I found this post: https://askubuntu.com/questions/902636/nvidia-smi-command-not-found-ubuntu-16-04/903781and,Which says that with IUEF secure boot enabled nvidia-smi could not found in ubuntu:
$ nvidia-smi nvidia-smi: command not found
Actually with secure boot enabled, UBUNTU could not found the addtional Nvidia GPU.
Any idea on how to enable secure boot with nvidai driver funcioning?
I found this article on solving the secure boot issue with virtual box, just still have little idea on how MOK manager works: