Variables in Terraform:

Variables in Terraform: variables.tf vs. .tfvars

variables.tf

• Purpose: The variables.tf file is used to declare the variables that your Terraform configuration will use. It doesn't store actual values; instead, it defines the variable name, type, description, and optional default value.

• Usage: The file provides a blueprint for the inputs that Terraform will expect when you run it.

• Example:

  variable "project_id" {
    description = "The GCP project ID"
    type        = string
  }
  
  variable "region" {
    description = "The region where resources will be deployed"
    type        = string
    default     = "us-central1"
  }
  

.tfvars

• Purpose: The .tfvars file is used to assign actual values to the variables declared in variables.tf. This is where you specify the specific configurations or settings that Terraform will use when it runs.

• Usage: You can have multiple .tfvars files for different environments (e.g., dev.tfvars, prod.tfvars) and specify which one to use at runtime.

• Example:

  project_id = "my-gcp-project"
  region     = "us-west1"
  

• Applying a Specific .tfvars File: You can pass the .tfvars file directly when you run Terraform:

  terraform apply -var-file="prod.tfvars"
  

Summary of Differences

Feature	variables.tf	.tfvars
Purpose	Declares variables and their types	Assigns values to the declared variables
Contents	Variable definitions (name, type)	Actual variable values
Usage	Used to specify what inputs Terraform expects	Used to provide environment-specific configurations

Best Practices

• Use variables.tf: Always declare variables in a variables.tf file to keep your configurations organized and understandable.
• Environment-Specific .tfvars: Use .tfvars files for environment-specific configurations, like dev.tfvars and prod.tfvars, to simplify switching between different setups.

By understanding these concepts—state, local vs. remote state, and the difference between variables.tf and .tfvars—you can better manage and organize your Terraform configurations, especially as your infrastructure grows in complexity.