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To delete orphaned volumes in Docker 1.9 and up you can also use the built-in docker volume commands instead of this docker-cleanup-volumes script. The built-in command also deletes any directory in /var/lib/docker/volumes that is not a volume so make sure you didn't put anything in there you want to save:
List:

$ docker volume ls -qf dangling=true

Cleanup:

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

Or, handling a no-op better but Linux specific:

$ docker volume ls -qf dangling=true | xargs -r docker volume rm