Forbid user control over ALSA

Tony Baldwin photodharma at
Tue Jun 16 22:01:57 UTC 2009

On Tue, Jun 16, 2009 at 11:44:39PM +0200, Christian Svensson wrote:
> Hello.
> I have a server that is running ALSA with MPD. It's essential that the users
> on the server is not allowed to change volume - piece of cake I thought.
> The server needs to have Xorg running (fluxbox + firefox). I figured it was
> a matter of simply not having the user in the group audio - man was I
> misstaken!
> I belive it's PolicyKit that kindly enough changed the permissions on
> /dev/snd/* to include an ACL-record of the user that logged on.
> I've spent a few hours googling around, but a solution is nowhere to be
> found - this is not your every day problem, I'm sure.
> So please, how would I disable this "feature"?

Yeah...doesn't removing them from group audio render them unable to 
use the soundsystem completely (ie. no sound at all)?

But, if they are just running a terminal with FF running in a flux session, 
how are they altering the volume (you don't have wmix or something in their fluxbox slit,
I assume) ?
Perhaps my perception is erroneous, but from what you've written, I'm kind of assuming that
users have access to some kind of web terminal only.
If you have no fluxbox menu item and don't give them access to a terminal or fbrun, etc.,
I don't see how they can find any other software or means to modify the volume, especially
if they are your typical clueless windows user types.

In any case, could you not just alter the permissions of whatever interface or software they 
are using to access volume?  Or is it a matter, of them having access to necessary plugins
for FF that are somehow giving them access to the audio volume?


art & photos | tony baldwin

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