Bug#881771: Unclear which interface name will be used
Greg Wooledge wrote:
> In the release notes, there's a udevadm command which is supposed to
> tell us what the new interface name will be, but I had some trouble
> interpreting the output.
>
> wooledg:~$ udevadm test-builtin net_id /sys/class/net/eno1 2>/dev/null
> ID_NET_NAMING_SCHEME=v240
> ID_NET_NAME_MAC=enxa08cfdc389e0
> ID_OUI_FROM_DATABASE=Hewlett Packard
> ID_NET_NAME_ONBOARD=eno1
> ID_NET_LABEL_ONBOARD=enOnboard Lan
> ID_NET_NAME_PATH=enp0s31f6
Adding a "| grep ID_NET_NAME" would still leave three hits; is it
worth the extra complication?
(Yes, in a sane world it would be something like
$ udevadm nicnames
eno1 (enp0s31f6, enxa08cfdc389e0, eth0)
but in a sane world all of those alternatives would be directly usable
as aliases, just like "mount LABEL=FOO", and we don't seem to be
anywhere near that world...)
>
> That's after the upgrade to buster; I did not save the results from
> before the upgrade, but basically it would have been the same command
> with /sys/class/net/eth0 as the final argument, with the same output.
>
> I thought the new interface name would be enp0s31f6 but it turned out
> to be eno1 instead.
>
> tl;dr: there's nothing "predicatable" about these names.
I have to agree, which is why I avoided the word! The complication
you've run into there is the fact that ID_NET_NAME_ONBOARD names,
where present, take priority over ID_NET_NAME_PATH names (and your
ID_NET_NAME_PATH name is itself a complicated one). It's hard to
summarise completely and concisely (there are further problems with
USB dongles and virtual machines and so on), so what we most need is
good external sources we can point to. The upstream docs at
https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/
*do* cover your case (the bit about "1. Names [...] for on-board
devices"), but it doesn't exactly leap out at you.
Maybe what we need is a good clear Debian Wiki page we can point at?
But https://wiki.debian.org/NetworkConfiguration isn't it...
Oh, looking at it again: maybe where it currently says
<para>
This should give enough information to devise a migration plan.
(The <literal>udevadm</literal> output will include a fallback
MAC-based name, sometimes needed for USB network hardware.)
</para>
We could fit in some sort of mention of ID_NET_NAME_ONBOARD as well?
--
JBR with qualifications in linguistics, experience as a Debian
sysadmin, and probably no clue about this particular package
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