All volumes are deleted when EC2 intance is deleted via terraform

Question

I am using a terraform template to create AWS resources. My count is 2, everything gets created as per plan, and, I am attaching a 2nd EBS volume of 1 GB to both machines, which is also happening well.

However, the only issue is when I try to delete one EC2 instance using the command below, both of the 2nd EBS volumes of 1 GB are getting destroyed. I checked they are connected on separate instances.

$ terraform destroy -target=aws_instance.jumpserver[1]
aws_vpc.main_vpc: Refreshing state... (ID: vpc-06b59734024ad6adc)
aws_key_pair.ProdKeypair: Refreshing state... (ID: ProdKeypair)
aws_security_group.sg_internet_facing: Refreshing state... (ID: sg-05a2739733f4f8a32)
aws_subnet.public_subnet: Refreshing state... (ID: subnet-0a8c6ea2718a44224)
aws_instance.jumpserver[1]: Refreshing state... (ID: i-05646d53baa34a988)

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  - destroy

Terraform will perform the following actions:

  - aws_ebs_volume.vol_generic_data[0]

  - aws_ebs_volume.vol_generic_data[1]

  - aws_instance.jumpserver[1]

  - aws_volume_attachment.generic_data_vol_att[0]

  - aws_volume_attachment.generic_data_vol_att[1]

This is the main.tf:

    # Define webserver inside the public subnets 
    resource "aws_instance" "jumpserver" {
      count                       = "${var.num_of_instances}"
      ami                         = "${var.ami}"
      instance_type               = "t2.micro"
      key_name                    = "${aws_key_pair.ProdKeypair.id}"
      subnet_id                   = "${aws_subnet.public_subnet.id}"
      vpc_security_group_ids      = ["${aws_security_group.sg_internet_facing.id}"]
      associate_public_ip_address = true
      source_dest_check           = false
      #   user_data = "${file("install.sh")}"
    
      root_block_device = {
        volume_type           = "gp2"
        volume_size           =  "8"  
        delete_on_termination = "${var.delete_on_termincation}"
      }
    
      tags {
        Name = "${format("jump-%01d",count.index+1)}"
      }
    
      provisioner "remote-exec" {
        inline = ["sudo apt-get  -y install python"]
    
        connection {
          type        = "ssh"
          user        = "ubuntu"
          private_key = "${file(var.private_key_path)}"
        }
      }
    }
    
    resource "aws_ebs_volume" "vol_generic_data" {
      size              = "1"
      count             = "${var.num_of_instances}"
      type              = "gp2"
      availability_zone = "${element(aws_instance.jumpserver.*.availability_zone, count.index)}"
    
     tags = {
        Name = "${format("jump-%01d",count.index+1)}"
      }
    }
    
    
    resource "aws_volume_attachment" "generic_data_vol_att" {
      device_name = "/dev/xvdf"
      volume_id   = "${element(aws_ebs_volume.vol_generic_data.*.id, count.index)}"
      instance_id = "${element(aws_instance.jumpserver.*.id, count.index)}"
      count       = "${var.num_of_instances}"
    }
    
    
    # Define webserver inside the private subnet
    resource "aws_instance" "backendserver" {
      ami                         = "${var.ami}"
      instance_type               = "t2.micro"
      key_name                    = "${aws_key_pair.ProdKeypair.id}"
      subnet_id                   = "${aws_subnet.private_subnet.id}"
      vpc_security_group_ids      = ["${aws_security_group.sg_backend.id}"]
      associate_public_ip_address = false
      source_dest_check           = false
      user_data                   = "${file("install.sh")}"
    
      tags {
        Name = "backendserver"
      }
    }

Answer 1

I could see some spelling mistakes in the below mentioned line, rest all are fine i think.

delete_on_termination = "${var.delete_on_termincation}"

Better you could avoid this line, This might be deleting the EBS when u terminating the ec2 instance. Skip this option and check.

Answer 2

There is an bug reported on TF AWS provider that is certainly related (terraform-provider-aws/issues/83). Unfortunately, there is no solution for it except waiting to see if the bug still exists with the config language improvements expected in TF 0.12.

What is your use case to delete this instance and ebs with terraform destroy -target=aws_instance.xxx[1] command? Do you want to recreate this instance in a second step or stay with only one instance?

What I would try as a workaround is tainting the instance and ebs volume you want to delete with terraform taint aws_instance.xxx.1 && terraform taint aws_ebs_volume.xxx.1. Then if you want to recreate them, just run terraform apply or if you want to stay with one instance run terraform apply -var 'count=1'