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TASK 145: Kubernetes Shared Volumes

Requirements​

We are working on an application that will be deployed on multiple containers within a pod on Kubernetes cluster. There is a requirement to share a volume among the containers to save some temporary data. The Nautilus DevOps team is developing a similar template to replicate the scenario. Below you can find more details about it.

  • Create a pod named volume-share-devops.

  • For the first container:

    • use image ubuntu with latest tag only and remember to mention the tag i.e ubuntu:latest,

    • container should be named as volume-container-devops-1, and

    • run a sleep command for it so that it remains in running state.

    • Volume volume-share should be mounted at path /tmp/media.

  • For the second container,

    • use image ubuntu with the latest tag only and remember to mention the tag i.e ubuntu:latest,

    • container should be named as volume-container-devops-2, and

    • again run a sleep command for it so that it remains in running state.

    • Volume volume-share should be mounted at path /tmp/cluster.

    • Volume name should be volume-share of type emptyDir.

  • After creating the pod:

    • exec into the first container i.e volume-container-devops-1, and

    • just for testing create a file media.txt with any content under the mounted path of first container i.e /tmp/media.

    • The file media.txt should be present under the mounted path /tmp/cluster on the second container volume-container-devops-2 as well, since they are using a shared volume.

Note: The kubectl utility on jump_host has been configured to work with the kubernetes cluster.

Note

This document focuses on the implementation approach. The task statement in Requirements is preserved as the source requirement.

Prerequisites​

  • Access to the configured Kubernetes cluster from jump_host.
  • kubectl is configured and points to the correct context.
  • Use the task-specified namespace, resource names, and images exactly.

Steps​

Check the existing resources.

thor@jump_host ~$ kubectl get all  

NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
service/kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   27m

Create the deploy.yml based on the requirements.

apiVersion: v1
kind: Pod
metadata:
  name: volume-share-devops
  labels:
    name: devops
spec:
  volumes:
    - name: volume-share
      emptyDir: {}
  containers:
    - name: volume-container-devops-1
      image: ubuntu:latest
      command: ["/bin/bash", "-c", "sleep 10000"]
      volumeMounts:
        - name: volume-share
          mountPath: /tmp/media
    - name: volume-container-devops-2
      image: ubuntu:latest
      command: ["/bin/bash", "-c", "sleep 10000"]
      volumeMounts:
        - name: volume-share
          mountPath: /tmp/cluster

Apply. Then verify.

kubectl apply -f .
thor@jump_host ~$ kubectl get all  
NAME                      READY   STATUS    RESTARTS   AGE
pod/volume-share-devops   2/2     Running   0          16s

NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
service/kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   35m

Use exec to create the specified file inside the first container and verify.

kubectl exec -it volume-share-devops -c volume-container-devops-1  -- touch /tmp/media/media.txt  
thor@jump_host ~$ kubectl exec -it volume-share-devops -c volume-container-devops-1  -- ls -la /tmp/media 

total 8
drwxrwxrwx 2 root root 4096 Jul  6 13:49 .
drwxrwxrwt 1 root root 4096 Jul  6 13:48 ..
-rw-r--r-- 1 root root    0 Jul  6 13:49 media.txt

Since both containers share the same volume, the same file should also be accesible from the second container.

thor@jump_host ~$ kubectl exec -it volume-share-devops -c volume-container-devops-2  -- ls -la /tmp/cluster/
total 8
drwxrwxrwx 2 root root 4096 Jul  6 13:49 .
drwxrwxrwt 1 root root 4096 Jul  6 13:48 ..
-rw-r--r-- 1 root root    0 Jul  6 13:49 media.txt

Verification​

  • Confirm the required pods/services/deployments/jobs are in the expected state.
  • Run kubectl get commands for the affected resource types and namespace.

Resources​