Can't mount the root partition r/w! :(

It's been a while since I last played with my NetBSD box (using one of
the 'daily' releases of 1.6), so I thought that I would do a fresh
install from scratch.

However, having fetched all the sets via ftp and unpacked them (all
under the control of sysinst), I then alter fastboot to load the
kernel from the NetBSD disk (I have wd1, on the RPC internal
interface, dedicated to BSD).  Fine - it boots up, but with the
partition mounted r/o, and whatever I do, I can't get it into a
writable state.

# mount
root_device on / type ffs (read-only, local)
# mount -u -w /
mount_ffs: root_device on /: No such file or directory

I reverted to the install kernel, loaded from the RO disc, in order to
edit rc.conf (rc_configured=YES).  But having done that, the system
now boots with lots of 'read-only file system' errors, before allowing
me to log in.

What have I done wrong??

-- 
Peter Bell - [email protected]