[kwlug-disc] Accessing recently-written NFS files

[Jason Eckert]

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> 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
> >
> >
> >
> > 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>> 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
> >
> >
> >     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
> >
> >
> >     (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>          Phone: +1-519-635-9413
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