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Kubernetes : Dynamic Volume Provisioning (NFS)2023/07/28

 

To use Dynamic Volume Provisioning feature when using Persistent Storage, it's possible to create PV (Persistent Volume) dynamically without creating PV manually by Cluster Administrator when created PVC (Persistent Volume Claim) by users.

This example is based on the environment like follows.

For example, run NFS Server on Control Plane Node and configure dynamic volume provisioning with NFS provisioner.

-----------+---------------------------+--------------------------+------------
           |                           |                          |
       eth0|10.0.0.25              eth0|10.0.0.71             eth0|10.0.0.72
+----------+-----------+   +-----------+-----------+   +-----------+-----------+
|  [ ctrl.srv.world ]  |   |  [snode01.srv.world]  |   |  [snode02.srv.world]  |
|     Control Plane    |   |      Worker Node      |   |      Worker Node      |
+----------------------+   +-----------------------+   +-----------------------+

[1]
Run NFS Server on Control Plane Node, refer to here.
On this example, configure [/home/nfsshare] directory as NFS share.
[2]
[3] Install NFS Client Provisioner with Helm.
root@ctrl:~#
helm repo add nfs-subdir-external-provisioner https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/
# nfs.server = (NFS server's hostname or IP address)
# nfs.path = (NFS share Path)

root@ctrl:~#
helm install nfs-client -n kube-system --set nfs.server=10.0.0.25 --set nfs.path=/home/nfsshare nfs-subdir-external-provisioner/nfs-subdir-external-provisioner
NAME: nfs-client
LAST DEPLOYED: Fri Jul 28 01:35:08 2023
NAMESPACE: kube-system
STATUS: deployed
REVISION: 1
TEST SUITE: None

root@ctrl:~#
kubectl get pods -n kube-system

NAME                                                         READY   STATUS    RESTARTS       AGE
.....
.....
nfs-client-nfs-subdir-external-provisioner-8689b9b8c6-n4s2f   1/1     Running   0          28s
[4] This is an example to use dynamic volume provisioning by a Pod.
root@ctrl:~#
kubectl get pv

No resources found in default namespace.
root@ctrl:~#
kubectl get pvc

No resources found in default namespace.
root@ctrl:~#
kubectl get storageclass

NAME         PROVISIONER                                                RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
nfs-client   cluster.local/nfs-client-nfs-subdir-external-provisioner   Delete          Immediate           true                   2m10s

# create PVC

root@ctrl:~#
vi my-pvc.yml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-provisioner
  annotations:
    # specify StorageClass name
    volume.beta.kubernetes.io/storage-class: nfs-client
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      # volume size
      storage: 5Gi

root@ctrl:~#
kubectl apply -f my-pvc.yml

persistentvolumeclaim/my-provisioner created
root@ctrl:~#
kubectl get pvc

NAME             STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
my-provisioner   Bound    pvc-b3f9795c-95c6-4fc5-926c-80bdbc2e4296   5Gi        RWO            nfs-client     9s

# PV is generated dynamically

root@ctrl:~#
kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                    STORAGECLASS   REASON   AGE
pvc-b3f9795c-95c6-4fc5-926c-80bdbc2e4296   5Gi        RWO            Delete           Bound    default/my-provisioner   nfs-client              34s

root@ctrl:~#
vi my-pod.yml
apiVersion: v1
kind: Pod
metadata:
  name: my-mginx
spec:
  containers:
    - name: my-mginx
      image: nginx
      ports:
        - containerPort: 80
          name: web
      volumeMounts:
      - mountPath: /usr/share/nginx/html
        name: nginx-pvc
  volumes:
    - name: nginx-pvc
      persistentVolumeClaim:
        # PVC name you created
        claimName: my-provisioner

root@ctrl:~#
kubectl apply -f my-pod.yml

pod/my-mginx created
root@ctrl:~#
kubectl get pod my-mginx -o wide

NAME       READY   STATUS    RESTARTS   AGE   IP                NODE                NOMINATED NODE   READINESS GATES
my-mginx   1/1     Running   0          6s    192.168.211.142   snode02.srv.world   <none>           <none>

root@ctrl:~#
kubectl exec my-mginx -- df /usr/share/nginx/html

Filesystem                                                                               1K-blocks    Used Available Use% Mounted on
10.0.0.25:/home/nfsshare/default-my-provisioner-pvc-b3f9795c-95c6-4fc5-926c-80bdbc2e4296  80503808 4645888  71723008   7% /usr/share/nginx/html

# verify accessing to create test index file

root@ctrl:~#
echo "Nginx Index" > index.html

root@ctrl:~#
kubectl cp index.html my-mginx:/usr/share/nginx/html/index.html

root@ctrl:~#
curl 192.168.211.142

Nginx Index
# when removing, to remove PVC, then PV is also removed dynamically

root@ctrl:~#
kubectl delete pod my-mginx

pod "my-mginx" deleted
root@ctrl:~#
kubectl delete pvc my-provisioner

persistentvolumeclaim "my-provisioner" deleted
root@ctrl:~#
kubectl get pv

No resources found in default namespace.
[5] To use StatefulSet, it's possible to specify [volumeClaimTemplates].
root@ctrl:~#
kubectl get pv

No resources found in default namespace.
root@ctrl:~#
kubectl get pvc

No resources found in default namespace.
root@ctrl:~#
kubectl get storageclass

NAME         PROVISIONER                                                RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
nfs-client   cluster.local/nfs-client-nfs-subdir-external-provisioner   Delete          Immediate           true                   6m54s

root@ctrl:~#
vi statefulset.yml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: my-mginx
spec:
  serviceName: my-mginx
  replicas: 1
  selector:
    matchLabels:
      app: my-mginx
  template:
    metadata:
      labels:
        app: my-mginx
    spec:
      containers:
      - name: my-mginx
        image: nginx
        volumeMounts:
        - name: data
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      # specify StorageClass name
      storageClassName: nfs-client
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 5Gi

root@ctrl:~#
kubectl apply -f statefulset.yml

statefulset.apps/my-mginx created
root@ctrl:~#
kubectl get statefulset

NAME       READY   AGE
my-mginx   1/1     10s

root@ctrl:~#
kubectl get pods -o wide

NAME         READY   STATUS    RESTARTS   AGE   IP                NODE                NOMINATED NODE   READINESS GATES
my-mginx-0   1/1     Running   0          17s   192.168.211.143   snode02.srv.world   <none>           <none>

root@ctrl:~#
kubectl get pvc

NAME              STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
data-my-mginx-0   Bound    pvc-0eff9731-5cb6-4b75-9772-202d2f9d27f7   5Gi        RWO            nfs-client     45s

root@ctrl:~#
kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                     STORAGECLASS   REASON   AGE
pvc-0eff9731-5cb6-4b75-9772-202d2f9d27f7   5Gi        RWO            Delete           Bound    default/data-my-mginx-0   nfs-client              59s
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