Where can i get the API_KEY in Kubernetes installation

Maybe you need token.

Can use anywhere secret in kube-system namespace:

$ kubectl get secrets -n kube-system 
$ kubectl describe secret/{secret_name} -n kube-system

[root@master1 ~]# APISERVER=$(kubectl config view --minify | grep server | cut -f 2- -d ":" | tr -d " ")
[root@master1 ~]# SECRET_NAME=$(kubectl get secrets | grep ^default | cut -f1 -d ' ')
[root@master1 ~]# TOKEN=$(kubectl describe secret $SECRET_NAME | grep -E '^token' | cut -f2 -d':' | tr -d " ")
[root@master1 ~]# curl $APISERVER/api --header "Authorization: Bearer $TOKEN" --insecure
{
  "kind": "APIVersions",
  "versions": [
    "v1"
  ],
  "serverAddressByClientCIDRs": [
    {
      "clientCIDR": "0.0.0.0/0",
      "serverAddress": "11.127.4.111:6443"
    }
  ]
}[root@master1 ~]#