*** This bug is a duplicate of bug 1676547 *** https://bugs.launchpad.net/bugs/1676547
I'm posting here instead of the bug at: https://bugs.launchpad.net/bugs/1676547 because it got me on the path that may have solved the problem (time will tell). My /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf also contained: [keyfile] unmanaged-devices=*,except:type:wifi,except:type:wwan When I cleared it out and rebooted, it was still empty and the problem was still there. At that point, I noticed that when I clicked on the Network Manager applet (↑↓) it displayed the lines: Ethernet Network (gray title) Wired connection 1 Disconnect enp0s25 VPN Connections Enable Networking (checkbox) Connection Information Edit Connections... But the machine has only one ethernet card, so I chose Edit Connections... and changed the connection name to the device name enp0s25. Using ifdown -a worked fine, but ifup -a gave me a long pause followed by: sudo unable to resolve host [hostname]: Resource temporarily unavailable When I then clicked on the Network Manager applet it showed enp0s25 above AND below Disconnect. When I then clicked Disconnect and then clicked enp0s25, it reconnected just fine. If I delete or restore the original /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf, it stops working; the file must be empty. On the machine I'm typing this on (also updated Bionic 64), /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf is not empty, but I don't do file sharing on it. Now that the other machine is working, I find I can access its shared folders on my network without a problem. So this bug probably has more than one cause. It's as if network connection information is being taken from at least 2 different locations, and one or more of them has/have been forgotten but should be gone. I do note that when I click Edit Connections... the connection information does not necessarily agree with what's in /etc/network/interfaces, in particular netmask refuses to keep the value 255.255.255.0 and reverts to 24 (could 24 refer to /24 in 192.168.15.109/24 ?), which is not the netmask /etc/network/interfaces requires for a static IP setting. My problem began with a clean install from a freshly downloaded ISO of Xubuntu 18.04 LTS 64 bit desktop (not server). Networking and Internet worked, but while setting it up for file sharing over the network (as the machine it replaced had done), I eventually lost all network access, and the network manager applet refused to connect, even when it said it "connection established"...before changing to say "disconnected". I previously reported a bug that suddenly disappeared by itself for a few months and that then recently reappeared: after some minutes connected to the Internet, my network connection would suddenly disconnect, and I'd have to reconnect it in the Network Manager applet. So I just made the change to it's name on that machine, and we'll see if that solves the problem or not (it's a pain to reproduce, because it requires rebooting and waiting an unknown amount of time. Getting file sharing in Linux is like finding an Android app: multiple choices to try, only to discover that none (or almost none) does the minimum that is reasonable to expect from it. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1658921 Title: NetworkManager does not manage wired connection Status in network-manager package in Ubuntu: Confirmed Bug description: NetworkManager does not manage my wired eth0 connection, no matter how I set /etc/network/interfaces or /etc/NetworkManager/NetworkManager.conf Using ubuntu 16.04, /etc/network/interfaces only managed lo, and [ifupdown] section of NetworkManager.conf had set managed=false. With these same settings, after upgrading to ubuntu 16.10, eth0 appears as unmanaged in nm-applet. If I modify /etc/network/interfaces and add auto eth0 iface eth0 inet dhcp And set managed=true in NetworkManager.conf [ifupdown] section, eth0 is still unmanaged despite it does get an IP from DHCP server. This is happening in my five computers (two laptops and three desktops). To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1658921/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp