Ansible Fundamentals

Ansible Fundamentals

Core principles and golden rules for writing production-quality Ansible automation.

Golden Rules

These rules apply to ALL Ansible code in this repository:

1. Use uv run prefix - Execute all Ansible commands through uv:

   uv run ansible-playbook playbooks/my-playbook.yml
   uv run ansible-lint
   uv run ansible-galaxy collection install -r requirements.yml
   

2. Fully Qualified Collection Names (FQCN) - Avoid short module names:

   # CORRECT
   - name: Install package
     ansible.builtin.apt:
       name: nginx
       state: present
   
   # WRONG - deprecated short names
   - name: Install package
     apt:
       name: nginx
   

3. Control command/shell modules - Add changed_when and failed_when:

   - name: Check if service exists
     ansible.builtin.command: systemctl status myservice
     register: service_check
     changed_when: false
     failed_when: false
   

4. Use set -euo pipefail - In all shell scripts and shell module calls:

   - name: Run pipeline command
     ansible.builtin.shell: |
       set -euo pipefail
       cat file.txt | grep pattern | wc -l
     args:
       executable: /bin/bash
   

5. Tag sensitive tasks - Use no_log: true for secrets:

   - name: Set database password
     ansible.builtin.command: set-password {{ db_password }}
     no_log: true
   

6. Idempotency first - Check before create, verify after.

7. Descriptive task names - Start with action verbs (Ensure, Configure, Install, Create).

Module Selection Guide

Decision Matrix

Prefer Native Modules

Native modules provide:

• Built-in idempotency (no need for changed_when)
• Better error handling
• Cross-platform compatibility
• Clear documentation

# PREFER native module
- name: Create user
  ansible.builtin.user:
    name: deploy
    groups: docker
    state: present

# AVOID command when module exists
- name: Create user
  ansible.builtin.command: useradd -G docker deploy
  # Requires: changed_when, failed_when, idempotency logic

When Command/Shell is Acceptable

Use command or shell modules when:

1. No native module exists for the operation
2. Interacting with vendor CLI tools (pvecm, pveceph, kubectl)
3. Running one-off scripts

Add proper controls:

- name: Create Proxmox API token
  ansible.builtin.command: >
    pveum user token add {{ username }}@pam {{ token_name }}
  register: token_result
  changed_when: "'already exists' not in token_result.stderr"
  failed_when:
    - token_result.rc != 0
    - "'already exists' not in token_result.stderr"
  no_log: true

Collections in Use

This repository uses these Ansible collections:

Installing Collections

# Install from requirements
cd ansible && uv run ansible-galaxy collection install -r requirements.yml

# Install specific collection
uv run ansible-galaxy collection install community.proxmox

Common Execution Patterns

Running Playbooks

# Basic execution
uv run ansible-playbook playbooks/my-playbook.yml

# With extra variables
uv run ansible-playbook playbooks/create-vm.yml \
  -e "vm_name=docker-01" \
  -e "vm_memory=4096"

# Limit to specific hosts
uv run ansible-playbook playbooks/update.yml --limit proxmox

# Check mode (dry run)
uv run ansible-playbook playbooks/deploy.yml --check --diff

# With tags
uv run ansible-playbook playbooks/setup.yml --tags "network,storage"

Linting

# Run ansible-lint
mise run ansible-lint

# Or directly
uv run ansible-lint ansible/playbooks/

Task Naming Conventions

Use descriptive names with action verbs:

Examples:

- name: Ensure Docker is installed
- name: Configure SSH security settings
- name: Create admin user account
- name: Deploy application configuration

Variable Naming

Use snake_case with descriptive names:

# GOOD - clear, descriptive
proxmox_api_user: terraform@pam
docker_compose_version: "2.24.0"
vm_memory_mb: 4096

# BAD - vague, abbreviated
pve_usr: terraform@pam
dc_ver: "2.24.0"
mem: 4096

Quick Reference Commands

# Lint all Ansible files
mise run ansible-lint

# Run playbook with secrets from Infisical
cd ansible && uv run ansible-playbook playbooks/my-playbook.yml

# Check syntax
uv run ansible-playbook --syntax-check playbooks/my-playbook.yml

# List hosts in inventory
uv run ansible-inventory --list

# Test connection
uv run ansible all -m ping

Common Anti-Patterns

Missing FQCN

# BAD
- name: Copy file
  copy:
    src: file.txt
    dest: /tmp/

# GOOD
- name: Copy file
  ansible.builtin.copy:
    src: file.txt
    dest: /tmp/

Uncontrolled Commands

# BAD - always shows changed, no error handling
- name: Check status
  ansible.builtin.command: systemctl status app

# GOOD
- name: Check status
  ansible.builtin.command: systemctl status app
  register: status_check
  changed_when: false
  failed_when: false

Using shell When command Suffices

# BAD - shell not needed
- name: List files
  ansible.builtin.shell: ls -la /tmp

# GOOD - command is sufficient
- name: List files
  ansible.builtin.command: ls -la /tmp
  changed_when: false

Missing no_log on Secrets

# BAD - password in logs
- name: Set password
  ansible.builtin.command: set-password {{ password }}

# GOOD
- name: Set password
  ansible.builtin.command: set-password {{ password }}
  no_log: true

Related Skills

• ansible-idempotency - Detailed changed_when/failed_when patterns
• ansible-secrets - Infisical integration and security
• ansible-proxmox - Proxmox-specific module selection
• ansible-error-handling - Block/rescue, retry patterns