Mailinglist Archive: opensuse-factory (1324 mails)

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Re: [opensuse-factory] Re: eth0 Vote
On Tue, Oct 27, 2015 at 3:45 PM, Bernhard M. Wiedemann
<bernhardout2@xxxxxxxx> wrote:
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On 2015-10-26 22:07, Jan Engelhardt wrote:

On Monday 2015-10-26 21:32, Thorolf Godawa wrote:

That is what I see too, laptops have three network ports maximum
(eth0, wlan0, ... ), desktops often only one and for server with
several IFs, you do not want that the name changes, just because
the extra card goes into an other slot.

Adding or removing a card does not change the naming of others
when going Predictable.

I once added a graphics card to my machine and it changed the name of
my enp2s0 or so network device (a 3 instead of 2 in the name) so that
I did not have network anymore.
So predictable names are not persistent names.
And thus I prefer persistent names most of the time.


It is not really related to Persistent vs. Predictable *names* but to
which criteria is used to assign them. If you base your Persistent
names on PCI path and PCI path changes you get the same problem (and
IIRC some SLES versions used PCI path to identify interfaces by
default). And you can set naming policy for Predictable interface
names to MAC and get persistent names in this case as well.

To solve it kernel needs to export some form of persistent device
path. The PCI D:B:S.F is not persistent because B is enumerated
sequentially; so if you plug in some bridge that happens to be
enumerated earlier you get this issue.

The real technical argument against Predictable as Michal mentioned is
name length which can create problems with layered drivers. One more
bug was recently reported on systemd list, which is related to using
slot-based names. Current udev assumes each card has only single PCI
device which is not always true; this makes it truly random which of
several devices on a card gets which name.
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