When you setup Fortinac you have to license it, and Fortinet asks you what the MAC and UUID of the device are when registering the license. You can get this information by SSH’ing into the NAC and running the following commands:
sysinfo -v | grep -i UU — This will bring back the UUID
and to get the mac – run ifconfig eth0
Copy those two settings into the registration of the license, and you can then get the license key.