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SULOGIN(8)            Linux System Administrator's Manual           SULOGIN(8)



NAME
       sulogin -- Single-user login

SYNOPSIS
       sulogin [ -e ] [ -p ] [ -t timeout ] [ tty-device ]

DESCRIPTION
       sulogin  is  invoked  by  init(8) when the system goes into single user
       mode (this is done through an entry in inittab(5)). Init also tries  to
       execute sulogin when it is passed the -b flag from the bootmonitor (eg,
       LILO).

       The user is prompted

            Give root password for system maintenance
            (or type Control-D for normal startup):

       sulogin will be connected to the current terminal, or to  the  optional
       device  that  can be specified on the command line (typically /dev/con-
       sole).

       If the -p flag was set, the single-user shell will be  invoked  with  a
       dash  as the first character in argv[0]. That will cause most shells to
       behave as a login shell. The default is not to do  this,  so  that  the
       shell will not read /etc/profile or $HOME/.profile at startup.

       After the user exits the single-user shell, or presses control-d at the
       prompt, the system will (continue to) boot to the default runlevel.

ENVIRONMENT VARIABLES
       sulogin looks for the environment variable SUSHELL or sushell to deter-
       mine  what  shell  to start. If the environment variable is not set, it
       will try to execute root's shell from /etc/passwd.  If  that  fails  it
       will fall back to /bin/sh.

       This  is  very  valuable together with the -b flag to init. To boot the
       system into single  user  mode,  with  the  root  file  system  mounted
       read/write,  using a special "failsafe" shell that is statically linked
       (this example is valid for the LILO bootprompt)

       boot: linux -b rw sushell=/sbin/sash

FALLBACK METHODS
       sulogin checks the root password using the standard  method  (getpwnam)
       first.   Then,  if  the -e option was specified, sulogin examines these
       files directly to find the root password:

       /etc/passwd,
       /etc/shadow (if present)

       If they are damaged or non-existant, sulogin will start  a  root  shell
       without  asking  for a password. Only use the -e option if you are sure
       the console is physically protected against unauthorized access.

AUTHOR
       Miquel van Smoorenburg <miquelsATcistron.nl>

SEE ALSO
       init(8), inittab(5).



                                  04 Nov 2003                       SULOGIN(8)