Use the same idea as prysm-beacon to set the user.

Author: thalin

modules/geth/default.nix

@@ -122,7 +122,10 @@ in {
               serviceConfig = mkMerge [
                 baseServiceConfig
                 {
-                  User = mkDefault serviceName;
+                  User =
+                    if cfg.user != null
+                    then cfg.user
+                    else mkDefault serviceName;
                   StateDirectory = mkDefault serviceName;
                   ExecStart = mkDefault "${cfg.package}/bin/geth ${scriptArgs}";
                 }

modules/geth/options.nix

@@ -9,6 +9,12 @@
     options = rec {
       enable = mkEnableOption "Go Ethereum Node";
 
+      user = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = "User to run the service as.";
+      };
+
       inherit args;
 
       extraArgs = mkOption {