hadoop環境搭建
-------------------------
	1.安裝hadoop
		a)下載hadoop-2.7.3.tar.gz
		b)tar開
			$>su centos ; cd ~
			$>cp /mnt/hdfs/downloads/bigdata/hadoop-2.7.3.tar.gz ~/downloads
			$>tar -xzvf hadoop-2.7.3.tar.gz
		c)無
		d)移動tar開的檔案到/soft下
			$>mv ~/downloads/hadoop-2.7.3 /soft/
		e)建立符號連線
			$>ln -s /soft/hadoop-2.7.3 /soft/hadoop
		f)驗證jdk安裝是否成功
			$>cd /soft/hadoop/bin
			$>./hadoop version
	
	2.配置hadoop環境變數（包括jdk和hadoop）
		$>sudo nano /etc/profile
		...
		export JAVA_HOME=/soft/jdk
		exprot PATH=$PATH:$JAVA_HOME/bin

		export HADOOP_HOME=/soft/hadoop
		export PATH=$PATH:$HADOOP_HOME/bin:$HADOOP_HOME/sbin
	
	3.使配置檔案生效
		$>source /etc/profile

配置hadoop
--------------------
	1.standalone(local)
		nothing !
		不需要啟用單獨的hadoop程序。
	
	2.Pseudodistributed mode
		偽分佈模式。
		a)進入${HADOOP_HOME}/etc/hadoop目錄
		b)編輯core-site.xml
			<?xml version="1.0"?>
			<configuration>
				<property>
					<name>fs.defaultFS</name>
					<value>hdfs://localhost/</value>
				</property>
			</configuration>
		c)編輯hdfs-site.xml
			<?xml version="1.0"?>
			<configuration>
				<property>
					<name>dfs.replication</name>
					<value>1</value>
				</property>
			</configuration>
		d)編輯mapred-site.xml
			注意:cp mapred-site.xml.template mapred-site.xml
			<?xml version="1.0"?>
			<configuration>
				<property>
					<name>mapreduce.framework.name</name>
					<value>yarn</value>
				</property>
			</configuration>
		e)編輯yarn-site.xml
			<?xml version="1.0"?>
			<configuration>
				<property>
					<name>yarn.resourcemanager.hostname</name>
					<value>localhost</value>
				</property>
				<property>
					<name>yarn.nodemanager.aux-services</name>
					<value>mapreduce_shuffle</value>
				</property>
			</configuration>

		f)配置SSH
			1)檢查是否安裝了ssh相關軟體包(openssh-server + openssh-clients + openssh)
				$yum list installed | grep ssh

			2)檢查是否啟動了sshd程序
				$>ps -Af | grep sshd
			
			3)在client側生成公私祕鑰對。
				$>ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa
			
			4)生成~/.ssh資料夾，裡面有id_rsa(私鑰) + id_rsa.pub(公鑰)

			5)追加公鑰到~/.ssh/authorized_keys檔案中(檔名、位置固定)
				$>cd ~/.ssh
				$>cat id_rsa.pub >> authorized_keys
			
			6)修改authorized_keys的許可權為644.
				$>chmod 644 authorized_keys
			
			7)測試
				$>ssh localhost