To detect whether a host is being isolated, that is, the host cannot reach the server instance anymore, the host needs to set an alternating value to a global extradata value within a time period. If this value is not set within that time period a timeout occurred and the so-called host isolation response will be performed to the VMs handled. Which VMs are handled can be controlled by defining VM groups and assigning VMs to those groups. By default no groups are set, meaning that all VMs on the server will be handled when no host response is received within 30 seconds.

Set the groups handled by the host isolation detection using the following command line:

--apimon-groups=<string[,stringN]>

Using a global extradata value, as follows:

VBoxManage setextradata global VBoxInternal2/Watchdog/APIMonitor/Groups <string[,stringN]>

Set the host isolation timeout using the following command line:

--apimon-isln-timeout=<ms>

Using a global extradata value, as follows:

VBoxManage setextradata global VBoxInternal2/Watchdog/APIMonitor/IsolationTimeoutMS <ms>

Set the actual host isolation response using the following command line:

--apimon-isln-response=<cmd>

Using a global extradata value, as follows:

VBoxManage setextradata global VBoxInternal2/Watchdog/APIMonitor/IsolationResponse <cmd>

The following response commands are available:

• none. This has no effect.

• pause. Pauses the execution of a VM.

• poweroff. Shuts down the VM by pressing the virtual power button. The VM will not have the chance of saving any data or veto the shutdown process.

• save. Saves the current machine state and then powers off the VM. If saving the machine state fails the VM will be paused.

• shutdown. Shuts down the VM in a gentle way by sending an ACPI shutdown event to the VM's operating system. The OS then has the chance of doing a clean shutdown.