# Admission Controller

* Admision controller helps us to enforce how a cluster is used
* Prebuilt admision controllers in k8s
  * AlwaysPullImages
  * DefaultStorageClass
  * EventRateLimit
  * NamespaceExists
  * Etc
* We can view enabled admission controllers in api server config
* Update admission controllers at flag `--enable-admission-plugins`
* To disable, ue flag `--disable-admission-plugins`

![Admission Controller](/files/w2eW7fDOMK7R9VgIcxBd)

* Admission controller is ued to validate requets from user

## Validating & Mutating Admission Controllers

* To create your own admiion control logic you are provided with "MutatingAdmision Webhook" and "ValidatingAdmision Webhook"

![Request Reponse](/files/3mzA5tzkrT39vTbbEHNO)

```yaml
apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
  name: "pod-policy.example.com"
webhooks:
- name: "pod-policy.example.com"
  clientConfig:
    service:
      name: "webhook-ns"
      namespace: "webhook-svc"
    caBundle: "xxxx"
  rules:
  - apiGroups: [""]
    apiVersions: ["v1"]
    operations: ["CREATE"]
```

## Lab Learnings

* Create tls ecrets from cert & Key

```bash
k create secret tls <name> --cert=cert/location --key=key/location
```


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