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SU(1)                            User Commands                           SU(1)

NAME
       su - run a command with substitute user and group ID
SYNOPSIS
       su [options...] [-] [user [args...]]
DESCRIPTION
       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
       PAM.
OPTIONS
       -c command, --command=command
              Pass command to the shell with the -c option.
       --session-command=command
              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  vari-
              ables are ignored unless the calling user is root.
       --help Display help text and exit.
       --version
              Display version information and exit.
CONFIG FILES
       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.
EXIT STATUS
       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
FILES
       /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
SEE ALSO
       runuser(8), pam(8), shells(5), login.defs(5)
AUTHOR
       Derived from coreutils' su which was based on  an  implementation  from
       David MacKenzie.
AVAILABILITY
       The  su command is part of the util-linux package and is available from
       Linux   Kernel   Archive    <ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux                         June 2012                             SU(1)