15.04 and systemd

[Martin Pitt]

Hey Tom,

Tom H [2014-12-05  8:03 -0500]:
> > | $ grep ifup /lib/udev/rules.d/99-systemd.rules
> > | SUBSYSTEM=="net", KERNEL!="lo", TAG+="systemd", ENV{SYSTEMD_ALIAS}+="/sys/subsystem/net/devices/$name", ENV{SYSTEMD_WANTS}+="ifup@$name.service"
> 
> I noticed this after sending my original email. I'm now using NM (I
> had to log on to a WEP network!) and I'd meant to check whether
> unmasking ifup at .service would result in the same errors because this
> rule doesn't have "check whether something other than ifupdown is
> bringing up the network" (if that's even possible in a udev rule).

The rule doesn't have to. ifup will know by itself (through
/etc/network/interfaces) if it's responsible for a particular
interface; if not, this is a no-op.

> > This will handle hotplugged interfaces which are covered by ifupdown,
> > i. e. /etc/network/interfaces.
> 
> Except that my "interfaces" file's empty.

Right, then the rule and ifup at .service are irrelevant for your system.
This is also why the disabled /etc/init.d/networking init script did
not cause acual damage on your system. systemd brings up lo on its
own, so you don't need ifupdown for "lo" even.

> By hotplugged do you mean when using Debian's "allow-hotplug"?

I meant "added the hardware while the computer/user session is
running". "allow-hotplug" is Debian's ifupdown declaration for this
(but not supported directly under Ubuntu).

> I hadn't seen the ifup udev rule when I wrote the above so I thought
> that systemd was using the sysvinit networking script to trigger
> ifup at .service.

The sysvinit script is called at boot to bring up the non-hotplugged
interfaces (lo, builtin ethernet or wifi cards), if they are tagged as
"auto".

> I'll set up a VM to try to reproduce this.
> 
> Do you mean upgrade trusty-to-utopic or utopic-to-vivid?

Well, finding out the upgrade path that causes /etc/init.d/networking
to be disabled is exactly the exercise :-) It might just be "clean
utopic install and upgrade to vivid", but it might be more complicated
than that.

Thanks!

Martin

-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)