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     $FreeBSD: doc/zh_TW.Big5/books/handbook/config/chapter.sgml,v 1.4 2006/07/08 03:01:13 vanilla Exp $
     Original revision: 1.213
     Chased revision: 1.217
-->

<chapter id="config-tuning">

      <sect3>
	<title>Base Partitions</title>

	<para>用 &man.bsdlabel.8; 或 &man.sysinstall.8; 來規劃檔案系統時，請記住：
	  硬碟在傳輸資料方面，(由於結構為碟片因素)外圈會比內圈來得快些。
	  因此，建議把較小、常會存取的分割區儘量放外圈，而較大的分割區像是 
	  <filename>/usr</filename> 則應放在較內圈。

        kill -9 `cat /var/run/utility.pid`
        ;;
*)
        echo "Usage: `basename $0` {start|stop}" &gt;&2
        exit 64
        ;;
esac

	the supported hardware and even the possible problems that
	could occur.</para>

      <note>
	<para><filename>NOTES</filename> does not exist on
	  &os;&nbsp;4.X.  Instead, check the <filename>LINT</filename>
	  file for information about various network interfaces.  See
	  <xref linkend="kernelconfig-config"> for a more detailed
	  summary of <filename>NOTES</filename> versus
	<filename>LINT</filename>.</para>
      </note>

      <para>If you own a common card, most of the time you will not
	have to look very hard for a driver.  Drivers for common
	network cards are present in the <filename>GENERIC</filename>

      syntax:</para>

    <screen>&prompt.root; <userinput>sysctl kern.maxfiles=5000</userinput>
kern.maxfiles: 2088 -&gt; 5000</screen>

    <para>Settings of sysctl variables are usually either strings,
      numbers, or booleans (a  boolean being <literal>1</literal> for yes

 	</para>

 	<para>There are various other buffer-cache and VM page cache
 	  related sysctls.  We do not recommend modifying these values,
 	  the VM system does an extremely good job of
 	  automatically tuning itself.</para>
       </sect3>


	it is mounted.  A good time to enable Soft Updates is before any
	partitions have been mounted, in single-user mode.</para>

      <note><para>As of &os;&nbsp;4.5, it is possible to enable Soft Updates
	at filesystem creation time, through use of the <literal>-U</literal>
	option to &man.newfs.8;.</para></note>

      <para>Soft Updates drastically improves meta-data performance, mainly
        file creation and deletion, through the use of a memory cache.  We
        recommend to use Soft Updates on all of your file systems.  There

          connected at once, the resources needed may be similar to a
          high-scale web server.</para>

	<para>The system will auto-tune
	  <literal>maxusers</literal> for you if you explicitly set it to
	  <literal>0</literal><footnote>
	    <para>The auto-tuning algorithm sets
	      <literal>maxusers</literal> equal to the amount of memory in the
	      system, with a minimum of 32, and a maximum of 384.</para>
	  </footnote>.  When setting this option, you will want to set
	  will default to <literal>0</literal> if not specified.  If you
	  are using an version of &os; earlier than 4.5, or you want to
	  manage it yourself you will want to set
	  <literal>maxusers</literal> to at least 4, especially if you are
	  using the X Window System or compiling software.  The reason is that
	  the most important table set by <literal>maxusers</literal> is the

	  3500) to get the desired effect.  Reducing these parameters
	  should be done as a last resort only.</para>

	<note>
	  <para>In 4.X and earlier releases of &os; the
	    <literal>inflight</literal> sysctl variables are directly under
	    <varname>net.inet.tcp</varname>.  Their names were
	    (in alphabetic order):
	    <varname>net.inet.tcp.inflight_debug</varname>,
	    <varname>net.inet.tcp.inflight_enable</varname>,
	    <varname>net.inet.tcp.inflight_max</varname>,
	    <varname>net.inet.tcp.inflight_min</varname>,
	    <varname>net.inet.tcp.inflight_stab</varname>.</para>
	</note>
      </sect3>
    </sect2>


      space: adding a new hard drive, enabling swap over NFS, and
      creating a swap file on an existing partition.</para>

    <para>For information on how to encrypt swap space, what options
      for this task exist and why it should be done, please refer to
      <xref linkend="swap-encrypting"> of the Handbook.</para>

    <sect2 id="new-drive-swap">
      <title>Swap on a New Hard Drive</title>


      <title>Swapping over NFS</title>

      <para>Swapping over NFS is only recommended if you do not have a
	local hard disk to swap to; NFS swapping will be limited
	inefficient in versions of &os; prior to 4.X.  It is
	reasonably fast and efficient in 4.0-RELEASE and newer.  Even
	with newer versions of &os;, NFS swapping will be limited
	by the available network bandwidth and puts an additional
	burden on the NFS server.</para>
    </sect2>

	want, of course.</para>

      <example>
        <title>Creating a Swapfile on &os;</title>

      <orderedlist>
        <listitem>
          <para>Be certain that your kernel configuration includes
            the vnode driver.  It is <emphasis>not</emphasis> in recent versions of
            <filename>GENERIC</filename>.</para>

          <programlisting>pseudo-device   vn 1   #Vnode driver (turns a file into a device)</programlisting>
        </listitem>

	<listitem>
	  <para>Create a vn-device:</para>
	  <screen>&prompt.root; <userinput>cd /dev</userinput>
&prompt.root; <userinput>sh MAKEDEV vn0</userinput></screen>
	</listitem>

	<listitem>
	  <para>Create a swapfile (<filename>/usr/swap0</filename>):</para>

	  <screen>&prompt.root; <userinput>dd if=/dev/zero of=/usr/swap0 bs=1024k count=64</userinput></screen>
	</listitem>

	<listitem>
	  <para>Set proper permissions on (<filename>/usr/swap0</filename>):</para>

	  <screen>&prompt.root; <userinput>chmod 0600 /usr/swap0</userinput></screen>
	</listitem>

	<listitem>
	  <para>Enable the swap file in <filename>/etc/rc.conf</filename>:</para>

	  <programlisting>swapfile="/usr/swap0"   # Set to name of swapfile if aux swapfile desired.</programlisting>
	</listitem>

