Warning: this is an old post I am consolidating as you can see from the OS X version. No comments on this Post, Thanks
How to Use an SMB Share in Ubuntu for TimeMachine on Mountain Lion 10.8.x OS X
I was trying to get TM to work via SMB on 10.8 and although I found articles on how to implement in Lion and Snow Leopard, I found that they did not work in ML as advertised. By leveraging multible sites I was able to get it to work successfully. The first step was to create an SMB server in Ubuntu server. I am running Ubuntu server version 12.04 on an Atom CPU 2 Cores, 4GB.
SMB Setup on Ubuntu
Enable SMB Share for Time Machine
Open the Terminal.app and enter the following command:
sudo defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
Mount the sparse bundle:
hdiutil attach -verbose /path/to/sparsebundle
Add the sparsebundle as the Time Machine destination:
sudo tmutil setdestination /Volumes/mounted_sprase_bundle
Now bring up Time Machine and you will see the disk as the default destination. In past versions you would have seen the disk and add it in the GUI but in ML it will not see it. You are able to add it via CLI and so far I have not seen any issues.