Copyright 2009, University of Alberta Introduction to Unix Produced by Jon Johansson Presented by...

Copyright 2009, University of Alberta

Introduction to UnixIntroduction to Unix

Produced by Jon Johansson

Presented by Waldemar Lysz

AICT

University of Alberta

May 4, 2009



Topics

• What is Unix?

• Your Unix environment

• The file system directory structure

• SSH connections

• Unix commands

• Compilers

UNIX is a registered trademark of The Open Group in the United States and other countries

LINUX is a trademark or a registered trademark of Linus Torvalds

UNIX Is an Operating System



Unix History: The People who brought us Unix

Douglas McIlroy

Ken Thompson Dennis Ritchie


Unix History

• 1969: Unix first written by AT&T employees

• Ken Thompson• Dennis Ritchie• Douglas McIlroy

• ~1985: development of the AT&T Unix splits into two main streams

• BSD (Berkley Source Dist.)• System V

• 1983: GNU project starts• 1991: Linux kernel

development begins

http://en.wikipedia.org/wiki/Image:Unix_history-simple.png

BSD System V Linux

ATT Unix

http://en.wikipedia.org/wiki/Image:Unix_history-simple.png


Linux Unix-like OS

Linus Torvalds


Unix-like GNU Project• Started by Richard Stallman in

1983• Develop a complete Unix-like

operating system composed entirely of free software

• Need lots of components:• a kernel → Linux• compilers• editors• text formatters• mail software• many other things …

Richard Stallman

GNU Logo


Unix You Can Try• IRIX

is the System V-based Unix Operating System with BSD extensions developed by Silicon Graphics (SGI)

nexus.westgrid.ca• AIX

(Advanced Interactive eXecutive) is an operating system developed by IBM based on UNIX System V

cortex.westgrid.ca• Linux

is a clone of the Unix operating system• Linux kernel has been written from scratch by Linus Torvalds and

others• GNU tools developed through the GNU Project

cluster.srv.ualberta.ca


Unix Components

You do not need to know anything about the kernel in order to use a UNIX system!

Copyright 2009 University of Alberta

Unix Components – Kernel

• The Kernel is the core of the UNIX system.• Loaded at system start up (boot)• memory-resident control program

• Manages the entire resources of the system, presenting them to you and every other user as a coherent system.

• Provides services to user applications such as device management, process scheduling, etc.



Unix Components – KernelExample functions performed by the kernel are:

• managing the machine's memory and allocating it to each process

• scheduling the work done by the CPU so that the work of each user is carried out as efficiently as is possible

• accomplishing the transfer of data from one part of the machine to another

• interpreting and executing instructions from the shell • enforcing file access permissions



Windows ShellA graphical user interface (GUI)

• allows a user to interact with the computer using a pointing device such as a mouse

• select words from drop down menus • select images such as icons on the display screen • icons represent commands for movement, activation or

some other action

aka the WIMP interface• Windows• Icons• Menus• Pointing Device


Browse directoriesBrowse directories

Edit filesEdit files

Command LineCommand Line


Unix Interface

• high performance Unix machines are generally accessed remotely

• connect through a command line


Unix Commands: Syntax• Usual command-line syntax is:

command• an executable to be run, you instruct what a system should do• the first word on the command line

option• this specifies how the command is run. Options are prefixed with a dash ” -

" character.

argument• what is to be affected, it could be a file, directory, stdin, stdout, user,

process, etc.

• Example format: command option(s) argument(s)

ls –al /home/wdl


Unix Commands: man pages• get help with commands through the man pages,

(man commands), for example:

• you might like to read:

• In Unix case matters!• For Example: LS is not equal to ls

$ man ps

$ man ls

$ man intro


Unix Commands: man pages

While viewing a man page you have few commands:

Spacebar move one screen further

Enter move one line further

b moves one screen back

/pattern searches forward for "pattern"

?pattern searches backward for "pattern"

n the next occurrence of the

"pattern"

q quits the man(1) command

h prints a help screen;


Unix Commands• Example of command options and output (most commands have many options, see the man pages for details).• The ls command with options to list all files in long format:$ ls -la

• file names starting in dot are normally hidden • permissions are: Read, Write, eXecute • columns are owner, group, and all


Unix Components – Shell• Whenever you login to a Unix system you are placed

in a shell program.• the shell's prompt is usually visible at the cursor's position on your

screen.• to get your work done, you enter commands at this prompt.

• The shell is a command interpreter.• it takes each command and passes it to the operating system

kernel to be acted upon.• it then displays the results of this operation on your screen.

• Several shells are usually available on any UNIX system, each with its own strengths and weaknesses.


Unix Components – Shell• Different users may use different shells.

• the system is set up with a default shell, which can be overridden or changed

• The most commonly available shells are: • Bourne shell (sh) • C shell (csh) • Korn shell (ksh) • TC Shell (tcsh) • Bourne Again Shell (bash)

• Each shell also includes its own programming language• command files, called "shell scripts" are used to accomplish a series of

tasks


Bourne Shell (sh)• This is the original Unix shell written by Steve Bourne

of Bell Labs. • /bin/sh, /sbin/sh• It is available on all UNIX systems.• This shell does not have the interactive facilities provided by

modern shells such as the C shell and Korn shell.

• The Bourne shell provides an easy to use language with which you can write shell scripts.


Bourne Again SHell (bash)• a public domain shell written by the Free Software

Foundation under their GNU initiative. • fairly standard default shell on Linux distributions• bash provides all the interactive features of the C

shell (csh) and the Korn shell (ksh)• bash’s programming language is compatible with the

Bourne shell (sh)• bash is one of the more popular shell choices


Agenda

• What is Unix?



• SSH connections

• Unix commands

• Compilers




Environment• Your working environment is defined whenever you

login or start another shell. • This environment is set using the values that the shell finds

in the initialization files (which it always reads as it starts up).• You can change your working environment by editing these

initialization files and setting new values for the various variables.

• Each shell handles its initialization files in a different way


Environment• Your working environment is defined whenever you login

or start another shell. • To see the list of environment variables being used:

printenv

• You can print the value of a particular environment variable with the “echo” command:

echo $SHELL

• You set an environment variable like this:

$ jon@um01:~>MY_NAME="Jon"

$ jon@um01:~>echo $MY_NAME

$ Jon


Unix Components – Utilities• UNIX provides several hundred utility programs, often

referred to as commands. • You can accomplish universal functions, such as:

• editing • file maintenance • printing • sorting • programming support • online info • etc.

• And they are modular, i.e., single functions can be grouped to perform more complex tasks.


Exercise 1:

Logging in and getting some basic information about the system.


Agenda

• What is Unix?



• SSH connections

• Unix commands

• Compilers




The Unix File System

• A file system is a logical method for organizing and storing large amounts of information in a way which makes it easy to manage.

• The file is the smallest unit in which information is stored.


The Unix File System/ Root directory of the file system./bin User utilities fundamental to both single-user and multi-

user environments./sbin System programs and administration utilities

fundamental to both single-user and multi-user environments./boot Programs and configuration files used during operating

system startup/dev Device nodes; see intro(4)./etc System configuration files and scripts./tmp Temporary files. The contents of /tmp are usually NOT

preserved across a system reboot. /usr The majority of user utilities and applications./var Multi-purpose log, temporary, transient, and spool files. /home User home directories on many Linux systems/root Home directory for the root account



• the file system resembles an inverted tree• the tree is anchored in the root directory

• designated with a ‘/’



• every item in the unix file system tree is either a directory or a file• a directory is like a file folder

• a directory can contain files, and other directories• a directory contained within another is called the child of the other



• different unix distributions put user home directories in different places

• you are placed in your home directory when you log in• the directory that you are in now is called the “current working

directory”• check the path with ‘pwd’ (print working directory)



• the location of an object in the file system is described by a “path”

• the “absolute path” includes all the directories starting from “/”• the “relative path” includes only subdirectories of the current

working directory



Slash / means the root directory

Tilde ~ means your home directory

Dot . means right here, current directory

Dot Dot .. means up one level


File System Commands

ls list directory contents

cd change the current working directory

pwd print the name of the current/working directory


Unix Commands

grep get regular expressionFinds word in a stream of text

| pipe text from one command to the next. This symbol is normally a shifted “\” key


Exercise 2:Understanding the structure of the file

system and obtaining information about it.


Agenda

• What is Unix?



• SSH

• Unix commands

• Compilers




SSH- Connecting To Unix Host• Secure Shell (ssh) is a set of programs to:

• log into another computer over a network, • to execute commands in a remote machine, • and to move files from one machine to another.

