Dell's e6430 discrete graphics card on Debian

Some new laptops have two graphics cards. One power-efficient integrated with CPU and one powerful discrete (separate board).

Bumblebee project provides support for NVIDIA Optimus laptops. Installing and usage is straightforward and described here. In short (if you want proprietary drivers):

1. make sure you have contrib and non-free repositories enabled 
2. Install packages:
   # apt-get install nvidia-glx nvidia-kernel-dkms bumblebee-nvidia primus
3. Installing nvidia driver package will automatically set it as a default rendering engine but it's not desired. Normally 3D would be rendered by integrated Intel card, so do:
   # update-alternatives --set glx /usr/lib/mesa-diverted

Normally this should be it, but unfortunately in current debian testing there is a bug causing an output:

$ optirun glxgears
[   42.214557] [ERROR]Cannot access secondary GPU - error: Could not load GPU driver
[   42.214599] [ERROR]Aborting because fallback start is disabled.

To fix this in file /etc/bumblebee/bumblebee.conf in section [driver-nvidia] change line:
KernelDriver=nvidia
to:
KernelDriver=nvidia-current

Debian - slow brightness responce on Dell laptop fix

On some Dell laptops with gnome3 brightness change takes veeeery long (seconds) and system is choppy in the meantime.

A workaround has been posted: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/828296/comments/5

The workaround is:

1. add acpi_backlight=vendor to GRUB_CMDLINE_LINUX_DEFAULT option in /etc/default/grub file
   (eg. GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_backlight=vendor")
2. run
   $ sudo update-grub

Bug for ubuntu is filed: https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/847001

Worked on my Dell e6430.