Hello all! I've set up NixOS on AWS by booting into a NixOS AMI, then doing nixos-install onto a custom EBS volume. After that, I switched the boot device of my EC2 instance from the AMI-created temporary EBS volume to my new custom volume and booting the instance from it.

Now I have the AMI-created EBS volume still, although it's not attached to anything. I'd like to get rid of it. I think the cleanest way would be to detach the NixOS AMI from the EC2 instance. AFAIK I don't need the AMI anymore, since I have the OS installed to EBS. But I don't find a way to have an EC2 instance without an AMI!

Any advice on how to get rid of the AMI or its EBS volume?

Note that the AMI is and EBS volume already

e.g. if you’re using Terraform:

data "aws_ami" "nixos_arm64" {
  owners      = ["427812963091"]
  most_recent = true

  filter {
    name   = "name"
    values = ["nixos/24.05*"]
  }
  filter {
    name   = "architecture"
    values = ["arm64"] # or "x86_64"
  }
}

resource “aws_instance” “my_instance” {

  ami           = data.aws_ami.nixos_arm64.id
  instance_type = "t4g.nano"
  root_block_device {
    volume_size = 500
    volume_type = “io2”
  }

}

Will boot the NixOS AMI on an io2 EBS volume of 500GB size. NixOS will resize the partition and file system automatically on first boot

EC2 instance must have an associated AMI and Root Block Device. You cant detach it

What exactly are you trying ot do?

I want to install NixOS on an EBS volume that's decoupled from the instance. For example, if I delete the EC2 instance with the NixOS AMI, then the default 4 GB EBS volume gets deleted. I want to be able to replace the instance with something larger or smaller without losing my OS install.

set delete_on_termination to false. it will keep the volume around

AMIs are not installation media. They’re fully working operating system snapshots. I would not suggest installing the OS on a secondary EBS volume.

If you want to boot a new instance with the old volume you can take a snapshot of the volume and use that as the AMI for the new instance

You might need to clone the AMI into your own account first (e.g. using CloneImage)