[systemd-devel] Systemd --session instance?

[Lennart Poettering]

On Sat, 22.04.17 14:07, Benno Fünfstück (benno.fuenfstueck at gmail.com) wrote:

> Hello list,
> 
> currenty, systemd runs a system instance and a per-user one. However,
> sometimes it would be nice to have a per-session instance, for example for
> users of lightweight desktop environments that don't have their own service
> manager. Then you could use systemd to spawn things like panels or desktop
> notification daemons etc. Would it be possible to add such a thing, even if
> it may require some work? Or are there any fundamental problems with it?

As Zbigniew already pointed out this was a deliberate design decision
not to support. In the general case software can't really deal with
multiple sessions of the same users. Some fail in friendlier ways (for
example, web browsers tend to take a lock at startup thus ensuring
they are only started once per user) and others in unfriendlier
ways. Yes, there are select few programs which are entirely fine with
running multiple times for the same users, but these tend to be the
exception, not the rule, and are usually on the more simple side of
things, with anything more complex not supporting it.

The idea of moving to a single-graphical-session-per-use scheme doesn't
mean you are restricted to a single screen however. It just means
every hw you have (be it a kbd, a screen, a mouse, ...) would be
merged in one way or another into a single session. (i.e. in a
xinerama-style setup)... After all, between a user and himself sharing
should be a good thing, not a bad thing. 

Yes, this is not how X11 used to handle things, but I figure what we
can learn from history is that multiple sessions per user is too hard,
and too exotic for app developers to implement it correctly.

Lennart

-- 
Lennart Poettering, Red Hat