Comment 3 for bug 1914784

Great, thanks for the background!

I've done a bit more experimentation, and on Ubuntu servers NetworkManager will own and configure devices without specific configuration too, so this is a more general issue. Looking through Netplan's reference doc[0], I can't see any way of disabling this behaviour, so:

> I think it's more accurate to describe this as an issue with cloud-init's sysconfig renderer.

I think it's even more accurate to describe me as wrong. ;)

This feels like something of a grey area: the problem we're hitting is the difference in behaviour between our various backends: NetworkManager is "greedy" by default and will configure any interface that it isn't instructed to ignore, whereas networkd(-via-netplan) is not (and configures only the interfaces for which configuration is provided).

We'll need to loop our netplan folks in to discuss how to introduce these semantics into the netplan configuration format (which is a superset of cloud-init's v2 format), and I'm sure they'll have more background than me.

[0] https://netplan.io/reference/