Solr won't start "Your current version of Java is too old to run this version of Solr"

Symptoms

After installing Dovecot Solr FTS, you find that it is not running, and the webmail interface errors when searching. 

Cause

The version of Java that is installed and in use is older than what Solr requires. 

Resolution

1. Access your server as the root via SSH, or access your WHM server and navigate to Terminal.

2. Run the following:

   # update-alternatives --config java

   You will be prompted to select the Java version installed. Enter 2 to select Java 11.

   CONFIG_TEXT: There are 2 programs which provide 'java'.
   Selection    Command
   -----------------------------------------------
   *+ 1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.422.b05-1.el7_9.tuxcare.els1.x86_64/jre/bin/java)
     2           java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-11.0.23.0.9-2.el7_9.x86_64/bin/java)
   Enter to keep the current selection[+], or type selection number: 2

3. With the correct Java version in use, Solr will need to be reinstalled. Remove Solr:

   # /scripts/uninstall_dovecot_fts

4. Move aside the Solr data directory:

   # mv /home/cpanelsolr{,.backup.broken}

5. Reinstall Solr:

   # /scripts/install_dovecot_fts

6. Confirm the service was able to start:

   # /scripts/restartsrv_cpanel_dovecot_solr --status