I know that one can override dbus session services in ~/.local/share/dbus-1/services
But it necessarily won't work for system services.
Under openrc, I don't get systemd's systemctl command therefore :
Is the quick and dirty (because service will be restored on next update) way consisting in renaming the associated service file in /usr/share/dbus-1/system-services, the only way to proceed ?
I just encountered this same problem, and after digging into the dbus code, I think I have a solution:
Files in /usr/local/share/dbus-1/system-services override the files in /usr/share/dbus-1/system-services. So, to prevent a service from autostarting, you can create an empty file. For example, to make sure dbus never starts login1 automatically:
mkdir -p /usr/local/share/dbus-1/system-services
touch /usr/local/share/dbus-1/system-services/org.freedesktop.login1.service
This also allows you to disable user services globally using /usr/local/share/dbus-1/services.
Another effective method to prevent it from launching services by itself is building dbus with -Dtraditional_activation=false. However, this disables all services.
Does the D-Bus service have a SystemdService= line pointing to a Systemd unit file, like SystemdService=systemd_unit_name.service?
If yes, you can add a symlink from /etc/systemd/system/systemd_unit_name.service to /dev/null. This is how systemctl mask systemd_unit_name.service works.
Then any attempt to activate the D-Bus service will fail since the linked Systemd service is masked. But you may see some annoying logs in the journal about a failed activation since the service is masked.
If there is no SystemdService= line, you can try adding a symlink from /etc/systemd/system/dbus_unit_name.service to /dev/null (not tested). I assume if there is no alias mapping from a D-Bus unit file named dbus_unit_name.service to a Systemd unit file name systemd_unit_name.service, the D-Bus activation will just look for a Systemd unit file with the same name as the D-Bus unit file, like dbus_unit_name.service.
You can also override D-Bus system services in /etc/dbus-1/system-services/, I believe (again, not tested).
I wanted to disable org.mate.ScreenSaver.service on Ubuntu 24.04, and the solution provided by @mid_kid worked for me, but only after I populated the local service config file with the content copied from the original file, except for the dummy executable:
$ cat /usr/local/share/dbus-1/services/org.mate.ScreenSaver.service
[D-BUS Service]
Name=org.mate.ScreenSaver
Exec=/bin/false
With this file in place the service was truly disabled.
Here are the contents of the original file for the reference:
$ cat /usr/share/dbus-1/services/org.mate.ScreenSaver.service
[D-BUS Service]
Name=org.mate.ScreenSaver
Exec=/usr/bin/mate-screensaver --no-daemon
