ExOS – an operating system kernel developed by the MIT Parallel and Distributed Operating Systems group, and also a class of similar operating systems.
An exokernel eliminates the notion that an operating system should provide abstractions on which applications are built. Instead, it concentrates solely on securely multiplexing the raw hardware: from basic hardware primitives, application-level libraries and servers can directly implement traditional operating system abstractions, specialized for appropriateness and speed.
The newest exokernel is XOK, which runs on PC hardware, and ExOS, our first library operating system (libos). The ExOS library provides a user-level and extensible implementation of an UNIX operating system. Most UNIX applications like gcc, perl, apache, tcsh, and telnet compile and work without changes using ExOS. Further, measurements of application performance show that ExOS performs at least as well as OpenBSD and FreeBSD and much better when using specialized libos’s. For example, the Cheetah web server built on top of XOK performs eight times faster than NCSA or Harvest and three to four times faster than IIS running on Windows NT Enterprise Edition.
The current exopc distribution contains the entire source tree for the XOK kernel, ExOS library operating system, and assorted user-level programs and tools for building the system. OpenBSD or Linux with libc6 is required to build the system and only certain disk and ethernet controllers are supported. It was written by a variety of people over the past four years under DARPA sponsorship. Currently, the system is still under active development by PDOS at MIT, Greg Ganger’s group at CMU, and Exotec.
Exopc is stable enough to do libos and application development but there are still many bugs and features that have not yet been implemented. Do not expect to compile everything and replace your current system with XOK/ExOS. However, things are progressing rapidly and hopefully with making the sources public the ‘net world at large can help speed development. Any additions or bug fixes are greatly welcomed and will be considered for incorporation into the main source tree.
Copyright (C) 1997 Massachusetts Institute of Technology; some code in this distribution is covered by the GNU General Public License; some files include the following copyright: Copyright (C) 1998 Exotec, Inc. (free).
Primary authors (alphabetical order):
– Hector Briceno
– Dawson Engler
– Greg Ganger
– Rusty Hunt
– John Jannotti
– Frans Kaashoek
– David Mazieres
– Tom Pinckney
Other authors (alphabetical order):
– Josh Cates
– George Candea
– Robert Grimm
– Eric Nygren
– Costa Sapuntzakis
– Yonah Schneidler
– Josh Stults
– Debby Wallach
– Doug Wyatt
