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line or via the VirtualBox GUI. Both of these methods provide several mecha-
nisms that can stop a guest.
An ACPI shutdown signal.
This is the recommended method. A shutdown
signal is sent to the guest and, if that signal is supported, the guest will begin
a normal shutdown. This process includes tasks such as flushing disk caches
and unmounting file systems. An ACPI signal is the safest of the external
shutdown methods.
■
Snapshot.
The guest machine's current state will be saved and can be re-
started from this point in the future. The snapshot approach is similar to a
hibernation feature found on modern laptops, but you can save many snap-
shots and roll them back as desired. This flexibility enables you to test the
effects of various operations, starting with a consistent state each time.
■
Reset.
This “hard stop” will cause a machine reset; it is recommended only
when the ACPI shutdown does not work. In this case, the guest disk buffers
are not flushed, and some of the uncommitted disk data may be corrupted.
Most modern operating systems feature some form of recovery in the event
of a power loss, so the chances of corruption are small, but this approach is
recommended only when no other method works.
■
Pause.
This option causes a virtual machine to stop execution. The guest
remains in memory, however, and its operation can be resumed. The state is
not saved by a pause operation.
■
Here is an example of a safe external host-initiated shutdown for the guest
named
Windows XP
:
%
VBoxManage controlvm "Windows XP" acpipowerbutton
This command sends an ACPI shutdown signal to the guest, which will start an
orderly shutdown process.
Although VirtualBox does not currently feature complete cloning of a virtual ma-
chine, it does provide a host-agnostic method of cloning disk images. This is done
via the
VBoxManage clonehd
command. The source disk image is copied in its
entirety and a new UUID is assigned. The disk can be registered in the user's
Media Manager or copied to another system to be used elsewhere. All that is re-
quired to complete the cloning of the virtual machine is to create the new guest
configuration, using either the command line or the GUI as shown before.
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