path: root/en_US.ISO8859-1/books/handbook/config/chapter.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!--
     The FreeBSD Documentation Project

     $FreeBSD$
-->
<chapter xmlns="http://docbook.org/ns/docbook"
  xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
  xml:id="config-tuning">

  <info>
    <title>Configuration and Tuning</title>

    <authorgroup>
      <author>
	<personname>
	  <firstname>Chern</firstname>
	  <surname>Lee</surname>
	</personname>
	<contrib>Written by </contrib>
      </author>
    </authorgroup>

    <authorgroup>
      <author>
	<personname>
	  <firstname>Mike</firstname>
	  <surname>Smith</surname>
	</personname>
	<contrib>Based on a tutorial written by </contrib>
      </author>
    </authorgroup>

    <authorgroup>
      <author>
	<personname>
	  <firstname>Matt</firstname>
	  <surname>Dillon</surname>
	</personname>
	<contrib>Also based on tuning(7) written by </contrib>
      </author>
    </authorgroup>
  </info>

  <sect1 xml:id="config-synopsis">
    <title>Synopsis</title>

    <indexterm>
      <primary>system configuration</primary>
    </indexterm>
    <indexterm>
      <primary>system optimization</primary>
    </indexterm>

    <para>One of the important aspects of &os; is proper system
      configuration.  This chapter explains much of the &os;
      configuration process, including some of the parameters which
      can be set to tune a &os; system.</para>

    <para>After reading this chapter, you will know:</para>

    <itemizedlist>
      <listitem>
	<para>The basics of <filename>rc.conf</filename> configuration
	  and <filename>/usr/local/etc/rc.d</filename> startup
	  scripts.</para>
      </listitem>

      <listitem>
	<para>How to configure and test a network card.</para>
      </listitem>

      <listitem>
	<para>How to configure virtual hosts on network
	  devices.</para>
      </listitem>

      <listitem>
	<para>How to use the various configuration files in
	  <filename>/etc</filename>.</para>
      </listitem>

      <listitem>
	<para>How to tune &os; using &man.sysctl.8; variables.</para>
      </listitem>

      <listitem>
	<para>How to tune disk performance and modify kernel
	  limitations.</para>
      </listitem>
    </itemizedlist>

    <para>Before reading this chapter, you should:</para>

    <itemizedlist>
      <listitem>
	<para>Understand &unix; and &os; basics
	  (<xref linkend="basics"/>).</para>
      </listitem>

      <listitem>
	<para>Be familiar with the basics of kernel configuration and
	  compilation (<xref linkend="kernelconfig"/>).</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 xml:id="configtuning-starting-services">
    <info>
      <title>Starting Services</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>services</primary>
    </indexterm>

    <para>Many users install third party software on &os; from the
      Ports Collection and require the installed services to be
      started upon system initialization.  Services, such as
      <package>mail/postfix</package> or
      <package>www/apache22</package> are just two of the many
      software packages which may be started during system
      initialization.  This section explains the procedures available
      for starting third party software.</para>

    <para>In &os;, most included services, such as &man.cron.8;, are
      started through the system start up scripts.</para>

    <sect2>
      <title>Extended Application Configuration</title>

      <para>Now that &os; includes <filename>rc.d</filename>,
	configuration of application startup is easier and provides
	more features.  Using the key words discussed in
	<xref linkend="configtuning-rcd"/>, applications can be set to
	start after certain other services and extra flags can be
	passed through <filename>/etc/rc.conf</filename> in place of
	hard coded flags in the start up script.  A basic script may
	look similar to the following:</para>

      <programlisting>#!/bin/sh
#
# PROVIDE: utility
# REQUIRE: DAEMON
# KEYWORD: shutdown

. /etc/rc.subr

name=utility
rcvar=utility_enable

command="/usr/local/sbin/utility"

load_rc_config $name

#
# DO NOT CHANGE THESE DEFAULT VALUES HERE
# SET THEM IN THE /etc/rc.conf FILE
#
utility_enable=${utility_enable-"NO"}
pidfile=${utility_pidfile-"/var/run/utility.pid"}

run_rc_command "$1"</programlisting>

      <para>This script will ensure that the provided
	<literal>utility</literal> will be started after the
	<literal>DAEMON</literal> pseudo-service.  It also provides a
	method for setting and tracking the process ID
	(<acronym>PID</acronym>).</para>

      <para>This application could then have the following line placed
	in <filename>/etc/rc.conf</filename>:</para>

      <programlisting>utility_enable="YES"</programlisting>

      <para>This method allows for easier manipulation of command
	line arguments, inclusion of the default functions provided
	in <filename>/etc/rc.subr</filename>, compatibility with
	&man.rcorder.8;, and provides for easier configuration via
	<filename>rc.conf</filename>.</para>
    </sect2>

    <sect2>
      <title>Using Services to Start Services</title>

      <para>Other services can be started using &man.inetd.8;.
	Working with &man.inetd.8; and its configuration is
	described in depth in
	<xref linkend="network-inetd"/>.</para>

      <para>In some cases, it may make more sense to use
	&man.cron.8; to start system services.  This approach
	has a number of advantages as &man.cron.8; runs these
	processes as the owner of the &man.crontab.5;.  This allows
	regular users to start and maintain their own
	applications.</para>

      <para>The <literal>@reboot</literal> feature of &man.cron.8;,
	may be used in place of the time specification.  This causes
	the job to run when &man.cron.8; is started, normally during
	system initialization.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-cron">
    <info>
      <title>Configuring &man.cron.8;</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>cron</primary>
      <secondary>configuration</secondary>
    </indexterm>

    <para>One of the most useful utilities in &os; is &man.cron.8;.
      This utility runs in the background and regularly checks
      <filename>/etc/crontab</filename> for tasks to execute and
      searches <filename>/var/cron/tabs</filename> for custom
      &man.crontab.5; files.  These files store information about
      specific functions which &man.cron.8; is supposed to perform at
      certain times.</para>

    <para>Two different types of configuration files are used by
      &man.cron.8;: the system <filename>crontab</filename> and user
      <filename>crontab</filename>s.  These formats only differ in the
      sixth field and later.  In the system
      <filename>crontab</filename>, &man.cron.8; runs the command as
      the user specified in the sixth field.  In a user
      <filename>crontab</filename>, all commands run as the user who
      created the <filename>crontab</filename>, so the sixth field is
      the last field; this is an important security feature.  The
      final field is always the command to run.</para>

    <note>
      <para>User crontabs allow individual users to schedule tasks
	without the need for
	<systemitem class="username">root</systemitem> privileges.
	Commands in a user's crontab run with the permissions of the
	user who owns the crontab.</para>

      <para>The <systemitem class="username">root</systemitem> user
	can have a user <filename>crontab</filename> just like any
	other user.  The
	<systemitem class="username">root</systemitem> user
	<filename>crontab</filename> is separate from the system
	<filename>crontab</filename>,
	<filename>/etc/crontab</filename>.  Because the system
	<filename>crontab</filename> invokes the specified commands as
	<systemitem class="username">root</systemitem>, there is
	usually no need to create a user <filename>crontab</filename>
	for <systemitem class="username">root</systemitem>.</para>
    </note>

    <para>Here is a sample entry from
      <filename>/etc/crontab</filename>:</para>

    <programlisting># /etc/crontab - root's crontab for FreeBSD
#
# $FreeBSD$
# <co xml:id="co-comments"/>
#
SHELL=/bin/sh
PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin <co xml:id="co-env"/>
#
#minute	hour	mday	month	wday	who	command <co xml:id="co-field-descr"/>
#
*/5	*	*	*	*	root	/usr/libexec/atrun <co xml:id="co-main"/></programlisting>

    <calloutlist>
      <callout arearefs="co-comments">
	<para>Like most &os; configuration files, lines that begin
	  with the <literal>#</literal> character are comments.  A
	  comment can be placed in the file as a reminder of what and
	  why a desired action is performed.  Comments cannot be on
	  the same line as a command or else they will be interpreted
	  as part of the command; they must be on a new line.  Blank
	  lines are ignored.</para>
      </callout>

      <callout arearefs="co-env">
	<para>The equals (<literal>=</literal>) character is used to
	  define any environment settings.  In this example, it is
	  used to define the <envar>SHELL</envar> and
	  <envar>PATH</envar>.  If the <envar>SHELL</envar> is
	  omitted, &man.cron.8; will use the default of &man.sh.1;.
	  If the <envar>PATH</envar> is omitted, no default will be
	  used and file locations will need to be absolute.</para>
      </callout>

      <callout arearefs="co-field-descr">
	<para>This line defines a total of seven fields:
	  <literal>minute</literal>,
	  <literal>hour</literal>, <literal>mday</literal>,
	  <literal>month</literal>, <literal>wday</literal>,
	  <literal>who</literal>, and <literal>command</literal>.
	  These are almost all self explanatory.
	  <literal>minute</literal> is the time in minutes when the
	  specified command will be run.  <literal>hour</literal> is
	  the hour when the specified command will be run.
	  <literal>mday</literal> stands for day of the month and
	  <literal>month</literal> designates the month.  The
	  <literal>wday</literal> option stands for day of the week.
	  These fields must be numeric values, representing the
	  twenty-four hour clock, or a <literal>*</literal>,
	  representing all values for that field.  The
	  <literal>who</literal> field only exists in the system
	  crontab.  This field specifies which user the command
	  should be run as.  The last field is the command to be
	  executed.</para>
      </callout>

      <callout arearefs="co-main">
	<para>This last line defines the values discussed above.
	  This example has a <literal>*/5</literal> listing,followed
	  by several more <literal>*</literal> characters.  These
	  <literal>*</literal> characters mean
	  <quote>first-last</quote>, and can be interpreted as
	  <emphasis>every</emphasis> time.  In this example,
	  &man.atrun.8; is invoked by
	  <systemitem class="username">root</systemitem> every five
	  minutes, regardless of the day or month.</para>

	<para>Commands can have any number of flags passed to them;
	  however, commands which extend to multiple lines need to be
	  broken with the backslash <quote>\</quote> continuation
	  character.</para>
      </callout>
    </calloutlist>

    <para>This is the basic setup for every &man.crontab.5;.
      However, field number six, which specifies the username, only
      exists in the system &man.crontab.5;.  This field should be
      omitted for individual user &man.crontab.5; files.</para>

    <sect2 xml:id="configtuning-installcrontab">
      <title>Installing a Crontab</title>

      <important>
	<para>Do not use the procedure described here to edit and
	  install the system <filename>crontab</filename>,
	  <filename>/etc/crontab</filename>.  Instead, use an editor
	  and &man.cron.8; will notice that the file has changed and
	  immediately begin using the updated version.  See <link
	    xlink:href="&url.books.faq;/admin.html#root-not-found-cron-errors">this
	    FAQ entry</link> for more information.</para>
      </important>

      <para>To install a freshly written user &man.crontab.5;, use
	an editor to create and save a file in the proper format.
	Then, specify the file name with &man.crontab.1;:</para>

      <screen>&prompt.user; <userinput>crontab crontab-file</userinput></screen>

      <para>In this example, <filename>crontab-file</filename> is the
	filename of a &man.crontab.5; that was previously
	created.</para>

      <para>To list installed &man.crontab.5; files, pass
	<option>-l</option> to &man.crontab.1;.</para>

      <para>Users who wish to begin their own
	<filename>crontab</filename> file from scratch, without the
	use of a template, can use <command>crontab -e</command>.
	This will invoke the default editor with an empty file.  When
	this file is saved, it will be automatically installed by
	&man.crontab.1;.</para>

      <para>In order to remove a user &man.crontab.5; completely,
	use <command>crontab -r</command>.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-rcd">
    <info>
      <title>Managing Services in &os;</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <para>&os; uses the &man.rc.8; system of startup scripts during
      system initialization and for managing services.  The scripts
      listed in <filename>/etc/rc.d</filename> provide basic services
      which can be controlled with the <option>start</option>,
      <option>stop</option>, and <option>restart</option> options to
      &man.service.8;.  For instance, &man.sshd.8; can be restarted
      with the following command:</para>

    <screen>&prompt.root; <userinput>service sshd restart</userinput></screen>

    <para>This procedure can be used to start services on a running
      system.  Services will be started automatically at boot time
      as specified in &man.rc.conf.5;.  For example, to enable
      &man.natd.8; at system startup, add the following line to
      <filename>/etc/rc.conf</filename>:</para>

    <programlisting>natd_enable="YES"</programlisting>

    <para>If a <option>natd_enable="NO"</option> line is already
      present, change the <literal>NO</literal> to
      <literal>YES</literal>.  The &man.rc.8; scripts will
      automatically load any dependent services during the next boot,
      as described below.</para>

    <para>Since the &man.rc.8; system is primarily intended to start
      and stop services at system startup and shutdown time, the
      <option>start</option>, <option>stop</option> and
      <option>restart</option> options will only perform their action
      if the appropriate <filename>/etc/rc.conf</filename> variable
      is set.  For instance, <command>sshd restart</command> will
      only work if <varname>sshd_enable</varname> is set to
      <option>YES</option> in <filename>/etc/rc.conf</filename>.
      To <option>start</option>, <option>stop</option> or
      <option>restart</option> a service regardless of the settings
      in <filename>/etc/rc.conf</filename>, these commands should be
      prefixed with <quote>one</quote>.  For instance, to restart
      &man.sshd.8; regardless of the current
      <filename>/etc/rc.conf</filename> setting, execute the following
      command:</para>

    <screen>&prompt.root; <userinput>service sshd onerestart</userinput></screen>

    <para>To check if a service is enabled in
      <filename>/etc/rc.conf</filename>, run the appropriate
      &man.rc.8; script with <option>rcvar</option>.  This example
      checks to see if &man.sshd.8; is enabled in
      <filename>/etc/rc.conf</filename>:</para>

    <screen>&prompt.root; <userinput>service sshd rcvar</userinput>
# sshd
#
sshd_enable="YES"
#   (default: "")</screen>

    <note>
      <para>The <literal># sshd</literal> line is output from the
	above command, not a
	<systemitem class="username">root</systemitem> console.</para>
    </note>

    <para>To determine whether or not a service is running, use
      <option>status</option>.  For instance, to verify that
      &man.sshd.8; is running:</para>

    <screen>&prompt.root; <userinput>service sshd status</userinput>
sshd is running as pid 433.</screen>

    <para>In some cases, it is also possible to
      <option>reload</option> a service.  This attempts to send a
      signal to an individual service, forcing the service to reload
      its configuration files.  In most cases, this means sending
      the service a <literal>SIGHUP</literal> signal.  Support for
      this feature is not included for every service.</para>

    <para>The &man.rc.8; system is used for network services and it
      also contributes to most of the system initialization.  For
      instance, when the
      <filename>/etc/rc.d/bgfsck</filename> script is executed, it
      prints out the following message:</para>

    <screen>Starting background file system checks in 60 seconds.</screen>

    <para>This script is used for background file system checks,
      which occur only during system initialization.</para>

    <para>Many system services depend on other services to function
      properly.  For example, &man.yp.8; and other
      <acronym>RPC</acronym>-based services may fail to start until
      after the &man.rpcbind.8; service has started.  To resolve this
      issue, information about dependencies and other meta-data is
      included in the comments at the top of each startup script.
      The &man.rcorder.8; program is used to parse these comments
      during system initialization to determine the order in which
      system services should be invoked to satisfy the
      dependencies.</para>

    <para>The following key word must be included in all startup
      scripts as it is required by &man.rc.subr.8; to
      <quote>enable</quote> the startup script:</para>

    <itemizedlist>
      <listitem>
	<para><literal>PROVIDE</literal>: Specifies the services this
	  file provides.</para>
      </listitem>
    </itemizedlist>

    <para>The following key words may be included at the top of each
      startup script.  They are not strictly necessary, but are
      useful as hints to &man.rcorder.8;:</para>

    <itemizedlist>
      <listitem>
	<para><literal>REQUIRE</literal>: Lists services which are
	  required for this service.  The script containing this key
	  word will run <emphasis>after</emphasis> the specified
	  services.</para>
      </listitem>

      <listitem>
	<para><literal>BEFORE</literal>: Lists services which depend
	  on this service.  The script containing this key word will
	  run <emphasis>before</emphasis> the specified
	  services.</para>
      </listitem>
    </itemizedlist>

    <para>By carefully setting these keywords for each startup script,
      an administrator has a fine-grained level of control of the
      startup order of the scripts, without the need for
      <quote>runlevels</quote> used by some &unix; operating
      systems.</para>

    <para>Additional information can be found in &man.rc.8; and
      &man.rc.subr.8;.  Refer to <link
	xlink:href="&url.articles.rc-scripting;">this article</link>
      for instructions on how to create custom &man.rc.8;
      scripts.</para>

    <sect2 xml:id="configtuning-core-configuration">
      <title>Managing System-Specific Configuration</title>

      <indexterm>
	<primary>rc files</primary>
	<secondary><filename>rc.conf</filename></secondary>
      </indexterm>

      <para>The principal location for system configuration
	information is <filename>/etc/rc.conf</filename>.  This file
	contains a wide range of configuration information and it is
	read at system startup to configure the system.  It provides
	the configuration information for the
	<filename>rc*</filename> files.</para>

      <para>The entries in <filename>/etc/rc.conf</filename> override
	the default settings in
	<filename>/etc/defaults/rc.conf</filename>.  The file
	containing the default settings should not be edited.
	Instead, all system-specific changes should be made to
	<filename>/etc/rc.conf</filename>.</para>

      <para>A number of strategies may be applied in clustered
	applications to separate site-wide configuration from
	system-specific configuration in order to keep administration
	overhead down.  The recommended approach is to place
	system-specific configuration into
	<filename>/etc/rc.conf.local</filename>.  For example, these
	entries in <filename>/etc/rc.conf</filename> apply to all
	systems:</para>

      <programlisting>sshd_enable="YES"
keyrate="fast"
defaultrouter="10.1.1.254"</programlisting>

      <para>Whereas these systems in
	<filename>/etc/rc.conf.local</filename> apply to this system
	only:</para>

      <programlisting>hostname="node1.example.org"
ifconfig_fxp0="inet 10.1.1.1/8"</programlisting>

      <para>Distribute <filename>/etc/rc.conf</filename> to every
	system using <command>rsync</command> or a similar program,
	while <filename>/etc/rc.conf.local</filename> remains
	unique.</para>

      <para>Upgrading the system will not overwrite
	<filename>/etc/rc.conf</filename>, so system configuration
	information will not be lost.</para>

      <tip>
	<para>The configuration in <filename>/etc/rc.conf</filename>
	  is parsed by &man.sh.1;.  This allows system operators to
	  create complex configuration scenarios.  Refer to
	  &man.rc.conf.5; for further information on this
	  topic.</para>
      </tip>
    </sect2>
  </sect1>

  <sect1 xml:id="config-network-setup">
    <info>
      <title>Setting Up Network Interface Cards</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Marc</firstname>
	    <surname>Fonvieille</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>network cards</primary>
      <secondary>configuration</secondary>
    </indexterm>

    <para>Adding and configuring a network interface card
      (<acronym>NIC</acronym>)  is a common task for any &os;
      administrator.</para>

    <sect2>
      <title>Locating the Correct Driver</title>

      <indexterm>
	<primary>network cards</primary>
	<secondary>driver</secondary>
      </indexterm>

      <para>First, determine the model of the <acronym>NIC</acronym>
	and the chip it uses.  &os; supports a wide variety of
	<acronym>NIC</acronym>s.  Check the Hardware Compatibility
	List for the &os; release to see if the <acronym>NIC</acronym>
	is supported.</para>

      <para>If the <acronym>NIC</acronym> is supported, determine
	the name of the &os; driver for the <acronym>NIC</acronym>.
	Refer to <filename>/usr/src/sys/conf/NOTES</filename> and
	<filename>/usr/src/sys/arch/conf/NOTES</filename>
	for the list of <acronym>NIC</acronym> drivers with some
	information about the supported chipsets.  When in doubt, read
	the manual page of the driver as it will provide more
	information about the supported hardware and any known
	limitations of the driver.</para>

      <para>The drivers for common <acronym>NIC</acronym>s are
	already present in the <filename>GENERIC</filename> kernel,
	meaning the <acronym>NIC</acronym> should show up during boot.
	In this example, two <acronym>NIC</acronym>s using the
	&man.dc.4; driver are present on the system:</para>

      <screen>dc0: &lt;82c169 PNIC 10/100BaseTX&gt; port 0xa000-0xa0ff mem 0xd3800000-0xd38
000ff irq 15 at device 11.0 on pci0
miibus0: &lt;MII bus&gt; on dc0
bmtphy0: &lt;BCM5201 10/100baseTX PHY&gt; PHY 1 on miibus0
bmtphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
dc0: Ethernet address: 00:a0:cc:da:da:da
dc0: [ITHREAD]
dc1: &lt;82c169 PNIC 10/100BaseTX&gt; port 0x9800-0x98ff mem 0xd3000000-0xd30
000ff irq 11 at device 12.0 on pci0
miibus1: &lt;MII bus&gt; on dc1
bmtphy1: &lt;BCM5201 10/100baseTX PHY&gt; PHY 1 on miibus1
bmtphy1:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
dc1: Ethernet address: 00:a0:cc:da:da:db
dc1: [ITHREAD]</screen>

      <para>If the driver for the <acronym>NIC</acronym> is not
	present in <filename>GENERIC</filename>, but a driver is
	available, the driver will need to be loaded before the
	<acronym>NIC</acronym> can be configured and used.  This may
	be accomplished in one of two ways:</para>

      <itemizedlist>
	<listitem>
	  <para>The easiest way is to load a kernel module for the
	    <acronym>NIC</acronym> using &man.kldload.8;.  To also
	    automatically load the driver at boot time, add the
	    appropriate line to
	    <filename>/boot/loader.conf</filename>.  Not all
	    <acronym>NIC</acronym> drivers are available as
	    modules.</para>
	</listitem>

	<listitem>
	  <para>Alternatively, statically compile support for the
	    <acronym>NIC</acronym> into a custom kernel.  Refer to
	    <filename>/usr/src/sys/conf/NOTES</filename>,
	    <filename>/usr/src/sys/arch/conf/NOTES</filename> and the
	    manual page of the driver to determine which line to add
	    to the custom kernel configuration file.  For more
	    information about recompiling the kernel, refer to
	    <xref linkend="kernelconfig"/>.  If the
	    <acronym>NIC</acronym> was detected at boot, the kernel
	    does not need to be recompiled.</para>
	</listitem>
      </itemizedlist>

      <sect3 xml:id="config-network-ndis">
	<title>Using &windows; <acronym>NDIS</acronym> Drivers</title>

	<indexterm>
	  <primary><acronym>NDIS</acronym></primary>
	</indexterm>
	<indexterm>
	  <primary>NDISulator</primary>
	</indexterm>
	<indexterm>
	  <primary>&windows; drivers</primary>
	</indexterm>
	<indexterm>
	  <primary>&microsoft.windows;</primary>
	  <secondary>device drivers</secondary>
	</indexterm>
	<indexterm>
	  <primary><acronym>KLD</acronym> (kernel loadable
	    object)</primary>
	</indexterm>
<!-- We should probably omit the expanded name, and add a <see> entry
for it.  Whatever is done must also be done to the same indexterm in
linuxemu/chapter.xml -->

	<para>Unfortunately, there are still many vendors that do not
	  provide schematics for their drivers to the open source
	  community because they regard such information as trade
	  secrets.  Consequently, the developers of &os; and other
	  operating systems are left with two choices: develop the
	  drivers by a long and pain-staking process of reverse
	  engineering or using the existing driver binaries available
	  for &microsoft.windows; platforms.</para>

	<para>&os; provides <quote>native</quote> support for the
	  Network Driver Interface Specification
	  (<acronym>NDIS</acronym>).  It includes &man.ndisgen.8;
	  which can be used to convert a &windowsxp; driver into a
	  format that can be used on &os;.  Because the &man.ndis.4;
	  driver uses a &windowsxp; binary, it only runs on &i386;
	  and amd64 systems.  <acronym>PCI</acronym>, CardBus,
	  <acronym>PCMCIA</acronym>, and <acronym>USB</acronym>
	  devices are supported.</para>

	<para>To use &man.ndisgen.8;, three things are needed:</para>

	<orderedlist>
	  <listitem>
	    <para>&os; kernel sources.</para>
	  </listitem>

	  <listitem>
	    <para>A &windowsxp; driver binary with a
	      <filename>.SYS</filename> extension.</para>
	  </listitem>

	  <listitem>
	    <para>A &windowsxp; driver configuration file with a
	      <filename>.INF</filename> extension.</para>
	  </listitem>
	</orderedlist>

	<para>Download the <filename>.SYS</filename> and
	  <filename>.INF</filename> files for the specific
	  <acronym>NIC</acronym>.  Generally, these can be found on
	  the driver CD or at the vendor's website.  The following
	  examples use <filename>W32DRIVER.SYS</filename> and
	  <filename>W32DRIVER.INF</filename>.</para>

	<para>The driver bit width must match the version of &os;.
	  For &os;/i386, use a &windows; 32-bit driver.  For
	  &os;/amd64, a &windows; 64-bit driver is needed.</para>

	<para>The next step is to compile the driver binary into a
	  loadable kernel module.  As
	  <systemitem class="username">root</systemitem>, use
	  &man.ndisgen.8;:</para>

	<screen>&prompt.root; <userinput>ndisgen /path/to/W32DRIVER.INF /path/to/W32DRIVER.SYS</userinput></screen>

	<para>This command is interactive and prompts for any extra
	  information it requires.  A new kernel module will be
	  generated in the current directory.  Use &man.kldload.8;
	  to load the new module:</para>

	<screen>&prompt.root; <userinput>kldload ./W32DRIVER_SYS.ko</userinput></screen>

	<para>In addition to the generated kernel module, the
	  <filename>ndis.ko</filename> and
	  <filename>if_ndis.ko</filename> modules must be loaded.
	  This should happen automatically when any module that
	  depends on &man.ndis.4; is loaded.  If not, load them
	  manually, using the following commands:</para>

	<screen>&prompt.root; <userinput>kldload ndis</userinput>
&prompt.root; <userinput>kldload if_ndis</userinput></screen>

	<para>The first command loads the &man.ndis.4; miniport driver
	  wrapper and the second loads the generated
	  <acronym>NIC</acronym> driver.</para>

	<para>Check &man.dmesg.8; to see if there were any load
	  errors.  If all went well, the output should be similar to
	  the following:</para>

	<screen>ndis0: &lt;Wireless-G PCI Adapter&gt; mem 0xf4100000-0xf4101fff irq 3 at device 8.0 on pci1
ndis0: NDIS API version: 5.0
ndis0: Ethernet address: 0a:b1:2c:d3:4e:f5
ndis0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
ndis0: 11g rates: 6Mbps 9Mbps 12Mbps 18Mbps 36Mbps 48Mbps 54Mbps</screen>

	<para>From here, <filename>ndis0</filename> can be
	  configured like any other <acronym>NIC</acronym>.</para>

	<para>To configure the system to load the &man.ndis.4; modules
	  at boot time, copy the generated module,
	  <filename>W32DRIVER_SYS.ko</filename>, to
	  <filename>/boot/modules</filename>.  Then, add the following
	  line to <filename>/boot/loader.conf</filename>:</para>

	<programlisting>W32DRIVER_SYS_load="YES"</programlisting>
      </sect3>
    </sect2>

    <sect2>
      <title>Configuring the Network Card</title>

      <indexterm>
	<primary>network cards</primary>
	<secondary>configuration</secondary>
      </indexterm>

      <para>Once the right driver is loaded for the
	<acronym>NIC</acronym>, the card needs to be configured.  It
	may have been configured at installation time by
	&man.sysinstall.8;.</para>

      <para>To display the <acronym>NIC</acronym> configuration,
	enter the following command:</para>

      <screen>&prompt.user; <userinput>ifconfig</userinput>
dc0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
        options=80008&lt;VLAN_MTU,LINKSTATE&gt;
        ether 00:a0:cc:da:da:da
        inet 192.168.1.3 netmask 0xffffff00 broadcast 192.168.1.255
        media: Ethernet autoselect (100baseTX &lt;full-duplex&gt;)
        status: active
dc1: flags=8802&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
        options=80008&lt;VLAN_MTU,LINKSTATE&gt;
        ether 00:a0:cc:da:da:db
        inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255
        media: Ethernet 10baseT/UTP
        status: no carrier
lo0: flags=8049&lt;UP,LOOPBACK,RUNNING,MULTICAST&gt; metric 0 mtu 16384
        options=3&lt;RXCSUM,TXCSUM&gt;
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
        inet6 ::1 prefixlen 128
        inet 127.0.0.1 netmask 0xff000000
        nd6 options=3&lt;PERFORMNUD,ACCEPT_RTADV&gt;</screen>

      <para>In this example, the following devices were
	displayed:</para>

      <itemizedlist>
	<listitem>
	  <para><filename>dc0</filename>: The first Ethernet
	    interface.</para>
	</listitem>

	<listitem>
	  <para><filename>dc1</filename>: The second Ethernet
	    interface.</para>
	</listitem>

	<listitem>
	  <para><filename>lo0</filename>: The loopback
	    device.</para>
	</listitem>
      </itemizedlist>

      <para>&os; uses the driver name followed by the order in which
	the card is detected at boot to name the
	<acronym>NIC</acronym>.  For example,
	<filename>sis2</filename> is the third
	<acronym>NIC</acronym> on the system using the &man.sis.4;
	driver.</para>

      <para>In this example, <filename>dc0</filename> is up and
	running.  The key indicators are:</para>

      <orderedlist>
	<listitem>
	  <para><literal>UP</literal> means that the card is
	    configured and ready.</para>
	</listitem>

	<listitem>
	  <para>The card has an Internet (<literal>inet</literal>)
	    address, <systemitem
	      class="ipaddress">192.168.1.3</systemitem>.</para>
	</listitem>

	<listitem>
	  <para>It has a valid subnet mask
	    (<literal>netmask</literal>), where
	    <systemitem class="netmask">0xffffff00</systemitem> is the
	    same as <systemitem
	      class="netmask">255.255.255.0</systemitem>.</para>
	</listitem>

	<listitem>
	  <para>It has a valid broadcast address, <systemitem
	      class="ipaddress">192.168.1.255</systemitem>.</para>
	</listitem>

	<listitem>
	  <para>The <acronym>MAC</acronym> address of the card
	    (<literal>ether</literal>) is <systemitem
	      class="etheraddress">00:a0:cc:da:da:da</systemitem>.</para>
	</listitem>

	<listitem>
	  <para>The physical media selection is on autoselection mode
	    (<literal>media: Ethernet autoselect (100baseTX
	      &lt;full-duplex&gt;)</literal>).  In this example,
	    <filename>dc1</filename> is configured to run with
	    <literal>10baseT/UTP</literal> media.  For more
	    information on available media types for a driver, refer
	    to its manual page.</para>
	</listitem>

	<listitem>
	  <para>The status of the link (<literal>status</literal>) is
	    <literal>active</literal>, indicating that the carrier
	    signal is detected.  For <filename>dc1</filename>, the
	    <literal>status: no carrier</literal> status is normal
	    when an Ethernet cable is not plugged into the
	    card.</para>
	</listitem>
      </orderedlist>

      <para>If the &man.ifconfig.8; output had shown something similar
	to:</para>

      <screen>dc0: flags=8843&lt;BROADCAST,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
        options=80008&lt;VLAN_MTU,LINKSTATE&gt;
        ether 00:a0:cc:da:da:da
        media: Ethernet autoselect (100baseTX &lt;full-duplex&gt;)
        status: active</screen>

      <para>it would indicate the card has not been configured.</para>

      <para>The card must be configured as
	<systemitem class="username">root</systemitem>.  The
	<acronym>NIC</acronym> configuration can be performed from the
	command line with &man.ifconfig.8; but will not persist after
	a reboot unless the configuration is also added to
	<filename>/etc/rc.conf</filename>.  Add a line for each
	<acronym>NIC</acronym> present on the system, as seen in this
	example:</para>

      <programlisting>ifconfig_dc0="inet 192.168.1.3 netmask 255.255.255.0"
ifconfig_dc1="inet 10.0.0.1 netmask 255.255.255.0 media 10baseT/UTP"</programlisting>

      <para>Replace <filename>dc0</filename> and
	<filename>dc1</filename> and the <acronym>IP</acronym>
	address information with the correct values for the system.
	Refer to the man page for the driver, &man.ifconfig.8;, and
	&man.rc.conf.5; for more details about the allowed options and
	the syntax of <filename>/etc/rc.conf</filename>.</para>

      <para>If the network was configured during installation, some
	entries for the <acronym>NIC</acronym>(s) may be already
	present.  Double check <filename>/etc/rc.conf</filename>
	before adding any lines.</para>

      <para>If the network is not using <acronym>DNS</acronym>, edit
	<filename>/etc/hosts</filename> to add the names and
	<acronym>IP</acronym> addresses of of the hosts on the
	<acronym>LAN</acronym>, if they are not already there.  For
	more information, refer to &man.hosts.5; and to
	<filename>/usr/share/examples/etc/hosts</filename>.</para>

      <note>
	<para>If there is no <acronym>DHCP</acronym> server and
	  access to the Internet is needed, manually configure the
	  default gateway and the nameserver:</para>

	<screen>&prompt.root; <userinput>echo 'defaultrouter="your_default_router"' &gt;&gt; /etc/rc.conf</userinput>
&prompt.root; <userinput>echo 'nameserver your_DNS_server' &gt;&gt; /etc/resolv.conf</userinput></screen>
      </note>
    </sect2>

    <sect2>
      <title>Testing and Troubleshooting</title>

      <para>Once the necessary changes to
	<filename>/etc/rc.conf</filename> are saved, a reboot can be
	used to test the network configuration and to verify that the
	system restarts without any configuration errors.
	Alternatively, apply the settings to the networking system
	with this command:</para>

      <screen>&prompt.root; <userinput>service netif restart</userinput></screen>

      <note>
	<para>If a default gateway has been set in
	  <filename>/etc/rc.conf</filename>, also issue this
	  command:</para>

	<screen>&prompt.root; <userinput>service routing restart</userinput></screen>
      </note>

      <para>Once the networking system has been relaunched, test the
	<acronym>NIC</acronym>s.</para>

      <sect3>
	<title>Testing the Ethernet Card</title>

	<indexterm>
	  <primary>network cards</primary>
	  <secondary>testing</secondary>
	</indexterm>

	<para>To verify that an Ethernet card is configured correctly,
	  &man.ping.8; the interface itself, and then &man.ping.8;
	  another machine on the <acronym>LAN</acronym>:</para>

	<screen>&prompt.user; <userinput>ping -c5 192.168.1.3</userinput>
PING 192.168.1.3 (192.168.1.3): 56 data bytes
64 bytes from 192.168.1.3: icmp_seq=0 ttl=64 time=0.082 ms
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.074 ms
64 bytes from 192.168.1.3: icmp_seq=2 ttl=64 time=0.076 ms
64 bytes from 192.168.1.3: icmp_seq=3 ttl=64 time=0.108 ms
64 bytes from 192.168.1.3: icmp_seq=4 ttl=64 time=0.076 ms

--- 192.168.1.3 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.074/0.083/0.108/0.013 ms</screen>

	<screen>&prompt.user; <userinput>ping -c5 192.168.1.2</userinput>
PING 192.168.1.2 (192.168.1.2): 56 data bytes
64 bytes from 192.168.1.2: icmp_seq=0 ttl=64 time=0.726 ms
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.766 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.700 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=0.747 ms
64 bytes from 192.168.1.2: icmp_seq=4 ttl=64 time=0.704 ms

--- 192.168.1.2 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.700/0.729/0.766/0.025 ms</screen>

	<para>To test network resolution, use the host name instead
	  of the <acronym>IP</acronym> address.  If there is no
	  <acronym>DNS</acronym> server on the network,
	  <filename>/etc/hosts</filename> must first be
	  configured.</para>
      </sect3>

      <sect3>
	<title>Troubleshooting</title>

	<indexterm>
	  <primary>network cards</primary>
	  <secondary>troubleshooting</secondary>
	</indexterm>

	<para>When troubleshooting hardware and software
	  configurations, check the simple things first.  Is the
	  network cable plugged in?  Are the network services properly
	  configured?  Is the firewall configured correctly?  Is the
	  <acronym>NIC</acronym> supported by &os;?  Before sending
	  a bug report, always check the Hardware Notes, update the
	  version of &os; to the latest STABLE version, check the
	  mailing list archives, and search the Internet.</para>

	<para>If the card works, yet performance is poor, read
	  through &man.tuning.7;.  Also, check the network
	  configuration as incorrect network settings can cause slow
	  connections.</para>

	<para>Some users experience one or two
	  <errorname>device timeout</errorname> messages, which is
	  normal for some cards.  If they continue, or are bothersome,
	  determine if the device is conflicting with another device.
	  Double check the cable connections.  Consider trying another
	  card.</para>

	<para>To resolve <errorname>watchdog timeout</errorname>
	  errors,  first check the network cable.  Many cards
	  require a <acronym>PCI</acronym> slot which supports bus
	  mastering.  On some old motherboards, only one
	  <acronym>PCI</acronym> slot allows it, usually slot 0.
	  Check the <acronym>NIC</acronym> and the motherboard
	  documentation to determine if that may be the
	  problem.</para>

	<para><errorname>No route to host</errorname> messages occur
	  if the system is unable to route a packet to the destination
	  host.  This can happen if no default route is specified or
	  if a cable is unplugged.  Check the output of
	  <command>netstat -rn</command> and make sure there is a
	  valid route to the host.  If there is not, read
	  <xref linkend="advanced-networking"/>.</para>

	<para><errorname>ping: sendto: Permission denied</errorname>
	  error messages are often caused by a misconfigured firewall.
	  If a firewall is enabled on &os; but no rules have been
	  defined, the default policy is to deny all traffic, even
	  &man.ping.8;.  Refer to
	  <xref linkend="firewalls"/> for more information.</para>

	<para>Sometimes performance of the card is poor or below
	  average.  In these cases, try setting the media
	  selection mode from <literal>autoselect</literal> to the
	  correct media selection.  While this works for most
	  hardware, it may or may not resolve the issue.  Again,
	  check all the network settings, and refer to
	  &man.tuning.7;.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-virtual-hosts">
    <title>Virtual Hosts</title>

    <indexterm><primary>virtual hosts</primary></indexterm>
    <indexterm><primary><acronym>IP</acronym>
	aliases</primary></indexterm>

    <para>A common use of &os; is virtual site hosting, where one
      server appears to the network as many servers.  This is achieved
      by assigning multiple network addresses to a single
      interface.</para>

    <para>A given network interface has one <quote>real</quote>
      address, and may have any number of <quote>alias</quote>
      addresses.  These aliases are normally added by placing alias
      entries in <filename>/etc/rc.conf</filename>, as seen in this
      example:</para>

    <programlisting>ifconfig_fxp0_alias0="inet xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx"</programlisting>

    <para>Alias entries must start with
      <literal>alias0</literal> using a
      sequential number such as
      <literal>alias0</literal>, <literal>alias1</literal>,
      and so on.  The configuration process will stop at the first
      missing number.</para>

    <para>The calculation of alias netmasks is important.  For a
      given interface, there must be one address which correctly
      represents the network's netmask.  Any other addresses which
      fall within this network must have a netmask of all
      <literal>1</literal>s, expressed as either
      <systemitem class="netmask">255.255.255.255</systemitem> or
      <systemitem class="netmask">0xffffffff</systemitem>.</para>

    <para>For example, consider the case where the
      <filename>fxp0</filename> interface is connected to two
      networks: <systemitem class="ipaddress">10.1.1.0</systemitem>
      with a netmask of
      <systemitem class="netmask">255.255.255.0</systemitem> and
      <systemitem class="ipaddress">202.0.75.16</systemitem> with a
      netmask of
      <systemitem class="netmask">255.255.255.240</systemitem>.  The
      system is to be configured to appear in the ranges
      <systemitem class="ipaddress">10.1.1.1</systemitem> through
      <systemitem class="ipaddress">10.1.1.5</systemitem> and
      <systemitem class="ipaddress">202.0.75.17</systemitem> through
      <systemitem class="ipaddress">202.0.75.20</systemitem>.  Only
      the first address in a given network range should have a real
      netmask.  All the rest
      (<systemitem class="ipaddress">10.1.1.2</systemitem> through
      <systemitem class="ipaddress">10.1.1.5</systemitem> and
      <systemitem class="ipaddress">202.0.75.18</systemitem> through
      <systemitem class="ipaddress">202.0.75.20</systemitem>) must be
      configured with a netmask of
      <systemitem class="netmask">255.255.255.255</systemitem>.</para>

    <para>The following <filename>/etc/rc.conf</filename> entries
      configure the adapter correctly for this scenario:</para>

    <programlisting>ifconfig_fxp0="inet 10.1.1.1 netmask 255.255.255.0"
ifconfig_fxp0_alias0="inet 10.1.1.2 netmask 255.255.255.255"
ifconfig_fxp0_alias1="inet 10.1.1.3 netmask 255.255.255.255"
ifconfig_fxp0_alias2="inet 10.1.1.4 netmask 255.255.255.255"
ifconfig_fxp0_alias3="inet 10.1.1.5 netmask 255.255.255.255"
ifconfig_fxp0_alias4="inet 202.0.75.17 netmask 255.255.255.240"
ifconfig_fxp0_alias5="inet 202.0.75.18 netmask 255.255.255.255"
ifconfig_fxp0_alias6="inet 202.0.75.19 netmask 255.255.255.255"
ifconfig_fxp0_alias7="inet 202.0.75.20 netmask 255.255.255.255"</programlisting>
  </sect1>

  <sect1 xml:id="configtuning-syslog">
    <info>
      <title>Configuring the System Logger,
	<command>syslogd</command></title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Niclas</firstname>
	    <surname>Zeising</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>system logging</primary>
    </indexterm>
    <indexterm>
      <primary>syslog</primary>
    </indexterm>
    <indexterm>
      <primary>&man.syslogd.8;</primary>
    </indexterm>

    <para>System logging is an important aspect of system
      administration.  It is used to detect hardware and software
      issues and errors in the system.  It plays an important role
      in security auditing and incident response.  System daemons
      without a controlling terminal usually log information to a
      system logging facility or other log file.</para>

    <para>This section describes how to configure and use the &os;
      system logger, &man.syslogd.8;, and how to perform log rotation
      and log management using &man.newsyslog.8;.  Focus will be on
      setting up and using &man.syslogd.8; on a local machine.  For
      more advanced setups using a separate loghost, see
      <xref linkend="network-syslogd"/>.</para>

    <sect2>
      <title>Using <command>syslogd</command></title>

      <para>In the default &os; configuration, &man.syslogd.8; is
	started at boot.  This is controlled by the variable
	<literal>syslogd_enable</literal> in
	<filename>/etc/rc.conf</filename>.  There are numerous
	application arguments that affect the behavior of
	&man.syslogd.8;.  To change them, use
	<literal>syslogd_flags</literal> in
	<filename>/etc/rc.conf</filename>.  Refer to &man.syslogd.8;
	for more information on the arguments, and &man.rc.conf.5;,
	<xref linkend="configtuning-core-configuration"/> and
	<xref linkend="configtuning-rcd"/> for more information about
	<filename>/etc/rc.conf</filename> and the &man.rc.8;
	subsystem.</para>
    </sect2>

    <sect2>
      <title>Configuring <command>syslogd</command></title>

      <indexterm><primary>syslog.conf</primary></indexterm>

      <para>The configuration file, by default
	<filename>/etc/syslog.conf</filename>, controls what
	&man.syslogd.8; does with the log entries once they are
	received.  There are several parameters to control the
	handling of incoming events, of which the most basic are
	<firstterm>facility</firstterm> and
	<firstterm>level</firstterm>.  The facility describes
	which subsystem generated the message, such as the kernel or a
	daemon, and the level describes the severity of the event that
	occurred.  This makes it possible to log the message to
	different log files, or discard it, depending on the facility
	and level.  It is also possible to take action depending on
	the application that sent the message, and in the case of
	remote logging, the hostname of the machine generating
	the logging event.</para>

      <para>The configuration file for &man.syslogd.8; contains one
	line per action, and the syntax for each line is a selector
	field followed by an action field.  The syntax of the selector
	field is <replaceable>facility.level</replaceable> which will
	match log messages from <replaceable>facility</replaceable>
	at level <replaceable>level</replaceable> or higher.  It is
	also possible to add an optional comparison flag before the
	level to specify more precisely what is logged.  Multiple
	selector fields can be used for the same action, and are
	separated with a semicolon (<literal>;</literal>).  Using
	<literal>*</literal> will match everything.  The action field
	denotes where to send the log message, such as to a file or
	remote log host.  As an example, here is the default
	<filename>syslog.conf</filename> from &os;:</para>

      <programlisting># &dollar;&os;&dollar;
#
#       Spaces ARE valid field separators in this file. However,
#       other *nix-like systems still insist on using tabs as field
#       separators. If you are sharing this file between systems, you
#       may want to use only tabs as field separators here.
#       Consult the syslog.conf(5) manpage.
*.err;kern.warning;auth.notice;mail.crit                /dev/console <co xml:id="co-syslog-many-match"/>
*.notice;authpriv.none;kern.debug;lpr.info;mail.crit;news.err   /var/log/messages
security.*                                      /var/log/security
auth.info;authpriv.info                         /var/log/auth.log
mail.info                                       /var/log/maillog <co xml:id="co-syslog-one-match"/>
lpr.info                                        /var/log/lpd-errs
ftp.info                                        /var/log/xferlog
cron.*                                          /var/log/cron
*.=debug                                        /var/log/debug.log <co xml:id="co-syslog-comparison"/>
*.emerg                                         *
# uncomment this to log all writes to /dev/console to /var/log/console.log
#console.info                                   /var/log/console.log
# uncomment this to enable logging of all log messages to /var/log/all.log
# touch /var/log/all.log and chmod it to mode 600 before it will work
#*.*                                            /var/log/all.log
# uncomment this to enable logging to a remote loghost named loghost
#*.*                                            @loghost
# uncomment these if you're running inn
# news.crit                                     /var/log/news/news.crit
# news.err                                      /var/log/news/news.err
# news.notice                                   /var/log/news/news.notice
!ppp <co xml:id="co-syslog-prog-spec"/>
*.*                                             /var/log/ppp.log
!*</programlisting>

