Ok, 

I've not built a boot floppy before so I've probably missed something.
Yet I get.

# cd /usr/src/distrib/i386/floppies
# make
===> ramdisk
dd if=/dev/zero of=ramdisk-13_ALPHA.fs count=2880
2880+0 records in
2880+0 records out
1474560 bytes transferred in 1 secs (1474560 bytes/sec)
vnconfig -t floppy3 -v -c /dev/vnd0d ramdisk-13_ALPHA.fs
/dev/vnd0d: 1474560 bytes on ramdisk-13_ALPHA.fs using geometry 512/18/2/80
disklabel -rw /dev/vnd0d floppy3
Nov  7 14:32:32 bilbo /netbsd: vnd0: no disk label
Nov  7 14:32:32 bilbo /netbsd: vnd0: no disk label
newfs -m 0 -o space -i 5120 -c 80 /dev/rvnd0a floppy3
newfs: /dev/rvnd0a: open: Device not configured
*** Error code 1


I just configured and booted a kernel to be sure that vnd's are
configured yet the result is the same.  If I try and run it again I
get: 

# make
===> ramdisk
dd if=/dev/zero of=ramdisk-13_ALPHA.fs count=2880
2880+0 records in
2880+0 records out
1474560 bytes transferred in 1 secs (1474560 bytes/sec)
vnconfig -t floppy3 -v -c /dev/vnd0d ramdisk-13_ALPHA.fs
vnconfig: Nov  7 14:38:54 bilbo /netbsd: vnd0: no disk label
/dev/vnd0d: VNDIOCSET: Nov  7 14:38:54 bilbo /netbsd: vnd0: no disk label
Device busy
*** Error code 1

which FM should I RT ? :-)

--sjg