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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
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Run-time environment
System services
Utilities
Libraries
User programs
Systems Supported by UNIX
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Multiprocessor Computers
High Performance Computers
Work Stations
Personal Computers
Embedded Processors
In short, all kinds of computers
UNIX Variants
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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?
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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
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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
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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