DNS in declarative container

I’m trying to write a declarative container and am having issues with host name resolution:

Setting this in my container’s config entry did not help:

      networking.useHostResolvConf = true;

My resolv.conf does not contain any nameserver.

Is there a way to fix this, particularly in a declarative fashion?

It looks like something is going on here though I’m not quite sure what, since it has --remove-destination.

In any case, my host and container resolv.conf files definitely do not match.

I was able to fix this using hte bindMounts container option, like:

  containers.flx_web =
  { autoStart = true;
    privateNetwork = true;
    hostAddress = "";
    localAddress = "";
    bindMounts = {
      "/etc/resolv.conf" = {
        hostPath = "/etc/resolv.conf";
        isReadOnly = true;

This is still an issue with 20.03. Maybe the container is created before networking is up in the host and there is no resolv.conf to copy?

Yes, I think the problem is this part of the systemd config:

          if containerConfig.autoStart then
              wantedBy = [ "machines.target" ];
              wants = [ "network.target" ];
              after = [ "network.target" ];
              restartTriggers = [

in https://github.com/NixOS/nixpkgs/blob/0023908b4ecef4e889a9bb524394f53c014950fe/nixos/modules/virtualisation/nixos-containers.nix. When the host uses DHCP, this means that the container is started before the host knows its DNS server. The wants/targets sections should be network-online.target instead.