bionic (5) apt_preferences.5.gz

Provided by: apt_1.6.17_amd64 bug

NAME

       apt_preferences - Preference control file for APT

DESCRIPTION

       The APT preferences file /etc/apt/preferences and the fragment files in the /etc/apt/preferences.d/
       folder can be used to control which versions of packages will be selected for installation.

       Several versions of a package may be available for installation when the sources.list(5) file contains
       references to more than one distribution (for example, stable and testing). APT assigns a priority to
       each version that is available. Subject to dependency constraints, apt-get selects the version with the
       highest priority for installation. 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.

       Several instances of the same version of a package may be available when the sources.list(5) file
       contains references to more than one source. In this case apt-get downloads the instance listed earliest
       in the sources.list(5) file. The APT preferences do not affect the choice of instance, only the choice of
       version.

       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.

       Note that the files in the /etc/apt/preferences.d directory are parsed in alphanumeric ascending order
       and need to obey the following naming convention: The files have either no or "pref" 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
       Dir::Ignore-Files-Silently configuration list - in which case it will be silently ignored.

   APT's Default Priority Assignments
       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 apt-get command
       line or in the APT configuration file /etc/apt/apt.conf. Note that this has precedence over any general
       priority you set in the /etc/apt/preferences file described later, but not over specifically pinned
       packages. For example,

           apt-get install -t testing some-package

           APT::Default-Release "stable";

       If the target release has been specified then APT uses the following algorithm to set the priorities of
       the versions of a package. Assign:

       priority 1
           to the versions coming from archives which in their Release files are marked as "NotAutomatic: yes"
           but not as "ButAutomaticUpgrades: yes" like the Debian experimental archive.

       priority 100
           to the version that is already installed (if any) and to the versions coming from archives which in
           their Release files are marked as "NotAutomatic: yes" and "ButAutomaticUpgrades: yes" like the Debian
           backports archive since squeeze-backports.

       priority 500
           to the versions that do not belong to the target release.

       priority 990
           to the versions that belong to the target release.
       The highest of those priorities whose description matches the version is assigned to the version.

       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 Release files are marked as "NotAutomatic: yes" - these versions get the priority
       1 or priority 100 if it is additionally marked as "ButAutomaticUpgrades: yes".

       APT then applies the following rules, listed in order of precedence, to determine which version of a
       package to install.

       •   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.)

       •   Install the highest priority version.

       •   If two or more versions have the same priority, install the most recent one (that is, the one with
           the higher version number).

       •   If two or more versions have the same priority and version number but either the packages differ in
           some of their metadata or the --reinstall option is given, install the uninstalled one.

       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(5) file (priority 500 or 990). Then the
       package will be upgraded when apt-get install some-package or apt-get upgrade is executed.

       More rarely, the installed version of a package is more recent than any of the other available versions.
       The package will not be downgraded when apt-get install some-package or apt-get upgrade is executed.

       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 when apt-get install some-package or apt-get upgrade is executed, because at least one of the
       available versions has a higher priority than the installed version.

   The Effect of APT Preferences
       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.

       •   The specific form assigns a priority (a "Pin-Priority") to one or more specified packages with a
           specified version or version range. For example, the following record assigns a high priority to all
           versions of the perl package whose version number begins with "5.20". Multiple packages can be
           separated by spaces.

               Package: perl
               Pin: version 5.20*
               Pin-Priority: 1001

       •   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 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.

           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.

               Package: *
               Pin: origin ""
               Pin-Priority: 999

           A note of caution: the keyword used here is "origin" 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"

               Package: *
               Pin: origin "ftp.de.debian.org"
               Pin-Priority: 999

           This should not be confused with the Origin of a distribution as specified in a Release file. What
           follows the "Origin:" tag in a Release file is not an Internet address but an author or vendor name,
           such as "Debian" or "Ximian".

           The following record assigns a low priority to all package versions belonging to any distribution
           whose Archive name is "unstable".

               Package: *
               Pin: release a=unstable
               Pin-Priority: 50

           The following record assigns a high priority to all package versions belonging to any distribution
           whose Codename is "buster".

               Package: *
               Pin: release n=buster
               Pin-Priority: 900

           The following record assigns a high priority to all package versions belonging to any release whose
           Archive name is "stable" and whose release Version number is "9".

               Package: *
               Pin: release a=stable, v=9
               Pin-Priority: 500

       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.

   Regular expressions and glob(7) syntax
       APT also supports pinning by glob(7) 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(7)-like expression) or contains the word kde (as a POSIX extended regular
       expression surrounded by slashes).

           Package: gnome* /kde/
           Pin: release a=experimental
           Pin-Priority: 500

       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 bionic.

           Package: *
           Pin: release n=bionic*
           Pin-Priority: 990

       If a regular expression occurs in a Package 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 "*" in a Package field is not considered a glob(7) expression in itself.

   How APT Interprets Priorities
       Priorities (P) assigned in the APT preferences file must be positive or negative integers. They are
       interpreted as follows (roughly speaking):

       P >= 1000
           causes a version to be installed even if this constitutes a downgrade of the package

       990 <= P < 1000
           causes a version to be installed even if it does not come from the target release, unless the
           installed version is more recent

       500 <= P < 990
           causes a version to be installed unless there is a version available belonging to the target release
           or the installed version is more recent

       100 <= P < 500
           causes a version to be installed unless there is a version available belonging to some other
           distribution or the installed version is more recent

       0 < P < 100
           causes a version to be installed only if there is no installed version of the package

       P < 0
           prevents the version from being installed

       P = 0
           has undefined behaviour, do not use it.

       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.

       For example, suppose the APT preferences file contains the three records presented earlier:

           Package: perl
           Pin: version 5.20*
           Pin-Priority: 1001

           Package: *
           Pin: origin ""
           Pin-Priority: 999

           Package: *
           Pin: release unstable
           Pin-Priority: 50

       Then:

       •   The most recent available version of the perl package will be installed, so long as that version's
           version number begins with "5.20". If any 5.20* version of perl is available and the installed
           version is 5.24*, then perl will be downgraded.

       •   A version of any package other than perl that is available from the local system has priority over
           other versions, even versions belonging to the target release.

       •   A version of a package whose origin is not the local system but some other site listed in
           sources.list(5) and which belongs to an unstable distribution is only installed if it is selected for
           installation and no version of the package is already installed.

   Determination of Package Version and Distribution Properties
       The locations listed in the sources.list(5) file should provide Packages and Release files to describe
       the packages available at that location.

       The Packages file is normally found in the directory .../dists/dist-name/component/arch: for example,
       .../dists/stable/main/binary-i386/Packages. It consists of a series of multi-line records, one for each
       package available in that directory. Only two lines in each record are relevant for setting APT
       priorities:

       the Package: line
           gives the package name

       the Version: line
           gives the version number for the named package

       The Release file is normally found in the directory .../dists/dist-name: for example,
       .../dists/stable/Release, or .../dists/stretch/Release. It consists of a single multi-line record which
       applies to all of the packages in the directory tree below its parent. Unlike the Packages file, nearly
       all of the lines in a Release file are relevant for setting APT priorities:

       the Archive: or Suite: line
           names the archive to which all the packages in the directory tree belong. For example, the line
           "Archive: stable" or "Suite: stable" specifies that all of the packages in the directory tree below
           the parent of the Release file are in a stable archive. Specifying this value in the APT preferences
           file would require the line:

               Pin: release a=stable

       the Codename: line
           names the codename to which all the packages in the directory tree belong. For example, the line
           "Codename: buster" specifies that all of the packages in the directory tree below the parent of the
           Release file belong to a version named buster. Specifying this value in the APT preferences file
           would require the line:

               Pin: release n=buster

       the Version: line
           names the release version. For example, the packages in the tree might belong to Debian release
           version 9. Note that there is normally no version number for the testing and unstable distributions
           because they have not been released yet. Specifying this in the APT preferences file would require
           one of the following lines.

               Pin: release v=9
               Pin: release a=stable, v=9
               Pin: release 9

       the Component: line
           names the licensing component associated with the packages in the directory tree of the Release file.
           For example, the line "Component: main" specifies that all the packages in the directory tree are
           from the 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:

               Pin: release c=main

       the Origin: line
           names the originator of the packages in the directory tree of the Release file. Most commonly, this
           is Debian. Specifying this origin in the APT preferences file would require the line:

               Pin: release o=Debian

       the Label: line
           names the label of the packages in the directory tree of the Release file. Most commonly, this is
           Debian. Specifying this label in the APT preferences file would require the line:

               Pin: release l=Debian

       All of the Packages and Release files retrieved from locations listed in the sources.list(5) file are
       stored in the directory /var/lib/apt/lists, or in the file named by the variable Dir::State::Lists in the
       apt.conf file. For example, the file debian.lcs.mit.edu_debian_dists_unstable_contrib_binary-i386_Release
       contains the Release file retrieved from the site debian.lcs.mit.edu for binary-i386 architecture files
       from the contrib component of the unstable distribution.

