1364 lines
58 KiB
Text
1364 lines
58 KiB
Text
<!--
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The FreeBSD Documentation Project
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$FreeBSD$
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-->
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<chapter id="kernelconfig">
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<chapterinfo>
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<authorgroup>
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<author>
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<firstname>Jim</firstname>
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<surname>Mock</surname>
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<contrib>Updated and restructured by </contrib>
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<!-- Mar 2000 -->
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</author>
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</authorgroup>
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<authorgroup>
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<author>
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<firstname>Jake</firstname>
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<surname>Hamby</surname>
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<contrib>Originally contributed by </contrib>
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<!-- 6 Oct 1995 -->
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</author>
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</authorgroup>
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</chapterinfo>
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<title>Configuring the FreeBSD Kernel</title>
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<sect1 id="kernelconfig-synopsis">
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<title>Synopsis</title>
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<indexterm>
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<primary>kernel</primary>
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<secondary>building a custom kernel</secondary>
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</indexterm>
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<para>The kernel is the core of the &os; operating system. It is
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responsible for managing memory, enforcing security controls,
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networking, disk access, and much more. While more and more of &os;
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becomes dynamically configurable it is still occasionally necessary to
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reconfigure and recompile your kernel.</para>
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<para>After reading this chapter, you will know:</para>
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<itemizedlist>
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<listitem>
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<para>Why you might need to build a custom kernel.</para>
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</listitem>
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<listitem>
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<para>How to write a kernel configuration file, or alter an existing
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configuration file.</para>
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</listitem>
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<listitem>
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<para>How to use the kernel configuration file to create and build a
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new kernel.</para>
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</listitem>
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<listitem>
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<para>How to install the new kernel.</para>
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</listitem>
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<listitem>
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<para>How to troubleshoot if things go wrong.</para>
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</listitem>
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</itemizedlist>
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<para>All of the commands listed within this chapter by way of example
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should be executed as <username>root</username> in order to
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succeed.</para>
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</sect1>
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<sect1 id="kernelconfig-custom-kernel">
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<title>Why Build a Custom Kernel?</title>
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<para>Traditionally, &os; has had what is called a
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<quote>monolithic</quote> kernel. This means that the kernel was one
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large program, supported a fixed list of devices, and if you wanted to
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change the kernel's behavior then you had to compile a new kernel, and
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then reboot your computer with the new kernel.</para>
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<para>Today, &os; is rapidly moving to a model where much of the
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kernel's functionality is contained in modules which can be
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dynamically loaded and unloaded from the kernel as necessary.
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This allows the kernel to adapt to new hardware suddenly
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becoming available (such as PCMCIA cards in a laptop), or for
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new functionality to be brought into the kernel that was not
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necessary when the kernel was originally compiled. This is
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known as a modular kernel.</para>
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<para>Despite this, it is still necessary to carry out some static kernel
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configuration. In some cases this is because the functionality is so
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tied to the kernel that it can not be made dynamically loadable. In
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others it may simply be because no one has yet taken the time to write a
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dynamic loadable kernel module for that functionality.</para>
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<para>Building a custom kernel is one of the most important rites of
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passage nearly every BSD user must endure. This process, while
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time consuming, will provide many benefits to your &os; system.
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Unlike the <filename>GENERIC</filename> kernel, which must support a
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wide range of hardware, a custom kernel only contains support for
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<emphasis>your</emphasis> PC's hardware. This has a number of
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benefits, such as:</para>
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<itemizedlist>
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<listitem>
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<para>Faster boot time. Since the kernel will only probe the
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hardware you have on your system, the time it takes your system to
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boot can decrease dramatically.</para>
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</listitem>
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<listitem>
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<para>Lower memory usage. A custom kernel often uses less memory
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than the <filename>GENERIC</filename> kernel, which is important
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because the kernel must always be present in real
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memory. For this reason, a custom kernel is especially useful
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on a system with a small amount of RAM.</para>
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</listitem>
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<listitem>
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<para>Additional hardware support. A custom kernel allows you to
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add in support for devices which are not
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present in the <filename>GENERIC</filename> kernel, such as
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sound cards.</para>
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</listitem>
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</itemizedlist>
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</sect1>
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<sect1 id="kernelconfig-building">
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<title>Building and Installing a Custom Kernel</title>
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<indexterm>
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<primary>kernel</primary>
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<secondary>building / installing</secondary>
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</indexterm>
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<para>First, let us take a quick tour of the kernel build directory.
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All directories mentioned will be relative to the main
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<filename>/usr/src/sys</filename> directory, which is also
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accessible through the path name <filename>/sys</filename>. There are a number of
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subdirectories here representing different parts of the kernel, but
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the most important for our purposes are
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<filename><replaceable>arch</replaceable>/conf</filename>, where you
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will edit your custom kernel configuration, and
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<filename>compile</filename>, which is the staging area where your
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kernel will be built. <replaceable>arch</replaceable> represents
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one of <filename>i386</filename>, <filename>alpha</filename>,
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<filename>amd64</filename>, <filename>ia64</filename>,
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<filename>powerpc</filename>, <filename>sparc64</filename>, or
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<filename>pc98</filename> (an alternative development branch of PC
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hardware, popular in Japan). Everything inside a particular
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architecture's directory deals with that architecture only; the rest
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of the code is machine independent code common to all platforms to which &os; could
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potentially be ported. Notice the logical organization of the
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directory structure, with each supported device, file system, and
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option in its own subdirectory.</para>
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<para>This chapter assumes that you are using the i386 architecture
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in the examples. If this is not the case for your situation,
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make appropriate adjustments to the path names for your system's
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architecture.</para>
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<note>
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<para>If there is <emphasis>not</emphasis> a
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<filename>/usr/src/sys</filename> directory on your system,
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then the kernel source has not been installed. The easiest
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way to do this is by running
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<command>sysinstall</command> as
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<username>root</username>, choosing
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<guimenuitem>Configure</guimenuitem>, then
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<guimenuitem>Distributions</guimenuitem>, then
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<guimenuitem>src</guimenuitem>, then
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<guimenuitem>base</guimenuitem> and
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<guimenuitem>sys</guimenuitem>. If you have an aversion to
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<application>sysinstall</application> and you have access to
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an <quote>official</quote> &os; CDROM, then you can also
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install the source from the command line:</para>
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<screen>&prompt.root; <userinput>mount /cdrom</userinput>
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&prompt.root; <userinput>mkdir -p /usr/src/sys</userinput>
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&prompt.root; <userinput>ln -s /usr/src/sys /sys</userinput>
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&prompt.root; <userinput>cat /cdrom/src/ssys.[a-d]* | tar -xzvf -</userinput>
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&prompt.root; <userinput>cat /cdrom/src/sbase.[a-d]* | tar -xzvf -</userinput></screen>
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</note>
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<para>Next, move to the
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<filename><replaceable>arch</replaceable>/conf</filename> directory
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and copy the <filename>GENERIC</filename> configuration file to the
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name you want to give your kernel. For example:</para>
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<screen>&prompt.root; <userinput>cd /usr/src/sys/<replaceable>i386</replaceable>/conf</userinput>
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&prompt.root; <userinput>cp GENERIC MYKERNEL</userinput></screen>
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<para>Traditionally, this name is in all capital letters and, if you
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are maintaining multiple &os; machines with different hardware,
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it is a good idea to name it after your machine's hostname. We will
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call it <filename>MYKERNEL</filename> for the purpose of this
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example.</para>
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<tip>
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<para>Storing your kernel configuration file directly under
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<filename>/usr/src</filename> can be a bad idea. If you are
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experiencing problems it can be tempting to just delete
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<filename>/usr/src</filename> and start again. After doing this,
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it usually only takes a few seconds for
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you to realize that you have deleted your custom kernel
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configuration file. Also, do not edit <filename>GENERIC</filename>
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directly, as it may get overwritten the next time you
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<link linkend="cutting-edge">update your source tree</link>, and
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your kernel modifications will be lost.</para>
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<para>You might want to keep your kernel configuration file
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elsewhere, and then create a symbolic link to the file in
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the <filename><replaceable>i386</replaceable></filename>
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directory.</para>
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<para>For example:</para>
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<screen>&prompt.root; <userinput>cd /usr/src/sys/<replaceable>i386</replaceable>/conf</userinput>
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&prompt.root; <userinput>mkdir /root/kernels</userinput>
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&prompt.root; <userinput>cp GENERIC /root/kernels/<replaceable>MYKERNEL</replaceable></userinput>
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&prompt.root; <userinput>ln -s /root/kernels/<replaceable>MYKERNEL</replaceable></userinput></screen>
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</tip>
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<para>Now, edit <filename>MYKERNEL</filename> with your favorite text
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editor. If you are just starting out, the only editor available
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will probably be <application>vi</application>, which is too complex to
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explain here, but is covered well in many books in the <link
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linkend="bibliography">bibliography</link>. However, &os; does
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offer an easier editor called <application>ee</application> which, if
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you are a beginner, should be your editor of choice. Feel free to
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change the comment lines at the top to reflect your configuration or
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the changes you have made to differentiate it from
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<filename>GENERIC</filename>.</para>
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<indexterm><primary>SunOS</primary></indexterm>
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<para>If you have built a kernel under &sunos; or some other BSD
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operating system, much of this file will be very familiar to you.
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If you are coming from some other operating system such as DOS, on
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the other hand, the <filename>GENERIC</filename> configuration file
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might seem overwhelming to you, so follow the descriptions in the
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<link linkend="kernelconfig-config">Configuration File</link>
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section slowly and carefully.</para>
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<note>
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<para>If you <link
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linkend="cutting-edge">sync your source tree</link> with the
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latest sources of the &os; project,
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be sure to always check the file
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<filename>/usr/src/UPDATING</filename> before you perform any update
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steps. This file describes any important issues or areas
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requiring special attention within the updated source code.
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<filename>/usr/src/UPDATING</filename> always matches
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your version of the &os; source, and is therefore more up to date
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with new information than this handbook.</para>
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</note>
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<para>You must now compile the source code for the kernel.</para>
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<procedure>
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<title>Building a Kernel</title>
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<step>
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<para>Change to the <filename
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role="directory">/usr/src</filename> directory:</para>
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<screen>&prompt.root; <userinput>cd /usr/src</userinput></screen>
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</step>
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<step>
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<para>Compile the kernel:</para>
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<screen>&prompt.root; <userinput>make buildkernel KERNCONF=<replaceable>MYKERNEL</replaceable></userinput></screen>
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</step>
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<step>
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<para>Install the new kernel:</para>
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<screen>&prompt.root; <userinput>make installkernel KERNCONF=<replaceable>MYKERNEL</replaceable></userinput></screen>
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</step>
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</procedure>
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<note>
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<para>It is required to have full &os; source tree to build the
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kernel.</para>
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</note>
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<tip>
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<para>By default, when you build a custom kernel,
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<emphasis>all</emphasis> kernel modules will be rebuilt as well.
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If you want to update a kernel faster or to build only custom
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modules, you should edit <filename>/etc/make.conf</filename>
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before starting to build the kernel:</para>
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<programlisting>MODULES_OVERRIDE = linux acpi sound/sound sound/driver/ds1 ntfs</programlisting>
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<para>This variable sets up a list of modules to build instead
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of all of them. For other variables which you may find useful
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in the process of building kernel, refer to &man.make.conf.5;
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manual page.</para>
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</tip>
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<indexterm>
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<primary><filename class="directory">/boot/kernel.old</filename></primary>
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</indexterm>
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<para>The new kernel will be copied to the <filename
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class="directory">/boot/kernel</filename> directory as
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<filename>/boot/kernel/kernel</filename> and the old kernel will be moved to
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<filename>/boot/kernel.old/kernel</filename>. Now, shutdown the system and
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reboot to use your new kernel. If something goes wrong, there are
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some <link linkend="kernelconfig-trouble">troubleshooting</link>
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instructions at the end of this chapter that you may find useful. Be sure to read the
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section which explains how to recover in case your new kernel <link
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linkend="kernelconfig-noboot">does not boot</link>.</para>
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<note>
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<para>Other files relating to the boot process, such as the boot
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&man.loader.8; and configuration are stored in
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<filename>/boot</filename>. Third party or custom modules
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can be placed in <filename class="directory">/boot/kernel</filename>, although
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users should be aware that keeping modules in sync with the
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compiled kernel is very important. Modules not intended
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to run with the compiled kernel may result in instability
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or incorrectness.</para>
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</note>
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</sect1>
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<sect1 id="kernelconfig-config">
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<sect1info>
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<authorgroup>
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<author>
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<firstname>Joel</firstname>
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<surname>Dahl</surname>
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<contrib>Updated for &os; 6.X by </contrib>
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</author>
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</authorgroup>
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</sect1info>
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<title>The Configuration File</title>
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<indexterm>
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<primary>kernel</primary>
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<secondary>NOTES</secondary>
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</indexterm>
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<indexterm><primary>NOTES</primary></indexterm>
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<indexterm>
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<primary>kernel</primary>
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<secondary>configuration file</secondary>
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</indexterm>
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<para>The general format of a configuration file is quite simple.
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Each line contains a keyword and one or more arguments. For
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simplicity, most lines only contain one argument. Anything
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following a <literal>#</literal> is considered a comment and
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ignored. The following sections describe each keyword, in
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the order they are listed in <filename>GENERIC</filename>.
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<anchor
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id="kernelconfig-options"> For an exhaustive list of architecture
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dependent options and devices, see the <filename>NOTES</filename>
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file in the same directory as the <filename>GENERIC</filename> file. For
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architecture independent options, see
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<filename>/usr/src/sys/conf/NOTES</filename>.</para>
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<note>
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<para>To build a file which contains all available options,
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as normally done for testing purposes, run the following
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command as <username>root</username>:</para>
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<screen>&prompt.root; <userinput>cd /usr/src/sys/<replaceable>i386</replaceable>/conf && make LINT</userinput></screen>
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</note>
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<indexterm>
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<primary>kernel</primary>
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<secondary>configuration file</secondary>
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</indexterm>
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<para>The following is an example of the <filename>GENERIC</filename> kernel
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configuration file with various additional comments where needed for
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clarity. This example should match your copy in
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<filename>/usr/src/sys/<replaceable>i386</replaceable>/conf/GENERIC</filename>
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fairly closely.</para>
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<indexterm>
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<primary>kernel options</primary>
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<secondary>machine</secondary>
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</indexterm>
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<programlisting>machine i386</programlisting>
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<para>This is the machine architecture. It must be either
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<literal>alpha</literal>, <literal>amd64</literal>,
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<literal>i386</literal>, <literal>ia64</literal>,
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<literal>pc98</literal>, <literal>powerpc</literal>, or
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<literal>sparc64</literal>.</para>
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<indexterm>
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<primary>kernel options</primary>
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<secondary>cpu</secondary>
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</indexterm>
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<programlisting>cpu I486_CPU
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cpu I586_CPU
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cpu I686_CPU</programlisting>
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<para>The above option specifies the type of CPU you have in your
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system. You may have multiple instances of the CPU line (if, for
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example, you are not sure whether you should use
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<literal>I586_CPU</literal> or <literal>I686_CPU</literal>),
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but for a custom kernel it is best to specify only the CPU
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you have. If you are unsure of your CPU type, you can check the
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<filename>/var/run/dmesg.boot</filename> file to view your boot
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messages.</para>
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<indexterm>
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<primary>kernel options</primary>
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<secondary>ident</secondary>
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</indexterm>
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<programlisting>ident GENERIC</programlisting>
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<para>This is the identification of the kernel. You should change
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this to whatever you named your kernel,
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i.e. <literal>MYKERNEL</literal> if you have followed the
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instructions of the previous examples. The value you put in the
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<literal>ident</literal> string will print when you boot up the
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kernel, so it is useful to give the new kernel a different name if you
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want to keep it separate from your usual kernel (e.g., you want to
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build an experimental kernel).</para>
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<programlisting>#To statically compile in device wiring instead of /boot/device.hints
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#hints "GENERIC.hints" # Default places to look for devices.</programlisting>
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<para>The &man.device.hints.5; is
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used to configure options of the device drivers. The default
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location that &man.loader.8; will check at boot time is
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<filename>/boot/device.hints</filename>. Using the
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<literal>hints</literal> option you can compile these hints
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statically into your kernel. Then there is no need to create a
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<filename>device.hints</filename> file in
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<filename>/boot</filename>.</para>
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<!-- XXX: Add a comment here that explains when compiling hints into
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the kernel is a good idea and why. -->
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<programlisting>makeoptions DEBUG=-g # Build kernel with gdb(1) debug symbols</programlisting>
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<para>The normal build process of &os; includes
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debugging information when building the kernel with the
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the <option>-g</option> option, which enables debugging
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information when passed to &man.gcc.1;.</para>
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<programlisting>options SCHED_4BSD # 4BSD scheduler</programlisting>
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<para>The traditional and default system scheduler for &os;. Keep this.</para>
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<programlisting>options PREEMPTION # Enable kernel thread preemption</programlisting>
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<para>Allows threads that are in the kernel to be preempted
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by higher priority threads. It helps with interactivity and
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allows interrupt threads to run sooner rather than waiting.</para>
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<programlisting>options INET # InterNETworking</programlisting>
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<para>Networking support. Leave this in, even if you do not plan to
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be connected to a network. Most programs require at least loopback
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networking (i.e., making network connections within your PC), so
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this is essentially mandatory.</para>
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<programlisting>options INET6 # IPv6 communications protocols</programlisting>
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<para>This enables the IPv6 communication protocols.</para>
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<programlisting>options FFS # Berkeley Fast Filesystem</programlisting>
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<para>This is the basic hard drive file system. Leave it in if you
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boot from the hard disk.</para>
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<programlisting>options SOFTUPDATES # Enable FFS Soft Updates support</programlisting>
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|
|
<para>This option enables Soft Updates in the kernel, this will
|
|
help speed up write access on the disks. Even when this
|
|
functionality is provided by the kernel, it must be turned on
|
|
for specific disks. Review the output from &man.mount.8; to see
|
|
if Soft Updates is enabled for your system disks. If you do not
|
|
see the <literal>soft-updates</literal> option then you will
|
|
need to activate it using the &man.tunefs.8; (for existing
|
|
file systems) or &man.newfs.8; (for new file systems)
|
|
commands.</para>
|
|
|
|
<programlisting>options UFS_ACL # Support for access control lists</programlisting>
|
|
|
|
<para>This option enables kernel support
|
|
for access control lists. This relies on the use of extended
|
|
attributes and <acronym>UFS2</acronym>, and the feature is described
|
|
in detail in <xref linkend="fs-acl">. <acronym>ACL</acronym>s are
|
|
enabled by default and should not be
|
|
disabled in the kernel if they have been used previously on a file
|
|
system, as this will remove the access control lists, changing the
|
|
way files are protected in unpredictable ways.</para>
|
|
|
|
<programlisting>options UFS_DIRHASH # Improve performance on big directories</programlisting>
|
|
|
|
<para>This option includes functionality to speed up disk
|
|
operations on large directories, at the expense of using
|
|
additional memory. You would normally keep this for a large
|
|
server, or interactive workstation, and remove it if you are
|
|
using &os; on a smaller system where memory is at a premium and
|
|
disk access speed is less important, such as a firewall.</para>
|
|
|
|
<programlisting>options MD_ROOT # MD is a potential root device</programlisting>
|
|
|
|
<para>This option enables support for a memory backed virtual disk
|
|
used as a root device.</para>
|
|
|
|
<indexterm>
|
|
<primary>kernel options</primary>
|
|
<secondary>NFS</secondary>
|
|
</indexterm>
|
|
<indexterm>
|
|
<primary>kernel options</primary>
|
|
<secondary>NFS_ROOT</secondary>
|
|
</indexterm>
|
|
<programlisting>options NFSCLIENT # Network Filesystem Client
|
|
options NFSSERVER # Network Filesystem Server
|
|
options NFS_ROOT # NFS usable as /, requires NFSCLIENT</programlisting>
|
|
|
|
<para>The network file system. Unless you plan to mount partitions
|
|
from a &unix; file server over TCP/IP, you can comment these
|
|
out.</para>
|
|
|
|
<indexterm>
|
|
<primary>kernel options</primary>
|
|
<secondary>MSDOSFS</secondary>
|
|
</indexterm>
|
|
<programlisting>options MSDOSFS # MSDOS Filesystem</programlisting>
|
|
|
|
<para>The &ms-dos; file system. Unless you plan to mount a DOS formatted
|
|
hard drive partition at boot time, you can safely comment this out.
|
|
It will be automatically loaded the first time you mount a DOS
|
|
partition, as described above. Also, the excellent
|
|
<filename role="package">emulators/mtools</filename> software
|
|
allows you to access DOS floppies without having to mount and
|
|
unmount them (and does not require <literal>MSDOSFS</literal> at
|
|
all).</para>
|
|
|
|
<programlisting>options CD9660 # ISO 9660 Filesystem</programlisting>
|
|
|
|
<para>The ISO 9660 file system for CDROMs. Comment it out if you do
|
|
not have a CDROM drive or only mount data CDs occasionally (since it
|
|
will be dynamically loaded the first time you mount a data CD).
