1. A system for controlling virtual servers comprising: a plurality of virtual servers running on a cluster having multiple hardware servers, the virtual servers sharing an operating system; each virtual server having an associated access identifier and a unique system-wide identifier; each virtual server including an internal control procedure for control of that virtual server using the associated access identifier and the unique system-wide identifier; and an external control interface operable outside the virtual server for control of the virtual server in response to commands sent by a remote user using the associated access identifier and the unique system-wide identifier, wherein, if a particular virtual server is non-responsive, the external control interface can be used to manage that virtual server using the associated access identifier and the unique system-wide identifier, wherein the external control interface is executed on any of the hardware servers and is available to the remote user when a particular virtual server is unresponsive, or when the internal control procedure of that virtual server is unreachable, or when services provided by the internal control procedure are unreachable.