Subject: Re: devfs (was Re: Not updating device file inode change times)
To: Todd Vierling <>
From: Stefan Grefen <>
List: tech-kern
Date: 09/06/1998 22:25:33
In message <>  Todd Vierling wrote:
> On Fri, 4 Sep 1998, Eduardo E. Horvath wrote:
> : > Make /dev be mounted dynamically inside the kernel at boot, before init is
> : > run.  This guarantees the existence of /dev/console, and allows the
> : > underlying /dev directory to be completely empty.
> : The only problem I see in my original idea is somehow getting the devfs
> : filesystem mounted underneath /dev.  But I think mount should be capable
> : of doing this.
> I preferred the idea of mounting it _over_ /dev, or at least not using the
> same semantics as the current unionfs, as /dev may be mounted on a
> filesystem that is:

You would have to mount over /dev ...

> - not capable of whiteouts
> - not capable of device nodes

I think a union-fs is a bad idea, as the purpose  of /devfs is NOT to have a
copy of the inode somewhere on stable storage.

I would suggest a plain-file just storing the non-default permissons,
with /devfs having r[w]-access.

> I'd _really_ like to see some kind of layer that can "translate" regular
> files into device nodes somehow ... for the purposes of a NFS /dev.  Real
> device nodes on a NFS-mounted /dev are, as said before, dangerous and a
> serious security risk.

But than a file just doesn't help here, or you have to authenticate the file
with secret  ...


> -- 
> -- Todd Vierling (Personal; Bus.

Stefan Grefen                                Tandem Computers Europe Inc.                       High Performance Research Center
 --- Hacking's just another word for nothing left to kludge. ---