Create the following file and save it as cluster-read-only-role.yaml:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
  name: read-only
rules:
- apiGroups:
  - ""
  resources: ["*"]
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - extensions
  resources: ["*"]
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - apps
  resources: ["*"]
  verbs:
  - get
  - list
  - watch

Run the following command to create a cluster-wide role named read-only that has read-only permissions across the cluster:

kubectl create -f cluster-read-only-role.yaml