you need to edit your grub file run these command in terminal sudo nano /etc/default/grub
change GRUB_CMDLINE_LINUX=""acpi_backlight=vendor to GRUB_CMDLINE_LINUX="acpi_backlight=vendor" save it and run sudo update-grub ** Changed in: unity (Ubuntu) Status: New => Invalid ** Description changed: Dell Inspiron 15 (3521) i5 64bit laptop With Ubuntu 12.04 and 12.10, the Dell Laptop would allow me to change screen brightness using Fn+F4 (brightness down) and Fn+F5 (brightness up). After upgrading to 13.10, the buttons respond but I can only adjust brightness one step down from maximum setting and back. System Settings > Brightness and Lock - does not allow me to change the brightness setting at all. Screen dimming to save power occurs if I enable it. ProblemType: Bug DistroRelease: Ubuntu 13.04 Package: unity 7.0.0daily13.04.18~13.04-0ubuntu1 ProcVersionSignature: Ubuntu 3.8.0-22.33-generic 3.8.11 Uname: Linux 3.8.0-22-generic x86_64 ApportVersion: 2.9.2-0ubuntu8 Architecture: amd64 CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell] Date: Sat May 18 17:16:40 2013 DistributionChannelDescriptor: - # This is a distribution channel descriptor - # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor - canonical-oem-somerville-precise-amd64-20120703-2 + # This is a distribution channel descriptor + # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor + canonical-oem-somerville-precise-amd64-20120703-2 EcryptfsInUse: Yes InstallationDate: Installed on 2013-03-12 (66 days ago) InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20120703-15:08 MarkForUpload: True ProcEnviron: - TERM=xterm - PATH=(custom, no user) - XDG_RUNTIME_DIR=<set> - LANG=en_US.UTF-8 - SHELL=/bin/bash + TERM=xterm + PATH=(custom, no user) + XDG_RUNTIME_DIR=<set> + LANG=en_US.UTF-8 + SHELL=/bin/bash SourcePackage: unity UpgradeStatus: Upgraded to raring on 2013-05-15 (2 days ago) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1181512 Title: Cannot adjust screen brightness To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1181512/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs