Weird issues with fdisk/dd

[Joe Holden <joe@xxxxxxxxxxxxxxx>]

Hello Collective,

I'm currently in the process of moving from FreeBSD to DragonFlyBSD for
some operations, as clearly DragonFly is the way forward.

I've got it installed on one of the production machines, but seemingly I
am unable to use the second disk.  There is an existing table on it, and
it is probably incorrect, however, I am getting the following messages:

kelley# fdisk /dev/ad6
******* Working on device /dev/ad6 *******
parameters extracted from device are:
cylinders=19457 heads=255 sectors/track=63 (16065 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=19457 heads=255 sectors/track=63 (16065 blks/cyl)

fdisk: can't read fdisk partition table
fdisk: /boot/mbr: length must be a multiple of sector size

kelley# dd if=/dev/zero of=/dev/ad6 bs=1024k count=10
dd: /dev/ad6: Invalid argument
1+0 records in
0+0 records out
0 bytes transferred in 0.018139 secs (0 bytes/sec)

After these, the kernel has logged the following to dmesg:

dscheck(#ad/0x10032): illegal partition number (2) for WHOLE_DISK_SLICE
access
dscheck(#ad/0x10032): illegal partition number (2) for WHOLE_DISK_SLICE
access


Is there anyway to rewrite/zero the mbr, as running fdisk -B /dev/ad6
also produces the above errors.

Thanks in advance,
Joe Holden