Conventional Approach of Supplying Environment Variables¶

Let's look at the conventional approach of supplying environment variables to containers running inside a pod.

Step 1: Create Pods That Uses Environment Variables¶

Let's create pods that uses environment variables. We'll use a deployment to create pods:

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apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        env:
        - name: key1
          value: value1
        - name: key2
          value: value2

Observe the following:

• We are using the keyword env to supply a list of environment variables to the nginx container
• In this example, we have supplied two environment variables; key1, and key2, with values value1 and value2, respectively.

Apply the manifest to create deployment:

kubectl apply -f my-deployment.yml

Step 2: Verify Deployment and Pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

Step 3: Verify Environment Variables¶

Start a shell session inside the container:

kubectl exec -it <pod-name> -- bash

List environment variables available to the container:

env

You'll see a list of environment variables available to the container. This includes both system-provided as well as user-provided environment variables.

Print values of the environment variables we set:

# Print value of the environment variable key1
echo $key1

# Print value of the environment variable key2
echo $key2

You'll notice the environment variables key1 and key2 are set to value1 and value2 respectively.

This method of supplying environment variables is acceptable if you have only a few of them. But, what if you have a significant number of environment variables? Adding all of them in the manifest file will needlessly bloat the manifest file.

In that case, you can use ConfigMap to supply a list of environment variables to containers in a pod. We'll explore this in the next section.

Clean Up¶

Assuming your folder structure looks like the one below:

|-- manifests
│   |-- my-deployment.yml

Let's delete all the resources we created:

kubectl delete -f manifests/