步骤

免密登录，先生存秘钥，在hadoop2和hadoop03上授权认证通过。
[root@Hadoop01 ~]# ssh-keygen -t rsa		#连续回车四次
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
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:
52:1e:06:fa:7e:01:3d:a6:1d:bd:cb:19:08:86:cc:ca root@hadoop01
The key's randomart image is:
+--[ RSA 2048]----+
|      .          |
|   o o o .       |
|    = + O .      |
| . . o X = .     |
|  E   + S o      |
|     . . o +     |
|      . . +      |
|       .         |
|                 |
+-----------------+
[root@Hadoop01 ~]# cd .ssh/
[root@hadoop01 .ssh]# ll
总用量 12
-rw-------. 1 root root 1675 10月 30 00:31 id_rsa
-rw-r--r--. 1 root root  392 10月 30 00:31 id_rsa.pub
-rw-r--r--. 1 root root 2359 10月 13 04:33 known_hosts
[root@hadoop01 .ssh]# ssh-copy-id hadoop02		#复制密钥给hadoo02
root@hadoop02's password: 
Now try logging into the machine, with "ssh 'hadoop02'", and check in:

  .ssh/authorized_keys

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

[root@hadoop01 .ssh]# ssh-copy-id hadoop03			#复制密钥给hadoo03
root@hadoop03's password: 
Now try logging into the machine, with "ssh 'hadoop03'", and check in:

  .ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.
测试免密登录
[root@hadoop01 .ssh]# ssh hadoop02
Last login: Mon Oct 30 00:25:33 2017 from hadoop01