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Day 2 of 5
⏱ ~60 minutes
Terraform in 5 Days — Day 2

Variables, Outputs, and State

Parameterize configurations with variables, expose values with outputs, and understand what Terraform state is.

Variables

variables.tf
variable "region" {
  description = "AWS region"
  type        = string
  default     = "us-east-1"
}

variable "environment" {
  description = "Deployment environment"
  type        = string
  # No default = required. Must be supplied.
}

variable "allowed_ips" {
  description = "IPs allowed to access the server"
  type        = list(string)
  default     = ["0.0.0.0/0"]
}
Using variables
# In main.tf
provider "aws" {
  region = var.region
}

resource "aws_s3_bucket" "main" {
  bucket = "my-bucket-${var.environment}"
}
terraform.tfvars
# Values for required variables
environment = "staging"
allowed_ips = ["192.168.1.0/24", "10.0.0.0/8"]

# Never commit sensitive values — use env vars instead:
# TF_VAR_environment=staging terraform apply
outputs.tf
output "bucket_name" {
  description = "Name of the created bucket"
  value       = aws_s3_bucket.main.bucket
}

output "bucket_arn" {
  value = aws_s3_bucket.main.arn
}

# After apply:
# Outputs:
# bucket_name = "my-bucket-staging"
# bucket_arn = "arn:aws:s3:::my-bucket-staging"
Terraform State
# terraform.tfstate is created after first apply
# It maps your config to real resources
# NEVER edit it manually
# NEVER commit it to git (may contain secrets)
# Add to .gitignore:
echo 'terraform.tfstate*' >> .gitignore
echo '.terraform/' >> .gitignore

# Remote state (team-friendly)
# terraform { backend "s3" { bucket = "my-tf-state" ... } }
⚠️
Terraform state is the source of truth. If you manually delete a resource in the console, Terraform doesn't know until the next plan. It will try to recreate it. Always use Terraform to manage resources that Terraform created.
📝 Day 2 Exercise
Parameterize Your Config
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Day 2 Summary

  • Variables make configs reusable. Types: string, number, bool, list, map, object.
  • terraform.tfvars supplies values. TF_VAR_name env vars work too — good for secrets.
  • Outputs expose values after apply. Use them to pass info between modules.
  • State maps config to real resources. Use remote state (S3, Terraform Cloud) for teams.
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