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MINIX is an open source, Unix-like operating system (OS) based on a microkernel architecture. Andrew S. Tanenbaum wrote the operating system to be used for educational purposes; MINIX also inspired the creation of Linux. Its name derives from the words minimal and Unix.
History
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 mainly 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, 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 was also available.
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 [http://dspace.dial.pipex.com/town/way/fr30/minix/] and the Hitachi SH3-based HP Jornada 680/690 PDA [http://web.archive.org/web/20021211135921/http://minixsh.tripod.co.jp/index.html] were also developed.
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
MINIX 3 was publicly announced on 24 October 2005 by Andrew Tanenbaum during his keynote speech at the ACM Symposium on 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 only IA-32 architecture PC compatible systems. It is available in a LiveCD 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, and Virtual PC.
Version 3.1.2 was released 8 May 2006. 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. Another feature of this version, which will be improved in future ones, is the ability of the system to withstand device driver crashes, and in many cases having them automatically replaced without affecting running processes. In this way, MINIX is self-healing and can be used in applications demanding high reliability. MINIX 3 is available for free at [http://www.MINIX3.org www.MINIX3.org].
MINIX and Linux
The design principles Tanenbaum applied to MINIX famously 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 famously disapproved by Tanenbaum in the Tanenbaum-Torvalds debate. Recently, Tanenbaum explained again his [http://www.cs.vu.nl/~ast/reliable-os 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 disk filesystem format.
Accusations of Linux being stolen from MINIX
In May 2004 Kenneth Brown of the right-wing Alexis de Tocqueville Institution raised the accusation ( Alexis de Tocqueville Institution/Kenneth Brown, 'Samizdat's critics... Brown replies', http://www.adti.net/samizdat/brown.reply.june.04.html ) that major parts of the Linux kernel have been stolen from the MINIX codebase.
These accusations were rebutted universally and in particular by Andrew Tanenbaum. ( Tanenbaum, Andrew S. 'Some Notes on the "Who wrote Linux" Kerfuffle', http://www.cs.vu.nl/~ast/brown/), ( Tanenbaum, Andrew S. 'MINIX 3 FAQ', http://www.MINIX3.org/doc/faq.html#legal )
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 open source Unix-like operating systems such as Linux and 386BSD became available in the early 1990s many volunteer software developers abandoned MINIX in favour of these. In April 2000, MINIX became open source under the BSD license, but by this time other operating systems had surpassed its capabilities, and it remained primarily an operating system for students and hobbyists.
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