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

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<chapter id="config-tuning">
  <chapterinfo>
    <authorgroup>
      <author>
        <firstname>Chern</firstname>
	<surname>Lee</surname>
	<contrib>Written by </contrib>
      </author>
    </authorgroup>
    <authorgroup>
      <author>
        <firstname>Mike</firstname>
	<surname>Smith</surname>
	<contrib>Based on a tutorial written by </contrib>
      </author>
    </authorgroup>
    <authorgroup>
      <author>
        <firstname>Matt</firstname>
	<surname>Dillon</surname>
	<contrib>Also based on tuning(7) written by </contrib>
      </author>
    </authorgroup>
  </chapterinfo>

  <title>Configuration and Tuning</title>

  <sect1 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 system configuration.
      Correct system configuration will help prevent headaches during future upgrades.
      This chapter will explain 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>How to efficiently work with
	  file systems and swap partitions.</para>
      </listitem>
      <listitem>
	<para>The basics of <filename>rc.conf</filename> configuration and
	  <filename>/usr/local/etc/rc.d</filename> startup systems.</para>
      </listitem>
      <listitem>
	<para>How to configure and test a network card.</para>
      </listitem>
      <listitem>
	<para>How to configure virtual hosts on your 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 <command>sysctl</command>
          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/compilation
	  (<xref linkend="kernelconfig">).</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 id="configtuning-initial">
    <title>Initial Configuration</title>

    <sect2>
      <title>Partition Layout</title>

      <indexterm><primary>partition layout</primary></indexterm>
      <indexterm>
        <primary><filename>/etc</filename></primary>
      </indexterm>
      <indexterm>
        <primary><filename>/var</filename></primary>
      </indexterm>
      <indexterm>
        <primary><filename>/usr</filename></primary>
      </indexterm>

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

	<para>When laying out file systems with &man.disklabel.8;
	  or &man.sysinstall.8;, remember that hard
	  drives transfer data faster from the outer
	  tracks to the inner.
	  Thus smaller and heavier-accessed file systems
	  should be closer to the outside of the drive, while
	  larger partitions like <filename>/usr</filename> should be placed
	  toward the inner.  It is a good idea to create
	  partitions in a similar order to: root, swap,
	  <filename>/var</filename>, <filename>/usr</filename>.</para>

	<para>The size of <filename>/var</filename>
	  reflects the intended machine usage.
	  <filename>/var</filename> is used to hold
	  mailboxes, log files, and printer spools.  Mailboxes and log
	  files can grow to unexpected sizes depending
	  on how many users exist and how long log
	  files are kept.  Most users would never require a gigabyte,
	  but remember that <filename>/var/tmp</filename>
	  must be large enough to contain packages.
	  </para>

	<para>The <filename>/usr</filename> partition holds much
	  of the files required to support the system, the &man.ports.7;
	  collection (recommended) and the source code (optional).  Both
	  of which are optional at install time.
	  At least 2 gigabytes would be recommended for this partition.</para>

	<para>When selecting partition sizes, keep the space
	  requirements in mind.  Running out of space in
	  one partition while barely using another can be a
	  hassle.</para>

	<note><para>Some users have found that &man.sysinstall.8;'s
	    <literal>Auto-defaults</literal> partition sizer will
	    sometimes select smaller than adequate <filename>/var</filename>
	    and <filename>/</filename> partitions.  Partition wisely and
	    generously.</para></note>

      </sect3>

      <sect3 id="swap-design">
	<title>Swap Partition</title>

	<indexterm><primary>swap sizing</primary></indexterm>
	<indexterm><primary>swap partition</primary></indexterm>

	<para>As a rule of thumb, the swap partition should be
	  about double the size of system memory (RAM).  For example,
	  if the machine has 128&nbsp;megabytes of memory,
	  the swap file should be 256&nbsp;megabytes.  Systems with
	  less memory may perform better with more swap.
	  Less than 256&nbsp;megabytes of swap is not recommended and
	  memory expansion should be considered.
	  The kernel's VM paging algorithms are tuned to
	  perform best when the swap partition is at least two times the
	  size of main memory.  Configuring too little swap can lead to
	  inefficiencies in the VM page scanning code and might create
	  issues later if more memory is added.</para>

	<para>On larger systems with multiple SCSI disks (or
	  multiple IDE disks operating on different controllers), it is
	  recommend that a swap is configured on each drive (up
	  to four drives).  The swap partitions should be
	  approximately the same size.  The kernel can handle arbitrary
	  sizes but internal data structures scale to 4 times the
	  largest swap partition.  Keeping the swap partitions near the
	  same size will allow the kernel to optimally stripe swap space
	  across disks.
	  Large swap sizes are fine, even if swap is not
	  used much.  It might be easier to recover
	  from a runaway program before being forced to reboot.</para>
      </sect3>

      <sect3>
	<title>Why Partition?</title>

	<para>Several users think a single large partition will be fine,
	  but there are several reasons why this is a bad idea.
	  First, each partition has different operational
	  characteristics and separating them allows the file system to
	  tune accordingly.  For example, the root
	  and <filename>/usr</filename> partitions are read-mostly, without
	  much writing.  While a lot of reading and writing could
	  occur in <filename>/var</filename> and
	  <filename>/var/tmp</filename>.</para>

	<para>By properly partitioning a system, fragmentation
	  introduced in the smaller write heavy partitions
	  will not bleed over into the mostly-read partitions.
	  Keeping the write-loaded partitions closer to
	  the disk's edge,
	  will
	  increase I/O performance in the partitions where it occurs
	  the most.  Now while I/O
	  performance in the larger partitions may be needed,
	  shifting them more toward the edge of the disk will not
	  lead to a significant performance improvement over moving
	  <filename>/var</filename> to the edge.
	  Finally, there are safety concerns.  A smaller, neater root
	  partition which is mostly read-only has a greater
	  chance of surviving a bad crash.</para>
      </sect3>
    </sect2>

  </sect1>

  <sect1 id="configtuning-core-configuration">
    <title>Core Configuration</title>

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

    <para>The principal location for system configuration information
      is within <filename>/etc/rc.conf</filename>.  This file
      contains a wide range of configuration information, principally
      used at system startup to configure the system.  Its name
      directly implies this; it is configuration information for the
      <filename>rc*</filename> files.</para>

    <para>An administrator should make entries in the
      <filename>rc.conf</filename> file to
      override the default settings from
      <filename>/etc/defaults/rc.conf</filename>.  The defaults file
      should not be copied verbatim to <filename>/etc</filename> - it
      contains default values, not examples.  All system-specific
      changes should be made in the <filename>rc.conf</filename>
      file itself.</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 site-wide
      configuration into another file,
      such as <filename>/etc/rc.conf.site</filename>, and then include
      this file into <filename>/etc/rc.conf</filename>, which will
      contain only system-specific information.</para>

    <para>As <filename>rc.conf</filename> is read by &man.sh.1; it is
      trivial to achieve this.  For example:</para>

    <itemizedlist>
      <listitem><para>rc.conf:</para>
<programlisting>	. rc.conf.site
	hostname="node15.example.com"
	network_interfaces="fxp0 lo0"
	ifconfig_fxp0="inet 10.1.1.1"</programlisting></listitem>
      <listitem><para>rc.conf.site:</para>
<programlisting>	defaultrouter="10.1.1.254"
	saver="daemon"
	blanktime="100"</programlisting></listitem>
    </itemizedlist>

    <para>The <filename>rc.conf.site</filename> file can then be
      distributed to every system using <command>rsync</command> or a
      similar program, while the <filename>rc.conf</filename> file
      remains unique.</para>

    <para>Upgrading the system using &man.sysinstall.8;
      or <command>make world</command> will not overwrite the
      <filename>rc.conf</filename>
      file, so system configuration information will not be lost.</para>

  </sect1>

  <sect1 id="configtuning-appconfig">
    <title>Application Configuration</title>

    <para>Typically, installed applications have their own
      configuration files, with their own syntax, etc.  It is
      important that these files be kept separate from the base
      system, so that they may be easily located and managed by the
      package management tools.</para>

    <indexterm><primary>/usr/local/etc</primary></indexterm>

    <para>Typically, these files are installed in
      <filename>/usr/local/etc</filename>.  In the case where an
      application has a large number of configuration files, a
      subdirectory will be created to hold them.</para>

    <para>Normally, when a port or package is installed, sample
      configuration files are also installed.  These are usually
      identified with a <filename>.default</filename> suffix.  If there
      are no existing
      configuration files for the application, they will be created by
      copying the <filename>.default</filename> files.</para>

    <para>For example, consider the contents of the directory
    <filename>/usr/local/etc/apache</filename>:</para>

<literallayout class="monospaced">-rw-r--r--  1 root  wheel   2184 May 20  1998 access.conf
-rw-r--r--  1 root  wheel   2184 May 20  1998 access.conf.default
-rw-r--r--  1 root  wheel   9555 May 20  1998 httpd.conf
-rw-r--r--  1 root  wheel   9555 May 20  1998 httpd.conf.default
-rw-r--r--  1 root  wheel  12205 May 20  1998 magic
-rw-r--r--  1 root  wheel  12205 May 20  1998 magic.default
-rw-r--r--  1 root  wheel   2700 May 20  1998 mime.types
-rw-r--r--  1 root  wheel   2700 May 20  1998 mime.types.default
-rw-r--r--  1 root  wheel   7980 May 20  1998 srm.conf
-rw-r--r--  1 root  wheel   7933 May 20  1998 srm.conf.default</literallayout>

