How to write an Ansible playbook to configure servers

What and why

Ansible is an agentless configuration-management tool. It connects to servers over SSH and runs tasks defined in YAML playbooks. Tasks are idempotent, so running a playbook twice leaves the system in the same desired state. This tutorial installs and configures a web server.

Prerequisites

• Ansible installed on a control machine.
• SSH access to one or more target hosts.
• Basic Linux administration knowledge.

Steps

1. Create an inventory

List your hosts in inventory.ini:

[web]
10.0.1.10
10.0.1.11

Groups like [web] let you target sets of hosts.

2. Test connectivity

ansible -i inventory.ini web -m ping

The ping module confirms Ansible can reach and authenticate to each host.

3. Write the playbook

Create site.yml:

- name: Configure web servers
  hosts: web
  become: true
  tasks: []

become: true runs tasks with privilege escalation (sudo).

4. Add tasks with modules

  tasks:
    - name: Install nginx
      ansible.builtin.package:
        name: nginx
        state: present
    - name: Deploy config
      ansible.builtin.copy:
        src: nginx.conf
        dest: /etc/nginx/nginx.conf
      notify: Restart nginx

Modules describe desired state; Ansible decides what to change.

5. Use handlers for restarts

  handlers:
    - name: Restart nginx
      ansible.builtin.service:
        name: nginx
        state: restarted

A handler runs only when notified, so the service restarts only if its config changed.

Verification

Run ansible-playbook -i inventory.ini site.yml. The first run reports changes. Run it again: the recap should show changed=0, proving idempotency. Visit a host to confirm the web server responds.

Next Steps

Organize tasks into roles for reuse. Store secrets in Ansible Vault. Use variables and templates to render host-specific configuration from one source.