From owner-freebsd-hackers Mon Sep 20 19: 6:17 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from mg-20425427-42.ricochet.net (mg-20425427-42.ricochet.net [204.254.27.42]) by hub.freebsd.org (Postfix) with ESMTP id 8EBC21557B for ; Mon, 20 Sep 1999 19:05:51 -0700 (PDT) (envelope-from gurney_j@efn.org) Received: (from jmg@localhost) by mg-20425427-42.ricochet.net (8.9.1/8.8.7) id TAA17080; Mon, 20 Sep 1999 19:05:40 -0700 (PDT) Message-ID: <19990920190533.16613@hydrogen.fircrest.net> Date: Mon, 20 Sep 1999 19:05:33 -0700 From: John-Mark Gurney To: Julian Elischer Cc: Brian Beattie , "Matthew N. Dodd" , Chuck Robey , Wayne Cuddy , FreeBSD Hackers List Subject: Re: what is devfs? References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.69 In-Reply-To: ; from Julian Elischer on Mon, Sep 20, 1999 at 06:52:28PM -0700 Reply-To: John-Mark Gurney Organization: Cu Networking X-Operating-System: FreeBSD 3.0-RELEASE i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Julian Elischer scribbled this message on Sep 20: > On Mon, 20 Sep 1999, Brian Beattie wrote: > > On Mon, 20 Sep 1999, Julian Elischer wrote: > > > While I sharply disagree, with your assertion, I also point out that if > > > you make such a all-singing-all-dancing devfsd, then you might as well get > > > rid of devfs entirely, and just have devfsd make the devices using normal > > > mknod commands. > > > Since I did not follow the original discussion, maybe this idea has been > > discussed and discarded, but what about a "translucent" like deal. > > Basically yu would mount the devfs on top of an existing directrory or > > filesystem. The underlying contents would "show through" by some set of > > rules. One rule would be that if a device node existed in the devfs and > > the real fs, and the device node in the real fs was for the "fake/null > > whatever you want to call it device", the resulting device node would have > > the major/minor fron the devfs and the owner/group/permissions from the > > real fs underneath. Any change to the node would affect the real fs > > underneath. I could probably expand on this futher if anybody is > > interested. > > Basically this is my scheme. Using something like a 'union mount'. > I expounded tis as a possibility a few years ago. It is about as close as > I can get using a filesystem to do the work. A daemon can do these things > easily but has other drawbacks. what happens in this case: mount /devfs cd /devfs mv ttyd1 da0c # sure you don't normally do this but you CAN! cd / umount /devfs mount /devfs sorry, that doesn't cut it as you loose your "dynamic" links from the umount to mount, and we are back to the major/minor number to keep track of which device node belongs to which device... -- John-Mark Gurney Voice: +1 408 975 9651 Cu Networking "The soul contains in itself the event that shall presently befall it. The event is only the actualizing of its thought." -- Ralph Waldo Emerson To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message