Introduction to Linux

1. Introduction to Linux Julien Thibault Julien.thibault@utah.edu

2. 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

3. 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

4. What a Linux distribution can look like today…

5. 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@host The -Y option is used to enable GUIs (it can be slow!!)

6. 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 cmdcmd command manual

7. 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

8. VI text editor Try out Emacs if you cant stand VI… http://www.cs.colostate.edu/helpdocs/emacs.html

9. 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

10. 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?

11. Administration

12. 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

13. 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=$HOME/programs export PATH=$PATH:$EXEC/bin/ • source apply changes to bash script for interactive shell • echo var display value of environment variable

14. Useful commands • which returns 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

15. 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.

16. 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

17. 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.