Create Persistent Volume

Learn how to use PersistentVolume with NFS as a backend

Deploy and configure NFS server

note

Pay attention to which commands to execute on the host and which on each VM

Install an NFS server on cp1:

sudo apt-get install -y nfs-kernel-server

Create an NFS export directory and set the correct permissions on cp1:

sudo mkdir /srv/share
sudo chmod 1777 /srv/share
echo "Hello World Simple Website" > /srv/share/index.html

Export the NFS directory to the Kubernetes cluster nodes on cp1:

sudo vim /etc/exports
/srv/share/ *(rw,sync,no_root_squash,subtree_check)

On cp1, trigger volume export to worker nodes:

sudo exportfs -ra

Install the nfs-common package on all* Kubernetes nodes:

for SRV in cp1 worker{1,2,3}; do
sudo ssh $SRV apt-get install nfs-common -y;
done

Check if nodes can connect to shares:

for SRV in cp1 worker{1,2,3}; do
sudo ssh $SRV showmount -e k8scp;
done

See expected output

Export list for k8scp:
/srv/share *
Export list for k8scp:
/srv/share *
Export list for k8scp:
/srv/share *
Export list for k8scp:
/srv/share *

Prepare a YAML manifest for PersistentVolume:

pv-nfs.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  nfs:
    path: /srv/share
    server: k8scp
    readOnly: false

Apply the PersistentVolume YAML manifest:

kubectl apply -f pv-nfs.yaml

Check the PersistentVolumes list in the cluster:

kubectl get pv

See output

NAME     CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pv-nfs   10Gi       RWX            Retain           Available                                   6s

Create a new Namespace for the service:

kubectl create namespace webapp

To use PersistentVolume, it is required to create a PersistentVolumeClaim YAML manifest:

pvc-nfs.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-nfs
  namespace: webapp
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Gi

Apply the PersistentVolumeClaim manifest:

kubectl apply -f pvc-nfs.yaml

Get the list of PersistentVolumeClaims:

kubectl get pvc -n webapp

See output

NAME      STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-nfs   Bound    pv-nfs   10Gi       RWX                           13s

Let's create a new application that will use the PVC:

deploy-webapp-nfs.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: webapp-nfs
  name: webapp
  namespace: webapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: webapp-nfs
  template:
    metadata:
      labels:
        app: webapp-nfs
    spec:
      containers:
      - image: nginx:1.23.2
        name: nginx
        volumeMounts:
          - mountPath: "/usr/share/nginx/html"
            name: vol-nfs
      volumes:
        - name: vol-nfs
          persistentVolumeClaim:
            claimName: pvc-nfs

Deploy a web application with an NFS volume mounted:

kubectl apply -f deploy-webapp-nfs.yaml

Check Deployment status:

kubectl get deploy,rs,pods -n webapp

Verify PersistentVolume and PersisentVolumeClaim:

kubectl get pvc,pv -n webapp

Get Events messages from Namespace:

kubectl get events --sort-by='.lastTimestamp' -n webapp

Get Pod description:

kubectl describe pod -n webapp webapp-<Tab>

Open a port tunnel to any Pod instance from the webapp Deployment:

kubectl port-forward -n webapp pod/webapp-<Tab> 8080:80 &

Check the webapp response on localhost:

curl http://127.0.0.1:8080

To cleanup, remove the webapp Namespace:

kubectl delete ns webapp