Include a new section explaining how to set up serial consoles. Rewrote

it slightly from the submission just to clean up some of the English,
but Kazutaka YOKOTA should get all the kudos for this.

Submitted by:   Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>

1 files changed, 729 insertions, 1 deletions

diff --git a/en/handbook/serialcomms/chapter.sgml b/en/handbook/serialcomms/chapter.sgml
index affa6dedb3..b6b6e26c22 100644
--- a/en/handbook/serialcomms/chapter.sgml
+++ b/en/handbook/serialcomms/chapter.sgml
@@ -1,7 +1,7 @@
 <!--
      The FreeBSD Documentation Project
 
-     $Id: chapter.sgml,v 1.10 1999-03-08 22:04:49 nik Exp $
+     $Id: chapter.sgml,v 1.11 1999-07-27 18:18:11 nik Exp $
 -->
 
 <chapter id="serialcomms">
@@ -1988,6 +1988,734 @@ raisechar=^^</programlisting>
 	to send them to the remote system.</para>
     </sect2>
   </sect1>
+
+  <sect1>
+    <title>Setting Up the Serial Console</title>
+    
+    <para><emphasis>&a.yokota; and &a.wpaul:</emphasis></para>
+    
+    <para><emphasis>The text is heavily based on
+	<filename>/sys/i386/boot/biosboot/README.serial</filename> written by
+	&a.wpaul;.</emphasis></para>
+  
+    <sect2 id="serialconsole-intro">
+      <title>Introduction</title>
+      
+      <para>The FreeBSD/i386 operating system can boot on a system with  only
+	a dumb terminal on a serial port as a console.  Such a configuration
+	should be useful for two classes of people; system administrators who
+	wish to install FreeBSD on a dedicated file/compute/terminal server
+	machines that have no keyboard or monitor attached, and developers who
+	want to debug the kernel or device drivers.</para>
+  
+      <para>Starting from version 3.1, FreeBSD/i386 employs a three stage
+	bootstrap.  The first two stages are in the boot block code which is
+	stored at the beginning of the FreeBSD slice on the boot disk.  The
+	boot block will then load and run the boot loader
+	(<filename>/boot/loader</filename>) as the third stage code. (See
+	&man.boot.8; and &man.loader.8; for more details on the boot
+	process.)</para>
+  
+      <para>In order to set up the serial console you must configure the boot
+	block code, the boot loader code and the kernel.</para>
+      
+      <para>In FreeBSD version 3.0, the boot loader does not exist and there
+	are only two stages in the bootstrap; the boot blocks directly load
+	the kernel into memory.  If you are using FreeBSD 3.0, then you should
+	disregard any reference to the boot loader in this section.  You can
+	still use the serial port as a console.</para>
+  
+      <para>FreeBSD versions 2.X are quite different from 3.X, in that the
+	serial port driver, &man.sio.4;, must be configured in a different
+	way.  This chapter will not describe the settings for version 2.X
+	systems.  If you are using these older versions of FreeBSD, please
+	consult <filename>/sys/i386/boot/biosboot/README.serial</filename>
+	instead.</para>
+    </sect2>
+    
+    <sect2 id="serialconsole-howto">
+      <title>6 Steps to Set up the Serial Console</title>
+  
+      <procedure>
+	<step>
+	  <para>Prepare a serial cable.</para>
+	  
+	  <para>You will need either a null-modem cable or a standard serial 
+	    cable and a null-modem adapter.  See <xref linkend="term"> for
+	    a discussion on serial cables.</para>
+	</step>
+	
+	<step>
+	  <para>Unplug your keyboard.</para>
+	  
+	  <para>Most PC systems probe for the keyboard during the Power-On
+	    Self-Test (POST) and will generate an error if the keyboard is not
+	    detected.  Some machines complain loudly about the lack of a
+	    keyboard and will not continue to boot until it is plugged
+	    in.</para>
+    
+	  <para>If your computer complains about the error, but boots anyway,
+	    then you do not have to do anything special.  (One machine with a
+	    Phoneix BIOS that I have here merely says <errorname>Keyboard
+	      failed</errorname> then continues to boot normally.)</para>
+
+	  <para>If your computer refuses to boot without a keyboard attached
+	    then you will have to configure the BIOS so that it ignores this
+	    error (if it can).  Consult your motherboard's manual for details
+	    on how to do this.</para>
+	  
+	  <tip>
+	    <para>Setting the keyboard to &ldquo;Not installed&rdquo; in the
+	      BIOS setup does <emphasis>not</emphasis> mean that you will not
+	      be able to use your keyboard.  All this does is tell the BIOS
+	      not to probe for a keyboard at power-on so that it will not
+	      complain if the keyboard is not plugged in.  You can leave the
+	      keyboard plugged in even with this flag set to &ldquo;Not
+	      installed&rdquo; and the keyboard will still work.</para>
+	  </tip>
+	  
+	  <note>
+	    <para>If your system has a PS/2 mouse, chances are very good  that
+	      you may have to unplug your mouse as well as your keyboard.
