su

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 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 configuration options found in
       other su implementations 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  supple‐
              mentary 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.

       --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  rele‐
       vant 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 specified 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)