Terraform Fundamentals: Infrastructure as Code Best Practices

# macOS (with Homebrew)# Ubuntu/Debian# Ubuntu/Debian# Ubuntu/Debian# Ubuntu/Debian# Ubuntu/Debian# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Windows (with Chocolatey)# Verify installation# Verify installationallation
terraform --version

# Comments start with hash// Or double slash# Blocks define configuration sections# Arguments use key = value syntax# Arguments use key = value syntax# Arguments use key = value syntax# Arguments use key = value syntax# Arguments use key = value syntax# Arguments use key = value syntax# Arguments use key = value syntax# Expressions reference other values# Strings support interpolation# Strings support interpolation# Strings support interpolation# Multiline strings use heredoc# Multiline strings use heredocuse heredoc
script = <<-EOF
  #!/bin/bash
  echo "Hello World"
EOF

# Strings# Numbers# Numbers# Numbers# Booleans# Booleans# Booleans# Lists# Lists# Lists# Lists# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Maps# Objects# Objects# Objects# Objects# Objects# Objects# Objects# Objects# Objectsts
instance_config = {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  monitoring    = true
}

# versions.tf - Provider version constraints# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Provider configuration# Multiple provider configurations with aliases# Multiple provider configurations with aliases# Multiple provider configurations with aliases# Multiple provider configurations with aliasesconfigurations with aliases
provider "aws" {
  alias  = "us_east"
  region = "us-east-1"
}

# Basic resource# Resource with dependencies# Resource with dependencies# Resource with dependencies# Resource with dependencies# Resource with dependencies# Resource with dependencies# Resource with dependencies# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with count# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_each# Resource with for_eacheach
resource "aws_s3_bucket" "buckets" {
  for_each = toset(["logs", "assets", "backups"])
  
  bucket = "my-company-${each.value}-${random_id.suffix.hex}"
}

# variables.tf

variable "environment" {
  description = "The deployment environment"
  type        = string
  default     = "development"
  
  validation {
    condition     = contains(["development", "staging", "production"], var.environment)
    error_message = "Environment must be development, staging, or production."
  }
}

variable "instance_count" {
  description = "Number of instances to create"
  type        = number
  default     = 1
}

variable "enable_monitoring" {
  description = "Enable detailed monitoring"
  type        = bool
  default     = false
}

variable "availability_zones" {
  description = "List of availability zones"
  type        = list(string)
  default     = ["eu-west-2a", "eu-west-2b"]
}

variable "instance_config" {
  description = "Instance configuration"
  type = object({
    ami           = string
    instance_type = string
    key_name      = optional(string)
  })
}

variable "tags" {
  description = "Tags to apply to resources"
  type        = map(string)
  default     = {}
}

# outputs.tf

output "vpc_id" {
  description = "The ID of the VPC"
  value       = aws_vpc.main.id
}

output "public_subnet_ids" {
  description = "List of public subnet IDs"
  value       = aws_subnet.public[*].id
}

output "instance_public_ips" {
  description = "Public IPs of EC2 instances"
  value       = aws_instance.web[*].public_ip
}

output "database_endpoint" {
  description = "Database connection endpoint"
  value       = aws_db_instance.main.endpoint
  sensitive   = true  # Marks output as sensitive
}

# terraform.tfvars# Command line# Command line# Command line# Command line# Command line# Command line# Environment variables# Environment variables# Environment variables# Variable file# Variable file# Variable file# Variable fileile
terraform apply -var-file="production.tfvars"

# backend.tf# Create the S3 bucket and DynamoDB table first# Create the S3 bucket and DynamoDB table first# Create the S3 bucket and DynamoDB table first# Create the S3 bucket and DynamoDB table first# Create the S3 bucket and DynamoDB table first# Create the S3 bucket and DynamoDB table firstket and DynamoDB table first
resource "aws_s3_bucket" "terraform_state" {
  bucket = "my-terraform-state"
  
  lifecycle {
    prevent_destroy = true
  }
}

resource "aws_s3_bucket_versioning" "terraform_state" {
  bucket = aws_s3_bucket.terraform_state.id
  versioning_configuration {
    status = "Enabled"
  }
}

resource "aws_dynamodb_table" "terraform_locks" {
  name         = "terraform-locks"
  billing_mode = "PAY_PER_REQUEST"
  hash_key     = "LockID"

  attribute {
    name = "LockID"
    type = "S"
  }
}

# List resources in state# Show resource details# Show resource details# Move resource in state# Move resource in state# Remove resource from state (without destroying)# Remove resource from state (without destroying)# Import existing infrastructure# Import existing infrastructure# Import existing infrastructure# Pull remote state locally# Pull remote state locally# Pull remote state locally locally
terraform state pull > backup.tfstate

# Create and switch workspaces# List workspaces# List workspaces# List workspaces# List workspaces# List workspaces# List workspaces# List workspaces# Switch workspace# Switch workspace# Show current workspace# Show current workspace# Show current workspace# Using workspace in configuration# Conditional count based on workspace# Conditional count based on workspace# Conditional count based on workspace# Conditional count based on workspace# Conditional count based on workspace# Conditional count based on workspace# Conditional count based on workspacee
resource "aws_instance" "worker" {
  count = terraform.workspace == "production" ? 5 : 1
  # ...
}

# Get latest Amazon Linux 2 AMI# Get current AWS region# Get current AWS region# Get current AWS region# Get current AWS region# Get current AWS region# Get current AWS region# Get current AWS region# Get current caller identity# Get current caller identity# Get availability zones# Get availability zones# Get availability zones# Using data sources# Using data sources# Using data sources# Using data sources# Using data sources sources
resource "aws_instance" "web" {
  ami               = data.aws_ami.amazon_linux.id
  instance_type     = "t3.micro"
  availability_zone = data.aws_availability_zones.available.names[0]
}

# 1. Initialise the working directory# 2. Format configuration files# 3. Validate configuration# 3. Validate configuration# 4. Create execution plan# 4. Create execution plan# 5. Apply the plan# 5. Apply the plan# 6. View outputs# 6. View outputs# 6. View outputs# 7. When done, destroy infrastructureestroy infrastructure
terraform destroy

terraform-project/
├── main.tf           # Primary resource definitions
├── variables.tf      # Input variable declarations
├── outputs.tf        # Output value declarations
├── versions.tf       # Provider and Terraform versions
├── backend.tf        # Backend configuration
├── data.tf           # Data source definitions
├── locals.tf         # Local values
├── terraform.tfvars  # Variable values (not in git)
├── modules/          # Local modules
│   └── vpc/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
└── environments/     # Environment-specific configs
    ├── dev.tfvars
    ├── staging.tfvars
    └── production.tfvars