instruction: Create a Dockerfile for configuration
output: ```dockerfile
  from application code.For example, imagine that you are developing an application that you can run on your
  own computer (for development) and in the cloud (to handle real traffic).
  You write the code to look in an environment variable named DATABASE_HOST.
  Locally, you set that variable to localhost. In the cloud, you set it to
  refer to a Kubernetes Service
  that exposes the database component to your cluster.
  This lets you fetch a container image running in the cloud and
  debug the exact same code locally if needed.Note:A ConfigMap is not designed to hold large chunks of data. The data stored in a
  ConfigMap cannot exceed 1 MiB. If you need to store settings that are
  larger than this limit, you may want to consider mounting a volume or use a
  separate database or file service.ConfigMap objectA ConfigMap is an API object
  that lets you store configuration for other objects to use. Unlike most
  Kubernetes objects that have a spec, a ConfigMap has data and binaryData
  fields. These fields accept key-value pairs as their values. Both the data
  field and the binaryData are optional. The data field is designed to
  contain UTF-8 strings while the binaryData field is designed to
  contain binary data as base64-encoded strings.The name of a ConfigMap must be a valid
  DNS subdomain name.Each key under the data or the binaryData field must consist of
  alphanumeric characters, -, _ or .. The keys stored in data must not
  overlap with the keys in the binaryData field.Starting
  ```