This is part two of a series of articles looking into the new udev “predictable” names. Part one is here and talks about the path-based names.
As Steve also asked on the comments from last post, isn’t it possible to just use the MAC address of an interface to point at it? Sure it’s possible! You just need to enable the mac-based name generator. But what does that mean? It means that your new interface names will be enx0026b9d7bf1f and wlx0023148f1cc8 — do you see yourself typing them?
Myself, I’m not going to type them. My favourite suggestion to solve the issue is to rely on rules similar to the previous persistent naming, but not re-using the eth prefix to avoid collisions (which will no longer be resolved by future versions of udev). I instead use the names wan0 and lan0 (and so on), when the two interfaces sit straddling between a private and a public network. How do I achieve that? Simple:
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="00:17:31:c6:4a:ca", NAME="lan0"
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="00:07:e9:12:07:36", NAME="wan0"
Yes these simple rules are doing all the work you need if you just want to make sure not to mix the two interfaces by mistake. If your server or vserver only has one interface, and you want to have it as wan0 no matter what its mac address is (easier to clone, for instance), then you can go for
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="*", NAME="wan0"
As long as you only have a single network interface, that will work just fine. For those who use Puppet, I also published a module that you can use to create the file, and ensure that the other methods to achieve “sticky” names are not present.
My reasoning to actually using this kind of names is relatively simple: the rare places where I do need to specify the interface name are usually in ACLs, the firewall, and so on. In these, the most important part to me is knowing whether the interface is public or not, so the wan/lan distinction is the most useful. I don’t intend trying to remember whether enp5s24k1f345totheright4nextothebaker is the public or private interface.
Speaking about which, one of the things that appears obvious even from Lennart’s comment to the previous post, is that there is no real assurance that the names are set in stone — he says that an udev upgrade won’t change them, but I guess most people would be sceptic, remembering the track record that udev and systemd has had over the past few months alone. In this situation my personal, informed opinion is that all this work on “predictable” names is a huge waste of time for almost everybody.
If you do care about stable interface names, you most definitely expect them to be more meaningful than 10-digits strings of paths or mac addresses, so you almost certainly want to go through with custom naming, so that at least you attach some sense into the names themselves.
On the other hand, if you do not care about interface names themselves, for instance because instead of running commands or scripts, you just use NetworkManager… well what the heck are you doing playing around with paths? If it doesn’t bother you that the interface for an USB device changes considerably between one port and another, how can it matter to you whether it’s called wwan0 or wwan123? And if the name of the interface does not matter to you, why are you spending useless time trying to get these “predictable” names working?
All in all, I think this is just an useless nice trick, that will only cause more headaches than it can possibly solve. Bahumbug!