By Dotan Nahum

Infrastructure as code (IaC) has become the de-facto method for dealing with infrastructure at scale. This codification of infrastructure configurations lets software development teams create version-controlled, reusable configurations. Moreover, it enables integrating infrastructure management as a part of the delivery pipeline.

Terraform and Ansible are two leading IaC tools with somewhat overlapping functionality. However, both of them aim to cater to specific infrastructure management requirements. It can be confusing to distinguish between these two tools and select the exact tool that matches your needs due to the similarity of their functionality. So in this blog, we’ll clarify the differences between these two tools and how to apply them in a DevOps environment.

What is Terraform?

Terraform is an open-source declarative infrastructure-as-code tool that aims to provision and manage infrastructure across different environments. Unlike other IaC tools, Terraform is vendor-neutral. You can use it to manage infrastructure in any supported platform or tool, such as Microsoft Azure, Google Cloud, AWS, Linode, and Oracle Cloud. First released in 2014 by HashiCorp as an open source tool, Terraform attracted almost 1,300 contributors within its first five years and has nearly 30,000 commits in its repository today. According to data gathered by StackShare, more than 1,600 companies report using Terraform in their tech stacks, including Uber, Slack, and Udemy, and the software’s popularity is widely credited to the fact that it excels at infrastructure management – including creating, updating, and deleting any infrastructure resources, from simple computational and database instances to entire Kubernetes clusters.

What is Ansible?

Ansible is an open-source configuration management tool targeted at provisioning and configuring applications. Now part of IBM/RedHat, the automation software was originally developed by Michael DeHaan to “provide a new way to think about managing systems and applications to better fit the digital world”. Ansible’s design goal was to provide an easy, quick solution for companies who employ full-time teams to spend hours or days managing cloud installations and configurations. The tool is agentless and connects to the desired environments using either PowerShell or ssh and carries out the necessary configuration changes. Ansible is more of a procedural tool with some declarative configurations.

As a configuration management tool, the functionality of Ansible gears more towards configuring existing infrastructure or platforms. It is the ideal tool if you have a fleet of servers and need to install and configure each server.

Key similarities and differences of Terraform and Ansible At a glance, both these tools seem to offer similar functionality. Both are infrastructure as code tools that provide you with the necessary toolset to provision, configure, and manage their infrastructure.

Similarities of Terraform and Ansible

Both Terraform and Ansible are agentless and masterless tools, which means they don’t need dedicated agents to be installed and configured in the infrastructure they manage. They also don’t require dedicated hardware to run. These tools directly connect with the respective platform APIs to provision resources and use standardized methods such as SSH or scripts to carry out the necessary configurations.

Differences between Terraform and Ansible

Terraform can provision infrastructure as well as deploy applications in supported platforms. Ansible can also provision infrastructure, deploy applications and configure resources. The difference lies in the purpose of each tool.

Terraform is mainly an infrastructure provisioning tool meaning it excels at creating, modifying, and managing infrastructure resources. Ansible, on the other hand, is primarily a configuration management tool that excels at configuring provisioned infrastructure like installing/updating software, configuring runtime environments, changing configuration files, etc.

Terraform is the better tool for managing and provisioning infrastructure such as servers, networks, firewalls, storage buckets, and database instances. It is facilitated by the relatively user-friendly configurations of Terraform powered by either domain-specific Hashicorp Configuration Language (HCL) or Cloud Development Kit. They allow users to integrate Terraform with any supported common programming languages like Python, JavaScript, etc., and facilitate infrastructure creation.

On the flip side, Ansible will provide you with all the necessary capabilities to provision any type of infrastructure configuration, such as installing and updating software, setting up security configurations, and implementing policies. Ansible uses Playbooks which uses simple YAML syntax to facilitate infrastructure configurations.

Terraform is designed to be declarative at an architectural level. It greatly simplifies the codification experience as developers only need to specify the desired configuration and not all the steps required to achieve the desired configuration. On the backend, Terraform manages all that and creates the infrastructure according to the specified configuration.

Ansible is a hybrid of procedural and declarative, leaning more toward procedural. Thus developers need to specify the exact steps needed to achieve the required configuration for most Ansible configurations. While it would be a cumbersome task compared to Terraform, it provides users far more control when managing configurations. The infrastructure provisioning capabilities of Ansible can be considered the declarative part of it.

