path: root/el_GR.ISO8859-7/books/handbook/network-servers/chapter.xml

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

  <title>ÅîõðçñåôçôÝò Äéêôýïõ</title>

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

    <para>Ôï êåöÜëáéï áõôü êáëýðôåé ïñéóìÝíåò áðü ôéò ðéï óõ÷íÜ
      ÷ñçóéìïðïéïýìåíåò äéêôõáêÝò õðçñåóßåò ôùí óõóôçìÜôùí &unix;. Èá
      ðáñïõóéÜóïõìå ôçí åãêáôÜóôáóç, ñýèìéóç, Ýëåã÷ï êáé óõíôÞñçóç ðïëëþí
      äéáöïñåôéêþí ôýðùí äéêôõáêþí õðçñåóéþí. Óå üëï ôï êåöÜëáéï, ãéá ôç
      äéêÞ óáò äéåõêüëõíóç, õðÜñ÷ïõí ðáñáäåßãìáôá äéáöüñùí áñ÷åßùí ñõèìßóåùí.</para>

    <para>Áöïý äéáâÜóåôå áõôü ôï êåöÜëáéï, èá îÝñåôå:</para>

    <itemizedlist>
      <listitem>
	<para>Ðùò íá äéá÷åéñßæåóôå ôçí õðçñåóßá <application>inetd</application>.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå Ýíá äéêôõáêü óýóôçìá áñ÷åßùí.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå Ýíá åîõðçñåôçôÞ äéêôõáêþí ðëçñïöïñéþí ãéá ôï
          äéáìïéñáóìü ëïãáñéáóìþí ÷ñçóôþí.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ÷ñçóéìïðïéÞóåôå ôï DHCP ãéá ôçí áõôüìáôç ñýèìéóç ôùí
          ðáñáìÝôñùí ôïõ äéêôýïõ.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå Ýíá åîõðçñåôçôÞ ïíïìáóßáò ðåñéï÷þí (DNS).</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå ôïí åîõðçñåôçôÞ
	  éóôïóåëßäùí <application>Apache</application>.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå Ýíá åîõðçñåôçôÞ ìåôáöïñÜò áñ÷åßùí (FTP).</para>
      </listitem>

      <listitem>
	<para>Ðùò íá ñõèìßóåôå Ýíá åîõðçñåôçôÞ áñ÷åßùí êáé åêôõðùôþí ãéá
          ðåëÜôåò &windows; ìå ÷ñÞóç ôçò åöáñìïãÞò <application>Samba</application>.</para>
      </listitem>

      <listitem>
	<para>Ðùò íá óõã÷ñïíßóåôå ôçí çìåñïìçíßá êáé ôçí þñá, êáé íá ñõèìßóåôå
          Ýíá åîõðçñåôçôÞ þñáò ìå ôç âïÞèåéá ôïõ NTP ðñùôïêüëëïõ.</para>
      </listitem>
    </itemizedlist>

    <para>Ðñéí äéáâÜóåôå áõôü êåöÜëáéï, èá ðñÝðåé:</para>

    <itemizedlist>
      <listitem>
	<para>Íá êáôáíïåßôå ôéò âáóéêÝò Ýííïéåò ôùí áñ÷åßùí script
	  <filename>/etc/rc</filename>.</para>
      </listitem>

      <listitem>
	<para>Íá åßóôå åîïéêåéùìÝíïé ìå ôç âáóéêÞ ïñïëïãßá ôùí äéêôýùí.</para>
      </listitem>

      <listitem>
      <para>Íá ãíùñßæåôå ðùò íá åãêáôáóôÞóåôå ðñüóèåôï ëïãéóìéêü ôñßôïõ
        êáôáóêåõáóôÞ (<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>
      <authorgroup>
	<author>
	  <contrib>Updated for &os; 6.1-RELEASE by </contrib>
	  <othername>The &os; Documentation Project</othername>
	</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 sometimes 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
	<application>inetd</application> for servers that are not heavily used can reduce the
	overall system load, when 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 &man.rc.8; system.  The
	<literal>inetd_enable</literal> option is set to
	<literal>NO</literal> by default, but may be turned on
	by <application>sysinstall</application> during installation,
	depending on the configuration chosen by the user.
	Placing:
	<programlisting>inetd_enable="YES"</programlisting> or
	<programlisting>inetd_enable="NO"</programlisting> into
	<filename>/etc/rc.conf</filename> will enable or disable
	<application>inetd</application> starting at boot time.
	The command:
	<programlisting>/etc/rc.d/inetd rcvar</programlisting>
	can be run to display the current effective setting.</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>Like most server daemons, <application>inetd</application>
	has a number of options that it can be passed in order to
	modify its behaviour.  The full list of options reads:</para>

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

      <para>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 -C 60</literal>, which turns on TCP wrapping for
	<application>inetd</application>'s services, and prevents any
	single IP address from requesting any service more than 60 times
	in any given minute.</para>

      <para>Novice users may be pleased to note that
	these parameters usually do not need to be modified,
	although we mention the rate-limiting options below as
	they be useful should you find that you are receiving an
	excessive amount of connections.  A full list of options
	can be found in the &man.inetd.8; manual.</para>

      <variablelist>
	<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>-s maximum</term>

	  <listitem>
	    <para>Specify the maximum number of times a service can be
	      invoked from a single IP address at any one time; the
	      default is unlimited.  May be overridden on a per-service
	      basis with the <option>max-child-per-ip</option>
	      parameter.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect2>

    <sect2 id="network-inetd-conf">
      <!-- XXX This section isn't very clear, and could do with some lovin' -->
      <title><filename>inetd.conf</filename></title>

      <para>Configuration of <application>inetd</application> is
	done via the file <filename>/etc/inetd.conf</filename>.</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 running the command:</para>

      <example id="network-inetd-reread">
	<title>Reloading the <application>inetd</application>
	  configuration file</title>

	<screen>&prompt.root; <userinput>/etc/rc.d/inetd reload</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 each entry in
	<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[/max-child-per-ip]]]
user[:group][/login-class]
server-program
server-program-arguments</programlisting>

      <para>An example entry for the &man.ftpd.8; daemon
	using IPv4 might read:</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[/max-child-per-ip]]]</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>.  Specifying <literal>/0</literal>
	      allows an unlimited number of children</para>

	    <para>In addition to <option>max-child</option>, two other
	      options which limit the maximum connections from a single
	      place to a particular daemon can be enabled.
	      <option>max-connections-per-ip-per-minute</option> limits
	      the number of connections from any particular IP address
	      per minutes, e.g. a value of ten would limit any particular
	      IP address connecting to a particular service to ten
	      attempts per minute.  <option>max-child-per-ip</option>
	      limits the number of children that can be started on
	      behalf on any single IP address at any moment. These
	      options are useful to prevent intentional or unintentional
 	      excessive resource consumption and Denial of Service (DoS)
	      attacks to a machine.</para>

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

	    <para>A stream-type multi-threaded daemon without any
	      <option>max-child</option>,
	      <option>max-connections-per-ip-per-minute</option> or
	      <option>max-child-per-ip</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>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 utilized by the default
	      settings of the &man.fingerd.8; daemon,
	      as seen here:</para>

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

	    <para>Finally, an example of this field with a maximum of
	      100 children in total, with a maximum of 5 for any one
	      IP address would read:
	      <literal>nowait/100/0/5</literal>.</para>
	  </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 choices made at install time, many
	of <application>inetd</application>'s services may be enabled
	by default.  If there is no apparent need for a particular
	daemon, consider disabling it.  Place a <quote>#</quote> in front of the
	daemon in question in <filename>/etc/inetd.conf</filename>,
	and then <link linkend="network-inetd-reread">reload the
	inetd configuration</link>.  Some daemons, such as
	<application>fingerd</application>, may not be desired at all
	because they provide
	information that may be useful to an attacker.</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>,
	<option>max-child</option> or <option>max-child-per-ip</option> limitations on certain
	daemons if you find that you have too many connections.</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
	network services, and is
	configurable to a certain degree, whilst the others are simply on or off.</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 file systems 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>

      <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>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
        file systems <acronym>NFS</acronym> should export (sometimes
        referred to as <quote>share</quote>).  Each line in
        <filename>/etc/exports</filename> specifies a file system to be
        exported and which machines have access to that file system.
        Along with what machines have access to that file system,
        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
        file systems, 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 file system
        read-only.  With this flag, the remote system will not be able
        to write any changes to the exported file system.</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 file system.
	The <option>-maproot=root</option> flag allows the
	<username>root</username> user on the remote system to write
	data on the exported file system 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 file system.</para>

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

      <para>In order for a client to access an exported file system,
	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 file system to one host.  A
	remote host can only be specified once per file system, and may
	only have one default entry.  For example, assume that
	<filename>/usr</filename> is a single file system.  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 file system, <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 file system 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
	file systems, 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 file systems:</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>The <application>mountd</application> daemon must be forced to
	recheck the <filename>/etc/exports</filename> file whenever it has
	been modified, so the changes can take effect.  This can be
	accomplished either by sending a HUP signal to the running daemon:</para>

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

      <para>or by invoking the <command>mountd</command> &man.rc.8; script
        with the appropriate parameter:</para>

      <screen>&prompt.root; <userinput>/etc/rc.d/mountd onereload</userinput></screen>

      <para>Please refer to <xref linkend="configtuning-rcd"/> for more
	information about using rc scripts.</para>

      <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 file system 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 file system
	each time the computer boots, add the file system 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>Locking</title>

      <para>Some applications (e.g. <application>mutt</application>)
	require file locking to operate correctly.  In the case of
	<acronym>NFS</acronym>, <application>rpc.lockd</application>
	can be used for file locking.  To enable it, add the following
	to the <filename>/etc/rc.conf</filename> file on both client
	and server (it is assumed that the <acronym>NFS</acronym>
	client and server are configured already):</para>

      <programlisting>rpc_lockd_enable="YES"
rpc_statd_enable="YES"</programlisting>

      <para>Start the application by using:</para>

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

      <para>If real locking between the <acronym>NFS</acronym> clients
	and <acronym>NFS</acronym> server is not required, it is
	possible to let the <acronym>NFS</acronym> client do locking
	locally by passing <option>-L</option> to &man.mount.nfs.8;.
	Refer to the &man.mount.nfs.8; manual page for further details.
      </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 file system whenever a file or directory within that
	file system 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
	file system 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 file system 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
	file system (see &man.exports.5;), and
	<filename>/project</filename> will be the mount point on the
	client for the exported file system.  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.</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>
          <listitem>
            <para>A <emphasis>NIS master server</emphasis><indexterm><primary>NIS</primary><secondary>master server</secondary></indexterm>.  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>

          <listitem>
            <para><emphasis>NIS slave servers</emphasis><indexterm><primary>NIS</primary><secondary>slave server</secondary></indexterm>.  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>

          <listitem>
            <para><emphasis>NIS clients</emphasis><indexterm><primary>NIS</primary><secondary>client</secondary></indexterm>.  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>

      <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 &amp;:/:/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
	versions prior to 6.0 use the ISC (Internet Software
	Consortium) DHCP client (&man.dhclient.8;) implementation.
	Later versions use the OpenBSD <command>dhclient</command>
	taken from OpenBSD&nbsp;3.7.  All
	information here regarding <command>dhclient</command> is for
	use with either of the ISC or OpenBSD DHCP clients. The DHCP
	server is the one included in the ISC distribution.</para>
    </sect2>

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

      <para>This section describes both the client-side components of the ISC and OpenBSD DHCP client 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>&os; fully integrates the ISC or OpenBSD DHCP client,
        <command>dhclient</command> (according to the &os; version you run).  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> 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
	    server.</para>

	  <para>The server 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> 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 should enable the DHCP server in
	    <filename>/etc/rc.conf</filename>, i.e. by adding:</para>

	  <programlisting>dhcpd_enable="YES"
dhcpd_ifaces="dc0"</programlisting>

	  <para>Replace the <literal>dc0</literal> interface name with the
	    interface (or interfaces, separated by whitespace) that your DHCP
	    server should listen on for DHCP client requests.</para>

	  <para>Then, 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>

	<author>
	  <firstname>Tom</firstname>
	  <surname>Rhodes</surname>
	</author>

	<author>
	  <firstname>Daniel</firstname>
	  <surname>Gerzo</surname>
	</author>
      </authorgroup>
    </sect1info>
    <title>Domain Name System (<acronym>DNS</acronym>)</title>

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

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

      <para>&os; currently comes with <acronym>BIND</acronym>9
	<acronym>DNS</acronym> server software by default.  Our
	installation provides enhanced security features, a new file
	system layout and automated &man.chroot.8; configuration.</para>

      <indexterm><primary>DNS</primary></indexterm>
      <para><acronym>DNS</acronym> is coordinated across the Internet
	through a somewhat complex system of authoritative root, Top
	Level Domain (<acronym>TLD</acronym>), and other smaller-scale
	name servers which host and cache individual domain
	information.</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
	<acronym>DNS</acronym> 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 <acronym>DNS</acronym></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
		&os;.</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 <acronym>DNS</acronym></entry>
	      <entry>The opposite of forward <acronym>DNS</acronym>;
		mapping of <acronym>IP</acronym> 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
		<acronym>DNS</acronym> 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 Top Level Domain
	    (<acronym>TLD</acronym>) under the root zone.</para>
	</listitem>

	<listitem>
	  <para><hostid role="domainname">example.org.</hostid> is a
	    zone under the <hostid>org.</hostid>
	    <acronym>TLD</acronym>.</para>
	</listitem>

	<listitem>
	  <para><hostid>1.168.192.in-addr.arpa</hostid> is a zone
	    referencing all <acronym>IP</acronym> addresses which fall
	    under the <hostid role="ipaddr">192.168.1.*</hostid>
	    <acronym>IP</acronym> 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 file system: the
	<filename class="directory">/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 <acronym>DNS</acronym> 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
	    <acronym>IP</acronym> addresses need to be assigned to
	    hostnames under it.</para>
	</listitem>

	<listitem>
	  <para>An <acronym>IP</acronym> address block requires reverse
	    <acronym>DNS</acronym> entries (<acronym>IP</acronym> to
	    hostname).</para>
	</listitem>

	<listitem>
	  <para>A backup or second name server, called a slave, will
	    reply to queries.</para>
	</listitem>
      </itemizedlist>

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

      <itemizedlist>
	<listitem>
	  <para>A local <acronym>DNS</acronym> server may cache and
	    respond more quickly than querying an outside name
	    server.</para>
	</listitem>
      </itemizedlist>

      <para>When one queries for <hostid
	role="fqdn">www.FreeBSD.org</hostid>, the resolver usually
	queries the uplink <acronym>ISP</acronym>'s name server, and
	retrieves the reply.  With a local, caching
	<acronym>DNS</acronym> server, the query only has to be made
	once to the outside world by the caching <acronym>DNS</acronym>
	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 &os;, 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>&man.named.8;</entry>
	      <entry>The BIND daemon.</entry>
	    </row>

	    <row>
	      <entry>&man.rndc.8;</entry>
	      <entry>Name server control utility.</entry>
	    </row>

	    <row>
	      <entry><filename class="directory">/etc/namedb</filename></entry>
	      <entry>Directory where BIND zone information resides.</entry>
	    </row>

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

      <para>Depending on how a given zone is configured on the server,
	the files related to that zone can be found in the <filename
	class="directory">master</filename>, <filename
	class="directory">slave</filename>, or <filename
	class="directory">dynamic</filename> subdirectories of the
	<filename class="directory">/etc/namedb</filename> directory.
	These files contain the <acronym>DNS</acronym> information that
	will be given out by the name server in response to queries.</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>The default <application>named</application> configuration
	is that of a basic resolving name server, ran in a
	&man.chroot.8; environment.  To start the server one time with
	this configuration, use the following command:</para>

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

      <para>To ensure the <application>named</application> daemon is
         started at boot each time, put the following line into the
         <filename>/etc/rc.conf</filename>:</para>

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

      <para>There are obviously many configuration options for
	<filename>/etc/namedb/named.conf</filename> that are beyond the
	scope of this document.  However, if you are interested in the
	startup options for <application>named</application> on &os;,
	take a look at the
	<literal>named_<replaceable>*</replaceable></literal> flags in
	<filename>/etc/defaults/rc.conf</filename> and consult the
	&man.rc.conf.5; manual page.  The
	<xref linkend="configtuning-rcd"/> section is also a good read.</para>
    </sect2>

    <sect2>
      <title>Configuration Files</title>
      <indexterm>
	<primary>BIND</primary>
	<secondary>configuration files</secondary>
      </indexterm>

      <para>Configuration files for <application>named</application>
	currently reside in
	<filename class="directory">/etc/namedb</filename> directory and
	will need modification before use, unless all that is needed is
	a simple resolver.  This is where most of the configuration will
	be performed.</para>

      <sect3>
	<title>Using <command>make-localhost</command></title>

	<para>To configure a master zone for the localhost visit the
	  <filename class="directory">/etc/namedb</filename> directory
	  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> subdirectory.
	  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, required information will
	  be present in the <filename>named.conf</filename> file.</para>
      </sect3>

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

	<programlisting>// &dollar;FreeBSD&dollar;
//
// Refer to the named.conf(5) and named(8) man pages, and the documentation
// in /usr/share/doc/bind9 for more details.
//
// If you are going to set up an authoritative server, make sure you
// understand the hairy details of how DNS works.  Even with
// simple mistakes, you can break connectivity for affected parties,
// or cause huge amounts of useless Internet traffic.

options {
	directory	"/etc/namedb";
	pid-file	"/var/run/named/pid";
	dump-file	"/var/dump/named_dump.db";
	statistics-file	"/var/stats/named.stats";

// If named is being used only as a local resolver, this is a safe default.
// For named to be accessible to the network, comment this option, specify
// the proper IP address, or delete this option.
	listen-on	{ 127.0.0.1; };

// If you have IPv6 enabled on this system, uncomment this option for
// use as a local resolver.  To give access to the network, specify
// an IPv6 address, or the keyword "any".
//	listen-on-v6	{ ::1; };

// 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
	    <acronym>IP</acronym> address to a name server at your
	    uplink.</para>
	</warning>

	<programlisting>	/*
	 * If there is a firewall between you and nameservers 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 versions 8 and later
	 * use a pseudo-random unprivileged UDP port by default.
	 */
	 // query-source address * port 53;
};

// If you enable a local name server, don't forget to enter 127.0.0.1
// first in your /etc/resolv.conf so this server will be queried.
// 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 "master/localhost.rev";
};

// RFC 3152
zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA" {
	type master;
	file "master/localhost-v6.rev";
};

// NB: Do not use the IP addresses below, they are faked, and only
// serve demonstration/documentation purposes!
//
// Example slave zone config entries.  It can be convenient to become
// a slave at least for the zone 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 named after the first bytes of the IP address, in reverse
// order, with ".IN-ADDR.ARPA" appended.)
//
// Before starting to set up a primary zone, make sure you fully
// understand how DNS and BIND works.  There are sometimes
// non-obvious pitfalls.  Setting up a slave zone is simpler.
//
// NB: Don't blindly enable the examples below. :-)  Use actual names
// and addresses instead.

/* An example master zone
zone "example.net" {
	type master;
	file "master/example.net";
};
*/

/* An example dynamic zone
key "exampleorgkey" {
	algorithm hmac-md5;
	secret "sf87HJqjkqh8ac87a02lla==";
};
zone "example.org" {
	type master;
	allow-update {
		key "exampleorgkey";
	};
	file "dynamic/example.org";
};
*/

/* Examples of forward and reverse slave zones
zone "example.com" {
	type slave;
	file "slave/example.com";
	masters {
		192.168.1.1;
	};
};
zone "1.168.192.in-addr.arpa" {
	type slave;
	file "slave/1.168.192.in-addr.arpa";
	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 "master/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/master/example.org</filename>
	  indicated by the <option>file</option> statement.</para>

	<programlisting>zone "example.org" {
	type slave;
	file "slave/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>
	<indexterm>
	  <primary>BIND</primary>
	  <secondary>zone files</secondary>
	</indexterm>

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

	<programlisting>&dollar;TTL 3600        ; 1 hour
example.org.    IN      SOA      ns1.example.org. admin.example.org. (
                                2006051501      ; Serial
                                10800           ; Refresh
                                3600            ; Retry
                                604800          ; Expire
                                86400           ; Minimum TTL
                        )

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

; MX Records
                IN      MX 10   mx.example.org.
                IN      MX 20   mail.example.org.

