/p/c/machine_specific/HOST/filesystem/etc/ssh
host-* luks keyfiles generated like:
-head -c 2048 /dev/urandom | od | s dd of=/q/root/luks/host-demohost
+h=demohost; head -c 2048 /dev/urandom | od | se dd of=/q/root/luks/host-$h
Configuration of which luks key to use is in
fai/config/hooks/partition.DEFAULT