qemu

Generic CPU emulator and virtualization (with KVM acceleration).

$ qemu-system-x86_64 -enable-kvm -m 4096 -smp 4 \
  -hda disk.qcow2 -cdrom install.iso -boot d

$ qemu-img create -f qcow2 disk.qcow2 20G
$ qemu-img info disk.qcow2