Bug#942042: systemd: Enabling systemd-networkd does not disable ifupdown management of /etc/network/interfaces

[Martin Pitt]

Hello Arthur,

Artur Pydo [2019-10-09 15:22 +0200]:
> I suggest to automatically disable the management of /etc/network/interfaces
> file (or rename that file ?) as long as the network interfaces is managed by
> another system such as systemd-networkd to avoid any confusion or a double
> configuration by different systems at the same time.

That would be a rather bad idea in general. You can certainly *make* ifupdown
and networkd (or NetworkManager, connman, etc.) conflict by configuring the
same interfaces in multiple places -- but usually, when you use more than one
subsystem for networking, they each configure different interfaces. E. g. NM
for dynamic wifi, networkd or ifupdown for ethernet. For these cases, a general
"starting networkd stops NM and ifdown" would be wrong and potentially
disastrous.

> I didn't see any recomendations in Debian documentation about
> /etc/network/interfaces and systemd-networkd conflict. It may be a good idea
> to point it out.

It really depends on what you put in them. But IMHO this shouldn't end up in a
battle of "different networking systems try to mutually stop themselves". Maybe
a better long-term approach would be to adopt Ubuntu's netplan
(https://netplan.io/, https://tracker.debian.org/pkg/netplan.io) that keeps
track of which particular backend manages a device, and you can switch between
them safely.

Martin