I installed Ubuntu 14.04.02 as dual boot in a macbook pro 2012 13 I noticed that all function buttons works but except those that regulate the brightness of the screen.How do I fix this problem?
I found an answer to this. However I have an iMac 2011, so it could solve your problem.
You need to edit the grub file
/etc/default/grub change the line
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi=Linux"
Rebooot your computer and voilà.