先记录下安装jdk出现的问题：

（1）首先删除掉已经安装的openjdk

sudo apt-get purge openjdk*

----以下出自：

http://blog.csdn.net/berryreload/article/details/7492012

Ubuntu 12.04 Precise

Clean up the historical open jdk:

sudo apt-get purge openjdk*

Add a new repo and install the sdk:

sudo add-apt-repository ppa:eugenesan/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

If you want the JRE and the browser plugin:

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

出现问题：

dpkg: error processing oracle-java7-installer (--configure):
 subprocess installed post-installation script returned error exit status 1
Setting up gsfonts-x11 (0.22) ...
Errors were encountered while processing:
 oracle-java7-installer
E: Sub-process /usr/bin/dpkg returned an error code (1)

解决方案：

1.$ sudo mv /var/lib/dpkg/info /var/lib/dpkg/info_old //现将info文件夹更名2.$ sudo mkdir /var/lib/dpkg/info //再新建一个新的info文件夹3.$ sudo apt-get update, apt-get -f install //不用解释了吧4.$ sudo mv /var/lib/dpkg/info/* /var/lib/dpkg/info_old //执行完上一步操作后会在新的info文件夹下生成一些文件，现将这些文件全部移到info_old文件夹下5.$ sudo rm -rf /var/lib/dpkg/info //把自己新建的info文件夹删掉6.$ sudo mv /var/lib/dpkg/info_old /var/lib/dpkg/info //把以前的info文件夹重新改回名字

参见：

http://jingyan.baidu.com/article/b2c186c8e95d1dc46ef6ff0c.html

结果还是不行！！！！！！！！！！

最后是这个最简单的方法：

Using Oracle Java 7 is not formally supported by Ubuntu. There’s plenty solutions for installing it, listed on https://help.ubuntu.com/community/Java .

The simplest one listed is this one:
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer
It’ll keep your java 7 installation up to date.
To automatically set up the Java 7 environment variables JAVA_HOME and PATH:
sudo apt-get install oracle-java7-set-default

转自：http://www.kankanews.com/ICkengine/archives/111362.shtml

看来还是要直接找官网上的资料啊。。

配置JAVA环境变量: sudo gedit /etc/environment在其中添加如下两行：

JAVA_HOME=/usr/lib/jvm/java-7-oracle
CLASSPATH=.:/usr/lib/jvm/java-7-oracle/lib

HADOOP的DATANODE启动失败：

http://blog.sina.com.cn/s/blog_4c248c5801014nd1.html

遇到了一个问题;

Hadoop
YARN job is getting stucked at map 0% and reduce 0%

解决方案：close the firewall -----sudo ufw disable