[plug] Multimedia users

James Devenish devenish at guild.uwa.edu.au
Mon Jun 16 08:30:34 WST 2003


In message <1055678710.16968.19.camel at jlmpc>
on Sun, Jun 15, 2003 at 08:05:10PM +0800, Jon Miller wrote:
> In fstab what is the setting for the /dev/[multimedia devices], mostly
> interested in the 4th field.

I'm not a Linux expert, but I would be surprised if fstab would be
relevant for anything other than the cdrom drive. In particular,
audio devices would not be covered.

In message <Law14-F308ZBLzusyLY00005e35 at hotmail.com>
on Sun, Jun 15, 2003 at 06:47:19PM +0800, John Clayton wrote:
> What I would like to know is if there is a way to change which user gets 
> control of these devices without having to log off/on in the necessary 
> sequence.

Unless there is a canonical solution, the best answer may depend on your
circumstances and purpose. For instance, one resolution may be to do
something like `chmod a+rw /dev/audio`. Then anyone could use that
device at any time (this might be highly desirable or completely
abhorrent, depending on what the computer is used for :). You could also
so something like `groupadd mmedia; usermod -G mmedia username; chgrp
mmedia /dev/audio` so that the 'username' user could access /dev/audio
at any time by virtue of being in the 'mmedia' group. If you need
additional intelligence, you might need to write your own script to
enforce the correct logic.

In message <Law14-F308ZBLzusyLY00005e35 at hotmail.com>
on Sun, Jun 15, 2003 at 06:47:19PM +0800, John Clayton wrote:
> When a normal user loggs on a whole bunch of /dev/[multimedia devices]
> get there owner changed from root to the user that logged in while
> leaving the group as root. Different users subsequently logging in
> does not change this.  But when the first user logs out  the /dev/
> entries go back to normal until another user subsequently logs in. I
> think this is a locking mechanism to make sure that only one user at a
> time has access to multimedia devices.

I believe I had a look at controlling this for a friend at the beginning
of the year and didn't end up with a unified solution. Under Solaris/
OpenBSD, would could use config files like /etc/logindevperm and
/etc/fbtab to configure something such as having vt logins effect the
changes (instead of merely console and X11 logins)---but I doubt you'd
really want that. Note, though, those files are used by login(1),
ttymon(1M) and init(8)...perhaps the Linux man pages for those
programmes (or equivalent) will indicate configuration options? Then
again, maybe it's your graphical login manager (e.g. xdm, kdm, gdm or
whatever it is for you). Perhaps your Linux/PAM setup has a directory
/etc/security that might be relevant?




More information about the plug mailing list