Save Screen Brightness in Ubuntu Linux

• Open the Linux Terminal (CTRL + ALT + T)
• Execute the below command to check the  maximum brightness

cat /sys/class/backlight/acpi_video0/max_brightness

If it's 100, you can set the brightness as 30.

• Add a startup script which will automatically adjust screen brightness when Ubuntu boots up

sudo -i

gedit /etc/rc.local

echo 30 > /sys/class/backlight/acpi_video0/brightness