   Optional Lines in an APT Preferences Record
       Each record in the APT preferences file can optionally begin with one or more lines beginning with the
       word Explanation:. This provides a place for comments.

EXAMPLES

   Tracking Stable
       The following APT preferences file will cause APT to assign a priority higher than the default (500) to
       all package versions belonging to a stable distribution and a prohibitively low priority to package
       versions belonging to other Debian distributions.

           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

           Package: *
           Pin: release o=Debian
           Pin-Priority: -10

       With a suitable sources.list(5) file and the above preferences file, any of the following commands will
       cause APT to upgrade to the latest stable version(s).

           apt-get install package-name
           apt-get upgrade
           apt-get dist-upgrade

       The following command will cause APT to upgrade the specified package to the latest version from the
       testing distribution; the package will not be upgraded again unless this command is given again.

           apt-get install package/testing

   Tracking Testing or Unstable
       The following APT preferences file will cause APT to assign a high priority to package versions from the
       testing distribution, a lower priority to package versions from the unstable distribution, and a
       prohibitively low priority to package versions from other Debian distributions.

           Package: *
           Pin: release a=testing
           Pin-Priority: 900

           Package: *
           Pin: release a=unstable
           Pin-Priority: 800

           Package: *
           Pin: release o=Debian
           Pin-Priority: -10

       With a suitable sources.list(5) file and the above preferences file, any of the following commands will
       cause APT to upgrade to the latest testing version(s).

           apt-get install package-name
           apt-get upgrade
           apt-get dist-upgrade

       The following command will cause APT to upgrade the specified package to the latest version from the
       unstable distribution. Thereafter, apt-get upgrade will upgrade the package to the most recent testing
       version if that is more recent than the installed version, otherwise, to the most recent unstable version
       if that is more recent than the installed version.

           apt-get install package/unstable

   Tracking the evolution of a codename release
       The following APT preferences file will cause APT to assign a priority higher than the default (500) to
       all package versions belonging to a specified codename of a distribution and a prohibitively low priority
       to package versions belonging to other Debian distributions, codenames and archives. Note that with this
       APT preference APT will follow the migration of a release from the archive testing to stable and later
       oldstable. If you want to follow for example the progress in testing notwithstanding the codename changes
       you should use the example configurations above.

           Explanation: Uninstall or do not install any Debian-originated package versions
           Explanation: other than those in the distribution codenamed with buster or sid
           Package: *
           Pin: release n=buster
           Pin-Priority: 900

           Explanation: Debian unstable is always codenamed with sid
           Package: *
           Pin: release n=sid
           Pin-Priority: 800

           Package: *
           Pin: release o=Debian
           Pin-Priority: -10

       With a suitable sources.list(5) 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 buster.

           apt-get install package-name
           apt-get upgrade
           apt-get dist-upgrade

       The following command will cause APT to upgrade the specified package to the latest version from the sid
       distribution. Thereafter, apt-get upgrade will upgrade the package to the most recent buster version if
       that is more recent than the installed version, otherwise, to the most recent sid version if that is more
       recent than the installed version.

           apt-get install package/sid

FILES

       /etc/apt/preferences
           Version preferences file. This is where you would specify "pinning", i.e. a preference to get certain
           packages from a separate source or from a different version of a distribution. Configuration Item:
           Dir::Etc::Preferences.

       /etc/apt/preferences.d/
           File fragments for the version preferences. Configuration Item: Dir::Etc::PreferencesParts.

SEE ALSO

       apt-get(8) apt-cache(8) apt.conf(5) sources.list(5)

BUGS

       APT bug page[1]. If you wish to report a bug in APT, please see /usr/share/doc/debian/bug-reporting.txt
       or the reportbug(1) command.

AUTHOR

       APT team

NOTES

        1. APT bug page
           http://bugs.debian.org/src:apt