mutable / nixstrap

This was an internal tool made by the team to make bootable nixos setups

Nixstrap

Nixstrap is a GCP image that is designed to be deployed as an initial bootstrap, to pull in a NixOS closure stored in a separate binary cache. This improves bringing up new GCP instances, bringing it closer to updating an existing system.

Metadata

The information necessary for downloading the NixOS system closure is stored in instance metadata keys:

• nixstrap-system: the path of the NixOS closure, e.g. /nix/store/wj2y92z38gbkjdi68ipfbc5011hhlxj0-nixos-system-unnamed-20.09pre-git

• nixstrap-keys: A list of Ed25519 keys (in nix.conf format) that are to be trusted, e.g. cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=

• nixstrap-substituters: A list of additional substituters that will be queried for store paths, e.g. https://cache.nixos.org/

Once the installation is done, a key is set in the guest attributes of the instance, in nixstrap/status. If success, the install succeeded and the VM is running the NixOS system. If fail, something went wrong and the serial logs can probably be queried to see what happened.