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Diffstat (limited to 'doc/apt_preferences.5.sgml')
| -rw-r--r-- | doc/apt_preferences.5.sgml | 58 |
1 files changed, 36 insertions, 22 deletions
diff --git a/doc/apt_preferences.5.sgml b/doc/apt_preferences.5.sgml index 817586548..1a6ddf9f7 100644 --- a/doc/apt_preferences.5.sgml +++ b/doc/apt_preferences.5.sgml @@ -34,42 +34,46 @@ 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. +version with the highest priority for installation. If multiple +versions are available with equal priorities, the higher version will +be selected. 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 +If the selected version of a package is available from more than one +source, for example if more than one mirror of the same packages is +listed in <filename>sources.list</>, apt will select the source listed earliest in the &sources-list; file. -The APT preferences file does not affect the choice of instance, only -the choice of version. + +The APT preferences file does not affect which download source is +used, only which versions of packages are selected for installation. </para> <RefSect2><Title>APT's Default Priority Assignments</> <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> +If there is no preferences file, or if there is no entry in the file +that applies to a particular version, then certain defaults are +supplied. </para> +<variablelist> +<varlistentry> +<term>Installed packages</term> +<listitem><simpara>The currently installed version of a package, if any, is +assigned priority 100.</simpara></listitem> +</varlistentry> + +<varlistentry> +<term></term> +<listitem><simpara>The currently installed version of a package, if any, is +assigned priority 100.</simpara></listitem> +</varlistentry> + <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> @@ -86,6 +90,16 @@ algorithm to set the priorities of the versions of a package. Assign: </variablelist> </para> +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 not been specified then APT simply assigns priority 100 to all installed package versions and priority 500 to all |