Subject: Re: marching unit numbers
To: Curt Sampson <>
From: Chris G. Demetriou <>
List: current-users
Date: 12/30/1999 13:35:31
Curt Sampson <> writes:
> E.g., I have two ethernet cards, foo3 and foo4. When I yank them
> out and insert them in reverse order, they still get their original
> device numbers back (because the driver recognises the MAC addresses).
> When I yank one out and insert a brand new one, it gets foo5.
> I don't know if this is really worth the effort, however.

I think in a sane world that does dynamic configuration, if you're
depending on unit numbers being hard-ish-coded and you've not (somehow)
wired them down in your config file, you'll lose.

e.g. what happens if you reboot, and the device which was foo4 is in
the system and the device which was foo3 isn't.  unless you make the
"unique identifier" (if there is one) <-> device mapping permanent, in
this case you'll get the unit numbers swapped.

Of course, there's no good way to add this type of configuration
information to config files, but that's more a bug than a feature.
(e.g. you can't say "i want this unit to correspond to this MAC
address," etc.)  If people are interested in solving it, i'd love to
see proposals...

Chris Demetriou - -
Disclaimer: Not speaking for NetBSD, just expressing my own opinion.