安装Hadoop

1. Linux 系统版本

[root@localhost local]# cat /proc/version 
Linux version 3.10.0-229.el7.x86_64 (builder@kbuilder.dev.centos.org) (gcc version 4.8.2 20140120 (Red Hat 4.8.2-16) (GCC) ) #1 SMP Fri Mar 6 11:36:42 UTC 2015

CentOS7

2. 环境准备

2.1. Java 官网下载

Java 官网下载

2.2. Hadoop 官网下载

Hadoop 官网下载

2.3. 解压缩文件

Java 解压至：/usr/local/jdk1.8.0_241

Hadoop 解压至：/usr/local/hadoop-2.10.0

2.3.1. 配置环境变量

设置 JAVA_HOME 和 HADOOP_HOME

打开文件：vi /etc/bashrc

export JAVA_HOME=/usr/local/jdk1.8.0_241
export HADOOP_HOME=/usr/local/hadoop-2.10.0/

export PATH=.:$JAVA_HOME/bin:$HADOOP_HOME/bin/:$HADOOP_HOME/sbin:$PATH

使配置实时生效

source /etc/bashrc

2.4. 安装 ssh 服务

通常CentOS系统默认是安装好的

yum install openssh-server

2.5. 配置免密登录

ssh-keygen -t rsa

生成两个文件，分别为公钥和私钥

如果 ~/.ssh/ 目录中没有 authorized_keys 文件，自己新建一个。并将公钥丢进该文件中

cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

3. Hadoop 介绍

官网介绍

Hadoop 主要包含模块:

Hadoop Common: The common utilities that support the other Hadoop modules.
Hadoop Distributed File System (HDFS™): A distributed file system that provides high-throughput access to application data.
Hadoop YARN: A framework for job scheduling and cluster resource management.
Hadoop MapReduce: A YARN-based system for parallel processing of large data sets.
Hadoop Ozone: An object store for Hadoop

Hadoop 支持三种启动模式

Local (Standalone) Mode - 本地模式
Pseudo-Distributed Mode - 伪分布式
Fully-Distributed Mode - 全分布式

3.1. Hadoop 生态圈

Hadoop 生态圈

4. Hadoop 安装过程

进入目录 cd /usr/local/hadoop-2.10.0/etc/hadoop

4.1. 编辑配置文件

编辑环境变量

文件名称：hadoop-env.sh

修改 JAVA_HOME 路径

编辑核心文件

文件名称：core-site.xml

<property>
        <name>fs.defaultFS</name>
        <value>hdfs://localhost:9000</value>
</property>

<property>
        <name>hadoop.tmp.dir</name>
        <value>/data/hadoop</value>
</property>

编辑 HDFS 文件

文件名称：hdfs-site.xml

<property>
        <name>dfs.repliction</name>
        <value>1</value>
</property>

<property>
        <name>dfs.namenode.secondary.http-address</name>
        <value>localhost:50090</value>
</property>

编辑 YARN 配置文件

文件名称：yarn-site.xml

<property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
</property>

编辑 mapred 配置文件

文件名称：mapred-site.xml

<property>
	<name>mapreduce.framework.name</name>
	<value>yarn</value>
</property>

<property>
	<name>mapreduce.jobhistory.address</name>
	<value>localhost:10020</value>
</property>

<property>
	<name>mapreduce.jobhistory.webapp.address</name>
	<value>localhost:19888</value>
</property>

4.2. 启动 Hadoop

第一次启动 Hadoop 需要进行初始化，执行如下命令：

hdfs namenode -format

启动所有服务节点：start-all.sh

停止所有服务节点：start-all.sh

单独启动HDFS服务：start-dfs.sh

单独启动YARN服务：start-yarn.sh

4.3. 访问HDFS地址

http://localhost:50070/

4.4. 访问YARN资源管理地址

http://localhost:8088/cluster

4.5. HDFS 常用命令

[root@localhost hadoop-2.10.0]# hdfs
Usage: hdfs [--config confdir] [--loglevel loglevel] COMMAND
       where COMMAND is one of:
  dfs                  run a filesystem command on the file systems supported in Hadoop.
  classpath            prints the classpath
  namenode -format     format the DFS filesystem
  secondarynamenode    run the DFS secondary namenode
  namenode             run the DFS namenode
  journalnode          run the DFS journalnode
  zkfc                 run the ZK Failover Controller daemon
  datanode             run a DFS datanode
  debug                run a Debug Admin to execute HDFS debug commands
  dfsadmin             run a DFS admin client
  dfsrouter            run the DFS router
  dfsrouteradmin       manage Router-based federation
  haadmin              run a DFS HA admin client
  fsck                 run a DFS filesystem checking utility
  balancer             run a cluster balancing utility
  jmxget               get JMX exported values from NameNode or DataNode.
  mover                run a utility to move block replicas across
                       storage types
  oiv                  apply the offline fsimage viewer to an fsimage
  oiv_legacy           apply the offline fsimage viewer to an legacy fsimage
  oev                  apply the offline edits viewer to an edits file
  fetchdt              fetch a delegation token from the NameNode
  getconf              get config values from configuration
  groups               get the groups which users belong to
  snapshotDiff         diff two snapshots of a directory or diff the
                       current directory contents with a snapshot
  lsSnapshottableDir   list all snapshottable dirs owned by the current user
						Use -help to see options
  portmap              run a portmap service
  nfs3                 run an NFS version 3 gateway
  cacheadmin           configure the HDFS cache
  crypto               configure HDFS encryption zones
  storagepolicies      list/get/set block storage policies
  version              print the version

5. 常见问题

5.1. mkdir: Cannot create directory /aaa. Name node is in safe mode.

# 强制离开安全模式
hdfs dfsadmin -safemode leave

5.2 如有发现一些节点启动不了，查看Hadoop日志

tail -f *.log