+	      This is because PS/2 mice share some hardware with the keyboard,
+	      and leaving the mouse plugged in can fool the keyboard probe
+	      into thinking the keyboard is still there.  It is said that a
+	      Gateway 2000 Pentium 90Mhz system with an AMI BIOS that behaves
+	      this way.  In general this is not a problem since the mouse is
+	      not much good without the keyboard anyway.</para>
+	  </note>
+	</step>
+	
+	<step>
+	  <para>Plug a dumb terminal into <devicename>COM1:</devicename>
+	    (<devicename>sio0</devicename>).</para>
+	  
+	  <para>If you do not have a dumb terminal, you can use an old PC/XT
+	    with a modem program, or the serial port on another UNIX box.  If
+	    you do not have a <devicename>COM1:</devicename>
+	    (<devicename>sio0</devicename>), get one.  At this time, there is
+	    no way to select a port other than <devicename>COM1:</devicename>
+	    for the boot blocks without recompiling the boot blocks.  If you
+	    are already using <devicename>COM1:</devicename> for another
+	    device, you will have to temporarily remove that device and
+	    install a new boot block and kernel once you get FreeBSD up and
+	    running. (It is assumed that <devicename>COM1:</devicename> will
+	    be available on a file/compute/terminal server anyway; if you
+	    really need <devicename>COM1:</devicename> for something else
+	    (and you can not switch that something else to
+	    <devicename>COM2:</devicename> (<devicename>sio1</devicename>)),
+	    then you probably should not even be bothering with all this in
+	    the first place.)</para>
+	</step>
+    
+	<step>
+	  <para>Make sure the configuration file of your kernel has
+	    appropriate flags set for <devicename>COM1:</devicename>
+	    (<devicename>sio0</devicename>).</para>
+	  
+	  <para>Relevant flags are:</para>
+	  
+	  <variablelist>
+	    <varlistentry>
+	      <term><literal>0x10</literal></term>
+	      
+	      <listitem>
+		<para>Enables console support for this unit.  The other
+		  console flags are ignored unless this is set. Currently, at
+		  most one unit can have console support;  the first one (in
+		  config file order) with this flag set is preferred.  This
+		  option alone will not make the serial port the console.  Set
+		  the following flag or use the <option>-h</option> option
+		  described below, together with this flag.</para>
+	      </listitem>
+	    </varlistentry>
+	    
+	    <varlistentry>
+	      <term><literal>0x20</literal></term>
+	      
+	      <listitem>
+		<para>Forces this unit to be the console (unless there is
+		  another higher priority console), regardless of the
+		  <option>-h</option> option discussed below.  This flag
+		  replaces the <literal>COMCONSOLE</literal> option in FreeBSD
+		  versions 2.X.  The flag <literal>0x20</literal> must be used
+		  together with the <option>0x10</option> flag.</para>
+	      </listitem>
+	    </varlistentry>
+	    
+	    <varlistentry>
+	      <term><literal>0x40</literal></term>
+	      
+	      <listitem>
+		<para>Reserves this unit (in conjunction with
+		  <literal>0x10</literal>) and makes the unit unavailable for
+		  normal access.  You should not set this flag to the serial
+		  port unit which you want to use as the serial console.  The
+		  only use of this flag is to designate the unit for kernel
+		  remote debugging.  See <xref linkend="kerneldebug"> for more
+		  information on remote debugging.</para>
+		
+		<note>
+		  <para>In FreeBSD 4.0-CURRENT or later the semantics of the
+		    flag <literal>0x40</literal> are slightly different and
+		    there is another flag to specify a serial port for remote
+		    debugging.</para>
+		</note>
+	      </listitem>
+	    </varlistentry>
+	  </variablelist>
+	  
+	  <para>Example:</para>
+	  
+	  <programlisting>
+device sio0 at isa? port "IO_COM1" tty flags 0x10 irq 4</programlisting>
+      
+	  <para>See &man.sio.4; for more details.</para>
+	  
+	  <para>If the flags were not set, you need to run UserConfig (on a
+	    different console) or recompile the kernel.</para>
+	</step>
+	
+	<step>
+	  <para>Create <filename>boot.config</filename> in the root directory
+	    of the <literal>a</literal> partition on the boot drive.</para>
+	  
+	  <para>This file will instruct the boot block code how you would like
+	    to boot the system.  In order to activate the serial console, you
+	    need one or more of the following options&mdash;if you want
+	    multiple options, include them all on the same line:</para>
+	  
+	  <variablelist>
+	    <varlistentry>
+	      <term><option>-h</option></term>
+	      
+	      <listitem>
+		<para>Toggles internal and serial consoles.  You can use this
+		  to switch console devices.  For instance, if you boot from
+		  the internal (video) console, you can use
+		  <option>-h</option> to direct the boot loader and the kernel
+		  to use the serial port as its console device. Alternatively,
+		  if you boot from the serial port, you can use the
+		  <option>-h</option> to tell the boot loader and the kernel
+		  to use the video display as the console instead.</para>
+	      </listitem>
+	    </varlistentry>
+	    
+	    <varlistentry>
+	      <term><option>-D</option></term>
+	      
+	      <listitem>
+		<para>Toggles single and dual console configurations.  In the
+		  single configuration the console will be either the internal
+		  console (video display) or the serial port, depending on the
+		  state of the <option>-h</option> option above.  In the dual
+		  console configuration, both the video display  and the
+		  serial port will become the console at the same time,
+		  regardless of the state of the <option>-h</option> option.
+		  However, that the dual console configuration takes  effect
+		  only during the boot block is running.  Once the boot loader
+		  gets control, the console specified by the
+		  <option>-h</option> option becomes the only console.</para>
+	      </listitem>
+	    </varlistentry>
+	    
+	    <varlistentry>
+	      <term><option>-P</option></term>
+	      
+	      <listitem>
+		<para>Makes the boot block probe the keyboard.  If no keyboard
+		  is found, the <option>-D</option> and <option>-h</option>
+		  options are automatically set.</para>
+		
+		<note>
+		  <para>Due to space constraints in the current version of the
+		    boot blocks, the <option>-P</option> option is capable of
+		    detecing extended keyboards only.  Keyboards with less
+		    than 101 keys (and without F11 and F12  keys) may not be
+		    detected.  Keyboards on some laptop computers may not be
+		    properly found because of this limitation.  If this is to
+		    be the case with your system, you have to abondan using
+		    the <option>-P</option> option.  Unfortunately there is no
+		    workaround for this problem.</para>
+		</note>
+	      </listitem>
+	    </varlistentry>
+	  </variablelist>
+      
+	  <para>Use either the <option>-P</option> option to select the
+	    console automatically, or the <option>-h</option> option to
+	    activate the serial console.</para>
+      
+	  <para>You may include other options described in &man.boot.8; as
+	    well.</para>
+      
+	  <para>The options, except for <option>-P</option>, will be passed to
+	    the boot loader (<filename>/boot/loader</filename>).  The boot
+	    loader will determine which of the internal video or the serial
