anchor.diff:          chown root /var/gvpe
           chmod 700 /var/gvpe
           cp ${finalConfig} /var/gvpe/gvpe.conf
  -	cp ${ifupScript} /var/gvpe/if-up
  +        cp ${ifupScript} /var/gvpe/if-up
         '';
   
         inherit exec;
  
positive.code: 
  let 
    inherit (pkgs.lib) mkOption mkIf;
    cfg = config.services.gvpe;
    finalConfig = if cfg.configFile != null then 
      cfg.configFile
    else if cfg.configText != null then
  
negative.code:     }
    else 
      throw "You must either specify contents of the config file or the config file itself for GVPE";
  
    ifupScript = if cfg.ipAddress == null || cfg.subnet == null then 
       throw "Specify IP address and subnet (with mask) for GVPE" 
     else if cfg.nodename == null then 
  