debconf / ifupdown / networkd / systemd

[Guus Sliepen]

On Thu, Jul 16, 2015 at 04:11:55PM +0200, Michael Biebl wrote:

> I was wondering if you are coming to Debconf this year. Martin and I
> will be there and I think it would be a great opportunity to sit down
> and discuss ifupdown, networkd and systemd and how we can integrate them
> better.

I'm afraid I can't be there at DebConf. But if there is the possibility
to do audio or videoconferencing, I could participate.

I'm sorry for not responding to #791920 yet, but I have read the
discussion. There is some conflation of hotplugging devices versus
hotplugging Ethernet cables. Furthermore, link detection is not
something instantaneous; most network cards need to be brought up in
order to be able to detect a link, and even then it might take quite a
number of seconds for it to detect a working link (especially if
low-power modes are being used on the card and/or the switch). The
ifup_hotplug() function in /etc/init.d/networking is unfortunately using
this wrong assumption.

The main issue seems to be perceived unnecessary delays during boot. Is
it necessary for the boot process to wait for the network to be up and
to have an IP address configured? If not, then the ifup at ... service
should not block any other services; the fact that the network is in the
process of being configured might be enough. Is there a difference
between waiting for the network to be completely up before trying to NFS
mount a partition, versus starting the network in parallel with NFS
mounting, and having to wait for the mount command to finish
establishing a link with the remote server?

Even having a working link and having gotten an IP address are no
guarantee that you actually have a working network.

I could have ifupdown pass the -nw option to dhclient, but there might
be some local post-up commands/scripts that rely on DHCP to have finished.

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