remove</tt>
3788 <var>postrm</var> <tt>purge</tt>
3791 <var>old-postrm</var> <tt>upgrade</tt>
3792 <var>new-version</var>
3795 <var>new-postrm</var> <tt>failed-upgrade</tt>
3796 <var>old-version</var>
3799 <var>new-postrm</var> <tt>abort-install</tt>
3802 <var>new-postrm</var> <tt>abort-install</tt>
3803 <var>old-version</var>
3806 <var>new-postrm</var> <tt>abort-upgrade</tt>
3807 <var>old-version</var>
3810 <var>disappearer's-postrm</var> <tt>disappear</tt>
3811 <var>overwriter</var>
3812 <var>overwriter-version</var>
3818 <sect id="unpackphase">
3819 <heading>Details of unpack phase of installation or upgrade</heading>
3822 The procedure on installation/upgrade/overwrite/disappear
3823 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3824 stage of <tt>dpkg --install</tt>) is as follows. In each
3825 case, if a major error occurs (unless listed below) the
3826 actions are, in general, run backwards - this means that the
3827 maintainer scripts are run with different arguments in
3828 reverse order. These are the "error unwind" calls listed
3835 If a version of the package is already installed, call
3836 <example compact="compact">
3837 <var>old-prerm</var> upgrade <var>new-version</var>
3841 If the script runs but exits with a non-zero
3842 exit status, <prgn>dpkg</prgn> will attempt:
3843 <example compact="compact">
3844 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3846 If this works, the upgrade continues. If this
3847 does not work, the error unwind:
3848 <example compact="compact">
3849 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3851 If this works, then the old-version is
3852 "Installed", if not, the old version is in a
3853 "Half-Configured" state.
3859 If a "conflicting" package is being removed at the same time,
3860 or if any package will be broken (due to <tt>Breaks</tt>):
3863 If <tt>--auto-deconfigure</tt> is
3864 specified, call, for each package to be deconfigured
3865 due to <tt>Breaks</tt>:
3866 <example compact="compact">
3867 <var>deconfigured's-prerm</var> deconfigure \
3868 in-favour <var>package-being-installed</var> <var>version</var>
3871 <example compact="compact">
3872 <var>deconfigured's-postinst</var> abort-deconfigure \
3873 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3875 The deconfigured packages are marked as
3876 requiring configuration, so that if
3877 <tt>--install</tt> is used they will be
3878 configured again if possible.
3881 If any packages depended on a conflicting
3882 package being removed and <tt>--auto-deconfigure</tt> is
3883 specified, call, for each such package:
3884 <example compact="compact">
3885 <var>deconfigured's-prerm</var> deconfigure \
3886 in-favour <var>package-being-installed</var> <var>version</var> \
3887 removing <var>conflicting-package</var> <var>version</var>
3890 <example compact="compact">
3891 <var>deconfigured's-postinst</var> abort-deconfigure \
3892 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3893 removing <var>conflicting-package</var> <var>version</var>
3895 The deconfigured packages are marked as
3896 requiring configuration, so that if
3897 <tt>--install</tt> is used they will be
3898 configured again if possible.
3901 To prepare for removal of each conflicting package, call:
3902 <example compact="compact">
3903 <var>conflictor's-prerm</var> remove \
3904 in-favour <var>package</var> <var>new-version</var>
3907 <example compact="compact">
3908 <var>conflictor's-postinst</var> abort-remove \
3909 in-favour <var>package</var> <var>new-version</var>
3918 If the package is being upgraded, call:
3919 <example compact="compact">
3920 <var>new-preinst</var> upgrade <var>old-version</var>
3922 If this fails, we call:
3924 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3931 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3933 is called. If this works, then the old version
3934 is in an "Installed" state, or else it is left
3935 in an "Unpacked" state.
3940 If it fails, then the old version is left
3941 in an "Half-Installed" state.
3948 Otherwise, if the package had some configuration
3949 files from a previous version installed (i.e., it
3950 is in the "configuration files only" state):
3951 <example compact="compact">
3952 <var>new-preinst</var> install <var>old-version</var>
3956 <var>new-postrm</var> abort-install <var>old-version</var>
3958 If this fails, the package is left in a
3959 "Half-Installed" state, which requires a
3960 reinstall. If it works, the packages is left in
3961 a "Config-Files" state.
3964 Otherwise (i.e., the package was completely purged):
3965 <example compact="compact">
3966 <var>new-preinst</var> install
3969 <example compact="compact">
3970 <var>new-postrm</var> abort-install
3972 If the error-unwind fails, the package is in a
3973 "Half-Installed" phase, and requires a
3974 reinstall. If the error unwind works, the
3975 package is in a not installed state.
3982 The new package's files are unpacked, overwriting any
3983 that may be on the system already, for example any
3984 from the old version of the same package or from
3985 another package. Backups of the old files are kept
3986 temporarily, and if anything goes wrong the package
3987 management system will attempt to put them back as
3988 part of the error unwind.
3992 It is an error for a package to contain files which
3993 are on the system in another package, unless
3994 <tt>Replaces</tt> is used (see <ref id="replaces">).
3996 The following paragraph is not currently the case:
3997 Currently the <tt>- - force-overwrite</tt> flag is
3998 enabled, downgrading it to a warning, but this may not
4004 It is a more serious error for a package to contain a
4005 plain file or other kind of non-directory where another
4006 package has a directory (again, unless
4007 <tt>Replaces</tt> is used). This error can be
4008 overridden if desired using
4009 <tt>--force-overwrite-dir</tt>, but this is not
4014 Packages which overwrite each other's files produce
4015 behavior which, though deterministic, is hard for the
4016 system administrator to understand. It can easily
4017 lead to "missing" programs if, for example, a package
4018 is installed which overwrites a file from another
4019 package, and is then removed again.<footnote>
4020 Part of the problem is due to what is arguably a
4021 bug in <prgn>dpkg</prgn>.
4026 A directory will never be replaced by a symbolic link
4027 to a directory or vice versa; instead, the existing
4028 state (symlink or not) will be left alone and
4029 <prgn>dpkg</prgn> will follow the symlink if there is
4038 If the package is being upgraded, call
4039 <example compact="compact">
4040 <var>old-postrm</var> upgrade <var>new-version</var>
4044 If this fails, <prgn>dpkg</prgn> will attempt:
4045 <example compact="compact">
4046 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4048 If this works, installation continues. If not,
4050 <example compact="compact">
4051 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4053 If this fails, the old version is left in a
4054 "Half-Installed" state. If it works, dpkg now
4056 <example compact="compact">
4057 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4059 If this fails, the old version is left in a
4060 "Half-Installed" state. If it works, dpkg now
4062 <example compact="compact">
4063 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4065 If this fails, the old version is in an
4072 This is the point of no return - if
4073 <prgn>dpkg</prgn> gets this far, it won't back off
4074 past this point if an error occurs. This will
4075 leave the package in a fairly bad state, which
4076 will require a successful re-installation to clear
4077 up, but it's when <prgn>dpkg</prgn> starts doing
4078 things that are irreversible.
4083 Any files which were in the old version of the package
4084 but not in the new are removed.
4088 The new file list replaces the old.
4092 The new maintainer scripts replace the old.
4096 Any packages all of whose files have been overwritten
4097 during the installation, and which aren't required for
4098 dependencies, are considered to have been removed.
4099 For each such package
4102 <prgn>dpkg</prgn> calls:
4103 <example compact="compact">
4104 <var>disappearer's-postrm</var> disappear \
4105 <var>overwriter</var> <var>overwriter-version</var>
4109 The package's maintainer scripts are removed.
4112 It is noted in the status database as being in a
4113 sane state, namely not installed (any conffiles
4114 it may have are ignored, rather than being
4115 removed by <prgn>dpkg</prgn>). Note that
4116 disappearing packages do not have their prerm
4117 called, because <prgn>dpkg</prgn> doesn't know
4118 in advance that the package is going to
4125 Any files in the package we're unpacking that are also
4126 listed in the file lists of other packages are removed
4127 from those lists. (This will lobotomize the file list
4128 of the "conflicting" package if there is one.)
4132 The backup files made during installation, above, are
4138 The new package's status is now sane, and recorded as
4143 Here is another point of no return - if the
4144 conflicting package's removal fails we do not unwind
4145 the rest of the installation; the conflicting package
4146 is left in a half-removed limbo.
4151 If there was a conflicting package we go and do the
4152 removal actions (described below), starting with the
4153 removal of the conflicting package's files (any that
4154 are also in the package being installed have already
4155 been removed from the conflicting package's file list,
4156 and so do not get removed now).
4162 <sect id="configdetails"><heading>Details of configuration</heading>
4165 When we configure a package (this happens with <tt>dpkg
4166 --install</tt> and <tt>dpkg --configure</tt>), we first
4167 update any <tt>conffile</tt>s and then call:
4168 <example compact="compact">
4169 <var>postinst</var> configure <var>most-recently-configured-version</var>
4174 No attempt is made to unwind after errors during
4175 configuration. If the configuration fails, the package is in
4176 a "Failed Config" state, and an error message is generated.
4180 If there is no most recently configured version
4181 <prgn>dpkg</prgn> will pass a null argument.
4184 Historical note: Truly ancient (pre-1997) versions of
4185 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4186 (including the angle brackets) in this case. Even older
4187 ones did not pass a second argument at all, under any
4188 circumstance. Note that upgrades using such an old dpkg
4189 version are unlikely to work for other reasons, even if
4190 this old argument behavior is handled by your postinst script.
4196 <sect id="removedetails"><heading>Details of removal and/or
4197 configuration purging</heading>
4203 <example compact="compact">
4204 <var>prerm</var> remove
4208 If prerm fails during replacement due to conflict
4210 <var>conflictor's-postinst</var> abort-remove \
4211 in-favour <var>package</var> <var>new-version</var>
4215 <var>postinst</var> abort-remove
4219 If this fails, the package is in a "Half-Configured"
4220 state, or else it remains "Installed".
4224 The package's files are removed (except <tt>conffile</tt>s).
4227 <example compact="compact">
4228 <var>postrm</var> remove
4232 If it fails, there's no error unwind, and the package is in
4233 an "Half-Installed" state.
4238 All the maintainer scripts except the <prgn>postrm</prgn>
4243 If we aren't purging the package we stop here. Note
4244 that packages which have no <prgn>postrm</prgn> and no
4245 <tt>conffile</tt>s are automatically purged when
4246 removed, as there is no difference except for the
4247 <prgn>dpkg</prgn> status.
4251 The <tt>conffile</tt>s and any backup files
4252 (<tt>~</tt>-files, <tt>#*#</tt> files,
4253 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4258 <example compact="compact">
4259 <var>postrm</var> purge
4263 If this fails, the package remains in a "Config-Files"
4268 The package's file list is removed.
4277 <chapt id="relationships">
4278 <heading>Declaring relationships between packages</heading>
4280 <sect id="depsyntax">
4281 <heading>Syntax of relationship fields</heading>
4284 These fields all have a uniform syntax. They are a list of
4285 package names separated by commas.
4289 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4290 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4291 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4292 control file fields of the package, which declare
4293 dependencies on other packages, the package names listed may
4294 also include lists of alternative package names, separated
4295 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4296 if any one of the alternative packages is installed, that
4297 part of the dependency is considered to be satisfied.
4301 All of the fields except for <tt>Provides</tt> may restrict
4302 their applicability to particular versions of each named
4303 package. This is done in parentheses after each individual
4304 package name; the parentheses should contain a relation from
4305 the list below followed by a version number, in the format
4306 described in <ref id="f-Version">.
4310 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4311 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4312 strictly earlier, earlier or equal, exactly equal, later or
4313 equal and strictly later, respectively. The deprecated
4314 forms <tt><</tt> and <tt>></tt> were used to mean
4315 earlier/later or equal, rather than strictly earlier/later,
4316 so they should not appear in new packages (though
4317 <prgn>dpkg</prgn> still supports them).
4321 Whitespace may appear at any point in the version
4322 specification subject to the rules in <ref
4323 id="controlsyntax">, and must appear where it's necessary to
4324 disambiguate; it is not otherwise significant. All of the
4325 relationship fields may span multiple lines. For
4326 consistency and in case of future changes to
4327 <prgn>dpkg</prgn> it is recommended that a single space be
4328 used after a version relationship and before a version
4329 number; it is also conventional to put a single space after
4330 each comma, on either side of each vertical bar, and before
4331 each open parenthesis. When wrapping a relationship field, it
4332 is conventional to do so after a comma and before the space
4333 following that comma.
4337 For example, a list of dependencies might appear as:
4338 <example compact="compact">
4341 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4346 All fields that specify build-time relationships
4347 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4348 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4349 may be restricted to a certain set of architectures. This
4350 is indicated in brackets after each individual package name and
4351 the optional version specification. The brackets enclose a
4352 list of Debian architecture names separated by whitespace.
4353 Exclamation marks may be prepended to each of the names.
4354 (It is not permitted for some names to be prepended with
4355 exclamation marks while others aren't.) If the current Debian
4356 host architecture is not in this list and there are no
4357 exclamation marks in the list, or it is in the list with a
4358 prepended exclamation mark, the package name and the
4359 associated version specification are ignored completely for
4360 the purposes of defining the relationships.
4365 <example compact="compact">
4367 Build-Depends-Indep: texinfo
4368 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4369 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4371 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4372 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4373 <tt>gnumach-dev</tt> only on hurd-i386.
4377 If the architecture-restricted dependency is part of a set of
4378 alternatives using <tt>|</tt>, that alternative is ignored
4379 completely on architectures that do not match the restriction.
4381 <example compact="compact">
4382 Build-Depends: foo [!i386] | bar [!amd64]
4384 is equivalent to <tt>bar</tt> on the i386 architecture, to
4385 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4386 bar</tt> on all other architectures.
4390 All fields that specify build-time relationships may also be
4391 restricted to a certain set of architectures using architecture
4392 wildcards. The syntax for declaring such restrictions is the
4393 same as declaring restrictions using a certain set of
4394 architectures without architecture wildcards. For example:
4395 <example compact="compact">
4396 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4398 is equivalent to <tt>foo</tt> on architectures using the Linux
4399 kernel and any cpu, <tt>bar</tt> on architectures using any
4400 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4401 using a kernel other than Linux.
4405 Note that the binary package relationship fields such as
4406 <tt>Depends</tt> appear in one of the binary package
4407 sections of the control file, whereas the build-time
4408 relationships such as <tt>Build-Depends</tt> appear in the
4409 source package section of the control file (which is the
4414 <sect id="binarydeps">
4415 <heading>Binary Dependencies - <tt>Depends</tt>,
4416 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4417 <tt>Pre-Depends</tt>
4421 Packages can declare in their control file that they have
4422 certain relationships to other packages - for example, that
4423 they may not be installed at the same time as certain other
4424 packages, and/or that they depend on the presence of others.
4428 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4429 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4430 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4431 <tt>Breaks</tt> is described in <ref id="breaks">, and
4432 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4433 rest are described below.
4437 These seven fields are used to declare a dependency
4438 relationship by one package on another. Except for
4439 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4440 depending (binary) package's control file.
4441 (<tt>Enhances</tt> appears in the recommending package's
4442 control file, and <tt>Breaks</tt> appears in the version of
4443 depended-on package which causes the named package to
4448 A <tt>Depends</tt> field takes effect <em>only</em> when a
4449 package is to be configured. It does not prevent a package
4450 being on the system in an unconfigured state while its
4451 dependencies are unsatisfied, and it is possible to replace
4452 a package whose dependencies are satisfied and which is
4453 properly installed with a different version whose
4454 dependencies are not and cannot be satisfied; when this is
4455 done the depending package will be left unconfigured (since
4456 attempts to configure it will give errors) and will not
4457 function properly. If it is necessary, a
4458 <tt>Pre-Depends</tt> field can be used, which has a partial
4459 effect even when a package is being unpacked, as explained
4460 in detail below. (The other three dependency fields,
4461 <tt>Recommends</tt>, <tt>Suggests</tt> and
4462 <tt>Enhances</tt>, are only used by the various front-ends
4463 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4464 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4468 For this reason packages in an installation run are usually
4469 all unpacked first and all configured later; this gives
4470 later versions of packages with dependencies on later
4471 versions of other packages the opportunity to have their
4472 dependencies satisfied.
4476 In case of circular dependencies, since installation or
4477 removal order honoring the dependency order can't be
4478 established, dependency loops are broken at some point
4479 (based on rules below), and some packages may not be able to
4480 rely on their dependencies being present when being
4481 installed or removed, depending on which side of the break
4482 of the circular dependency loop they happen to be on. If one
4483 of the packages in the loop has no postinst script, then the
4484 cycle will be broken at that package, so as to ensure that
4485 all postinst scripts run with the dependencies properly
4486 configured if this is possible. Otherwise the breaking point
4491 The <tt>Depends</tt> field thus allows package maintainers
4492 to impose an order in which packages should be configured.
4496 The meaning of the five dependency fields is as follows:
4498 <tag><tt>Depends</tt></tag>
4501 This declares an absolute dependency. A package will
4502 not be configured unless all of the packages listed in
4503 its <tt>Depends</tt> field have been correctly
4508 The <tt>Depends</tt> field should be used if the
4509 depended-on package is required for the depending
4510 package to provide a significant amount of
4515 The <tt>Depends</tt> field should also be used if the
4516 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4517 <prgn>postrm</prgn> scripts require the package to be
4518 present in order to run. Note, however, that the
4519 <prgn>postrm</prgn> cannot rely on any non-essential
4520 packages to be present during the <tt>purge</tt>
4524 <tag><tt>Recommends</tt></tag>
4527 This declares a strong, but not absolute, dependency.
4531 The <tt>Recommends</tt> field should list packages
4532 that would be found together with this one in all but
4533 unusual installations.
4537 <tag><tt>Suggests</tt></tag>
4539 This is used to declare that one package may be more
4540 useful with one or more others. Using this field
4541 tells the packaging system and the user that the
4542 listed packages are related to this one and can
4543 perhaps enhance its usefulness, but that installing
4544 this one without them is perfectly reasonable.
4547 <tag><tt>Enhances</tt></tag>
4549 This field is similar to Suggests but works in the
4550 opposite direction. It is used to declare that a
4551 package can enhance the functionality of another
4555 <tag><tt>Pre-Depends</tt></tag>
4558 This field is like <tt>Depends</tt>, except that it
4559 also forces <prgn>dpkg</prgn> to complete installation
4560 of the packages named before even starting the
4561 installation of the package which declares the
4562 pre-dependency, as follows:
4566 When a package declaring a pre-dependency is about to
4567 be <em>unpacked</em> the pre-dependency can be
4568 satisfied if the depended-on package is either fully
4569 configured, <em>or even if</em> the depended-on
4570 package(s) are only unpacked or in the "Half-Configured"
4571 state, provided that they have been configured
4572 correctly at some point in the past (and not removed
4573 or partially removed since). In this case, both the
4574 previously-configured and currently unpacked or
4575 "Half-Configured" versions must satisfy any version
4576 clause in the <tt>Pre-Depends</tt> field.
4580 When the package declaring a pre-dependency is about
4581 to be <em>configured</em>, the pre-dependency will be
4582 treated as a normal <tt>Depends</tt>, that is, it will
4583 be considered satisfied only if the depended-on
4584 package has been correctly configured.
4588 <tt>Pre-Depends</tt> should be used sparingly,
4589 preferably only by packages whose premature upgrade or
4590 installation would hamper the ability of the system to
4591 continue with any upgrade that might be in progress.
4595 <tt>Pre-Depends</tt> are also required if the
4596 <prgn>preinst</prgn> script depends on the named
4597 package. It is best to avoid this situation if
4605 When selecting which level of dependency to use you should
4606 consider how important the depended-on package is to the
4607 functionality of the one declaring the dependency. Some
4608 packages are composed of components of varying degrees of
4609 importance. Such a package should list using
4610 <tt>Depends</tt> the package(s) which are required by the
4611 more important components. The other components'
4612 requirements may be mentioned as Suggestions or
4613 Recommendations, as appropriate to the components' relative
4619 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4622 When one binary package declares that it breaks another,
4623 <prgn>dpkg</prgn> will refuse to allow the package which
4624 declares <tt>Breaks</tt> be installed unless the broken
4625 package is deconfigured first, and it will refuse to
4626 allow the broken package to be reconfigured.
4630 A package will not be regarded as causing breakage merely
4631 because its configuration files are still installed; it must
4632 be at least "Half-Installed".
4636 A special exception is made for packages which declare that
4637 they break their own package name or a virtual package which
4638 they provide (see below): this does not count as a real
4643 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4644 version clause; such a <tt>Breaks</tt> is introduced in the
4645 version of an (implicit or explicit) dependency which violates
4646 an assumption or reveals a bug in earlier versions of the broken
4647 package, or which takes over a file from earlier versions of the
4648 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4649 will inform higher-level package management tools that the
4650 broken package must be upgraded before the new one.
4654 If the breaking package also overwrites some files from the
4655 older package, it should use <tt>Replaces</tt> to ensure this
4656 goes smoothly. See <ref id="replaces"> for a full discussion
4657 of taking over files from other packages, including how to
4658 use <tt>Breaks</tt> in those cases.
4662 Many of the cases where <tt>Breaks</tt> should be used were
4663 previously handled with <tt>Conflicts</tt>
4664 because <tt>Breaks</tt> did not yet exist.
4665 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4666 See <ref id="conflicts"> for more information about the
4671 <sect id="conflicts">
4672 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4675 When one binary package declares a conflict with another
4676 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4677 refuse to allow them to be installed on the system at the
4678 same time. This is a stronger restriction than <tt>Breaks</tt>,
4679 which just prevents both packages from being configured at the
4680 same time. Conflicting packages cannot be unpacked on the
4681 system at the same time.
4685 If one package is to be installed, the other must be removed
4686 first. If the package being installed is marked as replacing
4687 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4688 normally be used in this case) the one on the system, or the one
4689 on the system is marked as deselected, or both packages are
4690 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4691 automatically remove the package which is causing the conflict.
4692 Otherwise, it will halt the installation of the new package with
4693 an error. This mechanism is specifically designed to produce an
4694 error when the installed package is <tt>Essential</tt>, but the
4699 A package will not cause a conflict merely because its
4700 configuration files are still installed; it must be at least
4705 A special exception is made for packages which declare a
4706 conflict with their own package name, or with a virtual
4707 package which they provide (see below): this does not
4708 prevent their installation, and allows a package to conflict
4709 with others providing a replacement for it. You use this
4710 feature when you want the package in question to be the only
4711 package providing some feature.
4715 Normally, <tt>Breaks</tt> should be used instead
4716 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4717 stronger restriction on the ordering of package installation or
4718 upgrade and can make it more difficult for the package manager
4719 to find a correct solution to an upgrade or installation
4720 problem. <tt>Breaks</tt> should be used
4722 <item>when moving a file from one package to another (see
4723 <ref id="replaces">),</item>
4724 <item>when splitting a package (a special case of the previous
4726 <item>when the breaking package exposes a bug in or interacts
4727 badly with particular versions of the broken
4730 <tt>Conflicts</tt> should be used
4732 <item>when two packages provide the same file and will
4733 continue to do so,</item>
4734 <item>in conjunction with <tt>Provides</tt> when only one
4735 package providing a given virtual facility may be installed
4736 at a time (see <ref id="virtual">),</item>
4737 <item>in other cases where one must prevent simultaneous
4738 installation of two packages for reasons that are ongoing
4739 (not fixed in a later version of one of the packages) or
4740 that must prevent both packages from being unpacked at the
4741 same time, not just configured.</item>
4743 Be aware that adding <tt>Conflicts</tt> is normally not the best
4744 solution when two packages provide the same files. Depending on
4745 the reason for that conflict, using alternatives or renaming the
4746 files is often a better approach. See, for
4747 example, <ref id="binaries">.
