目前有幾臺機器，主機器叫master，另一臺叫slave1。要在master上無密碼登入slave1，需要做無密碼登入操作。

步驟一

在master上操作下面命令：
輸入ssh-keygen -t rsa後一直按回車鍵，好像有3次

$ cd ~
$ ssh-keygen -t rsa
$ cd .ssh
$ cp id_rsa.pub authorized_keys
$ chmod 600 authorized_keys 

步驟二

在slave上操作下面命令

$ cd ~
$ ssh-keygen -t rsa
$ cd .ssh
$ cp id_rsa.pub authorized_keys
$ 
 
chmod 600 authorized_keys 

步驟三

接下來保證兩臺機是連通的，執行下面命令，拷貝master的公鑰到slave1機器去，需要輸入slave1的hadoop使用者密碼

scp ~/.ssh/id_rsa.pub hadoop@slave1:/home/hadoop/

步驟四

然後在slave1機器上就可以看到id_rsa.pub檔案了
執行下面命令：
合併id_rsa.pub內容到slave1的authorized_keys檔案上，然後刪除檔案id_rsa.pub

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

完成

執行完即可在master上無密碼登入slave1機器了，但是想要在slave1登入master就不行，還得反過來，拷貝slave1的id_rsa.pub內容到master機器上，然後合併到authorized_keys檔案上才行
注意：如果實在不行，只能互拷公鑰了，也就是兩條機器上的authorized_keys一模一樣

實操

下面是實操程式碼：
master

[hadoop@mester .ssh]$ scp id_rsa.pub   hadoop@slave2:/home/hadoop/
hadoop@slave2's password: 
id_rsa.pub                                           100%  395     0.4KB/s   00:00    
[
 
[email protected] .ssh]$ 

slave2

[hadoop@localhost ~]$ ls
id_rsa.pub  公共  模板  視訊  圖片  文件  下載  音樂  桌面
[hadoop@localhost ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/hadoop/.ssh/id_rsa): 
Created directory '/home/hadoop/.ssh'.
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:
50:2a:8e:e0:25:23:c8:4d:5f:49:f0:34:2d:3f:53:03 [email protected]
The key's randomart image is:
+--[ RSA 2048]----+
|   . .o=+E.      |
|o o . +=.. o     |
|++ o..o.o . .    |
|o.+o . . +       |
| .. .   S o      |
|                 |
|                 |
|                 |
|                 |
+-----------------+
[hadoop@localhost ~]$ 
[hadoop@localhost ~]$ cd .ssh
[hadoop@localhost .ssh]$ cp id_rsa.pub authorized_keys
[hadoop@localhost .ssh]$ chmod 600 authorized_keys 
[hadoop@localhost .ssh]$ cd ..
[hadoop@localhost ~]$ cat ~/id_rsa.pub >> ~/.ssh/authorized_keys
[hadoop@localhost ~]$ rm ~/id_rsa.pub
[hadoop@localhost ~]$ 

登入驗證：

[hadoop@mester .ssh]$ ssh slave2
Last login: Thu Jun 21 16:04:12 2018 from master
[hadoop@slave2 ~]$ exit
登出
Connection to slave2 closed.
[hadoop@mester .ssh]$