RHCSA (RED HAT SYSTEM ADMINITRATOR)

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[TOC]

Understand and Use Essenctial Tools

Essencials :

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>  #(std) satandar output
2> #(stderr) standar error
sort < list > sorted_list #combined input output
ls  2> error 2>&1

Commands

Three types of comands: * Aliases * excecuted before anything else * internal Commands * Is part of the sheel itself, doe snot have to be loaded from te disk, * External Commands * is a command that existe on the disk as a separate file.

type command can be used to know what type of command it is
which coomand can be use to find out which command the sheel will be using

VIM

vimtutor is ca coomand which helps you lest vim Vim basic:

command	explanation
esc	enter command mode
i	'insert' behind the carrot
a	'append' after the carrot
o	edit in new line below carrot
O	edit in line above carrot
:w	'write' do disk
q	'quit'
:w filename	'write' document into filename
dd	'delete' line
yy	'yank' line
v	enter 'visual' mode
u	'undo'
Crtl-r	'redo'
gg	gos to first line in doc
G	goes to last line in do
/text	searches for text in doc
?text	searches for text backward in doc
^	frist posicion in current line
$	last posicion in current line
!ls	adds the outlut of ls, into the file
:%s/old/new/g	'subtitudes' old with new in whole file'

Enviroment

Grep and Regex

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SSH (Secure Shell)

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system width configs

/etc/ssh/ssh_config

user file, overrides system configs

~/.ssh/config

Keys

Generates a public and privates keys

ssh-keygen

saves to

~/.ssh/id_rsa
~/.ssh/id_rsa.pub

Copies your public id over th te target

ssh-copy-id

X11 Forwarding

I think it sends a single window trough the ssh connection

ssh -X user@server

Old	Replaced by
Telnet	ssh
rcp (remote copy)	scp (secure copy)
ftp (file tranfer protocol)	sftp ( secure file tranfer protocol)

Logging in and Switchign users:

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suptitude user

su

Set up the enviroment when

su - lucy

Run a single command as an other user

su -C "fdisk -l"

Interactive shells

Means that the shell is run wit the interaction of the usr, suh as opening the terminal, as opposued to the non-interactive shell.

.bashrc runs when in interactive

Login shell

Runs as part to the user loggin into the system as opposued to a non-login which can be automated process

.bash_profile

Commands run when log out

• .bash_logout

Command history

• .bash_history
• search hisory crl-r

Compression and Archives:

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tar cvf home.tar /home

• create a tar archive
• verbose
• filename

tar xvf home.tar /home

• extracts a tar archive
• Verbose
• filename

-z or -j compresses behaivor

Compression - Gzip

gzip bigfile.stuff gzip -d bigfile.stuff.gz

Bzip

bzip2 bigfile.stuff bzip2 -d bigfile.stuff.bz2

Zip Files

zip -r zippedFileName.zip /home unzip zippedFileName.zp

Creating and Manipulation Files:

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A File:

A Pointer to a 'inode' which live on the disk ls -i file.stuff

Commands:

• find
• locate locate https.config
• cat
• less
• more
• head
• less
• sort -r revese
• wc -l line count
• diff
• patch

Using File Links:

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Hard Links:yy

Point to the same inode to the disk

Hard Links:yy

is a pointer to the filenames of other files

File Permissions:

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type of file: - => regualr files d => directory

Operate Running System

Managing the boot proccess

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UEFI/BIOS -> GRUP2

Grub

ls -> disks cat rd.break emergency rescue

Managing Individual Processes

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top

ps

acceps difrent rypes od opstions: UNIX: which may be a be a groupd and must be preceded by a dash ( -aux ) GNU: which my be grouped and must not be used with a dash ( aux ) BSD: long options wch are receded by two dashes ( --group ) a all process u display usr format x all Proceses

pgrep [options] pattern

compbines the grep and ps to give relevant infomation -l process nams -u Limited the matches to user -v incerse result

Kill Signals

kill [options] pattern compbines the grep and ps to give relevant infomation -l list kill signals 15 SIGTERM Ask the process to end politely 9 SIGKILL Stops thhe process imidetly (leave file open...) 9 SIGHUP Stops tthe process in the shell eviroment, the binary must be have the configuration to be able to to interact with it 2 SIGINT ( crl-c ) 19 SIGSTOP Tells a preocess to stop, similar to how the crtl-z 18 SIGCONT Tells a proccess to continue 20 SIGTSTP (Terminal Stop) relies on the binary on knowing how to process the signal

Niceness

The more priority a process has the less nice it is, and vv

High priority, not nice [-20, 19] nice, low propieirty The lower the level the highest the priority, the less nice it is renice 0 just share the CPU

Load Average

Average of teads or processes waiting for a resorces over a period of time 1, 5, 15 minustes

load average over the last 1 minute: 1.05 load average over the last 5 minutes: 0.70 load average over the last 15 minutes: 5.09

over the last 1 minute: The computer was overloaded by 5% on average. On average, .05 processes were waiting for the CPU. (1.05) over the last 5 minutes: The CPU idled for 30% of the time. (0.70) over the last 15 minutes: The computer was overloaded by 409% on average. On average, 4.09 processes were waiting for the CPU. (5.09)

/dev/null produces no output.
/dev/zero produces a continuous stream of NULL (zero value) bytes.

Logging

come back to it

VMs

come back to it

Configure Local Storage

Create and Configure File systems

Deloy, Configure, and Maintain Systems

Manage User and Groups

Manage Security

Exam Eviroment