Confusing systemd networking config warning

On rebuild, I get the following warning:

building the system configuration…
trace: warning: The combination of systemd.network.enable = true, networking.useDHCP = true and networking.useNetworkd = false can cause both networkd and dhcpcd to manage the same interfaces. This can lead to loss of networking. It is recommended you choose only one of networkd (by also enabling networking.useNetworkd) or scripting (by disabling systemd.network.enable)

I use networking.hostID and networking.hostName and networkmanager.enable = true; Removing the latter kills networking, and I need a hostID for ZFS.

I’m confused as to what the warning really means and how best to avoid it.

Any insights appreciated…

Without being able to see your configuration what I believe you’re running into is that networking.useDHCP is set to true by default. When you enable NetworkManager (or any other network management) you need to explicitly disable networking.useDHCP by setting it to false (Ex: networking.useDHCP = false).

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none of those have anything to do with it. They are not mentioned in the warning. Somewhere, you have systemd.network.enable = true; set. That is the problem. Or, possibly in combination with what @bzLem0n said.

Thanks - it was networking.useDHCP is set to true by default