<!--
     The FreeBSD Documentation Project

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<chapter id="network-servers">
  <chapterinfo>
    <authorgroup>
      <author>
        <firstname>Murray</firstname>
	<surname>Stokely</surname>
	<contrib>Reorganized by </contrib>
      </author>
    </authorgroup>
    <!-- 23 July 2004 -->
  </chapterinfo>

  <title>Network Servers</title>

  <sect1 id="network-servers-synopsis">
    <title>Synopsis</title>

    <para>This chapter will cover some of the more frequently used
      network services on &unix; systems.  We will cover how to
      install, configure, test, and maintain many different types of
      network services.  Example configuration files are included
      throughout this chapter for you to benefit from.</para>

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

    <itemizedlist>

      <listitem>
	<para>How to manage the <application>inetd</application>
	  daemon.</para>
      </listitem>

      <listitem>
	<para>How to set up a network filesystem.</para>
      </listitem>

      <listitem>
	<para>How to set up a network information server for sharing
	  user accounts.</para>
      </listitem>

      <listitem>
	<para>How to set up automatic network settings using DHCP.</para>
      </listitem>

      <listitem>
	<para>How to set up a domain name server.</para>
      </listitem>

      <listitem>
	<para>How to set up the <application>Apache</application> HTTP Server.</para>
      </listitem>

      <listitem>
	<para>How to set up a File Transfer Protocol (FTP) Server.</para>
      </listitem>

      <listitem>
	<para>How to set up a file and print server for &windows;
	  clients using <application>Samba</application>.</para>
      </listitem>

      <listitem>
	<para>How to synchronize the time and date, and set up a
	  time server, with the NTP protocol.</para>
      </listitem>

    </itemizedlist>

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

    <itemizedlist>
      <listitem>
	<para>Understand the basics of the
	  <filename>/etc/rc</filename> scripts.</para>
      </listitem>

      <listitem>
	<para>Be familiar with basic network terminology.</para>
      </listitem>

      <listitem>
      <para>Know how to install additional third-party
        software (<xref linkend="ports">).</para>
      </listitem>

    </itemizedlist>
  </sect1>

  <sect1 id="network-inetd">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Chern</firstname>
          <surname>Lee</surname>
          <contrib>Contributed by </contrib>
        </author>
      </authorgroup>
    </sect1info>

    <title>The <application>inetd</application> <quote>Super-Server</quote></title>

    <sect2 id="network-inetd-overview">
      <title>Overview</title>

      <para>&man.inetd.8; is referred to as the <quote>Internet
	Super-Server</quote> because it manages connections for
	several services.  When a
	connection is received by <application>inetd</application>, it
	determines which program the connection is destined for, spawns
	the particular process and delegates the socket to it (the program
	is invoked with the service socket as its standard input, output
	and error descriptors).  Running
	one instance of <application>inetd</application> reduces the
	overall system load as compared to running each daemon
	individually in stand-alone mode.</para>

      <para>Primarily, <application>inetd</application> is used to
	spawn other daemons, but several trivial protocols are handled
	directly, such as <application>chargen</application>,
	<application>auth</application>, and
	<application>daytime</application>.</para>

      <para>This section will cover the basics in configuring
	<application>inetd</application> through its command-line
	options and its configuration file,
	<filename>/etc/inetd.conf</filename>.</para>
    </sect2>

    <sect2 id="network-inetd-settings">
      <title>Settings</title>

      <para><application>inetd</application> is initialized through
	the <filename>/etc/rc.conf</filename> system.  The
	<literal>inetd_enable</literal> option is set to
	<literal>NO</literal> by default, but is often times turned on
	by <application>sysinstall</application> with the medium
	security profile.  Placing:
	<programlisting>inetd_enable="YES"</programlisting> or
	<programlisting>inetd_enable="NO"</programlisting> into
	<filename>/etc/rc.conf</filename> can enable or disable
	<application>inetd</application> starting at boot time.</para>

      <para>Additionally, different command-line options can be passed
	to <application>inetd</application> via the
	<literal>inetd_flags</literal> option.</para>
    </sect2>

    <sect2 id="network-inetd-cmdline">
      <title>Command-Line Options</title>

      <para><application>inetd</application> synopsis:</para>

      <para><option>     inetd [-d] [-l] [-w] [-W] [-c maximum] [-C rate] [-a address | hostname]
           [-p filename] [-R rate] [configuration file]</option></para>

      <variablelist>
	<varlistentry>
	  <term>-d</term>

	  <listitem>
	    <para>Turn on debugging.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-l</term>

	  <listitem>
	    <para>Turn on logging of successful connections.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-w</term>

	  <listitem>
	    <para>Turn on TCP Wrapping for external services (on by
	      default).</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-W</term>

	  <listitem>
	    <para>Turn on TCP Wrapping for internal services which are
	      built into <application>inetd</application> (on by
	      default).</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-c maximum</term>

	  <listitem>
	    <para>Specify the default maximum number of simultaneous
	      invocations of each service; the default is unlimited.
	      May be overridden on a per-service basis with the
	      <option>max-child</option> parameter.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-C rate</term>

	  <listitem>
	    <para>Specify the default maximum number of times a
	      service can be invoked from a single IP address in one
	      minute; the default is unlimited.  May be overridden on a
	      per-service basis with the
	      <option>max-connections-per-ip-per-minute</option>
	      parameter.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-R rate</term>

	  <listitem>
	    <para>Specify the maximum number of times a service can be
	      invoked in one minute; the default is 256.  A rate of 0
	      allows an unlimited number of invocations.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-a</term>

	  <listitem>
	    <para>Specify one specific IP address to bind to.
	      Alternatively, a hostname can be specified, in which case
	      the IPv4 or IPv6 address which corresponds to that
	      hostname is used.  Usually a hostname is specified when
	      <application>inetd</application> is run inside a
	      &man.jail.8;, in which case the hostname corresponds to
	      the &man.jail.8; environment.</para>

	    <para>When hostname specification is used and both IPv4
	      and IPv6 bindings are desired, one entry with the
	      appropriate protocol type for each binding is required
	      for each service in
	      <filename>/etc/inetd.conf</filename>.  For example, a
	      TCP-based service would need two entries, one using
	      <literal>tcp4</literal> for the protocol and the other
	      using <literal>tcp6</literal>.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>-p</term>

	  <listitem>
	    <para>Specify an alternate file in which to store the
	      process ID.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>These options can be passed to
	<application>inetd</application> using the
	<literal>inetd_flags</literal> option in
	<filename>/etc/rc.conf</filename>.  By default,
	<literal>inetd_flags</literal> is set to
	<literal>-wW</literal>, which turns on TCP wrapping for
	<application>inetd</application>'s internal and external
	services.  For novice users, these parameters usually do not
	need to be modified or even entered in
	<filename>/etc/rc.conf</filename>.</para>

      <note>
	<para>An external service is a daemon outside of
	  <application>inetd</application>, which is invoked when a
	  connection is received for it.  On the other hand, an
	  internal service is one that
	  <application>inetd</application> has the facility of
	  offering within itself.</para>
      </note>

    </sect2>

    <sect2 id="network-inetd-conf">
      <title><filename>inetd.conf</filename></title>

      <para>Configuration of <application>inetd</application> is
	controlled through the <filename>/etc/inetd.conf</filename>
	file.</para>

      <para>When a modification is made to
	<filename>/etc/inetd.conf</filename>,
	<application>inetd</application> can be forced to re-read its
	configuration file by sending a HangUP signal to the
	<application>inetd</application> process as shown:</para>

      <example id="network-inetd-hangup">
	<title>Sending <application>inetd</application> a HangUP Signal</title>

	<screen>&prompt.root; <userinput>kill -HUP `cat /var/run/inetd.pid`</userinput></screen>
      </example>

      <para>Each line of the configuration file specifies an
	individual daemon.  Comments in the file are preceded by a
	<quote>#</quote>.  The format of
	<filename>/etc/inetd.conf</filename> is as follows:</para>

      <programlisting>service-name
socket-type
protocol
{wait|nowait}[/max-child[/max-connections-per-ip-per-minute]]
user[:group][/login-class]
server-program
server-program-arguments</programlisting>

      <para>An example entry for the <application>ftpd</application> daemon
	using IPv4:</para>

      <programlisting>ftp     stream  tcp     nowait  root    /usr/libexec/ftpd       ftpd -l</programlisting>

      <variablelist>
	<varlistentry>
	  <term>service-name</term>

	  <listitem>
	    <para>This is the service name of the particular daemon.
	      It must correspond to a service listed in
	      <filename>/etc/services</filename>.  This determines
	      which port <application>inetd</application> must listen
	      to.  If a new service is being created, it must be
	      placed in <filename>/etc/services</filename>
	      first.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>socket-type</term>

	  <listitem>
	    <para>Either <literal>stream</literal>,
	      <literal>dgram</literal>, <literal>raw</literal>, or
	      <literal>seqpacket</literal>.  <literal>stream</literal>
	      must be used for connection-based, TCP daemons, while
	      <literal>dgram</literal> is used for daemons utilizing
	      the <acronym>UDP</acronym> transport protocol.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>protocol</term>

	  <listitem>
	    <para>One of the following:</para>

	    <informaltable frame="none" pgwide="1">
	      <tgroup cols="2">
		<thead>
		  <row>
		    <entry>Protocol</entry>
		    <entry>Explanation</entry>
		  </row>
		</thead>
		<tbody>
		  <row>
		    <entry>tcp, tcp4</entry>
		    <entry>TCP IPv4</entry>
		  </row>
		  <row>
		    <entry>udp, udp4</entry>
		    <entry>UDP IPv4</entry>
		  </row>
		  <row>
		    <entry>tcp6</entry>
		    <entry>TCP IPv6</entry>
		  </row>
		  <row>
		    <entry>udp6</entry>
		    <entry>UDP IPv6</entry>
		  </row>
		  <row>
		    <entry>tcp46</entry>
		    <entry>Both TCP IPv4 and v6</entry>
		  </row>
		  <row>
		    <entry>udp46</entry>
		    <entry>Both UDP IPv4 and v6</entry>
		  </row>
		</tbody>
	      </tgroup>
	    </informaltable>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>{wait|nowait}[/max-child[/max-connections-per-ip-per-minute]]</term>

	  <listitem>
	    <para><option>wait|nowait</option> indicates whether the
	      daemon invoked from <application>inetd</application> is
	      able to handle its own socket or not.
	      <option>dgram</option> socket types must use the
	      <option>wait</option> option, while stream socket
	      daemons, which are usually multi-threaded, should use
	      <option>nowait</option>.  <option>wait</option> usually
	      hands off multiple sockets to a single daemon, while
	      <option>nowait</option> spawns a child daemon for each
	      new socket.</para>

	    <para>The maximum number of child daemons
	      <application>inetd</application> may spawn can be set
	      using the <option>max-child</option> option.  If a limit
	      of ten instances of a particular daemon is needed, a
	      <literal>/10</literal> would be placed after
	      <option>nowait</option>.</para>

	    <para>In addition to <option>max-child</option>, another
	      option limiting the maximum connections from a single
	      place to a particular daemon can be enabled.
	      <option>max-connections-per-ip-per-minute</option> does
	      just this.  A value of ten here would limit any particular
	      IP address connecting to a particular service to ten
	      attempts per minute.  This is useful to prevent
	      intentional or unintentional resource consumption and
	      Denial of Service (DoS) attacks to a machine.</para>

	    <para>In this field, <option>wait</option> or
	      <option>nowait</option> is mandatory.
	      <option>max-child</option> and
	      <option>max-connections-per-ip-per-minute</option> are
	      optional.</para>

	    <para>A stream-type multi-threaded daemon without any
	      <option>max-child</option> or
	      <option>max-connections-per-ip-per-minute</option> limits
	      would simply be: <literal>nowait</literal>.</para>

	    <para>The same daemon with a maximum limit of ten daemons
	      would read: <literal>nowait/10</literal>.</para>

	    <para>Additionally, the same setup with a limit of twenty
	      connections per IP address per minute and a maximum
	      total limit of ten child daemons would read:
	      <literal>nowait/10/20</literal>.</para>

	    <para>These options are all utilized by the default
	      settings of the <application>fingerd</application> daemon,
	      as seen here:</para>

	    <programlisting>finger stream  tcp     nowait/3/10 nobody /usr/libexec/fingerd fingerd -s</programlisting>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>user</term>

	  <listitem>
	    <para>This is the username that the particular daemon
	      should run as.  Most commonly, daemons run as the
	      <username>root</username> user.  For security purposes, it is
	      common to find some servers running as the
	      <username>daemon</username> user, or the least privileged
	      <username>nobody</username> user.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>server-program</term>

	  <listitem>
	    <para>The full path of the daemon to be executed when a
	      connection is received.  If the daemon is a service
	      provided by <application>inetd</application> internally,
	      then <option>internal</option> should be
	      used.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>server-program-arguments</term>

	  <listitem>
	    <para>This works in conjunction with
	      <option>server-program</option> by specifying the
	      arguments, starting with <literal>argv[0]</literal>,
	      passed to the daemon on invocation.  If
	      <command>mydaemon -d</command> is the command line,
	      <literal>mydaemon -d</literal> would be the value of
	      <option>server-program-arguments</option>.  Again, if
	      the daemon is an internal service, use
	      <option>internal</option> here.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect2>

    <sect2 id="network-inetd-security">
      <title>Security</title>

      <para>Depending on the security profile chosen at install, many
	of <application>inetd</application>'s daemons may be enabled
	by default.  If there is no apparent need for a particular
	daemon, disable it!  Place a <quote>#</quote> in front of the
	daemon in question in <filename>/etc/inetd.conf</filename>,
	and then send a <link linkend="network-inetd-hangup">hangup
	signal to inetd</link>.  Some daemons, such as
	<application>fingerd</application>, may not be desired at all
	because they provide an attacker with too much
	information.</para>

      <para>Some daemons are not security-conscious and have long, or
	non-existent timeouts for connection attempts.  This allows an
	attacker to slowly send connections to a particular daemon,
	thus saturating available resources.  It may be a good idea to
	place <option>max-connections-per-ip-per-minute</option> and
	<option>max-child</option> limitations on certain
	daemons.</para>

      <para>By default, TCP wrapping is turned on.  Consult the
	&man.hosts.access.5; manual page for more information on placing
	TCP restrictions on various <application>inetd</application>
	invoked daemons.</para>
    </sect2>

    <sect2 id="network-inetd-misc">
      <title>Miscellaneous</title>

      <para><application>daytime</application>,
	<application>time</application>,
	<application>echo</application>,
	<application>discard</application>,
	<application>chargen</application>, and
	<application>auth</application> are all internally provided
	services of <application>inetd</application>.</para>

      <para>The <application>auth</application> service provides
	identity (<application>ident</application>,
	<application>identd</application>) network services, and is
	configurable to a certain degree.</para>

      <para>Consult the &man.inetd.8; manual page for more in-depth
	information.</para>
    </sect2>
  </sect1>

  <sect1 id="network-nfs">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Tom</firstname>
          <surname>Rhodes</surname>
          <contrib>Reorganized and enhanced by </contrib>
        </author>
      </authorgroup>
      <authorgroup>
        <author>
          <firstname>Bill</firstname>
      	  <surname>Swingle</surname>
	  <contrib>Written by </contrib>
        </author>
      </authorgroup>
    </sect1info>
    <title>Network File System (NFS)</title>

    <indexterm><primary>NFS</primary></indexterm>
    <para>Among the many different filesystems that FreeBSD supports
      is the Network File System, also known as <acronym role="Network
      File System">NFS</acronym>.  <acronym role="Network File
      System">NFS</acronym> allows a system to share directories and
      files with others over a network.  By using <acronym
      role="Network File System">NFS</acronym>, users and programs can
      access files on remote systems almost as if they were local
      files.</para>

    <para>Some of the most notable benefits that
      <acronym>NFS</acronym> can provide are:</para>

    <itemizedlist>
      <listitem>
	<para>Local workstations use less disk space because commonly
	  used data can be stored on a single machine and still remain
	  accessible to others over the network.</para>
      </listitem>

      <listitem>
	<para>There is no need for users to have separate home
	  directories on every network machine.  Home directories
	  could be set up on the <acronym>NFS</acronym> server and
	  made available throughout the network.</para>
      </listitem>

      <listitem>
	<para>Storage devices such as floppy disks, CDROM drives, and
	  &iomegazip; drives can be used by other machines on the network.
	  This may reduce the number of removable media drives
	  throughout the network.</para>
      </listitem>
    </itemizedlist>

    <sect2>
      <title>How <acronym>NFS</acronym> Works</title>

      <para><acronym>NFS</acronym> consists of at least two main
        parts: a server and one or more clients.  The client remotely
        accesses the data that is stored on the server machine.  In
        order for this to function properly a few processes have to be
        configured and running.</para>

      <note><para>Under &os;&nbsp;4.X, the <application>portmap</application>
	utility is used in place of the
	<application>rpcbind</application> utility.  Thus, in &os;&nbsp;4.X
	the user is required to replace every instance of
	<application>rpcbind</application> with
	<application>portmap</application> in the forthcoming
	examples.</para></note>

      <para>The server has to be running the following daemons:</para>
      <indexterm>
        <primary>NFS</primary>
        <secondary>server</secondary>
      </indexterm>
      <indexterm>
        <primary>file server</primary>
        <secondary>UNIX clients</secondary>
      </indexterm>

      <indexterm>
	<primary><application>rpcbind</application></primary>
      </indexterm>
      <indexterm>
        <primary><application>portmap</application></primary>
      </indexterm>
      <indexterm>
        <primary><application>mountd</application></primary>
      </indexterm>
      <indexterm>
        <primary><application>nfsd</application></primary>
      </indexterm>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	  <colspec colwidth="1*">
	  <colspec colwidth="3*">

	  <thead>
	    <row>
	      <entry>Daemon</entry>
	      <entry>Description</entry>
	    </row>
	  </thead>
	  <tbody>
	    <row>
	      <entry><application>nfsd</application></entry>
	      <entry>The <acronym>NFS</acronym> daemon which services
	      requests from the <acronym>NFS</acronym>
	      clients.</entry>
	    </row>
	    <row>
	      <entry><application>mountd</application></entry>
	      <entry>The <acronym>NFS</acronym> mount daemon which carries out
		the requests that &man.nfsd.8; passes on to it.</entry>
	    </row>
	    <row>
	      <entry><application>rpcbind</application></entry>
	      <entry> This daemon allows
	      <acronym>NFS</acronym> clients to discover which port
	      the <acronym>NFS</acronym> server is using.</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>

      <para>The client can also run a daemon, known as
        <application>nfsiod</application>.  The
        <application>nfsiod</application> daemon services the requests
        from the <acronym>NFS</acronym> server.  This is optional, and
        improves performance, but is not required for normal and
        correct operation.  See the &man.nfsiod.8; manual page for
        more information.
      </para>
    </sect2>

    <sect2 id="network-configuring-nfs">
      <title>Configuring <acronym>NFS</acronym></title>
      <indexterm>
        <primary>NFS</primary>
        <secondary>configuration</secondary>
      </indexterm>

      <para><acronym>NFS</acronym> configuration is a relatively
        straightforward process.  The processes that need to be
        running can all start at boot time with a few modifications to
        your <filename>/etc/rc.conf</filename> file.</para>

      <para>On the <acronym>NFS</acronym> server, make sure that the
        following options are configured in the
        <filename>/etc/rc.conf</filename> file:</para>

      <programlisting>rpcbind_enable="YES"
nfs_server_enable="YES"
mountd_flags="-r"</programlisting>

      <para><application>mountd</application> runs automatically
        whenever the <acronym>NFS</acronym> server is enabled.</para>

      <para>On the client, make sure this option is present in
        <filename>/etc/rc.conf</filename>:</para>

      <programlisting>nfs_client_enable="YES"</programlisting>

      <para>The <filename>/etc/exports</filename> file specifies which
        filesystems <acronym>NFS</acronym> should export (sometimes
        referred to as <quote>share</quote>).  Each line in
        <filename>/etc/exports</filename> specifies a filesystem to be
        exported and which machines have access to that filesystem.
        Along with what machines have access to that filesystem,
        access options may also be specified.  There are many such
        options that can be used in this file but only a few will be
        mentioned here.  You can easily discover other options by
        reading over the &man.exports.5; manual page.</para>

      <para>Here are a few example <filename>/etc/exports</filename>
	entries:</para>

      <indexterm>
        <primary>NFS</primary>
        <secondary>export examples</secondary>
      </indexterm>

      <para>The following examples give an idea of how to export
        filesystems, although the settings may be different depending
        on your environment and network configuration.  For instance,
        to export the <filename>/cdrom</filename> directory to three
        example machines that have the same domain name as the server
        (hence the lack of a domain name for each) or have entries in
        your <filename>/etc/hosts</filename> file.  The
        <option>-ro</option> flag makes the exported filesystem
        read-only.  With this flag, the remote system will not be able
        to write any changes to the exported filesystem.</para>

