Windows Server 2012 R2 omitted the Logoff button. This can be done using the start menu but the shutdown and restart t button options are as well not included. When faced with issues like, use the following commands to your specific need.
For Instant restart with time 0
Type shutdown -r -t 0
Note: Its zero (0)
For instant shutdown with time 0.
Type shutdown -s -t 0
This option can be found in other versions of windows. Simply hover your mouse to the right corner of your screen there you will find the for reboot and shutdown menu.