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Hadoop 配置出错信息汇总
1：INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 0 time(s).
运行
ximo@Ubuntu:~$ hadoop fs -ls
14/01/08 22:01:41 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 0 time(s).
14/01/08 22:01:42 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 1 time(s).
14/01/08 22:01:43 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 2 time(s).
14/01/08 22:01:44 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 3 time(s).
14/01/08 22:01:45 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 4 time(s).
14/01/08 22:01:46 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 5 time(s).
14/01/08 22:01:47 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 6 time(s).
14/01/08 22:01:48 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 7 time(s).
14/01/08 22:01:49 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 8 time(s).
14/01/08 22:01:50 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:12200. Already tried 9 time(s).
mkdir: Call From Lenovo-G460-LYH/127.0.0.1 to localhost:12200 failed on connection exception: Java.net.ConnectException: 拒绝连接; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
有几种原因：
1）hadoop 配置
主要是 $HADOOP_HOME/conf/hdfs-site.xml、mapred-site.xml、core-site.xml 中的配置是否正确，伪分布式模式可以参考前面的 blog，或是网上的文章，一大堆一大堆的。
2）机器连不通
如果是分布式的，还要看 hadoop 客户端机器能不能 ping 通 hdfs 机器，注意 hdfs 的端口号
3）namenode 没有启动（本人是这种原因）
$stop-all.sh 如果出现 no namenode stop 则表示是 namenode 的问题
$hadoop namenode -format
$start-all.sh
4）其他。
相关阅读：
Ubuntu 13.04 上搭建 Hadoop 环境 http://www.linuxidc.com/Linux/2013-06/86106.htm
Ubuntu 12.10 +Hadoop 1.2.1 版本集群配置 http://www.linuxidc.com/Linux/2013-09/90600.htm
Ubuntu 上搭建 Hadoop 环境（单机模式 + 伪分布模式）http://www.linuxidc.com/Linux/2013-01/77681.htm
Ubuntu 下 Hadoop 环境的配置 http://www.linuxidc.com/Linux/2012-11/74539.htm
单机版搭建 Hadoop 环境图文教程详解 http://www.linuxidc.com/Linux/2012-02/53927.htm
搭建 Hadoop 环境（在 Winodws 环境下用虚拟机虚拟两个 Ubuntu 系统进行搭建）http://www.linuxidc.com/Linux/2011-12/48894.htm
更多 Hadoop 相关信息见Hadoop 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=13
