raito-shared-public-infra/modules/auto-upgrade.nix

{ pkgs, ... }: {
  system.autoUpgrade = {
    enable = true;
    flake = "git+https://git.newtype.fr/newtype/newtype-org-configurations";
    flags = [ "--option" "accept-flake-config" "true" ];
  };

  # add a random jitter so not all machines reboot at the same time.
  systemd.timers.auto-reboot.timerConfig.RandomizedDelaySec = 60 * 20;

  systemd.services.auto-reboot = {
    path = [ pkgs.systemd pkgs.util-linux ];
    # The last saturday in a month
    startAt = "Sat *-*~07/1";
    script = ''
      booted="$(readlink /run/booted-system/{initrd,kernel,kernel-modules})"
      built="$(readlink /nix/var/nix/profiles/system/{initrd,kernel,kernel-modules})"
      if [ "''${booted}" = "''${built}" ]; then
        echo "No kernel update... skipping reboot"
      else
        # reboot in 24 hours
        msg=$(shutdown -r +${toString (60 * 24)} 2>&1)
        echo "$msg" | wall
      fi
    '';
  };
}