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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta name="generator" content="HTML Tidy, see www.w3.org" /><title>Why Build a Custom Kernel?</title><meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /><link rel="HOME" title="FreeBSD Handbook" href="index.html" /><link rel="UP" title="Configuring the FreeBSD Kernel" href="kernelconfig.html" /><link rel="PREVIOUS" title="Configuring the FreeBSD Kernel" href="kernelconfig.html" /><link rel="NEXT" title="Building and Installing a Custom Kernel"href="kernelconfig-building.html" /><link rel="STYLESHEET" type="text/css" href="docbook.css" /></head><body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"alink="#0000FF"><div class="NAVHEADER"><table summary="Header navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><th colspan="3" align="center">FreeBSD Handbook</th></tr><tr><td width="10%" align="left" valign="bottom"><a href="kernelconfig.html"accesskey="P">Prev</a></td><td width="80%" align="center" valign="bottom">Chapter 8 Configuring the FreeBSDKernel</td><td width="10%" align="right" valign="bottom"><a href="kernelconfig-building.html"accesskey="N">Next</a></td></tr></table><hr align="LEFT" width="100%" /></div><div class="SECT1"><h1 class="SECT1"><a id="KERNELCONFIG-CUSTOM-KERNEL"name="KERNELCONFIG-CUSTOM-KERNEL">8.2 Why Build a Custom Kernel?</a></h1><p>Traditionally, FreeBSD has had what is called a ``monolithic'' kernel. This means thatthe kernel was one large program, supported a fixed list of devices, and if you wanted tochange the kernel's behavior then you had to compile a new kernel, and then reboot yourcomputer with the new kernel.</p><p>Today, FreeBSD is rapidly moving to a model where much of the kernel's functionalityis contained in modules which can be dynamically loaded and unloaded from the kernel asnecessary. This allows the kernel to adapt to new hardware suddenly becoming available(such as PCMCIA cards in a laptop), or for new functionality to be brought into thekernel that was not necessary when the kernel was originally compiled. This is known as amodular kernel.</p><p>Despite this, it is still necessary to carry out some static kernel configuration. Insome cases this is because the functionality is so tied to the kernel that it can not bemade dynamically loadable. In others it may simply be because no one has yet taken thetime to write a dynamic loadable kernel module for that functionality.</p><p>Building a custom kernel is one of the most important rites of passage nearly everyBSD user must endure. This process, while time consuming, will provide many benefits toyour FreeBSD system. Unlike the <tt class="FILENAME">GENERIC</tt> kernel, which mustsupport a wide range of hardware, a custom kernel only contains support for <spanclass="emphasis"><i class="EMPHASIS">your</i></span> PC's hardware. This has a number ofbenefits, such as:</p><ul><li><p>Faster boot time. Since the kernel will only probe the hardware you have on yoursystem, the time it takes your system to boot can decrease dramatically.</p></li><li><p>Lower memory usage. A custom kernel often uses less memory than the <ttclass="FILENAME">GENERIC</tt> kernel, which is important because the kernel must alwaysbe present in real memory. For this reason, a custom kernel is especially useful on asystem with a small amount of RAM.</p></li><li><p>Additional hardware support. A custom kernel allows you to add in support for deviceswhich are not present in the <tt class="FILENAME">GENERIC</tt> kernel, such as soundcards.</p></li></ul></div><div class="NAVFOOTER"><hr align="LEFT" width="100%" /><table summary="Footer navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><td width="33%" align="left" valign="top"><a href="kernelconfig.html"accesskey="P">Prev</a></td><td width="34%" align="center" valign="top"><a href="index.html"accesskey="H">Home</a></td><td width="33%" align="right" valign="top"><a href="kernelconfig-building.html"accesskey="N">Next</a></td></tr><tr><td width="33%" align="left" valign="top">Configuring the FreeBSD Kernel</td><td width="34%" align="center" valign="top"><a href="kernelconfig.html"accesskey="U">Up</a></td><td width="33%" align="right" valign="top">Building and Installing a Custom Kernel</td></tr></table></div><p align="center"><small>This, and other documents, can be downloaded from <ahref="ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/">ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/</a>.</small></p><p align="center"><small>For questions about FreeBSD, read the <ahref="http://www.FreeBSD.org/docs.html">documentation</a> before contacting <<ahref="mailto:questions@FreeBSD.org">questions@FreeBSD.org</a>>.<br />For questions about this documentation, e-mail <<ahref="mailto:doc@FreeBSD.org">doc@FreeBSD.org</a>>.</small></p></body></html>⌨️ 快捷键说明
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