data-migrate utility

utils/data-migrate/README.md

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+1. run the application you need
+2. wait for its PVs to be created
+3. suspend the application: `kubectl scale deployment/statefulset/... NAME -n NAMESPACE --replicas=0`
+4. wait for it to scale down so that the ReadWriteOnce PVs are released (or data-migrate will not be able to mount them)
+5. look up the destination PVC name you need: `kubectl get pvc NAME -n NAMESPACE`
+6. put the source host(node) and dir and destination PVC name to `install.yaml`
+7. install the data-migrate: `kubectl create namespace data-migrate && kubectl delete pod data-migrate -n data-migrate --ignore-not-found=true && kubectl apply -f install.yaml`
+8. run the migration: `kubectl exec data-migrate -n data-migrate -- cp -a /old/. /new/` or anything you need instead of `cp`
+9. validate you have everything migrated: `kubectl exec data-migrate -n data-migrate -- ls -laR /new`
+10. uninstall the data-migrate: `kubectl delete pod data-migrate -n data-migrate`
+11. resume the application back: `kubectl scale deployment/statefulset/... NAME -n NAMESPACE --replicas=1`

utils/data-migrate/install.yaml

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+apiVersion: v1
+kind: Pod
+metadata:
+  name: data-migrate
+  namespace: data-migrate
+spec:
+  restartPolicy: Never
+  containers:
+    - name: migrate
+      image: busybox
+      command: ["sleep", "3600"]
+      volumeMounts:
+        - name: old-data
+          mountPath: /old
+        - name: new-data
+          mountPath: /new
+  nodeName: <NODE_NAME_THAT_HAS_DIR_YOU_WANT_TO_MIGRATE_FROM>
+  volumes:
+    - name: old-data
+      hostPath:
+        path: <DIR_YOU_WANT_TO_MIGRATE_FROM>
+    - name: new-data
+      persistentVolumeClaim:
+        claimName: <PVC_YOU_WANT_TO_MIGRATE_TO>