If your Nikon camera tethering is not working with gphoto2 under Linux, maybe this will be able to help you.
I have found out that when I switched to newer version of gphoto2 (2.5.X) tethering for my camera stopped working. Workaround is to downgrade to version 2.4.X.
First be sure that your camera is correctly detected as PTP USB device (you
need to configure your camera to act as PTP device, not as a mass storage).
Check it with
$ lsusb | grep Nikon Bus 003 Device 034: ID 04b0:0410 Nikon Corp. D200 (ptp)
$ sudo dpkg --remove gphoto2
After that you need to install older gphoto2 package. You can download it from Ubuntu » Packages » precise (12.04LTS) » utils » gphoto2 page. There are also links to other packages gphoto2 depends on, basically you need to instal only packages mentioned below.
I assume you had not working gphoto2 package installed with command
Packages installation example:
$ sudo dpkg --install --force-all gphoto2_2.4.11-2_amd64.deb \ libgphoto2-2_2.4.13-1ubuntu1_amd64.deb libgphoto2-port0_2.4.13-1ubuntu1_amd64.deb \ libgd2-xpm_2.0.36~rc1~dfsg-6ubuntu2_amd64.deb
To prevent installed packages upgrade/removal put them on hold by following command:
$ sudo apt-mark hold gphoto2 libgphoto2-2 libgphoto2-port0 libgd2-xpm
Camera tethering should be working after this downgrade. Output example:
$ gphoto2 --capture-tethered Waiting for events from camera. Press Ctrl-C to abort. UNKNOWN PTP Property 500d changed UNKNOWN PTP Property 500f changed UNKNOWN PTP Property d102 changed UNKNOWN PTP Property d103 changed Downloading 'PVK_6023.NEF' from folder '/store_00010001/DCIM/123ND200'... Saving file as PVK_6023.NEF Deleting 'PVK_6023.NEF' from folder '/store_00010001/DCIM/123ND200'... UNKNOWN PTP Event 400c, Param1 00010001 UNKNOWN PTP Property d103 changed ^C Cancelling...