You need to powercycle internal mSATA SSD to perform secure erase, while the NUC is powered on. Here's how to do it:
- Turn on the NUC power and boot the OS (preferably Linux).
- Open the bottom cover.
- Remove the small screw which holds the mSATA SSD board. This will make the board flip up.
- Carefully remove the SSD board from the mSATA connector.
- Wait for a few seconds.
- Carefully insert the SSD board to the mSATA connector.