boot-blocks.html

这是很好的学习嵌入式LINUX的文章

unload all modules, load modules, and then finally boot or reboot.</p>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="BOOT-LOADER-COMMANDS" name="BOOT-LOADER-COMMANDS">12.3.3.2
Loader Built-In Commands</a></h3>

<p>These are the most commonly used loader commands. For a complete discussion of all
available commands, please see <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=loader&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">loader</span>(8)</span></a>.</p>

<div class="VARIABLELIST">
<dl>
<dt>autoboot <var class="REPLACEABLE">seconds</var></dt>

<dd>
<p>Proceeds to boot the kernel if not interrupted within the time span given, in seconds.
It displays a countdown, and the default time span is 10 seconds.</p>
</dd>

<dt>boot [<span class="OPTIONAL"><var class="REPLACEABLE">-options</var></span>] [<span
class="OPTIONAL"><var class="REPLACEABLE">kernelname</var></span>]</dt>

<dd>
<p>Immediately proceeds to boot the kernel, with the given options, if any, and with the
kernel name given, if it is.</p>
</dd>

<dt>boot-conf</dt>

<dd>
<p>Goes through the same automatic configuration of modules based on variables as what
happens at boot. This only makes sense if you use <tt class="COMMAND">unload</tt> first,
and change some variables, most commonly <tt class="ENVAR">kernel</tt>.</p>
</dd>

<dt>help [<span class="OPTIONAL"><var class="REPLACEABLE">topic</var></span>]</dt>

<dd>
<p>Shows help messages read from <tt class="FILENAME">/boot/loader.help</tt>. If the
topic given is <var class="LITERAL">index</var>, then the list of available topics is
given.</p>
</dd>

<dt>include <var class="REPLACEABLE">filename</var> ...</dt>

<dd>
<p>Processes the file with the given filename. The file is read in, and interpreted line
by line. An error immediately stops the include command.</p>
</dd>

<dt>load [<span class="OPTIONAL"><var class="OPTION">-t</var> <var
class="REPLACEABLE">type</var></span>] <var class="REPLACEABLE">filename</var></dt>

<dd>
<p>Loads the kernel, kernel module, or file of the type given, with the filename given.
Any arguments after filename are passed to the file.</p>
</dd>

<dt>ls [<span class="OPTIONAL"><var class="OPTION">-l</var></span>] [<span
class="OPTIONAL"><var class="REPLACEABLE">path</var></span>]</dt>

<dd>
<p>Displays a listing of files in the given path, or the root directory, if the path is
not specified. If <var class="OPTION">-l</var> is specified, file sizes will be shown
too.</p>
</dd>

<dt>lsdev [<span class="OPTIONAL"><var class="OPTION">-v</var></span>]</dt>

<dd>
<p>Lists all of the devices from which it may be possible to load modules. If <var
class="OPTION">-v</var> is specified, more details are printed.</p>
</dd>

<dt>lsmod [<span class="OPTIONAL"><var class="OPTION">-v</var></span>]</dt>

<dd>
<p>Displays loaded modules. If <var class="OPTION">-v</var> is specified, more details
are shown.</p>
</dd>

<dt>more <var class="REPLACEABLE">filename</var></dt>

<dd>
<p>Displays the files specified, with a pause at each <var class="VARNAME">LINES</var>
displayed.</p>
</dd>

<dt>reboot</dt>

<dd>
<p>Immediately reboots the system.</p>
</dd>

<dt>set <var class="REPLACEABLE">variable</var>, set <var
class="REPLACEABLE">variable</var>=<var class="REPLACEABLE">value</var></dt>

<dd>
<p>Sets the loader's environment variables.</p>
</dd>

<dt>unload</dt>

<dd>
<p>Removes all loaded modules.</p>
</dd>
</dl>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="BOOT-LOADER-EXAMPLES" name="BOOT-LOADER-EXAMPLES">12.3.3.3
Loader Examples</a></h3>

<p>Here are some practical examples of loader usage:</p>

<ul>
<li>
<p>To simply boot your usual kernel, but in single-user mode:</p>

<pre class="SCREEN">
<kbd class="USERINPUT">boot -s</kbd>
</pre>
</li>

<li>
<p>To unload your usual kernel and modules, and then load just your old (or another)
kernel:</p>

<pre class="SCREEN">
<kbd class="USERINPUT">unload</kbd>
<kbd class="USERINPUT">load <var class="REPLACEABLE">kernel.old</var></kbd>
</pre>

<p>You can use <tt class="FILENAME">kernel.GENERIC</tt> to refer to the generic kernel
that comes on the install disk, or <tt class="FILENAME">kernel.old</tt> to refer to your
previously installed kernel (when you have upgraded or configured your own kernel, for
example).</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> Use the following to load your usual modules with another kernel:</p>

<pre class="SCREEN">
<kbd class="USERINPUT">unload</kbd>
<kbd class="USERINPUT">set kernel="<var class="REPLACEABLE">kernel.old</var>"</kbd>
<kbd class="USERINPUT">boot-conf</kbd>
</pre>
</blockquote>
</div>
</li>

<li>
<p>To load a kernel configuration script (an automated script which does the things you
would normally do in the kernel boot-time configurator):</p>

<pre class="SCREEN">
<kbd class="USERINPUT">load -t userconfig_script <var
class="REPLACEABLE">/boot/kernel.conf</var></kbd>
</pre>
</li>
</ul>
</div>
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