anchor.diff:  
   let
   
  -  inherit (pkgs) utillinux;
  +  inherit (pkgs) cryptsetup utillinux;
   
  -  toPath = x: if x.device != null then x.device else "/dev/disk/by-label/${x.label}";
  -  
   in
   
   {
  
positive.code: 
        type = types.list types.optionSet;
  
        options = {
  
          device = mkOption {
            default = null;
            example = "/dev/sda3";
            type = types.nullOr types.string;
            description = ''
              Path of the device.
            '';
          };
  
          label = mkOption {
            default = null;
            example = "swap";
            type = types.nullOr types.string;
            description = "
              Label of the device.  Can be used instead of <varname>device</varname>.
            ";
          };
  
        };
  
negative.code:         startOn = ["startup" "new-devices"];
  
          script =
            ''
              ${toString (map (x: x.command) config.swapDevices)}
  
              # Remove swap devices not listed in swapDevices.
              for used in $(cat /proc/swaps | grep '^/' | sed 's/ .*//'); do
  