Provided by: dpkg_1.13.11ubuntu6_i386 bug

NAME

       update-alternatives  -  maintain  symbolic  links  determining  default
       commands

SYNOPSIS

       update-alternatives [options] --install genname symlink altern priority
       [--slave genname symlink altern]...

       update-alternatives [options] --remove name path

       update-alternatives [options] --remove-all name

       update-alternatives [options] --all

       update-alternatives [options] --auto name

       update-alternatives [options] --display name

       update-alternatives [options] --list name

       update-alternatives [options] --config name

       update-alternatives [options] --set name path

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 of 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  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.

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

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 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.

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

OPTIONS

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

   COMMON OPTIONS
       --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.

       --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
              update-alternatives this is).

       --version
              Tell which version of update-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 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 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.

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.

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

       Debian update-alternatives is copyright 1995 Ian Jackson.  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.   This  is
       free  documentation;  see  the  GNU General Public Licence version 2 or
       later for copying conditions.  There is NO WARRANTY.

       You can find the  GNU  GPL  in  /usr/share/common-licenses/GPL  on  any
       Debian system.

SEE ALSO

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