[systemd-devel] Systemd --session instance?

[Simon McVittie]

On Tue, 25 Apr 2017 at 09:55:16 +0200, Lennart Poettering wrote:
> If you now
> introduce a third set of search paths /usr/lib/systemd/session, then
> you'll open an entirely new can of worms, as no apps install their
> unit files there, and you'd have to convince every single one of them
> to do so now too, and understand the complexity this involves, and the
> thin, vague difference between being called from --user and --system.
> 
> So, sorry, but this would have massive implications on the entire app
> ecosystem, and I am very sure this isn't worth it. Sorry!

This is essentially the same argument as the reason why
`dbus-daemon --session` can be configured (by a distro or sysadmin) to
be one per login session, or one per `systemd --user`, but never both at
the same time. Having both exist at the same time (a "user bus" *and* a
per-login-session bus) would just be too confusing, and everyone would
use the wrong one.

If a particular service does want to exist once per login session or
once per X11 display, instanced services (`xwallpaper@:0.service`)
are one possible solution.

    S