---
I think I addressed all comments in previous threads. This does not include the
change to lib.formats, but works around the limitation with a private cfgFormat
function. Given that the lib.formats patch is changing a somewhat corelib in
nixpkgs, I figure it will take a while to review and merge, so this patch is
available as an alternative in the meantime.

 nixos/modules/module-list.nix                 |  1 +
 .../modules/services/web-servers/gmnisrv.nix  | 70 +++++++++++++++++++
 2 files changed, 71 insertions(+)
 create mode 100644 nixos/modules/services/web-servers/gmnisrv.nix

diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix
index 41cbb501323..54cda99c85f 100644
--- a/nixos/modules/module-list.nix
+++ b/nixos/modules/module-list.nix
@@ -883,6 +883,7 @@
   ./services/web-servers/caddy.nix
   ./services/web-servers/darkhttpd.nix
   ./services/web-servers/fcgiwrap.nix
+  ./services/web-servers/gmnisrv.nix
   ./services/web-servers/hitch/default.nix
   ./services/web-servers/hydron.nix
   ./services/web-servers/jboss/default.nix
diff --git a/nixos/modules/services/web-servers/gmnisrv.nix b/nixos/modules/services/web-servers/gmnisrv.nix
new file mode 100644
index 00000000000..2dbe872329b
--- /dev/null
+++ b/nixos/modules/services/web-servers/gmnisrv.nix
@@ -0,0 +1,70 @@
+{ lib
+, options
+, config
+, pkgs
+, ...
+}:
+
+let
+  cfg = config.services.gmnisrv;
+
+  # from https://github.com/openlab-aux/vuizvui/blob/1576e1025d570851449f6668e0bda2b1b9b21e06/modules/programs/foot/default.nix#L15-L48
+  # this can be replaced with lib.formats.ini when
+  # https://github.com/NixOS/nixpkgs/pull/118925 is merged
+  cfgFormat = {
+    type = with lib.types;
+      let
+        iniAtom = nullOr (oneOf [ bool int float str ]) // {
+          description = "INI atom (null, bool, int, float, or string)";
+        };
+      in (attrsOf (either iniAtom (attrsOf iniAtom))) // {
+        description = ''
+          attribute set of either top-level INI atoms (bool, int, float or string)
+          or attribute sets (sections) of INI atoms
+        '';
+      };
+    generate = name: value:
+      let
+        isSection = builtins.isAttrs;
+        topLevel = lib.filterAttrs (_: v: !(isSection v)) value;
+        sections = lib.filterAttrs (_: v: isSection v) value;
+      in  pkgs.writeText name ''
+        ${lib.generators.toKeyValue {} topLevel}
+        ${lib.generators.toINI {} sections}
+      '';
+  };
+in {
+  options.services.gmnisrv = {
+    enable = lib.mkEnableOption "Enable the gmnisrv service";
+    settings = lib.mkOption {
+      type = cfgFormat.type;
+      description = ''
+        Configuration for gmnisrv. See gmnisrv.ini(5) for supported settings.
+      '';
+      default = {
+        "listen" = lib.mkDefault "0.0.0.0:1965 [::]:1965";
+        ":tls" = {
+          "store" = lib.mkDefault "${cfg.dataDir}/certs";
+        };
+      };
+    };
+    package = lib.mkOption {
+      type = lib.types.package;
+      default = pkgs.gmnisrv;
+      description = "gmnisrv package to use";
+    };
+    dataDir = lib.mkOption {
+      type = lib.types.str;
+      default = "/var/lib/gemini";
+      description = "Where gmnisrv should store certs and other data.";
+    };
+  };
+  config = lib.mkIf cfg.enable {
+    systemd.services.gmnisrv = {
+      description = "gmnisrv service";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network-online.target" ];
+      script = "${cfg.package}/bin/gmnisrv -C ${cfgFormat.generate "gmnisrv.ini" cfg.settings}";
+    };
+  };
+}
-- 
2.31.1

Reviewed-by: William Casarin <jb55@jb55.com>