There are different ways to configure a container with environment variables.

• In a deployment YAML file
• Using Config Map (this article)
• Using Secrets

Config Maps are typically used to mount configuration files in a container. However, they can also be used to pass environment variables and command line option arguments into a container. Secrets are similar, but typically used to pass sensitive data into a container (e.g. passwords). In this way, if a change is needed to a configuration file, variable, or command line option argument, you just need to update the config map or secret as opposed to having to make the change to your applications or deployments.

This assumes you have used the REST API to obtain an OAuth bearer token. Let's say the bearer token is sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U.

Here is how you could list the config maps in the openshift-kube-apiserver-operator namespace using curl. The oc config view or oc get apiserver commands can be used to display the API Server URL (api.openshift.example.com in this example).

curl
--insecure
--request GET
--header "Accept: application/json"
--header "Authorization: Bearer sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U"
--url "https://api.openshift.example.com:6443/api/v1/namespaces/openshift-kube-apiserver-operator/configmaps"

If something like this is returned, this means that there are no config maps in the namespace.

{
  "kind": "ConfigMapList",
  "apiVersion": "v1",
  "metadata": {
    "selfLink": "/api/v1/namespaces/openshift-kube-apiserver-operator/configmaps",
    "resourceVersion": "96466432"
  },
  "items": []
}

On the other hand, if the items array contains key value pairs, this means the namespace contains one or more config maps.

{
  "kind": "ConfigMapList",
  "apiVersion": "v1",
  "metadata": {
    "selfLink": "/api/v1/namespaces/openshift-kube-apiserver-operator/configmaps",
    "resourceVersion": "96464581"
  },
  "items": [
    {
      "metadata": {
        "name": "kube-apiserver-to-kubelet-client-ca",
        "namespace": "openshift-kube-apiserver-operator",
        "selfLink": "/api/v1/namespaces/openshift-kube-apiserver-operator/configmaps/kube-apiserver-to-kubelet-client-ca",
        "uid": "9103397e-9e0c-44f6-bcb4-852cbbc07ed8"

Or to return a specific config map, such as kube-control-plane-signer-ca.

curl
--insecure
--request GET
--header "Accept: application/json"
--header "Authorization: Bearer sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U"
--url "https://api.openshift.example.com:6443/api/v1/namespaces/openshift-kube-apiserver-operator/configmaps/kube-control-plane-signer-ca"