Yes, I managed to do this. Luckily I managed to re-enable the GDM3 graphical console on-start-up by using the debug serial port and then using the GUI through the TV to put the tick back to enable networking.  Yep, very much a noob mistake.

So, the question is when networking is disabled so eth0 and wlan0 disappear, leaving only lo, how do I get eth0 and wlan0 back just using the command line?  I can't easily find how to do this. I've looked, I've searched and now ....   help!  :-)

 

(I do also have the ability to put the MicroSD card into my laptop, so maybe it would be simpler to do that and change some configuration files to re-enable networking?)

 

This would be very useful information for anyone else who gets stuck in the same situation.

Unfortunately, it depends on what you did to disable networking?

 

By default, I think that networking services are managed by NetworkManager. You can check to see if the service is disabled with:

 

$ systemctl status NetworkManager 

 

If it's disabled, you can re-enable with:

 

$ sudo systemctl enable NetworkManager
$ sudo systemctl start NetworkManager

 

If you touched one of the network configurations, You can manually poke at the configs like this:

 

$ sudo -i
# cd /etc/NetworkManager/system-connections
# ls
my_connection
# nano -w my_connection

<Hit Control-O, Enter, then Control-X when done>

 

I accidentally took the tick off Enable Networking when I wanted to take the tick off Enable Wi-Fi.  I guess the question is what does the GUI do in the background to enable and disable networking.

 

Took a quick look on my system doing that.

 

Doing "systemctl status", I don't see any obvious services that were started or stopped.

 

You might learn more reading up on the options in the NetworkManager command line tool:

 

$ man nmcli

 

Or check with the XFCE guys over at https://forum.xfce.org/ what exactly that network widget does.

It does look like nmcli.  I thought maybe the interfaces were brought down and configured somewhere to stay down using ifconfig.  Now I have to study nmcli which I didn't know about.  I certainly will ask at the xfce forum.

Thank-you.