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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

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Grades

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

Review

  • Folders

    • /var and /tmp

  • Redirection

  • Grep and command-line grouping


Today

Today

  • Folders

    • /home/root/opt

  • Advanced redirection

  • Text editors (vi/vim)

  • Scripting


Folders home

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)


Folders 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

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

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

Redirection

  • Quick Refresher – what do these do?

    • |

    • >

    • <

  • What are the three file channels?

    • Standard


Advanced redirection

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

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 redirection1

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

Quick Demo


Text editors

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 - 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 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

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

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

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

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 demo1

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


Grades

Demo


Scripting

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

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

Own Study

  • Folders – p81

  • Advanced Redirection – p135

  • Vi – Chapter 6, p159

  • Scripting – p284 (a bit inside Ch8)


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