I got Timemachine to work against my Ubuntu fileserver using this guide.
And here’s a swedish article that seems to apply.
That one also includes a script for making the sparse file.
I haven’t tried any restores yet as the initial full-backup is still in progress.
Maybe I’ll post an update about it.
Update: It stopped working. After some more research I’ve found that there’s some command 78 or other extra apple-features added to the “netatalk” protocol. Having something todo with reclaiming space within the sparse-file or something… Without these commands, the backup-image self-destructs. Some sort of patch exists, but I haven’t the time to pursue… Also some third party “Drobo add-on project” seems to have sorted out this problem. If the code is available someone should implement and test that on Ubuntu. And if you do find a sollution please leave me a note. 😉
Update: I’m at it again, since I’ve found some articles that the issues should be fixed. It seems to work occasionally. I have setup my dhcp for mac address fixed IP:s and proper DNS records (maybe not needed, but useful). The afp “shares” or “disks” are only accessible by the macbook from it’s wireless or wired IP:s. It seems to work on and off, and I do full backups pretty often (like 2 every month at least) when Timemachine says the backup failed verification. I don’t know why this is happening. But my money is on either glitching automounting of netatalk afp:s or packets go missing when on wireless.
Next up is to remove the WIFI from the equation.