Managing application configuration using ConfigMaps and Secrets

To provide configuration for an application running on Kubernetes, there are a couple of possible approaches, documented in https://kubernetes.io/docs/tasks/inject-data-application/:

• Passing arguments to the container commands
• Defining system environment variables for the container
• Mounting ConfigMaps or Secrets as container volumes
• Optionally wrapping everything up using PodPresets

This section will focus on using ConfigMaps and Secrets, which are, in many aspects, similar but have very different purposes.

First, let's take a look at Secrets. In almost every application, you will have to manage sensitive information for accessing dependencies, such as passwords, OAuth tokens, or certificates. Putting such information in a Docker image as hardcoded values is out of the question due to obvious security concerns...