DevOps Classroom notes 12/Feb/2026

Inventories

• Refer Here for official docs
• inventory contains list of servers/systems to connect to.
• Inventory can be written in two formats
  • ini format (hosts)
  • yaml format
• Inventory allows us to group servers
• prompt: I want to learn writing ansible inventories, Explain ini format
• by default ansible uses all to represent all hosts in inventory file
• basic inventory without groups. consider this example1

10.100.0.11
10.100.0.12
10.100.0.13
10.100.0.14
10.100.0.15
10.100.0.16
10.100.0.17
10.100.0.18
10.100.0.19
10.100.0.10

* in yaml

all:
  hosts:
    10.100.0.11:
    10.100.0.12:
    10.100.0.13:
    10.100.0.14:
    10.100.0.15:
    10.100.0.16:
    10.100.0.17:
    10.100.0.18:
    10.100.0.19:
    10.100.0.10:

• consider this example2

[webservers]
10.100.0.11
10.100.0.12
10.100.0.13
10.100.0.14
10.100.0.15
10.100.0.16

[dbservers]
10.100.0.17
10.100.0.18
10.100.0.19
10.100.0.10

* same in yaml

all:
  children:
    webservers:
      hosts:
        10.100.0.11:
        10.100.0.12:
        10.100.0.13:
        10.100.0.14:
        10.100.0.15:
        10.100.0.16:

    dbservers:
      hosts:
        10.100.0.17:
        10.100.0.18:
        10.100.0.19:
        10.100.0.10:

• Example

[webservers]
www[01:06].example.com

• The above mentioned inventories are referred as static inventories.
• Inventories can be dynamic, i.e. it points to
  • an executable (Script) which generates a list of servers in a specific json format
  • Ansible also has plugins to get servers from cloud providers like aws, azure, gcp
• The default inventory file is in /etc/ansible/hosts

Ansible debug messages

• Consider the simple playbook

---
- name: sample playbook
  hosts: all
  become: yes
  tasks:
    - name: update packages and install tree
      ansible.builtin.apt:
        name: tree
        update_cache: yes
        state: present

• Explicit debug messages using debug module

---
- name: sample playbook
  hosts: all
  become: yes
  tasks:
    - ansible.builtin.debug:
        msg: "Installing tree package"
    - name: update packages and install tree
      ansible.builtin.apt:
        name: tree
        update_cache: yes
        state: present
    - ansible.builtin.debug:
        msg: "Installed tree package"

• Ansible also supports printing verbose information prompt: Ansible playbook verbose levels in a table

Bailout or failing ansible

• To fail ansible playbook we have a module called fail Refer Here

---
- name: sample bailout playbook
  hosts: all
  become: yes
  tasks:
    - ansible.builtin.fail:
        msg: "Under development"