<?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" [
+<!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;
+
]>
<refentry>
&apt-email;
&apt-product;
<!-- The last update date -->
- <date>04 May 2009</date>
+ <date>2012-06-09T00:00:00Z</date>
</refentryinfo>
<refmeta>
<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
+and the fragment files in the <filename>/etc/apt/preferences.d/</filename>
+folder 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
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 question the preferences, so wrong settings can
+lead to uninstallable packages or wrong decisions while upgrading packages.
+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 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 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, 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>
<para>If there is no preferences file or if there is no entry in the file
algorithm to set the priorities of the versions of a package. Assign:
<variablelist>
+<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" 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.</para>
+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 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>
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
+<simpara>A note of caution: the keyword used here is "<literal>origin</literal>"
+which can be used to match a hostname. The following record will assign a high priority
+to all versions available from the server identified by the hostname "ftp.de.debian.org"</simpara>
+<programlisting>
+Package: *
+Pin: origin "ftp.de.debian.org"
+Pin-Priority: 999
+</programlisting>
+<simpara>This should <emphasis>not</emphasis> 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>
</programlisting>
<simpara>The following record assigns a high priority to all package versions
-belonging to any distribution whose Codename is "<literal>squeeze</literal>".</simpara>
+belonging to any distribution whose Codename is "<literal>&testing-codename;</literal>".</simpara>
<programlisting>
Package: *
-Pin: release n=squeeze
+Pin: release n=&testing-codename;
Pin-Priority: 900
</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>
+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 n=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>
<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,
<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>.
+or <filename>.../dists/&stable-codename;/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>
<term>the <literal>Codename:</literal> line</term>
<listitem><simpara>names the codename to which all the packages
in the directory tree belong. For example, the line
-"Codename: squeeze"
+"Codename: &testing-codename;"
specifies that all of the packages in the directory
tree below the parent of the <filename>Release</filename> file belong to a version named
-<literal>squeeze</literal>. Specifying this value in the APT preferences file
+<literal>&testing-codename;</literal>. Specifying this value in the APT preferences file
would require the line:
</simpara>
<programlisting>
-Pin: release n=squeeze
+Pin: release n=&testing-codename;
</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
+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>
<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 assigns a priority of 1 less than the last value
-specified on a line beginning with <literal>Pin-Priority: release ...</literal>.</para>
</refsect2>
</refsect1>
<programlisting>
Explanation: Uninstall or do not install any Debian-originated package versions
-Explanation: other than those in the distribution codenamed with squeeze or sid
+Explanation: other than those in the distribution codenamed with &testing-codename; or sid
Package: *
-Pin: release n=squeeze
+Pin: release n=&testing-codename;
Pin-Priority: 900
Explanation: Debian unstable is always codenamed with sid
Package: *
-Pin: release a=sid
+Pin: release n=sid
Pin-Priority: 800
Package: *
<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 version(s) in the release codenamed with <literal>squeeze</literal>.
+latest version(s) in the release codenamed with <literal>&testing-codename;</literal>.
<programlisting>
apt-get install <replaceable>package-name</replaceable>
<para>The following command will cause APT to upgrade the specified
package to the latest version from the <literal>sid</literal> distribution.
Thereafter, <command>apt-get upgrade</command> will upgrade
-the package to the most recent <literal>squeeze</literal> version if that is
+the package to the most recent <literal>&testing-codename;</literal> version if that is
more recent than the installed version, otherwise, to the most recent
<literal>sid</literal> version if that is more recent than the installed
version.
</refsect2>
</refsect1>
+<refsect1>
+<title>Files</title>
+ <variablelist>
+ &file-preferences;
+ </variablelist>
+</refsect1>
+
<refsect1>
<title>See Also</title>
<para>&apt-get; &apt-cache; &apt-conf; &sources-list;
projects / apt.git / blobdiff