I just set up my Mac to save Time Machine backups to a regular SMB share. Doing this is actually quite easy:
Step 1: Create a .sparsebundle
Open Disk Utility and choose File => New Image => Blank Image.
Give the image a name and size (check the Time Machine settings first to see how large your backups will be).
- Set Format to Mac OS Extended (Journaled)
- Set Encryption to 128-bit AES encryption
- Set Partitions to Single partition - Apple Partition Map
- Set Image Format to sparse bundle disk image
Now click Create.
Step 2: Copy the .sparsebundle to your server
Unmount the .sparsebundle by clicking the eject icon next to the image's name in the Finder sidebar. Now copy the .sparsebundle onto your server. You can now delete the original version from your Mac, just make sure that the copy is on your server.
Step 3: Configure Time Machine
Open up a new Terminal window and type
sudo tmutil setdestination "/Volumes/NameOfYourImage"
(replace NameOfYourImage with the name of your .sparsebundle image)
Congratulations, you're done! Now you can start a new backup in the Time Machine settings.