How to Fix D-Bus Service Failures

[Simon McVittie]

On Sat, 08 Mar 2025 at 13:26:06 +0300, Abdullah Yıldız wrote:
> In /usr/share/dbus-1/, there are no commented-out default values available
> except session.conf:

Most likely either your version of dbus is older than 2014, or your
OS vendor has patched it. Please ask your OS vendor for support.

> Is there a way to check what the default is for the system bus as it (i.e.,
> max_completed_connections) is not visible at both /etc/bus-1 and /usr/share/
> dbus-1/?

Check your OS distribution's source code, or ask your OS vendor for
support.

In upstream dbus, the defaults for the system bus are the hard-coded
values in bus/config-parser.c. But if your OS vendor has patched or
otherwise altered dbus, then we can't know how that version might be
different; you'll need to ask them.

> > The default on the session bus is 100000, and the session bus normally
> > only allows connections from one user, so the limit on connections per
> > user is also 100000.
> 
> This is defined as 900 in /usr/share/dbus-1/session.conf as shown in the above
> code snippet.

Your version of dbus appears to have been patched, either by your
OS vendor or locally. As far as I can see, that has never been the
default in upstream dbus. (And that seems like a really low limit for
the session bus: most of the limits in the session bus are meant to be
"basically unlimited, but enough to prevent accidents".)

> > The default for the system bus is 256. The default for the session
> > bus is 100000, but the error messages you quoted are for the system bus.
> 
> max_connections_per_user is defined as 100000 in /usr/share/dbus-1/session.conf
> as shown in the above code snippet.

The session bus configuration does not affect the behaviour of the
system bus. If your system bus is producing errors, reconfiguring the
session bus cannot solve those errors.

> Is it possible that our D-Bus service is corrupted (as we never did any
> modifications on these files)?

I don't know what you or your OS vendor might have done.

    smcv