                IN      A       192.168.1.1

; Machine Names
localhost       IN      A       127.0.0.1
ns1             IN      A       192.168.1.2
ns2             IN      A       192.168.1.3
mx              IN      A       192.168.1.4
mail            IN      A       192.168.1.5

; Aliases
www             IN      CNAME   @</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. (
                        2006051501      ; 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>2006051501</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>2006051501</literal> would mean
		  last modified 05/15/2006, the latter
		  <literal>01</literal> being the first 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.
        </para>

        <programlisting>
localhost       IN      A       127.0.0.1
ns1             IN      A       192.168.1.2
ns2             IN      A       192.168.1.3
mx              IN      A       192.168.1.4
mail            IN      A       192.168.1.5</programlisting>

        <para>
          The A record indicates machine names.  As seen above,
          <hostid role="fqdn">ns1.example.org</hostid> would resolve
          to <hostid role="ipaddr">192.168.1.2</hostid>.
        </para>

        <programlisting>
                IN      A       192.168.1.1</programlisting>

	<para>This line assigns IP address
	  <hostid role="ipaddr">192.168.1.1</hostid> to the current origin,
	  in this case <hostid role="domainname">example.org</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 <quote>master</quote> machine which name equals
          to domain name <hostid role="domainname">example.org</hostid>
          (<hostid role="ipaddr">192.168.1.1</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 10,
          20 and so on.  A mail server attempting to deliver to <hostid
          role="domainname">example.org</hostid> would first try the
          highest priority MX (the record with the lowest priority
	  number), 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

1.168.192.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. (
                        2006051501      ; Serial
                        10800           ; Refresh
                        3600            ; Retry
                        604800          ; Expire
                        3600 )          ; Minimum

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

1       IN      PTR     example.org.
2       IN      PTR     ns1.example.org.
3       IN      PTR     ns2.example.org.
4       IN      PTR     mx.example.org.
5       IN      PTR     mail.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>
      <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>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>

      <para>It is always 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 &os; 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.rndc.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.isc.org/sw/guild/bf/">Official ISC BIND
	      Forum</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/dns5/">O'Reilly
	      DNS and BIND 5th 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-apache">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Murray</firstname>
	  <surname>Stokely</surname>
	  <contrib>ÓõíåéóöïñÜ ôïõ </contrib>
	</author>

	<author>
	  <firstname>ÂáããÝëçò</firstname>
	  <surname>ÔõðÜëäïò</surname>
	  <contrib>ÌåôÜöñáóç </contrib>
	</author>
      </authorgroup>
    </sect1info>

    <title>Ï åîõðçñåôçôÞò HTTP Apache</title>

    <indexterm><primary>åîõðçñåôçôÝò web</primary>
      <secondary>åãêáôÜóôáóç</secondary></indexterm>
    <indexterm><primary>Apache</primary></indexterm>

    <sect2>
      <title>Óýíïøç</title>

      <para>Ôï &os; ÷ñçóéìïðïéåßôáé ãéá íá öéëïîåíåß ðáãêïóìßùò éóôïóåëßäåò
        ìåãÜëçò åðéóêåøéìüôçôáò.  Ïé ðåñéóóüôåñïé äéáêïìéóôÝò web óôï
        äéáäßêôõï ÷ñçóéìïðïéïýí ôïí <application>åîõðçñåôçôÞ HTTP
        Apache</application>.  Ôá ðáêÝôá ëïãéóìéêïý
        ôïõ <application>Apache</application> èá ðñÝðåé íá ðåñéÝ÷ïíôáé óôï
        ìÝóï åãêáôáôÜóôáóçò ôïõ &os; ðïõ ÷ñçóéìïðïéåßôå. Áí äåí åãêáôáóôÞóáôå
        ôïí <application>Apache</application> êáôÜ ôçí äéÜñêåéá ôçò
        åãêáôÜóôáóçò ôïõ &os;, ôüôå ìðïñåßôå íá ôïí åãêáôáóôÞóåôå áðü ôï
        ðáêÝôï <filename role="package">www/apache13</filename> Þ áðü ôï
        ðáêÝôï <filename role="package">www/apache20</filename>.</para>

      <para>Áöïý ïëïêëçñþóåôå åðéôõ÷þò ôçí åãêáôÜóôáóç
        ôïõ <application>Apache</application>, èá ðñÝðåé íá êÜíåôå ôéò
        áðáñáßôçôåò ñõèìßóåéò.</para>

      <note>
	<para>ÁõôÞ ç åíüôçôá êáëýðôåé ôçí Ýêäïóç
          åîõðçñåôçôþí <application>Apache HTTP 1.3.X</application>, ìéáò ðïõ
          áõôÞ ç Ýêäïóç åßíáé ç ðéï äéáäåäïìÝíç ãéá ôï &os;.
          Ï <application>Apache</application>&nbsp;2.X ðáñïõóéÜæåé ðïëëÝò íÝåò
          ôå÷íïëïãßåò áëëÜ áõôÝò äåí ðåñéãñÜöïíôáé óå áõôÞ ôçí åíüôçôá.
          Ðåñéóóüôåñåò ðëçñïöïñßåò ãéá
          ôïí <application>Apache</application>&nbsp;2.X, ìðïñåßôå íá äåßôå
          óôçí óåëßäá <ulink url="http://httpd.apache.org/"></ulink>.</para>
      </note>
    </sect2>

    <sect2>
      <title>Ñõèìßóåéò</title>

      <indexterm>
	<primary>Apache</primary>
	<secondary>áñ÷åßï ñõèìßóåùí</secondary>
      </indexterm>

      <para>Óôï &os; ôï óçìáíôéêüôåñï áñ÷åßï ñõèìßóåùí
	ôïõ <application>ÅîõðçñåôçôÞ HTTP Apache</application> åßíáé
	ôï <filename>/usr/local/etc/apache/httpd.conf</filename>.  Åßíáé Ýíá
	ôõðéêü &unix; ñõèìéóôéêü áñ÷åßï êåéìÝíïõ, ìå ãñáììÝò ó÷ïëßùí ðïõ
	îåêéíïýí ìå ôïí ÷áñáêôÞñá <literal>#</literal>.  Óêïðüò ìáò åäþ äåí
	åßíáé ìéá ïëïêëçñùìÝíç ðåñéãñáöÞ üëùí ôùí ðéèáíþí åðéëïãþí, åðïìÝíùò
	èá ðåñéãñÜøïõìå ìüíï ôéò ðéï äçìïöéëåßò åðéëïãÝò ñõèìßóåéò
	(configuration directives).</para>

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

	  <listitem>
	    <para>Åäþ ðåñéãñÜöåôáé ï ðñïåðéëåãìÝíïò éåñáñ÷éêÜ êáôÜëïãïò
	      åãêáôÜóôáóçò ãéá ôïí <application>Apache</application>.  Ôá
	      åêôåëÝóéìá áñ÷åßá åßíáé áðïèçêåõìÝíá óôïõò
	      õðïêáôáëüãïõò <filename class="directory">bin</filename>
	      êáé <filename class="directory">sbin</filename> ôïõ
	      êáôáëüãïõ <quote>ServerRoot</quote> êáé ôá áñ÷åßá ñõèìßóåùí
	      áðïèçêåýïíôáé óôïí
	      êáôÜëïãï <filename class="directory">etc/apache</filename>.</para>
	  </listitem>
	</varlistentry>

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

	  <listitem>
	    <para>Ç çëåêôñïíéêÞ äéåýèõíóç óôçí ïðïßá èá ðñÝðåé íá
	      áðïóôÝëëïíôáé áíáöïñÝò ðñïâëçìÜôùí ó÷åôéêÜ ìå ôïí
	      åîõðçñåôçôÞ. ÁõôÞ ç äéåýèõíóç åìöáíßæåôáé óå êÜðïéåò óåëßäåò ðïõ
	      äçìéïõñãïýíôáé áðü ôïí åîõðçñåôçôÞ, üðùò ïé óåëßäåò
	      óöáëìÜôùí.</para>
	  </listitem>
	</varlistentry>

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

	  <listitem>
	    <para>Ôï <literal>ServerName</literal> óáò åðéôñÝðåé íá èÝóåôå Ýíá
	      üíïìá êüìâïõ (hostname) ãéá ôïí åîõðçñåôçôÞ óáò, ôï ïðïßï
	      áðïóôÝëëåôáé ðßóù óôïõò clients áí åßíáé äéáöïñåôéêü áðü åêåßíï
	      ðïõ Ý÷åôå Þäç ñõèìßóåé óôïí êüìâï óáò (åäþ ìðïñåßôå, ãéá
	      ðáñÜäåéãìá, íá ÷ñçóéìïðïéÞóåôå <hostid>www</hostid> áíôß ôïõ
	      ðñáãìáôéêïý ïíüìáôïò ôïõ êüìâïõ).</para>
	  </listitem>
	</varlistentry>

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

	  <listitem>
	    <para><literal>DocumentRoot</literal>: Åßíáé ï êáôÜëïãïò áðü ôïí
	      ïðïßï èá ðñïóöÝñïíôáé ôá Ýããñáöá óáò. ÐñïåðéëåãìÝíá, üëá ôá
	      áéôÞìáôá èá åîõðçñåôïýíôáé áðü áõôü ôïí êáôÜëïãï, áëëÜ ìðïñïýí
	      åðßóçò íá ÷ñçóéìïðïéçèïýí óõìâïëéêïß äåóìïß (symbolic link) Þ
	      ðáñùíýìéá (aliases) ðïõ èá óôï÷åýïõí óå Üëëåò ôïðïèåóßåò.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>Ðñéí êÜíåôå ïðïéáäÞðïôå áëëáãÞ, åßíáé êáëü íá äçìéïõñãåßôå
	áíôßãñáöá áóöáëåßáò (backup) ôïõ áñ÷åßïõ ñõèìßóåùí
	ôïõ <application>Apache</application>.  Ìüëéò êñßíåôå ðùò åßóôå
	éêáíïðïéçìÝíïò ìå ôéò áñ÷éêÝò ñõèìßóåéò ìðïñåßôå íá îåêéíÞóåôå ìå ôçí
	åêôÝëåóç ôïõ <application>Apache</application>.</para>

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

<!-- Advanced configuration section.

Performance tuning directives.

