Date: Tue, 19 Oct 1999 02:34:40 -0700 From: "Ronald F. Guilmette" <rfg@monkeys.com> To: Brooks Davis <brooks@one-eyed-alien.net> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Stupid file system tricks. Message-ID: <16653.940325680@monkeys.com> In-Reply-To: Your message of Tue, 19 Oct 1999 00:08:24 -0700. <19991019000824.A2650@orion.ac.hmc.edu>
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In message <19991019000824.A2650@orion.ac.hmc.edu>, you wrote: >On Mon, Oct 18, 1999 at 07:58:56PM -0700, Ronald F. Guilmette wrote: >> >> Dumb question #1: >> >> Why can't I mount a single physical (ufs) file system in two different >> (logical) places at once? > >I don't have a good answer for that. I believe it would lead to nasty >consistency problems because files would be represented twice. Yea. So? All disk I/O effectively goes thru the in-core buffer cache, right? You could mount the thing twice, in two different places, but as long as the kernel remembered that it was really only one filesystem/partition, and as long as it kept only one set of buffers for it, I would think that everything would work just fine. >> Dumb question #2: >> >> Given that I can't mount a (ufs) filesystem in two different places at >> once (perhaps because that would create some problem with synchronizing >> any writes to the filesystem and/or some problems with keeping in-core >> buffers always synched with what's on disk), why can't I at least mount >> a given filesystem *READ ONLY* in two different places at once? This, at the very least, should be supported, IMHO. >You might be able to use mount_null(8) to accomplish the desired effect. Hummm... Yes! Indeed! I didn't know about that thing but it is very inter- esting, and it is just what the doctor ordered in this case. And contrary to what the man page for it says, it _does_ seem to work! Thanks for the pointer! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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