How To: Change the Java version for DMC

If you find any security vulnerabilities with the Java version 11.0.8 that DMC uses, you can replace it with a different 11.x version of Java manually. (Be sure to keep a copy of the 11.0.8 java version because you will need it the next time you will upgrade your DMC.)

To update the Java version for DMC from 11.0.8 to a different 11.x version, do the following (fill in the actual java version number in the commands below):

From the terminal create a directory for your new Java 11.x version, run mkdir java<version>
Navigate to your new directory, run cd java<version>
Download the OpenJDK<version>.tar.gz file for the Java 11.x version you want to use and put it in your new java<version> directory.
Example: wget https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11.0.8+10/OpenJDK11U-jre_x64_linux_hotspot_11.0.8_10.tar.gz

Note: For more information on how to download and install prebuilt OpenJDK packages, see the OpenJDK installation page.

Run the following commands so DMC will use the other 11.x version of Java (that you already downloaded):

tar xzf OpenJDK<version>.tar.gz
sudo datical-control service stop datical-service
mv /opt/datical/jre /opt/datical/old_jre
cp /root/java11.xx.xx/jdk-11.xx.xx-jre /opt/datical/jre
sudo datical-control service start datical-service

IMPORTANT: If you have manually changed the java version used by DMC, you will need to restore DMC’s default version of Java (11.0.8) before any time that you upgrade DMC. Move or copy Java 11.0.8 from the /opt/datical/old_jre directory back to the /opt/datical/jre directory prior to starting your DMC upgrade. DMC expects Java version 11.0.8 to be in the /opt/datical/jre directory for the DMC upgrade process to be successful. After your DMC upgrade is complete, you can change to a different 11.x java version again.