Introduction

Terraform, a tool created by HashiCorp, has revolutionized the way we manage infrastructure as code (IaC). It allows users to define both cloud and on-premises resources using a high-level configuration language. One of the core concepts in Terraform that plays a critical role in how it tracks and manages infrastructure is the Terraform state. This article delves into what Terraform state is, why it’s important, and how to manage it effectively.

What is Terraform State?

Terraform state is a file that Terraform uses to map real-world resources to your configuration, keep track of metadata, and improve performance for large infrastructures. This file, typically named terraform.tfstate, contains the state of your managed infrastructure and configuration at the time it was last applied. It is crucial for Terraform to perform resource creation, modification, and deletion.

Why is Terraform State Important?

Terraform state serves several important purposes:

  • Resource Mapping: It maps the resources in your configuration to real-world resources, allowing Terraform to know what resources it is managing.
  • Dependency Tracking: It tracks resource dependencies to determine the correct order for creating, updating, or deleting resources.
  • Change Management: It stores the attributes of all managed resources, which Terraform uses to detect any changes to your infrastructure between updates.
  • Synchronization: For teams, the state file helps in synchronizing operations, ensuring that concurrent executions do not interfere with each other.

Managing Terraform State

Given its importance, managing the Terraform state file is a critical aspect of Terraform usage, especially in team environments or complex deployments. Here are some best practices for Terraform state management:

1. State File Storage

By default, Terraform stores the state file locally. However, in a team environment or CI/CD pipeline, it’s advisable to use remote state backends such as AWS S3, Azure Blob Storage, or Google Cloud Storage. Remote backends offer advantages like shared access, state locking, and versioning.

2. State Locking

State locking prevents concurrent Terraform executions from making simultaneous changes to the same state file, reducing the risk of state corruption. Most remote backends support state locking.

3. State Security

Since the state file can contain sensitive information, it’s crucial to secure access to the state file, especially when using remote backends. Utilize encryption at rest and in transit, and manage access using the backend’s IAM roles or policies.

4. State Backup

Always enable versioning on the remote backend to keep backups of your state file. This practice is vital for recovery in case of accidental deletion or corruption of the state file.

5. State Inspection and Manipulation

Use Terraform commands to inspect and manipulate the state:

  • terraform show to inspect the current state.

When the infrastructure was not deployed, the terraform show the command return:

No state.

Whereas after terraform apply commnad, the terraform show command displays the lsit of resources.

  • terraform state list to list resources in the state.

For example:

docker_container.nginx
docker_image.nginx
  • terraform state mv and terraform state rm to move or remove items from the state, respectively.

However, manipulating the state directly can be dangerous and should be done with caution.

6. Avoid Manual Edits

Never manually edit the state file. Always use Terraform commands to make changes. Manual edits can corrupt the state file, making it difficult for Terraform to manage your resources correctly.

Conclusion

Understanding and managing Terraform state is essential for anyone using Terraform to manage infrastructure. The state file is the bridge between your configuration and the real world, making it possible for Terraform to maintain idempotency and manage infrastructure changes efficiently. By following best practices for state management, you can ensure that your Terraform projects are stable, secure, and scalable, regardless of the size of your team or the complexity of your infrastructure.