anchor.diff:    cfgZfs = config.boot.zfs;
     cfgSnapshots = config.services.zfs.autoSnapshot;
     cfgSnapFlags = cfgSnapshots.flags;
  +  cfgScrub = config.services.zfs.autoScrub;
   
     inInitrd = any (fs: fs == "zfs") config.boot.initrd.supportedFilesystems;
     inSystem = any (fs: fs == "zfs") config.boot.supportedFilesystems;
   
     enableAutoSnapshots = cfgSnapshots.enable;
  -  enableZfs = inInitrd || inSystem || enableAutoSnapshots;
  +  enableAutoScrub = cfgScrub.enable;
  +  enableZfs = inInitrd || inSystem || enableAutoSnapshots || enableAutoScrub;
   
     kernel = config.boot.kernelPackages;
   
  
positive.code:         zfsSupport = true;
        };
  
        environment.etc."zfs/zed.d".source = "${packages.zfsUser}/etc/zfs/zed.d/*";
  
        system.fsPackages = [ packages.zfsUser ]; # XXX: needed? zfs doesn't have (need) a fsck
        environment.systemPackages = [ packages.zfsUser ]
  
negative.code:         type = types.int;
          description = ''
            Number of monthly auto-snapshots that you wish to keep.
          '';
        };
      };
  
      services.zfs.autoScrub = {
        enable = mkOption {
          default = false;
          type = types.bool;
          description = ''
            Enables periodic scrubbing of ZFS pools.
          '';
        };
  
        interval = mkOption {
          default = "Sun, 02:00";
          type = types.str;
          example = "daily";
          description = ''
            Systemd calendar expression when to scrub ZFS pools. See
            <citerefentry><refentrytitle>systemd.time</refentrytitle>
            <manvolnum>5</manvolnum></citerefentry>.
          '';
        };
  
        pools = mkOption {
          default = [];
          type = types.listOf types.str;
          example = [ "tank" ];
          description = ''
            List of ZFS pools to periodically scrub. If empty, all pools
            will be scrubbed.
          '';
        };
      };
  