source: postlfs/security/iptables.xml@ 8abd5653

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
  %general-entities;

  <!ENTITY iptables-download-http "http://www.iptables.org/files/iptables-&iptables-version;.tar.bz2">
  <!ENTITY iptables-download-ftp  "ftp://ftp.netfilter.org/pub/iptables/iptables-&iptables-version;.tar.bz2">
  <!ENTITY iptables-size          "157 KB">
  <!ENTITY iptables-buildsize     "4.4 MB">
  <!ENTITY iptables-time          "0.13 SBU">
]>

<sect1 id="postlfs-security-iptables">
<?dbhtml filename="iptables.html"?>
<title>iptables-&iptables-version;</title>

<para>The next part of this chapter deals with firewalls.  The principle
firewall tool for Linux, as of the 2.4 kernel series, is
<application>iptables</application>.  It replaces
<application>ipchains</application> from the 2.2 series and
<application>ipfwadm</application> from the 2.0 series. You will need to
install <application>iptables</application> if you intend on using any form of
a firewall.</para>

<sect2>
<title>Introduction to <application>iptables</application></title>

<para>To use a firewall, as well as installing
<application>iptables</application>, you will need
to configure the relevant options into your kernel.  This is discussed
in the next part of this chapter &ndash; 
<xref linkend="postlfs-security-fw-kernel"/>.</para>

<para>If you intend to use <acronym>IP</acronym>v6 you might consider extending
the kernel by running <command>make patch-o-matic</command> in the top-level
source tree directory of <application>iptables</application>.  If you are 
going to do this, on a freshly untarred kernel, you need to run 
<command>yes "" | make config &amp;&amp; make dep</command> first because 
otherwise the patch-o-matic command is likely to fail while setting up
some dependencies.</para>

<para>If you are going to patch the kernel, you need to do it before you
compile <application>iptables</application>, because during the compilation, 
the kernel source tree is checked (if it is available at <filename
class="directory">/usr/src/linux-<replaceable>[version]</replaceable>
</filename>) to see which features are available.  Support will only be compiled
into <application>iptables</application> for the features recognized at 
compile-time.  Applying a kernel patch may result in errors, often because the 
hooks for the patches have changed or because the <command>runme</command> 
script doesn't recognize that a patch has already been incorporated.</para>

<para>Note that for most people, patching the kernel is unnecessary.
With the later 2.4.x kernels, most functionality is already available
and those who need to patch it are generally those who need a specific
feature; if you don't know why you need to patch the kernel, you're 
unlikely to need to!</para>

<sect3><title>Package information</title>
<itemizedlist spacing='compact'>
<listitem><para>Download (HTTP): <ulink
url="&iptables-download-http;"/></para></listitem>
<listitem><para>Download (FTP): <ulink
url="&iptables-download-ftp;"/></para></listitem>
<listitem><para>Download size: &iptables-size;</para></listitem>
<listitem><para>Estimated Disk space required:
&iptables-buildsize;</para></listitem>
<listitem><para>Estimated build time:
&iptables-time;</para></listitem></itemizedlist>
</sect3>

</sect2>

<sect2>
<title>Installation of <application>iptables</application></title>

<para>Install <application>iptables</application> by running the following 
commands:</para>

<screen><userinput><command>make PREFIX=/usr LIBDIR=/lib BINDIR=/sbin &amp;&amp;
make PREFIX=/usr LIBDIR=/lib BINDIR=/sbin install</command></userinput></screen>

</sect2>

<sect2>
<title>Command explanations</title>

<para><parameter>PREFIX=/usr LIBDIR=/lib BINDIR=/sbin</parameter>: Compiles 
and installs <application>iptables</application> libraries into 
<filename class="directory">/lib</filename>, binaries into 
<filename class="directory">/sbin</filename> and the remainder into the 
<filename class="directory">/usr</filename> hierarchy instead of 
<filename class="directory">/usr/local</filename>. Firewalls are
generally activated during the boot process and 
<filename class="directory">/usr</filename> may not be mounted at that 
time.</para>

</sect2>

<sect2>
<title>Contents</title>

<para>The <application>iptables</application> package contains 
<command>iptables</command>, <command>iptables-restore</command>, 
<command>iptables-save</command>, <command>ip6tables</command> 
and the <filename class='libraryfile'>libip*.so</filename> library
modules.</para>

</sect2>

<sect2><title>Description</title>

<sect3><title>iptables</title>
<para><command>iptables</command> is used to set up, maintain, and inspect the 
tables of <acronym>IP</acronym> packet filter rules in the Linux kernel.</para>
</sect3>

<sect3><title>iptables-restore, iptables-save</title>
<para>These are used to save and to restore your elaborated set of chains and 
rules. Until <application>iptables</application>-1.2.5, they were declared 
experimental.</para>
</sect3>

<sect3 id="ip6tables" xreflabel="ip6tables"><title>ip6tables</title>
<para>This is the same as <command>iptables</command> but for use with
<acronym>IP</acronym>v6.  As of v1.2.5, it is not as complete as the standard 
<acronym>IP</acronym>v4 version, especially with regard to some of the 
modules.</para>
</sect3>

<sect3><title>libip*.so library modules</title>
<para>These are various modules (implemented as dynamic libraries) which
extend the core functionality of <command>iptables</command>.</para>
</sect3>

</sect2>

</sect1>