Migration to the current network interface naming
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On package upgrade systems will keep their current names, but they will need to
be manually migrated by Debian 10 / Ubuntu 18.04 LTS. If you rely on the old
names in custom ifupdown stanzas, firewall scripts or other networking
configuration, these need to be updated to the new names.

First, determine all relevant network interface names: those in
/etc/udev/rules.d/70-persistent-net.rules, or if that does not exist (in
virtual machines), in "ip link" or /sys/class/net/.

Then for every interface name use a command like

grep -r eth0 /etc

to find out where it is being used.

Then on "real hardware" machines, rename the file to
70-persistent-net.rules.old; on VMs remove the file
/etc/udev/rules.d/80-net-setup-link.rules instead.

Reboot, adjust configuration files, and test your system.