How to Import an AWS VPC Flow Log into Terraform

Import AWS VPC Flow Log with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Amazon VPC resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live AWS VPC Flow Log 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_flow_log.vpc
  id = "fl-0a1b2c3d4e5f6a7b8"
}

Example aws_flow_log configuration

Here is a realistic AWS VPC Flow Log block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "aws_flow_log" "vpc" {
  vpc_id               = "vpc-0a1b2c3d4e5f6a7b8"
  traffic_type         = "ALL"
  log_destination      = "arn:aws:s3:::my-flow-logs"
  log_destination_type = "s3"
}

Gotchas when importing a AWS VPC Flow Log

• Import by the fl- flow log ID, not the ID of the VPC, subnet, or ENI it monitors.
• Exactly one of vpc_id, subnet_id, or eni_id is set; copy the one the flow log actually targets.
• For CloudWatch Logs destinations the IAM role (iam_role_arn) and log group are separate resources; for S3 destinations the bucket and its policy are separate.
• log_destination_type is 'cloud-watch-logs' or 's3', and the matching destination field must agree or apply fails.

Doing it manually with terraform import

The native approach is to write the aws_flow_log block by hand, then run terraform import aws_flow_log.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