It looks like the JMX in Kafka and Kafka Connect does not work right now. There are two issues:

• First one is the error from #4467. This is caused by the new volume based /tmp => the JMX password file has special permissions and it is not possible to overwrite it when the container restarts (and the file is still there because we use volume for /tmp now). This is resolved by deleting the files first which seems to work.
• Second problem seems to be why does the container restart in the first place. I'm not sure this was the same case with #4467 (since in general, any restart would cause this and the issue was reported with 0.21.1 where this should not be an issue). But in master, it ends up with Port already in use: 9999 error. That seems to be caused by the master using KAFKA_JMX_OPTS instead of KAFKA_OPTS. That seems to cause this problem. Changing ti back to KAFKA_OPTS seems to solve the issue.