Some host power management events are handled by Oracle VM VirtualBox. The actual behavior depends on the platform:
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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.
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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.
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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.