Grades

1. Grades • Please hand in your homework • Quizzes coming back today • Current grade on back with missing assignments • Anything missing can be turned in late • There will be a 2 point penalty (as with late assignments)plus whatever you miss • You can re-submit any assignment • You must attach the original, and there will be a one-point penalty per re-submission (after the first)

2. Review • Folders • /var and /tmp • Redirection • Grep and command-line grouping

3. Today • Folders • /home /root /opt • Advanced redirection • Text editors (vi/vim) • Scripting

4. Folders (/home) • /home – user data • Most accounts exist under /home • useraddndillon • Will create /home/ndillon by default • To not use /home you must specify this at the time the account is created • useradd -d /var/log audit_user • Individual users are then responsible for the structure of everything under /home/<username> • Root user has a special home directory (/root)

5. Folders (/root) • /root – root user’s home directory • This is created on install • Permissions lock down to only the root user • Again, it is up to the admin (or admin team) to ensure structure of everything below this level • I usually have a backups directory, some admins use this as a staging area (instead of /tmp)

6. Folders (/opt) • /opt – application directory • What is an application as it relates to a server? • This is the directory these things should be installed in (unless well-known database or web server) • If the company has more than 20 people, there’s a 90% chance it will install into /opt • If the company has a decent Linux/Unix admin it will install into /opt • If it doesn’t it’s a possible red flag that they don’t know ‘best practice’ or standards

7. Quick Aside – ‘Best Practice’ • Does anyone know what this means as it relates to IT? • It is in every specialization under “IT” • For programmers there are ‘coding standards’ such as Google’s Java Standards • For sysadmins it’s how to set up and architect the system • For network admins it’s planning of a network, protocol handling, etc…

8. Redirection • Quick Refresher – what do these do? • | • > • < • What are the three file channels? • Standard

9. Advanced Redirection >> • What happens when you use > on an already existing file? • cat teams.txt > /tmp/teams2_copy.txt • We can use >> to append • cat teams.txt >> /tmp/teams2_copy.txt • >> Leaves all data that was in the original file, find the “EOF” marker at the bottom, and copies the newly redirected STDIN below the original file

10. Advanced Redirection 2> • We can also redirect standard error • ./script.sh will return an error • ./script.sh 2> err.out will redirect ONLY the error • This is incredibly useful when debugging a script, especially one that has a lot of output • So what do you think 2>> does? • ./script.sh 2>> /tmp/system_errors.txt

11. Advanced Redirection &> • We can also redirect everything • ./script.sh will output STDOUT and STDERR • ./script.sh &> all.out will redirect everything • Useful for “set it and forget it” tasks you’ve automated, or something that’s going to take a while • So what do you think &>> does? • ./script.sh &>> /tmp/all_output.txt

12. Quick Demo

13. Text Editors • On that note: text editors • So we created a user, how do we let it run administrative commands? • sudo - run single command as root • To add our new user, we use a text editor • There are three popular ones – vi, emacs, and nano • You can use whatever you want, but the homework (and the test) will be on vi

14. Emacs - Probably Best • emacs <flag> <file_path> • emacs teams.txt • Has built-in menus, which make it easy to navigate • Emacs is written in Lisp • Built-in documentation and tutorial • Full Unicode support • (aka) Supported on Linux, BSD, Unix, Solaris, Windows, and Mac

15. Nano is also very good as well • nano <flag> <file_path> • nano teams.txt • Originally a byte-by-byte match of Pico • Called TIP (TIP Isn't Pico – recursive name, like GNU – GNU's Not Unix) • FYI – Linux admins are weird about GNU & GPL • Now a 'superset' of Pico – includes Pico support, and more

16. VIM – Just Awful • vi <flag> <file_path> • No nice menu • Very common • Two modes – 'command' and 'insert' • Command mode allows saving, quitting, skipping around text, copying/pasting, replacing, the arrow keys, etc... • Insert mode allows typing, deleting, etc... • OLD ARCHIAC EVERYWHERE!

17. Guess What We’re Going to Use - vi • Two modes: command and insert • Very confusing • Usually (USUALLY) INSERT appears in bottom left • Insert mode – adding content to file (typing) • Command mode – manipulating content • copying, pasting, saving, moving, exiting, etc… • I always assume I’m in INSERT mode, and press Esc a few times, then go back to what I was doing

18. Insert Mode • We opened a text editor, we probably want to type • The i key takes you into 'insert' mode – you can type wherever the cursor is • a is 'append' – it will move the cursor over one space and then be in insert mode • What else puts you into ‘insert’ mode? • Once you’re in insert mode, you can type all you want until you press the escape key

19. Command Mode • Type in vi, you start in command mode • Already in vi, enter command mode by pressing, the escape key • Then the colon key • Save is <esc> :w • Quit is <esc> :q • Save & quit is <esc> :wq • You only have to press escape one time • Man vi (or Google ‘man vi’) • What does :wq! do?

20. Quick Demo • I will access vi by editing our teams.txt file • I will show you I am in command mode by copying/pasting • I will enter edit mode and undo my copy/paste by manually writing • I will save the file • I will save the file as a new file • I will edit the file again, realize I didn’t want to edit it, and then discard my changes

21. Demo

22. Scripting • What differentiates Linux with Windows • A script is a file that holds multiple commands • Starts at the top, works its way down • Executes everything as if you were at the command line typing it in • Does not stop on error – each line will be run • Only needs one thing • First line must be the ‘invocation’ of the shell • #!/bin/bash

23. Simple Script • What does this do? • #!/bin/bash • # this is a ‘comment’ and will not be run • ls –alh > filelist.txt • cp filelist.txt /tmp/ • # ps –ef > /tmp/processlist

24. Own Study • Folders – p81 • Advanced Redirection – p135 • Vi – Chapter 6, p159 • Scripting – p284 (a bit inside Ch8)