Introduction to Linux

1. Introduction to Linux ITS Research Computing University of North Carolina at Chapel Hill Instructors: Mark Reed, C.D. PoonEmails: markreed@unc.edu, cdpoon@unc.edu

2. Course Design and Logistics • Course Design: • Lecture – background & intro to commands (~30 min) • Short Lab (~15 min) • Lecture – commands in detail (~40 min) • Final Lab (~35 min) • Lab is an integral part of course. • Please play along • learn by doing! • Please ask questions • Restrooms • Breaks

3. Overview • Objectives • Operating Systems • History • Variations • User Interface • Commands • Conclusion

4. Objectives • What this course is: • An introduction to Linux hopefully to put it into a context for better understanding • Gain the perspective to see what it is, what it can do, why use it • What this course isn’t: • Just a list of Linux commands and what they do (although there will be plenty of that :) • Not just to answer “How do I … ?”

5. What is an OS (Operating System)? • The most important program that runs on a computer • Operating systems perform basic tasks : • recognizing input from keyboard and mouse • sending output to display screen • keeping track of files and directories on the disk • controlling peripheral devices such as disk drives and printers • networking, security, memory management, ....... http://www.webopedia.com/TERM/o/operating_system.htm

6. Examples of OS’s • DOS, MS-DOS • MS Windows (95, 98, NT, XP, Vista) • Linux (RedHat, SuSE, Ubuntu, ...) • Unix (Irix, Solaris, AIX, ...) • MacOS, MacOS X/Darwin

7. History of Unix/Linux • 1969 – First Unix was developed at AT&T Bell Labs by Ken Thompson and Dennis Ritchie. • 1977 - First BSD was released, spurred in part by sabbatical at UC-Berkeley by Thompson. Ken (seated) and Dennis (standing) at a PDP-11 in 1972.

8. History of Unix/Linux • 1991 - Linux was introduced by Linus Torvalds, a student in Finland, who posted to the comp.os.minix newsgroup with the words. • Hello everybody out there using minix - I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. … • 1993 – FreeBSD project was coordinated by Nate Williams, Rod Grimes, and Jordan Hubbard for running on 386 machines. Linus Torvalds at LinuxWorld 1999

9. History of Unix/Linux Cont’d • The GNU (Gnu’s Not Unix) was an effort to develop free and open source applications. • Torvalds combined his kernel with GNU software from Richard Stallman (of emacs fame) and the Free Software Foundation and Linux was off and running. • Linux grows with contributions world-wide. Richard Stallman

10. Linux Overview • Linux Features: • Multi-tasking • many programs running • Multi-user • many users on the same machine at once • Multi-platform • runs on many different processor types

11. Variations on a Theme • Two major branches of Unix • AT&T System V • BSD (Berkeley Software Distribution) • Lots of commercial Unix-like systems • AIX (IBM), IRIX (SGI), HP-UX (HP), OpenSolaris (Sun), MacOS X, … • Linux is a Unix-like system free of proprietary software for which source code is available and freely distributed. • There are minor variations among these. • much more alike than they are different

12. Linux Distributions • There are many groups packaging Linux for distribution. • some freely available • others commercial • A partial listing (in no particular order): • Red Hat • CentOS • Ubuntu • Debian • SuSE • Fedora • and on and on … :)

13. User Interface • The user interacts with the OS by giving it commands. This interface is either via • command line (e.g. through the shell) • graphical user interface (GUI) • Don’t confuse the user interface to the OS w/ the OS itself (which does much more). • Most OS’s can do both, e.g. Linux typically uses the command line but Konqueror is a GUI for Linux (web browser, file manager, document viewer).

14. Shell • The Command Line Interface (CLI) for Linux is through the shell. • This is the application (program) that interprets what you type and carries out your directions. • Common Shells: • tcsh – exTended C SHell • bash – Bourne Again SHell • ksh – Korn SHell • csh – C SHell (early popular shell) • sh – the original shell, often a synonym for bash now

15. OS as an Onion Heart of the OS • OS Modularization: • the kernel • an interpreter • and utilities The User Interface to the OS The Stuff you want the system to do

16. Linux Commands • Man pages • Working with files and directories • pwd, cd, ls, mkdir, rmdir, cp, mv, rm, scp, cat, more, less • Wildcards • *, ?, [] • Permissions • chmod, chown, chgrp • Finding stuff • find, which, whereis, locate

17. Linux Commands Cont'd • Packing and Unpacking stuff • tar, gzip, compress, gunzip, unzip, sort • Pipes and redirection • >, >>, <, | • Jobs and processes • ps, kill, pkill, ctrl-C, bg, ctrl-Z, &, fg, jobs • Quick and Easy: shortcuts and tricks of the trade • history, file completion, alias, environment variables

18. Some Caveats • There’s always more than one way to do things under Linux. • These commands just cover some of the basics and the more useful options. • the proverbial tip of the iceberg!! (not to worry, you’re not the Titanic :) • The man pages are your friend. • Lean on them!!

19. File System - Directory Structure

20. Some fun unix-y quotes • linux: the choice of a GNU generation • "Unix is user-friendly. It's just very selective about who its friends are." • "The box said 'Required Windows 95 or better'. So, I installed LINUX." • “If you have any trouble sounding condescending, find a Unix user to show you how it's done.” - Scott Adams

21. Some fun unix-y quotes "The university computer system was better than no computer at all. But Randy was humiliated. Like every other high-powered academic computing network, this one was based on an industrial-strength operating system called UNIX, which had a learning curve like the Matterhorn, and lacked the cuddly and stylish features of the personal computers then coming into vogue.” - Cryptonomicon by Neal Stephenson

22. Commands in General(and a General Giving Commands :) • Commands are case sensitive. • Arguments typically are given with a dash “-”. • multiple arguments usually only require the leading dash • Commands are programs or applications that the user invokes. • The system finds the command by • specifying the full path • shell built in commands • looking in all directories in your PATH, typically this includes /bin, /usr/bin, … (but maybe not “.”) Eisenhower on D-Day

23. man – Manual • man <command> • man formats and prints the online manual pages • -k keyword search • do keyword search for applicable man pages (same as the apropos command) in the whatis database • Note on the man pages that arguments that appear in square brackets […]are optional • Use these early and often

24. more man • Options at the prompt: (the “more” command options) • h - help • spacebar – scroll forward one screen • <CR> - scroll forward 1 line (can change this to be whatever number of lines you wish) • b – back, go back a screen (does not work w/ all mores) • q – quit • /<regexp> - search for regular expression • To find out lots and lots about the shell: • man tcsh • man bash • man ksh • Browse them for what you need, no need to read them cover to cover (unless you want to feed your inner geek :)

25. Working with Files and Directories

26. pwd – Print Working Directory • “pwd” displays the full absolute path to your current location in the filesystem. • Absolute paths (/…) • Relative paths (../work/…, bin/…) • “.” dot always refers to your current directory • “..” dot-dot always refers to your parent directory (i.e. the one “above” you in the directory hieararchy) • emerald% pwd/afs/isis.unc.edu/home/c/d/cdpoonemerald%

27. cd – Change Directory • cd <path> • Changes your current working directory to path (which can either an absolute or relative path). • a common relative paths to use is '..' (i.e. the parent directory of the current dir) • cd • by itself changes to your home directory • cd – • returns to previous directory • cd ~/projectA/run • ~ is a shortcut for your home directory

28. cd Example emerald% pwd/afs/isis.unc.edu/home/c/d/cdpoonemerald% cd /etcemerald% pwd/etcemerald% cdemerald% pwd/afs/isis.unc.edu/home/c/d/cdpoonemerald% cd - emerald% pwd /etc emerald% cd .. emerald% pwd / emerald%

29. ls – List • ls - lists the contents of a directory. • If no target is given, then the contents of the current working directory are displayed. • By default “ls” doesn't show you all the entries in a directory - files and directories that begin with a dot (.) are hidden (including '.' and '..' which are always present). • The reason for this is that files that begin with a “.” usually contain important configuration information and should not be changed under normal circumstances.

30. ls – Useful Options • ls –a, show all files (or –A, exclude ., ..) • ls –l, long listing • shows properties such as the size, type and ownership of files • ls –t, sort by time • ls –d, list directory name, not contents • ls –h, human readable file sizes • ls –F, classify, appends symbol indicating type • these can be combined, “ls -a –l -h”  (or, equivalently) “ls -alh “ 

31. ls -al ls -al (list directory with hidden files/directories in long listing) The command, ls -al, lists the contents of a directory including the hidden file/directory names starting with "." in a long listing.emerald% ls -altotal 1096drwxr-xr-x   27 root root   4096 2008-03-24 14:30 ./drwxr-xr-x   27 root root   4096 2008-03-24 14:30 ../drwxr-xr-x    2 root root   2048 2003-05-05 14:04 afs/-rw-r--r--    1 root root      0 2008-03-24 14:30 .autofsck...emerald%

32. ls –l - List Content in Long Form The command, ls -l, lists the contents of a directory in long listing.

33. mkdir - Make Directory • mkdir <New_Directory> • Creates a subdirectory called New_Directory in the current working directory. You can only create subdirectories in a directory for which you have write permission. • -p option • creates parent directories as needed, e.g. mkdir –p myprojects/projA/example2/test

34. mkdir Example The command, mkdir, makes directories.emerald% cdemerald% pwd/afs/isis.unc.edu/home/c/d/cdpoonemerald% alias ls ls -F emerald% lsDesktop/   intel/  nsmail/    private/  public_html/dumpster/  ms@     OldFiles/  public/   temp/emerald% mkdir new_diremerald% lsDesktop/   intel/  new_dir/  OldFiles/  public/       temp/dumpster/  ms@     nsmail/   private/   public_html/emerald%

35. rmdir/rm -r – Remove Directory • rmdir <uselessDirectory> • removes the subdirectory directory from the current working directory. You can only remove subdirectories if they are completely empty (i.e. of all entries besides the '.' and '..' directories). • Use “rm –r” to remove directories and contents in one step

36. Lab Exercises • Please try out all or some of the exercises that follow to get your feet wet. Then try the “Treasure Hunt” which we hope you’ll enjoy! • Accounts: Use any Linux machine you have access to, such as emerald.unc.edu OR • Use the VCL! There is an image for classroom use in the Virtual Computing Lab with data files already installed • go to vcl.unc.edu • click “New Reservation” on the menu on the left • select “RC Class Image” from the drop down menu • select “Now” for the time and “2 hours” for Duration • click “Create Reservation” • use the password and IP address to ssh to the machine.

37. Remote Login (Linux to Linux) • A secure shell is a program for logging into a remote machine providing encrypted communications between the machines: ssh [options] machine • options: • -l login name (or use ssh login@machine) • -Xsets environment variables for porting X-display, • -Y similar to -X, required for some programs. • Example: ssh emerald.isis.unc.edu –l cdpoon or ssh cdpoon@emerald.isis.unc.edu ssh emerald –X –l cdpoon

38. Connecting to a Linux system(e.g. Emerald) from This Lab • Using ssh, login to Emerald, full name is emerald.isis.unc.edu. To start ssh: • Start->Programs->Remote Services ->SecureCRT 5.<x> • Click the Quick Connect icon at the top. • Hostname: emerald.isis.unc.edu • Login with your ONYEN and password

39. Exercise 1 • Start up a terminal application (SecureCRT, F-Secure SSH Client, etc.) . • Log on a Linux machine (Emerald, Topsail, etc.) with your ONYEN and password. • 3. Enter the commands on the right at the prompt, hit "enter", and try to interpret the output. • Ask questions. • echo hello world • date • hostname • whoami • who am i • who • clear • history • cal 2008 • pwd • echo $SHELL

40. Exercise 2 • Enter the commands in sequence on the right at the prompt, hit "enter", and try to interpret the output. • Encounter error, check out why. cdpwdcd /etcpwdcd /ls -alls -l cdmkdir temp_dircd temp_dirmkdir temp_subdircdls -lls -l temp*rmdir temp_dirrm -r temp_dir

41. Wildcards

42. Wildcards • Multiple filenames can be specified using special pattern-matching characters. The rules are: • '?' matches any single character in that position in the filename • '*' matches zero or more characters in the filename. • ‘[…]’ Characters enclosed in square brackets match any name that has one of those characters in that position • Note that the UNIX shell performs these expansions before the command is executed.

43. Wildcard Examples Given: climate.01.2000.dat climate.06.2000.dat climate.07.2000.dat climate.12.2000.dat climate.02.2000.dat climate.06.2001.dat climate.08.2000.dat climate.total.dat climate.03.2000.dat climate.06.2002.dat climate.09.2000.dat Climate.txt climate.04.2000.dat climate.06.2003.dat climate.10.2000.dat seasonal.2000.dat climate.05.2000.dat climate.06.2004.dat climate.11.2000.dat seasonal.2001.dat • climate.0[6-8].*.dat • get only months Jun-Aug (ie. 6-8) for all years • clim*2001* • get only climate files for year 2001 • *.??.* • only files that have 2 characters between dots

44. cp - Copy • cp <source-file(s)> <destination> • “cp” copy files or entire directories    • <source-file(s)> and <destination> specify the source and destination of the copy respectively. • To copy entire directories (including their contents), use a recursive copy: • cp -r source-directories destination-directory • This copies all files in all subdirectories below source.

45. mv – Move/Rename • mv <source> <destination> • “mv” is used to rename files/directories and/or move them from one directory into another. • By default the destination will be silently overwritten by source. • -i option for interactive • this will prompt you before overwriting a file

46. rm - Remove • rm <target-file(s)> • Removes specified files. Works as advertised, it really removes the file, there isno backupfile orundeleteoption. • -i for interactive • use this to be prompted before deletion • -r for recursive • removes directories, subdirectories and their contents (files). • -f for force • removes w/o prompting 

47. scp – Secure Copy • “scp” is commonly used to copy files between any 2 hosts on a network using the ssh protocol. • commonly used to securely upload/download your files from your home machine to desired machine • Format: • scp [options] <host:file1> <host:file2> • form of host may be login@host (default login is your current login) • the “host:” is omitted if the target machine is the one you are on • file path is relative to your home directory • Options: • -r recursive (used for directories)

48. cat – Concatenate • cat <target-file(s)> • displays the contents of target-file(s) to standard out (typically your screen) one after the other • useful for combining files together • more and less are better to just display file content

49. more and less • more <target-file(s)> • “more” displays the contents of target-file(s)  on the screen, pausing at the end of each screenful and asking the user to press a key (useful for long files). • “less” is just like more, except that has a few extra features (such as allowing users to scroll backwards and forwards through the displayed file). • not a standard utility, therefore may not be present on all UNIX systems

50. More of more and less • Options at the prompt: • h - help • spacebar – scroll forward one screen • <CR> - scroll forward 1 line (can change this to be whatever number of lines you wish) • b – back, go back a screen (does not work w/ all mores) • q – quit • /<regexp> - search for regular expression