anchor.diff:    # configuration file can be generated by http://slurm.schedmd.com/configurator.html
     configFile = pkgs.writeText "slurm.conf" 
       ''
  -    ${cfg.extraConfig}
  +      ${optionalString (cfg.controlMachine != null) ''controlMachine=${cfg.controlMachine}''}
  +      ${optionalString (cfg.controlAddr != null) ''controlAddr=${cfg.controlAddr}''}
  +      ${optionalString (cfg.nodeName != null) ''nodeName=${cfg.nodeName}''}
  +      ${optionalString (cfg.partitionName != null) ''partitionName=${cfg.partitionName}''}
  +      ${cfg.extraConfig}
       '';
   in
   
  
positive.code:     services.slurm = {
  
        server = {
          enable = mkOption {
            default = false;
            type = types.bool;
            description = ''
              Whether to enable slurm control daemon.
            '';
          };
  
        };
        
        client = {
          enable = mkOption {
            default = false;
            type = types.bool;
            description = ''
              Whether to enable slurm client daemon.
            '';
          };
  
        };
  
        extraConfig = mkOption {
  
negative.code:           the end of the slurm configuration file.
          '';
        };
      };
  
    };
  