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Posting this because I've been googling frantically attempting to save my poor, poor eyes without much success. And I've not found anyone posting specifically about this specific laptop, so new post.

The problem is I have been unable to get the backlight to change. I've had configurations where the keyboard keys reported brightness changes, but no change in backlight occurs. I've never gotten writes to /sys/class/backlight/acpi_video0/brightness to change anything. xbacklight has not worked for me.

I've tried the following so far- grub configurations:

/sys/class/backlight/acpi_video0, editing no change. xbrightness not change. acpi acknowledges button

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux video.use_native_backlight=1" 

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=1" 

no /sys/class/backlight, no acpi, no xbrightness

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi=Linux video.use_native_backlight=1"

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force acpi_osi=Linux acpi_backlight=vendor" 

Before I started chronicling more closely, I did do a run through other settings, none of which worked, but I didn't write down.

I've attempted to force discrete graphics (no change) and hybrid graphics (hung on startup), so still on auto.

I've tried installing nvidia graphics 384, but that hung on boot so I purged that.

I've tried adding in an intel configuration to my xorg.conf.d, but that hung on startup.

Post-fix- xrandr output:

~$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm        1920x1080     60.01*+  40.01  
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 disconnected (normal left inverted right x axis y axis)
DP-6 disconnected (normal left inverted right x axis y axis)
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  • Can you update your question with the output from xrandr? Feb 2, 2018 at 2:05

2 Answers 2

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Adjusting brightness with software controls

When you lack hardware controls to adjust brightness the only option is via software.

Find your monitor name using xrandr

Run this command to find monitors connected to xrandr:

$ xrandr | grep connected | grep -v dis
eDP-1 connected primary 1920x1080+0+1080 (normal left inverted right x axis y axis) 382mm x 215mm
DP-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 1107mm x 623mm

For me it is eDP-1 but on your system it is DP-3

Set --brightness in xrandr

You can set brightness to screen off 0 to full bright 1.

You can set it above full bright ie 1.5 but your colors will become overly saturated.

A good starting point for a screen that is too bright (hard on your poor eyes) is .5

xrandr --output DP-3 --brightness .5

From there you can adjust accordingly.

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  • That is display brightness, which is not the same thing as adjusting the display backlight
    – ohshazbot
    Feb 6, 2018 at 4:31
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After talking with someone, I made another attempt at installing the nvidia drivers, following the instructions http://allskyee.blogspot.com/2017/02/installing-nvidia-drivers-on-ubuntu-1604.html

Though it turns out the hang may have been caused by the following bug, which I still experience but have worked around by disabling the quite splash portion of my grub launch https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1387107

However, this solution does not work for /sys/class/backlight/..., which makes this not work for the hardware controls in xfce-power-manager. xbacklight does work, as well as the power controls in Unity.

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