一.主机互信原理
两个主机之间ssh登录需要提示输入对方的密码，当频繁需要登录操作时,可以通过linux公钥和秘钥，建立双机信任关系。
把你源主机的公钥文件内容追加到目的主机对应用户下的authorized_keys文件中(如果没有这个文件，则创建一个)

二.操作流程

两台主机分别是node1的ip是1192.168.37.8，node2的ip是192.168.37.9
1. 生成秘钥(两台主机分别操作)

ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa              #生成rsa

1) node1节点操作 - 生成密钥

[root@node1 ~]# ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa   #node1节点生成密钥
Generating public/private rsa key pair.
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:
SHA256:1RzOG0HzkXAAZz6YdYMp6vgGev0zzv3zzM3VF5cKb30 root@node1
The key's randomart image is:
+---[RSA 2048]----+
|          .o@==. |
|          .%oB.o |
|         .+.O .  |
|        ..   +  .|
|       oS  ..  o.|
|      o .   o o +|
|     . +     + .E|
|    . . +.o.. .+=|
|     . . o+o...o*|
+----[SHA256]-----+
[root@node1 ~]#

2) node2节点操作 -生成密钥

[root@node2 ~]# ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa   #node2节点生成密钥
Generating public/private rsa key pair.
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:
SHA256:9mRYbTPIQ3pSYwdMO5/byswezu7uicSAF9AJAxPisqU root@node2
The key's randomart image is:
+---[RSA 2048]----+
|  . +o+o +B..    |
| . . . oo*.*     |
|. o     + O =    |
| =     . * = +   |
|E     . S o o    |
|       o *   o   |
|          + o .  |
|         . B +   |
|          .*#    |
+----[SHA256]-----+
[root@node2 ~]#

2.信任主机操作(两台主机分别操作)

ssh-copy-id -i  ~/.ssh/id_rsa.pub root@对方ip

1) node1节点设置互信

[root@node1 ~]# ssh-copy-id -i  ~/.ssh/id_rsa.pub root@192.168.37.9  #复制37的公钥到38机器上，这样就可以使用在37机器上免密码登录38机器了。
/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@192.168.37.9's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@192.168.37.9'"
and check to make sure that only the key(s) you wanted were added.

[root@node1 ~]#

2) node2节点设置互信

[root@node2 ~]# ssh-copy-id -i  ~/.ssh/id_rsa.pub root@192.168.37.8  #复制node2的公钥到node1机器上，这样就可以使用在node2机器上免密码登录node1机器了
/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@192.168.37.8's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@192.168.37.8'"
and check to make sure that only the key(s) you wanted were added.

[root@node2 ~]#

3.测试ssh机器免密

1) node1节点访问node2

[root@node1 ~]# 
[root@node1 ~]# ssh 192.168.37.9
Last login: Wed Oct 13 22:13:07 2021 from 192.168.37.8
[root@node2 ~]#

node2节点访问node1

[root@node2 ~]# ssh 192.168.37.8
Last login: Mon Sep 20 18:30:35 2021 from 192.168.37.9
[root@node1 ~]#