I set up a Arch Linux box with an external drive(Ext4) and netatalk 3, to be my backup server.
My conf file contains just this:
path = /media/backup
time machine = yes
It has been running for a few weeks now, and I already had trouble twice.
First I got "resource temporarily unavailable", which was resolved by rebooting everything.
Now, time machine failed to verify my backup and prompted me to start a new one. I'm not sure how to debug this, but an unreliable backup is as good as no backup at all.