In core /var/lib/systemd/backlight should be bind mounted to writable

[david butler]

So, I'm getting this:

Apr 19 07:26:00 localhost.localdomain systemd[1]: Stopped Load/Save Screen Backlight Brightness of backlight:acpi_video0.
Apr 19 07:26:00 localhost.localdomain systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:acpi_video0...
Apr 19 07:26:01 localhost.localdomain systemd-backlight[4936]: Failed to create backlight directory /var/lib/systemd/backlight: Read-only file system
Apr 19 07:26:01 localhost.localdomain systemd[1]: systemd-backlight@backlight:acpi_video0.service: Main process exited, code=exited, status=1/FAILURE
Apr 19 07:26:01 localhost.localdomain systemd[1]: Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0.
Apr 19 07:26:01 localhost.localdomain systemd[1]: systemd-backlight@backlight:acpi_video0.service: Unit entered failed state.
Apr 19 07:26:01 localhost.localdomain systemd[1]: systemd-backlight@backlight:acpi_video0.service: Failed with result 'exit-code'.

It looks like whatever was done for rfkill needs to be done for backlight

rfkill gets a generated fstab entry like this:
/writable/system-data/var/lib/systemd/rfkill /var/lib/systemd/rfkill none bind 0 0

I couldn't figure out where that came from after a few minutes of digging, I suspect some magic or voodoo related to systemd-fstab-generator

FWIW, the backlight stuff isn't important to me, but its noise in the logs and systemctl as a failure...

$ snap list
Name Version Rev Developer Notes
classic 16.04 17 canonical devmode
core 16-2 1689 canonical -
linuxium-kernel 4.4.0-45.66 x1 -
pc 16.04-0.8 9 canonical -

[Zygmunt Krynicki (zyga)]

I agree that the directory should be writable. Perhaps that's something that needs to be added to writable-paths (as a quick solution)?