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168 lines
8.4 KiB
HTML
168 lines
8.4 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<!--
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This file is autogenerated from python.html.in
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Do not edit this file. Changes will be lost.
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-->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
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<link rel="stylesheet" type="text/css" href="main.css" />
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<link rel="SHORTCUT ICON" href="32favicon.png" />
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<title>libvirt: Python API bindings</title>
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<meta name="description" content="libvirt, virtualization, virtualization API" />
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</head>
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<body>
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<div id="header">
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<div id="headerLogo"></div>
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<form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><div>
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<input id="query" name="query" type="text" size="12" value="" />
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<input id="submit" name="submit" type="submit" value="Search" />
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</div></form>
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<div id="menu">
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<ul class="l0"><li>
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<div>
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<a title="Front page of the libvirt website" class="inactive" href="index.html">Home</a>
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<a title="Get the latest source releases, binary builds and get access to the source repository" class="inactive" href="downloads.html">Downloads</a>
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</li><li>
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<div>
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<a title="Overview of the logical subsystems in the libvirt API" class="inactive" href="intro.html">Architecture</a>
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</li><li>
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<a title="Description of the XML formats used in libvirt" class="inactive" href="format.html">XML format</a>
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<a title="Hypervisor specific driver information" class="inactive" href="drivers.html">Drivers</a>
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<a title="Reference manual for the C public API" class="inactive" href="html/index.html">API reference</a>
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<span class="active">Python</span>
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<div id="content">
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<h1>Python API bindings</h1>
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<p>The Python binding should be complete and are mostly automatically
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generated from the formal description of the API in xml. The bindings are
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articulated around 2 classes <code>virConnect</code> and virDomain mapping to
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the C types. Functions in the C API taking either type as argument then
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becomes methods for the classes, their name is just stripped from the
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virConnect or virDomain(Get) prefix and the first letter gets converted to
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lower case, for example the C functions:</p>
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<p>
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<code>int <a href="html/libvirt-libvirt.html#virConnectNumOfDomains">virConnectNumOfDomains</a>
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(virConnectPtr conn);</code>
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</p>
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<p>
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<code>int <a href="html/libvirt-libvirt.html#virDomainSetMaxMemory">virDomainSetMaxMemory</a>
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(virDomainPtr domain, unsigned long memory);</code>
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</p>
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<p>become</p>
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<p>
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<code>virConn::numOfDomains(self)</code>
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</p>
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<p>
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<code>virDomain::setMaxMemory(self, memory)</code>
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</p>
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<p>This process is fully automated, you can get a summary of the conversion
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in the file libvirtclass.txt present in the python dir or in the docs.There
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is a couple of function who don't map directly to their C counterparts due to
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specificities in their argument conversions:</p>
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<ul><li><code><a href="html/libvirt-libvirt.html#virConnectListDomains">virConnectListDomains</a></code>
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is replaced by <code>virDomain::listDomainsID(self)</code> which returns
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a list of the integer ID for the currently running domains</li><li><code><a href="html/libvirt-libvirt.html#virDomainGetInfo">virDomainGetInfo</a></code>
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is replaced by <code>virDomain::info()</code> which returns a list of
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<ol><li>state: one of the state values (virDomainState)</li><li>maxMemory: the maximum memory used by the domain</li><li>memory: the current amount of memory used by the domain</li><li>nbVirtCPU: the number of virtual CPU</li><li>cpuTime: the time used by the domain in nanoseconds</li></ol></li></ul>
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<p>So let's look at a simple example inspired from the <code>basic.py</code>
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test found in <code>python/tests/</code> in the source tree:</p>
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<pre>import <span style="color: #0071FF; background-color: #FFFFFF">libvirt</span>
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import sys
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conn = <span style="color: #0071FF; background-color: #FFFFFF">libvirt</span>.openReadOnly(None)
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if conn == None:
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print 'Failed to open connection to the hypervisor'
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sys.exit(1)
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try:
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dom0 = conn.<span style="color: #007F00; background-color: #FFFFFF">lookupByName</span>("Domain-0")
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except:
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print 'Failed to find the main domain'
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sys.exit(1)
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print "Domain 0: id %d running %s" % (dom0.<span style="color: #FF0080; background-color: #FFFFFF">ID</span>(), dom0.<span style="color: #FF0080; background-color: #FFFFFF">OSType</span>())
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print dom0.<span style="color: #FF0080; background-color: #FFFFFF">info</span>()</pre>
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<p>There is not much to comment about it, it really is a straight mapping
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from the C API, the only points to notice are:</p>
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<ul><li>the import of the module called <code><span style="color: #0071FF; background-color: #FFFFFF">libvirt</span></code></li><li>getting a connection to the hypervisor, in that case using the
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openReadOnly function allows the code to execute as a normal user.</li><li>getting an object representing the Domain 0 using <span style="color: #007F00; background-color: #FFFFFF">lookupByName</span></li><li>if the domain is not found a libvirtError exception will be raised</li><li>extracting and printing some information about the domain using
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various <span style="color: #E50073; background-color: #FFFFFF">methods</span>
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associated to the virDomain class.</li></ul>
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</div>
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</div>
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<div id="footer">
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<p id="sponsor">
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Sponsored by:<br /><a href="http://et.redhat.com/"><img src="et.png" alt="Project sponsored by Red Hat Emerging Technology" /></a></p>
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