Hadoop namenode无法启动

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我是靠谱客的博主欣慰小鸭子，最近开发中收集的这篇文章主要介绍Hadoop namenode无法启动，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

转载http://blog.csdn.net/bychjzh/article/details/7830508

刚刚装好Pig，打算打开hadoop模式尝试下Pig，但是发现Pig报错

[root@master pig-0.9.1]# pig
2011-12-03 07:27:30,158 [main] INFO org.apache.pig.Main - Logging error messages to: /home/bell/software/hadoop-0.20.2/pig-0.9.1/pig_1322868450154.log
2011-12-03 07:27:30,403 [main] INFO org.apache.pig.backend.hadoop.executionengine.HExecutionEngine - Connecting to hadoop file system at: hdfs://localhost/
2011-12-03 07:27:31,544 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 0 time(s).
2011-12-03 07:27:32,545 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 1 time(s).
2011-12-03 07:27:33,546 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 2 time(s).
2011-12-03 07:27:34,547 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 3 time(s).
2011-12-03 07:27:35,548 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 4 time(s).
2011-12-03 07:27:36,549 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 5 time(s).
2011-12-03 07:27:37,550 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 6 time(s).
2011-12-03 07:27:38,550 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 7 time(s).
2011-12-03 07:27:39,551 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 8 time(s).
2011-12-03 07:27:40,552 [main] INFO org.apache.hadoop.ipc.Client - Retrying connect to server: localhost/127.0.0.1:8020. Already tried 9 time(s).
2011-12-03 07:27:40,582 [main] ERROR org.apache.pig.Main - ERROR 2999: Unexpected internal error. Failed to create DataStorage
Details at logfile: /home/bell/software/hadoop-0.20.2/pig-0.9.1/pig_1322868450154.log

发现错误后查看了下log，发现是connection refused，那么可能是namenode的问题，JPS查看进程，发现没有namenode进程，搜索网络发现如下解决方案：

最近遇到了一个问题，执行start-all.sh的时候发现JPS一下namenode没有启动

每次开机都得重新格式化一下namenode才可以
其实问题就出在tmp文件，默认的tmp文件每次重新开机会被清空，与此同时namenode的格式化信息就会丢失
于是我们得重新配置一个tmp文件目录
首先在home目录下建立一个hadoop_tmp目录
sudo mkdir ~/hadoop_tmp
然后修改hadoop/conf目录里面的core-site.xml文件，加入以下节点：
<property>
<name>hadoop.tmp.dir</name>
<value>/home/chjzh/hadoop_tmp</value>
<description>A base for other temporary directories.</description>
</property>
注意：我的用户是chjzh所以目录是/home/chjzh/hadoop_tmp

OK了，重新格式化Namenode
hadoop namenode -format
然后启动hadoop
start-all.sh
执行下JPS命令就可以看到NameNode了