Permanent runners need to be cleaned periodically
So we do not hit #360 (closed) again
To cleanup all the docker stuff: (see https://docs.docker.com/engine/reference/commandline/system_prune/#examples)
docker system prune -a --volumes
We could use this as well: https://gitlab.com/gitlab-org/gitlab-runner-docker-cleanup
Upstream issue: https://gitlab.com/gitlab-org/gitlab-runner/issues/2980
Edited by Javier Jardón