There are several ways to inject environment variables into containers. The configuration-file env_config.yaml demonstrates two of them. Apply the config using:
kubectl apply -f env_config.yaml
Note
If you had the nginx containers running before, you will see a rolling update of all instances. Watch it using kubectl get pods.
After the pods have restarted connect to one or more of them using:
kubectl exec -ti nginx-... sh
Find the complete name of the pod by using kubectl get pods. If you have shell completion installed for kubectl it might be enogh to press tab after nginx.
Inside the container try echoing the injected environment variables:
# echo $VIA_CONFIGMAP
From Configmap
# echo $VIA_SPEC
From Spec
In more complex scenarios you can store complete directories as configuration and mount them into a pod.
In this example we have a website stored in a directory www which will be mounted into a pod as the source for an nginx server. In order to store the directory as a configuration into the cluster we use a script that itself calls kubectl in an imperative way.
./create_config.sh
You can see the configuration by looking it up at the kubernetes dashboard or by querying it using the kubectl command:
kubectl get configmap
kubectl describe configmap content
The kubernetes configuration in config_nginx.yaml mounts the stored configuration data into the pods. To apply it use:
kubectl apply -f config_nginx.yaml
You can see the resulting website by opening a browser pointing to the service. For minikube use the following command:
minikube service nginx