README.md

12 - Infrastructure as Code with Terraform

Infrastructure as Code (IaC) with Terraform is a powerful approach to automate and manage infrastructure. Here's a simplified explanation and key points:

What is Terraform?

Terraform is a tool for automating and managing infrastructure. It allows you to define the infrastructure you want in a file, and then apply it. Terraform will create, update, or destroy the infrastructure as needed.

How Terraform Works:

1. Definition File:

   • You write a configuration file (e.g., main.tf) where you specify the desired infrastructure.

2. Apply Changes:

   • Run terraform apply to apply the configuration. Terraform will create the infrastructure as defined in the file.

3. State Management:

   • Terraform keeps track of the state of the infrastructure in a state file (terraform.tfstate). This file stores the current state of your resources.

4. Changes and Updates:

   • When you want to make changes, update the configuration file and re-run terraform apply. Terraform will figure out the changes needed and apply them.

Advantages of Terraform:

• Version Control:

  • Infrastructure changes are tracked, providing a history of changes (Infrastructure as Code).

• Replication:

  • Easily replicate infrastructure for different environments (dev, staging, production).

• Cleanup:

  • Simple cleanup with a single command (terraform destroy).

• Collaboration:

  • Facilitates team collaboration by providing visibility into created infrastructure and easy modifications.

Connecting to Platform Provider:

• Terraform connects to the platform provider (e.g., AWS) using the provider's API.
• For AWS, Terraform can deploy resources like EC2 servers using the AWS provider.

Key Terraform Files:

• main.tf: Contains the main Terraform configuration.
• variables.tf: Defines variables used in the configuration.
• outputs.tf: Specifies outputs that should be exposed.
• providers.tf: Lists all providers used.
• terraform.tfvars: Contains variable values.
• terraform.tfstate: Stores the state of the infrastructure.
• terraform.tfstate.backup: Backup of the state file.
• .terraform: Directory containing plugins and providers.

Important Terraform Commands:

• terraform refresh
• terraform plan
• terraform apply
• terraform destroy

Modules/Providers:

• Modules and providers are plugins used by Terraform to connect to platforms.
• Examples include the AWS provider for AWS resources.
• Modules help organize and reuse configurations.

Types of Resources:

• Resource: Used to create new infrastructure.
• Data: Used to query existing resources.

Variables:

• Variables can be defined in terraform.tfvars.
• Can be set via command line (-var flag) or environment variables (TF_VAR_).
• Default values can be set in variables.tf.

Provisioners:

• Used to execute commands after resource creation.
• Examples: "remote-exec" for running scripts on remote servers.

Modules:

• Logical units grouping multiple resources.
• Reusable configurations with inputs and outputs.

Remote State:

• Terraform can write data to a remote data store for team collaboration.
• Best practices include setting up remote storage backend (e.g., S3).

Best Practices:

• Change state using Terraform commands only.
• Use remote storage backend for team sharing.
• Enable state locking to avoid conflicts.
• Backup state file and enable versioning.
• Use separate states for different environments.
• Host Terraform scripts in a Git repository.
• Use continuous integration (CI) for Terraform code.
• Apply infrastructure changes only through a continuous deployment (CD) pipeline.

Declarative Nature:

• Terraform is declarative, defining the end result, and Terraform figures out how to achieve it.

Terraform vs. Ansible:

• Terraform is mainly for infrastructure provisioning.
• Ansible is a configuration management tool.