Date: Mon, 20 Sep 1999 19:05:33 -0700 From: John-Mark Gurney <gurney_j@efn.org> To: Julian Elischer <julian@whistle.com> Cc: Brian Beattie <beattie@aracnet.com>, "Matthew N. Dodd" <winter@jurai.net>, Chuck Robey <chuckr@mat.net>, Wayne Cuddy <wayne@crb-web.com>, FreeBSD Hackers List <freebsd-hackers@FreeBSD.ORG> Subject: Re: what is devfs? Message-ID: <19990920190533.16613@hydrogen.fircrest.net> In-Reply-To: <Pine.BSF.3.95.990920182431.6478K-100000@current1.whistle.com>; from Julian Elischer on Mon, Sep 20, 1999 at 06:52:28PM -0700 References: <Pine.LNX.4.10.9909201801520.19794-100000@shell2.aracnet.com> <Pine.BSF.3.95.990920182431.6478K-100000@current1.whistle.com>
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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
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