configuration.nix/hosts/skipper/rollback.nix

{...}: {
  boot.initrd.systemd.services.rollback = {
    description = "Rollback root subvolume to blank state";
    wantedBy = ["initrd.target"];
    after = ["dev-vg0-system.device"];
    before = ["sysroot.mount"];
    unitConfig.DefaultDependencies = "no";
    serviceConfig.Type = "oneshot";
    script = ''
      mkdir -p /mnt
      mount -o subvol=/ /dev/vg0/system /mnt

      btrfs subvolume list -o /mnt/@root | cut -f9 -d' ' | while read subvolume; do
        echo "deleting /$subvolume subvolume..."
        btrfs subvolume delete "/mnt/$subvolume"
      done &&
      echo "deleting /root subvolume..." &&
      btrfs subvolume delete "/mnt/@root"

      echo "restoring blank /root subvolume..."
      btrfs subvolume snapshot "/mnt/@root-blank" "/mnt/@root"

      echo "deleting /home subvolume..."
      btrfs subvolume delete "/mnt/@home"

      echo "restoring blank /home subvolume..."
      btrfs subvolume snapshot "/mnt/@home-blank" "/mnt/@home"

      umount /mnt
    '';
  };
}