ubuntu@ubuntu:~$ sudo airmon-ng start wlan0


Found 4 processes that could cause trouble.
If airodump-ng, aireplay-ng or airtun-ng stops working after
a short period of time, you may want to kill (some of) them!

PID     Name
2986    avahi-daemon
2988    avahi-daemon
3136    NetworkManager
3259    wpa_supplicant

Interface       Chipset         Driver

wlan0           Atheros         ath9k - [phy0]

ERROR: Neither the sysfs interface links nor the iw command is available.
Please download and install iw from
http://wireless.kernel.org/download/iw/iw-0.9.19.tar.bz2