1、备份文件

cd /etc/ssh/
scp sshd_config sshd_config.bak

2、生成密钥

[root@centos7-1 ssh]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):   #回车
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase):   #回车
Enter same passphrase again:    #回车
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:     #回车
SHA256:ERQjqOd4sCPq0XSZvS6nDPxtqKOQtV/vmP79hbzNd4o root@centos7-1
The key's randomart image is:
+---[RSA 2048]----+
|     ...=.       |
|    .  . o       |
|   .    .        |
|  o . +  .       |
|  .B + .S        |
|.oB.+   .  . .   |
|+o.*  o.    o .  |
|o .o++o* .   *  o|
|.o..+=O=+ ..E +o.|
+----[SHA256]-----+

[root@centos7-1 ssh]# ll /root/.ssh/
total 8
-rw-------. 1 root root 1675 Jun 12 10:37 id_rsa
-rw-r--r--. 1 root root 396 Jun 12 10:37 id_rsa.pub

3、安装公钥

[root@centos7-1 ssh]# cd /root/.ssh/
[root@centos7-1 .ssh]# cat id_rsa.pub >> authorized_keys
[root@centos7-1 .ssh]# chmod 600 authorized_keys
[root@centos7-1 .ssh]# chmod 700 ~/.ssh
[root@centos7-1 .ssh]# ll
total 12
-rw-------. 1 root root  396 Jun 12 10:39 authorized_keys
-rw-------. 1 root root 1675 Jun 12 10:37 id_rsa
-rw-r--r--. 1 root root  396 Jun 12 10:37 id_rsa.pub

4、修改文件

#删除以下配置行

[root@centos7-1 ~]# sed -i '/PasswordAuthentication.*/d' /etc/ssh/sshd_config
[root@centos7-1 ~]# sed -i '/PubkeyAuthentication.*/d' /etc/ssh/sshd_config
[root@centos7-1 ~]# sed -i '/RSAAuthentication.*/d' /etc/ssh/sshd_config
[root@centos7-1 ~]# sed -i '/AuthorizedKeysFile.*/d' /etc/ssh/sshd_config

#新增以下配置行
[root@centos7-1 ~]# cat >>/etc/ssh/sshd_config<<EOF
PasswordAuthentication no
PubkeyAuthentication yes
RSAAuthentication yes
AuthorizedKeysFile /root/.ssh/authorized_keys

EOF

5、重启sshd服务

[root@centos7-1 .ssh]# systemctl restart sshd

6、尝试密钥登录

将文件 id_rsa下载保存到本地

[root@centos7-1 .ssh]# ll
total 12
-rw-------. 1 root root  396 Jun 12 10:39 authorized_keys
-rw-------. 1 root root 1675 Jun 12 10:37 id_rsa
-rw-r--r--. 1 root root  396 Jun 12 10:37 id_rsa.pub

7、登录测试即可