Understanding #systemd # 16a
Say you want to change the way a unit works, such as sshd.service. You could edit the unit in the /usr directory, but if you do that then on an upgrade you'll lose your changes.
You could copy the /usr unit to /etc and make your changes there, but then any new changes on upgrade will be picked up.
Instead do a 'systemctl edit foo.service' to create a drop-in that systemd picks up the changes, but also you still get the benefits of upgrades.
Linux Geeks doing what Linux Geeks do..