How to fix uneven screen brightness with Debian on the Acer Aspire 4739 laptop

This guide assumes a Debian-based Linux distribution like Linux Mint. Some steps may be different in distinct bases. I had this issue with my laptop. It wasn't a hardware issue, since during the entire boot process the entire screen brightness was ok. To fix this issue, you need to add a kernel boot parameter. You can do that through: Summary Graphical interface Command-line Graphical interface 1.…