Terraform Interview Questions for Infrastructure Roles

3. What are the key Terraform commands, and what do they do?

Terraform provides several core commands to manage infrastructure:

• terraform init: Initializes a Terraform working directory, downloading necessary providers and modules.
• terraform plan: Generates an execution plan, showing what changes Terraform will make to reach the desired state.
• terraform apply: Executes the plan, provisioning or updating infrastructure.
• terraform destroy: Removes all resources managed by Terraform.
• terraform validate: Checks configuration files for syntax and consistency.

4. What is a Terraform state file, and why is it important?

The Terraform state file (terraform.tfstate) tracks the current state of infrastructure managed by Terraform. It maps real-world resources to your configuration, enabling Terraform to detect changes, manage dependencies, and ensure consistency. The state file is critical for collaboration, as it allows multiple team members to work on the same infrastructure without conflicts.

5. What are Terraform providers, and why are they important?

Providers are plugins that enable Terraform to interact with specific APIs or services, such as AWS, Azure, or Google Cloud. They define the resources and data sources Terraform can manage. Providers are essential for Terraform’s cloud-agnostic nature, allowing it to support a wide range of platforms and services.

6. What are Terraform modules, and how do they benefit infrastructure management?

Modules are reusable containers for multiple resources that are used together. They simplify complex configurations, promote code reuse, and ensure consistency across environments. For example, a module can define a VPC setup that can be reused across different projects, reducing duplication and errors.

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7. How does Terraform manage remote state, and why is it useful?

Remote state stores the Terraform state file in a remote backend, such as AWS S3 with DynamoDB for locking or Terraform Cloud. This enables secure collaboration, as multiple users can access and update the state file without conflicts. Remote state also enhances security by encrypting sensitive data and provides backup capabilities.

8. What are Terraform workspaces, and when should you use them?

Workspaces allow you to manage multiple isolated state files (e.g., for dev, staging, prod) within the same Terraform configuration. They are useful for simple setups where you want to maintain separate environments without duplicating code. For more complex scenarios, separate configurations or directories are often preferred.

9. How does Terraform handle importing existing infrastructure?

Terraform’s terraform import command allows you to bring existing resources into Terraform’s state file. You must manually define the resource in your configuration files to match the imported resource. This is useful for managing infrastructure created outside Terraform, though it requires careful alignment to avoid drift.

10. What are Terraform provisioners, and when should you use them?

Provisioners execute scripts on local or remote machines after resource creation, such as installing software or configuring services. They should be used sparingly, as they introduce external dependencies. Alternatives like Ansible or cloud-native configuration tools are often better for complex provisioning tasks.

Intermediate Terraform Interview Questions

These questions dive deeper into Terraform’s capabilities, testing your ability to handle real-world scenarios commonly encountered in mid-level roles.

11. What is drift detection in Terraform, and how can it be addressed?

Drift detection identifies discrepancies between the actual infrastructure and the Terraform configuration. During terraform plan, Terraform compares the state file with the configuration and highlights differences. To address drift, you can update the configuration to match the infrastructure and run terraform apply, or manually revert external changes to align with the configuration.

12. How would you implement a rolling update using Terraform?

A rolling update gradually replaces instances to minimize downtime. In Terraform, you can use count or for_each to manage multiple instances, updating them incrementally. For example, you might update an Auto Scaling group in AWS by modifying its launch configuration. Load balancers and health checks ensure traffic shifts smoothly, though Terraform alone may require integration with other tools for full automation.