anchor.diff:              exec > /dev/console 2>&1
               echo "mounting filesystems..."
               export PATH=${config.system.sbin.mount}/bin:${makeSearchPath "sbin" ([pkgs.utillinux] ++ fsPackages)}:$PATH
  -            ${optionalString needsBtrfsProgs "${pkgs.btrfsProgs}/bin/btrfs device scan"}
  +            ${optionalString usingBtrfs "${pkgs.btrfsProgs}/bin/btrfs device scan"}
               ${pkgs.mountall}/sbin/mountall
             '';
         };
  
positive.code:         target = "fstab";
        };
  
      jobs.mountall =
        { startOn = "started udev"
            # !!! The `started nfs-kernel-statd' condition shouldn't be
  
negative.code: with pkgs.lib;
  
  let
    usingSome = fsname: any (fs: fs.fsType == fsname) config.fileSystems;
    usingSomeStage1 =  fsname: any (fs: fs.fsType == fsname &&
      (fs.mountPoint == "/" || fs.neededForBoot)) config.fileSystems;
  
    usingBtrfs = usingSome "btrfs";
    usingBtrfsStage1 = usingSomeStage1 "btrfs";
  
    usingReiserfs = usingSome "reiserfs";
    usingReiserfsStage1 = usingSomeStage1 "reiserfs";
  
    # Packages that provide fsck backends.
    fsPackages = [ pkgs.e2fsprogs pkgs.dosfstools ]
      ++ optional usingReiserfs pkgs.btrfsProgs
      ++ optional usingBtrfs pkgs.btrfsProgs;
  
    fsKernelModules = optional usingBtrfsStage1 [ "btrfs" "crc32c" ]
      ++ optional usingReiserfsStage1 [ "reiserfs" ];
  
    fsExtraUtilsCommands = optionalString usingBtrfsStage1 ''
        cp -v ${pkgs.btrfsProgs}/bin/btrfsck $out/bin
        cp -v ${pkgs.btrfsProgs}/bin/btrfs $out/bin
        ln -sv btrfsck $out/bin/fsck.btrfs
      '';
  
    fsPostDeviceCommands = optionalString usingBtrfsStage1 ''
      btrfs device scan
    '';
  
  in
  
  