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backlightd user guide

backlightd controls laptop backlights and external DDC/CI monitors together. Use one CLI for desktop shortcuts, a status bar, and gradual automatic brightness.

• Installation — requirements, build, installation, and service commands.
• NixOS — Nix package and declarative system setup.
• CLI — brightness, power, JSON, refresh, and device listing.
• Configuration — every setting, validation, reload, and legacy overrides.
• Automatic-brightness — solar schedules, clock fallback, manual overrides.
• Brightness-and-calibration — limits, curves, monitor IDs, and accuracy.
• Integrations — shortcuts and a Waybar example without a wrapper script.
• Troubleshooting — missing screens, stale readings, logs, and recovery.

Quick start

backlightctl -b 60%
backlightctl -b +5%
backlightctl --auto
backlightctl --devices

New installations use a linear brightness scale and automatic logical targets between 10% and 100%. With no configured location, morning/evening ramps start at 06:00 and 18:00 local time and last four hours each. IP geolocation is disabled by default. There is no ambient-light sensor integration.

Settings live in /etc/backlightd/config.toml, with comments. After editing:

backlightd --check-config
sudo systemctl kill --signal=HUP backlightd

The code-focused reference is generated with rustdoc; this wiki is the user manual.