ConfigMaps: Kubernetes (k8s)

ConfigMaps in Kubernetes allow you to decouple configuration files from the container image. This allows you to change configuration without having to rebuild or redeploy the container image.

A ConfigMap can be created in Kubernetes in a variety of ways.

By creating a YAML file

By creating a YAML file with the configuration data and using the kubectl create command to create the ConfigMap.

Here is an example of a ConfigMap defined in a YAML file:

apiVersion: v1
kind: ConfigMap
metadata:
  name: example-config
data:
  example.property: value

This ConfigMap can be created by running the following command:

kubectl create -f example-config.yaml

By using the kubectl command

By using the kubectl create configmap command and specifying the configuration data on the command line.

kubectl create configmap example-config --from-literal=example.property=value

You can also use the --from-file option to create a ConfigMap from one or more files.

Once you have created a ConfigMap, you can reference it from a pod or deployment by using a volume and a volume mount. The following is an example of a pod that references a ConfigMap:

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  containers:
  - name: example
    image: nginx
    volumeMounts:
    - name: config
      mountPath: /etc/example
  volumes:
  - name: config
    configMap:
      name: example-config

In this example, the ConfigMap named “example-config” is mounted to the path “/etc/example” in the container. Now the configMap available inside pod container and the application running inside can use that configuration

You can also use ConfigMaps to set environment variables in a container. The following is an example of a pod that sets environment variables from a ConfigMap:

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  containers:
  - name: example
    image: nginx
    envFrom:
    - configMapRef:
        name: example-config

In this example, the pod’s container has all the key-value pairs in the example-config ConfigMap as environment variables.

You can also reference ConfigMap keys in the command and args sections of a pod spec. This allows you to use the ConfigMap data to configure the command and arguments that the container runs with.

Useful kubectl Commands

kubectl create configmap: This command creates a new ConfigMap. You can specify the configuration data using the --from-literal or --from-file options.

kubectl create configmap my-config --from-literal=key1=value1 --from-literal=key2=value2

kubectl create configmap my-config-file --from-file=path/to/configfile.txt

kubectl get configmap: This command retrieves information about one or more ConfigMaps.

kubectl get configmap my-config

kubectl describe configmap : This command provides detailed information about a specific ConfigMap.

kubectl describe configmap my-config

kubectl update configmap: This command updates an existing ConfigMap. You can use the --from-literal or --from-file options to update the configuration data.

kubectl update configmap my-config --from-literal=key1=new-value1

kubectl delete configmap: This command deletes one or more ConfigMaps.

kubectl delete configmap my-config

kubectl edit configmap : This command opens an editor to edit the ConfigMap in place.

kubectl edit configmap my-config

ConfigMaps are a powerful way to manage configuration data in Kubernetes. They allow you to decouple configuration files from container images, making it easier to update and manage configuration changes.