luc.run

Exercise

Create the folder /tmp/data on worker1
Create the specification of a PersistentVolume with the accessMode ReadWriteOnce, a storage capacity of 1Gi, a storage of type hostPath based on the folder /tmp/data, and specify the storage class manual
Modify the specification to make sure this PersistentVolume is related to worker1

Hint: you can use the nodeAffinity property in the PersistentVolume specification

Create the PersistentVolume
Create a PersistentVolumeClaim with accessMode ReadWriteOnce accessMode, a storage capacity of 500Mi and the storage class manual
Make sure the PVC is bound to the PV
Create a Pod named www, with a single nginx container based on nginx:1.20. Use the PersistentVolumeClaim as a volume and mount it in /usr/share/nginx/html. Where is this Pod scheduled ?
Create the file index.html containing the string hello in /tmp/data/ on worker1
Send a request to the nginx container and make sure you get the content of the previous file
Delete the Pod, the PV and the PVC. Also remove the /tmp/data folder on worker1

Documentation

Solution

Create the folder /tmp/data on worker1

From a shell on worker1

mkdir /tmp/data

Create a PersistentVolume with the accessMode ReadWriteOnce, a storage capacity of 1Gi, a storage of type hostPath based on the folder /tmp/data, and specify the storage class manual

cat <<EOF > pv.yaml
apiVersion: v1
kind: PersistentVolume
metadata: 
  name: pv
spec: 
  storageClassName: "manual"
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  hostPath:
    path: /tmp/data
EOF

Modify the specification to make sure this PersistentVolume is related to worker1

We had a nodeAffinity constraint that links the PersistentVolume to worker1

apiVersion: v1
kind: PersistentVolume
metadata: 
  name: pv
spec: 
  storageClassName: "manual"
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  hostPath:
    path: /tmp/data
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - worker1

Create the PersistentVolume

k apply -f pv.yaml

Create a PersistentVolumeClaim with accessMode ReadWriteOnce accessMode, a storage capacity of 500Mi and the storage class manual

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata: 
  name: pvc
spec: 
  storageClassName: "manual"
  accessModes:
    - ReadWriteOnce
  resources:
    requests: 
      storage: 500Mi
EOF

Make sure the PVC is bound to the PV

Because the characteristics needed by the PersistentVolumeClaim match the ones offered by the PersistentVolume, the PVC is bound to the PV

k get pvc,pv
NAME                        STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/pvc   Bound    pv       1Gi        RWO            manual         5s

NAME                  CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM         STORAGECLASS   REASON   AGE
persistentvolume/pv   1Gi        RWO            Retain           Bound    default/pvc   manual                  49s

Create a Pod named www, with a single nginx container based on nginx:1.20. Use the PersistentVolumeClaim as a volume and mount it in /usr/share/nginx/html. Where is this pod scheduled ?

Create a Pod specification

k run www --image=nginx:1.20 --dry-run=client -o yaml > www.yaml

Modification of the specification to define a volume and mount it into the container’s filesystem:

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: www
  name: www
spec:
  containers:
  - image: nginx:1.20
    name: www
    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html
  volumes:
  - name: data
    persistentVolumeClaim:
      claimName: pvc

Creation of the Pod

k apply -f www.yaml

This Pod is scheduled on worker1, the node associated to the PersistentVolume

k get po -o wide
NAME   READY   STATUS    RESTARTS   AGE   IP          NODE      NOMINATED NODE   READINESS GATES
www    1/1     Running   0          4s    10.32.0.2   worker1   <none>           <none>

Create the file index.html containing the string hello in /tmp/data/ on worker1

From a shell on worker1

echo "hello" | sudo tee /tmp/data/index.html

Send a request to the nginx container and make sure you get the content of the previous file

k exec www -- curl -s localhost
hello

Delete the Pod, the PV and the PVC. Also remove the /tmp/data folder on worker1

k delete po www
k delete pvc/pvc pv/pv

From a shell on worker1

rm -fr /tmp/data