      <programlisting>/cdrom -ro host1 host2 host3</programlisting>

      <para>The following line exports <filename>/home</filename> to
	three hosts by IP address.  This is a useful setup if you have
	a private network without a <acronym>DNS</acronym> server
	configured.  Optionally the <filename>/etc/hosts</filename>
	file could be configured for internal hostnames; please review
	&man.hosts.5; for more information.  The
	<option>-alldirs</option> flag allows the subdirectories to be
	mount points.  In other words, it will not mount the
	subdirectories but permit the client to mount only the
	directories that are required or needed.</para>

      <programlisting>/home  -alldirs  10.0.0.2 10.0.0.3 10.0.0.4</programlisting>

      <para>The following line exports <filename>/a</filename> so that
	two clients from different domains may access the filesystem.
	The <option>-maproot=root</option> flag allows the
	<username>root</username> user on the remote system to write
	data on the exported filesystem as <username>root</username>.
	If the <literal>-maproot=root</literal> flag is not specified,
	then even if a user has <username>root</username> access on
	the remote system, he will not be able to modify files on
	the exported filesystem.</para>

      <programlisting>/a  -maproot=root  host.example.com box.example.org</programlisting>

      <para>In order for a client to access an exported filesystem,
	the client must have permission to do so.  Make sure the
	client is listed in your <filename>/etc/exports</filename>
	file.</para>

      <para>In <filename>/etc/exports</filename>, each line represents
	the export information for one filesystem to one host.  A
	remote host can only be specified once per filesystem, and may
	only have one default entry.  For example, assume that
	<filename>/usr</filename> is a single filesystem.  The
	following <filename>/etc/exports</filename> would be
	invalid:</para>

      <programlisting># Invalid when /usr is one file system
/usr/src   client
/usr/ports client</programlisting>

      <para>One filesystem, <filename>/usr</filename>, has two lines
	specifying exports to the same host, <hostid>client</hostid>.
        The correct format for this situation is:</para>

      <programlisting>/usr/src /usr/ports  client</programlisting>

      <para>The properties of one filesystem exported to a given host
	must all occur on one line.  Lines without a client specified
	are treated as a single host.  This limits how you can export
	filesystems, but for most people this is not an issue.</para>

      <para>The following is an example of a valid export list, where
	<filename>/usr</filename> and <filename>/exports</filename>
	are local filesystems:</para>

      <programlisting># Export src and ports to client01 and client02, but only
# client01 has root privileges on it
/usr/src /usr/ports -maproot=root    client01
/usr/src /usr/ports               client02
# The client machines have root and can mount anywhere
# on /exports. Anyone in the world can mount /exports/obj read-only
/exports -alldirs -maproot=root      client01 client02
/exports/obj -ro</programlisting>

      <para>You must restart
        <application>mountd</application> whenever you modify
        <filename>/etc/exports</filename> so the changes can take effect.
        This can be accomplished by sending the HUP signal
        to the <command>mountd</command> process:</para>

      <screen>&prompt.root; <userinput>kill -HUP `cat /var/run/mountd.pid`</userinput></screen>

      <para>Alternatively, a reboot will make FreeBSD set everything
        up properly.  A reboot is not necessary though.
        Executing the following commands as <username>root</username>
        should start everything up.</para>

      <para>On the <acronym>NFS</acronym> server:</para>

      <screen>&prompt.root; <userinput>rpcbind</userinput>
&prompt.root; <userinput>nfsd -u -t -n 4</userinput>
&prompt.root; <userinput>mountd -r</userinput></screen>

      <para>On the <acronym>NFS</acronym> client:</para>

      <screen>&prompt.root; <userinput>nfsiod -n 4</userinput></screen>

      <para>Now everything should be ready to actually mount a remote file
	system.  In these examples the
	server's name will be <hostid>server</hostid> and the client's
	name will be <hostid>client</hostid>.  If you only want to
	temporarily mount a remote filesystem or would rather test the
	configuration, just execute a command like this as <username>root</username> on the
        client:</para>
      <indexterm>
        <primary>NFS</primary>
        <secondary>mounting</secondary>
      </indexterm>
      <screen>&prompt.root; <userinput>mount server:/home /mnt</userinput></screen>

      <para>This will mount the <filename>/home</filename> directory
	on the server at <filename>/mnt</filename> on the client.  If
	everything is set up correctly you should be able to enter
	<filename>/mnt</filename> on the client and see all the files
        that are on the server.</para>

      <para>If you want to automatically mount a remote filesystem
	each time the computer boots, add the filesystem to the
	<filename>/etc/fstab</filename> file.  Here is an example:</para>

      <programlisting>server:/home	/mnt	nfs	rw	0	0</programlisting>

      <para>The &man.fstab.5; manual page lists all the available
        options.</para>
    </sect2>

    <sect2>
      <title>Practical Uses</title>

      <para><acronym>NFS</acronym> has many practical uses.  Some of
        the more common ones are listed below:</para>

      <indexterm>
        <primary>NFS</primary>
        <secondary>uses</secondary>
      </indexterm>
      <itemizedlist>
        <listitem>
	  <para>Set several machines to share a CDROM or other media
	    among them.  This is cheaper and often a more convenient
	    method to install software on multiple machines.</para>
	</listitem>

	<listitem>
	  <para>On large networks, it might be more convenient to
	    configure a central <acronym>NFS</acronym> server in which
	    to store all the user home directories.  These home
	    directories can then be exported to the network so that
	    users would always have the same home directory,
	    regardless of which workstation they log in to.</para>
	</listitem>

	<listitem>
	  <para>Several machines could have a common
            <filename>/usr/ports/distfiles</filename> directory.  That
            way, when you need to install a port on several machines,
            you can quickly access the source without downloading it
            on each machine.</para>
	</listitem>
      </itemizedlist>
    </sect2>

    <sect2 id="network-amd">
      <sect2info>
	<authorgroup>
	  <author>
	    <firstname>Wylie</firstname>
	    <surname>Stilwell</surname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
	<authorgroup>
	  <author>
	    <firstname>Chern</firstname>
	    <surname>Lee</surname>
	    <contrib>Rewritten by </contrib>
	  </author>
	</authorgroup>
      </sect2info>
      <title>Automatic Mounts with <application>amd</application></title>

      <indexterm><primary>amd</primary></indexterm>
      <indexterm><primary>automatic mounter daemon</primary></indexterm>

      <para>&man.amd.8; (the automatic mounter daemon)
	automatically mounts a
	remote filesystem whenever a file or directory within that
	filesystem is accessed.  Filesystems that are inactive for a
	period of time will also be automatically unmounted by
	<application>amd</application>.  Using
	<application>amd</application> provides a simple alternative
	to permanent mounts, as permanent mounts are usually listed in
        <filename>/etc/fstab</filename>.</para>

      <para><application>amd</application> operates by attaching
	itself as an NFS server to the <filename>/host</filename> and
	<filename>/net</filename> directories.  When a file is accessed
	within one of these directories, <application>amd</application>
	looks up the corresponding remote mount and automatically mounts
	it.  <filename>/net</filename> is used to mount an exported
	filesystem from an IP address, while <filename>/host</filename>
	is used to mount an export from a remote hostname.</para>

      <para>An access to a file within
	<filename>/host/foobar/usr</filename> would tell
	<application>amd</application> to attempt to mount the
	<filename>/usr</filename> export on the host
	<hostid>foobar</hostid>.</para>

      <example>
	<title>Mounting an Export with <application>amd</application></title>

	<para>You can view the available mounts of a remote host with
	  the <command>showmount</command> command.  For example, to
	  view the mounts of a host named <hostid>foobar</hostid>, you
	  can use:</para>

	<screen>&prompt.user; <userinput>showmount -e foobar</userinput>
Exports list on foobar:
/usr                               10.10.10.0
/a                                 10.10.10.0
&prompt.user; <userinput>cd /host/foobar/usr</userinput></screen>
      </example>

      <para>As seen in the example, the <command>showmount</command> shows
	<filename>/usr</filename> as an export.  When changing directories to
	<filename>/host/foobar/usr</filename>, <application>amd</application>
	attempts to resolve the hostname <hostid>foobar</hostid> and
	automatically mount the desired export.</para>

      <para><application>amd</application> can be started by the
	startup scripts by placing the following lines in
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>amd_enable="YES"</programlisting>

      <para>Additionally, custom flags can be passed to
      <application>amd</application> from the
      <varname>amd_flags</varname> option.  By default,
      <varname>amd_flags</varname> is set to:</para>

      <programlisting>amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map"</programlisting>

      <para>The <filename>/etc/amd.map</filename> file defines the
	default options that exports are mounted with.  The
	<filename>/etc/amd.conf</filename> file defines some of the more
	advanced features of <application>amd</application>.</para>

      <para>Consult the &man.amd.8; and &man.amd.conf.5; manual pages for more
	information.</para>
    </sect2>

    <sect2 id="network-nfs-integration">
      <sect2info>
        <authorgroup>
          <author>
            <firstname>John</firstname>
            <surname>Lind</surname>
            <contrib>Contributed by </contrib>
          </author>
        </authorgroup>
      </sect2info>
      <title>Problems Integrating with Other Systems</title>

      <para>Certain Ethernet adapters for ISA PC systems have limitations
	which can lead to serious network problems, particularly with NFS.
	This difficulty is not specific to FreeBSD, but FreeBSD systems
	are affected by it.</para>

      <para>The problem nearly always occurs when (FreeBSD) PC systems are
	networked with high-performance workstations, such as those made
	by Silicon Graphics, Inc., and Sun Microsystems, Inc.  The NFS
	mount will work fine, and some operations may succeed, but
	suddenly the server will seem to become unresponsive to the
	client, even though requests to and from other systems continue to
	be processed.  This happens to the client system, whether the
	client is the FreeBSD system or the workstation.  On many systems,
	there is no way to shut down the client gracefully once this
	problem has manifested itself.  The only solution is often to
	reset the client, because the NFS situation cannot be
	resolved.</para>

      <para>Though the <quote>correct</quote> solution is to get a
	higher performance and capacity Ethernet adapter for the
	FreeBSD system, there is a simple workaround that will allow
	satisfactory operation.  If the FreeBSD system is the
	<emphasis>server</emphasis>, include the option
	<option>-w=1024</option> on the mount from the client.  If the
	FreeBSD system is the <emphasis>client</emphasis>, then mount
	the NFS filesystem with the option <option>-r=1024</option>.
	These options may be specified using the fourth field of the
	<filename>fstab</filename> entry on the client for automatic
	mounts, or by using the <option>-o</option> parameter of the
	&man.mount.8; command for manual mounts.</para>

      <para>It should be noted that there is a different problem,
	sometimes mistaken for this one, when the NFS servers and
	clients are on different networks.  If that is the case, make
	<emphasis>certain</emphasis> that your routers are routing the
	necessary <acronym>UDP</acronym> information, or you will not get anywhere, no
	matter what else you are doing.</para>

      <para>In the following examples, <hostid>fastws</hostid> is the host
	(interface) name of a high-performance workstation, and
	<hostid>freebox</hostid> is the host (interface) name of a FreeBSD
	system with a lower-performance Ethernet adapter.  Also,
	<filename>/sharedfs</filename> will be the exported NFS
	filesystem (see &man.exports.5;), and
	<filename>/project</filename> will be the mount point on the
	client for the exported filesystem.  In all cases, note that
	additional options, such as <option>hard</option> or
	<option>soft</option> and <option>bg</option> may be desirable in
	your application.</para>

      <para>Examples for the FreeBSD system (<hostid>freebox</hostid>)
	as the client in <filename>/etc/fstab</filename> on
	<hostid>freebox</hostid>:</para>

      <programlisting>fastws:/sharedfs /project nfs rw,-r=1024 0 0</programlisting>

      <para>As a manual mount command on <hostid>freebox</hostid>:</para>

      <screen>&prompt.root; <userinput>mount -t nfs -o -r=1024 fastws:/sharedfs /project</userinput></screen>

      <para>Examples for the FreeBSD system as the server in
	<filename>/etc/fstab</filename> on
	<hostid>fastws</hostid>:</para>

      <programlisting>freebox:/sharedfs /project nfs rw,-w=1024 0 0</programlisting>

      <para>As a manual mount command on <hostid>fastws</hostid>:</para>

      <screen>&prompt.root; <userinput>mount -t nfs -o -w=1024 freebox:/sharedfs /project</userinput></screen>

      <para>Nearly any 16-bit Ethernet adapter will allow operation
	without the above restrictions on the read or write size.</para>

      <para>For anyone who cares, here is what happens when the
	failure occurs, which also explains why it is unrecoverable.
	NFS typically works with a <quote>block</quote> size of
	8&nbsp;K (though it may do fragments of smaller sizes).  Since
	the maximum Ethernet packet is around 1500&nbsp;bytes, the NFS
	<quote>block</quote> gets split into multiple Ethernet
	packets, even though it is still a single unit to the
	upper-level code, and must be received, assembled, and
	<emphasis>acknowledged</emphasis> as a unit.  The
	high-performance workstations can pump out the packets which
	comprise the NFS unit one right after the other, just as close
	together as the standard allows.  On the smaller, lower
	capacity cards, the later packets overrun the earlier packets
	of the same unit before they can be transferred to the host
	and the unit as a whole cannot be reconstructed or
	acknowledged.  As a result, the workstation will time out and
	try again, but it will try again with the entire 8&nbsp;K
	unit, and the process will be repeated, ad infinitum.</para>

      <para>By keeping the unit size below the Ethernet packet size
	limitation, we ensure that any complete Ethernet packet
	received can be acknowledged individually, avoiding the
	deadlock situation.</para>

      <para>Overruns may still occur when a high-performance
	workstations is slamming data out to a PC system, but with the
	better cards, such overruns are not guaranteed on NFS
	<quote>units</quote>.  When an overrun occurs, the units
	affected will be retransmitted, and there will be a fair
	chance that they will be received, assembled, and
	acknowledged.</para>
    </sect2>
  </sect1>

  <sect1 id="network-nis">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Bill</firstname>
      	  <surname>Swingle</surname>
	  <contrib>Written by </contrib>
         </author>
      </authorgroup>
      <authorgroup>
	<author>
	  <firstname>Eric</firstname>
	  <surname>Ogren</surname>
	  <contrib>Enhanced by </contrib>
	</author>
	<author>
	  <firstname>Udo</firstname>
	  <surname>Erdelhoff</surname>
	</author>
      </authorgroup>
    </sect1info>
    <title>Network Information System (NIS/YP)</title>

    <sect2>
      <title>What Is It?</title>
      <indexterm><primary>NIS</primary></indexterm>
      <indexterm><primary>Solaris</primary></indexterm>
      <indexterm><primary>HP-UX</primary></indexterm>
      <indexterm><primary>AIX</primary></indexterm>
      <indexterm><primary>Linux</primary></indexterm>
      <indexterm><primary>NetBSD</primary></indexterm>
      <indexterm><primary>OpenBSD</primary></indexterm>

      <para><acronym role="Network Information System">NIS</acronym>,
        which stands for Network Information Services, was developed
        by Sun Microsystems to centralize administration of &unix;
        (originally &sunos;) systems.  It has now essentially become
        an industry standard; all major &unix; like systems
        (&solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, FreeBSD,
        etc) support <acronym role="Network Information
        System">NIS</acronym>.</para>

      <indexterm><primary>yellow pages</primary><see>NIS</see></indexterm>

      <para><acronym role="Network Information System">NIS</acronym>
	was formerly known as Yellow Pages, but because of trademark
	issues, Sun changed the name.  The old term (and yp) is still
	often seen and used.</para>

      <indexterm>
        <primary>NIS</primary>
        <secondary>domains</secondary>
      </indexterm>

      <para>It is a RPC-based client/server system that allows a group
	of machines within an NIS domain to share a common set of
	configuration files.  This permits a system administrator to
	set up NIS client systems with only minimal configuration data
	and add, remove or modify configuration data from a single
	location.</para>

      <indexterm><primary>Windows NT</primary></indexterm>

      <para>It is similar to the &windowsnt; domain system; although
        the internal implementation of the two are not at all similar,
        the basic functionality can be compared.</para>
    </sect2>

    <sect2>
      <title>Terms/Processes You Should Know</title>

      <para>There are several terms and several important user
        processes that you will come across when attempting to
        implement NIS on FreeBSD, whether you are trying to create an
        NIS server or act as an NIS client:</para>

      <indexterm>
	<primary><application>rpcbind</application></primary>
      </indexterm>
      <indexterm>
	<primary><application>portmap</application></primary>
      </indexterm>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	<colspec colwidth="1*">
	<colspec colwidth="3*">

	  <thead>
	    <row>
	      <entry>Term</entry>
	      <entry>Description</entry>
	    </row>
	  </thead>
	  <tbody>
	    <row>
	      <entry>NIS domainname</entry>

	      <entry>An NIS master server and all of its clients
		(including its slave servers) have a NIS domainname.
		Similar to an &windowsnt; domain name, the NIS
		domainname does not have anything to do with
		<acronym>DNS</acronym>.</entry>
	    </row>
	    <row>
	      <entry><application>rpcbind</application></entry>

	      <entry>Must be running in order to enable
		<acronym>RPC</acronym> (Remote Procedure Call, a
		network protocol used by NIS).  If
		<application>rpcbind</application> is not running, it
		will be impossible to run an NIS server, or to act as
		an NIS client (Under &os;&nbsp;4.X
		<application>portmap</application> is used in place of
		<application>rpcbind</application>).</entry>
	    </row>
	    <row>
	      <entry><application>ypbind</application></entry>

	      <entry><quote>Binds</quote> an NIS client to its NIS
		server.  It will take the NIS domainname from the
		system, and using <acronym>RPC</acronym>, connect to
		the server.  <application>ypbind</application> is the
		core of client-server communication in an NIS
		environment; if <application>ypbind</application> dies
		on a client machine, it will not be able to access the
		NIS server.</entry>
	    </row>
	    <row>
	      <entry><application>ypserv</application></entry>
	      <entry>Should only be running on NIS servers; this is
		the NIS server process itself.  If &man.ypserv.8;
		dies, then the server will no longer be able to
		respond to NIS requests (hopefully, there is a slave
		server to take over for it).  There are some
		implementations of NIS (but not the FreeBSD one), that
		do not try to reconnect to another server if the
		server it used before dies.  Often, the only thing
		that helps in this case is to restart the server
		process (or even the whole server) or the
		<application>ypbind</application> process on the
		client.
	      </entry>
	    </row>
	    <row>
	      <entry><application>rpc.yppasswdd</application></entry>
	      <entry>Another process that should only be running on
		NIS master servers; this is a daemon that will allow NIS
		clients to change their NIS passwords.  If this daemon
		is not running, users will have to login to the NIS
		master server and change their passwords there.</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>
      <!-- XXX Missing: rpc.ypxfrd (not important, though) May only run
      on the master -->

    </sect2>

    <sect2>
      <title>How Does It Work?</title>

      <para>There are three types of hosts in an NIS environment:
	master servers, slave servers, and clients.  Servers act as a
	central repository for host configuration information.  Master
	servers hold the authoritative copy of this information, while
	slave servers mirror this information for redundancy.  Clients
	rely on the servers to provide this information to
	them.</para>

      <para>Information in many files can be shared in this manner.
	The <filename>master.passwd</filename>,
	<filename>group</filename>, and <filename>hosts</filename>
	files are commonly shared via NIS.  Whenever a process on a
	client needs information that would normally be found in these
	files locally, it makes a query to the NIS server that it is
	bound to instead.</para>

      <sect3>
        <title>Machine Types</title>

        <itemizedlist>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>master server</secondary>
	  </indexterm>
          <listitem>
            <para>A <emphasis>NIS master server</emphasis>.  This
              server, analogous to a &windowsnt; primary domain
              controller, maintains the files used by all of the NIS
              clients.  The <filename>passwd</filename>,
              <filename>group</filename>, and other various files used
              by the NIS clients live on the master server.</para>

            <note><para>It is possible for one machine to be an NIS
              master server for more than one NIS domain.  However,
              this will not be covered in this introduction, which
              assumes a relatively small-scale NIS
              environment.</para></note>
          </listitem>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>slave server</secondary>
	  </indexterm>
          <listitem>
            <para><emphasis>NIS slave servers</emphasis>.  Similar to
              the &windowsnt; backup domain controllers, NIS slave
              servers maintain copies of the NIS master's data files.
              NIS slave servers provide the redundancy, which is
              needed in important environments.  They also help to
              balance the load of the master server: NIS Clients
              always attach to the NIS server whose response they get
              first, and this includes slave-server-replies.</para>
          </listitem>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>client</secondary>
	  </indexterm>
          <listitem>
            <para><emphasis>NIS clients</emphasis>.  NIS clients, like
              most &windowsnt; workstations, authenticate against the
              NIS server (or the &windowsnt; domain controller in the
              &windowsnt; workstations case) to log on.</para>
          </listitem>
        </itemizedlist>
      </sect3>
    </sect2>

    <sect2>
      <title>Using NIS/YP</title>

      <para>This section will deal with setting up a sample NIS
        environment.</para>

