AWS Import existing AWS infrastructure into terraform

출처: https://blog.ndk.name/import-existing-aws-infrastructure-into-terraform/

Amazon Web Services (AWS)

Amazon Web Services (AWS) is an on-demand cloud computing platform that offers us a lot of helpful and reliable services. AWS has friendly web interface which user can easily interact with to create virtual machines, networking stuffs, security policies, etc. However, in order to manage all the AWS configuration and keep track of the changes, it is neccessary to work with 3rd party tool like Terraform.

Terraform

Terraform is a tool for building, changing, and versioning infrastructure safely and efficiently. Terraform can manage existing and popular service providers as well as custom in-house solutions. You can see here the list of supported providers.

If you are building your IT infrastructure on AWS from scratch with Terraform, it is great, you don’t need to follow this article. But if you already had an existing aws infrastructure and now want to manage with Terraform, you might want to read more :-).

Terraform supports import command to import existing infrastructure into your Terraform state. It will find and import the specified resource into your Terraform state, allowing existing infrastructure to come under Terraform management without having to be initially created by Terraform.

1	$ terraform import [options] ADDR ID

Where:

ADDR is the address of your Terraform’s defined resource to import to.
ID is your AWS object ID.

Currently Terraform does not support to generate the resource’s code automatically. You will have to manually define them before performing the import commands. It is time consuming and might causes problem by human mistakes such as writing invalid syntax, putting wrong object id, etc. So it’s time to play with Terraforming.

Terraforming

Terraforming is a free and open-source tool written in Ruby. It helps you to export existing AWS resources to Terraform style (tf, tfstate).
Currently Terraforming requires Ruby 2.1 and supports Terraform v0.9.3 or higher. You can install Terraforming by gem command.

1	$ gem install terraforming

Access Requirements

Just like Terraform, Terraforming requires access to your AWS infrastructure to be able to export the configuration. You can set the AWS credential by exporting environment variables.

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$ export AWS_ACCESS_KEY_ID=xxxxxxxxxxxxx
$ export AWS_SECRET_ACCESS_KEY=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
$ export AWS_REGION=xx-yyyy-0

Or you can use ~/.aws/credentials file to manage the profiles then specify --profile <profile-name> in your terraforming commands.

$ cat ~/.aws/credentials
[khanh]
aws_access_key_id = xxxxxxxxxxxxx
aws_secret_access_key = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Terraforming command usage

Terraforming supports to export many type of AWS resrouce. For example EC2 instances, Security Group, Route53, VPC, IAM, etc. You can see the full list of supported options by running

$ terraforming --help
Commands:
  terraforming alb             # ALB
  terraforming asg             # AutoScaling Group
  terraforming cwa             # CloudWatch Alarm
  terraforming dbpg            # Database Parameter Group
  terraforming dbsg            # Database Security Group
  terraforming dbsn            # Database Subnet Group
  terraforming ec2             # EC2
  terraforming ecc             # ElastiCache Cluster
  terraforming ecsn            # ElastiCache Subnet Group
  terraforming efs             # EFS File System
  terraforming eip             # EIP
  terraforming elb             # ELB
  terraforming help [COMMAND]  # Describe available commands or one specific command
  terraforming iamg            # IAM Group
  terraforming iamgm           # IAM Group Membership
  terraforming iamgp           # IAM Group Policy
  terraforming iamip           # IAM Instance Profile
  terraforming iamp            # IAM Policy
  terraforming iampa           # IAM Policy Attachment
  terraforming iamr            # IAM Role
  terraforming iamrp           # IAM Role Policy
  terraforming iamu            # IAM User
  terraforming iamup           # IAM User Policy
  terraforming igw             # Internet Gateway
  terraforming kmsa            # KMS Key Alias
  terraforming kmsk            # KMS Key
  terraforming lc              # Launch Configuration
  terraforming nacl            # Network ACL
  terraforming nat             # NAT Gateway
  terraforming nif             # Network Interface
  terraforming r53r            # Route53 Record
  terraforming r53z            # Route53 Hosted Zone
  terraforming rds             # RDS
  terraforming rs              # Redshift
  terraforming rt              # Route Table
  terraforming rta             # Route Table Association
  terraforming s3              # S3
  terraforming sg              # Security Group
  terraforming sn              # Subnet
  terraforming snss            # SNS Subscription
  terraforming snst            # SNS Topic
  terraforming sqs             # SQS
  terraforming vgw             # VPN Gateway
  terraforming vpc             # VPC

Options:
  [--merge=MERGE]                                # tfstate file to merge
  [--overwrite], [--no-overwrite]                # Overwrite existing tfstate
  [--tfstate], [--no-tfstate]                    # Generate tfstate
  [--profile=PROFILE]                            # AWS credentials profile
  [--region=REGION]                              # AWS region
  [--assume=ASSUME]                              # Role ARN to assume
  [--use-bundled-cert], [--no-use-bundled-cert]  # Use the bundled CA certificate from AWS SDK

Export AWS resource into tf

Following is an example of exporting existing EC2 instances

$ terraforming ec2 --profile=khanh
resource "aws_instance" "ubuntu-server-01" {
    ami                         = "ami-51a7aa2d"
    availability_zone           = "ap-southeast-1b"
    ebs_optimized               = true
    instance_type               = "m5.4xlarge"
    monitoring                  = false
    key_name                    = "khanh"
    subnet_id                   = "subnet-37eada7e"
    vpc_security_group_ids      = ["sg-0a285254743cdcc51"]
    associate_public_ip_address = true
    private_ip                  = "172.16.1.101"
    source_dest_check           = true

    root_block_device {
        volume_type           = "standard"
        volume_size           = 50
        delete_on_termination = true
    }
}
...

Once you have tf code definitions above, you can just copy and paste them into your Terraform code. But you haven’t finished yet. You will also have to let Terraform know which AWS resource that code block should map to.

Mapping Terraform tf to existing AWS resource

Back to terrform import command, we will use it to do the mapping.

$ terraform import aws_instance.ubuntu-server-01 i-0421ae392a9e26277
aws_instance.ubuntu-server-01: Importing from ID "i-0421ae392a9e26277"...
aws_instance.ubuntu-server-01: Import complete!
Imported aws_instance (ID: i-0421ae392a9e26277)
aws_instance.ubuntu-server-01: Refreshing state... (ID: i-0421ae392a9e26277)

Import successful!

Note:

ubuntu-server-01 is the resource name you defined in Terraform.
i-0421ae392a9e26277 is the actual EC2 instance ID which you want to map to.

Now you can confirm the new resource definition by running terraform plan. If your Terraform does not show any changes to your AWS infrastructure, it means you imported the resource successfully.

$ terraform plan
...
No changes. Infrastructure is up-to-date.

This means that Terraform did not detect any differences between your
configuration and real physical resources that exist. As a result, no
actions need to be performed.

That’s all! Now you can do the same steps for other resouces such as Security Group, VPC, Subnet, etc to completely manage your AWS infrastructure under Terraform.

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