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diff --git a/doc/apt_preferences.5.sgml b/doc/apt_preferences.5.sgml index 2d9c9a052..7fa2afdf2 100644 --- a/doc/apt_preferences.5.sgml +++ b/doc/apt_preferences.5.sgml @@ -20,138 +20,138 @@ <refpurpose>Preference control file for APT</> </refnamediv> -<RefSect1><Title>Description</> +<RefSect1> +<Title>Description</Title> <para> The APT preferences file <filename>/etc/apt/preferences</> -can be used to control which version of a package will be selected +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 +<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>); -furthermore, several instances of the same version of a package may be -available when the file contains references to more than one download site -for a particular distribution. APT assigns a "priority" to each instance -that is available. (In what follows, an "instance" will be an instance of -a package that is available according to &sources-list;.) -Subject to dependency constraints, <command>apt-get</command> installs the -instance with the highest priority. If two instances have the same -priority then it installs the more recent one, that is, the one with the -higher version number. -</para> - -<para>The APT preferences file overrides the priorities that APT assigns -to package instances by default, thus giving the user control over which +(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. +</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 instance, then the priority assigned to that -instance is the priority of the distribution to which that instance -belongs. It is possible to single out a distribution, called the -"target release", which receives a higher priority than other distributions. +<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 to install the <literal/testing/ version of <replaceable>some-package</replaceable> <command>apt-get install -t testing <replaceable>some-package</replaceable></command> </programlisting> - <programlisting> -# Configuration setting to make <literal/stable/ the target release APT::Default-Release "stable"; </programlisting> </para> -<para>If a target release has been specified then APT uses the following -algorithm to set the priorities of the instances of a package. Assign: - +<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 instance that is already installed (if any). -</simpara></listitem> +<listitem><simpara>to the version that is already installed (if any).</simpara></listitem> </varlistentry> <varlistentry> <term>priority 500</term> -<listitem><simpara>to the instances that are not installed -and do not belong to the target release. -</simpara></listitem> +<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 instances that are not installed -and belong to the target release. -</simpara></listitem> +<listitem><simpara>to the versions that are not installed and belong to the target release.</simpara></listitem> </varlistentry> </variablelist> </para> -<para>If no target release has been specified then APT simply assigns -priority 100 to all installed package instances and priority 500 to all -uninstalled package instances. +<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 instance of a package to install. - +<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 instance -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.) -</simpara></listitem> -<listitem><simpara>Install the highest priority instance. -</simpara></listitem> -<listitem><simpara>If two or more instances have the same priority, -install the most recent one. -</simpara></listitem> -<listitem><simpara>If two or more instances have the same version number, -install the one whose source is listed earliest in &sources-list;. -(The installed instance, if there is one, is always preferred in such a -comparison unless <command>apt-get --reinstall</command> is used.) -</simpara></listitem> +<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/ option is given, install the uninstalled one.</simpara></listitem> </itemizedlist> </para> -<para>In a typical situation, the installed instance of a package (priority 100) -is not as recent as one of the instances available from the sources listed in -the &sources-list; file (priority 500 or 990). Then the package will be -upgraded with the command: -<command>apt-get install</command> or <command>apt-get dist-upgrade</command>. +<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>Rarely, the installed instance of a package is <emphasis/more/ recent -than any of the other available instances. The package will not be downgraded. +<para> +More rarely, the installed version of a package is <emphasis/more/ 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 instance of a package is more recent than the +<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, -because at least <emphasis/one/ of the available instances has a higher -priority than the installed instance. +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/ of the available versions has a higher +priority than the installed version. </para> </RefSect2> <RefSect2><Title>The Effect of APT Preferences</> -<para>The APT preferences file allows the system administrator to customize -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. +<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 pins a priority (a "Pin-Priority") to a -specified package and specified version or version range. For -example, the following record pins a high priority to all versions of -the <filename/perl/ package whose version number begins with -"<literal/5.8/". +<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/ package whose version number begins with "<literal/5.8/". </simpara> <programlisting> @@ -162,17 +162,17 @@ Pin-Priority: 1001 </listitem> <listitem><simpara> -The "general" form pins a priority to all of the package versions in a +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/ file), or to all of the package -instances coming from a particular Internet site, as identified by its -fully qualified domain name. +listed in a certain <filename/Release/ 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 causes APT to -assign a high priority to all package instances available from the local -site. +<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> @@ -181,16 +181,17 @@ Pin: origin "" Pin-Priority: 999 </programlisting> -<simpara>A note of caution: the keyword