You have now learned how to work with systemd units and the GRUB 2 boot loader. Before continuing, it is a good idea to work on some labs that help you ensure that you can apply the skills that you acquired in this chapter.
Make sure that the firewalld service is started on boot. Also make sure that the iptables service can never be started at the same time.
Change your GRUB 2 boot configuration so that you will see boot messages upon startup.