Building distributed operating systems benefits from the micro-kernel approach by allowing better support for modularization. The authors believe that a more modular, or object-oriented approach is needed to cross the barrier of complexity that is holding back distributed operating system development. The Chorus object-oriented layer (COOL) is a layer built above the Chorus micro-kernel designed to extend the micro-kernel abstractions with support for object-oriented systems. COOL v2, the second aeration of this layer provides generic support for clusters of objects, in a distributed virtual memory model. This approach allows one to build operating systems as collections of objects.