	<listitem>

          <para>Reboot the machine or to enable the swap file immediately,
            type:</para>

          <screen>&prompt.root; <userinput>vnconfig -e /dev/vn0b /usr/swap0 swap</userinput></screen>
        </listitem>
      </orderedlist>

      </example>
      <example>
	<title>Creating a Swapfile on &os; 5.X</title>

      <orderedlist>
	<listitem>

	  <para>Reboot the machine or to enable the swap file immediately,
            type:</para>

	  <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /usr/swap0 -u 0 &amp;&amp; swapon /dev/md0</userinput></screen>
        </listitem>
      </orderedlist>



    <para>In this section of the &os; Handbook, we will provide
      comprehensive information about <acronym>ACPI</acronym>.  References
      will be provided for further reading at the end.</para>
      that <acronym>ACPI</acronym> is available on &os;&nbsp;5.X and
      above systems as a default kernel module.  For &os;&nbsp;4.9,
      <acronym>ACPI</acronym> can be enabled by adding the line
      <literal>device acpica</literal> to a kernel configuration and
      rebuilding.</para>

    <sect2 id="acpi-intro">
      <title>What Is ACPI?</title>

	more control and flexibility to the operating system
	(<acronym>OS</acronym>).
	Modern systems <quote>stretched</quote> the limits of the
	current Plug and Play interfaces prior to the introduction of
	&os;&nbsp;4.X), prior to the introduction of
	<acronym>ACPI</acronym>.  <acronym>ACPI</acronym> is the direct
	successor to <acronym>APM</acronym>
	(Advanced Power Management).</para>




	  <row>
	    <entry>非標準規格光碟機</entry>
	    <entry>Mitsumi 光碟機用 <literal>mcd</literal>，
	      Sony 光碟機用 <literal>scd</literal>。
	      Matsushita/Pansonic 光碟機用 <literal>matcd</literal> 
		<footnote>
		  <para>2002 年 10 月 5 日 FreeBSD 4.X 移除了 &man.matcd.4; 驅動程式，
		  因此 FreeBSD 5.0 及以後的版本不再支援。</para>
		</footnote>
	    </entry>
	  </row>
	  <row>

	看一下 <filename>/var/run/dmesg.boot</filename> 以確認系統是否抓到新硬碟。
	繼續剛才的範例，新增的硬碟會是 <devicename>da1</devicename>，
	假設我們想將它掛載到 <filename>/1</filename> 這個位置
	(如果您新增的是 IDE 硬碟的話，請用
	 <devicename>wd1</devicename>，4.X 及之後的系統則是
	 <devicename>ad1</devicename>)。</para>

    <indexterm><primary>partitions</primary></indexterm>

	及 <filename>e</filename> BSD partition。在 dedicated 模式的話，
	新硬碟則是 <filename>/dev/da1e</filename>。</para>

    <para>因為 &man.bsdlabel.8;
	用 32-bit 整數來儲存 sector(磁區) 數，
	因此限制一個硬碟最大只能有 2^32-1 個 sector，亦即 2TB 的空間。
	而 &man.fdisk.8; 的格式容許起始 sector 編號不超過 2^32-1，

	  <title>操作 <application>Sysinstall</application></title>

	  <para>透過 <command>sysinstall</command>
		的選單介面，您可以輕易為硬碟分割 BIOS partition(slice) 
	    than 5.2) 的選單介面，您可以輕易為硬碟分割 BIOS partition(slice) 
		和 BSD patition。您必須以 root 身份使用 <command>sysinstall</command>，
		要嘛用 root 登入，要嘛用 <command>su</command> 切換到 root。
		執行 <command>sysinstall</command> 後，選 <Literal>Configure</literal>

	
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 bs=1k count=1</userinput>
&prompt.root; <userinput>fdisk -BI da1</userinput> # 初始您的硬碟。
&prompt.root; <userinput>bsdlabel -B -w -r da1s1 auto</userinput> # 建立 bsdlabel。
&prompt.root; <userinput>bsdlabel -e da1s1</userinput> # 編輯 bsdlabel 以新增 label。
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>newfs /dev/da1s1e</userinput> # 如果您新增了多個 label，對每個 label 重覆這個步驟。
&prompt.root; <userinput>mount /dev/da1s1e /1</userinput> # 掛載這些新 label。


	<para>如果您新增的是 IDE 硬碟，將 <filename>da</filename>
	  改成 <filename>da</filename> 即可
	  <footnote><para>譯註：da 是 direct access。</para></footnote>。</para>
	  而如果是 4.X 之前的系統，用 <filename>wd</filename>。</para>
      </sect3>

      <sect3>

	  not understand.</para></footnote>。</para>
	
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 bs=1k count=1</userinput>
&prompt.root; <userinput>bsdlabel -Brw da1 auto</userinput>
&prompt.root; <userinput>bsdlabel -e da1</userinput>				# 建立 `e' partition。
&prompt.root; <userinput>newfs -d0 /dev/da1e</userinput>
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>vi /etc/fstab</userinput>				# 新增一筆 /dev/da1e 的資訊。

	<para>另一種方法：</para>

	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 count=2</userinput>
&prompt.root; <userinput>bsdlabel /dev/da1 | bsdlabel -BrR da1 /dev/stdin</userinput>
&prompt.root; <userinput>newfs /dev/da1e</userinput>
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>vi /etc/fstab</userinput>					# 新增一筆 /dev/da1e 的資訊。
&prompt.root; <userinput>mount /1</userinput></screen>

	<note><para>從 &os;&nbsp;5.1-RELEASE 開始，&man.bsdlabel.8; 取代原本的
	  &man.disklabel.8; 程式，某些指令參數已經廢棄不用。
	  上面範例裡，如果用的是 &man.bsdlabel.8;，<option>-r</option>
	  參數應該拿掉。更多的資訊請參考 &man.bsdlabel.8; manual page。
	  </para></note>
      </sect3>
    </sect2>
  </sect1>

 	    Add this line to your kernel configuration file, rebuild, and
 	    reinstall the kernel:</para>

	  <programlisting>pseudo-device   ccd     4</programlisting>

	  <para>On 5.X systems, you have to use instead the following
	    line:</para>

	  <programlisting>device   ccd</programlisting>

	  <note><para>In FreeBSD&nbsp;5.X, it is not necessary to specify
	    a number of &man.ccd.4; devices, as the &man.ccd.4; device driver is now
	    self-cloning &mdash; new device instances will automatically be
	    created on demand.</para></note>

	  <para>The &man.ccd.4; support can also be
	    loaded as a kernel loadable module.</para>
	    later.</para>

 	  <para>To set up &man.ccd.4;, you must first use
 	    &man.bsdlabel.8; to label the disks:</para>

	  <programlisting>bsdlabel -r -w ad1 auto
bsdlabel -r -w ad2 auto
bsdlabel -r -w ad3 auto</programlisting>

 	  <para>This creates a bsdlabel for <devicename>ad1c</devicename>, <devicename>ad2c</devicename> and <devicename>ad3c</devicename> that
  	    spans the entire disk.</para>

	  <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	    utility replaces the old &man.disklabel.8; program.  With
	    &man.bsdlabel.8; a number of obsolete options and parameters
	    have been retired; in the examples above the option
	    <option>-r</option> should be removed.  For more
	    information, please refer to the &man.bsdlabel.8;
	    manual page.</para></note>

 	  <para>The next step is to change the disk label type.  You
 	    can use &man.bsdlabel.8; to edit the
 	    disks:</para>

	  <programlisting>bsdlabel -e ad1
bsdlabel -e ad2
bsdlabel -e ad3</programlisting>

 	  <para>This opens up the current disk label on each disk with
 	    the editor specified by the <envar>EDITOR</envar>

	<sect4 id="ccd-buildingfs">
	  <title>Building the File System</title>

            <para>The device node for
	    <devicename>ccd0c</devicename> may not exist yet, so to
	    create it, perform the following commands:</para>

	  <programlisting>cd /dev
sh MAKEDEV ccd0</programlisting>

	  <note><para>In FreeBSD 5.0, &man.devfs.5; will automatically
	    manage device nodes in <filename>/dev</filename>, so use of
	    <command>MAKEDEV</command> is not necessary.</para></note>

	  <para>Now that you have all the disks labeled, you must
	    build the &man.ccd.4;.  To do that,
	    use  &man.ccdconfig.8;, with options similar to the following:</para>

      </note>

      <para>Support for USB 2.0 controllers is provided on
	&os;; however, you must add:</para>
	You have to add:</para>

      <programlisting>device ehci</programlisting>

      <para>to your configuration file for USB 2.0 support.  Note
	&man.uhci.4; and &man.ohci.4; drivers are still needed if you
	want USB 1.X support.</para>

      <note>
	<para>On &os;&nbsp;4.X, the USB daemon (&man.usbd.8;) must be
	  running to be able to see some USB devices.   To enable it,
	  add <literal>usbd_enable="YES"</literal> to your
	  <filename>/etc/rc.conf</filename> file and reboot the
	  machine.</para>
      </note>
    </sect2>

    <sect2>


      <screen>&prompt.root; <userinput>mkisofs -R -no-emul-boot -b boot/cdboot -o /tmp/bootable.iso /tmp/myboot</userinput></screen>

      <para>Having done that, if you have <devicename>md</devicename>
	(FreeBSD&nbsp;4.X), or <devicename>md</devicename>
	(FreeBSD&nbsp;5.X)
	configured in your kernel, you can mount the file system with:</para>

      <screen>&prompt.root; <userinput>vnconfig -e vn0c /tmp/bootable.iso</userinput>
&prompt.root; <userinput>mount -t cd9660 /dev/vn0c /mnt</userinput></screen>

      <para>for FreeBSD&nbsp;4.X, and for FreeBSD&nbsp;5.X:</para>

      <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /tmp/bootable.iso -u 0</userinput>
&prompt.root; <userinput>mount -t cd9660 /dev/md0 /mnt</userinput></screen>



      <para>Will burn a copy of <replaceable>imagefile.iso</replaceable> on
	<replaceable>cddevice</replaceable>. The default device is
	<filename>/dev/acd0</filename>.  See &man.burncd.8; for options to
	set the write speed, eject the CD after burning, and write audio
	data.</para>
    </sect2>

        <secondary>burning</secondary>
      </indexterm>
      <screen>&prompt.root; <userinput>cdrecord -scanbus</userinput>
Cdrecord-Clone 2.01 (i386-unknown-freebsd7.0) Copyright (C) 1995-2004 J&ouml;rg Schilling
Using libscg version 'schily-0.1'
scsibus0:
        0,0,0     0) 'SEAGATE ' 'ST39236LW       ' '0004' Disk


	  <screen>&prompt.root; <userinput>dd if=/dev/acd0 of=/dev/null count=1</userinput></screen>

	  <note><para>In &os; 4.X, the entries are not prefixed with
	    zero.  If the necessary entries in <filename>/dev</filename>
	    are missing, use <command>MAKEDEV</command> to create
	    them:</para>

	  <screen>&prompt.root; <userinput>cd /dev</userinput>
&prompt.root; <userinput>sh MAKEDEV acd0t99</userinput></screen>
	  </note>

	</step>

	<step>

        &man.mkisofs.8;, and you can use it to duplicate
	any data CD.  The example given here assumes that your CDROM
	device is <devicename>acd0</devicename>.  Substitute your
	correct CDROM device.</para>
	to the end of the device name to indicate the entire partition
	or, in the case of CDROMs, the entire disc.</para>

      <screen>&prompt.root; <userinput>dd if=/dev/acd0 of=file.iso bs=2048</userinput></screen>


	oddly, however.  For example, Joliet disks store all filenames
	in two-byte Unicode characters.  The FreeBSD kernel does not
	speak Unicode (yet!), so non-English characters show up as
	question marks.  (The FreeBSD
	CD9660 driver includes hooks to load an appropriate Unicode
	conversion table on the fly.  Modules for some of the common
	encodings are available via the


	<para>Floppy disks are accessed through entries in
	  <filename>/dev</filename>, just like other devices.  To
	  access the raw floppy disk, simply use
	  uses
	  <filename>/dev/fd<replaceable>N</replaceable></filename>,
	  where <replaceable>N</replaceable> stands for the drive
	  number, usually 0, or
	  <filename>/dev/fd<replaceable>NX</replaceable></filename>,
	  where <replaceable>X</replaceable> stands for a
	  letter.</para>

	<para>In 5.0 or newer releases, simply use
	  <filename>/dev/fd<replaceable>N</replaceable></filename>.</para>

	<sect4>
	  <title>The Disk Size in 4.X and Earlier Releases</title>

	  <para>There are also <filename>/dev/fd<replaceable>N</replaceable>.<replaceable>size</replaceable></filename>
	    devices, where <replaceable>size</replaceable> is a floppy disk
	    size in kilobytes.  These entries are used at low-level format
	    time to determine the disk size.  1440kB is the size that will be
	    used in the following examples.</para>

	  <para>Sometimes the entries under <filename>/dev</filename> will
	    have to be (re)created.  To do that, issue:</para>

	  <screen>&prompt.root; <userinput>cd /dev &amp;&amp; ./MAKEDEV "fd*"</userinput></screen>
	</sect4>

	<sect4>
	  <title>The Disk Size in 5.0 and Newer Releases</title>

	  <para>In 5.0, &man.devfs.5; will automatically
	    manage device nodes in <filename>/dev</filename>, so use of
	    <command>MAKEDEV</command> is not necessary.</para>

	  <para>The desired disk size is passed to &man.fdformat.1; through
	    the <option>-f</option> flag.  Supported sizes are listed in
	  &man.fdcontrol.8;, but be advised that 1440kB is what works best.</para>
	</sect4>
      </sect3>

      <sect3>

	    determine if the disk is good or bad.</para>

	<sect4>
	  <title>Formatting Floppy Disks</title>

	  <para>Use the
	    <filename>/dev/fd<replaceable>N</replaceable>.<replaceable>size</replaceable></filename>
	    devices to format the floppy.  Insert a new 3.5inch floppy
	    disk in your drive and issue:</para>

	  <screen>&prompt.root; <userinput>/usr/sbin/fdformat /dev/fd0.1440</userinput></screen>

	</sect4>

	<sect4>
	  <title>Formatting in 5.0 and Newer Releases</title>

	  <para>Use the
	    <filename>/dev/fd<replaceable>N</replaceable></filename>

      </sect3>
    </sect2>



    <sect2>
      <title>The Disk Label</title>


	floppy.  The geometry values for the disk label are listed in
	<filename>/etc/disktab</filename>.</para>

      <para>You can run now &man.bsdlabel.8; like so:</para>

      <screen>&prompt.root; <userinput>/sbin/bsdlabel -B -r -w /dev/fd0 fd1440</userinput></screen>

      <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	utility replaces the old &man.bsdlabel.8; program.  With
	&man.bsdlabel.8; a number of obsolete options and parameters
	have been retired; in the example above the option
	<option>-r</option> should be removed.  For more

    <sect2>
      <title>Using the Floppy</title>

      <para>To use the floppy, mount it with &man.mount.msdos.8;. One can also use
	4.X and earlier releases) or &man.mount.msdosfs.8; (in 5.0 or
	newer releases).  One can also use
	<filename role="package">emulators/mtools</filename> from the ports
	collection.</para>
    </sect2>

	<para>There are only four steps that you need to perform in
	  preparation for any disaster that may occur.</para>
	<indexterm>
    <primary><command>bsdlabel</command></primary>
  </indexterm>

	<para>First, print the bsdlabel from each of your disks
	  (e.g. <command>bsdlabel da0 | lpr</command>), your file system table
	  (<filename>/etc/fstab</filename>) and all boot messages,
	  two copies of
	  each.</para>

	<para>Otherwise, you have to create two custom bootable
	  floppies which have a kernel that can mount all of your disks
	  and access your tape drive.  These floppies must contain:
	  <command>fdisk</command>, <command>bsdlabel</command>,
	  <command>newfs</command>, <command>mount</command>, and
	  whichever backup program you use.  These programs must be
	  statically linked.  If you use <command>dump</command>, the


# place boot blocks on the floppy
#
bsdlabel -w -B /dev/fd0c fd1440

#
# newfs the one and only partition

  </indexterm>
	<indexterm><primary>root partition</primary></indexterm>
	<indexterm>
    <primary><command>bsdlabel</command></primary>
  </indexterm>
	<indexterm>
    <primary><command>newfs</command></primary>
  </indexterm>
	<para>Try to <command>mount</command> (e.g. <command>mount /dev/da0a
	    /mnt</command>)  the root partition of your first disk.  If the
	  bsdlabel was damaged, use <command>bsdlabel</command> to re-partition and
	  label the disk to match the label that you printed and saved.  Use
	    <command>newfs</command> to re-create the file systems.  Re-mount the root
	  partition of the floppy read-write (<command>mount -u -o rw

      memory-based file systems.</para>

    <note>
      <para>Use &man.devfs.5; to allocate device nodes transparently for the
	to create the required devices.  FreeBSD&nbsp;5.0 and later use
	&man.devfs.5; to allocate device nodes transparently for the
	user.</para>
    </note>

    <sect2 id="disks-vnconfig">
      <title>File-Backed File System under FreeBSD&nbsp;4.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>file-backed (4.X)</secondary>
      </indexterm>

      <para>The utility &man.vnconfig.8; configures and enables vnode pseudo-disk
	devices.  A <firstterm>vnode</firstterm> is a representation
	of a file, and is the focus of file activity.  This means that
	&man.vnconfig.8; uses files to create and operate a
	file system.  One possible use is the mounting of floppy or CD
	images kept in files.</para>

      <para>To use &man.vnconfig.8;, you need &man.vn.4; support in your
	kernel configuration file:</para>

      <programlisting>pseudo-device vn</programlisting>

      <para>To mount an existing file system image:</para>

      <example>
	<title>Using vnconfig to Mount an Existing File System
	  Image under FreeBSD&nbsp;4.X</title>

	<screen>&prompt.root; <userinput>vnconfig vn<replaceable>0</replaceable> <replaceable>diskimage</replaceable></userinput>
&prompt.root; <userinput>mount /dev/vn<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput></screen>
      </example>

      <para>To create a new file system image with &man.vnconfig.8;:</para>

      <example>
	<title>Creating a New File-Backed Disk with <command>vnconfig</command></title>

	<screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>newimage</replaceable> bs=1k count=<replaceable>5</replaceable>k</userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>vnconfig -s labels -c vn<replaceable>0</replaceable> <replaceable>newimage</replaceable></userinput>
&prompt.root; <userinput>disklabel -r -w vn<replaceable>0</replaceable> auto</userinput>
&prompt.root; <userinput>newfs vn<replaceable>0</replaceable>c</userinput>
Warning: 2048 sector(s) in last cylinder unallocated
/dev/vn0c:     10240 sectors in 3 cylinders of 1 tracks, 4096 sectors
        5.0MB in 1 cyl groups (16 c/g, 32.00MB/g, 1280 i/g)
super-block backups (for fsck -b #) at:
 32
&prompt.root; <userinput>mount /dev/vn<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/vn0c        4927        1     4532     0%    /mnt</screen>
      </example>
    </sect2>

    <sect2 id="disks-mdconfig">
      <title>File-Backed File System</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>file-backed</secondary>
      </indexterm>

      <para>The utility &man.mdconfig.8; is used to configure and enable
	memory disks, &man.md.4;, under FreeBSD.  To use
	&man.mdconfig.8;, you have to load &man.md.4; module or to add
	the support in your kernel configuration file:</para>



      <example>
	<title>Using <command>mdconfig</command> to Mount an Existing File System
	  Image</title>

	<screen>&prompt.root; <userinput>mdconfig -a -t vnode -f <replaceable>diskimage</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

5120+0 records in
5120+0 records out
&prompt.root; <userinput>mdconfig -a -t vnode -f <replaceable>newimage</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>bsdlabel -w md<replaceable>0</replaceable> auto</userinput>
&prompt.root; <userinput>newfs md<replaceable>0</replaceable>a</userinput>
/dev/md0a: 5.0MB (10224 sectors) block size 16384, fragment size 2048
        using 4 cylinder groups of 1.25MB, 80 blks, 192 inodes.
super-block backups (for fsck -b #) at:
 160, 2720, 5280, 7840
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable>a <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md0a       4710    4  4330     0%    /mnt</screen>
      </example>

      <para>If you do not specify the unit number with the

	<devicename>md4</devicename>.  For more details about
	&man.mdconfig.8;, please refer to the manual page.</para>

      <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	utility replaces the old &man.disklabel.8; program.  With
	&man.bsdlabel.8; a number of obsolete options and parameters
	have been retired; in the example above the option
	<option>-r</option> should be removed.  For more
	information, please refer to the &man.bsdlabel.8;
	manual page.</para></note>

      <para>The utility &man.mdconfig.8; is very useful, however it
	asks many command lines to create a file-backed file system.
	FreeBSD also comes with a tool called &man.mdmfs.8;,
	this program configures a &man.md.4; disk using
	&man.mdconfig.8;, puts a UFS file system on it using
	&man.newfs.8;, and mounts it using &man.mount.8;.  For example,

&prompt.root; <userinput>mdmfs -F <replaceable>newimage</replaceable> -s <replaceable>5</replaceable>m md<replaceable>0</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md0        4718    4  4338     0%    /mnt</screen>
      </example>

      <para>If you use the option <option>md</option> without unit


    </sect2>

    <sect2 id="disks-md-freebsd4">
      <title>Memory-Based File System under FreeBSD&nbsp;4.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>memory file system (4.X)</secondary>
      </indexterm>

      <para>The &man.md.4; driver is a simple, efficient means to create memory
	file systems under FreeBSD&nbsp;4.X. &man.malloc.9; is used
	to allocate the memory.</para>

      <para>Simply take a file system you have prepared with, for
	example, &man.vnconfig.8;, and:</para>

      <example>
	<title>md Memory Disk under FreeBSD&nbsp;4.X</title>

	<screen>&prompt.root; <userinput>dd if=<replaceable>newimage</replaceable> of=/dev/md<replaceable>0</replaceable></userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>mount /dev/md<replaceable>0c</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/md0c        4927        1     4532     0%    /mnt</screen>
      </example>

      <para>For more details, please refer to &man.md.4; manual
	page.</para>
    </sect2>

    <sect2 id="disks-md-freebsd5">
      <title>Memory-Based File System</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>memory file system</secondary>
      </indexterm>

      <para>For a
	memory-based file system the <quote>swap backing</quote>
	should normally be used.  Using swap backing does not mean
	that the memory disk will be swapped out to disk by default,
	but merely that the memory disk will be allocated from a
	memory pool which can be swapped out to disk if needed.  It is
	also possible to create memory-based disk which are
	&man.malloc.9; backed, but using malloc backed memory disks,
	especially large ones, can result in a system panic if the
	kernel runs out of memory.</para>

      <example>
	<title>Creating a New Memory-Based Disk with

	&man.md.4; devices in using the command <command>mdconfig
	-l</command>.</para>

      <para>For FreeBSD&nbsp;4.X, &man.vnconfig.8; is used to detach
	the device.  For example to detach and free all resources
	used by <filename>/dev/vn4</filename>:</para>

      <screen>&prompt.root; <userinput>vnconfig -u vn<replaceable>4</replaceable></userinput></screen>


    </sect2>
  </sect1>


      <secondary>snapshots</secondary>
    </indexterm>

      <para>FreeBSD offers a feature in conjunction with
	<link linkend="soft-updates">Soft Updates</link>: File system snapshots.</para>

      <para>Snapshots allow a user to create images of specified file

	</step>

	<step>
	  <title>Verify the Operating System Version</title>

	  <para>&man.gbde.4; requires FreeBSD 5.0 or higher.</para>

	  <screen>&prompt.root; <userinput>uname -r</userinput>
5.0-RELEASE</screen>
	</step>

	<step>
	  <title>Add &man.gbde.4; Support to the Kernel Configuration File</title>

	  <para>Add the following line to the kernel configuration

	    initialize the old UFS1 file system, using &man.newfs.8; with
	    the <option>-O2</option> option is recommended.</para>

