> 'disklabel' always causes a bunch of error messages to occur when run
> for the first time.  It will say that it cannot modesense from sd1, and
> so it will use a fictitious geometry for the drive.

That's a problem with the Zip drive itself.

> Now, when I run
> 
>     disklabel -r /dev/sd1c
> 
> the output tells me the correct disk type: 'zip100' and the info I wrote
> to the Zip disk.  However,
> 
>     disklabel /dev/sd1c
> 
> tells me that the in-core kernel copy of the disklabel is still set to
> using the fictitious geometry.

Writing native disklabel on mac68k doesn't work, yet.  You should use a
partitioning tool on MacOS and make a partition that's marked as A/UX
something (usually Root, Root&Usr or Usr), so the kernel can build its
in-core disklabel from the partition table.

As for geometry, I understand that, if Zip doesn't support mode sense
command, there's no way for the kernel to tell Zip's real geometry, so
you are stuck with fictitious geometries.

ken