space issue on docker devmapper and CentOS7

Just run these three. No need to remove RUNNING containers.

1. Cleanup exited processes:

   docker rm $(docker ps -q -f status=exited)
   

2. Cleanup dangling volumes:

   docker volume rm $(docker volume ls -qf dangling=true)
   

3. Cleanup dangling images:

   docker rmi $(docker images --filter "dangling=true" -q --no-trunc)
   

You can use:

docker system prune -a -f --volumes

where:

• -a == removes all unused images
• -f == force
• --volumes == prune volumes.

see: https://docs.docker.com/engine/reference/commandline/system_prune/#description

as a side note, I had a lot of issues when I used devicemapper driver on my environment. I used to clean as I mentioned, but there were still other devicemapper issues. I strongly recommend moving to overlay2, it solved almost everything completely.