Hey netbsd folk.  All kinds of trouble here.  Perhaps some of you that are 
more experienced with netbsd can help me.

Am trying to fsck my root partition.  Here's what i get:

--------------------------------------------------------------
# mount -a
/dev/rz0a: file system not clean; please 
fsck(8)                         (to show that it sucks)
# mount
/dev/rz0a on / type ffs (local)
/dev/rz0d on /usr type ffs (local)
#

# umount -a                               (suggesting that everything 
unmounted alright)
# 
mount
/dev/rz0a on / type ffs (local)        (except of course the root 
partition)
#

# umount 
/
umount: /: Invalid argument           (okay, guess 
not)
#

# umount -t ffs /dev/rz0a 
/
umount: /: Invalid argument            (try 
again)
umount: /: Invalid 
argument
#

# mount -t ffs -o rdonly /dev/rz0a /      (decide to go the other 
route)
# 
mount
/dev/rz0a on / type ffs (local, read-only)       (you'd think it'd be ok to 
fsck now)
#

# fsck 
/
/dev/rrz0a (No such file or directory)Can't stat 
/dev/rrz0a
/dev/rrz0a (No such file or directory)Can't stat 
/dev/rrz0a
/dev/rz0a is not a character 
device
CONTINUE? [yn] 
y
                                                                             

an't open /dev/rz0a: Device busy                     (guess not)
#
---------------------------------------------------------------------------

I've tried a few other permutations all with the same result.  so, eh, 
what?  do you all have to fsck your root partitions from another one?  or, 
much more likely, am i just stupid?

thanks,
ben (newbie)