Data source block syntax in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a data block in Terraform?

A data block lets you fetch information from existing resources outside your Terraform configuration. It helps you use data created elsewhere.

beginner

What are the main parts of a Terraform data source block?

A data source block has three parts: the keyword data, the resource type (like aws_ami), and a name you choose to reference it later.

beginner

How do you reference a data source output in Terraform?

Use data.<resource_type>.<name>.<attribute>. For example, data.aws_ami.example.id gets the AMI ID.

intermediate

Example: What does this data block do?<br>

data "aws_ami" "ubuntu" {
  most_recent = true
  owners      = ["099720109477"]
  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
  }
}

It finds the most recent Ubuntu 20.04 AMI owned by the official Ubuntu account. This lets you use the latest Ubuntu image in your infrastructure.

beginner

Why use data sources instead of hardcoding values?

Data sources keep your config flexible and up-to-date. They fetch live info, so you avoid errors from outdated or manual values.

What keyword starts a data source block in Terraform?

A data

B resource

C variable

D output

The data keyword defines a data source block to fetch existing info.

How do you name a data source block?

A You use the resource type only

B You use the provider name

C You provide a unique name after the resource type

D You don't name data sources

You give a unique name after the resource type to reference the data source later.

Which of these is a valid way to reference a data source attribute?

A output.aws_instance.example.id

B data.aws_instance.example.id

C var.aws_instance.example.id

D resource.aws_instance.example.id

Data source attributes are referenced with data.<type>.<name>.<attribute>.

What does the filter block inside a data source do?

A It sets variables

B It creates a new resource

C It deletes resources

D It filters which existing resources to fetch

Filters narrow down which existing resources the data source returns.

Why is using data sources considered a best practice?

A They fetch live data to keep configs current

B They hardcode values for stability

C They speed up Terraform runs

D They replace variables

Data sources fetch live info, avoiding stale or manual values.

Explain the structure and purpose of a Terraform data source block.

Think about how you tell Terraform to look up info it doesn't create.

Describe how filters work inside a data source block and why they are useful.

Filters help you find exactly what you need from many options.