NAME | SYNOPSIS | DESCRIPTION | TERMINOLOGY | COMMANDS | OPTIONS | EXIT STATUS | ENVIRONMENT | FILES | QUERY FORMAT | DIAGNOSTICS | EXAMPLES | SEE ALSO | COLOPHON

update-alternatives(1)           dpkg suite           update-alternatives(1)

NAME         top

       update-alternatives  -  maintain  symbolic  links determining default
       commands

SYNOPSIS         top

       update-alternatives [option...] command

DESCRIPTION         top

       update-alternatives creates, removes, maintains and displays
       information about the symbolic links comprising the Debian
       alternatives system.

       It is possible for several programs fulfilling the same or similar
       functions to be installed on a single system at the same time.  For
       example, many systems have several text editors installed at once.
       This gives choice to the users of a system, allowing each to use a
       different editor, if desired, but makes it difficult for a program to
       make a good choice for an editor to invoke if the user has not
       specified a particular preference.

       Debian's alternatives system aims to solve this problem.  A generic
       name in the filesystem is shared by all files providing
       interchangeable functionality.  The alternatives system and the
       system administrator together determine which actual file is
       referenced by this generic name.  For example, if the text editors
       ed(1) and nvi(1) are both installed on the system, the alternatives
       system will cause the generic name /usr/bin/editor to refer to
       /usr/bin/nvi by default. The system administrator can override this
       and cause it to refer to /usr/bin/ed instead, and the alternatives
       system will not alter this setting until explicitly requested to do
       so.

       The generic name is not a direct symbolic link to the selected
       alternative.  Instead, it is a symbolic link to a name in the
       alternatives directory, which in turn is a symbolic link to the
       actual file referenced.  This is done so that the system
       administrator's changes can be confined within the /usr/local/etc
       directory: the FHS (q.v.) gives reasons why this is a Good Thing.

       When each package providing a file with a particular functionality is
       installed, changed or removed, update-alternatives is called to
       update information about that file in the alternatives system.
       update-alternatives is usually called from the postinst (configure)
       or prerm (remove and deconfigure) scripts in Debian packages.

       It is often useful for a number of alternatives to be synchronized,
       so that they are changed as a group; for example, when several
       versions of the vi(1) editor are installed, the man page referenced
       by /usr/share/man/man1/vi.1 should correspond to the executable
       referenced by /usr/bin/vi.  update-alternatives handles this by means
       of master and slave links; when the master is changed, any associated
       slaves are changed too.  A master link and its associated slaves make
       up a link group.

       Each link group is, at any given time, in one of two modes: automatic
       or manual.  When a group is in automatic mode, the alternatives
       system will automatically decide, as packages are installed and
       removed, whether and how to update the links.  In manual mode, the
       alternatives system will retain the choice of the administrator and
       avoid changing the links (except when something is broken).

       Link groups are in automatic mode when they are first introduced to
       the system.  If the system administrator makes changes to the
       system's automatic settings, this will be noticed the next time
       update-alternatives is run on the changed link's group, and the group
       will automatically be switched to manual mode.

       Each alternative has a priority associated with it.  When a link
       group is in automatic mode, the alternatives pointed to by members of
       the group will be those which have the highest priority.

       When using the --config option, update-alternatives will list all of
       the choices for the link group of which given name is the master
       alternative name.  The current choice is marked with a ‘*’.  You will
       then be prompted for your choice regarding this link group.
       Depending on the choice made, the link group might no longer be in
       auto mode. You will need to use the --auto option in order to return
       to the automatic mode (or you can rerun --config and select the entry
       marked as automatic).

       If you want to configure non-interactively you can use the --set
       option instead (see below).

       Different packages providing the same file need to do so
       cooperatively.  In other words, the usage of update-alternatives is
       mandatory for all involved packages in such case. It is not possible
       to override some file in a package that does not employ the
       update-alternatives mechanism.

TERMINOLOGY         top

       Since the activities of update-alternatives are quite involved, some
       specific terms will help to explain its operation.

       generic name (or alternative link)
              A name, like /usr/bin/editor, which refers, via the
              alternatives system, to one of a number of files of similar
              function.

       alternative name
              The name of a symbolic link in the alternatives directory.

       alternative (or alternative path)
              The name of a specific file in the filesystem, which may be
              made accessible via a generic name using the alternatives
              system.

       alternatives directory
              A directory, by default /usr/local/etc/alternatives,
              containing the symlinks.

       administrative directory
              A directory, by default /usr/local/var/lib/dpkg/alternatives,
              containing update-alternatives' state information.

       link group
              A set of related symlinks, intended to be updated as a group.

       master link
              The alternative link in a link group which determines how the
              other links in the group are configured.

       slave link
              An alternative link in a link group which is controlled by the
              setting of the master link.

       automatic mode
              When a link group is in automatic mode, the alternatives
              system ensures that the links in the group point to the
              highest priority alternative appropriate for the group.

       manual mode
              When a link group is in manual mode, the alternatives system
              will not make any changes to the system administrator's
              settings.

COMMANDS         top

       --install link name path priority [--slave link name path]...
              Add a group of alternatives to the system.  link is the
              generic name for the master link, name is the name of its
              symlink in the alternatives directory, and path is the
              alternative being introduced for the master link.  The
              arguments after --slave are the generic name, symlink name in
              the alternatives directory and the alternative path for a
              slave link.  Zero or more --slave options, each followed by
              three arguments, may be specified. Note that the master
              alternative must exist or the call will fail. However if a
              slave alternative doesn't exist, the corresponding slave
              alternative link will simply not be installed (a warning will
              still be displayed). If some real file is installed where an
              alternative link has to be installed, it is kept unless
              --force is used.

              If the alternative name specified exists already in the
              alternatives system's records, the information supplied will
              be added as a new set of alternatives for the group.
              Otherwise, a new group, set to automatic mode, will be added
              with this information.  If the group is in automatic mode, and
              the newly added alternatives' priority is higher than any
              other installed alternatives for this group, the symlinks will
              be updated to point to the newly added alternatives.

       --set name path
              Set the program path as alternative for name.  This is
              equivalent to --config but is non-interactive and thus
              scriptable.

       --remove name path
              Remove an alternative and all of its associated slave links.
              name is a name in the alternatives directory, and path is an
              absolute filename to which name could be linked. If name is
              indeed linked to path, name will be updated to point to
              another appropriate alternative (and the group is put back in
              automatic mode), or removed if there is no such alternative
              left.  Associated slave links will be updated or removed,
              correspondingly.  If the link is not currently pointing to
              path, no links are changed; only the information about the
              alternative is removed.

       --remove-all name
              Remove all alternatives and all of their associated slave
              links.  name is a name in the alternatives directory.

       --all  Call --config on all alternatives. It can be usefully combined
              with --skip-auto to review and configure all alternatives
              which are not configured in automatic mode. Broken
              alternatives are also displayed.  Thus a simple way to fix all
              broken alternatives is to call yes '' | update-alternatives
              --force --all.

       --auto name
              Switch the link group behind the alternative for name to
              automatic mode.  In the process, the master symlink and its
              slaves are updated to point to the highest priority installed
              alternatives.

       --display name
              Display information about the link group.  Information
              displayed includes the group's mode (auto or manual), the
              master and slave links, which alternative the master link
              currently points to, what other alternatives are available
              (and their corresponding slave alternatives), and the highest
              priority alternative currently installed.

       --get-selections
              List all master alternative names (those controlling a link
              group) and their status (since version 1.15.0).  Each line
              contains up to 3 fields (separated by one or more spaces). The
              first field is the alternative name, the second one is the
              status (either auto or manual), and the last one contains the
              current choice in the alternative (beware: it's a filename and
              thus might contain spaces).

       --set-selections
              Read configuration of alternatives on standard input in the
              format generated by --get-selections and reconfigure them
              accordingly (since version 1.15.0).

       --query name
              Display information about the link group like --display does,
              but in a machine parseable way (since version 1.15.0, see
              section QUERY FORMAT below).

       --list name
              Display all targets of the link group.

       --config name
              Show available alternatives for a link group and allow the
              user to interactively select which one to use. The link group
              is updated.

       --help Show the usage message and exit.

       --version
              Show the version and exit.

OPTIONS         top

       --altdir directory
              Specifies the alternatives directory, when this is to be
              different from the default.

       --admindir directory
              Specifies the administrative directory, when this is to be
              different from the default.

       --log file
              Specifies the log file (since version 1.15.0), when this is to
              be different from the default
              (/usr/local/var/log/alternatives.log).

       --force
              Allow replacing or dropping any real file that is installed
              where an alternative link has to be installed or removed.

       --skip-auto
              Skip configuration prompt for alternatives which are properly
              configured in automatic mode. This option is only relevant
              with --config or --all.

       --verbose
              Generate more comments about what is being done.

       --quiet
              Don't generate any comments unless errors occur.

EXIT STATUS         top

       0      The requested action was successfully performed.

       2      Problems were encountered whilst parsing the command line or
              performing the action.

ENVIRONMENT         top

       DPKG_ADMINDIR
              If set and the --admindir option has not been specified, it
              will be used as the base administrative directory.

FILES         top

       /usr/local/etc/alternatives/
              The default alternatives directory.  Can be overridden by the
              --altdir option.

       /usr/local/var/lib/dpkg/alternatives/
              The default administration directory.  Can be overridden by
              the --admindir option.

QUERY FORMAT         top

       The --query format is using an RFC822-like flat format. It's made of
       n + 1 blocks where n is the number of alternatives available in the
       queried link group. The first block contains the following fields:

       Name: name
              The alternative name in the alternative directory.

       Link: link
              The generic name of the alternative.

       Slaves: list-of-slaves
              When this field is present, the next lines hold all slave
              links associated to the master link of the alternative. There
              is one slave per line. Each line contains one space, the
              generic name of the slave alternative, another space, and the
              path to the slave link.

       Status: status
              The status of the alternative (auto or manual).

       Best: best-choice
              The path of the best alternative for this link group. Not
              present if there is no alternatives available.

       Value: currently-selected-alternative
              The path of the currently selected alternative. It can also
              take the magic value none. It is used if the link doesn't
              exist.

       The other blocks describe the available alternatives in the queried
       link group:

       Alternative: path-of-this-alternative
              Path to this block's alternative.

       Priority: priority-value
              Value of the priority of this alternative.

       Slaves: list-of-slaves
              When this field is present, the next lines hold all slave
              alternatives associated to the master link of the alternative.
              There is one slave per line. Each line contains one space, the
              generic name of the slave alternative, another space, and the
              path to the slave alternative.

   Example
       $ update-alternatives --query editor
       Name: editor
       Link: /usr/bin/editor
       Slaves:
        editor.1.gz /usr/share/man/man1/editor.1.gz
        editor.fr.1.gz /usr/share/man/fr/man1/editor.1.gz
        editor.it.1.gz /usr/share/man/it/man1/editor.1.gz
        editor.pl.1.gz /usr/share/man/pl/man1/editor.1.gz
        editor.ru.1.gz /usr/share/man/ru/man1/editor.1.gz
       Status: auto
       Best: /usr/bin/vim.basic
       Value: /usr/bin/vim.basic

       Alternative: /bin/ed
       Priority: -100
       Slaves:
        editor.1.gz /usr/share/man/man1/ed.1.gz

       Alternative: /usr/bin/vim.basic
       Priority: 50
       Slaves:
        editor.1.gz /usr/share/man/man1/vim.1.gz
        editor.fr.1.gz /usr/share/man/fr/man1/vim.1.gz
        editor.it.1.gz /usr/share/man/it/man1/vim.1.gz
        editor.pl.1.gz /usr/share/man/pl/man1/vim.1.gz
        editor.ru.1.gz /usr/share/man/ru/man1/vim.1.gz

DIAGNOSTICS         top

       With --verbose update-alternatives chatters incessantly about its
       activities on its standard output channel.  If problems occur,
       update-alternatives outputs error messages on its standard error
       channel and returns an exit status of 2.  These diagnostics should be
       self-explanatory; if you do not find them so, please report this as a
       bug.

EXAMPLES         top

       There are several packages which provide a text editor compatible
       with vi, for example nvi and vim. Which one is used is controlled by
       the link group vi, which includes links for the program itself and
       the associated manpage.

       To display the available packages which provide vi and the current
       setting for it, use the --display action:

              update-alternatives --display vi

       To choose a particular vi implementation, use this command as root
       and then select a number from the list:

              update-alternatives --config vi

       To go back to having the vi implementation chosen automatically, do
       this as root:

              update-alternatives --auto vi

SEE ALSO         top

       ln(1), FHS, the Filesystem Hierarchy Standard.

COLOPHON         top

       This page is part of the dpkg (Debian Package Manager) project.
       Information about the project can be found at 
       ⟨https://wiki.debian.org/Teams/Dpkg/⟩.  If you have a bug report for
       this manual page, see 
       ⟨http://bugs.debian.org/cgi-bin/pkgreport.cgi?src=dpkg⟩.  This page
       was obtained from the project's upstream Git repository 
       ⟨git://git.debian.org/git/dpkg/dpkg.git⟩ on 2017-07-05.  If you dis‐
       cover any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

1.18.15-3-ga2ef                  1970-01-01           update-alternatives(1)