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I'd like to reduce the screen brightness on my Lubuntu desktop (Ubuntu 16.04).

I googled but could not find any soluton that works. (like using xbacklight -set 45 command.

Appreciate a simple working solution.

Babr
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  • I believe you can change it in the power settings but I don't have my laptop handy and by the time I grab it someone will probably answer this already .. check your "start .. Settings... power manager" settings – John Orion Dec 15 '17 at 01:40
  • Well in System>Preferences>Xfce Powermanger I see no slider/option to change brightness. – Babr Dec 15 '17 at 01:45
  • I found a slider on the batter icon in the tray but that one doesn't seem to do anything on mine ... I see someone posted an answer below so maybe that will be more sufficient :D – John Orion Dec 15 '17 at 01:52
  • ok I was not able to use anything on ubuntu but .. on my laptop fn + F5 lowers my brightness and fn + F6 raises it but on the screen .. it doesn't seem to lower the brightness in the "on screen display" .. the screen seems the same brightness until the OSD goes to 0 and if I keep hitting it .. it starts to dim after the meter drops to 0 on the display .. if that makes sense :) – John Orion Dec 15 '17 at 03:31
  • I found the fix here in the answer that starts with Pre Ubuntu LTS 16.04 I used what it said in Since Ubuntu LTS 16.04 the ls command showed intel_backlight so I added the stuff he said in nano and rebooted .. now my fn buttons work correctly and the battery icon when I click on it and use the Display brightness .. that works too – John Orion Dec 15 '17 at 03:46

2 Answers2

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execute any of these inside root terminal

echo 1 > /sys/class/backlight/acpi_video0/brightness sudo echo 1 | sudo tee /sys/class/backlight/acpi_video0/brightness

if /sys/class/backlight/ folder is empty

nano /boot/grub/grub.cfg add this to kernel line

acpi_osi=Linux acpi_backlight=vendor

or

nano /etc/default/grub

see a line like GRUB_CMDLINE_LINUX_DEFAULT and add

acpi_osi=Linux acpi_backlight=vendor

save and run

update-grub

to save changes to grub

reboot

......

John Orion
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user688056
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  • need one more edit .. the nano /etc/derfauls/grub to nano /etc/default/grub – John Orion Dec 15 '17 at 01:54
  • I see # DO NOT EDIT THIS FILE on grub.cfg. I'm not going to mess with kernel to set the brightness. There should be a better way. – Babr Dec 15 '17 at 01:55
  • changed as@John Orion; @Babr the grub.cfg is a temporary solution.. its overridden every time by kernel updates; the permanent solution is /etc/defalts/grub; anw you need mods to grub only if /sys/class/backlight folder is empty – user688056 Dec 15 '17 at 02:00
  • you can add it in sudo /etc/default/grub and then run sudo update-grub I would not do it in the grub.cfg file – John Orion Dec 15 '17 at 02:03
  • but after adding it to my grub file .. I still see on my battery icon a place to change display brightness but .. it still doesn't work properly :( – John Orion Dec 15 '17 at 02:21
  • did you tested the CLI terminal lines? do they work? is/was your backlight folder empty? – user688056 Dec 15 '17 at 02:25
  • no .. they both gave errors .. not found.. but im having issues with the linux install ... and its using old kernel still .. cant get it to upgrade yet ... working on that before I can try those things again.. lol at the moment im installing about 150 updates – John Orion Dec 15 '17 at 02:26
  • can you post result of cat /proc/cmdline? – user688056 Dec 15 '17 at 02:29
  • like I say .. at this time im not able to do much .. im still on 4.4.0-21 so im very far behind .. getting current before I try those things again .. as for the command you listed it shows the lines added.. I don't have this open on the laptop so I cant copy and paste and as I say at the moment im upgrading to get to current first – John Orion Dec 15 '17 at 02:31
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I use Lubuntu with an Nvidia graphics card. The brightness setting is in the "NVIDIA X Server Settings" app. It's kind of buried though - you have to select the "HDMI-0" from the menu on the left, and then click the "color correction" tab.

You don't mention your graphics hardware, but if you don't use Nvidida, perhaps the setting is related to your graphics card as well.

Organic Marble
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