What is TFLint?
TFLint is a Terraform-specific linter that identifies potential errors in Terraform configurations. Unlike Terraform's built-in validation features, TFLint focuses on deeper analysis, such as checking for AWS-specific issues or catching errors that Terraform might not detect by default. Its pluggable architecture allows it to fit various cloud providers and custom rules, making it helpful for infrastructure as code (IaC) development.
TFLint primarily analyzes Terraform files, which are usually .tf and .tfvars files. It can evaluate Terraform configurations, variable definitions, and even automatically loaded environment variables to ensure your infrastructure code adheres to best practices and specific provider guidelines
Installing TFLint
With Trunk Check, you can automatically install and configure TFLint along with any relevant linters in a few straightforward steps. Here's how:
First, if you haven't already installed Trunk CLI, you can do so with the command below:
1curl https://get.trunk.io -fsSL | bash
Next, you can initialize Trunk from the root of your git repository:
1trunk init
This command will scan your repository and create a .trunk/trunk.yaml file that enables all linters, formatters, and security analyzers, recommended by Trunk Check. This includes TFLint if applicable to your project.
To see all available linters Trunk Check installed, simply run:
1trunk check list
If you find TFLint is not automatically enabled, you can do so by running:
1trunk check enable tflint
Alternatively, to disable TFLint run the command below. To disable other tooling applied by Trunk Check, simply replace tflint with the respective tool you're looking to disable.
1trunk check disable tflint
Configuring TFLint
Most linters provide some mechanism to tweak their configuration, e.g. .eslintrc or Cargo.toml. Trunk is aware of all the ways individual tools are configured and supports them. This means linters you've already configured will continue to work exactly the same, just now supercharged by Trunk Check.
Like many linters with Trunk, TFLint works out of the box so there's no need to set up a custom configuration. TFlint does have a .tflint.hcl file for optional tuning. You can learn more about TFLint and its config in our docs.
If you're interested in other tooling outside of TFLint, check out our open-source repository to see how we define and support 90+ linters.
Running TFLint
To check your code with TFLint, run the command below. This command executes TFLint, along with any other linters Trunk Check has enabled on files you've modified. Since Trunk is git-aware, it knows what you've changed, and by adding batched execution and caching, you end up with a much faster and smoother way to run TFLint and other tools.
1trunk check
If you prefer to check files you've modified with TFLint only, run the following:
1trunk check --filter=tflint
Although we'd recommend against it depending on the size of your repository, you can check all files with TFLint by running the command below.
1trunk check --all --filter=tflint
In most scenarios, you'll want to execute against modified files. Since Trunk is git-aware, it knows what you've changed, and by adding batched execution and caching, you end up with a much faster and smoother way to run TFLint and other tools.
Updating Trunk Check & TFLint
To upgrade the Trunk CLI along with all plugins and linters in your trunk.yaml simply run:
1trunk upgrade
We highly recommend running on the latest validated versions of tools as updates will frequently include important security fixes and additional valuable checks. Trunk only auto-suggests linter upgrades to versions that we have tested and support, so you may see a slight lag time when a new linter version is released.
Upgrade will also recommend new tools that have become applicable since the last time your repository was scanned. This can be a result of using new technologies in your repository or Trunk itself adding support for more tools. If you don't like a particular recommendation, you can always run trunk check disable <linter> to teach trunk not to recommend it.
Recommended Linters to Pair with TFLint
While TFLint is powerful on its own, pairing it with other linters can enhance your IaC development workflow. Here is what we recommend: