I have a problem on Ubuntu Server 18.04 running on a RPi 3B+. When booting with only the wifi connection, the system hangs for 2 mins waiting on eth0 to connect. I've added optional: true, but it is ignored.

My /etc/netplan:

# This file is generated from information provided by

# the datasource.  Changes to it will not persist across an instance.

# To disable cloud-init's network configuration capabilities, write a file

# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:

# network: {config: disabled}

network:

    version: 2

    renderer: networkd

    ethernets:

        eth0:

            dhcp4: true

            match:

                macaddress: b8:27:eb:db:7f:54

            set-name: eth0

            optional: true

    wifis:

        wlan0:

            dhcp4: true

            access-points:

                "Lagrange Point 5G":

                     password: "*****"

            nameservers:

                addresses: [10.0.1.1, 8.8.8.8]

Here is the tail end of dmesg:

[   19.540586] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready

[   19.540603] brcmfmac: power management disabled

[   19.546500] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready

[  145.054536] new mount options do not match the existing superblock, will be ignored

[  152.587186] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

Anyone know what I'm doing wrong?

EDIT: Added requested info...

$ sudo lshw -C network

  *-network:0               

       description: Wireless interface

       physical id: 2

       logical name: wlan0

       serial: b8:27:eb:9f:ba:34

       capabilities: ethernet physical wireless

       configuration: broadcast=yes driver=brcmfmac driverversion=7.45.154 firmware=01-4fbe0b04 ip=10.0.1.38 multicast=yes wireless=IEEE 802.11

  *-network:1 DISABLED

       description: Ethernet interface

       physical id: 3

       logical name: eth0

       serial: b8:27:eb:ca:ef:61

       capacity: 1Gbit/s

       capabilities: ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation

       configuration: autonegotiation=on broadcast=yes driver=lan78xx driverversion=1.0.6 link=no multicast=yes port=MII

And confirming netplan configuration:

$ cat /etc/network/interfaces

# ifupdown has been replaced by netplan(5) on this system.  See

# /etc/netplan for current configuration.

# To re-enable ifupdown on this system, you can run:

#    sudo apt install ifupdown

Btw, I have confirmed the exact same behavior on two different Raspberry Pi 3B+s, just to rule out bad hardware.

Edit #2: I updated my netplan as suggested by @heynnema and ran:

$ sudo netplan --debug generate

DEBUG:command generate: running ['/lib/netplan/generate']

** (generate:2077): DEBUG: 19:40:02.567: Processing input file /etc/netplan/50-cloud-init.yaml..

** (generate:2077): DEBUG: 19:40:02.567: starting new processing pass

** (generate:2077): DEBUG: 19:40:02.568: wlan0: adding wifi AP 'Lagrange Point 5G'

** (generate:2077): DEBUG: 19:40:02.568: wlan0: setting default backend to 1

** (generate:2077): DEBUG: 19:40:02.568: eth0: setting default backend to 1

** (generate:2077): DEBUG: 19:40:02.568: Generating output files..

** (generate:2077): DEBUG: 19:40:02.568: wlan0: Creating wpa_supplicant configuration file run/netplan/wpa-wlan0.conf

** (generate:2077): DEBUG: 19:40:02.569: Creating wpa_supplicant service enablement link /run/systemd/system/multi-user.target.wants/[email protected]

** (generate:2077): DEBUG: 19:40:02.569: NetworkManager: definition wlan0 is not for us (backend 1)

** (generate:2077): DEBUG: 19:40:02.569: NetworkManager: definition eth0 is not for us (backend 1)