UNIX FAQ Version 2.1 92/12/04 -- Question 6.3

Main Unix flavors. From: "Pierre (P.) Lewis" <lew@bnr.ca> Date: Sun, 11 Oct 1992 15:29:00 +0000 Version: 2.0 Until recently, there were basically two main flavors of Unix: System V (five) from AT&T, and the Berkeley Software Distribution (BSD). SVR4 is essentially a merge of these two flavors. End '91, OSF/1 from the Open Software Foundation was released (as a direct competitor to System V) and may (future will tell) change this picture. The following lists the main releases and features of System V, BSD and OSF/1. System V from AT&T. Typical of Intel hardware. Most often ported Unix, typically with BSD enhancements (csh, job control, termcap, curses, vi, symbolic links). System V evolution is now overseen by Unix International (UI). UI members include AT&T, Sun, .... Newsgroup: comp.unix.sysv[23]86. Main releases: - System III (1982): first commercial Unix from AT&T - FIFOs (named pipes) (later?) - System V (1983): - IPC package (shm, msg, sem) - SVR2 (1984): - shell functions (sh) - SVID (System V Interface Definition) - SVR3 (1986) for ? platforms: - STREAMS (inspired by V8), poll(), TLI (network software) - RFS - shared libs - SVID 2 - demand paging (if hardware supports) - SVR3.2: - merge with Xenix (Intel 80386) - networking - SVR4 (1988), mainstream of Unix implementations, merge of System V, BSD, and SunOS. - From SVR3: sysadmin, terminal I/F, printer (from BSD?), RFS, STREAMS, uucp - From BSD: FFS, TCP/IP, sockets, select(), csh - From SunOS: NFS, OpenLook GUI, X11/NeWS, virtual memory subsystem with memory-mapped files, shared libraries (!= SVR3 ones?) - ksh - ANSI C - Internationalization (8-bit clean) - ABI (Application Binary Interface -- routines instead of traps) - POSIX, X/Open, SVID3 - SVR4.1 - async I/O (from SunOS?) - SVR4.2 (based on SVR4.1ES) - Veritas FS, ACLs - Dynamically loadable kernel modules - Future: - SVR4 MP (multiprocessor) - Use of Chorus microkernel? Berkeley Software Distribution (BSD). Typical of VAXen, RISCs, many workstations. More dynamic, research versions now than System V. BSD is responsible for much of the popularity of Unix. Most enhancements to Unix started here. The group responsible at UCB (University of California at Berkeley) is the Computer System Research Group (CSRG). They closed down in 1992. Newsgroup: comp.unix.bsd. Main releases: (much reorganized wrt dates and releases, hope it's converging) - 2.xBSD (1978) for PDP-11, still of significance? (2.11BSD was released in 1992!). - csh - 3BSD (1978): - virtual memory - 4.?BSD: - termcap, curses - vi - 4.0BSD (1980): - 4.1BSD (?): base of later AT&T CRG versions - job control - automatic kernel config - vfork() - 4.2BSD (1983): - TCP/IP, sockets, ethernet - UFS: long file names, symbolic links - new reliable signals (4.1 reliable signals now in SVR3) - select() - 4.3BSD (1986) for VAX, ?: - 4.3 Tahoe (1988): 4.3BSD with sources, support for Tahoe (32-bit supermini) - Fat FFS - New TCP algorithms - 4.3 Reno (1990) for VAX, Tahoe, HP 9000/300: - most of P1003.1 - NFS (from Sun) - MFS (memory file system) - OSI: TP4, CLNP, ISODE's FTAM, VT and X.500; SLIP - Kerberos - 4.4BSD (will we ever see it?) for HP 9000, Sparc, 386, DEC, Tahoe: - new FS organization, new process internals, new virtual memory based on Mach 2.5 - POSIX compatibility - OSI (based on ISODE), X.25 The Open Software Foundation (OSF) released its Unix called OSF/1 end of 1991. Still requires an SVR2 license. Compatible/compliant with SVID 2 (and 3 coming), POSIX, X/Open, etc.. OSF members include Apollo, Dec, HP, IBM, .... - OSF/1 (1991): - based on Mach 2.5 kernel - symmetric multiprocessing, parallelized kernel, threads - logical volumes, disk mirroring, UFS (native), S5 FS, NFS - enhanced security (B1 with some B2, B3; or C2), 4.3BSD admin - STREAMS, TLI/XTI, sockets - shared libs, dynamic loader (incl. kernel) - Motif GUI - Future: - OSF/1 MK (mikrokernel) based on Mach 3.0 This list of major flavors should probably also include Xenix which has been the basis for many ports. Derived from V7, S III and finally System V, it is similar externally but significantly changed internally (performance-tuned for micros). Two very good books describe the internals of the two main flavors. These are: - System V: "Design of the Unix Operating SYstem", M.J. Bach. - BSD: "Design and Implementation of the 4.3BSD Unix Operating System", Leffler, McKusick, Karels, Quaterman. For a good introduction to OSF/1 (not quite as technical as the previous two), see: "Guide to OSF/1, A Technical Synopsis", published by O'Reilly. On SunOS, "Virtual Memory Architecture in SunOS" and "Shared Libraries in SunOS" in Summer 1989 USENIX Proceedings. A good set of articles on where Unix is going is "Unix Variants" in the Apr 92 issue of Unix Review. Other good sources of information include the bsd-faq file, and many of the newsgroups mentioned in the text.