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Environment Variables in Kubernetes.md

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Problem Statement: There are a number of parameters that are used by the applications. We need to define these as environment variables, so that we can use them as needed within different configs. Below is a scenario which needs to be configured on Kubernetes cluster. Please find below more details about the same.

  • Create a pod named envars.

  • Container name should be fieldref-container, use image busybox preferable latest tag, use command 'sh', '-c' and args should be

'while true; do echo -en '/n'; printenv NODE_NAME POD_NAME; printenv POD_IP POD_SERVICE_ACCOUNT; sleep 10; done;'

(Note: please take care of indentations)

  • Define Four environment variables as mentioned below: a.) The first env should be named as NODE_NAME, set valueFrom fieldref and fieldPath should be spec.nodeName.

    b.) The second env should be named as POD_NAME, set valueFrom fieldref and fieldPath should be metadata.name.

    c.) The third env should be named as POD_IP, set valueFrom fieldref and fieldPath should be status.podIP.

    d.) The fourth env should be named as POD_SERVICE_ACCOUNT, set valueFrom fieldref and fieldPath shoulbe be spec.serviceAccountName.

  • Set restart policy to Never.

  • To check the output, exec into the pod and use printenv command.

To configure and deploy the Kubernetes Pod with the specified environment variables and settings, follow the solution provided below:

Solution

1. Create the Pod Configuration

Create a YAML configuration file for the pod named envars that meets the requirements outlined. Save this YAML configuration to a file named envars-pod.yaml.

apiVersion: v1
kind: Pod
metadata:
  name: envars
spec:
  containers:
  - image: busybox:latest
    name: fieldref-container
    command: ["sh", "-c"]
    args:
    - |
      while true; do
        echo -en '/n';
        printenv NODE_NAME POD_NAME;
        printenv POD_IP POD_SERVICE_ACCOUNT;
        sleep 10;
      done;
    env:
    - name: NODE_NAME
      valueFrom:
        fieldRef:
          fieldPath: spec.nodeName
    - name: POD_NAME
      valueFrom:
        fieldRef:
          fieldPath: metadata.name
    - name: POD_IP
      valueFrom:
        fieldRef:
          fieldPath: status.podIP
    - name: POD_SERVICE_ACCOUNT
      valueFrom:
        fieldRef:
          fieldPath: spec.serviceAccountName
  restartPolicy: Never

2. Apply the YAML File

Deploy the pod using the kubectl apply command:

kubectl apply -f envars-pod.yaml

3. Verify the Pod Status

Check the status of the pod to ensure it's running correctly:

kubectl get pods

You should see output similar to:

NAME     READY   STATUS    RESTARTS   AGE
envars   1/1     Running   0          6s

4. Check the Environment Variables

To inspect the environment variables within the running pod, execute the printenv command inside the container:

kubectl exec -it envars -- sh

Once inside the pod, run:

printenv

Expected Output

You should see the environment variables along with other system environment variables:

POD_IP=10.244.0.5
KUBERNETES_SERVICE_PORT=443
KUBERNETES_PORT=tcp://10.96.0.1:443
HOSTNAME=envars
SHLVL=1
HOME=/root
NODE_NAME=kodekloud-control-plane
TERM=xterm
POD_NAME=envars
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
POD_SERVICE_ACCOUNT=default
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_SERVICE_HOST=10.96.0.1
PWD=/

Explanation

  • Pod Name: envars
  • Container Name: fieldref-container
  • Image: busybox:latest
  • Command: Executes a shell command that continually prints environment variables every 10 seconds.
  • Environment Variables:
    • NODE_NAME: Set to the node name where the pod is running.
    • POD_NAME: Set to the name of the pod.
    • POD_IP: Set to the IP address of the pod.
    • POD_SERVICE_ACCOUNT: Set to the service account name assigned to the pod.
  • Restart Policy: Set to Never to ensure the pod does not restart automatically.

This setup ensures that the pod continuously prints the environment variables, making it easy to verify their values.