nfsrooting

Most netbsd platforms have some ability to netboot & root off nfs.
The mac68k port is really only missing the ability to specify it in
the booter, and the kernel to take that from the booter and set the
boot device.  If the boot device is a NIC, the kernel already knows
how to bootp for the rest of the information.

I've made some changes to the booter and some minor changes to the
kernel to support this.  Ultimately, it might be neat to have either
the booter or a separate macos app that dhcp/bootp's to find the
kernel, then tftp's it, then boots it, much like the other ports.
For now, this requires a macos accessible kernel, which can be
located on an afp volume.

The changes are at:
http://synack.net/~bbraun/netbsd/mac68k-nfsroot/

nfsroot.png is a screenshot of the modified prefs screen to select
the device.
nfsroot.diff is the kernel diffs.
booter.diff is a diff of the changes to the booter, minus the 
resource changes for the dialog.
The other two files are the modified booter source, and a
booter binary.

The motivation for this is setting up an old mac's disk to run
netbsd can be one of the more challenging aspects of setting up
netbsd on it.  Since 68k macs are probably not anyone's primary
or only computing platform these days, nfsrooting can be a
reasonable alternative.  Plus, storage space becomes much less
of an issue.

Rob