Airmon-ng fails to create monitor interface

Question

When I try to start airmon-ng, I get the following output

# airmon-ng start wlan0

Found 5 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
993     avahi-daemon
994     NetworkManager
999     avahi-daemon
1539    wpa_supplicant
4568    dhclient
Process with PID 4568 (dhclient) is running on interface wlan0


Interface   Chipset     Driver

wlan0       Broadcom    b43 - [phy0]

When I kill those processes with

kill -9 993 994 999 1539 4568

it doesn't help. airodump-ng and aireplay-ng won't work.

Solution

You might want to check, whether your device is supported. See the list of supported devices.