Terraform vs Ansible : An In-Depth Comparison

Terraform vs Ansible : An In-Depth Comparison


In the realm of IT infrastructure and DevOps automation and efficient management are paramount. Two popular tools that facilitate these processes are Terraform and Ansible. Although they share the common goal of managing infrastructure, they operate in fundamentally different ways and cater to different aspects of the infrastructure lifecycle. This blog will provide a detailed comparison of Terraform and Ansible, covering their purposes, features, use cases and examples to illustrate their differences.

Overview of Terraform

Terraform developed by HashiCorp is an open-source tool that allows users to define and provision infrastructure as code (IaC). Terraform uses declarative configuration files to describe the desired state of infrastructure and then manages the provisioning and lifecycle of that infrastructure in a consistent and reproducible manner.

Key Features of Terraform

  1. Declarative Syntax :- Terraform uses HashiCorp Configuration Language (HCL) a declarative language that allows users to specify the desired state of infrastructure. This approach focuses on the "what" rather than the "how".

  2. State Management :- Terraform maintains a state file that tracks the current state of infrastructure. This state file is used to plan and apply changes ensuring idempotency.

  3. Resource Providers :- Terraform supports a wide range of providers enabling it to manage infrastructure across various platforms including AWS, Azure, Google Cloud and on-premises environments.

  4. Dependency Graph :- Terraform automatically creates a dependency graph of resources ensuring that they are provisioned in the correct order.

Overview of Ansible

Ansible developed by Red Hat is an open-source automation tool that focuses on configuration management, application deployment and task automation. Ansible uses playbooks written in YAML to define automation tasks in a human-readable format.

Key Features of Ansible

  1. Agentless Architecture :- Ansible operates over SSH (or WinRM for Windows) and does not require agents to be installed on managed nodes.

  2. Procedural Syntax :- Ansible uses a procedural approach where tasks are executed in the order they are defined in the playbook.

  3. Extensible Modules :- Ansible has a large collection of modules that can be used to manage various systems and services. Users can also write custom modules if needed.

  4. Inventory Management :- Ansible uses inventory files to define the hosts and groups of hosts that will be managed.

Use Cases

Understanding the primary use cases of Terraform and Ansible can help determine which tool is better suited for specific scenarios.

Terraform Use Cases

  1. Infrastructure Provisioning :- Terraform excels at provisioning and managing infrastructure resources across multiple cloud providers. It is ideal for creating complex infrastructure setups such as multi-tier applications, VPCs and Kubernetes clusters.

  2. Immutable Infrastructure :- Terraform is well-suited for implementing immutable infrastructure practices where infrastructure is replaced rather than modified in place.

  3. Multi-Cloud Management :- Terraform’s provider ecosystem allows users to manage resources across multiple cloud platforms from a single configuration.

Ansible Use Cases

  1. Configuration Management :- Ansible is ideal for managing the configuration of servers ensuring that they are in a desired state. It can install software, configure services and apply security settings.

  2. Application Deployment :- Ansible can automate the deployment of applications, managing the entire deployment process, including code updates, database migrations and service restarts.

  3. Orchestration :- Ansible can coordinate complex workflows that involve multiple systems and services ensuring that tasks are executed in the correct order.

Example :- Provisioning and Configuring a Web Server

To illustrate the differences between Terraform and Ansible, let's walk through an example of provisioning and configuring a web server on AWS.

Terraform Example

First we will use Terraform to provision an EC2 instance and a security group in AWS.

1. Create a Terraform configuration file (main.tf) :-

provider "aws" {
  region = "us-west-2"

resource "aws_security_group" "web" {
  name        = "web-sg"
  description = "Allow HTTP traffic"

  ingress {
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = [""]

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = [""]

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  security_groups = [aws_security_group.web.name]

  tags = {
    Name = "WebServer"

2. Initialize, plan and apply the configuration :-

terraform init
terraform plan
terraform apply

This configuration file defines a security group that allows HTTP traffic and an EC2 instance with the specified AMI and instance type. When terraform apply is executed, Terraform will create these resources in AWS.

Ansible Example

Next, we will use Ansible to configure the web server on the provisioned EC2 instance.

1. Create an Ansible inventory file (hosts) :-


2. Create an Ansible playbook (webserver.yml) :-

- name: Configure Web Server
  hosts: web
  become: yes
    - name: Install Apache
        name: apache2
        state: present

    - name: Ensure Apache is running
        name: apache2
        state: started
        enabled: yes

3. Run the playbook :-

ansible-playbook -i hosts webserver.yml

This playbook defines tasks to install Apache on the target server and ensure that the service is running and enabled. When ansible-playbook is executed Ansible will connect to the server and perform the specified tasks.

Comparison of Terraform and Ansible

Declarative vs. Procedural

Terraform uses a declarative approach where the user defines the desired state of the infrastructure and Terraform takes care of achieving that state. This approach makes it easier to understand the end goal and ensures that the infrastructure remains consistent with the defined state.

Ansible on the other hand uses a procedural approach where tasks are executed in the order they are defined. This approach provides more flexibility in defining complex workflows and allows for more fine-grained control over the execution process.

State Management

Terraform maintains a state file that keeps track of the current state of the infrastructure. This state file is used to determine what changes need to be made to achieve the desired state. State management is a key feature of Terraform enabling it to provide idempotency and ensure that changes are applied correctly.

Ansible does not maintain a state file. Instead it executes tasks based on the current state of the system. This approach can make it more challenging to ensure idempotency especially in complex environments.

Infrastructure Provisioning vs. Configuration Management

Terraform excels at provisioning infrastructure resources, such as virtual machines, networks and storage. It is designed to manage the lifecycle of these resources from creation to destruction.

Ansible is primarily focused on configuration management and application deployment. It is designed to manage the configuration of servers and services ensuring that they are in the desired state.

Agentless Architecture

Ansible operates without requiring agents to be installed on managed nodes. It uses SSH (or WinRM) to connect to servers and execute tasks. This agentless architecture simplifies the management of nodes and reduces the overhead associated with maintaining agents.

Terraform while not requiring agents relies on the capabilities of the underlying cloud provider’s APIs to manage resources.

Extensibility and Ecosystem

Both Terraform and Ansible have large and active communities with extensive collections of modules and providers.

  • Terraform’s ecosystem includes a wide range of providers enabling it to manage resources across multiple cloud platforms and on-premises environments.

  • Ansible’s ecosystem includes a vast collection of modules that can manage various systems and services from cloud infrastructure to networking devices.

Best Practices

To make the most out of Terraform and Ansible, it’s important to follow best practices tailored to each tool.

Terraform Best Practices

  1. Modularize Configurations :- Break down Terraform configurations into reusable modules to improve organization and maintainability.

  2. Version Control :- Store Terraform configurations in version control systems (e.g. Git) to track changes and collaborate with team members.

  3. Remote State Management :- Use remote state backends (e.g. AWS S3, Terraform Cloud) to store the state file securely and enable collaboration.

  4. Plan and Review :- Always use terraform plan to review changes before applying them to avoid unintended modifications.

Ansible Best Practices

  1. Use Playbooks :- Define automation tasks in playbooks to ensure they are easily readable and maintainable.

  2. Group Variables :- Use inventory and group variables to manage configuration settings for different groups of hosts.

  3. Idempotency :- Ensure that tasks are idempotent meaning they can be run multiple times without causing unintended side effects.

  4. Testing :- Use tools like Ansible Lint and Molecule to test playbooks and roles before applying them to production environments.


Terraform and Ansible are powerful tools that serve different purposes in the infrastructure lifecycle. Terraform excels at provisioning and managing infrastructure resources in a declarative manner making it ideal for infrastructure as code practices. Ansible with its procedural approach and agentless architecture is well-suited for configuration management, application deployment and task automation.

By understanding the strengths and use cases of each tool you can leverage their capabilities to create efficient and reliable infrastructure and automation workflows. Whether you’re provisioning cloud resources with Terraform or configuring servers with Ansible these tools will help you achieve greater consistency, repeatability and efficiency in your DevOps practices.

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Sudha Yadav