+	    port should become the console by examining the state of the
+	    <option>-h</option> option alone.  This means that if you specify
+	    the <option>-D</option> option but not the <option>-h</option>
+	    option in <filename>/boot.config</filename>, you can use the
+	    serial port as the console only during the boot block;  the boot
+	    loader will use the internal video display as the console.</para>
+	</step>
+	
+	<step>
+	  <para>Boot the machine.</para>
+	  
+	  <para>When you start your FreeBSD box, the boot blocks will echo the
+	    contents of <filename>/boot.config</filename> to the console.  For
+	    example;</para>
+    
+	  <screen>/boot.config: -P
+Keyboard: no</screen>
+    
+	  <para>The second line appears only if you put <option>-P</option> in
+	    <filename>/boot.config</filename> and indicates presense/absence
+	    of the keyboard.  These messages go to either serial or internal
+	    console, or both, depending on the option in
+	    <filename>/boot.config</filename>.</para>
+    
+	  <informaltable frame="none">
+	    <tgroup cols="2">
+	      <thead>
+		<row>
+		  <entry>Options</entry>
+		  <entry>Message goes to</entry>
+		</row>
+	      </thead>
+	      
+	      <tbody>
+		<row>
+		  <entry>none</entry>
+		  <entry>internal console</entry>
+		</row>
+		
+		<row>
+		  <entry><option>-h</option></entry>
+		  <entry>serial console</entry>
+		</row>
+		
+		<row>
+		  <entry><option>-D</option></entry>
+		  <entry>serial and internal consoles</entry>
+		</row>
+		
+		<row>
+		  <entry><option>-Dh</option></entry>
+		  <entry>serial and internal consoles</entry>
+		</row>
+		
+		<row>
+		  <entry><option>-P</option>, keyboard present</entry>
+		  <entry>internal console</entry>
+		</row>
+		
+		<row>
+		  <entry><option>-P</option>, keyboard absent</entry>
+		  <entry>serial console</entry>
+		</row>
+	      </tbody>
+	    </tgroup>
+	  </informaltable>
+	  
+	  <para>After the above messages, there will be a small pause before
+	    the boot blocks continue loading the boot loader and before any
+	    further messages printed to the console.  Under normal
+	    circumstances, you do not need to interrupt the boot blocks, but
+	    you may want to do so in order to make sure things are set up
+	    correctly.</para>
+    
+	  <para>Hit any key, other than Enter/Return, at the console to
+	    interrupt the boot process.  The boot blocks will then prompt you
+	    for further action.  You should now see something like:</para>
+    
+	  <screen>>> FreeBSD/i386 BOOT
+Default: 0:wd(0,a)/boot/loader
+boot:</screen>
+    
+	  <para>Verify the above message appears on either the serial or
+	    internal console or both, according to the options you put in
+	    <filename>/boot.config</filename>.  If the message appears in the
+	    correct console, hit Enter/Return to continue the boot
+	    process.</para>
+	  
+	  <para>If you want the serial console but you do not see the prompt
+	    on the serial terminal, something is wrong with your settings.  In
+	    the meantime, you enter <option>-h</option> and hit Enter/Return
+	    (if possible) to tell the boot block (and then the boot loader and
+	    the kernel) to choose the serial port for the console. Once the
+	    system is up, go back and check what went wrong.</para>
+	</step>
+      </procedure>
+      
+      <para>After the boot loader is loaded and you are in the third stage of
+	the boot process you can still switch between the internal console and
+	the serial console by setting appropriate environment variables in the
+	boot loader.  See <xref linkend="serialconsole-loader">.</para>
+    </sect2>
+  
+  <sect2 id="serialconsole-summary">
