1 <!doctype debiandoc system [
2 <!-- include version information so we don't have to hard code it
3 within the document -->
4 <!entity % versiondata SYSTEM "version.ent"> %versiondata;
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 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>comm</em>,
644 <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Only very few packages are allowed to form
1082 part of the base system, in order to keep the required disk
1087 The base system consists of all those packages with priority
1088 <tt>required</tt> or <tt>important</tt>. Many of them will
1089 be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>) using the
1551 <var>version</var> of the changelog entry.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1930 <tag><tt>patch</tt> (optional)</tag>
1933 This target performs whatever additional actions are
1934 required to make the source ready for editing (unpacking
1935 additional upstream archives, applying patches, etc.).
1936 It is recommended to be implemented for any package where
1937 <tt>dpkg-source -x</tt> does not result in source ready
1938 for additional modification. See
1939 <ref id="readmesource">.
1945 The <tt>build</tt>, <tt>binary</tt> and
1946 <tt>clean</tt> targets must be invoked with the current
1947 directory being the package's top-level directory.
1952 Additional targets may exist in <file>debian/rules</file>,
1953 either as published or undocumented interfaces or for the
1954 package's internal use.
1958 The architectures we build on and build for are determined
1959 by <prgn>make</prgn> variables using the utility
1960 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1961 You can determine the
1962 Debian architecture and the GNU style architecture
1963 specification string for the build machine (the machine type
1964 we are building on) as well as for the host machine (the
1965 machine type we are building for). Here is a list of
1966 supported <prgn>make</prgn> variables:
1967 <list compact="compact">
1969 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1972 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1973 specification string)
1976 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1977 <tt>DEB_*_GNU_TYPE</tt>)
1980 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1981 <tt>DEB_*_GNU_TYPE</tt>)
1983 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1984 the build machine or <tt>HOST</tt> for specification of the
1989 Backward compatibility can be provided in the rules file
1990 by setting the needed variables to suitable default
1991 values; please refer to the documentation of
1992 <prgn>dpkg-architecture</prgn> for details.
1996 It is important to understand that the <tt>DEB_*_ARCH</tt>
1997 string only determines which Debian architecture we are
1998 building on or for. It should not be used to get the CPU
1999 or system information; the GNU style variables should be
2003 <sect1 id="debianrules-options">
2004 <heading><file>debian/rules</file> and
2005 <tt>DEB_BUILD_OPTIONS</tt></heading>
2008 Supporting the standardized environment variable
2009 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2010 contain several flags to change how a package is compiled and
2011 built. Each flag must be in the form <var>flag</var> or
2012 <var>flag</var>=<var>options</var>. If multiple flags are
2013 given, they must be separated by whitespace.<footnote>
2014 Some packages support any delimiter, but whitespace is the
2015 easiest to parse inside a makefile and avoids ambiguity with
2016 flag values that contain commas.
2018 <var>flag</var> must start with a lowercase letter
2019 (<tt>a-z</tt>) and consist only of lowercase letters,
2020 numbers (<tt>0-9</tt>), and the characters
2021 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2022 <var>options</var> must not contain whitespace. The same
2023 tag should not be given multiple times with conflicting
2024 values. Package maintainers may assume that
2025 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2029 The meaning of the following tags has been standardized:
2033 This tag says to not run any build-time test suite
2034 provided by the package.
2038 The presence of this tag means that the package should
2039 be compiled with a minimum of optimization. For C
2040 programs, it is best to add <tt>-O0</tt> to
2041 <tt>CFLAGS</tt> (although this is usually the default).
2042 Some programs might fail to build or run at this level
2043 of optimization; it may be necessary to use
2044 <tt>-O1</tt>, for example.
2048 This tag means that the debugging symbols should not be
2049 stripped from the binary during installation, so that
2050 debugging information may be included in the package.
2052 <tag>parallel=n</tag>
2054 This tag means that the package should be built using up
2055 to <tt>n</tt> parallel processes if the package build
2056 system supports this.<footnote>
2057 Packages built with <tt>make</tt> can often implement
2058 this by passing the <tt>-j</tt><var>n</var> option to
2061 If the package build system does not support parallel
2062 builds, this string must be ignored. If the package
2063 build system only supports a lower level of concurrency
2064 than <var>n</var>, the package should be built using as
2065 many parallel processes as the package build system
2066 supports. It is up to the package maintainer to decide
2067 whether the package build times are long enough and the
2068 package build system is robust enough to make supporting
2069 parallel builds worthwhile.
2075 Unknown flags must be ignored by <file>debian/rules</file>.
2079 The following makefile snippet is an example of how one may
2080 implement the build options; you will probably have to
2081 massage this example in order to make it work for your
2083 <example compact="compact">
2086 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2087 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2088 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2089 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2091 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2096 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2097 INSTALL_PROGRAM += -s
2099 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2100 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2101 MAKEFLAGS += -j$(NUMJOBS)
2106 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2107 # Code to run the package test suite.
2114 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2115 <sect id="substvars">
2116 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2119 When <prgn>dpkg-gencontrol</prgn>,
2120 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2121 generate control files they perform variable substitutions
2122 on their output just before writing it. Variable
2123 substitutions have the form <tt>${<var>variable</var>}</tt>.
2124 The optional file <file>debian/substvars</file> contains
2125 variable substitutions to be used; variables can also be set
2126 directly from <file>debian/rules</file> using the <tt>-V</tt>
2127 option to the source packaging commands, and certain
2128 predefined variables are also available.
2132 The <file>debian/substvars</file> file is usually generated and
2133 modified dynamically by <file>debian/rules</file> targets, in
2134 which case it must be removed by the <tt>clean</tt> target.
2138 See <manref name="deb-substvars" section="5"> for full
2139 details about source variable substitutions, including the
2140 format of <file>debian/substvars</file>.</p>
2143 <sect id="debianwatch">
2144 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2147 This is an optional, recommended control file for the
2148 <tt>uscan</tt> utility which defines how to automatically
2149 scan ftp or http sites for newly available updates of the
2150 package. This is used by <url id="
2151 http://dehs.alioth.debian.org/"> and other Debian QA tools
2152 to help with quality control and maintenance of the
2153 distribution as a whole.
2158 <sect id="debianfiles">
2159 <heading>Generated files list: <file>debian/files</file></heading>
2162 This file is not a permanent part of the source tree; it
2163 is used while building packages to record which files are
2164 being generated. <prgn>dpkg-genchanges</prgn> uses it
2165 when it generates a <file>.changes</file> file.
2169 It should not exist in a shipped source package, and so it
2170 (and any backup files or temporary files such as
2171 <file>files.new</file><footnote>
2172 <file>files.new</file> is used as a temporary file by
2173 <prgn>dpkg-gencontrol</prgn> and
2174 <prgn>dpkg-distaddfile</prgn> - they write a new
2175 version of <tt>files</tt> here before renaming it,
2176 to avoid leaving a corrupted copy if an error
2178 </footnote>) should be removed by the
2179 <tt>clean</tt> target. It may also be wise to
2180 ensure a fresh start by emptying or removing it at the
2181 start of the <tt>binary</tt> target.
2185 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2186 package, it adds an entry to <file>debian/files</file> for the
2187 <file>.deb</file> file that will be created when <tt>dpkg-deb
2188 --build</tt> is run for that binary package. So for most
2189 packages all that needs to be done with this file is to
2190 delete it in the <tt>clean</tt> target.
2194 If a package upload includes files besides the source
2195 package and any binary packages whose control files were
2196 made with <prgn>dpkg-gencontrol</prgn> then they should be
2197 placed in the parent of the package's top-level directory
2198 and <prgn>dpkg-distaddfile</prgn> should be called to add
2199 the file to the list in <file>debian/files</file>.</p>
2202 <sect id="embeddedfiles">
2203 <heading>Convenience copies of code</heading>
2206 Some software packages include in their distribution convenience
2207 copies of code from other software packages, generally so that
2208 users compiling from source don't have to download multiple
2209 packages. Debian packages should not make use of these
2210 convenience copies unless the included package is explicitly
2211 intended to be used in this way.<footnote>
2212 For example, parts of the GNU build system work like this.
2214 If the included code is already in the Debian archive in the
2215 form of a library, the Debian packaging should ensure that
2216 binary packages reference the libraries already in Debian and
2217 the convenience copy is not used. If the included code is not
2218 already in Debian, it should be packaged separately as a
2219 prerequisite if possible.
2221 Having multiple copies of the same code in Debian is
2222 inefficient, often creates either static linking or shared
2223 library conflicts, and, most importantly, increases the
2224 difficulty of handling security vulnerabilities in the
2230 <sect id="readmesource">
2231 <heading>Source package handling:
2232 <file>debian/README.source</file></heading>
2235 If running <prgn>dpkg-source -x</prgn> on a source package
2236 doesn't produce the source of the package, ready for editing,
2237 and allow one to make changes and run
2238 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2239 without taking any additional steps, creating a
2240 <file>debian/README.source</file> documentation file is
2241 recommended. This file should explain how to do all of the
2244 <item>Generate the fully patched source, in a form ready for
2245 editing, that would be built to create Debian
2246 packages. Doing this with a <tt>patch</tt> target in
2247 <file>debian/rules</file> is recommended; see
2248 <ref id="debianrules">.</item>
2249 <item>Modify the source and save those modifications so that
2250 they will be applied when building the package.</item>
2251 <item>Remove source modifications that are currently being
2252 applied when building the package.</item>
2253 <item>Optionally, document what steps are necessary to
2254 upgrade the Debian source package to a new upstream version,
2255 if applicable.</item>
2257 This explanation should include specific commands and mention
2258 any additional required Debian packages. It should not assume
2259 familiarity with any specific Debian packaging system or patch
2264 This explanation may refer to a documentation file installed by
2265 one of the package's build dependencies provided that the
2266 referenced documentation clearly explains these tasks and is not
2267 a general reference manual.
2271 <file>debian/README.source</file> may also include any other
2272 information that would be helpful to someone modifying the
2273 source package. Even if the package doesn't fit the above
2274 description, maintainers are encouraged to document in a
2275 <file>debian/README.source</file> file any source package with a
2276 particularly complex or unintuitive source layout or build
2277 system (for example, a package that builds the same source
2278 multiple times to generate different binary packages).
2284 <chapt id="controlfields">
2285 <heading>Control files and their fields</heading>
2288 The package management system manipulates data represented in
2289 a common format, known as <em>control data</em>, stored in
2290 <em>control files</em>.
2291 Control files are used for source packages, binary packages and
2292 the <file>.changes</file> files which control the installation
2293 of uploaded files<footnote>
2294 <prgn>dpkg</prgn>'s internal databases are in a similar
2299 <sect id="controlsyntax">
2300 <heading>Syntax of control files</heading>
2303 A control file consists of one or more paragraphs of
2305 The paragraphs are also sometimes referred to as stanzas.
2307 The paragraphs are separated by blank lines. Some control
2308 files allow only one paragraph; others allow several, in
2309 which case each paragraph usually refers to a different
2310 package. (For example, in source packages, the first
2311 paragraph refers to the source package, and later paragraphs
2312 refer to binary packages generated from the source.)
2316 Each paragraph consists of a series of data fields; each
2317 field consists of the field name, followed by a colon and
2318 then the data/value associated with that field. It ends at
2319 the end of the (logical) line. Horizontal whitespace
2320 (spaces and tabs) may occur immediately before or after the
2321 value and is ignored there; it is conventional to put a
2322 single space after the colon. For example, a field might
2324 <example compact="compact">
2327 the field name is <tt>Package</tt> and the field value
2332 Many fields' values may span several lines; in this case
2333 each continuation line must start with a space or a tab.
2334 Any trailing spaces or tabs at the end of individual
2335 lines of a field value are ignored.
2339 In fields where it is specified that lines may not wrap,
2340 only a single line of data is allowed and whitespace is not
2341 significant in a field body. Whitespace must not appear
2342 inside names (of packages, architectures, files or anything
2343 else) or version numbers, or between the characters of
2344 multi-character version relationships.
2348 Field names are not case-sensitive, but it is usual to
2349 capitalize the field names using mixed case as shown below.
2353 Blank lines, or lines consisting only of spaces and tabs,
2354 are not allowed within field values or between fields - that
2355 would mean a new paragraph.
2360 <sect id="sourcecontrolfiles">
2361 <heading>Source package control files -- <file>debian/control</file></heading>
2364 The <file>debian/control</file> file contains the most vital
2365 (and version-independent) information about the source package
2366 and about the binary packages it creates.
2370 The first paragraph of the control file contains information about
2371 the source package in general. The subsequent sets each describe a
2372 binary package that the source tree builds.
2376 The fields in the general paragraph (the first one, for the source
2379 <list compact="compact">
2380 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2381 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2382 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2383 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2384 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2385 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2386 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2387 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2392 The fields in the binary package paragraphs are:
2394 <list compact="compact">
2395 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2396 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2397 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2398 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2399 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2400 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2401 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2402 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2407 The syntax and semantics of the fields are described below.
2413 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2414 generate control files for binary packages (see below), by
2415 <prgn>dpkg-genchanges</prgn> to generate the
2416 <tt>.changes</tt> file to accompany the upload, and by
2417 <prgn>dpkg-source</prgn> when it creates the
2418 <file>.dsc</file> source control file as part of a source
2419 archive. Many fields are permitted to span multiple lines in
2420 <file>debian/control</file> but not in any other control
2421 file. These tools are responsible for removing the line
2422 breaks from such fields when using fields from
2423 <file>debian/control</file> to generate other control files.
2427 The fields here may contain variable references - their
2428 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2429 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2430 when they generate output control files.
2431 See <ref id="substvars"> for details.
2436 <sect id="binarycontrolfiles">
2437 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2440 The <file>DEBIAN/control</file> file contains the most vital
2441 (and version-dependent) information about a binary package.
2445 The fields in this file are:
2447 <list compact="compact">
2448 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2449 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2450 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2451 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2452 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2453 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2454 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2455 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2456 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2457 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2458 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2459 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2464 <sect id="debiansourcecontrolfiles">
2465 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2468 This file contains a series of fields, identified and
2469 separated just like the fields in the control file of
2470 a binary package. The fields are listed below; their
2471 syntax is described above, in <ref id="pkg-controlfields">.
2473 <list compact="compact">
2474 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2475 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2476 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2477 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2478 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2479 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2480 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2481 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2482 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2483 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2484 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2489 The source package control file is generated by
2490 <prgn>dpkg-source</prgn> when it builds the source
2491 archive, from other files in the source package,
2492 described above. When unpacking, it is checked against
2493 the files and directories in the other parts of the
2499 <sect id="debianchangesfiles">
2500 <heading>Debian changes files -- <file>.changes</file></heading>
2503 The .changes files are used by the Debian archive maintenance
2504 software to process updates to packages. They contain one
2505 paragraph which contains information from the
2506 <tt>debian/control</tt> file and other data about the
2507 source package gathered via <tt>debian/changelog</tt>
2508 and <tt>debian/rules</tt>.
2512 The fields in this file are:
2514 <list compact="compact">
2515 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2518 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2519 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2520 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2522 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2523 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2524 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2525 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2526 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2527 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2528 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2533 <sect id="controlfieldslist">
2534 <heading>List of fields</heading>
2536 <sect1 id="f-Source">
2537 <heading><tt>Source</tt></heading>
2540 This field identifies the source package name.
2544 In <file>debian/control</file> or a <file>.dsc</file> file,
2545 this field must contain only the name of the source package.
2549 In a binary package control file or a <file>.changes</file>
2550 file, the source package name may be followed by a version
2551 number in parentheses<footnote>
2552 It is customary to leave a space after the package name
2553 if a version number is specified.
2555 This version number may be omitted (and is, by
2556 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2557 the <tt>Version</tt> field of the binary package in
2558 question. The field itself may be omitted from a binary
2559 package control file when the source package has the same
2560 name and version as the binary package.
2564 <sect1 id="f-Maintainer">
2565 <heading><tt>Maintainer</tt></heading>
2568 The package maintainer's name and email address. The name
2569 should come first, then the email address inside angle
2570 brackets <tt><></tt> (in RFC822 format).
2574 If the maintainer's name contains a full stop then the
2575 whole field will not work directly as an email address due
2576 to a misfeature in the syntax specified in RFC822; a
2577 program using this field as an address must check for this
2578 and correct the problem if necessary (for example by
2579 putting the name in round brackets and moving it to the
2580 end, and bringing the email address forward).
2584 <sect1 id="f-Uploaders">
2585 <heading><tt>Uploaders</tt></heading>
2588 List of the names and email addresses of co-maintainers of
2589 the package, if any. If the package has other maintainers
2590 beside the one named in the
2591 <qref id="f-Maintainer">Maintainer field</qref>, their
2592 names and email addresses should be listed here. The
2593 format is the same as that of the Maintainer tag, and
2594 multiple entries should be comma separated. Currently,
2595 this field is restricted to a single line of data. This
2596 is an optional field.
2599 Any parser that interprets the Uploaders field in
2600 <file>debian/control</file> must permit it to span multiple
2601 lines. Line breaks in an Uploaders field that spans multiple
2602 lines are not significant and the semantics of the field are
2603 the same as if the line breaks had not been present.
2607 <sect1 id="f-Changed-By">
2608 <heading><tt>Changed-By</tt></heading>
2611 The name and email address of the person who changed the
2612 said package. Usually the name of the maintainer.
2613 All the rules for the Maintainer field apply here, too.
2617 <sect1 id="f-Section">
2618 <heading><tt>Section</tt></heading>
2621 This field specifies an application area into which the package
2622 has been classified. See <ref id="subsections">.
2626 When it appears in the <file>debian/control</file> file,
2627 it gives the value for the subfield of the same name in
2628 the <tt>Files</tt> field of the <file>.changes</file> file.
2629 It also gives the default for the same field in the binary
2634 <sect1 id="f-Priority">
2635 <heading><tt>Priority</tt></heading>
2638 This field represents how important that it is that the user
2639 have the package installed. See <ref id="priorities">.
2643 When it appears in the <file>debian/control</file> file,
2644 it gives the value for the subfield of the same name in
2645 the <tt>Files</tt> field of the <file>.changes</file> file.
2646 It also gives the default for the same field in the binary
2651 <sect1 id="f-Package">
2652 <heading><tt>Package</tt></heading>
2655 The name of the binary package.
2659 Package names must consist only of lower case letters
2660 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2661 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2662 They must be at least two characters long and must start
2663 with an alphanumeric character.
2667 <sect1 id="f-Architecture">
2668 <heading><tt>Architecture</tt></heading>
2671 Depending on context and the control file used, the
2672 <tt>Architecture</tt> field can include the following sets of
2675 <item>A unique single word identifying a Debian machine
2676 architecture, see <ref id="arch-spec">.
2677 <item><tt>all</tt>, which indicates an
2678 architecture-independent package.
2679 <item><tt>any</tt>, which indicates a package available
2680 for building on any architecture.
2681 <item><tt>source</tt>, which indicates a source package.
2686 In the main <file>debian/control</file> file in the source
2687 package, or in the source package control file
2688 <file>.dsc</file>, one may specify a list of architectures
2689 separated by spaces, or the special values <tt>any</tt> or
2694 Specifying <tt>any</tt> indicates that the source package
2695 isn't dependent on any particular architecture and should
2696 compile fine on any one. The produced binary package(s)
2697 will be specific to whatever the current build architecture
2699 This is the most often used setting, and is recommended
2700 for new packages that aren't <tt>Architecture: all</tt>.
2705 Specifying a list of architectures indicates that the source
2706 will build an architecture-dependent package, and will only
2707 work correctly on the listed architectures.<footnote>
2708 This is a setting used for a minority of cases where the
2709 program is not portable. Generally, it should not be used
2715 In a <file>.changes</file> file, the <tt>Architecture</tt>
2716 field lists the architecture(s) of the package(s)
2717 currently being uploaded. This will be a list; if the
2718 source for the package is also being uploaded, the special
2719 entry <tt>source</tt> is also present.
2723 See <ref id="debianrules"> for information how to get the
2724 architecture for the build process.
2728 <sect1 id="f-Essential">
2729 <heading><tt>Essential</tt></heading>
2732 This is a boolean field which may occur only in the
2733 control file of a binary package or in a per-package fields
2734 paragraph of a main source control data file.
2738 If set to <tt>yes</tt> then the package management system
2739 will refuse to remove the package (upgrading and replacing
2740 it is still possible). The other possible value is <tt>no</tt>,
2741 which is the same as not having the field at all.
2746 <heading>Package interrelationship fields:
2747 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2748 <tt>Recommends</tt>, <tt>Suggests</tt>,
2749 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2750 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2754 These fields describe the package's relationships with
2755 other packages. Their syntax and semantics are described
2756 in <ref id="relationships">.</p>
2759 <sect1 id="f-Standards-Version">
2760 <heading><tt>Standards-Version</tt></heading>
2763 The most recent version of the standards (the policy
2764 manual and associated texts) with which the package
2769 The version number has four components: major and minor
2770 version number and major and minor patch level. When the
2771 standards change in a way that requires every package to
2772 change the major number will be changed. Significant
2773 changes that will require work in many packages will be
2774 signaled by a change to the minor number. The major patch
2775 level will be changed for any change to the meaning of the
2776 standards, however small; the minor patch level will be
2777 changed when only cosmetic, typographical or other edits
2778 are made which neither change the meaning of the document
2779 nor affect the contents of packages.
2783 Thus only the first three components of the policy version
2784 are significant in the <em>Standards-Version</em> control
2785 field, and so either these three components or the all
2786 four components may be specified.<footnote>
2787 In the past, people specified the full version number
2788 in the Standards-Version field, for example "2.3.0.0".
2789 Since minor patch-level changes don't introduce new
2790 policy, it was thought it would be better to relax
2791 policy and only require the first 3 components to be
2792 specified, in this example "2.3.0". All four
2793 components may still be used if someone wishes to do so.
2799 <sect1 id="f-Version">
2800 <heading><tt>Version</tt></heading>
2803 The version number of a package. The format is:
2804 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2808 The three components here are:
2810 <tag><var>epoch</var></tag>
2813 This is a single (generally small) unsigned integer. It
2814 may be omitted, in which case zero is assumed. If it is
2815 omitted then the <var>upstream_version</var> may not
2820 It is provided to allow mistakes in the version numbers
2821 of older versions of a package, and also a package's
2822 previous version numbering schemes, to be left behind.
2826 <tag><var>upstream_version</var></tag>
2829 This is the main part of the version number. It is
2830 usually the version number of the original ("upstream")
2831 package from which the <file>.deb</file> file has been made,
2832 if this is applicable. Usually this will be in the same
2833 format as that specified by the upstream author(s);
2834 however, it may need to be reformatted to fit into the
2835 package management system's format and comparison
2840 The comparison behavior of the package management system
2841 with respect to the <var>upstream_version</var> is
2842 described below. The <var>upstream_version</var>
2843 portion of the version number is mandatory.
2847 The <var>upstream_version</var> may contain only
2848 alphanumerics<footnote>
2849 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2851 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2852 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2853 tilde) and should start with a digit. If there is no
2854 <var>debian_revision</var> then hyphens are not allowed;
2855 if there is no <var>epoch</var> then colons are not
2860 <tag><var>debian_revision</var></tag>
2863 This part of the version number specifies the version of
2864 the Debian package based on the upstream version. It
2865 may contain only alphanumerics and the characters
2866 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2867 tilde) and is compared in the same way as the
2868 <var>upstream_version</var> is.
2872 It is optional; if it isn't present then the
2873 <var>upstream_version</var> may not contain a hyphen.
2874 This format represents the case where a piece of
2875 software was written specifically to be turned into a
2876 Debian package, and so there is only one "debianisation"
2877 of it and therefore no revision indication is required.
2881 It is conventional to restart the
2882 <var>debian_revision</var> at <tt>1</tt> each time the
2883 <var>upstream_version</var> is increased.
2887 The package management system will break the version
2888 number apart at the last hyphen in the string (if there
2889 is one) to determine the <var>upstream_version</var> and
2890 <var>debian_revision</var>. The absence of a
2891 <var>debian_revision</var> is equivalent to a
2892 <var>debian_revision</var> of <tt>0</tt>.
2899 When comparing two version numbers, first the <var>epoch</var>
2900 of each are compared, then the <var>upstream_version</var> if
2901 <var>epoch</var> is equal, and then <var>debian_revision</var>
2902 if <var>upstream_version</var> is also equal.
2903 <var>epoch</var> is compared numerically. The
2904 <var>upstream_version</var> and <var>debian_revision</var>
2905 parts are compared by the package management system using the
2906 following algorithm:
2910 The strings are compared from left to right.
2914 First the initial part of each string consisting entirely of
2915 non-digit characters is determined. These two parts (one of
2916 which may be empty) are compared lexically. If a difference
2917 is found it is returned. The lexical comparison is a
2918 comparison of ASCII values modified so that all the letters
2919 sort earlier than all the non-letters and so that a tilde
2920 sorts before anything, even the end of a part. For example,
2921 the following parts are in sorted order from earliest to
2922 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2923 <tt>a</tt>.<footnote>
2924 One common use of <tt>~</tt> is for upstream pre-releases.
2925 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2926 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2931 Then the initial part of the remainder of each string which
2932 consists entirely of digit characters is determined. The
2933 numerical values of these two parts are compared, and any
2934 difference found is returned as the result of the comparison.
2935 For these purposes an empty string (which can only occur at
2936 the end of one or both version strings being compared) counts
2941 These two steps (comparing and removing initial non-digit
2942 strings and initial digit strings) are repeated until a
2943 difference is found or both strings are exhausted.
2947 Note that the purpose of epochs is to allow us to leave behind
2948 mistakes in version numbering, and to cope with situations
2949 where the version numbering scheme changes. It is
2950 <em>not</em> intended to cope with version numbers containing
2951 strings of letters which the package management system cannot
2952 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2953 silly orderings (the author of this manual has heard of a
2954 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2955 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2956 <tt>2</tt> and so forth).
2960 <sect1 id="f-Description">
2961 <heading><tt>Description</tt></heading>
2964 In a source or binary control file, the <tt>Description</tt>
2965 field contains a description of the binary package, consisting
2966 of two parts, the synopsis or the short description, and the
2967 long description. The field's format is as follows:
2972 Description: <single line synopsis>
2973 <extended description over several lines>
2978 The lines in the extended description can have these formats:
2984 Those starting with a single space are part of a paragraph.
2985 Successive lines of this form will be word-wrapped when
2986 displayed. The leading space will usually be stripped off.
2990 Those starting with two or more spaces. These will be
2991 displayed verbatim. If the display cannot be panned
2992 horizontally, the displaying program will line wrap them "hard"
2993 (i.e., without taking account of word breaks). If it can they
2994 will be allowed to trail off to the right. None, one or two
2995 initial spaces may be deleted, but the number of spaces
2996 deleted from each line will be the same (so that you can have
2997 indenting work correctly, for example).
3001 Those containing a single space followed by a single full stop
3002 character. These are rendered as blank lines. This is the
3003 <em>only</em> way to get a blank line<footnote>
3004 Completely empty lines will not be rendered as blank lines.
3005 Instead, they will cause the parser to think you're starting
3006 a whole new record in the control file, and will therefore
3007 likely abort with an error.
3012 Those containing a space, a full stop and some more characters.
3013 These are for future expansion. Do not use them.
3019 Do not use tab characters. Their effect is not predictable.
3023 See <ref id="descriptions"> for further information on this.
3027 In a <file>.changes</file> file, the <tt>Description</tt> field
3028 contains a summary of the descriptions for the packages being
3033 The part of the field before the first newline is empty;
3034 thereafter each line has the name of a binary package and
3035 the summary description line from that binary package.
