create empty rados index from ceph-nfs role fails when distributed as it assumes availability of client.admin locally this is using ceph-ansible-3.1.0-0.1.rc9 1. https://github.com/ceph/ceph-ansible/blob/master/roles/ceph-nfs/tasks/start_nfs.yml#L11
The fix is in the upstream stable-3.1 branch, so this fix will be in the next upstream tag after v3.1.0rc10.
Following the steps from Comment 8 , Deployed a ceph 3.1 cluster with nfs role on a dedicated node,it worked fine,Moving to to verified state. version: ceph-ansible 3.1.0-0.1.rc17.el7cp,ceph 12.2.5-39.el7cp.x86_64
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2018:2819