[systemd-devel] Stable interface names even when hardware is added or removed, not true

[Pekka Sarnila]

On 11/16/16 18:11, Greg KH wrote:
> On Wed, Nov 16, 2016 at 03:33:42PM +0200, Pekka Sarnila wrote:
>> On 'Predictable Network Interface Names' it states as a benefit of the new
>> policy:
>>
>>   Stable interface names even when hardware is added or removed, i.e.
>>   no re-enumeration takes place
>>
>> Unfortunately this is not true.
>>
>> I'm running a mail server, kernel 4.8.6. Graphics card started to fail.
>> Replaced it with new one (newer model). Booted the system.
>>
>> All seemed to be fine, network seemed to work. But after some time got angry
>> cries: 'can't read the mail !!!'. A big headache.
>>
>> Although the new card was in the same slot as the old one kernel had changed
>> the name enp6s0 -> enp3s0 (no firmware/BIOS index available and kernel
>> policy was used as default). Since enp6s0 was not found our server instead
>> of fixed ip address used our dhcp-server to get a random temp address. Thus
>> network worked, but not in the mail-servers correct address.
>>
>> To figure this out took some nervous time.
>>
>> Now, I don't know why kernel driver got a different name for this network
>> interface (ethernet hardware is on the motherboard, and it is the only net
>> hardware on the system). But obviously it can happen.
>
> That is because your PCI devices renumbered themselves, which is quite
> common when changing PCI devices around (or adding/removing them).  Not
> much systemd can do about this, sorry.
>
> greg k-h
>

Well my first point was that the web page should not say

 >>   Stable interface names even when hardware is added or removed, i.e.
 >>   no re-enumeration takes place

But second was that in principle persistent naming would be possible for 
systems with only one interface. And it should possible to implement it 
in systemd-network, and make it systemd package default for such case.

pekka