產生 hosts 檔案

1. 下載 hosts.j2 樣板檔。
2. host2.j2 格式為 IP FQDN HOSTNAME (FQDN, Fully qualified domain name, 完全資格域名)，修改 host2.j2 產生所有 inventroy hosts。

   [deyu1@kvm19 ansible]$ vim hosts.j2
   [deyu1@kvm19 ansible]$ cat hosts.j2
   127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
   ::1 localhost localhost.localdomain localhost6 localhost6.localdomain
   
   {% for host in groups['all'] %}
   {{ hostvars[host]['ansible_default_ipv4']['address'] }} {{ hostvars[host]
   ['ansible_fqdn'] }} {{ hostvars[host]['ansible_hostname'] }}
   {% endfor %}
   

3. 建立 playbook 腳本 hosts.yml，當主機在 dev 群組時，使用 hosts.j2 樣板產生 /etc/myhosts。

   [deyu1@kvm19 ansible]$ vim hosts.yml 
   [deyu1@kvm19 ansible]$ cat hosts.yml
   ---
   - name: Create /etc/myhosts
     hosts: all 
     tasks:
     - name: Template a file to /etc/myhosts
       template:
         src: /home/deyu1/ansible/hosts.j2
         dest: /etc/myhosts
       when: '"dev" in group_names'