Basically, do this: https://documentation.ubuntu.com/server/how-to/backups/install-rsnapshot/
Reminder: on debian/ubuntu, you may need to "sudo apt-get install liblchown-perl" so rsnapshot can set symlink ownership.
To restrict the ability of the client to access or even change files on the server being backed up, use my rrsync.py, or perhaps the one from the rsync project.