Install nixos on equinix-metal system over iPXE by first booting into Ubuntu live disk available over https://boot.netboot.xyz . I needed to go via the Ubuntu live disk since the NixOS network install does not work on equinix-metal at the moment. This is for the c3.medium.x86 configuration.
Derived from https://gist.github.com/chris-martin/4ead9b0acbd2e3ce084576ee06961000 with its introduction quoted below
These are instructions for booting from an Ubuntu liveCD and installing NixOS on a machine. I needed to do this because the > NixOS liveCD doesn't work on my machine (NixOS/nixpkgs#5829), so I'm just using the Ubuntu installation media as something to boot into. >