mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-12-29 00:55:22 +00:00
137 lines
7.0 KiB
HTML
137 lines
7.0 KiB
HTML
|
<?xml version="1.0"?>
|
||
|
|
<html>
|
||
|
|
<body>
|
||
|
|
<h1>The libvirt API concepts</h1>
|
||
|
|
|
||
|
|
<p> This page describes the main principles and architecture choices
|
||
|
|
behind the definition of the libvirt API:
|
||
|
|
<ul>
|
||
|
|
<li>
|
||
|
|
<a href="#Objects">Objects exposed</a>
|
||
|
|
</li>
|
||
|
|
<li>
|
||
|
|
<a href="#Functions">Functions and naming conventions</a>
|
||
|
|
</li>
|
||
|
|
<li>
|
||
|
|
<a href="#Driver">The drivers</a>
|
||
|
|
</li>
|
||
|
|
<li>
|
||
|
|
<a href="#Remote">Daemon and remote access</a>
|
||
|
|
</li>
|
||
|
|
</ul>
|
||
|
|
<h2><a name="Objects" id="Objects">Objects exposed</a></h2>
|
||
|
|
<p> As defined in the <a href="goals.html">goals section</a>, libvirt
|
||
|
|
API need to expose all the resources needed to manage the virtualization
|
||
|
|
support of recent operating systems. The first object manipulated though
|
||
|
|
the API is <code>virConnectPtr</code> which represent a connection to
|
||
|
|
an hypervisor. Any application using libvirt is likely to start using the
|
||
|
|
API by calling one of <a href="html/libvirt-libvirt.html#virConnectOpen"
|
||
|
|
>the virConnectOpen functions</a>. You will note that those functions take
|
||
|
|
a name argument which is actually an URI to select the right hypervisor to
|
||
|
|
open, this is needed to allow remote connections and also select between
|
||
|
|
different possible hypervisors (for example on a Linux system it may be
|
||
|
|
possible to use both KVM and LinuxContainers on the same node). A NULL
|
||
|
|
name will default to a preselected hypervisor but it's probably not a
|
||
|
|
wise thing to do in most cases. See the <a href="uri.html">connection
|
||
|
|
URI</a> page for a full descriptions of the values allowed.<p>
|
||
|
|
<p> Once the application obtained a <code class='docref'>virConnectPtr</code>
|
||
|
|
connection to the
|
||
|
|
hypervisor it can then use it to manage domains and related resources
|
||
|
|
available for virtualization like storage and networking. All those are
|
||
|
|
exposed as first class objects, and connected to the hypervisor connection
|
||
|
|
(and the node or cluster where it is available).</p>
|
||
|
|
<p class="image">
|
||
|
|
<img alt="first class objects exposed by the API"
|
||
|
|
src="libvirt-object-model.png"/>
|
||
|
|
</p>
|
||
|
|
<p> The figure above shows the five main objects exported by the API:</p>
|
||
|
|
<ul>
|
||
|
|
<li>virConnectPtr: represent a connection to an hypervisor.</li>
|
||
|
|
<li>virDomainPtr: represent one domain either active or defined (i.e.
|
||
|
|
existing as permanent config file and storage but not currently running
|
||
|
|
on that node). The function <code class='docref'>virConnectListDomains</code>
|
||
|
|
allows to list all the IDs for the domains active on this hypervisor.</li>
|
||
|
|
<li>virNetworkPtr: represent one network either active or defined (i.e.
|
||
|
|
existing as permanent config file and storage but not currently activated.
|
||
|
|
The function <code class='docref'>virConnectListNetworks</code>
|
||
|
|
allows to list all the virtualization networks actived on this node.</li>
|
||
|
|
<li>virStorageVolPtr: represent one storage volume, usually this is used
|
||
|
|
as a block device available to one of the domains. The function
|
||
|
|
<code class="docref">virStorageVolLookupByPath</code> allows to find
|
||
|
|
the object based on its path on the node.</li>
|
||
|
|
<li>virStoragePoolPtr: represent a storage pool, i.e. a logical area
|
||
|
|
which can be used to allocate and store storage volumes. The function
|
||
|
|
<code class="docref">virStoragePoolLookupByVolume</code> allows to find
|
||
|
|
the storage pool containing a given storage volume.</li>
|
||
|
|
</ul>
|
||
|
|
<p> Most object manipulated by the library can also be represented using
|
||
|
|
XML descriptions. This is used primarily to create those object, but is
|
||
|
|
also helpful to modify or save their description back.</p>
|
||
|
|
<p> Domains, network and storage pools can be either <code>active</code>
|
||
|
|
i.e. either running or available for immediate use, or
|
||
|
|
<code>defined</code> in which case they are inactive but there is
|
||
|
|
a permanent definition available in the system for them. Based on this
|
||
|
|
thay can be activated dynamically in order to be used.</p>
|
||
|
|
<p> Most kind of object can also be named in various ways:<p>
|
||
|
|
<ul>
|
||
|
|
<li>by their <code>name</code>, an user friendly identifier but
|
||
|
|
whose unicity cannot be garanteed between two nodes.</li>
|
||
|
|
<li>by their <code>ID</code>, which is a runtime unique identifier
|
||
|
|
provided by the hypervisor for one given activation of the object,
|
||
|
|
but it becomes invalid once the resource is deactivated.</li >
|
||
|
|
<li>by their <code>UUID</code>, a 16 bytes unique identifier
|
||
|
|
as defined in <a href="http://www.ietf.org/rfc/rfc4122.txt">RFC 4122</a>,
|
||
|
|
which is garanteed to be unique for long term usage and across a
|
||
|
|
set of nodes.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<h2><a name="Functions" id="Functions">Functions and naming
|
||
|
|
conventions</a></h2>
|
||
|
|
<p> The naming of the functions present in the library is usually
|
||
|
|
made of a prefix describing the object associated to the function
|
||
|
|
and a verb describing the action on that object.</p>
|
||
|
|
<p> For each first class object you will find apis
|
||
|
|
for the following actions:</p>
|
||
|
|
<ul>
|
||
|
|
<li><b>Lookup</b>:...LookupByName,
|
||
|
|
<li><b>Enumeration</b>:virConnectList... and virConnectNumOf...:
|
||
|
|
those are used to enumerate a set of object available to an given
|
||
|
|
hypervisor connection like:
|
||
|
|
<code class='docref'>virConnectListDomains</code>,
|
||
|
|
<code class='docref'>virConnectNumOfDomains</code>,
|
||
|
|
<code class='docref'>virConnectListNetworks</code>,
|
||
|
|
<code class='docref'>virConnectListStoragePools</code>, etc.</li>
|
||
|
|
<li><b>Description</b>: ...GetInfo: those are generic accessor providing
|
||
|
|
a set of informations about an object, they are
|
||
|
|
<code class='docref'>virNodeGetInfo</code>,
|
||
|
|
<code class='docref'>virDomainGetInfo</code>,
|
||
|
|
<code class='docref'>virStoragePoolGetInfo</code>,
|
||
|
|
<code class='docref'>virStorageVolGetInfo</code>.</li>
|
||
|
|
<li><b>Accessors</b>: ...Get... and ...Set...: those are more specific
|
||
|
|
accessors to query or modify the given object, like
|
||
|
|
<code class='docref'>virConnectGetType</code>,
|
||
|
|
<code class='docref'>virDomainGetMaxMemory</code>,
|
||
|
|
<code class='docref'>virDomainSetMemory</code>,
|
||
|
|
<code class='docref'>virDomainGetVcpus</code>,
|
||
|
|
<code class='docref'>virStoragePoolSetAutostart</code>,
|
||
|
|
<code class='docref'>virNetworkGetBridgeName</code>, etc.</li>
|
||
|
|
<li><b>Creation</b>: </li>
|
||
|
|
<li><b>Destruction</b>: ... </li>
|
||
|
|
</ul>
|
||
|
|
<p> For more in-depth details of the storage related APIs see
|
||
|
|
<a href="storage.html">the storage management page</a>,
|
||
|
|
<h2><a name="Driver" id="Driver">The libvirt drivers</a></h2>
|
||
|
|
<p></p>
|
||
|
|
<p class="image">
|
||
|
|
<img alt="The libvirt driver architecture"
|
||
|
|
src="libvirt-driver-arch.png"/>
|
||
|
|
</p>
|
||
|
|
<h2><a name="Remote" id="Remote">Daemon and remote access</a></h2>
|
||
|
|
<p></p>
|
||
|
|
<p class="image">
|
||
|
|
<img alt="The libvirt daemon and remote architecture"
|
||
|
|
src="libvirt-daemon-arch.png"/>
|
||
|
|
</p>
|
||
|
|
</body>
|
||
|
|
</html>
|