We can declare variables in

• playbook
• inventory
• commands

Which can be used & Intropolate only in playbook Tasks but not in the files used in playbook.

Solution: Template
Using Template module you can Intropolate vars mentioned in the files used in playbook.

Rule for using template Module

• A file must be .j2 ext
• Must use a module call “template”

Example Code for Cento/RHEL

---
- name: Update web servers
  hosts: web
  vars:
    myname: "Rajesh Kumar"

  tasks:
  - name: Install Apache in centos7
    ansible.builtin.yum:
      name: httpd
      state: latest
  - name: Copy index.html
    ansible.builtin.copy:
      src: index.html
      dest: /var/www/html/index.html
  - name: Template index.html
    template:
      src: index.html.j2
      dest: /var/www/html/index-template.html
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: httpd
      state: started

index.html.j2

Project Requirement

• When you Change APACHE STATIC HTML Content -> HTTPD restart is not required
• When you Change APACHE Conf -> HTTPD restart is not required
• HTTP should be run 90
• No restart should be done on STATIC
• Restart must be done at conf changes

---
- name: Update web servers
  hosts: web
  vars:
    myname: "Rajesh Kumar"
    httpport: 8090

  tasks:
  - name: Install Apache in centos7
    ansible.builtin.yum:
      name: httpd
      state: latest
  - name: Copy index.html
    ansible.builtin.copy:
      src: index.html
      dest: /var/www/html/index.html
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: httpd
      state: started
  - name: stopped a Apache Server
    ansible.builtin.service:
      name: httpd
      state: stopped
  - name: Template for httpd.conf
    template:
      src: httpd.conf.j2
      dest: /etc/httpd/conf/httpd.conf
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: httpd
      state: started

Example code for Template for Ubuntu

---
- name: Update web servers
  hosts: web
  vars:
    myname: "Rajesh Kumar"
    port: 81

  tasks:
  - name: Install Apache in Ubuntu
    ansible.builtin.apt:
      name: apache2
      state: latest
  - name: Copy index.html
    ansible.builtin.copy:
      src: index.html
      dest: /var/www/html/index.html
  - name: stopped a Apache Server
    ansible.builtin.service:
      name: apache2
      state: stopped
  - name: Template for httpd.conf
    template:
      src: ports.conf.j2
      dest: /etc/apache2/ports.conf
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: apache2
      state: started

Problems

• No change in config file but STOP and START happening

Solution

• Handlers

What is Handlers?

• A section is plyabook similar to tasks section
• It contains multiple task similar to tasks section
• The Handler task would execute when you call from tasks’s task
• BUT one condition – ONLY when calling tasks’s task is CHANGED == TRUE

---
- name: Update web servers
  hosts: web
  vars:
    myname: "Rajesh Kumar"
    httpport: 8090

  tasks:
  - name: Install Apache in centos7
    ansible.builtin.yum:
      name: httpd
      state: latest
  - name: Copy index.html
    ansible.builtin.copy:
      src: index.html
      dest: /var/www/html/index.html
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: httpd
      state: started
  - name: Template for httpd.conf
    template:
      src: httpd.conf.j2
      dest: /etc/httpd/conf/httpd.conf
    notify:
      - ReStarting a Apache Server

  handlers:
  - name: ReStarting a Apache Server
    ansible.builtin.service:
      name: httpd
      state: restarted

Handlers Code Example for Ubuntu

---
- name: Update web servers
  hosts: localhost
  vars:
    myname: "Rajesh Kumar"
    port: 81

  tasks:
  - name: Install Apache in Ubuntu
    ansible.builtin.apt:
      name: apache2
      state: latest
  - name: Copy index.html
    ansible.builtin.copy:
      src: index.html
      dest: /var/www/html/index.html
  - name: Template for httpd.conf
    template:
      src: ports.conf.j2
      dest: /etc/apache2/ports.conf
    notify:
      - ReStarting a Apache Server
  - name: Starting a Apache Server
    ansible.builtin.service:
      name: apache2
      state: started

  handlers:
  - name: ReStarting a Apache Server
    ansible.builtin.service:
      name: apache2
      state: restarted

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Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I am working at Cotocus. I blog tech insights at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at I reviewed , and SEO strategies at Wizbrand. 

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