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Fedora 15 Changes Network Device Naming Scheme

Posted by timothy on from the shock-horror-horror-shock dept.

dkd903 writes "Fedora developer Matt Domsch has announced that Fedora 15 is breaking the conventional ethX naming scheme used for Ethernet devices by adopting a new scheme called Consistent Network Device Naming. The ethX naming scheme works fine as long as the system has only one Ethernet port. However if there are more than one Ethernet ports, the actual problem starts."

7 of 132 comments (clear)

  1. False by Issarlk · · Score: 4, Interesting

    "However if there are more than one Ethernet ports, a sort of race condition develops at every system boot and the ports may get their names in an arbitrary order"

    Wrong, udev handles this very fine. This is a complicated solution to a non-problem.

    1. Re:False by jnelson4765 · · Score: 4, Informative

      Actually, it doesn't. The interfaces can be named the same on reboot, but the initial numbering is semi-random.

      The problem arises when you're trying to deploy a large number of machines, and you know which devices are where on the PCI buses (modern servers are coming with 4 Ethernet ports on the motherboard now). That way, you can assign VLANs and IPs to specific ports in a kickstart file and the installer doesn't have to play the "which interface is eth1" game. Which is not fun. We should not be relying on automagic configuration for something as basic as ethernet...

      <rant>this is why I don't like the /dev/sd* interfaces in Linux - you have to dig deep into /proc to find out which port SATA and SAS devices are on</rant>

      This doesn't get into crappy BIOSes that enumerate devices badly, or NICs that have a bad habit of initializing late.

      --
      Why can't I mod "-1 Idiot"?
    2. Re:False by msauve · · Score: 5, Interesting

      There are multiple issues, some of which have already been solved:

      Persistency: once eth0, always eth0 - this is what most commentators here seem to think this is all about, but it's already taken care of by udev with most modern distributions.

      Enumeration: Lacking previous knowledge, the order in which interfaces are enumerated. I would think this would be deterministic, but you say it's random (what is "semi-random?"). I'll take your word for it. It seems this is the problem they're trying to address. MAC addresses are indeed useless for this, in a general case, since we may be trying to enumerate ports on plug in boards (e.g. there's no guarantee the MAC in slot 1 will be lower than the MAC in slot 2).

      Naming: The article says they're changing the naming. This is what makes no sense. It's not "required." ethx is just fine, as long as the names are enumerated consistently (meaning that on two "identical" boxes, the order is identical based on physical port).

      --
      "National Security is the chief cause of national insecurity." - Celine's First Law
  2. Re:Does this mean.... by LordFolken · · Score: 3, Informative

    You should use LLDP a protocol for discovering what iface is connected to what port on the switch. There is an lldpd available for pretty much all distros.

  3. Article is a joke and false by adosch · · Score: 3, Insightful

    So tell me, when, on a reboot, we cannot make sure that 'eth0' will remain 'eth0' if we have more than one ethernet device? Bullfish to the n-th factor. The boot strapping in /etc/init.d/network has MORE than compensated for this for years in any RedHat-related or spin-off distro I've been working with. For any sort of persistent device naming you can use udev rules (can be a bit over learning overhead so you don't trump rules or get your rules to work the way you want them to) or hack out one of the ifcfg-eth* network device scripts and edit the HWADDR parameter with the MAC address of the ethernet device you want to hard-line to that device name.

    To the articles defense, the new naming scheme does make sense, but regardless, it's just that: over engineered and way more complicated than it needs to be. If it isn't broke, don't fix it. And furthermore, don't call something broke when it's not.

    1. Re:Article is a joke and false by characterZer0 · · Score: 4, Informative

      With the existing system, if you wipe the disk and reinstall, will the interface names always be the same? It sounds like that is what they are trying to ensure. It could be helpful for frequently re-imaged machines and for diagnostics.

      --
      Go green: turn off your refrigerator.
  4. Re:Does this mean.... by Entrope · · Score: 3, Interesting

    Debian (and its derivatives, including Ubuntu) have been taking a less disruptive approach to this for years now by assigning persistent ethN device names based on MAC addresses. For example, if the system has no device names assigned and sees 01:23:45:67:89:ab as the first Ethernet device's address, that becomes eth0 from that point forward. The next Ethernet device that gets enumerated is going to be eth1, and so forth. This means it handles the USB device case in the way most users would expect.

    I suppose there is some advantage to using geographic addresses for people with lots of multi-NIC machines to build, and for people who need to hot-swap cards for reliability reasons. I suspect that Debian's udev-based approach could handle the latter either now or with minor tweaks, though.