Use ConfigMap to Supply Environment Variables¶

Let's see how we can use ConfigMap to supply environment variables to containers running inside in a pod.

Step 1: Create a ConfigMap¶

Let's create a ConfigMap with data that contains the required environment variables.

1
2
3
4
5
6
7

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-configmap
data:
  foo1: bar1
  foo2: bar2

Apply the manifest to create ConfigMap:

kubectl apply -f my-configmap.yml

Step 2: Verify ConfigMap¶

# List configmaps
kubectl get cm

# Describe the configmap
kubectl describe cm my-configmap

Step 3: Create Pods That Uses Environment Variables¶

Let's create pods that uses ConfigMap to set environment variables for the container. We'll use a deployment to create pods:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20

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
        envFrom:
        - configMapRef:
            name: my-configmap

Observe that we are using the keyword envFrom to supply a list of environment variables from the ConfigMap my-configmap.

Apply the manifest to create deployment:

kubectl apply -f my-deployment.yml

Step 4: Verify Deployment and Pods¶

# List deployments
kubectl get deployments

# List pods
kubectl get pods

Step 5: 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 foo1
echo $foo1

# Print value of the environment variable foo2
echo $foo2

You'll notice the environment variables foo1 and foo2 are set to bar1 and bar2 respectively.

Now, what if you want to use ConfigMap for the environemnt variables but also want to supply additional environment variables directly in the pod definition?

In that case, you can use both the env and envFrom field. We'll explore this in the next section.

Clean Up¶

Assuming your folder structure looks like the one below:

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

Let's delete all the resources we created:

kubectl delete -f manifests/