I cloned an Ubuntu Virtual Machine, but the networking wouldn’t start;
/etc/networking restart led to:
“failed to bring up eth0”
A lot of people have the answer to this one, this guy was nice and concise
cd /etc/udev/rules.d/
mv z25_persistent-net.rules z25_persistent-net.rules.old (in my case the name was 70-persistent-net.rules)
reboot
voila