» Provider Configuration

Terraform relies on plugins called "providers" to interact with remote systems.

Terraform configurations must declare which providers they require, so that Terraform can install and use them. Additionally, some providers require configuration (like endpoint URLs or cloud regions) before they can be used.

  • This page documents how to configure settings for providers.

  • The Provider Requirements page documents how to declare providers so Terraform can install them.

» Provider Configuration

Provider configurations belong in the root module of a Terraform configuration. (Child modules receive their provider configurations from the root module; for more information, see Providers Within Modules.)

A provider configuration is created using a provider block:

provider "google" {
  project = "acme-app"
  region  = "us-central1"
}

The name given in the block header ("google" in this example) is the local name of the provider to configure. This provider should already be included in a required_providers block.

The body of the block (between { and }) contains configuration arguments for the provider. Most arguments in this section are defined by the provider itself; in this example both project and region are specific to the google provider.

You can use expressions in the values of these configuration arguments, but can only reference values that are known before the configuration is applied. This means you can safely reference input variables, but not attributes exported by resources (with an exception for resource arguments that are specified directly in the configuration).

A provider's documentation should list which configuration arguments it expects. For providers distributed on the Terraform Registry, versioned documentation is available on each provider's page, via the "Documentation" link in the provider's header.

Some providers can use shell environment variables (or other alternate sources, like VM instance profiles) as values for some of their arguments; when available, we recommend using this as a way to keep credentials out of your version-controlled Terraform code.

There are also two "meta-arguments" that are defined by Terraform itself and available for all provider blocks:

Unlike many other objects in the Terraform language, a provider block may be omitted if its contents would otherwise be empty. Terraform assumes an empty default configuration for any provider that is not explicitly configured.

» alias: Multiple Provider Configurations

You can optionally define multiple configurations for the same provider, and select which one to use on a per-resource or per-module basis. The primary reason for this is to support multiple regions for a cloud platform; other examples include targeting multiple Docker hosts, multiple Consul hosts, etc.

To create multiple configurations for a given provider, include multiple provider blocks with the same provider name. For each additional non-default configuration, use the alias meta-argument to provide an extra name segment. For example:

# The default provider configuration; resources that begin with `aws_` will use
# it as the default, and it can be referenced as `aws`.
provider "aws" {
  region = "us-east-1"
}

# Additional provider configuration for west coast region; resources can
# reference this as `aws.west`.
provider "aws" {
  alias  = "west"
  region = "us-west-2"
}

» Default Provider Configurations

A provider block without an alias argument is the default configuration for that provider. Resources that don't set the provider meta-argument will use the default provider configuration that matches the first word of the resource type name. (For example, an aws_instance resource uses the default aws provider configuration unless otherwise stated.)

If every explicit configuration of a provider has an alias, Terraform uses the implied empty configuration as that provider's default configuration. (If the provider has any required configuration arguments, Terraform will raise an error when resources default to the empty configuration.)

» Referring to Alternate Provider Configurations

When Terraform needs the name of a provider configuration, it expects a reference of the form <PROVIDER NAME>.<ALIAS>. In the example above, aws.west would refer to the provider with the us-west-2 region.

These references are special expressions. Like references to other named entities (for example, var.image_id), they aren't strings and don't need to be quoted. But they are only valid in specific meta-arguments of resource, data, and module blocks, and can't be used in arbitrary expressions.

» Selecting Alternate Provider Configurations

By default, resources use a default provider configuration (one without an alias argument) inferred from the first word of the resource type name.

To use an alternate provider configuration for a resource or data source, set its provider meta-argument to a <PROVIDER NAME>.<ALIAS> reference:

resource "aws_instance" "foo" {
  provider = aws.west

  # ...
}

To select alternate provider configurations for a child module, use its providers meta-argument to specify which provider configurations should be mapped to which local provider names inside the module:

module "aws_vpc" {
  source = "./aws_vpc"
  providers = {
    aws = aws.west
  }
}

Modules have some special requirements when passing in providers; see Providers Within Modules for more details. In most cases, only root modules should define provider configurations, with all child modules obtaining their provider configurations from their parents.

» version: An Older Way to Manage Provider Versions

The version meta-argument specifies a version constraint for a provider, and works the same way as the version argument in a required_providers block. The version constraint in a provider configuration is only used if required_providers does not include one for that provider.

We do not recommend using the version argument in provider configurations. In Terraform 0.13 and later, version constraints should always be declared in the required_providers block.