This is my effort so far once openhab2 is installed via deb:
> mount -t tmpfs tmpfs /var/lib/openhab2/cache
mount -t tmpfs tmpfs /var/lib/openhab2/mapdb mount -t tmpfs tmpfs /var/lib/openhab2/tmp mount -t tmpfs tmpfs /var/lib/openhab2/log ln -s /var/lib/openhab2/tmp/port /var/lib/openhab2/port ln -s /var/lib/openhab2/tmp/lock /var/lib/openhab2/lock rm -rf /var/lib/openhab2/persistence && ln -s /mnt/rwdata/openhab2/persistence /var/lib/openhab2/persistence