alight

alight is a tiny backlight control utility for Linux.

Usage

alight                 # show current brightness (%)
alight 40              # set brightness to 40%
alight +10             # increase by 10 percentage points
alight -10             # decrease by 10 percentage points
alight -l              # list usable devices
alight -d acpi_video0  # use a specific device

Values are percentages from 0 to 100 and are clamped. alight 0 writes raw brightness 0, which can blank some displays.

By default, alight scans /sys/class/backlight and prefers devices in order of: firmware, platform, raw, then anything else; ties are resolved in lexicographic order. Use -d DEVICE or ALIGHT_DEVICE=DEVICE to choose one.

Build

make

Install

doas make install
doas udevadm control --reload-rules
doas udevadm trigger --subsystem-match=backlight --settle

Defaults: /usr/local/bin, /etc/udev/rules.d, and /usr/local/share/licenses/alight. Override PREFIX, BINDIR, UDEVDIR, LICENSEDIR, or DESTDIR as needed.

The udev rule gives the video group read/write access to backlight brightness files using /bin/chgrp and /bin/chmod; adjust 90-alight.rules if needed. Your user must be in video.

Uninstall

doas make uninstall
make clean

License

Copyright (C) 2026 Maika Namuo.

alight is licensed under the GNU General Public License v3.0 or later. See LICENSE for the full license text.