新增节点
ip:192.168.0.113

1.修改host ,在所有节点中添加新节点
echo "192.168.0.113  hadoop.slave2">>/etc/hosts
2，配置ssh等效性，在master节点上执行
ssh hadoop.slave2 cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
然后将其发送到所有节点：
scp ~/.ssh/authorized_keys hadoop.slave1:~/.ssh/authorized_keys
scp ~/.ssh/authorized_keys hadoop.slave2:~/.ssh/authorized_keys
3.修改namenode的配置文件/usr/local/hadoop-1.2.1/conf
  添加新增节点的ip或hostname 
echo "192.168.0.113">>/usr/local/hadoop-1.2.1/conf/slaves
4，配置java环境，设置环境变量
 scp -r /usr/local/hadoop-1.2.1/ hadoop.slave2:/usr/local/
 scp -r /usr/local/jdk1.7.0_51/ hadoop.slave2:/usr/local/
 chown -R hadoop:hadoop /usr/local/hadoop-1.2.1/
 chown -R hadoop:hadoop /usr/local/jdk1.7.0_51/

export  JAVA_HOME=/usr/local/jdk1.7.0_51
export  CLASSPATH=$CLASSPATH:$JAVA_HOME/lib:$JAVA_HOME/jre/lib
export  PATH=$JAVA_HOME/bin:$PATH:$JAVA_HOME/lib:$JAVA_HOME/jre/bin:$PATH:$HOME/bin
export  HADOOP_HOME=/usr/local/hadoop-1.2.1                
export PATH=$PATH:$HADOOP_HOME/bin 

5.启动新节点的机器服务 
hadoop-daemon.sh start datanode
hadoop-daemon.sh start tasktracker  
 6.平衡磁盘利用率：
start-balancer.sh