修改/etc/sysconfig/network
然后执行命令
hostname 主机名
这个时候可以注销一下系统，再重登录之后就行了
[root@localhost ~]# hostname
localhost.localdomain
[root@localhost ~]# hostname -i
::1 127.0.0.1
[root@localhost ~]#
[root@localhost ~]# cat /etc/sysconfig/network
# Created by anaconda
NETWORKING=yes
HOSTNAME=slave2
GATEWAY=192.168.48.2
# Oracle-rdbms-server-11gR2-preinstall : Add NOZEROCONF=yes
NOZEROCONF=yes
[root@localhost ~]# hostname slave2
[root@localhost ~]# hostname
slave2
[root@localhost ~]# su - hadoop
Last login: Sat Feb 24 14:25:48 CST 2018 on pts/1
[hadoop@slave2 ~]$ su - root
建datanode目录并改所有者
（此处的具体路径值，请参照namenode中/usr/hadoop/hadoop-2.7.5/etc/hadoop/hdfs-site.xml,core-site.xml中的dfs.name.dir，dfs.data.dir,dfs.tmp.dir等）
Su - root
# mkdir -p /usr/local/hadoop-2.7.5/tmp/dfs/data
# chmod -R 777 /usr/local/hadoop-2.7.5/tmp
# chown -R hadoop:hadoop /usr/local/hadoop-2.7.5
[root@slave2 ~]# mkdir -p /usr/local/hadoop-2.7.5/tmp/dfs/data
[root@slave2 ~]# chmod -R 777 /usr/local/hadoop-2.7.5/tmp
[root@slave2 ~]# chown -R hadoop:hadoop /usr/local/hadoop-2.7.5
[root@slave2 ~]# pwd
/root
[root@slave2 ~]# cd /usr/local/
[root@slave2 local]# ll
total 0
drwxr-xr-x. 2 root root 46 Mar 21 2017 bin
drwxr-xr-x. 2 root root 6 Jun 10 2014 etc
drwxr-xr-x. 2 root root 6 Jun 10 2014 games
drwxr-xr-x 3 hadoop hadoop 16 Feb 24 18:18 hadoop-2.7.5
drwxr-xr-x. 2 root root 6 Jun 10 2014 include
drwxr-xr-x. 2 root root 6 Jun 10 2014 lib
drwxr-xr-x. 2 root root 6 Jun 10 2014 lib64
drwxr-xr-x. 2 root root 6 Jun 10 2014 libexec
drwxr-xr-x. 2 root root 6 Jun 10 2014 sbin
drwxr-xr-x. 5 root root 46 Dec 17 2015 share
drwxr-xr-x. 2 root root 6 Jun 10 2014 src
[root@slave2 local]#
ssh互信，即实现 master-->slave2免密码
master:
[root@hadoop-master ~]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.48.129 hadoop-master
192.168.48.132 slave1
192.168.48.131 slave2
[hadoop@hadoop-master ~]$ scp /usr/hadoop/.ssh/authorized_keys hadoop@slave2:/usr/hadoop/.ssh
The authenticity of host 'slave2 (192.168.48.131)' can't be established.
ECDSA key fingerprint is 1e:cd:d1:3d:b0:5b:62:45:a3:63:df:c7:7a:0f:b8:7c.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'slave2,192.168.48.131' (ECDSA) to the list of known hosts.
hadoop@slave2's password:
authorized_keys
[hadoop@hadoop-master ~]$ ssh hadoop@slave2
Last login: Sat Feb 24 18:27:33 2018
[hadoop@slave2 ~]$
[hadoop@slave2 ~]$ exit
logout
Connection to slave2 closed.
[hadoop@hadoop-master ~]$
2. 修改namenode节点的slave文件,增加新节点信息
[hadoop@hadoop-master hadoop]$ pwd
/usr/hadoop/hadoop-2.7.5/etc/hadoop
[hadoop@hadoop-master hadoop]$ vi slaves
slave1
slave2
3. 在namenode节点上,将hadoop-2.7.3复制到新节点上,并在新节点上删除data和logs目录中的文件
Master
[hadoop@hadoop-master ~]$ scp -R hadoop-2.7.5 hadoop@slave2:/usr/hadoop
Slave2
[hadoop@slave2 hadoop-2.7.5]$ ll
total 124
drwxr-xr-x 2 hadoop hadoop 4096 Feb 24 14:29 bin
drwxr-xr-x 3 hadoop hadoop 19 Feb 24 14:30 etc
drwxr-xr-x 2 hadoop hadoop 101 Feb 24 14:30 include
drwxr-xr-x 3 hadoop hadoop 19 Feb 24 14:29 lib
drwxr-xr-x 2 hadoop hadoop 4096 Feb 24 14:29 libexec
-rw-r--r-- 1 hadoop hadoop 86424 Feb 24 18:44 LICENSE.txt
drwxrwxr-x 2 hadoop hadoop 4096 Feb 24 14:30 logs
-rw-r--r-- 1 hadoop hadoop 14978 Feb 24 18:44 NOTICE.txt
-rw-r--r-- 1 hadoop hadoop 1366 Feb 24 18:44 README.txt
drwxr-xr-x 2 hadoop hadoop 4096 Feb 24 14:29 sbin
drwxr-xr-x 4 hadoop hadoop 29 Feb 24 14:30 share
[hadoop@slave2 hadoop-2.7.5]$ pwd
/usr/hadoop/hadoop-2.7.5
[hadoop@slave2 hadoop-2.7.5]$ rm -R logs/*
4. 启动新datanode的datanode和nodemanger进程
先确认namenode和当前的datanode中，etc/hoadoop/excludes文件中无待加入的主机，再进行下面操作
[hadoop@slave2 hadoop-2.7.5]$ sbin/hadoop-daemon.sh start datanode
starting datanode, logging to /usr/hadoop/hadoop-2.7.5/logs/hadoop-hadoop-datanode-slave2.out
[hadoop@slave2 hadoop-2.7.5]$ sbin/yarn-daemon.sh start nodemanager
starting datanode, logging to /usr/hadoop/hadoop-2.7.5/logs/yarn-hadoop-datanode-slave2.out
[hadoop@slave2 hadoop-2.7.5]$
[hadoop@slave2 hadoop-2.7.5]$ jps
3897 DataNode
6772 NodeManager
8189 Jps
[hadoop@slave2 ~]$
5、在NameNode上刷新节点
[hadoop@hadoop-master ~]$ hdfs dfsadmin -refreshNodes
Refresh nodes successful
[hadoop@hadoop-master ~]$sbin/start-balancer.sh
6. 在namenode查看当前集群情况,
确认信节点已经正常加入