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Cloud services that provide virtualized computational clusters present a dichotomy of systems management challenges, as the virtual clusters may be owned and administered by one entity, while the underlying physical fabric may belong to a different entity. On the physical fabric, scalable tools that "push" configuration changes and software updates to the compute nodes are effective, since the physical system administrators have complete system access. However, virtual clusters executing atop federated Grid sites may not be directly reachable for management purposes, as network or policy limitations may prevent unsolicited connections to virtual compute nodes. For these systems, a distributed middleware solution could permit the compute nodes to "pull" updates from a centralized server, thereby permitting the management of virtual compute nodes that are inaccessible to the system administrator. This paper compares both models of system administration and describes emerging software utilities for managing both the physical fabric and the virtual clusters.