dpkg/doc/en/reference.sgml

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V3.1//EN" [
  <!ENTITY debian "<productname>Debian</productname>">
  <!ENTITY dpkg "<command>dpkg</command>">
  <!ENTITY dselect "<command>dselect</command>">
  <!ENTITY deb "<filename>.deb</filename>">
]>
<book id="reference">
<bookinfo>
  <title>dpkg reference Manual</title>
  <edition>draft</edition>

  <authorgroup>
    <author>
      <firstname>Wichert</firstname>
      <surname>Akkerman</surname>
      <affiliation>
	<address>
	  <email>wichert@deephackmode.org</email>
	</address>
      </affiliation>
    </author>
  </authorgroup>

  <copyright>
    <year>2001</year>
    <year>2002</year>
    <holder>Wichert Akkerman</holder>
  </copyright>

  <legalnotice>
    <para>
      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.1 or any
      later version published by the Free Software Foundation. There are
      no invariant sections. A copy of the license is included in the section
      entitled "GNU Free Documentation License".
    </para>
  </legalnotice>
</bookinfo>

<preface>
  <title>Preface</title>

  <para>
    This manual is a reference to the &debian; package management system.
  </para>

  <para>
    This manual is currently being written based on the previous packaging
    manual and as such is a work in progress.
  </para>
</preface>

<chapter id="intro">
  <title>Introduction</title>

  <para>
    The Debian package management system is build up from various seperate
    tools that work together form a comprehensive system to manage your
    system.
  </para>

  <para>
    This document describes all the tools that used to handle and produce
    them as well as the file formats used.
  </para>
</chapter>


<chapter id="versions">
  <title>Version numbers</title>

  <para>
    It is essential for a packaging system to have a documented method to
    compare version numbers. Unfortunately there are different ways of
    dealing with them, each with their own good and bad sides. This chapter
    describes how &dpkg; compares version numbers.
  </para>

  <para>
    Version numbers are ASCII strings made up from alphanumeric characters
    (letters and digits) and the hyphen (<keycap>-</keycap>), dot
    (<keycap>.</keycap>), plus (<keycap>+</keycap>), minus
    (<keycap>-</keycap>) and colon (<keycap>:</keycap>) characters.
  </para>

  <para>
    A version number consists of two parts: the upstream version, and
    optionally the package revision, which are seperated by a hyphen.
    If there is no seperate package revision then the upstream version is
    not allowed to contain a hyphen.
  </para>

  <para>
    Comparing version numbers is done by breaking them into pieces and
    comparing those from left to right. Pieces are seperated by a
    transition from numbers to letters and by non-alphanumeric
    characters. Starting from &dpkg; 1.10 numbers of unlimited length may
    be used. Olders versions converted numbers to integers before comparing
    them and as a result can not handle numbers that do not fit into the C
    type int (2^31-1 on 32bit architectures and 2^63-1 on 64bit
    architectures).
  </para>
</chapter>


<chapter id="diversions">
  <title>Managing diversions</title>

  <para>
    Diversions are a method to instruct &dpkg; to use a different filename
    when installing a file. This can be useful to prevent conflicts between
    related packages or when a system administator wants to replace a file
    with another version.
  </para>

  <para>
    Diversions are specific to either a package or the local system.  A
    package specific diversion will only divert a file if it does not
    belongs to a specific package that was given when the diversion was
    created. This allow a package to divert a file from other packages and
    replacing them with its own copy. Local diversions are applied to all
    packages and can be used by the system administrator.
  </para>

  <section>
    <title>Managing diversions with dpkg-divert</title>

    <tip>
      <para>
	The official documentation for <command>dpkg-divert</command> can always
	be found online in the
	<citerefentry><refentrytitle>dpkg-divert</refentrytitle>
	<manvolnum>8</manvolnum></citerefentry> manual page.
      </para>
    </tip>

    <section>
    <title>Adding new diversions</title>

    <para>New options can be added using the <emphasis>--add</emphasis>
    option for <command>dpkg-divert</command>. Its syntax is:
    </para>