+    <title>Summary</title>
+    
+      <para>Here is the summary of various settings discussed in this section
+	and the console eventually selected.</para>
+      
+      <sect3>
+	<title>Case 1: You set the flags to 0x10 for sio0</title>
+	
+	<programlisting>device sio0 at isa? port "IO_COM1" tty flags 0x10 irq 4</programlisting>
+	
+	<informaltable frame="none">
+	  <tgroup cols="4">
+	    <thead>
+	      <row>
+		<entry>Options in /boot.config</entry>
+		<entry>Console during boot blocks</entry>
+		<entry>Console during boot loader</entry>
+		<entry>Console in kernel</entry>
+	      </row>
+	    </thead>
+	    
+	    <tbody>
+	      <row>
+		<entry>nothing</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-h</option></entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-D</option></entry>
+		<entry>serial and internal</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-Dh</option></entry>
+		<entry>serial and internal</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-P</option>, keyboard present</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-P</option>, keyboard absent</entry>
+		<entry>serial and internal</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	    </tbody>
+	  </tgroup>
+	</informaltable>
+      </sect3>
+      
+      <sect3>
+	<title>Case 2: You set the flags to 0x30 for sio0</title>
+	
+	<programlisting>device sio0 at isa? port "IO_COM1" tty flags 0x30 irq 4</programlisting>
+  
+	<informaltable frame="none">
+	  <tgroup cols="4">
+	    <thead>
+	      <row>
+		<entry>Options in /boot.config</entry>
+		<entry>Console during boot blocks</entry>
+		<entry>Console during boot loader</entry>
+		<entry>Console in kernel</entry>
+	      </row>
+	    </thead>
+	    
+	    <tbody>
+	      <row>
+		<entry>nothing</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-h</option></entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-D</option></entry>
+		<entry>serial and internal</entry>
+		<entry>internal</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-Dh</option></entry>
+		<entry>serial and internal</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-P</option>, keyboard present</entry>
+		<entry>internal</entry>
+		<entry>internal</entry>
+		<entry>serial</entry>
+	      </row>
+	      
+	      <row>
+		<entry><option>-P</option>, keyboard absent</entry>
+		<entry>serial and internal</entry>
+		<entry>serial</entry>
+		<entry>serial</entry>
+	      </row>
+	    </tbody>
+	  </tgroup>
+	</informaltable>
+      </sect3>
+    </sect2>
+    
+    <sect2 id="serialconsole-tips">
+      <title>Tips for the Serial Console</title>
+  
+      <sect3>
+	<title>Setting A Faster Serial Port Speed</title>
+	
+	<para>By default the serial port settings are set to 9600 baud, 8
+	  bits, no parity, 1 stop bit.  If you wish to change the speed, you
+	  need to recompile at least the boot blocks.  Add the following line
+	  to <filename>/etc/make.conf</filename> and compile new boot
+	  blocks:</para>
+	
+	<programlisting>BOOT_COMCONSOLE_SPEED=19200</programlisting>
+  
+	<para>If the serial console is configured in some other way than by
+	  booting with <option>-h</option>, or if the serial console used by
+	  the kernel is different from the one used by the boot blocks, then
+	  you must also add the following option to the kernel configuration
+	  file and compile a new kernel:</para>
+  
+	<programlisting>options CONSPEED=19200</programlisting>
+      </sect3>
+      
+      <sect3 id="serialconsole-com2">
+	<title>Using Serial Port Other Than <devicename>sio0</devicename> For
+	  The Console</title>
+	
+	<para>Using a port other than <devicename>sio0</devicename> as the
