config kernel mumble mumble
line has been obsoleted and removed and with it went all knowledge of
devices on the part of config.
You can still configure a root device (which is used if you give
the "-r" flag) but now with an option:
options ROOTDEVNAME=\"da0s2e\"
The string is parsed by the same code as at the "boot -a" prompt.
At the same time, make the "boot -a" prompt both more able and more
informative.
ALPHA/PC98 people: You will have to adapt a few simple changes
(defining rootdev and dumpdev somewhere else) before config works
for you again, sorry, but it's all in the name of progress.