Terraform Example

This example is just enough to get started with Terraform.

Terraform Basics

Infrastructure as Code

Setup

Download terraform zip file from terraform.io Run unzip terraform to unzip the zip file Run mv terraform /usr/local/bin move it to the user bin folder as this folder is already in the PATH and you can invoke terraform from anywhere.

Terraform scripts are inside .tf file Terraform uses declarative language called HCL - Harshicorp Configuration Language (HCL is happy medium of JSON and YAML)

Basic Commands

terraform init will dowload the provider

terraform apply is idempotent.

To delete terraform destroy

To automatically approve (Without hitting yes everytime)

terraform apply --auto-approve

Never touch state file unless you are very sure what you are doing. (.tfstate)

To view the items in the current state : terraform state list

Example:

$ terraform state list

aws_eip.one
aws_instance.web_server_instance
aws_internet_gateway.prod_igw
aws_network_interface.web_server_nic
aws_route_table.prod_route_table
aws_route_table_association.prod_vpc_subnet_1_to_prod_route_table
aws_security_group.allow_web
aws_subnet.prod_vpc_subnet_1
aws_vpc.prod_vpc

To view specific details about a particular item terraform state show <resourcename>

Example:

~$ terraform state show aws_vpc.prod_vpc

# aws_vpc.prod_vpc:
resource "aws_vpc" "prod_vpc" {
    arn                              = "arn:aws:ec2:us-east-1:053500961007:vpc/vpc-0d96765da99979939"
    assign_generated_ipv6_cidr_block = false
    cidr_block                       = "10.0.0.0/16"
    default_network_acl_id           = "acl-0d78bdc962af760d9"
    default_route_table_id           = "rtb-0de67d63128bb8bd5"
    default_security_group_id        = "sg-02910956310a3e3f4"
    dhcp_options_id                  = "dopt-4b771f31"
    enable_classiclink               = false
    enable_classiclink_dns_support   = false
    enable_dns_hostnames             = false
    enable_dns_support               = true
    id                               = "vpc-0d96765da99979939"
    instance_tenancy                 = "default"
    main_route_table_id              = "rtb-0de67d63128bb8bd5"
    owner_id                         = "053500961007"
    tags                             = {
        "Name"    = "prod_vpc"
        "Warning" = "Created by terraform. Dont alter or delete manually"
    }
    tags_all                         = {
        "Name"    = "prod_vpc"
        "Warning" = "Created by terraform. Dont alter or delete manually"
    }
}

To output the state details when applying use the output

terraform output

If you are in production you dont want to use the output command. Instead try terraform refresh which will grab all the output statements and print out for us.

To delete/apply just one resource out of the list use the terraform target.

Example: This will destroy the webserve EC2 instance alone and refresh the state. terraform destroy -target aws_instance.web_server_instance This will just create the EC2 instance and refresh state terraform apply -target aws_instance.web_server_instance

Variables

variable "variable_name" {
description =""
default =""
type =string
}

Terraform supports various types. (Refer documentation) Variable values can be either keyed in , or passed as command line argument or be supplied from a .tfvars file.

Example: terraform apply -var-file example.tfvars (If you name the file as terraform.tfvars then you dont have to specify the file name)

This Project details below:

1. Create a VPC

2. Create an Internet Gateway

3. Create a Custom Route Table

4. Create a subnet

5. Associate the subnet from Step 4 with a Route Table

6. Create a Security Group to allow ports 22,80 and 443

7. Create a network interface with an ip in the subnet that was created in step 4

8. Assign Elastic IP to the Network Interface created in Step 7

9. Create an Ubuntu server and install/enable Apache2

10. Output properties of resources created.

NOTE: For your screts, create a secrets.tfvars file and provide values Example below

access_key = "ABCDEFGHIJKLMNOPQ"
secret_key = "AAsWlmnqweerd23rfdffj34113jfsj34KDB"

When you apply you have to specify terraform apply -var-file=./secrtes.tfvars