github.com/trawler/terraform@v0.10.8-0.20171106022149-4b1c7a1d9b48/website/docs/configuration/providers.html.md

---
layout: "docs"
page_title: "Configuring Providers"
sidebar_current: "docs-config-providers"
description: |-
  Providers are responsible in Terraform for managing the lifecycle of a resource: create, read, update, delete.
---

# Provider Configuration

Providers are responsible in Terraform for managing the lifecycle
of a [resource](/docs/configuration/resources.html): create,
read, update, delete.

Every resource in Terraform is mapped to a provider based
on longest-prefix matching. For example the `aws_instance`
resource type would map to the `aws` provider (if that exists).

Most providers require some sort of configuration to provide
authentication information, endpoint URLs, etc. Provider configuration
blocks are a way to set this information globally for all
matching resources.

This page assumes you're familiar with the
[configuration syntax](/docs/configuration/syntax.html)
already.

## Example

A provider configuration looks like the following:

```hcl
provider "aws" {
  access_key = "foo"
  secret_key = "bar"
  region     = "us-east-1"
}
```

## Description

The `provider` block configures the provider of the given `NAME`.
Multiple provider blocks can be used to configure multiple providers.

Terraform matches providers to resources by matching two criteria.
Both criteria must be matched for a provider to manage a resource:

- They must share a common prefix. Longest matching prefixes are tried first.
  For example, `aws_instance` would choose the `aws` provider.

- The provider must report that it supports the given resource type. Providers
  internally tell Terraform the list of resources they support.

Within the block (the `{ }`) is configuration for the resource.
The configuration is dependent on the type, and is documented
[for each provider](/docs/providers/index.html).

## Initialization

Each time a new provider is added to configuration -- either explicitly via
a `provider` block or by adding a resource from that provider -- it's necessary
to initialize that provider before use. Initialization downloads and installs
the provider's plugin and prepares it to be used.

Provider initialization is one of the actions of `terraform init`. Running
this command will download and initialize any providers that are not already
initialized.

For more information, see
[the `terraform init` command](/docs/commands/init.html).

## Provider Versions

Providers are released on a separate rhythm from Terraform itself, and thus
have their own version numbers. For production use, it is recommended to
constrain the acceptable provider versions via configuration, to ensure that
new versions with breaking changes will not be automatically installed by
`terraform init` in future.

When `terraform init` is run _without_ provider version constraints, it
prints a suggested version constraint string for each provider:

```
The following providers do not have any version constraints in configuration,
so the latest version was installed.

To prevent automatic upgrades to new major versions that may contain breaking
changes, it is recommended to add version = "..." constraints to the
corresponding provider blocks in configuration, with the constraint strings
suggested below.

* provider.aws: version = "~> 1.0"
```

To constrain the provider version as suggested, add a `version` argument to
the provider configuration block:

```hcl
provider "aws" {
  version = "~> 1.0"

  access_key = "foo"
  secret_key = "bar"
  region     = "us-east-1"
}
```

This special argument applies to _all_ providers.
[`terraform providers`](/docs/commands/providers.html) can be used to
view the specified version constraints for all providers used in the
current configuration.

When `terraform init` is re-run with providers already installed, it will
use an already-installed provider that meets the constraints in preference
to downloading a new version. To upgrade to the latest acceptable version
of each provider, run `terraform init -upgrade`. This command also upgrades
to the latest versions of all Terraform modules.

## Multiple Provider Instances

You can define multiple instances of the same provider in order to support
multiple regions, multiple hosts, etc. The primary use case for this is
utilizing multiple cloud regions. Other use cases include targeting multiple
Docker hosts, multiple Consul hosts, etc.

To define multiple provider instances, repeat the provider configuration
multiple times, but set the `alias` field and name the provider. For
example:

```hcl
# The default provider
provider "aws" {
  # ...
}

# West coast region
provider "aws" {
  alias  = "west"
  region = "us-west-2"
}
```

After naming a provider, you reference it in resources with the `provider`
field:

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

  # ...
}
```

If a provider isn't specified, then the default provider configuration
is used (the provider configuration with no `alias` set). The value of the
`provider` field is `TYPE.ALIAS`, such as "aws.west" above.

## Syntax

The full syntax is:

```text
provider NAME {
  CONFIG ...
  [alias = ALIAS]
}
```

where `CONFIG` is:

```text
KEY = VALUE

KEY {
  CONFIG
}
```

## Interpolation
Providers support [interpolation syntax](/docs/configuration/interpolation.html) allowing dynamic configuration at run time.

```hcl
provider "aws" {
  region = "${var.aws_region}"
}
```

An exception to this is the special `version` attribute that applies to all `provider` blocks for specifying [provider versions](#provider-versions); interpolation is not supported for provider versions since provider compatibility is a property of the configuration rather than something dynamic, and provider plugin installation happens too early for variables to be resolvable in this context.

-> **NOTE:** Because providers are one of the first things loaded when Terraform parses the graph, it is not possible to
use the output from modules or resources as inputs to the provider. At this time, only
[variables](/docs/configuration/variables.html) and [data sources](/docs/configuration/data-sources.html), including
[remote state](/docs/providers/terraform/d/remote_state.html) may be used in an interpolation inside a provider stanza.
[Local values](/docs/configuration/locals.html) can also be used, but currently may fail when running `terraform destroy`.


## Third-party Plugins

At present Terraform can automatically install only the providers distributed
by HashiCorp. Third-party providers can be manually installed by placing
their plugin executables in one of the following locations depending on the
host operating system:

* On Windows, in the sub-path `terraform.d/plugins` beneath your user's
  "Application Data" directory.
* On all other systems, in the sub-path `.terraform.d/plugins` in your
  user's home directory.

`terraform init` will search this directory for additional plugins during
plugin initialization.

The naming scheme for provider plugins is `terraform-provider-NAME-vX.Y.Z`,
and Terraform uses the name to understand the name and version of a particular
provider binary. Third-party plugins will often be distributed with an
appropriate filename already set in the distribution archive so that it can
be extracted directly into the plugin directory described above.

## Provider Plugin Cache

By default, `terraform init` downloads plugins into a subdirectory of the
working directory so that each working directory is self-contained. As a
consequence, if you have multiple configurations that use the same provider
then a separate copy of its plugin will be downloaded for each configuration.

Given that provider plugins can be quite large (on the order of hundreds of
megabytes), this default behavior can be inconvenient for those with slow
or metered Internet connections. Therefore Terraform optionally allows the
use of a local directory as a shared plugin cache, which then allows each
distinct plugin binary to be downloaded only once.

To enable the plugin cache, use the `plugin_cache_dir` setting in
[the CLI configuration file](https://www.terraform.io/docs/commands/cli-config.html).
For example:

```hcl
# (Note that the CLI configuration file is _not_ the same as the .tf files
#  used to configure infrastructure.)

plugin_cache_dir = "$HOME/.terraform.d/plugin-cache"
```

Please note that on Windows it is necessary to use forward slash separators
(`/`) rather than the conventional backslash (`\`) since the configuration
file parser considers a backslash to begin an escape sequence.

Setting this in the configuration file is the recommended approach for a
persistent setting. Alternatively, the `TF_PLUGIN_CACHE_DIR` environment
variable can be used to enable caching or to override an existing cache
directory within a particular shell session:

```bash
export TF_PLUGIN_CACHE_DIR="$HOME/.terraform.d/plugin-cache"
```

When a plugin cache directory is enabled, the `terraform init` command will
still access the plugin distribution server to obtain metadata about which
plugins are available, but once a suitable version has been selected it will
first check to see if the selected plugin is already available in the cache
directory. If so, the already-downloaded plugin binary will be used.

If the selected plugin is not already in the cache, it will be downloaded
into the cache first and then copied from there into the correct location
under your current working directory.

When possible, Terraform will use hardlinks or symlinks to avoid storing
a separate copy of a cached plugin in multiple directories. At present, this
is not supported on Windows and instead a copy is always created.

The plugin cache directory must *not* be the third-party plugin directory
or any other directory Terraform searches for pre-installed plugins, since
the cache management logic conflicts with the normal plugin discovery logic
when operating on the same directory.

Please note that Terraform will never itself delete a plugin from the
plugin cache once it's been placed there. Over time, as plugins are upgraded,
the cache directory may grow to contain several unused versions which must be
manually deleted.