I think I've found another way to reproduce the problem. I installed docker in a VM and it created its "docker0" interface. Then I changed the property ignore-auto-routes for the transient connection Network Manager created for the docker0 interface.
By doing that, the connection will be turned into a persistent connection. So far nothing crashed. The problem happened when I rebooted the VM, even though there is a persistent connection for docker0, Network Manager will create a new transient one: # nmcli -f name,uuid,filename connection show NAME UUID FILENAME lo 72244b8b-262f-4ff4-b473-c3555f6eddb8 /run/NetworkManager/system-connections/lo.nmconnection docker0 cfc97cd8-f11e-4067-a3f3-920f44d24475 /run/NetworkManager/system-connections/docker0.nmconnection docker0 4f89b08a-1454-459e-b6f6-7d10f21c9644 /run/NetworkManager/system-connections/netplan-docker0.nmconnection netplan-wlan0-mynetwork 56c626d3-3b3a-38e6-9ecc-ae103ea78e0f /run/NetworkManager/system-connections/netplan-wlan0-mynetwork.nmconnection Now if I try to change the first one, it will be persisted and will point to the same filename. That's where it crashes: # nmcli con modify cfc97cd8-f11e-4067-a3f3-920f44d24475 ipv4.ignore-auto-routes yes Error: Failed to modify connection 'docker0': Message recipient disconnected from message bus without replying If this is the scenario people have in their systems, the forticlient software might be trying to change that option for all the connections it finds (to workaround some problem maybe) and causing the crash. The persistent connection might have been created by a previous run of the forticlient software. When one asks Network Manager to not manage those external interfaces, transient connections will not be created so the problem will not happen. It seems this workaround also helps: # cat /etc/NetworkManager/NetworkManager.conf ... [device] wifi.scan-rand-mac-address=no keep-configuration=no Add "keep-configuration=no" to the [device] section. With this, Network Manager will not create transient connections for external interfaces. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2089930 Title: NetworManager crashes when modifing connection (ipv4.ignore-auto- routes yes) To manage notifications about this bug go to: https://bugs.launchpad.net/netplan/+bug/2089930/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs