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Chapter 1: Welcome to Linux. An intro to UNIX-related operating systems. In this chapter …. History of Unix GNU-Linux Why Linux?. Long ago, in a galaxy far away …. Computing power was costly UNIVAC cost $1 million CPU time was a premium

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chapter 1 welcome to linux

Chapter 1: Welcome to Linux

An intro to UNIX-related operating systems

in this chapter
In this chapter …
  • History of Unix
  • GNU-Linux
  • Why Linux?
long ago in a galaxy far away
Long ago, in a galaxy far away …
  • Computing power was costly
    • UNIVAC cost $1 million
  • CPU time was a premium
    • Most mainframes had less computing power than a calculator on the shelf at Wal-Mart
  • Jobs were submitted into a queue
    • Only one process at a time – scheduling nightmare
what was needed
What was needed
  • Allow multiple users to access the same data and resources simultaneously
  • Service many users more cheaply than buying each their own machine
  • The ability to run multiple processes at once
  • And do so while maintaining user segregation and data integrity
enter unix pride of bell labs
Enter Unix, pride of Bell Labs
  • Originally written in PDP-7 assembly language by Ken Thompson
  • To make it work on multiple architectures (portable), Thompson rewrote Unix in B
  • Dennis Ritchie developed C, and with Thompson, rewrote Unix in C
what was so great about it
What was so great about it?
  • Multiuser
  • Multiprocess
  • Non-proprietary
  • Economical for business
  • Initially given for free to colleges and universities (great tactic!)
descendents and bastards
Descendents and bastards …
  • Started at Bell Labs
  • Picked up and continued by AT&T (SVR4)
  • UC Berkeley derives BSD
  • Sun Solaris
  • IRIX
  • Minix, XINU
  • Linux
what happened
What happened?
  • UNIX became commercialized
  • Proprietary code, specialized distributions
  • Costs started to become a hindrance
  • So … let’s make our own Unix …
  • Richard Stallman decides that there should be a free version of Unix available
  • Forms the GNU project – GNU’s Not Unix
  • Writes all of the system programs and utilities to mimic Unix variants
  • Everything but a kernel (Hurd)
final piece
Final piece
  • Universities trying to teach Unix and OS design can’t afford Unix
  • Andrew Tanenbaum writes Minix
  • Linus Torvalds, dissatisfied with Minix, writes his own – Linux
gnu linux
  • Torvalds has a perfectly functioning kernel – but no system programs
  • Finds a perfect candidate in GNU
  • Together, the operating system world was changed dramatically
free you say
Free you say?
  • GNU-Linux is free …
  • Free as in speech, not free as in beer
  • Free to view, copy, modify, and release
  • Profit still to be had from packaging, support, and additional original code
why linux
Why Linux?
  • Software
  • Hardware
  • Portability
  • Standards
  • $$$
  • An almost limitless library of programs
  • Applications, services, utilities
  • Many free, some commercial
  • Source code often available along with pre-built binaries
  • Supports thousands of peripherals and pieces of hardware
  • Multi-platform: x86, PPC, Alpha, SPARC, MIPS, 64-bit, SMP (multiproc systems)
  • Emulation of hardware for testing and development
  • Entire operating system written in C
  • Shared system libraries available for all supported architectures
  • Code written on one platform can be compiled on any system with minimal, if any, tweaks
  • Much of GNU-Linux already meets POSIX (Portable Operating System Interface for Computer Environments) and Unix System V Interface Definition (SVID)
  • Standardized for commercial and government use
and don t forget
And don’t forget …
  • It’s free! (or at least really cheap!)
  • That’s why Linux is often the operating system of choice to teach OS design and Unix courses
  • We’ll be using RedHat Enterprise Linux 4 – not free but a fraction of the cost of Unix
features overview
Features Overview
  • Multiuser
  • Multiprocess / Multitasking
  • Hierarchical Filesystem
  • BASH Shell command line interface / programming language
  • Many useful utilities built-in
  • Rich networking support