Linux in a Nutshell, 6th Edition

XML Configuration Files

libvirt uses XML files to define or describe the capabilities and configuration of domains, networks, and hardware devices. Many of the command tools expect to receive information from an XML file. You don’t have to know the XML tags to get started, as the tools will build the required files for you, but you may want to edit an XML file directly to change the configuration of a guest.

The XML formats, as well as more in-depth information on virsh and the API, can be found on the libvirt website: http://libvirt.org.