The reason upowerd doesn't recognize keyboard backlighting anymore is https://gitlab.freedesktop.org/upower/upower/commit/b0cdb7e9fe93b662d4f4a29b3af7f66ef3763c67 which added several filesystem lockdown directives to upower.service
In my case (Apple MacBook Air), the kbd_backlight control file are in $ ls -l /sys/class/leds/smc::kbd_backlight lrwxrwxrwx 1 root root 0 Aug 22 20:02 /sys/class/leds/smc::kbd_backlight -> ../../devices/platform/applesmc.768/leds/smc::kbd_backlight/ i.e. /sys/devices/platform/applesmc.768/leds/smc::kbd_backlight I dropped the following upower.service override into /etc which made keyboard backlight control work again: --- /lib/systemd/system/upower.service 2018-07-05 14:07:56.000000000 +0200 +++ /etc/systemd/system/upower.service 2018-08-22 21:00:11.340079711 +0200 @@ -9,10 +9,10 @@ Restart=on-failure # Filesystem lockdown -ProtectSystem=strict -ProtectKernelTunables=true -ProtectControlGroups=true -ReadWritePaths=/var/lib/upower +#ProtectSystem=strict +#ProtectKernelTunables=true +#ProtectControlGroups=true +#ReadWritePaths=/var/lib/upower ProtectHome=true PrivateTmp=true Cheers, Roderich
