volume name is too short

[hanjiangxue20]

When I perform a quick installation，report an error，I'm using the master branch，How can I fix this, thank you.

`[root@Nian ceph-dev]# docker-compose up
WARNING: The CEPH_REPO_DIR variable is not set. Defaulting to a blank string.
WARNING: The ALERTMANAGER_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The GRAFANA_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The NODE_EXPORTER_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The PROMETHEUS_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The CEPH2_REPO_DIR variable is not set. Defaulting to a blank string.
Starting node-exporter ...
Creating ceph ... error
Starting node-exporter ... done
Starting prometheus ...
Starting alertmanager ... done
Starting prometheus ... done
Starting grafana ... done

ERROR: for ceph Cannot create container for service ceph: create .: volume name is too short, names should be at least two alphanumeric characters
ERROR: Encountered errors while bringing up the project.
`