That should be ifconfig with an f.iwconfig wlan0 up - unrecognised wireless request "up"
Try this:iwconfig wlan0 essid linksys channel 6
dhcpcd wlan0 - no response: ifconfig shows only loopback address
iwconfig wlan0 mode managed
iwconfig wlan0 essid linksys key off
ifconfig wlan0 up
dhclient wlan0 (or if you prefer, dhcpcd wlan0)
And To view networks in range:
Using airodump will put your card into monitor mode, so always remember to switch back to managed mode afterwards with: iwconfig wlan0 mode managed.
I've had the same problem with setting channel on my Alfa 500 mW. You don't need to set the channel if you give the essid. However if there's identical essid's in range, I specify the AP:iwconfig wifi0 essid linksys channel 6 - set failed on device wifi0: operation not supported
iwconfig wlan0 essid linksys key off ap 00:01:02:03:04:05