The QCOW2 format is the most powerful format supported by
KVM-QEMU. It does not pre-allocate disk space, it offers the ability
to create snapshots and, later, you can create new images that use a
previous image as a base to dramatically speed-up the setup of a
future VM. In this article we will look at some of the advanced features
available in the QCOW2 format through the QEMU Image tool. We
create a QCOW2 image, create snapshots within the image, create an
image that is based on a backing file and copy an image to get rid of
the reference to the backing file.