What are Blocks and Resources in Terraform??
Blocks: Blocks define different parts of your Terraform configuration. The main block types are:
Provider Blocks: Provider blocks configure a specific cloud provider for Terraform to use. For example, an AWS provider block would look like:
provider "aws" {
region = "us-east-1"
access_key = "..."
secret_key = "..."
}
This configures Terraform to use AWS as the cloud provider with the specified region, access key, and secret key.
Resource Blocks: Resource blocks define the actual infrastructure objects that Terraform will create. For example:
resource "aws_instance" "web" {
ami = "ami-1234"
instance_type = "t2.micro"
}
This defines an AWS EC2 instance resource named "web".
Variable Blocks: Variable blocks define variables that can be reused in your configuration. This allows flexibility and reusability. For example:
variable "ami_id" {
description = "The AMI ID to use for the EC2 instance"
}
Output Blocks: Output blocks define values that are output after running terraform apply. For example:
output "instance_id" {
value = "${aws_instance.web.id}"
}
This will output the ID of the EC2 instance after creation.
Resources: Resources represent the actual infrastructure objects that will be created. You define resources using resource blocks, as shown above. Common resource types are:
EC2 instances
S3 buckets
Load balancers
Virtual machines
When you run terraform apply, Terraform will provision the resources you've defined.
In summary, blocks configure different parts of your Terraform template, while resources represent the actual infrastructure objects that will be created when you apply your configuration.
Task-01: Create a Terraform script with Blocks and Resources
terraform {
required_providers {
docker = {
source = "kreuzwerker/docker"
version = "~> 2.21.0"
}
}
}
This is a Terraform configuration block that specifies a required provider for the docker resource type. The provider is defined using the kreuzwerker/docker source and version ~> 2.21.0.
The required_providers block is used to declare the minimum version of a provider required by the Terraform configuration. In this case, the docker provider with version 2.21.0 or greater is required to run the configuration. If the provider is not installed, Terraform will automatically download and install the provider at the specified version.
Provider Block
The provider block configures the specified provider, in this case, docker. A provider is a plugin that Terraform uses to create and manage your resources.
provider "docker" {}
Resource
Use resource blocks to define components of your infrastructure. A resource might be a physical or virtual component such as a Docker container, or it can be a logical resource such as a Heroku application.
Resource blocks have two strings before the block: the resource type and the resource name. In this example, the first resource type is docker_image and the name is Nginx.
Task-02: Create a resource Block for an nginx docker image
resource "docker_image" "nginx" {
name = "nginx:latest"
keep_locally = false
}
- Create a resource Block for running a docker container for nginx
resource "docker_container" "nginx" {
image = docker_image.nginx.latest
name = "tutorial"
ports {
internal = 80
external = 80
}
}
After you’ve created a Terraform configuration file (with a.tf extension), use the Terraform commands listed below to provision and manage your infrastructure:
terraform init : Downloads and installs any required providers and modules, initializes the backend, and downloads any necessary plugins in a new or existing Terraform working directory.
terraform init
Note: In case Docker is not installed use below commands.
sudo apt-get install docker.io
sudo docker ps
sudo chown $USER /var/run/docker.sock
Check docker container is created using the below command:
docker ps
terraform plan: The output of terraform plan gives a summary of the infrastructure modifications that will be made, such as creating, changing, or eliminating resources. It also displays any issues or warnings that must be handled prior to implementing the modifications.
terraform plan
terraform apply: When you run Terraform apply, Terraform generates or adjusts the configuration files’ resources to match the intended state. It also updates the state file to reflect the infrastructure changes. If Terraform encounters any faults or warnings during the application process, it will prompt you to confirm whether or not to proceed with the changes.
terraform apply
Browse public IP address, you can see the nginx default page.
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