Prerequisites

1. Ensure that Kubernetes cluster is at least as new as v1.16 ( to use admissionregistration.k8s.io/v1 ) or v1.9 ( to use admissionregistration.k8s.io/v1beta1 )

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2. Ensure that MutatingAdmissionWebhook admission controller is enabled. You can check if it is enabled by looking at the admission plugins that are enabled by running the following command in kube-apiserver:

     $ kube-apiserver -h | grep enable-admission-plugins
   

   If not enabled, then you can enable this plugin by running the following command in kube-apiserver:

     $ kube-apiserver --enable-admission-plugins=MutatingAdmissionWebhook  
   

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3. Ensure that the API (admissionregistration.k8s.io/v1 or admissionregistration.k8s.io/v1beta1 depending upon the k8s version being used) is enabled by using the following commands:

   • For admissionregistration.k8s.io/v1beta1 API:

   $ kubectl api-versions | grep admissionregistration.k8s.io/v1beta1
   

   Output should be:

     admissionregistration.k8s.io/v1beta1
   

   • For admissionregistration.k8s.io/v1 API:

     $ kubectl api-versions | grep admissionregistration.k8s.io/v1
   

   Output should be:

     admissionregistration.k8s.io/v1
   

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4. TLS Certificate Requirement:

In Kubernetes, in order for the API server to communicate with the webhook component, the webhook requires a TLS certificate that the API server is configured to trust. You can refer to the deployment section to understand more about it.

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