Kubernetes Quickie: Extract the Ca-Bundle

Today I came across a new little problem: Configuring a MutatingWebhookConfiguration for Nginx ingress controller.

The example looks like this:

apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
  name: ingress-nginx-admission
webhooks:
  - name: admission.ingress.k8s.io
    clientConfig:
      service:
        name: ingress-nginx-admission
        namespace: ingress-nginx
        path: /networking/v1/ingresses
      caBundle: <CA_BUNDLE> # This should be filled with the base64-encoded certificate of the CA used by your cluster.
    rules:
      - operations: ["CREATE", "UPDATE"]
        apiGroups: ["networking.k8s.io"]
        apiVersions: ["v1"]
        resources: ["ingresses"]
    admissionReviewVersions: ["v1"]
    sideEffects: None

See that caBundle thing? The value needed here has to be extracted from your cluster. Here is the command:

$kubectl config view --raw --minify --flatten -o jsonpath='{.clusters[].cluster.certificate-authority-data}'

This outputs something like this, only much longer.

LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURCVENDQWUyZ0F3SUJBZ0lJWm0vR2V3ZzNzMlF3RFFZSktvWklodmNOQVFFTEJRQXdGVEVUTUJFR0ExVUUKQXhNS2EzVmlaWEp1WlhSbGN6QWVGdzB5TlRBeE1qVXhOak14TXpGYUZ3MHpOVEF4TWpNeE5qTTJNekZhTUJVeApFekFSQmdOVkJBTVRDbXQxWW1WeWJtVjBaWE13Z2dFaU1BMEdDU3FHU0liM0RRRUJBUVVBQTRJQkR3QXdnZ0VLCkFvSUJBUURMWEIwcDZ1VTE4Y3N2Umw1NzFKdSt5

Fill that in your yaml and you are set.

Happy coding!