By Brian Fitzgerald

Introduction

Using Terraform, you can launch an AWS EC2 instance from any account and any region using a public AMI identified only by image name. Because you do not need to lookup the image id each time, your code can be simplified.

Approach

Red Hat account number

In the AWS console, notice that the Red Hat, Inc. account number is 309956199498.

AMI name

Find the Red Hat AMI image by name. In the console, navigate to EC2 Images AMIs. Filter on Owner: 309956199498, Architecture: 64-bit (x86), Virtualization type: HVM.

For example, “RHEL-7.9_HVM_GA-20200917-x86_64-0-Hourly2-GP2”. You could also search using the AWS command line:

$ aws ec2 describe-images --owners 309956199498 --filters "` cat filters.ami.json `" --region us-east-2

where filters.ami.json contains:

[
    {
        "Name": "architecture",
        "Values": [
             "x86_64"
        ]
    },
    {
        "Name": "virtualization-type",
        "Values": [
             "hvm"
        ]
    }
]

Terraform data source

Define a Terraform aws_ami data source.

ami-rhel.tf

data "aws_ami" "rhel" {
    most_recent = true
    owners = [
        "309956199498"
    ]
    filter {
        name   = "name"
        values = [
            "RHEL-7.9_HVM_GA-20200917-x86_64-0-Hourly2-GP2"
        ]
    }
}

aws instance resource

Use the data source in your Terraform aws_instance resource

provider "aws" {
    region      = var.region
}

resource "aws_instance" "your-ec2-rsrc" {
    ami           = data.aws_ami.rhel.image_id

and so on . . .

Launch the ec2 instance

Run “terraform apply”. Terraform determines the AMI ID. For example, ami-0d2bf41df19c4aac7.

Conclusion

By using the Terraform AWS AMI data source, you can launch a public AMI from any account and region. The AMI ID is different for each account and region.