Xubuntu 12.10 doesn't save screen brightness on reboot

Question

I have a laptop running Xubuntu 12.10 that doesn't save the brightness setting on reboot. There are some explanations on Ask Ubuntu about how to have a specific brightness be set on reboot, but not how to save the brightness from last time. How can this be done?

Answer 1

Create a Bash script to save the brightness:

sudo nano /etc/acpi/save-brightness.sh

It should contain this:

#!/bin/bash
# Saves brightness settings on reboot/shutdown

cat /sys/class/backlight/acpi_video0/brightness > /etc/acpi/brightness

Make it executable:

sudo chmod +x /etc/acpi/save-brightness.sh

Switch to the /etc/rc0.d directory and symlink the script to a link in /etc/rc0.d:

cd /etc/rc0.d
sudo ln -s ../acpi/save-brightness.sh K99-save-brightness

Do this again in the /etc/rc6.d directory (rc0 is for reboots and rc6 is for shutdowns).

Now edit /etc/rc.local to reload the brightness setting on boot.

On a separate line just before the last line that's already there (exit 0), put:

cat /etc/acpi/brightness > /sys/class/backlight/acpi_video0/brightness

Sources:

[1] http://en.kioskea.net/faq/3348-ubuntu-executing-a-script-at-startup-and-shutdown

[2] https://askubuntu.com/a/189485/30117