<p>The tool scans all files and directories, starting from an indicated
 *  root path. The following abnormal conditions are detected and handled:</p>
 * <ul>
 * <li>files with blocks that are completely missing from all datanodes.<br/>
 * In this case the tool can perform one of the following actions:
 *  <ul>
 *      <li>none ({@link #FIXING_NONE})</li>
 *      <li>move corrupted files to /lost+found directory on DFS
 *      ({@link #FIXING_MOVE}). Remaining data blocks are saved as a
 *      block chains, representing longest consecutive series of valid blocks.</li>
 *      <li>delete corrupted files ({@link #FIXING_DELETE})</li>
 *  </ul>
 *  </li>
 *  <li>detect files with under-replicated or over-replicated blocks</li>
 *  </ul>
 *  Additionally, the tool collects a detailed overall DFS statistics, and
 *  optionally can print detailed statistics on block locations and replication
 *  factors of each file.
<p>The tool scans all files and directories, starting from an indicated
 *  root path. The following abnormal conditions are detected and handled:</p>
 * <ul>
 * <li>files with blocks that are completely missing from all datanodes.<br/>
 * In this case the tool can perform one of the following actions:
 *  <ul>
 *      <li>none ({@link #FIXING_NONE})</li>
 *      <li>move corrupted files to /lost+found directory on DFS
 *      ({@link #FIXING_MOVE}). Remaining data blocks are saved as a
 *      block chains, representing longest consecutive series of valid blocks.</li>
 *      <li>delete corrupted files ({@link #FIXING_DELETE})</li>
 *  </ul>
 *  </li>
 *  <li>detect files with under-replicated or over-replicated blocks</li>
 *  </ul>
 *  Additionally, the tool collects a detailed overall DFS statistics, and
 *  optionally can print detailed statistics on block locations and replication
 *  factors of each file. | NamenodeFsck.java