Subject: Re: CFR: The Auto-Generation Block/Character Device Switch Tables
To: Darren Reed <>
From: Bill Studenmund <>
List: tech-kern
Date: 05/15/2002 16:16:31
On Thu, 16 May 2002, Darren Reed wrote:

> In some email I received from Bill Studenmund, sie wrote:
> > That's actually not the problem. The problem is that we need to be able to
> > boot a new kernel on an old (say a restore of a backup) file system with
> > old device nodes. So whatever was say /dev/wd1a needs to still be wd1a.
> >
> > That means that whatever we've allocated so far for device nodes can't get
> > reused. We can make new ones, we just can't reuse what we have used so
> > far. We can even make new, replacement ones (a new major/minor for wd1a
> > for instance). We just can't reuse old ones.
> Hmm, that is a problem.  Although I'm the mean kind of person who'd just
> declare a flag day and everything one side would work and everything the
> other side wouldn't :-)

Well, we had quite the discussion about this back when we were going to
change how minor numbers were split up. The decision was we don't want to
do that. :-)

> Then again, does it really matter if the major number for /dev/console is
> 1048219 or /dev/wd1a has a major number of 390342 ?  So long as MAKEDEV
> knows what they areit shouldn't be a problem, right ?  I mean people don't
> go doing "mknod /dev/console c 0 0" (or whatever) just because they've
> memorized that, do they, in times of emergencies ?

Nope. So what we could do is just allocate new numbers, starting somewhere
above all the other device majors, and have a compatability mapper that
deals with old device numbers. But I don't think we really need that yet.
:-) When we change unit/partition splitting, yes. But not now.

Take care,