Bug#806949: ifupdown: some tweaks to networking.service

Guus Sliepen guus at debian.org
Tue Dec 22 11:53:54 GMT 2015


On Tue, Dec 22, 2015 at 09:19:12AM +0100, Martin Pitt wrote:

> > I still think though, that we should consider allow-hotplug interfaces
> > when dealing with network-online.target.
> > 
> > The reason is, that the debian installer uses allow-hotplug by default.
> 
> Argh, this is indeed a tremendously bad default. So far I had the
> impression that "auto" is for "must be present for booting", and
> "allow-hotplug" is for "bring it up when present, but don't block on
> it on boot".

That's correct, from ifupdown's point of view.

> But if the installer always uses allow-hotplug, then I think that
> completely defies trying to make any difference between the two.

Probably because the installer itself cannot tell wether an interface
will be present right after the kernel booted or if it gets hotplugged
later. I don't blame the installer here.

> Guus, what is the difference from your POV?  It seems to me that this
> isn't cleanly defined.

There is nothing wrong with the above IMO, it's just that
network-online.target isn't defined in a useful way.

> > And mounting remote file systems under systemd requires a properly
> > hooked up network-online.target.
> > Which means, for the vast majority of users with remote (NFS) mounts we
> > currently ship a broken setup.
> 
> Indeed, and I don't see how this could even be fixed automatically
> with package maintainer scripts, as we don't know whether the admin
> configured a-h deliberately or whether it was put there by the
> installer. :-(

I believe the correct fix is to have the part that mounts the remote
filesystems wait until a route exists to the remote hosts. Everything I
do with networking.service will be an approximation that will never
satisfy every possible configuration.

-- 
Met vriendelijke groet / with kind regards,
      Guus Sliepen <guus at debian.org>
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