On 2019-06-25 at 08:11, Michael Stone wrote: > On Tue, Jun 25, 2019 at 11:09:12AM +0200, Hans wrote: > >> Might be, but this does not explain, why there are still scripts >> and configurations, which are still using the old names. And THAT >> is the problem. > > It isn't because: > 1) the new names are predictable but not constant, so you can't > configure a single default across all systems
Which seems reasonable to describe as "unpredictable". The way I usually describe it is as a difference of predictability "between computers" vs. "between boots". On a single computer with multiple interfaces of a given type (wired vs. wireless), the old names are not predictable from one boot to the next. This is the problem which the new-names approach was designed to solve. However, on a single computer with at most one interface of a given type, the names are 100% predictable from one boot to the next. On multiple computers with at most one interface of a given type, the names are likewise 100% predictable from one computer to the next. On a single computer with any number of interfaces of any type, the new names are 100% predictable from one boot to the next. (At least assuming you don't change which slot a given network device is connected to; IIRC that can change the assigned name, in at least some cases.) However, on multiple computers, the new names are not at all predictable from one computer to the next, unless the computers have "sufficiently" identical hardware configurations. Computers with multiple interfaces of the same type are, AFAIK always have been, and IMO are likely to always be, much less common than computers with at most one interface of a given type. As a result, the problems of unpredictability between boots (with the old names) are going to be much less commonly encountered than are the problems of unpredictability between computers (with the new ones). It is my opinion that the default should be set to produce predictable results in the more common case, both because it's easier to change away from the default on the smaller number of systems involved in the less common case, and because those computers (being more likely to be servers, et cetera) are more likely to be run by people who are skilled enough to figure out how to change away from the default. Regardless, IMO calling *either* approach "predictable network interface names" is inappropriate, because they're both unpredictable in different circumstances; all either one does is move the unpredictability around as compared with the other. >>> The default (Debian /has/ to settle for one default, since many >>> people installing Debian don't know or care what an interface >>> name is, let alone what the heck a /predictable interface name/ >>> is), is "predictable interface names". >>> >> Yes, I wrote about it. And I also told my opinion about it: If >> people shall use it, why change to predictable names? That makes no >> sense. > > They are tremendously helpful if you build servers with multiple > interfaces, or you ever have to swap out a broken nic. If you have a > simple system it gets set once at install time, so who cares? Among possibly other things: anyone who has to work with multiple systems with different hardware configurations, which have at most one interface of each type. Imagine carrying around a live-CD type of environment, for rescue-boot or maintenance-boot purposes, to use on end-user computers. I work in exactly that situation, and adapting - both scripts, and tech habits / expectations / etc. - to the way network interface names now vary between machines has been quite a pain. (Setting net.ifnames=0 for that environment would be possible, but a pain to maintain because of the way that environment gets updated from upstream, who are outside of our control and would reject requests to change their default because they need to support the multiple-interfaces configuration out of the box for people who don't have the skill to make the reverse change.) -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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