Overview

Gluu Server 4.5.14 ships with Java 21 by default.
However, administrators can upgrade the runtime to Java 25 without upgrading Gluu itself.

This is done by installing Amazon Corretto 25 and updating the /opt/jre symlink that Gluu services use.

This process changes only the Java runtime, not the Gluu binaries.

Prerequisites

Before proceeding, ensure:

• You are running Gluu Server 4.5.14 in Virtual Machine
• You have root or sudo access
• Internet access is available to download Corretto
• Services can be restarted safely

Recommended:

• Take a VM snapshot
• Backup /opt directory

Upgrade Procedure

Step 1 — Navigate to /opt

cd /opt/

Step 2 — Download Amazon Corretto 25

wget https://corretto.aws/downloads/latest/amazon-corretto-25-x64-linux-jdk.tar.gz

This downloads the latest Amazon Corretto Java 25 JDK.

Step 3 — Extract the archive

tar -xzf amazon-corretto-25-x64-linux-jdk.tar.gz

This will create a directory similar to:

/opt/amazon-corretto-25.x.x.x-linux-x64

Step 4 — Update the Java runtime symlink

Gluu services use:

/opt/jre

Update this symlink to point to the new Java installation.

ln -sfn /opt/amazon-corretto-25.0.2.10.1-linux-x64 /opt/jre

Explanation:

Step 5 — Remove downloaded archive (optional)

rm -rf amazon-corretto-25-x64-linux-jdk.tar.gz

Step 6 — Restart Gluu services

You can restart services individually or reboot the VM.

Verification

Confirm the Java version used by Gluu.

/opt/jre/bin/java -version

Expected output:

openjdk version "25.0.2" 2026-01-20 LTS
OpenJDK Runtime Environment Corretto-25.0.2.10.1 (build 25.0.2+10-LTS)
OpenJDK 64-Bit Server VM Corretto-25.0.2.10.1 (build 25.0.2+10-LTS, mixed mode, sharing)

You may also verify running Java processes:

ps -ef | grep java

Rollback Procedure

If problems occur, revert the symlink to the previous Java runtime.

Example:

ln -sfn /opt/jre-21 /opt/jre

Then restart services again.

Notes

• Test upgrades in non-production environments first
• Monitor logs after restart

Example:

/opt/gluu/jetty/oxauth/logs
/opt/gluu/jetty/identity/logs

Summary