* Replace SGML manpages with XML man pages from richard...

Author: mdz
Date: 2004-02-07 21:48:14 GMT
* Replace SGML manpages with XML man pages from richard.bos@xs4all.nl
(Closes: #230687)

1 files changed, 528 insertions, 0 deletions

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+<?xml version="1.0" encoding="utf-8" standalone="no"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+
+<!ENTITY % aptent SYSTEM "apt.ent">
+%aptent;
+
+]>
+
+<refentry>
+
+ <refmeta>
+   <refentrytitle>apt_preferences</refentrytitle>
+   <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <!-- Man page title -->
+ <refnamediv>
+    <refname>apt_preferences</refname>
+    <refpurpose>Preference control file for APT</refpurpose>
+ </refnamediv>
+
+<refsect1>
+<title>Description</title>
+<para>The APT preferences file <filename>/etc/apt/preferences</filename>
+can be used to control which versions of packages will be selected
+for installation.</para>
+
+<para>Several versions of a package may be available for installation when
+the &sources-list; file contains references to more than one distribution
+(for example, <literal>stable</literal> and <literal>testing</literal>).
+APT assigns a priority to each version that is available.
+Subject to dependency constraints, <command>apt-get</command> selects the
+version with the highest priority for installation.
+The APT preferences file overrides the priorities that APT assigns to
+package versions by default, thus giving the user control over which
+one is selected for installation.</para>
+
+<para>Several instances of the same version of a package may be available when
+the &sources-list; file contains references to more than one source.
+In this case <command>apt-get</command> downloads the instance listed
+earliest in the &sources-list; file.
+The APT preferences file does not affect the choice of instance, only
+the choice of version.</para>
+
+<refsect2><title>APT's Default Priority Assignments</title>
+
+<para>If there is no preferences file or if there is no entry in the file
+that applies to a particular version then the priority assigned to that
+version is the priority of the distribution to which that version
+belongs.  It is possible to single out a distribution, "the target release",
+which receives a higher priority than other distributions do by default.
+The target release can be set on the <command>apt-get</command> command
+line or in the APT configuration file <filename>/etc/apt/apt.conf</filename>.
+For example,
+
+<programlisting>
+<command>apt-get install -t testing <replaceable>some-package</replaceable></command>
+</programlisting>
+<programlisting>
+APT::Default-Release "stable";
+</programlisting>
+</para>
+
+<para>If the target release has been specified then APT uses the following
+algorithm to set the priorities of the versions of a package.  Assign:
+
+<variablelist>
+<varlistentry>
+<term>priority 100</term>
+<listitem><simpara>to the version that is already installed (if any).</simpara></listitem>
+</varlistentry>
+
+<varlistentry>
+<term>priority 500</term>
+<listitem><simpara>to the versions that are not installed and do not belong to the target release.</simpara></listitem>
+</varlistentry>
+
+<varlistentry>
+<term>priority 990</term>
+<listitem><simpara>to the versions that are not installed and belong to the target release.</simpara></listitem>
+</varlistentry>
+</variablelist>
+</para>
+
+<para>If the target release has not been specified then APT simply assigns
+priority 100 to all installed package versions and priority 500 to all
+uninstalled package versions.</para>
+
+<para>APT then applies the following rules, listed in order of precedence,
+to determine which version of a package to install.
+<itemizedlist>
+<listitem><simpara>Never downgrade unless the priority of an available
+version exceeds 1000.  ("Downgrading" is installing a less recent version
+of a package in place of a more recent version.  Note that none of APT's
+default priorities exceeds 1000; such high priorities can only be set in
+the preferences file.  Note also that downgrading a package
+can be risky.)</simpara></listitem>
+<listitem><simpara>Install the highest priority version.</simpara></listitem>
+<listitem><simpara>If two or more versions have the same priority,
+install the most recent one (that is, the one with the higher version
+number).</simpara></listitem>
+<listitem><simpara>If two or more versions have the same priority and
+version number but either the packages differ in some of their metadata or the
+<literal>--reinstall</literal> option is given, install the uninstalled one.</simpara></listitem>
+</itemizedlist>
+</para>
+
+<para>In a typical situation, the installed version of a package (priority 100)
+is not as recent as one of the versions available from the sources listed in
+the &sources-list; file (priority 500 or 990).  Then the package will be upgraded
+when <command>apt-get install <replaceable>some-package</replaceable></command>
+or <command>apt-get upgrade</command> is executed.
+</para>
+
+<para>More rarely, the installed version of a package is <emphasis>more</emphasis> recent
+than any of the other available versions.  The package will not be downgraded
+when <command>apt-get install <replaceable>some-package</replaceable></command>
+or <command>apt-get upgrade</command> is executed.</para>
+
+<para>Sometimes the installed version of a package is more recent than the
+version belonging to the target release, but not as recent as a version
+belonging to some other distribution.  Such a package will indeed be upgraded
+when <command>apt-get install <replaceable>some-package</replaceable></command>
+or <command>apt-get upgrade</command> is executed,
+because at least <emphasis>one</emphasis> of the available versions has a higher
+priority than the installed version.</para>
+</refsect2>
+
+<refsect2><title>The Effect of APT Preferences</title>
+
+<para>The APT preferences file allows the system administrator to control the
+assignment of priorities.  The file consists of one or more multi-line records
+separated by blank lines.  Records can have one of two forms, a specific form
+and a general form.
+<itemizedlist>
+<listitem>
+<simpara>The specific form assigns a priority (a "Pin-Priority") to a
+specified package and specified version or version range.  For example,
+the following record assigns a high priority to all versions of
+the <filename>perl</filename> package whose version number begins with "<literal>5.8</literal>".</simpara>
+
+<programlisting>
+Package: perl
+Pin: version 5.8*
+Pin-Priority: 1001
+</programlisting>
+</listitem>
+
+<listitem><simpara>The general form assigns a priority to all of the package versions in a
+given distribution (that is, to all the versions of packages that are
+listed in a certain <filename>Release</filename> file) or to all of the package
+versions coming from a particular Internet site, as identified by the
+site's fully qualified domain name.</simpara>
+
+<simpara>This general-form entry in the APT preferences file applies only
+to groups of packages.  For example, the following record assigns a high
+priority to all package versions available from the local site.</simpara>
+
+<programlisting>
+Package: *
+Pin: origin ""
+Pin-Priority: 999
+</programlisting>
+
+<simpara>A note of caution: the keyword used here is "<literal>origin</literal>".
+This should not be confused with the Origin of a distribution as
+specified in a <filename>Release</filename> file.  What follows the "Origin:" tag
+in a <filename>Release</filename> file is not an Internet address
+but an author or vendor name, such as "Debian" or "Ximian".</simpara>
+
+<simpara>The following record assigns a low priority to all package versions
+belonging to any distribution whose Archive name is "<literal>unstable</literal>".</simpara>
+
+<programlisting>
+Package: *
+Pin: release a=unstable
+Pin-Priority: 50
+</programlisting>
+
+<simpara>The following record assigns a high priority to all package versions
+belonging to any release whose Archive name is "<literal>stable</literal>"
+and whose release Version number is "<literal>3.0</literal>".</simpara>
+
+<programlisting>
+Package: *
+Pin: release a=unstable, v=3.0
+Pin-Priority: 50
+</programlisting>
+</listitem>
+</itemizedlist>
+</para>
+
+</refsect2>
+
+<refsect2>
+<title>How APT Interprets Priorities</title>
+
+<para>
+Priorities (P) assigned in the APT preferences file must be positive
+or negative integers.  They are interpreted as follows (roughly speaking):
+
+<variablelist>
+<varlistentry>
+<term>P &gt; 1000</term>
+<listitem><simpara>causes a version to be installed even if this
+constitutes a downgrade of the package</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>990 &lt; P &lt;=1000</term>
+<listitem><simpara>causes a version to be installed
+even if it does not come from the target release,
+unless the installed version is more recent</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>500 &lt; P &lt;=990</term>
+<listitem><simpara>causes a version to be installed
+unless there is a version available belonging to the target release
+or the installed version is more recent</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>100 &lt; P &lt;=500</term>
+<listitem><simpara>causes a version to be installed
+unless there is a version available belonging to some other
+distribution or the installed version is more recent</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>0 &lt; P &lt;=100</term>
+<listitem><simpara>causes a version to be installed
+only if there is no installed version of the package</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>P &lt; 0</term>
+<listitem><simpara>prevents the version from being installed</simpara></listitem>
+</varlistentry>
+</variablelist>
+</para>
+
+<para>If any specific-form records match an available package version then the
+first such record determines the priority of the package version.  
+Failing that,
+if any general-form records match an available package version then the
+first such record determines the priority of the package version.</para>
+
+<para>For example, suppose the APT preferences file contains the three
+records presented earlier:</para>
+
+<programlisting>
+Package: perl
+Pin: version 5.8*
+Pin-Priority: 1001
+
+Package: *
+Pin: origin ""
+Pin-Priority: 999
+
+Package: *
+Pin: release unstable
+Pin-Priority: 50
+</programlisting>
+
+<para>Then:
+<itemizedlist>
+<listitem><simpara>The most recent available version of the <literal>perl</literal>
+package will be installed, so long as that version's version number begins
+with "<literal>5.8</literal>".  If <emphasis>any</emphasis> 5.8* version of <literal>perl</literal> is
+available and the installed version is 5.9*, then <literal>perl</literal> will be
+downgraded.</simpara></listitem>
+<listitem><simpara>A version of any package other than <literal>perl</literal>
+that is available from the local system has priority over other versions,
+even versions belonging to the target release.
