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

NAME

       sulogin - Single-user login

SYNOPSIS

       sulogin [ -e ] [ -p ] [ -t SECONDS ] [ TTY ]

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 the boot loader (e.g., grub(8)) passes it the -b option.

       The user is prompted

	    Give root password for system login
	    (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 -t option is used then the program only waits the given number of seconds for user input.

       If  the	-p  option  is	used  then  the single-user shell is invoked with a dash as the first character in argv[0].  This causes the shell
       process 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 determine 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 option to init. To boot the system into single user mode, with  the  root  file  system  mounted
       read/write, using a special "fail safe" 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 nonexistent, 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 <miquels@cistron.nl>

SEE ALSO

       init(8), inittab(5).

								    17 Jan 2006 							SULOGIN(8)