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+<title>Selecting a Kernel</title>
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+<tr>
+<th colspan="3" align="center">Slackware Linux Essentials</th>
+</tr>
+
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+<td width="10%" align="left" valign="bottom"><a href="system-configuration.html"
+accesskey="P">Prev</a></td>
+<td width="80%" align="center" valign="bottom">Chapter 4 System Configuration</td>
+<td width="10%" align="right" valign="bottom"><a href="network-configuration.html"
+accesskey="N">Next</a></td>
+</tr>
+</table>
+
+<hr align="LEFT" width="100%" />
+</div>
+
+<div class="SECT1">
+<h1 class="SECT1"><a id="SYSTEM-CONFIGURATION-KERNEL"
+name="SYSTEM-CONFIGURATION-KERNEL">4.2 Selecting a Kernel</a></h1>
+
+<p>The kernel is the part of the operating system that provides hardware access, process
+control, and overall system control. The kernel contains support for your hardware
+devices, so picking one for your system is an important setup step.</p>
+
+<p>Slackware provides more than a dozen precompiled kernels that you can pick from, each
+with a standard set of drivers and additional specific drivers. You can run one of the
+precompiled kernels or you can build your own kernel from source. Either way, you need to
+make sure that your kernel has the hardware support your system needs.</p>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="AEN1581" name="AEN1581">4.2.1 The <tt
+class="FILENAME">/kernels</tt> Directory on the Slackware CD-ROM</a></h2>
+
+<p>The precompiled Slackware kernels are available in the <tt
+class="FILENAME">/kernels</tt> directory on the Slackware CD-ROM or on the FTP site in
+the main Slackware directory. The available kernels change as new releases are made, so
+the documentation in that directory is always the authoritative source. The <tt
+class="FILENAME">/kernels</tt> directory has subdirectories for each kernel available.
+The subdirectories have the same name as their accompanying boot disk. In each
+subdirectory you will find the following files:</p>
+
+<div class="INFORMALTABLE"><a id="AEN1587" name="AEN1587"></a>
+<table border="0" frame="void" width="100%" class="CALSTABLE">
+<col width="33%" />
+<col width="67%" />
+<thead>
+<tr>
+<th>File</th>
+<th>Purpose</th>
+</tr>
+</thead>
+
+<tbody>
+<tr>
+<td><tt class="FILENAME">System.map</tt></td>
+<td>The system map file for this kernel</td>
+</tr>
+
+<tr>
+<td><tt class="FILENAME">bzImage</tt></td>
+<td>The actual kernel image</td>
+</tr>
+
+<tr>
+<td><tt class="FILENAME">config</tt></td>
+<td>The source configuration file for this kernel</td>
+</tr>
+</tbody>
+</table>
+</div>
+
+<p>To use a kernel, copy the <tt class="FILENAME">System.map</tt> and <tt
+class="FILENAME">config</tt> files to your <tt class="FILENAME">/boot</tt> directory and
+copy the kernel image to <tt class="FILENAME">/boot/vmlinuz</tt>. Run <tt
+class="COMMAND">/sbin/lilo</tt>(8) to install LILO for the new kernel, and then reboot
+your system. That's all there is to installing a new kernel.</p>
+
+<p>The kernels that end with a .i are IDE kernels. That is, they include no SCSI support
+in the base kernel. The kernels that end with .s are SCSI kernels. They include all the
+IDE support in .i kernels, plus SCSI support.</p>
+</div>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="SYSTEM-CONFIGURATION-KERNEL-COMPILE"
+name="SYSTEM-CONFIGURATION-KERNEL-COMPILE">4.2.2 Compiling a Kernel from Source</a></h2>
+
+<p>The question &#8220;Should I compile a kernel for my system?&#8221; is often asked by
+new users. The answer is a definite maybe. There are few instances where you will need to
+compile a kernel specific to your system. Most users can use a precompiled kernel and the
+loadable kernel modules to achieve a fully working system. You will want to compile a
+kernel for your system if you are upgrading kernel versions to one that we do not
+currently offer in Slackware, or if you have patched the kernel source to get special
+device support that is not in the native kernel source. Anyone with an SMP system will
+definitely want to compile a kernel with SMP support. Also, many users find a custom
+compiled kernel runs much faster on their machine. You may find it useful to compile the
+kernel with optimizations for the specific processor in your machine.</p>
+
+<p>Building your own kernel is not that hard. The first step is to make sure you have the
+kernel source installed on your system. Make sure that you installed the packages from
+the K series during the installation. You will also want to make sure you have the D
+series installed, specifically the C compiler, GNU make, and GNU binutils. In general,
+it's a good idea to have the entire D series installed if you plan on doing any kind of
+development. You can also download the latest kernel source from <a
+href="http://www.kernel.org/mirrors" target="_top">http://www.kernel.org/mirrors</a>.</p>
+
+<div class="SECT3">
+<h3 class="SECT3"><a id="AEN1624" name="AEN1624">4.2.2.1 Linux Kernel version 2.4.x
+Compilation</a></h3>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">%</samp> <kbd class="USERINPUT">su -</kbd>
+Password:
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cd /usr/src/linux</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>The first step is to bring the kernel source into its base state. We issue this
+command to do that (note, you may wish to back-up the <tt class="FILENAME">.config</tt>
+file as this command will delete it without warning):</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make mrproper</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>Now you can configure the kernel for your system. The current kernel offers three ways
+of doing this. The first is the original text-based question and answer system. It asks a
+bunch of questions and then builds a configuration file. The problem with this method is
+that if you mess up, you must start over. The method that most people prefer is the menu
+driven one. Lastly, there is an X-based kernel configuration tool. Pick the one you want
+and issue the appropriate command:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">make config</kbd> (text-based Q&amp;A version)
