Ansible 101: install and core building blocks

This post is a quick orientation to Ansible — what it is, the moving parts you need to know, and a small Nginx example you can actually run. There's a companion GitHub repo at the end.

What is Ansible?

Ansible is an open-source configuration management and automation tool. Sysadmins and DevOps engineers use it to apply configuration to fleets of machines in a repeatable, declarative way. Compared to similar tools (Puppet, Chef, Salt), Ansible's selling point is agentless operation: it talks to target hosts over plain SSH, so there's nothing to install on the target except Python.

What you'd use it for

• Configuration management — keep a fleet of servers in a known, declarative state.
• Automation — replace manual SSH/runbook steps with playbooks.
• Software delivery — push application releases or runtime configs to many hosts at once.
• CI/CD — wire deployment into a pipeline.

Why it's nice

• Simple — YAML config files, no DSL to learn.
• Flexible — thousands of modules ship in the box, and writing your own is straightforward.
• Agentless — SSH and Python on the target is all you need.
• Cross-platform — Linux, macOS, and Windows targets.

Installing Ansible

Ubuntu / Debian

1sudo apt-get install ansible -y

CentOS / RHEL / Fedora

1sudo dnf install epel-release -y2sudo dnf install ansible -y

macOS

1brew install ansible

Or via pip if you want a specific version: pip install ansible.

The core building blocks

Inventory

The inventory file lists the hosts Ansible will talk to and (optionally) groups and per-host variables. INI is the classic format; YAML works too.

1# inventory.ini2[servers]3server ansible_host=192.168.1.1045[servers:vars]6nginx_worker_processes=47nginx_worker_connections=1024

Playbooks and roles

A playbook is a YAML file that says "run these tasks against these hosts." A role is a reusable bundle of tasks, variables, templates, and handlers — the unit of reuse in Ansible.

1---2- name: Configure Server3  hosts: servers4  roles:5    - role: nginx

Tasks, handlers, and variables

• Tasks — individual steps inside a playbook or role.
• Handlers — special tasks that run only when notified (typically to restart a service after its config changes).
• Variables — let you parameterize playbooks; can be set in inventory, role defaults, group/host vars, or on the command line.

A small role:

1# roles/nginx/tasks/main.yml2---3- name: Add Nginx GPG Key4  apt_key:5    url: https://nginx.org/keys/nginx_signing.key6    state: present78- name: Add official Nginx repository9  apt_repository:10    repo: "deb http://nginx.org/packages/ubuntu/ jammy nginx"11    state: present1213- name: Install Nginx14  apt:15    name: nginx16    state: latest1718- name: Copy Nginx configuration file19  template:20    src: nginx.conf.j221    dest: /etc/nginx/nginx.conf22  notify:23    - Restart Nginx

1# roles/nginx/handlers/main.yml2---3- name: Restart Nginx4  service:5    name: nginx6    state: restarted

Templates

Templates produce dynamic config files using Jinja2. Variables, conditionals, loops — anything Jinja2 supports.

1# roles/nginx/templates/nginx.conf.j22user www-data;3worker_processes {{ nginx_worker_processes }};45error_log /var/log/nginx/error.log warn;6pid /var/run/nginx.pid;78events {9    worker_connections {{ nginx_worker_connections }};10}1112http {13    include /etc/nginx/mime.types;14    default_type application/octet-stream;15    log_format main '$remote_addr - $remote_user [$time_local] "$request" '16                    '$status $body_bytes_sent "$http_referer" '17                    '"$http_user_agent" "$http_x_forwarded_for"';18    access_log /var/log/nginx/access.log main;1920    sendfile on;21    # ... more configuration ...22}

Modules and plugins

• Modules — the units of work Ansible runs on a target (apt, service, template, copy, user, …). The standard library is huge.
• Plugins — extend Ansible itself: connection plugins for non-SSH targets, callback plugins for output formatting, lookup plugins for fetching data, etc.

A real Nginx example

A small project that takes everything above and runs it end-to-end against a fresh Ubuntu/Debian VM, installing and configuring Nginx:

ansible101 on GitHub

Clone it, point the inventory at a test box, and run:

1ansible-playbook -i inventory.ini playbook.yml

References

• Ansible Docs — the official reference, from getting-started to advanced.
• r/ansible — community Q&A and patterns.
• GitHub — searching for ansible role <thing> usually turns up production-grade examples for whatever you're trying to configure.