	  <note><para>The <option>-O2</option> option is the default
	  with &os;&nbsp;5.1-RELEASE and later.</para></note>

	  <screen>&prompt.root; <userinput>newfs -U -O2 /dev/ad4s1c.bde</userinput></screen>

	  <note>

      </sect3>
    </sect2>	
  </sect1>


  <sect1 id="swap-encrypting">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Christian</firstname>
	  <surname>Br&uuml;ffer</surname>
	  <contrib>Written by </contrib>
	</author>
      </authorgroup>
    </sect1info>

    <title>Encrypting Swap Space</title>
    <indexterm>
      <primary>swap</primary>
      <secondary>encrypting</secondary>
    </indexterm>

    <para>Swap encryption in &os; is easy to configure and has been
      available since &os; 5.3-RELEASE.  Depending on which version
      of &os; is being used, different options are available
      and configuration can vary slightly.  From &os; 6.0-RELEASE onwards,
      the &man.gbde.8; or &man.geli.8; encryption systems can be used
      for swap encryption.  With earlier versions, only &man.gbde.8; is
      available.  Both systems use the <filename>encswap</filename>
      <link linkend="configtuning-rcd">rc.d</link> script.</para>

    <para>The previous section, <link linkend="disks-encrypting">Encrypting
      Disk Partitions</link>, includes a short discussion on the different
      encryption systems.</para>

    <sect2>
      <title>Why should Swap be Encrypted?</title>

      <para>Like the encryption of disk partitions, encryption of swap space
	is done to protect sensitive information.  Imagine an application
	that e.g. deals with passwords.  As long as these passwords stay in
	physical memory, all is well.  However, if the operating system starts
	swapping out memory pages to free space for other applications, the
	passwords may be written to the disk platters unencrypted and easy to
	retrieve for an adversary.  Encrypting swap space can be a solution for
	this scenario.</para>
    </sect2>

    <sect2>
      <title>Preparation</title>

      <note>
	<para>For the remainder of this section, <devicename>ad0s1b</devicename>
	  will be the swap partition.</para>
      </note>

      <para>Up to this point the swap has been unencrypted.  It is possible that
	there are already passwords or other sensitive data on the disk platters
	in cleartext.  To rectify this, the data on the swap partition should be
	overwritten with random garbage:</para>

      <screen>&prompt.root; <userinput>dd if=/dev/random of=/dev/ad0s1b bs=1m</userinput></screen>
    </sect2>

    <sect2>
      <title>Swap Encryption with &man.gbde.8;</title>

      <para>If &os; 6.0-RELEASE or newer is being used, the
	<literal>.bde</literal> suffix should be added to the device in the
	respective <filename>/etc/fstab</filename> swap line:</para>

      <screen>
# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/ad0s1b.bde         none            swap    sw              0       0
      </screen>

      <para>For systems prior to &os; 6.0-RELEASE, the following line
	in <filename>/etc/rc.conf</filename> is also needed:</para>

      <programlisting>gbde_swap_enable="YES"</programlisting>
    </sect2>

    <sect2>
      <title>Swap Encryption with &man.geli.8;</title>

      <para>Alternatively, the procedure for using &man.geli.8; for swap
	encryption is similar to that of using &man.gbde.8;.  The
	<literal>.eli</literal> suffix should be added to the device in the
	respective <filename>/etc/fstab</filename> swap line:</para>

      <screen>
# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/ad0s1b.eli         none            swap    sw              0       0
      </screen>

      <para>&man.geli.8; uses the <acronym>AES</acronym> algorithm with
	a key length of 256 bit by default.</para>

      <para>Optionally, these defaults can be altered using the
	<literal>geli_swap_flags</literal> option in
	<filename>/etc/rc.conf</filename>.  The following line tells the
	<filename>encswap</filename> rc.d script to create &man.geli.8; swap
	partitions using the Blowfish algorithm with a key length of 128 bit,
	a sectorsize of 4 kilobytes and the <quote>detach on last close</quote>
	option set:</para>

      <programlisting>geli_swap_flags="-a blowfish -l 128 -s 4096 -d"</programlisting>

      <para>Please refer to the description of the <command>onetime</command> command
	in the &man.geli.8; manual page for a list of possible options.</para>
    </sect2>

    <sect2>
      <title>Verifying that it Works</title>

      <para>Once the system has been rebooted, proper operation of the
	encrypted swap can be verified using the
	<command>swapinfo</command> command.</para>

      <para>If &man.gbde.8; is being used:</para>

      <screen>&prompt.user; <userinput>swapinfo</userinput>
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b.bde    542720        0   542720     0%
      </screen>

      <para>If &man.geli.8; is being used:</para>

      <screen>&prompt.user; <userinput>swapinfo</userinput>
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b.eli    542720        0   542720     0%
      </screen>
    </sect2>
  </sect1>
</chapter>

<!--

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Lines 3-8 Link Here

(-)config/chapter.sgml (-94 / +17 lines)
3		3
4	$FreeBSD: doc/zh_TW.Big5/books/handbook/config/chapter.sgml,v 1.4 2006/07/08 03:01:13 vanilla Exp $	4	$FreeBSD: doc/zh_TW.Big5/books/handbook/config/chapter.sgml,v 1.4 2006/07/08 03:01:13 vanilla Exp $
5	Original revision: 1.213	5	Original revision: 1.213
		6	Chased revision: 1.217
6	-->	7	-->
7		8
8	<chapter id="config-tuning">	9	<chapter id="config-tuning">
Lines 102-108 Link Here
102	<sect3>	103	<sect3>
103	<title>Base Partitions</title>	104	<title>Base Partitions</title>
104		105
105	<para>用 &man.disklabel.8; 或 &man.sysinstall.8; 來規劃檔案系統時，請記住：	106	<para>用 &man.bsdlabel.8; 或 &man.sysinstall.8; 來規劃檔案系統時，請記住：
106	硬碟在傳輸資料方面，(由於結構為碟片因素)外圈會比內圈來得快些。	107	硬碟在傳輸資料方面，(由於結構為碟片因素)外圈會比內圈來得快些。
107	因此，建議把較小、常會存取的分割區儘量放外圈，而較大的分割區像是	108	因此，建議把較小、常會存取的分割區儘量放外圈，而較大的分割區像是
108	<filename>/usr</filename> 則應放在較內圈。	109	<filename>/usr</filename> 則應放在較內圈。
Lines 370-376 Link Here
370	kill -9 `cat /var/run/utility.pid`	371	kill -9 `cat /var/run/utility.pid`
371	;;	372	;;
372	*)	373	*)
373	echo "Usage: `basename $0` {start\|stop}" >&2	374	echo "Usage: `basename $0` {start\|stop}" >&2
374	exit 64	375	exit 64
375	;;	376	;;
376	esac	377	esac
Lines 830-844 Link Here
830	the supported hardware and even the possible problems that	831	the supported hardware and even the possible problems that
831	could occur.</para>	832	could occur.</para>
832		833
833	<note>
834	<para><filename>NOTES</filename> does not exist on
835	&os; 4.X. Instead, check the <filename>LINT</filename>
836	file for information about various network interfaces. See
837	<xref linkend="kernelconfig-config"> for a more detailed
838	summary of <filename>NOTES</filename> versus
839	<filename>LINT</filename>.</para>
840	</note>
841
842	<para>If you own a common card, most of the time you will not	834	<para>If you own a common card, most of the time you will not
843	have to look very hard for a driver. Drivers for common	835	have to look very hard for a driver. Drivers for common
844	network cards are present in the <filename>GENERIC</filename>	836	network cards are present in the <filename>GENERIC</filename>
Lines 1578-1584 Link Here
1578	syntax:</para>	1570	syntax:</para>
1579		1571
1580	<screen>&prompt.root; <userinput>sysctl kern.maxfiles=5000</userinput>	1572	<screen>&prompt.root; <userinput>sysctl kern.maxfiles=5000</userinput>
1581	kern.maxfiles: 2088 -> 5000</screen>	1573	kern.maxfiles: 2088 -> 5000</screen>
1582		1574
1583	<para>Settings of sysctl variables are usually either strings,	1575	<para>Settings of sysctl variables are usually either strings,
1584	numbers, or booleans (a boolean being <literal>1</literal> for yes	1576	numbers, or booleans (a boolean being <literal>1</literal> for yes
Lines 1698-1705 Link Here
1698	</para>	1690	</para>
1699		1691
1700	<para>There are various other buffer-cache and VM page cache	1692	<para>There are various other buffer-cache and VM page cache
1701	related sysctls. We do not recommend modifying these values. As	1693	related sysctls. We do not recommend modifying these values,
1702	of &os; 4.3, the VM system does an extremely good job of	1694	the VM system does an extremely good job of
1703	automatically tuning itself.</para>	1695	automatically tuning itself.</para>
1704	</sect3>	1696	</sect3>
1705		1697
Lines 1801-1810 Link Here
1801	it is mounted. A good time to enable Soft Updates is before any	1793	it is mounted. A good time to enable Soft Updates is before any
1802	partitions have been mounted, in single-user mode.</para>	1794	partitions have been mounted, in single-user mode.</para>
1803		1795
1804	<note><para>As of &os; 4.5, it is possible to enable Soft Updates
1805	at filesystem creation time, through use of the <literal>-U</literal>
1806	option to &man.newfs.8;.</para></note>
1807
1808	<para>Soft Updates drastically improves meta-data performance, mainly	1796	<para>Soft Updates drastically improves meta-data performance, mainly
1809	file creation and deletion, through the use of a memory cache. We	1797	file creation and deletion, through the use of a memory cache. We
1810	recommend to use Soft Updates on all of your file systems. There	1798	recommend to use Soft Updates on all of your file systems. There
Lines 2011-2026 Link Here
2011	connected at once, the resources needed may be similar to a	1999	connected at once, the resources needed may be similar to a
2012	high-scale web server.</para>	2000	high-scale web server.</para>
2013		2001
2014	<para>Starting with &os; 4.5, the system will auto-tune	2002	<para>The system will auto-tune
2015	<literal>maxusers</literal> for you if you explicitly set it to	2003	<literal>maxusers</literal> for you if you explicitly set it to
2016	<literal>0</literal><footnote>	2004	<literal>0</literal><footnote>
2017	<para>The auto-tuning algorithm sets	2005	<para>The auto-tuning algorithm sets
2018	<literal>maxusers</literal> equal to the amount of memory in the	2006	<literal>maxusers</literal> equal to the amount of memory in the
2019	system, with a minimum of 32, and a maximum of 384.</para>	2007	system, with a minimum of 32, and a maximum of 384.</para>
2020	</footnote>. In &os; 5.X and above, <literal>maxusers</literal>	2008	</footnote>. When setting this option, you will want to set
2021	will default to <literal>0</literal> if not specified. If you
2022	are using an version of &os; earlier than 4.5, or you want to
2023	manage it yourself you will want to set
2024	<literal>maxusers</literal> to at least 4, especially if you are	2009	<literal>maxusers</literal> to at least 4, especially if you are
2025	using the X Window System or compiling software. The reason is that	2010	using the X Window System or compiling software. The reason is that
2026	the most important table set by <literal>maxusers</literal> is the	2011	the most important table set by <literal>maxusers</literal> is the
Lines 2207-2223 Link Here
2207	3500) to get the desired effect. Reducing these parameters	2192	3500) to get the desired effect. Reducing these parameters
2208	should be done as a last resort only.</para>	2193	should be done as a last resort only.</para>
2209		2194
2210	<note>
2211	<para>In 4.X and earlier releases of &os; the
2212	<literal>inflight</literal> sysctl variables are directly under
2213	<varname>net.inet.tcp</varname>. Their names were
2214	(in alphabetic order):
2215	<varname>net.inet.tcp.inflight_debug</varname>,
2216	<varname>net.inet.tcp.inflight_enable</varname>,
2217	<varname>net.inet.tcp.inflight_max</varname>,
2218	<varname>net.inet.tcp.inflight_min</varname>,
2219	<varname>net.inet.tcp.inflight_stab</varname>.</para>
2220	</note>
2221	</sect3>	2195	</sect3>
2222	</sect2>	2196	</sect2>
2223		2197
Lines 2267-2272 Link Here
2267	space: adding a new hard drive, enabling swap over NFS, and	2241	space: adding a new hard drive, enabling swap over NFS, and
2268	creating a swap file on an existing partition.</para>	2242	creating a swap file on an existing partition.</para>
2269		2243
		2244	<para>For information on how to encrypt swap space, what options
		2245	for this task exist and why it should be done, please refer to
		2246	<xref linkend="swap-encrypting"> of the Handbook.</para>
		2247
2270	<sect2 id="new-drive-swap">	2248	<sect2 id="new-drive-swap">
2271	<title>Swap on a New Hard Drive</title>	2249	<title>Swap on a New Hard Drive</title>
2272		2250
Lines 2283-2292 Link Here
2283	<title>Swapping over NFS</title>	2261	<title>Swapping over NFS</title>
2284		2262
2285	<para>Swapping over NFS is only recommended if you do not have a	2263	<para>Swapping over NFS is only recommended if you do not have a
2286	local hard disk to swap to. Swapping over NFS is slow and	2264	local hard disk to swap to; NFS swapping will be limited
2287	inefficient in versions of &os; prior to 4.X. It is
2288	reasonably fast and efficient in 4.0-RELEASE and newer. Even
2289	with newer versions of &os;, NFS swapping will be limited
2290	by the available network bandwidth and puts an additional	2265	by the available network bandwidth and puts an additional
2291	burden on the NFS server.</para>	2266	burden on the NFS server.</para>
2292	</sect2>	2267	</sect2>
Lines 2300-2352 Link Here
2300	want, of course.</para>	2275	want, of course.</para>
2301		2276
2302	<example>	2277	<example>
2303	<title>Creating a Swapfile on &os; 4.X</title>	2278	<title>Creating a Swapfile on &os;</title>
2304
2305	<orderedlist>
2306	<listitem>
2307	<para>Be certain that your kernel configuration includes
2308	the vnode driver. It is <emphasis>not</emphasis> in recent versions of
2309	<filename>GENERIC</filename>.</para>
2310
2311	<programlisting>pseudo-device vn 1 #Vnode driver (turns a file into a device)</programlisting>
2312	</listitem>
2313
2314	<listitem>
2315	<para>Create a vn-device:</para>
2316	<screen>&prompt.root; <userinput>cd /dev</userinput>
2317	&prompt.root; <userinput>sh MAKEDEV vn0</userinput></screen>
2318	</listitem>
2319
2320	<listitem>
2321	<para>Create a swapfile (<filename>/usr/swap0</filename>):</para>
2322
2323	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/usr/swap0 bs=1024k count=64</userinput></screen>
2324	</listitem>
2325
2326	<listitem>
2327	<para>Set proper permissions on (<filename>/usr/swap0</filename>):</para>
2328
2329	<screen>&prompt.root; <userinput>chmod 0600 /usr/swap0</userinput></screen>
2330	</listitem>
2331
2332	<listitem>
2333	<para>Enable the swap file in <filename>/etc/rc.conf</filename>:</para>
2334
2335	<programlisting>swapfile="/usr/swap0" # Set to name of swapfile if aux swapfile desired.</programlisting>
2336	</listitem>
2337
2338	<listitem>
2339
2340	<para>Reboot the machine or to enable the swap file immediately,
2341	type:</para>
2342
2343	<screen>&prompt.root; <userinput>vnconfig -e /dev/vn0b /usr/swap0 swap</userinput></screen>
2344	</listitem>
2345	</orderedlist>
2346
2347	</example>
2348	<example>
2349	<title>Creating a Swapfile on &os; 5.X</title>
2350		2279
2351	<orderedlist>	2280	<orderedlist>
2352	<listitem>	2281	<listitem>
Lines 2380-2386 Link Here
2380	<para>Reboot the machine or to enable the swap file immediately,	2309	<para>Reboot the machine or to enable the swap file immediately,
2381	type:</para>	2310	type:</para>
2382		2311
2383	<screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /usr/swap0 -u 0 && swapon /dev/md0</userinput></screen>	2312	<screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /usr/swap0 -u 0 && swapon /dev/md0</userinput></screen>
2384	</listitem>	2313	</listitem>
2385	</orderedlist>	2314	</orderedlist>
2386		2315
Lines 2419-2430 Link Here
2419		2348
2420	<para>In this section of the &os; Handbook, we will provide	2349	<para>In this section of the &os; Handbook, we will provide
2421	comprehensive information about <acronym>ACPI</acronym>. References	2350	comprehensive information about <acronym>ACPI</acronym>. References
2422	will be provided for further reading at the end. Please be aware	2351	will be provided for further reading at the end.</para>
2423	that <acronym>ACPI</acronym> is available on &os; 5.X and
2424	above systems as a default kernel module. For &os; 4.9,
2425	<acronym>ACPI</acronym> can be enabled by adding the line
2426	<literal>device acpica</literal> to a kernel configuration and
2427	rebuilding.</para>
2428		2352
2429	<sect2 id="acpi-intro">	2353	<sect2 id="acpi-intro">
2430	<title>What Is ACPI?</title>	2354	<title>What Is ACPI?</title>
Lines 2446-2453 Link Here
2446	more control and flexibility to the operating system	2370	more control and flexibility to the operating system
2447	(<acronym>OS</acronym>).	2371	(<acronym>OS</acronym>).
2448	Modern systems <quote>stretched</quote> the limits of the	2372	Modern systems <quote>stretched</quote> the limits of the
2449	current Plug and Play interfaces (such as APM, which is used in	2373	current Plug and Play interfaces prior to the introduction of
2450	&os; 4.X), prior to the introduction of
2451	<acronym>ACPI</acronym>. <acronym>ACPI</acronym> is the direct	2374	<acronym>ACPI</acronym>. <acronym>ACPI</acronym> is the direct
2452	successor to <acronym>APM</acronym>	2375	successor to <acronym>APM</acronym>
2453	(Advanced Power Management).</para>	2376	(Advanced Power Management).</para>