We already have an NFS server so the next step is to install NFS client as a StorageClass. We'll use kubernetes nfs-client-provisioner.
Since the provisioner will need to interact with Kube API and we have RBAC enabled, the first step is to create a ServiceAccount.
curl https://raw.githubusercontent.com/kubernetes-incubator/external-storage/master/nfs-client/deploy/auth/serviceaccount.yaml