kyverno/examples/policy_validate_nonRootUser.yaml

apiVersion: kyverno.io/v1alpha1
kind: Policy
metadata:
  name: check-container-security-context
spec:
  # validationFailureAction: "audit"
  rules:
  - name: check-root-user
    exclude:
      resources:
        namespaces: 
        - kube-system
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Root user is not allowed. Set runAsNonRoot to true."
      anyPattern:
        - spec:
            securityContext:
              runAsNonRoot: true
        - spec:
            containers:
            - name: "*"
              securityContext:
                runAsNonRoot: true