How to disable High Availability (active/passive) in CloudBees CI?

Issue

How to correctly disable High Availability (active/passive)?
Why is HA still running even after I have uninstalled the CloudBees High Availability (active/passive) Management plugin (cloudbees-ha)?

Environment

Resolution

Option 1: Pass the following Java argument to Jenkins:

-Dcom.cloudbees.jenkins.ha=false

Option 2: Use the environment variable:

JENKINS_HA=false

and then restart Jenkins.

Note: If you are running client controller or operations center using a Docker compose file, you will need to follow Option 2. A sample layout for that file would be:

...
services:
  jenkins:
    image: cloudbees/cloudbees-core-cm:VERSION
    restart: unless-stopped
    ports:
     - 8080:8080
     - 50000:50000
    environment:
     -  JENKINS_HA=false
    container_name: jenkins
    volumes:
...

Cleanup

If you are disabling permanently and would also like to remove the no longer used working files, you need to delete a directory specified in the HA_JGROUPS_DIR Java System Property which defaults to $JENKINS_HOME/jgroups. Advanced tuning is available via the $JENKINS_HOME/jgroups.xml file, so it can also be removed if it is present.

Reference

How to add Java arguments to Jenkins?