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Knowledge

This guide introduces key DevOps concepts, focusing on infrastructure as code (IaC) using Terraform, networking with Virtual Private Clouds (VPCs), and storage with AWS S3. Expanding in the future as people whom I help request more :)

Terraform Overview​

Terraform is an open-source tool for creating and managing resources through any API. It enables infrastructure as code, allowing engineers to define, provision, and manage cloud resources declaratively.

Providers​

Providers are plugins that Terraform uses to interact with specific APIs or services (e.g., AWS, Azure, Google Cloud). Each provider wraps the resources of a service into Terraform-compatible resources that engineers can manage.

provider "aws" {
  region = "us-east-1"
}

Modules​

A module is a collection of related resources, enabling code reuse and modularity. Modules can be custom-written or sourced from public repositories, such as the Terraform Registry. Public modules often accelerate development and serve as examples of best practices.

Variables​

Modules support variables for flexible configuration. Variables can have default values, which are often sufficient, but users can override them as needed.

variable "instance_type" {
  type    = string
  default = "t2.micro"
}

Outputs​

Outputs are values exported from a module, such as a resource's public IP, that can be used by other modules or for informational purposes.

output "instance_public_ip" {
  value = aws_instance.example.public_ip
}

Data Blocks​

Data blocks allow Terraform to read existing resources without managing their lifecycle (i.e., only "Read" operations, unlike resources that support full CRUD—Create, Read, Update, Delete). Data blocks are useful for referencing existing infrastructure in your configuration.

data "aws_ami" "example" {
  most_recent = true
  filter {
    name   = "name"
    values = ["amazon-linux-*"]
  }
}

resource "aws_instance" "example" {
  ami           = data.aws_ami.example.id
  instance_type = var.instance_type
}

Core Terraform Commands​

  • init: Downloads provider binaries and verifies the backend configuration (where the state file is stored).
  • plan: Previews changes to infrastructure.
  • apply: Applies changes to create or update resources.
  • destroy: Deletes managed resources.
terraform init
terraform plan
terraform apply
terraform destroy

Virtual Private Cloud (VPC)​

A Virtual Private Cloud (VPC) is a private network within a cloud provider, such as AWS, used to manage machines securely over private pathways. Private networks reduce costs (no public internet traffic fees) and enhance security by minimizing exposure to external threats.

IP Address Allocation​

When creating a VPC, you assign a CIDR block—a range of IP addresses—using CIDR notation (e.g., 10.0.0.0/20). These IPs can be assigned to machines automatically or manually. For example:

  • 10.0.0.0/32: 1 IP address
  • 10.0.0.0/22: 4,094 IP addresses

Private IPv4 CIDR Blocks​

Private IPv4 CIDR blocks, defined by RFC 1918, are reserved for internal networks and are not routable on the public internet. The three standard private CIDR blocks are:

CIDR BlockRangeTotal IPsUse Case
10.0.0.0/810.0.0.0 - 10.255.255.25516,777,216Large enterprise networks
172.16.0.0/12172.16.0.0 - 172.31.255.2551,048,576Medium-sized networks, cloud routing
192.168.0.0/16192.168.0.0 - 192.168.255.25565,536Small to medium networks, home routers

Calculating CIDR Blocks​

Tools like ipcalc simplify CIDR block calculations. For example, running ipcalc 10.0.0.0/20 provides:

  • Network: 10.0.0.0/20
  • Host Range: 10.0.0.1 - 10.0.15.254
  • Total IPs: 4,094
  • Broadcast: 10.0.15.255
Address:   10.0.0.0
Netmask:   255.255.240.0 = 20
Wildcard:  0.0.15.255
Network:   10.0.0.0/20
HostMin:   10.0.0.1
HostMax:   10.0.15.254
Broadcast: 10.0.15.255
Hosts/Net: 4094

AWS S3 Buckets​

AWS S3 (Simple Storage Service) is a scalable object storage service, often likened to a "cloud Google Drive." Files are stored in buckets, which support CRUD operations (Create, Read, Update, Delete).

Creating an S3 Bucket​

Buckets can be created using Terraform or the AWS CLI.

resource "aws_s3_bucket" "my_bucket" {
  bucket = "my-test-bucket"
}

Alternatively, using the AWS CLI:

aws s3 mb s3://my-test-bucket
aws s3 cp ~/Downloads/image.png s3://my-test-bucket/
aws s3 cp s3://my-test-bucket/image.png ~/Downloads/

Key Features of S3​

  • Unlimited Storage: Buckets have no size limit, though free tier usage has restrictions, and costs are incurred per GB stored or downloaded.
  • Access Control: Buckets can be private (secure storage) or public (e.g., hosting website images or static HTML sites).
  • Compatibility: S3 is a widely adopted standard, with many tools and services implementing S3-compatible APIs, enabling local testing or alternative cloud integrations.

Use Case Example​

A public S3 bucket can host static website content (e.g., HTML, CSS, images). By configuring DNS to point to the bucket, you can serve a fully functional static website.

Conclusion​

Terraform, VPCs, and S3 form the backbone of many DevOps workflows. Terraform simplifies infrastructure management through code, VPCs provide secure networking, and S3 offers flexible, scalable storage. Experiment with these tools in a free-tier AWS account to gain hands-on experience and explore their capabilities further.