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

[Michael Biebl]

Am 10.12.2015 um 15:12 schrieb Guus Sliepen:
> On Thu, Dec 10, 2015 at 01:59:42PM +0100, Michael Biebl wrote:

>> The benefit here is, that other services, that don't need
>> network-online.target would not be blocked unnecessarily during boot.
> 
> I don't understand this. Are services that don't need
> network-online.target blocked by networking.service in some way?

This used to be the case, since /etc/init.d/networking was a rcS init
script, i.e. is started in sysinit.target.

Every service which as DefaultDependencies=yes (the majority) get's an
implicit dependency on sysinit.target. So making networking.service
block for the network to be configured would block at least all
DefaultDependencies=yes services.

I just noticed that you moved networking.service into multi-user.target,
so this might not be a concern anymore, unless something from
rcS/sysinit.target pulls in networking.service.

> Anyway, if we are going for a script that polls stuff, then why not
> decouple it completely from ifupdown or whatever networking framework is
> used, and do the following?

..

> Which is just waiting until we have a default route. It can be made to
> respond more quickly by using the "ip monitor" command. It's still not
> perfect, but in general it's a better default criterion for being online
> than "a network interface was configured".

Interesting idea.
This would be one way to do it.

> So network-online.target is very ill-defined, and I'd rather not see
> anything depending on it, but if we have to, I'd like something that is
> as conservative as possible.

I guess everyone agrees that network-online.target (or $network in LSB)
is an ill-conceived concept [1] and should only be used if the software
in question can't be fixed to deal with dynamic networking, where
devices and networks can come and go.

Michael

[1] http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/
-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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