Ubuntu eth0 changed into eth1 or eth2, eth3 etc.

So are you running an Ubuntu based linux distro (I’m running Kubuntu).

Did your network configuration change eth0 into something else, for example eth1. I managed to get up to eth4, and after 2 reboots after a system reconfiguration, it wanted me to use eth5 then eth6… the interface card (NIC) is built-in into my motherboard, so why the sudden change?

Well one reason is the fact I had fiddled with the NIC’s MAC-address in the system setup, so basically the hardware address change made Ubuntu think I had installed a new card. So it assigns it a unique device name, eth1 and so on. I’m fairly certain I didn’t change the MAC that often, so there’s gotta be something else to it. Right, so the quick solution is to remove these hardware mappings which are stored in a peculiar place

Look in the folder /etc/udev/rules.d
for a file named 70-persistent-net.rules

Edit the file at your own peril. I removed most of the crap entries from there, since I prefer my NIC to be named eth0 no matter what MAC-address it happens to have. Changing the device name broke my munin-stats grapher/logger, so I’m happy to get rid of this piece-of-crap annoying feature for now. Don’t ask me how to disable udev from adding new entries there, I don’t know why it kept incrementing the interface number in the first place!