Bug#868002: udev: README.Debian interface naming improvements

[Martin Pitt]

Control: tag -1 pending
Control: user pkg-systemd-maintainers at lists.alioth.debian.org
Control: usertag -1 stretch-backport

Hello Christoph,

Christoph Anton Mitterer [2017-07-11  3:43 +0200]:
> 1)
> README.Debian, mentions:
> /lib/systemd/network/01-mac-for-usb.link
> however this seems to no longer exist.
> 
> 2)
> Also it mentions "on VMs remove the file /etc/udev/rules.d/80-net-setup-link.rules instead".

Indeed, thanks for spotting! Fixed both.

> 3) As for the "new" stable interface naming.
> [..]
> What I do however have is many bunches of nodes from different vendors or different generations
> in which the position is different, and thus I get different names.
> I do however want to have the primary network card have the same name accross the whole cluster

That touches the core of the problem: How do you define "primary" in a sensible
way that is right for all (or at least most) systems, i. e. what can be the
distro default?

> (whether it's eth0 or foobar), which brings one back to the MAC based way of naming, I guess,
> especially since these servers all typically have n NICs ... e.g. 2 "good" 10 GbEs and 4 on-board
> 1GbEs.

In this scenario it's really not obvious at all (even for me as a human) what
the "primary" card is; at least the udev names encode the type, the kernel
names are fairly arbitrary.

> Now README.Debian already gives example how to do that with an udev rule... even as "first" way,
> but it gives no example on doing it the systemd-way, which is AFAIU with a .link file, isn't it?

udev rules are more flexible, but also more error prone indeed. Beyond that
there's really not much difference in performance or effect.

> So perhaps for the custom naming, tell people how they can convert their old
> 70-persistent-net.rule to a .link file first (before the udev way) andgive an example like:

It's fine to at least point out link files, and refer to the
systemd.link(5) manpage (which already has plenty of examples).

Christoph Anton Mitterer [2017-07-12 15:12 +0200]:
> One addition on this, with 226-2, udev.postinst started to create:
> /etc/systemd/network/50-virtio-kernel-names.link
> on some systems.
> 
> AFAIU, this is only just there for "easy migration" of systems that
> used to have "old" interface naming.
> So it might be worth to tell people in README.Debian in the migration
> section, that this can/must be deleted, if they want to migrate to the
> new schema.

Agreed, fixed as well.

I committed

   https://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?id=e54b571bb

with the above.

Thanks,

Martin