You can use fetch commands to manage Nessus registration from the command line.
For online registration the commands include registering the scanner, confirming that Nessus has a valid registration code, and registering with Tenable Security Center. For offline registration, the commands include registering the scanner and providing the challenge code. The
nessuscli commands can also check that Nessus is properly configured with a valid registration code and can display the current activation code in use.
For more information, see the following: