Configuration as Code

Puppet Puppet · Ansible Ansible · Terraform
— What's the difference and when to use what? —

FinistDevs · 2026

Arnaud Prémel-Cabic

Tech Lead @ OVHCloud

arnaud.premel-cabic@ovhcloud.com

"It works on my server."

Why doesn't it work here when it works everywhere else?

You have a server. It works.

Great.

You have 10 servers.

10 SSH sessions
10 manual edits
10 chances to make a mistake

Now you have 100 servers.

Some 2 years old. Some a few months. Some brand new.
None of them are exactly alike.

Unique. Unreproducible. Undocumented.

Welcome to Snowflake Hell.

Configuration drift is silent…

Prod breaks on a Tuesday
Can't reproduce the bug locally
Can't scale reliably
Can't onboard a new server without fear

What if your infrastructure was just… code?

Your AI assistant can write it*. You still need to understand what it deploys.

*Like this presentation 🤖

Configuration as Code

Machine-readable files. Version-controlled. Automated.

Meet the three musketeers of infrastructure.

Puppet Puppet · Ansible Ansible · Terraform

Each solves a different problem.

Terraform

Start here. Before you configure a server, you need to have one.

What is Terraform?

Infrastructure as Code tool for provisioning cloud resources
Created by HashiCorp in 2014
Written in Go
BSL license since 2023 (was MPL)

HCL: HashiCorp Configuration Language

Declarative, human-readable — pure JSON works too.

The Terraform workflow

terraform plan — preview what will change
Review — validate the plan before proceeding
terraform apply — create or update resources
terraform destroy — tear everything down

Terraform remembers what it built.

The .tfstate file maps code to real-world resources
Store it remotely — never commit it to Git
May contain sensitive values: credentials, tokens, secrets

Handle with care.

One tool. Every API.

1000+ providers — AWS, GCP, Azure, Cloudflare, GitHub, Kubernetes…
Not just cloud — DNS, monitoring, CI/CD, anything with an API

If it has an API, there's a Terraform provider for it.

# main.tf


terraform {
  required_providers {
    openstack = { source = "terraform-provider-openstack/openstack", version = "~> 3.0" }
    ovh       = { source = "ovh/ovh", version = "~> 1.0" }
  }
}

resource "openstack_compute_instance_v2" "web" {
  name        = "finistdevs-web"
  image_name  = "Debian 12"
  flavor_name = "b3-8"
  network { name = "Ext-Net" }
}

resource "ovh_domain_zone_record" "web" {
  zone      = "example.com"
  subdomain = "finistdevs"
  fieldtype = "A"
  target    = openstack_compute_instance_v2.web.access_ip_v4
}

$ terminal


$ terraform init
Initializing provider plugins...
- Finding terraform-provider-openstack/openstack versions matching "~> 3.0"...
- Finding ovh/ovh versions matching "~> 1.0"...
- Installing terraform-provider-openstack/openstack v3.0.0...
- Installing ovh/ovh v1.3.0...
Terraform has been successfully initialized!

$ terraform plan
openstack_compute_instance_v2.web: Refreshing state...
Plan: 2 to add, 0 to change, 0 to destroy.

$ terraform apply
openstack_compute_instance_v2.web: Creating...
openstack_compute_instance_v2.web: Creation complete after 45s [id=abc-123]
ovh_domain_zone_record.web: Creating...
ovh_domain_zone_record.web: Creation complete after 3s [id=456]

Apply complete! Resources: 2 added, 0 changed, 0 destroyed.

HashiCorp changed Terraform's license.

BSL instead of MPL — no longer truly open-source
The community responded: OpenTofu, by the OpenTF Foundation

Drop-in replacement. Fully compatible. Community-driven.

Terraform at scale needs a platform.

Terraform Enterprise / HCP Terraform — remote state, RBAC, audit logs
Spacelift — GitOps-first CI/CD for Terraform and OpenTofu
Atlantis — open-source, plan & apply from pull requests
env0, Scalr — SaaS with policy & cost management

Ansible

Your servers are provisioned. Now make them do something.

What is Ansible?

Agentless automation tool for configuration and orchestration
Created by Michael DeHaan in 2012
Acquired by Red Hat in 2015
Written in Python — Apache 2.0 license

Push-based. Runs over SSH.

