config/nixos/roles/zeus/rollback.nix

{ pkgs, ... }:
let
  script = pkgs.writers.writeHaskell "rollback" {
    libraries = builtins.attrValues pkgs.myHaskellScriptPackages;
  } (builtins.readFile ./sysroot-rollback.hs);
in
{

  boot.initrd.systemd = {
    storePaths = [ script ];
    services.rollback = {
      description = "Rollback File System Root";
      wantedBy = [ "basic.target" ];
      before = [
        "initrd-root-fs.target"
        "sysroot-var-lib-nixos.mount"
      ];
      after = [ "sysroot.mount" ];
      unitConfig.DefaultDependencies = "no";
      serviceConfig = {
        Type = "oneshot";
        ExecStart = script;
      };
    };
  };
}