      <note><para>This section assumes that you are running
        FreeBSD&nbsp;3.3 or later.  The instructions given here will
        <emphasis>probably</emphasis> work for any version of FreeBSD
        greater than 3.0, but there are no guarantees that this is
        true.</para></note>


      <sect3>
        <title>Planning</title>

        <para>Let us assume that you are the administrator of a small
          university lab.  This lab, which consists of 15 FreeBSD
          machines, currently has no centralized point of
          administration; each machine has its own
          <filename>/etc/passwd</filename> and
          <filename>/etc/master.passwd</filename>.  These files are
          kept in sync with each other only through manual
          intervention; currently, when you add a user to the lab, you
          must run <command>adduser</command> on all 15 machines.
          Clearly, this has to change, so you have decided to convert
          the lab to use NIS, using two of the machines as
          servers.</para>

        <para>Therefore, the configuration of the lab now looks something
          like:</para>

        <informaltable frame="none" pgwide="1">
          <tgroup cols="3">
            <thead>
              <row>
                <entry>Machine name</entry>
                <entry>IP address</entry>
                <entry>Machine role</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry><hostid>ellington</hostid></entry>
                <entry><hostid role="ipaddr">10.0.0.2</hostid></entry>
                <entry>NIS master</entry>
              </row>
              <row>
                <entry><hostid>coltrane</hostid></entry>
                <entry><hostid role="ipaddr">10.0.0.3</hostid></entry>
                <entry>NIS slave</entry>
              </row>
              <row>
                <entry><hostid>basie</hostid></entry>
                <entry><hostid role="ipaddr">10.0.0.4</hostid></entry>
                <entry>Faculty workstation</entry>
              </row>
              <row>
                <entry><hostid>bird</hostid></entry>
                <entry><hostid role="ipaddr">10.0.0.5</hostid></entry>
                <entry>Client machine</entry>
              </row>
              <row>
                <entry><hostid>cli[1-11]</hostid></entry>
                <entry><hostid role="ipaddr">10.0.0.[6-17]</hostid></entry>
                <entry>Other client machines</entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>

        <para>If you are setting up a NIS scheme for the first time, it
	  is a good idea to think through how you want to go about it.  No
	  matter what the size of your network, there are a few decisions
	  that need to be made.</para>

        <sect4>
          <title>Choosing a NIS Domain Name</title>

	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>domainname</secondary>
	  </indexterm>
          <para>This might not be the <quote>domainname</quote> that
	    you are used to.  It is more accurately called the
	    <quote>NIS domainname</quote>.  When a client broadcasts
	    its requests for info, it includes the name of the NIS
	    domain that it is part of.  This is how multiple servers
	    on one network can tell which server should answer which
	    request.  Think of the NIS domainname as the name for a
	    group of hosts that are related in some way.</para>

	  <para>Some organizations choose to use their Internet
	    domainname for their NIS domainname.  This is not
	    recommended as it can cause confusion when trying to debug
	    network problems.  The NIS domainname should be unique
	    within your network and it is helpful if it describes the
	    group of machines it represents.  For example, the Art
	    department at Acme Inc. might be in the
	    <quote>acme-art</quote> NIS domain.  For this example,
	    assume you have chosen the name
	    <literal>test-domain</literal>.</para>

	  <indexterm><primary>SunOS</primary></indexterm>
          <para>However, some operating systems (notably &sunos;) use
          their NIS domain name as their Internet domain name.  If one
          or more machines on your network have this restriction, you
          <emphasis>must</emphasis> use the Internet domain name as
          your NIS domain name.</para>
        </sect4>

        <sect4>
          <title>Physical Server Requirements</title>

	  <para>There are several things to keep in mind when choosing
	    a machine to use as a NIS server.  One of the unfortunate
	    things about NIS is the level of dependency the clients
	    have on the server.  If a client cannot contact the server
	    for its NIS domain, very often the machine becomes
	    unusable.  The lack of user and group information causes
	    most systems to temporarily freeze up.  With this in mind
	    you should make sure to choose a machine that will not be
	    prone to being rebooted regularly, or one that might be
	    used for development.  The NIS server should ideally be a
	    stand alone machine whose sole purpose in life is to be an
	    NIS server.  If you have a network that is not very
	    heavily used, it is acceptable to put the NIS server on a
	    machine running other services, just keep in mind that if
	    the NIS server becomes unavailable, it will affect
	    <emphasis>all</emphasis> of your NIS clients
	    adversely.</para>
        </sect4>
      </sect3>

      <sect3>
        <title>NIS Servers</title>

	<para> The canonical copies of all NIS information are stored
	  on a single machine called the NIS master server.  The
	  databases used to store the information are called NIS maps.
	  In FreeBSD, these maps are stored in
	  <filename>/var/yp/[domainname]</filename> where
	  <filename>[domainname]</filename> is the name of the NIS
	  domain being served.  A single NIS server can support
	  several domains at once, therefore it is possible to have
	  several such directories, one for each supported domain.
	  Each domain will have its own independent set of
	  maps.</para>

	<para>NIS master and slave servers handle all NIS requests
	  with the <command>ypserv</command> daemon.
	  <command>ypserv</command> is responsible for receiving
	  incoming requests from NIS clients, translating the
	  requested domain and map name to a path to the corresponding
	  database file and transmitting data from the database back
	  to the client.</para>

        <sect4>
	  <title>Setting Up a NIS Master Server</title>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>server configuration</secondary>
	  </indexterm>
	  <para>Setting up a master NIS server can be relatively
	    straight forward, depending on your needs.  FreeBSD comes
	    with support for NIS out-of-the-box.  All you need is to
	    add the following lines to
	    <filename>/etc/rc.conf</filename>, and FreeBSD will do the
	    rest for you.</para>

          <procedure>
            <step>
              <para><programlisting>nisdomainname="test-domain"</programlisting>
                This line will set the NIS domainname to
                <literal>test-domain</literal>
                upon network setup (e.g. after reboot).</para>
            </step>
            <step>
              <para><programlisting>nis_server_enable="YES"</programlisting>
                This will tell FreeBSD to start up the NIS server processes
                when the networking is next brought up.</para>
            </step>
            <step>
              <para><programlisting>nis_yppasswdd_enable="YES"</programlisting>
                This will enable the <command>rpc.yppasswdd</command>
                daemon which, as mentioned above, will allow users to
                change their NIS password from a client machine.</para>
            </step>
          </procedure>

          <note>
            <para>Depending on your NIS setup, you may need to add
              further entries.  See the <link
              linkend="network-nis-server-is-client">section about NIS
              servers that are also NIS clients</link>, below, for
              details.</para>
          </note>

          <para>Now, all you have to do is to run the command
            <command>/etc/netstart</command> as superuser.  It will
            set up everything for you, using the values you defined in
            <filename>/etc/rc.conf</filename>.</para>
        </sect4>

        <sect4>
          <title>Initializing the NIS Maps</title>
          <indexterm>
            <primary>NIS</primary>
            <secondary>maps</secondary>
          </indexterm>
          <para>The <emphasis>NIS maps</emphasis> are database files,
            that are kept in the <filename>/var/yp</filename>
            directory.  They are generated from configuration files in
            the <filename>/etc</filename> directory of the NIS master,
            with one exception: the
            <filename>/etc/master.passwd</filename> file.  This is for
            a good reason, you do not want to propagate passwords to
            your <username>root</username> and other administrative
            accounts to all the servers in the NIS domain.  Therefore,
            before we initialize the NIS maps, you should:</para>

          <screen>&prompt.root; <userinput>cp /etc/master.passwd /var/yp/master.passwd</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>vi master.passwd</userinput></screen>

          <para>You should remove all entries regarding system
            accounts (<username>bin</username>,
            <username>tty</username>, <username>kmem</username>,
            <username>games</username>, etc), as well as any accounts
            that you do not want to be propagated to the NIS clients
            (for example <username>root</username> and any other UID 0
            (superuser) accounts).</para>

          <note><para>Make sure the
            <filename>/var/yp/master.passwd</filename> is neither group
            nor world readable (mode 600)!  Use the
            <command>chmod</command> command, if appropriate.</para></note>

	  <indexterm><primary>Tru64 UNIX</primary></indexterm>

          <para>When you have finished, it is time to initialize the
            NIS maps!  FreeBSD includes a script named
            <command>ypinit</command> to do this for you (see its
            manual page for more information).  Note that this script
            is available on most &unix; Operating Systems, but not on
            all.  On Digital UNIX/Compaq Tru64 UNIX it is called
            <command>ypsetup</command>.  Because we are generating
            maps for an NIS master, we are going to pass the
            <option>-m</option> option to <command>ypinit</command>.
            To generate the NIS maps, assuming you already performed
            the steps above, run:</para>

          <screen>ellington&prompt.root; <userinput>ypinit -m test-domain</userinput>
Server Type: MASTER Domain: test-domain
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] <userinput>n</userinput>
Ok, please remember to go back and redo manually whatever fails.
If you don't, something might not work.
At this point, we have to construct a list of this domains YP servers.
rod.darktech.org is already known as master server.
Please continue to add any slave servers, one per line. When you are
done with the list, type a &lt;control D&gt;.
master server   :  ellington
next host to add:  <userinput>coltrane</userinput>
next host to add:  <userinput>^D</userinput>
The current list of NIS servers looks like this:
ellington
coltrane
Is this correct?  [y/n: y] <userinput>y</userinput>

[..output from map generation..]

NIS Map update completed.
ellington has been setup as an YP master server without any errors.</screen>

          <para><command>ypinit</command> should have created
            <filename>/var/yp/Makefile</filename> from
            <filename>/var/yp/Makefile.dist</filename>.
            When created, this file assumes that you are operating
            in a single server NIS environment with only FreeBSD
            machines.  Since <literal>test-domain</literal> has
            a slave server as well, you must edit
            <filename>/var/yp/Makefile</filename>:</para>

          <screen>ellington&prompt.root; <userinput>vi /var/yp/Makefile</userinput></screen>

	  <para>You should comment out the line that says</para>

	  <programlisting>NOPUSH = "True"</programlisting>

	  <para>(if it is not commented out already).</para>
        </sect4>

        <sect4>
	  <title>Setting up a NIS Slave Server</title>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>slave server</secondary>
	  </indexterm>
	  <para>Setting up an NIS slave server is even more simple than
	    setting up the master.  Log on to the slave server and edit the
            file <filename>/etc/rc.conf</filename> as you did before.
            The only difference is that we now must use the
            <option>-s</option> option when running <command>ypinit</command>.
            The <option>-s</option> option requires the name of the NIS
            master be passed to it as well, so our command line looks
            like:</para>

  <screen>coltrane&prompt.root; <userinput>ypinit -s ellington test-domain</userinput>

Server Type: SLAVE Domain: test-domain Master: ellington

Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.

Do you want this procedure to quit on non-fatal errors? [y/n: n]  <userinput>n</userinput>

Ok, please remember to go back and redo manually whatever fails.
If you don't, something might not work.
There will be no further questions. The remainder of the procedure
should take a few minutes, to copy the databases from ellington.
Transferring netgroup...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byuser...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byhost...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring group.bygid...
ypxfr: Exiting: Map successfully transferred
Transferring group.byname...
ypxfr: Exiting: Map successfully transferred
Transferring services.byname...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.byname...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.byname...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring netid.byname...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring ypservers...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byname...
ypxfr: Exiting: Map successfully transferred

coltrane has been setup as an YP slave server without any errors.
Don't forget to update map ypservers on ellington.</screen>

	  <para>You should now have a directory called
	    <filename>/var/yp/test-domain</filename>.  Copies of the NIS
	    master server's maps should be in this directory.  You will
	    need to make sure that these stay updated.  The following
	    <filename>/etc/crontab</filename> entries on your slave
	    servers should do the job:</para>

	  <programlisting>20      *       *       *       *       root   /usr/libexec/ypxfr passwd.byname
21      *       *       *       *       root   /usr/libexec/ypxfr passwd.byuid</programlisting>

	  <para>These two lines force the slave to sync its maps with
	    the maps on the master server.  Although these entries are
	    not mandatory, since the master server attempts to ensure
	    any changes to its NIS maps are communicated to its slaves
	    and because password information is vital to systems
	    depending on the server, it is a good idea to force the
	    updates.  This is more important on busy networks where map
	    updates might not always complete.</para>

          <para>Now, run the command <command>/etc/netstart</command> on the
            slave server as well, which again starts the NIS server.</para>
	</sect4>
      </sect3>

      <sect3>
        <title>NIS Clients</title>

	<para> An NIS client establishes what is called a binding to a
	  particular NIS server using the
	  <command>ypbind</command> daemon.
	  <command>ypbind</command> checks the system's default
	  domain (as set by the <command>domainname</command> command),
	  and begins broadcasting RPC requests on the local network.
	  These requests specify the name of the domain for which
	  <command>ypbind</command> is attempting to establish a binding.
	  If a server that has been configured to serve the requested
	  domain receives one of the broadcasts, it will respond to
	  <command>ypbind</command>,  which will record the server's
	  address.  If there are several servers available (a master and
	  several slaves, for example), <command>ypbind</command> will
	  use the address of the first one to respond.  From that point
	  on, the client system will direct all of its NIS requests to
	  that server.  <command>ypbind</command> will
	  occasionally <quote>ping</quote> the server to make sure it is
	  still up and running.  If it fails to receive a reply to one of
	  its pings within a reasonable amount of time,
	  <command>ypbind</command> will mark the domain as unbound and
	  begin broadcasting again in the hopes of locating another
	  server.</para>

	<sect4>
	  <title>Setting Up a NIS Client</title>
	  <indexterm>
	    <primary>NIS</primary>
	    <secondary>client configuration</secondary>
	  </indexterm>
	  <para>Setting up a FreeBSD machine to be a NIS client is fairly
	    straightforward.</para>

	  <procedure>
	    <step>
	      <para>Edit the file <filename>/etc/rc.conf</filename> and
                add the following lines in order to set the NIS domainname
                and start <command>ypbind</command> upon network
                startup:</para>

	      <programlisting>nisdomainname="test-domain"
nis_client_enable="YES"</programlisting>
	    </step>

	    <step>
	      <para>To import all possible password entries from the NIS
		server, remove all user accounts from your
		<filename>/etc/master.passwd</filename> file and use
		<command>vipw</command> to add the following line to
                the end of the file:</para>

	      <programlisting>+:::::::::</programlisting>

	      <note>
		<para>This line will afford anyone with a valid account in
		  the NIS server's password maps an account.  There are
		  many ways to configure your NIS client by changing this
		  line.  See the <link linkend="network-netgroups">netgroups
		  section</link> below for more information.
                  For more detailed reading see O'Reilly's book on
		  <literal>Managing NFS and NIS</literal>.</para>
	      </note>

              <note>
                <para>You should keep at least one local account (i.e.
                  not imported via NIS) in your
                  <filename>/etc/master.passwd</filename> and this
                  account should also be a member of the group
                  <groupname>wheel</groupname>.  If there is something
                  wrong with NIS, this account can be used to log in
                  remotely, become <username>root</username>, and fix things.</para>
              </note>
            </step>

	    <step>
	      <para>To import all possible group entries from the NIS
		server, add this line to your
		<filename>/etc/group</filename> file:</para>

	      <programlisting>+:*::</programlisting>
	    </step>
	  </procedure>

	  <para>After completing these steps, you should be able to run
	    <command>ypcat passwd</command> and see the NIS server's
	    passwd map.</para>
	</sect4>
      </sect3>
    </sect2>

    <sect2>
      <title>NIS Security</title>

      <para>In general, any remote user can issue an RPC to
	&man.ypserv.8; and retrieve the contents of your NIS maps,
	provided the remote user knows your domainname.  To prevent
	such unauthorized transactions, &man.ypserv.8; supports a
	feature called <quote>securenets</quote> which can be used to
	restrict access to a given set of hosts.  At startup,
	&man.ypserv.8; will attempt to load the securenets information
	from a file called
	<filename>/var/yp/securenets</filename>.</para>

      <note>
	<para>This path varies depending on the path specified with the
	  <option>-p</option> option.  This file contains entries that
	  consist of a network specification and a network mask separated
	  by white space.  Lines starting with <quote>#</quote> are
	  considered to be comments.  A sample securenets file might look
	  like this:</para>
      </note>

      <programlisting># allow connections from local host -- mandatory
127.0.0.1     255.255.255.255
# allow connections from any host
# on the 192.168.128.0 network
192.168.128.0 255.255.255.0
# allow connections from any host
# between 10.0.0.0 to 10.0.15.255
# this includes the machines in the testlab
10.0.0.0      255.255.240.0</programlisting>

      <para>If &man.ypserv.8; receives a request from an address that
	matches one of these rules, it will process the request
	normally.  If the address fails to match a rule, the request
	will be ignored and a warning message will be logged.  If the
	<filename>/var/yp/securenets</filename> file does not exist,
	<command>ypserv</command> will allow connections from any
	host.</para>

      <para>The <command>ypserv</command> program also has support for
	Wietse Venema's <application>TCP Wrapper</application> package.
	This allows the administrator to use the
	<application>TCP Wrapper</application> configuration files for
	access control instead of
	<filename>/var/yp/securenets</filename>.</para>

      <note>
        <para>While both of these access control mechanisms provide some
          security, they, like the privileged port test, are
          vulnerable to <quote>IP spoofing</quote> attacks.  All
          NIS-related traffic should be blocked at your firewall.</para>

        <para>Servers using <filename>/var/yp/securenets</filename>
          may fail to serve legitimate NIS clients with archaic TCP/IP
          implementations.  Some of these implementations set all
          host bits to zero when doing broadcasts and/or fail to
          observe the subnet mask when calculating the broadcast
          address.  While some of these problems can be fixed by
          changing the client configuration, other problems may force
          the retirement of the client systems in question or the
          abandonment of <filename>/var/yp/securenets</filename>.</para>

        <para>Using <filename>/var/yp/securenets</filename> on a
          server with such an archaic implementation of TCP/IP is a
          really bad idea and will lead to loss of NIS functionality
          for large parts of your network.</para>

	<indexterm><primary>TCP Wrappers</primary></indexterm>
        <para>The use of the <application>TCP Wrapper</application>
          package increases the latency of your NIS server.  The
          additional delay may be long enough to cause timeouts in
          client programs, especially in busy networks or with slow
          NIS servers.  If one or more of your client systems
          suffers from these symptoms, you should convert the client
          systems in question into NIS slave servers and force them
          to bind to themselves.</para>
      </note>
    </sect2>

    <sect2>
      <title>Barring Some Users from Logging On</title>

      <para>In our lab, there is a machine <hostid>basie</hostid> that
        is supposed to be a faculty only workstation.  We do not want
        to take this machine out of the NIS domain, yet the
        <filename>passwd</filename> file on the master NIS server
        contains accounts for both faculty and students.  What can we
        do?</para>

      <para>There is a way to bar specific users from logging on to a
        machine, even if they are present in the NIS database.  To do
        this, all you must do is add
        <literal>-<replaceable>username</replaceable></literal> to the
        end of the <filename>/etc/master.passwd</filename> file on the
        client machine, where <replaceable>username</replaceable> is
        the username of the user you wish to bar from logging in.
        This should preferably be done using <command>vipw</command>,
        since <command>vipw</command> will sanity check your changes
        to <filename>/etc/master.passwd</filename>, as well as
        automatically rebuild the password database when you finish
        editing.  For example, if we wanted to bar user
        <username>bill</username> from logging on to
        <hostid>basie</hostid> we would:</para>

        <screen>basie&prompt.root; <userinput>vipw</userinput>
<userinput>[add -bill to the end, exit]</userinput>
vipw: rebuilding the database...
vipw: done

basie&prompt.root; <userinput>cat /etc/master.passwd</userinput>

root:[password]:0:0::0:0:The super-user:/root:/bin/csh
toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh
daemon:*:1:1::0:0:Owner of many system processes:/root:/sbin/nologin
operator:*:2:5::0:0:System &:/:/sbin/nologin
bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/sbin/nologin
tty:*:4:65533::0:0:Tty Sandbox:/:/sbin/nologin
kmem:*:5:65533::0:0:KMem Sandbox:/:/sbin/nologin
games:*:7:13::0:0:Games pseudo-user:/usr/games:/sbin/nologin
news:*:8:8::0:0:News Subsystem:/:/sbin/nologin
man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/sbin/nologin
bind:*:53:53::0:0:Bind Sandbox:/:/sbin/nologin
uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico
xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/sbin/nologin
pop:*:68:6::0:0:Post Office Owner:/nonexistent:/sbin/nologin
nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin
+:::::::::
-bill

basie&prompt.root;</screen>
    </sect2>

    <sect2 id="network-netgroups">
      <sect2info>
        <authorgroup>
          <author>
            <firstname>Udo</firstname>
            <surname>Erdelhoff</surname>
            <contrib>Contributed by </contrib>
          </author>
        </authorgroup>
      </sect2info>

      <title>Using Netgroups</title>
      <indexterm><primary>netgroups</primary></indexterm>

      <para>The method shown in the previous section works reasonably
        well if you need special rules for a very small number of
        users and/or machines.  On larger networks, you
        <emphasis>will</emphasis> forget to bar some users from logging
        onto sensitive machines, or you may even have to modify each
        machine separately, thus losing the main benefit of NIS:
        <emphasis>centralized</emphasis> administration.</para>

      <para>The NIS developers' solution for this problem is called
        <emphasis>netgroups</emphasis>.  Their purpose and semantics
        can be compared to the normal groups used by &unix; file
        systems.  The main differences are the lack of a numeric ID
        and the ability to define a netgroup by including both user
        accounts and other netgroups.</para>

      <para>Netgroups were developed to handle large, complex networks
        with hundreds of users and machines.  On one hand, this is
        a Good Thing if you are forced to deal with such a situation.
        On the other hand, this complexity makes it almost impossible to
        explain netgroups with really simple examples.  The example
        used in the remainder of this section demonstrates this
        problem.</para>

      <para>Let us assume that your successful introduction of NIS in
        your laboratory caught your superiors' interest.  Your next
        job is to extend your NIS domain to cover some of the other
        machines on campus.  The two tables contain the names of the
        new users and new machines as well as brief descriptions of
        them.</para>

      <informaltable frame="none" pgwide="1">
        <tgroup cols="2">
          <thead>
            <row>
              <entry>User Name(s)</entry>
              <entry>Description</entry>
            </row>
          </thead>

          <tbody>
            <row>
              <entry><username>alpha</username>, <username>beta</username></entry>
              <entry>Normal employees of the IT department</entry>
            </row>

            <row>
              <entry><username>charlie</username>, <username>delta</username></entry>
              <entry>The new apprentices of the IT department</entry>
            </row>

            <row>
              <entry><username>echo</username>, <username>foxtrott</username>, <username>golf</username>, ...</entry>
              <entry>Ordinary employees</entry>
            </row>

            <row>
              <entry><username>able</username>, <username>baker</username>, ...</entry>
              <entry>The current interns</entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>

      <informaltable frame="none" pgwide="1">
        <tgroup cols="2">
          <thead>
            <row>
              <entry>Machine Name(s)</entry>
              <entry>Description</entry>
            </row>
          </thead>

          <tbody>
            <row>
              <!--  Names taken from "Good Omens" by Neil Gaiman and Terry
                    Pratchett.  Many thanks for a brilliant book.  -->

              <entry><hostid>war</hostid>, <hostid>death</hostid>,
              <hostid>famine</hostid>,
              <hostid>pollution</hostid></entry>
              <entry>Your most important servers.  Only the IT
                employees are allowed to log onto these
                machines.</entry>
            </row>
            <row>
              <!-- gluttony was omitted because it was too fat -->

              <entry><hostid>pride</hostid>, <hostid>greed</hostid>,
              <hostid>envy</hostid>, <hostid>wrath</hostid>,
              <hostid>lust</hostid>, <hostid>sloth</hostid></entry>
              <entry>Less important servers.  All members of the IT
              department are allowed to login onto these
              machines.</entry>
            </row>

            <row>
              <entry><hostid>one</hostid>, <hostid>two</hostid>,
                <hostid>three</hostid>, <hostid>four</hostid>,
                ...</entry>

              <entry>Ordinary workstations.  Only the
                <emphasis>real</emphasis> employees are allowed to use
                these machines.</entry>
            </row>

            <row>
              <entry><hostid>trashcan</hostid></entry>
              <entry>A very old machine without any critical data.
                Even the intern is allowed to use this box.</entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>

      <para>If you tried to implement these restrictions by separately
        blocking each user, you would have to add one
        <literal>-<replaceable>user</replaceable></literal> line to
        each system's <filename>passwd</filename> for each user who is
        not allowed to login onto that system.  If you forget just one
        entry, you could be in trouble.  It may be feasible to do this
        correctly during the initial setup, however you
        <emphasis>will</emphasis> eventually forget to add the lines
        for new users during day-to-day operations.  After all, Murphy
        was an optimist.</para>

      <para>Handling this situation with netgroups offers several
        advantages.  Each user need not be handled separately; you
        assign a user to one or more netgroups and allow or forbid
        logins for all members of the netgroup.  If you add a new
        machine, you will only have to define login restrictions for
        netgroups.  If a new user is added, you will only have to add
        the user to one or more netgroups.  Those changes are
        independent of each other: no more <quote>for each combination
        of user and machine do...</quote> If your NIS setup is planned
        carefully, you will only have to modify exactly one central
        configuration file to grant or deny access to machines.</para>

      <para>The first step is the initialization of the NIS map
        netgroup.  FreeBSD's &man.ypinit.8; does not create this map by
        default, but its NIS implementation will support it once it has
        been created.  To create an empty map, simply type</para>

      <screen>ellington&prompt.root; <userinput>vi /var/yp/netgroup</userinput></screen>

      <para>and start adding content.  For our example, we need at
         least four netgroups: IT employees, IT apprentices, normal
         employees and interns.</para>

      <programlisting>IT_EMP  (,alpha,test-domain)    (,beta,test-domain)
IT_APP  (,charlie,test-domain)  (,delta,test-domain)
USERS   (,echo,test-domain)     (,foxtrott,test-domain) \
        (,golf,test-domain)
INTERNS (,able,test-domain)     (,baker,test-domain)</programlisting>

      <para><literal>IT_EMP</literal>, <literal>IT_APP</literal> etc.
        are the names of the netgroups.  Each bracketed group adds
        one or more user accounts to it.  The three fields inside a
        group are:</para>

      <orderedlist>
        <listitem>
          <para>The name of the host(s) where the following items are
            valid.  If you do not specify a hostname, the entry is
            valid on all hosts.  If you do specify a hostname, you
            will enter a realm of darkness, horror and utter confusion.</para>
        </listitem>

        <listitem>
          <para>The name of the account that belongs to this
            netgroup.</para>
        </listitem>

        <listitem>
          <para>The NIS domain for the account.  You can import
            accounts from other NIS domains into your netgroup if you
            are one of the unlucky fellows with more than one NIS
            domain.</para>
        </listitem>
      </orderedlist>

      <para>Each of these fields can contain wildcards.  See
        &man.netgroup.5; for details.</para>

      <note>
        <indexterm><primary>netgroups</primary></indexterm>
        <para>Netgroup names longer than 8 characters should not be
          used, especially if you have machines running other
          operating systems within your NIS domain.  The names are
          case sensitive; using capital letters for your netgroup
          names is an easy way to distinguish between user, machine
          and netgroup names.</para>

        <para>Some NIS clients (other than FreeBSD) cannot handle
          netgroups with a large number of entries.  For example, some
          older versions of &sunos; start to cause trouble if a netgroup
          contains more than 15 <emphasis>entries</emphasis>.  You can
          circumvent this limit by creating several sub-netgroups with
          15 users or less and a real netgroup that consists of the
          sub-netgroups:</para>

        <programlisting>BIGGRP1  (,joe1,domain)  (,joe2,domain)  (,joe3,domain) [...]
BIGGRP2  (,joe16,domain)  (,joe17,domain) [...]
BIGGRP3  (,joe31,domain)  (,joe32,domain)
BIGGROUP  BIGGRP1 BIGGRP2 BIGGRP3</programlisting>

        <para>You can repeat this process if you need more than 225
          users within a single netgroup.</para>
      </note>

      <para>Activating and distributing your new NIS map is
        easy:</para>

      <screen>ellington&prompt.root; <userinput>cd /var/yp</userinput>
ellington&prompt.root; <userinput>make</userinput></screen>

      <para>This will generate the three NIS maps
        <filename>netgroup</filename>,
        <filename>netgroup.byhost</filename> and
        <filename>netgroup.byuser</filename>.  Use &man.ypcat.1; to
        check if your new NIS maps are available:</para>

      <screen>ellington&prompt.user; <userinput>ypcat -k netgroup</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byhost</userinput>
ellington&prompt.user; <userinput>ypcat -k netgroup.byuser</userinput></screen>

      <para>The output of the first command should resemble the
        contents of <filename>/var/yp/netgroup</filename>.  The second
        command will not produce output if you have not specified
        host-specific netgroups.  The third command can be used to
        get the list of netgroups for a user.</para>

      <para>The client setup is quite simple.  To configure the server
        <hostid>war</hostid>, you only have to start
        &man.vipw.8; and replace the line</para>

      <programlisting>+:::::::::</programlisting>

      <para>with</para>

      <programlisting>+@IT_EMP:::::::::</programlisting>

      <para>Now, only the data for the users defined in the netgroup
        <literal>IT_EMP</literal> is imported into
        <hostid>war</hostid>'s password database and only
        these users are allowed to login.</para>

      <para>Unfortunately, this limitation also applies to the
	<literal>~</literal> function of the shell and all routines
	converting between user names and numerical user IDs.  In
	other words, <command>cd
	~<replaceable>user</replaceable></command> will not work,
	<command>ls -l</command> will show the numerical ID instead of
	the username and <command>find . -user joe -print</command>
	will fail with <errorname>No such user</errorname>.  To fix
	this, you will have to import all user entries
	<emphasis>without allowing them to login onto your
	servers</emphasis>.</para>

      <para>This can be achieved by adding another line to
        <filename>/etc/master.passwd</filename>.  This line should
        contain:</para>

      <para><literal>+:::::::::/sbin/nologin</literal>, meaning
        <quote>Import all entries but replace the shell with
        <filename>/sbin/nologin</filename> in the imported
        entries</quote>.  You can replace any field in the
        <literal>passwd</literal> entry by placing a default value in
        your <filename>/etc/master.passwd</filename>.</para>

      <!-- Been there, done that, got the scars to prove it - ue -->
      <warning>
        <para>Make sure that the line
        <literal>+:::::::::/sbin/nologin</literal> is placed after
        <literal>+@IT_EMP:::::::::</literal>.  Otherwise, all user
        accounts imported from NIS will have <filename>/sbin/nologin</filename> as their
        login shell.</para>
      </warning>

      <para>After this change, you will only have to change one NIS
        map if a new employee joins the IT department.  You could use
        a similar approach for the less important servers by replacing
        the old <literal>+:::::::::</literal> in their local version
        of <filename>/etc/master.passwd</filename> with something like
        this:</para>

      <programlisting>+@IT_EMP:::::::::
+@IT_APP:::::::::
+:::::::::/sbin/nologin</programlisting>

      <para>The corresponding lines for the normal workstations
        could be:</para>

      <programlisting>+@IT_EMP:::::::::
+@USERS:::::::::
+:::::::::/sbin/nologin</programlisting>

      <para>And everything would be fine until there is a policy
        change a few weeks later: The IT department starts hiring
        interns.  The IT interns are allowed to use the normal
        workstations and the less important servers; and the IT
        apprentices are allowed to login onto the main servers.  You
        add a new netgroup <literal>IT_INTERN</literal>, add the new
        IT interns to this netgroup and start to change the
        configuration on each and every machine...  As the old saying
        goes: <quote>Errors in centralized planning lead to global
        mess</quote>.</para>

      <para>NIS' ability to create netgroups from other netgroups can
        be used to prevent situations like these.  One possibility
        is the creation of role-based netgroups.  For example, you
        could create a netgroup called
        <literal>BIGSRV</literal> to define the login
        restrictions for the important servers, another netgroup
        called <literal>SMALLSRV</literal> for the less
        important servers and a third netgroup called
        <literal>USERBOX</literal> for the normal
        workstations.  Each of these netgroups contains the netgroups
        that are allowed to login onto these machines.  The new
        entries for your NIS map netgroup should look like this:</para>

      <programlisting>BIGSRV    IT_EMP  IT_APP
SMALLSRV  IT_EMP  IT_APP  ITINTERN
USERBOX   IT_EMP  ITINTERN USERS</programlisting>

      <para>This method of defining login restrictions works
        reasonably well if you can define groups of machines with
        identical restrictions.  Unfortunately, this is the exception
        and not the rule.  Most of the time, you will need the ability
        to define login restrictions on a per-machine basis.</para>

      <para>Machine-specific netgroup definitions are the other
        possibility to deal with the policy change outlined above.  In
        this scenario, the <filename>/etc/master.passwd</filename> of
        each box contains two lines starting with <quote>+</quote>.
        The first of them adds a netgroup with the accounts allowed to
        login onto this machine, the second one adds all other
        accounts with <filename>/sbin/nologin</filename> as shell.  It
        is a good idea to use the <quote>ALL-CAPS</quote> version of
        the machine name as the name of the netgroup.  In other words,
        the lines should look like this:</para>

      <programlisting>+@<replaceable>BOXNAME</replaceable>:::::::::
+:::::::::/sbin/nologin</programlisting>

      <para>Once you have completed this task for all your machines,
        you will not have to modify the local versions of
        <filename>/etc/master.passwd</filename> ever again.  All
        further changes can be handled by modifying the NIS map.  Here
        is an example of a possible netgroup map for this
        scenario with some additional goodies:</para>

      <programlisting># Define groups of users first
IT_EMP    (,alpha,test-domain)    (,beta,test-domain)
IT_APP    (,charlie,test-domain)  (,delta,test-domain)
DEPT1     (,echo,test-domain)     (,foxtrott,test-domain)
DEPT2     (,golf,test-domain)     (,hotel,test-domain)
DEPT3     (,india,test-domain)    (,juliet,test-domain)
ITINTERN  (,kilo,test-domain)     (,lima,test-domain)
D_INTERNS (,able,test-domain)     (,baker,test-domain)
#
# Now, define some groups based on roles
USERS     DEPT1   DEPT2     DEPT3
BIGSRV    IT_EMP  IT_APP
SMALLSRV  IT_EMP  IT_APP    ITINTERN
USERBOX   IT_EMP  ITINTERN  USERS
#
# And a groups for a special tasks
# Allow echo and golf to access our anti-virus-machine
SECURITY  IT_EMP  (,echo,test-domain)  (,golf,test-domain)
#
# machine-based netgroups
# Our main servers
WAR       BIGSRV
FAMINE    BIGSRV
# User india needs access to this server
POLLUTION  BIGSRV  (,india,test-domain)
#
# This one is really important and needs more access restrictions
DEATH     IT_EMP
#
# The anti-virus-machine mentioned above
ONE       SECURITY
#
# Restrict a machine to a single user
TWO       (,hotel,test-domain)
# [...more groups to follow]</programlisting>

      <para>If you are using some kind of database to manage your user
        accounts, you should be able to create the first part of the
        map with your database's report tools.  This way, new users
        will automatically have access to the boxes.</para>

      <para>One last word of caution: It may not always be advisable
        to use machine-based netgroups.  If you are deploying a couple of
        dozen or even hundreds of identical machines for student labs,
        you should use role-based netgroups instead of machine-based
        netgroups to keep the size of the NIS map within reasonable
        limits.</para>
    </sect2>

    <sect2>
      <title>Important Things to Remember</title>

      <para>There are still a couple of things that you will need to do
        differently now that you are in an NIS environment.</para>

      <itemizedlist>
        <listitem>
          <para>Every time you wish to add a user to the lab, you
            must add it to the master NIS server <emphasis>only</emphasis>,
            and <emphasis>you must remember to rebuild the NIS
            maps</emphasis>.  If you forget to do this, the new user will
            not be able to login anywhere except on the NIS master.
            For example, if we needed to add a new user
            <username>jsmith</username> to the lab, we would:</para>

          <screen>&prompt.root; <userinput>pw useradd jsmith</userinput>
&prompt.root; <userinput>cd /var/yp</userinput>
&prompt.root; <userinput>make test-domain</userinput></screen>

          <para>You could also run <command>adduser jsmith</command> instead
            of <command>pw useradd jsmith</command>.</para>
        </listitem>
        <listitem>
          <para><emphasis>Keep the administration accounts out of the
            NIS maps</emphasis>.  You do not want to be propagating
            administrative accounts and passwords to machines that
            will have users that should not have access to those
            accounts.</para>
        </listitem>
        <listitem>
          <para><emphasis>Keep the NIS master and slave secure, and
            minimize their downtime</emphasis>.  If somebody either
            hacks or simply turns off these machines, they have
            effectively rendered many people without the ability to
            login to the lab.</para>

          <para>This is the chief weakness of any centralized administration
            system.  If you do
            not protect your NIS servers, you will have a lot of angry
            users!</para>
        </listitem>
      </itemizedlist>
    </sect2>

    <sect2>
      <title>NIS v1 Compatibility</title>

      <para> FreeBSD's <application>ypserv</application> has some
	support for serving NIS v1 clients.  FreeBSD's NIS
	implementation only uses the NIS v2 protocol, however other
	implementations include support for the v1 protocol for
	backwards compatibility with older systems.  The
	<application>ypbind</application> daemons supplied with these
	systems will try to establish a binding to an NIS v1 server
	even though they may never actually need it (and they may
	persist in broadcasting in search of one even after they
	receive a response from a v2 server).  Note that while support
	for normal client calls is provided, this version of
	<application>ypserv</application> does not handle v1 map
	transfer requests; consequently, it cannot be used as a master
	or slave in conjunction with older NIS servers that only
	support the v1 protocol.  Fortunately, there probably are not
	any such servers still in use today.</para>
    </sect2>

    <sect2 id="network-nis-server-is-client">
      <title>NIS Servers That Are Also NIS Clients</title>

      <para> Care must be taken when running
	<application>ypserv</application> in a multi-server domain
	where the server machines are also NIS clients.  It is
	generally a good idea to force the servers to bind to
	themselves rather than allowing them to broadcast bind
	requests and possibly become bound to each other.  Strange
	failure modes can result if one server goes down and others
	are dependent upon it.  Eventually all the clients will time
	out and attempt to bind to other servers, but the delay
	involved can be considerable and the failure mode is still
	present since the servers might bind to each other all over
	again.</para>

      <para>You can force a host to bind to a particular server by running
	<command>ypbind</command> with the <option>-S</option>
	flag.  If you do not want to do this manually each time you
        reboot your NIS server, you can add the following lines to
        your <filename>/etc/rc.conf</filename>:</para>

      <programlisting>nis_client_enable="YES"	# run client stuff as well
nis_client_flags="-S <replaceable>NIS domain</replaceable>,<replaceable>server</replaceable>"</programlisting>

      <para>See &man.ypbind.8; for further information.</para>
    </sect2>

    <sect2>
      <title>Password Formats</title>
      <indexterm>
        <primary>NIS</primary>
	<secondary>password formats</secondary>
      </indexterm>
      <para>One of the most common issues that people run into when trying
	to implement NIS is password format compatibility.  If your NIS
	server is using DES encrypted passwords, it will only support
	clients that are also using DES.  For example, if you have
	&solaris; NIS clients in your network, then you will almost certainly
	need to use DES encrypted passwords.</para>

      <para>To check which format your servers
	and clients are using, look at <filename>/etc/login.conf</filename>.
	If the host is configured to use DES encrypted passwords, then the
	<literal>default</literal> class will contain an entry like this:</para>

      <programlisting>default:\
	:passwd_format=des:\
	:copyright=/etc/COPYRIGHT:\
	[Further entries elided]</programlisting>

      <para>Other possible values for the <literal>passwd_format</literal>
	capability include <literal>blf</literal> and <literal>md5</literal>
	(for Blowfish and MD5 encrypted passwords, respectively).</para>

      <para>If you have made changes to
	<filename>/etc/login.conf</filename>, you will also need to
	rebuild the login capability database, which is achieved by
	running the following command as
	<username>root</username>:</para>

      <screen>&prompt.root; <userinput>cap_mkdb /etc/login.conf</userinput></screen>

      <note><para>The format of passwords already in
	<filename>/etc/master.passwd</filename> will not be updated
	until a user changes his password for the first time
	<emphasis>after</emphasis> the login capability database is
	rebuilt.</para></note>

      <para>Next, in order to ensure that passwords are encrypted with
	the format that you have chosen, you should also check that
	the <literal>crypt_default</literal> in
	<filename>/etc/auth.conf</filename> gives precedence to your
	chosen password format.  To do this, place the format that you
	have chosen first in the list.  For example, when using DES
	encrypted passwords, the entry would be:</para>

      <programlisting>crypt_default	=	des blf md5</programlisting>

      <para>Having followed the above steps on each of the &os; based
	NIS servers and clients, you can be sure that they all agree
	on which password format is used within your network.  If you
	have trouble authenticating on an NIS client, this is a pretty
	good place to start looking for possible problems.  Remember:
	if you want to deploy an NIS server for a heterogenous
	network, you will probably have to use DES on all systems
	because it is the lowest common standard.</para>
    </sect2>
  </sect1>

  <sect1 id="network-dhcp">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Greg</firstname>
      	  <surname>Sutter</surname>
	  <contrib>Written by </contrib>
        </author>
      </authorgroup>
    </sect1info>
    <title>Automatic Network Configuration (DHCP)</title>

    <sect2>
      <title>What Is DHCP?</title>
      <indexterm>
        <primary>Dynamic Host Configuration Protocol</primary>
        <see>DHCP</see>
      </indexterm>
      <indexterm>
        <primary>Internet Software Consortium (ISC)</primary>
      </indexterm>

      <para>DHCP, the Dynamic Host Configuration Protocol, describes
        the means by which a system can connect to a network and obtain the
        necessary information for communication upon that network.  FreeBSD
        uses the ISC (Internet Software Consortium) DHCP implementation, so
        all implementation-specific information here is for use with the ISC
        distribution.</para>
    </sect2>

    <sect2>
      <title>What This Section Covers</title>

      <para>This section describes both the client-side and
        server-side components of the ISC DHCP system.  The
        client-side program, <command>dhclient</command>, comes
        integrated within FreeBSD, and the server-side portion is
        available from the <filename
        role="package">net/isc-dhcp3-server</filename> port.  The
        &man.dhclient.8;, &man.dhcp-options.5;, and
        &man.dhclient.conf.5; manual pages, in addition to the
        references below, are useful resources.</para>
    </sect2>

    <sect2>
      <title>How It Works</title>
      <indexterm><primary>UDP</primary></indexterm>
      <para>When <command>dhclient</command>, the DHCP client, is
	executed on the client machine, it begins broadcasting
	requests for configuration information.  By default, these
	requests are on UDP port 68.  The server replies on UDP 67,
	giving the client an IP address and other relevant network
	information such as netmask, router, and DNS servers.  All of
	this information comes in the form of a DHCP
	<quote>lease</quote> and is only valid for a certain time
	(configured by the DHCP server maintainer).  In this manner,
	stale IP addresses for clients no longer connected to the
	network can be automatically reclaimed.</para>

      <para>DHCP clients can obtain a great deal of information from
        the server.  An exhaustive list may be found in
        &man.dhcp-options.5;.</para>
    </sect2>

    <sect2>
      <title>FreeBSD Integration</title>

      <para>FreeBSD fully integrates the ISC DHCP client,
        <command>dhclient</command>.  DHCP client support is provided
        within both the installer and the base system, obviating the need
        for detailed knowledge of network configurations on any network
        that runs a DHCP server.  <command>dhclient</command> has been
        included in all FreeBSD distributions since 3.2.</para>
        <indexterm>
          <primary><application>sysinstall</application></primary>
        </indexterm>

        <para>DHCP is supported by
          <application>sysinstall</application>.  When configuring a
          network interface within
          <application>sysinstall</application>, the second question
          asked is: <quote>Do you want to try DHCP configuration of
          the interface?</quote>. Answering affirmatively will
          execute <command>dhclient</command>, and if successful, will
          fill in the network configuration information
          automatically.</para>

        <para>There are two things you must do to have your system use
	  DHCP upon startup:</para>
        <indexterm>
          <primary>DHCP</primary>
          <secondary>requirements</secondary>
        </indexterm>
	<itemizedlist>
	  <listitem>
            <para>Make sure that the <devicename>bpf</devicename>
	      device is compiled into your kernel.  To do this, add
	      <literal>device bpf</literal> (<literal>pseudo-device
	      bpf</literal> under &os;&nbsp;4.X) to your kernel
	      configuration file, and rebuild the kernel.  For more
	      information about building kernels, see <xref
	      linkend="kernelconfig">.</para> <para>The
	      <devicename>bpf</devicename> device is already part of
	      the <filename>GENERIC</filename> kernel that is supplied
	      with FreeBSD, so if you do not have a custom kernel, you
	      should not need to create one in order to get DHCP
	      working.</para>
	    <note>
	      <para>For those who are particularly security conscious,
	        you should be warned that <devicename>bpf</devicename>
		is also the device that allows packet sniffers to work
		correctly (although they still have to be run as
		<username>root</username>).  <devicename>bpf</devicename>
		<emphasis>is</emphasis> required to use DHCP, but if
		you are very sensitive about security, you probably
		should not add <devicename>bpf</devicename> to your
		kernel in the expectation that at some point in the
		future you will be using DHCP.</para>
	    </note>
	  </listitem>
          <listitem>
            <para>Edit your <filename>/etc/rc.conf</filename> to
	      include the following:</para>

            <programlisting>ifconfig_fxp0="DHCP"</programlisting>

            <note>
              <para>Be sure to replace <literal>fxp0</literal> with the
                designation for the interface that you wish to dynamically
                 configure, as described in
		 <xref linkend="config-network-setup">.</para>
            </note>

            <para>If you are using a different location for
              <command>dhclient</command>, or if you wish to pass additional
              flags to <command>dhclient</command>, also include the
              following (editing as necessary):</para>

            <programlisting>dhcp_program="/sbin/dhclient"
dhcp_flags=""</programlisting>
          </listitem>
        </itemizedlist>

        <indexterm>
          <primary>DHCP</primary>
          <secondary>server</secondary>
        </indexterm>
        <para>The DHCP server, <application>dhcpd</application>, is included
          as part of the <filename
          role="package">net/isc-dhcp3-server</filename> port in the ports
          collection.  This port contains the ISC DHCP server and
          documentation.</para>
    </sect2>

    <sect2>
      <title>Files</title>
      <indexterm>
        <primary>DHCP</primary>
        <secondary>configuration files</secondary>
      </indexterm>
      <itemizedlist>
        <listitem><para><filename>/etc/dhclient.conf</filename></para>
          <para><command>dhclient</command> requires a configuration file,
            <filename>/etc/dhclient.conf</filename>.  Typically the file
            contains only comments, the defaults being reasonably sane.  This
            configuration file is described by the &man.dhclient.conf.5;
            manual page.</para>
        </listitem>

        <listitem><para><filename>/sbin/dhclient</filename></para>
          <para><command>dhclient</command> is statically linked and
            resides in <filename>/sbin</filename>.  The &man.dhclient.8;
            manual page gives more information about
            <command>dhclient</command>.</para>
        </listitem>

        <listitem><para><filename>/sbin/dhclient-script</filename></para>
          <para><command>dhclient-script</command> is the FreeBSD-specific
            DHCP client configuration script.  It is described in
            &man.dhclient-script.8;, but should not need any user
            modification to function properly.</para>
        </listitem>

        <listitem><para><filename>/var/db/dhclient.leases</filename></para>
          <para>The DHCP client keeps a database of valid leases in this
            file, which is written as a log.  &man.dhclient.leases.5;
            gives a slightly longer description.</para>
        </listitem>
      </itemizedlist>
    </sect2>

    <sect2>
      <title>Further Reading</title>

      <para>The DHCP protocol is fully described in
        <ulink url="http://www.freesoft.org/CIE/RFC/2131/">RFC 2131</ulink>.
        An informational resource has also been set up at
        <ulink url="http://www.dhcp.org/"></ulink>.</para>
    </sect2>

    <sect2 id="network-dhcp-server">
	<title>Installing and Configuring a DHCP Server</title>

	<sect3>
	  <title>What This Section Covers</title>

	  <para>This section provides information on how to configure
	    a FreeBSD system to act as a DHCP server using the ISC
	    (Internet Software Consortium) implementation of the DHCP
	    suite.</para>

	  <para>The server portion of the suite is not provided as part of
	    FreeBSD, and so you will need to install the
	    <filename role="package">net/isc-dhcp3-server</filename>
	    port to provide this service.  See <xref linkend="ports"> for
	    more information on using the Ports Collection.</para>
	</sect3>

	<sect3>
	  <title>DHCP Server Installation</title>
	  <indexterm>
	    <primary>DHCP</primary>
	    <secondary>installation</secondary>
	  </indexterm>
	  <para>In order to configure your FreeBSD system as a DHCP
	    server, you will need to ensure that the &man.bpf.4;
	    device is compiled into your kernel.  To do this, add
	    <literal>device bpf</literal> (<literal>pseudo-device
	    bpf</literal> under &os;&nbsp;4.X) to your kernel
	    configuration file, and rebuild the kernel.  For more
	    information about building kernels, see <xref
	    linkend="kernelconfig">.</para>

	  <para>The <devicename>bpf</devicename> device is already
	    part of the <filename>GENERIC</filename> kernel that is
	    supplied with FreeBSD, so you do not need to create a custom
	    kernel in order to get DHCP working.</para>

	    <note>
	      <para>Those who are particularly security conscious
	        should note that <devicename>bpf</devicename>
		is also the device that allows packet sniffers to work
		correctly (although such programs still need privileged
		access).  <devicename>bpf</devicename>
		<emphasis>is</emphasis> required to use DHCP, but if
		you are very sensitive about security, you probably
		should not include <devicename>bpf</devicename> in your
		kernel purely because you expect to use DHCP at some
		point in the future.</para>
	    </note>

	  <para>The next thing that you will need to do is edit the sample
	    <filename>dhcpd.conf</filename> which was installed by the
	    <filename role="package">net/isc-dhcp3-server</filename> port.
	    By default, this will be
	    <filename>/usr/local/etc/dhcpd.conf.sample</filename>, and you
	    should copy this to
	    <filename>/usr/local/etc/dhcpd.conf</filename> before proceeding
	    to make changes.</para>
	</sect3>

	<sect3>
	  <title>Configuring the DHCP Server</title>
	  <indexterm>
	    <primary>DHCP</primary>
	    <secondary>dhcpd.conf</secondary>
	  </indexterm>
	  <para><filename>dhcpd.conf</filename> is
	    comprised of declarations regarding subnets and hosts, and is
	    perhaps most easily explained using an example :</para>

	  <programlisting>option domain-name "example.com";<co id="domain-name">
option domain-name-servers 192.168.4.100;<co id="domain-name-servers">
option subnet-mask 255.255.255.0;<co id="subnet-mask">

default-lease-time 3600;<co id="default-lease-time">
max-lease-time 86400;<co id="max-lease-time">
ddns-update-style none;<co id="ddns-update-style">

subnet 192.168.4.0 netmask 255.255.255.0 {
  range 192.168.4.129 192.168.4.254;<co id="range">
  option routers 192.168.4.1;<co id="routers">
}

host mailhost {
  hardware ethernet 02:03:04:05:06:07;<co id="hardware">
  fixed-address mailhost.example.com;<co id="fixed-address">
}</programlisting>

	  <calloutlist>
	    <callout arearefs="domain-name">
	      <para>This option specifies the domain that will be provided
		to clients as the default search domain.  See
		&man.resolv.conf.5; for more information on what this
		means.</para>
	    </callout>

	    <callout arearefs="domain-name-servers">
	      <para>This option specifies a comma separated list of DNS
		servers that the client should use.</para>
	    </callout>

	    <callout arearefs="subnet-mask">
	      <para>The netmask that will be provided to clients.</para>
	    </callout>

	    <callout arearefs="default-lease-time">
	      <para>A client may request a specific length of time that a
		lease will be valid.  Otherwise the server will assign
		a lease with this expiry value (in seconds).</para>
	    </callout>

	    <callout arearefs="max-lease-time">
	      <para>This is the maximum length of time that the server will
		lease for.  Should a client request a longer lease, a lease
		will be issued, although it will only be valid for
		<literal>max-lease-time</literal> seconds.</para>
	    </callout>

	    <callout arearefs="ddns-update-style">
	      <para>This option specifies whether the DHCP server should
		attempt to update DNS when a lease is accepted or released.
		In the ISC implementation, this option is
		<emphasis>required</emphasis>.</para>
	    </callout>

	    <callout arearefs="range">
	      <para>This denotes which IP addresses should be used in
		the pool reserved for allocating to clients.  IP
		addresses between, and including, the ones stated are
		handed out to clients.</para>
	    </callout>

	    <callout arearefs="routers">
	      <para>Declares the default gateway that will be provided to
		clients.</para>
	    </callout>

	    <callout arearefs="hardware">
	      <para>The hardware MAC address of a host (so that the DHCP server
		can recognize a host when it makes a request).</para>
	    </callout>

	    <callout arearefs="fixed-address">
	      <para>Specifies that the host should always be given the
		same IP address.  Note that using a hostname is
		correct here, since the DHCP server will resolve the
		hostname itself before returning the lease
		information.</para>
	    </callout>
	  </calloutlist>

	  <para>Once you have finished writing your
	    <filename>dhcpd.conf</filename>, you can proceed to start the
	    server by issuing the following command:</para>

	  <screen>&prompt.root; <userinput>/usr/local/etc/rc.d/isc-dhcpd.sh start</userinput></screen>

	  <para>Should you need to make changes to the configuration of your
	    server in the future, it is important to note that sending a
	    <literal>SIGHUP</literal> signal to
	    <application>dhcpd</application> does <emphasis>not</emphasis>
	    result in the configuration being reloaded, as it does with most
	    daemons.  You will need to send a <literal>SIGTERM</literal>
	    signal to stop the process, and then restart it using the command
	    above.</para>
	</sect3>

	<sect3>
	  <title>Files</title>
	  <indexterm>
	    <primary>DHCP</primary>
	    <secondary>configuration files</secondary>
	  </indexterm>
	  <itemizedlist>
	    <listitem><para><filename>/usr/local/sbin/dhcpd</filename></para>
	      <para><application>dhcpd</application> is statically linked and
		resides in <filename>/usr/local/sbin</filename>.  The
		&man.dhcpd.8; manual page installed with the
		port gives more information about
		<application>dhcpd</application>.</para>
	    </listitem>

	    <listitem><para><filename>/usr/local/etc/dhcpd.conf</filename></para>
	      <para><application>dhcpd</application> requires a configuration
		file, <filename>/usr/local/etc/dhcpd.conf</filename> before it
		will start providing service to clients.  This file needs to
		contain all the information that should be provided to clients
		that are being serviced, along with information regarding the
		operation of the server.  This configuration file is described
		by the &man.dhcpd.conf.5; manual page installed
		by the port.</para>
	    </listitem>

	    <listitem><para><filename>/var/db/dhcpd.leases</filename></para>
	      <para>The DHCP server keeps a database of leases it has issued
		in this file, which is written as a log.  The manual page
		&man.dhcpd.leases.5;, installed by the port
		gives a slightly longer description.</para>
	    </listitem>

	    <listitem><para><filename>/usr/local/sbin/dhcrelay</filename></para>
	      <para><application>dhcrelay</application> is used in advanced
		environments where one DHCP server forwards a request from a
		client to another DHCP server on a separate network.  If you
		require this functionality, then install the <filename
		role="package">net/isc-dhcp3-relay</filename> port.  The
		&man.dhcrelay.8; manual page provided with the
		port contains more detail.</para>
	    </listitem>
	  </itemizedlist>
	</sect3>

      </sect2>

  </sect1>

  <sect1 id="network-dns">
    <sect1info>
      <authorgroup>
        <author>
          <firstname>Chern</firstname>
          <surname>Lee</surname>
          <contrib>Contributed by </contrib>
        </author>
      </authorgroup>
    </sect1info>
    <title>Domain Name System (DNS)</title>

    <sect2>
      <title>Overview</title>
      <indexterm><primary>BIND</primary></indexterm>

      <para>FreeBSD utilizes, by default, a version of BIND (Berkeley
        Internet Name Domain), which is the most common implementation
        of the DNS protocol.  DNS is the protocol through which names
        are mapped to IP addresses, and vice versa.  For example, a
        query for <hostid role="fqdn">www.FreeBSD.org</hostid> will
        receive a reply with the IP address of The FreeBSD Project's
        web server, whereas, a query for <hostid
        role="fqdn">ftp.FreeBSD.org</hostid> will return the IP
        address of the corresponding FTP machine.  Likewise, the
        opposite can happen.  A query for an IP address can resolve
        its hostname.  It is not necessary to run a name server to
        perform DNS lookups on a system.
      </para>

      <indexterm><primary>DNS</primary></indexterm>
      <para>DNS is coordinated across the Internet through a somewhat
        complex system of authoritative root name servers, and other
        smaller-scale name servers who host and cache individual domain
        information.
      </para>

      <para>
        This document refers to BIND 8.x, as it is the stable version
	used in &os;.  Versions of &os;&nbsp;5.3 and beyond include
	<acronym>BIND</acronym>9 and the configuration instructions
	may be found later in this chapter.  Users of &os;&nbsp;5.2
	and other previous versions may install <acronym>BIND</acronym>9
	from the <filename role="package">net/bind9</filename> port.</para>

      <para>
        RFC1034 and RFC1035 dictate the DNS protocol.
      </para>

      <para>
        Currently, BIND is maintained by the
        Internet Software Consortium <ulink url="http://www.isc.org/"></ulink>.
      </para>
    </sect2>

    <sect2>
      <title>Terminology</title>

      <para>To understand this document, some terms related to DNS must be
	understood.</para>

      <indexterm><primary>resolver</primary></indexterm>
      <indexterm><primary>reverse DNS</primary></indexterm>
      <indexterm><primary>root zone</primary></indexterm>
      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	  <colspec colwidth="1*">
	  <colspec colwidth="3*">

	  <thead>
	    <row>
	      <entry>Term</entry>
	      <entry>Definition</entry>
	    </row>
	  </thead>

	  <tbody>
	    <row>
	      <entry>Forward DNS</entry>
	      <entry>Mapping of hostnames to IP addresses</entry>
	    </row>

	    <row>
	      <entry>Origin</entry>
	      <entry>Refers to the domain covered in a particular zone
		file</entry>
	    </row>

	    <row>
	      <entry><application>named</application>, BIND, name server</entry>
	      <entry>Common names for the BIND name server package within
		FreeBSD</entry>
	    </row>

	    <row>
	      <entry>Resolver</entry>
	      <entry>A system process through which a
		machine queries a name server for zone information</entry>
	    </row>

	    <row>
	      <entry>Reverse DNS</entry>
	      <entry>The opposite of forward DNS; mapping of IP addresses to
		hostnames</entry>
	    </row>

	    <row>
	      <entry>Root zone</entry>

	      <entry>The beginning of the Internet zone hierarchy.
		All zones fall under the root zone, similar to how
		all files in a file system fall under the root directory.</entry>
	    </row>

	    <row>
	      <entry>Zone</entry>
	      <entry>An individual domain, subdomain, or portion of the DNS administered by
		the same authority</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>

      <indexterm>
	<primary>zones</primary>
	<secondary>examples</secondary>
      </indexterm>

      <para>Examples of zones:
      </para>
      <itemizedlist>
        <listitem>
          <para><hostid>.</hostid> is the root zone</para>
        </listitem>
        <listitem>
          <para><hostid>org.</hostid> is a zone under the root zone</para>
        </listitem>
        <listitem>
          <para><hostid role="domainname">example.org.</hostid> is a
          zone under the <hostid>org.</hostid> zone</para>
        </listitem>
        <listitem>
          <para><hostid role="domainname">foo.example.org.</hostid> is
            a subdomain, a zone under the <hostid
            role="domainname">example.org.</hostid> zone</para>
        </listitem>
        <listitem>
          <para>
            <hostid>1.2.3.in-addr.arpa</hostid> is a zone referencing
	    all IP addresses which fall under the <hostid
	    role="ipaddr">3.2.1.*</hostid> IP space.
          </para>
        </listitem>
      </itemizedlist>

      <para>As one can see, the more specific part of a hostname
        appears to its left.  For example, <hostid
        role="domainname">example.org.</hostid> is more specific than
        <hostid>org.</hostid>, as <hostid>org.</hostid> is more
        specific than the root zone.  The layout of each part of a
        hostname is much like a filesystem: the
        <filename>/dev</filename> directory falls within the root, and
        so on.</para>


    </sect2>

    <sect2>
      <title>Reasons to Run a Name Server</title>

      <para>Name servers usually come in two forms: an authoritative
	name server, and a caching name server.</para>

      <para>An authoritative name server is needed when:</para>

      <itemizedlist>
	<listitem>
	  <para>one wants to serve DNS information to the
	    world, replying authoritatively to queries.</para>
	</listitem>
	<listitem>
	  <para>a domain, such as <hostid role="domainname">example.org</hostid>, is
	    registered and IP addresses need to be assigned to hostnames
	    under it.</para>
	</listitem>
	<listitem>
	  <para>an IP address block requires reverse DNS entries (IP to
	    hostname).</para>
	</listitem>
	<listitem>
	  <para>a backup name server, called a slave, must reply to queries
	    when the primary is down or inaccessible.</para>
	  </listitem>
      </itemizedlist>

      <para>A caching name server is needed when:</para>

      <itemizedlist>
	<listitem>
	  <para>a local DNS server may cache and respond more quickly
	    than querying an outside name server.</para>
	</listitem>
	<listitem>
	  <para>a reduction in overall network traffic is desired (DNS
	    traffic has been measured to account for 5% or more of total
	    Internet traffic).</para>
	</listitem>
      </itemizedlist>

      <para>When one queries for <hostid
	role="fqdn">www.FreeBSD.org</hostid>, the resolver usually
	queries the uplink ISP's name server, and retrieves the reply.
	With a local, caching DNS server, the query only has to be
	made once to the outside world by the caching DNS server.
	Every additional query will not have to look to the outside of
	the local network, since the information is cached
	locally.</para>

    </sect2>

    <sect2>
      <title>How It Works</title>
      <para>In FreeBSD, the BIND daemon is called
	<application>named</application> for obvious reasons.</para>

      <informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	  <thead>
	    <row>
	      <entry>File</entry>
	      <entry>Description</entry>
	    </row>
	  </thead>

