EXODOS is a distributed operating system we are developing at the University of Oregon. Our goal is to implement a portable, easily modifiable testbed for research in distributed operating systems. The EXODO5 kernel provides mechanisms to support basic functionality without mandating policies, for it is these policies that we wish to study. The EXODOS kernel is replicated on every node and supports local interprocess communication, primitive memory management, and basic process management. Higher level operating systems functions are provided by server processes which interact with the EXODOS kernel through a unified message-passing interface. By elevating these functions to the server level, EXODOS provides a convenient testbed for the study of policy-level algorithms for scheduling, process migration, and virtual shared memory.