    </section>

  </section>
</chapter>

<chapter id="permissions">
  <title>Managing file permissions / ownership</title>

  <para>
    When you install a package &dpkg; will use the ownership and permissions
    that are used inside the package. In some situations you might not agree
    with those defaults and would like to use other settings. To support this
    a feature called statoverrides was introduced in &dpkg; 1.8.0, and an
    accompanying tool called <command>dpkg-statoverride</command>.
  </para>

  <note>
    <para>
      Even though we use the word file here, this applies to all filesystem
      objects that &dpkg; handles, including directories,
      devices, etc.
    </para>
  </note>

  <caution>
    <para>
      If you look at the &dpkg; changelog you will see that statoverrides
      were actually added in version 1.7.0. However that version had
      some problems both in <command>dpkg-statoverrides</command> which
      broke adding and removing of overrides and in &dpkg; itself which
      made it only apply overrides to normal files. Both problems
      were fixed in version 1.8.0.
    </para>
  </caution>

  <section>
    <title>How permissions and ownership are applied</title>

    <para>
      &dpkg; uses the following logic to determine the ownership and
      permissions to use when installing a file:
    </para>

    <orderedlist>
      <listitem><para>Check if there is a statoverride registered for this file
      </para></listitem>

      <listitem><para>If an override is present use the ownership and permission
	specified in the override.</para></listitem>

      <listitem><para>If no override is present:</para>

	<orderedlist>
	  <listitem><para>Check if there is a system account with the same name
	    as the owner used inside the archive. If so use that as owner,
	    otherwise use the uid as used in the package.
	  </para></listitem>

	  <listitem><para>Check if there is a system group with the same name
	    as the group used inside the archive. If so use that as group,
	    otherwise use the gid as used in the package.
	  </para></listitem>

	  <listitem><para>Use the permissions as used in the package.
	  </para></listitem>
	</orderedlist>
      </listitem>
    </orderedlist>

    <para>
      The exact method that &dpkg; uses to set the ownership and permissions
      depends on the type of file that is being created:
    </para>

    <variablelist>
      <varlistentry>
	<term>regular files</term>
	<listitem><para>Created with owner and group set to
	  <filename>root</filename> and with mode 0. After the data has
	  been written to the file the ownership and mode are set to their
	  final values.
	</para></listitem>
      </varlistentry>

      <varlistentry>
	<term>FIFOs</term>
	<term>character and block devices</term>
	<term>directories</term>
	<listitem><para>Created with owner and group set to
	  <filename>root</filename> and with mode 0, and then updated
	  to set the ownership and mode to their final values.
	</para></listitem>
      </varlistentry>
	  
      <varlistentry>
	<term>Hardlinks</term>
	<listitem><para>After the link has been made its ownership and
	  permissions are setup. <emphasis>This means the original file
	  will also be changed!</emphasis>
	</para></listitem>
      </varlistentry>
    </variablelist>
  </section>

  <section>
    <title>Managing overrides with dpkg-statoverride</title>

    <tip>
      <para>
	The official documentation for <command>dpkg-statoverride</command> can
	always be found online in the
	<citerefentry><refentrytitle>dpkg-statoverride</refentrytitle>
	<manvolnum>8</manvolnum></citerefentry> manual page.
      </para>
    </tip>

    <section>
      <title>Listing overrides</title>

      <para>
	You can get a list of all overrides present in the database by using the
	<option>--list</option> option:
      </para>

      <blockquote><para>
	<synopsis><command>dpkg-statoverride</command> <option>--list</option> <parameter>&lt;glob&gt;</parameter></synopsis>
</para></blockquote>

      <para>
	There is an optional glob option that restricts the output from
	<option>--list</option> to overrides for files that match the glob
	expression. 
      <para>

      <footnote>
	<para>
	  Please see the <citerefentry><refentrytitle>sh</refentrytitle>
	  <manvolnum>1</manvolnum></citerefentry> or
	  <citerefentry><refentrytitle>glob</refentrytitle><manvolnum>7</manvolnum>
	  </citerefentry> for a description of glob syntax.
	</para>
      </footnote>

      <example>
	<title>Listing overrides</title>
	<programlisting>
[fog;~]-1# dpkg-statoverride --list
root root 0755 /bin/mount
root root 0755 /bin/ping
[fog;~]-2# dpkg-statoverride --list '*mount*'
root root 0755 /bin/mount
</programlisting>
      </example>
    </section>

    <section>
      <title>Adding new overrides</title>

      <para>
	New options can be added using the <option>--add</option> option
	for <command>dpkg-statoverride</command>. Its syntax is:
      </para>

      <blockquote><para>
	<synopsis><command>dpkg-statoverride</command> <option>--add</option> <parameter>&lt;user&gt;</parameter> <parameter>&lt;group&gt;</parameter> <parameter>&lt;mode&gt;</parameter> <parameter>&lt;file&gt;</parameter>
</synopsis></para></blockquote>
      
      <para>
	This will add an override for <filename>&lt;file&gt;</filename> by
	telling &dpkg; to use the user, group and mode given to
	<command>dpkg-statoverride</command>. The user and group can be
	specified in two ways: either by using the name as found in the
	system account database (ie <filename>/etc/passwd</filename>, NIS or
	another source configured in
	<filename>/etc/nsswitch.conf</filename>), or by using a number
	prefixed with <computeroutput>#</computeroutput>.
      </para>

      <example>
	<title>Adding an override</title>

      <programlisting>

[fog;~]-1# ls -l /bin/mount
-rwsr-xr-x    1 root     root        56284 Nov 23 06:14 /bin/mount
[fog;~]-2# dpkg-statoverride --add root root 0755 /bin/mount
[fog;~]-3# ls -l /bin/mount
-rwsr-xr-x    1 root     root        56284 Nov 23 06:14 /bin/mount
</programlisting>
      </example>

      <para>
	Adding an override does not update the file on the filesystem, unless
	you also specify the <option>--update</option> option.
      </para>

      <example>
	<title>Adding an override using --update</title>

	<programlisting>
[fog;~]-1# ls -l /bin/mount
-rwsr-xr-x    1 root     root        56284 Nov 23 06:14 /bin/mount
[fog;~]-2# dpkg-statoverride --update --add root root 0755 /bin/mount
[fog;~]-3# ls -l /bin/mount
-rwxr-xr-x    1 root     root        56284 Nov 23 06:14 /bin/mount
</programlisting>
    </example>

    <para>
      If an override already exists and you want to replace it you can
      use the <option>--force</option> to force <command>dpkg-statoverride
      </command> to replace the existing override.
    </para>

    <example>
      <title>Replacing an existing override</title>
      <programlisting>
[fog;~/sources/play/pkg-manual]-1# dpkg-statoverride --add root root 0755 /bin/mount
An override for "/bin/mount" already exists, aborting
[fog;~]-2# dpkg-statoverride --force --add root root 0755 /bin/mount
An override for "/bin/mount" already exists, but --force specified so lets ignore it.
[fog;~]-3# dpkg-statoverride --list /bin/mount
root root 0755 /bin/mount
</programlisting>
    </example>
  </section>

  <section>
    <title>Removing overrides</title>
    <para>
    Overrides can be removed using the <option>--remove</option> option,
    which takes a single filename as argument:
    </para>

    <blockquote><para>
      <synopsis><command>dpkg-statoverride</command> <option>--remove</option> <parameter>&lt;file&gt;</parameter></synopsis>
</para></blockquote>

    <para>
    This will remove the override for <filename>&lt;file&gt;</filename>
    from the database.
    </para>

    <note>
      <para>When an override for a file is removed its ownership and permission
      are <emphasis>not</emphasis> restored to the original value.
      </para>
    </note>

    <example>
      <title>Removing an override</title>
      <programlisting>
[fog;~]-1# dpkg-statoverride --list
root root 0755 /bin/mount
[fog;~]-2# dpkg-statoverride --remove /bin/mount
[fog;~]-3# dpkg-statoverride --list
[fog;~]-4#
</programlisting>
    </example>
  </section>

  </section>
</chapter>


<chapter id="formats">
  <title>File formats</title>
  <para>
    This chapter describes all the file formats used by the package tools.
    All files are text files which you can view and modify using any normal
    text editor if needed.
  </para>

  <para>
    Most file formats are based on the RFC822 format, which is best known
    as the format used in e-mail headers.
  </para>

  <para>
    Each format has a version number which indicates the revision of the
    format being used. This version is always of the form "X.Y". The
    first number (X) is the major version. Within a major version the only
    allowed changes in format are the addition of new fields. This guarantees
    that tools will always be fully backwards and upwards compatible within
    a major version.
  </para>

  <section>
    <title>RFC822</title>
    <para>
      A RFC822 style messages consists of one or more blocks, seperated by
      null lines (an empty line). Each block is made up of fields. Fields
      can be folded over multiple lines by inserting a 'newline whitespace'
      pair. This combination is interpreted as a single whitespace.
    </para>

    <para>
      Each fiels is a single line consisting of a field-name and a
      field-body, seperated by a colon (:). The field-name is made up
      from printable ASCII characters minus the colon. The field-body
      may be composed of all ASCII characters except CR or LF (they
      are automatically removed when unfolding lines).
    </para>

    <example>
      <title>RFC822 style file</title>

      <programlisting>
Header: value
Description: this is an example of an RFC822 style message

Section: new
Name: body
Description: this is block 2 of the example
X-Fortune:
 To be excellent when engaged in administration is to be like the North
 Star.  As it remains in its one position, all the other stars surround it.
 -- Confucius
</programlisting>
    </example>
  </section>

  <section>
    <title>changes file</title>

    <para>
      The <filename>.changse</filename> file is used to describe a set of
      files that is going to be installed in an archive. All files have to
      belong to the same source package. The data in a
      <filename>changes</filename> include  the changes made since the
      previous revision, version and architecture information and the list
      of files that form the change set along with a checksum
    </para>

    <para>
      Just like other dpkg datafiles this file is formated using RFC822
      syntax. In addition the file can signed as an OpenPGP ASCII armored
      message (see RFC2440). The table below lists the allowed fields
      in a <filename>.dsc</filename> file. The order used is not important,
      although <command>dpkg-genchanges</command> will output the fields using
      the ordering used in the table.
    </para>

    <table>
      <title>Fields in a <filename>.changes</filename> file</title>
      <tgroup cols="2">
        <thead>
	  <row>
	    <entry>Field</entry>
	    <entry>Description</entry>
	  </row>
	</thead>

	<tbody>
	  <row>
	    <entry>Format</entry>
	    <entry>
	      Version of the file format used. Currently 1.7.
	    </entry>
	  </row>
	  <row>
	    <entry>Date</entry>
	    <entry>
	      The date (in RFC822 format) when the change set was build.
	    </entry>
	  </row>
	  <row>
	    <entry>Source</entry>
	    <entry>
	      The name of the source package from which the changes were
	      build.
	    </entry>
	  </row>
	  <row>
	    <entry>Binary</entry>
	    <entry>
	      The binary packages (ie &deb; files) that are part of the
	      change set.
	    </entry>
	  </row>
	  <row>
	    <entry>Architecture</entry>
	    <entry>
	      A space seperate list of architectures for which files are
	      included in the set.
	    </entry>
	  </row>
	  <row>
	    <entry>Version</entry>
	    <entry>
	      Version number of the source from which the files were built.
	    </entry>
	  </row>
	  <row>
	    <entry>Distribution</entry>
	    <entry>
	      Distribution in which the changes should be installed, as taken from
	      <filename>debian/changelog</filename>.
	    </entry>
	  </row>
	  <row>
	    <entry>Urgency</entry>
	    <entry>
	      Urgency of the changes, as taken from
	      <filename>debian/changelog</filename>.
	    </entry>
	  </row>
	  <row>
	    <entry>Maintainer</entry>
	    <entry>
	      The maintainer of the package, as listed in
	      <filename>debian/control</filename>.
	    </entry>
	  </row>
	  <row>
	    <entry>Changed-By</entry>
	    <entry>
	      The person who made the last changes to the sources, as
	      listed in <filename>debian/changelog</filename>.
	    </entry>
	  </row>
	  <row>
	    <entry>Description</entry>
	    <entry>
	      Multi-line field describing the &deb; files in the package.
	      Each line describes a single package in the format
	      "packagename - short description".
	    </entry>
	  </row>
	  <row>
	    <entry>Closes</entry>
	    <entry>
	      Space seperate list of bugreports which are closed by this
	      change set. (Optional)
	    </entry>
	  </row>
	  <row>
	    <entry>Changes</entry>
	    <entry>
	      Multi-line field with the changes made since the previous
	      version, as taken from <filename>debian/changelog</filename>.
	      Can possibly mention changes for multiple versions.
	    </entry>
	  </row>
	  <row>
	    <entry>Files</entry>
	    <entry>
	      Multi-line field with the list of files in the change set.
	      Each line describes a single file in the format "MD5 filesize
	      filename".
	    </entry>
	  </row>
        </tbody>
      </tgroup>
    </table>
  </section>

