There are some system services that you can enable or disable by default. ssh is disabled by default, which I presume is due to security reasons, but for my purpose it is easier to manage the RPi’s if I have ssh access. For a start, I want my RPi’s to listen to ssh, will be putting in the security measures gradually.
To enable ssh by default, change
-systemctl disable ssh +systemctl enable ssh
There are other services in this page that you can choose to enable or disable