How do I prevent Ubuntu from changing my laptop screen brightness level?

I faced the same problem on my Dell XPS. Currently there is no other way to save it according to brightness key.

First try executing

sudo su -c 'echo 5 > /sys/class/backlight/acpi_video0/brightness'

If it succed,try with different value for 5 and choose your preference level.

Now edit /etc/rc.local file to execute this command at boot up.
```
gksu gedit /etc/rc.local
```

Just before exit in the file, add the following line,

echo 5 > /sys/class/backlight/acpi_video0/brightness

You can change value 5 to anything.

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