I Run Ubuntu on a Samsung N150+ netbook.
I have recently updated Ubuntu (to 13.04) and now the backlight control doesn't work...
If I start up with the mains pluged in the screen comes up bright enough to see clearly, but if I start up on battery power the screen is so dim I can barely see what I am doing. Either way I cannot alter the screen brightness.

This is not an entirely new problem. When I first installed Ubuntu it didn't work and I found the following solution:

sudo add-apt-repository ppa:voria/ppa
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install samsung-tools samsung-backlight
sudo reboot

So, I have tried this again. With no effect.

I have discovered that under Settings/Software & Updates/Other software it says:

Disabled on upgrade to Oneric (http://ppa.launchpad.net/voria/ppa)

So I guess that is why the above no longer works.

In addition, some of the other Hotkeys (Eg. wifi/bluetooth/sound/screen on/off) all work.
This is currently causing big problems. I'm away from home, using my netbook as my primary form of comunication in cafes etc. My ability to find a wifi connection with a power supply is limited.

Work Around: I have just discovered that if I start on a power supply and then 'Hibernate' I will have a bright screen if I restart on battery power. But still no brightness control.

Other than reverting to backup (My backups are at home) does anyone have a solution?

I looked on the Ubuntu forums and found this thread:

http://ubuntuforums.org/showthread.php?t=2163131&highlight=Samsung+Backlig ht

Which might help me, if I understood it. I'm not very good with the technical side of Ubuntu, as it usually just works.

I then found this thread:


Which asked for the some comands to be run (for Diagnostics?):

1 Your current kernel command line:

cat /proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-3.8.0-26-generic root=UUID=2a09def6-779f-4377-bf2d-72f44d877e5d ro quiet splash vt.handoff=7
2 Your video card and driver:

sudo lspci -vnn | grep -A12 VGA

00:02.0 VGA compatible controller [0300]: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller [8086:a011] (prog-if 00 [VGA controller])

 Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072]
Flags: bus master, fast devsel, latency 0, IRQ 46
Memory at f0300000 (32-bit, non-prefetchable) [size=512K]
I/O ports at 18d0 [size=8]
Memory at d0000000 (32-bit, prefetchable) [size=256M]
Memory at f0000000 (32-bit, non-prefetchable) [size=1M]
Expansion ROM at <unassigned> [disabled]
Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
Capabilities: [d0] Power Management version 2
Kernel driver in use: i915

    00:02.1 Display controller [0380]: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller [8086:a012]
3 Your backlight interfaces:

for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/max_brightness; done

So I have done likewise, in the hopes that they will be usefull...
I suspect that the first link above is probably the solution, if only I understood it.