Inventories

• Official Docs
• Inventory contains a list of servers/systems to connect to.
• Inventory can be written in two formats:
  • INI format (hosts file)
  • YAML format
• Inventory allows us to group servers.
• By default, Ansible uses all to represent all hosts in the inventory file.
• The default inventory file location is /etc/ansible/hosts.

---

Example 1 — Basic Inventory (No Groups)

INI format:

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

YAML format:

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:

---

Example 2 — Inventory with Groups

INI format:

[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

YAML format:

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 3 — Range Pattern

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

---

Static vs Dynamic Inventories

• The above examples are static inventories.
• Inventories can also be dynamic, which means they point to:
  • An executable (script) that generates a list of servers in a specific JSON format.
  • Ansible plugins to fetch servers from cloud providers like AWS, Azure, GCP.

---

Ansible Debug Messages

Simple Playbook (without debug)

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

Playbook with Explicit Debug Messages

Using the 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 — use the -v, -vv, -vvv, or -vvvv flags with ansible-playbook for increasing levels of verbosity.

---

Bailout / Failing an Ansible Playbook

• To intentionally fail a playbook, use the fail module.

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