anchor.diff:              # Ensure that this job is restarted when fstab changed:
               # ${fstab}
               echo "mounting filesystems..."
  +
  +            # Format devices.
  +            ${flip concatMapStrings config.fileSystems (fs: optionalString fs.autoFormat ''
  +              if [ -e "${fs.device}" ]; then
  +                type=$(blkid -p -s TYPE -o value "${fs.device}" || true)
  +                if [ -z "$type" ]; then
  +                  echo "creating ${fs.fsType} filesystem on ${fs.device}..."
  +                  mkfs.${fs.fsType} "${fs.device}"
  +                fi
  +              fi
  +            '')}
   
               # Create missing mount points.  Note that this won't work
               # if the mount point is under another mount point.
  
positive.code:           + " " + fs.fsType
            + " " + fs.options
            + " 0"
            + " " + (if fs.fsType == "none" || fs.noCheck then "0" else
                     if fs.mountPoint == "/" then "1" else "2")
            + "\n"
        )}
  
negative.code:           '';
          };
  
          autoFormat = mkOption {
            default = false;
            type = types.bool;
            description = ''
              If the device does not currently contain a filesystem (as
              determined by <command>blkid</command>, then automatically
              format it with the filesystem type specified in
              <option>fsType</option>.  Use with caution.
            '';
          };
  
          noCheck = mkOption {
            default = false;
            type = types.bool;
  