code: public boolean hardLink(String src, String dst) throws IOException {  
      checkOpen();  
      try { 
        return namenode.hardLink(src, dst); 
      } catch(RemoteException re) { 
        throw re.unwrapRemoteException(AccessControlException.class,  
                                       NSQuotaExceededException.class,  
                                       DSQuotaExceededException.class); 
      } 
    }
docs: See {@link ClientProtocol#hardLink(String, String)}.