4751 A <tt>Conflicts</tt> entry may have an "earlier than" version
4752 clause if the reason for the conflict is corrected in a later
4753 version of one of the packages. However, normally the presence
4754 of an "earlier than" version clause is a sign
4755 that <tt>Breaks</tt> should have been used instead. An "earlier
4756 than" version clause in <tt>Conflicts</tt>
4757 prevents <prgn>dpkg</prgn> from upgrading or installing the
4758 package which declares such a conflict until the upgrade or
4759 removal of the conflicted-with package has been completed, which
4760 is a strong restriction.
4764 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4768 As well as the names of actual ("concrete") packages, the
4769 package relationship fields <tt>Depends</tt>,
4770 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4771 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4772 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4773 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4774 may mention "virtual packages".
4778 A <em>virtual package</em> is one which appears in the
4779 <tt>Provides</tt> control file field of another package.
4780 The effect is as if the package(s) which provide a
4781 particular virtual package name had been listed by name
4782 everywhere the virtual package name appears. (See also <ref
4787 If there are both concrete and virtual packages of the same
4788 name, then the dependency may be satisfied (or the conflict
4789 caused) by either the concrete package with the name in
4790 question or any other concrete package which provides the
4791 virtual package with the name in question. This is so that,
4792 for example, supposing we have
4793 <example compact="compact">
4796 </example> and someone else releases an enhanced version of
4797 the <tt>bar</tt> package they can say:
4798 <example compact="compact">
4802 and the <tt>bar-plus</tt> package will now also satisfy the
4803 dependency for the <tt>foo</tt> package.
4807 If a relationship field has a version number attached, only real
4808 packages will be considered to see whether the relationship is
4809 satisfied (or the prohibition violated, for a conflict or
4810 breakage). In other words, if a version number is specified,
4811 this is a request to ignore all <tt>Provides</tt> for that
4812 package name and consider only real packages. The package
4813 manager will assume that a package providing that virtual
4814 package is not of the "right" version. A <tt>Provides</tt>
4815 field may not contain version numbers, and the version number of
4816 the concrete package which provides a particular virtual package
4817 will not be considered when considering a dependency on or
4818 conflict with the virtual package name.<footnote>
4819 It is possible that a future release of <prgn>dpkg</prgn> may
4820 add the ability to specify a version number for each virtual
4821 package it provides. This feature is not yet present,
4822 however, and is expected to be used only infrequently.
4827 To specify which of a set of real packages should be the default
4828 to satisfy a particular dependency on a virtual package, list
4829 the real package as an alternative before the virtual one.
4833 If the virtual package represents a facility that can only be
4834 provided by one real package at a time, such as
4835 the <package>mail-transport-agent</package> virtual package that
4836 requires installation of a binary that would conflict with all
4837 other providers of that virtual package (see
4838 <ref id="mail-transport-agents">), all packages providing that
4839 virtual package should also declare a conflict with it
4840 using <tt>Conflicts</tt>. This will ensure that at most one
4841 provider of that virtual package is unpacked or installed at a
4846 <sect id="replaces"><heading>Overwriting files and replacing
4847 packages - <tt>Replaces</tt></heading>
4850 Packages can declare in their control file that they should
4851 overwrite files in certain other packages, or completely
4852 replace other packages. The <tt>Replaces</tt> control file
4853 field has these two distinct purposes.
4856 <sect1><heading>Overwriting files in other packages</heading>
4859 It is usually an error for a package to contain files which
4860 are on the system in another package. However, if the
4861 overwriting package declares that it <tt>Replaces</tt> the one
4862 containing the file being overwritten, then <prgn>dpkg</prgn>
4863 will replace the file from the old package with that from the
4864 new. The file will no longer be listed as "owned" by the old
4865 package and will be taken over by the new package.
4866 Normally, <tt>Breaks</tt> should be used in conjunction
4867 with <tt>Replaces</tt>.<footnote>
4868 To see why <tt>Breaks</tt> is normally needed in addition
4869 to <tt>Replaces</tt>, consider the case of a file in the
4870 package <package>foo</package> being taken over by the
4871 package <package>foo-data</package>.
4872 <tt>Replaces</tt> will allow <package>foo-data</package> to
4873 be installed and take over that file. However,
4874 without <tt>Breaks</tt>, nothing
4875 requires <package>foo</package> to be upgraded to a newer
4876 version that knows it does not include that file and instead
4877 depends on <package>foo-data</package>. Nothing would
4878 prevent the new <package>foo-data</package> package from
4879 being installed and then removed, removing the file that it
4880 took over from <package>foo</package>. After that
4881 operation, the package manager would think the system was in
4882 a consistent state, but the <package>foo</package> package
4883 would be missing one of its files.
4888 For example, if a package <package>foo</package> is split
4889 into <package>foo</package> and <package>foo-data</package>
4890 starting at version 1.2-3, <package>foo-data</package> would
4892 <example compact="compact">
4893 Replaces: foo (<< 1.2-3)
4894 Breaks: foo (<< 1.2-3)
4896 in its control file. The new version of the
4897 package <package>foo</package> would normally have the field
4898 <example compact="compact">
4899 Depends: foo-data (>= 1.2-3)
4901 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4902 the files moved into <package>foo-data</package> are not
4903 required for normal operation).
4907 If a package is completely replaced in this way, so that
4908 <prgn>dpkg</prgn> does not know of any files it still
4909 contains, it is considered to have "disappeared". It will
4910 be marked as not wanted on the system (selected for
4911 removal) and not installed. Any <tt>conffile</tt>s
4912 details noted for the package will be ignored, as they
4913 will have been taken over by the overwriting package. The
4914 package's <prgn>postrm</prgn> script will be run with a
4915 special argument to allow the package to do any final
4916 cleanup required. See <ref id="mscriptsinstact">.
4918 Replaces is a one way relationship. You have to install
4919 the replacing package after the replaced package.
4924 For this usage of <tt>Replaces</tt>, virtual packages (see
4925 <ref id="virtual">) are not considered when looking at a
4926 <tt>Replaces</tt> field. The packages declared as being
4927 replaced must be mentioned by their real names.
4931 This usage of <tt>Replaces</tt> only takes effect when both
4932 packages are at least partially on the system at once. It is
4933 not relevant if the packages conflict unless the conflict has
4938 <sect1><heading>Replacing whole packages, forcing their
4942 Second, <tt>Replaces</tt> allows the packaging system to
4943 resolve which package should be removed when there is a
4944 conflict (see <ref id="conflicts">). This usage only takes
4945 effect when the two packages <em>do</em> conflict, so that the
4946 two usages of this field do not interfere with each other.
4950 In this situation, the package declared as being replaced
4951 can be a virtual package, so for example, all mail
4952 transport agents (MTAs) would have the following fields in
4953 their control files:
4954 <example compact="compact">
4955 Provides: mail-transport-agent
4956 Conflicts: mail-transport-agent
4957 Replaces: mail-transport-agent
4959 ensuring that only one MTA can be installed at any one
4960 time. See <ref id="virtual"> for more information about this
4965 <sect id="sourcebinarydeps">
4966 <heading>Relationships between source and binary packages -
4967 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4968 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4972 Source packages that require certain binary packages to be
4973 installed or absent at the time of building the package
4974 can declare relationships to those binary packages.
4978 This is done using the <tt>Build-Depends</tt>,
4979 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4980 <tt>Build-Conflicts-Indep</tt> control file fields.
4984 Build-dependencies on "build-essential" binary packages can be
4985 omitted. Please see <ref id="pkg-relations"> for more information.
4989 The dependencies and conflicts they define must be satisfied
4990 (as defined earlier for binary packages) in order to invoke
4991 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4993 There is no Build-Depends-Arch; this role is essentially
4994 met with Build-Depends. Anyone building the
4995 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
4996 assumed to be building the whole package, and therefore
4997 installation of all build dependencies is required.
5000 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5001 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5002 not yet know how to check for its existence, and
5003 <tt>binary-arch</tt>. The purpose of the original split
5004 between <tt>Build-Depends</tt> and
5005 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5006 wouldn't need to install extra packages needed only for the
5007 binary-indep targets. But without a build-arch/build-indep
5008 split, this didn't work, since most of the work is done in
5009 the build target, not in the binary target.
5013 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5014 <tt>binary-arch</tt></tag>
5016 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5017 fields must be satisfied when these targets are invoked.
5019 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5020 and <tt>binary-indep</tt></tag>
5022 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5023 <tt>Build-Depends-Indep</tt>, and
5024 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5025 these targets are invoked.
5033 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5036 Packages containing shared libraries must be constructed with
5037 a little care to make sure that the shared library is always
5038 available. This is especially important for packages whose
5039 shared libraries are vitally important, such as the C library
5040 (currently <tt>libc6</tt>).
5044 Packages involving shared libraries should be split up into
5045 several binary packages. This section mostly deals with how
5046 this separation is to be accomplished; rules for files within
5047 the shared library packages are in <ref id="libraries"> instead.
5050 <sect id="sharedlibs-runtime">
5051 <heading>Run-time shared libraries</heading>
5054 The run-time shared library needs to be placed in a package
5055 whose name changes whenever the shared object version
5058 Since it is common place to install several versions of a
5059 package that just provides shared libraries, it is a
5060 good idea that the library package should not
5061 contain any extraneous non-versioned files, unless they
5062 happen to be in versioned directories.</p>
5064 The most common mechanism is to place it in a package
5066 <package><var>libraryname</var><var>soversion</var></package>,
5067 where <file><var>soversion</var></file> is the version number
5068 in the soname of the shared library<footnote>
5069 The soname is the shared object name: it's the thing
5070 that has to match exactly between building an executable
5071 and running it for the dynamic linker to be able run the
5072 program. For example, if the soname of the library is
5073 <file>libfoo.so.6</file>, the library package would be
5074 called <file>libfoo6</file>.
5076 Alternatively, if it would be confusing to directly append
5077 <var>soversion</var> to <var>libraryname</var> (e.g. because
5078 <var>libraryname</var> itself ends in a number), you may use
5079 <package><var>libraryname</var>-<var>soversion</var></package> and
5080 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5085 If you have several shared libraries built from the same
5086 source tree you may lump them all together into a single
5087 shared library package, provided that you change all of
5088 their sonames at once (so that you don't get filename
5089 clashes if you try to install different versions of the
5090 combined shared libraries package).
5094 The package should install the shared libraries under
5095 their normal names. For example, the <package>libgdbm3</package>
5096 package should install <file>libgdbm.so.3.0.0</file> as
5097 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5098 renamed or re-linked by any <prgn>prerm</prgn> or
5099 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5100 of renaming things safely without affecting running programs,
5101 and attempts to interfere with this are likely to lead to
5106 Shared libraries should not be installed executable, since
5107 the dynamic linker does not require this and trying to
5108 execute a shared library usually results in a core dump.
5112 The run-time library package should include the symbolic link that
5113 <prgn>ldconfig</prgn> would create for the shared libraries.
5114 For example, the <package>libgdbm3</package> package should include
5115 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5116 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5117 linker (for example <prgn>ld.so</prgn> or
5118 <prgn>ld-linux.so.*</prgn>) can find the library between the
5119 time that <prgn>dpkg</prgn> installs it and the time that
5120 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5122 The package management system requires the library to be
5123 placed before the symbolic link pointing to it in the
5124 <file>.deb</file> file. This is so that when
5125 <prgn>dpkg</prgn> comes to install the symlink
5126 (overwriting the previous symlink pointing at an older
5127 version of the library), the new shared library is already
5128 in place. In the past, this was achieved by creating the
5129 library in the temporary packaging directory before
5130 creating the symlink. Unfortunately, this was not always
5131 effective, since the building of the tar file in the
5132 <file>.deb</file> depended on the behavior of the underlying
5133 file system. Some file systems (such as reiserfs) reorder
5134 the files so that the order of creation is forgotten.
5135 Since version 1.7.0, <prgn>dpkg</prgn>
5136 reorders the files itself as necessary when building a
5137 package. Thus it is no longer important to concern
5138 oneself with the order of file creation.
5142 <sect1 id="ldconfig">
5143 <heading><tt>ldconfig</tt></heading>
5146 Any package installing shared libraries in one of the default
5147 library directories of the dynamic linker (which are currently
5148 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5149 listed in <file>/etc/ld.so.conf</file><footnote>
5151 <list compact="compact">
5152 <item>/usr/local/lib</item>
5153 <item>/usr/lib/libc5-compat</item>
5154 <item>/lib/libc5-compat</item>
5157 must use <prgn>ldconfig</prgn> to update the shared library
5162 The package maintainer scripts must only call
5163 <prgn>ldconfig</prgn> under these circumstances:
5164 <list compact="compact">
5165 <item>When the <prgn>postinst</prgn> script is run with a
5166 first argument of <tt>configure</tt>, the script must call
5167 <prgn>ldconfig</prgn>, and may optionally invoke
5168 <prgn>ldconfig</prgn> at other times.
5170 <item>When the <prgn>postrm</prgn> script is run with a
5171 first argument of <tt>remove</tt>, the script should call
5172 <prgn>ldconfig</prgn>.
5177 During install or upgrade, the preinst is called before
5178 the new files are installed, so calling "ldconfig" is
5179 pointless. The preinst of an existing package can also be
5180 called if an upgrade fails. However, this happens during
5181 the critical time when a shared libs may exist on-disk
5182 under a temporary name. Thus, it is dangerous and
5183 forbidden by current policy to call "ldconfig" at this
5188 When a package is installed or upgraded, "postinst
5189 configure" runs after the new files are safely on-disk.
5190 Since it is perfectly safe to invoke ldconfig
5191 unconditionally in a postinst, it is OK for a package to
5192 simply put ldconfig in its postinst without checking the
5193 argument. The postinst can also be called to recover from
5194 a failed upgrade. This happens before any new files are
5195 unpacked, so there is no reason to call "ldconfig" at this
5200 For a package that is being removed, prerm is
5201 called with all the files intact, so calling ldconfig is
5202 useless. The other calls to "prerm" happen in the case of
5203 upgrade at a time when all the files of the old package
5204 are on-disk, so again calling "ldconfig" is pointless.
5208 postrm, on the other hand, is called with the "remove"
5209 argument just after the files are removed, so this is
5210 the proper time to call "ldconfig" to notify the system
5211 of the fact that the shared libraries from the package
5212 are removed. The postrm can be called at several other
5213 times. At the time of "postrm purge", "postrm
5214 abort-install", or "postrm abort-upgrade", calling
5215 "ldconfig" is useless because the shared lib files are
5216 not on-disk. However, when "postrm" is invoked with
5217 arguments "upgrade", "failed-upgrade", or "disappear", a
5218 shared lib may exist on-disk under a temporary filename.
5226 <sect id="sharedlibs-support-files">
5227 <heading>Shared library support files</heading>
5230 If your package contains files whose names do not change with
5231 each change in the library shared object version, you must not
5232 put them in the shared library package. Otherwise, several
5233 versions of the shared library cannot be installed at the same
5234 time without filename clashes, making upgrades and transitions
5235 unnecessarily difficult.
5239 It is recommended that supporting files and run-time support
5240 programs that do not need to be invoked manually by users, but
5241 are nevertheless required for the package to function, be placed
5242 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5243 preferably under <file>/usr/lib/</file><var>package-name</var>.
5244 If the program or file is architecture independent, the
5245 recommendation is for it to be placed in a subdirectory of
5246 <file>/usr/share</file> instead, preferably under
5247 <file>/usr/share/</file><var>package-name</var>. Following the
5248 <var>package-name</var> naming convention ensures that the file
5249 names change when the shared object version changes.
5253 Run-time support programs that use the shared library but are
5254 not required for the library to function or files used by the
5255 shared library that can be used by any version of the shared
5256 library package should instead be put in a separate package.
5257 This package might typically be named
5258 <package><var>libraryname</var>-tools</package>; note the
5259 absence of the <var>soversion</var> in the package name.
5263 Files and support programs only useful when compiling software
5264 against the library should be included in the development
5265 package for the library.<footnote>
5266 For example, a <file><var>package-name</var>-config</file>
5267 script or <package>pkg-config</package> configuration files.
5272 <sect id="sharedlibs-static">
5273 <heading>Static libraries</heading>
5276 The static library (<file><var>libraryname.a</var></file>)
5277 is usually provided in addition to the shared version.
5278 It is placed into the development package (see below).
5282 In some cases, it is acceptable for a library to be
5283 available in static form only; these cases include:
5285 <item>libraries for languages whose shared library support
5286 is immature or unstable</item>
5287 <item>libraries whose interfaces are in flux or under
5288 development (commonly the case when the library's
5289 major version number is zero, or where the ABI breaks
5290 across patchlevels)</item>
5291 <item>libraries which are explicitly intended to be
5292 available only in static form by their upstream
5297 <sect id="sharedlibs-dev">
5298 <heading>Development files</heading>
5301 If there are development files associated with a shared library,
5302 the source package needs to generate a binary development package
5303 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5304 or if you prefer only to support one development version at a
5305 time, <package><var>libraryname</var>-dev</package>. Installing
5306 the development package must result in installation of all the
5307 development files necessary for compiling programs against that
5308 shared library.<footnote>
5309 This wording allows the development files to be split into
5310 several packages, such as a separate architecture-independent
5311 <package><var>libraryname</var>-headers</package>, provided that
5312 the development package depends on all the required additional
5318 In case several development versions of a library exist, you may
5319 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5320 <ref id="conflicts">) to ensure that the user only installs one
5321 development version at a time (as different development versions are
5322 likely to have the same header files in them, which would cause a
5323 filename clash if both were installed).
5327 The development package should contain a symlink for the associated
5328 shared library without a version number. For example, the
5329 <package>libgdbm-dev</package> package should include a symlink
5330 from <file>/usr/lib/libgdbm.so</file> to
5331 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5332 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5333 <file>libgdbm.so</file> when compiling dynamically.
5337 <sect id="sharedlibs-intradeps">
5338 <heading>Dependencies between the packages of the same library</heading>
5341 Typically the development version should have an exact
5342 version dependency on the runtime library, to make sure that
5343 compilation and linking happens correctly. The
5344 <tt>${binary:Version}</tt> substitution variable can be
5345 useful for this purpose.
5347 Previously, <tt>${Source-Version}</tt> was used, but its name
5348 was confusing and it has been deprecated since dpkg 1.13.19.
5353 <sect id="sharedlibs-shlibdeps">
5354 <heading>Dependencies between the library and other packages -
5355 the <tt>shlibs</tt> system</heading>
5358 If a package contains a binary or library which links to a
5359 shared library, we must ensure that when the package is
5360 installed on the system, all of the libraries needed are
5361 also installed. This requirement led to the creation of the
5362 <tt>shlibs</tt> system, which is very simple in its design:
5363 any package which <em>provides</em> a shared library also
5364 provides information on the package dependencies required to
5365 ensure the presence of this library, and any package which
5366 <em>uses</em> a shared library uses this information to
5367 determine the dependencies it requires. The files which
5368 contain the mapping from shared libraries to the necessary
5369 dependency information are called <file>shlibs</file> files.
5373 Thus, when a package is built which contains any shared
5374 libraries, it must provide a <file>shlibs</file> file for other
5375 packages to use, and when a package is built which contains
5376 any shared libraries or compiled binaries, it must run
5377 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5378 on these to determine the libraries used and hence the
5379 dependencies needed by this package.<footnote>
5381 In the past, the shared libraries linked to were
5382 determined by calling <prgn>ldd</prgn>, but now
5383 <prgn>objdump</prgn> is used to do this. The only
5384 change this makes to package building is that
5385 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5386 libraries, whereas in the past this was unnecessary.
5387 The rest of this footnote explains the advantage that
5392 We say that a binary <tt>foo</tt> <em>directly</em> uses
5393 a library <tt>libbar</tt> if it is explicitly linked
5394 with that library (that is, it uses the flag
5395 <tt>-lbar</tt> during the linking stage). Other
5396 libraries that are needed by <tt>libbar</tt> are linked
5397 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5398 linker will load them automatically when it loads
5399 <tt>libbar</tt>. A package should depend on
5400 the libraries it directly uses, and the dependencies for
5401 those libraries should automatically pull in the other
5406 Unfortunately, the <prgn>ldd</prgn> program shows both
5407 the directly and indirectly used libraries, meaning that
5408 the dependencies determined included both direct and
5409 indirect dependencies. The use of <prgn>objdump</prgn>
5410 avoids this problem by determining only the directly
5415 A good example of where this helps is the following. We
5416 could update <tt>libimlib</tt> with a new version that
5417 supports a new graphics format called dgf (but retaining
5418 the same major version number). If we used the old
5419 <prgn>ldd</prgn> method, every package that uses
5420 <tt>libimlib</tt> would need to be recompiled so it
5421 would also depend on <tt>libdgf</tt> or it wouldn't run
5422 due to missing symbols. However with the new system,
5423 packages using <tt>libimlib</tt> can rely on
5424 <tt>libimlib</tt> itself having the dependency on
5425 <tt>libdgf</tt> and so they would not need rebuilding.
5431 In the following sections, we will first describe where the
5432 various <tt>shlibs</tt> files are to be found, then how to
5433 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5434 file format and how to create them if your package contains a
5439 <heading>The <tt>shlibs</tt> files present on the system</heading>
5442 There are several places where <tt>shlibs</tt> files are
5443 found. The following list gives them in the order in which
5445 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5446 (The first one which gives the required information is used.)
5452 <p><file>debian/shlibs.local</file></p>
5455 This lists overrides for this package. Its use is
5456 described below (see <ref id="shlibslocal">).
5461 <p><file>/etc/dpkg/shlibs.override</file></p>
5464 This lists global overrides. This list is normally
5465 empty. It is maintained by the local system
5471 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5474 When packages are being built, any
5475 <file>debian/shlibs</file> files are copied into the
5476 control file area of the temporary build directory and
5477 given the name <file>shlibs</file>. These files give
5478 details of any shared libraries included in the
5480 An example may help here. Let us say that the
5481 source package <tt>foo</tt> generates two binary
5482 packages, <tt>libfoo2</tt> and
5483 <tt>foo-runtime</tt>. When building the binary
5484 packages, the two packages are created in the
5485 directories <file>debian/libfoo2</file> and
5486 <file>debian/foo-runtime</file> respectively.
5487 (<file>debian/tmp</file> could be used instead of one
5488 of these.) Since <tt>libfoo2</tt> provides the
5489 <tt>libfoo</tt> shared library, it will require a
5490 <tt>shlibs</tt> file, which will be installed in
5491 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5493 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5494 when <prgn>dpkg-shlibdeps</prgn> is run on the
5496 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5498 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5499 determine whether <tt>foo-prog</tt>'s library
5500 dependencies are satisfied by any of the libraries
5501 provided by <tt>libfoo2</tt>. For this reason,
5502 <prgn>dpkg-shlibdeps</prgn> must only be run once
5503 all of the individual binary packages'
5504 <tt>shlibs</tt> files have been installed into the
5511 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5514 These are the <file>shlibs</file> files corresponding to
5515 all of the packages installed on the system, and are
5516 maintained by the relevant package maintainers.
5521 <p><file>/etc/dpkg/shlibs.default</file></p>
5524 This file lists any shared libraries whose packages
5525 have failed to provide correct <file>shlibs</file> files.
5526 It was used when the <file>shlibs</file> setup was first
5527 introduced, but it is now normally empty. It is
5528 maintained by the <tt>dpkg</tt> maintainer.
5536 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5537 <file>shlibs</file> files</heading>
5541 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5542 into your <file>debian/rules</file> file. If your package
5543 contains only compiled binaries and libraries (but no scripts),
5544 you can use a command such as:
5545 <example compact="compact">
5546 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5547 debian/tmp/usr/lib/*
5549 Otherwise, you will need to explicitly list the compiled
5550 binaries and libraries.<footnote>
5551 If you are using <tt>debhelper</tt>, the
5552 <prgn>dh_shlibdeps</prgn> program will do this work for
5553 you. It will also correctly handle multi-binary
5559 This command puts the dependency information into the
5560 <file>debian/substvars</file> file, which is then used by
5561 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5562 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5563 field in the control file for this to work.
5567 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5568 done. If it does complain you might need to create your own
5569 <file>debian/shlibs.local</file> file, as explained below (see
5570 <ref id="shlibslocal">).
5574 If you have multiple binary packages, you will need to call
5575 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5576 compiled libraries or binaries. In such a case, you will
5577 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5578 utilities to specify a different <file>substvars</file> file.
5582 If you are creating a udeb for use in the Debian Installer,
5583 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5584 should use the dependency line of type <tt>udeb</tt> by
5585 adding the <tt>-tudeb</tt> option<footnote>
5586 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5587 will automatically add this option if it knows it is
5589 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5590 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5591 fall back to the regular dependency line.
5595 For more details on dpkg-shlibdeps, please see
5596 <ref id="pkg-dpkg-shlibdeps"> and
5597 <manref name="dpkg-shlibdeps" section="1">.
5602 <heading>The <file>shlibs</file> File Format</heading>
5605 Each <file>shlibs</file> file has the same format. Lines
5606 beginning with <tt>#</tt> are considered to be comments and
5607 are ignored. Each line is of the form:
5608 <example compact="compact">
5609 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5614 We will explain this by reference to the example of the
5615 <tt>zlib1g</tt> package, which (at the time of writing)
5616 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5620 <var>type</var> is an optional element that indicates the type
5621 of package for which the line is valid. The only type currently
5622 in use is <tt>udeb</tt>. The colon and space after the type are
5627 <var>library-name</var> is the name of the shared library,
5628 in this case <tt>libz</tt>. (This must match the name part
5629 of the soname, see below.)
5633 <var>soname-version</var> is the version part of the soname of
5634 the library. The soname is the thing that must exactly match
5635 for the library to be recognized by the dynamic linker, and is
5637 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5638 example, <tt>libz.so.1</tt>.<footnote>
5639 This can be determined using the command
5640 <example compact="compact">
5641 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5644 The version part is the part which comes after
5645 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5649 <var>dependencies</var> has the same syntax as a dependency
5650 field in a binary package control file. It should give
5651 details of which packages are required to satisfy a binary
5652 built against the version of the library contained in the
5653 package. See <ref id="depsyntax"> for details.
5657 In our example, if the first version of the <tt>zlib1g</tt>
5658 package which contained a minor number of at least
5659 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5660 <tt>shlibs</tt> entry for this library could say:
5661 <example compact="compact">
5662 libz 1 zlib1g (>= 1:1.1.3)
5664 The version-specific dependency is to avoid warnings from
5665 the dynamic linker about using older shared libraries with
5670 As zlib1g also provides a udeb containing the shared library,
5671 there would also be a second line:
5672 <example compact="compact">
5673 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5679 <heading>Providing a <file>shlibs</file> file</heading>
5682 If your package provides a shared library, you need to create
5683 a <file>shlibs</file> file following the format described above.
5684 It is usual to call this file <file>debian/shlibs</file> (but if
5685 you have multiple binary packages, you might want to call it
5686 <file>debian/shlibs.<var>package</var></file> instead). Then
5687 let <file>debian/rules</file> install it in the control area:
5688 <example compact="compact">
5689 install -m644 debian/shlibs debian/tmp/DEBIAN
5691 or, in the case of a multi-binary package:
5692 <example compact="compact">
5693 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5695 An alternative way of doing this is to create the
5696 <file>shlibs</file> file in the control area directly from
5697 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5698 file at all,<footnote>
5699 This is what <prgn>dh_makeshlibs</prgn> in the
5700 <tt>debhelper</tt> suite does. If your package also has a udeb
5701 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5702 automatically generate the <tt>udeb:</tt> lines if you specify
5703 the name of the udeb with the <tt>--add-udeb</tt> option.
5705 since the <file>debian/shlibs</file> file itself is ignored by
5706 <prgn>dpkg-shlibdeps</prgn>.
5710 As <prgn>dpkg-shlibdeps</prgn> reads the
5711 <file>DEBIAN/shlibs</file> files in all of the binary packages
5712 being built from this source package, all of the
5713 <file>DEBIAN/shlibs</file> files should be installed before
5714 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5719 <sect1 id="shlibslocal">
5720 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5723 This file is intended only as a <em>temporary</em> fix if
5724 your binaries or libraries depend on a library whose package
5725 does not yet provide a correct <file>shlibs</file> file.
5729 We will assume that you are trying to package a binary
5730 <tt>foo</tt>. When you try running
5731 <prgn>dpkg-shlibdeps</prgn> you get the following error
5732 message (<tt>-O</tt> displays the dependency information on
5733 <tt>stdout</tt> instead of writing it to
5734 <tt>debian/substvars</tt>, and the lines have been wrapped
5735 for ease of reading):
5736 <example compact="compact">
5737 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5738 dpkg-shlibdeps: warning: unable to find dependency
5739 information for shared library libbar (soname 1,
5740 path /usr/lib/libbar.so.1, dependency field Depends)
5741 shlibs:Depends=libc6 (>= 2.2.2-2)
5743 You can then run <prgn>ldd</prgn> on the binary to find the
5744 full location of the library concerned:
5745 <example compact="compact">
5747 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5748 libc.so.6 => /lib/libc.so.6 (0x40032000)
5749 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5751 So the <prgn>foo</prgn> binary depends on the
5752 <prgn>libbar</prgn> shared library, but no package seems to
5753 provide a <file>*.shlibs</file> file handling
5754 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5755 determine the package responsible:
5756 <example compact="compact">
5757 $ dpkg -S /usr/lib/libbar.so.1
5758 bar1: /usr/lib/libbar.so.1
5759 $ dpkg -s bar1 | grep Version
5762 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5763 is the one we are using. Now we can file a bug against the
5764 <tt>bar1</tt> package and create our own
5765 <file>debian/shlibs.local</file> to locally fix the problem.
5766 Including the following line into your
5767 <file>debian/shlibs.local</file> file:
5768 <example compact="compact">
5769 libbar 1 bar1 (>= 1.0-1)
5771 should allow the package build to work.
5775 As soon as the maintainer of <tt>bar1</tt> provides a
5776 correct <file>shlibs</file> file, you should remove this line
5777 from your <file>debian/shlibs.local</file> file. (You should
5778 probably also then have a versioned <tt>Build-Depends</tt>
5779 on <tt>bar1</tt> to help ensure that others do not have the
5780 same problem building your package.)
5789 <chapt id="opersys"><heading>The Operating System</heading>
5792 <heading>File system hierarchy</heading>
5796 <heading>File System Structure</heading>
5799 The location of all installed files and directories must
5800 comply with the Filesystem Hierarchy Standard (FHS),
5801 version 2.3, with the exceptions noted below, and except
5802 where doing so would violate other terms of Debian
5803 Policy. The following exceptions to the FHS apply:
5808 The optional rules related to user specific
5809 configuration files for applications are stored in
5810 the user's home directory are relaxed. It is
5811 recommended that such files start with the
5812 '<tt>.</tt>' character (a "dot file"), and if an
5813 application needs to create more than one dot file
5814 then the preferred placement is in a subdirectory
5815 with a name starting with a '.' character, (a "dot
5816 directory"). In this case it is recommended the
5817 configuration files not start with the '.'
5823 The requirement for amd64 to use <file>/lib64</file>
5824 for 64 bit binaries is removed.
5829 The requirement for object files, internal binaries, and
5830 libraries, including <file>libc.so.*</file>, to be located
5831 directly under <file>/lib{,32}</file> and
5832 <file>/usr/lib{,32}</file> is amended, permitting files
5833 to instead be installed to
5834 <file>/lib/<var>triplet</var></file> and
5835 <file>/usr/lib/<var>triplet</var></file>, where
5836 <tt><var>triplet</var></tt> is the value returned by
5837 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5838 architecture of the package. Packages may <em>not</em>
5839 install files to any <var>triplet</var> path other
5840 than the one matching the architecture of that package;
5841 for instance, an <tt>Architecture: amd64</tt> package
5842 containing 32-bit x86 libraries may not install these
5843 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5845 This is necessary in order to reserve the directories for
5846 use in cross-installation of library packages from other
5847 architectures, as part of the planned deployment of
5852 Applications may also use a single subdirectory under
5853 <file>/usr/lib/<var>triplet</var></file>.
5856 The execution time linker/loader, ld*, must still be made
5857 available in the existing location under /lib or /lib64
5858 since this is part of the ELF ABI for the architecture.
5863 The requirement that
5864 <file>/usr/local/share/man</file> be "synonymous"
5865 with <file>/usr/local/man</file> is relaxed to a
5870 The requirement that windowmanagers with a single
5871 configuration file call it <file>system.*wmrc</file>
5872 is removed, as is the restriction that the window
5873 manager subdirectory be named identically to the
5874 window manager name itself.
5879 The requirement that boot manager configuration
5880 files live in <file>/etc</file>, or at least are
5881 symlinked there, is relaxed to a recommendation.
5886 The following directories in the root filesystem are
5887 additionally allowed: <file>/sys</file> and
5888 <file>/selinux</file>. <footnote>These directories
5889 are used as mount points to mount virtual filesystems
5890 to get access to kernel information.</footnote>
5897 The version of this document referred here can be
5898 found in the <tt>debian-policy</tt> package or on <url
5899 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5900 name="FHS (Debian copy)"> alongside this manual (or, if
5901 you have the <package>debian-policy</package> installed,
5903 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5904 (local copy)">). The
5905 latest version, which may be a more recent version, may
5907 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5908 Specific questions about following the standard may be
5909 asked on the <tt>debian-devel</tt> mailing list, or
5910 referred to the FHS mailing list (see the
5911 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5917 <heading>Site-specific programs</heading>
5920 As mandated by the FHS, packages must not place any
5921 files in <file>/usr/local</file>, either by putting them in
5922 the file system archive to be unpacked by <prgn>dpkg</prgn>
5923 or by manipulating them in their maintainer scripts.
5927 However, the package may create empty directories below
5928 <file>/usr/local</file> so that the system administrator knows
5929 where to place site-specific files. These are not
5930 directories <em>in</em> <file>/usr/local</file>, but are
5931 children of directories in <file>/usr/local</file>. These
5932 directories (<file>/usr/local/*/dir/</file>)
5933 should be removed on package removal if they are
5938 Note that this applies only to
5939 directories <em>below</em> <file>/usr/local</file>,
5940 not <em>in</em> <file>/usr/local</file>. Packages must
5941 not create sub-directories in the
5942 directory <file>/usr/local</file> itself, except those
5943 listed in FHS, section 4.5. However, you may create
5944 directories below them as you wish. You must not remove
5945 any of the directories listed in 4.5, even if you created
5950 Since <file>/usr/local</file> can be mounted read-only from a
5951 remote server, these directories must be created and
5952 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5953 maintainer scripts and not be included in the
5954 <file>.deb</file> archive. These scripts must not fail if
5955 either of these operations fail.
5959 For example, the <tt>emacsen-common</tt> package could
5960 contain something like
5961 <example compact="compact">
5962 if [ ! -e /usr/local/share/emacs ]
5964 if mkdir /usr/local/share/emacs 2>/dev/null
5966 chown root:staff /usr/local/share/emacs
5967 chmod 2775 /usr/local/share/emacs
5971 in its <prgn>postinst</prgn> script, and
5972 <example compact="compact">
5973 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5974 rmdir /usr/local/share/emacs 2>/dev/null || true
5976 in the <prgn>prerm</prgn> script. (Note that this form is
5977 used to ensure that if the script is interrupted, the
5978 directory <file>/usr/local/share/emacs</file> will still be
5983 If you do create a directory in <file>/usr/local</file> for
5984 local additions to a package, you should ensure that
5985 settings in <file>/usr/local</file> take precedence over the
5986 equivalents in <file>/usr</file>.
5990 However, because <file>/usr/local</file> and its contents are
5991 for exclusive use of the local administrator, a package
5992 must not rely on the presence or absence of files or
5993 directories in <file>/usr/local</file> for normal operation.
5997 The <file>/usr/local</file> directory itself and all the
5998 subdirectories created by the package should (by default) have
5999 permissions 2775 (group-writable and set-group-id) and be
6000 owned by <tt>root:staff</tt>.
6005 <heading>The system-wide mail directory</heading>
6007 The system-wide mail directory
6008 is <file>/var/mail</file>. This directory is part of the
6009 base system and should not be owned by any particular mail
6010 agents. The use of the old
6011 location <file>/var/spool/mail</file> is deprecated, even
6012 though the spool may still be physically located there.
6018 <heading>Users and groups</heading>
6021 <heading>Introduction</heading>
6023 The Debian system can be configured to use either plain or
6028 Some user ids (UIDs) and group ids (GIDs) are reserved
6029 globally for use by certain packages. Because some
6030 packages need to include files which are owned by these
6031 users or groups, or need the ids compiled into binaries,
6032 these ids must be used on any Debian system only for the
6033 purpose for which they are allocated. This is a serious
6034 restriction, and we should avoid getting in the way of
6035 local administration policies. In particular, many sites
6036 allocate users and/or local system groups starting at 100.
6040 Apart from this we should have dynamically allocated ids,
6041 which should by default be arranged in some sensible
6042 order, but the behavior should be configurable.
6046 Packages other than <tt>base-passwd</tt> must not modify
6047 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6048 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6053 <heading>UID and GID classes</heading>
6055 The UID and GID numbers are divided into classes as
6061 Globally allocated by the Debian project, the same
6062 on every Debian system. These ids will appear in
6063 the <file>passwd</file> and <file>group</file> files of all
6064 Debian systems, new ids in this range being added
6065 automatically as the <tt>base-passwd</tt> package is
6070 Packages which need a single statically allocated
6071 uid or gid should use one of these; their
6072 maintainers should ask the <tt>base-passwd</tt>
6080 Dynamically allocated system users and groups.
6081 Packages which need a user or group, but can have
6082 this user or group allocated dynamically and
6083 differently on each system, should use <tt>adduser
6084 --system</tt> to create the group and/or user.
6085 <prgn>adduser</prgn> will check for the existence of
6086 the user or group, and if necessary choose an unused
6087 id based on the ranges specified in
6088 <file>adduser.conf</file>.
6092 <tag>1000-59999:</tag>
6095 Dynamically allocated user accounts. By default
6096 <prgn>adduser</prgn> will choose UIDs and GIDs for
6097 user accounts in this range, though
6098 <file>adduser.conf</file> may be used to modify this
6103 <tag>60000-64999:</tag>
6106 Globally allocated by the Debian project, but only
6107 created on demand. The ids are allocated centrally
6108 and statically, but the actual accounts are only
6109 created on users' systems on demand.
6113 These ids are for packages which are obscure or
6114 which require many statically-allocated ids. These
6115 packages should check for and create the accounts in
6116 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6117 <prgn>adduser</prgn> if it has this facility) if
6118 necessary. Packages which are likely to require
6119 further allocations should have a "hole" left after
6120 them in the allocation, to give them room to
6125 <tag>65000-65533:</tag>
6133 User <tt>nobody</tt>. The corresponding gid refers
6134 to the group <tt>nogroup</tt>.
6141 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6142 not</em> be used, because it is the error return
6151 <sect id="sysvinit">
6152 <heading>System run levels and <file>init.d</file> scripts</heading>
6154 <sect1 id="/etc/init.d">
6155 <heading>Introduction</heading>
6158 The <file>/etc/init.d</file> directory contains the scripts
6159 executed by <prgn>init</prgn> at boot time and when the
6160 init state (or "runlevel") is changed (see <manref
6161 name="init" section="8">).
6165 There are at least two different, yet functionally
6166 equivalent, ways of handling these scripts. For the sake
6167 of simplicity, this document describes only the symbolic
6168 link method. However, it must not be assumed by maintainer
6169 scripts that this method is being used, and any automated
6170 manipulation of the various runlevel behaviors by
6171 maintainer scripts must be performed using
6172 <prgn>update-rc.d</prgn> as described below and not by
6173 manually installing or removing symlinks. For information
6174 on the implementation details of the other method,
6175 implemented in the <tt>file-rc</tt> package, please refer
6176 to the documentation of that package.
6180 These scripts are referenced by symbolic links in the
6181 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6182 runlevels, <prgn>init</prgn> looks in the directory
6183 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6184 execute, where <tt><var>n</var></tt> is the runlevel that
6185 is being changed to, or <tt>S</tt> for the boot-up
6190 The names of the links all have the form
6191 <file>S<var>mm</var><var>script</var></file> or
6192 <file>K<var>mm</var><var>script</var></file> where
6193 <var>mm</var> is a two-digit number and <var>script</var>
6194 is the name of the script (this should be the same as the
6195 name of the actual script in <file>/etc/init.d</file>).
6199 When <prgn>init</prgn> changes runlevel first the targets
6200 of the links whose names start with a <tt>K</tt> are
6201 executed, each with the single argument <tt>stop</tt>,
6202 followed by the scripts prefixed with an <tt>S</tt>, each
6203 with the single argument <tt>start</tt>. (The links are
6204 those in the <file>/etc/rc<var>n</var>.d</file> directory
6205 corresponding to the new runlevel.) The <tt>K</tt> links
6206 are responsible for killing services and the <tt>S</tt>
6207 link for starting services upon entering the runlevel.
6211 For example, if we are changing from runlevel 2 to
6212 runlevel 3, init will first execute all of the <tt>K</tt>
6213 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6214 all of the <tt>S</tt> prefixed scripts in that directory.
6215 The links starting with <tt>K</tt> will cause the
6216 referred-to file to be executed with an argument of
6217 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6222 The two-digit number <var>mm</var> is used to determine
6223 the order in which to run the scripts: low-numbered links
6224 have their scripts run first. For example, the
6225 <tt>K20</tt> scripts will be executed before the
6226 <tt>K30</tt> scripts. This is used when a certain service
6227 must be started before another. For example, the name
6228 server <prgn>bind</prgn> might need to be started before
6229 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6230 can set up its access lists. In this case, the script
6231 that starts <prgn>bind</prgn> would have a lower number
6232 than the script that starts <prgn>inn</prgn> so that it
6234 <example compact="compact">
6241 The two runlevels 0 (halt) and 6 (reboot) are slightly
6242 different. In these runlevels, the links with an
6243 <tt>S</tt> prefix are still called after those with a
6244 <tt>K</tt> prefix, but they too are called with the single
6245 argument <tt>stop</tt>.
6249 <sect1 id="writing-init">
6250 <heading>Writing the scripts</heading>
6253 Packages that include daemons for system services should
6254 place scripts in <file>/etc/init.d</file> to start or stop
6255 services at boot time or during a change of runlevel.
6256 These scripts should be named
6257 <file>/etc/init.d/<var>package</var></file>, and they should
6258 accept one argument, saying what to do:
6261 <tag><tt>start</tt></tag>
6262 <item>start the service,</item>
6264 <tag><tt>stop</tt></tag>
6265 <item>stop the service,</item>
6267 <tag><tt>restart</tt></tag>
6268 <item>stop and restart the service if it's already running,
6269 otherwise start the service</item>
6271 <tag><tt>reload</tt></tag>
6272 <item><p>cause the configuration of the service to be
6273 reloaded without actually stopping and restarting
6276 <tag><tt>force-reload</tt></tag>
6277 <item>cause the configuration to be reloaded if the
6278 service supports this, otherwise restart the
6282 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6283 <tt>force-reload</tt> options should be supported by all
6284 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6289 The <file>init.d</file> scripts must ensure that they will
6290 behave sensibly (i.e., returning success and not starting
6291 multiple copies of a service) if invoked with <tt>start</tt>
6292 when the service is already running, or with <tt>stop</tt>
6293 when it isn't, and that they don't kill unfortunately-named
6294 user processes. The best way to achieve this is usually to
6295 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6300 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6301 scripts. Writing correct <file>init.d</file> scripts requires
6302 accepting various error exit statuses when daemons are already
6303 running or already stopped without aborting
6304 the <file>init.d</file> script, and common <file>init.d</file>
6305 function libraries are not safe to call with <tt>set -e</tt>
6307 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6308 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6309 in effect and echoing status messages to the console fails,
6311 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6312 to not use <tt>set -e</tt> and instead check the result of
6313 each command separately.
6317 If a service reloads its configuration automatically (as
6318 in the case of <prgn>cron</prgn>, for example), the
6319 <tt>reload</tt> option of the <file>init.d</file> script
6320 should behave as if the configuration has been reloaded
6325 The <file>/etc/init.d</file> scripts must be treated as
6326 configuration files, either (if they are present in the
6327 package, that is, in the .deb file) by marking them as
6328 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6329 by managing them correctly in the maintainer scripts (see
6330 <ref id="config-files">). This is important since we want
6331 to give the local system administrator the chance to adapt
6332 the scripts to the local system, e.g., to disable a
6333 service without de-installing the package, or to specify
6334 some special command line options when starting a service,
6335 while making sure their changes aren't lost during the next
6340 These scripts should not fail obscurely when the
6341 configuration files remain but the package has been
6342 removed, as configuration files remain on the system after
6343 the package has been removed. Only when <prgn>dpkg</prgn>
6344 is executed with the <tt>--purge</tt> option will
6345 configuration files be removed. In particular, as the
6346 <file>/etc/init.d/<var>package</var></file> script itself is
6347 usually a <tt>conffile</tt>, it will remain on the system
6348 if the package is removed but not purged. Therefore, you
6349 should include a <tt>test</tt> statement at the top of the
6351 <example compact="compact">
6352 test -f <var>program-executed-later-in-script</var> || exit 0
6357 Often there are some variables in the <file>init.d</file>
6358 scripts whose values control the behavior of the scripts,
6359 and which a system administrator is likely to want to
6360 change. As the scripts themselves are frequently
6361 <tt>conffile</tt>s, modifying them requires that the
6362 administrator merge in their changes each time the package
6363 is upgraded and the <tt>conffile</tt> changes. To ease
6364 the burden on the system administrator, such configurable
6365 values should not be placed directly in the script.
6366 Instead, they should be placed in a file in
6367 <file>/etc/default</file>, which typically will have the same
6368 base name as the <file>init.d</file> script. This extra file
6369 should be sourced by the script when the script runs. It
6370 must contain only variable settings and comments in SUSv3
6371 <prgn>sh</prgn> format. It may either be a
6372 <tt>conffile</tt> or a configuration file maintained by
6373 the package maintainer scripts. See <ref id="config-files">
6378 To ensure that vital configurable values are always
6379 available, the <file>init.d</file> script should set default
6380 values for each of the shell variables it uses, either
6381 before sourcing the <file>/etc/default/</file> file or
6382 afterwards using something like the <tt>:
6383 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6384 script must behave sensibly and not fail if the
6385 <file>/etc/default</file> file is deleted.
6389 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6390 as temporary filesystems<footnote>
6391 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6392 options in <file>/etc/default/rcS</file>.
6393 </footnote>, so the <file>init.d</file> scripts must handle this
6394 correctly. This will typically amount to creating any required
6395 subdirectories dynamically when the <file>init.d</file> script
6396 is run, rather than including them in the package and relying on
6397 <prgn>dpkg</prgn> to create them.
6402 <heading>Interfacing with the initscript system</heading>
6405 Maintainers should use the abstraction layer provided by
6406 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6407 programs to deal with initscripts in their packages'
6408 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6409 and <prgn>postrm</prgn>.
6413 Directly managing the /etc/rc?.d links and directly
6414 invoking the <file>/etc/init.d/</file> initscripts should
6415 be done only by packages providing the initscript
6416 subsystem (such as <prgn>sysv-rc</prgn> and
6417 <prgn>file-rc</prgn>).