	  <tbody>
	    <row>
	      <entry><application>named</application></entry>
	      <entry>the BIND daemon</entry>
	    </row>

	    <row>
	      <entry><command>ndc</command></entry>
	      <entry>name daemon control program</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/namedb</filename></entry>
	      <entry>directory where BIND zone information resides</entry>
	    </row>

	    <row>
	      <entry><filename>/etc/namedb/named.conf</filename></entry>
	      <entry>daemon configuration file</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>

      <para>
        Zone files are usually contained within the
        <filename>/etc/namedb</filename>
        directory, and contain the DNS zone information
	served by the name server.
      </para>
    </sect2>

    <sect2>
      <title>Starting BIND</title>
      <indexterm>
        <primary>BIND</primary>
	<secondary>starting</secondary>
      </indexterm>
      <para>
        Since BIND is installed by default, configuring it all is
        relatively simple.
      </para>
      <para>
        To ensure the <application>named</application> daemon is
         started at boot, put the following line in
         <filename>/etc/rc.conf</filename>:
      </para>
      <programlisting>named_enable="YES"</programlisting>
      <para>To start the daemon manually (after configuring it):</para>
      <screen>&prompt.root; <userinput>ndc start</userinput></screen>
    </sect2>

    <sect2>
      <title>Configuration Files</title>
      <indexterm>
        <primary>BIND</primary>
	<secondary>configuration files</secondary>
      </indexterm>
      <sect3>
        <title>Using <command>make-localhost</command></title>
        <para>Be sure to:
        </para>
        <screen>&prompt.root; <userinput>cd /etc/namedb</userinput>
&prompt.root; <userinput>sh make-localhost</userinput></screen>
        <para>to properly create the local reverse DNS zone file in
          <filename>/etc/namedb/localhost.rev</filename>.
        </para>
      </sect3>

      <sect3>
        <title><filename>/etc/namedb/named.conf</filename></title>

        <programlisting>// &dollar;FreeBSD$
//
// Refer to the named(8) manual page for details.  If you are ever going
// to setup a primary server, make sure you've understood the hairy
// details of how DNS is working.  Even with simple mistakes, you can
// break connectivity for affected parties, or cause huge amount of
// useless Internet traffic.

options {
        directory "/etc/namedb";

// In addition to the "forwarders" clause, you can force your name
// server to never initiate queries of its own, but always ask its
// forwarders only, by enabling the following line:
//
//      forward only;

// If you've got a DNS server around at your upstream provider, enter
// its IP address here, and enable the line below.  This will make you
// benefit from its cache, thus reduce overall DNS traffic in the
Internet.
/*
        forwarders {
                127.0.0.1;
        };
*/</programlisting>

        <para>
	  Just as the comment says, to benefit from an uplink's cache,
          <literal>forwarders</literal> can be enabled here.  Under normal
          circumstances, a name server will recursively query the Internet
          looking at certain name servers until it finds the answer it is
          looking for.  Having this enabled will have it query the uplink's
          name server (or name server provided) first, taking advantage of
          its cache.  If the uplink name server in question is a heavily
          trafficked, fast name server, enabling this may be worthwhile.
        </para>

	<warning><para><hostid role="ipaddr">127.0.0.1</hostid>
            will <emphasis>not</emphasis> work here.
            Change this IP address to a name server at your uplink.</para>
        </warning>

        <programlisting>        /*
         * If there is a firewall between you and name servers you want
         * to talk to, you might need to uncomment the query-source
         * directive below.  Previous versions of BIND always asked
         * questions using port 53, but BIND 8.1 uses an unprivileged
         * port by default.
         */
        // query-source address * port 53;

        /*
         * If running in a sandbox, you may have to specify a different
         * location for the dumpfile.
         */
        // dump-file "s/named_dump.db";
};

// Note: the following will be supported in a future release.
/*
host { any; } {
        topology {
                127.0.0.0/8;
        };
};
*/

// Setting up secondaries is way easier and the rough picture for this
// is explained below.
//
// If you enable a local name server, don't forget to enter 127.0.0.1
// into your /etc/resolv.conf so this server will be queried first.
// Also, make sure to enable it in /etc/rc.conf.

zone "." {
        type hint;
        file "named.root";
};

zone "0.0.127.IN-ADDR.ARPA" {
        type master;
        file "localhost.rev";
};

zone
"0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.INT" {
        type master;
        file "localhost.rev";
};

// NB: Do not use the IP addresses below, they are faked, and only
// serve demonstration/documentation purposes!
//
// Example secondary config entries.  It can be convenient to become
// a secondary at least for the zone where your own domain is in.  Ask
// your network administrator for the IP address of the responsible
// primary.
//
// Never forget to include the reverse lookup (IN-ADDR.ARPA) zone!
// (This is the first bytes of the respective IP address, in reverse
// order, with ".IN-ADDR.ARPA" appended.)
//
// Before starting to setup a primary zone, better make sure you fully
// understand how DNS and BIND works, however.  There are sometimes
// unobvious pitfalls.  Setting up a secondary is comparably simpler.
//
// NB: Don't blindly enable the examples below. :-)  Use actual names
// and addresses instead.
//
// NOTE!!! FreeBSD runs BIND in a sandbox (see named_flags in rc.conf).
// The directory containing the secondary zones must be write accessible
// to BIND.  The following sequence is suggested:
//
//      mkdir /etc/namedb/s
//      chown bind:bind /etc/namedb/s
//      chmod 750 /etc/namedb/s</programlisting>

	<para>For more information on running BIND in a sandbox, see
	  <link linkend="network-named-sandbox">Running named in a sandbox</link>.
	</para>

	<programlisting>/*
zone "example.com" {
        type slave;
        file "s/example.com.bak";
        masters {
                192.168.1.1;
        };
};

zone "0.168.192.in-addr.arpa" {
        type slave;
        file "s/0.168.192.in-addr.arpa.bak";
        masters {
                192.168.1.1;
        };
};
*/</programlisting>
        <para>In <filename>named.conf</filename>, these are examples of slave
	  entries for a forward and reverse zone.</para>

        <para>For each new zone served, a new zone entry must be added to
	  <filename>named.conf</filename>.</para>

        <para>For example, the simplest zone entry for
	  <hostid role="domainname">example.org</hostid> can look like:</para>

        <programlisting>zone "example.org" {
	type master;
	file "example.org";
};</programlisting>

	<para>The zone is a master, as indicated by the <option>type</option>
	  statement, holding its zone information in
	  <filename>/etc/namedb/example.org</filename> indicated by
	  the <option>file</option> statement.</para>

        <programlisting>zone "example.org" {
	type slave;
	file "example.org";
};</programlisting>

        <para>In the slave case, the zone information is transferred from
	  the master name server for the particular zone, and saved in the
	  file specified.  If and when the master server dies or is
	  unreachable, the slave name server will have the transferred
	  zone information and will be able to serve it.</para>
      </sect3>

      <sect3>
        <title>Zone Files</title>
        <para>
          An example master zone file for <hostid
	  role="domainname">example.org</hostid> (existing within
	  <filename>/etc/namedb/example.org</filename>) is as follows:
        </para>

        <programlisting>$TTL 3600

example.org. IN SOA ns1.example.org. admin.example.org. (
                        5               ; Serial
                        10800           ; Refresh
                        3600            ; Retry
                        604800          ; Expire
                        86400 )         ; Minimum TTL

; DNS Servers
@       IN NS           ns1.example.org.
@       IN NS           ns2.example.org.

; Machine Names
localhost       IN A    127.0.0.1
ns1             IN A    3.2.1.2
ns2             IN A    3.2.1.3
mail            IN A    3.2.1.10
@               IN A    3.2.1.30

; Aliases
www             IN CNAME        @

; MX Record
@               IN MX   10      mail.example.org.</programlisting>

        <para>
          Note that every hostname ending in a <quote>.</quote> is an
          exact hostname, whereas everything without a trailing
          <quote>.</quote> is referenced to the origin.  For example,
          <literal>www</literal> is translated into
          <literal>www.<replaceable>origin</replaceable></literal>.
          In our fictitious zone file, our origin is
          <hostid>example.org.</hostid>, so <literal>www</literal>
          would translate to <hostid>www.example.org.</hostid>
        </para>

        <para>
          The format of a zone file follows:
        </para>
        <programlisting>recordname      IN recordtype   value</programlisting>

	<indexterm>
	  <primary>DNS</primary>
	  <secondary>records</secondary>
	</indexterm>
        <para>
          The most commonly used DNS records:
        </para>

	<variablelist>
	  <varlistentry>
	    <term>SOA</term>

	    <listitem><para>start of zone authority</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term>NS</term>

	    <listitem><para>an authoritative name server</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term>A</term>

	    <listitem><para>a host address</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term>CNAME</term>

	    <listitem><para>the canonical name for an alias</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term>MX</term>

	    <listitem><para>mail exchanger</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term>PTR</term>

	    <listitem><para>a domain name pointer (used in reverse DNS)
	      </para></listitem>
	  </varlistentry>
	</variablelist>

        <programlisting>
example.org. IN SOA ns1.example.org. admin.example.org. (
                        5               ; Serial
                        10800           ; Refresh after 3 hours
                        3600            ; Retry after 1 hour
                        604800          ; Expire after 1 week
                        86400 )         ; Minimum TTL of 1 day</programlisting>



	<variablelist>
	  <varlistentry>
	    <term><hostid role="domainname">example.org.</hostid></term>

	    <listitem><para>the domain name, also the origin for this
		zone file.</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><hostid role="fqdn">ns1.example.org.</hostid></term>

	    <listitem><para>the primary/authoritative name server for this
		zone.</para></listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>admin.example.org.</literal></term>

	    <listitem><para>the responsible person for this zone,
		email address with <quote>@</quote>
          replaced.  (<email>admin@example.org</email> becomes
		<literal>admin.example.org</literal>)</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>5</literal></term>

	      <listitem><para>the serial number of the file.  This
		  must be incremented each time the zone file is
		  modified.  Nowadays, many admins prefer a
		  <literal>yyyymmddrr</literal> format for the serial
		  number.  <literal>2001041002</literal> would mean
		  last modified 04/10/2001, the latter
		  <literal>02</literal> being the second time the zone
		  file has been modified this day.  The serial number
		  is important as it alerts slave name servers for a
		  zone when it is updated.</para>
	      </listitem>
	  </varlistentry>
	</variablelist>

        <programlisting>
@       IN NS           ns1.example.org.</programlisting>

        <para>
          This is an NS entry.  Every name server that is going to reply
          authoritatively for the zone must have one of these entries.
	  The <literal>@</literal> as seen here could have been
	  <hostid role="domainname">example.org.</hostid>
	  The <literal>@</literal> translates to the origin.
        </para>

        <programlisting>
localhost       IN A    127.0.0.1
ns1             IN A    3.2.1.2
ns2             IN A    3.2.1.3
mail            IN A    3.2.1.10
@               IN A    3.2.1.30</programlisting>

        <para>
          The A record indicates machine names.  As seen above,
          <hostid role="fqdn">ns1.example.org</hostid> would resolve
          to <hostid role="ipaddr">3.2.1.2</hostid>.  Again, the
          origin symbol, <literal>@</literal>, is used here, thus
          meaning <hostid role="domainname">example.org</hostid> would
          resolve to <hostid role="ipaddr">3.2.1.30</hostid>.
        </para>

        <programlisting>
www             IN CNAME        @</programlisting>

        <para>
          The canonical name record is usually used for giving aliases
          to a machine.  In the example, <hostid>www</hostid> is
          aliased to the machine addressed to the origin, or
          <hostid role="domainname">example.org</hostid>
          (<hostid role="ipaddr">3.2.1.30</hostid>).
          CNAMEs can be used to provide alias
          hostnames, or round robin one hostname among multiple
          machines.
        </para>

	<indexterm>
	  <primary>MX record</primary>
	</indexterm>

        <programlisting>
@               IN MX   10      mail.example.org.</programlisting>

        <para>
          The MX record indicates which mail
          servers are responsible for handling incoming mail for the
          zone.  <hostid role="fqdn">mail.example.org</hostid> is the
          hostname of the mail server, and 10 being the priority of
          that mail server.
        </para>

        <para>
          One can have several mail servers, with priorities of 3, 2,
          1.  A mail server attempting to deliver to <hostid
          role="domainname">example.org</hostid> would first try the
          highest priority MX, then the second highest, etc, until the
          mail can be properly delivered.
        </para>

        <para>
          For in-addr.arpa zone files (reverse DNS), the same format is
          used, except with PTR entries instead of
	  A or CNAME.
        </para>

        <programlisting>$TTL 3600

1.2.3.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. (
                        5               ; Serial
                        10800           ; Refresh
                        3600            ; Retry
                        604800          ; Expire
                        3600 )          ; Minimum

@       IN NS   ns1.example.org.
@       IN NS   ns2.example.org.

2       IN PTR  ns1.example.org.
3       IN PTR  ns2.example.org.
10      IN PTR  mail.example.org.
30      IN PTR  example.org.</programlisting>

        <para>This file gives the proper IP address to hostname
          mappings of our above fictitious domain.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>Caching Name Server</title>
      <indexterm>
        <primary>BIND</primary>
        <secondary>caching name server</secondary>
      </indexterm>

      <para>A caching name server is a name server that is not
        authoritative for any zones.  It simply asks queries of its
        own, and remembers them for later use.  To set one up, just
        configure the name server as usual, omitting any inclusions of
        zones.</para>
    </sect2>

    <sect2 id="network-named-sandbox">
      <title>Running <application>named</application> in a Sandbox</title>
      <indexterm>
        <primary>BIND</primary>
        <secondary>running in a sandbox</secondary>
      </indexterm>

      <indexterm>
        <primary><command>chroot</command></primary>
      </indexterm>
      <para>For added security you may want to run &man.named.8; as an
	unprivileged user, and configure it to &man.chroot.8; into a
	sandbox directory.  This makes everything outside of the
	sandbox inaccessible to the <application>named</application>
	daemon.  Should <application>named</application> be
	compromised, this will help to reduce the damage that can be
	caused.  By default, FreeBSD has a user and a group called
	<groupname>bind</groupname>, intended for this use.</para>

      <note><para>Various people would recommend that instead of configuring
	<application>named</application> to <command>chroot</command>, you
	should run <application>named</application> inside a &man.jail.8;.
	This section does not attempt to cover this situation.</para>
      </note>

      <para>Since <application>named</application> will not be able to
	access anything outside of the sandbox (such as shared
	libraries, log sockets, and so on), there are a number of steps
	that need to be followed in order to allow
	<application>named</application> to function correctly.  In the
	following checklist, it is assumed that the path to the sandbox
	is <filename>/etc/namedb</filename> and that you have made no
	prior modifications to the contents of this directory.  Perform
	the following steps as <username>root</username>:</para>

      <itemizedlist>
	<listitem>
	  <para>Create all directories that <application>named</application>
	    expects to see:</para>

	  <screen>&prompt.root; <userinput>cd /etc/namedb</userinput>
&prompt.root; <userinput>mkdir -p bin dev etc var/tmp var/run master slave</userinput>
&prompt.root; <userinput>chown bind:bind slave var/*</userinput><co id="chown-slave"></screen>



	  <calloutlist>
	    <callout arearefs="chown-slave">
	      <para><application>named</application> only needs write access to
		these directories, so that is all we give it.</para>
	    </callout>
	  </calloutlist>
	</listitem>

	<listitem>
	  <para>Rearrange and create basic zone and configuration files:</para>
	  <screen>&prompt.root; <userinput>cp /etc/localtime etc</userinput><co id="localtime">
&prompt.root; <userinput>mv named.conf etc && ln -sf etc/named.conf</userinput>
&prompt.root; <userinput>mv named.root master</userinput>
<!-- I don't like this next bit -->
&prompt.root; <userinput>sh make-localhost && mv localhost.rev localhost-v6.rev master</userinput>
&prompt.root; <userinput>cat > master/named.localhost
$ORIGIN localhost.
$TTL 6h
@	IN	SOA	localhost. postmaster.localhost. (
			1	; serial
			3600	; refresh
			1800	; retry
			604800	; expiration
			3600 )	; minimum
	IN	NS	localhost.
	IN	A		127.0.0.1
^D</userinput></screen>

	  <calloutlist>
	    <callout arearefs="localtime">
	      <para>This allows <application>named</application> to log the
		correct time to &man.syslogd.8;.</para>
	    </callout>
	  </calloutlist>
	</listitem>

	<listitem>

        <indexterm><primary>syslog</primary></indexterm>
        <indexterm><primary>log files</primary>
	  <secondary>named</secondary></indexterm>

	  <para>If you are running a version of &os; prior to 4.9-RELEASE, build a statically linked copy of
	    <application>named-xfer</application>, and copy it into the sandbox:</para>

	      <screen>&prompt.root; <userinput>cd /usr/src/lib/libisc</userinput>
&prompt.root; <userinput>make cleandir && make cleandir && make depend && make all</userinput>
&prompt.root; <userinput>cd /usr/src/lib/libbind</userinput>
&prompt.root; <userinput>make cleandir && make cleandir && make depend && make all</userinput>
&prompt.root; <userinput>cd /usr/src/libexec/named-xfer</userinput>
&prompt.root; <userinput>make cleandir && make cleandir && make depend && make NOSHARED=yes all</userinput>
&prompt.root; <userinput>cp named-xfer /etc/namedb/bin && chmod 555 /etc/namedb/bin/named-xfer</userinput><co id="clean-cruft"></screen>

	  <para>After your statically linked
	    <command>named-xfer</command> is installed some cleaning up
	    is required, to avoid leaving stale copies of libraries or
	    programs in your source tree:</para>

	  <screen>&prompt.root; <userinput>cd /usr/src/lib/libisc</userinput>
&prompt.root; <userinput>make cleandir</userinput>
&prompt.root; <userinput>cd /usr/src/lib/libbind</userinput>
&prompt.root; <userinput>make cleandir</userinput>
&prompt.root; <userinput>cd /usr/src/libexec/named-xfer</userinput>
&prompt.root; <userinput>make cleandir</userinput></screen>

	  <calloutlist>
	    <callout arearefs="clean-cruft">
	      <para>This step has been reported to fail occasionally.  If this
		happens to you, then issue the command:</para>

	      <screen>&prompt.root; <userinput>cd /usr/src && make cleandir && make cleandir</userinput></screen>

	      <para>and delete your <filename>/usr/obj</filename> tree:</para>

	      <screen>&prompt.root; <userinput>rm -fr /usr/obj && mkdir /usr/obj</userinput></screen>

		<para>This will clean out any <quote>cruft</quote> from your
		  source tree, and retrying the steps above should then work.</para>
	    </callout>
	  </calloutlist>

	  <para>If you are running &os; version 4.9-RELEASE or later,
	    then the copy of <command>named-xfer</command> in
	    <filename>/usr/libexec</filename> is statically linked by
	    default, and you can simply use &man.cp.1; to copy it into
	    your sandbox.</para>
	</listitem>

	<listitem>
	  <para>Make a <filename>dev/null</filename> that
	    <application>named</application> can see and write to:</para>

	  <screen>&prompt.root; <userinput>cd /etc/namedb/dev && mknod null c 2 2</userinput>
&prompt.root; <userinput>chmod 666 null</userinput></screen>
	</listitem>

	<listitem>
	  <para>Symlink <filename> /var/run/ndc</filename> to
	    <filename>/etc/namedb/var/run/ndc</filename>:</para>

	  <screen>&prompt.root; <userinput>ln -sf /etc/namedb/var/run/ndc /var/run/ndc</userinput></screen>

	  <note>
	    <para>This simply avoids having to specify the
	      <option>-c</option> option to &man.ndc.8; every time you
	      run it.  Since the contents of
	      <filename>/var/run</filename> are deleted on boot, it may
	      be useful to add this command to
	      <username>root</username>'s &man.crontab.5;, using the
	      <option>@reboot</option> option.</para>
	  </note>

	</listitem>

	<listitem>

        <indexterm><primary>syslog</primary></indexterm>
        <indexterm><primary>log files</primary>
	  <secondary>named</secondary></indexterm>

	  <para>Configure &man.syslogd.8; to create an extra
	    <devicename>log</devicename> socket that
	    <application>named</application> can write to.  To do this,
	    add <literal>-l /etc/namedb/dev/log</literal> to the
	    <varname>syslogd_flags</varname> variable in
	    <filename>/etc/rc.conf</filename>.</para>
	</listitem>

	<listitem>

          <indexterm><primary><command>chroot</command></primary></indexterm>

	  <para>Arrange to have <application>named</application> start
	    and <command>chroot</command> itself to the sandbox by
	    adding the following to
	    <filename>/etc/rc.conf</filename>:</para>

	  <programlisting>named_enable="YES"
named_flags="-u bind -g bind -t /etc/namedb /etc/named.conf"</programlisting>

	  <note>
	    <para>Note that the configuration file
	    <replaceable>/etc/named.conf</replaceable> is denoted by a full
	    pathname <emphasis>relative to the sandbox</emphasis>, i.e. in
	    the line above, the file referred to is actually
	    <filename>/etc/namedb/etc/named.conf</filename>.</para>
	  </note>
	</listitem>
      </itemizedlist>

      <para>The next step is to edit
	<filename>/etc/namedb/etc/named.conf</filename> so that
	<application>named</application> knows which zones to load and
	where to find them on the disk.  There follows a commented
	example (anything not specifically commented here is no
	different from the setup for a DNS server not running in a
	sandbox):</para>

	<programlisting>options {
        directory "/";<co id="directory">
        named-xfer "/bin/named-xfer";<co id="named-xfer">
        version "";		// Don't reveal BIND version
        query-source address * port 53;
};
// ndc control socket
controls {
        unix "/var/run/ndc" perm 0600 owner 0 group 0;
};
// Zones follow:
zone "localhost" IN {
        type master;
        file "master/named.localhost";<co id="master">
        allow-transfer { localhost; };
        notify no;
};
zone "0.0.127.in-addr.arpa" IN {
        type master;
        file "master/localhost.rev";
        allow-transfer { localhost; };
        notify no;
};
zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.int" {
	type master;
	file "master/localhost-v6.rev";
	allow-transfer { localhost; };
	notify no;
};
zone "." IN {
        type hint;
        file "master/named.root";
};
zone "private.example.net" in {
        type master;
        file "master/private.example.net.db";
	allow-transfer { 192.168.10.0/24; };
};
zone "10.168.192.in-addr.arpa" in {
        type slave;
        masters { 192.168.10.2; };
        file "slave/192.168.10.db";<co id="slave">
};</programlisting>

      <calloutlist>
	<callout arearefs="directory">
	  <para>The
	    <literal>directory</literal> statement is specified as
	    <filename>/</filename>, since all files that
	    <application>named</application> needs are within this
	    directory (recall that this is equivalent to a
	    <quote>normal</quote> user's
	    <filename>/etc/namedb</filename>).</para>
	</callout>

	<callout arearefs="named-xfer">
	  <para>Specifies the full path
	    to the <command>named-xfer</command> binary (from
	    <application>named</application>'s frame of reference).  This
	    is necessary since <application>named</application> is
	    compiled to look for <command>named-xfer</command> in
	    <filename>/usr/libexec</filename> by default.</para>
	</callout>
	<callout arearefs="master"><para>Specifies the filename (relative
	  to the <literal>directory</literal> statement above) where
	  <application>named</application> can find the zone file for this
	  zone.</para>
	</callout>
	<callout arearefs="slave"><para>Specifies the filename
	    (relative to the <literal>directory</literal> statement above)
	    where <application>named</application> should write a copy of
	    the zone file for this zone after successfully transferring it
	    from the master server.  This is why we needed to change the
	    ownership of the directory <filename>slave</filename> to
	    <groupname>bind</groupname> in the setup stages above.</para>
	</callout>
      </calloutlist>

      <para>After completing the steps above, either reboot your
	server or restart &man.syslogd.8; and start &man.named.8;, making
	sure to use the new options specified in
	<varname>syslogd_flags</varname> and
	<varname>named_flags</varname>.  You should now be running a
	sandboxed copy of <application>named</application>!</para>

    </sect2>

    <sect2>
      <title>Security</title>

      <para>Although BIND is the most common implementation of DNS,
        there is always the issue of security.  Possible and
        exploitable security holes are sometimes found.
      </para>

      <para>
        It is a good idea to read <ulink
        url="http://www.cert.org/">CERT</ulink>'s security advisories and
	to subscribe to the &a.security-notifications;
        to stay up to date with the current Internet and FreeBSD security
        issues.
      </para>

      <tip><para>If a problem arises, keeping sources up to date and
        having a fresh build of <application>named</application> would
        not hurt.</para></tip>
    </sect2>

    <sect2>
      <title>Further Reading</title>

      <para>BIND/<application>named</application> manual pages:
      &man.ndc.8; &man.named.8; &man.named.conf.5;</para>

      <itemizedlist>
	<listitem>
	  <para><ulink
	      url="http://www.isc.org/products/BIND/">Official ISC BIND
	      Page</ulink></para>
	</listitem>

	<listitem>
	  <para><ulink
	  url="http://www.nominum.com/getOpenSourceResource.php?id=6">
	  BIND FAQ</ulink></para>
	</listitem>

	<listitem>
	  <para><ulink url="http://www.oreilly.com/catalog/dns4/">O'Reilly
         DNS and BIND 4th Edition</ulink></para>
	</listitem>

	<listitem>
	  <para><ulink
	      url="ftp://ftp.isi.edu/in-notes/rfc1034.txt">RFC1034
	      - Domain Names - Concepts and Facilities</ulink></para>
	</listitem>

	<listitem>
	  <para><ulink
	      url="ftp://ftp.isi.edu/in-notes/rfc1035.txt">RFC1035
	      - Domain Names - Implementation and Specification</ulink></para>
	</listitem>
      </itemizedlist>
    </sect2>
  </sect1>

  <sect1 id="network-bind9">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Tom</firstname>
	  <surname>Rhodes</surname>
	  <contrib>Written by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title><acronym>BIND</acronym>9 and &os;</title>

<!-- This section is here to get users up with BIND9 configurations!  It
  does not cover the terminology, theoretical discussion (why run a name
  server) or the further reading which is still in the previous section.
  I did things this way to avoid repetition of content and obviously we
  cannot just remove the previous section since other supported releases
  use it.  When the previous section is removed then those comments
  should be moved here.  // Tom Rhodes -->

    <indexterm><primary>bind9</primary>
      <secondary>setting up</secondary></indexterm>

    <para>The release of &os;&nbsp;5.3 brought the
      <acronym>BIND</acronym>9 <acronym>DNS</acronym> server software
      into the distribution.  New security features, a new file system
      layout and automated &man.chroot.8; configuration came with the
      import.  This section has been written in two parts, the first
      will discuss new features and their configuration; the latter
      will cover upgrades to aid in move to &os;&nbsp;5.3.  From this
      moment on, the server will be referred to simply as
      &man.named.8; in place of <acronym>BIND</acronym>.  This section
      skips over the terminology described in the previous section as
      well as some of the theoretical discussions; thus, it is
      recommended that the previous section be consulted before reading
      any further here.</para>

    <para>Configuration files for <application>named</application> currently
      reside in
      <filename class="directory">/var/named/etc/namedb/</filename> and
      will need modification before use.  This is where most of the
      configuration will be performed.</para>

    <sect2>
      <title>Configuration of a Master Zone</title>

      <para>To configure a master zone visit
	<filename class="directory">/var/named/etc/namedb/</filename>
	and run the following command:</para>

      <screen>&prompt.root; <userinput>sh make-localhost</userinput></screen>

      <para>If all went well a new file should exist in the
	<filename class="directory">master</filename> directory.  The
	filenames should be <filename>localhost.rev</filename> for
	the local domain name and <filename>localhost-v6.rev</filename>
	for <acronym>IPv6</acronym> configurations.  As the default
	configuration file, configuration for its use will already
	be present in the <filename>named.conf</filename> file.</para>
    </sect2>

    <sect2>
      <title>Configuration of a Slave Zone</title>

      <para>Configuration for extra domains or sub domains may be
	done properly by setting them as a slave zone.  In most cases,
	the <filename>master/localhost.rev</filename> file could just be
	copied over into the <filename class="directory">slave</filename>
	directory and modified.  Once completed, the files need
	to be properly added in <filename>named.conf</filename> such
	as in the following configuration for
	<hostid role="domainname">example.com</hostid>:</para>

      <programlisting>zone "example.com" {
        type slave;
        file "slave/example.com";
        masters {
                10.0.0.1;
        };
};

zone "0.168.192.in-addr.arpa" {
        type slave;
        file "slave/0.168.192.in-addr.arpa";
        masters {
                10.0.0.1;
        };
};</programlisting>

      <para>Note well that in this example, the master
	<acronym>IP</acronym> address is the primary domain server
	from which the zones are transferred; it does not necessary serve
	as <acronym>DNS</acronym> server itself.</para>
    </sect2>

    <sect2>
      <title>System Initialization Configuration</title>

      <para>In order for the <application>named</application> daemon to start
	when the system is booted, the following option must be present
	in the <filename>rc.conf</filename> file:</para>

      <programlisting>named_enable="YES"</programlisting>

      <para>While other options exist, this is the bare minimal
	requirement.  Consult the &man.rc.conf.5; manual page for
	a list of the other options.  If nothing is entered in the
	<filename>rc.conf</filename> file then <application>named</application>
	may be started on the command line by invoking:</para>

      <screen>&prompt.root; <userinput>/etc/rc.d/named start</userinput></screen>
    </sect2>

    <sect2>
      <title><acronym>BIND</acronym>9 Security</title>

      <para>While &os; automatically drops <application>named</application>
	into a &man.chroot.8; environment; there are several other
	security mechanisms in place which could help to lure off
	possible <acronym>DNS</acronym> service attacks.</para>

      <sect3>
	<title>Query Access Control Lists</title>

	<para>A query access control list can be used to restrict
	  queries against the zones.  The configuration works by
	  defining the network inside of the <literal>acl</literal>
	  token and then listing <acronym>IP</acronym> addresses in
	  the zone configuration.  To permit domains to query the
	  example host, just define it like this:</para>

	<programlisting>acl "example.com" {
        192.168.0.0/24;
};

zone "example.com" {
        type slave;
        file "slave/example.com";
        masters {
                10.0.0.1;
        };
	allow-query { example.com; };
};

zone "0.168.192.in-addr.arpa" {
        type slave;
        file "slave/0.168.192.in-addr.arpa";
        masters {
                10.0.0.1;
        };
	allow-query { example.com; };
};</programlisting>
      </sect3>

      <sect3>
	<title>Restrict Version</title>

	<para>Permitting version lookups on the <acronym>DNS</acronym>
	  server could be opening the doors for an attacker.  A
	  malicious user may use this information to hunt up known
	  exploits or bugs to utilize against the host.</para>

	<warning>
	  <para>Setting a false version will not protect the server
	    from exploits.  Only upgrading to a version that is not
	    vulnerable will protect your server.</para>
	</warning>

	<para>A false version string can be placed the
	  <literal>options</literal> section of
	  <filename>named.conf</filename>:</para>

	<programlisting>options {
        directory       "/etc/namedb";
        pid-file        "/var/run/named/pid";
        dump-file       "/var/dump/named_dump.db";
        statistics-file "/var/stats/named.stats";
        version		"None of your business";
};</programlisting>
      </sect3>

<!-- Here is where I stopped for now
      <sect3>
        <title>Authentication</title>

	<para> ... </para>

-->
    </sect2>
  </sect1>


  <sect1 id="network-apache">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Murray</firstname>
	  <surname>Stokely</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>Apache HTTP Server</title>

    <indexterm><primary>web servers</primary>
      <secondary>setting up</secondary></indexterm>
    <indexterm><primary>Apache</primary></indexterm>

    <sect2>
      <title>Overview</title>

      <para>&os; is used to run some of the busiest web sites in the
        world.  The majority of web servers on the Internet are using
        the <application>Apache HTTP Server</application>.
        <application>Apache</application> software packages should be
        included on your FreeBSD installation media.  If you did not
        install <application>Apache</application> when you first
        installed FreeBSD, then you can install it from the <filename
        role="package">www/apache13</filename> or <filename
        role="package">www/apache2</filename> port.</para>

      <para>Once <application>Apache</application> has been installed
        successfully, it must be configured.</para>

      <note><para>This section covers version 1.3.X of the
        <application>Apache HTTP Server</application> as that is the
        most widely used version for &os;.  <application>Apache</application>&nbsp;2.X introduces many
        new technologies but they are not discussed here.  For more
        information about <application>Apache</application>&nbsp;2.X, please see <ulink
        url="http://httpd.apache.org/"></ulink>.</para></note>

    </sect2>

    <sect2>
      <title>Configuration</title>

      <indexterm><primary>Apache</primary>
	<secondary>configuration file</secondary></indexterm>

      <para>The main <application>Apache HTTP Server</application> configuration file is
	installed as
	<filename>/usr/local/etc/apache/httpd.conf</filename> on &os;.
	This file is a typical &unix; text configuration file with
	comment lines beginning with the <literal>#</literal>
	character.  A comprehensive description of all possible
	configuration options is outside the scope of this book, so
	only the most frequently modified directives will be described
	here.</para>

      <variablelist>
	<varlistentry>
	  <term><literal>ServerRoot "/usr/local"</literal></term>

	  <listitem>
	    <para>This specifies the default directory hierarchy for
	    the <application>Apache</application> installation.  Binaries are stored in the
	    <filename class="directory">bin</filename> and 
	    <filename class="directory">sbin</filename> subdirectories
	    of the server root, and configuration files are stored in
	    <filename class="directory">etc/apache</filename>.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>ServerAdmin you@your.address</literal></term>

	  <listitem>
	    <para>The address to which problems with the server should
	      be emailed.  This address appears on some
	      server-generated pages, such as error documents.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>ServerName www.example.com</literal></term>

	  <listitem>
	    <para><literal>ServerName</literal> allows you to set a host name which is
	      sent back to clients for your server if it is different
	      to the one that the host is configured with (i.e., use <hostid>www</hostid>
	      instead of the host's real name).</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><literal>DocumentRoot "/usr/local/www/data"</literal></term>

	  <listitem>
	    <para><literal>DocumentRoot</literal>: The directory out of which you will
	      serve your documents. By default, all requests are taken
	      from this directory, but symbolic links and aliases may
	      be used to point to other locations.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>It is always a good idea to make backup copies of your
	<application>Apache</application> configuration file before making changes.  Once you are
	satisfied with your initial configuration you are ready to
	start running <application>Apache</application>.</para>

<!-- sect3 for performance tuning directives?  maxservers minservers -->
<!-- etc..?? -->

<!-- Advanced configuration section.

Performance tuning directives.

Log file format -->

    </sect2>

    <sect2>
      <title>Running <application>Apache</application></title>

      <indexterm><primary>Apache</primary>
	<secondary>starting or stopping</secondary></indexterm>

      <para><application>Apache</application> does not run from the
        <application>inetd</application> super server as many other
        network servers do.  It is configured to run standalone for
        better performance for incoming HTTP requests from client web
        browsers.  A shell script wrapper is included to make
        starting, stopping, and restarting the server as simple as
        possible.  To start up <application>Apache</application> for
        the first time, just run:</para>

      <screen>&prompt.root; <userinput>/usr/local/sbin/apachectl start</userinput></screen>

      <para>You can stop the server at any time by typing:</para>

      <screen>&prompt.root; <userinput>/usr/local/sbin/apachectl stop</userinput></screen>

      <para>After making changes to the configuration file for any
      reason, you will need to restart the server:</para>

      <screen>&prompt.root; <userinput>/usr/local/sbin/apachectl restart</userinput></screen>

      <para>To restart <application>Apache</application> without
	aborting current connections, run:</para>

      <screen>&prompt.root; <userinput>/usr/local/sbin/apachectl graceful</userinput></screen>

      <para>Additional information available at
	&man.apachectl.8; manual page.</para>

      <para>To launch <application>Apache</application> at system
        startup, add the following line to
        <filename>/etc/rc.conf</filename>:</para>

      <programlisting>apache_enable="YES"</programlisting>

      <para>If you would like to supply additional command line
	options for the <application>Apache</application>
	<command>httpd</command> program started at system boot, you
	may specify them with an additional line in
	<filename>rc.conf</filename>:</para>

      <programlisting>apache_flags=""</programlisting>

      <para>Now that the web server is running, you can view your web
        site by pointing a web browser to
        <literal>http://localhost/</literal>.  The default web page
        that is displayed is
        <filename>/usr/local/www/data/index.html</filename>.</para>

    </sect2>

    <sect2>
      <title>Virtual Hosting</title>

      <para><application>Apache</application> supports two different
	types of Virtual Hosting. The first method is Name-based
	Virtual Hosting. Name-based virtual hosting uses the clients
	HTTP/1.1 headers to figure out the hostname. This allows many
	different domains to share the same IP address.</para>

      <para>To setup <application>Apache</application> to use
        Name-based Virtual Hosting add an entry like the following to
        your <filename>httpd.conf</filename>:</para>

      <programlisting>NameVirtualHost *</programlisting>

      <para>If your webserver was named <hostid role="fqdn">www.domain.tld</hostid> and
        you wanted to setup a virtual domain for
        <hostid role="fqdn">www.someotherdomain.tld</hostid> then you would add
        the following entries to
        <filename>httpd.conf</filename>:</para>

      <screen>&lt;VirtualHost *&gt;
ServerName www.domain.tld
DocumentRoot /www/domain.tld
&lt;/VirtualHost&gt;

&lt;VirtualHost *&gt;
ServerName www.someotherdomain.tld
DocumentRoot /www/someotherdomain.tld
&lt;/VirtualHost&gt;</screen>

      <para>Replace the addresses with the addresses you want to use
        and the path to the documents with what you are using.</para>

      <para>For more information about setting up virtual hosts,
        please consult the official <application>Apache</application>
        documentation at: <ulink
        url="http://httpd.apache.org/docs/vhosts/"></ulink>.</para>

    </sect2>

    <sect2>
      <title>Apache Modules</title>

      <indexterm><primary>Apache</primary>
	<secondary>modules</secondary></indexterm>

      <para>There are many different <application>Apache</application> modules available to add
        functionality to the basic server.  The FreeBSD Ports
        Collection provides an easy way to install
        <application>Apache</application> together with some of the
        more popular add-on modules.</para>

      <sect3>
        <title>mod_ssl</title>

	<indexterm><primary>web servers</primary>
          <secondary>secure</secondary></indexterm>
	<indexterm><primary>SSL</primary></indexterm>
	<indexterm><primary>cryptography</primary></indexterm>

        <para>The <application>mod_ssl</application> module uses the OpenSSL library to provide
          strong cryptography via the Secure Sockets Layer (SSL v2/v3)
          and Transport Layer Security (TLS v1) protocols.  This
          module provides everything necessary to request a signed
          certificate from a trusted certificate signing authority so
          that you can run a secure web server on &os;.</para>

	<para>If you have not yet installed
	  <application>Apache</application>, then a version of <application>Apache</application>
	  1.3.X that includes <application>mod_ssl</application> may be installed with the <filename
	  role="package">www/apache13-modssl</filename> port.  SSL
	  support is also available for <application>Apache</application>&nbsp;2.X in the
	  <filename role="package">www/apache2</filename> port,
	  where it is enabled by default.</para>

<!-- XXX add more information about configuring mod_ssl here. -->
<!-- Generating keys, getting the key signed, setting up your secure -->
<!-- web server! -->
      </sect3>

      <sect3>
        <title>mod_perl</title>

	<indexterm><primary>Perl</primary></indexterm>

        <para>The <application>Apache</application>/Perl integration project brings together the
	  full power of the Perl programming language and the <application>Apache
	  HTTP Server</application>.  With the <application>mod_perl</application> module it is possible to
	  write <application>Apache</application> modules entirely in Perl.  In addition, the
	  persistent interpreter embedded in the server avoids the
	  overhead of starting an external interpreter and the penalty
	  of Perl start-up time.</para>

	<para>If you have not yet installed
	  <application>Apache</application>, then a version of <application>Apache</application>
	  that includes <application>mod_perl</application> may be installed with the <filename
	  role="package">www/apache13-modperl</filename> port.</para>
      </sect3>

      <sect3>
	<sect3info>
	  <authorgroup>
	    <author>
	      <firstname>Tom</firstname>
	      <surname>Rhodes</surname>
	      <contrib>Written by </contrib>
	    </author>
	  </authorgroup>
	</sect3info>
        <title>PHP</title>

	<indexterm><primary>PHP</primary></indexterm>

        <para>In the past few years, more businesses have turned to the
	  Internet in order to enhance their revenue and increase
	  exposure.  This has also increased the need for interactive
	  web content.  While some companies, such as &microsoft;, have
	  introduced solutions into their proprietary products, the
	  open source community answered the call.  One answer, widely
	  used, is known as <acronym>PHP</acronym>.

