Machine is Acer Aspire laptop with Intel i5 CPU running Ubuntu 18.04 (proc/version = Linux version 4.15.0-33-generic (buildd@lcy01-amd64-024) (gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3)) #36-Ubuntu SMP Wed Aug 15 16:00:05 UTC 2018). This has been a problem ever since I installed 18.04.
When I pull down the power menu and click the power button and select "restart", Ubuntu reboots into a broken network state. The wired network displays a triangular triple-questionmark icon. Network status claims that the wired network is connected, but the wired network is unusable. I don't even know how this is possible (please point to an explanation if you've seen one).
Looking at wired-network settings, all is correct: IP address, gateway and DNS addresses are all as before, but I can't get any web pages or email or anything. Doing a sudo sys-whatever restart is not enough to enable the wired network.
I have two workarounds: Turning off the wired network and turning on wifi gets me to a single question mark but usable (though slower) connection. A complete shutdown followed by a cold start brings the wired network back to life.
Is this a known bug in Ubuntu 18.04? If so, my search should have turned up a rash of discussion, so I reckon that it is not.
Is this designed behavior in Ubuntu 18.04? Since I have idiosyncratic expectations, it is possible that millions of users accept this limitation and I am the first Ubuntu user in the world to complain. Please let me know if the only way to restart Ubuntu is to do a full shutdown followed by cold start. But then I have to ask: Why the hell does a "restart" selection even exist?
If you need more info, please tell me where to peek. Until I learn how to cure this inconvenience, I'll avoid restarts and use only cold shutdowns (I ran into the problem again today because an update used restart for me, leaving itself without a network on reboot -- grrrr...)