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Since my new xubuntu installation (after the previous LTS) I lost control over the brightness - there used to be a brightness adjustment applet on the top panel, and now it's gone. I tried to restore Fn keys functionality, or changing the grub, but none of

The Fn key wont work on Toshiba satellite L735?

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

worked for me (I did remember to do sudo update-grub before rebooting)

The fnfx client also did not change anything, when I try to run it fnfx it gives me an error:

FnFX Client v0.3 (c) 2003, 2004 Timo Hoenig <>

fatal error: Could not open "/home/chris/.fnfxrc". Please make sure that the default     config is accessible.

This command sudo setpci -s 00:02.0 F4.B=X does not work for me neither.

I cannot follow this Fn keys for Brightness not working on Toshiba Satellite L755 suggestion to edit BIOS settings (which are not defined in that post) - does anyone know which settings could be changed in BIOS, and how ?

I run out of possibilities. Any other suggestions that could perhaps enable me to control the brightness of my display? Pointing me in a good direction would be really helpful.

Thank you so much,


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Take a look at my answer Here, see if it helps. – Mitch Jul 6 '13 at 12:40

Chris, I found this in a previous similar question to your...check it out to see if it helps you and/or guides you in the right path...

How can I adjust brightness settings when I am on battery?

Good luck,


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Hi! Using xgamma -gamma 0.8 (to reduce the brightness - 1 is default) does not change the brightness but gamma correction, which alters colours, and does not look well for very low values of gammma, so this is not a good solution. What they suggest here… does not work because it is a setting for reducing the brightness after some time of inactivity. What I am after is to be able to change brightness with some keys, when the laptop is on AC. This functionality does not exist in my settings manager: – Chris S Jul 6 '13 at 13:10
[][img=http://… [][img=http://… Inspired by this solution… I thought that perhaps it could work in my case as well - to set two scripts which will increment / decrement the value stored in /sys/class/backlight/intel_backlight/brightness, and then – Chris S Jul 6 '13 at 13:10
associate execution of those scripts with some keys using Settings Editor. However I am not fluent with those scripts - does anyone know how it would look like to perform an increment of 0.1 in the value of that file? I tried to check how it should look like, but at the moment it does not even allow me to manually tweak the brightness. After permission problems – Chris S Jul 6 '13 at 13:10
sudo echo 0.8 > /sys/class/backlight/intel_backlight/brightness bash: /sys/class/backlight/intel_backlight/brightness: Permission deniedI changed permission of brightness file, to read ls -al /sys/class/backlight/intel_backlight/ -rwxrwxrwx 1 root root 4096 Jul 6 14:52 brightness But the command sudo echo 0.8 > /sys/class/backlight/intel_backlight/brightness results in echo: write error: Invalid argument So how should I change the value of that file? It seems that what worked for them in that script, might not work for me... Best wishes, Chris – Chris S Jul 6 '13 at 13:11

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