I am running Ubuntu 15.04.
I am extracting the QCOW2 files with the command located in the instructions here https://www.whonix.org/wiki/KVM
tar -xvf Whonix-Gateway*.libvirt.xz
tar -xvf Whonix-Workstation*.libvirt.xz
However when they extract, it appears they are not sparse or something - they expand out, it got up to ~30gb before I cancelled the extraction.
Can anyone advise how I can fix this?!