How to Import an AWS Auto Scaling Group into Terraform

Import AWS Auto Scaling Group with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Amazon EC2 Auto Scaling resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live AWS Auto Scaling Group to managed Terraform.

terraback scan all aws --region us-east-1

terraback aws import --method bulk

The Terraform import block

Terraback emits a Terraform 1.5+ import block like the one below. Because the block lives in your configuration, the import is reviewable in a pull request and repeatable across environments.

import {
  to = aws_autoscaling_group.web
  id = "web-asg"
}

Example aws_autoscaling_group configuration

Here is a realistic AWS Auto Scaling Group block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "aws_autoscaling_group" "web" {
  name                = "web-asg"
  min_size            = 2
  max_size            = 6
  desired_capacity    = 3
  vpc_zone_identifier = ["subnet-0bb1c79de3a1b2c3d"]

  launch_template {
    id      = "lt-0a1b2c3d4e5f6a7b8"
    version = "$Latest"
  }
}

Gotchas when importing a AWS Auto Scaling Group

• Import by the group name, not by ARN.
• Attached scaling policies, scheduled actions, and lifecycle hooks are separate resources (aws_autoscaling_policy, aws_autoscaling_schedule, aws_autoscaling_lifecycle_hook) and are not imported with the group.
• desired_capacity drifts as the group scales; the generated config commonly sets lifecycle { ignore_changes = [desired_capacity] } so Terraform does not fight Auto Scaling.
• A group references a launch template or launch configuration, not the launched instances; do not import those EC2 instances individually.

Doing it manually with terraform import

The native approach is to write the aws_autoscaling_group block by hand, then run terraform import aws_autoscaling_group.example <import-id> for every resource, one at a time. That works for a handful of resources, but it does not scale: you author all the HCL yourself and repeat the command for each item. Terraback generates the HCL and the import blocks for your whole account in one pass.

Import other AWS resources