Ansible vs Terraform: when to use which
Compare Ansible and Terraform for provisioning, configuration management, and infrastructure as code.
Ansible vs Terraform: when to use which
Ansible and Terraform both automate infrastructure, but Ansible excels at configuration management while Terraform excels at infrastructure provisioning.
How Ansible Manages Infrastructure
Ansible connects to existing servers via SSH and executes tasks defined in YAML playbooks. It operates in a push model — the control node initiates connections to managed nodes. Ansible manages software installation, configuration files, services, and users. Ansible is procedural at the task level but declarative at the module level (each module ensures a desired state).
How Terraform Provisions Infrastructure
Terraform defines infrastructure resources (VMs, networks, databases, DNS records) in HCL (HashiCorp Configuration Language) files. It communicates with cloud provider APIs (AWS, GCP, Azure, DigitalOcean) to create, modify, and destroy resources. Terraform maintains a state file that tracks which resources exist and their current configuration. Terraform is fully declarative — it computes the difference between the desired state and current state, then applies the minimum changes.
Feature Comparison: Ansible vs Terraform
| Feature | Ansible | Terraform |
|---|---|---|
| Primary use | Configuration management (software, services, files) | Infrastructure provisioning (VMs, networks, storage) |
| Language | YAML (playbooks) | HCL (HashiCorp Configuration Language) |
| Execution model | Push (connects via SSH) | API calls to cloud providers |
| State management | Stateless — checks current state on each run | Stateful — maintains a state file |
| Agent required | No (agentless, uses SSH) | No (uses provider APIs) |
| Idempotency | Module-level (most modules are idempotent) | Built-in (plan/apply model) |
| Cloud resource creation | Limited (cloud modules exist but are not primary use) | Primary use — native support for all major clouds |
| Server configuration | Primary use — install packages, manage services, deploy files | Not designed for this — use a provisioner to call Ansible |
When to Use Ansible
Use Ansible for configuring servers after they exist — installing packages, managing services, deploying application code, and maintaining configuration files. Ansible is the right choice for day-2 operations (ongoing management) and for environments where servers already exist.
When to Use Terraform
Use Terraform for creating and managing cloud infrastructure — VMs, load balancers, DNS records, VPCs, databases, and storage buckets. Terraform is the right choice for day-0/day-1 operations (initial provisioning and infrastructure changes).
Using Ansible and Terraform Together
Many teams use Terraform to provision infrastructure and Ansible to configure it. Terraform creates the VMs and network; Ansible installs software and deploys applications. This combination separates infrastructure provisioning (Terraform) from configuration management (Ansible).