Migrating to OpenTofu from Terraform 1.9.x

When migrating from Terraform 1.9.x, please migrate to OpenTofu 1.9.0 first, then upgrade your OpenTofu installation to the latest version.

OpenTofu 1.9.0 is largely compatible with Terraform 1.9.x with a few minor changes needed. This migration guide will take you through the process of switching from Terraform to OpenTofu.

Step 0: Prepare a disaster recovery plan​

Although OpenTofu 1.9.0 is very similar to Terraform 1.9.8, make sure you have an up to date and tested disaster recovery plan.

Step 1: Upgrading Terraform​

This migration guide is only valid for Terraform 1.9.8. If you are on a Terraform version below 1.9.8, please upgrade to at least Terraform version 1.9.8 before proceeding with the migration by following the Terraform upgrade guide. If you are on a higher Terraform version, please wait until an appropriate migration guide becomes available.

Step 2: Apply all changes with Terraform​

Before proceeding, make sure that you apply all changes with terraform apply. Running terraform plan should result in no planned changes. While you can switch to OpenTofu with pending changes, it is not recommended.

$ terraform plan

...

No changes. Your infrastructure matches the configuration.

Terraform has compared your real infrastructure against your
configuration and found no differences, so no changes are needed.

Step 3: Install OpenTofu 1.9.0​

As a first step, please follow the installation instructions for the OpenTofu CLI tool. Please test if you can successfully execute the tofu command:

$ tofu --version
OpenTofu v1.9.0
on linux_amd64

Step 4: Back up your state file and code​

Before you begin using the tofu binary on your Terraform code, make sure to back up your state file. If you are using a local state file, you can simply make a copy of your terraform.tfstate file in your project directory.

If you are using a remote backend such as an S3 bucket, make sure that you follow the backup procedures for the backend and that you exercise the restore procedure at least once.

Additionally, make sure you back up or version your code as the migration will require some code changes.

Step 5: Code changes​

For a successful migration, you will need to perform the following code changes

Functions​

The following functions are not supported in OpenTofu:

• encode_tfvars
• decode_tfvars
• encode_expr

If you rely on these functions, please refactor your code to work without them.

S3 backend​

If you are using the S3 backend, please change your code as follows:

1. If you are using the skip_s3_checksum option on the S3 backend, remove this option as OpenTofu does not need it.
2. If you are using the endpoints → sso option or the AWS_ENDPOINT_URL environment variable, remove this option and verify if your code still works as intended after the migration.

Removed block​

The OpenTofu removed block works differently from the Terraform variant. Please review the documentation and make the following changes:

1. Remove the lifecycle block. If you used the lifecycle → destroy = true setting, remove the entire removed block. Verify that the code still works as intended after the migration.
2. If you are using destroy-time provisioners with removed blocks, please restructure your code to work without them.

Input variable validation​

If your input variable validation refers to other variables or objects, restructure your code to work around the necessity for these. (See issue #1336.)

Testing changes​

If you are using the terraform test feature, you will need to perform the following changes:

1. If you are using override_resource or override_data nested in a mock_provider restructure your tests to work without these features (see OpenTofu issue #1204).

Step 6: Initialize OpenTofu​

Now you are ready to migrate. Run tofu init in the directory where your Terraform code resides. OpenTofu will download any providers and modules referenced in your configuration from the OpenTofu registry.

Step 7: Inspect the plan​

Once initialized, run tofu plan and ensure that there are no pending changes similar to step 1 above. If there are unexpected changes in the plan, roll back to Terraform and troubleshoot your migration. (See the Troubleshooting section below.)

$ tofu plan

...

No changes. Your infrastructure matches the configuration.

OpenTofu has compared your real infrastructure against your
configuration and found no differences, so no changes are needed.

Step 8: Apply​

Even though there should be no changes in your infrastructure, you should run tofu apply to ensure that OpenTofu updates the state file.

Step 9: Test out a small change​

Before you begin using OpenTofu for larger changes, test out tofu apply with a smaller, non-critical change.

Step 10: Upgrade to the latest OpenTofu version​

Now that the migration is complete, follow the upgrade guide for OpenTofu to upgrade to the latest version.

Rolling back to Terraform and reporting issues​

If you have issues migrating to OpenTofu you can follow these steps to roll back to Terraform:

1. Create another backup of your state file and code.
2. Remove any code changes you have made.
3. Run terraform init.
4. Run terraform plan and verify that no unexpected changes are in the plan.
5. Run terraform apply and verify that it runs properly with no changes.
6. Test the rollback with a small, non-critical change.

If you encountered a bug, please report it on GitHub.

Troubleshooting​

If you encounter any issues during the migration to OpenTofu, you can join the OpenTofu Slack or ask on GitHub Discussions.

Error: Failed to query available provider packages​

This error happens when a provider you specified in your configuration is not available in the OpenTofu registry. Please roll back to Terraform and make sure your code works with Terraform. If your code works, please submit an issue to include the provider in the registry.

Error: Module not found​

This error happens when a module you specified in your configuration is not available in the OpenTofu registry. Please roll back to Terraform and make sure your code works with Terraform. If your code works, please submit an issue to include the module in the registry.