Day 62 - Automating Docker Containers with Terraform!

What You’ll Learn

Understanding Terraform Blocks and Resources.
Using Terraform to pull an Nginx Docker image and deploy a Docker container.
Running the setup step-by-step with appropriate commands.

Step-by-Step Tasks

Task 01: Set Up Terraform with the Docker Provider

Terraform needs to know which provider to use. This is specified using the required_providers block in your main.tf file.

Create a main.tf File
Start by creating a Terraform configuration file:

 mkdir terraform-docker-setup
 cd terraform-docker-setup
 touch main.tf

Add the Terraform Block
This block tells Terraform to use the Docker provider plugin:
```
 terraform {
   required_providers {
     docker = {
       source  = "kreuzwerker/docker"  # Specify provider source
       version = "~> 2.21.0"          # Compatible provider version
     }
   }
 }
```
Note:
- kreuzwerker/docker refers to the plugin location on Terraform’s registry.
- The version ~> 2.21.0 ensures compatibility with the latest versions of the Docker provider plugin.
Add the Provider Block
The provider block configures the Docker provider:
```
 provider "docker" {}
```
Run Terraform Init
Initialize the Terraform working directory to download the required provider:
```
 terraform init
```
Expected Output:
- Terraform will download the Docker provider plugin.

You can use this script to run nginx: Summarized

terraform {
  required_providers {
    docker = {
      source  = "kreuzwerker/docker"  # Specify provider source
      version = "~> 2.21.0"          # Compatible provider version
    }
  }
}

provider "docker" {}

resource "docker_image" "nginx" {
  name         = "nginx:latest"  # Specify the image name
  keep_locally = false           # Do not keep the image locally if not in use
}

resource "docker_container" "nginx" {
  image = docker_image.nginx.image_id  # Use the correct attribute for the image ID
  name  = "tutorial"

  ports {
    internal = 80
    external = 80
  }
}

This script will make you run nginx in your localhost:80 web browser

Commands used for execution: terraform init
terraform plan
terraform apply

Task 02: Create Resource Blocks for Nginx

Now you will define two resource blocks:

One for pulling the Nginx Docker image.
Another for running the Nginx container.

Step 1: Pull the Nginx Docker Image

Add the following resource block to your main.tf file:

resource "docker_image" "nginx" {
  name         = "nginx:latest"  # Specify the image name
  keep_locally = false           # Do not keep the image locally if not in use
}

Explanation:

docker_image is the resource type for Docker images.
nginx is the logical name you give to this resource.
name specifies the image to pull from Docker Hub.
keep_locally = false ensures that unused images are removed.

Step 2: Create a Docker Container for Nginx

Now add this block to create an Nginx container:

resource "docker_container" "nginx" {
  image = docker_image.nginx.latest  # Use the pulled Nginx image
  name  = "tutorial"                 # Container name

  ports {
    internal = 80  # Port exposed inside the container
    external = 80  # Port mapped to your host machine
  }
}

Explanation:

docker_container is the resource type for containers.
nginx is the logical name of the resource.
image references the latest Nginx image you just pulled.
ports maps port 80 from the container to port 80 on your local machine.

Task 03: Apply Terraform Configuration

Run Terraform Plan
Verify the configuration and preview the changes:
```
 terraform plan
```
Apply the Configuration
Deploy the Nginx container using Terraform:
```
 terraform apply
```
Expected Behavior:
- Terraform will pull the Nginx image.
- Terraform will run a container named tutorial exposing port 80.
Verify the Container
Check if the container is running:
```
 sudo docker ps
```
Expected Output:
You should see the container with the name tutorial running and mapped to port 80.
Test the Nginx Setup
Open a browser and visit http://localhost:80. You should see the default Nginx welcome page. 🎉

Optional: Docker Installation Commands

If Docker is not installed on your machine, run the following: this is for linux ubuntu, for windows you can follow different steps.

sudo apt-get update
sudo apt-get install docker.io
sudo systemctl start docker
sudo systemctl enable docker
sudo chown $USER /var/run/docker.sock  # Grant Docker permissions to your user

Verify the installation: You can verify in your VS-code terminal also.

docker --version
docker ps