+</simpara></listitem>
+<listitem><simpara>A version of a package whose origin is not the local
+system but some other site listed in &sources-list; and which belongs to
+an <literal>unstable</literal> distribution is only installed if it is selected
+for installation and no version of the package is already installed.
+</simpara></listitem>
+</itemizedlist>
+</para>
+</refsect2>
+
+<refsect2>
+<title>Determination of Package Version and Distribution Properties</title>
+
+<para>The locations listed in the &sources-list; file should provide
+<filename>Packages</filename> and <filename>Release</filename> files
+to describe the packages available at that location. </para>
+
+<para>The <filename>Packages</filename> file is normally found in the directory
+<filename>.../dists/<replaceable>dist-name</replaceable>/<replaceable>component</replaceable>/<replaceable>arch</replaceable></filename>:
+for example, <filename>.../dists/stable/main/binary-i386/Packages</filename>.
+It consists of a series of multi-line records, one for each package available
+in that directory.  Only two lines in each record are relevant for setting
+APT priorities:
+<variablelist>
+<varlistentry>
+<term>the <literal>Package:</literal> line</term>
+<listitem><simpara>gives the package name</simpara></listitem>
+</varlistentry>
+<varlistentry>
+<term>the <literal>Version:</literal> line</term>
+<listitem><simpara>gives the version number for the named package</simpara></listitem>
+</varlistentry>
+</variablelist>
+</para>
+
+<para>The <filename>Release</filename> file is normally found in the directory
+<filename>.../dists/<replaceable>dist-name</replaceable></filename>:
+for example, <filename>.../dists/stable/Release</filename>,
+or <filename>.../dists/woody/Release</filename>.
+It consists of a single multi-line record which applies to <emphasis>all</emphasis> of
+the packages in the directory tree below its parent.  Unlike the
+<filename>Packages</filename> file, nearly all of the lines in a <filename>Release</filename>
+file are relevant for setting APT priorities:
+
+<variablelist>
+<varlistentry>
+<term>the <literal>Archive:</literal> line</term>
+<listitem><simpara>names the archive to which all the packages
+in the directory tree belong.  For example, the line
+"Archive: stable"
+specifies that all of the packages in the directory
+tree below the parent of the <filename>Release</filename> file are in a
+<literal>stable</literal> archive.  Specifying this value in the APT preferences file
+would require the line:
+</simpara>
+<programlisting>
+Pin: release a=stable
+</programlisting>
+</listitem>
+</varlistentry>
+
+<varlistentry>
+<term>the <literal>Version:</literal> line</term>
+<listitem><simpara>names the release version.  For example, the
+packages in the tree might belong to Debian GNU/Linux release
+version 3.0.  Note that there is normally no version number for the
+<literal>testing</literal> and <literal>unstable</literal> distributions because they
+have not been released yet.  Specifying this in the APT preferences
+file would require one of the following lines.
+</simpara>
+
+<programlisting>
+Pin: release v=3.0
+Pin: release a=stable, v=3.0
+Pin: release 3.0
+</programlisting>
+
+</listitem>
+</varlistentry>
+
+<varlistentry>
+<term>the <literal>Component:</literal> line</term>
+<listitem><simpara>names the licensing component associated with the
+packages in the directory tree of the <filename>Release</filename> file.
+For example, the line "Component: main" specifies that
+all the packages in the directory tree are from the <literal>main</literal>
+component, which entails that they are licensed under terms listed
+in the Debian Free Software Guidelines.  Specifying this component
+in the APT preferences file would require the line:
+</simpara>
+<programlisting>
+Pin: release c=main
+</programlisting>
+</listitem>
+</varlistentry>
+
+<varlistentry>
+<term>the <literal>Origin:</literal> line</term>
+<listitem><simpara>names the originator of the packages in the
+directory tree of the <filename>Release</filename> file.  Most commonly, this is
+<literal>Debian</literal>.  Specifying this origin in the APT preferences file
+would require the line:
+</simpara>
+<programlisting>
+Pin: release o=Debian
+</programlisting>
+</listitem>
+</varlistentry>
+
+<varlistentry>
+<term>the <literal>Label:</literal> line</term>
+<listitem><simpara>names the label of the packages in the directory tree
+of the <filename>Release</filename> file.  Most commonly, this is
+<literal>Debian</literal>.  Specifying this label in the APT preferences file
+would require the line:
+</simpara>
+<programlisting>
+Pin: release l=Debian
+</programlisting>
+</listitem>
+</varlistentry>
+</variablelist>
+</para>
+
+<para>All of the <filename>Packages</filename> and <filename>Release</filename>
+files retrieved from locations listed in the &sources-list; file are stored
+in the directory <filename>/var/lib/apt/lists</filename>, or in the file named
+by the variable <literal>Dir::State::Lists</literal> in the <filename>apt.conf</filename> file.
+For example, the file
+<filename>debian.lcs.mit.edu_debian_dists_unstable_contrib_binary-i386_Release</filename>
+contains the <filename>Release</filename> file retrieved from the site
+<literal>debian.lcs.mit.edu</literal> for <literal>binary-i386</literal> architecture
+files from the <literal>contrib</literal> component of the <literal>unstable</literal>
+distribution.</para>
+</refsect2>
+
+<refsect2>
+<title>Optional Lines in an APT Preferences Record</title>
+
+<para>Each record in the APT preferences file can optionally begin with
+one or more lines beginning with the word <literal>Explanation:</literal>.
+This provides a place for comments.</para>
+
+<para>The <literal>Pin-Priority:</literal> line in each APT preferences record is
+optional.  If omitted, APT assigs a priority of 1 less than the last value
+specified on a line beginning with <literal>Pin-Priority: release ...</literal>.</para>
+</refsect2>
+</refsect1>
+
+<refsect1>
+<title>Examples</title>
+<refsect2>
+<title>Tracking Stable</title>
+
+<para>The following APT preferences file will cause APT to assign a
+priority higher than the default (500) to all package versions belonging
+to a <literal>stable</literal> distribution and a prohibitively low priority to
+package versions belonging to other <literal>Debian</literal> distributions.
+
+<programlisting>
+Explanation: Uninstall or do not install any Debian-originated
+Explanation: package versions other than those in the stable distro
+Package: *
+Pin: release a=stable
+Pin-Priority: 900
+
+Package: *
+Pin: release o=Debian
+Pin-Priority: -10
+</programlisting>
+</para>
+
+<para>With a suitable &sources-list; file and the above preferences file,
+any of the following commands will cause APT to upgrade to the
+latest <literal>stable</literal> version(s).
+
+<programlisting>
+apt-get install <replaceable>package-name</replaceable>
+apt-get upgrade
+apt-get dist-upgrade
+</programlisting>
+</para>
+
+<para>The following command will cause APT to upgrade the specified
+package to the latest version from the <literal>testing</literal> distribution;
+the package will not be upgraded again unless this command is given
+again.
+
+<programlisting>
+apt-get install <replaceable>package</replaceable>/testing
+</programlisting>
+</para>
+</refsect2>
+
+ <refsect2>
+ <title>Tracking Testing or Unstable</title>
+
+<para>The following APT preferences file will cause APT to assign
+a high priority to package versions from the <literal>testing</literal>
+distribution, a lower priority to package versions from the
+<literal>unstable</literal> distribution, and a prohibitively low priority
+to package versions from other <literal>Debian</literal> distributions.
+
+<programlisting>
+Package: *
+Pin: release a=testing
+Pin-Priority: 900
+
+Package: *
+Pin: release a=unstable
+Pin-Priority: 800
+
+Package: *
+Pin: release o=Debian
+Pin-Priority: -10
+</programlisting>
+</para>
+
+<para>With a suitable &sources-list; file and the above preferences file,
+any of the following commands will cause APT to upgrade to the latest
+<literal>testing</literal> version(s).
+
+<programlisting>
+apt-get install <replaceable>package-name</replaceable>
+apt-get upgrade
+apt-get dist-upgrade
+</programlisting>
+</para>
+
+<para>The following command will cause APT to upgrade the specified
+package to the latest version from the <literal>unstable</literal> distribution.
+Thereafter, <command>apt-get upgrade</command> will upgrade
+the package to the most recent <literal>testing</literal> version if that is
+more recent than the installed version, otherwise, to the most recent
+<literal>unstable</literal> version if that is more recent than the installed
+version.
+
+<programlisting>
+apt-get install <replaceable>package</replaceable>/unstable
+</programlisting>
+</para>
+
+</refsect2>
+</refsect1>
+
+<refsect1>
+<title>See Also</title>
+<para>
+&apt-get; &apt-cache; &apt-conf; &sources-list;
+</para>
+</refsect1>
+
+ &manbugs;
+ &manauthor;
+
+</refentry>
+