Ubuntu 17.04 direct shared Ethernet connection fails with "Active connection could not be attached to the device."

Question

I had direct Ethernet connection without a router working in Ubuntu 16.04 for SSH as explained at: https://raspberrypi.stackexchange.com/a/53823/33424

But when I tested again 17.04, set "Shared to other computers", and select that connection, an error dialog appears:

Connection activation failed.

(0) Active connection could not be attached to the device

The only thread I could find was: https://askubuntu.com/questions/856007/failed-to-add-activate-connection but "All users may connect to this network" is already checked.

RPI 2 + Raspbian Jessie 2016-05-27 and 2017-04-10.

Answer 1

To find the cause of this issue it is advisable to inspect the system logs, while the problem occurs.

To do so, open a console (maybe as root/sudo) then you can follow the logs like so: Generally journalctl -f and specifically for NetworkManager issues journalctl -f -u NetworkManager.

Now try to activate the connection and see what might hint you to the cause of error.

In my case I think I upgraded like you did (16.something to 17.04) and found dnsmasq missing, with one log line saying <error> ... (eno1) failed to start dnsmasq: Could not find "dnsmasq" binary. This was solved by installing the package dnsmasq. It is recommended to install dnsmasq-base (e.g. sudo apt-get install dnsmasq-base).

There is a bug report to pre-install dnsmasq-base by default on Ubuntu at: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1678606 since it breaks the network sharing GUI feature.