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Old 12-23-2019, 01:09 AM   #1
mackowiakp
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Can not mount whole filesystem from NFS server for the second time


I export NFS share form server as described in /etc/exports:

Code:
/home/maciek/back/RSYNC 192.168.0.7(rw,no_root_squash,subtree_check,crossmnt)
This is the only entry in /etc/exports file. Both server and client use NFS v4.

Than I have such entry in fstab of NFS server:

Code:
LABEL=4TB /home/maciek/back/RSYNC ext4 user,noauto,defaults,noatime 0 0
HDD with LABEL=4TB is USB v3 connected external disk with one ext4 partition.

I use all of it for off-line backup, running from script. The script works as follows:

1 - mount USB HDD on server to /home/maciek/back/RSYNC dir using command:

Code:
/bin/mount LABEL=4TB
2 - client mount /home/maciek/back/RSYNC NFS share using command:

Code:
/bin/mount -w -v -t nfs -o rw -O user=root.password=pass 192.168.0.2:/home/maciek/back/RSYNC /share/CACHEDEV2_DATA/mnt
3 - script backup desired files using rsync
4 - client umount NFS share using command:

Code:
/bin/umount /share/CACHEDEV2_DATA/mnt
5 - server umount USB HDD:

Code:
/bin/umount -l $dev
$dev is formerly calculated device name of USB HDD ext4 partition.
When umount command has no "-l" option, it does not umount HDD partition because device is busy.
lsof for /home/maciek/back/RSYNC shows nothing.

Than I run the same script again. And it hangs when client try to mount NFS share from server.
The only solution I found so far is to restart nfs-server service on server.

So what I am doing wrong that mounting NFS share for the second time hangs? All logs shows that both NFS and local mounts are properly dismounted. If any additional info are necessary, will post ASAP.

Last edited by mackowiakp; 12-23-2019 at 01:15 AM.
 
Old 12-23-2019, 06:42 AM   #2
michaelk
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Looks like the nfs table might get screwed up by unmounting the drive. I might try removing it from the nfs table with the exportfs command before unmounting and adding the exportfs command prior to mounting in your script.
 
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Old 12-23-2019, 09:31 AM   #3
mackowiakp
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Yep. Logic will take you from A to B. So - I hope - from B to A too ;-)
So. I A is a NFS server (PC based) and B is a NFS client (QNAP NAS) I have a problem described above.
But if B is a server and A is a client, it is possible to mount/umount any share without problems.
It takes me to assumption that something is misconfigured on A. That is on PC based NFS server.
The question is what.
 
Old 12-23-2019, 09:51 AM   #4
michaelk
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I have not tested your steps but I believe the problem is due to you unmounting the hard drive and the nfs server getting confused. Check the log files.

My suggestion is to remove the share using exportfs before unmounting the hard drive.
 
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Old 12-23-2019, 09:57 AM   #5
mackowiakp
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OK. Will test everything without mounting/dismounting USB HDD, simply by automount this drive in fstab, during boot - as every HDD.
 
Old 12-24-2019, 02:11 AM   #6
MadeInGermany
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You must
exportfs -u /home/maciek/back/RSYNC
prior to
umount /home/maciek/back/RSYNC

The correct order is
mount, exportfs -a, client-mount
And
client-umount, exportfs -u, umount

Do not use -l for umount! (It is a last resort, a bit like "kill -9").
If the exportfs -u cannot release it, search for accessing processes with

fuser /home/maciek/back/RSYNC
lsof /home/maciek/back/RSYNC

If you have to frequently kill an accessing process, try to kill it with

fuser -k /home/maciek/back/RSYNC
 
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Old 12-24-2019, 03:44 AM   #7
mackowiakp
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THX @michaelk and @MadeInGermany. Looks to be solved. The trick was to use "exportfs -u".

Merry Christmas from Poland !! All I want for Christmas is June !!!

Last edited by mackowiakp; 12-24-2019 at 03:55 AM.
 
  


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