This allows to build an SD installer of NixOS for AArch64 systems (including Raspberry Pis) using native AArch64 AWS EC2 spot instances. It should cost no more than a few cents to build a full-fledged img file, and the entire process with Packer takes less than 10 minutes.

Ensure your Packer install is up to date, then just run (in this directory):

packer build build.pkr.hcl

This will set everything up, (hopefully) build an image and download it. If everything worked, you should see towards the end of your output something like:

Image successfully built and downloaded as nixos-sd-image-20.03pre-git-aarch64-linux.img

By default, this will run on the us-east-2 region and it will use us-east-2a as the availability zone. To change this, run Packer as follows:

packer build -var 'region=us-east-1' -var 'availability_zone=us-east-1a' build.pkr.hcl

The Packer specification will:

• create a new spot request as follows:
  • latest Debian Buster AMI
  • a1.2xlarge instance with a cap of the current on-demand price, which has 8 threads and 16 GiB of RAM
  • 16 GiB of EBS storage
• wait until the spot request is fulfilled
• copy the docker and config folders and run.sh to the remote instance
• install the required dependencies and execute run.sh remotely.

Packer will take care of removing all the used resources when the script ends. To troubleshoot, pass the -debug -on-error=ask flags. See also Debugging.

Feel free to customize the build.pkr.hcl file as needed. It's using the experimental HCL specification of Packer.

Any changes to the configuration or Docker build files can also be done -- Packer won't clone another instance of this repo, it will use your local copy.