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MINIX

1987 → today · Linux & Unix

A small Unix-like system that Andrew Tanenbaum wrote for teaching.1 Its full source code came with his 1987 textbook.1, 2

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Published
1987, with a textbook1, 2
Written by
Andrew S. Tanenbaum1
Design
A microkernel1
Newest stable release
MINIX 3.3.0, as of November 20264

Written for teaching

Andrew Tanenbaum taught operating systems using John Lions' book on Unix Version 6. When AT&T forbade teaching how Unix worked inside, he decided to write his own Unix-like system, free of AT&T code, and did it alone.1 He called it MINIX. Its full source code was printed in his 1987 book Operating Systems: Design and Implementation, and Prentice Hall sold the floppy disks for $69.1

Gray text on a black screen: 'Memory size = 640K MINIX = 89K RAM disk = 240K Available = 311K', messages about loading the RAM disk and mounting the /usr diskette, a request for the date, a note that the MINIX documentation is in the book Operating Systems: Design and Implementation by Andrew S. Tanenbaum, Prentice-Hall (1987), then 'Welcome to MINIX.' and a login: prompt.
Illustration · not a screenshot Our drawing of MINIX 1.1 starting on an IBM PC, drawn from the real screen in an emulator. Before the login prompt, it names the book that documents it. MINIX 1.1 for the IBM PC came on eight floppy disks.7 See the real screen

Small and tidy

MINIX was a microkernel: the memory manager and the file system ran as separate programs, outside the kernel. Tanenbaum says this made it cleaner and more reliable, and that it started in about 5 seconds, even on a 4.77 MHz 8088 processor.1 Its Usenet newsgroup, comp.os.minix, had 40,000 subscribers.1 One user was a Finnish student, Linus Torvalds, who learned from the book and went on to write Linux.2

Gray text on a black screen: the output of top, with load averages, memory and CPU figures, then a table of processes. The COMMAND column lists kernel, random, vm, vfs, top, procfs, mfs, pm, tty, memory, rs, sched, mfs, syslogd, update and ds.
MINIX 3.3.0 in our virtual PC. In top, the kernel is just one line; the file systems (vfs and mfs) and the process manager (pm) are programs of their own.

MINIX today

With MINIX 3, in 2006, the emphasis changed from teaching to a serious research and production system.2 If a driver crashes, MINIX 3 restarts it, and running programs don't even notice.3 Since 2000, MINIX has used the Berkeley license, which lets companies use it freely.2, 6 As of November 2026, the newest stable release on its download page is 3.3.0.4

Gray text on a black screen: the output of ps ax, listing programs such as /service/pci, /service/input, /service/pckbd, /service/floppy, /service/at_wini, /service/random, /service/printer, syslogd, the shell and ps ax itself.
MINIX 3.3.0 in our virtual PC. ps ax lists the drivers in /service, such as the keyboard (pckbd), the hard disk (at_wini) and the printer, as ordinary programs.

Key moments