<para>Once the kernel module is loaded or the kernel is statically

	built with PF support, it is possible to enable or disable

	<application>pf</application> with <command>pfctl</command>

	command.</para>

      <para>This example demonstrates how to enable the

	<application>pf</application>:</para>

      <screen>&prompt.root; <userinput>pfctl -e</userinput></screen>

      <para>The <command>pfctl</command> command provides a way to work

	with the <application>pf</application> firewall. It is a good

	idea to check the &man.pfctl.8; manual page to find out more

	information about using it.</para>

    </sect2>

    <sect2>

      <title>Creating Filtering Rules</title>

      <para>The Packet Filter reads it's configuration rules from the

	&man.pf.conf.5; file and it modifies, drops or passes packets

	according to the rules or definitions specified there.  The &os;

	installation comes with a default

	<filename>/etc/pf.conf</filename> which contains useful examples

	and explanations.</para>

      <para>Although &os; has it's own <filename>/etc/pf.conf</filename>

	the syntax is the same as one used in OpenBSD.  A great

	resource for configuring the <application>pf</application>

	firewall has been written by OpenBSD team and is available at

	<ulink url="http://www.openbsd.org/faq/pf/"></ulink>.</para>

      <warning>

	<para>The <application>pf</application> firewall in &os; 5.X is

	  at the level of OpenBSD version 3.5 and in &os; 6.X is at the

	  level of OpenBSD version 3.7.  The port from the &os; Ports

	  Collection is at the level of OpenBSD version 3.4.  Please,

	  keep that in mind when browsing the

	  <application>pf</application> user's guide.</para>

      </warning>

      <para>The &a.pf; is a good place to ask questions about

	configuring and running the <application>pf</application>

	firewall.  Do not forget to check the mailing list archives

	before asking questions.</para>