• Data sources provide dynamic information about entities that are not managed by the current Terraform and configuration.
• Variables provide static information.
• Referencing a resource defined in a data source won’t create the resource itself, and your plan will fail if you reference nonexistent data or infrastructure.
• Data sources allow data to be fetched or computed for use elsewhere in Terraform configuration.
• External data sources must return information in JSON format.

This may include:

• Configuration data from Consul
• Information about the state of manually-configured infrastructure components
• Another Terraform configuration
• Defined outside of Terraform
• Defined by another separate Terraform configuration.

data "azurerm_virtual_machine" "example" {
  name                = "simple-vm"
  resource_group_name = "demo"
}

output "virtual_machine_id" {
  value = data.azurerm_virtual_machine.example.id
}

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-20230325"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = ["099720109477"] # Canonical
}

data "aws_availability_zones" "available" {
  state = "available"
}

output "virtual_machine_id" {
  value = data.aws_availability_zones.available.names[0]
}

output "virtual_machine_id1" {
  value = data.aws_availability_zones.available.names[1]
}


output "ips_with_list_interpolation" {
  value = [ for name in data.aws_availability_zones.available.names : name ]
}

resource "aws_instance" "first-ec2" {
  ami           = data.aws_ami.ubuntu.id # us-west-2
  instance_type = "t2.micro"
  tags = {
    Name = "RajeshKumar"
  }
  }
  

** In this case, we can use the aws_ami data source to obtain information about the most recent AMI image **

that has the name prefix app-.

data "aws_ami" "app_ami" {
  most_recent = true
  filter {
    name   = "name"
    values = ["app-*"]
  }
}

Data sources export attributes, just like resources do. We can interpolate these attributes using the syntax data.TYPE.NAME.ATTR. In our example, we can interpolate the value of the AMI ID as data.aws_ami.app_ami.id, and pass it as the ami argument for our aws_instance resource.

resource "aws_instance" "app" {
  ami           = "${data.aws_ami.app_ami.id}"
  instance_type = "t2.micro"
}

data "azurerm_virtual_machine" "example" {
  name                = "myVM"
  resource_group_name = "myResourceGroup"
}

output "virtual_machine_id" {
  value = data.azurerm_virtual_machine.example.id
}

# name - Specifies the name of the Virtual Machine.
# resource_group_name - Specifies the name of the resource group the Virtual Machine is located in.

data "aws_ami" "app_ami" {
  most_recent = true
  owners = ["self"]
  filter {
    name   = "name"
    values = ["HelloWorld"]
  }
}

resource "aws_instance" "app" {
  ami           = "${data.aws_ami.app_ami.id}"
  instance_type = "t2.micro"
}

# AWS Image named with "HelloWorld" must be there in your account.

view raw DataSourcesinTerraform.md hosted with by GitHub

Here’s an example of using the AWS data source in Terraform to retrieve information about an existing Amazon S3 bucket

In this example, we’re using the aws_s3_bucket data source to retrieve information about an existing S3 bucket named example-bucket. We’re then outputting several attributes of the bucket using the output block.

The aws_s3_bucket data source retrieves the specified bucket’s attributes such as bucket, region, arn, policy, id, acceleration_status, versioning, website_domain, website_endpoint, and logging as per the below documentation. https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/s3_bucket

data "aws_s3_bucket" "example" {
  bucket = "example-bucket"
}

output "bucket_name" {
  value = data.aws_s3_bucket.example.bucket
}

output "bucket_region" {
  value = data.aws_s3_bucket.example.region
}

output "bucket_arn" {
  value = data.aws_s3_bucket.example.arn
}

output "bucket_policy" {
  value = data.aws_s3_bucket.example.policy
}

Here’s an example of using the AWS data source in Terraform to retrieve information about an existing availability zone

In this example, we’re using the aws_availability_zone data source to retrieve information about the availability zone named us-west-2a in the US West (Oregon) region. We’re then outputting the zone_id and zone_name attributes of the availability zone using the output block.

The aws_availability_zone data source retrieves the specified availability zone’s attributes such as zone_id, zone_name, region_name, and opt_in_status as per the below documentation. https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/availability_zone

data "aws_availability_zone" "example" {
  state = "available"
  name  = "us-west-2a"
}

output "zone_id" {
  value = data.aws_availability_zone.example.zone_id
}

output "zone_name" {
  value = data.aws_availability_zone.example.zone_name
}

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Terraform Basic Tutorial with Demo by Piyush 2020

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Terraform Fundamental Tutorial By Guru in 2020 Part-5

Terraform Advance Tutorial for Beginners with Demo 2020 — By DevOpsSchool

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Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I am working at Cotocus. I blog tech insights at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at I reviewed , and SEO strategies at Wizbrand. 

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