In my example, I am using the Paris region (eu-west-3) but what if I need to add new regions like Dublin (eu-west1) for instance !?

The above code will deploy an EC2 instance to a single region.

In order to seolve this problem, the first step to follow here, is finding the AMI we want to use (depending on the region) and then create a variable with the type “map”:

variable "my_ami" {
  type = "map"
  default = {
    eu-west-1 = "ami-f90a4880"
    eu-west-3 = "ami-0e55e373"
  }
  description = "I added only 2 regions: Paris and Dublin. You can use as many regions as you want."
}

According to the used region Terraform should create an EC2 machine with a different AMI.

This is done by changing the old AMI line by changing ami = "ami-0e55e373" to ami = "${lookup(var.my_ami, var.region)}" .

To test this, type terraform plan and you will get this output:

  + aws_instance.web
      id:                           <computed>
      ami:                          "ami-0e55e373"
      associate_public_ip_address:  <computed>
      availability_zone:            <computed>
      ebs_block_device.#:           <computed>
      ephemeral_block_device.#:     <computed>
      get_password_data:            "false"
      instance_state:               <computed>
      instance_type:                "t1.micro"
      ipv6_address_count:           <computed>
      ipv6_addresses.#:             <computed>
      key_name:                     <computed>
      network_interface.#:          <computed>
      network_interface_id:         <computed>
      password_data:                <computed>
      placement_group:              <computed>
      primary_network_interface_id: <computed>
      private_dns:                  <computed>
      private_ip:                   <computed>
      public_dns:                   <computed>
      public_ip:                    <computed>
      root_block_device.#:          <computed>
      security_groups.#:            <computed>
      source_dest_check:            "true"
      subnet_id:                    <computed>
      tags.%:                       "1"
      tags.Name:                    "eralabs"
      tenancy:                      <computed>
      volume_tags.%:                <computed>
      vpc_security_group_ids.#:     <computed>

If you manually change the region to eu-west-1 , you will notice that terraform plan will use the other AMI:

  + aws_instance.web
      id:                           <computed>
      ami:                          "ami-f90a4880"
      associate_public_ip_address:  <computed>
      availability_zone:            <computed>
      ebs_block_device.#:           <computed>
      ephemeral_block_device.#:     <computed>
      get_password_data:            "false"
      instance_state:               <computed>
      instance_type:                "t1.micro"
      ipv6_address_count:           <computed>
      ipv6_addresses.#:             <computed>
      key_name:                     <computed>
      network_interface.#:          <computed>
      network_interface_id:         <computed>
      password_data:                <computed>
      placement_group:              <computed>
      primary_network_interface_id: <computed>
      private_dns:                  <computed>
      private_ip:                   <computed>
      public_dns:                   <computed>
      public_ip:                    <computed>
      root_block_device.#:          <computed>
      security_groups.#:            <computed>
      source_dest_check:            "true"
      subnet_id:                    <computed>
      tags.%:                       "1"
      tags.Name:                    "eralabs"
      tenancy:                      <computed>
      volume_tags.%:                <computed>
      vpc_security_group_ids.#:     <computed>