to extend the standard NELK DVDK disk size from 16 GB to 20 GB. Please note that this works only with ''dynamic size'' disk image, and not with ''fixed size'' disk images. Please note that this command doesn't automatically extend the partition size. In order to do that, you need to modify the disk partition table. But since the virtual disk contains the root partition, you can't edit the partition table, because you can do such an operation only on a un-mounted device. So you need to start the virtual machine with a Live Linux distribution (for example, [http://gparted.sourceforge.net/download.php Gparted]) and launch the partition tool and modify the partition structure.