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api: Add text and references for daemon

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John Ferlan 2013-02-14 10:04:13 -05:00
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@ -186,9 +186,52 @@
support was added into libvirt.
</p>
<h2><a name="Remote">Daemon and Remote Access</a></h2>
<p>Access to libvirt drivers is primarily handled by the libvirtd
daemon through the <a href="remote.html">remote</a> driver via an
<a href="internals/rpc.html">RPC</a>. Some hypervisors do support
client-side connections and responses, such as Test, OpenVZ, VMware,
Power VM (phyp), VirtualBox (vbox), ESX, Hyper-V, Xen, and Parallels.
The libvirtd daemon service is started on the host at system boot
time and can also be restarted at any time by a properly privileged
user, such as root. The libvirtd daemon uses the same libvirt API
<code class='docref'>virInitialize</code> sequence as applications
for client-side driver registrations, but then extends the registered
driver list to encompass all known drivers supported for all driver
types supported on the host. </p>
<p>The libvirt client <a href="apps.html">applications</a> use a
<a href="uri.html">URI</a> to obtain the <code>virConnectPtr</code>.
The <code>virConnectPtr</code> keeps track of the driver connection
plus a variety of other connections (network, interface, storage, etc.).
The <code>virConnectPtr</code> is then used as a parameter to other
virtualization <a href="#Functions">functions</a>. Depending upon the
driver being used, calls will be routed through the remote driver to
the libvirtd daemon. The daemon will reference the connection specific
driver in order to retreive the requested information and then pass
back status and/or data through the connection back to the application.
The application can then decide what to do with that data, such as
display, write log data, etc. <a href="migration.html">Migration</a>
is an example of many facets of the architecture in use.</p>
<p class="image">
<img alt="The libvirt daemon and remote architecture"
src="libvirt-daemon-arch.png"/>
</p>
<p>
The key takeaway from the above diagram is that there is a remote driver
which handles transactions for a majority of the drivers. The libvirtd
daemon running on the host will receive transaction requests from the
remote driver and will then query the hypervisor driver as specified in
the <code>virConnectPtr</code> in order to fetch the data. The data will
then be returned through the remote driver to the client application
for processing.
</p>
<p>If you are interested in contributing to libvirt, read the
<a href="http://wiki.libvirt.org/page/FAQ">FAQ</a> and
<a href="hacking.html">hacking</a> guidelines to gain an understanding
of basic rules and guidelines. In order to add new API functionality
follow the instructions regarding
<a href="api_extension.html">implementing a new API in libvirt</a>.
</p>
</body>
</html>