This tutorial describes how to do scripted passwordless encrypted automatic rsync backups from an Ubuntu server to a Synology NAS. It is supposed to be a general guide, which can be used with other Linux variants as well. Only minor changes should be required.
I did this first of all in order to help other Synology NAS users perform efficient and secure backups to their NAS, but also to get get my scratch pad like personal installation notes in a more reasonable shape, so I can recall later on myself what I did, how, and why.