SU(1)				 User Commands				 SU(1)



NAME
       su - change user ID or become super-user

SYNOPSIS
       su [options] [LOGIN]

DESCRIPTION
       su is used to become another user during a login session. Invoked
       without a username, su defaults to becoming the super user. The
       optional argument - may be used to provide an environment similar to
       what the user would expect had the user logged in directly.

       Additional arguments may be provided after the username, in which case
       they are supplied to the users login shell. In particular, an argument
       of -c will cause the next argument to be treated as a command by most
       command interpreters. The command will be executed by the shell
       specified in /etc/passwd for the target user.

       You can use the -- argument to separate su options from the arguments
       supplied to the shell.

       The user will be prompted for a password, if appropriate. Invalid
       passwords will produce an error message. All attempts, both valid and
       invalid, are logged to detect abuse of the system.

       The current environment is passed to the new shell. The value of $PATH
       is reset to /bin:/usr/bin for normal users, or
       /sbin:/bin:/usr/sbin:/usr/bin for the super user. This may be changed
       with the ENV_PATH and ENV_SUPATH definitions in /etc/login.defs.

       A subsystem login is indicated by the presence of a "*" as the first
       character of the login shell. The given home directory will be used as
       the root of a new file system which the user is actually logged into.

OPTIONS
       The options which apply to the su command are:

       -c, --command SHELL
	  Specify a command that will be invoked by the shell using its -c.

       -, -l, --login
	  Provide an environment similar to what the user would expect had the
	  user logged in directly.

	  When - is used, it must be specified as the last su option. The
	  other forms (-l and --login) do not have this restriction.

       -s, --shell SHELL
	  The shell that will be invoked.

	  The invoked shell is choosen among (higest priority first):

	       The shell specified with --shell

	       If --preserve-environment is used, the shell specified by the
		$SHELL environment variable.

	       The shell indicated in the /etc/passwd entry for the target
		user.

		/bin/sh if a shell could not be found by any above method.



	     If the target user has a restricted shell (i.e. the shell field
	     of this users entry in /etc/passwd is not specified in
	     /etc/shell), then the --shell option or the $SHELL environment
	     variable wont be taken into account unless su is called by the
	     root.

       -m, -p, --preserve-environment
	  Preserve the current environment.

	  If the target user has a restricted shell, this option has no effect
	  (unless su is called by root).

CAVEATS
       This version of su has many compilation options, only some of which may
       be in use at any particular site.

FILES
       /etc/passwd
	  User account information.

       /etc/shadow
	  Secure user account information.

SEE ALSO
       login(1), login.defs(5), sh(1)



User Commands			  02/25/2007				 SU(1)