Introduction To Unix- CS 21

1. Introduction To Unix- CS 21 Lecture 1

2. Overview Of Today’s Lecture • Class introduction • Brief history of Unix • Hacker mentality • Unix design mentality

3. Syllabus • Instructor: Jason Villarreal • T.A. : Ioannis Drougas • Lecture Times: TR 9:40-11:00 • Lab Times: Thursday 2-5, 6-9 • Lab attendance is mandatory, there will be lab assignments each lab

4. Books • Required: “Teach Yourself Unix in 24 Hours” by Dave Taylor. • Recommended: • Unix Power Tools, 3rd Edition* • Perl in a Nutshell* • The LaTeX Companion *Available online for free to UCR students at library.ucr.edu/oreilly

5. Grading • 3 Quizzes – 15% total (5% each) • 1 Midterm – 20% • 1 Final – 30% • Lab Assignments – 25% total • Homework – 10%

6. Special Note On Cheating • Cheating will not be tolerated • What constitutes cheating? • Sharing of answers to questions on homework, assignments, or tests • Sharing of code • Using anyone else’s work as your own • Discussion of high level concepts and studying text is all right. • Moral: If you’re not sure, don’t do it!

7. What Are You Going To Get Out Of This Class? • First answer: Whatever you put into this class • Specifically: • Working knowledge to accomplish most tasks in Unix • From simply managing files to programming projects and scripting • Everything to get you familiar with what is necessary in the rest of the computer science curriculum • An appreciation for the way things are done in Unix

8. A Quick Movie Clip To Motivate Us

9. This Is NOT A Typical Unix System • Hollywood (and others) associate Unix with “smart” computer users • Unfortunately, Unix is not flashy • Nothing appealing about watching a command prompt • Navigating through a prompt would be much faster, but not nearly as exciting • Will knowledge of Unix help save you from rampaging dinosaurs?

10. History Of Unix • Unix has been around in one form or another since 1969 (probably before any of us were born) • Why is it important to know the history? • Why hasn’t it disappeared? • What has fueled its growth?

11. Today, Two Major Divisions Unix (1969) System V systems (1983) BSD systems (1978) Hurd HP-UX Mac OS X (Darwin) Linux IRIX FreeBSD Solaris

12. A Family Tree • Display

13. System V Versus BSD • If you know one, you can learn the other fairly quickly • Some programs have different flags and run in different ways • Some files are located in different areas • We will cover System V in this class (Linux in lab)

14. 1969 – The Origin of Unix • Multics – a timesharing operating system that grew too complex for its own good • Timesharing was novel, as batch processing was the accepted norm • Ken Thompson of Bell Labs • Bell Labs withdrew from Multics support, and Ken lost a system to play “Space Travel,” a game he wrote • He wrote the first version of UNIX (UNICS) on a PDP-7 • Soon joined by Dennis Ritchie

15. Computers of that age • No such thing as a video display • No keyboard as we know it • A teletype was used to communicate with the computer • Basically a glorified electronic typewriter

16. PDP-7

17. Unix features • From the very beginning, this was a programmer’s environment • Ability to code and test in one session • Interactive computing was stressed over batch processing • Batch processing involved coming up with a large volume of work that needed to be computed and feeding that work to the computer during your assigned time • Timesharing allows several programs to be run at once, although each takes a little more time

18. 1970’s • 1971-1973: In order to have this OS on other systems, Thompson and Ritchie create C and rewrite the OS in C • Unix use slowly spreads among academic circles • 1977: First BSD release (source code included!) • SCO created in 1978

19. The C Connection • From the early 1970’s, C and Unix have gone together • C was designed as a sort of “portable assembler” • Low level enough to do things fast • High level enough to be human readable • C remains the language of choice

20. 1980’s – The Unix Wars • 1983 – Networking gets added to BSD • Sun Microsystems gets founded • Early idea was to create a perfect Unix system with networking built in and sell it • Department of Justice breaks up AT&T • AT&T rushed to commercialize System V • Source code was no longer free • Error 2: Focus on the wrong market • Every version of Unix started competing with every other version, and Microsoft took over

21. 1985-93’s – FSF and Gnu • Once you give people something for free, they don’t want to have to pay for it • The Free Software Foundation (1985) • Gnu (Gnu’s not Unix) • Create free versions of popular tools (1986 – gcc, 1987 – most tools) • Overall goal was to develop a free kernel (It hadn’t happened by 1993) • Squabbling continued and Unix suffered

