TFLint
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:
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/terraform-linters/tflint/releases/download/v0.14.0/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, or try the following oneliner to download latest binary for AMD64 architecture.
$ curl -L "$(curl -Ls https://api.github.com/repos/terraform-linters/tflint/releases/latest, grep -o -E "https://.+?_linux_amd64.zip")" -o tflint.zip && unzip tflint.zip && rm tflint.zip
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
--langserver Start language server
-f, --format=[default, json, checkstyle] Output format (default: default)
-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
--var-file=FILE Terraform variable file name
--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
FAQ
Does TFLint check modules recursively?
- No. TFLint always checks only the current root module (no recursive check)
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.