Section (8) sulogin
sulogin — single-user login
sulogin [options] [tty]
sulogin is invoked by init when the system goes into single-user mode.
The user is prompted:
Give root password for system maintenance
(or type Control−D for normal startup):
If the root account is locked and --force is specified, no password is required.
be connected to the current terminal, or to the optional
tty device that can
be specified on the command line (typically
When the user exits from the single-user shell, or presses control−D at the prompt, the system will continue to boot.
If the default method of obtaining the root password from the system via getpwnam(3) fails, then examine
/etc/shadowto get the password. If these files are damaged or nonexistent, or when root account is locked by _zsingle_quotesz_!_zsingle_quotesz_ or _zsingle_quotesz_*_zsingle_quotesz_ at the begin of the password then sulogin will start a root shell without asking for a password.
Only use the
−eoption if you are sure the console is physically protected against unauthorized access.
Specifying this option causes sulogin to start the shell process as a login shell.
Specify the maximum amount of time to wait for user input. By default, sulogin will wait forever.
Display help text and exit.
Display version information and exit.
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_zsingle_quotesz_s shell from
/etc/passwd. If that fails, it will fall
sulogin was written by Miquel van Smoorenburg for sysvinit and later ported to util-linux by Dave Reisner and Karel Zak.
The sulogin command is part of the util-linux package and is available from Linux Kernel Archive
Copyright (C) 1998-2006 Miquel van Smoorenburg.
Copyright (C) 2012 Karel Zak <kzakredhat.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA