While hypervisors can control the starting and stopping of virtual machines, they can’t always shut them down gracefully. You may want to power off your systems by connecting to each system and initiating a shutdown in the normal way. Sometimes you can’t do that, though, and you need to do the virtual equivalent of pulling the plug on a system that isn’t responding. The commands listed here cover these basic operations.
Xen and KVM virtual guests can be managed with virsh commands. Use virsh list --all to get a list of all managed domains. The start, shutdown, reboot, and destroy commands are your virtual power and reset buttons. From the service console in Vmware’s ESX server you can do similar things with vmware-cmd.