alternatives man page on Oracle

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       alternatives - maintain symbolic links determining default commands

       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

       alternatives [options] --list name

       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

       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 of editor to invoke if the user has not specified a par‐
       ticular preference.

       The alternatives system aims to solve this problem.  A generic name  in
       the  filesystem	is shared by all files providing interchangeable func‐
       tionality.   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 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, alternatives is called to update infor‐
       mation 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.

       Since  the activities of 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/alternatives, containing alter‐
	      natives' 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 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 set‐

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

	      Generate more comments about what alternatives is doing.

	      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  alterna‐
	      tives this is).

	      Tell  which version of alternatives this is (and give some usage

       --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  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  pri‐
	      orities 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 specified.

	      If the master symlink specified exists already in	 the  alterna‐
	      tives  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 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.

	      If --initscript is used, the alternatives system will manage the
	      initscript associated with the alternative via chkconfig, regis‐
	      tering  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 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.

       --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 mas‐
	      ter  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 correspond‐
	      ing slave alternatives), and the	highest	 priority  alternative
	      currently installed.

       --list Display information about all link groups.

	      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.

       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
       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 Red Hat bug tracking sys‐
       tem at

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

       alternatives is copyright 2002 Red Hat, Inc..  It is free software; see
       the GNU General Public Licence version 2 or later  for  copying	condi‐
       tions.  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 WAR‐

       ln(1), FHS, the Filesystem Hierarchy Standard.  alternatives.c  chkcon‐
       fig.c COPYING leveldb.c leveldb.h Makefile ntsysv.c ook

				27 January 2001		UPDATE-ALTERNATIVES(8)

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