define nixos module

flake.nix

@@ -33,7 +33,10 @@
           mev-rs = pkgs.callPackage ./nix/mev-rs.nix { inherit pkgs; crane = craneLib; };
         in
         {
-          devShells.default = import ./shell.nix { inherit pkgs; };
           packages = { inherit mev-rs; };
+          devShells.default = import ./shell.nix { inherit pkgs; };
+          nixosModules.default = import ./nix/module.nix {
+            nixpkgs.overlays = self.overlays;
+          };
         });
 }

nix/module.nix

@@ -0,0 +1,46 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.services.mev-rs;
+
+  mev-rs = pkgs.mev-rs;
+
+  name = "mev-${cfg.enable}-rs";
+
+  cmd = ''
+    ${mev-rs}/bin/mev \
+    ${cfg.enable} \
+    ${cfg.config-file}
+  '';
+in
+{
+  options.services.mev-rs = {
+    enable = lib.mkOption {
+      type = lib.types.enum [ "boost" "build" ];
+      description = "which subcommand of `mev-rs` to run";
+    };
+    config-file = lib.mkOption {
+      type = lib.types.str;
+      description = ''
+        path to a config file suitable for the `mev-rs` toolkit
+      '';
+    };
+  };
+
+  config = {
+    environment.systemPackages = [
+      mev-rs
+    ];
+
+    systemd.services."${name}" = {
+      description = name;
+      wantedBy = [ "multi-user.target" ];
+      after = [ "vc.service" ];
+      serviceConfig = {
+        ExecStart = cmd;
+        Restart = "on-failure";
+        RestartSec = "10s";
+        SyslogIdentifier = name;
+      };
+    };
+  };
+}