Bug#883756: dbus-user-session: blocks upgrades; installing dbus-user-session yields a change of the init system

[Vincent Lefevre]

On 2017-12-08 11:22:02 -0300, Felipe Sateler wrote:
> On Thu, Dec 7, 2017 at 10:03 PM, Vincent Lefevre <vincent at vinc17.net> wrote:
> > On 2017-12-07 18:08:47 +0000, Simon McVittie wrote:
> >> The recommendation should ideally be something like
> >> "dbus-user-session | NOT(booted using systemd)", but we don't have the
> >> syntax to express that.
> >
> > How about a new package pulseaudio-no-systemd and a Recommends on
> > "dbus-user-session | pulseaudio-no-systemd"? This package would
> > do almost nothing. It could possibly change the configuration to
> > re-enable autospawn.
> 
> It would be weird to have two snippets installed, one that enables and
> the other disables pulseaudio.

Yes. But shouldn't the default be no-autospawn? Then the
/etc/pulse/client.conf.d/00-disable-autospawn.conf config file
would no longer be needed, and pulseaudio-no-systemd would just
add a config file to enable autospawn.

> > The very few users who boot using systemd but without systemd-sysv
> > would have to force an install of dbus-user-session anyway. So the
> > Recommends would be satisfied with just dbus-user-session for them.
> 
> I'm not sure I fully sympathize with the want to have all recommends
> fulfilled (after all, they are "weak" depends precisely to be able to
> break them!).

Even though they are "weak" depends, Debian tools may assume that
they are all fulfilled. For instance, "apt-get -f install" may
install Recommends that were never asked in the first place; see
the following bug (closed without a fix):

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=489896

More generally, having all Recommends fulfilled and not installing
Recommends by default (--no-install-recommends / APT::Install-Recommends
set to no) do not yield issues with Debian tools, but if one chooses to
install Recommends by default and break some of them, things do not get
so well...

> But I don't want to make it unnecessarily difficult either. I'm open
> to suggestions to improve the current situation, but they must
> fulfill the following properties:
> 
> 1. It should use the systemd --user manager by default
> 1b. We should keep a single place to disable, which would be the
> systemd --user manager, and thus autospawn needs to be disabled by
> default.
> 2. This configuration should not be changed unless explicitly chosen
> by the admin/user.

pulseaudio-no-systemd could also just ask the user whether he wants
to enable autospawn.

But you could also see autospawn as being the default configuration
for sysvinit (where pulseaudio-no-systemd would be installed by
default). Thus it would not really be a change.

Alternatively, couldn't the PulseAudio client library be smarter,
i.e. be able to know whether it should autospawn or not by default,
without the need of a configuration file?

-- 
Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)