  <section>
    <title>dsc file</title>

    <para>
      The <filename>.dsc</filename> file describes the source for a Debian
      package: it contains general information over the source such as the
      name of the package and which binary package it produces as well as
      the files that contain the sourcecode.
    </para>
    
    <para>
      Just like other dpkg datafiles this file is formated using RFC822
      syntax. In addition the file can signed as an OpenPGP ASCII armored
      message (see RFC2440). The table below lists the allowed fields
      in a <filename>.dsc</filename> file. The order used is not important,
      although <command>dpkg-source</command> will output the fields using
      the ordering used in the table.
    </para>

    <table>
      <title>Fields in a <filename>.dsc</filename> file</title>
      <tgroup cols="2">
	<thead>
	  <row><entry>Field</entry><entry>Description</entry></row>
	</thead>
	<tbody>
	  <row><entry>Format</entry>
	       <entry>Version of the file format used. Currently 1.0.
	       </entry></row>
	  <row><entry>Source</entry>
	       <entry>Name of the source package</entry></row>
	  <row><entry>Version</entry>
	       <entry>Version number of the source</entry></row>
	  <row><entry>Binary</entry>
	       <entry>comma seperated list of binary packages build from this
		  source</entry></row>
	  <row><entry>Origin</entry>
	       <entry>Name of the organization that procuded this package
		      </entry></row>
	  <row><entry>Maintainer</entry>
	       <entry>Maintainer of this package</entry></row>
	  <row><entry>Uploaders</entry>
	       <entry>Multi-line field with list of people authorized to make
		      uploads of a package (optional)</entry>
	  <row><entry>Architecture</entry>
	       <entry>Space seperated list of architectures for which package
		      are build from this source</entry></row>
	  <row><entry>Standards-Version</entry>
	       <entry>Version of &debian; policy this package is complient
		      with</entry></row>
	  <row><entry>Files</entry>
	       <entry>Multi-line field with list of files with the actual source
		      code</entry></row>
	</tbody>
      </tgroup>
    </table>

    <para>
      The Files field contains one line for each file that is
      contains source for this package (only 2 files are supported: a
      <filename>.tar.gz</filename> file with the (original) source, and
      an optional <filename>.diff.gz</filename> with Debian changes to the
      source). Each file description consists of 3 items, seperated by
      a single space:

      <orderedlist>
	<listitem><para>A MD5 checksum of the file</para></listitem>
	<listitem><para>The filesize in bytes</para></listitem>
	<listitem><para>The filename</para></listitem>
      </orderedlist>
    </para>

    <example>
      <title>modutils .dsc file</title>

      <programlisting>
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Format: 1.0
Source: modutils
Version: 2.4.1-1
Binary: modutils
Origin: debian
Maintainer: Wichert Akkerman &lt;wakkerma@debian.org&gt;
Architecture: any
Standards-Version: 3.2.0
Files: 
 6d69ff476c964e703659d950999e411c 246022 modutils_2.4.1.orig.tar.gz
 3de7100460662472404f8a83cccde6da 17219 modutils_2.4.1-1.diff.gz

