[kwlug-disc] Accessing recently-written NFS files
Bob Jonkman
bjonkman at sobac.com
Sat Dec 17 18:52:48 EST 2022
Right, so in 'command1 && command2' if command1 returns non-zero then
command2 will not run.
OTOH, Andrew is getting permission failures on the mv command, implying
that the part before the && is returning 0.
Andrew, do you get the failures if you create just a single file of
10,000 bytes?
--Bob.
On 2022-12-17 18:12, Jason Eckert wrote:
> 0 is just the exit status.
> Each command returns a 0 exit status to the shell if it executes
> successfully (you can see this by running "echo $?" immediately
> following the command as $? is a special variable that stores the exit
> status of the previous command).
> If a command fails for any reason, it will return an exit status of
> 1-255 (the developer can choose which number to use - e.g., for fsck, an
> exit status of 4 indicates that there are still errors on the filesystem
> that fsck couldn't fix).
>
>
>
> On Sat, 17 Dec 2022 at 17:59, Bob Jonkman <bjonkman at sobac.com
> <mailto:bjonkman at sobac.com>> wrote:
>
> I understand the phrase 'command1 && command2' to mean "execute
> command2
> if and only if command1 returns 0' -- so what does command1 return? And
> if that's not 0, then why?
>
> --Bob.
>
>
> On 2022-12-13 07:48, Adam Glauser wrote:
> > While I was trying to look up rpcdebug I ran into (what
> else?) the
> > ArchLinux wiki:
> >
> https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close> <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close>>
> >
> >
> > Thanks Paul. This is not something I'd come across as of yet.
> >
> > (Apologies if this is something you have already
> investigated. I
> > am aware you are also capable of using a search engine.)
> >
> >
> > Not capable enough it seems!
> >
> > If 'mv' works after some time, then probably you may be right.
> >
> > NOTE: Depending on your current working directory, you may
> want to quote
> > the glob, like
> > -name 'test_file*'
> >
> >
> > Thanks William, and good point on the quoting. In this instance the
> > working directory is mostly empty, but good practice is always
> worth it.
> >
> > On Mon, Dec 12, 2022 at 7:25 PM Paul Nijjar via kwlug-disc
> > <kwlug-disc at kwlug.org <mailto:kwlug-disc at kwlug.org>
> <mailto:kwlug-disc at kwlug.org <mailto:kwlug-disc at kwlug.org>>> wrote:
> >
> >
> > I do not have direct experience with this. I was going to suggest
> > enabling logging with the "rpcdebug" command, but maybe that
> command
> > has been deprecated? It does not seem to exist on Debian any
> more.
> >
> > While I was trying to look up rpcdebug I ran into (what
> else?) the
> > ArchLinux wiki:
> >
> https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close> <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close <https://wiki.archlinux.org/title/NFS/Troubleshooting#Close-to-open/flush-on-close>>
> >
> > But do not think that 10 byte vs 10k files would be the
> difference
> > here? Do you get permission denied errors if you run the
> below loop
> > with 10 byte files, but run it 10000 times? Still, this seems
> like it
> > might be worth investigating if you haven't done so already.
> >
> > Windows also comes with its own logs, which can sometimes be
> helpful.
> > If the FS is being served by a Windows machine is it serving
> as the
> > NFS server, and RH7 is the client? You can look in Event
> Viewer for
> > logs on the Windows side:
> >
> https://techcommunity.microsoft.com/t5/storage-at-microsoft/server-for-nfs-diagnostics/ba-p/424632 <https://techcommunity.microsoft.com/t5/storage-at-microsoft/server-for-nfs-diagnostics/ba-p/424632> <https://techcommunity.microsoft.com/t5/storage-at-microsoft/server-for-nfs-diagnostics/ba-p/424632 <https://techcommunity.microsoft.com/t5/storage-at-microsoft/server-for-nfs-diagnostics/ba-p/424632>>
> >
> > (Apologies if this is something you have already
> investigated. I am
> > aware you are also capable of using a search engine.)
> >
> > - Paul
> >
> > On Mon, Dec 12, 2022 at 05:45:04PM -0500, Adam Glauser wrote:
> > > I've got a bit of a head-scratcher on my hands.
> > >
> > > I have a filesystem on my application's host (Oracle/RH
> Linux 7)
> > that is
> > > mounted via NFS. I believe the FS is served by a Windows
> machine.
> > >
> > > If I do something like this, everything is fine
> > > $ for i in {1..100};
> > > do
> > > head -c 10 </dev/urandom >"/nfs_share/tmp/test_file${i}";
> > > done && find /nfs_share/tmp/ -name test_file* -exec mv {}
> > > /nfs_share/final_location
> > > \;
> > >
> > > However, if I bump up the file size to 10K, suddenly they all
> > fail to mv
> > > with "Permission denied" errors. Waiting some time and
> retrying
> > the 'mv'
> > > causes it to complete successfully.
> > >
> > > I think this means that there is some kind of client-side
> caching
> > > happening, so that the file appears to be written, while
> NFS is still
> > > working away on transferring it to the storage location.
> Trying
> > to unlink
> > > the file before the cache is emptied is disallowed,
> presumably to
> > avoid
> > > data loss.
> > >
> > > Am I headed in the right direction by trying to delve into the
> > details of
> > > NFS caching and file locking? Any other avenues that
> someone can
> > suggest?
> > >
> > > Thanks,
> > > Adam
> >
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> --
> Bob Jonkman <bjonkman at sobac.com <mailto:bjonkman at sobac.com>>
> Phone: +1-519-635-9413
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--
Bob Jonkman <bjonkman at sobac.com> Phone: +1-519-635-9413
SOBAC Microcomputer Services http://sobac.com/sobac/
Software --- Office & Business Automation --- Consulting
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