Screen brightness adjustment not working in Ubuntu 14.04

Question

When I try adjusting the screen brightness using the function keys on the keyboard, the adjustment scale is shown on the screen responding but the screen brightness is not adjusted.

Tried https://askubuntu.com/a/467869/375346 but it did not work. The GUI failed to load upon reboot, I had to delete the /usr/share/X11/xorg.conf.d/20-intel.conf using recovery mode.

Solution

This https://askubuntu.com/a/505079/375346 worked for me. In /etc/default/grub make sure you have acpi_backlight=vendor in GRUB_CMDLINE_LINUX_DEFAULT.

Here is mine:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor" Then run update-grub and reboot.

Fixed it for me, HP15 with Intel® Bay Trail Graphics using Ubuntu 14.04