kubernetes - How to manual recover a PV

Question

according to the official docs https://kubernetes.io/docs/tasks/administer-cluster/change-pv-reclaim-policy/ with the “Retain” policy a PV can be manually recovered . What does that actually mean and is there a tool how I can read the data from that "retained" PV and write it into to another PV , or does it mean you can mount that volume manual in order to gain access ?

Answer 1

The process to manually recover the volume is as below.

You can use the same PV to mount to different pod along with the data even after the PVC is deleted (PV must exist, will typically exist if the reclaim policy of storageclass is Retain)

Verify that PV is in released state. (ie no pvc has claimed it currently)

 ?  ~ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM                     STORAGECLASS   REASON   AGE
pvc-eae6acda-59c7-11e9-ab12-06151ee9837e   16Gi       RWO            Retain           Released   default/dhanvi-test-pvc   gp2                     52m

Edit the PV (kubectl edit pv pvc-eae6acda-59c7-11e9-ab12-06151ee9837e) and remove the spec.claimRef part. The PV claim would be unset like below.

 ?  ~ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pvc-eae6acda-59c7-11e9-ab12-06151ee9837e   16Gi       RWO            Retain           Available           gp2                     57m

Then claim the PV using PVC as below.

---

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: dhanvi-test-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 16Gi
  volumeName: "pvc-eae6acda-59c7-11e9-ab12-06151ee9837e"

Can be used in the pods as below.

volumes:
- name: dhanvi-test-volume
  persistentVolumeClaim:
    claimName: dhanvi-test-pvc

Update: Volume cloning might help https://kubernetes.io/blog/2019/06/21/introducing-volume-cloning-alpha-for-kubernetes/