OpenBSD disk on FreeBSD.

[R. Clayton]

I have a usb external hard drive from a dead OpenBSD x86 system, and I want to
mount the drive on

  $ uname -a
  FreeBSD AngkorWat 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17 02:41:51 UTC 2011     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

  $

fdisk on the FreeBSD system looks like

  Disk name:      da0                                    FDISK Partition Editor
  DISK Geometry:  20023 cyls/255 heads/63 sectors = 321669495 sectors (157065MB)

  Offset       Size(ST)        End     Name  PType       Desc  Subtype    Flags

           0         63         62        -     12     unused        0
          63  321669432  321669494    da0s4      4 OpenBSD FFS      166   =
   321669495       3465  321672959        -     12     unused        0          

The OpenBSD fstab is gone, and the backup copy is (of course) on the disk I
want to mount.  How do I go about mounting this disk on FreeBSD?  The following
don't work:

  # mount /dev/da0 mnt
  mount: /dev/da0 : Invalid argument

  # mount /dev/da0s4 mnt
  mount: /dev/da0s4 : Operation not permitted

  #