Thoughts about HAL, Ivman and Pmount.

Martin Pitt martin at
Fri Oct 28 06:56:16 PDT 2005

Hi Jonatan, hi all,

Jonatan Liljedahl [2005-10-27 22:20 -0200]:
> > Jonatan Liljedahl [2005-10-26 21:31 -0200]:
> > > IMHO, automounting should be done by system (hald or ivman running
> > > as root), since if two users are running ivman at the same time
> > > there will be big trouble when both tries to mount the same thing
> > > under /media. There will be a war about who owns the mountpoint.
> > 
> > Mounting the device by hal does not solve this "war" at all.
> No? If hal (or another system service) mounts it, then there will be
> only ONE app that tries to mount the device, so no war.

The war is not about which process mounts the device, but which *user*
the device belongs to.

> Unless pmount is called by ivman running as root, then it will be
> mounted as ivman.plugdev with uid and gid mount options set accordingly,
> and with umask 0002. And with my patch for pmount it allows any user in
> "plugdev" group to unmount the device. (Yes I know, not an ideal
> solution but it works for a small family LAN with one box and n
> X-terminals).

You are welcome to use the patch for your own purposes. There is "add
support for changing the group" on pmount's TODO list, so that you can
tell pmount to assign any group your user is in to the mount point.

> Not very nice, you're right. So probably it would be better still to
> don't automount anything at all, but only create the mountpoints and
> then let the users mount/unmount it and the first user who mounts it
> will own it.

Maybe this is a little better, but not the thing we would want to do
in Ubuntu. But since this is just a matter of setting the prefered
default gconf schema values, it is easy for distros to customize the
default behaviour.

> > I see two options to mitigate this:
> > 
> >   - In Ubuntu, gnome-volume-manager has a patch that adds support for
> >     multiseat, like found in the HP441. So by configuring
> >     /etc/multiseat.conf properly, you can solve the conflict if you
> >     have more than one head on your box.
> In which way is it solved? Never heard of the HP441...

In this file you can configure the "heads", i. e. define which
keyboards, monitors, and USB ports belong to a terminal.

> What do you mean "active" ? Can't two users be active at the same time?
> For example, when I'm sitting here (logged in to X trough xdm) and my
> girlfriend has logged in also, trough another box in this room acting as
> an X terminal?

In this case both of you are really active at the same time. I meant
that if multiple user are logged in at the same time on a single head,
then only one desktop is actually displayed, and the other one sits
around in the background. (cf. gdmflexiserver).

Martin Pitt
Ubuntu Developer
Debian Developer
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