apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-readonly-rootfs
  annotations:
    policies.kyverno.io/title: Require Read-Only Root Filesystem
    policies.kyverno.io/category: Zero Trust
    policies.kyverno.io/severity: low
spec:
  validationFailureAction: Audit
  background: true
  rules:
    - name: require-ro-rootfs
      skipBackgroundRequests: true
      match:
        any:
          - resources:
              kinds:
                - Pod
      exclude:
        any:
          - resources:
              namespaces:
                - kube-system
                - rook-ceph
                - istio-system
                - kyverno
                - tetragon
                - prometheus
                - authentik
                - gitlab
                - nextcloud
                - home-assistant
      validate:
        allowExistingViolations: true
        message: "Containers should use a read-only root filesystem."
        pattern:
          spec:
            containers:
              - =(securityContext):
                  =(readOnlyRootFilesystem): true