Anatomy of the libvirt virtualization library

“When it comes to scale-out computing (such as cloud computing),
libvirt may be one of the most important libraries you’ve never
heard of. Libvirt provides a hypervisor-agnostic API to securely
manage guest operating systems running on a host. Libvirt isn’t a
tool per se but an API to build tools to manage guest operating
systems. Libvirt itself is built on the idea of abstraction. It
provides a common API for common functionality that the supported
hypervisors implement. Libvirt was originally designed as a
management API for Xen, but it has since been extended to support a
number of hypervisors.

“Let’s start our discussion of libvirt with a view of the use
model, then dig into its architecture and use. Libvirt exists as a
set of APIs designed to be used by a management application (see
Figure 1). Libvirt, through a hypervisor-specific mechanism,
communicates with each available hypervisor to perform the API
requests. I explore how this is done with QEMU later in the
article.

“Also shown is a comparison of the terminology that libvirt
uses. This terminology is important, as these terms are used in API
naming. The two fundamental differences are that libvirt calls the
physical host a node, and the guest operating system is called a
domain. Note here that libvirt (and its application) runs in the
domain of the host Linux operating system (domain 0).”

Complete Story