imgbased provides a specific management method to derive writable file-system
layers from read-only base images. It also takes care that the layer which
shall be used can be selected at boot time.
In a nutshell this works by:
* having a boot partition
* and having a default LVM volume group (HostVG)
* which has a thinpool
* each base is kept in a read-only thin logical volume in the thinpool
* for each base at least one writable layer, which is a thin logical volume, is
created in the thinpool
* for each layer a boot entry is created which can be used to boot in a
specific layer
