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<?xml version="1.0" encoding="UTF-8"?>
<!--
   Copyright (c) 1989 - 1992, Julianne Frances Haugh
   Copyright (c) 2007 - 2008, Nicolas François
   All rights reserved.
  
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:
   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
   2. Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
   3. The name of the copyright holders or contributors may not be used to
      endorse or promote products derived from this software without
      specific prior written permission.
  
   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
   HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY ENV_HZ                SYSTEM "login.defs.d/ENV_HZ.xml">
<!ENTITY ENV_TZ                SYSTEM "login.defs.d/ENV_TZ.xml">
<!-- SHADOW-CONFIG-HERE -->
]>
<refentry id='sulogin.8'>
  <!--  $Id$ -->
  <refentryinfo>
    <author>
      <firstname>Julianne Frances</firstname>
      <surname>Haugh</surname>
      <contrib>Creation, 1989</contrib>
    </author>
    <author>
      <firstname>Thomas</firstname>
      <surname>Kłoczko</surname>
      <email>kloczek@pld.org.pl</email>
      <contrib>shadow-utils maintainer, 2000 - 2007</contrib>
    </author>
    <author>
      <firstname>Nicolas</firstname>
      <surname>François</surname>
      <email>nicolas.francois@centraliens.net</email>
      <contrib>shadow-utils maintainer, 2007 - now</contrib>
    </author>
  </refentryinfo>
  <refmeta>
    <refentrytitle>sulogin</refentrytitle>
    <manvolnum>8</manvolnum>
    <refmiscinfo class="sectdesc">System Management Commands</refmiscinfo>
    <refmiscinfo class="source">shadow-utils</refmiscinfo>
    <refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>sulogin</refname>
    <refpurpose>Single-user login</refpurpose>
  </refnamediv>

  <refsect1 id='syntax'>
    <title>SYNTAX</title>
    <para><command>sulogin</command> [<emphasis remap='I'>tty-device</emphasis>]
    </para>
  </refsect1>

  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para>
      The <command>sulogin</command> command is invoked by <command>init</command>
      prior to allowing the user access to the system when in single user mode.
      This feature may only be available on certain systems where
      <command>init</command> has been modified accordingly, or where the
      <filename>/etc/inittab</filename> has an entry for a single user
      login.
    </para>

    <para>The user is prompted</para>

    <para>Type control-d to proceed with normal startup,
      <!-- .br -->
      (or give root password for system maintenance):
    </para>

    <para>
      Input and output will be performed with the standard file descriptors
      unless the optional device name argument is provided.
    </para>

    <para>
      If the user enters the correct root password, a login session is
      initiated. When <emphasis>EOF</emphasis> is pressed instead, the
      system enters multi-user mode.
    </para>

    <para>
      After the user exits the single-user shell, or presses
      <emphasis>EOF</emphasis>, the system begins the initialization process
      required to enter multi-user mode.
    </para>
  </refsect1>

  <refsect1 id='caveats'>
    <title>CAVEATS</title>
    <para>
      This command can only be used if <command>init</command> has been
      modified to call <command>sulogin</command> instead of
      <filename>/bin/sh</filename>, or if the user has set the <emphasis
      remap='I'>inittab</emphasis> to support a single user login. For
      example, the line:
    </para>

    <para>co:s:respawn:/etc/sulogin /dev/console</para>

    <para>should execute the sulogin command in single user mode.</para>

    <para>
      As complete an environment as possible is created. However, various
      devices may be unmounted or uninitialized and many of the user
      commands may be unavailable or nonfunctional as a result.
    </para>
  </refsect1>

  <refsect1 id='configuration'>
    <title>CONFIGURATION</title>
    <para>
      The following configuration variables in
      <filename>/etc/login.defs</filename> change the behavior of this
      tool:
    </para>
    <variablelist>
      &ENV_HZ;
      &ENV_TZ;
    </variablelist>
  </refsect1>

  <refsect1 id='files'>
    <title>FILES</title>
    <variablelist>
      <varlistentry>
	<term><filename>/etc/passwd</filename></term>
	<listitem>
	  <para>User account information.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/shadow</filename></term>
	<listitem>
	  <para>Secure user account information.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para>
      <citerefentry>
	<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>init</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>.
    </para>
  </refsect1>
</refentry>