*設定 SSH Keys

1. Ansible 控制節點與受管節點間藉由 ssh 連線，必須設定免密碼連線，或執行 ansible 時使用 –ask-pass 選項要求輸入密碼。為方便自動完成任務一般會使用免密碼連線。
2. 產生一組金鑰

   [root@kvm19 ~]# ssh-keygen 
   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:F9OoHjIT3jPlN95CnwEAKnrIQsySYaZMQOZU6wVpwsA root@kvm19.deyu.wang
   The key's randomart image is:
   +---[RSA 2048]----+
   |XB.o.   ...      |
   |%E oo  .   +     |
   |+*o...o   = o    |
   |o..o.o o + o .   |
   |. +.. = S o + .  |
   | . .   = = + + o |
   |        .   o +  |
   |             .   |
   |                 |
   +----[SHA256]-----+
   

3. 查看 .ssh 目錄下新增了 id_rsa 私鑰及 id_rsa.pub 公鑰。

   [root@kvm19 ~]# ll .ssh/
   total 12
   -rw-r--r--. 1 root root  401 Mar  2 10:32 authorized_keys
   -rw-------. 1 root root 1831 Mar  5 10:59 id_rsa
   -rw-r--r--. 1 root root  402 Mar  5 10:59 id_rsa.pub
   

4. ssh-copy-id 將 id_rsa.pub 公鑰匯入到 kvm11，輸入密碼完成匯入。

   [root@kvm19 ~]# ssh-copy-id kvm11.deyu.wang
   /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed:
    "/root/.ssh/id_rsa.pub"
   The authenticity of host 'kvm11.deyu.wang (192.168.122.11)' can't be established.
   ECDSA key fingerprint is SHA256:l6jIMoK+z82ydTlG8MKarNcUDLVSfjCRjWRzhGOtDNc.
   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@kvm11.deyu.wang's password: 
   
   Number of key(s) added: 1
   
   Now try logging into the machine, with:   "ssh 'kvm11.deyu.wang'"
   and check to make sure that only the key(s) you wanted were added.
   

5. ssh 試著連線 kvm11，不用輸入密碼即可登入。

   [root@kvm19 ~]# ssh kvm11.deyu.wang
   Last login: Mon Mar  2 18:40:01 2020 from 192.168.122.1
   

6. 退出 kvm11。

   [root@kvm11 ~]# exit
   logout
   Connection to kvm11.deyu.wang closed.