serialconsole-setup.html

FreeBSD操作系统的详细使用手册

<div class="INFORMALTABLE"><a id="AEN29760" name="AEN29760"></a>
<table border="0" frame="void" class="CALSTABLE">
<col />
<col />
<col />
<col />
<thead>
<tr>
<th>Options in /boot.config</th>
<th>Console during boot blocks</th>
<th>Console during boot loader</th>
<th>Console in kernel</th>
</tr>
</thead>

<tbody>
<tr>
<td>nothing</td>
<td>internal</td>
<td>internal</td>
<td>internal</td>
</tr>

<tr>
<td><var class="OPTION">-h</var></td>
<td>serial</td>
<td>serial</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-D</var></td>
<td>serial and internal</td>
<td>internal</td>
<td>internal</td>
</tr>

<tr>
<td><var class="OPTION">-Dh</var></td>
<td>serial and internal</td>
<td>serial</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-P</var>, keyboard present</td>
<td>internal</td>
<td>internal</td>
<td>internal</td>
</tr>

<tr>
<td><var class="OPTION">-P</var>, keyboard absent</td>
<td>serial and internal</td>
<td>serial</td>
<td>serial</td>
</tr>
</tbody>
</table>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN29804" name="AEN29804">20.6.4.2 Case 2: You Set the Flags to
0x30 for sio0</a></h3>

<pre class="PROGRAMLISTING">
device sio0 at isa? port IO_COM1 flags 0x30 irq 4
</pre>

<div class="INFORMALTABLE"><a id="AEN29807" name="AEN29807"></a>
<table border="0" frame="void" class="CALSTABLE">
<col />
<col />
<col />
<col />
<thead>
<tr>
<th>Options in /boot.config</th>
<th>Console during boot blocks</th>
<th>Console during boot loader</th>
<th>Console in kernel</th>
</tr>
</thead>

<tbody>
<tr>
<td>nothing</td>
<td>internal</td>
<td>internal</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-h</var></td>
<td>serial</td>
<td>serial</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-D</var></td>
<td>serial and internal</td>
<td>internal</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-Dh</var></td>
<td>serial and internal</td>
<td>serial</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-P</var>, keyboard present</td>
<td>internal</td>
<td>internal</td>
<td>serial</td>
</tr>

<tr>
<td><var class="OPTION">-P</var>, keyboard absent</td>
<td>serial and internal</td>
<td>serial</td>
<td>serial</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="SERIALCONSOLE-TIPS" name="SERIALCONSOLE-TIPS">20.6.5 Tips for
the Serial Console</a></h2>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN29853" name="AEN29853">20.6.5.1 Setting a Faster Serial Port
Speed</a></h3>

<p>By default, the serial port settings are: 9600 baud, 8 bits, no parity, and 1 stop
bit. If you wish to change the speed, you need to recompile at least the boot blocks. Add
the following line to <tt class="FILENAME">/etc/make.conf</tt> and compile new boot
blocks:</p>

<pre class="PROGRAMLISTING">
BOOT_COMCONSOLE_SPEED=19200
</pre>

<p>See <a href="serialconsole-setup.html#SERIALCONSOLE-COM2">Section 20.6.5.2</a> for
detailed instructions about building and installing new boot blocks.</p>

<p>If the serial console is configured in some other way than by booting with <var
class="OPTION">-h</var>, 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:</p>

<pre class="PROGRAMLISTING">
options CONSPEED=19200
</pre>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="SERIALCONSOLE-COM2" name="SERIALCONSOLE-COM2">20.6.5.2 Using
Serial Port Other Than <tt class="DEVICENAME">sio0</tt> for the Console</a></h3>

<p>Using a port other than <tt class="DEVICENAME">sio0</tt> 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.</p>

<div class="PROCEDURE">
<ol type="1">
<li>
<p>Get the kernel source. (See <a href="cutting-edge.html">Chapter 19</a>)</p>
</li>

<li>
<p>Edit <tt class="FILENAME">/etc/make.conf</tt> and set <var
class="LITERAL">BOOT_COMCONSOLE_PORT</var> to the address of the port you want to use
(0x3F8, 0x2F8, 0x3E8 or 0x2E8). Only <tt class="DEVICENAME">sio0</tt> through <tt
class="DEVICENAME">sio3</tt> (<tt class="DEVICENAME">COM1</tt> through <tt
class="DEVICENAME">COM4</tt>) can be used; multiport serial cards will not work. No
interrupt setting is needed.</p>
</li>

<li>
<p>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 <tt class="DEVICENAME">sio1</tt>
(<tt class="DEVICENAME">COM2</tt>) the console:</p>

<pre class="PROGRAMLISTING">
device sio1 at isa? port IO_COM2 flags 0x10 irq 3
</pre>

<p>or</p>

<pre class="PROGRAMLISTING">
device sio1 at isa? port IO_COM2 flags 0x30 irq 3
</pre>