3036 Each line is indented by one space.
3041 <sect1 id="f-Distribution">
3042 <heading><tt>Distribution</tt></heading>
3045 In a <file>.changes</file> file or parsed changelog output
3046 this contains the (space-separated) name(s) of the
3047 distribution(s) where this version of the package should
3048 be installed. Valid distributions are determined by the
3049 archive maintainers.<footnote>
3050 Current distribution names are:
3051 <taglist compact="compact">
3052 <tag><em>stable</em></tag>
3054 This is the current "released" version of Debian
3055 GNU/Linux. Once the distribution is
3056 <em>stable</em> only security fixes and other
3057 major bug fixes are allowed. When changes are
3058 made to this distribution, the release number is
3059 increased (for example: 2.2r1 becomes 2.2r2 then
3063 <tag><em>unstable</em></tag>
3065 This distribution value refers to the
3066 <em>developmental</em> part of the Debian
3067 distribution tree. New packages, new upstream
3068 versions of packages and bug fixes go into the
3069 <em>unstable</em> directory tree. Download from
3070 this distribution at your own risk.
3073 <tag><em>testing</em></tag>
3075 This distribution value refers to the
3076 <em>testing</em> part of the Debian distribution
3077 tree. It receives its packages from the
3078 unstable distribution after a short time lag to
3079 ensure that there are no major issues with the
3080 unstable packages. It is less prone to breakage
3081 than unstable, but still risky. It is not
3082 possible to upload packages directly to
3086 <tag><em>frozen</em></tag>
3088 From time to time, the <em>testing</em>
3089 distribution enters a state of "code-freeze" in
3090 anticipation of release as a <em>stable</em>
3091 version. During this period of testing only
3092 fixes for existing or newly-discovered bugs will
3093 be allowed. The exact details of this stage are
3094 determined by the Release Manager.
3097 <tag><em>experimental</em></tag>
3099 The packages with this distribution value are
3100 deemed by their maintainers to be high
3101 risk. Oftentimes they represent early beta or
3102 developmental packages from various sources that
3103 the maintainers want people to try, but are not
3104 ready to be a part of the other parts of the
3105 Debian distribution tree. Download at your own
3111 You should list <em>all</em> distributions that the
3112 package should be installed into.
3116 More information is available in the Debian Developer's
3117 Reference, section "The Debian archive".
3124 <heading><tt>Date</tt></heading>
3127 This field includes the date the package was built or last edited.
3131 The value of this field is usually extracted from the
3132 <file>debian/changelog</file> file - see
3133 <ref id="dpkgchangelog">).
3137 <sect1 id="f-Format">
3138 <heading><tt>Format</tt></heading>
3141 This field specifies a format revision for the file.
3142 The most current format described in the Policy Manual
3143 is version <strong>1.5</strong>. The syntax of the
3144 format value is the same as that of a package version
3145 number except that no epoch or Debian revision is allowed
3146 - see <ref id="f-Version">.
3150 <sect1 id="f-Urgency">
3151 <heading><tt>Urgency</tt></heading>
3154 This is a description of how important it is to upgrade to
3155 this version from previous ones. It consists of a single
3156 keyword taking one of the values <tt>low</tt>,
3157 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3158 <tt>critical</tt><footnote>
3159 Other urgency values are supported with configuration
3160 changes in the archive software but are not used in Debian.
3161 The urgency affects how quickly a package will be considered
3162 for inclusion into the <tt>testing</tt> distribution and
3163 gives an indication of the importance of any fixes included
3164 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3165 treated as synonymous.
3166 </footnote> (not case-sensitive) followed by an optional
3167 commentary (separated by a space) which is usually in
3168 parentheses. For example:
3171 Urgency: low (HIGH for users of diversions)
3177 The value of this field is usually extracted from the
3178 <file>debian/changelog</file> file - see
3179 <ref id="dpkgchangelog">.
3183 <sect1 id="f-Changes">
3184 <heading><tt>Changes</tt></heading>
3187 This field contains the human-readable changes data, describing
3188 the differences between the last version and the current one.
3192 There should be nothing in this field before the first
3193 newline; all the subsequent lines must be indented by at
3194 least one space; blank lines must be represented by a line
3195 consisting only of a space and a full stop.
3199 The value of this field is usually extracted from the
3200 <file>debian/changelog</file> file - see
3201 <ref id="dpkgchangelog">).
3205 Each version's change information should be preceded by a
3206 "title" line giving at least the version, distribution(s)
3207 and urgency, in a human-readable way.
3211 If data from several versions is being returned the entry
3212 for the most recent version should be returned first, and
3213 entries should be separated by the representation of a
3214 blank line (the "title" line may also be followed by the
3215 representation of blank line).
3219 <sect1 id="f-Binary">
3220 <heading><tt>Binary</tt></heading>
3223 This field is a list of binary packages.
3227 When it appears in the <file>.dsc</file> file it is the list
3228 of binary packages which a source package can produce. It
3229 does not necessarily produce all of these binary packages
3230 for every architecture. The source control file doesn't
3231 contain details of which architectures are appropriate for
3232 which of the binary packages.
3236 When it appears in a <file>.changes</file> file it lists the
3237 names of the binary packages actually being uploaded.
3241 The syntax is a list of binary packages separated by
3243 A space after each comma is conventional.
3244 </footnote>. Currently the packages must be separated using
3245 only spaces in the <file>.changes</file> file.
3249 <sect1 id="f-Installed-Size">
3250 <heading><tt>Installed-Size</tt></heading>
3253 This field appears in the control files of binary
3254 packages, and in the <file>Packages</file> files. It gives
3255 the total amount of disk space required to install the
3260 The disk space is represented in kilobytes as a simple
3265 <sect1 id="f-Files">
3266 <heading><tt>Files</tt></heading>
3269 This field contains a list of files with information about
3270 each one. The exact information and syntax varies with
3271 the context. In all cases the part of the field
3272 contents on the same line as the field name is empty. The
3273 remainder of the field is one line per file, each line
3274 being indented by one space and containing a number of
3275 sub-fields separated by spaces.
3279 In the <file>.dsc</file> file, each line contains the MD5
3280 checksum, size and filename of the tar file and (if applicable)
3281 diff file which make up the remainder of the source
3283 That is, the parts which are not the <tt>.dsc</tt>.
3285 The exact forms of the filenames are described
3286 in <ref id="pkg-sourcearchives">.
3290 In the <file>.changes</file> file this contains one line per
3291 file being uploaded. Each line contains the MD5 checksum,
3292 size, section and priority and the filename.
3293 The <qref id="f-Section">section</qref>
3294 and <qref id="f-Priority">priority</qref>
3295 are the values of the corresponding fields in
3296 the main source control file. If no section or priority is
3297 specified then <tt>-</tt> should be used, though section
3298 and priority values must be specified for new packages to
3299 be installed properly.
3303 The special value <tt>byhand</tt> for the section in a
3304 <tt>.changes</tt> file indicates that the file in question
3305 is not an ordinary package file and must by installed by
3306 hand by the distribution maintainers. If the section is
3307 <tt>byhand</tt> the priority should be <tt>-</tt>.
3311 If a new Debian revision of a package is being shipped and
3312 no new original source archive is being distributed the
3313 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3314 entry for the original source archive
3315 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3316 but the <file>.changes</file> file should leave it out. In
3317 this case the original source archive on the distribution
3318 site must match exactly, byte-for-byte, the original
3319 source archive which was used to generate the
3320 <file>.dsc</file> file and diff which are being uploaded.</p>
3323 <sect1 id="f-Closes">
3324 <heading><tt>Closes</tt></heading>
3327 A space-separated list of bug report numbers that the upload
3328 governed by the .changes file closes.
3332 <sect1 id="f-Homepage">
3333 <heading><tt>Homepage</tt></heading>
3336 The URL of the web site for this package, preferably (when
3337 applicable) the site from which the original source can be
3338 obtained and any additional upstream documentation or
3339 information may be found. The content of this field is a
3340 simple URL without any surrounding characters such as
3348 <heading>User-defined fields</heading>
3351 Additional user-defined fields may be added to the
3352 source package control file. Such fields will be
3353 ignored, and not copied to (for example) binary or
3354 source package control files or upload control files.
3358 If you wish to add additional unsupported fields to
3359 these output files you should use the mechanism
3364 Fields in the main source control information file with
3365 names starting <tt>X</tt>, followed by one or more of
3366 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3367 be copied to the output files. Only the part of the
3368 field name after the hyphen will be used in the output
3369 file. Where the letter <tt>B</tt> is used the field
3370 will appear in binary package control files, where the
3371 letter <tt>S</tt> is used in source package control
3372 files and where <tt>C</tt> is used in upload control
3373 (<tt>.changes</tt>) files.
3377 For example, if the main source information control file
3380 XBS-Comment: I stand between the candle and the star.
3382 then the binary and source package control files will contain the
3385 Comment: I stand between the candle and the star.
3394 <chapt id="maintainerscripts">
3395 <heading>Package maintainer scripts and installation procedure</heading>
3398 <heading>Introduction to package maintainer scripts</heading>
3401 It is possible to supply scripts as part of a package which
3402 the package management system will run for you when your
3403 package is installed, upgraded or removed.
3407 These scripts are the files <prgn>preinst</prgn>,
3408 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3409 <prgn>postrm</prgn> in the control area of the package.
3410 They must be proper executable files; if they are scripts
3411 (which is recommended), they must start with the usual
3412 <tt>#!</tt> convention. They should be readable and
3413 executable by anyone, and must not be world-writable.
3417 The package management system looks at the exit status from
3418 these scripts. It is important that they exit with a
3419 non-zero status if there is an error, so that the package
3420 management system can stop its processing. For shell
3421 scripts this means that you <em>almost always</em> need to
3422 use <tt>set -e</tt> (this is usually true when writing shell
3423 scripts, in fact). It is also important, of course, that
3424 they don't exit with a non-zero status if everything went
3429 Additionally, packages interacting with users using
3430 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3431 install a <prgn>config</prgn> script in the control area,
3432 see <ref id="maintscriptprompt"> for details.
3436 When a package is upgraded a combination of the scripts from
3437 the old and new packages is called during the upgrade
3438 procedure. If your scripts are going to be at all
3439 complicated you need to be aware of this, and may need to
3440 check the arguments to your scripts.
3444 Broadly speaking the <prgn>preinst</prgn> is called before
3445 (a particular version of) a package is installed, and the
3446 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3447 before (a version of) a package is removed and the
3448 <prgn>postrm</prgn> afterwards.
3452 Programs called from maintainer scripts should not normally
3453 have a path prepended to them. Before installation is
3454 started, the package management system checks to see if the
3455 programs <prgn>ldconfig</prgn>,
3456 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3457 and <prgn>update-rc.d</prgn> can be found via the
3458 <tt>PATH</tt> environment variable. Those programs, and any
3459 other program that one would expect to be in the
3460 <tt>PATH</tt>, should thus be invoked without an absolute
3461 pathname. Maintainer scripts should also not reset the
3462 <tt>PATH</tt>, though they might choose to modify it by
3463 prepending or appending package-specific directories. These
3464 considerations really apply to all shell scripts.</p>
3467 <sect id="idempotency">
3468 <heading>Maintainer scripts idempotency</heading>
3471 It is necessary for the error recovery procedures that the
3472 scripts be idempotent. This means that if it is run
3473 successfully, and then it is called again, it doesn't bomb
3474 out or cause any harm, but just ensures that everything is
3475 the way it ought to be. If the first call failed, or
3476 aborted half way through for some reason, the second call
3477 should merely do the things that were left undone the first
3478 time, if any, and exit with a success status if everything
3480 This is so that if an error occurs, the user interrupts
3481 <prgn>dpkg</prgn> or some other unforeseen circumstance
3482 happens you don't leave the user with a badly-broken
3483 package when <prgn>dpkg</prgn> attempts to repeat the
3489 <sect id="controllingterminal">
3490 <heading>Controlling terminal for maintainer scripts</heading>
3493 The maintainer scripts are guaranteed to run with a
3494 controlling terminal and can interact with the user.
3495 Because these scripts may be executed with standard output
3496 redirected into a pipe for logging purposes, Perl scripts
3497 should set unbuffered output by setting <tt>$|=1</tt> so
3498 that the output is printed immediately rather than being
3502 <sect id="exitstatus">
3503 <heading>Exit status</heading>
3506 Each script must return a zero exit status for
3507 success, or a nonzero one for failure, since the package
3508 management system looks for the exit status of these scripts
3509 and determines what action to take next based on that datum.
3513 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3518 <list compact="compact">
3520 <var>new-preinst</var> <tt>install</tt>
3523 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3526 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3529 <var>old-preinst</var> <tt>abort-upgrade</tt>
3530 <var>new-version</var>
3535 <list compact="compact">
3537 <var>postinst</var> <tt>configure</tt>
3538 <var>most-recently-configured-version</var>
3541 <var>old-postinst</var> <tt>abort-upgrade</tt>
3542 <var>new-version</var>
3545 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3546 <tt>in-favour</tt> <var>package</var>
3547 <var>new-version</var>
3550 <var>postinst</var> <tt>abort-remove</tt>
3553 <var>deconfigured's-postinst</var>
3554 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3555 <var>failed-install-package</var> <var>version</var>
3556 [<tt>removing</tt> <var>conflicting-package</var>
3562 <list compact="compact">
3564 <var>prerm</var> <tt>remove</tt>
3567 <var>old-prerm</var> <tt>upgrade</tt>
3568 <var>new-version</var>
3571 <var>new-prerm</var> <tt>failed-upgrade</tt>
3572 <var>old-version</var>
3575 <var>conflictor's-prerm</var> <tt>remove</tt>
3576 <tt>in-favour</tt> <var>package</var>
3577 <var>new-version</var>
3580 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3581 <tt>in-favour</tt> <var>package-being-installed</var>
3582 <var>version</var> [<tt>removing</tt>
3583 <var>conflicting-package</var>
3589 <list compact="compact">
3591 <var>postrm</var> <tt>remove</tt>
3594 <var>postrm</var> <tt>purge</tt>
3597 <var>old-postrm</var> <tt>upgrade</tt>
3598 <var>new-version</var>
3601 <var>new-postrm</var> <tt>failed-upgrade</tt>
3602 <var>old-version</var>
3605 <var>new-postrm</var> <tt>abort-install</tt>
3608 <var>new-postrm</var> <tt>abort-install</tt>
3609 <var>old-version</var>
3612 <var>new-postrm</var> <tt>abort-upgrade</tt>
3613 <var>old-version</var>
3616 <var>disappearer's-postrm</var> <tt>disappear</tt>
3617 <var>overwriter</var>
3618 <var>overwriter-version</var>
3624 <sect id="unpackphase">
3625 <heading>Details of unpack phase of installation or upgrade</heading>
3628 The procedure on installation/upgrade/overwrite/disappear
3629 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3630 stage of <tt>dpkg --install</tt>) is as follows. In each
3631 case, if a major error occurs (unless listed below) the
3632 actions are, in general, run backwards - this means that the
3633 maintainer scripts are run with different arguments in
3634 reverse order. These are the "error unwind" calls listed
3641 If a version of the package is already installed, call
3642 <example compact="compact">
3643 <var>old-prerm</var> upgrade <var>new-version</var>
3647 If the script runs but exits with a non-zero
3648 exit status, <prgn>dpkg</prgn> will attempt:
3649 <example compact="compact">
3650 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3652 If this works, the upgrade continues. If this
3653 does not work, the error unwind:
3654 <example compact="compact">
3655 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3657 If this works, then the old-version is
3658 "Installed", if not, the old version is in a
3659 "Failed-Config" state.
3665 If a "conflicting" package is being removed at the same time,
3666 or if any package will be broken (due to <tt>Breaks</tt>):
3669 If <tt>--auto-deconfigure</tt> is
3670 specified, call, for each package to be deconfigured
3671 due to <tt>Breaks</tt>:
3672 <example compact="compact">
3673 <var>deconfigured's-prerm</var> deconfigure \
3674 in-favour <var>package-being-installed</var> <var>version</var>
3677 <example compact="compact">
3678 <var>deconfigured's-postinst</var> abort-deconfigure \
3679 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3681 The deconfigured packages are marked as
3682 requiring configuration, so that if
3683 <tt>--install</tt> is used they will be
3684 configured again if possible.
3687 If any packages depended on a conflicting
3688 package being removed and <tt>--auto-deconfigure</tt> is
3689 specified, call, for each such package:
3690 <example compact="compact">
3691 <var>deconfigured's-prerm</var> deconfigure \
3692 in-favour <var>package-being-installed</var> <var>version</var> \
3693 removing <var>conflicting-package</var> <var>version</var>
3696 <example compact="compact">
3697 <var>deconfigured's-postinst</var> abort-deconfigure \
3698 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3699 removing <var>conflicting-package</var> <var>version</var>
3701 The deconfigured packages are marked as
3702 requiring configuration, so that if
3703 <tt>--install</tt> is used they will be
3704 configured again if possible.
3707 To prepare for removal of each conflicting package, call:
3708 <example compact="compact">
3709 <var>conflictor's-prerm</var> remove \
3710 in-favour <var>package</var> <var>new-version</var>
3713 <example compact="compact">
3714 <var>conflictor's-postinst</var> abort-remove \
3715 in-favour <var>package</var> <var>new-version</var>
3724 If the package is being upgraded, call:
3725 <example compact="compact">
3726 <var>new-preinst</var> upgrade <var>old-version</var>
3728 If this fails, we call:
3730 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3737 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3739 is called. If this works, then the old version
3740 is in an "Installed" state, or else it is left
3741 in an "Unpacked" state.
3746 If it fails, then the old version is left
3747 in an "Half-Installed" state.
3754 Otherwise, if the package had some configuration
3755 files from a previous version installed (i.e., it
3756 is in the "configuration files only" state):
3757 <example compact="compact">
3758 <var>new-preinst</var> install <var>old-version</var>
3762 <var>new-postrm</var> abort-install <var>old-version</var>
3764 If this fails, the package is left in a
3765 "Half-Installed" state, which requires a
3766 reinstall. If it works, the packages is left in
3767 a "Config Files" state.
3770 Otherwise (i.e., the package was completely purged):
3771 <example compact="compact">
3772 <var>new-preinst</var> install
3775 <example compact="compact">
3776 <var>new-postrm</var> abort-install
3778 If the error-unwind fails, the package is in a
3779 "Half Installed" phase, and requires a
3780 reinstall. If the error unwind works, the
3781 package is in a not installed state.
3788 The new package's files are unpacked, overwriting any
3789 that may be on the system already, for example any
3790 from the old version of the same package or from
3791 another package. Backups of the old files are kept
3792 temporarily, and if anything goes wrong the package
3793 management system will attempt to put them back as
3794 part of the error unwind.
3798 It is an error for a package to contain files which
3799 are on the system in another package, unless
3800 <tt>Replaces</tt> is used (see <ref id="replaces">).
3802 The following paragraph is not currently the case:
3803 Currently the <tt>- - force-overwrite</tt> flag is
3804 enabled, downgrading it to a warning, but this may not
3810 It is a more serious error for a package to contain a
3811 plain file or other kind of non-directory where another
3812 package has a directory (again, unless
3813 <tt>Replaces</tt> is used). This error can be
3814 overridden if desired using
3815 <tt>--force-overwrite-dir</tt>, but this is not
3820 Packages which overwrite each other's files produce
3821 behavior which, though deterministic, is hard for the
3822 system administrator to understand. It can easily
3823 lead to "missing" programs if, for example, a package
3824 is installed which overwrites a file from another
3825 package, and is then removed again.<footnote>
3826 Part of the problem is due to what is arguably a
3827 bug in <prgn>dpkg</prgn>.
3832 A directory will never be replaced by a symbolic link
3833 to a directory or vice versa; instead, the existing
3834 state (symlink or not) will be left alone and
3835 <prgn>dpkg</prgn> will follow the symlink if there is
3844 If the package is being upgraded, call
3845 <example compact="compact">
3846 <var>old-postrm</var> upgrade <var>new-version</var>
3850 If this fails, <prgn>dpkg</prgn> will attempt:
3851 <example compact="compact">
3852 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3854 If this works, installation continues. If not,
3856 <example compact="compact">
3857 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3859 If this fails, the old version is left in an
3860 "Half Installed" state. If it works, dpkg now
3862 <example compact="compact">
3863 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3865 If this fails, the old version is left in an
3866 "Half Installed" state. If it works, dpkg now
3868 <example compact="compact">
3869 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3871 If this fails, the old version is in an
3878 This is the point of no return - if
3879 <prgn>dpkg</prgn> gets this far, it won't back off
3880 past this point if an error occurs. This will
3881 leave the package in a fairly bad state, which
3882 will require a successful re-installation to clear
3883 up, but it's when <prgn>dpkg</prgn> starts doing
3884 things that are irreversible.
3889 Any files which were in the old version of the package
3890 but not in the new are removed.
3894 The new file list replaces the old.
3898 The new maintainer scripts replace the old.
3902 Any packages all of whose files have been overwritten
3903 during the installation, and which aren't required for
3904 dependencies, are considered to have been removed.
3905 For each such package
3908 <prgn>dpkg</prgn> calls:
3909 <example compact="compact">
3910 <var>disappearer's-postrm</var> disappear \
3911 <var>overwriter</var> <var>overwriter-version</var>
3915 The package's maintainer scripts are removed.
3918 It is noted in the status database as being in a
3919 sane state, namely not installed (any conffiles
3920 it may have are ignored, rather than being
3921 removed by <prgn>dpkg</prgn>). Note that
3922 disappearing packages do not have their prerm
3923 called, because <prgn>dpkg</prgn> doesn't know
3924 in advance that the package is going to
3931 Any files in the package we're unpacking that are also
3932 listed in the file lists of other packages are removed
3933 from those lists. (This will lobotomize the file list
3934 of the "conflicting" package if there is one.)
3938 The backup files made during installation, above, are
3944 The new package's status is now sane, and recorded as
3949 Here is another point of no return - if the
3950 conflicting package's removal fails we do not unwind
3951 the rest of the installation; the conflicting package
3952 is left in a half-removed limbo.
3957 If there was a conflicting package we go and do the
3958 removal actions (described below), starting with the
3959 removal of the conflicting package's files (any that
3960 are also in the package being installed have already
3961 been removed from the conflicting package's file list,
3962 and so do not get removed now).
3968 <sect id="configdetails"><heading>Details of configuration</heading>
3971 When we configure a package (this happens with <tt>dpkg
3972 --install</tt> and <tt>dpkg --configure</tt>), we first
3973 update any <tt>conffile</tt>s and then call:
3974 <example compact="compact">
3975 <var>postinst</var> configure <var>most-recently-configured-version</var>
3980 No attempt is made to unwind after errors during
3981 configuration. If the configuration fails, the package is in
3982 a "Failed Config" state, and an error message is generated.
3986 If there is no most recently configured version
3987 <prgn>dpkg</prgn> will pass a null argument.
3990 Historical note: Truly ancient (pre-1997) versions of
3991 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3992 (including the angle brackets) in this case. Even older
3993 ones did not pass a second argument at all, under any
3994 circumstance. Note that upgrades using such an old dpkg
3995 version are unlikely to work for other reasons, even if
3996 this old argument behavior is handled by your postinst script.
4002 <sect id="removedetails"><heading>Details of removal and/or
4003 configuration purging</heading>
4009 <example compact="compact">
4010 <var>prerm</var> remove
4014 If prerm fails during replacement due to conflict
4016 <var>conflictor's-postinst</var> abort-remove \
4017 in-favour <var>package</var> <var>new-version</var>
4021 <var>postinst</var> abort-remove
4025 If this fails, the package is in a "Failed-Config"
4026 state, or else it remains "Installed".
4030 The package's files are removed (except <tt>conffile</tt>s).
4033 <example compact="compact">
4034 <var>postrm</var> remove
4038 If it fails, there's no error unwind, and the package is in
4039 an "Half-Installed" state.
4044 All the maintainer scripts except the <prgn>postrm</prgn>
4049 If we aren't purging the package we stop here. Note
4050 that packages which have no <prgn>postrm</prgn> and no
4051 <tt>conffile</tt>s are automatically purged when
4052 removed, as there is no difference except for the
4053 <prgn>dpkg</prgn> status.
4057 The <tt>conffile</tt>s and any backup files
4058 (<tt>~</tt>-files, <tt>#*#</tt> files,
4059 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4064 <example compact="compact">
4065 <var>postrm</var> purge
4069 If this fails, the package remains in a "Config-Files"
4074 The package's file list is removed.
4083 <chapt id="relationships">
4084 <heading>Declaring relationships between packages</heading>
4086 <sect id="depsyntax">
4087 <heading>Syntax of relationship fields</heading>
4090 These fields all have a uniform syntax. They are a list of
4091 package names separated by commas.
4095 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4096 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4097 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4098 control file fields of the package, which declare
4099 dependencies on other packages, the package names listed may
4100 also include lists of alternative package names, separated
4101 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4102 if any one of the alternative packages is installed, that
4103 part of the dependency is considered to be satisfied.
4107 All of the fields except for <tt>Provides</tt> may restrict
4108 their applicability to particular versions of each named
4109 package. This is done in parentheses after each individual
4110 package name; the parentheses should contain a relation from
4111 the list below followed by a version number, in the format
4112 described in <ref id="f-Version">.
4116 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4117 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4118 strictly earlier, earlier or equal, exactly equal, later or
4119 equal and strictly later, respectively. The deprecated
4120 forms <tt><</tt> and <tt>></tt> were used to mean
4121 earlier/later or equal, rather than strictly earlier/later,
4122 so they should not appear in new packages (though
4123 <prgn>dpkg</prgn> still supports them).
4127 Whitespace may appear at any point in the version
4128 specification subject to the rules in <ref
4129 id="controlsyntax">, and must appear where it's necessary to
4130 disambiguate; it is not otherwise significant. All of the
4131 relationship fields may span multiple lines. For
4132 consistency and in case of future changes to
4133 <prgn>dpkg</prgn> it is recommended that a single space be
4134 used after a version relationship and before a version
4135 number; it is also conventional to put a single space after
4136 each comma, on either side of each vertical bar, and before
4137 each open parenthesis. When wrapping a relationship field, it
4138 is conventional to do so after a comma and before the space
4139 following that comma.
4143 For example, a list of dependencies might appear as:
4144 <example compact="compact">
4147 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4152 All fields that specify build-time relationships
4153 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4154 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4155 may be restricted to a certain set of architectures. This
4156 is indicated in brackets after each individual package name and
4157 the optional version specification. The brackets enclose a
4158 list of Debian architecture names separated by whitespace.
4159 Exclamation marks may be prepended to each of the names.
4160 (It is not permitted for some names to be prepended with
4161 exclamation marks while others aren't.) If the current Debian
4162 host architecture is not in this list and there are no
4163 exclamation marks in the list, or it is in the list with a
4164 prepended exclamation mark, the package name and the
4165 associated version specification are ignored completely for
4166 the purposes of defining the relationships.
4171 <example compact="compact">
4173 Build-Depends-Indep: texinfo
4174 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4175 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4180 Note that the binary package relationship fields such as
4181 <tt>Depends</tt> appear in one of the binary package
4182 sections of the control file, whereas the build-time
4183 relationships such as <tt>Build-Depends</tt> appear in the
4184 source package section of the control file (which is the
4189 <sect id="binarydeps">
4190 <heading>Binary Dependencies - <tt>Depends</tt>,
4191 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4192 <tt>Pre-Depends</tt>
4196 Packages can declare in their control file that they have
4197 certain relationships to other packages - for example, that
4198 they may not be installed at the same time as certain other
4199 packages, and/or that they depend on the presence of others.
4203 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4204 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4205 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4209 These seven fields are used to declare a dependency
4210 relationship by one package on another. Except for
4211 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4212 depending (binary) package's control file.
4213 (<tt>Enhances</tt> appears in the recommending package's
4214 control file, and <tt>Breaks</tt> appears in the version of
4215 depended-on package which causes the named package to
4220 A <tt>Depends</tt> field takes effect <em>only</em> when a
4221 package is to be configured. It does not prevent a package
4222 being on the system in an unconfigured state while its
4223 dependencies are unsatisfied, and it is possible to replace
4224 a package whose dependencies are satisfied and which is
4225 properly installed with a different version whose
4226 dependencies are not and cannot be satisfied; when this is
4227 done the depending package will be left unconfigured (since
4228 attempts to configure it will give errors) and will not
4229 function properly. If it is necessary, a
4230 <tt>Pre-Depends</tt> field can be used, which has a partial
4231 effect even when a package is being unpacked, as explained
4232 in detail below. (The other three dependency fields,
4233 <tt>Recommends</tt>, <tt>Suggests</tt> and
4234 <tt>Enhances</tt>, are only used by the various front-ends
4235 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4236 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4240 For this reason packages in an installation run are usually
4241 all unpacked first and all configured later; this gives
4242 later versions of packages with dependencies on later
4243 versions of other packages the opportunity to have their
4244 dependencies satisfied.
4248 In case of circular dependencies, since installation or
4249 removal order honoring the dependency order can't be
4250 established, dependency loops are broken at some point
4251 (based on rules below), and some packages may not be able to
4252 rely on their dependencies being present when being
4253 installed or removed, depending on which side of the break
4254 of the circular dependency loop they happen to be on. If one
4255 of the packages in the loop has no postinst script, then the
4256 cycle will be broken at that package, so as to ensure that
4257 all postinst scripts run with the dependencies properly
4258 configured if this is possible. Otherwise the breaking point
4263 The <tt>Depends</tt> field thus allows package maintainers
4264 to impose an order in which packages should be configured.
4268 The meaning of the five dependency fields is as follows:
4270 <tag><tt>Depends</tt></tag>
4273 This declares an absolute dependency. A package will
4274 not be configured unless all of the packages listed in
4275 its <tt>Depends</tt> field have been correctly
4280 The <tt>Depends</tt> field should be used if the
4281 depended-on package is required for the depending
4282 package to provide a significant amount of
4287 The <tt>Depends</tt> field should also be used if the
4288 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4289 <prgn>postrm</prgn> scripts require the package to be
4290 present in order to run. Note, however, that the
4291 <prgn>postrm</prgn> cannot rely on any non-essential
4292 packages to be present during the <tt>purge</tt>
4296 <tag><tt>Recommends</tt></tag>
4299 This declares a strong, but not absolute, dependency.
4303 The <tt>Recommends</tt> field should list packages
4304 that would be found together with this one in all but
4305 unusual installations.
4309 <tag><tt>Suggests</tt></tag>
4311 This is used to declare that one package may be more
4312 useful with one or more others. Using this field
4313 tells the packaging system and the user that the
4314 listed packages are related to this one and can
4315 perhaps enhance its usefulness, but that installing
4316 this one without them is perfectly reasonable.
4319 <tag><tt>Enhances</tt></tag>
4321 This field is similar to Suggests but works in the
4322 opposite direction. It is used to declare that a
4323 package can enhance the functionality of another
4327 <tag><tt>Pre-Depends</tt></tag>
4330 This field is like <tt>Depends</tt>, except that it
4331 also forces <prgn>dpkg</prgn> to complete installation
4332 of the packages named before even starting the
4333 installation of the package which declares the
4334 pre-dependency, as follows:
4338 When a package declaring a pre-dependency is about to
4339 be <em>unpacked</em> the pre-dependency can be
4340 satisfied if the depended-on package is either fully
4341 configured, <em>or even if</em> the depended-on
4342 package(s) are only unpacked or half-configured,
4343 provided that they have been configured correctly at
4344 some point in the past (and not removed or partially
4345 removed since). In this case, both the
4346 previously-configured and currently unpacked or
4347 half-configured versions must satisfy any version
4348 clause in the <tt>Pre-Depends</tt> field.
4352 When the package declaring a pre-dependency is about
4353 to be <em>configured</em>, the pre-dependency will be
4354 treated as a normal <tt>Depends</tt>, that is, it will
4355 be considered satisfied only if the depended-on
4356 package has been correctly configured.
4360 <tt>Pre-Depends</tt> should be used sparingly,
4361 preferably only by packages whose premature upgrade or
4362 installation would hamper the ability of the system to
4363 continue with any upgrade that might be in progress.
4367 <tt>Pre-Depends</tt> are also required if the
4368 <prgn>preinst</prgn> script depends on the named
4369 package. It is best to avoid this situation if
4377 When selecting which level of dependency to use you should
4378 consider how important the depended-on package is to the
4379 functionality of the one declaring the dependency. Some
4380 packages are composed of components of varying degrees of
4381 importance. Such a package should list using
4382 <tt>Depends</tt> the package(s) which are required by the
4383 more important components. The other components'
4384 requirements may be mentioned as Suggestions or
4385 Recommendations, as appropriate to the components' relative
4391 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4394 Using <tt>Breaks</tt> may cause problems for upgrades from older
4395 versions of Debian and should not be used until the stable
4396 release of Debian supports <tt>Breaks</tt>.
4400 When one binary package declares that it breaks another,
4401 <prgn>dpkg</prgn> will refuse to allow the package which
4402 declares <tt>Breaks</tt> be installed unless the broken
4403 package is deconfigured first, and it will refuse to
4404 allow the broken package to be reconfigured.
4408 A package will not be regarded as causing breakage merely
4409 because its configuration files are still installed; it must
4410 be at least half-installed.
4414 A special exception is made for packages which declare that
4415 they break their own package name or a virtual package which
4416 they provide (see below): this does not count as a real
4421 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4422 version clause; such a <tt>Breaks</tt> is introduced in the
4423 version of an (implicit or explicit) dependency which
4424 violates an assumption or reveals a bug in earlier versions
4425 of the broken package. This use of <tt>Breaks</tt> will
4426 inform higher-level package management tools that broken
4427 package must be upgraded before the new one.
4431 If the breaking package also overwrites some files from the
4432 older package, it should use <tt>Replaces</tt> (not
4433 <tt>Conflicts</tt>) to ensure this goes smoothly.
4437 <sect id="conflicts">
4438 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4441 When one binary package declares a conflict with another
4442 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4443 refuse to allow them to be installed on the system at the
4448 If one package is to be installed, the other must be removed
4449 first - if the package being installed is marked as
4450 replacing (see <ref id="replaces">) the one on the system,
4451 or the one on the system is marked as deselected, or both
4452 packages are marked <tt>Essential</tt>, then
4453 <prgn>dpkg</prgn> will automatically remove the package
4454 which is causing the conflict, otherwise it will halt the
4455 installation of the new package with an error. This
4456 mechanism is specifically designed to produce an error when
4457 the installed package is <tt>Essential</tt>, but the new
4462 A package will not cause a conflict merely because its
4463 configuration files are still installed; it must be at least
4468 A special exception is made for packages which declare a
4469 conflict with their own package name, or with a virtual
4470 package which they provide (see below): this does not
4471 prevent their installation, and allows a package to conflict
4472 with others providing a replacement for it. You use this
4473 feature when you want the package in question to be the only
4474 package providing some feature.
4478 A <tt>Conflicts</tt> entry should almost never have an
4479 "earlier than" version clause. This would prevent
4480 <prgn>dpkg</prgn> from upgrading or installing the package
4481 which declared such a conflict until the upgrade or removal
4482 of the conflicted-with package had been completed. Instead,
4483 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4484 by the stable release of Debian).
4488 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4492 As well as the names of actual ("concrete") packages, the
4493 package relationship fields <tt>Depends</tt>,
4494 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4495 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4496 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4497 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4498 may mention "virtual packages".
4502 A <em>virtual package</em> is one which appears in the
4503 <tt>Provides</tt> control file field of another package.
4504 The effect is as if the package(s) which provide a
4505 particular virtual package name had been listed by name
4506 everywhere the virtual package name appears. (See also <ref
4511 If there are both concrete and virtual packages of the same
4512 name, then the dependency may be satisfied (or the conflict
4513 caused) by either the concrete package with the name in
4514 question or any other concrete package which provides the
4515 virtual package with the name in question. This is so that,
4516 for example, supposing we have
4517 <example compact="compact">
4520 </example> and someone else releases an enhanced version of
4521 the <tt>bar</tt> package they can say:
4522 <example compact="compact">
4526 and the <tt>bar-plus</tt> package will now also satisfy the
4527 dependency for the <tt>foo</tt> package.
4531 If a relationship field has a version number attached
4532 then only real packages will be considered to see whether
4533 the relationship is satisfied (or the prohibition violated,
4534 for a conflict or breakage) - it is assumed that a real
4535 package which provides the virtual package is not of the
4536 "right" version. So, a <tt>Provides</tt> field may not
4537 contain version numbers, and the version number of the
4538 concrete package which provides a particular virtual package
4539 will not be looked at when considering a dependency on or
4540 conflict with the virtual package name.
4544 It is likely that the ability will be added in a future
4545 release of <prgn>dpkg</prgn> to specify a version number for
4546 each virtual package it provides. This feature is not yet
4547 present, however, and is expected to be used only
4552 If you want to specify which of a set of real packages
4553 should be the default to satisfy a particular dependency on
4554 a virtual package, you should list the real package as an
4555 alternative before the virtual one.
4560 <sect id="replaces"><heading>Overwriting files and replacing
4561 packages - <tt>Replaces</tt></heading>
4564 Packages can declare in their control file that they should
4565 overwrite files in certain other packages, or completely
4566 replace other packages. The <tt>Replaces</tt> control file
4567 field has these two distinct purposes.
4570 <sect1><heading>Overwriting files in other packages</heading>
4573 Firstly, as mentioned before, it is usually an error for a
4574 package to contain files which are on the system in
4579 However, if the overwriting package declares that it
4580 <tt>Replaces</tt> the one containing the file being
4581 overwritten, then <prgn>dpkg</prgn> will replace the file
4582 from the old package with that from the new. The file
4583 will no longer be listed as "owned" by the old package.
4587 If a package is completely replaced in this way, so that
4588 <prgn>dpkg</prgn> does not know of any files it still
4589 contains, it is considered to have "disappeared". It will
4590 be marked as not wanted on the system (selected for
4591 removal) and not installed. Any <tt>conffile</tt>s
4592 details noted for the package will be ignored, as they
4593 will have been taken over by the overwriting package. The
4594 package's <prgn>postrm</prgn> script will be run with a
4595 special argument to allow the package to do any final
4596 cleanup required. See <ref id="mscriptsinstact">.
4599 Replaces is a one way relationship -- you have to
4600 install the replacing package after the replaced
4607 For this usage of <tt>Replaces</tt>, virtual packages (see
4608 <ref id="virtual">) are not considered when looking at a
4609 <tt>Replaces</tt> field - the packages declared as being
4610 replaced must be mentioned by their real names.
4614 Furthermore, this usage of <tt>Replaces</tt> only takes
4615 effect when both packages are at least partially on the
4616 system at once, so that it can only happen if they do not
4617 conflict or if the conflict has been overridden.
4622 <sect1><heading>Replacing whole packages, forcing their
4626 Secondly, <tt>Replaces</tt> allows the packaging system to
4627 resolve which package should be removed when there is a
4628 conflict - see <ref id="conflicts">. This usage only
4629 takes effect when the two packages <em>do</em> conflict,
4630 so that the two usages of this field do not interfere with
4635 In this situation, the package declared as being replaced
4636 can be a virtual package, so for example, all mail
4637 transport agents (MTAs) would have the following fields in
4638 their control files:
4639 <example compact="compact">
4640 Provides: mail-transport-agent
4641 Conflicts: mail-transport-agent
4642 Replaces: mail-transport-agent
4644 ensuring that only one MTA can be installed at any one
4649 <sect id="sourcebinarydeps">
4650 <heading>Relationships between source and binary packages -
4651 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4652 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4656 Source packages that require certain binary packages to be
4657 installed or absent at the time of building the package
4658 can declare relationships to those binary packages.
4662 This is done using the <tt>Build-Depends</tt>,
4663 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4664 <tt>Build-Conflicts-Indep</tt> control file fields.
4668 Build-dependencies on "build-essential" binary packages can be
4669 omitted. Please see <ref id="pkg-relations"> for more information.
4673 The dependencies and conflicts they define must be satisfied
4674 (as defined earlier for binary packages) in order to invoke
4675 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4677 If you make "build-arch" or "binary-arch", you need
4678 Build-Depends. If you make "build-indep" or
4679 "binary-indep", you need Build-Depends and
4680 Build-Depends-Indep. If you make "build" or "binary",
4684 There is no Build-Depends-Arch; this role is essentially
4685 met with Build-Depends. Anyone building the
4686 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4687 is basically assumed to be building the whole package
4688 anyway and so installs all build dependencies. The
4689 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4690 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4691 does not yet know how to check for its existence) and
4692 <tt>binary-arch</tt>.
4695 The purpose of the original split, I recall, was so that
4696 the autobuilders wouldn't need to install extra packages
4697 needed only for the binary-indep targets. But without a
4698 build-arch/build-indep split, this didn't work, since
4699 most of the work is done in the build target, not in the
4705 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4707 The <tt>Build-Depends</tt> and
4708 <tt>Build-Conflicts</tt> fields must be satisfied when
4709 any of the following targets is invoked:
4710 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4711 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4712 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4714 <tag><tt>Build-Depends-Indep</tt>,
4715 <tt>Build-Conflicts-Indep</tt></tag>
4717 The <tt>Build-Depends-Indep</tt> and
4718 <tt>Build-Conflicts-Indep</tt> fields must be
4719 satisfied when any of the following targets is
4720 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4721 <tt>binary</tt> and <tt>binary-indep</tt>.
4731 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4734 Packages containing shared libraries must be constructed with
4735 a little care to make sure that the shared library is always
4736 available. This is especially important for packages whose
4737 shared libraries are vitally important, such as the C library
4738 (currently <tt>libc6</tt>).
4742 Packages involving shared libraries should be split up into
4743 several binary packages. This section mostly deals with how
4744 this separation is to be accomplished; rules for files within
4745 the shared library packages are in <ref id="libraries"> instead.
4748 <sect id="sharedlibs-runtime">
4749 <heading>Run-time shared libraries</heading>
4752 The run-time shared library needs to be placed in a package
4753 whose name changes whenever the shared object version
4756 Since it is common place to install several versions of a
4757 package that just provides shared libraries, it is a
4758 good idea that the library package should not
4759 contain any extraneous non-versioned files, unless they
4760 happen to be in versioned directories.</p>
4762 The most common mechanism is to place it in a package
4764 <package><var>libraryname</var><var>soversion</var></package>,
4765 where <file><var>soversion</var></file> is the version number
4766 in the soname of the shared library<footnote>
4767 The soname is the shared object name: it's the thing
4768 that has to match exactly between building an executable
4769 and running it for the dynamic linker to be able run the
4770 program. For example, if the soname of the library is
4771 <file>libfoo.so.6</file>, the library package would be
4772 called <file>libfoo6</file>.
4774 Alternatively, if it would be confusing to directly append
4775 <var>soversion</var> to <var>libraryname</var> (e.g. because
4776 <var>libraryname</var> itself ends in a number), you may use
4777 <package><var>libraryname</var>-<var>soversion</var></package> and
4778 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4783 If you have several shared libraries built from the same
4784 source tree you may lump them all together into a single
4785 shared library package, provided that you change all of
4786 their sonames at once (so that you don't get filename
4787 clashes if you try to install different versions of the
4788 combined shared libraries package).
4792 The package should install the shared libraries under
4793 their normal names. For example, the <package>libgdbm3</package>
4794 package should install <file>libgdbm.so.3.0.0</file> as
4795 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4796 renamed or re-linked by any <prgn>prerm</prgn> or
4797 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4798 of renaming things safely without affecting running programs,
4799 and attempts to interfere with this are likely to lead to
4804 Shared libraries should not be installed executable, since
4805 the dynamic linker does not require this and trying to
4806 execute a shared library usually results in a core dump.
4810 The run-time library package should include the symbolic link that
4811 <prgn>ldconfig</prgn> would create for the shared libraries.
4812 For example, the <package>libgdbm3</package> package should include
4813 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4814 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4815 linker (for example <prgn>ld.so</prgn> or
4816 <prgn>ld-linux.so.*</prgn>) can find the library between the
4817 time that <prgn>dpkg</prgn> installs it and the time that
4818 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4820 The package management system requires the library to be
4821 placed before the symbolic link pointing to it in the
4822 <file>.deb</file> file. This is so that when
4823 <prgn>dpkg</prgn> comes to install the symlink
4824 (overwriting the previous symlink pointing at an older
4825 version of the library), the new shared library is already
4826 in place. In the past, this was achieved by creating the
4827 library in the temporary packaging directory before
4828 creating the symlink. Unfortunately, this was not always
4829 effective, since the building of the tar file in the
4830 <file>.deb</file> depended on the behavior of the underlying
4831 file system. Some file systems (such as reiserfs) reorder
4832 the files so that the order of creation is forgotten.
4833 Since version 1.7.0, <prgn>dpkg</prgn>
4834 reorders the files itself as necessary when building a
4835 package. Thus it is no longer important to concern
4836 oneself with the order of file creation.
4840 <sect1 id="ldconfig">
4841 <heading><tt>ldconfig</tt></heading>
4844 Any package installing shared libraries in one of the default
4845 library directories of the dynamic linker (which are currently
4846 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4847 listed in <file>/etc/ld.so.conf</file><footnote>
4849 <list compact="compact">
4850 <item>/usr/local/lib</item>
4851 <item>/usr/lib/libc5-compat</item>
4852 <item>/lib/libc5-compat</item>
4855 must use <prgn>ldconfig</prgn> to update the shared library
4860 The package maintainer scripts must only call
4861 <prgn>ldconfig</prgn> under these circumstances:
4862 <list compact="compact">
4863 <item>When the <prgn>postinst</prgn> script is run with a
4864 first argument of <tt>configure</tt>, the script must call
4865 <prgn>ldconfig</prgn>, and may optionally invoke
4866 <prgn>ldconfig</prgn> at other times.
4868 <item>When the <prgn>postrm</prgn> script is run with a
4869 first argument of <tt>remove</tt>, the script should call
4870 <prgn>ldconfig</prgn>.
4875 During install or upgrade, the preinst is called before
4876 the new files are installed, so calling "ldconfig" is
4877 pointless. The preinst of an existing package can also be
4878 called if an upgrade fails. However, this happens during
4879 the critical time when a shared libs may exist on-disk
4880 under a temporary name. Thus, it is dangerous and
4881 forbidden by current policy to call "ldconfig" at this
4886 When a package is installed or upgraded, "postinst
4887 configure" runs after the new files are safely on-disk.
4888 Since it is perfectly safe to invoke ldconfig
4889 unconditionally in a postinst, it is OK for a package to
4890 simply put ldconfig in its postinst without checking the
4891 argument. The postinst can also be called to recover from
4892 a failed upgrade. This happens before any new files are
4893 unpacked, so there is no reason to call "ldconfig" at this
4898 For a package that is being removed, prerm is
4899 called with all the files intact, so calling ldconfig is
4900 useless. The other calls to "prerm" happen in the case of
4901 upgrade at a time when all the files of the old package
4902 are on-disk, so again calling "ldconfig" is pointless.
4906 postrm, on the other hand, is called with the "remove"
4907 argument just after the files are removed, so this is
4908 the proper time to call "ldconfig" to notify the system
4909 of the fact that the shared libraries from the package
4910 are removed. The postrm can be called at several other
4911 times. At the time of "postrm purge", "postrm
4912 abort-install", or "postrm abort-upgrade", calling
4913 "ldconfig" is useless because the shared lib files are
4914 not on-disk. However, when "postrm" is invoked with
4915 arguments "upgrade", "failed-upgrade", or "disappear", a
4916 shared lib may exist on-disk under a temporary filename.
4924 <sect id="sharedlibs-support-files">
4925 <heading>Shared library support files</heading>
4928 If your package contains files whose names do not change with
4929 each change in the library shared object version, you must not
4930 put them in the shared library package. Otherwise, several
4931 versions of the shared library cannot be installed at the same
4932 time without filename clashes, making upgrades and transitions
4933 unnecessarily difficult.
4937 It is recommended that supporting files and run-time support
4938 programs that do not need to be invoked manually by users, but
4939 are nevertheless required for the package to function, be placed
4940 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4941 preferably under <file>/usr/lib/</file><var>package-name</var>.
4942 If the program or file is architecture independent, the
4943 recommendation is for it to be placed in a subdirectory of
4944 <file>/usr/share</file> instead, preferably under
4945 <file>/usr/share/</file><var>package-name</var>. Following the
4946 <var>package-name</var> naming convention ensures that the file
4947 names change when the shared object version changes.
4951 Run-time support programs that use the shared library but are
4952 not required for the library to function or files used by the
4953 shared library that can be used by any version of the shared
4954 library package should instead be put in a separate package.
4955 This package might typically be named
4956 <package><var>libraryname</var>-tools</package>; note the
4957 absence of the <var>soversion</var> in the package name.
4961 Files and support programs only useful when compiling software
4962 against the library should be included in the development
4963 package for the library.<footnote>
4964 For example, a <file><var>package-name</var>-config</file>
4965 script or <package>pkg-config</package> configuration files.
4970 <sect id="sharedlibs-static">
4971 <heading>Static libraries</heading>
4974 The static library (<file><var>libraryname.a</var></file>)
4975 is usually provided in addition to the shared version.
4976 It is placed into the development package (see below).
4980 In some cases, it is acceptable for a library to be
4981 available in static form only; these cases include:
4983 <item>libraries for languages whose shared library support
4984 is immature or unstable</item>
4985 <item>libraries whose interfaces are in flux or under
4986 development (commonly the case when the library's
4987 major version number is zero, or where the ABI breaks
4988 across patchlevels)</item>
4989 <item>libraries which are explicitly intended to be
4990 available only in static form by their upstream
4995 <sect id="sharedlibs-dev">
4996 <heading>Development files</heading>
4999 The development files associated to a shared library need to be
5000 placed in a package called
5001 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5002 or if you prefer only to support one development version at a
5003 time, <package><var>libraryname</var>-dev</package>.
5007 In case several development versions of a library exist, you may
5008 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5009 <ref id="conflicts">) to ensure that the user only installs one
5010 development version at a time (as different development versions are
5011 likely to have the same header files in them, which would cause a
5012 filename clash if both were installed).
5016 The development package should contain a symlink for the associated
5017 shared library without a version number. For example, the
5018 <package>libgdbm-dev</package> package should include a symlink
5019 from <file>/usr/lib/libgdbm.so</file> to
5020 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5021 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5022 <file>libgdbm.so</file> when compiling dynamically.
5026 <sect id="sharedlibs-intradeps">
5027 <heading>Dependencies between the packages of the same library</heading>
5030 Typically the development version should have an exact
5031 version dependency on the runtime library, to make sure that
5032 compilation and linking happens correctly. The
5033 <tt>${binary:Version}</tt> substitution variable can be
5034 useful for this purpose.
5036 Previously, <tt>${Source-Version}</tt> was used, but its name
5037 was confusing and it has been deprecated since dpkg 1.13.19.
5042 <sect id="sharedlibs-shlibdeps">
5043 <heading>Dependencies between the library and other packages -
5044 the <tt>shlibs</tt> system</heading>
5047 If a package contains a binary or library which links to a
5048 shared library, we must ensure that when the package is
5049 installed on the system, all of the libraries needed are
5050 also installed. This requirement led to the creation of the
5051 <tt>shlibs</tt> system, which is very simple in its design:
5052 any package which <em>provides</em> a shared library also
5053 provides information on the package dependencies required to
5054 ensure the presence of this library, and any package which
5055 <em>uses</em> a shared library uses this information to
5056 determine the dependencies it requires. The files which
5057 contain the mapping from shared libraries to the necessary
5058 dependency information are called <file>shlibs</file> files.
5062 Thus, when a package is built which contains any shared
5063 libraries, it must provide a <file>shlibs</file> file for other
5064 packages to use, and when a package is built which contains
5065 any shared libraries or compiled binaries, it must run
5066 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5067 on these to determine the libraries used and hence the
5068 dependencies needed by this package.<footnote>
5070 In the past, the shared libraries linked to were
5071 determined by calling <prgn>ldd</prgn>, but now
5072 <prgn>objdump</prgn> is used to do this. The only
5073 change this makes to package building is that
5074 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5075 libraries, whereas in the past this was unnecessary.
5076 The rest of this footnote explains the advantage that
5081 We say that a binary <tt>foo</tt> <em>directly</em> uses
5082 a library <tt>libbar</tt> if it is explicitly linked
5083 with that library (that is, it uses the flag
5084 <tt>-lbar</tt> during the linking stage). Other
5085 libraries that are needed by <tt>libbar</tt> are linked
5086 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5087 linker will load them automatically when it loads
5088 <tt>libbar</tt>. A package should depend on
5089 the libraries it directly uses, and the dependencies for
5090 those libraries should automatically pull in the other
5095 Unfortunately, the <prgn>ldd</prgn> program shows both
5096 the directly and indirectly used libraries, meaning that
5097 the dependencies determined included both direct and
5098 indirect dependencies. The use of <prgn>objdump</prgn>
5099 avoids this problem by determining only the directly
5104 A good example of where this helps is the following. We
5105 could update <tt>libimlib</tt> with a new version that
5106 supports a new graphics format called dgf (but retaining
5107 the same major version number). If we used the old
5108 <prgn>ldd</prgn> method, every package that uses
5109 <tt>libimlib</tt> would need to be recompiled so it
5110 would also depend on <tt>libdgf</tt> or it wouldn't run
5111 due to missing symbols. However with the new system,
5112 packages using <tt>libimlib</tt> can rely on
5113 <tt>libimlib</tt> itself having the dependency on
5114 <tt>libdgf</tt> and so they would not need rebuilding.
5120 In the following sections, we will first describe where the
5121 various <tt>shlibs</tt> files are to be found, then how to
5122 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5123 file format and how to create them if your package contains a
5128 <heading>The <tt>shlibs</tt> files present on the system</heading>
5131 There are several places where <tt>shlibs</tt> files are
5132 found. The following list gives them in the order in which
5134 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5135 (The first one which gives the required information is used.)
5141 <p><file>debian/shlibs.local</file></p>
5144 This lists overrides for this package. Its use is
5145 described below (see <ref id="shlibslocal">).
5150 <p><file>/etc/dpkg/shlibs.override</file></p>
5153 This lists global overrides. This list is normally
5154 empty. It is maintained by the local system
5160 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5163 When packages are being built, any
5164 <file>debian/shlibs</file> files are copied into the
5165 control file area of the temporary build directory and
5166 given the name <file>shlibs</file>. These files give
5167 details of any shared libraries included in the
5169 An example may help here. Let us say that the
5170 source package <tt>foo</tt> generates two binary
5171 packages, <tt>libfoo2</tt> and
5172 <tt>foo-runtime</tt>. When building the binary
5173 packages, the two packages are created in the
5174 directories <file>debian/libfoo2</file> and
5175 <file>debian/foo-runtime</file> respectively.
5176 (<file>debian/tmp</file> could be used instead of one
5177 of these.) Since <tt>libfoo2</tt> provides the
5178 <tt>libfoo</tt> shared library, it will require a
5179 <tt>shlibs</tt> file, which will be installed in
5180 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5182 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5183 when <prgn>dpkg-shlibdeps</prgn> is run on the
5185 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5187 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5188 determine whether <tt>foo-prog</tt>'s library
5189 dependencies are satisfied by any of the libraries
5190 provided by <tt>libfoo2</tt>. For this reason,
5191 <prgn>dpkg-shlibdeps</prgn> must only be run once
5192 all of the individual binary packages'
5193 <tt>shlibs</tt> files have been installed into the
5200 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5203 These are the <file>shlibs</file> files corresponding to
5204 all of the packages installed on the system, and are
5205 maintained by the relevant package maintainers.
5210 <p><file>/etc/dpkg/shlibs.default</file></p>
5213 This file lists any shared libraries whose packages
5214 have failed to provide correct <file>shlibs</file> files.
5215 It was used when the <file>shlibs</file> setup was first
5216 introduced, but it is now normally empty. It is
5217 maintained by the <tt>dpkg</tt> maintainer.
