Comment # 7 on bug 1229813 from Fabian Vogt

(In reply to Thorsten Kukuk from comment #6)
> (In reply to Dominique Leuenberger from comment #5)
> > (In reply to Thorsten Kukuk from comment #0)
> > 
> > > dbus-broker has no dbus.service file, thus this dependencies are broken and
> > > a boot only succeeds by pure luck.
> > 
> > That part is only partially true: when dbus-broker is enabled, systemd
> > creates
> > /etc/systemd/system/dbus.service (and also /etc/systemd/user/dbus.service)
> > due to the alias present in dbus-broker.service)
> 
> Could it be that this get's only created when systemd starts the service,
> but it is needed already upfront?

No, it gets created when dbus-broker.service gets enabled, i.e. during
dbus-broker package install or preset update.

> wtmpdb got started on one failing machine before dbus got started and
> systemd-logind reported dbus errors.

Logs would be helpful here.