[root@server ~]# vim /etc/hosts
配置IP 主机名
192.168.193.129 server.explame.com
192.168.193.134 a1.explame.com
192.168.193.135 a2.explame.com

[root@BBB ~]# ssh-keygen -t rsa  ---指定加密算法
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
---保存私钥的文件全路径
Created directory '/root/.ssh'.
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:wkC11BzXR/Ccvs3IQvDhIOz7UhhRE35pYAvhHcZUDgY root@BBB
The key's randomart image is:
+---[RSA 3072]----+
|    ..ooEB&+oo.  |
|   . . ++O.B.+.. |
|    . . +.* *.+  |
|     o ... B o   |
|      o So  + .  |
|       ..... . = |
|        ..  . + o|
|        ..   .   |
|         ..      |
+----[SHA256]-----+
默认的证书目录：/root/.ssh
默认创建的公钥文件：/root/.ssh/id_rsa.pub
在保存私钥的文件全路径的目录下生成密钥对
[root@BBB ~]# ll /root/.ssh/
total 8
-rw-------. 1 root root 2590 Jul 28 23:21 id_rsa
-rw-r--r--. 1 root root  562 Jul 28 23:21 id_rsa.pub
然后将公钥追加到192.168.193.134这个服务器上的~/.ssh/authorized_keys文件
1、将公钥通过scp拷贝到服务器上，然后追加到~/.ssh/authorized_keys文件中。scp -P 22 ~/.ssh/id_rsa.pub user@host:~/。
2、通过ssh-copy-id程序，ssh-copyid user@host
3、可以通过cat ~/.ssh/id_rsa.pub | ssh -p 22 user@host ‘cat >> ~/.ssh/authorized_keys’，这个可以更改端口号。
如果另外一台服务器没有.ssh目录
输入# ssh localhost
 .ssh 是记录密码信息的文件夹，如果没有登录过root的话，就没有 .ssh 文件夹，因此登录 localhost ，并输入密码就会生成了。
.ssh目录的权限为700，其下文件authorized_keys和私钥的权限为600。否则会因为权限问题导致无法免密码登录。我们可以看到登陆后会有known_hosts文件生成。
最后通过ssh root@192.168.193.134验证

[root@a2 ~]# yum install -y ansible
Updating Subscription Management repositories.
Unable to read consumer identity
This system is not registered with an entitlement server. You can use subscription-manager to register.
Repository AppStream is listed more than once in the configuration
Last metadata expiration check: 2:28:10 ago on Tue 02 Aug 2022 03:07:37 PM CST.
Error: 
 Problem: conflicting requests
  - nothing provides (ansible-core >= 2.12.2 with ansible-core < 2.13) needed by ansible-5.4.0-3.el8.noarch
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

[root@server ~]# ansible --version
ansible [core 2.12.7]
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.8/site-packages/ansible
  ansible collection location = /root/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/bin/ansible
  python version = 3.8.13 (default, Jun 24 2022, 15:27:57) [GCC 8.5.0 20210514 (Red Hat 8.5.0-13)]
  jinja version = 2.11.3
  libyaml = True

[A]
a1.example.com
a2.example.com

[root@server ~]# ansible A -m ping
a1.explame.com | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/libexec/platform-python"
    },
    "changed": false,
    "ping": "pong"
}
a2.explame.com | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/libexec/platform-python"
    },
    "changed": false,
    "ping": "pong"
}