The two tasks at [1] and [2] for creation of the ceph_nfs rados index object assume the 'rados' command is available on the baremetal node where ceph_nfs is deployed, but that's not always true when deploying in containers. 1. https://github.com/ceph/ceph-ansible/blob/master/roles/ceph-nfs/tasks/start_nfs.yml#L3 2. https://github.com/ceph/ceph-ansible/blob/master/roles/ceph-nfs/tasks/start_nfs.yml#L11
The latest GA version of ceph-ansible is ceph-ansible-3.1.5-1.el7cp, from https://access.redhat.com/errata/RHBA-2018:2819