su

SU(1)                                                                    SU(1)



NAME
       su - Change user ID or become super-user

SYNOPSIS
       su [OPTS] [-] [username [ARGS]]

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 similiar to
       what the user would expect had the user logged in directly.

       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 abuses of the system.

       An optional command can be executed. This is done by the  shell  speci-
       fied in /etc/passwd for the target user unless the -s or -m options are
       used.  Any arguments supplied after the username will be passed to  the
       invoked  shell  (shell must support the -c command line option in order
       for a command to be passed to it).

       Unless the -m or -p options are used, the current environment is passed
       to  the  new  shell  with  alterations.  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.  $IFS, if is set, is reset  to  contain
       space,  tab, and newline.  $USER is set to the name of the target user,
       $HOME is set to the home directory of the target user,  and  $SHELL  is
       set  to the shell of the target user.  When using the -m or -p options,
       the user's environment is not changed.

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

OPTIONS
       -      make this a login shell

       -c, --commmand=<command>
              pass command to the invoked shell using its -c option

       -m, -p, --preserve-environment
              do not reset environment variables, and keep the same shell

       -s, --shell=<shell>
              use shell instead of the default in /etc/passwd


NOTES
       The -m, -p and -s options are restricted by  the  target  user's  shell
       being  listed  in /etc/shells. If it's not listed, then it's assumed to
       be a restricted account, a normal su is performed,  and  those  options
       are ignored silently.

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

       Much of the behavior of this command can be altered via its pam config-
       uration - see pam(7)

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 - encrypted passwords and age information
       /etc/shells - valid user shells
       $HOME/.profile - initialization script for default shell

SEE ALSO
       login(1), sh(1), login.defs(5), shells(5), pam(7)

AUTHOR
       Julianne Frances Haugh (jfh AT austin.com)



                                                                         SU(1)