[mertvij@localhost ~]$ optirun -vv glxgear
[ 7937.309316] [DEBUG]Reading file: /etc/bumblebee/bumblebee.conf
[ 7937.309441] [INFO]Configured driver: nouveau
[ 7937.309622] [DEBUG]optirun version 3.2.1 starting...
[ 7937.309630] [DEBUG]Active configuration:
[ 7937.309632] [DEBUG] bumblebeed config file: /etc/bumblebee/bumblebee.conf
[ 7937.309634] [DEBUG] X display: :8
[ 7937.309635] [DEBUG] LD_LIBRARY_PATH: 
[ 7937.309637] [DEBUG] Socket path: /var/run/bumblebee.socket
[ 7937.309639] [DEBUG] Accel/display bridge: auto
[ 7937.309640] [DEBUG] VGL Compression: proxy
[ 7937.309642] [DEBUG] VGLrun extra options: 
[ 7937.309644] [DEBUG] Primus LD Path: /usr/lib/primus:/usr/lib64/primus
[ 7937.309661] [DEBUG]Using auto-detected bridge virtualgl
[ 7937.516562] [INFO]Response: No - error: [XORG] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied

[ 7937.516573] [ERROR]Cannot access secondary GPU - error: [XORG] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied

[ 7937.516576] [DEBUG]Socket closed.
[ 7937.516582] [ERROR]Aborting because fallback start is disabled.
[ 7937.516584] [DEBUG]Killing all remaining processes. 

[mertvij@localhost ~]$ lspci | egrep 'VGA|3D'
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06)
01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 850M] (rev a2)

[mertvij@localhost ~]$ cat /etc/bumblebee/bumblebee.conf          
# Configuration file for Bumblebee. Values should **not** be put between quotes

## Server options. Any change made in this section will need a server restart
# to take effect.
[bumblebeed]
# The secondary Xorg server DISPLAY number
VirtualDisplay=:8
# Should the unused Xorg server be kept running? Set this to true if waiting
# for X to be ready is too long and don't need power management at all.
KeepUnusedXServer=false
# The name of the Bumbleblee server group name (GID name)
ServerGroup=bumblebee
# Card power state at exit. Set to false if the card shoud be ON when Bumblebee
# server exits.
TurnCardOffAtExit=false
# The default behavior of '-f' option on optirun. If set to "true", '-f' will
# be ignored.
NoEcoModeOverride=false
# The Driver used by Bumblebee server. If this value is not set (or empty),
# auto-detection is performed. The available drivers are nvidia and nouveau
# (See also the driver-specific sections below)
Driver=nouveau
# Directory with a dummy config file to pass as a -configdir to secondary X
XorgConfDir=/etc/bumblebee/xorg.conf.d

## Client options. Will take effect on the next optirun executed.
[optirun]
# Acceleration/ rendering bridge, possible values are auto, virtualgl and
# primus.
Bridge=auto
# The method used for VirtualGL to transport frames between X servers.
# Possible values are proxy, jpeg, rgb, xv and yuv.
VGLTransport=proxy
# List of paths which are searched for the primus libGL.so.1 when using
# the primus bridge
PrimusLibraryPath=/usr/lib/primus:/usr/lib64/primus
# Should the program run under optirun even if Bumblebee server or nvidia card
# is not available?
AllowFallbackToIGC=false


# Driver-specific settings are grouped under [driver-NAME]. The sections are
# parsed if the Driver setting in [bumblebeed] is set to NAME (or if auto-
# detection resolves to NAME).
# PMMethod: method to use for saving power by disabling the nvidia card, valid
# values are: auto - automatically detect which PM method to use
#         bbswitch - new in BB 3, recommended if available
#       switcheroo - vga_switcheroo method, use at your own risk
#             none - disable PM completely
# https://github.com/Bumblebee-Project/Bumblebee/wiki/Comparison-of-PM-methods

## Section with nvidia driver specific options, only parsed if Driver=nvidia
[driver-nvidia]
# Module name to load, defaults to Driver if empty or unset
KernelDriver=
PMMethod=auto
# colon-separated path to the nvidia libraries
LibraryPath=
# comma-separated path of the directory containing nvidia_drv.so and the
# default Xorg modules path
XorgModulePath=
XorgConfFile=/etc/bumblebee/xorg.conf.nvidia

## Section with nouveau driver specific options, only parsed if Driver=nouveau
[driver-nouveau]
KernelDriver=nouveau
PMMethod=auto
XorgConfFile=/etc/bumblebee/xorg.conf.nouveau

[mertvij@localhost ~]$ cat /etc/bumblebee/xorg.conf.nouveau 
Section "ServerLayout"
    Identifier  "Layout0"
    Option      "AutoAddDevices" "false"
    Option      "AutoAddGPU" "false"
EndSection

Section "Device"
    Identifier  "DiscreteNvidia"
    Driver      "nouveau"

#   If the X server does not automatically detect your VGA device,
#   you can manually set it here.
#   To get the BusID prop, run `lspci | egrep 'VGA|3D'` and input the data
#   as you see in the commented example.
#   This Setting is needed on Ubuntu 13.04.
#   BusID "PCI:01:00.0"

EndSection