Where Does brightnessctl Keep Permissions?
brightnessctl backlight access on Linux, sysfs nodes plus udev rules for permissions.
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brightnessctl writes backlight values under /sys/class/backlight and keeps no config file. Permissions come from udev rules you add yourself. Device names differ per laptop.
The durable artifacts are your rules and scripts. Keep the udev file in configuration management. Values reset at boot by design, so script defaults.
Where brightnessctl stores this, by platform
/etc/udev/rules.d/90-backlight.rules
Grant video group write access here for passwordless control. Backlight values themselves live transiently in sysfs. Script defaults for boot.
Frequently asked questions
How do I run brightnessctl without sudo?
Add a udev rule granting the video group write on backlight class devices, add the user to video, then replug or retrigger. That beats running bright tools as root.
Which backlight device do I target?
List /sys/class/backlight to see available controllers. Some desktops expose one name, others two. Point brightnessctl at the right device flag.
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