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.4 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iEYEARECAAYFAjpbNIAACgkQPLiSUC+jvC1CFQCePvKBH6qT7/BKXVHCamKXZvZq
Be8An1QDPcyDFtMddYJw/BwTVphbwzU6
=Zl3g
-----END PGP SIGNATURE-----
</programlisting>
    </example>
  </section>

  <section>
    <title>control</title>

    <table>
      <title>Fields in the source section of the <filename>control</filename>
	     file</title>
      <tgroup cols="2">
	<thead>
	  <row><entry>Field</entry>
	       <entry>required</entry>
	       <entry>Description</entry>
	  </row>
	</thead>
	<tbody>
	  <row><entry>Source</entry><entry>yes</entry>
	       <entry>Name of the source package</entry></row>
	  <row><entry>Section</entry><entry>no</entry>
	       <entry>Package category for this package, used by frontends.
		      </entry></row>
	  <row><entry>Priority</entry><entry>no</entry>
	       <entry>Indication of package importance. Legal values are
		      extra, important, optional, required and standard.
		      </entry></row>
	  <row><entry>Maintainer</entry><entry>yes</entry>
	       <entry>Name of the source package</entry></row>
	  <row><entry>Standards-Version</entry><entry>no</entry>
	       <entry>Version of &debian; policy this package is complient
		      with</entry></row>
	  <row><entry>Build-Depends, Build-Conflicts,
		      Build-Depends-Indep, Build-Conflicts-Indep</entry><entry>no</entry>
	       <entry>Specify demands on the build environment</entry></row>
	  <row><entry>Bugs</entry><entry>no</entry>
	       <entry>Name of the source package</entry></row>
	  <row><entry>Origin</entry><entry>no</entry>
	       <entry>Name of the source package</entry></row>
	</tbody>
      </tgroup>
    </table>


    <table>
      <title>Fields in the package section of the <filename>control</filename>
	     file</title>
      <tgroup cols="2">
	<thead>
	  <row><entry>Field</entry>
	       <entry>required</entry>
	       <entry>Description</entry>
	  </row>
	</thead>
	<tbody>
	  <row><entry>Package</entry><entry>yes</entry>
	       <entry>Name of the package</entry></row>
	  <row><entry>Architecture</entry><entry>yes</entry>
	       <entry>Space seperated list of architectures for which package
		      are build from this source</entry></row>
	  <row><entry>Essential</entry><entry>no</entry>
	       <entry>Indicates if a package is essential to the system
		      </entry></row>
	  <row><entry>Pre-Depends, Depends, Recommends, Suggests, Replaces,
		      Conflicts</entry><entry>no</entry>
	       <entry>Specify relations to other packages</entry></row>
	  <row><entry>Description</entry><entry>yes</entry>
	       <entry>Description of the package</entry></row>
	</tbody>
      </tgroup>
    </table>
  </section>

  <section>
    <title>diversions</title>

    <para>
      The <filename>diversions</filename> file contains all the alternatives
      defined on this system. It is located in the &dpkg; admin directory.
    </para>

    <note>
      <para>
	This is an internal &dpkg; file: do not edit it by hand unless really
	needed, but use the <command>dpkg-divert</command> tool instead.
      </para>
    </note>

    <para>
      For each diversion there are 3 lines in the diversions file:
      <orderedlist>
	<listitem><para>
	  The name of the file that will be diverted.
	</para></listitem>

       <listitem><para>
	 The filename that the diverted file will be diverted to.
       </para></listitem>

       <listitem><para>
	 The name of the package that made this diversion. If it is a
	 local (ie user) diversion the magic packagename `:' is used
	 instead.
       </para></listitem>
      </orderedlist>
    </para>

    <example>
      <title>Example <filename>diversions</filename> file</title>

      <programlisting>
/sbin/modprobe
/sbin/modprobe.orig
:
/usr/bin/locate
/usr/bin/locate.notslocate
slocate
</programlisting>
    </example>
  </section>

