<?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;
-
-<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent">
-%aptverbatiment;
-
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY % aptent SYSTEM "apt.ent"> %aptent;
+<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment;
+<!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor;
]>
<refentry>
&apt-email;
&apt-product;
<!-- The last update date -->
- <date>16 February 2010</date>
+ <date>2012-06-09T00:00:00Z</date>
</refentryinfo>
<refmeta>
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
+The APT preferences override the priorities that APT assigns to
package versions by default, thus giving the user control over which
one is selected for installation.</para>
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 APT preferences do not affect the choice of instance, only
the choice of version.</para>
<para>Preferences are a strong power in the hands of a system administrator
but they can become also their biggest nightmare if used without care!
-APT will not questioning the preferences so wrong settings will therefore
+APT will not question the preferences, so wrong settings can
lead to uninstallable packages or wrong decisions while upgrading packages.
-Even more problems will arise if multiply distribution releases are mixed
+Even more problems will arise if multiple distribution releases are mixed
without a good understanding of the following paragraphs.
-Packages included in a specific release aren't tested in and
-therefore doesn't always work as expected in older or newer releases or
+Packages included in a specific release aren't tested in (and
+therefore don't always work as expected in) older or newer releases, or
together with other packages from different releases.
You have been warned.</para>
<para>Note that the files in the <filename>/etc/apt/preferences.d</filename>
directory are parsed in alphanumeric ascending order and need to obey the
-following naming convention: The files have no or "<literal>pref</literal>"
-as filename extension and which only contain alphanumeric, hyphen (-),
+following naming convention: The files have either no or "<literal>pref</literal>"
+as filename extension and only contain alphanumeric, hyphen (-),
underscore (_) and period (.) characters.
-Otherwise APT will print a notice that it has ignored a file if the file
-doesn't match a pattern in the <literal>Dir::Ignore-Files-Silently</literal>
-configuration list - in this case it will be silently ignored.</para>
+Otherwise APT will print a notice that it has ignored a file, unless that
+file matches a pattern in the <literal>Dir::Ignore-Files-Silently</literal>
+configuration list - in which case it will be silently ignored.</para>
<refsect2><title>APT's Default Priority Assignments</title>
<varlistentry>
<term>priority 1</term>
<listitem><simpara>to the versions coming from archives which in their <filename>Release</filename>
-files are marked as "NotAutomatic: yes" like the debian experimental archive.</simpara></listitem>
+files are marked as "NotAutomatic: yes" but <emphasis>not</emphasis> as "ButAutomaticUpgrades: yes"
+like the Debian <literal>experimental</literal> archive.</simpara></listitem>
</varlistentry>
<varlistentry>
<term>priority 100</term>
-<listitem><simpara>to the version that is already installed (if any).</simpara></listitem>
+<listitem><simpara>to the version that is already installed (if any) and to the versions coming
+from archives which in their <filename>Release</filename> files are marked as "NotAutomatic: yes" and
+"ButAutomaticUpgrades: yes" like the Debian backports archive since <literal>squeeze-backports</literal>.
+</simpara></listitem>
</varlistentry>
<varlistentry>
<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, expect versions coming from archives which
+uninstalled package versions, except versions coming from archives which
in their <filename>Release</filename> files are marked as "NotAutomatic: yes" -
-these versions get the priority 1.</para>
+these versions get the priority 1 or priority 100 if it is additionally marked
+as "ButAutomaticUpgrades: yes".</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>The specific form assigns a priority (a "Pin-Priority") to one or more
-specified packages and specified version or version range. For example,
+specified packages with a 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>".
+the <filename>perl</filename> package whose version number begins with "<literal>&good-perl;</literal>".
Multiple packages can be separated by spaces.</simpara>
<programlisting>
Package: perl
-Pin: version 5.8*
+Pin: version &good-perl;*
Pin-Priority: 1001
</programlisting>
</listitem>
<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>
+and whose release Version number is "<literal>&stable-version;</literal>".</simpara>
<programlisting>
Package: *
-Pin: release a=stable, v=3.0
+Pin: release a=stable, v=&stable-version;
Pin-Priority: 500
</programlisting>
</listitem>
</refsect2>
+<refsect2><title>Regular expressions and &glob; syntax</title>
+<para>
+APT also supports pinning by &glob; expressions, and regular
+expressions surrounded by slashes. For example, the following
+example assigns the priority 500 to all packages from
+experimental where the name starts with gnome (as a &glob;-like
+expression) or contains the word kde (as a POSIX extended regular
+expression surrounded by slashes).
+</para>
+
+<programlisting>
+Package: gnome* /kde/
+Pin: release a=experimental
+Pin-Priority: 500
+</programlisting>
+
+<para>
+The rule for those expressions is that they can occur anywhere
+where a string can occur. Thus, the following pin assigns the
+priority 990 to all packages from a release starting with &ubuntu-codename;.
+</para>
+
+<programlisting>
+Package: *
+Pin: release n=&ubuntu-codename;*
+Pin-Priority: 990
+</programlisting>
+
+<para>
+If a regular expression occurs in a <literal>Package</literal> field,
+the behavior is the same as if this regular expression were replaced
+with a list of all package names it matches. It is undecided whether
+this will change in the future; thus you should always list wild-card
+pins first, so later specific pins override it.
+
+The pattern "<literal>*</literal>" in a Package field is not considered
+a &glob; expression in itself.
+</para>
+</refsect2>
+
+
+
+
+
<refsect2>
<title>How APT Interprets Priorities</title>
<variablelist>
<varlistentry>
-<term>P > 1000</term>
+<term>P >= 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 < P <=1000</term>
+<term>990 <= P < 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 < P <=990</term>
+<term>500 <= P < 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 < P <=500</term>
+<term>100 <= P < 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 < P <=100</term>
+<term>0 < P < 100</term>
<listitem><simpara>causes a version to be installed
only if there is no installed version of the package</simpara></listitem>
</varlistentry>
<term>P < 0</term>
<listitem><simpara>prevents the version from being installed</simpara></listitem>
</varlistentry>
+<varlistentry>
+<term>P = 0</term>
+<listitem><simpara>has undefined behaviour, do not use it.</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>
+The first specific-form record matching an available package version determines
+the priority of the package version.
+Failing that, the priority of the package is defined as the maximum of all
+priorities defined by generic-form records matching the version.
+Records defined using patterns in the Pin field other than "*" are treated like
+specific-form records.
+</para>
<para>For example, suppose the APT preferences file contains the three
records presented earlier:</para>
<programlisting>
Package: perl
-Pin: version 5.8*
+Pin: version &good-perl;*
Pin-Priority: 1001
Package: *
<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
+with "<literal>&good-perl;</literal>". If <emphasis>any</emphasis> &good-perl;* version of <literal>perl</literal> is
+available and the installed version is &bad-perl;*, 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,
<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
+packages in the tree might belong to Debian release
+version &stable-version;. 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
+Pin: release v=&stable-version;
+Pin: release a=stable, v=&stable-version;
+Pin: release &stable-version;
</programlisting>
</listitem>
projects / apt.git / blobdiff