What I was trying to say, Netatalk is suppose to be able to handle the metadata, regardless whether you're using HFS/+ or not on the Ubuntu server.

http://forums.freebsd.org/showpost.php?p=163559&postcount=2

... for the file server it is not exactly necessary to have the same file system as the clients. It has to store the files correctly, though (incl. resource forks and other metadata).... This is a full fledged AFP server that can do everything that a modern Mac OS X AFP server can do... Netatalk transparently deals with resource forks...

Click to expand...

If Netatalk isn't preserving the metadata, it may be possible that something was mis-configured. Doing a HFS+ partition would probably work too, last time I messed with HFS+ in Linux it worked fine as long as it wasn't Journaled. (I think it could only read from HFS+ Journaled partitions.) But this was back in Linux 2.6 with Slackintosh 12.1. The Linux 3.x kernel probably has better support now. (Speaking of which, I recall mounting my OSX partition with the Lubuntu 12.04 Live CD on my PBG4 with no problems.)