Remote Control of Volume

Hello, everyone. Here's a problem I'm trying to solve using two platforms
running Fedora Core:

Computer A (local) - Has vncserver, sshd, XMMS, and has sound output
connected to amplifier/speakers.

Computer B (remote) - Has vncviewer and is networked to Computer A.

I would like to control the playing of sound files on Computer A from
Computer B. Currently I have to first log on to Computer A prior to
logging on from Computer B for a functional remote session. Vncviewer or,
alternatively, SSH (with X11 forwarding) is used with XMMS to exercise
remote control of Computer A. With a local logon first, everything works
as expected.

If I attempt to logon from Computer B without local logon at Computer A,
the connection is established but Computer A cannot connect (hardware
device not found) the local sound mixer/volume control to the local
soundcard in this scenario. If using a remote desktop (vncviewer) this is
also confirmed by the absence of the speaker icon on the Gnome taskbar.
Of course XMMS needs the sound mixer applet connected to the soundcard in
order to function. Other than this, the remote control is established.
Does anyone know a workaround that would not require a local logon? Thanks
for your time and comment. Sincerely,

John Wood (Code 5550) e-mail: (E-Mail Removed)
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

["Followup-To:" header set to comp.os.linux.misc.]
On Tue, 26 Sep 2006 07:44:54 -0400, J. B. Wood staggered into the Black
Sun and said:
> Computer A (local) - vncserver, sshd, XMMS, and connected to
> amplifier/speakers.
> Computer B (remote) - vncviewer and is networked to Computer A.
>
> I would like to control the playing of sound files on Computer A from
> Computer B.

No problem, just make sure the permissions on the device files used to
play sounds are set properly. I think they're using udev on Fedora now,
so that's everything under /dev/sound/ and /dev/snd/ . In many cases,
these devices are 0660 and owned by root:audio, so everybody who wants
to play sounds needs to be in the audio group.

> Currently I have to first log on to Computer A prior to logging on
> from Computer B for a functional remote session.

Is Fedora doing something dumb wrt device ownership? Often, whoever's
logged in to the local console gets ownership of many devices. If
nobody's logged in to the local console, these devices should be
root:somegroup , but it's difficult to know what's really going on
without being able to ls -l. Fortunately, you can ssh in to this
machine and check.

> vncviewer or, alternatively, SSH (with X11 forwarding) is used with
> XMMS to exercise remote control of Computer A. With a local logon
> first, everything works as expected. If I attempt to logon from
> Computer B without local logon at Computer A, the connection is
> established but Computer A cannot [use] the local sound mixer/volume
> control

Device permissions, probably. Check those first.

> Of course XMMS needs the sound mixer applet connected to the soundcard
> in order to function.

The problem is almost certainly at a lower layer than xmms or any GUI app.

> Does anyone know a workaround that would not require a local logon?

Force the audio device nodes to 0660 , root:audio , make sure all users
who need to use sound are in group audio, and see what happens. You
need to change rules under /etc/udev/ if udev's being used for changes
to persist. HTH,

--
Due to inflation, your 40 acres and a mule have now been reduced to
400 square feet and a guinea pig.
There is no Darkness in Eternity/But only Light too dim for us to see

Dances With Crows wrote:
>
> No problem, just make sure the permissions on the device files used to
> play sounds are set properly. I think they're using udev on Fedora now,
> so that's everything under /dev/sound/ and /dev/snd/ . In many cases,
> these devices are 0660 and owned by root:audio, so everybody who wants
> to play sounds needs to be in the audio group.

> Device permissions, probably. Check those first.
>
Hello, Dances, and thanks for replying. I do not have a /dev/sound
directory but do have a /dev/snd directory on my Fedora Core 5 platform.
There is no "audio" group. Logging in from the local computer gives
temporary ownership of /dev/snd to the login user name. However, when
remotely logging in via SSH using the same user name does not
temporarily transfer ownership of /dev/snd (it is still shown with an
owner of root).

I did a groupadd audio then a usermod -Gaudio wood and then a chown -R
root:audio on /dev/snd but still had the same problem associating the
local sound mixer with the local sound card when doing a remote login.

If I permanently do a chown -R wood:root /dev/snd this fixes the remote
login issue but now I've made myself (wood) the permanent owner of /dev/snd.

There seems to be a distinction as far as obtaining temporary
file/directory ownership when one logs on at a console vs remotely using
the same user name in both cases. Sincerely,