What Is Terraform Import Used For?
What is Terraform? Terraform is one of the world’s most popular Infrastructure as Code (IaC) tools. It uses a declarative language and stores the current state of all deployed and managed infrastructure into a file, which can be stored locally or remotely. This file describes current infrastructure configurations and is used to plan and deploy changes via files and modules that define the new state.
How does Terraform import help integrate untracked resources into Terraform management?
Occasionally, there is a need to manage resources via Terraform that were created externally. In such cases, we can use the Terraform Import command to onboard these preexisting resources.
What problems does Terraform import resolve?
1. Import old resource
Organizations can import resources created with alternative tools or methods
2. Import resources created outside Terraform
When Terraform is deployed, it may not have been universally adopted. As such, there may have been infrastructure additions/amendments made outside of Terraform.
3. Loss of Terraform state file
The state file can be deleted or become irreversibly corrupt.
4. Re-factoring / Amending Terraform code structure
As an environment scales, there may be a need to re-factor or re-structure Terraform modules and other constructs.
Why Use the Terraform Import Command?
Terraform Import offers several critical benefits that make the tool invaluable.
- It helps prevent resource duplication, making it easier to manage your infrastructure. This is especially useful if you are working with legacy issues in your infrastructure that you wish to manage using Terraform.
- Terraform Import ensures all your resources are managed consistently, regardless of their origin, and helps prevent manual configuration drift. It also maintains a single source of truth for all your infrastructure resources.
- Terraform Import allows you to adopt Terraform incrementally for existing resources without having to start from scratch. This means you can gradually manage your infrastructure with Terraform without causing any disruptions.
- Importing resources using Terraform Import allows you to collaborate with your team using a shared version-controlled Terraform state. This enhances team collaboration and ensures every team member is working with the same infrastructure definitions, promoting a higher level of consistency and accuracy among your team.
By using Terraform Import, you can effectively manage your infrastructure, prevent resource duplication, and ensure your team has a shared understanding of your infrastructure. Terraform Import is a valuable tool for ensuring configuration consistency, facilitating incremental adoption, and enhancing collaboration.
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Related Reading
How to Use Terraform Import to Manage Existing Resources
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Importing Resources
Prepare the EC2 instance
Create an EC2 instance in your AWS account. An example of the details of the EC2 instance is as follows:
Name: MyVM
Instance ID: i-0b9be609418aa0609
Type: t2.micro
VPC ID: vpc-1827ff72
Create main.tf and set provider configuration
In your desired path, create `main.tf` and configure the AWS provider. The file should look something like this:
Run `Terraform init` to initialize the Terraform modules.
Write config for the resource to be imported
Add the following configuration for the EC2 instance to the `main.tf` file
Run the import command
Run the import command to map the aws_instance.myvm configuration to the EC2 instance using the ID:
Observe state files and plan output
After importing, observe the state file and run `Terraform plan` to see if there are any changes needed.
Improve config to avoid replacement
Adjust the configuration to avoid the replacement of the EC2 instance by updating the `ami` attribute to the correct value.
Improve config to avoid changes
Further align the resource block to avoid changes highlighted in the plan output.
Importing Modules
Terraform Import AWS VPC module example
To import a resource in a module's configuration, run the command as follows:
Importing IAM roles using for_each
Define a Terraform configuration for roles and then import them using the following commands:
Terraform 1.5 import - How to use the import block
To use the import block in Terraform 1.5, define the import block in your code to allow import operations. For example, you can import S3 buckets using the import block as follows:
After running `Terraform plan`, review the generated configuration and then apply it to add the resources to the state.
4 Common Issues When Using Terraform Import
1. Error-prone Manual Configuration
When using Terraform import, one of the challenges is that it does not automatically generate corresponding configuration files for the imported resources. This means that you must manually create the configuration, which can be both time-consuming and prone to errors. You would have to collect all the necessary attributes from the external resource and write them as a configuration file which may result in mistakes and omissions if not done correctly.
2. Require Exact Resource Ids
Terraform needs to know the exact resource ID of the resource you're trying to import. This can be a challenge, especially when dealing with resources that have dependencies or require a tuple of identifiers.
For example, to import an AWS autoscaling policy, you would need the autoscaling group and scaling policy names. If you are importing resources with dependencies, you have to know the actual names of these resources from the AWS console and execute the import command multiple times.
