slides from Nove Hrady

Havoc Pennington hp at
Thu Aug 28 03:34:50 EEST 2003

On Tue, Aug 26, 2003 at 03:53:48PM -0400, Navindra Umanee wrote:
> Havoc Pennington <hp at> wrote:
> >
> Interesting.  Does using D-BUS for both the system and the user
> session require running two (or more, depending on number of user
> sessions) separate bus processes?

Yes, by design. The system bus and each user session bus are all
separate process instances that don't connect to each other in any
way.  The only relationship is that they all use the same
/usr/bin/dbus-daemon executable. But they launch that executable with
distinct config files (see the example config files in the slides).

The system bus is much more tightly restricted than the session bus -
right now in Red Hat Rawhide for example, the only message that's even
allowed over the system bus is "print queue changed" and that message 
can only be sent by the cups daemon and no other user.

You could create a per-session process that monitored and forwarded
system messages, though, if you wanted. This could be used to avoid 
connecting individual apps to the system bus.

The interfaces exported from an app to the bus are set up
per-bus-connection, so even if individual apps connected to the system
bus, they would not have the large interfaces exposed that e.g. DCOP
currently exposes. Those interfaces would be only on the session bus.
> PS Great photo:  :-)

I had that "many hours on the plane" look even ;-)


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