[arch-general] Systemd screen brightness

[Norbert Zeh]

Aurko Roy [2012.08.15 1140 +0530]:
> On Wed, Aug 15, 2012 at 7:00 AM, Michael Nawrocki <zaedrake at gmail.com>wrote:
> 
> > Hey everyone,
> >
> > I'm trying to get my laptop backlight keys (fn+f6/f7) to adjust the
> > brightness of my toshiba laptop backlight. Previously, I had entered the
> > following in my /etc/acpi/handler.sh to handle the acpi events generated
> > when those keys were pressed:
> >
> >     video/brightnessdown)
> >       echo $(($(cat /sys/class/backlight/acpi_video0/brightness) -1)) >
> > /sys/class/backlight/acpi_video0/brightness
> >       ;;
> >
> >     video/brightnessup)
> >       echo $(($(cat /sys/class/backlight/acpi_video0/brightness) +1)) >
> > /sys/class/backlight/acpi_video0/brightness
> >       ;;
> >
> > However, as I am working on migrating to systemd, acpid no longer runs
> > and hence does not handle these events. How can I write a similar
> > handler into systemd?
> >
> > Thanks,
> >
> > Mike
> >
> >
> I used to reduce my brightness using a similar command in /etc/rc.local
> (/bin/echo -n 0 > /sys/class/backlight/acpi_video0/brightness) but for the
> reasons that you mention this won't work anymore. I then switched to using
> X's brightness handler (xbacklight -set 0) which reduces display brightness
> as X starts. This is an easy solution but only works if you use X or if the
> delayed reduction in brightness is acceptable to you.

You can achieve the same by adding the instructions to write to
/sys/class/backlight/acpi_video0/brightness to an appropriate file in tmpfiles.d.
Read the section on temporary files in the systemd page on the archwiki.

Cheers,
Norbert