I'm trying to upgrade a fairly old server that's been running Hoary for the last five years. I followed the directions on the wiki, but when I restarted after upgrading to Dapper, eth0 disappeared from ifconfig -a. I can see two ethernet adapters in lspci and lshw, and if I put in an Ubuntu 10.10 LiveCD it registers eth0 and eth1 perfectly well. Their MAC addresses also match what's in /etc/iftab.

It was working fine before the upgrade, and I have no idea what else I should be trying at this point. The server is entirely cut off from the network right now.

EDIT: /etc/udev/rules.d/70-persistent-net.rules doesn't exist, either.