If you’re like me and you own a Mac (or two) but also like to use Ubuntu for home computing tasks like file storage and backups, you’ll be glad to hear that there’s a way to use Ubuntu as a File Server and Time Machine backup destination.
If you’ve used Time Machine before, you’ll know that it cannot see standard Windows-type file shares (Samba shares in Linux) as a backup destination. This requires Appletalk support and the Bonjour protocol which announces shares on the network to Apple systems. The required Ubuntu packages are ‘netatalk’ and ‘avahi’.
There’s a much better explanation than I could provide here:
http://www.kremalicious.com/2008/06/ubuntu-as-mac-file-server-and-time-machine-volume/
I have this working here at home and it seems to be great so far; my little HP Microserver even shows up as an ‘Apple XServe’ in the Finder!
Good tip Phil. I also noticed the other day that from Ubuntu 11.10 onwards, they are going to be supporting Deja Dup on the desktop, which does a similar thing to Time Machine, for those that don’t own a Mac 
You can download it now for Ubuntu 11.04 from the Ubuntu software store, and it works really well with external hard drives etc.
Nick