linux crash course chapter 01 3

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 – 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 • 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 so while maintaining user segregation and data integrity 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? • • • • • Multiuser Multiprocess Non-proprietary Economical for business Initially given for free to colleges and universities (great tactic!) 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? • UNIX became commercialized • Proprietary code, specialized distributions • Costs started to become a hindrance • So … let’s make our own Unix … GNU • 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 • 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? • • • • 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? • • • • • Software Hardware Portability Standards $$$ Software • • • • An almost limitless library of programs Applications, services, utilities Many free, some commercial Source code often available along with prebuilt binaries Hardware • 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 Portability • 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 Standards • 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 … • 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 – not free but a fraction of the cost of Unix Features Overview • • • • Multiuser Multiprocess / Multitasking Hierarchical Filesystem BASH Shell command line interface / programming language • Many useful utilities built-in • Rich networking support ...In this chapter … • History of Unix • GNU -Linux • Why Linux? Long ago, in a galaxy far away … • Computing power was costly – UNIVAC... 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 – not free but a fraction of the... • • 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? •