Darktable Tethering Tutorial
Before that, please read about Darktable 1.0 release post http://www.darktable.org/2012/03/darktable-1-0-released/
I just know that Darktable supports tethering mode, because the developer put the link to the mode right on top side of the application. And here are the simplest tutorial on how to make it usable.

By reading this post here, seems that the new generation of digital camera is supported by this mode. Okay, if your camera is on the list, then let’s skip the testing part, and let get it done.
- Plug your camera to your computer
- Make sure that the Memory Card / SD Card is not mounted. You can do this by go to Nautilus (Gnome) or Dolphin (KDE), and unmount the respective drive. Remember, this is the important part, so make sure you unmount it.
- Start Darktable
- Click the Tethering link on top-right of the application.
- Now you’re up and runnig …
See?? Easy huh? Now I just have to find a longer USB cable to play with ^^