docs: add note about MKE CA rotation, which is potentially dangerous
@@ -81,6 +81,13 @@ gyg5u9Iliel99l7SuMhNeLkrU7fXs+Of1nTyyM73ig==
### <a name="rotate"></a> Root CA rotation (--rotate)
+> **Note**
+>
+> Mirantis Kubernetes Engine (MKE), formerly known as Docker UCP, provides an external
+> certificate manager service for the swarm. If you run swarm on MKE, you shouldn't
+> rotate the CA certificates manually. Instead, contact Mirantis support if you need
+> to rotate a certificate.
+
Root CA Rotation is recommended if one or more of the swarm managers have been
compromised, so that those managers can no longer connect to or be trusted by
any other node in the cluster.
