Upgraded to unstable - lost network connectivity

[Simon Kitching <simon@ecnetwork.co.nz>]

Hi,

I recently added unstable to my sources.list, and did a dist-upgrade.
After some mucking around, I now have a working system again - except
for networking.

I'm on a LAN with DHCP etc. Normally, interface eth0 comes up
automatically. However now when I boot I get no network connection, and:

  su -
  ifup eth0

just gives me:

<begin output>
pcsimon:~# ifup eth0
Internet Software Consortium DHCP Client 2.0pl5
Copyright 1995, 1996, 1997, 1998, 1999 The Internet Software Consortium.
All rights reserved.
 
Please contribute if you find this software useful.
For info, please visit http://www.isc.org/dhcp-contrib.html
 
eth0: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
exiting.
Failed to bring up eth0.
<end output>

Fortunately I backed up the previous system onto a separate partition,
and am able to boot into that to get this working system.

I have tried:
  diff -r /etc/network   {badsystem}/etc/network
and this shows that everything in the /etc/network directory of the
"bad" system is identical to the scripts in the "good" system, except
the "ifstate" file which is as expected, ie they weren't touched by the
update:
<begin output>
pcsimon:~# diff -r /etc/network /mnt/hda6/etc/network
diff -r /etc/network/ifstate /mnt/hda6/etc/network/ifstate
1,2d0
< lo=lo
< eth0=eth0
<end output>

Does anyone have any ideas how I can get network connectivity back
again? Where might I start diagnosing this problem?

One thing I would like to do is try an apt-get dist-upgrade again, in
case there are some updated packages to fix this. But of course that is
difficult without network connectivity. Is there a way I can upgrade the
"bad" OS install which is on a separate partition?

Thanks,

Simon