"
The fact that shutdown and reboot work correctly from the console but not from the web GUI makes me think this is less likely to be an ACPI or VM power-management issue and more likely something in the path between the GUI and the underlying system command. If ACPI were the main problem, I would expect both methods to fail in a similar way or at least reach the same point before hanging.
I'd be interested to know whether anything relevant appears in the system log at the exact moment you click Reboot or Power Off in the GUI. If the GUI displays "shutdown in progress" but nothing appears on the console, it almost sounds as if the request is being accepted by the interface but never actually reaching the process responsible for initiating the shutdown.
The suggestion regarding UEFI is still worth testing, though. Virtualized environments sometimes behave differently enough that seemingly unrelated settings end up affecting system control actions in unexpected ways.
I'd be interested to know whether anything relevant appears in the system log at the exact moment you click Reboot or Power Off in the GUI. If the GUI displays "shutdown in progress" but nothing appears on the console, it almost sounds as if the request is being accepted by the interface but never actually reaching the process responsible for initiating the shutdown.
The suggestion regarding UEFI is still worth testing, though. Virtualized environments sometimes behave differently enough that seemingly unrelated settings end up affecting system control actions in unexpected ways.