Log file format -->
    </sect2>

    <sect2>
      <title>ÅêôÝëåóç ôïõ <application>Apache</application></title>

      <indexterm>
	<primary>Apache</primary>
	<secondary>åêêßíçóç Þ óôáìÜôçìá</secondary>
      </indexterm>

      <para>O <application>Apache</application> äåí ôñÝ÷åé äéáìÝóïõ ôïõ
	õðåñ-äéáêïìéóôÞ <application>inetd</application> üðùò êÜíïõí ðïëëïß
	Üëëïé äéêôõáêïß åîõðçñåôçôÝò.  Åßíáé ñõèìéóìÝíïò íá ôñÝ÷åé áõôüíïìá
	ãéá íá åîõðçñåôåß êáëýôåñá ôéò áéôÞóåéò HTTP ôùí ðåëáôþí ôïõ, äçëáäÞ
	ôùí ðñïãñáììÜôùí ðëïÞãçóçò (browsers).  Ç åãêáôÜóôáóç
	ôïõ <application>Apache</application> áðü ôá &os; Ports ðåñéÝ÷åé Ýíá
	âïçèçôéêü shell script ãéá ôçí åêêßíçóç, ôï óôáìÜôçìá êáé ôçí
	åðáíåêêßíçóç ôïõ åîõðçñåôçôÞ.  Ãéá íá îåêéíÞóåôå
	ôïí <application>Apache</application> ãéá ðñþôç öïñÜ, áðëÜ
	ôñÝîôå:</para>

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

      <para>Ìðïñåßôå ïðïéáäÞðïôå óôéãìÞ íá óôáìáôÞóåôå ôïí åîõðçñåôçôÞ,
	ðëçêôñïëïãþíôáò:</para>

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

      <para>ÌåôÜ áðü áëëáãÝò ðïõ ðéèáíþò íá êÜíáôå ãéá ïðïéïíäÞðïôå ëüãï óôï
	áñ÷åßï ñõèìßóåùí, èá ÷ñåéáóôåß íá åðáíåêêéíÞóåôå ôïí
	åîõðçñåôçôÞ:</para>

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

      <para>Ãéá íá åðáíåêêéíÞóåôå ôïí <application>Apache</application> äß÷ùò
        íá äéáêüøåôå ôéò ôñÝ÷ïõóåò óõíäÝóåéò, ôñÝîôå:</para>

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

      <para>Ðåñéóóüôåñåò ðëçñïöïñßåò èá âñåßôå óôç óåëßäá âïÞèåéáò ôïõ
	&man.apachectl.8;.</para>

      <para>Ãéá íá îåêéíÜåé ï <application>Apache</application> áõôüìáôá êáôÜ
        ôç äéÜñêåéá åêêßíçóçò ôïõ óõóôÞìáôïò, ðñïóèÝóôå ôçí áêüëïõèç ãñáììÞ
        óôï <filename>/etc/rc.conf</filename>:</para>

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

      <para>Áí åðéèõìåßôå íá ðáñÝ÷ïíôáé êáôÜ ôçí åêêßíçóç ôïõ óõóôÞìáôïò
	ðñüóèåôåò åðéëïãÝò óôçí ãñáììÞ åíôïëþí ãéá ôï
	ðñüãñáììá <application>Apache</application> <command>httpd</command>
	ìðïñåßôå íá ôéò äçëþóåôå ìå ìéá ðñüóèåôç ãñáììÞ
	óôï <filename>rc.conf</filename>:</para>

      <programlisting>apache_flags=""</programlisting>

      <para>Ôþñá ðïõ Ý÷åé îåêéíÞóåé ï åîõðçñåôÞò web, ìðïñåßôå íá äåßôå ôçí
        éóôïóåëßäá óáò óôï÷åýïíôáò ôï ðñüãñáììá ðëïÞãçóçò
        óôï <literal>http://localhost/</literal>.  Ç ðñïêáèïñéóìÝíç óåëßäá ðïõ
        åìöáíßæåôáé åßíáé
        ç <filename>/usr/local/www/data/index.html</filename>.</para>
    </sect2>

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

      <para>Ï <application>Apache</application> õðïóôçñßæåé äýï äéáöïñåôéêïýò
        ôýðïõò Virtual Hosting.  Ôï Ïíïìáóôéêü virtual hosting ÷ñçóéìïðïéåß
        ôïõò HTTP/1.1 headers ãéá íá êáèïñßóåé ôïí êüìâï.  Áõôü åðéôñÝðåé ôçí
        êïéíÞ ÷ñÞóç ôçò ßäéáò IP ãéá ðïëëÜ êáé äéáöïñåôéêÜ domains.</para>

      <para>Ãéá íá ñõèìßóåôå ôïí <application>Apache</application> íá
        ÷ñçóéìïðïéåß ôï Ïíïìáóôéêü Virtual Hosting åéóÜãåôå ìéá êáôá÷þñéóç
        óôï <filename>httpd.conf</filename> óáí ôçí áêüëïõèç:</para>

      <programlisting>NameVirtualHost *</programlisting>

      <para>Áí ï äéáêïìéóôÞò web
	ïíïìÜæåôáé <hostid role="fqdn">www.domain.tld</hostid> êáé åðéèõìåßôå
	íá åãêáôáóôÞóåôå Ýíá virtual domain ãéá
	ôï <hostid role="fqdn">www.someotherdomain.tld</hostid> ôüôå èá ðñÝðåé
	íá ðñïóèÝóåôå ôéò áêüëïõèåò êáôá÷ùñÞóåéò
	óôï<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>ÁíôéêáôáóôÞóôå ôéò ðáñáðÜíù äéåõèýíóåéò ìå åêåßíåò ðïõ åðéèõìåßôå
	íá ÷ñçóéìïðïéÞóåôå êáé ôçí êáôÜëëçëç äéáäñïìÞ ðñïò ôá ÝããñáöÜ
	óáò.</para>

      <para>Ãéá ðåñéóóüôåñåò ðëçñïöïñßåò ó÷åôéêÜ ìå ôéò ñõèìßóåéò ãéá ôá
	virtual host, óáò ðñïôñÝðïõìå íá óõìâïõëåõôåßôå ôçí åðßóçìç ôåêìçñßùóç
	ôïõ <application>Apache</application>
	óôï <ulink url="http://httpd.apache.org/docs/vhosts/"></ulink>.</para>
    </sect2>

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

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

      <para>ÕðÜñ÷ïõí ðïëëïß êáé äéÜöïñïé äéáèÝóéìïé ôýðïé áñèñùìÜôùí (modules)
	ãéá ôïí <application>Apache</application>, ôá ïðïßá åðåêôåßíïõí êé
	åìðëïõôßæïõí ôéò ëåéôïõñãßåò ôïõ âáóéêïý åîõðçñåôçôÞ.  Ç ÓõëëïãÞ ôùí
	Ports ôïõ &os; ðáñÝ÷åé Ýíáí åýêïëï ôñüðï ãéá íá åãêáôáóôÞóåôå
	ôïí <application>Apache</application> êáé ìåñéêÜ áðü ôá ðéï äçìïöéëÞ
	áñèñþìáôá.</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>Ôï Üñèñùìá <application>mod_ssl</application> ÷ñçóéìïðïéåß ôçí
          âéâëéïèÞêç OpenSSL ãéá íá ðáñÝ÷åé éó÷õñÞ êñõðôïãñÜöçóç äéáìÝóïõ ôùí
          ðñùôïêüëùí Secure Sockets Layer (SSL v2/v3) êáé Transport Layer
          Security (TLS v1).  Ôï Üñèñùìá ðáñÝ÷åé üëá ôá áðáñáßôçôá óõóôáôéêÜ
          ãéá íá ìðïñåß íá áéôåßôáé õðïãåããñáììÝíá ðéóôïðïéçôéêÜ áðü Ýìðéóôïõò
          åîïõóéïäïôçìÝíïõò öïñåßò ðéóôïðïßçóçò Ýôóé þóôå íá ìðïñåßôå íá
          ôñÝ÷åôå Ýíáí áóöáëÞ åîõðçñåôçôÞ web óôï &os;.</para>

	<para>ÅÜí äåí Ý÷åôå åãêáôáóôÞóåé áêüìç
	  ôïí <application>Apache</application>, ìðïñåßôå íá åãêáôáóôÞóåôå ôçí
	  Ýêäïóç ôïõ <application>Apache</application> 1.3.X ðïõ ðåñéëáìâÜíåé
	  ôï <application>mod_ssl</application> áðü ôçí
	  port <filename role="package">www/apache13-modssl</filename> . Ôï
	  SSL åßíáé åðßóçò äéáèÝóéìï ãéá
	  ôïí <application>Apache</application>&nbsp;2.X óôçí
	  port <filename role="package">www/apache20</filename>, üðïõ ôï SSL
	  åßíáé åíåñãïðïéçìÝíï áðü ðñïåðéëïãÞ.</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>ÄõíáìéêÝò Éóôïóåëßäåò ìå  Perl &amp; PHP</title>

        <para>Ôçí ôåëåõôáßá äåêáåôßá, ðïëëÝò åðé÷åéñÞóåéò óôñÝøáíå ôéò
          äñáóôçñéüôçôåò ôïõò ðñïò ôï ºíôåñíåô ìå óêïðü íá âåëôéþóïõí ôá Ýóïäá
          ôïõò êáé ãéá ìåãáëýôåñç ðñïâïëÞ.  Áõôü ìå ôç óåéñÜ ôïõ äçìéïýñãçóå
          ôçí áíÜãêç ãéá äéáäñáóôéêü äéáäéêôõáêü ðåñéå÷üìåíï.  Åíþ êÜðïéåò
          åôáéñåßåò, üðùò ç &microsoft;, ðáñïõóßáóáí ëýóåéò åíóùìáôùìÝíåò óôá
          éäéüêôçôá ðñïúüíôá ôïõò, ç êïéíüôçôá áíïé÷ôïý ëïãéóìéêïý Ýëáâå ôï
          ìÞíõìá. Óôéò óýã÷ñïíåò åðéëïãÝò ãéá äéáäéêôõáêÝò óåëßäåò äõíáìéêïý
          ðåñéå÷ïìÝíïõ ðåñéëáìâÜíïíôáé ôá Django, Ruby on Rails, mod_perl êáé
          mod_php.

          <application>mod_perl</application> &amp;
          <application>mod_php</application>.</para>

        <sect4>
        <title>mod_perl</title>

	<indexterm>
          <primary>mod_perl</primary>
          <secondary>Perl</secondary>
        </indexterm>

        <para>Ôï ãåãïíüò óõíýðáñîçò <application>Apache</application>/Perl
	  öÝñíåé êïíôÜ ôç ìåãÜëç äýíáìç ôçò ãëþóóáò ðñïãñáììáôéóìïý Perl êáé
	  ôïí <application>åîõðçñåôçôÞ HTTP Apache</application>.  Ìå ôï
	  Üñèñùìá <application>mod_perl</application> Ý÷åôå ôç äõíáôüôçôá íá
	  ãñÜøåôå åðåêôÜóåéò ãéá ôïí <application>Apache</application> åî'
	  ïëïêëÞñïõ óå Perl.  ÅðéðëÝïí, ï äéáôçñÞóéìïò ìåôáãëùôôéóôÞò ðïõ
	  åßíáé åíóùìáôùìÝíïò óôïí åîõðçñåôçôÞ óáò åðéôñÝðåé íá áðïöýãåôå ôçí
	  ÷ñÞóç åíüò åîùôåñéêïý ìåôáãëùôôéóôÞ Perl êáé íá åðéâáñõíèåßôå áðü ôï
	  ÷ñüíï åêêßíçóçò ôïõ.</para>

        <para>Ôï <application>mod_perl</application> äéáôßèåôáé ìå äéÜöïñïõò
          ôñüðïõò.  Ãéá íá ÷ñçóéìïðïéÞóåôå
          ôï <application>mod_perl</application> íá èõìÜóôå üôé ôï mod_perl
          1.0 <application>mod_perl</application> 1.0 äïõëåýåé ìüíï ìå
          ôïí <application>Apache</application> 1.3 êáé
          ôï <application>mod_perl</application> 2.0 äïõëåýåé ìüíï ìå
          ôïí <application>Apache</application> 2.
          Ôï <application>mod_perl</application> 1.0 åßíáé äéáèÝóéìï óôï
          port <filename role="package">www/mod_perl</filename> åíþ ìéá
          óôáôéêÜ ìåôáãëùôôéóìÝíç Ýêäïóç åßíáé äéáèÝóéìç
          óôï <filename role="package">www/apache13-modperl</filename>.
          Ôï <application>mod_perl</application> 2.0 äéáôßèåôáé óôï
          port <filename role="package">www/mod_perl2</filename>.</para>
        </sect4>

        <sect4>
          <sect4info>
	  <authorgroup>
	    <author>
	      <firstname>Tom</firstname>
	      <surname>Rhodes</surname>
	      <contrib>ÓõããñáöÞ áðü ôïí </contrib>
	    </author>
	  </authorgroup>
        </sect4info>
        <title>mod_php</title>

	<indexterm>
          <primary>mod_php</primary>
          <secondary>PHP</secondary>
        </indexterm>

	<para>Ôï <acronym>PHP</acronym>, ãíùóôü êáé ùò <quote>PHP: Hypertext
            Preprocessor</quote> åßíáé ìéá script ãëþóóá ðñïãñáììáôéóìïý
          ãåíéêÞò ÷ñÞóçò áëëÜ éäéáßôåñá êáôÜëëçëç ãéá áíÜðôõîç ëïãéóìéêïý Web.
          Ç óýíôáîÞ ôçò ðñïÝñ÷åôáé áðü ôéò C, &java; êáé Perl êáé Ý÷åé ôçí
          äõíáôüôçôá íá åíóùìáôþíåôáé óå êþäéêá <acronym>HTML</acronym>, ìå
          óêïðü íá åðéôñÝðåé óôïõò ðñïãñáììáôéóôÝò web íá ãñÜöïõí ãñÞãïñá
          äõíáìéêÝò éóôïóåëßäåò.</para>

	<para>Ï <application>Apache</application> õðïóôçñßæåé
          ôï <acronym>PHP</acronym>5.  Ìðïñåßôå íá îåêéíÞóåôå åãêáèéóôþíôáò ôï
          ðáêÝôï <filename role="package">lang/php5</filename>.</para>

	<para>Áí ôï ðáêÝôï <filename role="package">lang/php5</filename>
	  åãêáèßóôáôáé ãéá ðñþôç öïñÜ, áõôüìáôá èá óáò åìöáíéóôïýí üëåò ïé
	  äõíáôÝò åðéëïãÝò <literal>OPTIONS</literal>. Áí êÜðïéï ìåíïý äåí
	  åìöáíßæåôáé, ð.÷. åðåéäÞ ôï
	  ðáêÝôï <filename role="package">lang/php5</filename> åß÷å
	  åãêáôáóôáèåß óôï ðáñåëèüí, ìðïñåßôå ðÜíôá íá ñõèìßóåôå áðü ôçí áñ÷Þ
	  ôï ðáêÝôï, ôñÝ÷ïíôáò óôïí êáôÜëïãï ôïõ port:</para>

	<screen>&prompt.root; <userinput>make config</userinput></screen>

	<para>Óôéò åðéëïãÝò åãêáôÜóôáóçò, äéáëÝîôå ôçí
	  åðéëïãÞ <literal>APACHE</literal> þóôå íá óõìðåñéëçöèåß êáé ôï
	  Üñèñùìá <application>mod_php</application> ãéá ôïí
	  åîõðçñåôçôÞ <application>Apache</application>.</para>

	<note>
	  <para>ÌåñéêÝò ôïðïèåóßåò ÷ñçóéìïðïéïýí áêüìç
	    ôï <acronym>PHP</acronym>4 ãéá äéÜöïñïõò ëüãïõò (ð.÷. èÝìáôá
	    óõìâáôüôçôïò Þ åðåéäÞ Ý÷ïõí Þäç åãêáôåóôçìÝíåò åöáñìïãÝò ðïõ ôï
	    áðáéôïýí).  Áí åßíáé áíÜãêç íá ÷ñçóéìïðïéÞóåôå
	    ôï <application>mod_php4</application> áíôß
	    ôïõ <application>mod_php5</application>, ôüôå ÷ñçóéìïðïéåßóôå ôï
	    port <filename role="package">lang/php4</filename>.  Ôï
	    port <filename role="package">lang/php4</filename> õðïóôçñßæåé
	    ðïëëÝò áðü ôéò ñõèìßóåéò êáé ôéò åðéëïãÝò åãêáôÜóôáóçò ôïõ
	    port <filename role="package">lang/php5</filename>.</para>
	</note>

	<para>Ìå áõôü ôïí ôñüðï èá åãêáôáóôáèïýí êáé èá ñõèìéóôïýí ôá
          áðáéôïýìåíá áñèñþìáôá þóôå íá õðïóôçñßæïõí äõíáìéêÝò
          åöáñìïãÝò <acronym>PHP</acronym>. Ãéá åðéâåâáßùóç åëÝãîôå ðùò Ý÷ïõí
          ðñïóôåèåß óôéò áíôßóôïé÷åò åíüôçôåò
          ôïõ <filename>/usr/local/etc/apache/httpd.conf</filename> ôá
          áêüëïõèá::</para>

	<programlisting>LoadModule php5_module        libexec/apache/libphp5.so</programlisting>

        <programlisting>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>Áöïý ïëïêëçñþóåôå ôïí Ýëåã÷ï, ãéá íá öïñôùèåß ôï
          Üñèñùìá <acronym>PHP</acronym> ÷ñåéÜæåôáé ìéá áðëÞ êëÞóç ìå ôçí
          åíôïëÞ <command>apachectl</command> ãéá ìéá êáíïíéêÞ (graceful)
          åðáíåêêßíçóç:</para>

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

	<para>Ãéá ìåëëïíôéêÝò áíáâáèìßóåéò ôïõ <acronym>PHP</acronym>, äåí
	  áðáéôåßôáé ç åíôïëÞ <command>make config</command>.  Ïé
	  åðéëåãìÝíåò <literal>OPTIONS</literal> áðïèçêåýïíôáé áõôüìáôá áðü ôï
	  ìç÷áíéóìü åãêáôÜóôáóçò ôùí Ports ôïõ &os;.</para>

        <para>Ç óýíèåóç ôïõ <acronym>PHP</acronym> óôï &os;, åßíáé åîáéñåôéêÜ
	  óôïé÷åéáêÞ, êáé ï âáóéêüò êïñìüò ðïõ Ý÷åé åãêáôáóôáèåß åßíáé ðïëý
	  ðåñéïñéóìÝíïò.  Åßíáé ðïëý åýêïëï üìùò íá ðñïóèÝóïõìå åðåêôÜóåéò
	  ÷ñçóéìïðïéþíôáò ôï
	  port <filename role="package">lang/php5-extensions</filename>.  Áõôü
	  ôï port ðáñÝ÷åé ìåíïý åðéëïãþí ãéá ôçí åãêáôÜóôáóç ôùí åðåêôÜóéìùí
	  óõóôáôéêþí ôïõ <acronym>PHP</acronym>.  ÅíáëëáêôéêÜ, ìðïñåßôå íá
	  åãêáôáóôÞóåôå êáèåìßá åðÝêôáóç îå÷ùñéóôÜ ÷ñçóéìïðïéþíôáò ôï
	  êáôÜëëçëï port.</para>

	<para>Ãéá ðáñÜäåéãìá, ãéá íá ðñïóèÝóåôå óôï <acronym>PHP</acronym>5,
	  ôç äõíáôüôçôá õðïóôÞñéîçò ãéá âÜóåéò
	  äåäïìÝíùí<application>MySQL</application> áðëÜ åãêáôáóôÞóôå ôï
	  port <filename role="package">databases/php5-mysql</filename>.</para>

        <para>ÌåôÜ ôçí åãêáôÜóôáóç åíüò íÝïõ áñèñþìáôïò Þ êÜðïéáò Üëëçò
	  åðÝêôáóçò, ï åîõðçñåôçôÞò <application>Apache</application> èá
	  ðñÝðåé íá åðáíáöïñôùèåß ãéá íá åíåñãïðïéçèïýí ïé íÝåò
	  ñõèìßóåéò:</para>

	<screen>&prompt.root; <userinput>apachectl graceful</userinput></screen>
        </sect4>
      </sect3>
    </sect2>
  </sect1>

  <sect1 id="network-ftp">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Murray</firstname>
	  <surname>Stokely</surname>
	  <contrib>ÓõíåéóöïñÜ ôïõ </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>Ðñùôüêïëï ÌåôáöïñÜò Áñ÷åßùí (FTP)</title>

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

    <sect2>
      <title>Óýíïøç</title>

      <para>Ôï Ðñùôüêïëï ÌåôáöïñÜò Áñ÷åßùí (File Transfer Protocol - FTP)
	ðáñÝ÷åé óôïõò ÷ñÞóôåò Ýíáí åýêïëï ôñüðï ãéá íá ìåôáöÝñïõí ôá áñ÷åßá
	ôïõò áðü êáé ðñïò Ýíáí åîõðçñåôçôÞ <acronym role="File Transfer
	Protocol">FTP</acronym>.  Ôï âáóéêü óýóôçìá ôïõ &os; ðåñéëáìâÜíåé Ýíá
	åîõðçñåôçôÞ FTP, ôï <application>ftpd</application>.  Áõôü êáèéóôÜ ôçí
	åãêáôÜóôáóç êáé ôçí äéá÷åßñéóç ôïõ åîõðçñåôçôÞ <acronym role="File
	Transfer Protocol">FTP</acronym> ðïëý åýêïëç õðüèåóç.</para>
    </sect2>

    <sect2>
      <title>Ñõèìßóåéò</title>

      <para>Ôï ðéï óçìáíôéêü âÞìá óôéò ñõèìßóåéò åßíáé íá áðïöáóßóåôå óå
	ðïéïýò ëïãáñéáóìïýò èá åðéôñáðåß ç ðñüóâáóç óôïí åîõðçñåôçôÞ FTP.  ¸íá
	óõíçèéóìÝíï óýóôçìá &os; äçìéïõñãåß ìåñéêïýò ëïãáñéáóìïýò óõóôÞìáôïò
	ãéá äéÜöïñïõò äáßìïíåò, áëëÜ äåí ðñÝðåé íá åðéôñÝðåôáé ç ðñüóâáóç óôï
	óýóôçìá ìå áõôïýò ôïõò ëïãáñéáóìïýò.  Ôï
	áñ÷åßï <filename>/etc/ftpusers</filename> ðåñéÝ÷åé ìéá ëßóôá áðü
	÷ñÞóôåò ãéá ôïõò ïðïßïõò áðïññßðôåôáé ç ðñüóâáóç ìÝóù FTP.
	ÐñïåðéëåãìÝíá, ðåñéÝ÷ïíôáé ïé ðñïáíáöåñèÝíôåò ëïãáñéáóìïß ôïõ
	óõóôÞìáôïò, áëëÜ ìðïñåßôå åðßóçò íá ðñïóèÝóåôå óõãêåêñéìÝíïõò ÷ñÞóôåò
	ðïõ äå èá ðñÝðåé íá Ý÷ïõí ðñüóâáóç ìÝóù FTP.</para>

      <para>Ìðïñåßôå áí èÝëåôå íá ðåñéïñßóåôå ôçí ðñüóâáóç óå êÜðïéïõò
	÷ñÞóôåò, äß÷ùò üìùò íá ôïõò åìðïäßóåôå ðëÞñùò.  Áõôü ìðïñåß íá óõìâåß
	ìå ôéò ñõèìßóåéò ôïõ áñ÷åßïõ <filename>/etc/ftpchroot</filename>.
	Áõôü ôï áñ÷åßï ðåñéÝ÷åé ëßóôåò ÷ñçóôþí êáé ïìÜäùí ðåñéïñéóìÝíçò
	ðñüóâáóçò FTP.  Ç óåëßäá âïÞèåéáò &man.ftpchroot.5; ðåñéÝ÷åé üëåò ôéò
	áðáñáßôçôåò ëåðôïìÝñåéåò, åðïìÝíùò äå èá ÷ñåéáóôåß íá ìðïýìå óå
	ëåðôïìÝñåéåò åäþ.</para>

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

      <para>Áí åðéèõìåßôå íá åíåñãïðïéÞóåôå áíþíõìç ðñüóâáóç FTP óôïí
	åîõðçñåôçôÞ óáò, èá ðñÝðåé íá äçìéïõñãÞóåôå, óôï &os; óýóôçìá óáò, Ýíá
	÷ñÞóôç ìå üíïìá <username>ftp</username> . Ïé áíþíõìïé ÷ñÞóôåò èá
	ìðïñïýí íá åéóÝñ÷ïíôáé óôïí åîõðçñåôçôÞ FTP ìå ôï ãåíéêü üíïìá
	÷ñÞóôç <username>ftp</username> Þ ìå <username>anonymous</username>
	êáé ìå ïðïéáäÞðïôå êùäéêü ðñüóâáóçò (óõíçèßæåôáé íá æçôåßôáé ç
	äéåýèõíóç email ôïõ ÷ñÞóôç ùò êùäéêüò ðñüóâáóçò).  Ï åîõðçñåôçôÞò FTP
	èá êáëÝóåé ôï &man.chroot.2; ìüëéò åéóÝëèç ï áíþíõìïò ÷ñÞóôçò, ãéá íá
	ôïõ ðåñéïñßóåé ôçí ðñüóâáóç, åðéôñÝðïíôáò ôïõ ìüíï ôïí áñ÷éêü êáôÜëïãï
	(home directory) ôïõ ÷ñÞóôç <username>ftp</username>.</para>

      <para>ÕðÜñ÷ïõí äýï áñ÷åßá êåéìÝíïõ ãéá ôïí ïñéóìü ìçíõìÜôùí
	êáëùóïñßóìáôïò ðïõ èá åìöáíßæïíôáé óôïõò ðåëÜôåò FTP.  Ôï ðåñéå÷üìåíï
	ôïõ áñ÷åßïõ <filename>/etc/ftpwelcome</filename> åìöáíßæåôáé óôïõò
	÷ñÞóôåò ðñéí öôÜóïõí óôçí ðñïôñïðÞ åéóüäïõ.  ÌåôÜ áðü ìéá ðåôõ÷çìÝíç
	åßóïäï óôï óýóôçìá, åìöáíßæåôáé ôï ðåñéå÷üìåíï ôïõ
	áñ÷åßïõ <filename>/etc/ftpmotd</filename>.  ÐáñáôçñÞóôå ðùò ç äéáäñïìÞ
	óå áõôü ôï áñ÷åßï åßíáé ó÷åôéêÞ ìå ôï ðåñéâÜëëïí ðñüóâáóçò, åðïìÝíùò
	ãéá ôïõò áíþíõìïõò ÷ñÞóôåò èá åìöáíßæåôáé ôï ðåñéå÷üìåíï ôïõ
	áñ÷åßïõ <filename>~ftp/etc/ftpmotd</filename>.</para>

      <para>Áöïý ñõèìßóåôå êáôÜëëçëá ôïí åîõðçñåôçôÞ FTP, èá ðñÝðåé íá ôïí
	åíåñãïðïéÞóåôå óôï áñ÷åßï <filename>/etc/inetd.conf</filename>.  Ôï
	ìüíï ðïõ ÷ñåéÜæåôáé íá êÜíåôå åßíáé íá áöáéñÝóåôå ôï óýìâïëï
	ó÷ïëéáóìïý <quote>#</quote> ìðñïóôÜ áðü ôçí õðÜñ÷ïõóá
	ãñáììÞ <application>ftpd</application> :</para>

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

      <para>¼ðùò åîçãÞóáìå óôï <xref linkend="network-inetd-reread"/>, ç
	äéåñãáóßá <application>inetd</application> èá ðñÝðåé íá îáíáöïñôþíåôáé
	áí Ý÷ïõí ãßíåé áëëáãÝò óôï áñ÷åßï ñõèìßóåùí ôçò.</para>

      <para>Ôþñá ìðïñåßôå íá äþóåôå ôá óôïé÷åßá ôïõ ëïãáñéáóìïý óáò ãéá íá
	åéóÝëèåôå óôïí åîõðçñåôçôÞ FTP.</para>

      <screen>&prompt.user; <userinput>ftp localhost</userinput></screen>
    </sect2>

    <sect2>
      <title>ÓõíôÞñçóç</title>

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

      <para>Ï äáßìïíáò <application>ftpd</application> ÷ñçóéìïðïéåß ôï
	&man.syslog.3; ãéá ôçí äçìéïõñãßá ìçíõìÜôùí áíáöïñÜò.  ÐñïåðéëåãìÝíá,
	ï äáßìïíáò ôùí log ôïõ óõóôÞìáôïò èá åíáðïèÝôåé ôéò ó÷åôéêÝò ìå ôï FTP
	áíáöïñÝò óôï áñ÷åßï <filename>/var/log/xferlog</filename>.  Ç
	ôïðïèåóßá ôïõ áñ÷åßïõ áíáöïñÜò ìðïñåß íá ôñïðïðïéçèåß áëëÜæïíôáò ôçí
	áêüëïõèç ãñáììÞ óôï <filename>/etc/syslog.conf</filename>:</para>

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

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

      <para>ÐñÝðåé íá åßóôå åíÞìåñïé ãéá ôá ðñïâëÞìáôá ðïõ ìðïñïýí íá
	ðáñïõóéáóôïýí ó÷åôéêÜ ìå ôç ëåéôïõñãßá åíüò áíþíõìïõ åîõðçñåôçôÞ FTP.
	Åéäéêüôåñá, èá ðñÝðåé íá óêåöôåßôå óïâáñÜ áí üíôùò åðéèõìåßôå íá Ý÷ïõí
	äõíáôüôçôá íá áíåâÜæïõí áñ÷åßá ïé áíþíõìïé ÷ñÞóôåò óáò.  Áí áöÞóåôå
	ïðïéïíäÞðïôå áíþíõìï ÷ñÞóôç íá áíåâÜæåé áñ÷åßá, ìðïñåß îáöíéêÜ íá
	áíáêáëýøåôå ðùò ï åîõðçñåôçôÞò óáò FTP ÷ñçóéìïðïéåßôáé ãéá äéáêßíçóç
	ðåéñáôéêïý åìðïñéêïý ëïãéóìéêïý Þ ãéá Üëëï, áêüìá ÷åéñüôåñï, ðáñÜíïìï
	õëéêü.  ÅÜí üíôùò ÷ñåéÜæåôáé ïé ÷ñÞóôåò íá Ý÷ïõí Üäåéá ðñïóèÞêçò
	áñ÷åßùí, ôüôå èá ðñÝðåé íá ñõèìßóåôå ôéò Üäåéåò Ýôóé þóôå ôá áñ÷åßá
	áõôÜ íá ìçí åßíáé ïñáôÜ áðü Üëëïõò áíþíõìïõò ÷ñÞóôåò, Ýùò üôïõ íá
	ðÜñïõí ôçí áóöáëÞ Ýãêñéóç óáò.</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>file system 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-reread"/>,
          the <application>inetd</application> must be reloaded 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>

	    <listitem>
	      <indexterm><primary>NetBIOS</primary></indexterm>

	      <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>

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

	      <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
	  your &unix; user accounts access from &windows; clients, use the
	  following command:</para>

	<screen>&prompt.root; <userinput>smbpasswd -a username</userinput></screen>

	<para>Please see the
	  <ulink
	  url="http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/">Official Samba HOWTO</ulink>
	  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>The <filename role="package">net/samba3</filename> port adds
	a new startup script, which can be used to control
	<application>Samba</application>.  To enable this script, so
	that it can be used for example to start, stop or restart
	<application>Samba</application>, add the following line to the
	<filename>/etc/rc.conf</filename> file:</para>

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

      <note>
	<para>This will also configure <application>Samba</application>
	  to automatically start at system boot time.</para>
      </note>

      <para>It is possible then to start
	<application>Samba</application> at any time by typing:</para>

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

      <para>Please refer to <xref linkend="configtuning-rcd"/> for more
	information about using rc scripts.</para>

      <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>ÓõíåéóöïñÜ ôïõ </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>Óõã÷ñïíéóìüò Ñïëïãéïý ÓõóôÞìáôïò ìå NTP</title>

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

    <sect2>
      <title>Óýíïøç</title>

      <para>Ìå ôï ðÝñáóìá ôïõ ÷ñüíïõ, ôï ñïëüé óõóôÞìáôïò åíüò õðïëïãéóôÞ Ý÷åé
	ôçí ôÜóç íá áðïóõã÷ñïíßæåôáé. Ôï Ðñùôüêïëï ×ñïíéóìïý Äéêôýùí (Network
	Time Protocol Þ NTP) ðáñÝ÷åé Ýíá ôñüðï ãéá íá åîáóöáëßóåôå ôçí
	áêñßâåéá ôïõ clock óáò. </para>

      <para>ÐïëëÝò äéáäéêôõáêÝò õðçñåóßåò âáóßæïíôáé Þ ùöåëïýíôáé óå ìåãÜëï
	âáèìü áðü ôçí áêñßâåéá ôïõ ñïëïãéïý óõóôÞìáôïò åíüò õðïëïãéóôÞ.  Ãéá
	ðáñÜäåéãìá, Ýíáò åîõðçñåôçôÞò web ìðïñåß íá äå÷èåß áéôÞóåéò ãéá
	áðïóôïëÞ åíüò áñ÷åßïõ üôáí ôï áñ÷åßï áõôü Ý÷åé ôñïðïðïéçèåß ìÝ÷ñé
	êÜðïéá óõãêåêñéìÝíç þñá. Óå Ýíá ðåñéâÜëëïí ôïðéêïý äéêôýïõ, åßíáé
	èåìåëéþäçò áñ÷Þ ïé õðïëïãéóôÝò ðïõ èá äéáìïéñáóôïýí áñ÷åßá áðü ôïí
	ßäéï äéáêïìéóôÞ áñ÷åßùí íá Ý÷ïõí óõã÷ñïíéóìÝíá ñïëüãéá, Ýôóé þóôå ôá
	÷ñïíéêÜ ÷áñáêôçñéóôéêÜ ôïõ áñ÷åßïõ íá óõìöùíïýí.  Åðßóçò äéåñãáóßåò
	üðùò ç &man.cron.8; âáóßæïíôáé óå Ýíá áêñéâÝò ñïëüé þóôå íá ìðïñïýí íá
	ôñÝ÷ïõí åíôïëÝò óôïõò ðñïêáèïñéóìÝíïõò ÷ñüíïõò.</para>

      <indexterm>
	<primary>NTP</primary>
	<secondary>ntpd</secondary>
      </indexterm>
      <para>Ôï &os; äéáôßèåôáé ìå ôïí åîõðçñåôçôÞ <acronym role="Network Time
	Protocol">NTP</acronym> &man.ntpd.8;, ï ïðïßïò ìðïñåß íá
	÷ñçóéìïðïéçèåß ãéá íá óõã÷ñïíßæåé ôï ñïëüé óõóôÞìáôïò ôïõ õðïëïãéóôÞ
	óáò, åîåôÜæïíôáò Üëëïõò åîõðçñåôçôÝò <acronym role="Network Time
	Protocol">NTP</acronym> Þ íá ðáñÝ÷åé ï ßäéïò õðçñåóßåò óõã÷ñïíéóìïý óå
	Üëëá ìç÷áíÞìáôá.</para>
    </sect2>

    <sect2>
      <title>ÅðéëïãÞ ôùí ÊáôÜëëçëùí Åîõðçñåôçôþí NTP</title>

      <indexterm>
	<primary>NTP</primary>
	<secondary>åðéëïãÞ åîõðçñåôçôþí</secondary>
      </indexterm>

      <para>Ãéá íá óõã÷ñïíßóåôå ôï ñïëüé óõóôÞìáôïò ôïõ õðïëïãéóôÞ óáò èá
	ðñÝðåé íá âñåßôå Ýíáí Þ ðåñéóóüôåñïõò
	äéáèÝóéìïõò <acronym role="Network Time Protocol">NTP</acronym>
	åîõðçñåôçôÝò ãéá íá ÷ñçóéìïðïéÞóåôå. Ï äéá÷åéñéóôÞò äéêôýïõ Þ ï ISP
	óáò ìðïñåß íá Ý÷ïõí åãêáôáóôÞóåé êÜðïéïí åîõðçñåôçôÞ NTP ãéá áõôü ôï
	óêïðü&nbsp;&mdash; åëÝãîôå ôçí ôåêìçñßùóç ôïõò íá äåßôå áí õðÜñ÷åé
	ôÝôïéá ðåñßðôùóç. ÅðéðëÝïí, õðÜñ÷åé
	ìßá <ulink url="http://ntp.isc.org/bin/view/Servers/WebHome">online
	ëßóôá åîõðçñåôçôþí äçìüóéáò ðñüóâáóçò</ulink>, ðïõ ìðïñåßôå íá
	÷ñçóéìïðïéÞóåôå ãéá íá âñåßôå Ýíáí êïíôéíü åîõðçñåôçôÞ NTP.  ¼ðïéïí
	åîõðçñåôçôÞ êé áí åðéëÝîåôå, åíçìåñùèåßôå ãéá ôçí ðïëéôéêÞ ÷ñÞóçò ôïõ
	êáé æçôÞóôå Üäåéá íá ôïí ÷ñçóéìïðïéÞóåôå áí ÷ñåéÜæåôáé ôÝôïéá
	Üäåéá.</para>

      <para> Åßíáé êáëÞ éäÝá íá åðéëÝîåôå ðïëëïýò åîõðçñåôçôÝò NTP, ïé ïðïßïé
	íá ìçí óõíäÝïíôáé ìåôáîý ôïõò, óôçí ðåñßðôùóç ðïõ êÜðïéïò áðü ôïõò
	åîõðçñåôçôÝò ðïõ ÷ñçóéìïðïéåßôå ãßíåé áðñüóéôïò Þ ôï ñïëüé ôïõ åßíáé
	áíáêñéâÝò.  Ï åîõðçñåôçôÞò &man.ntpd.8; ôïõ &os; ÷åéñßæåôáé Ýîõðíá ôéò
	áðáíôÞóåéò ðïõ ëáìâÜíåé áðü ôïõò õðüëïéðïõò åîõðçñåôçôÝò&nbsp;&mdash;
	åõíïåß ôïõò ðéï áîéüðéóôïõò êáé äåß÷íåé ìéêñüôåñç ðñïôßìçóç óôïõò
	ëéãüôåñï áîéüðéóôïõò åîõðçñåôçôÝò.</para>
    </sect2>

    <sect2>
      <title>Ñõèìßóôå Ôï Ìç÷Üíçìá Óáò</title>

      <indexterm>
	<primary>NTP</primary>
	<secondary>ñõèìßóåéò</secondary>
      </indexterm>

      <sect3>
	<title>ÂáóéêÝò Ñõèìßóåéò</title>
	<indexterm><primary>ntpdate</primary></indexterm>

	<para>Áí åðéèõìåßôå íá óõã÷ñïíßæåôáé ôï clock óáò ìüíï êáôÜ ôçí
	  åêêßíçóç ëåéôïõñãßáò ôïõ ìç÷áíÞìáôïò, ôüôå ìðïñåßôå íá
	  ÷ñçóéìïðïéÞóåôå ôï &man.ntpdate.8;. Áõôüò ï ôñüðïò óõã÷ñïíéóìïý
	  åßíáé êáôÜëëçëïò ãéá ìç÷áíÞìáôá desktop ôá ïðïßá êÜíïõí åðáíáêêßíçóç
	  áíÜ ôáêôÜ ÷ñïíéêÜ äéáóôÞìáôá êáé ìüíï óå åéäéêÝò ðåñéðôþóåéò Ý÷ïõí
	  áíÜãêç óõã÷ñïíéóìïý.  ÁíôéèÝôùò, ôá õðüëïéðá ìç÷áíÞìáôá èá ðñÝðåé íá
	  ôñÝ÷ïõí ôçí äéåñãáóßá &man.ntpd.8;.</para>

	<para>Åßíáé êáëÞ ðñáêôéêÞ ôá ìç÷áíÞìáôá ðïõ ôñÝ÷ïõí &man.ntpd.8; íá
	  ÷ñçóéìïðïéïýí êáé ôï &man.ntpdate.8; êáôÜ ôç äéÜñêåéá åêêßíçóçò
	  ôïõò.  Ôï &man.ntpd.8; ìåôáâÜëëåé ôï clock âáèìéáßá, åíþ ôï
	  &man.ntpdate.8; ñõèìßæåé Üìåóá ôï clock áíåîÜñôçôá áðü ôï ðüóï
	  ìåãÜëç åßíáé ç ÷ñïíéêÞ äéáöïñÜ ìåôáîý ðñáãìáôéêÞò êáé ôñÝ÷ïõóáò þñáò
	  ôïõ clock ôïõ ìç÷áíÞìáôïò.</para>

	<para>Ãéá íá åíåñãïðïéÞóåôå ôï &man.ntpdate.8; êáôÜ ôçí åêêßíçóç,
	  ðñïóèÝóôå <literal>ntpdate_enable="YES"</literal>
	  óôï <filename>/etc/rc.conf</filename>.  Èá ðñÝðåé íá ðñïóäéïñßóåôå
	  óôï <varname>ntpdate_flags</varname> üëïõò ôïõò äéáêïìéóôÝò ìå ôïõò
	  ïðïßïõò åðéèõìåßôå íá óõã÷ñïíßæåóôå êáé üëá ôá flag ðïõ èÝëåôå íá
	  óõíïäåýïõí ôï&man.ntpdate.8;.</para>
      </sect3>

      <sect3>
	<title>ÃåíéêÝò Ñõèìßóåéò</title>

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

	<para>Ïé ñõèìßóåéò ôïõ NTP âñßóêïíôáé óôï
	  áñ÷åßï <filename>/etc/ntp.conf</filename> êáé åßíáé óôç ìïñöÞ ðïõ
	  ðåñéãñÜöåôáé óôï &man.ntp.conf.5;. Áêïëïõèåß Ýíá áðëü
	  ðáñÜäåéãìá:</para>

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

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

	<para>Ç åðéëïãÞ <literal>server</literal> ðñïóäéïñßæåé ðïéïé
	  åîõðçñåôçôÝò èá ÷ñçóéìïðïéçèïýí, ðáñáèÝôïíôáò Ýíáí óå êÜèå
	  ãñáììÞ. Áí Ýíáò åîõðçñåôçôÞò öÝñåé ôï
	  ðñüèåìá <literal>prefer</literal>, üðùò óõìâáßíåé ìå
	  ôïí <hostid role="fqdn">ntplocal.example.com</hostid>, ôüôå áõôüò ï
	  åîõðçñåôçôÞò åßíáé ï ðñïôéìþìåíïò. Èá áðïññéöèåß ç áðÜíôçóç áðü ôïí
	  ðñïôéìþìåíï åîõðçñåôçôÞ óå ðåñßðôùóç ðïõ äéáöÝñåé óçìáíôéêÜ áðü
	  üëïõò ôïõò Üëëïõò åîõðçñåôçôÝò, Óå ðåñßðôùóç ðïõ äåí õðÜñ÷åé ìåãÜëç
	  áðüêëéóç èá ÷ñçóéìïðïéçèåß äß÷ùò íá ëçöèïýí õðüøéí ïé Üëëåò
	  áðáíôÞóåéò. Ôï ðñüèåìá <literal>prefer</literal> óõíÞèùò
	  ÷ñçóéìïðïéåßôáé ìå åîõðçñåôçôÝò NTP áêñéâåßáò, üðùò áõôïß ðïõ öÝñïõí
	  åéäéêïýò ìç÷áíéóìïýò ðáñáêïëïýèçóçò ÷ñïíéóìïý.</para>

	<para>Ç åðéëïãÞ <literal>driftfile</literal> ðñïóäéïñßæåé ðïéü áñ÷åßï
	  ÷ñçóéìïðïéåßôáé ãéá íá äéáôçñåß ôç óõ÷íüôçôá äéüñèùóçò ôïõ clock ôïõ
	  óõóôÞìáôïò. Ôï ðñüãñáììá &man.ntpd.8; ÷ñçóéìïðïéåß áõôüìáôá áõôÞ ôç
	  ôéìÞ ãéá íá áíôéóôáèìßæåé ôéò öõóéêÝò áðïêëßóåéò ôïõ clock,
	  åðéôñÝðïíôáò ôïõ íá äéáôçñåß ìéá ëïãéêÞ ñýèìéóç, áêüìç êé áí ôïõ
	  áðáãïñåõôåß ãéá êÜðïéï ÷ñïíéêü äéÜóôçìá ç ðñüóâáóç ðñïò üëåò ôéò
	  åîùôåñéêÝò ðçãÝò óõã÷ñïíéóìïý.</para>

	<para>Ç åðéëïãÞ <literal>driftfile</literal> ðñïóäéïñßæåé ðïéü áñ÷åßï
	  ÷ñçóéìïðïéåßôáé ãéá íá áðïèçêåýåé ðëçñïöïñßåò ó÷åôéêÜ ìå ôéò
	  ðñïçãïýìåíåò áðáíôÞóåéò áðü ôïõò åîõðçñåôçôÝò NTP. Áõôü ôï áñ÷åßï
	  ðåñéÝ÷åé åóùôåñéêÝò ðëçñïöïñßåò ôïõ NTP. Äåí èá Ýðñåðå íá
	  ôñïðïðïéåßôå áðü êáììßá Üëëç äéåñãáóßá.</para>
      </sect3>

      <sect3>
	<title>¸ëåã÷ïò Ðñüóâáóçò óôïí ÅîõðçñåôçôÞ Óáò</title>

	<para>ÐñïåðéëåãìÝíá, ï åîõðçñåôçôÞò óáò NTP èá åßíáé ðñïóâÜóéìïò áðü
	  üëïõò ôïõò êüìâïõò óôï äéáäßêôõï. Ç
	  åðéëïãÞ <literal>restrict</literal>
	  óôï <filename>/etc/ntp.conf</filename> óáò åðéôñÝðåé íá åëÝã÷åôå
	  ðïéá ìç÷áíÞìáôá èá ìðïñïýí íá Ý÷ïõí ðñüóâáóç óôïí åîõðçñåôÞ
	  óáò. </para>

	<para>Áí åðéèõìåßôå íá áðïññßøåôå ôçí ðñüóâáóç ðñïò ôïí åîõðçñåôçôÞ
	  óáò NTP ãéá üëá ôá ìç÷áíÞìáôá, ðñïóèÝóôå ôçí áêüëïõèç ãñáììÞ
	  óôï <filename>/etc/ntp.conf</filename>:</para>

        <programlisting>restrict default ignore</programlisting>

        <para>Áí èÝëåôå ìüíï íá åðéôñÝøåôå ôïí óõã÷ñïíéóìü ôïõ åîõðçñåôçôÞ óáò
	  ìå ìç÷áíÞìáôá åíôüò ôïõ äéêôýïõ óáò, áëëÜ äß÷ùò äõíáôüôçôá ñýèìéóçò
	  ôïõ åîõðçñåôçôÞ Þ íá ãßíïõí ïìïéüâáèìá ìå Üäåéá óõã÷ñïíéóìïý, ôüôå
	  áíôéèÝôùò ðñïóèÝóôå:</para>

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

	<para>üðïõ <hostid role="ipaddr">192.168.1.0</hostid> åßíáé ç
	  äéåýèõíóç IP ôïõ äéêôýïõ
	  êáé <hostid role="netmask">255.255.255.0</hostid> åßíáé ç ìÜóêá ôïõ
	  äéêôýïõ óáò.</para>

	<para>Ôï <filename>/etc/ntp.conf</filename> ìðïñåß íá ðåñéÝ÷åé
	  ðïëëáðëÝò åðéëïãÝò <literal>restrict</literal>. Ãéá ðåñéóóüôåñåò
	  ðëçñïöïñßåò, äåßôå ôçí õðïåíüôçôá <literal>ÕðïóôÞñéîç ÅëÝã÷ïõ
	  Ðñüóâáóçò (Access Control Support)</literal>, õðïåíüôçôá ôïõ
	  &man.ntp.conf.5;.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>ÅêôÝëåóç ôïõ NTP ÅîõðçñåôçôÞ Óáò</title>

      <para>Ãéá íá âåâáéùèåßôå ðùò ï åîõðçñåôçôÞò NTP èá îåêéíÜåé êáôÜ ôçí
	äéÜñêåéá åêêßíçóçò ôïõ óõóôÞìáôïò, ðñïóèÝóôå ôç
	ãñáììÞ <literal>ntpd_enable="YES"</literal>óôï<filename>/etc/rc.conf</filename>.
	Ãéá íá îåêéíÞóåôå ôïí åîõðçñåôçôÞ äß÷ùò íá åðáíåêêéíÞóåôå ôï ìç÷Üíçìá
	óáò, ôñÝîôå &man.ntpd.8; ðñïóäéïñßæïíôáò êÜèå åðéðñüóèåôç ðáñÜìåôñï
	áðü ôá <varname>ntpd_flags</varname>
	óôï <filename>/etc/rc.conf</filename>. Ãéá ðáñÜäåéãìá:</para>

      <screen>&prompt.root; <userinput>ntpd -p /var/run/ntpd.pid</userinput></screen>
    </sect2>

    <sect2>
      <title>×ñÞóç ôïõ ntpd ìå ÐñïóùñéíÞ Óýíäåóç óôï ºíôåñíåô</title>

      <para>Ôï ðñüãñáììá &man.ntpd.8; äåí ÷ñåéÜæåôáé ìéá ìüíéìç óýíäåóç óôï
	ºíôåñíåô ãéá íá äïõëÝøåé óùóôÜ. Áí Ý÷åôå ìéá ðñïóùñéíÞ óýíäåóç ðïõ
	åßíáé ñõèìéóìÝíç íá êÜíåé êëÞóåéò ìÝóù ôçëåöþíïõ (dial out on demand),
	åßíáé êáëü íá ìçí åßíáé ç êßíçóç äåäïìÝíùí ôïõ NTP ôï áßôéï ôçò êëÞóçò
	Þ áõôÞ ðïõ èá êñáôÜåé åíåñãÞ ôçí óýíäåóç. Áí ÷ñçóéìïðïéåßôå PPP
	÷ñÞóôç, ìðïñåßôå íá ÷ñçóéìïðïéÞóåôå <literal>ößëôñá</literal> óôïõò
	êþäéêåò ðáñáðïìðÞò ôïõ <filename>/etc/ppp/ppp.conf</filename>, üðùò
	ãéá ðáñÜäåéãìá:</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>Ãéá ðåñéóóüôåñåò ëåðôïìÝñåéåò äåßôå ôï <literal>PACKET
	FILTERING</literal> óôçí åíüôçôá &man.ppp.8; êáé ôá ðáñáäåßãìáôá
	óôï <filename>/usr/share/examples/ppp/</filename>.</para>

      <note>
	<para>Óçìåßùóç: Ìåñéêïß ISP ìðëïêÜñïõí ôçí ÷ñÞóç èýñáò ìå ÷áìçëü
	  áñéèìü, åìðïäßæïíôáò óôï NTP íá äïõëåýåé áöïý ïé áðáíôÞóåéò äåí
	  öôÜíïõí ðïôÝ óôï ìç÷Üíçìá óáò.</para>
      </note>
    </sect2>

    <sect2>
      <title>ÐåñáéôÝñù Ðëçñïöïñßåò</title>

      <para>Ç ôåêìçñßùóç ãéá ôïõò åîõðçñåôçôÝò NTP äéáôßèåôáé êáé óå öüñìá
	HTML óôï <filename>/usr/share/doc/ntp/</filename>.</para>
    </sect2>
  </sect1>

</chapter>