Ted Lemon writes:

 >	I can't remember for sure, but I think /usr/mdec/bootblks is
 > meant to be placed on the disk starting at sector 1, not sector 0.
 > So you would do ``dd if=/usr/mdec/bootblks of=/dev/rrz0c seek=1''.   I
 > make no promises, though - I'd say you have about a 2% chance of
 > success.   :'(

I've still got machines running Ultrix.  Empirically, it looks like,
at least under Ultrix 4.3a, /usr/mdec/bootblks starts at the front of
the disk (and the first 512 bytes are blank ;-)

At least dd if=/dev/rz1c of=foo count=14, then truncating foo to 6816
yields a file that is identical to /usr/mdec/bootblks.

Drew