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UPDATE-ALTERNATIVES(8)                                  UPDATE-ALTERNATIVES(8)



NAME
       alternatives - maintain symbolic links determining default commands

SYNOPSIS
       alternatives [options] --install link name path priority [--slave link name path]...  [--initscript service]

       alternatives [options] --remove name path

       alternatives [options] --set name path

       alternatives [options] --auto name

       alternatives [options] --display name

       alternatives [options] --config name

DESCRIPTION
       alternatives  creates,  removes,  maintains  and  displays  information about the symbolic links comprising the
       alternatives system. The alternatives system is a reimplementation of the Debian alternatives  system.  It  was
       rewritten  primarily  to remove the dependence on perl; it is intended to be a drop in replacement for Debian's
       update-dependencies script. This man page is a slightly modified version  of  the  man  page  from  the  Debian
       project.

       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 pro-
       gram to make a good choice of editor to invoke if the user has not specified a particular preference.

       The 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 deter-
       mine 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 /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,  alterna-
       tives  is  called  to  update  information about that file in the alternatives system.  alternatives is usually
       called from the %post or %pre scripts in RPM packages.

       It is often useful for a number of alternatives to be synchronised, 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.   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 not change the links; it will leave all  the
       decisions to the system administrator.

       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 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, alternatives will list all of the choices for the link  group  of  which  given
       name  is  the  master link.  You will then be prompted for which of the choices to use for the link group. Once
       you make a change, the link group will no longer be in auto mode. You will need to use  the  --auto  option  in
       order to return to the automatic state.

TERMINOLOGY
       Since  the  activities  of alternatives are quite involved, some specific terms will help to explain its opera-
       tion.

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

       symlink
              Without  any  further qualification, this means a symbolic link in the alternatives directory: one which
              the system administrator is expected to adjust.

       alternative
              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 /etc/alternatives, containing the symlinks.

       administrative directory
              A directory, by default /var/lib/alternatives, containing alternatives' state information.

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

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

       slave link
              A 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 alternatives 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.

OPTIONS
       Exactly one action must be specified if alternatives is to perform any meaningful task.  Any number of the com-
       mon options may be specified together with any action.

   COMMON OPTIONS
       --verbose
              Generate more comments about what alternatives is doing.

       --quiet
              Don't generate any comments unless errors occur.  This option is not yet implemented.

       --test Don't actually do anything, just say what would be done.  This option is not yet implemented.

       --help Give some usage information (and say which version of alternatives this is).

       --version
              Tell which version of alternatives this is (and give some usage information).

       --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.

   ACTIONS
       --install link name path priority [--slave slink sname spath] [--initscript service]...
              Add a group of alternatives to the system.  name is the generic name for the master link,  link  is  the
              name  of  its symlink, path is the alternative being introduced for the master link, and priority is the
              priority of the alternatives group. Higher priorities take precendence if  no  alternative  is  manually
              selected.   sname,  slink and spath are the generic name, symlink name and alternative for a slave link,
              and service is the name of any associated initscript for the alternative.  NOTE: --initscript is  a  Red
              Hat Linux specific option.  Zero or more --slave options, each followed by three arguments, may be spec-
              ified.

              If the master symlink 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 auto-
              matic 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.

              If --initscript is used, the alternatives system will manage the initscript associated with the alterna-
              tive  via  chkconfig,  registering  and  unregistering the init script depending on which alternative is
              active.

              NOTE: --initscript is a Red Hat Linux specific option.

       --remove name path
              Remove an alternative and all of its associated slave links.  name is a name in the alternatives  direc-
              tory, 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, or removed if there is no such  alter-
              native  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.

       --set name path
              The symbolic link and slaves for link group name set to those configured for path, and the link group is
              set to manual mode.  This option is not in the original Debian implementation.

       --config name
              Present the user with a configuration menu for choosing the master link and slaves for link group  name.
              Once chosen, the link group is set to manual mode.

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

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

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

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

EXIT STATUS
       0      The requested action was successfully performed.

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

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

BUGS
       If you find a bug, please report it using the Red Hat bug tracking system at http://bugzilla.redhat.com.

       If  you find any discrepancy between the operation of alternatives and this manual page, it is a bug, either in
       the implementation or the documentation; please report it.  Any significant differences between this  implemen-
       tation and Debian's is also a bug and should be reported, unless otherwise noted in this man page.

AUTHOR
       alternatives  is copyright 2002 Red Hat, Inc..  It is free software; see the GNU General Public Licence version
       2 or later for copying conditions.  There is NO warranty.

       This manual page is copyright 1997/98 Charles Briscoe-Smith and 2002 Red Hat, Inc.  This is free documentation;
       see the GNU General Public Licence version 2 or later for copying conditions.  There is NO WARRANTY.

SEE ALSO
       ln(1), FHS, the Filesystem Hierarchy Standard.  alternatives.c chkconfig.c COPYING leveldb.c leveldb.h Makefile
       ntsysv.c ook



                                27 January 2001         UPDATE-ALTERNATIVES(8)