The L4 µ-Kernel Family

Overview

What is L4?

Originally, L4 is the name of a second-generation µ-kernel (microkernel) designed and implemented by Jochen Liedtke, running on i486 and Pentium CPUs.

However, there are now numerous implementations of the L4 API (application programming interface) on several hardware architectures. That's why, on this website we usually refer to the ``L4 µ-kernel interface'' (see below). When we refer to Jochen's original implementation, we say ``L4/x86''.

What is a µ-kernel?

Please refer to the corresponding entry in the Fiasco FAQ.

What is the L4 µ-kernel interface?

It is a definition of an API for µ-kernels.

Kernels based on the L4 API are second-generation µ-kernels. They are very lean and feature fast, message-based, synchronous IPC, simple-to-use external paging mechanisms, and a security mechanism based on secure domains (tasks, clans and chiefs). The kernels try to implement only a minimal set of abstractions on which operating systems can be built flexibly.

What implementations of the L4 µ-kernel interface do exist?

There are implementations for x86, Alpha, ARM, and R4x00 CPUs. Please see the implementations page for more information.

What is L3?

L3 is a microkernel implementation running on x86 CPUs. It is a predecessor to L4/x86. It is not compatible with L4.

Developers welcome!

Please consider subscribing to our public developer's mailing list at <l4-hackers-request@os.inf.tu-dresden.de> (use "subscribe" in the message body). The discussion language for this mailing list is English.

Before posting to the mailing list, you may want to check out the mailing list archive and the FAQs for the various kernel implementations.