Run out of inodes

Today we encountered the problem that our build were failing during npm installs.

Running the gitlab-runner-docker-cleanup container did not help. Maybe because it did not run from the beginning in parallel.

I found we had endless volumes from old builds in /var/lib/docker/volumes of container which didn't exist any longer.

Running the following command freed the inodes: docker volume rm $(docker volume ls -qf dangling=true)

Maybe it's something to put in the docs here or for ci in general @ayufan