> Cool. Thought so. But just to make a silly thought even sillier, what 
> happens when you don't even define d? Does disklabel make an assumption 
> based on the provided geometry? If not, why not?

If you explicitly run disklabel without defining any partitions, then all
the partitions from 0 to the number of partitions you specify are of zero
size starting at cylinder zero -- because disklabel bzero's the disklabel
structure before reading it in.  It does not presume to "do what you mean".

If you have an unlabelled disk, I think the kernel invents a fictitious
(there, I finally spelled it right today) disklabel whose d partition spans
the whole disk (according to whatever the kernel thinks the geometry is)
and is of type FS_UNUSED (newfs will thus refuse to use it, I think).
Removable disks tend to have problems reporting geometry (since the
geometry might depend on the media), especially Iomega disks (whose
programmers apparently are incapable of getting the MODE SENSE command
right...).