[pulseaudio-discuss] Accessing audio as root

Colin Guthrie gmane at colin.guthr.ie
Thu Dec 24 04:29:02 PST 2009

'Twas brillig, and Halim Sahin at 23/12/09 14:26 did gyre and gimble:
> Hi Col,
> 1. I gave you some examples what doesn't work as expected.
> How should I run my text-to-speech server before login to have
> audiooutput for reading the login screen?

GDM runs under the gdm user and starts it's own PulseAudio process. This
can be easily used to do the reading of the login screen. I'm not
familiar with how screen readers work but that software should also be
launched as the gdm user. When a real user logs in, gdm's PA and
screenreader services will die or be suspended and the real user's PA
and screenreader service takes over.

> 2. Running daemons worked well under alsa (see my previous post).
> I am using every day this setup.
> Speechd runs with uid speech-dispatcher and I can also play sound as
> user halim.

I don't see any reason why speech-dispatcher needs to run as it's own
user. Why not just run it as the user who is actually using it?

At the end of the day the fact that a uid "speech-dispatcher" can access
a users' sound is disturbing. If that user is compromised they can
evesdrop on your user which is not very nice.

> But it introduced problems wich should be fixed.

I agree it has introduced problems for certain applications but just
because something has changed, it doesn't mean that PA needs to support
an obsolete, weird or insecure way of working that was permitted in the

> Your given examples are related to x-sessions.
> Go one step back.
> gdm starts and the screenreader->speech-server (before login).
> If pulseaudio starts at this time, it would use gdm uid.

This is indeed what happens.

> In this case the audiocard can't be used by another pulseaudio after
> successful login.

Yes it can. After login the gdm user is no longer permitted access to
the audio devices and the logging in user take over control, starts
their own PA etc. It all works nicely.

Hope this helps.



Colin Guthrie

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