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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
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<refentry id='su.1'>
  <!--  $Id: su.1.xml,v 1.9 2005/06/15 12:39:27 kloczek Exp $ -->
  <refmeta>
    <refentrytitle>su</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class="sectdesc">User Commands</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>su</refname>
    <refpurpose>change user ID or become super-user</refpurpose>
  </refnamediv>
  <refsynopsisdiv id='synopsis'>
    <cmdsynopsis>
      <command>su</command>
      <arg choice='opt'>- </arg>
      <arg choice='opt'>
        <arg choice='plain'>
          <replaceable>username</replaceable>
        </arg>
        <arg choice='opt'>
          <replaceable>args</replaceable>
        </arg>
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>
  
  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para><command>su</command> is used to become another user during a login
      session. Invoked without a username, <command>su</command> defaults to
      becoming the super user. The optional argument <option>-</option> may
      be used to provide an environment similar to what the user would
      expect had the user logged in directly.
    </para>
    
    <para>Additional arguments may be provided after the username, in which
      case they are supplied to the user&acute;s login shell. In particular,
      an argument of <option>-c</option> will cause the next argument to be
      treated as a command by most command interpreters. The command will be
      executed by the shell specified in <filename>/etc/passwd</filename>
      for the target user.
    </para>
    
    <para>The user will be prompted for a password, if appropriate. Invalid
      passwords will produce an error message. All attempts, both valid and
      invalid, are logged to detect abuses of the system.
    </para>
    
    <para>The current environment is passed to the new shell. The value of
      <emphasis remap='B'>$PATH</emphasis> is reset to
      <filename>/bin:/usr/bin</filename> for normal users, or
      <filename>/sbin:/bin:/usr/sbin:/usr/bin</filename> for the super user. 
      This may be changed with the <emphasis remap='B'>ENV_PATH</emphasis>
      and <emphasis remap='B'>ENV_SUPATH</emphasis> definitions in
      <filename>/etc/login.defs</filename>.
    </para>
    
    <para>A subsystem login is indicated by the presense of a "*" as the
      first character of the login shell. The given home directory will be
      used as the root of a new filesystem which the user is actually logged
      into.
    </para>
  </refsect1>
  
  <refsect1 id='caveats'>
    <title>CAVEATS</title>
    <para>
      This version of <command>su</command> has many compilation options,
      only some of which may be in use at any particular site.
    </para>
  </refsect1>
  
  <refsect1 id='files'>
    <title>FILES</title>
    <variablelist>
      <varlistentry>
        <term><filename>/etc/passwd</filename></term>
        <listitem>user account information</listitem>
      </varlistentry>
      <varlistentry>
        <term><filename>/etc/shadow</filename></term>
        <listitem>secure user account information</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>login.defs</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>suauth</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>
    </para>
  </refsect1>
  
  <refsect1 id='author'>
    <title>AUTHOR</title>
    <para>Julianne Frances Haugh &lt;jockgrrl@ix.netcom.com&gt;</para>
  </refsect1>
</refentry>
