This happened some hours after I upgraded to Debian Buster on my Bandwagonhost VPS. The IP timed out all over the world. Then I did a research in the root shell. It turned out to be
ifup: Failed to bring up eth1. systemd: networking.service: Failed with result 'exit-code'.
Searched and found a solution1:
# apt install network-manager # systemctl enable systemd-networkd # systemctl enable systemd-resolved # systemctl start systemd-networkd # systemctl start systemd-resolved # apt install isc-dhcp-client # dpkg-reconfigure resolvconf
Then the IP worked again, but
networking.service still failed with the same error. I searched again and found it related to
/etc/network/interfaces looked like this:
source /etc/network/interfaces.d/* auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp auto eth1 iface eth1 inet dhcp
Meanwhile the output of
networkctl looked like this:
IDX LINK TYPE OPERATIONAL SETUP 1 lo loopback carrier unmanaged 2 eth0 ether routable unmanaged
There's nothing to do with so-called eth1, so this is my edited
source /etc/network/interfaces.d/* auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp #auto eth1 #iface eth1 inet dhcp
The reason why that happened might be due to my selection of using the config file from maintainer's package when I did the upgrade.