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shorewall_code/docs/KVM.xml
2008-08-15 01:26:15 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article>
<!--$Id$-->
<articleinfo>
<title>KVM (Kernel-mode Virtual Machine)</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2008</year>
<holder>Thomas M. Eastep</holder>
</copyright>
<legalnotice>
<para>Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
License</ulink></quote>.</para>
</legalnotice>
</articleinfo>
<section>
<title>Introduction</title>
<para>Kernel-mode Virtual Machines (<ulink
url="http://kvm.qumranet.com/">http://kvm.qumranet.com/</ulink>) is a
virtualization platform that leverages the virtualization capabilities
available with current microprocessors from both
<trademark>Intel</trademark> and <trademark>AMD</trademark>. For an
overview of KVM, please see my <ulink
url="http://www.shorewall.net/Linuxfest-2008.pdf">2008 Linuxfest Northwest
presentation</ulink>.</para>
<para>I use KVM to implement a number of virtual machines running various
Linux Distributions. The following diagram shows the entire
network.</para>
<graphic align="center" fileref="images/Network2008.png" />
<para>My personal laptop (Ursa) hosts the virtual machines. As shown in
the diagram, Ursa has routes to the Internet through both the
<trademark>Linksys</trademark> WRT300N and through my Shorewall firewall.
This allows me to test the <ulink url="MultiISP.html">Shorewall Multi-ISP
feature</ulink>, even though I only have a single Internet
connection</para>
<para>The Linux Bridges shown in the diagram are, of course, actually
within their associated system (Firewall or Ursa) but I've pictured them
separately.</para>
</section>
<section>
<title>Networking Configuration</title>
<para>I use a network configuration where each VM has it's own VNET and
tap device and the tap devices are all configured as ports on a Linux
Bridge. For clarity, I've only shown four of the virtual machines
available on the system.</para>
<graphic align="center" fileref="images/KVM1.png" />
<para>I run a DHCP server on the host to assign IP addresses to the VMs
and I also run dmsmasq to act as a nameserver for the VMs. The latter is
important when I take the laptop on the road. I'm currently running a
separate ISC DHCP server but I have it on my todo list to configure
dnsmasq as a DHCP server, thus eliminating one process on the
system.</para>
<para>The bridge is configured using the script described in my Linuxfest
presentation linked above. The script may be found at <ulink
url="http://www.shorewall.net/pub/shorewall/contrib/kvm/kvm">http://www.shorewall.net/pub/shorewall/contrib/kvm/kvm</ulink>.</para>
<para>With this configuration, and with only a single network interface on
the laptop, this is just a simple <ulink
url="two-interface.xml">two-interface masquerading setup</ulink> where the
local network interface is <filename class="devicefile">br0</filename>. As
with all bridges, <filename class="devicefile">br0</filename> must be
configured with the <option>routeback</option> option in <ulink
url="manpages/shorewall-interfaces.html">shorewall-interfaces</ulink>(5).</para>
</section>
</article>