Ubuntu OS must disable the x86 Ctrl-Alt-Delete key sequence.

A locally logged-on user who presses Ctrl-Alt-Delete, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot.

Verify Ubuntu OS is not configured to reboot the system when Ctrl-Alt-Delete is pressed by using the following command:

     $ systemctl status ctrl-alt-del.target 
     ctrl-alt-del.target 
          Loaded: masked (Reason: Unit ctrl-alt-del.target is masked.) 
          Active: inactive (dead) 

If the "ctrl-alt-del.target" is not masked, this is a finding.

Configure Ubuntu OS to disable the Ctrl-Alt-Delete sequence for the command line by using the following commands:

     $ sudo systemctl disable ctrl-alt-del.target 

     $ sudo systemctl mask ctrl-alt-del.target 

Reload the daemon to take effect:

     $ sudo systemctl daemon-reload