DHCP in initrd

[sjau]

Issue description

I'm having issues to get dhcp address into the initrd and still have network manager work properly. The reason is I have a native root encrypted zfs notebook that I'd like to reboot remotely. So since the notebook is sometimes at home, sometimes at the office (with different subnets) I need to use dhcp in the initrd, otherwise I can't login remotely.

Steps to reproduce

Add:

networking.useDHCP

to your configuration.nix and enable it. It will provide you with dynamic ip address in the initrd. However, useDHCP and networking.networkmanager.enable = true; don't mix so networkmanager has to be disabled. The problem with this approach is that once the system is fully booted (into KDE), there's no network manager available to easily turn on/off eth0, wifi0 etc......

Another option I tried is to add

boot.kernelParams = [ "ip=dhcp" ];

to the configuration.nix. This works with some caveats: Suddenly my resolv.conf only had as single entry options edns0 and wasn't able to resolve anything. I had to manually add nameserver x.x.x.x. A little solution was to use SystemD Resolved:

    services.resolved = {
        enable = true;
        fallbackDns = [ "10.0.0.1" "10.10.10.1" "10.100.100.1" "8.8.4.4" "8.8.8.8" ];
    };

That worked with some minor caveats. However the main problem with using boot.kernelParams = [ "ip=dhcp" ]; was that I just stopped the initrd bootup process waiting to obtain an ip address.

So, how can I get simple dhcp obtained ip in the initrd while still being able to use network manager later on?

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

[stale]

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[c0deaddict]

still important to me

[sjau]

still important to me

[matthias-t]

If all you want from networkmanager is turning interfaces on or off, you can do this with ip link set <interface> <up|down>. You can also do ad-hoc connections to wifi using wpa_cli. I guess initrd networking is mostly used on servers, so demand for networkmanager interoperability might be scarce. As a last resort I guess you could take a look at

nixpkgs/nixos/modules/system/boot/initrd-network.nix

Lines 123 to 135 in 236eb73

	+ optionalString doDhcp ''
	# Bring up all interfaces.
	for iface in ${dhcpIfShellExpr}; do
	echo "bringing up network interface $iface..."
	ip link set "$iface" up && ifaces="$ifaces $iface"
	done
	# Acquire DHCP leases.
	for iface in ${dhcpIfShellExpr}; do
	echo "acquiring IP address via DHCP on $iface..."
	udhcpc --quit --now -i $iface -O staticroutes --script ${udhcpcScript} ${udhcpcArgs}
	done
	''

and implement this yourself using boot.initrd.preLVMCommands and postMountCommands.

[stale]

I marked this as stale due to inactivity. → More info

[b2ag]

still important to me

[jrobsonchase]

Just ran across this as well. It seems like NetworkManager sees the already-existing connection left over from the initrd and creates a "Manual" entry for it that loses its DNS configuration.

[Doc-Steve]

I used these options (without boot.kernelParams = [ "ip=dhcp" ];)

boot.initrd.network.udhcpc.enable = true;
boot.initrd.network.flushBeforeStage2 = true;

Then networking.networkmanager.enable = true; worked.