I'm using my iMac in targeted display mode as my ubuntu pc display, but I can't control the backglight levels at all. My /sys/class/backlight folder is empty.

I located the brightness and maxbrightness files in another folder and am trying to create a symlink:

sudo ln -s /sys/devices/pci0000:00/0000:00:1c.3/0000:06:00.0/leds/phy0-led /sys/class/backlight

However, I get this message:

ln: failed to create symbolic link '/sys/class/backlight/phy0-led': Operation not permitted

The reason I am trying to create a symlink is because I read that there must be brightness and maxbrightness files in my /sys/class/backlight folder if I want to be able to easily change my screen's backlight levels. Is this correct? Or is there another way to allow for a gui app to conviently control led backlight levels? FYI: I'm a complete noob at ubuntu and linux in general.

My iMac is the iMac 11,3. I am using the GTX 970's second DisplayPort from the left GTX 970 Ports, using a DisplayPort to Mini DisplayPort cable.

In terminal I ran the command lsb release -a and got:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.1 LTS
Release:        16.04
Codename:       xenial

I then ran the code: lspci -nnk | grep "VGA" -A2 and got:

03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM204 [GeForce GTX 970] [10de:13c2] (rev a1)
        Subsystem: Gigabyte Technology Co., Ltd GM204 [GeForce GTX 970] [1458:3683]
        Kernel driver in use: nvidia
  • This is a wrong solution anyway. It is an meta.stackexchange.com/questions/66377/what-is-the-xy-problem – Pilot6 Jan 19 '17 at 20:56
  • you made a copy/paste error Those ... do NOT belong in the command. – Rinzwind Jan 19 '17 at 21:01
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    @Rinzwind Even if OP didn't use the periods an ellipsis and actually used them in the command, no error message would be displayed. The link created would just be broken. – UTF-8 Jan 19 '17 at 21:16
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    You can't create files in /sys; they are created by the kernel to represent real hardware. Why are you trying to do this? – psusi Jan 19 '17 at 23:40
  • As I understand, I need those files in /sys/class/backlight in order to have any meaningful and convenient way to change my led backlight levels with a gui, correct? I read making a symlink can accomplish this, from another stackexchange answer. askubuntu.com/questions/715306/… – CPLTarun Jan 20 '17 at 18:41

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