Changing brightness in Unity settings results in dead SAMSUNG 300e5z-s08

Question

I experienced the following problem when trying to change brightness either through the system settings of the shell, or by using fn + f2 fn+f3 combinations. The brightness bar appears in the top left corner of the screen and the whole system becomes non-responsive. Trying to change the brightness with xrandr works without problems, though. The laptop uses an Nvidia optimus card. The problem appears both with the nvidia-current driver installed and without it.

Is there any way to disable what causes this failure?

---

Thank you for your help it almost works now. I can reduce the brightness with the buttons and through the shell, though I can't increase it back. In this path /sys/class/backlight i have two similar directories. One called Samsung and one called intel_backlight. If I try to modify the values in the Samsung I cannot get more than 3 out of 8. However if I modify the intel_backlight I can increase back to max.

Answer 1

To get working brightness key. try following

execute sudo gedit /etc/default/grub

Change this line

GRUB_CMLINE_LINUX_DEFAULT="quiet splash"

to something like below

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Execute sudo update-grub and reboot . See if brightness keys are working.

It is still possible ubuntu won't remember your brightness settings. So you have to change brightness each time.

---

This is for setting brightness manually after doing the above steps.

Try following for paths shown by ls /sys/class/backlight/*/brightness and replace accordingly.

example paths will be like

/sys/class/backlight/acpi_video0/brightness

1. For the above path Get the maximum brightness:

cat /sys/class/backlight/acpi_video0/max_brightness

Try a lower value to set the brightness, say output is 16 so I will try with half of it

echo 8 | sudo tee /sys/class/backlight/acpi_video0/brightness

If this works, make this happen in each login automatically by doing the following

sudo gedit /etc/rc.local

Enter this line just before exit 0. It should look like

echo YOUR_VALUE_HERE > /sys/class/backlight/acpi_video0/brightness
exit 0

Also don't install nvidia-drivers in an optimus enabled laptop, you need bumblebee. See discussion over here Is a NVIDIA GeForce with Optimus Technology supported by Ubuntu?

Please let us know the results.