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update-alternatives(8)		dpkg utilities		update-alternatives(8)

       update-alternatives  - maintain symbolic links determining default com

       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

       update-alternatives  creates,  removes, maintains and displays informa
       tion about the symbolic links comprising the Debian  alternatives  sys

       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 dif
       ferent 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.

       Debians	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 alterna
       tive.   Instead,  it  is  a symbolic link to a name in the alternatives
       directory, which in turn is a symbolic link to the actual  file	refer
       enced.	This is done so that the system administrators 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-alter
       natives is usually called from the postinst or prerm scripts in	Debian

       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

       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  systems
       automatic  settings, this will be noticed the next time update-alterna
       tives is run on the changed links group, and the group will  automati
       cally 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 regard
       ing  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 mecha

       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.

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

	      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 sym

       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	prior
	      ity 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  administrators  set

       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 set
       ting 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

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

	      Generate	more comments about what update-alternatives is doing.

	      Dont generate any comments unless errors occur.  This option is
	      not yet implemented.

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

       --help Give some usage information.

	      Tell which version of update-alternatives this is.

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

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

       --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	alter
	      native  being  introduced  for  the  master link.  The arguments
	      after --slave are the generic name, symlink name in the alterna
	      tives  directory	and the alternative for a slave link.  Zero or
	      more --slave options, each followed by three arguments,  may  be

	      If  the  master symlink specified exists already in the alterna
	      tives systems 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  informa
	      tion.   If  the  group is in automatic mode, and the newly added
	      alternatives priority is higher than any other installed alter
	      natives 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  equiva
	      lent 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 alterna
	      tive 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  pro
	      cess,  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 groups mode
	      (auto or manual), which alternative the symlink currently points
	      to, what other alternatives are available (and their correspond
	      ing 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.

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

	      The default administration directory.  Can be overridden by  the
	      --admindir option.

       0      The requested action was successfully performed.

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

       update-alternatives chatters incessantly about its  activities  on  its
       standard  output  channel.  If problems occur, update-alternatives out
       puts 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.

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

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

       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.

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

Debian Project			  2006-11-24		update-alternatives(8)

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