OK, It's happened again on a fresh box, here is some crystal-clear output irrefutably demonstrating the problem, checking all the places you've asked for (and my 2-line workaround at the end):
(a dist-upgrade has just completed kicked off using the update icon, not the command line, and I've just rebooted to discover the network doesn't work anymore) [EMAIL PROTECTED]:/localhome/localadmin# cat /etc/iftab # This file assigns persistent names to network interfaces. See iftab(5). eth0 mac 00:0e:0c:3e:9b:14 [EMAIL PROTECTED]:/localhome/localadmin# ifconfig eth0 Link encap:Ethernet HWaddr 00:0E:0C:3E:9B:14 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Base address:0xee80 Memory:feba0000-febc0000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:1480 errors:0 dropped:0 overruns:0 frame:0 TX packets:1480 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:93240 (91.0 KiB) TX bytes:93240 (91.0 KiB) [EMAIL PROTECTED]:/localhome/localadmin# ls -la /var/dist-upgrade* ls: /var/dist-upgrade*: No such file or directory [EMAIL PROTECTED]:/etc/network# perl -pi -e "s/eth0/eth1/g" /etc/network/interfaces [EMAIL PROTECTED]:/etc/network# /etc/init.d/networking restart * Reconfiguring network interfaces... Ignoring unknown interface eth0=eth0. Internet Systems Consortium DHCP Client V3.0.3 Copyright 2004-2005 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/products/DHCP Listening on LPF/eth1/00:08:c7:e9:8c:89 Sending on LPF/eth1/00:08:c7:e9:8c:89 Sending on Socket/fallback DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 4 DHCPOFFER from 10.50.128.5 DHCPREQUEST on eth1 to 255.255.255.255 port 67 DHCPACK from 10.50.128.5 bound to 10.50.129.252 -- renewal in 121866 seconds. -- after dist-upgrade from breezy to dapper, networking stops working https://launchpad.net/bugs/47407 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs