Clusters of standard components are becoming a viable alternative to traditional supercomputers. The typical architecture of these clusters is standard PCs connected by a high performance network. The operating system used on this kind of platform is generally Linux because it is stable, and flexible: it can be studied, modified and tuned. A new kind of network has been available recently, not based on message passing but on remote memory mapping. One of the best-known network of this family is SCI. In this paper we present an extension of the LinuxThreads library to provide a migration service for Linux system threads. It takes advantage of the SCI network for a complete transparency of the migration and since it handles standard LinuxThreads, it doesn't need to use a new threads model or library. We explain how we modified the LinuxThreads library to add this functionality and give some preliminary performance results.