microkernels
A microkernel is a minimal core of an operating system that provides only the essential facilities needed to run programs. It implements inter-process communication, address space management, thread management, and basic scheduling; all other services such as device drivers, file systems, and networks run in user space as separate processes and communicate with the kernel via IPC.
The design emphasizes modularity and fault isolation. Running services in user space improves reliability, as a
Origins trace to 1980s research at Carnegie Mellon University, led by Jochen Liedtke, and the development of
Advantages include isolation, security, easier maintenance and verification, and portability to different hardware. In safety-critical and
Limitations include potential performance overhead from context switches and IPC, design complexity of externalizing services, and
Notable examples include seL4 (formally verified), the L4 family (various implementations), MINIX 3, and QNX.