The easiest option for installing Java is to use the version packaged with Ubuntu. By default, Ubuntu 20.04 includes Open JDK 11, which is an open-source variant of the JRE and JDK.
To install this version, first update the package index:
sudo apt update
Next, check if Java is already installed:
If Java is not currently installed, you’ll see the following output:
Execute the following command to install the default Java Runtime Environment (JRE), which will install the JRE from OpenJDK 11:
sudo apt install default-jre
The JRE will allow you to run almost all Java software.
Verify the installation with:
You’ll see output similar to the following:
You may need the Java Development Kit (JDK) in addition to the JRE in order to compile and run some specific Java-based software. To install the JDK, execute the following command, which will also install the JRE:
sudo apt install default-jdk
Verify that the JDK is installed by checking the version of javac, the Java compiler:
Step 2 – Installing Jenkins:
The version of Jenkins included with the default Ubuntu packages is often behind the latest available version from the project itself. To ensure you have the latest fixes and features, use the project-maintained packages to install Jenkins.
Copy the 32-character alphanumeric password from the terminal and paste it into the Administrator password field, then click Continue.
The next screen presents the option of installing suggested plugins or selecting specific plugins:
We’ll click the Install suggested plugins option, which will immediately begin the installation process.
When the installation is complete, you’ll be prompted to set up the first administrative user. It’s possible to skip this step and continue as admin using the initial password we used above, but we’ll take a moment to create the user.
Enter the name and password for your user:
You’ll receive an Instance Configuration page that will ask you to confirm the preferred URL for your Jenkins instance. Confirm either the domain name for your server or your server’s IP address:
After confirming the appropriate information, click Save and Finish. You’ll receive a confirmation page confirming that “Jenkins is Ready!”:
Click Start using Jenkins to visit the main Jenkins dashboard: