README for aircrack-ng POST-INSTALL 1. The airmon-ng tool included in aircrack-ng requires 'iw' to be installed. Otherwise they will just abort with an error saying: ERROR: Neither the sysfs interface links nor the iw command is available. Please download and install iw from http://dl.aircrack-ng.org/iw.tar.bz2 So, you can safely install 'iw' from contrib ports by doing: # ports -u contrib; prt-get install iw