Section (8) sulogin

Linux manual pages Section 8  


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.

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

When the user exits from the single-user shell, or presses control−D at the prompt, the system will continue to boot.


−e, −−force

If the default method of obtaining the root password from the system via getpwnam(3) fails, then examine /etc/passwd and /etc/shadow to 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 −e option if you are sure the console is physically protected against unauthorized access.

    −p, −−login−shell

    Specifying this option causes sulogin to start the shell process as a login shell.

    −t, −−timeout seconds

    Specify the maximum amount of time to wait for user input. By default, sulogin will wait forever.

    −h, −−help

    Display help text and exit.

    −V, −−version

    Display version information and exit.


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_zsingle_quotesz_s shell from /etc/passwd. If that fails, it will fall back to /bin/sh.


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 <>

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
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