      <calloutlist>
	<callout arearefs="co-syslog-many-match">
	  <para>Match all messages with a level of
	    <literal>err</literal> or higher, as well as
	    <literal>kern.warning</literal>,
	    <literal>auth.notice</literal> and
	    <literal>mail.crit</literal>, and send these log messages
	    to the console
	    (<filename>/dev/console</filename>).</para>
	</callout>

	<callout arearefs="co-syslog-one-match">
	  <para>Match all messages from the <literal>mail</literal>
	    facility at level <literal>info</literal> or above, and
	    log the messages to
	    <filename>/var/log/maillog</filename>.</para>
	</callout>

	<callout arearefs="co-syslog-comparison">
	  <para>This line uses a comparison flag, <literal>=</literal>
	    to only match messages at level <literal>debug</literal>,
	    and log them in
	    <filename>/var/log/debug.log</filename>.</para>
	</callout>

	<callout arearefs="co-syslog-prog-spec">
	  <para>Here is an example usage of a <emphasis>program
	      specification</emphasis>.  This makes the rules
	    following it only valid for the program in the program
	    specification.  In this case, this and the following
	    lines log all messages from &man.ppp.8;, but no other
	    programs, to
	    <filename>/var/log/ppp.log</filename>.</para>
	</callout>
      </calloutlist>

      <para>This example shows that there are plenty of levels and
	subsystems.  The levels are, in order from most to least
	critical: <literal>emerg</literal>, <literal>alert</literal>,
	<literal>crit</literal>, <literal>err</literal>,
	<literal>warning</literal>, <literal>notice</literal>,
	<literal>info</literal>, and <literal>debug</literal>.</para>

      <para>The facilities are, in no particular order:
	<literal>auth</literal>, <literal>authpriv</literal>,
	<literal>console</literal>, <literal>cron</literal>,
	<literal>daemon</literal>, <literal>ftp</literal>,
	<literal>kern</literal>, <literal>lpr</literal>,
	<literal>mail</literal>, <literal>mark</literal>,
	<literal>news</literal>, <literal>security</literal>,
	<literal>syslog</literal>, <literal>user</literal>,
	<literal>uucp</literal>, and <literal>local0</literal> through
	<literal>local7</literal>.  Be aware that other operating
	systems might have different facilities.</para>

      <para>With this knowledge, it is easy to add a new line to
	<filename>/etc/syslog.conf</filename> to log everything from
	the different daemons on level <literal>notice</literal> and
	higher to <filename>/var/log/daemon.log</filename>.  Just add
	the following:</para>

      <programlisting>daemon.notice                                        /var/log/daemon.log</programlisting>

      <para>For more information about the different levels and
	facilities, refer to &man.syslog.3; and &man.syslogd.8;.
	For more information about
	<filename>/etc/syslog.conf</filename>, its syntax, and more
	advanced usage examples, see &man.syslog.conf.5; and
	<xref linkend="network-syslogd"/>.</para>
    </sect2>

    <sect2>
      <title>Log Management and Rotation with
	<command>newsyslog</command></title>

      <indexterm><primary>newsyslog</primary></indexterm>
      <indexterm><primary>newsyslog.conf</primary></indexterm>
      <indexterm><primary>log rotation</primary></indexterm>
      <indexterm><primary>log management</primary></indexterm>

      <para>Log files tend to grow quickly and accumulate steadily.
	This leads to the files being full of less immediately useful
	information while filling up the hard drive.  Log management
	attempts to mitigate this.  In &os;, &man.newsyslog.8; is used
	to manage log files.  This program periodically rotates and
	compresses log files, and optionally creates missing log files
	and signals programs when log files are moved.  The log files
	are not necessarily generated by &man.syslogd.8; as
	&man.newsyslog.8; works with any logs written from any
	program.  While &man.newsyslog.8; is normally run from
	&man.cron.8;, it is not a system daemon.  In the default
	configuration, it is run every hour.</para>

      <sect3>
	<title>Configuring
	  <command>newsyslog</command></title>

	<para>To know which actions to take, &man.newsyslog.8; reads
	  its configuration file, by default
	  <filename>/etc/newsyslog.conf</filename>.  This
	  configuration file contains one line for each file that
	  &man.newsyslog.8; manages.  Each line states the file
	  owner, permissions, when to rotate that file, optional flags
	  that affect log rotation, such as compression, and programs
	  to signal when the log is rotated.  Here is the default
	  configuration in &os;:</para>

	<programlisting># configuration file for newsyslog
# $FreeBSD$
#
# Entries which do not specify the '/pid_file' field will cause the
# syslogd process to be signalled when that log file is rotated.  This
# action is only appropriate for log files which are written to by the
# syslogd process (ie, files listed in /etc/syslog.conf).  If there
# is no process which needs to be signalled when a given log file is
# rotated, then the entry for that file should include the 'N' flag.
#
# The 'flags' field is one or more of the letters: BCDGJNUXZ or a '-'.
#
# Note: some sites will want to select more restrictive protections than the
# defaults.  In particular, it may be desirable to switch many of the 644
# entries to 640 or 600.  For example, some sites will consider the
# contents of maillog, messages, and lpd-errs to be confidential.  In the
# future, these defaults may change to more conservative ones.
#
# logfilename          [owner:group]    mode count size when  flags [/pid_file] [sig_num]
/var/log/all.log                        600  7     *    @T00  J
/var/log/amd.log                        644  7     100  *     J
/var/log/auth.log                       600  7     100  @0101T JC
/var/log/console.log                    600  5     100  *     J
/var/log/cron                           600  3     100  *     JC
/var/log/daily.log                      640  7     *    @T00  JN
/var/log/debug.log                      600  7     100  *     JC
/var/log/kerberos.log                   600  7     100  *     J
/var/log/lpd-errs                       644  7     100  *     JC
/var/log/maillog                        640  7     *    @T00  JC
/var/log/messages                       644  5     100  @0101T JC
/var/log/monthly.log                    640  12    *    $M1D0 JN
/var/log/pflog                          600  3     100  *     JB    /var/run/pflogd.pid
/var/log/ppp.log        root:network    640  3     100  *     JC
/var/log/security                       600  10    100  *     JC
/var/log/sendmail.st                    640  10    *    168   B
/var/log/utx.log                        644  3     *    @01T05 B
/var/log/weekly.log                     640  5     1    $W6D0 JN
/var/log/xferlog                        600  7     100  *     JC</programlisting>

	<para>Each line starts with the name of the file to be
	  rotated, optionally followed by an owner and group for both
	  rotated and newly created files.  The
	  <literal>mode</literal> field sets the permissions on the
	  log file and <literal>count</literal> denotes how many
	  rotated log files should be kept.  The
	  <literal>size</literal> and <literal>when</literal> fields
	  tell &man.newsyslog.8; when to rotate the file.  A log
	  file is rotated when either its size is larger than the
	  <literal>size</literal> field, or when the time in the
	  <literal>when</literal> filed has passed.
	  <literal>*</literal> means that this field is ignored.  The
	  <replaceable>flags</replaceable> field gives
	  &man.newsyslog.8; further instructions, such as how to
	  compress the rotated file or to create the log file if it
	  is missing.  The last two fields are optional, and
	  specify the
	  <acronym role="Process Identifier">PID</acronym> file of a
	  process and a signal number to send to that process when the
	  file is rotated.  For more information on all fields, valid
	  flags, and how to specify the rotation time, refer to
	  &man.newsyslog.conf.5;.  Since &man.newsyslog.8; is run from
	  &man.cron.8;, it can not rotate files more often than it is
	  run from &man.cron.8;.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-configfiles">
    <title>Configuration Files</title>

    <sect2>
      <title><filename>/etc</filename>
	Layout</title>

      <para>There are a number of directories in which configuration
	information is kept.  These include:</para>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	  <colspec colwidth="1*"/>
	  <colspec colwidth="2*"/>

	  <tbody>
	    <row>
	      <entry><filename>/etc</filename></entry>
	      <entry>Generic system-specific configuration
		information.</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/defaults</filename></entry>
	      <entry>Default versions of system configuration
		files.</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/mail</filename></entry>
	      <entry>Extra &man.sendmail.8; configuration and other
		<acronym>MTA</acronym> configuration files.</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/ppp</filename></entry>
	      <entry>Configuration for both user- and kernel-ppp
		programs.</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/namedb</filename></entry>
	      <entry>Default location for &man.named.8; data.
		Normally <filename>named.conf</filename> and zone
		files are stored here.</entry>
	    </row>

	    <row>
	      <entry><filename>/usr/local/etc</filename></entry>
	      <entry>Configuration files for installed applications.
		May contain per-application subdirectories.</entry>
	    </row>

	    <row>
	      <entry><filename>/usr/local/etc/rc.d</filename></entry>
	      <entry>&man.rc.8; scripts for installed
		applications.</entry>
	    </row>

	    <row>
	      <entry><filename>/var/db</filename></entry>
	      <entry>Automatically generated system-specific database
		files, such as the package database and the
		&man.locate.1; database.</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>
    </sect2>

    <sect2>
      <title>Hostnames</title>

      <indexterm><primary>hostname</primary></indexterm>
      <indexterm><primary>DNS</primary></indexterm>

      <sect3>
	<title><filename>/etc/resolv.conf</filename></title>

	<indexterm>
	  <primary><filename>resolv.conf</filename></primary>
	</indexterm>

	<para>How a &os; system accesses the Internet Domain Name
	  System (<acronym>DNS</acronym>) is controlled by
	  &man.resolv.conf.5;.</para>

	<para>The most common entries to
	  <filename>/etc/resolv.conf</filename> are:</para>

	<informaltable frame="none" pgwide="1">
	  <tgroup cols="2">
	    <colspec colwidth="1*"/>
	    <colspec colwidth="2*"/>

	    <tbody>
	      <row>
		<entry><literal>nameserver</literal></entry>
		<entry>The <acronym>IP</acronym> address of a name
		  server the resolver should query.  The servers are
		  queried in the order listed with a maximum of
		  three.</entry>
	      </row>

	      <row>
		<entry><literal>search</literal></entry>
		<entry>Search list for hostname lookup.  This is
		  normally determined by the domain of the local
		  hostname.</entry>
	      </row>

	      <row>
		<entry><literal>domain</literal></entry>
		<entry>The local domain name.</entry>
	      </row>
	    </tbody>
	  </tgroup>
	</informaltable>

	<para>A typical <filename>/etc/resolv.conf</filename> looks
	  like this:</para>

	<programlisting>search example.com
nameserver 147.11.1.11
nameserver 147.11.100.30</programlisting>

	<note>
	  <para>Only one of the <literal>search</literal> and
	    <literal>domain</literal> options should be used.</para>
	</note>

	<para>When using <acronym>DHCP</acronym>, &man.dhclient.8;
	  usually rewrites <filename>/etc/resolv.conf</filename>
	  with information received from the <acronym>DHCP</acronym>
	  server.</para>
      </sect3>

      <sect3>
	<title><filename>/etc/hosts</filename></title>

	<indexterm><primary>hosts</primary></indexterm>

	<para><filename>/etc/hosts</filename> is a simple text
	  database which works in conjunction with
	  <acronym>DNS</acronym> and
	  <acronym>NIS</acronym> to provide host name to
	  <acronym>IP</acronym> address mappings.  Entries for local
	  computers connected via a <acronym>LAN</acronym> can be
	  added to this file for simplistic naming purposes instead
	  of setting up a &man.named.8; server.  Additionally,
	  <filename>/etc/hosts</filename> can be used to provide a
	  local record of Internet names, reducing the need to query
	  external <acronym>DNS</acronym> servers for commonly
	  accessed names.</para>

	<programlisting># &dollar;&os;&dollar;
#
#
# Host Database
#
# This file should contain the addresses and aliases for local hosts that
# share this file.  Replace 'my.domain' below with the domainname of your
# machine.
#
# In the presence of the domain name service or NIS, this file may
# not be consulted at all; see /etc/nsswitch.conf for the resolution order.
#
#
::1			localhost localhost.my.domain
127.0.0.1		localhost localhost.my.domain
#
# Imaginary network.
#10.0.0.2		myname.my.domain myname
#10.0.0.3		myfriend.my.domain myfriend
#
# According to RFC 1918, you can use the following IP networks for
# private nets which will never be connected to the Internet:
#
#	10.0.0.0	-   10.255.255.255
#	172.16.0.0	-   172.31.255.255
#	192.168.0.0	-   192.168.255.255
#
# In case you want to be able to connect to the Internet, you need
# real official assigned numbers.  Do not try to invent your own network
# numbers but instead get one from your network provider (if any) or
# from your regional registry (ARIN, APNIC, LACNIC, RIPE NCC, or AfriNIC.)
#</programlisting>

	<para>The format of <filename>/etc/hosts</filename> is as
	  follows:</para>

	<programlisting>[Internet address] [official hostname] [alias1] [alias2] ...</programlisting>

	<para>For example:</para>

	<programlisting>10.0.0.1 myRealHostname.example.com myRealHostname foobar1 foobar2</programlisting>

	<para>Consult &man.hosts.5; for more information.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-sysctl">
    <title>Tuning with &man.sysctl.8;</title>

    <indexterm><primary>sysctl</primary></indexterm>
    <indexterm>
      <primary>tuning</primary>
      <secondary>with sysctl</secondary>
    </indexterm>

    <para>&man.sysctl.8; is used to make changes to a running &os;
      system.  This includes many advanced options of the
      <acronym>TCP/IP</acronym> stack and virtual memory system
      that can dramatically improve performance for an experienced
      system administrator.  Over five hundred system variables can
      be read and set using &man.sysctl.8;.</para>

    <para>At its core, &man.sysctl.8; serves two functions: to read
      and to modify system settings.</para>

    <para>To view all readable variables:</para>

    <screen>&prompt.user; <userinput>sysctl -a</userinput></screen>

    <para>To read a particular variable, specify its name:</para>

    <screen>&prompt.user; <userinput>sysctl kern.maxproc</userinput>
kern.maxproc: 1044</screen>

    <para>To set a particular variable, use the
      <replaceable>variable</replaceable>=<replaceable>value</replaceable>
      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, where a boolean is <literal>1</literal>
      for yes or <literal>0</literal> for no.</para>

    <para>To automatically set some variables each time the machine
      boots, add them to <filename>/etc/sysctl.conf</filename>.  For
      more information, refer to &man.sysctl.conf.5; and
      <xref linkend="configtuning-sysctlconf"/>.</para>

    <sect2 xml:id="configtuning-sysctlconf">
      <title><filename>sysctl.conf</filename></title>

      <indexterm><primary>sysctl.conf</primary></indexterm>
      <indexterm><primary>sysctl</primary></indexterm>

      <para>The configuration file for &man.sysctl.8;,
	<filename>/etc/sysctl.conf</filename>, looks much like
	<filename>/etc/rc.conf</filename>.  Values are set in a
	<literal>variable=value</literal> form.  The specified values
	are set after the system goes into multi-user mode.  Not all
	variables are settable in this mode.</para>

      <para>For example, to turn off logging of fatal signal exits
	and prevent users from seeing processes started by other
	users, the following tunables can be set in
	<filename>/etc/sysctl.conf</filename>:</para>

      <programlisting># Do not log fatal signal exits (e.g., sig 11)
kern.logsigexit=0

# Prevent users from seeing information about processes that
# are being run under another UID.
security.bsd.see_other_uids=0</programlisting>
    </sect2>

    <sect2 xml:id="sysctl-readonly">
      <info>
	<title>&man.sysctl.8; Read-only</title>

	<authorgroup>
	  <author>
	    <personname>
	      <firstname>Tom</firstname>
	      <surname>Rhodes</surname>
	    </personname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </info>

      <para>In some cases it may be desirable to modify read-only
	&man.sysctl.8; values, which will require a reboot of the
	system.</para>

      <para>For instance, on some laptop models the &man.cardbus.4;
	device will not probe memory ranges and will fail with errors
	similar to:</para>

      <screen>cbb0: Could not map register memory
device_probe_and_attach: cbb0 attach returned 12</screen>

      <para>The fix requires the modification of a read-only
	&man.sysctl.8; setting.  Add
	<option>hw.pci.allow_unsupported_io_range=1</option> to
	<filename>/boot/loader.conf</filename> and reboot.  Now
	&man.cardbus.4; should work properly.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-disk">
    <title>Tuning Disks</title>

    <para>The following section will discuss various tuning
      mechanisms and options which may be applied to disk
      devices.  In many cases, disks with mechanical parts,
      such as <acronym>SCSI</acronym> drives, will be the
      bottleneck driving down the overall system performance.  While
      a solution is to install a drive without mechanical parts,
      such as a solid state drive, mechanical drives are not
      going away anytime in the near future.  When tuning disks,
      it is advisable to utilize the features of the &man.iostat.8;
      command to test various changes to the system.  This
      command will allow the user to obtain valuable information
      on system <acronym>IO</acronym>.</para>

    <sect2>
      <title>Sysctl Variables</title>

      <sect3>
	<title><varname>vfs.vmiodirenable</varname></title>

	<indexterm>
	  <primary><varname>vfs.vmiodirenable</varname></primary>
	</indexterm>

	<para>The <varname>vfs.vmiodirenable</varname> &man.sysctl.8;
	  variable
	  may be set to either <literal>0</literal> (off) or
	  <literal>1</literal> (on).  It is set to
	  <literal>1</literal> by default.  This variable controls
	  how directories are cached by the system.  Most directories
	  are small, using just a single fragment (typically 1&nbsp;K)
	  in the file system and typically 512&nbsp;bytes in the
	  buffer cache.  With this variable turned off, the buffer
	  cache will only cache a fixed number of directories, even
	  if the system has a huge amount of memory.  When turned on,
	  this &man.sysctl.8; allows the buffer cache to use the
	  <acronym>VM</acronym> page cache to cache the directories,
	  making all the memory available for caching directories.
	  However, the minimum in-core memory used to cache a
	  directory is the physical page size (typically 4&nbsp;K)
	  rather than 512&nbsp; bytes.  Keeping this option enabled
	  is recommended if the system is running any services which
	  manipulate large numbers of files.  Such services can
	  include web caches, large mail systems, and news systems.
	  Keeping this option on will generally not reduce
	  performance, even with the wasted memory, but one should
	  experiment to find out.</para>
      </sect3>

      <sect3>
	<title><varname>vfs.write_behind</varname></title>

	<indexterm>
	  <primary><varname>vfs.write_behind</varname></primary>
	</indexterm>

	<para>The <varname>vfs.write_behind</varname> &man.sysctl.8;
	  variable
	  defaults to <literal>1</literal> (on).  This tells the file
	  system to issue media writes as full clusters are collected,
	  which typically occurs when writing large sequential files.
	  This avoids saturating the buffer cache with dirty buffers
	  when it would not benefit I/O performance.  However, this
	  may stall processes and under certain circumstances should
	  be turned off.</para>
      </sect3>

      <sect3>
	<title><varname>vfs.hirunningspace</varname></title>

	<indexterm>
	  <primary><varname>vfs.hirunningspace</varname></primary>
	</indexterm>

	<para>The <varname>vfs.hirunningspace</varname> &man.sysctl.8;
	  variable determines how much outstanding write I/O may be
	  queued to disk controllers system-wide at any given
	  instance.  The default is usually sufficient, but on
	  machines with many disks, try bumping it up to four or five
	  <emphasis>megabytes</emphasis>.  Setting too high a value
	  which exceeds the buffer cache's write threshold can lead
	  to bad clustering performance.  Do not set this value
	  arbitrarily high as higher write values may add latency to
	  reads occurring at the same time.</para>

	<para>There are various other buffer cache and
	  <acronym>VM</acronym> page cache related &man.sysctl.8;
	  values.  Modifying these values is not recommended as the
	  <acronym>VM</acronym> system does a good job of
	  automatically tuning itself.</para>
      </sect3>

      <sect3>
	<title><varname>vm.swap_idle_enabled</varname></title>

	<indexterm>
	  <primary><varname>vm.swap_idle_enabled</varname></primary>
	</indexterm>

	<para>The <varname>vm.swap_idle_enabled</varname>
	  &man.sysctl.8; variable is useful in large multi-user
	  systems with many active login users and lots of idle
	  processes.  Such systems tend to generate continuous
	  pressure on free memory reserves.  Turning this feature on
	  and tweaking the swapout hysteresis (in idle seconds) via
	  <varname>vm.swap_idle_threshold1</varname> and
	  <varname>vm.swap_idle_threshold2</varname> depresses the
	  priority of memory pages associated with idle processes more
	  quickly then the normal pageout algorithm.  This gives a
	  helping hand to the pageout daemon.  Only turn this option
	  on if needed, because the tradeoff is essentially pre-page
	  memory sooner rather than later which eats more swap and
	  disk bandwidth.  In a small system this option will have a
	  determinable effect, but in a large system that is already
	  doing moderate paging, this option allows the
	  <acronym>VM</acronym> system to stage whole processes into
	  and out of memory easily.</para>
      </sect3>

      <sect3>
	<title><varname>hw.ata.wc</varname></title>

	<indexterm>
	  <primary><varname>hw.ata.wc</varname></primary>
	</indexterm>

	<para>Turning off <acronym>IDE</acronym> write caching reduces
	  write bandwidth to <acronym>IDE</acronym> disks, but may
	  sometimes be necessary due to data consistency issues
	  introduced by hard drive vendors.  The problem is that
	  some <acronym>IDE</acronym> drives lie about when a write
	  completes.  With <acronym>IDE</acronym> write caching
	  turned on, <acronym>IDE</acronym> hard drives write data
	  to disk out of order and will sometimes delay writing some
	  blocks indefinitely when under heavy disk load.  A crash or
	  power failure may cause serious file system corruption.
	  Check the default on the system by observing the
	  <varname>hw.ata.wc</varname> &man.sysctl.8; variable.  If
	  <acronym>IDE</acronym> write caching is turned off, one can
	  set this read-only variable to
	  <literal>1</literal> in
	  <filename>/boot/loader.conf</filename> in order to enable
	  it at boot time.</para>

	<para>For more information, refer to &man.ata.4;.</para>
      </sect3>

      <sect3>
	<title><literal>SCSI_DELAY</literal>
	  (<varname>kern.cam.scsi_delay</varname>)</title>

	<indexterm>
	  <primary><varname>kern.cam.scsi_delay</varname></primary>
	</indexterm>

	<indexterm>
	  <primary>kernel options</primary>
	  <secondary><literal>SCSI DELAY</literal></secondary>
	</indexterm>

	<para>The <literal>SCSI_DELAY</literal> kernel configuration
	  option may be used to reduce system boot times.  The
	  defaults are fairly high and can be responsible for
	  <literal>15</literal> seconds of delay in the boot process.
	  Reducing it to <literal>5</literal> seconds usually works
	  with modern drives.  The
	  <varname>kern.cam.scsi_delay</varname> boot time tunable
	  should be used.  The tunable and kernel configuration
	  option accept values in terms of
	  <emphasis>milliseconds</emphasis> and
	  <emphasis>not</emphasis>
	  <emphasis>seconds</emphasis>.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="soft-updates">
      <title>Soft Updates</title>

      <indexterm><primary>Soft Updates</primary></indexterm>
      <indexterm><primary>&man.tunefs.8;</primary></indexterm>

      <para>To fine-tune a file system, use &man.tunefs.8;.  This
	program has many different options.  To toggle Soft Updates
	on and off, use:</para>

      <screen>&prompt.root; <userinput>tunefs -n enable /filesystem</userinput>
&prompt.root; <userinput>tunefs -n disable /filesystem</userinput></screen>

      <para>A file system cannot be modified with &man.tunefs.8; while
	it is mounted.  A good time to enable Soft Updates is before
	any partitions have been mounted, in single-user mode.</para>

      <para>Soft Updates is recommended for <acronym>UFS</acronym>
	file systems as it drastically improves meta-data performance,
	mainly file creation and deletion, through the use of a memory
	cache.  There are two downsides to Soft Updates to be aware
	of.  First, Soft Updates guarantee file system consistency
	in the case of a crash, but could easily be several seconds
	or even a minute behind updating the physical disk.  If the
	system crashes, unwritten data may be lost.  Secondly, Soft
	Updates delay the freeing of file system blocks.  If the
	root file system is almost full, performing a major update,
	such as <command>make installworld</command>, can cause the
	file system to run out of space and the update to fail.</para>

      <sect3>
	<title>More Details About Soft Updates</title>

	<indexterm>
	  <primary>Soft Updates</primary>
	  <secondary>details</secondary>
	</indexterm>

	<para>Meta-data updates are updates to non-content data like
	  inodes or directories.  There are two traditional approaches
	  to writing a file system's meta-data back to disk.</para>

	<para>Historically, the default behavior was to write out
	  meta-data updates synchronously.  If a directory changed,
	  the system waited until the change was actually written to
	  disk.  The file data buffers (file contents) were passed
	  through the buffer cache and backed up to disk later on
	  asynchronously.  The advantage of this implementation is
	  that it operates safely.  If there is a failure during an
	  update, meta-data is always in a consistent state.  A
	  file is either created completely or not at all.  If the
	  data blocks of a file did not find their way out of the
	  buffer cache onto the disk by the time of the crash,
	  &man.fsck.8; recognizes this and repairs the file system
	  by setting the file length to <literal>0</literal>.
	  Additionally, the implementation is clear and simple.  The
	  disadvantage is that meta-data changes are slow.  For
	  example, <command>rm -r</command> touches all the files in a
	  directory sequentially, but each directory change will be
	  written synchronously to the disk.  This includes updates to
	  the directory itself, to the inode table, and possibly to
	  indirect blocks allocated by the file.  Similar
	  considerations apply for unrolling large hierarchies using
	  <command>tar -x</command>.</para>

	<para>The second approach is to use asynchronous meta-data
	  updates.  This is the default for a <acronym>UFS</acronym>
	  file system mounted with <command>mount -o async</command>.
	  Since all meta-data updates are also passed through the
	  buffer cache, they will be intermixed with the updates of
	  the file content data.  The advantage of this
	  implementation is there is no need to wait until each
	  meta-data update has been written to disk, so all operations
	  which cause huge amounts of meta-data updates work much
	  faster than in the synchronous case.  This implementation
	  is still clear and simple, so there is a low risk for bugs
	  creeping into the code.  The disadvantage is that there is
	  no guarantee for a consistent state of the file system.
	  If there is a failure during an operation that updated
	  large amounts of meta-data, like a power failure or someone
	  pressing the reset button, the file system will be left
	  in an unpredictable state.  There is no opportunity to
	  examine the state of the file system when the system comes
	  up again as the data blocks of a file could already have
	  been written to the disk while the updates of the inode
	  table or the associated directory were not.  It is
	  impossible to implement a &man.fsck.8; which is able to
	  clean up the resulting chaos because the necessary
	  information is not available on the disk.  If the file
	  system has been damaged beyond repair, the only choice
	  is to reformat it and restore from backup.</para>

	<para>The usual solution for this problem is to implement
	  <emphasis>dirty region logging</emphasis>, which is also
	  referred to as <emphasis>journaling</emphasis>.
	  Meta-data updates are still written synchronously, but only
	  into a small region of the disk.  Later on, they are moved
	  to their proper location.  Because the logging area is a
	  small, contiguous region on the disk, there are no long
	  distances for the disk heads to move, even during heavy
	  operations, so these operations are quicker than synchronous
	  updates.  Additionally, the complexity of the implementation
	  is limited, so the risk of bugs being present is low.  A
	  disadvantage is that all meta-data is written twice, once
	  into the logging region and once to the proper location, so
	  performance <quote>pessimization</quote> might result.  On
	  the other hand, in case of a crash, all pending meta-data
	  operations can be either quickly rolled back or completed
	  from the logging area after the system comes up again,
	  resulting in a fast file system startup.</para>

	<para>Kirk McKusick, the developer of Berkeley
	  <acronym>FFS</acronym>, solved this problem with Soft
	  Updates.  All pending meta-data updates are kept in memory
	  and written out to disk in a sorted sequence
	  (<quote>ordered meta-data updates</quote>).  This has the
	  effect that, in case of heavy meta-data operations, later
	  updates to an item <quote>catch</quote> the earlier ones
	  which are still in memory and have not already been written
	  to disk.  All operations are generally performed in memory
	  before the update is written to disk and the data blocks are
	  sorted according to their position so that they will not be
	  on the disk ahead of their meta-data.  If the system
	  crashes, an implicit <quote>log rewind</quote> causes all
	  operations which were not written to the disk appear as if
	  they never happened.  A consistent file system state is
	  maintained that appears to be the one of 30 to 60 seconds
	  earlier.  The algorithm used guarantees that all resources
	  in use are marked as such in their blocks and inodes.
	  After a crash, the only resource allocation error that
	  occurs is that resources are marked as <quote>used</quote>
	  which are actually <quote>free</quote>.  &man.fsck.8;
	  recognizes this situation, and frees the resources that
	  are no longer used.  It is safe to ignore the dirty state
	  of the file system after a crash by forcibly mounting it
	  with <command>mount -f</command>.  In order to free
	  resources that may be unused, &man.fsck.8; needs to be run
	  at a later time.  This is the idea behind the
	  <emphasis>background &man.fsck.8;</emphasis>: at system
	  startup time, only a <emphasis>snapshot</emphasis> of the
	  file system is recorded and &man.fsck.8; is run afterwards.
	  All file systems can then be mounted
	  <quote>dirty</quote>, so the system startup proceeds in
	  multi-user mode.  Then, background &man.fsck.8; is
	  scheduled for all file systems where this is required, to
	  free resources that may be unused.  File systems that do
	  not use Soft Updates still need the usual foreground
	  &man.fsck.8;.</para>

	<para>The advantage is that meta-data operations are nearly
	  as fast as asynchronous updates and are faster than
	  <emphasis>logging</emphasis>, which has to write the
	  meta-data twice.  The disadvantages are the complexity of
	  the code, a higher memory consumption, and some
	  idiosyncrasies.  After a crash, the state of the file
	  system appears to be somewhat <quote>older</quote>.  In
	  situations where the standard synchronous approach would
	  have caused some zero-length files to remain after the
	  &man.fsck.8;, these files do not exist at all with Soft
	  Updates because neither the meta-data nor the file contents
	  have been written to disk.  Disk space is not released until
	  the updates have been written to disk, which may take place
	  some time after running &man.rm.1;.  This may cause problems
	  when installing large amounts of data on a file system
	  that does not have enough free space to hold all the files
	  twice.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 xml:id="configtuning-kernel-limits">
    <title>Tuning Kernel Limits</title>

    <indexterm>
      <primary>tuning</primary>
      <secondary>kernel limits</secondary>
    </indexterm>

    <sect2 xml:id="file-process-limits">
      <title>File/Process Limits</title>

      <sect3 xml:id="kern-maxfiles">
	<title><varname>kern.maxfiles</varname></title>

	<indexterm>
	  <primary><varname>kern.maxfiles</varname></primary>
	</indexterm>

	<para>The <varname>kern.maxfiles</varname> &man.sysctl.8;
	  variable can be raised or lowered based upon system
	  requirements.  This variable indicates the maximum number
	  of file descriptors on the system.  When the file descriptor
	  table is full, <errorname>file: table is full</errorname>
	  will show up repeatedly in the system message buffer, which
	  can be viewed using &man.dmesg.8;.</para>

	<para>Each open file, socket, or fifo uses one file
	  descriptor.  A large-scale production server may easily
	  require many thousands of file descriptors, depending on the
	  kind and number of services running concurrently.</para>

	<para>In older &os; releases, the default value of
	  <varname>kern.maxfiles</varname> is derived from
	  <option>maxusers</option> in the kernel configuration file.
	  <varname>kern.maxfiles</varname> grows proportionally to the
	  value of <option>maxusers</option>.  When compiling a custom
	  kernel, consider setting this kernel configuration option
	  according to the use of the system.  From this number, the
	  kernel is given most of its pre-defined limits.  Even though
	  a production machine may not have 256 concurrent users, the
	  resources needed may be similar to a high-scale web
	  server.</para>

	<para>The read-only &man.sysctl.8; variable
	  <varname>kern.maxusers</varname> is automatically sized at
	  boot based on the amount of memory available in the system,
	  and may be determined at run-time by inspecting the value
	  of <varname>kern.maxusers</varname>.  Some systems require
	  larger or smaller values of
	  <varname>kern.maxusers</varname> and values of
	  <literal>64</literal>, <literal>128</literal>, and
	  <literal>256</literal> are not uncommon.  Going above
	  <literal>256</literal> is not recommended  unless a huge
	  number of file descriptors is needed.  Many of the tunable
	  values set to their defaults by
	  <varname>kern.maxusers</varname> may be individually
	  overridden at boot-time or run-time in
	  <filename>/boot/loader.conf</filename>.  Refer to
	  &man.loader.conf.5; and
	  <filename>/boot/defaults/loader.conf</filename> for more
	  details and some hints.</para>

	<para>In older releases, the system will auto-tune
	  <literal>maxusers</literal> if it is set 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
	      <literal>32</literal>, and a maximum of
	      <literal>384</literal>.</para></footnote>.  When
	  setting this option, set <literal>maxusers</literal> to
	  at least <literal>4</literal>, especially if the system
	  runs <application>&xorg;</application> or is used to
	  compile software.  The most important table set by
	  <literal>maxusers</literal> is the maximum number of
	  processes, which is set to
	  <literal>20 + 16 * maxusers</literal>.  If
	  <literal>maxusers</literal> is set to <literal>1</literal>,
	  there can only be
	  <literal>36</literal> simultaneous processes, including
	  the <literal>18</literal> or so that the system starts up
	  at boot time and the <literal>15</literal> or so used by
	  <application>&xorg;</application>.  Even a simple task like
	  reading a manual page will start up nine processes to
	  filter, decompress, and view it.  Setting
	  <literal>maxusers</literal> to <literal>64</literal> allows
	  up to <literal>1044</literal> simultaneous processes, which
	  should be enough for nearly all uses.  If, however, the
	  <errortype>proc table full</errortype> error is displayed
	  when trying to start another program, or a server is
	  running with a large number of simultaneous users, increase
	  the number and rebuild.</para>

	<note>
	  <para><literal>maxusers</literal> does
	    <emphasis>not</emphasis> limit the number of users which
	    can log into the machine.  It instead sets various table
	    sizes to reasonable values considering the maximum number
	    of users on the system and how many processes each user
	    will be running.</para>
	</note>
      </sect3>

      <sect3>
	<title><varname>kern.ipc.somaxconn</varname></title>

	<indexterm>
	  <primary><varname>kern.ipc.somaxconn</varname></primary>
	</indexterm>

	<para>The <varname>kern.ipc.somaxconn</varname> &man.sysctl.8;
	  variable limits the size of the listen queue for accepting
	  new <literal>TCP</literal> connections.  The default value
	  of <literal>128</literal> is typically too low for robust
	  handling of new connections on a heavily loaded web server.
	  For such environments, it is recommended to increase this
	  value to <literal>1024</literal> or higher.  A service
	  such as &man.sendmail.8;, or
	  <application>Apache</application> may itself limit the
	  listen queue size, but will often have a directive in its
	  configuration file to adjust the queue size.  Large listen
	  queues do a better job of avoiding Denial of Service
	  (<acronym>DoS</acronym>) attacks.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="nmbclusters">
      <title>Network Limits</title>

      <para>The <literal>NMBCLUSTERS</literal> kernel configuration
	option dictates the amount of network Mbufs available to the
	system.  A heavily-trafficked server with a low number of
	Mbufs will hinder performance.  Each cluster represents
	approximately 2&nbsp;K of memory, so a value of
	<literal>1024</literal> represents <literal>2</literal>
	megabytes of kernel memory reserved for network buffers.  A
	simple calculation can be done to figure out how many are
	needed.  A web server which maxes out at
	<literal>1000</literal> simultaneous connections where each
	connection uses a 6&nbsp;K receive and 16&nbsp;K send buffer,
	requires approximately 32&nbsp;MB worth of network buffers
	to cover the web server.  A good rule of thumb is to multiply
	by <literal>2</literal>, so
	2x32&nbsp;MB&nbsp;/&nbsp;2&nbsp;KB&nbsp;=
	64&nbsp;MB&nbsp;/&nbsp;2&nbsp;kB&nbsp;=
	<literal>32768</literal>.  Values between
	<literal>4096</literal> and <literal>32768</literal> are
	recommended for machines with greater amounts of memory.
	Never specify an arbitrarily high value for this parameter
	as it could lead to a boot time crash.  To observe network
	cluster usage, use <option>-m</option> with
	&man.netstat.1;.</para>

      <para>The <varname>kern.ipc.nmbclusters</varname> loader tunable
	should be used to tune this at boot time.  Only older versions
	of &os; will require the use of the
	<literal>NMBCLUSTERS</literal> kernel &man.config.8;
	option.</para>

      <para>For busy servers that make extensive use of the
	&man.sendfile.2; system call, it may be necessary to increase
	the number of &man.sendfile.2; buffers via the
	<literal>NSFBUFS</literal> kernel configuration option or by
	setting its value in <filename>/boot/loader.conf</filename>
	(see &man.loader.8; for details).  A common indicator that
	this parameter needs to be adjusted is when processes are seen
	in the <literal>sfbufa</literal> state.  The &man.sysctl.8;
	variable <varname>kern.ipc.nsfbufs</varname> is read-only.
	This parameter nominally scales with
	<varname>kern.maxusers</varname>, however it may be necessary
	to tune accordingly.</para>

      <important>
	<para>Even though a socket has been marked as non-blocking,
	  calling &man.sendfile.2; on the non-blocking socket may
	  result in the &man.sendfile.2; call blocking until enough
	  <literal>struct sf_buf</literal>'s are made
	  available.</para>
      </important>

      <sect3>
	<title><varname>net.inet.ip.portrange.*</varname></title>

	<indexterm>
	  <primary>net.inet.ip.portrange.*</primary>
	</indexterm>

	<para>The <varname>net.inet.ip.portrange.*</varname>
	  &man.sysctl.8; variables control the port number ranges
	  automatically bound to <literal>TCP</literal> and
	  <literal>UDP</literal> sockets.  There are three ranges: a
	  low range, a default range, and a high range.  Most network
	  programs use the default range which is controlled by
	  <varname>net.inet.ip.portrange.first</varname> and
	  <varname>net.inet.ip.portrange.last</varname>, which default
	  to <literal>1024</literal> and <literal>5000</literal>,
	  respectively.  Bound port ranges are used for outgoing
	  connections and it is possible to run the system out of
	  ports under certain circumstances.  This most commonly
	  occurs when running a heavily loaded web proxy.  The port
	  range is not an issue when running a server which handles
	  mainly incoming connections, such as a web server, or has
	  a limited number of outgoing connections, such as a mail
	  relay.  For situations where there is a shortage of ports,
	  it is recommended to increase
	  <varname>net.inet.ip.portrange.last</varname> modestly.  A
	  value of <literal>10000</literal>, <literal>20000</literal>
	  or <literal>30000</literal> may be reasonable.  Consider
	  firewall effects when changing the port range.  Some
	  firewalls may block large ranges of ports, usually
	  low-numbered ports, and expect systems to use higher ranges
	  of ports for outgoing connections.  For this reason, it
	  is not recommended that the value of
	  <varname>net.inet.ip.portrange.first</varname> be
	  lowered.</para>
      </sect3>

      <sect3>
	<title><literal>TCP</literal> Bandwidth Delay Product</title>

	<indexterm>
	  <primary><literal>TCP</literal> Bandwidth Delay Product
	      Limiting</primary>
	  <secondary><varname>net.inet.tcp.inflight.enable</varname></secondary>
	</indexterm>

	<para><literal>TCP</literal> bandwidth delay product limiting
	  can be enabled by setting the
	  <varname>net.inet.tcp.inflight.enable</varname>
	  &man.sysctl.8; variable to <literal>1</literal>.  This
	  instructs the system to attempt to calculate the bandwidth
	  delay product for each connection and limit the amount of
	  data queued to the network to just the amount required to
	  maintain optimum throughput.</para>

	<para>This feature is useful when serving data over modems,
	  Gigabit Ethernet, high speed <literal>WAN</literal> links,
	  or any other link with a high bandwidth delay product,
	  especially when also using window scaling or when a large
	  send window has been configured.  When enabling this option,
	  also set <varname>net.inet.tcp.inflight.debug</varname> to
	  <literal>0</literal> to disable debugging.  For production
	  use, setting <varname>net.inet.tcp.inflight.min</varname>
	  to at least <literal>6144</literal> may be beneficial.
	  Setting high minimums may effectively disable bandwidth
	  limiting, depending on the link.  The limiting feature
	  reduces the amount of data built up in intermediate route
	  and switch packet queues and reduces the amount of data
	  built up in the local host's interface queue.  With fewer
	  queued packets, interactive connections, especially over
	  slow modems, will operate with lower
	  <emphasis>Round Trip Times</emphasis>.  This feature only
	  effects server side data transmission such as uploading.
	  It has no effect on data reception or downloading.</para>

	<para>Adjusting <varname>net.inet.tcp.inflight.stab</varname>
	  is <emphasis>not</emphasis> recommended.  This parameter
	  defaults to <literal>20</literal>, representing 2 maximal
	  packets added to the bandwidth delay product window
	  calculation.  The additional window is required to stabilize
	  the algorithm and improve responsiveness to changing
	  conditions, but it can also result in higher &man.ping.8;
	  times over slow links, though still much lower than without
	  the inflight algorithm.  In such cases, try reducing this
	  parameter to <literal>15</literal>, <literal>10</literal>,
	  or <literal>5</literal> and reducing
	  <varname>net.inet.tcp.inflight.min</varname> to a value such
	  as <literal>3500</literal> to get the desired effect.
	  Reducing these parameters should be done as a last resort
	  only.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>Virtual Memory</title>

      <sect3>
	<title><varname>kern.maxvnodes</varname></title>

	<para>A vnode is the internal representation of a file or
	  directory.  Increasing the number of vnodes available to
	  the operating system reduces disk I/O.  Normally, this is
	  handled by the operating system and does not need to be
	  changed.  In some cases where disk I/O is a bottleneck and
	  the system is running out of vnodes, this setting needs
	  to be increased.  The amount of inactive and free
	  <acronym>RAM</acronym> will need to be taken into
	  account.</para>

	<para>To see the current number of vnodes in use:</para>

	<screen>&prompt.root; <userinput>sysctl vfs.numvnodes</userinput>
vfs.numvnodes: 91349</screen>

	<para>To see the maximum vnodes:</para>

	<screen>&prompt.root; <userinput>sysctl kern.maxvnodes</userinput>
kern.maxvnodes: 100000</screen>

	<para>If the current vnode usage is near the maximum, try
	  increasing <varname>kern.maxvnodes</varname> by a value of
	  <literal>1000</literal>.  Keep an eye on the number of
	  <varname>vfs.numvnodes</varname>.  If it climbs up to the
	  maximum again, <varname>kern.maxvnodes</varname> will need
	  to be increased further.  Otherwise, a shift in memory
	  usage as reported by &man.top.1; should be visible and
	  more memory should be active.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 xml:id="adding-swap-space">
    <title>Adding Swap Space</title>

    <para>Sometimes a system requires more swap space.  There are
      three ways to increase swap space: add a new hard drive,
      enable swap over <literal>NFS</literal>, or create a swap file
      on an existing partition.</para>

    <para>For information on how to encrypt swap space, which options
      exist, and why it should be done, refer to
      <xref linkend="swap-encrypting"/>.</para>

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

      <para>Adding a new hard drive for swap gives better performance
	than adding a partition on an existing drive.  Setting up
	partitions and hard drives is explained in
	<xref linkend="disks-adding"/> while
	<xref linkend="configtuning-initial"/> discusses partition
	layouts and swap partition size considerations.</para>

      <para>Use &man.swapon.8; to add a swap partition to the system.
	For example:</para>

      <screen>&prompt.root; <userinput>swapon /dev/ada1s1b</userinput></screen>

      <warning>
	<para>It is possible to use any partition not currently
	  mounted, even if it already contains data.  Using
	  &man.swapon.8; on a partition that contains data will
	  overwrite and destroy that data.  Make sure that the
	  partition to be added as swap is really the intended
	  partition before running &man.swapon.8;.</para>
      </warning>

      <para>To automatically add this swap partition on boot, add an
	entry to <filename>/etc/fstab</filename>:</para>

      <programlisting><replaceable>/dev/ada1s1b</replaceable>	none	swap	sw	0	0</programlisting>

      <para>See &man.fstab.5; for an explanation of the entries in
	<filename>/etc/fstab</filename>.</para>
    </sect2>

    <sect2 xml:id="nfs-swap">
      <title>Swapping over <literal>NFS</literal></title>

      <para>Swapping over <literal>NFS</literal> is only recommended
	when there is no local hard disk to swap to.
	<literal>NFS</literal> swapping will be limited by the
	available network bandwidth and puts an additional burden
	on &man.nfsd.8;.</para>
    </sect2>

    <sect2 xml:id="create-swapfile">
      <title>Swapfiles</title>

      <para>To create a swap file, specify its size.  The following
	example creates a 64MB file named
	<filename>/usr/swap0</filename>.</para>

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

	<orderedlist>
	  <listitem>
	    <para>The <filename>GENERIC</filename> kernel already
	      includes the memory disk driver (&man.md.4;) required
	      for this operation.  When building a custom kernel,
	      make sure to include the following line in the custom
	      configuration file:</para>

	    <programlisting>device   md</programlisting>

	    <para>For information on building a custom kernel, refer
	      to <xref linkend="kernelconfig"/>.</para>
	  </listitem>

	  <listitem>
	    <para>First, create the 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>Then, 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>mdconfig -a -t vnode -f /usr/swap0 -u 0 &amp;&amp; swapon /dev/md0</userinput></screen>
	  </listitem>
	</orderedlist>
      </example>
    </sect2>
  </sect1>

  <sect1 xml:id="acpi-overview">
    <info>
      <title>Power and Resource Management</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Hiten</firstname>
	    <surname>Pandya</surname>
	  </personname>
	  <contrib>Written by </contrib>
	</author>

	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	</author>
      </authorgroup>
    </info>

    <para>It is important to utilize hardware resources in an
      efficient manner.  Before the Advanced Configuration and Power
      Interface (<acronym>ACPI</acronym>) was introduced, it was
      difficult and inflexible for operating systems to manage the
      power usage and thermal properties of a system.  The hardware
      was managed by the <acronym>BIOS</acronym> and the user had less
      control and visibility into the power management settings.  Some
      limited configurability was available via <emphasis>Advanced
	Power Management (<acronym>APM</acronym>)</emphasis>.  Power
      and resource management allows the operating system to monitor
      system limits and to possibly provide an alert if the system
      temperature increases unexpectedly.</para>

    <para>This section provides comprehensive information about
      <acronym>ACPI</acronym>.  References will be provided for
      further reading.</para>

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

      <indexterm>
	<primary>ACPI</primary>
      </indexterm>

      <indexterm>
	<primary>APM</primary>
      </indexterm>

      <para><acronym>ACPI</acronym> is a standard written by an
	alliance of vendors to provide a standard interface for
	hardware resources and power management.  It is a key
	element in <emphasis>Operating System-directed configuration
	and Power Management</emphasis> as it provides more control
	and flexibility to the operating system.  Modern systems
	<quote>stretched</quote> the limits of the current Plug and
	Play interfaces prior to the introduction of
	<acronym>ACPI</acronym>.  <acronym>ACPI</acronym> is the
	direct successor to <acronym>APM</acronym>.</para>
    </sect2>

    <sect2 xml:id="acpi-old-spec">
      <title>Shortcomings of Advanced Power Management</title>

      <para>The <acronym>APM</acronym> facility controls the power
	usage of a system based on its activity.  The
	<acronym>APM</acronym> <acronym>BIOS</acronym> is supplied
	by the vendor and is specific to the hardware platform.  An
	<acronym>APM</acronym> driver in the operating system
	mediates access to the <emphasis><acronym>APM</acronym>
	  Software Interface</emphasis>, which allows management of
	power levels.  <acronym>APM</acronym> should still be used
	for systems manufactured at or before the year 2000.</para>

      <para>There are four major problems in <acronym>APM</acronym>.
	First, power management is done by the vendor-specific
	<acronym>BIOS</acronym>, separate from the operating system.
	For example, the user can set idle-time values for a hard
	drive in the <acronym>APM</acronym> <acronym>BIOS</acronym>
	so that, when exceeded, the <acronym>BIOS</acronym> spins
	down the hard drive without the consent of the operating
	system.  Second, the <acronym>APM</acronym> logic is embedded
	in the <acronym>BIOS</acronym>, and it operates outside the
	scope of the operating system.  This means that users can
	only fix problems in the <acronym>APM</acronym>
	<acronym>BIOS</acronym> by flashing a new one into the
	<acronym>ROM</acronym>, which is a dangerous procedure with
	the potential to leave the system in an unrecoverable state
	if it fails.  Third, <acronym>APM</acronym> is a
	vendor-specific technology, meaning that there is a lot of
	duplication of efforts and bugs found in one vendor's
	<acronym>BIOS</acronym> may not be solved in others.  Lastly,
	the <acronym>APM</acronym> <acronym>BIOS</acronym> did not
	have enough room to implement a sophisticated power policy
	or one that can adapt well to the purpose of the
	machine.</para>

      <para>The <emphasis>Plug and Play <acronym>BIOS</acronym>
	  (<acronym>PNPBIOS</acronym>)</emphasis> was unreliable in
	many situations.  <acronym>PNPBIOS</acronym> is 16-bit
	technology, so the operating system has to use 16-bit
	emulation in order to interface with
	<acronym>PNPBIOS</acronym> methods.</para>

      <para>The &os; <acronym>APM</acronym> driver is documented in
	&man.apm.4;.</para>
    </sect2>

    <sect2 xml:id="acpi-config">
      <title>Configuring <acronym>ACPI</acronym></title>

      <para>The &man.acpi.4; driver is loaded by default at start
	up by &man.loader.8; and should
	<emphasis>not</emphasis> be compiled into the kernel.  The
	reasoning is that modules are easier to work with and do not
	require a kernel rebuild.  This has the advantage of making
	testing easier.  Another reason is that starting
	<acronym>ACPI</acronym> after a system has been brought up
	often does not work well.  If experiencing problems,
	<acronym>ACPI</acronym> can be disabled altogether.  This
	driver should not and can not be unloaded because the system
	bus uses it for various hardware interactions.
	<acronym>ACPI</acronym> can be disabled by rebooting after
	setting <literal>hint.acpi.0.disabled="1"</literal> in
	<filename>/boot/loader.conf</filename> or by setting this
	variable at the &man.loader.8; prompt.</para>

      <note>
	<para><acronym>ACPI</acronym> and <acronym>APM</acronym>
	  cannot coexist and should be used separately.  The last one
	  to load will terminate if the driver notices the other is
	  running.</para>
      </note>

      <para><acronym>ACPI</acronym> can be used to put the system into
	a sleep mode with &man.acpiconf.8;, the <option>-s</option>
	flag, and a <literal>1-5</literal> option.  Most users
	only need <literal>1</literal> (quick suspend to
	<acronym>RAM</acronym>) or <literal>3</literal> (suspend to
	<acronym>RAM</acronym>).  Option <literal>5</literal> performs
	a soft-off which is the same action as:</para>

      <screen>&prompt.root; <userinput>halt -p</userinput></screen>

      <para>Other options are available via &man.sysctl.8;.  Refer to
	&man.acpi.4; and &man.acpiconf.8; for more information.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="ACPI-debug">
    <info>
      <title>Using and Debugging &os; <acronym>ACPI</acronym></title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Nate</firstname>
	    <surname>Lawson</surname>
	  </personname>
	  <contrib>Written by </contrib>
	</author>
      </authorgroup>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Peter</firstname>
	    <surname>Schultz</surname>
	  </personname>
	  <contrib>With contributions from </contrib>
	</author>

	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>ACPI</primary>
      <secondary>problems</secondary>
    </indexterm>

    <para><acronym>ACPI</acronym> is a fundamentally new way of
      discovering devices, managing power usage, and providing
      standardized access to various hardware previously managed by
      the <acronym>BIOS</acronym>.  Progress is being made toward
      <acronym>ACPI</acronym> working on all systems, but bugs in some
      motherboards' <firstterm><acronym>ACPI</acronym> Machine
      Language</firstterm> (<acronym>AML</acronym>) bytecode,
      incompleteness in &os;'s kernel subsystems, and bugs in the
      &intel; <acronym>ACPI-CA</acronym> interpreter continue to
      appear.</para>

    <para>This section is intended to help users assist the &os;
      <acronym>ACPI</acronym> maintainers in identifying the root
      cause of problems and in debugging and developing a
      solution.</para>

    <sect2 xml:id="ACPI-submitdebug">
      <title>Submitting Debugging Information</title>

      <note>
	<para>Before submitting a problem, ensure the latest
	  <acronym>BIOS</acronym> version is installed and, if
	  available, the embedded controller firmware version.</para>
      </note>

      <para>When submitting a problem, send the following information
	to <link xlink:href="mailto:freebsd-acpi@FreeBSD.org">
	  freebsd-acpi@FreeBSD.org</link>:</para>

      <itemizedlist>
	<listitem>
	  <para>Description of the buggy behavior, including system
	    type and model and anything that causes the bug to appear.
	    Note as accurately as possible when the bug began
	    occurring if it is new.</para>
	</listitem>

	<listitem>
	  <para>The output of &man.dmesg.8; after running
	    <command>boot -v</command>, including any error messages
	    generated by the bug.</para>
	</listitem>

	<listitem>
	  <para>The &man.dmesg.8; output from <command>boot
	      -v</command> with <acronym>ACPI</acronym> disabled,
	    if disabling it helps to fix the problem.</para>
	</listitem>

	<listitem>
	  <para>Output from <command>sysctl hw.acpi</command>.  This
	    lists which features the system offers.</para>
	</listitem>

	<listitem>
	  <para>The <acronym>URL</acronym> to a pasted version of the
	    <firstterm><acronym>ACPI</acronym> Source
	      Language</firstterm> (<acronym>ASL</acronym>).  Do
	    <emphasis>not</emphasis> send the
	    <acronym>ASL</acronym> directly to the list as it can be
	    very large.  Generate a copy of the
	    <acronym>ASL</acronym> by running this command:</para>

	  <screen>&prompt.root; <userinput>acpidump -dt &gt; name-system.asl</userinput></screen>

	  <para>Substitute the login name for
	    <replaceable>name</replaceable> and manufacturer/model for
	    <replaceable>system</replaceable>.  For example, use
	    <filename>njl-FooCo6000.asl</filename>.</para>
	</listitem>
      </itemizedlist>

      <para>Most &os; developers watch &a.current;, but one should
	submit problems to &a.acpi.name; to be sure it is seen.  Be
	patient when waiting for a response.  If the bug is not
	immediately apparent, submit a <acronym>PR</acronym> using
	&man.send-pr.1;.  When entering a <acronym>PR</acronym>,
	include the same information as requested above.  This helps
	developers to track the problem and resolve it.  Do not send a
	<acronym>PR</acronym> without emailing &a.acpi.name; first as
	it is likely that the problem has been reported before.</para>
    </sect2>

    <sect2 xml:id="ACPI-background">
      <title>Background</title>

      <indexterm>
	<primary><acronym>ACPI</acronym></primary>
      </indexterm>

      <para><acronym>ACPI</acronym> is present in all modern computers
	that conform to the ia32 (x86), ia64 (Itanium), and amd64
	(AMD) architectures.  The full standard has many features
	including <acronym>CPU</acronym> performance management, power
	planes control, thermal zones, various battery systems,
	embedded controllers, and bus enumeration.  Most systems
	implement less than the full standard.  For instance, a
	desktop system usually only implements bus enumeration
	while a laptop might have cooling and battery management
	support as well.  Laptops also have suspend and resume, with
	their own associated complexity.</para>

      <para>An <acronym>ACPI</acronym>-compliant system has various
	components.  The <acronym>BIOS</acronym> and chipset vendors
	provide various fixed tables, such as <acronym>FADT</acronym>,
	in memory that specify things like the <acronym>APIC</acronym>
	map (used for <acronym>SMP</acronym>), config registers, and
	simple configuration values.  Additionally, a bytecode table,
	the <firstterm>Differentiated System Description
	  Table</firstterm> <acronym>DSDT</acronym>, specifies a
	tree-like name space of devices and methods.</para>

      <para>The <acronym>ACPI</acronym> driver must parse the fixed
	tables, implement an interpreter for the bytecode, and modify
	device drivers and the kernel to accept information from the
	<acronym>ACPI</acronym> subsystem.  For &os;, &intel; has
	provided an interpreter (<acronym>ACPI-CA</acronym>) that is
	shared with &linux; and NetBSD.  The path to the
	<acronym>ACPI-CA</acronym> source code is
	<filename>src/sys/contrib/dev/acpica</filename>.  The glue
	code that allows <acronym>ACPI-CA</acronym> to work on &os; is
	in <filename>src/sys/dev/acpica/Osd</filename>.  Finally,
	drivers that implement various <acronym>ACPI</acronym> devices
	are found in <filename>src/sys/dev/acpica</filename>.</para>
    </sect2>

    <sect2 xml:id="ACPI-comprob">
      <title>Common Problems</title>

      <indexterm>
	<primary>ACPI</primary>
	<secondary>problems</secondary>
      </indexterm>

      <para>For <acronym>ACPI</acronym> to work correctly, all the
	parts have to work correctly.  Here are some common problems,
	in order of frequency of appearance, and some possible
	workarounds or fixes.</para>

      <sect3>
	<title>Mouse Issues</title>

	<para>In some cases, resuming from a suspend operation will
	  cause the mouse to fail.  A known work around is to add
	  <literal>hint.psm.0.flags="0x3000"</literal> to
	  <filename>/boot/loader.conf</filename>.  If this does not
	  work, consider sending a bug report using
	  &man.send-pr.1;.</para>
      </sect3>

      <sect3>
	<title>Suspend/Resume</title>

	<para><acronym>ACPI</acronym> has three suspend to
	  <acronym>RAM</acronym> (<acronym>STR</acronym>) states,
	  <literal>S1</literal>-<literal>S3</literal>, and one suspend
	  to disk state (<literal>STD</literal>), called
	  <literal>S4</literal>.  <literal>S5</literal> is
	  <quote>soft off</quote> and is the normal state the system
	  is in when plugged in but not powered up.
	  <literal>S4</literal> can be implemented in two separate
	  ways.  <literal>S4</literal><acronym>BIOS</acronym> is a
	  <acronym>BIOS</acronym>-assisted suspend to disk.
	  <literal>S4</literal><acronym>OS</acronym> is implemented
	  entirely by the operating system.</para>

	<para>Start by checking <command>sysctl hw.acpi</command>
	  for the suspend-related items.  Here are the results for a
	  Thinkpad:</para>

	<screen>hw.acpi.supported_sleep_state: S3 S4 S5
hw.acpi.s4bios: 0</screen>

	<para>Use <command>acpiconf -s</command> to test
	  <literal>S3</literal>,
	  <literal>S4</literal><acronym>OS</acronym>, and
	  <literal>S5</literal>.  An <option>s4bios</option> of one
	  (<literal>1</literal>), indicates
	  <literal>S4</literal><acronym>BIOS</acronym> support instead
	  of <literal>S4</literal> <acronym>OS</acronym>.</para>

	<para>When testing suspend/resume, start with
	  <literal>S1</literal>, if supported.  This state is most
	  likely to work since it does not require much driver
	  support.  No one has implemented <literal>S2</literal>,
	  which is similar to <literal>S1</literal>.  Next, try
	  <literal>S3</literal>.  This is the deepest
	  <acronym>STR</acronym> state and requires a lot of driver
	  support to properly reinitialize the hardware.  If there are
	  problems resuming, email &a.acpi.name;.  However, the
	  problem may not be resolved quickly since due to the amount
	  of drivers and hardware that need more testing and
	  work.</para>

	<para>A common problem with suspend/resume is that many device
	  drivers do not save, restore, or reinitialize their
	  firmware, registers, or device memory properly.  As a first
	  attempt at debugging the problem, try:</para>

	<screen>&prompt.root; <userinput>sysctl debug.bootverbose=1</userinput>
&prompt.root; <userinput>sysctl debug.acpi.suspend_bounce=1</userinput>
&prompt.root; <userinput>acpiconf -s 3</userinput></screen>

	<para>This test emulates the suspend/resume cycle of all
	  device drivers without actually going into
	  <literal>S3</literal> state.  In some cases, problems such
	  as losing firmware state, device watchdog time out, and
	  retrying forever, can be captured with this method.  Note
	  that the system will not really enter <literal>S3</literal>
	  state, which means devices may not lose power, and many
	  will work fine even if suspend/resume methods are totally
	  missing, unlike real <literal>S3</literal> state.</para>

	<para>Harder cases require additional hardware, such as a
	  serial port and cable for debugging through a serial
	  console, a Firewire port and cable for using &man.dcons.4;,
	  and kernel debugging skills.</para>

	<para>To help isolate the problem, remove as many drivers
	  from the kernel as possible.  If it works, narrow down which
	  driver is the problem by loading drivers until it fails
	  again.  Typically, binary drivers like
	  <filename>nvidia.ko</filename>, display drivers, and
	  <acronym>USB</acronym> will have the most problems while
	  Ethernet interfaces usually work fine.  If drivers can be
	  properly loaded and unloaded, automate this by putting the
	  appropriate commands in
	  <filename>/etc/rc.suspend</filename> and
	  <filename>/etc/rc.resume</filename>.
	  Try setting <option>hw.acpi.reset_video</option> to
	  <literal>0</literal> if the display is messed up after
	  resume.  Try setting longer or shorter values for
	  <option>hw.acpi.sleep_delay</option> to see if that
	  helps.</para>

	<para>Try loading a recent &linux; distribution to see if
	  suspend/resume works on the same hardware.  If it works on
	  &linux;, it is likely a &os; driver problem.  Narrowing down
	  which driver causes the problem will assist developers in
	  fixing the problem.  Since the <acronym>ACPI</acronym>
	  maintainers rarely maintain other drivers, such as sound
	  or <acronym>ATA</acronym>, any driver problems should also
	  be posted to the &a.current.name; list and mailed to the
	  driver maintainer.  Advanced users can include debugging
	  &man.printf.3;s in a problematic driver to track down where
	  in its resume function it hangs.</para>

	<para>Finally, try disabling <acronym>ACPI</acronym> and
	  enabling <acronym>APM</acronym> instead.  If suspend/resume
	  works with <acronym>APM</acronym>, stick with
	  <acronym>APM</acronym>, especially on older hardware
	  (pre-2000).  It took vendors a while to get
	  <acronym>ACPI</acronym> support correct and older hardware
	  is more likely to have <acronym>BIOS</acronym> problems with
	  <acronym>ACPI</acronym>.</para>
      </sect3>

      <sect3>
	<title>System Hangs</title>

	<para>Most system hangs are a result of lost interrupts or an
	  interrupt storm.  Chipsets may have problems based on boot,
	  how the <acronym>BIOS</acronym> configures interrupts before
	  correctness of the <acronym>APIC</acronym>
	  (<acronym>MADT</acronym>) table, and routing of the
	  <firstterm>System Control Interrupt</firstterm>
	  (<acronym>SCI</acronym>).</para>

	<indexterm>
	  <primary>interrupt storms</primary>
	</indexterm>

	<para>Interrupt storms can be distinguished from lost
	  interrupts by checking the output of
	  <command>vmstat -i</command> and looking at the line that
	  has <literal>acpi0</literal>.  If the counter is increasing
	  at more than a couple per second, there is an interrupt
	  storm.  If the system appears hung, try breaking to
	  <acronym>DDB</acronym> (<keycombo action="simul">
	    <keycap>CTRL</keycap>
	    <keycap>ALT</keycap>
	    <keycap>ESC</keycap>
	  </keycombo> on console) and type
	  <literal>show interrupts</literal>.</para>

	<indexterm>
	  <primary>APIC</primary>
	  <secondary>disabling</secondary>
	</indexterm>

	<para>When dealing with interrupt problems, try disabling
	  <acronym>APIC</acronym> support with
	  <literal>hint.apic.0.disabled="1"</literal> in
	  <filename>/boot/loader.conf</filename>.</para>
      </sect3>

      <sect3>
	<title>Panics</title>

	<para>Panics are relatively rare for <acronym>ACPI</acronym>
	  and are the top priority to be fixed.  The first step is to
	  isolate the steps to reproduce the panic, if possible, and
	  get a backtrace.  Follow the advice for enabling
	  <literal>options DDB</literal> and setting up a serial
	  console in <xref linkend="serialconsole-ddb"/> or setting
	  up a &man.dump.8; partition.  To get a backtrace in
	  <acronym>DDB</acronym>, use <literal>tr</literal>.  When
	  handwriting the backtrace, get at least the last five
	  and the top five lines in the trace.</para>

	<para>Then, try to isolate the problem by booting with
	  <acronym>ACPI</acronym> disabled.  If that works, isolate
	  the <acronym>ACPI</acronym> subsystem by using various
	  values of <option>debug.acpi.disable</option>.  See
	  &man.acpi.4; for some examples.</para>
      </sect3>

      <sect3>
	<title>System Powers Up After Suspend or Shutdown</title>

	<para>First, try setting
	  <literal>hw.acpi.disable_on_poweroff="0"</literal> in
	  &man.loader.conf.5;.  This keeps <acronym>ACPI</acronym>
	  from disabling various events during the shutdown process.
	  Some systems need this value set to <literal>1</literal>
	  (the default) for the same reason.  This usually fixes the
	  problem of a system powering up spontaneously after a
	  suspend or poweroff.</para>
      </sect3>

      <sect3>
	<title>Other Problems</title>

	<para>For other problems with <acronym>ACPI</acronym>, such as
	  it not working with a docking station or devices not being
	  detected, email a description to &a.acpi.name;.  Some
	  issues may be related to unfinished parts of the
	  <acronym>ACPI</acronym> subsystem which might take a while
	  to be implemented.  Be patient and prepared to test
	  patches.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="ACPI-aslanddump">
      <title><acronym>ASL</acronym>, &man.acpidump.8;, and
	<acronym>IASL</acronym></title>

      <indexterm>
	<primary><acronym>ACPI</acronym></primary>
	<secondary><acronym>ASL</acronym></secondary>
      </indexterm>

      <para>Some <acronym>BIOS</acronym> vendors provide incorrect
	or buggy bytecode.  This is usually manifested by kernel
	console messages like this:</para>

      <screen>ACPI-1287: *** Error: Method execution failed [\\_SB_.PCI0.LPC0.FIGD._STA] \\
(Node 0xc3f6d160), AE_NOT_FOUND</screen>

      <para>Often, these problems may be resolved by updating the
	<acronym>BIOS</acronym> to the latest revision.  Most console
	messages are harmless, but if there are other problems like
	the battery status is not working, these messages are a
	good place to start looking for problems.  The bytecode,
	known as <acronym>AML</acronym>, is compiled from a source
	language called <acronym>ASL</acronym>.  The
	<acronym>AML</acronym> is found in the table known as the
	<acronym>DSDT</acronym>.  To get a copy of the system's
	<acronym>ASL</acronym>, use &man.acpidump.8;.  Include both
	<option>-t</option>, to show the contents of the fixed tables,
	and <option>-d</option>, to disassemble the
	<acronym>AML</acronym>.  Refer to
	<xref linkend="ACPI-submitdebug"/> for an example
	syntax.</para>

      <para>The simplest first check is to recompile the
	<acronym>ASL</acronym> to check for errors.  Warnings can
	usually be ignored, but errors are bugs that will usually
	prevent <acronym>ACPI</acronym> from working correctly.  To
	recompile the <acronym>ASL</acronym>, issue the following
	command:</para>

      <screen>&prompt.root; <userinput>iasl your.asl</userinput></screen>
    </sect2>

    <sect2 xml:id="ACPI-fixasl">
      <title>Fixing the <acronym>ASL</acronym></title>

      <indexterm>
	<primary><acronym>ACPI</acronym></primary>
	<secondary><acronym>ASL</acronym></secondary>
      </indexterm>

      <para>The goal of &os; is for everyone to have working
	<acronym>ACPI</acronym> without any user intervention.  At
	this point, workarounds are still being developed for common
	mistakes made by <acronym>BIOS</acronym>  vendors.  The
	&microsoft; interpreter (<filename>acpi.sys</filename> and
	<filename>acpiec.sys</filename>) does not strictly check for
	adherence to the standard, and thus many
	<acronym>BIOS</acronym> vendors who only test
	<acronym>ACPI</acronym> under &windows; never fix their
	<acronym>ASL</acronym>.  &os; developers continue to identify
	and document which non-standard behavior is allowed by
	&microsoft;'s interpreter and replicate it so that &os; can
	work without forcing users to fix the <acronym>ASL</acronym>.
	As a workaround, and to help identify behavior, fix the
	<acronym>ASL</acronym> manually.  If this works, send a
	&man.diff.1; of the old and new <acronym>ASL</acronym> so
	developers can possibly work around the buggy behavior in
	<acronym>ACPI-CA</acronym>.</para>

      <indexterm>
	<primary><acronym>ACPI</acronym></primary>
	<secondary>error messages</secondary>
      </indexterm>

      <para>Here is a list of common error messages, their cause, and
	how to fix them:</para>

      <sect3>
	<title>Operating System Dependencies</title>

	<para>Some <acronym>AML</acronym> versions assume the user is
	  running &windows;.  To override this, set
	  <literal>hw.acpi.osname="Windows
	    2001"</literal> in
	  <filename>/boot/loader.conf</filename>, using the strings
	  in the <acronym>ASL</acronym>.</para>
      </sect3>

      <sect3>
	<title>Missing Return Statements</title>

	<para>Some methods do not explicitly return a value as the
	  standard requires.  While <acronym>ACPI-CA</acronym>
	  does not handle this, &os; has a workaround that allows it
	  to return the value implicitly.  Explicit return statements
	  can be added where required if the value which should be
	  returned is known.  To force &man.iasl.8; to compile the
	  <acronym>ASL</acronym>, use the <option>-f</option>
	  flag.</para>
      </sect3>

      <sect3>
	<title>Overriding the Default <acronym>AML</acronym></title>

	<para>After customizing <filename>your.asl</filename>, compile
	  it with this command:</para>

	<screen>&prompt.root; <userinput>iasl your.asl</userinput></screen>

	<para>Adding the <option>-f</option> flag forces creation
	  of the <acronym>AML</acronym>, even if there are errors
	  during compilation.  Some errors, such as missing return
	  statements, are automatically worked around by the
	  interpreter.</para>

	<para>The default output filename for &man.iasl.8; is
	  <filename>DSDT.aml</filename>.  Load this file instead of
	  the <acronym>BIOS</acronym>'s buggy copy, which is still
	  present in flash memory, by editing
	  <filename>/boot/loader.conf</filename> as follows:</para>

	<programlisting>acpi_dsdt_load="YES"
acpi_dsdt_name="/boot/DSDT.aml"</programlisting>

	<para>Be sure to copy <filename>DSDT.aml</filename> to
	  <filename>/boot</filename>.</para>
      </sect3>
    </sect2>

    <sect2 xml:id="ACPI-debugoutput">
      <title>Getting Debugging Output from
	<acronym>ACPI</acronym></title>

      <indexterm>
	<primary>ACPI</primary>
	<secondary>problems</secondary>
      </indexterm>

      <indexterm>
	<primary>ACPI</primary>
	<secondary>debugging</secondary>
      </indexterm>

      <para>The <acronym>ACPI</acronym> driver has a flexible
	debugging facility.  A set of subsystems and the level of
	verbosity can be specified.  The subsystems to debug are
	specified as <quote>layers</quote> and are broken down into
	<acronym>ACPI-CA</acronym> components (ACPI_ALL_COMPONENTS)
	and <acronym>ACPI</acronym> hardware support
	(ACPI_ALL_DRIVERS).  The verbosity of debugging output is
	specified as the <quote>level</quote> and ranges from
	ACPI_LV_ERROR (just report errors) to ACPI_LV_VERBOSE
	(everything).  The <quote>level</quote> is a bitmask so
	multiple options can be set at once, separated by spaces.  In
	practice, a serial console should be used to log the output
	so it is not lost as the console message buffer flushes.
	A full list of the individual layers and levels is found in
	&man.acpi.4;.</para>

      <para>Debugging output is not enabled by default.  To enable it,
	add <literal>options ACPI_DEBUG</literal> to the kernel
	configuration file if <acronym>ACPI</acronym> is compiled into
	the kernel.  Add <literal>ACPI_DEBUG=1</literal> to
	<filename>/etc/make.conf</filename> to enable it globally.
	If it is a module, recompile just the
	<filename>acpi.ko</filename> module as follows:</para>

      <screen>&prompt.root; <userinput>cd /sys/modules/acpi/acpi
&amp;&amp; make clean &amp;&amp;
make ACPI_DEBUG=1</userinput></screen>

      <para>Install <filename>acpi.ko</filename> in
	<filename>/boot/kernel</filename> and add the desired level
	and layer to <filename>/boot/loader.conf</filename>.  This
	example enables debug messages for all
	<acronym>ACPI-CA</acronym> components and all
	<acronym>ACPI</acronym> hardware drivers such as
	(<acronym>CPU</acronym> and <acronym>LID</acronym>.  It only
	outputs error messages at the least verbose level.</para>

      <programlisting>debug.acpi.layer="ACPI_ALL_COMPONENTS ACPI_ALL_DRIVERS"
debug.acpi.level="ACPI_LV_ERROR"</programlisting>

      <para>If the required information is triggered by a specific
	event, such as a suspend and then resume, leave out changes to
	<filename>/boot/loader.conf</filename> and instead use
	&man.sysctl.8; to specify the layer and level after booting
	and preparing the system for the specific event.  The
	variables which can be set using &man.sysctl.8; are named
	the same as the tunables in
	<filename>/boot/loader.conf</filename>.</para>
    </sect2>

    <sect2 xml:id="ACPI-References">
      <title>References</title>

      <para>More information about <acronym>ACPI</acronym> may be
	found in the following locations:</para>

      <itemizedlist>
	<listitem>
	  <para>The &a.acpi;</para>
	</listitem>

	<listitem>
	  <para>The <acronym>ACPI</acronym> Mailing List Archives <uri
	      xlink:href="http://lists.freebsd.org/pipermail/freebsd-acpi/">http://lists.freebsd.org/pipermail/freebsd-acpi/</uri></para>
	</listitem>

	<listitem>
	  <para>The old <acronym>ACPI</acronym> Mailing List Archives
	    <uri
	      xlink:href="http://home.jp.FreeBSD.org/mail-list/acpi-jp/">http://home.jp.FreeBSD.org/mail-list/acpi-jp/</uri></para>
	</listitem>

	<listitem>
	  <para>The <acronym>ACPI</acronym> 2.0 Specification <uri
	      xlink:href="http://acpi.info/spec.htm">http://acpi.info/spec.htm</uri></para>
	</listitem>

	<listitem>
	  <para>&man.acpi.4;, &man.acpi.thermal.4;, &man.acpidump.8;,
	    &man.iasl.8;, and &man.acpidb.8;</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.cpqlinux.com/acpi-howto.html#fix_broken_dsdt"><acronym>DSDT</acronym>
	      debugging resource</link>.</para>
	</listitem>
      </itemizedlist>
    </sect2>
  </sect1>
</chapter>