|
|
Audio CDs do not need this file system.</para>
|
|
|
|
<programlisting>options PROCFS # Process filesystem (requires PSEUDOFS)</programlisting>
|
|
|
|
<para>The process file system. This is a <quote>pretend</quote>
|
|
file system mounted on <filename>/proc</filename> which allows
|
|
programs like &man.ps.1; to give you more information on what
|
|
processes are running. Use of <literal>PROCFS</literal>
|
|
is not required under most circumstances, as most
|
|
debugging and monitoring tools have been adapted to run without
|
|
<literal>PROCFS</literal>: installs will not mount this file
|
|
system by default.</para>
|
|
|
|
<programlisting>options PSEUDOFS # Pseudo-filesystem framework</programlisting>
|
|
|
|
<para>6.X kernels making use of <literal>PROCFS</literal> must also
|
|
include support for <literal>PSEUDOFS</literal>.</para>
|
|
|
|
<programlisting>options GEOM_GPT # GUID Partition Tables.</programlisting>
|
|
|
|
<para>This option brings the ability to have a large number of
|
|
partitions on a single disk.</para>
|
|
|
|
<programlisting>options COMPAT_43 # Compatible with BSD 4.3 [KEEP THIS!]</programlisting>
|
|
|
|
<para>Compatibility with 4.3BSD. Leave this in; some programs will
|
|
act strangely if you comment this out.</para>
|
|
|
|
<programlisting>options COMPAT_FREEBSD4 # Compatible with &os;4</programlisting>
|
|
|
|
<para>This option is required on &os; 5.X &i386; and Alpha systems
|
|
to support applications compiled on older versions of &os;
|
|
that use older system call interfaces. It is recommended that
|
|
this option be used on all &i386; and Alpha systems that may
|
|
run older applications; platforms that gained support only in
|
|
5.X, such as ia64 and &sparc64;, do not require this option.</para>
|
|
|
|
<programlisting>options SCSI_DELAY=5000 # Delay (in ms) before probing SCSI</programlisting>
|
|
|
|
<para>This causes the kernel to pause for 5 seconds before probing
|
|
each SCSI device in your system. If you only have IDE hard drives,
|
|
you can ignore this, otherwise you can try to lower this
|
|
number, to speed up booting. Of course, if
|
|
you do this and &os; has trouble recognizing your SCSI devices,
|
|
you will have to raise it again.</para>
|
|
|
|
<programlisting>options KTRACE # ktrace(1) support</programlisting>
|
|
|
|
<para>This enables kernel process tracing, which is useful in
|
|
debugging.</para>
|
|
|
|
<programlisting>options SYSVSHM # SYSV-style shared memory</programlisting>
|
|
|
|
<para>This option provides for System V shared memory. The most
|
|
common use of this is the XSHM extension in X, which many
|
|
graphics-intensive programs will automatically take advantage of for
|
|
extra speed. If you use X, you will definitely want to include
|
|
this.</para>
|
|
|
|
<programlisting>options SYSVMSG # SYSV-style message queues</programlisting>
|
|
|
|
<para>Support for System V messages. This option only adds
|
|
a few hundred bytes to the kernel.</para>
|
|
|
|
<programlisting>options SYSVSEM # SYSV-style semaphores</programlisting>
|
|
|
|
<para>Support for System V semaphores. Less commonly used but only
|
|
adds a few hundred bytes to the kernel.</para>
|
|
|
|
<note>
|
|
<para>The <option>-p</option> option of the &man.ipcs.1; command will
|
|
list any processes using each of these System V facilities.</para>
|
|
</note>
|
|
|
|
<programlisting>options _KPOSIX_PRIORITY_SCHEDULING # POSIX P1003_1B real-time extensions</programlisting>
|
|
|
|
<para>Real-time extensions added in the 1993 &posix;. Certain
|
|
applications in the Ports Collection use these
|
|
(such as <application>&staroffice;</application>).</para>
|
|
|
|
<programlisting>options KBD_INSTALL_CDEV # install a CDEV entry in /dev</programlisting>
|
|
|
|
<para>This option is related to the keyboard. It installs a CDEV entry
|
|
in <filename>/dev</filename>.</para>
|
|
|
|
<programlisting>options AHC_REG_PRETTY_PRINT # Print register bitfields in debug
|
|
# output. Adds ~128k to driver.
|
|
options AHD_REG_PRETTY_PRINT # Print register bitfields in debug
|
|
# output. Adds ~215k to driver.</programlisting>
|
|
|
|
<para>This helps debugging by printing easier register definitions for
|
|
reading.</para>
|
|
|
|
<programlisting>options ADAPTIVE_GIANT # Giant mutex is adaptive.</programlisting>
|
|
|
|
<para>Giant is the name of a mutual exclusion mechanism (a sleep mutex)
|
|
that protects a large set of kernel resources. Today, this is an
|
|
unacceptable performance bottleneck which is actively being replaced
|
|
with locks that protect individual resources. The
|
|
<literal>ADAPTIVE_GIANT</literal> option causes Giant to be included
|
|
in the set of mutexes adaptively spun on. That is, when a thread
|
|
wants to lock the Giant mutex, but it is already locked by a thread
|
|
on another CPU, the first thread will keep running and wait for the
|
|
lock to be released. Normally, the thread would instead go back to
|
|
sleep and wait for its next chance to run. If you are not sure,
|
|
leave this in.</para>
|
|
|
|
<indexterm>
|
|
<primary>kernel options</primary>
|
|
<secondary>SMP</secondary>
|
|
</indexterm>
|
|
<programlisting>device apic # I/O APIC</programlisting>
|
|
|
|
<para>The apic device enables the use of the I/O APIC for interrupt
|
|
delivery. The apic device can be used in both UP and SMP kernels, but
|
|
is required for SMP kernels. Add <literal>options SMP</literal> to
|
|
include support for multiple processors.</para>
|
|
|
|
<note>
|
|
<para>The apic device exists only on the i386 architecture, this
|
|
configuration line should not be used on other
|
|
architectures.</para>
|
|
</note>
|
|
|
|
<programlisting>device eisa</programlisting>
|
|
|
|
<para>Include this if you have an EISA motherboard. This enables
|
|
auto-detection and configuration support for all devices on the EISA
|
|
bus.</para>
|
|
|
|
<programlisting>device pci</programlisting>
|
|
|
|
<para>Include this if you have a PCI motherboard. This enables
|
|
auto-detection of PCI cards and gatewaying from the PCI to ISA
|
|
bus.</para>
|
|
|
|
<programlisting># Floppy drives
|
|
device fdc</programlisting>
|
|
|
|
<para>This is the floppy drive controller.</para>
|
|
|
|
<programlisting># ATA and ATAPI devices
|
|
device ata</programlisting>
|
|
|
|
<para>This driver supports all ATA and ATAPI devices. You only need
|
|
one <literal>device ata</literal> line for the kernel to detect all
|
|
PCI ATA/ATAPI devices on modern machines.</para>
|
|
|
|
<programlisting>device atadisk # ATA disk drives</programlisting>
|
|
|
|
<para>This is needed along with <literal>device ata</literal> for
|
|
ATA disk drives.</para>
|
|
|
|
<programlisting>device ataraid # ATA RAID drives</programlisting>
|
|
|
|
<para>This is needed along with <literal>device ata</literal> for ATA
|
|
RAID drives.</para>
|
|
|
|
<programlisting><anchor id="kernelconfig-atapi">
|
|
device atapicd # ATAPI CDROM drives</programlisting>
|
|
|
|
<para>This is needed along with <literal>device ata</literal> for
|
|
ATAPI CDROM drives.</para>
|
|
|
|
<programlisting>device atapifd # ATAPI floppy drives</programlisting>
|
|
|
|
<para>This is needed along with <literal>device ata</literal> for
|
|
ATAPI floppy drives.</para>
|
|
|
|
<programlisting>device atapist # ATAPI tape drives</programlisting>
|
|
|
|
<para>This is needed along with <literal>device ata</literal> for
|
|
ATAPI tape drives.</para>
|
|
|
|
<programlisting>options ATA_STATIC_ID # Static device numbering</programlisting>
|
|
|
|
<para>This makes the controller number static; without this,
|
|
the device numbers are dynamically allocated.</para>
|
|
|
|
<programlisting># SCSI Controllers
|
|
device ahb # EISA AHA1742 family
|
|
device ahc # AHA2940 and onboard AIC7xxx devices
|
|
device ahd # AHA39320/29320 and onboard AIC79xx devices
|
|
device amd # AMD 53C974 (Teckram DC-390(T))
|
|
device isp # Qlogic family
|
|
#device ispfw # Firmware for QLogic HBAs- normally a module
|
|
device mpt # LSI-Logic MPT-Fusion
|
|
#device ncr # NCR/Symbios Logic
|
|
device sym # NCR/Symbios Logic (newer chipsets)
|
|
device trm # Tekram DC395U/UW/F DC315U adapters
|
|
|
|
device adv # Advansys SCSI adapters
|
|
device adw # Advansys wide SCSI adapters
|
|
device aha # Adaptec 154x SCSI adapters
|
|
device aic # Adaptec 15[012]x SCSI adapters, AIC-6[23]60.
|
|
device bt # Buslogic/Mylex MultiMaster SCSI adapters
|
|
|
|
device ncv # NCR 53C500
|
|
device nsp # Workbit Ninja SCSI-3
|
|
device stg # TMC 18C30/18C50</programlisting>
|
|
|
|
<para>SCSI controllers. Comment out any you do not have in your
|
|
system. If you have an IDE only system, you can remove these
|
|
altogether.</para>
|
|
|
|
<programlisting># SCSI peripherals
|
|
device scbus # SCSI bus (required for SCSI)
|
|
device ch # SCSI media changers
|
|
device da # Direct Access (disks)
|
|
device sa # Sequential Access (tape etc)
|
|
device cd # CD
|
|
device pass # Passthrough device (direct SCSI access)
|
|
device ses # SCSI Environmental Services (and SAF-TE)</programlisting>
|
|
|
|
<para>SCSI peripherals. Again, comment out any you do not have, or if
|
|
you have only IDE hardware, you can remove them completely.</para>
|
|
|
|
<note>
|
|
<para>The USB &man.umass.4; driver and a few other drivers use
|
|
the SCSI subsystem even though they are not real SCSI devices.
|
|
Therefore make sure not to remove SCSI support, if any such
|
|
drivers are included in the kernel configuration.</para>
|
|
</note>
|
|
|
|
<programlisting># RAID controllers interfaced to the SCSI subsystem
|
|
device amr # AMI MegaRAID
|
|
device arcmsr # Areca SATA II RAID
|
|
device asr # DPT SmartRAID V, VI and Adaptec SCSI RAID
|
|
device ciss # Compaq Smart RAID 5*
|
|
device dpt # DPT Smartcache III, IV - See NOTES for options
|
|
device hptmv # Highpoint RocketRAID 182x
|
|
device rr232x # Highpoint RocketRAID 232x
|
|
device iir # Intel Integrated RAID
|
|
device ips # IBM (Adaptec) ServeRAID
|
|
device mly # Mylex AcceleRAID/eXtremeRAID
|
|
device twa # 3ware 9000 series PATA/SATA RAID
|
|
|
|
# RAID controllers
|
|
device aac # Adaptec FSA RAID
|
|
device aacp # SCSI passthrough for aac (requires CAM)
|
|
device ida # Compaq Smart RAID
|
|
device mfi # LSI MegaRAID SAS
|
|
device mlx # Mylex DAC960 family
|
|
device pst # Promise Supertrak SX6000
|
|
device twe # 3ware ATA RAID</programlisting>
|
|
|
|
<para>Supported RAID controllers. If you do not have any of these,
|
|
you can comment them out or remove them.</para>
|
|
|
|
<programlisting># atkbdc0 controls both the keyboard and the PS/2 mouse
|
|
device atkbdc # AT keyboard controller</programlisting>
|
|
|
|
<para>The keyboard controller (<literal>atkbdc</literal>) provides I/O
|
|
services for the AT keyboard and PS/2 style pointing devices. This
|
|
controller is required by the keyboard driver
|
|
(<literal>atkbd</literal>) and the PS/2 pointing device driver
|
|
(<literal>psm</literal>).</para>
|
|
|
|
<programlisting>device atkbd # AT keyboard</programlisting>
|
|
|
|
<para>The <literal>atkbd</literal> driver, together with
|
|
<literal>atkbdc</literal> controller, provides access to the AT 84
|
|
keyboard or the AT enhanced keyboard which is connected to the AT
|
|
keyboard controller.</para>
|
|
|
|
<programlisting>device psm # PS/2 mouse</programlisting>
|
|
|
|
<para>Use this device if your mouse plugs into the PS/2 mouse
|
|
port.</para>
|
|
|
|
<programlisting>device kbdmux # keyboard multiplexer</programlisting>
|
|
|
|
<para>Basic support for keyboard multiplexing.</para>
|
|
|
|
<programlisting>device vga # VGA video card driver</programlisting>
|
|
|
|
<para>The video card driver.</para>
|
|
|
|
<programlisting>
|
|
device splash # Splash screen and screen saver support</programlisting>
|
|
|
|
<para>Splash screen at start up! Screen savers require this
|
|
too.</para>
|
|
|
|
<programlisting># syscons is the default console driver, resembling an SCO console
|
|
device sc</programlisting>
|
|
|
|
<para><literal>sc</literal> is the default console driver and
|
|
resembles a SCO console. Since most full-screen programs access the
|
|
console through a terminal database library like
|
|
<filename>termcap</filename>, it should not matter whether you use
|
|
this or <literal>vt</literal>, the <literal>VT220</literal>
|
|
compatible console driver. When you log in, set your
|
|
<envar>TERM</envar> variable to <literal>scoansi</literal> if
|
|
full-screen programs have trouble running under this console.</para>
|
|
|
|
<programlisting># Enable this for the pcvt (VT220 compatible) console driver
|
|
#device vt
|
|
#options XSERVER # support for X server on a vt console
|
|
#options FAT_CURSOR # start with block cursor</programlisting>
|
|
|
|
<para>This is a VT220-compatible console driver, backward compatible to
|
|
VT100/102. It works well on some laptops which have hardware
|
|
incompatibilities with <literal>sc</literal>. Also set your
|
|
<envar>TERM</envar> variable to <literal>vt100</literal> or
|
|
<literal>vt220</literal> when you log in. This driver might also
|
|
prove useful when connecting to a large number of different machines
|
|
over the network, where <filename>termcap</filename> or
|
|
<filename>terminfo</filename> entries for the <literal>sc</literal>
|
|
device are often not available — <literal>vt100</literal>
|
|
should be available on virtually any platform.</para>
|
|
|
|
<programlisting>device agp</programlisting>
|
|
|
|
<para>Include this if you have an AGP card in the system. This
|
|
will enable support for AGP, and AGP GART for boards which
|
|
have these features.</para>
|
|
|
|
<indexterm>
|
|
<primary>APM</primary>
|
|
</indexterm>
|
|
|
|
<programlisting># Power management support (see NOTES for more options)
|
|
#device apm</programlisting>
|
|
|
|
<para>Advanced Power Management support. Useful for laptops,
|
|
although in &os; 5.X and above this is disabled in
|
|
<filename>GENERIC</filename> by default.</para>
|
|
|
|
<programlisting># Add suspend/resume support for the i8254.
|
|
device pmtimer</programlisting>
|
|
|
|
<para>Timer device driver for power management events, such as APM and
|
|
ACPI.</para>
|
|
|
|
<programlisting># PCCARD (PCMCIA) support
|
|
# PCMCIA and cardbus bridge support
|
|
device cbb # cardbus (yenta) bridge
|
|
device pccard # PC Card (16-bit) bus
|
|
device cardbus # CardBus (32-bit) bus</programlisting>
|
|
|
|
<para>PCMCIA support. You want this if you are using a
|
|
laptop.</para>
|
|
|
|
<programlisting># Serial (COM) ports
|
|
device sio # 8250, 16[45]50 based serial ports</programlisting>
|
|
|
|
<para>These are the serial ports referred to as
|
|
<devicename>COM</devicename> ports in the &ms-dos;/&windows;
|
|
world.</para>
|
|
|
|
<note>
|
|
<para>If you have an internal modem on <devicename>COM4</devicename>
|
|
and a serial port at <devicename>COM2</devicename>, you will have
|
|
to change the IRQ of the modem to 2 (for obscure technical reasons,
|
|
IRQ2 = IRQ 9) in order to access it
|
|
from &os;. If you have a multiport serial card, check the
|
|
manual page for &man.sio.4; for more information on the proper
|
|
values to add to your <filename>/boot/device.hints</filename>.
|
|
Some video cards (notably those based on
|
|
S3 chips) use IO addresses in the form of
|
|
<literal>0x*2e8</literal>, and since many cheap serial cards do
|
|
not fully decode the 16-bit IO address space, they clash with
|
|
these cards making the <devicename>COM4</devicename> port
|
|
practically unavailable.</para>
|
|
|
|
<para>Each serial port is required to have a unique IRQ (unless you
|
|
are using one of the multiport cards where shared interrupts are
|
|
supported), so the default IRQs for <devicename>COM3</devicename>
|
|
and <devicename>COM4</devicename> cannot be used.</para>
|
|
</note>
|
|
|
|
<programlisting># Parallel port
|
|
device ppc</programlisting>
|
|
|
|
<para>This is the ISA-bus parallel port interface.</para>
|
|
|
|
<programlisting>device ppbus # Parallel port bus (required)</programlisting>
|
|
|
|
<para>Provides support for the parallel port bus.</para>
|
|
|
|
<programlisting>device lpt # Printer</programlisting>
|
|
|
|
<para>Support for parallel port printers.</para>
|
|
|
|
<note>
|
|
<para>All three of the above are required to enable parallel printer
|
|
support.</para>
|
|
</note>
|
|
|
|
<programlisting>device plip # TCP/IP over parallel</programlisting>
|
|
|
|
<para>This is the driver for the parallel network interface.</para>
|
|
|
|
<programlisting>device ppi # Parallel port interface device</programlisting>
|
|
|
|
<para>The general-purpose I/O (<quote>geek port</quote>) + IEEE1284
|
|
I/O.</para>
|
|
|
|
<programlisting>#device vpo # Requires scbus and da</programlisting>
|
|
|
|
<indexterm><primary>zip drive</primary></indexterm>
|
|
<para>This is for an Iomega Zip drive. It requires
|
|
<literal>scbus</literal> and <literal>da</literal> support. Best
|
|
performance is achieved with ports in EPP 1.9 mode.</para>
|
|
|
|
<programlisting>#device puc</programlisting>
|
|
|
|
<para>Uncomment this device if you have a <quote>dumb</quote> serial
|
|
or parallel PCI card that is supported by the &man.puc.4; glue
|
|
driver.</para>
|
|
|
|
<programlisting># PCI Ethernet NICs.
|
|
device de # DEC/Intel DC21x4x (<quote>Tulip</quote>)
|
|
device em # Intel PRO/1000 adapter Gigabit Ethernet Card
|
|
device ixgb # Intel PRO/10GbE Ethernet Card
|
|
device txp # 3Com 3cR990 (<quote>Typhoon</quote>)
|
|
device vx # 3Com 3c590, 3c595 (<quote>Vortex</quote>)</programlisting>
|
|
|
|
<para>Various PCI network card drivers. Comment out or remove any of
|
|
these not present in your system.</para>
|
|
|
|
<programlisting># PCI Ethernet NICs that use the common MII bus controller code.
|
|
# NOTE: Be sure to keep the 'device miibus' line in order to use these NICs!
|
|
device miibus # MII bus support</programlisting>
|
|
|
|
<para>MII bus support is required for some PCI 10/100 Ethernet NICs,
|
|
namely those which use MII-compliant transceivers or implement
|
|
transceiver control interfaces that operate like an MII. Adding
|
|
<literal>device miibus</literal> to the kernel config pulls in
|
|
support for the generic miibus API and all of the PHY drivers,
|
|
including a generic one for PHYs that are not specifically handled
|
|
by an individual driver.</para>
|
|
|
|
<programlisting>device bce # Broadcom BCM5706/BCM5708 Gigabit Ethernet
|
|
device bfe # Broadcom BCM440x 10/100 Ethernet
|
|
device bge # Broadcom BCM570xx Gigabit Ethernet
|
|
device dc # DEC/Intel 21143 and various workalikes
|
|
device fxp # Intel EtherExpress PRO/100B (82557, 82558)
|
|
device lge # Level 1 LXT1001 gigabit ethernet
|
|
device nge # NatSemi DP83820 gigabit ethernet
|
|
device nve # nVidia nForce MCP on-board Ethernet Networking
|
|
device pcn # AMD Am79C97x PCI 10/100 (precedence over 'lnc')
|
|
device re # RealTek 8139C+/8169/8169S/8110S
|
|
device rl # RealTek 8129/8139
|
|
device sf # Adaptec AIC-6915 (<quote>Starfire</quote>)
|
|
device sis # Silicon Integrated Systems SiS 900/SiS 7016
|
|
device sk # SysKonnect SK-984x & SK-982x gigabit Ethernet
|
|
device ste # Sundance ST201 (D-Link DFE-550TX)
|
|
device ti # Alteon Networks Tigon I/II gigabit Ethernet
|
|
device tl # Texas Instruments ThunderLAN
|
|
device tx # SMC EtherPower II (83c170 <quote>EPIC</quote>)
|
|
device vge # VIA VT612x gigabit ethernet
|
|
device vr # VIA Rhine, Rhine II
|
|
device wb # Winbond W89C840F
|
|
device xl # 3Com 3c90x (<quote>Boomerang</quote>, <quote>Cyclone</quote>)</programlisting>
|
|
|
|
<para>Drivers that use the MII bus controller code.</para>
|
|
|
|
<programlisting># ISA Ethernet NICs. pccard NICs included.
|
|
device cs # Crystal Semiconductor CS89x0 NIC
|
|
# 'device ed' requires 'device miibus'
|
|
device ed # NE[12]000, SMC Ultra, 3c503, DS8390 cards
|
|
device ex # Intel EtherExpress Pro/10 and Pro/10+
|
|
device ep # Etherlink III based cards
|
|
device fe # Fujitsu MB8696x based cards
|
|
device ie # EtherExpress 8/16, 3C507, StarLAN 10 etc.
|
|
device lnc # NE2100, NE32-VL Lance Ethernet cards
|
|
device sn # SMC's 9000 series of Ethernet chips
|
|
device xe # Xircom pccard Ethernet
|
|
|
|
# ISA devices that use the old ISA shims
|
|
#device le</programlisting>
|
|
|
|
<para>ISA Ethernet drivers. See
|
|
<filename>/usr/src/sys/<replaceable>i386</replaceable>/conf/NOTES</filename> for details
|
|
of which cards are
|
|
supported by which driver.</para>
|
|
|
|
<programlisting># Wireless NIC cards
|
|
device wlan # 802.11 support
|
|
device an # Aironet 4500/4800 802.11 wireless NICs.
|
|
device awi # BayStack 660 and others
|
|
device ral # Ralink Technology RT2500 wireless NICs.
|
|
device wi # WaveLAN/Intersil/Symbol 802.11 wireless NICs.
|
|
#device wl # Older non 802.11 Wavelan wireless NIC.</programlisting>
|
|
|
|
<para>Support for various wireless cards.</para>
|
|
|
|
<programlisting># Pseudo devices
|
|
device loop # Network loopback</programlisting>
|
|
|
|
<para>This is the generic loopback device for TCP/IP. If you telnet
|
|
or FTP to <hostid>localhost</hostid> (a.k.a. <hostid
|
|
role="ipaddr">127.0.0.1</hostid>) it will come back at you through
|
|
this device. This is <emphasis>mandatory</emphasis>.</para>
|
|
|
|
<programlisting>device random # Entropy device</programlisting>
|
|
|
|
<para>Cryptographically secure random number generator.</para>
|
|
|
|
<programlisting>device ether # Ethernet support</programlisting>
|
|
|
|
<para><literal>ether</literal> is only needed if you have an Ethernet
|
|
card. It includes generic Ethernet protocol code.</para>
|
|
|
|
<programlisting>device sl # Kernel SLIP</programlisting>
|
|
|
|
<para><literal>sl</literal> is for SLIP support. This has been almost
|
|
entirely supplanted by PPP, which is easier to set up, better suited
|
|
for modem-to-modem connection, and more powerful.</para>
|
|
|
|
<programlisting>device ppp # Kernel PPP</programlisting>
|
|
|
|
<para>This is for kernel PPP support for dial-up connections. There
|
|
is also a version of PPP implemented as a userland application that
|
|
uses <literal>tun</literal> and offers more flexibility and features
|
|
such as demand dialing.</para>
|
|
|
|
<programlisting>device tun # Packet tunnel.</programlisting>
|
|
|
|
<para>This is used by the userland PPP software.
|
|
See
|
|
the <link linkend="userppp">PPP</link> section of this book for more
|
|
information.</para>
|
|
|
|
<programlisting><anchor id="kernelconfig-ptys">
|
|
device pty # Pseudo-ttys (telnet etc)</programlisting>
|
|
|
|
<para>This is a <quote>pseudo-terminal</quote> or simulated login port.
|
|
It is used by incoming <command>telnet</command> and
|
|
<command>rlogin</command> sessions,
|
|
<application>xterm</application>, and some other applications such
|
|
as <application>Emacs</application>.</para>
|
|
|
|
<programlisting>device md # Memory <quote>disks</quote></programlisting>
|
|
|
|
<para>Memory disk pseudo-devices.</para>
|
|
|
|
<programlisting>device gif # IPv6 and IPv4 tunneling</programlisting>
|
|
|
|
<para>This implements IPv6 over IPv4 tunneling, IPv4 over IPv6 tunneling,
|
|
IPv4 over IPv4 tunneling, and IPv6 over IPv6 tunneling. The
|
|
<literal>gif</literal> device is
|
|
<quote>auto-cloning</quote>, and will create device nodes as
|
|
needed.</para>
|
|
|
|
<programlisting>device faith # IPv6-to-IPv4 relaying (translation)</programlisting>
|
|
|
|
<para>This pseudo-device captures packets that are sent to it and
|
|
diverts them to the IPv4/IPv6 translation daemon.</para>
|
|
|
|
<programlisting># The `bpf' device enables the Berkeley Packet Filter.
|
|
# Be aware of the administrative consequences of enabling this!
|
|
# Note that 'bpf' is required for DHCP.
|
|
device bpf # Berkeley packet filter</programlisting>
|
|
|
|
<para>This is the Berkeley Packet Filter. This pseudo-device allows
|
|
network interfaces to be placed in promiscuous mode, capturing every
|
|
packet on a broadcast network (e.g., an Ethernet). These packets
|
|
can be captured to disk and or examined with the &man.tcpdump.1;
|
|
program.</para>
|
|
|
|
<note>
|
|
<para>The &man.bpf.4; device is also used by
|
|
&man.dhclient.8; to obtain the IP address of the default router
|
|
(gateway) and so on. If you use DHCP, leave this
|
|
uncommented.</para>
|
|
</note>
|
|
|
|
<programlisting># USB support
|
|
device uhci # UHCI PCI->USB interface
|
|
device ohci # OHCI PCI->USB interface
|
|
#device ehci # EHCI PCI->USB interface (USB 2.0)
|
|
device usb # USB Bus (required)
|
|
#device udbp # USB Double Bulk Pipe devices
|
|
device ugen # Generic
|
|
device uhid # <quote>Human Interface Devices</quote>
|
|
device ukbd # Keyboard
|
|
device ulpt # Printer
|
|
device umass # Disks/Mass storage - Requires scbus and da
|
|
device ums # Mouse
|
|
device urio # Diamond Rio 500 MP3 player
|
|
device uscanner # Scanners
|
|
# USB Ethernet, requires mii
|
|
device aue # ADMtek USB Ethernet
|
|
device axe # ASIX Electronics USB Ethernet
|
|
device cdce # Generic USB over Ethernet
|
|
device cue # CATC USB Ethernet
|
|
device kue # Kawasaki LSI USB Ethernet
|
|
device rue # RealTek RTL8150 USB Ethernet</programlisting>
|
|
|
|
<para>Support for various USB devices.</para>
|
|
|
|
<programlisting># FireWire support
|
|
device firewire # FireWire bus code
|
|
device sbp # SCSI over FireWire (Requires scbus and da)
|
|
device fwe # Ethernet over FireWire (non-standard!)</programlisting>
|
|
|
|
<para>Support for various Firewire devices.</para>
|
|
|
|
<para>For more information and additional devices supported by
|
|
&os;, see
|
|
<filename>/usr/src/sys/<replaceable>i386</replaceable>/conf/NOTES</filename>.</para>
|
|
|
|
<sect2>
|
|
<title>Large Memory Configurations (<acronym>PAE</acronym>)</title>
|
|
<indexterm>
|
|
<primary>Physical Address Extensions
|
|
(<acronym>PAE</acronym>)</primary>
|
|
<secondary>large memory</secondary>
|
|
</indexterm>
|
|
|
|
<para>Large memory configuration machines require access to
|
|
more than the 4 gigabyte limit on User+Kernel Virtual
|
|
Address (<acronym>KVA</acronym>) space. Due to this
|
|
limitation, Intel added support for 36-bit physical address
|
|
space access in the &pentium; Pro and later line of CPUs.</para>
|
|
|
|
<para>The Physical Address Extension (<acronym>PAE</acronym>)
|
|
capability of the &intel; &pentium; Pro and later CPUs
|
|
allows memory configurations of up to 64 gigabytes.
