When you bought a readynas 2120 with the new software version 6.0. And your looking seriously for the option to shutdown or reboot the ReadyNas.
The solution is on the first page you can find. ( It’s the default over view page you get to see when you login for the first time to the Nas )
The button is quiet hidden beside the name Devices if you press there. A popup will shown with the option for shutdown or restart.