How to write sample index.html to nginx/www user dir

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Hi all,

I have a nginx module where I want to write a sample index.html to the www user public dir (i.e. "${config.users.users.www.home}/public, aka /var/lib/www/public)

How can I do that? Right now I use writeTextDir "index.html" which writes index.html to the nix store. Is thre a reason why I would want to keep using writeTextDir and pointing root to the nix store instead of /var/lib/www/public

How can I test modules? I do nixos-rebuild build-vm --flake .#machine, but is it possible to get just the result of the module?

The nginx module

{ config, pkgs, ... }:

let
  domain = "xx.xx.xx.xx";
  # https://nixos.org/manual/nixpkgs/stable/#trivial-builder-writeText
  nginxWebRoot = pkgs.writeTextDir "index.html" ''
    <html><body><h1>Hello from NGINX</h1></body></html>
  '';
in
    {
      networking.firewall.allowedTCPPorts = [ 80 443 ];
      services.nginx = {
        enable = true;
        virtualHosts = {
          ${domain} = {
            root = "${nginxWebRoot}";
            # root = "${config.users.users.www.home}/public";
            locations."= /" = {
            };
          };
        };
      };

      users.users.www = {
        description = "Owns the web root for www";
        isSystemUser = true;
        home = "/var/lib/www";
        createHome = true;
        homeMode = "755";
        group = "www";
        useDefaultShell = true;
        openssh.authorizedKeys.keys = [ ];
      };
      users.groups.www = { };
    }
}

FWIW, here’s the full module

{ config, lib, pkgs, ... }:

with lib;
let
  domain = "xx.xx.xx.xx";
  # https://nixos.org/manual/nixpkgs/stable/#trivial-builder-writeText
  nginxWebRoot = pkgs.writeTextDir "index.html" ''
    <html><body><h1>Hello from NGINX</h1></body></html>
  '';

  cfg = config.modules.services.nginx;
in {
  options.modules.services.nginx = {
    enableCloudflareSupport = mkOption {
      type = types.bool;
      default = false;
    };
  };

  config = mkMerge [
    {
      networking.firewall.allowedTCPPorts = [ 80 443 ];
      services.nginx = {
        enable = true;

        recommendedOptimisation = true;
        recommendedBrotliSettings = true;
        recommendedGzipSettings = true;
        recommendedZstdSettings = true;
        recommendedProxySettings = true;

        # Reduce the permitted size of client requests, to reduce the likelihood
        # of buffer overflow attacks. This can be tweaked on a per-vhost basis,
        # as needed.
        clientMaxBodySize = "256k"; # default 10m
        # Significantly speed up regex matchers
        appendConfig = "pcre_jit on;";
        commonHttpConfig = ''
          client_body_buffer_size  4k;       # default: 8k
          large_client_header_buffers 2 4k;  # default: 4 8k

          map $sent_http_content_type $expires {
              default                    off;
              text/html                  10m;
              text/css                   max;
              application/javascript     max;
              application/pdf            max;
              ~image/                    max;
          }

          log_format main '$remote_addr - $remote_user [$time_iso8601] '
                          '"$host" "$request" $status $body_bytes_sent $request_time '
                          '"$http_referer" "$http_user_agent"';
          access_log /var/log/nginx/access.log main;
        '';

        virtualHosts = {
          ${domain} = {
            root = "${nginxWebRoot}";
            # root = "${config.users.users.www.home}/public";
            locations."= /" = {
            };
            locations."/transmission" = {
              proxyPass = "http://127.0.0.1:9091/transmission";
              proxyWebsockets = true;
              extraConfig = ''
                deny all;
              '';
            };
          };
        };
      };

      users.users.www = {
        description = "Owns the web root for www";
        isSystemUser = true;
        home = "/var/lib/www";
        createHome = true;
        homeMode = "755";
        group = "www";
        useDefaultShell = true;
        openssh.authorizedKeys.keys = [ ];
      };
      users.groups.www = { };
    }

    (lib.mkIf cfg.enableCloudflareSupport {
      services.nginx.commonHttpConfig = ''
        ${concatMapStrings (ip: ''
          set_real_ip_from ${ip};
        '') (filter (line: line != "") (splitString "\n" ''
          ${readFile (fetchurl "https://www.cloudflare.com/ips-v4/")}
          ${readFile (fetchurl "https://www.cloudflare.com/ips-v6/")}
        ''))}
        real_ip_header CF-Connecting-IP;
      '';
    })
  ];
}