Replacing mainboard broke network with Ubuntu Server 10.04

[NewtownGuy]

My mainboard died, so I replaced it with an identical one. I moved the hard drive to the new mainboard. The machine boots and runs ok except that the network interface does not work anymore. ifdown and ifup report that no network interface is present. lspci sees the network interface hardware.

As a test, I booted from the installation CD and went into Rescue a Broken System, and the network works fine there. So my hardware is ok.

I researched UUID, which I thought might be involved, but I didn't change the hard drive so I could not find anything applicable.

I thought Rescue Mode might automatically fix the network, but apparently not. After leaving Rescue Mode and rebooting to hard disk, the network still does not work. What commands do I need to give, and in what environment, to restore the network interface ?

Thank you in advance.

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[Annihilannic]

Does /sbin/ifconfig -a list your (unconfigured) interfaces?

If so I suspect the problem may be mismatching MACs in the interface configuration scripts. I'm not an Ubuntu/Debian user so I'm not sure what the protocol is there...

Annihilannic.

 

[NewtownGuy]

It looks like a MAC problem, as you suggested, but how do I fix it ? I don't see any MAC addresses in /etc/network/ or the scripts there.

'ifconfig -a' lists eth1 instead of eth0, and wlan1 instead of wlan0. /var/log/syslog says eth0 was renamed eth1. (I didn't check wlan0.)

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[Noway2]

The file you need to look at is: /etc/udev/rules.d/70-persistent-net.rules

This file lists the MAC address and associates it with a device ID like eth0. What has happened is that the old boards MAC address is tied to eth0 and the software doesn't know that it is no longer in existence. You can simply delete the old entry line from the file.

 

[NewtownGuy]

TO: Noway2

Thank you for your post. I looked at the file you mentioned and there were entries for eth0 (the one for the old mainboard) and eth1 (the one for the replacement mainboard). But there were also entries for wlan0 and wlan1, but it is the same PCIe mini-card because I moved it from the old mainboard to the new one.

I fixed the entries for eth0 and eth1, and now the unit can access the network again (mostly). But there is still a problem with wlan. In the rules file, wlan1 has a different MAC address than wlan0 for some reason.

I say "mostly" because there are many error messages in syslog about network access. I don't know where they are coming from. How do I find out ?

Also, why is there a problem with wlan since it did not change ? Did the system get confused because of the eth problem ? In dmesg, you can see that wlan0 keeps getting changed to wlan1.

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[Noway2]

One thing I would try would be saving the file to a different location, and then blanking the contents. See what is created. You might also need to look in the other files in that directory too.

I would also look up the part and rev level of the adapter and make sure you have the right driver. Unfortunately, the HW manufacturers sometimes seem to declare war on Linux and change the HW and you may need a different driver, aka module.

dmesg (command) may provide you some information regarding hw error messages.