Providers explored for fun and profit.

This one is all about Terraform providers. Where do they reside and where are they retrieved from? Let's start with how you specify a provider.

You can specify a provider implicitly, explicitly, and bound it by version. Check out the three example folders I have set up.

But wait, there's more!

You can use the public registry for Terraform and have done with it. There's a ton of providers there and it's pretty easy to reference them. You simply add the full provider's source address, like registry.terraform.io/hashicorp/azurerm. Oh course if you're using registry.terraform.io you don't actually need to specify that part.

You can host your own private registry by setting up one according to the provider registry protocol. I'm not going to go into too much detail, but basically the provider should be found at an address composed of hostname/namespace/type. If you're implementing this sucker, there is a laundry list of operations you need to support, like listing available versions and finding a provider package. It's fun!

This is only if you wanted to host your own private registry. If you're simply trying to keep a local copy, you've got options.

1. Configure provider_installation settings in your CLI configuration block
2. Filesystem mirror - A local mirror holding copies of your plugins. You provide the path and what domains to include and exclude.
3. Network mirror - Kind of the same as the local filesystem mirror, but on the network using HTTPS
4. Direct - Pulls the information from the normal remote registry. You provider include and exclude.
5. Implied local mirror - Terraform sets a local file mirror based on the operating system you are using automatically. It doesn't populate those directories, but it will use what it finds there.
6. Cache - the optional plugin cache is set by adding a plugin_cache_dir setting in the CLI config file. Once you've configured it and run terraform init, the files will be copied to the cache location. Terraform will try to use symlinks to prevent multiple instances of a file.
7. Plugin directory - You can manually specify a plugin directory during initialization. This overrides everything and it probably a bad idea. Don't do this.