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, 完整網域名稱)，修改 host2.j2 產生所有 inventroy hosts。

   ceuser@deyu:/ansible_pb$ vi hosts.j2
   ceuser@deyu:/ansible_pb$ 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. 查詢 template 模組文件的範例。

   ceuser@deyu:~/ansible_pb$ ansible-doc template | grep ^EX -A8
   EXAMPLES:
   
   - name: Template a file to /etc/file.conf
     ansible.builtin.template:
       src: /mytemplates/foo.j2
       dest: /etc/file.conf
       owner: bin
       group: wheel
       mode: '0644'
   

4. 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。

   ceuser@deyu:/ansible_pb$ vi hosts.yml 
   ceuser@deyu:/ansible_pb$ cat hosts.yml
   ---
   - name: Create /etc/myhosts
     hosts: all
     tasks:
     - name: Template a file to /etc/myhosts
       ansible.builtin.template:
         src: /home/ceuser/ansible_pb/hosts.j2
         dest: /etc/myhosts
       when: '"dev" in group_names'