在hadoop1.2.1的安装说明中有说明要预先安装java，我安装了好多版本的java以及好多版本的hadoop，然后发现oracle-java7与hadoop1.2.1是可以匹配的。

一，安装具体步骤如下：

1. 安装java： sudo apt-get install oracle-java7-installer

2. 安装hadoop1.2.1： http://hadoop.apache.org/docs/r1.2.1/single_node_setup.html#Download

二，测试是否安装成功（伪分布式模式）：

Format a new distributed-filesystem:
$ bin/hadoop namenode -format

Start the hadoop daemons:
$ bin/start-all.sh

The hadoop daemon log output is written to the ${HADOOP_LOG_DIR} directory (defaults to ${HADOOP_HOME}/logs).
Browse the web interface for the NameNode and the JobTracker; by default they are available at:
NameNode - http://localhost:50070/
JobTracker - http://localhost:50030/
Copy the input files into the distributed filesystem:
$ bin/hadoop fs -put conf input

Run some of the examples provided:
$ bin/hadoop jar hadoop-examples-*.jar grep input output ‘dfs[a-z.]+‘

Examine the output files:
Copy the output files from the distributed filesystem to the local filesytem and examine them:
$ bin/hadoop fs -get output output 
$ cat output/*

When you‘re done, stop the daemons with:
$ bin/stop-all.sh

三，web UI

1. NameNode：http://localhost:50070/
2. JobTracker ：http://localhost:50030/