6421 <heading>Managing the links</heading>
6424 The program <prgn>update-rc.d</prgn> is provided for
6425 package maintainers to arrange for the proper creation and
6426 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6427 or their functional equivalent if another method is being
6428 used. This may be used by maintainers in their packages'
6429 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6433 You must not include any <file>/etc/rc<var>n</var>.d</file>
6434 symbolic links in the actual archive or manually create or
6435 remove the symbolic links in maintainer scripts; you must
6436 use the <prgn>update-rc.d</prgn> program instead. (The
6437 former will fail if an alternative method of maintaining
6438 runlevel information is being used.) You must not include
6439 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6440 in the archive either. (Only the <tt>sysvinit</tt>
6445 By default <prgn>update-rc.d</prgn> will start services in
6446 each of the multi-user state runlevels (2, 3, 4, and 5)
6447 and stop them in the halt runlevel (0), the single-user
6448 runlevel (1) and the reboot runlevel (6). The system
6449 administrator will have the opportunity to customize
6450 runlevels by simply adding, moving, or removing the
6451 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6452 symbolic links are being used, or by modifying
6453 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6458 To get the default behavior for your package, put in your
6459 <prgn>postinst</prgn> script
6460 <example compact="compact">
6461 update-rc.d <var>package</var> defaults
6463 and in your <prgn>postrm</prgn>
6464 <example compact="compact">
6465 if [ "$1" = purge ]; then
6466 update-rc.d <var>package</var> remove
6468 </example>. Note that if your package changes runlevels
6469 or priority, you may have to remove and recreate the links,
6470 since otherwise the old links may persist. Refer to the
6471 documentation of <prgn>update-rc.d</prgn>.
6475 This will use a default sequence number of 20. If it does
6476 not matter when or in which order the <file>init.d</file>
6477 script is run, use this default. If it does, then you
6478 should talk to the maintainer of the <prgn>sysvinit</prgn>
6479 package or post to <tt>debian-devel</tt>, and they will
6480 help you choose a number.
6484 For more information about using <tt>update-rc.d</tt>,
6485 please consult its man page <manref name="update-rc.d"
6491 <heading>Running initscripts</heading>
6493 The program <prgn>invoke-rc.d</prgn> is provided to make
6494 it easier for package maintainers to properly invoke an
6495 initscript, obeying runlevel and other locally-defined
6496 constraints that might limit a package's right to start,
6497 stop and otherwise manage services. This program may be
6498 used by maintainers in their packages' scripts.
6502 The package maintainer scripts must use
6503 <prgn>invoke-rc.d</prgn> to invoke the
6504 <file>/etc/init.d/*</file> initscripts, instead of
6505 calling them directly.
6509 By default, <prgn>invoke-rc.d</prgn> will pass any
6510 action requests (start, stop, reload, restart...) to the
6511 <file>/etc/init.d</file> script, filtering out requests
6512 to start or restart a service out of its intended
6517 Most packages will simply need to change:
6518 <example compact="compact">/etc/init.d/<package>
6519 <action></example> in their <prgn>postinst</prgn>
6520 and <prgn>prerm</prgn> scripts to:
6521 <example compact="compact">
6522 if which invoke-rc.d >/dev/null 2>&1; then
6523 invoke-rc.d <var>package</var> <action>
6525 /etc/init.d/<var>package</var> <action>
6531 A package should register its initscript services using
6532 <prgn>update-rc.d</prgn> before it tries to invoke them
6533 using <prgn>invoke-rc.d</prgn>. Invocation of
6534 unregistered services may fail.
6538 For more information about using
6539 <prgn>invoke-rc.d</prgn>, please consult its man page
6540 <manref name="invoke-rc.d" section="8">.
6546 <heading>Boot-time initialization</heading>
6549 There used to be another directory, <file>/etc/rc.boot</file>,
6550 which contained scripts which were run once per machine
6551 boot. This has been deprecated in favour of links from
6552 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6553 described in <ref id="/etc/init.d">. Packages must not
6554 place files in <file>/etc/rc.boot</file>.
6559 <heading>Example</heading>
6562 An example on which you can base your
6563 <file>/etc/init.d</file> scripts is found in
6564 <file>/etc/init.d/skeleton</file>.
6571 <heading>Console messages from <file>init.d</file> scripts</heading>
6574 This section describes the formats to be used for messages
6575 written to standard output by the <file>/etc/init.d</file>
6576 scripts. The intent is to improve the consistency of
6577 Debian's startup and shutdown look and feel. For this
6578 reason, please look very carefully at the details. We want
6579 the messages to have the same format in terms of wording,
6580 spaces, punctuation and case of letters.
6584 Here is a list of overall rules that should be used for
6585 messages generated by <file>/etc/init.d</file> scripts.
6591 The message should fit in one line (fewer than 80
6592 characters), start with a capital letter and end with
6593 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6597 If the script is performing some time consuming task in
6598 the background (not merely starting or stopping a
6599 program, for instance), an ellipsis (three dots:
6600 <tt>...</tt>) should be output to the screen, with no
6601 leading or tailing whitespace or line feeds.
6605 The messages should appear as if the computer is telling
6606 the user what it is doing (politely :-), but should not
6607 mention "it" directly. For example, instead of:
6608 <example compact="compact">
6609 I'm starting network daemons: nfsd mountd.
6611 the message should say
6612 <example compact="compact">
6613 Starting network daemons: nfsd mountd.
6620 <tt>init.d</tt> script should use the following standard
6621 message formats for the situations enumerated below.
6627 <p>When daemons are started</p>
6630 If the script starts one or more daemons, the output
6631 should look like this (a single line, no leading
6633 <example compact="compact">
6634 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6636 The <var>description</var> should describe the
6637 subsystem the daemon or set of daemons are part of,
6638 while <var>daemon-1</var> up to <var>daemon-n</var>
6639 denote each daemon's name (typically the file name of
6644 For example, the output of <file>/etc/init.d/lpd</file>
6646 <example compact="compact">
6647 Starting printer spooler: lpd.
6652 This can be achieved by saying
6653 <example compact="compact">
6654 echo -n "Starting printer spooler: lpd"
6655 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6658 in the script. If there are more than one daemon to
6659 start, the output should look like this:
6660 <example compact="compact">
6661 echo -n "Starting remote file system services:"
6662 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6663 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6664 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6667 This makes it possible for the user to see what is
6668 happening and when the final daemon has been started.
6669 Care should be taken in the placement of white spaces:
6670 in the example above the system administrators can
6671 easily comment out a line if they don't want to start
6672 a specific daemon, while the displayed message still
6678 <p>When a system parameter is being set</p>
6681 If you have to set up different system parameters
6682 during the system boot, you should use this format:
6683 <example compact="compact">
6684 Setting <var>parameter</var> to "<var>value</var>".
6689 You can use a statement such as the following to get
6691 <example compact="compact">
6692 echo "Setting DNS domainname to \"$domainname\"."
6697 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6698 for the left and right quotation marks. A grave accent
6699 (<tt>`</tt>) is not a quote character; neither is an
6700 apostrophe (<tt>'</tt>).
6705 <p>When a daemon is stopped or restarted</p>
6708 When you stop or restart a daemon, you should issue a
6709 message identical to the startup message, except that
6710 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6711 or <tt>Restarting</tt> respectively.
6715 For example, stopping the printer daemon will look like
6717 <example compact="compact">
6718 Stopping printer spooler: lpd.
6724 <p>When something is executed</p>
6727 There are several examples where you have to run a
6728 program at system startup or shutdown to perform a
6729 specific task, for example, setting the system's clock
6730 using <prgn>netdate</prgn> or killing all processes
6731 when the system shuts down. Your message should look
6733 <example compact="compact">
6734 Doing something very useful...done.
6736 You should print the <tt>done.</tt> immediately after
6737 the job has been completed, so that the user is
6738 informed why they have to wait. You can get this
6740 <example compact="compact">
6741 echo -n "Doing something very useful..."
6750 <p>When the configuration is reloaded</p>
6753 When a daemon is forced to reload its configuration
6754 files you should use the following format:
6755 <example compact="compact">
6756 Reloading <var>description</var> configuration...done.
6758 where <var>description</var> is the same as in the
6759 daemon starting message.
6767 <heading>Cron jobs</heading>
6770 Packages must not modify the configuration file
6771 <file>/etc/crontab</file>, and they must not modify the files in
6772 <file>/var/spool/cron/crontabs</file>.</p>
6775 If a package wants to install a job that has to be executed
6776 via cron, it should place a file with the name of the
6777 package in one or more of the following directories:
6778 <example compact="compact">
6784 As these directory names imply, the files within them are
6785 executed on an hourly, daily, weekly, or monthly basis,
6786 respectively. The exact times are listed in
6787 <file>/etc/crontab</file>.</p>
6790 All files installed in any of these directories must be
6791 scripts (e.g., shell scripts or Perl scripts) so that they
6792 can easily be modified by the local system administrator.
6793 In addition, they must be treated as configuration files.
6797 If a certain job has to be executed at some other frequency or
6798 at a specific time, the package should install a file
6799 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6800 same syntax as <file>/etc/crontab</file> and is processed by
6801 <prgn>cron</prgn> automatically. The file must also be
6802 treated as a configuration file. (Note that entries in the
6803 <file>/etc/cron.d</file> directory are not handled by
6804 <prgn>anacron</prgn>. Thus, you should only use this
6805 directory for jobs which may be skipped if the system is not
6808 Unlike <file>crontab</file> files described in the IEEE Std
6809 1003.1-2008 (POSIX.1) available from
6810 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6811 name="The Open Group">, the files in
6812 <file>/etc/cron.d</file> and the file
6813 <file>/etc/crontab</file> have seven fields; namely:
6815 <item>Minute [0,59]</item>
6816 <item>Hour [0,23]</item>
6817 <item>Day of the month [1,31]</item>
6818 <item>Month of the year [1,12]</item>
6819 <item>Day of the week ([0,6] with 0=Sunday)</item>
6820 <item>Username</item>
6821 <item>Command to be run</item>
6823 Ranges of numbers are allowed. Ranges are two numbers
6824 separated with a hyphen. The specified range is inclusive.
6825 Lists are allowed. A list is a set of numbers (or ranges)
6826 separated by commas. Step values can be used in conjunction
6831 The scripts or <tt>crontab</tt> entries in these directories should
6832 check if all necessary programs are installed before they
6833 try to execute them. Otherwise, problems will arise when a
6834 package was removed but not purged since configuration files
6835 are kept on the system in this situation.
6839 Any <tt>cron</tt> daemon must provide
6840 <file>/usr/bin/crontab</file> and support normal
6841 <tt>crontab</tt> entries as specified in POSIX. The daemon
6842 must also support names for days and months, ranges, and
6843 step values. It has to support <file>/etc/crontab</file>,
6844 and correctly execute the scripts in
6845 <file>/etc/cron.d</file>. The daemon must also correctly
6847 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6852 <heading>Menus</heading>
6855 The Debian <tt>menu</tt> package provides a standard
6856 interface between packages providing applications and
6857 <em>menu programs</em> (either X window managers or
6858 text-based menu programs such as <prgn>pdmenu</prgn>).
6862 All packages that provide applications that need not be
6863 passed any special command line arguments for normal
6864 operation should register a menu entry for those
6865 applications, so that users of the <tt>menu</tt> package
6866 will automatically get menu entries in their window
6867 managers, as well in shells like <tt>pdmenu</tt>.
6871 Menu entries should follow the current menu policy.
6875 The menu policy can be found in the <tt>menu-policy</tt>
6876 files in the <tt>debian-policy</tt> package.
6877 It is also available from the Debian web mirrors at
6878 <tt><url name="/doc/packaging-manuals/menu-policy/"
6879 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6883 Please also refer to the <em>Debian Menu System</em>
6884 documentation that comes with the <package>menu</package>
6885 package for information about how to register your
6891 <heading>Multimedia handlers</heading>
6894 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6895 is a mechanism for encoding files and data streams and
6896 providing meta-information about them, in particular their
6897 type (e.g. audio or video) and format (e.g. PNG, HTML,
6902 Registration of MIME type handlers allows programs like mail
6903 user agents and web browsers to invoke these handlers to
6904 view, edit or display MIME types they don't support directly.
6908 Packages which provide the ability to view/show/play,
6909 compose, edit or print MIME types should register themselves
6910 as such following the current MIME support policy.
6914 The MIME support policy can be found in the <tt>mime-policy</tt>
6915 files in the <tt>debian-policy</tt> package.
6916 It is also available from the Debian web mirrors at
6917 <tt><url name="/doc/packaging-manuals/mime-policy/"
6918 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6924 <heading>Keyboard configuration</heading>
6927 To achieve a consistent keyboard configuration so that all
6928 applications interpret a keyboard event the same way, all
6929 programs in the Debian distribution must be configured to
6930 comply with the following guidelines.
6934 The following keys must have the specified interpretations:
6937 <tag><tt><--</tt></tag>
6938 <item>delete the character to the left of the cursor</item>
6940 <tag><tt>Delete</tt></tag>
6941 <item>delete the character to the right of the cursor</item>
6943 <tag><tt>Control+H</tt></tag>
6944 <item>emacs: the help prefix</item>
6947 The interpretation of any keyboard events should be
6948 independent of the terminal that is used, be it a virtual
6949 console, an X terminal emulator, an rlogin/telnet session,
6954 The following list explains how the different programs
6955 should be set up to achieve this:
6961 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6965 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6969 X translations are set up to make
6970 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6971 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6972 is the vt220 escape code for the "delete character"
6973 key). This must be done by loading the X resources
6974 using <prgn>xrdb</prgn> on all local X displays, not
6975 using the application defaults, so that the
6976 translation resources used correspond to the
6977 <prgn>xmodmap</prgn> settings.
6981 The Linux console is configured to make
6982 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6983 generate <tt>ESC [ 3 ~</tt>.
6987 X applications are configured so that <tt><</tt>
6988 deletes left, and <tt>Delete</tt> deletes right. Motif
6989 applications already work like this.
6993 Terminals should have <tt>stty erase ^?</tt> .
6997 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6998 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6999 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7003 Emacs is programmed to map <tt>KB_Backspace</tt> or
7004 the <tt>stty erase</tt> character to
7005 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7006 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7007 <tt>^H</tt> to <tt>help</tt> as always.
7011 Other applications use the <tt>stty erase</tt>
7012 character and <tt>kdch1</tt> for the two delete keys,
7013 with ASCII DEL being "delete previous character" and
7014 <tt>kdch1</tt> being "delete character under
7022 This will solve the problem except for the following
7029 Some terminals have a <tt><--</tt> key that cannot
7030 be made to produce anything except <tt>^H</tt>. On
7031 these terminals Emacs help will be unavailable on
7032 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7033 character takes precedence in Emacs, and has been set
7034 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7035 available) can be used instead.
7039 Some operating systems use <tt>^H</tt> for <tt>stty
7040 erase</tt>. However, modern telnet versions and all
7041 rlogin versions propagate <tt>stty</tt> settings, and
7042 almost all UNIX versions honour <tt>stty erase</tt>.
7043 Where the <tt>stty</tt> settings are not propagated
7044 correctly, things can be made to work by using
7045 <tt>stty</tt> manually.
7049 Some systems (including previous Debian versions) use
7050 <prgn>xmodmap</prgn> to arrange for both
7051 <tt><--</tt> and <tt>Delete</tt> to generate
7052 <tt>KB_Delete</tt>. We can change the behavior of
7053 their X clients using the same X resources that we use
7054 to do it for our own clients, or configure our clients
7055 using their resources when things are the other way
7056 around. On displays configured like this
7057 <tt>Delete</tt> will not work, but <tt><--</tt>
7062 Some operating systems have different <tt>kdch1</tt>
7063 settings in their <tt>terminfo</tt> database for
7064 <tt>xterm</tt> and others. On these systems the
7065 <tt>Delete</tt> key will not work correctly when you
7066 log in from a system conforming to our policy, but
7067 <tt><--</tt> will.
7074 <heading>Environment variables</heading>
7077 A program must not depend on environment variables to get
7078 reasonable defaults. (That's because these environment
7079 variables would have to be set in a system-wide
7080 configuration file like <file>/etc/profile</file>, which is not
7081 supported by all shells.)
7085 If a program usually depends on environment variables for its
7086 configuration, the program should be changed to fall back to
7087 a reasonable default configuration if these environment
7088 variables are not present. If this cannot be done easily
7089 (e.g., if the source code of a non-free program is not
7090 available), the program must be replaced by a small
7091 "wrapper" shell script which sets the environment variables
7092 if they are not already defined, and calls the original program.
7096 Here is an example of a wrapper script for this purpose:
7098 <example compact="compact">
7100 BAR=${BAR:-/var/lib/fubar}
7102 exec /usr/lib/foo/foo "$@"
7107 Furthermore, as <file>/etc/profile</file> is a configuration
7108 file of the <prgn>base-files</prgn> package, other packages must
7109 not put any environment variables or other commands into that
7114 <sect id="doc-base">
7115 <heading>Registering Documents using doc-base</heading>
7118 The <package>doc-base</package> package implements a
7119 flexible mechanism for handling and presenting
7120 documentation. The recommended practice is for every Debian
7121 package that provides online documentation (other than just
7122 manual pages) to register these documents with
7123 <package>doc-base</package> by installing a
7124 <package>doc-base</package> control file via the
7125 <prgn/install-docs/ script at installation time and
7126 de-register the manuals again when the package is removed.
7129 Please refer to the documentation that comes with the
7130 <package>doc-base</package> package for information and
7139 <heading>Files</heading>
7141 <sect id="binaries">
7142 <heading>Binaries</heading>
7145 Two different packages must not install programs with
7146 different functionality but with the same filenames. (The
7147 case of two programs having the same functionality but
7148 different implementations is handled via "alternatives" or
7149 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7150 <ref id="conflicts"> respectively.) If this case happens,
7151 one of the programs must be renamed. The maintainers should
7152 report this to the <tt>debian-devel</tt> mailing list and
7153 try to find a consensus about which program will have to be
7154 renamed. If a consensus cannot be reached, <em>both</em>
7155 programs must be renamed.
7159 By default, when a package is being built, any binaries
7160 created should include debugging information, as well as
7161 being compiled with optimization. You should also turn on
7162 as many reasonable compilation warnings as possible; this
7163 makes life easier for porters, who can then look at build
7164 logs for possible problems. For the C programming language,
7165 this means the following compilation parameters should be
7167 <example compact="compact">
7169 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7171 INSTALL = install -s # (or use strip on the files in debian/tmp)
7176 Note that by default all installed binaries should be stripped,
7177 either by using the <tt>-s</tt> flag to
7178 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7179 the binaries after they have been copied into
7180 <file>debian/tmp</file> but before the tree is made into a
7185 Although binaries in the build tree should be compiled with
7186 debugging information by default, it can often be difficult to
7187 debug programs if they are also subjected to compiler
7188 optimization. For this reason, it is recommended to support the
7189 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7190 (see <ref id="debianrules-options">). This variable can contain
7191 several flags to change how a package is compiled and built.
7195 It is up to the package maintainer to decide what
7196 compilation options are best for the package. Certain
7197 binaries (such as computationally-intensive programs) will
7198 function better with certain flags (<tt>-O3</tt>, for
7199 example); feel free to use them. Please use good judgment
7200 here. Don't use flags for the sake of it; only use them
7201 if there is good reason to do so. Feel free to override
7202 the upstream author's ideas about which compilation
7203 options are best: they are often inappropriate for our
7209 <sect id="libraries">
7210 <heading>Libraries</heading>
7213 If the package is <strong>architecture: any</strong>, then
7214 the shared library compilation and linking flags must have
7215 <tt>-fPIC</tt>, or the package shall not build on some of
7216 the supported architectures<footnote>
7218 If you are using GCC, <tt>-fPIC</tt> produces code with
7219 relocatable position independent code, which is required for
7220 most architectures to create a shared library, with i386 and
7221 perhaps some others where non position independent code is
7222 permitted in a shared library.
7225 Position independent code may have a performance penalty,
7226 especially on <tt>i386</tt>. However, in most cases the
7227 speed penalty must be measured against the memory wasted on
7228 the few architectures where non position independent code is
7231 </footnote>. Any exception to this rule must be discussed on
7232 the mailing list <em>debian-devel@lists.debian.org</em>, and
7233 a rough consensus obtained. The reasons for not compiling
7234 with <tt>-fPIC</tt> flag must be recorded in the file
7235 <tt>README.Debian</tt>, and care must be taken to either
7236 restrict the architecture or arrange for <tt>-fPIC</tt> to
7237 be used on architectures where it is required.<footnote>
7239 Some of the reasons why this might be required is if the
7240 library contains hand crafted assembly code that is not
7241 relocatable, the speed penalty is excessive for compute
7242 intensive libs, and similar reasons.
7247 As to the static libraries, the common case is not to have
7248 relocatable code, since there is no benefit, unless in specific
7249 cases; therefore the static version must not be compiled
7250 with the <tt>-fPIC</tt> flag. Any exception to this rule
7251 should be discussed on the mailing list
7252 <em>debian-devel@lists.debian.org</em>, and the reasons for
7253 compiling with the <tt>-fPIC</tt> flag must be recorded in
7254 the file <tt>README.Debian</tt>. <footnote>
7256 Some of the reasons for linking static libraries with
7257 the <tt>-fPIC</tt> flag are if, for example, one needs a
7258 Perl API for a library that is under rapid development,
7259 and has an unstable API, so shared libraries are
7260 pointless at this phase of the library's development. In
7261 that case, since Perl needs a library with relocatable
7262 code, it may make sense to create a static library with
7263 relocatable code. Another reason cited is if you are
7264 distilling various libraries into a common shared
7265 library, like <tt>mklibs</tt> does in the Debian
7271 In other words, if both a shared and a static library is
7272 being built, each source unit (<tt>*.c</tt>, for example,
7273 for C files) will need to be compiled twice, for the normal
7277 You must specify the gcc option <tt>-D_REENTRANT</tt>
7278 when building a library (either static or shared) to make
7279 the library compatible with LinuxThreads.
7283 Although not enforced by the build tools, shared libraries
7284 must be linked against all libraries that they use symbols from
7285 in the same way that binaries are. This ensures the correct
7286 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7287 system and guarantees that all libraries can be safely opened
7288 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7289 option <tt>-Wl,-z,defs</tt> when building a shared library.
7290 Since this option enforces symbol resolution at build time,
7291 a missing library reference will be caught early as a fatal
7296 All installed shared libraries should be stripped with
7297 <example compact="compact">
7298 strip --strip-unneeded <var>your-lib</var>
7300 (The option <tt>--strip-unneeded</tt> makes
7301 <prgn>strip</prgn> remove only the symbols which aren't
7302 needed for relocation processing.) Shared libraries can
7303 function perfectly well when stripped, since the symbols for
7304 dynamic linking are in a separate part of the ELF object
7306 You might also want to use the options
7307 <tt>--remove-section=.comment</tt> and
7308 <tt>--remove-section=.note</tt> on both shared libraries
7309 and executables, and <tt>--strip-debug</tt> on static
7315 Note that under some circumstances it may be useful to
7316 install a shared library unstripped, for example when
7317 building a separate package to support debugging.
7321 Shared object files (often <file>.so</file> files) that are not
7322 public libraries, that is, they are not meant to be linked
7323 to by third party executables (binaries of other packages),
7324 should be installed in subdirectories of the
7325 <file>/usr/lib</file> directory. Such files are exempt from the
7326 rules that govern ordinary shared libraries, except that
7327 they must not be installed executable and should be
7329 A common example are the so-called "plug-ins",
7330 internal shared objects that are dynamically loaded by
7331 programs using <manref name="dlopen" section="3">.
7336 An ever increasing number of packages are using
7337 <prgn>libtool</prgn> to do their linking. The latest GNU
7338 libtools (>= 1.3a) can take advantage of the metadata in the
7339 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7340 files). The main advantage of <prgn>libtool</prgn>'s
7341 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7342 store and subsequently access metadata with respect to the
7343 libraries it builds. <prgn>libtool</prgn> will search for
7344 those files, which contain a lot of useful information about
7345 a library (such as library dependency information for static
7346 linking). Also, they're <em>essential</em> for programs
7347 using <tt>libltdl</tt>.<footnote>
7348 Although <prgn>libtool</prgn> is fully capable of
7349 linking against shared libraries which don't have
7350 <tt>.la</tt> files, as it is a mere shell script it can
7351 add considerably to the build time of a
7352 <prgn>libtool</prgn>-using package if that shell script
7353 has to derive all this information from first principles
7354 for each library every time it is linked. With the
7355 advent of <prgn>libtool</prgn> version 1.4 (and to a
7356 lesser extent <prgn>libtool</prgn> version 1.3), the
7357 <file>.la</file> files also store information about
7358 inter-library dependencies which cannot necessarily be
7359 derived after the <file>.la</file> file is deleted.
7364 Packages that use <prgn>libtool</prgn> to create shared
7365 libraries should include the <file>.la</file> files in the
7366 <tt>-dev</tt> package, unless the package relies on
7367 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7368 the <tt>.la</tt> files must go in the run-time library
7373 You must make sure that you use only released versions of
7374 shared libraries to build your packages; otherwise other
7375 users will not be able to run your binaries
7376 properly. Producing source packages that depend on
7377 unreleased compilers is also usually a bad
7384 <heading>Shared libraries</heading>
7386 This section has moved to <ref id="sharedlibs">.
7392 <heading>Scripts</heading>
7395 All command scripts, including the package maintainer
7396 scripts inside the package and used by <prgn>dpkg</prgn>,
7397 should have a <tt>#!</tt> line naming the shell to be used
7402 In the case of Perl scripts this should be
7403 <tt>#!/usr/bin/perl</tt>.
7407 When scripts are installed into a directory in the system
7408 PATH, the script name should not include an extension such
7409 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7410 language currently used to implement it.
7413 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7414 <file>init.d</file> scripts should almost certainly start
7415 with <tt>set -e</tt> so that errors are detected.
7416 <file>init.d</file> scripts are something of a special case, due
7417 to how frequently they need to call commands that are allowed to
7418 fail, and it may instead be easier to check the exit status of
7419 commands directly. See <ref id="writing-init"> for more
7420 information about writing <file>init.d</file> scripts.
7423 Every script should use <tt>set -e</tt> or check the exit status
7424 of <em>every</em> command.
7427 Scripts may assume that <file>/bin/sh</file> implements the
7428 SUSv3 Shell Command Language<footnote>
7429 Single UNIX Specification, version 3, which is also IEEE
7430 1003.1-2004 (POSIX), and is available on the World Wide Web
7431 from <url id="http://www.unix.org/version3/online.html"
7432 name="The Open Group"> after free
7433 registration.</footnote>
7434 plus the following additional features not mandated by
7436 These features are in widespread use in the Linux community
7437 and are implemented in all of bash, dash, and ksh, the most
7438 common shells users may wish to use as <file>/bin/sh</file>.
7441 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7442 must not generate a newline.</item>
7443 <item><tt>test</tt>, if implemented as a shell built-in, must
7444 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7446 <item><tt>local</tt> to create a scoped variable must be
7447 supported, including listing multiple variables in a single
7448 local command and assigning a value to a variable at the
7449 same time as localizing it. <tt>local</tt> may or
7450 may not preserve the variable value from an outer scope if
7451 no assignment is present. Uses such as:
7455 # ... use a, b, c, d ...
7458 must be supported and must set the value of <tt>c</tt> to
7462 If a shell script requires non-SUSv3 features from the shell
7463 interpreter other than those listed above, the appropriate shell
7464 must be specified in the first line of the script (e.g.,
7465 <tt>#!/bin/bash</tt>) and the package must depend on the package
7466 providing the shell (unless the shell package is marked
7467 "Essential", as in the case of <prgn>bash</prgn>).
7471 You may wish to restrict your script to SUSv3 features plus the
7472 above set when possible so that it may use <file>/bin/sh</file>
7473 as its interpreter. If your script works with <prgn>dash</prgn>
7474 (originally called <prgn>ash</prgn>), it probably complies with
7475 the above requirements, but if you are in doubt, use
7476 <file>/bin/bash</file>.
7480 Perl scripts should check for errors when making any
7481 system calls, including <tt>open</tt>, <tt>print</tt>,
7482 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7486 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7487 scripting languages. See <em>Csh Programming Considered
7488 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7489 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7490 If an upstream package comes with <prgn>csh</prgn> scripts
7491 then you must make sure that they start with
7492 <tt>#!/bin/csh</tt> and make your package depend on the
7493 <prgn>c-shell</prgn> virtual package.
7497 Any scripts which create files in world-writeable
7498 directories (e.g., in <file>/tmp</file>) must use a
7499 mechanism which will fail atomically if a file with the same
7500 name already exists.
7504 The Debian base system provides the <prgn>tempfile</prgn>
7505 and <prgn>mktemp</prgn> utilities for use by scripts for
7512 <heading>Symbolic links</heading>
7515 In general, symbolic links within a top-level directory
7516 should be relative, and symbolic links pointing from one
7517 top-level directory into another should be absolute. (A
7518 top-level directory is a sub-directory of the root
7519 directory <file>/</file>.)
7523 In addition, symbolic links should be specified as short as
7524 possible, i.e., link targets like <file>foo/../bar</file> are
7529 Note that when creating a relative link using
7530 <prgn>ln</prgn> it is not necessary for the target of the
7531 link to exist relative to the working directory you're
7532 running <prgn>ln</prgn> from, nor is it necessary to change
7533 directory to the directory where the link is to be made.
7534 Simply include the string that should appear as the target
7535 of the link (this will be a pathname relative to the
7536 directory in which the link resides) as the first argument
7541 For example, in your <prgn>Makefile</prgn> or
7542 <file>debian/rules</file>, you can do things like:
7543 <example compact="compact">
7544 ln -fs gcc $(prefix)/bin/cc
7545 ln -fs gcc debian/tmp/usr/bin/cc
7546 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7547 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7552 A symbolic link pointing to a compressed file should always
7553 have the same file extension as the referenced file. (For
7554 example, if a file <file>foo.gz</file> is referenced by a
7555 symbolic link, the filename of the link has to end with
7556 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7561 <heading>Device files</heading>
7564 Packages must not include device files or named pipes in the
7569 If a package needs any special device files that are not
7570 included in the base system, it must call
7571 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7572 after notifying the user<footnote>
7573 This notification could be done via a (low-priority)
7574 debconf message, or an echo (printf) statement.
7579 Packages must not remove any device files in the
7580 <prgn>postrm</prgn> or any other script. This is left to the
7581 system administrator.
7585 Debian uses the serial devices
7586 <file>/dev/ttyS*</file>. Programs using the old
7587 <file>/dev/cu*</file> devices should be changed to use
7588 <file>/dev/ttyS*</file>.
7592 Named pipes needed by the package must be created in
7593 the <prgn>postinst</prgn> script<footnote>
7594 It's better to use <prgn>mkfifo</prgn> rather
7595 than <prgn>mknod</prgn> to create named pipes so that
7596 automated checks for packages incorrectly creating device
7597 files with <prgn>mknod</prgn> won't have false positives.
7598 </footnote> and removed in
7599 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7604 <sect id="config-files">
7605 <heading>Configuration files</heading>
7608 <heading>Definitions</heading>
7612 <tag>configuration file</tag>
7614 A file that affects the operation of a program, or
7615 provides site- or host-specific information, or
7616 otherwise customizes the behavior of a program.
7617 Typically, configuration files are intended to be
7618 modified by the system administrator (if needed or
7619 desired) to conform to local policy or to provide
7620 more useful site-specific behavior.
7623 <tag><tt>conffile</tt></tag>
7625 A file listed in a package's <tt>conffiles</tt>
7626 file, and is treated specially by <prgn>dpkg</prgn>
7627 (see <ref id="configdetails">).
7633 The distinction between these two is important; they are
7634 not interchangeable concepts. Almost all
7635 <tt>conffile</tt>s are configuration files, but many
7636 configuration files are not <tt>conffiles</tt>.
7640 As noted elsewhere, <file>/etc/init.d</file> scripts,
7641 <file>/etc/default</file> files, scripts installed in
7642 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7643 configuration installed in <file>/etc/cron.d</file> must be
7644 treated as configuration files. In general, any script that
7645 embeds configuration information is de-facto a configuration
7646 file and should be treated as such.
7651 <heading>Location</heading>
7654 Any configuration files created or used by your package
7655 must reside in <file>/etc</file>. If there are several,
7656 consider creating a subdirectory of <file>/etc</file>
7657 named after your package.
7661 If your package creates or uses configuration files
7662 outside of <file>/etc</file>, and it is not feasible to modify
7663 the package to use <file>/etc</file> directly, put the files
7664 in <file>/etc</file> and create symbolic links to those files
7665 from the location that the package requires.
7670 <heading>Behavior</heading>
7673 Configuration file handling must conform to the following
7675 <list compact="compact">
7677 local changes must be preserved during a package
7681 configuration files must be preserved when the
7682 package is removed, and only deleted when the
7686 Obsolete configuration files without local changes may be
7687 removed by the package during upgrade.
7691 The easy way to achieve this behavior is to make the
7692 configuration file a <tt>conffile</tt>. This is
7693 appropriate only if it is possible to distribute a default
7694 version that will work for most installations, although
7695 some system administrators may choose to modify it. This
7696 implies that the default version will be part of the
7697 package distribution, and must not be modified by the
7698 maintainer scripts during installation (or at any other
7703 In order to ensure that local changes are preserved
7704 correctly, no package may contain or make hard links to
7705 conffiles.<footnote>
7706 Rationale: There are two problems with hard links.
7707 The first is that some editors break the link while
7708 editing one of the files, so that the two files may
7709 unwittingly become unlinked and different. The second
7710 is that <prgn>dpkg</prgn> might break the hard link
7711 while upgrading <tt>conffile</tt>s.
7716 The other way to do it is via the maintainer scripts. In
7717 this case, the configuration file must not be listed as a
7718 <tt>conffile</tt> and must not be part of the package
7719 distribution. If the existence of a file is required for
7720 the package to be sensibly configured it is the
7721 responsibility of the package maintainer to provide
7722 maintainer scripts which correctly create, update and
7723 maintain the file and remove it on purge. (See <ref
7724 id="maintainerscripts"> for more information.) These
7725 scripts must be idempotent (i.e., must work correctly if
7726 <prgn>dpkg</prgn> needs to re-run them due to errors
7727 during installation or removal), must cope with all the
7728 variety of ways <prgn>dpkg</prgn> can call maintainer
7729 scripts, must not overwrite or otherwise mangle the user's
7730 configuration without asking, must not ask unnecessary
7731 questions (particularly during upgrades), and must
7732 otherwise be good citizens.
7736 The scripts are not required to configure every possible
7737 option for the package, but only those necessary to get
7738 the package running on a given system. Ideally the
7739 sysadmin should not have to do any configuration other
7740 than that done (semi-)automatically by the
7741 <prgn>postinst</prgn> script.
7745 A common practice is to create a script called
7746 <file><var>package</var>-configure</file> and have the
7747 package's <prgn>postinst</prgn> call it if and only if the
7748 configuration file does not already exist. In certain
7749 cases it is useful for there to be an example or template
7750 file which the maintainer scripts use. Such files should
7751 be in <file>/usr/share/<var>package</var></file> or
7752 <file>/usr/lib/<var>package</var></file> (depending on whether
7753 they are architecture-independent or not). There should
7754 be symbolic links to them from
7755 <file>/usr/share/doc/<var>package</var>/examples</file> if
7756 they are examples, and should be perfectly ordinary
7757 <prgn>dpkg</prgn>-handled files (<em>not</em>
7758 configuration files).
7762 These two styles of configuration file handling must
7763 not be mixed, for that way lies madness:
7764 <prgn>dpkg</prgn> will ask about overwriting the file
7765 every time the package is upgraded.
7770 <heading>Sharing configuration files</heading>
7773 Packages which specify the same file as a
7774 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7775 with each other. (This is an instance of the general rule
7776 about not sharing files. Note that neither alternatives
7777 nor diversions are likely to be appropriate in this case;
7778 in particular, <prgn>dpkg</prgn> does not handle diverted
7779 <tt>conffile</tt>s well.)
7783 The maintainer scripts must not alter a <tt>conffile</tt>
7784 of <em>any</em> package, including the one the scripts
7789 If two or more packages use the same configuration file
7790 and it is reasonable for both to be installed at the same
7791 time, one of these packages must be defined as
7792 <em>owner</em> of the configuration file, i.e., it will be
7793 the package which handles that file as a configuration
7794 file. Other packages that use the configuration file must
7795 depend on the owning package if they require the
7796 configuration file to operate. If the other package will
7797 use the configuration file if present, but is capable of
7798 operating without it, no dependency need be declared.
7802 If it is desirable for two or more related packages to
7803 share a configuration file <em>and</em> for all of the
7804 related packages to be able to modify that configuration
7805 file, then the following should be done:
7806 <enumlist compact="compact">
7808 One of the related packages (the "owning" package)
7809 will manage the configuration file with maintainer
7810 scripts as described in the previous section.
7813 The owning package should also provide a program
7814 that the other packages may use to modify the
7818 The related packages must use the provided program
7819 to make any desired modifications to the
7820 configuration file. They should either depend on
7821 the core package to guarantee that the configuration
7822 modifier program is available or accept gracefully
7823 that they cannot modify the configuration file if it
7824 is not. (This is in addition to the fact that the
7825 configuration file may not even be present in the
7832 Sometimes it's appropriate to create a new package which
7833 provides the basic infrastructure for the other packages
7834 and which manages the shared configuration files. (The
7835 <tt>sgml-base</tt> package is a good example.)
7840 <heading>User configuration files ("dotfiles")</heading>
7843 The files in <file>/etc/skel</file> will automatically be
7844 copied into new user accounts by <prgn>adduser</prgn>.
7845 No other program should reference the files in
7846 <file>/etc/skel</file>.
7850 Therefore, if a program needs a dotfile to exist in
7851 advance in <file>$HOME</file> to work sensibly, that dotfile
7852 should be installed in <file>/etc/skel</file> and treated as a
7857 However, programs that require dotfiles in order to
7858 operate sensibly are a bad thing, unless they do create
7859 the dotfiles themselves automatically.
7863 Furthermore, programs should be configured by the Debian
7864 default installation to behave as closely to the upstream
7865 default behavior as possible.
7869 Therefore, if a program in a Debian package needs to be
7870 configured in some way in order to operate sensibly, that
7871 should be done using a site-wide configuration file placed
7872 in <file>/etc</file>. Only if the program doesn't support a
7873 site-wide default configuration and the package maintainer
7874 doesn't have time to add it may a default per-user file be
7875 placed in <file>/etc/skel</file>.
7879 <file>/etc/skel</file> should be as empty as we can make it.
7880 This is particularly true because there is no easy (or
7881 necessarily desirable) mechanism for ensuring that the
7882 appropriate dotfiles are copied into the accounts of
7883 existing users when a package is installed.
7889 <heading>Log files</heading>
7891 Log files should usually be named
7892 <file>/var/log/<var>package</var>.log</file>. If you have many
7893 log files, or need a separate directory for permission
7894 reasons (<file>/var/log</file> is writable only by
7895 <file>root</file>), you should usually create a directory named
7896 <file>/var/log/<var>package</var></file> and place your log
7901 Log files must be rotated occasionally so that they don't
7902 grow indefinitely; the best way to do this is to drop a log
7903 rotation configuration file into the directory
7904 <file>/etc/logrotate.d</file> and use the facilities provided by
7905 logrotate.<footnote>
7907 The traditional approach to log files has been to set up
7908 <em>ad hoc</em> log rotation schemes using simple shell
7909 scripts and cron. While this approach is highly
7910 customizable, it requires quite a lot of sysadmin work.
7911 Even though the original Debian system helped a little
7912 by automatically installing a system which can be used
7913 as a template, this was deemed not enough.
7917 The use of <prgn>logrotate</prgn>, a program developed
7918 by Red Hat, is better, as it centralizes log management.
7919 It has both a configuration file
7920 (<file>/etc/logrotate.conf</file>) and a directory where
7921 packages can drop their individual log rotation
7922 configurations (<file>/etc/logrotate.d</file>).
7925 Here is a good example for a logrotate config
7926 file (for more information see <manref name="logrotate"
7928 <example compact="compact">
7929 /var/log/foo/*.log {
7934 /etc/init.d/foo force-reload
7938 This rotates all files under <file>/var/log/foo</file>, saves 12
7939 compressed generations, and forces the daemon to reload its
7940 configuration information after the log rotation.
7944 Log files should be removed when the package is
7945 purged (but not when it is only removed). This should be
7946 done by the <prgn>postrm</prgn> script when it is called
7947 with the argument <tt>purge</tt> (see <ref
7948 id="removedetails">).
7953 <heading>Permissions and owners</heading>
7956 The rules in this section are guidelines for general use.
7957 If necessary you may deviate from the details below.
7958 However, if you do so you must make sure that what is done
7959 is secure and you should try to be as consistent as possible
7960 with the rest of the system. You should probably also
7961 discuss it on <prgn>debian-devel</prgn> first.
7965 Files should be owned by <tt>root:root</tt>, and made
7966 writable only by the owner and universally readable (and
7967 executable, if appropriate), that is mode 644 or 755.
7971 Directories should be mode 755 or (for group-writability)
7972 mode 2775. The ownership of the directory should be
7973 consistent with its mode: if a directory is mode 2775, it
7974 should be owned by the group that needs write access to
7977 When a package is upgraded, and the owner or permissions
7978 of a file included in the package has changed, dpkg
7979 arranges for the ownership and permissions to be
7980 correctly set upon installation. However, this does not
7981 extend to directories; the permissions and ownership of
7982 directories already on the system does not change on
7983 install or upgrade of packages. This makes sense, since
7984 otherwise common directories like <tt>/usr</tt> would
7985 always be in flux. To correctly change permissions of a
7986 directory the package owns, explicit action is required,
7987 usually in the <tt>postinst</tt> script. Care must be
7988 taken to handle downgrades as well, in that case.
7995 Setuid and setgid executables should be mode 4755 or 2755
7996 respectively, and owned by the appropriate user or group.
7997 They should not be made unreadable (modes like 4711 or
7998 2711 or even 4111); doing so achieves no extra security,
7999 because anyone can find the binary in the freely available
8000 Debian package; it is merely inconvenient. For the same
8001 reason you should not restrict read or execute permissions
8002 on non-set-id executables.
8006 Some setuid programs need to be restricted to particular
8007 sets of users, using file permissions. In this case they
8008 should be owned by the uid to which they are set-id, and by
8009 the group which should be allowed to execute them. They
8010 should have mode 4754; again there is no point in making
8011 them unreadable to those users who must not be allowed to
8016 It is possible to arrange that the system administrator can
8017 reconfigure the package to correspond to their local
8018 security policy by changing the permissions on a binary:
8019 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8020 described below.<footnote>
8021 Ordinary files installed by <prgn>dpkg</prgn> (as
8022 opposed to <tt>conffile</tt>s and other similar objects)
8023 normally have their permissions reset to the distributed
8024 permissions when the package is reinstalled. However,
8025 the use of <prgn>dpkg-statoverride</prgn> overrides this
8028 Another method you should consider is to create a group for
8029 people allowed to use the program(s) and make any setuid
8030 executables executable only by that group.
8034 If you need to create a new user or group for your package
8035 there are two possibilities. Firstly, you may need to
8036 make some files in the binary package be owned by this
8037 user or group, or you may need to compile the user or
8038 group id (rather than just the name) into the binary
8039 (though this latter should be avoided if possible, as in
8040 this case you need a statically allocated id).</p>
8043 If you need a statically allocated id, you must ask for a
8044 user or group id from the <tt>base-passwd</tt> maintainer,
8045 and must not release the package until you have been
8046 allocated one. Once you have been allocated one you must
8047 either make the package depend on a version of the
8048 <tt>base-passwd</tt> package with the id present in
8049 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8050 your package to create the user or group itself with the
8051 correct id (using <tt>adduser</tt>) in its
8052 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8053 the <prgn>postinst</prgn> is to be preferred if it is
8054 possible, otherwise a pre-dependency will be needed on the
8055 <tt>adduser</tt> package.)
8059 On the other hand, the program might be able to determine
8060 the uid or gid from the user or group name at runtime, so
8061 that a dynamically allocated id can be used. In this case
8062 you should choose an appropriate user or group name,
8063 discussing this on <prgn>debian-devel</prgn> and checking
8064 with the <package/base-passwd/ maintainer that it is unique and that
8065 they do not wish you to use a statically allocated id
8066 instead. When this has been checked you must arrange for
8067 your package to create the user or group if necessary using
8068 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8069 <prgn>postinst</prgn> script (again, the latter is to be
8070 preferred if it is possible).
8074 Note that changing the numeric value of an id associated
8075 with a name is very difficult, and involves searching the
8076 file system for all appropriate files. You need to think
8077 carefully whether a static or dynamic id is required, since
8078 changing your mind later will cause problems.
8081 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8083 This section is not intended as policy, but as a
8084 description of the use of <prgn>dpkg-statoverride</prgn>.
8088 If a system administrator wishes to have a file (or
8089 directory or other such thing) installed with owner and
8090 permissions different from those in the distributed Debian
8091 package, they can use the <prgn>dpkg-statoverride</prgn>
8092 program to instruct <prgn>dpkg</prgn> to use the different
8093 settings every time the file is installed. Thus the
8094 package maintainer should distribute the files with their
8095 normal permissions, and leave it for the system
8096 administrator to make any desired changes. For example, a
8097 daemon which is normally required to be setuid root, but
8098 in certain situations could be used without being setuid,
8099 should be installed setuid in the <tt>.deb</tt>. Then the
8100 local system administrator can change this if they wish.
8101 If there are two standard ways of doing it, the package
8102 maintainer can use <tt>debconf</tt> to find out the
8103 preference, and call <prgn>dpkg-statoverride</prgn> in the
8104 maintainer script if necessary to accommodate the system
8105 administrator's choice. Care must be taken during
8106 upgrades to not override an existing setting.
8110 Given the above, <prgn>dpkg-statoverride</prgn> is
8111 essentially a tool for system administrators and would not
8112 normally be needed in the maintainer scripts. There is
8113 one type of situation, though, where calls to
8114 <prgn>dpkg-statoverride</prgn> would be needed in the
8115 maintainer scripts, and that involves packages which use
8116 dynamically allocated user or group ids. In such a
8117 situation, something like the following idiom can be very
8118 helpful in the package's <prgn>postinst</prgn>, where
8119 <tt>sysuser</tt> is a dynamically allocated id:
8121 for i in /usr/bin/foo /usr/sbin/bar
8123 # only do something when no setting exists
8124 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8126 #include: debconf processing, question about foo and bar
8127 if [ "$RET" = "true" ] ; then
8128 dpkg-statoverride --update --add sysuser root 4755 $i
8133 The corresponding code to remove the override when the package
8136 for i in /usr/bin/foo /usr/sbin/bar
8138 if dpkg-statoverride --list $i >/dev/null 2>&1
8140 dpkg-statoverride --remove $i
8150 <chapt id="customized-programs">
8151 <heading>Customized programs</heading>
8153 <sect id="arch-spec">
8154 <heading>Architecture specification strings</heading>
8157 If a program needs to specify an <em>architecture specification
8158 string</em> in some place, it should select one of the strings
8159 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8160 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8161 part is sometimes elided, as when the OS is Linux.
