In case of need reboot (shutdown) of the dedicated or private server without login it is possible to allow it through the use of gpedit. Server shutdown is not allowed in the default setting.
- Log as server administrator and run gpedit.msc through Start - Run
- Set value Enabled in: Computer Configuration - Windows Settings - Security Settings - Local Policies - Security Option - Alow system to be shut down without having to log on
- It is not necessary to restart the server after the setting.
The information was taken from http://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2012-R2-and-2012/jj852274(v=ws.11)