|
|
&os; provides support for this capability via the
|
|
<option>PAE</option> kernel configuration option, available
|
|
in all current release versions of &os;. Due to
|
|
the limitations of the Intel memory architecture, no distinction
|
|
is made for memory above or below 4 gigabytes. Memory allocated
|
|
above 4 gigabytes is simply added to the pool of available
|
|
memory.</para>
|
|
|
|
<para>To enable <acronym>PAE</acronym> support in the kernel,
|
|
simply add the following line to your kernel configuration
|
|
file:</para>
|
|
|
|
<programlisting>options PAE</programlisting>
|
|
|
|
<note>
|
|
<para>The <acronym>PAE</acronym> support in &os; is only
|
|
available for &intel; IA-32 processors. It should also be
|
|
noted, that the <acronym>PAE</acronym> support in &os; has
|
|
not received wide testing, and should be considered beta
|
|
quality compared to other stable features of &os;.</para>
|
|
</note>
|
|
|
|
<para><acronym>PAE</acronym> support in &os; has a few limitations:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>A process is not able to access more than 4
|
|
gigabytes of VM space.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><acronym>KLD</acronym> modules cannot be loaded into
|
|
a <acronym>PAE</acronym> enabled kernel, due to the
|
|
differences in the build framework of a module and the
|
|
kernel.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Device drivers that do not use the &man.bus.dma.9;
|
|
interface will cause data corruption in a
|
|
<acronym>PAE</acronym> enabled kernel and are not
|
|
recommended for use. For this reason, a
|
|
<filename>PAE</filename> kernel
|
|
configuration file is provided in &os; which
|
|
excludes all drivers not known to work in a <acronym>PAE</acronym> enabled
|
|
kernel.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Some system tunables determine memory resource usage
|
|
by the amount of available physical memory. Such
|
|
tunables can unnecessarily over-allocate due to the
|
|
large memory nature of a <acronym>PAE</acronym> system.
|
|
One such example is the <option>kern.maxvnodes</option>
|
|
sysctl, which controls the maximum number of vnodes allowed
|
|
in the kernel. It is advised to adjust this and other
|
|
such tunables to a reasonable value.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>It might be necessary to increase the kernel virtual
|
|
address (<acronym>KVA</acronym>) space or to reduce the
|
|
amount of specific kernel resource that is heavily used
|
|
(see above) in order to avoid <acronym>KVA</acronym>
|
|
exhaustion. The <option>KVA_PAGES</option> kernel option
|
|
can be used for increasing the
|
|
<acronym>KVA</acronym> space.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>For performance and stability concerns, it is advised to
|
|
consult the &man.tuning.7; manual page. The &man.pae.4;
|
|
manual page contains up-to-date information on &os;'s
|
|
<acronym>PAE</acronym> support.</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="kernelconfig-trouble">
|
|
<title>If Something Goes Wrong</title>
|
|
|
|
<para>There are five categories of trouble that can occur when
|
|
building a custom kernel. They are:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><command>config</command> fails:</term>
|
|
|
|
<listitem>
|
|
<para>If the &man.config.8; command fails when you
|
|
give it your kernel description, you have probably made a
|
|
simple error somewhere. Fortunately,
|
|
&man.config.8; will print the line number that it
|
|
had trouble with, so that you can quickly locate the line
|
|
containing the error. For example, if you see:</para>
|
|
|
|
<screen>config: line 17: syntax error</screen>
|
|
|
|
<para>Make sure the
|
|
keyword is typed correctly by comparing it to the
|
|
<filename>GENERIC</filename> kernel or another
|
|
reference.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><command>make</command> fails:</term>
|
|
|
|
<listitem>
|
|
<para>If the <command>make</command> command fails, it usually
|
|
signals an error in your kernel description which is not severe
|
|
enough for &man.config.8; to catch. Again, look
|
|
over your configuration, and if you still cannot resolve the
|
|
problem, send mail to the &a.questions; with your kernel
|
|
configuration, and it should be diagnosed quickly.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>The kernel does not boot:<anchor
|
|
id="kernelconfig-noboot"></term>
|
|
|
|
<listitem>
|
|
<para>If your new kernel does not boot, or fails to
|
|
recognize your devices, do not panic! Fortunately, &os; has
|
|
an excellent mechanism for recovering from incompatible
|
|
kernels. Simply choose the kernel you want to boot from at
|
|
the &os; boot loader. You can access this when the system
|
|
boot menu appears. Select the <quote>Escape to a loader
|
|
prompt</quote> option, number six. At the prompt, type
|
|
<command>unload kernel</command>
|
|
and then type
|
|
<command>boot /boot/<replaceable>kernel.old</replaceable>/kernel</command>,
|
|
or the filename of any other kernel that will boot properly.
|
|
When reconfiguring a kernel, it is always a good idea to keep
|
|
a kernel that is known to work on hand.</para>
|
|
|
|
<para>After booting with a good kernel you can check over your
|
|
configuration file and try to build it again. One helpful
|
|
resource is the <filename>/var/log/messages</filename> file
|
|
which records, among other things, all of the kernel messages
|
|
from every successful boot. Also, the &man.dmesg.8; command
|
|
will print the kernel messages from the current boot.</para>
|
|
|
|
<note>
|
|
<para>If you are having trouble building a kernel, make sure
|
|
to keep a <filename>GENERIC</filename>, or some other kernel
|
|
that is known to work on hand as a different name that will
|
|
not get erased on the next build. You cannot rely on
|
|
<filename>kernel.old</filename> because when installing a
|
|
new kernel, <filename>kernel.old</filename> is overwritten
|
|
with the last installed kernel which may be non-functional.
|
|
Also, as soon as possible, move the working kernel to the
|
|
proper <filename class="directory">/boot/kernel</filename>
|
|
location or commands such
|
|
as &man.ps.1; may not work properly. To do this, simply
|
|
rename the directory containing the good kernel:</para>
|
|
|
|
<screen>&prompt.root; <userinput>mv /boot/kernel /boot/kernel.bad</userinput>
|
|
&prompt.root; <userinput>mv /boot/<replaceable>kernel.good</replaceable> /boot/kernel</userinput></screen>
|
|
|
|
</note>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>The kernel works, but &man.ps.1; does not work
|
|
any more:</term>
|
|
|
|
<listitem>
|
|
<para>If you have installed a different version of the kernel
|
|
from the one that the system utilities have been built with,
|
|
for example, a -CURRENT kernel on a -RELEASE, many system-status
|
|
commands like &man.ps.1; and &man.vmstat.8; will not work any
|
|
more. You should <link linkend="makeworld">recompile and install
|
|
a world</link> built with the same version of the source tree as
|
|
your kernel. This is one reason it is
|
|
not normally a good idea to use a different version of the
|
|
kernel from the rest of the operating system.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect1>
|
|
</chapter>
|
|
|
|
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|
|
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