Introduction to Linux

Julien ThibaultJulien.thibault@utah.edu

A little bit of History

1969 - Bells Labs develop a new operating system called “UNIX” Written in C instead of assembly code Able to recycle code Improved compatibility between systems

Beginning of the 90’s PC becomes popular UNIX too slow for these machines and not free People switch to Windows 3.1 or MS-DOS

1991 – Linus Torvalds (University of Helsinki) starts working on the “Linux” project Free OS Compliant with the original UNIX

Today – why do you care? De-facto OS for high-performance computing (clusters) More and more popular in federal agencies and large

companies

Linus Torvalds

Linux distributions

Pros Free and open source Large community Secure, almost no virus (compared to Windows) Scalable: from palm to cluster with more 100 nodes

Cons Not as user-friendly as Windows or Mac but getting there Many distributions available: Ubuntu, RedHat, Fedora, SUSE,

Mandriva, Debian… See:

http://futurist.se/gldt/wp-content/uploads/11.04/gldt1104.png

What a Linux distribution can look like today…

Connecting to CHPC

Host: sanddunearch.chpc.utah.edu

Login: uNID Password:uNID password

Using PuTTY (Windows): Just enter the host name

Using ssh (Mac or Linux):ssh [-Y] login@hostThe -Y option is used to enable GUIs (it can be slow!!)

Basic commands to survive cd change current directory ls [-la] list files pwd show path to current directory mkdir create new directory mv move file/dir to new location cp [-r] copy file (use -r for directory)

scp [-r] secured copy over the network ssh secured remote login

man cmd cmd command manual

Exercise 1

Create the directory ~/workshops/linux/test in your home directory

Copy the test directory to ~/workshops/linux/test2

Move test2 to your home directory and rename it testlinux

VI text editor

Try out Emacs if you cant stand VI…

http://www.cs.colostate.edu/helpdocs/emacs.html

VI basic commands

Insertion mode: i Command mode: ESC

dd delete current line (and copy) yy copy current line p paste before cursor u undo

/string or ?string search string after or before cursor n or N go to next or previous match

:s/pattern/string/g replace pattern by new string

:w Save changes :q Exit :q! Exit and ignore any changes

More commands at: http://www.lagmonster.org/docs/vi.html

Exercise 2

Create a new text document, insert “Hello world” and save it as helloworld.txt

Download Moby Dick from http://www.gutenberg.org/ebooks/2701.txt.utf8 and rename it mobydick.txt

Delete everything that is before chapter 1

What is the title of chapter 107?

What is the last line?

Move the first paragraph (chapter 1) to be after the second one

How many times does the word ‘France’ appear in the text?

Administration

Using Linux in command-line Permissions

Root (super user)▪ Can control machine configuration and programs for all the

user ls -l will display the permissions for a file/dir

Interactive shell configuration aliases (e.g. “ll” instead of “ls -l”) environment variables

▪ $PATH: path to the executables▪ $HOME: point to your home directory

bash / C shell▪ 2 different scripting methods▪ .bashrc , .bash_profile , .profile / .tcshrc

Configuration scripts

Inside the configuration script: setenv / export Set environment variable alias Create alias

C shell script example (CHPC)

alias ll “ls -l”setenv EXEC “$HOME/programs”setenv PATH $EXEC/bin/:$PATH

Bash script example

alias ll=“ls -l”export EXEC=$HOME/programsexport PATH=$PATH:$EXEC/bin/

source apply changes to bash script for interactive shell echo var display value of environment variable

Useful commands

whichreturns the path to the command executable ps [aux] list of active processes top list of top active processes (updated ) find find a file or directory grep find a phrase in text cat display content of a file tail [–n] display the last lines of a file

su switch to superuser. Need root privileges

chmod change permissions on a file/dir chown change owner of a file/dir

wget download file from URL

Exercise 3

Find the location of the Matlab install at CHPC

Create an environment variable called $MATLAB_HOME that points to the install of Matlab version R2006 and add it to your PATH so it becomes the default version

Create an alias to display the version of java

Create a script called hello.sh that says “hello world” when you run it.

Managing jobs

Ctrl-C Cancel job Ctrl-Z Stop job

cmd & execute cmd in the background bg move job to background fg move job to foreground jobs list current jobs

Exercise 4

$ sleep 100 — Start a dummy job in foreground.   (sleep = waits a x amount of second)Press Ctrl+z to stop the current job.

$ bg — Move the last stopped job to background.

$ sleep 150 — Dummy job 1Press Ctrl+z to stop the current job.

$ sleep 140 — Dummy job 2Press Ctrl+z to stop the current job.

$ sleep 130 — Dummy job 3Press Ctrl+z to stop the current job.

$ jobs — List all active jobs.

$ bg 2 — Move the 2nd active job to background.