terraform.md

terraform

Infrastructure as Code (IaC) tool that lets you define cloud resources in human-readable configuration files

core concepts

• provider: plugin that allows Terraform to interact with cloud platforms (AWS, Azure, GCP)
• resource: infrastructure object you want to manage (EC2 instance, S3 bucket)
• state: Terraform's record of all managed infrastructure
• module: directory with .tf files
  • enables reusability
  • 2 types:
    • root module: directory where terraform init and terraform apply is run, the entry point
    • child module: any module referenced from another modul

basic structure

# Provider configuration
provider "aws" {
  region = "us-west-2"
}

# Resource example
resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

setup steps

1. install terraform
2. export provider credential variables: e.g. AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY
3. run terraform init in project's root directory
4. create terraform files (.tf extension)
5. run terraform plan -var-file="terraform.tfvars" -out=tfplan
6. run terraform apply tfplan

main commands

• terraform init: initialize working directory, download providers
• terraform plan: preview changes before applying
  • terraform plan -var-file="terraform.tfvars" -out=tfplan
    • -var-file="terraform.tfvars": loads variable values from a file named terraform.tfvars
    • -out=tfplan: seves the plan to a file named tfplan, apply it with terraform apply tfplan
• terraform apply: apply changes to create/modify resources
• terraform destroy: remove all resources managed by Terraform
• terraform fmt: format code per HCL standards
• terraform validate: validate configuration files
• terraform output ec2_public_ip: print terraform variables

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

you can destroy resources with:

terraform apply -destroy -target=aws_instance.app_instance -auto-approve
terraform apply -auto-approve

best practices

• version control your terraform code
• use variables for reusable values
• organize code into modules
• always review plan before applying
• store state files securely
• use workspaces for different environments

types of resources

• aws_instance: EC2 instance
• aws_vpc: Virtual Private Cloud
• aws_subnet: subnet within a VPC
• aws_security_group: security group for EC2 instances
• aws_s3_bucket: S3 bucket
• aws_iam_role: Identity and Access Management role