Every single one of the blogspam sites (lifehacker, howtogeek, etc.) told you to use AFP/HFS+/Netatalk. I had so many problems with this. Time Machine would work well the first few times and then slow to a crawl. If there was a power outage, look out. The whole thing would be corrupted. It wasn't the network. FTP and scp worked just fine.

Eventually I found one blog that told you how to do it with SMB and ext4. It was that site that I learned about the much malignment of AFP and HFS+. SMB/ext4 worked like a charm. Six years later and not a single hiccup.