Provided by: dpkg_1.14.16.6ubuntu3_i386 bug

NAME

       update-alternatives  -  maintain  symbolic  links  determining  default
       commands

SYNOPSIS

       update-alternatives [options] command

DESCRIPTION

       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 /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  or prerm
       scripts in Debian 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.  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  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
       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 link.
       The current choice is marked with a ’*’ and the choice with the highest
       priority  with  a  ’+’.   You  will  then  be  prompted for your choice
       regarding this 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 mode.

       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.
       That is -  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

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

       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/dpkg/alternatives, containing
              update-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 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

       --install genname symlink  altern  priority  [--slave  genname  symlink
       altern]...
              Add a group of alternatives  to  the  system.   genname  is  the
              generic  name  for  the  master link, symlink is the name of its
              symlink  in  the  alternatives  directory,  and  altern  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 for a slave link.
              Zero or more --slave options, each followed by three  arguments,
              may be specified.

              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  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,  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.

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

       --display link
              Display  information  about  the link group of which link 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.

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

       --config link
              Show available alternatives for a link group and allow the  user
              to  interactively  select  which  one  to use. The link group is
              updated and taken out of auto mode.

       --help Show the usage message and exit.

       --version
              Show the version and exit.

OPTIONS

       --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.

       --verbose
              Generate more comments about what update-alternatives is  doing.

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

FILES

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

       /var/lib/dpkg/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

       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

       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

BUGS

       If  you  find  a  bug,  please  report it using the Debian bug-tracking
       system, or, if that is not possible, email the author directly.

       If   you   find   any   discrepancy   between    the    operation    of
       update-alternatives  and  this  manual page, it is a bug, either in the
       implementation or the documentation; please report it.

AUTHOR

       Copyright (C) 1995 Ian Jackson

       This 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 1997,1998 Charles Briscoe-Smith.

       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.