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su(1)

NAME

     su -- substitute user identity

SYNOPSIS

     su [-] [-flms] [-c class] [login [args]]

DESCRIPTION

     The su utility requests appropriate user credentials via PAM and switches
     to that user ID (the default user is the superuser).  A shell is then
     executed.

     PAM is used to set all policy.

     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
     one belonging to the target login.  This is the traditional behavior of
     su.  Resource limits and session priority applicable to the original
     user's login class (see login.conf(5)) are also normally retained unless
     the target login has a user ID of 0.

     The options are as follows:

     -f      If the invoked shell is csh(1), this option prevents it from
	     reading 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 environ-
	     ment.  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 directory to the target login's home directory.
	     Resource limits and session priority are modified to that for the
	     target account's login 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
	     precaution, if the target user's shell is a non-standard shell
	     (as defined by getusershell(3)) and the caller's real uid is non-
	     zero, su will fail.

     -s      Set the MAC label to the user's default label as part of the user
	     credential setup.	Setting the MAC label may fail if the MAC
	     label of the invoking process is not sufficient to transition to
	     the user's default MAC label.  If the label cannot be set, 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 speci-
     prompt is set to ``#'' to remind one of its awesome power.

FILES

     /etc/pam.d/su  PAM configuration for su.

SEE ALSO

     csh(1), sh(1), group(5), login.conf(5), passwd(5), environ(7), pam(8)

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 sin-
	    gle 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
	    limits 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 5.4			October 3, 2004 		   FreeBSD 5.4

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