If you’ve ever created a Linux virtual machine image for distribution, you have probably encountered this problem. The Virtualization is not really important – the problem exists on VirtualBox, VMWare, KVM, Xen and others supporting Linux guests.
So, what is the issue exactly?
The problem is that when you recreate a a virtual machine using an existing image, a new MAC address is generated. Udev sees this new address and creates a static name for it – e.g. eth1. Keeping the original – now removed – eth0 in the persistant naming file.
This interface typically does not exist in the /etc/network/interfaces file, and therefore is never “upped”. This leaves you with a machine that has no network connection out of the box.
Well, how do I fix it then?
The simple solution is to remove the /etc/udev/rules.d/70-persistent-net.rules file and reboot.
This means you have to remove the file as the last thing you do before shipping the image. I you make changes to the image, and reship it – you must do this every time. Plus it prevents easy redistribution of your image.
So, I’ve placed a small bash script at /usr/local/bin/reenumerate_interfaces and called it from /etc/rc.local.
This script also have the advantage, that you do not have to reboot the machine for the changes to take effect.
#! /bin/sh echo Re-enumerating the network interfaces... # Stop networking /etc/init.d/networking stop <pre lang="bash"> # Get the drivers and bounce the NICs lspci -nnv | awk '{ if ($0 ~ /^$/) { getDriver = 0; } if (getDriver == 0 && $0 ~ /.*Ethernet controller.*/) { getDriver=1; } if (getDriver == 1 && $0 ~ /.*Kernel driver.*/) { printf ("%s\n", $5); } }' | sort | uniq | while read a; do echo Unloading network module $a from kernel space rmmod $a done # Remove the static enumerations rm /etc/udev/rules.d/70-persistent-net.rules echo Reloading driver via udev # Tickle udev /sbin/udevadm trigger # Start networking /etc/init.d/networking start