• It provides strong authentication and secure communications over un-secure channels. • It is intended as a replacement for telnet, rlogin, rsh, and rcp. • For SSH2, there is a replacement for FTP: sftp.


SSH• Secure Shell also provides secure X connections and

secure forwarding of arbitrary TCP connections. • ssh connects and logs into the specified hostname • the user must prove his/her identity to the remote

machine using one of several methods• see the man page for details• we only use the password


SSH - How it Works• ssh works by the exchange and verification of

information, using public and private keys, to identify hosts and users• we will only be concerned with a password exchange• after you've authenticated (successfully logged in)

communications are encrypted


SSH daemon• sshd is the daemon that listens for connections from

clients• it forks a new daemon for each incoming connection• the forked daemons handle key exchange,

encryption, authentication, command execution, and data exchange.


SSH

In order to connect to a remote machine you must:

1. run the ssh client on your desktop machine

2. the client connects to the sshd server running on the remote machine

3. the client and server establish a connection and run through a protocol which attempts to establish that you have the right to make a connection

4. enter your password


How to run SSH• To login to a remote host:

ssh <hostname>

• To login to a remote host with a different username:ssh -l <username> <hostname>

• To login to a remote host and send a command:ssh <hostname> <command>

• To login to a remote host and forward X11:ssh +x <hostname>


SSH – scp Unix Data Mover• Secure Copy, scp, is used in copying files over the

network securely• It uses ssh for data transfer, and uses the same

authentication and provides the same security as ssh• How to run scp:

scp <source> <destination>• where the source and destination can be paths in the

local file system or have the formuser@host:/dir/for/file


SSH – scp to use scp to copy a file to a remote system:

scp localdir/to/filelocation user@host:/dir/for/file

to use scp to copy a remote file to the local system:scp user@host:/dir/for/file localdir/to/filelocation

to keep the file attributes of the source file from the source host, use -p:scp -p user@host:/dir/for/file localdir/to/filelocation

scp test [email protected]:/home/dsk05/cshome/jon

scp [email protected]:/scratch_large/jonj/ibm/test .


SSH – More Info

• Tutorials• http://csociety.ecn.purdue.edu/~sigos/projects/ssh• http://kimmo.suominen.com/docs/ssh/

• FAQ:• http://www.employees.org/~satch/ssh/faq

http://csociety.ecn.purdue.edu/~sigos/projects/ssh

http://kimmo.suominen.com/docs/ssh/

http://www.employees.org/~satch/ssh/faq


Exercise 3:1. Connect to remote sites

2. Moving data between machines• use one of other lab machines or:

• cluster.srv.ualberta.ca• nexus.westgrid.ca• cortex.westgrid.ca


Agenda

• What is Unix?



• SSH

• Unix commands

• Compilers




Unix Commands: man pages• get help with commands through the man pages,

(man commands), for example:

• you might like to read:

• In Unix case matters!• For Example: LS is not equal to ls

$ man ps

$ man ls

$ man intro


Unix Commands: more/less• The commands more and less are “pagers”

• They display text on the screen one page at a time• more <filename>

• press the space-bar to display the next page• press the enter-key to display the next line• press the q to exit the program • this is how man pages are displayed

• less is like more, but is more flexible• it allows the up and down arrow keys to be used to scroll

around a document


Unix Commands: Text Editors• a text editor is a program which enables you to create and

manipulate character data (text) in a computer file• a text editor is not a word processor although some text editors

do include word processing facilities• text editors often require "memorizing" commands in order to

perform editing tasks• the more you use them, the easier it becomes• there is a "learning curve" in most cases


Unix Commands: Text Editors

There are several text editors available by default on most UNIX systems:

ed standard line editor ex extended line editor vi visual editor; full screen;

• uses ed/ex line-mode commands for global file editing a favourite of system administrators

sed stream editor for batch processing of files

In addition other editors may be available: emacs a full screen editor and much more

a favourite of programmers

pico an easy "beginner's" editorand countless others….


Unix Commands: Text Editors• nedit – the Nirvana editor

• initially developed by Mark Edel for Fermilab • it is now distributed under the GNU General Public License

nedit has an interface similar to text editors on Microsoft Windows and Macintosh!


