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概述

业务场景中经常需要进行跨服务器的操作，即从一台服务器上登录到另外一台服务器，默认情况下，SSH远程登录时需要输入远程服务器密码。当需要在可信任的服务器之间进行频繁或自动化的操作时，输入密码就会带来不便，本文介绍如何实现SSH远程免密登录。

配置免密登录

• 在本地服务器上运行命令，生成公钥、私钥

ssh-keygen -t rsa

执行该命令后，系统提示时直接三次回车即可（一般按默认值）

[cenots@nnkin ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/nnkin/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/nnkin/.ssh/id_rsa.
Your public key has been saved in /home/nnkin/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:Ct6HIbAfypJpr/VLzxOeWX4WngQPUaSrJTguPN23Eh4 centos@nnkin
The key's randomart image is:
+---[RSA 2048]----+
|          oo     |
|         ..      |
|  .      ..      |
|   o  .  o.      |
|  . +o..So+      |
| +.+o=oE+. +     |
|+.o=o+*oX.o o    |
|..o = oO...=     |
| ... o.oo.o      |
+----[SHA256]-----+
[cenots@nnkin ~]$

• 公钥储存在 /root/.ssh/id_rsa.pub
• 私钥储存在 /root/.ssh/id_rsa

[cenots@nnkin ~]$ cd ~/.ssh/
[cenots@nnkin .ssh]$ ls
id_rsa  id_rsa.pub  known_hosts

• 在本地服务器上运行命令，拷贝公钥至远程服务器

ssh-copy-id -i /root/.ssh/id_rsa.pub root@<IP_ADDRESS>

执行此命令需要输入远程服务器密码

• 在本地服务器上运行命令，测试ssh免密登录远程服务器

ssh <IP_ADDRESS>

此时就可以直接免密登录远程服务器进行操作了。