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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>Adding Swap Space</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="Configuration and Tuning" href="config-tuning.html" /><link rel="PREVIOUS" title="Tuning Kernel Limits"href="configtuning-kernel-limits.html" /><link rel="NEXT" title="Power and Resource Management" href="acpi-overview.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="configtuning-kernel-limits.html"accesskey="P">Prev</a></td><td width="80%" align="center" valign="bottom">Chapter 11 Configuration and Tuning</td><td width="10%" align="right" valign="bottom"><a href="acpi-overview.html"accesskey="N">Next</a></td></tr></table><hr align="LEFT" width="100%" /></div><div class="SECT1"><h1 class="SECT1"><a id="ADDING-SWAP-SPACE" name="ADDING-SWAP-SPACE">11.14 Adding SwapSpace</a></h1><p>No matter how well you plan, sometimes a system does not run as you expect. If youfind you need more swap space, it is simple enough to add. You have three ways toincrease swap space: adding a new hard drive, enabling swap over NFS, and creating a swapfile on an existing partition.</p><div class="SECT2"><h2 class="SECT2"><a id="NEW-DRIVE-SWAP" name="NEW-DRIVE-SWAP">11.14.1 Swap on a New HardDrive</a></h2><p>The best way to add swap, of course, is to use this as an excuse to add another harddrive. You can always use another hard drive, after all. If you can do this, go rereadthe discussion of swap space in <a href="configtuning-initial.html">Section 11.2</a> ofthe Handbook for some suggestions on how to best arrange your swap.</p></div><div class="SECT2"><h2 class="SECT2"><a id="NFS-SWAP" name="NFS-SWAP">11.14.2 Swapping over NFS</a></h2><p>Swapping over NFS is only recommended if you do not have a local hard disk to swap to.Swapping over NFS is slow and inefficient in versions of FreeBSD prior to 4.X. It isreasonably fast and efficient in 4.0-RELEASE and newer. Even with newer versions ofFreeBSD, NFS swapping will be limited by the available network bandwidth and puts anadditional burden on the NFS server.</p></div><div class="SECT2"><h2 class="SECT2"><a id="CREATE-SWAPFILE" name="CREATE-SWAPFILE">11.14.3Swapfiles</a></h2><p>You can create a file of a specified size to use as a swap file. In our example herewe will use a 64MB file called <tt class="FILENAME">/usr/swap0</tt>. You can use any nameyou want, of course.</p><div class="EXAMPLE"><a id="AEN16835" name="AEN16835"></a><p><b>Example 11-1. Creating a Swapfile on FreeBSD 4.X</b></p><ol type="1"><li><p>Be certain that your kernel configuration includes the vnode driver. It is <spanclass="emphasis"><i class="EMPHASIS">not</i></span> in recent versions of <ttclass="FILENAME">GENERIC</tt>.</p><pre class="PROGRAMLISTING">pseudo-device vn 1 #Vnode driver (turns a file into a device)</pre></li><li><p>Create a vn-device:</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbd class="USERINPUT">cd /dev</kbd><samp class="PROMPT">#</samp> <kbd class="USERINPUT">sh MAKEDEV vn0</kbd></pre></li><li><p>Create a swapfile (<tt class="FILENAME">/usr/swap0</tt>):</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbdclass="USERINPUT">dd if=/dev/zero of=/usr/swap0 bs=1024k count=64</kbd></pre></li><li><p>Set proper permissions on (<tt class="FILENAME">/usr/swap0</tt>):</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbd class="USERINPUT">chmod 0600 /usr/swap0</kbd></pre></li><li><p>Enable the swap file in <tt class="FILENAME">/etc/rc.conf</tt>:</p><pre class="PROGRAMLISTING">swapfile="/usr/swap0" # Set to name of swapfile if aux swapfile desired.</pre></li><li><p>Reboot the machine or to enable the swap file immediately, type:</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbdclass="USERINPUT">vnconfig -e /dev/vn0b /usr/swap0 swap</kbd></pre></li></ol></div><div class="EXAMPLE"><a id="AEN16871" name="AEN16871"></a><p><b>Example 11-2. Creating a Swapfile on FreeBSD 5.X</b></p><ol type="1"><li><p>Be certain that your kernel configuration includes the memory disk driver (<ahref="http://www.FreeBSD.org/cgi/man.cgi?query=md&sektion=4"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">md</span>(4)</span></a>). It is defaultin <tt class="FILENAME">GENERIC</tt> kernel.</p><pre class="PROGRAMLISTING">device md # Memory "disks"</pre></li><li><p>Create a swapfile (<tt class="FILENAME">/usr/swap0</tt>):</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbdclass="USERINPUT">dd if=/dev/zero of=/usr/swap0 bs=1024k count=64</kbd></pre></li><li><p>Set proper permissions on (<tt class="FILENAME">/usr/swap0</tt>):</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbd class="USERINPUT">chmod 0600 /usr/swap0</kbd></pre></li><li><p>Enable the swap file in <tt class="FILENAME">/etc/rc.conf</tt>:</p><pre class="PROGRAMLISTING">swapfile="/usr/swap0" # Set to name of swapfile if aux swapfile desired.</pre></li><li><p>Reboot the machine or to enable the swap file immediately, type:</p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbdclass="USERINPUT">mdconfig -a -t vnode -f /usr/swap0 -u 0 && swapon /dev/md0</kbd></pre></li></ol></div></div></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="configtuning-kernel-limits.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="acpi-overview.html"accesskey="N">Next</a></td></tr><tr><td width="33%" align="left" valign="top">Tuning Kernel Limits</td><td width="34%" align="center" valign="top"><a href="config-tuning.html"accesskey="U">Up</a></td><td width="33%" align="right" valign="top">Power and Resource Management</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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