Resources and Data Sources

Resources and data sources are the building blocks of every Terraform configuration. Resources create and manage infrastructure, while data sources read existing information. This lesson covers how to define, reference, and connect them.

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Resources

A resource block declares a piece of infrastructure that Terraform will manage:

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t3.micro"

  tags = {
    Name = "web-server"
  }
}

Resource Address

Every resource has a unique address: <type>.<name>

• aws_instance.web — the resource above
• google_compute_instance.api — a GCP compute instance named "api"

Resource Arguments vs Attributes

Term	When Set	Example
Argument	In your configuration (input)	instance_type = "t3.micro"
Attribute	After creation (output)	aws_instance.web.public_ip

You reference attributes of one resource in another to create implicit dependencies.

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Meta-Arguments

Resources support special meta-arguments that change their behaviour:

count

Create multiple instances of a resource:

resource "aws_instance" "web" {
  count         = 3
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t3.micro"

  tags = {
    Name = "web-${count.index}"
  }
}

Access individual instances: aws_instance.web[0], aws_instance.web[1], etc.

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