22. Linux • In 1991, Linus Torvalds announced the Linux project • A free Unix kernel for x86 systems • Used Gnu tools from the very beginning • By 1993, Linux had both internet capability and X capability • Just in time for the big internet boom

23. Linux’s Success • Internet culture and newsgroup postings caused a group of similar minded people to contribute and create a worthwhile kernel • A competing free attempt had problems • The free BSD attempt was mired in a lawsuit (3 files were copied illegally) • The Berkeley development group disbanded

24. Free Software Foundation • Founded by Richard Stallman • Wrote original version of gcc and gdb • Software should be free, because it should be free • As in “free speech, not free beer” • Wrote the General Public License (GPL) • You are free to do whatever you want as long as the source code goes with it no matter what • Controversy: Anything derived from a GPL’d work must itself be GPL’d

25. Open Source Movement • Software should be free just because – FSF viewpoint • Software should be free because free software is better – Open Source Movement viewpoint • Every problem can be eliminated if more people look at it

26. The Hacker Connection • The entire history of Unix has been co-mingled with the history of hackers • The hacker mentality continues to drive the use and progress of Unix • Groups of people create and maintain Linux and BSD systems for fun (and to better their resume)

27. Where Are We Today, And Where Are We Going? • The Single Unix Specification have been approved as an international standard • If a system wants to be called Unix, it has to conform to the guidelines in this standard • The open source movement continues to thrive and shows no slowing down • As anger and resentment for Microsoft continues (some unwarranted), people continue to look for a better alternative

28. History of Hacker Culture • People have been tinkering and building for a long time • Cars, radios, woodworking, etc. • Why wouldn’t people tinker around with computers and operating systems? • You need the source code in order to tinker with an operating system • Hacking Unix is fun

29. Important distinctions • Hacker • One who likes to build tools, programs, or systems for the fun of it • Enjoys stretching capabilities of systems rather than just doing the minimum necessary • Media’s use of the word: Evil man out to get you! • Cracker • One who breaks into systems with the express purpose of monetary gains or to cause trouble • Script kiddie: lowest form of cracker

30. Some Handy Web Sites • Jargon file • All the definitions necessary for understanding the hacker culture • Slashdot.org • The site where information “that matters” is posted • Freshmeat.net • New tools and projects postings

31. Hacker Mentality • Prefer an elegant solution to a kludge • Information sharing is a good goal • Not a necessary evil, but something to strive for • Some may exploit software to make the software better and not for personal gain

32. Mentality Of Unix • Unix was designed with the K.I.S.S. principle • Keep It Simple, Stupid! • Why do something repetitive when you can automate? • Write scripts and programs for simple or commonly used tasks • Don’t overly complicate matters

33. “Third System Effect” • First system: a simple prototype that is missing needed functionality • Second system: overly complex system that throws everything in • Multics was a second system • Collapses under its own weight • Third system: simple system with improved functionality

34. ?? = Unix Commands Analogy • Do one thing, but do it well • Hidden menu is like command line options • Still getting a burger, just different

35. Unix Versus Windows • Is Unix purposefully anti-GUI? • Not really… • Several window managers exist for X-windows • Basing an OS on a GUI makes it more complicated than it needs to be • Simple interfaces allow for different programs to easily communicate • Counterexample: How many different formats does Microsoft Word save as? How many of those can WordPad read correctly?

36. Common Differences Between Unix And Windows • Registry • Unix programs keep track of their own files • GUI • Built on top of Unix • Built in the middle of Windows (recently) • Command line • In Unix, the main interface with a program • In Windows, barely supported if at all

37. Multitasking/Multiuser (Multichoice) • Unix was always designed as a multiuser/multitasking system • More than one user can be logged on one machine at a time • More than one process can be running at one time (time sharing) • Many different ways exist to do things in Unix • Different graphical interfaces, different commands, etc.

38. For more information • Read chapter 1 in the book • Read “In the Beginning was the Command Line” by Neal Stephenson • joesacher.com/documents/commandline.php • Visit www.faqs.org/docs/artu/ • Don’t worry about most of the book, but look at the philosophy and history sections