libvirt/docs/architecture.html

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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="stylesheet" type="text/css" href="libvir.css" /><title>libvir architecture</title></head><body><div id="main"><div id="top"><img src="libvirHeader.png" alt="Libvir the virtualization API" /></div><div id="left"><div class="left"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><div class="box"><h2 class="box_title">main menu</h2></div><p><a href="index.html">Home</a></p><p><a href="news.html">Releases</a></p><p><a href="intro.html">Introduction</a></p><p><a href="architecture.html">libvir architecture</a></p><p><a href="downloads.html">Downloads</a></p><p><a href="FAQ.html">FAQ</a></p><p><a href="bugs.html">Reporting bugs and getting help</a></p><p><a style="font-weight:bold" href="html/index.html">API Menu</a></p><p><a href="ChangeLog.html">Recent Changes</a></p><div class="box"><h2 class="box_title">related links</h2></div><p><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></p><p><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></p><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></div></div><div id="right"><h3 class="title">libvir architecture</h3><p>In a Xen environment, programs using libvir have to execute in "Domain 0",
which is the primary Linux OS loaded on the machine. That OS kernel provides
most if not all of the actual drivers used by the set of domains. It also
runs the Xen Store, a database of informations shared by the hypervisor, the
kernels, the drivers and the xen daemon. Xend, the xen daemon, also runs in
Domain0 and supervise the control and execution of the sets of domains. The
hypervisor, drivers, kernels and daemons communicate though a shared system
bus implemented in the hypervisor. The figure below tries to provide a view
of this environment: </p><img src="architecture.gif" alt="The Xen architecture" /><p>The library can be initialized in 2 ways depending on the level of
priviledge of the embedding program. If it runs with root access,
virConnectOpen() can be used, it will use a read/write connection to the Xen
Store and use Xen Hypervisor calls when possible. If it runs without root
access virConnectOpenReadOnly() should be used, it will try to open the
read-only socket <code>/var/run/xenstored/socket_ro</code> to connect to the
Xen Store. In this case use of hypervisor calls and write to the Xen Store
will not be possible, restraining the amount of APIs available and slowing
down information gathering about domains. We expect libvir will also conmnect
to the Xend daemon for some of the domain control operations, though this is
not the case in the 0.0.1 initial version.</p></div><div id="copyright"></div></div></body></html>
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* doc/* : total revamp of the web site based on Diana Fong design but not completely integrated yet Daniel 2006-01-20 09:49:04 -06:00			<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="stylesheet" type="text/css" href="libvir.css" /><title>libvir architecture</title></head><body><div id="main"><div id="top"><img src="libvirHeader.png" alt="Libvir the virtualization API" /></div><div id="left"><div class="left"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><div class="box"><h2 class="box_title">main menu</h2></div><p><a href="index.html">Home</a></p><p><a href="news.html">Releases</a></p><p><a href="intro.html">Introduction</a></p><p><a href="architecture.html">libvir architecture</a></p><p><a href="downloads.html">Downloads</a></p><p><a href="FAQ.html">FAQ</a></p><p><a href="bugs.html">Reporting bugs and getting help</a></p><p><a style="font-weight:bold" href="html/index.html">API Menu</a></p><p><a href="ChangeLog.html">Recent Changes</a></p><div class="box"><h2 class="box_title">related links</h2></div><p><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></p><p><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></p><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></div></div><div id="right"><h3 class="title">libvir architecture</h3><p>In a Xen environment, programs using libvir have to execute in "Domain 0",
* docs/architecture.* docs/*: added a section on the architecture and regenerated the docs. Daniel 2005-12-21 10:59:34 -06:00			`which is the primary Linux OS loaded on the machine. That OS kernel provides`
			`most if not all of the actual drivers used by the set of domains. It also`
			`runs the Xen Store, a database of informations shared by the hypervisor, the`
			`kernels, the drivers and the xen daemon. Xend, the xen daemon, also runs in`
			`Domain0 and supervise the control and execution of the sets of domains. The`
			`hypervisor, drivers, kernels and daemons communicate though a shared system`
			`bus implemented in the hypervisor. The figure below tries to provide a view`
			`of this environment: </p><img src="architecture.gif" alt="The Xen architecture" /><p>The library can be initialized in 2 ways depending on the level of`
			`priviledge of the embedding program. If it runs with root access,`
			`virConnectOpen() can be used, it will use a read/write connection to the Xen`
			`Store and use Xen Hypervisor calls when possible. If it runs without root`
			`access virConnectOpenReadOnly() should be used, it will try to open the`
			`read-only socket <code>/var/run/xenstored/socket_ro</code> to connect to the`
			`Xen Store. In this case use of hypervisor calls and write to the Xen Store`
			`will not be possible, restraining the amount of APIs available and slowing`
			`down information gathering about domains. We expect libvir will also conmnect`
			`to the Xend daemon for some of the domain control operations, though this is`
* doc/* : total revamp of the web site based on Diana Fong design but not completely integrated yet Daniel 2006-01-20 09:49:04 -06:00			`not the case in the 0.0.1 initial version.</p></div><div id="copyright"></div></div></body></html>`