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)

Review

Folders /var and /tmp

Redirection Grep and command-line grouping

Today

Folders /home /root /opt

Advanced redirection Text editors (vi/vim) Scripting

Folders (/home)

/home – user data Most accounts exist under /home useradd ndillon

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)

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)

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

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…

Redirection Quick Refresher – what do these do?

|

>

< What are the three file channels?

Standard

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

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

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

Quick Demo

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

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

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

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!

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

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

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?

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

Demo

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

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

Own Study

• Folders – p81

• Advanced Redirection – p135

• Vi – Chapter 6, p159

• Scripting – p284 (a bit inside Ch8)