What is OpenTofu? Terraform’s open-source alternative

OpenTofu is an open-source fork of Terraform, emerging from a significant shift in HashiCorp’s licensing model for Terraform and other tools. This development has shaped its role within the larger context of Infrastructure as Code (IaC).

Infrastructure as Code (IaC) and Terraform’s Foundation: Infrastructure as Code is a practice where infrastructure is built and managed using automated tools that define servers, networking, and other elements in code-like files. This approach is a cornerstone of the DevOps movement, promoting culture, automation, measurement, and sharing (“CAMS”). Terraform, developed by HashiCorp, is a leading IaC tool that allows users to define their infrastructure declaratively in configuration files (HCL or JSON) and manage it across various cloud providers and virtualization platforms. It automates provisioning, reduces human errors, ensures consistency, and makes scaling effortless.

The Genesis of OpenTofu: In late 2023, HashiCorp announced a change to the license of Terraform, moving it from the open-source Mozilla Public License (MPL) to a custom proprietary license for versions 1.6 and beyond. This decision sparked widespread debate and strong reactions within the open-source community, with many feeling it was a “rug pull” given Terraform’s popularity largely stemmed from open-source contributions and third-party provider development.

In response to HashiCorp’s license change and lack of response to community concerns, a group of companies and developers initiated the OpenTofu project, forking Terraform into a new open-source endeavor. OpenTofu was accepted into the Linux Foundation and aims to join the Cloud Native Computing Foundation, ensuring its future is not solely dependent on a single company. Several companies, including Scalr, env0, Spacelift, and Harness, committed to supporting OpenTofu with dedicated developers. Tools like Terratest and Terragrunt, originally developed to fill gaps around Terraform, have also committed to supporting OpenTofu.

OpenTofu’s Characteristics and Compatibility - OpenTofu positions itself as a compatible alternative to HashiCorp Terraform:

• Open Source: Unlike newer versions of HashiCorp Terraform, OpenTofu remains fully open source.
• Command-Line Interface (CLI): OpenTofu uses a tofu CLI that offers the same commands as the terraform CLI, making it a drop-in replacement for most users.
• Language Compatibility: OpenTofu generally maintains compatibility with code written in Terraform HCL. Most examples in the sources work with both, with differences explicitly noted.
• Superset of Terraform: OpenTofu has begun implementing long-requested features from the community, making it a superset of the Terraform language with additional functionalities. This means transitioning from Terraform to OpenTofu is relatively easy, but returning to Terraform might be harder if OpenTofu-specific features are utilized.
• Release Cadence: OpenTofu’s releases may have a slight delay compared to Terraform as it needs to review and reimplement new features from Terraform.
• Package Manager Support: Many package managers (e.g., Homebrew) have stopped carrying new proprietary versions of Terraform, while OpenTofu is widely supported by open-source package managers.
• Tofu Files: OpenTofu introduces .tofu files, allowing developers to write code compatible with both engines. If a .tofu file with the same name as a .tf file exists, OpenTofu will prioritize the .tofu file, while Terraform ignores .tofu files.

Implications for IaC and DevOps - The emergence of OpenTofu offers choices for teams when integrating IaC into their DevOps pipelines.

• CI/CD Platforms: HashiCorp’s proprietary solution, HCP Terraform (formerly Terraform Cloud), is heavily integrated with HashiCorp Terraform and is the primary way HashiCorp monetizes Terraform. Other commercial CD platforms like Spacelift, Env0, and Scalr, being OpenTofu sponsors, support OpenTofu for newer versions of IaC automation, often integrating with tools like Infracost for cost estimation and Open Policy Agent (OPA) for policy enforcement. Self-hosted open-source solutions like Terrakube and Atlantis can also run both Terraform and OpenTofu.
• Vendor Lock-in: OpenTofu provides an option for teams to avoid vendor lock-in, enabling them to choose platforms and tools that align with a fully open-source ecosystem.
• Testing and Code Quality: The concept of “tofu files” allows for easier testing and validation across both Terraform and OpenTofu, contributing to higher code quality and resilience. Automated tests are crucial for IaC, and frameworks like Terratest (Go-based) and the native Terraform testing framework (HCL-based) can be used, with the latter also having differing implementation details between Terraform and OpenTofu.

In summary, OpenTofu represents the community’s commitment to maintaining an open-source option for IaC, providing a compatible and increasingly feature-rich alternative to HashiCorp Terraform within the dynamic DevOps landscape.

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Adam Lloyd-Jones

Adam is a privacy-first SaaS builder, technical educator, and automation strategist. He leads modular infrastructure projects across AWS, Azure, and GCP, blending deep cloud expertise with ethical marketing and content strategy.

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