Hi guys,

I don't know if this is the proper section, feel free to move the thread in a more appropriate one if needed.

Anyway, I'm writing here because I have a strange behavior in my Linux server.

Scenario: Linux VM running debian and NAS with a NFS share available.

What I did is to create a mountpoint on the debian box and then use this command to mount the NFS share:

The command worked perfectly, and I started using the NAS share to store some files.

Now, I was looking after this a couple of weeks later, discovering that the NFS share is still mounted and perfectly reachable/writable and so on, BUT if I do

whatever to show the mount point, the one who belongs to the NFS share does not appear.

How can this be possible?

The command to umount the share does not work (thinking that maybe just umounting and remounting it will solve this small issue) instead I'm stuck at this point because it's really strange to me that I cannot see where this mount is on the filesystem.

If there's some information missing, let me know.


THanks,
Cr45h

Did you add an entry for the share in your fstab file? From what you posted it just looks like you manually mounted the share.

How do you know the NAS is reachable/writeable? Can you look at the files on the NAS via a web interface or ssh, ftp etc and see that they are actually written to it?

Did you shut down the VM or computer? Have both been running continuously? A mount point is just a directory. If the share is not mounted then the files will be written to the VMs disk and not the NAS share.

Well,
At the moment there's no entry on fstab to have it mounted at every reboot, I was planning to do it as a second step.

The NAS is reachable/writeable because if I ls -l or cd into the /nas folder I can see the files; moreover, the share is managed by a third party web app that writes the files there so it works.

Also doing I can see the NAS shares and reach mine; the same from the NAS web interface.

It's just strange to me that everything seems working as expected, apart that I'm not able to list the NFS mounted drive on the linux box.

Actually, I'm not even able to do "umount /nas".


EDIT: Wait a sec.. I had a look at the nas shared folder from the NAS web interface... you're right, there're differences... So do you think he's just writing on the VM disk instead of the NAS one?
Even if the directory is supposed to be the NAS mountpoint?


That's it.

As stated /nas is just a directory. If the share is not mounted the files are written to the local file system vs the NAS device itself. Just because you can ls or cd into the /nas folder does not mean the share is mounted or the files seen are actually located on the NAS device. For example if you copy a file to /nas and check the / file system for a change in size then if it increases then the share isn't mounted.

If you can write files to /nas and see them via the web app at this very moment in time then I will submit to say the share is still mounted.

From the sound of it, your VM has been rebooted sometime between when you originally ran the mount command and now. From that moment on, all writes to /nas went onto the VM's local storage, since the NFS share was no longer mounted there.

Thanks michaelk for the suggestion.

The problem now is "how can I be sure that the /nas folder is actually the mountpoint of my NFS shared drive instead of the local system?"

I'll have a look on the forum/internet before submitting a possible other thread. :P

@suicidaleggroll: no, it's impossible that the VM restarted because of 2 factors:

1- is monitored by Nagios, so if there was a restart (e.g. a connection loss to the VM) I would receive an email.
2- is LVM encrypted, so without the encryption key it won't restart anyway (that ends on point 1).

look into autofs instead of using fstab for your mount point. what happens is that every time you access the /nas directory it will automagically mount the share before you have access to it, therefore you know the files are sent to the NAS, and not stored local like they are now.

One way is to store your data in a subdirectory, rather than on the root of the NFS share.

If you can't access the subdirectory to read/write your data, then the NFS share isn't mounted, and you're just looking at the empty mount point on the local system.