Ubuntu wireless network connection in command line

After installed the the graphical card driver in Ubuntu, the gnome desktop was not working anymore, needs to install and setup the wireless network in command line, herewith the procedure, 1, scan the available wifi network, sudo iwlist scan 2, receive the wifi network password   wpa_passphrase YOURSSID YOURWIFIPASSWORD the result is similar as:   network={ ssid="YOURSSID" #psk="YOURWIFIPASSWORD" psk=fe727aa8b64ac9b3f54c72432da14faed933ea511ecab1 5bbc6c52e7522f709a } 3, edit the /etc/network/interfaces   sudo vim /etc/network/interfaces my configuration is as:   auto wlan0 iface wlan0 inet dhcp gateway 192.168.2.1 wpa-psk "the password psk just generated" wpa-ssid "YOURSSID" 4, restart the network and wlan0   sudo /etc/init.d/networking restart     sudo ifdown wlan0 sudo ifup wlan0   5, problem encountered, canno access the external network   ping 8.8.8.8 failed, ping www.google.com failed.