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Terraform: From Beginner to Master with Examples in AWS

Data Sources in Detail

Explore how to use Terraform data sources to fetch and reference existing AWS resources such as S3 buckets. Understand the configuration syntax, how to read resource attributes, and integrate them within IAM policies. This lesson helps you manage external dependencies effectively in your Terraform projects.

We'll cover the following...

Terraform data source

A data source in Terraform is used to fetch data from a resource that is not managed by the current Terraform project. This allows it to be used in the current project. You can think of it as a read-only resource that already exists; the object exists, but you want to read specific properties of that object for use in your project.

Project example

Let’s dive into an example:

C++
provider "aws" {
    region = "us-east-2"
}
data "aws_s3_bucket" "bucket" {
    bucket = "kevholditch-already-exists"
}
resource "aws_iam_policy" "my_bucket_policy" {
    name = "my-bucket-policy"
    policy = <<EOF
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "s3:ListBucket"
            ],
            "Effect": "Allow",
            "Resource": [
                "${data.aws_s3_bucket.bucket.arn}"
            ]
        }
    ]
}
EOF
}

As you can see from the above project, a data source block starts with the word “data”. The next word is the type of data source. We are using an aws_s3_bucket data source, which is used to lookup an S3 bucket. After the data ...