The following procedure works for Ubuntu 18.04 (Bionic Beaver)

I. Reinstall the ifupdown package:

# apt-get update
# apt-get install ifupdown

II. Configure your /etc/network/interfaces file with configuration stanzas such as:

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

allow-hotplug enp0s3
auto enp0s3
iface enp0s3 inet static
address 192.168.1.133
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.1
# Only relevant if you make use of RESOLVCONF(8)
# or similar...
dns-nameservers 1.1.1.1 1.0.0.1

III. Make the configuration effective (no reboot needed): Continue reading “Ubuntu 18.04: Disable Netplan switch back to networking /etc/network/interfaces” »