    <para>The file sizes show that only the <filename>srm.conf</filename>
      file has been changed.  A later update of the <application>Apache</application> port would not
      overwrite this changed file.</para>

  </sect1>

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

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

    <para>It is common for a system to host a number of services.
      These may be started in several different fashions, each having
      different advantages.</para>

    <indexterm><primary>/usr/local/etc/rc.d</primary></indexterm>

    <para>Software installed from a port or the packages collection
      will often place a script in
      <filename>/usr/local/etc/rc.d</filename> which is invoked at
      system startup with a <option>start</option> argument, and at
      system shutdown with a <option>stop</option> argument.
      This is the recommended way for
      starting system-wide services that are to be run as
      <username>root</username>, or that
      expect to be started as <username>root</username>.
      These scripts are registered as
      part of the installation of the package, and will be removed
      when the package is removed.</para>

    <para>A generic startup script in
      <filename>/usr/local/etc/rc.d</filename> looks like:</para>

    <programlisting>#!/bin/sh
echo -n ' FooBar'

case "$1" in
start)
        /usr/local/bin/foobar
        ;;
stop)
        kill -9 `cat /var/run/foobar.pid`
        ;;
*)
        echo "Usage: `basename $0` {start|stop}" >&2
        exit 64
        ;;
esac

exit 0
    </programlisting>

    <para>The startup scripts of &os; will look in
      <filename>/usr/local/etc/rc.d</filename> for scripts that have an
      <literal>.sh</literal> extension and are executable by
      <username>root</username>.  Those scripts that are found are called with
      an option <option>start</option> at startup, and <option>stop</option>
      at shutdown to allow them to carry out their purpose.  So if you wanted
      the above sample script to be picked up and run at the proper time during
      system startup, you should save it to a file called
      <filename>FooBar.sh</filename> in
      <filename>/usr/local/etc/rc.d</filename> and make sure it is
      executable.  You can make a shell script executable with &man.chmod.1;
      as shown below:</para>

    <screen>&prompt.root; <userinput>chmod 755 <replaceable>FooBar.sh</replaceable></userinput></screen>

    <para>Some services expect to be invoked by &man.inetd.8; when a
      connection is received on a suitable port.  This is common for
      mail reader servers (POP and IMAP, etc.).  These services are
      enabled by editing the file <filename>/etc/inetd.conf</filename>.
      See &man.inetd.8; for details on editing this file.</para>

    <para>Some additional system services may not be covered by the
      toggles in <filename>/etc/rc.conf</filename>.  These are
      traditionally enabled by placing the command(s) to invoke them
      in <filename>/etc/rc.local</filename>.  As of &os;&nbsp;3.1 there
      is no default <filename>/etc/rc.local</filename>; if it is
      created by the administrator it will however be honored in the
      normal fashion.  Note that <filename>rc.local</filename> is
      generally regarded as the location of last resort; if there is a
      better place to start a service, do it there.</para>

    <note><para>Do <emphasis>not</emphasis> place any commands in
      <filename>/etc/rc.conf</filename>.  To start daemons, or
      run any commands at boot time, place a script in
      <filename>/usr/local/etc/rc.d</filename> instead.</para>
    </note>

    <para>It is also possible to use the &man.cron.8; daemon to start
      system services.  This approach has a number of advantages, not
      least being that because &man.cron.8; runs these processes as the
      owner of the <command>crontab</command>, services may be started
      and maintained by non-<username>root</username> users.</para>

    <para>This takes advantage of a feature of &man.cron.8;: the
      time specification may be replaced by <literal>@reboot</literal>,
      which will
      cause the job to be run when &man.cron.8; is started shortly after
      system boot.</para>
  </sect1>

  <sect1 id="configtuning-cron">
    <sect1info>
      <authorgroup>
        <author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Contributed by </contrib>
	<!-- 20 May 2003 -->
	</author>
      </authorgroup>
    </sect1info>
    <title>Configuring the <command>cron</command> Utility</title>

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

    <para>One of the most useful utilities in &os; is &man.cron.8;.  The
      <command>cron</command> utility runs in the background and constantly
      checks the <filename>/etc/crontab</filename> file.  The <command>cron</command>
      utility also checks the <filename>/var/cron/tabs</filename> directory, in
      search of new <filename>crontab</filename> files.  These
      <filename>crontab</filename> files store information about specific
      functions which <command>cron</command> is supposed to perform at
      certain times.</para>

    <para>The <command>cron</command> utility uses two different
      types of configuration files, the system crontab and user crontabs. The
      only difference between these two formats is the sixth field.  In the
      system crontab, the sixth field is the name of a user for the command
      to run as. This gives the system crontab the ability to run commands
      as any user. In a user crontab, the sixth field is the command to run,
      and all commands run as the user who created the crontab; this is an
      important security feature.</para>

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

      <para>The <username>root</username> user can have a user crontab just like
        any other user. This one is different from
        <filename>/etc/crontab</filename> (the system crontab). Because of the
        system crontab, there's usually no need to create a user crontab
        for <username>root</username>.</para>
    </note>

    <para>Let us take a look at the <filename>/etc/crontab</filename> file
      (the system crontab):</para>


    <programlisting># /etc/crontab - root's crontab for &os;
#
# &dollar;&os;: src/etc/crontab,v 1.32 2002/11/22 16:13:39 tom Exp &dollar;
# <co id="co-comments">
#
SHELL=/bin/sh
PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin <co id="co-env">
HOME=/var/log
#
#
#minute	hour	mday	month	wday	who	command <co id="co-field-descr">
#
#
*/5	*	*	*	*	root	/usr/libexec/atrun <co id="co-main">
</programlisting>

    <calloutlist>
      <callout arearefs="co-comments">
	<para>Like most &os; configuration files, the <literal>#</literal>
	  character represents a comment.  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>First, the environment must be defined.  The equals
	  (<literal>=</literal>) character is used to define any environment
	  settings, as with this example where it is used for the <envar>SHELL</envar>,
	  <envar>PATH</envar>, and <envar>HOME</envar> options.  If the shell line is
	  omitted, <command>cron</command> will use the default, which is
	  <command>sh</command>.  If the <envar>PATH</envar> variable is
	  omitted, no default will be used and file locations will need to
	  be absolute.  If <envar>HOME</envar> is omitted, <command>cron</command>
	  will use the invoking users home directory.</para>
      </callout>

      <callout arearefs="co-field-descr">
	<para>This line defines a total of seven fields.  Listed here are the
	  values <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 the
	  command will be run.  <literal>hour</literal> is similar to the <literal>minute</literal> option, just in
	  hours.  <literal>mday</literal> stands for day of the month.  <literal>month</literal> is similar to <literal>hour</literal>
	  and <literal>minute</literal>, as it designates the month.  The <literal>wday</literal> option stands for
	  day of the week.  All these fields must be numeric values, and follow
	  the twenty-four hour clock.  The <literal>who</literal> field is special,
	  and only exists in the <filename>/etc/crontab</filename> file.
	  This field specifies which user the command should be run as.
	  When a user installs his or her <filename>crontab</filename> file, they
	  will not have this option. Finally, the <literal>command</literal> option is listed.
	  This is the last field, so naturally it should designate the command
	  to be executed.</para>
      </callout>

      <callout arearefs="co-main">
	<para>This last line will define the values discussed above.  Notice here
	  we have 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.  So, judging by this line,
	  it is apparent that the <command>atrun</command> command is to be invoked by
	  <username>root</username> every five minutes regardless of what
	  day or month it is.  For more information on the <command>atrun</command> command,
	  see the &man.atrun.8; manual page.</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 set up for every
      <filename>crontab</filename> file, although there is one thing
      different about this one.  Field number six, where we specified
      the username, only exists in the system
      <filename>/etc/crontab</filename> file.  This field should be
      omitted for individual user <filename>crontab</filename>
      files.</para>


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

      <important>
      <para>You must not use the procedure described here to
        edit/install the system crontab. Simply use your favorite
        editor: the <command>cron</command> utility will notice that the file
        has changed and immediately begin using the updated version. 
        See
        <ulink url="../faq/admin.html#ROOT-NOT-FOUND-CRON-ERRORS">
        this FAQ entry </ulink> for more information.</para>
      </important>

      <para>To install a freshly written user
	<filename>crontab</filename>, first use your favorite editor to create
	a file in the proper format, and then use the
	<command>crontab</command> utility.  The most common usage
	is:</para>

      <screen>&prompt.user; <userinput>crontab crontab-file</userinput></screen>
      
      <para>In this example, <filename>crontab-file</filename> is the filename
    of a <filename>crontab</filename> that was previously created.</para>

      <para>There is also an option to list installed
	<filename>crontab</filename> files: just pass the
	<option>-l</option> option to <command>crontab</command> and look
	over the output.</para>

      <para>For users who wish to begin their own crontab file from scratch,
	without the use of a template, the <command>crontab -e</command>
	option is available.  This will invoke the selected editor
	with an empty file.  When the file is saved, it will be
	automatically installed by the <command>crontab</command> command.
      </para>
      
      <para>If you later want to remove your user <filename>crontab</filename>
	completely, use <command>crontab</command> with the <option>-r</option>
	option.
      </para>

    </sect2>
  </sect1>

  <sect1 id="configtuning-rcNG">
    <sect1info>
      <authorgroup>
        <author>
	 <firstname>Tom</firstname>
	 <surname>Rhodes</surname>
	 <contrib>Contributed by </contrib>
	 <!-- 16 May 2003 -->
        </author>
      </authorgroup>
    </sect1info>

    <title>Using rc under FreeBSD 5.X</title>

    <indexterm><primary>rcNG</primary></indexterm>

    <para>&os; has recently integrated the NetBSD
      <filename>rc.d</filename> system for system initialization.
      Users should notice the files listed in the
      <filename>/etc/rc.d</filename> directory.  Many of these files
      are for basic services which can be controlled with the
      <option>start</option>, <option>stop</option>,
      and <option>restart</option> options.
      For instance, &man.sshd.8; can be restarted with the following
      command:</para>

    <screen>&prompt.root; <userinput>/etc/rc.d/sshd restart</userinput></screen>

    <para>This procedure is similar for other services.  Of course,
      services are usually started automatically as specified in
      &man.rc.conf.5;.  For example, enabling the Network Address
      Translation daemon at startup is as simple as adding 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, then simply change the <option>NO</option> to
       <option>YES</option>.  The rc scripts will automatically load
       any other dependent services during the next reboot, as
       described below.</para>

    <para>Since the <filename>rc.d</filename> system is primarily
      intended to start/stop services at system startup/shutdown time,
      the standard <option>start</option>,
      <option>stop</option> and <option>restart</option> options will only
      perform their action if the appropriate
      <filename>/etc/rc.conf</filename> variables are set.  For
      instance the above <command>sshd restart</command> 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>, the commands should be
      prefixed with <quote>force</quote>.  For instance to restart
      <command>sshd</command> regardless of the current
      <filename>/etc/rc.conf</filename> setting, execute the following
      command:</para>

    <screen>&prompt.root; <userinput>/etc/rc.d/sshd forcerestart</userinput></screen>

    <para>It is easy to check if a service is enabled in
      <filename>/etc/rc.conf</filename> by running the appropriate
      <filename>rc.d</filename> script with the option
      <option>rcvar</option>.  Thus, an administrator can check that
      <command>sshd</command> is in fact enabled in
      <filename>/etc/rc.conf</filename> by running:</para>

    <screen>&prompt.root; <userinput>/etc/rc.d/sshd rcvar</userinput>
# sshd
$sshd_enable=YES</screen>

    <note>
      <para>The second line (<literal># sshd</literal>) is the output
        from the <command>sshd</command> command, not a <username>root</username>
        console.</para>
    </note>

    <para>To determine if a service is running, a
      <option>status</option> option is available.  For instance to
      verify that <command>sshd</command> is actually started:</para>

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

    <para>It is also possible to <option>reload</option> a service.
      This will attempt 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.</para>

    <para>The <application>rcNG</application> structure is not only used for network services, it also
      contributes to most of the system initialization.  For
      instance, consider the <filename>bgfsck</filename> file.  When
      this script is executed, it will print out the following
      message:</para>

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

    <para>Therefore this file is used for background file system
      checks, which are done only during system initialization.</para>

    <para>Many system services depend on other services to function
      properly.  For example, NIS and other RPC-based services may
      fail to start until after the <command>rpcbind</command>
      (portmapper) 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 then used to parse these comments
      during system initialization to determine the order in which
      system services should be invoked to satisfy the dependencies.
      The following words may be included at the top of each startup
      file:</para>

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

      <listitem>
	<para><literal>REQUIRE</literal>: Lists services which are required for this
	  service.  This file will run <emphasis>after</emphasis>
	  the specified services.</para>
      </listitem>

      <listitem>
	<para><literal>BEFORE</literal>: Lists services which depend on this service.
	  This file will run <emphasis>before</emphasis>
	  the specified services.</para>
      </listitem>

      <listitem>
	<para>KEYWORD: &os; or NetBSD.  This is used for *BSD dependent features.</para>
      </listitem>
    </itemizedlist>

    <para>By using this method, an administrator can easily control system
      services without the hassle of <quote>runlevels</quote> like
      some other &unix; operating systems.</para>

    <para>Additional information about the &os; 5.X
      <filename>rc.d</filename> system can be found in the &man.rc.8;
      and &man.rc.subr.8; manual pages.</para>
  </sect1>

  <sect1 id="config-network-setup">
    <sect1info>
      <authorgroup>
        <author>
	 <firstname>Marc</firstname>
	 <surname>Fonvieille</surname>
	 <contrib>Contributed by </contrib>
	 <!-- 6 October 2002 -->
        </author>
      </authorgroup>
    </sect1info>

    <title>Setting Up Network Interface Cards</title>

    <indexterm><primary>network card configuration</primary></indexterm>

    <para>Nowadays we can not think about a computer without thinking
      about a network connection.  Adding and configuring a network
      card is a common task for any &os; administrator.</para>

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

      <indexterm>
	<primary>network card configuration</primary>
	<secondary>locating the driver</secondary>
      </indexterm>

      <para>Before you begin, you should know the model of the card
	you have, the chip it uses, and whether it is a PCI or ISA card.
	&os; supports a wide variety of both PCI and ISA cards.
	Check the Hardware Compatibility List for your release to see
	if your card is supported.</para>

      <para>Once you are sure your card is supported, you need
	to determine the proper driver for the card.  The file
	<filename>/usr/src/sys/i386/conf/LINT</filename> will give you
	the list of network interfaces drivers with some information
	about the supported chipsets/cards.  If you have doubts about
	which driver is the correct one, read the manual page of the
	driver.  The manual page will give you more information about
	the supported hardware and even the possible problems that
	could occur.</para>

      <para>If you own a common card, most of the time you will not
	have to look very hard for a driver.  Drivers for common
	network cards are present in the <filename>GENERIC</filename>
	kernel, so your card should show up during boot, like so:</para>

<screen>dc0: &lt;82c169 PNIC 10/100BaseTX&gt; port 0xa000-0xa0ff mem 0xd3800000-0xd38
000ff irq 15 at device 11.0 on pci0
dc0: Ethernet address: 00:a0:cc:da:da:da
miibus0: &lt;MII bus&gt; on dc0
ukphy0: &lt;Generic IEEE 802.3u media interface&gt; on miibus0
ukphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
dc1: &lt;82c169 PNIC 10/100BaseTX&gt; port 0x9800-0x98ff mem 0xd3000000-0xd30
000ff irq 11 at device 12.0 on pci0
dc1: Ethernet address: 00:a0:cc:da:da:db
miibus1: &lt;MII bus&gt; on dc1
ukphy1: &lt;Generic IEEE 802.3u media interface&gt; on miibus1
ukphy1:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto</screen>

      <para>In this example, we see that two cards using the &man.dc.4;
	driver are present on the system.</para>

      <para>To use your network card, you will need to load the proper
	driver.  This may be accomplished in one of two ways.  The
	easiest way is to simply load a kernel module for your network
	card with &man.kldload.8;.  A module is not available for all
	network card drivers (ISA cards and cards using the &man.ed.4;
	driver, for example).  Alternatively, you may statically compile
	the support for your card into your kernel.  Check
	<filename>/usr/src/sys/i386/conf/LINT</filename> and the
	manual page of the driver to know what to add in your kernel
	configuration file.  For more information about recompiling your
	kernel, please see <xref linkend="kernelconfig">.  If your card
	was detected at boot by your kernel (<filename>GENERIC</filename>)
	you do not have to build a new kernel.</para>
    </sect2>

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

      <indexterm>
	<primary>Network card configuration</primary>
	<secondary>configuration</secondary>
      </indexterm>

      <para>Once the right driver is loaded for the network card, the
	card needs to be configured.  As with many other things, the
	network card may have been configured at installation time by
	<application>sysinstall</application>.</para>

      <para>To display the configuration for the network interfaces on
	your system, enter the following command:</para>

<screen>&prompt.user; <userinput>ifconfig</userinput>
dc0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; mtu 1500
        inet 192.168.1.3 netmask 0xffffff00 broadcast 192.168.1.255
        ether 00:a0:cc:da:da:da
        media: Ethernet autoselect (100baseTX &lt;full-duplex&gt;)
        status: active
dc1: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; mtu 1500
        inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255
        ether 00:a0:cc:da:da:db
        media: Ethernet 10baseT/UTP
        status: no carrier
lp0: flags=8810&lt;POINTOPOINT,SIMPLEX,MULTICAST&gt; mtu 1500
lo0: flags=8049&lt;UP,LOOPBACK,RUNNING,MULTICAST&gt; mtu 16384
        inet 127.0.0.1 netmask 0xff000000
tun0: flags=8010&lt;POINTOPOINT,MULTICAST&gt; mtu 1500</screen>

      <note>
	<para>Old versions of &os; may require the <option>-a</option>
	  option following &man.ifconfig.8;, for more details about the
	  correct syntax of &man.ifconfig.8;, please refer to the manual
	  page.  Note also that entries concerning IPv6
	  (<literal>inet6</literal> etc.) were omitted in this
	  example.</para>
      </note>

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

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

	<listitem>
	  <para><devicename>dc1</devicename>: The second Ethernet
	    interface</para>
	</listitem>

	<listitem>
	  <para><devicename>lp0</devicename>: The parallel port
	    interface</para>
	</listitem>

	<listitem>
	  <para><devicename>lo0</devicename>: The loopback device</para>
	</listitem>

	<listitem>
	  <para><devicename>tun0</devicename>: The tunnel device used by
	    <application>ppp</application></para>
	</listitem>
      </itemizedlist>

      <para>&os; uses the driver name followed by the order in
	which one the card is detected at the kernel boot to name the
	network card.  For example <devicename>sis2</devicename> would
	be the third network card on the system using the &man.sis.4;
	driver.</para>

      <para>In this example, the <devicename>dc0</devicename> device 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 (in this case
	    <hostid role="ipaddr">192.168.1.3</hostid>).</para>
	</listitem>

	<listitem>
	  <para>It has a valid subnet mask (<literal>netmask</literal>;
	    <hostid role="netmask">0xffffff00</hostid> is the same as
	    <hostid role="netmask">255.255.255.0</hostid>).</para>
	</listitem>

	<listitem>
	  <para>It has a valid broadcast address (in this case,
	    <hostid role="ipaddr">192.168.1.255</hostid>).</para>
	</listitem>

	<listitem>
	  <para>The MAC address of the card (<literal>ether</literal>)
	    is <hostid role="mac">00:a0:cc:da:da:da</hostid></para>
	</listitem>

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

	<listitem>
	  <para>The status of the link (<literal>status</literal>)
	    is <literal>active</literal>, i.e. the carrier is detected.
	    For <devicename>dc1</devicename>, we see
	    <literal>status: no carrier</literal>.  This 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; mtu 1500
	        ether 00:a0:cc:da:da:da</screen>

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

      <para>To configure your card, you need <username>root</username>
	privileges.  The network card configuration can be done from the
	command line with &man.ifconfig.8; but you would have to do it
	after each reboot of the system.  The file
	<filename>/etc/rc.conf</filename> is where to add the network
	card's configuration.</para>

      <para>Open <filename>/etc/rc.conf</filename> in your favorite
	editor.  You need to add a line for each network card present on
	the system, for example in our case, we added these lines:</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>You have to replace <devicename>dc0</devicename>,
	<devicename>dc1</devicename>, and so on, with
	the correct device for your cards, and the addresses with the
	proper ones.  You should read the card driver and
	&man.ifconfig.8; manual pages for more details about the allowed
	options and also &man.rc.conf.5; manual page for more
	information on the syntax of
	<filename>/etc/rc.conf</filename>.</para>

      <para>If you configured the network during installation, some
	lines about the network card(s) may be already present.  Double
	check <filename>/etc/rc.conf</filename> before adding any
	lines.</para>

      <para>You will also have to edit the file
	<filename>/etc/hosts</filename> to add the names and the IP
	addresses of various machines of the LAN, if they are not already
	there.  For more information please refer to &man.hosts.5;
	and to <filename>/usr/share/examples/etc/hosts</filename>.</para>
    </sect2>

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

      <para>Once you have made the necessary changes in
	<filename>/etc/rc.conf</filename>, you should reboot your
	system.  This will allow the change(s) to the interface(s) to
	be applied, and verify that the system restarts without any
	configuration errors.</para>

      <para>Once the system has been rebooted, you should test the
	network interfaces.</para>

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

	<indexterm>
	  <primary>network card configuration</primary>
	  <secondary>testing the card</secondary>
	</indexterm>

	<para>To verify that an Ethernet card is configured correctly,
	  you have to try two things.  First, ping the interface itself,
	  and then ping another machine on the LAN.</para>

	<para>First test the local interface:</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>

	<para>Now we have to ping another machine on the LAN:</para>

<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>You could also use the machine name instead of
	  <hostid role="ipaddr">192.168.1.2</hostid> if you have set up the
	  <filename>/etc/hosts</filename> file.</para>
      </sect3>

      <sect3>
	<title>Troubleshooting</title>

      <indexterm>
	<primary>network card configuration</primary>
	<secondary>troubleshooting</secondary>
      </indexterm>

      <para>Troubleshooting hardware and software configurations is always
	a pain, and a pain which can be alleviated by checking the simple
	things first.  Is your network cable plugged in?  Have you properly
	configured the network services?  Did you configure the firewall
	correctly?  Is the card you are using supported by &os;?  Always
	check the hardware notes before sending off a bug report.  Update
	your version of &os; to the latest STABLE version.  Check the
	mailing list archives, or perhaps search the Internet.</para>

      <para>If the card works, yet performance is poor, it would be
	worthwhile to read over the &man.tuning.7; manual page.  You
	can also check the network configuration as incorrect network
	settings can cause slow connections.</para>

      <para>Some users experience one or two <quote>device
	timeouts</quote>, which is normal for some cards.  If they
	continue, or are bothersome, you may wish to be sure the
	device is not conflicting with another device.  Double check
	the cable connections.  Perhaps you may just need to get
	another card.</para>

      <para>At times, users see a few <errorname>watchdog timeout</errorname>
	errors.  The first thing to do here is to check your network
	cable. Many cards require a PCI slot which supports Bus
	Mastering. On some old motherboards, only one PCI slot allows
	it (usually slot 0). Check the network card 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
	you are trying to reach.  If there is not, read on to <xref
	linkend="advanced-networking">.</para>

      <para><errorname>ping: sendto: Permission denied</errorname> error
	messages are often caused by a misconfigured firewall.  If
	<command>ipfw</command> is enabled in the kernel but no rules
	have been defined, then the default policy is to deny all
	traffic, even ping requests!  Read on to <xref
	linkend="firewalls"> for more information.</para>

      <para>Sometimes performance of the card is poor, or below average.
	In these cases it is best to set the media selection mode
	from <literal>autoselect</literal> to the correct media selection.
	While this usually works for most hardware, it may not resolve
	this issue for everyone.  Again, check all the network settings,
	and read over the &man.tuning.7; manual page.</para>

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

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

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

    <para>A very 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>.</para>

    <para>An alias entry for the interface <devicename>fxp0</devicename>
      looks like:</para>

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

    <para>Note that alias entries must start with alias0 and proceed
      upwards in order, (for example, _alias1, _alias2, and so on).
      The configuration process will stop at the first missing number.
    </para>

    <para>The calculation of alias netmasks is important, but
      fortunately quite simple.  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.</para>

    <para>For example, consider the case where the
      <devicename>fxp0</devicename> interface is
      connected to two networks, the <hostid role="ipaddr">10.1.1.0</hostid>
      network with a netmask of <hostid role="netmask">255.255.255.0</hostid>
      and the <hostid role="ipaddr">202.0.75.16</hostid> network with
      a netmask of <hostid role="netmask">255.255.255.240</hostid>.
      We want the system to appear at <hostid role="ipaddr">10.1.1.1</hostid>
      through <hostid role="ipaddr">10.1.1.5</hostid> and at
      <hostid role="ipaddr">202.0.75.17</hostid> through
      <hostid role="ipaddr">202.0.75.20</hostid>.</para>

    <para>The following entries configure the adapter correctly for
      this arrangement:</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 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">
	<tgroup cols="2">
	  <colspec colwidth="1*">
	  <colspec colwidth="2*">

	  <tbody>
	    <row>
	      <entry><filename>/etc</filename></entry>
	      <entry>Generic system configuration information; data here is
		system-specific.</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, other
		MTA 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>Start/stop 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, the locate database, and so
                 on</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><filename>/etc/resolv.conf</filename> dictates how &os;'s
	  resolver accesses the Internet Domain Name System (DNS).</para>

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

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

	    <tbody>
	      <row>
		<entry><literal>nameserver</literal></entry>
		<entry>The IP 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>resolv.conf</filename>:</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>If you are using DHCP, &man.dhclient.8; usually rewrites
	  <filename>resolv.conf</filename> with information received from the
	  DHCP 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 reminiscent of the old Internet.  It works in
	  conjunction with DNS and NIS providing name to IP address
	  mappings.  Local computers connected via a LAN can be placed
	  in here 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
	  externally 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.
# 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 myname.my.domain
127.0.0.1               localhost localhost.my.domain myname.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.  PLEASE PLEASE PLEASE do not try
# to invent your own network numbers but instead get one from your
# network provider (if any) or from the Internet Registry (ftp to
# rs.internic.net, directory `/templates').
#</programlisting>

	<para><filename>/etc/hosts</filename> takes on the simple format
	  of:</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>

    <sect2>
      <title>Log File Configuration</title>

      <indexterm><primary>log files</primary></indexterm>

      <sect3>
	<title><filename>syslog.conf</filename></title>

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

	<para><filename>syslog.conf</filename> is the configuration file
	  for the &man.syslogd.8; program.  It indicates which types
	  of <command>syslog</command> messages are logged to particular
	  log files.</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) manual page.
*.err;kern.debug;auth.notice;mail.crit          /dev/console
*.notice;kern.debug;lpr.info;mail.crit;news.err /var/log/messages
security.*                                      /var/log/security
mail.info                                       /var/log/maillog
lpr.info                                        /var/log/lpd-errs
cron.*                                          /var/log/cron
*.err                                           root
*.notice;news.err                               root
*.alert                                         root
*.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
#*.*                                            /var/log/all.log
# uncomment this to enable logging to a remote log host 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
!startslip
*.*                                             /var/log/slip.log
!ppp
*.*                                             /var/log/ppp.log</programlisting>

	<para>Consult the &man.syslog.conf.5; manual page for more
	  information.</para>
      </sect3>

      <sect3>
	<title><filename>newsyslog.conf</filename></title>

	<indexterm><primary>newsyslog.conf</primary></indexterm>

	<para><filename>newsyslog.conf</filename> is the configuration
	  file for &man.newsyslog.8;, a program that is normally scheduled
	  to run by &man.cron.8;.  &man.newsyslog.8; determines when log
	  files require archiving or rearranging.
	  <filename>logfile</filename> is moved to
	  <filename>logfile.0</filename>, <filename>logfile.0</filename>
	  is moved to <filename>logfile.1</filename>, and so on.
	  Alternatively, the log files may be archived in &man.gzip.1; format
	  causing them to be named: <filename>logfile.0.gz</filename>,
	  <filename>logfile.1.gz</filename>, and so on.</para>

	<para><filename>newsyslog.conf</filename> indicates which log
	  files are to be managed, how many are to be kept, and when
	  they are to be touched.  Log files can be rearranged and/or
	  archived when they have either reached a certain size, or at a
	  certain periodic time/date.</para>

	<programlisting># configuration file for newsyslog
# &dollar;&os;&dollar;
#
# filename          [owner:group]    mode count size when [ZB] [/pid_file] [sig_num]
/var/log/cron                           600  3     100  *     Z
/var/log/amd.log                        644  7     100  *     Z
/var/log/kerberos.log                   644  7     100  *     Z
/var/log/lpd-errs                       644  7     100  *     Z
/var/log/maillog                        644  7     *    @T00  Z
/var/log/sendmail.st                    644  10    *    168   B
/var/log/messages                       644  5     100  *     Z
/var/log/all.log                        600  7     *    @T00  Z
/var/log/slip.log                       600  3     100  *     Z
/var/log/ppp.log                        600  3     100  *     Z
/var/log/security                       600  10    100  *     Z
/var/log/wtmp                           644  3     *    @01T05 B
/var/log/daily.log                      640  7     *    @T00  Z
/var/log/weekly.log                     640  5     1    $W6D0 Z
/var/log/monthly.log                    640  12    *    $M1D0 Z
/var/log/console.log                    640  5     100  *     Z</programlisting>

	<para>Consult the &man.newsyslog.8; manual page for more
	  information.</para>
      </sect3>
    </sect2>

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

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

      <para><filename>sysctl.conf</filename> looks much like
	<filename>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>A sample <filename>sysctl.conf</filename> turning off logging
	of fatal signal exits and letting Linux programs know they are really
	running under &os;:</para>

      <programlisting>kern.logsigexit=0       # Do not log fatal signal exits (e.g. sig 11)
compat.linux.osname=&os;
compat.linux.osrelease=4.3-STABLE</programlisting>
    </sect2>
  </sect1>

  <sect1 id="configtuning-sysctl">
    <title>Tuning with sysctl</title>

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

    <para>&man.sysctl.8; is an interface that allows you to make changes
      to a running &os; system.  This includes many advanced
      options of the TCP/IP 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, for example,
      <varname>kern.maxproc</varname>:</para>

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

    <para>To set a particular variable, use the intuitive
      <replaceable>variable</replaceable>=<replaceable>value</replaceable>
      syntax:</para>

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

    <para>Settings of sysctl variables are usually either strings,
      numbers, or booleans (a  boolean being <literal>1</literal> for yes
      or a <literal>0</literal> for no).</para>

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

  <sect2 id="sysctl-readonly">
    <sect2info>
      <authorgroup>
        <author>
	 <firstname>Tom</firstname>
	 <surname>Rhodes</surname>
	 <contrib>Contributed by </contrib>
	 <!-- 31 January 2003 -->
        </author>
      </authorgroup>
    </sect2info>
    <title>&man.sysctl.8; Read-only</title>

    <para>In some cases it may be desirable to modify read-only &man.sysctl.8;
      values.  While this is not recommended, it is also sometimes unavoidable.</para>

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

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

    <para>Cases like the one above usually require the modification of some
      default &man.sysctl.8; settings which are set read only.  To overcome
      these situations a user can put &man.sysctl.8; <quote>OIDs</quote>
      in their local <filename>/boot/loader.conf</filename>.  Default
      settings are located in the <filename>/boot/defaults/loader.conf</filename>
      file.</para>

    <para>Fixing the problem mentioned above would require a user to set
      <option>hw.pci.allow_unsupported_io_range=1</option> in the aforementioned
      file.  Now &man.cardbus.4; will work properly.</para>

    </sect2>
  </sect1>

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

    <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> sysctl variable
	  may be set to either 0 (off) or 1 (on); it is 1 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 less
	  (typically 512&nbsp;bytes) in the buffer cache.
	  However, when operating in the default mode the buffer
	  cache will only cache a fixed number of directories even if
	  you have a huge amount of memory.  Turning on this sysctl
	  allows the buffer cache to use the VM 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.  We recommend turning this option on if you are running
	  any services which manipulate large numbers of files.  Such
	  services can include web caches, large mail systems, and news
	  systems.  Turning on this option will generally not reduce
	  performance even with the wasted memory but you 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> sysctl 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.  The idea
 	  is to avoid saturating the buffer cache with dirty buffers when
 	  it would not benefit I/O performance.  However, this may stall
 	  processes and under certain circumstances you may wish to turn it
 	  off.</para>
       </sect3>

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

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

 	<para>The <varname>vfs.hirunningspace</varname> sysctl 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 lots of disks you may
 	  want to bump it up to four or five <emphasis>megabytes</emphasis>.
 	  Note that setting too high a value (exceeding the buffer cache's
 	  write threshold) can lead to extremely bad clustering
 	  performance.  Do not set this value arbitrarily high!  Higher
 	  write values may add latency to reads occurring at the same time.
 	</para>

 	<para>There are various other buffer-cache and VM page cache
 	  related sysctls.  We do not recommend modifying these values.  As
 	  of &os; 4.3, the VM system does an extremely 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> sysctl variable
 	  is useful in large multi-user systems where you have lots of
 	  users entering and leaving the system and lots of idle processes.
 	  Such systems tend to generate a great deal of 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> allows you to depress
 	  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.  Do not turn this option on unless
 	  you need it, because the tradeoff you are making is essentially
 	  pre-page memory sooner rather than later; thus eating 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 VM 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>&os;&nbsp;4.3 flirted with turning off IDE write caching.
	  This reduced write bandwidth to IDE disks but was considered
	  necessary due to serious data consistency issues introduced
	  by hard drive vendors.  The problem is that IDE
	  drives lie about when a write completes.  With IDE write
	  caching turned on, IDE hard drives not only write data
	  to disk out of order, but will sometimes delay writing some
	  blocks indefinitely when under heavy disk loads.  A crash or
	  power failure may cause serious file system corruption.
	  &os;'s default was changed to be safe.  Unfortunately, the
	  result was such a huge performance loss that we changed
	  write caching back to on by default after the release.  You
	  should check the default on your system by observing the
	  <varname>hw.ata.wc</varname> sysctl variable.  If IDE write
	  caching is turned off, you can turn it back on by setting
	  the kernel variable back to 1.  This must be done from the
	  boot loader at boot time.  Attempting to do it after the
	  kernel boots will have no effect.</para>

	<para>For more information, please see &man.ata.4;.</para>
      </sect3>

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

	<indexterm>
	  <primary><option>SCSI_DELAY</option></primary>
	  <secondary><varname>kern.cam.scsi_delay</varname></secondary>
	</indexterm>

	<para>The <option>SCSI_DELAY</option> kernel config 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 (especially with modern drives).  Newer versions of &os;
	  (5.0+) should use the <varname>kern.cam.scsi_delay</varname>
	  boot time tunable.  The tunable, and kernel config option accept
	  values in terms of <emphasis>milliseconds</emphasis> and
	  <emphasis>not</emphasis> <emphasis>seconds</emphasis>.</para>
      </sect3>
    </sect2>

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

      <indexterm><primary>Soft Updates</primary></indexterm>
      <indexterm><primary>tunefs</primary></indexterm>

      <para>The &man.tunefs.8; program can be used to fine-tune a
	file system.  This program has many different options, but for
	now we are only concerned with toggling Soft Updates on and
	off, which is done by:</para>

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

      <para>A filesystem 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>

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

      <para>Soft Updates drastically improves meta-data performance, mainly
        file creation and deletion, through the use of a memory cache.  We
        recommend to use Soft Updates on all of your file systems.  There
        are two downsides to Soft Updates that you should be aware of:  First,
        Soft Updates guarantees filesystem consistency in the case of a crash
        but could very easily be several seconds (even a minute!) behind
        updating the physical disk.  If your system crashes you may lose more
        work than otherwise.  Secondly, Soft Updates delays the freeing of
        filesystem blocks.  If you have a filesystem (such as the root
	filesystem) which is almost full, performing a major update, such as
        <command>make installworld</command>, can cause the filesystem 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>There are two traditional approaches to writing a file
	  systems meta-data back to disk.  (Meta-data updates are
	  updates to non-content data like inodes or
	  directories.)</para>

	<para>Historically, the default behavior was to write out
	  meta-data updates synchronously.  If a directory had been
	  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, the meta-data are 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; is able to recognize this and
	  repair the filesystem by setting the file length to
	  0.  Additionally, the implementation is clear and simple.
	  The disadvantage is that meta-data changes are slow.  An
	  <command>rm -r</command>, for instance, touches all the files
	  in a directory sequentially, but each directory
	  change (deletion of a file) 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 (<command>tar -x</command>).</para>

	<para>The second case is asynchronous meta-data updates.  This
  	  is the default for Linux/ext2fs and
  	  <command>mount -o async</command> for *BSD ufs.  All
  	  meta-data updates are simply being passed through the buffer
  	  cache too, that is, 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.  Also, the
  	  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 at all for a consistent state of
  	  the filesystem.  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 filesystem
  	  will be left in an unpredictable state.  There is no opportunity
  	  to examine the state of the filesystem when the system
  	  comes up again; 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 actually
  	  impossible to implement a <command>fsck</command> which is
  	  able to clean up the resulting chaos (because the necessary
  	  information is not available on the disk).  If the
	  filesystem has been damaged beyond repair, the only choice
	  is to use &man.newfs.8; on it and restore it from backup.
	  </para>

	<para>The usual solution for this problem was to implement
	  <emphasis>dirty region logging</emphasis>, which is also
	  referred to as <emphasis>journaling</emphasis>, although that
	  term is not used consistently and is occasionally applied
	  to other forms of transaction logging as well.  Meta-data
	  updates are still written synchronously, but only into a
	  small region of the disk.  Later on they will be 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 fairly
	  limited, so the risk of bugs being present is low.  A disadvantage
	  is that all meta-data are written twice (once into the
	  logging region and once to the proper location) so for
	  normal work, a performance <quote>pessimization</quote>
	  might result.  On the other hand, in case of a crash, all
	  pending meta-data operations can be quickly either rolled-back
	  or completed from the logging area after the system comes
	  up again, resulting in a fast filesystem startup.</para>

	<para>Kirk McKusick, the developer of Berkeley FFS,
	   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 if the earlier ones are still in
	   memory and have not already been written to disk.  So all
	   operations on, say, a directory are generally performed in
	   memory before the update is written to disk (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, this causes an implicit <quote>log
	   rewind</quote>: all operations which did not find their way
	   to the disk appear as if they had never happened.  A
	   consistent filesystem 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 appropriate bitmaps: 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 filesystem 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 fsck</emphasis>: at system startup
	   time, only a <emphasis>snapshot</emphasis> of the
	   filesystem is recorded.  The <command>fsck</command> can be
	   run later on.  All file systems can then be mounted
	   <quote>dirty</quote>, so the system startup proceeds in
	   multiuser mode.  Then, background <command>fsck</command>s
	   will be 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
	   <command>fsck</command> though.)</para>

	 <para>The advantage is that meta-data operations are nearly as
	   fast as asynchronous updates (i.e. faster than with
	   <emphasis>logging</emphasis>, which has to write the
	   meta-data twice).  The disadvantages are the complexity of
	   the code (implying a higher risk for bugs in an area that
	   is highly sensitive regarding loss of user data), and a
	   higher memory consumption.  Additionally there are some
	   idiosyncrasies one has to get used to.
	   After a crash, the state of the filesystem 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
	   <command>fsck</command>, these files do not exist at all
	   with a Soft Updates filesystem because neither the meta-data
	   nor the file contents have ever 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 <command>rm</command>.  This may cause problems
	   when installing large amounts of data on a filesystem
	   that does not have enough free space to hold all the files
	   twice.</para>
      </sect3>
    </sect2>
  </sect1>

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

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

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

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

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

	<para><varname>kern.maxfiles</varname> can be raised or
	  lowered based upon your system requirements.  This variable
	  indicates the maximum number of file descriptors on your
	  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 with the
	  <command>dmesg</command> command.</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><varname>kern.maxfile</varname>'s default value is
	  dictated by the <option>MAXUSERS</option> option in your
          kernel configuration file.  <varname>kern.maxfiles</varname> grows
          proportionally to the value of <option>MAXUSERS</option>.  When
          compiling a custom kernel, it is a good idea to set this kernel
          configuration option according to the uses of your system.  From
          this number, the kernel is given most of its pre-defined limits.
          Even though a production machine may not actually have 256 users
          connected at once, the resources needed may be similar to a
          high-scale web server.</para>

	<note><para>As of &os;&nbsp;4.5, setting <option>MAXUSERS</option> to
	  <literal>0</literal> in your kernel configuration file will choose
	  a reasonable default value based on the amount of RAM present in
	  your system.</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> sysctl variable
	  limits the size of the listen queue for accepting new TCP
	  connections.  The default value of <literal>128</literal> is
	  typically too low for robust handling of new connections in a
	  heavily loaded web server environment.  For such environments, it
	  is recommended to increase this value to <literal>1024</literal> or
	  higher.  The service daemon may itself limit the listen queue size
	  (e.g. &man.sendmail.8;, or <application>Apache</application>) but
	  will often have a directive in its configuration file to adjust
	  the queue size.  Large listen queues also do a better job of
	  avoiding Denial of Service (<abbrev>DoS</abbrev>) attacks.</para>
      </sect3>

    </sect2>
    <sect2>
      <title>Network Limits</title>

      <para>The <option>NMBCLUSTERS</option> 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 &os;'s ability.  Each cluster represents
	approximately 2&nbsp;K of memory, so a value of 1024 represents 2
	megabytes of kernel memory reserved for network buffers.  A
	simple calculation can be done to figure out how many are
	needed.  If you have a web server which maxes out at 1000
	simultaneous connections, and each connection eats a 16&nbsp;K receive
	and 16&nbsp;K send buffer, you need approximately 32&nbsp;MB worth of
	network buffers to cover the web server.  A good rule of thumb is
	to multiply by 2, so 2x32&nbsp;MB&nbsp;/&nbsp;2&nbsp;KB&nbsp;=
	64&nbsp;MB&nbsp;/&nbsp;2&nbsp;kB&nbsp;= 32768.  We recommend
	values between 4096 and 32768 for machines with greater amounts
	of memory.  Under no circumstances should you specify an
	arbitrarily high value for this parameter as it could lead to a
	boot time crash.  The <option>-m</option> option to
	&man.netstat.1; may be used to observe network cluster
	use.</para>

      <para><varname>kern.ipc.nmbclusters</varname> loader tunable should
        be used to tune this at boot time.  Only older versions of &os;
        will require you to use the <option>NMBCLUSTERS</option> 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
	<option>NSFBUFS</option> 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 <errorname>sfbufa</errorname> state.  The sysctl
	variable <varname>kern.ipc.nsfbufs</varname> is a read-only
	glimpse at the kernel configured variable.  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> sysctl
	  variables control the port number ranges automatically bound to TCP
	  and UDP 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 the
	  <varname>net.inet.ip.portrange.first</varname> and
	  <varname>net.inet.ip.portrange.last</varname>, which default to
	  1024 and 5000, 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 you are running a heavily loaded web proxy.  The port range
	  is not an issue when running servers which handle mainly incoming
	  connections, such as a normal web server, or has a limited number
	  of outgoing connections, such as a mail relay.  For situations
	  where you may run yourself out 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.  You should also
	  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 &mdash; for this reason it is recommended that
	  <varname>net.inet.ip.portrange.first</varname> be lowered.</para>
      </sect3>

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

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

	<para>The TCP Bandwidth Delay Product Limiting is similar to
	  TCP/Vegas in <application>NetBSD</application>.  It can be
	  enabled by setting <varname>net.inet.tcp.inflight_enable</varname>
	  sysctl variable to <literal>1</literal>.  The system will 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 if you are serving data over modems,
	  Gigabit Ethernet, or even high speed WAN links (or any other link
	  with a high bandwidth delay product), especially if you are also
	  using window scaling or have configured a large send window.  If
	  you enable this option, you should also be sure to set
	  <varname>net.inet.tcp.inflight_debug</varname> to
	  <literal>0</literal> (disable debugging), and for production use
	  setting <varname>net.inet.tcp.inflight_min</varname> to at least
	  <literal>6144</literal> may be beneficial.  However, note that
	  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 as
	  well as reduces the amount of data built up in the local host's
	  interface queue.  With fewer packets queued up, interactive
	  connections, especially over slow modems, will also be able to
	  operate with lower <emphasis>Round Trip Times</emphasis>.  However,
	  note that this feature only effects data transmission (uploading
	  / server side).  It has no effect on data reception (downloading).
	</para>

	<para>Adjusting <varname>net.inet.tcp.inflight_stab</varname> is
	  <emphasis>not</emphasis> recommended.  This parameter defaults to
	  20, 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 ping times over slow
	  links (though still much lower than you would get without the
	  inflight algorithm).  In such cases, you may wish to try reducing
	  this parameter to 15, 10, or 5; and may also have to reduce
	  <varname>net.inet.tcp.inflight_min</varname> (for example, to
	  3500) to get the desired effect.  Reducing these parameters
	  should be done as a last resort only.</para>
      </sect3>
    </sect2>
  </sect1>

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

    <para>No matter how well you plan, sometimes a system does not run
      as you expect.  If you find you need more swap space, it is
      simple enough to add.  You have three ways to increase swap
      space: adding a new hard drive, enabling swap over NFS, and
      creating a swap file on an existing partition.</para>

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

      <para>The best way to add swap, of course, is to use this as an
	excuse to add another hard drive.  You can always use another
	hard drive, after all.  If you can do this, go reread the
	discussion of swap space
	in <xref linkend="configtuning-initial">
	of the Handbook for some suggestions on how to best
	arrange your swap.</para>
    </sect2>

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

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

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

      <para>You can create a file of a specified size to use as a swap
	file.  In our example here we will use a 64MB file called
	<filename>/usr/swap0</filename>.  You can use any name you
	want, of course.</para>

      <example>
        <title>Creating a Swapfile on &os; 4.X</title>

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

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

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

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

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

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

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

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

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

	<listitem>

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

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

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

      <orderedlist>
	<listitem>
	  <para>Be certain that your kernel configuration includes
	    the memory disk driver (&man.md.4;).  It is default in
	    <filename>GENERIC</filename> kernel.</para>

	  <programlisting>device   md   # Memory "disks"</programlisting>
	</listitem>

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

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

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

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

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

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

	<listitem>

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

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

      </example>
    </sect2>
  </sect1>

  <sect1 id="acpi-overview">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Hiten</firstname>
	  <surname>Pandya</surname>
	  <contrib>Written by </contrib>
	</author>
	<author>
	  <firstname>Tom</firstname>
	  <surname>Rhodes</surname>
	</author>
      </authorgroup>
    </sect1info>

    <title>Power and Resource Management</title>

    <para>It is very important to utilize hardware resources in an
      efficient manner.  Before <acronym>ACPI</acronym> was introduced,
      it was very difficult and inflexible for operating systems to manage
      the power usage and thermal properties of a system.  The hardware was
      controlled by some sort of <acronym>BIOS</acronym> embedded
      interface, such as <emphasis>Plug and Play BIOS (PNPBIOS)</emphasis>, or
      <emphasis>Advanced Power Management (APM)</emphasis> and so on.
      Power and Resource Management is one of the key components of a modern
      operating system.  For example, you may want an operating system to
      monitor system limits (and possibly alert you) in case your system
      temperature increased unexpectedly.</para>

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

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

      <para>Advanced Configuration and Power Interface
	(<acronym>ACPI</acronym>) is a standard written by
	an alliance of vendors to provide a standard interface for
	hardware resources and power management (hence the name).
	It is a key element in <emphasis>Operating System-directed
	configuration and Power Management</emphasis>, i.e.: it provides
	more control and flexibility to the operating system
	(<acronym>OS</acronym>).
	Modern systems <quote>stretched</quote> the limits of the
	current Plug and Play interfaces (such as APM, which is used in
	&os;&nbsp;4.X), prior to the introduction of
	<acronym>ACPI</acronym>.  <acronym>ACPI</acronym> is the direct
	successor to <acronym>APM</acronym>
	(Advanced Power Management).</para>
    </sect2>

    <sect2 id="acpi-old-spec">
      <title>Shortcomings of Advanced Power Management (APM)</title>

      <para>The <emphasis>Advanced Power Management (APM)</emphasis>
      facility control's the power usage of a system based on its
      activity.  The APM BIOS is supplied by the (system) vendor and
      it is specific to the hardware platform.  An APM driver in the
      OS mediates access to the <emphasis>APM Software Interface</emphasis>,
      which allows management of power levels.</para>

      <para>There are four major problems in APM.  Firstly, power
      management is done by the (vendor-specific) BIOS, and the OS
      does not have any knowledge of it.  One example of this, is when
      the user sets idle-time values for a hard drive in the APM BIOS,
      that when exceeded, it (BIOS) would spin down the hard drive,
      without the consent of the OS.  Secondly, the APM logic is
      embedded in the BIOS, and it operates outside the scope of the
      OS.  This means users can only fix problems in their APM BIOS by
      flashing a new one into the ROM; which, is a very dangerous
      procedure, and if it fails, it could leave the system in an
      unrecoverable state. Thirdly, APM is a vendor-specific
      technology, which, means that there is a lot or parity
      (duplication of efforts) and bugs found in one vendor's BIOS,
      may not be solved in others.  Last but not the least, the APM
      BIOS did not have enough room to implement a sophisticated power
      policy, or one that can adapt very well to the purpose of the
      machine.</para>

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

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

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

      <para>The <filename>acpi.ko</filename> driver is loaded by default
	at start up by the &man.loader.8; and should <emphasis>not</emphasis>
	be compiled into the kernel.  The reasoning behind this is that modules
	are easier to work with, say if switching to another <filename>acpi.ko</filename>
	without doing 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 is not too useful, and in some cases can be fatal.  In doubt, just
	disable <acronym>ACPI</acronym> all together. 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 with the &man.acpiconf.8; utility.
	In fact most of the interaction with <acronym>ACPI</acronym> can be done via
	&man.acpiconf.8;.  Basically this means, if anything about <acronym>ACPI</acronym>
	is in the &man.dmesg.8; output, then most likely it is already running.</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 running.</para></note>

      <para>In the simplest form, <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 will only need
	<literal>1</literal>.  Option <literal>5</literal> will do a soft-off
	which is the same action as:</para>

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

      <para>The other options are available.  Check out the &man.acpiconf.8;
	manual page for more information.</para>
    </sect2>
  </sect1>

  <sect1 id="ACPI-debug">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Nate</firstname>
          <surname>Lawson</surname>
          <contrib>Written by </contrib>
        </author>
      </authorgroup>
      <authorgroup>
        <author>
          <firstname>Peter</firstname>
          <surname>Schultz</surname>
          <contrib>With contributions from </contrib>
        </author>
        <author>
          <firstname>Tom</firstname>
          <surname>Rhodes</surname>
        </author>
      </authorgroup>
    </sect1info>

    <title>Using and Debugging &os; <acronym>ACPI</acronym></title>

    <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 document is intended to help you assist the &os;
      <acronym>ACPI</acronym> maintainers in identifying the root cause
      of problems you observe and debugging and developing a solution.
      Thanks for reading this and we hope we can solve your system's
      problems.</para>

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

      <note>
	<para>Before submitting a problem, be sure you are running the latest
	  <acronym>BIOS</acronym> version and, if available, embedded
	  controller firmware version.</para>
      </note>

      <para>For those of you that want to submit a problem right away,
	please send the following information to
	<ulink url="mailto:freebsd-acpi@FreeBSD.org">
	freebsd-acpi@FreeBSD.org</ulink></para>

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

	<listitem>
	  <para>The dmesg output after <quote>boot
	    <option>-v</option></quote>, including any error messages
	    generated by you exercising the bug.</para>
	</listitem>

	<listitem>
	  <para>dmesg output from <quote>boot
	    <option>-v</option></quote> with <acronym>ACPI</acronym>
	    disabled, if disabling it helps fix the problem.</para>
	</listitem>

	<listitem>
	  <para>Output from <quote>sysctl hw.acpi</quote>.  This is also
	    a good way of figuring out what features your system
	    offers.</para>
	</listitem>

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

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

	  <para>(Substitute your login name for
	    <replaceable>name</replaceable> and manufacturer/model for
	    <replaceable>system</replaceable>.  Example:
	    <filename>njl-FooCo6000.asl</filename>)</para>
	</listitem>
      </itemizedlist>

      <para>Most of the developers watch the &a.current;
        but please submit problems to &a.acpi.name; to be sure it is
	seen.  Please be patient, all of us have full-time jobs
	elsewhere.  If your bug is not immediately apparent, we will
	probably ask you to submit a <acronym>PR</acronym> via
	&man.send-pr.1;.  When entering a <acronym>PR</acronym>, please
	include the same information as requested above.  This will help
	us track the problem and resolve it.  Do not send a
	<acronym>PR</acronym> without emailing &a.acpi.name; first as we use
	<acronym>PR</acronym>s as reminders of existing problems, not a
	reporting mechanism.  It is likely that your problem has been
	reported by someone before.</para>
    </sect2>

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

      <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 the bus enumeration parts 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 (e.g., <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 table of bytecode
	(the <firstterm>Differentiated System Description Table</firstterm>
	<acronym>DSDT</acronym>) is provided that 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 role="directory">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 role="directory">src/sys/dev/acpica</filename>.</para>
    </sect2>

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

      <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>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 your system
	  is in when plugged in but not powered up.
	  <literal>S4</literal> can actually be implemented 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</command>
	  <option>hw.acpi</option> for the suspend-related items.  Here
	  are the results for my Thinkpad:</para>

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

	<para>This means that I can use <command>acpiconf -s</command>
	  to test <literal>S3</literal>,
	  <literal>S4</literal><acronym>OS</acronym>, and
	  <literal>S5</literal>.  If <option>s4bios</option> was one
	  (<literal>1</literal>), I would have
	  <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 doesn't require much driver support.
	  No one has implemented <literal>S2</literal> but if you have
	  it, it's similar to <literal>S1</literal>.  The next thing
	  to try is <literal>S3</literal>.  This is the deepest
	  <acronym>STR</acronym> state and requires a lot of driver
	  support to properly reinitialize your hardware.  If you have
	  problems resuming, feel free to email the &a.acpi.name; list but
	  do not expect the problem to be resolved since there are a lot
	  of drivers/hardware that need more testing and work.</para>

	<para>To help isolate the problem, remove as many drivers from
	  your kernel as possible.  If it works, you can narrow down
	  which driver is the problem by loading drivers until it fails
	  again.  Typically binary drivers like
	  <filename>nvidia.ko</filename>, <application>X11</application>
	  display drivers, and <acronym>USB</acronym> will have the most
	  problems while Ethernet interfaces usually work fine.  If you
	  can load/unload the drivers ok, you can automate this by
	  putting the appropriate commands in
	  <filename>/etc/rc.suspend</filename> and
	  <filename>/etc/rc.resume</filename>.  There is a
	  commented-out example for unloading and loading a driver.  Try
	  setting <option>hw.acpi.reset_video</option> to zero (0) if
	  your 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>Another thing to try is load a recent Linux distribution
	  with <acronym>ACPI</acronym> support and test their
	  suspend/resume support on the same hardware.  If it works
	  on Linux, it's likely a &os; driver problem and narrowing down
	  which driver causes the problems will help us fix the problem.
	  Note that the <acronym>ACPI</acronym> maintainers do not
	  usually maintain other drivers (e.g sound,
	  <acronym>ATA</acronym>, etc.) so any work done on tracking
	  down a driver problem should probably eventually be posted
	  to the &a.current.name; list and mailed to the driver
	  maintainer.  If you are feeling adventurous, go ahead and
	  start putting some 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>, you may be better off
	  sticking 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 (temporary or permanent)</title>

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

	<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, you have 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 <option>show interrupts</option>.</para>

	<para>Your best hope when dealing with interrupt problems is to
	  try disabling <acronym>APIC</acronym> support with
	  <literal>hint.apic.0.disabled="1"</literal> in
	  <filename>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
	  <option>options DDB</option> and setting up a serial console
	  (see <xref linkend="serialconsole-ddb">)
	  or setting up a &man.dump.8; partition.  You can get a
	  backtrace in <acronym>DDB</acronym> with
	  <option>tr</option>.  If you have to handwrite the
	  backtrace, be sure to at least get the lowest five (5) and top
	  five (5) lines in the trace.</para>

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

      <sect3>
	<title>System Powers Up After Suspend or Shutdown</title>
	<para>First, try setting
	  <option>hw.acpi.disable_on_poweroff=</option><quote>0</quote>
	  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 <quote>1</quote> (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>If you have other problems with <acronym>ACPI</acronym>
	  (working with a docking station, devices not detected, etc.),
	  please email a description to the mailing list as well;
	  however, some of these issues may be related to unfinished
	  parts of the <acronym>ACPI</acronym> subsystem so they might
	  take a while to be implemented.  Please be patient and
	  prepared to test patches we may send you.</para>
      </sect3>
    </sect2>

    <sect2 id="ACPI-aslanddump">
      <title><acronym>ASL</acronym>, <command>acpidump</command>, and
        <acronym>IASL</acronym></title>

      <para>The most common problem is the <acronym>BIOS</acronym>
	vendors providing incorrect (or outright 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, you can resolve these problems by updating your
	<acronym>BIOS</acronym> to the latest revision.  Most console
	messages are harmless but if you have other problems like
	battery status not working, they're a good place to start
	looking for problems in the <acronym>AML</acronym>.  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 your
	<acronym>ASL</acronym>, use &man.acpidump.8;.  You should use
	both the <option>-t</option> (show contents of the fixed tables)
	and <option>-d</option> (disassemble <acronym>AML</acronym> to
	<acronym>ASL</acronym>) options.  See the
	<link linkend="ACPI-submitdebug">Submitting Debugging
	Information</link> section for an example syntax.</para>

      <para>The simplest first check you can do is to recompile your
	<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
	your <acronym>ASL</acronym>, issue the following command:</para>

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

    <sect2 id="ACPI-fixasl">
      <title>Fixing Your <acronym>ASL</acronym></title>

      <para>In the long run, our goal is for almost everyone to have
	<acronym>ACPI</acronym> work without any user intervention.  At
	this point, however, we are still developing workarounds for
	common mistakes made by the <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>.  We hope to continue to
	identify and document exactly what non-standard behavior is
	allowed by Microsoft's interpreter and replicate it so &os; can
	work without forcing users to fix the <acronym>ASL</acronym>.
	As a workaround and to help us identify behavior, you can fix
	the <acronym>ASL</acronym> manually.  If this works for you,
	please send a &man.diff.1; of the old and new
	<acronym>ASL</acronym> so we can possibly work around the buggy
	behavior in <acronym>ACPI-CA</acronym> and thus make your fix
	unnecessary.</para>

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

      <sect3>
	<title>_OS dependencies</title>

	<para>Some <acronym>AML</acronym> assumes the world consists of
	  various Windows versions.  You can tell &os; to claim it is
	  any <acronym>OS</acronym> to see if this fixes problems you
	  may have.  An easy way to override this is to set
	  <option>hw.acpi.osname</option>=<quote>Windows 2001</quote>
	  in <filename>/boot/loader.conf</filename> or other similar
	  strings you find 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.  You can also add explicit
	  Return statements where required if you know what value should
	  be returned.  To force <command>iasl</command> 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 you customize <filename>your.asl</filename>, you
	  will want to compile it, run:</para>

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

	<para>You can add the <option>-f</option> flag to force creation
	  of the <acronym>AML</acronym>, even if there are errors during
	  compilation.  Remember that some errors (e.g., missing Return
	  statements) are automatically worked around by the
	  interpreter.</para>

	<para><filename>DSDT.aml</filename> is the default output
	  filename for <command>iasl</command>.  You can load this
	  instead of your <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 your <filename>DSDT.aml</filename> to the
	  <filename role="directory">/boot</filename> directory.</para>
      </sect3>
    </sect2>

    <sect2 id="ACPI-debugoutput">
      <title>Getting Debugging Output From
	<acronym>ACPI</acronym></title>

      <para>The <acronym>ACPI</acronym> driver has a very flexible
	debugging facility.  It allows you to specify a set of subsystems
	as well as the level of verbosity.  The subsystems you wish 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, you will want to use
	a serial console to log the output if it is so long
	it flushes the console message buffer.  A full list of the
	individual layers and levels is found in the &man.acpi.4; manual
	page.</para>

      <para>Debugging output is not enabled by default.  To enable it,
	add <option>options ACPI_DEBUG</option> to your kernel config
	if <acronym>ACPI</acronym> is compiled into the kernel.  You can
	add <option>ACPI_DEBUG=1</option> to your
	<filename>/etc/make.conf</filename> to enable it globally.  If
	it is a module, you can recompile just your
	<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 role="directory">/boot/kernel</filename> and add your
	desired level and layer to <filename>loader.conf</filename>.
	This example enables debug messages for all
	<acronym>ACPI-CA</acronym> components and all
	<acronym>ACPI</acronym> hardware drivers
	(<acronym>CPU</acronym>, <acronym>LID</acronym>, etc.)  It will
	only output error messages, 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 information you want is triggered by a specific event
	(say, a suspend and then resume), you can leave out changes to
	<filename>loader.conf</filename> and instead use
	<command>sysctl</command> to specify the layer and level after
	booting and preparing your system for the specific event.  The
	<command>sysctl</command>s are named the same as the tunables
	in <filename>loader.conf</filename>.</para>
    </sect2>

    <sect2 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
	    <ulink url="http://lists.freebsd.org/pipermail/freebsd-acpi/"></ulink></para>
	</listitem>

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

	<listitem>
	  <para>The <acronym>ACPI</acronym> 2.0 Specification
	    <ulink url="http://acpi.info/spec.htm"></ulink></para>
	</listitem>

	<listitem>
	  <para>&os; Manual pages: &man.acpi.4;,
	    &man.acpi.thermal.4;, &man.acpidump.8;, &man.iasl.8;,
	    &man.acpidb.8;</para>
	</listitem>

	<listitem>
	  <para><ulink
	    url="http://www.cpqlinux.com/acpi-howto.html#fix_broken_dsdt">
	    <acronym>DSDT</acronym> debugging resource</ulink>.
	    (Uses Compaq as an example but generally useful.)</para>
	</listitem>
      </itemizedlist>
    </sect2>
  </sect1>
</chapter>

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