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Kubernetes Shared Volumes.md

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Problem Statement

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-datacenter

  • For the first container, use image debian with latest tag only and remember to mention the tag i.e debian:latest, container should be named as volume-container-datacenter-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 debian with the latest tag only and remember to mention the tag i.e debian:latest, container should be named as volume-container-datacenter-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/games

  • Volume name should be volume-share of type emptyDir

  • After creating the pod, exec into the first container i.e volume-container-datacenter-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/games on the second container volume-container-datacenter-2 as well, since they are using a shared volume

To achieve the goal of sharing a volume between two containers within a Kubernetes pod, follow these steps to configure and verify the shared volume. Here’s how you can set up and test this scenario:

Solution

1. Create the Pod Configuration

We will create a pod named volume-share-datacenter with two containers:

  • Container 1 (volume-container-datacenter-1): Uses the debian:latest image and mounts the shared volume at /tmp/media.
  • Container 2 (volume-container-datacenter-2): Also uses the debian:latest image and mounts the same shared volume at /tmp/games.

The shared volume will be of type emptyDir, which provides a temporary storage that is shared between the containers in the pod.

Save the following YAML configuration to a file named volume-share-pod.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: volume-share-datacenter
spec:
  containers:
  - name: volume-container-datacenter-1
    image: debian:latest
    command:
    - "/bin/sh"
    - "-c"
    - "sleep 3600"  # Keeps the container running
    volumeMounts:
    - name: volume-share
      mountPath: /tmp/media

  - name: volume-container-datacenter-2
    image: debian:latest
    command:
    - "/bin/sh"
    - "-c"
    - "sleep 3600"  # Keeps the container running
    volumeMounts:
    - name: volume-share
      mountPath: /tmp/games

  volumes:
  - name: volume-share
    emptyDir: {}

Apply the Pod configuration:

kubectl apply -f volume-share-pod.yaml

Check the status of the pod:

kubectl get pods

You should see the pod volume-share-datacenter with the status Running.

2. Create a File in the Shared Volume

Next, exec into the first container to create a file in the shared volume.

kubectl exec -it volume-share-datacenter -c volume-container-datacenter-1 -- /bin/bash

Inside the container, navigate to the mounted path and create a file:

cd /tmp/media
echo "This is a test file." > media.txt

3. Verify File Presence in the Second Container

Now, exec into the second container and check if the file is visible in the shared volume:

kubectl exec -it volume-share-datacenter -c volume-container-datacenter-2 -- /bin/bash

Navigate to the mounted path and list the files:

cd /tmp/games
ls

You should see media.txt listed, confirming that the file created in the first container is visible in the second container as well.

Summary

  1. Pod Configuration: A pod volume-share-datacenter is created with two containers, both using the debian:latest image. A shared volume named volume-share is mounted at different paths in each container.
  2. Volume Sharing: The emptyDir volume type is used to create a temporary shared storage.
  3. Testing: After deploying the pod, you create a file in the shared volume from one container and verify its presence in the other container to ensure proper volume sharing.

This setup confirms that the shared volume between containers works as expected, allowing data to be exchanged between the containers in the same pod.