"gmirror load" broken in 8.1 memstick

[perryh at pluto.rain.com]

Fixit# gmirror label -vb round-robin gm0 /dev/ad0s2a

appeared to work properly.  (I didn't write down the exact
message, but it said something about the metadata having
been written successfully.)  However:

Fixit# gmirror load
gmirror: Command 'load' not available.

and it did not create /dev/mirror/gm0 or even the /dev/mirror
directory.

How do I fix this?