I'm trying to mount mongo /data directory on to a NFS volume in my kubernetes master machine for persisting mongo data. I see the volume is mounted successfully but I can see only configdb and db dirs but not their subdirectories. And I see the data is not even persisting in the volume. when I kubectl describe <my_pv> it shows NFS (an NFS mount that lasts the lifetime of a pod)

Why is that so?

I see in kubernetes docs stating that:

An nfs volume allows an existing NFS (Network File System) share to be mounted into your pod. Unlike emptyDir, which is erased when a Pod is removed, the contents of an nfs volume are preserved and the volume is merely unmounted. This means that an NFS volume can be pre-populated with data, and that data can be “handed off” between pods. NFS can be mounted by multiple writers simultaneously.

I'm using kubernetes version 1.8.3.

mongo-deployment.yml:

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: mongo
  labels:
    name: mongo
    app: mongo
spec:
  replicas: 3
  selector:
    matchLabels:
      name: mongo
      app: mongo
  template:
    metadata:
      name: mongo
      labels:
        name: mongo
        app: mongo
    spec:
      containers:
        - name: mongo
          image: mongo:3.4.9
          ports:
            - name: mongo
              containerPort: 27017
              protocol: TCP
          volumeMounts:
            - name: mongovol
              mountPath: "/data"
      volumes:
      - name: mongovol
        persistentVolumeClaim:
          claimName: mongo-pvc

mongo-pv.yml:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mongo-pv
  labels:
    type: NFS
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: slow
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: "/mongodata"
    server: 172.20.33.81

mongo-pvc.yml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mongo-pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 3Gi
  storageClassName: slow
  selector:
    matchLabels:
      type: NFS

The way I mounted my nfs share on my kubernetes master machine:

1) apt-get install nfs-kernel-server
2) mkdir /mongodata
3) chown nobody:nogroup -R /mongodata
4) vi /etc/exports
5) added the line "/mongodata *(rw,sync,all_squash,no_subtree_check)"
6) exportfs -ra
7) service nfs-kernel-server restart
8) showmount -e ----> shows the share

I logged into the bash of my pod and I see the directory is mounted correctly but data is not persisting in my nfs server (kubernetes master machine).

Please help me see what I am doing wrong here.