5225 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5226 <file>shlibs</file> files</heading>
5230 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5231 into your <file>debian/rules</file> file. If your package
5232 contains only compiled binaries and libraries (but no scripts),
5233 you can use a command such as:
5234 <example compact="compact">
5235 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5236 debian/tmp/usr/lib/*
5238 Otherwise, you will need to explicitly list the compiled
5239 binaries and libraries.<footnote>
5240 If you are using <tt>debhelper</tt>, the
5241 <prgn>dh_shlibdeps</prgn> program will do this work for
5242 you. It will also correctly handle multi-binary
5248 This command puts the dependency information into the
5249 <file>debian/substvars</file> file, which is then used by
5250 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5251 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5252 field in the control file for this to work.
5256 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5257 done. If it does complain you might need to create your own
5258 <file>debian/shlibs.local</file> file, as explained below (see
5259 <ref id="shlibslocal">).
5263 If you have multiple binary packages, you will need to call
5264 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5265 compiled libraries or binaries. In such a case, you will
5266 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5267 utilities to specify a different <file>substvars</file> file.
5271 If you are creating a udeb for use in the Debian Installer, you
5272 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5273 the dependency line of type <tt>udeb</tt> by adding
5274 <tt>-tudeb</tt> as option<footnote>
5275 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5276 will automatically add this option if it knows it is
5278 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5279 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5280 fall back to the regular dependency line.
5284 For more details on dpkg-shlibdeps, please see
5285 <ref id="pkg-dpkg-shlibdeps"> and
5286 <manref name="dpkg-shlibdeps" section="1">.
5291 <heading>The <file>shlibs</file> File Format</heading>
5294 Each <file>shlibs</file> file has the same format. Lines
5295 beginning with <tt>#</tt> are considered to be comments and
5296 are ignored. Each line is of the form:
5297 <example compact="compact">
5298 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5303 We will explain this by reference to the example of the
5304 <tt>zlib1g</tt> package, which (at the time of writing)
5305 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5309 <var>type</var> is an optional element that indicates the type
5310 of package for which the line is valid. The only type currently
5311 in use is <tt>udeb</tt>. The colon and space after the type are
5316 <var>library-name</var> is the name of the shared library,
5317 in this case <tt>libz</tt>. (This must match the name part
5318 of the soname, see below.)
5322 <var>soname-version</var> is the version part of the soname of
5323 the library. The soname is the thing that must exactly match
5324 for the library to be recognized by the dynamic linker, and is
5326 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5327 example, <tt>libz.so.1</tt>.<footnote>
5328 This can be determined using the command
5329 <example compact="compact">
5330 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5333 The version part is the part which comes after
5334 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5338 <var>dependencies</var> has the same syntax as a dependency
5339 field in a binary package control file. It should give
5340 details of which packages are required to satisfy a binary
5341 built against the version of the library contained in the
5342 package. See <ref id="depsyntax"> for details.
5346 In our example, if the first version of the <tt>zlib1g</tt>
5347 package which contained a minor number of at least
5348 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5349 <tt>shlibs</tt> entry for this library could say:
5350 <example compact="compact">
5351 libz 1 zlib1g (>= 1:1.1.3)
5353 The version-specific dependency is to avoid warnings from
5354 the dynamic linker about using older shared libraries with
5359 As zlib1g also provides a udeb containing the shared library,
5360 there would also be a second line:
5361 <example compact="compact">
5362 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5368 <heading>Providing a <file>shlibs</file> file</heading>
5371 If your package provides a shared library, you need to create
5372 a <file>shlibs</file> file following the format described above.
5373 It is usual to call this file <file>debian/shlibs</file> (but if
5374 you have multiple binary packages, you might want to call it
5375 <file>debian/shlibs.<var>package</var></file> instead). Then
5376 let <file>debian/rules</file> install it in the control area:
5377 <example compact="compact">
5378 install -m644 debian/shlibs debian/tmp/DEBIAN
5380 or, in the case of a multi-binary package:
5381 <example compact="compact">
5382 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5384 An alternative way of doing this is to create the
5385 <file>shlibs</file> file in the control area directly from
5386 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5387 file at all,<footnote>
5388 This is what <prgn>dh_makeshlibs</prgn> in the
5389 <tt>debhelper</tt> suite does. If your package also has a udeb
5390 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5391 automatically generate the <tt>udeb:</tt> lines if you specify
5392 the name of the udeb with the <tt>--add-udeb</tt> option.
5394 since the <file>debian/shlibs</file> file itself is ignored by
5395 <prgn>dpkg-shlibdeps</prgn>.
5399 As <prgn>dpkg-shlibdeps</prgn> reads the
5400 <file>DEBIAN/shlibs</file> files in all of the binary packages
5401 being built from this source package, all of the
5402 <file>DEBIAN/shlibs</file> files should be installed before
5403 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5408 <sect1 id="shlibslocal">
5409 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5412 This file is intended only as a <em>temporary</em> fix if
5413 your binaries or libraries depend on a library whose package
5414 does not yet provide a correct <file>shlibs</file> file.
5418 We will assume that you are trying to package a binary
5419 <tt>foo</tt>. When you try running
5420 <prgn>dpkg-shlibdeps</prgn> you get the following error
5421 message (<tt>-O</tt> displays the dependency information on
5422 <tt>stdout</tt> instead of writing it to
5423 <tt>debian/substvars</tt>, and the lines have been wrapped
5424 for ease of reading):
5425 <example compact="compact">
5426 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5427 dpkg-shlibdeps: warning: unable to find dependency
5428 information for shared library libbar (soname 1,
5429 path /usr/lib/libbar.so.1, dependency field Depends)
5430 shlibs:Depends=libc6 (>= 2.2.2-2)
5432 You can then run <prgn>ldd</prgn> on the binary to find the
5433 full location of the library concerned:
5434 <example compact="compact">
5436 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5437 libc.so.6 => /lib/libc.so.6 (0x40032000)
5438 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5440 So the <prgn>foo</prgn> binary depends on the
5441 <prgn>libbar</prgn> shared library, but no package seems to
5442 provide a <file>*.shlibs</file> file handling
5443 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5444 determine the package responsible:
5445 <example compact="compact">
5446 $ dpkg -S /usr/lib/libbar.so.1
5447 bar1: /usr/lib/libbar.so.1
5448 $ dpkg -s bar1 | grep Version
5451 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5452 is the one we are using. Now we can file a bug against the
5453 <tt>bar1</tt> package and create our own
5454 <file>debian/shlibs.local</file> to locally fix the problem.
5455 Including the following line into your
5456 <file>debian/shlibs.local</file> file:
5457 <example compact="compact">
5458 libbar 1 bar1 (>= 1.0-1)
5460 should allow the package build to work.
5464 As soon as the maintainer of <tt>bar1</tt> provides a
5465 correct <file>shlibs</file> file, you should remove this line
5466 from your <file>debian/shlibs.local</file> file. (You should
5467 probably also then have a versioned <tt>Build-Depends</tt>
5468 on <tt>bar1</tt> to help ensure that others do not have the
5469 same problem building your package.)
5478 <chapt id="opersys"><heading>The Operating System</heading>
5481 <heading>File system hierarchy</heading>
5485 <heading>File system Structure</heading>
5488 The location of all installed files and directories must
5489 comply with the File system Hierarchy Standard (FHS),
5490 version 2.3, with the exceptions noted below, and except
5491 where doing so would violate other terms of Debian
5492 Policy. The following exceptions to the FHS apply:
5497 Legacy XFree86 servers are permitted to retain the
5498 configuration file location
5499 <file>/etc/X11/XF86Config-4</file>.
5504 The optional rules related to user specific
5505 configuration files for applications are stored in
5506 the user's home directory are relaxed. It is
5507 recommended that such files start with the
5508 '<tt>.</tt>' character (a "dot file"), and if an
5509 application needs to create more than one dot file
5510 then the preferred placement is in a subdirectory
5511 with a name starting with a '.' character, (a "dot
5512 directory"). In this case it is recommended the
5513 configuration files not start with the '.'
5519 The requirement for amd64 to use <file>/lib64</file>
5520 for 64 bit binaries is removed.
5525 The requirement that
5526 <file>/usr/local/share/man</file> be "synonymous"
5527 with <file>/usr/local/man</file> is relaxed to a
5532 The requirement that windowmanagers with a single
5533 configuration file call it <file>system.*wmrc</file>
5534 is removed, as is the restriction that the window
5535 manager subdirectory be named identically to the
5536 window manager name itself.
5541 The requirement that boot manager configuration
5542 files live in <file>/etc</file>, or at least are
5543 symlinked there, is relaxed to a recommendation.
5550 The version of this document referred here can be
5551 found in the <tt>debian-policy</tt> package or on <url
5552 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5553 name="FHS (Debian copy)"> alongside this manual (or, if
5554 you have the <package>debian-policy</package> installed,
5556 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5557 (local copy)">). The
5558 latest version, which may be a more recent version, may
5560 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5561 Specific questions about following the standard may be
5562 asked on the <tt>debian-devel</tt> mailing list, or
5563 referred to the FHS mailing list (see the
5564 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5570 <heading>Site-specific programs</heading>
5573 As mandated by the FHS, packages must not place any
5574 files in <file>/usr/local</file>, either by putting them in
5575 the file system archive to be unpacked by <prgn>dpkg</prgn>
5576 or by manipulating them in their maintainer scripts.
5580 However, the package may create empty directories below
5581 <file>/usr/local</file> so that the system administrator knows
5582 where to place site-specific files. These are not
5583 directories <em>in</em> <file>/usr/local</file>, but are
5584 children of directories in <file>/usr/local</file>. These
5585 directories (<file>/usr/local/*/dir/</file>)
5586 should be removed on package removal if they are
5591 Note, that this applies only to directories <em>below</em>
5592 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5593 Packages must not create sub-directories in the directory
5594 <file>/usr/local</file> itself, except those listed in FHS,
5595 section 4.5. However, you may create directories below
5596 them as you wish. You must not remove any of the
5597 directories listed in 4.5, even if you created them.
5601 Since <file>/usr/local</file> can be mounted read-only from a
5602 remote server, these directories must be created and
5603 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5604 maintainer scripts and not be included in the
5605 <file>.deb</file> archive. These scripts must not fail if
5606 either of these operations fail.
5610 For example, the <tt>emacsen-common</tt> package could
5611 contain something like
5612 <example compact="compact">
5613 if [ ! -e /usr/local/share/emacs ]
5615 if mkdir /usr/local/share/emacs 2>/dev/null
5617 chown root:staff /usr/local/share/emacs
5618 chmod 2775 /usr/local/share/emacs
5622 in its <prgn>postinst</prgn> script, and
5623 <example compact="compact">
5624 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5625 rmdir /usr/local/share/emacs 2>/dev/null || true
5627 in the <prgn>prerm</prgn> script. (Note that this form is
5628 used to ensure that if the script is interrupted, the
5629 directory <file>/usr/local/share/emacs</file> will still be
5634 If you do create a directory in <file>/usr/local</file> for
5635 local additions to a package, you should ensure that
5636 settings in <file>/usr/local</file> take precedence over the
5637 equivalents in <file>/usr</file>.
5641 However, because <file>/usr/local</file> and its contents are
5642 for exclusive use of the local administrator, a package
5643 must not rely on the presence or absence of files or
5644 directories in <file>/usr/local</file> for normal operation.
5648 The <file>/usr/local</file> directory itself and all the
5649 subdirectories created by the package should (by default) have
5650 permissions 2775 (group-writable and set-group-id) and be
5651 owned by <tt>root:staff</tt>.
5656 <heading>The system-wide mail directory</heading>
5658 The system-wide mail directory is <file>/var/mail</file>. This
5659 directory is part of the base system and should not owned
5660 by any particular mail agents. The use of the old
5661 location <file>/var/spool/mail</file> is deprecated, even
5662 though the spool may still be physically located there.
5663 To maintain partial upgrade compatibility for systems
5664 which have <file>/var/spool/mail</file> as their physical mail
5665 spool, packages using <file>/var/mail</file> must depend on
5666 either <package>libc6</package> (>= 2.1.3-13), or on
5667 <package>base-files</package> (>= 2.2.0), or on later
5668 versions of either one of these packages.
5674 <heading>Users and groups</heading>
5677 <heading>Introduction</heading>
5679 The Debian system can be configured to use either plain or
5684 Some user ids (UIDs) and group ids (GIDs) are reserved
5685 globally for use by certain packages. Because some
5686 packages need to include files which are owned by these
5687 users or groups, or need the ids compiled into binaries,
5688 these ids must be used on any Debian system only for the
5689 purpose for which they are allocated. This is a serious
5690 restriction, and we should avoid getting in the way of
5691 local administration policies. In particular, many sites
5692 allocate users and/or local system groups starting at 100.
5696 Apart from this we should have dynamically allocated ids,
5697 which should by default be arranged in some sensible
5698 order, but the behavior should be configurable.
5702 Packages other than <tt>base-passwd</tt> must not modify
5703 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5704 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5709 <heading>UID and GID classes</heading>
5711 The UID and GID numbers are divided into classes as
5717 Globally allocated by the Debian project, the same
5718 on every Debian system. These ids will appear in
5719 the <file>passwd</file> and <file>group</file> files of all
5720 Debian systems, new ids in this range being added
5721 automatically as the <tt>base-passwd</tt> package is
5726 Packages which need a single statically allocated
5727 uid or gid should use one of these; their
5728 maintainers should ask the <tt>base-passwd</tt>
5736 Dynamically allocated system users and groups.
5737 Packages which need a user or group, but can have
5738 this user or group allocated dynamically and
5739 differently on each system, should use <tt>adduser
5740 --system</tt> to create the group and/or user.
5741 <prgn>adduser</prgn> will check for the existence of
5742 the user or group, and if necessary choose an unused
5743 id based on the ranges specified in
5744 <file>adduser.conf</file>.
5748 <tag>1000-29999:</tag>
5751 Dynamically allocated user accounts. By default
5752 <prgn>adduser</prgn> will choose UIDs and GIDs for
5753 user accounts in this range, though
5754 <file>adduser.conf</file> may be used to modify this
5759 <tag>30000-59999:</tag>
5764 <tag>60000-64999:</tag>
5767 Globally allocated by the Debian project, but only
5768 created on demand. The ids are allocated centrally
5769 and statically, but the actual accounts are only
5770 created on users' systems on demand.
5774 These ids are for packages which are obscure or
5775 which require many statically-allocated ids. These
5776 packages should check for and create the accounts in
5777 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5778 <prgn>adduser</prgn> if it has this facility) if
5779 necessary. Packages which are likely to require
5780 further allocations should have a "hole" left after
5781 them in the allocation, to give them room to
5786 <tag>65000-65533:</tag>
5794 User <tt>nobody</tt>. The corresponding gid refers
5795 to the group <tt>nogroup</tt>.
5802 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5803 not</em> be used, because it is the error return
5812 <sect id="sysvinit">
5813 <heading>System run levels and <file>init.d</file> scripts</heading>
5815 <sect1 id="/etc/init.d">
5816 <heading>Introduction</heading>
5819 The <file>/etc/init.d</file> directory contains the scripts
5820 executed by <prgn>init</prgn> at boot time and when the
5821 init state (or "runlevel") is changed (see <manref
5822 name="init" section="8">).
5826 There are at least two different, yet functionally
5827 equivalent, ways of handling these scripts. For the sake
5828 of simplicity, this document describes only the symbolic
5829 link method. However, it must not be assumed by maintainer
5830 scripts that this method is being used, and any automated
5831 manipulation of the various runlevel behaviors by
5832 maintainer scripts must be performed using
5833 <prgn>update-rc.d</prgn> as described below and not by
5834 manually installing or removing symlinks. For information
5835 on the implementation details of the other method,
5836 implemented in the <tt>file-rc</tt> package, please refer
5837 to the documentation of that package.
5841 These scripts are referenced by symbolic links in the
5842 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5843 runlevels, <prgn>init</prgn> looks in the directory
5844 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5845 execute, where <tt><var>n</var></tt> is the runlevel that
5846 is being changed to, or <tt>S</tt> for the boot-up
5851 The names of the links all have the form
5852 <file>S<var>mm</var><var>script</var></file> or
5853 <file>K<var>mm</var><var>script</var></file> where
5854 <var>mm</var> is a two-digit number and <var>script</var>
5855 is the name of the script (this should be the same as the
5856 name of the actual script in <file>/etc/init.d</file>).
5860 When <prgn>init</prgn> changes runlevel first the targets
5861 of the links whose names start with a <tt>K</tt> are
5862 executed, each with the single argument <tt>stop</tt>,
5863 followed by the scripts prefixed with an <tt>S</tt>, each
5864 with the single argument <tt>start</tt>. (The links are
5865 those in the <file>/etc/rc<var>n</var>.d</file> directory
5866 corresponding to the new runlevel.) The <tt>K</tt> links
5867 are responsible for killing services and the <tt>S</tt>
5868 link for starting services upon entering the runlevel.
5872 For example, if we are changing from runlevel 2 to
5873 runlevel 3, init will first execute all of the <tt>K</tt>
5874 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5875 all of the <tt>S</tt> prefixed scripts in that directory.
5876 The links starting with <tt>K</tt> will cause the
5877 referred-to file to be executed with an argument of
5878 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5883 The two-digit number <var>mm</var> is used to determine
5884 the order in which to run the scripts: low-numbered links
5885 have their scripts run first. For example, the
5886 <tt>K20</tt> scripts will be executed before the
5887 <tt>K30</tt> scripts. This is used when a certain service
5888 must be started before another. For example, the name
5889 server <prgn>bind</prgn> might need to be started before
5890 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5891 can set up its access lists. In this case, the script
5892 that starts <prgn>bind</prgn> would have a lower number
5893 than the script that starts <prgn>inn</prgn> so that it
5895 <example compact="compact">
5902 The two runlevels 0 (halt) and 6 (reboot) are slightly
5903 different. In these runlevels, the links with an
5904 <tt>S</tt> prefix are still called after those with a
5905 <tt>K</tt> prefix, but they too are called with the single
5906 argument <tt>stop</tt>.
5910 Also, if the script name ends in <tt>.sh</tt>, the script
5911 will be sourced in runlevel <tt>S</tt> rather than being
5912 run in a forked subprocess, but will be explicitly run by
5913 <prgn>sh</prgn> in all other runlevels.
5918 <heading>Writing the scripts</heading>
5921 Packages that include daemons for system services should
5922 place scripts in <file>/etc/init.d</file> to start or stop
5923 services at boot time or during a change of runlevel.
5924 These scripts should be named
5925 <file>/etc/init.d/<var>package</var></file>, and they should
5926 accept one argument, saying what to do:
5929 <tag><tt>start</tt></tag>
5930 <item>start the service,</item>
5932 <tag><tt>stop</tt></tag>
5933 <item>stop the service,</item>
5935 <tag><tt>restart</tt></tag>
5936 <item>stop and restart the service if it's already running,
5937 otherwise start the service</item>
5939 <tag><tt>reload</tt></tag>
5940 <item><p>cause the configuration of the service to be
5941 reloaded without actually stopping and restarting
5944 <tag><tt>force-reload</tt></tag>
5945 <item>cause the configuration to be reloaded if the
5946 service supports this, otherwise restart the
5950 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5951 <tt>force-reload</tt> options should be supported by all
5952 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5957 The <file>init.d</file> scripts must ensure that they will
5958 behave sensibly if invoked with <tt>start</tt> when the
5959 service is already running, or with <tt>stop</tt> when it
5960 isn't, and that they don't kill unfortunately-named user
5961 processes. The best way to achieve this is usually to use
5962 <prgn>start-stop-daemon</prgn>.
5966 If a service reloads its configuration automatically (as
5967 in the case of <prgn>cron</prgn>, for example), the
5968 <tt>reload</tt> option of the <file>init.d</file> script
5969 should behave as if the configuration has been reloaded
5974 The <file>/etc/init.d</file> scripts must be treated as
5975 configuration files, either (if they are present in the
5976 package, that is, in the .deb file) by marking them as
5977 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5978 by managing them correctly in the maintainer scripts (see
5979 <ref id="config-files">). This is important since we want
5980 to give the local system administrator the chance to adapt
5981 the scripts to the local system, e.g., to disable a
5982 service without de-installing the package, or to specify
5983 some special command line options when starting a service,
5984 while making sure their changes aren't lost during the next
5989 These scripts should not fail obscurely when the
5990 configuration files remain but the package has been
5991 removed, as configuration files remain on the system after
5992 the package has been removed. Only when <prgn>dpkg</prgn>
5993 is executed with the <tt>--purge</tt> option will
5994 configuration files be removed. In particular, as the
5995 <file>/etc/init.d/<var>package</var></file> script itself is
5996 usually a <tt>conffile</tt>, it will remain on the system
5997 if the package is removed but not purged. Therefore, you
5998 should include a <tt>test</tt> statement at the top of the
6000 <example compact="compact">
6001 test -f <var>program-executed-later-in-script</var> || exit 0
6006 Often there are some variables in the <file>init.d</file>
6007 scripts whose values control the behavior of the scripts,
6008 and which a system administrator is likely to want to
6009 change. As the scripts themselves are frequently
6010 <tt>conffile</tt>s, modifying them requires that the
6011 administrator merge in their changes each time the package
6012 is upgraded and the <tt>conffile</tt> changes. To ease
6013 the burden on the system administrator, such configurable
6014 values should not be placed directly in the script.
6015 Instead, they should be placed in a file in
6016 <file>/etc/default</file>, which typically will have the same
6017 base name as the <file>init.d</file> script. This extra file
6018 should be sourced by the script when the script runs. It
6019 must contain only variable settings and comments in SUSv3
6020 <prgn>sh</prgn> format. It may either be a
6021 <tt>conffile</tt> or a configuration file maintained by
6022 the package maintainer scripts. See <ref id="config-files">
6027 To ensure that vital configurable values are always
6028 available, the <file>init.d</file> script should set default
6029 values for each of the shell variables it uses, either
6030 before sourcing the <file>/etc/default/</file> file or
6031 afterwards using something like the <tt>:
6032 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6033 script must behave sensibly and not fail if the
6034 <file>/etc/default</file> file is deleted.
6039 <heading>Interfacing with the initscript system</heading>
6042 Maintainers should use the abstraction layer provided by
6043 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6044 programs to deal with initscripts in their packages'
6045 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6046 and <prgn>postrm</prgn>.
6050 Directly managing the /etc/rc?.d links and directly
6051 invoking the <file>/etc/init.d/</file> initscripts should
6052 be done only by packages providing the initscript
6053 subsystem (such as <prgn>sysv-rc</prgn> and
6054 <prgn>file-rc</prgn>).
6058 <heading>Managing the links</heading>
6061 The program <prgn>update-rc.d</prgn> is provided for
6062 package maintainers to arrange for the proper creation and
6063 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6064 or their functional equivalent if another method is being
6065 used. This may be used by maintainers in their packages'
6066 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6070 You must not include any <file>/etc/rc<var>n</var>.d</file>
6071 symbolic links in the actual archive or manually create or
6072 remove the symbolic links in maintainer scripts; you must
6073 use the <prgn>update-rc.d</prgn> program instead. (The
6074 former will fail if an alternative method of maintaining
6075 runlevel information is being used.) You must not include
6076 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6077 in the archive either. (Only the <tt>sysvinit</tt>
6082 By default <prgn>update-rc.d</prgn> will start services in
6083 each of the multi-user state runlevels (2, 3, 4, and 5)
6084 and stop them in the halt runlevel (0), the single-user
6085 runlevel (1) and the reboot runlevel (6). The system
6086 administrator will have the opportunity to customize
6087 runlevels by simply adding, moving, or removing the
6088 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6089 symbolic links are being used, or by modifying
6090 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6095 To get the default behavior for your package, put in your
6096 <prgn>postinst</prgn> script
6097 <example compact="compact">
6098 update-rc.d <var>package</var> defaults
6100 and in your <prgn>postrm</prgn>
6101 <example compact="compact">
6102 if [ "$1" = purge ]; then
6103 update-rc.d <var>package</var> remove
6105 </example>. Note that if your package changes runlevels
6106 or priority, you may have to remove and recreate the links,
6107 since otherwise the old links may persist. Refer to the
6108 documentation of <prgn>update-rc.d</prgn>.
6112 This will use a default sequence number of 20. If it does
6113 not matter when or in which order the <file>init.d</file>
6114 script is run, use this default. If it does, then you
6115 should talk to the maintainer of the <prgn>sysvinit</prgn>
6116 package or post to <tt>debian-devel</tt>, and they will
6117 help you choose a number.
6121 For more information about using <tt>update-rc.d</tt>,
6122 please consult its man page <manref name="update-rc.d"
6128 <heading>Running initscripts</heading>
6130 The program <prgn>invoke-rc.d</prgn> is provided to make
6131 it easier for package maintainers to properly invoke an
6132 initscript, obeying runlevel and other locally-defined
6133 constraints that might limit a package's right to start,
6134 stop and otherwise manage services. This program may be
6135 used by maintainers in their packages' scripts.
6139 The package maintainer scripts must use
6140 <prgn>invoke-rc.d</prgn> to invoke the
6141 <file>/etc/init.d/*</file> initscripts, instead of
6142 calling them directly.
6146 By default, <prgn>invoke-rc.d</prgn> will pass any
6147 action requests (start, stop, reload, restart...) to the
6148 <file>/etc/init.d</file> script, filtering out requests
6149 to start or restart a service out of its intended
6154 Most packages will simply need to change:
6155 <example compact="compact">/etc/init.d/<package>
6156 <action></example> in their <prgn>postinst</prgn>
6157 and <prgn>prerm</prgn> scripts to:
6158 <example compact="compact">
6159 if which invoke-rc.d >/dev/null 2>&1; then
6160 invoke-rc.d <var>package</var> <action>
6162 /etc/init.d/<var>package</var> <action>
6168 A package should register its initscript services using
6169 <prgn>update-rc.d</prgn> before it tries to invoke them
6170 using <prgn>invoke-rc.d</prgn>. Invocation of
6171 unregistered services may fail.
6175 For more information about using
6176 <prgn>invoke-rc.d</prgn>, please consult its man page
6177 <manref name="invoke-rc.d" section="8">.
6183 <heading>Boot-time initialization</heading>
6186 There used to be another directory, <file>/etc/rc.boot</file>,
6187 which contained scripts which were run once per machine
6188 boot. This has been deprecated in favour of links from
6189 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6190 described in <ref id="/etc/init.d">. Packages must not
6191 place files in <file>/etc/rc.boot</file>.
6196 <heading>Example</heading>
6199 An example on which you can base your
6200 <file>/etc/init.d</file> scripts is found in
6201 <file>/etc/init.d/skeleton</file>.
6208 <heading>Console messages from <file>init.d</file> scripts</heading>
6211 This section describes the formats to be used for messages
6212 written to standard output by the <file>/etc/init.d</file>
6213 scripts. The intent is to improve the consistency of
6214 Debian's startup and shutdown look and feel. For this
6215 reason, please look very carefully at the details. We want
6216 the messages to have the same format in terms of wording,
6217 spaces, punctuation and case of letters.
6221 Here is a list of overall rules that should be used for
6222 messages generated by <file>/etc/init.d</file> scripts.
6228 The message should fit in one line (fewer than 80
6229 characters), start with a capital letter and end with
6230 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6234 If the script is performing some time consuming task in
6235 the background (not merely starting or stopping a
6236 program, for instance), an ellipsis (three dots:
6237 <tt>...</tt>) should be output to the screen, with no
6238 leading or tailing whitespace or line feeds.
6242 The messages should appear as if the computer is telling
6243 the user what it is doing (politely :-), but should not
6244 mention "it" directly. For example, instead of:
6245 <example compact="compact">
6246 I'm starting network daemons: nfsd mountd.
6248 the message should say
6249 <example compact="compact">
6250 Starting network daemons: nfsd mountd.
6257 <tt>init.d</tt> script should use the following standard
6258 message formats for the situations enumerated below.
