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Re: Should libpam-elogind Provide libpam-systemd ?




Simon McVittie writes ("Re: Should libpam-elogind Provide libpam-systemd ?"):
> On Mon, 05 Nov 2018 at 13:32:40 +0000, Ian Jackson wrote:
> > pinentry-gnome3 and pulseaudio seem wrong to me.  PINs should not be
> > shared between login sessions and sound control should be per-session,
> > not per-uid.
> 
> First of all, these are Recommends, not Depends.

I don't think violating Recommends is a practical alternative for our
non-systemd users.  The packaging system makes that too hard.

> If we had a way to spell "Recommends: dbus-user-session if init is
> systemd" or "Depends: dbus-user-session if init is systemd" then these
> packages could use it, but as far as I'm aware we don't, so they can't.

Recommends: dbus-user-session | sysvinit-core ?

We can probably find another way of spelling this.  But I remain to be
convinced that the three uses I found are correct even on those terms.

> The pinentry-gnome3 Recommends is because gpg-agent is shared between
> login sessions, so anything that is invoked by gpg-agent had better
> have all its dependencies similarly shared.

I don't understand how anyone could expect this to work, when there
are multiple login sessions.  Popping up a pin entry prompt on a
different display to the one the user is currently typing at is not
useful.  Obviously there are fundamental architectural problems with
the gnupg2 agent and there is little point rehearsing them again, but
starting the agent on demand does work better because pinentry
requests go to the right place.

But since pinentry-gnome3 comes from src:gnupg2, this is all part of
the same source package: the bug is in gnupg2 and should be fixed
there.

> Similarly, I think pulseaudio's Recommends is because pulseaudio is
> frequently a systemd user service (one per uid). One of pulseaudio's
> control protocols is that it can be sent commands via D-Bus IPC, but
> again, that isn't going to work if the D-Bus session bus is shorter-lived
> than the pulseaudio daemon.

If you have multiple concurrent login sessions they each need their
own pulseaudio setup, because sounds from one session should not
appear in another.

> > I'm not sure about rygel but it doesn't seem likely to me that this
> > dependency on dbus-user-session is necessary.  Perhaps there is
> > another way to implement this on non-systemd systems.
> 
> It's another Recommends. Rygel is a long-running per-user D-Bus service
> that requires a D-Bus session bus with a scope at least as long as rygel
> itself; on systemd systems, making it a `systemd --user` service is
> desirable; but that user-service can't start without dbus-user-session.
> This would be "Depends: dbus-user-session if init is systemd" if we had
> a way to spell that in dependencies.

This still doesn't explain to me why Rygel is per-user rather than
per-login-session.

Ian.

-- 
Ian Jackson <ijackson@xxxxxxxxxxxxxxxxxxxxxx>   These opinions are my own.

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