Comment 41 for bug 1666432

Perhaps this can help: The symptoms I experience started sometime during the past year after an update (sudo apt update && sudo apt upgrade && sudo apt autoremove) are that some indefinite time (usually less than ½ hour) after I log on, the network disconnects without warning or error. Clicking on the up/down arrows of the indicator plugin and selecting the interface reconnects; however, I recently discovered that if, as soon as I log on, I select "Disconnect" and then select the adapter to reconnect, my session will be fine until I log out and back in again. So perhaps the bug is not with network-manager, samba or ifupdown, but with the logon process(es). My version is 18.04 and I'm using LiteDM GTK+. I haven't the faintest idea where to look for a cause that might be related to the logon process(s), but none of the very many "solutions" offered on various web pages I found on the problem have fixed it for me.

One other unexpected thing I've noticed is that in editing Ethernet connections (I don't used wireless enough to have noticed a problem), I can't edit (or delete) the one the system creates without first adding another (even if it's the same, e.g., enp2s0, with the same settings) and switching to it; however, after I did that the first time, and deleted the system's entry ("Wired connection 1", I think it was called), at some point the system added another entry, identical in every way to the one I had added, but called "Ifupdown (enp2s0)" and connects to that when I log on, not to the one I created (which I have since deleted, but the original problem still occurs, and disconnecting and reconnecting still prevents the random disconnect).

All of this applies to 2 other machines, also running up-to-date xubuntu 18.04, although on one of the other machines, the adapter is enp4s25. It also occurs with xubuntu and xfce sessions. I suspect the difficutly in finding the cause(s) is in part due to the confusing way samba/network settings are stored, with the same setting sometimes stored in different locations, entered via GUI or command line or both, possibly leading to conflicts.

I have spent many hours on this problem, and have only the above work-around, not a fix. Even though this problem has been around longer than 18.04, since 18.04, samba has clearly been broken, and until networking is as reliable and as easy to set up as in Windows, (x/l/k)ubuntu will not be suitable for typical home users.