DNS

Exercise

List the Pods running the kubernetes dns
Show the whole specification of the related Deployment
Which ServiceAccount is used by the dns Pods ?
Which Roles / ClusterRoles are associated to this ServiceAccount ?

Documentation

https://kubernetes.io/docs/concepts/security/service-accounts/

Solution

List the Pods running the kubernetes dns

kubectl -n kube-system get po -l k8s-app=kube-dns

Show the whole specification of the related Deployment

kubectl -n kube-system get deploy/coredns -o yaml

Which ServiceAccount is used by the dns Pods ?

kubectl -n kube-system get deploy/coredns -o jsonpath={.spec.template.spec.serviceAccountName}

Which Roles / ClusterRoles are associated to this ServiceAccount ?

There is no Roles associated to the coredns ServiceAccount:

kubectl get rolebinding -o yaml -A | grep coredns

There is a ClusterRole associated to coredns:

$ kubectl get clusterrolebinding system:coredns -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  creationTimestamp: "2022-04-04T10:41:04Z"
  name: system:coredns
  resourceVersion: "227"
  uid: 4c0c7f71-e3a3-4ab4-8491-c24dfccea4e2
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:coredns
subjects:
- kind: ServiceAccount
  name: coredns
  namespace: kube-system

The rules of this ClusterRole are the following ones:

kubectl get clusterrole system:coredns -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  creationTimestamp: "2022-04-04T10:41:04Z"
  name: system:coredns
  resourceVersion: "226"
  uid: 3253cce0-51e2-4f8f-b7a2-026bb42b8ab5
rules:
- apiGroups:
  - ""
  resources:
  - endpoints
  - services
  - pods
  - namespaces
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - get
- apiGroups:
  - discovery.k8s.io
  resources:
  - endpointslices
  verbs:
  - list
  - watch