Deploy NGINX container using Terraform

Create Terraform Config

Terraform works based on a configuration file, in this case config.tf. The configuration defines your infrastructure, in this instance as providers and resources.

A provider is an abstract way of handling the underlying infrastructure and responsible for managing the lifecycle of a resource.

A resource are components of your infrastructure, for example a container or image.

The editor allows us to write the config.tf file. The first section defines a docker host where we want to apply our configuration too.

provider "docker" {
  host = "tcp://docker:2345/"
}

We can now start defining the resources of our infrastructure. The first resource is our Docker image. A resource has two parameters, one is a TYPE and second a NAME. The type is docker_image and the name is nginx. Within the block we define the name and tag of the Docker Image.

resource "docker_image" "nginx" {
  name = "nginx:1.11-alpine"
}

We can define our container resource. The resource type is docker_container and name as nginx-server. Within the block we set the resource parameters. We can reference other resources, such as a the image.

resource "docker_container" "nginx-server" {
  name = "nginx-server"
  image = "${docker_image.nginx.latest}"
  ports {
    internal = 80
  }
  volumes {
    container_path  = "/usr/share/nginx/html"
    host_path = "/home/scrapbook/tutorial/www"
    read_only = true
  }
}

Plan Terraform Actions

Once the configuration has been defined we need to create an execution plan. Terraform describes the actions required to achieve the desired state. The plan can be saved using -out. We'll apply the execution plan in the next step.

To create a plan, use the CLI

terraform plan -out config.tfplan

The output of the command indicates the changes. In this case, you'll see a _+ dockercontainer.nginx-server and _+ dockerimage.nginx to highlight adding the new resources. Finally a summary of Plan: 2 to add, 0 to change, 0 to destroy.

Apply Terraform Actions

Once the plan has been created we need to apply it to reach our desired state.

Using the CLI, terraform will pull any images required and launch new containers.

terraform apply

The output will indicate the changes and the resulting configuration.

Inspecting Infrastructure

You can use the Docker CLI to view the changes and see the newly launched container.

docker ps

You can inspect this in future using the terraform CLI

terraform show

Updating Infrastructure

As our infrastructure grows and changes, terraform will manage and ensure we always have our defined desired state.

We can change our container to launch two instances, each with different names.

resource "docker_container" "nginx-server" {
  count = 2
  name = "nginx-server-${count.index+1}"
  image = "${docker_image.nginx.latest}"
  ports {
    internal = 80
  }
  volumes {
    container_path  = "/usr/share/nginx/html"
    host_path = "/home/scrapbook/tutorial/www"
    read_only = true
  }
}

If we create a plan you will see the actions Terraform will need to apply to adapt our infrastructure to match our configuration.

terraform plan -out config.tfplan

The plan will outline the changes. Because we're changing the name and adding a resource we'll see Plan: 1 to add, 1 to change, 0 to destroy.

In the details it will explain that changing a container name forces the resource to be recreated name: "nginx-server" => "nginx-server-1" (forces new resource) along with adding the new container _+ dockercontainer.nginx-server.1

We can then apply the plan as we did in the previous step.

terraform apply

cd <directory>	Change directory
ls	List directory
echo 'contents' > <file>	Write contents to a file
cat <file>	Output contents of file

i	In Command Mode	Change into Insert Mode, you can now insert and edit text in the file
esc	In Insert Mode	Change into Command Mode, you can now execute commands
:wq	In Command Mode	Save and Exit

Welcome!

Congratulations!

You've completed the scenario!

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