9.1.2 Persistent volumes and claims

Figure 9.2 A Pod that references a PersistentVolumeClaim that gets bound to a PersistentVolume, which references a disk

Figure 9.3 The lifecycle of a PersistentVolumeClaim and PersistentVolume in a dynamically provisioned system

$ kubectl create -f Chapter09/9.1.2_PersistentVolume/pvc-mariadb.yaml
pod/mariadb-demo created
persistentvolumeclaim/mariadb-pv-claim created

Wait for the Pod, and the PVC to be created

$ kubectl get pvc -w
NAME               STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
mariadb-pv-claim   Pending                                      standard-rwo   36s
mariadb-pv-claim   Pending                                      standard-rwo   68s
mariadb-pv-claim   Pending                                      standard-rwo   68s
mariadb-pv-claim   Pending   pvc-45271397-f998-4ba4-9657-8df3fa0b1427   0                         standard-rwo   87s
mariadb-pv-claim   Bound     pvc-45271397-f998-4ba4-9657-8df3fa0b1427   2Gi        RWO            standard-rwo   87s

View the associate PV

$ kubectl get -o yaml pv pvc-45271397-f998-4ba4-9657-8df3fa0b1427
apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    pv.kubernetes.io/provisioned-by: pd.csi.storage.gke.io
    volume.kubernetes.io/provisioner-deletion-secret-name: ""
    volume.kubernetes.io/provisioner-deletion-secret-namespace: ""
  creationTimestamp: "2023-11-12T21:12:46Z"
  finalizers:
  - kubernetes.io/pv-protection
  - external-attacher/pd-csi-storage-gke-io
  name: pvc-45271397-f998-4ba4-9657-8df3fa0b1427
  resourceVersion: "583596"
  uid: 9afc9344-16d1-4a25-8edb-bcc4a0df959f
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 2Gi
  claimRef:
    apiVersion: v1
    kind: PersistentVolumeClaim
    name: mariadb-pv-claim
    namespace: default
    resourceVersion: "583340"
    uid: 45271397-f998-4ba4-9657-8df3fa0b1427
  csi:
    driver: pd.csi.storage.gke.io
    fsType: ext4
    volumeAttributes:
      storage.kubernetes.io/csiProvisionerIdentity: 1699782108094-9721-pd.csi.storage.gke.io
    volumeHandle: projects/gke-autopilot-test/zones/us-west1-b/disks/pvc-45271397-f998-4ba4-9657-8df3fa0b1427
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: topology.gke.io/zone
          operator: In
          values:
          - us-west1-b
  persistentVolumeReclaimPolicy: Delete
  storageClassName: standard-rwo
  volumeMode: Filesystem
status:
  phase: Bound

Figure 9.4 The PersistentVolumeClaim and PersistentVolume after the latter was provisioned, and they were bound together

Now the fun part, try it out:

kubectl port-forward pod/mariadb-demo 3306:3306

docker run --net=host -it --rm mariadb mariadb -h localhost -P 3306 \
-u root -p

The password, as shown in the deployment is your database password.

Run an example query:

MariaDB [(none)]> SELECT user, host FROM mysql.user;
+-------------+-----------+
| User        | Host      |
+-------------+-----------+
| root        | %         |
| healthcheck | 127.0.0.1 |
| healthcheck | ::1       |
| healthcheck | localhost |
| mariadb.sys | localhost |
| root        | localhost |
+-------------+-----------+
6 rows in set (0.007 sec)

MariaDB [(none)]> CREATE DATABASE foo;
Query OK, 1 row affected (0.004 sec)

MariaDB [(none)]> exit
Bye

Cleanup

kubectl delete pod/mariadb-demo
kubectl delete pvc/mariadb-pv-claim

Kubernetes for Developers

Practical learning guide to Kubernetes

9.1.2 Persistent volumes and claims

Cleanup