Category: DevOps Tools

Kubernetes volumes offer a simple way to mount external storage to containers. This lab will test your knowledge of volumes as you provide storage to some containers according to a provided specification. This will allow you to practice what you know about using Kubernetes volumes.

Create a Pod That Outputs Data to the Host Using a Volume

• Create a Pod that will interact with the host file system by using vi maintenance-pod.yml.

apiVersion: v1
kind: Pod
metadata:
    name: maintenance-pod
spec:
    containers:
    - name: busybox
      image: busybox
      command: ['sh', '-c', 'while true; do echo Success! >> /output/output.txt; sleep 5; done']

• Under the basic YAML, begin creating volumes, which should be level with the containers spec:

volumes:
- name: output-vol
  hostPath:
      path: /var/data

• In the containers spec of the basic YAML, add a line for volume mounts:

volumeMounts:
- name: output-vol
  mountPath: /output

The complete YAML will be

apiVersion: v1
kind: Pod
metadata:
    name: maintenance-pod
spec:
  containers:
    - name: busybox
      image: busybox
      command: ['sh', '-c', 'while true; do echo Success! >> /output/output.txt; sleep 5; done']
      volumeMounts:
      - name: output-vol
        mountPath: /output
  volumes:
   - name: output-vol
     hostPath:
      path: /var/data

Create a Multi-Container Pod That Shares Data Between Containers Using a Volume

1. Create another YAML file for a shared-data multi-container Pod by using vi shared-data-pod.yml
2. Start with the basic Pod definition and add multiple containers, where the first container will write the output.txt file and the second container will read the output.txt file:

apiVersion: v1
kind: Pod
metadata:
    name: shared-data-pod
spec:
    containers:
    - name: busybox1
      image: busybox
      command: ['sh', '-c', 'while true; do echo Success! >> /output/output.txt; sleep 5; done']
    - name: busybox2
      image: busybox
      command: ['sh', '-c', 'while true; do cat /input/output.txt; sleep 5; done']

Set up the volumes, again at the same level as containers with an emptyDir volume that only exists to share data between two containers in a simple way:

volumes:
- name: shared-vol
  emptyDir: {}

Mount that volume between the two containers by adding the following lines under command for the busybox1 container:

volumeMounts:
- name: shared-vol
  mountPath: /output

For the busybox2 container, add the following lines to mount the same volume under command to complete creating the shared file:

volumeMounts:
- name: shared-vol
  mountPath: /input

The complete file

Finish creating the multi-container Pod using kubectl create -f shared-data-pod.yml.

apiVersion: v1
kind: Pod
metadata:
    name: shared-data-pod
spec:
    containers:
    - name: busybox1
      image: busybox
      command: ['sh', '-c', 'while true; do echo Success! >> /output/output.txt; sleep 5; done']
      volumeMounts:
        - name: shared-vol
          mountPath: /output
    - name: busybox2
      image: busybox
      command: ['sh', '-c', 'while true; do cat /input/output.txt; sleep 5; done']
      volumeMounts:
        - name: shared-vol
          mountPath: /input
    volumes:
    - name: shared-vol
    emptyDir: {}

And you can now apply the YAML file.

Cheers

Osama