Install Jenkins on Ubuntu 20.04

 To Install Jenkins on Ubuntu 20.04

#java

java --version

openjdk 11.0.13 2021-10-19

#add jenkins public key

wget -q -O - https://pkg.jenkins.io/debian-stable/jenkins.io.key | sudo apt-key add -

OK

#add jenkins repository 

sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'

sudo apt update

sudo apt install jenkins

#service status

sudo service jenkins status

Ctrl+C #exit

sudo systemctl start jenkins

sudo service jenkins status

#In the browser

http://localhost:8080/

#to get Administrator password

sudo cat /var/lib/jenkins/secrets/initialAdminPassword

#Follow the pages to complete

Install suggested plugins 

Create Frist Admin User

Instance Configuration

Jenkins is Ready!

Jenkins⇒Manage Jenkins⇒Jenkins CLI⇒download "jenkins-cli.jar"

#or go to http://localhost:8080/cli/ 

sudo java -jar jenkins-cli.jar -s http://localhost:8080/ -version

Version: 2.319.3

Add JDK Maven and Git Plugins with Jenkins

Ref:- how-to-install-jenkins-on-ubuntu-20-04