8165 Note that we don't want to use
8166 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8167 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8168 since this would make our programs incompatible with other
8169 Linux distributions. We also don't use something like
8170 <tt><var>arch</var>-unknown-linux</tt>, since the
8171 <tt>unknown</tt> does not look very good.
8174 <sect1 id="arch-wildcard-spec">
8175 <heading>Architecture wildcards</heading>
8178 A package may specify an architecture wildcard. Architecture
8179 wildcards are in the format <tt>any</tt> (which matches every
8180 architecture), <tt><var>os</var></tt>-any, or
8181 any-<tt><var>cpu</var></tt>. <footnote>
8182 Internally, the package system normalizes the GNU triplets
8183 and the Debian arches into Debian arch triplets (which are
8184 kind of inverted GNU triplets), with the first component of
8185 the triplet representing the libc and ABI in use, and then
8186 does matching against those triplets. However, such
8187 triplets are an internal implementation detail that should
8188 not be used by packages directly. The libc and ABI portion
8189 is handled internally by the package system based on
8190 the <var>os</var> and <var>cpu</var>.
8197 <heading>Daemons</heading>
8200 The configuration files <file>/etc/services</file>,
8201 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8202 by the <prgn>netbase</prgn> package and must not be modified
8207 If a package requires a new entry in one of these files, the
8208 maintainer should get in contact with the
8209 <prgn>netbase</prgn> maintainer, who will add the entries
8210 and release a new version of the <prgn>netbase</prgn>
8215 The configuration file <file>/etc/inetd.conf</file> must not be
8216 modified by the package's scripts except via the
8217 <prgn>update-inetd</prgn> script or the
8218 <file>DebianNet.pm</file> Perl module. See their documentation
8219 for details on how to add entries.
8223 If a package wants to install an example entry into
8224 <file>/etc/inetd.conf</file>, the entry must be preceded with
8225 exactly one hash character (<tt>#</tt>). Such lines are
8226 treated as "commented out by user" by the
8227 <prgn>update-inetd</prgn> script and are not changed or
8228 activated during package updates.
8233 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8237 Some programs need to create pseudo-ttys. This should be done
8238 using Unix98 ptys if the C library supports it. The resulting
8239 program must not be installed setuid root, unless that
8240 is required for other functionality.
8244 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8245 <file>/var/log/lastlog</file> must be installed writable by
8246 group <tt>utmp</tt>. Programs which need to modify those
8247 files must be installed setgid <tt>utmp</tt>.
8252 <heading>Editors and pagers</heading>
8255 Some programs have the ability to launch an editor or pager
8256 program to edit or display a text document. Since there are
8257 lots of different editors and pagers available in the Debian
8258 distribution, the system administrator and each user should
8259 have the possibility to choose their preferred editor and
8264 In addition, every program should choose a good default
8265 editor/pager if none is selected by the user or system
8270 Thus, every program that launches an editor or pager must
8271 use the EDITOR or PAGER environment variable to determine
8272 the editor or pager the user wishes to use. If these
8273 variables are not set, the programs <file>/usr/bin/editor</file>
8274 and <file>/usr/bin/pager</file> should be used, respectively.
8278 These two files are managed through the <prgn>dpkg</prgn>
8279 "alternatives" mechanism. Thus every package providing an
8280 editor or pager must call the
8281 <prgn>update-alternatives</prgn> script to register these
8286 If it is very hard to adapt a program to make use of the
8287 EDITOR or PAGER variables, that program may be configured to
8288 use <file>/usr/bin/sensible-editor</file> and
8289 <file>/usr/bin/sensible-pager</file> as the editor or pager
8290 program respectively. These are two scripts provided in the
8291 <package>sensible-utils</package> package that check the EDITOR
8292 and PAGER variables and launch the appropriate program, and fall
8293 back to <file>/usr/bin/editor</file>
8294 and <file>/usr/bin/pager</file> if the variable is not set.
8298 A program may also use the VISUAL environment variable to
8299 determine the user's choice of editor. If it exists, it
8300 should take precedence over EDITOR. This is in fact what
8301 <file>/usr/bin/sensible-editor</file> does.
8305 It is not required for a package to depend on
8306 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8307 package to provide such virtual packages.<footnote>
8308 The Debian base system already provides an editor and a
8314 <sect id="web-appl">
8315 <heading>Web servers and applications</heading>
8318 This section describes the locations and URLs that should
8319 be used by all web servers and web applications in the
8326 Cgi-bin executable files are installed in the
8328 <example compact="compact">
8329 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8331 and should be referred to as
8332 <example compact="compact">
8333 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8339 <p>Access to HTML documents</p>
8342 HTML documents for a package are stored in
8343 <file>/usr/share/doc/<var>package</var></file>
8344 and can be referred to as
8345 <example compact="compact">
8346 http://localhost/doc/<var>package</var>/<var>filename</var>
8351 The web server should restrict access to the document
8352 tree so that only clients on the same host can read
8353 the documents. If the web server does not support such
8354 access controls, then it should not provide access at
8355 all, or ask about providing access during installation.
8360 <p>Access to images</p>
8362 It is recommended that images for a package be stored
8363 in <tt>/usr/share/images/<var>package</var></tt> and
8364 may be referred to through an alias <tt>/images/</tt>
8367 http://localhost/images/<package>/<filename>
8374 <p>Web Document Root</p>
8377 Web Applications should try to avoid storing files in
8378 the Web Document Root. Instead they should use the
8379 /usr/share/doc/<var>package</var> directory for
8380 documents and register the Web Application via the
8381 <package>doc-base</package> package. If access to the
8382 web document root is unavoidable then use
8383 <example compact="compact">
8386 as the Document Root. This might be just a symbolic
8387 link to the location where the system administrator
8388 has put the real document root.
8391 <item><p>Providing httpd and/or httpd-cgi</p>
8393 All web servers should provide the virtual package
8394 <tt>httpd</tt>. If a web server has CGI support it should
8395 provide <tt>httpd-cgi</tt> additionally.
8398 All web applications which do not contain CGI scripts should
8399 depend on <tt>httpd</tt>, all those web applications which
8400 <tt>do</tt> contain CGI scripts, should depend on
8408 <sect id="mail-transport-agents">
8409 <heading>Mail transport, delivery and user agents</heading>
8412 Debian packages which process electronic mail, whether mail
8413 user agents (MUAs) or mail transport agents (MTAs), must
8414 ensure that they are compatible with the configuration
8415 decisions below. Failure to do this may result in lost
8416 mail, broken <tt>From:</tt> lines, and other serious brain
8421 The mail spool is <file>/var/mail</file> and the interface to
8422 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8423 the FHS). On older systems, the mail spool may be
8424 physically located in <file>/var/spool/mail</file>, but all
8425 access to the mail spool should be via the
8426 <file>/var/mail</file> symlink. The mail spool is part of the
8427 base system and not part of the MTA package.
8431 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8432 programs (such as IMAP daemons) must lock the mailbox in an
8433 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8434 be combined with dot locking. To avoid deadlocks, a program
8435 should use <tt>fcntl()</tt> first and dot locking after
8436 this, or alternatively implement the two locking methods in
8437 a non blocking way<footnote>
8438 If it is not possible to establish both locks, the
8439 system shouldn't wait for the second lock to be
8440 established, but remove the first lock, wait a (random)
8441 time, and start over locking again.
8442 </footnote>. Using the functions <tt>maillock</tt> and
8443 <tt>mailunlock</tt> provided by the
8444 <tt>liblockfile*</tt><footnote>
8445 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8446 to use these functions.
8447 </footnote> packages is the recommended way to realize this.
8451 Mailboxes are generally either mode 600 and owned by
8452 <var>user</var> or mode 660 and owned by
8453 <tt><var>user</var>:mail</tt><footnote>
8454 There are two traditional permission schemes for mail spools:
8455 mode 600 with all mail delivery done by processes running as
8456 the destination user, or mode 660 and owned by group mail with
8457 mail delivery done by a process running as a system user in
8458 group mail. Historically, Debian required mode 660 mail
8459 spools to enable the latter model, but that model has become
8460 increasingly uncommon and the principle of least privilege
8461 indicates that mail systems that use the first model should
8462 use permissions of 600. If delivery to programs is permitted,
8463 it's easier to keep the mail system secure if the delivery
8464 agent runs as the destination user. Debian Policy therefore
8465 permits either scheme.
8466 </footnote>. The local system administrator may choose a
8467 different permission scheme; packages should not make
8468 assumptions about the permission and ownership of mailboxes
8469 unless required (such as when creating a new mailbox). A MUA
8470 may remove a mailbox (unless it has nonstandard permissions) in
8471 which case the MTA or another MUA must recreate it if needed.
8475 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8476 be setgid mail to do the locking mentioned above (and
8477 must obviously avoid accessing other users' mailboxes
8478 using this privilege).</p>
8481 <file>/etc/aliases</file> is the source file for the system mail
8482 aliases (e.g., postmaster, usenet, etc.), it is the one
8483 which the sysadmin and <prgn>postinst</prgn> scripts may
8484 edit. After <file>/etc/aliases</file> is edited the program or
8485 human editing it must call <prgn>newaliases</prgn>. All MTA
8486 packages must come with a <prgn>newaliases</prgn> program,
8487 even if it does nothing, but older MTA packages did not do
8488 this so programs should not fail if <prgn>newaliases</prgn>
8489 cannot be found. Note that because of this, all MTA
8490 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8491 <tt>Replaces: mail-transport-agent</tt> control file
8496 The convention of writing <tt>forward to
8497 <var>address</var></tt> in the mailbox itself is not
8498 supported. Use a <tt>.forward</tt> file instead.</p>
8501 The <prgn>rmail</prgn> program used by UUCP
8502 for incoming mail should be <file>/usr/sbin/rmail</file>.
8503 Likewise, <prgn>rsmtp</prgn>, for receiving
8504 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8508 If your package needs to know what hostname to use on (for
8509 example) outgoing news and mail messages which are generated
8510 locally, you should use the file <file>/etc/mailname</file>. It
8511 will contain the portion after the username and <tt>@</tt>
8512 (at) sign for email addresses of users on the machine
8513 (followed by a newline).
8517 Such a package should check for the existence of this file
8518 when it is being configured. If it exists, it should be
8519 used without comment, although an MTA's configuration script
8520 may wish to prompt the user even if it finds that this file
8521 exists. If the file does not exist, the package should
8522 prompt the user for the value (preferably using
8523 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8524 as well as using it in the package's configuration. The
8525 prompt should make it clear that the name will not just be
8526 used by that package. For example, in this situation the
8527 <tt>inn</tt> package could say something like:
8528 <example compact="compact">
8529 Please enter the "mail name" of your system. This is the
8530 hostname portion of the address to be shown on outgoing
8531 news and mail messages. The default is
8532 <var>syshostname</var>, your system's host name. Mail
8533 name ["<var>syshostname</var>"]:
8535 where <var>syshostname</var> is the output of <tt>hostname
8541 <heading>News system configuration</heading>
8544 All the configuration files related to the NNTP (news)
8545 servers and clients should be located under
8546 <file>/etc/news</file>.</p>
8549 There are some configuration issues that apply to a number
8550 of news clients and server packages on the machine. These
8554 <tag><file>/etc/news/organization</file></tag>
8556 A string which should appear as the
8557 organization header for all messages posted
8558 by NNTP clients on the machine
8561 <tag><file>/etc/news/server</file></tag>
8563 Contains the FQDN of the upstream NNTP
8564 server, or localhost if the local machine is
8569 Other global files may be added as required for cross-package news
8576 <heading>Programs for the X Window System</heading>
8579 <heading>Providing X support and package priorities</heading>
8582 Programs that can be configured with support for the X
8583 Window System must be configured to do so and must declare
8584 any package dependencies necessary to satisfy their
8585 runtime requirements when using the X Window System. If
8586 such a package is of higher priority than the X packages
8587 on which it depends, it is required that either the
8588 X-specific components be split into a separate package, or
8589 that an alternative version of the package, which includes
8590 X support, be provided, or that the package's priority be
8596 <heading>Packages providing an X server</heading>
8599 Packages that provide an X server that, directly or
8600 indirectly, communicates with real input and display
8601 hardware should declare in their control data that they
8602 provide the virtual package <tt>xserver</tt>.<footnote>
8603 This implements current practice, and provides an
8604 actual policy for usage of the <tt>xserver</tt>
8605 virtual package which appears in the virtual packages
8606 list. In a nutshell, X servers that interface
8607 directly with the display and input hardware or via
8608 another subsystem (e.g., GGI) should provide
8609 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8610 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8616 <heading>Packages providing a terminal emulator</heading>
8619 Packages that provide a terminal emulator for the X Window
8620 System which meet the criteria listed below should declare
8621 in their control data that they provide the virtual
8622 package <tt>x-terminal-emulator</tt>. They should also
8623 register themselves as an alternative for
8624 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8629 To be an <tt>x-terminal-emulator</tt>, a program must:
8630 <list compact="compact">
8632 Be able to emulate a DEC VT100 terminal, or a
8633 compatible terminal.
8637 Support the command-line option <tt>-e
8638 <var>command</var></tt>, which creates a new
8639 terminal window<footnote>
8640 "New terminal window" does not necessarily mean
8641 a new top-level X window directly parented by
8642 the window manager; it could, if the terminal
8643 emulator application were so coded, be a new
8644 "view" in a multiple-document interface (MDI).
8646 and runs the specified <var>command</var>,
8647 interpreting the entirety of the rest of the command
8648 line as a command to pass straight to exec, in the
8649 manner that <tt>xterm</tt> does.
8653 Support the command-line option <tt>-T
8654 <var>title</var></tt>, which creates a new terminal
8655 window with the window title <var>title</var>.
8662 <heading>Packages providing a window manager</heading>
8665 Packages that provide a window manager should declare in
8666 their control data that they provide the virtual package
8667 <tt>x-window-manager</tt>. They should also register
8668 themselves as an alternative for
8669 <file>/usr/bin/x-window-manager</file>, with a priority
8670 calculated as follows:
8671 <list compact="compact">
8673 Start with a priority of 20.
8677 If the window manager supports the Debian menu
8678 system, add 20 points if this support is available
8679 in the package's default configuration (i.e., no
8680 configuration files belonging to the system or user
8681 have to be edited to activate the feature); if
8682 configuration files must be modified, add only 10
8688 If the window manager complies with <url
8689 id="http://www.freedesktop.org/Standards/wm-spec"
8690 name="The Window Manager Specification Project">,
8691 written by the <url id="http://www.freedesktop.org/"
8692 name="Free Desktop Group">, add 40 points.
8696 If the window manager permits the X session to be
8697 restarted using a <em>different</em> window manager
8698 (without killing the X server) in its default
8699 configuration, add 10 points; otherwise add none.
8706 <heading>Packages providing fonts</heading>
8709 Packages that provide fonts for the X Window
8711 For the purposes of Debian Policy, a "font for the X
8712 Window System" is one which is accessed via X protocol
8713 requests. Fonts for the Linux console, for PostScript
8714 renderer, or any other purpose, do not fit this
8715 definition. Any tool which makes such fonts available
8716 to the X Window System, however, must abide by this
8719 must do a number of things to ensure that they are both
8720 available without modification of the X or font server
8721 configuration, and that they do not corrupt files used by
8722 other font packages to register information about
8726 Fonts of any type supported by the X Window System
8727 must be in a separate binary package from any
8728 executables, libraries, or documentation (except
8729 that specific to the fonts shipped, such as their
8730 license information). If one or more of the fonts
8731 so packaged are necessary for proper operation of
8732 the package with which they are associated the font
8733 package may be Recommended; if the fonts merely
8734 provide an enhancement, a Suggests relationship may
8735 be used. Packages must not Depend on font
8737 This is because the X server may retrieve fonts
8738 from the local file system or over the network
8739 from an X font server; the Debian package system
8740 is empowered to deal only with the local
8746 BDF fonts must be converted to PCF fonts with the
8747 <prgn>bdftopcf</prgn> utility (available in the
8748 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8749 placed in a directory that corresponds to their
8751 <list compact="compact">
8753 100 dpi fonts must be placed in
8754 <file>/usr/share/fonts/X11/100dpi/</file>.
8758 75 dpi fonts must be placed in
8759 <file>/usr/share/fonts/X11/75dpi/</file>.
8763 Character-cell fonts, cursor fonts, and other
8764 low-resolution fonts must be placed in
8765 <file>/usr/share/fonts/X11/misc/</file>.
8771 Type 1 fonts must be placed in
8772 <file>/usr/share/fonts/X11/Type1/</file>. If font
8773 metric files are available, they must be placed here
8778 Subdirectories of <file>/usr/share/fonts/X11/</file>
8779 other than those listed above must be neither
8780 created nor used. (The <file>PEX</file>, <file>CID</file>,
8781 <file>Speedo</file>, and <file>cyrillic</file> directories
8782 are excepted for historical reasons, but installation of
8783 files into these directories remains discouraged.)
8787 Font packages may, instead of placing files directly
8788 in the X font directories listed above, provide
8789 symbolic links in that font directory pointing to
8790 the files' actual location in the filesystem. Such
8791 a location must comply with the FHS.
8795 Font packages should not contain both 75dpi and
8796 100dpi versions of a font. If both are available,
8797 they should be provided in separate binary packages
8798 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8799 the names of the packages containing the
8800 corresponding fonts.
8804 Fonts destined for the <file>misc</file> subdirectory
8805 should not be included in the same package as 75dpi
8806 or 100dpi fonts; instead, they should be provided in
8807 a separate package with <tt>-misc</tt> appended to
8812 Font packages must not provide the files
8813 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8814 <file>fonts.scale</file> in a font directory:
8817 <file>fonts.dir</file> files must not be provided at all.
8821 <file>fonts.alias</file> and <file>fonts.scale</file>
8822 files, if needed, should be provided in the
8824 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8825 where <var>fontdir</var> is the name of the
8827 <file>/usr/share/fonts/X11/</file> where the
8828 package's corresponding fonts are stored
8829 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8830 <var>package</var> is the name of the package
8831 that provides these fonts, and
8832 <var>extension</var> is either <tt>scale</tt>
8833 or <tt>alias</tt>, whichever corresponds to
8840 Font packages must declare a dependency on
8841 <tt>xfonts-utils</tt> in their control
8846 Font packages that provide one or more
8847 <file>fonts.scale</file> files as described above must
8848 invoke <prgn>update-fonts-scale</prgn> on each
8849 directory into which they installed fonts
8850 <em>before</em> invoking
8851 <prgn>update-fonts-dir</prgn> on that directory.
8852 This invocation must occur in both the
8853 <prgn>postinst</prgn> (for all arguments) and
8854 <prgn>postrm</prgn> (for all arguments except
8855 <tt>upgrade</tt>) scripts.
8859 Font packages that provide one or more
8860 <file>fonts.alias</file> files as described above must
8861 invoke <prgn>update-fonts-alias</prgn> on each
8862 directory into which they installed fonts. This
8863 invocation must occur in both the
8864 <prgn>postinst</prgn> (for all arguments) and
8865 <prgn>postrm</prgn> (for all arguments except
8866 <tt>upgrade</tt>) scripts.
8870 Font packages must invoke
8871 <prgn>update-fonts-dir</prgn> on each directory into
8872 which they installed fonts. This invocation must
8873 occur in both the <prgn>postinst</prgn> (for all
8874 arguments) and <prgn>postrm</prgn> (for all
8875 arguments except <tt>upgrade</tt>) scripts.
8879 Font packages must not provide alias names for the
8880 fonts they include which collide with alias names
8881 already in use by fonts already packaged.
8885 Font packages must not provide fonts with the same
8886 XLFD registry name as another font already packaged.
8892 <sect1 id="appdefaults">
8893 <heading>Application defaults files</heading>
8896 Application defaults files must be installed in the
8897 directory <file>/etc/X11/app-defaults/</file> (use of a
8898 localized subdirectory of <file>/etc/X11/</file> as described
8899 in the <em>X Toolkit Intrinsics - C Language
8900 Interface</em> manual is also permitted). They must be
8901 registered as <tt>conffile</tt>s or handled as
8902 configuration files.
8906 Customization of programs' X resources may also be
8907 supported with the provision of a file with the same name
8908 as that of the package placed in
8909 the <file>/etc/X11/Xresources/</file> directory, which
8910 must be registered as a <tt>conffile</tt> or handled as a
8911 configuration file.<footnote>
8912 Note that this mechanism is not the same as using
8913 app-defaults; app-defaults are tied to the client
8914 binary on the local file system, whereas X resources
8915 are stored in the X server and affect all connecting
8922 <heading>Installation directory issues</heading>
8925 Historically, packages using the X Window System used a
8926 separate set of installation directories from other packages.
8927 This practice has been discontinued and packages using the X
8928 Window System should now generally be installed in the same
8929 directories as any other package. Specifically, packages must
8930 not install files under the <file>/usr/X11R6/</file> directory
8931 and the <file>/usr/X11R6/</file> directory hierarchy should be
8932 regarded as obsolete.
8936 Include files previously installed under
8937 <file>/usr/X11R6/include/X11/</file> should be installed into
8938 <file>/usr/include/X11/</file>. For files previously
8939 installed into subdirectories of
8940 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8941 determine if subdirectories of <file>/usr/lib/</file> and
8942 <file>/usr/share/</file> can be used. If not, a subdirectory
8943 of <file>/usr/lib/X11/</file> should be used.
8947 Configuration files for window, display, or session managers
8948 or other applications that are tightly integrated with the X
8949 Window System may be placed in a subdirectory
8950 of <file>/etc/X11/</file> corresponding to the package name.
8951 Other X Window System applications should use
8952 the <file>/etc/</file> directory unless otherwise mandated by
8953 policy (such as for <ref id="appdefaults">).
8958 <heading>The OSF/Motif and OpenMotif libraries</heading>
8961 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8962 OpenMotif libraries</em><footnote>
8963 OSF/Motif and OpenMotif are collectively referred to as
8964 "Motif" in this policy document.
8966 should be compiled against and tested with LessTif (a free
8967 re-implementation of Motif) instead. If the maintainer
8968 judges that the program or programs do not work
8969 sufficiently well with LessTif to be distributed and
8970 supported, but do so when compiled against Motif, then two
8971 versions of the package should be created; one linked
8972 statically against Motif and with <tt>-smotif</tt>
8973 appended to the package name, and one linked dynamically
8974 against Motif and with <tt>-dmotif</tt> appended to the
8979 Both Motif-linked versions are dependent
8980 upon non-DFSG-compliant software and thus cannot be
8981 uploaded to the <em>main</em> distribution; if the
8982 software is itself DFSG-compliant it may be uploaded to
8983 the <em>contrib</em> distribution. While known existing
8984 versions of Motif permit unlimited redistribution of
8985 binaries linked against the library (whether statically or
8986 dynamically), it is the package maintainer's
8987 responsibility to determine whether this is permitted by
8988 the license of the copy of Motif in their possession.
8994 <heading>Perl programs and modules</heading>
8997 Perl programs and modules should follow the current Perl policy.
9001 The Perl policy can be found in the <tt>perl-policy</tt>
9002 files in the <tt>debian-policy</tt> package.
9003 It is also available from the Debian web mirrors at
9004 <tt><url name="/doc/packaging-manuals/perl-policy/"
9005 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9010 <heading>Emacs lisp programs</heading>
9013 Please refer to the "Debian Emacs Policy" for details of how to
9014 package emacs lisp programs.
9018 The Emacs policy is available in
9019 <file>debian-emacs-policy.gz</file> of the
9020 <package>emacsen-common</package> package.
9021 It is also available from the Debian web mirrors at
9022 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9023 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9028 <heading>Games</heading>
9031 The permissions on <file>/var/games</file> are mode 755, owner
9032 <tt>root</tt> and group <tt>root</tt>.
