What is the difference between optirun and primusrun (bumblebee) I have installed the Lightworks video editor on Debian Jessie. For best performance it needs to run on a discrete video card with the proprietary driver. A Nvidia GTX 860M in my case. I have installed Bumblebee to switch between video cards as needed. With `optirun` or `primusrun` it is possible to run an application using the Nvidia card. When I use optirun for Lightworks it crashes after startup. When I use primusrun it doesn't and performance is okay. Why is that? What is the difference between the two? This question has been asked before, but remains unanswered. This answer on a different question does allude to a difference, but doesn't explain it.

Bumblebee, earlier, was using `VirtualGL` as its core and now switched to `Primus` technology.

`optirun` uses VirtualGL and `primusrun` uses the Primus technology. That must be the reason.

**Note:** Though the question was posted long back, the answer would help those want to understand the difference.