ssh免密登录免提示登录

背景：机器A免密码登录机器B，需要用bash实现；之后服务器C也可以直接用bash代码免密登录机器B；

机器A上配置：
（1）root登录；生成公钥私钥

$ ssh-keygen
#直接全部回车
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
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:#####
root@localhost.localdomain
The key's randomart image is:
+---[RSA 2048]----+
|        .*BX+oB.o|
|         .*B+B =.|
|    . . o o.* B o|
|E. . . o . o.o.*.|
|...     S .oo.o..|
|.        .. .+ o |
|          . . o  |
|           o     |
|          .      |
+----[SHA256]-----+
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（2）拷贝公钥到服务器B

ssh-copy-id -i ~/.ssh/id_rsa.pub -p port 'username@ip'
#ssh-copy-id -i ~/.ssh/id_rsa.pub -p 28488 'root@45.62.123.*'
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执行结果如下， 可以到服务器B上去看下是否有文件生成/root/.ssh/authorized_keys

/root/.ssh/authorized_keys文件内容如下图：

（3）服务器A免提示，免密登录服务器B；

ssh-keyscan  -p port ip > ~/.ssh/known_hosts  //替换为远程服务器的地址
chmod 644 ~/.ssh/known_hosts
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尝试免密登录服务器B，免提示登录服务器B

ssh -p port ip 
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结果如下，不需要登录提示

（4）服务器C免密免提示登录服务器B；
前提：自行拷贝服务器A生成的文件id_rsa文件到服务器C（/root/.ssh/id_rsa）

#升级ssh-agent
#which ssh-agent || ( yum update -y && yum install openssh-client git -y )
eval $(ssh-agent -s)
#echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add -
cat id_rsa | ssh-add -
mkdir -p ~/.ssh
chmod 700 ~/.ssh
ssh-keyscan  -p port ip > ~/.ssh/known_hosts  //替换为远程服务器的地址
chmod 644 ~/.ssh/known_hosts
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执行结果如下

参考：

https://blog.csdn.net/zt15732625878/article/details/119558733
https://blog.csdn.net/weixin_47656385/article/details/123043020