For some weird reason the Ubuntu 16.04 Bumblebee’s default version was not being able to switch on/off my discrete video card NVIDIA Corporation GF108M [GeForce GT 540M]. I was getting the following error:
$ optirun glxgears
[ 7224.163607] [ERROR]Cannot access secondary GPU – error: [XORG] (EE)
[ 7224.163722] [ERROR]Aborting because fallback start is disabled.
I was able to solve the aforementioned issue in this way:
1) Adding the repository with fresh bumbleblee packages:
$ sudo add-apt-repository ppa:bumblebee/testing
2) Updating the repositories and upgrade bumblebee:
$ sudo apt-get update; sudo apt-get upgrade
3) Adjusting /etc/bumblebee/bumblebee.conf file:
4) Adjusting the /etc/bumblebee/xorg.conf-nvidia , as well:
PS.: I suggest you to use the official nvidia-340 video driver, which is the one that I’m currently using with this laptop.
And that’s it! Reboot and pray! =)