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SU(1)                                     User Commands                                     SU(1)

       su - run a command with substitute user and group ID

       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 directory 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 con-
       figuration options found in other su implementations such as e.g. support of a wheel group
       have to be configured via PAM.

       -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 only

       -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 shell a login shell

       -m, -p, --preserve-environment
              Preserves the whole environment, ie does not set HOME,  SHELL,  USER  nor  LOGNAME.
              The option is ignored if the option --login is specified.

       -s SHELL, --shell=SHELL
              Runs  the  specified  shell  instead  of the default.  The shell to run is selected
              according to the following rules in order:

                 o      the shell specified with --shell

                 o      The shell specified in the environment variable SHELL if the  --preserve-
                        environment option is used.

                 o      the shell listed in the passwd entry of the target user

                 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 variables 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 con-
       figuration items are relevant for su(1):

       FAIL_DELAY (number)
           Delay in seconds in case of authentication failure.  Number  must  be  a  non-negative

       ENV_PATH (string)
           Defines  the  PATH  environment  variable  for  a  regular user.  The default value is

       ENV_ROOTPATH (string)
       ENV_SUPATH (string)
           Defines the PATH environment variable for root. The default value is  /usr/local/sbin:

       ALWAYS_SET_PATH (boolean)
           If set to yes and --login and --preserve-environment were not specified su initializes

       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
       /etc/pam.d/su-l  PAM configuration file if --login is specified
       /etc/default/su  command specific logindef config file
       /etc/login.defs  global logindef config file

       runuser(8), pam(8), shells(5), login.defs(5)

       Derived from coreutils' su which was based on an implementation from David MacKenzie.

       The  su  command  is  part  of  the  util-linux package and is available from Linux Kernel
       Archive <>.

util-linux                                  June 2012                                       SU(1)

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