Working with Pods

Simple Nginx Pod

Let's create a simple pod with Nginx container. We can create this in two ways - imperative or declarative (manifests).

Imperative command

kubectl run nginx-pod --image=nginx

kubectl run nginx-pod --image=nginx
pod/nginx-pod created

Manifest

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-container
    image: nginx

kubectl apply -f 1-pod.yaml
pod/nginx-pod created

Once the Pod is created, check the status:

kubectl get pods

kubectl get pods
NAME        READY   STATUS    RESTARTS   AGE
nginx-pod   1/1     Running   0          10m

Pod with Env

Let's create a pod with an environment variable. We can create this in two ways - imperative or declarative (manifests).

Imperative command

kubectl run sample-pod --image=nginx --env="TEST_ENV=Hello!"

Manifest

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-container
    image: nginx
    env:
    - name: TEST_ENV
      value: "Hello!"

How do we check if this environment variable is set in the container?

Normally on a server, you set an environment variable and execute the command echo $TEST_ENV to verify. Below is a way to verify the same in kubernetes.

kubectl exec sample-pod -c nginx-container -- sh -c 'echo $TEST_ENV'

kubectl exec sample-pod -c nginx-container -- sh -c 'echo $TEST_ENV'
Hello!

The -- in the command separates the kubectl command and the command to run inside the container. You may ask that we can directly run the command echo $TEST_ENV after the --.

If you run:

kubectl exec sample-pod -c nginx-container -- echo $TEST_ENV

we get an empty output. It will check for the TEST_ENV on the host. But the variable is set inside the container. So, we pass the actual command as arguments to the sh -c.