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<refentry id='login.1'>
  <!--  $Id: login.1.xml,v 1.10 2005/07/10 20:10:09 kloczek Exp $ -->
  <refmeta>
    <refentrytitle>LOGIN</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class="sectdesc">User Commands</refmiscinfo>
  </refmeta>
  <refnamediv id='name'>
    <refname>login</refname>
    <refpurpose>begin session on the system</refpurpose>
  </refnamediv>
  <!-- body begins here -->
  <refsynopsisdiv id='synopsis'>
    <cmdsynopsis>
      <command>login</command>
      <arg choice='opt'>-p </arg>
      <arg choice='opt'>
      <replaceable>username</replaceable></arg>
      <arg choice='opt' rep='repeat'> <replaceable>ENV=VAR</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>login</command>
      <arg choice='opt'>-p </arg>
      <arg choice='opt'>-h <replaceable>host</replaceable></arg>
      <arg choice='opt'>-f <replaceable>username</replaceable></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>login</command>
      <arg choice='opt'>-p </arg>
      <arg choice='plain'>-r <replaceable>host</replaceable></arg>
    </cmdsynopsis>
  </refsynopsisdiv>
  
  <refsect1 id='description'>
    <title>DESCRIPTION</title>
    <para><command>login</command> is used to establish a new session with the
      system. It is normally invoked automatically by responding to the
      <emphasis remap='I'>login:</emphasis> prompt on the user&acute;s
      terminal. <command>login</command> may be special to the shell and may
      not be invoked as a sub-process. Typically, <command>login</command>
      is treated by the shell as <emphasis remap='B'>exec login</emphasis>
      which causes the user to exit from the current shell. Attempting to
      execute <command>login</command> from any shell but the login shell
      will produce an error message.
    </para>
    
    <para>The user is then prompted for a password, where appropriate. 
      Echoing is disabled to prevent revealing the password. Only a small
      number of password failures are permitted before
      <command>login</command> exits and the communications link is severed.
    </para>
    
    <para>If password aging has been enabled for your account, you may be
      prompted for a new password before proceeding. You will be forced to
      provide your old password and the new password before continuing. 
      Please refer to <citerefentry>
      <refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry> for more information.
    </para>
    
    <para>After a successful login, you will be informed of any system
      messages and the presence of mail. You may turn off the printing of
      the system message file, <filename>/etc/motd</filename>, by creating a
      zero-length file <markup>.hushlogin</markup> in your login directory. 
      The mail message will be one of "<emphasis remap='B'>You have new
      mail.</emphasis> ", "<emphasis remap='B'>You have mail.</emphasis>",
      or "<emphasis remap='B'>No Mail.</emphasis> "according to the
      condition of your mailbox.
    </para>
    
    <para>Your user and group ID will be set according to their values in
      the <filename>/etc/passwd</filename> file. The value for <emphasis
      remap='B'>$HOME</emphasis>, <emphasis remap='B'>$SHELL</emphasis>,
      <emphasis remap='B'>$PATH</emphasis>, <emphasis remap='B'>$LOGNAME</emphasis>,
      and <emphasis remap='B'>$MAIL</emphasis> are set according to the
      appropriate fields in the password entry. Ulimit, umask and nice
      values may also be set according to entries in the GECOS field.
    </para>
    
    <para>On some installations, the environmental variable <emphasis
      remap='B'>$TERM</emphasis> will be initialized to the terminal type on
      your tty line, as specified in <filename>/etc/ttytype</filename>.
    </para>
    
    <para>An initialization script for your command interpreter may also be
      executed. Please see the appropriate manual section for more
      information on
      this function.
    </para>
    
    <para>A subsystem login is indicated by the presence of a "*" as the
      first character of the login shell. The given home directory will be
      used as the root of a new file system which the user is actually
      logged into.
    </para>

    <para>The <command>login</command> program is NOT responsible for
      removing users from the utmp file. It is the responsibility of
      <refentrytitle>getty</refentrytitle><manvolnum>8</manvolnum> and
      <refentrytitle>init</refentrytitle><manvolnum>8</manvolnum> to clean
      up apparent ownership of a terminal session. If you use
      <command>login</command> from the shell prompt without
      <command>exec</command>, the user you use will continue to appear to
      be logged in even after you log out of the "subsession".
    </para>

  </refsect1>
  
  <refsect1 id='options'>
    <title>OPTIONS</title>
    <variablelist remap='IP'>
      <varlistentry>
        <term>
          <option>-f</option>
        </term>
        <listitem>
          <para>Do not perform authentication, user is preauthenticated.
          </para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>
          <option>-h</option>
        </term>
        <listitem>
          <para>Name of the remote host for this login.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>
          <option>-p</option>
        </term>
        <listitem>
          <para>Preserve environment.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term>
          <option>-r</option>
        </term>
        <listitem>
          <para>Perform autologin protocol for rlogin.</para>
        </listitem>
      </varlistentry>
    </variablelist>
    
    <para>The <option>-r</option>, <option>-h</option> and
      <option>-f</option> options are only used when
      <command>login</command> is invoked by root.
    </para>
  </refsect1>
  
  <refsect1 id='caveats'>
    <title>CAVEATS</title>
    <para>
      This version of <command>login</command> has many compilation options,
      only some of which may be in use at any particular site.
    </para>
    
    <para>The location of files is subject to differences in system
      configuration.
    </para>
  </refsect1>
  
  <refsect1 id='files'>
    <title>FILES</title>
    <variablelist>
      <varlistentry>
        <term><filename>/var/run/utmp</filename></term>
        <listitem>list of current login sessions</listitem>
      </varlistentry>
      <varlistentry>
        <term><filename>/var/log/wtmp</filename></term>
        <listitem>list of previous login sessions</listitem>
      </varlistentry>
      <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>
      <varlistentry>
        <term><filename>/etc/motd</filename></term>
        <listitem>system message of the day file</listitem>
      </varlistentry>
      <varlistentry>
        <term><filename>/etc/nologin</filename></term>
        <listitem>prevent non-root users from logging in</listitem>
      </varlistentry>
      <varlistentry>
        <term><filename>/etc/ttytype</filename></term>
        <listitem>list of terminal types</listitem>
      </varlistentry>
      <varlistentry>
        <term><filename>$HOME/.hushlogin</filename></term>
        <listitem>suppress printing of system messages</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1 id='see_also'>
    <title>SEE ALSO</title>
    <para><citerefentry>
        <refentrytitle>mail</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>passwd</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>su</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>nologin</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>,
      <citerefentry>
        <refentrytitle>getty</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>
    </para>
  </refsect1>
  
  <refsect1 id='author'>
    <title>AUTHOR</title>
    <para>Julianne Frances Haugh &lt;jockgrrl@ix.netcom.com&gt;</para>
  </refsect1>
</refentry>
