首先，要说明的一点的是，我不想重复发明轮子。如果想要搭建hadoop环境，网上有很多详细的步骤和命令代码，我不想再重复记录。
其次，我要说的是我也是新手，对于hadoop也不是很熟悉。但是就是想实际搭建好环境，看看他的庐山真面目，还好，还好，最好看到了。当运行wordcount词频统计的时候，实在是感叹hadoop已经把分布式做的如此之好，即使没有分布式相关经验的人，也只需要做一些配置即可运行分布式集群环境。
好了，言归真传。
在搭建hadoop环境中你要知道的一些事儿：
1.hadoop运行于linux系统之上，你要安装linux操作系统
2.你需要搭建一个运行hadoop的集群，例如局域网内能互相访问的linux系统
3.为了实现集群之间的相互访问，你需要做到ssh无密钥登录
4.hadoop的运行在jvm上的，也就是说你需要安装java的jdk，并配置好java_home
5.hadoop的各个组件是通过xml来配置的。在官网上下载好hadoop之后解压缩，修改/etc/hadoop目录中相应的配置文件
工欲善其事，必先利其器。这里也要说一下，在搭建hadoop环境中使用到的相关软件和工具：
1.virtualbox——毕竟要模拟几台linux，条件有限，就在virtualbox中创建几台虚拟机楼
2.centos——下载的centos7的iso镜像，加载到virtualbox中，安装运行
3.securecrt——可以ssh远程访问linux的软件
4.winscp——实现windows和linux的通信
5.jdk for linux——oracle官网上下载，解压缩之后配置一下即可
6.hadoop2.7.1——可在apache官网上下载
好了，下面分三个步骤来讲解
linux环境准备
配置ip
为了实现本机和虚拟机以及虚拟机和虚拟机之间的通信，virtualbox中设置centos的连接模式为host-only模式，并且手动设置ip，注意虚拟机的网关和本机中host-only network 的ip地址相同。配置ip完成后还要重启网络服务以使得配置有效。这里搭建了三台linux，如下图所示
配置主机名字
对于192.168.56.101设置主机名字hadoop01。并在hosts文件中配置集群的ip和主机名。其余两个主机的操作与此类似
[root@hadoop01 ~]# cat /etc/sysconfig/network # created by anaconda networking = yes hostname = hadoop01 [root@hadoop01 ~]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.56.101 hadoop01 192.168.56.102 hadoop02 192.168.56.103 hadoop03
永久关闭防火墙
service iptables stop(1.下次重启机器后，防火墙又会启动，故需要永久关闭防火墙的命令；2由于用的是centos 7,关闭防火墙的命令如下）
systemctl stop firewalld.service #停止firewall systemctl disable firewalld.service #禁止firewall开机启动
关闭selinux防护系统
改为disabled 。reboot重启机器，使配置生效
[root@hadoop02 ~]# cat /etc/sysconfig/selinux # this file controls the state of selinux on the system # selinux= can take one of these three values: # enforcing - selinux security policy is enforced # permissive - selinux prints warnings instead of enforcing # disabled - no selinux policy is loaded selinux=disabled # selinuxtype= can take one of three two values: # targeted - targeted processes are protected, # minimum - modification of targeted policy only selected processes are protected # mls - multi level security protection selinuxtype=targeted
集群ssh免密码登录
首先设置ssh密钥
ssh-keygen -t rsa
拷贝ssh密钥到三台机器
ssh-copy-id 192.168.56.101 <pre name="code" class="plain">ssh-copy-id 192.168.56.102
ssh-copy-id 192.168.56.103
这样如果hadoop01的机器想要登录hadoop02，直接输入ssh hadoop02
<pre name="code" class="plain">ssh hadoop02
配置jdk
这里在/home忠诚创建三个文件夹中
tools——存放工具包
softwares——存放软件
data——存放数据
通过winscp将下载好的linux jdk上传到hadoop01的/home/tools中
解压缩jdk到softwares中
<pre name="code" class="plain">tar -zxf jdk-7u76-linux-x64.tar.gz -c /home/softwares
可见jdk的家目录在/home/softwares/jdk.x.x.x，将该目录拷贝粘贴到/etc/profile文件中，并且在文件中设置java_home
export java_home=/home/softwares/jdk0_111 export path=$path:$java_home/bin
保存修改,执行source /etc/profile使配置生效
查看java jdk是否安装成功:
java -version
可以将当前节点中设置的文件拷贝到其他节点
scp -r /home/* root@192.168.56.10x:/home
hadoop集群安装
集群的规划如下：
101节点作为hdfs的namenode ,其余作为datanode;102作为yarn的resourcemanager，其余作为nodemanager。103作为secondarynamenode。分别在101和102节点启动jobhistoryserver和webappproxyserver
下载hadoop-2.7.3
并将其放在/home/softwares文件夹中。由于hadoop需要jdk的安装环境，所以首先配置/etc/hadoop/hadoop-env.sh的java_home
（ps：感觉我用的jdk版本过高了）
接下来依次修改hadoop相应组件对应的xml
修改core-site.xml ：
指定namenode地址
修改hadoop的缓存目录
hadoop的垃圾回收机制
我要评论
<configuration>
<property>
<name>fsdefaultfs</name>
<value>hdfs://101:8020</value>
</property>
<property>
<name>hadooptmpdir</name>
<value>/home/softwares/hadoop-3/data/tmp</value>
</property>
<property>
<name>fstrashinterval</name>
<value>10080</value>
</property>
</configuration>
hdfs-site.xml
设置备份数目
关闭权限
设置http访问接口
设置secondary namenode 的ip地址
<configuration>
<property>
<name>dfsreplication</name>
<value>3</value>
</property>
<property>
<name>dfspermissionsenabled</name>
<value>false</value>
</property>
<property>
<name>dfsnamenodehttp-address</name>
<value>101:50070</value>
</property>
<property>
<name>dfsnamenodesecondaryhttp-address</name>
<value>103:50090</value>
</property>
</configuration>
修改mapred-site.xml.template名字为mapred-site.xml
指定mapreduce的框架为yarn，通过yarn来调度
指定jobhitory
指定jobhitory的web端口
开启uber模式——这是针对mapreduce的优化
<configuration>
<property>
<name>mapreduceframeworkname</name>
<value>yarn</value>
</property>
<property>
<name>mapreducejobhistoryaddress</name>
<value>101:10020</value>
</property>
<property>
<name>mapreducejobhistorywebappaddress</name>
<value>101:19888</value>
</property>
<property>
<name>mapreducejobubertaskenable</name>
<value>true</value>
</property>
</configuration>
修改yarn-site.xml
指定mapreduce为shuffle
指定102节点为resourcemanager
指定102节点的安全代理
开启yarn的日志
指定yarn日志删除时间
指定nodemanager的内存：8g
指定nodemanager的cpu：8核
<configuration>
<!-- site specific yarn configuration properties -->
<property>
<name>yarnnodemanageraux-services</name>
<value>mapreduce_shuffle</value>
</property>
<property>
<name>yarnresourcemanagerhostname</name>
<value>102</value>
</property>
<property>
<name>yarnweb-proxyaddress</name>
<value>102:8888</value>
</property>
<property>
<name>yarnlog-aggregation-enable</name>
<value>true</value>
</property>
<property>
<name>yarnlog-aggregationretain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarnnodemanagerresourcememory-mb</name>
<value>8192</value>
</property>
<property>
<name>yarnnodemanagerresourcecpu-vcores</name>
<value>8</value>
</property>
</configuration>
配置slaves
指定计算节点，即运行datanode和nodemanager的节点
192.168.56.101
192.168.56.102
192.168.56.103
先在namenode节点格式化，即101节点上执行：
进入到hadoop主目录： cd /home/softwares/hadoop-3
执行bin目录下的hadoop脚本： bin/hadoop namenode -format
出现successful format才算是执行成功（ps，这里是盗用别人的图，不要介意哈） 
以上配置完成后，将其拷贝到其他的机器
hadoop环境测试
进入hadoop主目录下执行相应的脚本文件
jps命令——java virtual machine process status，显示运行的java进程
在namenode节点101机器上开启hdfs
[root@hadoop01 hadoop-3]# sbin/start-dfssh java hotspot(tm) client vm warning: you have loaded library /home/softwares/hadoop-3/lib/native/libhadoopso which might have disabled stack guard the vm will try to fix the stack guard now it's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack' 16/11/07 16:49:19 warn utilnativecodeloader: unable to load native-hadoop library for your platform using builtin-java classes where applicable starting namenodes on [hadoop01] hadoop01: starting namenode, logging to /home/softwares/hadoop-3/logs/hadoop-root-namenode-hadoopout 102: starting datanode, logging to /home/softwares/hadoop-3/logs/hadoop-root-datanode-hadoopout 103: starting datanode, logging to /home/softwares/hadoop-3/logs/hadoop-root-datanode-hadoopout 101: starting datanode, logging to /home/softwares/hadoop-3/logs/hadoop-root-datanode-hadoopout starting secondary namenodes [hadoop03] hadoop03: starting secondarynamenode, logging to /home/softwares/hadoop-3/logs/hadoop-root-secondarynamenode-hadoopout
此时101节点上执行jps，可以看到namenode和datanode已经启动
[root@hadoop01 hadoop-3]# jps 7826 jps 7270 datanode 7052 namenode
在102和103节点执行jps，则可以看到datanode已经启动
[root@hadoop02 bin]# jps 4260 datanode 4488 jps [root@hadoop03 ~]# jps 6436 secondarynamenode 6750 jps 6191 datanode
启动yarn
在102节点执行
[root@hadoop02 hadoop-3]# sbin/start-yarnsh starting yarn daemons starting resourcemanager, logging to /home/softwares/hadoop-3/logs/yarn-root-resourcemanager-hadoopout 101: starting nodemanager, logging to /home/softwares/hadoop-3/logs/yarn-root-nodemanager-hadoopout 103: starting nodemanager, logging to /home/softwares/hadoop-3/logs/yarn-root-nodemanager-hadoopout 102: starting nodemanager, logging to /home/softwares/hadoop-3/logs/yarn-root-nodemanager-hadoopout
jps查看各节点：
[root@hadoop02 hadoop-3]# jps 4641 resourcemanager 4260 datanode 4765 nodemanager 5165 jps [root@hadoop01 hadoop-3]# jps 7270 datanode 8375 jps 7976 nodemanager 7052 namenode [root@hadoop03 ~]# jps 6915 nodemanager 6436 secondarynamenode 7287 jps 6191 datanode
分别启动相应节点的jobhistory和防护进程
[root@hadoop01 hadoop-3]# sbin/mr-jobhistory-daemonsh start historyserver starting historyserver, logging to /home/softwares/hadoop-3/logs/mapred-root-historyserver-hadoopout [root@hadoop01 hadoop-3]# jps 8624 jps 7270 datanode 7976 nodemanager 8553 jobhistoryserver 7052 namenode [root@hadoop02 hadoop-3]# sbin/yarn-daemonsh start proxyserver starting proxyserver, logging to /home/softwares/hadoop-3/logs/yarn-root-proxyserver-hadoopout [root@hadoop02 hadoop-3]# jps 4641 resourcemanager 4260 datanode 5367 webappproxyserver 5402 jps 4765 nodemanager
在hadoop01节点，即101节点上，通过浏览器查看节点状况 
hdfs上传文件
[root@hadoop01 hadoop-3]# bin/hdfs dfs -put /etc/profile /profile
运行wordcount程序
[root@hadoop01 hadoop-3]# bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-jar wordcount /profile /fll_out
java hotspot(tm) client vm warning: you have loaded library /home/softwares/hadoop-3/lib/native/libhadoopso which might have disabled stack guard the vm will try to fix the stack guard now
it's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'
16/11/07 17:17:10 warn utilnativecodeloader: unable to load native-hadoop library for your platform using builtin-java classes where applicable
16/11/07 17:17:12 info clientrmproxy: connecting to resourcemanager at /102:8032
16/11/07 17:17:18 info inputfileinputformat: total input paths to process : 1
16/11/07 17:17:19 info mapreducejobsubmitter: number of splits:1
16/11/07 17:17:19 info mapreducejobsubmitter: submitting tokens for job: job_1478509135878_0001
16/11/07 17:17:20 info implyarnclientimpl: submitted application application_1478509135878_0001
16/11/07 17:17:20 info mapreducejob: the url to track the job: http://www.lhsxpumps.com/_102:8888/proxy/application_1478509135878_0001/
16/11/07 17:17:20 info mapreducejob: running job: job_1478509135878_0001
16/11/07 17:18:34 info mapreducejob: job job_1478509135878_0001 running in uber mode : true
16/11/07 17:18:35 info mapreducejob: map 0% reduce 0%
16/11/07 17:18:43 info mapreducejob: map 100% reduce 0%
16/11/07 17:18:50 info mapreducejob: map 100% reduce 100%
16/11/07 17:18:55 info mapreducejob: job job_1478509135878_0001 completed successfully
16/11/07 17:18:59 info mapreducejob: counters: 52
file system counters
file: number of bytes read=4264
file: number of bytes written=6412
file: number of read operations=0
file: number of large read operations=0
file: number of write operations=0
hdfs: number of bytes read=3940
hdfs: number of bytes written=261673
hdfs: number of read operations=35
hdfs: number of large read operations=0
hdfs: number of write operations=8
job counters
launched map tasks=1
launched reduce tasks=1
other local map tasks=1
total time spent by all maps in occupied slots (ms)=8246
total time spent by all reduces in occupied slots (ms)=7538
total_launched_ubertasks=2
num_uber_submaps=1
num_uber_subreduces=1
total time spent by all map tasks (ms)=8246
total time spent by all reduce tasks (ms)=7538
total vcore-milliseconds taken by all map tasks=8246
total vcore-milliseconds taken by all reduce tasks=7538
total megabyte-milliseconds taken by all map tasks=8443904
total megabyte-milliseconds taken by all reduce tasks=7718912
map-reduce framework
map input records=78
map output records=256
map output bytes=2605
map output materialized bytes=2116
input split bytes=99
combine input records=256
combine output records=156
reduce input groups=156
reduce shuffle bytes=2116
reduce input records=156
reduce output records=156
spilled records=312
shuffled maps =1
failed shuffles=0
merged map outputs=1
gc time elapsed (ms)=870
cpu time spent (ms)=1970
physical memory (bytes) snapshot=243326976
virtual memory (bytes) snapshot=2666557440
total committed heap usage (bytes)=256876544
shuffle errors
bad_id=0
connection=0
io_error=0
wrong_length=0
wrong_map=0
wrong_reduce=0
file input format counters
bytes read=1829
file output format counters
bytes written=1487
浏览器中通过yarn查看运行状态 
查看最后的词频统计结果
浏览器中查看hdfs的文件系统
[root@hadoop01 hadoop-3]# bin/hdfs dfs -cat /fll_out/part-r-00000
java hotspot(tm) client vm warning: you have loaded library /home/softwares/hadoop-3/lib/native/libhadoopso which might have disabled stack guard the vm will try to fix the stack guard now
it's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'
16/11/07 17:29:17 warn utilnativecodeloader: unable to load native-hadoop library for your platform using builtin-java classes where applicable
!= 1
"$-" 1
"$2" 1
"$euid" 2
"$histcontrol" 1
"$i" 3
"${-#*i}" 1
"0" 1
":${path}:" 1
"`id 2
"after" 1
"ignorespace" 1
# 13
$uid 1
&& 1
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*:"$1":*) 1
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/etc/profiled/ 1
/etc/profiled/*sh 1
/usr/bin/id 1
/usr/local/sbin 2
/usr/sbin 2
/usr/share/doc/setup-*/uidgid 1
002 1
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199 1
200 1
2>/dev/null` 1
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>/dev/null 1
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euid=`id 1
functions 1
histcontrol 1
histcontrol=ignoreboth 1
histcontrol=ignoredups 1
histsize 1
histsize=1000 1
hostname 1
hostname=`/usr/bin/hostname 1
it's 2
java_home=/home/softwares/jdk0_111 1
logname 1
logname=$user 1
mail 1
mail="/var/spool/mail/$user" 1
not 1
path 1
path=$1:$path 1
path=$path:$1 1
path=$path:$java_home/bin 1
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这就代表hadoop集群正确
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