used here is "<literal/origin/". -This should not be confused with the "Origin:" of a distribution as +<simpara> +A note of caution: the keyword used here is "<literal/origin/". +This should not be confused with the Origin of a distribution as specified in a <filename/Release/ file. What follows the "Origin:" tag -in a <filename/Release/ file is usually not an Internet site address +in a <filename/Release/ file is not an Internet address but an author or vendor name, such as "Debian" or "Ximian". </simpara> -<simpara>The following record causes APT to assign a low priority to all -package versions belonging to any distribution whose "Archive" -(<literal/a/) name is "<literal/unstable/". +<simpara> +The following record assigns a low priority to all package versions +belonging to any distribution whose Archive name is "<literal/unstable/". </simpara> <programlisting> @@ -199,10 +200,10 @@ Pin: release a=unstable Pin-Priority: 50 </programlisting> -<simpara>The following record causes APT to assign a high priority to all -package versions belonging to any release whose "Archive" (<literal/a/) -name is "<literal/stable/" and whose release "Version" (<literal/v/) -number is "<literal/3.0/". +<simpara> +The following record assigns a high priority to all package versions +belonging to any release whose Archive name is "<literal/stable/" +and whose release Version number is "<literal/3.0/". </simpara> <programlisting> @@ -216,55 +217,58 @@ Pin-Priority: 50 </RefSect2> -<RefSect2><Title>How APT Interprets Priorities</Title> +<RefSect2> +<Title>How APT Interprets Priorities</Title> -<para>Priorities (P) assigned in the APT preferences file must be positive +<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 > 1000</term> -<listitem><simpara>causes an instance to be installed -even if this constitutes a downgrade of the package -</simpara></listitem> +<varlistentry> +<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> -<listitem><simpara>causes an instance to be installed +<varlistentry> +<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 instance is more recent -</simpara></listitem> +unless the installed version is more recent</simpara></listitem> </varlistentry> -<varlistentry><term>500 < P <=990</term> -<listitem><simpara>causes an instance to be installed -unless there is an instance available belonging to the target release -or the installed version is more recent -</simpara></listitem> +<varlistentry> +<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> -<listitem><simpara>causes an instance to be installed -unless there is an instance available belonging to some other -distribution or the installed version is more recent -</simpara></listitem> -<varlistentry><term>0 <= P <=100</term> -<listitem><simpara>causes an instance to be installed -only if there is no installed instance of the package -</simpara></listitem> +<varlistentry> +<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> +<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> -<varlistentry><term>P < 0</term> -<listitem><simpara>prevents the instance from being installed -</simpara></listitem> +<varlistentry> +<term>P < 0</term> +<listitem><simpara>prevents the version from being installed</simpara></listitem> </varlistentry> </variablelist> </para> -<para>If one of the specific-form records described above matches an -available package instance, then that record determines the priority of -the instance. If two specific-form records match an available instance, -then the first record encountered determines the priority. If two -general-form records match an available instance, then the first record -encountered determines the priority. +<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 +<para> +For example, suppose the APT preferences file contains the three records presented earlier: <programlisting> @@ -289,27 +293,30 @@ package will be installed, so long as that version's version number begins with "<literal/5.8/". If <emphasis/any/ 5.8* version of <literal/perl/ is available and the installed version is 5.9*, then <literal/perl/ will be downgraded.</simpara></listitem> -<listitem><simpara>An instance of any package other than <literal/perl/ -that is available from the local system has priority over other instances, -even instances belonging to the target release. +<listitem><simpara>A version of any package other than <literal/perl/ +that is available from the local system has priority over other versions, +even versions belonging to the target release. </simpara></listitem> -<listitem><simpara>An instance 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/" distribution, is only installed if it is selected -for installation and no instance of the package is already installed. +<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/ 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> +<RefSect2> +<Title>Determination of Package Version and Distribution Properties</Title> -<para>The locations listed in a system's &sources-list; file should provide +<para> +The locations listed in the &sources-list; file should provide <filename>Packages</filename> and <filename>Release</filename> files -to describe the package instances available at that location. +to describe the packages available at that location. </para> -<para>The <filename>Packages</filename> file is normally found in the directory +<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 @@ -327,26 +334,27 @@ APT priorities: </variablelist> </para> -<para>The <filename>Release</filename> file is normally found in the directory +<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/ of -the package instances in the directory tree below its parent. Unlike the +the packages in the directory tree below its parent. Unlike the <filename/Packages/ file, nearly all of the lines in a <filename/Release/ file are relevant for setting APT priorities: <variablelist> <varlistentry> <term>the <literal/Archive:/ line</term> -<listitem><simpara>names the archive to which all the package instances +<listitem><simpara>names the archive to which all the packages in the directory tree belong. For example, the line -<literal/Archive: stable/ specifies that all of the packages in the directory -tree below the parent of the <filename/Release/ file are in the +"Archive: stable" +specifies that all of the packages in the directory +tree below the parent of the <filename/Release/ file are in a <literal/stable/ archive. Specifying this value in the APT preferences file would require the line: </simpara> - <programlisting> Pin: release a=stable </programlisting> @@ -356,11 +364,11 @@ Pin: release a=stable <varlistentry> <term>the <literal/Version:/ line</term> <listitem><simpara>names the release version. For example, the -package instances in the tree might belong to Debian GNU/Linux release -version 3.0. There is normally no version number for the "testing" and -"unstable" distributions because they have not yet been released. -Specifying this in the APT preferences file would require one of the -following lines. +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/ and <literal/unstable/ distributions because they +have not been released yet. Specifying this in the APT preferences +file would require one of the following lines. </simpara> <programlisting> @@ -375,14 +383,13 @@ Pin: release 3.0 <varlistentry> <term>the <literal/Component:/ line</term> <listitem><simpara>names the licensing component associated with the -package instances in the directory tree of the <filename/Release/ -file. For example, the line <literal/Component: main/ specifies that -all the instances in the directory tree are from the <literal/main/ -component, meaning 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: +packages in the directory tree of the <filename/Release/ file. +For example, the line "Component: main" specifies that +all the packages in the directory tree are from the <literal/main/ +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> @@ -391,12 +398,11 @@ Pin: release c=main <varlistentry> <term>the <literal/Origin:/ line</term> -<listitem><simpara>names the producer of the package instances in the +<listitem><simpara>names the originator of the packages in the directory tree of the <filename/Release/ file. Most commonly, this is <literal/Debian/. Specifying this origin in the APT preferences file would require the line: </simpara> - <programlisting> Pin: release o=Debian </programlisting> @@ -405,11 +411,11 @@ Pin: release o=Debian <varlistentry> <term>the <literal/Label:/ line</term> -<listitem><simpara>seems redundant. Most commonly, this is +<listitem><simpara>names the label of the packages in the directory tree +of the <filename/Release/ file. Most commonly, this is <literal/Debian/. Specifying this label in the APT preferences file would require the line: </simpara> - <programlisting> Pin: release l=Debian </programlisting> @@ -418,8 +424,9 @@ Pin: release l=Debian </variablelist> </para> -<para>All of the <filename>Packages</filename> and <filename>Release</filename> -files retrieved from locations listed in the &sources-list; file are kept +<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/ in the <filename/apt.conf/ file. For example, the file @@ -432,35 +439,41 @@ distribution. </RefSect2> -<RefSect2><Title>Optional Lines in an APT Preferences Record</Title> +<RefSect2> +<Title>Optional Lines in an APT Preferences Record</Title> -<para>Each record in the APT preferences file can optionally begin with +<para> +Each record in the APT preferences file can optionally begin with one or more lines beginning with the word <literal/Explanation:/. -This provides an opportunity to comment on the record. +This provides a place for comments. </para> -<para>The <literal/Pin-Priority:/ line in each APT preferences record is +<para> +The <literal/Pin-Priority:/ 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 .../. </para> </RefSect2> </RefSect1> -<RefSect1><Title>Examples</> -<RefSect2><Title>Tracking Stable</Title> +<RefSect1> +<Title>Examples</Title> +<RefSect2> +<Title>Tracking Stable</Title> -<para>The following APT preferences file will cause APT to assign a +<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/ distribution and a prohibitively low priority to package versions belonging to other <literal/Debian/ 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 -Explanation: Uninstall or do not install any Debian-originated -Explanation: instances other than those in the stable distro Package: * Pin: release o=Debian Pin-Priority: -10 @@ -479,20 +492,24 @@ apt-get dist-upgrade </programlisting> </para> -<para>The following command will cause APT to upgrade the specified +<para> +The following command will cause APT to upgrade the specified package to the latest version from the <literal/testing/ distribution; -further upgrades will not occur automatically, however. +the package will not be upgraded again unless this command is given +again. <programlisting> apt-get install <replaceable>package</replaceable>/testing </programlisting> </RefSect2> - <RefSect2><Title>Tracking Testing</Title> + <RefSect2> + <Title>Tracking Testing or Unstable</Title> -<para>The following APT preferences file will cause APT to assign +<para> +The following APT preferences file will cause APT to assign a high priority to package versions from the <literal/testing/ -distribution, a lesser priority to package versions from the +distribution, a lower priority to package versions from the <literal/unstable/ distribution, and a prohibitively low priority to package versions from other <literal/Debian/ distributions. @@ -512,8 +529,8 @@ Pin-Priority: -10 </para> <para> -With the above APT preferences file, any of the -following commands will cause APT to upgrade to the latest +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/ version(s). <programlisting> @@ -525,9 +542,11 @@ apt-get dist-upgrade <para>The following command will cause APT to upgrade the specified package to the latest version from the <literal/unstable/ distribution. -Thereafter, <command>apt-get dist-upgrade</command> and the others -<emphasis/will/ cause upgrade of the package to the latest -<literal/unstable/ version. +Thereafter, <command>apt-get upgrade</command> will upgrade +the package to the most recent <literal/testing/ version if that is +more recent than the installed version, otherwise, to the most recent +<literal/unstable/ version if that is more recent than the installed +version. <programlisting> apt-get install <replaceable>package</replaceable>/unstable @@ -537,10 +556,12 @@ apt-get install <replaceable>package</replaceable>/unstable </RefSect2> </RefSect1> - <RefSect1><Title>See Also</> +<RefSect1> +<Title>See Also</Title> <para> &apt-get; &apt-cache; &apt-conf; &sources-list; - </RefSect1> +</para> +</RefSect1> &manbugs; &manauthor; |