hostPath Volume Demo¶

Let's see how we can use emptyDir volume as temporary storage.

Here is the Docker Image used in this tutorial: reyanshkharga/nginx

Step 1: Create a Deployment With hostPath Volume¶

Let's create a deployment as follows:

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apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: reyanshkharga/nginx:v1
        imagePullPolicy: Always
        command: ["/bin/sh"]
        args: ["-c", "while true; do echo $(date -u) >> /my-data/my-persistent-data.txt; sleep 5; done"]
        volumeMounts:
        - name: my-volume
          mountPath: /my-data
      volumes:
      - name: my-volume
        hostPath:
          path: /data
          type: DirectoryOrCreate

Observe the following:

1. We have added an hostPath volume in the pod template
2. Directory location for hostPath volume on host is /data
3. The pod has only one container
4. The hostPath volume is mounted on /my-data directory of the container
5. The container writes some data in the my-persistent-data.txt file every 5 seconds

Apply the manifest to create the deployment:

kubectl apply -f my-deployment.yml

Step 2: Verify Deployment and Pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

Step 3: Verify Volume Mount and Data¶

Let's verify if the hostPath volume was mounted in the container.

1. Start a shell session inside the container:

   kubectl exec -it <pod-name> -- bash
   

2. Verify if /my-data directory is present in the container:

   ls /my-data
   

3. View the content of /my-data/my-persistent-data.txt file:

   tail -f /my-data/my-persistent-data.txt
   

Step 4: Verify hostPath Volume on Worker Node¶

Let's verify if the /data directory was created on the host machine where the pod is running.

1. Find node where the pod is running:

   kubectl get pods -o wide
   

2. Access the worker node (EC2 Instance) by logging in through SSH or session manager.

3. Verify if /data directory is present and has my-persistent-data.txt file in it:

   ls /data
   

4. View the content of /data/my-persistent-data.txt file:

   tail -f /data/my-persistent-data.txt
   

Step 5: Delete the Deployment¶

Let's delete the deployment and see what happens to the hostPath volume.

kubectl delete -f manifests/

Step 6: Verify hostPath Volume on Worker Node Again¶

Access the node by logging in through SSH or session manager and verify if the data persists.

Observation:

1. The directory and files created by pods persists
2. Any data generated by pods persists.

Clean Up¶

Assuming your folder structure looks like the one below:

|-- manifests
│   |-- my-deployment.yml

Let's delete all the resources we created:

kubectl delete -f manifests/