I have not yet reproduced this on my Ubuntu 21.10 for lack of time, but I ran into it on a Debian 11 machine I was converting to Netplan and preparing to port the ifupdown scripts.
I tried ignoring unimportant interfaces, but no dice. So I ran an strace on /lib/systemd/systemd-networkd-wait-online (attached). I failed to understand what is really going on, but the program configures a epoll instance. After some successful use of that something fails to happen and the two minute timeout strikes. During that timeout, the program is repeatedly looking at /run/systemd/netif/links/1, but it does not change. The machine has four interfaces: lo, ens3, dummy1 and tun0. /run/systemd/netif/links/2 and /run/systemd/netif/links/3 are ens3 and dummy1, 4 is probably tun0, being the last created, and the state is ADDRESS_STATE=routable. But /run/systemd/netif/links/1 is strange. This should be lo, but lo is configured: 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever but /run/systemd/netif/links/1 is ADMIN_STATE=unmanaged OPER_STATE=carrier CARRIER_STATE=carrier ADDRESS_STATE=off So I thought that adding a netplan configuration for lo might help. Well, it doesn't. The strace is the same, except for the contents of the netif file. Please reopen this ticket and push it upstream. There is something uncouth about systemd-networkd-wait-online's relationship with lo. ** Attachment added: "wait-online.strace" https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1779340/+attachment/5577039/+files/wait-online.strace -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1779340 Title: systemd-networkd-wait-online.service Failed to start Wait for Network to be Configured with bridge Status in systemd package in Ubuntu: Invalid Bug description: The following simple netplan config results in a 2-minut unneccessary delay on boot. Everything works like it should in the end. The bridge has no interfaces due to a regression in Ubuntu migrating to netplan (see https://bugs.launchpad.net/ubuntu/+source/netplan.io/+bug/1779341). ubuntu@molnix3:~$ cat /etc/netplan/01-netcfg.yaml # This file describes the network interfaces available on your system # For more information, see netplan(5). network: version: 2 renderer: networkd ethernets: enp4s0: dhcp4: yes dhcp6: yes ubuntu@molnix3:~$ cat /etc/netplan/br1.yaml network: version: 2 bridges: br1: addresses: [10.1.0.9/16] interfaces: [] ubuntu@molnix3:~$ cat /usr/lib/networkd-dispatcher/routable.d/tap0 #!/bin/sh set -e if [ "$IFACE" = tap0 ]; then brctl addif br1 tap0 ip link set tap0 promisc on ifmetric tap0 5 fi ubuntu@molnix3:~$ journalctl -u systemd-networkd-wait-online.service -b -- Logs begin at Thu 2018-06-28 10:07:29 UTC, end at Fri 2018-06-29 14:09:18 UTC. -- Jun 29 13:58:16 molnix3 systemd[1]: Starting Wait for Network to be Configured... Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:16 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:17 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:17 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:17 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:17 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:18 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:18 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:19 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:20 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:20 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 13:58:21 molnix3 systemd-networkd-wait-online[1468]: ignoring: lo Jun 29 14:00:16 molnix3 systemd-networkd-wait-online[1468]: Event loop failed: Connection timed out Jun 29 14:00:16 molnix3 systemd[1]: systemd-networkd-wait-online.service: Main process exited, code=exited, status=1/FAILURE Jun 29 14:00:16 molnix3 systemd[1]: systemd-networkd-wait-online.service: Failed with result 'exit-code'. Jun 29 14:00:16 molnix3 systemd[1]: Failed to start Wait for Network to be Configured. ubuntu@molnix3:~$ /lib/systemd/systemd-networkd-wait-online managing: br1 managing: enp4s0 ignoring: lo ubuntu@molnix3:~$ networkctl IDX LINK TYPE OPERATIONAL SETUP 1 lo loopback carrier unmanaged 2 enp4s0 ether routable configured 3 br1 ether routable configured 4 tap0 ether routable unmanaged 4 links listed. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1779340/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp