SU(1)				 User Commands				 SU(1)



NAME
       su - run a command with substitute user and group ID

SYNOPSIS
       su [options...] [-] [user [args...]]

DESCRIPTION
       su allows to run commands with substitute user and group ID.

       When  called  without  arguments	 su defaults to running an interactive
       shell as root.

       For backward compatibility su defaults to not change the current direc-
       tory  and  to  only  set the environment variables HOME and SHELL (plus
       USER and LOGNAME if the target user is not root).  It is recommended to
       always  use  the --login option (instead it's shortcut -) to avoid side
       effects caused by mixing environments.

       This version of su uses PAM for	authentication,	 account  and  session
       management.   Some  configuration options found in other su implementa-
       tions such as e.g. support of a wheel group have to be  configured  via
       PAM.

OPTIONS
       -c command, --command=command
	      Pass command to the shell with the -c option.

       --session-command=command
	      Same as -c but do not create a new session (discouraged).

       -f, --fast
	      Pass -f to the shell which may or may not be useful depending on
	      the shell.

       -g, --group=group
	      specify the primary group, this option is allowed for root  user
	      only

       -G, --supp-group=group
	      Specify  a  supplemental group.  This option is available to the
	      root user only.  The first specified supplementary group is also
	      used as a primary group if the option --group is unspecified.

       -, -l, --login
	      Starts the shell as login shell with an environment similar to a
	      real login:

		 o	clears all environment variables except for TERM

		 o	initializes the	 environment  variables	 HOME,	SHELL,
			USER, LOGNAME, PATH

		 o	changes to the target user's home directory

		 o	sets  argv[0] of the shell to '-' in order to make the
			shell a login shell

       -m, -p, --preserve-environment
	      Preserves the whole environment, ie does not  set	 HOME,	SHELL,
	      USER  nor	 LOGNAME.  The option is ignored if the option --login
	      is specified.

       -s SHELL, --shell=SHELL
	      Runs the specified shell instead of the default.	The  shell  to
	      run is selected according to the following rules in order:

		 o	the shell specified with --shell

		 o	The  shell specified in the environment variable SHELL
			if the --preserve-environment option is used.

		 o	the shell listed in the passwd	entry  of  the	target
			user

		 o	/bin/sh

	      If  the  target  user has a restricted shell (i.e. not listed in
	      /etc/shells) the --shell option and the SHELL environment	 vari-
	      ables are ignored unless the calling user is root.

       --help Display help text and exit.

       --version
	      Display version information and exit.

CONFIG FILES
       su  reads  the /etc/default/su and /etc/login.defs configuration files.
       The following configuration items are relevant for su(1):

       FAIL_DELAY (number)
	   Delay in seconds in case of authentication failure.	Number must be
	   a non-negative integer.

       ENV_PATH (string)
	   Defines  the	 PATH  environment  variable  for a regular user.  The
	   default value is /usr/local/bin:/bin:/usr/bin.

       ENV_ROOTPATH (string)
       ENV_SUPATH (string)
	   Defines the PATH environment variable for root. The	default	 value
	   is /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin.

       ALWAYS_SET_PATH (boolean)
	   If set to yes and --login and --preserve-environment were not spec-
	   ified su initializes PATH.

EXIT STATUS
       su normally returns the exit status of the command it executed.	If the
       command	was  killed  by	 a signal, su returns the number of the signal
       plus 128.

       Exit status generated by su itself:

		 1	Generic error before executing the requested command

		 126	The requested command could not be executed

		 127	The requested command could was not found

FILES
       /etc/pam.d/su	default PAM configuration file
       /etc/pam.d/su-l	PAM configuration file if --login is specified
       /etc/default/su	command specific logindef config file
       /etc/login.defs	global logindef config file

SEE ALSO
       runuser(8), pam(8), shells(5), login.defs(5)

AUTHOR
       Derived from coreutils' su which was based on  an  implementation  from
       David MacKenzie.

AVAILABILITY
       The  su command is part of the util-linux package and is available from
       Linux   Kernel	Archive	   <ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/>.



util-linux			   June 2012				 SU(1)