[LightDM] change volume when greeter appears

[Adam Nielsen]

> Therefore I am asking: Is there any way how to run shell commands in 
> scope of the lightdm user when the login screen appears and before the 
> screenreader is started?

You can run set up commands with the configuration parameters
display-setup-script and greeter-setup-script set in the LightDM config file.

The display one is usually used to configure the monitors (e.g. for
multimonitor setups or perhaps in your case to activate high-contrast
modes or override the DPI to be lower to enlarge the text size) so the
greeter script is probably the one you are after for audio.  However if
you have auto-login enabled I am guessing the greeter won't run, so you
may prefer putting everything into display-setup-script so you can be
confident that it will always run.

If you need to run more than one command or use complex redirection,
it's probably easier to give these options the path to a shell script
that does the work.

Cheers,
Adam.