notes/session-05.txt at main · daws-88s/notes · GitHub

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:q -> quit
:q! -> force quit
:wq -> write quit
:/ -> search from top
:? search from bottom
:set nu -> display numbers
:noh -> no highlight
:<line-number>
:%d -> delete everything
:%s -> substituion

Esc Mode
=======
u -> undo
Ctrl+r -> redo
gg -> takes to top
Shift+g -> takes to bottom
yy -> copy
p -> paste
dd -> cut
shift+p -> paste above the line

useradd <user-name>
/etc/passwd
id user-name

/etc/group

usermod -g group-name user-name
usermod -aG group-name user-name

passwd user-name
/etc/ssh/sshd_config
sshd -t

/etc/sudoers
vimsudo -c

gpasswd -d <user-name> <group-name>
userdel

tar -xf *.tar.gz
tar -cf *.tar.gz folder_name

awk and cut commands

Permissions
============
- 	rw- 		r-- 	r--
	User/owner	group	others
	u			g		o

chmod o+w perm
either owner of the file or root user can only change access levels

R -> 4
W -> 2
X -> 1

chmod 764

Ownership
===========
chown <user>:<group>
ownership can only be changed by root user. not even owner of the file can change the ownership

employee joins organisation
==========================
1. He should generate keys
2. send public key to admins
3. admin creates .ssh folder inside user home directory
4. permission should be 700 for .ssh
5. ownershop should be user including group
6. create authorized_keys inside .ssh folder and paste public key in it
7. authorized_keys permission should be max 600

then user can login

ssh -i rahim rahim@3.85.244.109
add him to wheel group
/etc/sudoers

package management
=================
yum -> old rhel
dnf -> latest

apt-get or apt install

dnf install <package-name> -> redhat based instances

/etc/yum.repos.d/ -> all URLS are configured

he developed Linux kernel from the scratch using c language... he invented git also..

flavours or distributions

Redhat -> commands + apps -> Redhat flavour/distribution -> CentOs/fedora
Redhat family = redhat = centos = fedora = aws linux
Ubuntu
Oracle
Suse
IBM

1. community edition -> free
2. enterprise edition -> support redhat

dnf install <package-name>

sudo wget -O /etc/yum.repos.d/jenkins.repo \
    https://pkg.jenkins.io/redhat-stable/jenkins.repo
sudo yum upgrade
# Add required dependencies for the jenkins package
sudo yum install fontconfig java-21-openjdk
sudo yum install jenkins
sudo systemctl daemon-reload

Service Management
===================
0-65,535

https://facebook.com

ssh facebook.com
port 22 sshd service is running

1. get the facebook.com IP address
2. connect to the service running on port 443

Delhi -> Hyderabad

HYD pincode -> HYD central office
Street name ->
Apartment name ->
Flat number ->

systemctl start <service-name>
systemctl restart <service-name>
systemctl status <service-name>
systemctl enable <service-name> -> auto start
systemctl disable <service-name>

systemctl start wget
systemctl start curl

nginx -> http/web server -> port 80

systemctl status <service-name> -> check service is running or not

network management
=================
netstat -lntp -> check port is running or not and accessible to internet