What do the Shutdown, Hard Power Off and Hard Reset buttons do?
The shutdown button sends an ACPI power button signal to the server operating system, exactly as the ‘soft power-off’ button does when pressed on a physical machine. Normally operating systems are configured to shutdown or hibernate when this is done. The hard reset button sends a non-maskable interrupt to the server CPU in exactly the same way the reset button does on a physical machine. You should only use this if your server has crashed; otherwise you should reboot from inside your operating system. The hard power off button behaves exactly as if you have switched off a physical machine by turning off the power. You should only use this if your server has crashed; otherwise you should shutdown using the button or from inside your operating system.
