免密钥方式登陆配置

1.使用 ssh-keygen 生成公钥和私钥

[root@localhost ~]# ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 　　#默认回车就可以
Enter passphrase (empty for no passphrase): 　　　　　　　　　　#默认回车就可以
Enter same passphrase again: 　　　　　　　　　　　　　　　　　　#默认回车就可以
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:
SHA256:mgyB4mVBPdMaPPbYZbXDJzycMZ6nOmTT9RsetKFtDOY root@localhost.localdomain
The key's randomart image is:
+---[RSA 2048]----+
|  .oo .   .+     |
|   ..O . o= *    |
|. .oo X o  % * o |
|..o  + o  . @ B o|
| .  .   S+ o E O |
|     o oo o   o +|
|      +  o     o |
|          .      |
|                 |
+----[SHA256]-----+

2.查看/root/.ssh/目录，发现多了两个文件

[root@localhost ~]# ll .ssh/
total 12
-rw------- 1 root root 1679 Aug  1 00:46 id_rsa
-rw-r--r-- 1 root root  408 Aug  1 00:46 id_rsa.pub

3.使用 ssh-copy-id 命令发送公钥至指定主机

[root@localhost ~]# ssh-copy-id -i /root/.ssh/
id_rsa       id_rsa.pub   known_hosts  
[root@localhost ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub 192.168.249.132
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.249.132's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh '192.168.249.132'"
and check to make sure that only the key(s) you wanted were added.

4.现在尝试 ssh -l IP 进行免密登陆

[root@localhost ~]# ssh -l root 192.168.249.132
Last login: Thu Aug  1 00:35:11 2019 from 192.168.249.135

大功告成。