on a tear with terraform

By | December 11, 2020

Imagine if you could write code that would set up your infrastructure on any cloud system and would not have change if you switch providers. This is the concept of infrastructure as code.

Terraform is one of the most popular tools to do this and will be the subject of this post. Let’s get started by installing Terraform and create a ngnix server.

Install terraform on the mac

Install and update it using the following commands.

brew tap hashicorp/tap
brew install hashicorp/tap/terraform
brew upgrade hashicorp/tap/terraform

Verify the installation

Verify that the installation worked by opening a new terminal session and listing Terraform’s available subcommands using terraform -help.

terraform -help
Usage: terraform [global options] <subcommand> [args]

The available commands for execution are listed below.
The primary workflow commands are given first, followed by
less common or more advanced commands.

Main commands:
  init          Prepare your working directory for other commands
  validate      Check whether the configuration is valid
  plan          Show changes required by the current configuration
  apply         Create or update infrastructure
  destroy       Destroy previously-created infrastructure

All other commands:
  console       Try Terraform expressions at an interactive command prompt
  fmt           Reformat your configuration in the standard style
  force-unlock  Release a stuck lock on the current workspace
  get           Install or upgrade remote Terraform modules
  graph         Generate a Graphviz graph of the steps in an operation
  import        Associate existing infrastructure with a Terraform resource
  login         Obtain and save credentials for a remote host
  logout        Remove locally-stored credentials for a remote host
  output        Show output values from your root module
  providers     Show the providers required for this configuration
  refresh       Update the state to match remote systems
  show          Show the current state or a saved plan
  state         Advanced state management
  taint         Mark a resource instance as not fully functional
  untaint       Remove the 'tainted' state from a resource instance
  version       Show the current Terraform version
  workspace     Workspace management

Global options (use these before the subcommand, if any):
  -chdir=DIR    Switch to a different working directory before executing the
                given subcommand.
  -help         Show this help output, or the help for a specified subcommand.
  -version      An alias for the "version" subcommand.

Add any subcommand to terraform <subcommand> -help to learn more about what it does and available options.

terraform init -help
Usage: terraform init [options] [DIR]

  Initialize a new or existing Terraform working directory by creating
  initial files, loading any remote state, downloading modules, etc.

  This is the first command that should be run for any new or existing
  Terraform configuration per machine. This sets up all the local data
  necessary to run Terraform that is typically not committed to version
  control.

  This command is always safe to run multiple times. Though subsequent runs
  may give errors, this command will never delete your configuration or
  state. Even so, if you have important information, please back it up prior
  to running this command, just in case.

  If no arguments are given, the configuration in this working directory
  is initialized.

Options:

  -backend=true        Configure the backend for this configuration.

  -backend-config=path This can be either a path to an HCL file with key/value
                       assignments (same format as terraform.tfvars) or a
                       'key=value' format. This is merged with what is in the
                       configuration file. This can be specified multiple
                       times. The backend type must be in the configuration
                       itself.

  -force-copy          Suppress prompts about copying state data. This is
                       equivalent to providing a "yes" to all confirmation
                       prompts.

  -from-module=SOURCE  Copy the contents of the given module into the target
                       directory before initialization.

  -get=true            Download any modules for this configuration.

  -get-plugins=true    Download any missing plugins for this configuration.

  -input=true          Ask for input if necessary. If false, will error if
                       input was required.

  -lock=true           Lock the state file when locking is supported.

  -lock-timeout=0s     Duration to retry a state lock.

  -no-color            If specified, output won't contain any color.

  -plugin-dir          Directory containing plugin binaries. This overrides all
                       default search paths for plugins, and prevents the 
                       automatic installation of plugins. This flag can be used
                       multiple times.

  -reconfigure         Reconfigure the backend, ignoring any saved
                       configuration.

  -upgrade=false       If installing modules (-get) or plugins (-get-plugins),
                       ignore previously-downloaded objects and install the
                       latest version allowed within configured constraints.

  -verify-plugins=true Verify the authenticity and integrity of automatically
                       downloaded plugins.

Enable tab completion

To enable autocomplete, run the following command and then restart your shell.

terraform -install-autocomplete

Lets have some fun with Terraform!

The next steps require Docker. If you are unfamiliar with Docker read our previous blog post don’t dock docker, and come back here once you installed it and played with it a little.

After you install Terraform and Docker on your local machine, start Docker Desktop.

open -a Docker

Create a ngnix server

Create a directory named terraform-docker-demo.

mkdir terraform-docker-demo
cd terraform-docker-demo

Create a new file using vim main.tf then press i and paste the following Terraform configuration. Then save the file by entering esc then :wq.

terraform {
  required_providers {
    docker = {
      source = "terraform-providers/docker"
    }
  }
}

provider "docker" {}

resource "docker_image" "nginx" {
  name         = "nginx:latest"
  keep_locally = false
}

resource "docker_container" "nginx" {
  image = docker_image.nginx.latest
  name  = "tutorial"
  ports {
    internal = 80
    external = 8080
  }
}

Enter cat main.tf to make sure the file has been updated.

Initialize the project, which downloads a plugin that allows Terraform to interact with Docker.

terraform init

Initializing the backend...

Initializing provider plugins...
- Finding latest version of terraform-providers/docker...
- Installing terraform-providers/docker v2.7.2...
- Installed terraform-providers/docker v2.7.2 (signed by HashiCorp)

Terraform has created a lock file .terraform.lock.hcl to record the provider
selections it made above. Include this file in your version control repository
so that Terraform can guarantee to make the same selections by default when
you run "terraform init" in the future.


Warning: Additional provider information from registry

The remote registry returned warnings for
registry.terraform.io/terraform-providers/docker:
- For users on Terraform 0.13 or greater, this provider has moved to
kreuzwerker/docker. Please update your source in required_providers.

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.

Provision the NGINX server container with apply. When Terraform asks you to confirm type yes and press ENTER. If you unable to pull an image from nginx:latest make sure you are logged into Docker Hub.

terraform apply

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # docker_container.nginx will be created
  + resource "docker_container" "nginx" {
      + attach           = false
      + bridge           = (known after apply)
      + command          = (known after apply)
      + container_logs   = (known after apply)
      + dns              = (known after apply)
      + dns_opts         = (known after apply)
      + entrypoint       = (known after apply)
      + exit_code        = (known after apply)
      + gateway          = (known after apply)
      + hostname         = (known after apply)
      + id               = (known after apply)
      + image            = (known after apply)
      + ip_address       = (known after apply)
      + ip_prefix_length = (known after apply)
      + ipc_mode         = (known after apply)
      + log_driver       = (known after apply)
      + log_opts         = (known after apply)
      + logs             = false
      + must_run         = true
      + name             = "tutorial"
      + network_data     = (known after apply)
      + read_only        = false
      + restart          = "no"
      + rm               = false
      + shm_size         = (known after apply)
      + start            = true
      + user             = (known after apply)
      + working_dir      = (known after apply)

      + ports {
          + external = 8000
          + internal = 80
          + ip       = "0.0.0.0"
          + protocol = "tcp"
        }
    }

  # docker_image.nginx will be created
  + resource "docker_image" "nginx" {
      + id           = (known after apply)
      + keep_locally = false
      + latest       = (known after apply)
      + name         = "nginx:latest"
    }

Plan: 2 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes 

Verify the existence of the NGINX container by visiting http://localhost:8080. Wow that was easy!

To stop the container, run terraform destroy.

$ terraform destroy

What is really cool about using terraform destroy is that all the docker containers, images, and networks are automatically deleted. This saves a lot of time.

In our next post, we will create real infrastructure in AWS.