	<para>PHP, also known as <quote>Hypertext Preprocessor</quote>
	  is a general-purpose scripting language that is especially
	  suited for Web development.  Capable of being embedded into
	  <acronym>HTML</acronym> its syntax draws upon C, &java;,
	  and Perl with the intention of allowing web developers
	  write dynamically generated webpages quickly.</para>

	<para>To gain support for <acronym>PHP</acronym>5 for the
	  <application>Apache</application> web server, begin by
	  installing the
	  <filename role="package">www/mod_php5</filename>
	  port.</para>

	<para>This will install and configure the modules required
	  to support dynamic web applications.  Check to ensure the
	  following lines have been added to
	  <filename>/usr/local/etc/apache/httpd.conf</filename>:

	<programlisting>LoadModule php5_module        libexec/apache/libphp5.so
AddModule mod_php5.c
    &lt;IfModule mod_php5.c&gt;
        DirectoryIndex index.php index.html
    &lt;/IfModule&gt;
    
    &lt;IfModule mod_php5.c&gt;
        AddType application/x-httpd-php .php
        AddType application/x-httpd-php-source .phps
    &lt;/IfModule&gt;</programlisting>

	<para>Once completed, a simple call to the
	  <command>apachectl</command> command for a graceful
	  restart:</para>

	<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>

	<para>The <acronym>PHP</acronym> support in &os; is extremely
	  modular.  If support for any extensions is required, an
	  administrator only needs to install the appropriate port
	  and restart <application>Apache</application> like recommended
	  above.</para>

	<para>For instance, to add support for the
	  <application>MySQL</application> database server to
	  <acronym>PHP</acronym>5, simply install the
	  <filename role="package">databases/php5-mysql</filename>
	  and issue the following command:</para>

	<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>

	<para>Which will enable <application>MySQL</application>
	  support in <acronym>PHP</acronym>.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 id="network-ftp">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Murray</firstname>
	  <surname>Stokely</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>File Transfer Protocol (FTP)</title>

    <indexterm><primary>FTP servers</primary></indexterm>

    <sect2>
      <title>Overview</title>

      <para>The File Transfer Protocol (FTP) provides users with a
	simple way to transfer files to and from an <acronym
	role="File Transfer Protocol">FTP</acronym> server.  &os;
	includes <acronym role="File Transfer Protocol">FTP</acronym>
	server software, <application>ftpd</application>, in the base
	system.  This makes setting up and administering an <acronym
	role="File Transfer Protocol">FTP</acronym> server on FreeBSD
	very straightforward.</para>
    </sect2>

    <sect2>
      <title>Configuration</title>

      <para>The most important configuration step is deciding which
	accounts will be allowed access to the FTP server.  A normal
	FreeBSD system has a number of system accounts used for
	various daemons, but unknown users should not be allowed to
	log in with these accounts.  The
	<filename>/etc/ftpusers</filename> file is a list of users
	disallowed any FTP access.  By default, it includes the
	aforementioned system accounts, but it is possible to add
	specific users here that should not be allowed access to
	FTP.</para>

      <para>You may want to restrict the access of some users without
	preventing them completely from using FTP.  This can be
	accomplished with the <filename>/etc/ftpchroot</filename>
	file.  This file lists users and groups subject to FTP access
	restrictions.  The &man.ftpchroot.5; manual page has all of
	the details so it will not be described in detail here.</para>

      <indexterm>
	<primary>FTP</primary>
	<secondary>anonymous</secondary>
      </indexterm>

      <para>If you would like to enable anonymous FTP access to your
	server, then you must create a user named
	<username>ftp</username> on your &os; system.  Users will then
	be able to log on to your FTP server with a username of
	<username>ftp</username> or <username>anonymous</username> and
	with any password (by convention an email address for the user
	should be used as the password).  The FTP server will call
	&man.chroot.2; when an anonymous user logs in, to restrict
	access to only the home directory of the
	<username>ftp</username> user.</para>

      <para>There are two text files that specify welcome messages to
	be displayed to FTP clients.  The contents of the file
	<filename>/etc/ftpwelcome</filename> will be displayed to
	users before they reach the login prompt.  After a successful
	login, the contents of the file
	<filename>/etc/ftpmotd</filename> will be displayed.  Note
	that the path to this file is relative to the login environment, so the
	file <filename>~ftp/etc/ftpmotd</filename> would be displayed
	for anonymous users.</para>

      <para>Once the FTP server has been configured properly, it must
        be enabled in <filename>/etc/inetd.conf</filename>.  All that
        is required here is to remove the comment symbol
        <quote>#</quote> from in front of the existing
        <application>ftpd</application> line :</para>

      <programlisting>ftp	stream	tcp	nowait	root	/usr/libexec/ftpd	ftpd -l</programlisting>

      <para>As explained in <xref linkend="network-inetd-hangup">, a
        HangUP Signal must be sent to <application>inetd</application>
        after this configuration file is changed.</para>

      <para>You can now log on to your FTP server by typing:</para>

      <screen>&prompt.user; <userinput>ftp localhost</userinput></screen>

    </sect2>

    <sect2>
      <title>Maintaining</title>

      <indexterm><primary>syslog</primary></indexterm>
      <indexterm><primary>log files</primary>
	<secondary>FTP</secondary></indexterm>

      <para>The <application>ftpd</application> daemon uses
        &man.syslog.3; to log messages.  By default, the system log
        daemon will put messages related to FTP in the
        <filename>/var/log/xferlog</filename> file.  The location of
        the FTP log can be modified by changing the following line in
        <filename>/etc/syslog.conf</filename>:</para>

      <programlisting>ftp.info      /var/log/xferlog</programlisting>

      <indexterm>
	<primary>FTP</primary>
	<secondary>anonymous</secondary>
      </indexterm>

      <para>Be aware of the potential problems involved with running
        an anonymous FTP server.  In particular, you should think
        twice about allowing anonymous users to upload files.  You may
        find that your FTP site becomes a forum for the trade of
        unlicensed commercial software or worse.  If you do need to
        allow anonymous FTP uploads, then you should set up the
        permissions so that these files can not be read by other
        anonymous users until they have been reviewed.</para>

    </sect2>
  </sect1>

  <sect1 id="network-samba">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Murray</firstname>
	  <surname>Stokely</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>File and Print Services for &microsoft.windows; clients (Samba)</title>

    <indexterm><primary>Samba server</primary></indexterm>
    <indexterm><primary>Microsoft Windows</primary></indexterm>
    <indexterm>
      <primary>file server</primary>
      <secondary>Windows clients</secondary>
    </indexterm>
    <indexterm>
      <primary>print server</primary>
      <secondary>Windows clients</secondary>
    </indexterm>

    <sect2>
      <title>Overview</title>

      <para><application>Samba</application> is a popular open source
        software package that provides file and print services for
        &microsoft.windows; clients.  Such clients can connect to and
        use FreeBSD filespace as if it was a local disk drive, or
        FreeBSD printers as if they were local printers.</para>

      <para><application>Samba</application> software packages should
        be included on your FreeBSD installation media.  If you did
        not install <application>Samba</application> when you first
        installed FreeBSD, then you can install it from the <filename
        role="package">net/samba3</filename> port or package.</para>

<!-- mention LDAP, Active Directory, WinBIND, ACL, Quotas, PAM, .. -->

    </sect2>

    <sect2>
      <title>Configuration</title>

      <para>A default <application>Samba</application> configuration
        file is installed as
        <filename>/usr/local/etc/smb.conf.default</filename>.  This
        file must be copied to
        <filename>/usr/local/etc/smb.conf</filename> and customized
        before <application>Samba</application> can be used.</para>

      <para>The <filename>smb.conf</filename> file contains runtime
        configuration information for
        <application>Samba</application>, such as definitions of the
        printers and <quote>filesystem shares</quote> that you would
        like to share with &windows; clients.  The
        <application>Samba</application> package includes a web based
        tool called <application>swat</application> which provides a
        simple way of configuring the <filename>smb.conf</filename>
        file.</para>

      <sect3>
	<title>Using the Samba Web Administration Tool (SWAT)</title>

	<para>The Samba Web Administration Tool (SWAT) runs as a
	  daemon from <application>inetd</application>.  Therefore, the
	  following line in <filename>/etc/inetd.conf</filename>
	  should be uncommented before <application>swat</application> can be
	  used to configure <application>Samba</application>:</para>

	<programlisting>swat   stream  tcp     nowait/400      root    /usr/local/sbin/swat</programlisting>
        <para>As explained in <xref linkend="network-inetd-hangup">, a
          HangUP Signal must be sent to
          <application>inetd</application> after this configuration
          file is changed.</para>

	<para>Once <application>swat</application> has been enabled in
	  <filename>inetd.conf</filename>, you can use a browser to
	  connect to <ulink url="http://localhost:901"></ulink>.  You will
	  first have to log on with the system <username>root</username> account.</para>

<!-- XXX screenshots go here, loader is creating them -->

	<para>Once you have successfully logged on to the main
	  <application>Samba</application> configuration page, you can
	  browse the system documentation, or begin by clicking on the
	  <guimenu>Globals</guimenu> tab.  The <guimenu>Globals</guimenu> section corresponds to the
	  variables that are set in the <literal>[global]</literal>
	  section of
	  <filename>/usr/local/etc/smb.conf</filename>.</para>
      </sect3>

      <sect3>
	<title>Global Settings</title>

	<para>Whether you are using <application>swat</application> or
	  editing <filename>/usr/local/etc/smb.conf</filename>
	  directly, the first directives you are likely to encounter
	  when configuring <application>Samba</application>
	  are:</para>

        <variablelist>
	  <varlistentry>
	    <term><literal>workgroup</literal></term>

	    <listitem>
	      <para>NT Domain-Name or Workgroup-Name for the computers
	        that will be accessing this server.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>netbios name</literal></term>
	    <indexterm><primary>NetBIOS</primary></indexterm>

	    <listitem>
	      <para>This sets the NetBIOS name by which a <application>Samba</application> server
		is known. By default it is the same as the first
		component of the host's DNS name.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>server string</literal></term>

	    <listitem>
	      <para>This sets the string that will be displayed with
		the <command>net view</command> command and some other
		networking tools that seek to display descriptive text
		about the server.</para>
	    </listitem>
	  </varlistentry>
        </variablelist>
      </sect3>

      <sect3>
	<title>Security Settings</title>

	<para>Two of the most important settings in
	  <filename>/usr/local/etc/smb.conf</filename> are the
	  security model chosen, and the backend password format for
	  client users.  The following directives control these
	  options:</para>

        <variablelist>
	  <varlistentry>
	    <term><literal>security</literal></term>

	    <listitem>
	      <para>The two most common options here are
	        <literal>security = share</literal> and <literal>security
	        = user</literal>.  If your clients use usernames that
	        are the same as their usernames on your &os; machine
	        then you will want to use user level security.  This
	        is the default security policy and it requires clients
	        to first log on before they can access shared
	        resources.</para>

	      <para>In share level security, client do not need to log
	        onto the server with a valid username and password
	        before attempting to connect to a shared resource.
	        This was the default security model for older versions
	        of <application>Samba</application>.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>passdb backend</literal></term>

	    <indexterm><primary>NIS+</primary></indexterm>
	    <indexterm><primary>LDAP</primary></indexterm>
	    <indexterm><primary>SQL database</primary></indexterm>

	    <listitem>
	      <para><application>Samba</application> has several
	        different backend authentication models.  You can
	        authenticate clients with LDAP, NIS+, a SQL database,
	        or a modified password file.  The default
	        authentication method is <literal>smbpasswd</literal>,
	        and that is all that will be covered here.</para>
	    </listitem>
	  </varlistentry>
	</variablelist>

	<para>Assuming that the default <literal>smbpasswd</literal>
	  backend is used, the
	  <filename>/usr/local/private/smbpasswd</filename> file must
	  be created to allow <application>Samba</application> to
	  authenticate clients.  If you would like to give all of
	  your &unix; user accounts access from &windows; clients, use the
	  following command:</para>

	<screen>&prompt.root; <userinput>grep -v "^#" /etc/passwd | make_smbpasswd &gt; /usr/local/private/smbpasswd</userinput>
&prompt.root; <userinput>chmod 600 /usr/local/private/smbpasswd</userinput></screen>

	<para>Please see the <application>Samba</application>
	  documentation for additional information about configuration
	  options.  With the basics outlined here, you should have
	  everything you need to start running
	  <application>Samba</application>.</para>
      </sect3>

    </sect2>
    <sect2>
      <title>Starting <application>Samba</application></title>

      <para>To enable <application>Samba</application> when your
        system boots, add the following line to
        <filename>/etc/rc.conf</filename>:</para>

      <programlisting>samba_enable="YES"</programlisting>

      <para>You can then start <application>Samba</application> at any
        time by typing:</para>

      <screen>&prompt.root; <userinput>/usr/local/etc/rc.d/samba.sh start</userinput>
Starting SAMBA: removing stale tdbs :
Starting nmbd.
Starting smbd.</screen>

      <para><application>Samba</application> actually consists of
        three separate daemons.  You should see that both the
        <application>nmbd</application> and <application>smbd</application> daemons
        are started by the <filename>samba.sh</filename> script.  If
        you enabled winbind name resolution services in
        <filename>smb.conf</filename>, then you will also see that
        the <application>winbindd</application> daemon is started.</para>

      <para>You can stop <application>Samba</application> at any time
        by typing :</para>

      <screen>&prompt.root; <userinput>/usr/local/etc/rc.d/samba.sh stop</userinput></screen>

      <para><application>Samba</application> is a complex software
        suite with functionality that allows broad integration with
        &microsoft.windows; networks.  For more information about
        functionality beyond the basic installation described here,
        please see <ulink url="http://www.samba.org"></ulink>.</para>
    </sect2>

  </sect1>

  <sect1 id="network-ntp">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Tom</firstname>
	  <surname>Hukins</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>Clock Synchronization with NTP</title>

    <indexterm><primary>NTP</primary></indexterm>

    <sect2>
      <title>Overview</title>

      <para>Over time, a computer's clock is prone to drift.  The
	Network Time Protocol (NTP) is one way to ensure your clock stays
	accurate.</para>

      <para>Many Internet services rely on, or greatly benefit from,
	computers' clocks being accurate.  For example, a web server
	may receive requests to send a file if it has been modified since a
	certain time.  In a local area network environment, it is
	essential that computers sharing files from the same file
	server have synchronized clocks so that file timestamps stay
	consistent.  Services such as &man.cron.8; also rely on
	an accurate system clock to run commands at the specified
	times.</para>

      <indexterm>
	<primary>NTP</primary>
	<secondary>ntpd</secondary>
      </indexterm>
      <para>FreeBSD ships with the &man.ntpd.8; <acronym role="Network
	Time Protocol">NTP</acronym> server which can be used to query
	other <acronym role="Network Time Protocol">NTP</acronym>
	servers to set the clock on your machine or provide time
	services to others.</para>
    </sect2>

    <sect2>
      <title>Choosing Appropriate NTP Servers</title>

      <indexterm>
	<primary>NTP</primary>
	<secondary>choosing servers</secondary>
      </indexterm>

      <para>In order to synchronize your clock, you will need to find
	one or more <acronym role="Network Time
	Protocol">NTP</acronym> servers to use.  Your network
	administrator or ISP may have set up an NTP server for this
	purpose&mdash;check their documentation to see if this is the
	case.  There is an <ulink
	url="http://ntp.isc.org/bin/view/Servers/WebHome">online
	list of publicly accessible NTP servers</ulink> which you can
	use to find an NTP server near to you.  Make sure you are
	aware of the policy for any servers you choose, and ask for
	permission if required.</para>

      <para>Choosing several unconnected NTP servers is a good idea in
	case one of the servers you are using becomes unreachable or
	its clock is unreliable.  &man.ntpd.8; uses the responses it
	receives from other servers intelligently&mdash;it will favor
	unreliable servers less than reliable ones.</para>
    </sect2>

    <sect2>
      <title>Configuring Your Machine</title>

      <indexterm>
	<primary>NTP</primary>
	<secondary>configuration</secondary>
      </indexterm>

      <sect3>
	<title>Basic Configuration</title>
	<indexterm><primary>ntpdate</primary></indexterm>

	<para>If you only wish to synchronize your clock when the
	  machine boots up, you can use &man.ntpdate.8;.  This may be
	  appropriate for some desktop machines which are frequently
	  rebooted and only require infrequent synchronization, but
	  most machines should run &man.ntpd.8;.</para>

	<para>Using &man.ntpdate.8; at boot time is also a good idea
	  for machines that run &man.ntpd.8;.  The &man.ntpd.8;
	  program changes the clock gradually, whereas &man.ntpdate.8;
	  sets the clock, no matter how great the difference between a
	  machine's current clock setting and the correct time.</para>

	<para>To enable &man.ntpdate.8; at boot time, add
	  <literal>ntpdate_enable="YES"</literal> to
	  <filename>/etc/rc.conf</filename>.  You will also need to
	  specify all servers you wish to synchronize with and any
	  flags to be passed to &man.ntpdate.8; in
	  <varname>ntpdate_flags</varname>.</para>
      </sect3>

      <sect3>
	<indexterm>
	  <primary>NTP</primary>
	  <secondary>ntp.conf</secondary>
	</indexterm>

	<title>General Configuration</title>

	<para>NTP is configured by the
	  <filename>/etc/ntp.conf</filename> file in the format
	  described in &man.ntp.conf.5;.  Here is a simple
	  example:</para>

	<programlisting>server ntplocal.example.com prefer
server timeserver.example.org
server ntp2a.example.net

driftfile /var/db/ntp.drift</programlisting>

	<para>The <literal>server</literal> option specifies which
	  servers are to be used, with one server listed on each line.
	  If a server is specified with the <literal>prefer</literal>
	  argument, as with <hostid
	  role="fqdn">ntplocal.example.com</hostid>, that server is
	  preferred over other servers.  A response from a preferred
	  server will be discarded if it differs significantly from
	  other servers' responses, otherwise it will be used without
	  any consideration to other responses.  The
	  <literal>prefer</literal> argument is normally used for NTP
	  servers that are known to be highly accurate, such as those
	  with special time monitoring hardware.</para>

	<para>The <literal>driftfile</literal> option specifies which
	  file is used to store the system clock's frequency offset.
	  The &man.ntpd.8; program uses this to automatically
	  compensate for the clock's natural drift, allowing it to
	  maintain a reasonably correct setting even if it is cut off
	  from all external time sources for a period of time.</para>

	<para>The <literal>driftfile</literal> option specifies which
	  file is used to store information about previous responses
	  from the NTP servers you are using.  This file contains
	  internal information for NTP.  It should not be modified by
	  any other process.</para>
      </sect3>

      <sect3>
	<title>Controlling Access to Your Server</title>

	<para>By default, your NTP server will be accessible to all
	  hosts on the Internet.  The <literal>restrict</literal>
	  option in <filename>/etc/ntp.conf</filename> allows you to
	  control which machines can access your server.</para>

	<para>If you want to deny all machines from accessing your NTP
	  server, add the following line to
	  <filename>/etc/ntp.conf</filename>:</para>

        <programlisting>restrict default ignore</programlisting>

        <para>If you only want to allow machines within your own
	  network to synchronize their clocks with your server, but
	  ensure they are not allowed to configure the server or used
	  as peers to synchronize against, add</para>

        <programlisting>restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap</programlisting>

	<para>instead, where <hostid role="ipaddr">192.168.1.0</hostid> is
	  an IP address on your network and <hostid
	  role="netmask">255.255.255.0</hostid> is your network's
	  netmask.</para>

	<para><filename>/etc/ntp.conf</filename> can contain multiple
	  <literal>restrict</literal> options.  For more details, see
	  the <literal>Access Control Support</literal> subsection of
	  &man.ntp.conf.5;.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>Running the NTP Server</title>

      <para>To ensure the NTP server is started at boot time, add the
	line <literal>ntpd_enable="YES"</literal> to
	<filename>/etc/rc.conf</filename>.  If you wish to pass
	additional flags to &man.ntpd.8;, edit the
	<varname>ntpd_flags</varname> parameter in
	<filename>/etc/rc.conf</filename>.</para>

      <para>To start the server without rebooting your machine, run
	<command>ntpd</command> being sure to specify any additional
	parameters from <varname>ntpd_flags</varname> in
	<filename>/etc/rc.conf</filename>.  For example:</para>

      <screen>&prompt.root; <userinput>ntpd -p /var/run/ntpd.pid</userinput></screen>

      <note>
	<para>Under &os;&nbsp;4.X,
	  you have to replace every instance of <literal>ntpd</literal>
	  with <literal>xntpd</literal> in the options above.</para></note>
    </sect2>

    <sect2>
      <title>Using ntpd with a Temporary Internet
	Connection</title>

      <para>The &man.ntpd.8; program does not need a permanent
	connection to the Internet to function properly.  However, if
	you have a temporary connection that is configured to dial out
	on demand, it is a good idea to prevent NTP traffic from
	triggering a dial out or keeping the connection alive.  If you
	are using user PPP, you can use <literal>filter</literal>
	directives in <filename>/etc/ppp/ppp.conf</filename>.  For
	example:</para>

      <programlisting> set filter dial 0 deny udp src eq 123
 # Prevent NTP traffic from initiating dial out
 set filter dial 1 permit 0 0
 set filter alive 0 deny udp src eq 123
 # Prevent incoming NTP traffic from keeping the connection open
 set filter alive 1 deny udp dst eq 123
 # Prevent outgoing NTP traffic from keeping the connection open
 set filter alive 2 permit 0/0 0/0</programlisting>

      <para>For more details see the <literal>PACKET
	FILTERING</literal> section in &man.ppp.8; and the examples in
	<filename>/usr/share/examples/ppp/</filename>.</para>

      <note>
	<para>Some Internet access providers block low-numbered ports,
	  preventing NTP from functioning since replies never
	  reach your machine.</para>
      </note>
    </sect2>

    <sect2>
      <title>Further Information</title>

      <para>Documentation for the NTP server can be found in
	<filename>/usr/share/doc/ntp/</filename> in HTML
	format.</para>
    </sect2>
  </sect1>

</chapter>

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