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">make menuconfig</kbd> (menu driven, text-based version)
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">make xconfig</kbd> (X-based version, make sure you are in X first)
+</pre>
+</td>
+</tr>
+</table>
+
+<div class="FIGURE"><a id="SYSTEM-CONFIGURATION-MAKE-MENUCONFIG"
+name="SYSTEM-CONFIGURATION-MAKE-MENUCONFIG"></a>
+<p><b>Figure 4-1. Kernel Configuration Menu</b></p>
+
+<p><img src="system-configuration/make-menuconfig-w.png" /></p>
+</div>
+
+<p>New users will probably find <tt class="COMMAND">menuconfig</tt> to be the easiest to
+use. Help screens are provided that explain the various parts of the kernel. After
+configuring your kernel, exit the configuration program. It will write the necessary
+configuration files. Now we can prepare the source tree for a build:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make dep</kbd>
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make clean</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>The next step is to compile the kernel. First try issuing the <tt
+class="COMMAND">bzImage</tt> command below.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make bzImage</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>This may take a while, depending on your CPU speed. During the build process, you will
+see the compiler messages. After building the kernel image, you will want to build any
+parts of the kernel that you flagged as modular.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make modules</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>We can now install the kernel and modules that you compiled. To install the kernel on
+a Slackware system, these commands should be issued:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">mv /boot/vmlinuz /boot/vmlinuz.old</kbd>
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">cat arch/i386/boot/bzImage &#62; /vmlinuz</kbd>
+<samp class="PROMPT">#</samp> <kbd
+class="USERINPUT">mv /boot/System.map /boot/System.map.old</kbd>
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">cp System.map /boot/System.map</kbd>
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make modules_install</kbd>
+</pre>
+</td>
+</tr>
+</table>
+
+<p>You will want to edit <tt class="FILENAME">/etc/lilo.conf</tt> and add a section to
+boot your old kernel in case your new one does not work. After doing that, run <tt
+class="COMMAND">/sbin/lilo</tt> to install the new boot block. You can now reboot with
+your new kernel.</p>
+</div>
+
+<div class="SECT3">
+<h3 class="SECT3"><a id="AEN1686" name="AEN1686">4.2.2.2 Linux Kernel Version
+2.6.x</a></h3>
+
+<p>The compilation of a 2.6 kernel is only slightly different from a 2.4 or a 2.2 kernel,
+but it is important that you understand the differences before delving in. It's no longer
+necessary to run <tt class="COMMAND">make dep</tt> and <tt class="COMMAND">make
+clean</tt>. Also, the kernel compilation process is not as verbose in the 2.6 kernel
+series. This results in a build process that is easier to understand, but has some short
+comings as well. If you have trouble building the kernel, it's highly recommended that
+you turn verbosity back up. You do this simply by appending <var class="OPTION">V=1</var>
+to the build. This allows you to log more information that could help a kernel developer
+or other friendly geek aid you in resolving the issue.</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">make bzImage V=1</kbd>
+</pre>
+</td>
+</tr>
+</table>
+</div>
+</div>
+
+<div class="SECT2">
+<h2 class="SECT2"><a id="SYSTEM-CONFIGURATION-KERNEL-MODULES"
+name="SYSTEM-CONFIGURATION-KERNEL-MODULES">4.2.3 Using Kernel Modules</a></h2>
+
+<p>Kernel modules are another name for device drivers that can be inserted into a running
+kernel. They allow you to extend the hardware supported by your kernel without needing to
+pick another kernel or compile one yourself.</p>
+
+<p>Modules can also be loaded and unloaded at any time, even when the system is running.
+This makes upgrading specific drivers easy for system administrators. A new module can be
+compiled, the old one removed, and the new one loaded, all without rebooting the
+machine.</p>
+
+<p>Modules are stored in the <tt class="FILENAME">/lib/modules/<var
+class="REPLACEABLE">kernel version</var></tt> directory on your system. They can be
+loaded at boot time through the <tt class="FILENAME">rc.modules</tt> file. This file is
+very well commented and offers examples for major hardware components. To see a list of
+modules that are currently active, use the <tt class="COMMAND">lsmod</tt>(1) command:</p>
+
+<table border="0" bgcolor="#E0E0E0" width="100%">
+<tr>
+<td>
+<pre class="SCREEN">
+<samp class="PROMPT">#</samp> <kbd class="USERINPUT">lsmod</kbd>
+Module Size Used by
+parport_pc 7220 0
+parport 7844 0 [parport_pc]
+</pre>
+</td>
+</tr>
+</table>
+
+<p>You can see here that I only have the parallel port module loaded. To remove a module,
+you use the <tt class="COMMAND">rmmod</tt>(1) command. Modules can be loaded by the <tt
+class="COMMAND">modprobe</tt>(1) or <tt class="COMMAND">insmod</tt>(1) command. <tt
+class="COMMAND">modprobe</tt> is usually safer because it will load any modules that the
+one you're trying to load depends on.</p>
+
+<p>A lot of users never have to load or unload modules by hand. They use the kernel
+autoloader for module management. By default, Slackware includes <var
+class="OPTION">kmod</var> in its kernels. <var class="OPTION">kmod</var> is a kernel
+option that enables the kernel to automatically load modules as they are requested. For
+more information on <var class="OPTION">kmod</var> and how it is configured, see <tt
+class="FILENAME">/usr/src/linux/Documentation/kmod.txt</tt>. You'll have needed to have
+the kernel source package, or downloaded kernel source from <a href="http://kernel.org"
+target="_top">http://kernel.org</a>.</p>
+
+<p>More information can be found in the man pages for each of these commands, plus the
+<tt class="FILENAME">rc.modules</tt> file.</p>
+</div>
+</div>
+
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