What are Terraform and Ansible used for?

With a better understanding of Terraform and Ansible, let’s now see what exactly they’re used for. 

As the tool with better infrastructure management capabilities, Terraform is used for the following tasks:

External resource management – Terraform can support most infrastructure provisioning and configuration needs with support for public and private cloud infrastructure, software appliances, and SaaS.

  • Multi-cloud deployment – The support for multiple providers enables Terraform to natively support multi-cloud environments and simplify the overall provisioning and management.
  • Application infrastructure deployment, scaling, and monitoring – This tool can be used to deploy, release, scale, and monitor infrastructure for multi-tier applications with any type of architecture. As each resource can be individually managed, even significant changes can be carried out with minimum downtime and interruptions to the application.
  • Self-service clusters – Allow the creation of self-contained infrastructure configurations that can be managed independently by different teams within the organization without interfering with each other. Features like custom modules allow users to codify different resource groups and freely provision them as needed while ensuring the standardized particles.
  • Policy compliance and management – Terraform itself can help to standardize the infrastructure. Yet, it can be further extended to enforce policies by integrating a policy as code framework to enforce compliance and governance policies across their environments and completing a secure code review.
  • PaaS application setup -Terraform can directly create and configure applications and set up supported services such as email, databases, DNS in supported platforms like Heroku.
  • Software-Defined Networking (SDN) – The ability to interface with SDNs allows Terraform to automatically configure networking according to the application requirements without any manual configuration.
  • Kubernetes clusters deployment and management – Terraform can be used to provision and manage Kubernetes clusters in any supported cloud environment and easily scale when needed.
  • Parallel environments spin up and decommissioning – The ability to quickly spin up and decommission entire infrastructure configurations enables users to provision parallel environments.
  • Software demo creation, provisioning, and bootstrapping – As this tool can be used to create infrastructure on different providers, users can easily facilitate demo applications on provisioned resources and even allow for quick configuration changes.

As a configuration management tool, Ansible is used for:

  • Provisioning – To create new infrastructure and manage application orchestration and configuration management at any scale.
  • Configuration Management – Reliably and securely manage configuration across different types of resources without any agents. Ansible allows for increased automation which simplifies the management of the overall environment.
  • App Deployment – Easily deploy any type of application from a simple single-node service to multi-tier applications from a common framework. Configure the necessary services, push artifacts, and create the runtime through Ansible.
  • Continuous Delivery – Since Ansible can fulfill all the configuration needs, it can be easily integrated into any CD tool without having to rely on multiple tools or being limited to CD tools that support specific IaC tools.
  • Security Automation – Implement security policies and roles across all endpoints and resources in an environment. It ensures that security best practices and controls are implemented across the environment.
  • Orchestration – Provide configurations for any resource type, from single servers and clustered applications to data centers and cloud services. Automate all configurations and orchestrate all the resources ensuring the desired configurations on all resources.
  • Endpoint Protection – The ability to install and manage any software makes Ansible the ideal solution to implement endpoint protection across an environment by automatically installing security software and policies.

Determining which one is right for you

Selecting the right tool comes down to your exact requirements. As mentioned previously, go with Terraform if you want a tool to provision and manage infrastructure. On the other hand, choose Ansible if you want a tool for configuration management. And remember: they are not mutually exclusive tools.

You are free to use both Terraform and Ansible in their environments as they excel at different tasks in the overall infrastructure management process. Using both allows you to combine their strengths and create the best possible automated infrastructure management experience. It all comes down to evaluating your exact needs and selecting the best tool with the features to cover them.

Terraform and Ansible are two leading IaC tools for managing infrastructure. While both are capable tools with some overlapping functionally, each offers specific functionality aimed at different use cases in the infrastructure management process. Terraform is better at infrastructure provisioning and management, while Ansible excels at configuration management.  Considering just how powerful both Terraform and Ansible are in managing infrastructure resources at a click, it’s no wonder hackers and malefactors are quick to exploit misconfigurations and exposed code secrets in configuration files and containers.  To prevent a Terraform or Ansible misconfiguration from turning into a security breach, Spectral lets you incorporate security directly into your CI/CD pipeline, to empower developers to build and ship software without worry.