centos7系统下，实现1台服务器免密登录多台服务器功能

SSH案例：实现kafka01服务器能够免密登录kafka02和kafka03服务器的需求（不然后面一键启动的脚本将无法使用）⭐

• 1：检查每台服务器是否都安装了SSH：

[root@kafka01 ~]# rpm -qa |grep ssh
openssh-clients-7.4p1-21.el7.x86_64
libssh2-1.8.0-4.el7.x86_64
openssh-7.4p1-21.el7.x86_64
openssh-server-7.4p1-21.el7.x86_64
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• 2：在kafka01服务器上执行：（一直按回车即可！）

[root@kafka01 ~]# cd /root
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[root@kafka01 ~]# ssh-keygen
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• 3：查看kafka01的.ssh目录：
  • id_rsa （私钥）
  • id_rsa.pub (公钥)

[root@kafka01 ~]# cd /root/.ssh && ls 
id_rsa  id_rsa.pub
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• 4：在kafka01服务器上执行如下命令，将公钥传给kafka02服务器，实现kafka01能够免密登录kafka02：
  • 然后中途需要我们输入kafka02的密码，再按回车即可！

[root@kafka01 .ssh]# ssh-copy-id -i ~/.ssh/id_rsa.pub kafka02
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'kafka02 (192.168.184.202)' can't be established.
ECDSA key fingerprint is SHA256:VgM185hBJVyOYeb0tUEXlfALadKx63UcN0OeWAWf1CI.
ECDSA key fingerprint is MD5:6e:8a:c1:a5:c7:9a:a0:a9:47:bc:ad:76:1b:93:c7:5f.
Are you sure you want to continue connecting (yes/no)? yes
/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@kafka02's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'kafka02'"
and check to make sure that only the key(s) you wanted were added.
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• 5：测试kafka01服务器是否可以免密登录kafka02服务器：（测试成功了如下）

[root@kafka01 ~]# ssh kafka02
Last failed login: Wed Aug 31 12:43:58 CST 2022 from kafka01 on ssh:notty
There were 5 failed login attempts since the last successful login.
Last login: Wed Aug 31 10:56:46 2022 from 192.168.184.1
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• 6：在kafka01服务器上，把公钥发给kafka03服务器（实现kafka01能够免密登录kafka02和kafka03服务器）：
  • 然后中途需要我们输入kafka03的密码，再按回车即可！

[root@kafka01 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub kafka03
/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@kafka03's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'kafka03'"
and check to make sure that only the key(s) you wanted were added.
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• 7：测试kafka01服务器是否可以免密登录kafka03服务器：（测试成功了如下）

[root@kafka01 ~]# ssh kafka03
Last login: Wed Aug 31 13:14:03 2022 from kafka01
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