9036 Each game decides on its own security policy.</p>
9039 Games which require protected, privileged access to
9040 high-score files, saved games, etc., may be made
9041 set-<em>group</em>-id (mode 2755) and owned by
9042 <tt>root:games</tt>, and use files and directories with
9043 appropriate permissions (770 <tt>root:games</tt>, for
9044 example). They must not be made
9045 set-<em>user</em>-id, as this causes security problems. (If
9046 an attacker can subvert any set-user-id game they can
9047 overwrite the executable of any other, causing other players
9048 of these games to run a Trojan horse program. With a
9049 set-group-id game the attacker only gets access to less
9050 important game data, and if they can get at the other
9051 players' accounts at all it will take considerably more
9055 Some packages, for example some fortune cookie programs, are
9056 configured by the upstream authors to install with their
9057 data files or other static information made unreadable so
9058 that they can only be accessed through set-id programs
9059 provided. You should not do this in a Debian package: anyone can
9060 download the <file>.deb</file> file and read the data from it,
9061 so there is no point making the files unreadable. Not
9062 making the files unreadable also means that you don't have
9063 to make so many programs set-id, which reduces the risk of a
9067 As described in the FHS, binaries of games should be
9068 installed in the directory <file>/usr/games</file>. This also
9069 applies to games that use the X Window System. Manual pages
9070 for games (X and non-X games) should be installed in
9071 <file>/usr/share/man/man6</file>.</p>
9077 <heading>Documentation</heading>
9080 <heading>Manual pages</heading>
9083 You should install manual pages in <prgn>nroff</prgn> source
9084 form, in appropriate places under <file>/usr/share/man</file>.
9085 You should only use sections 1 to 9 (see the FHS for more
9086 details). You must not install a pre-formatted "cat page".
9090 Each program, utility, and function should have an
9091 associated manual page included in the same package. It is
9092 suggested that all configuration files also have a manual
9093 page included as well. Manual pages for protocols and other
9094 auxiliary things are optional.
9098 If no manual page is available, this is considered as a bug
9099 and should be reported to the Debian Bug Tracking System (the
9100 maintainer of the package is allowed to write this bug report
9101 themselves, if they so desire). Do not close the bug report
9102 until a proper man page is available.<footnote>
9103 It is not very hard to write a man page. See the
9104 <url id="http://www.schweikhardt.net/man_page_howto.html"
9105 name="Man-Page-HOWTO">,
9106 <manref name="man" section="7">, the examples
9107 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9108 the helper program <prgn>help2man</prgn>, or the
9109 directory <file>/usr/share/doc/man-db/examples</file>.
9114 You may forward a complaint about a missing man page to the
9115 upstream authors, and mark the bug as forwarded in the
9116 Debian bug tracking system. Even though the GNU Project do
9117 not in general consider the lack of a man page to be a bug,
9118 we do; if they tell you that they don't consider it a bug
9119 you should leave the bug in our bug tracking system open
9124 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9128 If one man page needs to be accessible via several names it
9129 is better to use a symbolic link than the <file>.so</file>
9130 feature, but there is no need to fiddle with the relevant
9131 parts of the upstream source to change from <file>.so</file> to
9132 symlinks: don't do it unless it's easy. You should not
9133 create hard links in the manual page directories, nor put
9134 absolute filenames in <file>.so</file> directives. The filename
9135 in a <file>.so</file> in a man page should be relative to the
9136 base of the man page tree (usually
9137 <file>/usr/share/man</file>). If you do not create any links
9138 (whether symlinks, hard links, or <tt>.so</tt> directives)
9139 in the file system to the alternate names of the man page,
9140 then you should not rely on <prgn>man</prgn> finding your
9141 man page under those names based solely on the information in
9142 the man page's header.<footnote>
9143 Supporting this in <prgn>man</prgn> often requires
9144 unreasonable processing time to find a manual page or to
9145 report that none exists, and moves knowledge into man's
9146 database that would be better left in the file system.
9147 This support is therefore deprecated and will cease to
9148 be present in the future.
9153 Manual pages in locale-specific subdirectories of
9154 <file>/usr/share/man</file> should use either UTF-8 or the usual
9155 legacy encoding for that language (normally the one corresponding
9156 to the shortest relevant locale name in
9157 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9158 <file>/usr/share/man/fr</file> should use either UTF-8 or
9159 ISO-8859-1.<footnote>
9160 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9161 use. In future, all manual pages will be required to use
9167 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9168 included in the subdirectory name unless it indicates a
9169 significant difference in the language, as this excludes
9170 speakers of the language in other countries.<footnote>
9171 At the time of writing, Chinese and Portuguese are the main
9172 languages with such differences, so <file>pt_BR</file>,
9173 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9178 If a localized version of a manual page is provided, it should
9179 either be up-to-date or it should be obvious to the reader that
9180 it is outdated and the original manual page should be used
9181 instead. This can be done either by a note at the beginning of
9182 the manual page or by showing the missing or changed portions in
9183 the original language instead of the target language.
9188 <heading>Info documents</heading>
9191 Info documents should be installed in <file>/usr/share/info</file>.
9192 They should be compressed with <tt>gzip -9</tt>.
9196 The <prgn>install-info</prgn> program maintains a directory of
9197 installed info documents in <file>/usr/share/info/dir</file> for
9198 the use of info readers.<footnote>
9199 It was previously necessary for packages installing info
9200 documents to run <prgn>install-info</prgn> from maintainer
9201 scripts. This is no longer necessary. The installation
9202 system now uses dpkg triggers.
9204 This file must not be included in packages. Packages containing
9205 info documents should depend on <tt>dpkg (>= 1.15.4) |
9206 install-info</tt> to ensure that the directory file is properly
9207 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9212 Info documents should contain section and directory entry
9213 information in the document for the use
9214 of <prgn>install-info</prgn>. The section should be specified
9215 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9216 space and the section of this info page. The directory entry or
9217 entries should be included between
9218 a <tt>START-INFO-DIR-ENTRY</tt> line and
9219 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9221 INFO-DIR-SECTION Individual utilities
9222 START-INFO-DIR-ENTRY
9223 * example: (example). An example info directory entry.
9226 To determine which section to use, you should look
9227 at <file>/usr/share/info/dir</file> on your system and choose
9228 the most relevant (or create a new section if none of the
9229 current sections are relevant).<footnote>
9230 Normally, info documents are generated from Texinfo source.
9231 To include this information in the generated info document, if
9232 it is absent, add commands like:
9234 @dircategory Individual utilities
9236 * example: (example). An example info directory entry.
9239 to the Texinfo source of the document and ensure that the info
9240 documents are rebuilt from source during the package build.
9246 <heading>Additional documentation</heading>
9249 Any additional documentation that comes with the package may
9250 be installed at the discretion of the package maintainer.
9251 Plain text documentation should be installed in the directory
9252 <file>/usr/share/doc/<var>package</var></file>, where
9253 <var>package</var> is the name of the package, and
9254 compressed with <tt>gzip -9</tt> unless it is small.
9258 If a package comes with large amounts of documentation which
9259 many users of the package will not require you should create
9260 a separate binary package to contain it, so that it does not
9261 take up disk space on the machines of users who do not need
9262 or want it installed.</p>
9265 It is often a good idea to put text information files
9266 (<file>README</file>s, changelogs, and so forth) that come with
9267 the source package in <file>/usr/share/doc/<var>package</var></file>
9268 in the binary package. However, you don't need to install
9269 the instructions for building and installing the package, of
9273 Packages must not require the existence of any files in
9274 <file>/usr/share/doc/</file> in order to function
9276 The system administrator should be able to
9277 delete files in <file>/usr/share/doc/</file> without causing
9278 any programs to break.
9280 Any files that are referenced by programs but are also
9281 useful as stand alone documentation should be installed under
9282 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9283 <file>/usr/share/doc/<var>package</var></file>.
9287 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9288 link to another directory in <file>/usr/share/doc</file> only if
9289 the two packages both come from the same source and the
9290 first package Depends on the second.<footnote>
9292 Please note that this does not override the section on
9293 changelog files below, so the file
9294 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9295 must refer to the changelog for the current version of
9296 <var>package</var> in question. In practice, this means
9297 that the sources of the target and the destination of the
9298 symlink must be the same (same source package and
9305 Former Debian releases placed all additional documentation
9306 in <file>/usr/doc/<var>package</var></file>. This has been
9307 changed to <file>/usr/share/doc/<var>package</var></file>,
9308 and packages must not put documentation in the directory
9309 <file>/usr/doc/<var>package</var></file>. <footnote>
9310 At this phase of the transition, we no longer require a
9311 symbolic link in <file>/usr/doc/</file>. At a later point,
9312 policy shall change to make the symbolic links a bug.
9318 <heading>Preferred documentation formats</heading>
9321 The unification of Debian documentation is being carried out
9325 If your package comes with extensive documentation in a
9326 markup format that can be converted to various other formats
9327 you should if possible ship HTML versions in a binary
9328 package, in the directory
9329 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9330 its subdirectories.<footnote>
9331 The rationale: The important thing here is that HTML
9332 docs should be available in <em>some</em> package, not
9333 necessarily in the main binary package.
9338 Other formats such as PostScript may be provided at the
9339 package maintainer's discretion.
9343 <sect id="copyrightfile">
9344 <heading>Copyright information</heading>
9347 Every package must be accompanied by a verbatim copy of its
9348 copyright information and distribution license in the file
9349 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9350 file must neither be compressed nor be a symbolic link.
9354 In addition, the copyright file must say where the upstream
9355 sources (if any) were obtained. It should name the original
9356 authors of the package and the Debian maintainer(s) who were
9357 involved with its creation.
9361 Packages in the <em>contrib</em> or <em>non-free</em> archive
9362 areas should state in the copyright file that the package is not
9363 part of the Debian GNU/Linux distribution and briefly explain
9368 A copy of the file which will be installed in
9369 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9370 be in <file>debian/copyright</file> in the source package.
9374 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9375 link to another directory in <file>/usr/share/doc</file> only if
9376 the two packages both come from the same source and the
9377 first package Depends on the second. These rules are
9378 important because copyrights must be extractable by
9383 Packages distributed under the Apache license (version 2.0), the
9384 Artistic license, the GNU GPL (version 2 or 3), the GNU LGPL
9385 (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or 1.3)
9386 should refer to the corresponding files
9387 under <file>/usr/share/common-licenses</file>,<footnote>
9390 <file>/usr/share/common-licenses/Apache-2.0</file>,
9391 <file>/usr/share/common-licenses/Artistic</file>,
9392 <file>/usr/share/common-licenses/GPL-2</file>,
9393 <file>/usr/share/common-licenses/GPL-3</file>,
9394 <file>/usr/share/common-licenses/LGPL-2</file>,
9395 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9396 <file>/usr/share/common-licenses/LGPL-3</file>,
9397 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9398 <file>/usr/share/common-licenses/GFDL-1.3</file>
9399 respectively. The University of California BSD license is
9400 also included in <package>base-files</package> as
9401 <file>/usr/share/common-licenses/BSD</file>, but given the
9402 brevity of this license, its specificity to code whose
9403 copyright is held by the Regents of the University of
9404 California, and the frequency of minor wording changes, its
9405 text should be included in the copyright file rather than
9406 referencing this file.
9408 </footnote> rather than quoting them in the copyright
9413 You should not use the copyright file as a general <file>README</file>
9414 file. If your package has such a file it should be
9415 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9416 <file>README.Debian</file> or some other appropriate place.</p>
9420 <heading>Examples</heading>
9423 Any examples (configurations, source files, whatever),
9424 should be installed in a directory
9425 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9426 files should not be referenced by any program: they're there
9427 for the benefit of the system administrator and users as
9428 documentation only. Architecture-specific example files
9429 should be installed in a directory
9430 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9432 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9433 latter directory itself may be a symbolic link to the
9438 If the purpose of a package is to provide examples, then the
9439 example files may be installed into
9440 <file>/usr/share/doc/<var>package</var></file>.
9444 <sect id="changelogs">
9445 <heading>Changelog files</heading>
9448 Packages that are not Debian-native must contain a
9449 compressed copy of the <file>debian/changelog</file> file from
9450 the Debian source tree in
9451 <file>/usr/share/doc/<var>package</var></file> with the name
9452 <file>changelog.Debian.gz</file>.
9456 If an upstream changelog is available, it should be accessible as
9457 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9458 plain text. If the upstream changelog is distributed in
9459 HTML, it should be made available in that form as
9460 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9461 and a plain text <file>changelog.gz</file> should be generated
9462 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9463 the upstream changelog files do not already conform to this
9464 naming convention, then this may be achieved either by
9465 renaming the files, or by adding a symbolic link, at the
9466 maintainer's discretion.<footnote>
9467 Rationale: People should not have to look in places for
9468 upstream changelogs merely because they are given
9469 different names or are distributed in HTML format.
9474 All of these files should be installed compressed using
9475 <tt>gzip -9</tt>, as they will become large with time even
9476 if they start out small.
9480 If the package has only one changelog which is used both as
9481 the Debian changelog and the upstream one because there is
9482 no separate upstream maintainer then that changelog should
9483 usually be installed as
9484 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9485 there is a separate upstream maintainer, but no upstream
9486 changelog, then the Debian changelog should still be called
9487 <file>changelog.Debian.gz</file>.
9491 For details about the format and contents of the Debian
9492 changelog file, please see <ref id="dpkgchangelog">.
9497 <appendix id="pkg-scope">
9498 <heading>Introduction and scope of these appendices</heading>
9501 These appendices are taken essentially verbatim from the
9502 now-deprecated Packaging Manual, version 3.2.1.0. They are
9503 the chapters which are likely to be of use to package
9504 maintainers and which have not already been included in the
9505 policy document itself. Most of these sections are very likely
9506 not relevant to policy; they should be treated as
9507 documentation for the packaging system. Please note that these
9508 appendices are included for convenience, and for historical
9509 reasons: they used to be part of policy package, and they have
9510 not yet been incorporated into dpkg documentation. However,
9511 they still have value, and hence they are presented here.
9515 They have not yet been checked to ensure that they are
9516 compatible with the contents of policy, and if there are any
9517 contradictions, the version in the main policy document takes
9518 precedence. The remaining chapters of the old Packaging
9519 Manual have also not been read in detail to ensure that there
9520 are not parts which have been left out. Both of these will be
9525 Certain parts of the Packaging manual were integrated into the
9526 Policy Manual proper, and removed from the appendices. Links
9527 have been placed from the old locations to the new ones.
9531 <prgn>dpkg</prgn> is a suite of programs for creating binary
9532 package files and installing and removing them on Unix
9534 <prgn>dpkg</prgn> is targeted primarily at Debian
9535 GNU/Linux, but may work on or be ported to other
9541 The binary packages are designed for the management of
9542 installed executable programs (usually compiled binaries) and
9543 their associated data, though source code examples and
9544 documentation are provided as part of some packages.</p>
9547 This manual describes the technical aspects of creating Debian
9548 binary packages (<file>.deb</file> files). It documents the
9549 behavior of the package management programs
9550 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9551 they interact with packages.</p>
9554 It also documents the interaction between
9555 <prgn>dselect</prgn>'s core and the access method scripts it
9556 uses to actually install the selected packages, and describes
9557 how to create a new access method.</p>
9560 This manual does not go into detail about the options and
9561 usage of the package building and installation tools. It
9562 should therefore be read in conjunction with those programs'
9567 The utility programs which are provided with <prgn>dpkg</prgn>
9568 for managing various system configuration and similar issues,
9569 such as <prgn>update-rc.d</prgn> and
9570 <prgn>install-info</prgn>, are not described in detail here -
9571 please see their man pages.
9575 It is assumed that the reader is reasonably familiar with the
9576 <prgn>dpkg</prgn> System Administrators' manual.
9577 Unfortunately this manual does not yet exist.
9581 The Debian version of the FSF's GNU hello program is provided
9582 as an example for people wishing to create Debian
9583 packages. The Debian <prgn>debmake</prgn> package is
9584 recommended as a very helpful tool in creating and maintaining
9585 Debian packages. However, while the tools and examples are
9586 helpful, they do not replace the need to read and follow the
9587 Policy and Programmer's Manual.</p>
9590 <appendix id="pkg-binarypkg">
9591 <heading>Binary packages (from old Packaging Manual)</heading>
9594 The binary package has two main sections. The first part
9595 consists of various control information files and scripts used
9596 by <prgn>dpkg</prgn> when installing and removing. See <ref
9597 id="pkg-controlarea">.
9601 The second part is an archive containing the files and
9602 directories to be installed.
9606 In the future binary packages may also contain other
9607 components, such as checksums and digital signatures. The
9608 format for the archive is described in full in the
9609 <file>deb(5)</file> man page.
9613 <sect id="pkg-bincreating"><heading>Creating package files -
9614 <prgn>dpkg-deb</prgn>
9618 All manipulation of binary package files is done by
9619 <prgn>dpkg-deb</prgn>; it's the only program that has
9620 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9621 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9622 will spot that the options requested are appropriate to
9623 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9628 In order to create a binary package you must make a
9629 directory tree which contains all the files and directories
9630 you want to have in the file system data part of the package.
9631 In Debian-format source packages this directory is usually
9632 <file>debian/tmp</file>, relative to the top of the package's
9637 They should have the locations (relative to the root of the
9638 directory tree you're constructing) ownerships and
9639 permissions which you want them to have on the system when
9644 With current versions of <prgn>dpkg</prgn> the uid/username
9645 and gid/groupname mappings for the users and groups being
9646 used should be the same on the system where the package is
9647 built and the one where it is installed.
9651 You need to add one special directory to the root of the
9652 miniature file system tree you're creating:
9653 <prgn>DEBIAN</prgn>. It should contain the control
9654 information files, notably the binary package control file
9655 (see <ref id="pkg-controlfile">).
9659 The <prgn>DEBIAN</prgn> directory will not appear in the
9660 file system archive of the package, and so won't be installed
9661 by <prgn>dpkg</prgn> when the package is installed.
9665 When you've prepared the package, you should invoke:
9667 dpkg --build <var>directory</var>
9672 This will build the package in
9673 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9674 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9675 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9680 See the man page <manref name="dpkg-deb" section="8"> for details of how
9681 to examine the contents of this newly-created file. You may find the
9682 output of following commands enlightening:
9684 dpkg-deb --info <var>filename</var>.deb
9685 dpkg-deb --contents <var>filename</var>.deb
9686 dpkg --contents <var>filename</var>.deb
9688 To view the copyright file for a package you could use this command:
9690 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9695 <sect id="pkg-controlarea">
9696 <heading>Package control information files</heading>
9699 The control information portion of a binary package is a
9700 collection of files with names known to <prgn>dpkg</prgn>.
9701 It will treat the contents of these files specially - some
9702 of them contain information used by <prgn>dpkg</prgn> when
9703 installing or removing the package; others are scripts which
9704 the package maintainer wants <prgn>dpkg</prgn> to run.
9708 It is possible to put other files in the package control
9709 area, but this is not generally a good idea (though they
9710 will largely be ignored).
9714 Here is a brief list of the control info files supported by
9715 <prgn>dpkg</prgn> and a summary of what they're used for.
9720 <tag><tt>control</tt>
9723 This is the key description file used by
9724 <prgn>dpkg</prgn>. It specifies the package's name
9725 and version, gives its description for the user,
9726 states its relationships with other packages, and so
9727 forth. See <ref id="sourcecontrolfiles"> and
9728 <ref id="binarycontrolfiles">.
9732 It is usually generated automatically from information
9733 in the source package by the
9734 <prgn>dpkg-gencontrol</prgn> program, and with
9735 assistance from <prgn>dpkg-shlibdeps</prgn>.
9736 See <ref id="pkg-sourcetools">.
9740 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9745 These are executable files (usually scripts) which
9746 <prgn>dpkg</prgn> runs during installation, upgrade
9747 and removal of packages. They allow the package to
9748 deal with matters which are particular to that package
9749 or require more complicated processing than that
9750 provided by <prgn>dpkg</prgn>. Details of when and
9751 how they are called are in <ref id="maintainerscripts">.
9755 It is very important to make these scripts idempotent.
9756 See <ref id="idempotency">.
9760 The maintainer scripts are not guaranteed to run with a
9761 controlling terminal and may not be able to interact with
9762 the user. See <ref id="controllingterminal">.
9766 <tag><tt>conffiles</tt>
9769 This file contains a list of configuration files which
9770 are to be handled automatically by <prgn>dpkg</prgn>
9771 (see <ref id="pkg-conffiles">). Note that not necessarily
9772 every configuration file should be listed here.
9775 <tag><tt>shlibs</tt>
9778 This file contains a list of the shared libraries
9779 supplied by the package, with dependency details for
9780 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9781 when it determines what dependencies are required in a
9782 package control file. The <tt>shlibs</tt> file format
9783 is described on <ref id="shlibs">.
9788 <sect id="pkg-controlfile">
9789 <heading>The main control information file: <tt>control</tt></heading>
9792 The most important control information file used by
9793 <prgn>dpkg</prgn> when it installs a package is
9794 <tt>control</tt>. It contains all the package's "vital
9799 The binary package control files of packages built from
9800 Debian sources are made by a special tool,
9801 <prgn>dpkg-gencontrol</prgn>, which reads
9802 <file>debian/control</file> and <file>debian/changelog</file> to
9803 find the information it needs. See <ref id="pkg-sourcepkg"> for
9808 The fields in binary package control files are listed in
9809 <ref id="binarycontrolfiles">.
9813 A description of the syntax of control files and the purpose
9814 of the fields is available in <ref id="controlfields">.
9819 <heading>Time Stamps</heading>
9822 See <ref id="timestamps">.
9827 <appendix id="pkg-sourcepkg">
9828 <heading>Source packages (from old Packaging Manual) </heading>
9831 The Debian binary packages in the distribution are generated
9832 from Debian sources, which are in a special format to assist
9833 the easy and automatic building of binaries.
9836 <sect id="pkg-sourcetools">
9837 <heading>Tools for processing source packages</heading>
9840 Various tools are provided for manipulating source packages;
9841 they pack and unpack sources and help build of binary
9842 packages and help manage the distribution of new versions.
9846 They are introduced and typical uses described here; see
9847 <manref name="dpkg-source" section="1"> for full
9848 documentation about their arguments and operation.
9852 For examples of how to construct a Debian source package,
9853 and how to use those utilities that are used by Debian
9854 source packages, please see the <prgn>hello</prgn> example
9858 <sect1 id="pkg-dpkg-source">
9860 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9865 This program is frequently used by hand, and is also
9866 called from package-independent automated building scripts
9867 such as <prgn>dpkg-buildpackage</prgn>.
9871 To unpack a package it is typically invoked with
9873 dpkg-source -x <var>.../path/to/filename</var>.dsc
9878 with the <file><var>filename</var>.tar.gz</file> and
9879 <file><var>filename</var>.diff.gz</file> (if applicable) in
9880 the same directory. It unpacks into
9881 <file><var>package</var>-<var>version</var></file>, and if
9883 <file><var>package</var>-<var>version</var>.orig</file>, in
9884 the current directory.
9888 To create a packed source archive it is typically invoked:
9890 dpkg-source -b <var>package</var>-<var>version</var>
9895 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9896 <file>.diff.gz</file> (if appropriate) in the current
9897 directory. <prgn>dpkg-source</prgn> does not clean the
9898 source tree first - this must be done separately if it is
9903 See also <ref id="pkg-sourcearchives">.</p>
9907 <sect1 id="pkg-dpkg-buildpackage">
9909 <prgn>dpkg-buildpackage</prgn> - overall package-building
9914 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9915 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9916 targets <tt>clean</tt>, <tt>build</tt> and
9917 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9918 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9919 source and binary package upload.
