backlight_control: Practical Linux backlight tweaks

backlight_control: Practical Linux backlight tweaks

A focused guide to adjusting your display backlight using the backlight_control command. It offers simple percentage-based adjustments and direct percentage setting.

Quickstart (how to use it)

  • Increase backlight by a percentage:
backlight_control +5
  • Decrease backlight by a percentage:
backlight_control -5
  • Set backlight to a specific percentage (e.g., 90%):
backlight_control 90
  • Show help and usage:
backlight_control

What this command does

  • It adjusts the display backlight intensity in percent, either by relative changes (±) or by an absolute value.
  • It relies on your system’s backlight interfaces (e.g., /sys/class/backlight) and appropriate permissions.

Quick examples

  • Restore a safe brightness (50%):
backlight_control 50
  • Slightly brighten the screen by 10%:
backlight_control +10
  • Dim the screen by 20%:
backlight_control -20

Common pitfalls

  • Not running as a user with permission to write the backlight interface. If you see permission denied, try running with sudo or fix permissions for the backlight path.
  • The available range may be 0-100%. Some hardware or drivers may cap at a lower maximum; if you set 100% and it doesn’t max out, it’s a hardware/driver limit, not an error.
  • Using relative changes on systems where the current brightness is unknown can lead to unexpected results. Prefer absolute values if you’re unsure.

Troubleshooting tips

  • Check the current brightness before changing it:
cat /sys/class/backlight/*/brightness
cat /sys/class/backlight/*/max_brightness
  • If the command isn’t found, install it from your distro’s repository:
# Debian/Ubuntu
sudo apt-get install backlight-control

# Fedora
sudo dnf install backlight-control
  • If the brightness doesn’t change after running the command, verify permissions on the backlight interface and consider using a udev rule to grant access or run with sudo as a quick test.

Alternatives and notes

  • Some desktops expose brightness adjustments via your desktop environment’s power settings. If you prefer GUI, those options can be more intuitive.
  • For scripting or automation, you can wrap backlight_control calls in a shell script and log results for auditing.

TL;DR

  • Use backlight_control for simple percentage-based brightness tweaks or absolute values.
  • Start with small adjustments, verify permissions, and respect hardware limits.
  • If you hit a wall, check permissions and the current max_brightness value.

See Also