100-Days-Of-DevOps-Challenge-KodeKloud

Kubernetes Shared Volumes

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-nautilus.

• For the first container, use image fedora with latest tag only and remember to mention the tag i.e fedora:latest, container should be named as volume-container-nautilus-1, and run a sleep command for it so that it remains in running state. Volume volume-share should be mounted at path /tmp/news.

• For the second container, use image fedora with the latest tag only and remember to mention the tag i.e fedora:latest, container should be named as volume-container-nautilus-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/demo.

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

• After creating the pod, exec into the first container i.e volume-container-nautilus-1, and just for testing create a file news.txt with any content under the mounted path of first container i.e /tmp/news.

• The file news.txt should be present under the mounted path /tmp/demo on the second container volume-container-nautilus-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.

Steps

1. Let’s create the k3s-pod.yml file using the contnets

2. Create the pod

    kubectl apply -f k3s-pod.yml
   

3. Execute the first container

    kubectl exec -it volume-share-nautilus -c volume-container-nautilus-1 /bin/sh
   

   Create news.txt file

    touch /tmp/news/news.txt
   

4. Execute the 2nd container

    kubectl exec -it volume-share-nautilus -c volume-container-nautilus-2 /bin/sh
   

   Verify the created files under shared directory

    ls /tmp/demo
   

Good to Know?

Shared Volumes

• emptyDir: Temporary storage shared between containers
• Pod Lifetime: Volume exists for pod’s lifetime
• Memory Storage: Can use memory as storage medium
• Data Sharing: Enable inter-container communication

Volume Types

• emptyDir: Empty directory, deleted when pod removed
• hostPath: Mount directory from host node
• persistentVolumeClaim: Persistent storage
• configMap/secret: Configuration and sensitive data

Multi-Container Use Cases

• Log Shipping: Sidecar collects and ships logs
• Data Processing: One container produces, another consumes
• Configuration Sharing: Share config files between containers
• Backup Operations: Backup container accesses main app data

Container Communication

• Shared Filesystem: Files written by one, read by another
• Localhost Network: Containers share network namespace
• Process Signals: Containers can send signals to each other
• Resource Sharing: Share CPU, memory, and storage resources

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