On Thu, 15.11.12 10:06, Matthew Miller (mattdm@xxxxxxxxxxxxxxxxx) wrote: > On Thu, Nov 15, 2012 at 01:53:32AM +0100, Lennart Poettering wrote: > > In fact, all system bus services should be configured to defer > > activation to systemd, so that all services regardless how they are > > triggered are executed in the same clean execution environment, and can > > be manipulated with the same commands (systemctl > > stop/kill/restart/mask/...) as any other services. > [...] > > It's really not that hard. I think it's a really good rule to make all > > low-level system daemons work that way, to keep things robust and > > resource usage minimal. > > I was looking for resources on systemd and dbus activation. I realized that > the documentation here is very scarce -- there's this tutorial on just dbus > activation <http://raphael.slinckx.net/blog/documents/dbus-tutorial> and our > wiki page <http://fedoraproject.org/wiki/Packaging:Systemd#DBus_activation>, > but it seems like it might make a nice "systemd for Developers", if you > feel inspired at any point. There's indeed not much documentation around. This is primarily because we were kinda waiting for kernel dbus to materialize which would probably shuffle a few things around in this area. Here's the gist of it: 1) In /usr/share/dbus-1/system-services/*.service use the SystemdService= setting to declare that activation of a specific D-Bus service should be done with systemd. 2) Basically, that's already it. However, here's a twist: instead of directly specifiying the systemd service file name I recommend specifying the name of a symlink which point to the actual service, and is available only if the service is actually enabled. Then, add Alias= for this symlink name to [Install] in the unit file. This way you can now enable/disable the service and this affects bus activation as administrators would expect. Here's an example for Avahi: In /usr/share/dbus-1/system-services/org.freedesktop.Avahi.service: [D-BUS Service] Name=org.freedesktop.Avahi SystemdService=dbus-org.freedesktop.Avahi.service And in /usr/lib/systemd/system/avahi-daemon.service: [Unit] Description=Avahi mDNS/DNS-SD Stack Requires=avahi-daemon.socket [Service] Type=dbus BusName=org.freedesktop.Avahi ExecStart=/usr/sbin/avahi-daemon -s ExecReload=/usr/sbin/avahi-daemon -r NotifyAccess=main [Install] WantedBy=multi-user.target Also=avahi-daemon.socket Alias=dbus-org.freedesktop.Avahi.service The important line here is the last, which has the effect that the symlink /etc/systemd/system/dbus-org.freedesktop.Avahi.service is managed by "systemctl enable" and "systemctl disable" so that the bus activation only works when avahi is actually enabled. Naming the symlinks "dbus-xyz.service" (with xyz being the actual bus name) is a just a recommendation, nothing is requiring that... Lennart -- Lennart Poettering - Red Hat, Inc. -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
