The Fedora Project is getting ready to break a lot of networking scripts that depend on the ethX naming convention — by being the first major distro to ship Consistent Network Device Naming.
Matt Domsch, Fedora contributor and technology strategy in Dell's office of the CTO, put out a call for testing the new naming scheme this Thursday with a description of the new system. Systems that have a single network device have no problems — one Ethernet port means you have one device name (eth0). But two or more network devices, and the naming is not assured on startup.
A number of proposals have been put forward to solve this, but nothing permanent or that satisfied everyone. So Dell has put together a tool called biosdevname that renames network interfaces according to the BIOS names of the devices. This ensures that devices get the same name every time.
The short-term trade-off is that biosdevname uses a new naming convention for devices. Instead of eth0, your first device would be em1 instead. Which means that scripts that depend on the old naming scheme are going to have to be revisited. For add-in PCI cards, the naming convention will be a bit more complex: pciN#port, where N is the PCI slot and port is the Ethernet port. You'll see this in machines that have add-in cards with Ethernet ports or in virtual machines (like in VMware) that expose a virtual Ethernet interface as an add-in PCI card.
For desktop users with a single Ethernet port, it won't make much of a difference. It also won't touch wireless devices or USB devices, so the change is really only something that needs to be dealt with on the server side.
Fedora is the first distro that will be rolling this out, but it will likely make its way into the other distributions over the next year. Domsch says that there is a blueprint for integrating this in Ubuntu 11.04, and feature requests for inclusion in openSUSE/SUSE Linux Enterprise, as well as Red Hat Enterprise Linux. It will probably be another year or two before this filters down to the enterprise distros, but that's one reason to pay attention to Fedora — it's a good way to see what's going to be running in the enterprise server rooms in a few years.
The Fedora Project is looking for a few folks to test this out on their hardware. If you have a few minutes and test hardware to spare, check out the Fedora Test Day page on the Fedora wiki and grab a live CD.