Introduction To Unix- CS 21

Lecture 1

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

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

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

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

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!

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

A Quick Movie Clip To Motivate Us

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?

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?

Today, Two Major Divisions

Linux

Mac OS X (Darwin)

FreeBSD Solaris

Unix (1969)

System V systems (1983)

BSD systems (1978)

IRIX

Hurd HP-UX

A Family Tree Display

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)

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

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

PDP-7

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

“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

Analogy

Do one thing, but do it well Hidden menu is like command

line options Still getting a burger, just different

= Unix Commands

??

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?

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

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.

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