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" /><link rel="SHORTCUT ICON" href="/32favicon.png" /><title>libvir architecture</title></head><body><div id="container"><div id="intro"><div id="adjustments"></div><div id="pageHeader"></div><div id="content2"><h1 class="style1">libvir architecture</h1><p>When running 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
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 three different ways to connect to
the Xen infrastructure:</p><ul><li>a connection to the Xen Daemon though an HTTP RPC layer</li>
  <li>a read/write connection to the Xen Store</li>
  <li>use Xen Hypervisor calls</li>
</ul><p>The library will usually interract with the Xen daemon for any operation
changing the state of the system, but for performance and accuracy reasons
may talk directly to the hypervisor when gathering state informations at
least when possible (i.e. when the running program using libvir has root
priviledge access). </p><p> If it runs without root access virConnectOpenReadOnly() should be used to
connect to initialize the library. It will try to open the read-only socket
<code>/var/run/xenstored/socket_ro</code> to connect to the Xen Store and
also try to use the RPC to the Xen daemon. 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. </p></div></div><div class="linkList2"><div class="llinks2"><h3 class="links2"><span>main menu</span></h3><ul><li><a href="index.html">Home</a></li><li><a href="news.html">Releases</a></li><li><a href="intro.html">Introduction</a></li><li><a href="architecture.html">libvir architecture</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a style="font-weight:bold" href="html/index.html">API Menu</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></div><div class="llinks2"><h3 class="links2"><span>related links</span></h3><ul><li><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></li><li><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></li><li><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="12" value="Search..." /><input name="submit" type="submit" value="Go" /></form></li><li><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></li></ul></div></div><div id="bottom"><p class="p1"></p></div></div></body></html>
* docs/*: extended the documentation Daniel 2005-12-09 13:04:05 +00:00			`<?xml version="1.0" encoding="ISO-8859-1"?>`
			`<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">`
* docs/site.xsl docs/.png docs/.html: update the images from Diana, added favicon to page. * src/libvir.c: reorganized the include imports. Daniel 2006-01-23 22:55:41 +00:00			<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" /><link rel="SHORTCUT ICON" href="/32favicon.png" /><title>libvir architecture</title></head><body><div id="container"><div id="intro"><div id="adjustments"></div><div id="pageHeader"></div><div id="content2"><h1 class="style1">libvir architecture</h1><p>When running in a Xen environment, programs using libvir have to execute
* doc/*: augment and try to complete the doc in its current state Daniel 2006-01-23 13:24:07 +00:00			`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`
			`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`
* docs/architecture.* docs/*: added a section on the architecture and regenerated the docs. Daniel 2005-12-21 16:59:34 +00:00			`priviledge of the embedding program. If it runs with root access,`
* doc/*: started to augment and update the documentation Daniel 2006-01-22 16:27:09 +00:00			`virConnectOpen() can be used, it will use three different ways to connect to`
			`the Xen infrastructure:</p><ul><li>a connection to the Xen Daemon though an HTTP RPC layer</li>`
			`<li>a read/write connection to the Xen Store</li>`
			`<li>use Xen Hypervisor calls</li>`
* doc/*: augment and try to complete the doc in its current state Daniel 2006-01-23 13:24:07 +00:00			`</ul><p>The library will usually interract with the Xen daemon for any operation`
			`changing the state of the system, but for performance and accuracy reasons`
			`may talk directly to the hypervisor when gathering state informations at`
			`least when possible (i.e. when the running program using libvir has root`
			`priviledge access). </p><p> If it runs without root access virConnectOpenReadOnly() should be used to`
			`connect to initialize the library. It will try to open the read-only socket`
* doc/*: started to augment and update the documentation Daniel 2006-01-22 16:27:09 +00:00			`<code>/var/run/xenstored/socket_ro</code> to connect to the Xen Store and`
			`also try to use the RPC to the Xen daemon. 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. </p></div></div><div class="linkList2"><div class="llinks2"><h3 class="links2"><span>main menu</span></h3><ul><li><a href="index.html">Home</a></li><li><a href="news.html">Releases</a></li><li><a href="intro.html">Introduction</a></li><li><a href="architecture.html">libvir architecture</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a style="font-weight:bold" href="html/index.html">API Menu</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></div><div class="llinks2"><h3 class="links2"><span>related links</span></h3><ul><li><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></li><li><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></li><li><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="12" value="Search..." /><input name="submit" type="submit" value="Go" /></form></li><li><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></li></ul></div></div><div id="bottom"><p class="p1"></p></div></div></body></html>