[systemd-devel] how to call dbus ListUnits for user units?

[Mantas Mikulėnas]

On Tue, May 26, 2015 at 10:32 PM, Chris Morgan <chmorgan at gmail.com> wrote:

> On Tue, May 26, 2015 at 3:22 PM, Mantas Mikulėnas <grawity at gmail.com>
> wrote:
> > On Tue, May 26, 2015 at 9:33 PM, Chris Morgan <chmorgan at gmail.com>
> wrote:
> >>
> >> But I can't seem to figure out how to do the same for user units.
> >> There doesn't seem to be an org.freedesktop.systemd1 interface on my
> >> current user's session bus and I wasn't able to spot anything in the
> >> interfaces on the system bus that had a nested interface of
> >> org.freedesktop.system1.Manager...
> >
> >
> > The first "org.freedesktop.systemd1" here is a /service/ name; the usual
> > hierarchy is bus - service - object - interface - method, no such thing
> as
> > nested interfaces.
> >
> > Anyway. The user processes are not allowed to own service names on the
> > system bus. And `systemd --user` is a per-user service, not a per-session
> > one, so it cannot be on the session bus for various reasons: it doesn't
> know
> > the bus address; it needs to outlive the session bus; the user might
> > sometimes have multiple sessions with their own 'session bus' instances.
> >
> > So the idea is that `systemd --user` would be found on the /user/ bus,
> which
> > would someday replace the 'session' bus entirely.
> >
> > But right now, the 'user' bus does not exist by default. To create it,
> you
> > need either
> > a) enable/install/boot with kdbus,
> > or b) obtain the "dbus.service" & "dbus.socket" user units. (They're in
> > dbus-git, or various other places like
> > <https://wiki.archlinux.org/index.php/Systemd/User#D-Bus>.)
> >
> > Configured this way, the 'user' bus won't replace the session bus yet,
> but
> > you *will* be able to connect to it and reach systemd, at address
> > "kernel:path=/dev/kdbus/$UID-user/bus;unix:path=$XDG_RUNTIME_DIR/bus".
> >
> > --
> > Mantas Mikulėnas <grawity at gmail.com>
>
> Hmm. I guess user services aren't used as much as system ones are?
>
> Is there another way to interface with systemctl like functionality
> programmatically? I have a c application that today is shelling out to
> systemctl to start services (which is fine for me since I'm not that
> concerned if it fails but it would be nice to know right at that


Note that systemctl *does* report failure as the process exit status +
stderr output.


> time), but once everything is started I'd like to go through the
> services to make sure they all got started successfully. I didn't want
> to shell out to 'systemctl --user status xxx' and parse the output....
>

Well, systemctl uses a private socket, at $XDG_RUNTIME_DIR/systemd/private.
It speaks the same DBus protocol, but using a direct peer-to-peer
connection (it's not a bus address).

Remember that it's named "private" for a reason -- it's not part of the
supported API and can go away at any time (e.g. it won't exist anymore with
kdbus), so use it at your own risk.

-- 
Mantas Mikulėnas <grawity at gmail.com>
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