The Secondary User Authentication Parameter
Secondary user authentication provides a method for additional identification of users that log in to a Linux Client computer (in case any users share the same credentials).
If the Enable secondary user authentication on login checkbox is selected (on the Editing Client / Editing Client Group page, on the Authentication Options tab, scroll down to the Two-factor and Secondary Authentication section) to enable this option, the Client will display a message requiring the user to enter their secondary user authentication credentials on login to the Linux Client computer.
NOTE: Secondary user authentication can only be enabled by editing Clients (or Client groups) in the Management Tool.