vt_ev_request
vt_ev_request(VT_EV_LOCK, display_num);
vt_ev_request(VT_EV_ACTIVATE, target_vt);
vt_ev_request(VT_EV_ACTIVATE, target_vt);
vt_ev_request(VT_EV_AUTH, target_vt);
vt_ev_request(VT_EV_TERMINATE_AUTH, 0);