Often having some tablet or smartphone running linux connected to my usb port and I always have to look up how to enable NAT-ing on my laptop so that those devices can access the internet via usb-ethernet connection. So here is how to do it:
sysctl net.ipv4.ip_forward=1 iptables -t nat -A POSTROUTING -j MASQUERADE
But I will not need this reminder anymore because this is how to make the setup persistant between reboots:
$ echo net.ipv4.ip_forward = 1 > /etc/sysctl.d/ip_forward.conf $ cat /etc/iptables/rules.v4 *nat -A POSTROUTING -j MASQUERADE COMMIT
The content in /etc/iptables/rules.v4 is normally generated via iptables-save so there might be some extra work needed to combine this with possible existing content. The initscript required to run iptables-restore with this file as input is provided as the iptables-persistent package.