CLI-driven remote run: "error looking up module versions: 401 Unauthorized"

Problem

When running terraform init for a Terraform Enterprise or HCP Terraform workspace using the remotebackend or cloudconfiguration, you receive a 401 Unauthorized error.

│ Error: Error accessing remote module registry
│
│ on main.tf line 39:
│ 39: module "example" {
│
│ Failed to retrieve available versions for module "example"
│ (main.tf:39) from app.terraform.io:
│ error looking up module versions: 401 Unauthorized.

Prerequisites

• You are using a local, CLI-driven Terraform execution workflow.
• The module referenced in your configuration is located in a Private Module Registry.

Cause

This error occurs because Terraform does not have a valid API token to authenticate to the Private Module Registry. The CLI requires credentials stored locally, either from running terraform login or from a credentials block in the CLI configuration file.

Supplying a token argument directly within the cloud or remote configuration block is not sufficient for authenticating to the Private Module Registry.

Solution

To resolve this issue, you must provide a valid API token by authenticating the Terraform CLI to Terraform Enterprise or HCP Terraform. You can do this in one of two ways:

1. Use the terraform login command. This is the recommended method, as it securely stores the token for you.

   $ terraform login

2. Manually create a CLI configuration file. You can create a CLI configuration file with credentials that contains a valid token.

After authenticating with either method, run terraform init again. The command should succeed without error.

Additional Information

• The requirement to authenticate is often displayed in the HCP Terraform or Terraform Enterprise UI, as shown below.

  

• For more details on credential storage, refer to the documentation on Terraform CLI Credentials.