code: void registerMBean(Configuration conf) {
      // We wrap to bypass standard mbean naming convention.
      // This wraping can be removed in java 6 as it is more flexible in
      // package naming for mbeans and their impl.
      StandardMBean bean;
      try {
        versionBeanName = VersionInfo.registerJMX("NameNode");
        myFSMetrics = new FSNamesystemMetrics(conf, this);
        bean = new StandardMBean(this, FSNamesystemMBean.class);
        mbeanName = MBeanUtil.registerMBean("NameNode", "FSNamesystemState", bean);
      } catch (NotCompliantMBeanException e) {
        e.printStackTrace();
      }
  
      LOG.info("Registered FSNamesystemStatusMBean");
    }
docs: Register the FSNamesystem MBean using the name
  "hadoop:service=NameNode,name=FSNamesystemState"