nixos-on-scaleway.sh

# This isn't meant to be ran as a script, but line-by-line
# Props to Binary (benary.org) for helping me with this

# 0: Create a Scaleway instance and SSH into it
ssh root@...

# 1: Install Nix
  adduser user          # set a password, doesn't matter what because it's not staying long
  adduser user sudo
  su -l user
    curl https://nixos.org/nix/install | sh
    source ~/.nix-profile/etc/profile.d/nix.sh

# 2: Build a NixOS tarball (this takes a while)
    nix-build '<nixpkgs/nixos/release-combined.nix>' -A nixos.containerTarball.x86_64-linux
    cp result/tarball/nixos-system-x86_64-linux.tar.xz nixos.tar.xz

# 3: Set Scaleway server to boot in rescue script and reboot
# read: https://www.scaleway.com/docs/perform-rescue-action-on-my-server/
  exit
reboot
  
# -: Wait a bit and reconnect
!ssh

# 4: Mount your volume and fetch the tarball
  mount /dev/vda /mnt
  mv /mnt/home/user/nixos.tar.xz .

# 5: Replace volume contents with NixOS
  rm -rf /mnt/*                 # takes a few moments
  tar xf nixos.tar.xz -C /mnt/  # same for this
  mkdir /mnt/sbin
  ln -s /mnt/init /mnt/sbin/init

# 6: Set the bootscript back to normal (pick whichever option is named stable)
reboot

# 7: Use the Scaleway terminal to configure your OS
# Replace the current configuration with a nixos-generate-config
# Delete anything related to grub2 and add those options:
  boot.isContainer = true; # LOOK UP WHAT THIS DOES (disable kmod and therefore iptables, a bunch of other things)
  boot.loader.initScript.enable = true;
# You also probably should replace the root shell by a nologin -- ONLY AFTER OTHER USERS AND SUDO IS SET UP
  users.users.root.shell = pkgs.nologin;
  
# Enjoy

ha, tar was missing after the rm -rf /mnt/* command. I think I missed the rescue