How do I adjust the screen brightness on an Acer Aspire One D270?

Possibly, the second solution posted in this thread applies to your laptop as well: passing the options acpi_osi=Linux acpi_backlight=vendor to grub. Try to edit the line starting with "GRUB_CMDLINE_LINUX" in the file /etc/default/grub to:

GRUB_CMDLINE_LINUX="quiet splash acpi_osi=Linux acpi_backlight=vendor"

and then run

sudo update-grub

Maybe this will help.

Optionally you can install XBACKLIGHT

XBACKLIGHT

The review : "For those of you whos laptop starts up with the screen brighter than the surface of the sun, this one is it. You can easily set this terminal program to stop your eyes from being bleeched by your laptop's screen brightness. Download the app, then go to the system tab, which is the cog shaped thing in the top right corner of your screen. Go to startup applications, and then set the command line to "xbacklight -set 0" (or whatever percentage you want your backlight to snap to on start up) and obviously, remove the quotes from that command. Wallah, that should straighten all of those pesky backlight problems out. Tell your friends, because this one is a keeper"

Edit: The following solution seems to work for some Acer Computers.

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux i915.i915_enable_rc6=1"

in /etc/default/grub (and then updating with sudo update-grub) [the first option enables hardware control of backlight, the second implements a workaround for Intel graphics]

Source : http://ubuntuforums.org/showthread.php?t=1850190

I've kept this thread bookmarked and I check it from time to time. I finally found a way to solve this problem (for my hardware), so I'm writing this answer for archive and hopefully help someone else.

I've been struggling with the same problem for nearly a year and a half. I have an Acer Aspire 5750G running Ubuntu 12.04.04 (64 bits), Debian Wheezy (64 bits) and Windows 7 Ultimate.

The problem with the backlight sliding bar that should appear when hitting Fn+Left/Right arrow keys never worked for me except in Windows (I had to install Acer drivers after a fresh reinstall). I've put together something that seems to work using things I found here and in other places.

First: get the widget to show up

This method worked both in Debian Wheezy and Ubuntu 12.04

Edit /etc/default/grub and add at the end of the GRUB_CMDLINE_LINUX line acpi_backlight=vendor, and then run sudo update-grub2 (please notice the 2 at the end, since I'm using GRUB2). And this should work after next boot.

Second: preserve backlight

Make sure there's something in /sys/class/backlight. I have there a symlink intel_backlight that points to ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight

This folder has some files in it:

$ cd /sys/class/backlight/intel_backlight
$ ls
actual_brightness  bl_power  brightness  device  max_brightness  power  subsystem  type  uevent

When I dim the brightness, the value in file actual_brightness decreases

$ cat  actual_brightness
976
$ cat  actual_brightness
304
$ cat  actual_brightness
160

976 is the value in max_brightness, and it's the max allowed value, so it won't go any further.

I made a little script and tried to set it up as a cron job. It stored the value as it was supposed to but was unable to restore it on boot.

A few days ago I found this book: Upstart Intro, Cookbook and Best Practices

So I made two upstart jobs to save and restore the value of the screen brightness.

Upstart is packaged on Ubuntu since version 6.10 (I think) and is an option on Debian. Check you have upstart and its version:

$ sudo initctl --version
initctl (upstart 1.5)
Copyright (C) 2012 Scott James Remnant, Canonical Ltd.

This is free software; see the source for copying conditions.  There is NO warranty; not even for     MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.

You can call it anything you like: anything.conf and it must be placed in /etc/init/ This job is triggered when the computer is shutting down or rebooting and copies the file /sys/class/backlight/intel_backlight/actual_brightness to /var/backups/actualb (this too can be changed to whatever you like, but on the second job it has to be same).

# upstart job to save the actual screen brightness on shutdown
# file: /etc/init/backlightsave.conf

start on runlevel [!2345]

script
    cp /sys/class/backlight/intel_backlight/actual_brightness /var/backups/actualb
end script

This job loads the value that has been stored and sets the screen backlight according to it. You can call it whatever.conf and place it in /etc/init/ too.

# upstart job to restore the screen brightness on boot
# file: /etc/init/backlightrestore.conf   

start on runlevel [2345]

script
    read brightness < "/var/backups/actualb"
    pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness $brightness
end script

You can test the jobs by typing in a terminal:

$ sudo initctl name_of_the_job

Now everything works fine for me, the screen backlight is restored even before the login screen shows up.

Hope this helps