How to Install Jenkins on Ubuntu 20.04

Jenkins is a free and open-source Java-based server for solving automation problems. It provides a variety of plugins that make continuous delivery and continuous integration easy. Continuous integration is the key practice area of DevOps where several developers continuously update their code and commit the changes to the version control repository. In short, the Jenkins streamlines the continuous delivery, continuous integration, deployment, and testing of new code.

Installing Jenkins on Ubuntu 20.04

As Jenkin is based on Java, therefore it requires Java 8 or later version to be installed on Ubuntu 20.04. Hence, we will install OpenJDK 11 to use Jenkins on Ubuntu 20.04. Complete the below-given steps to install Jenkins on Ubuntu 20.04:

Step 1: Update apt package listing

Before installing any new package or application, update apt existing apt packages:

$ sudo apt update

The apt cache will be updated.

Step 2: Get OpenJDK 11

Subsequently, install the OpenJDK 11 by executing:

$ sudo apt install openjdk-11-jre-headless

Upon successful installation, verify the installation with the below-given command:

$ java --version

The output displays that the OpenJDK 11 is successfully installed.

Step 3: Add Jenkins repository key

Jenkins is not included in the Ubuntu 20.04 base repository, therefore, we need to add the Jenkins repository key with the command:

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

Next, placed the repository in sources.list.d.

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

The repository is placed to the sources.list.d.

Step 4: Install Jenkins

Upon adding Jenkins repository to server’s list, update the apt cache:

$ sudo apt update

Now, install the Jenkins using the command:

$ sudo apt install jenkins

During the installation, when the command line prompts about additional disk space information, press y on the terminal to continue the Jenkins installation.

The Jenkins will be installed successfully.

Step 5: Check Jenkins service status

Upon successful installation, the Jenkins service will start automatically. To check the Jenkins service status, type the below-given command:

$ sudo systemctl status jenkins

The output displays that the Jenkin service is started. However, for any reason, if the Jenkin service does not start, then type the command given-below to start it:

$ sudo systemctl start jenkins

Configure the Firewall

Configure the firewall to access Jenkins from the web browser. First, let’s enable the firewall by executing the commands in the given order:

$ sudo apt install ssh

$ sudo ufw allow OpenSSH

$ sudo ufw enable

The Jenkins uses port 8080 to perform functionality, open the ufw port 8080 with the command:

$ sudo ufw allow 8080

Let’s check the ufw’s status with the command:

$ sudo ufw status

The port 8080 allows traffic from anywhere.

Getting started with Jenkins

Use the IP address of your server or domain name with port 8080 to access and perform the initial configuration for Jenkins. To find the IP address, type the below-given command:

$ ifconfig

Now, open your favorite browser and enter the URL:http://server_ip_or_domain:8080

In my case, it would be http://10.0.2.15:8080

The Unlock Jenkins screen will be displayed. To ensure Jenkins security, a password has been written to the log file.

Execute the cat command with the sudo privileges to get the password:

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

Note the password value and enter or paste it into the ‘Administrator password’ field, and press ‘Continue’.

You can install the suggested plugins and can select various plugins to install. It is better to install the suggested plugins as they are widely used by the community.

Next, create the first admin user. Enter the appropriate data in all the fields and click on ‘Save and Continue’. We also have an option of skipping the account creation and continue as admin.