[hadoop@hadoop_master sbin]$ ./start-dfs.sh
Incorrect configuration: namenode address dfs.namenode.servicerpc-address or dfs.namenode.rpc-address is not configured.
Starting namenodes on []
而且每台机器都启动了namenode，datanode，但是都没有启动成功。。。
jps看不到任何东西。启动失败
实在是莫名其妙，配置检查了一遍又一遍，没发现任何问题。。
后来考虑了下是不是机器名得问题，就将hadoop_master 修改成 hadoopmaster，所有得机器名都去掉了下划线，结果（真是奇葩得问题）。。
[hadoop@hadoopmaster sbin]$ ./start-dfs.sh
Starting namenodes on [hadoopmaster]
hadoopmaster: starting namenode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-namenode-hadoopmaster.out
hadoopslave2: starting datanode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-datanode-hadoopslave2.out
hadoopslave1: starting datanode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-datanode-hadoopslave1.out
hadoopmaster: starting datanode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-datanode-hadoopmaster.out
hadooporacle: starting datanode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-datanode-hadooporacle.out
Starting secondary namenodes [hadoopmaster]
hadoopmaster: starting secondarynamenode, logging to /app/hadoop/hadoop-2.2.0/logs/hadoop-hadoop-secondarynamenode-hadoopmaster.out