It is typical for fixed disk devices to be partitioned so, by default, you are
not permitted to create a filesystem across the entire device.
will complain and tell you that it refuses to work. This is different
when using MO disks. One doesn't always need partitions on MO disks.
The file system can go directly to the whole disk. Under other OSes
this is known as the 'superfloppy' format.
This switch will force
to work properly.