Date: Mon, 26 Apr 2004 20:16:50 -0600 From: Tillman Hodgson <tillman@seekingfire.com> To: FreeBSD-Questions <freebsd-questions@freebsd.org> Subject: Re: NFS occassionally gives "permission" denied in the middle of a large transfer Message-ID: <20040427021650.GQ92049@seekingfire.com> In-Reply-To: <20040426230855.GB22344@dan.emsphone.com> References: <20040426182547.GF92049@seekingfire.com> <20040426183717.GF2771@dan.emsphone.com> <20040426184324.GH92049@seekingfire.com> <20040426184710.GA22344@dan.emsphone.com> <20040426224633.GN92049@seekingfire.com> <20040426230855.GB22344@dan.emsphone.com>
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On Mon, Apr 26, 2004 at 06:08:56PM -0500, Dan Nelson wrote: > In the last episode (Apr 26), Tillman Hodgson said: > > On Mon, Apr 26, 2004 at 01:47:10PM -0500, Dan Nelson wrote: > > > In the last episode (Apr 26), Tillman Hodgson said: > > > > On Mon, Apr 26, 2004 at 01:37:17PM -0500, Dan Nelson wrote: > > > > > The only time I've seen incorrect permission denied messages is > > > > > when mountd is refreshing the exports list. It's not atomic, > > > > > so there's a small window where the old exports have been > > > > > deleted but the new ones aren't in place yet. > > > > > > > > Is there anything in the default weekly cron jobs that would do > > > > something like that on the file server? > > > > > > I don't think so. Mounting or dismounting local (not NFS) > > > filesystems might do it, but I'm not sure. > > > > Including local filesystems that aren't exported? > > > > If so, that's interesting because I do that in my weekly periodic > > cron job. It's a simple script that umounts a backup partition, > > newfs's it, dumps a local copy of /home over to it, and then > > re-mounts it (for easy user-accessible near-line backup storage that > > doesn't require going to tape for the "real" backup). > > That's probably it, then. /sbin/mount has code that sends SIGHUP to > mountd on any mount operation. Which implies that any manual mount > request, including NFS mounts would, cause the problem. Amd calls the > mount syscall directly, bypassing /sbin/mount. > > Ideally, mountd would be able to compare the current and new export > settings and only update the ones that changed, or have a way to create > a new mountlist and ask the kernel to replace the old one in a single > atomic operation. I'll disable the umount/mount stuff from my dump script for /home and run periodic/weekly by hand to test this. Thanks for the insight! -T -- Unix does not stop you from doing stupid things, because that would also stop you from doing clever things.
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