  <section>
    <title>statoverrides</title>
    <para>
      This file contains the list of all statoverrides that &dpkg; uses
      when unpacking packages. It is located in the &dpkg; admin
      directory. Each line in the file represents one override, and
      comments are not allowed.
    </para>

    <note>
      <para>
	This is an internal &dpkg; file: do not edit it by hand unless really
	needed, but use the <command>dpkg-statoverride</command> tool instead.
      </para>
    </note>

    <para>
      Each line contains 4 items, seperated by whitespace:
      <orderedlist>
	<listitem><para>
	  The owner to use. This can be either an accountname that must
	  be present on the system, or a numerical uid. Uids are prefixed
	  with a <computeroutput>#</computeroutput>.
	</para></listitem>

	<listitem><para>
	  The group to use. This can be either a group that must be present on
	  the system, or a numerical gid. Gids are prefixed
	  with a <computeroutput>#</computeroutput>.
	</para></listitem>

	<listitem><para>
	  Mode to use for this file. This is an octal number.
	</para></listitem>

	<listitem><para>
	  The filesystem object (file, directory, device, FIFO or link)
	  to which this override should be applied. Since this is the
	  last item on a line it may contain whitespace.
	</para></listitem>
      </orderedlist>
    </para>

    <example>
      <title>Example <filename>statoverride</filename> file</title>
      <programlisting>
root wheel 04750 /bin/su
root adm 0750 /var/log/apache
</programlisting>

      <para>
        This will tell &dpkg; to do the following:
      </para>

      <itemizedlist>
	<listitem><para><filename>/bin/su</filename> is installed owned by
	  user <computeroutput>root</computeroutput> and group
	  <computeroutput>wheel</computeroutput> with mode 04750. This means
	  that only people in the <computeroutput>wheel</computeroutput>
	  group are allowed to run <command>su</command>.
        </para></listitem>
  
	<listitem><para><filename>/var/log/apache</filename> is installed
	  owned by user <computeroutput>root</computeroutput> and group
	  <computeroutput>adm</computeroutput> with mode 0750. This
	  restricts the ability to view the
	  <productname>apache</productname> to people in the
	  <computeroutput>adm</computeroutput> group by disallowing others
	  to access the <filename>/var/log/apache</filename> directory.
        </para></listitem>
      </itemizedlist>
    </example>
  </section>

  <section>
    <title>alternatives</title>

    <para>
      The configuration for alternatives is spread over two places: the
      symlink to the selected alternative is stored in /etc/alternatives
      and the list of available alternatives is kept in a series of files
      in <filename>/var/lib/dpkg/alternatives/</filename>.
    </para>

    <para>
      For each alternative there is a single file in
      <filename>/var/lib/dpkg/alternatives/</filename> named after the
      the alternative it describes. The file is a normal text file:
    </para>

    <itemizedlist>
      <listitem>
	<para>
	  The first line lists the state of the alternative, either
	  `manual' or `auto'. 
	</para>
      </listitem>

      <listitem>
	<para>
	  The second line is the filename that the alternative will
	  provide.
	</para>
      </listitem>

      <listitem>
	<para>
	  A list of zero or more slave links. For each slave there are
	  two lines: the first contains the name of the slave and the
	  second contains the filename.
	</para>
      </listitem>

      <listitem>
	<para>
	  An empty line
	</para>
      </listitem>

      <listitem>
	<para>
	  A list of one or more alternatives. Each alternative is made up
	  as follows:
	</para>

	<itemizedlist>
	  <listitem>
	    <para>
	      The filename of the file providing the alternative.
	    </para>
	  </listitem>

	  <listitem>
	    <para>
	      The priority
	    </para>
	  </listitem>

	  <listitem>
	    <para>
	      For each slave link a single line with the file providing
	      the link. An empty line can be used to indicate an
	      alternative does not provide a slave.
	    </para>
	  </listitem>
	</itemizedlist>
      </listitem>
    </itemizedlist>
  </section>
</chapter>

</book>

<!-- vi: sw=2 tw=75
-->