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Thread: Backlight switching off when logging into KDE Plasma Desktop

  1. #1
    Join Date
    Mar 2007

    Backlight switching off when logging into KDE Plasma Desktop

    Hi everyone,

    Happy New Year! I've got a problem with using KDE with Ubuntu 11.10 on an Acer 5336. There is a general problem with Acer laptops anyway when using Ubuntu in that, at boot, the backlight is switched off but there are solutions for that which means that I can get it switched on again and the login screen shows up fine.

    If I log in to standard Ubuntu (Unity) there is no problem and the backlight stays on, but I wanted to try KDE, and when I try to login to the KDE Plasma Workspace, the backlight switches off again! It's a bit annoying, to be honest. To get the backlight working again requires running the command:

    setpci -s 00:02.0 F4.b=00

    I wrote a script for this and tried to get KDE Autostart to run it, but it won't because it needs to be run as root - result: my screen stays black!

    Is there a way I can get KDE to run this script as root, or is there another way to run the command so that I can get my backlight on again? I can't see to input the command into a terminal, which would be the other way to do it, but it's a pain!

    Any help would be appreciated.

  2. #2
    Join Date
    Mar 2007

    Re: Backlight switching off when logging into KDE Plasma Desktop

    For anyone else who is having this problem, here is an answer I found here:

    Open a terminal and type in the terminal:

    gedit ./etc/rc.local
    This will open rc.local file. Now at the bottom make sure it looks like below and save.

    sudo setpci -s 00:02.0 F4.B=00
    exit 0
    You should be fine, reboot and check it out.

    My system's backlight comes back on fine during boot up with this modification. There's also a really helpful script for switching the backlight back on when you 'wake up' from suspend or hibernate

    Good luck!

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