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SU(1)			     General Commands Manual			   SU(1)

NAME
     su -- substitute user identity

SYNOPSIS
     su [-] [-Kflm] [-c class] [login [args]]

DESCRIPTION
     Su requests the Kerberos password for login (or for "login.root", if no lo-
     gin  is provided), and switches to that user and group ID after obtaining a
     Kerberos ticket granting ticket.  A shell is then executed.  Su will resort
     to the local password file to find the password for login	if  there  is  a
     Kerberos  error.  If su is executed by root, no password is requested and a
     shell with the appropriate user ID  is  executed;	no  additional	Kerberos
     tickets are obtained.

     By default, the environment is unmodified with the exception of USER, HOME,
     and  SHELL.   HOME  and SHELL are set to the target login's default values.
     USER is set to the target login, unless the target login has a user  ID  of
     0,  in  which  case  it is unmodified.  The invoked shell is the target lo-
     gin's.  This is the traditional behavior of su.  Resource limits  and  ses-
     sion  priority  applicable  to  the  original  user's  login class (See lo-
     gin.conf(5)) are also normally retained unless the target login has a  user
     ID of 0.

     The options are as follows:

     -K      Do not attempt to use Kerberos to authenticate the user.

     -f      If  the invoked shell is csh(1), this option prevents it from read-
	     ing the ".cshrc" file.

     -l      Simulate a full login.  The environment  is  discarded  except  for
	     HOME,  SHELL, PATH, TERM, and USER.  HOME and SHELL are modified as
	     above.   USER  is	set  to  the  target  login.   PATH  is  set  to
	     "/bin:/usr/bin".	TERM  is imported from your current environment.
	     Environment variables may be set or overridden from the login class
	     capabilities database according to the class of the  target  login.
	     The  invoked shell is the target login's, and su will change direc-
	     tory to the target login's home  directory.   Resource  limits  and
	     session  priority are modified to that for the target account's lo-
	     gin class.

     -	     (no letter) The same as -l.

     -m      Leave the environment unmodified.	The invoked shell is your  login
	     shell,  and  no  directory changes are made.  As a security precau-
	     tion, if the target user's shell is a non-standard  shell	(as  de-
	     fined by getusershell(3)) and the caller's real uid is non-zero, su
	     will fail.

     -c class
	     Use  the  settings  of the specified login class.	Only allowed for
	     the super-user.

     The -l (or -) and -m options are mutually exclusive; the last one specified
     overrides any previous ones.

     If the optional args are provided on the command line, they are  passed  to
     the login shell of the target login.

     Only users who are a member of group 0 (normally "wheel") can su to "root".
      If group 0 is missing or empty, any user can su to "root".

     By  default  (unless  the prompt is reset by a startup file) the super-user
     prompt is set to "#" to remind one of its awesome power.

FILES
     /etc/auth.conf  configure authentication services

SEE ALSO
     csh(1), kerberos(1), kinit(1), login(1),  sh(1),  group(5),  login.conf(5),
     passwd(5), environ(7)

ENVIRONMENT
     Environment variables used by su:

     HOME  Default  home  directory of real user ID unless modified as specified
	   above.

     PATH  Default search path of real user  ID  unless  modified  as  specified
	   above.

     TERM  Provides terminal type which may be retained for the substituted user
	   ID.

     USER  The	user ID is always the effective ID (the target user ID) after an
	   su unless the user ID is 0 (root).

EXAMPLES
     su man -c catman
	    Runs the command catman as user man.  You will be  asked  for  man's
	    password unless your real UID is 0.
     su man -c 'catman /usr/share/man /usr/local/man /usr/X11R6/man'
	    Same as above, but the target command consists of more than a single
	    word  and hence is quoted for use with the -c option being passed to
	    the shell.	(Most shells expect the argument to -c to  be  a  single
	    word).
     su -c staff man -c 'catman /usr/share/man /usr/local/man /usr/X11R6/man'
	    Same  as above, but the target command is run with the resource lim-
	    its of the login class "staff".  Note: in this example, the first -c
	    option applies to su while the second is an argument  to  the  shell
	    being invoked.
     su -l foo
	    Simulate a login for user foo.
     su - foo
	    Same as above.
     su -
	    Simulate a login for root.

HISTORY
     A su command appeared in Version 1 AT&T UNIX.

FreeBSD 4.6			 April 18, 1994 			   SU(1)
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