Increasing screen brightness with the /proc filesystem
17 October 2010
I installed Fedora/LXDE on an old laptop this weekend, and it went well -- but when I told it to hibernate and then booted it back up, the screen was painfully dim. I wonder why that happened ... but since I'm not planning to go fixing any bugs in the hibernate code of either Fedora or LXDE, the why it happened wasn't nearly as pressing a question as what do you do about it?
So I started digging around in the /proc filesystem, after not finding anything obviously related to screen brightness in 5 seconds of looking through the GUI tools. The /proc/acpi/video/VGA/LCDD/brightness file looked promising.
[root@flower sirsean]# cat /proc/acpi/video/VGA/LCDD/brightness levels: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 current: 0
Ah ha, no wonder the screen was so dim! I just had to tell it to increase the brightness.
[root@flower sirsean]# echo 5 > /proc/acpi/video/VGA/LCDD/brightness
The screen immediately got much brighter, more usable. I was kind of surprised by that, to be honest, but I liked it.
[root@flower sirsean]# cat /proc/acpi/video/VGA/LCDD/brightness levels: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 current: 5
Yup. I have a feeling I'll be needing to do this again at some point.