本章主要介紹下在Linux系統下的Hadoop2.5.0偽分布式環境搭建步驟。首先要搭建Hadoop偽分布式環境，需要完成一些前置依賴工作，包括創建用戶、安裝JDK、關閉防火墻等。

一、創建hadoop用戶

使用root賬戶創建hadoop用戶，為了在實驗環境下便于操作，賦予hadoop用戶sudo權限。具體操作代碼如下：

useradd hadoop # 添加hadoop用戶
passwd hadoop # 設置密碼
visudo
hadoop ALL=(root)NOPASSWD:ALL

二、Hadoop偽分布式環境搭建

1、關閉Linux中的防火墻和selinux

禁用selinux，代碼如下：

sudo vi /etc/sysconfig/selinux # 打開selinux配置文件
SELINUX=disabled # 修改SELINUX屬性值為disabled

關閉防火墻，代碼如下：

sudo service iptables status # 查看防火墻狀態
sudo service iptables stop # 關閉防火墻
sudo chkconfig iptables off # 關閉防火墻開機啟動設置

2、安裝jdk

首先，查看系統中是否有安裝自帶的jdk，如果存在，則先卸載，代碼如下：

rpm -qa | grep java # 查看是否有安裝jdk
sudo rpm -e –nodeps java-1.6.0-openjdk-1.6.0.0-1.50.1.11.5.el6_3.x86_64 tzdata-java-2012j-1.el6.noarch java-1.7.0-openjdk-1.7.0.9-2.3.4.1.el6_3.x86_64 # 卸載自帶jdk

接著，安裝jdk，步驟如下：

step1.解壓安裝包：

tar -zxf jdk-7u67-linux-x64.tar.gz -C /usr/local/

step2.配置環境變量及檢查是否安裝成功：

sudo vi /etc/profile # 打開profile文件
##JAVA_HOME
export JAVA_HOME=/usr/local/jdk1.7.0_67
export PATH=$PATH:$JAVA_HOME/bin

# 生效文件
source /etc/profile # 使用root用戶操作

# 查看是否配置成功
java -version

3、安裝hadoop

step1：解壓hadoop安裝包

tar -zxvf /opt/software/hadoop-2.5.0.tar.gz -C /opt/software/

建議：將/opt/software/hadoop-2.5.0/share下的doc目錄刪除。

step2：修改etc/hadoop目錄下hadoop-env.sh、mapred-env.sh、yarn-env.sh三個配置文件中的JAVA_HOME

export JAVA_HOME=/usr/local/jdk1.7.0_67

step3：修改core-site.xml

<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<!–
  Licensed under the Apache License, Version 2.0 (the “License”);
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an “AS IS” BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. See accompanying LICENSE file.
–>

<!– Put site-specific property overrides in this file. –>

<configuration>
    <property>
        <name>name</name>
        <value>my-study-cluster</value>
    </property>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://bigdata01:8020</value>
    </property>
        <!– 指定Hadoop系統生成文件的臨時目錄地址 –>
    <property>
        <name>hadoop.tmp.dir</name>
        <value>/opt/software/hadoop-2.5.0/data/tmp</value>
    </property>
    <property>
        <name>fs.trash.interval</name>
        <value>1440</value>
    </property>
    <property>
        <name>hadoop.http.staticuser.user</name>
        <value>hadoop</value>
    </property>
        <property>
                <name>hadoop.proxyuser.hadoop.hosts</name>
                <value>bigdata01</value>
        </property>
        <property>
                <name>hadoop.proxyuser.hadoop.groups</name>
                <value>*</value>
        </property>
</configuration>

step4：修改hdfs-site.xml

<?xml version=”1.0″ encoding=”UTF-8″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<!–
  Licensed under the Apache License, Version 2.0 (the “License”);
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an “AS IS” BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. See accompanying LICENSE file.
–>

<!– Put site-specific property overrides in this file. –>

<configuration>
    <property>
        <name>dfs.replication</name>
        <value>1</value>
    </property>
    <property>
        <name>dfs.permissions.enabled</name>
        <value>false</value>
    </property>
    <property>
        <name>dfs.namenode.name.dir</name>
        <value>/opt/software/hadoop-2.5.0/data/name</value>
    </property>
    <property>
        <name>dfs.datanode.data.dir</name>
        <value>/opt/software/hadoop-2.5.0/data/data</value>
    </property>
</configuration>

step5：修改mapred-site.xml

<?xml version=”1.0″?>
<?xml-stylesheet type=”text/xsl” href=”configuration.xsl”?>
<!–
  Licensed under the Apache License, Version 2.0 (the “License”);
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an “AS IS” BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. See accompanying LICENSE file.
–>

<!– Put site-specific property overrides in this file. –>

<configuration>
    <property>
        <name>mapreduce.framework.name</name>
        <value>yarn</value>
    </property>
    <property>
        <name>mapreduce.jobhistory.address</name>
        <value>bigdata01:10020</value>
    </property>
    <property>
        <name>mapreduce.jobhistory.webapp.address</name>
        <value>bigdata01:19888</value>
    </property>
</configuration>

step6：修改yarn-site.xml

<?xml version=”1.0″?>
<!–
  Licensed under the Apache License, Version 2.0 (the “License”);
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an “AS IS” BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License. See accompanying LICENSE file.
–>
<configuration>

<!– Site specific YARN configuration properties –>

    <property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
    </property>
    <property>
        <name>yarn.resourcemanager.hostname</name>
        <value>bigdata01</value>
    </property>
    <property>
        <name>yarn.log-aggregation-enable</name>
        <value>true</value>
    </property>
    <property>
        <name>yarn.log-aggregation.retain-seconds</name>
        <value>106800</value>
    </property>
    <property>
        <name>yarn.log.server.url</name>
        <value>http://bigdata01:19888/jobhistory/job/</value>
    </property>
</configuration>

step7：修改slaves文件

bigdata01

step8：格式化namenode

bin/hdfs namenode -format

step9：啟動進程

## 方式一：單獨啟動一個進程
# 啟動namenode
sbin/hadoop-daemon.sh start namenode
# 啟動datanode
sbin/hadoop-daemon.sh start datanode
# 啟動resourcemanager
sbin/yarn-daemon.sh start resourcemanager
# 啟動nodemanager
sbin/yarn-daemon.sh start nodemanager
# 啟動secondarynamenode
sbin/hadoop-daemon.sh start secondarynamenode
# 啟動歷史服務器
sbin/mr-jobhistory-daemon.sh start historyserver

## 方式二：
sbin/start-dfs.sh # 啟動namenode、datanode、secondarynamenode
sbin/start-yarn.sh # 啟動resourcemanager、nodemanager
sbin/mr-jobhistory-daemon.sh start historyserver # 啟動歷史服務器

step10：檢查

1.通過瀏覽器訪問HDFS的外部UI界面，加上外部交互端口號：50070

　　http://bigdata01:50070

2.通過瀏覽器訪問YARN的外部UI界面，加上外部交互端口號：8088

　　http://bigdata01:8088

3.執行Wordcount程序

　　bin/yarn jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.0.jar wordcount input output

　　注：輸入輸出目錄自定義

結束！

以上為Hadoop2.5.0偽分布式環境搭建步驟，如有問題，請指出，謝謝！