screen brightness slider has no effect

[Kevin Leeds]

Trusty Tahr 14.04 LTS, seems to be fully updated.

The problem is: When I go to System Settings -> Brightness & Lock, the slider has no effect. I can decrease the brightness slider to any level and the actual brightness of the monitors apparently does not change in any way.

f.lux - I was saying this doesn't work either, but I found out it doesn't really install correctly, and it gives error messages when I try to start it, so that doesn't mean much. redshift does work, so my monitors are not completely insensitive or broken ...

Also when i try to do

 echo 50 | sudo tee /sys/class/backlight/acpi_video0/brightness

it has no effect

product: OptiPlex 7010 (OptiPlex 7010)

 *-cpu
          description: CPU
          product: Intel(R) Core(TM) i3-3240 CPU @ 3.40GHz
*-pci
          description: Host bridge
          product: Xeon E3-1200 v2/3rd Gen Core processor DRAM Controller
          vendor: Intel Corporation
 *-display
             description: VGA compatible controller
             product: Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller

I would love to help provide some more help on my dual monitor setup.
I found this documentation: https://wiki.ubuntu.com/X/Config/Resolution
It says I should run $gnome-display-properties. Seems to be out of date.
gnome-display-properties: command not found

I guess it would be annoying to say it's a security vulnerability although if my screen isn't dim someone could more easily look through the window and see what I am typing on the screen.

[Gunnar Hjalmarsson (gunnarhj)]

Hi Kevin,

I do not know much about this topic, but...

On 2016-02-13 13:03, Kevin Leeds wrote:
> Also when i try to do
> sudo echo 50 > /sys/class/backlight/acpi_video0/brightness
> then it says 'bash: brightness: permission denied'.
> (From this page: http://pastebin.com/HzzHrS2g).

That command would need to be changed to e.g.:

sudo sh -c 'echo 50 > /sys/class/backlight/acpi_video0/brightness'

> I would love to help provide some more help on my dual monitor setup.

Did you see these pages in the official documentation:

https://help.ubuntu.com/stable/ubuntu-help/display-dual-monitors-desktop.html

https://help.ubuntu.com/stable/ubuntu-help/display-dual-monitors.html

[Kevin Leeds (knleeds)]

The steps outlined in the official documentation are working fine - I have set up the two monitors, and both are usable in many ways. But I can not find a way to use software to adjust the brightness of them.

I had another computer which was a laptop, and it worked to use f.lux on the external monitor but not on the integrated monitor, under Trusty 14.04, so I would like it to work on this computer too, with the two integrated monitors.

I am linking another thread, where I had a bug report that I could not figure out how to edit, that I changed into a Question, so I have three IDs for this problem now. The question version seems somewhat useful. I marked the bug version of that one invalid. I think it may be best if I merge all the information into this report.

[Kevin Leeds (knleeds)]

https://answers.launchpad.net/ubuntu/+source/ubuntu-docs/+question/285285
Supposedly this is answered, but I think it was because of the duplication.

Here's the output of this command

$sudo dmidecode -t 1; lsb_release -a; uname -a

# dmidecode 2.12
SMBIOS 2.7 present.

Handle 0x0001, DMI type 1, 27 bytes
System Information
 Manufacturer: Dell Inc.
 Product Name: OptiPlex 7010
 Version: 01
 Serial Number: .............
 UUID: ,,,,,,,,,,,,,,,,,,
 Wake-up Type: Power Switch
 SKU Number: OptiPlex 7010
 Family: Not Specified

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.3 LTS
Release: 14.04
Codename: trusty
Linux kevin-desktop 3.19.0-49-generic #55~14.04.1-Ubuntu SMP Fri Jan 22 11:24:31 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

[Kevin Leeds (knleeds)]

When I try to change the brightness, it is System Settings -> Brightness & Lock
I have identified the package as unity-control-center, not ubuntu docs as I reported erroneously at first.
It is not a bug against ubuntu-docs that I know of.

[Kevin Leeds (knleeds)]

What is an LSB module?