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Set Screen Brightness from the Terminal (/sys Backlight)

Read and write /sys/class/backlight/.../brightness to change laptop screen brightness, or use brightnessctl for a friendlier percentage-based interface.

LinuxbacklightdisplaylaptopbrightnessMedium risk
Write a numeric level to /sys/class/backlight/*/brightness with `echo N | sudo tee /sys/class/backlight/intel_backlight/brightness`, or run `brightnessctl set 80%`.

01Command

Command
$ echo 700 | sudo tee /sys/class/backlight/intel_backlight/brightness

02What it does

First check the maximum with `cat /sys/class/backlight/*/max_brightness`, then write a value between 0 and that maximum. The exact folder name depends on your GPU driver — intel_backlight, amdgpu_bl0, or acpi_video0 are common. For everyday use, brightnessctl is easier: `brightnessctl set +10%` brightens by ten percent and `brightnessctl set 50%` sets an exact level.

03Risk

RiskMedium risk
RequirementsWorks on most laptops with an ACPI backlight; the folder under /sys/class/backlight/ may be named acpi_video0 or amdgpu_bl0 instead of intel_backlight. brightnessctl (packaged in most distros) does the same without sudo: brightnessctl set 80%
!Warning: Never write to max_brightness or use shell redirection with sudo in the form `sudo echo N > file` — the redirection happens as your own user and fails; use `sudo tee` instead.

04Undo

Undo
$ echo 900 | sudo tee /sys/class/backlight/intel_backlight/brightness

05Sources

  • brightnessctl(1) - Linux manual page
    Ubuntu Manpages · technical · 2026-09-17
    Evidence: brightnessctl reads and writes the brightness of backlight devices; commands like 'brightnessctl set 80%' adjust the current brightness as a percentage without root when the user is in the video group.
  • Backlight - ArchWiki
    Arch Linux Wiki · technical · 2026-09-17
    Evidence: Documents that backlight brightness is controlled by writing to /sys/class/backlight/<device>/brightness and lists device names such as intel_backlight and acpi_video0.

Last verified: 2026-09-18 · Category: System & Settings