very current won't mount /tmp

very current (08:00gmt the 11th)
thinkpad t40p

make world and kernel
boot single abuser to do the installworld

can mount drives one at a time until i get to /tmp which is
defined as

    md /tmp mfs -s131072,rw,nosuid,nodev,noatime 0 0

locks up

as installworld has not happened, it should not be the new
automagic /tmp mfs.  or am i misunderstanding that?

randy