是hadoop文件系统依赖的基础配置，很多路径都依赖它。它默认的位置是在/tmp/{$user}下面，但是在/tmp路径下的存储是不安全的，因为linux一次重启，文件就可能被删除。
按照hadoop Getting Start中Single Node Setup一节中的步骤走下来之后，伪分布式已经运行起来了。怎么更改默认的路径，并使其生效?请按照下面的步骤来：
1、编辑conf/,在里面加上如下属性:
<property>
<name></name>
<value>/home/had/hadoop/data</value>
<description>A base for other temporary directories.</description>
</property>
2、停止hadoop: bin/
3、重新格式化namenode节点。bin/hadoop namenode -format
注意：此处至关重要，否则namenode会启动不起来。
4、启动 bin/
5、测试bin/hadoop fs -put conf conf
总结：第三步尤为重要，一开始我使用了错误的命令：bin/hadoop fs -format 来进行格式化，但一直报连不上服务器的错误：
11/11/20 17:14:14 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 0 time(s).
11/11/20 17:14:15 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 1 time(s).
11/11/20 17:14:16 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 2 time(s).
11/11/20 17:14:17 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 3 time(s).
11/11/20 17:14:18 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 4 time(s).
11/11/20 17:14:19 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 5 time(s).
11/11/20 17:14:20 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 6 time(s).
11/11/20 17:14:21 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 7 time(s).
11/11/20 17:14:22 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 8 time(s).
11/11/20 17:14:23 INFO : Retrying connect to server: localhost/127.0.0.1:9000. Already tried 9 time(s).
Bad connection to FS. command aborted. exception: Call to localhost/127.0.0.1:9000 failed on connection exception: : Connection refused
使用jps命令查看java进程发现没有NameNode的进程。
最后发现是命令用错了。应该使用bin/hadoop namenode -format 这个命令来格式化文件系统，并且应该是在启动hadoop之前进行操作。
总的来说，按照本文的步骤便可以对默认的进行更改。
本文列出作者实践过程中出现的失误，以及它们的解决办法，希望对后来者有用。