使用此链接，尝试在ubuntu 12.04（64位计算机）中安装hadoop版本2.2.0（单节点群集）
http://bigdatahandler.com/hadoop-hdfs/installing-single-node-hadoop-2-2-0-on-ubuntu/
使用以下命令通过namenode格式化hdfs文件系统时

hadoop namenode -format

当我这么做的时候，得到以下问题，
14/08/07 10:38:39 fatal namenode.namenode:namenode join java.lang.runtimeexception异常：org.xml.sax.saxpasseeption；systemid:file:/usr/local/hadoop/etc/hadoop/mapred-site.xml；行号：27；列数：1；尾随节中不允许有内容。
为了解决下列问题，我需要做什么？
mapred-site.xml:

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!--
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. See accompanying LICENSE file.
-->

<!-- Put site-specific property overrides in this file. -->

<configuration>

<property>
<name>mapreduce.framework.name</name>
<value>yarn</value>
</property>

</configuration>