vi /etc/profile #系统变量
[root@CentOS ~]# vi /root/.bashrc # 用户变量
JAVA_HOME=/usr/java/latest
PATH=$PATH:$JAVA_HOME/bin
CLASSPATH=.
export JAVA_HOME
export PATH
export CLASSPATH
[root@CentOS ~]# source /root/.bashrc 
[root@CentOS ~]# jps
1495 Jps

[root@CentOS ~]# vi /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.169.139 CentOS

[root@CentOS ~]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=CentOS

[root@CentOS ~]# service iptables stop #关闭服务
iptables: Setting chains to policy ACCEPT: filter [  OK  ]
iptables: Flushing firewall rules: [  OK  ]
iptables: Unloading modules: [  OK  ]
[root@CentOS ~]# chkconfig iptables off #关闭开机自起
[root@CentOS ~]# chkconfig --list | grep iptables 
iptables        0:off   1:off   2:off   3:off   4:off   5:off   6:off

[root@CentOS ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
c3:b7:c4:e3:5e:6f:db:69:48:23:1e:f7:81:9b:d1:8e root@CentOS
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|                 |
|       . .       |
|        S =   o  |
|         = = * o |
|          + * X .|
|         . o E.=.|
|          .  .+o.|
+-----------------+
[root@CentOS ~]# ssh-copy-id CentOS
The authenticity of host 'centos (192.168.169.139)' can't be established.
RSA key fingerprint is f0:63:ed:d6:21:3b:b5:47:ad:e2:7f:98:bd:8f:54:94.
Are you sure you want to continue connecting (yes/no)? `yes`
Warning: Permanently added 'centos,192.168.169.139' (RSA) to the list of known hosts.
root@centos's password:`****` 
Now try logging into the machine, with "ssh 'CentOS'", and check in:

  .ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

[root@CentOS ~]# tar -zxf hadoop-2.6.0_x64.tar.gz -C /usr/

HADOOP_HOME=/usr/hadoop-2.6.0
JAVA_HOME=/usr/java/latest
PATH=$PATH:$JAVA_HOME/bin:$HADOOP_HOME/bin:$HADOOP_HOME/sbin
CLASSPATH=.
export JAVA_HOME
export PATH
export CLASSPATH
export HADOOP_HOME

[root@CentOS ~]# source /root/.bashrc 
[root@CentOS ~]# echo $HADOOP_HOME

[root@CentOS ~]# hdfs namenode -format
...
19/01/02 20:19:37 INFO common.Storage: Storage directory /usr/hadoop-2.6.0/hadoop-root/dfs/name has been successfully formatted.
...
再次启动需要删除/usr/hadoop-2.6.0/hadoop-root/

[root@CentOS ~]# start-dfs.sh 
Starting namenodes on [CentOS]
CentOS: namenode running as process 1846. Stop it first.
CentOS: starting datanode, logging to /usr/hadoop-2.6.0/logs/hadoop-root-datanode-CentOS.out
Starting secondary namenodes [0.0.0.0]
The authenticity of host '0.0.0.0 (0.0.0.0)' can't be established.
RSA key fingerprint is f0:63:ed:d6:21:3b:b5:47:ad:e2:7f:98:bd:8f:54:94.
Are you sure you want to continue connecting (yes/no)? yes
0.0.0.0: Warning: Permanently added '0.0.0.0' (RSA) to the list of known hosts.
0.0.0.0: starting secondarynamenode, logging to /usr/hadoop-2.6.0/logs/hadoop-root-secondarynamenode-CentOS.out
[root@CentOS ~]# jps
2370 Jps
2133 DataNode
1846 NameNode
2267 SecondaryNameNode
[root@CentOS ~]# stop-dfs.sh 
Stopping namenodes on [CentOS]
CentOS: stopping namenode
CentOS: stopping datanode
Stopping secondary namenodes [0.0.0.0]
0.0.0.0: stopping secondarynamenode

[root@CentOS ~]# hdfs dfs -put /root/jdk-8u171-linux-x64.rpm  /
[root@CentOS ~]# hdfs dfs -ls  /
Found 1 items
-rw-r--r--   1 root supergroup  175262413 2019-01-02 20:29 /jdk-8u171-linux-x64.rpm