+	  console requires some recompiling.  If you want to use another
+	  serial port for whatever reasons, recompile the boot blocks, the
+	  boot loader and the kernel as follows.</para>
+  
+	<procedure>
+	  <step>
+	    <para>Get the kernel source.</para>
+	  </step>
+	  
+	  <step>
+	    <para>Edit <filename>/etc/make.conf</filename> and set
+	      <literal>BOOT_COMCONSOLE_PORT</literal> to the address of the
+	      port you want to use (0x3F8, 0x2F8, 0x3E8 or 0x2E8).  Only
+	      <devicename>sio0</devicename> through
+	      <devicename>sio3</devicename> (<devicename>COM1:</devicename>
+	      through <devicename>COM4:</devicename>) can be used;  multiport
+	      serial cards will not work.  No interrupt setting is
+	      needed.</para>
+	  </step>
+	  
+	  <step>
+	    <para>Create a custom kernel configuration file and add
+	      appropriate flags for the serial port you want to use. For
+	      example, if you want to make <devicename>sio1</devicename>
+	      (<devicename>COM2:</devicename>) the console:</para>
+  
+	    <programlisting>device sio1 at isa? port "IO_COM2" tty flags 0x10 irq 3</programlisting>
+  
+	    <para>or</para>
+	    
+	    <programlisting>device sio1 at isa? port "IO_COM2" tty flags 0x30 irq 3</programlisting>
+  
+	    <para>The console flags for the other serial ports should not be
+	      set.</para>
+	  </step>
+	  
+	  <step>
+	    <para>Recompile and install the boot blocks:</para>
+	    
+	    <screen>&prompt.root; <userinput>cd /sys/boot/i386/boot2</userinput>
+&prompt.root; <userinput>make</userinput>
+&prompt.root; <userinput>make install</userinput></screen>
+	  </step>
+	  
+	  <step>
+	    <para>Recompile and install the boot loader:</para>
+	    
+	    <screen>&prompt.root; <userinput>cd /sys/boot/i386/loader</userinput>
+&prompt.root; <userinput>make</userinput>
+&prompt.root; <userinput>make install</userinput></screen>
+        </step>
+	  
+	  <step>
+	    <para>Rebuild and install the kernel.</para>
+	  </step>
+	  
+	  <step>
+	    <para>Write the boot blocks to the boot disk with
+		&man.disklabel.8; and boot from the new kernel.</para>
+	  </step>
+	</procedure>
+      </sect3>
+      
+      <sect3>
+	<title>Entering the DDB Debugger from the Serial Line</title>
+	
+	<para>If you wish to drop into the kernel debugger from the serial
+	  console (useful for remote diagnostics, but also dangerous if you
+	  generate a spurious BREAK on the serial port!) then you should
+	  compile your kernel with the following options:</para>
+  
+	<programlisting>options BREAK_TO_DEBUGGER
+options DDB</programlisting>
+      </sect3>
+      
+      <sect3>
+	<title>Getting a Login Prompt on the Serial Console</title>
+	
+	<para>While this is not required, you may wish to get a
+	  <emphasis>login</emphasis> prompt over the serial line, now that you
+	  can see boot messages and can enter the kernel debugging session
+	  through the serial console.  Here is how to do it.</para>
+  
+	<para>Open the file <filename>/etc/ttys</filename> with an editor 
+	  and locate the lines:</para>
+  
+      <programlisting>ttyd0 "/usr/libexec/getty std.9600" unknown off secure
+ttyd1 "/usr/libexec/getty std.9600" unknown off secure
+ttyd2 "/usr/libexec/getty std.9600" unknown off secure
+ttyd3 "/usr/libexec/getty std.9600" unknown off secure</programlisting>
+  
+	<para><literal>ttyd0</literal> through <literal>ttyd3</literal>
+	  corresponds to <devicename>COM1</devicename> through
+	  <devicename>COM4</devicename>.  Change <literal>off</literal> to
+	  <literal>on</literal> for the desired port.  If you have changed the
+	  speed of the serial port, you need to change
+	  <literal>std.9600</literal> to match the current setting, e.g.
