terraform/tools/terraform-bundle/README.md

# terraform-bundle

`terraform-bundle` is a helper program to create "bundle archives", which are
zip files that contain both a particular version of Terraform and a number
of provider plugins.

Normally `terraform init` will download and install the plugins necessary to
work with a particular configuration, but sometimes Terraform is deployed in
a network that, for one reason or another, cannot access the official
plugin repository for automatic download.

`terraform-bundle` provides an alternative, by allowing the auto-download
process to be run out-of-band on a separate machine that _does_ have access
to the repository. The result is a zip file that can be extracted onto the
target system to install both the desired Terraform version and a selection
of providers, thus avoiding the need for on-the-fly plugin installation.

## Building

To build `terraform-bundle` from source, set up a Terraform development
environment per [Terraform's own README](../../README.md) and then install
this tool from within it:

```
$ go install ./tools/terraform-bundle
```

This will install `terraform-bundle` in `$GOPATH/bin`, which is assumed by
the rest of this README to be in `PATH`.

## Usage

`terraform-bundle` uses a simple configuration file to define what should
be included in a bundle. This is designed so that it can be checked into
version control and used by an automated build and deploy process.

The configuration file format works as follows:

```hcl
terraform {
  # Version of Terraform to include in the bundle. An exact version number
  # is required.
  version = "0.10.0"
}

# Define which provider plugins are to be included
providers {
  # Include the newest "aws" provider version in the 1.0 series.
  aws = ["~> 1.0"]

  # Include both the newest 1.0 and 2.0 versions of the "google" provider.
  # Each item in these lists allows a distinct version to be added. If the
  # two expressions match different versions then _both_ are included in
  # the bundle archive.
  google = ["~> 1.0", "~> 2.0"]
}

```

The `terraform` block defines which version of Terraform will be included
in the bundle. An exact version is required here.

The `providers` block defines zero or more providers to include in the bundle
along with core Terraform. Each attribute in this block is a provider name,
and its value is a list of version constraints. For each given constraint,
`terraform-bundle` will find the newest available version matching the
constraint and include it in the bundle.

It is allowed to specify multiple constraints for the same provider, in which
case multiple versions can be included in the resulting bundle. Each constraint
string given results in a separate plugin in the bundle, unless two constraints
resolve to the same concrete plugin.

Including multiple versions of the same provider allows several configurations
running on the same system to share an installation of the bundle and to
choose a version using version constraints within the main Terraform
configuration. This avoids the need to upgrade all configurations to newer
versions in lockstep.

After creating the configuration file, e.g. `terraform-bundle.hcl`, a bundle
zip file can be produced as follows:

```
$ terraform-bundle package terraform-bundle.hcl
```

By default the bundle package will target the operating system and CPU
architecture where the tool is being run. To override this, use the `-os` and
`-arch` options. For example, to build a bundle for on-premises Terraform
Enterprise:

```
$ terraform-bundle package -os=linux -arch=amd64 terraform-bundle.hcl
```

The bundle file is assigned a name that includes the core Terraform version
number, a timestamp to the nearest hour of when the bundle was built, and the
target OS and CPU architecture. It is recommended to refer to a bundle using
this composite version number so that bundle archives can be easily
distinguished from official release archives and from each other when multiple
bundles contain the same core Terraform version.

## Provider Resolution Behavior

Terraform's provider resolution behavior is such that if a given constraint
can be resolved by any plugin already installed on the system it will use
the newest matching plugin and not attempt automatic installation.

Therefore if automatic installation is not desired, it is important to ensure
that version constraints within Terraform configurations do not exclude all
of the versions available from the bundle. If a suitable version cannot be
found in the bundle, Terraform _will_ attempt to satisfy that dependency by
automatic installation from the official repository.

To disable automatic installation altogether -- and thus cause a hard failure
if no local plugins match -- the `-plugin-dir` option can be passed to
`terraform init`, giving the directory into which the bundle was extracted.
The presence of this option overrides all of the normal automatic discovery
and installation behavior, and thus forces the use of only the plugins that
can be found in the directory indicated.

The downloaded provider archives are verified using the same signature check
that is used for auto-installed plugins, using Hashicorp's release key. At
this time, the core Terraform archive itself is _not_ verified in this way;
that may change in a future version of this tool.

## Installing a Bundle in On-premises Terraform Enterprise

If using a private install of Terraform Enterprise in an "air-gapped"
environment, this tool can produce a custom _tool package_ for Terraform, which
includes a set of provider plugins along with core Terraform.

To create a suitable bundle, use the `-os` and `-arch` options as described
above to produce a bundle targeting `linux_amd64`. You can then place this
archive on an HTTP server reachable by the Terraform Enterprise hosts and
install it as per
[Managing Tool Versions](https://github.com/hashicorp/terraform-enterprise-modules/blob/master/docs/managing-tool-versions.md).

After choosing the "Add Tool Version" button, be sure to set the Tool to
"terraform" and then enter as the Version the generated bundle version from
the bundle filename, which will be of the form `N.N.N-bundleYYYYMMDDHH`.
Enter the URL at which the generated bundle archive can be found, and the
SHA256 hash of the file which can be determined by running the tool
`sha256sum` with the given file.

The new bundle version can then be selected as the Terraform version for
any workspace. When selected, configurations that require only plugins
included in the bundle will run without trying to auto-install.

Note that the above does _not_ apply to Terraform Pro, or to Terraform Premium
when not running a private install. In these packages, Terraform versions
are managed centrally across _all_ organizations and so custom bundles are not
supported.

For more information on the available Terraform Enterprise packages, see
[the Terraform product site](https://www.hashicorp.com/products/terraform/).