Abstract: A mainframe computer executes multiple instances of virtual machines. An administrator uses a set of manager instances to create and manage a set of managed instances. The manager instances include a configuration manager that creates managed instances according to templates. A template describes aspects of a managed instance, including the resources and software available to it. The manager instances also include a file server that maps file access requests from managed instances to files in a storage device. The administrator installs software in the storage device and uses the templates and other data to create mappings in the file server that allow multiple managed instances to independently execute the software. The administrator can easily maintain the managed instances and software executed by the machines.