6264 <p>When daemons are started</p>
6267 If the script starts one or more daemons, the output
6268 should look like this (a single line, no leading
6270 <example compact="compact">
6271 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6273 The <var>description</var> should describe the
6274 subsystem the daemon or set of daemons are part of,
6275 while <var>daemon-1</var> up to <var>daemon-n</var>
6276 denote each daemon's name (typically the file name of
6281 For example, the output of <file>/etc/init.d/lpd</file>
6283 <example compact="compact">
6284 Starting printer spooler: lpd.
6289 This can be achieved by saying
6290 <example compact="compact">
6291 echo -n "Starting printer spooler: lpd"
6292 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6295 in the script. If there are more than one daemon to
6296 start, the output should look like this:
6297 <example compact="compact">
6298 echo -n "Starting remote file system services:"
6299 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6300 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6301 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6304 This makes it possible for the user to see what is
6305 happening and when the final daemon has been started.
6306 Care should be taken in the placement of white spaces:
6307 in the example above the system administrators can
6308 easily comment out a line if they don't want to start
6309 a specific daemon, while the displayed message still
6315 <p>When a system parameter is being set</p>
6318 If you have to set up different system parameters
6319 during the system boot, you should use this format:
6320 <example compact="compact">
6321 Setting <var>parameter</var> to "<var>value</var>".
6326 You can use a statement such as the following to get
6328 <example compact="compact">
6329 echo "Setting DNS domainname to \"$domainname\"."
6334 Note that the same symbol (<tt>"</tt>) is used for the left
6335 and right quotation marks. A grave accent (<tt>`</tt>) is
6336 not a quote character; neither is an apostrophe
6342 <p>When a daemon is stopped or restarted</p>
6345 When you stop or restart a daemon, you should issue a
6346 message identical to the startup message, except that
6347 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6348 or <tt>Restarting</tt> respectively.
6352 For example, stopping the printer daemon will look like
6354 <example compact="compact">
6355 Stopping printer spooler: lpd.
6361 <p>When something is executed</p>
6364 There are several examples where you have to run a
6365 program at system startup or shutdown to perform a
6366 specific task, for example, setting the system's clock
6367 using <prgn>netdate</prgn> or killing all processes
6368 when the system shuts down. Your message should look
6370 <example compact="compact">
6371 Doing something very useful...done.
6373 You should print the <tt>done.</tt> immediately after
6374 the job has been completed, so that the user is
6375 informed why they have to wait. You can get this
6377 <example compact="compact">
6378 echo -n "Doing something very useful..."
6387 <p>When the configuration is reloaded</p>
6390 When a daemon is forced to reload its configuration
6391 files you should use the following format:
6392 <example compact="compact">
6393 Reloading <var>description</var> configuration...done.
6395 where <var>description</var> is the same as in the
6396 daemon starting message.
6404 <heading>Cron jobs</heading>
6407 Packages must not modify the configuration file
6408 <file>/etc/crontab</file>, and they must not modify the files in
6409 <file>/var/spool/cron/crontabs</file>.</p>
6412 If a package wants to install a job that has to be executed
6413 via cron, it should place a file with the name of the
6414 package in one or more of the following directories:
6415 <example compact="compact">
6421 As these directory names imply, the files within them are
6422 executed on an hourly, daily, weekly, or monthly basis,
6423 respectively. The exact times are listed in
6424 <file>/etc/crontab</file>.</p>
6427 All files installed in any of these directories must be
6428 scripts (e.g., shell scripts or Perl scripts) so that they
6429 can easily be modified by the local system administrator.
6430 In addition, they must be treated as configuration files.
6434 If a certain job has to be executed at some other frequency or
6435 at a specific time, the package should install a file
6436 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6437 same syntax as <file>/etc/crontab</file> and is processed by
6438 <prgn>cron</prgn> automatically. The file must also be
6439 treated as a configuration file. (Note that entries in the
6440 <file>/etc/cron.d</file> directory are not handled by
6441 <prgn>anacron</prgn>. Thus, you should only use this
6442 directory for jobs which may be skipped if the system is not
6446 The scripts or crontab entries in these directories should
6447 check if all necessary programs are installed before they
6448 try to execute them. Otherwise, problems will arise when a
6449 package was removed but not purged since configuration files
6450 are kept on the system in this situation.</p>
6454 <heading>Menus</heading>
6457 The Debian <tt>menu</tt> package provides a standard
6458 interface between packages providing applications and
6459 <em>menu programs</em> (either X window managers or
6460 text-based menu programs such as <prgn>pdmenu</prgn>).
6464 All packages that provide applications that need not be
6465 passed any special command line arguments for normal
6466 operation should register a menu entry for those
6467 applications, so that users of the <tt>menu</tt> package
6468 will automatically get menu entries in their window
6469 managers, as well in shells like <tt>pdmenu</tt>.
6473 Menu entries should follow the current menu policy.
6477 The menu policy can be found in the <tt>menu-policy</tt>
6478 files in the <tt>debian-policy</tt> package.
6479 It is also available from the Debian web mirrors at
6480 <tt><url name="/doc/packaging-manuals/menu-policy/"
6481 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6485 Please also refer to the <em>Debian Menu System</em>
6486 documentation that comes with the <package>menu</package>
6487 package for information about how to register your
6493 <heading>Multimedia handlers</heading>
6496 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6497 is a mechanism for encoding files and data streams and
6498 providing meta-information about them, in particular their
6499 type (e.g. audio or video) and format (e.g. PNG, HTML,
6504 Registration of MIME type handlers allows programs like mail
6505 user agents and web browsers to invoke these handlers to
6506 view, edit or display MIME types they don't support directly.
6510 Packages which provide the ability to view/show/play,
6511 compose, edit or print MIME types should register themselves
6512 as such following the current MIME support policy.
6516 The MIME support policy can be found in the <tt>mime-policy</tt>
6517 files in the <tt>debian-policy</tt> package.
6518 It is also available from the Debian web mirrors at
6519 <tt><url name="/doc/packaging-manuals/mime-policy/"
6520 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6526 <heading>Keyboard configuration</heading>
6529 To achieve a consistent keyboard configuration so that all
6530 applications interpret a keyboard event the same way, all
6531 programs in the Debian distribution must be configured to
6532 comply with the following guidelines.
6536 The following keys must have the specified interpretations:
6539 <tag><tt><--</tt></tag>
6540 <item>delete the character to the left of the cursor</item>
6542 <tag><tt>Delete</tt></tag>
6543 <item>delete the character to the right of the cursor</item>
6545 <tag><tt>Control+H</tt></tag>
6546 <item>emacs: the help prefix</item>
6549 The interpretation of any keyboard events should be
6550 independent of the terminal that is used, be it a virtual
6551 console, an X terminal emulator, an rlogin/telnet session,
6556 The following list explains how the different programs
6557 should be set up to achieve this:
6563 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6567 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6571 X translations are set up to make
6572 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6573 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6574 is the vt220 escape code for the "delete character"
6575 key). This must be done by loading the X resources
6576 using <prgn>xrdb</prgn> on all local X displays, not
6577 using the application defaults, so that the
6578 translation resources used correspond to the
6579 <prgn>xmodmap</prgn> settings.
6583 The Linux console is configured to make
6584 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6585 generate <tt>ESC [ 3 ~</tt>.
6589 X applications are configured so that <tt><</tt>
6590 deletes left, and <tt>Delete</tt> deletes right. Motif
6591 applications already work like this.
6595 Terminals should have <tt>stty erase ^?</tt> .
6599 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6600 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6601 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6605 Emacs is programmed to map <tt>KB_Backspace</tt> or
6606 the <tt>stty erase</tt> character to
6607 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6608 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6609 <tt>^H</tt> to <tt>help</tt> as always.
6613 Other applications use the <tt>stty erase</tt>
6614 character and <tt>kdch1</tt> for the two delete keys,
6615 with ASCII DEL being "delete previous character" and
6616 <tt>kdch1</tt> being "delete character under
6624 This will solve the problem except for the following
6631 Some terminals have a <tt><--</tt> key that cannot
6632 be made to produce anything except <tt>^H</tt>. On
6633 these terminals Emacs help will be unavailable on
6634 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6635 character takes precedence in Emacs, and has been set
6636 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6637 available) can be used instead.
6641 Some operating systems use <tt>^H</tt> for <tt>stty
6642 erase</tt>. However, modern telnet versions and all
6643 rlogin versions propagate <tt>stty</tt> settings, and
6644 almost all UNIX versions honour <tt>stty erase</tt>.
6645 Where the <tt>stty</tt> settings are not propagated
6646 correctly, things can be made to work by using
6647 <tt>stty</tt> manually.
6651 Some systems (including previous Debian versions) use
6652 <prgn>xmodmap</prgn> to arrange for both
6653 <tt><--</tt> and <tt>Delete</tt> to generate
6654 <tt>KB_Delete</tt>. We can change the behavior of
6655 their X clients using the same X resources that we use
6656 to do it for our own clients, or configure our clients
6657 using their resources when things are the other way
6658 around. On displays configured like this
6659 <tt>Delete</tt> will not work, but <tt><--</tt>
6664 Some operating systems have different <tt>kdch1</tt>
6665 settings in their <tt>terminfo</tt> database for
6666 <tt>xterm</tt> and others. On these systems the
6667 <tt>Delete</tt> key will not work correctly when you
6668 log in from a system conforming to our policy, but
6669 <tt><--</tt> will.
6676 <heading>Environment variables</heading>
6679 A program must not depend on environment variables to get
6680 reasonable defaults. (That's because these environment
6681 variables would have to be set in a system-wide
6682 configuration file like <file>/etc/profile</file>, which is not
6683 supported by all shells.)
6687 If a program usually depends on environment variables for its
6688 configuration, the program should be changed to fall back to
6689 a reasonable default configuration if these environment
6690 variables are not present. If this cannot be done easily
6691 (e.g., if the source code of a non-free program is not
6692 available), the program must be replaced by a small
6693 "wrapper" shell script which sets the environment variables
6694 if they are not already defined, and calls the original program.
6698 Here is an example of a wrapper script for this purpose:
6700 <example compact="compact">
6702 BAR=${BAR:-/var/lib/fubar}
6704 exec /usr/lib/foo/foo "$@"
6709 Furthermore, as <file>/etc/profile</file> is a configuration
6710 file of the <prgn>base-files</prgn> package, other packages must
6711 not put any environment variables or other commands into that
6716 <sect id="doc-base">
6717 <heading>Registering Documents using doc-base</heading>
6720 The <package>doc-base</package> package implements a
6721 flexible mechanism for handling and presenting
6722 documentation. The recommended practice is for every Debian
6723 package that provides online documentation (other than just
6724 manual pages) to register these documents with
6725 <package>doc-base</package> by installing a
6726 <package>doc-base</package> control file via the
6727 <prgn/install-docs/ script at installation time and
6728 de-register the manuals again when the package is removed.
6731 Please refer to the documentation that comes with the
6732 <package>doc-base</package> package for information and
6741 <heading>Files</heading>
6744 <heading>Binaries</heading>
6747 Two different packages must not install programs with
6748 different functionality but with the same filenames. (The
6749 case of two programs having the same functionality but
6750 different implementations is handled via "alternatives" or
6751 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6752 <ref id="conflicts"> respectively.) If this case happens,
6753 one of the programs must be renamed. The maintainers should
6754 report this to the <tt>debian-devel</tt> mailing list and
6755 try to find a consensus about which program will have to be
6756 renamed. If a consensus cannot be reached, <em>both</em>
6757 programs must be renamed.
6761 By default, when a package is being built, any binaries
6762 created should include debugging information, as well as
6763 being compiled with optimization. You should also turn on
6764 as many reasonable compilation warnings as possible; this
6765 makes life easier for porters, who can then look at build
6766 logs for possible problems. For the C programming language,
6767 this means the following compilation parameters should be
6769 <example compact="compact">
6771 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6773 INSTALL = install -s # (or use strip on the files in debian/tmp)
6778 Note that by default all installed binaries should be stripped,
6779 either by using the <tt>-s</tt> flag to
6780 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6781 the binaries after they have been copied into
6782 <file>debian/tmp</file> but before the tree is made into a
6787 Although binaries in the build tree should be compiled with
6788 debugging information by default, it can often be difficult to
6789 debug programs if they are also subjected to compiler
6790 optimization. For this reason, it is recommended to support the
6791 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6792 (see <ref id="debianrules-options">). This variable can contain
6793 several flags to change how a package is compiled and built.
6797 It is up to the package maintainer to decide what
6798 compilation options are best for the package. Certain
6799 binaries (such as computationally-intensive programs) will
6800 function better with certain flags (<tt>-O3</tt>, for
6801 example); feel free to use them. Please use good judgment
6802 here. Don't use flags for the sake of it; only use them
6803 if there is good reason to do so. Feel free to override
6804 the upstream author's ideas about which compilation
6805 options are best: they are often inappropriate for our
6811 <sect id="libraries">
6812 <heading>Libraries</heading>
6815 If the package is <strong>architecture: any</strong>, then
6816 the shared library compilation and linking flags must have
6817 <tt>-fPIC</tt>, or the package shall not build on some of
6818 the supported architectures<footnote>
6820 If you are using GCC, <tt>-fPIC</tt> produces code with
6821 relocatable position independent code, which is required for
6822 most architectures to create a shared library, with i386 and
6823 perhaps some others where non position independent code is
6824 permitted in a shared library.
6827 Position independent code may have a performance penalty,
6828 especially on <tt>i386</tt>. However, in most cases the
6829 speed penalty must be measured against the memory wasted on
6830 the few architectures where non position independent code is
6833 </footnote>. Any exception to this rule must be discussed on
6834 the mailing list <em>debian-devel@lists.debian.org</em>, and
6835 a rough consensus obtained. The reasons for not compiling
6836 with <tt>-fPIC</tt> flag must be recorded in the file
6837 <tt>README.Debian</tt>, and care must be taken to either
6838 restrict the architecture or arrange for <tt>-fPIC</tt> to
6839 be used on architectures where it is required.<footnote>
6841 Some of the reasons why this might be required is if the
6842 library contains hand crafted assembly code that is not
6843 relocatable, the speed penalty is excessive for compute
6844 intensive libs, and similar reasons.
6849 As to the static libraries, the common case is not to have
6850 relocatable code, since there is no benefit, unless in specific
6851 cases; therefore the static version must not be compiled
6852 with the <tt>-fPIC</tt> flag. Any exception to this rule
6853 should be discussed on the mailing list
6854 <em>debian-devel@lists.debian.org</em>, and the reasons for
6855 compiling with the <tt>-fPIC</tt> flag must be recorded in
6856 the file <tt>README.Debian</tt>. <footnote>
6858 Some of the reasons for linking static libraries with
6859 the <tt>-fPIC</tt> flag are if, for example, one needs a
6860 Perl API for a library that is under rapid development,
6861 and has an unstable API, so shared libraries are
6862 pointless at this phase of the library's development. In
6863 that case, since Perl needs a library with relocatable
6864 code, it may make sense to create a static library with
6865 relocatable code. Another reason cited is if you are
6866 distilling various libraries into a common shared
6867 library, like <tt>mklibs</tt> does in the Debian
6873 In other words, if both a shared and a static library is
6874 being built, each source unit (<tt>*.c</tt>, for example,
6875 for C files) will need to be compiled twice, for the normal
6879 You must specify the gcc option <tt>-D_REENTRANT</tt>
6880 when building a library (either static or shared) to make
6881 the library compatible with LinuxThreads.
6885 Although not enforced by the build tools, shared libraries
6886 must be linked against all libraries that they use symbols from
6887 in the same way that binaries are. This ensures the correct
6888 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6889 system and guarantees that all libraries can be safely opened
6890 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6891 option <tt>-Wl,-z,defs</tt> when building a shared library.
6892 Since this option enforces symbol resolution at build time,
6893 a missing library reference will be caught early as a fatal
6898 All installed shared libraries should be stripped with
6899 <example compact="compact">
6900 strip --strip-unneeded <var>your-lib</var>
6902 (The option <tt>--strip-unneeded</tt> makes
6903 <prgn>strip</prgn> remove only the symbols which aren't
6904 needed for relocation processing.) Shared libraries can
6905 function perfectly well when stripped, since the symbols for
6906 dynamic linking are in a separate part of the ELF object
6908 You might also want to use the options
6909 <tt>--remove-section=.comment</tt> and
6910 <tt>--remove-section=.note</tt> on both shared libraries
6911 and executables, and <tt>--strip-debug</tt> on static
6917 Note that under some circumstances it may be useful to
6918 install a shared library unstripped, for example when
6919 building a separate package to support debugging.
6923 Shared object files (often <file>.so</file> files) that are not
6924 public libraries, that is, they are not meant to be linked
6925 to by third party executables (binaries of other packages),
6926 should be installed in subdirectories of the
6927 <file>/usr/lib</file> directory. Such files are exempt from the
6928 rules that govern ordinary shared libraries, except that
6929 they must not be installed executable and should be
6931 A common example are the so-called "plug-ins",
6932 internal shared objects that are dynamically loaded by
6933 programs using <manref name="dlopen" section="3">.
6938 Packages containing shared libraries that may be linked to
6939 by other packages' binaries, but which for some
6940 <em>compelling</em> reason can not be installed in
6941 <file>/usr/lib</file> directory, may install the shared library
6942 files in subdirectories of the <file>/usr/lib</file> directory,
6943 in which case they should arrange to add that directory in
6944 <file>/etc/ld.so.conf</file> in the package's post-installation
6945 script, and remove it in the package's post-removal script.
6949 An ever increasing number of packages are using
6950 <prgn>libtool</prgn> to do their linking. The latest GNU
6951 libtools (>= 1.3a) can take advantage of the metadata in the
6952 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6953 files). The main advantage of <prgn>libtool</prgn>'s
6954 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6955 store and subsequently access metadata with respect to the
6956 libraries it builds. <prgn>libtool</prgn> will search for
6957 those files, which contain a lot of useful information about
6958 a library (such as library dependency information for static
6959 linking). Also, they're <em>essential</em> for programs
6960 using <tt>libltdl</tt>.<footnote>
6961 Although <prgn>libtool</prgn> is fully capable of
6962 linking against shared libraries which don't have
6963 <tt>.la</tt> files, as it is a mere shell script it can
6964 add considerably to the build time of a
6965 <prgn>libtool</prgn>-using package if that shell script
6966 has to derive all this information from first principles
6967 for each library every time it is linked. With the
6968 advent of <prgn>libtool</prgn> version 1.4 (and to a
6969 lesser extent <prgn>libtool</prgn> version 1.3), the
6970 <file>.la</file> files also store information about
6971 inter-library dependencies which cannot necessarily be
6972 derived after the <file>.la</file> file is deleted.
6977 Packages that use <prgn>libtool</prgn> to create shared
6978 libraries should include the <file>.la</file> files in the
6979 <tt>-dev</tt> package, unless the package relies on
6980 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6981 the <tt>.la</tt> files must go in the run-time library
6986 You must make sure that you use only released versions of
6987 shared libraries to build your packages; otherwise other
6988 users will not be able to run your binaries
6989 properly. Producing source packages that depend on
6990 unreleased compilers is also usually a bad
6997 <heading>Shared libraries</heading>
6999 This section has moved to <ref id="sharedlibs">.
7005 <heading>Scripts</heading>
7008 All command scripts, including the package maintainer
7009 scripts inside the package and used by <prgn>dpkg</prgn>,
7010 should have a <tt>#!</tt> line naming the shell to be used
7015 In the case of Perl scripts this should be
7016 <tt>#!/usr/bin/perl</tt>.
7020 When scripts are installed into a directory in the system
7021 PATH, the script name should not include an extension such
7022 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7023 language currently used to implement it.
7026 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7027 should almost certainly start with <tt>set -e</tt> so that
7028 errors are detected. Every script should use
7029 <tt>set -e</tt> or check the exit status of <em>every</em>
7034 Scripts may assume that <file>/bin/sh</file> implements the
7035 SUSv3 Shell Command Language<footnote>
7036 Single UNIX Specification, version 3, which is also IEEE
7037 1003.1-2004 (POSIX), and is available on the World Wide Web
7038 from <url id="http://www.unix.org/version3/online.html"
7039 name="The Open Group"> after free
7040 registration.</footnote>
7041 plus the following additional features not mandated by
7043 These features are in widespread use in the Linux community
7044 and are implemented in all of bash, dash, and ksh, the most
7045 common shells users may wish to use as <file>/bin/sh</file>.
7048 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7049 must not generate a newline.</item>
7050 <item><tt>test</tt>, if implemented as a shell built-in, must
7051 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7053 <item><tt>local</tt> to create a scoped variable must be
7054 supported; however, <tt>local</tt> may or may not preserve
7055 the variable value from an outer scope and may or may not
7056 support arguments more complex than simple variables. Only
7068 If a shell script requires non-SUSv3 features from the shell
7069 interpreter other than those listed above, the appropriate shell
7070 must be specified in the first line of the script (e.g.,
7071 <tt>#!/bin/bash</tt>) and the package must depend on the package
7072 providing the shell (unless the shell package is marked
7073 "Essential", as in the case of <prgn>bash</prgn>).
7077 You may wish to restrict your script to SUSv3 features plus the
7078 above set when possible so that it may use <file>/bin/sh</file>
7079 as its interpreter. If your script works with <prgn>dash</prgn>
7080 (originally called <prgn>ash</prgn>), it probably complies with
7081 the above requirements, but if you are in doubt, use
7082 <file>/bin/bash</file>.
7086 Perl scripts should check for errors when making any
7087 system calls, including <tt>open</tt>, <tt>print</tt>,
7088 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7092 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7093 scripting languages. See <em>Csh Programming Considered
7094 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7095 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7096 If an upstream package comes with <prgn>csh</prgn> scripts
7097 then you must make sure that they start with
7098 <tt>#!/bin/csh</tt> and make your package depend on the
7099 <prgn>c-shell</prgn> virtual package.
7103 Any scripts which create files in world-writeable
7104 directories (e.g., in <file>/tmp</file>) must use a
7105 mechanism which will fail atomically if a file with the same
7106 name already exists.
7110 The Debian base system provides the <prgn>tempfile</prgn>
7111 and <prgn>mktemp</prgn> utilities for use by scripts for
7118 <heading>Symbolic links</heading>
7121 In general, symbolic links within a top-level directory
7122 should be relative, and symbolic links pointing from one
7123 top-level directory into another should be absolute. (A
7124 top-level directory is a sub-directory of the root
7125 directory <file>/</file>.)
7129 In addition, symbolic links should be specified as short as
7130 possible, i.e., link targets like <file>foo/../bar</file> are
7135 Note that when creating a relative link using
7136 <prgn>ln</prgn> it is not necessary for the target of the
7137 link to exist relative to the working directory you're
7138 running <prgn>ln</prgn> from, nor is it necessary to change
7139 directory to the directory where the link is to be made.
7140 Simply include the string that should appear as the target
7141 of the link (this will be a pathname relative to the
7142 directory in which the link resides) as the first argument
7147 For example, in your <prgn>Makefile</prgn> or
7148 <file>debian/rules</file>, you can do things like:
7149 <example compact="compact">
7150 ln -fs gcc $(prefix)/bin/cc
7151 ln -fs gcc debian/tmp/usr/bin/cc
7152 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7153 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7158 A symbolic link pointing to a compressed file should always
7159 have the same file extension as the referenced file. (For
7160 example, if a file <file>foo.gz</file> is referenced by a
7161 symbolic link, the filename of the link has to end with
7162 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7167 <heading>Device files</heading>
7170 Packages must not include device files in the package file
7175 If a package needs any special device files that are not
7176 included in the base system, it must call
7177 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7178 after notifying the user<footnote>
7179 This notification could be done via a (low-priority)
7180 debconf message, or an echo (printf) statement.
7185 Packages must not remove any device files in the
7186 <prgn>postrm</prgn> or any other script. This is left to the
7187 system administrator.
7191 Debian uses the serial devices
7192 <file>/dev/ttyS*</file>. Programs using the old
7193 <file>/dev/cu*</file> devices should be changed to use
7194 <file>/dev/ttyS*</file>.
7198 <sect id="config-files">
7199 <heading>Configuration files</heading>
7202 <heading>Definitions</heading>
7206 <tag>configuration file</tag>
7208 A file that affects the operation of a program, or
7209 provides site- or host-specific information, or
7210 otherwise customizes the behavior of a program.
7211 Typically, configuration files are intended to be
7212 modified by the system administrator (if needed or
7213 desired) to conform to local policy or to provide
7214 more useful site-specific behavior.
7217 <tag><tt>conffile</tt></tag>
7219 A file listed in a package's <tt>conffiles</tt>
7220 file, and is treated specially by <prgn>dpkg</prgn>
7221 (see <ref id="configdetails">).
7227 The distinction between these two is important; they are
7228 not interchangeable concepts. Almost all
7229 <tt>conffile</tt>s are configuration files, but many
7230 configuration files are not <tt>conffiles</tt>.
7234 As noted elsewhere, <file>/etc/init.d</file> scripts,
7235 <file>/etc/default</file> files, scripts installed in
7236 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7237 configuration installed in <file>/etc/cron.d</file> must be
7238 treated as configuration files. In general, any script that
7239 embeds configuration information is de-facto a configuration
7240 file and should be treated as such.
7245 <heading>Location</heading>
7248 Any configuration files created or used by your package
7249 must reside in <file>/etc</file>. If there are several,
7250 consider creating a subdirectory of <file>/etc</file>
7251 named after your package.
7255 If your package creates or uses configuration files
7256 outside of <file>/etc</file>, and it is not feasible to modify
7257 the package to use <file>/etc</file> directly, put the files
7258 in <file>/etc</file> and create symbolic links to those files
7259 from the location that the package requires.
7264 <heading>Behavior</heading>
7267 Configuration file handling must conform to the following
7269 <list compact="compact">
7271 local changes must be preserved during a package
7275 configuration files must be preserved when the
7276 package is removed, and only deleted when the
7283 The easy way to achieve this behavior is to make the
7284 configuration file a <tt>conffile</tt>. This is
7285 appropriate only if it is possible to distribute a default
7286 version that will work for most installations, although
7287 some system administrators may choose to modify it. This
7288 implies that the default version will be part of the
7289 package distribution, and must not be modified by the
7290 maintainer scripts during installation (or at any other
7295 In order to ensure that local changes are preserved
7296 correctly, no package may contain or make hard links to
7297 conffiles.<footnote>
7298 Rationale: There are two problems with hard links.
7299 The first is that some editors break the link while
7300 editing one of the files, so that the two files may
7301 unwittingly become unlinked and different. The second
7302 is that <prgn>dpkg</prgn> might break the hard link
7303 while upgrading <tt>conffile</tt>s.
7308 The other way to do it is via the maintainer scripts. In
7309 this case, the configuration file must not be listed as a
7310 <tt>conffile</tt> and must not be part of the package
7311 distribution. If the existence of a file is required for
7312 the package to be sensibly configured it is the
7313 responsibility of the package maintainer to provide
7314 maintainer scripts which correctly create, update and
7315 maintain the file and remove it on purge. (See <ref
7316 id="maintainerscripts"> for more information.) These
7317 scripts must be idempotent (i.e., must work correctly if
7318 <prgn>dpkg</prgn> needs to re-run them due to errors
7319 during installation or removal), must cope with all the
7320 variety of ways <prgn>dpkg</prgn> can call maintainer
7321 scripts, must not overwrite or otherwise mangle the user's
7322 configuration without asking, must not ask unnecessary
7323 questions (particularly during upgrades), and must
7324 otherwise be good citizens.
7328 The scripts are not required to configure every possible
7329 option for the package, but only those necessary to get
7330 the package running on a given system. Ideally the
7331 sysadmin should not have to do any configuration other
7332 than that done (semi-)automatically by the
7333 <prgn>postinst</prgn> script.
7337 A common practice is to create a script called
7338 <file><var>package</var>-configure</file> and have the
7339 package's <prgn>postinst</prgn> call it if and only if the
7340 configuration file does not already exist. In certain
7341 cases it is useful for there to be an example or template
7342 file which the maintainer scripts use. Such files should
7343 be in <file>/usr/share/<var>package</var></file> or
7344 <file>/usr/lib/<var>package</var></file> (depending on whether
7345 they are architecture-independent or not). There should
7346 be symbolic links to them from
7347 <file>/usr/share/doc/<var>package</var>/examples</file> if
7348 they are examples, and should be perfectly ordinary
7349 <prgn>dpkg</prgn>-handled files (<em>not</em>
7350 configuration files).
7354 These two styles of configuration file handling must
7355 not be mixed, for that way lies madness:
7356 <prgn>dpkg</prgn> will ask about overwriting the file
7357 every time the package is upgraded.
7362 <heading>Sharing configuration files</heading>
7365 Packages which specify the same file as a
7366 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7367 with each other. (This is an instance of the general rule
7368 about not sharing files. Note that neither alternatives
7369 nor diversions are likely to be appropriate in this case;
7370 in particular, <prgn>dpkg</prgn> does not handle diverted
7371 <tt>conffile</tt>s well.)
7375 The maintainer scripts must not alter a <tt>conffile</tt>
7376 of <em>any</em> package, including the one the scripts
7381 If two or more packages use the same configuration file
7382 and it is reasonable for both to be installed at the same
7383 time, one of these packages must be defined as
7384 <em>owner</em> of the configuration file, i.e., it will be
7385 the package which handles that file as a configuration
7386 file. Other packages that use the configuration file must
7387 depend on the owning package if they require the
7388 configuration file to operate. If the other package will
7389 use the configuration file if present, but is capable of
7390 operating without it, no dependency need be declared.
7394 If it is desirable for two or more related packages to
7395 share a configuration file <em>and</em> for all of the
7396 related packages to be able to modify that configuration
7397 file, then the following should be done:
7398 <enumlist compact="compact">
7400 One of the related packages (the "owning" package)
7401 will manage the configuration file with maintainer
7402 scripts as described in the previous section.
7405 The owning package should also provide a program
7406 that the other packages may use to modify the
7410 The related packages must use the provided program
7411 to make any desired modifications to the
7412 configuration file. They should either depend on
7413 the core package to guarantee that the configuration
7414 modifier program is available or accept gracefully
7415 that they cannot modify the configuration file if it
7416 is not. (This is in addition to the fact that the
7417 configuration file may not even be present in the
7424 Sometimes it's appropriate to create a new package which
7425 provides the basic infrastructure for the other packages
7426 and which manages the shared configuration files. (The
7427 <tt>sgml-base</tt> package is a good example.)
7432 <heading>User configuration files ("dotfiles")</heading>
7435 The files in <file>/etc/skel</file> will automatically be
7436 copied into new user accounts by <prgn>adduser</prgn>.
7437 No other program should reference the files in
7438 <file>/etc/skel</file>.
7442 Therefore, if a program needs a dotfile to exist in
7443 advance in <file>$HOME</file> to work sensibly, that dotfile
7444 should be installed in <file>/etc/skel</file> and treated as a
7449 However, programs that require dotfiles in order to
7450 operate sensibly are a bad thing, unless they do create
7451 the dotfiles themselves automatically.
7455 Furthermore, programs should be configured by the Debian
7456 default installation to behave as closely to the upstream
7457 default behavior as possible.
7461 Therefore, if a program in a Debian package needs to be
7462 configured in some way in order to operate sensibly, that
7463 should be done using a site-wide configuration file placed
7464 in <file>/etc</file>. Only if the program doesn't support a
7465 site-wide default configuration and the package maintainer
7466 doesn't have time to add it may a default per-user file be
7467 placed in <file>/etc/skel</file>.
7471 <file>/etc/skel</file> should be as empty as we can make it.
7472 This is particularly true because there is no easy (or
7473 necessarily desirable) mechanism for ensuring that the
7474 appropriate dotfiles are copied into the accounts of
7475 existing users when a package is installed.
7481 <heading>Log files</heading>
7483 Log files should usually be named
7484 <file>/var/log/<var>package</var>.log</file>. If you have many
7485 log files, or need a separate directory for permission
7486 reasons (<file>/var/log</file> is writable only by
7487 <file>root</file>), you should usually create a directory named
7488 <file>/var/log/<var>package</var></file> and place your log
7493 Log files must be rotated occasionally so that they don't
7494 grow indefinitely; the best way to do this is to drop a log
7495 rotation configuration file into the directory
7496 <file>/etc/logrotate.d</file> and use the facilities provided by
7497 logrotate.<footnote>
7499 The traditional approach to log files has been to set up
7500 <em>ad hoc</em> log rotation schemes using simple shell
7501 scripts and cron. While this approach is highly
7502 customizable, it requires quite a lot of sysadmin work.
7503 Even though the original Debian system helped a little
7504 by automatically installing a system which can be used
7505 as a template, this was deemed not enough.
7509 The use of <prgn>logrotate</prgn>, a program developed
7510 by Red Hat, is better, as it centralizes log management.
7511 It has both a configuration file
7512 (<file>/etc/logrotate.conf</file>) and a directory where
7513 packages can drop their individual log rotation
7514 configurations (<file>/etc/logrotate.d</file>).
7517 Here is a good example for a logrotate config
7518 file (for more information see <manref name="logrotate"
7520 <example compact="compact">
7521 /var/log/foo/*.log {
7526 /etc/init.d/foo force-reload
7530 This rotates all files under <file>/var/log/foo</file>, saves 12
7531 compressed generations, and forces the daemon to reload its
7532 configuration information after the log rotation.
7536 Log files should be removed when the package is
7537 purged (but not when it is only removed). This should be
7538 done by the <prgn>postrm</prgn> script when it is called
7539 with the argument <tt>purge</tt> (see <ref
7540 id="removedetails">).
7545 <heading>Permissions and owners</heading>
7548 The rules in this section are guidelines for general use.
7549 If necessary you may deviate from the details below.
7550 However, if you do so you must make sure that what is done
7551 is secure and you should try to be as consistent as possible
7552 with the rest of the system. You should probably also
7553 discuss it on <prgn>debian-devel</prgn> first.
7557 Files should be owned by <tt>root:root</tt>, and made
7558 writable only by the owner and universally readable (and
7559 executable, if appropriate), that is mode 644 or 755.
7563 Directories should be mode 755 or (for group-writability)
7564 mode 2775. The ownership of the directory should be
7565 consistent with its mode: if a directory is mode 2775, it
7566 should be owned by the group that needs write access to
7569 When a package is upgraded, and the owner or permissions
7570 of a file included in the package has changed, dpkg
7571 arranges for the ownership and permissions to be
7572 correctly set upon installation. However, this does not
7573 extend to directories; the permissions and ownership of
7574 directories already on the system does not change on
7575 install or upgrade of packages. This makes sense, since
7576 otherwise common directories like <tt>/usr</tt> would
7577 always be in flux. To correctly change permissions of a
7578 directory the package owns, explicit action is required,
7579 usually in the <tt>postinst</tt> script. Care must be
7580 taken to handle downgrades as well, in that case.
7587 Setuid and setgid executables should be mode 4755 or 2755
7588 respectively, and owned by the appropriate user or group.
7589 They should not be made unreadable (modes like 4711 or
7590 2711 or even 4111); doing so achieves no extra security,
7591 because anyone can find the binary in the freely available
7592 Debian package; it is merely inconvenient. For the same
7593 reason you should not restrict read or execute permissions
7594 on non-set-id executables.
7598 Some setuid programs need to be restricted to particular
7599 sets of users, using file permissions. In this case they
7600 should be owned by the uid to which they are set-id, and by
7601 the group which should be allowed to execute them. They
7602 should have mode 4754; again there is no point in making
7603 them unreadable to those users who must not be allowed to
7608 It is possible to arrange that the system administrator can
7609 reconfigure the package to correspond to their local
7610 security policy by changing the permissions on a binary:
7611 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7612 described below.<footnote>
7613 Ordinary files installed by <prgn>dpkg</prgn> (as
7614 opposed to <tt>conffile</tt>s and other similar objects)
7615 normally have their permissions reset to the distributed
7616 permissions when the package is reinstalled. However,
7617 the use of <prgn>dpkg-statoverride</prgn> overrides this
7618 default behavior. If you use this method, you should
7619 remember to describe <prgn>dpkg-statoverride</prgn> in
7620 the package documentation; being a relatively new
7621 addition to Debian, it is probably not yet well-known.
7623 Another method you should consider is to create a group for
7624 people allowed to use the program(s) and make any setuid
7625 executables executable only by that group.
7629 If you need to create a new user or group for your package
7630 there are two possibilities. Firstly, you may need to
7631 make some files in the binary package be owned by this
7632 user or group, or you may need to compile the user or
7633 group id (rather than just the name) into the binary
7634 (though this latter should be avoided if possible, as in
7635 this case you need a statically allocated id).</p>
7638 If you need a statically allocated id, you must ask for a
7639 user or group id from the <tt>base-passwd</tt> maintainer,
7640 and must not release the package until you have been
7641 allocated one. Once you have been allocated one you must
7642 either make the package depend on a version of the
7643 <tt>base-passwd</tt> package with the id present in
7644 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7645 your package to create the user or group itself with the
7646 correct id (using <tt>adduser</tt>) in its
7647 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7648 the <prgn>postinst</prgn> is to be preferred if it is
7649 possible, otherwise a pre-dependency will be needed on the
7650 <tt>adduser</tt> package.)
7654 On the other hand, the program might be able to determine
7655 the uid or gid from the user or group name at runtime, so
7656 that a dynamically allocated id can be used. In this case
7657 you should choose an appropriate user or group name,
7658 discussing this on <prgn>debian-devel</prgn> and checking
7659 with the <package/base-passwd/ maintainer that it is unique and that
7660 they do not wish you to use a statically allocated id
7661 instead. When this has been checked you must arrange for
7662 your package to create the user or group if necessary using
7663 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7664 <prgn>postinst</prgn> script (again, the latter is to be
7665 preferred if it is possible).
7669 Note that changing the numeric value of an id associated
7670 with a name is very difficult, and involves searching the
7671 file system for all appropriate files. You need to think
7672 carefully whether a static or dynamic id is required, since
7673 changing your mind later will cause problems.
7676 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7678 This section is not intended as policy, but as a
7679 description of the use of <prgn>dpkg-statoverride</prgn>.
7683 If a system administrator wishes to have a file (or
7684 directory or other such thing) installed with owner and
7685 permissions different from those in the distributed Debian
7686 package, they can use the <prgn>dpkg-statoverride</prgn>
7687 program to instruct <prgn>dpkg</prgn> to use the different
7688 settings every time the file is installed. Thus the
7689 package maintainer should distribute the files with their
7690 normal permissions, and leave it for the system
7691 administrator to make any desired changes. For example, a
7692 daemon which is normally required to be setuid root, but
7693 in certain situations could be used without being setuid,
7694 should be installed setuid in the <tt>.deb</tt>. Then the
7695 local system administrator can change this if they wish.
7696 If there are two standard ways of doing it, the package
7697 maintainer can use <tt>debconf</tt> to find out the
7698 preference, and call <prgn>dpkg-statoverride</prgn> in the
7699 maintainer script if necessary to accommodate the system
7700 administrator's choice. Care must be taken during
7701 upgrades to not override an existing setting.
7705 Given the above, <prgn>dpkg-statoverride</prgn> is
7706 essentially a tool for system administrators and would not
7707 normally be needed in the maintainer scripts. There is
7708 one type of situation, though, where calls to
7709 <prgn>dpkg-statoverride</prgn> would be needed in the
7710 maintainer scripts, and that involves packages which use
7711 dynamically allocated user or group ids. In such a
7712 situation, something like the following idiom can be very
7713 helpful in the package's <prgn>postinst</prgn>, where
7714 <tt>sysuser</tt> is a dynamically allocated id:
7716 for i in /usr/bin/foo /usr/sbin/bar
7718 # only do something when no setting exists
7719 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7721 #include: debconf processing, question about foo and bar
7722 if [ "$RET" = "true" ] ; then
7723 dpkg-statoverride --update --add sysuser root 4755 $i
7728 The corresponding <tt>dpkg-statoverride --remove</tt>
7729 calls can then be made unconditionally when the package is
7737 <chapt id="customized-programs">
7738 <heading>Customized programs</heading>
7740 <sect id="arch-spec">
7741 <heading>Architecture specification strings</heading>
7744 If a program needs to specify an <em>architecture specification
7745 string</em> in some place, it should select one of the
7746 strings provided by <tt>dpkg-architecture -L</tt>. The
7747 strings are in the format
7748 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7749 is sometimes elided, as when the OS is Linux.<footnote>
7750 <p>Currently, the strings are:
7751 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7752 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7753 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7754 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7755 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7756 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7757 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7758 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7759 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7760 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7761 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7762 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7763 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7764 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7765 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7766 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7767 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7768 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7769 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7770 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7771 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7772 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7773 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7774 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7775 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7776 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7777 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7778 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7779 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7780 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7781 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7782 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7783 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7784 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7785 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7786 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7787 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7793 Note that we don't want to use
7794 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7795 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7796 since this would make our programs incompatible with other
7797 Linux distributions. We also don't use something like
7798 <tt><var>arch</var>-unknown-linux</tt>, since the
7799 <tt>unknown</tt> does not look very good.
7804 <heading>Daemons</heading>
7807 The configuration files <file>/etc/services</file>,
7808 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7809 by the <prgn>netbase</prgn> package and must not be modified
7814 If a package requires a new entry in one of these files, the
7815 maintainer should get in contact with the
7816 <prgn>netbase</prgn> maintainer, who will add the entries
7817 and release a new version of the <prgn>netbase</prgn>
7822 The configuration file <file>/etc/inetd.conf</file> must not be
7823 modified by the package's scripts except via the
7824 <prgn>update-inetd</prgn> script or the
7825 <file>DebianNet.pm</file> Perl module. See their documentation
7826 for details on how to add entries.
7830 If a package wants to install an example entry into
7831 <file>/etc/inetd.conf</file>, the entry must be preceded with
7832 exactly one hash character (<tt>#</tt>). Such lines are
7833 treated as "commented out by user" by the
7834 <prgn>update-inetd</prgn> script and are not changed or
7835 activated during package updates.
7840 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7844 Some programs need to create pseudo-ttys. This should be done
7845 using Unix98 ptys if the C library supports it. The resulting
7846 program must not be installed setuid root, unless that
7847 is required for other functionality.
7851 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7852 <file>/var/log/lastlog</file> must be installed writable by
7853 group <tt>utmp</tt>. Programs which need to modify those
7854 files must be installed setgid <tt>utmp</tt>.
7859 <heading>Editors and pagers</heading>
7862 Some programs have the ability to launch an editor or pager
7863 program to edit or display a text document. Since there are
7864 lots of different editors and pagers available in the Debian
7865 distribution, the system administrator and each user should
7866 have the possibility to choose their preferred editor and
7871 In addition, every program should choose a good default
7872 editor/pager if none is selected by the user or system
7877 Thus, every program that launches an editor or pager must
7878 use the EDITOR or PAGER environment variable to determine
7879 the editor or pager the user wishes to use. If these
7880 variables are not set, the programs <file>/usr/bin/editor</file>
7881 and <file>/usr/bin/pager</file> should be used, respectively.
7885 These two files are managed through the <prgn>dpkg</prgn>
7886 "alternatives" mechanism. Thus every package providing an
7887 editor or pager must call the
7888 <prgn>update-alternatives</prgn> script to register these
7893 If it is very hard to adapt a program to make use of the
7894 EDITOR or PAGER variables, that program may be configured to
7895 use <file>/usr/bin/sensible-editor</file> and
7896 <file>/usr/bin/sensible-pager</file> as the editor or pager
7897 program respectively. These are two scripts provided in the
7898 Debian base system that check the EDITOR and PAGER variables
7899 and launch the appropriate program, and fall back to
7900 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7901 variable is not set.
7905 A program may also use the VISUAL environment variable to
7906 determine the user's choice of editor. If it exists, it
7907 should take precedence over EDITOR. This is in fact what
7908 <file>/usr/bin/sensible-editor</file> does.
7912 It is not required for a package to depend on
7913 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7914 package to provide such virtual packages.<footnote>
7915 The Debian base system already provides an editor and a
7921 <sect id="web-appl">
7922 <heading>Web servers and applications</heading>
7925 This section describes the locations and URLs that should
7926 be used by all web servers and web applications in the
7933 Cgi-bin executable files are installed in the
7935 <example compact="compact">
7936 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7938 and should be referred to as
7939 <example compact="compact">
7940 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7946 <p>Access to HTML documents</p>
7949 HTML documents for a package are stored in
7950 <file>/usr/share/doc/<var>package</var></file>
7951 and can be referred to as
7952 <example compact="compact">
7953 http://localhost/doc/<var>package</var>/<var>filename</var>
7958 The web server should restrict access to the document
7959 tree so that only clients on the same host can read
7960 the documents. If the web server does not support such
7961 access controls, then it should not provide access at
7962 all, or ask about providing access during installation.
7967 <p>Access to images</p>
7969 It is recommended that images for a package be stored
7970 in <tt>/usr/share/images/<var>package</var></tt> and
7971 may be referred to through an alias <tt>/images/</tt>
7974 http://localhost/images/<package>/<filename>
7981 <p>Web Document Root</p>
7984 Web Applications should try to avoid storing files in
7985 the Web Document Root. Instead they should use the
7986 /usr/share/doc/<var>package</var> directory for
7987 documents and register the Web Application via the
7988 <package>doc-base</package> package. If access to the
7989 web document root is unavoidable then use
7990 <example compact="compact">
7993 as the Document Root. This might be just a symbolic
7994 link to the location where the system administrator
7995 has put the real document root.
7998 <item><p>Providing httpd and/or httpd-cgi</p>
8000 All web servers should provide the virtual package
8001 <tt>httpd</tt>. If a web server has CGI support it should
8002 provide <tt>httpd-cgi</tt> additionally.
8005 All web applications which do not contain CGI scripts should
8006 depend on <tt>httpd</tt>, all those web applications which
8007 <tt>do</tt> contain CGI scripts, should depend on
8015 <sect id="mail-transport-agents">
8016 <heading>Mail transport, delivery and user agents</heading>
8019 Debian packages which process electronic mail, whether mail
8020 user agents (MUAs) or mail transport agents (MTAs), must
8021 ensure that they are compatible with the configuration
8022 decisions below. Failure to do this may result in lost
8023 mail, broken <tt>From:</tt> lines, and other serious brain
8028 The mail spool is <file>/var/mail</file> and the interface to
8029 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8030 the FHS). On older systems, the mail spool may be
8031 physically located in <file>/var/spool/mail</file>, but all
8032 access to the mail spool should be via the
8033 <file>/var/mail</file> symlink. The mail spool is part of the
8034 base system and not part of the MTA package.
8038 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8039 programs (such as IMAP daemons) must lock the mailbox in an
8040 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8041 be combined with dot locking. To avoid deadlocks, a program
8042 should use <tt>fcntl()</tt> first and dot locking after
8043 this, or alternatively implement the two locking methods in
8044 a non blocking way<footnote>
8045 If it is not possible to establish both locks, the
8046 system shouldn't wait for the second lock to be
8047 established, but remove the first lock, wait a (random)
8048 time, and start over locking again.
8049 </footnote>. Using the functions <tt>maillock</tt> and
8050 <tt>mailunlock</tt> provided by the
8051 <tt>liblockfile*</tt><footnote>
8052 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8053 to use these functions.
8054 </footnote> packages is the recommended way to realize this.
8058 Mailboxes are generally mode 660
8059 <tt><var>user</var>:mail</tt> unless the system
8060 administrator has chosen otherwise. A MUA may remove a
8061 mailbox (unless it has nonstandard permissions) in which
8062 case the MTA or another MUA must recreate it if needed.
8063 Mailboxes must be writable by group mail.
8067 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8068 be setgid mail to do the locking mentioned above (and
8069 must obviously avoid accessing other users' mailboxes
8070 using this privilege).</p>
8073 <file>/etc/aliases</file> is the source file for the system mail
8074 aliases (e.g., postmaster, usenet, etc.), it is the one
8075 which the sysadmin and <prgn>postinst</prgn> scripts may
8076 edit. After <file>/etc/aliases</file> is edited the program or
8077 human editing it must call <prgn>newaliases</prgn>. All MTA
8078 packages must come with a <prgn>newaliases</prgn> program,
8079 even if it does nothing, but older MTA packages did not do
8080 this so programs should not fail if <prgn>newaliases</prgn>
8081 cannot be found. Note that because of this, all MTA
8082 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8083 <tt>Replaces: mail-transport-agent</tt> control file
8088 The convention of writing <tt>forward to
8089 <var>address</var></tt> in the mailbox itself is not
8090 supported. Use a <tt>.forward</tt> file instead.</p>
8093 The <prgn>rmail</prgn> program used by UUCP
8094 for incoming mail should be <file>/usr/sbin/rmail</file>.
8095 Likewise, <prgn>rsmtp</prgn>, for receiving
8096 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8100 If your package needs to know what hostname to use on (for
8101 example) outgoing news and mail messages which are generated
8102 locally, you should use the file <file>/etc/mailname</file>. It
8103 will contain the portion after the username and <tt>@</tt>
8104 (at) sign for email addresses of users on the machine
8105 (followed by a newline).
8109 Such a package should check for the existence of this file
8110 when it is being configured. If it exists, it should be
8111 used without comment, although an MTA's configuration script
8112 may wish to prompt the user even if it finds that this file
8113 exists. If the file does not exist, the package should
8114 prompt the user for the value (preferably using
8115 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8116 as well as using it in the package's configuration. The
8117 prompt should make it clear that the name will not just be
8118 used by that package. For example, in this situation the
8119 <tt>inn</tt> package could say something like:
8120 <example compact="compact">
8121 Please enter the "mail name" of your system. This is the
8122 hostname portion of the address to be shown on outgoing
8123 news and mail messages. The default is
8124 <var>syshostname</var>, your system's host name. Mail
8125 name ["<var>syshostname</var>"]:
8127 where <var>syshostname</var> is the output of <tt>hostname
8133 <heading>News system configuration</heading>
8136 All the configuration files related to the NNTP (news)
8137 servers and clients should be located under
8138 <file>/etc/news</file>.</p>
8141 There are some configuration issues that apply to a number
8142 of news clients and server packages on the machine. These
8146 <tag><file>/etc/news/organization</file></tag>
8148 A string which should appear as the
8149 organization header for all messages posted
8150 by NNTP clients on the machine
8153 <tag><file>/etc/news/server</file></tag>
8155 Contains the FQDN of the upstream NNTP
8156 server, or localhost if the local machine is
8161 Other global files may be added as required for cross-package news
8168 <heading>Programs for the X Window System</heading>
8171 <heading>Providing X support and package priorities</heading>
8174 Programs that can be configured with support for the X
8175 Window System must be configured to do so and must declare
8176 any package dependencies necessary to satisfy their
8177 runtime requirements when using the X Window System. If
8178 such a package is of higher priority than the X packages
8179 on which it depends, it is required that either the
8180 X-specific components be split into a separate package, or
8181 that an alternative version of the package, which includes
8182 X support, be provided, or that the package's priority be
8188 <heading>Packages providing an X server</heading>
8191 Packages that provide an X server that, directly or
8192 indirectly, communicates with real input and display
8193 hardware should declare in their control data that they
8194 provide the virtual package <tt>xserver</tt>.<footnote>
8195 This implements current practice, and provides an
8196 actual policy for usage of the <tt>xserver</tt>
8197 virtual package which appears in the virtual packages
8198 list. In a nutshell, X servers that interface
8199 directly with the display and input hardware or via
8200 another subsystem (e.g., GGI) should provide
8201 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8202 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8208 <heading>Packages providing a terminal emulator</heading>
8211 Packages that provide a terminal emulator for the X Window
8212 System which meet the criteria listed below should declare
8213 in their control data that they provide the virtual
8214 package <tt>x-terminal-emulator</tt>. They should also
8215 register themselves as an alternative for
8216 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8221 To be an <tt>x-terminal-emulator</tt>, a program must:
8222 <list compact="compact">
8224 Be able to emulate a DEC VT100 terminal, or a
8225 compatible terminal.
8229 Support the command-line option <tt>-e
8230 <var>command</var></tt>, which creates a new
8231 terminal window<footnote>
8232 "New terminal window" does not necessarily mean
8233 a new top-level X window directly parented by
8234 the window manager; it could, if the terminal
8235 emulator application were so coded, be a new
8236 "view" in a multiple-document interface (MDI).
8238 and runs the specified <var>command</var>,
8239 interpreting the entirety of the rest of the command
8240 line as a command to pass straight to exec, in the
8241 manner that <tt>xterm</tt> does.
8245 Support the command-line option <tt>-T
8246 <var>title</var></tt>, which creates a new terminal
8247 window with the window title <var>title</var>.
8254 <heading>Packages providing a window manager</heading>
8257 Packages that provide a window manager should declare in
8258 their control data that they provide the virtual package
8259 <tt>x-window-manager</tt>. They should also register
8260 themselves as an alternative for
8261 <file>/usr/bin/x-window-manager</file>, with a priority
8262 calculated as follows:
8263 <list compact="compact">
8265 Start with a priority of 20.
8269 If the window manager supports the Debian menu
8270 system, add 20 points if this support is available
8271 in the package's default configuration (i.e., no
8272 configuration files belonging to the system or user
8273 have to be edited to activate the feature); if
8274 configuration files must be modified, add only 10
8280 If the window manager complies with <url
8281 id="http://www.freedesktop.org/Standards/wm-spec"
8282 name="The Window Manager Specification Project">,
8283 written by the <url id="http://www.freedesktop.org/"
8284 name="Free Desktop Group">, add 40 points.
8288 If the window manager permits the X session to be
8289 restarted using a <em>different</em> window manager
8290 (without killing the X server) in its default
8291 configuration, add 10 points; otherwise add none.
8298 <heading>Packages providing fonts</heading>
8301 Packages that provide fonts for the X Window
8303 For the purposes of Debian Policy, a "font for the X
8304 Window System" is one which is accessed via X protocol
8305 requests. Fonts for the Linux console, for PostScript
8306 renderer, or any other purpose, do not fit this
8307 definition. Any tool which makes such fonts available
8308 to the X Window System, however, must abide by this
8311 must do a number of things to ensure that they are both
8312 available without modification of the X or font server
8313 configuration, and that they do not corrupt files used by
8314 other font packages to register information about
8318 Fonts of any type supported by the X Window System
8319 must be in a separate binary package from any
8320 executables, libraries, or documentation (except
8321 that specific to the fonts shipped, such as their
8322 license information). If one or more of the fonts
8323 so packaged are necessary for proper operation of
8324 the package with which they are associated the font
8325 package may be Recommended; if the fonts merely
8326 provide an enhancement, a Suggests relationship may
8327 be used. Packages must not Depend on font
8329 This is because the X server may retrieve fonts
8330 from the local file system or over the network
8331 from an X font server; the Debian package system
8332 is empowered to deal only with the local
8338 BDF fonts must be converted to PCF fonts with the
8339 <prgn>bdftopcf</prgn> utility (available in the
8340 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8341 placed in a directory that corresponds to their
8343 <list compact="compact">
8345 100 dpi fonts must be placed in
8346 <file>/usr/share/fonts/X11/100dpi/</file>.
8350 75 dpi fonts must be placed in
8351 <file>/usr/share/fonts/X11/75dpi/</file>.
8355 Character-cell fonts, cursor fonts, and other
8356 low-resolution fonts must be placed in
8357 <file>/usr/share/fonts/X11/misc/</file>.
8363 Speedo fonts must be placed in
8364 <file>/usr/share/fonts/X11/Speedo/</file>.
8368 Type 1 fonts must be placed in
8369 <file>/usr/share/fonts/X11/Type1/</file>. If font
8370 metric files are available, they must be placed here
8375 Subdirectories of <file>/usr/share/fonts/X11/</file>
8376 other than those listed above must be neither
8377 created nor used. (The <file>PEX</file>, <file>CID</file>,
8378 and <file>cyrillic</file> directories are excepted for
8379 historical reasons, but installation of files into
8380 these directories remains discouraged.)
8384 Font packages may, instead of placing files directly
8385 in the X font directories listed above, provide
8386 symbolic links in that font directory pointing to
8387 the files' actual location in the filesystem. Such
8388 a location must comply with the FHS.
8392 Font packages should not contain both 75dpi and
8393 100dpi versions of a font. If both are available,
8394 they should be provided in separate binary packages
8395 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8396 the names of the packages containing the
8397 corresponding fonts.
8401 Fonts destined for the <file>misc</file> subdirectory
8402 should not be included in the same package as 75dpi
8403 or 100dpi fonts; instead, they should be provided in
8404 a separate package with <tt>-misc</tt> appended to
8409 Font packages must not provide the files
8410 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8411 <file>fonts.scale</file> in a font directory:
8414 <file>fonts.dir</file> files must not be provided at all.
8418 <file>fonts.alias</file> and <file>fonts.scale</file>
8419 files, if needed, should be provided in the
8421 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8422 where <var>fontdir</var> is the name of the
8424 <file>/usr/share/fonts/X11/</file> where the
8425 package's corresponding fonts are stored
8426 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8427 <var>package</var> is the name of the package
8428 that provides these fonts, and
8429 <var>extension</var> is either <tt>scale</tt>
8430 or <tt>alias</tt>, whichever corresponds to
8437 Font packages must declare a dependency on
8438 <tt>xfonts-utils</tt> in their control
8443 Font packages that provide one or more
8444 <file>fonts.scale</file> files as described above must
8445 invoke <prgn>update-fonts-scale</prgn> on each
8446 directory into which they installed fonts
8447 <em>before</em> invoking
8448 <prgn>update-fonts-dir</prgn> on that directory.
8449 This invocation must occur in both the
8450 <prgn>postinst</prgn> (for all arguments) and
8451 <prgn>postrm</prgn> (for all arguments except
8452 <tt>upgrade</tt>) scripts.
8456 Font packages that provide one or more
8457 <file>fonts.alias</file> files as described above must
8458 invoke <prgn>update-fonts-alias</prgn> on each
8459 directory into which they installed fonts. This
8460 invocation must occur in both the
8461 <prgn>postinst</prgn> (for all arguments) and
8462 <prgn>postrm</prgn> (for all arguments except
8463 <tt>upgrade</tt>) scripts.
8467 Font packages must invoke
8468 <prgn>update-fonts-dir</prgn> on each directory into
8469 which they installed fonts. This invocation must
8470 occur in both the <prgn>postinst</prgn> (for all
8471 arguments) and <prgn>postrm</prgn> (for all
8472 arguments except <tt>upgrade</tt>) scripts.
8476 Font packages must not provide alias names for the
8477 fonts they include which collide with alias names
8478 already in use by fonts already packaged.
8482 Font packages must not provide fonts with the same
8483 XLFD registry name as another font already packaged.
8490 <heading>Application defaults files</heading>
8493 Application defaults files must be installed in the
8494 directory <file>/etc/X11/app-defaults/</file> (use of a
8495 localized subdirectory of <file>/etc/X11/</file> as described
8496 in the <em>X Toolkit Intrinsics - C Language
8497 Interface</em> manual is also permitted). They must be
8498 registered as <tt>conffile</tt>s or handled as
8499 configuration files.
8503 Customization of programs' X resources may also be
8504 supported with the provision of a file with the same name
8505 as that of the package placed in the
8506 <file>/etc/X11/Xresources/</file> directory, which must
8507 registered as a <tt>conffile</tt> or handled as a
8508 configuration file.<footnote>
8509 Note that this mechanism is not the same as using
8510 app-defaults; app-defaults are tied to the client
8511 binary on the local file system, whereas X resources
8512 are stored in the X server and affect all connecting
8519 <heading>Installation directory issues</heading>
8522 Packages using the X Window System should not be
8523 configured to install files under the
8524 <file>/usr/X11R6/</file> directory. The
8525 <file>/usr/X11R6/</file> directory hierarchy should be
8526 regarded as obsolete.
8530 Programs that use GNU <prgn>autoconf</prgn> and
8531 <prgn>automake</prgn> are usually easily configured at
8532 compile time to use <file>/usr/</file> instead of
8533 <file>/usr/X11R6/</file>, and this should be done whenever
8534 possible. Configuration files for window managers and
8535 display managers should be placed in a subdirectory of
8536 <file>/etc/X11/</file> corresponding to the package name due
8537 to these programs' tight integration with the mechanisms
8538 of the X Window System. Application-level programs should
8539 use the <file>/etc/</file> directory unless otherwise mandated
8544 The installation of files into subdirectories
8545 of <file>/usr/X11R6/include/X11/</file> and
8546 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8547 package maintainers should determine if subdirectories of
8548 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8553 Packages should install any relevant files into the
8554 directories <file>/usr/include/X11/</file> and
8555 <file>/usr/lib/X11/</file>, but if they do so, they must
8556 pre-depend on <tt>x11-common (>=
8557 1:7.0.0)</tt><footnote>
8559 These libraries used to be all symbolic
8560 links. However, with <tt>X11R7</tt>,
8561 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8562 are now real directories, and packages
8563 <strong>should</strong> ship their files here instead
8564 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8565 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8566 responsible for converting these symlinks into
8574 <heading>The OSF/Motif and OpenMotif libraries</heading>
8577 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8578 OpenMotif libraries</em><footnote>
8579 OSF/Motif and OpenMotif are collectively referred to as
8580 "Motif" in this policy document.
8582 should be compiled against and tested with LessTif (a free
8583 re-implementation of Motif) instead. If the maintainer
8584 judges that the program or programs do not work
8585 sufficiently well with LessTif to be distributed and
8586 supported, but do so when compiled against Motif, then two
8587 versions of the package should be created; one linked
8588 statically against Motif and with <tt>-smotif</tt>
8589 appended to the package name, and one linked dynamically
8590 against Motif and with <tt>-dmotif</tt> appended to the
8595 Both Motif-linked versions are dependent
8596 upon non-DFSG-compliant software and thus cannot be
8597 uploaded to the <em>main</em> distribution; if the
8598 software is itself DFSG-compliant it may be uploaded to
8599 the <em>contrib</em> distribution. While known existing
8600 versions of Motif permit unlimited redistribution of
8601 binaries linked against the library (whether statically or
8602 dynamically), it is the package maintainer's
8603 responsibility to determine whether this is permitted by
8604 the license of the copy of Motif in their possession.
8610 <heading>Perl programs and modules</heading>
8613 Perl programs and modules should follow the current Perl policy.
8617 The Perl policy can be found in the <tt>perl-policy</tt>
8618 files in the <tt>debian-policy</tt> package.
8619 It is also available from the Debian web mirrors at
8620 <tt><url name="/doc/packaging-manuals/perl-policy/"
8621 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8626 <heading>Emacs lisp programs</heading>
8629 Please refer to the "Debian Emacs Policy" for details of how to
8630 package emacs lisp programs.
8634 The Emacs policy is available in
8635 <file>debian-emacs-policy.gz</file> of the
8636 <package>emacsen-common</package> package.
8637 It is also available from the Debian web mirrors at
8638 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8639 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8644 <heading>Games</heading>
8647 The permissions on <file>/var/games</file> are mode 755, owner
8648 <tt>root</tt> and group <tt>root</tt>.
8652 Each game decides on its own security policy.</p>
8655 Games which require protected, privileged access to
8656 high-score files, saved games, etc., may be made
8657 set-<em>group</em>-id (mode 2755) and owned by
8658 <tt>root:games</tt>, and use files and directories with
8659 appropriate permissions (770 <tt>root:games</tt>, for
8660 example). They must not be made
8661 set-<em>user</em>-id, as this causes security problems. (If
8662 an attacker can subvert any set-user-id game they can
8663 overwrite the executable of any other, causing other players
8664 of these games to run a Trojan horse program. With a
8665 set-group-id game the attacker only gets access to less
8666 important game data, and if they can get at the other
8667 players' accounts at all it will take considerably more
8671 Some packages, for example some fortune cookie programs, are
8672 configured by the upstream authors to install with their
8673 data files or other static information made unreadable so
8674 that they can only be accessed through set-id programs
8675 provided. You should not do this in a Debian package: anyone can
8676 download the <file>.deb</file> file and read the data from it,
8677 so there is no point making the files unreadable. Not
8678 making the files unreadable also means that you don't have
8679 to make so many programs set-id, which reduces the risk of a
8683 As described in the FHS, binaries of games should be
8684 installed in the directory <file>/usr/games</file>. This also
8685 applies to games that use the X Window System. Manual pages
8686 for games (X and non-X games) should be installed in
8687 <file>/usr/share/man/man6</file>.</p>
8693 <heading>Documentation</heading>
8696 <heading>Manual pages</heading>
8699 You should install manual pages in <prgn>nroff</prgn> source
8700 form, in appropriate places under <file>/usr/share/man</file>.
8701 You should only use sections 1 to 9 (see the FHS for more
8702 details). You must not install a pre-formatted "cat page".
8706 Each program, utility, and function should have an
8707 associated manual page included in the same package. It is
8708 suggested that all configuration files also have a manual
8709 page included as well. Manual pages for protocols and other
8710 auxiliary things are optional.
8714 If no manual page is available, this is considered as a bug
8715 and should be reported to the Debian Bug Tracking System (the
8716 maintainer of the package is allowed to write this bug report
8717 themselves, if they so desire). Do not close the bug report
8718 until a proper man page is available.<footnote>
8719 It is not very hard to write a man page. See the
8720 <url id="http://www.schweikhardt.net/man_page_howto.html"
8721 name="Man-Page-HOWTO">,
8722 <manref name="man" section="7">, the examples
8723 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8724 the helper programs <prgn>help2man</prgn>, or the
8725 directory <file>/usr/share/doc/man-db/examples</file>.
8730 You may forward a complaint about a missing man page to the
8731 upstream authors, and mark the bug as forwarded in the
8732 Debian bug tracking system. Even though the GNU Project do
8733 not in general consider the lack of a man page to be a bug,
8734 we do; if they tell you that they don't consider it a bug
8735 you should leave the bug in our bug tracking system open
8740 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8744 If one man page needs to be accessible via several names it
8745 is better to use a symbolic link than the <file>.so</file>
8746 feature, but there is no need to fiddle with the relevant
8747 parts of the upstream source to change from <file>.so</file> to
8748 symlinks: don't do it unless it's easy. You should not
8749 create hard links in the manual page directories, nor put
8750 absolute filenames in <file>.so</file> directives. The filename
8751 in a <file>.so</file> in a man page should be relative to the
8752 base of the man page tree (usually
8753 <file>/usr/share/man</file>). If you do not create any links
8754 (whether symlinks, hard links, or <tt>.so</tt> directives)
8755 in the file system to the alternate names of the man page,
8756 then you should not rely on <prgn>man</prgn> finding your
8757 man page under those names based solely on the information in
8758 the man page's header.<footnote>
8759 Supporting this in <prgn>man</prgn> often requires
8760 unreasonable processing time to find a manual page or to
8761 report that none exists, and moves knowledge into man's
8762 database that would be better left in the file system.
8763 This support is therefore deprecated and will cease to
8764 be present in the future.
8769 Manual pages in locale-specific subdirectories of
8770 <file>/usr/share/man</file> should use either UTF-8 or the usual
8771 legacy encoding for that language (normally the one corresponding
8772 to the shortest relevant locale name in
8773 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8774 <file>/usr/share/man/fr</file> should use either UTF-8 or
8775 ISO-8859-1.<footnote>
8776 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8777 use. In future, all manual pages will be required to use
8783 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8784 included in the subdirectory name unless it indicates a
8785 significant difference in the language, as this excludes
8786 speakers of the language in other countries.<footnote>
8787 At the time of writing, Chinese and Portuguese are the main
8788 languages with such differences, so <file>pt_BR</file>,
8789 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8794 Due to limitations in current implementations, all characters
8795 in the manual page source should be representable in the usual
8796 legacy encoding for that language, even if the file is
8797 actually encoded in UTF-8. Safe alternative ways to write many
8798 characters outside that range may be found in
8799 <manref name="groff_char" section="7">.
8804 <heading>Info documents</heading>
8807 Info documents should be installed in <file>/usr/share/info</file>.
8808 They should be compressed with <tt>gzip -9</tt>.
8812 Your package should call <prgn>install-info</prgn> to update
8813 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8814 script when called with a <tt>configure</tt> argument, for
8816 <example compact="compact">
8817 install-info --quiet --section Development Development \
8818 /usr/share/info/foobar.info
8822 It is a good idea to specify a section for the location of
8823 your program; this is done with the <tt>--section</tt>
8824 switch. To determine which section to use, you should look
8825 at <file>/usr/share/info/dir</file> on your system and choose the most
8826 relevant (or create a new section if none of the current
8827 sections are relevant). Note that the <tt>--section</tt>
8828 flag takes two arguments; the first is a regular expression
8829 to match (case-insensitively) against an existing section,
8830 the second is used when creating a new one.</p>
8833 You should remove the entries in the <prgn>prerm</prgn>
8834 script when called with a <tt>remove</tt> argument:
8835 <example compact="compact">
8836 install-info --quiet --remove /usr/share/info/foobar.info
8840 If <prgn>install-info</prgn> cannot find a description entry
8841 in the Info file you must supply one. See <manref
8842 name="install-info" section="8"> for details.</p>
8846 <heading>Additional documentation</heading>
8849 Any additional documentation that comes with the package may
8850 be installed at the discretion of the package maintainer.
8851 Plain text documentation should be installed in the directory
8852 <file>/usr/share/doc/<var>package</var></file>, where
8853 <var>package</var> is the name of the package, and
8854 compressed with <tt>gzip -9</tt> unless it is small.
8858 If a package comes with large amounts of documentation which
8859 many users of the package will not require you should create
8860 a separate binary package to contain it, so that it does not
8861 take up disk space on the machines of users who do not need
8862 or want it installed.</p>
8865 It is often a good idea to put text information files
8866 (<file>README</file>s, changelogs, and so forth) that come with
8867 the source package in <file>/usr/share/doc/<var>package</var></file>
8868 in the binary package. However, you don't need to install
8869 the instructions for building and installing the package, of
8873 Packages must not require the existence of any files in
8874 <file>/usr/share/doc/</file> in order to function
8876 The system administrator should be able to
8877 delete files in <file>/usr/share/doc/</file> without causing
8878 any programs to break.
8880 Any files that are referenced by programs but are also
8881 useful as stand alone documentation should be installed under
8882 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8883 <file>/usr/share/doc/<var>package</var></file>.
8887 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8888 link to another directory in <file>/usr/share/doc</file> only if
8889 the two packages both come from the same source and the
8890 first package Depends on the second.<footnote>
8892 Please note that this does not override the section on
8893 changelog files below, so the file
8894 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8895 must refer to the changelog for the current version of
8896 <var>package</var> in question. In practice, this means
8897 that the sources of the target and the destination of the
8898 symlink must be the same (same source package and
8905 Former Debian releases placed all additional documentation
8906 in <file>/usr/doc/<var>package</var></file>. This has been
8907 changed to <file>/usr/share/doc/<var>package</var></file>,
8908 and packages must not put documentation in the directory
8909 <file>/usr/doc/<var>package</var></file>. <footnote>
8910 At this phase of the transition, we no longer require a
8911 symbolic link in <file>/usr/doc/</file>. At a later point,
8912 policy shall change to make the symbolic links a bug.
8918 <heading>Preferred documentation formats</heading>
8921 The unification of Debian documentation is being carried out
8925 If your package comes with extensive documentation in a
8926 markup format that can be converted to various other formats
8927 you should if possible ship HTML versions in a binary
8928 package, in the directory
8929 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8930 its subdirectories.<footnote>
8931 The rationale: The important thing here is that HTML
8932 docs should be available in <em>some</em> package, not
8933 necessarily in the main binary package.
8938 Other formats such as PostScript may be provided at the
8939 package maintainer's discretion.
8943 <sect id="copyrightfile">
8944 <heading>Copyright information</heading>
8947 Every package must be accompanied by a verbatim copy of its
8948 copyright and distribution license in the file
8949 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8950 file must neither be compressed nor be a symbolic link.
8954 In addition, the copyright file must say where the upstream
8955 sources (if any) were obtained. It should name the original
8956 authors of the package and the Debian maintainer(s) who were
8957 involved with its creation.
8961 Packages in the <em>contrib</em> or <em>non-free</em> categories
8962 should state in the copyright file that the package is not part
8963 of the Debian GNU/Linux distribution and briefly explain why.
8967 A copy of the file which will be installed in
8968 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8969 be in <file>debian/copyright</file> in the source package.
8973 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8974 link to another directory in <file>/usr/share/doc</file> only if
8975 the two packages both come from the same source and the
8976 first package Depends on the second. These rules are
8977 important because copyrights must be extractable by
8982 Packages distributed under the UCB BSD license, the Apache
8983 license (version 2.0), the Artistic license, the GNU GPL
8984 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8985 the GNU FDL (version 1.2) should refer to the corresponding
8986 files under <file>/usr/share/common-licenses</file>,<footnote>
8989 <file>/usr/share/common-licenses/BSD</file>,
8990 <file>/usr/share/common-licenses/Apache-2.0</file>,
8991 <file>/usr/share/common-licenses/Artistic</file>,
8992 <file>/usr/share/common-licenses/GPL-2</file>,
8993 <file>/usr/share/common-licenses/GPL-3</file>,
8994 <file>/usr/share/common-licenses/LGPL-2</file>,
8995 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8996 <file>/usr/share/common-licenses/LGPL-3</file>, and
8997 <file>/usr/share/common-licenses/GFDL-1.2</file>
9000 </footnote> rather than quoting them in the copyright
9005 You should not use the copyright file as a general <file>README</file>
9006 file. If your package has such a file it should be
9007 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9008 <file>README.Debian</file> or some other appropriate place.</p>
9012 <heading>Examples</heading>
9015 Any examples (configurations, source files, whatever),
9016 should be installed in a directory
9017 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9018 files should not be referenced by any program: they're there
9019 for the benefit of the system administrator and users as
9020 documentation only. Architecture-specific example files
9021 should be installed in a directory
9022 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9024 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9025 latter directory itself may be a symbolic link to the
9030 If the purpose of a package is to provide examples, then the
9031 example files may be installed into
9032 <file>/usr/share/doc/<var>package</var></file>.
9036 <sect id="changelogs">
9037 <heading>Changelog files</heading>
9040 Packages that are not Debian-native must contain a
9041 compressed copy of the <file>debian/changelog</file> file from
9042 the Debian source tree in
9043 <file>/usr/share/doc/<var>package</var></file> with the name
9044 <file>changelog.Debian.gz</file>.
9048 If an upstream changelog is available, it should be accessible as
9049 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9050 plain text. If the upstream changelog is distributed in
9051 HTML, it should be made available in that form as
9052 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9053 and a plain text <file>changelog.gz</file> should be generated
9054 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9055 the upstream changelog files do not already conform to this
9056 naming convention, then this may be achieved either by
9057 renaming the files, or by adding a symbolic link, at the
9058 maintainer's discretion.<footnote>
9059 Rationale: People should not have to look in places for
9060 upstream changelogs merely because they are given
9061 different names or are distributed in HTML format.
9066 All of these files should be installed compressed using
9067 <tt>gzip -9</tt>, as they will become large with time even
9068 if they start out small.
9072 If the package has only one changelog which is used both as
9073 the Debian changelog and the upstream one because there is
9074 no separate upstream maintainer then that changelog should
9075 usually be installed as
9076 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9077 there is a separate upstream maintainer, but no upstream
9078 changelog, then the Debian changelog should still be called
9079 <file>changelog.Debian.gz</file>.
9083 For details about the format and contents of the Debian
9084 changelog file, please see <ref id="dpkgchangelog">.
9089 <appendix id="pkg-scope">
9090 <heading>Introduction and scope of these appendices</heading>
9093 These appendices are taken essentially verbatim from the
9094 now-deprecated Packaging Manual, version 3.2.1.0. They are
9095 the chapters which are likely to be of use to package
9096 maintainers and which have not already been included in the
9097 policy document itself. Most of these sections are very likely
9098 not relevant to policy; they should be treated as
9099 documentation for the packaging system. Please note that these
9100 appendices are included for convenience, and for historical
9101 reasons: they used to be part of policy package, and they have
9102 not yet been incorporated into dpkg documentation. However,
9103 they still have value, and hence they are presented here.
9107 They have not yet been checked to ensure that they are
9108 compatible with the contents of policy, and if there are any
9109 contradictions, the version in the main policy document takes
9110 precedence. The remaining chapters of the old Packaging
9111 Manual have also not been read in detail to ensure that there
9112 are not parts which have been left out. Both of these will be
9117 Certain parts of the Packaging manual were integrated into the
9118 Policy Manual proper, and removed from the appendices. Links
9119 have been placed from the old locations to the new ones.
9123 <prgn>dpkg</prgn> is a suite of programs for creating binary
9124 package files and installing and removing them on Unix
9126 <prgn>dpkg</prgn> is targeted primarily at Debian
9127 GNU/Linux, but may work on or be ported to other
9133 The binary packages are designed for the management of
9134 installed executable programs (usually compiled binaries) and
9135 their associated data, though source code examples and
9136 documentation are provided as part of some packages.</p>
9139 This manual describes the technical aspects of creating Debian
9140 binary packages (<file>.deb</file> files). It documents the
9141 behavior of the package management programs
9142 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9143 they interact with packages.</p>
9146 It also documents the interaction between
9147 <prgn>dselect</prgn>'s core and the access method scripts it
9148 uses to actually install the selected packages, and describes
9149 how to create a new access method.</p>
9152 This manual does not go into detail about the options and
9153 usage of the package building and installation tools. It
9154 should therefore be read in conjunction with those programs'
9159 The utility programs which are provided with <prgn>dpkg</prgn>
9160 for managing various system configuration and similar issues,
9161 such as <prgn>update-rc.d</prgn> and
9162 <prgn>install-info</prgn>, are not described in detail here -
9163 please see their man pages.
9167 It is assumed that the reader is reasonably familiar with the
9168 <prgn>dpkg</prgn> System Administrators' manual.
9169 Unfortunately this manual does not yet exist.
9173 The Debian version of the FSF's GNU hello program is provided
9174 as an example for people wishing to create Debian
9175 packages. The Debian <prgn>debmake</prgn> package is
9176 recommended as a very helpful tool in creating and maintaining
9177 Debian packages. However, while the tools and examples are
9178 helpful, they do not replace the need to read and follow the
9179 Policy and Programmer's Manual.</p>
9182 <appendix id="pkg-binarypkg">
9183 <heading>Binary packages (from old Packaging Manual)</heading>
9186 The binary package has two main sections. The first part
9187 consists of various control information files and scripts used
9188 by <prgn>dpkg</prgn> when installing and removing. See <ref
9189 id="pkg-controlarea">.
9193 The second part is an archive containing the files and
9194 directories to be installed.
9198 In the future binary packages may also contain other
9199 components, such as checksums and digital signatures. The
9200 format for the archive is described in full in the
9201 <file>deb(5)</file> man page.
9205 <sect id="pkg-bincreating"><heading>Creating package files -
9206 <prgn>dpkg-deb</prgn>
9210 All manipulation of binary package files is done by
9211 <prgn>dpkg-deb</prgn>; it's the only program that has
9212 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9213 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9214 will spot that the options requested are appropriate to
9215 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9220 In order to create a binary package you must make a
9221 directory tree which contains all the files and directories
9222 you want to have in the file system data part of the package.
9223 In Debian-format source packages this directory is usually
9224 <file>debian/tmp</file>, relative to the top of the package's
9229 They should have the locations (relative to the root of the
9230 directory tree you're constructing) ownerships and
9231 permissions which you want them to have on the system when
9236 With current versions of <prgn>dpkg</prgn> the uid/username
9237 and gid/groupname mappings for the users and groups being
9238 used should be the same on the system where the package is
9239 built and the one where it is installed.
9243 You need to add one special directory to the root of the
9244 miniature file system tree you're creating:
9245 <prgn>DEBIAN</prgn>. It should contain the control
9246 information files, notably the binary package control file
9247 (see <ref id="pkg-controlfile">).
9251 The <prgn>DEBIAN</prgn> directory will not appear in the
9252 file system archive of the package, and so won't be installed
9253 by <prgn>dpkg</prgn> when the package is installed.
9257 When you've prepared the package, you should invoke:
9259 dpkg --build <var>directory</var>
9264 This will build the package in
9265 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9266 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9267 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9272 See the man page <manref name="dpkg-deb" section="8"> for details of how
9273 to examine the contents of this newly-created file. You may find the
9274 output of following commands enlightening:
9276 dpkg-deb --info <var>filename</var>.deb
9277 dpkg-deb --contents <var>filename</var>.deb
9278 dpkg --contents <var>filename</var>.deb
9280 To view the copyright file for a package you could use this command:
9282 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9287 <sect id="pkg-controlarea">
9288 <heading>Package control information files</heading>
9291 The control information portion of a binary package is a
9292 collection of files with names known to <prgn>dpkg</prgn>.
9293 It will treat the contents of these files specially - some
9294 of them contain information used by <prgn>dpkg</prgn> when
9295 installing or removing the package; others are scripts which
9296 the package maintainer wants <prgn>dpkg</prgn> to run.
9300 It is possible to put other files in the package control
9301 area, but this is not generally a good idea (though they
9302 will largely be ignored).
9306 Here is a brief list of the control info files supported by
9307 <prgn>dpkg</prgn> and a summary of what they're used for.
9312 <tag><tt>control</tt>
9315 This is the key description file used by
9316 <prgn>dpkg</prgn>. It specifies the package's name
9317 and version, gives its description for the user,
9318 states its relationships with other packages, and so
9319 forth. See <ref id="sourcecontrolfiles"> and
9320 <ref id="binarycontrolfiles">.
9324 It is usually generated automatically from information
9325 in the source package by the
9326 <prgn>dpkg-gencontrol</prgn> program, and with
9327 assistance from <prgn>dpkg-shlibdeps</prgn>.
9328 See <ref id="pkg-sourcetools">.
9332 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9337 These are executable files (usually scripts) which
9338 <prgn>dpkg</prgn> runs during installation, upgrade
9339 and removal of packages. They allow the package to
9340 deal with matters which are particular to that package
9341 or require more complicated processing than that
9342 provided by <prgn>dpkg</prgn>. Details of when and
9343 how they are called are in <ref id="maintainerscripts">.
9347 It is very important to make these scripts idempotent.
9348 See <ref id="idempotency">.
9352 The maintainer scripts are guaranteed to run with a
9353 controlling terminal and can interact with the user.
9354 See <ref id="controllingterminal">.
9358 <tag><tt>conffiles</tt>
9361 This file contains a list of configuration files which
9362 are to be handled automatically by <prgn>dpkg</prgn>
9363 (see <ref id="pkg-conffiles">). Note that not necessarily
9364 every configuration file should be listed here.
9367 <tag><tt>shlibs</tt>
9370 This file contains a list of the shared libraries
9371 supplied by the package, with dependency details for
9372 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9373 when it determines what dependencies are required in a
9374 package control file. The <tt>shlibs</tt> file format
9375 is described on <ref id="shlibs">.
9380 <sect id="pkg-controlfile">
9381 <heading>The main control information file: <tt>control</tt></heading>
9384 The most important control information file used by
9385 <prgn>dpkg</prgn> when it installs a package is
9386 <tt>control</tt>. It contains all the package's "vital
9391 The binary package control files of packages built from
9392 Debian sources are made by a special tool,
9393 <prgn>dpkg-gencontrol</prgn>, which reads
9394 <file>debian/control</file> and <file>debian/changelog</file> to
9395 find the information it needs. See <ref id="pkg-sourcepkg"> for
9400 The fields in binary package control files are listed in
9401 <ref id="binarycontrolfiles">.
9405 A description of the syntax of control files and the purpose
9406 of the fields is available in <ref id="controlfields">.
9411 <heading>Time Stamps</heading>
9414 See <ref id="timestamps">.
9419 <appendix id="pkg-sourcepkg">
9420 <heading>Source packages (from old Packaging Manual) </heading>
9423 The Debian binary packages in the distribution are generated
9424 from Debian sources, which are in a special format to assist
9425 the easy and automatic building of binaries.
