Config maps

“https://kubernetes.io/docs/concepts/configuration/configmap/”

There are four different ways that you can use a ConfigMap to configure a container inside a Pod:

1. Inside a container command and args
2. Environment variables for a container
3. Add a file in read-only volume, for the application to read
4. Write code to run inside the Pod that uses the Kubernetes API to read a ConfigMap

Gotchas

• ConfigMap does not provide secrecy or encryption.
• ConfigMaps consumed as environment variables are not updated automatically and require a pod restart.
  • When a ConfigMap currently consumed in a volume is updated, projected keys are eventually updated as well
    • A container using a ConfigMap as a subPath volume mount will not receive ConfigMap updates.
• A ConfigMap is not designed to hold large chunks of data. The data stored in a ConfigMap cannot exceed 1 MiB
• The name of a ConfigMap must be a valid DNS subdomain name.
• The Pod and the ConfigMap must be in the same namespace.
  • You can bypass this and access a ConfigMap in a different namespace by accessing cm using k8s api
• The spec of a static Pod cannot refer to a ConfigMap
• A ConfigMap doesn’t differentiate between single line property values and multi-line file-like values. What matters is how Pods and other objects consume those values.

Immutable Configmap

you can add an immutable field to a ConfigMap definition to create an immutable ConfigMap.

“https://kubernetes.io/docs/concepts/configuration/configmap/#configmap-immutable”