public BackupHdfs() {
    try {
      m_wrMkdirs = new PrintWriter(new BufferedWriter(new FileWriter("hdfs-mkdirs.sh")));
      m_wrMkdirs.println("hadoop fs -mkdir /mapred");
      m_wrMkdirs.println("hadoop fs -mkdir /mapred/system");

      m_wrChmods = new PrintWriter(new BufferedWriter(new FileWriter("hdfs-chmods.sh")));
      m_wrChmods.println("hadoop fs -chmod 775 /");
      m_wrChmods.println("hadoop fs -chown hdfs:hadoop /");
      m_wrChmods.println("hadoop fs -chown mapred:hadoop /mapred/system");
      m_wrChmods.println("hadoop fs -chmod 700 /mapred/system");
    } catch (IOException e) {
      System.err.println("ERROR: failed to open files for writing: " + e.toString());
    }
  }
  /**
   * Compare the checksums of the hdfs file as well as the local copied file.
   *
   * @author [email protected]
   * @date Fri Jan 27 06:06:00 2012
   */
  boolean compareChecksums(FileSystem fs, Path p, String sFsPath) {
    try {
      // get hdfs file info
      FileStatus stat = fs.getFileStatus(p);

      // get HDFS checksum
      FileChecksum ck = fs.getFileChecksum(p);
      String sCk, sCkShort;
      if (ck == null) {
        sCk = sCkShort = "<null>";
      } else {
        sCk = ck.toString();
        sCkShort = sCk.replaceAll("^.*:", "");
      }

      // System.out.println(p.toUri().getPath() + " len=" + stat.getLen()
      // + " " + stat.getOwner() + "/" + stat.getGroup()
      // + " checksum=" + sCk);

      // find the local file
      File fLocal = new File(sFsPath);
      if (!fLocal.exists()) {
        System.out.println("CHECKSUM-ERROR: file does not exist: " + sFsPath);
        return false;
      }
      if (!fLocal.isFile()) {
        System.out.println("CHECKSUM-ERROR: path is not a file: " + sFsPath);
        return false;
      }
      if (stat.getLen() != fLocal.length()) {
        System.out.println(
            "CHECKSUM-ERROR: length mismatch: "
                + sFsPath
                + " hdfslen="
                + stat.getLen()
                + " fslen="
                + fLocal.length());
        return false;
      }

      // get local fs checksum
      FileChecksum ckLocal = getLocalFileChecksum(sFsPath);
      if (ckLocal == null) {
        System.out.println("ERROR Failed to get checksum for local file " + sFsPath);
        return false;
      }

      // compare checksums as a string, after stripping the
      // algorithm name from the beginning
      String sCkLocal = ckLocal.toString();
      String sCkLocalShort = sCkLocal.replaceAll("^.*:", "");

      if (false == sCkShort.equals(sCkLocalShort)) {
        System.out.println(
            "CHECKSUM-ERROR: checksum mismatch: "
                + sFsPath
                + "\nhdfs = "
                + sCk
                + "\nlocal= "
                + sCkLocal);
        return false;
      }

      return true;
    } catch (IOException e) {
      System.out.println("CHECKSUM-ERROR: " + sFsPath + " exception " + e.toString());
    }

    return false;
  }