TFLint
A Pluggable Terraform Linter
Features
TFLint is a framework and each feature is provided by plugins, the key features are as follows:
- Find possible errors (like invalid instance types) for Major Cloud providers (AWS/Azure/GCP).
- Warn about deprecated syntax, unused declarations.
- Enforce best practices, naming conventions.
Installation
Bash script (Linux):
curl -s https://raw.githubusercontent.com/terraform-linters/tflint/master/install_linux.sh | bashHomebrew (macOS):
brew install tflintChocolatey (Windows):
choco install tflintNOTE: The Chocolatey package is NOT directly maintained by the TFLint maintainers. The latest version is always available by manual installation.
Verification
Releases are signed by Cosign. cosign verify-blob ensures that the release was built with this repository's GitHub Actions.
cosign verify-blob --certificate=checksums.txt.pem --signature=checksums.txt.keyless.sig --certificate-identity-regexp="^https://github.com/terraform-linters/tflint" --certificate-oidc-issuer=https://token.actions.githubusercontent.com checksums.txt
sha256sum --ignore-missing -c checksums.txt
Docker
Instead of installing directly, you can use the Docker images:
| Name | Description |
|---|---|
| ghcr.io/terraform-linters/tflint | Basic image |
| ghcr.io/terraform-linters/tflint-bundle | A Docker image with TFLint and ruleset plugins |
Example:
docker run --rm -v $(pwd):/data -t ghcr.io/terraform-linters/tflintGitHub Actions
If you want to run on GitHub Actions, setup-tflint action is available.
Getting Started
First, enable rules for Terraform Language (e.g. warn about deprecated syntax, unused declarations). TFLint Ruleset for Terraform Language is bundled with TFLint, so you can use it without installing it separately.
The bundled plugin enables the "recommended" preset by default, but you can disable the plugin or use a different preset. Declare the plugin block in .tflint.hcl like this:
plugin "terraform" {
enabled = true
preset = "recommended"
}See the tflint-ruleset-terraform documentation for more information.
Next, If you are using an AWS/Azure/GCP provider, it is a good idea to install the plugin and try it according to each usage:
If you want to extend TFLint with other plugins, you can declare the plugins in the config file and easily install them with tflint --init.
plugin "foo" {
enabled = true
version = "0.1.0"
source = "github.com/org/tflint-ruleset-foo"
signing_key = <<-KEY
-----BEGIN PGP PUBLIC KEY BLOCK-----
mQINBFzpPOMBEADOat4P4z0jvXaYdhfy+UcGivb2XYgGSPQycTgeW1YuGLYdfrwz
9okJj9pMMWgt/HpW8WrJOLv7fGecFT3eIVGDOzyT8j2GIRJdXjv8ZbZIn1Q+1V72
AkqlyThflWOZf8GFrOw+UAR1OASzR00EDxC9BqWtW5YZYfwFUQnmhxU+9Cd92e6i
...
KEY
}See also Configuring Plugins.
If you want to add custom rules that are not in existing plugins, you can build your own plugin or write your own policy in Rego. See Writing Plugins or OPA Ruleset.
Usage
TFLint inspects files under the current directory by default. You can change the behavior with the following options/arguments:
$ tflint --help
Usage:
tflint --chdir=DIR/--recursive [OPTIONS]
Application Options:
-v, --version Print TFLint version
--init Install plugins
--langserver Start language server
-f, --format=[default|json|checkstyle|junit|compact|sarif] Output format
-c, --config=FILE Config file name (default: .tflint.hcl)
--ignore-module=SOURCE Ignore module sources
--enable-rule=RULE_NAME Enable rules from the command line
--disable-rule=RULE_NAME Disable rules from the command line
--only=RULE_NAME Enable only this rule, disabling all other defaults. Can be specified multiple times
--enable-plugin=PLUGIN_NAME Enable plugins from the command line
--var-file=FILE Terraform variable file name
--var='foo=bar' Set a Terraform variable
--module Enable module inspection
--no-module Disable module inspection
--chdir=DIR Switch to a different working directory before executing the command
--recursive Run command in each directory recursively
--filter=FILE Filter issues by file names or globs
--force Return zero exit status even if issues found
--minimum-failure-severity=[error|warning|notice] Sets minimum severity level for exiting with a non-zero error code
--color Enable colorized output
--no-color Disable colorized output
--fix Fix issues automatically
Help Options:
-h, --help Show this help message
See User Guide for details.
Debugging
If you don't get the expected behavior, you can see the detailed logs when running with TFLINT_LOG environment variable.
$ TFLINT_LOG=debug tflintDeveloping
See Developer Guide.
Security
If you find a security vulnerability, please refer our security policy.
