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SU(1)                        BSD Reference Manual                        SU(1)

NAME
     su - substitute user identity

SYNOPSIS
     su [-Kflm] [login]

DESCRIPTION
     Su requests the Kerberos password for login (or for ``login.root'', if no
     login is provided), and switches to that user and group ID after obtain-
     ing 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 re-
     quested and a shell with the appropriate user ID is executed; no addi-
     tional 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 login's.  This is the traditional behavior of su.

     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
             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.  The invoked shell is the target login's, and su will
             change directory to the target login's home directory.

     -m      Leave the environment unmodified.  The invoked shell is your lo-
             gin shell, and no directory changes are made.  As a security pre-
             caution, 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.

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

     Only users in group 0 (normally ``wheel'') 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.

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

HISTORY
     A su command appeared in Version 7 AT&T UNIX.

4.4BSD                          April 18, 1994                               2