9923 It is usually invoked by hand from the top level of the
9924 built or unbuilt source directory. It may be invoked with
9925 no arguments; useful arguments include:
9926 <taglist compact="compact">
9927 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9930 Do not sign the <tt>.changes</tt> file or the
9931 source package <tt>.dsc</tt> file, respectively.</p>
9933 <tag><tt>-p<var>sign-command</var></tt></tag>
9936 Invoke <var>sign-command</var> instead of finding
9937 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9938 <var>sign-command</var> must behave just like
9939 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9941 <tag><tt>-r<var>root-command</var></tt></tag>
9944 When root privilege is required, invoke the command
9945 <var>root-command</var>. <var>root-command</var>
9946 should invoke its first argument as a command, from
9947 the <prgn>PATH</prgn> if necessary, and pass its
9948 second and subsequent arguments to the command it
9949 calls. If no <var>root-command</var> is supplied
9950 then <var>dpkg-buildpackage</var> will take no
9951 special action to gain root privilege, so that for
9952 most packages it will have to be invoked as root to
9955 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9958 Two types of binary-only build and upload - see
9959 <manref name="dpkg-source" section="1">.
9966 <sect1 id="pkg-dpkg-gencontrol">
9968 <prgn>dpkg-gencontrol</prgn> - generates binary package
9973 This program is usually called from <file>debian/rules</file>
9974 (see <ref id="pkg-sourcetree">) in the top level of the source
9979 This is usually done just before the files and directories in the
9980 temporary directory tree where the package is being built have their
9981 permissions and ownerships set and the package is constructed using
9982 <prgn>dpkg-deb/</prgn>
9984 This is so that the control file which is produced has
9985 the right permissions
9990 <prgn>dpkg-gencontrol</prgn> must be called after all the
9991 files which are to go into the package have been placed in
9992 the temporary build directory, so that its calculation of
9993 the installed size of a package is correct.
9997 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9998 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9999 variable substitutions created by
10000 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10005 For a package which generates only one binary package, and
10006 which builds it in <file>debian/tmp</file> relative to the top
10007 of the source package, it is usually sufficient to call
10008 <prgn>dpkg-gencontrol</prgn>.
10012 Sources which build several binaries will typically need
10015 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10016 </example> The <tt>-P</tt> tells
10017 <prgn>dpkg-gencontrol</prgn> that the package is being
10018 built in a non-default directory, and the <tt>-p</tt>
10019 tells it which package's control file should be generated.
10023 <prgn>dpkg-gencontrol</prgn> also adds information to the
10024 list of files in <file>debian/files</file>, for the benefit of
10025 (for example) a future invocation of
10026 <prgn>dpkg-genchanges</prgn>.</p>
10029 <sect1 id="pkg-dpkg-shlibdeps">
10031 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10036 This program is usually called from <file>debian/rules</file>
10037 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10038 id="pkg-sourcetree">), in the top level of the source tree.
10042 Its arguments are executables and shared libraries
10045 They may be specified either in the locations in the
10046 source tree where they are created or in the locations
10047 in the temporary build tree where they are installed
10048 prior to binary package creation.
10050 </footnote> for which shared library dependencies should
10051 be included in the binary package's control file.
10055 If some of the found shared libraries should only
10056 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10057 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10058 by using the <tt>-d<var>dependency-field</var></tt> option
10059 before those executable(s). (Each <tt>-d</tt> option
10060 takes effect until the next <tt>-d</tt>.)
10064 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10065 output control file to be modified. Instead by default it
10066 adds to the <file>debian/substvars</file> file variable
10067 settings like <tt>shlibs:Depends</tt>. These variable
10068 settings must be referenced in dependency fields in the
10069 appropriate per-binary-package sections of the source
10074 For example, a package that generates an essential part
10075 which requires dependencies, and optional parts that
10076 which only require a recommendation, would separate those
10077 two sets of dependencies into two different fields.<footnote>
10078 At the time of writing, an example for this was the
10079 <package/xmms/ package, with Depends used for the xmms
10080 executable, Recommends for the plug-ins and Suggests for
10081 even more optional features provided by unzip.
10083 It can say in its <file>debian/rules</file>:
10085 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10086 -dRecommends <var>optionalpart anotheroptionalpart</var>
10088 and then in its main control file <file>debian/control</file>:
10091 Depends: ${shlibs:Depends}
10092 Recommends: ${shlibs:Recommends}
10098 Sources which produce several binary packages with
10099 different shared library dependency requirements can use
10100 the <tt>-p<var>varnameprefix</var></tt> option to override
10101 the default <tt>shlibs:</tt> prefix (one invocation of
10102 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10103 They can thus produce several sets of dependency
10104 variables, each of the form
10105 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10106 which can be referred to in the appropriate parts of the
10107 binary package control files.
10112 <sect1 id="pkg-dpkg-distaddfile">
10114 <prgn>dpkg-distaddfile</prgn> - adds a file to
10115 <file>debian/files</file>
10119 Some packages' uploads need to include files other than
10120 the source and binary package files.
10124 <prgn>dpkg-distaddfile</prgn> adds a file to the
10125 <file>debian/files</file> file so that it will be included in
10126 the <file>.changes</file> file when
10127 <prgn>dpkg-genchanges</prgn> is run.
10131 It is usually invoked from the <tt>binary</tt> target of
10132 <file>debian/rules</file>:
10134 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10136 The <var>filename</var> is relative to the directory where
10137 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10138 is usually the directory above the top level of the source
10139 tree. The <file>debian/rules</file> target should put the
10140 file there just before or just after calling
10141 <prgn>dpkg-distaddfile</prgn>.
10145 The <var>section</var> and <var>priority</var> are passed
10146 unchanged into the resulting <file>.changes</file> file.
10151 <sect1 id="pkg-dpkg-genchanges">
10153 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10154 upload control file
10158 This program is usually called by package-independent
10159 automatic building scripts such as
10160 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10165 It is usually called in the top level of a built source
10166 tree, and when invoked with no arguments will print out a
10167 straightforward <file>.changes</file> file based on the
10168 information in the source package's changelog and control
10169 file and the binary and source packages which should have
10175 <sect1 id="pkg-dpkg-parsechangelog">
10177 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10178 representation of a changelog
10182 This program is used internally by
10183 <prgn>dpkg-source</prgn> et al. It may also occasionally
10184 be useful in <file>debian/rules</file> and elsewhere. It
10185 parses a changelog, <file>debian/changelog</file> by default,
10186 and prints a control-file format representation of the
10187 information in it to standard output.
10191 <sect1 id="pkg-dpkg-architecture">
10193 <prgn>dpkg-architecture</prgn> - information about the build and
10198 This program can be used manually, but is also invoked by
10199 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10200 environment or make variables which specify the build and host
10201 architecture for the package building process.
10206 <sect id="pkg-sourcetree">
10207 <heading>The Debian package source tree</heading>
10210 The source archive scheme described later is intended to
10211 allow a Debian package source tree with some associated
10212 control information to be reproduced and transported easily.
10213 The Debian package source tree is a version of the original
10214 program with certain files added for the benefit of the
10215 packaging process, and with any other changes required
10216 made to the rest of the source code and installation
10221 The extra files created for Debian are in the subdirectory
10222 <file>debian</file> of the top level of the Debian package
10223 source tree. They are described below.
10226 <sect1 id="pkg-debianrules">
10227 <heading><file>debian/rules</file> - the main building script</heading>
10230 See <ref id="debianrules">.
10234 <sect1 id="pkg-srcsubstvars">
10235 <heading><file>debian/substvars</file> and variable substitutions</heading>
10238 See <ref id="substvars">.
10244 <heading><file>debian/files</file></heading>
10247 See <ref id="debianfiles">.
10251 <sect1><heading><file>debian/tmp</file>
10255 This is the canonical temporary location for the
10256 construction of binary packages by the <tt>binary</tt>
10257 target. The directory <file>tmp</file> serves as the root of
10258 the file system tree as it is being constructed (for
10259 example, by using the package's upstream makefiles install
10260 targets and redirecting the output there), and it also
10261 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10262 id="pkg-bincreating">.
10266 If several binary packages are generated from the same
10267 source tree it is usual to use several
10268 <file>debian/tmp<var>something</var></file> directories, for
10269 example <file>tmp-a</file> or <file>tmp-doc</file>.
10273 Whatever <file>tmp</file> directories are created and used by
10274 <tt>binary</tt> must of course be removed by the
10275 <tt>clean</tt> target.</p></sect1>
10279 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10283 As it exists on the FTP site, a Debian source package
10284 consists of three related files. You must have the right
10285 versions of all three to be able to use them.
10290 <tag>Debian source control file - <tt>.dsc</tt></tag>
10292 This file is a control file used by <prgn>dpkg-source</prgn>
10293 to extract a source package.
10294 See <ref id="debiansourcecontrolfiles">.
10298 Original source archive -
10300 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10306 This is a compressed (with <tt>gzip -9</tt>)
10307 <prgn>tar</prgn> file containing the source code from
10308 the upstream authors of the program.
10313 Debian package diff -
10315 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10321 This is a unified context diff (<tt>diff -u</tt>)
10322 giving the changes which are required to turn the
10323 original source into the Debian source. These changes
10324 may only include editing and creating plain files.
10325 The permissions of files, the targets of symbolic
10326 links and the characteristics of special files or
10327 pipes may not be changed and no files may be removed
10332 All the directories in the diff must exist, except the
10333 <file>debian</file> subdirectory of the top of the source
10334 tree, which will be created by
10335 <prgn>dpkg-source</prgn> if necessary when unpacking.
10339 The <prgn>dpkg-source</prgn> program will
10340 automatically make the <file>debian/rules</file> file
10341 executable (see below).</p></item>
10346 If there is no original source code - for example, if the
10347 package is specially prepared for Debian or the Debian
10348 maintainer is the same as the upstream maintainer - the
10349 format is slightly different: then there is no diff, and the
10351 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10352 and preferably contains a directory named
10353 <file><var>package</var>-<var>version</var></file>.
10358 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10361 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10362 Debian source package. However, if it is not available it
10363 is possible to unpack a Debian source archive as follows:
10364 <enumlist compact="compact">
10367 Untar the tarfile, which will create a <file>.orig</file>
10371 <p>Rename the <file>.orig</file> directory to
10372 <file><var>package</var>-<var>version</var></file>.</p>
10376 Create the subdirectory <file>debian</file> at the top of
10377 the source tree.</p>
10379 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10381 <item><p>Untar the tarfile again if you want a copy of the original
10382 source code alongside the Debian version.</p>
10387 It is not possible to generate a valid Debian source archive
10388 without using <prgn>dpkg-source</prgn>. In particular,
10389 attempting to use <prgn>diff</prgn> directly to generate the
10390 <file>.diff.gz</file> file will not work.
10394 <heading>Restrictions on objects in source packages</heading>
10397 The source package may not contain any hard links
10399 This is not currently detected when building source
10400 packages, but only when extracting
10404 Hard links may be permitted at some point in the
10405 future, but would require a fair amount of
10407 </footnote>, device special files, sockets or setuid or
10410 Setgid directories are allowed.
10415 The source packaging tools manage the changes between the
10416 original and Debian source using <prgn>diff</prgn> and
10417 <prgn>patch</prgn>. Turning the original source tree as
10418 included in the <file>.orig.tar.gz</file> into the Debian
10419 package source must not involve any changes which cannot be
10420 handled by these tools. Problematic changes which cause
10421 <prgn>dpkg-source</prgn> to halt with an error when
10422 building the source package are:
10423 <list compact="compact">
10424 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10426 <item><p>Changing the targets of symbolic links.</p>
10428 <item><p>Creating directories, other than <file>debian</file>.</p>
10430 <item><p>Changes to the contents of binary files.</p></item>
10431 </list> Changes which cause <prgn>dpkg-source</prgn> to
10432 print a warning but continue anyway are:
10433 <list compact="compact">
10436 Removing files, directories or symlinks.
10438 Renaming a file is not treated specially - it is
10439 seen as the removal of the old file (which
10440 generates a warning, but is otherwise ignored),
10441 and the creation of the new one.
10447 Changed text files which are missing the usual final
10448 newline (either in the original or the modified
10453 Changes which are not represented, but which are not detected by
10454 <prgn>dpkg-source</prgn>, are:
10455 <list compact="compact">
10456 <item><p>Changing the permissions of files (other than
10457 <file>debian/rules</file>) and directories.</p></item>
10462 The <file>debian</file> directory and <file>debian/rules</file>
10463 are handled specially by <prgn>dpkg-source</prgn> - before
10464 applying the changes it will create the <file>debian</file>
10465 directory, and afterwards it will make
10466 <file>debian/rules</file> world-executable.
10472 <appendix id="pkg-controlfields">
10473 <heading>Control files and their fields (from old Packaging Manual)</heading>
10476 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10477 data in a common format, known as control files. Binary and
10478 source packages have control data as do the <file>.changes</file>
10479 files which control the installation of uploaded files, and
10480 <prgn>dpkg</prgn>'s internal databases are in a similar
10485 <heading>Syntax of control files</heading>
10488 See <ref id="controlsyntax">.
10492 It is important to note that there are several fields which
10493 are optional as far as <prgn>dpkg</prgn> and the related
10494 tools are concerned, but which must appear in every Debian
10495 package, or whose omission may cause problems.
10500 <heading>List of fields</heading>
10503 See <ref id="controlfieldslist">.
10507 This section now contains only the fields that didn't belong
10508 to the Policy manual.
10511 <sect1 id="pkg-f-Filename">
10512 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10515 These fields in <tt>Packages</tt> files give the
10516 filename(s) of (the parts of) a package in the
10517 distribution directories, relative to the root of the
10518 Debian hierarchy. If the package has been split into
10519 several parts the parts are all listed in order, separated
10524 <sect1 id="pkg-f-Size">
10525 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10528 These fields in <file>Packages</file> files give the size (in
10529 bytes, expressed in decimal) and MD5 checksum of the
10530 file(s) which make(s) up a binary package in the
10531 distribution. If the package is split into several parts
10532 the values for the parts are listed in order, separated by
10537 <sect1 id="pkg-f-Status">
10538 <heading><tt>Status</tt></heading>
10541 This field in <prgn>dpkg</prgn>'s status file records
10542 whether the user wants a package installed, removed or
10543 left alone, whether it is broken (requiring
10544 re-installation) or not and what its current state on the
10545 system is. Each of these pieces of information is a
10550 <sect1 id="pkg-f-Config-Version">
10551 <heading><tt>Config-Version</tt></heading>
10554 If a package is not installed or not configured, this
10555 field in <prgn>dpkg</prgn>'s status file records the last
10556 version of the package which was successfully
10561 <sect1 id="pkg-f-Conffiles">
10562 <heading><tt>Conffiles</tt></heading>
10565 This field in <prgn>dpkg</prgn>'s status file contains
10566 information about the automatically-managed configuration
10567 files held by a package. This field should <em>not</em>
10568 appear anywhere in a package!
10573 <heading>Obsolete fields</heading>
10576 These are still recognized by <prgn>dpkg</prgn> but should
10577 not appear anywhere any more.
10579 <taglist compact="compact">
10581 <tag><tt>Revision</tt></tag>
10582 <tag><tt>Package-Revision</tt></tag>
10583 <tag><tt>Package_Revision</tt></tag>
10585 The Debian revision part of the package version was
10586 at one point in a separate control file field. This
10587 field went through several names.
10590 <tag><tt>Recommended</tt></tag>
10591 <item>Old name for <tt>Recommends</tt>.</item>
10593 <tag><tt>Optional</tt></tag>
10594 <item>Old name for <tt>Suggests</tt>.</item>
10596 <tag><tt>Class</tt></tag>
10597 <item>Old name for <tt>Priority</tt>.</item>
10606 <appendix id="pkg-conffiles">
10607 <heading>Configuration file handling (from old Packaging Manual)</heading>
10610 <prgn>dpkg</prgn> can do a certain amount of automatic
10611 handling of package configuration files.
10615 Whether this mechanism is appropriate depends on a number of
10616 factors, but basically there are two approaches to any
10617 particular configuration file.
10621 The easy method is to ship a best-effort configuration in the
10622 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10623 handle updates. If the user is unlikely to want to edit the
10624 file, but you need them to be able to without losing their
10625 changes, and a new package with a changed version of the file
10626 is only released infrequently, this is a good approach.
10630 The hard method is to build the configuration file from
10631 scratch in the <prgn>postinst</prgn> script, and to take the
10632 responsibility for fixing any mistakes made in earlier
10633 versions of the package automatically. This will be
10634 appropriate if the file is likely to need to be different on
10638 <sect><heading>Automatic handling of configuration files by
10643 A package may contain a control area file called
10644 <tt>conffiles</tt>. This file should be a list of filenames
10645 of configuration files needing automatic handling, separated
10646 by newlines. The filenames should be absolute pathnames,
10647 and the files referred to should actually exist in the
10652 When a package is upgraded <prgn>dpkg</prgn> will process
10653 the configuration files during the configuration stage,
10654 shortly before it runs the package's <prgn>postinst</prgn>
10659 For each file it checks to see whether the version of the
10660 file included in the package is the same as the one that was
10661 included in the last version of the package (the one that is
10662 being upgraded from); it also compares the version currently
10663 installed on the system with the one shipped with the last
10668 If neither the user nor the package maintainer has changed
10669 the file, it is left alone. If one or the other has changed
10670 their version, then the changed version is preferred - i.e.,
10671 if the user edits their file, but the package maintainer
10672 doesn't ship a different version, the user's changes will
10673 stay, silently, but if the maintainer ships a new version
10674 and the user hasn't edited it the new version will be
10675 installed (with an informative message). If both have
10676 changed their version the user is prompted about the problem
10677 and must resolve the differences themselves.
10681 The comparisons are done by calculating the MD5 message
10682 digests of the files, and storing the MD5 of the file as it
10683 was included in the most recent version of the package.
10687 When a package is installed for the first time
10688 <prgn>dpkg</prgn> will install the file that comes with it,
10689 unless that would mean overwriting a file already on the
10694 However, note that <prgn>dpkg</prgn> will <em>not</em>
10695 replace a conffile that was removed by the user (or by a
10696 script). This is necessary because with some programs a
10697 missing file produces an effect hard or impossible to
10698 achieve in another way, so that a missing file needs to be
10699 kept that way if the user did it.
10703 Note that a package should <em>not</em> modify a
10704 <prgn>dpkg</prgn>-handled conffile in its maintainer
10705 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10706 the user confusing and possibly dangerous options for
10707 conffile update when the package is upgraded.</p>
10710 <sect><heading>Fully-featured maintainer script configuration
10715 For files which contain site-specific information such as
10716 the hostname and networking details and so forth, it is
10717 better to create the file in the package's
10718 <prgn>postinst</prgn> script.
10722 This will typically involve examining the state of the rest
10723 of the system to determine values and other information, and
10724 may involve prompting the user for some information which
10725 can't be obtained some other way.
10729 When using this method there are a couple of important
10730 issues which should be considered:
10734 If you discover a bug in the program which generates the
10735 configuration file, or if the format of the file changes
10736 from one version to the next, you will have to arrange for
10737 the postinst script to do something sensible - usually this
10738 will mean editing the installed configuration file to remove
10739 the problem or change the syntax. You will have to do this
10740 very carefully, since the user may have changed the file,
10741 perhaps to fix the very problem that your script is trying
10742 to deal with - you will have to detect these situations and
10743 deal with them correctly.
10747 If you do go down this route it's probably a good idea to
10748 make the program that generates the configuration file(s) a
10749 separate program in <file>/usr/sbin</file>, by convention called
10750 <file><var>package</var>config</file> and then run that if
10751 appropriate from the post-installation script. The
10752 <tt><var>package</var>config</tt> program should not
10753 unquestioningly overwrite an existing configuration - if its
10754 mode of operation is geared towards setting up a package for
10755 the first time (rather than any arbitrary reconfiguration
10756 later) you should have it check whether the configuration
10757 already exists, and require a <tt>--force</tt> flag to
10758 overwrite it.</p></sect>
10761 <appendix id="pkg-alternatives"><heading>Alternative versions of
10762 an interface - <prgn>update-alternatives</prgn> (from old
10767 When several packages all provide different versions of the
10768 same program or file it is useful to have the system select a
10769 default, but to allow the system administrator to change it
10770 and have their decisions respected.
10774 For example, there are several versions of the <prgn>vi</prgn>
10775 editor, and there is no reason to prevent all of them from
10776 being installed at once, each under their own name
10777 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10778 Nevertheless it is desirable to have the name <tt>vi</tt>
10779 refer to something, at least by default.
10783 If all the packages involved cooperate, this can be done with
10784 <prgn>update-alternatives</prgn>.
10788 Each package provides its own version under its own name, and
10789 calls <prgn>update-alternatives</prgn> in its postinst to
10790 register its version (and again in its prerm to deregister
10795 See the man page <manref name="update-alternatives"
10796 section="8"> for details.
10800 If <prgn>update-alternatives</prgn> does not seem appropriate
10801 you may wish to consider using diversions instead.</p>
10804 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10805 package's version of a file (from old Packaging Manual)
10809 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10810 when it reinstalls the package it belongs to, and to have it
10811 put the file from the package somewhere else instead.
10815 This can be used locally to override a package's version of a
10816 file, or by one package to override another's version (or
10817 provide a wrapper for it).
10821 Before deciding to use a diversion, read <ref
10822 id="pkg-alternatives"> to see if you really want a diversion
10823 rather than several alternative versions of a program.
10827 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10828 and updated by a special program <prgn>dpkg-divert</prgn>.
10829 Please see <manref name="dpkg-divert" section="8"> for full
10830 details of its operation.
10834 When a package wishes to divert a file from another, it should
10835 call <prgn>dpkg-divert</prgn> in its preinst to add the
10836 diversion and rename the existing file. For example,
10837 supposing that a <prgn>smailwrapper</prgn> package wishes to
10838 install a wrapper around <file>/usr/sbin/smail</file>:
10840 dpkg-divert --package smailwrapper --add --rename \
10841 --divert /usr/sbin/smail.real /usr/sbin/smail
10842 </example> The <tt>--package smailwrapper</tt> ensures that
10843 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10844 can bypass the diversion and get installed as the true version.
10845 It's safe to add the diversion unconditionally on upgrades since
10846 it will be left unchanged if it already exists, but
10847 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10848 message, make the command conditional on the version from which
10849 the package is being upgraded:
10851 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10852 dpkg-divert --package smailwrapper --add --rename \
10853 --divert /usr/sbin/smail.real /usr/sbin/smail
10855 </example> where <tt>1.0-2</tt> is the version at which the
10856 diversion was first added to the package. Running the command
10857 during abort-upgrade is pointless but harmless.
10861 The postrm has to do the reverse:
10863 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10864 dpkg-divert --package smailwrapper --remove --rename \
10865 --divert /usr/sbin/smail.real /usr/sbin/smail
10867 </example> If the diversion was added at a particular version, the
10868 postrm should also handle the failure case of upgrading from an
10869 older version (unless the older version is so old that direct
10870 upgrades are no longer supported):
10872 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10873 dpkg-divert --package smailwrapper --remove --rename \
10874 --divert /usr/sbin/smail.real /usr/sbin/smail
10876 </example> where <tt>1.02-2</tt> is the version at which the
10877 diversion was first added to the package. The postrm should not
10878 remove the diversion on upgrades both because there's no reason to
10879 remove the diversion only to immediately re-add it and since the
10880 postrm of the old package is run after unpacking so the removal of
10881 the diversion will fail.
10885 Do not attempt to divert a file which is vitally important for
10886 the system's operation - when using <prgn>dpkg-divert</prgn>
10887 there is a time, after it has been diverted but before
10888 <prgn>dpkg</prgn> has installed the new version, when the file
10889 does not exist.</p>
10894 <!-- Local variables: -->
10895 <!-- indent-tabs-mode: t -->
10897 <!-- vim:set ai et sts=2 sw=2 tw=76: -->