What is Jenkins ?
Jenkins is an open source automation server which is used for continuous integration and continuous delivery in software development its help to automate the parts of software development related like building , testing, deploying and delivery the software

how you can install Jenkins on Ubuntu:
Step 1:
You need to read documentation of Jenkins that what are the minimum requirement for installing Jenkins
documentation link : https://www.jenkins.io/doc/book/installing/linux/

The point that are being in the knowledge.

1. Which java version is required for which jenkins version first install that version of java

(source: Jenkins Documentation)

Step 2:
First Update your System:

sudo apt update

Step 3;
install Java as per the requirement of Jenkins version
observe the picture

(source: Jenkins Documentation)

sudo apt install openjdk-21-jre-headless

Step 4:
Now follow the documentation command

(source: Jenkins Documentation)

sudo wget -O /usr/share/keyrings/jenkins-keyring.asc \
  https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key
echo "deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc]" \
  https://pkg.jenkins.io/debian-stable binary/ | sudo tee \
  /etc/apt/sources.list.d/jenkins.list > /dev/null

Step 5:
update it again

sudo apt-get update

Step 6:
Install Jenkins

sudo apt-get install jenkins

Step 7:
enable means start the service when machine is rebooted

sudo systemctl enable jenkins

Step 8:

sudo systemctl start jenkins

Now
Jenkins is install so open it with port 8080

and the password is at
/var/lib/jenkins/secrets/initialAdminPassword
it's mention in the browser

So use Cmd

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

copy the password and paste it there in browser
and configure the setting that you need.

Script For Provisioning in cloud

#!/bin/bash
sudo apt update 
sudo apt install openjdk-21-jre-headless -y
sudo wget -O /usr/share/keyrings/jenkins-keyring.asc \
  https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key
echo "deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc]" \
  https://pkg.jenkins.io/debian-stable binary/ | sudo tee \
  /etc/apt/sources.list.d/jenkins.list > /dev/null
sudo apt-get update
sudo apt-get install jenkins -y
sudo systemctl enable jenkins
sudo systemctl start jenkins

Thanks