Enhancements to ifupdown in systemd
ifup-all-auto.service
This systemd unit should make sure that all of the network interfaces that
are enabled by allow-auto parameter are up before the
network-online.target is reached. This makes that target usable on
Debian/Ubuntu hosts; services that depend on that target should work properly
with the assumption that the host has network connectivity at that point.
ifup-allow-boot.service
This systemd unit will bring up all network interfaces that are
marked by allow-boot and allow-hotplug parameters at system boot time.
It is run after the networking.service unit and will use the command
systemctl start ifup@<interface>.service to start the interfaces, so
that any processes that are attached to them will be put in their separate
cgroups. This allows better network management on systemd hosts.