3. Handling Drifts
After importing resources using Terraform import, you should run the 'Terraform Plan' command to ensure that there are no drifts between the configuration and the real-world resource. A 'drift' refers to a discrepancy between the desired state in the configuration file and the actual state of the resource.
If there are any differences, the physical resource may be updated, deleted, or created. Another challenge is the possibility of missing attribute values, which can lead to drift. You should refer to the resource documentation before importing to identify default values and ensure they are included in the configuration file.
4. Destruction of Resources
One of the risks of using Terraform import is the potential to destroy existing resources if mistakes are made in the configuration. For instance, if you provide an incorrect AMI ID, Terraform may destroy the existing EC2 instance and create a new one.
It's essential to review the 'Terraform Plan' output to ensure that no resources are unintentionally destroyed. Be cautious when using the 'Terraform Apply' command, especially with the '--auto-approve' option, as this could lead to unintended destruction of resources.
Related Reading
- Terraform Apply Auto Approve
- Terraform Module
- Terraform vs Cloudformation
- Terraform AWS Security Group
- Terraform Kubernetes Provider
- Terraform AWS Lambda
- Datadog Terraform
- Terraform Cloud Pricing
- Terraform IAM Role
- Terraform Debug
- Terraform Docker
- Github Actions Terraform
- Terraform Import Existing Resources
- Terraform ECS
- DevOps Terraform
- Terraform Automation
- Terraform CI CD
- Terraform Workflow
- Terraform Security
- Terraform Orchestration
- Terraform Multi Cloud
- Terraform No Code Provisioning
- Terraform Migrate State
- Terraform State Management
- Terraform AWS RDS
- What is Terragrunt
- Terragrunt vs Terraspace
- Terraform Multiple Environments
- Terraform Multiple Users
- Upgrade Terraform Version
- Terraform Test
- Terraform Commands
- Terraform Alternatives
- Terraform Stacks
- Crossplane Vs Terraform
- Terraform Tutorial
- Terraform for_each
- Terraform Dynamic Block
10 Best Practices for Using Terraform Import
1. Planning is crucial
You must include not only the resources you intend to import but also any resources that interact with those, and so on
2. Write your Terraform code
As part of the planning process, write your Terraform code before any changes to help quicken deployment. When importing multiple resources, automate the import commands via a script
3. Schedule all changes
Schedule all changes with your colleagues and ensure other modifications are suspended, especially when using CI/CD pipelines for deployment
4. Consider stopping tasks
If using CI/CD pipelines, consider stopping these tasks and running the import commands (and subsequent plan and apply commands) manually. Doing so will give you more time to review any changes and allow colleagues to critique your plan. Triggering any Terraform processes you’re not aware of can also be prevented this way
5. Carry out import tasks in small batches
Carry out import tasks in small batches rather than in bulk. Use the Terraform plan and apply commands regularly to ensure no unexpected consequences
6. Keep your state file in a shared storage
It’s generally recommended to keep your Terraform state file in a shared storage location rather than on your local machine for a few reasons
Consistency
A shared state file ensures that everyone uses the same state of the infrastructure. If each team member has a copy of the state file, it can be challenging to ensure consistency across different environments and prevent drift.
Backup and Recovery
A shared storage location provides a central point for backing up and recovering your state file. If your local machine crashes or your state file becomes corrupted, storing a backup in a shared location can save you time and effort.
Remote Execution
Storing state files on shared storage makes running Terraform in a remote environment, such as a build server or a continuous integration/continuous deployment (CI/CD) pipeline, easier.
Using a shared storage location for your Terraform state file helps ensure consistency, collaboration, and ease of use, making it a critical best practice when using Terraform for infrastructure management.
7. Back up frequently
Back up the state file frequently, allowing for easy recovery should anything go wrong
8. Use Terraform workspaces
Use Terraform workspaces to limit the “blast radius” of any Terraform state issues and reduce the complexity of recovery
9. Proper documentation
Keeping good documentation about imported Terraform resources is vital in the long run. If new members join the team in the future, they can refer to the documentation and learn about imported resources and the process of managing those resources.
10. Consider why you are importing resources
Carefully consider why you are importing the resources – is it essential? Balance the risk and reward of importing the resource vs. managing them outside Terraform.
Related Reading
- Atlantis Terraform
- Terraform Tools
- Terraform Cloud Alternatives
- Spacelift vs Terraform Cloud
- Atlantis Alternatives
- Scalr vs Terraform
- Env0 vs Terraform Cloud
- Terraform Testing Tools
- Ansible vs Terraform
- Terraform vs Ansible
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