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Chapter 2 LINUX History Unix History “The number of UNIX installations has grown to 10, with more expected” - UNIX Programmer’s Manual, 1972 UNIX as an Operating System • • • • • Run-time environment System services Utilities Libraries User programs Systems Supported by UNIX • • • • • Multiprocessor Computers High Performance Computers Work Stations Personal Computers Embedded Processors In short, all kinds of computers UNIX Variants • • • • • • • System V Release 4 (SVR4) by Novell, Inc. University of California Berkeley UNIX (4.xBSD) SUN OS Solaris Digital UNIX HP-UX, XENIX, AIX, VENIX Clones, such as Linux UNIX Variants Features Commonalities: • A core set of interfaces • A core set of features • Applications Differences: • Internal Implementation • Interface Semantics • Some features Historic Milestones • Multics Project at Bell Labs (1966 – 1969) • Thompson and Ritchie’s first UNIX on a PDP-7: a mechanism to support program development (1969) • Thompson’s B language (interpreted) used as a language for development (1970) • Ritchie evolved B into C, a compiled language (1971) • UNIX rewritten in C (1973) Historic Milestones (cont.) • AT&T provides UNIX free to Universities (starting with Berkeley in 1973) • UNIX version 7 released as the first portable version (1979) • Users improved performance of version 7 and AT&T incorporated user changes in later versions Historic Milestones (cont.) • First 32 bit version developed for the VAX-11 (1978) and later evolved into 3BSD (1979) • 3BSD: first version to use virtual memory – the VAX-11 had a 32-bit address space and only 4 MB of physical memory • 4BSD first to integrate TCP/IP (1980) under ARPA funding Historic Milestones (cont.) • 4.x BSD introduced: – FAST File System (FFS) – Signals – Sockets • 4.4BSD (1993): last version from Berkeley • Berkeley Software Design, INC. was formed to market BSD Commercial Releases • SunOS based on 4.2BSD introduced the NFS file system • Solaris from Sun based on SVR4 • XENIX by Microsoft • AIX by IBM • HP-UX from HP • ULTRIX (Digital UNIX) from Digital first Multiprocessor UNIX AT&T Releases • System III: 1982 • System V: 1983 - A different virtual memory architecture • System V Release 2 (SVR2): 1984 • SVR3: 1987 • Introduced interprocess communication, shared memory, semaphores, message passing, remote file sharing, shared libraries • SVR4:1989 SVR4 Joint effort by AT&T and Sun • Integrates features from all other versions (SVR3, 4BSD, SunOS, XENIX) • Introduced real-time scheduling • AT&T sold its interest in UNIX to Novell in 1993 Solaris • Sun purchased SVR4 rights in 1994 • Solaris was developed based on SVR4 • Introduced: – A multithreaded kernel – Support for Multiprocessors Mach • Introduced by Carnegie-Mellon University in 1986 • An implementation from Scratch to avoid the problems associated with UNIX’s legacy code • First Object-oriented operating system Standardization • SVID (System V Interface Definition) from AT&T: 1984 • POSIX (Portable Operating Systems based on UNIX) from IEEE: 1986 • X/Open: 1990 Motivations for Change • Functionality – User-level tools and utilities – System functionality, e.g. interprocess communications, concurrency, advanced file systems • Networking – Distributed file systems – Client-server support – Distributed operating systems Motivations for Change (cont.) • Performance – Improved performance – Multiprocessor support • Hardware Changes • Quality Improvement • Paradigm Shift: – Server with terminals – Workstations – Client-server computing Motivations for Change (cont.) Specialized Applications: • Multimedia • Scientific Application • Embedded systems • Real-time systems What Helped UNIX Grow? • • • • • • • Initially free Open source Small kernel Simple approach to most functions Text representation of system data files Uniform (file-like) interface to all devices Portability UNIX Weaknesses • • • • Did not stay simple The lack of a simple uniform user interface Small building block commands Too many (often incompatible) versions LINUX “I am doing a (free) operating system (just a hobby, won’t be big and professional like GNU) for 386 AT clones” Linus Torvalds, 1991 LINUX • LINUX is a child of the Internet • Based on Minix (Unix-like educational operating system developed by Andrew Tanenbaum) • Based on open source philosophy • Originally developed by Linus Trovald • Enhanced and maintained by community of users Reasons for LINUX Success • • • • Free Open Source Huge support network Frequent releases incorporating updates/fixes based on user feedback LINUX Distribution • Free online download • Company-provided media for a fee only for the enhancements provided by the company • Current users estimated at 20 million Table 2.1 Web Resources (continued on next slide) Table 2.1 Web Resources (continued from previous slide) Table 2.2 Major LINUX Distributions