This article is for those looking for a detailed and clear guide on how to install OpenJDK on Ubuntu Server.

With the release of Java 11, Oracle JDK became commercial and is no longer free.

OpenJDK is an open-source implementation of the Java Standard Edition platform with contributions from Oracle and the Java open community. The Oracle JDK build process is built from the OpenJDK source, so there isn’t much difference between Oracle JDK and OpenJDK.

OpenJDK is free but will need to be updated every 6 months.

In this guide, we will consider the case when you already have a server with the Ubuntu Server 20.04 LTS operating system installed on it.

You can read more about how to install Ubuntu Server 20.04 LTS in my guide “Install Ubuntu Server 20.04 LTS”.

In addition, OpenSSH must be installed on the server, and port 22 must be open in order to be able to connect to the server using the SSH protocol.

To install OpenSSH on a server, you can use the command:

sudo apt install openssh-server

This guide describes how to connect to a server using the iTerm2 terminal emulator installed on the macOS operating system.

We connect to the server on which you plan to install OpenJDK.

Update the local package index to the latest changes in the repositories using the command:

sudo apt update

Install OpenJDK on Ubuntu Server

You may need a Java Development Kit (JDK) in addition to the JRE in order to compile and run certain Java-based software.

To install the JDK, run the following command, which will also install the JRE:

sudo apt-get install -y default-jdk

Install OpenJDK on Ubuntu Server

Now you need to make sure that OpenJDK is installed correctly. To do this, you need to run the command:

java -version

Install OpenJDK on Ubuntu Server

Based on the message received, OpenJDK is installed correctly.

Many programs written with Java use the “JAVA_HOME” environment variable to determine where Java is installed. Therefore, you need to define this variable and assign it a value containing the path to the Java installation location.

Let’s define the path to the Java installation location using the command:

sudo update-alternatives --config java

Install OpenJDK on Ubuntu Server

In this example, the path to the Java installation location looks like this:

/usr/lib/jvm/java-11-openjdk-amd64/bin/

In order to define an environment variable and assign a value to it, you need to make changes to the “environment” file by opening it in a text editor using the command:

sudo vim /etc/environment

Install OpenJDK on Ubuntu Server

Press the “i” button to switch to edit mode, then at the end of the file define a new variable “JAVA_HOME” and assign it a value containing the path to the Java installation location obtained earlier.

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/bin/"

Please note that the path to the Java installation location must be specified up to and including the “bin” folder.

Install OpenJDK on Ubuntu Server

Now press the “Esc” button to exit edit mode, then type “:x” and press the “Enter” button to save your changes and exit the editor.

Install OpenJDK on Ubuntu Server

Next, you need to apply the changes made to the current session using the command:

source /etc/environment

Install OpenJDK on Ubuntu Server

Now let’s make sure that the environment variable has the correct value using the command:

echo $JAVA_HOME

Install OpenJDK on Ubuntu Server

Based on the message received, the environment variable has the correct value.

Install OpenJDK on Ubuntu Server

Vladimir Mikhalev
hey, I’m Vladimir Mikhalev, but my friends call me Valdemar. I have a lot of experience in the design and maintenance of various information systems.

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