Gerix suffers from a bad packetforge-ng invocation:

Code:
in: /pentest/wireless/gerix-wifi-cracker-ng/gerix.py

    #
    # Create the ARP packet to be injected on the victim access point (Client Fragmentation)
    #
    def slot_wep_create_arp_cfrag(self):
        command = 'packetforge-ng -o -a ' + self.ac + ' -h ' + self.ac_victim + ' -k 255.255.255.255 -l 255.255.255.255 -y ' + config_dir + '/*.xor -w ' + config_dir + 'cfrag'

    #
    # Create the ARP packet to be injected on the victim self.access point (Fragmentation)
    #
    def slot_wep_create_arp_frag(self):
        command = 'packetforge-ng -o -a ' + self.ac + ' -h ' + self.mymac + ' -k 255.255.255.255 -l 255.255.255.255 -y ' + config_dir + '*.xor -w ' + config_dir + 'output_FORGED2'
packetforge needs a 'mode' argument (typically -0 (ARP creation)). "-o" (literal 'Oh') has been misused in place of -0 ('zero'), therefore:

Code:
# sed -i 's/packetforge-ng -o/packetforge-ng -0/g' /pentest/wireless/gerix-wifi-cracker-ng/gerix.py
Or, wait for the fix to get committed on the repos.