On 08/01/15 17:42, Dimitri John Ledkov wrote: > On 8 January 2015 at 17:24, Simon McVittie > <simon.mcvit...@collabora.co.uk> wrote: >> I personally think having only the user bus (and having >> (G_|DBUS_)BUS_TYPE_SESSION connect to it) is the best long-term setup, >> because it's easy to understand and does not try to impose isolation >> between sessions that are not actually a privilege boundary (same uid, >> can ptrace each other, etc.). >> >> Having only the session bus (as we do in e.g. Debian 8) is the next best >> thing; it's at least an internally consistent model, even if it does >> have a bunch of stupid corner cases. > > only the session bus, but per-session though?! If i have two graphical > sessions on tty1 & tty2 they will have different > DBUS_SESSION_BUS_ADDRESS, right?!
The difference between those two models is exactly: is that last sentence true or not? In the "only the session bus" world: yes, they have distinct session buses. In the "only the user bus" world: no, DBUS_SESSION_BUS_ADDRESS points to the user bus, probably unix:path=/run/user/1234/bus (where 1234 is your uid) or some analogous kdbus thing. Typical general-purpose distributions are currently (as of e.g. Debian 8) living in the "only the session bus" world. However, it seems that systemd's kdbus userland is set to have "only the user bus", unless someone changes its developers' minds; and as far as I know, every previous attempt to make "dbus-daemon --session" into a systemd --user service has also followed the "only the user bus" model. > But I'm sure bits of graphical apps stack would then > need to be adjusted to be seats or at least active_seat aware in > system/user bus configuration. (e.g. pop a window up on > active_seat/session, rather than the one you were > dbus/socket-activated on). Yes, if the graphical environment supports more than one simultaneous graphical session per uid per machine at all. Another example of something that would have to change if that situation was to be supported on a user bus is that the X11 parts of gnome-settings-daemon (mainly the Xsettings manager) would have to have one instance per X11 display, with different D-Bus names. As usual, there is a trade-off here. The advocates of a user bus believe that the benefits of a user bus outweigh the costs (or to put it another way, that the benefits of multiple session buses do not outweigh their costs). The advocates of a session bus per $DISPLAY believe the opposite. S _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel