Bug#940034: libelogind0: replacing a core system library and conflicting against the default init considered harmful

[Mark Hindley]

On Mon, Sep 23, 2019 at 03:03:57PM -0400, Sam Hartman wrote:
> Foo-package depends on the latest libsystemd0.  I'm running unstable or
> testing.  The latest libsystemd0 isn't building on my arch yet.  But
> elogind is simpler and has build fine on my arch.  I install foo-package
> and suddenly end up with libelogind0 instead of libsystemd0
> 
> This is probably a problem.
> Libsystemd0 and libelogind0 probably behave differently and you probably
> do care which one you have.
> The specific problems depend on what init system I have, on whether I
> have elogind running or systemd-logind, etc.
> But it's probably not a good situation.

I believe we have guarded against exactly this already because libelogind0
conflicts with systemd, so you couldn't change from libsystemd0 to libelogind0
on a systemd install without removing the running systemd (which won't happen).

> The concern is there might be other cases where the dependency resolver
> gives you an answer that is inappropriate for your environment.  We're
> not sure we have confidence we can enumerate and think about all these
> situations.

I agree we can't envisage all cases, but that is what testing is for.

Anyway, I am happy to try to work up a dpkg-divert solution if that is likely to
be more acceptable.

Thanks.

Mark