Review

1. Review • Did you get an email from me? • Last class we had an introduction to Linux and the command-line • Linux: Kernel vs OS • It is a kernel (brain of an OS) • It’s a reference to OS’ that use Linux kernel • ‘Logical leap’ of command-line • Today we are going to review all these and learn basic commands

2. Today • The shell • 3 File Channels • Files • Directories • Moving around • Looking around

3. A Quick Note • Plagiarism is highly frowned upon, even more so in the Open Source world (which Linux is a huge part of) • If I can take any four words in a row and match them to an article, you have plagiarized • Don’t just copy wikipedia or a manpage • Rewrite it in your own words • You’ll get a 0 for that assignment and have to take plagiarism training

4. First – Please Log In • Ensure VM’s are on your systems: • C:\Users\Public\Documents\Shared Virtual Machines • If not, we have to add them from • \\srv12\FileShare\Instructor Images\Nathaniel Dillon

5. VM’s Are Now Available • While it copies, we’re going to go on, however once it’s complete: • Open VMWare • Double-click VMWare icon on desktop • VMWare will open, so click ‘Open a Virtual Machine’ • Scroll to your VM’s folder, click our vm file • Click this, click okay, then, the green arrow starts it up

6. Linux – What is it? • Like Windows, but better • It’s what you see when you boot the computer and are ready to tell it to do stuff (can be GUI, can be command line) • The kernel is like the brain of what you see when you boot up – it tells everything else how to behave (Windows has a kernel too) • The “bodies” (flavors) are as diverse as people – RedHat (CentOS) is for business, Ubuntu is the “popular” one, Slackware is the jerk I don’t like • Like using Mozilla web browser vs Opera vs Chrome vs IE

7. Why is it Good? • Linux allows the admins more power and more control over everything • Commands came first – the GUI maps to the command • Windows is the opposite • Linux is free • You can modify it and see what it's doing – all source code is out there • A bunch of really smart people add to it

8. Equivalencies • Linux has everything Windows has (almost) • What it doesn't have – .NET (Eclipse?) • What it does have – everything else • Word processor – Open Office looks exactly like MS Office; Libre is getting more popular • Mail – Evolution; Media Players – Brasero, VLC • Photoshop – GIMP; Eclipse – Eclipse • Backups - tar/gzip/bz2 • What is does better – Security Tools – Backtraq (metasploit, sniffers, aircrack, etc...) - Cloud – Hadoop, OpenStack – Monitoring/Automation

9. Directory Structure • In a ‘hierarchical’ file structure, you care about two things: • 1) Where you want to go • 2) Where you are right now • You can get these things two ways: • 1) Starting at the root or ‘top-level’ directory • 2) Moving up levels from where you are • In the next slide, there is no direct connection between C:\Windows and E:\Jack • You have to go back up to My Computer

10. Directory Structure Windows

11. Directory Structure • Linux is also a ‘tree’ or ‘hierarchical’ directory structure • http://www.linux4windows.com/Articles/linux_directory_structure.png

12. First Login • When you log in, you will be taken to the home directory of the user you logged in as • Windows Vista/7/8 has this at C:\Users\<username> • Linux is /home/<username> • We use the student user • /home/student • Any other user: /home/anyotheruser • Previous slide had: /home/tom • This is a ‘path’ or a ‘file path’

13. First Login, pt 2 • The only thing displayed will be this funky thing: • [student@it136centos65vm ~]$ • That is our shell • The shell (command prompt/command line) is how we will interact with the system • This is the default look for the BASH shell • Tells us our current username (student) • Hostname (it136centos65vm) • Directory (~) • And we can type in commands after the $

14. A note on commands • We will be talking about many different commands • We looked at the command prompt • [student@it136centos58vm ~]$ ls • This is an example of a command ready at the command prompt, to see the result of the command, press enter • We have a model for commands • command <flag> <arg> • Does the ls command above fit or break our model?

15. Inside Tom’s Home Folder • [tom@example ~]$ ls • documents • Notice we don’t see inside documents, nor do we see /home/tom • Our VMs: • [student@it136centos65vm ~]$ ls • pslist teams.txt teams2.txt script.sh

16. $PATH • [student@it136centos65vm ~]$ ls • pslist teams.txt teams2.txt script.sh • So what just happened? • The BASH shell took our ‘standard input’ • We provided two letters (not a file path), so the BASH shell looked in something called the PATH variable to see if it knew what to do with those letters • It found a program called /bin/ls (which is our ls command), and ran it • This ‘listed’ the items in our directory

17. Standard Input/Output/Error • The Shell classifies three file channels • STDIN – standard input • STDOUT – standard output • STDERR – standard error • Standard input is what you type into the shell (commands) • Standard output is what the shell outputs if the command (STDIN) works • Standard error is what the shell outputs if the command (STDIN) doesn’t work

18. Command, Flag, Argument • So we have the command, flag, argument model • What is what? • Command: anything we type into the system to get it to do something useful (ls, cd) • Argument: usually a path to what we want to work on (/home/tom) • Flag: symbol that modifies how a command is run (-l, -cvf)

19. Command, Flag, Argument, ex • Running ls -l command • [student@it136centos58vm ~]$ ls -l • total 12 • -rw-rw-r-- 1 student student 0 Jan 24 00:34 mytest • -rw-rw-r-- 1 student student 0 Jan 24 00:34 pslist • -rw-rw-r-- 1 student student 0 Jan 24 00:34 teams.txt • -rw-rw-r-- 1 student student 0 Jan 24 00:34 teams2.txt • permissions user date filename • The -l changed the way ls showed the information

20. Flags Are Very Useful • Flags allow us to do more specific stuff • Show more data about a file/directory • Add arguments (to make commands more specific, or more general) • In useradd command, we add arguments to tell the system to not use its own defaults, but the values we give it • In the grep command we add arguments to tell the system to not worry about capitalization, but to look for upper and lower case • How do you find them? • Remember our best friends?

21. Flags 2 • Flags change the output of a given command, but are different per command • command <flag> <argument> • [student@it136centos65vm ~]$ rm –f • The rm command removes or deletes a file, the –f flag is ‘force’ and will remove without asking • When run as the root user this will kill an entire system • [student@it136centos65vm ~]$ tail –f messages • The tail command shows the last 10 lines of a file, the –f flag is persistent follow so it will show updates to the file as they occur

22. Arguments • cmd <flag> <argument> • [student@it136centos65vm ~]$ ls –l /home/student • ls is the command, -l is the flag, and /home/student/ is the argument • In this case the argument is a directory path • The argument could also be something we want to create • [student@it136centos65vm ~]$ useraddndillon • This would add a new user (named ndillon) to the system

23. Commands • So we have ls to ‘list’ what files are in our folder • We can use cp to ‘copy’ files from one place to another • cp teams.txt newfile • cmd <flag> <arg> <arg> • We can use rm to ‘remove’ our extra file • rmnewfile • We can use less to look through files without changing them • less teams.txt

24. More Commands • We can use hostname to determine the name of the system we are on • hostname • We can use head and tail to look at the beginning/end of a file • head pslist • tail pslist • We can get info on a file with the file command • file script.sh • We can show the differences between files with diff • diff teams.txt teams2.txt

25. Even More Commands • We can use echo to print things out to the command line • echo “Hello!” • echo $PATH • We can print the system’s date with • date • We can use whereis and find to locate things on the system • whereis ifconfig • find / -name authlog

26. Final Group of Commands • We can list users on a system with w, who, or finger • w • who • finger • We can display memory useage info with • free • We can make/restore backups of things with the tar command • tar -cvf scratchspace.tar /tmp /home • tar -xvvf scratchspace.tar

27. Command Flag Argument • When typing on the shell, commands are always required • Most other stuff will depend on what you want to do • cmd <flag1> <flag2> <arg1> <arg2> • tar -cvf backup.tar /home /tmp • tar is the command, -cvf are flags (3), and the arguments (3) are the new file to create, as well as the two directories to back up

28. I Lied (One More Command) • cmd <flag> <arg> • useradd will allow us to add/change accounts and account details on a system • useradd -d /home/newuser -s /bin/zshnewuser • Cannot do • useradd -ds /home/newuser /bin/zshnewuser • Order matters with the useradd command! • So what tells you the order, what is/isn’t required?

29. Practicals and Homework • Questions on anything up to this point? • Practicals • Today and Monday everything will be for a completion grade (homework & practicals) • After that, grades will be for accuracy

30. Topics For Own Study • Keywords: • Command, flag, argument • Commands: ls, rm, tail, echo, diff, whereis, copy, cat • Chapter 3 of Sobell • Online Surrey Unix Tutorial for Beginners tutorials one and two • Online Stanford tutorial – First two under intro section and first two under search section

31. VMWare • You can get it for free! • Go to: http://seattlecentralitprograms.com/ • Click on the VMWare link • Register with your SID as the username and fill out the remaining info • Download/order software of your choosing