So I created a new Netboot image with AutoCasperNBI with a 10.10.5 base with 9.81 casper imaging.
I made sure to set modified rc.netboot file was checked.
Booted to it and did a mount in terminal and it shows - /dev/disk0s2 on /private/var/netboot
Any ideas would be great - could love not having to make a ram disk.
