github.com/iaas-resource-provision/iaas-rpc@v1.0.7-0.20211021023331-ed21f798c408/website/docs/language/providers/configuration.html.md

---
layout: "language"
page_title: "Provider Configuration - Configuration Language"
sidebar_current: "docs-config-providers"
description: "Learn how to set up providers, including how to use the alias meta-argument to specify multiple configurations for a single provider."
---

# 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](/docs/language/providers/requirements.html) 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
[The Module `providers` Meta-Argument](/docs/language/meta-arguments/module-providers.html)
and [Module Development: Providers Within Modules](/docs/language/modules/develop/providers.html).)

A provider configuration is created using a `provider` block:

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

The name given in the block header (`"google"` in this example) is the
[local name](/docs/language/providers/requirements.html#local-names) 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](/docs/language/expressions/index.html) 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](https://registry.terraform.io), 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:

- [`alias`, for using the same provider with different configurations for different resources][inpage-alias]
- [`version`, which we no longer recommend][inpage-versions] (use
  [provider requirements](/docs/language/providers/requirements.html) instead)

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

[inpage-alias]: #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:

```hcl
# 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"
}
```

To declare a configuration alias within a module in order to receive an
alternate provider configuration from the parent module, add the
`configuration_aliases` argument to that provider's `required_providers`
entry. The following example declares both the `mycloud` and
`mycloud.alternate` provider configuration names within the containing module:

```hcl
terraform {
  required_providers {
    mycloud = {
      source  = "mycorp/mycloud"
      version = "~> 1.0"
      configuration_aliases = [ mycloud.alternate ]
    }
  }
}
```

### 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:

```hcl
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:

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

Modules have some special requirements when passing in providers; see
[The Module `providers` Meta-Argument](/docs/language/meta-arguments/module-providers.html)
for more details. In most cases, only _root modules_ should define provider
configurations, with all child modules obtaining their provider configurations
from their parents.

<a id="provider-versions"></a>

## `version`: An Older Way to Manage Provider Versions

[inpage-versions]: #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](/docs/language/providers/requirements.html). The version
constraint in a provider configuration is only used if `required_providers`
does not include one for that provider.

**The `version` argument in provider configurations is deprecated.**
In Terraform 0.13 and later, version constraints should always be declared in
[the `required_providers` block](/docs/language/providers/requirements.html). The `version`
argument will be removed in a future version of Terraform.

-> **Note:** The `version` meta-argument made sense before Terraform 0.13, since
Terraform could only install providers that were distributed by HashiCorp. Now
that Terraform can install providers from multiple sources, it makes more sense
to keep version constraints and provider source addresses together.