As you attach network interfaces to Linux it will give it names.
The first network interface that is connected will usually be called eth0 if is a wired network interface.
If you have changed you network interface some times, your standard interface can now be called eth5 or something like that. It doesn’t bother a regular user, but it might be annoying from an administrators point of view that you don’t know the name of the interface.
Anyway, to change the name of the ethernet interface from eth5 to eth0 in ubuntu you just need to edit the file:
/etc/udev/rules.d/70-persistent-net.rules</li>
An example of the content of the file is:
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="52:54:00:76:da:63", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2"
Just change the NAME from eth2 to eth0 if that is what you want to do.
