OK. So I finally got this all working (with the Debian Jessie RFS no less) by
exporting a file system for each target board. So overall directory structure
is something like this:
/home/bone/tftp -- vmlinuzXXX and /dtbs/ for TFTP boot
/home/bone/mac_suffix - 1st NFS root file system export
*/home/bone/tftp -- vmlinuzXXX and /dtbs/ for TFTP boot*
* /home/bone/mac_suffix - 1st NFS root file system export*
* /home/bone/mac_suffix - 2nd NFS root file system export*
Only thing I can think of here is that when a board mounts, and takes over
a rootfs, it somehow becomes locked