YAML playbooks run tasks in order, across any number of hosts
Nothing to install on target servers — just Python + SSH
Idempotent modules — same playbook runs safely again and again

# playbook/webserver.yml


- name: Configure web server
  hosts: webservers
  become: true

  tasks:
    - name: Install nginx
      ansible.builtin.package:
        name: nginx
        state: present

    - name: Deploy nginx config
      ansible.builtin.template:
        src: nginx.conf.j2
        dest: /etc/nginx/nginx.conf
      notify: Restart nginx

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

$ terminal


$ ansible-playbook -i inventory playbook/webserver.yml

PLAY [Configure web server] ***************************************************

TASK [Gathering Facts] ********************************************************
ok: [finistdevs-web]

TASK [Install nginx] **********************************************************
changed: [finistdevs-web]

TASK [Deploy nginx config] ****************************************************
changed: [finistdevs-web]

RUNNING HANDLER [Restart nginx] ***********************************************
changed: [finistdevs-web]

PLAY RECAP ********************************************************************
finistdevs-web : ok=4  changed=3  unreachable=0  failed=0  skipped=0

Not just configuration. Operations.

Patch 200 servers tonight
Roll out a kernel upgrade with a canary strategy
Run a compliance audit across your whole fleet

The go-to tool for one-off tasks and recurring operations.

The community does the heavy lifting.

Ansible Galaxy — 10,000+ ready-made roles and collections
Don't write a playbook to install Docker from scratch — someone already did

Just ansible-galaxy install geerlingguy.docker.

Ansible at scale: open-source vs enterprise.

AWX — open-source web UI, API, and scheduler
Ansible Automation Platform (Red Hat) — enterprise AWX with support
Semaphore — lightweight open-source alternative

Core engine remains Apache 2.0 — truly open-source.

Puppet

Your servers are configured. Now keep them that way.

What is Puppet?

Configuration management tool for enforcing system state
Created by Luke Kanies in 2005
Puppet Inc. acquired by Perforce in 2022
Written in Ruby and Clojure

Pull, not push. Agents, not SSH.

Every 30 minutes, each puppet-agent polls the Puppet Server
Compiles a catalog and enforces it locally

Drift is corrected automatically.

# manifests/webserver.pp


class webserver {
  package { 'nginx':
    ensure => installed,
  }

  file { '/etc/nginx/nginx.conf':
    ensure  => file,
    content => template('webserver/nginx.conf.erb'),
    notify  => Service['nginx'],
  }

  service { 'nginx':
    ensure => running,
    enable => true,
  }
}

$ terminal


$ puppet agent -t
Info: Using environment 'production'
Info: Retrieving pluginfacts
Info: Caching catalog for finistdevs-web.example.com
Info: Applying configuration version '1713052408'

Notice: /Stage[main]/Webserver/Package[nginx]/ensure: created
Notice: /Stage[main]/Webserver/File[/etc/nginx/nginx.conf]/content:
  --- /etc/nginx/nginx.conf
  +++ /tmp/puppet-file20260413
Notice: /Stage[main]/Webserver/Service[nginx]/ensure: started

Notice: Applied catalog in 12.34 seconds

Someone SSH'd in and changed something.

Puppet noticed. Puppet fixed it.
Continuous compliance — not just at deploy time. Every. 30. Minutes.
No manual remediation

Puppet: large fleets, zero drift.

Continuous compliance, auditability, and guaranteed state — at scale
Best suited for enterprises with hundreds or thousands of long-lived servers
Fewer SaaS options than Terraform or Ansible

Puppet Enterprise and Foreman are self-hosted. No managed cloud offering.

The ecosystem outlives the company.

Vox Pupuli — 100+ open-source Puppet modules, community-maintained
OpenVox — an emerging open-source fork of the Puppet core

The community is strong, with or without Puppet Inc.

They're not competing. They're complementary.

Each solves a different layer of the same problem.

A common production setup:

Terraform provisions the VM
Ansible configures it and deploys the app
Puppet continuously enforces compliance

Questions?

Thank you!

Arnaud Prémel-Cabic · arnaud.premel-cabic@ovhcloud.com
Slides: ministicraft.pages.git.cloud.arnaud-pc.fr/finistdev-configuration-as-code/

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