Changed VMware Ethernet Devices

(2016-04-05)

Problem

You've started up your CentOS 6.x VM and the ethernet device has changed.

Usually you'll notice that either there is an eth1 device where once there was an eth0 device; sometimes you won't see any ethernet devices at all.

Discussion

At some point during the recent boot processes, VMware asked you a question: Did you move or copy this VM? and you answered: I Copied It (which is the safe answer and what VMware tells you to answer if you don't know).

This is triggered by the VM waking up and thinking it isn't where it is supposed to be -- usually the datastore path has changed, but sometimes if you just import it from a shared datastore into a new node it will complain about this.

VMware is trying to be safe for you and is giving your "new copy" of the VM new MAC addresses so that your "new copy" won't collide with the original VM which may be running somewhere.

Avoiding In The Future

If you know for sure that this is the only instance of the VM, ie you've had to unmount the datastore and remount it, or mounted a new datastore on a different VM server, then you can use the answer I Moved It and you won't have to deal with this problem.

Solution

To fix this situation:

1. Remove the file /etc/udev/rules.d/70-persistent-net.rules
2. Go into your /etc/sysconfig/network-scripts/ifcfg-eth* files and delete the HWADDR lines.
3. Reboot.

Your network configuration should come back. Note that you will still have a new MAC address so if this VM has a DHCP reservation you'll still have to deal with that separately.