<?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>
<term>priority 500</term>
-<listitem><simpara>to the versions that are not installed and do not belong to the target release.</simpara></listitem>
+<listitem><simpara>to the versions that 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>
+<listitem><simpara>to the versions that belong to the target release.</simpara></listitem>
</varlistentry>
</variablelist>
+
+The highest of those priorities whose description matches the version is assigned to the
+version.
</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, 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>
</itemizedlist>
+
+The effect of the comma operator is similar to an "and" in logic: All
+conditions must be satisfied for the pin to match. There is one exception:
+For any type of condition (such as two "a" conditions), only the last such
+condition is checked.
</para>
</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