sulogin
SULOGIN(8) Linux System Administrator's Manual SULOGIN(8)
NAME
sulogin -- Single-user login
SYNOPSIS
sulogin [ -e ] [ -p ] [ -t timeout ] [ tty-device ]
DESCRIPTION
sulogin can be 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 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 methods first. If
the -e option was specified, sulogin examines the next files to find
the root password. If they are damaged, or non-existant, it will use
fallback methods that even go so far as to provide you with a shell
prompt without asking for the root password if they are irrepairably
damaged.
/etc/passwd,
/etc/shadow (if present)
AUTHOR
Miquel van Smoorenburg <miquels@cistron.nl>
SEE ALSO
init(8), inittab(5).
11 Sep 2000 SULOGIN(8)