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TFLint is a Terraform linter focused on possible errors, best practices, etc. (Terraform >= 0.12)
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README.md

TFLint

Build Status GitHub release Terraform Compatibility Docker Hub License: MPL 2.0 Go Report Card

TFLint is a Terraform linter focused on possible errors, best practices, etc.

Why TFLint is required?

Terraform is a great tool for Infrastructure as Code. However, many of these tools don't validate provider-specific issues. For example, see the following configuration file:

resource "aws_instance" "foo" {
  ami           = "ami-0ff8a91507f77f867"
  instance_type = "t1.2xlarge" # invalid type!
}

Since t1.2xlarge is a nonexistent instance type, an error will occur when you run terraform apply. But terraform plan and terraform validate cannot find this possible error beforehand. That's because it's an AWS provider-specific issue and it's valid as a Terraform configuration.

TFLint finds such errors in advance:

demo

Installation

You can download the binary built for your architecture from the latest release. The following is an example of installation on macOS:

$ wget https://github.com/wata727/tflint/releases/download/v0.11.0/tflint_darwin_amd64.zip
$ unzip tflint_darwin_amd64.zip
Archive:  tflint_darwin_amd64.zip
  inflating: tflint
$ mkdir -p /usr/local/tflint/bin
$ export PATH=/usr/local/tflint/bin:$PATH
$ install tflint /usr/local/tflint/bin
$ tflint -v

For Linux based OS, you can use the install_linux.sh to automate the installation process.

Homebrew

macOS users can also use Homebrew to install TFLint:

$ brew install tflint

Docker

You can also use TFLint via Docker.

$ docker run --rm -v $(pwd):/data -t wata727/tflint

Features

700+ rules are available. See Rules.

Limitations

TFLint currently only inspects Terraform-specific issues and AWS issues.

Also, load configurations in the same way as Terraform v0.12. This means that it cannot inspect configurations that cannot be parsed on Terraform v0.12.

See Compatibility with Terraform for details.

Usage

TFLint inspects all configurations under the current directory by default. You can also change the behavior with the following options:

$ tflint --help
Usage:
  tflint [OPTIONS] [FILE or DIR...]

Application Options:
  -v, --version                             Print TFLint version
  -f, --format=[default|json|checkstyle]    Output format (default: default)
  -c, --config=FILE                         Config file name (default: .tflint.hcl)
      --ignore-module=SOURCE1,SOURCE2...    Ignore module sources
      --ignore-rule=RULE1,RULE2...          Ignore rule names
      --var-file=FILE1,FILE2...             Terraform variable file names
      --var='foo=bar'                       Set a Terraform variable
      --module                              Inspect modules
      --deep                                Enable deep check mode
      --aws-access-key=ACCESS_KEY           AWS access key used in deep check mode
      --aws-secret-key=SECRET_KEY           AWS secret key used in deep check mode
      --aws-profile=PROFILE                 AWS shared credential profile name used in deep check mode
      --aws-creds-file=FILE                 AWS shared credentials file path used in deep checking
      --aws-region=REGION                   AWS region used in deep check mode
      --force                               Return zero exit status even if issues found
      --no-color                            Disable colorized output

Help Options:
  -h, --help                                Show this help message

See User guide for each option.

Exit Statuses

TFLint returns the following exit statuses on exit:

  • 0: No issues found
  • 2: Errors occurred
  • 3: No errors occurred, but issues found

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 tflint

Developing

See Developer guide.

Author

Kazuma Watanabe

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