1. In a system including a host computer having one or more virtual machines configured therein, a primary storage unit for each of the virtual machines, and a central storage unit, a method for managing the virtual machines in a central manner, comprising: receiving a file operation requested by a virtual machine including a resolved filename determined from a namespace map that provides a mapping of filenames used by the virtual machines to filenames used by the central storage unit, the namespace mapping allowing multiple virtual machines to share a file associated with the resolved filename that is stored in the central storage unit; in response to receiving the file operation, determining if a management program is registered with the file operation and should be invoked for this file operation, wherein the management program provides a management service that needs to be performed before the file operation is performed; and if the management program is registered and should be invoked, invoking the management program on the file stored in the central storage unit using the resolved filename, wherein the management program is configured to access the file from the central storage unit using the resolved filename and execute a management service operation associated with the management service for the accessed file different from the file operation requested before the file operation is performed.