How to Use terraform.tfvars for Variable Configuration

Use a terraform.tfvars file to set values for variables declared in your Terraform configuration. Terraform automatically loads this file to apply variable values without needing to specify them on the command line.

Syntax

The terraform.tfvars file contains variable assignments in key = value format. Each key matches a variable name declared in your Terraform files. Values can be strings, numbers, booleans, lists, or maps.

This file should be placed in the same directory as your Terraform configuration files. Terraform automatically loads it when you run commands like terraform apply.

terraform

variable "region" {
  description = "AWS region"
  type        = string
}

variable "instance_count" {
  description = "Number of instances"
  type        = number
}

# terraform.tfvars
region         = "us-west-2"
instance_count = 3

Example

This example shows how to declare variables in Terraform and set their values using terraform.tfvars. When you run terraform apply, Terraform reads the values from the terraform.tfvars file automatically.

terraform

# main.tf
variable "region" {
  description = "AWS region"
  type        = string
}

variable "instance_count" {
  description = "Number of instances"
  type        = number
}

provider "aws" {
  region = var.region
}

resource "aws_instance" "example" {
  count         = var.instance_count
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

# terraform.tfvars
region         = "us-west-2"
instance_count = 2

Output

Terraform will create 2 AWS EC2 instances in the us-west-2 region using the specified AMI and instance type.

Common Pitfalls

• File name typo: The file must be named exactly terraform.tfvars or terraform.tfvars.json to be auto-loaded.
• Variable name mismatch: Keys in terraform.tfvars must match variable names declared in Terraform files.
• Wrong value types: Values must match the declared variable types (string, number, list, etc.).
• Multiple tfvars files: If you use multiple .tfvars files, only terraform.tfvars is auto-loaded; others require explicit loading with -var-file.

terraform

/* Wrong: variable name mismatch */
# terraform.tfvars
region_wrong = "us-west-2"

/* Correct: matching variable name */
region = "us-west-2"

Quick Reference

Tips for using terraform.tfvars:

• Place terraform.tfvars in the root of your Terraform project.
• Use key = value pairs matching your variable names.
• For sensitive values, consider using environment variables or terraform.tfvars.json with encryption.
• To override terraform.tfvars, use -var or -var-file options.

Key Takeaways

terraform.tfvars sets variable values automatically when placed in the Terraform project directory.

Variable names in terraform.tfvars must exactly match those declared in Terraform configuration files.

Values in terraform.tfvars must match the expected variable types to avoid errors.

Only terraform.tfvars and terraform.tfvars.json are auto-loaded; other files need explicit loading.

Use terraform.tfvars for cleaner variable management instead of passing variables via command line.