Hadoop namenode无法启动

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