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

[Greg KH]

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