+	  <literal>std.19200</literal>.</para>
+  
+	<para>You may also want to change the terminal type from
+	  <literal>unknown</literal> to the actual type of your serial
+	  terminal.</para>
+
+	<para>After editing the file, you must <command>kill -HUP 1</command>
+	  to make this change take effect.</para>
+      </sect3>
+    </sect2>
+  
+    <sect2 id="serialconsole-loader">
+      <title>Changing Console from the Boot Loader</title>
+      
+      <para>Previous sections described how to set up the serial console by
+	tweaking the boot block.  This section shows that you can specify the
+	console by entering some commands and environment variables in the
+	boot loader.  As the boot loader is invoked as the third stage of the
+	boot process, after the boot block, the settings in the boot loader
+	will override the settings in the boot block.</para>
+      
+      <sect3>
+	<title>Setting Up the Serial Console</title>
+	
+	<para>You can easily specify the boot loader and the kernel to use the
+	  serial console by writing just one line in
+	  <filename>/boot/loader.rc</filename>:</para>
+  
+	<programlisting>set console=comconsole</programlisting>
+  
+	<para>This will take effect regardless of the settings in the boot
+	  block discussed in the previous section.</para>
+  
+	<para>You had better put the above line as the first line of
+	  <filename>/boot/loader.rc</filename> so as to see boot messages  on
+	  the serial console as early as possible.</para>
+  
+	<para>Likewise, you can specify the internal console as:</para>
+	
+	<programlisting>set console=vidconsole</programlisting>
+  
+	<para>If you do not set the boot loader environment variable
+	  <envar>console</envar>, the boot loader, and subsequently the
+	  kernel, will use whichever console indicated by the
+	  <option>-h</option> option in the  boot block.</para>
+  
+	<para>In versions 3.2 or later, you may specify the console in
+	  <filename>/boot/loader.conf.local</filename> or
+	  <filename>/boot/loader.conf</filename>, rather than in
+	  <filename>/boot/loader.rc</filename>.  In this method your
+	  <filename>/boot/loader.rc</filename> should look like:</para>
+  
+	<programlisting>include /boot/loader.4th
+start</programlisting>
+  
+	<para>Then, create <filename>/boot/loader.conf.local</filename>  and
+	  put the following line there.</para>
+  
+	<programlisting>console=comconsole</programlisting>
+  
+	<para>or</para>
+	
+	<programlisting>console=vidconsole</programlisting>
+  
+	<para>See &man.loader.conf.5; for more information.</para>
+	
+	<note>
+	  <para>At the moment, the boot loader has no option equivalent to the
+	    <option>-P</option> option in the boot block, and there is no
+	    provision to automatically select the internal console and the
+	    serial console based on the presense of the keyboard.</para>
+	</note>
+      </sect3>
+  
+      <sect3>
+	<title>Using Serial Port Other than <devicename>sio0</devicename> for
+	  the Console</title>
+	
+	<para>You need to recompile the boot loader to use a serial port other
+	  than <devicename>sio0</devicename> for the serial console. Follow the
+	  procedure described in <xref linkend="serialconsole-com2">.</para>
+      </sect3>
+    </sect2>
+    
+    <sect2 id="serialconsole-caveats">
+      <title>Caveats</title>
+      
+      <para>The idea here is to allow people to set up dedicated servers  that
+	require no graphics hardware or attached keyboards.  Unfortunately,
+	while (most?) every system will let you boot without a keyboard, there
+	are quite a few that will not let you boot without a graphics adapter.
+	Machines with AMI BIOSes can be configured to  boot with no graphics
+	adapter installed simply by changing the `graphics adapter' setting in
+	the CMOS configuration to `Not installed.'</para>
+  
+      <para>However, many machines do not support this option and will refuse
+	to boot if you have no display hardware in the system.  With these
+	machines, you'll have to leave some kind of graphics card plugged in,
+	(even if it's just a junky mono board) although you will not have to
+	attach a monitor into it. You might also try installing an AMI
+	BIOS.</para>
+    </sect2>
+  </sect1>
 </chapter>
 
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