> I was expecting that vnconfig would be what I'm after, but vnconfig(8)
> talks about wanting geometries or disktab entries.
> 
> If someone has the answer I'd appreciate it - I've only got access to
> the CD writer for a couple of days.

 See "man vnconfig"

 vnconfig vnd0 /tmp/myISO9660diskimage
 mkdir /tmp/cdrom
 mount -t cd9660 /dev/vnd0c /tmp/cdrom
 cd /tmp/cdrom 
 ls
 cd /
 umount /tmp/cdrom
 vnconfig -u vnd0

-- 
Markus Illenseer