To get working brightness keys, try the following.
Run the command:
sudo -H gedit /etc/default/grub
Change this line
to something like below
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor
sudo update-grub and reboot. See if brightness keys are working.
It is still possible Ubuntu won't remember your brightness settings. So you have to change brightness each time.
Please let us know the result as many Sony users are facing this problem.
This is for setting brightness manually after doing the above steps.
Try following for paths shown by
ls /sys/class/backlight/*/brightness and replace accordingly.
For example, paths will be like:
For the above path Get the maximum brightness:
Try a lower value to set the brightness, say output is 16 so I will try with half of it:
echo 8 | sudo tee /sys/class/backlight/acpi_video0/brightness
If this works, make this happen in each login automatically by doing the following
sudo -H gedit /etc/rc.local
Enter this line just before
exit 0. It should look like:
echo YOUR_VALUE_HERE > /sys/class/backlight/acpi_video0/brightness
Also you can try with xdotool