FreeBSD 5.x Mount
# mdconfig -a -t vnode -f image.iso -u 0
# mount -t cd9660 /dev/md0 /mnt/whatever
FreeBSD 5.x Unmount
# umount /mnt/whatever
# mdconfig -d -u 0
FreeBSD 4.x Mount
# vnconfig -c vn0c image.iso
# mount -t cd9660 /dev/vn0c /mnt/whatever
FreeBSD 4.x Unmount
# umount /mnt/whatever
# vnconfig -u vn0c