How to Install OpenJDK 21 on AlmaLinux 10

Published: 2026-06-24

Introduction

Java 21 is the latest Long-Term Support (LTS) release of the Java platform. It introduces performance improvements, virtual threads, enhanced pattern matching, and long-term maintenance support.

This guide explains how to install OpenJDK 21 on AlmaLinux 10 and verify that the installation is working correctly.

Prerequisites

Before starting, ensure that:

You are running AlmaLinux 10.

You have sudo or root privileges.

Your system packages are up to date.

Update the system:

sudo dnf update -y

Check Available Java Packages

Search for available Java packages:

sudo dnf search openjdk

You should see OpenJDK 21 packages in the repository.

Install OpenJDK 21

Install Java 21:

sudo dnf install java-21-openjdk java-21-openjdk-devel -y

The package includes:

Java Runtime Environment (JRE)

Java Development Kit (JDK)

Compiler tools such as javac

Verify the Installation

Check the Java version:

java -version

Example output:

openjdk version "21"
OpenJDK Runtime Environment
OpenJDK 64-Bit Server VM

Verify the compiler:

javac -version

Expected output:

javac 21.0.11

Locate the Java Installation Directory

Display the Java binary path:

which java

Find the actual installation location:

readlink -f $(which java)

Typical installation path:

/usr/lib/jvm/java-21-openjdk

Configure JAVA_HOME

Most applications can automatically detect the Java installation path. However, some enterprise software may still require JAVA_HOME to be configured manually.

Open the profile file:

sudo vi /etc/profile.d/java.sh

Add the following lines:

export JAVA_HOME=/usr/lib/jvm/java-21-openjdk
export PATH=$JAVA_HOME/bin:$PATH

Apply the changes:

source /etc/profile.d/java.sh

Verify:

echo $JAVA_HOME

Test Java

Create a test file:

vi HelloWorld.java

Insert:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello AlmaLinux 10");
    }
}

Compile:

javac HelloWorld.java

Run:

java HelloWorld

Output:

Hello AlmaLinux 10

Conclusion

Installing OpenJDK 21 on AlmaLinux 10 is straightforward using the default DNF repositories. After installation, verify the Java version, configure JAVA_HOME if needed, and run a simple program to confirm that the environment is working correctly.