anchor.diff:          description = "Definition of systemd per-user service units.";
         };
   
  +      sockets = mkOption {
  +        default = {};
  +        type = types.attrs;
  +        description = "Definition of systemd per-user sockets";
  +      };
  +
         targets = mkOption {
           default = {};
           type = types.attrs;
  
positive.code:           message =
              let
                names = concatStringsSep ", " (
                    attrNames (cfg.services // cfg.targets // cfg.timers)
                );
              in
                "Must use Linux for modules that require systemd: " + names;
  
negative.code: 
    cfg = config.systemd.user;
  
    enabled = cfg.services != {}
        || cfg.sockets != {}
        || cfg.targets != {}
        || cfg.timers != {};
  
    toSystemdIni = (import lib/generators.nix).toINI {
      mkKeyValue = key: value:
  