Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC The Background and Short History of UNIX & Linux Instructor: Joseph DiVerdi, Ph.D., MBA

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Early Steps It is useful to learn the history of OS –Provides insights into current state of affairs "Those that ignore history are doomed to repeat it"

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC In the 1960s... MIT, AT&T Bell Labs, & General Electric Developed an OS Named MULTICS –Multiplexed Information and Computing System Designed to Be an Interactive OS –Specifically for GE645 Mainframe Computer –Designed to Allow Information Sharing While Providing Security Development Was Problematic –OS Was Really Slow to Execute & Required Extensive Memory Bell Labs Pulled Out of Project

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Trouble in Paradise In 1969, Ken Thompson –Bell Labs Scientist Involved With MULTICS Effort –Wrote a Game for GE 645 Computer Called Space Travel Program Ran Poorly –Jerky Performance Usage Was Expensive –Cost $75 Per Run

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Spare Computer Program Rewritten to Run on a Spare Computer –PDP-7 From Digital Equipment Corporation –With the Help of Dennis Ritchie This Work Provided Thompson With an Opportunity to Write a New OS –Multitasking Was Integral Soon Other Facilities Were Added –File System, Command Interpreter & Utilities Space Travel Was Added Also Many UNIX Features Are Traced to This OS

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC A New Name Emerges OS Could Support Two Users –Woo-hoo! –Advanced for Its Time Humorously Named UNICS –Uniplexed Information and Computing System –Attributed to Brian Kernighan In 1970 –Name Changed Slightly to UNIX It Stuck Ever Since Progress Was Due to Project's Smaller Scope

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Small Beginnings In –Second Edition of UNIX Programmer's Manual "...There Are Exactly Ten Computers Using UNIX..." "...However, More Are Expected..." In 1977 –500 Computers Were Using UNIX 125 at Universities

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC C Programming Language In 1973 –Thompson Rewrote UNIX in Ritchie's C –C Was Designed to Be Simple & Portable –C Programs Could Run on Different Computers With Little or No Modification

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC UC - Berkeley In –UC Berkeley Ordered a Copy of UNIX For Its Shiny New PDP-11/45 Computer Purchased for $400 (Including Source Code) –Two Bright Graduate Students Chuck Haley & Bill Joy –Does CTO of Sun Microsystems Ring a Bell? Started Making Modifications & Sharing In –Free Copies of OS Were Sent Out –Called Berkeley Software Distribution or BSD –Included Ethernet & Internet Network Support

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC A Split Occurs System I, II, III, IV, & V –Maintained & Supported by AT&T 2BSD, 3BSD, 4BSD, 4.2BSD, 4.4BSD –Maintained & Supported by UC - Berkeley AT&T Always Offered Source Code –Free To Academic Users Because of Early Funding Rules –Expensive to Non-academic Users One Goal of BSD - Eliminate All AT&T Code –Tedious, Difficult, & Time-consuming Process

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Modern UNIX End of An Era –Final From Berkeley - 4.4bsd-lite –Final From AT&T - System V Release 4 Computer Manufacturers Created Versions for Their Hardware Software Manufacturers Created Versions for Others' Hardware –XENIX - Microsoft & SCO for & –HP-UX - Hewlett-Packard –Solaris - Sun Microsystems –AIX - IBM

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC A Grand Unification Several Attempts at Standardization –Independent Definition of Standard Environment –Portable Operating System Interface for Computer Environments POSIX –A Family of Standards Defining How Applications Interact With OS –An Organizing Principle

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Post-Modern UNIX In –An Unknown Finnish Graduate Re-wrote the UNIX Kernel From Scratch & Made It Public Under the New Open Software Foundation Rules Linus Torvalds & Linux –Grown to Full-Featured, Production-Quality Kernel Supported by Many Vendors As Primary System –Big-ticket Commercial Software Packages Have Been Ported to Linux –Oracle & Others

Background & History of UNIX & Linux Fort Collins, CO Copyright © XTR Systems, LLC Example Systems Solaris –Sun Microsystems Hardware –System V Derivative Even With Joy's Presence HP-UX –Hewlett-packard Hardware –System V & Berkeley Hybrid Has Its Own Surprises Red Hat Linux –Intel Hardware –Torvald's Kernel With Red Hat Components