【IT Notes】RHCE測驗第十題 Generate a hosts file

• Download an initial template file from http://example.classroom.com/cd/materials/hosts.j2 to /home/student/ansible

• Complete the template so that it can be used to generate a file with a line for each inventory host in the same format as /etc/hosts

• Download the file from http://example.classroom.com/cd/materials/hosts.yml to /home/student/ansible/hosts.yml. This playbook will use the template to generate the file /etc/myhosts on hosts in the dev host group.

  • Do not make any changes to the playbook.

When the playbook is run, the file /etc/myhosts on hosts in the dev host group should have a line for each managed host:

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

172.25.250.10 node1.example.com node1
172.25.250.11 node2.example.com node2
172.25.250.12 node3.example.com node3
172.25.250.13 node4.example.com node4
172.25.250.14 node5.example.com node5

NOTE: The order in which the inventory host names appear is not important.

【題前說明】

這一題要做的是去data主機下載兩個檔案，一個是hosts.j2作為template；另一個是hosts.yml作部署用檔案，比較困難的是又要用到查詢ansible facts的能力，將查詢到的node上的facts，寫在hosts.j2裡面當作變數，並且作一個迴圈，讓最後ansible跑部署的時候把五台node的IP address、FQDN和Hostname寫成一個myhost檔，然後只放在dev群組的主機指定路徑底下。

一．解題過程：

[student@workstation ansible]$ wget http://example.classoom.com/cd/exam_ehce8/hosts.j2
[student@workstation ansible]$ wget http://example.classoom.com/cd/exam_ehce8/hosts.yml
[student@workstation ansible]$ vim hosts.j2

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

{% for host in groups.all %}
{{ hostvars[host].ansible_facts.default_ipv4.address }} {{ hostvars[host].ansible_facts.fqdn }} {{ hostvars[host].ansible_facts.hostname }}
{% endfor %}

[student@workstation ansible]$ vim hosts.yml

---
- name: create myhosts
  hosts: all
  tasks:
    - name: create myhosts
      template:
        src: hosts.j2
        dest: /etc/myhosts
      when: ansible_hostname in groups.dev

二．驗證結果

[student@workstation ansible]$ ansible-play -C hosts.yml

[student@workstation ansible]$ ansible-play hosts.yml

[student@workstation ansible]$ ansible dev -m shell -a 'cat /etc/myhosts'

驗證myhosts有沒有出現在dev群組中主機所被指定的路徑下

三．恢復解題前的環境

[student@workstation ansible]$ vim 10-lab-hosts-stop.yml

---

- name: remove hosts.yml
  hosts: 127.0.0.1
  tasks:
    - name: remove hosts.yml
      file:
        path: /home/student/ansible/hosts.yml
        state: absent

- name: remove hosts.j2
  hosts: 127.0.0.1
  tasks:
    - name: remove hosts.j2
      file:
        path: /home/student/ansible/hosts.j2
        state: absent

- name: remove dev myhosts
  hosts: dev
  tasks:
    - name: remove dev myhosts
      file:
        path: /etc/myhosts
        state: absent

[student@workstation ansible]$ ansible-playbook 10-lab-hosts-stop.yml