Version: main

Deploy an Application

This document explains how to deploy an application that uses OpenEBS Local Persistent Volumes (PV) backed by Hostpath. It walks through deploying a Pod that consumes a PersistentVolumeClaim (PVC) and verifying that the storage is dynamically provisioned and attached to the application.

Before You Begin

Install OpenEBS by following the Installation guide.
Create the local-hostpath-pvc PVC by following Create PersistentVolumeClaim. The PVC remains in Pending state until a Pod that uses it is scheduled, which is expected.

Create a Pod to Consume OpenEBS Local PV Hostpath Storage

Save the following Pod definition as local-hostpath-pod.yaml.

apiVersion: v1
kind: Pod
metadata:
  name: hello-local-hostpath-pod
spec:
  volumes:
  - name: local-storage
    persistentVolumeClaim:
      claimName: local-hostpath-pvc
  containers:
  - name: hello-container
    image: busybox
    command:
       - sh
       - -c
       - 'while true; do echo "`date` [`hostname`] Hello from OpenEBS Local PV." >> /mnt/store/greet.txt; sleep $(($RANDOM % 5 + 300)); done'
    volumeMounts:
    - mountPath: /mnt/store
      name: local-storage

note

The Local PV StorageClasses use WaitForFirstConsumer. Do not use nodeName in the Pod spec to select a node. If you do, the PVC remains in Pending state. Refer to the issue #2915 for more details.

Create the Pod.

kubectl apply -f local-hostpath-pod.yaml

Verify the Deployment

Verify that the container in the Pod is running.

Command
```
kubectl get pod hello-local-hostpath-pod
```

Verify that the data is being written to the volume.

Command

kubectl exec hello-local-hostpath-pod -- cat /mnt/store/greet.txt

Verify that the container is using the Local PV Hostpath.

Command

kubectl describe pod hello-local-hostpath-pod

The output shows the node that the Pod is running on and the persistent volume provided by local-hostpath-pvc.

Sample Output

Name:         hello-local-hostpath-pod
Namespace:    default
Priority:     0
Node:         gke-user-helm-default-pool-3a63aff5-1tmf/10.128.0.28
Start Time:   Thu, 16 Apr 2020 17:56:04 +0000
...
Volumes:
  local-storage:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  local-hostpath-pvc
    ReadOnly:   false
...

Check the PVC again to see the dynamically provisioned Local PV.

Command

kubectl get pvc local-hostpath-pvc

The STATUS is now Bound, and a new PV is listed under VOLUME.

Sample Output

NAME                 STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS       AGE
local-hostpath-pvc   Bound    pvc-864a5ac8-dd3f-416b-9f4b-ffd7d285b425   5Gi        RWO            openebs-hostpath   28m

Look at the PV details to see where the data is stored. Replace the PV name with the one displayed in the previous step.

Command

kubectl get pv pvc-864a5ac8-dd3f-416b-9f4b-ffd7d285b425 -o yaml

The output shows that the PV was provisioned in response to the PVC request spec.claimRef.name: local-hostpath-pvc.

Sample Output

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pvc-864a5ac8-dd3f-416b-9f4b-ffd7d285b425
  annotations:
    pv.kubernetes.io/provisioned-by: openebs.io/local
  ...
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 5Gi
  claimRef:
    apiVersion: v1
    kind: PersistentVolumeClaim
    name: local-hostpath-pvc
    namespace: default
    ...
  local:
    fsType: ""
    path: /var/openebs/local/pvc-864a5ac8-dd3f-416b-9f4b-ffd7d285b425
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - gke-user-helm-default-pool-3a63aff5-1tmf
  persistentVolumeReclaimPolicy: Delete
  storageClassName: openebs-hostpath
  volumeMode: Filesystem
status:
  phase: Bound

note

The output shows the following characteristics of an OpenEBS Local PV:

spec.nodeAffinity specifies the Kubernetes node where the Pod that uses the Hostpath volume is scheduled.
spec.local.path specifies the unique subdirectory under the BasePath defined in the StorageClass. The default BasePath is /var/openebs/local.

Cleanup

Delete the Pod and the PersistentVolumeClaim that you created.

kubectl delete pod hello-local-hostpath-pod
kubectl delete pvc local-hostpath-pvc

Verify that the PV that was dynamically created is also deleted.

kubectl get pv

Support

If you encounter issues or have a question, file a Github issue, or talk to us on the #openebs channel on the Kubernetes Slack server.

Before You Begin​

Create a Pod to Consume OpenEBS Local PV Hostpath Storage​

Verify the Deployment​

Cleanup​

Support​

See Also​

Before You Begin

Create a Pod to Consume OpenEBS Local PV Hostpath Storage

Verify the Deployment

Cleanup

Support

See Also