update engine is the daemon started at boot  update engine client is a tool to communicate with the running daemon  both programs are using d bus for ipc right now also note that update engine is using d bus now and we are planning to migrate off d bus  so to avoid dbus te polluting external sepolicy i amend the update engine selinux policy c i suppose we do not need to label update engine client as it is only used from a shell or we can label it in the brillo specific selinux policy in 