9428 <sect id="pkg-sourcetools">
9429 <heading>Tools for processing source packages</heading>
9432 Various tools are provided for manipulating source packages;
9433 they pack and unpack sources and help build of binary
9434 packages and help manage the distribution of new versions.
9438 They are introduced and typical uses described here; see
9439 <manref name="dpkg-source" section="1"> for full
9440 documentation about their arguments and operation.
9444 For examples of how to construct a Debian source package,
9445 and how to use those utilities that are used by Debian
9446 source packages, please see the <prgn>hello</prgn> example
9450 <sect1 id="pkg-dpkg-source">
9452 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9457 This program is frequently used by hand, and is also
9458 called from package-independent automated building scripts
9459 such as <prgn>dpkg-buildpackage</prgn>.
9463 To unpack a package it is typically invoked with
9465 dpkg-source -x <var>.../path/to/filename</var>.dsc
9470 with the <file><var>filename</var>.tar.gz</file> and
9471 <file><var>filename</var>.diff.gz</file> (if applicable) in
9472 the same directory. It unpacks into
9473 <file><var>package</var>-<var>version</var></file>, and if
9475 <file><var>package</var>-<var>version</var>.orig</file>, in
9476 the current directory.
9480 To create a packed source archive it is typically invoked:
9482 dpkg-source -b <var>package</var>-<var>version</var>
9487 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9488 <file>.diff.gz</file> (if appropriate) in the current
9489 directory. <prgn>dpkg-source</prgn> does not clean the
9490 source tree first - this must be done separately if it is
9495 See also <ref id="pkg-sourcearchives">.</p>
9499 <sect1 id="pkg-dpkg-buildpackage">
9501 <prgn>dpkg-buildpackage</prgn> - overall package-building
9506 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9507 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9508 targets <tt>clean</tt>, <tt>build</tt> and
9509 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9510 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9511 source and binary package upload.
9515 It is usually invoked by hand from the top level of the
9516 built or unbuilt source directory. It may be invoked with
9517 no arguments; useful arguments include:
9518 <taglist compact="compact">
9519 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9522 Do not sign the <tt>.changes</tt> file or the
9523 source package <tt>.dsc</tt> file, respectively.</p>
9525 <tag><tt>-p<var>sign-command</var></tt></tag>
9528 Invoke <var>sign-command</var> instead of finding
9529 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9530 <var>sign-command</var> must behave just like
9531 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9533 <tag><tt>-r<var>root-command</var></tt></tag>
9536 When root privilege is required, invoke the command
9537 <var>root-command</var>. <var>root-command</var>
9538 should invoke its first argument as a command, from
9539 the <prgn>PATH</prgn> if necessary, and pass its
9540 second and subsequent arguments to the command it
9541 calls. If no <var>root-command</var> is supplied
9542 then <var>dpkg-buildpackage</var> will take no
9543 special action to gain root privilege, so that for
9544 most packages it will have to be invoked as root to
9547 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9550 Two types of binary-only build and upload - see
9551 <manref name="dpkg-source" section="1">.
9558 <sect1 id="pkg-dpkg-gencontrol">
9560 <prgn>dpkg-gencontrol</prgn> - generates binary package
9565 This program is usually called from <file>debian/rules</file>
9566 (see <ref id="pkg-sourcetree">) in the top level of the source
9571 This is usually done just before the files and directories in the
9572 temporary directory tree where the package is being built have their
9573 permissions and ownerships set and the package is constructed using
9574 <prgn>dpkg-deb/</prgn>
9576 This is so that the control file which is produced has
9577 the right permissions
9582 <prgn>dpkg-gencontrol</prgn> must be called after all the
9583 files which are to go into the package have been placed in
9584 the temporary build directory, so that its calculation of
9585 the installed size of a package is correct.
9589 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9590 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9591 variable substitutions created by
9592 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9597 For a package which generates only one binary package, and
9598 which builds it in <file>debian/tmp</file> relative to the top
9599 of the source package, it is usually sufficient to call
9600 <prgn>dpkg-gencontrol</prgn>.
9604 Sources which build several binaries will typically need
9607 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9608 </example> The <tt>-P</tt> tells
9609 <prgn>dpkg-gencontrol</prgn> that the package is being
9610 built in a non-default directory, and the <tt>-p</tt>
9611 tells it which package's control file should be generated.
9615 <prgn>dpkg-gencontrol</prgn> also adds information to the
9616 list of files in <file>debian/files</file>, for the benefit of
9617 (for example) a future invocation of
9618 <prgn>dpkg-genchanges</prgn>.</p>
9621 <sect1 id="pkg-dpkg-shlibdeps">
9623 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9628 This program is usually called from <file>debian/rules</file>
9629 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9630 id="pkg-sourcetree">), in the top level of the source tree.
9634 Its arguments are executables and shared libraries
9637 They may be specified either in the locations in the
9638 source tree where they are created or in the locations
9639 in the temporary build tree where they are installed
9640 prior to binary package creation.
9642 </footnote> for which shared library dependencies should
9643 be included in the binary package's control file.
9647 If some of the found shared libraries should only
9648 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9649 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9650 by using the <tt>-d<var>dependency-field</var></tt> option
9651 before those executable(s). (Each <tt>-d</tt> option
9652 takes effect until the next <tt>-d</tt>.)
9656 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9657 output control file to be modified. Instead by default it
9658 adds to the <file>debian/substvars</file> file variable
9659 settings like <tt>shlibs:Depends</tt>. These variable
9660 settings must be referenced in dependency fields in the
9661 appropriate per-binary-package sections of the source
9666 For example, a package that generates an essential part
9667 which requires dependencies, and optional parts that
9668 which only require a recommendation, would separate those
9669 two sets of dependencies into two different fields.<footnote>
9670 At the time of writing, an example for this was the
9671 <package/xmms/ package, with Depends used for the xmms
9672 executable, Recommends for the plug-ins and Suggests for
9673 even more optional features provided by unzip.
9675 It can say in its <file>debian/rules</file>:
9677 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9678 -dRecommends <var>optionalpart anotheroptionalpart</var>
9680 and then in its main control file <file>debian/control</file>:
9683 Depends: ${shlibs:Depends}
9684 Recommends: ${shlibs:Recommends}
9690 Sources which produce several binary packages with
9691 different shared library dependency requirements can use
9692 the <tt>-p<var>varnameprefix</var></tt> option to override
9693 the default <tt>shlibs:</tt> prefix (one invocation of
9694 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9695 They can thus produce several sets of dependency
9696 variables, each of the form
9697 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9698 which can be referred to in the appropriate parts of the
9699 binary package control files.
9704 <sect1 id="pkg-dpkg-distaddfile">
9706 <prgn>dpkg-distaddfile</prgn> - adds a file to
9707 <file>debian/files</file>
9711 Some packages' uploads need to include files other than
9712 the source and binary package files.
9716 <prgn>dpkg-distaddfile</prgn> adds a file to the
9717 <file>debian/files</file> file so that it will be included in
9718 the <file>.changes</file> file when
9719 <prgn>dpkg-genchanges</prgn> is run.
9723 It is usually invoked from the <tt>binary</tt> target of
9724 <file>debian/rules</file>:
9726 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9728 The <var>filename</var> is relative to the directory where
9729 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9730 is usually the directory above the top level of the source
9731 tree. The <file>debian/rules</file> target should put the
9732 file there just before or just after calling
9733 <prgn>dpkg-distaddfile</prgn>.
9737 The <var>section</var> and <var>priority</var> are passed
9738 unchanged into the resulting <file>.changes</file> file.
9743 <sect1 id="pkg-dpkg-genchanges">
9745 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9750 This program is usually called by package-independent
9751 automatic building scripts such as
9752 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9757 It is usually called in the top level of a built source
9758 tree, and when invoked with no arguments will print out a
9759 straightforward <file>.changes</file> file based on the
9760 information in the source package's changelog and control
9761 file and the binary and source packages which should have
9767 <sect1 id="pkg-dpkg-parsechangelog">
9769 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9770 representation of a changelog
9774 This program is used internally by
9775 <prgn>dpkg-source</prgn> et al. It may also occasionally
9776 be useful in <file>debian/rules</file> and elsewhere. It
9777 parses a changelog, <file>debian/changelog</file> by default,
9778 and prints a control-file format representation of the
9779 information in it to standard output.
9783 <sect1 id="pkg-dpkg-architecture">
9785 <prgn>dpkg-architecture</prgn> - information about the build and
9790 This program can be used manually, but is also invoked by
9791 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9792 environment or make variables which specify the build and host
9793 architecture for the package building process.
9798 <sect id="pkg-sourcetree">
9799 <heading>The Debianised source tree</heading>
9802 The source archive scheme described later is intended to
9803 allow a Debianised source tree with some associated control
9804 information to be reproduced and transported easily. The
9805 Debianised source tree is a version of the original program
9806 with certain files added for the benefit of the
9807 Debianisation process, and with any other changes required
9808 made to the rest of the source code and installation
9813 The extra files created for Debian are in the subdirectory
9814 <file>debian</file> of the top level of the Debianised source
9815 tree. They are described below.
9818 <sect1 id="pkg-debianrules">
9819 <heading><file>debian/rules</file> - the main building script</heading>
9822 See <ref id="debianrules">.
9827 <sect1 id="pkg-dpkgchangelog">
9828 <heading><file>debian/changelog</file></heading>
9831 See <ref id="dpkgchangelog">.
9835 It is recommended that the entire changelog be encoded in the
9836 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9838 <url id="http://www.unicode.org/"
9839 name="Unicode">.<footnote>
9841 I think it is fairly obvious that we need to
9842 eventually transition to UTF-8 for our package
9843 infrastructure; it is really the only sane char-set in
9844 an international environment. Now, we can't switch to
9845 using UTF-8 for package control fields and the like
9846 until dpkg has better support, but one thing we can
9847 start doing today is requesting that Debian changelogs
9848 are UTF-8 encoded. At some point in time, we can start
9849 requiring them to do so.
9852 Checking for non-UTF8 characters in a changelog is
9853 trivial. Dump the file through
9854 <example>iconv -f utf-8 -t ucs-4</example>
9855 discard the output, and check the return
9856 value. If there are any characters in the stream
9857 which are invalid UTF-8 sequences, iconv will exit
9858 with an error code; and this will be the case for the
9859 vast majority of other character sets.
9864 <sect2><heading>Defining alternative changelog formats
9868 It is possible to use a different format to the standard
9869 one, by providing a parser for the format you wish to
9874 In order to have <tt>dpkg-parsechangelog</tt> run your
9875 parser, you must include a line within the last 40 lines
9876 of your file matching the Perl regular expression:
9877 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9878 parentheses should be the name of the format. For
9879 example, you might say:
9881 @@@ changelog-format: joebloggs @@@
9883 Changelog format names are non-empty strings of alphanumerics.
9887 If such a line exists then <tt>dpkg-parsechangelog</tt>
9888 will look for the parser as
9889 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9891 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9892 it is an error for it not to find it, or for it not to
9893 be an executable program. The default changelog format
9894 is <tt>dpkg</tt>, and a parser for it is provided with
9895 the <tt>dpkg</tt> package.
9899 The parser will be invoked with the changelog open on
9900 standard input at the start of the file. It should read
9901 the file (it may seek if it wishes) to determine the
9902 information required and return the parsed information
9903 to standard output in the form of a series of control
9904 fields in the standard format. By default it should
9905 return information about only the most recent version in
9906 the changelog; it should accept a
9907 <tt>-v<var>version</var></tt> option to return changes
9908 information from all versions present <em>strictly
9909 after</em> <var>version</var>, and it should then be an
9910 error for <var>version</var> not to be present in the
9916 <list compact="compact">
9917 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9918 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9919 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9920 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9921 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9922 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9923 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9928 If several versions are being returned (due to the use
9929 of <tt>-v</tt>), the urgency value should be of the
9930 highest urgency code listed at the start of any of the
9931 versions requested followed by the concatenated
9932 (space-separated) comments from all the versions
9933 requested; the maintainer, version, distribution and
9934 date should always be from the most recent version.
9938 For the format of the <tt>Changes</tt> field see
9939 <ref id="f-Changes">.
9943 If the changelog format which is being parsed always or
9944 almost always leaves a blank line between individual
9945 change notes these blank lines should be stripped out,
9946 so as to make the resulting output compact.
9950 If the changelog format does not contain date or package
9951 name information this information should be omitted from
9952 the output. The parser should not attempt to synthesize
9953 it or find it from other sources.
9957 If the changelog does not have the expected format the
9958 parser should exit with a nonzero exit status, rather
9959 than trying to muddle through and possibly generating
9964 A changelog parser may not interact with the user at
9970 <sect1 id="pkg-srcsubstvars">
9971 <heading><file>debian/substvars</file> and variable substitutions</heading>
9974 See <ref id="substvars">.
9980 <heading><file>debian/files</file></heading>
9983 See <ref id="debianfiles">.
9987 <sect1><heading><file>debian/tmp</file>
9991 This is the canonical temporary location for the
9992 construction of binary packages by the <tt>binary</tt>
9993 target. The directory <file>tmp</file> serves as the root of
9994 the file system tree as it is being constructed (for
9995 example, by using the package's upstream makefiles install
9996 targets and redirecting the output there), and it also
9997 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9998 id="pkg-bincreating">.
10002 If several binary packages are generated from the same
10003 source tree it is usual to use several
10004 <file>debian/tmp<var>something</var></file> directories, for
10005 example <file>tmp-a</file> or <file>tmp-doc</file>.
10009 Whatever <file>tmp</file> directories are created and used by
10010 <tt>binary</tt> must of course be removed by the
10011 <tt>clean</tt> target.</p></sect1>
10015 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10019 As it exists on the FTP site, a Debian source package
10020 consists of three related files. You must have the right
10021 versions of all three to be able to use them.
10026 <tag>Debian source control file - <tt>.dsc</tt></tag>
10028 This file is a control file used by <prgn>dpkg-source</prgn>
10029 to extract a source package.
10030 See <ref id="debiansourcecontrolfiles">.
10034 Original source archive -
10036 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10042 This is a compressed (with <tt>gzip -9</tt>)
10043 <prgn>tar</prgn> file containing the source code from
10044 the upstream authors of the program.
10049 Debianisation diff -
10051 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10057 This is a unified context diff (<tt>diff -u</tt>)
10058 giving the changes which are required to turn the
10059 original source into the Debian source. These changes
10060 may only include editing and creating plain files.
10061 The permissions of files, the targets of symbolic
10062 links and the characteristics of special files or
10063 pipes may not be changed and no files may be removed
10068 All the directories in the diff must exist, except the
10069 <file>debian</file> subdirectory of the top of the source
10070 tree, which will be created by
10071 <prgn>dpkg-source</prgn> if necessary when unpacking.
10075 The <prgn>dpkg-source</prgn> program will
10076 automatically make the <file>debian/rules</file> file
10077 executable (see below).</p></item>
10082 If there is no original source code - for example, if the
10083 package is specially prepared for Debian or the Debian
10084 maintainer is the same as the upstream maintainer - the
10085 format is slightly different: then there is no diff, and the
10087 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10088 and preferably contains a directory named
10089 <file><var>package</var>-<var>version</var></file>.
10094 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10097 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10098 Debian source package. However, if it is not available it
10099 is possible to unpack a Debian source archive as follows:
10100 <enumlist compact="compact">
10103 Untar the tarfile, which will create a <file>.orig</file>
10107 <p>Rename the <file>.orig</file> directory to
10108 <file><var>package</var>-<var>version</var></file>.</p>
10112 Create the subdirectory <file>debian</file> at the top of
10113 the source tree.</p>
10115 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10117 <item><p>Untar the tarfile again if you want a copy of the original
10118 source code alongside the Debianised version.</p>
10123 It is not possible to generate a valid Debian source archive
10124 without using <prgn>dpkg-source</prgn>. In particular,
10125 attempting to use <prgn>diff</prgn> directly to generate the
10126 <file>.diff.gz</file> file will not work.
10130 <heading>Restrictions on objects in source packages</heading>
10133 The source package may not contain any hard links
10135 This is not currently detected when building source
10136 packages, but only when extracting
10140 Hard links may be permitted at some point in the
10141 future, but would require a fair amount of
10143 </footnote>, device special files, sockets or setuid or
10146 Setgid directories are allowed.
10151 The source packaging tools manage the changes between the
10152 original and Debianised source using <prgn>diff</prgn> and
10153 <prgn>patch</prgn>. Turning the original source tree as
10154 included in the <file>.orig.tar.gz</file> into the debianised
10155 source must not involve any changes which cannot be
10156 handled by these tools. Problematic changes which cause
10157 <prgn>dpkg-source</prgn> to halt with an error when
10158 building the source package are:
10159 <list compact="compact">
10160 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10162 <item><p>Changing the targets of symbolic links.</p>
10164 <item><p>Creating directories, other than <file>debian</file>.</p>
10166 <item><p>Changes to the contents of binary files.</p></item>
10167 </list> Changes which cause <prgn>dpkg-source</prgn> to
10168 print a warning but continue anyway are:
10169 <list compact="compact">
10172 Removing files, directories or symlinks.
10174 Renaming a file is not treated specially - it is
10175 seen as the removal of the old file (which
10176 generates a warning, but is otherwise ignored),
10177 and the creation of the new one.
10183 Changed text files which are missing the usual final
10184 newline (either in the original or the modified
10189 Changes which are not represented, but which are not detected by
10190 <prgn>dpkg-source</prgn>, are:
10191 <list compact="compact">
10192 <item><p>Changing the permissions of files (other than
10193 <file>debian/rules</file>) and directories.</p></item>
10198 The <file>debian</file> directory and <file>debian/rules</file>
10199 are handled specially by <prgn>dpkg-source</prgn> - before
10200 applying the changes it will create the <file>debian</file>
10201 directory, and afterwards it will make
10202 <file>debian/rules</file> world-executable.
10208 <appendix id="pkg-controlfields">
10209 <heading>Control files and their fields (from old Packaging Manual)</heading>
10212 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10213 data in a common format, known as control files. Binary and
10214 source packages have control data as do the <file>.changes</file>
10215 files which control the installation of uploaded files, and
10216 <prgn>dpkg</prgn>'s internal databases are in a similar
10221 <heading>Syntax of control files</heading>
10224 See <ref id="controlsyntax">.
10228 It is important to note that there are several fields which
10229 are optional as far as <prgn>dpkg</prgn> and the related
10230 tools are concerned, but which must appear in every Debian
10231 package, or whose omission may cause problems.
10236 <heading>List of fields</heading>
10239 See <ref id="controlfieldslist">.
10243 This section now contains only the fields that didn't belong
10244 to the Policy manual.
10247 <sect1 id="pkg-f-Filename">
10248 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10251 These fields in <tt>Packages</tt> files give the
10252 filename(s) of (the parts of) a package in the
10253 distribution directories, relative to the root of the
10254 Debian hierarchy. If the package has been split into
10255 several parts the parts are all listed in order, separated
10260 <sect1 id="pkg-f-Size">
10261 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10264 These fields in <file>Packages</file> files give the size (in
10265 bytes, expressed in decimal) and MD5 checksum of the
10266 file(s) which make(s) up a binary package in the
10267 distribution. If the package is split into several parts
10268 the values for the parts are listed in order, separated by
10273 <sect1 id="pkg-f-Status">
10274 <heading><tt>Status</tt></heading>
10277 This field in <prgn>dpkg</prgn>'s status file records
10278 whether the user wants a package installed, removed or
10279 left alone, whether it is broken (requiring
10280 re-installation) or not and what its current state on the
10281 system is. Each of these pieces of information is a
10286 <sect1 id="pkg-f-Config-Version">
10287 <heading><tt>Config-Version</tt></heading>
10290 If a package is not installed or not configured, this
10291 field in <prgn>dpkg</prgn>'s status file records the last
10292 version of the package which was successfully
10297 <sect1 id="pkg-f-Conffiles">
10298 <heading><tt>Conffiles</tt></heading>
10301 This field in <prgn>dpkg</prgn>'s status file contains
10302 information about the automatically-managed configuration
10303 files held by a package. This field should <em>not</em>
10304 appear anywhere in a package!
10309 <heading>Obsolete fields</heading>
10312 These are still recognized by <prgn>dpkg</prgn> but should
10313 not appear anywhere any more.
10315 <taglist compact="compact">
10317 <tag><tt>Revision</tt></tag>
10318 <tag><tt>Package-Revision</tt></tag>
10319 <tag><tt>Package_Revision</tt></tag>
10321 The Debian revision part of the package version was
10322 at one point in a separate control file field. This
10323 field went through several names.
10326 <tag><tt>Recommended</tt></tag>
10327 <item>Old name for <tt>Recommends</tt>.</item>
10329 <tag><tt>Optional</tt></tag>
10330 <item>Old name for <tt>Suggests</tt>.</item>
10332 <tag><tt>Class</tt></tag>
10333 <item>Old name for <tt>Priority</tt>.</item>
10342 <appendix id="pkg-conffiles">
10343 <heading>Configuration file handling (from old Packaging Manual)</heading>
10346 <prgn>dpkg</prgn> can do a certain amount of automatic
10347 handling of package configuration files.
10351 Whether this mechanism is appropriate depends on a number of
10352 factors, but basically there are two approaches to any
10353 particular configuration file.
10357 The easy method is to ship a best-effort configuration in the
10358 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10359 handle updates. If the user is unlikely to want to edit the
10360 file, but you need them to be able to without losing their
10361 changes, and a new package with a changed version of the file
10362 is only released infrequently, this is a good approach.
10366 The hard method is to build the configuration file from
10367 scratch in the <prgn>postinst</prgn> script, and to take the
10368 responsibility for fixing any mistakes made in earlier
10369 versions of the package automatically. This will be
10370 appropriate if the file is likely to need to be different on
10374 <sect><heading>Automatic handling of configuration files by
10379 A package may contain a control area file called
10380 <tt>conffiles</tt>. This file should be a list of filenames
10381 of configuration files needing automatic handling, separated
10382 by newlines. The filenames should be absolute pathnames,
10383 and the files referred to should actually exist in the
10388 When a package is upgraded <prgn>dpkg</prgn> will process
10389 the configuration files during the configuration stage,
10390 shortly before it runs the package's <prgn>postinst</prgn>
10395 For each file it checks to see whether the version of the
10396 file included in the package is the same as the one that was
10397 included in the last version of the package (the one that is
10398 being upgraded from); it also compares the version currently
10399 installed on the system with the one shipped with the last
10404 If neither the user nor the package maintainer has changed
10405 the file, it is left alone. If one or the other has changed
10406 their version, then the changed version is preferred - i.e.,
10407 if the user edits their file, but the package maintainer
10408 doesn't ship a different version, the user's changes will
10409 stay, silently, but if the maintainer ships a new version
10410 and the user hasn't edited it the new version will be
10411 installed (with an informative message). If both have
10412 changed their version the user is prompted about the problem
10413 and must resolve the differences themselves.
10417 The comparisons are done by calculating the MD5 message
10418 digests of the files, and storing the MD5 of the file as it
10419 was included in the most recent version of the package.
10423 When a package is installed for the first time
10424 <prgn>dpkg</prgn> will install the file that comes with it,
10425 unless that would mean overwriting a file already on the
10430 However, note that <prgn>dpkg</prgn> will <em>not</em>
10431 replace a conffile that was removed by the user (or by a
10432 script). This is necessary because with some programs a
10433 missing file produces an effect hard or impossible to
10434 achieve in another way, so that a missing file needs to be
10435 kept that way if the user did it.
10439 Note that a package should <em>not</em> modify a
10440 <prgn>dpkg</prgn>-handled conffile in its maintainer
10441 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10442 the user confusing and possibly dangerous options for
10443 conffile update when the package is upgraded.</p>
10446 <sect><heading>Fully-featured maintainer script configuration
10451 For files which contain site-specific information such as
10452 the hostname and networking details and so forth, it is
10453 better to create the file in the package's
10454 <prgn>postinst</prgn> script.
10458 This will typically involve examining the state of the rest
10459 of the system to determine values and other information, and
10460 may involve prompting the user for some information which
10461 can't be obtained some other way.
10465 When using this method there are a couple of important
10466 issues which should be considered:
10470 If you discover a bug in the program which generates the
10471 configuration file, or if the format of the file changes
10472 from one version to the next, you will have to arrange for
10473 the postinst script to do something sensible - usually this
10474 will mean editing the installed configuration file to remove
10475 the problem or change the syntax. You will have to do this
10476 very carefully, since the user may have changed the file,
10477 perhaps to fix the very problem that your script is trying
10478 to deal with - you will have to detect these situations and
10479 deal with them correctly.
10483 If you do go down this route it's probably a good idea to
10484 make the program that generates the configuration file(s) a
10485 separate program in <file>/usr/sbin</file>, by convention called
10486 <file><var>package</var>config</file> and then run that if
10487 appropriate from the post-installation script. The
10488 <tt><var>package</var>config</tt> program should not
10489 unquestioningly overwrite an existing configuration - if its
10490 mode of operation is geared towards setting up a package for
10491 the first time (rather than any arbitrary reconfiguration
10492 later) you should have it check whether the configuration
10493 already exists, and require a <tt>--force</tt> flag to
10494 overwrite it.</p></sect>
10497 <appendix id="pkg-alternatives"><heading>Alternative versions of
10498 an interface - <prgn>update-alternatives</prgn> (from old
10503 When several packages all provide different versions of the
10504 same program or file it is useful to have the system select a
10505 default, but to allow the system administrator to change it
10506 and have their decisions respected.
10510 For example, there are several versions of the <prgn>vi</prgn>
10511 editor, and there is no reason to prevent all of them from
10512 being installed at once, each under their own name
10513 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10514 Nevertheless it is desirable to have the name <tt>vi</tt>
10515 refer to something, at least by default.
10519 If all the packages involved cooperate, this can be done with
10520 <prgn>update-alternatives</prgn>.
10524 Each package provides its own version under its own name, and
10525 calls <prgn>update-alternatives</prgn> in its postinst to
10526 register its version (and again in its prerm to deregister
10531 See the man page <manref name="update-alternatives"
10532 section="8"> for details.
10536 If <prgn>update-alternatives</prgn> does not seem appropriate
10537 you may wish to consider using diversions instead.</p>
10540 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10541 package's version of a file (from old Packaging Manual)
10545 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10546 when it reinstalls the package it belongs to, and to have it
10547 put the file from the package somewhere else instead.
10551 This can be used locally to override a package's version of a
10552 file, or by one package to override another's version (or
10553 provide a wrapper for it).
10557 Before deciding to use a diversion, read <ref
10558 id="pkg-alternatives"> to see if you really want a diversion
10559 rather than several alternative versions of a program.
10563 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10564 and updated by a special program <prgn>dpkg-divert</prgn>.
10565 Please see <manref name="dpkg-divert" section="8"> for full
10566 details of its operation.
10570 When a package wishes to divert a file from another, it should
10571 call <prgn>dpkg-divert</prgn> in its preinst to add the
10572 diversion and rename the existing file. For example,
10573 supposing that a <prgn>smailwrapper</prgn> package wishes to
10574 install a wrapper around <file>/usr/sbin/smail</file>:
10576 if [ install = "$1" ]; then
10577 dpkg-divert --package smailwrapper --add --rename \
10578 --divert /usr/sbin/smail.real /usr/sbin/smail
10580 </example> Testing <tt>$1</tt> is necessary so that the script
10581 doesn't try to add the diversion again when
10582 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10583 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10584 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10585 get installed as the true version.
10589 The postrm has to do the reverse:
10591 if [ remove = "$1" ]; then
10592 dpkg-divert --package smailwrapper --remove --rename \
10593 --divert /usr/sbin/smail.real /usr/sbin/smail
10599 Do not attempt to divert a file which is vitally important for
10600 the system's operation - when using <prgn>dpkg-divert</prgn>
10601 there is a time, after it has been diverted but before
10602 <prgn>dpkg</prgn> has installed the new version, when the file
10603 does not exist.</p>
10608 <!-- Local variables: -->
10609 <!-- indent-tabs-mode: t -->
10611 <!-- vim:set ai et sts=2 sw=2 tw=76: -->