Network interfaces names changed in KVM guest cloned with virt-clone

[Andres Rodriguez]

Binary package hint: kvm

I used virt-clone to clone KVM guests. The hosts uses KVM 72 in Intrepid Ibex, and the Guests are Hardy Heron. After cloning, the machine works perfectly, everything gets cloned the way it should, but the network interface names are changed. ie. form eth0 to eth3.

The question is how can I change the network interfaces back to its original name.

[Andres Rodriguez (andreserl)]

Btw... I try to bring up networking with: sudo ifup eth0.

[Lennart Karssen (l.c.karssen)]

I'm experiencing the same thing here. The host runs Ubuntu 9.10 server, the guest as well.
I think this bug results from the fact that virt-clone changes the MAC address of the quest. If I remember correctly debian-based distributions change the name of a network interface if they detect a new MAC address.

[Lennart Karssen (l.c.karssen)]

I found this thread on the Ubuntu forums that also discusses this problem (in combination with VMware, but that's beside the point, since this happens whenever an ubuntu/debian system is cloned): http://ubuntuforums.org/showthread.php?t=1045715

There are several solutions to this bug:
- Simply delete /etc/udev/rules.d/70-persistent-net.rules either before or after the cloning, or edit the file after cloning.
- Remove execute permissions from /lib//udev/write_net_rules, but that results in an error on startup
- Edit /lib/udev/rules.d/75-persistent-net-generator.rules so that it ignores MAC addresses from VMware or KVM. For Xen such a line already exists:
# ignore Xen virtual interfaces
SUBSYSTEMS=="xen", GOTO="persistent_net_generator_end"

From the forum post above, add the following for VMware
# ignore VMware network interfaces identified by vendor part of MAC addr
ENV{MATCHADDR}=="00:0c:29:*", GOTO="persistent_net_generator_end"

For KVM and virt-clone I added these:
# ignore KVM virtual interfaces
ENV{MATCHADDR}=="52:54:00:*", GOTO="persistent_net_generator_end"
# This eems to be the range used by Xen, but also by virt-clone
ENV{MATCHADDR}=="00:16:36:*", GOTO="persistent_net_generator_end"

Make sure these lines are after the following lines:
# read MAC address
ENV{MATCHADDR}="$attr{address}"

This worked for me.

[Lennart Karssen (l.c.karssen)]

I consider this to be a bug, since only Xen devices seem to be taken care of, but KVM/Qemu devices aren't. A fix for this is mentioned in the comments.