要想實現主節點 對 從節點的管理：
需要配置主節點對從節點的免密登入。
**主節點hostname：vdevops
從節點hostname：test2
hadoop版本：2.8.2
主從節點可以相互通訊**

1.主節點中產生RSA金鑰

1.1

首先檢查目錄/home/hadoop/.ssh下是否有id_rsa、 id_rsa.pub兩個檔案，如有，刪除之

1. 2

在主節點中執行，產生金鑰

[hadoop@vdevops ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in
 
 which to save the key (/home/hadoop/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/hadoop/.ssh/id_rsa.
Your public key has been saved in /home/hadoop/.ssh/id_rsa.pub.
The key fingerprint is:
b9:18:3b:50:cd:d9:48:eb:be:84:c0:49
 
:fb:8e:1e:0a hadoop@vdevops
The key's randomart image is:
+--[ RSA 2048]----+
|        .        |
|       + =       |
|    . . * .      |
|   o + . .       |
|    * . S        |
|     + * .       |
|E   . * +        |
| . . + o .       |
|  ..o . .        |
+-----------------+

1.3 生成金鑰之後，公鑰的形式：

[
 
[email protected] .ssh]$ cat id_rsa.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCpmiWNRvoBJ5w3f9V58nnHfitKOYxMMvCyOLP0siXtCAUHcOdfJkQQ00Qe9USRAFseosuzL7vDwYBk4jdwrbb1o/OIwbZB7qh8JuNfFHkmKqdwHToze85cRSnXDz7R/YJ7K+/v0AdNVM9XIB6xKXPXiEFp8Cp1S1p00Ld4nJpvxYcjFNl1JLi/l/DVlPyNv4KS3RD4SqFNbVzFgXdEoi3nL5i48Jgjb0XNXSsrGz03trLRRkqGPPqdFQW4bXww1f+pZpRmzU0c1Ng+Azf1SMNq4D3YOIKEePodw28n9ajOpy4NyOz0yvKIXQx8vArKw8ho5QKSEN5EDWCJfC09pAjP [email protected]
[[email protected] .ssh]$ pwd
/home/hadoop/.ssh

2. 將主節點中產生RSA金鑰分佈到從節點中

[hadoop@vdevops .ssh]$ scp id_rsa.pub hadoop@test2:~/vdevops_key
The authenticity of host 'test2 (192.168.1.127)' can't be established.
ECDSA key fingerprint is a7:8a:dc:21:a9:73:ba:92:74:08:02:14:c4:ba:01:0d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'test2,192.168.1.127' (ECDSA) to the list of known hosts.
[email protected]'s password: 
id_rsa.pub   

解釋：scp id_rsa.pub [email protected]:~/vdevops_key： 將 id_rsa.pub傳到test2上，並且重新命名為vdevops_key，即檔案vdevops_key內容與id_rsa.pub 相同

3. 在從節點中設定主節點的金鑰為授權金鑰

[hadoop@test2 ~]$ mv ~/vdevops_key ~/.ssh/authorized_keys #移動vdevops_key並重命名為authorized_keys 

[hadoop@test2 ~]$ chmod 600 ~/.ssh/authorized_keys #設定許可權

4.嘗試主節點登入到從節點

可以直接登入從節點 而不需要密碼，顯示如下：

[[email protected] ~]$ ssh test2
Last login: Wed Dec 20 14:07:09 2017 from 192.168.1.247