apiVersion: kyverno.io/v1alpha1
kind: ClusterPolicy
metadata:
  name: validate-not-readonly-rootfilesystem
spec:
  rules:
  - name: validate-not-readonly-rootfilesystem
    exclude:
      resources:
        namespaces: 
        - kube-system
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Container should not have read-only rootfilesystem"
      anyPattern:
      - spec:
          container:
          - securityContext:
              readOnlyRootFilesystem: false