DevOps Classroom notes 08/Mar/2025

Parametrization

• To make the playbook generic, we need to define variables.
• Ansible variables can be passed from multiple locations
• Lets look at the following playbook

---
- name: deploy website into apache webserver
  hosts: all
  become: yes
  vars:
    web_package_name: apache2
    unzip_package_name: unzip
    download_url: https://www.free-css.com/assets/files/free-css-templates/download/page291/goind.zip
  tasks:
    - name: install apache2
      ansible.builtin.apt:
        name: "{{ web_package_name  }}"
        update_cache: yes
        state: present
    - name: enable and ensure apache is started
      ansible.builtin.systemd_service:
        name: "{{ web_package_name  }}"
        enabled: yes
        state: started
    - name: ensure unzip is installed
      ansible.builtin.apt:
        name: "{{ unzip_package_name }}"
        state: present
    - name: download and extract website
      ansible.builtin.unarchive:
        src: "{{ download_url }}"
        dest: /tmp
        remote_src: yes
    - name: copy the html folder to naukri
      ansible.builtin.copy:
        src: /tmp/html/
        dest: /var/www/html/naukri
        remote_src: yes

• In the above playbook we have defined the vars section
• Now while executing playbook the command which we use ansible-playbook -i hosts web-deploy.yaml
• Now if you want to change the variable

`ansible-playbook -e web_package=nginx -i hosts web-deploy.yaml`

Lets consider a scenario

• You are asked to deploy website by executing above playbook on two hosts
• one will use nginx
• other will use apache2
• Playbook

---
- name: deploy website into apache webserver
  hosts: all
  become: yes
  vars:
    unzip_package_name: unzip
    download_url: https://www.free-css.com/assets/files/free-css-templates/download/page291/goind.zip
  tasks:
    - name: display the web package name
      ansible.builtin.debug:
        msg: "web pacakage name is {{ web_package_name  }}"
    - name: "install web package"
      ansible.builtin.apt:
        name: "{{ web_package_name  }}"
        update_cache: yes
        state: present
    - name: "enable and ensure web package is started"
      ansible.builtin.systemd_service:
        name: "{{ web_package_name  }}"
        enabled: yes
        state: started
    - name: ensure unzip is installed
      ansible.builtin.apt:
        name: "{{ unzip_package_name }}"
        state: present
    - name: download and extract website
      ansible.builtin.unarchive:
        src: "{{ download_url }}"
        dest: /tmp
        remote_src: yes
    - name: copy the html folder to naukri
      ansible.builtin.copy:
        src: /tmp/html/
        dest: /var/www/html/naukri
        remote_src: yes

• Inventory

172.31.4.82 web_package_name=nginx
localhost web_package_name=apache2

Inventory in ansible

• Ansible on a broader note supports two types of inventories
  • static: For static we have two formats
    • ini
    • yaml
  • dynamic: To fetch the inventory dynamically we have two options
    • plugins
    • script

Static

• ini: This format helps in writing static inventory
• All server names/ips

172.31.4.82
localhost

• Categorize into groups

[web]
localhost
172.31.4.82

[db]
172.31.4.83
172.31.4.84
localhost

[app]
172.31.4.85
172.31.4.86
localhost

• We can add variables in the inventory file (not recommended)

[web]
localhost
172.31.4.82 web_package_name=nginx

[web:vars]
web_package_name=apache2
unzip_package_name=unzip
download_url= https://www.free-css.com/assets/files/free-css-templates/download/page291/goind.zip

[db]
172.31.4.83
172.31.4.84
localhost

[app]
172.31.4.85
172.31.4.86
localhost

* Writing variables relative to inventory file
* Refer Here for host_vars and group_vars

• Inventories can also be written in YAML Format

web:
  hosts:
    localhost:
    172.31.4.82:
db:
  hosts:
    172.31.4.83:
    172.31.4.84:
    localhost:
app:
  hosts:
    172.31.4.85:
    172.31.4.86:
    localhost: