specically I have a /bin/sh script in /etc/network/if-pre-up.d/myfilter: #! /bin/sh iptables -X iptables -F iptables -A OUTPUT -p tcp --destination-port telnet -j REJECT which DOES work. I wonder why it's complaining about the line #! /bin/sh during the boot messages. Note no such output is in dmesg. NOTE if I take it out it completely fails...