managing-configuration

Configuration Management

Purpose

This skill provides guidance for automating server and application configuration using Ansible and related tools. It covers playbook creation, role structure, inventory management (static and dynamic), secret management, testing patterns, and idempotency best practices to ensure safe, repeatable configuration deployments.

When to Use This Skill

Invoke this skill when:

• Creating Ansible playbooks to configure servers or deploy applications
• Structuring reusable Ansible roles with proper directory layout
• Managing inventories (static files or dynamic cloud-based)
• Securing secrets with ansible-vault or HashiCorp Vault integration
• Testing roles with Molecule before production deployment
• Ensuring idempotent playbooks that safely run multiple times
• Migrating from Chef or Puppet to Ansible
• Implementing GitOps workflows for configuration as code
• Debugging playbook failures or handler issues

Quick Start

Basic Playbook Example

---
# site.yml
- name: Configure web servers
  hosts: webservers
  become: yes

  tasks:
    - name: Ensure nginx is installed
      apt:
        name: nginx
        state: present
      notify: Restart nginx

    - name: Start nginx service
      service:
        name: nginx
        state: started
        enabled: yes

  handlers:
    - name: Restart nginx
      service:
        name: nginx
        state: restarted

Run with:

ansible-playbook -i inventory/production site.yml

Core Concepts

1. Idempotency

Run playbooks multiple times without unintended side effects. Use state-based modules (present, started, latest) instead of imperative commands.

Idempotent (good):

- name: Ensure package installed
  apt:
    name: nginx
    state: present

Not idempotent (avoid):

- name: Install package
  command: apt-get install -y nginx

See references/idempotency-guide.md for detailed patterns.

2. Inventory Management

Static Inventory: INI or YAML files for stable environments. Dynamic Inventory: Scripts or plugins for cloud environments (AWS, Azure, GCP).

Example static inventory (INI):

[webservers]
web1.example.com ansible_host=10.0.1.10
web2.example.com ansible_host=10.0.1.11

[webservers:vars]
nginx_worker_processes=4

See references/inventory-management.md for dynamic inventory setup.

3. Roles vs Playbooks

Playbooks: Orchestrate multiple tasks and roles for specific deployments. Roles: Reusable, self-contained configuration units with standardized directory structure.

Standard role structure:

roles/nginx/
├── defaults/     # Default variables
├── tasks/        # Task files
├── handlers/     # Change handlers
├── templates/    # Jinja2 templates
├── files/        # Static files
└── meta/         # Dependencies

See references/role-structure.md for complete role patterns.

4. Secret Management

ansible-vault: Built-in encryption for sensitive data. HashiCorp Vault: Enterprise-grade secrets management with dynamic credentials.

Encrypt secrets:

ansible-vault create group_vars/all/vault.yml
ansible-playbook site.yml --ask-vault-pass

See references/secrets-management.md for Vault integration.

Common Workflows

Workflow 1: Create New Playbook

Step 1: Define inventory

# inventory/production
[webservers]
web1.example.com
web2.example.com

Step 2: Create playbook structure

---
- name: Configure application
  hosts: webservers
  become: yes

  pre_tasks:
    - name: Update package cache
      apt:
        update_cache: yes

  roles:
    - common
    - application

  post_tasks:
    - name: Verify service
      uri:
        url: http://localhost:8080/health
        status_code: 200

Step 3: Test with check mode

ansible-playbook -i inventory/production site.yml --check --diff

Step 4: Execute playbook

ansible-playbook -i inventory/production site.yml

See references/playbook-patterns.md for advanced patterns.

Workflow 2: Create and Test Role

Step 1: Initialize role structure

ansible-galaxy init roles/myapp

Step 2: Define tasks

# roles/myapp/tasks/main.yml
---
- name: Install application dependencies
  apt:
    name: "{{ item }}"
    state: present
  loop: "{{ myapp_dependencies }}"

- name: Deploy application
  template:
    src: app.conf.j2
    dest: /etc/myapp/app.conf
  notify: Restart myapp

Step 3: Add handler

# roles/myapp/handlers/main.yml
---
- name: Restart myapp
  service:
    name: myapp
    state: restarted

Step 4: Initialize Molecule testing

cd roles/myapp
molecule init scenario default --driver-name docker

Step 5: Run tests

molecule test

See references/testing-guide.md for comprehensive testing patterns.

Workflow 3: Set Up Dynamic Inventory (AWS)

Step 1: Install AWS collection

ansible-galaxy collection install amazon.aws

Step 2: Configure dynamic inventory

# inventory/aws_ec2.yml
plugin: aws_ec2
regions:
  - us-east-1
filters:
  tag:Environment: production
  instance-state-name: running
keyed_groups:
  - key: tags.Role
    prefix: role
hostnames:
  - tag:Name
compose:
  ansible_host: private_ip_address

Step 3: Verify inventory

ansible-inventory -i inventory/aws_ec2.yml --list

Step 4: Run playbook

ansible-playbook -i inventory/aws_ec2.yml site.yml

See references/inventory-management.md for multi-cloud patterns.

Workflow 4: Secure Secrets with ansible-vault

Step 1: Create encrypted vault file

ansible-vault create group_vars/all/vault.yml

Step 2: Add secrets

# group_vars/all/vault.yml (encrypted)
vault_db_password: "SuperSecretPassword"
vault_api_key: "sk-1234567890"

Step 3: Reference in variables

# group_vars/all/vars.yml (unencrypted)
db_password: "{{ vault_db_password }}"
api_key: "{{ vault_api_key }}"

Step 4: Use in playbook

- name: Configure database
  template:
    src: db.conf.j2
    dest: /etc/app/db.conf
  vars:
    database_password: "{{ db_password }}"

Step 5: Run with vault password

ansible-playbook site.yml --vault-password-file ~/.vault_pass

See references/secrets-management.md for HashiCorp Vault integration.

Tool Selection

When to Use Ansible

• Configuring servers/VMs after provisioning
• Deploying applications to existing infrastructure
• Managing OS-level settings (users, packages, services)
• Orchestrating multi-step workflows across hosts
• Cloud-native environments (agentless SSH/WinRM)
• Teams new to configuration management (easiest learning curve)

When to Use Alternatives

Infrastructure-as-Code (Terraform): Creating cloud infrastructure resources. Kubernetes: Container orchestration and configuration. Chef/Puppet: Existing deployments with high migration costs.

Ansible vs IaC Integration

Best practice: Terraform provisions, Ansible configures.

Workflow:

1. Terraform creates AWS EC2 instances, security groups, load balancers
2. Terraform outputs instance IPs to Ansible inventory
3. Ansible configures OS, installs packages, deploys applications
4. Ansible sets up monitoring, backups, operational tasks

See references/decision-framework.md for detailed decision trees.

Testing and Quality

Pre-Deployment Validation

Step 1: Lint playbooks

ansible-lint playbooks/

Step 2: Check mode (dry run)

ansible-playbook site.yml --check --diff

Step 3: Test roles with Molecule

cd roles/myapp
molecule test

Step 4: Verify idempotence

molecule idempotence

Configuration Files

.ansible-lint:

---
exclude_paths:
  - molecule/
  - venv/
skip_list:
  - name[casing]
warn_list:
  - experimental

molecule.yml:

---
driver:
  name: docker
platforms:
  - nam