The L4Re Microkernel, alias Fiasco, is a 3rd-generation microkernel (µ-kernel).

The L4Re Microkernel can be used to construct flexible systems. The microkernel is the base for the L4Re system which supports running real-time, time-sharing and virtualization applications concurrently on one system. The L4Re Microkernel is both suitable for big and complex systems as well as small, embedded applications. We have developed the L4Re Operating System Framework which provides the necessary infrastructure on top of the microkernel for conveniently developing applications. Please refer to the Features page for more information on the capabilities of the microkernel and L4Re overall.

3rd-generation microkernels use the state-of-the-art security concept of object capabilities that implements the principle of least authority (POLA) for every address space. This allows fine-grained access control to resources throughout the system. Resources on this level are microkernel objects, memory pages and communication channels upon which user-level infrastructure is built.