dim brightness on login linux mint on 2015 macbook air

my fix for using a system d daemon on startup that uses intel_backlight

to check if thats the right one to use for you use

ls /sys/class/backlight/

create the systemd service file

sudo vim /etc/systemd/system/backlight.service

write the file

[Unit]
Description=Set Intel backlight brightness on startup
After=multi-user.target

[Service]
Type=oneshot
ExecStart=/bin/bash -c 'echo 40 > /sys/class/backlight/intel_backlight/brightness'

[Install]
WantedBy=multi-user.target

reload system d and enable the service

sudo systemctl daemon-reload
sudo systemctl enable backlight.service

optional: manually test the service with

sudo systemctl start backlight.service

then sudo reboot