Unix Commands: File Manipulation

cp copy files and directoriesgrep print lines from the input stream matching a

patternrm remove files or directoriesumask set initial file permissions on a newly-created

filechown changes the user and/or group ownership of

each given filechgrp changes the group ownership of each given file


Directory Manipulationcd change the current working directory

pwd print working directory

ls list directory contents

mkdir creates directories with the specified names

rmdir removes empty directories• To remove a nonempty directory, together with everything

below, use “rm -r foo”


Unix Commands: tar“Tape Archive” program: tar• Save a bunch of files into a single archive

• historically this archive was on tape, now it’s frequently just a regular file

• To generate a tar file:• tar -cvf filename.tar list-of-files

• this puts the files into tar format and stores them in filename.tar

• To extract files from a tarfile:• tar -xvf filename.tar


Unix Commands: tar• Some of the options for tar are:

c create a new tarfile

v verbose, print out the file names as they are archived

f use the next argument as the archive file

t list the files

x extract files from an archive

(Remember to use a “-” for options)


Unix Commands: Processes ps process status

top monitor system activity

kill end a process

^z suspend

bg run the suspended job in the background

who show who is logged on

su substitute user


Exiting the system

logout exit a login shell• a login shell is the shell you get when you're

prompted with your username and you have to enter your password

exit exit the shell• a non-login shell is a shell that is started

after we login• we typically use these to work in, for

example bash, sh, csh , ksh, or another shell


Exercise 4Practice a couple of useful commands:

1. tar (tape archive)

2. compression


Agenda

• What is Unix?



• SSH

• Unix commands

• Compilers




Compilers

There are a variety of compilers available for different systems

• gnu compiler is available for many systems• GCC stands for “GNU Compiler Collection”. • GCC is an integrated distribution of compilers for several

major programming languages. • currently includes C, C++, Objective-C, Objective-C++,

Java, Fortran, and Ada


Compilers• Common compiler flags:

-o specify executable name

-O2 optimization level

-g debugging


Compilers• The makers of large machines generally provide

compilers and libraries designed to provide executables which make the best use of the hardware

• Try to use the manufacturer’s compilers on a system for best performance


Compiler Names

Language Cortex Nexus Glacier

Fortran IBM XL 10.1 (xlf_r, xlf90_r, xlf95_r, f77)

MIPSpro Compilers Version 7.4 (f77, f90) GNU 3.2.2 (g77)

Portland Group 6.0-5 (pgf77, pgf90) Intel 8.0 (ifort) Absoft 8.2 (f90) GNU 3.2.2 (g77)

C IBM XL C 8.0 (xlc, cc, c89, c99) GNU 3.3.2 (gcc)

MIPSpro Compilers Version 7.4 (cc, c89, c99) GNU 3.2.2 (gcc)

Portland Group 6.0-5 (pgc, pgcc) Intel 8.0 (icc) GNU 3.2.2 (cc, gcc)

C++ IBM XL C/C++ 8.0 (xlC) GNU 3.3.2 (g++)

MIPSpro Compilers Version 7.4 (CC) GNU 3.2.2 (g++)

Portland Group 6.0-5 (pgCC) Intel 8.0 (icc) GNU 3.2.2 (g++)


Compiling• The one step compile and link:

→ a.out

• the program doesn’t depend on libraries that the linker can’t find

• get an executable named “a.out”• no matter what the name of the source file is

• Run the executable with the command:

$ gcc prog.c

$ ./a.out


f77 prog.f

prog.fcompile

prog.o

linka.out

libraries

Creating an executable is really a two-step process:1. Generate an “object” file (extension “.o”)

→ prog.o

2. Link the object to any library dependencies to get the executable

→ prog

Compilers

$gcc –c –o prog.o prog.c

$gcc –o prog prog.o


Exercise 5:

• Edit files

• Compile

• Move files between machines


Exercise 6:

• monitor and kill processes


Unix – More Info on Line

• Tutorials• http://library.thinkquest.org/05aug/00669/en/history/software/u

nix.html• http://www.ee.surrey.ac.uk/Teaching/Unix/unixintro.html• http://www.unixtutorial.org/

• FAQ:• http://www.faqs.org/faqs/unix-faq• http://www.unixguide.net/unix/programming/

http://library.thinkquest.org/05aug/00669/en/history/software/unix.html

http://library.thinkquest.org/05aug/00669/en/history/software/unix.html

http://www.ee.surrey.ac.uk/Teaching/Unix/unixintro.html



http://www.faqs.org/faqs/unix-faq



More Info on Line


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