MINIX

MINIX

The MINIX 3.1.8 boot screen
Developer	Andrew S. Tanenbaum
Written in	C
OS family	Unix-like
Working state	Current
Source model	Open source
Initial release	1987 (1987)
Latest release	3.3.0 / September 16, 2014 (2014-09-16)
Marketing target	Teaching (v1, v2) embedded systems (v3)
Available in	English
Platforms	PC compatibles, PC, PC/AT, PS/2, Motorola 68000, SPARC, Atari ST, Commodore Amiga, Macintosh, SPARCstation, Intel 386, NS32532, ARM, INMOS transputer
Kernel type	Microkernel
License	Originally proprietary, BSD license since 2000
Official website	minix3.org

MINIX (from "mini-Unix") is a POSIX-compliant, Unix-like computer operating system based on a microkernel architecture.

Early versions of MINIX were created by Andrew S. Tanenbaum for educational purposes. Starting with MINIX 3, the primary aim of development shifted from education to the creation of a highly reliable and self-healing microkernel OS. MINIX is now developed as open-source software.

MINIX was first released in 1987, with its complete source code made available to universities for study in courses and research. It has been free and open source software since it was re-licensed under the BSD license in April 2000.

Implementation

MINIX 1.0

Andrew S. Tanenbaum created MINIX at Vrije Universiteit in Amsterdam to exemplify the principles conveyed in his textbook, Operating Systems: Design and Implementation (1987).

An abridged 12,000 lines of the C source code of the kernel, memory manager, and file system of MINIX 1.0 are printed in the book. Prentice-Hall also released MINIX source code and binaries on floppy disk with a reference manual. MINIX 1 was system-call compatible with Seventh Edition Unix.

Tanenbaum originally developed MINIX for compatibility with the IBM PC and IBM PC/AT microcomputers available at the time.

MINIX 1.5

MINIX 1.5, released in 1991, included support for MicroChannel IBM PS/2 systems and was also ported to the Motorola 68000 and SPARC architectures, supporting the Atari ST, Commodore Amiga, Apple Macintosh and Sun SPARCstation computer platforms. There were also unofficial ports to Intel 386 PC compatibles (in 32-bit protected mode), National Semiconductor NS32532, ARM and INMOS transputer processors. Meiko Scientific used an early version of MINIX as the basis for the MeikOS operating system for its transputer-based Computing Surface parallel computers. A version of MINIX running as a user process under SunOS and Solaris was also available, a simulator called SMX.

MINIX 2.0

MINIX 2.0.4 system startup and login prompt

MINIX 2.0.4 shell interaction

Demand for the 68k-based architectures waned, however, and MINIX 2.0, released in 1997, was only available for the x86 and Solaris-hosted SPARC architectures. It was the subject of the second edition of Tanenbaum's textbook, co-written with Albert Woodhull and was distributed on a CD-ROM included with the book. MINIX 2.0 added POSIX.1 compliance, support for 386 and later processors in 32-bit mode and replaced the Amoeba network protocols included in MINIX 1.5 with a TCP/IP stack. Unofficial ports of MINIX 2.0.2 to the 68020-based ISICAD Prisma 700 workstation and the Hitachi SH3-based HP Jornada 680/690 PDA were also developed.

Minix-vmd

Main article: Minix-vmd

Minix-vmd is a variant of MINIX 2 for Intel IA-32-compatible processors, created by two Vrije Universiteit researchers, which adds virtual memory and support for the X Window System.

MINIX 3

Main article: MINIX 3

MINIX 3.2 running the "top" system monitoring command

MINIX 3 running X11 with the twm window manager

MINIX 3 was publicly announced on 24 October 2005 by Andrew Tanenbaum during his keynote speech on top of the ACM Symposium Operating Systems Principles conference. Although it still serves as an example for the new edition of Tanenbaum and Woodhull's textbook, it is comprehensively redesigned to be "usable as a serious system on resource-limited and embedded computers and for applications requiring high reliability."

MINIX 3 currently supports IA-32 and ARM Architecture systems. It is available in a Live CD format that allows it to be used on a computer without installing it on the hard drive, and in versions compatible with hardware emulation/virtualization systems, including Bochs, QEMU, VMware Workstation/Fusion, VirtualBox and Microsoft Virtual PC.

Version 3.1.5 was released 5 November 2009. It contains X11, emacs, vi, cc, gcc, perl, python, ash, bash, zsh, ftp, ssh, telnet, pine, and over 400 other common Unix utility programs. With the addition of X11, this version marks the transition away from a text-only system. It can also withstand driver crashes. In many cases it can automatically restart drivers without affecting running processes. In this way, MINIX is self-healing and can be used in applications demanding high reliability. MINIX 3 also has support for virtual memory management, making it suitable for desktop OS use. Desktop applications such as Firefox and OpenOffice.org are not yet available for MINIX 3 however.

As of version 3.2.0, the userland was mostly replaced by that of NetBSD and support from pkgsrc became possible, increasing the available software applications that MINIX can use. Clang replaced the previous compiler (with GCC optionally supported), and GDB, the GNU debugger, was ported.

Minix 3.3.0, released in September 2014, brought ARM support.

Relationship with Linux

Early influence

The design principles Tanenbaum applied to MINIX greatly influenced the design decisions Linus Torvalds applied in the creation of the Linux kernel. Torvalds used and appreciated MINIX, but his design deviated from the MINIX architecture in significant ways, most notably by employing a monolithic kernel instead of a microkernel. This was disapproved of by Tanenbaum in the Tanenbaum–Torvalds debate. Tanenbaum explained again his rationale for using a microkernel in May 2006.

Early Linux kernel development was done on a MINIX host system, which led to Linux inheriting various features from MINIX, such as the MINIX file system.

Samizdat claims

In May 2004, Kenneth Brown of the Alexis de Tocqueville Institution made the accusation that major parts of the Linux kernel had been copied from the MINIX codebase, in a book called Samizdat. These accusations were rebutted universally—most prominently by Andrew Tanenbaum himself, who strongly criticised Kenneth Brown and published a long rebuttal on his own personal Web site, also pointing out that Brown was funded by Microsoft.

Licensing

At the time of its original development, the license for MINIX was considered to be rather liberal. Its licensing fee was very small ($69) compared to those of other operating systems. Although Tanenbaum wished for MINIX to be as accessible as possible to students, his publisher was not prepared to offer material (such as the source code) that could be copied freely, so a restrictive license requiring a nominal fee (included in the price of Tanenbaum's book) was applied as a compromise. This prevented the use of MINIX as the basis for a freely distributed software system.

When free and open source Unix-like operating systems such as Linux and 386BSD became available in the early 1990s, many volunteer software developers abandoned MINIX in favor of these. In April 2000, MINIX became free/open source software under a permissive free software license, but by this time other operating systems had surpassed its capabilities, and it remained primarily an operating system for students and hobbyists.

See also

• MINIX file system
• Minix-vmd
• MINIX 3

External links

• Official website
• MINIX at DMOZ
• History of MINIX from Andrew Tanenbaum
• MINIX 3: a Modular, Self-Healing POSIX-compatible Operating System on YouTube