Some host power management events are handled by Oracle VM VirtualBox. The actual behavior depends on the platform:
Host Suspends. This event is generated when the host is about to suspend, that is, the host saves the state to some non-volatile storage and powers off.
This event is currently only handled on Windows hosts and Mac OS X hosts. When this event is generated, Oracle VM VirtualBox will pause all running VMs.
Host Resumes. This event is generated when the host woke up from the suspended state.
This event is currently only handled on Windows hosts and Mac OS X hosts. When this event is generated, Oracle VM VirtualBox will resume all VMs which are where paused before.
Battery Low. The battery level reached a critical level, usually less than 5 percent charged.
This event is currently only handled on Windows hosts and Mac OS X hosts. When this event is generated, Oracle VM VirtualBox will save the state and terminate all VMs in preparation of a potential host powerdown.
The behavior can be configured. By executing the following command, no VM is saved:
$ VBoxManage setextradata global "VBoxInternal2/SavestateOnBatteryLow" 0
This is a global setting as well as a per-VM setting. The per-VM value has higher precedence than the global value. The following command will save the state of all VMs but will not save the state of VM "foo":
$ VBoxManage setextradata global "VBoxInternal2/SavestateOnBatteryLow" 1 $ VBoxManage setextradata "foo" "VBoxInternal2/SavestateOnBatteryLow" 0
The first line is actually not required as by default the savestate action is performed.