Mastering Kubernetes One Task at a Time - Ephemeral Storage Volumes with 'emptyDir'-Shared emptyDir volume in a Pod

emptydir-shared-pod.sh

#!/usr/bin/bash

# Purpose: Mastering Kubernetes One Task at a Time - Ephemeral Storage Volumes with 'emptyDir'-Shared emptyDir Volume in a Pod
# Blog Ref: https://medium.com/the-aws-way/mastering-kubernetes-one-task-at-a-time-ephemeral-storage-volumes-with-emptydir-6cb08546b0ff
# GitHub Ref: https://github.com/jdluther2020/jdluther-kubernetes-io-tasks/

# Author's NOTE
#  1. # are comment lines
#  2. Command output wherever helpful is shown inside {}
#  3. Everything is executed on a local dev environment (MacOS)

#
# OBJECTIVE 1 - CREATE AN EMPTYDIR SHARED VOLUME FOR INTER-CONTAINER COMMUNICATION IN A POD
# - Create a pod with three containers, two sharing an emptyDir volumes type to communicate with each other
# - Ref: https://kubernetes.io/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/
#

cat <<EOF | tee emptydir-shared-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: emptydir-shared-pod
spec:
  volumes:
  - name: ehpemeral-volume
    emptyDir: {}
  containers:
  - name: nginx-container
    image: nginx
    volumeMounts:
    - name: ehpemeral-volume
      mountPath: /usr/share/nginx/html
  - name: debian-container
    image: debian
    volumeMounts:
    - name: ehpemeral-volume
      mountPath: /debian-data
    command: ['sh', '-c', 'echo "$HOSTNAME: Welcome to Nginx! Message written by Debian at `date`!!" > /debian-data/index.html']
  - name: busyboxplus-container
    image: radial/busyboxplus
    command: ['sh', '-c', 'sleep 3600']
  restartPolicy: Never
EOF

# Create pod
kubectl apply -f emptydir-shared-pod.yaml
{
pod/emptydir-shared-pod created
}

# Get pod status details and obtain POD_IP for next command
kubectl get -f emptydir-shared-pod.yaml -o wide
{
NAME                  READY   STATUS     RESTARTS   AGE   IP           NODE                               NOMINATED NODE   READINESS GATES
emptydir-shared-pod   2/3     NotReady   0          20s   10.244.1.2   basic-multi-node-cluster-worker2   <none>           <none>
}

# Access nginx web server via busyboxplus container
# See message from running nginx rcontainer written by terminated debian continaer.
kubectl exec emptydir-shared-pod -c busyboxplus-container -- curl -s 10.244.1.2
{
emptydir-shared-pod: Welcome to Nginx! Message written by Debian at Fri Apr 14 01:35:35 UTC 2023!!
}

# Proceed to OBJECTIVE 2