Structure of monolithic and microkernel-based operating systems, respectively

Near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS).

- Microkernel

174 related topics


Protection ring

In computer science, hierarchical protection domains, often called protection rings, are mechanisms to protect data and functionality from faults (by improving fault tolerance) and malicious behavior (by providing computer security).

Privilege rings for the x86 available in protected mode

A renewed interest in this design structure came with the proliferation of the Xen VMM software, ongoing discussion on monolithic vs. micro-kernels (particularly in Usenet newsgroups and Web forums), Microsoft's Ring-1 design structure as part of their NGSCB initiative, and hypervisors based on x86 virtualization such as Intel VT-x (formerly Vanderpool).

Monolithic kernel

Operating system architecture where the entire operating system is working in kernel space.


The monolithic model differs from other operating system architectures (such as the microkernel architecture) in that it alone defines a high-level virtual interface over computer hardware.

Mach (kernel)

Kernel developed at Carnegie Mellon University by Richard Rashid and Avie Tevanian to support operating system research, primarily distributed and parallel computing.

A kernel connects the application software to the hardware of a computer

Mach is often mentioned as one of the earliest examples of a microkernel.


Commercial Unix-like real-time operating system, aimed primarily at the embedded systems market.

The default desktop in QNX 6.4.1
The default desktop in QNX 6.4.1

QNX was one of the first commercially successful microkernel operating systems.

Message passing

Technique for invoking behavior on a computer.

Charles Babbage, sometimes referred to as the "father of computing".

For example, modern microkernels generally only provide a synchronous messaging primitive and asynchronous messaging can be implemented on top by using helper threads.

Inter-process communication

Operating system provides to allow the processes to manage shared data.

A grid computing system that connects many personal computers over the Internet via inter-process network communication

IPC is very important to the design process for microkernels and nanokernels, which reduce the number of functionalities provided by the kernel.

GNU Hurd

General structure of monolithic, microkernel and hybrid kernel-based operating systems, respectively.
Debian GNU/Hurd with Xfce

GNU Hurd is a collection of microkernel servers written as part of GNU, for the GNU Mach microkernel.

Windows NT

Proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993.

Original Windows NT wordmark
Windows 2000 architecture

This was designed as a modified microkernel, as the Windows NT kernel was influenced by the Mach microkernel developed by Richard Rashid at Carnegie Mellon University, but does not meet all of the criteria of a pure microkernel.

L4 microkernel family

L4 family tree

L4 is a family of second-generation microkernels, used to implement a variety of types of operating systems (OS), though mostly for Unix-like, Portable Operating System Interface (POSIX) compliant types.


Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993.

Debian 11 (Bullseye) running its default desktop environment, GNOME version 3.38
Debian 11 (Bullseye) running its default desktop environment, GNOME version 3.38
Debian 4 (Etch), 2007
Iceweasel logo
Debian 6 (Squeeze), 2011
Debian 10 installation menu (BIOS Mode)
Text version of the Debian Installer
Graphical version of the Debian Installer
Debian 10 console login and welcome message
XFCE is default on CD images and non-Linux ports
Using Aptitude to view Debian package details
Package installed with Aptitude
Screenshot of GDebi Package installer
A Debian 10.0 Buster box cover
Logo of Debian GNU/kFreeBSD
Logo of GNU Hurd
Debian GNU/Hurd running on Xfce
HP 9000 C110 PA-RISC workstation booting Debian Lenny

Debian GNU/Hurd is a flavor based on the Hurd microkernel, instead of Linux.