"After all, the engineers only needed to refuse to fix anything, and modern industry would grind to a halt." -Michael Lewis

For Doers

How to Provision a Linux Server With Any Version of Java via a Bash Script

2018-10-28

While we would all like to be up to date, sometimes legacy systems handcuff us into using an older version of software. Java is no exception, and in some cases we have to resort to using, say, Java 8, instead of the latest version with all of the security updates that we need.

From my scrounging on the internet, it turns out this isn't an extremely straightforward process via any package manager. Some solutions flat out don't work on newer systems. So, it's in everyone's best interest to try to understand a little bit more about how a Linux OS works and unpack the tarball from the source.

First, head over to the OpenJDK archives page and select the link appropriate for your needs. This tutorial will use Open-JDK 10.0.1, which (as of this writing), has the link:

https://download.java.net/java/GA/jdk10/10.0.1/fb4372174a714e6b8c52526dc134031e/10/openjdk-10.0.1_linux-x64_bin.tar.gz

Once you have that, run a wget on your target system:

# Get tarball for JDK 10.0.1
wget https://download.java.net/java/GA/jdk10/10.0.1/fb4372174a714e6b8c52526dc134031e/10/openjdk-10.0.1_linux-x64_bin.tar.gz

You'll also need to create a target directory to actually keep the version of java you're installing:

# make java 10 directory
mkdir -p /usr/lib/java10

Then unpack the tarball into your freshly minted directory:

# unpack tarball
tar -C /usr/lib/java10/ -xvzf ./openjdk-10.0.1_linux-x64_bin.tar.gz 

You'll need to update alternatives for Java. Updating alternatives is like creating a hierarchical symbolic link. Recall that a symbolic link is just a fake file that points to a real one.

The advantage of updating alternatives is that you can have multiple version in your system and more easily change between all of them, but that's a subject for another post. Here's the commands you need:

# update alternatives
update-alternatives --install /usr/bin/java java /usr/lib/java10/jdk-10.0.1/bin/java 20000
update-alternatives --install /usr/bin/javac javac /usr/lib/java10/jdk-10.0.1/bin/javac 20000

Finally, we can verify that this all worked by running:

# update alternatives
update-alternatives --install /usr/bin/java java /usr/lib/java10/jdk-10.0.1/bin/java 20000
update-alternatives --install /usr/bin/javac javac /usr/lib/java10/jdk-10.0.1/bin/javac 20000

We can then package all of this up into a reusable bash script:

#!/bin/bash
 
# Get tarball for JDK 10.0.1
wget https://download.java.net/java/GA/jdk10/10.0.1/fb4372174a714e6b8c52526dc134031e/10/openjdk-10.0.1_linux-x64_bin.tar.gz

# make java 10 directory
mkdir -p /usr/lib/java10

# unpack tarball
tar -C /usr/lib/java10/ -xvzf ./openjdk-10.0.1_linux-x64_bin.tar.gz 

# update alternatives
update-alternatives --install /usr/bin/java java /usr/lib/java10/jdk-10.0.1/bin/java 20000
update-alternatives --install /usr/bin/javac javac /usr/lib/java10/jdk-10.0.1/bin/javac 20000

# verify with a version check
java -version

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