Hello! Linux filesystems have no need of being defragmented because they prevent fragments from occurring

Hello!
Linux filesystems have no need of being defragmented because they prevent fragments from occurring. So, I don't think you need to defragment. For a better understanding you could take a look here.
Anyway, there is one (as far as I know) Linux defragmenter. You can download it from sourceforge: http://sourceforge.net/projects/defragfs/