anchor.diff:        ++ config.system.fsPackages;
   
       environment.etc = singleton
  -      { source = pkgs.writeText "fstab"
  -          ''
  -            # This is a generated file.  Do not edit!
  -
  -            # Filesystems.
  -            ${flip concatMapStrings config.fileSystems (fs:
  -                (if fs.device != null then fs.device else "/dev/disk/by-label/${fs.label}")
  -                + " " + fs.mountPoint
  -                + " " + fs.fsType
  -                + " " + fs.options
  -                + " 0"
  -                + " " + (if fs.fsType == "none" || fs.noCheck then "0" else
  -                         if fs.mountPoint == "/" then "1" else "2")
  -                + "\n"
  -            )}
  -
  -            # Swap devices.
  -            ${flip concatMapStrings config.swapDevices (sw:
  -                 "${sw.device} none swap\n"
  -            )}
  -          '';
  +      { source = fstab;
           target = "fstab";
         };
   
  
positive.code: 
  with pkgs.lib;
  
  {
  
    ###### interface
  
negative.code: 
          script =
            ''
              # Ensure that this job is restarted when fstab changed:
              # ${fstab}
              exec > /dev/console 2>&1
              echo "mounting filesystems..."
              ${pkgs.mountall}/sbin/mountall
  