terraform-provider-virtualbox | VirtualBox provider for Terraform | Infrastructure Automation library

Terraform looks for plugins in a number of locations, but the primary place for manually-installed plugins is in the "User Plugins Directory", which is either ~/.terraform.d/plugins on Unix systems or %APPDATA%\terraform.d\plugins on Windows.

The .terraform/plugins directory is not the place to put plugins you're installing manually. That directory is managed by Terraform itself and is the location for automatically-installed plugins. If you place plugins in that directory manually, terraform init may delete them as part of plugin installation.

Terraform also requires the provider executable to follow a particular naming scheme: terraform-provider-providername_vX.Y.Z, where the _vX.Y.Z part is technically optional but strongly recommended in order for version constraints to operate correctly. On Windows in particular, the file must also have the suffix .exe, because Terraform plugins are separate programs that Terraform will launch.

To debug Terraform's plugin discovery process, you can set the environment variable TF_LOG=debug before you run terraform init. In that output there will be lines like this: