注：大家常说的ssh其实就是一个免密码访问的东西，为了简化操作的，不用每次访问其他节点重新输入密码。但是要想配置如下：
1.在每台机器上执行 ssh-keygen -t rsa，连敲三次回车键(即设置空密码)
2.然后在每台机器上都执行cd ~/.ssh，并分别把id_rsa.pub复制到authorized_keys中，
即执行 cp id_rsa.pub authorized_keys
3.然后分别把slave0，slave1的authorized_keys都复制到master主节点的authorized_keys中，
即分别在两个从节点slave0和slave1中执行 ssh-copy-id -i master
4.再分别复制到slave0，slave1中(即每一个节点的authorized_keys中都有这三个节点的密钥)
即在主节点master上执行 scp -r ~/.ssh/authorized_keys slave0:~/.ssh/
scp -r ~/.ssh/authorized_keys slave1:~/.ssh/
此时成功。
简单测试：比如说在master上执行ssh slave0，这时候发现不需要输入密码即可转
到slave0从节点上，这时成功
hadoop-0.20.2的配置文件
hadoop-0.20.0的配置文件：
core-site.xml
<property>
<name>fs.default.name</name>
<value>hdfs://cMaster:9000</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/joe/cloudData</value>
</property>
hdfs-site.xml
<property>
<name>dfs.name.dir</name>
<value>/home/joe/hdfs/name</value>
</property>
<property>
<name>dfs.data.dir</name>
<value>/home/joe/hdfs/data</value>
</property>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
mapred-site.xml
<property>
<name>mapred.job.tracker</name>
<value>cMaster:9001</value>
</property>
hadoop-0.20.2集群操作命令：
hadoop-0.20.2的集群操作命令
上传本地文件至hdfs：[rio@cMaster hadoop-0.20.2]#bin/hadoop dfs -put /home/rio/input/* /in
用WordCount计算数据：[rio@cMaster hadoop-2.2.0]#bin/hadoop jar hadoop-0.20.2-examples.jar
wordcount /in /out/wc-01
hadoop-2.2.0的配置文件：
hadoop-2.2.0的配置文件：
core-site.xml
<property>
<name>fs.defaultFS</name>
<value>hdfs://cMaster:8020</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/joe/cloudData</value>
</property>
yarn-site.xml
<property>
<name>yarn.resourcemanager.hostname</name>
<value>cMaster</value>
</property>
<property>
<name>yarn.nodemanager.aux-services</name>
<value>mapreduce_shuffle</value>
</property>
mapred-site.xml(注:将mapred-site.xml.template重命名为mapred-site.xml)
<property>
<name>mapreduce.framework.name</name>
<value>yarn</value>
</property>
hadoop-2.2.0进程启动命令：
启动(或关闭)全部服务：[rio@cMaster hadoop-2.2.0]#sbin/start-all.sh
[rio@cMaster hadoop-2.2.0]#sbin/stop-all.sh
格式化主节点：[rio@cMaster hadoop-2.2.0]#bin/hdfs namenode -format(注：仅格式化一次)
启动主节点上的namenode：[rio@cMaster hadoop-2.2.0]#sbin/hadoop-daemon.sh start namenode
启动主节点上的resourcemanager：[rio@cMaster hadoop-2.2.0]#sbin/yarn-daemon.sh start resourcemanager
启动从节点上的datanode：[rio@cMaster hadoop-2.2.0]#sbin/hadoop-daemon.sh start datanode
启动从节点上的nodemanager：[rio@cMaster hadoop-2.2.0]#sbin/yarn-daemon.sh start nodemanager
启动日志历史查询：[rio@cMaster hadoop-2.2.0]#sbin/mr-jobhistory-daemon.sh start historyserver
查看服务是否启动：[rio@cMaster hadoop-2.2.0]#/usr/java/jdk1.8.0_71/bin/jps
hadoop-2.2.0集群操作命令：
创建目录：[rio@cMaster hadoop-2.2.0]#bin/hdfs dfs -mkidr /in
删除文件及目录：[rio@cMaster hadoop-2.2.0]#bin/hdfs dfs -rmr /out/input
上传本地文件至hdfs：[rio@cMaster hadoop-2.2.0]#bin/hdfs dfs -put /home/rio/input/* /in
查看hdfs里的文件：[rio@cMaster hadoop-2.2.0]#bin/hdfs dfs -cat /in/*
[rio@cMaster hadoop-2.2.0]#bin/hdfs dfs -cat /out/wc-01/*
用WordCount计算数据：[rio@cMaster hadoop-2.2.0]#bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-example-2.2.0.jar
wordcount /in /out/wc-01
当神已无能为力，那便是魔渡众生
