pmm-client in centos 6 docker container

I have a Centos 6 docker container running ProxySQL, and I’d like to try and use pmm to monitor it. Starting the pmm-server docker container was pretty straight-forward, and pmm-admin config --server works just fine. But the pmm-admin add proxysql:metrics fails with this msg: Error adding proxysql metrics: “initctl” failed: exit status 1. This is running in Docker Swarm mode, so I can’t run the container in Privileged mode. Is there any other workaround to get the metrics collection running?