On 11/16/16 23:26, Dave Reisner wrote:


On Wed, Nov 16, 2016 at 4:19 PM, Pekka Sarnila <sarn...@adit.fi
<mailto:sarn...@adit.fi>> wrote:



    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.


No, it's not. It sounds more like you want to disable the naming policy,
which means you get "eth0" for the first device that shows up.

No thats not at all what I'm suggesting. I have also had my time getting gray hair for this 'is it eth0 or eth1 this time'.

But on servers that have only one interface (and no one is allowed to hot plug anything what so ever) the old method was better: always eth0. And you didn't need to understand how the names are given even when upgrading hardware. Of course for other cases the old way was not good.

I still believe that people who's job is to see that servers hardware is running don't in most cases know how to configure systemd or much anything about the os to that matter.

I'm sure systemd could be developed to count the interfaces right after boot, and there could be in the configuration setting saying that if there is only one interface at the boot time a name in that configuration would be given to that interface.

So what I'm saying, it should be possible the have the good of the old and good of the new way in the same package. I don't believe it is alway win loose situation

Anyway no big deal.

pekka



    pekka

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