If you created infrastructure before you started using Terraform, you can use the terraform import command to add that infrastructure to Terraform’s state file so that Terraform is aware of and can manage that infrastructure. The import command takes two arguments. The first argument is the “address” of the resource in your Terraform configuration files. This makes use of the same syntax as resource references, such as _. (e.g., aws_iam_user.existing_user). The second argument is a resource-specific ID that identifies the resource to import. For example, the ID for an aws_iam_user resource is the name of the user (e.g., yevgeniy.brikman), and the ID for an aws_instance is the EC2 Instance ID (e.g., i-190e22e5). The documentation at the bottom of the page for each resource typically specifies how to import it.

For example, here is the import command that you can use to sync the aws_iam_user you just added in your Terraform configurations with the IAM user you created back in Part 2 of this blog post series (obviously, you should replace “yevgeniy.brikman” with your own username in this command):

$ terraform import aws_iam_user.existing_user yevgeniy.brikman

Terraform will use the AWS API to find your IAM user and create an association in its state file between that user and the aws_iam_user.existing_user resource in your Terraform configurations. From then on, when you run the plan command, Terraform will know that an IAM user already exists and not try to create it again.

Note that if you have a lot of existing resources that you want to import into Terraform, writing the Terraform code for them from scratch and importing them one at a time can be painful, so you might want to look into tools such as terraformer and terracognita, which can import both code and state from supported cloud environments automatically.