Ethernet connection not working in Debian after fresh installation

Just after I installed Debian Squeeze, at first boot, the wired ethernet connection, which worked so well during the install, was not working in the X system (Gnome).

I wondered a lot trying to find an error in ifconfig or dmesg, but could find none. After a while, I noticed that the "status" of the connection in Gnome whenever I clicked on the network manager icon was:

 "Wired device not managed"


The device was simply not activated in the interfaces!

In order to activate it, type from a terminal:

$ sudo emacs /etc/NetworkManager/NetworkManager.conf

(or 'vi' or 'nano' instead of emacs, depending on your favourite text editor)

Then change the line:

[ifupdown]

managed=false

to

[ifupdown]

managed=true

Then save the file and restart the network manager:

$ sudo service network-manager restart

And the wired connection should be working straight away.