[systemd-devel] on the default for PredictableNetworkInterfaceNames

[Andrei Borzenkov]

10.04.2016 11:17, Martin Pitt пишет:
> Hello,
> 
> Xen [2016-04-09 20:29 +0200]:
>> 1. I believe most users do not like the "enp5s0" scheme
>> 2. I do not think there are any good reasons for making it the default.
> 
> There are very good reasons for having a mechanism for stable names by
> default. Most importantly, to keep your machine actually
> booting/working .. when names suddenly move around and your server is
> suddenly not online any more, or your firewall silently stops working,
> this is a tad bad. :-)
> 

There was no problem having interface names based on PCI location before
as well. So this is irrelevant. If PCI enumeration changes between
reboot, your new names will change as well.

>> "Finally, many distributions support renaming interfaces to user-chosen
>> names (think: "internet0", "dmz0", ...) keyed off their MAC addresses or
>> physical locations as part of their networking scripts. This is a very
>> good choice but does have the problem that it implies that the user is
>> willing and capable of choosing and assigning these names."
> 
> This isn't true -- having the option of customizing the names doesn't
> mean that you *have* to do it. That's precisely why we must provide
> some schema for stable names by default -- because the majority of
> users does not care and should not *have* to care.
> 
>> What is really the amount of systems or proportion thereof that have
>> multiple NICs?
> 
> I actually think "most" (at least an ethernet and a wifi card), but
> this question is also fairly irrelenvant -- even if it's just 5% we
> still want those to function correctly.
> 

Most of those users have single eth0 and single wlan0. So yes, from
perspective of interface naming they have single NIC with given name
pattern.

>> Any user running a system with multiple NICs should be willing and
>> capable of choosing and assigning these names.
> 
> To be frank, this is the attitude of the 90's when you had to sit down
> with a thick book and spend a week until your Linux system was up and
> running.
> 

It had been working out of the box for quite a lot of users actually.

> If a user wants to customize the names, nothing stops them, and it's
> well-documented how to do that. But that doesn't mean that we aren't
> responsible for being correct and safe by default.
> 
>> The new biosdev scheme is so meaningless that mostly any user WILL want
>> to change this scheme to become something meaningful, but the obstacles
>> to it are too great currently for the regular user.
> 
> From my POV of a desktop-oriented developer and distro engineer who
> sees a lot of bug reports -- "most users" don't care. It's totally
> irrelevant on a desktop where the network is usually configured
> dynamically (NetworkManager) and it's mostly irrelevant for virtual
> environments which most of the time only have one network card which
> the OS installer sets up by default. It is highly relevant for
> embedded setups (think RasPi board) and servers with multiple NICs,
> and there a location-based naming matches people's intuition a lot
> better than the old MAC-based enumeration from
> persistent-net-generator.
> 

Again - configuring location based naming was pretty easy in the past.
You need to explain why your new naming scheme is better than that.

And the fact that it is mistakenly named "predictable" makes things no
better, because it is anything else than predictable - please try to
predict interface names on random system out there *before* you have
installed Linux on it.