kyverno/examples/best_practices/policy_validate_fsgroup.yaml

apiVersion: kyverno.io/v1alpha1
kind: ClusterPolicy
metadata:
  name: validate-fsgroup
spec:
  validationFailureAction: "audit"
  rules:
  - name: validate-fsgroup
    exclude:
      resources:
        namespaces: 
        - kube-system
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "directory should have group ID 2000"
      pattern:
        spec:
          securityContext:
            fsGroup: 2000