Terraform: How to read the volume ID of one instance? - amazon-web-services

Question

I create instances with a default CentOS 7 AMI. This AMI creates automatically a volume and attached to the instance. Is it possible to read thats volume ID using terraform? I create the instance using the next code:
resource "aws_instance" "DCOS-master3" {
ami = "${var.aws_centos_ami}"
availability_zone = "eu-west-1b"
instance_type = "t2.medium"
key_name = "${var.aws_key_name}"
security_groups = ["${aws_security_group.bastion.id}"]
associate_public_ip_address = true
private_ip = "10.0.0.13"
source_dest_check = false
subnet_id = "${aws_subnet.eu-west-1b-public.id}"
tags {
Name = "master3"
}
}

Answer 1

You won't be able to extract EBS details from aws_instance since it's AWS side that provides an EBS volume to the resource.
But you can define a EBS data source with some filter.
data "aws_ebs_volume" "ebs_volume" {
most_recent = true
filter {
name = "attachment.instance-id"
values = ["${aws_instance.DCOS-master3.id}"]
}
}
output "ebs_volume_id" {
value = "${data.aws_ebs_volume.ebs_volume.id}"
}
You can refer EBS filters here:
http://docs.aws.amazon.com/cli/latest/reference/ec2/describe-volumes.html

Answer 2

You can: aws_instance.DCOS-master3.root_block_device.0.volume_id
As described in Terraform docs:
For any root_block_device and ebs_block_device the volume_id is exported. e.g. aws_instance.web.root_block_device.0.volume_id

Answer 3

output "volume-id-C" {
description = "root volume-id"
#get the root volume id form the instance
value = element(tolist(data.aws_instance.DCOS-master3.root_block_device.*.volume_id),0)
}
output "volume-id-D" {
description = "ebs-volume-id"
#get the 1st esb volume id form the instance
value = element(tolist(data.aws_instance.DCOS-master3.ebs_block_device.*.volume_id),0)
}

Answer 4

You can get the volume name of an aws_instance like this:
output "instance" {
value = aws_instance.ec2_instance.volume_tags["Name"]
}
And you can set it as follows:
resource "aws_instance" "ec2_instance" {
ami = var.instance_ami
instance_type = var.instance_type
key_name = var.instance_key
...
tags = {
Name = "${var.server_name}_${var.instance_name[count.index]}"
}
volume_tags = {
Name = "local_${var.instance_name[count.index]}"
}
}