🚀 Terraform Learning Journey

From Oracle DBA to Cloud DevOps/DBRE — Day-by-Day Terraform Notes
Author: Naresh Sajwani | Goal: HashiCorp Terraform Associate (003) Certification
Environment: RHEL VM (VirtualBox) + AWS Free Tier

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📌 Repository Description

A real-world, mistake-documented Terraform learning diary. 
Covers installation, first EC2 deployment, all beginner blunders, 
and how to fix them. Built by an Oracle DBA for other newbies.

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🎯 What This Repo Is

This is NOT a polished tutorial written by an expert. This is a raw learning diary written by someone who broke things, got confused, fixed them, and wrote it all down.

If you're an Oracle DBA (or any IT professional) trying to learn Terraform from zero, you'll find every mistake I made here — so you don't have to make them yourself.

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🚀 Quick Start — Run Your First Terraform Script

Prerequisites

• RHEL/CentOS VM (or any Linux)
• AWS Free Tier account
• AWS Access Key & Secret Key

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🧠 Key Concepts Explained Simply

The "Dot" Notation: aws_vpc.my_vpc.id

aws_vpc     .    my_vpc     .     id
   ↑              ↑                ↑
  Type         Name            Attribute
(What?)       (Which?)        (What detail?)

Oracle Analogy:

• resource "aws_vpc" "my_vpc" = INSERT INTO vpc_table (name, cidr) VALUES ('my_vpc', '10.0.0.0/16')
• aws_vpc.my_vpc.id = SELECT id FROM vpc_table WHERE name = 'my_vpc'

Terraform does the "SELECT" automatically.

Implicit Dependency

resource "aws_subnet" "my_subnet" {
  vpc_id = aws_vpc.my_vpc.id  # Terraform sees this and creates VPC FIRST
}

Terraform is smart. It sees the reference and knows the order.

State File = Terraform's Memory

File	Purpose
terraform.tfstate	Terraform's notebook — remembers everything it created
terraform.tfstate.backup	Backup before last change
terraform.tfstate.1234567890.backup	Backup before state rm or import

Golden Rule: Never delete terraform.tfstate. The .backup files are safe to clean up.

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📋 Terraform Command Cheat Sheet

Command	What It Does	When to Use
terraform init	Download plugins	First time only per project
terraform fmt	Auto-format code	Before every commit
terraform validate	Check syntax	Before plan
terraform plan	Dry run / preview	Before every apply
terraform apply	Create/Update resources	When plan looks good
terraform apply -auto-approve	Apply without confirmation	Scripts/CI only
terraform plan -out=file.tfplan	Save plan to file	For locked/safe applies
terraform apply file.tfplan	Apply saved plan	Ignores code changes
terraform destroy	Delete everything	When done practicing
terraform show	Show current state	To see what Terraform knows
terraform state list	List managed resources	Check what's tracked
terraform state rm <resource>	Remove from state (not AWS)	When Terraform should forget
terraform import <resource> <id>	Bring existing resource under management	For resources created manually
terraform refresh	Sync state with AWS reality	After manual console changes

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🔗 Useful Resources

• HashiCorp Terraform Docs
• Terraform Registry (AWS Modules)
• HashiCorp Learn (Free Tutorials)
• AWS Free Tier Limits
• Terraform Associate Exam Objectives

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🤝 Contributing

This is a personal learning repo, but if you spot errors or have suggestions, feel free to open an issue or PR!