How to Configure NFS based Persistent Volume in Kubernetes

It is recommended to place pod’s data into some persistent volume so that data will be available even after pod termination. In Kubernetes (k8s), NFS based persistent volumes can be used inside the pods. In this article we will learn how to configure persistent volume and persistent volume claim and then we will discuss, how we can use the persistent volume via its claim name in k8s pods.

I am assuming we have a functional k8s cluster and NFS Server. Following are details for lab setup,

• NFS Server IP = 192.168.1.40
• NFS Share = /opt/k8s-pods/data
• K8s Cluster = One master and two worker Nodes

Note: Make sure NFS server is reachable from worker nodes and try to mount nfs share on each worker once for testing.

Create a Index.html file inside the nfs share because we will be mounting this share in nginx pod later in article.

[kadmin@k8s-master ~]$ echo "Hello, NFS Storage NGINX" > /opt/k8s-pods/data/index.html

Configure NFS based PV (Persistent Volume)

To create an NFS based persistent volume in K8s, create the yaml file on master node with the following contents,

[kadmin@k8s-master ~]$ vim nfs-pv.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
spec:
  capacity:
    storage: 10Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: nfs
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: /opt/k8s-pods/data
    server: 192.168.1.40

Save and exit the file

Now create persistent volume using above created yaml file, run

[kadmin@k8s-master ~]$ kubectl create -f nfs-pv.yaml
persistentvolume/nfs-pv created
[kadmin@k8s-master ~]$

Run following kubectl command to verify the status of persistent volume

[kadmin@k8s-master ~]$ kubectl get pv
NAME     CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
nfs-pv   10Gi       RWX            Recycle          Available           nfs                     20s
[kadmin@k8s-master ~]$

Above output confirms that PV has been created successfully and it is available.

Configure Persistent Volume Claim

To mount persistent volume inside a pod, we have to specify its persistent volume claim. So,let’s create persistent volume claim using the following yaml file

[kadmin@k8s-master ~]$ vi nfs-pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-pvc
spec:
  storageClassName: nfs
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 10Gi

Save and exit file.

Run the beneath kubectl command to create pvc using above yaml file,

[kadmin@k8s-master ~]$ kubectl create -f nfs-pvc.yaml
persistentvolumeclaim/nfs-pvc created
[kadmin@k8s-master ~]$

After executing above, control plane will look for persistent volume which satisfy the claim requirement with same storage class name and then it will bind the claim to persistent volume, example is shown below:

[kadmin@k8s-master ~]$ kubectl get pvc nfs-pvc
NAME      STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
nfs-pvc   Bound    nfs-pv   10Gi       RWX            nfs            3m54s
[kadmin@k8s-master ~]$
[kadmin@k8s-master ~]$ kubectl get pv nfs-pv
NAME     CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM             STORAGECLASS   REASON   AGE
nfs-pv   10Gi       RWX            Recycle          Bound    default/nfs-pvc   nfs                     18m
[kadmin@k8s-master ~]$

Above output confirms that claim (nfs-pvc) is bound with persistent volume (nfs-pv).

Now we are ready to use nfs based persistent volume nside the pods.

Use NFS based Persistent Volume inside a Pod

Create a nginx pod using beneath yaml file, it will mount persistent volume claim on ‘/usr/share/nginx/html’

[kadmin@k8s-master ~]$ vi nfs-pv-pod
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pv-pod
spec:
  volumes:
    - name: nginx-pv-storage
      persistentVolumeClaim:
        claimName: nfs-pvc
  containers:
    - name: nginx
      image: nginx
      ports:
        - containerPort: 80
          name: "nginx-server"
      volumeMounts:
        - mountPath: "/usr/share/nginx/html"
          name: nginx-pv-storage

Save and close the file.

Now create the pod using above yaml file, run

[kadmin@k8s-master ~]$ kubectl create -f nfs-pv-pod.yaml
pod/nginx-pv-pod created
[kadmin@k8s-master ~]$
[kadmin@k8s-master ~]$ kubectl get pod nginx-pv-pod -o wide
NAME           READY   STATUS    RESTARTS   AGE   IP           NODE           NOMINATED NODE   READINESS GATES
nginx-pv-pod   1/1     Running   0          66s   172.16.140.28 k8s-worker-2   <none>           <none>
[kadmin@k8s-master ~]$

Note: To get more details about pod, kubectl describe pod <pod-name>

Above commands output confirm that pod has been created successfully. Now try to access nginx page using curl command

[kadmin@k8s-master ~]$ curl http://172.16.140.28
Hello, NFS Storage NGINX
[kadmin@k8s-master ~]$

Perfect, above curl command’s output confirms that persistent volume is mounted correctly inside pod as we are getting the contents of index.html file which is present on NFS share.

This concludes the article, I believe you guys got some basic idea on how to configure and use NFS based persistent volume inside Kubernetes pods.

Also Read : How to Setup Kubernetes(k8s) Cluster in HA with Kubeadm

Also Read : How to Install and Use Helm in Kubernetes