<p>The console flags for the other serial ports should not be set.</p>
</li>

<li>
<p>Recompile and install the boot blocks and the boot loader:</p>

<pre class="SCREEN">
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cd /sys/boot</kbd>
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make clean</kbd>
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make</kbd>
<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make install</kbd>
</pre>
</li>

<li>
<p>Rebuild and install the kernel.</p>
</li>

<li>
<p>Write the boot blocks to the boot disk with <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=disklabel&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">disklabel</span>(8)</span></a> and boot
from the new kernel.</p>
</li>
</ol>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="SERIALCONSOLE-DDB" name="SERIALCONSOLE-DDB">20.6.5.3 Entering
the DDB Debugger from the Serial Line</a></h3>

<p>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:</p>

<pre class="PROGRAMLISTING">
options BREAK_TO_DEBUGGER
options DDB
</pre>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN29910" name="AEN29910">20.6.5.4 Getting a Login Prompt on the
Serial Console</a></h3>

<p>While this is not required, you may wish to get a <span class="emphasis"><i
class="EMPHASIS">login</i></span> 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.</p>

<p>Open the file <tt class="FILENAME">/etc/ttys</tt> with an editor and locate the
lines:</p>

<pre class="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
</pre>

<p><var class="LITERAL">ttyd0</var> through <var class="LITERAL">ttyd3</var> corresponds
to <tt class="DEVICENAME">COM1</tt> through <tt class="DEVICENAME">COM4</tt>. Change <var
class="LITERAL">off</var> to <var class="LITERAL">on</var> for the desired port. If you
have changed the speed of the serial port, you need to change <var
class="LITERAL">std.9600</var> to match the current setting, e.g. <var
class="LITERAL">std.19200</var>.</p>

<p>You may also want to change the terminal type from <var class="LITERAL">unknown</var>
to the actual type of your serial terminal.</p>

<p>After editing the file, you must <tt class="COMMAND">kill -HUP 1</tt> to make this
change take effect.</p>
</div>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="SERIALCONSOLE-LOADER" name="SERIALCONSOLE-LOADER">20.6.6
Changing Console from the Boot Loader</a></h2>

<p>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 at 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.</p>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN29933" name="AEN29933">20.6.6.1 Setting Up the Serial
Console</a></h3>

<p>You can easily specify the boot loader and the kernel to use the serial console by
writing just one line in <tt class="FILENAME">/boot/loader.rc</tt>:</p>

<pre class="PROGRAMLISTING">
set console=comconsole
</pre>

<p>This will take effect regardless of the settings in the boot block discussed in the
previous section.</p>

<p>You had better put the above line as the first line of <tt
class="FILENAME">/boot/loader.rc</tt> so as to see boot messages on the serial console as
early as possible.</p>

<p>Likewise, you can specify the internal console as:</p>

<pre class="PROGRAMLISTING">
set console=vidconsole
</pre>

<p>If you do not set the boot loader environment variable <tt class="ENVAR">console</tt>,
the boot loader, and subsequently the kernel, will use whichever console indicated by the
<var class="OPTION">-h</var> option in the boot block.</p>

<p>In versions 3.2 or later, you may specify the console in <tt
class="FILENAME">/boot/loader.conf.local</tt> or <tt
class="FILENAME">/boot/loader.conf</tt>, rather than in <tt
class="FILENAME">/boot/loader.rc</tt>. In this method your <tt
class="FILENAME">/boot/loader.rc</tt> should look like:</p>

<pre class="PROGRAMLISTING">
include /boot/loader.4th
start
</pre>

<p>Then, create <tt class="FILENAME">/boot/loader.conf.local</tt> and put the following
line there.</p>

<pre class="PROGRAMLISTING">
console=comconsole
</pre>

<p>or</p>

<pre class="PROGRAMLISTING">
console=vidconsole
</pre>

<p>See <a href="http://www.FreeBSD.org/cgi/man.cgi?query=loader.conf&sektion=5"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">loader.conf</span>(5)</span></a> for
more information.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> At the moment, the boot loader has no option equivalent to the <var
class="OPTION">-P</var> option in the boot block, and there is no provision to
automatically select the internal console and the serial console based on the presence of
the keyboard.</p>
</blockquote>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN29964" name="AEN29964">20.6.6.2 Using a Serial Port Other
Than <tt class="DEVICENAME">sio0</tt> for the Console</a></h3>

<p>You need to recompile the boot loader to use a serial port other than <tt
class="DEVICENAME">sio0</tt> for the serial console. Follow the procedure described in <a
href="serialconsole-setup.html#SERIALCONSOLE-COM2">Section 20.6.5.2</a>.</p>
</div>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="SERIALCONSOLE-CAVEATS" name="SERIALCONSOLE-CAVEATS">20.6.7
Caveats</a></h2>

<p>The idea here is to allow people to set up dedicated servers that require no graphics
hardware or attached keyboards. Unfortunately, while most systems 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.''</p>

<p>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 will have to leave some kind
of graphics card plugged in, (even if it is just a junky mono board) although you will
not have to attach a monitor. You might also try installing an AMI BIOS.</p>
</div>
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