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


       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


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

              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

       -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
                        if the --preserve-environment option is used.

                 o      the shell listed in the passwd  entry  of  the  target

                 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.

              Display version information and exit.


       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.


       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


       /etc/pam.d/su    default PAM configuration file

util-linux June 2012 SU(1)

Subscribe to us on YouTube