It seems there is a misunderstanding about brightness control , specially as regards the last line of my previous answer, which I thought was self-explanatory about the remaining issue: I only stated in that post that now
the Fn/F5 works (with some trouble sometimes),which was not the case before, but
that the brightness control problem remains unsolved.
In fact in that last answer I said nothing about the Fn/Up & DOWN, which means they still do not have any effect on the real brightness of the screen, although the brightness bubble is correctly displayed and the level it shows is increased/decreased by the Fn/UP or DOWN action.
This is with the 190.53 NVIDIA driver I use now, and was already the case with the "official" (185) driver I used before, as far as the Fn /UP & DOWN keys are concerned.
As already told, as the Fn/F5 works with the 190.53 driver, I did not even try the beta 195 NVIDIA driver you mentioned as I thought is was then useless.
Do you think I should have a go with this beta driver for the Fn /UP & DOWN...and what are my risks?
I would not like to break everything and restart from scratch if the Xserver is not pleased with that driver....I already made some mistakes (as you understood very well each time it happened
trying to implement what you explained, so..
About the backlight command using the terminal, it seems it does not always work well.
When it works correctly, backlight is shut off.
Then when typing (in the dark!) the same command, backlight comes ON again, and I can see that after the first command, I was given back the hand by the terminal: the line of the backlight ON same command (typed without seeing it) begins with xxxx@MyNetbook:~$, which is expected.
When it does not work properly , I have to type Fn/F5 to have backlight ON again..and read what has happened in the terminal.
In that case, hand has not been given back to terminal, so the second typed command has not been executed, as the line does not begin by xxxx@MyNetbook:~$
It can be the other way around: backlight is on, I type the command in terminal, backlight stays ON, and I can see that the second command line (for backlight OFF) is just at the beginning of the next line, meaning that also in this cas hand has not been given back to the terminal.
Please note that I checked each time very carefully to avoid any typo. mistake , so it does not come from some kind of unknown command (terminal never answered that when the command did not work).
All this seems consistant with what happens with the Fn/F5 strike having sometimes no effect at the first strike.
I am sorry I am not in a position to help you rewriting anything, although I would be happy to do so.
Only someone who really understands how these things work , and has a good knowledge about the similarities as well as differences between the different Samsung netbooks is really able to design and write an efficient tutorial about them.
My lack of knowledge in Linux really prevents me to do so, sorry again.