生成公钥

命令ssh-keygen可在机器上生成公钥和相关文件，等待输入的时候可以直接回车使用默认配置

[admin@iZ280626x93Z ~]$ ssh-keygen
Generating public/private rsa key pair.

Enter file in which to save the key (/home/admin/.ssh/id_rsa): Created directory '/home/admin/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/admin/.ssh/id_rsa.
Your public key has been saved in /home/admin/.ssh/id_rsa.pub.
The key fingerprint is:
a4:ae:8b:25:cd:3f:89:2a:ad:46:47:55:a2:92:4f:4e admin@iZ280626x93Z
The key's randomart image is:
+--[ RSA 2048]----+
|     ...         |
|  . ...          |
| o E.   .        |
|  *.   o         |
|  .o  . S        |
| . + .           |
|..o +...         |
|...+.oo          |
|ooo.o...         |
+————————+

这个时候在用户目录下就会生成一个.ssh文件夹，里面有公钥相关文件，其中id_rsa.pub就是当前机器B的公钥，只要在机器A上的~/.ssh/authorized_keys文件中把B机器的公钥加进去，B机器就可以免密码登录A，用户名取决于公钥在A机器那个用户目录下。

➜  ~ cd ~/.ssh 
➜  .ssh ls
id_rsa      id_rsa.pub  known_hosts
➜  .ssh 

修改远程机器

vim authorized_keys //把B机器的公钥加进去
chmod 600 authorized_keys //修改文件权限

如果希望ssh公钥生效需满足至少下面两个条件：

• .ssh目录的权限必须是700
• .ssh/authorized_keys文件权限必须是600