{ config, pkgs, ... }:
let
  update-containers = pkgs.writeShellScriptBin "update-containers" ''
    SUDO=""
    if [[ $(id -u) -ne 0 ]]; then
      SUDO="sudo"
    fi

      images=$($SUDO ${pkgs.podman}/bin/podman ps -a --format="{{.Image}}" | sort -u)

      for image in $images
      do
        $SUDO ${pkgs.podman}/bin/podman pull $image
      done
  '';
in {
  systemd.timers = {
    # ...
    updatecontainers = {
      timerConfig = {
        Unit = "updatecontainers.service";
        OnCalendar = "02:00";
      };
      wantedBy = [ "timers.target" ];
    };
    # ...
  };

  systemd.services = {
    # ...
    updatecontainers = {
      serviceConfig = {
        Type = "oneshot";
        ExecStart = "update-containers";
      };
    };
    # ...
  };
}