groupadd hadoop

useradd -d /home/hadoop -g hadoop hadoop
chown -R hadoop:hadoop /usr/local/hadoop

[hadoop@hadoop2 ~]$ java -version
openjdk version "1.8.0_131"
OpenJDK Runtime Environment (build 1.8.0_131-b12)
OpenJDK 64-Bit Server VM (build 25.131-b12, mixed mode)
[hadoop@hadoop2 ~]$ rpm -qa | grep java
java-1.8.0-openjdk-headless-1.8.0.131-11.b12.el7.x86_64
javapackages-tools-3.4.1-11.el7.noarch
tzdata-java-2017b-1.el7.noarch
java-1.7.0-openjdk-headless-1.7.0.141-2.6.10.5.el7.x86_64
java-1.7.0-openjdk-1.7.0.141-2.6.10.5.el7.x86_64
java-1.8.0-openjdk-1.8.0.131-11.b12.el7.x86_64
python-javapackages-3.4.1-11.el7.noarch

rpm -qa | grep java | xargs yum -y remove

vim /etc/profile  末尾添加如下内容
export JAVA_HOME=/usr/local/jdk
export JRE_HOME=${JAVA_HOME}/jre
export PATH=${JAVA_HOME}/bin:${PATH}
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib:${CLASSPATH}

[root@hadoop2 local]# java -version
java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

[hadoop@hadoop1 ~]$ ssh-keygen -t rsa -P \'\'  #一路直接回车
发送master 机器~/.ssh/id_rsa.pub 到所有slave节点
Scp id_rsa.pub hadoop@10.11.84.5:~
Scp id_rsa.pub hadoop@10.11.84.6:~
让后在每台slave节点hadoop 用户下执行如下命令
Cd ~/.ssh
Cat ../id_rsa.pub >> authorized_keys
Chmod 644 authorized_keys

1）centos 7 以下
防火墙
查看防火墙状态
service iptables status
临时关闭防火墙
service iptables stop
永久关闭防火墙
chkconfig iptables off
 selinux
setenforce 0 #临时关闭
永久关闭需要修改如下文件
vim /etc/selinux/config
将SELINUX=enforcing改为SELINUX=disabled
2)centos 7
firewall-cmd --reload #重启firewall
systemctl stop firewalld.service #停止firewall
systemctl disable firewalld.service #禁止firewall开机启动
firewall-cmd --state #查看默认防火墙状态（关闭后显示notrunning，开启后显示running）
selinux 同上

Core-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- Put site-specific property overrides in this file. -->
<configuration>
<property>
<name>hadoop.tmp.dir</name>
<value>/home/hadoop/tmp</value>
<description>Abase for other temporary directories.</description>
</property>
<property>
<name>fs.default.name</name>
<value>hdfs://web-crawler--1.novalocal:9000</value>  注：web-crawler--1.novalocal是hostname 可以在 /etc/hostname中设置，hostname是ip的别名
</property>
</configuration>
hadoop-env.sh 添加java_home
 export JAVA_HOME=/usr/local/jdk
hdfs-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- Put site-specific property overrides in this file. -->
<configuration>
<property>
<name>dfs.replication</name>
<value>2</value>
</property>
<property>
<name>dfs.name.dir</name>
<value>/home/hadoop/name</value>
</property>
<property>
<name>dfs.data.dir</name>
<value>/home/hadoop/data</value>
</property>
</configuration>
mapred-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- Put site-specific property overrides in this file. -->
<configuration>
 <property>
        <name>mapred.job.tracker</name>
        <value>http://web-crawler--1.novalocal:9001</value>;;;
    </property>
<property>
        <name>mapred.system.dir</name>
        <value>/home/hadoop/mapred/system</value>
    </property>
<property>
        <name>mapred.local.dir</name>
        <value>/home/hadoop/mapred/local</value>
    </property>
</configuration>
5)masters
web-crawler--1.novalocal
6)slaves
web-crawler--1.novalocal
web-crawler--2.novalocal 
web-crawler--3.novalocal

Vim /etc/profile (root)
export ANT_HOME=/usr/local/ant
export PATH=${PATH}:${ANT_HOME}/bin
export HADOOP_HOME=/usr/local/hadoop-1.2.1
export JAVA_HOME=/usr/local/jdk
export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$PATH
export CLASSPATH=$JAVA_HOME/lib:$JAVA_HOME/jre/lib:$CLASSPATH
export PATH=/usr/local/lib/phantomjs/bin:$PATH
export ANT_HOME=/usr/local/ant
export PATH=${PATH}:${ANT_HOME}/bin
export PATH=$PATH:${HADOOP_HOME}/bin:${HADOOP_HOME}/sbin

1）在master上format namenode
hadoop namenode -format
2)启动hadoop
sh /user/local/hadoop/bin/start-all.sh

Hadoop fs -mkdir -p /user/hadoop/private/in
Hadoop fs -put /user/local/hadoop/bin/start-all.sh /user/hadoop/private/in
Cd /usr/local/hadoop
Hadoop jar hadoop-examples-1.2.1.jar wordcount /user/hadoop/private/in /user/hadoop/private/out